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1、5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,1,-Honors Thesis Defense- In Situ Ellipsometry of Surfaces in an Ultrahigh Vacuum Thin Film Deposition Chamber,Joseph Choi Department of Physics and Astronomy, Brigham Young University June 19, 2001,5/24/2019,Joseph Choi, Dept. of Phy
2、sics, Brigham Young University,2,Definition of Terms,UHV (ultrahigh vacuum)- Base pressure 10-9 torr. (Atmospheric pressure is 7.6 x 102 torr) Ellipsometry- Optical measurement technique of reflection, transmission, optical constants, and thickness using polarization of light. In situ- Measurement i
3、nside the chamber without opening to the atmosphere. Evaporation- Deposition of material by thermally heating it using metallic boats with high resistance. Sputtering- Deposition by bombarding positive ions onto the material, and physically vaporizing it.,5/24/2019,Joseph Choi, Dept. of Physics, Bri
4、gham Young University,3,Research Goals,Building: Build a UHV (ultrahigh vacuum) chamber with in situ ellipsometry, sputtering, and evaporation capabilities. Measurement / Modeling: Measure and develop model for thin film oxidation.,5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,4,
5、Motivation Study of Oxidation,Reflectance of a silicon film can vary from 70% to below 5% dependent on oxidation. Immediate oxidization when exposed to atmosphere.,(Model of a silicon film produced using IMD),5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,5,Thesis Description,Desi
6、gn and building of vacuum chamber from stainless steel body made by Varian, Inc. Since April 2000. UHV, ellipsometry, deposition, procedures. Ruthenium thin film ( 290 ) sputtered in HV (high vacuum;10-8-10-6 torr). Real-time in situ ellipsometric measurements to analyze Ru thin film and its oxidati
7、on.,5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,6,UHV Vacuum (10-9 torr),Benefit- Purity of film: - Comparison with HV (10-6 torr): Gas flux 1 cm2/sec. Achieving UHV: - Cleanliness: No oil; cleaning agents (hexane, methanol). - Bake out: 250 C to eliminate water, hydrogen, spee
8、d degassing. - Parts: Minimize o-rings, use metal-to-metal seals. - Material: Low outgas rates (Aluminum, stainless steel). - Machining: Inert gas welding or vacuum brazing.,5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,7,Conflat flange- Copper seal,Thermocouple,Heating tape- Bak
9、e out,Cleaning agent- Methanol,Bake out power control- Variac + Transformer,5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,8,Vacuum Pumps,Principle - Cold trap. - Large surface area. Sorption pumps - Atmosphere to roughing pressure (10-3 torr). Cryopump - To UHV pressure.,5/24/201
10、9,Joseph Choi, Dept. of Physics, Brigham Young University,9,Overview of Components,The Ellipsometer1 Usage of p- and s- polarization of the E(Electric)-field. Measurement of and : : Magnitude of p- to s- reflectance ratio. : Difference in phase of p- and s- reflection. and related by reflectance: Op
11、tical constants, thickness obtainable with computer using , .,1J.A.Woollam Co., Inc., Guide to Using WVASE32TM.,Geometry of an ellipsometric experiment, showing the p- and s- directions,5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,10,5/24/2019,Joseph Choi, Dept. of Physics, Brig
12、ham Young University,11,Overview of Components (cont.),Sputter Gun We use Mighty MAK 4” from US Inc. Principle of Operation:2 1. Under vacuum, fill chamber with noble gas. Our chamber uses Ar. 2. By applying a mostly negative potential (0.5 - 5kV) to the target material, while grounding the outer pa
13、rts, Ar is positively ionized and bombards the target material, physically knocking the atoms off onto the film.,2 http:/ Choi, Dept. of Physics, Brigham Young University,12,Sputter Gun Mechanism in Vacuum Chamber,5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,13,Overview of Compo
14、nents (cont.),Evaporator A 3 boat evaporator using 4 medium current feedthroughs from MDC. Alumina ceramic shields to protect cross-contamination. Principle of Operation: Heating of metallic boats using current; thermally evaporate material.,5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young Uni
15、versity,14,Overview of Components (cont.),Sample Stage - Hold film. Shutter - Controlled deposition. Crystal Monitor (MaxTek, Inc.) - Measure deposition rate and amount.,5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,15,Overview of Components (cont.),Oxygen line - UHV leak valve.
16、- Controlled oxidation of sample. Argon line - Gas medium for plasma. - To vent chamber.,O2,Ar,5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,16,Ruthenium Thin Film,May 3, 2001: Ru sputtered in 1x10-6 torr. Real-time in situ analysis: in HV, Ar venting, atmosphere. Improved Ru opt
17、ical constants. RuO2 thickness fit. Little apparent oxidation .,5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,17,Current Status,Base vacuum pressure- 1.5 x 10-7 torr. Training: Evaporator installed with chromium boat. Bake out and pump down chamber. In situ analysis of chromium.,
18、5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,18,Comments on Length of Thesis,Majority of research was in building the UHV system- over a year. Training purpose: Recording of effort that goes into building a vacuum deposition system. Understanding of procedures and components. De
19、tails to clarify possible questions of system.,5/24/2019,Joseph Choi, Dept. of Physics, Brigham Young University,19,Credits and Thanks,Dr. David Allred J.J. Warriner, Greg Harris Zach Barton, Brian Schramm Department of Physics and Astronomy, Honors Department ORCA, Multi-cultural Scholarship, SPIE,