April 2021 - Libresilicon-developers

coating / chemicals / litho / strategy
by Martin Geisse 02 May '21

02 May '21

Hi, - spin coating I finally tried to build a makeshift spin coater the way Sam Zeloof did, by mounting a plastic can on top of a CPU fan (actually a case fan from another device I had lying around). I can't say this is the way to go... the fan is way too weak to spin the can at a meaningful speed. It is also very hard to center the can exactly, so it wobbles a lot and that probably reduces the speed even more. Mounting a die without a container would allow the fan to spin faster, but would likely clog the fan with chemicals in no time. I'll next try my original idea, to mount the can to an axle that I'll stick into a power drill. One thing I did find out is that the coating liquid should be evenly applied before spinning. It will NOT spread to the whole surface by itself, but rather run to a single direction in a concentrated stream, probably due to surface tension. - chemicals I did find this resist which is meant for PCB etching, so I don't know yet whether it has some kind of "grain size" that limits the resolution. The datasheet explicitly states that it can take up to 40% hydrofluoric acid, though, and be used for glass etching (so I hope it will actually stick to glass). It is also liquid until soft-baking, so spin-coating should be possible. https://www.reichelt.de/fotopositiv-resist-positiv-20-200-ml-kontakt-235-p9… WRT hydrofluoric acid, there is something called "glass etching cream", the best-known brand being "Armour Etch". This contains fluorides, i.e. HF salts, is *somewhat* safer than HF itself (less fumes I think, but don't get it on your skin), and can be ordered by private individuals. The downside is that I could not find any information on whether it contains an abrasive. - photolithography Sam Zeloof used a modified DLP projector for his litho setup. He either used magic to do that or chose exactly the right projector. I took apart a used DLP and the UV filter is the only thing that could be taken out without destroying the projector. The color wheel, and even more so the optics, are buried under tons of other stuff, most of which is glued together. Also, the optics path itself is mostly glued. So I think David's plan of taking the DMD chip and building his own optics setup is a far better idea than modding a projector. To me as a layman in these things, stiching a larger image together from multiple images with a stepper sounds more logical than using multiple DMD chips. This XY table is cheap and has stepper motors that can position the table in increments of 5 microns. I have actually wondered if a first prototype should use a DMD at all, or just focus a single UV LED and "draw" by moving the XY table. https://www.amazon.de/Proxxon-27100-MICRO-Koordinatentisch-KT/dp/B000S81MHY - strategy I also thought a bit about who would be interested in making your own chips. High-volume production has far better, established processes, and low-volume production would use an FPGA or other off-the-shelf parts. Silicon testing before production isn't useful when the process is different. This leaves education and hobbyists. In other words, a free silicon process must be sustainable based solely on education and hobbyists, otherwise it won't stand a chance. There is another problem that goes in the same direction: a "democratized" chip making process should not rely on actors like INL, because there are too few of them -- less than 10 in the whole of Europe. Even if INL agrees to host the LibreSilicon process, a single decision by INL that chip making isn't interesting anymore can shut the whole thing down. I'm not particularly enthusiatic about the "glove box" idea either because I don't think it is practical, nor doable in a useful price range. The usual answer to the "expensive tools" problem is shared labs, usually as "fab labs", "makerspaces" or similar. I think this is a way in which chip making could actually work, especially if it works on dual-use tools that benefit a makerspace in other ways, like an XY table, microscope etc. I wanted to contact a local makerspace in my town, but unfortunately Germany just went into full Covid lockdown, so it's going to take a while until that. Greetings, Martin

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Announcement - Mumble session on Sunday 2021-05-02 @ 18:00 UTC
by Hagen SANKOWSKI 30 Apr '21

30 Apr '21

Hello List! This is our weekly announcement for the next Mumble Sessions on Sunday 2021-05-02 @ 18:00 UTC. Please join us as usual at our Mumble Server murmur.libresilicon.com at Port 64738, the Channel is IC. We like to follow-up our topics from mumble sessions before. Regards, Hagen.

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Particle Counter
by Hagen SANKOWSKI 25 Apr '21

25 Apr '21

Hello List. A couple of Mumble Sessions before we talked about our Glove Box design once again.. Well, one action item was to figure out, how we can verify the clean room quality inside the Glove Box. And I remembered some nice handy-size Analyzer I saw already for this purpose (to check 'dirtyness' behind machines in the productive clean room behind machines or to check air flow in and outs). Fortunately, due to German Engineering Art in cheating with diesel engines (Volkswagen, Audi etc..) "fine dust" is a big topic nowadays. Okay, is was joke.. But, instruments to measure the fine dust in our daily environment, in cities along heavy used streets or so, are already available in bigger super markets like Kaufland here in Germany now. And this instruments offers 2 fine dust classes - one with 10 Micron and another with 2.5 Micron particle size. Of course, this is still a dimension away from particle sizes which matters for real clean room classes - regardless of which clean room class system (ISO 14644-1 or US Federal Standard 209 E) we are looking at. Anyway, IMHO this instruments are a great and quite reasonable priced step into particle measurements at all :-) The mentioned super market has currently an offer round about 200 Euros; on ebay.com similar instruments are available from 150 Euros upwards. Maybe we can even "update" the firmware on such a instrument for smaller particle sizes :-o Regards, Hagen.

