A simple and effective lift-off with positive photoresist

This paper describes a simple and effective lift-off method which relies upon a single layer of positive photoresist and the insertion of a diffuser in the conventional lithography. The inserted diffuser randomizes the paths of incident ultraviolet light, which creates the re-entrant photoresist profile necessary for proper metal lift-off. This method was applied to photoresists, with different thicknesses from 1.3 mu m to 10 mu m, showing a uniform undercut of 0.3 mu m to 2.0 mu m, depending upon the photoresist thickness. The gold lift-off test was performed to show the suitability of the photoresist profile generated by the proposed method. We could obtain very neat gold sidewall patterns after evaporation onto the fabricated photoresist pattern. The simplicity and versatility of the proposed method will provide wider options for meeting the strong demands for a simple and effective lift-off method.