JP2724749B2 - Annual ring type refractory electric furnace and heating / cooling control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a reflection type electric furnace, and more particularly, to a reverberation type electric furnace having an annual ring-shaped circular heating portion, which can be heated at an arbitrary temperature gradient in a radial direction. The present invention relates to a reflection electric furnace and a heating / cooling method using the same.

(Conventional technology and problems to be solved) Conventionally, electric furnaces capable of adjusting a temperature gradient include:
There is a cylindrical type in which a plurality of heat generating parts are provided in parallel with a cylindrical axis, and the temperature of each part is independently controlled. However, in this electric furnace, there is a temperature gradient in the cylindrical axis direction, and it is not possible to heat and cool a disk-shaped object to be heated with an arbitrary temperature gradient in the radial direction.

In addition, there is a box-type electric furnace in which a plurality of heating sections are provided in the longitudinal direction of the box and the temperature is controlled independently of each other. In this electric furnace, as in the case of the cylindrical type, a disk-shaped electric furnace is used. Could not be heated and cooled at an arbitrary temperature gradient in the radial direction.

On the other hand, in recent years, it has been remarkably desired to increase the size of a single crystal. Defects and strains inside the crystal are increasing. It is well known that this is mainly due to an inappropriate heat distribution in the central part and the peripheral part of the large crystal. Also, a single crystal for practical use is required to have a large diameter and a thin shape. However, the above method requires an extra step of growing a large columnar crystal and slicing it, which is not economical.

One of the reasons why it is difficult to grow a large single crystal in this way
Finally, there has been no development of an electric furnace capable of obtaining the required accurate heat distribution.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned disadvantages of the prior art and to meet such a demand. The present invention has a novel object capable of heating and cooling an object to be heated such as a disk at an arbitrary temperature gradient in a radial direction thereof. Another object of the present invention is to provide a method for heating and cooling an object to be heated which is suitable for growing a single crystal using an electric furnace.

(Means for Solving the Problems) In order to achieve the above object, the present inventors have conducted intensive studies, and as a result, provided a plurality of heating elements constituting an electric furnace in an annual ring shape, and set an interval between each heating element. To minimize the interaction between the heating elements and radiation and heat conduction,
We have developed an electric furnace with a completely new structural design that effectively arranges the heat reflection surface and the water cooling section, and according to this electric furnace, obtain an arbitrary temperature gradient by independently controlling the temperature of each heating element This is what made the present invention.

That is, according to the present invention, a plurality of heat reflecting concave surfaces are provided in a ring shape on one surface of a cooled substrate, and a heating element is disposed in the concave portion, and means for independently controlling the temperature of each heating element is provided. The heating substrate having such a configuration is connected to the
The gist is an annual ring-type reflex electric furnace characterized by being opposed to each other.

Another aspect of the present invention provides a method of heating and cooling an object to be heated using the above-mentioned annual ring-type reflex electric furnace, by shifting a predetermined heat pattern radially outward from the center of the annual ring radially with time, The gist of the present invention is a heating / cooling control method characterized by heating or cooling a heated object.

Hereinafter, the present invention will be described in more detail with reference to examples.

(Example) FIGS. 1 (a) to 1 (c) show an example of an annual-ring type reflection electric furnace according to the present invention, wherein FIG.
(B) is a front view of a heating surface, and (c) is a front view of a water cooling surface.

In FIG. 1A, a pair of heating substrates 5 are arranged to face each other via a space. That is, each heating substrate 5 has a structure in which a plurality of water-cooling grooves 2 are provided on one surface of the substrate 1, and the cooling is performed by sealing with a packing 3 and a shield lid 4 on the grooves. A plurality of heat reflecting concave surfaces 6 are provided on the other surface of the device 1 in an annual ring shape, and an independent heating element 7 and a thermocouple 8 are arranged in each concave portion. The pair of heating substrates 5 are opposed to each other via the space 9. When the present invention is applied to the growth of a single crystal as in main cooling, a projection 11 cooled by a water cooling unit 10 is further provided at the center of the annual ring of the substrate 1, and a thermocouple 12 for seed temperature measurement is provided at the tip. It has been placed.

