Measurements and consequences of nonuniform radio frequency plasma potential due to surface asymmetry in large area radio frequency capacitive reactors

In large area reactors, a local asymmetry of the electrode area, due to lateral grounded walls, causes a perturbation in rf plasma potential, due to the redistribution of lateral rf current, which propagates along the resistive plasma between capacitive sheaths. This perturbation can be described by a telegraph equation, for which a typical damping length can be determined. In this study, the existence of this rf plasma potential perturbation is confirmed using electrostatic surface probe measurements in argon plasma. Furthermore, uniformity analysis of a-Si:H thin film deposited using silane plasma have shown that this nonuniform rf plasma potential can have a strong effect on the uniformity of plasma enhanced chemical vapor deposition processes. It is also shown that this perturbation and its effect on the deposition uniformity can be suppressed by symmetrizing the reactor walls. (c) 2005 American Vacuum Society.