DOCSLIB.ORG

Lecture06-Thin Film Deposition

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

EE143 – Fall 2016
Microfabrication Technologies

Lecture 6: Thin Film Deposition
Reading: Jaeger Chapter 6

Prof. Ming C. Wu [email protected]
511 Sutardja Dai Hall (SDH)

1

Vacuum Basics

• Units

– 1 atmosphere = 760 torr = 1.013x105 Pa – 1 bar = 105 Pa = 750 torr – 1 torr = 1 mm Hg – 1 mtorr = 1 micron Hg – 1 Pa = 7.5 mtorr = 1 newton/m2 – 1 torr = 133.3 Pa

• Ideal as Law: PV = NkT

– k = 1.38E-23 Joules/K
= 1.37E-22 atm cm3/K
– N = # of molecules (note the typo in your book) – T = absolute temperature in K

2

1

Dalton’s Law of Partial Pressure

• For mixture of non-reactive gases in a common vessel, each gas exerts its pressure independent of others

• ꢀꢁꢂꢁꢃꢄ = ꢀꢅ + ꢀꢆ + ⋯ . +ꢀꢇ

– Total pressure = Sum of partial pressures

• ꢇꢁꢂꢁꢃꢄ = ꢇꢅ + ꢇꢆ + ⋯ . +ꢇꢇ

– Total number of molecules = sum of individual molecules

• Ideal gas law observed by each gas, as well as all gases

– ꢀꢅꢈ = ꢇꢅꢉꢊ – ꢀꢆꢈ = ꢇꢆꢉꢊ – ꢀꢇꢈ = ꢇꢇꢉꢊ

3

Average Molecular Velocity

• Assumes Maxwell- Boltzman Velocity Distribution

ꢌꢉꢊ
3ꢋ =
ꢍꢎ

• where m = molecular weight of gas molecule

4

2

Mean Free Path between collisions

ꢉꢊ
ꢏ =
ꢆꢍꢐꢆꢀ

• where

– K = Boltzmann constant – T = temperature in Kelvin – d = molecular diameter – P = pressure

• For air at 300K

  • ꢓ. ꢓ
  • ꢔ. ꢔꢕ

  • ꢏ(ꢑꢒ ꢎꢎ) =
  • =

ꢀ (ꢑꢒ ꢀꢃ) ꢀ (ꢑꢒ ꢁꢂꢖꢖ)

5

Impingement Rate

• ꢗ = number of molecules striking a surface per unit area per unit time 1/cm2-sec]

ꢀ
ꢗ = ꢘ. ꢕ×ꢅꢔꢆꢆ
ꢙꢊ

• where

– P = pressure in torr – M = molecular weight

6

3

Question

• How long does it take to form a monolayer of gas on the surface of a substrate?

7

Vacuum Basics (Cont.)

At 25oC

P

I

M

1 µm/min

Plasma Processing
Residual Vacuum
CVD

Pressure (Torr)

8

4

Thin Film Deposition

Physical Methods
Chemical Methods

Evaporation Sputtering
Chemical Vapor Deposition (CVD) Atomic Layer Deposition (ALD)

Film substrate

• Applications

– Metalization (e.g., Al, TiN, W, Silicide) – Polysilicon – Dielectric layers (SiO2, Si3N4)

9

Evaporation

wafer wafer

Al vapor
Al
Al vapor

deposited

Al fill

deposited Al fill

ecrucible is water cooled heating hot boat (e.g. W) electron

source

  • Thermal Evaporation
  • Electron Beam Evaporation

as Pressure: 10-5 Torr

10

5

Evaporation: Filament & Electron
Beam

(a) Filament evaporation with loops of wire hanging from a heated filament

(b) Electron beam is focused on metal charge by a magnetic field

11

Sputtering

Negative Bias ( kV)

I

Al target

Ar+ Ar+

Al
Al

Ar plasma

Al

Deposited Al film

wafer

heat substrate to ~ 00oC (optional)

•

as pressure 1 to 10 mTorr
• Deposition rate = constant × ꢚ × ꢛ

– Where ꢚ = ion current

–

ꢛ = sputtering yield

12

6

Plasma Basics

13

Basic Properties of Plasma

• The bulk of plasma contains equal concentrations of ions and electrons.

