[labnetwork] CVD Diborane Diffusion

[Robert M. Hamilton]

Siva Penmetsa,

Can you better describe your process, i.e. is it 
atmospheric  or subatmospheric? Have you considered BCl3 in 
a diluent such as Ar in lieu of diborane?

I am not qualified to write about your resistivity issues; 
however, I have fair experience using diborane in gas 
jungles and in furnace applications. Diborane is usually 
diluted in hydrogen (10%, bal. H2 is common) when used as a 
gas source in semiconductor applications. Diborane is 
unstable and forms higher order boranes which deposit on the 
surfaces of gas jungles. This can be problematic with valves 
and mass flow controller.  I have witnessed the issues with 
regulators and valves, and read discussions about drift in 
mfc's because of polymerization of diborane within the 
capillary of the heated gas bypass sensor. Because of this 
we routinely programmed our recipes to pump diborane from 
the gas jungle upon completing a process. There's no cost or 
downside with this precaution. .

Because diboranes decompose at high temperatures it can be 
difficult to maintain uniform dopant distribution within the 
wafer load. This is even more problematic when diborane is 
used via an injector tube because of the higher pressure 
within an injector, the greater surface to volume ratio and 
that injectors invariably pass through the guard zones of a 
furnace, which operate at higher temperature than the flat zone.

We have obviated diborane for furnace processing and we 
currently use a 1% BCl3 in Ar for both atmospheric doping 
and for lpcvd Si/Ge films with good success.

Bob Hamilton

Robert M. Hamilton
Marvel NanoLab
University of CA at Berkeley
Rm 520 Sutardja Dai Hall
Berkeley, CA 94720-1754
bob at eecs.berkeley.edu
(e-mail preferred)
510-809-8600
510-325-7557 (mobile - emergencies)

On 8/9/2012 4:44 AM, Siva Penmetsa wrote:
> Hi All,
> We are trying to optimise Diborane furnace in a new CVD 
> equipment.
> We have performed few trials(all the souces are gases) at
> Temperature 1000 C
> Diborane Flow rate in the range 40 sccm to 100 sccm
> Oxygen flow rate 2 SLPM
> Nitrogen flow rate is 3 SLPM
> Time 30 minutes
> Instead of decrese in resistance we observed that the 
> resistance incresed to around 500 ohm/sq from around 50 ohm/sq
> We apprecite your experience and inputs on how we can 
> resduce the resisitivity with better Diborane diffussion.
>
> -- 
> Thanks & Regards,
> *Siva Prasad Raju Penmetsa*
> /Senior Facility Technologist/
> National Nano Fabrication Center
> /Indian Institute of Science(IISc)/
> Bangalore, India 560 054
>
>
>
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