EP4217528A1

EP4217528A1 - Method for growing single crystals

Info

Publication number: EP4217528A1
Application number: EP21794711.8A
Authority: EP
Inventors: Kanaparin Ariyawong; Ghassan Barbar; Robert Ebner; Chih-Yung Hsiung
Original assignee: Ebner Industrieofenbau GmbH
Current assignee: Ebner Industrieofenbau GmbH
Priority date: 2020-09-28
Filing date: 2021-09-23
Publication date: 2023-08-02
Also published as: WO2022061387A1; AT524251A1; US20230357952A1; TW202219332A; CN116324053A; AT524251B1

Abstract

The invention relates to a device (501) for growing single crystals, in particular silicium carbide single crystals, and comprises a crucible (502), the crucible (502) defining an outer surface (503) and delimiting a receptacle (504) having an axial extent between a bottom portion (505) and an opening portion (506). The receptacle (504) is designed for crystal growth and at least one seed crystal layer (507) is located in the opening portion (506), the seed crystal layer (507) being weighted down by means of a weighting mass (508) at a side remote from the receptacle (504) and being fixed, in particular exclusively, by the weight force of the weighting mass (508) in its position against at least one holding portion (509) located in the opening portion.

Description

DEVICE FOR GROWING MONOCRYSTALS

The invention relates to a device for growing single crystals, in particular single crystals made of silicon carbide, comprising a crucible, which crucible defines an outer lateral surface and further delimits a receiving space with an axial extension between a bottom section and an opening s section, the receiving space being used for growing the Crystals is formed, the device having at least one seed crystal layer.

Today, single crystals are artificially produced on an industrial scale for many technical applications. According to the phase transitions that lead to the crystal, growth from the melt, from the solution and from the gas phase can be differentiated. In the case of growth from the gas phase, the production methods of sublimation or physical gas phase deposition and the method of chemical gas phase deposition can also be distinguished. In physical vapor deposition, the substance to be grown is vaporized by heating so that it transitions into the gas phase. Under suitable conditions, the gas can resublimate on a seed crystal, as a result of which the crystal grows. The raw material (powder or granules), which is usually polycrystalline, undergoes recrystallization in this way. Chemical vapor deposition works in a similar way. With this, the transition of the substance to be grown into the gas phase is only possible through an auxiliary substance to which the substance binds chemically, since otherwise the vapor pressure would be too low. In connection with the auxiliary substance, a higher transport rate towards the seed crystal is thus achieved.

There is great interest in silicon carbide monocrystals, particularly because of their semiconductor properties. They are manufactured in furnaces with a crucible, in which the silicon carbide raw material is heated, and a seed crystal, on which further crystal growth takes place through accumulation. The interior of the process chamber is also evacuated. Graphite is used as the material for the innermost process chamber with the crucible. The seed crystal is usually located directly on a lid of a crucible containing the raw material. One problem that occurs with known methods is detaching the ingot that is produced when the crystals are grown from the lid, since the ingot has grown together with the lid in the conventional methods. Cutting or sawing methods are usually used for this purpose. In addition, the conventional solutions favor the formation of imperfections in a transition region between the cover and edge regions of the seed crystal, since deposits can occur on side edges of the seed crystal that are not intended for crystal growth in the known solutions.

The object of the present invention was to overcome the disadvantages of the prior art and to simplify the production of single crystals.

This object is achieved according to the invention in that the seed crystal layer is weighted down on a side facing away from the receiving space by means of a weight and, in particular only, is fixed in its position against at least one holding section of the crucible by the weight of the weight.

The solution according to the invention makes it possible in a simple manner to remove the ingot from the crucible without having to cut off or detach the ingot from the lid for this purpose.

In order to cover regions that are not used for crystallization, it can be provided that the seed crystal layer bears against the at least one holding section with at least one outer edge region.

It has proven to be particularly advantageous that the at least one holding section is designed to run around an opening of the opening section.

According to a preferred development of the invention, it can be provided that the at least one holding section is formed by at least one section of a holder facing a central longitudinal axis of the crucible with an annular or tubular base body, with the at least one holding section protruding from the base body.

