Laser doping a PN junction
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- Опубликовано: 31 май 2024
- Today we're doping silicon wafers with a phosphoric acid and a fiber laser.
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==== Details ====
Impurity dopants are traditionally introduced into a wafer via thermal diffusion, or ion implant. There is an alternate method using lasers to drive the dopant into the wafer, a sort of targeted thermal diffusion. This technique is used in the solar panel industry to form back contacts and selective emitters.
The laser selectively vaporizes the phosphoric acid and melts the silicon, allowing phosphorus to diffuse into the molten region. After the laser pulse ends, the silicon resolidifies and the impurity is trapped inside.
Sam's video on RIE: • Etching Silicon with P...
==== Analysis Equipment ====
nGauge AFM from ICSPI (www.icspicorp.com/)
Phenom XL SEM from Thermo
Gwyddion for AFM post-processing
Blender for 3D AFM rendering
==== Timeline ====
0:00 Intro
0:39 I have no idea what I'm doing
1:09 Doping silicon
2:21 Thermal diffusion
3:19 Ion implantation
4:36 Laser doping
10:06 Resistivity test
10:40 Hot probe test
12:20 Diode test?
15:57 SEM Archive
17:06 Next steps
17:26 New hat! 
Наука
thanks for sharing! I loved seeing the process and SEM pics. This is def promising for home chip fab. If the resistance goes down then the doping is working! For a while all my PN junction curves looked like that too, fixed it by using Al with a few % Cu mixed in for both P and N contacts and annealing at 450c. Pure aluminum tends to alloy with the silicon and forms spikes that go deep into the wafer and shorts your junction to the undoped silicon below. Not sure if this is a problem with Ti/Al. Also, your sputtered metal electrodes overhang the doped regions. Is there thick oxide on the non-overlapped regions? If the doped regions are 1x1mm, maybe try sputtering metal only on the center 0.5x0.5mm of each to be safe
Can also check your junction by shining a bright light on it and measuring the voltage cross the diode, like a solar cell, should be able to get 100mV
Dang dude! Is that your experience from hobby building😲
Thanks Sam, appreciate the tips! Good to know about Al/Cu contacts, I'll look around for a sputter target. Did you make your own target, or something that can be bought commercially (or maybe layer thin Cu first then thick Al)?
Yeah, I was irritated at my shoddy mask alignment there 😭 The wafers did have a reasonably thick thermal oxide (500nm-1um, just based on time/temp) protecting the other regions. But the laser might be churning up the edge and could be unprotected. I'll try again with smaller contacts!
Will check with a flashlight too. Not sure why I didn't think about that 🙃 Appreciate all the help!
@@Mwwwwwwwwe that dude is actually insane, definitely check out his channel if you haven't already. he's on another level.
@@Alexander_Sannikov DUH🤦♂️ didn't see that he had a YT chanel... thanks will check it out😁
Ion Implant process engineer here. Your description of my process was spot on! I'm impressed how you succinctly and thoroughly explained what I do in just over a minute and might have to steal your explanation when people ask me what I do!
You also mention that ion implant will probably never be feasible in a home fab setup, and that's probably true under one condition... if you are concerned with purity of the energies and species being implanted. If you are OK just implanting everything in your source gas, it may be feasible for someone to setup a "shotgun" implanter, which is basically a plasma chamber fed by some dopant-containing gas over the wafer with an acceleration grid in between that sends all the positive ions into the wafer, dopant included. This was actually the first type of implanter ever used in industry. One issue with this design may be uniformity, not sure how this was solved in industrial applications. Another issue is that you still have to anneal the silicon to "activate" the dopant... speaking of, have you considered sending your laser doped wafers through an anneal furnace to "wash out" some of the nonuniformities?
This makes me think that there should be a sub-section of each scientific field (similar to this one at least) that focuses exclusively on the minimization/simplification of all techniques, tools, etc. needed to do certain experiments or create certain devices.
