I think this is hands-down the best introduction to electron/hole transport physics I've ever seen. Just enough to be accurate, but not enough detail to overwhelm a newbie. Totally putting this into my list of semiconductor physics videos to show to beginners. Great job!
Really refreshing to see this all presented in such a clear and accessible way, both in education and actual practical use. Excited to see where this series goes!
out of all my hobby reading and learning about electronics since 1995, this is the best explanation and the way people should be taught about semiconductors... really great overview and easy to understand. i bet this whole video series will end up being shown in school. thank you and keep them coming
@@projectsinflight Are you refering to semiconductor manufacturing startups or the type that provides with development tools for electrical engineers and outsource manufacturing to an actual fab? I'm talking about Tiny Tapeout here for example. If you mean the actual manufacturing startups would you mind sharing some info here please?
Dopant precision really depends on the device. TTL is a little sensitive, while CMOS is not too worried, it just affects threshold voltage slightly, and breakdown voltage, which mostly is going to manifest as leakage. Most extreme example is things like unijunction transistors and Jfets, devices that have a very wide spread in charactaristics, depending on the doping level. Jfet it affects the pinch off voltage, and also the current flow when it is connected as a constant current diode, and in unijunctions affects the stand off ratio and current capacity. That is why you get so many different Jfet and unijunction part numbers, with them all being almost all the same aside from a variation in either pinch off voltage, or stand off ratio, and with the devices in the base part number being sold with a massive variation in those, with the others being binned from these big pools during manufacture, with the variation coming from the slight variation across the wafer during production, so if you got hold of a single tested but unseparated wafer, you can probe each chip, and get a pattern of how doping varied across the wafer that run. That is why you always see test patterns on any larger die, there using a small amount of space to have a test pattern that is placed there early on, and probed during manufacture, so that any wafer that had a bad day can be weeded out early, as the test structures make for easy to test devices, that they know how they react according to the doping and such. digital logic can handle a little error, analogue that is complex not so much, and precision analogue not much at all, especially if you are using Jfet in the design, you want to hit the mark every wafer, and scrap any that are likely to be faulty early on.
@@projectsinflight No, just have been using them for years, so learned why the Jfet and UJT have such a wide spread, while regular TTL is reasonably stable, and CMOS is pretty much immune in regards to threshold, really mostly being depending on gate oxide thickness for how it works.
While there are test patterns all across the wafer, it is infeasible to test anything electrically until the wafer is almost all the way through manufacturing. You need ohmic contacts from the semiconductor to the metal on top, which comes late in the process, because they have processing limitations and need to be at the very top of the wafer. So for example, the n++/p++ doping that is mentioned in the video could be used for a semiconductor-metal contact. But there is no way to check if the doping worked until after the wafer is completed. After ion implantation/for diffusion you need very high temperatures for a long time, then you need to apply the metal for the sc-metal contact and it's associated processing and only then could you test if the sc-metal contact works. And don't forget, each of the steps comes with photoresist application, patterning and cleaning!
CMOS functionally isn't too critical to doping, but not to say specs are unaffected: this is part of the reason why speed grades, input threshold, and output current, vary so much. The other part of the reason is they just DGAF and want wide guard bands on their process, lol. (You'll almost certainly never measure a 74HC or other gate in the wild that hits the datasheet worst-case limit say for propagation delay. Unfortunately, this is needlessly conservative when doing actual timing chains -- the one upside is, no one does that anymore, if you're doing logic, you're writing for an FPGA or ASIC... or building a hobby computer that you can test, select parts, and repair as needed.)
This series is excellent, you are doing a great job at taking the device physics concepts and making them digestible. Not to mention actually performing it at a home lab.
This is so excellent. Electronic Band Structure is one of the most complicated theories in physics and engineering, and I was missing some key details. But just through your presentation style, you've made it so accessible! Thank you! You made a patreon subscriber out of me.
I am absolutely in awe of your ability to educate. I did physics as a bachelors degree including semiconductor theory and throughout that final year I never grasped this subject anywhere as near as well as I have watching your video. Thanks
As an electronics nerd with an interest in chemistry... this series is absolutely superb! But now my history of science nerd wants to know how these processes were first worked out. :)
5:35 "Because there is one extra electron and no hole..." - could have used clarification; the atom of phosphorus does mean there is an additional proton, so when its extra electron moves around why doesn't that create a "hole"? The answer is that a hole is absence of an electron *from a covalent bond*, and that is not happening: all the bonds with the surrounding silicon atoms are satisfied.
Yeah this could use more emphasis (if one want to get deeper into semiconductor physics). The remaining phosphor atom will be positively charged, which has huge effects - mostly creating pn-junctions, but also causing coulomb scattering.
Amazing video, really good supplementation to my Electrical Engineering class! I learnt a lot from this one and the last video, as this really goes into the details, while still making the process of following through and understanding really easy!
Great stuff! Can't wait until the next video! Cheap but reliable dopants will be awesome to have haha. Now I wonder if it would be possible to also make a diy photoresist that could enable micrometer features :P
Actually I have been also working on DIY photoresist for months now. I'm not sure how close I am to a video, but I have at least one working formula. I'm also trying to recreate a novolak based resist from the 70s/80s. I will 100% make a video on all this when i am satisfied by my results!
@@projectsinflight Awesome, will be looking forward to that, as it would definitely be much easier to make the photoresist in the amounts that one actually needs, rather than buying a half a liter bottle and then 400ml of it goes bad two years later haha.
