Update on thick resist work

Gary J Sosa gsosa at stanford.edu
Thu Apr 14 16:49:08 PDT 2011

Hi All

   Here is an update of the work performed on Monday and Wednesday with respect to thick resist processing. We created several recipes with different methods of applying the photoresist. This included a center to edge technique, center dispense, center dispense with no spin. For each recipe, there were variations of dispense arm timing, pump didpense rate/volume, speed of wafer during dispensing. The results were very mixed but still showed the unusual artifact in the center of the wafer which has large impact on overall thickness uniformity. The artifact seems to appear when the wafer goes into the high speed step for casting the resist thickness. The artifact appears as a tiny dot that grows to the size of a quarter or larger during the casting step. Created a program that slowly ramped the speed up to 3500 RPM in 500 RPM increments. This did not solve the problem and overall spin quality suffered. We will continue to work on the issue and update you as we go along.

     Thanks.. The Litho Team

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