Problem stsetch SNF 2010-11-11 19:31:45: severe grass formation in smooshal recipe

dongrip at dongrip at
Thu Nov 11 19:31:45 PST 2010

I etched Si wafers with 400 nm thick oxide mask using smooshal recipe for 13 min to aim 8~9 microns thick etch. However, huge grass was formed on the left bottom (3/4) of the wafers. Two days ago, I etched the same type of samples with the exactly same recipe and time, and I had very good results under SEM. I don't know what happened to the machine in a couple of days.  
The helium flow rate was quite stable for the entire runs (~2.76~2.78 sccm). Please fix this issue ASAP. 
Thank you!

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