共查询到20条相似文献，搜索用时 15 毫秒
1.
A triple frequency capacitively coupled plasma(TF-CCP) has been considered to investigate the behavior of the sheath parameters.A self-consistent time-independent collisionless model has been developed.The sheath width and potential are calculated using the present model and compared with those calculated using a single-frequency(SF),a dual-frequency(DF)and a triple-frequency(TF) model for time independent collisionless cases.The sheath motion and sheath potential are found to be larger compared with those of SF and DF CCPs for an inhomogeneous sheath,and that of TF CCP for a homogeneous sheath.The effects of the source parameters,i.e.,current magnitudes,frequencies and phase difference,on the sheath parameters are investigated.The sheath parameters show higher values at higher source currents whereas they decrease with the increase of excitation frequencies.It has also been found that,by the proper choice of source frequencies and phase differences,it is possible to adjust the energy of ions when they hit the electrode. 相似文献
2.
LU Yijia 《等离子体科学和技术》2016,18(12):1175-1180
Dual-electrode capacitively coupled plasma discharges are investigated here to lower the non-uniformity of plasma density. The dual-electrode structure proposed by Jung splits the electrode region and increases the flexibility of fine tuning non-uniformity. Different RF voltages,frequencies, phase-shifts and electrode areas are simulated and the influences are discussed. RF voltage and electrode area have a non-monotonic effect on non-uniformity, while frequency has a monotonic effect. Phase-shift has a cyclical influence on non-uniformity. A special combination of 224 V voltage and 11% area ratio with 10 MHz lowers the non-uniformity of the original set(200 V voltage and 0% area ratio with 10 MHz) by 46.5%. The position of the plasma density peak at the probe line has been tracked and properly tuning the phase-shift can obtain the same trace as tuning frequency or voltage. 相似文献
3.
A one-dimensional fluid model is proposed to simulate the dual-frequency capacitively coupled plasma for Ar discharges. The influences of the low frequency on the plasma density, electron temperature, sheath voltage drop, and ion energy distribution at the powered electrode are investigated. The decoupling effect of the two radio-frequency sources on the plasma parameters, especially in the sheath region, is discussed in detail. 相似文献
4.
A novel technique to generate high-density plasma-called inductively coupled plasma (ICP), enhanced capacitively coupled plasma (CCP)- is successfully developed. The plasma can be generated using different frequency configurations, such as ICP-enhanced single-frequency ca- pacitively coupled plasma (SFCCP) and dual-frequency capacitively coupled plasma (DFCCP). The characteristics of the plasma in the following frequency combinations are mainly investigated using a Langmuir probe, SFCCP (60 MHz), DFCCP (60 MHz, 13.56 MHz), SFCCP (60 MHz) and inductively coupled plasma (13.56 MHz), DFCCP (60 MHz, 13.56 MHz) and inductively coupled plasma (13.56 MHz). In this letter, the nitrogen and hydrogen mixture gas discharge charac- teristics of different configurations are studied. After the analysis, we can acquire the electron temperature and ion density. Then, the effect of inductively coupled discharge on SFCCP and DFCCP can be summarized. In our preliminary investigations, the main results can be given as follows. ICP can make the density of SFCCP increase and the distribution of the electron temper- ature in a radial direction more uniform. In addition, ICP not only can make the ion density of DFCCP increase, but also can improve the radial uniformity. Further experiments may be needed to clarify the mechanism. 相似文献
5.
王森;张权治;马方方;王友年 《等离子体科学和技术》2024,26(6):064009-1-064009-9
A two-dimensional fluid model based on COMSOL Multiphysics is developed to investigate the modulation of static magnetic field on plasma homogeneity in a capacitively coupled plasma (CCP) chamber. To generate a static magnetic field, direct current is applied to a circular coil located at the top of the chamber. By adjusting the magnetic field’s configuration, which is done by altering the coil current and position, both the plasma uniformity and density can be significantly modulated. In the absence of the magnetic field, the plasma density exhibits an inhomogeneous distribution characterized by higher values at the plasma edge and lower values at the center. The introduction of a magnetic field generated by coils results in a significant increase in electron density near the coils. Furthermore, an increase in the sets of coils improves the uniformity of the plasma. By flexibly adjusting the positions of the coils and the applied current, a substantial enhancement in overall uniformity can be achieved. These findings demonstrate the feasibility of using this method for achieving uniform plasma densities in industrial applications. 相似文献
6.
