Softbake of Photoresist Films

After coating, the resist film contains a remaining solvent concentration depending on the resist, the solvent, the resist film thickness and the resist coating technique. The softbake reduces the remaining solvent content in order to: avoid mask contamination and/or sticking to the mask, prevent popping or foaming of the resist by N2 created during exposure, improve resist adhesion to the substrate, minimize dark erosion during development, prevent dissolving one resist layer by a following multiple coating, and prevent bubbling during subsequent thermal processes (coating, dry etching).