It would be interesting to see a scientific group that actually worked to figure out the minimal setup needed to create usable chips and to shrink those needs.
Think of how much more accessible cutting edge research would be, for undergrad courses or whatever, if the researchers who knew their own work the best did the marginal extra work to create a "minimized" version of their procedures. It would be fantastic!!
@@michaelandersen7535 lol "marginal". There are many things that are so sensitive and complex that simplifying it is more work than the original research. Getting something ready for production is mostly that simplification, and it is much harder and is the reason that it takes so long for new inventions to be brought to market. Not to mention that researchers are almost always under funded, limited on time, and under huge pressure to publish more papers, and fill out grant/funding proposals.
I can assure you this exists, but it lives behind NDAs and the privacy of industrial semiconductor fab methods. Makes one wonder how fast this research would advance if it weren't all hidden and competitive in this manner.
That’s called RUclips.
We could call it the Foundation.
5:08 I am in tears. What a wonderful image.
Edit: Just saw that you were trying to make a diode. Well, the contacts are of paramount importance. Who on earth did tell you to use Al as a p contact???!!! Generally, you need high Workfunction (Φ) if you need an ohmic contact to a p-type semiconductor. You can think of it like this: the n-type semiconductor has a high fermi level and generally likes to give electrons, so you match it with a metal that likes to give electrons, such as: Cesium, Na, K, Aluminium. On the other hand, you match a p-type semiconductor with a metal that likes to retain its electrons, such as: Platinum, Selenium, Copper, Gold. Platinum and Selenium are kings with a work-function Φm being 6.35eV!!!!
If you input an AC wave into the wafer while using x/y deflection on the scope, you can apply the the AC signal to the x probe, while reading the output with the y probe. You will get a hysteresis curve telling the function of the pn junction at that AC frequency. The freq to use will depend on the capacitance of the junction.
Interesting, I'll look into that! Is that what the curve tracer is doing? I have a cheap "octopus tracer" which I was using to generate the curves, but not entirely sure the circuit or if it would function differently (there aren't really any controls, so I can't change the AC freq for example). Thanks!
This channel is amazing and deserves a lot more followers. If a video starts with "Hey folks, short video today talking about doping silicon with phosphoric acid and lasers" it's guaranteed to be good.
And then lasts twenty minutes! Short,😉
I love seeing work-in-progress content! It's really cool to watch projects evolve
YEAH! It's amazing!
Also people can help out if they know something, instead of researching everything your self.
Some times small pieces of information can save you hours.
This is dope!
No, really - it's doping silicon. Will you be making a video about transistors with this technique?
You stole my dumb joke.
@@bsgconsulting Ohm my!
If you want to play around with it.. I have a 600W (1 joule/pulse x 600hz) 308nm XeCl laser used for surface annealing flat panel displays in OLED production.
Yeah, much better. It would take more passes but you could move faster... That would let you fine tune the surface texture while still getting a good deep implant structure. 👊
Oh wow, that's quite a laser! Where'd you get that beauty?
I might take you up on that offer at some point in the future. I'm in the middle of moving my shop to a new location at the moment, so I wouldn't be able to put it to use for a while. But perhaps in the future! I did recently find a 1W q-switched 355nm laser which I'm hoping to get commissioned soon, but unsure if the power will be high enough to do anything at that wavelength.
@@BreakingTaps Work - we repair lasers used in semiconductor photolithography, typically 193nm and 248nm systems that put out 10-40W.
The 600W 308nm system is for flat panel displays. The only problem is the thing is a bit of a 'sledge hammer' compared to the 'scalpel' you're currently using.. It's just the light source and there's no beam steering/exposure tool attached. The raw beam is very large (~40mm x 25mm) so you would need some masking if you want to limit your exposure area.
@@sooocheesy Oh, that changes the equation... Gonna have to get in touch with Hoygans optics and see if a collaboration is in order.
