Characteristics of a dual‐radio‐frequency cylindrical inductively coupled plasma

The plasma parameters such as electron density, effective electron temperature, plasma potential, and uniformity are investigated in a new dual‐frequency cylindrical inductively coupled plasma (ICP) source operating at two frequencies (2 and 13.56 MHz) and two antennas (a two‐turn high‐frequency antenna and a six‐turn low‐frequency (LF) antenna). It is found that the electron density increases with 2 MHz power, whereas the electron temperature and plasma potential decrease with 2 MHz power at a fixed 13.56 MHz power. Moreover, the plasma uniformity can be improved by adjusting the LF power. These results indicate that a dual‐frequency synergistic discharge in a cylindrical ICP can produce a high‐density, low‐potential, low‐effective‐electron‐temperature, and uniform plasma.     

N_2-H_2容性耦合等离子体电非对称效应的particle-in-cell/Monte Carlo模拟

H_2-N_2混合气体电容性耦合射频放电在有机低介电系数材料刻蚀中具潜在研究意义.采用paxticle-incell/Monte Carlo模型模拟了双频(13.56 MHz/27.12 MHz)电压源分别接在结构对称的两个电极上的H_2-N_2容性耦合等离子体特征,研究了其电非对称效应.模拟结果表明,通过调节两谐波间的相位角θ,可以改变其电场、等离子体密度、离子流密度的轴向分布及离子轰击电极的能量分布.当相位角θ为0°时,低频电极(晶片)附近主要离子(H_3~+)的密度最小,离子(H_3~+,H_2~+,H~+)轰击低频电极的流密度及平均能量最高;当θ从0°变化90°时,低频电极的自偏压从-103V到106V近似线性增加,轰击电极的离子流密度变化约±18%,H~+离子轰击低频电极的最大能量约减小2.5倍,轰击电极的平均能量约变化2倍,表明氢离子能量和离子流几乎能独立控制.     

Effects of discharge frequency on plasma characteristics andetching characteristics in high density Cl2 plasma:comparison of ultrahigh-frequency plasma and radio-frequency plasma

We investigated the effects of discharge frequency on the characteristics of polycrystalline-silicon etching rates and on the etching selectivity on the gate oxide (SiO₂). An ultrahigh-frequency (UHF) plasma excited at 500 MHz was found to possess a wider process window for highly selective polycrystalline silicon etching than did an inductively coupled plasma excited at 13.56 MHz. The ionization rate in the UHF plasma is nearly constant at discharge pressures from 3-20 mtorr because the discharge frequency is higher than the electron-collision frequency in that plasma     

Discharge characteristic of very high frequency capacitively coupled argon plasma

The discharge characteristics of capacitively coupled argon plasmas driven by very high frequency discharge are studied. The mean electron temperature and electron density are calculated by using the Ar spectral lines at different values of power(20 W–70 W) and four different frequencies(13.56 MHz, 40.68 MHz, 94.92 MHz, and 100 MHz). The mean electron temperature decreases with the increase of power at a fixed frequency. The mean electron temperature varies nonlinearly with frequency increasing at constant power. At 40.68 MHz, the mean electron temperature is the largest. The electron density increases with the increase of power at a fixed frequency. In the cases of driving frequencies of 94.92 MHz and 100 MHz, the obtained electron temperatures are almost the same, so are the electron densities. Particle-in-cell/MonteCarlo collision(PIC/MCC) method developed within the Vsim 8.0 simulation package is used to simulate the electron density, the potential distribution, and the electron energy probability function(EEPF) under the experimental condition.The sheath width increases with the power increasing. The EEPF of 13.56 MHz and 40.68 MHz are both bi-Maxwellian with a large population of low-energy electrons. The EEPF of 94.92 MHz and 100 MHz are almost the same and both are nearly Maxwellian.     

气压对于低气压双频容性耦合Ar/O2 等离子体放电特性影响的研究

 研究了气压对双射频氩氧混合等离子体电子温度和电子密度的影响。在13.56MHz低频功率和94.92MHz高频功率固定为60W和氩氧气体比为1:9的情况下，利用发射光谱法分析了气压不同时氩氧混合等离子体的放电光谱中的特征谱线的变化规律。使用一维质点网格法(PIC-MC)静电模型计算了电子温度和电子密度。结果表明：电子温度随着气压的增加先降低后升高，与实验结果趋势相吻合；电子密度随着气压的增加先增大后减小。     

