Realizing multimodal lithography effects by adjusting laser exposure power ranges for TeO_x inorganic photoresist

Abstract

Suboxide chalcogenide thin films like TeO x are promising inorganic lithography materials. Different from previous reports of single-mode lithography based on TeO x films at low laser power, this study proposes multimodal lithography effects at low, medium, and high laser power ranges. The TeO x films were fabricated by reactive magnetron sputtering, exhibiting super smooth surface with an RMS 0.33 nm. The lithographic performance was researched using a laser direct writing system with a wavelength of 780 nm. The experiment results showed that different kind of lithographic patterns were achieved by changing laser power ranges. At low exposure powers (5 mW to 9 mW), TeO x film transforms from amorphous to crystalline, generating patterns with single-trench since only the crystalline state dissolves in alkaline developers. At medium exposure powers (10 mW to 15 mW), the center of the laser spot that has greater power turns the film from amorphous to crystalline and then back to amorphous due to the rapid quenching process, while the outer region cools slowly to form crystalline, resulting in the patterns with double-trenches, with feature size 119 nm (about 1/7 λ). At high exposure powers (>16 mW), the laser power is capable of ablating the TeO x film, resulting in the ablation and redeposition patterns. Therefore, multimodal lithographic nano-patterns on the same TeO x photoresist film can be realized with only one lithography process by precisely manipulating the laser power ranges, which has significant implications in the fields of nano-manufacturing and optical storage.