Novolak Design For High Resolution Positive Photoresists(II): Stone Wall Model For Positive Photoresist Development

Abstract

The relationship between the molecular weight distribution(Mw/Mn) of novolak resins and performance of positive photoresists was investigated from the standpoint of the image formation process. Dissolution rates were measured on photoresists containing cresol-novolak resins having various Mw/Mn values. It was found that there is an optimum Mw/Mn value to exhibit high resolution capabilities. On the basis of experimental results, we discuss the roles of high molecular weight components and low molecular weight components of novolak resins in resist performance. Finally, we propose a new model for positive photoresist development---"Stone wall model", which is consistent with our azocoupling model for the dissolution inhibition mechanism. This model is applicable to design novolak resins for high resolution positive photoresists.