Polymeric Electron Beam Resists

Crosslinking polymers may be used as negative acting resists. The product of the minimum charge dose Q required and the weight average molecular weight M ¯ ω is a constant and is a characteristic of the polymer. At an electron beam voltage of 10 kV, this Q ‐ M product is found experimentally to be 6.3 coul‐g/cm 2 ‐mole for polystyrene, 1 coul‐g/cm 2 ‐mole for poly (vinyl chloride), and 14 coul‐g/cm 2 ‐mole for polyacrylamide. Degrading polymers may be used as positive acting resists. Their average molecular weights have only a very minor effect on their efficiency as positive resists. Their glass transition temperatures T g are an important factor. It is recommended that these resists be prebaked at T > T g , stored and developed at T < T g , and postbaked at T > T g .