Device and method for growing PVT-AlN single crystal with adjustable supersaturation degree
By rotating the upper cover of the crucible in the PVT-AlN single crystal growth device to control the degree of connectivity between the internal and external cavity, the problem of supersaturation regulation of the crystal surface is solved, and stable and efficient single crystal growth is achieved.
Patent Information
- Application Number
- CN202411736365.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-29
- Publication Date
- 2025-02-14
AI Technical Summary
During the growth of PVT-AlN single crystal material, it is difficult to effectively regulate the crystal surface supersaturation, resulting in unstable growth rate, and prone to problems such as polycrystal deposition and single crystal growth failure.
A PVT-AlN single crystal growth device with adjustable supersaturation is designed to adjust the degree of communication between the inner and outer cavity by rotating the upper cover of the crucible to adjust the supersaturation of the seed crystal surface. In the early stage, the high degree of communication reduces supersaturation and promotes single crystal nucleation growth, and then the reduction of communication reduces and improves supersaturation to improve crystal growth efficiency.
The supersaturation of the AlN crystal surface is effectively regulated, the success rate and growth efficiency of single crystal growth are improved, and the interference of polycrystalline deposition on crystals is avoided.
Smart Images
Figure CN119433692A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of aluminum nitride single crystal growth devices, and in particular to a PVT-AlN single crystal growth device and method with adjustable supersaturation. Background Art
[0002] Since AlN has a high melting point and high decomposition pressure, it decomposes violently before melting, making it difficult to grow AlN single crystal materials using methods similar to pulling single crystals. The physical vapor transport (PVT) method uses the decomposition characteristics of AlN at high temperatures to make AlN powder or ceramic raw materials sublime in high temperature areas and condense and crystallize in low temperature areas, ultimately achieving the preparation of AlN single crystal ingots.
[0003] In the process of PVT-AlN preparation, the preparation of AlN single crystal is affected by many factors, such as the temperature gradient between the high and low temperature zones of the crucible, the surface temperature of the seed crystal, the radial temperature field of the crucible, the pressure of the reactor, etc. The regulation of these factors that can be directly characterized will eventually reflect the core issue of "crystal surface supersaturation regulation". Saturation refers to the ratio of the vapor pressure of a substance in the steam to the saturated vapor pressure at a specific temperature and pressure. When this value is less than 100%, the substance will not precipitate from the gas phase to produce other phases. When this value exceeds 100%, other phases can be precipitated from the gas phase, and it becomes "supersaturated". The higher the "supersaturation", the faster the rate of generating other phases. For AlN crystals, crystal growth can only be achieved when the AlN partial pressure in the gas phase reaches a supersaturated state. The greater the supersaturation, the faster the crystal growth rate.
[0004] However, the window for regulating the supersaturation of the seed crystal surface by adjusting the longitudinal temperature difference of the crucible, the pressure of the reactor, etc. is very small. When the supersaturation of the seed crystal surface is too high, the AlN growth rate will be too fast, polycrystals will be generated on the seed crystal, and even unoriented polycrystals will be deposited on the crucible around the seed crystal to compete with the seed crystal, resulting in the failure of single crystal growth; and when the supersaturation of the seed crystal surface is too low, the AlN single crystal will grow too slowly. Summary of the invention
[0005] In order to solve the above problems, the present invention provides a PVT-AlN single crystal growth device and method with adjustable supersaturation.
[0006] The first object of the present invention is to provide a PVT-AlN single crystal growth device with adjustable supersaturation, comprising a crucible body for placing aluminum nitride raw materials, and a crucible cover arranged on the top of the crucible body; the inner diameter of the outer edge of the crucible cover matches the outer diameter of the crucible body; The crucible body comprises a crucible inner cavity and a crucible outer cavity; The inner cavity of the crucible is used for growing AlN crystals. The inner cavity wall of the crucible is provided with n inner cavity wall notches, and the inner cavity wall notches are centrally symmetrical with respect to the crucible body; n is an even number ≥2; The crucible upper cover is provided with n upper cover protrusions, and the upper cover protrusions correspond to the inner cavity wall recesses one by one; the upper cover protrusions are driven to rotate by rotating the crucible upper cover, so that the inner cavity wall recesses are partially blocked or completely covered; when the inner cavity wall recesses are completely covered by the upper cover protrusions, the crucible inner cavity and the crucible outer cavity are not connected.
