Problem stsetch2 SNF 2012-05-22 18:26:22: resist etch rate doubled overnight

grahamab at snf.stanford.edu grahamab at snf.stanford.edu
Tue May 22 18:26:22 PDT 2012


Reporting this as a problem and not a shutdown just in case there's someone who desparetely needs the tool and doesn't care at all about resist etch rate, etch profile, or possible consistency between wafers.  
Etched one test wafer yesterday before the cooling issues.  The resist etch rate was similar to before shutdown.  The silicon etch rate was also similar to before shutdown.  Etch profile was quite a bit different.  What was normally a mostly straight sidewall with a slight taper turned into a very barrel-shaped etch.  
After running two wafers this evening, photoresist etch rate has doubled since yesterday.  Feature width has drastically increased and the etch rate is more than 2X what it was yesterday even with slightly decreasing the etch cycle time.  Temperatures indicated on the process monitor appear no different than yesterday, but unsure if lower platen temperature reads accurately now or not.  Unsure if related to the major misalignment seen upon wafer unloading, but it passes leak checks okay.  




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