High ortho-ortho bonded novolak binder resins and their use in a process for forming positive resist patterns

摘要

A phenolic novolak composition prepared by a process comprising the steps of: (1) reacting a first phenolic monomer comprising a major portion of at least one trifunctional phenolic monomer with a first aldehyde source in the absence of a catalyst at a reaction temperature from about 100 DEG C. to about 200 DEG C. and at a reaction pressure of about 2 to about 15 atmospheres to form a phenolic oligomer having a weight average molecular weight from about 500 to about 2,000, having ortho-ortho bonding of about 55% to about 75% of the methylene bonds between the phenolic moieties; and having a time to clear of less than 125 seconds per micron; wherein the mole ratio of said first aldehyde source to said first phenolic monomer is from about 0.3:1.0 to about 0.55:1.0; and (2) then reacting said oligomer with an optional second phenolic source and a second aldehyde source at a temperature from about 80 DEG C. to about 150 DEG C. to form a phenolic novolak having a weight average molecular weight of 3,000 to 40,000, having ortho-ortho bonding of between 50% and 70% of the methylene bonds between the phenolic moieties, and having a time to clear of at least 20 seconds per micron; wherein the mole ratio of said second aldehyde source to said total phenolic moieties is less than about 0.8:1.0.