Etching results and comparison of low pressure electron cyclotron resonance and radio frequency discharge sources

Abstract

As the lateral dimensions of ultra-large-scale integration (ULSI) circuit features approach a few-tenths of a micron, demands on the etch transfer of patterns into thin films become increasingly challenging. These demands, combined with the greater susceptibility to create damage, require that new methods are evaluated and compared for etching fine structures in order to establish processing technologies. Submicron polysilicon etching has been performed on a single-wafer etcher using two different sources that sustain intense discharges at low pressure (≲10−3 Torr). The first is an electron cyclotron resonance (ECR) source operated at 2.45 GHz. The second source is a simple helical resonator (HR) structure operated at radio frequencies (RF). The comparisons made between the two sources were the etched profiles of polysilicon, material selectivity, polysilicon etch rates, and etch uniformity. These preliminary experiments show that both systems have great promise to successfully pattern ULSI structures. The advantages and disadvantages of ECR and improved HR sources will be discussed.