MODELING AND SIMULATION OF A DEEP-ULTRAVIOLET ACID HARDENING RESIST

A modeling methodology for a class of resist materials that rely on the acid catalyzed crosslinking of the resin matrix during a post-exposure bake is presented. This methodology is used to derive a complete and quantitative model for a production worthy deep-ultraviolet (UV) resist, Shipley XP-8843 (also known commercially as SNR 248). The modeling is based on the chemical and physical mechanisms which determine resist behavior during the exposure, post-exposure bake, and development processes. The IR absorption bands near 990 and 1070 cm-1 are used to monitor the extent of crosslinking during the bake as a function of bake temperature, bake time, and photogenerated acid concentration. The post-exposure bake model consists of a primary crosslinking reaction with an order of 1.42 in photogenerated acid and an acid loss reaction to account for dose dependent saturation of the crosslinking. Resist development is modeled by relating the dissolution rate to the extent of crosslinking during the post-exposure bake and to the number of sites on the crosslinking agent (six for melamine). Good correlation is obtained between simulated development profiles and experimental results with several post-exposure bake conditions.