AINODIC BONDING
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DATE: 23/04/2005 AUTHORS: Jun Shen Yanfei Van SUPERVISOR: RSillen Bachelor of Science in Engineering Product Design
This thesi presentes si bacheloe th r dfo r Degre Sciencf eo : eat
Hogeschool Van Utrecht
Facult Sciencf yo Technologd ean y Industrial Technology
Mediatheek HvU l $Ctf. ipfói
Abstract
This paper presents our efforts in anodic bonding, anodic bonding process and anodic bonder. We are going to try to design simple and suitable anodic bond equipment. Firstly foune severat ,w dou l different bonding ways, suc direcs ha t bonding, intermediate bonding and anodic bonding, and then we studied the theory of anodic bonding and tried to investigate the several important anodic bonding processes. Several process parameters: bonding temperature, voltages, bonding time, vacuüm condition, flatness, pressure are considered. Compared with these parameters bese th tt anodige e ,w c bonding process. Accordin procese th go e t sar needed choose w , bondine eth g temperatur voltage th d ean applied ranging from 400°Cto 50 0 100far d o kne'150Co e t S an ,0w . V 0wV several processee th f so anodic bonding, such as Si-Si; Glass-Glass; Si-Glass and so on. Based on this, we master the different parameters can be used in the different process. All of these are introduced in the following.
Final Project Anodic Bonding HOGESCHOO UTRECHN LVA T 4/28/2005
Introduction
Wafe mose rth f bondint o powerfu e on gs i l processing techniques e useth n di fabricatio packagind nan MEMf go S devices. Different approache currentle sar n yi use: direct bonding, intermediate layer bonding anodid an , c bonding.
Anodic bonding is probably the most versatile bonding process that can be used permanentlo t y bon wafersubstrateso o dtw tw r so . considereIs ti workhorse dth f eo MEMS packaging and accounts for the majority of all packing application. It is also quite common in MOEMS (optical MEMS). Anodic bonding was first discovered and performed in 1969.Since then it has been established as a Standard process in MEMS technology.
Direct bonding became widespread during the 1990s .{l }The technique is based on the principle that hydrophilic surfaces created by wet chemistry or plasma activation will immediately bond upo Waalr nde contacn s va attraction a tvi s between adsorbed water groups.{2}
Intermediate bonding (indirect bonding) use intermediatn sa e laye creato rt ea bond between two wafers. Several different polymers have been used as intermediate material adhesivr sfo e bonding including polyimides, epoxies, thermoplast adhesive photoresistsd san .
Final Project Anodic Bonding l l fl HOGESCHOO UTRECHN LVA T 4/28/2005 l I ChapteM. Bonding Wafer bonding has increasingly become a key technology for materialsintegration in various areas of microelectromechanical systems (MEMS), microelectronics optoelectronicsd ,an . alsIs ti o widely use vacuür dfo m packaging, hermetic sealin encapsulationd gan .
To bond wafers or substrates together, numerous techniques have been developed. These technique categorizee b n ca s d into direct bonding, intermediate layer bonding anodid an , c bonding. (Figurel).
Wafer Bonding UMM Temperaturc BoaAn High Temperabiic Bondi
Ttrhti^its whirat nltt «einte Ityei Icciu^its with ültmtdiale lajti
1 i < i Diitct B*«diig A ••dit BMtliig EifettBitdiig Aikfiivc Bcwtitg Claas frit Boniug
Fig.lOvervie wwafeo t r bonding techniques
somBuw tno e anodic bonding process usin glayea r deposite electroy db n beam I evaporation. t 1.1 Direct bonding {3} Direct bondin makn gca e permanent bonding between different materials with t out adhesive. Polished surfaces are contacted and heated to form bonding. l 6 I Final Project Anodic Bonding l I I l HOGESCHOO UTRECHN LVA T 4/28/2005 1.1.1 Fusion bonding
Fusion bonding is a kind of direct bonding. It is one of the three methods l available for joining composite and dissimilar materials. Fusion bonding offersa number of advantages over traditional joining techniques and it is anticipated that its ft use will increase dramatically in the future because of the rise in the use of m thermoplastic matrix composites and the growing necessity for recyclability of '* engineering assemblies. Fusion Bonding of Polymer Composites provides an in- ft depth understanding of the physical mechanisms involved in the fusion bonding process, covering such topics as:
l. Heat transfe fusion ri n bonding
• 2. Modeling thermal degradation
. Consolidatio3 n mechanism t f s
| 4. Crystallization kinetics
5. Processing-microstructure-property relationship
6. Full-scale fusion bonding
. Fusio7 n bondin thermosettingcomposite/thermoplastif go c compositd ean metal/thermoplastic joints
1.1.2 Mechanical fastening bonding {4}
Mechanical fastenin oldese gth mos d f bondino tan te commonon s gi s joining methods. Bolts, screws, and nuts are common fasteners for machine component and structures, which are likely to be taken apart for maintenance, ease of transportation,
Final Project Anodic Bonding 7 HOGESCHOOL VAN UTRECHT 4/28/2005 and various other reasons. Rivets are semi permanent or permanent fasteners used in buildings, bridges, and transportation equipment. A wide variety of other fasteners and fastening techniques are available for numerous permanent or semi permanent applications.
1.2 Intermediate layers {5}
A wide range of bonding processes using various intermediate layers has been used for MEMS fabrication. Techniques include:
• 1.2.1 Glass frit bonding
• 1.2.2 Thermocompression bonding
• 1.2.3 Solder bonding
• 1.2.4 Adhesive bonding
• 1.2.5 Eutectic bonding
1.2.1 Glass frit bonding
Low melting point glasses have been use industrn di manr yfo y decader sfo forming hermetic seals procese .Th typicalls i s temperature y th carrie n i t dou e range 400 -650 °C and contact pressures of ~105Pa. The thermal expansion coëfficiënt of the glass is normally chosen to be between the two values for the wafers being bonde wida d edan rang sealinf eo g glasse commercialls si y available.
The glass layer can be applied as a performance, spin-on, screen print, sputtered patterned filman c et , defindo t e sealing areas.
Final Project Anodic Bonding HOGESCHOOL VAN UTRECHT 4/28/2005 1.2.2 Thermo compression bonding
Thermo compression bonding is simply the joining of two surfaces via the weiding of a layer of soft metals on each surface. The most common metal for MEMS application golds i s , wit hsuitabla e adhesion layer. Moderate temperatures (~300°C) and pressures (106MPa) are needed.
The technique offers very low out gassing and therefore is attractive for the sealing of evacuated cavities.
1.2.3 Solder bonding
soldee Th r bonding process work reflowiny sb meltinw glo g point metal foro st m seala . Typica -Sn b appliemetale e P b l.d Th n metalan y sca d b n Au-Sn e S sar - u C , various thin film deposition techniques refloe .Th w process means that methot no s di recommended where accurate alignmen needes i t case d th andes i wit s ,a h thermocompression bonding, the metallic nature of the bond makes it incompatible with the inclusion of metal tracks for interfacing with sealed device. The technique differs from thermocompression bonding in that the metallic intermediate layer need meltee b o soldesr t dfo r bonding soldee Th . r techniqu tolerans ei particleo t s and is most widely for electrical contacts (e.g. flip chip bonding).
1.2.4 Adhesive bonding
Various adhesives (epoxies, silicones, photoresists, polyimides, etc.) can be used to form wafer bonds. In-situ alignment can be used with this technique but like other processes that rel somn yo eintermediate floth wn i e layer, alignment accuracs yi compromised adhesive appliee Th .b n spinningy eca db , sprayine g th etc. d ,an process normally requires some heat (typically between room temperaturd ean
Final Project Anodic Bonding 9 HOGESCHOOL VAN UTRECHT 4/28/2005 400°C dependin adhesive th n go e being used pressured )an technique .Th tolerans ei t particleo t usefus i d slan whe wafere nth s hav severea e temperature limitation.
1.2.5 Eutectic Bonding
The eutectic temperature of a two-component system corresponds to the lowest melting point compositio componentso tw e th f no . This propert exploitee b n yca o dt form bonding betwee wafer o wafere ntw th coatiny f sb o s e wit componene gon hon t of the system and the other wafer with the second component. When the wafers are heate broughd dan t into contact, diffusion occur interface th t sa alloyd ean e sar formed eutectie Th . c composition interface alloth t loweya a s eha r melting point than the materials either side of it, and hence the melting is restricted to a thin layer. It is this melted eutectic layer that forms the bond.
Anodi3 1. c bonding
Anodic bonding is being widely used for bonding glass substrate to other conductive materials due to its good bond quality. It can serve as a hermetic and mechanical connection between glass- and metal-substrates or a connection between glass and semiconductor substrates.
In anodic bonding, the substrates are typically heated to a temperature between 400 °C and 500°C. A voltage of 1000 to 1500 V is usually applied to the glass and othee th r substrate bondede b o st . Bondin vacuün gi m environment possible wels a , l as aligned anodic bonding.
Anodic bonding possibilities: Silicon/silico- n - Glass/glass
0 1 Final Project Anodic Bonding r i i TOGESCHOOL VAN UTRECHT 4/28/2005 - Glass/silicon i • Glass/SOI (silicon-on-insulator) i - Glass/ SOI/ Glass • Glass/silicon/glass i • Glass/Metal
*,;: •Etc. i MethoMrthod Temp-. Vots RoughnesRougjhness Precise Hetmetic Vacuim Ki«CI MIWI ) (nnJnmmutm» l O*nOap** Sea«•*!l Anodic Bonding 500-500 -500 20 Y Y n To 0 ^1 «a«*Flft 400-500 N Y - 10 Ton Au-Sf Elltectfc 363 N Y < lor3 Toti Adheslves RT-20D N N N Hiemwcompffes sion 100-250 N Y <; 10T3 TWÏ SoUer $00-450 N Y IQ"< 3 Torr Direct Bonding 1000 0.5-1 Y Y n To 0 •1 v
Table l wafer bonding comparison
We talked about all kinds of bonding, now we have to focus on anodic bonding.
Direct bonding, intermediate layer bonding anodid an , c bonding have their own advantages and disadvantages. But anodic bonding is most popular and widely .it has found many applications in the field of MST, MEMS or microengineering. These includ fabricatioe eth pressurf no e sensors, accelerometers, micropumpd san other fluid handling devices procese Th . alss si o use firsr dfo t order packaginf go silicon microstucture isolato st e package induced stresses haviny .B sensitive gth e microstructure bonded to a relatively thick (~lmm) glass base the device can be mounted on PCB's and other substrates having a thermal expansion mismatch with silicon. In this manner, the high stress regions, which would have occurred in the silicon microstructure, instea mane se alsde yn occuw glass oe benefitca d th n ri An . s
Final Project Anodic Bonding 11 l l
HOGESCHOOL VAN UTRECHT 4/28/2005 of anodic bonding {5} l • Low bonding temperature giving more design flexibility
• Thermally matched stress free bond; stable mechanical dimensions with t temperature
Fla• t assembl•y
• • No measurable flowofthe glass occurs, hence enabling sealing around ™ previously machined grooves, cavities etc. withou losy dimensionaf so an t l tolerances l Since glass is an electrical insulator, parasitic capacitances are kept extremely small
• Hermetic seals sealine .Th • g process can readil performee yb vacuümn di , • allowing hermetically sealed reference cavitie formee b thr o st ed (o sealin n gi of specia mixturess lga )
• Glass transparenc opticat ya l wavelengths enables simple highlt bu , y accurate, • alignment of pre-patterned glass and silicon wafers. This transparency can also be exploited via optical addressing, and to 'see' inside micro-fluidic | devices
• High yield process • . Toleran partiëlo tt e contamination and wafer warp (the electrostatic field generate higsa h clamping force which overcomes these C surface irregularities)
cosw t Lo wafe • r scale procesg firsr sfo t order packagin done b chit n ea gca p l 2 1 F iProjecl na t Anodic Bonding I
l l I
HOGESCHOO UTRECHN LVA T 4/28/2005 level if required
• Multi-layer stacks allow an easy route to complex 3-D microstructures • * High strength bon highed- r tha fracture nth e strengt glassf ho . I l l l I l l l l l I l l l Final Project Anodic Bonding 13 l l HOGESCHOO UTRECHN LVA T 4/28/2005
Chapter 2. The anodic bonding process
Abstract: In normal situation, the requirement of anodic bonding is the wafer surfaces to be bonded must be smooth and flat .in this chapter, we are going to give more details about Glass-Glass, Glass-Si, Glass-Metal processes.
