Subject: Changes in your ZEP 520 A process --> changes in resist dose to clear. Have you observed lower doses to clear on your work since January 20th, 2010?
From: "James W. Conway" <>
Date: Thu, 18 Mar 2010 09:21:22 -0800

Greetings RAITH and ZEP-520A Users:

I have observed in my characterization work that the current batch of 
ZEP-520A seems to have a slightly different exposure dosing 
characteristic that all previous batches.  Formerly at 10 kV using the 
10 or 20 Ám aperture my dose threshold to clear was on the order of 37 
to 40 ÁC/cm**2 on Silicon and SOI with 250 nm resist thickness.  In my 
recent work both on Quartz with Cr and a small number of Silicon 
substrates my current dose to clear has dropped to between 27 and 32 

(At 30 kV on the Hitachi currently is 80 to 90 ÁC/cm**2 for larger area 
patterns, formerly between 120 and 135 ÁC/cm**2.)

Please report to this list if you also have observed similar changes in 
your EBL work on any system.  This may be just statistical variation in 
my measurements.

Thank you for your support!

James Conway