WO2021072239A1 - Method, system and apparatus for growing hollow core silicon single crystals - Google Patents

Abstract

A method of growing a substantially dislocation-free hollowed core silicon crystal is disclosed, the method including providing a substantially circular silicon seed, the seed including a top surface, a bottom surface, an outer surface and a notch within the outer surface; securing the seed into a chuck by inserting a retainer piece into the notch on the outer surface of the silicon seed; lowering the silicon seed into molten silicon within a crucible; gradually withdrawing the silicon seed from the molten silicon to form a substantially dislocation-free hollowed core silicon crystal. Silicon crystal seeds are also disclosed, as are systems and apparatus for forming hollow silicon crystals.

Description

METHOD, SYSTEM AND APPARATUS FOR GROWING HOLLOW CORE

SILICON SINGLE CRYSTALS

This application is being filed as a PCT International Patent application on October 9, 2020, in the name of GCL Solar Materials III, LLC, a U.S. national corporation, applicant for the designation of all countries, Arash Mehdizadeh Dehkordi, a Uranian Citizen, inventor for the designation of all countries and Rituraj Nandan, an Indian Citizen, inventor for the designation of all countries. This application claims priority to U.S. Provisional Application No. 62/913,012 filed October 9, 2019, the content of which is herein incorporated by reference in its entirety.

Field

Embodiments herein relate to methods, systems, and apparatuses for growing silicon materials, in particular for growing hollow core silicon cylinders for creation of silicon focus rings.

Summary

In an embodiment, a method of growing a substantially dislocation-free hollowed core silicon crystal, the method is included, the method providing a substantially circular silicon seed, the seed including a top surface, a bottom surface, an outer surface and a notch within the outer surface; securing the seed into a chuck by inserting a retainer piece into the notch on the outer surface of the silicon seed; lowering the silicon seed into molten silicon within a crucible; gradually withdrawing the silicon seed from the molten silicon to form a substantially dislocation-free hollowed core silicon crystal.

In an embodiment the notch in the outer surface of the silicon seed extends around the entire silicon seed.

In an embodiment the notch in the outer surface of the silicon seed extends around a portion of the silicon seed.

In an embodiment the notch in the outer surface of the silicon seed extends intermittently around the entire silicon seed.

In an embodiment the seed has a thickness less than its diameter.

In an embodiment a neck forms during initial withdrawing of the silicon seed from the molten silicon.

In an embodiment, the seed has an outer diameter of 330 to 360 millimeters and an inner diameter of 280 to 320 millimeters.

In an embodiment the notch is located between the top surface and bottom surface of the seed.

In an embodiment the silicon seed is a single crystal.

In an embodiment the Continuous Czochralski (CCz) technique is used to draw the silicon.

In an embodiment the Recharge Czochralski (RCz) technique is used to draw the silicon.

In an embodiment, the method can include cutting the substantially dislocation-free hollowed core silicon crystal into silicon focus rings.

In an embodiment, the hollowed core silicon crystal has a thickness between its outer surface and its inner surface that varies less than 10 percent.

In an embodiment, a substantially dislocation-free hollowed core silicon crystal is formed using the method of: providing a substantially circular silicon seed, the seed including a top surface, a bottom surface, an outer surface and a notch within the outer surface; securing the seed into a chuck by inserting a retainer piece into the notch on the outer surface of the silicon seed; lowering the silicon seed into molten silicon within a crucible; gradually withdrawing the silicon seed from the molten silicon to form a substantially dislocation-free hollowed core silicon crystal.

This summary is an overview of some of the teachings of the present application and is not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details are found in the detailed description and appended claims. Other aspects will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which is not to be taken in a limiting sense. The scope herein is defined by the appended claims and their legal equivalents.

Brief Description of the Figures

Aspects may be more completely understood in connection with the following figures (FIGS.), in which:

FIG. l is a perspective view of a silicon focus ring made in accordance with various embodiments herein. FIG. 2 is a top view of a silicon focus ring made in accordance with various embodiments herein.

FIG. 3 is a perspective view of a hollow core silicon crystal made in accordance with various embodiments herein.

FIG. 4 is a perspective view of silicon seed crystal made in accordance with various embodiments herein.

FIG. 5 is a partial cross-sectional view of a silicon seed crystal along with a portion of a hollow core silicon crystal growing from the seed crystal in accordance with various embodiments herein.

FIG. 6 is a cross sectional schematic view of system for making hollow core silicon crystals in accordance with various embodiments herein.

While embodiments are susceptible to various modifications and alternative forms, specifics thereof have been shown by way of example and drawings, and will be described in detail. It should be understood, however, that the scope herein is not limited to the particular aspects described. On the contrary, the intention is to cover modifications, equivalents, and alternatives falling within the spirit and scope herein.

