Alignment and Overlay

Appendix ....................................................................................................................................324

References ....................................................................................................................................327

This chapter discusses the problem of alignment in an exposure tool and its net result:

overlay. Relevant concepts are described and standard industry terminology is defined.

The discussion has purposely been kept broad and tool-nonspecific. The content should be

sufficient to make understanding the details and issues of alignment and overlay in

particular tools relatively straightforward. The following conventions will be used:

orthogonal Cartesian in-plane wafer coordinates are (x,y) and the normal to the wafer

or out-of-plane direction will be the z axis.