Numerical analysis for optimization of the sidewall conditions in a capacitively coupled plasma deposition reactor

Abstract

Capacitively coupled plasma (CCP) is mainly being used in the semiconductor industry for plasma-enhanced chemical vapor deposition of uniform thin films. Because a discharge volume in the standard configuration of a CCP reactor is surrounded not only with electrode surfaces but also with a sidewall, the sidewall conditions affect the deposition rate profiles noticeably. By toggling the boundary condition from a grounded conductor to dielectrics with the variations of the relative permittivity and the thickness, we compare the spatial profiles for the species densities, ionization rate, power absorption, and particle fluxes in a SiH4/He CCP. Through the SiH4/He CCP fluid model, it is found that a thick and low-permittivity insulator achieves the most uniform plasma density distribution in the interelectrode region and, consequently, the best uniformity in the deposition rate profile of an a-Si:H film. As a validation, experimental results are compared with fluid modeling results, and they match well. For additional validation, a particle-in-cell simulation of pure Ar discharge is also performed. Although simulation conditions are totally different from those of the SiH4/He fluid model, it consistently demonstrates that the dielectric sidewall brings about more uniform distributions of the plasma parameters than the grounded sidewall.