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Comment by ISL | Hacker News Reader

Awesome. For those considering exploring some of these steps in their own garage -- the chemistry is dangerous, perhaps HF in particular, as it doesn't hurt, it just kills you a few hours later.

Can you do this in a garage? Absolutely, but learn everything you need to know from an ensemble of safety-minded mentors before you strike out on your own.

It's not just about safety for you, proper disposal of these chemicals is essential for the many generations to come. Sometimes it is inexpensive, sometimes it is costly. You need to know how before you start, or it costs a lot more.

(Also, you can get someone else to pay for the hardware, the infrastructure, the material, the resists, the reagents, the safety training, and the waste disposal if you work/volunteer at a university's photolithography facility. They'll probably pay you, too.)

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Nice HF technical overview: https://ehs.unc.edu/files/2015/09/hydrofluoricacid.pdf (tldr; nope; read it.)

I needed to dissolve(ha!) fluorite once. You can get it started by adding a few drops of conc H2SO4 to your beautiful aqua regia solution. It goes deeper red, some happy bubbles appear, and as long as it stays put, makes it's own "aqua nasty"(pg88) as you gently add your powdered sample.

I thought AQR+SA was called aqua nasty, but I cant get any hits other than this AA pdf with explicit HF added. Maybe an actual chemist can chime in, is there another name for the aqua regia +H2SO4 mix?

https://archive-resources.coleparmer.com/Manual_pdfs/28750-1...

If I remember correctly in the book: "1636: The Chronicles of Dr. Gribbleflotz" he made "aqua regia" from "aqua fortis" and "acidum salis" I don't know if either of those were his name for aqua-regia + HydroSulphuric Acid. I know he called ethanol "aqua vitae" by repeatedly distilling wine. He also had "Oil of Vitriol" which he added to saltpeter to make "aqua fortis". He also talked about adding "Oil of Vitriol" to "aqua fortis" but doesn't say what it makes. I think maybe "oil of vitriol" was hydro sulfuric acid, but I am not sure. Perhaps you can find more or someone else can remember. (I used: https://www.ericflint.net/index.php/2016/06/03/1636-the-chro... to quote what I mentioned here.)

Aqua regia is just the name for a mixture of nitric and hydrochloric acid which has the ability to dissolve gold. Aqua fortis was simply an archaic name for nitric acid; acidum salis (literally "salt acid") is likewise an old alchemical name for hydrochloric acid, rather straightforwardly named because it was an acid that was synthesized from salt. (If you ever see hydrochloric acid referred to as "muriatic acid", this is just a somewhat more modernized version of the same name: brine-y/salty acid.)

Oil of vitriol is sulfuric acid. This was also quite a logical name at the time - it's an oily liquid that was made from vitriol (a common term for a class of brightly colored metal sulfate crystals).

So, in the reaction given, when the sulfuric acid is added to saltpeter (potassium nitrate), the sulfate ion swaps places with the nitrate ion and you instead get nitric acid and potassium sulfate.

Source: Have spent far, far too much time researching alchemical nomenclature because I thought it was cool.

> Rectal administration has caused acute colitis with perforation.

disturbing that we know this

Not really. Rectal administration of drugs is one of the fastest ways to administer a drug outside of IV.

Unfortunately, I found out about it because of a now-deceased friend who succumbed to alcoholism. Near the end, he would drink rectally, since his esophagus was effectively destroyed. Also, since there's no gag reflex to keep you safe, this way is one of the easiest ways to kill yourself with alcohol.

I love learning new things... but not always.

From your link:

    INHALATION

    Estimates of the lowest lethal concentrations for hydrogen fluoride range from 50-250 ppm for 5-minute exposure and are based on accidental, ***voluntary*** and occupational exposure information.

Someone volunteered to be exposed to this stuff??

>> For those considering exploring some of these steps in their own garage -- the chemistry is dangerous, perhaps HF in particular, as it doesn't hurt, it just kills you a few hours later.

I was hoping that with 50 years of development behind us, the home fabricators could use less complex methods and less hazardous chemicals. In other words, can the folks who lived it help people like this by saying "If we had to do it over, I'd go about it like...."

Any suggestions? If you had to reboot the chip fab business on a budget what would be a more practical approach?

There's just...no reason at all to do it for business purposes. If you're a prepper or looking for a science project I can understand it, it's a cool project. But from a business perspective you can buy the same thing but better for dollars and have it the next day.

The lowest-cost options I know of for commercial custom chip fabrication are MOSIS and CMP. Their pricing starts at €650 for 0.35 μm, but it's true that the result is much better. However, turnaround time is measured in weeks. You seem to be suggesting that there are options that are one order of magnitude faster and two orders of magnitude cheaper (but perhaps with a much coarser feature size).

