[labnetwork] RTP Oxidation

[Robert M. HAMILTON]

Kamal Yadav,

I held back offering a response to your question about RTP/infrared
pyrometry windows because the UC Berkeley NanoLab does not have experience
with AnnealSys RTP systems. We operate five AllWin21 Corp RTP's which are
improvements of the historic AG Heatpulse designs.

The IR pyrometry of our systems relies on providing constant temperature
cooling for the units IR sensor via a small, remote chiller (we use one
unit per two RTP's to save on space).

Our RTP chambers have windows made of a special grade of hydroxy-free (OH)
fused silica. Low-OH fused silica, such as Heraeus "Suprasil" resolves
issues with an IR absorption peak at ~2.7u:



These windows are made very thin to minimize IR absorption and therefore
fragile. The IR intensity is proportional to temperature of the substrate
being viewed. Any occlusion of this optical path, such as deposition on the
window surfaces, will result in a lower-than-actual temperature reading.

We clean the interior of our chambers and these window surfaces with ~5% HF
in water. Some mild mechanical force from a cotton swab to the window
surface helps speed up the process and reduces etching of the window.
Because HF cleaning reduces the thickness of these windows we re-calibrate
the system after cleaning. The system software is automated to correlate
the IR pyrometer against a reference Type-K TC built as an
"instrumented-wafer" (SenseArray).

Following a calibration run this TC-wafer is removed and we rely on the IR
pyrometer for our high temperature runs. For runs at temperatures lower
than ~600 C, where the IR signal is nil we use an instrumented off-axis
Type-K TC built onto a silicon support structure

Regards,
Bob Hamilton


Robert Hamilton
University of CA, Berkeley
Marvell NanoLab Equipment Manager
Rm 520 Sutardja Dai Hall, MC 1754
Berkeley, CA 94720
Phone 510-809-8618 (desk - preferred)
Mobile 510-325-7557 (my personal mobile)
E-mail preferred: bob at eecs.berkeley.edu
http://nanolab.berkeley.edu/



On Tue, Jul 7, 2015 at 12:45 AM, Kamal Yadav <kamal.yadav at gmail.com> wrote:

> Dear All,
>
> Query regarding RTP:
>
> 1. We have AnnealSys RTP: ASOne
> 2. We need to clean pyrometer windows regularly to maintain the equality
> in the actual temperature and set temperature. After around one month, and
> after heavy usage, the temperature drift around 80 Deg C. Pyrometer
> measures 80 Deg less than actual [randomply measured by TC]. When we clean
> the windows this difference is around 2 degrees.
>
> Queries:
> 1. Is cleaning pyrometer windows a standard practice in your systems as
> well?
> 2. Our 30 sec base line recipe, at 900 deg C, excluding ramp and ramp down
> steps. This recipe does not yield consistent thickness and ranges from 7 to
> 14 nm thickness. At this thickness other factors such as native oxide
> thickness variation, ambiance also plays critical role. Any comments would
> really help.
>
> Thanks a lot!
>
> --
> Thanks,
> Kamal Yadav
> Sr. Process Technologist
> Electrical Engineering
> IIT Bombay
> Mobile: 7506144798
>
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