We investigated the swelling behavior of dry film photoresist in rinse process after development by varying the hardness of water. We inspected the appearance of sidewalls and the foot of the resist. We also measured the depth of once swollen resist using a FIB (focused ion beam) and analyzed the chemistry of the resist after rinse using an XPS (X-ray photoelectron spectroscopy). We experimentally proved that divalent cations such as Ca2+ and Mg2+ in hard water could be exchanged with Na+ on the resist surface and quench swelling of the exposed resist in rinse. This study indicates that the use of hard water in rinse process may result in better line definition and resolution in PCB (printed circuit board).

SEM analysis of 193-nm photoresist profiles after cross section is seen to be critical because of the shrinkage of the photoresist material during electron beam exposure. With a combination of AFM and SEM investigations on AuPd sputter prepared samples an averaged shrinkage behaviour of height and width of resist lines of varying geometry can be quantitatively determined. This helps to a more accurate determination of resist line profiles.