JP6051109B2 - Seed crystal holder, crystal manufacturing apparatus and crystal manufacturing method - Google Patents

Description

  The present invention relates to a seed crystal holder used for growing a silicon carbide crystal, a crystal manufacturing apparatus and a crystal manufacturing method using the same.

Currently, silicon carbide (SiC), which is a compound of carbon and silicon, has attracted attention as a substrate material for forming devices such as transistors. Silicon carbide has attracted attention because of its wide band gap compared to silicon and high electric field strength leading to dielectric breakdown. Crystals of silicon carbide are manufactured by a solution growth method using a solution containing carbon and silicon (see, for example, Patent Document 1).

JP 2000-264790 A

  In the invention described in Patent Document 1, for example, due to the convection state of the solution in the crucible, the crystal grows rapidly only in the portion where the crystal tends to grow on the lower surface of the seed crystal, and the crystal of the lower surface of the seed crystal grows. The difference in the crystal growth rate between the fast-growing portion and the slow-growing portion becomes large, and there is a risk that defects such as formation of grooves in the grown crystal may occur.

  The present invention has been devised in view of such circumstances, and an object of the present invention is to suppress the occurrence of defects such as formation of grooves in a grown crystal and improve the quality of the crystal.

  The seed crystal holding body according to one embodiment of the present invention is formed by bringing the lower surface of a seed crystal made of silicon carbide into contact with a solution containing carbon and silicon held in a crucible having an opening at the upper end, and pulling up the seed crystal holder. A columnar seed crystal holder used in a solution growth method for growing a silicon carbide crystal from the solution on the lower surface of a seed crystal, holding the seed crystal on the lower surface, and in a region excluding the outer peripheral portion of the upper surface A first holding body having an open cavity; and a columnar second holding body fixed to an outer peripheral portion of an upper surface of the first holding body so as to close the opening.

  A crystal manufacturing apparatus according to an embodiment of the present invention includes the above-mentioned seed crystal holder, a crucible that holds an opening into which the seed crystal holder is inserted, and holds a solution containing carbon and silicon inside. Is provided.

  The method for producing a crystal according to an embodiment of the present invention includes a step of preparing the seed crystal holder and a crucible holding a solution containing carbon and silicon therein, and the first holding of the seed crystal holder. A holding step of holding a seed crystal made of silicon carbide on the lower surface of the body, a contacting step of bringing the lower surface of the seed crystal held in the seed crystal holding body into contact with the solution held in the crucible, and the seed crystal And a crystal growth step of growing silicon carbide crystals from the solution on the lower surface of the seed crystal.

According to the present invention, by forming a cavity in the first holding body, a heat insulating portion is formed in the first holding body, and heat transfer from the seed crystal to the first holding body is reduced. As a result, the temperature difference between the solution and the seed crystal is reduced, and the maximum value of the growth rate of the crystal growing on the lower surface of the seed crystal can be reduced. Therefore, rapid growth of the crystal at the portion where the crystal tends to grow can be suppressed on the lower surface of the seed crystal. The difference in the growth rate of the crystals can be reduced, and as a result, the occurrence of defects such as the formation of grooves in the grown crystals can be suppressed, and the quality of the crystals can be improved.

It is sectional drawing which showed typically the crystal manufacturing apparatus which concerns on one Embodiment of this invention. It is the enlarged view to which the cross section of the seed crystal holding body which concerns on one Embodiment of this invention was expanded. It is the enlarged view to which the upper surface of the 1st holding body of the seed crystal holding body which concerns on one Embodiment of this invention was expanded. It is the enlarged view to which the lower surface of the 1st holding body of the seed crystal holding body which concerns on one Embodiment of this invention was expanded. It is the enlarged view which expanded further the cross section of the seed crystal holding body shown in FIG. It is the enlarged view to which the cross section of the seed crystal holding body which concerns on the modification of one Embodiment of this invention was expanded. It is the enlarged view to which the cross section of the seed crystal holding body which concerns on the modification different from FIG. 6 of one Embodiment of this invention was expanded.

<Seed crystal holder and crystal manufacturing apparatus>
A seed crystal holding body and a crystal manufacturing apparatus including the seed crystal holding body according to an embodiment of the present invention will be described with reference to FIGS. In addition, this invention is not limited to the following embodiment.

  As shown in FIG. 1, the crystal manufacturing apparatus 1 includes a crucible 3 that mainly contains and holds a solution 2, and a seed crystal holder 5 that holds a seed crystal 4. With this configuration, the crystal manufacturing apparatus 1 can manufacture a crystal by bringing the lower surface of the seed crystal 4 into contact with the solution 2 and growing the crystal on the lower surface of the seed crystal 4.

  FIG. 1 is a cross-sectional view schematically showing the crystal manufacturing apparatus 1 and shows an outline of the crystal manufacturing apparatus 1.

