Crystal preparation device for controlling stable sublimation of aluminum nitride raw material

Abstract

The invention discloses a crystal preparation device for controlling stable sublimation of an aluminum nitride raw material. The crystal preparation device comprises a crucible body, a crucible cover, a sheet-shaped structural part and a flow guide part, the crucible cover covers the crucible body; the flaky structural part is placed in the middle of the crucible body and divides an inner cavity of the crucible body into a raw material sublimation area and a crystal growth area which are arranged in the vertical direction and are communicated with each other, and the raw material sublimation area is located below the crystal growth area; the sheet-shaped structural member is used for controlling the sublimation amount of the aluminum nitride raw material in different growth periods; the flow guide part is arranged on the sheet-shaped structural part and is used for guiding a gas-phase substance sublimated by the aluminum nitride raw material in the raw material sublimation area to the surface of the aluminum nitride seed crystal in the crystal growth area. According to the invention, the structure of the crystal preparation device is improved, and the aluminum nitride sublimation rate which can meet experimental requirements in the front, middle and later periods of growth is realized by arranging the sheet-shaped structural member and screening the granularity of the aluminum nitride material, so that the grown aluminum nitride crystal has higher quality.

Description

Technical Field

[0001] The invention relates to the technical field of crystal preparation, and in particular to a crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials. Background Art

[0002] In recent years, aluminum nitride, as one of the representatives of ultra-wide bandgap semiconductor materials, has excellent properties such as large bandgap width (6.2eV), high thermal conductivity (3.4W·cm-1·K-1), high breakdown field strength (1.17-107V·cm-1), acid and alkali corrosion resistance, and radiation resistance. In addition, aluminum nitride, gallium nitride, and indium nitride can form solid solution compounds in any proportion, and their spectrum covers from infrared to deep ultraviolet bands, and the spectrum is continuously adjustable through band engineering. It has obvious advantages in ultraviolet lasers and deep ultraviolet LEDs, especially in the solar blind zone (230-280nm). Therefore, aluminum nitride has great application potential in the fields of ultraviolet optoelectronic devices and high-frequency and high-power electronic devices.

[0003] Physical vapor transport (PVT) is recognized as one of the most effective methods for growing aluminum nitride crystals. The PVT method for growing aluminum nitride is that the aluminum nitride raw material is sublimated in a high temperature zone, the sublimated aluminum nitride raw material is transported in a crucible, and deposited in a low temperature zone to finally obtain aluminum nitride crystals.

[0004] The existing crucible device for growing aluminum nitride single crystals usually includes a crucible body for placing aluminum nitride powder source or aluminum nitride sintered body, a crucible cover arranged on the top of the crucible body, a seed crystal table fixed on the inner surface of the crucible cover, and a flow guide cover fixed on the seed crystal table at the upper end, and the flow guide cover gradually opens radially downward in the direction away from the seed crystal table. However, this crucible device has poor controllability over the sublimation rate of the raw material, and the quality of the prepared aluminum nitride crystals is poor, especially 3-4 inch aluminum nitride crystals. Summary of the invention

[0005] The main purpose of the present invention is to provide a crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials, aiming to improve the controllability of the sublimation rate of the raw materials and thus improve the crystallization quality of aluminum nitride crystals.

[0006] To achieve the above object, the present invention provides a crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials, comprising:

[0007] Crucible body;

[0008] A crucible cover, which is disposed on the crucible body;

[0009] a sheet-like structure, which is disposed in the middle of the crucible body and divides the inner cavity of the crucible body into a raw material sublimation zone and a crystal growth zone which are arranged in the vertical direction and communicated with each other, wherein the raw material sublimation zone is located below the crystal growth zone, wherein aluminum nitride raw material is placed in the raw material sublimation zone, and aluminum nitride seed crystals are placed in the crystal growth zone; the sheet-like structure is used to control the sublimation amount of aluminum nitride raw material in different growth periods; and

[0010] The guide member is arranged on the sheet-like structural member and is used to guide the gas phase material sublimated from the aluminum nitride raw material in the raw material sublimation zone to the surface of the aluminum nitride seed crystal in the crystal growth zone.

[0011] Optionally, the sheet-like structural member has a thickness of 0.3-2 mm; and / or

[0012] The sheet-like structural member is provided with a through hole, and the shape of the through hole is circular, annular or arc-shaped.

