MODELING HIGHLY NONLINEAR RESISTS

A master rate equation based on Bose-Einstein statistics is presented that accurately describes the dissolution characteristics of any highly nonlinear resist. Nonlinear resists exhibit long time delays or induction times before the onset of rapid development rates. The master rate equation requires a maximum of five adjustable fitting parameters, may be used for both optical and electron beam lithography modeling, and avoids problems with local negative development rates, discontinuities, and infinites whenever other dissolution rate equations are used. The least-squares fit of the master rate equation to experimental dissolution data is rapid and stable. The accuracy of the master rate equation has been verified for electron beam modeling by comparison with experimentally determined nonlinear resist profiles.