[0007] Preferably, the number n of the inner cavity wall recesses is 4.
[0008] The number of the inner cavity wall notches n=2; the arc length of the inner cavity wall notches accounts for 40% of the circumference of the inner cavity wall of the crucible.
[0009] Preferably, the crucible upper cover, the crucible inner cavity wall and the crucible outer cavity wall have the same thickness; the inner diameter of the outer edge of the crucible upper cover matches the outer diameter of the crucible outer cavity wall.
[0010] Preferably, the crucible further comprises a seed crystal stage disposed below the upper cover of the crucible, wherein the seed crystal stage is used for growing AlN seed crystals.
[0011] Preferably, the material of the PVT-AlN single crystal growth device with adjustable supersaturation is tungsten, graphite or tantalum carbide.
[0012] Preferably, the aluminum nitride raw material is at least one of aluminum nitride powder, aluminum nitride ceramic material, aluminum nitride crystallized porous material or aluminum nitride crystal block material.
[0013] The second object of the present invention is to provide a method for growing a PVT-AlN single crystal with adjustable supersaturation, which uses a PVT-AlN single crystal growth device with adjustable supersaturation to carry out a reaction, and specifically comprises the following steps: S1. Placing the aluminum nitride raw material in the inner cavity of the crucible; S2. In the early stage of seed crystal growth, the crucible cover is rotated to expose the inner cavity wall notch, so that the inner cavity of the crucible and the outer cavity of the crucible are connected, the supersaturation of the seed crystal surface is reduced, and the nucleation growth of the AlN single crystal is promoted; S3. After the seed crystal grows to a certain size, the crucible cover is rotated to reduce the degree of connectivity between the inner and outer cavities of the crucible, thereby increasing the supersaturation of the seed crystal surface and increasing the AlN crystal growth efficiency.
[0014] Preferably, the growth temperature of the AlN crystal is ≥2000° C.; and the cavity pressure in the device is 30-80 kPa.
[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: In order to control the crystal surface supersaturation during the growth of PVT-AlN crystals, a crucible device was designed that can adjust the degree of connection between the inner and outer cavities by rotating the upper cover of the crucible. In the early stage of crystal growth, the connection between the inner and outer cavities can be adjusted to a large extent, reducing the AlN supersaturation in the low temperature zone atmosphere and promoting the nucleation and growth of single crystals; during the crystal growth process, the degree of connection between the inner and outer cavities can be reduced, increasing the AlN supersaturation in the low temperature zone atmosphere and improving the crystal growth efficiency.
[0016] In summary, the PVT-AlN single crystal growth device and method provided by the present invention can effectively regulate the surface supersaturation of AlN crystal during crystal growth, thereby improving the single crystal growth success rate and growth efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 It is a schematic diagram of the cross section and material transport of a dual-chamber crucible of a PVT-AlN single crystal growth device with adjustable supersaturation provided according to an embodiment of the present invention when the degree of connectivity between the inner and outer cavities is 100%.
[0018] Figure 2 It is a schematic top view of the crucible wall of the dual-chamber crucible of the PVT-AlN single crystal growth device with adjustable supersaturation provided according to an embodiment of the present invention when the degree of connectivity between the inner and outer cavities is 100%.
[0019] Figure 3 It is a schematic diagram of the cross section and material transport of a double-chamber crucible of a PVT-AlN single crystal growth device with adjustable supersaturation provided according to an embodiment of the present invention when the inner and outer chambers are not connected.
[0020] Figure 4 It is a schematic top view of the crucible wall of the double-chamber crucible of the PVT-AlN single crystal growth device with adjustable supersaturation provided according to an embodiment of the present invention when the inner and outer cavities are not connected.
[0021] Figure 5 This is the seed crystal growth effect when the degree of connectivity between the inner and outer cavities of the double-chamber crucible is 100% in the initial stage of crystal growth according to an embodiment of the present invention.
