CN210529104U - Crucible assembly for preparing high-quality crystals - Google Patents

Abstract

The application relates to a crucible assembly for preparing high-quality crystals, and belongs to the field of crystal preparation. The crucible assembly for producing high quality crystals comprises: the crucible comprises a crucible main body and a crucible cover covering the crucible main body; the seed crystal support is fixed in the crucible and used for fixing the seed crystal; and the raw material block support is arranged in the crucible and used for supporting the raw material blocks. The crucible assembly is used for preparing single crystals by using the raw material blocks as raw materials, and the crucible assembly can be arranged in a mode of preparing high-quality single crystals; the crucible assembly can be arranged at the position of the raw material block according to actual needs, so that the positions of the raw material and the seed crystal in the thermal field can be conveniently adjusted, and the high-quality single crystal can be prepared.

Description

Crucible assembly for preparing high-quality crystals

Technical Field

The application relates to a crucible assembly for preparing high-quality crystals, and belongs to the field of crystal preparation.

Background

With the increasing demand for power electronic devices in the rapid development of industries such as 5G communication, new energy automobiles and the like, third-generation semiconductor materials represented by silicon carbide (SiC) semiconductors are receiving attention due to excellent physical properties such as wide forbidden band, high thermal conductivity, high critical breakdown field strength and high saturated electron drift rate. Because the difficulty in preparing the SiC single crystal is great and the cost of the SiC single crystal substrate is high, how to efficiently prepare the low-cost SiC single crystal substrate becomes a core problem for solving the requirements of the emerging industry on power devices.

Currently, the most mature preparation technology for preparing SiC single crystals is a Physical Vapor Transport (PVT) method, i.e. a new SiC single crystal is formed by heating synthetic SiC powder to a certain temperature to sublimate the powder and transmitting the sublimated powder to a seed crystal along a temperature gradient to crystallize under a lower pressure. The key point of the PVT method for preparing the SiC single crystal is reasonable design and control of the thermal field condition so that gas phase components obtained by sublimating synthetic powder are orderly transmitted to the seed crystal for recrystallization. Therefore, the quality (including purity) of the synthetic powder and the control of the gas-phase component transport path become the core of the PVT process. The structure of the crucible assembly used in the preparation of the crystal influences the arrangement mode of the raw materials and the seed crystal to further influence the crystal growth quality, so that the provision of the proper crucible assembly has great influence on the improvement of the crystal growth quality.

SUMMERY OF THE UTILITY MODEL

In order to solve the above problems, the present application proposes a crucible assembly for producing a high quality crystal, which is used for producing a single crystal using a raw material block as a raw material, and is arranged in such a manner as to produce a high quality single crystal; the crucible assembly can be arranged at the position of the raw material block according to actual needs, so that the positions of the raw material and the seed crystal in the thermal field can be conveniently adjusted, and the high-quality single crystal can be prepared.

The crucible assembly for preparing high-quality crystals is characterized by comprising:

the crucible comprises a crucible main body and a crucible cover covering the crucible main body;

the seed crystal support is fixed in the crucible and used for fixing the seed crystal; and

the raw material block support is arranged in the crucible and used for supporting the raw material blocks.

Optionally, the seed crystal holder is arranged in the middle of the crucible, and the raw material block holders are respectively arranged above and below the seed crystal holder.

Optionally, the raw material block support comprises an annular support portion and at least one bearing portion fixed on the support portion, the bearing portion extends inwards along the radial direction of the support portion, and the bearing portion is used for placing the raw material block.

Optionally, the supporting portion is an annular supporting plate structure, and the bearing portion is a plate structure.

Optionally, the support portion fixes a bearing portion, and a plurality of raw material block supports are stacked in the crucible main body along the axial direction of the crucible main body.

Optionally, the seed crystal support is arranged to be fixed on a first boss protruding inwards on the inner side wall of the crucible main body.

Optionally, the first boss is integrally formed with the inner side wall of the crucible main body.

Optionally, the first boss is annular.

