Discharge mode and particle transport in radio frequency capacitively coupled Ar/O_(2) plasma discharges

Simulations are conducted on capacitively coupled Ar/O_(2)mixed gas discharges employing a one-dimensional fluid coupled with an electron Monte Carlo(MC)model.The research explores the impact of different O_(2)ratio and pressures on the discharge characteristics of Ar/O_(2)plasma.At a fixed Ar/O_(2)gas ratio,with the increasing pressure,higher ion densities,as well as a slight increase in electron density in the bulk region can be observed.The discharge remains dominated by the drift-ambipolar(DA)mode,and the flux of O(3P)at the electrode increases with the increasing pressure due to higher background gas density,while the fluxes of O(1D)and Ardecrease due to the pronounced loss rate.With the increasing proportion of O_(2),a change in the dominant discharge mode from a mode to DA mode can be detected,and the O_(2)-associated charged particle densities are significantly increased.However,Ar+density shows a trend of increasing and then decreasing,while for neutral fluxes at the electrode,Arflux decreases,and O(3P)flux increases with the reduced Ar gas proportion,while trends in O(1D)flux show slight differences.The evolution of the densities of the charged particle and the neutral fluxes under different discharge parameters are discussed in detail using the ionization characteristics as well as the transport properties.Hopefully,more comprehensive understanding of Ar/O_(2)discharge characteristics in this work will provide a valuable reference for the industry.

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快速调节迈克尔逊干涉仪的方法

本文介绍了一种快速调节迈克尔逊干涉仪的方法 ,此方法符合物理规律 ,学生易于掌握 ,在教学中取得了很好的效果。

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传感器测温实验装置的研制

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Fe-Cr-V-Ti系永磁体在机械力作用下的稳定性

研究了冲击和振动对四种Fe-Cr-Co-V-Ti系永磁体磁性的影响。结果发现:退磁率在冲击开始时比较大,随着冲击次数的增加逐渐减小,以致趋于稳定状态。磁稳定性的大小与冲击力大小有关。退磁率随振动频率的增加呈波动式变化;实验曲线的振幅随振动频率增加而渐减,最后都趋于稳定状态。退磁率在振动初期变化的比较快,随着时间的增长而趋于稳定状态。但含Mo的合金在2.5h附近有增磁现象。

Simulations of Ion Behaviors in a Photoresist Trench During Plasma Etching Driven by a Radio-Frequency Source

Ion＇s behavior plays an important role in plasma etching processes and is determined by the local electric potential in the etched trenches. In this study, with the trench powered by a radio frequency （rf） source, the Laplace equation is solved to obtain the electric potential. The ion trajectories and the ion energy distribution （IED） at the bottom of the trench are obtained self-consistently by tracking the ions in the trench. The results show that the aspect ratio of depth- to-width of the photoresist trench and the voltage amplitude of the rf source applied to the electrode are important parameters. The larger the aspect ratio and the smaller the amplitude are, the more ions hit the sidewalls, which results in a notching phenomenon. Meanwhile, there are a higher high-energy peak and a lower low-energy peak in the IED with the increase in aspect ratio.

Comparison between Dual Radio Frequency- and Pulse-Driven Sheath near Insulating Substrates

We carry out a comparison between the characteristics of radio frequency- and pulse-sheath near insulating substrates driven by dual frequency （DF） sources making use of the fluid model in which the self-bias voltage on the electrode is obtained consistently under a current balance condition. The results show that the combination of the higher and lower frequency source modulate the characteristics of the radio-frequency- and pulse-sheath： the higher frequency makes the physical quantities oscillate fast while the slow oscillating contour of variation in physical quantities is modulated by the lower frequency source. However, there are some differences between the capacity of mitigating the charging effects on the surface of the insulator, i.e., the pulsed driven plasma gains an advantage over the radio-frequency driven one because the insulating surface to neutralize the positive charge the ＇off＇ state of the pulse allow more electrons to reach due to the incident ion as the pulse being in the pulse＇s duty. In addition, the ion energy distribution （IED） bombarding the surface of the insulator has a range of energy for the radio-frequency bias while that for the pulse bias is discontinuous.

