CN213172678U - Crucible for growing large-size silicon carbide single crystal - Google Patents

Abstract

The crucible for growing the large-size silicon carbide single crystal is divided into an upper crucible body and a lower crucible body, a crucible cover is arranged to be buckled on the top of the upper crucible body, and the bottom of the upper crucible body is connected with the top of the lower crucible body; the resistivity of the lower crucible body is less than that of the upper crucible body, and the resistivity of the upper crucible body is less than or equal to that of the crucible cover. When the silicon carbide single crystal grows, because the graphite resistivity of the lower crucible body is lower than that of the upper crucible body, the corresponding crucible wall alternating current of the lower crucible body is larger than that of the upper crucible body, the heating efficiency is high, and the temperature of the silicon carbide polycrystalline powder contacted with the lower crucible body is high; the resistivity of the graphite of the upper crucible body and the crucible cover is higher than that of the graphite of the lower crucible body, and correspondingly, the alternating current generated by the upper crucible body and the crucible cover is relatively small, so that the temperature of the silicon carbide seed crystal area is low. Therefore, an axial temperature gradient can be created from the bottom to the top of the crucible body, and the requirement of the crystal growth rate is met.

Description

Crucible for growing large-size silicon carbide single crystal

Technical Field

The application relates to the technical field of silicon carbide crystal preparation, in particular to a crucible for growing silicon carbide single crystals by a physical vapor transport method.

Background

Silicon carbide (SiC) is a preferred substrate material for manufacturing new devices such as high-performance power electronic devices, solid microwave devices, solid sensors and the like, and high-temperature-resistant integrated circuits, because it has excellent physicochemical characteristics such as large forbidden band width, high critical breakdown field strength, high thermal conductivity, good chemical stability and the like, as a third-generation wide-band-gap semiconductor material developed after Si and GaAs. In recent years, the SiC single crystal material and device industry has become a strategic industry in the high-tech field, and the research of SiC devices has risen worldwide.

Currently, the most mature and effective method for growing large-size bulk SiC single crystals is the Physical Vapor Transport (PVT) method, wherein the SiC single crystal growth system usually adopts a medium-frequency induction heating mode. Specifically, during crystal growth, a heat insulation material is wound on the periphery of a graphite crucible and then placed in the center of an induction coil, a high-frequency alternating current is introduced into the coil to generate an alternating magnetic field, the graphite crucible is positioned in the alternating magnetic field to generate eddy currents, the eddy currents generate joule heat to raise the temperature of the crucible, and the heat is transferred into the crucible through heat conduction, heat radiation and heat convection heat transfer modes, so that a growth raw material and seed crystals are heated, and a temperature field for SiC single crystal growth is established. For this temperature field, two important parameters are the axial temperature gradient and the radial temperature gradient, respectively. Wherein, the axial temperature gradient is the driving force for transporting the gas phase component decomposed by the powder to the crystal growth surface, and determines the growth rate of the crystal; the radial temperature gradient influences the unevenness of the crystal growth interface shape and the internal stress distribution condition. For controlling the axial temperature gradient, the size and shape of a temperature measuring hole (upper temperature measuring hole for short) of a heat insulating material on the upper part of the graphite crucible are usually changed, and heat is dissipated through the temperature measuring hole while temperature is measured through the temperature measuring hole, so that a certain axial temperature gradient is formed in a growth chamber of the graphite crucible, and the sublimed gas-phase material is driven to be transmitted from a powder region in the growth chamber to a seed crystal region at the top of the crucible for crystallization. Especially for large-size silicon carbide single crystal growth (such as 4 inches, 6 inches, 8 inches and the like), the temperature measuring holes of the heat insulating material are required to be enlarged to provide a temperature field with a large enough axial temperature gradient and promote the transportation of gas-phase components to a growth interface.

However, the above method of increasing the axial temperature gradient by changing the temperature measurement holes of the thermal insulation material may increase the radial temperature gradient at the same time. The larger radial gradient can introduce the problems of increased crystal stress, uneven distribution of impurities and defects, and the like into the crystal, and also can introduce a large amount of defects such as dislocation, stacking faults and the like into the crystal, even directly cause the direct cracking of the single crystal, thereby seriously affecting the quality and the yield of the crystal.

SUMMERY OF THE UTILITY MODEL

The embodiment of the application provides a novel crucible to solve the problem that the axial growth temperature gradient of a crystal cannot be independently adjusted and controlled in the process of single crystal growth in the prior art without influencing the radial temperature gradient.

