Switching circuit

A semiconductor processing tool comprising:

• a plasma chamber configured to deposit a material onto a substrate or etch a material from the substrate;
• and
• an impedance matching circuit operably coupled to the plasma chamber, the matching circuit comprising:
• an RF input configured to couple to an RF source;
• an RF output configured to couple to the plasma chamber;
• and
• a control circuit;
• and
• a variable reactance circuit operably coupled to the control circuit and configured to provide a variable reactance, the variable reactance circuit comprising fixed reactance components and corresponding switching circuits, wherein each of the switching circuits comprises:
• a diode;
• and
• a driver circuit operably coupled to the diode and configured to switch the diode, the driver circuit comprising:
• a biasing current source positioned to provide a bias current to bias the diode;
• a first switch operably coupled to the diode and the biasing current source;
• a second switch operably coupled to the diode;
• and
• a resistor coupled to the biasing current source;
• wherein, for each diode of each switching circuit, the control circuit is configured to (a) receive a value related to a voltage drop on the resistor, and (b) based on the value related to the voltage drop, adjust the bias current being provided by the biasing current source.

A method of impedance matching comprising:

• operably coupling a matching network between an RF source and a plasma chamber, the matching network comprising:
• a control circuit;
• and
• a variable reactance circuit operably coupled to the control circuit, the variable reactance circuit comprising fixed reactance components and corresponding switching circuits, wherein each of the switching circuits comprises:
• a diode;
• and
• a driver circuit operably coupled to the diode and configured to switch the diode, the driver circuit comprising:
• a biasing current source positioned to provide a bias current to bias the diode;
• a first switch operably coupled to the diode and the biasing current source;
• a second switch operably coupled to the diode;
• and
• a resistor coupled to biasing current source;
• altering a reactance of the variable reactance circuit by altering a state of at least one of the switching circuits;
• for each diode of each switching circuit:
• receiving a value related to a voltage drop on the resistor;
• based on the value related to the voltage drop, adjusting the bias current being provided by the biasing current source.