[labnetwork] LPCVD film anomaly

[Albert William (Bill) Flounders]

Terre,
Bob Hamilton wrote to me also and advised your issue is possibly caused by
entrainment when the gate valve is closed and the tube is backfilled.
I welcome an offline discussion to describe our "flow path around the gate
valve" which we call the "shunt bypass"
and it includes integrated pressure gauge to insure operational. The last
addition was the pin for clearing the bypass
when it became clogged.

Bill Flounders
UC Berkeley

On Tue, Aug 3, 2021 at 4:49 PM Tony Whipple <whipp003 at umn.edu> 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: image.png]
>
>
>
>
> On Tue, Aug 3, 2021 at 11:20 AM Terre Briggs <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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