One-dimensional Simulation Of Pulse Modulated Radio-frequency SiH₄/N₂/N₂O Discharge

Plasma enhanced chemical vapor deposition technique is widely used in industrial fields for its critical role played in thin film deposition technique. As a high quality thin film that contains the advantages of silicon oxide film and silicon nitride film, silicon oxynitride film plays an increasingly important role in solar photovoltaic filed. In recent years, pulse modulated RF discharge plasma gradually attracts much attention because its modulation parameters can be more flexible, and the speed and quality of the deposited films are improved by studying the plasma discharge characteristics under different pulse parameters so that we can achieve the purpose.Currently, the study on CCP numerical simulation of silicon film is seldom for its complicated discharge reaction processes. Especially, lots of the corresponding numerical simulation concentrated on pulse modulated discharges in SiH4/N2/O2mixture gas, instead of those in SiH4/N2/O2mixture gas discharge which is commonly used in practical microelectronics application. So it is necessary to analyze the detailed discharge characteristics because that N2O can be a good oxygen source in silicon films deposition processes.First, the reason that we choose the SiH4/N2/O2mixture gas is presented by comparing the discharge parameters between the SiH4/N2/O2and the SiH4/N2/O2mixture gas. Then we discuss and analyze how the pulse modulated parameters effect various particles physical characteristics in SiH4/N2/N2O mixture gas discharge. These parameters include the duty cycle of the pulse modulation, discharge voltage, gas pressure and pulse frequency. It turns out that, comparing with SiH4/N2/O2mixture gas, the SiH4/N2/O2mixture gas can improve the plasma density and the deposition rate, which is good for the deposited film; different duty cycles selected can change the deposition rate of the plasma density, on the other hand, it can also change the number of negative ions in the discharge chamber which escape to the lower electrode plate at the afterglow period; the pulse-on time will become longer by reducing the pulse frequency, while the electron density propagation will keep stable when the discharged time reaches a certain level. However, the electron temperature is effected less by the pulse frequency. The increase of voltage of course have positive effect on the increase of deposition rate, but the electron temperature will change dramatically with the voltage; the ion density that strike on the plate will be increased by increasing the pressure, while the corresponding energy is reduced, which is good for adjusting the electrical properties and reducing the ion bombardment.Therefore we can conclude that higher deposition rate can be obtained by using the SiH4/N2/N2O mixture instead of SiH4/N2/O2mixed gas; the plasma discharge characteristics can be flexibly controlled by changing the parameters of the pulse modulation discharge.