One of the more interesting bits of physics unveiling before my eyes was watching gold diffuse into copper, in plain air, under a microscope. Coworker had ordered some garbage tier RC power connectors that use hopes and dreams for their current rating, instead of real life figures. But it probably wouldnt have set itself on fire in the application it was destined for so I humored him and was installing the connectors onto leads. As I soldered them, the whole outside of the solder cup (not exposed to solder, that was on the inside) went from the gold color of the plating to copper color. Looked it up, and turns out gold diffuses into copper really starts to pick up at 200C, right around what the solder would have been. Normal good gold plating has a nickel layer underneath to stop this (and oxidation beneath the gold) But because my coworker was being a cheapskate, and whatever factory in china didn't think that nickel bath was particularly needed, I got to watch solid metal dissolve into another solid metal under a microscope.
Yup, silver and zinc as well. Hence the ~high school experiment plating a penny with zinc then heating it to brassify the surface -- you really are getting a brass layer, it's not just the thin layer of zinc oxidizing to an interference pattern or something. Silver (directly on copper) is semi-commonly used for PCB plating, but usually it disappears into the solder by the time diffusion would matter much. Along with tarnishing, it can be a concern in storage though. These also illustrate the Kirkendall effect, where the diffusion of atoms into each others' bulk reduces the density in each, creating voids. Well designed plating sequences (or diffusion schedules) avoid this in most cases, but there are industrially important applications where the voiding affects joint strength -- Sn-Cu diffusion (and intermetallic formation) in solder joints, for example.
Thank U for your consistency with one great project along with high quality videos! Have been watching whole series and here I especially love the quite in depth explanation what elements are bad or good and why as well as describing doping level difference; also thanks for avoiding hard to get/ very expensive or deadly materials in the process so, that it could be really recreated by others:)
I remember skimming over a paper about doping wafers with plain phosphoric acid a few years ago. It was from the solar industry, but I don't see how it wouldn't translate to other semiconductors. I can't find the exact paper anymore, but some very similar ones about the same topic were published recently: 10.1007/s12633-022-02231-3 and 10.1007/s12633-023-02658-2
I tried plain phosphoric acid but it really doesn't seem clean enough for my purposes. high concentrations leave a horrible residue (silicon phosphide maybe) on the surface that cannot be etched away
Also holy shit I was looking for something which you could use to dope silicon that can be applied above. I had this plan of making more accessible hobby scale implantation by using basically lasers directly to implant the ions. Eagerly waiting your next video
I'll be honest- the dopant I was able to make isn't perfect- it has to be stored at low temperature to have a decent shelf life. However, I think that it's the best i've seen so far. Maybe a real chemist can do better :)
The part where they were talking about dopant gasses and then showed the LD-50 was very funny, I laughed in a video that I did not expect to laugh in. I've only really heard of phosphenes toxicity when it came to dopant gasses, but the other ones being extremely deadly don't surprise me at all.
Love this theory series. I find it electrical engineer-friendly while at the same time involving chemistry topics I didn't even think of before. Good work!
A time will come, perhaps, when YT hobbyist will replace much of academic courses. I really think such videos (and if you show the experiments) are much better way to learn than to attend boring lectures with constant fear of grades. Great work!
while i love learning from youtube, i feel that education requires closing the loop on knowledge, meaning that you need a way to check that knowledge is actually being absorbed. I will say that i think there are better ways to close the loop than just taking tests though.
For the longest time [growing up], I thought you could just take two blocks of the stuff, *now kiss .png* and boom, diode, transistor, whatever. (I tested, and wondered aloud, why wiring two diodes together doesn't make a transistor. Hey, I was... probably 9 at the time?) Sadly, all those early/easy/common references neglect to mention two things: 1. charges move by diffusion, and only travel so far before recombination dominates (in Si, a few µm, maybe 10 tops); 2. you need a metallurgical bond; a random misaligned crystal boundary with oxide inbetween, ain't gonna cut it. Astonishingly, reasonably-well-aligned crystals, and vacuum-clean and atomically-polished surfaces, can be created, and bonded metallurgically, so we can actually do this if need be(!), but it's a lot more work than rubbing two rocks together, hah. Equally surprising, it is still true that you can rub rocks together -- or more to the point, poke them with wires, "whiskers". Rough (read: non atomically polished) surface contact is dominated by asperities, where rough spots stick out enough to touch, give or take contact pressure and the elastic modulus of the material; this can happen with enough force to scrape off the oxides and get direct semiconductor contact (or a thin enough line of oxide, adsorbed air, and other surface contaminants, that charge carriers can tunnel through the barrier), and thus a diode is born. Transistors are harder: MOS is out of course, but BJTs can be made by microscopically-aligned point contacts. They also fairly early-on discovered you can fuse the whiskers into the chip, making a much more consistent, reliable, robust device; the 1N34 germanium diode is such an example, and the whisker (tungsten I think) is coated with a dopant so that when the device is assembled (glass sealed body) and activated (pulsed with near-fatal current), the point contact is melted and a PN junction formed. Or on a more mundane level, we can for example probe the carrier type of a semiconductor by simply poking probes at it, making sure they scratch the surface (ohmmeter reads ~finite), and then heating one or the other probe (or from that side of the wafer) to cause charges to move. Some 10s of mV are created in this way without too much trouble, so a pristine contact isn't required; the polarity vs. thermal gradient depends on the carrier type.
I hope you great,your content is extremely too good,and i saw your all lecture, I wish you complete this playlist upto mosfet and other devices working ,its realy help to current and future engineers.