Anodic bonding is a method of hermetically and permanently joining glass to silico adhesivesnf o withoue us silico e e glasd tth Th . nan s wafer heatee sar a o dt temperature (typically in the range 400-500"C depending on the glass type) at which the alkali-metal ions in the glass become mobile. The components are brought into contrac higa d h tan voltag e applied across them. This cause alkale sth t ion ica o st migrate from the interface resulting in a depletion layer with high electric field strength. The resulting electrostatic attraction brings the silicon and glass into intimate contact. Further curren oxygete floth f wo n anions fro e glase th m th o st silicon result anodin a n si c reactio interface resule th t th n a tha s d glasi te ean tth s becomes bonde silicoe th do t n wit hpermanena t chemical bond.
Fig.2 Glass-Silicon sandwich
4 1 Final Project Anodic Bonding l l l HOGESCHOO UTRECHN LVA T 4/28/2005 Anodic bondin cost-effectiva gs i e metho wafer-lever dfo l assembl MEMSf yo . • MEMS packaging is a multidisciplinary field where both the assembly and integration process have to be considered. To continue the miniaturization of m microelectronics, efforts madhave b eo et towards increased packaging density m substrate minimized san d area engage passivy db e components. {6}
Anodic bonding is commonly used for joining glass to silicon for I micromechamcal applications utilite Th .anodif yo c bonding arises fro loe mwth • process temperature, since the glass and silicon surface preserving grooves in either glase th siliconr so , which allows formatio devicef no s suc pressurs ha e transducer. l The physical processes occurring during bonding are of importance in determining the surface conditions required and the process conditions (temperature, voltage, and • time) required formin permanentga , high quality bond.
| 2.1 Si-Glass {7}
procedure Th electrostatir efo c bondin folis a gs oi ws (Si-Glass) glase d :Th s an silicon wafers are placed in contact with one another and heated on a hot plate in the rang 250°f e o uppe e 450CTh o t r. limi°C thif to s temperature rang determines ei d softenine byth g glaspoine th f sto used. The nvoltaga e potentia100o t 0 0 60 f lo volts is applied to the glass/silicon arrangement so that the glass is negative with respect to the silicon wafer. The combination of the elevated temperature and high voltage potential becaus positive eth e mobil eglase negativione th drif o th s t n s i o t t e electrode, resulting in a thin space charge layer that develops between the glass and g. silicon. Once the two samples are in intimate contact, the full DC potential is ™ dropped acros space sth e charge regio higa d hn an electri c field develops that pulls • oxyge ot f thnou e glas created san thisa n oxide layer betwee glas silicone d nth san . This create irreversibln sa e chemical bond betwee waferso tw e n.th An important l Final Project Anodic Bonding 15 l l l l
HOGESCHOOL VAN UTRECHT 4/28/2005 thin keego t minn pi thas di t ideall externao yn l pressur requires ei foro dt e mth • bond. In practice, a slight amount of pressure is typically used. The process does not change the physical condition of the glass or the silicon wafer, retaining the • patterned design. si-glas Basee th n dso anodic bonding process people ,th e develop m the new materials in the bonding processes, such as si with glass with si, glass+si folloe witTh . wh glass+sion figur o s mucd ew showan ,ho h u configurationsyo n si l the anodic multitasks bonding.
l l l
Doubfe-SMted iMattng: u550*po t 0 I Cooocifoft* 1-1000N Hitfli-voitage supfHy: O-ZOOOMhSOwA m Bonding aroosphsrt lE-S-3000möw
• Fi Configurationg3 . s for anodic multitask bonding
| 2.2 Glass-Glass {8} l Glass-Glass wafer bondin beet no ns investigategha d extensively. However, Glass-Glass bonding has useful applications in bio-MEMS, microfluidic, displays othe uniqud e th an r o areaet e propertsdu y o• f glass materials thin .I s work, glass-to- glass wafer bonding with the assistance of a nano-scale amorphous and hydrogen | free silicon film has been performed.
glase sTh commonle waferth e sar y used • 4-inch Pyrex 7740 borosilicate glass l 6 1 Final Project Anodic Bonding l
l l l
HOGESCHOOL VAN UTRECHT 4/28/2005 wafers surface Th . e roughnes glase e th th f s so d wafers less i an , , s A thaRa , 5 n1 • flatness is better than 5 um. The thickness of the glass wafer is about 500 um. An amorphou d hydrogean s n free silicon thin s depositefilmwa d onte glasth o s • substrates using a DC magnetron sputtering system (Unaxis LLSEVO). To achieve a • hydrogen-free film, the base pressure of chamber was pumped down to 5 x l O"5 Pa. A high-purity 99.99% silicon planar target was mounted at a distance of 10 cm from sputterine useth s s dfloa s wa substrat e r wgga typicallth A s e ratgasd ewa Th .ean y l 100 sccm (standard cubic centimete minute)r pressure rpe th . d abous Pa an , e2 wa t0. | The target power density was in the range of 1.1 to 1.5 W/cm2. By controlling the deposition time, a film thickness of about 100 nm was obtained, as measured by an I ellipsometer (J.A. WOOLLAM Co., HS-190™). l • 2.3 Glass-Metal {9}
formatioe Th n of anodic bond• satisfactorils si y explaine oxidatioy db n of the metal surface into the glass. Sufficient charge transfer occurs to allow the oxidation • and the observation of charge neutrality in the depletion layer indicates that oxygen ion deliveree s ar anodcas e e silicoth th f eo n o dei t n anodes. Electrostatic attraction | is important when the parts are not initially brought in intimate contact by an applied _ pressure. Joule heatin depletioe th f go n requiret layeno s ri bondinr dfo occurgo t , • and is inconsistent with minimal filling of surface topography on silicon anodes. l l l l 7 1 Final Project Anodic Bonding l
l l l l HOGESCHOOL VAN UTRECHT 4/28/2005 l . Chapter 3. Physical parameters of anodic bonding proces resultind san g effect
Abstract: The physical parameters affect bonding quality directly. We are • going to discuss about physical parameters which are important.
| Anodic bonding necessitates stringent cleanliness and flatness of the surfaces to e bondeb required an d Ma higs h annealing temperatur o achievt e e reliable bond • quality. The influencing parameters on the bonding quality include the bonding • temperature, the applied voltage, the pressure, the bonding time and vacuüm level, etc. However, the temperature and the voltage play the most important role in anodic l bonding process.
3.1 Physical parameters of anodic bonding process
3.1.1 Pressure {6}
In most applications, bonding must be carried out in reduced pressure of ultra- pure inert gases undet Bu . r atmospheric pressure, almost perfect junctione sar | feasible using the proposed system and procedures.Fig.4 shows the proposed system. procedurese th n i d mose An th , t critica cleaninf o le _ste th surface e s pgi th e b o st B bonded atmospherit .A c pressure temperaturee th , almose sar t equae thath o lt f to • heating plate. An important thing to keep in mind is that ideally no external pressure is require foro d t bond e mth practice n I . sligh,a t amoun pressurf to typicalls ei y • used. The process does not change the physical condition of the glass or the silicon wafer, retaining the patterned design.
F in al Project Anodic Bonding 18 l
l l l l HOGESCHOO UTRECHN LVA T 4/28/2005 i A !SP TW
rt•H h•••• * 1 Si Al G 1 H P |" Th
Fig.4 Disposition of the elements in the bonding chamber (HP: hot plate, Th: thermocouple, G: glass wafer, Al: aluminium layer silico: Si , n wafer, L: electric lamp, SPA: single panodet oin , l TW: transparent window). l 3.1.2 Vacuüm {6} l importanVacuün a t no ms i t paramete anodie th f ro c bonding process. Mostly, use e atmospherie on sth c pressure conditions undef i t rBu . vacuüm wilt i , l fore mth l less dense populations of several sized voids. The use of an aluminum layer deposite wafee th n dro surfac contacn ei t wit heatine hth g plat anothed ean r wafer l heatin electrin a y gb c lamp improve signifïcantl populatioe yth n characteristicsr .Fo l example, if at lOOPa, these modiflcations limit the decrease in the minimum bond density to 22% if the potential difference equals 250 V and to 13% at 750V. So it l mean bonf si d densit highys i , tha voide nth s will become lessopposited an , e ,th voids will become mor mored e an term n .I mechanicaf so l strengt productiod han n yield, results were observed under vacuüm at different temperatures.
3.1.3 Voltag Temperature& e {9}
The temperature is the dominant factor to affect the electrostatic force which would cause the firm contact of two wafer surfaces facilitating the bonding reaction occuro t . l l Final Project Anodic Bonding 19 l l l
HOGESCHOOL VAN UTRECHT 4/28/2005 voltage Th alss ei o significan controe maximue th r th f tfo lo m electrostatic force. • When a voltage is applied, the power source charges this special capacitor. It is worth to note that during charging, the electrons in bonding wafer move toward the l positive electrod holee th sd movean oppositn ei e directio accumulatd nan e th n eo « inner surface of wafer near the other wafer in a very short time. On the other hand, ™ at the driving of electric force due to applied voltage, the mobile positive alkali ions • in wafer diffuse toward the cathode and neutralize with the electrons from the power source leavd negative ,an eth e oxyge wafervoltag ne e bode ionth th th f o yn o sS i . e oe f thon ee mosth s i t important • parameter bondine th n si g process.
l A higher applied voltage is expected to increase the mobility of the Na+ ions. A higher voltage produce highea s r electric field highee Th . r electric field will increase | the drift velocity of the sodium ions. Higher voltage will also accelerate the _ detachmen e sodiuth f o mt ions froe latticmth e matrix d contributan ,e th o t e • concentration of free sodium ions. This is the likely reason for the higher current and • the longer time required to establish the equilibrium state Therefore, a higher applied voltage can generate more free sodium ions, and subsequently, contributes to a • larger electrostatic force.
• High temperatures caused high current and result in good bond quality. At high
temperatures, more ions decompose from Na Kd 2O 2Omigratan o t cathodee th o et . | The equilibrium state is easily obtained and the transition period is shorter. (The detail of voltage see chapter 4) l l l Final Project Anodic Bonding 20 l
l l l l HOGESCHOO UTRECHN LVA T 4/28/2005 l l l l l
l .5g SchematiFi c showin joinine gth silicof go n wafe Pyred r an Anodi n xi c bonding
l Except the above we discuss, we found the thermal expansion coëfficiënt also l has relationship with the temperature. The follow picture can explain this l relationship: l l l l l l l l Final Project Anodic Bonding 21 l l l l HOGESCHOO UTRECHN LVA T 4/28/2005 l l Anodic Bonding Temperature l • Bonding temperatur 280°undei e> S > Cr-- tension • Bonding temperature < 280°C --> Si under l *Tr l l l l l »O 1OO ISO 2OO 23O O 3O-*O33 OO -43O 3OO l relationshie Th 6 . g Fi p between thermal expansion coëfficiën temperaturd an t e l 3.1.4 Flatnes Roughness& s {10} l The bonding strength largely depends on the flatness of the surfaces. Two factors l vere ar y importan Surfacr fo t e flatness: l 1. Wafer deformation. 2. Depend on bonding energy. (l) l (l)Fo particulay ran r chemica lcovalen e bondth y ,sa t bond between hydroge oxygend nan e ,th l l Final Project Anodic Bonding 22 l l l
HOGESCHOO UTRECHN LVA T 4/28/2005 amount of energy it takes to break that bond is exactly the same as the amount of energy released • when the bond is formed. This value is cal led the bonding energy.
« Flatnes cleanlinesd san surfacee th f s o critica e sar successfua o lt l bonde th n .I • process locaa , l surface roughnes angstrom7 5- f sufficienso s swa t bondinfoe rth g • forc pulo et l the surfaces together.
