Using Hydrofluoric Acid to Etch Oxide Layers

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In this video I evaluate three easy-to-obtain sources for low-concentration Hydrofluoric Acid (HF) and use them to etch Silicon Dioxide layers. I also go over the dangers of Hydrofluoric Acid and the differences between it and other acids, such as Sulfuric Acid.
DISCLAIMER: The videos on this channel feature materials, equipment, and activities that may be hazardous. By choosing to replicate or participate in any demonstrated activities, you acknowledge and assume all associated risks. You the viewer are responsible for your own safety. ProjectsInFlight and its creators are not liable for any resulting harm or damages.
Affiliate Links to Chemicals & Tools (I earn small commissions on these links):
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Butyl Gloves: amzn.to/3LsDopA
Eyewash: amzn.to/3EF9BWT
Face Shield: amzn.to/3F0Oa2N
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Apron: amzn.to/48hYZL2
Respirator Mask: amzn.to/3PHylEf
Acid Vapor Respirator Cartridge: amzn.to/3sYm31n
Whink Rust Remover: amzn.to/3rf9RZq
Armour Etch: amzn.to/48hoqfE
Porcelain Etch: ebay.us/oATP5e
Scribe Tool: amzn.to/3Pksrrg
Silicon Wafer (P-type): amzn.to/3PGDgoV
Silicon Wafer (N-type): amzn.to/3rdP8W1
Links to Sources:
SDS Pages:
2% HF SDS: www.riccachemi...
10% HF SDS: www.riccachemi...
50% HF SDS: www.riccachemi...
Sulferic Acid SDS: www.riccachemi...
Whink Rust Remover SDS:web.faa.illino...
Porcelain Etch SDS: www.pulpdent.c...
Armour Etch SDS: www.richelieu....
Other Info:
SDS Toxicity Categories: www.ilo.org/st...
Vapor Pressure: www.physics.pu...
Toxicity: www.ncbi.nlm.n...
Toxicity: ehs.stanford.e....
Toxicity: www.cdc.gov/ni...
Dermal: www.sciencedir...
Chemical Compatibility: www.graco.com/...
Chemical Compatibility: at.vwr.com/ass...
Toxicity: www.ncbi.nlm.n....
Toxicity: ehs.unc.edu/wp...
Accident List: www.osha.gov/o...

[@aftbit]

I appreciate the detailed safety investigation.

[@projectsinflight]

Thanks! I wanted to do my best to provide a reasonable summary without being biased in either way.

[@JaenEngineering]

Absolutely. So many other channels say little more that "it's dangerous, don't try this at home" or "wear appropriate PPE" but that just feels more like boiler plate litigation mitigation than an anything else. This actually forces you to pay a little more attention.

[@sazafrass]

Absolutely. Being an idiot myself, seeing the methodology rather than "don't if stupid" has greatly extended my statistical life span. You've saved my life @projectsinflight

[@orbatos]

​@@JaenEngineeringAny time they don't at least refer to the MSDS is a red flag.

[@custos3249]

Agreed. Trying to get info from actual chemists I know, it's always "NOPENOPENOPENOPE!" Best way to ensure someone walks into something blind is to tell them not to and stop there as if you've done something of value. The only right thing to do can be gleaned from the phrase, "If you're going to do something stupid, best be smart about it." Never assume refusing to provide information will stop someone.

[@commander-tomalak]

Excellent video. I'm working in the semiconductor industry, and we have literal pipes running along the ceiling for transporting highly concentrated HF. This stuff is no joke and I appreciate that you are taking it seriously. Apart from that, I suspect that the armour etch will be difficult to use with a resist mask, unless you manage to get the resist very mechanically stable. If you have to scrub it off, you will probably damage the resist in the process. I'd try to dilute it and check if you can clean it off easier. It will also make the etch rate easier to handle. If you're going for a CMOS platform, you'll never need more than maybe 300 - 500 nm of oxide, and there's really no point in chewing through that within a minute, especially if the time you need to rinse it off is not perfectly controlled. It will result in inconsistent etches, especially when it comes to underetching. Getting the etch duration to something like 5 minutes should be the sweet spot between wait time and the effect of handling uncertainties. I'm excited to see how you are going to tackle doping and lithography :D

[@superdupergrover9857]

Do you know what the pipes are made out of? The shear size and length of the pipe over such a large, expensive and easily disrupted facility makes for interesting choice parameters.

[@commander-tomalak]

@@superdupergrover9857 It's actually a hose within a pipe (double walled for safety, including sensors in the outer shell). And bog standard plastic is perfectly resistant to HF, so no issues here. That thing is also completely routed indoors high enough that you wouldn't get close to it by accident, so nothing about it is easily disrupted unless someone with access to the area would do so on purpose.

[@superdupergrover9857]

@@commander-tomalak The best solutions are always the boring and obvious ones. Not always true, but true more often than i ever expect. I knew a lot of plastics are resistant to HF and other plastics, I just figured that long term, not stagnant flow would have some long term degradation effect. Thanks for the reply, i really appreciate it.

[@ElectraFlarefire]

The safety intro for this video alone was worth the watch. It might be more fun to go on about how dangerous this stuff is, but a sane and careful evaluation of the risks involved is far more useful. That just got you a subscribe.

[@foolwise4703]

Wow. When I saw your oven built video, my thought was immediately "but he isn't going to use HF in his shed, is he?". I personally successfully avoided working with the stuff so far, but your careful considerations at least took away some of the horror I feel for the stuff. Good job and keep being careful!

