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