CN109234804B

CN109234804B - Silicon carbide single crystal growth method

Info

Publication number: CN109234804B
Application number: CN201811302567.9A
Authority: CN
Inventors: 宁秀秀; 高超; 梁晓亮; 李霞; 宗艳民; 刘家朋; 窦文涛
Original assignee: SICC Science and Technology Co Ltd
Current assignee: Shandong Tianyue Advanced Technology Co Ltd
Priority date: 2018-11-02
Filing date: 2018-11-02
Publication date: 2020-01-14
Anticipated expiration: 2038-11-02
Also published as: CN109234804A

Abstract

The application relates to a silicon carbide single crystal growth method, which comprises the steps of placing raw materials in a silicon carbide single crystal growth device, heating the raw materials to sublimate the raw materials to form silicon carbide single crystals, wherein a Si element supplementing device containing a mixture of Si and SiC or Si powder is arranged in the crystal growth device, the Si element supplementing device is arranged in the raw materials, and a plurality of through holes are formed in the Si element supplementing device; the Si element supplementing device is a tantalum material crucible or a tantalum-graphite-plated material crucible; in the crystal growth process, the mixture of Si and SiC or Si powder can pass through the through holes to supplement Si element for the growth of the silicon carbide single crystal. The silicon carbide single crystal growth chamber can effectively adjust the Si/C ratio in the growth chamber during the growth of the silicon carbide single crystal, thereby reducing the defects of a carbon inclusion generated by the growth of the single crystal, adjusting the temperature field distribution of a raw material area, and reducing the carbonization of the raw material.

Description

Silicon carbide single crystal growth method

The technical field is as follows:

the application belongs to the field of crystal growth, and particularly relates to a silicon carbide single crystal growth method.

Background art:

silicon carbide single crystal is one of the most important third-generation semiconductor materials, and is widely applied to the fields of power electronics, radio frequency devices, photoelectronic devices and the like because of the excellent properties of large forbidden bandwidth, high saturated electron mobility, strong breakdown field, high thermal conductivity and the like.

The high-purity silicon carbide single crystal is a preferred material for preparing high-frequency and high-power microwave devices, but the high-purity semi-insulating silicon carbide single crystal has high purity requirement, so the single crystal preparation technology has great difficulty and the production cost is high. And the main reason for the high production cost is that the size of the SiC single crystal ingot is limited during the growth process. At present, the most mature method for realizing the mass production of SiC single crystals is a PVT method, namely, a gas phase source generated by sublimating a silicon carbide raw material is transported to a seed crystal for recrystallization at high temperature. In the process of growing SiC single crystals by the PVT method, because of the low melting point characteristic of the Si component, the Si component is preferentially evaporated and sublimated and permeates outwards through the wall of the graphite crucible, the Si/C ratio is gradually reduced along with the reaction, the growth defect of the single crystal is increased, the quality is reduced, the size of the usable ingot cannot be continuously increased, and the growth of high-quality single crystals and the reduction of the cost are limited.

There are related patents and literature reports on adding Si or SiO to the raw material₂Composition to adjust the Si/C ratio, but the direct addition of Si also has the problem of early volatilization of Si, as well as the possibility of erosion and damage of the seed crystal by Si vapor before the start of crystal growth, while SiO₂Oxygen in the gas (H) may react with the gas (H) introduced₂) The components react or react with the C powder to burn, which has adverse effect on the growth of high-purity SiC crystals.

