Macroscopic Uniformity of Oxygen Concentration in Czochralski Silicon Crystals Closely Related to Evaporation of SiO from the Free Surface of Melts

To propose a new concept of macroscopic uniformity of oxygen concentration for large diameter Czochralski silicon single crystal, two kinds of experiments from the viewpoint of SiO evaporating from free surface of melts were explored. First, evaporation rate of SiO were measured by using a thermogravimetric method. Subsequently, several CZ crystals with various increasing diameters were grown by the two characteristic growth conditions, the speed control and the temperature control, respectively. It was revealed, from comparison of diverse analysis of the oxygen concentration in these silicon crystals with the evaporation rate of SiO, that the oxygen heterogeneity induced by the speed control was closely related to the enhanced variation of evaporation rate of SiO. We have newly developed the evaporation rate mapping as a function of A c / A s ration (Ac, contact area between melt and silica crucible; A s , area of free melt surface) by using the melt temperature as a parameter. It was concluded that introducing a new parameter Δ q e which denotes the variation of the evaporation rate and to suppress Δ q e would achieve the macroscopic oxygen uniformity in the silicon crystal.