Photolithography on Silicon with PCB Chemicals
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- เผยแพร่เมื่อ 26 ก.ย. 2024
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In this video I attempt to use a laser printer and off-the-shelf PCB photoresist to do photolithography on silicon. I run into a bunch of potential pitfalls, but in the end I got some workable results!
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I have not been this invested in a youtube series in years. Please continue this project, its incredibly interesting and motivating!!!
Thanks! i am doing my best!
@@projectsinflight this thing is the second best project after clicksprings antikythera project on all of youtube :D
and i know that sounds mean but thats high praise!
Ben from Applied Science addresses the problem of photomask density in his video on photomechanical machining. He ends up using a screenprinting ink in an inkjet and a transparency with a special emulsion. His techniques do stretch the limits of DIY.
Which video is this? Not sure i've seen it
th-cam.com/video/bR9EN3kUlfg/w-d-xo.html this one?
th-cam.com/video/NS8Q9LUIKA8/w-d-xo.htmlsi=bCrGyb-nrxubePBe
@@projectsinflight "How to make precise sheet metal parts (photochemical machining)" from 11 months ago. watch?v=bR9EN3kUlfg
@@projectsinflight th-cam.com/video/YAPt_DcWAvw/w-d-xo.html
People might poo poo me for putting it like this, but it's pretty goddamned hype to see a second DIY semiconductor fab spinning up on TH-cam. The more people doing stuff and communicating how they are doing the stuff, the more everyone can learn and that's just stellar.
My dream is to make this hobby more attainable for the average hobbyist. I hope I can do that :)
hell yeah brother. I once kicked around the idea of reducing home depot play sand grade SiO2 into silicon, crystalizing it with a diy HHO Verneuil furnace, and then trying to dope my own wafers with stuff like borax or phosphorus bearing fertilizer, but in the end i realized there was no way id make something pure enough to exhibit the necessary properties . Maybe one day, but realistically thats probably outside the scope of mere mortals like me. @@projectsinflight
@@arealhumanname4150 Yeah definitly recommend buying wafers. The process of making them involves a lot of flammable and toxic chemicals
You can try to expose the film directly to UV without using a printed mask by using a DLP or SLA 3d resin printer's laser bed, it probably has greater precision than the paper printer
Ya, a Mars 4 9K for example has an 18um (1410dpi) resolution.
I've definitely wanted to try this once i get my hands on a suitable printer
This is what I do when I etch PCB's at home. Works great.
@@projectsinflight reach out to your local college with a technology campus and they can help you out
@@projectsinflight Do the liquids used in resin 3d printers work as photoresists; I mean they are things that harden under UV exposure?
An easy way to get a photomask with microscale features is to use a film camera.
Yeah i considered that. they even have lithographic film which is super high contrast B&W film for just this reason
Been waiting weeks for this video. Absolutely made my day. Really loving the ground up approach on semiconductors in a home lab
Thanks! It means a lot to me :)
Really cool problem solving with the in holes man. You are making basic homemade semiconductors seem a lot more accessible.
Thanks! there were even more minor pitfalls that didn't make it into this video, but I think i covered the most consequential stuff
You might want to research PMMA (Poly Methyl Methacrylate). It's generally used for e-beam lithography, but I believe it can be used with UV exposure, though it may need a light source like low pressure mercury vapor. I've bought PMMA in the past without any problems (for e-beam lithography). Another really cool thing with PMMA is you can layer different percentages and wind up being able to create tailored undercuts allowing 3 dimensional structures instead of just 2D.
I had marginal success with standard screen printing emulsion, though my research indicated there were emulsion forms that could get higher resolution. I thinned the material (a green gunk; I believe with water) and using a brush (I think; it was years ago) was able to get a somewhat reproducible layer. I'm sure spin coating would be way better. I believe I was getting feature sizes close to a micron (I was aiming for 100 -50 nm) when my investors ghosted me and I dropped the project.
Feel free to reach out if you'd like me to try and dig up more details.
Can probably get a UV led short enough now to do the job without mucking about with the mercury lamps
@@zyeborm My research on UV LEDs seems to have a hard limit around 350 nm, which may not be enough for PMMA.
