Crucible for inhibiting low-temperature nucleation in growth process of AlN crystal through PVT method and growth process
By designing a crucible structure including pre-sintering and shaped AlN raw material blocks and AlN multi-wafer, the problem of low-temperature nucleation suppression in the growth of AlN crystal PVT method is solved, and the equipment stability and temperature control simplification effect is achieved.
Patent Information
- Application Number
- CN202510077221.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-17
- Publication Date
- 2025-04-11
AI Technical Summary
During the growth process of AlN crystal PVT method, it is difficult to suppress low-temperature nucleation, and the prior art such as the "temperature gradient inversion method" is complex and the temperature control process is difficult.
A crucible structure is designed, including a seed crater, a crucible cylinder and a crucible bottom. A fixed AlN raw material block is arranged in the crucible cylinder in advance, and AlN multi-wafer is distributed at the bottom edge of the crucible to regulate the start time of crystal growth.
The thermal field structure is simplified, the equipment cost and complexity are reduced, and the temperature control process is simplified and the crystal growth is high.
Smart Images
Figure CN119800492A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of artificial crystal growth, in particular to a crucible and a growth process for suppressing low-temperature nucleation of AlN crystals during a PVT method growth process. Background Art
[0002] AlN crystal is a direct bandgap semiconductor material with ultra-wide bandgap width, extremely high breakdown field strength, extremely high thermal conductivity, good optical and mechanical properties, and has great application potential in microwave power devices, power electronic devices, ultraviolet LEDs, and solar-blind ultraviolet detection. AlN crystals are mainly grown by physical vapor transport (PVT). The basic process is as follows: AlN raw materials decompose at high temperatures, and the generated gas phase components Al vapor and N2 are transported to the AlN seed crystal in the low temperature zone driven by the axial temperature gradient, and adsorption, migration, crystallization and desorption occur on the growth surface. The growth surface continues to move toward the raw material area, and the AlN crystal continues to grow. In the PVT growth process, as long as the seed crystal temperature is lower than the raw material temperature, crystallization will occur, that is, there is no definite crystallization temperature. In order to obtain high-quality crystals, crystallization must occur within a certain temperature range. The optimal crystallization temperature of AlN crystals is between 2000 ℃ and 2300 ℃ (slightly different due to different growth conditions such as gas pressure). When the temperature is lower than 2000 ℃, polycrystalline or whiskers are often obtained. This requires that nucleation and growth at the seed crystal be avoided as much as possible before the temperature rises to 2000 ℃.
[0003] At present, people mainly use the "temperature gradient reversal method" to achieve this goal, that is, during the heating process, the seed crystal temperature is slightly higher than the raw material temperature to avoid low-temperature nucleation, and after reaching the target temperature, the seed crystal temperature is lowered to a lower temperature than the raw material temperature to trigger crystal growth; However, the thermal field structure of this method is relatively complex, requiring at least two upper and lower heaters, and the temperature control process is also difficult to achieve, requiring a lot of trial and error experiments in the early stage. Therefore, it is necessary to develop a simpler and more effective technology to inhibit the growth of AlN crystals at low temperatures.
[0004] Based on this, the present invention designs a crucible and a growth process for suppressing low-temperature nucleation of AlN crystals during the PVT growth process, so as to solve the above problems. Summary of the invention
[0005] The object of the present invention is to provide a crucible and a growth process for suppressing low-temperature nucleation of AlN crystals during the PVT growth process, so as to solve the above technical problems.
[0006] To achieve the above object, the present invention provides the following technical solution: a crucible for suppressing low-temperature nucleation during the growth of AlN crystals by PVT method, comprising: a seed crystal holder, a crucible tube and a crucible bottom; An AlN seed crystal is fixed on the lower surface of the seed crystal holder and covers the top of the crucible tube. An AlN raw material block sintered and shaped in advance is arranged inside the crucible tube. The AlN raw material block is placed on the top of the crucible bottom. The crucible bottom is in a convex shape, and a plurality of AlN multi-crystalline sheets are evenly distributed in the concave part of its edge. The bottom of the crucible tube is supported by a plurality of the AlN multi-crystalline sheets so as to be located above the bottom of the crucible.
