JP2016169126A - Manufacturing method of crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a silicon carbide crystal by a solution process capable of suppressing generation of miscellaneous crystals caused by rapid fluctuation of temperature distribution in a solution when a seed crystal is brought into contact with the solution, and thus improving crystal quality.SOLUTION: A manufacturing method of a silicon carbide crystal includes a preparation step for preparing a seed crystal 3, a crucible 5, a heater 10 arranged around the crucible 5, and a solution 6 heated by the heater 10, a contacting step for bringing the seed crystal 3 into contact with the solution 6, and a growing step for drawing up the seed crystal 3 to grow a silicon carbide crystal on the surface of the seed crystal 3. After the seed crystal 3 is brought into contact with the solution 6 in the contacting step so as to keep temperature distribution in the solution 6 before and after the contact of the seed crystal 3 with the solution 6, a crystal 2 of silicon carbide is grown from the solution 6 on the surface of the seed crystal 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a silicon carbide crystal.

  Conventionally, it is known to grow a silicon carbide (SiC) crystal on a seed crystal using a solution containing carbon (C) and silicon (Si) (see Patent Document 1).

Japanese Unexamined Patent Publication No. H7-172998

  In such an invention, when the seed crystal is simply brought into contact with the solution, for example, when the seed crystal having a lower temperature than the solution is brought into contact with the solution, the temperature distribution in the solution fluctuates abruptly, so Is likely to occur. As a result, the quality of the growing crystal tends to deteriorate.

  An object of the present invention is to improve the quality of crystals in a method for producing silicon carbide crystals by a solution method.

A method for manufacturing a crystal according to an embodiment of the present invention is a method for manufacturing a crystal of silicon carbide, comprising a seed crystal, a crucible, a heating device for heating the crucible, and a crystal in the crucible by the heating device. A preparation step of preparing a solution formed by melting the raw material, a contact step of bringing the lower surface of the seed crystal into contact with the solution, and pulling up the seed crystal to grow a silicon carbide crystal on the lower surface of the seed crystal And a growth step for maintaining the temperature distribution in the solution before and after contact with the seed crystal in the contact step.

  According to the method for producing a crystal according to an embodiment of the present invention, the quality of the crystal can be improved.

It is sectional drawing which shows typically an example of the crystal manufacturing apparatus used for the manufacturing method of the crystal which concerns on one Embodiment of this invention.

<Crystal production equipment>
Hereinafter, the present embodiment will be described with reference to FIG. 1 as an example of a crystal manufacturing apparatus used in a crystal manufacturing method according to an embodiment of the present invention. FIG. 1 shows an outline of an example of a crystal manufacturing apparatus. Note that the present invention is not limited to the present embodiment, and various modifications and improvements can be made without departing from the spirit of the present invention.

  The crystal manufacturing apparatus 1 is an apparatus for manufacturing a silicon carbide crystal 2 used for a semiconductor component or the like. The crystal manufacturing apparatus 1 manufactures the crystal 2 by growing the crystal 2 on the lower surface of the seed crystal 3. As shown in FIG. 1, the crystal manufacturing apparatus 1 mainly includes a holding member 4 and a crucible 5, a seed crystal 3 is fixed to the holding member 4, and a solution 6 is accommodated in the crucible 5. The crystal manufacturing apparatus 1 causes the lower surface of the seed crystal 3 to contact the solution 6 to grow the crystal 2 on the lower surface of the seed crystal 3.

  The crystal 2 becomes a part of the semiconductor component through the semiconductor component manufacturing process. Crystal 2 is a lump of silicon carbide crystals grown on the lower surface of seed crystal 3. The crystal 2 is formed in a plate shape or a column shape having, for example, a circular shape or a polygonal planar shape. Crystal 2 is made of a single crystal of silicon carbide. The diameter or width of the crystal 2 is set to, for example, 25 mm or more and 200 mm or less. The height of the crystal 2 is set to, for example, 30 mm or more and 300 mm or less.

