Mike,

Thanks a lot for your prompt reply. Just one little question, how do you
protect back side of the Si wafer when you etch for long time? If I am not
wrong, from the etching set-up image, you etch the whole wafer, right?

Best regards,
Nam

On 8/25/06, Michael D Martin  wrote:
>
> Le Cao,
>    There are a few tricks to use for long TMAH etches. First, make sure
> you have a good seal around the top of the reflux condesnsor.  We often
> put a strip of electrical tape around the top of the beaker to improve
> the seal with the reflux condensor. Second, add about 17% v/v isopropyl
> alcohol to the solution to stabilize the etch rate and selectivity as a
> function of time.
>
> Here's a link to one of our lab write ups on bulk silicon etching:
> http://www.mems.louisville.edu/index3.html