»

• Electric potential is constant inside bulk of plasma. The voltage drop is mostly across the sheath regions

• Plasma used in IC processing is a “weak” plasma, containing mostly neutral atoms/molecules.

– Degree of ionization is

»

10-3 to 10-6

14

7

Outcomes of Plasma bombardment

15

Sputtering Yield

Al
Ar

Al

Al

Sputtering ieel S

# f   jej e cj e c rgjc   c om

S º

in e oing i   n n

  • 0.1
  • S
  • 0

16

8

Sputtering of Compound Targets

AxBy

Ar+

Aflux Bflux

Target

¹

Because SA SB, target surface will acquire a composition Ax’By’ at steady state.

17

Reactive Sputtering

Sputtering deposition

Ti Target

while introducing a reactive gas into the plasma.

N2 plasma

Example: • Formation of TiN

+

– Sputter a Ti target with a nitrogen plasma

Ti, N2
TiN

Substrate

18

9

Step Coverage Problem with PVD

• Both evaporation and sputtering have directional fluxes

“geometrical shadowing”

Flux film

step film

wafer

19

Step Coverage concerns in contacts

20

10

Methods to Minimize Step Coverage
Problems

• Rotate + Tilt substrate during deposition • Elevate substrate temperature (why?) • Use large-area deposition source

Sputtering Target

21

Advantages of Sputtering over
Evaporation

• For multi-component thin films, sputtering gives better composition control using compound targets.

– Evaporation depends on vapor pressure of various vapor components and is difficult to control.

• Better lateral thickness uniformity

– Superposition of multiple point sources

Sputtering Target Superposition of all small-area sources

Profile due to one small-area source

22

11

Chemical Vapor Deposition (CVD)

source chemical reaction film substrate

More conformal deposition than PVD

t

Shown here is 100%

t

conformal deposition

step

23

LPCVD Examples

• SiO2

ꢛꢑꢜꢝ + ꢞꢆ ꢘꢕꢔ~ꢕꢔꢔꢟ ꢛꢑꢞꢆ + ꢆꢜꢆ ↑

• PS (phosphosilicate glass): doped glass

– (~ ꢕꢠ ꢀꢆꢞꢕ + ꢡꢕꢠ ꢛꢑꢞꢆ) – The film “reflows” at 900ꢟ

ꢝꢀꢜꢘ + ꢕꢞꢆ ꢘꢕꢔ~ꢕꢔꢔꢟ ꢆꢀꢆꢞꢕ + ꢓꢜꢆ ↑
ꢛꢑꢜꢝ + ꢞꢆ ꢘꢕꢔ~ꢕꢔꢔꢟ ꢛꢑꢞꢆ + ꢆꢜꢆ ↑

24

12

LPCVD Examples

• TEOS (Tetraethylorthosilicate) Si(OC2H5)4

ꢛꢑ(ꢞꢢꢆꢜꢕ)ꢝ→ ꢛꢑꢞꢆ + ꢢꢣꢜꢤꢞꢥ ↑

– The liquid chemical TEOS is a safer alternative to gases silane or dichlorosilane

Molecular structure of TEOS

25

LPCVD Examples

• Si3N4

ꢘꢛꢑꢜꢝ + ꢝꢇꢜꢘ → ꢛꢑꢘꢇꢝ + ꢅꢆꢜꢆ ↑

• Polysilicon

Vꢦꢦ°Y

  • ꢛꢑꢜꢝ
  • ꢛꢑ + ꢆꢜꢆ ↑

• Tungsten

ꢧꢨꢓ + ꢘꢜꢆ → ꢧ + ꢓꢜꢨ ↑

26

13

CVD Mechanisms

reactant

  • 5
  • stagnant

gas layer
12surface diffusion
4

Substrate

1 = Diffusion of reactant to surface 2 = Absorption of reactant to surface 3 = Chemical reaction 4 = Desorption of gas by-products 5 = Out-diffusion of by-product gas