Optionally, the raw material block support is a second boss fixed on the inner side wall of the crucible main body and protruding inwards, and the second boss and the inner side wall of the crucible main body are integrally formed.

Optionally, a plurality of second bosses are arranged in the raw material area in the crucible main body and used as raw material block supports, and the second bosses are of annular structures.

Benefits that can be produced by the present application include, but are not limited to:

1. the crucible assembly for preparing high-quality crystals is provided with the crucible assembly for preparing single crystals by taking raw material blocks as raw materials, and the arrangement mode of the crucible assembly is used for preparing high-quality single crystals;

2. according to the crucible assembly for preparing the high-quality crystal, the position of the raw material block can be arranged according to actual needs, the positions of the raw material and the seed crystal in the thermal field can be conveniently adjusted, and the high-quality single crystal is prepared.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

FIG. 1 is a schematic cross-sectional view of a crucible assembly in growing a silicon carbide single crystal according to an embodiment of the present application.

Fig. 2 is a schematic view of a raw material block holder supporting a raw material block according to an embodiment of the present application.

FIG. 3 is a schematic cross-sectional view of a crucible assembly according to an embodiment of the present application.

Detailed Description

In order to more clearly explain the overall concept of the present application, the following detailed description is given by way of example in conjunction with the accompanying drawings.

So that the manner in which the above recited objects, features and advantages of the present application can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, however, the present application may be practiced in other ways than those described herein, and therefore the scope of the present application is not limited by the specific embodiments disclosed below.

In addition, in the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", and the like, indicate orientations and positional relationships based on those shown in the drawings, are only for convenience of description and simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present application.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.

In this application, unless expressly stated or limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can include, for example, fixed connections, removable connections, or integral parts; the connection can be mechanical connection, electrical connection or communication; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The crucible assembly of the present application can be used for physical vapor transport growth of a single crystal, and the following example of a crucible assembly for the present application will be described by taking a silicon carbide single crystal as an example.

Referring to fig. 1 and 2, a crucible assembly used in a method of producing a high-quality and high-purity silicon carbide single crystal is schematically illustrated in cross section. The crucible assembly includes a crucible, a seed crystal holder, and a raw material block holder 300. The crucible comprises a crucible body 110 and a crucible cover 120 covering the crucible body 110, at least one seed crystal support is arranged in the crucible, and a raw material block support 300 is arranged in a raw material area in the crucible body 110.

The mode of fixing the seed crystal holder in the crucible is not limited, and different fixing modes are set according to different positions of the seed crystal 400 to be fixed in the crucible. For example, when the seed crystal 400 is fixed in the middle of the crucible, the seed crystal holder is provided as a first boss protruding inward with respect to the inner sidewall of the crucible main body 110, or the seed crystal 400 is adhered to the inner sidewall of the crucible main body 110; when the seed crystal 400 is fixed on the top of the crucible, the seed crystal 400 is adhered or clamped on the inner side surface of the crucible cover; when the seed crystal 400 is fixed to the bottom of the crucible, the seed crystal 400 may be directly placed on the bottom of the crucible body 110.

Raw material block holder 300 is not limited as long as it can support raw material block 500. As an embodiment, feedstock piece holder 300 includes an annular support column and at least one support table secured to the support column that is inwardly convex; preferably, the support column extends along the inner sidewall of the crucible body 110, and the support table extends in the radial direction of the crucible body 110. In a preferred embodiment, the raw material block holder 300 includes a ring-shaped support column and a support base, and when a plurality of raw material blocks 500 are used as raw materials, the raw material blocks 500 are placed in the raw material block holder 300, and then the raw material blocks 500 and the raw material block holder 300 are sequentially stacked inside the crucible, and the center of the crucible main body 110 is used to place the seed crystal 400 for crystal growth, so that the raw material blocks 500 can be fixed above and below the seed crystal 400, respectively, and the silicon carbide single crystal 610 and the silicon carbide single crystal 620 can be grown above and below the seed crystal 400, respectively. The feedstock pieces may be selected from polycrystalline, single crystal pieces, or powder compacts, and the like.