[0007] Preferably, the seed crystal holder has a diameter between 56 mm and 85 mm, and a thickness between 1 mm and 5 mm.
[0008] Preferably, the crucible tube has a height between 50 mm and 80 mm, an inner diameter between 50 mm and 80 mm, and an outer diameter of the crucible tube is equal to a diameter of the seed crystal holder.
[0009] Preferably, the diameter of the AlN raw material block is 0.5 mm to 6 mm smaller than the inner diameter of the crucible tube, and the height is 5 mm to 15 mm smaller than the crucible tube.
[0010] Preferably, the thickness of the AlN multi-crystalline wafer is between 0.5 mm and 5 mm.
[0011] A growth process for inhibiting low temperature nucleation of AlN crystals during PVT growth, comprising the following steps: S1. The AlN raw material block is sintered using the crucible structure. There is no AlN seed crystal on the seed crystal holder. The crucible tube is directly placed on the bottom of the crucible. The sintering time is adjusted so that an AlN polycrystalline layer with a thickness of more than 2 mm is deposited on the seed crystal holder after the sintering is completed. S2, assembling a crucible structure: taking 3 or 4 AlN polycrystalline sheets of equal thickness from the AlN polycrystalline layer in step S1, and evenly placing them on the edge of the bottom of the crucible, placing a crucible barrel on the AlN polycrystalline sheet, placing a sintered and shaped AlN raw material block inside the crucible barrel, and placing a seed crystal holder with an AlN seed crystal fixed on the lower surface on the crucible barrel; S3, placing the crucible structure assembled in step S2 into a growth furnace for growth; S4, after step S3, the growth result is taken out; S5. According to the growth result obtained in step S4: if the weight of the crystal increases and the crystal quality is high, it means that the thickness of the AlN multi-crystalline sheet is appropriate; if the newly grown part of the crystal has a clear boundary with the original part, and the crystal quality of the newly grown part is poor, the thickness of the AlN multi-crystalline sheet is appropriately increased during subsequent growth; if the weight of the crystal increases less or even decreases, and the AlN raw material block becomes significantly smaller, the thickness of the AlN multi-crystalline sheet is appropriately reduced during subsequent growth.
[0012] Compared with the prior art, the present invention has the following beneficial effects: Compared with the traditional "temperature gradient reversal method", the present invention has greatly reduced requirements on the thermal field structure and can adopt a single heater, which can improve the stability of the equipment and reduce the equipment cost. During the growth process, it is only necessary to maintain high temperature and low temperature in the raw material area and seed crystal area respectively, without changing the high temperature area and low temperature area in real time, which greatly simplifies the temperature control process. The mass transfer process inside the crucible is regulated by using the AlN multi-crystalline sheet and the gap formed at the bottom of the crucible. The start time of crystal growth can be controlled by simply selecting an AlN multi-crystalline sheet of appropriate thickness. The operation is simple and the reliability is high. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.
[0014] Figure 1 To highlight the overall structural schematic diagram of the crucible suitable for suppressing low-temperature nucleation during the growth process of AlN crystal PVT method according to the present invention; the list of components represented by each number is as follows: 1. seed crystal holder; 2. AlN seed crystal; 3. crucible tube; 4. raw material block; 5. AlN multi-crystal wafer; 6. crucible bottom.
[0015] Figure 2 Schematic diagram of the crucible structure after the AlN multi-wafer is completely volatilized.