27

CVD Deposition Rate [ rove Model]

film

ꢩ
= ꢬꢪ
ꢫ

Si

ꢮꢯ ꢉꢊ

ꢉꢛ = ꢉꢔꢭb

F1

F

d

= thickness of stagnant layer

d

ꢢꢪ − ꢢꢛ
ꢨꢅ = ꢩ
ꢫ

ꢨꢘ = ꢉꢛꢢꢛ

At steady state, ꢨꢅ = ꢨꢘ

28

14

rove model of CVD (cont’d)

ꢢꢪ − ꢢꢛ

  • ꢨꢅ = ꢩ
  • = ꢬꢪ ꢢꢪ − ꢢꢛ = ꢉꢛꢢꢛ = ꢨꢘ

ꢬꢪ

ꢫ
ꢢꢛ =

ꢢꢪ

ꢉꢛ + ꢬꢪ

ꢉꢛꢬꢪ

ꢅ
ꢨꢘ =

ꢢꢪ

=

ꢢꢪ

  • ꢅ
  • ꢅ

ꢉꢛ + ꢬꢪ

+

ꢬꢪ ꢉꢛ

Film growth rate is constant with time:

ꢐꢰ ꢐꢁ

ꢨꢘ

ꢇ
=

where ꢇ = atomic density of deposited film

Note: This result is exactly the same as the Deal- rove model for thermal oxidation with oxide thickness = 0

29

Deposition Rate vs. Temperature

ꢘꢆ

gas transport

ꢱ ∝ ꢊ

limited surface-reaction limited

1 / T

0

  • high T
  • low T

30

15

rowth Rate Dependence on Flow
Velocity

31

CVD Features

1. More conformal deposition if T is uniform

Wafer topography

2. Inter-wafer and intra-wafer thickness uniformity less sensitive to gas flow patterns. (i.e. wafer placement).

32

16

Comments about CVD

(1) Sensitivity to gas flow pattern
Furnace tube

in

wafers
(2) Mass depletion problem

  • more
  • less

in out

33

Plasma Enhanced CVD (PECVD)

• Ionized chemical species allows a lower process temperature to be used

– Plasma helps dissociate the precursor molecules at lower temperatures).

• Film properties (e.g. mechanical stress) can be tailored by controlling ion bombardment with substrate bias voltage.

34

17

Atomic Layer Deposition (ALD)

• The process involves two self-limiting half reactions that are repeated in cycles

• Unlike CVD, in ALD pulses of precursors are introduced in each cycle

• ALD is highly conformal and enables excellent thickness uniformity and control down to nm-scale

35

ALD for High-k ate Dielectric

36

18

Recommended publications
  • Plasma Enhanced Chemical Vapor Deposition of Organic Polymers

    Plasma Enhanced Chemical Vapor Deposition of Organic Polymers

    processes Review Plasma Enhanced Chemical Vapor Deposition of Organic Polymers Gerhard Franz Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences (MUAS), 34 Lothstrasse, Munich, D-80335 Bavaria, Germany; [email protected] Abstract: Chemical Vapor Deposition (CVD) with its plasma-enhanced variation (PECVD) is a mighty instrument in the toolbox of surface refinement to cover it with a layer with very even thickness. Remarkable the lateral and vertical conformity which is second to none. Originating from the evaporation of elements, this was soon applied to deposit compound layers by simultaneous evaporation of two or three elemental sources and today, CVD is rather applied for vaporous reactants, whereas the evaporation of solid sources has almost completely shifted to epitaxial processes with even lower deposition rates but growth which is adapted to the crystalline substrate. CVD means first breaking of chemical bonds which is followed by an atomic reorientation. As result, a new compound has been generated. Breaking of bonds requires energy, i.e., heat. Therefore, it was a giant step forward to use plasmas for this rate-limiting step. In most cases, the maximum temperature could be significantly reduced, and eventually, also organic compounds moved into the preparative focus. Even molecules with saturated bonds (CH4) were subjected to plasmas—and the result was diamond! In this article, some of these strategies are portrayed. One issue is the variety of reaction paths which can happen in a low-pressure plasma. It can act as a source for deposition and etching which turn out to be two sides of the same medal.
  • Deposition Lecture Day 2 Deposition