[0022] Figure 6 This is the seed crystal growth effect when the inner and outer cavities of the double-chamber crucible are not connected in the initial stage of crystal growth provided by an embodiment of the present invention.
[0023] Reference numerals: 1. Crucible cover; 101. Upper cover convex block; 2. Crucible body; 3. Seed crystal platform; 4. AlN crystal growth raw materials; 5. AlN material transport route; 6. Crucible inner wall; 7. Notch in the inner cavity wall; 8. The outer wall of the crucible. DETAILED DESCRIPTION
[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.
[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.
[0026] The present invention provides a PVT-AlN single crystal growth device with adjustable supersaturation, comprising: a crucible body for placing aluminum nitride raw materials, a crucible cover arranged on the top of the crucible body, and a seed crystal platform arranged below the crucible cover; The inner diameter of the outer edge of the crucible upper cover matches the outer diameter of the crucible body; The crucible body includes two chambers, namely the crucible inner chamber and the crucible outer chamber; The inner cavity of the crucible is used for growing AlN crystals. The inner cavity wall of the crucible is provided with n inner cavity wall notches, and the inner cavity wall notches are centrally symmetrical with respect to the crucible body; n is an even number ≥2; The outer cavity of the crucible is used as a supersaturation chamber for the surface of the AlN seed crystal; The crucible upper cover is provided with n upper cover protrusions, and the upper cover protrusions correspond to the inner cavity wall recesses one by one; the upper cover protrusions are driven to rotate by rotating the crucible upper cover, so that the inner cavity wall recesses are partially blocked or completely covered; when the inner cavity wall recesses are completely covered by the upper cover protrusions, the crucible inner cavity and the crucible outer cavity are not connected.
[0027] Specifically, the inner diameter of the outer edge of the crucible upper cover matches the outer diameter of the outer cavity wall of the crucible.
[0028] Specifically, the material of the device is tungsten, graphite or tantalum carbide, etc.; the aluminum nitride raw material is at least one of aluminum nitride powder, aluminum nitride ceramic material, aluminum nitride crystallized porous material or aluminum nitride crystal block material.
[0029] Specifically, the crucible upper cover, the crucible inner cavity wall and the crucible outer cavity wall have the same thickness.
[0030] Specifically, the number of notches on the inner cavity wall is n=4.
[0031] Specifically, the number of the inner cavity wall notches n=2; the arc length of the inner cavity wall notches accounts for 40% of the circumference of the inner cavity wall of the crucible.
[0032] The present invention provides a PVT-AlN single crystal growth method with adjustable supersaturation, which specifically comprises the following steps: S1. Placing AlN crystal growth raw material in the inner cavity of the crucible; S2. In the early stage of seed crystal growth, the crucible cover is rotated to expose the inner cavity wall notch, so that the inner cavity of the crucible and the outer cavity of the crucible are connected, the supersaturation of the seed crystal surface is reduced, and the nucleation growth of pure AlN single crystal is promoted; S3. After the seed crystal grows to a certain size, the upper cover of the crucible is rotated to reduce the degree of connectivity between the inner and outer cavities of the crucible, thereby increasing the supersaturation of the seed crystal surface and the growth efficiency of AlN crystals (polycrystalline).
[0033] Specifically, the growth temperature of the AlN crystal is ≥2000° C.; the cavity pressure in the device is between 30 and 80 kPa.
