Radio Frequency Hollow Cathode Discharge And Its Application In Microcrystalline Silicon (μc-Si:H) Thin Films

Radio frequency hollow cathode discharge (RF-HCD) is one of the most measures forrapid deposition of microcrystalline silicon (μc-Si:H) thin films due to the ability ofgenerating high density plasma. This thesis focuses on the discharge process of RF-HCD andits application in the deposition of μc-Si:H thin films. The researches include four parts asfollows.Firstly, the discharge character of RF-HCD in a semi-cylindrical hollow cathode in argonwas investigated. The power voltage characteristics, the image of discharge plasmas and theoptical emission spectrum (OES) from the plasma were measured under different conditions.The results show that stable RF-HCD can be obtained in the appreciate conditions. The gaspressure, the hole diameter and hole depth of the cathode, the discharge voltage and frequencyhave great influence on the discharge characteristics. Discharge mode can transit from-modeto γ-mode as the input power increases, accompanying by a significant change in thedischarge image, the OES and the plasma parameters. The hole diameter, the gas pressure andthe frequency also influence the discharge mode.Secondly, the RF-HCD was studied by using a2D fluid model. The spatial and temporaldistribution of the electron/ion density, the ionization rate, the electric potential and theelectron energy dissipation in the plasma were calculated. The results show that there are fourstages for the discharge to reach stable. The hollow cathode effect can be onset at the laststage (or stable stage). The periodic changing electric field has a significant impact on thedistribution of electron density and ionization rate. The RF-HCD can sustain whether or notthere is the second electron emission from the cathode due to the mechanism of sheathoscillation heating.Thirdly, the influence of the voltage, the pressure, the hole diameter and depth, the powerfrequency and the bias voltage on the RF-HCD characteristics have been studied by the2Dfluid model. The results show that, with voltage increase, the electric field in the sheath layerenhanced, then the ionizaition rate and electron density increased; the hollow cathode effectexist optimal conditions of hole diameter and pressure in radio frequency; the increase of holedeep cause hollow cathode effect area in the hole expanded, then the electron density increase, while when the hole depth is larger, electron density changing with deep hole tends to besaturated; power frequency increase make the electron can get more energy in unit time,increased the risk of collision ionization, so electron density increase with power frequency.Finally, the RF-HCD has been used to deposit the intrinsic microcrystalline silicon(μc-Si:H) thin film. The influences of the deposition parameters on the intrinsicmicrocrystalline silicon (μc-Si:H) thin film deposition rate and the performance aresystemically investigate. The microstructure and morphology of films obtained underdifferent conditions were measured. The results show that good quality of μc-Si:H thin filmwas achieved in crystalline of40%~50%. A higher crystalline causes more defects. Thedeposition rate can reach as high as2.5nm/s under optimized conditions and the crystalline is50%.