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Annealing Al/Si contact increases resistance?!?!

  1. May 26, 2015 #1
    I'm trying to make an ohmic contact with p-type doped silicon. Using Aluminum.
    Under what condition of an Al/Si contact would annealing increase the resistance of the contact? or the silicon?
    two regions are defined using photolithography. A brief exposure to buffered oxide etch (6:1 H2O to HF) is followed by placing the sample in a vacuum chamber and, several hours later, with aluminum depostion.
    Initially, 2-pt probe measurements from two separated aluminum regions were somewhat non-linear.
    After annealing the sample, for 1 hr, the resistance increased by ~3 orders of magnitude!
    I would have thought that annealing would decrease the resistance and increase the linearity of the i-v curve.
    What is the problem? is there contamination or some other issue? thanks for your help or opinion.
  2. jcsd
  3. May 27, 2015 #2
    You could have diffusion of aluminium into the silicon. Aluminium would be a donor in silicon.
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