The effects of process conditions on the plasma characteristic in radio-frequency capacitively coupled SiH_4/NH_3/N_2 plasmas: Two-dimensional simulations

A two-dimensional （2D） fluid model is presented to study the behavior of silicon plasma mixed with SiH4 , N2 , and NH3 in a radio-frequency capacitively coupled plasma （CCP） reactor. The plasma–wall interaction （including the deposition） is modeled by using surface reaction coefficients. In the present paper we try to identify, by numerical simulations, the effect of variations of the process parameters on the plasma properties. It is found from our simulations that by increasing the gas pressure and the discharge gap, the electron density profile shape changes continuously from an edge-high to a center-high, thus the thin films become more uniform. Moreover, as the N2 /NH3 ratio increases from 6/13 to 10/9, the hydrogen content can be significantly decreased, without decreasing the electron density significantly.

Effect of Addition of Nitrogen to a Capacitively Radio-Frequency Hydrogen Discharge

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.

One-Dimensional Fluid Model of Pulse Modulated Radio-Frequency SiH_4 /N_2 /O_2 Discharge

Driven by pulse modulated radio-frequency plasma in capacitively coupled discharge are studied by source, the behavior of SiH4/N2/02 using a one-dimensional fluid model. Totally, 48 different species （electrons, ions, neutrals, radicals and excited species） are involved in this simulation. Time evolution of the particle densities and electron temperature with different duty cycles are obtained, as well as the electronegativity nsiH-3 /ne of the main negative ion （Sill3 ）. The results show that, by reducing the duty cycle, higher electron temperature and particle density can be achieved for the same average dissipated power, and the ion energy can also be effectively reduced, which will offer evident improvement in plasma deposition processes compared with the case of continuous wave discharge.

大气压双频容性耦合Ar/O_(2)等离子体特性研究

文章利用二维流体模型对双频调制大气压Ar/O_(2)放电特性进行了研究,着重讨论高低频电压、低频频率等不同匹配方式对等离子体参数的影响,并且通过对电子加热模式、电子密度、中性粒子密度、正离子能量以及正离子总通量等分析了大气压Ar/O_(2)放电双频调控机制。结果表明,低频源电压的改变使得电子加热模式由α模式转变为DA/α混合模式,且等离子体密度、正离子总通量及离子能量均随着低频电压的升高而增大,发生了解耦现象。与低频源电压不同,高频源电压和低频源频率对电子加热模式不产生影响。此外,高频源电压对等离子体密度及正离子总通量影响较大,对刻蚀工业中易对材料造成损伤的离子能量影响很小;而低频源频率对工业中影响影响较大的离子能量和离子总通量影响较大,对等离子体密度影响较小,实现了等离子体密度和离子能量的独立控制。