Method for image enhancement in positive photoresist by vapor diffusion image reversal

摘要

An image reversal method for forming a negative image on a surface using positive photoresist material includes the first step of coating the positive photoresist material on the surface, and soft baking the photoresist or the like to form a uniform layer on the surface. The photoresist layer is then exposed by actinic radiation through a mask or the like in image forming fashion, the exposed portions reacting to form a carboxylic acid or other acid which is soluble in aqueous base solutions. The photoresist is then exposed to a treatment with a vapour of chemical base (e.g. of an amine; tetramethylammonium hydroxide, triethanolamine or ammonia) which renders the acid insoluble to alkali solutions and relatively insensitive to further light exposure. The vapor treatment is followed by a flood exposure of the entire surface to render soluble the photoresist portions which were originally unexposed by the mask. The photoresist is then developed by immersion in an alkali developer to remove the flood exposed portions. The remaining photoresist areas comprise the mask exposed portions in relief from the surface and defining the negative image of the original mask exposure.