A Novel Thermally Evaporated Etching Mask for Low-Damage Dry Etching

Dry etching is widely used for nanofabrication and it requires reliable etching masks. However, hard dry etching masks usually need high temperature and/or plasma deposition, which may cause damage to temperature-sensitive materials and semiconductor surface. Here, we develop a novel etching mask material, silicon monoxide (SiO), which is thermally evaporated and hence can avoid such drawbacks. The etching selectivity of evaporated SiO is shown to be higher than 50:1, comparable to sputtered SiO
₂
. A nanochannel device, called self-switching diode (SSD), is fabricated to evaluate the mask-deposition-process damage because of its high sensitivity to surface states. In comparison to commonly used sputtered SiO
₂
and polymethyl methacrylate mask, the SSD fabricated using evaporated SiO exhibits the highest channel conductance, the strongest nonlinearity, and the best high-frequency performance. Hall measurements also reveal that the carrier mobility of nanochannels etched with SiO mask is twice that of similar channels with SiO
₂
mask.