[@projectsinflight]

Yeah HF was the main reason I haven't done this until now. I decided that as long as I understand the risks and make informed choices then it's reasonable to move forward

[@nekomakhea9440]

You showed the metal layer directly contacting the silicon in that diagram, but this is generally not done in practice with the two most common metal layers, aluminum and copper. Aluminum in contact with silicon forms spikes into the transistor that damage it, and copper will aggressively dissolve into silicon and disrupt the effects of dopant highly erratically. Typically, there is a tungsten plug in the oxide hole that the metal layer makes contact with, to act as a condom to prevent these problems. There are some metals that can directly contact silicon without issues, like Cobalt, Nickel, Tungsten, and Ruthenium, if I remember right. Current research into sub-2nm process nodes is leaning towards replacing the copper layers with cobalt or ruthenium, because the structures needed to keep copper from touching the silicon takes up too much space at those scales, leaving less room for actual copper conductor, and thus causing high resistive losses due to the conductors being so narrow.

[@projectsinflight]

Gotta keep the diagrams simple!

[@christopherleubner6633]

They usually use a silicon nitride buffer layer under the aluminum or copper via layer.

[@Jan-zw2se]

You should be able to use aluminium but keep the point small or divide into multiple as spikes become a problem with big size

[@ThantiK]

@@projectsinflight -- I would much rather they be correct than simple. Anyone interested in this stuff is going to be probably above average in ability to comprehend this stuff, so please give us more detail rather than less.

[@BioTechproject27]

@@ThantiK Exactly. It's better to stay to the truth of current research, rather than horribly simplify. At the very least things should be briefly mentioned so that anyone interested can dig deeper. That's why I hated school. They always dumbed everything down, often to the point that it's inaccurate, when the real world is so much more complex and exciting!!!

[@GoingtoHecq]

It is really cool to see someone tackling silicon circuit production from the ground up.

[@projectsinflight]

Thanks! I'm super happy so many people are along for the ride :)

[@GerinoMorn]

Will come useful when we have to rebuild the civilisation

[@robertstratton6444]

That was a great safety review. One dark secret of the car wash world is that operators were spiking their detergent mixes with HF to cut dirt, though the occasional customer windshield might be etched. Some fell back to ammonium bifluoride, but even that has some history of nasty industrial health impacts.

[@projectsinflight]

Yeah- I saw some aluminum wheel cleaner that was 15% HF! Sold by the gallon! Crazy...

[@Spirit532]

Great explanation and a nice deep dive into safety. If you really want multiple concentrations of HF, I think the best and simplest option is to just bite the bullet, buy a small amount of high concentration(20-30%) solution, and then carefully perform a single dilution operation to the concentration you want. One benefit of a fully liquid etch that you didn't cover is that you get a very uniform result - pastes and such tend to etch slightly less evenly. I'd probably stick to the rust remover, or would make my own solution that's maybe 2-3x more concentrated(5-8%). After all, waiting a few minutes for a slow and controlled etch is better than having to deal with paste removal and extra wafer cleaning.

[@projectsinflight]

I don't currently have a safe space to use 30% HF so I'll stick with the weak stuff for now

[@frankgarcia8378]

I think this is a rare instance where buying the concentrated chemical and diluting it down is actually more expensive. looking online, I was able to find 32oz (946ml) of whinks for ~$15, and the same amount of 49% HF for $135. A little math, and you find that whinks charges $1.26 / ml HF, whereas the concentrated chemical costs $3.43/ml. I think the increased price is mostly due to low volume production (you would probably be right, on an industrial scale), but for small scale consumer items, it's actually cheaper to buy dilute!

[@lilyp4369]

man your quality and research is top notch. i really appreciate how serious you take the topic of handling HF and actually deep dive the concerns and dangers. 10/10 video, great job

[@projectsinflight]

Thank you! I was really nervous I was gonna get eaten alive for posting this video, and it makes me happy that you are satisfied with it :)

[@soubs242]

may the algorithm guide more attention to your impressive work.

[@projectsinflight]

I need to make an altar to the youtube algorithm ;) What do I sacrifice?

[@yagobueno2785]

​@@projectsinflighta Z80 chip for the KZbin Algorithm

[@NaviYT]

Just found your channel last night and this was at the top of my reccomended this morning. Very happy :) Keep doing what you're doing! You're growing so fast!

[@projectsinflight]

Thanks! It's really motivating that people are so interested in this work!

[@nekomakhea9440]

Armor Etch might need to be diluted to control the etch rate, or perhaps mixed with a surfactant so it doesn't glue itself to the wafer

[@projectsinflight]

I suspect they make it adhere so strongly so that it won't run off vertical surfaces

[@T3sl4]

Yeah, and dilution may let the BaSO4 settle out, leaving a clearer, easier to use solution.

[@PendragonDaGreat]

@@projectsinflight Very likely. My mom uses it to etch glassware and stuff like that. You can get blank cups from basically anywhere and then use something like a cricut (or other cutter) to cut out a vinyl mask. Allows you to make cool commemorative pieces for birthday gifts or the like super fast.