@@mitakeetFrom some quick searching on the web, 255nm UV LED lamps seems to be rather readily avaible.
@@Gin-toki I'm sure it was just a few months ago I was looking for exactly this. Either my search skills have atrophied or these are relatively new... Thanks!
I've been looking into PMMA and it does seem to be a good prospect. I wasn't aware deep UV would expose it without an additional synthesizer chemical so that's interesting. I also am in the process of building my own e-beam source :)
For the printer DPI issue, you usually need to specifically go into some kind of control panel or print settings menu to enable the 1200dpi mode, as it's not the default printing mode for nearly any printer.
Have you considered replacing the mask all together with a set of UV/blue laser galvos? They use mirrors on precise motors to move a laser beam around. With that kind of laser power, you should be able to expose the photoresist really quickly. So, moving the laser slowly across the chip might work. As a bonus, you don't need to worry about the opacity of a mask. Though, the beam width would be a limiting factor.
I've considered galvos but i don't have any experience with them and i don't want to get too sidetracked right now. I'll come back at some point and improve the technique, either with galvos or something similar to improve resolution
Photolithography is much more repeatable and accurate, there's a reason photo transfers are still used.
I wonder if it also might work if you replaced the lamp of a DLP projector with a UV one?
i bet you could use galvos and photosensitive materials to *make* a mask though
Why not just set up a basic LLC for $100? Then you can just directly order from these photoresist suppliers, plus if youtube is your business venture for the company you can probably even deduct these expenses.
This is a great idea for this specific project, but it would be great if someone knows of a supplier that can sell to individuals, that way this project can be replicated more easily.
@@josuelservin Perhaps whomever sets up that initial basic LLC might then sell on to individuals? 😉
My goal is to do stuff that anyone can replicate so i'm doing my best to keep from using stuff gated behind lab suppliers and commercial adresses
Yes, you could do that. But IIRC Ben from Applied Science made his own, or found another solution. He also used a thinner lacquer with a spincoating process, which leads to a thinner layer and thus a finer resolution.
@@projectsinflight I wanna start a business that produces semiconductors and lets everyone design their own ICs and test whatever architecture they want. I plan on starting with mcirometer-sized transistors. Keep posting stuff and hit me up if you're into this kinda stuff, I plan on making my research as much as possible public too. Another goal would be designing a consumer-available litho machine. Looking to make connections right now so anyone can hit me up if they're interested
You might be able to get a finer resolution on the mask by using a material that shrinks uniformly when heated (I've always heard them called shrinky-dinks)
Some of them are transparent and can shrink to several times smaller than they started
This also has the side effect of making pigments darker, which would mean no need to stack multiple transparencies.
Not a bad idea- though i don't know if it would be consistent enough for multiple mask layers. most semiconductors need several masks for different steps and they'd all need to be the same exact size
@@projectsinflight I believe shrinky-dink film is made by stretching the polystyrene film, so that it relaxes when heated. It reliably contracts the same amount. Whether it's viable is another question, but the darkening effect is a good point- th-cam.com/video/a15AqeJs3W8/w-d-xo.html
@@projectsinflight Actually I recall hearing about a Collage or University students that used something similar for making tiny flow channels. Originally they had issues making the markings precise at the small scale, however it was found that Shrinky-Dinks or at least the generic material would shrink in a predictable manner. Each test/set-up was a minimum of three layers. Such that they could make very precise designs, just needing to make sure that it was held flat during the Shrinking to avoid curling. It was clear for filming the internals.
I applaud your bravery for trying to use dry film. These are amazing results for such a low-tech process!
Thank you! I wanted to make sure this was as approachable as possible
A thousand little pitfalls, thanks for your effort on working trough them. Already excited about the next one.
