Subject: Re: Raith not working - beam blanking problem Current Status WED. June 30, 2004 1815 hours.
From: James Conway <jwc@snf.stanford.edu>
Date: Wed, 30 Jun 2004 18:31:50 -0700
Wed, 30 Jun 2004 18:31:50 -0700
Greetings:

The Raith is working... 
Note that Ken is writing on Si3N4 layers and this material will charge 
up if not coated with a charge compensation layer.
No other users yet to report this particular defect being encountered.  
Nor have there been any further reports of 'comets' or 'trillium shaped' 
blanking artifacts or other strange features written, as we observed 
before I adjusted the LEO blanking spot position Thursday a week ago. 
Yesterday evening, I once again moved the position of the LEO Beam 
Blanking spot farther away from the apertures on the suggestion of CARL 
ZEISS SMT (formerly LEO).

I observed a very small amount of leakage when the LEO is unblanked and 
the RAITH is blanked.  This is below the noise threshold for the 
picoammeter and is only evident when you really bring up the gain of the 
In-Lens SED detector.
 It is well below the threshold of nearly all resist we are employing 
for EBL by a factor of  ~20.

This afternoon I ran several test that RAITH requested we try to 
evaluate this and we again confirmed that there is a very low level of 
"leakage"  This is likely normal in the column as that even when the 
beam is blanked there will always be some scattering of electrons of 
which a very small amount will exit through the apertures.

We are watching this problem carefully.  I am doing writes on UV-N 30 at 
very low doses and did not any problems with this in last week's JPL 
NASA writes.  I will be on the system tomorrow 10 - 6 too!  This should 
clear up this issue.

ACTION REQUESTED OF YOU:
USERS ARE REQUESTED TO CAREFULLY INSPECT ALL WRITES PERFORMED SINCE LAST 
THURSDAY A WEEK AGO AND REPORT TO THIS LIST AND TO jwc@snf.stanford.edu  
Plz. Bring me some pictures...

Today I also inspected 15 nm shots for charging and drift artifacts upon 
unblanking and did not observe any of these problems.  If we observed 
drift in the image this would indicate that the column had become 
contaminated again and this would certainly contribute to the problem 
observed as the beam blanking position would also have been drifting or 
changed with the charging!

Unfortunately the only way to reposition the RAITH blanking spot is to 
rotate the RAITH beam blanker mechanically and this would require we 
open up the column and gun section, move the beam blanker and then bake 
out the system for several days again.  The gun vacuum is currently 
superb and I do not desire to open up the column unless absolutely 
necessary.

Your comments and suggestions are invited.  RAITH and LEO are working 
closely with me on this problem.

Thank you for your support!

James Conway
Ebeam Technology Group



Kenneth Brian Crozier wrote:

>
>
> Hi everyone,
>
> James and I noticed that the specimen current was much higher than 
> normal with the beam blanked by the Raith (1400 fA).  This could be 
> the cause of the "splotch" problem reported earlier and detailed on 
> the Raith swiki at: http://elrey.stanford.edu:8080/Raith/34.  Over a 
> long exposure (e.g. the photonic crystal pattern shown takes about 90 
> min) this could lead to the large "splotch" being exposed when the 
> beam is meant to be blanked.
>
> It'd be great if anyone who has experienced similar problems could let 
> both James and I know about it.
>
> thanks,
> Ken
> ---------------------------------------------
> Ken Crozier, Ph.D.
> room GL 51, Ginzton Laboratory,
> Stanford University, Stanford, CA 94305, USA
> tel : 650-723-1945  fax : 650-725-2533 



Greetings:

The Raith is working... 
Note that Ken is writing on Si3N4 layers and this material will charge up if not coated with a charge compensation layer.
No other users yet to report this particular defect being encountered.  Nor have there been any further reports of 'comets' or 'trillium shaped' blanking artifacts or other strange features written, as we observed before I adjusted the LEO blanking spot position Thursday a week ago. Yesterday evening, I once again moved the position of the LEO Beam Blanking spot farther away from the apertures on the suggestion of CARL ZEISS SMT (formerly LEO).

I observed a very small amount of leakage when the LEO is unblanked and the RAITH is blanked.  This is below the noise threshold for the picoammeter and is only evident when you really bring up the gain of the In-Lens SED detector.
 It is well below the threshold of nearly all resist we are employing for EBL by a factor of  ~20.

This afternoon I ran several test that RAITH requested we try to evaluate this and we again confirmed that there is a very low level of "leakage"  This is likely normal in the column as that even when the beam is blanked there will always be some scattering of electrons of which a very small amount will exit through the apertures.

We are watching this problem carefully.  I am doing writes on UV-N 30 at very low doses and did not any problems with this in last week's JPL NASA writes.  I will be on the system tomorrow 10 - 6 too!  This should clear up this issue.

ACTION REQUESTED OF YOU:
USERS ARE REQUESTED TO CAREFULLY INSPECT ALL WRITES PERFORMED SINCE LAST THURSDAY A WEEK AGO AND REPORT TO THIS LIST AND TO jwc@snf.stanford.edu  Plz. Bring me some pictures...

Today I also inspected 15 nm shots for charging and drift artifacts upon unblanking and did not observe any of these problems.  If we observed drift in the image this would indicate that the column had become contaminated again and this would certainly contribute to the problem observed as the beam blanking position would also have been drifting or changed with the charging!

Unfortunately the only way to reposition the RAITH blanking spot is to rotate the RAITH beam blanker mechanically and this would require we open up the column and gun section, move the beam blanker and then bake out the system for several days again.  The gun vacuum is currently superb and I do not desire to open up the column unless absolutely necessary.

Your comments and suggestions are invited.  RAITH and LEO are working closely with me on this problem.

Thank you for your support!

James Conway
Ebeam Technology Group



Kenneth Brian Crozier wrote:


Hi everyone,

James and I noticed that the specimen current was much higher than normal with the beam blanked by the Raith (1400 fA).  This could be the cause of the "splotch" problem reported earlier and detailed on the Raith swiki at: http://elrey.stanford.edu:8080/Raith/34.  Over a long exposure (e.g. the photonic crystal pattern shown takes about 90 min) this could lead to the large "splotch" being exposed when the beam is meant to be blanked.

It'd be great if anyone who has experienced similar problems could let both James and I know about it.

thanks,
Ken
---------------------------------------------
Ken Crozier, Ph.D.
room GL 51, Ginzton Laboratory,
Stanford University, Stanford, CA 94305, USA
tel : 650-723-1945  fax : 650-725-2533