  The solution 2 has a function of supplying a crystal raw material to be grown on the lower surface of the seed crystal 4 in order to grow the crystal on the lower surface of the seed crystal 4. Solution 2 comprises the same material as the crystal to be grown. That is, when it is desired to grow silicon carbide crystals, the solution 2 contains carbon and silicon. In this embodiment, the solution 2 is configured by dissolving carbon (solute) in silicon (solvent).

  The solubility of the element that becomes the solute increases as the temperature of the element that becomes the solvent increases. For this reason, when the solution 2 in which many solutes are dissolved in a solvent at a high temperature is cooled, the solute is precipitated at the boundary of thermal equilibrium. In the solution growth method in the present embodiment, a silicon carbide crystal is grown on the lower surface of the seed crystal 4 by utilizing precipitation due to this thermal equilibrium.

  The crucible 3 serves as a vessel for melting the raw material of silicon carbide crystals to be produced. In this embodiment, the crystal raw materials (carbon and silicon) are melted in the crucible 3 and stored as the solution 2. The crucible 3 is made of, for example, carbon (graphite). By constituting the crucible 3 with carbon, a part of the crucible 3 dissolves into the solution 2 and carbon can be supplied to the solution 2.

The crucible 3 is arrange | positioned inside the crucible container 6 with which the crystal manufacturing apparatus 1 is provided, as shown in FIG. The crucible container 6 holds the crucible 3. A heat insulating material 7 is disposed between the crucible container 6 and the crucible 3 so as to surround the crucible 3. The heat insulating material 7 suppresses heat radiation from the crucible 3 and contributes to maintaining the temperature of the crucible 3 stably.

  Heat is applied to the crucible 3 by the heating mechanism 8. The heating mechanism 8 of the present embodiment employs an electromagnetic induction heating system that heats the crucible 3 with electromagnetic waves, and includes a coil 9 and an AC power supply 10.

  The coil 9 is composed of a conductor and is disposed so as to surround the periphery of the crucible 3. The AC power supply 10 is for supplying an AC current to the coil 9, and the heating time up to the set temperature in the crucible 3 can be shortened by increasing the AC current.

  In this embodiment, the crucible 3 is heated as follows. First, a current is passed through the coil 9 using the AC power supply 10 to generate a magnetic field in the space including the heat insulating material 7. An induced current flows in the crucible 3 by this magnetic field. The induced current flowing through the crucible 3 is converted into thermal energy by Joule heat generation due to electric resistance, heat generation due to hysteresis loss, and the like. That is, the crucible 3 is heated by the heat loss of the induced current. Note that the magnetic field may generate heat by causing an induced current to flow through the solution 2 itself. When the solution 2 itself generates heat as described above, the crucible 3 itself does not need to generate heat.

  In the present embodiment, an electromagnetic induction heating method is employed as the heating mechanism 8, but heating may be performed using other methods. The heating mechanism 8 can employ other methods such as a method of transferring heat generated by a heating resistor such as carbon. When this heating mechanism is used, for example, a heating resistor is disposed between the crucible 3 and the heat insulating material 7.

  The seed crystal 4 is a crystal seed to be grown by the crystal manufacturing apparatus 1. The seed crystal 4 has, for example, a disk shape, and is fixed to the lower surface of the seed crystal holding body 5 via, for example, a seed crystal adhesive (not shown) containing carbon. The material of the seed crystal 4 is made of the same material as the crystal to be grown. That is, when it is desired to grow a silicon carbide crystal, seed crystal 4 is made of silicon carbide.

  The seed crystal 4 is brought into contact with the solution 2 by being moved up and down by the transport mechanism 11. The transport mechanism 11 also has a function of carrying out crystals produced from the solution 2. As shown in FIG. 1, the transport mechanism 11 includes a seed crystal holder 5 and a power source 12. The seed crystal holder 5 carries in and out the seed crystal 4 and the crystal grown on the lower surface of the seed crystal 4. The seed crystal 4 is attached to the lower surface of the seed crystal holder 5, and the movement of the seed crystal holder 5 in the vertical direction (Z-axis direction) is controlled by the power source 12.

  In the present embodiment, the AC power source 10 of the heating mechanism 8 and the power source 12 of the transport mechanism 11 are connected to the control unit 13 and controlled. That is, in the crystal manufacturing apparatus 1, the heating and temperature control of the solution 2 and the carry-in / out of the seed crystal 4 are controlled by the control unit 13 in conjunction with each other. The control unit 13 includes a central processing unit and a storage device such as a memory, and is composed of, for example, a known computer.

  The seed crystal holding body 5 has a function of holding the seed crystal 4 and a crystal that grows on the lower surface of the seed crystal 4. The seed crystal holder 5 is formed in a column shape. As shown in FIG. 2, the seed crystal holding body 5 includes a first holding body 14 that holds the seed crystal 4 and a second holding body 15 that is fixed to the upper surface of the first holding body 14. . The end of the second holding body 15, that is, the end of the seed crystal holding body 5 is held by the power source 12 in the crystal manufacturing apparatus 1.

