RF impedance matching network

A method of matching an impedance, the method comprising:

• determining a variable plasma impedance of a plasma chamber, with an impedance matching network electrically coupled between the plasma chamber and an RF source, wherein the RF source has a fixed RF source impedance, and the impedance matching network includes:
• a series electronically variable capacitor (“series EVC”) having a series variable capacitance and comprising a first plurality of capacitors, the series EVC coupled in series between the plasma chamber and the RF source;
• a shunt electronically variable capacitor (“shunt EVC”) having a shunt variable capacitance and comprising a second plurality of capacitors, the shunt EVC coupled in parallel between a ground and one of the plasma chamber and the RF source;
• and
• an inductor electrically coupled in series between the RF input and the RF output;
• determining a series capacitance value for the series variable capacitance and a shunt capacitance value for the shunt variable capacitance for creating an impedance match at an RF input of the impedance matching network;
• and
• generating a control signal to alter at least one of the series variable capacitance and the shunt variable capacitance to the series capacitance value and the shunt capacitance value, respectively, the control signal comprising a common input signal;
• wherein the alteration of the at least one of the series variable capacitance and the shunt variable capacitance is caused by at least one of a plurality of switching circuits, wherein each of the plurality of switching circuits is configured to switch one capacitor of the first plurality of capacitors and the second plurality of capacitors such that each of the first plurality of capacitors and the second plurality of capacitors is configured to be switched, each switching circuit comprising:
• an electronic switch electrically coupled to the one capacitor;
• and
• a driver circuit having a common output electrically coupled to the electronic switch, the driver circuit comprising:
• a first power switch receiving the common input signal and a first voltage and configured to switchably provide the first voltage to the common output in response to the common input signal, the first power switch comprising a plurality of optocoupler phototransistors connected in series;
• and
• a second power switch receiving the common input signal and a second voltage and configured to switchably provide the second voltage to the common output in response to the common input signal, wherein:
• the second voltage is opposite in polarity to the first voltage;
• the first power switch and the second power switch are configured to asynchronously provide the first voltage and the second voltage, respectively, to the common output in response to the common input signal, the electronic switch being switched according to the first voltage or the second voltage being provided to the common output;
• and
• when the plurality of optocoupler phototransistors of the first power switch are switched off, a voltage drop from the first voltage to the second voltage occurs across the plurality of optocoupler phototransistors.

A method of manufacturing a semiconductor comprising:

• placing a substrate in a plasma chamber configured to deposit a material layer onto the substrate or etch a material layer from the substrate;
• and
• energizing plasma within the plasma chamber by coupling RF power from an RF source into the plasma chamber to perform a deposition or etching, and while energizing the plasma:
• determining a variable plasma impedance of the plasma chamber, with an impedance matching network electrically coupled between the plasma chamber and the RF source, wherein the RF source has a fixed RF source impedance, and the impedance matching network includes:
• a series electronically variable capacitor (“series EVC”) having a series variable capacitance and comprising a first plurality of capacitors, the series EVC coupled in series between the plasma chamber and the RF source;
• a shunt electronically variable capacitor (“shunt EVC”) having a shunt variable capacitance and comprising a second plurality of capacitors, the shunt EVC coupled in parallel between a ground and one of the plasma chamber and the RF source;
• and
• an inductor electrically coupled in series between the RF input and the RF output;
• determining a series capacitance value for the series variable capacitance and a shunt capacitance value for the shunt variable capacitance for creating an impedance match at an RF input of the impedance matching network;
• and
• generating a control signal to alter at least one of the series variable capacitance and the shunt variable capacitance to the series capacitance value and the shunt capacitance value, respectively, the control signal comprising a common input signal;
• wherein the alteration of the at least one of the series variable capacitance and the shunt variable capacitance is caused by at least one of a plurality of switching circuits, wherein each of the plurality of switching circuits is configured to switch one capacitor of the first plurality of capacitors and the second plurality of capacitors such that each of the first plurality of capacitors and the second plurality of capacitors is configured to be switched, each switching circuit comprising:
• an electronic switch electrically coupled to the one capacitor;
• and
• a driver circuit having a common output electrically coupled to the electronic switch, the driver circuit comprising:
• a first power switch receiving the common input signal and a first voltage and configured to switchably provide the first voltage to the common output in response to the common input signal, the first power switch comprising a plurality of optocoupler phototransistors connected in series;
• and
• a second power switch receiving the common input signal and a second voltage and configured to switchably provide the second voltage to the common output in response to the common input signal, wherein:
• the second voltage is opposite in polarity to the first voltage;
• the first power switch and the second power switch are configured to asynchronously provide the first voltage and the second voltage, respectively, to the common output in response to the common input signal, the electronic switch being switched according to the first voltage or the second voltage being provided to the common output;
• and
• when the plurality of optocoupler phototransistors of the first power switch are switched off, a voltage drop from the first voltage to the second voltage occurs across the plurality of optocoupler phototransistors.