A particularly reliable positioning of the holder in the crucible provides that the holder is screwed into the crucible. According to a preferred variant, it can be provided here that the holder has an external thread on a lateral surface of the base body, with a lateral surface delimiting the opening having an internal thread corresponding to the external thread.

In an advantageous development, the weight is arranged between the seed crystal layer and a cover of the crucible, the weight and cover being formed separately from one another.

It has turned out to be particularly favorable that the weighting mass is arranged loosely between the cover and the seed crystal layer.

A variant of the invention consists in the at least one seed crystal layer being applied to a carrier substrate and the weighting mass resting on the carrier substrate.

The carrier substrate can advantageously be formed from graphite.

The weighting mass and/or the mount can be made of metal, ceramic, mineral or plastic, in particular refractory materials, carbides, oxides or nitrides.

Provision is preferably made for the crucible to be arranged in a chamber of an inductively heated furnace.

For a better understanding of the invention, it is explained in more detail with reference to the following figures.

They each show in a greatly simplified, schematic representation:

1 shows an apparatus for the production of single crystals by means of physical vapor deposition with a conventional attachment of a seed crystal;

2 shows a section through a crucible of a first variant of a device according to the invention;

3 shows a section through a crucible of a second variant of a device according to the invention; 4 shows a section through a crucible of a second variant of a device according to the invention.

As an introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numbers or the same component designations, it being possible for the disclosures contained throughout the description to be applied to the same parts with the same reference numbers or the same component designations. The position information selected in the description, such as top, bottom, side, etc., is related to the directly described and illustrated figure and these position information are to be transferred to the new position in the event of a change in position.

1 shows a furnace 401 for producing single crystals by means of physical vapor deposition. The furnace 401 comprises an evacuatable chamber 402 with a crucible 403 accommodated therein. The crucible 403 is essentially pot-shaped, with an upper end region being closed by a cover 404. In this case, an underside of the cover 404 of the crucible 403 is usually designed for fastening a seed crystal 405 . In a bottom area 406 of the crucible 403 there is a starting material 407 which serves as a raw material for the crystal growth on the seed crystal 405 and which is gradually used up during the production process.

The transition of the starting material 407 into the gas phase is achieved by heating using a heater 408 . According to this exemplary embodiment, the starting material 407 and the crucible 403 are heated inductively by the heater 408 . The crucible 403 arranged in the chamber 402 is also encased by an insulation 409 for thermal insulation. At the same time, the insulation 409 prevents heat losses from the crucible 403 and achieves a heat distribution in the interior of the crucible 403 that is favorable for the growth process of the crystal on the seed crystal 405 .

A glass material, in particular a quartz glass, is preferably used as the material for the chamber 402 . The crucible 403 and the insulation 409 surrounding it are preferably made of graphite, with the insulation 409 being formed by a graphite felt.

By heating the starting material 407 and causing atoms or molecules thereof to gaseous phase, they can diffuse in the interior of the crucible 403 to the seed crystal 405 and be deposited thereon, as a result of which crystal growth takes place. According to Fig. 2, a device 501 according to the invention for growing single crystals, in particular single crystals made of silicon carbide, comprises a crucible 502. The crucible 502 defines an outer lateral surface 503 and also delimits a receiving space 504 with an axial extent between a bottom section 505 and an opening section 506. The accommodation space 504 is formed for growing the crystals, with at least one seed crystal layer 507 being arranged in the opening portion 506 . The crucible 502 can be arranged in a chamber, as it corresponds to the chamber 402 and can also be inductively heated.

In contrast to the embodiment according to Fig. 1, according to the invention, seed crystal layer 507 is weighted down on a side facing away from receiving space 504 by means of a weight 508 and is fixed in its position against at least one holding portion 509 arranged in the opening portion by the weight of weight of weight 508. Provision is preferably made for the seed crystal layer 507 to be formed only by the weight of the weight 508. In other respects, the device 501 and the furnace can be designed from FIG.

As can also be seen from FIG. 2 , at least one outer edge region of the seed crystal layer 507 can bear against the at least one holding section 509 .

The holding section 509 can be configured to run around an opening 510 of the opening section 506 .