  The seed crystal 3 is a seed for the crystal 2. The seed crystal 3 is formed in a flat plate shape having, for example, a circular or polygonal planar shape. The seed crystal 3 is a crystal made of the same material as the crystal 2. That is, in the present embodiment, the seed crystal 3 made of a silicon carbide crystal is used to produce the silicon carbide crystal 2. The seed crystal 3 is made of a single crystal or polycrystal. In the present embodiment, the seed crystal 3 is a single crystal.

  The seed crystal 3 is fixed to the lower surface of the holding member 4. The seed crystal 3 is fixed to the holding member 4 by, for example, an adhesive (not shown) containing carbon. The seed crystal 3 can be moved in the vertical direction by the holding member 4.

  The holding member 4 holds the seed crystal 3 and carries the seed crystal 3 into and out of the solution 6. Specifically, the carrying-in / out means that the holding member 4 has a function of bringing the seed crystal 3 into contact with the solution 6 or moving the crystal 2 away from the solution 6. As shown in FIG. 1, the holding member 4 is fixed to a moving mechanism (not shown) of the moving device 7. The moving device 7 has a moving mechanism that moves the holding member 4 fixed to the moving device 7 in the vertical direction using, for example, a motor. As a result, the holding member 4 moves up and down by the moving device 7, and the seed crystal 3 moves up and down as the holding member 4 moves.

  The holding member 4 is formed in a columnar shape, for example. The holding member 4 is made of, for example, a polycrystal of carbon or a fired body obtained by firing carbon. The holding member 4 may be fixed to the moving device 7 in a state in which the holding member 4 can rotate around an axis extending through the center of the planar shape of the holding member 4 and extending in the vertical direction. That is, the holding member 4 may be capable of rotating.

  The solution 6 is stored (accommodated) inside the crucible 5 and has a function of supplying the raw material of the crystal 2 to the seed crystal 3 in order to grow the crystal 2. Solution 6 contains the same material as crystal 2. That is, since the crystal 2 is a silicon carbide crystal, the solution 6 contains carbon and silicon. In this embodiment, the solution 6 is obtained by dissolving carbon as a solute in a silicon solvent. The solution 6 is made of, for example, neodymium (Nd), aluminum (Al), tantalum (Ta), scandium (Sc), chromium (Cr), zirconium (Zr), nickel (for example, for improving the solubility of carbon. One or more kinds of metallic materials such as Ni) or yttrium (Y) may be included as an additive.

  The crucible 5 accommodates the solution 6. Further, the crucible 5 has a function as a container for melting the raw material of the crystal 2 inside. The crucible 5 is formed of a material containing carbon. Specifically, the crucible 5 is made of, for example, graphite. In this embodiment, the solution 6 is obtained by melting silicon in the crucible 5 and dissolving a part (carbon) of the crucible 5 in the melted silicon. The crucible 5 is formed in a concave shape having an opening on the upper surface, for example, in order to store the solution 6.

In this embodiment, a solution method is used as a method for growing the silicon carbide crystal 2. In the solution method, the temperature of the seed crystal 3 is maintained while maintaining the solution 6 in a metastable state (a state that is extremely close to a stable state in which precipitation and elution of crystals are thermodynamically balanced) on the lower surface of the seed crystal 3. The crystal 2 is grown on the lower surface of the seed crystal 3 by controlling the conditions so that the precipitation of the crystal 2 proceeds slightly more than the elution. That is, in the solution 6, carbon (solute) is dissolved in silicon (solvent), and the solubility of carbon increases as the temperature of the solvent increases. Here, when the solution 6 heated to a high temperature is cooled by contact with the seed crystal 3, the dissolved carbon becomes supersaturated, and the solution 6 is locally metastable in the vicinity of the seed crystal 3. . Then, the solution 6 is deposited as a silicon carbide crystal 2 on the lower surface of the seed crystal 3 in an attempt to shift to a stable state (thermodynamic equilibrium state). As a result, the crystal 2 grows on the lower surface of the seed crystal 3.

