DIY Laser Lithography: Micron resolution 

Hah, thanks for answering that. What about a stage that is based on one of those flexure designs? That would allow tiny movements.

Thank you for the considered answer! Have you also thought about using a Wicked Lasers LaserCube? Its blue diode is 1300mW at 445nm, which is within the range (350nm-450nm) specified by Microposit's datasheet.

Is there any way you can see how far off the laser is coming out of the galvo and just use the stage to correct it? You could try to make the lines straighter and maybe even see if for some reason it's repeatably off mark the same amounts in when doing similar things? Kind of like how the Shaper Origin handheld cnc router uses a small but accurate cnc to improve the positioning you do by hand.

Like fgbhrl suggested flexure xyz stages can be very precise, zero backlash, readily characterized and driven by very standard gcode. Any speed lost due to greater inertial mass may be offset by running many parallel beams at once. You could even make mirror images cut at the same time that would register perfectly with their counterparts - which may be useful somehow in the construction of MEMS devices. Another argument for using a mechanical stage is that your beams (and thus the walls of your resist) could be made to be exclusively perpendicular to the substrate rather than all converging at the microscope lens.

I mean, you already have a sub-micron stepping stage, you just had to make a spatial filter for your laser and half a decent focusing optics to get better results with less effort... Also, is your laser polarized, and was the dichroic designed to work at 45°? Most of the off-the-shelf dichroic are designed to work at normal incidence and suffer big degradation in performance at high angle, especially if the laser is polarized in the wrong direction

Thanks Ben! Glad you enjoyed it ♥

@@BreakingTapsI’m a big fan of both of you. You guys do amazing work!

Between the 2 of you I would expect to learn how to like a video twice

Beginner mistake, no worries, it´ll go away... By "Breaking Taps" u click "like" always before starting the video, everyone knows... ;-)

I see a colab in the future

That is amazing to see so many wizards in one comment section!

Thanks for the tips, that's great to know! I wasn't really sure what thickness to be aiming for, so just chose an arbitrary speed near from the datasheet (3500RPM) and left it constant so there was one less variable to think about. Good news is that it seems pretty consistent, around 1.7-2um each time. I'll try increasing the speed and get a thinner layer for my next tests, thanks!

@@BreakingTaps if 2um is your thickness at 3500rpm, then increasing RPMs is probably not going to give you a significantly thinner layer. Adding a little solvent is a better strategy. Or alternatively you could use a resist like az1505.

Hm yeah, the datasheet maxes out with 500nm @ 7000 RPM. My coater should be able to hit that, I'll give it a shot and see. Good idea about adding some solvent. Will look into AZ1505! I've been wanting to get some SU8 as well, just because it looks very useful for "structural" applications where the resist is left in place.

@@BreakingTaps Be careful with exposed SU8! This stuff is ridiculously hard to remove, nearly had to scrap several fully structured 8" MEMS wafer because someone was curious about my stuff and opened the box outside the yellow light area... (partially my fault because I stored the box outside the litho area, but the stepper was down and all shelfs were full). The thickness of 150µm wasn't helping this either. Warm acetone or NMP over several hours followed by plasma ashing in a O2/Ar plasma somewhat removed it (I also read that warm Piranha solution makes quick process of the SU8 but would have definitely destroyed my wafer) . At least some devices survived.

