Polycrystalline silicon rod for floating zone method and a process for the production thereof

摘要

#CMT# #/CMT# The polysilicon rod obtained onto a filament rod by depositing high-purity silicon from a silicon-containing reaction gas for floating zone applications, comprises four different regions having different microstructures in the radial cross section of the rod. The reaction gas is thermally decomposed or reduced by hydrogen. A polycrystalline thin rod is present in the innermost region A at the center of the polycrystalline rod. A region B of deposited polycrystalline silicon is characterized no or only very few needle crystals and is present around the thin rod A. #CMT# : #/CMT# The polysilicon rod obtained onto a filament rod by depositing high-purity silicon from a silicon-containing reaction gas for floating zone (FZ) applications, comprises four different regions having different microstructures in the radial cross section of the rod. The reaction gas is thermally decomposed or reduced by hydrogen. A polycrystalline thin rod is present in the innermost region A at the center of the polycrystalline rod. A region B of deposited polycrystalline silicon is characterized no or only very few needle crystals and is present around the thin rod A. The proportion by area of needle crystals is less than 7% in an outer region D of the polycrystalline silicon rod. The needle crystal has a length of less than 15 mm and the width of less than 2 mm. The length of the microcrystals not exceeds the matrix of 0.2 mm in the outer region of the polycrystalline silicon rod. A mixed zone C is present between the region B and D. The crystal microstructure in the mixed zone is fluidly passes over from the microstructure in region B to the microstructure in region D. The diameter of the polysilicon rod is greater than 120 mm. The filament rod has a square cross section having an edge length of 5-10 mm. The microstructure of the filament rod corresponds to the microstructure of zones B or D. The diameter of the region B lying around the filament rod is as large as the melting zone of an FZ-method that is to be used to form a monocrystalline silicon rod. The diameter of the region B is greater than 30 mm. The proportion by area of the needle crystals in the region B is less than 1%. The needle crystals are not longer than 5 mm and not wider than 1 mm. The outer region D begins at a diameter of 120 mm of the polysilicon rod. The polysilicon rod cross section contains no deposition rings. An independent claim is included for a method for producing polysilicon rod. #CMT#USE : #/CMT# Polysilicon rod obtained onto a filament rod by depositing high-purity silicon from a silicon-containing reaction gas useful for floating zone applications, and for the production of a monocrystalline rod by a floating zone process. #CMT#ADVANTAGE : #/CMT# The polysilicon rod can be economically and simply produced with high yield without loss of material and time in efficient manner, and can be refined in monocrystalline fashion without any defects. #CMT#DESCRIPTION OF DRAWINGS : #/CMT# The diagram shows a schematic view of a cross section of polycrystalline silicon rod. #CMT#POLYMERS : #/CMT# Preferred Components: The filament rod consists of polycrystalline silicon.