Hi all,

I am also trying to etch Si using PMMA (as well as AZ5214 photoresist) as a
soft mask with a 'normal' RIE (no Bosch and no ICP, but ICP is available in
the system).

Unfortunately, the selectivity I obtain is only about 1:4 Si:PMMA.
My recipe is:

SF6 (0.4sccm) + He (10sccm)
Power between 50 and 150W
Pressure = 0.03mbar.

I tried also Al2O3 as hard mask but obtained with the same recipe also a
rather low selectivity of 10:1 Si:Al2O3. This should be much higher, isn't
it?

I want to etch 'only' between 100nm and 500nm, which is not possible with
the current recipe.
Anybody any suggestions?

Ciao
Daniel



-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org]
On Behalf Of Jie Zou
Sent: 25 August 2009 08:35
To: General MEMS discussion
Subject: Re: [mems-talk] PMMA as hard mask

huge. Even more than 100 if you choose some recipes aiming at fast etching.

On Mon, Aug 24, 2009 at 7:20 AM, renil kumar
wrote:
> Hi all,
>             Can I use PMMA as hard mask during Silicon DRIE. What is the
selectivity between PMMA and Silicon during Bosch process. Any suggestions
regarding this will be grately appreciated.
>
> renil