Numerical Analysis of Gas Diffusion in CVD Chambers

In this study, a numerical simulation is performed to analyze the structural nonuniformity caused by the wafer gate in a chemical vapor deposition (CVD) chamber. The effect of the process gap on the O3 mole fraction, flow velocity, and wall shear stress is investigated. Increasing the gap improves the wafer surface uniformity from 0.138% to 0.122% as the gap approaches 50 mm. The difference in the O3 mole fraction at the gate is minimal, thus signifying mild diffusion. The wall shear stress increases up to 3.91 times at the gate floor under wider gaps, whereasit decreases by 6% on the wafer. A wider gap decreases the deposition rate but enhances the cleaning efficiency. To reduce nonuniformity, a process gap of 10 mm or less is recommended for CVD processes, whereas a gap of 50 mm or more significantly improves cleaning efficiency.