[0013] Optionally, the flow guide is in the shape of a hollow frustum, and the crucible cover, the flow guide, the sheet-like structural member and the crucible body are arranged concentrically.

[0014] Optionally, the outer diameter of the sheet-like structure is the same as the inner diameter of the crucible body, and the outer diameter of the sheet-like structure is the same as the inner diameter of the flow guide.

[0015] Optionally, the height of the guide member is 8-45 mm, and the cone angle thereof is 20-80°.

[0016] Optionally, the crucible body has a diameter of 50-200 mm, a height of 60-260 mm, and a wall thickness of 1-5 mm.

[0017] Optionally, the shape of the crucible cover is cylindrical or cylindrical with steps, and the thickness of the crucible cover is 0.5-2 mm.

[0018] Optionally, the crucible body, the crucible cover, the flow guide and the sheet structure are all made of tungsten, tantalum, tantalum carbide, rhenium or an alloy thereof.

[0019] Optionally, the middle of the inner wall of the crucible cover is suitable for sticking or embedding aluminum nitride seed crystals.

[0020] Optionally, the raw material sublimation zone is suitable for placing aluminum nitride raw material with a particle size of 0.05-2 mm and impurity elements not exceeding 100 ppm.

[0021] In the technical solution of the present invention, the crystal preparation device includes a crucible body, a crucible cover, a sheet-like structure and a guide member; the crucible cover is arranged on the crucible body; the sheet-like structure member is arranged in the middle of the crucible body and divides the inner cavity of the crucible body into a raw material sublimation zone and a crystal growth zone arranged in the vertical direction and interconnected with each other, and the raw material sublimation zone is located below the crystal growth zone; the sheet-like structure member is used to control the sublimation amount of aluminum nitride raw material in different growth periods; the guide member is arranged on the sheet-like structure member, and is used to guide the gas phase material sublimated from the aluminum nitride raw material in the raw material sublimation zone to the surface of the aluminum nitride seed crystal in the crystal growth zone. It can be understood that the present invention optimizes the internal structure of the aluminum nitride crystal growth crucible, and sets a sheet-like structure member that controls the sublimation amount of aluminum nitride raw material in different growth periods, so as to achieve stable control of the sublimation rate of aluminum nitride raw material, which can meet the growth of 3-4 inch aluminum nitride crystals, and the growth process is stable, and the obtained aluminum nitride crystals have high crystal quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0023] Figure 1 It is a structural schematic diagram of an embodiment of a crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to the present invention;

[0024] Figure 2 It is a structural schematic diagram of another embodiment of a crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to the present invention;

[0025] Figure 3 This is a schematic diagram of the structure of a sheet-like structural member in one embodiment of a crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to the present invention;

[0026] Figure 4 This is a schematic diagram of the structure of a sheet-like structural member in another embodiment of the crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials of the present invention.

[0027] Description of Figure Numbers:

[0028] 10. Crucible body; 20. Crucible cover; 30. Sheet structure; 40. Flow guide; 111. Aluminum nitride raw material; 112. Aluminum nitride seed crystal; 30a. Through hole.

[0029] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0032] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text is to include three parallel solutions. Taking "A and / or B" as an example, it includes solution A, or solution B, or a solution that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0033] Physical vapor transport (PVT) is recognized as one of the most effective methods for growing aluminum nitride crystals. The PVT method for growing aluminum nitride is that the aluminum nitride raw material is sublimated in a high temperature zone, the sublimated aluminum nitride raw material is transported in a crucible, and deposited in a low temperature zone to finally obtain aluminum nitride crystals.

[0034] At present, the growth of 3-4 inch aluminum nitride crystals faces many problems. One of the more important problems is that it is difficult to achieve stable and controllable sublimation rate of raw materials, which is mainly manifested in the following aspects:

[0035] (1) During the growth of aluminum nitride crystals, the aluminum nitride raw materials are coarsened and the diameter is reduced by sublimation, which results in differences in the sublimation rate of aluminum nitride materials during the nucleation period, early growth period, middle growth period and late growth period of aluminum nitride. This results in a large difference in supersaturation during the growth period, which will affect the quality of aluminum nitride crystals. More seriously, it will lead to the enrichment of aluminum atoms, resulting in an imbalance in the deposition area V / III of the aluminum nitride crystal, which is manifested as more aluminum atoms and fewer nitrogen atoms, making the grown aluminum nitride crystals amber in color and significantly increasing the nitrogen vacancy defects in the crystals. At present, the sublimation rate of aluminum nitride is usually adjusted by adjusting the temperature field and adjusting the temperature process curve, but this method is only applicable to the growth and preparation of small-sized crystals. For large-sized (3-4) inch aluminum nitride crystals, this method can only slightly improve the sublimation rate of aluminum nitride and cannot fully achieve the sublimation curve required by the experimental scheme. At the same time, adjusting the temperature field and adjusting the temperature process curve will also increase the thermal stress inside the crystal, and also reduce the quality of the crystal to some extent, and cannot fully achieve high-quality crystal growth.

