Effects of gas pressure on 60/13.56 MHz dual-frequency capacitively coupled plasmas

Abstract

The electron energy probability functions (EEPFs) were measured with increasing gas pressure in 60/13.56 MHz dual-frequency capacitively coupled plasma (DF-CCP) using compensated Langmiur electrostatic probe. The transition pressure of heating mode from collisionless to collisional heating in 60/13.56 MHz DF-CCP is found to be significantly lower than that in 13.56 MHz single-frequency CCP. As the pressure increases, the EEPFs change from bi-Maxwellian to Druyvesteyn type which is similar with that in 60 MHz single-frequency CCP. The pressure dependence of electron densities, effective electron temperatures, floating potentials, and plasma potentials in 60/13.56 MHz DF-CCP were measured and were compared with that in 60 MHz single-frequency CCP. The pressure dependence of these plasma parameters in 60/13.56 MHz DF-CCP is similar with that in 60 MHz single-frequency CCP.

Experimental and numerical investigations of electron density in low-pressure dual-frequency capacitively coupled oxygen discharges

“…Chung 17 investigated the scaling laws of plasma density and plasma potential versus the drive frequencies and applied voltages in the Ar discharge based on a homogeneous analytic model, and the results were compared with numerical simulations. In experiment Booth et al 20 and Curley et al 23 investigated the influences of low frequency (LF) power and gas flow rate on the electron density by the hairpin probe in the Ar/C 4 F 8 /O 2 discharge respectively, and Yuan et al 21 studied the effects of gas pressure on the electron density in 13.56/60 MHz capacitively coupled plasmas by using a compensated Langmuir probe. So far, most of theoretical and numerical studies focus on the argon discharge and experimental studies on the dependence of electron density on the control parameters for low-pressure oxygen discharges in DF-CCPs (Refs.…”

“…[13][14][15][16][17][18][19][20][21][22] Wakayama et al 13 studied the dynamic structure (e.g., electron density) of the DF-CCPs in the argon (25 mTorr) discharge by means of the particle-incell/Monte Carlo (PIC/MC) simulation and Yang et al 14 investigated the influences of high frequency (HF) frequency on the electron density in Ar and Ar/CF 4 discharges by an two-dimensional (2D) hybrid model and found that the peak of electron density transits from the edge to the center with increasing HF frequency. Kim et al 15 developed an analytic model for DF-CCPs to obtain the analytic expressions of plasma parameters (e.g., electron density) as a function of the effective parameters (e.g., effective frequency and effective voltage).…”

Effects of gas pressure on plasma characteristics in dual frequency argon capacitive glow discharges at low pressure by a self-consistent fluid model

“…The increases of electron density with increasing pressure in dual frequency of 30 MHz/2 MHz show similar results to those presented by Yuan et al, in experiments. [22] In the bulk plasma region, the electron density grows greatly as the gas pressure increases. Both in the powered sheath region and in the grounded sheath region, the electron densities increase slightly as the gas pressure increases.…”

“…A significant number of research studies have been done experimentally, theoretically and also by modeling to study dual frequency CCP in order to improve its application efficiency. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] For the dual frequency of (2 + 27) MHz and the gas pressure of 6.7 Pa with silicon electrodes, Kim et al measured the electron density and ion flux. [9] Li et al used a dual frequency CCP device to study the ion energy distributions in Ar/CF 4 plasma.…”

“…The effects of the gas pressure on the electron density, the effective electron temperature, the floating potential, and the plasma potential in 60-MHz/13.56-MHz dual frequency CCP were measured and compared with those of a 60-MHz single frequency CCP: the results were found to be similar. [22] Electron heating is the sum of the electron ohmic heating (collisional) and the electron pressure heating (collisionless). The collisionless electron heating is based on a strongly simplified version of the electron momentum balance equation, where inertia terms are ignored.…”