[@CharlesVanNoland]

Wow, you were very thorough about the danger of working with HF! You very easily could've just made a video etching the silicon with it and just included one sentence "I'm wearing gear because it's super dangerous" and left it at that, but you took the time to illustrate how, why, and how much that HF acid is dangerous. I love to see it! :)

[@projectsinflight]

Thanks- i am glad you appreciated it! I was worried i'd get a thousand comments of "Boring" lol

[@pinlap3875]

@@projectsinflight I've rarely seen analysis of the individual risks like that outside of industry, you've done a service just by demonstrating the process, let alone enumerating the actual HF risk outside of "nope". I learned a lot. Thank you for taking the risk.

[@peterfireflylund]

I have a really old chemistry book for hobbyists that goes into great details about how to build and equip one’s lab. Part of that involves etching writing into the sides of glassware by smearing a layer of wax on, writing with piece of metal or wood to selectively remove the wax… and then etching the glass using HF. No biggie! I have never dared perform a single experiment from that book.

[@JaenEngineering]

I like the idea of having different HF sources for different jobs. The armour etch will be good for bulk oxide removal when making oxide masks and the rust remover will be great for whe you need a controlled oxide thickness for FET gate insulators.

[@projectsinflight]

Yeah, I definitely expect the rust remover will be good for that!

[@setoman1]

I like starting with 40% HF and diluting it down to any concentration the job requires.

[@RoyaltyInTraining.]

@@setoman1 I think it is clear from the video that 40% HF is impossible to obtain for most people

[@__lasevix_]

​@@RoyaltyInTraining.And even more impossible to handle without shortening your lifespan by a few years

[@setoman1]

@@RoyaltyInTraining. 40% HF is easy to get for an average Joe, if you ask smaller chemical suppliers. It also pops up on eBay every so often.

[@excitedbox5705]

Doing gods work. This series has done heaps for the home semiconductor hobby already. I think the syringe might be good for spin coating when you are making an entire IC. The armor etch might be great if you can dilute it to get it to flow and maybe slow it down a bit for more control. The rust remover seems like the easiest to use for the home though. In a DIY setting speed is less important than result. Trying to make precise layer thicknesses for MEMS structures will be awesome when you know you have a high safety margin in a product that is easy to remove as well. Great work. I am considering creating an online community to advance this hobby with equipment build guides + kits, supplies and guides/tutorials.

[@tissuepaper9962]

don't even talk about spin-coating HF. that's a bad, bad idea, and there's no reason to do it in the first place. just dunk your wafers in the liquid etchant.

[@r0cketplumber]

When we used Silane as a hypergolic igniter for rocket engines at RotRock, I had the unenviable task of cleaning the resulting fused silica slag out of the combustion chambers and injectors. I had experience with HF in college semiconductor lab, so I selected ammonium bifluoride as a FAR less hazardous etchant. It did a great job without scaring the hell out of me and did not require such a high level of PPE for protection. That was more than 20 years ago and I don't recall the concentration of the premixed fluid but it was probably similar to the armor etch. Gloves and goggles were all I needed.

[@Ben-ex1kv]

Exceptional video, you're doing wonderful work! I dug the dive into hf safety. I remember my high school chem teacher talking about the stuff. Apparently she once spilled literally a drop onto her hand, which immediately ate thru her glove before absorbing into her skin. It damaged the bone and she talked about getting random pains in it despite the accident being decades ago

[@projectsinflight]

Yeah... HF is very good at penetrating gloves unfortunately

[@zyeborm]

From memory the mix in the armour etch is a multi-stage process, one part "lifts" and another "captures" but it was a long time ago that I looked at it. But it may explain how much faster it was than the 10% gel. I wonder how you'd go diluting it some to make it more of a liquid than a paste. As it is it looks like it'll be hard to apply and remove easily and at small feature sizes having it creep under your mask may become an issue so timely removal is probably going to be desired. Honestly don't worry about the youtube comments section, you could be using pure water and you'd get people saying "if it's too pure you'll die if you drink it" and 4 people saying they knew somebody who drank water and they died.

[@projectsinflight]

Everyone I know who's died drank water though. COINCIDENCE?!?

[@rogergriffin9893]

Very excellent safety outline. Thank you for showing each of the potential etchants as well.

[@projectsinflight]

Thanks! I did my best

[@ahmedmustafamoatasam6020]

You are doing great My opinion is to test the armor etch for volatility and check if the reation in the etchent causes hf vapor to determine the danger of the product And if you can accurately calculate the time of the rust remover you could probably reuse the old silicon wafers which you failed to oxidate to a certain nano meter

[@projectsinflight]

Oh yeah, that's a good idea for sure. I'll take a look

[@goldencpu3559]

seeing the armor etch spot size vs the actual etch indicates there was definitely a cloud of vapor. was really neat to see 8n the video.

[@BrilliantDesignOnline]

A suggestion: give the Armor Etch MFR a phone call and discuss issues with them, since they are probably the most knowledgeable.

[@carterbeaver4437]

I really like how much you emphasize safety with HF I worked at a place for 4 years that I had handled this stuff all the time. We made small metal parts for medical devices and I cleaned them and that often involved HF somewhere in the clean line. Plus it was in a ultra sonic that sits at 170F. The strongest we had was 3% but even that would stink up the room a bit even with several massive fume hoods

[@n3r0z3r0]

Back in the school days I asked a chemistry teacher to show the HF reaction with the glass. She told me this is not possible, but didn't explained why. Thanks for excellent explanation!