On the other hand, the growth process of growing a silicon carbide single crystal by the PVT method is performed in a closed graphite crucible, and thus the growth environment is in a carbon-rich atmosphere at a high temperature. At the initial stage of crystal growth, the crystal growth interface is in a state of equilibrium between the silicon component and the carbon component because the vapor partial pressure of the silicon component is high. As the growth of the crystal proceeds, the silicon component in the silicon carbide raw material is continuously sublimated and reduced, so that the gas phase component in the growth chamber is gradually unbalanced and becomes a carbon-rich state, and the growth is generally seriously carbonized at the bottom of the raw material region and near the bottom of the crucible wall. Under the growth environment rich in carbon, the front interface of the crystal growth has the enrichment of carbon and forms carbon inclusion defects. The inclusion can further induce the defects of micropipes, dislocation, stacking faults and the like, and the quality of the silicon carbide substrate is seriously influenced, so that the quality of an epitaxial layer and the performance of a device are further influenced.

In the prior art, in order to eliminate the defect of carbon inclusion in the PVT method for growing silicon carbide, Avinash KGupta et al propose to add solid silicon oxide (such as solid SiO or SiO) in the growth chamber₂) In order to act as a supplementary source of silicon components during crystal growth, thereby reducing the formation of carbon-rich components and further inhibiting the formation of carbon inclusions [ US 2008/0115719A1 ]]. However, this method cannot sufficiently suppress the carbonization of the silicon carbide raw material, resulting in a relatively late growth of the crystalHigh concentrations of carbon inclusion defects lead to a large reduction in crystal quality and substrate quality. The technique proposed by Avinash K Gupta et al, which adds solid silicon oxide to the growth chamber to replenish the silicon composition, introduces additional impurities, which may cause unstable fluctuations in the impurity concentration in the crystal, which may affect the conductivity of the silicon carbide substrate.

JP4962205B2 discloses a silicon carbide single crystal production apparatus and method for promoting the growth rate of SiC single crystal, prolonging the growth time of SiC single crystal, and reducing the residual amount of SiC powder raw material. According to the device, a plurality of porous hollow pipes are arranged in a crucible, an ascending channel is provided for heating and sublimating SiC powder at the lower part in the porous hollow pipes, and generated sublimating gas passes through the porous pipes to reach a space region at the upper part of the crucible. The technical scheme substantially reduces the growth time of SiC and improves the growth speed of the SiC, but the technical scheme does not have the capability of adjusting Si/C for the conversion of SiC raw materials into single crystals.

JP2010280546A discloses a method for producing a silicon carbide single crystal by burying a silicon carbide single crystal in a mixed powder of carbon and silicon carbide in a crucible for annealing treatment under high temperature conditions, suppressing the occurrence of defects accompanying carbonization. Although the method can reduce the defect generation problem of the silicon carbide crystal caused in the crystal synthesis process, the method does not solve the problem in the silicon carbide growth process, most of carbon coatings appear in the silicon carbide growth process, but the process steps are prolonged, the defects in the previous stage are overcome by using an annealing process, the influence cannot be reduced simply through the annealing and other steps after the crystal lattice defects are generated, the whole synthesis process is more complicated, and the product quality is more uncontrollable. In the prior art, a better method for supplementing a silicon source is not provided, so that the problem of carbon coating cannot be fundamentally solved.

The application contents are as follows:

in order to solve the problems, the application provides a silicon carbide single crystal growth method, which comprises the steps of placing raw materials in a silicon carbide single crystal growth device, heating the raw materials to sublimate the raw materials to form silicon carbide single crystals, wherein a Si element supplement device containing a mixture of Si and SiC or Si powder is arranged in the crystal growth device, the Si element supplement device is arranged in the raw materials, and a plurality of through holes are formed in the Si element supplement device; the Si element supplementing device is a tantalum material crucible or a tantalum-graphite-plated material crucible;

in the crystal growth process, the mixture of Si and SiC or Si powder can pass through the through holes to supplement Si element for the growth of the silicon carbide single crystal.

Preferably, in the single crystal growth apparatus, the mass ratio of the Si powder to the SiC powder is 1% to 4%, and preferably, the mass ratio of the Si powder to the SiC powder is 1.8% to 3.1%.

Preferably, the number of the Si element supplementing means put into the silicon carbide raw material is 5 to 9.