    Deposition Lecture Day 2 Deposition

    Deposition Lecture Day 2 Deposition PVD - Physical Vapor Deposition E-beam Evaporation Thermal Evaporation (wire feed vs boat) Sputtering CVD - Chemical Vapor Deposition PECVD LPCVD MVD ALD MBE Plating Parylene Coating Vacuum Systems, pumps and support equipment Differences, Pros and Cons for depositing various materials Physical vs. Chemical Deposition Metallization - depositing metal layers or thin films - E-beam & Thermal Evaporation, Sputtering, Plating - Contact layer, mask/protection layer, interface layers Dielectric Deposition - depositing dielectric layers or thin films -CVD, e-beam, sputtering - insulating/capacitor layer, mask/protecting layer, interface layers *Dielectric = an electrical insulator that can be polarized by an applied electric field. ~energy storing capacity → capacitor Environment of the Deposition *Cleanroom is not enough! Must also be in vacuum! Purity of the deposited film depends on the quality of the vacuum, and on the purity of the source material. Cryo pumps Evaporation is a common method of thin-film deposition. The source material is evaporated in a vacuum. The vacuum allows vapor particles to travel directly to the target object (substrate), where they condense back to a solid state. Evaporation is used in microfabrication, and to make macro-scale products such as metallized plastic film. Any evaporation system includes a vacuum pump. It also includes an energy source that evaporates the material to be deposited. Many different energy sources exist: ● In the thermal method, metal material (in the form of wire, pellets, shot) is fed onto heated semimetal (ceramic) evaporators known as "boats" due to their shape. A pool of melted metal forms in the boat cavity and evaporates into a cloud above the source.
  • Evaporation Sources

    Evaporation Sources

    MATERIALS EVAPORATION I SOURCES • Evaporation Source Selection Guide ................... .I 02 • Tungsten Filaments for Vacuum Metalizing.......... .I 04 I • Tungsten Rod Source ..................................... .I 07 • Point Source Loop Filaments............................. .I 08 • Heater Filaments ............................................ I 10 • Baskets ........................................................ .I 11 • Crucibles ...................................................... .I 14 • Heat Shielded Crucible Heaters ......................... .I 16 • Boat Sources ................................................. .I 18 • Folded Boats ................................................. .I 29 • Alumina Coated Evaporation Sources.................. .I 31 • Special Tantalum Boats.................................... I 37 • Folded Baffled Box Sources .............................. .I 41 • Baffled Box Sources for SiO, ZnS ....................... .I 43 • Microelectronic Sources Tungsten – Tantalum – Molybdenum .................................. .I 48 • Chrome Plated Tungsten Rods .......................... .I 53 • Tungsten Screens .......................................... .I 54 I 01 MATERIALS EvaporatioN SOUrces ManufacturingEvaporation Source Processes Selection Guide Evaporation Source Selection Guide This source selection guide is provided to help you determine which evaporation source type might fit your needs. How to use the Guide: 1. Determine how much current your power supply is capable of safely producing. 2. Establish the vapor
  • Technical Paper

