“Wafer Bow” is the result of the difference in stress between the cured SUEX layer and the substrate because the resin film has shrunk during cure but also has been firmly attached to the wafer. If the stress is too high the SUEX will delaminate from the substrate leading to defects. This stress is caused by the shrinkage of the resist film during the PEB and the rate of cooling after the PEB. SUEX and ADEX films will bow after cure but adjusting the process conditions can minimize this.  Stress can be reduced, but not eliminated, by using a lower PEB temperature, conducting the PEB in an oven not on a hot-plate, and slowly cooling the PEB’d cured SUEX coated substrate to under 50C over at least 3-5 hours, preferably overnight. The slow cooling is highly effective but not always sufficient depending on the adhesion of the SUEX to the substrate, which is dependent on the substrate material (see the Pre-Processing Conditions section above).