Referring to fig. 3, an embodiment of a crucible assembly, a crucible includes a crucible body 110 and a crucible cover 120, a raw material block 500 is placed in the crucible body 110, at least one raw material block holder 300 is disposed on an inner side wall of the crucible body 110, the raw material block holder 300 is used for supporting the raw material block 500, a seed crystal 400 fixing portion is disposed on an inner side surface of the crucible cover 120, or the seed crystal 400 is supported and fixed by a seed crystal holder fixed on an inner side wall of the crucible body 110. The number of raw material block holders 300 provided in the crucible shown in fig. 3 is 1, and the number of raw material block holders 300 provided in the axial direction in the long cavity formed by the crucible in the embodiment not shown is more than 1.

FIG. 3 is a schematic cross-sectional view of a crucible before crystal growth, in which a raw material block 500 is fixed to a raw material block holder 300 in the crucible and a seed crystal 400 is fixed to the inner side surface of a crucible cover 120. Preferably, the raw material block 500 and the seed crystal 400 are both sheet-like structures. More preferably, the raw material block 500 divides a growth chamber formed by the crucible into a raw material chamber and a primary growth chamber.

Further, the raw material block holder 300 is a ring-shaped second boss provided on the inner side wall of the crucible main body 110 and protruding into the crucible, and the raw material block 500 is placed on the top surface of the ring-shaped second boss.

Further, the seed crystal holder, the raw material block holder, the crucible main body, and the crucible cover are made of graphite, preferably high-purity graphite.

As an embodiment, a method for preparing a high purity semi-insulating silicon carbide single crystal using a crucible assembly includes the steps of:

1) assembling: a raw material area and seed crystals are arranged in the crucible, at least one silicon carbide polycrystalline block opposite to the seed crystals is placed in the raw material area, the raw material area is located in a high-temperature area, the seed crystals are located in a low-temperature area, the silicon carbide polycrystalline block is provided with a pore structure, a gas phase outlet is formed in one end, close to the seed crystals, of the pore structure, and part of gas phase raw materials A in the raw material area are transmitted to the seed crystals from the gas phase outlet through the pore structure;

2) crystal growth: placing the assembled crucible in a crystal growth furnace, controlling the crystal growth condition of the crystal growth furnace to enable the silicon carbide polycrystalline block to be sublimated into a gas phase raw material, and transmitting the gas phase raw material from the raw material area to seed crystals for crystal growth to obtain the high-purity semi-insulating silicon carbide single crystal;

the area of the graphite crucible main body, in which the silicon carbide polycrystalline block is placed, is a raw material area.

Referring to fig. 1, the pore structure may be a through hole or a groove structure, the groove structure being a structure recessed with respect to the seed crystal; preferably, the pore structure is a through hole arranged along the axial direction of the silicon carbide polycrystalline block; more preferably, the channel structure is disposed in correspondence with a central region of the seed crystal. The pore structure is beneficial to improving the sublimation surface area of the polycrystalline block, improving the sublimation rate and improving the crystal growth rate.

The growth feedstock may be 1 or more polycrystalline blocks of silicon carbide. When the raw material is a plurality of silicon carbide polycrystalline blocks, the structures of the plurality of silicon carbide polycrystalline blocks can be the same or different; preferably, the structures of the plurality of silicon carbide polycrystalline blocks are the same, the plurality of silicon carbide polycrystalline blocks are arranged along the axial direction of the crucible, the pore channel structures of the silicon carbide polycrystalline blocks are correspondingly arranged, a radial channel is formed between the adjacent silicon carbide polycrystalline blocks, and the radial channel is communicated with the pore channel structures. The arrangement mode of the plurality of silicon carbide polycrystalline blocks not only further improves the crystal growth efficiency, but also is beneficial to further improving the purity of the prepared silicon carbide single crystal.

