Subject: [Fwd: Re: Problem raith SNF 2005-02-15 17:24:20: 20 um aperture scatter when blanked is above spec.]
From: James Conway <jwc@snf.stanford.edu>
Date: Thu, 17 Feb 2005 18:29:52 -0800

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Subject: [Fwd: Re: Problem raith SNF 2005-02-15 17:24:20: 20 um aperture scatter when blanked is above spec.]
From: James Conway <jwc@snf.stanford.edu>
Date: Thu, 17 Feb 2005 18:29:52 -0800

Greetings:
We continue to experience scatter from the column that is affecting users whom either write within a single writefield for a long period of time or those that place dose arrays very close together.  Most apertures are within specifications with the exception of the 20 um aperture. Measurements are continuing to evaluate this issue. To observe  this effect you must expose an area for sufficient dwell time to approach or exceed the dose to clear your resist film.

This week I was able to make several measurements of the actual area involved in this scatter and it is on the order of 185 um in the SSW direction from the center point.  This is the largest lobe of emission of three or more lobes of emission and the most evident artifact in exposure results.  The image in the background of this email was likely many hours of  the beam being blanked over this position, likely the final position at the end of an exposure.

To avoid this problem:

  1. Spread out your dose arrays in distances greater than 200 um U and V in your layouts.
  2. Avoid patterns that take a very long time to expose within a single write field.  I am finding on some users patterns that the exposure time can be radically reduced if you ' reorder your pattern by location' and let the RAITH editor select the order automatically. This will expose your pattern from the lower left  to upper write in sequence minimizing the stage moves and waits and beam translations and waits within each pattern's structures.
  3. Avoid very sensitive resist if possible.
  4. Avoid overexposure and over development of your ebeam resist.
  5. At the end of a exposure write either a dummy pattern or a Text Label well away from your critical areas. I routinely expose the flower.csf  or the demo.csf near the flat of my wafer were I established my U,V, and origin coordinates.
I expect that it will take some time and effort to correctly identify the root cause of this problem and likely I will need to open up the column to effect a repair.  We will continue to work closely with RAITH USA and members of the technical staff at RAITH GmbH to agilently address this issue.  If you follow the guidelines put forward above you should obtain useable results in your exposures.
Thank you for your support!
JAMES CONWAY







-------- Original Message --------
Subject: Re: Problem raith SNF 2005-02-15 17:24:20: 20 um aperture scatter when blanked is above spec.
Date: Thu, 17 Feb. 2005 17:57:34 -0800
From: jwc@snf.stanford.edu
To: raith-pcs@snf.stanford.edu


Cleared as no further reports of user problems reported.
Scattering at elevated levels for this aperture continue.
RAITH has requested further measurements before any action from them will occur.
This likely will take the long term to correct the root of the problem.
JWC 02172005:17:58:00
Thu, 17 Feb 2005 18:29:52 -0800

Subject: [Fwd: Re: Problem raith SNF 2005-02-15 17:24:20: 20 um aperture scatter when blanked is above spec.]
From: James Conway <jwc@snf.stanford.edu>
Date: Thu, 17 Feb 2005 18:29:52 -0800

["image/jpeg" not shown] Thu, 17 Feb 2005 18:29:52 -0800