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Announcement - Mumble session on Sunday 2021-04-25 @ 18:00 UTC
by Hagen SANKOWSKI 24 Apr '21

24 Apr '21

Hello List! This is our weekly announcement for the next Mumble Sessions on Sunday 2021-04-25 @ 18:00 UTC. Please join us as usual at our Mumble Server murmur.libresilicon.com at Port 64738, the Channel is IC. We like to follow-up our topics from mumble sessions before. Regards, Hagen.

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Stepper resolution
by David Lanzendörfer 16 Apr '21

16 Apr '21

Hi So turns out there's another way to achieve higher resolutions (below 100nm), without having to use EUV light and low pressure. You can give your exposure unit a nice bath :-) https://en.wikipedia.org/wiki/Immersion_lithography What do you folks think? Worth considering putting on our TODO list for future stepper iterations? Cheers -lev

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Announcement - Mumble session on Sunday 2021-04-18 @ 18:00 UTC
by Hagen SANKOWSKI 16 Apr '21

16 Apr '21

Hello List! This is our weekly announcement for the next Mumble Sessions on Sunday 2021-04-18 @ 18:00 UTC. Please join us as usual at our Mumble Server murmur.libresilicon.com at Port 64738, the Channel is IC. We like to follow-up our topics from mumble sessions before. Regards, Hagen.

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Ouch!
by Hagen SANKOWSKI 16 Apr '21

16 Apr '21

https://asia.nikkei.com/Business/Tech/Semiconductors/Chip-tools-become-late…

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Re: [Libre-silicon-devel] Stepper resolution
by David Lanzendörfer 16 Apr '21

16 Apr '21

Hi I'm aware of the complexity... That's I said "future iterations" :-) Cheers -lev On Friday, April 16, 2021 10:19:48 AM WEST ludwig jaffe wrote: > Hi all, > > this looks interesting, but beware complexity! > Polarization and other effects are to be taken care of. > > One idea for this would be to use oil immersion lenses > of microscopes and to try to reverse the beam pattern and > to step these. > > But we are hobbyists, and the only advantage we have is > access to knowledge but we also dont get all the details. > > So being part time scientists we should aim for low hanging fruit > first. > > Cheers, > > Ludwig > > On 4/15/21, David Lanzendörfer <leviathan(a)libresilicon.com> wrote: > > Hi > > So turns out there's another way to achieve higher resolutions (below > > 100nm), > > without having to use EUV light and low pressure. > > You can give your exposure unit a nice bath :-) > > https://en.wikipedia.org/wiki/Immersion_lithography > > > > What do you folks think? Worth considering putting on our TODO list for > > future > > stepper iterations? > > > > Cheers > > -lev > > > > _______________________________________________ > > Libresilicon-developers mailing list > > Libresilicon-developers(a)list.libresilicon.com > > https://list.libresilicon.com/mailman/listinfo/libresilicon-developers

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Stepper
by David Lanzendörfer 15 Apr '21

15 Apr '21

Hi I guess I'll probably build something like this table here with linear ball bearings and a fixed gear shift which divides the steps of the stepper motor, so that I can have an appropriate stepping resolution for positioning. https://de.aliexpress.com/item/4001178550238.html I'm aware of the trouble with parallel alignment of two linear rail bars, but I'm afraid I'll have to deal with it, for at least one of the axis. I'll probably start ordering the parts as soon as I'm done moving into the new location next week and then I'll start extending the construction from there until I've got at least the x-y-positioning figured out. The loading mechanism also is pretty annoying... Besides having to build my own custom guided ball bearing for the angular alignment, I'll need at least 4 customely made metal parts... :-/ Cheers -lev

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GloveBox
by David Lanzendörfer 15 Apr '21

15 Apr '21

Hi I was thinking about using sheet metal for everything which doesn't need to be transparent (even cheaper than acrylic glas). For the airlock I was figuring I could do a cut out like in the attached screen and fold it, then either weld or screw an aluminum box made from folded sheet metal as well. What do you think? Cheers -lev

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Libresilicon-developers April 2021