Polycrystal silicon rod and production process therefor

• US 5,976,481 A
• Filed: 01/20/1998
• Issued: 11/02/1999
• Est. Priority Date: 05/21/1996
• Status: Expired due to Term

• Current Assignee: Tokuyama Corporation
• Original Assignee: Tokuyama Corporation
• Inventors: Kubota, Junichi, Oda, Hiroyuki
• Primary Examiner(s): NGUYEN, NGOC YEN M
• Application Number:
  US09/000,033
• Time in Patent Office: 651 Days
• Field of Search: 423/348, 423/349, 423/350
• US Class Current: 423/348
• CPC Class Codes: C01B 33/035 by decomposition or reduction of gaseous or vaporised silicon compounds in the presence of heated filaments of silicon, carbon or a refractory metal, e.g. tantalum or tungsten, or in the presence of heated silicon rods on which the formed silicon is deposited, a silicon rod being obtained, e.g. Siemens process
• CPC Class Codes: C30B 25/00 Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
• CPC Class Codes: C30B 29/06 Silicon

Abstract

A polycrystal silicon rod characterized in that it has a half value width of a peak indicative of crystal orientation (111) of an X-ray diffraction pattern, of 0.3° or less, an internal strain rate in a radial direction of less than 5.0×10^-5 cm^-1 and an internal iron concentration of 0.5 ppba or less. The above polycrystal silicon rod having high crystallinity, high purity and low internal strain is produced by heating a core material in a gaseous atmosphere comprising trichlorosilane and hydrogen to deposit silicon on the silicon core material to produce a polycrystal silicon rod, and subjecting the polycrystal silicon rod to a heat treatment without allowing it to contact with the air, to remove strain contained therein.

Claims

1. A polycrystal silicon rod comprising a half value width of a peak indicative of crystal orientation ( 111) of an X-ray diffraction pattern, of 0.3°

or less, an internal strain rate in a radial direction, of less than 5.0×

10^-5 cm^-1 and an internal iron concentration of 0.5 ppba or less.

2. A process for producing a polycrystal silicon rod comprising a half value width of a peak indicative of crystal orientation (111) of an X-ray diffraction pattern, of 0.3°

or less, an internal strain rate in a radial direction, of less than 5.0×

10^-5 cm^-1 and an internal iron concentration of 0.5 ppba or less, which comprises the steps of;

heating a silicon core material in a gaseous atmosphere comprising trichlorosilane and hydrogen to deposit silicon on the silicon core material to produce a polycrystal silicon rod,

heating the polycrystal silicon rod by applying an electric current without allowing the polycrystal silicon rod to contact with air so that the surface temperature of the polycrystal silicon rod is higher than the deposition reaction temperature of silicon and is 1,030°

C. or higher, and

shutting off the electric current after said heating by reducing the applied current as sharply as possible, thereby reducing the internal strain rate of said polycrystal silicon rod.

3. The process of claim 2, wherein said electric current is applied to the polycrystal silicon rod in the presence of hydrogen or an inert gas to beat the polycrystal silicon rod.