Optimization of Ge-Sb-Sn-O Films for Thermal Lithography of Submicron Structures

Ge–Sb–Sn inorganic resist materials are developed to fabricate submicron structures that have a pattern size smaller than 150 nm and a depth over 100 nm via thermal lithography. The materials are sputtered under Ar:O2 atmospheres by varying O2 flow rate and Ge level. Both increasing O2 flow rate and Ge level can decrease the extinction coefficient, k, at 405 nm wavelength to within a range of 0.58–0.89. Films with appropriate absorption of laser power are chosen to optimize exposure and development processes. A continuous 2.0 mW laser power is used to crystallize the Ge–Sb–Sn–O films. 175-nm-wide and 107-nm-deep grooves are formed after development using alkaline solutions. The 175 nm width is well below half of the 380 nm diffraction limit. A laser pulse strategy is also developed to fabricate discrete dot patterns. By shortening the write 1 time to 0.5 T (7.8 ns), the dot patterns change from oval to round shape. A pit pattern as small as 140 nm diameter and 100 nm depth is achieved.