    Technical Paper

    TECHNICAL PAPER Materials & Deposition Technology for Coating Optical Surfaces Understanding the Components of the Process Author: Samuel Pellicori Materion Coating Materials News The materials and deposition processes employed to make coatings that are intended for use at wavelength regions between UV and far IR are described in this overview of the technology. Coatings composed of special materials are deposited as nano- and micro- meter thicknesses by specific techniques to control the optical, mechanical, chemical and electrical properties of optical surfaces. Design & Engineering Considerations for Coating Optical Components The components of the deposition process, starting with the performance specifications and continuing through the finished coated surface, are diagrammed in Figure 1. It is evident from the number and descriptions of the process components that material science and deposition technology play complex interdependent roles in the overall process of producing optical coatings. It is important for the system designer to understand the individual components of the process and their interactions. When presented with the spectral and environmental requirements and the substrate material to be coated, the coating engineer has the responsibility of selecting the appropriate coating materials and deposition process. A thin-film design is then generated that includes the wavelength dependencies of the optical constants, refractive index and extinction coefficient - quantities that need to be pre-determined for specific materials and their deposition process parameters. From this theoretical layer-by-layer design, the performance is predicted and evaluated with respect to spectral coverage, incidence angle, surface shape, substrate temperature constraints, mechanical durability and verification measurement. The technology of preparing the coating material is equally complex and includes consideration of such factors as chemical composition, form, and deposition technique.
  • Physical Vapor Deposition

    Physical Vapor Deposition

    EE-527: MicroFabrication Physical Vapor Deposition R. B. Darling / EE-527 / Winter 2013 Physical Vapor Deposition (PVD) Gas Phase Gas Phase Transport Evaporation Condensation Condensed Phase Condensed Phase (solid or liquid) (usually solid) R. B. Darling / EE-527 / Winter 2013 Equilibrium Vapor Pressure • P* is the partial pressure of a gas in equilibrium with its condensed phase at a given temperature T. – There is no net transfer of material from one state to the other. • For a given material, P* is only a function of T. – But the dependence of P* on T is rather complicated. R. B. Darling / EE-527 / Winter 2013 Evaporation Rates - 1 • P* is the equilibrium vapor pressure of the evaporant at T. • P is the ambient hydrostatic pressure acting upon the evaporant in the condensed phase. • Heinrich Hertz found experimentally that the evaporation rate was proportional to (P* - P). – This is consistent with kinetic theory in which the impingement rates are proportional to pressure. – Hertz also found that the evaporation rate could not be increased by supplying more heat unless the equilibrium vapor pressure was also increased by this action. – Thus, there is a maximum evaporation rate set by P*, and this is only achieved in a vacuum, where P = 0. R. B. Darling / EE-527 / Winter 2013 Evaporation Rates - 2 • This can be viewed as two opposing fluxes: The net evaporation flux is the difference between the impingement rates for the evaporant vapor two fluxes: rate goes as P dNe 1/ 2 * 2mkBT P P Aedt rate goes as P* condensed evaporant R. B.
  • 1. Methods of Physical Vapor Deposition. Thermal Evaporation

    1. Methods of Physical Vapor Deposition. Thermal Evaporation

    Andrey Shishkin 1. Methods of physical vapor deposition. Thermal evaporation. Adhesion. Role of vacuum. Monitoring of the deposition process. 2. Magnetron and RF-diod sputtering. 3. Electron-beam evaporation. 4. Engineering aspects of physical vapor deposition: vacuum chambers, pumps, cooling systems. 5. Monitoring and control of the deposition processes. 6. MBE based technologies. Physical vapor deposition, PVD Physical vapor deposition (PVD) systems deposit thin films and coatings by a process in which a target material is vaporized, transported in vacuum, and condensed on to a substrate. PVD processes include Sputtering, Electron beam, and Thermal Evaporation. • Thermal evaporation • In-situ control of the film thickness. Estimations of the film uniformity. • Electron-beam physical vapor deposition • Sputtering deposition, magnetron sputtering deposition • Cathodic arc deposition. • Reactive deposition • Laser ablation • Role of vacuum conditions • Vacuum systems for the physical vapor deposition. Pumping systems. • Adhesion of coatings. • Types (modes) of thin film growth. • Several important examples of different coatings. Thermal evaporation Thermal evaporation is realized by thermal heating (usually resistive) of an evaporated material placed in an evaporation source. It is carried out in a vacuum at pressure P<10-5 torr. The thermal evaporation is the most gentle PVD method with evaporated particle energies ~1500 K (0.12 eV). This method is the simplest PVD method and needs comparatively low power consumption. Main types of simple evaporation sources are metallic boats (1,2) and heaters made of refractory wires (3) (Wo, Mo,…) which can be covered by a passive material (2) (Al2O3) More complicated effusion cells with a crucible made of passive material (e.g., boron nitride, BN) and an external heater are used for precision evaporation processes like the molecular beam epitaxy.
  • Study of Ohmic Contact Formation on Algan/Gan Heterostructures

