[labnetwork] Anneal temp for aluminum on silicon with forming gas

[Fouad Karouta]

Hi,

 

Indeed I do agree with John about the issue related to an open furnace tube.
I assumed a sealed furnace tube with vacuum pump.

 

Regards, Fouad 

 

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu]
On Behalf Of John Shott
Sent: Wednesday, 14 November 2012 12:09 PM
To: labnetwork at mtl.mit.edu; Aebersold,Julia Weyer
Subject: Re: [labnetwork] Anneal temp for aluminum on silicon with forming
gas

 

Julia:

Fouad is correct that things like epitaxial reactors and MOCVD equipment run
pure hydrogen at high temperatures.  They also have careful pre- and
post-run purging to remove residual air before hydrogen is introduced and
typically also have some form of hydrogen burning/scrubbing at the exhaust
end.  In short, epi reactors and MOCVD systems go to great lengths to make
sure that oxygen and hydrogen NEVER mix at high temperatures.  I certainly
wouldn't want to be in the room if you tried to run pure hydrogen at 800 C
in a typical horizontal annealing furnace.  I suspect that Fouad would agree
that this would be a very bad idea.  Long ago, when running an oxidation
furnace with a hydrogen torch to generate steam, I learned why you want to
make sure that the ratio of hydrogen to oxygen is safely less than 2.0: I
turned a cassette of wafers into fine glitter all over the laboratory floor.

But, back to the issue of forming gas anneals:

For a comparatively open forming gas anneal setup, I believe that your
numbers of 5% forming gas at 400 C or slightly higher are right in the
proper ball park.  I'll be surprised if others aren't very close to this
range in their own usage.

We at Stanford run 4% forming gas and the great majority of our lab members
likely do their annealing at either 400 or 450 C typically for about 30
minutes.  The furnace used for this typically idles close to 400 C so there
isn't  too much of a ramp up/down even if the actual anneal will be at 450
C.

At 450 you probably get slightly better annealing of interface traps than
you would at 400 C ... but you can also see more in the way of hillock
formation if you have aluminum or aluminum-alloy metalization on your
wafers.

Good luck,

John


On 11/13/2012 2:07 PM, Fouad Karouta wrote: 

Hi Julia,

 

Pure H2 is commonly used in epitaxy reactors at temperature well above
600°C. MOCVD of GaAs/AlGaAs is performed at T=600-800C.

In the past I did liquid phase epitaxy of GaAs/AlGaAs around 800C in pure
H2.

Moreover Flammability of H2 in air is between 4 to 80%. So in inert gas like
N2 the flammability are different.

 

Hope this would help.

Fouad Karouta

 

 

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