computer controlled electron beam pattern generator operating at 15 kev until exposures greater than 2 4 u00d7 10 5 c cm 2 are obtained the exposed resist images in the 0 70 micron thick resist film are then selectively removed to the substrate after a 2 minute n 2 purge by a 2 minute spray development in benzonitrile or 3 1 benzonitrile methyl cellosolve mixture no measurable loss in the unexposed resist area occurs during development it should be noted in regard to the preparation of the resist that the spinning solvent for the mca mcn copolymer must dissolve a high enough concentration of copolymer to result in a viscous solution that can be applied as a smooth uniform resist film of about 0 3 to 1 0 micron in thickness the use of nitromethane as the spinning solvent has been very successful another spinning solvent that can be used is a solvent mixture of 7 3 acetonitrile and nitromethane films ranging from 0 28 micron to 1 30 microns can be cast using 2 to 3 percent solutions of mca mcn copolymer in nitromethane a particularly desirable range of spinning frequencies is 1000 to 4000 rpm as the substrate one can use any material on which circuit patterns are delineated a variety of substrate.