[labnetwork] Oxide growth in Nitrogen

[Robert M. Hamilton]

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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