KrF Excimer Laser Process: Lateral and Surface Modification for Enhancing Resist Contrast

A KrF excimer laser process, “lateral and surface modification for enhancing resist contrast” (LASER), combining alkali treatment before exposure and step development was investigated to improve the resolution capability of a novolac-diazoquinone-type positive tone photoresist. It has been found that a thin insoluble layer formed on both the resist surface and side wall maintains the resist thickness and the resist profile during development. As a result, a 0.35-µm line-and-space pattern with a steep profile can be obtained. The insoluble layer formation is due to the concentration of a photoactive compound, which is caused by the water rinse processes after the alkali treatment and the first step development.