• 3.1.5 Current {9}
M Current, temperatur voltagd ean e relate each other thesd .An e parametere sar ™ importan bondingr tfo . Higher bonding temperature voltaged san s will yield higher • bond quality. We can see this in the below. (Fig.7)
• Anodic bonding takes place immediatel applicatioe th externa e n th o y f o nl voltage. At the start of the bonding process, the value of the current is high but falls • rapidly, especially for high bonding temperatures. In Glass-Glass bonding process, hige se h n wtemperatureeca s generate hig mobilitn hio glase th sn yi substrates A . temperature th raiseds ei J conductivit e th , glasf yo s increases exponentially rapiA . d _ build up of the space charge occurs at the interface, giving rise to electrostatic • forces, which brings the two wafers into intimate contact. Therefore, high • temperatures cause high current (Fig. 7(a) resuld goo)n an i t d bond quality higt A . h
temperatures, more ions decompose from Na2O and K2O to migrate to the cathode. • The equilibrium state is easily obtained and the transition period is shorter.
l A higher applied voltage is expected to increase the mobility of the Na+ ions. A higher voltage produce highesa r electric field highee Th . r electric field will increase drife th t velocit sodiue th f Jymo ions. Higher voltage will also accelerate eth _ detachment of the sodium ions from the lattice matrix, and contribute to the • concentratio fref no e sodium ions likel.e Thith ys si reason highefoe rth r currend tan l Final Project Anodic Bonding 23 l
l HOGESCHOOL VAN UTRECHT 4/28/2005 longee th r time require establiso dt equilibriue hth m state (Fig.7 (b)). Thereforea , higher applied voltag generatn eca e more free sodium ions subsequentlyd an , , contributes to a larger electrostatic force.
Final Project Anodic Bonding 24 HOGESCHOO UTRECHN LVA T 4/28/2005
O-Ö-2DDU OO+ODu O-G-600/
tDD 12DG
Fig.7 The current-time relationship under different temperatures at voltage of 600 V (a) and under different voltages at temperature of 250°C. Force is 200 N and vacuüm is l Pa.
3.1.6 Polarity {10}
There are the two setup configurations: negative polarity configuration and
Final Project Anodic Bonding 25 l l l HOGESCHOO UTRECHN LVA T 4/28/2005 positive polarity configuration.
The negative polarity configuration is Pyrex on top; it has a longer bonding time l and better bond quality than the positive polarity configuration, which is Pyrex on bottom. It is thought that the difference between the two step ups is the way the | electrical field is generated.
• In the negative polarity setup, the electrical field is generated through an electrod poina t ea t contact fiele Th d. strength decrease distance th s sa e froe mth | electrode increases. Thus the bonding is formed first at the contact point of the « electrode, then propagate outwards. This bonding formation minimizes trapped voids ™ acros wafee sth r surface.
• In the positive polarity setup, the current travels through the wafer chuck first • rather than throug electrodese hth createt .I uniforsa m electron field acrose sth wafer. A bond is formed simultaneously across the wafer, rather than propagating l fro singlma e point allowance Th . e fo shortera r bonding tim requireds ei . However, it has the tendency of trapping voids in -the interface. This results in lower bond l quality than the previous configuration. l Normally, the polarity is only considered when glass and si bond
l together wo eS . just discuss glass-si and si-glass this situation. l l l l Final Project Anodic Bonding 26 l l i i m
HOGESCHOOL VAN UTRECHT 4/28/2005 ^^^P •
| 1. with glas ssilico- n configuration (negative polarity) 1 r Negative Electrodes» 1 ^n II^L - Pvrex.*—— > U [ SS,. • Silicon* ——— > ^^HIHHHI^H m Chuck»^*. ^^^^^^^^^^^^^^^^^•^^^^^^^^^^^^^^^^^^•^•B« ® I (a)
• 2. With Silicon - glass configuration (positive polarity) 1 Positive Pdaritv» • Electrodes» 1 ^\^| 1 '^ II ©l 1
^"^^rHÉlHlilii Qj^or, 1 Pvrex»-* — chuck»HkHBHHHHlllHIIHIIHil 1 O 1 (b) polarite Th 8 . y g configurationFi negativs i ) s(a e polarity positivs i ) (b . e polarity. • Resultin2 3. g Effect 1 3.2.1 Bond Strength {9} | bone Th d strengt importann a s hi t facto r bonfo r d qualit reliabilityd yan . High • bond strength indicates that a good bond has been formed. 1 Final Project Anodic Bonding 27 1
1 l l l HOGESCHOO UTRECHN LVA T 4/28/2005 Fig8 shows the bond strength versus bonding temperature and voltage. The l tensile strength of the bonded pairs is higher than 10 MPa for all the bonding conditions bone Th . d strength obtaine thidn i s stud comparablys i thaeo t f Si/glasto s l wafers bonded using higher bonding temperature othey b s r researchers.{9e }Th l bond strength increases with an increase in the bonding temperature. l l au l 20- . l »0 . a l «au zou 2üo aso l Khsndnfi t B m por l 2-1 J. t l 10 . (b) l —i— l 3QU aua l Fig.9 Bond strength (MPa) under different temperatureunded an ) r (a V t voltaga s0 60 f eo l different voltages at temperature of 250°C and (b) Bonding force of 200 N, bonding l time of 10 min and vacuüm of 1 Pa. l Final Project Anodic Bonding 28 l l l l HOGESCHOO UTRECHN LVA T 4/28/2005 3.2.2 Thermal Residual Stress
The thermal residual stres temperaturw slo inducee th y db e anodic bonding • proceschang curvature e th wafers th e a n eth i sexpectedvi s f eo A . temperaturw lo , e bonding largely reduced the induced stress. Normally, all the bonded wafers under | different conditions were measured by the researchers. {9} l l l l I l l l l l l l l Final Project Anodic Bonding 29 l l i i i HOGESCHOOL VAN UTRECHT 4/28/2005 i i Chapter 4. Materials Of Bonding Abstract: Ther some ear e material usee b bonding n dn i sca . Normallyd an i S ,
l glass are widely used. Different types of glass are introduced in this chapter.
The anodic bonding of various conductive materials to glass has been realized successfully for the first time in 1969 by Wallis and Pomerantz. {11 }They l demonstrated that it was possible to irreversibly bond different metals and l semiconductors to an ion-containing glass by applying a potential between the two samples and heating them at a relatively low temperature.
knows A n some typica™ l configuration anodin si c bonding process. Sucs ha • sodium rich glass (conductive glass) +silicon, any metal(detail in next paragraph), or (silicon dioxide, silicon nitride, polysilicon) on silicon glass, Pyrex 7740, 7070 • and soda lime 0080 ,except above those, some special materials can be used ,such as: l 1) Foturan square chips. l 2) Sodium-borosilicate glass Tempax. l 3) Stoichiometri) c(2 (2) Stoichiometry: In chemistry, Stoichiometry is the study of the combination of elements in chemical l reactions. The related term stoichiometric is often used in thermodynamic to refer to the "perfect mixture" of a ftiel and air. Stoichiometry rests upon the law of definite proportions (i.e., the law of constant proportions) and multiplf o w la ee proportionsth generan I . l chemical reactions will combine definite ratio chemicalsf so . • Stoichiometr oftes yi n use balanco dt e chemical equations) silico casene nitridth l , silicoal n ed i t etcnan bu . • Pyrex 774 ths 0i e most commonly used in the field.) | 4.1 Glass-Glass {12} l 0 3 Final Project Anodic Bonding l
l l l l HOGESCHOO UTRECHN LVA T 4/28/2005 When people use the glass with glass to achieve the anodic bonding process, • mostly we use Pyrex 7740 borosilicate wafer with one wafer surface sputtered with a layer of amorphous Si. And when these two wafers are succeeding to bond together • using anodic bonding techniqu different ea t process parameters suc: has
| (1). Bonding temperature is ranging from 200 °C to 400 °C.
| (2). Voltage applied is ranging from 400V to 1200V.
• (3). Bonding duration is from 10 min to 30 min.
fl (4). Vacuüm lever is from 0.1 mbar to O.OOlmbar.
• Based on the model established experimentae th , l results were evaluated theoreticall founs wa dt i {12} y ythatthb d .An e bonding temperatur voltagd ean e • has significant effects on the magnitude of the electrostatic force.
| 4.2 Glass-Metal {13}
anodie Th c bondin metaf go glaso lt s• can greaf also e otb interest for sensors encapsulation metalf o increase n sus ca e robustnese Th e.th packagine th f so d gan | eliminate the use of glue. And metals having a coëfficiënt of thermal expansion clos Pyrexo et , suc d invas ha an Ni)) % r ,Ni (64 36 Allo , % % (58Fe 2 42 y 4 , %Fe l Kovar (54 29, 17, %%Fe % Ni Co), were investigate {11}y db . This metald san m titanium to ion-containing glasses, Pyrex (Corning 7740) and Foturan (Schott) glasses was evaluated in terms of samples preparation, bonding parameters, and • bonding characteristics. At a bonding temperature below 300 "C, the stress induced to Pyrex was smaller when the Invar was used; however, a weak bonding was • obtaine lowese th t dta bonding temperatures investigated comparison I . n with invar l 1 3 Final Project Anodic Bonding l
l l l
HOGESCHOO UTRECHN LVA T 4/28/2005 and Allo bonde2 y4 Pyrexo dt , Kovar induce dsmallea r stres bondinr sfo g • temperatures highe rbondinr tha°C0 Fo . n35 g temperature0 35 betweed n si an 0 n30 • °C, a similar value of stress as obtained for Kovar and Alloy 42 bonded to Pyrex as • welhiga s hla bonding strength post-annealinA . g temperaturstea t pa anf eo d higher V tha bondine nth g temperatur shows ewa decreaso nt bondine eth e b gn stresca d san used to improve the bonding strength of samples bonded at low temperature. Kovar Allod an bonde2 y4 Pyreo dt g temperaturet x a highed an f rso tha °0 C nwer25 e tight _ to liquid at a pressure of l .5 bars. In the case of titanium, Pyrex and Foturan were ™ successfully bonded to titanium thin films and sheets. The table 2 is the thermal • expansion coefficients of materials used for the anodic bonding of metal to glass, we can see the Pyrex (Corning 7740) and Foturan (Schott) glasses with Respectively a • Coefficients of thermal expansion (CTE) close to Si and close to Ti.
l ItapoiturefC) Ctó&óos of taul oposuxi (ppD Si FOÖIE Ti l Pyra AD2 *4 te lorc «00 3.0 3.1 4J 5J i; _ «00 3.3 3.] 4J 5.1 45 U 5^ l «50 3.4 3.! 5.0 - *.« - WOG 3.5 3.3 «.0 45 ".3 _ l
Table 2 Thermal expansion coefficients of materials used for the anodic bonding of metals to I glass l 4.2.1 Pyrex and Foturan square chips
Pyre Foturad xan n square chips (15mm, 500um thick) were anodically bonded • on small metal square plates (40mm diameter, 500um thick) with the aim of l 2 3 Final Project Anodic Bonding l l l l
HOGESCHOOL VAN UTRECHT 4/28/2005 investigatin y {14 gb e influenc } th e surfacth f o ee bondine roughnesth f o gd an s • condition characteristice th n o s metalf o s s bonde glasstemperatureo de t Th . e sar varying from 200 to 450 °C and voltages from 500V to 1500V. And these samples • were cleane acetonn di e and isopropanol before bonding them together.
l 4.2.2 Polished Invar, Kovar and AHo2 y4
| Polished Invar, Kovar and Alloy 42 were successfully bonded for bonding M temperatures also between 200 and 450 °C, and the voltages also between 500 and 1 500 V. However, bondings performed at temperatures below 250 °C were found to • be weak just by manually putting pressure on the samples. The bonding performed to evaluat bondine eth g characteristics, suc s stressha , strengt tightnesd han s were l done at a constant voltage of 1 000 V.
ff 4.2.3 Anodically bond glasse titaniuo st m {14}
• Anodically bond glasses to titanium were performed at temperatures between firse 0 °CTh t.40 attemptd an 0 bono st 30 d Fotura i sheetT o nt s were performed " successfully at 400 "C and at a lower voltage of 300-400V. At higher voltages, ff electrical breakdown occurre Foturae th crackd n i d an n s could propagate th n i e material and black spots be formed. However, the results were hard to reproduce. J Bonding Pyrex to Ti sheets was not performed successfully. However Pyrex was ^ bonded with succesthii T na filo st m (SOOnm thickd °0 Can 40 ) d betweean 0 n30 ™ thii 800VT ne filmTh . s were deposite e-beay db m evaporatio u5 m52 thica n i nko S • wafers on which an 80nm thermally dry silicon oxide was grown. So Pyrex to Pyrex plates could be anodically bonded together (300-400 °C, 800 V) using an ff intermediate Ti thin film deposited on one Pyrex plate. So actully, we talk about
l 3 3 F iProjecl na t Anodic Bonding l
l l l
HOGESCHOOL VAN UTRECHT 4/28/2005 anodic bond of glass to titamium was failed in this experiment, and this experiment • should belong to intermediate bonding. But in this experiment they are failed, it didn't mean the titamium and Pyrex can not bonded in anodic bonding process, | because we also found another experiment they are successful in anodic bonding of f titamiu Pyred nan x (detai chaptee table se l non-industriaf th eo r5 l machine)
. 4.3 Silicon and glass
m 4.3.1 Silicon and glass (Pyrex 7740) (l 5}
Anodic bonding between silicon and glass (Pyrex 7740) is a well-know process. • The bonding was performed at the temperature range from 250 T to 500 °C and • voltage range from 400 V100o t hig0e Vh.Th yield process (very toleran partiëlo t e contamination and wafer warp) hermetically and permanently joins glass to silicon • producing a thermally match stress, high strength bond without using adhesives.