  The crucible 5 is arranged inside the crucible container 8. The crucible container 8 has a function of holding the crucible 5. A heat insulating material 9 is disposed between the crucible container 8 and the crucible 5. This heat insulating material 9 surrounds the periphery of the crucible 5. The heat insulating material 9 suppresses heat radiation from the crucible 5 and brings the temperature distribution in the crucible 5 closer to uniform. The crucible 5 may be arranged inside the crucible container 8 so as to be rotatable around an axis extending through the center of the bottom surface of the crucible 5 and extending in the vertical direction. That is, the crucible 5 may be capable of rotating.

  Heat is applied to the crucible 5 by the heating device 10. The heating device 10 according to the present embodiment includes a coil 11 and an AC power source 12, and heats the crucible 5 by, for example, an induction heating method using electromagnetic waves. In addition, the heating apparatus 10 can employ | adopt other systems, such as a system which transfers the heat which generate | occur | produced with exothermic resistors, such as carbon, for example. When this heat transfer type heating device is adopted, a heating resistor is disposed (between the crucible 5 and the heat insulating material 9).

  The coil 11 is formed of a conductor and surrounds the crucible 5. The heating device 10 having the coil 11 has a cylindrical heating region formed by the coil 11.

  The AC power supply 12 is for flowing an AC current through the coil 11. When an electric current flows through the coil 11 and an electric field is generated, an induced current is generated in the crucible container 8 located in the electric field. The crucible container 8 is heated by the Joule heat of the induced current. And the heat | fever of the crucible container 8 is transmitted to the crucible 5 through the heat insulating material 9, and the crucible 5 is heated. By adjusting the frequency of the alternating current so that the induced current easily flows through the crucible container 8, the heating time to the set temperature in the crucible 5 can be shortened, and the power efficiency can be improved.

  In the present embodiment, the AC power supply 12 and the moving device 7 are connected to the control device 13 and controlled. That is, in the crystal manufacturing apparatus 1, the heating and temperature control of the solution 6 and the carry-in / out of the seed crystal 3 are controlled by the control device 13 in conjunction with each other. The control device 13 includes a central processing unit and a storage device such as a memory, and is composed of, for example, a known computer.

<Crystal production method>
Hereinafter, the manufacturing method of the crystal concerning the embodiment of the present invention is explained. Note that the present invention is not limited to the present embodiment, and various modifications and improvements can be made without departing from the spirit of the present invention.

  The crystal manufacturing method mainly includes a preparation process, a contact process, a growth process, and a separation process.

(Preparation process)
A seed crystal 3 is prepared. As the seed crystal 3, for example, a silicon carbide crystal lump manufactured by a sublimation method, a solution growth method, or the like is processed into a flat plate shape by cutting or the like.

The holding member 4 is prepared. Next, the seed crystal 3 is fixed to the lower surface of the holding member 4. Specifically, an adhesive is applied to the lower surface of the holding member 4. Thereafter, the seed crystal 3 is arranged on the lower surface of the holding member 4 with the adhesive interposed therebetween, and the seed crystal 3 is fixed to the holding member 4.

  A crucible 5 is prepared. And the silicon | silicone particle | grains used as the raw material of silicon are put in the crucible 5, and the solution 6 is prepared by heating the crucible 5 more than melting | fusing point (1420 degreeC) of silicon. Specifically, the solution 6 can be prepared by dissolving carbon (solute) forming the crucible 5 in liquefied silicon (solvent).

  After dissolving the silicon raw material in the preparation step, the temperature of the solution 6 may be raised to the temperature during the contact step while maintaining the temperature distribution in the solution 6. That is, the temperature of the solution 6 may be raised while maintaining the temperature gradient when there is a temperature gradient in the solution 6 or maintaining the uniform state when the temperature within the solution 6 is uniform. As a result, generation of miscellaneous crystals in the solution 6 can be reduced. In this case, the distance between the lower surface of the seed crystal 3 and the liquid surface of the solution 6 is set to, for example, 2 mm or more and 20 mm or less.

  Further, the temperature of the solution 6 may be increased so that the temperature in the solution 6 becomes uniform. By making the temperature in the solution 6 uniform, the generation of miscellaneous crystals in the solution 6 can be effectively reduced. In the present embodiment, the uniform temperature in the solution 6 means a state in which the difference between the maximum temperature and the minimum temperature in the solution 6 is within 10 ° C., for example.

