A positive photoresist adhesion promoter for PMMA on GaAs MESFETs

The positive photoresist as an adhesion promoter for polymethylmethacrylate (PMMA) resist on GaAs is presented. It can be used with PMMA for both e-beam direct write patterning and deep-UV patterning levels. Using only 60 Å of positive photoresist as the interfacial adhesion promoter, the integrity of the PMMA is maintained during either wet chemical etching or plasma etching. The photoresist will clean up with standard metallization liftoff techniques. While only the results of adhesion with PMMA are reported, this technique can be applied to other resist systems as well