[@projectsinflight]

It's also not the most interesting reaction. It just sits there for a while and you remove it. Not the kind of flashy stuff that keeps the interests of distractible high school students

[@kenmercer2721]

In the past I was peripherally involved with a palynologist and one place they get pollen from (actually its outer wall called the exine) is by coring a lake bed. So, Fun Fact, HF is used in processing the samples to dissolve the sand (silicon dioxide) and leave the exine intact for later examination under a microscope. It's tough stuff. I have been enjoying your videos and appreciate the thorough way you are conducting your calibration experiments.

[@projectsinflight]

Thanks! I appreciate that people aren't too bored by constant calibrations lol

[@RoyaltyInTraining.]

I had no idea commercially available HF sources were this good. It kinda gives me some hope back for DIY microchip fabrication. One nasty blocker that remains is obtaining a usable photoresist. Idk if the stuff for etching PCBs and metals works for this application. Edit: Apparently Kontakt Chemie sells a novolac-based resist that can withstand HF and other "strong acidic etching products". It's called Positiv 20. Maybe it's an option if you can get enough liquid out of the spray can and thin it down for spin-coating.

[@projectsinflight]

Yeah... Photoresist is REALLY Hard to find these days. Makes me sad. If you have any links for ANY usable photoresists that arent the dry film please let me know. Feel free to email me at my gmail (projectsinflight) if you have any info.

[@carborane818]

I really liked the extended investigation of HF safety, pretty much every other video I've seen has done little more than say "don't try this at home" or "HF is very dangerous" and definitely doesn't bring up the MSDS. Armor Etch definitely sounds rather sketchy, I'd like to see some more experiments around its strength and behavior.

[@freyjaandersdottir3311]

thank you for such a detailed and well-presented safety presentation, it is very much appreciated

[@projectsinflight]

I am glad people didn't find it too boring ;)

[@samuelcrace9056]

Fantastic to see this. Love how much detail you went into on the hazards. I used HF in geochemistry research for solid rock digestions, as well as having it as a product from some other isotope related purification processes. Ended up using an ammonium bifluoride method as a replacement in order to make sample prep and handling easier but it was still as PITA for weighing since in the raw it comes in a sticky kind of crystalline form. When learning the methods we would usually be wearing heavier thicker gloves (like what you have in the video), plus rubber aprons, and face shield (in a hood, in a clean room no less), once we were more familiar it was always double gloved, in clean room suit, plus face shield.

[@zJericho101z]

I think you went above and beyond with the chemical safety education. Great video and im loving the progress you are making with this series of videos.

[@projectsinflight]

Thanks, I was really worried about making this video because the prevailing opinion online seemed to be "HF = DEAD" and I didn't want people to think I was gonna die lol

[@snfx93]

I would kind of like a similar video for other dangerous chemicals. Especially ones easily sourced from box stores. Shows how important ppe is.

[@projectsinflight]

I'll do one for sulferic acid + peroxide soon

[@manoffudge8250]

excited for the progression of this series! amazing process i woudlve never known about

[@projectsinflight]

Thanks! I'm excited for the next video

[@Araajakta]

It's absolutely amazing that a non certified professional can still achieve the results but their efforts. The scale of the development might be different but it will not be incomprehensible. Your uploads have surely boosted my confidence in a fresh start for me in doing what could be peaceful for me. All the best.

[@projectsinflight]

Glad to be of service :)

[@TimMcgimpsey]

I don't know why youtube recommended your channel but I'm really glad it did. Very interesting and great quality content.

[@projectsinflight]

Thank you! I try very hard to explain this stuff well

[@bazooka93]

I used to work with HF a lot doing microwave extractions of coal ash and marine sediment for ICP analysis. We used boric acid solution to neutralise it, always keeping a full 10L tank of the stuff. I recommend you doing the same for the cleanup.

[@projectsinflight]

Oh interesting- I have boric acid on hand already too. I'll look into this

[@princetikki]

Yes, an upload, made my Saturday night!!

[@quantx6572]

Ok, so now I’m binge watching all your videos. Really well done in terms of explaining everything. Really interesting content.

[@russtuff]

This channel is solid gold.

[@Andro500]

I like how you tell additional details about this process. Thanks you.

[@Cucazikf]

That's the kind of content to be recommended to me after passing the exam on advanced IC fabrication technologies!

[@andrewlonero8003]

This was a good explanation about HF hazards. I use 50% HF in my lab fairly often. It is definitely scary stuff, but it can be used safely when the right PPE and procedures are followed. Nice video.

[@joseph.d5187]

Another great video. Thank you so much. Also I hope this comment will help the algorithm bring your channel up to other DIY enthusiasts.

[@red_rassmueller1716]

Love the quality of your content. And at that speed... this is so amazing. I'm loocking foreward to see u making working transistors and more complex chip geometry

[@projectsinflight]

I sure hope to get to devices soon! I've got three more videos on process stuff first

[@johpfit760]

I love your videos, your channel is criminally underrated

[@pvc988]

I really like the idea of being able to make semiconductor devices at home lab. I wish you much success with it.

[@projectsinflight]

I'm determined!

[@JohnMeacham]

Great stuff. Something you will have to check is if the extra chemicals in armor etch play nice with your photoresist.

[@projectsinflight]

Yeah that's the next video!

[@tfairfield42]

Loving this series. Very interesting and informative

[@TopDedCenter]

Two questions: 1. Can you dilute the armour etch? It would make it easier to apply and remove. 2. Can you use an ultrasonic cleaner to strip away the armor etch in your first wash to eliminate the physical scrubbing step? (Probably not necessary if the answer to the first question is 'yes')

[@projectsinflight]

i'm pretty sure i can dilute armor etch with water if i want. The ultrasonic cleaner isn't a bad idea.

