JP2011195375A - Method and apparatus for growing single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for producing a crystal having a structure with which a high quality single crystal is stably obtained by a simple process, in a growth apparatus of a single crystal by a vertical Bridgman method.SOLUTION: The apparatus for producing a crystal is constituted of: a support member 10 for supporting the lower part of a crucible 1 for growing a single crystal 3 and pulling down the crucible 1; and an inclined member 20 which has an inclined part tapered downward, wherein a lower part of the inclined part is attached to the support member 10, and an upper part of the inclined part is attached to the bottom face of the crucible 1. The temperature distribution of the bottom face of the crucible 1 is optimized so that the central part of the crystal 3 is projected upward.

Description

  The present invention relates to a single crystal growth apparatus and manufacturing method by the vertical Bridgman method.

  The vertical Bridgman method, which is a manufacturing method for growing crystals, is easy to control because the crystal shape depends on the shape of the crucible. However, since the crystal grows in direct contact with the crucible, A temperature gradient occurs between the central portion and the outer peripheral portion, which causes defects in crystal growth.

  FIG. 6 shows a structure of a crystal growth apparatus formed by a conventional vertical Bridgman method. In the structure of the conventional apparatus shown in FIG. 6, a seed crystal is positioned at the bottom of the crucible 1, and the raw material melt 2 is put on the seed crystal to grow the crystal 3 with the crucible 1. There is a liquid interface 4.

  And the support body 5 which supports the crucible 1, and the furnace core tube 6 are provided so that the circumference | surroundings of the crucible 1 may be covered, and the side surface heater 7 which can set the temperature of an up-down direction arbitrarily is arrange | positioned in the circumference | surroundings. 8, the inside of the housing 8 prevents heat from escaping to the outside by the heat insulating material 9.

  Further, in another conventional apparatus configuration shown in FIG. 7, the center portion of the bottom surface of the crucible 1 is supported by the support rod 10 so as to prevent the heat escape from the center portion of the bottom portion of the crucible 1 from increasing. The heater 11 for preferentially heating the support rod 10 is provided. (Patent Document 1)

JP-A-10-101484

  As for the shape of the solid-liquid interface 4 of the crystal, if it is convex downward, defects generated on the inner wall of the crucible 1 are taken into the crystal, making it difficult to make a single crystal, There is a problem that foreign matters are likely to collect in the central portion and defects are generated in the central portion of the crystal.

For this reason, it is necessary to make the solid-liquid interface 4 of the crystal convex upward.
Whether the solid-liquid interface 4 of the crystal is convex upward or downward is that the temperature of the peripheral portion of the raw material melt in contact with the crucible 1 is higher than the temperature at the center of the raw material melt. Is it going to be lower?

  In the conventional apparatus shown in FIG. 6 (a), the temperature difference between the vicinity of the crucible 1 wall and the center of the crystal melt is such that the temperature in the vicinity of the crucible 1 is low and the temperature in the center is high. The bottom surface of FIG. 6 has the temperature characteristics shown in FIG. With such temperature characteristics, the crystal solid-liquid interface 4 has a downwardly convex crystal as shown in FIG. As a cause of this, the escape of heat from the support that supports the crucible also has an effect.

  Further, as shown in FIG. 7, the crucible 1 may be supported by a support rod 10, and in this conventional example, the support rod 10 is heated by a heater 11 so that the temperature distribution of the raw material melt is substantially uniform. There is also a method of controlling the amount of heat (for example, Patent Document 1).

  However, in the configuration as shown in FIG. 7 (a), the bottom of the crucible is more greatly affected by the heat from the heater 11 than the side surface, so that the temperature at the center as shown in the temperature characteristic shown in FIG. 7 (b). Becomes higher. Therefore, as shown in FIG. 7C, a depression is formed at the center of the crystal.

  In addition, the conventional technique is characterized in that the interface is raised by using a cylindrical member having thermal conductivity anisotropy between the support rod and the crucible. However, since the cylindrical member has little inflow of heat from the side surface, it is difficult for heat to be transmitted to the whole.

As described above, a temperature difference is likely to occur between the side surface portion and the center portion, and it is difficult to obtain a high-quality single crystal due to the temperature difference or temperature gradient.
Accordingly, an object of the present invention is to provide a crystal manufacturing apparatus having a structure capable of stably obtaining a high-quality single crystal by a simple method.

  In order to solve the above-mentioned problems, the present invention has a crucible for holding a raw material melt of a crystalline substance, and a side heater disposed around the crucible, and is housed in a casing covered with a heat insulating material. An apparatus for growing a single crystal by pulling down the crucible, attached to the bottom surface of the crucible and tapered downward with respect to an axis in the pulling direction; And a support member for supporting and lowering the portion.