    Study of Ohmic Contact Formation on Algan/Gan Heterostructures

    DEGREE PROJECT IN INFORMATION AND COMMUNICATION TECHNOLOGY, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2019 Study of ohmic contact formation on AlGaN/GaN heterostructures KAI-HSIN WEN KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE DF KTH Royal Institute of Technology Study of ohmic contact formation on Al- GaN/GaN heterostructures Master’s thesis in Nanotechnology Kai-hsin Wen Information and Communication Technology KTH ROYAL INSTITUTE OF TECHNOLOGY Stockholm, Sweden 2019 Master’s thesis 2019 Study of ohmic contact formation on AlGaN/GaN heterostructures Kai-hsin Wen Information and Communication Technology KTH Royal Institute of Technology Stockholm, Sweden 2019 Study of ohmic contact formation on AlGaN/GaN heterostructures Kai-hsin Wen © Kai-hsin Wen, 2019. Supervisors: Niklas Rorsman, Chalmers University of Technology Ding-yuan Chen, Chalmers University of Technology Examiner: Mattias Hammar, KTH Royal Institute of Technology Master’s Thesis 2019 Information and Communication Technology KTH Royal Institute of Technology SE-100 44 Stockholm Telephone +46 8 790 60 00 Cover: The contour plot of the obtained Rc from the laser focus/dose matrix. Typeset in LATEX, template by David Frisk Printed by KTH Stockholm, Sweden 2019 iv Study of ohmic contacts formation on AlGaN/GaN heterostructures Kai-hsin Wen Information and Communication Technology KTH Royal Institute of Technology SE-100 44 Stockholm Abstract It is challenging to achieve low-resistive ohmic contacts to III-nitride semiconductors due to their wide bandgap. A common way to reduce the contact resistance is to recess the ohmic area prior to metallization. In the minimization of the contact resistance, parameters like the recess depth, anneal temperature and design of the metal stack are commonly optimized.
  • Metallization – Deposition and Etching

    Metallization – Deposition and Etching

    Metallization – deposition and etching Material mainly taken from Campbell, UCCS Application • Metallization is back-end processing • Metals used are aluminum and copper • Mainly involves deposition and etching, also planarization • Similar (but typically less complicated) process flows as in front-end processing 6 metal level copper dual damascene process crossection at 0.18µm node (R. DeJule, “Dual-damascene: overcoming process issues”, Semiconductor International, pp. 94, June 2000) 3D SEM of 9 metal level Cu process (H. Ruelke, C. Streck, M. -Van. Ngo, L. You, S. Weiher-Telford, O. Chretien, J. Matusche, D. Dugiarto, J. Sabharwal, “Manufacturing implementation of low-k dielectrics for copper damascene technology”, Advanced Semiconductor Manufacturing Conference, pp. 356–9, 2002.) CMOS/Process steps – Process step: Metal interconnect 1 (1) • Deposit layer of metal over the entire wafer Common metals: Aluminium or copper p+ n+ n+ p+ p+ n+ n-well p-substrate CMOS/Process steps – Process step: Metal interconnect 1 (2) • Photolithography sequence using “Metal 1 mask” • Metal selectively etched p+ n+ n+ p+ p+ n+ n-well p-substrate CMOS/Process steps – Process step: Via windows • Cover wafer with a layer of SiN3 • Lithography using the “via mask” • Plasma etching p+ n+ n+ p+ p+ n+ n-well p-substrate CMOS/Process steps – Process step: Metal interconnect 2 (1) • Deposit layer of metal over the entire wafer p+ n+ n+ p+ p+ n+ n-well p-substrate CMOS/Process steps – Process step: Metal interconnect 2 (2) • Photolithography sequence using “Metal 2 mask” • Metal selectively etched – Metal interconnect layers: • Two masks required for each additional metal layer: “via n mask” and “metal n mask” • Reliability: Dimensions of contacts/vias cannot be changed by layout designer (to avoid “contact spiking”).

