This preview shows pages 1–6. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Coupled Mass Transport and Reaction in LPCVD Reactors Coupled Mass Transport and Reaction in LPCVD Reactors Dilute A in B e.g., SiH 4 in H 2 2R w 2R t r z z= /2 z= /2 r=0 r=R w c=c b Separate reactor into two regions, intrawafer & annular Continuity Continuity Eqn Eqn : Convection : ConvectionDiffusion DiffusionReaction Reaction Eqns Eqns Assumptions ! Dilute species i in major carrier gas (e.g., H 2 ) i=SiH 4 ! Isothermal ! Constant D i and density Assume stagnant in the intrawafer region ~ 0 No rxn in the gas Steady state t c R c u c D i i i i i = + r 2 Equations and Boundary Conditions for the Equations and Boundary Conditions for the intrawafer intrawafer region region 1 2 2 = + z c r c r r r 2 2 / z @ r z c D / z @ r z c D R r @ c c r @ r c s s w b = = = = = = = = r s = surface reaction rate (net loss rate of SiH 4 ); related to the deposition rate ! If r s is linear in c then there is an analytic solution ! If r s is nonlinear we have to seek numerical solution Approximate solution Approximate solution Fin Approximation Fin Approximation ! Take r s =kc & average over z direction ! Averaging over the small dimension (z) is called the fin approximation: an approximation which is very good for 2D regions with high aspect ratio (R/ ) 2 1 1 1 1 2 2 2 2 2 2 2 2 = = + = + = + = = kC r C r r r D D kC D kC r C r r r z C z C r C r r r dz z c dz r c r r r / z / z / / / / = = 2 2 2 2 2 2 1 / / / / / / dz ) z , r ( c dz dz ) z , r ( c ) r ( C let volume area surface R R w w = = 2 2 2 2 note Nondimensionalization Nondimensionalization & Solution & Solution D kR D kR c C R r w w b w 2 2 2 2 2 1 = = = =...
View
Full
Document
This note was uploaded on 12/29/2011 for the course CHE 142 taught by Professor Ceweb during the Fall '09 term at UCSB.
 Fall '09
 Ceweb
 Reaction

Click to edit the document details