As someone who binge watches youtube videos on whatever subject I'm interested in that day, I very much appreciate your meticulously planned and edited videos. As I am usually searching for explanations of certain phenomenon, or in the case of many of your videos, diy versions of expensive processes or simply exposure to those processes I wouldn't normally get to see, I personally don't care so much that you put out videos on a strict schedule. I watch your videos because of how detailed you get and seeing what results you can achieve (and issues you had to resolve) once you've dialed everything in. Needless to say it's still fun to see everything you get to play with.
Multi-layer contacts can be done using, for example, one or more of Mo/W/Ti/Cr as a Shottky or Ohmic contact, depending on your application and diffusion layer doping. Consider making a four probe resistance measurement setup (linear or square) for example with tiny pogo pins. You could also make the opposite side of the wafer back side electrode and measure your diode structures (e.g. pnn or even pin with more pure silicon) through the wafer.
Good idea.
Noted, thanks! Will look into constructing a four probe setup, that's a good idea with pogo pins too. Would be a lot simpler and less fiddly :) Cheers for the tips!
Definitely appreciate the updates along the way on projects!
The fact I can follow what you’re saying for the most part, shows how good you are at these educational videos. Thanks for sharing. 😄
Awesome content. Nice micrographs too. I never know what to expect when you post a new video, but I'm always glad you did. It's so fascinating to watch you work through the issues and figure out what your data is telling you.
This was really great. Thank you for sharing it with us. I can't wait to see more.
Nah, you've done it! looks great and it's so cool your having a go and showing us, I worked as final test for Applied Materials their Implant division and know what you have is great and you should keep going ...wow ! just as writing this you showed your hat and yeah keep going ! my two favourite subjects Mass Spec and semiconductor stuff, oh yeah and microscopy ! can we have a lab tour soon please ? have a great holiday and I can't wait for more, blistering hot channel by the way....cheers.
Thanks! Lab tour in the future for sure! I'm moving to a new location (about 50% done at this point), so once the new space gets setup I want to do a tour and show it off :) Outgrew my garage and wanted a bit more space to work on projects :)
I always find that it's amazing that you can make garage-semiconductor
You dig into such interesting projects, love your channel, thanks
Thank you for taking the time to inform me on such an understandable manner i had not heard of any of this despite my interest in electronics and diy hobbies
Oh yeah, work-in-progress is always awesome to me! I mean, with a fully perfected video, while very nice, it does feel a bit like magic. Seeing work-in-progress and sometimes simply failures, makes it real, makes me feel like maybe I can do it as well. So I'm all for it! :) I'll become a Patreon as well in the new year as I finally will have a bit more to spend again. :)
This is really interesting. I wouldn't have thought something like this could remotely work in a home shop at all. I do love that you're talking about it even though it's not quite there yet, I really hope that some other more knowledgeable people help you figure it out. I like these sorts of "work in progress" videos.
The algorithm brought me here because the intricacies of all this is all way over my head but the general gist of it absolutely fascinating. Thanks.
Bro. Keep up the good work. See something like this in a home lab gives me mad hope for the future.
Enjoying your content! I always chuckle when you say "There are a lot of better explanations on the internet about this topic, but..." quickly followed by the best explanation of said topic on the internet, lol.
Whoever does the lighting/set design is a genius. It's absolutely beautiful.
So glad I found your channel! Very interesting stuff!!
Your projects are always inspiring! Love your presentation style. Ah and your old cap is epic, don't stop wearing it!
Kind sir, you are making beautiful and highly engaging videos. As a videographer I really appreciate the great looking floating head setup you got going - great looking grading! Keep doing what you’re doing!
"short video" - 18 minutes.... Mmmmmmm.
Yummy science content
"It's not a documentary!"
The struggle is real. I always start out thinking it'll be short, and end up cursing myself while editing 🙂
In college when we built mosefts, diodes, and capacitors we purged the chamber with nitrogen at the end of annealing. I think the final aneal had some hydrogen to get rid of dangling bonds. Been years since I have done it tho. I look forward to your content and my own lab once I can afford to set up my own lab.
