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据日本《电子材料》1992年第11期报道,日本NEC公司采用拉晶法生长单晶时,在Si熔液对流中发现具有涡流结构的非轴对称流和没有涡流结构的轴对称流现象。这种现象的存在与否明显地影响着生长单晶的质量。为了制作氧均匀分布的优质单晶,首次得出应在无涡流条件下制作单晶的结论。 该公司为了制作优质的Si单晶,对熔液对流的理解并进行控制极为重要,开发了独特的X射线透视装置。该装置在高温下,可直接观察不透明Si熔体的对流。进行三维性Si对流观察,结果发现,在Si单晶生长中,由于温度梯度、坩埚和单晶的旋转速度等原因,在Si熔液的对流中也存在非轴对称流。由于这种涡流的存在,使Si熔液内的温度和氧的分布发生很大变化,从而妨碍了氧的均匀分布与优质Si单晶的生长。
According to Japan's “Electronic Materials” in 1992 No. 11 reported that the Japanese NEC company crystal growth by single-crystal pulling in the Si melt convection with eddy current structure is found non-axisymmetric flow and eddy current structure without axisymmetric flow phenomenon. The existence of this phenomenon obviously affects the quality of single crystals grown. For the first time, the conclusion that single crystal should be made without eddy current was obtained for the first time to produce high quality single crystal with uniform oxygen distribution. In order to produce high-quality Si single crystals, it is extremely important that the company understand and control melt convection and developed a unique X-ray fluoroscopy device. The device can directly observe the convection of the opaque Si melt at high temperatures. Three-dimensional Si convection was observed. As a result, it was found that non-axisymmetric flow exists in the convection of the Si melt due to the temperature gradient, the rotation speed of the crucible and the single crystal during the growth of the Si single crystal. Because of this eddy current, the temperature and the distribution of oxygen in the Si melt greatly change, hindering the uniform distribution of oxygen and the growth of high-quality Si single crystals.