A system used to provide linewidth control in a IC manufacturing facility is described. It combines the use of interferometry, real time endpoint detection, and automation to tighten linewidth distributions by adjusting development times. The use of Fourier Transforms provide consistent endpoint detection for a variety of part, process, and substrate types. The system increases throughput and reduces rework by eliminating the need for trial wafers. It also provides a means for process monitoring as well as a tool for troubleshooting, and process development. The paper describes the Automatic Linewidth Control System: its operation, algorithms for endpoint detection and its performance.
Laura J. Uhler,
"Automatic Linewidth Control System", Proc. SPIE 0775, Integrated Circuit Metrology, Inspection, & Process Control, (17 April 1987); doi: 10.1117/12.940405; http://dx.doi.org/10.1117/12.940405