Raith system down time planned for WED 11242004:1300 - TUE. 11302004:1400 hours.

James Conway jwc at snf.stanford.edu
Mon Nov 15 15:51:44 PST 2004

Greetings Raith Users:

During the last three months we have been troubleshooting several items 
on the RAITH 150 that I will wish to address in the next few weeks.  In 
order to effectively repair these problems we will need to bring the 
system off line and replace the FE-Gun and aperture plate in the system, 
perform a column bake out, then finally once adjust calibrations and 
alignments to the Electron Optics Card functions.  This is the same 
routine as an annual PM we performed last May.  Due to the large number 
of users on the system we are nearly ready to have this performed already.

Performance Issues of Concern:

1. RAITH Blanking issues: 
Some Users have been observing blanking artifacts on their sample 
patterns when exposing a single write field for a long period of time. 
This is mainly observed by users working with high resolution and 
sensitive resist such as UVN-30 and ZEP-520 at 10 kV.

2. Extra beam inpingement spots:
I have observed contamination dots or beam inpingement spots appearing 
adjacent to, but outside of, the reduced raster scan field.  This could 
possibly be due to damage to the FE-Gun during the last series of arcing 
event(s) resulting in the tip emitting from several points and not just 
one emission source.  Strange but true...

3. Beam Current Issues:
The beam current for various apertures have been steadily declining as 
the tip begins to show signs of wearing out and the delta in the 
measurement of EXT I gun-off versus EXT I gun-on are now not within 
specifications of -20%.  Simply stated, 'The tip is nearing the end of 
its useful life time'.  Adjustments made to the EXT Voltage of the 
FE-gun last week did not return the emission to suitable values. (-7 - 
10%) Currently we have 5235 hours on the tip since we started it up.

4. Contamination Issues:
The level of hydrocarbon contamination is increasing in the column and 
blanking aperture section. There is a reduction in Beam Current measured 
for the 30 and 10 um apertures which indicate we are at the normal time 
to perform an aperture replacement.   We observe the amount of image 
drift upon blanking and unblanking the beam to be steadily increasing.  
Charge up of hydrocarbons in the system at the aperture plate causes 
this image drift effect.  Beam Current measurements have been  steadily 
falling through out the PM interval which is normal, but we are getting 
a bit too low in Beam I  to be practical for most users.

With this in mind I must come to a decision to perform the PM routine as 
soon as we can get the proper parts and ZEISS field service personnel in 
place to perform these task.  I have tentatively blocked out on the 
CORAL reservation system from 1 PM WED. November 24 through 2 PM Tuesday 
November 30, 2004 to complete this service.  I am still waiting for 
confirmation from ZEISS that they will be available to perform this 
service at this time.  Full update and a schedule when I have this 
information.  All efforts will be made to perform this routine perfectly 
the first time to avoid extended downtime from negatively impacting 
users deadlines and research.

Thank you for your support!

James Conway

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