Etching processes and characteristics for the fabrication of refractory x-ray masks

Abstract

Refractory x-ray masks for a wide variety of pattern types were fabricated using tantalum silicon as the absorber material. Both positive (Shipley UVIII®) and negative (Shipley SNR200®) chemically amplified electron beam resists were exposed and the patterns transferred into a silicon oxynitride hardmask. The amorphous TaSi absorber was then etched using a Cl2/O2 reactive ion etch (RIE). From a mask manufacturing standpoint, the challenge is etching the wide variety of feature types that commonly occur in device processing. The overall etch process was characterized for the formation of both freestanding lines (using negative electron beam resist) and narrow trenches (using positive resist). RIE lag, feature shape dependence, and cross-mask uniformity in the etch bias were characterized for feature sizes down to 125 nm. The etch process has been implemented in a pilot line environment and is being used to produce product masks.