Subject: RAITH STATUS: PASSED qualification. No blanking artifacts noted! SYSTEM is up... details inside...
From: James Conway <jwc@snf.stanford.edu>
Date: Tue, 27 Jul 2004 17:26:41 -0700


Greeting:

I developed and optically inspected the patterns written yesterday for the RAITH Qualification run 07262004_1

Three test patterns were written:

Finally THE BLANKING ARTIFACT PROBLEM WAS CORRECTED!
Details below...

Last week working with LEO (now ZEISS!) and Raith USA application specialist Joe Klingfus we determined that the RAITH blanking plate orientation to the Aperture plate was incorrect from the RAITH specifications.

 There is a difference in the orientation between the default LEO Gemini 1530 column and the RAITH 150 system that had not been communicated to LEO-USA from LEO - Oberkocken in Germany at the time of the PM routine in March. This was the root cause of the two blanking problems we were experiencing making it very difficult to troubleshoot:

  1. The Electron beam when blanked was leaking a small amount of Beam Current during RAITH blanking functions.  This value was measured at between  400 and 500 fAmps.  This is just slightly above the normal background leakage that any SEM column has in normal use from scattering events in the column. (typcially 350 - 400 fA.) 
Users whom were exposing a single write field for long periods of time had seen this artifact of the blanker leakage.  Threshold was about 38 minutes writing in PMMA, and 12 - 14 minutes in ZEP -520.

2. Upon switching to the LEO camera  during a load lock wafer exchange, the beam was swept across several aperture holes when sweeping the beam from the RAITH blanker position to the LEO Blanker position. (Note: There are two separate blankers and two distinct  blanking positions.)  This was evidenced by a much larger blanking artifact that most users had observed at the stage position at the end of their write sessions.

I am placing the system back into UP mode with the Green Light 'ON".
Users are encouraged to carefully inspect their patterns and verify no further problems are evident.
More patterns will be tested on the system over the next few days.
Another additional email will list other work and repairs performed last week.

Thank you for your support!

James Conway