[labnetwork] BCL3 - Gas Line Heaters and Protocols

[Bob Hamilton]

Colleagues,

I can share a UC Berkeley anecdote about delivering SICL4 via a long gas 
delivery line. SiCL4 has similar issues to Dean's query about BCl3 
delivery experience. SiCl4 has similar issues of a liquid/gas phase 
transition at low pressures, at 20 C.

Without problem, we delivered SICl4 to an etcher using one of our 
standard cylinder gas automated gas panels by adjusting the delivery 
pressure to about half the cylinder pressure. We felt confident the 
SiCl4 would remain in a gas phase.  Thus, we delivered at ~ 2 psi absolute.

As it turned out, one of a series of fan-coil units that delivered 
tempered air to the HEPA banks had been out of order since we 
commissioned the lab. This did not cause a significant problem as we had 
excess cooling capacity; however, we eventually got around to fixing it.

Shortly thereafter we began seeing BCL3 delivery problems to an etcher. 
It took a while to associate this fan-coil repair with BCl3 delivery 
problems. The BCL3 line had been routed directly under one of the 
cold-air discharge points. The fix for this problem was obvious; 
however, it took a while to make the association between a air-handler 
fix and the BCl3 delivery issue.

The lesson I learned is gas panels for subambient pressure need better 
low-pressure gauging than standard gas panels and better regulators. It 
is worth purchasing a dedicated subambient-delivery regulator.

Regards,
Bob Hamilton


On 8/26/2013 12:09 PM, Dean Sutter wrote:
> Hello,
>
> AT GT Nano we have a hard plumbed BCL3 line coming from a central gas 
> room, running several hundred feet into the sub fab eventually 
> connecting to the tools.
>
> We have been internally debating the necessary protocols and physical 
> installations necessary  to ensure a safe and properly functioning 
> delivery mechanism.
>
> These discussions have included the elimination of the central 
> approach, replaced with a local gas cabinet and shorter runs since 
> maintaining and being able to monitor line heaters on a several 
> hundred foot of line, buried in plumbing up in the ceiling  is our 
> primary concern.
>
> So, we are seeking a benchmark from existing facilities that use BCL3.
>
> Anyone care to volunteer to explain their installation and 
> operating/safety protocols?
>
> Thanks
>

-- 
Robert Hamilton
University of California at Berkeley
Marvell NanoLab
Equipment Eng. Mgr.
Room 520 Sutardja Dai Hall
Berkeley, CA 94720-1754
bob at eecs.berkeley.edu
Phone: 510-809-8600
Mobile: 510-325-7557
e-mail preferred