Abstract: A novolak resin precursor is composed of bonded phenolic moieties, one of the hydrogen atoms in the o- or p-positions relative to the hydroxy group of each phenolic moiety is substituted with an alkyl or alkenyl group having 1 to 3 carbon atoms, and the other two hydrogen atoms are bonded through methylene bonds. The content of ortho-ortho bonding is 30 to 70% relative to the number of total methylene bonds and the weight average molecular weight of the precursor is 300 to 10,000. A novolak resin is obtained from this precursor, and a positive photoresist composition comprises this novolak resin. The invention provides a positive photoresist composition that comprises less binuclear compounds, suppresses scum formation, is excellent in terms of definition and coating performance and provides a resist pattern having satisfactory heat resistance.

Abstract: A novolak resin precursor is composed of bonded phenolic moieties, one of the hydrogen atoms in the o- or p-positions relative to the hydroxy group of each phenolic moiety is substituted with an alkyl or alkenyl group having 1 to 3 carbon atoms, and the other two hydrogen atoms are bonded through methylene bonds. The content of ortho—ortho bonding is 30 to 70% relative to the number of total methylene bonds and the weight average molecular weight of the precursor is 300 to 10,000. A novolak resin is obtained from this precursor, and a positive photoresist composition comprises this novolak resin. The invention provides a positive photoresist composition that comprises less binuclear compounds, suppresses scum formation, is excellent in terms of definition and coating performance and provides a resist pattern having satisfactory heat resistance.