Detailed Description

The present disclosure relates to growth of crystal silicon ingots, in particular dislocation-free single crystal silicon ingots with a hollowed core that can be used to manufacture silicon focus rings, which are also sometimes referred to edge rings, hot rings, cover rings, for oxide etch processes. Focus rings are used to surround a silicon wafer during oxide etch processes, and typically cover the electrostatic chuck used in that oxide etch process. The crystal growth process described herein is capable of significantly reducing the silicon focus ring production cost by eliminating the core drilling step currently used to produce silicon focus rings.

The system, apparatus, and method can significantly reduce the materials loss of the silicon focus ring manufacturing process due to traditional core drilling and reduces total manufacturing cost of the silicon ring parts in the crystal growth process by reducing the polysilicon feedstock used. It can also add value by eliminating/minimizing core drilling step commonly used. Thus the method and system described herein as well as the silicon ring itself, can be produced with a savings in both material and labor. With regard to material savings, as an example, for a 1.0 meter ingot 380 millimeters in diameter, assuming a 50 millimeter wide ring (measured from inside of the focus ring to the outside of the focus ring) mass of the hollowed core ingot pulled would be 65 kilograms. In contrast, a normal solid ingot would weigh about 265 kilograms weight of a normal ingot, showing an approximately 75 percent reduction in polysilicon used, but also a significant reduction in time and expense from hollowing out a normal solid silicon ingot.

Among other benefits of the process described herein are smaller thermal mass, more efficient heat removal from interfaces and potentially higher pull rate and productivity.

The growth process described utilizes a notched single-crystalline ring-shaped seed with a seed chuck to pull a cylindrical hollowed core silicon ingot from silicon melt using the Continuous Czochralski (CCz) technique. The growth method can also be implemented using the Recharge Czochralski (RCz) technique, however, it is expected that the more stable growth interface provide by the CCz method.

Referring now to the drawings, FIG. l is a perspective view of a silicon focus ring 102, showing the open center 104 and mounting screws 106. FIG. 2 is a top view of the silicon focus ring 102, showing the open center 104, along with mounting screws 106, plus inner surface 208 and outer surface 210. The focus ring shown has an outer diameter A and an inner diameter A. Typically the focus ring will have an interior diameter A of about 300 mm and an outer diameter A of about 345 mm, although other dimensions can be used.

FIG. 3 is a perspective view of a hollow core silicon crystal 312 made in accordance with various embodiments herein, including a hollow interior 314 and a top 316 and a bottom 318. The hollow core silicon crystal 312 is preferably dislocation-free or at least substantially dislocation-free. Also, the hollow core silicon crystal 312 generally has a substantially uniform diameter and substantially uniform will thickness. Typically the diameter of the crystal 312, measured from 10 percent below the top to 10 percent from the bottom, does not vary more than 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, 10 percent, 15 percent, or 20 percent in various constructions. Typically the thickness of the wall of the crystal 312, measured from 10 percent below the top to 10 percent from the bottom, does not vary more than 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, 10 percent, 15 percent, or 20 percent in various constructions. FIG. 4 is a perspective view of silicon crystal seed 420 made in accordance with various embodiments herein, the silicon crystal seed 420 has an open interior 422 surrounded by interior surface 429 along with a top surface 424 and a bottom surface 426, plus a notch 430 around the outer surface 428. This silicon crystal seed generally defines the outer diameter, inner diameter, and width of silicon focus rings produced using the silicon crystal seed 420. The silicon crystal seed 420 generally has an interior diameter and exterior diameter close to the diameter of a desired silicon focus ring.

FIG. 5 is a partial cross-sectional view of a silicon crystal seed 420 (with a portion of outer surface 428 in cross section and interior surface 429 also shown), along with a portion of a hollow core silicon crystal 312, the hollow core silicon crystal 312 having a neck 532 growing from the silicon crystal seed 420 and a walls 534 growing from the neck 532. The point of connection where the neck 532 forms on the bottom of the silicon crystal seed 420 is shown at transition 533. A notch 430 in the silicon crystal seed is made to receive a retainer pieces on a chuck, shown in FIG. 6 and discussed below. The seed 420 is used only once to form a hollow core silicon crystal 312.

FIG. 6 shows a schematic of an overall system, including the cylindrical silicon crystal seed 420, neck 532, cylindrical hollow core silicon crystal 312, silicon melt 642 (with top surface 644), chuck 636, and crucible 640 during body growth. Walls 534 of the hollow core silicon crystal 312 are shown, along with retainer pieces 638 that fit into the notch 430 As shown the sequence of the process includes: lowering the cylindrical seed close to the melt, necking (here a cylindrical neck film wall form), and growth of the main body of the hollow core silicon crystal 312.

