JP2019131440A - SiC SINGLE CRYSTAL MANUFACTURING APPARATUS, AND SiC SINGLE CRYSTAL MANUFACTURING METHOD - Google Patents

Abstract

To provide a SiC single crystal manufacturing apparatus and a SiC single crystal manufacturing method capable of manufacturing stably a SiC single crystal not containing impurities.SOLUTION: A SiC single crystal manufacturing apparatus includes a crucible for holding a raw material solution containing Si, C and Al, and a seed crystal holding body for holding a SiC seed crystal for growing a SiC single crystal by being brought into contact with the raw material solution, in which the seed crystal holding body has a first Al penetration prevention film on the surface.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an SiC single crystal manufacturing apparatus and an SiC single crystal manufacturing method.

  Silicon carbide (SiC) has a dielectric breakdown electric field one order of magnitude larger than silicon (Si) and a band gap three times larger. Silicon carbide (SiC) has characteristics such as about three times higher thermal conductivity than silicon (Si). Therefore, silicon carbide (SiC) is expected to be applied to power devices, high frequency devices, high temperature operation devices, and the like.

  In particular, 4H—SiC single crystal has high mobility and is expected to be used for power devices. For example, Patent Document 1 describes that the specific resistance of an n-type 4H—SiC single crystal in which a donor element and an acceptor element are co-doped is small.

  On the other hand, the resistance reduction of the p-type 4H—SiC single crystal has not progressed sufficiently. This is because holes, which are p-type carriers, have a lower mobility than electrons, which are n-type carriers, and aluminum and boron, which are p-type SiC acceptors, are ionized compared to nitrogen, which is an n-type SiC donor. This is because there are problems such as high energy and low activation rate, and increasing the doping amount of aluminum or the like, resulting in increased polymorphism and decreased crystallinity.

  By the way, a sublimation method (for example, Patent Literature 1 and Patent Literature 2) and a solution method (for example, Patent Literature 3) are known as main methods for growing a bulk of a high-quality SiC single crystal.

The sublimation method is a method in which SiC polycrystalline powder, which is a SiC raw material, is sublimated, and a SiC crystal layer is grown on a SiC seed crystal by sublimation recrystallization. In the sublimation method, it is possible to produce a p-type 4H—SiC single crystal by simultaneously or separately sublimating SiC polycrystalline powder, which is a SiC raw material, and Al ₄ C ₃ powder, which is a raw material of Al, which is a dopant. . However, since the sublimation temperatures of SiC and Al ₄ C ₃ are extremely different, it is difficult to dope Al stably. In addition, when high-concentration doping of Al is performed by the sublimation method, high Al vapor pressure adversely affects nucleation on the crystal growth surface, resulting in polymorphic instability and crystal defects, which can be used industrially. Such a low resistance p-type 4H—SiC (herein, low resistance means that the specific resistance is less than 1 Ωcm) is not easy (Non-Patent Document 1).

In the solution method, a p-type 4H—SiC single crystal having low resistance can be produced by immersing and growing a SiC seed crystal in a high-temperature raw material solution containing at least Si, Al, and C (for example, Patent Documents). 3). In general, a solution method is known in which a transition metal element such as Cr or Ti is mixed with a raw material solution for the purpose of increasing the solubility of C in the raw material solution and increasing the growth rate.
However, when a SiC single crystal is manufactured with a raw material solution in which transition metal elements such as Cr and Ti are mixed, a transition metal element of about 1.0 × 10 ¹⁷ / cm ³ is mixed as an impurity in the manufactured SiC single crystal. It is known. These impurities are undesirable because they can cause problems in the semiconductor device manufacturing process. In order for a SiC single crystal not to contain these impurities, it is necessary to produce a SiC single crystal using a raw material solution made of Si, C, and Al without containing a transition metal element such as Cr or Ti (for example, Non-Patent Document 2).

JP 2014-187113 A JP 2017-65959 A Japanese Patent Laid-Open No. 2006-172675

Eto et al. Journal of Crystal Growth 470 (2017) 154-158. Mitani et al. , “Bulk Growth of p-type 4H-SiC Crystals from Si-C-Al solution”, Book of Abstracts of the 11th European Conference on Silicon 16

  However, the inventors of the present invention have a problem that when the raw material solution does not contain a transition metal element such as Cr, the graphite seed crystal holder is likely to be broken as compared with the case where the raw material solution contains a transition metal. I found it. If the seed crystal holder is broken, not only the temperature distribution during the production of the SiC single crystal changes, but also the SiC seed crystal may fall, which is not preferable.