Thank you :) It really did feel like it would never come together but it turns out if you just refuse to fail you eventually succeed lol
Have you looked into using using a resin 3d printer to exposing your photoresist? That would allow direct exposing of the photoresist. They use a UV light to cure the resin. Some of the more expensive printer claim over 1000dpi resolution. Also the resin itself could be evaluated for spin coating and use as a resist.
i actually had a conversation about the 3d printer as an exposure source yesterday, and i'm definitely interested in doing that if i can
3D printer is the way to go. So much easier than the transparency method. I use an Anycubic Photon Mono 4k to expose dry film for PCBs. I can easily and reliably get 250 micron traces, and I had success with test patterns down to 70 micron with 70 micron gaps, or 2 pixels across. I used to do exactly what you did in the video, with that exact model printer even (except the acetone smoothing - wish I'd thought of that!).
For your own sanity, ditch the transparency. You even get a 3D printer as a bonus!
I wonder if your plain old photography film would work as a precise mask. By printing the transparency on a regular printer then optically shrinking it down and exposing the film. Then developing it as if it was a normal photography negative.
Film will work- there is even a film specifically for this called lithography film. Its basically super high contrast B&W film.
Small piece of feedback, when you're talking about the mask at ~2:40 I think it would be helpful to animate/highlight the appropriate portion of the mask as you mention it, i.e. transparent vs opaque. When I initially saw the mask I assumed the black bars would indicate the transparent areas and that would have just made things a little more clear.
Whoops- sorry about that. I'm still learning how to do these animations
Nothing to apologize for!@@projectsinflight
Have one of the amazing chemistry TH-camrs just create The GOOD Stuff for you. Sounds like a really cool project for them. One of the ingredients is Cyclopentanone which half of them have made w/ the Cubane wars.
I would LOVE to collaborate with one of them at some point. I'm just concerned because a lot of the chemicals you need for light-sensitive chemistry are pretty toxic, so i wouldn't want to put them at risk
I had a project where I wanted to produce diffraction gratings using photoresist on glass - so I had the same problem finding a resist. I had quite good results using a commonly available positive PCB spray resist "Kontak Chemie Positiv20" which comes in a spray bottle and resolved 10µm lines quite well (dont know what resolution you are aiming for). It contains mainly acetone as a solvent wich evaporates a little too fast for Spincoating uniform films. The solution was to mix it with a solvent called "1-Methoxy-2-propanol", which is also part of the resist itself and is easely available on abay. If you are interested in more details let me know. I can also share some experience with building a simple exposure unit.
I am interested, but I was not able to find any of the positiv 20 available for sale in the US
@@projectsinflight Is farnell an option for you? Maybe they sell and ship to US ?
@@projectsinflight Our good 'ol German Company was bought by CRC (Belgium). Maybe this helps when searching.
(TH-cam censorBS, Splitting Post into parts, Part 1 here)
Edit: PLEASE MOVE DOWN TO MY LAST 3 POSTS AND IGNORE THE OTHERS TO PREVENT EYE-CANCER!!!
I am letting this mess here for everyone to see instead of erasing it, just that everyone can see the hell I went through ... My apologies!
@@projectsinflight Alternatives(separated by semicolon): ELECTROLUBE PRP - POSITIVE PHOTORESIST
(TH-cam censorBS, Splitting Post into parts, Part 2 here)
@@projectsinflight mungolux (company for photoetching supply): R1000 ~ 25µm. Shipping worldwide
(TH-cam censorBS, Splitting Post into parts, Part 4 here)
I have no idea if it would work because it is for PCBs but Kontakt Chemie sells a product called Positiv 20 that is a UV reactive positive paint that comes in a spray paint can and it's specifically made for very high resolution circuit boards. It's like 20 bucks so it might be worth checking out if there are no other options
I would love some but i was unable to find a source in the US
Amazing !!!
You are the only one who is able to reproduce the magical world of ICs. Congratulations.
Honestly, this is pretty incredible work. It is for sure the most interesting series I've seen in ages.
“This allows us to walk around with devices in our pocket that can do more calculations in a second than we can do in our entire lifetimes.” 😮
Regarding photoresist, i think you could try to use any novolac-based spray-on pcb photoresist, like Positiv-20 by Kontakt Chemie. It is very close to the novolac non-chemically amplified resists like AZ15xx, but maybe has a little less controlled quality. You can even try to spin-coat it.
