Abstract: A phenol novolak resin has a peak intensity ratio of ortho-ortho bond (o-o)/ortho-para bond (o-p)/para-para bond (p-p) in a resin structure not substantially varying in each molecular weight fraction and has a weight average molecular weight (Mw) of 3000 to 20000 in terms of polystyrene, which peak intensity ratio is detected by 13C-NMR analysis. The phenol novolak resin can form both dense pattern and isolation pattern with good shapes in the formation of a fine resist pattern of not more than 0.35 ?m and has satisfactory sensitivity, definition, and focal depth range properties, and has a resin composition being uniform in each molecular weight fraction. A process for producing the phenol novolak resin, and a positive photoresist composition using the resin are also provided.

Abstract: A phenol novolak resin has a peak intensity ratio of ortho-ortho bond (o-o)/ortho-para bond (o-p)/para-para bond (p-p) in a resin structure not substantially varying in each molecular weight fraction and has a weight average molecular weight (Mw) of 3000 to 20000 in terms of polystyrene, which peak intensity ratio is detected by 13C-NMR analysis. The phenol novolak resin can form both dense pattern and isolation pattern with good shapes in the formation of a fine resist pattern of not more than 0.35 &mgr;m and has satisfactory sensitivity, definition, and focal depth range properties, and has a resin composition being uniform in each molecular weight fraction. A process for producing the phenol novolak resin, and a positive photoresist composition using the resin are also provided.

Abstract: A positive photoresist composition includes (A) an alkali-soluble resin, in which part of phenolic hydroxyl groups is protected by an acid-decomposable group; (B) a quinonediazide ester; and (C) a compound which generates an acid upon irradiation of light with a wavelength of 365 nm. This positive photoresist composition can form a fine pattern of about 0.35 &mgr;m in the photolithographic process using i-ray (365 nm), is excellent in focal depth range properties in such an ultrafine region, and has a high sensitivity.

Abstract: A positive photoresist composition includes (A) an alkali-soluble resin, in which part of phenolic hydroxyl groups is protected by an acid-decomposable group; (B) a quinonediazide ester; and (C) a compound which generates an acid upon irradiation of light with a wavelength of 365 nm. This positive photoresist composition can form a fine pattern of about 0.35 &mgr;m in the photolithographic process using i-ray (365 nm), is excellent in focal depth range properties in such an ultrafine region, and has a high sensitivity.

Abstract: A phenol novolak resin has a peak intensity ratio of ortho-ortho bond (o-o)/ortho-para bond (o-p)/para-para bond (p-p) in a resin structure not substantially varying in each molecular weight fraction and has a weight average molecular weight (Mw) of 3000 to 20000 in terms of polystyrene, which peak intensity ratio is detected by 13C-NMR analysis. The phenol novolak resin can form both dense pattern and isolation pattern with good shapes in the formation of a fine resist pattern of not more than 0.35 &mgr;m and has satisfactory sensitivity, definition, and focal depth range properties, and has a resin composition being uniform in each molecular weight fraction. A process for producing the phenol novolak resin, and a positive photoresist composition using the resin are also provided.

Abstract: In a positive photoresist composition including (A) an alkali-soluble novolak resin and (B) a naphthoquinonediazide ester, the alkali-soluble novolak resin is obtained synthetically by condensation of phenol compounds and an aldehyde or ketone, and the phenol compounds include, for example, 1% to 20% by mole of hydroquinone, 30% to 95% by mole of m-cresol and 2% to 50% by mole of 2,5-xylenol. Thus, a high-definition positive photoresist composition can be obtained, which inhibits the formation of scum, and is satisfactory in sensitivity, sectional shape, focal depth range and other properties even in a process for the formation of an ultrafine resist pattern of 0.30 &mgr;m or below by lithography using i-ray.