The present inventors have intensively studied why the fracture frequency of the seed crystal holder made of graphite changes depending on whether the raw material solution contains a transition metal element or not. The present inventors estimated that there is a phenomenon in which the proportion of evaporation of each element from the raw material solution containing Si, C, and Al increases when the transition metal element is not included. That is, the addition of the transition metal element has an effect of suppressing evaporation of Si, C, and Al from the raw material solution.
Furthermore, the present inventors have found that the increase of Al vapor is the main cause of the breakage of the seed crystal holder. That is, Al that evaporated from the raw material solution is re-agglomerated at the fracture portion of the graphite seed crystal holder, and the re-agglomerated Al reacts with C of the seed crystal holder, and the surface of the seed crystal holder It was found that it changed to aluminum carbide. Furthermore, the present inventors may cause deformation or cracks in the seed crystal holder due to the density difference between the reaction site and the graphite forming the seed crystal holder, and may eventually break. I found out.
Further, when a SiC single crystal is produced using a raw material solution that does not contain a transition metal element, the C solubility in the raw material solution is extremely small (about 1/100) compared to the case where the raw material solution contains a transition metal element. . When a SiC single crystal is produced using a raw material solution that does not contain a transition metal element, the temperature of the raw material solution may be increased in order to increase the C solubility in the raw material solution. Specifically, the raw material solution is heated to about 2000 ° C. to 2500 ° C. to produce a SiC single crystal. It has been found that the operation of increasing the temperature of the raw material solution is also the cause of increasing the evaporation of the raw material solution containing Al and easily causing the fracture of the graphite seed crystal holder.

  The present invention has been made in view of the above circumstances, and provides an SiC single crystal manufacturing apparatus and an SiC single crystal manufacturing method capable of stably manufacturing an SiC single crystal that does not contain impurities of a transition metal. Objective.

  Representative means for solving the above problems are as follows.

(1) A SiC single crystal manufacturing apparatus according to a first aspect includes a crucible for holding a raw material solution containing Si, C and Al, and a SiC seed for growing a SiC single crystal in contact with the raw material solution. A seed crystal holder for holding crystals, and the seed crystal holder has a first Al permeation preventive film on the surface thereof.

(2) In the SiC single crystal manufacturing apparatus according to the above aspect, the seed crystal holding body is provided with the first Al permeation preventive film at a site that is higher than the melting point of Al and lower than the melting point of Si during SiC single crystal growth. You may have.

(3) In the SiC single crystal manufacturing apparatus according to the above aspect, even if the first Al permeation prevention film is made of any one or more materials selected from the group consisting of Si, SiC, W, Ta, and Mo. Good.

(4) In the SiC single crystal manufacturing apparatus according to the above aspect, the material of the seed crystal holding body may be graphite, and the film thickness of the first Al permeation preventive film may be 10 μm to 1 mm.

(5) In the SiC single crystal manufacturing apparatus according to the above aspect, the crucible may have a second Al permeation preventive film on an inner surface thereof.

(6) In the method for producing an SiC single crystal according to the second aspect of the present invention, a step of preparing a raw material solution containing Si, C and Al in a crucible, and an SiC seed crystal held in a seed crystal holder And a step of growing the crystal on the SiC seed crystal in contact with the raw material solution, and using the seed crystal holder having the first Al permeation preventive film on the surface.

(7) In the method for producing a SiC single crystal according to the above aspect, in the step of preparing the raw material solution, it is not necessary to add a transition metal element to the raw material solution.

  According to each aspect described above, it is possible to provide an SiC single crystal manufacturing apparatus and an SiC single crystal manufacturing method capable of stably manufacturing an SiC single crystal that does not contain impurities of transition metals.

It is principal part sectional drawing which shows the whole structure of the SiC single crystal manufacturing apparatus which concerns on this embodiment. It is a schematic diagram which shows the structure of the seed crystal holding body which concerns on this embodiment. It is a photograph of the principal part cross section which shows the seed crystal holding body which concerns on a prior art. It is a photograph of an important section showing a seed crystal holding object concerning this embodiment. It is the result of having performed the simulation of the temperature distribution produced when manufacturing a SiC single crystal using the SiC single crystal manufacturing apparatus which concerns on this embodiment.

  The present inventors have studied various factors that are considered to cause breakage in the seed crystal holder. As a result, it was found that the temperature distribution during the production of the SiC single crystal is one of the causes of fracture.

FIG. 5 shows the result of a simulation of the temperature distribution generated when an SiC single crystal is manufactured using the SiC single crystal manufacturing apparatus according to the present embodiment. When the temperature distribution shown in FIG. 5 is analyzed by comparing with the reaggregation site of Al, the site where the amount of Al reaggregation is large in the seed crystal holder 30 is the melting point of Al (660 ° C.) during the production of the SiC single crystal. As described above, it has been clarified that the material is heated to a temperature range below the melting point (1414 ° C.) of Si (hereinafter sometimes referred to as a specific temperature range).
In the simulation, the crucible 10 and the seed crystal holder 30 were made of graphite, and the temperature of the raw material solution was 2000 ° C.

The cause of the reaggregation of a large amount of Al at a portion heated to a temperature higher than the melting point of Al and lower than the melting point of Si during the production of the SiC single crystal is considered as follows.
When a raw material solution composed of Si, C and Al is heated to about 2000 ° C. to 2500 ° C., the heating temperature is considerably higher than the melting point of Si or Al (close to the boiling point of Al (2470 ° C.)). It evaporates from the raw material solution as gas, Al gas, or gas such as Si-containing gas or Al-containing gas.

  These gases or vapors rise in the crucible 10 and move from the gap between the crucible 10 and the seed crystal holder 30 to the low temperature part. The gas or vapor that has moved to the low temperature part is cooled and becomes a liquid or solid state and aggregates in the low temperature part including the specific temperature range. As shown in FIG. 5, the specific temperature range during the growth of the SiC single crystal is the upper end portion 400 (of the crucible 10 when viewed along the cross section in the height direction of the SiC single crystal manufacturing apparatus. In the case where the crucible 10 is composed of a main body and an upper lid, the range is from the vicinity of the upper lid) to part of the heat insulating material 40.