The crucible for growing large-size silicon carbide single crystals provided by the embodiment of the application mainly comprises a crucible cover and a crucible body which are made of graphite materials, wherein:

the crucible body comprises an upper crucible body and a lower crucible body, and the lower crucible body is used for placing silicon carbide polycrystalline powder;

the crucible cover is buckled at the top of the upper crucible body, and the bottom of the upper crucible body is connected with the top of the lower crucible body;

the resistivity of the lower crucible body is smaller than that of the upper crucible body, and the resistivity of the upper crucible body is smaller than or equal to that of the crucible cover.

Optionally, follow crucible body bottom to top direction down, the lateral wall of crucible body comprises two sections or more than two sections lower crucible body sub-lateral walls down, wherein:

and along the direction from the bottom to the top of the lower crucible body, the resistivity of the side wall of each lower crucible body is increased in sequence.

Optionally, along the direction from the bottom to the top of the upper crucible body, the side wall of the upper crucible body is composed of two or more sections of sub side walls of the upper crucible body, wherein:

and the resistivity of the side wall of each upper crucible body is sequentially increased along the direction from the bottom to the top of the upper crucible body.

Optionally, the upper crucible body and the lower crucible body are detachably connected.

Optionally, the upper crucible body and the lower crucible body are of an integrally formed structure.

Optionally, first fixed orifices have been seted up on the crucible cover, the second fixed orifices has been seted up at the top of going up the crucible body, wherein:

the inner wall of the second fixing hole is provided with threads;

the crucible cover and the crucible body are fastened through screws penetrating through the first fixing hole and the second fixing hole.

According to the crucible for growing the large-size silicon carbide single crystal, the crucible body is divided into an upper crucible body and a lower crucible body, the crucible cover is arranged at the top of the upper crucible body in a buckled mode, and the bottom of the upper crucible body is connected with the top of the lower crucible body; the resistivity of the lower crucible body is less than that of the upper crucible body, and the resistivity of the upper crucible body is less than or equal to that of the crucible cover. Because the upper crucible body and the lower crucible body are made of graphite materials with different resistivities, the resistivity of the graphite of the lower crucible body is lower than that of the graphite of the upper crucible body, the corresponding alternating current of the crucible wall of the lower crucible body is larger than that of the upper crucible body, the heating efficiency is high, and the temperature of the silicon carbide polycrystalline powder contacted with the lower crucible body is high; the graphite resistivity of the upper crucible body and the crucible cover is higher than that of the lower crucible body, and the corresponding alternating current generated by the upper crucible body and the crucible cover is smaller than that of the lower crucible body, so that the heating efficiency is low, and the temperature of the silicon carbide seed crystal area is low. Like this, from the crucible body to crucible cover direction down, can build axial temperature gradient, satisfy crystal growth rate requirement, so need not to go up the heat preservation hole and enlarge, avoid going up the problem that radial temperature gradient that the heat preservation hole enlarges and bring simultaneously is big, and then can realize under little radial temperature gradient, when satisfying crystal growth rate requirement, reduce the thermal stress in the crystal to the crystallization quality of crystal has been improved greatly.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive labor.

FIG. 1 is a schematic structural diagram of a first crucible provided in an embodiment of the present application;

FIG. 2 is a schematic view of the crucible and the insulating member of FIG. 1 after assembly;

FIG. 3 is a schematic structural view of a second crucible provided in the embodiments of the present application;

FIG. 4 is an exploded view of a third crucible according to an embodiment of the present disclosure;

FIG. 5 is a schematic view of an assembly structure of the crucible of FIG. 4.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.

According to the embodiment of the application, the traditional method for manufacturing the axial temperature gradient in the crucible through heat dissipation of the upper heat-insulating hole is changed, the crucible is made of graphite materials with different resistivities, the axial temperature gradient is manufactured, the thermal field in the large-size crucible is uniformly distributed in the radial direction, and the silicon carbide single crystal with uniform radial impurity distribution and low stress is prepared.

FIG. 1 is a schematic structural diagram of a first crucible provided in an embodiment of the present application. As shown in FIG. 1, the crucible is mainly divided into two parts, namely a crucible cover 10 and a crucible body 20, wherein the crucible cover 10 and the crucible body 20 are both made of graphite material, the density of the graphite is required to be more than 1.7g/cm3, the total impurity content is required to be less than 30ppm, and the porosity is required to be less than 15%, and of course, graphite with other parameters can be selected in other embodiments.

