Research Of Diagnostics Of A Novel Atmospheric Pressure RF Ar/H₂/SiCl₄ Plasma Jet And Its Deposition Of Silicon Film

Atmospheric pressure cold plasma jet has many applications in various areas, such as materials modification and sterilization because of its low temperature and activity species contained. This technique is easy to handle and can work in an open environment, which makes it very popular. In this thesis we design two experimental equipments to generate atmospheric pressure cold plasma jet. diagnose plasma parameters, and attempt to use it in film deposition. The silicon film has successful use in solar cell, integrated circuit and thin film transistors. The preparation of the silicon film works at low pressure and high temperature mostly, which need vacuum equipment and complicatedly to operate. This thesis aims to experiment a novel method to deposit silicon film at open air using atmospheric pressure plasma and SiCl4 as raw materials. This thesis is divided into exordium, the device for generation of the atmospheric pressure plasma jet. the diagnostics of plasma parameter and the deposition of silicon film.We describe two self-designed devices for the generation of atmospheric pressure plasma jet. Some photographs of the discharge, the discharge waveform and its current-voltage curve are presented, base on which the explanation of the change of the discharge phenomena are discussed. The discharge phenomena using deferent electrodes are compared to select a good electrode structure for film deposition. The discharges translate from a-mode to y-mode for both the electrodes with rectangle holes and round holes. The two discharge modes exist together in some power range at different flow rate of discharge gas. which for 5slpm of pure Argon is 50W-70W.A novel method to diagnose the electron density of the atmospheric plasma jet using an equivalent circuit of the plasma discharge is studied. Based on the circuit model, the electron density can be obtained according to the Ohm’s law. By using the method, the effects of the electrode shape, the gas flow rate and the discharge gap on the electron density are discussed. The electron density increases with the increase of input power and the decrease of electrodes gap. The electron density decreases as flow rate increasing for the electrodes with rectangle holes, but almost no response for the electrodes with round holes due to its smaller outlet area. By using this method the electron density in atmospheric pressure radio frequency conductive pure gas discharge can be determined. whenωpe>>ωand vm2>>ωpe2 are satisfied.OES has been used to diagnose the rotational and vibrational temperature in Ar discharge, and the electron excitation temperature in the Ar/SiCl4 mixture discharge. In Ar discharge as increasing the RF power the rotational temperature increases and the vibrational temperature decreases, which mean that the system trends to thermal balance. The electron excitation temperature has little change with RF power. In Ar/SiCl4 discharge the electron excitation temperature is calculated by the Si atom spectral lines. The electron excitation temperature belongs to the remained electrons.after dissociate SiCl4. The electron excitation temperature decreases with the increasing of the RF power. the SiCl4 flow rate and the Ar flow rate. The bond energy of H2 and SiCl4 are close, while partial electron energy is consumed to dissociate H2. As a result, the H2 influx weakens the discharge.We deposit the film with the layered structure on the substrate of monocrystalline silicon. ceramic and glass, using self-assembled radio frequency atmospheric plasma jet in open air. The discharge gas is the mixture of Ar, H2 and SiCl4 gas bubbled by Ar. The film thickness, the film content, the content profile along the depth and surface topography have been investigated by step profiler. XPS and SEM respectively. The film has been layered from pure silicon near the substrate to SiO2 close to the film surface. We analyze the mechanism of oxidation process during film deposition, and investigate the reason of layered structure of the films. At the beginning of the film deposition the substrate temperature is low and the oxidation process is attributed to the oxidative radicals, which were generated from decomposition of O2 in the air by atmospheric plasma jet. As time passed by. the substrate temperature becomes higher. When it reached the decomposition temperature of met silicate (150℃). the SiO2 produced by decomposition of met silicate was the primary film pollutant. The flow rate of SiCl4 is the key factor of oxidation rate at the high substrate temperature. The H2 flow rate is very important for Si film growth and oxidation, because it determines the plasma temperature and density. Besides, the hydrogen atom bonding to silicon atom to form Si-H group is an important reason to stop the film oxidation. Therefore although the deposited film is oxidative partially, but properly control the discharge gas flow rate and the substrate temperature should be beneficial to form pure silicon film.