WO2019222997A1 - Apparatus and method for preparing aluminum nitride crystal - Google Patents

Abstract

An apparatus and method for preparing an aluminum nitride crystal, relating to the technical field of material preparation. The apparatus comprises: a first crucible (101), a second crucible (102), a substrate (103), and a temperature adjustment platform (104). The first crucible (101) comprises a raw material chamber and a reaction chamber; the diameter of the reaction chamber is greater than that of the raw material chamber; the raw material chamber is located at the bottom of the first crucible (101); the reaction chamber is located at the opening of the first crucible (101). The substrate (103) covers the opening of the first crucible (101) so that an aluminum nitride crystal can condense on the substrate (103) after sublimation in the reaction chamber. The temperature adjustment platform (104) is a hollow structure, and the side of the hollow portion having the minimum diameter is placed on the substrate (103), so as to adjust the contact area between the substrate (103) and outside air. The second crucible (102) comprises a raw material chamber and a reaction chamber; the raw material chamber of the second crucible (102) is located at the bottom of the second crucible (102); the diameter of the raw material chamber of the second crucible (102) is smaller than that of the reaction chamber of the second crucible (102).

Description

Device and method for preparing aluminum nitride crystal Technical field

The invention belongs to the technical field of material preparation, and particularly relates to a device and method for preparing aluminum nitride crystals.

Background technique

Deep ultraviolet light-emitting devices have a wide range of applications in sterilization, water purification, biomedicine, and deep ultraviolet light sources. Among them, aluminum nitride crystals have high temperature and pressure resistance, extremely high piezoelectric effect, and high electron mobility. It has broad prospects in applications such as high-power electronic devices and is an ideal semiconductor material for the preparation of deep ultraviolet light-emitting devices. However, the preparation of aluminum nitride crystal materials is difficult. At present, the research on aluminum nitride crystals at home and abroad still stays on the preparation size of the centimeter level. The sublimation method (also known as physical vapor transmission method) is considered to be the most promising method. Its basic process is: under nitrogen environment and high temperature conditions (usually> 1900 ℃), the aluminum nitride material sublimates in the high temperature region, and then re-evaluates in the low temperature region. Crystals form crystals. However, the aluminum nitride single crystal prepared by this method has the following disadvantages: (1) Due to the strong anisotropy shown during the growth of aluminum nitride crystals, the nucleation rate of spontaneous nucleation of aluminum nitride in the early stage of growth is difficult. Got control. (2) Expand the size of aluminum nitride crystals. The seed crystal induction method currently used cannot find a suitable seed crystal, which is difficult to implement.

In order to solve the above problems, the following methods are mainly used at present. One is the lateral gas transmission method. The closed crucible structure with a conical shape at the end of the crucible (as the crystal selection area) is used to control the nucleation rate and grow a larger size However, the crucible in this method cannot be used repeatedly, the cost is high, and the repeatability of the experiment is not high, resulting in poor quality of the aluminum nitride crystal.

One is to use tantalum carbide (TaC) as the crucible material, and place a grid plate with holes above the material, so that the grid plate can be a single crystal growth area, and the top cover of the crucible is a polycrystalline deposition area. The numerical simulation through this method can obtain the supersaturation range (0.25 ~ 0.3) suitable for crystal growth. In actual experiments, the content of carbon impurities in the crystals grown by this method is high, which affects the quality of the crystals. It is also difficult to obtain large-sized crystals, and the growth period is longer.

The other is a three-zone resistance heating inversion temperature field physical vapor transmission method to control nucleation. However, in this method, the growth of aluminum nitride crystals is more random. Although the nucleation is restricted by using a geometric structure by opening holes in the substrate The nucleation rate is better controlled, but it makes it difficult to expand the crystal in the later stage, which is not conducive to the growth of large-sized aluminum nitride single crystals.

technical problem

The present invention provides an apparatus and method for preparing aluminum nitride crystals, which aims to solve the problems of high carbon impurity content, poor quality, difficulty in obtaining large-sized crystals, and long growth cycles in the existing aluminum nitride crystals.

Technical solutions

An apparatus for preparing an aluminum nitride crystal provided by the present invention includes: a first crucible, a second crucible, a substrate, and a temperature adjustment table;

The first crucible includes a raw material cavity and a reaction cavity, wherein the diameter of the reaction cavity is larger than the diameter of the raw material cavity, the raw material cavity is located at the bottom of the first crucible, and the reaction cavity is located at the first crucible. Opening

The substrate covers the opening of the first crucible, so that the aluminum nitride crystals are condensed on the substrate after the reaction chamber is sublimed;

The temperature adjustment platform is a hollow structure, and the side with the smallest diameter of the hollow part is placed on the substrate to adjust the contact area between the substrate and outside air;

The second crucible includes a raw material cavity and a reaction cavity, wherein the raw material cavity of the second crucible is located at the bottom of the second crucible, and the diameter of the raw material cavity of the second crucible is smaller than the reaction cavity of the second crucible. diameter of.

