Good morning Dilek ^^
Fantastic! Thanks so much! I will put those resists onto the wiki page as examples for resists to use, and will mention that we'd be glad about reports of results using alternative resists within that wave length range.
And yes. I already had a discussion about the toxic chemical waste a while ago, where I made the usual joke that I'd follow "all the laws and regulations of the PRC", when I was told that I'd be in Portugal now and they'd have laws making it illegal to flush it down the toilet xD
I already checked, where the collection centers are here in Portugal and what chemicals are actually legal to buy as a private citizen.
Cheers, David
On Friday, August 13, 2021 2:49:45 PM WEST Dilek Isik Akcakaya wrote:
Good morning,
Greyscale PR is not a good option overall. It is meant for a different process. We will go with regular resists AZ series probably due to their process being cheaper. We can look for others too. High contrast resists are better at giving vertical sidewall.
AZ1512 1.2um thick positive 310-440 nm abs AZ9260 5-20 um thick positive 365-435 nm.
But we do not need to state these at the moment do we? We can basically say that any PR absorbing in this range would be sufficient to work with. We are not adbertising products after all :)
Semiconductor manufacturing chemicals are usually highly toxic to person and aquatic life. I see youtubers being very brave about their use without any fume hoods etc. I believe we will need to prepare a safety notice for people who are interested in the fieldnand have no idea what they are doing. You can not pour thess chems into the drain they need to be collected and sent to facilities for neutralization. Some cause cancer... Some can kill you with a drop.
Thank you,
Dilek
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On Aug 13, 2021, 6:15 AM, David Lanzendörfer wrote:
Hi Dilek
About the choice of the PR: I just went for one which has a sufficient energy absorption within the visible UV range still tolerated by the inexpensive DMD chip chosen. Now that you pointed out the issue with TMAH I realize that my choice of PR wasn't the best. Can you suggest alternatives which do not require super toxic and dangerous developers but still work within the specified UV range of 420nm - 450nm? I'm aware how dangerous TMAH is, it even etches silicon, which I observed myself while doing some tests for the ultra low tech process flow variant, where I used it to etch the trench isolation. The absorption wave length was basically the only criteria which led me to suggest this specific resists, but as I've said, if we could collect a list of alternative resists delivering sufficient results in the above mentioned range, we HAVE TO put it onto our wiki page as well.
About the certainty of being able to reproduce 25 um (featuresize 50um -> lambda 25um): In order to be sure, we've got to build a prototype and test it :-)
Cheers, David
On Friday, August 13, 2021 8:03:33 AM WEST Dilek Isik Akcakaya wrote:
Hi All, David,
I see that you selected a greyscale PR for photolithography, it uses TMAH based developers I do not know the range of other developers it can make use of. Can we list them? This series of PR are foreign to me. I used Shipley, AZ etc. You must not buy and use TMAH based developers at home labs due to safety reasons it is extremely toxic! Second chemical I will beware of is HF in the same way in a home environment.
Second, What is the reason for going for a grayscale PR and not a regular one?
Third, The UV range depends on the PR we will be using, the smaller the wavelength, more precise will be the features if we can use the right optical system of course (De Broglies eqn.). Because I am new to the project please let me know why we decide don this set of PRs.
As per UV range of the DLP once again this depends on the PRs to be used and because DLP works by reflection, you may loose power due to reflectance, absorption and other optical phenomena therefore I think we need to be as precise as possible with our selections.
Let me point out: The rail system precision+ DLP resolution (not the pixel size) as an end result of multiple selections such as good focus etc+ PR thickness+ Development time + Light source wavelength + overlay reproducibility = approximately OUR RESOLUTION.
With current selections are we sure we will be able to reproduce 50 um features and have a good overlay if we need a second layer alignment on top?
Thank you,
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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
David Lanzendörfer leviathan@libresilicon.com 11 Ağustos 2021 Çarşamba
saat 12:51 tarihinde yazdı:
Hi Dilek, hi list
Sorry again about the downtime of the infrastructure during the day yesterday.
The infrastructure of the data center I've got my rack server in was down.
Now to the topic:
I've started writing down the BOM and I'm not sure whether 420 nm UV already
has too much energy, although the data sheet of the DMD chip says it's ok to
be operated until 400nm.
Here's the BOM:
https://redmine.libresilicon.com/projects/maskless-lithography/wiki
It would be cool to get feedback on that from Texas Instruments.
Cheers
David
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