Composite crucible and crystal growth equipment

Abstract

The utility model provides a composite crucible and a crystal growth device, wherein the composite crucible comprises a graphite crucible body and a tantalum foil layer; the graphite crucible body comprises a bottom wall and a side wall, the lower edge of the side wall is sealed and connected to the edge of the bottom wall, so as to form a growth cavity for performing a crystal growth process together with the bottom wall; the tantalum foil layer comprises at least one layer of tantalum foil; at least one layer of tantalum foil is covered on the upper surface of the bottom wall and the inner peripheral surface of the side wall, so as to isolate the bottom wall and the side wall from the growth cavity, so as to reduce the carbon impurity content in the prepared crystal; and because the tantalum foil is relatively thin, less tantalum material can be used while ensuring that the inner surface of the graphite crucible body is completely covered, thereby reducing the manufacturing cost of the composite crucible.

Description

Technical Field

[0001] The utility model belongs to the field of crystal growth technology, and specifically relates to a composite crucible and a crystal growth device. Background Art

[0002] At present, AlN (aluminum nitride) single crystal has become one of the best substrates for epitaxially growing AlN and AlGaN (aluminum gallium nitride) structures to make deep ultraviolet optoelectronic components, MEMS (Micro-Electro-Mechanical System) devices and other electronic devices due to its excellent characteristics such as ultra-wide bandgap, high breakdown field strength, high thermal conductivity, high hardness, and excellent electrical properties. In addition, the lattice and thermal matching between AlN and AlGaN with high Al content is very high, so high-quality AlN single crystal as a homogeneous / near homogeneous epitaxial substrate can significantly reduce the dislocation density of the epitaxial layer, thereby improving the substrate quality.

[0003] The preparation of AlN single crystal substrates usually adopts the physical vapor transport process (hereinafter referred to as PVT). The principle of this process is to make AlN source powder undergo thermal sublimation in a high temperature environment and grow a single crystal on the seed crystal. However, in the absence of large-sized AlN seed crystals, the existing technical solutions usually use SiC (silicon carbide) seed crystals to heterogeneously grow AlN single crystals on SiC seed crystals, and then peel the AlN single crystals from the SiC seed crystals by cutting, so as to obtain large-sized AlN seed crystals for homogeneous growth of AlN single crystals on the AlN seed crystals in subsequent processes. Since SiC seed crystals are used in the PVT process, graphite crucibles are usually used as induction heat sources to create a high-temperature environment.

[0004] However, since Al atoms will etch with the graphite crucible at high temperatures, if the AlN source powder and SiC seed crystal are placed directly in the graphite crucible, it is easy to cause excessive carbon impurities to be added to the final AlN single crystal, thereby affecting the quality of the AlN single crystal. In addition, the surface emissivity of the graphite material is high, which is not conducive to the formation of a temperature gradient suitable for crystal growth in the temperature field inside the graphite crucible.

[0005] In order to avoid this problem, the existing technical solution usually places an additional tantalum carbide crucible in the graphite crucible, and the tantalum carbide crucible needs to fit the inner surface of the graphite crucible as much as possible to ensure the heat conduction from the heat source of the graphite crucible to the inside. In this way, the tantalum carbide crucible can be used to isolate the sublimation growth area of ​​the AlN source powder from the graphite crucible as much as possible to reduce the introduction of carbon impurities, and the low emissivity and strong thermal radiation reflection ability of the tantalum carbide material can be used to form a temperature gradient suitable for crystal growth.

[0006] However, tantalum carbide crucibles are usually formed by carbonizing the tantalum crucible base. If the carbonization is uneven, it will affect the service life. In addition, the price of tantalum material is expensive, and the outer wall of the tantalum carbide crucible needs to be thick enough to ensure that it will not crack when thermal mismatch occurs, which leads to a high manufacturing cost of tantalum carbide crucibles. Utility Model Content

[0007] The utility model at least partially solves the problems of high manufacturing cost and great manufacturing difficulty of the existing tantalum carbide crucible, and provides a composite crucible and semiconductor process equipment.

[0008] The present invention provides a composite crucible for use in a crystal growth process; the composite crucible comprises:

[0009] A graphite crucible body, comprising a bottom wall and a side wall, wherein the lower edge of the side wall is sealedly connected to the edge of the bottom wall to form a growth cavity together with the bottom wall for performing the crystal growth process;

[0010] The tantalum foil layer comprises at least one layer of tantalum foil; at least one layer of the tantalum foil covers the upper surface of the bottom wall and the inner peripheral surface of the side wall to isolate the bottom wall and the side wall from the growth cavity.