(Contact process)
The lower surface of the seed crystal 3 is brought into contact with the solution 6. The seed crystal 3 is brought into contact with the solution 6 by moving the holding member 4 downward. In this embodiment, the seed crystal 3 is brought into contact with the solution 6 by moving the seed crystal 3 downward. However, the seed crystal 3 is brought into contact with the solution 6 by moving the crucible 5 upward. May be.

  It suffices that at least part of the lower surface of the seed crystal 3 is in contact with the liquid surface of the solution 6. Therefore, the entire lower surface of the seed crystal 3 may be brought into contact with the solution 6, or the solution 6 may be brought into contact with the side surface or the upper surface of the seed crystal 3.

  Here, the contact of the seed crystal 3 is performed so as to maintain the temperature distribution in the solution 6 before and after the contact of the seed crystal 3. As a result, it is possible to reduce the generation of miscellaneous crystals due to a rapid change in the temperature distribution in the solution 6 caused by the contact of the seed crystal 3. Note that “before and after contact” does not include “the moment of contact”. That is, the present invention. A slight temperature change in the solution 6 when the seed crystal 3 is in contact is acceptable.

  Specifically, the contact of the seed crystal 3 is preferably performed after the seed crystal 3 is held for a certain time immediately above the liquid surface of the solution 6. Thereby, the temperature distribution in the solution 6 can be maintained before and after the contact of the seed crystal 3. That is, by holding the seed crystal 3 immediately above the liquid surface of the solution 6 for a certain period of time, the amount of heat radiation of the solution 6 is such that the heat radiation of the solution 6 in a state where the seed crystal 3 is in contact with the solution 6. Approaches the amount of heat. As a result, the temperature distribution in the solution 6 becomes a state in which the seed crystal 3 is in contact with the solution 6 in a pseudo manner, and the temperature distribution in the solution 6 is easily maintained before and after the contact with the seed crystal 3.

  In this case, the temperature distribution in the solution 6 can be maintained without changing the heating position of the solution 6 or the like. As a result, the temperature change in the solution 6 when the seed crystal 3 is in contact can be reduced. In this case, the distance between the lower surface of the seed crystal 3 and the liquid surface of the solution 6 is set to, for example, 2 mm or more and 20 mm or less. Further, the distance between the lower surface of the seed crystal 3 and the liquid surface of the solution 6 is appropriately set according to various conditions such as the temperature of the seed crystal 3 or the temperature of the solution 6. Moreover, the time for holding the seed crystal 3 immediately above the liquid surface of the solution 6 before the contact with the seed crystal 3 is set to, for example, 5 minutes or more and 60 minutes or less.

  Further, the seed crystal 3 may be rotated when the seed crystal 3 is held immediately above the liquid surface of the solution 6. As a result, when the solution 6 evaporates, it becomes easy to fly the droplet adhering to the lower surface of the seed crystal 3, and generation of miscellaneous crystals due to the droplet can be reduced.

  On the other hand, the temperature distribution in the solution 6 may be maintained before and after the contact of the seed crystal 3 by changing the heating position of the solution 6 when the seed crystal 3 is in contact. As a result, the time for holding the seed crystal 3 on the liquid surface can be shortened, and the production efficiency can be improved. Specifically, the heating position of the solution 6 is changed by moving the heating device 10 upward. Since the seed crystal 3 is cooler than the solution 6, when the seed crystal 3 is brought into contact with the solution 6, the hottest point in the solution 6 (hereinafter referred to as a hot point) moves downward. Therefore, by moving the heating device 10 upward, fluctuations in hot points in the solution 6 can be reduced even if the seed crystal 3 is brought into contact.

  In the contact step, the contact of the seed crystal 3 may be performed after raising the temperature of the solution 6 to the temperature at the later growth step. As a result, the step of raising the temperature of the solution 6 to the growth temperature of the crystal 2 after the contact with the seed crystal 3 can be omitted. Therefore, the production efficiency of the crystal 2 can be improved.

