ASYMMETRIC MICROTRENCHING DURING INDUCTIVELY-COUPLED PLASMA OXIDE ETCHING IN THE PRESENCE OF A WEAK MAGNETIC-FIELD

When fabricating microscopic features in SiO2 layers using low pressur e, high-density fluorocarbon plasmas, microtrenching has commonly been observed. Microtrenching has been explained either as due to ion scat tering from sloped sidewalls or negative charging of the sidewalls by electrons, and the influence of the associated electric held on ion tr ajectories. In this work, we show that a weak magnetic held produces a significant asymmetry in microtrenching. Our results demonstrate unam biguously that electron-based sidewall charging is to a significant ex tent responsible for microtrenching, and, more generally, that differe ntial charging is an important effect in microstructure fabrication us ing high-density plasmas. (C) 1998 American Institute of Physics.