  • ANGLE-RESOLVED PHOTOEMISSION SPECTROSCOPY of Sr1−Xlaxcuo2 THIN FILMS GROWN by MOLECULAR-BEAM EPITAXY

    ANGLE-RESOLVED PHOTOEMISSION SPECTROSCOPY OF Sr1−xLaxCuO2 THIN FILMS GROWN BY MOLECULAR-BEAM EPITAXY A Dissertation Presented to the Faculty of the Graduate School of Cornell University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by John Wallace Harter May 2013 c 2013 John Wallace Harter ALL RIGHTS RESERVED ANGLE-RESOLVED PHOTOEMISSION SPECTROSCOPY OF Sr1−xLaxCuO2 THIN FILMS GROWN BY MOLECULAR-BEAM EPITAXY John Wallace Harter, Ph.D. Cornell University 2013 Among the multitude of known cuprate material families and associated structures, the archetype is “infinite-layer” ACuO2, where perfectly square and flat CuO2 planes are separated by layers of alkaline earth atoms. The infinite-layer structure is free of mag- netic rare earth ions, oxygen chains, orthorhombic distortions, incommensurate super- structures, ordered vacancies, and other complications that abound among the other ma- terial families. Furthermore, it is the only cuprate that can be made superconducting by both electron and hole doping, making it a potential platform for decoding the complex many-body interactions responsible for high-temperature superconductivity. Research on the infinite-layer compound has been severely hindered by the inability to synthesize bulk single crystals, but recent progress has led to high-quality superconducting thin film samples. Here we report in situ angle-resolved photoemission spectroscopy measurements of epitaxially-stabilized Sr1−xLaxCuO2 thin films grown by molecular-beam epitaxy. At low doping, the material exhibits a dispersive lower Hubbard band typical of other cuprate parent compounds. As carriers are added to the system, a continuous evolution from Mott insulator to superconducting metal is observed as a coherent low-energy band de- velops on top of a concomitant remnant lower Hubbard band, gradually filling in the Mott gap.
  • Thin Film Deposition & Vacuum Technology

    Thin Film Deposition & Vacuum Technology

    Thin Film Deposition & Vacuum Technology THIN FILM DEPOSITION & VACUUM TECHNOLOGY By Stefan Cannon Lofgran A senior thesis submitted to the faculty of Brigham Young University{Idaho in partial fulfillment of the requirements for the degree of Bachelor of Science Department of Physics Brigham Young University{Idaho April 2013 2013 c Stefan Lofgran All Rights Reserved Brigham Young University{Idaho Department Approval of a senior thesis submitted by Stefan Cannon Lofgran This thesis has been reviewed by the research committee, senior thesis coor- dinator and department chair and has been found to be satisfactory. Date David Oliphant, Advisor Date Ryan Nielson, Committee Member Date Stephen McNeil, Senior Thesis Coordinator ABSTRACT THIN FILM DEPOSITION & VACUUM TECHNOLOGY Stefan Cannon Lofgran Department of Physics Bachelor of Science The study and development of thin films via physical vapor deposition has played a significant role in the development of optical coatings, semiconduc- tors, and solar cells. Closely related to the study of thin films is the de- velopment of vacuum technology and systems capable of reaching pressures suitable for growing uniform films at reasonable deposition rates. This paper explores the method of physical vapor deposition known as thermal evapo- ration via resistive or Joule heating as a means for growing thin aluminum (Al) films on a mineral glass substrate. Methods for measuring thickness are also discussed and investigated in an attempt to determine the experimen- tally produced film thickness. A detailed explanation of the development and operation of the vacuum system in which the Al films were grown is given as well as future improvements that could be made.
  • 8-Vacuum Coating Evaporation Materials 0510:Layout 1 17/6/10 16:44 Page 197