FIG. 1 (b) is a front view of the substrate 1 as viewed from the space portion 9 side. Both ends of a plurality of independent ring-shaped heating elements 7 are provided outside the heating board 5 by respective heating element entrances / exit holes 13. Has been taken out.

FIG. 1 (c) is a front view of the substrate 1 as viewed from the water cooling groove 2 side.
A cooling water is supplied and discharged by a water inlet 15 and a water outlet 16. At the center of the substrate 1, there is a protrusion insertion opening 17 for the protrusion 11. The cooling method is not limited to the above, and a mode in which a parallel hole is provided in the base slope or a cooling pipe is brazed on the substrate is also possible.

FIGS. 2A and 2B show an embodiment of the heating element holder portion of the annual ring type reflection electric furnace according to the present invention.

That is, in the case of FIG. 2A, the heat generating holder 19 is inserted into the holder hole 18 formed in the bottom of the heat reflecting concave surface 6, the holder fixing pin 20 is attached, and the heat generating element 7 is passed through the heat generating hole 21. This is the configuration held.

FIG. 2 (b) shows an example in which the heating element holder 19 holds the heating element 7 without penetrating the substrate 1, and the tip of the heating element holder 19 is held down and fixed by the quartz plate 22. is there. In the case of this example, the inside of the heat reflecting concave surface 6, that is, the inside of the heat reflecting concave surface 6 sealed with the quartz plate 22 can be evacuated. Heat conduction is reduced, and radiation efficiency can be improved. Of course, it is also possible to provide a through-hole at the bottom of the heat reflection concave surface 6 to evacuate the entire space between the shield lid 4 and the quartz plate 22 (through hole and inside the heat reflective concave surface 6).

FIG. 3 shows an embodiment in which the heating element 7 is attached to the electrode portion. An insulating tube 23 is inserted into the heating element entrance 13 at the bottom of the heat reflecting concave surface 6, through which the heating element 7 is connected to the terminal. It is connected to the unit 24.

FIG. 4 shows an example in which a plurality of cooling gas inlets / outlets 25 are provided at the bottom of each heat reflecting concave surface 6 in order to enhance the cooling effect of the annual heating element 7.

(Operation) Next, a usage mode of the annual ring type electric furnace having the above configuration will be described.

FIG. 5 and FIG. 6 show an example applied to the case of growing a single thin disk by using the annual ring type reflection electric furnace according to the present invention.

In FIG. 5 (a), a pair of opposed heating substrates 5
A crucible 26 is placed in the space 9 of the above, and a seed crystal 27 sandwiched between the cooled projections 11 is provided at the center thereof, and the seed crystal is cooled. The temperature of each annual heating element 7 is independently controlled, but the temperature of the inner heating element is set so that the side surface of the seed crystal 27 placed at the center position of the annual heating element is in a molten state. The temperatures of the other heating elements are set so that the outer growth crystal raw material 28 is sufficiently melted.

If the upper portion of the crucible 26 is covered with a quartz plate or the like, the upper and lower surfaces of the crucible can be set to the same heating condition.

Next, in order to move the temperature and temperature gradient obtained by the inner ring heating element 7 in the radial direction, the temperature of each of the other annual ring heating elements is program-controlled, and the temperature and temperature gradient are transferred to the outer ring heating element. After the completion of the above, all the annual heating elements are cooled to room temperature. As a result, the seed crystal 27
A thin, disk-shaped, large crystal grown more radially can be easily obtained.

FIG. 5B shows the seed crystal 27 sandwiched between the protrusions 11.
Shows a state in which a crystal is grown in a disk shape. In the figure, 29 is a seed melting surface, 30 is a growth surface, and 31 is a grown single crystal.

FIG. 5C shows an example in which the protruding portion 11 is provided only in the upper portion, and the seed crystal 27 is cooled from above to grow the crystal.

FIG. 5 (d) shows an example in which a projection is provided only at the lower portion, and the seed crystal 27 is cooled from below to grow the crystal.

