Hh. Richter et al., SILICON DRY-ETCHING IN HYDROGEN IODIDE PLASMAS - SURFACE DIAGNOSTICS AND TECHNOLOGICAL APPLICATIONS, JPN J A P 1, 36(7B), 1997, pp. 4849-4853
We have investigated hydrogen iodide (HI) as an alternative to convent
ional chlorine or bromine chemistry for dry etching. Plasma exposed Si
surfaces show damage, as revealed by photoluminescence studies. These
defects can be annealed out by thermal treatment at 550 degrees C. We
have developed an anisotropic polysilicon gate etch process for 0.35
mu m MOS technology based on iodine chemistry. The selectivity between
polysilicon and oxide is determined as a function of various process
parameters. Decreasing the rf source power from 350 to 100 W increases
the selectivity between polysilicon and SiO2 from approx. 30:1 to 180
:1. Profiles with a degree of anisotropy close to unity can be obtaine
d without trenching or other undesirable anomalies. Iodine-based plasm
as are characterized by very low self-biased voltages, typically less
than 70 V.