Effects of Cascade Reactions in CVD: COMSOL Model

Assumed electron density profile
Parent molecule:
HMDSO= (CH3)3-Si-O-Si-(CH3)3

Simplified cascade reactions assumed in the model.
Reaction 1 to produce org/inorg. hybrid precursors
HMDSO + e --> (CH3)3SiOSi + 3CH3
Reaction 2 to produce inorganic precursors
(CH3)3SiOSi + e --> SiOSi + 3CH3

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Density profile of parent gas
i.e. HMDSO

Density profile of by-product
i.e. CH3
HMDSO molecules are going to run out except the area near the source-gas feed port in the steady-state condition. Since CH3 radicals are not assumed to be decposited, their density profile becoems uniform in the steady-state condition.

Density profile of the 1st product
i.e. (CH3)3SiOSi

Density profile of the 2nd product
i.e. SiOSi
Since the parent molecules are running out except the area near the gas-feed port, the 1st product distribute only around the gas-feed port. Namely, organic/inorganic hybrid precursors contribute only on the substrate surface being close to the feed port. The source species for the 2nd product is the 1st product. Since density profile of the 1st product is relatively uniform compared to that of parent HMDSO, the density profile of the 2nd product becomes rather uniform.