DOCSLIB.ORG

Fabrication of Semiconductors by Wet Chemical Etch

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Fabrication of Semiconductors by Wet Chemical Etch THE JOURNAL OF UNDERGRADUATE RESEARCH University of Kansas | Summer 2008 Fabrication of Semiconductors by Wet Chemical Etch Selective Etching of GaAs Over InGaP in Dilute H2SO4:H2O2 Fabrication engineering of semi- terial. !e plasma etch process is car- conductor devices has made possi- ried out in a chamber in which a gas ble optoelectronic instruments, laser mixture is partially ionized to create diodes and wireless communica- a plasma, or glow discharge. High en- tion devices among many other mod- ergy ions in the plasma bombard the ern devices. Beginning with Bardeen, semiconductor material and chemi- Brittain and Shockley’s invention of cally reactive components in the gas the transistor in Bell Labs in 1947 and mixture form etch products with the Kilby and Noyce’s introduction of the semiconductor. !e process produces integrated circuit about a decade later, accurately etched features and is one semiconductor devices have dramat- of the primary reasons for the reduc- ically advanced the computing and tion in device size that has made tech- electronics industries. nology such as cell phones and laptop Semiconducting materials, such computers possible. as silicon, germanium, gallium ar- senide, and indium phosphide, are INTRODUCTION neither good insulators nor good con- Semiconductors such as InGaP ductors, but they have intrinsic electri- and InGaAsSb are important for light- cal properties so that by controlled ad- emitting devices as well as communi- dition of impurities, their conductivity cations devices and electronics. Fab- can be altered. With the need to manu- rication of these devices is achieved facture devices at the micro- and nano- by plasma etching in which an ion- scale, the semiconductor industry has ized gas mixture etches the substrate followed “Moore’s Law,” the trend that by both chemical reaction and phys- the number of transistors placed on ical bombardment. In plasma etch- an integrated circuit increases expo- ing for these purposes, indium prod- nentially about every two years. Pro- ucts are not as volatile and are usually duction of the tiny features to create more di#cult to remove than other these integrated circuits is achieved by semiconductor materials. For this ex- plasma etching of semiconductor ma- periment, only wafers with an existing LAURA FRANCOVIGLIA is a senior in chemical engineering at the University of Kansas. 57 epitaxial GaAs cap layer grown over Delta Si Doping 1.1E12/cm2 an underlying InGaP layer were avail- Superlattice Buffer GaAs Buffer able. For the development of an In- S.I. GaAs Substrate ductively Coupled Plasma (ICP) etch process for the InGaP layer, the top Epi Layer Structures of V3339 GaAs layer must "rst be etched o$ to 350 Å GaAs 5E18 Si Doping (Top) expose the underlying InGaP layer. A 400 Å GaAs 1E17 Si Doping common technique used to do this is- 130 Å InGaP not intentionally doped (i) nvolves a selective wet chemical etch Delta Si Doping 4.4E12/cm2 that will remove the GaAs layer with- 30 Å AlGaAs not intentionally doped (i) out etching or damaging the InGaP 130 Å InGaAs not intentionally doped (i) 1 30 Å AlGaAs not intentionally doped (i) layer. Determining the selectivity and Delta Si Doping 1.1E12/cm2 etch rate for removing the GaAs layer Superlattice Buffer are the primary goals of chemical wet GaAs Buffer etch development. Once this has been S.I. GaAs Substrate accomplished, a “recipe” for remov- ing the epitaxial GaAs layer can be cre- ated. EXPERIMENTAL Chemical wet etching selectively Using a 1:8:640 chemical wet etch removes the cap layer of the wafer solution of H2SO4:H2O2:deionized through a series of chemical reactions water, an etch rate of 10 Å/s was ex- in a liquid solution. For this etch pro- pected to remove the 750Å GaAs epi- cess, H2SO4:H2O2:deionized water, a taxial layer and an etch rate of ~ 0 Å/s common solution for removing GaAs, was expected in the InGaP layer. !ese was used in the proportions of 1:8:640. results would be indicative of good se- !e reaction occurs in a sequence of lectivity. steps involving an oxidation reaction of the hydroxide ions when the semi- conductor is immersed in an electro- lyte system to produce Ga2O3 and As2O3. !ese oxides dissolve in the acid of the etchant solution and form soluble salts.2 Wafer samples with a 750Å cap layer of GaAs on top, middle layer of InGaP and thick base layer of GaAs were used. !e layer structure of these wafers is shown below. Later etching will use InGaAsSb wafers. However, because indium is the most di#cult Fig. 1 is a simpli#ed representation of the layer to etch, InGaP is a good starting layers of the wafer. On top of the wafer point. is photoresist. !e gap in between the photoresist has been developed in such way Epi Layer Structures of V3338 that the wafer is ready for chemical wet 350 Å GaAs 5E18 Si Doping (Top) etching in that region. 