Lec_14 - Professor N Cheung, U.C. Berkeley Lecture 14 EE143...

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Professor N Cheung, U.C. Berkeley Lecture 14 EE143 F2010 1 Etching • Etching Terminology • Etching Considerations for ICs • Wet Etching • Reactive Ion Etching (plasma etching)
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Professor N Cheung, U.C. Berkeley Lecture 14 EE143 F2010 2 Etch Process - Figures of Merit • Etch rate • Etch rate uniformity • Selectivity • Anisotropy
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Professor N Cheung, U.C. Berkeley Lecture 14 EE143 F2010 3 (1) Bias substrate d f h f film d m etching mask d f substrate d m Bias B d d B can be or f m 0 0.
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Professor N Cheung, U.C. Berkeley Lecture 14 EE143 F2010 4 Complete Isotropic Etching B h f = 2 Vertical Etching = Lateral Etching Rate Lateral Etching rate = 0 B = 0 Complete Anisotropic Etching
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Professor N Cheung, U.C. Berkeley Lecture 14 EE143 F2010 5 1 0 2 1 f f f A h B A 0 2 B f h B anisotropic isotropic (2) Degree of Anisotropy
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Professor N Cheung, U.C. Berkeley Lecture 14 EE143 F2010 6 (3) Etching Selectivity S Wet Etching S is controlled by: chemicals, concentration, temperature RIE S is controlled by: plasma parameters, plasma chemistry, gas pressure, ) B materal of velocity etching vertical ( v ) A materal of velocity etching vertical ( v S B A AB
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Professor N Cheung, U.C. Berkeley Lecture 14 EE143 F2010 7 SiO 2 Si S SiO2, Si Selectivity is very large ( ~ infinity) SiO 2 /Si etched by HF solution SiO 2 /Si etched by RIE (e.g. CF 4 plasma) S SiO2, Si Selectivity is finite ( ~ 10 ) Selectivity Example
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Professor N Cheung, U.C. Berkeley Lecture 14 EE143 F2010 8 Etching of Steps with a Slope rate etch lateral v etch rate vertical v t time etching Let l v x v t x v t x x x v v t v l v l 1 2 1 2          cot cot substrate start final film v t v x 1 x 2 vt v cot = 1/ tan = b / a * Etching velocity has vertical component v v and lateral component v l
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Professor N Cheung, U.C. Berkeley Lecture 14 EE143 F2010 9 o o 0 90 v v t
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This note was uploaded on 03/03/2012 for the course EECS 142 taught by Professor Ee142 during the Spring '04 term at Berkeley.

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Lec_14 - Professor N Cheung, U.C. Berkeley Lecture 14 EE143...

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