Method of pattern forming in a photosensitive composition having a reciprocity law failing property

A process for forming a pattern which comprises the steps of:

• (a) preparing a photoresist layer consisting essentially of at least one water-soluble polymer selected from the group consisting of poly-N-vinylpyrrolidone, copolymers of N-vinylpyrrolidone and acrylamide-diacetoneacrylamide copolymer and a water-soluble aromatic bisazide compound on a surface of a substrate for the desired pattern, said water-soluble aromatic bisazide compound being at least one compound represented by the following general formula:
• ##STR14## wherein n is 1 or 0, R.sub.1 represents a hydrogen atom or an alkyl group, R.sub.2 represents a hydrogen atom or an alkyl group, R.sub.1 and R.sub.2 may be linked with each other at their terminals to form a cyclic ketone structure in the molecule, M represents an atom or atomic group capable of being converted to a cation in an aqueous solution, and M' represents an atom or atomic group capable of being converted to a cation in an aqueous solution, said photoresist layer consisting of 70 to 98% by weight of said water-soluble polymer and 2 to 30% by weight of said water-soluble aromatic bisazide compound based on the total amount of photoresist,
• (b) applying light to said photoresist layer by passing the light through a mask having said pattern, in the presence of an oxygen containing gas and with the Schwarzschild's constant p being in the range of greater than 0 and smaller than 0.76, to harden the photoresist layer at a surface area substantially equal to or smaller than that of apertures of said mask through which beams pass, and
• (c) developing the light-applied photoresist layer to form the pattern having a surface area substantially equal to or smaller than that of apertures of said mask through which beams pass.