  Here, FIG. 2 shows an enlarged part of a longitudinal section of the seed crystal holder 5 cut in the vertical direction, and shows the structure of the first holder 14 in detail.

  The first holding body 14 holds the seed crystal 4 on the lower surface. The first holding body 14 is made of carbon, for example. The 1st holding body 14 should just be comprised with the material which has carbon as a main component from a viewpoint of reducing the difference in the amount of thermal expansion with the seed crystal 4 which consists of silicon carbide. The carbon of the first holding body 14 is included as, for example, a polycrystalline carbon or a fired body obtained by firing carbon.

  The area of the surface that defines the outer shape of the lower surface of the first holding body 14 may be larger or smaller than the area of the upper surface of the seed crystal 4. When the area of the surface that defines the outer shape of the lower surface of the first holding body 14 is larger than the area of the upper surface of the seed crystal 4, the entire upper surface of the seed crystal 4 can be fixed. Peeling from the body 14 can be suppressed. On the other hand, when the area of the surface that defines the outer shape of the lower surface of the first holding body 14 is smaller than the area of the upper surface of the seed crystal 4, the seed crystal 4 is less susceptible to thermal contraction due to the seed crystal adhesive. can do. In the present embodiment, the area of the surface that defines the outer shape of the lower surface of the first holding body 14 is smaller than the area of the upper surface of the seed crystal 4.

  The outer shape of the first holding body 14 is, for example, a columnar shape or a polygonal column shape having a polygonal bottom surface such as a quadrangular shape or a hexagonal shape. In the present embodiment, the outer shape of the first holding body 14 is formed in a columnar shape in which a circle having a radius of, for example, 5 mm or more and 100 mm or less is set as a bottom surface and a height is set, for example, of 5 mm or more and 100 mm or less.

  As shown in FIG. 2, the first holding body 14 has a first through hole A <b> 1 formed so as to penetrate the first holding body 14 in the vertical direction. That is, the first holding body 14 has the cavity B.

  Here, when a crystal is grown by the solution growth method, for example, if the temperature in the solution 2 becomes irregular due to the convection state of the solution 2 in the crucible 3, the growth surface of the growing crystal becomes uneven. Multiple crystal planes may be formed on the growth surface. At this time, since the growth rate of the crystal to be grown varies from crystal plane to crystal plane, when the difference between the temperature in the solution 2 and the temperature of the seed crystal 4 is large, the supersaturated state in the solution 2 is applied only to the crystal plane that is likely to grow. In some cases, the silicon carbide thus deposited is rapidly precipitated and grows rapidly as crystals. As a result, the difference in the crystal growth rate between the portion where the crystal growth is fast and the portion where the crystal growth is slow in the lower surface of the seed crystal 4 becomes large, and there is a risk that problems such as formation of grooves in the grown crystal may occur. There is.

  On the other hand, in the present invention, by having the above-described configuration, the cavity B (first through hole A1) formed in the first holding body 14 forms a heat insulating portion in the first holding body 14, and the seed Heat transfer from the crystal 4 to the first holding body 14 is reduced. As a result, the temperature difference between the solution 2 and the seed crystal 4 is reduced, and the supersaturation degree of silicon carbide in the solution 2 can be reduced, so that the maximum value of the growth rate of the crystal growing on the lower surface of the seed crystal 4 is reduced. Can do. Accordingly, since the rapid growth of the crystal at the portion where the crystal tends to grow can be suppressed on the lower surface of the seed crystal 4, the portion where the crystal growth is fast and the portion where the crystal growth is slow on the lower surface of the seed crystal 4. The difference in the growth rate of the crystal can be reduced, and as a result, the occurrence of defects such as the formation of grooves in the grown crystal can be suppressed, and the quality of the grown crystal can be improved.

  Further, as shown in FIG. 2, the cavity B (first through-hole A <b> 1) is open to a region excluding the outer peripheral portion of the upper surface of the first holding body 14. That is, the first opening C <b> 1 is formed by the cavity B on the upper surface of the first holding body 14. With such a configuration, the contact area between the first holding body 14 and the second holding body 15 is reduced, so that heat transfer from the first holding body 14 to the second holding body 15 is reduced. As a result, the heat transferred from the seed crystal 4 stays in the first holding body 14, so that heat transfer from the seed crystal 4 to the first holding body 14 is suppressed, and the crystal on a part of the lower surface of the seed crystal 4 is reduced. Rapid growth can be suppressed.

  The first opening C1 is formed in, for example, a circular shape or a polygonal shape such as a quadrangular shape or a hexagonal shape. In the present embodiment, the first opening C <b> 1 is formed in a circular shape, and the area thereof is set to, for example, 10% or more and 98% or less of the surface that defines the outer shape of the upper surface of the first holding body 14.

