Method and apparatus for coupling a microwave source in an electron cyclotron resonance system
First Claim
1. An electron cyclotron resonance apparatus comprising:
- a processing chamber;
gas supplying means for supplying gas to said processing chamber;
microwave generating means for generating microwave energy;
circular polarizing means coupled to said microwave generating means, for circularly polarizing the microwave energy in a first angular direction and for suppressing circularly polarized microwave energy in a second angular direction opposite the first angular direction;
magnetic field generating means for generating a magnetic field in said processing chamber, the magnetic field causing electrons in said processing chamber to rotate in the first angular direction in electron cyclotron resonance to thereby generate a plasma of the gas in the processing chamber;
transforming means coupled between said circular polarizing means and said processing chamber, for matching the impedance of said circularly polarized microwave energy in the first angular direction, to the impedance of said plasma, to thereby couple the circularly polarized microwave energy in the first angular direction to the plasma; and
means for adjusting said magnetic field generating means to minimize remnants of microwave energy which are reflected from the plasma;
wherein said adjusting means comprises;
means, coupled to said processing chamber, for measuring said remnants of reflected microwave energy in said chamber; and
an electronic controller, responsive to said measuring means and operatively connected to said magnetic field generating means, for adjusting said magnetic field generating means to minimize the measured remnants of reflected microwave energy.
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Abstract
A microwave source is coupled to an electron cyclotron resonance (ECR) system by circularly polarizing the microwave energy from the source in an angular direction with cooperates with the ECR system'"'"'s magnetic field to produce electron cyclotron resonance, and coupling the circularly polarized microwave energy to the plasma using a quarter wave vacuum window transformer having a dielectric constant which matches the impedance of the circularly polarized microwave energy to the impedance of the plasma. The impedance matching transformer is preferably a vacuum window of the ECR chamber having quarter wave thickness and the appropriate dielectric constant. For high density plasmas in a standard ECR system of 6 cm radius an alumina window 0.98 cm thick procides optimum coupling. The reflected power from the plasma is thereby minimized to provide a dense plasma for the ECR tool while reducing or eliminating the need for manual external tuners for the microwave source.
102 Citations
15 Claims
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1. An electron cyclotron resonance apparatus comprising:
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a processing chamber; gas supplying means for supplying gas to said processing chamber; microwave generating means for generating microwave energy; circular polarizing means coupled to said microwave generating means, for circularly polarizing the microwave energy in a first angular direction and for suppressing circularly polarized microwave energy in a second angular direction opposite the first angular direction; magnetic field generating means for generating a magnetic field in said processing chamber, the magnetic field causing electrons in said processing chamber to rotate in the first angular direction in electron cyclotron resonance to thereby generate a plasma of the gas in the processing chamber; transforming means coupled between said circular polarizing means and said processing chamber, for matching the impedance of said circularly polarized microwave energy in the first angular direction, to the impedance of said plasma, to thereby couple the circularly polarized microwave energy in the first angular direction to the plasma; and means for adjusting said magnetic field generating means to minimize remnants of microwave energy which are reflected from the plasma; wherein said adjusting means comprises; means, coupled to said processing chamber, for measuring said remnants of reflected microwave energy in said chamber; and an electronic controller, responsive to said measuring means and operatively connected to said magnetic field generating means, for adjusting said magnetic field generating means to minimize the measured remnants of reflected microwave energy. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. The method for coupling a microwave source in an electron cyclotron resonance system, the electron cyclotron resonance system including a processing chamber, means for supplying gas to the processing chamber, and means for generating a magnetic field in the processing chamber, the magnetic field causing electrons in the processing chamber to rotate in a first angular direction in electron cyclotron resonance to thereby generate a plasma of the gas in the processing chamber, said method comprising the steps of:
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circularly polarizing the microwave energy from the microwave source in the first angular direction and suppressing circularly polarized microwave energy in a second angular direction opposite the first angular direction; matching the impedance of the circularly polarized microwave energy in the first angular direction to the impedance of the plasma; and adjusting the magnetic field generating means to minimize remnants of microwave energy which are reflected from the plasma; wherein said adjustment step comprises the steps of; measuring the remnants of microwave energy which are reflected from the plasma; and adjusting the magnetic field generating means to minimize the remnants of the measured reflected microwave energy. - View Dependent Claims (12, 13, 14, 15)
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Specification