[0016] Figure 3 To highlight the traditional crucible structure during the growth of AlN crystals by PVT method; the list of components represented by each number is as follows: 1. Seed crystal holder; 2. AlN seed crystal; 3. Crucible tube; 4. Raw material block. DETAILED DESCRIPTION
[0017] 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; The size, crystal quality and surface treatment process of all AlN seed crystals 2 are the same, and the preparation process of all raw material blocks 4 and AlN multi-crystalline crystals 5 is the same. Example
[0018] Use Figure 3The traditional crucible structure shown in the figure. The growth structure dimensions are: the seed crystal holder 1 has a diameter of 56 mm and a thickness of 4 mm, the AlN seed crystal 2 has a diameter of 25 mm and a thickness of 5 mm, the crucible tube 3 has a height of 53 mm, an outer diameter of 56 mm, an inner diameter of 50 mm, and a bottom thickness of 3 mm, and the raw material block 4 has a height of 35 mm and a diameter of 49.5 mm.
[0019] Growth process: In a nitrogen atmosphere of 800 mbar, the temperature of the growth chamber was raised to 2200°C at a heating rate of 280°C / h, and then immediately cooled at a cooling rate of 280°C / h.
[0020] Growth results: An optical microscope showed that a layer of AlN polycrystalline layer was deposited on the growth surface. Example
[0021] The crucible structure designed by the present invention is as follows: Figure 1 The growth structure dimensions are as follows: the seed crystal holder 1 has a diameter of 56 mm and a thickness of 4 mm, the AlN seed crystal 2 has a diameter of 25 mm and a thickness of 5 mm, the crucible tube 3 has a height of 50 mm, an outer diameter of 56 mm and an inner diameter of 50 mm, the raw material block 4 has a height of 35 mm and a diameter of 49.5 mm, the AlN multi-crystal 5 has a thickness of 2 mm, a length of 3 mm and a width of 3 mm, and the 4 pieces are evenly distributed on the edge of the crucible bottom 6, which has a thickness of 3 mm, a diameter of 58 mm, an edge thickness of 2 mm and an edge width of 5 mm.
[0022] The growth process is the same as that in Example 1.
[0023] Growth results: Optical microscopy showed that there was no obvious change in the growth surface compared with before growth. Example
[0024] The growth structure is the same as in Example 2.
[0025] Growth process: In a nitrogen atmosphere of 800 mbar, the temperature of the growth chamber was raised to 2200°C at a heating rate of 280°C / h, maintained at 2200°C for 20h, and then cooled at a cooling rate of 280°C / h.
[0026] Growth results: The crystal thickness increased by 2.4 mm, the growth surface remained flat and smooth, and no polycrystals were produced. Example
[0027] The crucible structure designed by the present invention is adopted, the AlN multi-crystalline wafer 5 is 4 mm thick, and the other structural dimensions are the same as those of Example 3.
[0028] The growth process is the same as in Example 3.
[0029] Growth results: The crystal thickness increased by 2.0 mm, the growth surface remained flat and smooth, and no polycrystals were produced.
[0030] The specific application is: the present invention designs an improved crucible structure for AlN crystal growth, aiming to effectively suppress the nucleation and growth problems in the low temperature stage.
[0031] The crucible structure is designed as Figure 1 As shown, a seed crystal holder 1 with an AlN seed crystal 2 fixed at the bottom is covered on a crucible tube 3, and an AlN raw material block 4 that has been sintered and shaped in advance is placed inside the crucible tube 3. The AlN raw material block 4 is placed on the crucible bottom 6. The crucible tube 3 is not in direct contact with the crucible bottom 6, but is supported by several AlN multi-crystalline sheets 5 evenly distributed on the edge of the crucible bottom 6. During growth, before the temperature rises to the target temperature, the AlN raw material block 4 and the AlN multi-crystalline sheets 5 between the crucible tube 3 and the crucible bottom 6 have begun to sublime. Since there is a large gap between the crucible tube 3 and the crucible bottom 6, and the concentration of the Al(g) component outside the crucible is extremely low, the Al(g) component inside the crucible mainly diffuses through the gap to the outside of the crucible, rather than being deposited upward onto the surface of the seed crystal 2 prematurely at the low temperature stage. After the temperature reaches the growth temperature, the AlN multi-crystalline sheet 5 between the crucible tube 3 and the crucible bottom 6 is completely volatilized, and the gap is closed (such as Figure 2 As shown in FIG. 1 ), the gas phase components in the crucible begin to deposit on the surface of the seed crystal 2, and crystal growth begins, and finally a high-quality crystal is obtained.
