IMPORTANCE OF GRID REFINEMENT IN NUMERICAL MODELING OF CHEMICAL VAPOR DEPOSITION PROCESSES

Abstract

The importance of grid resolution near the substrate surface for accurate prediction of the deposition rates in chemical vapor deposition modeling has been demonstrated. The exercise is conducted through numerical modeling of the chemical vapor deposition of silicon in an atmospheric-pressure, circular, impinging-jet reactor. Silicon is deposited from gaseous silane (SiH 4 ) supplied in a dilute condition premixed in a hydrogen carrier gas. The substrate temperature is kept fixed at 1,333 K. The model includes variable fluid properties and buoyancy forces in the hydrodynamic model. The Bousinesq approximation is not used because the temperature gradient is large. In addition to the hydrodynamic and thermal solution, both gas-phase reactions in the bulk gas and surface reactions on the susceptor are included in the model. The mesh-independent solution and the deposition rate of silicon on the wafer surface are presented. It is observed that a very fine mesh near the substrate surface, within the concentration boundary layer for the intermediate species such as silylene (SiH 2 ), is required to establish grid independency and accurate prediction of the deposition rate. For the specific deposition process modeled in this study, about 7 control volumes had to be placed within the SiH 2 concentration boundary layer at the substrate surface.