Yeah, I posted that one in the comments of the last video too. It's datasheet specifically mentions it's ability to be used as a resist for glass (SiO2) etching with strong HF. I think you can't easily get a more ideal photoresist than that. Farnell sells it in a lot of countries, so it's easy to get.
I considered that one, but was unable to find it for sale anywhere
@@projectsinflight If you can figure out where it's sold you have 2 solid options:
1. Find a company that is willing to buy and ship it for a fee
2. Find a Patreon member that lives there and ask them nicely to send some to you
You can use a resin 3d printer lcd display to project the pattern to the photoresists
I want to try that whenever i get access to a suitable printer
Nice to see that cheap PCB photoresist works at least somewhat! There are options for acquiring semicon photoresist as a hobbyist.
You might have a pretty good chance of getting the stuff by contacting the manufacturers directly, *not* the distributors, or looking overseas(China, Korea, Japan). You can also try UV glue, clear SLA resin, or even PMMA(it works without an ebeam too!). I've emailed you with more info on where to start digging.
Thank you so much for providing this information- I'll check out the email soon!
@@projectsinflight> You could also look into the UV setting nail polish that the trendier kids/tweenies paint their nails with, seems cheap enough for an experiment or two, and it looks like it could be almost the right consistency for spin coating given it's usually applied with a small paint brush.
Please forward me this email, I'd like to know how to as well, as this process is very confusing to me!
Applied Science's video on "Patterning aluminum with the photoresist "lift-off" method" seems to be relevant. Also relevant are the Breaking Taps channel, and Sam Zeloof, though both of those seem to be a little out of reach for the average viewer. I've heard that Cooking with Jeri, by Jeri Ellsworth is worth a look, but I can't attest to it myself.
Yeah, I'd love to do some kind of collaboration in the future!
acetone vapour trick on toner was crazy
Hey! Great video, I absolutely love youtubers who educate people about science. I have a tangent idea for you: PMMA, which is essentially acrylic, is used as a resist for electron beam lithography on silicon. Although this process is extremely challenging for a hobbyist, you can snatch high power electron gun, beam steering columns, and accompanying electronics from a CRT, construct a crude vacuum chamber, and try to perform maskless lithography. I believe, PMMA solvents and solutions are somewhat easier to come by as an individual. Small amounts of chemicals with pre-coated silicone chips are usually sold as a student training kits by SEM manufacturers, so you could try to pose as one, and maybe you'll get lucky.
Hi, great video! I love this serie!
You can also use a modified DLP projector to replace the masks. Sam Zeloof tried this some time ago.
Yep i saw that video. I'm gonna try it at some point I think. I suspect I might also try a resin printer LCD as the pixel density is higher
@@projectsinflight Yeah, it can be interesting to compare multiple methods!
I've seen someone use this for PCBs and it seems to work well, but there are a few drawbacks:
- pixels are not totally opaque, so some light pass through
- UV LED arrays on resin printers don't produce a very uniform light, I had a few problems when trying to print microfluidics, but it's probably not a problem here especially if you use your own light source
- LCDs screens have a limited lifespan when exposed to UV light
I can't wait to see what happens next in any case!
Good luck with your projects.
Many have spoken of doing this, you seem to be the one making the most progress the fastest. I wish you all the success in the world and an following avidly!
Thanks! I'm doing my best
THANK YOU for all this tedious work !
The lack of photoresist for hobbyist is a plague.
You can get dense masks with high resolution from places that run film imagesetters (for Computer-to-Film typography process)
Never heard of this- do you have a link?
@@projectsinflightSeems I cannot post links (my comment with links got discarded), but you should be able to find something in your area by searching for "digital film output" or "digital film output for offset printing"
This is slightly outdated technology (in modern offset printing they expose photoresist on plates directly), but it is still present.
The fact that it is purposely made for curing UV photoresist makes it appealing in my eyes.
You should be able to negotiate submitting your files as 1-bit tiff at target machine resolution (typically people send vector graphics which are being rasterized and then sent to the machine; so you need to skip a step in order to get perfect result).
There are also options on which side you would like to get photoemulsion and if you want a negative or positive output.
This is premium content right here!
Wonderful! As someone very interested in semiconductors this series is fantastic!