  As shown in FIG. 3, the area of the first opening C1 is larger than the area of the upper surface of the first holding body 14 (the surface excluding the first opening C1 from the surface defining the outer shape of the upper surface of the first holding body 14). It is desirable to be small. As a result, compared with the case where the area of the first opening C1 is larger than the area of the upper surface of the first holding body 14, the strength of the first holding body 14 can be improved, for example, the heat of air in the cavity B It is possible to prevent the first holding body 14 from cracking due to expansion or the like.

  Here, FIG. 3 shows the upper surface of the first holding body 14, and shows the shape of the first holding body 14, the shape of the first opening C1, and the like in detail.

  As shown in FIG. 2, the cavity B has a first inclined region R <b> 1 whose width increases from the lower surface to the upper surface of the first holding body 14 when the first holding body 14 is viewed in a longitudinal section. desirable. With such a configuration, the temperature gradient in the seed crystal 4 can be reduced, so that the crystal is easily grown uniformly. That is, when the temperature gradient in the seed crystal 4 is too large, the crystal may grow extremely only in a portion where the temperature in the seed crystal 4 is low, but according to the above configuration, the crystal is formed by the cavity B. Since the heat insulation part adjacent to the seed crystal 4 becomes smaller among the heat insulation parts, the heat transfer from the seed crystal 4 to the first holding body 14 in the adjacent region of the heat insulation part is prevented from being excessively reduced due to the influence of the heat insulation part. be able to. As a result, it is possible to suppress the temperature from rising extremely in the vicinity of the heat insulating portion in the seed crystal 4 by the heat insulating portion, and to reduce the temperature gradient in the seed crystal 4. Therefore, it is possible to suppress the extreme crystal growth only at a part of the lower surface of the seed crystal 4 and to suppress the occurrence of defects such as formation of grooves in the grown crystal.

  On the other hand, since the cavity B becomes larger toward the upper surface of the first holding body 14, the bonding area between the first holding body 14 and the second holding body 15 can be reduced. Therefore, heat transfer from the first holding body 14 to the second holding body 15 can be reduced, heat transfer from the seed crystal 4 to the first holding body 14 can be suppressed, and a part of the lower surface of the seed crystal 4 can be suppressed. The rapid growth of crystals can be suppressed.

  As shown in FIG. 2, the cavity B preferably has a vertical region R <b> 2 that extends from the first inclined region R <b> 1 to the upper surface side of the first holding body 14 and extends along the side surface of the first holding body 14. . With such a configuration, the heat that moves around the cavity B in the first holding body 14 as compared with the case where the first inclined region R1 is formed from the upper surface to the lower surface of the first holding body 14. As a result, the heat transferred from the seed crystal 4 stays in the first holding body 14, so that the heat transfer from the seed crystal 4 to the first holding body 14 is suppressed, Rapid crystal growth on a part of the lower surface of the seed crystal 4 can be suppressed.

  The height (length along the Z-axis direction) of the first inclined region R1 is desirably smaller than the height of the vertical region R2, as shown in FIG. With such a configuration, heat transferred from the crystal 4 can be effectively retained in the first holding body 14, and heat transfer from the seed crystal 4 to the first holding body 14 can be suppressed.

The cavity B continues from the vertical region R2 to the upper surface side of the first holding body 14 and the width decreases toward the upper surface of the first holding body 14 when the first holding body 14 is viewed in a longitudinal section. An area (not shown) may be included. In such a configuration, since the bonding area between the first holding body 14 and the second holding body 15 is increased, the bonding strength between the first holding body 14 and the second holding body 15 can be improved. it can.

  As shown in FIG. 2, the cavity B is preferably composed of one first through hole A1. With such a configuration, the cavity B can be made smaller compared to the case where the cavity B is composed of a plurality of first through holes A1, so that the strength of the first holding body 14 can be improved, For example, the first holding body 14 can be prevented from cracking due to thermal expansion of air in the cavity B or the like.

  The cavity B may be composed of a plurality of first through holes A1 arranged so as to be point-symmetric with respect to the center of the first holding body 14 in a top view. In the case of such a configuration, heat transfer from the seed crystal 4 to the first holding body 14 can be made to be uniform, and a temperature gradient in the seed crystal 4 can be reduced.

  As shown in FIG. 2, the cavity B is preferably formed in the center of the first holding body 14. That is, the cavity B is desirably formed so as to include the center of the first holding body 14 in a top view. With such a configuration, for example, when the crystal is grown while rotating the seed crystal holding body 5, the seed B is formed in comparison with the case where the cavity B is formed away from the center of the first holding body 14. It becomes easy to keep the temperature in the crystal 4 constant, and the crystal can be grown stably.

  As shown in FIG. 4, the area of the second opening C2 formed in the lower surface of the first holding body 14 by the first through-hole A1 is the lower surface of the first holding body 14 (the outer shape of the lower surface of the first holding body 14). It is desirable that the area is smaller than the area of the bottom surface defining the second surface C2 excluding the second opening C2. With such a configuration, the heat insulating portion in the adjacent region of the seed crystal 4 is reduced, the influence of the heat insulation on the seed crystal 4 can be reduced, and the temperature gradient in the seed crystal 4 can be reduced.

