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

[Henk van Zeijl - EWI]

Hello,

At Delft University we have an atmospheric exhaust system (scavenger) on the alloy furnace using 10% hydrogen in nitrogen, the system works fine since 1991.

Kind regards, Henk


Delft University of Technology / DIMES
POBox 5053
NL-2600 GB DELFT
The Netherlands
phone: ++31 15 2781092
Mobile: ++31 6 24373305
fax: ++31 15 2787369
Email: h.w.vanzeijl at tudelft.nl

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Fouad Karouta
Sent: 14 November 2012 03:44
To: labnetwork at mtl.mit.edu; 'Aebersold,Julia Weyer'
Subject: Re: [labnetwork] Anneal temp for aluminum on silicon with forming gas

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> [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<mailto: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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