Thank you! I'm doing my best
After a lot of trial and error with my laser printer at 600dpi that is great for toner transfer of pcbs, i found that an inkjet printer with 1200dpi is the best solution for a better resolution and black coverage for the transparency film, many of my pcb tracks are 10 mils and its very easy and reliable to get this result with the inkjet printer. After loosing a lot of time with bubles i gave up the dry film and i use only the paint with an oven for drying pcbs.
Yeah, I hate the dry film and I'm hoping to find a substitute soon. I also want to try an inkjet to see if it works better for me. I was concerned that the ink would be even less opaque than the toner
A small SLA printer like the Phrozen Mini 8K with 7" screen may get you close to 20 um and has a well columnated UV light. This is such amazing work!
I wake up 4 hours early by accident, and what do you know, this video has been published. No chance I'm not watching this before trying to sleep again...
[Edit:] Regarding the photoresist lifting due to water exposure, some colleagues use an HF vapour etcher. The vapour pressure of HF isn't much higher than water, but perhaps not being submerged could be critical.
Also wondered about you making your own photoresist from 'near-enough' constituent components, or equivalent replacements, but I'll investigate how realistic this is.
Another thing occurred to me was to use an ultrasonic bath when developing the resist, rather than scrubbing with a cotton bud. Could also use a high-sided dish, and spin the complete assembly to create a small vortex with the resultant flow of developer to achieve more consistent removal. Just throwing these ideas out there.
Finally, are you aware of Sam Zeloof's work?
it's a cool idea but I'm gonna avoid HF vapors for the foreseeable future due to toxicity concerns. I want to make photoresist but i haven't yet found a suitable recipe that doesn't use toxic and carcinogenic chemicals. I've considered the ultrasonic cleaner but I think spray jets might be better (at least according to the datasheet of the resist). I am aware of sam's work and considered the DLP-maskless lithography source as a future project. I thought it was silly at first but it turns out masks are hard to make lol
@@projectsinflight Fair enough! I stay as far away from the stuff as possible tbh - vapour or otherwise. The one in work is basically the same as doing a normal etch, it's just not submerged. It looks like the Idonus model they use, but will ask them tomorrow.
Sent you mail btw; thought I'd mention as I'm guessing the PIF address isn't your main one.
Possibly one of the most interesting youtube channels, keep up the great work!
Thank you so much for the compliment!
Dude, good job. Last year I did think to dive in this hobby. My big problem was to get the silicon wafer and the HF safety problem.
yeah i feel you. i delayed this project for years out of fear of HF. i eventually decided that every hobby is risky to some extent, and that as long as i was using HF in a safe manner i was ok with the level of risk.
You're tenacious. Nicely done. Can't wait for the next chapter.
Thank you! i'm working my hardest on it
dude you're videos are incredible good, i have no idea how you aren't any bigger
I'm pretty surprised how many people are already here, and I hope that I can continue to grow larger as I make more videos :)
Salivating over the thought of becoming a chem PhD for the express purpose of cornering the global consumer-grade lithography photo-resist liquid market 🦀 💰
haha I know right. I looked into the chemistry but got scared off by too many carcinogenic and toxic chemicals
Have you considered using a small fish tank pump for the developer solution and a some blunt needles for spraying. It wouldn't take much to put together and would be gentler than cotton swabs.
Should try adding a surfactant like Triton before anything complex like that, various developers have them added in to help with wetting. In my experience manual agitation should be fine without any sort of scrubbing (for development, liftoff is another story) but I've never worked with dry films before.
Photoresist datasheet calls for several bars of pressure. Do you think that would be attainable using one of these pumps?
Let's go!!!! That's a great video, can't wait for those logic gates to appear 😅
I used to make PCBs at home - a messy and awkward process. I found that my colour laser printer could print much darker blacks than my b&w laser. It may be worth checking a few different printers.
Yeah, i've heard that you can get darker blacks on color printers by printing all the colors at once + black too!
Acetone vapour bath: As I recall, you want to lightly heat the acetone when smoothing 3D prints,. Easy to do when you're printing ABS with a heated bed: just put the acetone bath on the bed and warm it to like 40C.
