That is true for most etching processes the larger the openning the
faster the etching but for Xe etching it is the case. As the features
get smaller etching depth per round gets shorter.

Mehmet Aykol
USC Electrophysics

On Feb 21, 2009, at 12:47 PM, junjun wu  wrote:

> Hi,
>
> I'm using XeF2 to etch a Si wafer that has different feature sizes
> (squares)
> on the same surface, like 1mm, 0.3mm, 0.1mm etc. I found that the
> etch rate
> decreases as the feature size decreases. I used 3 torr of XeF2 for
> 30 sec
> and various cycle numbers. I wonder if this is common with XeF2
> etching or
> has something to do with the patter of the gas inlet holes over the
> wafer
> surface. Please advise if there are any ways to obtain uniform etch
> rate on
> different feature sizes on the same wafer surface using XeF2.
>
> Thanks,
>
> --
> Junjun Wu
> Twin Creeks Technologies