[0011] Optionally, the composite crucible also includes a first bonding layer, which is located between the tantalum foil layer and the bottom wall and the side wall, and covers the upper surface of the bottom wall and the inner circumference of the side wall; the first bonding layer is used to bond the tantalum foil layer to the upper surface of the bottom wall and the inner circumference of the side wall.

[0012] Optionally, the tantalum foil layer includes multiple layers of tantalum foil;

[0013] The composite crucible further includes a second bonding layer located between two adjacent layers of the tantalum foils, and the second bonding layer is used for bonding the two adjacent layers of the tantalum foils.

[0014] Optionally, the first bonding layer is an amorphous carbon material layer.

[0015] Optionally, the second bonding layer is an amorphous carbon material layer.

[0016] Optionally, the amorphous carbon material layer is formed by thermal decomposition and carbonization of an organic glue.

[0017] Optionally, the thickness of the tantalum foil in the tantalum foil layer covering the inner circumferential surface of the side wall is in the range of 0.05 mm to 0.1 mm.

[0018] Optionally, the thickness of the tantalum foil layer covering the upper surface of the bottom wall is in the range of 0.2 mm to 0.3 mm.

[0019] Optionally, the composite crucible further comprises a graphite crucible cover; the graphite crucible cover is used to be detachably connected to the upper edge of the side wall, and the graphite crucible cover can completely cover the upper edge of the side wall; the lower surface of the graphite crucible cover is used to be fixedly connected to the seed crystal.

[0020] As another technical solution, the utility model also provides a crystal growth device, which includes a heating furnace and the composite crucible as described above;

[0021] The composite crucible is used to contain seed crystals and source powders; the heating furnace is used to heat the composite crucible so as to thermally sublimate the source powder inside the composite crucible and grow crystals on the seed crystals.

[0022] The utility model has the following beneficial effects:

[0023] The composite crucible provided by the embodiment of the utility model covers the upper surface of the bottom wall of the graphite crucible body and the inner circumference of the side wall with a tantalum foil layer to completely isolate the inner surface of the graphite crucible body from the growth cavity inside the graphite crucible body, thereby avoiding contact between the source powder and the graphite material in the growth cavity, and further minimizing the carbon impurity content in the prepared crystal. Moreover, the tantalum foil layer is mainly composed of at least one layer of tantalum foil; and because the tantalum foil is relatively thin, less tantalum material is used while ensuring that the inner surface of the graphite crucible body is completely covered, thereby reducing the manufacturing cost. Moreover, because the tantalum foil is highly flexible and easy to deform, the tantalum foil is easy to cover on a surface of any shape, reducing the difficulty of processing, and is suitable for graphite crucible bodies of various sizes and shapes, and can also avoid the occurrence of thermal mismatch due to insufficient fitting. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the structure of a composite crucible provided in an embodiment of the utility model;

[0025] Figure 2 The Omega rocking curve of an AlN crystal made by using the composite crucible provided by the embodiment of the utility model. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0027] It should be understood that the specific embodiments and drawings described herein are only used to explain the present invention, rather than to limit the present invention.

[0028] It can be understood that, in the absence of conflict, the various embodiments of the present utility model and the various features in the embodiments can be combined with each other.

[0029] It can be understood that, for the convenience of description, the drawings of the present invention only show the parts related to the embodiments of the present invention, while the parts unrelated to the embodiments of the present invention are not shown in the drawings.

[0030] It is understandable that, in the absence of conflict, the functions and steps marked in the flowcharts and block diagrams of the embodiments of the present utility model may occur in an order different from that marked in the drawings.

[0031] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

[0032] This embodiment provides a composite crucible for use in a crystal growth process, such as Figure 1 As shown, the composite crucible includes a graphite crucible body 1 and a tantalum foil layer 2.

[0033] The graphite crucible body 1 includes a bottom wall 11 and a side wall 12, wherein the lower edge of the side wall 12 is sealed and connected to the edge of the bottom wall 11, so as to enclose a growth cavity for performing a crystal growth process together with the bottom wall 11. Specifically, the growth cavity is used to contain source powder. The graphite crucible body 1 has good electrical conductivity and thermal conductivity, and is therefore suitable for heating it using electromagnetic eddy currents to heat the source powder in the growth cavity, thereby causing thermal sublimation of the source powder.

