Automatic emissive probe apparatus for accurate plasma and vacuum space potential measurements

We have developed an automatic emissive probe apparatus based on the improved inflection point method of the emissive probe for accurate measurements of both plasma potential and vacuum space potential.The apparatus consists of a computer controlled data acquisition card,a working circuit composed by a biasing unit and a heating unit,as well as an emissive probe.With the set parameters of the probe scanning bias,the probe heating current and the fitting range,the apparatus can automatically execute the improved inflection point method and give the measured result.The validity of the automatic emissive probe apparatus is demonstrated in a test measurement of vacuum potential distribution between two parallel plates,showing an excellent accuracy of 0.1 V.Plasma potential was also measured,exhibiting high efficiency and convenient use of the apparatus for space potential measurements.     

Self-consistent Kinetic Description of the Low-Pressure Solenoidal Inductively Coupled Argon Discharge

Using an one-dimensional slab model, we have studied the electron energy distribution, the anomalous skin effect, and power absorption in the solenoidal-inductively-coupled argon discharge under low pressures (≤1.33 Pa). The electron energy distribution function and rf electromagnetic field in the plasma are determined self-consistently by the linearized Bolztmann equation incorporating with the Maxwell equations. The numerical results show that, at low pressures, the electron energy distribution function exhibits a non-Maxwellian distribution with a long high-energy tail. The anomalous skin effect is greatly enhanced under low pressures and the negative power absorption is also obtained.     

A Numerical Study on Tuned Substrate Self-Bias in a Radio-Frequency Inductively Coupled Plasma

The tuned substrate self-bias in a radio-frequency inductively coupled plasma is controlled by varying the impedance of an external tuning LCR （inductor, capacitor and resistor） network inserted between the substrate and the ground. In experiments, it was found that the variation of the tuned substrate self-bias with the tuning capacitance demonstrated three features, namely, continuity, instability and bistability. In this paper, a numerical study is focused on the elucidation of the physical mechanisms underlying continuity and bistability. For the sake of simplicity and feasibility to include the key factors influencing the tuned substrate bias, the tedious calculation of inductive-coupling to obtain the plasma density axtd electron temperature is omitted, and discussion of the tuned substrate self-bias is made under the prescribed plasma density and electron temperature. On the other hand, the parameters influencing capacitive- coupling are retained in modeling the system with an equivalent circuit. It is found that multi-stable state appears when one of the parameters, such as the resistance in LCR, substrate area and plasma density, decreased to its critical value, or the rf voltage or electron temperature increased to the critical value individually. In the reverse cases, the tuned substrate self-bias varies continuously with the tuning capacitance.     

分子离子在金属表面层区域飞行时的产生的感应电势

本文采用“镜反射”模型研究了快速运动的双原子分子离子在金属表面层飞行时产生的感应电势，并借助于一种局域介电函数，分别推导出当离子平行于表面飞行及垂直于表面飞行时感应势的解析形式。     

Transition from Spark Discharge to Constricted Glow Discharge in Atmospheric Air by Capacitor Coupled Discharge

The transition from a spark discharge to a constricted glow discharge in atmospheric air was studied with a capacitor coupled pin-to-water plasma reactor. The reason of the transition is considered to be of various factors, namely the change of the air gap due to the polarization of water molecules by the electric field, the feedback effect of the capacitors, and the ion trapping mechanism. The effects of the frequency of the power supply, inter-electrode gap, and coupled capacitance on the discharge transition were also investigated.     

直流辉光和磁控增强放电等离子体的空间分辨发射光谱技术

光学发射光谱(OES)方法是等离子体诊断的有力工具之一,可以定量地给出等离子体的多种重要参数,如等离子体中的物种成分、粒子能态分布、激发温度、粒子相对密度等.本文介绍了一种用于电子回旋共振(ECR)微波等离子体磁控溅射靶附近的增强放电和直流辉光放电等离子体空间分辨诊断的发射光谱装置.其特点是光学收集系统的位置可以水平精细移动,因而可以对放电区域进行空间分辨发射光谱测量.作者利用这套装置对氩气的ECR微波等离子体和直流辉光放电等离子体进行诊断.在ECR微波等离子体的下游区内氩离子谱线的发射强度很弱,主要是高激发态原子的辐射.在磁共振增强放电区,离子谱线强度有所增加但仍比原子谱线弱,类似于直流辉光放电正柱区的光发射特性.     

Characteristics of a Collisional Sheath Biased by a Dual Frequency Source

A hybrid model is used to simulate the characteristics of a collisional sheath in a capacitively coupled plasma （CCP） driven by a dual frequency source includin...     

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.     

InfluenCe of Downstream Flow on Conduction Phase of Coaxial Plasma Opening Switch

Plasma behaviour and the scaling relations in a coaxial plasma opening switch （POS） using hydrogen plasma are studied self-consistently based on the two-dimensional magnetohydrodynamic （MHD） equations in conjunction with the generalized Ohm＇s law. The vacuum region on the right of POS is included in the model and the influence of downstream flow on the conduction characteristics is discussed. It is found that with the penetration of magnetic field, the pure hydrogen plasma is pushed downstream significantly; and POS still conducts current after the magnetic field arrives at the load edge of POS, which is different from the previous experimental results in a multispecies POS. It is because that the noticeable downstream plasma in the pure hydrogen POS may continue to conduct the current, while in the multispecies POS, the downstream plasma is unimportant so that the conduction phase ends soon after the magnetic field reaches the load edge. The scaling relation obtained from the simulations including the downstream region is consistent with the experimental results.