It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

It should also be noted that, as used in this specification and the appended claims, the phrase “configured” describes a system, apparatus, or other structure that is constructed or configured to perform a particular task or adopt a particular configuration. The phrase "configured" can be used interchangeably with other similar phrases such as arranged and configured, constructed and arranged, constructed, manufactured and arranged, and the like. All publications and patent applications in this specification are indicative of the level of ordinary skill in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated by reference.

The embodiments described herein are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art can appreciate and understand the principles and practices. As such, aspects have been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope herein.

Claims

The Claims Are:

1. A method of growing a substantially dislocation-free hollowed core silicon crystal, the method comprising: providing a substantially circular silicon seed, the seed including a top surface, a bottom surface, an outer surface and a notch within the outer surface; securing the seed into a chuck by inserting a retainer piece into the notch on the outer surface of the silicon seed; lowering the silicon seed into molten silicon within a crucible; gradually withdrawing the silicon seed from the molten silicon to form a substantially dislocation-free hollowed core silicon crystal.

2. The method of claim 1 of growing a substantially dislocation-free hollowed core silicon crystal, wherein the notch in the outer surface of the silicon seed extends around the entire silicon seed.

3. The method of claim 1 of growing a substantially dislocation-free hollowed core silicon crystal, wherein the notch in the outer surface of the silicon seed extends around a portion of the silicon seed.

4. The method of claim 1 of growing a substantially dislocation-free hollowed core silicon crystal, wherein the notch in the outer surface of the silicon seed extends intermittently around the entire silicon seed.

5. The method of claim 1 of growing a substantially dislocation-free hollowed core silicon crystal, wherein the seed has a thickness less than its diameter.

6. The method of claim 1 of growing a substantially dislocation-free hollowed core silicon crystal, wherein a neck forms during initial withdrawing of the silicon seed from the molten silicon.

7. The method of claim 1 of growing a substantially dislocation-free hollowed core silicon crystal, wherein the seed has an outer diameter of 330 to 360 millimeters and an inner diameter of 280 to 320 millimeters.

8. The method of claim 1 of growing a substantially dislocation-free hollowed core silicon crystal, wherein notch is located between the top surface and bottom surface of the seed.

9. The method of claim 1 of growing a substantially dislocation-free hollowed core silicon crystal, wherein the silicon seed is a single crystal.

10. The method of claim 1 of growing a substantially dislocation-free hollowed core silicon crystal, wherein the Continuous Czochralski (CCz) technique is used to draw the silicon.

11. The method of claim 1 of growing a substantially dislocation-free hollowed core silicon crystal, wherein the Recharge Czochralski (RCz) technique is used to draw the silicon.

12. The method of claim 1 of growing a substantially dislocation-free hollowed core silicon crystal, further comprising cutting the substantially dislocation-free hollowed core silicon crystal into silicon focus rings.

13. The method of growing a substantially dislocation-free hollowed core silicon crystal of claim 1, wherein the hollowed core silicon crystal has a thickness between its outer surface and its inner surface that varies less than 10 percent.

14. A substantially dislocation-free hollowed core silicon crystal formed using the method of: providing a substantially circular silicon seed, the seed including a top surface, a bottom surface, an outer surface and a notch within the outer surface; securing the seed into a chuck by inserting a retainer piece into the notch on the outer surface of the silicon seed; lowering the silicon seed into molten silicon within a crucible; gradually withdrawing the silicon seed from the molten silicon to form a substantially dislocation-free hollowed core silicon crystal.

15. A silicon seed for growing a hollow core silicon crystal, the seed including a top surface, a bottom surface, an outer surface and a notch within the outer surface.

16. The silicon seed for growing a hollow core silicon crystal of claim 15, wherein the notch in the outer surface of the silicon seed extends around the entire silicon seed.

17. The silicon seed for growing a hollow core silicon crystal of claim 15, wherein the notch in the outer surface of the silicon seed extends around a portion of the silicon seed.

18. The silicon seed for growing a hollow core silicon crystal of claim 15, wherein the notch in the outer surface of the silicon seed extends intermittently around the entire silicon seed.

19. The silicon seed for growing a hollow core silicon crystal of claim 15, wherein the seed has a thickness less than its diameter.

20. The silicon seed for growing a hollow core silicon crystal of claim 15, wherein the seed has an outer diameter of 330 to 360 millimeters and an inner diameter of 280 to 320 millimeters.