Study of Characteristics of the Radio-Frequency Sheath over a Substrate with a Circular Trench

Since processed substrates usually exhibit nonplanar surface structures in micro- electro-mechmfical-systems （MEMS） etching, a two-dimensional （2D） fluid model is developed to simulate the characteristics of the sheath near a conductive substrate with a circular trench, which is placed in an argon discharge powered by a radio-frequency （RF） current source. The model consists of 2D time-dependent fluid equations, the Poisson equation, and a current balance equation that can self-consistently determine the instantaneous voltage oll the substrate placed on a powered electrode. The effects of both the aspect ratio （depth/width） and the structure of the trench on the characteristics of the sheath are simulated. The time-averaged potential and electric field in the sheath are calculated and compared for different discharge parameters. The results show that the radial sheath profile is not uniform and always tends to adapt to the contour of the substrate, which is believed to be the moulding effect. Affected by the structure of the substrate surface, the potential and electric field near the inner and outer sidewalls of the trench exhibit obvious non-uniforlnity, which will inevitably lead to non-uniformity in etching, such as notching. Furthermore, with a fixed amplitude of the RF current source, the potential drops and the sheath thickness decrease with an increase in aspect ratio.

Two-Dimensional Simulation of a Dual Frequency Sheath Near an Electrode with a Cylindrical Hole

The characteristics of a collisional dual frequency （DF） sheath near an electrode with a cylindrical hole are studied by utilizing a two-dimensional model which includes time-dependent fluid equations coupled with the Poisson equation and an equivalent-circuit model, The effects of the gas pressure on the two-dimensional profiles of the potential, electric field, ion fluid velocity in a DF sheath are investigated. The simulation results show that the cylindrical hole on the electrode has a significant influence on the DF sheath structure, i.e., the sheath profile tends to wrap around the contour of the hole feature. Moreover, it is shown that the structure of the DF sheath is different from that of a single frequency （SF） sheath because the profile of the DF sheath is modulated by the combination of the high and low frequency sources. In addition the characteristics of the DF sheath are obviously affected by the collisional effects in the DF sheath.

高功率微波输出窗内侧击穿动力学的PIC/MCC模拟研究

高功率微波在受控热核聚变加热、微波高梯度加速器、高功率雷达、定向能武器、超级干扰机及冲击雷达等方面有着重要的应用.本文针对高功率微波输出窗内侧氩气放电击穿过程,建立了二次电子倍增和气体电离的一维空间分布、三维速度分布(1D3V)模型,并开发了相应的PIC/MC程序代码.研究了气压、微波频率、微波振幅对放电击穿的影响.结果表明:在真空情况下,介质窗放电击穿只存在二次电子倍增过程;在低气压和稍高气压时,二次电子倍增和气体电离共存;在极高气压时,气体电离占主导.给出了不同气压下电子、离子的密度和静电场的空间分布.此外还观察到,在500 mTorr时,随着微波振幅或微波频率的变化,气体电离出现的时刻和电离产生的等离子体峰值位置有较大差异,尤其是当微波频率(GHz)在数值上是微波振幅(MV/m)的2倍时,气体电离出现的较早.

A Multi-Scale Study on Silicon-Oxide Etching Processes in C_4F_8/Ar Plasmas

A multi-scale numerical method coupled with the reactor,sheath and trench model is constructed to simulate dry etching of SiO_2 in inductively coupled C_4F_8 plasmas.Firstly,ion and neutral particle densities in the reactor are decided using the CFD-ACE＋ commercial software.Then,the ion energy and angular distributions（IEDs and IADs） are obtained in the sheath model with the sheath boundary conditions provided with CFD-ACE＋.Finally,the trench profile evolution is simulated in the trench model.What we principally focus on is the effects of the discharge parameters on the etching results.It is found that the discharge parameters,including discharge pressure,radio-frequency（rf） power,gas mixture ratios,bias voltage and frequency,have synergistic effects on IEDs and IADs on the etched material surface,thus further affecting the trench profiles evolution.

Investigation of Dual Radio-Frequency Driven Sheaths and Ion Energy Distributions Bombarding an Insulating Substrate

Dual radio-frequency （rf） sources at widely different frequencies are often simultaneously used to separately optimize the plasma parameters and ion energy distributions （IEDs） incident onto a substrate. Characteristics of collisionless dual rf biased-sheaths and IEDs impinging on an insulating substrate are studied with a self- consistent one-dimensional fluid model. In order to describe the sheath dynamics over a wide range of frequency, the model includes all the time-dependent terms in the ion fluid equation. Meanwhile, an equivalent circuit model is used to self-consistently determine the relationship among the instantaneous voltage on the insulating substrate, the instantaneous sheath thickness, and the dual currents applied to the electrode. The numerical results show that some parameters such as the bias frequency and bias power of the lower frequency source are crucial for determining the parameters of dual rf biased-sheaths and IEDs arriving at the insulating substrate.