Further, the crucible body 20 is divided into two parts, which are an upper crucible body 21 and a lower crucible body 22, wherein the lower crucible body 22 is a structure surrounded by a bottom cover and a side wall extending from the bottom plate, and is used for placing the silicon carbide polycrystalline powder. The bottom cover and the side wall can be of an integrated structure or a detachable structure. The upper crucible body 21 is of a two-piece open cylindrical configuration in which the cross-section is generally circular, although other shapes are possible. The bottom of the upper crucible body 21 is connected to the bottom of the lower crucible body 22. The upper crucible body 21 and the lower crucible body 22 can be fastened by means of threads, clamping and the like, and of course, in other embodiments, can also be connected by other means; preferably, in order to prevent the silicon carbide polycrystal growth process, the gas phase component decomposed by the SiC polycrystal powder is diffused to the outer part of the crucible body from the joint gap between the upper crucible body 21 and the lower crucible body 22, and the upper crucible body 21 and the lower crucible body 22 can be prepared into an integrated structure.

Meanwhile, the crucible cover 10 is fastened to the top of the upper crucible body 21, wherein the crucible cover 10 and the upper crucible body 21 are fastened in a threaded manner, and of course, in other embodiments, other manners of connection may be adopted.

In this embodiment, one end of the upper crucible body 21 near the crucible cover 10 is referred to as a top portion thereof, and the other end is referred to as a bottom portion thereof.

Further, the resistivity of the lower crucible body 22 is set to be smaller than the resistivity of the upper crucible body 21, and the resistivity of the upper crucible body 21 is set to be smaller than or equal to the resistivity of the crucible cover 10. FIG. 2 is a schematic view of the crucible and the insulating member of FIG. 1 after assembly. As shown in FIG. 2, during the growth of silicon carbide single crystal, a silicon carbide seed crystal 30 is arranged on a crucible cover 10, a silicon carbide polycrystalline powder 40 is put into a crucible body 20, then the crucible cover 10 is buckled on the crucible body 20, finally, a heat preservation part 50 is arranged outside the whole crucible and then is placed in the center of an induction coil, an alternating magnetic field is generated after high-frequency alternating current is introduced into the coil, and an eddy current is generated in the alternating magnetic field when the crucible is positioned in the alternating magnetic field.

Because the crucible body 20 in the embodiment of the present application is divided into an upper and a lower two-part structure, the upper crucible body 21 and the lower crucible body 22 are made of graphite materials with different resistivity, and the graphite resistivity of the lower crucible body 22 is lower than the graphite resistivity of the upper crucible body 21 and the crucible cover 10, the corresponding crucible wall alternating current of the lower crucible body 22 is larger than that of the upper crucible body 21 and the crucible cover 10, the heating efficiency is high, and the temperature of the silicon carbide polycrystalline powder 40 in contact with the lower crucible body is high; the graphite resistivity of the upper crucible body 21 and the crucible cover 10 is higher than that of the lower crucible body 22, and the corresponding alternating current generated by the graphite resistivity is smaller than that of the lower crucible body 22, so that the heating efficiency is low, and the temperature of the silicon carbide seed crystal 30 region is low. Like this, from the direction of the lower crucible body 22 to crucible cover 10, can build axial temperature gradient, satisfy crystal growth rate requirement, so need not to go up hole 51 and enlarge, avoid going up the problem that radial temperature gradient that hole 51 enlarges and bring simultaneously is big, and then can realize under little radial temperature gradient, when satisfying crystal growth rate requirement, reduce the thermal stress in the crystal to the crystallization quality of crystal has been improved greatly.

FIG. 3 is a schematic structural diagram of a second crucible provided in the embodiments of the present application. As shown in fig. 3, the present embodiment is different from the crucible provided in the above-described first embodiment in that the upper crucible body 21 is composed of a first sub upper crucible body 211 and a second sub upper crucible body 212, i.e., the sidewall of the upper crucible body 21 in the direction of the central axis of the crucible body is divided into upper and lower sections, and the resistivity of the first sub upper crucible body 211 is greater than that of the second sub upper crucible body 212. That is, the whole crucible body 20 is divided into a three-section structure, and the resistivity of each section of the crucible body is sequentially increased along the direction from the bottom to the top of the crucible body 20. Thus, the gradient axial temperature gradient is created to meet the requirement of crystal growth rate.

Of course, in other embodiments, the upper crucible body 21 may be divided into more sections, for example, three sections, four sections, etc., and the resistivity of the sidewalls of each upper sub-crucible body is sequentially increased along the bottom to top direction of the crucible body.

FIG. 4 is an exploded view of a third crucible according to an embodiment of the present disclosure, and FIG. 5 is an assembled view of the crucible of FIG. 4. As shown in fig. 4 and 5, the main difference between the crucible body of the present embodiment and the crucible bodies of the first and second embodiments is that the lower crucible body 22 of the present embodiment is composed of a first sub-lower crucible body 221 and a second sub-lower crucible body 222, and the side wall of the lower crucible body 22 is divided into upper and lower sections along the central axis direction of the crucible body, and the resistivity of the first sub-lower crucible body 221 is greater than that of the second sub-lower crucible body 222. Simultaneously, because go up the crucible body 21 and constitute by crucible body 211 on first son and crucible body 212 on the second son, like this, whole crucible body is divided into the four-section structure, and along crucible body 20's bottom to top direction, and the resistivity of each section crucible lateral wall increases in proper order to build the axial temperature gradient of gradual change, satisfy crystal growth rate requirement.

