Determining high frequency operating parameters in a plasma system

Abstract

Determining a high frequency operating parameter in a plasma system including a plasma power supply device coupled to a plasma load using a hybrid coupler having four ports is accomplished by: generating two high frequency source signals of identical frequency, the signals phase shifted by 90° with respect to one another; generating a high frequency output signal by combining the high frequency source signals in the hybrid coupler; transmitting the high frequency output signal to the plasma load; detecting two or more signals, each signal corresponding to a respective port of the hybrid coupler and related to an amplitude of a high frequency signal present at the respective port; and based on an evaluation of the two or more signals, determining the high frequency operating parameter.

What is claimed is: 
     
         1 . A plasma power evaluation device comprising:
 a measurement circuit configured to be coupled to a port of a hybrid coupler in a plasma system having two high frequency power sources coupled to a plasma load through the hybrid coupler;   a detector coupled to the measurement circuit and configured to generate a signal corresponding to an amplitude of a high frequency signal received by the detector; and   a processing device coupled to the detector to receive the signal and operable to determine one or more high frequency operating parameters based on the signal;   wherein the one or more high frequency operating parameters are selected from the group consisting of:
 a reflection factor of the plasma load, 
 a voltage standing wave ratio, 
 a phase angle between a wave running to the plasma load and a wave reflected by the plasma load, 
 a power of a high frequency signal reflected by the plasma load, 
 a sum of a power of the high frequency output signal and the power of the high frequency signal reflected by the plasma load, and 
 a sum of powers reflected by the high frequency power sources. 
   
     
     
         2 . The device of  claim 1 , wherein the processing device is operable to determine at least two high frequency operating parameters from signals received from two or more detectors. 
     
     
         3 . The device of  claim 1 , further comprising:
 an A/D converter coupled between the detector and the processing device to convert the signal from an analog signal to a digital signal;   wherein the processing device comprises a digital signal processor configured to receive and process the digital signal.   
     
     
         4 . The device of  claim 1 , wherein the processing device includes a control output to transmit control signals to the two high frequency power sources. 
     
     
         5 . The device of  claim 1 , wherein the processing device includes a control output to transmit control signals to an impedance matching circuit coupled between the hybrid coupler and the plasma load. 
     
     
         6 . A plasma processing power control system for a plasma power system having two high frequency power sources coupled to a hybrid coupler to generate a high frequency output signal for a plasma load, the system comprising:
 a set of detection circuits configured to be coupled to respective ports of the hybrid coupler and to generate respective signals corresponding to an amplitude of a high frequency signal detected at the respective port of the hybrid coupler; and   a processing device coupled to the detection circuits to receive the signals and operable to determine a parameter value based on the signals, the parameter value representing a power transfer characteristic associated with power being transferred between the high frequency power sources and the plasma load.   
     
     
         7 . The system of  claim 6 , wherein the processing device is further operable to control the high frequency power sources based on the determined parameter value so as to maintain a constant high frequency output signal. 
     
     
         8 . The system of  claim 6 , wherein the processing device is further operable to control an impedance matching circuit based on the determined parameter value to match an impedance of the plasma load to an output impedance of the plasma power system. 
     
     
         9 . The system of  claim 6 , wherein the power transfer characteristic is a forward power, a reverse power, or a phase angle characteristic. 
     
     
         10 . The system of  claim 6 , wherein each detection circuit of the set of detection circuits includes a respective measurement circuit to couple the detection circuit to the respective port.