Hi,

I got good results with 5%KOH @ 80°C without ultrasonic support with no
additional additives! The only thing I do is to etch some Silicon Dummies
for
about 1/2 an hour before I start etching the "good" wafers.
The etch rate is around 1.2 micron/per min. .I use SiO2 mask layer.

Rgds

Marc

-----Ursprüngliche Nachricht-----
Von: GARCIA BLANCO Sonia [mailto:Sonia.Garcia.Blanco@ino.ca]
Gesendet: Freitag, 11. November 2005 15:47
An: 'General MEMS discussion'
Betreff: [mems-talk] KOH etch fo silicon with very low surface roughness

Hi,

I am starting to setup a KOH silicon etch bath. I would like to get 54.7deg
and 45deg grooves with very good surface roughness (less than 30nm would be
ideal).

Could anybody give me some suggestions about an starting point for my
experiments and an idea of what are the most important parameters and in
which way they will influence my etch?

(I did a first trial with 35%wt KOH, 20% vol IPA, 80C, ultrasounds, very
strong agitation and orientation of the sample vertical with the patterns
facing the current of the flow and the surface roughness was really bad. I
etched 80microns in 1.5h, so I think the etch rate is as reported in the
literature. I used a PECVD silicon nitride mask).

thanks a lot for your help!!

Best regards,

Sonia.