Preferably, the shielding gas is one or a mixture of more than two of argon, neon or helium in any proportion.

Preferably, the method comprises the following steps:

s1, filling a silicon carbide raw material and seed crystals in a silicon carbide single crystal growth device, burying a plurality of Si element supplement devices in the silicon carbide raw material, filling Si powder or a mixture of the Si powder and the SiC powder in the Si element supplement devices, fixing the silicon carbide single crystal growth device on a heat source, and introducing protective gas;

s2, heating the silicon carbide single crystal growth device, raising the temperature to a first temperature, and maintaining the gas pressure at the first pressure;

s3, gradually reducing the pressure in the silicon carbide single crystal growth device to a second pressure, and simultaneously gradually increasing the furnace temperature to a second temperature;

s4, after the growth is finished, slowly increasing the pressure to a third pressure within a first time range, and simultaneously keeping the temperature stable;

and S5, finally, rapidly increasing the pressure to one atmospheric pressure, and naturally cooling the temperature to room temperature to finish the crystal growth.

Preferably, the first temperature in S2 is 1400-1800 ℃, and the first pressure is 700-900 mbar; the second temperature in S3 is 2000-; the first time range in S4 is 20-50h, and the third pressure is 50-100 mbar.

Preferably, the silicon carbide single crystal growth device comprises a growth chamber, wherein the growth chamber is used for placing raw materials and providing a place for heating and sublimating the raw materials, and the growth chamber is divided into a raw material part for placing the raw materials and a gas phase part for sublimating and crystallizing the raw materials; the growth chamber is internally provided with a plurality of Si element supplementing devices, the Si element supplementing devices are arranged at the raw material part and are isolated from the inner wall of the growth chamber. The method comprises the following steps that a Si element supplementing device is arranged in a growth cavity, on one hand, in order to place substances to be supplemented in the Si element supplementing device, in the method, the Si/C ratio can be unbalanced in the growth process of the silicon carbide single crystal, and under the carbon-rich growth environment, the front edge interface of crystal growth can be enriched with carbon and form a carbon inclusion defect, so that Si powder is placed in the Si element supplementing device to supplement silicon components, and the Si/C ratio is adjusted; on the other hand, since the Si element supplementing device has thermal conductivity, the temperature field distribution of the raw material portion can be adjusted in the growth chamber, and carbonization of the raw material can be reduced.

Adding Si powder or a mixture of Si powder and SiC powder into a Si element supplementing device, placing the raw material into a raw material part, placing the Si element supplementing device into the raw material, heating under the action of a protective gas atmosphere to sublimate the raw material, and supplementing Si elements by the mixture in the Si element supplementing device.

The Si element supplementing device is used for placing a supplementing substance, the supplementing substance at least contains silicon element and carbon element, and in the single crystal growth device, the mass ratio of Si powder to SiC powder is 1-4%, preferably, the mass ratio of Si powder to SiC powder is 1.8-3.1%. . The method comprises the following steps that a Si element supplementing device is arranged in a growth cavity, on one hand, substances needing to be supplemented are placed in the Si element supplementing device, in the method, the Si/C ratio can be unbalanced in the growth process of the silicon carbide single crystal, and under the carbon-rich growth environment, the front edge interface of crystal growth can be enriched with carbon and form a carbon inclusion defect, so that a mixture of Si powder and SiC powder is placed in the Si element supplementing device to supplement silicon components, and the Si/C ratio is adjusted; on the other hand, since the Si element supplementing device has thermal conductivity, the temperature field distribution of the raw material portion can be adjusted in the growth chamber, and carbonization of the raw material can be reduced.

Preferably, the Si element supplementing device includes a container body and a container cover. The container cover is arranged to facilitate the taking and placing of the supplementary materials.

Preferably, the container body and/or the container cover are provided with a plurality of through holes. The through holes are arranged to facilitate the transmission of gas phase after the Si powder or the Si powder and the SiC powder are heated and sublimated in the container body, so that the supplement of silicon components in the raw materials is more convenient.

