Problem tylan2 SNF 2011-05-24 03:51:41: dark spot on all of my wafers

[kokab at snf.stanford.edu]

I don't know what exactly has happened during my run but it looks like that at one point there was a lot source of oxygen or heatat one point. there is a dark spot on my wafers and the darkness decreases from wafer to another wafer and at the end it is disappeared.