Method of and apparatus for controlling reactive impedances of a matching network connected between an RF source and an RF plasma processor

Apparatus for supplying an r.f. field to a plasma in a vacuum plasma chamber for processing a workpiece, comprising a reactive impedance element for supplying the r.f. field to the plasma, the reactive impedance element being connected via a matching network to an r.f. source, the r.f. field having a frequency and power level sufficient to ignite the gas into the plasma and to maintain the plasma, the matching network including first and second variable reactances for controlling loading of the source and tuning a load including the reactive impedance element and the plasma to the source, a controller for (1) determining the amount the first variable reactance is to change for each unit change of the second variable reactance to attain the best match between the impedances seen looking into and out of output terminals of the r.f. source by changing the values of the first and second variable reactances, and (2) then varying the values of the first and second variable reactances based on the determination of (1) until the best impedance match between the impedances seen looking into and out of output terminals of the r.f. source is attained.

A memory for use with a computer for controlling an r.f. field supplied to a plasma in a vacuum plasma chamber for processing a workpiece, the r.f. field being supplied to the plasma by a reactive impedance element connected via a matching network to an r.f. source, the r.f. field having a frequency and power level sufficient to ignite the gas into the plasma and to maintain the plasma, the matching network including first and second variable reactances that control loading of the source and resonating a load including the reactive impedance element and the plasma to the source, the memory storing signals to cause the computer to:

• (1) determine the amount the first of the variable reactances is to change for each unit change of the second of the variable reactances to attain the best match between the impedances seen looking into and out of output terminals of the r.f. source by commanding the computer to change the values of the first and second variable reactances;
• and (2) then vary the values of the first and second variable reactances based on the determination (1) until the computer determines the best impedance match between the impedances seen looking into and out of output terminals of the r.f. source is attained.

A method of supplying an r.f. field to a plasma in a vacuum plasma chamber processing a workpiece, the r.f. field being supplied to the plasma by a reactive impedance element connected via a matching network to an r.f. source, the r.f. field having a frequency and power level sufficient to ignite the gas into the plasma and to maintain the plasma, the matching network including first and second variable reactances that control loading of the source and tuning a load including the reactive impedance element and the plasma to the source, the method comprising (1) determining the amount the first variable reactance is to change for each unit change of the second variable reactance by changing the values of the first and second variable reactances until an initial best match is attained between the impedances seen looking into and out of output terminals of the r.f. source, and (2) then varying the values of the first and second variable reactances based on the determination made in step (1) until the best impedance match between the impedances seen looking into and out of output terminals of the r.f. source is attained.

Apparatus for supplying an r.f. field to a plasma in a vacuum plasma chamber for processing a workpiece, comprising a reactive impedance element for supplying the r.f. field to the plasma, the reactive impedance element being connected via a matching network to an r.f. source, the r.f. field having a frequency and power level sufficient to ignite the gas into the plasma and to maintain the plasma, the matching network including first and second variable reactances for controlling loading of the source and tuning a load including the reactive impedance element and the plasma to the source, a controller for (1) determining the amount the first variable reactance is to change for each unit change of the second variable reactance by changing the values of the first and second variable reactances until the best initial match between the impedances as seen looking into and out of output terminals of the r.f. source is attained, and (2) then varying the values of the first and second variable reactances based on the determination of (1) until the best impedance match between the impedances seen looking into and out of output terminals of the r.f. source is attained.

A memory for use with a computer for controlling an r.f. field supplied to a plasma in a vacuum plasma chamber for processing a workpiece, the r.f. field being supplied to the plasma by a reactive impedance element connected via a matching network to an r.f. source, the r.f. field having a frequency and power level sufficient to ignite the gas into the plasma and to maintain the plasma, the matching network including first and second variable reactances that control loading of the source and resonating a load including the reactive impedance element and the plasma to the source, the memory storing signals to cause the computer to:

• (1) determine the amount the first of the variable reactances is to change for each unit change of the second of the variable reactances by commanding the computer to change the values of the first and second variable reactances until the best initial match between the impedances seen looking into and out of output terminals of the r.f. source is attained;
• and (2) then vary the values of the first and second variable reactances based on the determination (1) until the computer determines the best impedance match between the impedances seen looking into and out of output terminals of the r.f. source is attained.