Problem RAITH SNF 2007-02-14 16:21:21: Standard sample holder not landing onto piezo post properly

James Conway jwc at snf.stanford.edu
Wed Feb 14 19:18:34 PST 2007


kevin or cole,

Hope to speak with you in the morning tomorrow.

I mapped both wafer height on the Std. Sample holder and the surface of 
the sample holder itself after driving the center of the wafer (0,0 UV) 
to 5 mm and see significant offsets from level despite using a 
calibrated center positions of the piezo post.  Up to 0.5 mm across the 
pallet.  I made some maps of heights from two different loads on the 
Std. Sample Holder.

Following up with phone with Kevin last Friday:
Yes I think we have a problem with P1 the fixed piezo post.

I have been troubleshooting some strange reports from users whom 
indicated that initially the Z drive was loosing its calibration; when 
in fact the sample holder may not be landing correctly onto the P mounts 
  or now more likely the jewel tip on P1 may have become damaged or 
simply worn itself out.

Also have been troubleshooting several reports of strange EBL results 
such as triangles and 100 nm squares being circular and not well defined 
. I suspected out of focus by users now I suspect the P1 Post.

Flatness of the Std. sample holder appears fine when placed on  machine 
plate gage. i.e., it doesn't rock or appear bent. But I don't have any 
dimensions or specs for this assembly to check to.

I have some SEM's of each post...  P1 looks really different that the 
others. cracked or worn on the periphery.






Problem RAITH SNF 2007-02-14 16:21:21: SUBJECT: Standard sample holder 
not landing onto piezo post properly.

Attention All RAITH Users:
PROBLEM ON RAITH: STANDARD SAMPLE HOLDER NOT LANDING ON KINETIC MOUNTS 
-- DAMAGED PIEZO POST...
I have been troubleshooting several user reports of irregularly shaped 
or poorly defined written structures on the exposures made since January 
11, 2007.  This issue has become more apparent through the month, and as 
we perform hi resolution measurements of our structures in SEM review 
written in early January.

I have observed several incidents of out of focus or poorly focused 
structures written at the extreme edges of wafers ( E.g., targets and 
SPLines @ 0, -45 UV :: 0 +45 UV) Within the normal +- 10 mm range I 
often write within, I also observed significant changes in working 
distance as I moved through this small range of positions.

Monday and today we made measurements of the surface of both a 100 mm 
wafer clipped to the standard sample holder and upon the Std. sample 
holder itself and have collected data that the holder is not landing 
precisely flat into the kinetic mounts.  The range of non-flatness is ~ 
0.500 mm!

Visual and SEM inspection of the ceramic balls and points or 'jewel' 
tips in the Piezo post yield information that indicated that Piezo one 
post ceramic ball may have become damaged and/or the point may be 
missing. All piezo post exhibit wear on their surfaces.

Users are requested to be vigilant of their actual working distances, 
and to report their WD data for specific positions across their samples 
and promptly report to this list if you see significant changes in WD as 
you move across your wafers greater than 250 um.
RAITH has been contacted last Friday and we will strive to correct this 
issue ASAP.
System is now in YELLOW Light Mode.
Thank you for your support!
James Conway





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