[labnetwork] Oxide growth in Nitrogen

[Savitha P]

Hello!

 We have a horizontal furnace, but the exhaust system is not a scavenger
type. We have individual 1 inch exhaust tubes from each of the furnace,
connecting to a common exhaust pipe which in turn is connected to a local
scrubber system. There are 4 tubes in each of the furnace stack and we see
this problem in all the tubes.

When you say, the thickness is >5nm, could you please let me know what is
the upper limits that you see and whether you do this experiments on the
tubes in the stack and is there a trend in the thickness with respect to
their position in the stack.

Thanks and regards,

Savitha

> Savitha P.,
>
> It is difficult to predict the purity of the N2 in your
> atmospheric process tube without knowing more about the
> geometry of the tube. Is it a horizontal or vertical furnace?
>
> Backstreaming will play a role in the furnace atmosphere.
> One presumes the tube has an exit opening(s) which ports
> into a scavenger. Back-diffusion/partial pressure laws will
> invariably increase O2, CO2 and water vapor partial
> pressures in the furnace environment.
>
> At Berkeley, we reduced O2 contamination by modifying our
> OEM's furnace tube exit port design. In addition to reducing
> overall exit orifice area, we increased the number of exit
> ports and positioned them symmetrically around the
> circumference for better cross-wafer uniformity.
>
> Our go/no go standard for N2 atmospheres in our atmospheric
> furnaces was >5 nm oxide/1000 C/12 hours.
>
> Also, the furnace pre-clean step is important. I'll defer to
> others on the labnetwork who are more qualified to discuss this.
>
> Bob Hamilton
>
> Bob 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 2/11/2013 3:22 AM, Savitha P wrote:
>> Dear Colleagues:
>>   We had done a N2 anneal in our atmospheric furnace for 10hrs at 1100
>> deg
>> C, substrate was silicon <100>, P-type. The oxide thickness obtained
was
>> ~16nm (variation of 15.2 - 17.6nm). For one hr anneal, the thickness
obtained was ~5nm. It would be really helpful if we could know the
silicon
>> dioxide thickness expected for N2 annealing experiments. The percentage of
>> O2 impurity in our N2 is supposed to be <1.000 ppb according to our
purifier specs.
>> Regards,
>> Savitha
>
>
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-- 
Dr.Savitha P
Facility Technology Manager
National Nanofabrication Centre
Centre for Nano Science and Engineering (CeNSE)
Indian Institute of Science
Bangalore - 560012
Ph: +91 80 2293 3254
www.nano.iisc.ernet.in




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