| 摘要 |
PURPOSE:To prevent diffusion of heavy metal to a semiconductor substrate and remarkably improve the yield of pressure resistance by providing a low temperature part to the one side of sealed quartz pipe and precipitating heavy metal substance within the quartz pipe to such part. CONSTITUTION:The Si pipe 1, Si substrate 3 surrounded by the Si ingot 2 and Al diffusion source 4 loaded to the Si base are housed to the main part 10 of quartz pipe and it is sealed to the vacuum condition by a plate 11. The left half side B has smaller diameter, the right half side A is kept at 1,200-1,250 deg.C and the part B is kept at 1,100-1,150 deg.C. The optimum temperature difference between the portions A and B is 50-100 deg.C and when it exceeds 100 deg.C, concentration of aluminum becomes lower than the target value or aluminum is all transported to the part B and is not diffused to the substrate. When temperature is 50 deg.C or less, the heavy metal capturing effect is almost not generated. According to this structure, heavy metal is precipitated to the low temperature part B and does not diffuse to the semiconductor substrate. Therefore, defect of pressure resistance due to defective interior of substrate is not almost generated and the yield can be improved. This process can also be applied to other elements such as Ga.
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