Post Exposure Delay Considerations in a 193-nm Chemically Amplified Resist

Abstract

The deprotection of a 193-nm chemically amplified resist is amplified by photo-generated acid during the post exposure bake. The acid concentration is changed through reactions such as diffusion, evaporation, and acid neutralization with atmospheric base contaminations during post exposure delay. Since the acid concentration greatly effects the final critical dimension, it is very important to control the post exposure delay time. Thus, the characteristics of the post exposure delay effect on photoresist profiles were studied. We measured the transmittance and the thickness change of a 193-nm chemically amplified resist with respect to the post exposure delay time. From this result, the imaginary refractive index change with post exposure delay time was also obtained. This post exposure delay effect was included in our simulator, LUV (lithography for ultraviolet), and resist profiles were obtained.