Two-Dimensional Self-Consistent Kinetic Model for Solenoidal Inductively Coupled Plasma

A two-dimensional self-consistent kinetic model was developed to study the influence of the various factors on the electron energy distribution function. These factors include gas pressure the driving frequency, the radius and length of the inductively coupled plasma equipment, the amplitude of the radio-frequency coil current, and the number of turns of rf coils. The spatial profiles of the rf electric field and power density have also been calculated under the same parameters. Numerical results show that the electron energy distribution functions are significantly modified and the spatial profiles of the rf electric field and rf power density are also demonstrated.

Study on atomic layer etching of Si in inductively coupled Ar/Cl_2 plasmas driven by tailored bias waveforms

Plasma atomic layer etching is proposed to attain layer-by-layer etching, as it has atomic-scale resolution, and can etch monolayer materials. In the etching process, ion energy and angular distributions（IEADs） bombarding the wafer placed on the substrate play a critical role in trench profile evolution, thus importantly flexibly controlling IEADs in the process. Tailored bias voltage waveform is an advisable method to modulate the IEADs effectively, and then improve the trench profile. In this paper, a multi-scale model, coupling the reaction chamber model,sheath model, and trench model, is used to research the effects of bias waveforms on the atomic layer etching of Si in Ar/Cl2 inductively coupled plasmas. Results show that different discharge parameters, such as pressure and radio-frequency power influence the trench evolution progress with bias waveforms synergistically. Tailored bias waveforms can provide nearly monoenergetic ions, thereby obtaining more anisotropic trench profile.？？？

Ion Transport to a Photoresist Trench in a Radio Frequency Sheath

We present a model which is used to study ion transport in capacitively coupled plasma （CCP） discharge driven by a radio-frequency （rf） source for an etching process. The model combines a collisional sheath model with a trench model. The sheath model can calculate the ion energy distributions （IEDs） and ion angular distributions （IADs） to specify the initial conditions of the ions incident into the trench domain （a simulation area near and in the trench）. Then, considering the charging effect on the photoresist sidewalls and the rf-bias applied to the substrate, the electric potentials in the trench domain are computed by solving the Laplace equation. Finally, the trajectories, IEDs and IADs of ions impacting on the bottom of the trench are obtained using the trench model. Numerical results show that as the pressure increases, ions tend to strike the trench bottom with smaller impact energies and larger incident angles due to the collision processes, and the existence of the trench has distinct influences on the shape of the IEDs and IADs. In addition, as the bias amplitude increases, heights of both peaks decrease and the IEDs spread to a higher energy region.

Effects of Tailed Pulse-Bias on Ion Energy Distributions and Charging Effects on Insulating Substrates

Abstract A hybrid sheath model, including a fluid model and a Monte Carlo （MC） method, is proposed to study ion energy distributions （IEDs） driven by a radiofrequency （RF） with a tailed pulse-bias on an insulating substrate, where a charging effect is obviously caused by the ions accumulated. This surface charging effect will significantly affect the IEDs on the insulating substrate. In this paper, a voltage compensation method is employed to eliminate the charging effect by making the pulse-bias waveform have a certain gradient. Furthermore, we investigate the IEDs under the condition of different pulse-bias duty ratios, waveforms, amplitudes, and cycle proportions. It is found that the parameters of the pulsed source can effectively modulate the IEDs on the insulating substrate and the charging effect, and more desired IEDs are obtained by using the voltage compensation method with modulations of pulse parameters.

Effects of Low-Frequency Source on a Dual-Frequency Capacitive Sheath near a Concave Electrode

A self-consistent two-dimensional （2D） collisionless fluid model is developed to sim- ulate the effects of the low-frequency （LF） power on a dual frequency （DF） capacitive sheath over an electrode with a cylindrical hole. In this paper, the time-averaged potential, electric field （E- field）, ion density in the sheath, and ion energy distributions （IEDs） at the center of the cylindrical hole＇s bottom are calculated and compared for different LF powers. The results show that the LF power is crucial for determining the sheath structure. As the LF power decreases, the potential drop decreases, the sheath becomes thinner, and the plasma molding effect seems to be more significant. The existence of a radial E-field near the sidewalls of a hole may cause a significant portion of ions to strike the sidewall and lead to the phenomenon of notching.