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Making your own NMOS transistors — Parallax Forums

Making your own NMOS transistors

LeonLeon Posts: 7,620
edited 2010-07-12 14:53 in General Discussion
I've heard of people making their own point-contact transistors, but this is a lot more impressive:

www.youtube.com/watch?v=w_znRopGtbE&feature=player_embedded

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Leon Heller
Amateur radio callsign: G1HSM

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2010-07-10 23:06
    Years ago, Bell Labs made a kit for home construction of simple solar cells. I managed to get invited there to talk to the physicist who had come up with the kit to discuss the possibility of making a junction transistor for a high school science project. He gave me a tour of his LED lab, showed a very primitive green and a blue LED, made some suggestions for doping and general construction principles, and sent me home with a couple of kits for supplies. I eventually made a very poor transistor, but several satisfactory diodes. Obviously, techniques and precision of features have improved much since those times. Very cool
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2010-07-11 10:03
    Wonderful demonstration, very empowering to youth just getting into electronics.

    Of course it is easier and cheaper to just buy a 2n7000 or whatever, but the point is that you can explore the process. And you might think of a better way.

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    Ain't gadetry a wonderful thing?

    aka G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2010-07-11 15:19
    Jeri is wayyyy out there... In a very cool way.. [noparse]:)[/noparse]

    She was the one who encouraged me to get into microcontrollers back when I bought my first PICAXE chip.
    (Met her though the Commodore expos, as she's big into that community.)

    Neat stuff! I'm betting she'll be doing gate arrays next. [noparse]:)[/noparse]

    OBC

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    Visit the: PROPELLERPOWERED SIG forum kindly hosted by Savage Circuits.
  • LeonLeon Posts: 7,620
    edited 2010-07-11 16:36
    A CMOS transistor would be a start.

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    Leon Heller
    Amateur radio callsign: G1HSM
  • UnknownUnknown
    edited 2010-07-11 18:11
    I took pictures of Commodore's MOS Technology plant and it looked like they had a bunch of large ovens in their building.
  • LeonLeon Posts: 7,620
    edited 2010-07-11 19:37
    I think they put the wafers in silica "boats".

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    Leon Heller
    Amateur radio callsign: G1HSM
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-07-11 20:22
    Leon said...
    A CMOS transistor would be a start.
    You're just messing with us, right? smile.gif

    The term "CMOS" refers to a complimentary pair consisting of a PMOS and an NMOS transistor in an output stage capable of both source and sink driving. I don't believe there's any such thing as a single "CMOS transistor". But I'm sure you'll correct me if I'm wrong!

    -Phil
  • localrogerlocalroger Posts: 3,452
    edited 2010-07-11 20:30
    One problem with making a transistor kit is that toxic chemicals are used. Jeri's project used hydroflouric acid, and one of the common dopants for silicon is arsenic.
  • Mike GreenMike Green Posts: 23,101
    edited 2010-07-11 21:40
    The Bell Labs kit I mentioned used boric acid for the P dopant and they suggested phosphoric acid for the N dopant, both made up as a slurry. I forgot how they got the hydrofluoric acid, but I think it was as an intermediate reactant. There never was any hydrofluoric acid used directly.
  • UnknownUnknown
    edited 2010-07-12 12:14
    localroger said...
    One problem with making a transistor kit is that toxic chemicals are used. Jeri's project used hydroflouric acid, and one of the common dopants for silicon is arsenic.
    Commodore had a tank where hazardous chemicals were stored.· It began leaking and chemicals were detected in people's wells·and ground water.· The EPA stepped in and fined Commodore $1,000,000 dollars.·

    GMT Electronics bought the building and worked there but the EPA closed them down.· They installed equipment to remediate the soil and ground but the last I heard the building was scheduled for demolition and was to become a velodrome (racing circuit).

    What I was told at another plant was the law says they have to manufacture one product or they have to have all the dirt scraped off of the bedrock and incinerated.· That is why these companies are renting out their property to pay the taxes and why some companies are only producing one product; they don't want the clean up costs.· They can all live old and stay away from liability and it will be someone else's problem when they die.

    I think that is why FPGA and CPLDs are promoted.
  • pharseidpharseid Posts: 192
    edited 2010-07-12 12:14
    I didn't watch this whole video, I've seen another one of hers and she mentions using phosphorus as a dopant, I think she says she once tried using Pepsi for that purpose. One facet of her work that I don't know if she mentions on this video is that her methods tend to introduce sodium into the gate, which has its problems. On the Yahoo homebrew transistor site, they mention that the etchant she used wasn't HF, but a much safer proprietary glass cleaner or etchant. For the record, getting even a small amount of hydrofluoric acid on your skin can be lethal.

    I stumbled across this looking for information on those printable organic semiconductors, if somebody were making a homebrew transistor kit today, I would think you would use those. Maybe I didn't look hard enough, but this seems like this would be one of those technologies that·would have·a following, but I couldn't find it.

    -phar
  • LeonLeon Posts: 7,620
    edited 2010-07-12 14:53
    Coke and Pepsi contain phosphoric acid, to counteract the sweetness of all the sugar they contain. It's very good at dissolving tooth enamel, BTW.

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    Leon Heller
    Amateur radio callsign: G1HSM
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