Using laser surface scanning and bare wafer review to diagnose photolithography track developer process-induced defect issues

Abstract

With the growing complexity of I-line and DUV (Deep Ultraviolet) photolithography processes, defect monitoring and yield improvement is becoming more critical and challenging. In addition to product wafer scans, reliable unpatterned wafer scans, with their advantage of much quicker feedback time for tool qualification and/or process monitoring must be developed and implemented. Especially with the more wide spread use of the newer chemically amplified resists, a high sensitivity, easy to review and trouble-shoot monitor is essential. A laser scanning unpatterned wafer defect detection tool was used to scan developed unpatterned photoresist coated wafers. Defect recipe creation for detecting these defects involved using the method of "signal to noise" to set the tool to find real defects. The conventional method of applying latex spheres of a known size for a calibration media was not used since it is not at all representative of the way real process defects scatter light. A novel, non-destructive unpatterned wafer review method was used to actually review the defects using darkfield microscopy, and to determine real defects (signal) from false calls (noise). From this work we were able to detect defect process signatures and defects that were related to the develop dispense configuration. Darkfield microscopy revealed the defects were indeed developer related since they appeared as liquid spot type defects and/or residue. Subsequent use of this method has been established as an excellent troubleshooting method to finding and fixing photo defect issues. The methods and results of this work will be discussed.

Spot scanning imaging calibration method based on deviation model for wafer inspection

“…KLA-Tencor, an industry-leading semiconductor equipment manufacturer, adapts non-imaging inspection technology in their systems using brightfield illumination, darkfield illumination, or a combination of both [6]. Non-imaging-based laser scanning defect detection technology has been widely researched and applied because of its high sensitivity and high productivity [7][8][9].…”