Development of an incremental structural parameter model for predicting reactive ion etch rates of 193 nm photoresist polymers

The design of 193 nm photoresists with improved reactive ion etch (RIE) resistance has been a longstanding aim of both industrial and academic research and development programs. A variety of correlations between photoresist polymer structure and etch resistance have been developed,(1-3) however, the universality of these approaches, and in particular, the practicality of making comparisons across specific polymer families and specific RIE processes has recently been called in to question.(4) In order to examine structure:RIE correlations in more detail, we have developed anew model based on the incremental structural parameter (ISP.) This model makes use of a molecular fragment-based definition of polymer structure which incorporates and extends aspects of previous parameters such as the Ohnishi and Ring parameters. An initial study revealed that this model allowed quantitative correlations between polymer families and across etch processes to be made. Continuing studies which examine the use of the ISP model in integrating 193 mn photoresists in prototype production processes will be described. Various polymer families used in deep-UV and 193 nm photoresists including methacrylates, alternating copolymers, styrenes, and cyclic olefins will be compared. We will present a more detailed description of the ISP model and of the follow-on 'new' ISP method which has been developed based on insights gained from the original ISP model, and make extended comparisons between the two ISP models.