Hi Sheeja,
 is your agitation sufficient? have you used a magnetic stirrer or
ultrasonic?
regds
Ravi Shankar


On 2/8/07, sheeja mathew  wrote:
>
>
> Hi all,
>
> Sub: Precipitate during KOH etching
>
> We have a problem of black precipitate formation
>
> during KOH etching of Si. SiO2 is masking layer,
>
> Si is being etched in 30% KOH(30g KOH and 100ml
>
> DI water)   solution with 30ml tert-butanol*.
>
> The thickness of Si to be etched   is 10-12um.
>
> The tert butanol is added to avoid undercuts which
>
> will destroy   the right-angled beams.
>
> The etching solution is kept at 80C and once the
>
> solution stabilizes at the temperature the sample is
>
> put. A black deposition   is found on the sample especially on
>
> the pattern. Once the black precipitate   comes, further etching doesn't
> take place.
>
> Can anyone please suggest a solution?