For developing: could you put the wafer and developer into an ultrasound bath? I imagine that might help with agitation in an inexpensive way. Also, some models have heaters in them, which might be good for faster developing times.
You're setting up for spin coating for other steps, aren't you? Wouldn't spin coating the resist mask be easier than the troubles the film is giving you?
Finally, I feel like you really need a small simple photo enlarger, and then set it up wrong to get an image reduction of 2x to 4x. Nothing too ambitious, but it would allow you get simpler prints *and* higher resolutions. It would also allow you to look at other printers and printing processes. Maybe an inkjet or pen plotter would give better contrast without fiddling with the acetone vapour smoothing. Oh! I know! you could print on the laser at 16x, expose onto copper-clad glass with a photo reduction of 4x, and then use that to expose the silicon! :D
I tried heating the acetone and it did indeed produce more vapor, but it condensed onto the mask and dissolved away the toner. I would probably need to heat the lid as well to keep that from happening
@@projectsinflight Ew. Yeah, I can understand why you didn't do it then...
Oh and looking forward to the next part :)
I love ur videos, please stick to ur methode of producing. It is super easy to understand even if you are new to the topic. I glad that TH-cam brought us together ❤
Somewhere there's some old dude laughing like "I remember those days; you have it easy".
about the lamination issue with dry film, it can be greatly improved by applying it wet, similar to vinyl stickers etc. Pass it through the laminator while still a bit wet and able to slide on surface.
unfortunately that didn't seem to work for me. the silicon is so perfectly smooth that any moisture underneath causes a total lack of adhesion.
Man found this channel about a week ago and I absolutely love the content you are making
Thank you! I'm doing my best
I'm amazed at how quickly yet thoroughly this series is progressing, phenomenal work!
Only found your channel recently but I'm pretty invested already.
Thank you! It's been a really fun and challenging project!
im absolutely loving this project. the idea of taking something that seems like magic, only able to be done by large industry and working it out in a garage is just awesome. do you have any plans for what you want your first chips or circuits to be? or i guess the first thing would be to make loads of single transistors to test right?
Diodes -> Transistors -> 2-transistor IC -> 1st stage of op amp
that's the tentatve plan i think
As hobbyists we should start exploring e-beam lithography as it is more suitable for small scale production
it is quite the apparatus to construct though. still, i would like to try it
I used the paint, you can use toluene to thin it and the smallest that work reasonably well is 0.02mm(on copper) as for glass it's 50/50 after cleaning 0.1mm detail. Any smaller detail, resist start to peel off.
i'll have to try toluene then. does that work to remove the paint once it's cured?
@@projectsinflight it doesn't seem to have much or any affect after it cured, it work the same as the dry one other than the colour change. As for mask I make it on glass (etch then use silver mirror process on it so it can build a thicker layer to electroplated or other) it might be overkill for few testing uses.
I'm very impressed by this video. Great content, instant subscribe.
Thank you! Glad to produce something interesting :)
There is and maskless photolithography with DLP projector with removed UV filter and microscope objective. On that way it is possible to achieve very high resolution.
I hope you can make more videos about semiconductor packing
Good for making higher voltage circuits.. that can control a lot of VA
An experiment I have been looking into doing is using Elegoo's photosensitive polymers for 3d printers as a negative resist. It should be possible to estimate the exposure dose and resolution if you know your way around a 3d resin printer
In the rainbow glass video, you used a hot plate to produce steam, and I can see a stir knob on it as well. You should be able to find a stir bar small enough to fit in that dish next to the chip, and it will circulate the developer for you.