94-GHz 25-kW CW low-voltage harmonic gyrotron

A low-voltage second-harmonic gyrotron intended as a compact lightweight source has been designed and evaluated with a particle-tracing code and the particle-in-cell code MAGIC. The two codes are shown to be in good agreement when applied to a conventional fundamental-frequency gyrotron and also to the novel second-harmonic gyrotron. The 25-kW continuous wave (CW) 94-GHz gyrotron with a predicted conversion efficiency of 32% and device efficiency of 22.5% is driven by a 25-kV 4.5-A (υ_⊥/υ₂=1.5, Δυ_z/υ_z=7%) electron beam from a magnetron injection gun and employs a low-loss TE₀₂₁/TE₀₃₁ complex cavity for mode control. Although the 17-kG CW gyrotron will use a cryogen-free high-T_c superconducting magnet, a 94-GHz prototype will be tested at low duty with a conventional low-T_c superconducting magnet     

CHF3双频电容耦合放电等离子体特性研究

研究了用于SiCOH 低介电常数薄膜刻蚀的CHF₃气体在1356 MHz/2 MHz,2712 MHz/2 MHz和60 MHz/2 MHz双频电容耦合放电时的等离子体性质.发现2 MHz低频源功率的增大主要导致F基团密度的增大;而高频频率从1356,2712增大到60 MHz,导致CF₂基团的密度增大和电极之间F基团密度的轴向空间不均匀性增加.根据电子温度的分布规律及离子能量随高频源频率的变化关系,提出CF₂基团的产生主要通过电子-中性气体碰撞,而F基团的产生是离子-中性气体碰撞的结果. 关键词： 双频电容耦合放电 3等离子体')" href="#">CHF₃等离子体     

Slotted third-harmonic gyro-TWT amplifier experiment

The first operation of a slotted third-harmonic gyrotron traveling-wave amplifier is reported. The low-magnetic-field moderate-voltage gyrotron amplifier's 62-keV 2.5-A υ_⊥ /υ_∥=1.2 axis-encircling electron beam was supplied by a gyroresonant RF accelerator. The 10-GHz 1.3-kG single-section slotted third-harmonic amplifier is stable and yielded 12.5 dB of small signal gain with a bandwidth of 2.5%. The experiment was performed as a scaled proof-of-principle test of the 95-GHz multisection slotted amplifier under development at CPI (formerly Varian)     

激发频率对高氢稀释下纳米晶硅薄膜生长特性的影响

利用等离子体增强化学气相沉积技术,在高氢稀释条件下,研究不同激发频率对纳米晶硅薄膜生长特性的影响.剖面透射电子显微镜(TEM)分析结果显示,不同激发频率下制备的纳米晶硅薄膜晶化区均呈锥状结构生长,但13.56 MHz激发频率下制备的纳米晶硅薄膜最初生长阶段存在非晶态孵化层,即纳米晶硅薄膜的形成经历了由非晶态孵化层到晶态结构层的转变.而高激发频率(40.68 MHz)下硅纳米晶则能直接在非晶态衬底上生长形成.Raman谱和红外吸收谱测量结果表明高激发频率(40.68 MHz)下制备的纳米晶硅薄膜不但具有较高     

Study of gain in C-band deflection cavities for afrequency-doubling magnicon amplifier

An experimental study of the gain between two half-wavelength, 5.7-GHz TM₁₁₀ mode pillbox cavities, separated by a quarter-wavelength drift space, and powered by a 170-A, 500-keV electron beam immersed in an 8.1-kG magnetic field is reported. These cavities constitute the first section of a planned multicavity deflection system, whose purpose is to spin up an electron beam to high transverse momentum (α≡υ⊥/υ_z⩾1) for injection into the output cavity of a frequency-doubling magnicon amplifier. A gain of ~15 dB was observed in the preferred circular polarization, at a frequency shift of approximately -0.18%, in the opposite circular polarization, at a frequency shift of approximately +0.06%. These results are in good agreement with theory     

13.56 MHz 低频功率对60 MHz射频容性耦合等离子体的电特性的影响

使用补偿朗缪尔探针诊断技术,研究了60MHz/13.56MHz双频激发容性耦合等离子体的空间电子行为,得到了电子能量概率函数(EEPF)随径向位置和低频输入功率的演变行为. 实验结果表明,13.56MHz射频输入功率的变化主要影响低能电子的布居,其影响随气压升高而加大. 在等离子体放电中心以外,EEPF呈现出双峰分布的特性,同时发现从放电中心到极板边缘,次能峰有逐渐向高能区漂移的现象,次能峰的出现显示了中能电子的增强的加热效应. 通过EEPF方法,计算了等离子体的电子温度、电子密度. 讨论了等离子体中的电 关键词： 双频激发容性耦合等离子体 朗缪尔探针诊断 电子加热模式     