  Here, since the specific temperature range is a temperature range lower than the melting point of Si during the growth of the SiC single crystal, it can be said that there is almost no Si gas in the specific temperature range as compared with the Al gas.

  When viewed along the cross section in the height direction of the SiC single crystal manufacturing apparatus, the specific temperature range exists in a range including the vicinity of the upper end portion 400 of the crucible 10 to a part of the heat insulating material 40, and in this range, the high temperature range is high. A seed crystal support member 300 is provided along the vertical direction. That is, the steam heated to the specific temperature range exists so as to surround the seed crystal support member 300.

As described above, the steam heated to the specific temperature range mainly contains Al and exists so as to surround the seed crystal support member 300. Thereby, it is considered that a part of the Al in the vapor is re-aggregated on the seed crystal support member 300 at the portion heated to the specific temperature range.
This finding has been revealed for the first time in the present invention.

  The present invention has been made based on the above findings. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

[SiC single crystal growth manufacturing equipment]
FIG. 1 is a cross-sectional view of the main part showing the overall structure of the SiC single crystal manufacturing apparatus according to the present embodiment.
As shown in FIG. 1, the SiC single crystal manufacturing apparatus 100 includes a crucible 10, a heating means 20, a seed crystal holder 30, a heat insulating material 40, a quartz tube 50, a temperature measuring device 60, and a sealed container body. 90, an upper shaft 150, and a lower shaft 160.

(crucible)
The crucible 10 is filled with a raw material 70 (hereinafter, the same reference numeral 70 is used for both the raw material before heating and the raw material solution after heating) before the growth of the SiC single crystal (before heating).
The material (material) of the crucible 10 is not particularly limited as long as it can withstand heating. However, it is preferable to use graphite because the raw material can be heated to supply C (carbon) to the raw material solution 70.
The material of the crucible 10 may be a material that does not supply C to the raw material solution 70. When a container made of a material that does not supply C is used for the raw material solution 70, a raw material C source is introduced into the container, or a gaseous C source is blown into the raw material solution 70 or mixed with an atmospheric gas. C can be supplied to the solution 70. As the solid C source, graphite such as block, rod, granule and powder, metal carbide, SiC and the like can be used. As the C source gas may be a hydrocarbon gas such as CH _4.

The raw material solution 70 in the crucible 10 is made of Si, C, and Al. That is, the raw material solution 70 does not contain transition metal elements such as Cr, Ti, Fe, Ni, Mo, and Mn. Thereby, since the SiC single crystal manufactured using the SiC single crystal manufacturing apparatus 100 does not contain a transition metal element as an impurity, it is suitable in a semiconductor device manufacturing process or the like.
In addition, in the raw material solution 70, in addition to Si, C, and Al, impurities inevitably mixed in the adjustment process or the like are within a range that does not affect the characteristics of the low-resistance p-type SiC single crystal that is the effect of the present invention. May be included.

Examples of the raw material (each element source) used for the preparation of the raw material solution 70 include the following (for example, carbide of each element, silicide of each element, etc. can be used).
Si source: Si, SiC, aluminum silicide.
Al source: metal Al, aluminum carbide, aluminum silicide.

  The supply source of C in the raw material solution 70 may be a raw material used for preparing the raw material solution 70 or the crucible 10. That is, the raw material used for the preparation of the raw material solution 70 does not necessarily include C.

(Heating means)
The heating means 20 heats the crucible 10 filled with the raw material 70. Specifically, the heating means 20 heats the raw material solution 70 to a temperature range of 2000 ° C to 2500 ° C.

  The heating unit 20 is not particularly limited as long as the raw material 70 can be heated to the above temperature range, and examples thereof include an induction heating method and a resistance heating method.

(Seed crystal holder)
FIG. 2 is a schematic view showing the structure of the seed crystal holder according to the present embodiment.
As shown in FIG. 2, the seed crystal holding body 30 includes a seed crystal support member 300 having an Al permeation prevention film (first Al permeation prevention film) 350 and a seed crystal holding member 310, and includes a seed crystal holding member. SiC seed crystal 80 can be attached to the surface of 310 on the raw material solution side.
Here, the “Al permeation preventive film” is a film having a function of preventing re-aggregated Al from passing through (transmitting through) the film and reaching the surface of the seed crystal holder.
The seed crystal holding body 30 is not particularly limited as long as the seed crystal holding body 30 holds the SiC seed crystal 80. However, since it is often a cylindrical bar-like member, it is generally called a seed crystal support bar or simply a support bar. .
In the seed crystal holding body 30 shown in FIG. 2, the seed crystal support member 300 and the seed crystal holding member 310 are separately connected bodies, but they may be integrated.

(Seed crystal support member)
The seed crystal support member 300 includes a base material portion 330 and an Al permeation preventive film (first Al permeation preventive film) 350, and the SiC seed crystal 80 is brought into contact with the raw material solution 70 at an appropriate position during crystal growth. It is possible to move in the longitudinal direction so that

"Position of Al permeation prevention film"
Although the seed crystal support member 300 includes the Al permeation preventive film 350, the Al permeation preventive film 350 may be provided on all or part of the seed crystal support member 300. In the case where the Al permeation preventive film 350 is provided in part, it is sufficient if the Al permeation preventive film 350 is within a range where aluminum carbide can be formed to such a degree as to cause deterioration or deformation.