It actually not as useful as one would hope. the used-up developer sticks to the surface so you really need high pressure jets and not just general stirring to remove it
@@projectsinflightyou might be able to buy a cheap parastaltic pump and make a nozzel, they generate decent pressure and that may be enough ❤
@@projectsinflightwell, then what if we get silly and glue a little brush to the stirrer? (probably heat-welded, and two, and one of those 4+ limb or puck stirrers so it's stable)
Can't wait for the chemists to weigh in and tell you how to make your own photoresist
Oh my god i really hope so. The only recipes i found were pretty poor and used toxic chromium compounds
Super impressive 👍
Nice work, with this pace, we will soon see a video from you with probably your first 100 micrometer working chip :) Great achievements always start from below so I am looking forward to it, Your video forced me to hit the like button :)
you can put it under uv light after developing to get stronger photoresist
I actually know about this one. My classmates thesis on this was using non-linear optics to allow for finer resolution
Fairy sure those overhead projectors are still ubiquitous used today in schools
Haha probably. I didn't check but i suspect regular projectors for computers are probably more favored now
Shorts of failures would be informative too.
Unfortunately you are on the wrong continent.
At our place no one would even notice then 50-100ml of resist vanished 😅
I use SU-8, AZ 1518 and OIR 908 only a daily basis.
Overall a very nice video, keep them coming!
I use the dry film to make circuit boards for tht and smd and it works really well for that if you expose enough. As a mask i print on inkjet foil using a epson eco tank et 1810. You have to look through the settings a little to find the setting that uses the most ink but the masks work really well and the printer can print in a very high resolution. I also noticed that the dry film is sensitive to wavelength that get fully blocked by kapton tape. Something that might interest you… the dry film can be dissolved in a solvent to create a liquid film that can be spin coated but be aware that this doesn’t get close to commercial photo resists. You can get a better resolution though. With the dryfilm it’s very important to know that there are two different foils on it’ one is a bit stretchy the other is hard. The hard one is heat resistant the other is not. Also the laminator should be one with two heated rollers. I hope this helps a little for future experiments
Thanks- that is good info. Regarding dissolving the resist in acetone and spinning it on, I actually tried that. It spins on nicely but something about the dissolving step ruined the development process. It just dissolved off almost immediately, rather than making the pattern. Not sure why
Wow this was incredible! I’m at the edge of my seat! Can’t wait for the next one!!!!
Next up is probably diffusion!
@@projectsinflight AWESOME! :D Really looking forward to it!
You might be able to ask some TH-cam chemists if they could order some photoresist for you
I contemplated doing that, but I'd like to find a solution that anyone can do, and one that isn't tied to the availability of a single individual for photoresist supply. I would love to synthesize it myself though
if the dry resist is soluble in acetone, have you considered making a solution of it and evaporating off the acetone after spin coating?
I did exactly this actually! The dry film dissolves nicely into acetone and spins on in a perfectly even coat. Unfortunately, something about the process ruins the ability to develop it, and it will just dissolve entirely when you try. Haven't come up with a solution yet to fix that.
Super cool!
Thanks!
Amazing! Thank you for make all these videos.
maybe a fish tank pump or a small fan could blow the developer around to keep fresh developer moving over the chip?
electron beam lithography often uses acrylic or PDMS (silicone rubber) for resist, maybe they can be used for UV resists too. Or maybe the photopolymers used to make 3D printer resin could be bought online and used as a resist.
The used-up developer sticks pretty well to the surface, so you really have to use high pressure jets rather than gentle stirring. I want to try PMMA and e-beam lithography as soon as I have an E-beam source. I don't think SLA resin will work because I don't think it dissolves well but i don't know for certain
We early again on a good channel bois. Sheeesh
You might find that putting a drop of the liquid resist on a chip then covering with transparency and spreading using a soft scraper works.
It is with great pleasure that I look forward to each of your videos, they are incredible and a real motivation for me. Thank you very much, may Jesus bless you.
thanks! I appreciate it
Very cool series! Excited to see more :3
This is Applied Science quality stuff
That is a huge compliment- I have been watching Ben for years!
The dry film works fine! But u need to get the thin stuff!! 85-120μm and u need to bake it!! I made nickel chips on glass!
