Hi,

Make a 40 % by weight solution for best results - i.e. 40% of the
final weight of the solution needs to be KOH pellets. Add the water
slowly, whilst stirring... and (if possible) immerse the in a cold
water bath during mixing to bring down the temperature. This is
because the reaction is very exothermic and excessive heating during
mixing can degrade the performance of the solution. Try etching in the
temperature range 70-80 deg C.

It may simply be that you are etching with the wrong concentration of
KOH at the wrong temp.

Let us know how you get on.

Michael


> jeeva S  wrote:  Hi all,
>   I did KOH (anisotropic ) wet etching of silicon. I
> used 10g of KOH
> pellets and mixed it with 100ml of DI water at 65 deg.
> Then I immersed the Silicon substrate in this
> solution. After one
> minute (as
> it was the time limit for 1 micron depth of substrate)
> when I removed
> the
> substrate from this solution, it was rough on the
> surface and also it
> was
> darkened (Black colored rough surface).
> Can anyone explain me why this has happened and give
> me correct
> procedure
> for the KOH wet etching with composition of KOH and
> water?