Hello Dimitar,
When developing SU-8 with PGMEA you should see the unexposed polymer dissolving
rather quickly. If it’s taking you forever I suspect there may be a problem with
the baking steps or with the SU-8 itself.
Although I’ve never worked with Pyrex and that particular SU-8 — I work with Si
and mainly with SU-8 2015 and 50 — I can only advise you to start by using the
protocol suggested by Microchem, i.e.:
* Spin coat
* 65 ºC, 2 min, increase to 95 ºC (leave the sample on the hotplate), 95 ºC,
7 min
* Expose
* 65 ºC, 1 min, increase to 95 ºC (leave the sample on the hotplate), 95 ºC,
6 min
* Develop
I usually let the sample cool down 2-3 min after each baking step and, at times,
I just put the hotplate back to 65 ºC and let the sample on top of it.
I’m assuming that you’re using a (contact) hotplate. If you’re using a
convection oven these times should be higher.
If the substrate is clean (and this is another important point) and the steps
were properly performed, you don’t have to be very gentle in your developing.
Substrate cleanliness is a vital aspect for both photoresist adhesion and the
prevention of bubble and defect formation, so this might also be a point to
consider.
Please let me know how it went.
Cheerio,
__________________________________________
João Tiago dos Santos Fernandes
INESC Microsistemas e Nanotecnologias
Rua Alves Redol, 9
1000-029 Lisbon
Portugal
Tel: +351 21 310 02 31
URL: http://www.inesc-mn.pt
and
Institute of Nanoscience and Nanotechnology (IN) - Associated Laboratory
URL: www.in-nano.net
On 07 Jul 2014, at 18:25, Dimitar Dimitrov
> wrote:
Hello,
I am graduate student in Brooklyn College and I am trying to reinvent the whole
MEMS procedure as I do not have any professional help. My science adviser is
from another field.
I am having difficulties with the developing of SU-8 2025. Here is what I am
doing:
I am spin - coating 4 inch Si or Pyrex wafer to 50 - 60 um thin film
Pre - baking at 96 degrees for 15 min
Sometimes instead I am putting the wafer in the vacuum chamber of my UV
imprinter. The vacuum is taking away the solvent and clear most of the bubbles.
UV exposure with a hand made Imprinter: Xenon lamp 22kV at 10 microsec. pulses.
Three 30 seconds exposures with couple of seconds pause.
UV lamp creates heat so the wafer is let for 2 - 3 min to relax.
Post bake of 15 min at 95 degrees.
Developing by tenderly shaking the wafer in a vessel with Propylene glycol
monomethyl ether forever.
The result is that I clearly can see my pattern as exposed SU-8 is yelowish but
the unexposed parts are not removed and form thin film with the exposed part.
Less exposure leads to removing all of the polymer.
(This is happening even without any mask but the pattern is formed by metal
structure that divides 4 inch wafer into several smaller regions.)
Can anybody figure out what is my mistake?
Thank you
Dimitar Dimitrov
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