Effects of process parameters and chamber structure on plasma uniformity in a large-area capacitively coupled discharge

Abstract

For 13.56 MHz large-area capacitively coupled plasma (CCP) discharges, the increase of plasma enhanced chemical vapor deposition (PECVD) chamber radius to 500 mm is likely to exacerbate the impact of edge effect. In this paper, based on COMSOL Multiphysics, a two-dimensional fluid model combined with the full set of Maxwell's equations is developed and validated. Simulation results indicate that the existence of the edge effect destroys the radial plasma uniformity of large-area discharges. The decrease of the RF voltage amplitude or chamber pressure causes an improvement in plasma radial uniformity, but the plasma density reduces. Only by adjusting the process parameters, the optimization of plasma uniformity degree is not obvious and the edge effect cannot be eliminated. Furthermore, the chamber structure has a significant influence on plasma uniformity. And enlarging the electrode gap or extending the grounded electrode length could help to obtain a uniform deposition by impairing the edge effect. The experiment results show that the film uniformity is improved by optimizing. The results obtained in this work could play a useful role in weakening the edge effect and raising the plasma uniformity of large-area CCP discharge.