Study On Diagnostics Of Dusty Plasma Formation In Radio-Frequency SiH₄/C₂H₄/Ar Discharge

This paper is mainly about the dust void observation and measurement,Langmuir probe and optical emission spectroscopy diagnostics in dusty plasma,which was created in a radio-frequency capacitively coupled discharge chamber.I summarize my research work as follows:In chapter one,the introduction to the dusty plasma is presented.In chapter two,I illustrate the experimental set-up which I used in the research project. Confined in the chamber in various ways,dust particles were formed in the radio-frequency capacitively coupled discharge of reactive mixtures(SiH₄/C₂H₄/Ar) in a cylindrical chamber. The experimental setup should be suitable for simulating the microelectronic manufacturing processes,and for giving basic parameters for improving the quality of discharge.In chapter three,I report how the EDS,XRD,and SEM spectroscopies were used to analyze the dust particles.CCD photos were taken from the top and the side of the discharge chamber.Dust cloud and void in the sheath of radio-frequency discharge was observed. Evaluation of the dust void diameter and depth versus experimental conditions are carried out; and their characteristics versus RF power and gas pressure are further investigated experimentally.In chapter four,measurement of dusty plasma parameters were conducted in the discharges of mixtures(SiH₄/C₂H₄/Ar).Langmuir probe was employed for diagnostics and measurement of important plasma parameters,such as electron density and electron temperature.The results show that the electron density dropped while the electron temperature rise when the dust particles were formed.The curves of the electron density and temperature versus the RF power and pressure are presented and analyzed.Then,a novel method,based on the experimental data of the electron density,corrected ion density and a known theoretical model,is developed in this research project for measuring the density and the charges of dust particles.The curves of densities and charges of dust particles versus RF power and gas pressure are presented under various experimental conditions,respectively. The influence of dust density on the charges of dust particles has also been investigated. Furthermore,optical emission spectroscopy analysis of dusty plasma was reported in this chapter.I add the optical emission spectroscopy into the diagnostic system.Based on the calculation of excitation temperature by using Boltzmann distribution to fit experimental data, I present the curves of excitation temperature versus gas pressure and RF power in SiH₄/C₂H₄ /Ar discharges on different discharge conditions.I also measure the emission intensities of spectral lines as functions of pressure,RF power,and flow rates of SiH₄/C₂H₄.In chapter five,a one dimension steady dusty plasma sheath model is introduced. Through the solution of this model,I could gain more information of the dusty plasma:the densities distributions of electrons,positive ions and dust particles in the sheath,the Bohm velocity in the sheath boundary as a function of dust density,the relationship between the dust scharge and density.The results showed that,with the increase of dust density and temperature,all the parameters—plasma sheath,electron density,particles charges and the dust density near the sheath boundary and in the sheath—changed,following a certain pattern.