Of course, in other embodiments, the lower crucible body 22 may be divided into a greater number of sections, such as three sections, four sections, etc., and the resistivity of the sidewalls of each lower sub-crucible body may be sequentially increased along the bottom to top direction of the crucible body.

In the present embodiment, after the crucible cover 10 and the crucible body 20 are assembled, in order to fasten the crucible cover 10 and the crucible body 20, as shown in fig. 4, a first fixing hole 62 is formed in the crucible cover 10, and the first fixing hole 62 is a through hole penetrating through the crucible cover 10. In order to facilitate the tightness and flatness of the crucible cover 10 assembled with the crucible body 20, the crucible cover 10 may be provided with first fixing holes distributed along the central axis thereof.

Meanwhile, the top of the upper crucible body 21, namely, the port face of the crucible body 20 is provided with a second fixing hole 63, the inner wall of the second fixing hole 63 is provided with threads, the outer wall of the screw 61 with threads is taken as a crucible fastening component, the screw 61 can be made of graphite, and then the crucible cover 10 is fastened with the crucible body 20 through the screw 61 penetrating through the first fixing hole 62 and the second fixing hole 63. In addition, in the embodiment, the first fixing hole 62 is designed as a smooth hole with a non-threaded inner wall, so that machining errors exist between the first fixing hole 62 and the corresponding second fixing hole 63, and the crucible can be fastened.

Further, a cap head of the screw 61 may be provided with an inner hexagonal recess, and when in use, the screw 61 may be rotated by using an inner hexagonal wrench to achieve an effect of loosening or tightening the screw 61, or of course, other pattern structures may be provided, such as a cross structure.

In the embodiment, the crucible cover 10 and the crucible body 20 are fastened by adopting a screw rod mode, and compared with a screw thread mode, Si in gas phase components decomposed by SiC polycrystalline powder can be prevented from being diffused to screw threads in the growth process of silicon carbide polycrystal, so that the screw threads become shallow and lose the sealing effect, and the whole service life of the crucible can be further prolonged.

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. Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.

It will be understood that the present application is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.

Claims (6)

1. A crucible for growing a large-sized silicon carbide single crystal, comprising a crucible cover (10) and a crucible body (20) made of a graphite material, wherein:

the crucible body (20) comprises an upper crucible body (21) and a lower crucible body (22), and the lower crucible body (22) is used for placing polycrystalline silicon carbide powder;

the crucible cover (10) is used for arranging silicon carbide seed crystals, the crucible cover (10) is buckled on the top of the upper crucible body (21), and the bottom of the upper crucible body (21) is connected with the top of the lower crucible body (22);

the resistivity of the lower crucible body (22) is smaller than that of the upper crucible body (21), and the resistivity of the upper crucible body (21) is smaller than or equal to that of the crucible cover (10).

2. The crucible for growing a large-sized silicon carbide single crystal according to claim 1, wherein the side wall of the lower crucible body (22) is composed of two or more sections of the sub-side walls of the lower crucible body along the bottom-to-top direction of the lower crucible body (22), wherein:

and along the direction from the bottom to the top of the lower crucible body (22), the resistivity of the side wall of each lower crucible body is increased in sequence.

3. Crucible for growing large-size silicon carbide single crystals according to claim 1 or 2, characterized in that the side wall of the upper crucible body (21) is composed of two or more sections of the upper crucible body sub-side walls in the bottom to top direction of the upper crucible body (21), wherein:

the resistivity of the side walls of the upper crucible body (21) is increased in sequence along the direction from the bottom to the top of the upper crucible body.

4. Crucible for growing large-size silicon carbide single crystals according to claim 1, characterized in that the upper crucible body (21) is detachably connected to the lower crucible body (22).

5. Crucible for growing large-size silicon carbide single crystals according to claim 1, characterized in that the upper crucible body (21) and the lower crucible body (22) are of one-piece construction.

6. The crucible for growing large-size silicon carbide single crystals according to claim 1, wherein the crucible cover (10) is provided with a first fixing hole, and the top of the upper crucible body (21) is provided with a second fixing hole, wherein:

the inner wall of the second fixing hole is provided with threads;

the crucible cover and the crucible body are fastened through screws penetrating through the first fixing hole and the second fixing hole.

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