Hardened photoresist master image mask process

Abstract

An improved mask fabrication process is disclosed which may be broadly applied to ion-implantation, reactive plasma etching, or the etching of semiconductor structures. The process is based upon the deposition onto an oxide coated or bare semiconductor surface, of a first photoresist layer having formed therein a plurality of windows and which is hardened by a wet chemical technique so as to have an increased resistance to dissolution in solvents. A second photoresist layer is deposited over the surface and windows of the first layer and a subplurality of windows are formed therein over selected windows in the first photoresist layer so as to selectively block a portion of the plurality of windows in the first layer. This composite mask invention may then be employed to carry out an ion-implantation step, wet etching step or reactive plasma etching step on the oxide or semiconductor surface exposed through composite windows. The second layer of photoresist may then be removed and a substitute photoresist layer may be deposited on the surface and windows of the first, hardened photoresist layer and a different subplurality of windows in the substitute layer may be selectively formed over selected windows in the hardened photoresist layer, thereby selectively blocking a different combination of windows in the first, hardened layer.