# US 2014/0360425 A1 · Method For Controlling The Diameter Of A Single Crystal To A Set Point Diameter

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- Number: US 2014/0360425 A1
- Document ID: US20140360425A1
- Status: Published application
- Kind: A1
- Application number: 14/285,752
- Filed: 2014-05-23
- Published: 2014-12-11
- Earliest claimed: 2013-06-07
- Assignees: Siltronic AG
- Applicants: Siltronic AG
- Inventors: Thomas SCHROECK
- Web page: https://patentgrep.com/patent/US20140360425A1

## CPC

- C30B 15/22: Stabilisation or shape controlling of the molten zone near the pulled crystal; Controlling the section of the crystal
- C30B 15/26: using television detectors; using photo or X-ray detectors
- C30B 29/00: Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B 29/06: Silicon
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR

## Abstract

The diameter of a single crystal is controlled to a set point diameter during pulling of the single crystal from a melt contained in a crucible and which forms a meniscus at a phase boundary on the edge of the single crystal, the meniscus having a height which corresponds to the distance between the phase boundary and a level of the surface of the melt outside the meniscus, comprising repeatedly: determining the diameter of a bright ring on the meniscus; calculating a diameter of the single crystal while taking into account the diameter of the bright ring and the dependency of the diameter of the bright ring on the height of the meniscus and on the diameter of the single crystal itself; and calculating at least one manipulated variable for controlling the diameter of the single crystal on the basis of the difference between the calculated diameter of the single crystal and the set point diameter of the single crystal.

## Claims

### Claim 1

1. A method for controlling the diameter of a single crystal to a set point diameter during the pulling of the single crystal from a melt contained in a crucible wherein the melt forms a meniscus at a phase boundary on the edge of the single crystal, the meniscus having a height which corresponds to the distance between the phase boundary and a level of the surface of the melt outside the meniscus, comprising repeatedly conducting the following steps:
determining the diameter of a bright ring on the meniscus;
calculating a diameter of the single crystal while taking into account the diameter of the bright ring and the dependency of the diameter of the bright ring on the height of the meniscus and on the diameter of the single crystal itself; and
calculating at least one manipulated variable for controlling the diameter of the single crystal on the basis of the difference between the calculated diameter of the single crystal and the set point diameter of the single crystal,
wherein the calculated manipulated variable is supplied to a control unit which controls the diameter of the single crystal.

### Claim 2 (depends on 1)

The method of claim 1, further comprising forming a look-up table which is based on simulation data and which allocates the height of the meniscus to the derivative of the diameter of the bright ring as a function of time.

### Claim 3 (depends on 1)

The method of claim 1, wherein the height of the meniscus is calculated from a linearized determination equation.

### Claim 4 (depends on 1)

The method of claim 1, comprising calculation of the manipulated variable as an output variable of a PID controller.

### Claim 5 (depends on 1)

The method of claim 1, comprising calculation of the manipulated variable as an output variable of a state feedback control.

### Claim 6 (depends on 1)

The method of claim 1, wherein a lift rate is calculated as a manipulated variable.

### Claim 7 (depends on 1)

The method of claim 1, wherein an electrical power of a heat source, which annularly encloses the single crystal, is calculated as a manipulated variable.

### Claim 8 (depends on 1)

The method of claim 1, wherein a lift rate is calculated as a first manipulated variable and an electrical power of a heat source, which annularly encloses the single crystal, is calculated as a second manipulated variable.

### Claim 9 (depends on 1)

The method of claim 1, further comprising establishing a control loop which reacts in the event of deviations of the lift rate vp from the set point lift rate vps or deviations of the electrical power Lr from the set point power Lrs, the manipulated variable of which modifies the electrical power Lf of one or more heat sources which are arranged around the crucible.