Your spin-on diffusion doping process is ingenious. If I am thinking right, you can apply the liquid dopant solution on top of a photo mask. Making the doping steps very similar to the other process and you can basically use it with the precision of your lithography process x3
unfortunately, the diffusion step has to take place at ~1000C so the photo mask alone won't hold up at those temps. An oxide layer that has been patterned using a photomask will though
Hello for the guy behind this video. I found it interesting since I am aiming a research base on temperature difference form thermal to electrical energy. This video help me imagine what i am going to do. although there is a device existed in this theory, i want to upgrade my research such that it can use in a daily bases. hope you dig more on semiconductor topic for future students preference and understanding.
Amazing video, definitely one of the best explanations I’ve seen. One thing I’m now a bit confused about is why the metal contacts on transistors don’t introduce intraband states?
I'm not 100% sure on this answer, but my understanding is that as long as the discontinuity between the metal and semiconductor is thin enough, the electrons tunnel through and basically ignore the junction.
Maybe you can answer this question for me because all the electrical engineers on stackoverflow or google seem to turn a blind eye. The question goes like this: In an npn transistor, lets say you leave the base floating, why does current not flow from emitter to collector. You might say "oh, that's easy, there is a potential barrier" but then alot of people seem to forget that the potential barrier is a measley 0.7 volts. And in my experience bjts have a lot more voltage. between them than 0.7v. So how is this 0.7 volts depletion layer potential able to stop greater voltages like 20v, 12v etc from allowing current flowing from emitter to collector. I know bjts are rarely operated in the open base configuration but understanding this will help me understand why it takes a small bias to do what a large voltage couldnt (bias is the name given to voltage applied to base terminal in bjt)
My impression was that it was only suitable for very shallow junctions and wasn't a good general purpose solution. To be completely honest though, I haven't really studied GILD all that much. It's possible I should consider it more closely
can someone please explain to me what happens at the pn junctions, how is the depletion region formed? This was a great explanation of the n-type and p-type regions I just need someone to put the two together and dumb down the depletion region for me.
I wonder if you could use pure boron or phosphorus in an inert atmosphere that's at a different pressure. A phase change diagram likely would have to be consulted but just a thought.
I'm sure you can make it work somehow, but I definitely wouldn't trust my furnace to run at substantially higher than atmosphere. I'd hate for it to break again lol
@@projectsinflight Ah ok, then nevermind 😂 Pretty interesting though. When you wanna go into simulating a multi-electron system, you usually simplify a lot first. E.g. Hartree-Fock assumes that the electron in your material experiences not only the potential from the nucleus, but also a mean-field averaged over all electrons around it. But obviously, this is only an approximation and ignores direct electron-electron interactions (electronic correlations). These correlations occur a lot, e.g. for transition metal oxides
What puzzles me is how chemical bonds work (not a chemist). I always thought you needed an electron on each side, and all electrons must be taken. Like, why phosphorus would have this "dangling electron"? Why can that electron leave P and jump to Si, wouldn't that leave a huge positive charge behind, like a stone suddenly flying into space from the surface of the Earth? I also had a question if we can add an element with 3 extra electrons then and have more charge carriers and create "metals" with "electron clouds" at will, but thanks, you've explained it with the "trap energy levels"! (Will they be shiny too like metals, btw?) Overall, thank you so very much for your videos! It's an incredible opportunity to understand the processes as if looking over the shoulder of a scientist who's been inventing them, while him doing God's work by explaining in simple terms decomposed ideas and "what if"'s, which you'll NEVER get from any textbooks.
I think you left out a fourth doping method but i could be wrong. I know there also is neutron transmutation doping, but i don't know if it has any industrial significance. Great video btw!
I was considering adding it, mostly to come full circle on the "exposed core of the nuclear reactor" joke from earlier but it got cut because nuclear transmutation doping is really never used outside of a couple research experiments
Thank you for this amazing video But I have a question when the si is doping by P there is a new energy level is added this new energy level how many electrons can hold because pauli principle says we can't have two electron in the same state
Hey saw you have a fiber laser. You can deposit simple Al contacts on Si by simply wrapping the Si in Aluminum foil and lasering squares into it. For my 50W, I use 35% power, 500mm/s, 20kHz or 30kHz rep rate and 0.01mm hatch. Evaporates a nice square of Al, giving ohmic contact and even contacting through native oxide.
Nice video. Good quality explanation of a very complex process in practice. One thing. 19:59 That's not burning in air, that's almost certainly pure oxygen... it burns with a wispy ethereal flame resembling sulfur in air. But the point stands lol... "it's reactive" 🤣
You can! In fact, back in the day they'd actually make electrical contacts by applying a tiny bead of aluminum and putting it into a furnace. Some aluminum would diffuse into the chip, making a doped region and then the rest would stay behind on the surface as an electrical contact.
@@suncrafterspielt9479 It depends on the doping amount. If you have a metal-semiconductor junction where the silicon is lightly doped you get a diode, if it's heavily doped you get an ohmic contact In the process i described in the first comment it results in a heavily doped region, so it should make a non-rectifying junction
We would dope a 10kg charge of Polysilicon with Red Phosphorus using a dope tube on a Czochralski furnace by tipping the tube (hose) filled with dopant and dumping into a very hot melt. It was actually the most mass of measured dopant as much of it burned off on the surface of the melt. Arsenic, Antimony, and Boron were weighed on precision balances and just dumped on the polysilicon before melting in the crucible, and the amount was in milligrams. GOOD TIMES, GOOD TIMES 😉
oh yeah, you can basically overwrite a N doped region with a p doped region if it's at a higher dipping level. so if you do a 10^16 region first you can do a 10^18 region next, etc
YEEEEEEES the deep level impurities is what i was looking for to make the afformebtuoned battery i soecified in the previous video,cz the way i see it atoms closer to silicon form switches and atoms further from silicon form batteries when doped onto silicon based on the deep level impurities you mentioend,,,now atleast my research is heading somewhere...nkw if only i had a means to fabricate semiconductor chips to teat out this battery hypothesis
if you're looking for information on energy storage in silicon you should read up on quantum wells and things like charge coupled devices. That being said, the energy density will likely never approach that of chemical batteries.
