Method of using a positive electron beam resist medium

In a method of forming a patterned layer on a substrate comprising:

• (a) coating said substrate with a composition comprising a positive acting polymeric resist material and a suitable solvent therefor;
• (b) drying said coating to form a positive recording medium;
• (c) irradiating selected portions of said medium with an electron beam, a modulated electron beam or x-ray;
• and
• (d) developing the irradiated portions of said medium with a suitable developer, the improvement comprising utilizing as the resist material a terpolymer comprising a monomer component and sulfur dioxide in a 1:1 molar ratio, said monomer component comprising from about 10 mole percent to about 50 mole percent of 3-methylcyclopentene and from about 50 mole percent to about 90 mole percent of vinyl acetate, said terpolymer having a molecular weight of from about 300,000 to about 1,200,000.