FIG. 6 shows a change in the temperature distribution when a thin disk single crystal is grown using the annual ring type reflection electric furnace according to the present invention. The vertical axis represents the temperature, and the horizontal axis represents the center of the crystal. Represents the radial distance from the starting point. In the initial stage of crystal growth, each annual ring-shaped heating element is programmed to have a temperature distribution curve A having a constant temperature gradient, and then the curve B → C → D → E → F → G is sequentially continued. By continuously changing the temperature program of each annual ring-shaped heating element so as to shift (shift), a constant temperature gradient is moved in the direction of the outer ring, and the disk-shaped single crystal is radially radially from the center in the radial direction. To foster.

(Example of use) As a design example of the annual ring type electric furnace of the present invention, the heating substrate is 300 mm in diameter and 25 mm in thickness, the heating element and the water cooling groove are each nine, and the heat reflection concave part is a gold-plated curved surface.
The projection had a diameter of 20 mm, and the diameter of the tip was narrowed to 10 mm. A transparent quartz disk was attached to the upper part of the nine Fe-Al-based metal heating elements, and two heating substrates with the inside of the heat reflection concave portion evacuated were opposed to each other via upper and lower spaces.

In growing a radial single crystal, KC with a diameter of 15 mm and a height of 25 mm was centered on a quartz crucible with a diameter of 240 mm and a height of 30 mm.
The seed crystal was placed, and the KCl raw material was filled around the seed crystal. Insert the crucible into the space of the upper and lower heating substrates, sandwich the upper and lower sides of the seed crystal in the crucible with the protruding parts, and furthermore, set the transparent quartz disk to a height of 30 mm.
mm crucible is suppressed. In addition, when operating the electric furnace, it is now described that the ring-shaped heating element is received from the inner ring in the outer ring direction and numbered as an annual ring-shaped heating element.
In the early stage of crystal growth, the heating element is 830 ° C, the heating element is 880 ° C,
The temperature of the heating element was 910 ° C., and that of the heating element was 920 ° C. Then, while moving the temperature gradient created by the heating element in the outer peripheral direction, and raising the temperature of the
The temperature of each heating element was controlled by program temperature so as to maintain the temperature. After completion of the entire crystal growth, each heating element was cooled to room temperature at the same cooling rate. The single crystal grown by the above radial single crystal manufacturing method was a high-quality disc single crystal having a diameter of 230 mm and a thickness of 15 mm.

Further, by further narrowing the interval between the ring-shaped heating elements, it is possible to realize a steep radial temperature gradient and a highly accurate temperature movement. Further, by changing the heating element to a material for high temperature and improving its mounting structure and the like, a disk single crystal with a high melting point can be grown.

Further, in addition to the above KCl, low-melting substances NaCl, LiF, KBr, NaI, Csl, K
l, AgCl, TiCl, Ge, etc. are also easily obtained. Also, Ta, Mo
By using a heating element for high temperature such as BaF ₂ , CaF ₂ ,
In addition to MgF ₂ , LiNbO ₃ , LiTaO _{3 and the} like, oxide magnetic materials can also be single-crystallized.

Of course, the present invention is not limited to the growth of a single crystal, and the desired annual ring-shaped temperature gradient can be shifted radially as shown in FIG. For example,
It goes without saying that zone melting refining (zone refining) is also possible.

(Effects of the Invention) As described in detail above, the electric furnace according to the present invention has extremely low thermal interaction between the heating elements due to the heat insulating effect and the heat collecting effect of the heat reflecting concave surface of the cooled heating substrate. The number of heating elements can be arbitrarily selected by reducing the distance between the ring-shaped heating elements.The temperature can be controlled independently for each of these ring-shaped heating elements. A steep temperature gradient such as 250 ° C. or any temperature gradient can be easily obtained. Further, by independently controlling the temperature of each annual ring-shaped heating element and sequentially moving its temperature gradient radially, an effect similar to the movement of the heated object can be obtained without moving the heated object.

Further, when the present invention is applied to a specific object to be heated, the following excellent effects can be obtained.

(1) A large-diameter, large-diameter, single-crystal single crystal having extremely small thermal distortion with extremely small diameter can be easily obtained without growing a large-diameter cylindrical single crystal.

(2) Since the crystal is grown radially, the crystal growth rate is high and the diameter can be increased in a short time.

