E-BEAM PROXIMITY CORRECTION FOR NEGATIVE TONE CHEMICALLY AMPLIFIED RESISTS TAKING INTO ACCOUNT POST-BAKE EFFECTS

The use of chemically amplified resists (CARs) in electron beam lithog raphy required an additional processing lithography step i.e. post exp osure bake (PEB). During this step the acid produced during exposure d iffuses and drain reactions occur. In this paper, the method of single pixel exposures is used in order to evaluate the diffusion coefficien t. This approach is applied in the case of three resists, namely AZPN1 14 (Hoechst), SAL601 (Shipley) and the experimental EPR. In the case o f AZPN114 diffusion is limited for the higher Theta values in the cent er of the pattern but is considerably larger at the edge. EPR represen ts an extreme case where diffusion is limited by a strong cage effect due to a fast completion of the reaction while SAL601 represents an in termediate case. The diffusion coefficient is used in combination with the e-beam simulator SELID to provide data for proximity correction. The reaction-diffusion system for the specific values of the thermal p rocessing parameters is used to modify the point spread function I. Th e resulting actual acid concentration for a point exposure is convolut ed for a given layout. Subsequently proximity correction is performed as in the case of conventional resists.