Hello.


>Hi Everyone,
>
>   I am trying to etch 2 micron thick membrane. I am
>using TMAH as the etchant, but the etchrate of TMAH
>maintained at 80C is varying a lot.


Are you using an etch-stop technique?
Is the main problem the reproducibility of membrane thickness? Thickness
homogenity across the wafer?

> Can anyone suggest a procedure that is reproduce able
>to a fairly large extent.

I assume the membrane is made of silicon. You can use an electrochemical
etch stop. This will stop the etching at about the depth of the
implantation, depending on stopping voltage.
Or use SOI wafers, with 2 um device layer. Etch the handle wafer, and use
the oxide layer as etch stop.

Regards

Burkhard