On Fri, 5 Jun 1998, 18@ZGv wrote:

> I have got some questions regarding to anisotropic etching of  <100>
> wafers
> we are etching v-grooves on 4" <100> wafers.  there are some problems
> about  silicon undercutting.
> I heard that isopropyl alcohol may be added to reduce the undercutting.
> but Isopropyl alcohol does not mix with water .

You will get a two phase mixture. The upper liquid is IPA
rich with a small concentration of water and KOH. The lower
liquid is the etchant and is primary water, KOH and a small
amount of IPA. For details of the etchant see: J B Price,
Anisotrop etching of silicon with KOH-H20-Isopropyl alcohol,
Semiconductor Silicon symposium, The Electrochemical society
series, 1973, pp 339-353.

> We are now using KOH+ D.I water etchant  and considering new method to
> add  isopropyl alcohol.
> I want to know the way to mix with isopropyl alcohol. we tried some
> methods using stirrer etc but failed.

It all depends on the solubility of IPA in aqueous KOH.
Quite concentrated solutions of IPA should be possible
to form in dilute solutions of KOH in H2O.

> If you have a good method. please tell me the method as soon as
> possible!
>
>

Good luck!

Leiv