-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 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Joseph Choi, Dept. of Physics, Brigham Young University 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 inside 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. 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Joseph Choi, Dept. of Physics, Brigham Young University 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. 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

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©) 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Joseph Choi, Dept. of Physics, Brigham Young University Thesis Description Design and building of vacuum chamber from stainless steel body made by Varian, Inc. – Since April 2000. UHV, ellipsometry, deposition, procedures. Ruthenium thin film ( 290 Å) sputtered in HV (high vacuum;10-8-10-6 torr). Real-time in situ ellipsometric measurements to analyze Ru thin film and its oxidation. 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Joseph Choi, Dept. of Physics, Brigham Young University 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 ºC to eliminate water, hydrogen, speed degassing. - Parts: Minimize o-rings, use metal-to-metal seals. - Material: Low outgas rates (Aluminum, stainless steel). - Machining: Inert gas welding or vacuum brazing. 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Conflat flange- Copper seal Thermocouple Bake out power control- Variac + Transformer Cleaning agent- Methanol Heating tape- Bake out 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Joseph Choi, Dept. of Physics, Brigham Young University Vacuum Pumps Principle - Cold trap. - Large surface area. Sorption pumps - Atmosphere to roughing pressure (10-3 torr). Cryopump - To UHV pressure. 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Overview of Components The Ellipsometer[1] Usage of p- and s- polarization of the E(Electric)-field. Measurement of Ψ and Δ: Ψ: Magnitude of p- to s- reflectance ratio. Δ: Difference in phase of p- and s- reflection. Ψ and Δ related by reflectance: Optical constants, thickness obtainable with computer using Ψ, Δ. Geometry of an ellipsometric experiment, showing the p- and s- directions [1]J.A.Woollam Co., Inc., Guide to Using WVASE32TM. 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Joseph Choi, Dept. of Physics, Brigham Young University 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

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 parts, Ar is positively ionized and bombards the target material, physically knocking the atoms off onto the film. [2] http://www.sputteringmaterials.com/sputtering_technology.htm 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Sputter Gun Mechanism in Vacuum Chamber 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Overview of Components (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. 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Overview of Components (cont.) Sample Stage - Hold film. Shutter - Controlled deposition. Crystal Monitor (MaxTek, Inc.) - Measure deposition rate and amount. 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Overview of Components (cont.) Oxygen line - UHV leak valve. - Controlled oxidation of sample. Argon line - Gas medium for plasma. - To vent chamber. O2 Ar 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Joseph Choi, Dept. of Physics, Brigham Young University Ruthenium Thin Film May 3, 2001: Ru sputtered in 1x10-6 torr. Real-time in situ analysis: in HV, Ar venting, atmosphere. Improved Ru optical constants. RuO2 thickness fit. Little apparent oxidation . 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Joseph Choi, Dept. of Physics, Brigham Young University 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. 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

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. Details to clarify possible questions of system. 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University

Joseph Choi, Dept. of Physics, Brigham Young University 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 11/17/2018 Joseph Choi, Dept. of Physics, Brigham Young University