SIMULATION ANALYSIS OF A CHEMICALLY AMPLIFIED POSITIVE RESIST FOR KRFLITHOGRAPHY

The reactions of a chemically amplified positive resist, CAMP6, which is composed of poly tert-butoxy carbonyl (t-BOC)-styrene copolymer as a base resin and 2,6-dinitrobenzyl tosylate as a photoacid generator, were analyzed. The acid generation and t-BOC deprotection reactions we re analyzed by FTIR spectrometer and modeled successfully. The dissolu tion rates were measured by a Development Rate Monitor (DRM). A new an d simple dissolution rate model is presented, since the dissolution ra te behavior of chemically amplified positive resists cannot be explain ed by the conventional models that are designed primarily for novolac/ dissolution inhibition systems. Furthermore, this new model can also e xplain the surface inhibition effect by considering acid loss (deactiv ation) due to airborne contaminant diffusion from the resist surface. Simulation software, Prolith/2, was modified to incorporate the model, and profile simulations were carried out successfully. Based on this accurate resist profile simulation, a new process window concept will be presented. This process window is defined on an exposure-defocus pl ane as the areas that are determined by linewidth error and sidewall a ngle at the resist thicknesses corresponding to maximum and minimum li newidths on a swing curve. This window concept can give a practical pr ocess margin, since the standing wave effects are incorporated. This m ethod is applied to the process window analysis for KrF excimer laser lithography.