400 Å GaAs 1E17 Si Doping 160 Å InGaP not intentionly doped (i) Delta Si Doping 4.4E12/cm2 30 Å AlGaAs not intentionally doped (i) 130 Å InGaAs not intentionally doped (i) 30 Å AlGaAs not intentionally doped (i) 58 Before etching the wafers, a pat- to get a baseline, pre-etch, topograph- tern must "rst be imprinted on the ical pro"le of the photoresist for each wafer surface so that a contrast can sample. In taking this measurement, be seen between the etched and non- it was possible to determine the fea- etched areas. Photolithography, a pro- ture depth prior to etching. It was sus- cess similar to "lm exposure, was used pected that the etch solution would to imprint the pattern by using a mask attack the photoresist as well as the to create an image on the wafers in wafer. !e baseline measurement was a light-sensitive, protective layer of a preparatory step to establish the ini- polymer material called photoresist. tial thickness of photoresist. !e wa- !e photoresist used was Microposit fers were then dipped into a 1:30 so- S1818. !e wafers were exposed using lution of NH4OH:deionized water and a mask aligner, which is a UV exposure agitated for about 45 seconds, rinsed system, and were tested under various in deionized water and blown dry with exposure times until well de"ned fea- nitrogen in order to remove native tures were seen on the wafer surfaces. oxide. An adequate exposure time was 75 sec- !e exposed wafers were then onds for the mask aligner used. (Light cleaved into two or three pieces, so intensity can be controlled to help de- that more data would be available for termine proper exposure time, but for analysis. !e etch solution of 1:8:640 this experiment the intensity poten- of H2SO4:H2O2:deionized water was tiometer was not available, therefore prepared under the hood in manage- a trial-and-error method had to be able proportions of 0.2:1.6:128 mL. used.) After exposure, the wafers were Samples were individually immersed developed in a NaOH-based solution. in the etch solution and gently agi- tated. !ree etch times were used: 35, !e following is a description of 75 and 110 seconds. !e lower and the photolithography and develop- upper ranges from the expected etch ment procedure: time of 75 seconds were used to help verify the etch rate and selectivity. r$MFBWFXBGFSJOUPDNYDNTBNQMFTVTJOH After etching, the wafers were mea- UXFF[FSTBOETDSJCF sured again using the pro"lometer to r$MFBOVTJOHJTPQSPQBOPM BDFUPOFBOEBHBJOJTP- QSPQBOPMJOBCBUIPOBIPUQMBUFBU$GPS compare to the pre-etch results and minutes each estimate etch depth. r#MPXESZXJUIOJUSPHFO r$PBUTBNQMFTXJUIQIPUPSFTJTUVTJOHTQJOOFSBU 3700 rpm for 30 seconds RESULTS AND DISCUSSION r 4PGU CBLF TBNQMFT PO IPUQMBUF GPS NJOVUF BU$ Results were inconclusive after r&YQPTFTBNQMFTVOEFSNBTLBMJHOFSGPSTFD- the "rst round of the etch process. It onds appeared that the wet etch solution r 1PTU CBLF TBNQMFT PO IPUQMBUF GPS NJOVUF did not selectively etch the wafers. BU$ It was hypothesized that the wafers r%FWFMPQTBNQMFTCZBHJUBUJOHJO/B0)CBTFE developer for 1 minute could have been upside down, mean- r 3JOTF XBGFST JO EFJPOJ[FE XBUFS GPS TFD- ing that the thicker, bottom layer of onds GaAs was being etched instead of the r#MPXESZXJUIOJUSPHFO 750Å top layer. In the second round r6TFNJDSPTDPQFUPMPPLGPSIJHIEFàOJUJPOPG of the etch process, care was taken to features patterned onto samples mark the bottom sides of each sam- ple using a scribe. A control wafer was !e developed wafers were mea- also used in the second round, which sured with a pro"lometer (Dektak II) was purposefully %ipped bottom side 59 up for etching. In the second round, a ing the wafers with nitrogen. !e pro- sample from each wafer type was also cess was repeated until all of the pho- used. toresist was removed. !e wafers were Because the etch solution attacked then measured again with the pro- the photoresist, which can be seen in "lometer to determine the actual etch the negative etch rates in Fig. 3 and in rate and depth. Reproducible etch etch depths greater than 750Å in Fig. rates were achieved as shown in Fig. 4, the wafers had to be stripped of the 3. !e etch rate for samples stripped of PR to measure accurate etch depths. PR averaged 8.37Å/s with a standard !is was done by agitating the wafers deviation of 0.92Å/s, which was near in acetone for 2 minutes, rinsing with the expected etch rate of 10Å/s. methanol for 2 minutes, and blow dry- Fig. 2 is an example of the results from the pro#lometer, which gives a cross-sectional view of the wafer.
