Determination Of Trace Metal Impurities In Solar Grade Polysilicon By ICP-MS

As a clean renewable source, solar energy has good prospects for solving the energy and environment problems in the future. So far, the solar PV industry is basically built on the material of silicon, and most of the world solar photovoltaic devices are manufactured using crystalline silicon. Solar-grade silicon material usually refers to a silicon material with purity more than 99.9999%. In recent years, with the rapidly increasing of demand for solar-grade silicon, the need of its purity has become higher and higher. In order to determine the purity of solar grade silicon level accurately, it is necessary to establish an effective testing methods. But there is no common and standard protocol on solar-grade silicon, which will be bound to cause a contradiction between material manufacturers and battery manufacturers, is not conducive to the development of photovoltaic industry.This paper studied the trace metal impurities in silicon materials, discussed their electrical properties for the materials, and established a method for the determination of trace Al,Fe,Ca,Mg,Cu,Zn,Cr,Ni and Mn in solar grade polysilicon by inductively coupled plasma mass spectrometry .ICP-MS is a new advanced chemical element analysis technology that has been quickly developed since 1980s'. The technology has many characteristics such as high sensitivity, broad dynamic linear scope, simple background lines, multi-elements simultaneous analysis as well as easy to be operated. It has been widely used in many fields, such as semiconductor, environmental, metallurgy and so on. In this paper, the structure and principle of ICP-MS were analyzed, the operating parameters were optimized and the interferences were corrected. The instrument was calibrated with mass, detector and response. The interferences was studied in the measurement of trace metal impurities in solar grade polysilicon by ICP-MS, such as oxide interference, double-charge ion, multi-atom ion interference, overlap interference and the matrix effects. Sc and Rh were used as internal standard to corrected the interference due to the effects of matrix and interface efficiently. Under the optimum conditions the detection limits for impurities were in the range of 0.030?g/L～0.500?g/L. The recoveries were within 90.0%～107.1% and relative standard deviation within 0.9%～3.4%.