• sodium-borosilicat4.3.e 2Th e glass Tempax (Schof 8330t# , almost identica Pyrexo lt , Cornin 7740g# ) {15}
The sodium-borosilicate glass Tempax (Schor 8330t# , almost identicao t l l Pyrex, Corning # 7740) was investigated by {13}; it is widely used in Microsystems technology becaus thermas eit l expansion coëfficiënt (3 closs )i thao et siliconf o t . temperature Th thesf eo Be materials junctio rangins ni g from 200-45e th 0d °Can • voltage in the range is only 200-500V.
Stoichiometri4 4. c • silicon nitrid glaso et s (Schoft 8330) {16}
• Stoichiometric silicon nitride wit thicknesha lOOnf s depositeo C s ° m0 wa 80 t da onto polished Si wafer. The nitride covered wafer was bonded to thick bulk glass
l 4 3 Final Project Anodic Bonding l
l 1 1 1 HOGESCHOOL VAN UTRECHT 4/28/2005 ^Pt substrates (Schott 8330) bondine Th . performewits C ° gwa h 0 40 t da a voltage of 1 800 V applied. Bonding min tim5 1 s .ei
I ) Therma(3 l expansion coëfficiënt: 1 The (volume) thermal expansion coëfficiënt ais definey db 1 a = J -— -l (9P\ O) 1 P P (2) 1 v(dr)p _ *ïCp_ Cv f 1 K.V f lV/ H$vV \T * (3) p (9p/dT)p densitye whertemperaturee th th s i s i e ,T , indicate derivativsa constant ea t pressure, Cv •y K volume e heae th th s ti s i capacitV , heae yth tratios i capacit. constant ya te volumeth s i , T Cp KS 1 isothermal bulk modulusheae th ts i capacit. constant ya t s pressurei d ,an the adiabatic bulk modulus. 1 4.5 Intermediate layer in anodic bonding 1 In anodic bonding process field, we also use intermediate layer to success the 1 bonding quality.
1 4.5.1 Silicon wafer have been anodically bonded to sputtered lithium 1 borosilicate glass layers (Itb 1060) on Silicon {16} Silicon wafer have been anodically bonde sputtereo dt d lithium borosilicate glass 1 layers (Itb 1060 Silicon )o temperaturt na los ea 150-ws a 1 80 e °C .Th bonding 1 voltage leve selectes lthawa o s onlts d V a electri 0 y5 c breakdow glase th f sn o layer was avoided reliably. The bonding time resulted from the bonding current curve 1 F in al Project Anodic Bonding 35 1 1 l l
HOGESCHOO UTRECHN LVA T 4/28/2005 recorde samt da e tim mine0 6 rang o .t n e fromi 0 m3
And the researcher also found the experimental analysis on the anodic bonding • with an evaporated glass layer.
• 4.5.2 Silicon to silicon anodic bonding process using a glass layer deposited by electron beam evaporation {16}
The researcher found a silicon to silicon anodic bonding process always using a • glass layer deposite electroy db n beam evaporation bondin effecte e th n Th . so g process were investigated by {16} as a function of the thickness of the glass layer l and the concentration of sodium ions in the glass layer and the concentration of • sodium glase ionth sn slayeri surfac e Th . e roughness of the glass layer decreased with increasing thickness of the glass layer. It was observed that the deposited glass l layers of more than l.Sum thickness had very small surface roughness. The performanc bondine th f eo g temperatur range th f 135-24n ei o s ei 0 °C witn ha | electrostatic vo Itage in the range of 3 5 -100 V.
l 4.5.3 Bonding lead zirconate titanate (PZT) ceramic silicoo st n wafer {17}
Anodic bonding was investigated for bonding lead zirconate titanate (PZT) ceramics to silicon wafer. Sputtered borosilicate glass was used as an intermediate layer. Piezoelectric ceramic lead zirconate titanate Pb (Zr, Ti) O3, or PZT, is one of M the most practical materials for converting mechanical energy to electrical energy • and vice versa, and is widely used for mechanical sensors, piezoelectric actuators, l and ultrasonic transducers. Well-bonded wafers were obtained by applying voltage bonde e TC500r 0 °3000 f Co o Th .40 50 V t Vt a da area increased while applied l voltage was kept constant. The size of the bonded area depended on the resistivity of l 6 3 Final Project Anodic Bonding l
l l l l HOGESCHOOL VAN UTRECHT 4/28/2005 the ceramics at bonding temperatures. Fig. 10 show relative thermal expansion of the l unpolarison and polarized PZT and the unpolarized PLZT. l l l l l l Fig.10 Relative thermal expansion PZTf so ,. PLZSi d Tan l The Fig. 11 shows the bonding setup the glass layer on the ceramic wafer adn the polishe surfaci dS places ewa contac heaten de i th n ro t plate. l l l l l Fig.11 Bonding setup seee PZT-Sb e nn th Figca s .ia 1wafe, 2a wels i r l bonde therd d an neithe s ei r clear ceramic-glase gaster th pt pno a glass-Sd san i boundaries. Fig.l2b showe sth l l Final Project Anodic Bonding 37 l l l l HOGESCHOOL VAN UTRECHT 4/28/2005 unpolarized PLZT-Si wafer bonded unde same rth e conditions. Fig.l2 PLZe th s cTi l and Si are also well bonded, but cracks along the grain bondaries are observed. The l cracks reach a distance of 110-130 um form the PLZT-glass bound. l l l l l
l Fig.12 SEM photogrïq>hs of broken-off sections of bonded wafer: (a) PZT-Si PLZT-S) (b . overal) i(c l vie PLZT-Siwf o wafere Th . s were bonde 50t da 0 "C, 300r Vfo l l O min. l Fig.13 shows the photographs of the PZT-Si bonded wafers under different bonding l conditions white .Th electrodesel regionA centee e th th e n si rar . l l l Fig.13 Photographs of PZT-Si wafers bonded under different conditions. l (a) SOOt, 300V, 20 min; (b) 400"C, 500V, 200 min; (c) 350t, 600V, 200 min. The white l electrode regions A in the center and the dark regions B around the electrodes are bonded. l Final Project Anodic Bonding 38 l l l l HOGESCHOOL VAN UTRECHT 4/28/2005 l regione Th sbondedt markeno e ar .dC l l l l l l l l l l l l l l l l Final Project Anodic Bonding 39 l l l l HOGESCHOOL VAN UTRECHT 4/28/2005 l l Chapter 5. Industrial & Non-lndustrial Machine
• Abstract kin Io Therdtw e ofear bonde r available: Industrial machind ean non industrial-machine severat go e l.W industrial machines informatione th t bu , | machines are expensive for us. And non-industrial machine also called self-made • machine, they alway use e experimenty sar db , the usefu e alsd yar o an lhav e good •_ quality and low price. So in this chapter we will compare with industrial machine industrial-machinen no d an , the wil• e nlw fin gooda d combination self-mad for rou e machine.
5.1 Industrial machine
• 5.1.1 AML-WB04 bonder
featurA e of the Bonde • thas ri t alignmen bondind tan performe e gar d in-sita n ui • high vacuüm chamber wafere loadee .Th sar d cold and procesheatee th n di s chamber. For high accuracy alignment (2-5 um), they are only aligned and brought • into contact after the process temperature is reached, thus avoiding differential thermal expansion effects which can compromise alignment. ™ NB although designed primarily as an Anodic Bonder, the AML-WB04 can also • perform Direct silico nsilico- n aligned pre-fusion bonding, glass frit, adhesive, Temporary, Solde eutectid ran c bondin wels g a ALIGNE s la D EMBOSSING where capabilitiee th s of th • e machin termn ei s of temperature, forces and alignment capability allow.
l 0 4 Final Project Anodic Bonding l
l l l
HOGESCHOO UTRECHN LVA T 4/28/2005 5.1.2 SB6/8e Substrate Bonder
The SB6/8e is a semi-automatic, computer controlled, stand-alone substrate l bonder accommodatin wafers" 8 & " g. 6 uo pt
• 5.1.3 SWS-100IRV/IRT bonder Temporary fixing syste multiplf mo e layer circuit board anodir sfo c bonding. This l system is to temporarily fix silicon and glass substrates as part of the fabrication processe smalf o s l part micromachiningr sfo , semiconductor pressure sensors, l acceleration sensors, etc., before fïrmly bonding them together through, anodic and • direct bonding processes m 5.1.4 EVG 501 Wafer Bonder
_ EVG 501 Universal Bonder 4" & 6" Wafer-to-wafer bonder for anodic • bonding (Si to Pyrex, Pyrex to Pyrex) and adhesion bonding of different materials • (e.g. SU-8, BCB) bondine Th . g proces fulls si y computer controlled. Bonding recipecreatee b n storedd sca d an vacuüA . m system with maintenance-free pums pi • attached. Bonding can be performed in vacuüm, air or Nitrogen atmosphere. The currently available bond tooi allows bonding of 4 inch wafers. Alignment of wafers | is done with the AL6 mask aligner. • (This industrial machine's specification will see in Appendix)
_ 5.2 Non-industrial machine
We make a tab Ie to compare with different parameters of different non industry l machine, and the choose n suitablw e eth e parameter mako st neea w machine. l 5.2.1 The table of non-industrial machine l Final Project Anodic Bonding 41 l l l l l HOGESCHOOL VAN UTRECHT 4/28/2005
Experiment Experim Experiment Experiment Experiment 5 Experi Experimen 1(16} ent 2 3(18} 4(19} ment 6 t? {17} Materials P-Type 3-4" Silicon and Titanium Pyrex 7740 Silicon Glasd san Silicod nan (silicon borosilicate and Pyrex glass and with silicon Borosilicate and glass glass silicon sputtere glass Pyrex Corning d Pyrex glass) 7740 thin flim and silicon Power Stanford supply Research Systems Inc. Model PS310-0- 1200V Hot plate Thermolyne Hotplate - 40-540°C Anode Cu wire wafer on a hotplate and wired Cathode 5x5l "A conductiva e Plate metal hotplate Temperature 540°C 350- 400°C 300°C 400°C 400°C 200°C 450°C ~500°C Voltage 900V 200V 1000 V Upto 100V-1200V 20V 200V -1250V -400V 2000V -200V -1000V Current ImA ImA Pressure Mbar Upto 0~2000bar 0-2000 15-250KP region 3mBar bar a (mecha nical pumpin g) Vacuüm IxlO- 4mBar Polarity Negative
5.3 Defining the problem
Final Project Anodic Bonding 42 l l
HOGESCHOO UTRECHN LVA T 4/28/2005 From the introduction of anodic bonding until now, we have a lot of information design mak minn ow r fïnallnr d ca foeou de ou an r n yi w anodi c bondin • g process. After all the process we see, we knows the material is the first step for every process, | we saw a lot of processes the researchers made before, the mostly they use silicon « and Pyrex, because these two materials is the common materials they choose in this ™ field. Because silicon has some advantages in technological properties and physical • properties. See the table below:
TWimoloieal • Abuodant element -28% . AppTOptiatebandgap-UeV
Simplepurificatio• | n _ High breakdown voltage • GoodcrystalquaUty _ No «Jeep trap* • • Strong&hanlmjrterialTGPa _ Indi«ct4ugh «inier lifctime • • controilable doping . Reasonablemobility Goo* d oxid•e SlO , / • _.„, . * - Electrons 1400cm2/Vs • — Diuusiou orask - Demepm-boJefitedKtectric ~ Holes SOOcm'/Vs Goodadhesio- n • • - Suc£ace passivabou l Tabladvantagee Th e3 silicof so n l And about Pyrex wile w , l choos comine eth g 7740 because Pyrex code 7740 8 glas borosilicata s si e composition tha uses i t providdo t e unique chemical, thermal, . mechanical and optical properties. Because of its composition, Pyrex code 7740 • brand glass resists acidattacl al sy k b excep t hydrofluori phosphorict ho d can e .Th • low coëfficiënt of thermal expansio Pyref no x code 7740 glass allow withstano t t si d higher temperatures and temperature excursions than ordinary window glass. It has • higher transmission than ordinary soda-lime glass, particularly in the infrared and
l Final Project Anodic Bonding 43 l
l l l
HOGESCHOOL VAN UTRECHT 4/28/2005 ultraviolet regions. These properties enabl provido t t ei e long servic fulfid ean l • requirements which common window glass cannot meet. Pyrex code 7740 can be useneutroa s da n absorbe poison i r n rodranchind san g rings. Tempering 7740 glass | enables it to withstand tension stresses of 3000 psi and increases its thermal shock M resistance as well. But of course except these two materials, another kind of ™ materials suc Pyres ha x 7070, soda linie 008 Foturad 0an n square chips, Sodium- • borosilicate glass Tempax, Stoichiometric. Because their parameter quiee sar t similar with the common materials, so they also can use in the in our bonding J process design.
