Alton,

AZ9260 is not truly a thicker resist than AZP4620 - they actually nearly the
same spin-curves. The primary difference between the two has more to do with
transparency.

I have actually successfully coated and patterned AZP4620 in excess of 60 µm
(although at that thickness, exposure did become more difficult due to
transparency issues).  The thicker this material is, the more difficult it is
for the exposure radiation to penetrate all the way through. However, for 30µm,
this is not too bad (depending, of course, on minimum feature size).

If aspect ratio is a little more critical, you can use AZ9260.  Just like
AZP4620, if you can manage to spin at somewhere around 1000 RPM, you should be
able to get to ~25µm (depending on coating system, of course).

Best Regards,
Chad Brubaker

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Hsiu-Jen Wang
Sent: Saturday, October 14, 2006 9:48 AM
To: [email protected]
Subject: [mems-talk] AZ 4620 as the mask of DRIE

HI all,

    I used AZ 4260 as the mask of DRIE to etch through Si Wafer (
500~550um). The origin recipe can reach 19 um thickness of AZ 4620
(double coating), and the ideal selectivitiy of AZ to Si is 54:1.
However, 19 um AZ 4620 seems not thick enough in entire process. Is it
because of too large expose area (Area where want to be etched in
DRIE)? My expose area is almost 50%. Or can someone suggest me to use
thicker one like AZ 9260? If so, could some experience be offered? I
pretty much appreciate it.