Influence of magnetic field strength on capacitively coupled CF₄ discharge at different pressures

Abstract

The influence of a homogeneous magnetic field parallel to the electrodes on the plasma properties and electron heating mode was investigated by a one-dimensional PIC/MCC simulations in electronegative CF4 discharges. The discharge conditions are Z = 3.5 cm, f = 13.56 MHz, V0 = 300 V, and the various gas pressure of 10 mTorr, 100 mTorr and 200 mTorr. It is found that, in the absence of a magnetic field, the discharges are electronegative at different pressures and the electronegativity is stronger at higher pressure. When a homogeneous magnetic field is applied, the electron density significantly increases and the electronegativity decreases to varying degrees at different pressures. At p = 10 mTorr and p = 100 mTorr, a transition from a hybrid combination of α and DA modes into a pure α mode is induced by a weak magnetic field. At p = 200 mTorr, a transition from a DA mode into a hybrid combination of α and DA modes is induced by a relatively high magnetic field. The strength of the magnetic field required to induce mode transition becomes stronger at higher gas pressures. This is because increasing the pressure reduces the mean free path and the frequent electron-neutral collisions disrupt electron gyromotion, thus the effects of the magnetic field are greatly reduced.

Numerical characterization of capacitively coupled CF4 plasmas modulated by anion beam injection

“…In this study, our team developed an open source 1D3V PIC/MC code [22], developed in Fortran code, to investigate the gas discharge process CF 4 . This code has been completed in series work, such as the breakdown process of CF 4 /SF 6 RF-CCP [23,24] and Ar dual-frequency (DF) CCP [25], MAE of CF 4 RF-CCP [17], IB RF-CCP [19] and EB RF-CCP [21].…”

“…The electron is difficult to achieve high energy of the dissociative ionization for creating CF + 2 , CF + , C + , F + . Thus, only electrons and F − , CF + 3 , CF − 3 are the mainly charged particles that must be calculated in CF 4 simulation [17,23,32]. Therefore, in our simulation code, four types of charged particles are considered.…”

“…Georgieva et al report on the simulation of 1D3V particle-in-cell/Monte Carlo (PIC/MC) of hybrid gas plasma (Ar/CF 4 /N 2 , with a ratio of 0.8/0.1/0.1), illustrating that the electron and CF3 + density can be modified by the electrode area ratio and the HF/LF voltage [16]. Additionally, modulation of electronegative plasma parameters can be achieved by applying a homogeneous magnetic field, known as the magnetic asymmetry effect (MAE) [17]. This study demonstrates the hybrid combination of the α-DA mode, initiated by a relatively strong magnetic field.…”

The electrical asymmetry effect in electronegative CF4 capacitive RF plasmas operated in the striation mode

“…The use of plasma etching for patterning thin film layers for the manufacturing of integrated circuits is of increasing importance [3]. Such etch processes [4][5][6] typically use electronegative gases such as CF 4 , C 4 F 8 , and SF 6 [7][8][9]. With the increase in complexity of such applications and the reduction of the minimum feature size of individual circuit elements, empirical methods fail and a detailed fundamental understanding of the plasma physics of such discharges is required as a basis for knowledge based plasma process development.…”