Stripping of the Positive-tone Diazonaphthoquinone / Novolak Resist using Laser Irradiation from Visible to Near Infrared Wavelength

摘要

Laser resist stripping (1) for the positive-tone diazonaphthoquinone (2) / novolak resist (3) was successful without an occurring the laser damage (5) to a Si wafer (6). The fundamental (1064 nm) of pulsed Nd:YAG laser irradiation (4) in the water can improve the resist stripping effect as compared with that of atmosphere irradiation. In the case of the laser irradiation in water, the heat that occurred at Si wafer surface reaches the water on the resist surface across a thin resist layer. The effect of this heat occurs at the interface between resist surface and the water. By momentary cubical expansion of the water at the resist surface, the resist catches the pressure from water. The water on the resist surface will be worked like a wall rejecting a pressure. The resist stripping effect in the water condition was thought to improve by both thermal expansion of the Si wafer and pressure from the water. And also, a laser irradiation of 532 nm having large photon energy was found to be higher resist stripping efficiency than that of the wavelength 1064 nm.