[labnetwork] LPCVD film anomaly

[Mary Tang]

Thanks Tony!

Yes, I was trying to remember what Ted Berg, our furnace guy at the 
time, did about the "champagne nitride".  I don't recall the plumbing 
solution exactly, but he took a cue from Berkeley and found a way to 
ensure a constant, low draw during unload.

Mary

-- 
Mary X. Tang, Ph.D.
Managing Director
Stanford Nanofabrication Facility
Paul G. Allen Building
420 Via Palou Mall
Stanford, CA 94305
https://snf.stanford.edu
mtang at stanford.edu


On 8/3/2021 2:29 PM, Tony Whipple wrote:
> Hello Terre;
> I thought I saw this type of image before and we had a similar problem 
> with our LSN process, see image below.
> It turned out that with our setup we were having a reaction with 
> residual that would react when we vented the tube.  This
> reaction would cause particles to fall ( rain ) on the wafers when the 
> tube was vented and being unloaded. We had talked
> with Bob Hamilton at Berekley while visiting there and noticed his 
> LPCVD setup and his solution before we noticed the
> same problem with our LPCVD.    After installing the fix we did not 
> have this issue anymore.
>
> The solution is to provide a very limited small low flowing path 
> around the gate valve so that when the gate valve is closed
> ( such as during tube vent ) the tube still has a small draw on it 
> pulling any reactions toward the pump and away from the
> wafers.  If you have this type of bypass already, the only thing would 
> be to confirm that it is still working I guess. We had a
> pressure gauge installed next to this to confirm that it was working 
> and not plugged.  We would see a pressure change
> that indicated it needed cleaning soon.
>
> Regards, Tony W.
>
>
> image.png
>
>
>
>
> On Tue, Aug 3, 2021 at 11:20 AM Terre Briggs <terreb at umich.edu 
> <mailto:terreb at umich.edu>> wrote:
>
>     Hello All,
>         We are currently having film quality issues with our LPCVD Low
>     Stress Nitride, HTO and Nitride films. Without getting into all of
>     the details just yet I am sharing with you some SEM images. The
>     anomaly, as our furnace manufacturer describes it, are what look
>     like spheres, or bubbles on the surface of the films. We are
>     pretty confident that the spheres are only on the surface and not
>     down into the film itself.
>     It is very random across the wafers and across the wafer load.
>     After further processing, the spheres come off and leave behind a
>     divot, or crater on the surface. This can also be seen in the SEM
>     images.
>        My question is, has anyone ever seen anything like this with
>     any of your LPCVD films? I have been working with Tempress for the
>     last several months to resolve the issue, but they have never seen
>     anything like this, and so far we have not made any progress
>     in determining the source. Any help would be appreciated.
>
>     Thanks.....Terre
>
>     Terre Briggs
>     Engineer in Research Sr.
>     Lurie Nanofabrication Laboratory
>     University of Michigan
>     1301 Beal Ave.
>     Ann Arbor, MI 48109
>     734-320-4470
>
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