anodie th n cI bonding process mos e • th , t important ste chooss pi powee eth r supply and hotplate reae anodie ,w dth c bonding specifïcatio e theorth d yan industriaf no l | and self-made machine, then we knew the anodic bonding process need the voltage H rangin 1000V~gs i degree l 500th d Vean rangin °C-500 40 foune gs i 0 w t °Co dou S . several power supplies and hotplates and they are suitable to this case. l According to these above, we will design ourselves-made machine in the following chapter. l l l l l l l 4 4 Final Project Anodic Bonding l
l l l l HOGESCHOOL VAN UTRECHT 4/28/2005 l Chapter 6. Design of Utrecht anodic bonding * apparatus
Abstract :goin e Nowar desige go t ,w n our-selves made machine. Firstlye ,th l most important thin thas gi t suitable power platet pricsupple ho Th .d e yneedan o st be considered.
6.1 Quality table
IB The first idea of the whole assignment was to make a complete quality table for | anodic bonder, in order to analyze the Structural and Functional model of the anodic
• bond equipment, the following steps were undertaken:
n analysiA f Customeo s . 1 r Requirement • s (CREngineerind an ) g Characteristic e relatione sproductth th (EC d f o an )s , between them • (Interaction Table). l 2. An analysis of the product structure and the relation between EC, • presented above, and the components of the product.2
6.1.1 Interaction table l In the table below, a translation of the customer statements which stated above into Engineering Characteristics is presented (an interaction table):
1 "Product Design and Developmenf. Ulrich and Eppinger, Ch. 4 and 5; "'Integrated Product and Process Design and
• Developmenf', Magrab. Ch.5 2 "Integrated Product and Process Design and Developmenf', Magrab. Ch 4. l 5 4 Final Project Anodic Bonding l
l l l l HOGESCHOOL VAN UTRECHT 4/28/2005 l Engineering Characteristics l l 's l p !l l 1 '%& * M Customer ï S ca i|
o u G e Requirements Voltag e l Eas bonyo t d X l Safety X X Low cost l Hand able l Operate easily X X X Small size X l Light weight l Stability X l Table 4 Customer Requirements - Engineering Characteristics l 6.1.2 Anatysi relationshie th f so p betwee (EngineerinC nE g Characteristics) and Co m ponen ts of the product l In order to realized the importance of each component of the product they are related with the Engineering Specification as presented foliows: l This chart indicate importance sth componenf eo tassembl/ systeme th n yi . l l l Final Project Anodic Bonding 46 l l l l HOGESCHOOL VAN UTRECHT 4/28/2005 l l Components l l \ 's- §en• l Engineering \v l-l 1 0> "o, •p Characteristics N. 1 g 0) \ ffi (2 W -i *- l Current(Ma) X
l Voltag) e(V X X l Temperature(°C) X X Width (cm) X l Height (cm) X l Depth(cm) X Cost ( €) X X l Mass ( kg) X X
Geometrie shape th f eo X l model (radius: cm) l Table 5 Engineering Characteristics - Components l l l l F in al Project Anodic Bonding 47 l l l l HOGESCHOOL VAN UTRECHT 4/28/2005 l l Target specifïcation
N*L Product Customer Needs lm p. l 1. Anodic bonder Easy to bond 9 2. Anodic bonder Safety 5 l 3. Anodic bonder Low cost 7 4. Anodic bonder Hand able 3 5. Anodic bonder Operate easily 3 l 6. Anodic bonder Small size 7 7. Anodic bonder Stability 7 l Tabl Levee6 l of Importanc Functior efo n of anodic bonder l Making of level of importance is set between values of 1,3,5,7 and 9, to realize greater differences between specifications ,mose wherth s ti importane9 s i l d an t l least important. l We finish this quality table completely. Thasay o finist e s w ,translatioi te hth n fro voice mth custome f eo voice th designerf eo o rt . From these charts cleas i t i o ,rt l thae se t hotplat powed ean r suppl vere yar y important followinge th n i , wile w ; l l identify possible and alternative design solutions of hotplate and power supply. l l l l l l Final Project Anodic Bonding 48 l l l l HOGESCHOO UTRECHN LVA T 4/28/2005 l l 6.2 Power supply and hotplate l 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 concèpts l criteria ^\ Voltage D s s + + s s S ~ " " " " " " " " l Current A s l polarity T + s s + s + Regulation U + + — s l voltage M + adjustment continuous l accuracy +
_ __ __ l Price + + + + + + — "^ ^~ Stability + s l + 1 1 1 1 3 3 2 0 0 1 1 1 1 0 0 0 0 l — 2 2 1 1 1 1 3 2 4 2 1 3 2 2 2 1 2 S 0 0 1 1 0 0 0 1 1 0 1 1 3 1 0 1 0 l Tabte? Evaluation matrix for power supplies Datum: 0-2000V, 0~60mA, regulation 0.005%, polarity is positive or negative, accuracy is 0.01%, l voltage adjustment continuou 5s si V steps ,euro 0 pric50 ,s ei Stabilit ±0.01s yi hour %pe r +: meaning better than, less than, less prone to, easierthan, etc., relative to the datum. -: meaning worse than, more expensive than, more difficult to develop than, more complex than, l more pron harde, eto r than, etc., relativ datume th o et . Wher douby ean t exist whetheo t s sa concepra bettes ti worsr ro e tha datume nth , then use: l S: meaning same as datum l We saw this list of power supplies, the best power supply is considered that l Final Project Anodic Bonding 49 l i i i HOGESCHOO UTRECHN LVA T 4/28/2005 number (14) Glassman PS/ER05R60.0-11, because the current is the best of our i design. The spec of this power supply you can see in (Appendix III). i ~^--\^concept 1 2 3 4 5 6 7 i criteria^^"---^ temperature D — — — + + + i Plate size A s — - s — — Overall size T + + — + — — i Voltage U + s s s s s Watt M + — — + — — i + 3 1 0 3 1 1 i — 1 3 4 0 3 3 i S 1 1 1 2 1 1 TableS Evaluation matrix for hot plates Datum: temperature 200-55 , plat0C ° e siz overal e 4"~6s ei th d "lan siz 20Wx20Dxl5Hs ei , i voltage 240V and watt is 0-2000W meanin: + g better than, less than, small than, etc., relativ datume th o et . i -: meaning worse than, bigger than, more difïïcul develoo t p thaharded nan r than, etc., relativo et datume th . i meanin: S g sam datums ea . We will choose (5) model HP66YH, because the size 6"x6" and the degree max i 537°C, the bote yar h enoug thir hfo s process. (The picture show Appendin si x III) and we choose this model also have another season, because the power is 120/240V i and 1100W (Appendix III), it's just like a normal electric appliance, so we don't i hav fino et speciada l socke. it r fo t After these wile w , l make some detail decisions ,anode e sucth cathodes e ha ,th , i polarite th . electrodd on yan o s d ean i Normally, we use the 32 elements of the Product Design Specification to make i Final Project Anodic Bonding 50 i l l
HOGESCHOOL VAN UTRECHT 4/28/2005 qualitr ou y table complete studiee W . d this method fro booe mth k named TOTAL l DESIGN written by Stuart Pugh. PD3 6. S (Produc • t Design Specification) PDS (Product Design Specification) plays important roles in the process of • designing a new product. The PDS is essential in all fields of design activity from architecture to shipbuilding, electronics to mechanical engineering. A PDS must be l comprehensive and unambiguous od f then . eAne desigth dt a n activity desige th , n « of the product must be in 'balance' with the PDS, even though the PDS may have • changed on the way through. • elementTher2 3 e ear s of the product design specifications .foliowing s Thea e yar :
• (1) Performance • (2) Environment (3) Life in service • (4)Maintenance (5) Target product cost • (ó)Competition • (7)Shipping (S)Packing • (9) Quality (10) Manufacturing facility l (ll)Size _ (12)Weight ™ (13) Aesthetics, appearanc finisd ean h • (l 4) Materials (15) Product life span l 1 5 Final Project Anodic Bonding l
l l l l HOGESCHOO UTRECHN LVA T 4/28/2005 (16) Standards and specification l (17) Ergonomics (18)Customer l (19) Quality and reliability m (20)Shelflife(storage) (21)Processes • (22) Time-scales (23) Testing | (24) Safety _ (25) Company constraints • (26) Market constraints • (27) Patents, literature and product data (28) Politica sociad an l l implications | (29) Legal (30) Installation | (31) Documentation _ (32) Disposal
• 6.4 The selection from the PDS
• We selec importan9 t t elements we consider from thos element2 e3 s of PDS and • add them into our prior quality table. They are as following.
• (1) Performance (2) Environment l (3 ) Target product cost • (4) Competition (5) Size l Final Project Anodic Bonding 52 l l l l
HOGESCHOO UTRECHN LVA T 4/28/2005 (6) Weight l (7) Product Hfe span ( 8 ) Quality and reliability l (9) Safety • In our opinions, those 9 elements are very important and necessary in every design activity. And those 9 elements play important roles for each other. In our • opinions qualite reliabilit,th d yan y affec safetye th t . An qualite d reliabilitth d yan y influencee ar maintenancee th y db . Thos elemente8 s affec competitioe th t e th f no | products. When a company or a design group wants to design a new product, they _ have to think about those aspects so as to make their products perfect.
Now wile ,w l analyze thes elemente9 s individually.
| • Performance: performance Th e demandeM likelr ddemandee o b yo t d shoul fulle db y defined; ™ for our anodic bonding process, how fast, how often and the rate of working, these • thin have gthinw o et k befor designr eou thoughmachin.I e th wile e tw lus e every single day at least 10 hours. The transient response has to be so fast like <1 second. J • Environment: All aspect product'e th f so s likely environment shoul consideree db d dan l investigated: • i. Temperature processranger ou temperaturn e :i ,th e range quit wila e elb important part, becaus neee ew higda h temperatur succeeo et operatione dth . • The temperature range is 400°C~500°C . 2. Pressure range: this part not really important in our process, but if we want to • have a good result for our bonding process, then we are going to choose a • pressure range range ,th e wil betweee lb n 5x10"5 xlO"mba2 d 6r an mbar.
l 3 5 Final Project Anodic Bonding l
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HOGESCHOO UTRECHN LVA T 4/28/2005 3. Dirt dustyr yo wile : w clealo t fin eas e y , afte ndit machinth e y wa th r coos ei l • down, then we can just use water to clean the hotplate surface and the electrode. • Target produc l t cost: • Target product costs shoul establishee db d fro outsee mth t and checked against existin likr go e products afte o compare S . w r e with competitor's products wile w ,l • choose some of parts we can buy and the others we will try to make by ourselves. • Competition J In the market, the strong competition exists among those manufacturers. All of them want their own products to be the main stream and the most popular one in the • market. They hope their product must-bue th e ar s y goods of the customers. Thao t s i t • say, they want themselves to be the winner in the competitions. How can they get the good position in the market? They depend on their own products to be the winner. • So from the time they had a good idea to design a type products to the day they started the program to design it, the competition is the essential and necessary aspect | they must think about. We have said before that they depend on their own products _ to be the winner. It means that as a designer, hè has to design something by some • new concepts or by some creative approaches. • In this case, the product is the anodic bonder which can bond two wafers improvementogetherw ne e focue th W .n higt so ge t h thao t qualit s i t y bond, bonding • strong. As a designer, we collect those information from the main customers in the marke internetd an t thed ,nan convert the mconcepw int ne products oouw r a tfo rne . l Here, we regard the suggestion from the information as a new concept and according • to it to improve our product. We are sure that our type of the anodic bonder has strong competitio attrac n markee ca th d n n i tcustomers e mostan th f to .