In the case where the Al permeation preventive film 350 is provided on a part of the seed crystal support member 300, among the seed crystal support member 300, during the growth of the SiC single crystal, the Al melting point (about 660 ° C.) or higher and Si It is preferable that an Al permeation preventive film 350 is provided in a portion heated to a melting point (about 1414 ° C.) or lower (hereinafter referred to as a specific temperature portion). In the specific temperature region of the seed crystal support member 300, the Al gas tends to re-aggregate during the growth of the SiC single crystal.
By providing the Al permeation preventive film 350 at a specific temperature site, it becomes possible to prevent the reaggregated Al from reacting with C in the seed crystal support member 300 to form aluminum carbide, and Al It is possible to prevent the seed crystal holding body 30 (seed crystal support member 300) from being broken due to the re-aggregation.

  When the position of the specific temperature region cannot be confirmed in advance, the position 50 mm above the liquid surface of the raw material solution 70 during crystal growth (in the state where the SiC seed crystal 80 is in contact with the liquid surface of the raw material solution 70). It is preferable to cover the seed crystal support member 300 held in a range corresponding to a position 60 mm above the upper end 400 of the crucible 10 with an Al permeation prevention film 350.

  If the Al permeation preventive film 350 is not provided on the seed crystal support member 300 as in the prior art, the Al evaporated from the raw material solution 70 re-aggregates in the base material of the seed crystal support member 300 and is contained in the base material. C reacts with Al, and aluminum carbide may be formed at the reaggregation site of Al. When aluminum carbide is formed, due to the density difference between the aluminum carbide and the base material of the seed crystal support member 300, the seed crystal support member 300 is deformed due to cracks and the like. It may break.

  When the seed crystal support member 300 is broken, the broken seed crystal support member 300 or the seed crystal holding member 310 provided closer to the crucible 10 than the seed crystal support member 300 falls into the raw material solution 70, which is preferable. Absent. Further, when the seed crystal support member 300 is deformed, not only the temperature distribution during the production of the SiC single crystal is changed, but also the inner wall of the crucible and the SiC single crystal are in contact with each other, and the SiC single crystal is cracked. It is not preferable. Further, when the seed crystal holder is broken, the SiC seed crystal 80 falls and the seed crystal and the grown crystal cannot be used, which is not preferable.

“Al Permeation Prevention Material”
The material used for the Al permeation preventive film 350 is not particularly limited as long as it has an Al permeation preventive effect, but it is preferable to use a material having a high melting point as much as possible. When the melting point of the material of the Al permeation preventive film 350 is low, the Al permeation preventive film 350 is easily melted and deteriorated during the growth of the SiC single crystal, so that the seed crystal support member 300 as a base material is exposed and re-aggregated. Al and the base material C combine to form aluminum carbide. This is not preferable because the seed crystal support member 300 may break.
In order to achieve the Al permeation preventive effect, the material used for the Al permeation preventive film 350 is preferably a material in which Al atoms hardly pass through the film, for example, a material that becomes a dense film.

  In order to satisfy the condition of having a high melting point, the Al permeation preventive film 350 is preferably made of any one or more materials selected from the group consisting of Si, SiC, W, Ta, and Mo. Among these materials, Si is particularly preferable in view of the Al permeation preventing function and economy.

"Thickness of Al permeation prevention film"
The thickness of the Al permeation preventive film 350 is not particularly limited, but is preferably 10 μm to 1 mm. If the thickness of the Al permeation preventive film 350 is less than 10 μm, the Al permeation preventive effect of the Al permeation preventive film 350 is not sufficient, and the reaggregated Al and C in the base material of the seed crystal support member 300 are combined. Since aluminum carbide may be formed, it is not preferable. If the film thickness of the Al permeation preventive film 350 exceeds 1 mm, the Al permeation preventive effect of the Al permeation preventive film 350 is saturated, and the amount of adhesion is excessive. Since cracks may be generated or peeled off at the portion, the denseness as the Al permeation preventive film is impaired.

"Method of forming Al permeation preventive film"
The method for forming the Al permeation preventive film 350 on the surface of the seed crystal support member 300 is not particularly limited. The formation method includes a method of immersing the seed crystal support member 300 in a raw material solution of the Al permeation prevention film 350 (without the Al permeation prevention film 350), or heating the raw material of the Al permeation prevention film 350 to generate steam. Examples include a method of exposing the seed crystal support member 300 to the vapor, a method of using CVD coating, and the like. The Al permeation prevention film formed by these forming methods can be said to be an Al permeation prevention melt dip film, an Al permeation prevention vapor deposition film, or an Al permeation prevention CVD film.

Although the seed crystal support member 300 having the Al permeation preventive film 350 formed on the surface by the above-described method may be used as it is, the seed crystal support member 300 having the Al permeation preventive film 350 formed on the surface is used as the Al permeation preventive film 350. It may be used as seed crystal support member 300 by joining to seed crystal support member 300 that is not formed (site that becomes base material portion 330 after joining).
The seed crystal support member 300 shown in FIGS. 1 and 2 is a seed crystal in which the Al permeation preventive film 350 is not formed on each of both ends in the longitudinal direction of the seed crystal support member 300 having the Al permeation preventive film 350 formed on the surface. It is formed by joining the support member 300 by an arbitrary method.