[@gwandrer]

Can't thanks you enough for the detailed safety section of the video, which was a great warning for me. As soon as I saw those charts and heard your explanations, I stopped the video, got up and moved all the etching liquids that I have to the outdoors. Probably, as also @sazafrass said, you've probably saved many lives just with that part of the video, so thank you again.

[@IanMacKaye-eg8hd]

In my opinion the best glass etchant on the consumer market is Etch Bath. It’s made by the same company as Armour Etch but it’s a liquid, not a cream, and it’s quite a bit stronger.

[@projectsinflight]

I was going to include that but they didn't have an SDS on it and they wouldn't respond to my emails :(

[@infestus5657]

Your channel gets better with every video.

[@JordynnMills]

I appreciate the detailed safety investigation.. I appreciate the detailed safety investigation..

[@projectsinflight]

Thank you so much!

[@alelasantillan]

Best video on the subject I could find! Congrats!

[@jttttttt138]

Great video! Loved the safety briefing, stay safe! I feel like the armour etch should be illegal though? It really looks like the manufacturer is trying to bypass some kind of regulation.

[@projectsinflight]

I want to do a follow-up where i measure the strength of armour etch

[@Splarkszter]

I love learning stuff that isn't directly related to what i study, makes me exited about trying new things and allows me to implement them on what i do. Thank you soooo much for this free knowledge and education. Thank you!

[@projectsinflight]

you are very welcome :)

[@chgenly]

Thanks! Outstanding video. Good trade-off between complexity and understandability. Can't wait for the next one.

[@BobCat0]

When @Jeriellsworth told me she wanted to make transistors at home, some 20 years ago, she complained that no one would sell her HF - but then she found Whink at the grocery store and made some NMOS devices in her kitchen. Her videos are on KZbin.

[@projectsinflight]

Yeah- i've seen a couple of her videos on the subject. I think she also used armor etch as well

[@XA--pb9ni]

This is one of my new most liked channels! Keep up the great work!

[@NotToast859]

There's a weird disconnect between how dangerous things are and how dangerous people think they are, when I was reading through the medical treatment for HF their notes for exposure to dilute HF was that the first aid treatment was the same as what a medical professional would do (calcium gluconate), and that if it was from dilute HF and applied by someone knowledgeable quickly further treatment may not be required. Tbh it seems like with concentrations as low as the rust remover the higher risk would be from repeated small exposures adding up to flourosis over time rather than rather than anything acute, excepting cases of ingestion I guess. You might want to validate the concentrations of HF by seeing how much sodium carbonate is needed to neutralize the HF though

[@projectsinflight]

Yeah, I really want to test the concentration of each but I'm having difficulty finding an appropriate method. Titration seems like it's not gonna work.. Any ideas?

[@T3sl4]

@@projectsinflight Gravimetric would be easy enough (precipitate it all as CaF2 or the like?), if maybe not the most accurate (particularly at low concentrations where solubility matters, and, recovery of small amounts of solid, and purity thereof, is tricky). I don't know of an indicator offhand unfortunately.

[@NotToast859]

@@projectsinflight I'm not a chemist so not sure, but what's the issue with doing a titration?

[@npsfam]

This was very useful and interesting. Since I have begun some semiconductor DIY work, it has always been the most perplexing area is etching with HF. Your vid has helped to further my understanding of doing this process.

[@whompronnie]

I'm a miserly person, so seeing the effectiveness of the cheap Armour Etch was really satisfying

[@projectsinflight]

Haha I know right. I hate seeing super expensive lab chemicals vs cheap stuff like that. That being said, usually what you pay for is purity above all else

[@MaX271]

I remember chemical experiments at school using HF. My buddy and myself clumsily spilled some on the floor. When trying to wipe it off, the sponge instantly disappeared and left a green fuming goo behind. Good memories haha

[@projectsinflight]

You sure that wasn't sulferic? If that had been concentrated HF I feel like you'd have been dead

[@mrtoastyman07]

Dude - this is top tier. I am very excited to see where this goes. A well earned sub.

[@T3sl4]

Wow, you can really see the fumes from those stronger (Porcelain Etch and Armor Etch) mixes! Not so much directly, but the halo effect while etching! I wonder how quickly etch rate increases versus vapor emission. If reaction rate accelerates quicker, it might be worthwhile to use a lower concentration at higher temperature. This does need to be balanced for the overall process, of course: a heater is more steps, more equipment, more process, so it does increase the "attack surface" of the procedure's overall safety. On the other hand, it's also another process variable, simultaneously a liability (one more thing to keep track of) and an advantage (a parameter to optimize, and a means of controlling what is otherwise potentially-poorly-controlled ambient temperature plus handling (body heat)).

[@projectsinflight]

For now i'm just gonna resort to waiting longer but i'm in the market for a good fume-extraction solution for further testing!

[@JustinKoenigSilica]

Quick side note, HF is a weak acid, not a strong acid. This of course doesn't make it any easier to work with or healthier. Great video!

[@projectsinflight]

Yeah- I feel like the whole pKa thing is so misleading that i didn't bother calling it a weak acid

[@hamjudo]

I phrase it this way: "HF is an incredibly toxic chemical, that is weakly acidic."

