Hi David,

In my experience this line of Futurrex resists are very sensitive to both
bake temperatures.  I also found that they seem to require slightly higher
temperatures than listed in the Futurrex literature.  We did 160C/2:00 and
110C/1:00 for very thin germanium chips.  Consider putting a upside down
beaker over the glass slide when it is on the hotplate to help even out the
temperature a bit.  We generally developed for ~20 sec in a 3:1 mixture of
water and RD6 (http://grover.mirc.gatech.edu/data/msds/160.pdf)

-Alex

On Tue, May 11, 2010 at 9:26 AM, David Casale  wrote:

> Hi Brad,
>
> The exposure dose I am shooting for is around 300mJ/cm^2 on 2.5 micron
> thick resist, I am controlling by time not by actual dose, but I try to be
> consistent in terms of exposure time and how long the lamp has been on, etc.
> I am using lab hotplates, nothing made for resist processings (vacuum chucks
> etc.). Temperature uniformity once the plate is at steady state isn't bad,
> ±3°F over my active area, but I haven't checked with substrate in place. The
> substrate is also 0.060" glass, so it's very thick in comparison to a Si
> wafer. The %TMAH is the standard 0.24N stuff, I believe it works out to be
> 2.4% but I'd need to check the data sheet, Microposit 319. Do you suggest
> using a diluted developer? I didn't have much luck when I tried 3:1 dilution
> in getting much development at all.
>
> I can run a bunch of samples at the same exposure and vary PAB/PEB to see
> how it turns out. I am used to s18xx resists, and all that the baking is
> doing is getting rid of casting solvent, exposure is most important, just
> varies a bit depending on how much residual solvent there is. Do you happen
> to know if the PEB is used to finish crosslinking, or for diffusion purposes
> as well (I couldn't get a clear answer from the sales guy I spoke with)? I
> have had samples where the image appeared to be reversed even. Mind you,
> this was just shaking down the resist and trying to get a feel for it
> quickly, I have an OK procedure now but I have found that it is really hard
> to get consistent results, but the PEB and PAB haven't been my concern, I
> was playing with exposure dose. So maybe I will try again, varying PEB. Is
> 150°C OK for PEB? I have been doing 4 minutes @100°C for PAB and 10 minutes
> @150°C for PEB.
>
> Thanks,
> David Casale