Hi, Moffat

I am using AZ4620 with normal litho process to get the hole with diameter of 6
um and height of 13 um or more but I never get vertical wall.

Do you think I must use 90 degrees C in a vacuum the step 2.

Best regards!

XiaoQiang

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Bill Moffat
Sent: 星期三, 16 五月, 2007 PM 11:07
To: General MEMS discussion
Subject: RE: [mems-talk] AZ5214E in image reversal mode

Jeffrey,
        Here goes.  The secret of image reversal as a tool for lift off
is you can profile the resist side wall to present a reversal angle that
metal will not deposit on.  Using negative resist does not achieve this.
If you want to run some free experiments contact me.  Suggest the
following process:-
1) Coat SiO2 with any positive resist spun to any thickness.  We have
used from 1 micron to 40 microns.
2) Soft bake preferred 90 degrees C in a vacuum.  Any temperature over
90 starts to destroy the sensitizer and the critical dimensions suffer.
3) Expose at 405 nM near UV light intensity of 7.5 mW/cm2 for about 6
seconds.
4) Reversal bake at 90 in an ammonia YES oven for 45 minutes. The
ammonia will diffuse through the resist and neutralize the acid created
by exposure.
5) Flood expose same intensity, 6 seconds will give you a negative
slope. 9 seconds will give you 90 degrees vertical, 12 seconds will give
you about 20 degrees negative slope.
6) Develop in positive developer not too strong not too hot.
7) Deposit metal.