Studies On Properties And Structure Of Si-rich Silicon Nitride Thin Films Containing Amorphous Silicon Quantum Dots

Silicon nitride is considered to be a greater prospect of silicon-based light emitting material because of its many excellent properties, so widely used in many fields. Based on these advantages, this text further to research the effect of deposition parameters on the structure and properties of silicon-rich silicon nitride and research how to optimize its luminescence properties, in order to regulate the best preparation technology parameters, used in the film production process. Silicon-rich silicon nitride thin films were deposited by plasma enhanced chemical vapor deposition method using SiH4, NH3,N2 and H2 as reaction gas. The structures and properties of the materials were characterized by Fourier transform infrared absorption spectroscopy, ultraviolet-visible transmission spectra, XRD and photoluminescence spectra, Scanning electron microscope, respectively. The results showed that:1. Using SiH4, NH3,N2 and H2 as reaction gas, researching the effect of changing H2 flow rates on the structure and properties of silicon-rich silicon nitride. The experimental results show that, properly increasing nitrogen flow rate helps to improve the bonding probability of thin film, the order degree of films improve gradually, at the same time becouse of its refractive index is close to ideal so it used to make minus reflection film. But increas too much nitrogen flow will prevent the nitrogen atoms into the film, which resulting in the reduction of defect states, damage film quality.2. Silicon-rich silicon nitride thin films were deposited by plasma enhanced chemical vapor deposition method using SiH4 NH3 and N2 as reaction gas source with changing of radio-frequency power. The structures and properties of the film materials were characterized by Fourier transform infrared absorption spectroscopy, ultraviolet-visible transmission spectra and SEM, respectively. The results showed that, with radio-frequency power increasing, the bandgap width of the film materials decrease slowly, the order degree of films improve gradually. and the Si-N、N-H bonds in the films decrease, with increasing of the Si-N bonds gradually. Analysis of the results find that, properly increasing radio-frequency power is beneficial to the enhancing of the ion reaction rate in films, the improving of film order degree, the enhancing of film compactness, the getting better of film quality. But the outrageous radio-frequency power will damage film quality.3. Silicon-rich silicon nitride thin films were deposited by plasma enhanced chemical vapor deposition method using SiH4, NH3 and H2 as reaction gas source with changing of H2 flow rates. The structures and properties of the materials were characterized by Fourier transform infrared absorption spectroscopy, ultraviolet-visible transmission spectra, XRD and photoluminescence spectra, respectively. The results showed that, properly increasing hydrogen flow rate helps to improve the bonding probability between hydrogen ion and Si and N dangling bonds in deposition process. Thus hydrogen play an important role in passivation of dangling bonds. When hydrogen flow rates change from 10 to 20sccm, hydrogen ions mainly play a role of dangling bond passivation, which resulting in the reduction of defect states and weakening of defect state photoluminescence effect, so that bandgap of the film widening slowly. When hydrogen flow rates increase, the amounts of nitrogen atoms grow up continuously, with the increase of defect states again, enhancement radiation, and leading to the optical bandgap rapidly broadening. When the hydrogen flow rates is 30sccm, silicon nitride grain size and numbers increase in the films, photoluminescence effects of defect states disappear, the luminescence effects caused by amorphous silicon cluster quantum dots in the silicon nitride matrix appear. It indicated that amorphous silicon cluster quantum dots create in the films. Therefore, properly increasing hydrogen flow rate helps to passivate films and grow out of the structures of amorphous silicon cluster quantum dots embedded amorphous silicon nitride matrix in the process of structure transition from rich silicon nitride to Si3N4 phase.