The effect of a negative DC bias, |V dc|, on the electrical parameters and discharge mode is investigated experimentally in a radiofrequency (RF) capacitively coupled Ar plasma operated at different RF voltage amplitudes and gas pressures. The electron density is measured using a hairpin probe and the spatio-temporal distribution of the electron-impact excitation rate is determined by phase-resolved optical emission spectroscopy. The electrical parameters are obtained based on the waveforms of the electrode voltage and plasma current measured by a voltage probe and a current probe. It was found that at a low |V dc|, i.e. in α-mode, the electron density and RF current decline with increasing |V dc|; meanwhile, the plasma impedance becomes more capacitive due to a widened sheath. Therefore, RF power deposition is suppressed. When |V dc| exceeds a certain value, the plasma changes to α–γ hybrid mode (or the discharge becomes dominated by the γ-mode), manifesting a drastically growing electron density and a moderately increasing RF current. Meanwhile, the plasma impedance becomes more resistive, so RF power deposition is enhanced with |V dc|. We also found that the electrical parameters show similar dependence on |V dc| at different RF voltages, and α–γ mode transition occurs at a lower |V dc| at a higher RF voltage. By increasing the pressure, plasma impedance becomes more resistive, so RF power deposition and electron density are enhanced. In particular, the α–γ mode transition tends to occur at a lower |V dc| with increase in pressure. 相似文献
7.
Local measurement of plasma radial uniformity was performed in a dual frequency capacitively coupled argon plasma (DF-CCP) reactor using an optical probe. The optical probe collects the light emission from a small separate volume in plasma, thus enabling to diagnose the plasma uniformity for different experimental parameters. Both the gas pressure and the low-frequency (LF) power have apparent effects on the radial uniformity of argon plasma. With the increase in either pressure or LF power, the emission profiles changed from a bell-shaped to a double-peak distribution. The influence of a fused-silica ring around the electrodes on the plasma uniformity was also studied using the optical probe. Possible reasons that result in nonuniform plasmas in our experiments are discussed. 相似文献
8.
Although some progress in plasma modification of the polytetrafluoroethylene (PTFE) surface has been made recently, its adhesion strength still needs to be further improved. In this work, the surface of a PTFE sample was treated with a two-step in-situ method. Firstly, the PTFE surface was treated with capacitively coupled Ar plasma to improve its mechanical interlocking performance; then, Ar+NH3+CH4 plasma was used to deposit an a-CNx :H cross-linking layer on the PTFE surface to improve the molecular bonding ability. After treatment, a high specific surface area of 2.20 and a low F/C ratio of 0.32 were achieved on the PTFE surface. Its surface free energy was increased significantly and its maximum adhesion strength reached 77.1 N−10 mm−1, which is 56% higher than that of the single-step Ar plasma-treated sample and 32% higher than that of the single-step Ar+CH4+NH3 plasma-treated sample. 相似文献
9.
You HE;Yeong-Min LIM;Jun-Ho LEE;Ju-Ho KIM;Moo-Young LEE;Chin-Wook CHUNG 《等离子体科学和技术》2023,25(4):045401-045401
In general, as the radio frequency (RF) power increases in a capacitively coupled plasma (CCP), the power transfer efficiency decreases because the resistance of the CCP decreases. In this work, a parallel resonance circuit is applied to improve the power transfer efficiency at high RF power, and the effect of the parallel resonance on the electron energy distribution function (EEDF) is investigated in a 60 MHz CCP. The CCP consists of a power feed line, the electrodes, and plasma. The reactance of the CCP is positive at 60 MHz and acts like an inductive load. A vacuum variable capacitor (VVC) is connected in parallel with the inductive load, and then the parallel resonance between the VVC and the inductive load can be achieved. As the capacitance of the VVC approaches the parallel resonance condition, the equivalent resistance of the parallel circuit is considerably larger than that without the VVC, and the current flowing through the matching network is greatly reduced. Therefore, the power transfer efficiency of the discharge is improved from 76%, 70%, and 68% to 81%, 77%, and 76% at RF powers of 100 W, 150 W, and 200 W, respectively. At parallel resonance conditions, the electron heating in bulk plasma is enhanced, which cannot be achieved without the VVC even at the higher RF powers. This enhancement of electron heating results in the evolution of the shape of the EEDF from a bi-Maxwellian distribution to a distribution with the smaller temperature difference between high-energy electrons and low-energy electrons. Due to the parallel resonance effect, the electron density increases by approximately 4%, 18%, and 21% at RF powers of 100 W, 150 W, and 200 W, respectively. 相似文献
10.