Computer simulation of a carbon-deposition plasma in CH4

A transport and reaction model of a low-pressure, high-frequency (13.56 MHz) CH₄ plasma used for diamondlike carbon (a-C:H) deposition was developed. The model includes reactions among four molecular species (CH₄, C₂ H₆, C₂H₄, and H₂), five radicals and atom (CH₃, CH₂, CH, C₂H₅, and H), and four ions (CH₄⁺ , CH₃⁺, CH₅⁺, and C ₂H₅⁺). It also accounts for the influence of the sticking coefficient of species at the walls. Calculated values of the dissociation degree for several flow rates are in good agreement with experimental measurements made by quadrupole mass spectroscopy. A simple surface-model based on the hydrogen coverage of surface and ion flux and energy at the substrate surface was established. This model permitted the calculation of the deposition rate on the powered electrode as a function of the power applied to this electrode. Good agreement between experimental and calculated growth rates was obtained when CH₃, C₂H₅, and CH₂ were assumed to participate in film formation, and when hydrogen removal by ion bombardment with variable energy as a function of the power was included in the model     

CHF3 Dual-Frequency Capacitively Coupled Plasma by Optical Emission Spectroscopy

We investigate the intermediate gas phase in the CHFs 13.56 MHz/2 MHz dual-frequency capacitively couple plasma （CCP） for the SiCOH low dielectric constant （low-k） film etching, and the effect of 2MHz power on radicals concentration. The major dissociation reactions of CHF3 in 13.56MHz CCP are the low dissociation bond energy reactions, which lead to the low F and high CF2 concentrations. The addition of 2MHz power can raise the probability of high dissociation bond energy reactions and lead to the increase of F concentration while keeping the CF2 concentration almost a constant, which is of advantage to the SiCOH low-k films etching. The radical spatial uniformity is dependent on the power coupling of two sources. The increase of 2 MHz power leads to a poor uniformity, however, the uniformity can be improved by increasing 13.56 MHz power.     

Characterization and investigation of the unique plasma behavior caused by variable driving frequencies in the formation of cold atmospheric plasma

The study presents the characterization of a novel variable frequency (11–50 kHz) Atmospheric Pressure Plasma Jet (APPJ) source and comparison of the results with 13.56 MHz source, in terms of species generation and species temperature. The behavior of variable frequency APPJ at different frequency regimes was investigated using optical emission spectroscopy to understand the interaction with the ambient environment. The quantitative dependence of the radical generation on driving frequency and time of treatment was also analyzed by direct synthesis of H₂O₂ by plasma-water interaction. The plasma formed with a kHz driving frequency had a low treatment temperature, which was suitable for biological species, but the plasma generated with a 13.56 MHz driving frequency had a substantially higher radical density than the kHz plasma. As a result, the APPJ device's ability to tune the radical density and treatment temperature with a change in kHz frequency has been demonstrated.     

Feasibility study on high current ion beam extraction from anode spot plasma for large area ion implantation

In this paper, we have investigated the feasibility of the high current beam extraction from anode spot plasma as an ion source for large area ion implantation. Experiments have been carried out with the ambient plasma produced by inductive coupling with radio-frequency (RF) power of 200 W at the frequency of 13.56 MHz. Anode spot plasmas are generated near the extraction hole of 2 mm in diameter at the center of a bias electrode whose area exposed to the ambient plasma can be changed. It is found that the maximum ion beam current is extracted at the optimum operating pressure at which the area of bias electrode exposed to ambient plasma is fully covered with the anode spot plasma whose size is dominantly determined by the operating pressure for given gas species. It is also observed that the extracted ion beam current increases nonlinearly with the bias power due to the changes in size and shape of the anode spot plasma. With the well-established anode spot plasma operating at the optimum gas pressure, we have successfully extracted high current ion beam of 6.4 mA (204 mA/cm²) at the bias power of 22 W (∼10% of RF power), which is 43 times larger than that extracted from the plasma without anode spot. Based on the experimental results, criteria for electrode design and operating pressure for ion beam extraction from larger extraction aperture are suggested. In addition, the stability of anode spot plasma in the presence of ion beam extraction through an extraction hole is discussed in terms of the particle balance model.     

电子回旋共振-射频双等离子体沉积氧化硅薄膜过程中的射频偏压效应

本文利用六甲基乙硅氧烷(HMDSO)和氧气(O2)为反应气体,利用微波电子回旋共振-射频双等离子体化学气相沉积法沉积氧化硅薄膜,并利用发射光谱对等离子体特性进行原位诊断.研究表明,RF偏压对氧化硅薄膜沉积速率和薄膜中的化学键结构产生有意义的影响.小的直流自偏压会略微提高沉积速率;但随着直流自偏压的增加,离子轰击效应及刻蚀作用加强,薄膜的沉积速率下降.在13.56MHz和400kHz两个不同射频频率条件下所沉积的薄膜中,O和Si的比例基本相同,均超过2∶1;但400kHz射频偏压下薄膜中的碳成分比例比13.56MHz条件下的要高得多.这可以归因为高的射频偏压的应用不仅可增强离子轰击效应,而且与体等离子体相互作用,使高活性的氧原子增多;而低频偏压的作用主要是增强离子轰击效应.     