Thanks! I'm not sure what v2 will look like to be honest. The deflections are pretty big (+/- 20degrees? something like that), but that could be changed... I was trying to maximize the full range of the galvos because I figured they would not have much accuracy if trying to make very small deviations. If the a piezo galvo or whatever had very small range, we can tweak the focal distances in the relay system to make it work, probably just with much longer focal distances. I have a few options that I'm thinking about: - Getting a better galvo, the "digital" ones designed for etching should be tuned better. - Some kind of tip/tilt flexure mechanism, actuated by voice coils or high TPI threads or something. I don't _technically_ need all the speed of the galvo, so we can use a slightly slower mechanism too - a few different more "mechanical" designs (coupling a ballscrew to a rotary mechanism), so we can take advantage of high resolution in the ballscrew mechanism - A sorta silly idea someone mentioned on Discord which is growing on me: a CoreXY style 3d printer mechanism that "rasters" above the tube lens in the system, replacing the galvo entirely. Similar to how CO2 laser cutters have a traveling mirror, but coupled into a microscope objective. Still mulling that one over. - Or just admitting defeat and using the wafer stepper for all motions. Would be very slow though. The "demo raster" was an "X" shape and just about filled the entire field of view (I used it to help align various components). It depends where you look, but on the first lens it travels a few mm, on the second lens it's traveling a centimeter or two. And ultimately the FOV is either 2x2mm (20x objective) or 500x500um (40x objective).

I suggest looking either for proper galvos (like for actually your purpose) or to keep in mind that the mirror surface of your galvos has optical quality. I assume the galvos you used don't actually have the needed surface quality and that this might create the "wobbly" structure of your trial structures. Just a suggestion from my side - I hope I'm not too late 😅

@@1xBublex1 theoretically if error is repeatable u could calibrate wobble into "control system". But yeah if there is huge variation and bad repeatability is another case.

This guy is doing some crazy work I would never have dreamed could be approached in a DIY setup. The other channel I have seen that blew my mind in this regard is Thought Emporium.

Do you know if commercial LSMs have enough power to bleach the photoresist?

Powered by project-ADHD 😂 I usually have 3-4 projects going at once, and when I get bored or burnt out I switch to a different one :) This project for example was 90% done in January but I just couldn't make myself finish, so went off to do other things until I got interested again :)

does the beam need to enter the fiber parallel or can it enter it focused to a point? what angular distribution does is have when it exits?

Thanks Les, means a lot coming from an actual optical and laser expert! :) I haven't really looked into fiber coupling to be honest, and no real reason either, just didn't ocurr to me 🙂 Can you couple in multiple wavelengths to a fiber (so I can also include the red focusing laser)? I assume I'd need a single mode fiber instead of the bigger multi-mode stuff? Thanks for the help! My fiber-fu is pretty weak 😅

@@BreakingTaps I've never done it but I believe so. You'll have to make sure that the fiber is rated for the range of wavelengths used. You also need a lens that optimally couples the free space laser to the single mode fiber. Newport has a good article on this if you search for "Fiber Optic Coupling".

Thanks for the tips, appreciate getting help from actual experts! Yeah I definitely think vibration is playing a role, although I might have underestimated how much. v2 will probably sit on a granite plate, and I might put some kind of air damper underneath to help with vibrations just to rule it out. That's a clever tip with the camera, will keep that in mind! And re: laser, I probably explained it poorly. The diode has an integral lens which is focused onto the pinhole, so the efficiency isn't as bad as it seems. But I have the pinhole intentionally misaligned because the aberration from a misaligned pinhole ended up giving better results than full intensity through the too-large-pinhole. That's why the ultimate spot ended up looking so dim. :)

yep, that was amazing

huygens spheres are problematic with singular rays that can't actually exist. as in, they only exist because the beam is much thicker than the wavelength but its wave structure is inconvenient to visualize and it also causes inevitable diversion over distance.

I love Robin! That man has so much knowledge packed into his head it's amazing. Not sure I saw the custom mirror mounts though, will go dig through his videos to find it. Thanks for the tip!

Oh! Interesting! I wasn't aware of these devices, looks super cool. Will do some more reading, cheers for the tip!

I was pretty shocked to be honest, much better than I expected!

♥

Dr Nick, can you share the company that you used to print the masks?

@@arguetav ProArt BV in Groningen, The Netherlands. Ask for film with high density in black/white. Transparant for UV and black silver blocks UV. Resolution in micrometers. Just give them a call and discuss your needs.