[labnetwork] LPCVD film anomaly

Wed Aug 4 17:43:03 EDT 2021

I want to thank everyone who has replied up to this point. I have several
new directions to head in and several items that I need to check out.
Unfortunately our furnaces suffered a hard shutdown due to loss of power. I
will be quite busy bringing them back on line and won't have time to look
into this at the moment. I am planning to email each one of you when I have
some free time, so look for a response in the future. Thank you again for
your willingness to help us resolve this issue. I will also reply to the
thread once this problem is finally solved.

Terre

On Wed, Aug 4, 2021 at 10:12 AM mark cooper <markc at exper-tech.com> wrote:

> The soft pump, (sometimes called the half gate) should be non interlocked
> and allow you to open while you are pulling the load. We did custom tools
> with a slow pump valve with standard 1/2 inch nupro, a medium pump with a
> NW25 gate, and a main vacuum valve with ISO 80 valve, gave more options in
> the pump down and backfill.
> The ammonium chloride will build up on Nitride, so blanket heaters are
> always important.
> The N2 backfill should be able to flow while the process door is open, but
> make sure the flow it attached to the load area either through a connection
> to the front flange, or through an rear connected injector.
> We had built some CVD polysilicon configurations with a blanket or curtain
> purge in the scavenger box so the wafers would pass through N2.
>
>
>
> *Mark Cooper*
>
> *Expertech General Manager*
>
> *10 Victor Square, Suite 100*
>
> *Scotts Valley, CA.  95066*
>
> *Office: (831) 439-9300*
>
> *Direct:(831) 440-4422*
>
> *Mobile:(831) 332-9396*
>
> *markc at exper-tech.com <markc at exper-tech.com>*
>
>
> ------------------------------
> *From:* labnetwork <labnetwork-bounces at mtl.mit.edu> on behalf of Mary
> Tang <mtang at stanford.edu>
> *Sent:* 03 August 2021 17:03
> *To:* Tony Whipple <whipp003 at umn.edu>; Terre Briggs <terreb at umich.edu>
> *Cc:* Labnetwork <labnetwork at mtl.mit.edu>
> *Subject:* Re: [labnetwork] LPCVD film anomaly
>
>
> 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 94305https://snf.stanford.edumtang@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: 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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> mark cooper
>
> Expert Semiconductor Technology, Inc.
>
> Phone: (831) 439-9300
>
> Fax: (831) 439-8139
>
> This email message is for the sole use of the addressee(s) and may contain
> Expertech confidential and legally privileged information. Access, review,
> use, disclosure or distribution of this email by anyone other than the
> intended addressee is unauthorized and prohibited. If you are not the
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> paper and electronic copies of the original message and any attachments.
>

-- 
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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