[0036] (2) Traditional aluminum nitride crystal growth uses aluminum nitride raw materials of a single particle size, which causes the raw materials near the crucible wall to coarsen and sublimate first, resulting in different aluminum nitride sublimation rates in the early and middle stages of growth, which also affects the crystal quality of aluminum nitride.

[0037] The above two problems are not obvious in the growth process of small-sized (1-2 inches) aluminum nitride crystals, but as the growth size of the aluminum nitride crystals increases, the impact of these problems on the growth process increases significantly.

[0038] In this regard, the present invention proposes a crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials.

[0039] Reference Figure 1 In one embodiment of the present invention, the crystal preparation device for controlling the stable sublimation of aluminum nitride raw material includes a crucible body 10, a crucible cover 20, a sheet structure 30 and a guide member 40; the crucible cover 20 is arranged on the crucible body 10; the sheet structure 30 is arranged in the middle of the crucible body 10 and divides the inner cavity of the crucible body 10 into a raw material sublimation zone and a crystal growth zone arranged in a vertical direction and interconnected with each other, the raw material sublimation zone is located below the crystal growth zone, aluminum nitride raw material 111 is placed in the raw material sublimation zone, and aluminum nitride seed crystal 112 is placed in the crystal growth zone; the sheet structure 30 is used to control the sublimation amount of aluminum nitride raw material 111 in different growth periods; the guide member 40 is arranged on the sheet structure 30, and is used to guide the gas phase material sublimated from the aluminum nitride raw material 111 in the raw material sublimation zone to the surface of the aluminum nitride seed crystal 112 in the crystal growth zone.

[0040] In this embodiment, the materials of the crucible body 10 , the crucible cover 20 , the flow guide 40 and the sheet structure 30 can all be tungsten, tantalum, tantalum carbide, rhenium or an alloy of these materials.

[0041] The crystal preparation device can prepare aluminum nitride crystals by metal resistance heating or induction heating, and the crystal preparation heating method is not limited here.

[0042] The aluminum nitride seed crystal 112 can be pasted or embedded in the middle of the inner wall of the crucible cover 20. The particle size of the aluminum nitride raw material 111 can be 0.05-2 mm, preferably 0.1-2 mm, and the maximum impurity element in the aluminum nitride raw material 111 does not exceed 100 ppm.

[0043] Need to explain, such as Figure 3 and Figure 4 As shown, the sheet structure 30 needs to be provided with a through hole 30a for connecting the raw material sublimation zone and the crystal growth zone, and the through hole 30a is in a circular, annular or arc shape, etc. The sheet structure 30 can be processed into any shape by laser cutting, etc. Due to the crystal growth reason, a symmetrical structure is generally adopted, which is not specifically limited here.

[0044] The sheet-like structural member 30 may be placed in the middle of the crucible body 10 , or may be fixed in the middle of the crucible body 10 by means of clamping, bonding or welding, etc., which is not limited here.

[0045] It can be understood that the present invention optimizes the internal structure of the aluminum nitride crystal growth crucible and provides a sheet structure 30 for controlling the sublimation amount of the aluminum nitride raw material 111 at different growth periods, thereby achieving stable control of the sublimation rate of the aluminum nitride raw material 111, which can meet the growth of 3-4 inch aluminum nitride crystals, and the growth process is stable, and the obtained aluminum nitride crystals have high crystallization quality.

