Consideration of photoresist outgassing for MeV ion implantation and cryopump selection

Photoresist outgassing is one of the inherent issues of application of high energy (MeV) ion implantation due to the use of thick photoresist and relatively low dose (low E13 for typical well formations) compared to the critical dose of carbonization of the photoresist. In the present work, photoresist outgassing characteristics of high energy (MeV) ion implantation have been investigated from various points of view, i.e., collision processes of incident ions with various gases, dynamical analysis of residual gases during actual implantation, end station pumping speed effect, etc. One of the conclusions drawn from this work is that pumping speed of high-mass species is critical in reducing the amount of dose shift due to photoresist outgassing even though H₂ is a dominant species during outgassing process