ASTM F1708-96

1.1 This practice describes a procedure to consolidate granular polysilicon into a solid rod and then to convert the polysilicon rod into a single crystal by a float-zone technique. The resultant single crystal ingot is used for the determination of trace impurities in the polysilicon. These impurities are acceptor and donor components (usually boron, aluminum, phosphorus, arsenic, and antimony) as well as substitutional carbon.

1.2 The useful range of impurity concentration covered by this practice is 0.002 to 100 parts per billion atomic (ppba) for acceptor and donor impurities, and 0.03 to 5 parts per million atomic (ppma) for carbon. The acceptor and donor impurities are analyzed in a slice taken from the single crystal ingot by photoluminescence or infrared spectroscopies. The carbon impurity is determined by analysis of a slice by infrared spectroscopy.

1.3 This practice is applicable only to evaluation of polysilicon granules as produced by thermal deposition of silane, or one of the chlorosilanes, onto high purity seeds of polysilicon in a continuous fluid bed reactor. The granules are near spherical in shape and range in size from 200 to 2500 µm with a mean size of about 900 µm.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 9 and in 12.1.1.