Novel novolak resins using substituted phenols for high-performance positive photoresist

摘要

Abstract: The present paper describes the effects of methyl groups, substituted on aromatic rings of novolak resins, on positive photoresist characteristics. And some aspects of the dissolution mechanism of the novolak-quinonediazide resist system are also elucidated. We have found that the use of m-methyl substituted phenols, especially 3,5-dimethyl substituted phenols, is effective to increase the ratio of intra-/inter- molecular hydrogen bonds, and the ratio is controllable by selecting phenolic monomer composition. Our study has also revealed that there is an optimum range of the ratio for the resist performance, mainly depending on the PAC (Photo Active Compound)'s structure and the resin itself. In order to understand this phenomenon, we carried out several experiments in respect of the dissolution behavior of some selected novolak-inhibitor systems and found that the interaction between o-o units of the novolak resin and the NQD moiety in the PAC structure plays a important role on an alkaline dissolution mechanism. The resists adopting these novel novolak resins with the optimum hydrogen bond ratio show resolution of 0.34 $mu@m L/S with excellent pattern profile on an i-line stepper (NA $EQ 0.50) and good thermal stability.!