Dear Jared,
we had similar problems when we first tried to structure SiN membranes. I
can't tell you every detail about how we do it, and also I don't know every
detail about your process. Some hints and questions, anyway:
1. What kind of SiN are you using? What thickness?
Depending on the depositing process and the thickness of your layer the
intrinsic tension may be high enough to shatter your membranes even without
scratches. A thick oxide layer will add to this problem. KOH-temperature
usually is above room-temperature.
2. Have you tried photoresist as a protective layer?
3. In order to protect a wafer from scratches from the vaccuum chuck, don't
use a vacuum chuck. Build a frame from sheet metal with a wafer-size
cut-out. Must be quite accurate and only the wafer edges must touch the
bottom. This works for spin coating.
For our membranes we are using thin LP-CVD Nitride (strainreduced, if
neccessary) or strainreduced PE-Nitride for thick membranes.
If you need more help, please contact my company, for I will leave the
company next week. They could certainly tell you more details about our
process, but then, it is a commercial company ... :-)
Cheers,
Ralf.
_______________________________
Ralf G. Longwitz
Dipl.-Ing., B.Sc.
Private e-Mail: [email protected]
CiS Institut fur Mikrosensorik e.V.
Haarbergstr. 61
D - 99097 Erfurt
Tel.: (0) 361 - 420 51 - 0
Fax.: (0) 361 - 420 51 - 13
_______________________________
-----Ursprungliche Nachricht-----
Von: JARED_LERA/electronics_singlekh2_kihung_grp0@gp_man
[SMTP:JARED_LERA/electronics_singlekh2_kihung_grp0@gp_man]
Gesendet am: Donnerstag, 26. November 1998 08:44
An: [email protected]
Betreff: Defects due to photo patterning
Dear colleagues:
I am having a problem with making SiN membranes. When I pattern the
backside of the
wafer the SiN coating on the front side gets all scratched up due to the
chucking and
handling used in our photo lithography process. These scrathes then cause
our membranes
to shatter when the SiN layer is exposed after the silicon is all etched
away. I have
tried to place a thick oxide layer (2 microns) over the SiN to protect it
during the
back side patterning. But still many defects appear. Is there any kind of
chucking machine
that protects the side which is being handled?
Thanks in advance for you help,
Jared Lera
Semiconductor R&D
Samsung Electronics