(3) If this method is applied to zone melting refining (zone refining), high-quality materials can be obtained at high speed.

(4) In this growing method, the degree of freedom in mounting the seed crystal is large, so that it can be used for various crystals.

(5) In a crystal having a transformation point at a high temperature, the whole crystal can be rapidly cooled at a stretch after holding the grown crystal in a temperature region higher than the transformation point.

(6) A large-diameter sample can be heat-treated at a high speed without thermal distortion, and further, can be heated and cooled from the inside, and can be heated and cooled from the outer side, and can be freely heat-treated.

(7) The processing steps can be shortened by making the crucible shape close to the product shape and growing crystals.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (a) to 1 (c) are explanatory views showing an example of an annual ring-type reflection electric furnace according to the present invention, wherein FIG. 1 (a) is a longitudinal sectional view, and FIG. FIG. 2 (a) and FIG. 2 (b) are cross-sectional views of mounting a heating element holder, FIG. 3 is a cross-sectional view of mounting an electrode unit, FIG. Is a cross-sectional view of the cooling part of the heating element, and FIGS. 5 (a) to (d) are explanatory views of the case where the present invention is applied to the growth of a single crystal, and FIG. FIG. 5 (b) is a cross-sectional view of a growth state when the seed crystal is cooled from above and below, and FIG. 5 (c) is a cross-sectional view of the growth state when the seed crystal is cooled from above. FIG. 5 (d) is a cross-sectional view of the growth state when the seed crystal is cooled from below, and FIGS. 6 (a) and 6 (b) are the temperatures when the seed crystal is grown radially. Fabric and the change is a diagram as described relative to the crucible installation position. 1 ... substrate, 2 ... water cooling groove, 3 ... packing, 4 ...
Shield lid, 5: heating substrate, 6: heat reflection concave surface, 7
... heating element, 8 ... thermocouple, 9 ... space part, 10 ... water cooling part, 11 ... projecting part, 12 ... seed thermocouple, 13 ... heating element entrance and exit, 14 ... water cooling connection part, 15 ... water inlet, 16 ... water outlet, 17 ... projection insertion port, 18 ... holder hole, 19 ...
Heating element holder, 20: Holder fixing pin, 21: Heating element hole, 22: Quartz plate, 23: Insulating tube, 24: Terminal, 25: Gas inlet / outlet, 26: Crucible, 27 ... Seed crystal, 28 ... Growth crystal raw material, 29 ... Seed melting surface, 30 ...
Growth surface, 31 ... Growth single crystal.

Claims (7)

(57) [Claims] 1. A cooled substrate having a plurality of heat-reflecting concave surfaces provided in an annual ring shape on one surface of the substrate, and a heating element disposed in the concave portion, and means for independently controlling the temperature of each heating element. An annual ring-type reflection electric furnace, wherein two heating substrates having such a configuration are opposed to each other via a space. 2. The annual ring-type reflection electric furnace according to claim 1, wherein a cooled projection is provided at a center position of the annual ring of the heating substrate. 3. The annual ring-type reflex electric furnace according to claim 1, wherein the heat reflecting concave surface is a curved surface having a quadratic curve or a parabolic curvature. 4. The annual ring according to claim 1, wherein the heating element is formed by forming a spiral wire, a round bar, a square plate, or a thin film in a circular shape in a heat reflecting recess of a heating substrate. Reflex electric furnace. 5. The method according to claim 1, wherein the inside of the heat reflecting recess is evacuated.
5. The annual ring type reflex electric furnace according to any one of 2, 3 and 4. 6. When heating and cooling an object to be heated using the annual ring type reflection electric furnace according to claim 1, a predetermined heat pattern is shifted radially outward from the center position of the annual ring radially with time. And heating and cooling the object to be heated. 7. The method according to claim 6, wherein a cooled projection is provided at a center position of the annual ring of the heating substrate of the annual ring type refractory electric furnace, and a single crystal seed is placed between the two projections. A method for producing a single crystal, comprising: inserting a raw material for growing a crystal on an outer periphery thereof; and independently controlling the temperature of each heating element to grow the crystal radially.