Raith UPDATE: Electrostatic Chuck Leveling and blanker leakage test results

James Conway jwc at snf.stanford.edu
Wed Oct 6 16:24:05 PDT 2004


Hello Everyone on the RAITH 150:


RE: ESC chuck leveling mechanical adjustments:
I was able to complete the Electrostatic Chuck (ESC)  leveling 
mechanical adjustments and we have tested this five times and the ESC w/ 
piezo's all centered measures a delta of  25 -28 um between the 3 
different post positions at reference at WD of 5 mm.

After performing the SW leveling routine -- which now completes with no 
problem or errors we are leveled to within a delta of 18 um difference 
between the three post positions on the ESC. Note this is on 150 mm 
wafers on the ESC only.

This task I now will consider complete. Note that I will be mapping this 
reference double sided polished Prime <100> Si wafer to determine if we 
are able to leveling consistently, as well as to ensure the ESC is 
landing the same way every time.  This map will give me a baseline to 
similar measurement I wish to do on the Std. Sample Holder in the future 
as my time allows...

RE:  RAITH Beam Blanker Leakage Test was completed today.


Conclusion:
There is some emission evident when the LEO is unblanked and the RAITH 
blanker is blanked.  The emission level is between 400 and 1000 fA above 
the background value of 0.0005 -0.0006 nA.  This measurement was 
variable from measurement to measurement but averages out to the same 
value and range when taking measurements over several minutes of time.

 This result is just slightly above the one percent leakage value 
proposed by Joe Klingfus at RAITH USA as being an acceptable amount of 
blanker leakage.  The blanked exposure artifact has been observed on 
many EBL writes by users, specifically those whom are writing for a very 
long time within one writefield such as in a waveguide or Photonic 
Crystal, and/or when the stage is held in one position for any period of 
time such as at the end of a write.


 Workaround to be implemented at SNF:
 Add in an extra position to the position list at the end of the write 
session placed this artifact into a non critical area of the sample.

Further action:  To be determined by RAITH field service.
SNF will continue to monitor this situation closely in the coming weeks.

Hopefully these measurements will establish a baseline to compare to on 
other systems.

Thank you for your support!

James Conway


Aperture
	
I-beam
(10 kV, 5 mm WD)
	
Drift (nm)
	
Direction of drift
	
Recovery Time (s)
7.5 	 0.0076 	3.57
	160 degrees  -- South EAST
	< 0.25 sec No evident drift
10 	 0.0156 	1.77
	90 degrees -- EAST
	 < 0.25 sec No evident drift
20 	 0.0668 	1.03
	180 degrees -- SOUTH
	 < 0.25 sec No evident drift
30 	 0.1275 	4.47
	180 degrees -- SOUTH
	 < 0.5 sec slightest drift movement evident
60 	 0.5888 	none
	none
	 No movement evident
Beam spot ovoid and irregular in shape
120 	 2.2077 	none
	none
	 No movement evident
Spot is very large!


Addendum:  Beam drift specification is <10 nm/minute.  All measurements 
made at 10 kV and 5 mm working distance.

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