Method and system for controlling ion flux in an RF plasma

A plasma treatment system for generating an ion flow asymmetry comprising:

• a capacitively coupled radiofrequency plasma reactor, containing a gas or mixed gases under a total pressure P, wherein the plasma reactor includes a first electrode supplied with radiofrequency energy and a second electrode, and
• means for adjusting the total pressure P of the gas or of the mixed gases;
• and
• a voltage waveform generator, connected to the first electrode through a coupling capacitor, configured for generating a periodic radiofrequency voltage waveform V(t) having a lower frequency corresponding to a fundamental harmonic of the waveform of fundamental period T;
• wherein
• a standardized voltage waveform in time and in amplitude on an interval [−1;
• 1], f(u) is an approximate waveform with a degree of approximation of a standardized sawtooth radiofrequency function fSAW(u), u being a standardized time defined as the ratio of the time t over the fundamental period T, and
• the standardized sawtooth radiofrequency function fSAW(u) has a periodic pattern of fundamental period T consisting in a first linear portion of time-dependent change in the standardized voltage with a first slope p1, immediately followed by a second linear portion of time-dependent change of the standardized voltage with a second slope p2, the first and second slopes being of different amplitudes and of opposite signs, a minimum and a maximum of the pattern having the same unit amplitude;
• and
• the degree of approximation of the approximate waveform and the total pressure P of the gas or of the mixed gases are sufficient for causing appearance of an asymmetry of the ion flows between the ion flow at the first electrode and the ion flow at the second electrode.