Method of growing hexagonal single crystals and use of same as substrates for semiconductor elements

US7255740B2 · kind B2 · utility

Assignee

• Schott AG · DE

Inventors

• Dirk Sprenger · Stadecken-Elsheim, DE
• Burkhard Speit · Mainz, DE
• Markus Schweizer · Klein-Winternheim, DE

Key dates

• Filing date: Feb 17, 2004
• Grant date: Aug 14, 2007
• Expiry date: Jun 11, 2024

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C30B29/20
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

A method is described for making low-stress single crystals with a hexagonal crystal structure, which has a crystallographic c-axis perpendicular to a [0001] surface. A single crystal maintained at a temperature under the melting point of the crystal raw material is dipped in a melt of the crystal raw material, whereby a solid-liquid phase boundary is formed. The crystal is subsequently drawn with an upwardly directed drawing motion e.g. by the Czochralski method. The method is characterized by drawing the crystal along the c-axis so that a temperature gradient of at least 30 K/cm is present in the crystal within a centimeter of the solid-liquid phase boundary and by subsequently performing a tempering treatment on the resulting single crystal. The method is especially suitable for corundum crystals, such as sapphire, which are used as substrates for semiconductor components, such as LEDs.