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Cleaning Viewing Ports on a Magnetron System

  1. Aug 22, 2008 #1
    I am currently usig a dc magnetron system to produce thin films on various different ypes of substrate, my problem is, the main viewing port (around 8" diameter) keeps getting a build up of thin film on it, effectively turning it into a mirror; this happens every time a sputter making it difficult to see inside the chamber.

    I have 2 questions regarding this-:

    1) What is the best solution to use to clean off this metallic build up (I have been using acetone, but it still needs alot of elbow grease!!)??

    2) Would it be possible to cover the inside of the window with say cling-film, and then just peel this off to stop the window always getting coated?

    Any help with this would be greatly appreciated.
     
  2. jcsd
  3. Aug 22, 2008 #2

    ZapperZ

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    1. You may need to scrap off the build-up. Just be careful to use non-metallic objects because you don't want to scratch too much of the mirror, and if you're cleaning it after you remove the window, you don't want to dink the knife edge (assuming you're using a CF flange for the window).

    2. Putting in cling-film is a bad idea if you are trying to maintain vacuum cleanliness. Besides, you might melt the plastic since the vapor is HOT! In general, you do not want any form of hydrocarbon inside a clean vacuum system. You may want to consider replacing the window with a window that has a shutter that you can close and open under vacuum. Many vacuum components company carry that (such as MDC, A&N, and Kurt Lesker). That may be the best solution to prevent such a thing.

    Zz.
     
  4. Aug 22, 2008 #3

    Redbelly98

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    djqcquinn, welcome to PF.

    Perhaps wrapping some heater tape around the window would prevent the buildup from happening there. Vapors tend to condense on the coldest surface available.

    You'd have to watch how hot you get the window. The window material or gasket (if rubber and not copper) will determine how hot you can get.
     
  5. Aug 22, 2008 #4

    MATLABdude

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    Here's what I've seen used:

    1) Pre-cleaned glass slides + scotch tape. Apply as many slides as desired/fit, and tape them to the window. The bigger the glass slides, the easier this'll be to do. You may get some virtual leaks with this method, but it'll just take a little longer to rough down.

    2) Get a piece of thicker (1/8", 3/16"? glass cut in roughly the shape of your window. Apply glass in view port, take out periodically and etch away the metal, or just get another piece cut.

    3) Remove the glass from the view port and perform the etch. Unfortunately, this opens up the chamber for as long as it requires to do the etching. You may also have (real) leaks from taking and putting this thing back together all the time

    4) Have your machine shop build you a "shutter" for the window controlled by one of your target shutters (if you've got one / can add one). I don't think Lesker makes anything like this, but you should check with whoever makes your system.

    5) Take a scour pad or steel wool to the glass window. May scratch your window, especially with the bits of film which act like a fine to not-so-fine grit. Good if you only care whether the plasma is on/off.
     
  6. Aug 23, 2008 #5

    Redbelly98

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    MATLABdude, I'm curious about what vacuum levels were achieved with the scotch tape method? I could see that working in a 10^ -5 or -6 Torr system. But I wouldn't expect it to work in a 10^ -9 or -10 Torr system.

    Disclaimer: it's been 10 years since I last worked with vacuum systems.
     
  7. Aug 23, 2008 #6

    ZapperZ

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    UHV systems (i.e. better than 10^-9 Torr) cannot have any "scotch tape" or hydrocarbons, as I've mentioned earlier. I think most sputtering system can work in the 10^-5 to 10^-8 Torr region, which does not require as strict of a vacuum hygiene.

    Still, when I train students in vacuum systems, I would never recommend such practices no matter what the vacuum level is, simply because if you start taking short cuts like this, you'll find it hard later on to get rid of the bad habits when you really have to deal with system that require a lot of care.

    Zz.
     
  8. Aug 23, 2008 #7

    MATLABdude

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    As ZapperZ says we get 10^-6 Torr easily, regularly achieve -7 and sometimes -8 as a base pressure. We take that with a bit of a grain of salt since the Ion gauge hasn't been calibrated in a while, either.
     
  9. Feb 19, 2009 #8
    hi guys... if the vacuum isnt beyond 10-6 mbar ..ona coating system we have useda a product called duraclit ..its a cleaning compound primarily for silver it easily removes this metal deposists on windows.the only dowside is you need to liberally clean with alcohol or ipa afterwards..
     
    Last edited by a moderator: Feb 19, 2009
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