[labnetwork] Forming gas: 5% or 10% hydrogen

[Andrei Alamariu]

Hello,
Safety first:
You can purchase tanks with up 5.5%H2 in Nitrogen electronic grade mixture; and use it with some simple recipe interlocks ( 5 minute N2 flush before & after Forming Gas run), and check the gas exhaust scrubber.
Please note that while this is an homogeneous mixture under high pressure, inside the tank, its concentration ratio could be different outside: accumulation of more than 6% Hydrogen in air is a hazard. Low probability but theoretically possible.
5%Hydrogen Forming Gas is historical standard for MOS capacitor final annealing.
For higher H2 concentrations, strict additional hardware interlocks are required.

The final Annealing aka Sintering process has 3 main functions:
1. Interface states density reduction by H2 saturation
2. Metal adherence to the substrate 
3. Annealing of the crystalline damage by the plasma assisted previous processes.
H2 diffuses very fast in Si above 400C.
The second one limits the Temeprature/Time process budget, depending of the metal-substrate combination. Historically the Al - Si combination is limited to 550C, and it’s
alloy process is called Sinter. Time dependent to avoid Al spiking. 
The process runs usually at 400-425C for 10 minutes, which might be too long for a RTA machine. Anyway any Sinter is better than none.
Thanks, Andrei
Sent from my iPad

> On Feb 27, 2024, at 3:56 PM, Beaudoin, Mario <beaudoin at physics.ubc.ca> wrote:
> 
> 
> Dear Network,
> 
> We're setting up a new RTA and will run it with Ar, N2 and forming gas.  We're uncertain about the % level of hydrogen we want in our forming gas.  Can someone recomment the best hydrogen % to use for MOS capacitor annealing?
> 
> Regards,
> 
> Mario
> 
> -- 
> 
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