Two-dimensional modeling of pulsed inductively coupled plasmas with and without a substrate bias

Abstract

Summary form only given. Pulsed electronegative plasmas are promising candidates for improving etch selectivity and anisotropy during microelectronics fabrication. With pulsed sources, plasma induced damage can be suppressed by equilibrating the flux of positive and negative charge carriers to all surfaces of a feature. We have developed a two dimensional hybrid model using moderate computational parallelism to investigate pulsed inductively coupled plasmas (ICPs) with and without RF substrate biases. Using this computational technique we simultaneously resolve kinetic electron energy transport, fluid equations for continuity, momentum and energy, and electromagnetic wave propagation on separate processors. This methodology enables the hybrid approach to model long term transients. In this paper we report on investigations of pulsed ICPs in electronegative gas mixtures, including Ar/Cl/sub 2/, at pressures of 10s mTorr. Results of a comparison of plasma properties with and without substrate biases will be discussed. We found that the transition from an electron-ion to a negative ion-positive-ion plasma typically occurs late in the afterglow. Negative ions are not extracted until electron densities decay to below the ambipolar limit. We found that with a substrate bias, significant electron heating can occur in the late afterglow as a result of the thickening of the sheath with the decrease in electron density. Consequences of varying pulse repetition frequency and duty cycle will also be discussed.