  By determining the optimum height of the inclined member according to the specifications of the equipment and the operating conditions of the crystal growth equipment, if there are no changes in the operating conditions including the surrounding environment, no special control is required and the bottom of the crucible As for the temperature characteristics, the central part of the crucible can be lowered with a gentle inclination with respect to the surroundings, so that a crystal in which the solid-liquid interface is convex upward is obtained.

  In addition, the inclined member is formed of a member having a good thermal conductivity, for example, copper or the like, or having a hollow structure in which the outer periphery is made of a member having an excellent outer thermal conductivity. In addition, it is possible to have a configuration in which a fluid excellent in thermal conductivity is filled inside.

  Further, the inclined member and the support member are screw-connected, and contact between the inclined member and the bottom surface of the crucible through application of the heat conductive paste can improve heat transfer. Is a preferred form.

  When there is a possibility that the ambient environment such as room temperature may change during crystal growth, it is preferable to have a means for heating and cooling the support member, so that the crystal at the solid-liquid interface is on the top. It is preferable to control the amount of heat transferred between the support member and the crucible so as to have a convex shape.

  According to the present invention, the contact portion between the support rod that supports the crucible and the bottom portion of the crucible is provided with the inclined portion that tapers downward so as to be wide in the direction of the crucible and narrow toward the support rod. The lower part of the crucible is attached to the support rod and the upper part is attached to the bottom surface of the crucible to reduce the temperature escape from the wall of the crucible. Since the solid-liquid interface of the crystal can be convex upward so that the portion is lowered, a high-quality single crystal can be stably obtained.

(a) is a cross-sectional view of a single crystal growth apparatus in an embodiment of the present invention (b) is a temperature characteristic graph (c) at a solid-liquid interface of a crystal in an embodiment of the present invention, according to the embodiment of the present invention Cross section of a grown crystal Explanatory drawing of the principal part in embodiment of this invention Sectional drawing of the principal part which shows embodiment of this invention Sectional drawing of the principal part which shows another embodiment of this invention The figure which shows the relative temperature value distribution simulation result from the central axis to the side of the crucible (a) Cross-sectional view of single crystal growth equipment used in the prior art (b) Temperature characteristic graph at the solid-liquid interface of the crystal in the prior art (a) Cross-sectional view of single crystal growth device used in another prior art (b) Temperature characteristic graph at the solid-liquid interface of crystal in another prior art (c) Cross-sectional view of crystal grown by another prior art

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.
FIG. 1 shows an apparatus to which the present invention is applied in a single crystal growth apparatus using the vertical Bridgman method.

The difference from the conventional FIG. 7 is that the support bar 10 is connected to the lower support of the crucible 1 via the inclined member 20 of the present invention.
The inclined member 20 is positioned between the crucible 1 and the support rod 10 and is inclined in the axial direction of the support rod 10, and the inclination direction becomes wider in the direction of the crucible 1. It has become thinner. The inclined member 20 preferably has a contact portion with the bottom of the crucible 1 extending to the same diameter as the crucible 1, but may be smaller than the diameter of the crucible 1. Further, as shown in FIG. 1, the inclined member 20 may be inclined to the contact portion of the bottom portion of the crucible 1, or after being inclined to a diameter to be brought into contact with the bottom portion of the crucible 1, You may make it provide the thickness part extended in a direction (shape which piled up the column member). The support member 10 side of the inclined member 20 is desirably thinned to the same diameter as the support rod 10, but is not particularly limited to this shape.

  The inclined member 20 may be formed integrally with the bottom of the crucible 1 or may be formed integrally with the support rod 10. However, in order to use the inclined member 20 having a different shape as being easily replaceable, the inclined member 20 is used. 20 may be a separate component from the crucible 1 and the support rod 10.

  The optimum shape of the inclined member 20 is such that the central portion is lowered with a gentle inclination from the periphery of the crucible as the temperature characteristics at the bottom of the crucible 1 depending on the specifications of the crystal growth apparatus and the apparatus operating conditions for actual crystal growth. Then, the optimum shape (height) of the inclined member 20 is determined using simulation or the like.

  If there is no change in the operating conditions including the surrounding environment (ambient ambient temperature) during crystal growth, the inclined member 20 according to the present invention is used to grow without requiring temperature control of the bottom surface of the crucible 1. The solid-liquid interface of the crystal to be formed can be convex upward, and a high quality single crystal can be obtained.

  When there is a possibility that the ambient environment such as room temperature may change during crystal growth depending on the installation location or environment of the crystal growth apparatus, the supporting member 20 can be heated and cooled to have a means for fixing. It is preferable to control the amount of heat transferred between the support member and the crucible so that the crystal at the liquid interface has a convex shape upward. In FIG. 1, a heater 11 and a cooling unit 23 are provided on the support rod 10, and an appropriate temperature distribution is obtained while monitoring the temperature of the bottom surface of the crucible 1 by a temperature control unit 24 having both a heater power source and a cooling function device. Such control is performed.

