Functional separation of biasing and sustaining voltages in two-frequency capacitively coupled plasma

Abstract

Separation of the effects of rf sources used for biasing the wafer and for sustaining the plasma is studied by measuring the space profiles of net excitation rate of Ar(3p5) for a two-frequency capacitively coupled plasma as a representation of a typical oxide etcher. Measurements were performed in Ar and in CF4/Ar mixtures. For biasing supply operating at low frequency, 700 kHz, it was shown that the effect of the voltage becomes significantly smaller as the sustaining voltage is changed from high frequency, 13.56 MHz, to very high frequency (VHF), 100 MHz, and it even disappears for pulsed operation in mixtures. This is the result of the low dc self-bias at the VHF electrode that allows the high energy secondary electrons to leave the plasma without excessive contribution to ionization and dissociation.

Control of plasma properties in capacitively coupled oxygen discharges via the electrical asymmetry effect

“…In most of these applications, separate control of the ion flux and the ion bombarding energy onto the processing surface is of great importance for manufacturing efficiency and quality control [1]. The concept of dual frequency discharges, i.e., driving the plasma with two substantially different radio frequencies, had, therefore, been introduced as a promising way to achieve this separate control [2][3][4][5][6][7][8]. However, it is known that the coupling of both frequencies [9][10][11][12][13][14][15][16][17][18][19] and the effect of secondary electrons [8,[20][21][22] places a strong limitation to realize this goal.…”

Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas

“…[1][2][3][4][5][6][7][8] Fundamental insight is essential for the exponentially rising interest in homogeneous non-thermal plasmas at ambient pressure. [9][10][11][12][13][14] These plasmas are highly susceptible to instabilities initiated through mode transitions and associated variations in plasma ionization mechanisms.…”

Effects of the Capacitive Field in an Inductively Coupled Plasma Discharge

“…Theoretical and experimental investigations [1][2][3] were carried to find out characteristics of the ICP discharge. Among these research works, simulation is a useful tool for the analysis and prediction of ICP discharge.…”