We performed an experimental investigation on the electromagnetic effect and the plasma radial uniformity in a larger-area, cylindrical capacitively coupled plasma reactor. By utilizing a floating hairpin probe, dependences of the plasma radial density on the driving frequency and the radio-frequency power over a wide pressure range of 5–40 Pa were presented. At a relatively low frequency(LF, e.g. 27 MHz), an evident peak generally appears near the electrode edge for all pressures investigated here due to the edge field effect, while at a very high frequency(VHF, e.g.60 or 100 MHz), the plasma density shows a sharp peak at the discharge center at lower pressures, indicating a strong standing wave effect. As the RF power increases, the center-peak structure of plasma density becomes more evident. With increasing the pressure, the standing wave effect is gradually overwhelmed by the ‘stop band' effect, resulting in a transition in the plasma density profile from a central peak to an edge peak. To improve the plasma radial uniformity, a LF source is introduced into the VHF plasma by balancing the standing wave effect with the edge effect. A much better plasma uniformity can be obtained if one chooses appropriate LF powers, pressures and other corresponding discharge parameters. 相似文献
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13.
The self-excited second harmonic in radio-frequency capacitively coupled plasma was significantly enhanced by adjusting the external variable capacitor. At a lower pressure of 3 Pa, the excitation of the second harmonic caused an abnormal transition of the electron energy probability function, resulting in abrupt changes in the electron density and temperature. Such changes in the electron energy probability function as well as the electron density and temperature were not observed at the higher pressure of 16 Pa under similar harmonic changes. The phenomena are related to the influence of the second harmonic on stochastic heating, which is determined by both amplitude and the relative phase of the harmonics. The results suggest that the self-excited high-order harmonics must be considered in practical applications of low-pressure radio-frequency capacitively coupled plasmas. 相似文献
14.
余乐怡;陆文琪;张丽娜 《等离子体科学和技术》2024,26(8):085402-1-085402-6
The self-excited second harmonic in radio-frequency capacitively coupled plasma was significantly enhanced by adjusting the external variable capacitor.At a lower pressure of 3 Pa,the excitation of the second harmonic caused an abnormal transition of the electron energy probability function,resulting in abrupt changes in the electron density and temperature.Such changes in the electron energy probability function as well as the electron density and temperature were not observed at the higher pressure of 16 Pa under similar harmonic changes.The phenomena are related to the influence of the second harmonic on stochastic heating,which is determined by both amplitude and the relative phase of the harmonics.The results suggest that the self-excited high-order harmonics must be considered in practical applications of low-pressure radio-frequency capacitively coupled plasmas. 相似文献
15.
贺柳良;何锋;欧阳吉庭 《等离子体科学和技术》2024,26(4):044003-1-044003-8
The plasma density enhancement outside hollow electrodes in capacitively coupled radio-frequency(RF)discharges is investigated by a two-dimensional(2D)particle-in-cell/Monte-Carlo collision(PIC/MCC)model.Results show that plasma exists inside the cavity when the sheath inside the hollow electrode hole is fully collapsed,which is an essential condition for the plasma density enhancement outside hollow electrodes.In addition,the existence of the electron density peak at the orifice is generated via the hollow cathode effect(HCE),which plays an important role in the density enhancement.It is also found that the radial width of bulk plasma at the orifice affects the magnitude of the density enhancement,and narrow radial plasma bulk width at the orifice is not beneficial to obtain high-density plasma outside hollow electrodes.Higher electron density at the orifice,combined with larger radial plasma bulk width at the orifice,causes higher electron density outside hollow electrodes.The results also imply that the HCE strength inside the cavity cannot be determined by the magnitude of the electron density outside hollow electrodes. 相似文献
16.