  The holding of the seed crystal 3 immediately above the liquid surface of the solution 6 may be performed after the crystal raw material is melted in the preparation step. Moreover, you may raise the temperature of the solution 6 to the temperature at the time of a growth process. As a result, it becomes easy to maintain the temperature distribution in the solution 6 consistently from the preparation step to the growth step, and generation of miscellaneous crystals in the solution 6 can be reduced.

  The contact of the seed crystal 3 may be performed so that the temperature in the solution 6 becomes uniform before and after the contact of the seed crystal 3. By making the temperature in the solution 6 uniform, the generation of miscellaneous crystals in the solution 6 can be effectively reduced. In the present embodiment, the uniform temperature in the solution 6 means a state in which the difference between the maximum temperature and the minimum temperature in the solution 6 is within 10 ° C., for example.

(Growth process)
Crystals of silicon carbide are grown from the solution 6 on the surface of the seed crystal 3 brought into contact with the solution 6 in the contact step. That is, by bringing the seed crystal 3 into contact with the solution 6, a temperature difference can be created between the surface of the seed crystal 3 and the solution 6 near the surface of the seed crystal 3. Then, due to the temperature difference, the carbon is supersaturated, and the carbon and silicon in the solution 6 can be deposited on the lower surface of the seed crystal 3 as the silicon carbide crystal ingot 1.

  Next, the seed crystal 3 is pulled up from the solution 6 to grow the ingot 1 in a columnar shape. In addition, the ingot 1 can be grown while maintaining a constant diameter by gradually pulling the seed crystal 3 upward while adjusting the growth rate in the plane direction and downward of the ingot 1. Specifically, the pulling speed of the seed crystal 3 can be set to, for example, 50 μm / h or more and 150 μm / h or less.

  The temperature of the solution 6 is set to be 1400 ° C. or more and 2000 ° C. or less, for example. When the temperature of the solution 6 fluctuates, as the temperature of the solution 6, for example, a temperature obtained by averaging temperatures measured a plurality of times in a certain time can be used. As a method of measuring the temperature of the solution 6, for example, a method of directly measuring with a thermocouple or a method of measuring indirectly with a radiation thermometer can be used.

(Separation process)
After the silicon carbide crystal is grown, the grown silicon carbide crystal ingot 1 is pulled away from the solution 6 to finish the crystal growth. Subsequently, the grown silicon carbide crystal ingot 1 is cut off from the seed crystal 3. Thereby, the ingot 1 can be manufactured.

DESCRIPTION OF SYMBOLS 1 Crystal manufacturing apparatus 2 Crystal 3 Seed crystal 4 Holding member 5 Crucible 6 Solution 7 Moving apparatus 8 Crucible container 9 Insulating material 10 Heating apparatus 11 Coil 12 AC power supply 13 Controller

Claims (5)

A method for producing a silicon carbide crystal comprising:
Preparing a seed crystal, a crucible, a heating device arranged around the crucible, and a solution heated by the heating device;
Contacting the seed crystal with the solution;
A step of pulling up the seed crystal and growing a silicon carbide crystal on the surface of the seed crystal,
In the contact step, a method for producing a crystal, wherein the seed crystal is brought into contact with the solution so as to maintain a temperature distribution in the solution before and after the contact of the seed crystal with the solution.   2. The method for producing a crystal according to claim 1, wherein in the contacting step, the contact of the seed crystal is performed after raising the temperature of the solution to the temperature during the growth step.   In the contacting step, the temperature distribution in the solution before and after the contact of the seed crystal is maintained by bringing the seed crystal into contact with the solution after holding the seed crystal immediately above the liquid surface of the solution for a certain period of time. The manufacturing method of the crystal | crystallization of Claim 1 maintained.   2. The method for producing a crystal according to claim 1, wherein, in the contacting step, the temperature distribution in the solution is maintained before and after the contact of the seed crystal by changing a heating position of the solution at the time of contact of the seed crystal. In the preparation step, the raw material of the crystal is melted to prepare the solution, and the temperature of the solution is increased to the temperature at the time of the contact step while maintaining the temperature distribution in the solution. The manufacturing method of the crystal | crystallization in any one of.

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