Dynamics of R.F. Discharges for Materials Etching

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

0139956 Lieberman Chemically reactive plasma discharges are widely used in the semiconductor and flat panel display industries for etching and deposition processes: moreover, their use has become critical for very large scale integrated (VLSI) circuit and thin film transistor (TFT) production. High density rf inductively coupled plasma sources are playing an increasing role in processing as feature sizes shrink and as wafer and TFT substrate sizes increase. This proposal is for continuation of research on such discharges. Almost all processing applications require the use of fluorine, chlorine or oxygen-containing feedstock gases, which produces an electronegative discharge plasma containing a high concentration of negative ions. Such discharges have been found to be unstable in certain regimes of discharge pressure and applied radio frequency power, adversely affecting processing performance. The proposed research program has the following components: (a) Experiments will be performed and analytical models will be developed for instabilities in inductively coupled plasma sources with electronega-tive gas feedstocks. The program continues the PIs experiments with more complete diagnostics and improves the chemistry in their present models, which now only qualitatively agree with the experimental results. (b) They will perform general theo-retical studies of electronegative discharges in support of (a) above, continuing a program to develop increasingly accurate models. The experimental studies of electronegative discharge equilibrium, hysteresis, and instabilities will be performed in a planar inductive discharge (transformer-coupled plasma, or TCP) of the conventional type used for VLSI processing. A sulfur hexafluoride/argon feedstock gas mixture allowing control of the negative ion density will be used.