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<p>Hi all -</p>
<p>Last summer, Phil Himmer and I met with a European company that
produces a conversion kit for the common contact aligner models
(Suss, EV Group). If anyone is interested, we can send you the
contact info. We've been seriously thinking about this, but the
cost is not trivial and it's not clear that the lamp replacements
and energy savings can fully justify. Certainly, there is other
value added, process-wise. But as an upgrade, the costs would
need to come out of our limited, precious capital budget. We'd be
interested in hearing about what other labs are considering and
why.</p>
<p>Cheers -<br>
</p>
<p>Mary</p>
<p>___<br>
Mary X. Tang, Ph.D.<br>
Managing Director<br>
Stanford Nanofabrication Facility<br>
Paul G. Allen Building, Room 141<br>
Stanford, CA. 94305<br>
<a class="moz-txt-link-abbreviated" href="mailto:mtang@stanford.edu">mtang@stanford.edu</a><br>
<a class="moz-txt-link-freetext" href="https://snf.stanford.edu">https://snf.stanford.edu</a><br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 2/23/2020 4:37 AM, Mario Portillo
wrote:<br>
</div>
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I have to say that I was very interested in responding to your
first email, as I am looking for ways to eliminate the use of
mercury arc lamps to LEDs....
<div><br>
</div>
<div>Anybody out there with the same thought let me know,</div>
<div><br>
</div>
<div>Regards <br>
<br>
<br>
<a href="https://yho.com/footer0" moz-do-not-send="true">Sent
from Yahoo Mail for iPhone</a><br>
<div>Mario Portillo, <a class="moz-txt-link-abbreviated" href="mailto:hbtusainc@yahoo.com">hbtusainc@yahoo.com</a></div>
<br>
<p class="yahoo-quoted-begin" style="font-size: 15px; color:
#715FFA; padding-top: 15px; margin-top: 0">On Sunday, February
23, 2020, 11:40 AM, <a class="moz-txt-link-abbreviated" href="mailto:martin@algoshift.com">martin@algoshift.com</a> wrote:</p>
<blockquote class="iosymail">
<div dir="ltr">Based on a couple of responses it looks like I
did a confusing job of <br clear="none">
explaining what I am working on.<br clear="none">
<br clear="none">
I am focusing on lights to illuminate the lab, the room, not
to cure <br clear="none">
PMMA. So, yes, this is about lights on the ceiling.<br
clear="none">
<br clear="none">
Also, I said "above 500 nm" when I was thinking frequency.
I should <br clear="none">
have said "below 500 nm". The point is, as I understand it
today, the <br clear="none">
goal is to not have much energy in the blue and UV range of
emissions.<br clear="none">
<br clear="none">
Sorry for the confusion.<br clear="none">
<br clear="none">
Thanks,<br clear="none">
<br clear="none">
-Martin<br clear="none">
<br clear="none">
---<br clear="none">
<br clear="none">
<br clear="none">
On 2020-02-21 23:55, <a shape="rect"
ymailto="mailto:martin@algoshift.com"
href="mailto:martin@algoshift.com" moz-do-not-send="true">martin@algoshift.com</a>
wrote:<br clear="none">
> I am currently working on the development of LED-based
lights for<br clear="none">
> lithography applications. I came across this list and
was kindly<br clear="none">
> allowed to join.<br clear="none">
> <br clear="none">
> I have a background in high-performance, high accuracy
LED-based<br clear="none">
> applications going back some twenty years. In addition
to that I<br clear="none">
> worked in aerospace engineering, robotics and other
work I can't talk<br clear="none">
> about (most recently, SpaceX).<br clear="none">
> <br clear="none">
> At this stage in my new mission I am trying to confirm
what I have<br clear="none">
> learned in order to start developing a few prototypes
for testing.<br clear="none">
> This is what I know and don't know so far:<br
clear="none">
> <br clear="none">
> - Energy above 500 nm should be below 0.001%<br
clear="none">
> - Operator metamerism doesn't seem to be much of a
concern in these<br clear="none">
> environments (?)<br clear="none">
> - Outgassing is not desirable (I don't have any kind of
a<br clear="none">
> specification for this)<br clear="none">
> - No specification on acceptable flicker<br
clear="none">
> - No specification on required efficiency (Lumen/Watt)<br
clear="none">
> - No specification on the amount of light required,
either:<br clear="none">
> - Illuminance (intensity of light on a surface, lux)
or,<br clear="none">
> - Luminance (light energy emitted, lumens)<br
clear="none">
> <br clear="none">
> Frankly, there really isn't very much data out there.