J So the competition is very important for a new product. It determines the position I Final Project Anodic Bonding 54 l
l l l
HOGESCHOO UTRECHN LVA T 4/28/2005 is good or bad in the market. It determines the success or failure of a product. That is • why we add this element • Size: l Size constraints shoul specifiee db d mindr initiallyou ,n i becaus o S . thin e ew k it's M have to be easy way to do the process in the lab, so the size should be not large, so ™ we decided the size is less than 50cm(L)X50cm(W)X30cm(H). • • Weight: Allied to size, weight is important when it comes to handling the product on the J shop dur ing manufacture, in transit and so on. So the total weight of the product should less tha kilos0 n3 . • • Materials: choice Th materialf eo s fo particulara • r product desig invariabls ni y lefdesigo t t n processr teamou n material.I e ,th quits si e important have w ,choos o et e eth l materials suitabl operationr ou o et . The maximum temperature heae t,th transfer, and corrosion resist of the materials and so on, we all have to think about it. So the | materials should be specified. • Product• lif e span: • Some indication of the life of a product as a marketable entity should be sought. • Of course we want to our production remain in the marketing for as long as possible, produce th t bu t life spa reducins ni g rapidly producr ou o ,s separate s i t , tha cat ni n • not be easy change for every part. • Quality and reliability | The people concerned in the market including the customer, the designer, the m design grouwhole th r peo company mus enougy tpa h attentio qualite th d o nt yan ™ reliabilit producte th f yo fact n qualitI .e th , reliabilitd yan y determine a fate f sth eo • mosproducte th ts i importan t I . t elemen whole elementth 2 en 3 i t thf so e product design specifications. l Final Project Anodic Bonding 55 l
l l l
HOGESCHOO UTRECHN LVA T 4/28/2005 If the designers want their product to be in a good position
markete th n I , they shoul l d spend plent timf y o gettin requirementn ee i th o gt s of the M product meeo s t custome e tth r demand mose th thet te .yBu difficular t aspecto st ™ quantify in absolute terms, although statistical data from company product • precedents are helpful here. And the company must ensure adequate feedback of any failure analysis to the design team.
• Here qualite th , y and reliability also play important role designinn si r go • improving our jack exampler Fo . , if the anodic bonde brokes ri n suddenly becausf eo the poor quality and reliability during the process that the wafers are bonding, it is dangerouo to s peopldamagefos e i requipmentth d e l ean th o dt . Of course, nobody wants it happens. That is why we focus on this element. So improving the quality | and the reliability is main aim and task for the designers.
• • Safety The safety aspect proposef so d markeplace s desigit th d n ei nan t muse tb • considered processr ou n i t , becausBu . procesr eou special s safetsi e th reall s yo i s , y important and every single part we need to think over for the safety protection. | Until now, we have finished the analysis about those 9 elements we select from . the product design specifications .We think those 9 elements are quite important for ™ ourselves anodic bonder. l 6.5 Planning and designing a appropriate structure which includes _ drawings
6.5.1 Gathering Information • According to the non-industrial machine experiment l, finally, we built the following environments: • The anod Cs ei u wir • e and the cathod 6x6"As ei l plates.
l 6 5 Final Project Anodic Bonding l
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HOGESCHOOL VAN UTRECHT 4/28/2005 • The polarity is the negative polarity configuration, because in Chapter 3.1.6 • we talk about the negative polarity configuration can get the better bond quality tha positive nth e polarity configuration. 8 • Bonding environment: under atmospheric pressure conditions, because this is M the easy way to do the bonding process without special apparatus for vacuüm. But the bonding quality is not so perfect. (So if we want to get the better bonding quality, then we can choose under vacuüm, or process gas.
I - s Vacuüm Chamber: Vacuüm: >5xlO mbar and <2 xlO mbar) Wafe• |r size in mostly process, they all choose the 4"~6" wafer, so we will hav same eth e decision. l We see in the industrial machines, they almost use the star shaped electrode in • article th thei ew {22}r sa researcher processe e ,th w t multiplbu ,e sus e point electrodes in a spiral arrangement, because then they not only can solve the gas- I trapping problem but also reduce the bonding time in anodic bonding.
• 6.5.2 Design method:
• Electrode conducto:a r that delivers electricity int celoa l without necessarily entering int cele oth l reaction. Also systea , whicmn i conductoha contacn i s i r t with l a mixture of oxidized and reduced forms of some chemical species. We choose the material for the electrode is Poly (P-Phenylene)-Based Carbon, | because the PPP-based carbon electrode can obtain by heat treatment at 700 °C and • this materia economis i l e cost and high endurance. Firstly, we will introducé the some possible arrangement of electrodes matrix. l We can see in fig.13, there are several different arrangements of electrodes matrix. To design those electrodes matrix, each point electrode that forms electric field is J assumed the same as a planar electrode. In order to distribute the force of the
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HOGESCHOOL VAN UTRECHT 4/28/2005 electrode uniformly ove poinl ral t electrodes sprin,a installes gi eacr dfo h electrode guaranteo t e eac • h of the point electrode contaco st glase tth s wafer with equal pressure. The heater and the anode electrode plate can be installed properly to let • average heat transfer to the wafer. With the above hardware arrangement, it is H practical to assume every point electrode can make the same bonding region, and the bonding regio extenn samnca a t da e speed outwardly. l l l Fig.14 Different arrangemen electrodef o t s matrix l With these assumptions no discuse n ww , bondinca e sth g effects with those different • electrodes matrix. The electrodes (a) in fig.13, which are arranged in terms of radiation, expellee b fan-shapedn e frot exica th e dou mf s th o t ga e th . However, becaus edge eth e l of wafer directly contact fre aire e e,th sth oxygen fro helpr anodime ai sth c bondino gt occurbondine th o S . gwafee timth f ero edg fastes ei r than other positio wafere th f no t ,i | may trap gas. The electrodes (b) expand the fan-shaped area to solve the problem of the _ electrode (a), but expand they are also make the bonding time last longer. If choosing • electrode (c) mat i , y solv problee eth m of the electrod solvt e no eth n e stil t (b)ca t li bu , • problem of electrode solvin r (a) problemFo . e gth s of the electrode an) sd(a (b), using non symmetrical way to arrange point electrode may be a good idea. Electrode (d) is • nonsymmetrical way to arrange point electrode, this spriral type of electrodes will build spiral-unbouna d pathway durin withis g ga bonding interface e t awanth th ge d yn an ,eca | through this spiral unbonded pathway. At last the spiral unbound region will disappear . from center to edge, and then the bonding is accomplished. Consequently the type of l™ electrodbese th ts i choic ) e(d thin ei s study. l Final Project Anodic Bonding 58 l l l l HOGESCHOOL VAN UTRECHT 4/28/2005 l l l l
l Creatin6 6. Prototypga e l I 04
l in l 01 l l LY * l tolerancFoelectrodee e th rth 0.003e - us +/ s e i ,,w becaus accurace th r efo y this si enough, and for the technology if the requirement is higher than this, It will be hard l to make it. l I l l Final Project Anodic Bonding 59 l l I l HOGESCHOOL VAN UTRECHT 4/28/2005 l l l I l l l t I Fig.15. the drawing of electrode l \n l on o ir in l in OJ l
l 0 35 55XL Y l L, 1250 l l Final Project Anodic Bonding 60 l i l l HOGESCHOO UTRECHN LVA T 4/28/2005 l l l l l l l l l The safety cover 55cm(L)X55cm(W)X35cm(H) l l Finally desige w , anodin na c bonder concept (Fig 16.) l l l l l 61 l Final Project Anodic Bonding l 1 1 pl&ft 1 HOGESCHOO UTRECHN LVA T 4/28/2005
1
1 «nrnnotar 1 /""A H ***.. ] ^JW,., ?ÏAn flU*« -U.-4-ir I v —— • _c — mmmiilnmmm siiicon w*f»r _L (+) = I hot plet* TC TUT'" l_J 1
1 _ Fig.16 Apparatus used for electrostatic bonding
H TthermocouplC= r measurinfo e g plate temperature voltag= V e supplfy Ammeter = Extech digital multimeter (measuring current) m Safet7 6. bondinf yo g process alreade W y mentioned safet• y above now we say it again, because it really important. In our anodic bonding process, the safety is a more important in others, 1 because in this process, the requiremen temperaturf to voltage th d quies ei an t high, 1 so the safety becomes necessary. Our design is step by step, firstly, for the power supply, we choose the power supply | to buy, so it's become easy to solve the problem, the power supply self has the safety protection, it has automatic current regulation protects agains overloadsl tal , • • including arcs and short circuits. Fuses, surge-limiting resistors, and low-energy 1 Final Project Anodic Bonding 62 1
1 l l l HOGESCHOOL VAN UTRECHT 4/28/2005 components provide ultimate protection. £ Then the hot plate, we also choose to buy one, so it's not difficult any more, and we choose ar materiale eth ~stainless si s steel, becaus temx 81eps ma i 5 °C . Uniformity , ' heat transfer, corrosion resist and wear resist are very good, release is just fair. Butt • for the safet hat yi s own protection already. We will make the electrode for our self, so the safety problem we will also solve for • ourselves , so we decide to put a ammeter and a voltmeter in our process, because ammeter is • an instrumen measurinr tfo electrie gth c curren ampèren ti branca electrin sn i a f ho c m circuit voltmeted an , measurn rca change eth voltagn ei e between two pointn a n si electric circuit and therefore must be connected in parallel with the portion of the l circuit on which the measurement is made. Because we choose the ammeter and voltmeter in our process, then we can always know how it's going on there, and we £ can control the voltage and current. And before the ac outlet we still set a fuse there, _ becaus casn e voltagi e eth currend ean higho ts , then the ston ypca befor becomet ei s • a big damage. And because the voltage is so high, so we choose the high voltage • wires type (WHVs th ,ei ) 16-2KV-W, 2000 AW6 V1 G tinned stranded (19/29), Polyrad (white) jacket .045"OD. 2500' spools. M lifr Laseou tsafetyr stefo s pi , because when they make bonding together degree th , e will become so high, and it not is careful, it will hurt the person who is doing the fl[ process, so we make a cover for the experiment, we use the stainless steel to make a . length 55cm; width 55cm and high 35cm cover. Then people can not touct hi • directly.
processe Inth , becaus temperature eth voltagd higho es an it'dangerouse o o ,s es ar , wo es decid mako et safetea • y cover switce th n .ho Safety switches PSENmag and PSENcode, safety switches PSENmech and l 3 6 Final Project Anodic Bonding l
l l l l HOGESCHOO UTRECHN LVA T 4/28/2005 optoelectronic protective equipment PSENopt provide effective personal security l and industrial safety in automated production and logistics processes. PSENmech ensure tha open ta n safety gat unsafr eo e positio detecte s nmachini e th d dan e l stopped. They can be used for fïnger, hand and body protection. l M8 l h l 3m 6m 6 mm 1,42 inch 26 mm U PS£N 1.1p-20, PSEN 1.1-20 1,02 inch l fTHTI26 13mm l 1,02 inch 0,51 inch l l 3 mm t PSEN 1.1p-10, PSEN 1.1-10 l l l l l l l Final Project Anodic Bonding 64 l HOGESCHOO UTRECHN LVA T 4/28/2005
Chapter?. Experiment
Abstract: timIs ti builo et d our-selves anodic bonder have w , e enough informatio desigo nt modena l
7.1 Prépar experimenr éfo t
This experiment ca succeee nb not r cleade o th , n wafe vers i r y importante w o s , must remove all foreign matter from the surface of the silicon wafers (dirt, scum, silicon dust, etc.) prio processingo rt . This procedur solutiono tw f o e e sentailus e sth
which contain hydrogen peroxide (H2O2) to remove residual organic, ionic and metallic contamination left behin conventionae th y db l cleaninsolvenF H d tan g procedure.
