Subject: Rx: Charging in the blanking aperture causing problems some users have seen...
From: James Conway <>
Date: Mon, 08 Mar 2004 18:21:14 -0800


No access no use overnight.

LEO adjustments made Friday caused the 120 um aperture to be misaligned so we cannot use that aperture.
The mechanical alignment performed to the gun seemed to be ok and I am not sure what else is affecting these problems yet.

I am seeing significant image drift occurring as we unblank the beam.  The small spot shot image drifts in from above a 100 um field of view and then stabilizes in the center where it should be.  This is possibly due to charging occurring in the column and not on the samples.  Likely the blanking or deflection section  became contaminated for reasons unknown.

The qualification writes performed Friday looked ok, but on SEM examination I do see some artifacts of beam placement drift early in the shot.  What I did see is some dot shots in the origin targets appear astigmatic and their position was consistently offset from the center of the target in the +U and +V directions.

LEO will be returning and I will also be requesting RAITH Field service engineer to join us for this fun.

NO use attempting to write lets just let it pump down and see if vacuum improves -- we are still in the 2.0 E -009 torr range and it should be below that by now.  Again contamination is suspected.

Thank you,

James Conway