[labnetwork] LED Lights for Lithography

Wed Feb 26 01:20:26 EST 2020

Paul, thank you for your response, I am familiar with the LED’s used for resist exposure.  FYI, I have been in photolithography 45 years now, 35 independently as Hbtusainc, I am very interested into switching 9 microlithography systems from using Ushio 350 watts short arc lamps to LEDs, 405nm(h-line) and 436nm(g-line) the light sources I use were manufacture by Tamarack many moons ago, they can be reconfigured with the LED upgrade, ir has been done before on these systems .
What added info I can give you to look into this at your end.
Regards 

Sent from Yahoo Mail for iPhone
Mario Portillo, hbtusainc at yahoo.com

On Monday, February 24, 2020, 8:28 AM, Paul Maciel <paulmaciel at outlook.com> wrote:

Hello Mario,

If you looking to learn more about UV LED light sources for resist exposure please take a look at the Idonus SARL web page<https://www.idonus.com/activities/products/mems-products/uv-exposure-system/12-company.html>.

Idonus offers UV LED sources for mask aligner retrofits and stand alone, with or without tooling.

Drop me an email and I'd be glad to help you find a configuration that works best for your application.

Regards,
---Paul

Paul Maciel
paulmaciel at outlook.com

On 2/23/2020 7:37 AM, Mario Portillo wrote:

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....
Anybody out there with the same thought let me know,
Regards 

Sent from Yahoo Mail for iPhone
Mario Portillo, hbtusainc at yahoo.com

On Sunday, February 23, 2020, 11:40 AM, martin at algoshift.com wrote:

Based on a couple of responses it looks like I did a confusing job of
explaining what I am working on.

I am focusing on lights to illuminate the lab, the room, not to cure 
PMMA.  So, yes, this is about lights on the ceiling.

Also, I said "above 500 nm" when I was thinking frequency.  I should 
have said "below 500 nm".  The point is, as I understand it today, the 
goal is to not have much energy in the blue and UV range of emissions.

Sorry for the confusion.

Thanks,

-Martin

---

On 2020-02-21 23:55, martin at algoshift.com wrote:
> I am currently working on the development of LED-based lights for
> lithography applications.  I came across this list and was kindly
> allowed to join.
> 
> I have a background in high-performance, high accuracy LED-based
> applications going back some twenty years.  In addition to that I
> worked in aerospace engineering, robotics and other work I can't talk
> about (most recently, SpaceX).
> 
> At this stage in my new mission I am trying to confirm what I have
> learned in order to start developing a few prototypes for testing.
> This is what I know and don't know so far:
> 
> - Energy above 500 nm should be below 0.001%
> - Operator metamerism doesn't seem to be much of a concern in these
> environments (?)
> - Outgassing is not desirable (I don't have any kind of a
> specification for this)
> - No specification on acceptable flicker
> - No specification on required efficiency (Lumen/Watt)
> - No specification on the amount of light required, either:
>    - Illuminance (intensity of light on a surface, lux) or,
>    - Luminance (light energy emitted, lumens)
> 
> Frankly, there really isn't very much data out there.  It also seems
> that semiconductor companies keep their lithography illumination
> requirements somewhat close to the vest.  At least this is what I've
> come across.  I wonder if this is because these kinds of
> specifications might reveal process details?  Don't know.
> 
> The three main trades I have in front of me at the moment for this 
> design are:
> 
> - White LEDs with carefully selected film or coating-based filter to
> cut blue + UV
> - Green and Red LEDs only, no blue; filtration is still needed
> - A combination of carefully selected white LEDs with low spectral
> power above 500 nm along with, perhaps, green and red to enhance;
> filtration still needed
> 
> To clarify, the Green+Red LED option still requires filtration because
> green LEDs produce some energy above 500 nm.  If I am to take the
> 0.001% specification to be true, an optical filter would still be
> required.
> 
> White LED's, which, of course, are nothing more than blue LEDs with a
> phosphor coating are the most readily available high efficiency units
> in the market.  Frankly, if high light output at the lowest possible
> cost is a requirement it is hard to beat them with a combination of
> red and green LEDs.  That said, depending on how they are selected, a
> significant portion of the spectral power they emit will have to be
> converted into heat at a filter or bad things will happen in the lab.
> 
> The third option involves selecting very warm white LEDs that have
> almost no blue spike.  This means less heating of the filter element
> and, likely, longer life.  This could be an interesting solution.
> 
> Plastic film based filters degrade over time, particularly if there's
> a lot of heating due to having too much energy in the undesirable
> portion of the spectrum.  This is where thin film deposition
> (sputtering?) could exhibit far more favorable band-pass
> characteristics as long a longevity.  Cost, of course, could be an
> issue.
> 
> I am very familiar with material out-gassing issues in the context of
> aerospace applications.  Not so for lab usage.  Understanding where
> these limits might lie would be very useful.  The perfectionist in me
> wants to design a T5-class 4 ft LED light fully encased and
> appropriately sealed in a durable glass tube that is both internally
> and externally coated to not pass light above 500 nm.  At the same
> time, I do understand that a real solution has to fit a budget as well
> as technical specifications.  Not sure where that intersection lies
> but I am aware of it.
> 
> I introduced a term above that might not be familiar to everyone here;
> observer metamerism.  This is a by-product of the spectral power
> distributions of light, reflection and the human vision system
> interacting in such a way that two colors that are different might
> appear the same (or, in general, you have trouble discerning colors
> that are easy to see under different conditions).  If you've ever
> tried to determine if a steak is well done under a typical white LED
> light and could not, that's observer metamerism.  Mitigation requires
> "filling in" the emitted spectra in areas relevant to the task at
> hand.
> 
> This is why I asked myself this question in the red+green LED case.
> Both of these have narrow emission spectra.  Our brains can function
> with this kind of light and, yes, we will see it as yellow.  However,
> any colors in the portion of the visible spectrum lacking energy will
> become challenging to deal with.  It's like being color blind.  Given
> that lithography labs are already built to work with yellow light, I
> find myself wondering how much of a problem, if any, might be posed by
> observer metamerism in the case of the proposed red+green LED
> solution.
> 
> I think that's the basics at this point.  I would appreciate any and
> all feedback, questions and even a good shove in the right direction.
> 
> Thank you,
> 
> Martin Euredjian
> AlgoShift, LLC
> Los Angeles, CA
> 661-305-9320
> 
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