Effect of inline dose and focus monitoring and control on post-etch CD

Abstract

Due to the continuous shrinking of the design rules and, implicitly, of the lithographic process window, it becomes more and more important to implement a dynamic, on product, process monitoring and control based on both dose and focus parameters. The method we present targets lot-to-lot, inter-field and intra-field dose and focus effect monitoring and control. The advantage of simultaneous dose and focus control over the currently used CD correction by adjusting exposure dose only is visible in improvement of the CD distributions both at pre-etch and at post-etch phases. The 'On Product' monitoring and compensation is based on the optical measurement of a special compact line end shortening target which provides the unique ability to separate dose from focus on production wafers.