Methods for critical dimension and focus mapping using critical dimension test marks

Abstract

Methods for using critical dimension test marks (test marks) for the rapid determination of the best focus position of lithographic processing equipment and critical dimension measurement analysis across a wafer's surface are described. In a first embodiment, a plurality of test mark arrays are distributed across the surface of a wafer, a different plurality being created at a plurality of focus positions. Measurement of the length or area of the resultant test marks allows for the determination of the best focus position of the processing equipment. Critical dimension measurements at multiple points on a wafer with test marks allow for the determination of process accuracy and repeatability and further allows for the real-time detection of process degradation. Using test marks which require only a relatively simple optical scanner and sensor to measure their length or area, it is possible to measure hundreds of measurement values across a wafer in thirty minutes. Comparable measurements with a Scanning Electron Microscope (SEM) require at least five hours.