It also seems<br clear="none">
> that semiconductor companies keep their lithography
illumination<br clear="none">
> requirements somewhat close to the vest. At least this
is what I've<br clear="none">
> come across. I wonder if this is because these kinds
of<br clear="none">
> specifications might reveal process details? Don't
know.<br clear="none">
> <br clear="none">
> The three main trades I have in front of me at the
moment for this <br clear="none">
> design are:<br clear="none">
> <br clear="none">
> - White LEDs with carefully selected film or
coating-based filter to<br clear="none">
> cut blue + UV<br clear="none">
> - Green and Red LEDs only, no blue; filtration is still
needed<br clear="none">
> - A combination of carefully selected white LEDs with
low spectral<br clear="none">
> power above 500 nm along with, perhaps, green and red
to enhance;<br clear="none">
> filtration still needed<br clear="none">
> <br clear="none">
> To clarify, the Green+Red LED option still requires
filtration because<br clear="none">
> green LEDs produce some energy above 500 nm. If I am
to take the<br clear="none">
> 0.001% specification to be true, an optical filter
would still be<br clear="none">
> required.<br clear="none">
> <br clear="none">
> White LED's, which, of course, are nothing more than
blue LEDs with a<br clear="none">
> phosphor coating are the most readily available high
efficiency units<br clear="none">
> in the market. Frankly, if high light output at the
lowest possible<br clear="none">
> cost is a requirement it is hard to beat them with a
combination of<br clear="none">
> red and green LEDs. That said, depending on how they
are selected, a<br clear="none">
> significant portion of the spectral power they emit
will have to be<br clear="none">
> converted into heat at a filter or bad things will
happen in the lab.<br clear="none">
> <br clear="none">
> The third option involves selecting very warm white
LEDs that have<br clear="none">
> almost no blue spike. This means less heating of the
filter element<br clear="none">
> and, likely, longer life. This could be an interesting
solution.<br clear="none">
> <br clear="none">
> Plastic film based filters degrade over time,
particularly if there's<br clear="none">
> a lot of heating due to having too much energy in the
undesirable<br clear="none">
> portion of the spectrum. This is where thin film
deposition<br clear="none">
> (sputtering?) could exhibit far more favorable
band-pass<br clear="none">
> characteristics as long a longevity. Cost, of course,
could be an<br clear="none">
> issue.<br clear="none">
> <br clear="none">
> I am very familiar with material out-gassing issues in
the context of<br clear="none">
> aerospace applications. Not so for lab usage.
Understanding where<br clear="none">
> these limits might lie would be very useful. The
perfectionist in me<br clear="none">
> wants to design a T5-class 4 ft LED light fully encased
and<br clear="none">
> appropriately sealed in a durable glass tube that is
both internally<br clear="none">
> and externally coated to not pass light above 500 nm.
At the same<br clear="none">
> time, I do understand that a real solution has to fit a
budget as well<br clear="none">
> as technical specifications. Not sure where that
intersection lies<br clear="none">
> but I am aware of it.<br clear="none">
> <br clear="none">
> I introduced a term above that might not be familiar to
everyone here;<br clear="none">
> observer metamerism. This is a by-product of the
spectral power<br clear="none">
> distributions of light, reflection and the human vision
system<br clear="none">
> interacting in such a way that two colors that are
different might<br clear="none">
> appear the same (or, in general, you have trouble
discerning colors<br clear="none">
> that are easy to see under different conditions). If
you've ever<br clear="none">
> tried to determine if a steak is well done under a
typical white LED<br clear="none">
> light and could not, that's observer metamerism.
Mitigation requires<br clear="none">
> "filling in" the emitted spectra in areas relevant to
the task at<br clear="none">
> hand.<br clear="none">
> <br clear="none">
> This is why I asked myself this question in the
red+green LED case.<br clear="none">
> Both of these have narrow emission spectra. Our brains
can function<br clear="none">
> with this kind of light and, yes, we will see it as
yellow. However,<br clear="none">
> any colors in the portion of the visible spectrum
lacking energy will<br clear="none">
> become challenging to deal with. It's like being color
blind. Given<br clear="none">
> that lithography labs are already built to work with
yellow light, I<br clear="none">
> find myself wondering how much of a problem, if any,
might be posed by<br clear="none">
> observer metamerism in the case of the proposed
red+green LED<br clear="none">
> solution.<br clear="none">
> <br clear="none">
> I think that's the basics at this point. I would
appreciate any and<br clear="none">
> all feedback, questions and even a good shove in the
right direction.<br clear="none">
> <br clear="none">
> Thank you,<br clear="none">
> <br clear="none">
> Martin Euredjian<br clear="none">
> AlgoShift, LLC<br clear="none">
> Los Angeles, CA<br clear="none">
> 661-305-9320<br clear="none">
> <br clear="none">
> _______________________________________________<br
clear="none">
> labnetwork mailing list<br clear="none">
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