  Of the seed crystal support member 300, a portion where the Al permeation preventive film 350 is not formed is the base material portion 330. In principle, the base material portion 330 exposes the base material of the seed crystal support member 300, but a coating other than the Al permeation prevention film may be formed.

(Seed crystal holding member)
The seed crystal holding member 310 is attached to the front end surface on the crucible 10 side of the seed crystal support member 300 at one end surface in the longitudinal direction, and holds the SiC seed crystal 80 at the other end surface in the longitudinal direction.
The method for attaching the seed crystal holding member 310 to the seed crystal support member 300 and the method for holding the SiC seed crystal 80 by the seed crystal holding member 310 are not particularly limited. Further, the shape of seed crystal holding member 310 is not particularly limited.

(SiC seed crystal)
As the SiC seed crystal 80, for example, a wafer manufactured by a sublimation method and having a surface polished can be used. The shape of the SiC seed crystal 80 may be a plate shape such as a disc shape, a hexagonal flat plate shape, or a quadrangular flat plate shape, or a cubic shape, but a plate shape is preferable. Moreover, if the magnitude | size is a disk shape, for example, a diameter of 0.1 cm or more is preferable, 0.5 cm or more is more preferable, and 1 cm or more is further more preferable. A preferable upper limit of the diameter is not particularly limited, and may be adjusted according to the capacity of the crystal growth apparatus, and may be, for example, 10 cm.

  The crystal structure of the SiC seed crystal 80 can be appropriately selected in accordance with the type of polymorph of the target SiC single crystal, and for example, 2H type, 3C type, 4H type, 6H type and the like can be used. For example, in order to obtain a 2H type SiC single crystal, it is preferable to use a 2H type SiC seed crystal 80. In the present embodiment, it is preferable to use 4H-type SiC seed crystal 80 (4H—SiC single crystal wafer) manufactured by a vapor phase method or the like as SiC seed crystal 80.

  Since the SiC single crystal (not shown) has a structure in which Si and C are laminated in layers, the SiC seed crystal 80 has an exposed C surface where C is aligned on the crystal surface, and Si where Si is aligned. Some have exposed surfaces. In the present embodiment, either SiC seed crystal 80 can be used, but a crystal with better surface morphology can be produced by starting crystal growth from the C plane.

  In the present embodiment, as a growth surface of the SiC seed crystal 80, a (0001) plane (C-polarity and Si-polar on-axis plane) is normally used, but from the (0001) plane, An inclined plane (C-polar and Si-polar off-axis plane) may be used.

(Insulation material)
The heat insulating material 40 covers the crucible 10 filled with the raw material solution 70 and the seed crystal holding body 30 holding the SiC seed crystal 80 for heat insulation. The material of the heat insulating material 40 is not particularly limited as long as desired heat insulation can be realized.

(Quartz tube)
The quartz tube 50 electrically insulates the heating means 20 from the heat insulating material 40 that covers the crucible 10 filled with the raw material solution 70 and the seed crystal holder 30 that holds the SiC seed crystal 80.

(Sealed container body)
The sealed container main body 90 accommodates the crucible 10, the heating means 20, the seed crystal holder 30, the heat insulating material 40, and the quartz tube 50 therein. In order to allow gas to enter and exit from the inside and outside of the sealed container body 90, an inert gas inlet (not shown) and a gas exhaust port (not shown) may be provided in the sealed container body 90.
Although the raw material of the airtight container main body 90 is not specifically limited, For example, stainless steel is mentioned.

(Upper shaft)
The upper shaft 150 is connected to the seed crystal holding body 30 (base material part 330), and is provided so as to penetrate the sealed container main body 90.
The upper shaft 150 and the seed crystal holding body 30 (base material part 330) are connected so that their axes coincide. The connection may be performed by bonding with an adhesive or the like, or may be mechanically held by forming a screw structure.
The upper shaft 150 penetrates the sealed container main body 90 in a form having no gap with the sealed container main body 90, and has a function of rotating and moving up and down. The connection portion between the upper shaft 150 and the sealed container body 90 can maintain an airtight structure by using an arbitrary seal structure (not shown) such as an O-ring seal or a magnetic seal. Thereby, the inside of the airtight container main body 90 can be maintained in a desired atmosphere.

(Lower shaft)
The lower shaft 160 is provided so as to penetrate the sealed container main body 90, and has a function of rotating and moving up and down while holding the crucible 10 including the raw material solution 70 and the heat insulating material 40. Other points regarding the lower shaft 160 are not particularly limited.
Similar to the upper shaft 150, the lower shaft 160 penetrates the sealed container body 90 in a manner that there is no gap between the lower shaft 160 and the lower shaft 160. Thereby, the inside of the airtight container main body 90 can be maintained in a desired atmosphere.

The upper shaft 150 and the lower shaft 160 may be hollow members or solid members. When the upper shaft 150 and / or the lower shaft 160 are hollow members, one end located outside the sealed container main body 90 may be sealed with a sealing member (not shown) such as quartz glass.
The material of the upper shaft 150 and the lower shaft 160 is not particularly limited, and examples thereof include stainless steel.