Load more

Recommended publications
  • Fabrication of Sharp Silicon Hollow Microneedles by Deep-Reactive Ion
    Li et al. Microsystems & Nanoengineering (2019) 5:41 Microsystems & Nanoengineering https://doi.org/10.1038/s41378-019-0077-y www.nature.com/micronano ARTICLE Open Access Fabrication of sharp silicon hollow microneedles by deep-reactive ion etching towards minimally invasive diagnostics Yan Li1,2,HangZhang1, Ruifeng Yang1, Yohan Laffitte2, Ulises Schmill2,WenhanHu1, Moufeed Kaddoura2, Eric J. M. Blondeel2 and Bo Cui1 Abstract Microneedle technologies have the potential for expanding the capabilities of wearable health monitoring from physiology to biochemistry. This paper presents the fabrication of silicon hollow microneedles by a deep-reactive ion etching (DRIE) process, with the aim of exploring the feasibility of microneedle-based in-vivo monitoring of biomarkers in skin fluid. Such devices shall have the ability to allow the sensing elements to be integrated either within the needle borehole or on the backside of the device, relying on capillary filling of the borehole with dermal interstitial fluid (ISF) for transporting clinically relevant biomarkers to the sensor sites. The modified DRIE process was utilized for the anisotropic etching of circular holes with diameters as small as 30 μm to a depth of >300 μm by enhancing ion bombardment to efficiently remove the fluorocarbon passivation polymer. Afterward, isotropic wet and/or dry etching was utilized to sharpen the needle due to faster etching at the pillar top, achieving tip radii as small as 5 μm. Such sharp microneedles have been demonstrated to be sufficiently robust to penetrate porcine skin without needing any aids such as an impact-insertion applicator, with the needles remaining mechanically intact after repetitive fi 1234567890():,; 1234567890():,; 1234567890():,; 1234567890():,; penetrations.
    [Show full text]
  • Introduction to Plasma Etching
    Introduction to Plasma Etching Dr. Steve Sirard Technical Director Lam Research Corporation Lam Research Corp. 1 Day 1 Review – Plasma Fundamentals ► Plasmas consists of electrons, ions, neutrals, radiation ▪ ne ~ ni << ng (weakly ionized) Collisional Processes - -Ionization + e -Dissociation ► Collisional -Excitation processes sustain - the plasma and e h create radicals (etchant) + * + e- * ▪ Electrons are very hot e- + + ► Sheaths form at the walls/substrate to confine electrons and directionally accelerate ions Lam Research Corp. 2 Day 1 Review – Anisotropic Plasma Etching + + 0.015 0.010 + IED 0.005 Ion Flux Ion 1000V) 0.000 0 20 40 60 80 100 – Ion Energy (eV) Ion Energy (eV) V ~ 10 + + SiO2(s) + CxFy + I (Ei) SiF4(g) + CO(g) Vertical, anisotropic etch Sheath ( Sheath Electrode Synergy! Lam Research Corp. 3 Day 2 - Outline ► Primary etching variables available to process engineers ► Common pattern transfer issues ► Advanced etch strategies: Pulsing strategies, Atomic layer etching ► Within-wafer etch uniformity control ► Plasma & surface diagnostics Lam Research Corp. 4 What “knobs” are available to tune etch processes? ► Etching in general is very complex! ► Advanced plasma etch chambers are equipped with a lot of “knobs” for controlling the etch process ▪ Wafer temperature ▪ Upper electrode temperature ▪ Temperature gradients ▪ Chamber pressure ▪ Gas chemistry (~20 gases on a chamber to choose from) ▪ Gas ratios (gas partial pressures) ▪ Gas flow rate (residence time) ▪ Total RF power ▪ Multiple RF excitation frequencies (up to 3 generators) ▪ Pulsing of RF powers (duty cycle, frequency) ▪ Pulsing of gases (duty cycle, frequency) ▪ Etch time ▪ Multiple uniformity knobs ► Overall, a tremendously large process space long development cycles! Lam Research Corp.