Preferably, the Si element supplementing device is a tantalum material crucible or a tantalum graphite material crucible. Because the Si powder is sublimated into gas phase at high temperature and high pressure, the graphite crucible is eroded, if the Si element supplementing device is a tantalum material crucible or a tantalum-plated graphite material crucible, the crucible is well prevented from being eroded, and the silicon carbide single crystal can be taken out by a certain method after the growth of the silicon carbide single crystal is finished, so that the reutilization is realized, and the cost is reduced.

Preferably, the Si element supplementing device is arranged in the middle area of the bottom of the raw material part or the area close to the side wall of the growth cavity. The arrangement is that the Si element supplementing device can better play a role in adjusting the thermal field of the raw material area. Since Si/C is not unbalanced in the early stage, burying below is also a control of the timing of Si replenishment to some extent.

This application can bring following beneficial effect:

1. the method can effectively adjust the Si/C ratio in the growth chamber in each process of the growth of the silicon carbide single crystal, thereby reducing the setting and avoiding the defect of a carbon inclusion generated by the growth of the single crystal.

2. The temperature field distribution of the raw material area can be effectively adjusted, and the carbonization of the raw material is reduced;

3. the application has the characteristics of convenience in use, simple and reliable structure and strong economy;

4. the application has the characteristics of simple operation, strong safety, strong practicability and suitability for popularization and use.

Description of the 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 view showing the structure of a silicon carbide single crystal growth apparatus;

FIG. 2 is a schematic view of the structure of a container lid of the Si element replenishing apparatus.

The specific implementation mode is as follows:

in order to clearly explain the technical features of the present invention, the present application will be explained in detail by the following embodiments in combination with the accompanying drawings.

As shown in the drawings, the following detailed description is given by way of example in order to more clearly explain the overall concept of the present application.

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.

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.

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.

Example 1: silicon carbide single crystal growth apparatus:

as shown in fig. 1, the present application provides a silicon carbide single crystal growth apparatus comprising: the growth chamber 1 is used for placing raw materials and providing a place for heating and sublimating the raw materials, and the growth chamber 1 is divided into a raw material part 11 for placing the raw materials and a gas phase part 12 for sublimating and crystallizing the raw materials; the growth chamber 1 is a crucible or other container capable of realizing the growth of silicon carbide, and the raw material part 11 and the gas phase part 12 can be divided into an upper part and a lower part in a closed space, such as: the growth cavity 1 is a crucible, the raw material part 11 is a region for placing raw materials at the bottom of the inner cavity of the crucible, and the gas phase part 12 is a gas phase space without raw materials at the upper part in the crucible; the feed section 11 and the gas phase section 12 may be separate and independent components, and may be distributed in other ways that may be realized by those skilled in the art.

A plurality of Si element supplementing devices 111 are arranged in the growth cavity 1, the Si element supplementing devices 111 are arranged in the raw material part 11, the Si element supplementing devices 111 are arranged in a mode of being isolated from the inner wall of the growth cavity 1, and the Si element supplementing devices 111 are arranged in the middle area of the bottom of the raw material part 11 or the area close to the side wall of the growth cavity 1. As to how much Si element supplement device 111 is properly placed, it depends on the amount of the raw material placed and the size of growth chamber 1.

The Si element supplementing device 111 in the present embodiment includes a container body and a container lid 112. As shown in fig. 2, the container body and/or the container cover 112 are provided with a plurality of through holes 113, the Si element supplement device 111 is a tantalum material crucible or a tantalum-graphite-plated material crucible, and the material of the Si element supplement device 111 in this embodiment is not limited to tantalum material or tantalum-graphite-plated material, as long as it can satisfy heat conduction and is not eroded by Si powder at high temperature.

