Characterization Of Electrical Properties On Monocrystal Silicon By Surface Oxidation Treatment

With the rapid development of science and technology, energy dependence has been becoming increasingly serious ever since the Industrial Revolution. Especially in the21th century, the energy crisis and deterioration of the environment to human sounded the alarm. Searching for a new energy alternative to substitute traditional energy sources has become a common goal all over the world. Solar energy, as one of the new energies, has been given extensive national attention and application due to its wide distribution, safe use and pollution-free. As the main form of solar applications, photovoltaic is the most important object to study and explore. However, as the main raw material used for solar cells, high-purity poly-silicon is in serious shortage and can’t meet the requirement of solar power generation technology with rapid development. The most important issue is to look for a new technology to fill up the gap of this raw material. As a low-cost, low energy consumption and low pollution method, metallurgy method is an effective way for high purity poly-silicon preparation. The key feature of metallurgical method is targeted for effective removal of metal, phosphorus (P) and boron (B) impurities in the polycrystalline silicon, resulting in a6N purity level required by solar power generation. Both the removal of metal and P impurities have made significant breakthroughs and formed stable process routes. There are a lot of researches on metallurgical method to remove B impurity in the poly-silicon, but methods that can meet the requirements of industrial production are still in lack. It’s urgent to find a reliable method to remove B impurity, leading the metallurgical method to a large industrial scale.SiO2films are prepared by thermal oxidation under the different thermal oxidation parameters. The valence bond, structure, thickness and morphology are analyzed by the Fourier transform infrared spectrometer(FTIR), X-ray diffractometer(XRD), Spectroscopic ellipsometry and Scanning electron microscopy (SEM), respectively. The removal of B impurity is made indirect qualitative analysis by the resistivity of silicon, which is measured by the resistivity tester. There are the symmetric stretching vibration peak and the asymmetric stretching vibration peak of Si-O-Si at800cm"1and1100cm-1, respectively by FTIR. With the increase of oxidation temperature,the atomic ratio of Oxygen and Silicon increases. With the increase of oxidation temperature and time, the thickness of SiO2film increases. In this work, the SiO2film has a thickness of483.7nm by thermal oxidation for6h at1100℃. The parabolic oxidation rate constant is4914.3nm2·cm-1at900℃. The higher temperature is, the more thickness of SiO2film is. It makes for B accumulation in SiO2at the interface, which is good for the removal of B. The segregation coefficient of B is0.46at900℃by calculation.The removal of B can be enhanced by electron beam injection. The defects of SiO2reduce after heat treatment in argon atmosphere, which reduces the removal of B. Electron beam makes thermal effect and electric effect on the samples. It is electric effect that is the reason of enhancing the B removal enhanced.