    [Show full text]
  • Selective Plasma Etching of Polymeric Substrates for Advanced Applications
    nanomaterials Review Selective Plasma Etching of Polymeric Substrates for Advanced Applications Harinarayanan Puliyalil 1,2,† and Uroš Cvelbar 1,2,*,† 1 Jožef Stefan International Postgraduate School, Jamova cesta 39, 1000 Ljubljana, Slovenia; [email protected] 2 Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia * Correspondence: [email protected]; Tel.: +386-14773536 † These authors contributed equally to this work. Academic Editors: Krasimir Vasilev and Melanie Ramiasa Received: 2 February 2016; Accepted: 30 May 2016; Published: 7 June 2016 Abstract: In today’s nanoworld, there is a strong need to manipulate and process materials on an atom-by-atom scale with new tools such as reactive plasma, which in some states enables high selectivity of interaction between plasma species and materials. These interactions first involve preferential interactions with precise bonds in materials and later cause etching. This typically occurs based on material stability, which leads to preferential etching of one material over other. This process is especially interesting for polymeric substrates with increasing complexity and a “zoo” of bonds, which are used in numerous applications. In this comprehensive summary, we encompass the complete selective etching of polymers and polymer matrix micro-/nanocomposites with plasma and unravel the mechanisms behind the scenes, which ultimately leads to the enhancement of surface properties and device performance. Keywords: plasma etching; selectivity; surface chemistry; nanomesh; nanostructuring; polymer composite; biomaterials; adhesion; etch mask; radical atoms 1. Introduction Plasma technology is one of the fastest developing branches of science, which is replacing numerous conventional wet-chemical methods in high-tech laboratories and industries, with a huge impact in renewable energy, environmental protection, biomedical applications, nanotechnology, microelectronics, and other fields.
    [Show full text]
  • Electron Beam Lithography and Plasma Etching to Fabricate Supports for Studying Nanomaterials
    DOI: 10.24178/ijrs.2017.3.2.18 IJRS Vol 3(2) Jun 2017 Electron Beam Lithography and Plasma Etching To Fabricate Supports for Studying Nanomaterials Mona Alyobi1,2 & Richard Cobley1 1College of Engineering, Swansea University, Swansea, UK 2College of science, Taibah University, Medina, Kingdom of Saudi Arabia [email protected] Abstract—The fabrication processes of different nano- structures II. EXPERIMENT by electron beam lithography (EBL) and plasma dry etching are The electron beam writing was performed with a shown. The periodic circle and square patterns with different RaitheLiNE lithography system. First, the design of the square sizes were defined in the resist by EBL and then formed in the and circle arrays of different sizes (from 1um to 5um) was substrates by plasma etching. The holes were created with a created using Raith software. A substrate of a <100> oriented, diameter ranging from 1um to 5um and an etch depth from around 500nm to 1um. The quality and the size of fabricated p-type silicon wafer was cleaned in an ultrasound bath of patterns and their dependence on the etching time were acetone and isopropanol, washed with DI water, and dried with investigated using top-down and cross-sectional scanning a nitrogen gun. A layer of PMMA resist (1 PMMA: 1 electron microscopy (SEM). It was found that the structures are chlorobenzene) was spin coated on top of a Si wafer and then well-resolved in the patterns with high levels of quality and good baked on a hotplate at 180°C for three minutes. The baking is size uniformity.
