Improvements of Resolution and Surface Roughness using Alkaline Treatment of Photoresist Surface in High-Density Optical Disk Mastering

Abstract

In the next-generation optical disk using blue laser diodes, the track pitch will be reduced to 0.3 µm, that is about half of the track pitch of digital versatile disks. To realize such high-density optical disks, it is important to develop a high-density optical disk mastering technique. In particular, in this mastering technique, two major improvements, resolution improvement and surface roughness reduction, are required. In this work, we fabricate grooves with track pitches of 0.28–0.40 µm land/groove using an ultraviolet laser beam recorder, and investigate the influences of an alkaline treatment of positive photoresist surface on the resolution and the surface roughness of the grooves. We confirm experimentally that the alkaline treatment is effective for the resolution improvement and the roughness reductions of the surface and sidewall. We also show that these effects are attributed to the contrast enhancement and the decrease of photoresist film thickness loss.