So ther three ear e conditions that mus satisfiee tb thir dfo s techniqu worko et . 1) The glass must be slightly conductive at the bonding temperature. 2) The glass and silicon/metal must typically have a surface roughness of less than 2ums rms. glase silicon/meta3d )Th san l should have closely matched coefficient thermaf so l expansion
Although there are so many kinds of materials can be bond together, during our experiment choose w , e glass (Corning7740 silicod )an n thes waferso etw . Because believe ofw e these wafereasiee b bonn o rt s ca d together higt ge hd quality,an .
Anodic bonding is the process of bonding silicon to glass at a relatively low
5 6 Final Project Anodic Bonding HOGESCHOOL VAN UTRECHT 4/28/2005 temperature throug combinee hth heaf electrostatid o e tan dus c forces wafee Th . s ri place dowp dto n ont oconductina g surfac hotplata n eo wire anoded n a e an s da A . peac borosilicatf eo e glass suc Cornins ha g 7740, whic thermaa s hha l coëfficiënf to expansion equa silicoe siliconth o lt f no p wafeplacs ,i to n eo r without oxide obstructions. A voltage of around lOOOv and a temperature of 400°C are applied to the glass and wafer to complete the bonding process.
Now, we are going to start, and we use the anodic bonded (Fig.15)
7.2Equipment:{23)
7.2.1 Supplies:
Glassman High Voltage Power supply Hot P late
Model Plate Overall Size Power Max Temp HP66YX 6x6" 18Wx18Dx6"H 1.8 KW 1500F (81 5C)*
Multimete monitorinr rfo g current
Final Project Anodic Bonding 66 HOGESCHOOL VAN UTRECHT 4/28/2005 7.2.2 Materials
Hydrogen Peroxide, H2O2 7740 Glass Wafer Silicon Wafer We have to do this thing, Use extreme caution when performing this experiment. ver a platt t a y ho s ehigi e Th h temperatur voltage th d ean use extremels di y high. Both are potentially hazardous.
7.3 Lab Procedures:
1. Perform all parts of the initial wafer clean on the Corning 7740 glass sample sectionF H excepe th .r Remembertfo etcheF ,H s glass.
2. Place the silicon wafer, followed by the glass wafer onto the hot plate. If the samples were cleaned properly in step l, a fringe pattern will be evident betwee samplese nth .
3. Move the probe tip into contact with the glass and silicon wafer sandwich, positionin ontt gi centee glasse oth th f r.o
4. Check the contact between electrodes and wafer sandwich, in order to let the electrode contact adequately with wafer sandwich firstle w , y unscree wth electrode from the top board and turn on the power supply little bit, let the surfac electrodf eo e really touc wafee hth r surface scree n , th theca wp e u n w electrode. One by one, we check all the electrodes contact with wafer sandwich like this.
7 6 Final Project Anodic Bonding HOGESCHOOL VAN UTRECHT 4/28/2005 5. Heat the hot plate to 450° C. Refer to the settings posted on the side of the temperature controlle expecter rfo platt dho e temperature.
voltag. e Tur6 th n no e supply. Slowly ram voltage pth e u 1000Vpo t .
7. Observe the current using a digital multimeter. A drastic current drop was observed in the first minute of the bonding experiments, which is due to the surge of Na+ ions drifted to the cathode. The current reaches a steady state at longea r time.
8. Watch what happens to the silicon-glass sandwich as the voltage is increased. The required bonding time drops signifïcantly as the applied voltage increases from 100 to 1000V .this can be explained with respect to the bonding mechanism discussed at nA . elevated temperature glase ion+ th sn si Na , become so mobile that they are attracted toward the cathode as a result of the applied voltage.
bone Th d strengt importann a s hi t facto bonr rfo d qualit reliabilityd yan .A high bond strength indicates tha goota d bon bees dha n formed bone Th .d strength versus bonding temperature and voltage.
. Tur9 platet nleavt ho of e voltag, bu e abou fr th e th minutesfo n n tte e o . Then turn poweofe fth r supply.
10.Allo platt ho coo o et e w100°o th lt thed Cnan slowly remov bondee eth d wafers.
11 .D reporte oth .
8 6 Final Project Anodic Bonding HOGESCHOO UTRECHN LVA T 4/28/2005 7.4 Interface integrity
After anodic bonding, the bonded pair will be checked, put the bonded wafers under different temperatures, voltages, bonding time (10 min) and vacuüm (l Pa.)At low bonding temperatures (say, 200°C), more and larger voids are found at the interface. With increased bonding temperature, the number of voids and the void size decrease noticeably. Whe bondine nth g temperatur highes ei r than 400°d Can voltage th highes ei r thavolts0 nvoid80 o n ,founde s ar bondin e .Th g temperature anvoltage dth e hav significanea t influenc voidse unbondeth e n eo .Th d arer ao void mainle sar y attribute entrapmens ga o dt t betwee matine nth go surfacetw e th f so wafers voido N . s arise from partiële contamination, thus indicating tha cleanine tth g procedure is effective.
9 6 Final Project Anodic Bonding HOGESCHOOL VAN UTRECHT 4/28/2005
Final Conclusion:
Thi knoe sw reporws u Anodit le t c bondin wela s gi l developed bonding technolog silicor yfo borosilicatno t e glasses. However desire ,th e exist exteno st d technique th otheo et r materials bondin e alloo t th r d w etchefo f an ,go d wafersn A . experimental program is underway to investigate the possibilities of achieving this goal. Through this study, it is hoped that a more comprehensive understanding of bondine th g technique wil developede lb .
0 7 Final Project Anodic Bonding HOGESCHOOL VAN UTRECHT 4/28/2005
Appendix I : (1) AML-WB04 bonder
Fig.l7AML-WB04 bonder
Bonding environment:
Vacuüm or process gas
Vacuüm Chamber:
Vacuüm: <2xlO mBar
71 Final Project Anodic Bonding HOGESCHOOL VAN UTRECHT 4/28/2005 Spare port (KF16)
Vacuüm System:
Fully automated Turbo pumping station
Waf er sizes:
wafer" 8 & s" 6 Standar , 5" , d4" , Platens3" : Min. glass thicknes aligner sfo d anodic bonding: 0.4 mm (unbevelled) Maximum overall thickness of wafers to be bonded is lOmm.
Temperature:
Both Upper and Lower Platens heated up to 560°C, adjustable in 1°C steps. (High temperature 600°C operation is available as an option.)
Heatin Cooling& g rate programmable sar e
Temperature uniformity: +/- 2°C at 400°C for 4" wafers & +/- 3.5°C for 6" wafers
Anodic Bond cycl mine0 2 stdtimr ~ sfo . s ei Silico 774. o nt °C 00 glas36 t sa
Electrodes:
Uppe lowe& r r full size planar platens:
High Voltage Supply:
0-2.5kV DC, up to 40mA
Constant current or constant voltage operation.
2 7 Final Project Anodic Bonding HOGESCHOOL VAN UTRECHT 4/28/2005 Required services:
3 * IEC socket - 13A 230V AC Power supply + safety earth bonding point. (l 10V option available)
Dry Nitroge Compressen& liner dAi gauger s pressurBa 5 Bar.5 4. 0. D , eD Hose adapter (ODm )8m : tube, push coupling
l Gas exhaust G1/8" male thread
(2) SB6/8e Substrate Bonder
Fig.18 SB6/8e Substrate Bonder
Voltage:
Bonding Voltage: Upto 2000 Volts
Temperature:
Bonding Temperature: Upto 580°C
Final Project Anodic Bonding 73 HOGESCHOO UTRECHN LVA T 4/28/2005 Optional Low Temperature Bond Module for increased bonding strength already at annealing temperatures of 200°C
Wafer size:
For all types of wafers and substrates up to 200mm diameter, stack thickness up to 6mm (larger thicknes request)f so .
Electrode:
Star Shaped Electrode
Vacuüm:
Vacuum/evacuation time: 5 X 10~5 mbar/10 min.
(3) SWS-100IRV/IRT bonder
Fig.19 SWS-100 IRV/IRT bonder
Wafer size:
O 4 inches Thickness 0.4mm-l .0 mm
4 7 Final Project Anodic Bonding HOGESCHOOL VAN UTRECHT 4/28/2005 Wafe1 50 G r BondeEV ) (4 r r
Fig.20EVG501 Wafer Bonder
Temperature:
550 °C
Typical Application:
Bonding silicon and quartz wafers
Wafer size:
4" wafers glas" 4 , s (tooiin availabls gi inc6 r hefo wafers )
Specimen:
100 mm substrates
Main characteristics:
Bonding plan parallel substrates
5 7 Final Project Anodic Bonding HOGESCHOO UTRECHN LVA T 4/28/2005 Bonding voltage:
0-1200 V/ 50mA Pressure:
Up to 3,4 KN
Facilities:
Bonding under vacuü controlled man d ambient
6 7 Final Project Anodic Bonding HOGESCHOOL VAN UTRECHT 4/28/2005
Appendix II:
Spec power sfo r supplies Price SINGLE POWE B OUTPULA RC TD SUPPLIE liste( S y b d Us$ output voltage ratin) g
ISC 3 O49 0-1OOOV, 0-400mA 200m( lA OOO@ V )Constant voltage0 39 , current or power mode Electrophoresis power supply Keithley 240 0-1200V, lOmA Constant voltage, 10V resolution. 290 Reversiable polarity.
ISCO 494 0-2000V, 0-200mA (l OOmA @ 2000V )Constant voltage, 390 curren power to r mode Electrophoresis power supply
Kepco 0-2000V, 0-1 OmA Power supply-Amplfier. 0 Constan35 t APH2000 voltag constanr eo t current mod operatiof eo n PS32S SR 5 resolution0-2500VV l , Wt 5 ,2 , 0.001% regulation,0 0.0565 % accuracy
HP6110 Avoltagy an t eSe fro 0-3000A m 6m 0-3000 , VDC 0 V45 with 20mV resolution, 0.001% regulation NE Scientific 0-5000V DC, lOmA, reversable polarity, voltage 300 RQE-5001 adjustment continuou 10n i Vr so steps.
Agilent / HP Precision HV Power Supply 3000V/6mA Call 6110A
Agilent/ HP HV Power Supply 1600V/5mA 550 6515A
Bertan 205A- High Voltage Power Supply lkV/30mA Call 01R
Fluke 412B 0-2000 V High Voltage Power Supply Call
Fluke 415B High Voltage Power Supply 3kV/ 30mA 1295
Final Project Anodic Bonding 77 HOGESCHOO UTRECHN LVA T 4/28/2005 Glassman HV Power Supply 5kV / 60 mA 1495 PS/ER05R60.0- 11 Keithle 7 y24 High Voltage Power Supply 2kV/6mA 895
Physik Stablized 3 Channel Voltage Source IkV 650 Instrumente P- 198 Spellman Power SupplyA 0-2km 0 3 V / Call SL2PN60 i Voltronics High Voltag PoweC eD r Suppl /5.A V 5k m y 6 Call BAM-6-5.5
Spec Higr sfo h Temperatur Platet eHo s
Final Project Anodic Bonding 78 HOGESCHOOL VAN UTRECHT 4/28/2005
Model Plate Overall Size Power Max Temp HP66YH 6X6" 12WX12DX5"H 120/24, 0V 1000F (537C) 1100W HP99YH 9X9" 18WX18DX5"H 240 V, 2600W 1000F (537C) HP1212YH 12X12" 24W X 24 D X 240V,4600W 1000F (537C) 5"H HP66YX 6x6" 18Wx 18Dx6" H, 1800V 0 W24 1500F (815Q* HP99YX 9X9" 21 W x 21Dx6"H 240V, 3500W 1500F (815C)* HP1212YX 12x12" 24W x 24D x 6" H6000, V 0 W24 1500F (815C)*
*Maximum temperature with hood. Maximum without hood is 121 IF (654C)
Final Project Anodic Bonding 79 HOGESCHOO UTRECHN LVA T 4/28/2005
Char Platf to e Material Characteristics
heat corrosie n MATERIAL max temp uniformity release wear resist transfer resist Anodized 700F-371C very good very good good good good aluminum ., ...... 1500F- Steel,unfinished fair good poor fair very good 815C Steel,hard chrome 900F^82C fair good good fair very good 1500F- Stainless steel fair good very good fair very good 815C Ceramic coar to 1500F- very good very good very good fair very good solid 815C _ ...... Reinforced Teflon very 550F-287C good good very good good coat good
Final Project Anodic Bonding 80 HOGESCHOO UTRECHN LVA T 4/28/2005
Appendix UI
PS/ER05R60.0-1 PoweV A H 1m r0 6 Suppl / V y5k
Features
Air Insulated. As in all Standard Glassman power supplies, the ER Series features "air" as the primary dielectric medium. No oil or encapsulation to impede serviceability or increase weight.
