Contrast enhancement of resist images by surface cross-linkage

Abstract

A general method of contrast enhancement which provides control of resist image wall profiles and is applicable to both positive and negative working resists may be obtained by surface cross‐linking. The cross‐linking is used in our process to retard dissolution at the resist surface. The creation of a slower dissolving surface layer affords greater control of wall profiles and enhanced contrast or sensitivity. One method is to use mid‐ and deep‐UV flood exposure. For a negative working electron beam resist this method is the same as surface photo absorption for contrast enhancement. With our experimental resist containing 4,4’‐diazido‐diphenylsulfide as a sensitizer, the improvement in its electron beam sensitivity was not substantial. For a positive working photoresist, the same aromatic bisazide was added to conventional positive working photoresists composed of a diazo‐naphthoquinone‐type photosensitizer and novolac resin. A short‐300‐nm UV flood exposure followed the G‐line imagewise exposures. Anoth...