Actually you can use a nuclear reactor to produce semiconductors. The processes is called Neutron Transmutation Doping and involves neutrons diverted out from the nuclear reactor. These neutrons are absorbed by the silicon atoms forming an unstable heavier silicon isotope. This isotople quickly undergoes beta minus decay converting the excess neutron to a proton and becoming phosporus. Since neutrons can penetrate deep into matter and don't care about chemical composition or such they can evenly dope the silicon quite deep without much issue. This costly and involves radioactrivity so it's not really common. I know you were joking but for those who don't know uranium is safely sealed in the reactor and only the neutrons are coming out so there shouldn't be any uranium contamination. Besides if uranium has become a gas semiconductor purity will be your last concern. Certainly this will be your preferred doping method in the future right?
Yeah, I thought about including this to come full circle on the "exposed core of a nuclear reactor" joke but ended up cutting it because nuclear transmutation doping is basically not used outside of research labs
Having accidentally produced phosphine, whilst not monitoring my setup, I can confirm that it is definitely not something you want to deal with if you can possibly avoid it!
@@projectsinflight I wouldn't pay me for my editing skills either lol. I'd just upload the raw footage with a single incoherent comment for context and call it a day 😆
the bubble analogy is one of the best analogies for holes I've ever heard
yeah the first time i heard it i was like "ooooooooooh i get it now"
same analogy written in Solid states of physics by Donald Neeman.
Man you're singlehandedly driving me towards building a closed loop patterning CNC system and honestly I don't know if my wallet will handle it
Haha if you do please show off your work!
time to drop everything and watch ProjectsInFlight!
I appreciate it :)
I think this is hands-down the best introduction to electron/hole transport physics I've ever seen. Just enough to be accurate, but not enough detail to overwhelm a newbie. Totally putting this into my list of semiconductor physics videos to show to beginners. Great job!
Thank you very much for the support!
Aaah! finally an understandable description of holes!
Thank you for the compliment :) I did my best to make sure I didn't go into the weeds too much
Really refreshing to see this all presented in such a clear and accessible way, both in education and actual practical use. Excited to see where this series goes!
i strive to make it correct and also digestible. it means a lot to hear this
out of all my hobby reading and learning about electronics since 1995, this is the best explanation and the way people should be taught about semiconductors... really great overview and easy to understand. i bet this whole video series will end up being shown in school. thank you and keep them coming
Thank you so much for your support!
Its so wonderful to see that production of semiconductor chips get in the realm of hobbyists instead of million or billion dollar companies
There are actually some startups with the goal to make small scale fabs that fit in a single room. I am hopeful they succeed
@@projectsinflight Are you refering to semiconductor manufacturing startups or the type that provides with development tools for electrical engineers and outsource manufacturing to an actual fab? I'm talking about Tiny Tapeout here for example.
If you mean the actual manufacturing startups would you mind sharing some info here please?
Just wait... This will be a core part of von neumann replicators!!!
@@pavlokachor6544lookup Atomic Semi by Sam Zeloof 😉
@@pavlokachor6544 checkout “atomic semi”, they’re trying to do what 3d printing is to injection moulding but for semis.
Dopant precision really depends on the device. TTL is a little sensitive, while CMOS is not too worried, it just affects threshold voltage slightly, and breakdown voltage, which mostly is going to manifest as leakage. Most extreme example is things like unijunction transistors and Jfets, devices that have a very wide spread in charactaristics, depending on the doping level. Jfet it affects the pinch off voltage, and also the current flow when it is connected as a constant current diode, and in unijunctions affects the stand off ratio and current capacity. That is why you get so many different Jfet and unijunction part numbers, with them all being almost all the same aside from a variation in either pinch off voltage, or stand off ratio, and with the devices in the base part number being sold with a massive variation in those, with the others being binned from these big pools during manufacture, with the variation coming from the slight variation across the wafer during production, so if you got hold of a single tested but unseparated wafer, you can probe each chip, and get a pattern of how doping varied across the wafer that run.
That is why you always see test patterns on any larger die, there using a small amount of space to have a test pattern that is placed there early on, and probed during manufacture, so that any wafer that had a bad day can be weeded out early, as the test structures make for easy to test devices, that they know how they react according to the doping and such. digital logic can handle a little error, analogue that is complex not so much, and precision analogue not much at all, especially if you are using Jfet in the design, you want to hit the mark every wafer, and scrap any that are likely to be faulty early on.
Wow! Thank you for such a comprehensive overview on this subject. I take it you are in the industry yourself?
@@projectsinflight No, just have been using them for years, so learned why the Jfet and UJT have such a wide spread, while regular TTL is reasonably stable, and CMOS is pretty much immune in regards to threshold, really mostly being depending on gate oxide thickness for how it works.
While there are test patterns all across the wafer, it is infeasible to test anything electrically until the wafer is almost all the way through manufacturing. You need ohmic contacts from the semiconductor to the metal on top, which comes late in the process, because they have processing limitations and need to be at the very top of the wafer.
