Method to Control Image Size Uniformity in High Contrast Photoresist
Original Publication Date: 1988-Jan-01
Included in the Prior Art Database: 2005-Feb-14
Thickness of exposed photoresist is monitored and used to control post- exposure bake time as a means to assure image size uniformity in high contrast photoresist. Previous methods of linewidth uniformity control by fixed development time beyond endpoint detected during photoresist development are ineffective for high contrast resists since there is so little image size change after endpoint is reached. Image size control via exposure dose variation, send-ahead development, and subsequent image size measurement is unattractive due to inherent process delay and difficulty in automating the control process. As shown in Fig. 1, high contrast photoresist thickness decreases linearly with increasing post-exposure bake time until an image formation endpoint 2 is reached, whereupon there is no further measureable thickness change.