[0032] It should be understood that in the description of the present invention, the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.
[0033] In the present invention, unless otherwise clearly stipulated and limited, the terms should be understood in a broad sense. For example, it can be directly connected or indirectly connected through an intermediate medium. It can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to specific circumstances.
[0034] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A crucible for inhibiting low-temperature nucleation during the growth of AlN crystals by PVT method, characterized in that: include: A seed crystal holder (1), a crucible tube (3) and a crucible bottom (6); An AlN seed crystal (2) is fixed on the lower surface of the seed crystal holder (1) and covers the top of the crucible tube (3); a pre-sintered and shaped AlN raw material block (4) is arranged inside the crucible tube (3); the AlN raw material block (4) is placed on the top of the crucible bottom (6); the crucible bottom (6) is in a convex shape, and a plurality of AlN multi-crystalline sheets (5) are evenly distributed in the concave portion of the edge; The bottom of the crucible tube (3) is supported by a plurality of AlN multi-crystalline sheets (5) so that it is located above the crucible bottom (6).
2. The crucible for suppressing low temperature nucleation of AlN crystal during PVT growth according to claim 1, characterized in that: The seed crystal holder (1) has a diameter between 56 mm and 85 mm and a thickness between 1 mm and 5 mm.
3. The crucible for suppressing low temperature nucleation during the growth of AlN crystals by PVT method according to claim 2, characterized in that: The crucible tube (3) has a height between 50 mm and 80 mm, an inner diameter between 50 mm and 80 mm, and an outer diameter of the crucible tube (3) is equal to the diameter of the seed crystal holder (1).
4. The crucible for suppressing low temperature nucleation during the growth of AlN crystals by PVT method according to claim 3, characterized in that: The diameter of the AlN raw material block (4) is 0.5 mm to 6 mm smaller than the inner diameter of the crucible tube (3), and the height is 5 mm to 15 mm smaller than the crucible tube (3).
5. The crucible for suppressing low temperature nucleation during the growth of AlN crystals by PVT method according to claim 1, characterized in that: The AlN multi-crystalline wafer (5) has a thickness between 0.5 mm and 5 mm.
6. A growth process for inhibiting low temperature nucleation during the growth of AlN crystals by PVT method, characterized in that: The following steps are involved: S1. The AlN raw material block (4) is sintered using the crucible structure, the seed crystal holder (1) has no AlN seed crystal (2), the crucible tube (3) is directly placed on the crucible bottom (6), and the sintering time is adjusted so that an AlN polycrystalline layer with a thickness of more than 2 mm is deposited on the seed crystal holder (1) after the sintering is completed; S2, assembling a crucible structure: taking three or four AlN polycrystalline sheets (5) of equal thickness from the AlN polycrystalline layer in step S1, and evenly placing them on the edge of the crucible bottom (6), placing a crucible tube (3) on the AlN polycrystalline sheets (5), placing a sintered and shaped AlN raw material block (4) inside the crucible tube (3), and covering the crucible tube (3) with a seed crystal holder (1) having an AlN seed crystal (2) fixed on its lower surface; S3, placing the crucible structure assembled in step S2 into a growth furnace for growth; S4, after step S3, the growth result is taken out; S5. According to the growth result obtained in step S4: if the weight of the crystal increases and the crystal quality is high, it means that the thickness of the AlN multi-crystal sheet (5) is appropriate; if the newly grown part of the crystal has a clear boundary with the original part, and the crystal quality of the newly grown part is poor, then the thickness of the AlN multi-crystal sheet (5) is appropriately increased during subsequent growth; if the weight of the crystal increases less or even decreases, and the AlN raw material block (4) becomes significantly smaller, then the thickness of the AlN multi-crystal sheet (5) is appropriately reduced during subsequent growth.