So for example, the n++/p++ doping that is mentioned in the video could be used for a semiconductor-metal contact. But there is no way to check if the doping worked until after the wafer is completed. After ion implantation/for diffusion you need very high temperatures for a long time, then you need to apply the metal for the sc-metal contact and it's associated processing and only then could you test if the sc-metal contact works. And don't forget, each of the steps comes with photoresist application, patterning and cleaning!
CMOS functionally isn't too critical to doping, but not to say specs are unaffected: this is part of the reason why speed grades, input threshold, and output current, vary so much. The other part of the reason is they just DGAF and want wide guard bands on their process, lol. (You'll almost certainly never measure a 74HC or other gate in the wild that hits the datasheet worst-case limit say for propagation delay. Unfortunately, this is needlessly conservative when doing actual timing chains -- the one upside is, no one does that anymore, if you're doing logic, you're writing for an FPGA or ASIC... or building a hobby computer that you can test, select parts, and repair as needed.)
This series is excellent, you are doing a great job at taking the device physics concepts and making them digestible. Not to mention actually performing it at a home lab.
I appreciate it!!
I found this channel from the previous video and it just keeps getting better! Great videos with crystal clear explanation
Thank you! I try very hard to be as clear as possible
This is so excellent. Electronic Band Structure is one of the most complicated theories in physics and engineering, and I was missing some key details. But just through your presentation style, you've made it so accessible! Thank you! You made a patreon subscriber out of me.
thank you very much! i appreciate it
LET'S GOOOO NEW projectsinflight VIDEO!
i'm hoping i can also get the next video out soon
Man you are really underrated
Thank you! I am trying my best
I am absolutely in awe of your ability to educate.
I did physics as a bachelors degree including semiconductor theory and throughout that final year I never grasped this subject anywhere as near as well as I have watching your video.
Thanks
21:33
The crossed-out "First Aid" cabinet is insane, haha keep up the good work!
Bro, your videos are amazing. It teaches semiconductors and doping very well.
Love the explanation, I understand so much more after watching these but I'm looking forward to getting back to the hands on videos!
The next video will definitely contain lots of lab work!
This something I've actually been curious about for a while so i apreciate this vid
Bro you're one of my favourite TH-camrs! Please keep it up, you're helping so much❤
Thanks!
Thanks! I appreciate the support
As an electronics nerd with an interest in chemistry... this series is absolutely superb!
But now my history of science nerd wants to know how these processes were first worked out. :)
i've been contemplating a history-focused video
5:35 "Because there is one extra electron and no hole..." - could have used clarification; the atom of phosphorus does mean there is an additional proton, so when its extra electron moves around why doesn't that create a "hole"? The answer is that a hole is absence of an electron *from a covalent bond*, and that is not happening: all the bonds with the surrounding silicon atoms are satisfied.
Yeah this could use more emphasis (if one want to get deeper into semiconductor physics).
The remaining phosphor atom will be positively charged, which has huge effects - mostly creating pn-junctions, but also causing coulomb scattering.
Amazing video, really good supplementation to my Electrical Engineering class! I learnt a lot from this one and the last video, as this really goes into the details, while still making the process of following through and understanding really easy!
Thank you for posting this.🤗
Great stuff! Can't wait until the next video! Cheap but reliable dopants will be awesome to have haha. Now I wonder if it would be possible to also make a diy photoresist that could enable micrometer features :P
Actually I have been also working on DIY photoresist for months now. I'm not sure how close I am to a video, but I have at least one working formula. I'm also trying to recreate a novolak based resist from the 70s/80s. I will 100% make a video on all this when i am satisfied by my results!
@@projectsinflight Awesome, will be looking forward to that, as it would definitely be much easier to make the photoresist in the amounts that one actually needs, rather than buying a half a liter bottle and then 400ml of it goes bad two years later haha.
One of the more interesting bits of physics unveiling before my eyes was watching gold diffuse into copper, in plain air, under a microscope. Coworker had ordered some garbage tier RC power connectors that use hopes and dreams for their current rating, instead of real life figures. But it probably wouldnt have set itself on fire in the application it was destined for so I humored him and was installing the connectors onto leads. As I soldered them, the whole outside of the solder cup (not exposed to solder, that was on the inside) went from the gold color of the plating to copper color. Looked it up, and turns out gold diffuses into copper really starts to pick up at 200C, right around what the solder would have been. Normal good gold plating has a nickel layer underneath to stop this (and oxidation beneath the gold) But because my coworker was being a cheapskate, and whatever factory in china didn't think that nickel bath was particularly needed, I got to watch solid metal dissolve into another solid metal under a microscope.
that's wild! i have never witnessed that
Yup, silver and zinc as well. Hence the ~high school experiment plating a penny with zinc then heating it to brassify the surface -- you really are getting a brass layer, it's not just the thin layer of zinc oxidizing to an interference pattern or something.
Silver (directly on copper) is semi-commonly used for PCB plating, but usually it disappears into the solder by the time diffusion would matter much. Along with tarnishing, it can be a concern in storage though.
These also illustrate the Kirkendall effect, where the diffusion of atoms into each others' bulk reduces the density in each, creating voids. Well designed plating sequences (or diffusion schedules) avoid this in most cases, but there are industrially important applications where the voiding affects joint strength -- Sn-Cu diffusion (and intermetallic formation) in solder joints, for example.