[@sdk6450]

I remember looking up HF years back and coming across an amazon review of armor etch where some hobbyist was using their bare fingers to smear the cream on glass, claiming it wasn't an issue... Always wondered what became of that person. Apparently warning labels aren't good enough.

[@projectsinflight]

aaAAAAaaaaaAAAAAaaaaaaAAAAaaaa RIP

[@jonathanseagraves8140]

Dude, I cannot express to you strongly enough how much I would love a series focused on practical and accurate safety information. The "cover your ass" tendency of every company to over label is creating a dangerous situation where there is too much noise to the signal. If they are always yelling, what do you do when you really need to yell?

[@projectsinflight]

Yeah I agree. I would love to make a series like this when I feel competent enough to do a really deep dive into more on the subject.

[@Alexander_Sannikov]

why didn't you address the way porcelain etch spread around the drops you placed? as if it diffused around or the fumes chewed through the oxide as well.

[@projectsinflight]

Not yet but i may make a follow-up video investigating that

[@bruno_kid_]

Ok, this fast new video was unexpected ahhaahah

[@projectsinflight]

I really pushed myself to get this one out today lol

[@bruno_kid_]

Really appreciated, I will follow this journey 🎉 congratz and stay safe o/

[@soubs242]

@@projectsinflight your work is noticed!

[@solvarianforesthaven58]

I am not a professional chemist, however I do have a degree in chemistry (BS) and I can appreciate the dedication to safety. However this chemical (HF) is on a short list of chemicals that I will not work with given a choice. HF is new degrees of nasty and toxic. This stuff can eat your glassware, burn your skin even with most common gloves, kill you, and cause no end of issues. If you do plan on using HF for your etching I would recommend getting gloves that are resistant to HF concentrations up to 30% or using tools to handle the containers of HF at a distance. Also, you might want to consider having a stock of a neutralizing agent nearby in case of any spills. Now you might already have this and just didn't state it, but if you don't I would highly advise you have one on hand. All that said, very nice video! I have always been curious about the process of manufacturing of silicone devices and I will be watching with interest going forwards. I just found your channel and you have earned a sub!

[@projectsinflight]

I appreciate that you took the time to write this. I don't have any real chemistry education (other than a couple college lab classes) so I am always looking for info from others who are knowledgable :) I have a pair of 14mil butyl gloves for handling HF and I am looking for some better nitrile disposable gloves as well. For neutralizing I am currently using sodium carbonate, but i'm looking for something better. I think the main thing that I should improve on is wearing better quality nitrile gloves and keeping the HF inside other containers. I feel like the main liklihood of injury at the current time would be some kind of mistake where I didn't notice a spill, so I'm looking for an indicator solution that works for HF- in case you have any ideas. Feel free to email me at my gmail as well- ProjectsInFlight- same as the channel name! It's true that HF isn't a chemical to be taken lightly and I'm doing my best to minimize the risks. I think in the future I'll do a more comprehensive video on PPE.

[@solvarianforesthaven58]

@@projectsinflight The Butyl gloves will work to if you are very careful, but I would not rely on them solely. The recommend gloves for handling HF by OSHA is Neoprene gloves. Neoprene can resist HF up to 48% concentration and are not super expensive (still pricey though), Nitrile can work if they are thick enough, but are not the top recommended gloves by OSHA. Double gloving is always recommended as well. If you do go with Nitrile, get the black Nitrile gloves as they are thicker seeing how they are designed for industrial applications. Or use your Butyl gloves with a Nitrile glove as a liner or inner glove. Your neutralizing agent is fine, in fact when I was in university we used a saturated solution of sodium bicarbonate as our neutralizing agent. I'm glad you have that on hand for a just in case situation :) and having something like kitty litter (cheapest one) to soak up the neutralized spill. For the HF indicator, any pH indicator will work and if you are concerned about vapors of HF, hang some kind of indicator strip(s) in your hood. But these will only let you know if there are fumes, not what consecration the fumes are at. I know there are dedicated meters for measuring HF fumes, but these tend to be extremely expensive and hard to get. So hanging strips at regular intervals on the side of your hood should be fine. But if your hood is in good working order and is removing the fumes there should be nothing to worry about (test your hood using a blown out candle and see if the smoke is pulled away). And keeping the HF containers inside of another container is a good idea to contain any spills, which we all say will never happen but always seems to at the least convenient time.

[@fatiheneskuru4332]

Your detailed investigation shows your concern and careful consideration. Note that hydrofluoric acid or ammonium bifluoride reacts with glass to produce toxic byproducts, H2SiF6 and SiF4, respectively. Both the acid and the byproducts of glass etching are toxic and must be avoided from inhaling.

[@projectsinflight]

This is true, but in my case the amount of glass that is being removed is so small that the silicon byproducts should be in such tiny quantities as to be irrelevant. Hopefully...

[@Delta7Smith]

Can't wait to see your next video, I've greatly enjoyed the journey starting at the tube furnace

[@projectsinflight]

Thanks! Glad to have you aboard! Next stop- photolithography

[@charlvanniekerk8009]

armour etch blew everyone out the water ( or sodium carbonate XD). really enjoyed the video!!

[@projectsinflight]

I'm considering seeing if i can source some 5-10% liquid hf solution, to see if i can have the best of both worlds.

[@joachimsingh2929]

I would highly recommend that you ad a strong dye to each of the products to see any remains. Like whats in the porcelain etch.

