[labnetwork] KOH Tank Design

[Bill Flounders]

KOH bath is electro-polished stainless steel extruded (soft corners) 
vessel.
Heated via an immersion heater, controlled by a PID controller.
Thermocouple and backup OT thermocouples are internal to the bath,
Type J with PFA cladding. Bath has lid, no reflux.

We sparge KOH bath with O2 to react with generated H2 and minimize 
hillock formation
J. Micromech. Microeng. 9 (1999) 139--145.

Members mix their own KOH, use for period of hours, can reserve for up to
2 days, then dispose. KOH is mixed from solid source with DI so material
cost is modest compared to CMOS grade acid bath


Bill Flounders
UC Berkeley NanoLab



Tony L Olsen wrote:
>
> Dear Labnetwork
>
> We are building a new wet bench and would like to include a dedicated 
> KOH etch bath to replace the current methodology of glassware with 
> stir bars on a hotplate.  We generally use a bath of 80°C.
>
> Our wetbench vendor initially quoted a recirculated bath in a 
> stainless steel tank.  We are concerned about the stainless, nor do we 
> believe the Teflon or PVDF wetted surfaces in the proposed diaphragm 
> pump will hold up to the hot KOH.  Another option we are aware of is a 
> quartz tank heated externally by recirculated water.  I'm certain 
> there are other options, too.
>
> Can you share your experience with dedicated KOH baths?  What is the 
> configuration?  What are the materials?  How do you mix/stir the 
> bath?  What problems have you experienced?  What would you do next time?
>
> Thank You,
>
> tonyO
>
> Tony Olsen
>
> Nanofab Cleanroom Supervisor/Process Engineer
>
> 36 S Wasatch Dr, Suite 2500 SMBB
>
> Salt Lake City,  UT  84112
>
> 801-587-0651 office
>
> 801-587-3077 fax
>
> www.nanofab.utah.edu <http://www.nanofab.utah.edu/>
>
>
>
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