Development of neutral-beam-assisted etcher

Abstract

Advanced neutral-beam-assisted etching machines have been developed for very low-damage SiO2 etching. The etching reactions are enhanced by a neutral beam and neutral radicals. This enhancement effect was first demonstrated by a prototype etcher equipped with independent sources for the neutral beam and neutral radicals. Next, a simple co-axial type etcher was developed. Only one co-axial discharge tube generates two cylindrical plasmas: the inner one is a neutral beam source; the outer one is a neutral radical source. The typical SiO2 etch rate was 60 nm/min. To further increase the etch rate, the beam and etching characteristics were studied in detail. We found that the neutral radical density had to be increased. To achieve a high etch rate, a tandem type etcher was designed and developed. It generates two plasmas side by side in only one discharge tube. This etcher can supply high-density uniform neutral radicals from one of the tandem plasmas very close to the specimen. This new etcher is expected to be a significant advance toward the development of a practical, low-damage, high rate etcher.