What are the adhesion features of photoresists on different wafers?

Adhesion between coating and substrates is a very sensitive issue. Smallest changes of the cleaning procedures or the process parameters can have a fatal impact on the adhesive strength. Silica, silicon nitride, and base metals (such as aluminium, copper) generally exhibit good resist adhesion properties, while adhesion is reduced on SiO₂, glass, noble metals such as gold and silver, as well as on gallium arsenide. For the last-mentioned substrates, adhesion promoters are absolutely required to improve the adhesion strength ( Question 4: Optimal pre-treatment of substrates). If the air humidity is too high (> 60 %), adhesion is also substantially reduced.