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I Semiconductor doping

  1. Oct 31, 2017 #1
    I have a pressing question, but I don't exactly know how best to articulate, or where. I am a wafer fab operator in the semiconductor industry. I usually operate ion implanters. The highest energy ion beams we use are a little over 3.5 MeV. As an aside, I am looking for a way, given that, to calculate the percentage of the speed of light at which the ions are traveling.

    I have a much bigger question. When particle accelerators were first being built and studied, I doubt that it occurred to any of the first-gen builders and researchers that their machines would soon be used to embed dopants into silicon substrate to modify its electrical properties. Perhaps I'm mistaken; it just seems more likely that implant was a next-gen development.

    Higher beam energies allow dopants to be deeply embedded into the substrate, which allowed engineers to bypass a few earlier semiconductor design steps, which translates into huge cost savings. Now, my billion-dollar question; does anyone savvy here have any idea if any design work is being done to capitalize on much, much higher beam energies - at speeds where relativistic effects become significant? Any ideas what those sorts of relativistic effects may practically mean in this context?

    I'm out of time, but I'll leave it at that in hopes that someone here groks what I'm getting at.

    Cheers!

    ~X
     
  2. jcsd
  3. Oct 31, 2017 #2
    I have a spare moment.

    Essentially, I'm imagining the situation where, at the end of its life as a cutting-edge research tool, the LHC is converted into an ion implanter for practical manufacturing uses. What would/could these uses be?
     
  4. Oct 31, 2017 #3

    ZapperZ

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    Question: why do you need to use LHC for this? In other words, why do you need THAT high of an energy in the first place? You have presented no physics justification for wanting to smash an ion into a substrate at 7 TeV.

    When you increase the energy of the bombarding particles, a bunch of OTHER things will happen. At the LHC energies, you will damage or change the nature of the target. That is a given. Not only that, you will also cause the material to have residual radiation due to activation (why do you think one can't open and walk into the detectors at LHC and Tevatron as soon as the beam shuts down?)

    And speaking of "practical" manufacturing uses, do you think it makes economic sense to run the LHC to use it for JUST ion implantation? How much do you think it costs (both operational and manpower) to run the LHC per day?

    Zz.
     
  5. Oct 31, 2017 #4
    Thank you for your reply. I am assuming an entire hypothetical future context wherein operating the LHC as a manufacturing tool *does* make economic sense. This has a lot of implications. These are specifically the sorts of implications I am asking about.
     
  6. Oct 31, 2017 #5

    ZapperZ

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    But you haven't justified any reason for ion implantation at that energy level.

    I mean, if you walk into a meeting at a company with a proposal to use a VERY expensive machine to do something, shouldn't you also describe WHY you wish to use it? The physics justification for it has not been shown here, and the economic justification has also not been shown.

    I, on the other hand, have shown why I'm skeptical that this is "practical", and also of the fact that your target can easily be damaged or destroyed in the process. I do not see this as being a "practical" manufacturing tool.

    Zz.
     
  7. Oct 31, 2017 #6
    Do you suppose the first builders of particle accelerators knew they were designing what would become ion implanters?

    That's the position we're in, here.
     
  8. Oct 31, 2017 #7

    ZapperZ

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    No, but when they saw it, they then make a proposal to (i) use it (ii) describe the parameters of the accelerator that is needed and (iii) use the existing physics to describe what will happen with the experiment.

    You just don't build or use a multimillion dollar facility based on just the excuse that it should be done. You need justification. You haven't given any. I have given reason why it isn't practical.

    And for your information, I'm an accelerator physicist with a condensed matter physics background.

    Zz.
     
  9. Oct 31, 2017 #8
    Excellent; let's forget about ion implant for a bit. The reason I mentioned it is because it's a practical and profitable application of what began as a family of theoretical research tools, and not manufacturing tools.

    Regardless of the initial justification for the construction of the LHC, it exists already, and may eventually be repurposed, or perhaps simply serve as a model for how to build a family of manufacturing tools that capitalize on relativistic effects.

    At this stage, we do not seem to know what manufacturing techniques, if any, will emerge from this. Nevertheless, I suspect there will be some. If I had the answers that you are expecting of me, you better believe I wouldn't be wasting time posting in physics forums. I'd be out doing it.
     
  10. Oct 31, 2017 #9

    ZapperZ

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    And if there is actually a practical use of such a facility, they wouldn't have mothballed the Tevatron!

    These types of facilities HAVE been used to study the application in other areas. Fermilab was the hotbed of things on proton therapy research and other accelerator applications. So they DO know of such uses when they come up since many have already been implemented. My own research have veered off into everything from phototubes to CW sources for material sterilization. So trust me, there ARE people who are continuously looking for acceleration applications.

    BTW, in case you don't know it, read Micheal Turner's article "Dinosaurs and Accelerators" in Physics Today (Sept. 2003). Here's a quote from that article:

    Zz.
     
  11. Oct 31, 2017 #10
    I really appreciate the time you are taking to answer this. Correct me if I'm wrong, but I get the impression you are highly skeptical of the notion that relativistic energies will find any use in ion implantation. I see your point, and am inclined to agree that industrial applications for so high of energies as these imply tech that has gone far beyond doping silicon wafers. Clearly, I cannot seriously be saying a 300mm wafer could withstand trillions of electron volts, any more than I could argue for thermonuclear temperatures in diffusion furnaces. But this isn't to say that such energies or temperatures have *no* manufacturing potential. On the contrary, our present information age is built on discoveries and applications that couldn't have been imagined a hundred years ago; so I have every reason to believe further advances depend on pushing the envelope of what we can safely harness.

    That's really what I want to know about. I'd really like to understand the sorts of things that trillions of electron volts actually *do* to stuff. I'm an amateur, but I've heard that Relativity implies things like that causality somehow and in some ways appears to be reversed depending on one's inertial frame of reference relative to and observer approaching light speed. How could this *not* have serious industrial ramifications?
     
  12. Oct 31, 2017 #11

    ZapperZ

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    This is wrong. I never said such a thing. Protons at several MeV are already "relativistic". Yet, they can be used in many applications. I specifically asked why you would want to use the protons at the LHC (you did bring up the LHC) at 7 TeV. What can you do that 7 TeV that not only is beneficial when compared to significantly lower energies, and why aren't the damages done at 7 TeV a part of your consideration?

    So what are they? You can't simply say something like this, on a science forum, without backing it up.

    Electron beams at just 1 MeV are already considered relativistic. Many calculations on beam dynamics at this energy simply round off their velocity to "c". MeV energy ranges for many heavy ions are already considered to be relativistic. So you have a bit of misunderstanding of what "relativistic" means. This means that relativistic beams are already in use!

    But there is a HUGE difference between beams at MeV's versus beams at TeV's. There has been zero compelling arguments on how TeV beams would not only be beneficial for industrial application, but also not destroy the material in question. We already know A LOT of what happens in material damage when being bombarded by such energies.

    I'm still waiting for examples of these "serious industrial ramifications" beyond just speculation.

    Zz.
     
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