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

The process for forming positive resist patterns on a substrate comprising:

• A. coating said substrate with a radiation composition useful as a positive-working photoresist, said composition comprising an admixture of at least one o-quinonediazide compound and a novolak resin composition having a weight average molecular weight from 3,000 to 40,000, having ortho-ortho bonding of between 55% and 70% of the methylene bonds between the phenolic moieties in the novolak, a time to clear of at least 20 seconds per micron and 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.degree. C. to about 200.degree. C. and at a reaction pressure of about 2 atmospheres 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 15 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;
• (2) then reacting said phenolic oligomer with a second aldehyde source and an optional second phenolic source at a temperature from about 80.degree. C. to about 150.degree. C. to form a phenolic novolak having a weight average molecular weight of 3,000 to 40,000, having ortho-ortho bonding of between 55% 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;
• and wherein the amount of said o-quinonediazide compound being about 5% to about 40% by weight and the amount of said binder resin being about 60% to 95% by weight, based on the total solid content of said radiation-sensitive composition;
• B. subjecting said coating on said substrate to an image-wise exposure of radiant energy;
• and
• C. subjecting said image-wise exposed coated substrate to a developing solution wherein the exposed areas of said exposed coating are dissolved and removed from the substrate, thereby resulting in a positive image-wise pattern in the coating.