半導体用析出ケイ素棒の品位と原料精製法および反応容器の材質, 構造との関係

抄録

From the pilot plant experiments for production of high purity deposited silicon rod, the following matters were revealed. Among various purifing processes of trichlorosilane, such a process was most excellent that the raw trichlorosilane was primarily rectified after phosphorus in it was converted to POCl₂·AlCl₂ and the purified trichlorosilane was rectified secondarily just before it was used for depositing silicon. Among various purifing processes of hydrogen, such a process was most effective that the raw hydrogen was washed with sulphuric acid solution containing an oxidizing agent, e. g. K₂Cr₂O₇, subsequently with KOH aqua, thereafter moisture and oxygen in the hydrogen was removed by common process, and finally thus purified hydrogen was washed with the purified trichlorosilane. This purifing process of hydrogen was not less effective than the process in which hydrogen was diffused through a paradium diaphragm. As the material of reaction vessel, the water cooled stainless steel was satisfactory. The vessel should be so constructed that the all parts of vessel except the silicon rod heated by direct passage of electric current were cooled sufficiently by water, and the parts heated unavoidably should be made with transparent quartz. When the trichlorosilane and the hydrogen purified by above stated process were used, the deposited silicon rods produced in the reaction vessel of pilot plant had the resistivities higher than n 150 ohm cm and carrier lifetime longer 200μsec after 2 zone passes of floating zone refining in argon.