Characterization of etch-induced damage for Si etched in Cl2 plasma generated by an electron cyclotron resonance source

Abstract

A Cl2 plasma generated by a multipolar electron cyclotron resonance source is used for Si etching, and the effects of etch-induced damage are studied using Schottky diodes and metal–oxide–semiconductor (MOS) capacitors to investigate the effects of dry etching on device performance. The Schottky diode characteristics improved with increasing microwave power when the self-induced bias voltage was kept at −150 V, but degraded with increasing microwave power at −50 V. The diode characteristics were close to an ideal diode when low rf power, high Cl2 percentage, and close source distance were used. Varying the sample temperature during etching from −130 to 350 °C has no effect on the Schottky diode characteristics. The damaged layer was removed by reactive chlorine radicals and by wet etching. After removing 60 nm from the dry-etched surface, the Schottky diode performance was comparable to that of an ideal diode. Annealing at 800 °C in Ar for 5 min has similar effects. When the oxide was etched and MOS capacitors were fabricated on the etched oxide, no electrical degradation was observed. When Si was etched and the etched surface was oxidized to form MOS capacitors. The breakdown field was found to decrease with high microwave power, high rf power, and low Cl2 concentration. However, dry etching has no influence on fixed charge density, and the interface state density only increases slightly from 1.2 to 2.5×1010 cm−2.