电极间距对μc-Si_(1-x)Ge_x:H薄膜结构特性的影响

采用射频等离子体增强化学气相沉积(RF-PECVD)技术,使用SiH4加GeH4的反应气源组合生长微晶硅锗(μc-Si1-x Gex:H)薄膜.研究了电极间距对μc-Si1-x Gex:H薄膜结构特性的影响.发现薄膜中的Ge含量随电极间距的降低逐渐增加.当电极间距降至7 mm时,μc-Si1-x Gex:H薄膜具有较大的晶粒尺寸并呈现较强的(220)择优取向,同时具有较低的微结构因子.通过薄膜结构特性的变化分析了反应气源的分解状态,认为Ge含量的提高主要是SiH4的分解率降低所导致的.在较窄的电极间距(7 mm)下,等离子体中GeH3基团的比例较大,增强了Ge前驱物的扩散能力,使μc-Si1-x Gex:H薄膜的质量得到提高.     

Effect of driving frequency on electron heating in capacitively coupled RF argon glow discharges at low pressure

A one-dimensional(1D) fluid model on capacitively coupled radio frequency(RF) argon glow discharge between parallel-plates electrodes at low pressure is established to test the effect of the driving frequency on electron heating. The model is solved numerically by a finite difference method. The numerical results show that the discharge process may be divided into three stages: the growing rapidly stage, the growing slowly stage, and the steady stage. In the steady stage,the maximal electron density increases as the driving frequency increases. The results show that the discharge region has three parts: the powered electrode sheath region, the bulk plasma region and the grounded electrode sheath region. In the growing rapidly stage(at 18 μs), the results of the cycle-averaged electric field, electron temperature, electron density, and electric potentials for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are compared, respectively. Furthermore,the results of cycle-averaged electron pressure cooling, electron ohmic heating, electron heating, and electron energy loss for the driving frequencies of 3.39, 6.78, 13.56, and 27.12 MHz are discussed, respectively. It is also found that the effect of the cycle-averaged electron pressure cooling on the electrons is to "cool" the electrons; the effect of the electron ohmic heating on the electrons is always to "heat" the electrons; the effect of the cycle-averaged electron ohmic heating on the electrons is stronger than the effect of the cycle-averaged electron pressure cooling on the electrons in the discharge region except in the regions near the electrodes. Therefore, the effect of the cycle-averaged electron heating on the electrons is to "heat" the electrons in the discharge region except in the regions near the electrodes. However, in the regions near the electrodes, the effect of the cycle-averaged electron heating on the electron is to "cool" the electrons. Finally, the space distributions of the electron pressure cooling the electron ohmic heating and the electron heating at 1/4 T, 2/4 T, 3/4 T, and 4/4 T in one RF-cycle are presented and compared.     

RF discharges at atmospheric pressure

The described plasma source is based on the RF torch discharge. The powered RF electrode of the torch discharge plasma source is made from the thin metal pipe with an inner diameter of 1–2 mm and with a length of several cm. The working gas (argon pure or with an admixture of reactive components) flows through the RF electrode as the nozzle. The electrode is connected through the matching unit to the RF generator of the frequency of 13.56 MHz.The advantage of this described plasma source consists in the fact that the torch discharge remains stable up to the atmospherical pressure of the working gas even in the liquid environments. Up to now the torch discharge has been used only for treatment in liquid environment only for archaeological artefacts. For further applications it is necessary to additional study of this phenomenon. While in previous papers we presented a measurement of different temperatures from spectra emitted by plasma, there is drawn attention to equiintensity maps inside the nozzle.     

13.56 MHz/2 MHz柱状感性耦合等离子体参数的对比研究

通过Langmuir双探针和发射光谱诊断方法,对比研究了驱动频率为13.56 MHz和2 MHz柱状感性耦合等离子体中电子密度和电子温度的径向分布规律.结果表明:在高频和低频放电中,输入功率的增加对等离子体参数产生了不同的影响,高频放电中主要提升了电子密度,低频放电中则主要提升了电子温度.固定气压为10 Pa,分别由高频和低频驱动时,电子密度的径向分布均为"凸型".而电子温度的分布差异比较明显,高频驱动时,电子温度在腔室中心较为平坦,在边缘略有上升;低频驱动时,电子温度随径向距离的增加而逐渐下降.为了进一步分析造成这种差异的原因,在相同放电条件下采集了氩等离子体的发射光谱图,利用分支比法计算了亚稳态粒子的数密度,发现电子温度的径向分布始终与亚稳态粒子的径向分布相反.继续升高气压到100 Pa,发现不论高频还是低频放电,电子密度的径向分布均从"凸型"转变为"马鞍形",较低气压时电子密度的均匀性有了一定的提升,但低频的均匀性更好.