[mems-talk] Best resist for HF etching

[Mikael Evander]

Hi!

How long are you able to etch with just chromium as a mask? I've done some fast tests with chromium and chromium/gold but I've never been able to etch very deep without the chromium being dissolved by the HF :(

/mikael

----- Original Message -----
From: Michael Larsson <michael.larsson at gmail.com>
Date: Friday, November 16, 2007 2:57 pm
Subject: [mems-talk] Best resist for HF etching

> Hi Mike,
> 
> Why use photoresist at all? You could just use a patterned layer 
> of a
> Cr as the mask. In my experience, even buffered HF attacks
> photoresist. It may stick, but it will degrade the longer it remains
> in the etchant. Of course there is no harm in leaving the photoresist
> layer on the Cr, but as it absorbs liquid from the solution, the edges
> will soften, expand and warp, affecting the resolution of pattern
> transfer. Also, if you wet-etch the Cr, the Cr etchant will attack the
> photoresist so you will no longer have a pristine photoresist mask for
> the subsequent HF step.
> Pattern the Cr, strip off the resist, run an O2 plasma descum, then
> etch the Pyrex in your chosen HF mixture. Good luck! :)
> 
> Regards,
> 
> Michael