Hi Nimo,

   Two things come to mind:

1. You might need more BHF?
2. Bubbles may be preventing the BHF from reaching certain areas?

Good luck!

Felix

On Jul 19, 2010, at 2:29 PM, antwi nimo wrote:

> Hello Friends,
>
> I was wondering if there are some silicon-dioxide which will not
> etch in
> BHF(31°C).
>
> I was etching the buried oxide of an SOI  which has the device layer
> DRIE'ed and
> i experienced this suprising effect whereby some of the oxide is
> somewhat
> resistant to the BHF. most of the oxide is etched but on some parts,
> there is
> still oxide which seems to be resistant to the BHF. There has not
> been any high
> temperature oven  process either......so i cant explain this effect.
> Has anybody experienced this effect and possible explanation why some
> silicon-dioxide will not etch in BHF.
>
> thanks in advance.
> Nimo

Felix Lu
felix_lu@yahoo.com