What are they?

I used to work in a fab. As far as I know, there's no acceptable way to remove native oxide without HF. We do have another etch process -- dry etch -- that uses plasma instead, but it causes surface damage, and you don't want that under the gate. Also, dry etch chambers are a lot more work to maintain than a fume hood where you do wet etch. Furthermore, dry etch has its own set of hazards, and you have to deal with a lot more potentially toxic vapor.

Thinking a little more outside the box, you might look into using germanium instead of silicon. I don't know much about the germanium system, except that it supposedly grows less oxide. You're still going to have to deposit and remove oxide somehow, though, which means CVD reactors and silane. It's not going to be easy to get away from explosive toxic gases and dirty processes.

Not to mention DiBorane and Arsene... 1000C anneal cycles, teratogenic photoresist ethers, UHV equipment, and muti-kW RF sources. It's possible to demonstrate um scale MOS with a small lab, but not safely in anything resembling a normal garage. Hoping to replicate a multi-$B process at home is a fool's errand.

While we're at it, a modern scanner costs many million dollars, weighs tons, and sits on its own separate foundation on pilings that go down to bedrock so that it doesn't pick up vibrations from the air handling systems. DIY it ain't :)

what is a scanner in this context? what is its role?

or is this a stepper? or scanning electron microscope?

A scanner is a photolithography tool like a stepper, except instead of exposing the entire shot at once, it sweeps (scans) a narrow rectangular exposure across the shot, and then steps to the next one. This allows for lighter, more precise optics. Confusingly, there's a piece of standard office equipment with the same name. Even more confusingly, Canon makes both kinds! Be sure you call the right technician for service.

I use "Armour Etch" to remove oxide from chips for reverse engineering, so it might work instead of HF for home chip fabrication. It contains bifluroride salts so it's somewhat safer (although I'm still very careful with it). You can buy it in craft stores for etching glass.

I think removing oxides inherently requires fantastically reactive (and hence fantastically toxic and/or flammable) chemicals.

I'm here to second the recommendation to work, volunteer, or take a class at a university. I took a class on MEMS at my university, and for only a few hundred bucks got access to a fully stocked lab with proper training and supervision. It was a good experience I would recommend to anyone interested.

> It's not just about safety for you, proper disposal of these chemicals is essential for the many generations to come.

Yes Gordon Moore created a superfund site or two in California.

Citation needed? The inorganic materials used in semiconductor fabrication, especially in the early days, tend to be fairly benign and are used only in small quantities relative to other industry.

The HF monster everyone is talking about in this thread is dangerous only as a concentrated acid. It's highly soluble -- reduce it with a rainstorm or two and let it recombine to a neutral pH and you rapidly get to (literally!) toothpaste-level toxicity.

There's a VERY serious discussion to be had about the safety for a backyard chip fabricator. But the idea that this is some kind of long term pollutant (relative to much more serious issues like the cleaning solutions in your very own closet!) is pretty spun.

Edit: yeah, as the responses point out, the "superfund" sites in question are things like VOC contamination you see with any urban industry, nothing particular to semiconductor fabrication that would justify the upthread quote about contamination "for many generations to come".

Here is one of them: https://cumulis.epa.gov/supercpad/cursites/csitinfo.cfm?id=0...

Intel graciously paid for trees to brighten up the street and has a nice street sign saying so. (It doesn’t say why they did.)

This one is not directly related to silicon production, but the QA that came after.

No citation is needed when a simple internet search reveals plenty of references, and that the issue is not HF specifically - volatile organics are an important issue.

Intel superfund site #1: https://cumulis.epa.gov/supercpad/cursites/csitinfo.cfm?id=0...

Intel superfund site #2: https://cumulis.epa.gov/supercpad/cursites/csitinfo.cfm?id=0...

Intel superfund site #3: https://cumulis.epa.gov/supercpad/cursites/csitinfo.cfm?id=0...

“We were putting into industrial production a lot of really nasty chemicals. There was just no knowledge of these things, and we were pouring stuff down into the city sewer system.” - Gordon Moore

https://www.bloomberg.com/news/features/2017-06-15/american-... (cites the main source that is no longer on the web)

https://www.youtube.com/watch?v=hrtyUnad7Jo (audio from the interview)

Despite the quote, what a lot of people question is Gordon Moore's ignorance. He has a PhD in chemistry afterall.

We know a lot more now than we did.

There’s a generation or two of chemists, pharmacists, etc who habitually mouth pipetted common lab solvents that we now know to be carcinogenic.