[0034] Example 1 See also Figure 1-Figure 4 As shown, this embodiment provides a PVT-AlN single crystal growth device with adjustable supersaturation, comprising: a crucible body 2 for placing aluminum nitride raw materials, a crucible cover 1 arranged on the top of the crucible body, and a seed crystal platform 3 arranged below the crucible cover; The inner diameter of the outer edge of the crucible upper cover 1 matches the outer diameter of the crucible body 2; The crucible body 2 includes two chambers, namely, the crucible inner chamber and the crucible outer chamber; The inner cavity of the crucible is used for growing AlN crystals, and the AlN crystal growth raw material 4 is placed at the bottom of the inner cavity of the crucible; n inner cavity wall notches 7 are provided on the inner cavity wall 6 of the crucible, and the inner cavity wall notches 7 are centrally symmetrical with respect to the crucible body 2; n is an even number ≥ 2; in this embodiment, n=4; The inner diameter of the outer edge of the crucible upper cover 1 matches the outer diameter of the crucible outer cavity wall 8; the crucible outer cavity is used as the AlN seed crystal surface supersaturation chamber; The crucible upper cover 1 is provided with n upper cover protrusions 101, and the upper cover protrusions 101 correspond to the inner cavity wall recesses 7 one by one; the upper cover protrusions 101 are driven to rotate by rotating the crucible upper cover 1, so that the inner cavity wall recesses 7 are partially blocked or completely covered; the degree of connectivity between the crucible inner cavity and the crucible outer cavity is determined by the size of the gap formed by the upper cover protrusions 101 and the inner cavity wall recesses 7, and the connectivity range is continuously adjustable between 0 and 100%, and can be adjusted by rotating the crucible upper cover 1 according to the purpose of crystal growth before crystal growth.
[0035] Depend on Figure 1It can be seen that when AlN is grown at high temperature, due to a certain temperature difference between the upper and lower parts of the device, the AlN crystal growth raw material 4 will be sublimated from the high temperature area; and the AlN material sublimated in the high temperature area will be transported to the low temperature area under the action of concentration difference, resulting in an increase in supersaturation in the low temperature area, which tends to produce condensation crystallization. When the inner cavity of the crucible and the outer cavity of the crucible are connected, the AlN in the gas phase will be transported outward, thereby reducing the supersaturation of the seed crystal surface in the low temperature area, reducing the crystallization rate, and facilitating the growth of single crystals; and it can avoid the non-directional crystallization on the crucible cover 1 due to the AlN supersaturation, and prevent the polycrystals on the crucible cover 1 from interfering with the growth of the seed crystal; it is conducive to the initial growth of the seed crystal.
[0036] By indication Figure 2 It can be seen that when AlN is grown at high temperature, when the degree of connectivity between the inner and outer chambers of the crucible is 0%, the AlN gas sublimated from the AlN raw material will not be transmitted to the outer chamber of the crucible, but will be concentrated in the low-temperature zone of the inner chamber of the crucible. This increases the supersaturation of the seed crystal surface in the low-temperature zone, improves the crystallization rate, and is beneficial to the crystal growth rate.
[0037] Example 2 This embodiment provides a PVT-AlN single crystal growth device with adjustable supersaturation, comprising: a crucible body for placing aluminum nitride raw materials, a crucible cover arranged on the top of the crucible body, and a seed crystal stage arranged below the crucible cover; The inner diameter of the crucible cover matches the outer diameter of the crucible body; The crucible body includes two chambers, namely the crucible inner chamber and the crucible outer chamber; The inner cavity of the crucible is used for growing AlN crystals, and the AlN crystal growth raw material is placed at the bottom of the inner cavity of the crucible; two inner cavity wall notches are arranged on the inner cavity wall of the crucible, and the inner cavity wall notches are symmetrical with respect to the center of the crucible body; The inner diameter of the outer edge of the crucible upper cover matches the outer diameter of the crucible outer cavity wall; the crucible outer cavity is used as the AlN seed crystal surface supersaturation chamber; The crucible upper cover is provided with two upper cover convex blocks, and the upper cover convex blocks correspond to the inner cavity wall concave holes one by one; the upper cover convex blocks are driven to rotate by rotating the crucible upper cover, so that the inner cavity wall concave holes are partially blocked or completely covered.
[0038] Figure 5 This is the crystal growth effect directly on the inner surface of the crucible cover and the seed crystal stage when the internal and external cavities of the device are 100% connected in the initial stage of crystal growth; the number of notches in the inner cavity wall of the crucible used is 2, and the arc length of the notch in the inner cavity wall is 40% of the circumference of the inner cavity wall of the crucible. It can be seen from the figure that since the surface supersaturation at the crucible cover is greatly reduced by the double-cavity crucible, the AlN crystal density at the seed crystal stage of the crucible cover is small and the size of the single crystal area is large; while the amount of crystal generated on the inner surface of the crucible cover is very small, which will not affect the crystal growth at the seed crystal stage; Figure 6 This is the crystal growth effect directly on the inner surface of the crucible cover and the seed crystal table when the degree of connection between the inner and outer cavities of the device is 0 in the initial stage of crystal growth. It can be seen that due to the large surface supersaturation at the crucible cover, the AlN crystal growth rate is fast, and polycrystalline growth will occur on the crucible cover and the AlN seed crystal table. The grain density is large and the size is extremely small, covering a whole layer of polycrystalline.
