Muk:
i found initially some literature stating that agitation/sonication was a
must to remove H+ molecules stuck at the Si surface, which can inhibits the
wet etching. However, without it, i still can get a fairly got etch rate; i
just follow the process mentioned earlier here:
1. use a short dip time of a BOE, ambient temperature
2. Full rinse with DIW
3. TMAH solution (from 5% to 25%, the more diluted the higher the etch rate)
at high T (60C - 90C), since it's high temperature make sure to reduce DIW
loss. Sonication is optional.

depending on how much Si you are etching, some Si-biproduct remains in
solution, slowing the etch rate slightly, nevertheless, this should give you
etch rates between 200nm - 600nm/min

_fm

On Mon, Jul 28, 2008 at 7:57 AM, Muk Mei Yu  wrote:

> Hi Shay,
>
> Sorry to mention that 'BOE prior to etch' is already incorporated in my
> process, but yet I still encounter etch initiation failure. Do you mean
> fluorine contamination will prohibit the etching?
>
> Thanks,
> Muk

--
_fm