    8-Vacuum Coating Evaporation Materials 0510:Layout 1 17/6/10 16:44 Page 197

    8-Vacuum coating_evaporation_materials_0510:Layout 1 17/6/10 16:44 Page 197 8 - Vacuum coating and evaporation materials The Agar range of coating units offers the user a wide choice of options to suit all the coating requirements needed in support of SEM and TEM applications. These compact bench-top coating units are built to a high specification and incorporate microprocessor technology. A guide to selecting the correct coater Basic coating For routine gold sputtering of SEM samples, the manual sputter coater (B7340) provides a low cost solution. For high sample throughputs, or occasions where alternative target materials, such as gold/palladium, are required to achieve finer grained coatings, the automatic coating unit (B7341) should be selected. For microanalytical applications where gold coating may not be appropriate, the carbon coater (B7367A) is ideal. The dual carbon rod source, with unique current feedback control, gives highly reproducible carbon coatings for SEM samples. The pumping system (B7366) is designed for use with the coating units. It includes an anti-vibration platform, stainless steel bellows connection and vacuum fittings. If both carbon and gold sputtering are required, the dual pumping system (B7736) with changeover valve can be used to pump two coating units. Where an accurate determination of coating thickness is required, the manual film thickness monitor (B7348) can be used with all the units. It can also be shared between two coaters, by the addition of the hardware kit (B7735). Further automation of the coating process can be achieved by fitting the film thickness monitor with terminator (B7349) to the automatic sputter coater.
  • In-Situ Angle-Resolved Photoemission Spectroscopy of Copper-Oxide Thin Films Synthesized by Molecular Beam Epitaxy

    In-Situ Angle-Resolved Photoemission Spectroscopy of Copper-Oxide Thin Films Synthesized by Molecular Beam Epitaxy

    In-situ angle-resolved photoemission spectroscopy of copper-oxide thin films synthesized by molecular beam epitaxy Chung Koo Kima, Ilya K. Drozdova, Kazuhiro Fujitaa, J. C. Séamus Davisa,c,d,e, Ivan Božovića,b, Tonica Vallaa a. CMPMS Department, Brookhaven National Laboratory, Upton, NY 11973, USA b. Applied Physics Department, Yale University, New Haven, Connecticut 06520, USA c. LASSP, Department of Physics, Cornell University, Ithaca, NY 14853, USA d. School of Physics and Astronomy, University of St. Andrews, Fife KY16 9SS, Scotland e. Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA Angle-resolved photoemission spectroscopy (ARPES) is the key momentum-resolved technique for direct probing of the electronic structure of a material. However, since it is very surface-sensitive, it has been ap- plied to a relatively small set of complex oxides that can be easily cleaved in ultra-high vacuum. Here we describe a new multi-module system at Brookhaven National Laboratory (BNL) in which an oxide molecular beam epitaxy (OMBE) is interconnected with an ARPES and a spectroscopic-imaging scanning tunneling microscopy (SI-STM) module. This new capability largely expands the range of complex-oxide materials and artificial heterostructures accessible to these two most powerful and complementary techniques for stud- ies of electronic structure of materials. We also present the first experimental results obtained using this system — the ARPES studies of electronic band structure of a La2-xSrxCuO4 (LSCO) thin film grown by OMBE. Keywords: molecular-beam epitaxy, angle-resolved photoemission spectroscopy, scanning tunneling micros- copy, electronic properties, high-temperature superconductivity 1 Introduction Transition metal oxides host a variety of interesting electronic properties such as high-temperature superconductivity, colossal magneto-resistance, giant thermopower, piezo- and ferro-electricity, magnetism, topological states, etc.