Raith update, Joe coming next week
jk at raithusa.com
Thu Jul 15 17:45:22 PDT 2004
It is a puzzle why 600 worked before, but now you need 580. No explanations
as of yet, but I would accept 580 and go with it. It should be standard
operating procedure to do an AlignWF before an exposure so you will always
be sure the field size is correctly calibrated.
I will be in the lab on Wednesday and Thursday of next week installing a new
Raith computer. Perhaps on Thursday afternoon we could discuss the simple
test I outlined and I can describe what I would be looking for in steps 5,
6, and 9.
Likewise, if any users are having any difficulties on the system, please
prepare something if coming to see me. It does little good to "wave hands"
in the air trying to describe what the GDSII design looks like compared to
the end result. Please have a few images and patterns ready.
I know several users have been suffering from beam current leakage through
the beam blanker. This is being handled through our service department.
Perhaps they will have some ideas for me to try when I am on-site. Lets
we did what you suggested and everything seems fine in terms of slowscan
images, although I'm not sure what I should look for exactly. Anyway, we
tried decereasing the MAG to 580 (instead of 600) and the zoom x and zoom y
go back within the limits and I can complete the align writefield. I haven't
tried a test pattern yet (other users where using the system today and they
don't really need and precide align writefield), I'll try tomorrow.
The only thing I'm worried about is the realtive value of the zoom
at 580X they are zoom X:1.37, Y: 1.47, which means 0.1 difference, where it
used to be 0.01. Should this still be ok? Does this ring any bell?
To RAITH USERS:
in the following days please report your results, especially stitch error
and deformations, so that we can check if the anomalous zoom values are
affecting the writes.
On Wed, 14 Jul 2004, Joseph Klingfus wrote:
> Hi there Gigi,
> My apologies, of course I shouldn't assume that the pattern generator
> (PG) couldn't be broken. It might be. Please do the following as a
> 1) Turn the PG off, wait a short time and power back on.
> 2) Restart both PC's.
> 2) Check Polaroid 545 setting again on the LEO.
> 3) Load the Chessy calibration target (as square as possible on the
> stage) and go to your normal working distance (stage Z) and set a 100
> µm WF.
> 4) Because the Chessy is sitting squarely on the stage, the SEM scan
> rotation should be 0 and AlignWF rotation values should be nearly 0.
> 5) Collect a SlowScan image of the Chessy with the PG and see if
> looks OK.
> 6) Have the AlignWF window visible on the desktop and try an align WF
> procedure. (Remember, be very aware of your Scansize and Placement
> There are 1 µm squares composing larger 10 µm squares. Don't confuse which
> box intersections are the correct targets.)
> 7) Write down the calculated zoom correction factors that the system tries
> to apply.
> 8) Hopefully accept the corrections without errors and collect another
> SlowScan image.
> 9) If you selected the right box intersections the Chessy should be
> perfectly aligned and sized in the image.
> Please let me know how this turns out.
> To answer your question of WD...
> The Zoom U/V parameters do not depend so much on WD because the SEM
> takes care of this internally. Imagine setting a MAG of 600 X (~ 100
> µm WF) both at high and low Z height. The MAG determines the scale of
> things we see on the display screen. It still takes a voltage sweep
> of +/- 5 Volts on the external column inputs to raster the electron
> beam from side to side across the image. (just using 5 V as an
> example, all SEMs are different) This is why we (Raith litho) don't see
any great effect on Zoom U/V parameters as WD
> changes. Although, for good stitching results do an AlignWF at the Z
> height you are writing at.
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