(Temperature measuring device)
An arbitrary number of temperature measuring devices 60 are provided, and measure the temperature of arbitrary parts such as the crucible 10 and the seed crystal holder 30. In the example shown in FIG. 1, a radiation thermometer is used as the temperature measuring device 60, and two radiation thermometers 60 are provided in total, and the radiation thermometer 60 provided above the seed crystal holder 30 is a seed. A temperature near the crystal holding member 310 is measured, and a radiation thermometer 60 provided below the heat insulating material 40 measures the temperature of the bottom bottom of the crucible 10.
The temperature measurement method is not particularly limited, and a radiation thermometer, a thermocouple, or the like can be used as the temperature measurement device.

[Method for producing SiC single crystal]
Next, the manufacturing method of the SiC single crystal according to the present embodiment will be described.
The method for producing an SiC single crystal according to the present embodiment is a method for producing an SiC single crystal by a solution method (solution growth method). Here, the “solution method” or “solution growth method” is a method in which a SiC single crystal is grown on a SiC seed crystal by bringing the SiC seed crystal into contact with a raw material solution.
The manufacturing method of the SiC single crystal according to the present embodiment can use a known manufacturing method, for example, a preparation step for preparing crystal growth, a generation step for generating a raw material solution, and a surface remaining on the surface of the SiC seed crystal. A meltback process for removing impurities and a deteriorated layer, and a growth process for growing a SiC single crystal are provided.

(Preparation process)
First, the crucible 10 is filled with the raw material, and the SiC seed crystal 80 held on the lower end face of the seed crystal holding member 310 is disposed away from the liquid surface of the raw material.
Here, the method for holding the SiC seed crystal 80 by the seed crystal holding member 310 is not particularly limited, but an example is a method of holding the seed crystal holding member 310 and the SiC seed crystal 80 with an adhesive interposed therebetween. It is done. Alternatively, the seed crystal holding member 310 may be provided with a holding structure (not shown), and the SiC seed crystal 80 may be held by the holding structure (not shown). However, the holding structure (not shown) is preferably provided so as to be in thermal contact with the seed crystal holding member 310 and not to inhibit crystal growth in the SiC seed crystal 80.

(Generation process)
Next, the raw material solution 70 is produced | generated. That is, a raw material solution 70 containing Si, C and Al is prepared in the crucible 10.
The raw material in the crucible 10 is heated to 2000 ° C. or higher by the heating means 20. When the crucible 10 is made of graphite, when the crucible 10 is heated, C dissolves in the melt from the crucible 10 and a raw material solution 70 is generated. When C in the crucible 10 is dissolved in the raw material solution 70, the C concentration in the raw material solution 70 approaches the saturated concentration. When the crucible 10 cannot be used as a C supply source, a material containing C is used as the raw material of the raw material solution 70.

(Meltback process)
Next, SiC seed crystal 80 held on seed crystal holder 30 is brought into contact with raw material solution 70 to melt back SiC seed crystal 80. The method of meltback is not particularly limited, and can be appropriately determined according to the size of the SiC single crystal to be produced, the composition ratio of Si, C, Al in the raw material solution 70, and the like.

(Growth process)
Next, an SiC single crystal is grown on SiC seed crystal 80 held on seed crystal holder 30. Specifically, it is as follows.

  First, in the state where the C concentration of the raw material solution 70 is saturated at the crystal growth temperature, the vicinity of the SiC seed crystal 80 in the raw material solution 70 is cooled to bring the C in the solution into a supersaturated state. That is, when C in the vicinity of the SiC seed crystal 80 in the raw material solution 70 becomes supersaturated, the meltback of the SiC seed crystal 80 is completed.

  When the vicinity of the SiC seed crystal 80 in the raw material solution 70 is cooled, the temperature gradient immediately below the SiC seed crystal 80 in the raw material solution 70 is larger than 0 ° C./cm from the SiC seed crystal surface toward the crucible bottom, and 19 ° C./cm or less. When the temperature gradient is 0 ° C./cm, crystal growth does not start. When the temperature gradient exceeds 19 ° C./cm, the degree of supersaturation becomes too large. Therefore, island growth occurs on the terrace, and step flow growth is hindered. As a result, surface roughness increases and defects such as voids and solvent entrainment may occur, which is not preferable. The upper limit of the temperature gradient is preferably 5 ° C./cm.

  The method for cooling the vicinity of the SiC seed crystal 80 in the raw material solution 70 is not particularly limited. For example, the heating means 20 is controlled so that the temperature in the region near the SiC seed crystal 80 in the raw material solution 70 is lower than the temperature in other regions. Alternatively, the vicinity of the SiC seed crystal 80 in the raw material solution 70 may be cooled by a refrigerant.

The SiC seed crystal 80 and the raw material solution 70 (the crucible 10) are rotated while SiC in a region near the SiC seed crystal 80 in the raw material solution 70 is in a supersaturated state. By rotating the upper shaft 150 connected to the seed crystal support member 300, the SiC seed crystal 80 rotates. Moreover, the crucible 10 rotates by rotating the lower shaft 160. The rotation direction of SiC seed crystal 80 may be the opposite direction to the rotation direction of crucible 10 or the same direction. The rotation speed may be constant or may vary. The upper shaft 150 connected to the seed crystal support member 300 and the lower shaft 160 connected to the crucible 10 may be raised or lowered at an arbitrary speed while rotating. At this time, a SiC single crystal grows on the SiC seed crystal 80 in contact with the raw material solution 70. Note that the upper shaft 150 connected to the seed crystal support member 300 and the lower shaft 160 connected to the crucible 10 may rotate without being raised, and may not be raised or rotated.
The rotation speed may be constant, for example, in the range of about 2 to 300 rpm, or may be changed periodically.

