Hi Andrew,
For Question # 2, I suspect you will have difficulty finding a selective wet
etch of gold to aluminum. If your process would allow it, you could try a
liftoff process for patterning the gold, since you are evaporating it,
liftoff should be easy well up to 3,000 angstroms of gold thickness using
AZ5214 image reversal-type of processing.
You could also choose to stick with your current mask and photo pattern
method and try a dry etch process for the gold, like ion beam etching with
Argon. S1813 is a good resist for this, make sure you use a postbake to
roll the resist sidewalls out of the way, and strip in some NMP-based
solvent after etch, using ultrasonics if possible.
- Justin
Justin C. Borski
MEMS Program Manager
Advanced MicroSensors Inc.
[email protected]
www.advancedmicrosensors.com
-----Original Message-----
From: Andrew Turton [mailto:[email protected]]
Sent: Friday, December 12, 2003 12:08 PM
To: [email protected]
Subject: [mems-talk] Pad Etch for Aluminium
Dear All
I need to etch through 2.5 microns of CVD SiO2 to access Aluminium contact
pads. The pad etch recipe I am using is equal parts of Ammonium Fluoride,
DI water and Acetic acid. The resultant etch rate means 40 minutes is
required to etch through the 2.5 microns, opening the Al pads, but leaving
them matt in appearance and crazed.
A subsequent Gold evaporation (for subsequent masking) and removal with
Potassium Iodide (4) / Iodine (1) / DI Water (8) etch resulted in complete
removal of the contact pads.
I have two questions :
1. Does anyone know the above Pad etch recipe attacking Aluminium, and if
so, are there any alternative etches suitable for 2.5 microns of SiO2?
2. Has anyone had any problems with the above Gold etch attacking aluminium
and do they know of any alternatives?
Thanks,
Andrew Turton
School of Engineering
University of Durham
South Road
Durham
DH1 3LE
ENGLAND
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