PHOTOCHROMIC SPIROPYRAN RESISTS

In all the resist applications described, the photochromic (PC) spiropyrans have the following important advantages over some, or all, commercial photoresists-the PC exposure time to UV light is not critical and is consequently not a troublesome process parameter-the PC image pattern is delineated clearly by the intensely colored exposed PC-both the unexposed and exposed PC are washed away readily with volatile solvents under normal operating conditions-both the unexposed and exposed PC are recoverable from solutions in the solvents by distillation or evaporation-the PC solids and their solutions are stableindefinitely when protected from light and heat. The chemical etching resist application is limited mostly to pattern preparation in metals and bilayers thereof, which can be etched with mild agents such as aqueous FeCl, dilute HCl and HF acids.