  The time required for the growth step is not particularly limited, and examples include about 50 hours to 100 hours.

  As described above, the raw material solution 70 used in the present embodiment is made of Si, C, and Al, and no transition metal element such as Cr or Ti is added to the raw material solution 70.

  In a general solution growth method, the raw material solution is heated to 1800 ° C. to 2200 ° C. in the growth step. However, in order to increase the solubility of C in the raw material solution 70, in the growth step of this embodiment, the raw material solution 70 is heated by the heating means 20. Is heated to about 2000 ° C to 2500 ° C.

  By heating the raw material solution 70 to about 2000 ° C. to 2500 ° C. in the growth process, Si and Al in the raw material solution 70 are evaporated. Si or Al evaporated from the raw material solution 70 rises in the crucible 10.

  Similarly, the seed crystal holder 30 is also heated by the heating means 20. In the heated seed crystal holding body 30, Al reaggregates at a specific temperature portion where the temperature is higher than the melting point of Al and lower than the melting point of Si.

The vapor around the specific temperature region of the seed crystal holder 30 contains a large amount of Al. In particular, steam having a temperature of 1100 ° C. to 1300 ° C. contains a large amount of Al. Therefore, reaggregation of Al or SiAl containing a large amount of Al occurs at a specific temperature region.
On the other hand, the steam around the part closer to the crucible 10 than the specific temperature part of the seed crystal holder 30 and the steam in the crucible 10 contain a large amount of Si.

  The seed crystal holding body 30 includes a seed crystal support member 300 and a seed crystal support member 310, but Al is regenerated at a specific temperature portion of the seed crystal support member 300 from the relationship with the temperature distribution shown in FIG. Often aggregates. Since the seed crystal holding member 310 is at a distance close to the surface of the raw material solution 70, the temperature is relatively high and Al re-aggregation hardly occurs. In addition, in the part closer to the raw material solution 70 than the specific temperature part of the seed crystal support member 300, vapor containing Al is present in the surroundings, but the vapor scatters further upward, so that the specific temperature of the seed crystal support member 300 is increased. Reaggregation to a site closer to the raw material solution 70 than the site hardly occurs.

Here, the seed crystal holding body 30 (seed crystal support member 300) of the present embodiment has an Al permeation preventive film 350. As a result, the re-aggregated Al can be prevented from coming into direct contact with the base material of the seed crystal holding body 30 (seed crystal support member 300), and the formation of aluminum carbide that causes breakage can be prevented.
As described above, the Al permeation preventive film 350 is preferably provided at a specific temperature portion of the seed crystal holder 30 (seed crystal support member 300). More preferably, the Al permeation preventive film 350 is provided at a site of the seed crystal holding body 30 (seed crystal support member 300) that is heated to 1100 ° C. to 1300 ° C. during the production of the SiC single crystal.

[SiC single crystal]
Depending on the method for producing the SiC single crystal of the present invention, various crystal polymorphisms such as 2H, 3C, 4H, and 6H SiC single crystals can be selected by selecting the crystal polymorph (polytype) of the SiC seed crystal. Can be obtained. Among these, since it can be suitably used for a power control device substrate or the like, the SiC single crystal of the present embodiment is preferably a 4H type SiC single crystal.

  The SiC single crystal produced by the method for producing an SiC single crystal of the present invention is produced using a raw material solution 70 that does not contain a transition metal element. Therefore, the obtained SiC single crystal does not contain transition metal elements such as Cr, Ti, Fe, Ni, Mo, and Mn. However, “not containing a transition metal element” excludes a transition metal element inevitably mixed from the crucible 10 or the like in the manufacturing process.

  The concentration of Al in the SiC single crystal and the concentration of transition metal elements such as Cr and Ti should be measured by secondary ion mass spectrometry (SIMS) and glow discharge mass spectrometry (Glow Discharge Mass Spectrometry). Can do.

  The content of the transition metal element in the SiC single crystal that can inevitably be mixed is below the lower detection limit concentration (0.05 to 0.001 ppm or less) of secondary ion mass spectrometry or glow discharge mass spectrometry, The SiC single crystal of this embodiment can be suitably used as a semiconductor device material or the like.

By the method for producing a SiC single crystal of the present invention, a p-type SiC single crystal having an aluminum concentration (Al concentration) of 3.0 × 10 ¹⁸ atoms / cm ³ or more can be produced.

  In the SiC single crystal of the present embodiment, the Al concentration can be controlled by adjusting the blending amount of the Al source in the raw material 70 used in the above-described SiC single crystal manufacturing method.

  The embodiment of the present invention has been described in detail with reference to the drawings, but each configuration in the embodiment and combinations thereof are examples, and additions, omissions, and configurations of the configuration are within the scope of the present invention. Substitutions and other changes are possible.

