Study On Oxygen Control In The Growth Process Of Large-size Czochralski Silicon Single Crystal

Czochralski monocrystalline silicon is widely used in the preparation of crystalline silicon solar cells because of its excellent semiconductor properties.In order to reduce production costs and improve the utilization efficiency of battery components,largescale monocrystalline silicon wafers have become the mainstream development trend,but the accompanying problems of high oxygen impurity content and uneven distribution in monocrystalline silicon have become more prominent.At present,it has become one of the main factors limiting the yield rate and photoelectric conversion efficiency of battery components.In this paper,by establishing a steady-state numerical model of the Czochralski silicon growth process,on the one hand,the effects of different process parameters on the shape of the growth interface,the flow of the melt,and the distribution of V/G values near the growth interface are studied.Therefore,the difference in the concentration and distribution of oxygen impurities in single crystal silicon is caused,and the optimal process parameter range suitable for growing low oxygen single crystal silicon is explored.On the other hand,the structure of the heater and the draft tube in the thermal system is optimized and improved,and its oxygen reduction effect is evaluated.The influence of the shape of the heater on the temperature distribution and the concentration distribution of oxygen impurities in the melt during the growth process and the influence of the shape of the guide tube on the flow process of argon gas were studied respectively,and the optimization of the thermal field structure that is conducive to the growth of low-oxygen single crystal silicon was proposed.suggestion.The research results are as follows.(1)With the increase of the crystal growth rate,the shape of the growth interface gradually changes from the "m" type convex to the melt to the "n" type convex to the crystal,and the contact area between the crystal and the silicon melt first decreases and then increases.The oxygen content in crystalline silicon rods shows an overall upward trend.When the growth rate is maintained between 0.9 and 1.1mm/min during the crystal growth process,it is more conducive to the growth of low-oxygen single crystal silicon.(2)Under the condition of low crucible rotation speed(3～5rpm),the convection in the silicon melt not only helps to enhance the volatilization of oxygen on the free liquid surface,but also prevents oxygen from entering the silicon crystal from the growth interface,so that the oxygen in the single crystal silicon content decreased significantly.However,under the condition of high crystal rotation speed(9～11rpm),the strength of the Taylor-Proudman vortex in the melt can be increased,and the oxygen content in the single crystal silicon can be appropriately reduced.(3)When the height of the heater increases,the decomposition reaction rate at the bottom corner of the crucible decreases,and the oxygen content in the silicon melt and single crystal silicon rods also decreases,and the oxygen content in single crystal silicon drops by about 1.6ppma at most.When the heating area of the heater increases,the maximum temperature in the melt decreases,which reduces the overall dissolution rate of the crucible,and the oxygen content in the single crystal silicon decreases by up to about 1.2ppma,and the power of the heater also decreases slightly at this time.Played a certain role in energy saving.After changing the bottom of the draft tube to be parallel to the plane of the free liquid surface,the flow of argon on the free liquid surface is enhanced,so that it takes away more volatile oxygen,and the oxygen content in the single crystal silicon decreases.About 1.1ppma.