Sub- 100 nm nanolithography and pattern transfer on compound semiconductor using sol-gel-derived TiO₂ resist

Typical methods for sub- 100 nm compound semiconductor patterning are based on indirect pattern transfer using Si O2 or Si N4 as intermediate masks, which inevitably increase the complexity of pattern transfer and cause potential damage to samples. We present an approach of direct pattern transfer using Ti (O Bun)4 sol-gel-derived Ti O2 resist as mask. The optimal dose of Ti O2 resist for E-beam lithography is ∼220 mC cm2. The sample InP compound semiconductor etching selectivity to Ti O2 resist is as high as 9:1 with aspect ratio of over 30:1. Various sub- 100 nm scale inductively coupled plasma etching patterns are obtained with a high-quality etching profile. The smallest feature is as small as 20 nm wide with a depth of over 600 nm.