Thanks, Joe. I'll try the horizontal setup. We are using a
glass top with DI flowing in it for condensation. N2 bubbler
seems like a nice thing to try as well.

Elena
---- Original message ----
>Date: Wed, 20 Apr 2005 11:41:54 -0400
>From: "Joe Lonjin" 
>Subject: RE: [mems-talk] back-side etch: uniform temperature

>You can simply use a hot plate for heating so long as you re-circulate
>the solution. You can do this by using a small pump with the input tube
>at the bottom of your container and the return at the top of the
>container. Use the shortest tubing possible. Also use a hotplate with a
>spinner so you can put a magnetic stir bar in the bottom for added
>agitation, and maybe a tube with n2 bubbling for extra agitation. This
>will all improve the temp and mixture stabilization. Once final note,
>use a lid with a hole for a probe for constant feed back to the
>hotplate, the lid will help to keep the TMAH from evaporating away,
>which changes etch rate, and surface roughness as the solution depletes.
>