Lift-off method of fabricating thin films and a structure utilizable as

Abstract

A method for use in forming thin film patterns in the fabrication of integrated circuits. The method involves depositing a bottom layer of positive photoresist material on a substrate, and forming over the bottom layer, a discrete light-transparent top layer of positive photoresist material which is less solubilized in developer after exposure to light than is the material in the bottom layer. The top and bottom layers are preferably separated by an intermediate layer of a light-transparent polymeric material which is immiscible in the bottom layer and unaffected by the subsequently applied top layer. The composite structure is exposed to a selected pattern of light, e.g., through a mask, and developer for the positive photoresist material is applied to the top and bottom layers. In the case where an intermediate layer is used, the top layer is developed first. Then, the intermediate layer is removed where exposed in the apertures through the top layer, preferably by ashing, after which, the bottom layer is subjected to the developer. In the resulting structure, the bottom layer has an aperture pattern coincident with and laterally wider than that of the top layer. The thin films are then deposited onto a substrate through the coincident aperture patterns with the photoresist layer serving as a deposition mask.