Hello,
there are several bottom side anti reflective coatings (BARC). I had good
experience with the one from Brewer Science.
Shay

William Lanford-Crick wrote:

> Hi Group,
> I am having difficulty patterning wide-bandgap semiconductors which are
> transparent to the 436 nm in our g-line stepper.  The incident radiation
> seems to be reflecting off the wafer chuck and back up into the photoresist.
> The causes the entire die to be somewhat exposed.  How can I prevent this?
>
> I have found some improvement by additionally spinning photoresist onto the
> backside of the wafer (AZ5214E at 2k rpm--I have not measured the thickness
> at that speed).  I suspect that using a very thick PR layer would solve the
> problem (by absorbing the radiation) but I would need to remove it
> immediately after developing the patterns, and I don't see an easy way to do
> that.
>
> Any suggestions?  Are there any spin-on materials that have high absorption
> at 436 nm and are easy to remove (without disturbing PR)?
>
> Thanks for any suggestions,
> William B Lanford-Crick
> Micro and Nanotechnology Lab, UIUC
>
> _______________________________________________
> [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/