[@projectsinflight]

I would consider it if I could figure out what dye they used. I do want to minimize other contaminants though since silicon fabrication is sensitive to impurities

[@ronnetgrazer362]

A laser-activated etchant like the ones for metal could help with the patterning step. Like something that would prevent the armor etch from doing its thing until that and only that ingredient gets burned off, localized.

[@edwardpaulsen1074]

I am very glad he did not skimp on revealing the dangers with using HF and I just wanted to reiterate the warning about Hydroflouric acid or HF... If it just covers 25 square inches of skin, (basically the surface area of your hand flat on a table) without immediate treatment it can and likely *WILL* cost you that limb... It burns down to the bone and rapidly travels up the calcium in your bones. Wear the proper gloves, face shield, apron and be very careful while using it!!! I know two people who had to have an amputation of the next higher joint to save them from death at around 40% concentration. It can be safe enough if handled carefully at the below 10% concentrations.

[@azertyQ]

really excited to see where this goes. i've always wondered how hard it would be to make the (IGBT?) transistors used in EV drive units; I'd imagine that their structure size wouldn't be as much of a performance limiter compared to homemade ASICs, but I've always given up the task when hearing the horror stories about HF (admittedly most at industrial scales)

[@w__a__l__e]

glad you made the video and didn't poison yourself!

[@allrightenergy]

I am totally thankful that I watched your very educational video. You are so smart.

[@sapiosuicide1552]

Amazing videos, please keep doing more this is some of the best content on KZbin on the subject

[@projectsinflight]

Thank you- that really means a lot to me :)

[@Laski-be3jg]

This is so sick, can’t wait for the next video!

[@agranero6]

Rust remover in US uses HF? In Brazil they can only use Phosphoric Acid for metal or Oxalic acid for fabric. The heavier acids you can acquire in supermarkets is Sulphonic acid for cleaning Aluminium. For buying HCl for cleaning concrete or stone you need to buy it at hardware stores. Even so they are heavily diluted (5% or less). But you can buy HF as dental products but again in very small quantities and heavily diluted. More than that it controlled I don't know to what extent.

[@ShrirajHegde]

Excellent video. 100% in every part.

[@projectsinflight]

Thank you so much. It means a lot to me that people are supportive :)

[@blackmosman3731]

Amazing video, Great explanations and animations.

[@projectsinflight]

Thanks! I spent a lot of time on that slideshow lol

[@Djambo57]

another step completed! Can't wait for the next one

[@projectsinflight]

I think I'm gonna do photolithography next!

[@Djambo57]

@@projectsinflight that's awesome. You really created something special here. I know how much work it must have been to create these few videos but it's amazing to see how quickly you're growing.

[@freakyjason477]

The benchmark with sulfuric acid is a bit misleading. I know from experience that 96% sulfuric acid on skin is not *that* big of a deal, depending on how dry the skin is you can have minutes before it starts reacting. Certainly not something to visit the hospital for. A drop of 50% HF on skin *does* warrant a hasty trip to the ER. I will not keep HF around for that reason.

[@projectsinflight]

the point of the comparison was to highlight the areas in which the dangers are similar and then explain how the fluoride toxicity and delayed reaction are two areas where HF is MUCH more dangerous than sulfuric acid.

[@freakyjason477]

@@projectsinflight Not exactly the message I initially took home from that, I'd say any concentration of HF is more dangerous than H2SO4. But I agree, if you're working with HF and you've any doubt you've come into contact with it, see a doctor right away.

[@DeminJanu]

Awesome vid and experiments! I’d probably just use the Wisk Rust Remover and let it sit for Long enough - eg. 30-60min to remove 500nm of oxide. The safety benefits seem worth it to be more patient. Love the safety discussion and details, incredibly valuable. Thanks for the excellent explanations and deep-dive.

[@DeminJanu]

Safety benefits AND easy water rinse only. Such great info, I’ll plan to use this in upcoming educational activities.

[@projectsinflight]

Yeah TBH the ease of cleanup makes the rust remover a really convenient choice

[@CharlesVanNoland]

@16:28 Wow you can see just how the vapor emitted from the blob etches the surrounding silicon.

[@projectsinflight]

Quite possibly. Or it was from when i put it into the water bath. needs further investigation

[@auxiliusm]

I was wondering how sensitive the etching rate is to temperature. Heating up rust remover or any HF-containing chemical might be (very) ill-advised, though. Again thx for this, very interesting to follow along.

[@projectsinflight]

The etch rate will increase dramatically with temperature, but so will the vapor pressure and fuming.

[@Palerider1942]

@@projectsinflight in that case then would the opposite be true? if you wanted to use the armor etch in a more controlled manner could you chill it to reduce its speed? perhaps to a point where it is comparable to the Dental stuff without the expense?

[@auxiliusm]

@@projectsinflight Expected, well, considering the designs won't necessitate too many etchings, the current rates should be fine. Do you already have an approximate goal in mind design-wise, and if so, how many deposition and etch steps do you expect?

[@VeLawrence]

You're doing a great job there man it's really nice to see you share all this valuable knowledge, I guess you occupy a honor position along with Jery and Sam in making semiconductors at home, I'm looking forward for your next videos, thanks!

[@allesklarklaus147]

Really good video. I know HF from metalworking as a stainless steel etchant in a mixture with other acids. It is used to grow a passivation layer on welded stainless steel parts.

[@projectsinflight]

What strength did you use?