  Here, FIG. 4 shows the lower surface of the first holding body 14, and shows the shape of the first holding body 14, the shape of the second opening C2, and the like in detail.

  The second opening C2 is formed in, for example, a circular shape, or a polygonal shape such as a quadrangular shape or a hexagonal shape. In the present embodiment, the second opening C2 is formed in a circular shape, and the radius thereof is set to, for example, 1% to 80% of the bottom surface that defines the outer shape of the lower surface of the first holding body 14. In the present embodiment, the area of the second opening C2 is set smaller than the area of the first opening C1.

  As shown in FIG. 2, the first holding body 14 preferably has a vent hole D formed on the inner surface of the cavity B and the side surface of the first holding body 14. With such a configuration, the air confined in the cavity B is thermally expanded by heating the crucible 3, and the first holding body 14 or the seed crystal 4 is broken, or the seed crystal 4 is broken into the first holding body 14. Can be prevented from peeling off.

  The second holding body 15 has an upper end held by the power source 12 and holds the first holding body 14 on the lower surface. As shown in FIG. 5, the second holding body 15 is fixed to the upper surface of the first holding body 14 so as to close the first opening C <b> 1 of the first holding body 14. Moreover, the 2nd holding body 15 is being fixed to the 1st holding body 14 via the holding body adhesive material 16 which contains carbon, for example. Due to such a configuration, the first holding body 14 and the second holding body 15 are separated from each other as compared with the case where the first holding body 14 and the second holding body 15 are integrally formed. Therefore, heat transfer from the first holding body 14 to the second holding body 15 is reduced. As a result, it is possible to suppress rapid crystal growth on a part of the lower surface of the seed crystal 4.

  Here, FIG. 5 is an enlarged view in which a part of the longitudinal section of the seed crystal holding body 5 shown in FIG. 2 is further enlarged, and a fixing portion between the first holding body 14 and the second holding body 15 is shown in detail. Show.

  The holding body adhesive 16 enters the cavity B of the first holding body 14. Then, as shown in FIG. 5, it is desirable that a meniscus is formed across the inner surface of the cavity B of the first holding body 14 and the lower surface of the second holding body 15. With such a configuration, the adhesive strength between the first holding body 14 and the second holding body 15 can be improved, and the first holding body 14 can be prevented from being detached from the second holding body 15. it can.

  As shown in FIG. 5, the holding body adhesive 16 is preferably disposed over the side surface of the first holding body 14 and the side surface of the second holding body 15. With such a configuration, the adhesive strength between the first holding body 14 and the second holding body 15 can be improved.

  The holding body adhesive 16 may enter inside the side surfaces of the first holding body 14 and the second holding body 15. In the case of such a configuration, heat transfer from the first holding body 14 to the second holding body 15 can be reduced, and rapid crystal growth can be suppressed.

  The second holding body 15 is preferably made of the same material as the first holding body 7. Compared to the case where the first holding body 14 and the second holding body 15 are made of different materials, the amount of thermal expansion between the first holding body 14 and the second holding body 15 is such a configuration. And the thermal stress applied to the holding body adhesive 16 is reduced, so that the first holding body 14 can be prevented from being peeled off from the second holding body 15. Such a configuration is particularly effective when the bonding area between the first holding body 14 and the second holding body 15 is reduced in order to reduce heat transfer from the first holding body 14 to the second holding body 15. Is.

  As shown in FIG. 2, the area of the lower surface of the second holding body 15 is preferably the same as the area of the surface that defines the outer shape of the upper surface of the first holding body 14. That is, it is desirable that the side surface of the second holding body 15 and the side surface of the first holding body 14 coincide with each other when viewed through the top surface. With such a configuration, heat transfer from the first holding body 14 to the second holding body 15 can be reduced while improving the adhesive strength between the first holding body 14 and the second holding body 15. .

  The second holding body 15 is formed in, for example, a cylindrical shape or a polygonal column shape having a polygonal bottom surface such as a quadrangular shape or a hexagonal shape. In the present embodiment, the second holding body 15 is formed in a columnar shape whose radius is set to, for example, 5 mm to 100 mm as a bottom surface and whose height is set to, for example, 100 mm to 1000 mm. In the present embodiment, the height of the second holding body 15 is set larger than the height of the first holding body 14.

(Variation 1 of seed crystal holder)
As shown in FIG. 6, the first holding body 14 includes a shaft portion 17 having a second through hole A <b> 2 (cavity B) extending over the upper and lower end surfaces in the longitudinal direction, and the second through hole A <b> 2 at the lower end surface of the shaft portion 17. You may have the seed crystal holding | maintenance part 18 provided so that opening might be plugged up. With such a configuration, the heat insulation portion in the vicinity of the seed crystal 4 is reduced, the influence of the heat insulation on the seed crystal 4 can be reduced, and the temperature gradient in the seed crystal 4 can be reduced. In the present modification, the second through hole A2 of the shaft portion 17 becomes the cavity B of the first holding body 14.

