[labnetwork] Heating of BCl3 lines

Tue Aug 23 18:51:47 EDT 2016

Hi Nava,

I completely agree with Bob’s comments.  We do the same at UCSB.  We have a negative pressure regulator and are still capable of supplying the low sccm requirements of multiple systems.  Cylinder temp will make a difference as our gas rooms are not conditioned, but we are in CA so it is not drastic climate change.  If your cabinet is located behind the tool you should have no problem with this technique.  I would have a quality two stage reg, set it as low a pressure (+10-20%) as possible to meet your tool requirements and make sure no one readjusts after that.  It will be much simpler and we have not had an issue since this was implemented in more than 10 years.

Thanks, Tom

--------------------------------------------------------------

Tom Reynolds,  Lab Manager

UCSB Nanofabrication Facility

Electrical and Computer Engineering Dept.

Engineering Science Bldg #225, Room 1109E

Santa Barbara, CA 93106

805-893-3918 x215  office

805-451-3979  cell

805-893-3918  fax

reynolds at ece.ucsb.edu

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Robert M. HAMILTON
Sent: Tuesday, August 23, 2016 10:13 AM
To: Nava Ariel Sternberg <na2661 at columbia.edu>
Cc: Labnetwork <labnetwork at mtl.mit.edu>
Subject: Re: [labnetwork] Heating of BCl3 lines

Nava Ariel,

I recommend you do not heat (heat-trace) a BCl3 delivery line. Liquid BCL3 will then condense at any location along that line that is cooled and will pool as a liquid. I say this with decades of experience delivering BCl3 as an etch gas and as a dopant. There are several simple ways to deliver BCl3; the easiest being a low pressure or sub atmospheric pressure regulator. 

The vapor pressure of BCl3 at room temp is ~ 19.4 psia or about 4.7 psi gauge. Use a regulator to reduce this pressure by ~ 50% of cylinder pressure, for the delivery you are assured BCl3 will remain a gas everwhere along the delivery line and within the tool. This pressure is also low enough to preclude adiabetic expansion with an associated phase change across the orifice of a gas flow controller or mass flow controller. We have been able to deliver several hundred sccm's, to multiple etchers using this delivery scheme. Note, our typical BCL3 cylinder is a 15 lb supply kept in a ventilated gas cabinet. Air movement in the cabinet adds enough heat to keep the cylinder temperature relatively constant given our delivery rates (we the same scheme for SiCl4).  

The only cylinder gas issues I've seen in a research lab delivering a gas where the addition of heat was considered was at high NH3 flow rates. The cylinder temperature dramatically dropped at high flows thus reducing the available pressure and starving the line. Nitrous oxide is touted to have similar issues; however, our use rates are too small to be an issue.

There's a caveat, however. We do not use outdoor storage our online cylinders and we live along a coast with moderated temperatures. A cold winter day might obviate the above approach. 

Regards,

Bob Hamilton

Robert Hamilton

University of CA, Berkeley
Marvell NanoLab Equipment Manager

Rm 520 Sutardja Dai Hall, MC 1754

Berkeley, CA 94720

Phone 510-809-8618 (desk - preferred)

Mobile 510-325-7557 (my personal mobile)

E-mail preferred: bob at eecs.berkeley.edu <mailto:bob at eecs.berkeley.edu> 
http://nanolab.berkeley.edu/

On Tue, Aug 23, 2016 at 5:51 AM, Nava Ariel Sternberg <na2661 at columbia.edu <mailto:na2661 at columbia.edu> > wrote:

Dear all, 

We have recently purchased a new Oxford Plasma Pro System100 Cobra RIE that we intend to use with Cl chemistry (III-V etc.). Oxford recommended heating the gas lines of BCl3. Does anyone have experience with it? We are low on $$$ right now. How necessary that is? What is the best way to do this? 

Any thought would be appreciated. 

Thanks!

Nava

Nava Ariel-Sternberg, Ph.D.

Director of CNI Facilities

Columbia University

530 W120th Street, NY 10027
Room 1015/MC 8903
Office: 212-854-9927 <tel:212-854-9927> 

Cell: 201-562-7600 <tel:201-562-7600> 

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