  For example, when the temperature difference does not depend on time and can be regarded as a substantially steady state, the amount of heat transferred to the support rod 10 is obtained from the temperature difference of a specific section in the support rod 10 from Equation (1) and Equation (2). be able to.

  Then, as a temperature characteristic at the bottom surface of the crucible, the amount of heat that moves the support rod 10 is controlled using a heating / cooling device so that the center portion is in a low optimum state with a gentle inclination with respect to the surroundings. Thus, it is possible to finely control the temperature difference between the central portion and the surrounding (side surface).

  As for the shape of the inclined member 20, as shown in FIG. 2, the inclined member 20 is changed in height by changing the inclination angle θ. If the height h1 is increased as in the inclined member 20a in FIG. 2 (a), or the height h2 is decreased in the inclined member 20b in FIG. 2 (b), the inside of the crucible 1 The amount of heat passing from the raw material melt 2 side through the crystal 3 to the lower part of the crucible 1 changes, and the shape of the crystal can be controlled by adjusting the temperature difference between the periphery and the center.

About the form of the inclination member 20, as shown in FIG. 3, the whole can be formed with the member excellent in thermal conductivity, such as copper, for example with favorable thermal conductivity.
The inclined member 20c and the support member 10a are connected to each other with a screw connection. When the inclined member 20c and the bottom surface of the crucible 1 are brought into contact with each other after the heat conductive paste is applied, heat transfer can be improved. .

When a screw is used as the joint portion, the contact area increases. Therefore, the screw connection between the inclined member 20c and the support member 10a enhances the effect of heat conduction.
As another form of the inclined member 20, as shown in FIG. 4, the inclined member 20 d has a hollow structure made of a member whose outer periphery is excellent in thermal conductivity, and the fluid 21 excellent in thermal conductivity is filled therein. It can also be configured.

  As an effect of the present invention, the crystal growth apparatus using the inclined member 20 of the present invention was compared with the conventional apparatus shown in FIG. 7, and the temperature distribution at the bottom of the crucible 1 was simulated. The result is shown in FIG. FIG. 5 shows the relationship between the radius of the crucible and the relative temperature of the solid-liquid interface temperature at an arbitrary height.

  Further, in FIG. 5, the present invention is a result when the inclination angle θ (see FIG. 2) of the inclined member 20 is 45 ° or less, and the conventional technique uses the heater of the support rod shown in FIG. Is the result of the case.

  In the case of the conventional configuration of FIG. 7, the result of FIG. 5 shows that the temperature at the center is high, the temperature rapidly decreases toward the periphery (side surface) of the crucible, and then gradually decreases. . In such a temperature distribution, the shape of the solid-liquid interface of the crystal becomes a downward convex shape, and the quality of the crystal is lowered.

  Therefore, when the inclined member 20 is used as in the present invention, the temperature gradually decreases from the periphery (side surface) of the crucible toward the center, and a good crystal with a convex shape is formed on the top. It can be seen that the resulting temperature distribution is obtained.

  In the present invention, in order to change and optimize the height h of the inclined member 20 as shown in FIG. 2 from the specifications and operating conditions of the crystal growth apparatus, a support rod and a crystal model are created, By setting the physical properties such as conductivity and determining the temperature distribution at the solid-liquid interface 4 between the crystal and the raw material melt by simulation, the temperature distribution is lower at the center of the crucible 1 than the surrounding (side surface). The optimum shape of the inclined member 20 with the height h can be determined.

1 crucible
2 Raw material melt
3 Crystal
4 Solid-liquid interface
5 Support
6 Core tube
7 Side heater 8 Housing 9 Heat insulating material 10 Support rod 11 Heater 12 Heater control device 20 Inclined member 21 Heat transfer fluid 22 Heat transfer paste material
23 Cooling unit 24 Temperature control device

Claims (5)

In a crystal growth apparatus that has a crucible for holding a raw material melt of a crystalline substance, and a side heater disposed around the crucible, and pulls down the crucible to grow a single crystal.
An inclined member attached to the bottom surface of the crucible and tapering downward;
A crystal growth apparatus comprising: a support member for supporting and lowering the lower portion of the inclined member. 2. The crystal growth apparatus according to claim 1, wherein the inclined member is made of a member that is more excellent in thermal conductivity than the bottom surface of the crucible. 2. The inclined member according to claim 1, wherein the inclined member is formed of a member having a hollow structure and an outer periphery having excellent heat conductivity, and the inside of the hollow structure is filled with a fluid having excellent heat conductivity. Crystal growth equipment. 4. The crystal according to claim 1, wherein the inclined member is screw-connected to the support member, and is in contact with a bottom surface of the crucible through application of a conductive paste. Growth equipment. 5. The crystal growth apparatus according to claim 1, wherein the support member has heating and cooling means, and controls the amount of heat transferred between the support member and the crucible.