Satish,

What is the power and pressure regims that you are using.
Typically it is better to use CF4 with O2 to etch SiO2 and this usually has
very good selectivity between Si and SiO2.

The C: F ratio determines the selectivity.
You can also try a combination of CF4/CHF3/O2.

Rashmi


On 4/10/08, Satish wrote:
>
> Hi all
>
> I am wondering if someone can suggest me a good plasma chemistry to
> get a very good selectivity between SiO2 and Si
>
> I am using Trion's minilock phanthom III series ICP RIE etch system. I
> have access to Ar, N2, O2, BCl3, Cl2, CF4 gases.
>
> CF4 is etching both Si and SiO2, even Cl2/BCl3 combination is etching
> both.
>
> Thanks a lot
> Satish