A SELECTION PRINCIPLE OF PHENOLIC-COMPOUNDS FOR NOVOLAK RESINS IN HIGH-PERFORMANCE POSITIVE PHOTORESISTS

The relationship between resist performance and the kinds of phenolic compounds for novolak resins was investigated from the standpoint of the image formation process. Dissolution rates were measured on photoresists containing novolak resins made from various phenolic compounds including phenol, cresol, ethylphenol, butylphenol, and their copolymers. It was found that there are suitable combinations of phenolic compounds to exhibit high resist performance. On the basis of the experimental results, we discuss the effect of the kinds of phenolic compounds on the dissolution characteristics and the structure of novolak resins. Finally, we propose a selection principle of phenolic compounds for novolak resins useful to design high performance positive photoresists.