Novolak resins and their use in radiation-sensitive compositions wherein the novolak resins are made by condensing 2,6-dimethylphenol, 2,3-dimethylphenol, a para-substituted phenol and an aldehyde

A radiation-sensitive composition useful as a positive-working photoresist dissolved in a solvent comprising an admixture of:

• (A) a photoactive compound;
• (B) an alkali-soluble novolak binder resin made by the condensation reaction of a mixture of phenolic monomers with at least one aldehyde source, said phenolic monomers consisting of:
• (1) about 2-18% by weight of said mixture being 2,6-dimethylphenol;
• (2) about 55-75% by weight of said mixture being 2,3-dimethylphenol;
• and
• (3) about 16-40% by weight of said mixture being a para-substituted lower alkyl phenol selected from the group consisting of 3,4-dimethylphenol, para-cresol, and para-cresol dimer;
• the amount of said aldehyde source being at least a stoichiometric amount to react with all of said phenolic moieties;
• and wherein the photoactive compound is from about 5% to about 40% by weight of the solids in said radiation-sensitive composition;
• and the alkali-soluble novolak resin is from about 95% to about 60% by weight of the solids in said radiation-sensitive composition.