Furthermore, the silicon carbide polycrystalline block is arranged into a circular ring structure which is matched with the inner diameter of the crucible, and the pore channel structure is a cylindrical space. Preferably, the ratio of the inner diameter of the channel structure to the outer diameter of the silicon carbide polycrystalline mass is 0.25 to 0.5. The ratio of the pore structure to the outer diameter of the silicon carbide polycrystalline block can keep the consistency of gas-phase raw material transmission.

The thickness of the silicon carbide polycrystalline block is 5-30 mm; preferably, the thickness of the silicon carbide polycrystalline block is 15 to 20 mm. The thickness of the silicon carbide polycrystalline mass facilitates sufficient sublimation of the silicon carbide while ensuring the mass quantity to provide sufficient gas phase reaction components. The diameter of the silicon carbide polycrystal is determined depending on the inner diameter of the crucible used for the single crystal growth.

In order to further improve the crystal growth efficiency and reduce the cost. The raw material area comprises a first raw material area and a second raw material area, and the first raw material area and the second raw material area are respectively arranged on two sides of the seed crystal. The first raw material area and the second raw material area are respectively located in a high-temperature area of the thermal field, the seed crystal is located in a low-temperature area of the thermal field, the silicon carbide polycrystalline block is heated at high temperature to be sublimated, and gas phase components are rapidly transmitted to the seed crystal from the upper part and the lower part to be crystallized to form an upper silicon carbide single crystal and a lower silicon carbide single crystal, so that the high-purity SiC single crystal is efficiently prepared.

As one embodiment, a method for growing a high-purity semi-insulating silicon carbide single crystal includes the steps of:

preparing a silicon carbide polycrystalline block: placing silicon carbide powder with the impurity content not higher than 10ppm in a graphite crucible, sublimating the silicon carbide powder to the top of the graphite crucible under the conditions of 2000-2300 ℃ and 5-50mbar of pressure, and mechanically treating the initial silicon carbide polycrystalline block prepared by sublimation to ensure that the initial silicon carbide polycrystalline block has a hollow pore channel structure, namely the silicon carbide polycrystalline block is prepared;

a first crystal growth stage: placing seed crystals and the silicon carbide polycrystalline block in a crucible, then packaging, placing the packaged crucible in a growth hearth, sealing and vacuumizing, and introducing inert gas (preferably argon gas and helium gas) into a 200L hearth at room temperature after the vacuum is finished and with the gas flow rate of 50-100SLM, and quickly boosting the pressure to 200mbar-400 mbar; after the pressure rise is finished, slowly raising the temperature to be more than 2100 ℃ so that the silicon carbide polycrystalline block is sublimated to the seed crystal for crystallization, and keeping the nucleation for 10-30h under high pressure;

a second crystal growth stage: gradually reducing the pressure to 10-50mabr at the rate of 1-10mbar/h, and gradually increasing the growth rate of the polycrystalline block so as to keep the gas phase reaction components at the seed crystal sufficient and stable.

A high purity silicon carbide single crystal was produced by the above-described growing method, and referring to FIG. 1, a crucible assembly was used which comprises: the seed crystal is located in the middle of the crucible, the first raw material area is located above the seed crystal, the second raw material area is located below the seed crystal, 5 silicon carbide polycrystalline blocks are arranged in the first raw material area, 5 silicon carbide polycrystalline blocks are arranged in the second raw material area, the silicon carbide polycrystalline blocks are identical in structure and are arranged coaxially with the crucible and the seed crystal, and radial channels are formed between the adjacent silicon carbide polycrystalline blocks.

The difference between the specific preparation parameters and the crystal growth method is shown in Table 1, the ratio of the inner diameter of the pore channel structure to the outer diameter of the silicon carbide polycrystalline block is R/R, the inert gas filled is argon, and the high-purity semi-insulating silicon carbide single crystal No. 1-4 and the comparative high-purity semi-insulating silicon carbide single crystal No. D1-D3 are prepared. The difference between the high purity semi-insulating silicon carbide single crystal D3# and the high purity semi-insulating silicon carbide single crystal 1# was that the first material region and the second material region were each provided with a polycrystalline block of primary silicon carbide having the same volume as that of the polycrystalline block of silicon carbide in the high purity semi-insulating silicon carbide single crystal 1 #.

