(Chapter 10) EE 403/503 Introduction to Plasma Processing

Transcription

1 (Chapter 10) EE 403/503 Introdution to Plasma Proessing November 9, 011

2 Average Eletron Energy, [ev] P = 100 Hz P = 10 KHz P = 1 MHz P = MHz P = 100 MHz P =.45 GHz P = 10 GHz P = 1 THz T e,mw > T e,rf & T e, DC (5-15 ev) (1- ev) * GHz.45 * GHz 300 GHz 33 m 1.4 m 1 mm Eletron Beam Thermonulear Plasmas 10 6 Torr pressure 1 atm 10 Solar Corona 10 mtorr Magnetized ECR At frequenies above 10 GHz --> Water absorption MW Unmagnetized ECR Colletive interation regime Radiation interat with plasma as a dieletri medium Interstellar Gas Gaseous Nebulae Ionosphere Glow Disharge MHD Generator Ar Disharge Solid Eletron Number Density, [m -3 ] Partile interation regime Radiation interat with plasma as it interat with individual eletrons

3 Desription * GHz.45 * GHz 300 GHz 33 m 1.4 m 1 mm Funny Information

4 - Higher eletron kineti temperatures and lower pressures - Higher fration of ionization and dissoiation than DC and low frequeny disharges - Lower voltages aross the sheath -> Less sputtering of the wall - No eletrodes -> less ontamination - More stable over a wide range of bakground gas pressures relative to DC & RF

5 Appliations ECR: for Miroeletronis Plasma Proessing Fusion; for initial, steady state and high density plasmas Soures: for Photons, ions, free radials, exited atoms and dissoiated neutral speies Laser: to pump laser medium Continuous flow plasmas: Chemial reators

6 Continuous Flow Non-resonant Mirowave Plasma (High eletri field of radiation aligned with the axis of the tube) Waveguide (atmospheri Pressure) Reatants Quartz Tube oolant Tapered Resonator Produt Plasma (low pressure, KW)

7 Resonant or multimode avity reator Tuning Tube Waveguide and Tuner R Plasma d Window Resonant Cavity: R= 0 ; d= 0 Multimode Cavity: R>> 0 ; d>> 0 (Remember:.45 GHz -> 1.4 m)

8 .45 GHz, KW Mirowave Power Supply Magnetron Isolator Tuner Isolates the magnetron from the variable plasma load. It funtions like one way valve for mirowave power. Minimizes the refleted power, while maximizing the forward power absorbed by the load Gas Quartz Tube separates the working gas pressue from the one within the waveguide Sliding Short Cavity A variable load

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10 Cathode (heated filament) Anode B X

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12 Grape Plasma 0:34 Mirowave experiment plasmaball 0:57

13 Eletron Cylotron Resonane (ECR) Plasma Reator MW gyration gyration qb m Resonane Surfae Cerami Window Input Waveguide Magneti Resonane Coil Plasma Magneti Nozzle Trim Coil B B B B B Target Material

14 Power Coupling to the Plasma ) ( 1 ) ( g g e m n e E P (with B) U p * g g ) ( ) ( * g g p ) ( 1 * p Low pressure High pressure B n gyro e Plasma Energy transfer frequeny

15 Optimum Power oupling to Plasma (with B) g g p ) ( 1 ) ( 1 * 1/ 4, 1 0 * opt g g d d 3 g 3 g g g opt d d 1/ * ) ( 0 *, g opt d d Pages

16 Immersed ECR System Page 504

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18 Distributed ECR System

19 Ion Thruster Ion Soure

20 mv ee mv e( v B) E from radiation plus the effet of surrounding plasma E B Stati bakground magneti field B of radiation is neglegibly small E B B t j E t Maxwell Equation Propagation Equation: Attenuation onstant 1/ I( z, t) I exp( z)exp[ j( t kz)] 0 Wave number Page 471

21 Mirowave Breakdown of Gases Breakdown Eletri Field E b Free Spae Wavelength Ionization Potential of the Gas E(, V, l, ) i Eletron Mean Free Path Charateristi Diffusion Length With five variables and two independent dimensions (Length and voltage), three dimensionless variables are suffiient to desribe the relationship implied by the above equation e.g. E V, E El,,, l l V i i V i The impliation is that it requires a three-dimensional surfae to speify the RF and mirowave breakdown onditions in the gas. l 1 p & V i onst E, E p,, E p p, Page 484

22 Signal Attenuation (db) =0 MHz =40 MHz Collision frequeny e 4.00 Example: e =4.0 GHz pe =1.0 GHz Plasma Diameter =1 m uh =4.13 GHz 130 MHz UH Upper hybrid frequeny pe uh e Upper Hybrid Frequeny Wave Frequeny, (GHz) Page 479

23 Phase Shift (Degrees) =40 MHz =0 MHz UH =4.13 GHz e =4.0 GHz pe =1.0 GHz D=1 m UH Wave Frequeny, (GHz) Page 479

24 Mirowave Horn Plasma n e, Esin t + B 0 waveguide Network Analyzer Pages

25 Heald and Wharton Propagation Equation Complex refrative index j Propagation Constant Real refrative index How muh the radiation is slowed down in the medium relative to propagation in vauum Attenuation index How muh is the wave is attenuated 1- Propagation in an unmagnetized plasma (P 47) - Propagation in a magnetized (B 0 ) plasma (P 473) a- angle between E and B 0 (P. 474) b- =0; right irularly polarized wave (P 475) - =0; left irularly polarized wave (P 475) d- =90; B 0 E (P 476) e- =90; B 0 B (P 476) Pages