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Method for controlling ion energy distribution

  • US 9,208,992 B2
  • Filed: 01/27/2015
  • Issued: 12/08/2015
  • Est. Priority Date: 04/26/2010
  • Status: Active Grant
First Claim
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1. A method for plasma-based processing, comprising:

  • placing a substrate in a substrate support inside of a plasma chamber;

    forming a plasma in the plasma chamber;

    generating a periodic voltage function at a surface the substrate inside the plasma chamber, each cycle of the periodic voltage function at the surface of the substrate including a positive pulse peak followed by a constant negative voltage, a magnitude of the constant negative voltage is constant within each cycle of the periodic voltage function, and the constant negative voltage results in a monoenergetic distribution of ion energy at the surface of the substrate;

    wherein generating the periodic voltage function at the surface the substrate includes;

    producing a positive DC voltage outside of the plasma chamber with a DC voltage source, a magnitude of the DC voltage defines a magnitude of the constant negative voltage at the surface of the substrate and establishes an energy level of the monoenergetic distribution of ion energy at the surface of the substrate;

    coupling the positive DC voltage to the substrate support to apply a positive voltage pulse peak to the substrate support that effectuates the positive pulse peak at the surface of the substrate, a magnitude of the positive DC voltage is unvarying while the positive DC voltage is coupled to the substrate support;

    decoupling the positive DC voltage from the substrate support and coupling a ground potential to the substrate support after the positive DC voltage is decoupled from the substrate support, wherein the application of the ground potential effectuates a drop in a voltage of the substrate support to a first-lower-level and effectuates a drop in the positive pulse peak at the surface of the substrate to the constant negative voltage at the surface of the substrate;

    decoupling the ground potential from the substrate support while maintaining the positive DC voltage decoupled from the substrate support; and

    providing, while the ground potential and the positive DC voltage are decoupled from the substrate support, an uninterrupted compensation current, which is fixed in magnitude, to the substrate support with a current source that is separate from the DC voltage source to ramp down the voltage of the substrate support from the first-lower-level to a second-negative-lower-level, wherein the ramp down of the voltage at the substrate support maintains the constant negative voltage at the surface of the substrate, and the constant negative voltage at the surface of the substrate effectuates the monoenergetic distribution of ion energy at the surface of the substrate.

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