Hello,
I hope the following resolution helps you or others in
some way with regards to Oxide RIE Etch:

Whilst try to obtain an selectivity of 1:1, between Si3N4 and SiO2 in the
past, Using Freon 23 and Oxygen, I found that:

1) Reducing  the pressure increase the Oxide to nitride selectivity, and
reduce sidewall attack ==> greater ion:radical ratio (etc.).

2) increasing Freon23, to some degree, inhibit sidewall
attack, but adds to uniformity woes - also reduces oxide:nitride
selectivity.


Phil

(PS: nitride is used in the 'semi industry' as a H/Mask during oxide etch -
which I'm sure you knew)

----- Original Message -----
From: "Ravi Shankar" 
To: 
Sent: Saturday, August 24, 2002 10:11 PM
Subject: [mems-talk] plasma etching problem


> hi
>  I am facing a problem in plasma etching. My process is to make MESA like
> structures of silicon di oxide on silicon nitride substrate. during the
> dry plasma etch there is etching into silicon nitride only along the sides
> of the features. does anyone has an answer to why its happening.
>
> regds
> ravi shankar
> semiconductor complex ltd
> India
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