Submicrometer optical lithography using a double-layer resist by a single development technology

Submicrometer photoresist patterns having 3:1 vertical/ horizontal aspect ratios have been fabricated on a nonplanar wafer surface with steps of up to 1 µm by a new technology which can use a conventional LSI photolithographic system. The new technology is simply composed of forming the first layer with a blanket exposure including special surface treatment and the second layer, all in the same spinner, with the UV mask exposure, and patterning by a single development step. Although some ambiguities about the mechanism of the stable double-layer formation remain, the technology is proved to have high throughput, stable reproducibility, and fine patterning ability even on a reflective metal such as aluminum.