Constant Voltage/Constant Current Operation. Automatic crossover from voltagr eo current regulated mode dependent on the load conditions.
Low Ripple. Bette thar n 0.02 %ratef o d voltag fult ea l load.
Tight Regulation. Voltage regulation bette r than 0.005% line or load: current regulation better than 0.05% from short circui rateo t t d voltage.
Fast Transient Response. Less than 3 milliseconds for a 50% load transient.
Front Panel Controls (Analog and Digital Verslons). Ten-turn voltage and current controls with locking vemier dials. AC power ON/OFF and high voltage enable switches.
Remote Control Facilities.As standard SerieR E l s,al power supplies provide output voltage and current program/monitorterminals, TTL high voltage enable/disable, safety interlock terminals, and a +10 volt reference source.
Small Size and Weight. ER Series power supplies consume only 3.5" of vertical panel height. Total weigh pounds8 1 s ti .
Final Project Anodic Bonding 81 HOGESCHOO UTRECHN LVA T 4/28/2005
Warranty. Standard power supplies are warranted for three years; OEM and modified power supplies are warranted for one year. A formal warranty statement is available.
Specifications
(From 5% to 100% rated voltage. All units operate down to zero output with very slight degradation of performance.)
Input: 105-12 RMS5V , 48-6 singlz 3H e wit0 phase Connecto. h32 A matinC 6 < ,IE r gpe r line cord.
Efficiency: Typically 85% at full load.
Output: Continuous, stable adjustment, fro rateo t mO d voltag currenr eo paney b t l mounted 10-turn potentiometers with 0.05% resolution, or by external O + 10V signals is provided. f ratedo Linearit f setting% o . Accurac<1 f rate % o s y i 1 .% d + 1 Repeatabilit s yi <0.1s yi f %o rated.
Stored Energy modelV k joules model5 0 V :1. 2 ,k joules0 4 6 ;< , .
Voltage Regulation: <0.005% +lmV/mA, loadlind ean .
Ripple: <0.02% RM f rateSo d voltage +0.5V at full load; models 1.5k lowerd Van , 400mV (500mV Japan).
Current Regulation: <0.05% from short circuit to rated voltage at any set current.
Voltagzerr fo rateo t C D deV current Monitor0 +1 o t . Accuracy:O f o f readin o % % .1 1 , g+ rated voltage.
Current Monitor: O to + 10 V DC for zero to rated current. Accuracy, 1% of reading + .05% of rated current.
Stabilfty: 0.01% per hour after 1/2 hour warm-up, 0.05% per 8 hours.
Voltage Rise/Decay Time Constant: Typicall m0 ys5 r i sdecar eo y time constant (300 ms modelV k 5 7 )r usinfo g H V (on/off r remoto ) e voltage control resistivwit% h75 e load.
Temperature Coëfficiënt: 0.01%/°C.
Ambient Temperature: -20 to +40°C operating, -40 to +85°C storage.
Polarity: Positive, negative, or reversible with respect to chassis ground.
Protection: Automatic current regulation protects agains l overloadstal , including arcd san short circuits. Fuses, surge-limiting resistors low-energd ,an y components provide ultimate protection.
2 8 Final Project Anodic Bonding 1 1 m 1 HOGESCHOOL VAN UTRECHT 4/28/2005 JM|
1 Accessories: Detachable 8-foot shielded HV cable (see Model Char r cablfo t e type6 d an ) foot detachable line cord provided. 1 Remote Controls: Common, +1 reference0V , interlock, current monitor, current program, voltage monitor, voltage program, TTL, and ground, provided on a rear panel mounted terminal block.
1 External Interlock: Open off, close, don . Normally latching except for blank front panel version where it is non-latching. 1 HV Enable/Disable: 0-1. off5V , 2.5-15 V on.
1 Options
1 Symbol Description 100 100 V input, rated 90-110 V RMS, 48-63 Hz. inputV 0 ,22 rated 0 200-2622 R 4V MS, 48-63 Hz. 1 0 40 48-42 availabl, 0Hz Standarn eo d mode220d optiond an .an l0 s10 DM 3-1/2 panedigiD LC t l meters. 1 NC Blank front panel (power switch only). Current trip. Power supply trips off when the load current reaches the programmed CT level. This option has a rear panel switch that selects either "trip" operation or 1 current limiting.
-,D Zero start interlock. Voltage control must be at zero before accepting an enable signal. 1 SS Slow start ramp of up to 30 seconds available. Specify time. GE9 RS-232 control and monitor. 1 1 1 1 1 1 Final Project Anodic Bonding 83 1 1 l l l HOGESCHOOL VAN UTRECHT 4/28/2005 l l Models l modee Clicth n ko l number belo requeswo t completr quotfo a t d ean e ordering part number. l ER1R300 kV1 0- 0-300mA RG-59 ER1.5R200 0-1. 5kV 0-200mA RG-59 Reversïble ER2R150 0-2kV 0-150mA RG-59 Poliirity l Oiily ER3R100 0-3kV 0-100mA RG-59 ER5R60 0-5kV 0-60mA RG-59 l ER6R50 0-6kV 0-50mA RG-58 ER10P30 ER10N30 ER10R30 0-10kV 0-30mA RG-8U ER15P20 ER15N20 ER15R20 0-15kV 0-20mA RG-8U l ER20P15 ER20N15 ER20R15 0-20kV 0-1 5mA RG-8U ER25P12 ER25N12 ER25R12 0-25kV 0-12mA RG-8U l ER30P10 ER30N10 ER30R10 0-30kV 0-10mA RG-8U ER40P7.5 ER40N7.5 ER40R7.5 0-4V 0k 0-7.5mA RG-8U l ER50P6 ER50N6 ER50R6 0-50kV 0-6mA RG-8U ER60P5 ER60N5 ER60R5 0-60kV 0-5mA RG-8U l ER75P4 ER75N4 ER75R4 0-75kV 0-4mA DS2124 l l l l l l l Final Project Anodic Bonding 84 l l l l HOGESCHOOL VAN UTRECHT 4/28/2005 l l Outline Drawing l n J1 INM /s El //s*^/
Reference: (1)Bonding via intermediate layers Applied Microengineering (AML)Ltd Curie173 Avenue, Didcot, Oxon, OX11 OQG, United Kingdom Tel: +44 (0)1235 833934 Fax: +44 (0)1235 833935 e-mail: amm.amlco.uk (2)This Homepage supervise by student ofQuality Control andInstrumentationUnversitiSains Malaysia, 1999. For question or comment regarding thispage, contact Nienick(a).Hotmail.com (3) Printed glassfor anodic bonding-a pachaging concept for MEMS and system on a chip Leifbergstedt and katrin person, the imego institute, Aschebergsgatan 46, SE-411 33 Goteborg, Sweden, phone: 7501800,31 46 7501801,31 fax: 46 e-mail: leif.berestedt(q).imego.com (4)Silicon glass anodic bonding underpartial vacuüm conditions: problems and solutions Gabriel blasquez, Patrickfavoro CNRS-LAAS, Avenue7 Roche, 31077 Toulouse Cedex Francs04, (5) Influence of bonding parameters electrostaticon force anodicin wafer bonding G..Y.LÏ, L.Wang School ofmaterials Engineering, Nanyang Technological University, Singapore 639798, Singapore Institute ofmaterial research and engineering, Singapore (6) Mechanisms of anodic bonding ofsilicon Pyrexto glass Kevin B.Albaugh Paul CadeE. IBM General Technology Division Essex Junction, VT 05452 RasmussenH. Don Department of Chemical Engineering Clarkson University Potsdam,NY13676 (7) (9) Bonding properties ofmetals anodically bonded to glass Danick Briand, Patrick weber, Nicolaas F. de Rooij Institute ofMicrotechnology, University ofNeuchatel, Rue Jaquet-Droz l, P.O. box 3, CH-2007 Neuchatel, Switzerland
6 8 Final Project Anodic Bonding HOGESCHOO UTRECHN LVA T 4/28/2005 (8) Modeling of Electrostatic Forcefor Glass-to-Glass Anodic Bonding S.M.L Nai, J. Wei, C.K.and Wong (10) Anodic bonding joins silicon wafers glass Product news received March24 on 2000 from Applied Micreongineering (11) In situ investigation of ion drift processes in glass during anodic bonding B.Schmidt, P. Nitzsche, K, lange, S. Grigull, U.Kreissing, B.Thomas, K. Herzog Forschungszentrum Rossendorf, Institutfur lonenstrahiphysik und Materialforschung, Postfach 510119, D-01314 Dresden, Germany Institutfur Analytische Chemie, TUBergahademie Freiberg, D-09596 Freiberg, Germany (12) low-temperature anodic bonding to silicon nitride S.Weichel, R.de Reus, S.Bouaidat, Rasmussen,P.A Hansen,O. K.Birkelund, H.Dirac Mikroelekronik Centret, Building,DTU 345-east, DK-2800 Lyngby, Denmark Danfoss, Department ofBC-ER, DK-6430 Nordborg, Denmark (13) low-temperature anodic bonding of silicon to silicon wafers by means of intermediate glass layers A.Gerlash, D.Maas, D.Seidel, H.Bartuch, S.Schundau, K.Kaschlik (14) Experimental analysis on the anodic bonding with an evaporated glass layer Woo-Beom Choiï, Byeong-Kwon Ju\, Yun-Hi Lee\ Jee-Won Jeong\, MRHaskard\, Nam-Yang Lee§, Man-Young Sung\\ and Myung-Hwan Oh\ \Division of Electronics and Information Technology, Korea Institute of Science and Technology, 130-650, 131,Box Cheongryang,PO Seoul, Korea \Microelectronics Centre, University of South Australia, 5098,SA, Australia Information§ Display Research Institute, Orion Electric Co., Suwon, Korea Department\\ ofElectrical Engineering, Korea University, Seoul, Korea (15) Anodic bonding ofleadzirconate titanate ceramics to silicon with intermediate glass layer Katsuhiko Tanaka, Eiichi Takate, Kuniki ohwada Murata manufacturing Ltd.Co. 2-26-10 tenjin, Nagaokakyo-shi, Kyoto 617, Japan
(16) WTC Microfab Lab - Authorized User Equipment Menu
Saturday 12/11/2004 Microfabrication process development productionand emergingfor industries
Final Project Anodic Bonding 87 HOGESCHOO UTRECHN LVA T 4/28/2005 (l 7) http://micronova.tkk.fi/equipment/anodicJbonder,html Anodic bonder
(18) mitghmr.spd.louisville.edu/course2000/exp8_2000.html Experiment Eight Anodic Bonding Filmand Deposition Sputteringby
(19) Titanium MEMS: Anodic Bonding ofTitanium to Pyrex Glass Faculty Lab: Noel MacDonald
Mentor:Lab Yanting Zhang Group Members: DanAubrey Warren Hoplins Jesus Roman Deizely Santana (20) M.A. Schmidt, "Wafer-to-wafer bonding microstructurefor formation", Proc. IEEE, ofthe Vol. 86, pp. 1575-1585, (1998).
(21) W.H. J.T.Ko, Suminto G.J.and Yeh, "Bonding techniques microsensors",for Micromachining Micropackagingand Transducers,for Elsevier, Amsterdam, (1985). (22). Improvement of bonding time andquality ofanodic bonding using spiralthe arrangementof multiple pointel extrudes Jung-Tang Huang, Hsueh-Ah Yang Institute of Manufacturing Technology, Natoinal Taipei University of Technology, l, Sec.3, Chung-Hsiao E.Rd., 106 Taipei, Taiwan, ROC (23) Revie\ved WalshDr. 8-6-97on by
8 8 Final Project Anodic Bonding