What degree were you studying where you got to do this ?
@@shawnm8232 Electrical engineering with a focus on nano device physics.
I had a difficult time getting a job after college though. Awesome subject, didn't end up paying my bills though. Software is soooo much cheaper and faster.
Duude, nothing short of amazing. BTW Happy new year 🎉🎉
color me surprised and highly interested to try this on my own, thanks a lot for the great content as always!
Work in progress stuff is important. It's a big reason why I think the internet is even useful at all.
My parents always told me doping was bad but this seems pretty cool
18:09 The laughter at the end, was the best part!
Wow! I bet this kind of thing would really help for small scale retro chip production.
This is very exciting! Please keep going
If you have a 1064 nm fibre laser you could just use SHG to generate 532 nm pulses. Should work if you only need like 40 % max power at 1064 nm. And you should probably get a system to remove those white clouds when you're doping, maybe immerse the wafer in phosphoric acid and use a small pump to circulate the fluid?
that would be incredible, but I once read it's nor known how to double frequency with fiber lasers as is done with yag. Do you have useful information about this?
Yeah, definitely investigating some kind of flow chamber to keep the phosphoric moving across the surface and clear bubbles. In some cases you can see where the bubbles have disrupted the underlying laser path, which we'd want to avoid for precision paths.
SHG is on the potential todo list! I'd love to have a pulsed green laser, would open up a few projects. I don't _think_ it would be too hard to put a crystal in the optical path but haven't looked too closely yet.
very interesting video. I learned a lot from it. Thank you!
this is so awesome please keep us updated :D
Nice work,
Cant wait to see the first garage-semiconductor CMOS chip-collab
Enjoying your channel. Merry Christmas! Oh, nice hat. The old one rocks, too.
Really cool effort towards individual / garage scale integrated circuits. Me and friends have dreamed about simplified processes to make this possible for many years. BTW I've watched a whole bunch of your videos and never even noted your hat :)
Kick ass work! I love watching people smarter then me, it pushes me to advance to new levels. There was a time this would have been like listening to people having a conversation in Mandarin, but now I actually understand what you're talking about. I hope one day I will be doing these experiments on my own in my own homemade lab. The way I view things is if an apocalypse happened I'm not smart enough to rebuild our world with what I know now and I want to have those skills even though that won't ever happen it's better to know as much as you can about everything you don't already understand.
Oh my, this video is a gem ! I've been interested by the Silicon world for more than 2 decades and yet never heard about this technique :-O
glad i found ur channel, great content.
hey, you making exceptionally great content! keep on going!
This is unbelievable , thanks for your effort. These are perhaps the first stones for free as freedom semiconductors technology for humanity. The same as Linus did for software. We are far far away from industry but this is a start.
Fiber pulsed lasers are great and cheap, now we need more frequency, it would be a god send if we could double or triple the frequency with crystals.
Amazing work.
Cool. Thanks for sharing.
"I dont really know what I'm talking about"
the honesty of that statement is underappreciated.
I don't have any idea about this niche of computing, however the lasers are cool. Subscribed, hopefully I can learn more!
Found your channel just now and you immediately received a sub and bell turned on, Great content and presentation.
Great Christmas morning watching this vid!
And now have just watched successful JWST launch, it really is Christmas
this is really dope!
This is so cool. Thank you.
I like how 18 minutes counts as a short video
I can help you with some ion implantations. We have a 1.7MV NEC tandem accelerator, we don't get the very high currents like a implanter would. But we can go deep and do direct write without the lithography.
seems like twitter might be the way to reach out, since I don't think he can DM you via youtube anymore
Oh wow, thanks for the offer! I'm on the road at the moment (holidays), but if you get a minute send me a note on twitter (@BreakingTaps) or email (info@breakingtaps.com) and we can go from there. Almost feels like cheating to have real equipment do the job haha. But could make for a really interesting video! Cheers!
