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Soft pulsing

  • US 10,157,729 B2
  • Filed: 04/23/2014
  • Issued: 12/18/2018
  • Est. Priority Date: 02/22/2012
  • Status: Active Grant
First Claim
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1. A plasma system comprising:

  • a master radiofrequency (RF) generator for generating a first portion of a master RF signal during a first state of a digital pulsed signal, a second portion of the master RF signal during a second state of the digital pulsed signal, and a third portion of the master RF signal during a third state of the digital pulsed signal, wherein the master RF signal is a sinusoidal signal;

    a slave RF generator for generating a slave RF signal in synchronization with the master RF generator, wherein the slave RF generator is configured to generate a first portion of the slave RF signal during the first state of the digital pulsed signal, a second portion of the slave RF signal during the second state of the digital pulsed signal, and a third portion of the slave RF signal during the third state of the digital pulsed signal, wherein during the first state, the digital pulsed signal has a first horizontal level, during the second state, the digital pulsed signal has a second horizontal level, and during the third state, the digital pulsed signal has a third horizontal level, wherein the third horizontal level is different from the first horizontal level and from the second horizontal level and the second horizontal level is different from the first horizontal level, wherein the digital pulsed signal transitions from an instance of the first horizontal level to an instance of the second horizontal level, transitions from the instance of the second horizontal level to an instance of the third horizontal level, and transitions from the instance of the third horizontal level to another instance of the first horizontal level to repeat the first, second, and third horizontal levels periodically;

    an impedance matching circuit coupled to the master RF generator via an RF cable, wherein the impedance matching circuit is coupled to the slave RF generator via another RF cable, wherein the impedance matching circuit is configured to modify the master RF signal and the slave RF signal to generate a modified RF signal; and

    a plasma chamber having an electrode coupled to the impedance matching circuit via an RF transmission line, the plasma chamber is configured to generate plasma based on the modified RF signal received by the electrode,wherein an envelope of the first portion of the master RF signal has a positive slope,wherein an envelope of the second portion of the master RF signal has a slope different from the positive slope of the envelope of the first portion of the master RF signal, andwherein an envelope of the third portion of the master RF signal has a slope of zero and the slope of zero is different from the slope of the envelope of the second portion of the master RF signal.

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