Visualization of the develop process

Variations in critical dimension (CD) as a function of the proximity of an individual feature to other exposed areas are continuing to be a problem in the lithography process. For example, the CD uniformity (CDU) may degrade significantly depending on the proximity to densely or sparsely exposed areas. These pattern density effects will continue to get worse and become more complex as feature sizes decrease. Pattern density effects are believed to arise from several sources and may simultaneously contribute to a net observed CD variation [1]. One such source, develop loading, results in local depletion of developer in highly exposed regions, reducing the dissolution rate and thereby locally affecting CD. In this report we describe our results in visualizing develop loading by using pH sensitive dyes. Two different types of dyes are explored: acid/base pH indicators and a fluorescent dye bound to the resist polymer. © 2011 SPIE.