Numerical simulation of dual frequency etching reactors: Influence of the external process parameters on the plasma characteristics

Abstract

A one-dimensional particle-in-cell/Monte Carlo model is used to investigate Ar/ CF 4 /N 2 discharges sustained in capacitively coupled dual frequency reactors, with special emphasis on the influence of the reactor parameters such as applied voltage amplitudes and frequencies of the two voltage sources. The presented calculation results include plasma density, ion current, average sheath potential and width, electron and ion average energies and energy distributions, and ionization rates. The simulations were carried out for high frequencies ͑HFs͒ of 27, 40, 60, and 100 MHz and a low frequency ͑LF͒ of 1 or 2 MHz, varying the LF voltage and keeping the HF voltage constant and vice versa. It is observed that the decoupling of the two sources is possible by increasing the applied HF to very high values ͑above 60 MHz͒ and it is not defined by the frequency ratio. Both voltage sources have influence on the plasma characteristics at a HF of 27 MHz and to some extent at 40 MHz. At HFs of 60 and 100 MHz, the plasma density and ion flux are determined only by the HF voltage source. The ion energy increases and the ion energy distribution function ͑IEDF͒ becomes broader with HF or LF voltage amplitude, when the other voltage is kept constant. The IEDF is broader with the increase of HF or the decrease of LF.

Slope and amplitude asymmetry effects on low frequency capacitively coupled carbon tetrafluoride plasmas

“…Although more species may be present, it has been shown in previous studies that these are the dominant ones. [27][28][29][30][31][32][33] The energy-dependent cross sections for the electron-CF 4 collision processes are presented in Fig. 2(a).…”

Electron heating modes and frequency coupling effects in dual-frequency capacitive CF4 plasmas

“…This PIC/MCC code, which has been used in a previous study under different conditions [16], is one-dimensional in space and three dimensional in velocity (1D3V). Here, geometrically symmetric dual-frequency discharges are investigated in pure CF 4 . The electrodes are considered to be infinite, plane parallel, and separated by a distance of d=1.5 cm.…”

“…The plasma species traced in the model are electrons, and CF 3 + , CF 3 -and F -ions, found to be the dominant charged species in previous studies of CF 4 discharges [3][4][5][6][7]. The electron-neutral collision processes taken into account in the model are listed in Table 1, the cross sections for these collisions are taken from [72][73][74].…”

“…The electron-neutral collision processes taken into account in the model are listed in Table 1, the cross sections for these collisions are taken from [72][73][74]. The collision processes involving different ions and CF 4 molecules considered in the model are listed in Table 2. These processes are treated according to [3,[75][76].…”

“…CF 4 discharges exhibit a complex chemistry and become strongly electronegative under typical operating conditions. Under these conditions the plasma composition, the electron heating and ionization dynamics, and the discharge operation differ significantly from those of electropositive discharges [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”