Thank U for your consistency with one great project along with high quality videos! Have been watching whole series and here I especially love the quite in depth explanation what elements are bad or good and why as well as describing doping level difference; also thanks for avoiding hard to get/ very expensive or deadly materials in the process so, that it could be really recreated by others:)
I remember skimming over a paper about doping wafers with plain phosphoric acid a few years ago. It was from the solar industry, but I don't see how it wouldn't translate to other semiconductors. I can't find the exact paper anymore, but some very similar ones about the same topic were published recently: 10.1007/s12633-022-02231-3 and 10.1007/s12633-023-02658-2
I tried plain phosphoric acid but it really doesn't seem clean enough for my purposes. high concentrations leave a horrible residue (silicon phosphide maybe) on the surface that cannot be etched away
A very through explanation, thank you.
Baest and most detailed explanation of dopants I've seen! Thank you
thank you very much too :)
Love your videos helping me study solid state electronics
You are so good at explaining these topics!! Thank you so much for making this video.
thank you for watching :)
Also holy shit I was looking for something which you could use to dope silicon that can be applied above. I had this plan of making more accessible hobby scale implantation by using basically lasers directly to implant the ions. Eagerly waiting your next video
I'll be honest- the dopant I was able to make isn't perfect- it has to be stored at low temperature to have a decent shelf life. However, I think that it's the best i've seen so far. Maybe a real chemist can do better :)
haven't lol in a long while, perfect setup @20:52 thanks for the hardwork!
absolutely! glad to make something interesting
Great stuff, looking forward to seeing it in action in the next video!
i'm very excited to show the progress:)
This actually helped me understand so well. Thank you so much.
I'm glad you enjoyed it!
this is such good material to understand the matter. much better than at uni
I appreciate the compliment!
The part where they were talking about dopant gasses and then showed the LD-50 was very funny, I laughed in a video that I did not expect to laugh in. I've only really heard of phosphenes toxicity when it came to dopant gasses, but the other ones being extremely deadly don't surprise me at all.
To be fair one of them are percusors of chemical weapons.... No wonder it gets deadly real fast
Love this theory series. I find it electrical engineer-friendly while at the same time involving chemistry topics I didn't even think of before.
Good work!
oh i can't wait to start talking about some of the chemistry i've learned about recently
first time in my life i clicked the bell button to get notification for next. Thank you so much for all your efforts...
that means a lot! thank you :)
Amazing series! Cant wait for the next one!
soooooooooooooon
Yes man continue please ❤❤❤🎉🎉🎉🎉 finally new video ❤❤❤❤❤❤
Oh i'm definitely continuing. Thnak you for your patience though- this last one took FOREVER to get right
A time will come, perhaps, when YT hobbyist will replace much of academic courses. I really think such videos (and if you show the experiments) are much better way to learn than to attend boring lectures with constant fear of grades.
Great work!
while i love learning from youtube, i feel that education requires closing the loop on knowledge, meaning that you need a way to check that knowledge is actually being absorbed. I will say that i think there are better ways to close the loop than just taking tests though.
this channel is do underrated
I hope to become even better in the future :)
This is absolutely jawdropingly interesting
that's very high praise :)
When you mentioned N-type, I got excited because I knew the other would be P-type because of NPN/PNP transistors!
Don't forget PN diodes as well!
For the longest time [growing up], I thought you could just take two blocks of the stuff, *now kiss .png* and boom, diode, transistor, whatever. (I tested, and wondered aloud, why wiring two diodes together doesn't make a transistor. Hey, I was... probably 9 at the time?) Sadly, all those early/easy/common references neglect to mention two things: 1. charges move by diffusion, and only travel so far before recombination dominates (in Si, a few µm, maybe 10 tops); 2. you need a metallurgical bond; a random misaligned crystal boundary with oxide inbetween, ain't gonna cut it. Astonishingly, reasonably-well-aligned crystals, and vacuum-clean and atomically-polished surfaces, can be created, and bonded metallurgically, so we can actually do this if need be(!), but it's a lot more work than rubbing two rocks together, hah.
Equally surprising, it is still true that you can rub rocks together -- or more to the point, poke them with wires, "whiskers". Rough (read: non atomically polished) surface contact is dominated by asperities, where rough spots stick out enough to touch, give or take contact pressure and the elastic modulus of the material; this can happen with enough force to scrape off the oxides and get direct semiconductor contact (or a thin enough line of oxide, adsorbed air, and other surface contaminants, that charge carriers can tunnel through the barrier), and thus a diode is born. Transistors are harder: MOS is out of course, but BJTs can be made by microscopically-aligned point contacts. They also fairly early-on discovered you can fuse the whiskers into the chip, making a much more consistent, reliable, robust device; the 1N34 germanium diode is such an example, and the whisker (tungsten I think) is coated with a dopant so that when the device is assembled (glass sealed body) and activated (pulsed with near-fatal current), the point contact is melted and a PN junction formed.
Or on a more mundane level, we can for example probe the carrier type of a semiconductor by simply poking probes at it, making sure they scratch the surface (ohmmeter reads ~finite), and then heating one or the other probe (or from that side of the wafer) to cause charges to move. Some 10s of mV are created in this way without too much trouble, so a pristine contact isn't required; the polarity vs. thermal gradient depends on the carrier type.
I hope you will continue making more videos. I am a big fan of this youtube channel.
thank you- it means a lot :)
I hope you great,your content is extremely too good,and i saw your all lecture, I wish you complete this playlist upto mosfet and other devices working ,its realy help to current and future engineers.