The invention provides a method for preparing an aluminum nitride crystal, including:

Placing aluminum nitride in the reaction chamber of the first crucible, placing a substrate on the top of the first crucible, placing the side of the hollow part of the temperature adjustment table with the smallest diameter on the substrate, and The center of the temperature adjustment platform coincides with the center of the substrate, and the temperature is raised to 2250 ° C to 2400 ° C in a nitrogen atmosphere at 1 to 1.5 atmospheres with a heating rate of 400 to 600 ° C / h, and the temperature is maintained for 3.5 to 10 hours. A single crystal of aluminum nitride is obtained at the center of

When aluminum nitride single crystal is used as a seed crystal, the diameter of the hollow part of the temperature adjustment table is increased, and the temperature is increased to 400 ° C to 600 ° C / h to 1900 ° C to 2000 ° C in a nitrogen atmosphere of 1 to 1.5 atmospheres. Keep it warm for 0.5 ~ 2h, continue to heat up to 2250 ℃ ~ 2400 ℃, keep warm for 3.5 ~ 10 hours, cool down to 400 ~ 600 ℃ / h to 1900 ℃ ~ 2000 ℃, keep warm for 0.5 ~ 2h, get the grown aluminum nitride Crystal

The grown aluminum nitride crystal was used as a seed crystal, and the substrate containing the seed crystal was placed on a second crucible. The diameter of the hollow part of the temperature adjustment table was increased, and the temperature was raised to 400 to 600 ° C / h to 1900. ℃ ~ 2000 ℃, keep warm for 0.5 ~ 2h, continue to heat up to 2250 ℃ ~ 2400 ℃, keep warm for 3.5 ~ 10 hours, cool down to 400 ~ 600 ℃ / h to 1900 ℃ ~ 2000 ℃, hold for 0.5 ~ 2h, get Aluminum nitride crystal.

Beneficial effect

The invention provides a device and a method for preparing aluminum nitride crystals. The structure of the reaction chamber and the raw material cavity of the first crucible is used to reduce the nucleation, and the temperature of the center of the substrate is adjusted by using a temperature adjustment table, thereby forming an aluminum nitride unit And a substrate on which an aluminum nitride single crystal is formed is placed on a second crucible, and the characteristics of the reaction cavity and the structure cavity are used to increase the growth rate of the aluminum nitride single crystal to obtain an aluminum nitride crystal. The aluminum nitride crystal does not contain impurities, has high quality, and is controllable in size, and can obtain a large-sized aluminum nitride crystal.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly explain the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely Are some embodiments of the invention.

1 and 2 are schematic structural diagrams of an apparatus for preparing an aluminum nitride crystal according to an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a temperature adjustment platform according to an embodiment of the present invention; FIG.

FIG. 4 is a schematic structural diagram of a temperature adjustment platform according to an embodiment of the present invention; FIG.

FIG. 5 is a schematic structural diagram of a temperature adjustment platform according to an embodiment of the present invention; FIG.

FIG. 6 is a schematic diagram of an aluminum nitride crystal prepared according to an embodiment of the present invention.

Best Mode of the Invention

In order to make the objectives, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be described clearly and completely in combination with the drawings in the embodiments of the present invention. Obviously, the description The embodiments are only a part of the embodiments of the present invention, but not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work fall into the protection scope of the present invention.

Please refer to FIGS. 1 to 2. FIGS. 1 to 2 are schematic structural diagrams of an apparatus for preparing aluminum nitride crystals according to an embodiment of the present invention. The apparatus for preparing aluminum nitride crystals includes a first crucible 101 and a second crucible. 102, the substrate 103, and the temperature adjustment table 104;

The first crucible 101 includes a raw material cavity and a reaction cavity. The diameter of the reaction cavity is larger than the diameter of the raw material cavity. The raw material cavity is located at the bottom of the first crucible 101 and the reaction cavity is located at the opening of the first crucible 102.

Specifically, the height of the raw material cavity of the first crucible 101 is 30 to 60 mm and the diameter is 15 to 45 mm. The height of the reaction cavity of the first crucible 101 is 50 to 20 mm and the diameter is 30 to 50 mm. The diameter of the reaction cavity is larger than that of the raw material cavity. The diameter is 5 to 15 mm, and the wall thickness of the first crucible 101 is 2 to 5 mm.

