Photo Resist Processing
Processing of resist is a common process in the manufacture of Semiconductors, MEMS or opto-electronic devices, commonly referred to as resist stripping or resist ashing. The method of choice utilizes a plasma system typically with microwave excitation, as it offers the best combination of high stripping rates and low device damage. This dry stripping process can be used to completely remove the resist or do a partial removal only for special requirement of the subsequent process step.
Depending on the nature of the device and the requirement for cost effective production, the wafers are processed in batches of 25 or even 50 wafers for wafer sizes up to 200mm. The advantages of this processing mode are of course the unbeatable cost of ownership and the possibility of removing the resist from both wafer sides simultaneously.
The advanced control for batch systems allows processing the wafers at a pre-set temperature, which is monitored during process using an IR-spectrometer.
Processing in single wafer mode is preferred for advanced device requirements and 300mm wafers, as it provides better control for process uniformity and end point detection.
Most commonly the process is based on oxygen plasma, sometimes in combination with specialty gasses for special applications and requirements. In case of layers sensitive to oxidation, hydrogen can be used as alternative process gas to prevent oxidation.