Plasma monitoring apparatus

• US 6,291,999 B1
• Filed: 09/30/1998
• Issued: 09/18/2001
• Est. Priority Date: 09/30/1997
• Status: Expired due to Term

• Current Assignee: Daihen Corporation
• Original Assignee: Daihen Corporation
• Inventors: Kondo, Kazuki, Nishimori, Yasuhiro, Taniguchi, Michio
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): LEROUX, ETIENNE PIERRE
• Application Number:
  US09/163,536
• Time in Patent Office: 1,084 Days
• Field of Search: 324/95, 324/638, 324/464, 216/58, 216/67, 216/69, 333/17.3, 333/99 PL, 333/124, 73/19.01, 73/23.2, 73/35.08
• US Class Current: 324/464
• CPC Class Codes: H01J 37/32174 Circuits specially adapted for controlling the RF discharge
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence

Abstract

A plasma monitoring apparatus for monitoring a condition of plasma of a plasma load to which power is supplied from a high frequency power source through an impedance matcher provides with a first input impedance calculator for calculating an impedance as a first input impedance from a supply-side terminal of the matcher to the plasma load-side based on voltage, current and phase difference detected at the supply-side terminal of the matcher, a second input impedance calculator for calculating an impedance as a second input impedance from a load-side terminal of the matcher to the plasma load based on a impedance of a element of the matcher and the first input impedance and a plasma impedance calculator for calculating an impedance of the plasma load from the second input impedance and an impedance of a supply-side connecting the matcher and the plasma load.

Claims

1. A plasma monitoring apparatus for monitoring a status of a plasma load, comprising:

a high frequency power supply for supplying high frequency power to the plasma load;

an impedance matching circuit coupled between the high frequency power supply and the plasma load, said impedance matching circuit having a load-side terminal connected to the plasma load;

a voltage detector for detecting a voltage at the load-side terminal of the impedance matching circuit;

a current detector for detecting a current at the load-side terminal of the impedance matching circuit;

a phase difference detector for detecting a difference in phase between the voltage detected by the voltage detector and the current detected by the current detector;

an input impedance calculator for calculating a first impedance at the load-side terminal of the impedance matching circuit, based upon the detected voltage, the detected current and the detected phase difference; and

a plasma impedance calculator for calculating a second impedance of the plasma load, based upon both the first calculated impedance and a measured impedance of a line coupled between the load-side terminal of the impedance matching circuit and the plasma load.

2. The plasma monitoring apparatus of claim 1, further comprising a voltage calculator for calculating a peak-to-peak voltage of the plasma load based upon the second calculated impedance calculated by the plasma impedance calculator, and the current detected by the current detector.

3. A plasma monitoring apparatus for monitoring a status of a plasma load, comprising:

a high frequency power supply for supplying high frequency power to the plasma load;

an impedance matching circuit coupled between the high frequency power supply and the plasma load, said impedance matching circuit having a load-side terminal connected with the plasma load;

a voltage detector for detecting a first voltage at the load-side terminal of the impedance matching circuit;

a current detector for detecting a first current at the load-side terminal of the impedance matching circuit;

a phase difference detector for detecting a difference in phase between the first voltage detected by the voltage detector and the first current detected by the current detector;

a voltage and current calculator for calculating a second voltage and a second current at the load-side terminal of the impedance matching circuit, based upon the first detected voltage, the first detected current and the detected phase difference, and for also calculating a third voltage and a third current at a second end of a line coupled between the load-side terminal of the impedance matching circuit and the plasma load, based upon the second calculated voltage and the second calculated current; and

a plasma impedance calculator for calculating an impedance of the plasma load based upon the third calculated voltage and the third calculated current.

7. The plasma monitoring apparatus of claim 3, further comprising a voltage calculator for calculating a peak-to-peak voltage of the plasma load based upon the third calculated voltage at the first end of the line.

4. A plasma monitoring apparatus for monitoring a status of a plasma load, comprising:

a high frequency power supply for supplying a high frequency power to the plasma load;

an impedance matching circuit coupled between the high frequency power supply and the plasma load, said impedance matching circuit having a power input terminal coupled to the power supply and a load-side terminal connected to the plasma load;

a voltage detector for detecting a first voltage at the power input terminal of the impedance matching circuit;

a current detector for detecting a first current at the power input terminal of the impedance matching circuit;

a phase difference detector for detecting a difference in phase between the first voltage detected by the voltage detector and the first current detected by the current detector;

a first impedance calculator for calculating a first input impedance at the power input terminal of the impedance matching circuit based upon the first detected voltage, the first detected current and the detected phase difference;

a second impedance calculator for calculating a second input impedance at the load-side terminal of the impedance matching circuit based upon the first calculated input impedance and known and calculated impedances of elements forming the impedance matching circuit; and

a plasma impedance calculator for calculating an impedance of the plasma load based upon the second calculated input impedance and a measured impedance of a line coupled between the load-side terminal of the impedance matching circuit and the plasma load.

5. The plasma monitoring apparatus of claim 4, further comprising a current calculator for calculating a second current at the load-side terminal of the impedance matching circuit based upon the first detected voltage, the first detected current and the known and calculated impedances, and a voltage calculator for calculating a peak-to-peak voltage of the plasma load based upon the second calculated impedance and the second calculated current at the load-side terminal of the impedance matching circuit.

6. A plasma monitoring apparatus for monitoring a status of a plasma load, comprising:

a high frequency power supply for supplying high frequency power to the plasma load;

an impedance matching circuit coupled between the high frequency power supply and the plasma load, said impedance matching circuit having a power input terminal connected to the power supply and a load-side terminal connected to the plasma load;

a voltage detector for detecting a first voltage at the power input terminal of the impedance matching circuit;

a current detector for detecting a first current at the power input terminal of the impedance matching circuit;

a phase difference detector for detecting a difference in phase between the first voltage detected by the voltage detector and the first current detected by the current detector;

a first impedance calculator for calculating a first input impedance at the power input terminal of the impedance matching circuit based upon the first detected voltage, the first detected current and the detected phase difference;

a second impedance calculator for calculating a second input impedance at the load-side terminal of the impedance matching circuit based upon the first calculated input impedance and known and calculated impedances of elements forming the impedance matching circuit;

an effective power calculator for calculating an effective power of the high frequency power supply based upon the first detected voltage, the first detected current and the detected phase difference;

a first voltage and current calculator for calculating a second voltage and a second current at the load-side terminal of the impedance matching circuit, based upon the second calculated impedance and the calculated effective power; and

a second voltage and current calculator for calculating a third voltage and a third current at a first end of a line coupled between the load-side terminal of the impedance matching circuit and the plasma load, based upon the second calculated voltage and the second calculated current; and

a plasma impedance calculator for calculating an impedance of the plasma load based upon the third calculated voltage and the third calculated current at the first end of the line.

8. The plasma monitoring apparatus of claim 6, further comprising a voltage calculator for calculating a peak-to-peak voltage of the plasma load based upon the third calculated voltage at the first end of the line.