In the actual preparation process, the raw material cavity is used to store materials, namely aluminum nitride, which is a low temperature region, which can reduce the sublimation speed of aluminum nitride, the diameter of the reaction cavity is large, and the mass transmission area of the gas can be increased. The larger volume of the cavity can reduce the partial pressure of aluminum vapor during nucleation, control the supersaturation at a lower level, and increase the overall temperature of the substrate 103 while increasing the temperature in this region, so that the temperature of the substrate 103 Above the temperature of the raw material cavity, the nucleation is reduced.

The substrate 103 covers the opening of the first crucible 101, so that the aluminum nitride crystal is condensed on the substrate 103 after the reaction chamber is sublimed;

The temperature adjusting table 104 has a hollow structure, and the side with the smallest diameter of the hollow portion is placed on the substrate 103 to adjust the contact area between the substrate 103 and the outside air.

An embodiment of the present invention is shown in FIG. 3. FIG. 3 shows a schematic structural diagram of a temperature adjustment table in this embodiment. The temperature adjustment table 104 is composed of a plurality of hollow cylinders. Layers increase. Among them, the diameter of the cylinder with the smallest diameter in the temperature adjustment table is 1 mm, and the diameter of the cylinder with the largest diameter is 25 mm.

An embodiment of the present invention is shown in FIG. 4. FIG. 4 shows a schematic structural diagram of a temperature adjustment table in this embodiment. The temperature adjustment table 104 is a multi-layer hollow cylinder, and the hollow portion is a cone structure. The diameter of the top of the cone in the middle of the temperature control platform is 1 mm, and the diameter of the bottom of the cone is 25 mm.

An embodiment of the present invention is shown in FIG. 5. FIG. 5 shows a schematic structural diagram of a temperature adjustment table in this embodiment. The temperature adjustment table 104 is a plurality of plates with central openings, and each plate is opened in the middle. The diameter of the holes gradually increases. The diameter of the plurality of centrally-opened plates in the temperature adjustment table 104 ranges from 1 to 25 mm.

It should be noted that the maximum diameter of the temperature adjustment table 104 is between the diameter of the reaction chamber of the first crucible 101 and the diameter of the raw material chamber.

In practical applications, the effect of the temperature adjustment table 104 is the same. The radial temperature field distribution of the substrate 103 can be adjusted so that the temperature of the substrate 103 increases linearly from the geometric center to the edge. The center position of the substrate 103 is a very low temperature region. Since the gas flows from high temperature to low temperature, the gas flows to the center position of the substrate 103, and the aluminum vapor partial pressure in the center of the substrate 103 increases; at the same time, the crystals are at a lower temperature. Nucleation, so the crystal nucleates at the geometric center of the substrate 103, greatly reducing the nucleation rate, so that only one aluminum nitride single crystal is grown.

The second crucible 104 includes a raw material cavity and a reaction cavity, wherein the raw material cavity of the second crucible 104 is located at the bottom of the second crucible 104, and the diameter of the raw material cavity of the second crucible 102 is smaller than the diameter of the reaction cavity of the second crucible 102.

Specifically, the height of the raw material cavity of the second crucible 102 is 30 to 60 mm and the diameter is 35 to 75 mm. The height of the reaction cavity of the second crucible 102 is 50 to 20 mm and the diameter is 30 to 50 mm. The wall thickness of the second crucible 102 I 2 ~ 5mm, the diameter of the raw material cavity in the second crucible 102 is 5 ~ 25mm larger than the diameter of the reaction cavity. In the specific preparation of aluminum nitride crystals, the single crystal prepared in the first crucible 101 is transferred to the second crucible together with the substrate. In general, the volume of the raw material cavity makes the material contained in the raw material cavity nitride. There is more aluminum, which can ensure that the raw material has a sufficiently high sublimation rate, and the volume of the reaction chamber is small. The partial pressure of aluminum vapor can be increased to form a larger supersaturation environment to ensure a larger growth rate. For larger aluminum nitride crystals, the following is the reaction process: 2AlN (s) ⇌2Al (g) + N2 (g) Optionally, the device for preparing aluminum nitride crystals further includes: crucible lid 105, crucible lid 105 It is placed at the opening of the second crucible 104.

Specifically, the thickness of the crucible cover 105 is 1 to 3 mm. The diameter of the crucible cover 105 is greater than or equal to the diameter of the second crucible 104. In this way, it is possible to prevent steam from diffusing to the outside of the crucible, reduce the partial pressure of gas, and cause waste of raw materials.

