Wafer with regions of low oxygen concentration

Patent metadata

Field	Value
Publication number	US-2025389050-A1
Application number	US-202519241168-A
Country	US
Kind code	A1
Filing date	Jun 17, 2025
Priority date	Aug 9, 2019
Publication date	Dec 25, 2025
Grant date	—

Abstract

A single crystal silicon wafer has a thickness between a first surface and an opposite second surface from 50 μm to 300 μm. The wafer includes a first region extending a first depth from the first surface. The first region has a reduced oxygen concentration relative to an adjacent region of the wafer. The wafer has a bulk minority carrier lifetime greater than 100 μs.

First claim

What is claimed is:

1 . A method of forming a single crystal silicon ribbon, the method comprising:
providing molten silicon in a crucible; initiating crystal growth at a surface of the molten silicon; pulling a single crystal silicon ribbon from the molten silicon such that the ribbon floats on the surface of the molten silicon during the pulling; and forming asymmetric denuded zones in the ribbon during the crystal growth, wherein the floating and associated thermal conditions produce a first denuded zone extending from a front surface of the ribbon to a first depth, and a second denuded zone extending from a back surface of the ribbon to a second depth less than the first depth.

2 . The method of claim 1 , wherein the front surface of the ribbon faces away from the molten silicon during pulling while the back surface contacts or faces the molten silicon.

3 . The method of claim 1 , wherein a rate of the pulling is controlled to maintain a substantially stable floating condition of the ribbon during the crystal growth.

4 . The method of claim 1 , further comprising creating a thermal asymmetry between the front and the back surfaces by exposing the front surface to radiant energy and allowing the back surface to remain in conductive contact with the molten silicon.

5 . The method of claim 1 , wherein the first denuded zone has a thickness between 10 and 50 microns, and the second denuded zone has a thickness less than 20 microns.

6 . The method of claim 1 , further comprising forming an epitaxial layer over the front surface of the ribbon after the crystal growth.

7 . A method of forming a single crystal silicon ribbon, the method comprising:
providing molten silicon in a crucible; initiating crystal growth at a surface of the molten silicon; pulling a single crystal silicon ribbon from the molten silicon such that the ribbon floats on the surface of the molten silicon during the pulling; and subjecting the ribbon to a thermal treatment after the pulling, the thermal treatment comprising: heating the ribbon to a temperature sufficient to enable oxygen diffusion, maintaining the ribbon at or near the temperature for a period of time, and
cooling the ribbon at a controlled rate;
wherein the thermal treatment produces a first denuded zone extending from a front surface of the ribbon to a first depth and a second denuded zone extending from a back surface of the ribbon to a second depth less than the first depth.

8 . The method of claim 7 , wherein the front surface of the ribbon faces away from the molten silicon during the pulling while the back surface contacts or faces the molten silicon.

9 . The method of claim 7 , wherein the temperature during the thermal treatment is between 900° C. and 1150° C.

10 . The method of claim 7 , wherein the period of time for maintaining the ribbon at the temperature is between 10 and 60 minutes.

11 . The method of claim 7 , wherein the thermal treatment is configured to maintain a higher average temperature at the front surface of the ribbon than at the back surface.

12 . The method of claim 7 , wherein the first denuded zone has a thickness at least twice that of the second denuded zone.

13 . The method of claim 7 , further comprising polishing or etching the front surface of the ribbon before forming an epitaxial layer thereon.

14 . A single crystal silicon ribbon comprising:
a front surface and a back surface; a first denuded zone extending from the front surface to a first depth; a second denuded zone extending from the back surface to a second depth less than the first depth; and a bulk region disposed between the first and second denuded zones, the bulk region having an oxygen concentration greater than 2×10 17 atoms/cm 3 , wherein the ribbon is formed such that it floats on a surface of molten silicon during crystal growth.

15 . The ribbon of claim 14 , wherein the front surface is polished or etched to a depth less than the first depth.

16 . The ribbon of claim 14 , wherein an epitaxial silicon layer is disposed over the front surface.

17 . The ribbon of claim 16 , wherein one or more semiconductor devices are formed in the epitaxial silicon layer.

18 . The ribbon of claim 14 , wherein the oxygen concentration within the bulk region is substantially uniform across at least 80% of the thickness of the ribbon.

19 . The ribbon of claim 14 , wherein the first denuded zone has a thickness between 10 and 50 microns, and the second denuded zone has a thickness less than 20 microns.

20 . The ribbon of claim 14 , wherein the difference in depth between the first denuded zone and the second denuded zone results from a thermal gradient applied during crystal growth or from a post-growth thermal treatment.

Assignees

• Blue Origin Mfg Llc

Inventors

• Appel Jesse S
• Greenlee Alison
• Stoddard Nathan
• Kellerman Peter
• Daggolu Parthiv
• Martinez Alexander
• Pirooz Saeed

Classifications

• H10F77/122 Primary

  comprising only Group IV materials · CPC title

• C30B15/06

  Non-vertical pulling · CPC title

• C30B29/06 Primary

  Silicon · CPC title

• H10F77/1223

  characterised by the dopants · CPC title