Further, since the bonding area between the first holding body 14 and the seed crystal 4 is increased by having the above configuration, the bonding strength between the first holding body 14 and the seed crystal 4 can be improved. The peeling from the first holding body 14 can be prevented. For example, when there is no vent hole D, the thermal expansion of the air confined in the cavity B can be suppressed, and the seed crystal 4 can be prevented from cracking.

  The seed crystal holding part 18 is preferably fixed to the shaft part 17 via the holding body adhesive 16. With such a configuration, since the shaft portion 17 and the seed crystal holding portion 18 are arranged apart from each other, heat transfer from the seed crystal holding portion 18 to the shaft portion 17 is reduced. As a result, heat transfer in the plane direction (XY plane direction) can be improved in the crystal holding unit 18, so that the temperature gradient in the seed crystal 4 can be reduced.

  The seed crystal holding part 18 and the shaft part 17 may be integrally formed. In such a configuration, it is possible to prevent the seed crystal holding part 18 from being peeled off from the shaft part 17 due to the difference in thermal expansion between the seed crystal holding part 18 and the shaft part 17.

  The shaft portion 17 has, for example, a cylindrical shape or a polygonal column shape having a polygonal bottom surface such as a quadrangular shape or a hexagonal shape. In the present embodiment, the shaft portion 17 is formed in a columnar shape, and the height thereof is set to, for example, 60% or more and 90% or less of the height of the first holding body 14.

  The seed crystal holding unit 18 has, for example, a circular or polygonal plate shape. In the present embodiment, the seed crystal holding unit 18 is formed in a disk shape, and the thickness thereof is set to, for example, 10% or more and 40% or less of the height of the first holding body 14. In the present embodiment, the thickness of the seed crystal holding portion 18 is smaller than the height of the shaft portion 17.

(Variation 2 of seed crystal holder)
As shown in FIG. 7, the first holding body 14 includes a shaft portion 17 having a second through hole A <b> 2 (cavity B) over the upper and lower end surfaces in the longitudinal direction, and the second through hole A <b> 2 at the lower end surface of the shaft portion 17. You may have the seed crystal holding | maintenance part 18 provided so that opening might be blocked | closed, and the pillar part 19 distribute | arranged to the center part in 2nd through-hole A2 of the axial part 17. FIG. With such a configuration, it is possible to reduce the temperature at the center of the seed crystal 4 from becoming extremely high, and to reduce the temperature gradient in the seed crystal 4. In the present modification, the second through hole A2 of the shaft portion 17 becomes the cavity B of the first holding body 14.

  As shown in FIG. 7, the column portion 19 preferably has an inclined portion 20 whose width decreases from the lower surface to the upper surface of the column portion 19 when the column portion 19 is viewed in a longitudinal section. With such a configuration, the area of the lower surface of the column part 19 is increased, so that the temperature gradient in the seed crystal 4 can be reduced and the area of the upper surface of the column part 19 is decreased. Heat transfer from the seed crystal 4 to the first holding body 14 can be reduced.

  As shown in FIG. 7, the column portion 19 continues to the upper surface side of the column portion 19 of the inclined portion 20 and extends along the inner surface of the second through-hole A2 when the column portion 19 is viewed in a longitudinal section. It is desirable to have a vertical portion 21. With such a configuration, the heat transfer region of the heat transmitted through the first holding body 14 can be reduced, so that the heat transfer from the seed crystal 4 to the first holding body 14 can be reduced.

  In the present embodiment, the upper end of the column portion 19 is fixed to the lower surface of the second holding body 15 via the holding body adhesive 16. Further, the lower end of the column part 19 is fixed to the seed crystal holding part 18 via the holding body adhesive 16. The column part 19 may be fitted in the cavity B.

<Crystal production method>
A method for producing a crystal according to an embodiment of the present invention will be described. The crystal manufacturing method of the present embodiment includes a preparation process, a holding process, a contacting process, and a supplying process.

  A crystal made of silicon carbide can be manufactured by, for example, the crystal manufacturing apparatus 1. The crystal manufacturing apparatus 1 mainly includes a crucible 3, a crucible container 6, a heating mechanism 8, a transport mechanism 11, and a control unit 13. The crystal manufacturing method of the present embodiment is a method for manufacturing a crystal using the solution growth method in the crystal manufacturing apparatus 1.

(Preparation process and holding process)
A crucible 3 and a silicon-containing silicon solution 2 disposed in the crucible 3 are prepared. Specifically, silicon particles as a silicon raw material and carbon particles as a carbon raw material are placed in the crucible 3 and heated to a melting point of silicon (about 1414 ° C.) or higher. Thereby, the silicon solution 2 containing carbon can be arranged and held in the crucible 3. The carbon contained in the solution 2 may be supplied from a crucible 3 made of graphite.