The device for preparing an aluminum nitride crystal provided by the embodiment of the present invention uses the structure of the reaction chamber and the raw material cavity of the first crucible to reduce nucleation, and uses a temperature adjustment table to adjust the temperature of the center of the substrate to form an aluminum nitride single crystal. And the substrate forming the aluminum nitride single crystal is placed on the second crucible, and the characteristics of the reaction cavity and the structure cavity are used to increase the growth rate of the aluminum nitride single crystal to obtain the aluminum nitride crystal. The aluminum nitride crystal does not contain impurities, has high quality, and is controllable in size, and can obtain a large-sized aluminum nitride crystal.

The invention provides a method for preparing an aluminum nitride crystal. The method is applied to the above device for preparing an aluminum nitride crystal. The method includes:

Step 1: Place aluminum nitride in the reaction chamber of the first crucible, place the substrate on the top of the first crucible, and place the side with the smallest diameter of the hollow part of the temperature adjustment table on the substrate. And the center of the temperature adjustment table coincides with the center of the substrate, and the temperature is raised to 2000 ° C to 3000 ° C in a nitrogen atmosphere of 1 to 1.5 atmospheres at a heating rate of 400 to 600 ° C / h, and the temperature is maintained for 3.5 to 10 hours. A single crystal of aluminum nitride is obtained at the center of the substrate;

In practical application, through step one, an aluminum nitride single crystal having the same diameter as the hollow portion of the temperature control table can be obtained, and the diameter of the aluminum nitride single crystal can be 1 to 10 mm, as shown in FIG. 6. Preferably, the holding temperature is from 2250 ° C to 2400 ° C.

Step 2: Use the aluminum nitride single crystal as the seed crystal, increase the diameter of the hollow part of the temperature adjustment table, and heat up to 1900 ° C to 2000 ° C at a temperature increase rate of 400 to 600 ° C / h under a nitrogen atmosphere of 1 to 1.5 atmospheres. At ℃, hold for 0.5 ~ 2h, keep warming to 2000 ℃ ~ 3000 ℃, keep warm for 3.5 ~ 10 hours, reduce the temperature to 400 ~ 600 ℃ / h to 1900 ℃ ~ 2000 ℃, and keep it for 0.5 ~ 2h. Aluminum nitride crystal

It should be noted that the second step can be repeated multiple times, and the diameter of the hollow part of the temperature control table is increased by 2 to 6 mm each time. By repeating it several times, the aluminum nitride crystal can be sublimated, and the seed crystal will not be severely decomposed. It is ensured that there is a suitable supersaturation at the early stage of the high-temperature growth stage, and the aluminum nitride seed crystal is prevented from decomposing. In addition, the number of cracks in the aluminum nitride crystal can be reduced by annealing at a lower temperature. Preferably, the holding temperature is from 2250 ° C to 2400 ° C.

Step 3: Use the grown aluminum nitride crystal as the seed crystal, and place the substrate containing the seed crystal on the second crucible, increase the diameter of the hollow part of the temperature adjustment table, and increase the temperature at a temperature of 400 ~ 600 ° C / h When warming to 1900 ℃ ~ 2000 ℃, keep warm for 0.5 ~ 2h, continue to warm to 2250 ℃ ~ 2400 ℃, keep warm for 3.5 ~ 10 hours, reduce temperature to 400 ~ 600 ℃ / h to 1900 ℃ ~ 2000 ℃, keep warm for 0.5 ~ 2h, aluminum nitride crystals were obtained.

In general, the large volume of the raw material cavity in the second crucible causes more aluminum nitride to be contained in the raw material cavity, which can ensure that the raw material has a sufficiently high sublimation rate, the volume of the reaction cavity is small, and the aluminum vapor partial pressure can be increased. A larger supersaturation environment is formed to ensure a larger growth rate, so that the reaction proceeds in reverse, and a larger size aluminum nitride crystal is obtained.

Optionally, before step one, the method further includes:

The aluminum nitride powder was heated to 1500 ° C. to 2000 ° C. for 3 to 6 hours under a nitrogen atmosphere, and repeated 2 to 5 times to obtain sintered aluminum nitride.

In the method for preparing an aluminum nitride crystal provided by the embodiment of the present invention, the structure of the reaction chamber and the raw material cavity of the first crucible is used to reduce nucleation, and the temperature of the center of the substrate is adjusted by using a temperature adjustment table to form an aluminum nitride single crystal. And the substrate forming the aluminum nitride single crystal is placed on the second crucible, and the characteristics of the reaction cavity and the structure cavity are used to increase the growth rate of the aluminum nitride single crystal to obtain the aluminum nitride crystal. The aluminum nitride crystal does not contain impurities, has high quality, and is controllable in size, and can obtain a large-sized aluminum nitride crystal.