[0046] It has been found through experiments that by designing the shape of the sheet structural member 30, the sublimation amount in different growth periods can be controlled, and by adding different material filling methods, a stable control can be performed on different crystal growth periods; by adding the sheet structural member 30, a preliminary control can be performed on the flow field inside the crucible; the addition of the sheet structural member 30 can also play a role in heat insulation; in addition, the addition of the structural sheet divides the crucible into two parts, the upper part is the crystal growth area, and the lower part is the raw material sublimation area. It can be seen from the crystal growth formula that the crystal growth rate is proportional to the temperature difference. The addition of the sheet structural member 30 increases the temperature difference between the top of the raw material sublimation and the crystal growth, which has a positive effect on improving the crystal growth rate.

[0047] In order to facilitate the processing of the sheet-like structure 30 and further improve the controllability of the sublimation rate of aluminum nitride, in one embodiment, the thickness of the sheet-like structure 30 may be 0.3-2 mm.

[0048] In this embodiment, the flow guide 40 may be in the shape of a hollow truncated cone, and the crucible cover 20 , the flow guide 40 , the sheet-like structure 30 and the crucible body 10 may be concentrically disposed.

[0049] Furthermore, the outer diameter of the sheet-like structure 30 may be the same as the inner diameter of the crucible body 10, and the outer diameter of the sheet-like structure 30 may be the same as the inner diameter of the flow guide 40. This is beneficial for controlling the temperature inside the crucible.

[0050] To further enhance the flow guiding effect and improve the crystal preparation efficiency, in one embodiment, the flow guiding member 40 is in the shape of a hollow frustum, the height of the flow guiding member 40 may be 8-45 mm, and the cone angle thereof may be 20-80°.

[0051] In one embodiment, the crucible body 10 may have a diameter of 50-200 mm, a height of 60-260 mm, and a wall thickness of 1-5 mm, so that the controllability of the temperature inside the crucible body 10 can be effectively improved, so that the aluminum nitride seed crystal 112 is at a suitable growth temperature.

[0052] In this embodiment, the shape of the crucible cover 20 may be cylindrical or cylindrical with steps, and the thickness of the crucible cover 20 may be 0.5-2 mm.

[0053] In a specific application scenario, refer to Figure 2 , aluminum nitride crystals are prepared by tungsten metal resistance heating, and aluminum nitride of different particle sizes is selected as raw material. The center of the crucible is taken as the starting point, and the aluminum nitride raw material 111 closer to the crucible wall has a larger particle size. Since in the tungsten metal resistance heating method, the heat received by the crucible comes from the thermal radiation of the tungsten metal, and the crucible wall is closer to the tungsten heater and receives more heat, the temperature distribution of the crucible is high at the crucible wall, low inside the crucible, and the closer to the center, the lower. Therefore, the aluminum nitride raw material 111 near the center of the crucible uses a small particle size, while the raw material near the crucible wall has a larger particle size.

[0054] It should be noted that the above-mentioned setting of the particle size of the aluminum nitride raw material 111 is also applicable to the preparation of aluminum nitride crystals by the induction heating method. In the induction heating furnace, the crucible acts as a heating element. When only the radial situation is considered, the temperature at the center of the crucible will still be lower than the temperature of the crucible wall. Therefore, the aluminum nitride raw material 111 near the center of the crucible is small in particle size, while the raw material near the crucible wall is larger in particle size. This can also ensure a stable aluminum nitride sublimation rate in the early stage of crystal nucleation, early stage of growth, middle stage of growth and late stage of growth.

[0055] In this embodiment, the aluminum nitride crystal prepared by the tungsten metal resistance heating method is light amber in color, the crystal size is 3 inches, the center is 2 mm higher than the crystal edge, and the half-peak width of the HRXRD (high resolution X-ray diffraction) of the crystal is 106 arcsec.

[0056] In another application scenario, refer to Figure 1 and Figure 3 , aluminum nitride crystals were prepared by tungsten metal resistance heating, and aluminum nitride raw materials 111 with the same particle size were selected. Figure 3 The sheet structure 30 of the shape shown, because in the method of tungsten metal resistance heating, the heat received by the crucible comes from the thermal radiation of tungsten metal, and the crucible wall is closer to the tungsten heater and receives more heat, so the temperature distribution of the crucible is high at the crucible wall, low inside the crucible, and the closer to the center, the lower. Therefore, the aluminum nitride raw material 111 near the center of the crucible sublimates less at the same time, while the raw material near the crucible wall sublimates more at the same time. Therefore, the center part of the sheet structure 30 is unblocked, while the edge part is blocked with a shape.

[0057] It should be noted that the above-mentioned arrangement of the sheet-like structural member 30 is also applicable to the preparation of aluminum nitride crystals by the induction heating method. In this embodiment, the material of the sheet-like structural member 30 is preferably tantalum carbide.

