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.

Positive-tone diazonaphthoquinone / novolak (DNQ / novolak) resist was stripped from Si wafer by using a pulsed laser beam from visible to near infrared. Silicon wafer with resist was sunk in water to utilize irradiated laser energy effectively. When the resist was irradiated with the fundamental wavelength of the Nd:YAG laser, the resist was stripped from the Si wafer. No damage could be detected from the processed silicon wafer surface. The resist stripping effect in water condition was improved due to both the thermal expansion of the Si wafer and pressure from water. And also, laser irradiation of wavelength 532 nm, having large photon energy, was found to have a higher resist stripping effect than that of wavelength 1064 nm.

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