The above description is only the preferred embodiments of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention shall be included in the protection of the present invention. Within range.

Claims (10)

 An apparatus for preparing an aluminum nitride crystal, characterized in that the apparatus includes: a first crucible, a second crucible, a substrate, and a temperature adjustment table; The first crucible includes a raw material cavity and a reaction cavity, wherein the diameter of the reaction cavity is larger than the diameter of the raw material cavity, the raw material cavity is located at the bottom of the first crucible, and the reaction cavity is located at the first crucible. Opening The substrate covers the opening of the first crucible, so that the aluminum nitride crystals are condensed on the substrate after the reaction chamber is sublimed; The temperature adjustment platform is a hollow structure, and the side with the smallest diameter of the hollow part is placed on the substrate to adjust the contact area between the substrate and outside air; The second crucible includes a raw material cavity and a reaction cavity, wherein the raw material cavity of the second crucible is located at the bottom of the second crucible, and the diameter of the raw material cavity of the second crucible is smaller than the reaction cavity of the second crucible. diameter of.  The device according to claim 1, wherein the temperature adjustment table is composed of a plurality of hollow cylinders, and the hollow diameter of each layer of the cylinder is increased layer by layer.  The device according to claim 1, wherein the temperature control platform is a multi-layer hollow cylinder, and the hollow portion has a cone structure.  The device according to claim 1, wherein the temperature adjusting table is a plurality of plates with central openings, and the diameter of the openings in each plate gradually increases.  The device according to claim 1, wherein a height of a raw material cavity of the first crucible is 30 to 60 mm and a diameter of 15 to 45 mm, and a height of the reaction cavity of the first crucible is 50 to 20 mm and a diameter It is 30 ~ 50mm.  The device according to claim 2, wherein the diameter of the cylinder with the smallest diameter in the temperature adjustment table is 1 mm, and the diameter of the cylinder with the largest diameter is 25 mm.  The device according to claim 3, wherein the diameter of the top of the cone of the hollow portion of the temperature control platform is 1 mm, and the diameter of the bottom of the cone is 25 mm.  The device according to claim 4, wherein a diameter of a plurality of plates with central openings in the temperature adjustment table ranges from 1 to 25 mm.  A method for preparing an aluminum nitride crystal, wherein the method is applied to an apparatus for preparing an aluminum nitride crystal according to any one of claims 1 to 8, and the method includes: Placing aluminum nitride in the reaction chamber of the first crucible, placing a substrate on the top of the first crucible, placing the side of the hollow part of the temperature adjustment table with the smallest diameter on the substrate, and The center of the temperature adjustment table coincides with the center of the substrate, and the temperature is raised to 2000 ° C to 3000 ° C in a nitrogen atmosphere of 1 to 1.5 atmospheres with a heating rate of 400 to 600 ° C / h, and the temperature is maintained for 3.5 to 10 hours. A single crystal of aluminum nitride is obtained at the center of When aluminum nitride single crystal is used as a seed crystal, the diameter of the hollow part of the temperature adjustment table is increased, and the temperature is increased to 400 ° C to 600 ° C / h to 1900 ° C to 2000 ° C in a nitrogen atmosphere of 1 to 1.5 atmospheres. Keep it warm for 0.5 ~ 2h, continue to warm to 2000 ℃ ~ 3000 ℃, keep warm for 3.5 ~ 10 hours, cool down to 1900 ℃ ~ 2000 ℃ at a cooling rate of 400 ~ 600 ℃ / h, and keep it for 0.5 ~ 2h to obtain the grown aluminum nitride. Crystal The grown aluminum nitride crystal was used as a seed crystal, and the substrate containing the seed crystal was placed on a second crucible. The diameter of the hollow part of the temperature adjustment table was increased, and the temperature was raised to 400 to 600 ° C / h to 1900. ℃ ~ 2000 ℃, keep warm for 0.5 ~ 2h, continue to warm to 2000 ℃ ~ 3000 ℃, keep warm for 3.5 ~ 10 hours, cool down to 1900 ℃ ~ 2000 ℃ at a cooling rate of 400 ~ 600 ℃ / h, keep for 0.5 ~ 2h, get Aluminum nitride crystal. The method according to claim 9, further comprising: The aluminum nitride powder was heated to 1500 ° C. to 2000 ° C. for 3 to 6 hours under a nitrogen atmosphere, and repeated 2 to 5 times to obtain sintered aluminum nitride.