[@allesklarklaus147]

@@projectsinflight From the MSDS the product contains 5-10% HF and 5-10% nitric acid and it was a gel thing and not a liquid. I believe there are more dangerous products for the same purpose but it always scared me a bit. In some shops they have like 1000 Litre tanks of a similar HF-containing liquid used to submerge parts.

[@flip_flap22]

The legend is back!!

[@AndyMcBlane]

Really excellent video! Thanks for the effort that went into researching and creating it.

[@youtubasoarus]

Awesome followup video! I would argue that the lesser concentrations provide a safer and more forgiving option for pursuing this. Whereas the others seem to me like they would be less forgiving and force you to be quick, which would lead to mistakes and possibly an accident. Couple that with the dangers of the higher concentrations and it would seem the best option, at least in my view, is the least concentrated and to take more time. Avoiding accidents, working slower and more methodically means less wasted material from hurried batches. All pluses in my book. I look forward to the upcoming videos! Also, the needle applicator seems like a glove puncture hazard to me, even if negligible.

[@projectsinflight]

Fortunately the needle on the applicator is smooth and not sharp like hypodermic needles

[@Tommybean7]

Wow, very knowledgable! 👍

[@PCBWay]

This is truly AMAZING!

[@Niohimself]

This video is fascinating, and HF is terrifying. As en electrical engineer, I feel more at home with ion beam etching, cause I can sort of figure out the physics of the device, but chemistry is beyond me. I kinda wish somebody made an equally involved video explaining the safety concerns of ion guns. The dangerous parts are probably the beam itself (don't stick your hand in there), the possibility of accidental X-ray production, high vacuum implosion, and also electrocution due to high voltage.

[@AlexanderBurgers]

HF is definitely the microwave oven transformer of chemicals.

[@projectsinflight]

The dangers you listed are all valid. There is one more I can think of: When you do reactive ion etching you often add additional chemicals to the chamber to achieve better results. Most of these chemicals are pretty dangerous, either because they are toxic or pyrophoric (burn on contact with air). That being said, it's still something I'd like to try at some point because it's a super valuable tool

[@0x80O0oOverfl0w]

This is super helpful! Thank you. I've seen the crazy videos and heard the horror stories about Hf and it's def not something I want to mess with. My interest is in chip decapping, so this is very useful information! One thing that would have been helpful is if there are any glove restrictions with Hf. From what I understand certain chemicals are not compatible with certain types of gloves.

[@defenestrated23]

You can make your own HF in-situ with ammonium bifluoride and sulfuric acid, this avoids the "stickyness" of Armor Etch. You can get effective concentrations of essentially any value by dialing in the amount of fluoride.

[@projectsinflight]

I've considered the sulferic acid + sodium fluoride route as well, but I just don't think it's safe enough for me right now

[@yagobueno2785]

You have no rights to motivate me to persue the career of "chip designer"/ "chip maker" / "chip researcher" 😂... anyway, this an excellent job are you doing here, keep going!

[@projectsinflight]

Thanks!

[@tfairfield42]

Great video, can't wait till the next. Made sure to subscribe

[@titter3648]

I have worked two different places that used lots of HF acid. A solar cell manufacturing plant and a quartz refining plant. They got it in IBC containers and i think it was 60% both places. The quartz plant used around 2000 kg a day. And at the solar cell plant they told me about one guy that got 2 drops of HF on his neck and they had to restart his heart 5 times on the way to the hospital that is around 1.5 hours away when driving at normal speed, but i'm sure the ambulance drove faster. At the quartz plant one operator got diluted HF running down into his gloves, but it was dilute enough that he only got some rashes on his arms. I was in maintenance and never liked working on the machines after the operators had hosed them down. I was always thinking what if they missed a spot when hosing them down...

[@projectsinflight]

2000kg!?! JEEEEEZ Thats a scary story

[@christopherleubner6633]

IBC cage tote full of HF would be unbelievably scary to go near. Several years ago I worked for a chemical recycling and disposal company and a semi company had 60% nitric with 3% HF plus minor contamination with silicon aluminum phosphorus boron etc they couldn't find any disposal plant to take it. After a while we found a fertilizer company that would take it once we let them know that all that would be required would be to react it with calcium nitrate solution then filter the calcium fluoride out. Next combine with KOH and CaOH to make the fertilizer. ❤

[@titter3648]

@@christopherleubner6633 We got the IBC's on semi-trucks and apparently the truck drivers did not read the manifest of what they where carrying. So one time one of the IBC's leaked, and when we noticed it when he arrived the truckdriver just said that he had noticed it when he checked the cargo a few hours earlier in the trip but did not think it was a big deal so he just tightened the straps and kept driving to his destination. I guess he got luckily. But i bet the trailer rusted like hell after that. And everything on every machine that was in contact with the HF was plastic (PTFE was best but PP also hold up pretty good and is cheaper), even the screws because it would just eat trough anything made of any metal.

[@titter3648]

@@projectsinflight And all of it was then just dumped into the sea actually. The building where they acid washed the quartz was down by the sea, and there was a concrete "tank" where the seawater could flow in and out of freely where the HF was dumped after it had been used to wash the quartz. That way the HF would be further diluted in the concrete tank before it flowed out into the sea. But even though the HF was already diluted by water by the time it got into the concrete tank after a few years the concrete was etched away pretty badly and the walls needed to be sand blasted and reapplied. One supplier joked and asked if the fish around the area had any bones left in them.