镍对冶金法制备多晶硅电学性能的影响

Effect of Nickel Element on Electrical Resistivity of Polycrystalline Silicon

电阻率是多晶硅材料最重要的参数之一,通过高温扩散镍杂质到多晶硅中,利用四探针电阻测试仪、金相显微镜、扫描电镜(SEM)、电感耦合等离子发射光谱仪(ICP)、能谱分析(EDS),X射线衍射仪(XRD)等设备,研究了镍对多晶硅电阻率的影响及机制。研究结果表明:镍杂质使N型多晶硅电阻率增加,使P型多晶硅电阻率减小;高温冷却后,大量的镍与硅形成NiSi2析出相在多晶硅表面析出,并对硅中的铁有吸附作用,由于铁含量少而形成Fe0.42Si2.67新相且在表面析出,这些硅化物会引起电阻率的变化。

It is considered pensive metallurgical grade that using relatively inexsilicon （MG-Si） as a starting material for making solar grade silicon （SOG-Si） would be one of the ways to make solar cells less expensive. Resistivity of polycrystalline silicon is one of the most important parameters for the material use. Using the four point resistivity test system, metalloscope, scanning electron microscope （SEM）, inductively-coupled plasma spectrometer （ICP）, energy spectrum analysis （EDS）, X-ray diffraction instrument （XRD） etc., the influence of nickel diffused at high temperature on electrical properties of polycrystalline silicon, obtained by metallurgic method and its mechanism were investigated. The results showed that Ni impurity made the resistivity of N type polycrystalline silicon increased, and of P type decreased; and after cooling from high temperature, much more Ni atoms were combined with Si atoms to form NiSi2 precipitate, on the silicon surface, which played as an absorbent of Fe to form Fe0.42Si2.67 owing to a little of Fe. The silicides caused the change of resistivity of polycrystalline silicon.