Patent ID: 9384945
Filing Date: 2016-07-05
CPC Classification: H01J

Claim Text:
1. An automatic matching unit for automatically matching an impedance between a load and a radio frequency (RF) power supply for outputting a RF power having a predetermined frequency, the automatic matching unit comprising: a first variable capacitor connected in parallel to the load with respect to the RF power supply; a first stepwise capacitance varying mechanism configured to vary an electrostatic capacitance of the first variable capacitor in a stepwise manner; a second variable capacitor connected in series to the load with respect to the RF power supply; a second stepwise capacitance varying mechanism configured to vary an electrostatic capacitance of the second variable capacitor in a stepwise manner; an impedance measuring unit configured to measure an absolute value and a phase of an impedance of a load seen from an output terminal of the RF power supply; and a controller configured to variably control electrostatic capacitances of the first variable capacitor and the second variable capacitor via the first stepwise capacitance varying mechanism and the second stepwise capacitance varying mechanism such that the measured absolute value and the measured phase of the load impedance obtained by the impedance measuring unit become close to a predetermined reference absolute value and a predetermined phase, respectively, wherein the controller includes: a first matching control unit configured to variably control at least one of the electrostatic capacitances of the first variable capacitor and the second variable capacitor such that an operating point indicated by impedance coordinates representing the measured absolute value and the measured phase is moved to be within a first proximity range of a matching point, wherein said moving uses as a movement target a first reference line passing through the matching point and having a first inclination or uses a second reference line passing through the matching point and having a second inclination, wherein the first reference line is formed in a coordinate system having one orthogonal axis representing absolute value of the load impedance and another orthogonal axis representing phase of the load impedance, wherein the first inclination is defined with respect to the coordinate system, wherein the second reference line is formed in the coordinate system and wherein the second inclination is defined with respect to the coordinate system, the first inclination corresponding to variation rates of the absolute value of the load impedance and the phase of the load impedance in relation to the electrostatic capacitance of the first variable capacitor, the second inclination corresponding to variation rates of the absolute value of the load impedance and the phase of the load impedance in relation to the electrostatic capacitance of the second variable capacitor; and a second matching control unit configured to variably control at least one of the electrostatic capacitances of the first variable capacitor and the second variable capacitor after the operating point is positioned within the first proximity range, wherein the second matching control unit is configured to move the operating point to be within a second proximity range of the matching point with respect to the impedance coordinates by using as a movement target a third reference line that is formed in the coordinate system and that is perpendicular to the first reference line or to the second reference line with respect to the coordinate system and that passes through the matching point.