    [Show full text]
  • Characterization of Sio2 Etching Profiles in Pulse-Modulated
    materials Article Characterization of SiO2 Etching Profiles in Pulse-Modulated Capacitively Coupled Plasmas Chulhee Cho 1, Kwangho You 1, Sijun Kim 2, Youngseok Lee 1, Jangjae Lee 1 and Shinjae You 1,3,* 1 Department of Physics, Chungnam National University, 99 Daehak-ro, Daejeon 34134, Korea; [email protected] (C.C.); [email protected] (K.Y.); [email protected] (Y.L.); [email protected] (J.L.) 2 Nanotech, Yongin 28431, Korea; [email protected] 3 Institute of Quantum System (IQS), Chungnam National University, Daejeon 34134, Korea * Correspondence: [email protected] Abstract: Although pulse-modulated plasma has overcome various problems encountered during the development of the high aspect ratio contact hole etching process, there is still a lack of under- standing in terms of precisely how the pulse-modulated plasma solves the issues. In this research, to gain insight into previously observed phenomena, SiO2 etching characteristics were investigated under various pulsed plasma conditions and analyzed through plasma diagnostics. Specifically, the disappearance of micro-trenching from the use of pulse-modulated plasma is analyzed via self-bias, and the phenomenon that as power off-time increases, the sidewall angle increases is interpreted via radical species density and self-bias. Further, the change from etching to deposition with decreased peak power during processing is understood via self-bias and electron density. It is expected that this research will provide an informative window for the optimization of SiO2 etching and for basic Citation: Cho, C.; You, K.; Kim, S.; processing databases including plasma diagnosis for advanced plasma processing simulators. Lee, Y.; Lee, J.; You, S.
    [Show full text]
  • PZT Stack Etch for MEMS Devices in a Capacitively Coupled High Density Plasma Reactor
    PZT stack etch for MEMS devices in a capacitively coupled high density plasma reactor Paul Werbaneth*, John Almerico, Les Jerde, Steve Marks Tegal Corporation ABSTRACT Ferroelectric thin films like lead zirconate titanate (PZT) are used to form several different families of MEMS devices. Moving mirrors for optical switching applications utilize the piezoelectric properties of PZT; varactors depend on its dielectric nonlinearity. The oxidizing environment during PZT deposition means that some material capable of resisting oxidation, like platinum, must be used as the metal electrode in any metal-ferroelectric-metal (MFM) stack. Ion milling has been used in laboratory applications for patterning MFM stacks. However, ion milling removal rates are low (~400Å/min), the throughputs are low, and the etched materials tend to redeposit along the edge of the etch mask, creating veils, or fences, after the etch mask is removed. These residues can lead to yield-limiting defects in finished devices. We report here on MFM stack etch results from a capacitively coupled high density plasma etch reactor. Using photoresist masks, we have demonstrated platinum and PZT etch rates greater than 1000Å/min at moderate (80ºC) wafer temperatures. Good etch profiles with no post-etch residue are produced for MFM stacks like those used for a MEMS- based Atomic Force Microscopy application, for example, which employs a bottom platinum layer 1500Å thick, 2800Å of PZT, and a platinum top electrode of 1500Å. Keywords: PZT etch, platinum etch, MFM stack etch, plasma etch 1. INTRODUCTION Plasma etch is employed in modern microelectronic fabrication processes to faithfully reproduce masking image features into the permanent layers of a device or circuit.
    [Show full text]
  • The Study of Reactive Ion Etching of Heavily Doped Polysilicon Based on Hbr/O2/He Plasmas for Thermopile Devices
    materials Article The Study of Reactive Ion Etching of Heavily Doped Polysilicon Based on HBr/O2/He Plasmas for Thermopile Devices Na Zhou 1,*, Junjie Li 1 , Haiyang Mao 1,2,*, Hao Liu 3, Jinbiao Liu 1, Jianfeng Gao 1, Jinjuan Xiang 1, Yanpeng Hu 1, Meng Shi 1, Jiaxin Ju 4, Yuxiao Lei 4, Tao Yang 1, Junfeng Li 1 and Wenwu Wang 1 1 Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China; [email protected] (J.L.); [email protected] (J.L.); [email protected] (J.G.); [email protected] (J.X.); [email protected] (Y.H.); [email protected] (M.S.); [email protected] (T.Y.); [email protected] (J.L.); [email protected] (W.W.) 2 Advanced Sensing Department, Wuxi Internet of Things Innovation Center Co. Ltd., Wuxi 214001, China 3 School of Science, China University of Geosciences, Beijing 10083, China; [email protected] 4 College of Electronic and Information Engineering, North China University of Technology, Beijing 100144, China; [email protected] (J.J.); [email protected] (Y.L.) * Correspondence: [email protected] (N.Z.); [email protected] (H.M.); Tel.: +86-010-8299-5794 (N.Z.) Received: 7 August 2020; Accepted: 21 September 2020; Published: 25 September 2020 Abstract: Heavily doped polysilicon layers have been widely used in the fabrication of microelectromechanical systems (MEMS). However, the investigation of high selectivity, anisotropy, and excellent uniformity of heavily doped polysilicon etching is limited.