If you have a source for thinner photoresist film feel free to shoot me an email and I'll check it out
About the mask, why not use a black and white, positive, super low iso sheet film and a large format camera? It would result in INSANE resolution
That would definitely improve the resolution. I'm looking into a solution like that. My main concern is repeatability on scaling, as I'd need several masks that all are exactly the same dimensions so that subsequent fabrication steps will match up exactly.
positiv 20 is liquid and sprayable photoresist
I can't find it for sale anywhere in the US
amazing video, i'm always so excited to see your progress with the project
Thank you! I am doing my best
I heard about PMMA being used as photoresist
Yeah, PMMA is an excellent E-beam resist and needs a special chemical additive to make it into photoresist. I don't have the means to make the additive though right now
@@projectsinflight for some reason I'm thinking about 3d printing photopolymer resins. They have photoinitiators out-of-box. I'm not chemist, but I think you can also buy photoinitiator instead of making it.
is it possible to use just film camera and lenses?
Yes, in fact there is a special film type for this called lithography film that is basically super high-contrast B&W film
Hi, did you consider using an ultrasonic cleaner? It should be quite affordabl, accessible, and i guess should agitate the solution enough so the chemicals gets renewed where it shold be while moving the disolved particles.
I would definitely like to try the ulrasonic cleaner whenever i get my hands on one
@@projectsinflight
They are sometimes sold as jewelry cleaners, and the price is mostly driven by the volume of the bath. Since you are working on a very small scale, it should be quite affordable!
maybe making your laser print bigger and then using a lens to focus the light could help increasing image sharpness and reduse overall errors?
another great video as always
great content Sir. For “blacking” toner I use a product used for cleaning offset films from printing industry, it’s called limpiafilm kopi very cheap and can be used directly on top of toner without worries. I cant find other alternative outside Spain, if you are interested could try to send you a sample. For developing you can use an aquarium air pump and a bubbling stone.
Very cool
Thank you! I worked very hard on this one. almost 2 weeks of lab work alone!
This one had the perfect balance between theory and practice @@projectsinflight
Very well done, keep up the good work, one of the more exciting series in my nerd-YT-collection for sure.
So Sam Zeloof hasn't uploaded in about two years, but he made come ICs and possibly could tell you how to get the good photo-resist.
Photolithography. Where is this going? Well, its obvious where but this is super difficult and if you can make the cmos process cheap enough to do at home, you can guarantee that I will be doing this at home.
I was wondering, how do you plan on doing doping? I've been looking into home cmos-ing and have been considering laser doping and was interested in your plan. You already have a furnace so laser doping may not be needed.
Also, do you think that electron beam lithography would work here too? You can get smaller feature sizes.
CMOS will not be easy. Even for companies like Intel it wasn't easy. They took small steps from PMOS to NMOS to finaly CMOS. Any sort of metalic contaminants, especially sodium ond potassium, was causing troubles with CMOS. So for printed circuits boards sodium carbonate or sodium hydroxide is cheap and accessible. But CMOS would require nastier stuff like TMAH, which is even toxic.
I was able to get some success using diffusion of dopants like phosphorous and boron, but i'm still working out bugs in the process.
@@projectsinflight I am excitedly waiting for each episode. Good luck!
I'm thinking 425 450 will let you get away with smaller/denser and still be pretty good
OMG. I never made the connection between positive and negative resists and (de)polymerisation. Great insight!
Yeah the world of chemistry is super interesting
Your spincoating issue is that your lacquer is to thick and you're probably too slow as well. You can find out what solventvis used in the lacquer and try adding more.
you'd be surprised how hard it is to figure out which solvent is in that resist
we have a lift off🚀
Here is an idea so stupid it just might work: can you take the unprotected blue photo resist and dissolve it in acetone, then apply a thin layer of that to the wafer? Acetone might boil off too quickly which would leave a bad surface finish, but there are non-polar solvents you can use with a higher boiling point that should give a better finish.
Also, I got the ball bonder moved into my garage. It is missing the part that actually touches the silicon though. Hoping to be able to fire it up sometime soon to see what can be done with it.
Actually I tried that. The acetone indeed dissolved the film and i was able to spin on a thin layer. The layer didn't develop properly for some reason.
@@projectsinflight I wonder if a catalyst got washed out or something. Could also have a much different polarity. Might be interesting to put a sample on a TLC plate to see if anything moves. If you are willing to mail me a 3x5" square I could play around with it to see if I can come up with something.
@@seeigecannon feel free to email me and we can get the ball rolling