Example 2: the growth method of the silicon carbide single crystal comprises the following steps:

s1, filling a silicon carbide raw material and seed crystals in the silicon carbide single crystal growth device, burying a plurality of Si element supplement devices in the silicon carbide raw material, filling Si powder in the Si element supplement devices, fixing the silicon carbide single crystal growth device on a heat source, and introducing protective gas;

The specific implementation conditions are as follows:

example 3: characterization of

The method for testing the inclusion concentration comprises the following steps: selecting 10 grown crystals, slicing the crystals, observing the conditions of other inclusions under a microscope, uniformly extracting the 10 th piece and the 20 th piece from each crystal, and counting the inclusion concentration under the magnification of 50 times.

The thickness difference is: the average of the difference between the maximum thickness and the minimum thickness of the edge of the growing crystal 10 is selected.

The number of microtubes is: the number of macro-clustered micro-tubes present in the grown crystal 10 is selected.

According to the comparison of experimental data of a comparative example, a sample 1 and a sample 2, the silicon carbide single crystal growth device is provided with the Si element supplement device, so that the carbon wrapping concentration is obviously reduced, the thickness difference of the edge of the crystal and the number of the micro-tubes are obviously reduced, and the result shows that the quality of the obtained crystal is obviously improved by arranging the Si element supplement device in the silicon carbide single crystal growth device, placing a mixture of Si powder and SiC powder in the Si element supplement device, supplementing Si in the silicon carbide growth process and adjusting the Si/C ratio.

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

1. A silicon carbide single crystal growth method comprising the steps of placing a raw material in a silicon carbide single crystal growth apparatus, and heating to sublimate the raw material to form a silicon carbide single crystal, characterized in that:

the silicon carbide single crystal growth device is internally provided with a Si element supplementing device for adjusting the temperature field distribution in the raw material region, the Si element supplementing device is filled with a mixture of Si and SiC or Si powder, the Si element supplementing device is arranged in the raw material, and the Si element supplementing device is provided with a plurality of through holes; the Si element supplementing device is a tantalum material crucible or a tantalum-graphite-plated material crucible;

in the crystal growth process, the mixture of Si and SiC or Si powder can pass through the through hole to supplement Si element for the growth of the silicon carbide single crystal;

the silicon carbide single crystal growth apparatus includes: the growth chamber is used for placing raw materials and providing a place for heating and sublimating the raw materials, and is divided into a raw material part for placing the raw materials and a gas phase part for sublimating and crystallizing the raw materials; a plurality of Si element supplementing devices are arranged in the growth cavity, the Si element supplementing devices are arranged in the raw material part, and the Si element supplementing devices are isolated from the inner wall of the growth cavity;

the Si element supplementing device is arranged in the middle area of the bottom of the raw material part or an area close to the side wall of the growth cavity;

in the single crystal growth device, the mass ratio of the Si powder to the SiC powder is 1-4%.

2. A silicon carbide single crystal growth method according to claim 1, characterized in that: the mass ratio of the Si powder to the SiC powder is 1.8-3.1%.

3. A silicon carbide single crystal growth method according to claim 1, characterized in that: the number of the Si element supplementing devices put into the silicon carbide raw material is 5-9.

4. A method for growing a silicon carbide single crystal according to claim 1, wherein: the method comprises the following steps:

5. A silicon carbide single crystal growth method according to claim 4, characterized in that: the protective gas is one or a mixture of more than two of argon, neon or helium in any proportion.

6. A silicon carbide single crystal growth method according to claim 4, characterized in that: the first temperature in S2 is 1400-1800 ℃, and the first pressure is 700-900 mbar; the second temperature in S3 is 2000-; the first time range in S4 is 20-50h, and the third pressure is 50-100 mbar.

7. A silicon carbide single crystal growth method according to claim 1, characterized in that: the Si element supplementing device comprises a container body and a container cover.

8. A silicon carbide single crystal growth method according to claim 7, characterized in that: the container cover is provided with a plurality of through holes.