[0058] In this embodiment, the aluminum nitride crystal prepared by the tungsten metal resistance heating method is light amber in color, the crystal size is 3 inches, the center is 1.5 mm higher than the crystal edge, and the half-peak width of the HRXRD of the crystal is 92 arcsec.

[0059] In another application scenario, refer to Figure 1 and Figure 4 , aluminum nitride crystals were prepared by tungsten metal resistance heating, aluminum nitride raw materials of different particle sizes were used 111, and Figure 4 The sheet-shaped structural member 30 is shaped like a sheet. In this embodiment, more emphasis is placed on the process curve of the sublimation of aluminum nitride materials of a special process. In this embodiment, the sublimation rate of aluminum nitride is controlled in the early stage of nucleation, and the supersaturation of aluminum nitride in the early stage of nucleation is controlled to reduce the nucleation density of the crystal, so that the aluminum nitride crystal has a better development in the growth stage, and the grown aluminum nitride crystal has a higher quality.

[0060] It should be noted that the above arrangement is also applicable to the preparation of aluminum nitride crystals by induction heating.

[0061] In this embodiment, the aluminum nitride crystal prepared by the tungsten metal resistance heating method is light amber in color, the crystal size is 3 inches, the center is 1 mm higher than the crystal edge, and the half-peak width of the HRXRD of the crystal is 58 arcsec.

[0062] The present invention achieves a stable sublimation rate of the aluminum nitride raw material 111 by optimizing the internal structure and materials of the aluminum nitride crystal growth crucible. The aluminum nitride crystal grown by the present invention can be applied to the growth of 3-4 inch aluminum nitride crystals, and the growth process is stable, and the obtained aluminum nitride crystals have high crystal quality.

[0063] The above descriptions are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials, characterized in that: include: Crucible body; A crucible cover, which is disposed on the crucible body; a sheet-like structure, which is disposed in the middle of the crucible body and divides the inner cavity of the crucible body into a raw material sublimation zone and a crystal growth zone which are arranged in the vertical direction and communicated with each other, wherein the raw material sublimation zone is located below the crystal growth zone, wherein aluminum nitride raw material is placed in the raw material sublimation zone, and aluminum nitride seed crystals are placed in the crystal growth zone; the sheet-like structure is used to control the sublimation amount of aluminum nitride raw material in different growth periods; and The guide member is arranged on the sheet-like structural member and is used to guide the gas phase material sublimated from the aluminum nitride raw material in the raw material sublimation zone to the surface of the aluminum nitride seed crystal in the crystal growth zone.

2. The crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to claim 1, characterized in that: The thickness of the sheet-like structure is 0.3-2 mm; and / or The sheet-like structural member is provided with a through hole, and the shape of the through hole is circular, annular or arc-shaped.

3. The crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to claim 1, characterized in that: The flow guide is in the shape of a hollow truncated cone, and the crucible cover, the flow guide, the sheet-like structural member and the crucible body are arranged concentrically.

4. The crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to claim 3, characterized in that: The outer diameter of the sheet-like structure is the same as the inner diameter of the crucible body, and the outer diameter of the sheet-like structure is the same as the inner diameter of the flow guide.

5. The crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to claim 3, characterized in that: The height of the guide member is 8-45 mm, and the cone angle thereof is 20-80°.

6. The crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to claim 1, characterized in that: The crucible body has a diameter of 50-200 mm, a height of 60-260 mm, and a wall thickness of 1-5 mm.

7. The crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to claim 1, characterized in that: The shape of the crucible cover is cylindrical or cylindrical with steps, and the thickness of the crucible cover is 0.5-2 mm.

8. The crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to claim 1, characterized in that: The materials of the crucible body, the crucible cover, the flow guide and the sheet-like structural member are all tungsten, tantalum, tantalum carbide, rhenium or alloys thereof.

9. The crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to claim 1, characterized in that: The middle of the inner wall of the crucible cover is suitable for sticking or embedding aluminum nitride seed crystals.

10. The crystal preparation device for controlling the stable sublimation of aluminum nitride raw materials according to claim 1, characterized in that: The raw material sublimation zone is suitable for placing aluminum nitride raw materials with a particle size of 0.05-2 mm and impurity elements not exceeding 100 ppm.

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