Functional design of a pulsed two-frequency capacitively coupled plasma in CF4/Ar for SiO2 etching

Abstract

A capacitively coupled plasma (CCP) with a different frequency source at each of two parallel plates is a powerful tool for SiO2 etching. A time modulation of two-frequency CCP by a pulsed-power operation will be one of the practical solutions in the next generation of etchers, and will allow charging-free plasma processes for high-aspect-ratio holes or trench etching. We numerically predict the structure and functions of a pulsed two-frequency CCP in CF4(5%)/Ar, and discuss its ability to generate charge-free plasma processes. We also investigate the functional separation between plasma production by very high frequency (100 MHz) and bias voltage application by low frequency (1 MHz). Alternate injections of high-energy positive and negative ions are predicted during the off-phase of a pulsed two-frequency CCP.

Modeling of N<tex>$_2$</tex>–H<tex>$_2$</tex>Capacitively Coupled Plasma for Low-k Material Etching

“…In this paper, we present the simulation results of a two-frequency capacitively coupled plasma (2f-CCP) [13], [14] based on relaxation continuum (RCT) model [15]- [17] with an N -H gas mixture. The plasma and neutrals are simulated self-consistently in the calculation by considering the reactions and transport of both.…”

Comparison of etching characteristics of SiO2 with ArF photoresist in C4F6 and C4F8 based dual-frequency superimposed capacitively coupled plasmas

“…Although various research works have been reported in which numerical simulations [9][10][11][12][13][14][15][19][20][21][22][23][24][25][26] and plasma diagnostics [8,28,29,31] were performed to investigate the characteristics of the 2f-CCP etcher, only a few experimental works have been conducted on oxide etching [3,6]. The C 4 F 8 /CH 2 F 2 /O 2 /Ar and C 4 F 6 /CH 2 F 2 /O 2 /Ar mixture gas chemistries have been typically used for SiO 2 contact etching, but no detailed experimental works on the DFS-CCP etching system have been reported [3,6,8,16,18,22,31,36].…”

“…Moreover, in the case where an f LF of less than 2-4 MHz is used, the use of a higher f HF in the generation of the plasma is advantageous in achieving the functional separation of the HF and LF sources, i.e. independent control of the ion flux and energy bombarding the wafer surface [8,[12][13][14]19,20,25,26,31]. Numerical simulations [12][13][14]19,20,25,26] and experiments [8,31] also indicated that a higher ratio of f HF to f LF (f HF /f LF ) is required to retain independent control of the ion flux and energy on the wafer surface in a 2f-CCP etcher when the voltage in the HF power source is increased.…”

Discharge asymmetry induced by the pulsed radio-frequency current

“…For example, the pulsed plasmas have attracted much attention. [5][6][7][8][9] However, most of these works on pulsed plasmas have been limited only for the discharge driven by the pulsed form of the voltage rather than the current.…”