Excellent explanation. Appreciate the effort you put in.
thank for the support:)
Your spin-on diffusion doping process is ingenious. If I am thinking right, you can apply the liquid dopant solution on top of a photo mask. Making the doping steps very similar to the other process and you can basically use it with the precision of your lithography process x3
unfortunately, the diffusion step has to take place at ~1000C so the photo mask alone won't hold up at those temps. An oxide layer that has been patterned using a photomask will though
This is DOPE!!!
You're really good at this. I'm sure you have a successful career but you can always fall back on science youtube!
honestly i feel like my dream job would be to work for a company that manufactures or uses electron microscopes. i love SEMs
excited to see what's next!
hopefully some actual lab work ;)
wow that was an awesome presentation, I look forward to going back over your previous videos! 🔔🎵
thanks! i appreciate the compliment
Look forward to hearing from you
Excellent video. Thanks
Hello for the guy behind this video. I found it interesting since I am aiming a research base on temperature difference form thermal to electrical energy. This video help me imagine what i am going to do. although there is a device existed in this theory, i want to upgrade my research such that it can use in a daily bases. hope you dig more on semiconductor topic for future students preference and understanding.
have you heard of thermionic generators? Those might be similar to what you are looking for
Amazing video, definitely one of the best explanations I’ve seen. One thing I’m now a bit confused about is why the metal contacts on transistors don’t introduce intraband states?
I'm not 100% sure on this answer, but my understanding is that as long as the discontinuity between the metal and semiconductor is thin enough, the electrons tunnel through and basically ignore the junction.
Maybe you can answer this question for me because all the electrical engineers on stackoverflow or google seem to turn a blind eye. The question goes like this: In an npn transistor, lets say you leave the base floating, why does current not flow from emitter to collector. You might say "oh, that's easy, there is a potential barrier" but then alot of people seem to forget that the potential barrier is a measley 0.7 volts. And in my experience bjts have a lot more voltage. between them than 0.7v. So how is this 0.7 volts depletion layer potential able to stop greater voltages like 20v, 12v etc from allowing current flowing from emitter to collector. I know bjts are rarely operated in the open base configuration but understanding this will help me understand why it takes a small bias to do what a large voltage couldnt (bias is the name given to voltage applied to base terminal in bjt)
what do you think about laser doping? its used for solar panels, do you think theres any hobbyist potential in applying it for ICs?
My impression was that it was only suitable for very shallow junctions and wasn't a good general purpose solution. To be completely honest though, I haven't really studied GILD all that much. It's possible I should consider it more closely
What a dope video
I see what you did there :P
can someone please explain to me what happens at the pn junctions, how is the depletion region formed? This was a great explanation of the n-type and p-type regions I just need someone to put the two together and dumb down the depletion region for me.
i'm going to cover that one on my next physics video
Amazing explanation. Thank you!
i'm glad i was able to help :)
I wonder if you could use pure boron or phosphorus in an inert atmosphere that's at a different pressure. A phase change diagram likely would have to be consulted but just a thought.
I'm sure you can make it work somehow, but I definitely wouldn't trust my furnace to run at substantially higher than atmosphere. I'd hate for it to break again lol
Thank you so much for your videos, they helped me a lot! Can you also make a video about strongly correlated systems?
i'm not sure i know what those are
@@projectsinflight Ah ok, then nevermind 😂 Pretty interesting though. When you wanna go into simulating a multi-electron system, you usually simplify a lot first. E.g. Hartree-Fock assumes that the electron in your material experiences not only the potential from the nucleus, but also a mean-field averaged over all electrons around it. But obviously, this is only an approximation and ignores direct electron-electron interactions (electronic correlations). These correlations occur a lot, e.g. for transition metal oxides
i cant wait for the next vid... some diode, tansisitor or maybe photodiode.THANKS REALLY ENJOYED THE LEARNING :)
i expect the next video will contain a very poor diode lol
What puzzles me is how chemical bonds work (not a chemist). I always thought you needed an electron on each side, and all electrons must be taken.
Like, why phosphorus would have this "dangling electron"?
Why can that electron leave P and jump to Si, wouldn't that leave a huge positive charge behind, like a stone suddenly flying into space from the surface of the Earth?
I also had a question if we can add an element with 3 extra electrons then and have more charge carriers and create "metals" with "electron clouds" at will, but thanks, you've explained it with the "trap energy levels"!
(Will they be shiny too like metals, btw?)
Overall, thank you so very much for your videos! It's an incredible opportunity to understand the processes as if looking over the shoulder of a scientist who's been inventing them, while him doing God's work by explaining in simple terms decomposed ideas and "what if"'s, which you'll NEVER get from any textbooks.
I think you left out a fourth doping method but i could be wrong. I know there also is neutron transmutation doping, but i don't know if it has any industrial significance. Great video btw!
I was considering adding it, mostly to come full circle on the "exposed core of the nuclear reactor" joke from earlier but it got cut because nuclear transmutation doping is really never used outside of a couple research experiments
Thank you for this amazing video
But I have a question when the si is doping by P there is a new energy level is added this new energy level how many electrons can hold because pauli principle says we can't have two electron in the same state
Hey saw you have a fiber laser. You can deposit simple Al contacts on Si by simply wrapping the Si in Aluminum foil and lasering squares into it. For my 50W, I use 35% power, 500mm/s, 20kHz or 30kHz rep rate and 0.01mm hatch. Evaporates a nice square of Al, giving ohmic contact and even contacting through native oxide.
to my knowledge i don't have a fiber laser but i appreciate the suggestion!
Oops my mistake! Good excuse for a new toy, though.
