Neutral-Beam-Assisted Etching System for Low-Damage SiO2 Etching of 8-Inch Wafers

Abstract

A novel neutral-beam-assisted etching apparatus has been developed for large-diameter etching. Neutral radicals from halide molecules and energetic neutral beams are irradiated on the specimen surface. The etching reaction of these neutral radicals is enhanced by neutral-beam bombardment. The neutral-beam source and the neutral-radical source are produced from a magneto-microwave plasma source. These plasmas are arranged in tandem in front of the specimen. This arrangement enables highly uniform supply of neutral radicals over a large area. This etching system was applied to SiO2 etching using Ar and CHF3 mixed gas. The SiO2 etch rate was 76 nm/min, and the etch rate uniformity was within ±7.4% for an 8-inch-diameter specimen and ±3.4% for a 6-inch-diameter specimen. In addition, highly anisotropic etching shapes of submicron patterns were obtained.