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1、-Honors Thesis Defense-In Situ Ellipsometry of Surfaces in an Ultrahigh Vacuum Thin Film Deposition ChamberJoseph ChoiDepartment of Physics and Astronomy, Brigham Young UniversityJune 19, 20018/24/20241Joseph Choi, Dept. of Physics, Brigham Young UniversityDefinition of TermsUHV (ultrahigh vacuum)-
2、Base pressure 250 C 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.8/24/20246Joseph Choi, Dept. of Physics, Brigham Young UniversityConflat fla
3、nge- Copper sealThermocoupleHeating tape- Bake outCleaning agent- MethanolBake out power control- Variac + Transformer8/24/20247Joseph Choi, Dept. of Physics, Brigham Young UniversityVacuum PumpsPrinciple- Cold trap.- Large surface area.Sorption pumps- Atmosphere to roughing pressure (10-3 torr).Cry
4、opump- To UHV pressure.8/24/20248Joseph Choi, Dept. of Physics, Brigham Young UniversityOverview of ComponentsThe 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.- an
5、d related by reflectance:-Optical constants, thickness obtainable with computer using , .1J.A.Woollam Co., Inc., Guide to Using WVASE32TM.Geometryofanellipsometricexperiment,showingtheGeometryofanellipsometricexperiment,showingthep-ands-directionsp-ands-directions8/24/20249Joseph Choi, Dept. of Phys
6、ics, Brigham Young University 8/24/202410Joseph Choi, Dept. of Physics, Brigham Young UniversityOverview of Components (cont.)Sputter Gun-We use Mighty MAK 4” from US Inc.-Principle of Operation:21. Under vacuum, fill chamber with noble gas. Our chamber uses Ar.2. By applying a mostly negative poten
7、tial (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:/ Choi, Dept. of Physics, Brigham Young UniversitySputter Gun Mechanism in Vacuum Chamber8/24/202412Joseph Choi,
8、 Dept. of Physics, Brigham Young UniversityOverview 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.
9、 8/24/202413Joseph Choi, Dept. of Physics, Brigham Young UniversityOverview of Components (cont.)Sample Stage- Hold film.Shutter- Controlled deposition.Crystal Monitor (MaxTek, Inc.) - Measure deposition rate and amount.8/24/202414Joseph Choi, Dept. of Physics, Brigham Young UniversityOverview of Co
10、mponents (cont.)Oxygen line- UHV leak valve.- Controlled oxidation of sample.Argon line- Gas medium for plasma.- To vent chamber.O2Ar8/24/202415Joseph Choi, Dept. of Physics, Brigham Young UniversityRuthenium Thin FilmMay 3, 2001: Ru sputtered in 1x10-6 torr.Real-time in situ analysis: in HV, Ar ven
11、ting, atmosphere.Improved Ru optical constants.RuO2 thickness fit.Little apparent oxidation .8/24/202416Joseph Choi, Dept. of Physics, Brigham Young UniversityCurrent StatusBase vacuum pressure- 1.5 x 10-7 torr.Training:Evaporator installed with chromium boat.Bake out and pump down chamber.In situ a
12、nalysis of chromium.8/24/202417Joseph Choi, Dept. of Physics, Brigham Young UniversityComments on Length of ThesisMajority 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 c
13、omponents.Details to clarify possible questions of system.8/24/202418Joseph Choi, Dept. of Physics, Brigham Young UniversityCredits and ThanksDr. David AllredJ.J. Warriner, Greg HarrisZach Barton, Brian SchrammDepartment of Physics and Astronomy, Honors DepartmentORCA, Multi-cultural Scholarship, SPIE8/24/202419Joseph Choi, Dept. of Physics, Brigham Young University
