Impedance matching circuit for operation with a kilohertz rf generator and a megahertz rf generator to control plasma processes

An impedance matching circuit, comprising:

• a first circuit including,
• a first shunt circuit;
• a first series circuit coupled to the first shunt circuit;
• a second shunt circuit coupled to the first series circuit;
• a second series circuit coupled to the first series circuit and the second shunt circuit;
• a third shunt circuit coupled to the second series circuit;
• a third series circuit coupled to the third shunt circuit and the second series circuit;
• wherein the first circuit has an input coupled to a kilohertz (kHz) radio frequency (RF) generator;
• a second circuit including,
• a fourth series circuit;
• a fourth shunt circuit coupled to the fourth series circuit;
• a fifth series circuit coupled to the fourth series circuit and the fourth shunt circuit;
• a fifth shunt circuit coupled to the fifth series circuit;
• a sixth series circuit coupled to the fifth series circuit and the fifth series circuit;
• a sixth shunt circuit coupled to the sixth series circuit;
• a seventh series circuit coupled to the sixth series circuit and the sixth shunt circuit,
• wherein the second circuit has an input coupled to a low frequency megahertz (MHz) RF generator;
• a third circuit including,
• a seventh shunt circuit;
• an eighth shunt circuit coupled to the seventh shunt circuit;
• an eighth series circuit coupled to the seventh shunt circuit and eighth shunt circuit,
• wherein the third circuit has an input coupled to a high frequency MHz RF generator;
• an output of the first, second, and third circuits coupled to an input of an RF transmission line, and an output of the RF transmission line is coupled to an electrode of a plasma chamber,
• wherein the first circuit and the second circuit provide isolation between a kHz RF signal sent through the first circuit and a low frequency MHz RF signal sent through the second circuit, wherein the isolation between the kHz RF signal and the low frequency MHz RF signal is provided by an increased number of tuning elements at an interface between the kHz and MHz RF signals as compared to an interface between the low frequency MHz RF signal and a high frequency MHz RF signal sent through the third circuit.

A plasma processing system comprising:

• a kilohertz (kHz) radio frequency (RF) signal generator for generating a first RF signal;
• a low frequency megahertz (MHz) generator for generating a second RF signal;
• a high frequency MHz generator for generating a third RF signal;
• an impedance matching circuit coupled to the kHz RF generator, the low frequency MHz RF generator, and the high frequency MHz RF generator for receiving the first, second, and third RF signals to generate a modified RF signal, wherein the impedance matching circuit includes,
• a first circuit coupled at an end to the kHz RF signal generator for transferring the first RF signal;
• a second circuit coupled at an end to the low frequency MHz RF generator for transferring the second RF signal;
• a third circuit coupled at an end to the high frequency MHz RF generator for transferring the third RF signal;
• wherein the first circuit includes a first number of tuning elements greater than a second number of tuning elements of the third circuit and the second circuit includes a third number of tuning elements greater than the second number of tuning elements of the third circuit to increase an amount of isolation between the first RF signal that is transferred via the first circuit and the second RF signal that is transferred via the second circuit compared to an amount of isolation between the second RF signal and the third RF signal;
• and
• a plasma chamber having an electrode for receiving the modified RF signal to generate plasma within the plasma chamber.