An RF sheath model for high plasma density equipment simulations

Abstract

Summary form only given. In modeling plasma etching equipment, accurate representation of the RF sheath is required to properly simulate the DC bias, ambipolar field and electron heating. From a practical standpoint, numerically resolving the thin sheath encountered in high plasma density reactors ([e]>10/sup 11/-10/sup 12/ cm/sup -3/) in computer models of these devices is not feasible. We have developed a sheath model which can be solved self-consistently within the framework of a 2-dimensional plasma equipment model. Due to the fact that the sheath is thin compared to the dimensions of interest, the sheath locally appears to be 1-dimensional. The sheath simulation we developed takes advantage of this scaling. It consists of a 1-dimensional local model which is implemented at each mesh point along the boundary of the reactor. The sheath model tracks the charging/discharging of the sheath during the RF cycle. The sheath model has been incorporated into the fluid and electron Monte Carlo modules of a 2-dimensional hybrid model for inductively coupled plasmas (ICP). Results will be presented for plasma potential profiles and electron heating in ICP reactors in which the substrate is independently biased.