The plasma density enhancement outside hollow electrodes in capacitively coupled radio-frequency (RF) discharges is investigated by a two-dimensional (2D) particle-in-cell/Monte-Carlo collision (PIC/MCC) model. Results show that plasma exists inside the cavity when the sheath inside the hollow electrode hole is fully collapsed, which is an essential condition for the plasma density enhancement outside hollow electrodes. In addition, the existence of the electron density peak at the orifice is generated via the hollow cathode effect (HCE), which plays an important role in the density enhancement. It is also found that the radial width of bulk plasma at the orifice affects the magnitude of the density enhancement, and narrow radial plasma bulk width at the orifice is not beneficial to obtain high-density plasma outside hollow electrodes. Higher electron density at the orifice, combined with larger radial plasma bulk width at the orifice, causes higher electron density outside hollow electrodes. The results also imply that the HCE strength inside the cavity cannot be determined by the magnitude of the electron density outside hollow electrodes. 相似文献
17.
A hybrid PIC/MC model is developed in this work for H2-xN2 capacitively coupled radio-frequency （CCRF） discharges in which we take into account 43 kinds of collisions reaction processes between charged particles （e-, H3＋, H＋, H＋, N＋, N＋） and ground-state molecules （H2, H＋ N2）. In addition, the mean energies and densities of electrons and ions （ 3, H＋, H＋）, and electric field distributions in the H2-N2 CCRF discharge are simulated by this model. Furthermore, the effects of addition of a variable percentage of nitrogen （0-30%） into the H2 discharge on the plasma processes and discharge characteristics are studied. It is shown that by increasing the percentage of nitrogen added to the system, the RF sheath thickness will narrow, the sheath electric field will be enhanced, and the mean energy of hydrogen ions impacting the electrodes will be increased. Because the electron impact ionization and dissociative ionization rates increase when N2 is added to the system, the electron mean density will increase while the electron mean energy and hydrogen ion density near the electrodes will decrease. This work aims to provide a theoretical basis for experimental studies and technological developments with regard to H2-N2 CCRF plasmas. 相似文献
18.
Dry etching of 6H silicon carbide （6H-SiC） wafers in a C4Fs/Ar dual-frequency capacitively coupled plasma （DF-CCP） was investigated. Atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS） were used to measure the SiC surface structure and compositions, respectively. Optical emission spectroscopy （OES） was used to measure the relative concentration of F radicals in the plasma. It was found that the roughness of the etched SiC surface and the etching rate are directly related to the power of low-frequency （LF） source. At lower LF power, a smaller surface roughness and a lower etching rate are obtained due to weak bombardment of low energy ions on the SiC wafers. At higher LF power the etching rate can be efficiently increased, but the surface roughness increases too. Compared with other plasma dry etching methods, the DF-CCP can effectively inhibit CχFγ films＇ deposition, and reduce surface residues. 相似文献
19.
Dry etching of 6H silicon carbide(6H-SiC)wafers in a C_4Fs/Ar dual-frequency capacitively coupled plasma(DF-CCP)was investigated.Atomic force microscopy(AFM)and X-ray photoelectron spectroscopy(XPS)were used to measure the SiC surface structure and compositions,respectively.Optical emission spectroscopy(OES)was used to measure the relative concentration of F radicals in the plasma.It was found that the roughness of the etched SiC surface and the etching rate are directly related to the power of low-frequency(LF)source.At lower LF power,a smaller surface roughness and a lower etching rate are obtained due to weak bombardment of low energy ions on the SiC wafers.At higher LF power the etching rate can be efficiently increased,but the surface roughness increases too.Compared with other plasma dry etching methods,the DF-CCP can effectively inhibit C_xF_y films'deposition,and reduce surface residues. 相似文献
20.
Haiyun TAN 《等离子体科学和技术》2022,24(10):105403
The electron heating characteristics of magnetic enhancement capacitively coupled argon plasmas in presence of both longitudinal and transverse uniform magnetic field have been explored through both theoretical and numerical calculations. It is found that the longitudinal magnetic field can affect the heating by changing the level of the pressure heating along the longitudinal direction and that of the Ohmic heating along the direction which is perpendicular to both driving electric field and the applied transverse magnetic field, and a continuously increased longitudinal magnetic field can induce pressure heating to become dominant. Moreover, the electron temperature as well as proportion of some low energy electrons will increase if a small longitudinal magnetic field is introduced, which is attributed to the increased average electron energy. We believe that the research will provide guidance for optimizing the magnetic field configuration of some discharge systems having both transverse and longitudinal magnetic field. 相似文献