Silicon single crystal produced by crucible-free float zone pulling

US6840998B2 · kind B2 · utility

Assignee

• Siltronic AG · DE

Inventors

• Ludwig Altmannshofer · Lenggries, DE
• Manfred Grundner · Burghausen, DE
• Janis Virbulis · Burghausen, DE

Key dates

• Filing date: Jul 23, 2002
• Grant date: Jan 11, 2005
• Expiry date: Apr 15, 2023

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/21
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

A silicon single crystal is produced by crucible-free float zone pulling, has a diameter of at least 200 mm over a length of at least 200 mm and is free of dislocations in the region of this length. A silicon wafer is separated from the silicon single crystal by a process for producing the silicon single crystal. The silicon single crystal is produced by crucible-free float zone pulling in a receptacle, in which an atmosphere of inert gas and nitrogen exerts a pressure of 1.5-2.2 bar, the atmosphere being continuously exchanged, with the volume of the receptacle being exchanged at least twice per hour. A flat coil with an external diameter of at least 220 mm is inserted in order to melt a stock ingot. The single crystal is pulled at a rate in a range from 1.4-2.2 mm/min and is periodically rotated through a sequence of rotation angles. The direction of rotation is changed, after each rotation, by a rotation angle belonging to the sequence, a change in the direction of rotating defining a turning point on the circumference of the single crystal, and at least one recurring pattern of turning points is formed, in which the turning points are distributed on straight lines which are ori…