    [Show full text]
  • Role of Plasma-Aided Manufacturing in Semiconductor Fabrication Noah Hershkowitz, Fellow, IEEE
    1610 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 26, NO. 6, DECEMBER 1998 Role of Plasma-Aided Manufacturing in Semiconductor Fabrication Noah Hershkowitz, Fellow, IEEE (Invited Review) Abstract— A brief review is presented of the application of plasma-aided manufacturing to semiconductor fabrication. Em- phasis is placed on current state-of-the-art techniques for which plasma physics plays a significant role and on current problems that remain to be solved. I. INTRODUCTION LASMA-aided manufacturing takes advantage of the Punique properties of plasmas to modify surfaces. It is a rapidly growing body of techniques, which are carried out over pressures ranging below 1 mtorr to greater than 1 atmosphere (atm) (see Fig. 1). At low pressures (below 1 mtorr), the presence of charged particles is the most important characteristic employed in manufacturing. Examples are ion implantation out of plasmas (PSII) [1], [2] or sputtering [3], [4]. At higher pressures (1 mtorr–1 torr), plasma etching [5] and deposition take advantage of a combination of charged particle physics, plasma chemistry, and material science. Fig. 1. Examples of important plasma-aided manufacturing techniques for At still higher pressures (1 torr–1 atm), the plasma serves surface modification with partially ionized gases. Techniques are shown mainly as a heat source in arcjet/plasma spray applications [6]. schematically as a function of neutral pressure and the most relevant academic Corona discharges [79], silent discharges [9], and intermittent discipline. glow discharges [10] are an exception. They are employed at atmospheric pressure to modify surfaces and bulk gases and size structures have decreased to 250 nm and gate thicknesses take advantage of plasma chemistry.
    [Show full text]
  • Lecture 26: Etching and Deposition
    Lecture 26: Etching and deposition Contents 1 Etching 1 1.1 Wet etching . .2 1.2 Etching challenges . .3 1.2.1 Incomplete etch . .3 1.2.2 Over etch and undercutting . .5 1.2.3 Etch selectivity . .5 2 Dry etching 6 2.1 Plasma etch . .8 2.2 Ion beam etch . 10 2.3 Reactive ion etching . 10 3 Deposition 12 3.1 Chemical vapor deposition (CVD) . 13 3.2 Molecular beam epitaxy (MBE) . 15 3.3 Deposited Si . 16 1 Etching Etching refers to the removal of material from the wafer surface. The process is usually combined with lithography in order to select specific areas on the wafer from which material is to be removed. Etching represents one way of permanently transferring the mask pattern from the photoresist to the wafer surface. The complementary process to etching is deposition (or growth), where new material is added. Unlike oxidation (or nitridation), where the underlying Si is consumed to form the oxide (nitride) layer, in deposition, new material is added without consuming the underlying wafer. There are two main types of etching 1. Wet etching 1 MM5017: Electronic materials, devices, and fabrication Figure 1: Schematic of the wet etching process. A controlled portion of the wafer surface is exposed to the etchant which then removes materials by chemical reaction. Adapted from Fundamentals of semiconductor manufac- turing and process control - May and Spanos. 2. Dry etching 1.1 Wet etching In wet etching, the wafers are immersed in a tank of the etchant (mix of chemicals), as shown in figure 1.