  Next, the first holding body 14 and the second holding body 15 in which the cavity B is formed by mechanical processing are prepared, and the seed crystal 4 made of silicon carbide is fixed and held on the lower surface of the first holding body 14. Then, the seed crystal holding body 5 is prepared by fixing the first holding body 14 and the second holding body 15 using the holding body adhesive 16. As a result, the seed crystal 4 is held by the seed crystal holder 5.

(Contact process)
Thereafter, the lower surface of the seed crystal 4 is brought into contact with the solution 2. The seed crystal 4 is brought into contact with the solution 2 by changing the height of the solution 2 relative to the liquid surface by moving the seed crystal holder 5 in the vertical direction (Z-axis direction). In the present embodiment, means for moving the seed crystal 4 as means for bringing the solution 2 and the seed crystal 4 into contact will be described. However, means for moving the crucible 3 or means for moving the seed crystal 4 and the crucible 3 is used. May be.

  It suffices that at least a part of the lower surface of the seed crystal 4 is in contact with the solution 2. Therefore, the entire lower surface of the seed crystal 4 may be brought into contact with the solution 2, or the seed crystal 4 may be brought into contact with the solution 2 so that the side surface or the upper surface of the seed crystal 4 is immersed. When the seed crystal 4 is placed in the solution 2 so that the side surface or the upper surface of the seed crystal 4 is immersed, the entire lower surface of the seed crystal 4 can be reliably brought into contact with the solution 2 and the productivity can be improved.

  The temperature of the solution 2 is set to be 1400 ° C. or more and 2000 ° C. or less, for example. When the temperature of the solution 2 fluctuates, as the temperature of the solution 2, for example, a temperature obtained by averaging temperatures measured a plurality of times in a certain time can be used. As a method for measuring the temperature of the solution 2, for example, a method of directly measuring with a thermocouple or a method of indirectly measuring with a laser can be used.

  By bringing the lower surface of the seed crystal 4 into contact with the solution 2, a temperature difference is created between the lower surface and the solution 2 in the vicinity thereof, so that the growth of silicon carbide crystals can be started on the lower surface. After bringing the lower surface of the seed crystal 4 into contact, the crystal grown on the lower surface can be elongated in the thickness direction by pulling the seed crystal 4 upward little by little. The speed at which the seed crystal 4 is pulled up can be set to, for example, 50 μm / h or more.

  When crystals grow on the lower surface of the seed crystal 4, the carbon in the solution 2 is consumed by crystals and miscellaneous crystals, but a part of the inner wall of the crucible 3 made of carbon is dissolved in the solution 2. Therefore, the carbon concentration of the solution 2 is maintained within a certain range. Therefore, the crystal can be continuously grown.

(Variation 1 of crystal manufacturing method)
In the supplying step, gallium or the like which is a material for reducing the viscosity of the solution 2 may be supplied as an additive. In the conventional crystal manufacturing method, when the crystal growth is completed and the seed crystal holder 5 is pulled up, the droplet of the solution 2 adheres to the lower surface of the grown crystal and the thermal stress when the droplet dries Occurring near the interface with the grown crystal may cause the grown crystal to break or cause new dislocations.

  Therefore, before pulling up the crystal grown on the lower surface of the seed crystal 4 to finish the crystal growth, a material for reducing the viscosity of the solution 2 is supplied, so that the droplet of the solution 2 adheres to the lower surface of the grown crystal. Can be suppressed. Gallium can be supplied, for example, so as to be 1 mass% or more and 10 mass% or less with respect to the solution 2.

  Further, silicon may be supplied to reduce the viscosity of the solution 2. By supplying silicon to the solution 2, the ratio of silicon in the solution 2 can be increased and the viscosity of the solution 2 can be decreased. What is necessary is just to set the supply amount of silicon so that the silicon contained in the solution 2 after supplying silicon may be 85 mass% or more. When silicon is supplied to reduce the viscosity of the solution 2, it is possible to prevent impurities from being contained in the crystal to be grown.

(Variation 2 of crystal production method)
After the supplying step, the method further comprises a step of separating the lower surface of the grown crystal from the solution 2, starting the temperature of the solution 2 below the melting point of silicon, and then bringing the separated lower surface of the crystal into contact with the solution 2 again. You may do it.

  Specifically, after supplying a material that lowers the viscosity of the solution 2, the grown crystal is separated from the solution 2. Thereafter, the temperature of the solution 2 is lowered below the melting point of silicon, and the solution 2 is phase-converted from a liquid to a solid. By contacting the grown crystal again with the solution 2 during or after the phase conversion as described above, even when the droplet is attached to the lower surface, the droplet is attached to the solution 2 side. be able to. As a result, the amount of droplets attached to the lower surface can be reduced, and as a result, the thermal stress caused by the droplets can be reduced.

