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.