For example, the example in which the Al permeation prevention film 350 is provided on the seed crystal support member 300 has been described above, but the Al permeation prevention film (second Al permeation prevention film, non-permeability film) is not formed on the inner surface of the crucible 10 that does not contact the heat insulating material 40. (Shown) may be provided. Thereby, it is possible to prevent aluminum contained in the steam and C in the crucible 10 base material from forming aluminum carbide.
If the crucible 10 breaks, the raw material solution 70 may leak out of the crucible 10, and not only the desired SiC single crystal cannot be obtained, but the members such as the heat insulating material 40 react with the raw material solution 70 and change in quality. Therefore, there is a possibility of causing a failure of the apparatus. However, since the Al permeation preventive film is provided on the inner surface of the crucible 10, the crucible 10 can be prevented from being broken.

Example 1
A SiC single crystal was manufactured using the seed crystal holder 30 according to the present embodiment. The manufacturing conditions are as shown below.
Temperature of SiC seed crystal 80: 2250 ° C.
Temperature gradient: 5 ° C./cm or less Raw material solution 70: Si _0.93 Al _0.07 solution crucible: Graphite seed crystal holder: Graphite, with Si coating film (film thickness 20 μm)
Composition of Al permeation preventive film 350: Si (100%)
Method for manufacturing seed crystal support member 300 having Al permeation prevention film 350: manufactured by immersing seed crystal support member 300 in an Si solution

FIG. 4 is a photograph of a cross section in the longitudinal direction of the seed crystal holder 30 when the crystal growth is performed for 100 hours under the above growth conditions. As shown in FIG. 4, when the SiC single crystal is manufactured using the seed crystal holder 30 according to the present embodiment, no special alteration is observed in the seed crystal holder 30 even after the crystal growth is performed for 100 hours. I couldn't
This is because Al re-aggregates on the Al permeation preventive film 350, so that Al can be prevented from re-aggregating on the base material of the seed crystal holder 30, and the formation of aluminum carbide that causes breakage can be prevented. This is thought to be because it was able to be prevented.

(Comparative Example 1)
A SiC single crystal was manufactured in the same manner as in Example 1 except that the seed crystal holder 30 having no Al permeation preventive film 350 was used.
FIG. 3 is a photograph of a cross section in the longitudinal direction of a seed crystal holding body 500 according to the prior art when crystal growth is performed for 45 hours under the conditions of Comparative Example 1. As shown in FIG. 3, it was found that when the seed crystal holding body 500 according to the prior art was used, the seed crystal holding body 500 had a crack 520 and was about to break. In such a situation, fluctuations occur in the rotational movement of the seed crystal support member 300 during crystal growth, and as a result, the inner wall of the crucible 10 and the SiC seed crystal 80 may come into contact with each other and vibration may occur, which is not preferable.
In addition, aluminum carbide 510 was formed on the surface of the crack 520. From these results, it is considered that the re-agglomerated Al is combined with C in the base material to form aluminum carbide 510, and cracks 520 are caused due to the density difference between the base material and aluminum carbide 510. .

  In Comparative Example 1, formation of aluminum carbide was observed after about 20 to 30 hours from the start of production of the SiC single crystal.

  DESCRIPTION OF SYMBOLS 10 ... Crucible, 20 ... Heating means, 30 ... Seed crystal holder, 40 ... Insulating material, 50 ... Quartz tube, 60 ... Temperature measuring device (radiation thermometer), 70 ... Raw material solution, 80 ... SiC seed crystal, 90 ... Sealed container body, 100 ... SiC single crystal manufacturing apparatus, 150 ... Upper shaft, 160 ... Lower shaft, 300 ... Seed crystal support member, 310 ... Seed crystal holding member, 330 ... Base material part, 350 ... Al permeation prevention film (No. 1) 1 ... Al permeation preventive film), 400 ... upper end of crucible, 500 ... seed crystal support according to prior art, 510 ... aluminum carbide, 520 ... crack

Claims (7)

A crucible for holding a raw material solution containing Si, C and Al;
A seed crystal holder for holding a SiC seed crystal for growing a SiC single crystal in contact with the raw material solution;
The SiC seed crystal holding apparatus has a first Al permeation preventive film on a surface thereof. 2. The SiC according to claim 1, wherein the seed crystal holding body has the first Al permeation preventive film at a portion that is higher than the melting point of Al and lower than the melting point of Si during SiC single crystal growth. Single crystal manufacturing equipment. 3. The SiC single crystal according to claim 1, wherein the first Al permeation preventive film is made of one or more materials selected from the group consisting of Si, SiC, W, Ta, and Mo. 4. manufacturing device. The seed crystal holder is made of graphite,
4. The SiC single crystal manufacturing apparatus according to claim 1, wherein a thickness of the first Al permeation preventive film is 10 μm to 1 mm. 5. The SiC single crystal manufacturing apparatus according to any one of claims 1 to 4, wherein the crucible has a second Al permeation preventive film on an inner surface thereof. Preparing a raw material solution containing Si, C and Al in the crucible;
A step of bringing the SiC seed crystal held by the seed crystal holder into contact with the raw material solution and performing crystal growth on the SiC seed crystal,
A method for producing a SiC single crystal, wherein the seed crystal holding body has a first Al permeation preventive film on its surface. The method for producing a SiC single crystal according to claim 6, wherein a transition metal element is not added to the raw material solution in the step of preparing the raw material solution.