12 CVD 10

12 CVD 10 - Chemical vapor deposition This lecture covers...

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Deposition is used extensively instead of “growth” in deposition all film components are contained in the reactant gases, e.g. deposition of silicon nitride. in growth, substrate is reacted with gas phase species to form film, e.g. oxidation of silicon (lecture 11). CVD is used for dielectrics (not gate and field oxides), epi, poly-Si, and some metals. Chemical vapor deposition This lecture covers how materials are deposited from the gas phase…
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Chemical Vapor Deposition (CVD) AP CVD a tmospheric p ressure rapid deposition LP CVD l ow p ressure (few hundred mTorr) generally good conformality PE CVD p lasma e nhanced (glow discharge)
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Vacuum processes Since many CVD processes occur at reduced pressure, here is some useful info… Pressure conversions … 1 atm = 14.7 lb/in 2 = 101,325 Pa = 760 mm Hg = 760 torr 1 Pa = 1 N/m 2 = 7.5 mtorr Mean free path (m) = 0.05/P(mtorr) P(mtorr) mfp Low pressure means high gas phase 760,000 65 nm diffusivity - good transport 100 500 μ m 1 50 mm 0.001 50 m What’s the relationship between mfp and gas phase diffusivity?
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Basic CVD modeling Gas phase reaction - generally avoided - only used in “plasma enhanced” processes Transport to Surface - 1 Absorption on Surface - 2 Reaction - 3 Desorption - 4 Transport from Surface - 5 1 2 3 4 5 Reactants By-products CVD generally follows a 5 step series of events Mostly diffusion! Arrhenius! X
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CVD film-growth model Gas Film C s C g F 1 F 2 Simple model only considers reactant flux (F 1 ), and reaction flux (F 2 ) – assumes that absorption, desorption and product transport are not major factors overall!
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k s : Chemical surface reaction By Fick’s First Law h g : Gas-phase mass- transfer ) ( 1 s g C C F - ) ( 1 s g g C C h F - = s C F 2 s s C k F = 2 kT E s A e k k / 0 - = Steady state condition F F F = = 2 1
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This note was uploaded on 05/11/2010 for the course EEE EEE-530 taught by Professor Kozicki during the Spring '10 term at ASU.

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12 CVD 10 - Chemical vapor deposition This lecture covers...

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