You are on the right track with reducing the exposure.
The mouse bites are probably from nitrogen that is evolved in novolac
resists during exposure.
One solution is do part of the exposure, wait a minute so the nitrogen can
diffusively spread,
then complete the exposure, in sort of a pulsed exposure mode.
I think Suss designed this ability into some of their older aligners.
If your system does not allow such a pulsed exposure, at least try waiting
10 minutes before developing
so the nitrogen can diffuse.
    --Kirt Williams, Ph.D.   consultant

----- Original Message -----
From: Magali Brunet 
To: 
Sent: Thursday, April 24, 2003 9:50 AM
Subject: [mems-talk] mouse bites in photoresist


> Hi All,
>
> I am spinning a thick photoresist (novolac-type): around 60um. The bake is
> done at 90C for 40min.
> After exposure (typically 1680mJ/cm2), we are seeing mouse bites on the
> photoresist near the exposed area.
>
> I've tried to reduce the exposure time but without success.
>
> As anyone experienced this as well? would anyone know how to get rid of
> these mouse bites?
>
> Thanks a lot in advance
>
> Magali Brunet
>
> --
> Energy Processing for ICT
> NMRC, Lee Maltings, Cork, Ireland
>
> Tel: +353 (0)21 4 904279
> Fax: +353 (0)21 4 270271
>
>
> _______________________________________________
> [email protected] mailing list: to unsubscribe or change your list
> options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
> Hosted by the MEMS Exchange, providers of MEMS processing services.
> Visit us at http://www.memsnet.org/