Method for growing a single crystal by crystallizing the single crystal from a float zone

Patent metadata

Field	Value
Publication number	US-9932691-B2
Application number	US-201514945840-A
Country	US
Kind code	B2
Filing date	Nov 19, 2015
Priority date	Dec 18, 2014
Publication date	Apr 3, 2018
Grant date	Apr 3, 2018

Abstract

A single crystal is grown in a float zone which is inductively heated and the crystallizing single crystal is rotated in a direction of rotation which is periodically reversed at intervals in accordance with an alternating plan, wherein a dwell time during which the single crystal is in a state of rest because of the reversal of the direction of rotation is limited to no more than 60 ms.

First claim

What is claimed is:

1. A method for growing a single crystal, comprising
crystallizing the single crystal from a float zone, the float zone being inductively heated and the crystallizing single crystal being rotated in a direction of rotation which is reversed at intervals in accordance with an alternating plan, a dwell time during which the single crystal is in a state of rest because of the reversal of the direction of rotation being limited to no more than 60 ms, the method further comprising initiating the rotational movement of the single crystal by a drive, thereby transmitting a force by way of a belt from a drive shaft to a shaft which holds the single crystal, further comprising controlling the rotational speed of the drive during an acceleration phase in accordance with a presetting of a speed profile, such that the increase in the rotational speed of the drive at the beginning of the acceleration phase, during a time period of no less than ¼ of the acceleration phase, is no less than 3000 rpm 2 , and wherein the amount of increase in the rotational speed of the drive according to the presetting of the speed profile at the beginning of the acceleration phase, during the time period of at least ¼ of the acceleration phase, is greater than the amount of the decrease in the rotational speed of the drive according to the presetting of the speed profile during a corresponding time period before the end of a deceleration phase that precedes a next acceleration phase.

2. The method of claim 1 , wherein the float zone is heated with an induction heating coil which is formed as a flat coil with one turn, the ends of which overlap.

3. The method of claim 1 , wherein the float zone is heated with an induction heating coil which is formed as a flat coil with one turn and has a height that is no more than 20 mm.

4. The method of claim 1 , wherein the state of rest is no more than 40 ms.

5. The method of claim 1 , wherein the state of rest is no more than 30 ms.

6. The method of claim 1 , wherein the increase in rotational speed during the acceleration phase is not more than 4500 rpm 2 .

Assignees

• Siltronic Ag

Inventors

• Raming Georg
• Altmannshofer Ludwig
• Ratnieks Gundars
• Moeller Martin
• Muemmler Frank

Classifications

• C30B13/32 Primary

  Mechanisms for moving either the charge or the heater · CPC title

• C30B13/26

  Stirring of the molten zone · CPC title

• C30B29/06

  Silicon · CPC title

• C30B13/20

  by induction, e.g. hot wire technique (C30B13/18 takes precedence) · CPC title