Awesome video!
I've been interested I making integrated circuits at home lately, this tech is good to know about!
Great content as always, and sweet hat!
Glad for the shift, as seeing what does not work well or work at all, is a good way to document paths in the road with "warning" signs, though with caveats that someone might go "well that is excellent that is what I needed" and not just "ah that does not work ok let me try this other direction, since I don't have a good *this works for sure* path".
I really wish more people would do this documentation of everything including what does not work and what it actually did as far as they can tell.
Thanks a bunch, one of these days I will have some money I can spare to throw your way, and this is why you and others doing this will get first crack at that extra money :)
Hopefully I will soon have my lab and workshop moved too so I can offer trade of skill and tool set with people since I really need an electron microscope, but access to one might be even better as it would add the validity of the person doing the scanning to the already valuable view of what is accomplished (or not accomplished) to make up for the pestering others and then having to wait for shipping and the like (and trusting the shipper to not damage or alter the item being scanned or something LOL) That bit if the person has good reputation for just showing the work and not trying to alter it's results for any particular reason, well makes up for the negatives I would say.
Wish you had taught my semi conductor physics class, because this video was 100x more interesting than any of my professor's lectures.
Christmas came early!
For your resistance measurements, you should really be using a 4 wire measurement
Dope video bro!
Tips from Jeri???
That's awesome!
This was a great video
Thanks!
I like the worn out hats! It gives them character and a story to tell!
as a patron, i can't care any less about any perks. the only benefit i want from supporting you is you continuing to make good videos.
♥♥♥♥
Well done, keep it up
please let us see behind the scenes and the ones that you don't finish. This is where most of the learning is done!
Best Christmas present
Amazing stuff.
This is fascinating! Please do more semiconductor stuff!
A video list that a high school STEM teacher can use for some courses would be great. Maybe put together a equipment list for a high school lab so we can propose a budget. How to make diodes, and such. I recommend for Jr. high school how to make capacitors (big ones) as a lab. Having to write reports on what they find interesting will help develop the other skills a person needs to succeed in life. My hope is for the next generation, as the current one has lost ground vs. what our grandparents did in the past.
Merry xmas, this must be one of the best presents :)
This is soooooooooooo cool! Would be really neat to get a basic IC made.
The supporting tech tree needed to actually do this is probably too much for me to attempt myself, but it's amazing that garage-scale IC fab is becoming a reality. Who knows, in 10-20 years someone might have come up with a simple and cheap high vacuum solution that makes MSI fab on the scale of a small 5 axis CNC machine feasible.
I dont know how I got here, but this is very cool. Love the explanation and details.
Man this stuff is cool!
On the chalkboard in the background:
"Photo litho
nano particles
Potato"
Yes...potato!
The one thing we can all agree with.
I saw the potato as well
🥔
How in the hell have I never seen your content? SUBBED!
Loved seeing WIP
That's Dope bro.
Awesome new hat, with dope science content
Thanks.
@Breaking Taps, "Design of Experiments" may help you optimize your parameters.
Will take a look, thanks!
I'll say it if nobody else will. This is pretty dope.
I love your old hat :) The new one looks good too. But the best thing is your personality, it looks really good on you
5:51 - whoa that is cool. This means means this is a valid alternative for precision wafer sensitizations which today uses ion implantation. This means the laser method is much more affordable and doable. I wonder why big companies haven’t done this before…
Love for both hats. :)
That's dope.
I like the old hat. But the new one is fantastic.
Also the doping stuff is dope. Love your projects and vids about them regardless the outcome.
Thanks
I just started a job as a technician for marking lasers... found a fun experiment to do :D
This video is dope
Thank you so much for sharing! Great video! Love to see more.
#Subscribed
You should try some tests with some of the multiple 405nm "compressed spot" focused beam. Looks to possibly be a inexpensive home shop method