According to FIGS. 3 and 4, the holding section 509 can be formed by at least one section of a holder 510 facing a longitudinal central axis of the crucible with an annular or tubular base body 511, with the holding section 509 protruding from the base body 511. The holder 510 can be screwed into the crucible 502, as shown in FIG. 3, or plugged in, as shown in FIG.

According to the embodiment shown in FIG. 3, the holder 510 can have an external thread 512 on a lateral surface of the base body 511, wherein a lateral surface delimiting the opening can have an internal thread 513 corresponding to the external thread. According to FIG. 4, the holder 510 inserted into the crucible can be located on a projection

514 of the crucible 502. The projection 514 can be formed, for example, around the opening of the opening portion 506 encircling.

The weighting mass 508 can be placed between the seed crystal layer 507 and a cover

515 of the crucible 502 can be arranged, the weight 508 and cover 515 being formed separately from one another. The weighting mass 508 is preferably arranged loosely between the cover 515 and the seed crystal layer 507 .

The seed crystal layer 507 can be in the form of a mechanically self-supporting layer or can also be applied to a carrier substrate. If the seed crystal layer 507 is applied to a carrier substrate, the weighting mass 508 can rest on the carrier substrate. Graphite has proven to be particularly suitable for the carrier substrate.

The weight 508 and/or the mount 510 may be made of metal, ceramic, mineral, or plastic. For example, refractory materials, carbides, oxides or nitrides have proven to be particularly suitable.

Finally, for the sake of clarity, it should be pointed out that some elements are shown not to scale and/or enlarged and/or reduced in size for a better understanding of the structure.

list of reference numbers

oven

chamber

crucible

lid

seed crystal

bottom section

starting material

heating

insulation

contraption

crucible

lateral surface

recording room

bottom section

opening section

seed layer

weighting mass

holding section

bracket

body

external thread

inner thread

head Start

lid

Claims

- 8 -Claims

1. Device (501) for growing single crystals, in particular single crystals made of silicon carbide, comprising a crucible (502), which crucible (502) defines an outer lateral surface (503) and furthermore a receiving space (504) with an axial extent between a bottom section ( 505) and an opening section (506), the receiving space (504) being designed for growing the crystals, the device having at least one seed crystal layer (507), characterized in that the seed crystal layer (507) is attached to one of the receiving space (504) on the opposite side by means of a weight (508) and is fixed in its position against at least one holding section (509) of the crucible, in particular only by the weight of the weight (508).

2. Device according to claim 1, characterized in that the seed crystal layer (507) rests with at least one outer edge area on the at least one holding section (509).

3. Device according to claim 2, characterized in that the at least one holding section (509) is designed to run around an opening (510) of the opening section (506).

4. The device according to claim 2 or 3, characterized in that the at least one holding section (509) is formed by at least one section of a holder (510) facing a central longitudinal axis of the crucible with an annular or tubular base body (511), the at least one holding section (509) protrudes from the base body (511).

5. Device according to claim 4, characterized in that the holder (510) is screwed into the crucible (502).

6. The device according to claim 5, characterized in that the holder (510) on a lateral surface of the base body (511) has an external thread (512), wherein a - 9 - the lateral surface delimiting the opening has an internal thread (513) corresponding to the external thread.

7. Device according to one of claims 1 to 6, characterized in that the weight (508) is arranged between the seed crystal layer (507) and a cover (514) of the crucible (502), the weight (508) and cover (514) are formed separately from each other.

8. The device according to claim 7, characterized in that the weight (508) is arranged loosely between the cover (514) and seed crystal layer (507).

9. Device according to one of claims 1 to 8, characterized in that the at least one seed crystal layer (507) is applied to a carrier substrate and the weighting mass (508) rests on the carrier substrate.

10. Device according to one of claims 1 to 9, characterized in that the carrier substrate is formed from graphite.

11. Device according to one of claims 1 to 10, characterized in that the weight (508) and/or the holder (510) is made of metal, ceramic, mineral or plastic, in particular of refractory materials, carbides, oxides or the like - the nitrides.

12. Device according to one of claims 1 to 11, characterized in that the crucible (502) is arranged in a chamber of an inductively heated furnace.