TABLE 1

From the results in table 1, it can be seen that: the high-purity semi-insulating silicon carbide single crystal prepared by the silicon carbide polycrystalline block with the pore channel structure has the advantages of high crystal growth efficiency, low cost, short crystal growth path and easy control of a gas phase transmission path.

Two silicon carbide single crystals grow on the same seed crystal at the same time, so that the preparation cost of the silicon carbide single crystals can be greatly reduced; the silicon carbide single crystal prepared by the same seed crystal can ensure the similarity of the single crystal quality to the maximum extent, thereby improving the quality consistency of the silicon carbide single crystal and the substrate.

The sublimation rate of polycrystalline blocks is affected by the partial vapor pressure of the silicon and carbon components. Because the polycrystalline blocks are compact polycrystalline structures, if no pores exist among the blocks, the vapor partial pressure difference of silicon and carbon components does not exist among the blocks, and the silicon carbide blocks can not be sublimated to decompose gas-phase components required by the growth of single crystals. In addition, the arrangement of the pore channel enables the decomposed gas-phase components to be transmitted along a uniform path, thereby ensuring the stability and consistency of gas-phase flow transmission and further ensuring the crystallization quality of subsequent single crystals. The method is equally applicable to arrangements in which seed crystals are placed on both sides of the polycrystalline block.

By controlling the pressure change and the pressure value of the crystal growth of the silicon carbide single crystal, the nucleation disorder of preparing the high-purity semi-insulating silicon carbide single crystal caused by the compactness of the silicon carbide polycrystalline block is avoided, and the crystal growth quality is improved.

The prepared high-purity semi-insulating silicon carbide single crystal 1# -4# and the comparative high-purity semi-insulating silicon carbide single crystal D1# -D3# are respectively subjected to the same cutting, grinding and polishing methods to respectively prepare a high-purity semi-insulating silicon carbide single crystal substrate 1# -4# and a comparative high-purity semi-insulating silicon carbide single crystal substrate D1# -D3#, and the high-purity semi-insulating silicon carbide single crystal substrate has high purity, few defects, high quality and good uniformity.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.

The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims (10)

1. A crucible assembly for producing high quality crystals, comprising:

the crucible comprises a crucible main body and a crucible cover covering the crucible main body;

the seed crystal support is fixed in the crucible and used for fixing the seed crystal; and

the raw material block support is arranged in the crucible and used for supporting the raw material blocks.

2. The crucible assembly of claim 1, wherein the seed holder is disposed in a middle portion of the crucible and the feedstock piece holder is disposed above and below the seed holder, respectively.

3. The crucible assembly of claim 1, wherein the feedstock piece holder includes an annular support portion and at least one bearing portion secured to the support portion, the bearing portion extending radially inward of the support portion, the bearing portion for receiving a feedstock piece.

4. The crucible assembly of claim 3, wherein the support portion is an annular support plate structure and the bearing portion is a plate structure.

5. The crucible assembly of claim 3, wherein the support portion holds a carrying portion, and a plurality of raw material block holders are stacked in the crucible main body in an axial direction of the crucible main body.

6. The crucible assembly of claim 5, wherein the seed crystal holder is configured to be secured to an inwardly projecting first boss on an inner sidewall of the crucible body.

7. The crucible assembly of claim 6, wherein the first boss is integrally formed with the inner sidewall of the crucible body.

8. The crucible assembly of claim 6, wherein the first boss is annular.

9. The crucible assembly of claim 1, wherein the raw material block holder is a second boss protruding inward and fixed to an inner side wall of the crucible main body, and the second boss is integrally formed with the inner side wall of the crucible main body.

10. The crucible assembly of claim 9, wherein the feedstock region within the crucible body is provided with a plurality of second bosses as feedstock block supports, the second bosses being of annular configuration.

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