As early as 1969 chemists were identified as having increased cancer risk

https://pubs.acs.org/doi/abs/10.1021/cen-v047n008.p014b

> So it was that while running, but not so much as to force my body into open rebellion, I noticed something odd. When I was heading down the gently sloping hill on Peter Coutts Road towards Stanford Avenue, I turned right as usual to head back home, passed along the edge of a grassy area, and smelled...cookies. But not really cookies. Raw cookie dough. Outside.

http://www.aarongreenspan.com/writing/20130404/in-search-of-...

Lot's of information about the situation in that article. TL;DR: Palo Alto is a toxic cesspit.

And I would argue that individuals have the right to commence with research and creation. Science is not 'easy stuff that harms nobody'. The Curies suffered radiological poisoning but furthered chemistry and physics a great deal. I would think that "computer science" has mollified people in thinking that science is painless, harmless venture of fun exploration. Go read up about the countless physicists and chemists who tried to crack fluorine.

If you are a scientist, and not in a sciency-y setting (lab), have a laminated clipboard stating chemical threats, electrical threats, biogenic threats, and particulate threats.

You may end up killing yourself. If you do, you did so in the name of science. Please, don't have others die because you failed to properly notify first responders of a threat.

I understand why it's necessary, but I was shocked that he uses piranha in his home garage. I cannot echo the above sentiment enough.

Thanks for saying this. I worked for a few years at a semiconductor fab r&d facility. (As a tenant) Seemingly everything associated with this stuff is toxic and polluting. The old timer war stories include stuff like accidental releases that stripped paint from all of the cars in the adjacent lot.

Nasty stuff — the wisdom promoting garage stuff like this is questionable. :)

For those curious about the HF danger mentioned above, Wikipedia has an interesting (and scary) summary:

https://en.wikipedia.org/wiki/Hydrofluoric_acid#Health_and_s...

Good 'ole HF

http://blogs.sciencemag.org/pipeline/archives/2004/03/03/thi...

TL;DR "hydrofluoric acid is a water solution of hydrogen fluoride, HF. That’s a gas, and it’s a lot worse. ... As soon as it hits anything moist – like your lungs – it dissolves in the water and turns into hydrofluoric acid again."

"The straight liquid must really be a treat, but I’ve never seen it in that form, and would only wish to through binoculars."

The fact that it is liquid at relatively balmy temperatures makes it a bit easier to handle than most gases, but then you better have great urethane seals, gloves and clothing everywhere. (Silicones are permeable, PTFE is damaged over time, nitrile and vinyl gloves also leak.)

8mil nitrile x2 with no extended(!) contact option. Like silane: http://amo-csd.lbl.gov/downloads/Chemical%20Resistance%20of%...

Oh, yeah. I knew someone would get around to linking to Derek Lowe and his inimitable "Things I Won't Work With" series. His best-known entry in that series, about chlorine triflouride, also has mention of HF and semiconductors:

http://blogs.sciencemag.org/pipeline/archives/2008/02/26/san...

> The compound also a stronger oxidizing agent than oxygen itself, which also puts it into rare territory. That means that it can potentially go on to “burn” things that you would normally consider already burnt to hell and gone, and a practical consequence of that is that it’ll start roaring reactions with things like bricks and asbestos tile. It’s been used in the semiconductor industry to clean oxides off of surfaces, at which activity it no doubt excels.

> There’s a report from the early 1950s (in this PDF) of a one-ton spill of the stuff. It burned its way through a foot of concrete floor and chewed up another meter of sand and gravel beneath, completing a day that I’m sure no one involved ever forgot. That process, I should add, would necessarily have been accompanied by copious amounts of horribly toxic and corrosive by-products: it’s bad enough when your reagent ignites wet sand, but the clouds of hot hydrofluoric acid are your special door prize if you’re foolhardy enough to hang around and watch the fireworks

Here's a video of some French people introducing the substance to things like a rubber glove and leather:

http://blogs.sciencemag.org/pipeline/archives/2013/04/05/chl...

TL;DW: FIRE!

Besides IC fabrication, you can also use HF for making mouthwash: https://www.youtube.com/watch?v=gHoUCyQR7h8

And then you have Phosphene gas used to dope silicon, where people have died changing empty supply tanks.

The exhaust lines on high-energy implanters (the ones that do P doping) are a treat. They get coated up with deposits of solid phosphorus. If accidentally exposed to atmosphere, they do what phosphorus does. We used to call it "unscheduled exhaust system PM." Medium and high current implanters where I worked accumulated arsenic in the exhaust system, but at least that doesn't explode on you.

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