  In the step of separating the grown crystal from the solution 2, the crystal is pulled upward so that the lower surface of the crystal is separated from the liquid surface of the solution 2. After the grown crystal is separated from the solution 2, the crystal is maintained at a position at a certain height from the liquid surface. At this time, the height of the lower surface of the crystal from the liquid level may be a position where the lower surface of the crystal does not come into contact with the solution 2, and can be set to be, for example, 1 mm or more and 3 cm or less. Thereby, since the vapor | steam of the solution 2 becomes easy to hit the lower surface of a crystal so that it is closer to the solution 2, it can suppress that the surface temperature of the lower surface of a crystal falls, and it makes it difficult to generate a miscellaneous crystal on the lower surface of the grown crystal. be able to.

  Moreover, you may have the process of separating the lower surface of the grown crystal | crystallization from the solution 2 before a supply process. Thus, by separating the crystal grown before the supplying step from the solution 2, it is possible to stop the crystal growth that proceeds in the time when the raw material or additive is mixed in the solution 2 after the supplying step. The time during which the grown crystal is separated from the solution 2 may be set to a time until the carbon concentration of the solution 2 reaches a saturation concentration when the raw material is supplied. You may set to the time until.

(Modification 3 of crystal manufacturing method)
You may have the heating process heated in order to raise the temperature of the solution 2 after a supply process. By having such a process, when the raw material or the additive is supplied to the solution 2, it is possible to suppress the temperature of the solution 2 from dropping. Moreover, since the solubility of the solution 2 can be made high, a raw material or an additive can be made easy to melt | dissolve.

In the heating step, the temperature of the solution 2 is higher than the temperature in the contact step, and the boiling point of silicon (235
Lower than 5 ° C.). As temperature which raises the solution 2, it can be 40 degreeC or more and 150 degrees C or less with respect to the temperature of the solution 2 in a contact process, for example. As a method for increasing the temperature of the solution 2, a method can be used in which the current flowing through the coil 9 is increased to increase the electromagnetic wave that heats the crucible 3.

  The temperature of the solution 2 may be gradually increased or may be rapidly increased. When the temperature of the solution 2 is gradually increased, for example, the temperature can be set to 5 ° C./h or more and 30 ° C./h or less. When the temperature of the solution 2 is gradually increased as described above, the temperature of the solution 2 can be increased while the temperature difference between the crucible 3 and the solution 2 is small. The evaporation of the solution 2 in the vicinity of the interface can be suppressed.

DESCRIPTION OF SYMBOLS 1 Crystal manufacturing apparatus 2 Solution 3 Crucible 4 Seed crystal 5 Seed crystal holding body 6 Crucible container 7 Insulating material 8 Heating mechanism 9 Coil 10 AC power supply 11 Conveying mechanism 12 Power source 13 Control unit 14 First holding body 15 Second holding body 16 Holding body adhesive 17 Shaft portion 18 Seed crystal holding portion 19 Column portion 20 Inclined portion 21 Vertical portion A1 First through hole A2 Second through hole B Cavity C1 First opening C2 Second opening D Vent hole R1 First inclined region R2 Vertical area

Claims (6)

A silicon carbide crystal is grown from the solution on the lower surface of the seed crystal by pulling the lower surface of the seed crystal made of silicon carbide in contact with a solution containing carbon and silicon held in a crucible having an opening at the upper end. A columnar seed crystal holder used in a solution growth method,
A first holding body that holds the seed crystal on the lower surface and has a cavity opened in a region of the upper surface excluding the outer peripheral portion, and is fixed to the outer peripheral portion of the upper surface of the first holding body so as to close the opening. have a second holder of the columnar being,
The second holder is a seed crystal holder that is longer than the first holder . The seed crystal holder according to claim 1,
The hollow has a seed crystal holding body having an inclined region whose width increases from the lower surface to the upper surface of the first holding body when the first holding body is viewed in a longitudinal section. The seed crystal holder according to claim 1 or 2,
A seed crystal holder in which a ventilation hole is formed in the first holder over the inner surface of the cavity and the side surface of the first holder. In the seed-crystal holding body in any one of Claims 1-3,
The first holding body has a shaft portion having a through-hole extending over the upper and lower end surfaces in the longitudinal direction, and a seed crystal holding portion provided at the lower end surface of the shaft portion so as to close the opening of the through-hole,
A seed crystal holder in which the through hole is the cavity. The seed crystal holder according to any one of claims 1 to 4,
A crystal manufacturing apparatus comprising an opening into which the seed crystal holder is inserted at an upper end and a crucible for holding a solution containing carbon and silicon inside. Preparing a crucible holding a seed crystal holder according to any one of claims 1 to 4 and a solution containing carbon and silicon inside;
A holding step of holding a seed crystal made of silicon carbide on a lower surface of the first holding body of the seed crystal holding body;
Contacting the lower surface of the seed crystal held in the seed crystal holder with the solution held in the crucible;
A crystal growth step of pulling up the seed crystal from the solution and growing a crystal of silicon carbide from the solution on the lower surface of the seed crystal.

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