The mechanism of overhang formation in a diazide/novolak photoresist film by the chlorobenzene soak process for lift-off stencil fabrication is investigated by gel permeation chromatography. The experimental results show that overhang profile formation is controlled mainly by the removal of photoactive compounds (PAC’s) from a resist film. The amount of PAC loss within the modified region in a resist film must be precisely controlled to form a desired overhang profile. The amount of PAC loss depends mainly upon the molecular weight of the PAC’s and the kind of soaking solvent used.
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Yoshiaki Mimura (1986) studied this question.