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I previously worked on Virtual Reality and other hardware at Valve.  I currently work at Google[x].

Prior to starting at Valve, I built computer peripherals such as keyboards, mice, and joysticks that were designed to be used inside MRI machines.  My company, Mag Design and Engineering, sold these devices directly to researchers at academic institutions who used them to publish scientific papers in peer-reviewed journals.

After work, I spend time on many different types of projects that usually involve circuit design, machining, material selection, and general fabrication/hacking.  My favorite place to be is my home workshop.

ben dot krasnow at gmail

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Monday, December 30, 2013

More info about sputtering: process parameters, chamber construction

I describe a few more details about the sputter process that I have used to make ITO coatings.


13 comments:

  1. Hi Ben
    I really love the vacuum stuff you do and I'm really thinking about building my self a system like yours, I already got myself an old Turbo Molekular Pump. I'm tweaking myself a controller together, right now.

    I wonder how you seal the Belljar, because an appropriate Vacuumchamber is right now my biggest Problem. Is that some kind of seal tape?

    Best wishes from Germany, and a happy new Year.

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  2. I have started to try this in my lowly position in academia, unfortunately no one else has done it for 20+ years, so I really appreciate the insight. From my experience and reading, the distance causes the rate to reduce exponentially regardless of sputter target geometry. So my guess is that is the reason for your slow sputtering rate.

    Personally I position my sample ~10cm from the sputter target, pump to between 1E-5 to 1E-6mbar and backfill with Ar to 1E-3mbar and sputter with a RF power of 15W for around 5-10 min.

    Would it also pre-long the life of the target and reduce the cooling demands on the system to use a lower power and closer distance?

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  3. I'm interested in hearing about the cut down version! What are some of the drawbacks?

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  4. also, whats the out of pocket expense for the whole system?

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  5. Anonymous, it's true that putting the substrate closer to the target will increase the deposition rate. In this case, the ITO coating is sensitive to the plasma as it is being formed on the substrate, and it seems possible to make high-conductivity ITO coatings in pure argon only when the substrate is relatively far away from the target and plasma. When using proper argon+oxygen, the substrate can be much closer. I'm still figuring this out, though, and information is difficult to find.

    asldsvrslhf, the drawbacks would be ability to sputter fewer materials, and having a more contaminated final coating. I think it should be possible to build a sputter system for a few hundred dollars, but I've spent more than that because I like exploring DIY lab equipment.

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  6. Florian, I used a commercially-available belljar seal from Duniway Stockroom. I've seen that some people use a sheet of rubber from McMaster-Carr with a glass bowl from a kitchen supply store.

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  7. Interesting thanks Ben, I will try and increase the distance to improve the film quality, I'll try and retain a low power too to reduce the damage. I'll let you know what happens

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  8. Awesome as always Ben... really enjoyed the extra detail. Also really appreciate the effort you put into sharing all of your work, and would love to see a cut down version.

    Cheers,
    Brad

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  9. so Ive been doing a little research and see why RF and the ability to control levels of reactive gases is useful. I was reading a paper on depositing amorphous hydrogenated silicon and they said they tested it at different ph and temperature.

    My question is how do they control the temperature (they said between 300 and 700k, with the best results being over 600k for clear photoconductive surfaces)

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  10. asldsvrslhf, it's common to use radiative tungsten heaters to maintain the correct substrate temperature. Basically, a light bulb focused onto the substrate with a temperature controller.

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  11. I just took apart a diffusion pump I got, well, took apart the T bracket on it anyway. Interesting thing. I'm wondering if the thing that fits through the T opposite the valve is suposed to be filled with liquid nitrogen or something? its interesting that the valve is on the other side of the T and not on top. It also came with a penning gague built right into the side (I just got one in the mail today).

    Anyway, besides all that, I was wondering about the wiring at the bottom, if I take a picture can you tell me what might go where? for the power supply and whatever else is hooked up in there (im guessing a thermocouple or something?)

    I was also looking at bell jars, man those are expensive, way more expensive than the electron microscope I got that I am now planning as using as the sputtering chamber. I also thought of turning the tube on its side and connecting the valve over what looks like a water cooled baffle between the pump and T and using it as a chamber.
    What do you think about this?

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  12. asldsvrslf, diffusion pump wiring usually consists of the heater terminals, and a thermal safety switch. The switch is wired in-line with the power connection. It's very common for diffusion pumps to have water-cooled baffles, and many have liquid nitrogen traps as well. Without a baffle, the oil from the diffusion pump will drift up into your chamber and contaminate everything. I'm not sure what part looks like a T. Maybe your pump has a large vacuum fitting on the top? You can use anything for a chamber as long as you have enough space to accomplish your task.

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    Replies
    1. http://i.imgur.com/87uAky0.jpg

      To the right of the t you can see the plastic covering with the nitrogen traps hole misaligned. The valve is blue followed by a variety of holes for interesting pluming options.

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