Crystal pulling systems having a cover member for covering the silicon charge and methods for growing a melt of silicon in a crucible assembly

Patent metadata

Field	Value
Publication number	US-2022064816-A1
Application number	US-202117396370-A
Country	US
Kind code	A1
Filing date	Aug 6, 2021
Priority date	Sep 1, 2020
Publication date	Mar 3, 2022
Grant date	—

Abstract

Crystal pulling system having a housing and a crucible assembly are disclosed. The system includes a heat shield that defines a central passage through which an ingot passes during ingot growth. A cover member is moveable within the heat shield along a pull axis. The cover member may include an insulation layer. The cover member covers at least a portion of the charge during meltdown.

First claim

What is claimed is:

1 . A crystal pulling system for growing a monocrystalline ingot from a silicon melt, the system having a pull axis and comprising:
a housing defining a growth chamber; a crucible assembly disposed within the growth chamber for containing the silicon melt; a heat shield that defines a central passage through which an ingot passes during ingot growth; and a cover member that is moveable within the heat shield along the pull axis, the cover member comprising one or more insulation layers.

2 . The crystal pulling system as set forth in claim 1 wherein the cover member comprises
a first plate having a first plate axis that is parallel to the pull axis;
and a second plate having a second plate axis that is parallel to the pull axis, the second plate being disposed above the first plate, the insulation layer being disposed between the first plate and the second plate.

3 . The crystal pulling system as set forth in claim 2 wherein the first and second plates are both made of graphite.

4 . The crystal pulling system as set forth in claim 3 wherein the first and second plates are silicon carbide coated.

5 . The crystal pulling system as set forth in claim 1 wherein the heat shield has a bottom, the central passage of the heat shield having a diameter at the bottom of the heat shield, the cover member having a diameter, wherein the diameter of the cover member is at least 0.75 times the diameter of the central passage at the bottom of the heat shield.

6 . The crystal pulling system as set forth in claim 1 wherein the crystal pulling system comprises a pulling mechanism comprising a chuck, the pulling mechanism capable of raising and lowering a chuck along the pull axis, the cover member being removably connectable to the chuck.

7 . The crystal pulling system as set forth in claim 6 wherein the chuck is connectable to a seed crystal for initiating ingot growth.

8 . The crystal pulling system as set forth in claim 1 wherein the crucible assembly comprises a bottom, an outer sidewall, and an inner weir that extends upward from the bottom.

9 . The crystal pulling system as set forth in claim 8 wherein the crucible assembly comprises a central weir disposed between the outer sidewall and inner weir.

10 . The crystal pulling system as set forth in claim 9 wherein the crucible assembly comprises three nested crucibles.

11 . A method for preparing a melt of silicon in a crucible of a crystal pulling system, the crystal pulling system comprising a housing defining a growth chamber, a crucible assembly disposed within the growth chamber for containing the silicon melt and a heat shield that defines a central passage through which an ingot passes during ingot growth, the method comprising:
adding a charge of solid polycrystalline silicon to the crucible assembly; lowering a cover member through the central passage defined by the heat shield to cover at least a portion of the charge; heating the silicon charge to produce a silicon melt in the crucible assembly while the cover member covers a portion of the charge; and raising the cover member after the melt has been formed.

12 . The method as set forth in claim 11 wherein the crucible assembly comprises a bottom, an outer sidewall, an inner weir that extends upward from the bottom, and a central weir disposed between the outer sidewall and inner weir.

13 . The method as set forth in claim 12 comprising adding polycrystalline silicon to a crucible melt zone disposed between the outer sidewall and the central weir, the silicon melt flowing through a central weir opening to an intermediate zone disposed between the central weir and the inner weir, the silicon melt flowing through an inner weir opening to a growth zone disposed within the inner weir, the cover member covering at least a portion of the silicon melt while adding polycrystalline silicon to the crucible melt zone.

14 . The method as set forth in claim 11 , wherein the cover member is lowered to within less than 30 mm from a bottom of the heat shield.

15 . The method as set forth in claim 11 , wherein the cover member is lowered to a bottom of the heat shield.

16 . The method as set forth in claim 11 where the cover member includes an insulation layer and a silicon carbide coated graphite plate.

17 . A method for forming a single crystal silicon ingot comprising:
preparing a melt of silicon in a crucible of a crystal pulling system by the method of claim 11 ; and lowering a seed crystal to contact the melt after the cover member has been raised.

18 . The method as set forth in claim 17 wherein the crucible assembly comprises a bottom, an outer sidewall, an inner weir that extends upward from the bottom, and a central weir disposed between the outer sidewall and inner weir, the method comprising adding polycrystalline silicon to a crucible melt zone disposed between the outer sidewall and the central weir, the silicon melt flowing through a central weir opening to an intermediate zone disposed between the central weir and the inner weir, the silicon melt flowing through an inner weir opening to a growth zone disposed within the inner weir, the cover member covering at least a portion of the silicon melt while adding polycrystalline silicon to the crucible melt zone.

19 . The method as set forth in claim 17 wherein the cover member and seed crystal are raised and lowered by a pulling mechanism comprising a chuck, the method comprising:
disconnecting the cover member from the chuck after the cover member is raised; and
connecting the seed crystal to the chuck after the cover member is disconnected from the chuck.

20 . A crystal pulling system for growing a monocrystalline ingot from a silicon melt, the system having a pull axis and comprising:
a housing defining a growth chamber; a crucible assembly disposed within the growth chamber for containing the silicon melt; a heat shield that defines a central passage through which an ingot passes during ingot growth; and a cover member that is moveable within the heat shield along the pull axis, the cover member comprising:
a first plate having a first plate axis that is parallel to the pull axis; and
a second plate having a second plate axis that is parallel to the pull axis, the second plate being disposed above the first plate.

Assignees

• Globalwafers Co Ltd

Inventors

• Tosi Paolo
• Pannocchia Matteo
• Scala Roberto

Classifications

• Y10T117/1068

  including heating or cooling details [e.g., shield configuration] · CPC title

• Y10T117/1052

  including a sectioned crucible [e.g., double crucible, baffle] · CPC title

• C30B29/06 Primary

  Silicon · CPC title

• C30B15/14

  Heating of the melt or the crystallised materials · CPC title

• C30B15/10 Primary

  Crucibles or containers for supporting the melt · CPC title