Sumitomo Chemical Company, Limited

Osamu Hiroaki

Seimei Yasui

Akihiro Furuta

Makoto Hanabata

Naoyoshi Jinno

A positive type photoresist composition comprising a novolak resin and O-quinone diazide compound, the novolak resin being one which is obtained by the addition condensation reaction of a phenol and formaldehyde which is performed in one stage by using as a catalyst an organic acid salt of a divalent metal which is more electropositive than hydrogen, or in two stages by using an acid catalyst in the subsequent stage, the phenol being at least one compound represented by the formula ##STR1## wherein R is hydrogen or an alkyl group of carbon number 1 to 4, the compound being such that the average carbon number in the substituent per one phenol nucelus is 0.5 to 1.5 and the ones with the substituent at the ortho- or para-position with respect to the hydroxyl group account for less than 50 mol %, is disclosed. The positive type photoresist composition of the invention has an improved resolving power, i.e., .gamma.-value.

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Osaka, Japan

Osamu Hiroaki