[0039] Figure 5 , Figure 6 The results demonstrate the feasibility and importance of regulating the surface supersaturation of AlN crystal growth by the double-cavity crucible of the present invention.
[0040] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.
[0041] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A PVT-AlN single crystal growth device with adjustable supersaturation, comprising a crucible body for placing aluminum nitride raw materials and a crucible cover arranged on the top of the crucible body; characterized in that: The inner diameter of the outer edge of the crucible upper cover matches the outer diameter of the crucible body; The crucible body comprises a crucible inner cavity and a crucible outer cavity; The inner cavity of the crucible is used for growing AlN crystals. The inner cavity wall of the crucible is provided with n inner cavity wall notches, and the inner cavity wall notches are centrally symmetrical with respect to the crucible body; n is an even number ≥2; The crucible upper cover is provided with n upper cover protrusions, and the upper cover protrusions correspond to the inner cavity wall recesses one by one; the upper cover protrusions are driven to rotate by rotating the crucible upper cover, so that the inner cavity wall recesses are partially blocked or completely covered; when the inner cavity wall recesses are completely covered by the upper cover protrusions, the crucible inner cavity and the crucible outer cavity are not connected.
2. The PVT-AlN single crystal growth device with adjustable supersaturation according to claim 1, characterized in that: The number of the inner cavity wall recesses n=4.
3. The PVT-AlN single crystal growth device with adjustable supersaturation according to claim 1, characterized in that: The number of the inner cavity wall notches n=2; the arc length of the inner cavity wall notches accounts for 40% of the circumference of the inner cavity wall of the crucible.
4. The PVT-AlN single crystal growth device with adjustable supersaturation according to claim 1, characterized in that: The thickness of the crucible upper cover, the inner cavity wall of the crucible and the outer cavity wall of the crucible are the same; the inner diameter of the outer edge of the crucible upper cover matches the outer diameter of the outer cavity wall of the crucible.
5. The PVT-AlN single crystal growth device with adjustable supersaturation according to claim 1, characterized in that: The invention also comprises a seed crystal stage arranged below the upper cover of the crucible, wherein the seed crystal stage is used for growing AlN seed crystals.
6. A PVT-AlN single crystal growth device with adjustable supersaturation according to any one of claims 1 to 5, characterized in that: The material of the PVT-AlN single crystal growth device with adjustable supersaturation is tungsten, graphite or tantalum carbide.
7. The PVT-AlN single crystal growth device with adjustable supersaturation according to claim 6, characterized in that: The aluminum nitride raw material is at least one of aluminum nitride powder, aluminum nitride ceramic material, aluminum nitride crystallized porous material or aluminum nitride crystal block material.
8. A method for growing a PVT-AlN single crystal with adjustable supersaturation, using the PVT-AlN single crystal growth device with adjustable supersaturation according to claim 1 for reaction, characterized in that: The specific steps include: S1. Placing the aluminum nitride raw material in the inner cavity of the crucible; S2. In the early stage of seed crystal growth, the crucible cover is rotated to expose the inner cavity wall notch, so that the inner cavity of the crucible and the outer cavity of the crucible are connected, the supersaturation of the seed crystal surface is reduced, and the nucleation growth of the AlN single crystal is promoted; S3. After the seed crystal grows to a certain size, the crucible cover is rotated to reduce the degree of connectivity between the inner and outer cavities of the crucible, thereby increasing the supersaturation of the seed crystal surface and increasing the AlN crystal growth efficiency.
9. The method for growing a PVT-AlN single crystal with adjustable supersaturation according to claim 8, characterized in that: The growth temperature of AlN crystal is ≥2000°C; the cavity pressure in the device is 30~80kPa.