Problem evalign SNF 2004-08-15 14:53:42: in anodic recipe, WEC problems lots of shift

lindaw at lindaw at
Sun Aug 15 14:53:42 PDT 2004

ran some fused silica wafers through the anodic recipe. There were huge shifts of image from cross hair during top wafer WEC. Also, after bottom wafer WEC and pre-align, left side of wafers much farther apart than right.  When trying to align, both top and bottom wafer shift when moving the bottom wafers, so they are in contact somehow.  I made sure that the load chuck was centered to the bond chuck.  After clamping wafers and removing chuck, wafers were indeed centered on the chuck. I checked the back of the wafer load bond chuck to see if there might be something causing bad WEC, but it was smooth to the touch. O-rings on the bond chuck/mask holder frame were all in place, so I don't suspect that as the cause of the shift at WEC. You may not get good results if you use this to align Si wafers for bonding or backside align.

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