Great video. If electricity is magic your are a level 20 wizard. Thanks for sharing your knowledge.
haha thank you very much
Nice video. Good quality explanation of a very complex process in practice.
One thing. 19:59
That's not burning in air, that's almost certainly pure oxygen... it burns with a wispy ethereal flame resembling sulfur in air. But the point stands lol... "it's reactive" 🤣
oh interesting- i've never seen it in person
21:02 ah yes the funny table for funny times
The very scary table you mean :P
What a dope video!
Awesome. Thanks for the video.
thank you for watching :)
What a *dope* video!
i see what you did there
Amazing stuff
thank you :) i do my best
why dont we use aluminum as p type doping? shouldnt the atom be more similar to silicon instead of boron?
You can! In fact, back in the day they'd actually make electrical contacts by applying a tiny bead of aluminum and putting it into a furnace. Some aluminum would diffuse into the chip, making a doped region and then the rest would stay behind on the surface as an electrical contact.
doesnt that also give you a shottky connection?
@@suncrafterspielt9479 It depends on the doping amount. If you have a metal-semiconductor junction where the silicon is lightly doped you get a diode, if it's heavily doped you get an ohmic contact
In the process i described in the first comment it results in a heavily doped region, so it should make a non-rectifying junction
Thanks a lot for all the explanation :D
We would dope a 10kg charge of Polysilicon with Red Phosphorus using a dope tube on a Czochralski furnace by tipping the tube (hose) filled with dopant and dumping into a very hot melt. It was actually the most mass of measured dopant as much of it burned off on the surface of the melt. Arsenic, Antimony, and Boron were weighed on precision balances and just dumped on the polysilicon before melting in the crucible, and the amount was in milligrams. GOOD TIMES, GOOD TIMES 😉
Yooo hes back!😊
glad to be back:)
What happens if you introduce both n type and p type dopants? Do they just cancel each other out, or can you get something interesting from it?
oh yeah, you can basically overwrite a N doped region with a p doped region if it's at a higher dipping level. so if you do a 10^16 region first you can do a 10^18 region next, etc
NEW VIDEO, YAY!
👍
try photonic transistors instead, you only cut mems flex membrane walls and wave guides of suitable size, choose proper light frequency, infrared visible e/uv x-ray etc
Do you know where to find good information on this topic? i've never heard of them
@@projectsinflight what do you think they are and how they work
This was pretty dope 😏...
I see what you did there :P
Iam very exciting to next video man 🌝🌚🌜🌛🕐❤❤❤❤
Me too! I hope to have it out in a few weeks
@@projectsinflight please man speedup 🥹❤️🤝💪💪💪
Really cool video ^^
Thank you!
YEEES! It continues!
Thank you for your patience- the next video took quite a while to figure out
YEEEEEEES the deep level impurities is what i was looking for to make the afformebtuoned battery i soecified in the previous video,cz the way i see it atoms closer to silicon form switches and atoms further from silicon form batteries when doped onto silicon based on the deep level impurities you mentioend,,,now atleast my research is heading somewhere...nkw if only i had a means to fabricate semiconductor chips to teat out this battery hypothesis
if you're looking for information on energy storage in silicon you should read up on quantum wells and things like charge coupled devices. That being said, the energy density will likely never approach that of chemical batteries.
thanx bro u realy perfected the vidio
I appreciate it :)
Was/is that a bragg mirror?
SWEET!
glad you liked it :)
Actually you can use a nuclear reactor to produce semiconductors. The processes is called Neutron Transmutation Doping and involves neutrons diverted out from the nuclear reactor. These neutrons are absorbed by the silicon atoms forming an unstable heavier silicon isotope. This isotople quickly undergoes beta minus decay converting the excess neutron to a proton and becoming phosporus. Since neutrons can penetrate deep into matter and don't care about chemical composition or such they can evenly dope the silicon quite deep without much issue. This costly and involves radioactrivity so it's not really common. I know you were joking but for those who don't know uranium is safely sealed in the reactor and only the neutrons are coming out so there shouldn't be any uranium contamination. Besides if uranium has become a gas semiconductor purity will be your last concern. Certainly this will be your preferred doping method in the future right?
Yeah, I thought about including this to come full circle on the "exposed core of a nuclear reactor" joke but ended up cutting it because nuclear transmutation doping is basically not used outside of research labs
Dude please sell that dopant online or something I would 100% buy it but I don't have the material to make it myself
i was thinking about it but it needs to be kept very cold or else it goes bad in a week. haven't figured a way around that one yet
Having accidentally produced phosphine, whilst not monitoring my setup, I can confirm that it is definitely not something you want to deal with if you can possibly avoid it!
Yeah- I am desperately trying to avoid hurting myself. I need to study more chemistry
great!
thanks!
It's too bad you can't just take the SI to a local nuclear reactor to dope it.
I see someone is a fan of neutron activation doping ;)
22:18 "video should be out in a couple of weeks"
It's been more than 3 😭
probably one more week
@@projectsinflight **1.06 weeks later**
Sup, you got da spinny go go dope? I'm on a quest to make sand think and need the good stuff 😂
@@cgarzs I'm taking applications for unpaid video editors if you'd like to apply
@@projectsinflight I wouldn't pay me for my editing skills either lol. I'd just upload the raw footage with a single incoherent comment for context and call it a day 😆
it's out now finally ;)
I wanna make cmos switches on reasonbly thick cvd diamond films...
you know i've always wondered how it would work trying to use diamond as a semiconductor...
All atoms have frequencies no ?. Each different atom of a specific materials has a different frequency.