Hi,

I am  using YES oven for image reversal of positive PR
(SPR 220). The PR is 5 microns thick and the
underlying substrate was Sio2. After exposing the
wafer to NH3 atmosphere in the YES oven, the PR
appears to be crystallised. I can see small crumbles
of white powder emanating from the edges of the wafer.
They appear to be more like salt crumbles. This powder
can be blown off by the N2 gun but not all of them.
This powder is affecting the yield of my devices
especially at the edges. Can you suggest me regarding
this problem.

I would appreciate your help.


Thanks,
Kris