    [Show full text]
  • Plasma Etch Properties of Organic Barcs [6923-98]
    Plasma etch properties of organic BARCs Runhui Huang, Michael Weigand Brewer Science, Inc., 2401 Brewer Drive, Rolla, MO 65401, USA ABSTRACT Plasma etching is an integral part of semiconductor integrated circuit (IC) processing and is widely used to produce high-resolution patterns and to remove sacrificial layers. Bottom anti-reflective coatings (BARCs) under the resist absorb light to minimize reflectivity during lithography and are typically opened during pattern transfer using plasma etching. High etch selectivity is required in the BARC opening process to minimize resist loss to allow further substrate etching. Because the plasma etch process combines physical bombardment and chemical reaction, the factors affecting etch rate and selectivity are complex. The results are related to etch conditions and the chemical nature of polymer. This paper addresses plasma etch properties as they relate to polymer type and etch gas composition. Polyacrylate, polyester, and polymers containing nitrogen and halogens have been investigated. The research was carried out by a series of designs of experiments (DOEs), which varied the flow rate of Ar, CF4, and O2 in plasma gas. The selectivity of BARC to resist depends not only on the carbon content but also on the different ways polymer compositions and structures respond to an oxidizing gas, a reducing gas, and plasma bombardment. Based on a polymer decomposition mechanism, we discuss what could happen physically and chemically during the polymer’s exposure to the high-energy reactive plasmas. We also modified the Ohnishi parameter for the polymers containing nitrogen and halogen using our polymer decomposition theory. The contribution of nitrogen and halogen in the etch equation can be positive or negative depending on the chemical properties of the plasma.
    [Show full text]
  • Plasma Cleaning Techniques and Future Applications in Environmentally Conscious Manufacturing
    PLASMA CLEANING TECHNIQUES AND FUTURE APPLICATIONS IN ENVIRONMENTALLY CONSCIOUS MANUFACTURING Pamela P. Ward Dept. 1812, Sandia National Laboratories Albuquerque, New Mexico Abstract Plasmas have frequently been used in industry as a last step surface preparation technique in an otherwise predominantly wet-etch process. The limiting factor in the usefulness of plasma cleaning techniques has been the rate at which organic materials are removed. Recent research in the field of plasma chemistry has provided some understanding of plasma processes. By controlling plasma conditions and gas mixtures, ultra-fast plasma cleaning and etching is possible. With enhanced organic removal rates, plasma processes become more desirable as an environmentally sound alternative to traditional solvent or acid dominated process, not only as a cleaning tool, but also as a patterning and machining tool. In this paper, innovations in plasma processes are discussed including enhanced plasma etch rates via plasma environment control and aggressive gas mixtures. Applications that have not been possible with the limited usefulness of past plasma processes are now approaching the realm of possibility. Some of these possible applications will be discussed along with their impact to environmentally conscious manufacturing. Introduction Industrial cleaning with solvents produces large volumes of waste. Often the purpose of the solvent cleaning process is to remove organic oils, fluxes or polymers from surfaces either to promote adhesion or to mitigate corrosion. A typical production-scale cleaning process can generate very large volumes of solvents tainted with various contaminants. Some of the solvents can be recycled, but the majority must be disposed of by incineration or landfill. This work was performed at Sandia National Laboratories supported by the U.S.
    [Show full text]
  • Plasma Etching
    Plasma Etching Patrick Verdonck 1. Plasmas: useful but complex. Plasma etching is a relatively new technique in the fabrication of integrated circuits. It was introduced in the seventies, mainly for stripping resists. In the eighties, plasma etching became a mature technique to etch layers and was introduced in the production of integrated circuits. Reactive Ion Etching was the main technology, but new techniques were developed. In the nineties new techniques, such as electron cyclotron resonance (ECR) ,and inductively coupled plasmas (ICP), were introduced, with mixed success. The use of plasma etching is widespread in the industry, but contrary to other techniques (e.g. lithography ), the theoretical understanding of the different mechanisms involved in plasma etching is still very poor. This explains why no reliable (TCAD) simulator for plasma etching exists (yet). The use of plasmas in general is also increasing for other applications. In the semiconductor industry, plasmas are used also for e.g. sputtering and PECVD. Other industries are relying increasingly on plasmas to improve their products. One of the newest applications of plasmas is in the reduction of air pollution, where plasmas neutralise the harmful components of certain exhausts. As will become clear later in this text, plasmas are very complex “entities”, what makes them difficult to understand and to describe. The physical and chemical reactions in plasma etching, the electrical interaction between the different particles themselves and between electrically charged particles and electromagnetic fields are not simple. initially, literature described only the main reactions in plasma etching, as e.g. in [1,2]. The chapters on plasma etching in books on semiconductor manufacturing are in general quite easy to read, even for beginners in the field, but rather limited to the description of general principles.
    [Show full text]