CN212451742U - Crystal growth furnace and crucible cover plate - Google Patents

Abstract

The utility model discloses a crystal growth furnace and crucible apron that uses thereof, crystal growth furnace are used for kyropoulos method growth crystal, include: the crucible cover plate with the central hole is covered on the opening of the crucible, the central hole of the crucible cover plate gradually becomes smaller along the aperture direction from the center, the temperature sudden change cross section formed by the original circular hole crucible cover plate is eliminated in the process of growing crystals, the thermal stress of the crystals near the circular hole is remarkably reduced, and the probability of cracking of large-size crystals is reduced.

Description

Crystal growth furnace and crucible cover plate

Technical Field

The utility model relates to a crystal growth field especially relates to a crystal growth furnace.

Background

The kyropoulos method is the most common method for growing sapphire crystals at present, and among numerous sapphire crystal growing methods, the kyropoulos method has the advantages of large crystal size, lowest defect density and high crystal quality, and 80% of sapphire substrates used by current LEDs are grown by the kyropoulos method.

Referring to fig. 1 and 2, the kyropoulos method is developed from the czochralski method, and one of the differences is that a cover plate with a small aperture is arranged on a crucible opening of the kyropoulos method from the viewpoint of a thermal field structure. The whole crystal growth process of the kyropoulos method is completed in the crucible, so that the sapphire crystal with low defect density is obtained. The cover plate divides the thermal field into two temperature areas, a low temperature area is arranged above the cover plate, and a high temperature area is arranged below the cover plate (namely inside the crucible), so that the crystal growth can be smoothly carried out from top to bottom. However, two regions with large temperature difference are formed on the surface of the head of the crystal, usually, in order to connect with the seed crystal, the cover plate is provided with a circular central hole, the temperature of the surface of the crystal exposed outside the central hole of the cover plate is low, the temperature of the surface of the crystal covered by the cover plate is high, and the temperature on the interface of the two has sudden change, so that great thermal stress is generated, and the crystal is easy to crack. Due to the continuous improvement of crystal growth technology, the size of sapphire crystals is also increased, and 500kg of sapphire crystals can be grown at present. In the growth process of the large-size sapphire crystal, if local large thermal stress exists, the crystal is easy to crack.

There are patents at home and abroad describing the technology of growing sapphire by kyropoulos method, such as patents CN103046135A, CN104451892A, CN102851745A, etc., which adopt multi-stage, independently controlled heaters to adjust the temperature gradient, but only can adjust the longitudinal and radial temperature gradients in a large range, and have little effect on adjusting the local temperature gradient on the central surface of the head of the crystal.

SUMMERY OF THE UTILITY MODEL

In order to solve the problem of the background art that the local accumulation of the thermal stress at the position of the crystal close to the central hole of the cover plate is large, a crystal growing furnace is provided, which is used for growing the crystal by the kyropoulos method and comprises the following steps: the crucible cover plate is provided with a central hole, and the removal amount of the central hole of the crucible cover plate is gradually reduced from the center along the hole diameter to the direction far away from the center.

Preferably, according to the present invention, the crystal comprises sapphire, silicon or silicon carbide.

According to the utility model discloses, preferably, the shape of the centre bore of crucible apron is cockscomb structure or star, and the implementation effect according to these two kinds of figures of experimental conditions is comparatively ideal.

According to the utility model discloses, preferred, the internal diameter of the centre bore of crucible apron is 50~200mm, and the external diameter is 80~350 mm.

According to the utility model discloses, preferred, sawtooth or star angle quantity of the centre bore of crucible apron are 5~ 50.

According to the utility model discloses, it is preferred, the thickness of crucible cover plate is 0.5~15 mm.

According to the present invention, preferably, the weight of the grown crystal in the crystal growth furnace is 200 to 400kg or more than 400 kg.

According to the utility model discloses, preferred, the centre bore provides the stress buffering for the growth crystal, reduces the thermal stress of centre bore department growth crystal.

The beneficial effects of the utility model include: the removal amount of the central hole of the crucible cover plate is gradually reduced from the central hole to the direction far away from the center, the area of the through hole at the edge is small, the area of the through hole at the center is large, the change gradient of a thermal field is reduced as far as possible, a buffer area with temperature change can be formed on the surface of the head of the crystal, a temperature abrupt change interface formed by the original circular hole cover plate is eliminated, the thermal stress at the position is remarkably reduced, and the cracking probability of a large-size crystal is reduced.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the invention and not to limit the invention. Furthermore, the drawing figures are for a descriptive summary and are not drawn to scale.

FIG. 1 is a schematic cross-sectional view of a crystal growth furnace according to the prior art;

FIG. 2 is a schematic top view of a crucible cover plate of the prior art;

FIG. 3 is a schematic view of a partial cross-sectional structure of a prior art crystal growth furnace;

FIG. 4 is a schematic cross-sectional view of a crystal growth furnace according to an embodiment of the present invention;

FIG. 5 is a schematic top view of a crucible cover plate according to an embodiment of the present invention;

FIG. 6 is a schematic view of a partial cross-sectional structure of a crystal growth furnace according to an embodiment of the present invention.

The following are marked in the figure: 1. an upper heat-insulating layer; 2. a heater; 3. an intermediate insulating layer; 4. a cover plate; 41. a central bore; 5. a crystal; 6. a crucible; 7. melting liquid; 8. and lifting the pull rod.

Detailed Description

Several embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following description and illustrations of the embodiments do not limit the scope of the present invention in any way.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components, and/or groups thereof.

