The Application Of Zone Melting Single Crystal Silicon To The Detection Of Primary Polysilicon Components

Poly-silicon is the cornerstone of the electronic information industry and photovoltaic industry.Poly-silicon produced by the modified Siemens method accounts for about 80% of the total output of poly-silicon in the world.Modified Siemens method is also known as the TCS(trichlorosilane)reduction method.Its process is to pass high-purity gaseous TCS and hydrogen into the reactor to deposit on the silicon filament which is used as the heating body and the deposition center.Virgin poly-silicon cannot be directly tested for physical properties and composition because of its structure.According to the national standard GB/T4059-2007 and GB/T4060-2007,it is necessary to take the poly-silicon sample core at the specified position,and prepare single crystal sample with the diameter of10-12 mm by float zone method under specified atmosphere,and then conduct the resistivity and conductivity type detection and analysis.And then,convert the resistivity into base boron and base phosphorus impurity content according to GB/T13389-1992.In addition,the minority carrier lifetime of the float zone silicon rod sample is an important criterion for determining the bulk metal content of the virgin poly-silicon.However,in the actual testing process,the physical properties of the float zone single crystal samples do not meet the standard requirements occasionally.Based on the problems exposed in the company's production,the thesis carried out research and concluded: 1)As long as the samples of abnormal resistivity curve are applicable to segregation theory,and the phosphorus test samples are obtained by primary zone melting,the impurity content can be used as the virgin poly-silicon component.2)The trend of the resistivity curve of the base phosphorus test sample is directly related to the content ratio of the donor and acceptor impurities.The conductivity type and resistivity should be considered comprehensively for analysis,and the net carrier method should be used to calculate the resistivity.3)For float zone samples,there is a direct correlation between minority carrier lifetime and crystal defects.Lifetime reflects about the technological level of sample preparation,and cannot be used as a criterion for determining the metal impurity content of virgin poly-silicon rod.4)Multiple times float zone will cause the measurement result of the basic phosphorus test sample is better than the actual impurity content and should be avoided.This paper proposes a method to identify multiple times float zone and analyzes the influence coefficient of the number of zone melts on the measurement results by theoretical analysis.