Unless defined otherwise, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, as used herein, should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The utility model provides a crystal growth furnace for kyropoulos method growth crystal 5, crystal 5 can be sapphire, silicon or carborundum, the long brilliant stove of sapphire is taken as the example to this embodiment, 200~400 kg's crystal 5 can grow in this embodiment, especially be fit for growing the heavy weight crystal 5 more than 400kg, on the whole, the subassembly that is the growth furnace includes the crucible that has the opening, crucible 6 is used for holding crystal and crystal solution during the growth crystal; the birdcage type heater 2 that sets up around crucible 6 covers the heat preservation in 6 tops of crucible, and in this embodiment, the heat preservation is divided into heat preservation 1 and middle heat preservation 3 from long brilliant stove position, and both designs for the insulation construction that multilayer tungsten molybdenum metal constitutes, utilizes the principle of absorption heat radiation to keep warm, also can consider to adopt the hard felt of graphite to keep warm.

The crucible cover plate 4 with a central hole 41 is covered on the opening of the crucible 6, the crystal 5 is connected with the lifting rod 8 through the central hole 41, and in order to ensure the smooth growth of the crystal 5 from top to bottom, the thermal field is divided into a low temperature area and a high temperature area by utilizing the heat insulation effect of the crucible cover plate 4. The part above the cover plate 4 is a low-temperature area, and the part below the cover plate 4 is a high-temperature area.

Referring to fig. 3, in the prior art, the cover plate 4 with a circular central hole 41 is used, the crystal exposed outside the central hole cover plate 4 is more easily cooled to the outside, the temperature is low, and the crystal part shielded by the central hole cover plate 4 has high temperature, so that a low-temperature and high-temperature boundary line a is formed. The temperature gradient at the boundary line a is large, and when the crystal 5 grows to the boundary line a, the diameter is difficult to expand outwards, and a step is left on the surface of the crystal 5, so that the crystal growth is not smooth. And an interface with highly concentrated thermal stress is generated, so that the crystal 5 is easy to crack.

Referring to fig. 4 to 6, in the present embodiment, the cover plate 4 is formed by a saw-tooth hole or a star-shaped cover plate, the inner diameter of the central hole 41 of the crucible cover plate is 50 to 200mm, the inner diameter refers to the distance from the top of the saw-tooth of the cover plate 4 to the center of the circle, the outer diameter is 80 to 350mm, the outer diameter refers to the distance from the bottom of the saw-tooth of the cover plate 4 to the center of the circle, and the central hole 41 forms two boundary lines of high and low temperatures, i.e.. As the width of the saw teeth is gradually reduced, the removing amount of the central hole 41 of the crucible cover plate is gradually reduced from the center along the direction from the hole diameter to the direction far away from the center, the temperature from the boundary line a to the boundary line b is gradually increased, a natural buffer zone with the temperature from low to high is formed, the growth and the expansion of the crystal 5 in the zone can be smoothly carried out, meanwhile, stress buffering is provided, and the thermal stress of the crystal in the zone is also greatly reduced. The sawtooth hole cover plate 4 can obviously reduce the cracking probability of the crystal 5, and the effect is particularly obvious when large-size sapphire crystals grow.

In the embodiment, the number of the sawteeth or star angles of the central hole 41 of the crucible cover plate is designed to be 5-50, and the thickness of the crucible cover plate 4 is 0.5-15 mm, so that stress buffering can be well realized for growing the crystal 5, and the thermal stress of the growing crystal 5 at the central hole 41 can be reduced.

It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may be made depending on design requirements and other factors as long as they are within the scope of the appended claims or their equivalents.

Claims (16)

1. A crystal growing furnace for growing crystals by the kyropoulos method, comprising: the crucible with the opening, the heater that sets up around the crucible, the heat preservation above the crucible, the crucible apron with centre bore covers on the opening of crucible, characterized by that, the removal volume of the centre bore of crucible apron becomes progressively less along the direction of the aperture to keeping away from the center along the center.

2. The crystal growth furnace of claim 1, wherein the crystal comprises sapphire, silicon, or silicon carbide.

3. The crystal growth furnace of claim 1, wherein the center hole of the crucible cover plate is shaped like a saw tooth or a star.

4. A crystal growth furnace according to claim 3, wherein the crucible cover plate has a center hole with an inner diameter of 50 to 200mm and an outer diameter of 80 to 350 mm.

5. A crystal growth furnace as claimed in claim 3, wherein the number of the saw teeth or star-shaped corners of the center hole of the crucible cover plate is 5-50.

6. The crystal growth furnace of claim 1, wherein the thickness of the crucible cover plate is 0.5 to 15 mm.

7. The crystal growth furnace according to claim 1, wherein the weight of the grown crystal in the crystal growth furnace is 200 to 400kg or more.

8. The crystal growth furnace of claim 1, wherein the central aperture provides a stress buffer for growing crystals.

9. A crucible cover plate for covering a crucible in a crystal growth furnace during crystal growth, characterized in that the crucible cover plate has a center hole, and the center hole of the crucible cover plate becomes smaller gradually from the center toward a direction away from the center along the diameter of the hole.

10. The crucible cover plate of claim 9, wherein the crystal comprises sapphire, silicon or silicon carbide.

11. The crucible cover plate according to claim 9, wherein the center hole of the crucible cover plate is shaped like a saw tooth or a star.

12. The crucible cover plate according to claim 11, wherein the center hole of the crucible cover plate has an inner diameter of 50 to 200mm and an outer diameter of 80 to 350 mm.

13. The crucible cover plate according to claim 11, wherein the number of the saw teeth or the star angles of the center hole of the crucible cover plate is 5-50.

14. The crucible cover plate according to claim 9, wherein the thickness of the crucible cover plate is 0.5 to 15 mm.

15. The crucible cover plate according to claim 9, wherein the weight of the grown crystal in the crystal growing furnace is 200 to 400kg or more.

16. The crucible cover plate of claim 9, wherein the central aperture provides a stress buffer for the growing crystal.

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