[0034] The tantalum foil layer 2 covers the upper surface of the bottom wall 11 and the inner circumference of the side wall 12, that is, completely covers the inner surface of the graphite crucible body 1, so as to completely isolate the bottom wall 11 and the side wall 12 of the graphite crucible body 1 from the growth chamber, thereby avoiding contact between the source powder and the graphite material (i.e., the graphite crucible body) in the growth chamber during the process, thereby minimizing the carbon impurity content in the prepared crystal. Moreover, since the tantalum material has a low emissivity and a strong heat radiation reflection ability, it is easy to form a temperature gradient suitable for crystal growth in the temperature field inside the growth chamber.

[0035] The tantalum foil layer 2 includes at least one layer of tantalum foil. It should be noted that the "tantalum foil" in this article is a pure tantalum metal sheet. Since the tantalum foil is relatively thin, less tantalum material is used while ensuring that the inner surface of the graphite crucible body 1 is completely covered, thereby reducing the manufacturing cost.

[0036] Moreover, the tantalum foil has the characteristics of high flexibility and easy deformation, so the tantalum foil can be easily covered on the surface of any shape, which reduces the processing difficulty, and is suitable for graphite crucible bodies 1 of various sizes and shapes, and can also avoid the occurrence of thermal mismatch due to insufficient fitting. In comparison, the existing tantalum carbide crucible requires the tantalum crucible substrate to be formed by a carburization process, and tantalum crucible substrates of different sizes and shapes need to be designed, drawn, and machined separately, which results in a high time cost for manufacturing tantalum carbide crucibles. The composite crucible provided in this embodiment can save the design and drawing steps by covering the inner surface of the existing graphite crucible with tantalum foil, thereby reducing the time cost and design cost of manufacturing. In some embodiments, the composite crucible also includes a first bonding layer, which is used to bond the tantalum foil layer 2 to the upper surface of the bottom wall 11 and the inner circumferential surface of the side wall 12. The first adhesive layer is located between the tantalum foil layer 2 and the bottom wall 11 and the side wall 12, and the first adhesive layer covers the upper surface of the bottom wall 11 and the inner circumference of the side wall 12 to ensure that the tantalum foil layer 2 is tightly fitted to the inner surface of the graphite crucible body 1 at all locations, thereby improving the thermal conductivity between the graphite crucible body 1 and the tantalum foil layer 2 as much as possible; moreover, at the process temperature, the tantalum material can undergo corresponding deformation with the thermal expansion of the graphite crucible body 1, thereby ensuring that the tantalum foil layer 2 will not fall off the surface of the graphite crucible body 1.

[0037] In some embodiments, the number of tantalum foils is multiple layers. The composite crucible also includes a second bonding layer located between two adjacent layers of tantalum foils, which is used to bond the two adjacent layers of tantalum foils. Specifically, the second bonding layer can cover the surface of the corresponding tantalum foil so that the two adjacent layers of tantalum foils are closely attached to each other, thereby ensuring the thermal conductivity and connection strength between the two adjacent layers of tantalum foils.

[0038] Specifically, the multi-layer tantalum foil can be attached to the inner circumference of the side wall 12 of the graphite crucible body 1; this is because the inner circumference of the side wall 12 of the graphite crucible body 1 is usually a curved surface, so a thinner and more easily bendable tantalum foil can be selected to cover the inner circumference of the side wall 12, thereby reducing the difficulty of attaching the tantalum foil layer 2 as a whole and increasing the overall thickness of the tantalum foil layer 2 to avoid damage to the tantalum foil layer 2 during the process. For example, a tantalum foil with a thickness range of 0.05 mm to 0.1 mm is used.

[0039] In this case, the upper surface of the bottom wall 11 of the graphite crucible body 1 can be covered with a single layer of tantalum foil, because the upper surface of the bottom wall 11 of the graphite crucible body 1 is usually flat, and even a thicker tantalum foil that is not easy to bend can easily cover the upper surface of the bottom wall 11. Alternatively, the upper surface of the bottom wall 11 of the graphite crucible body 1 can also be covered with multiple layers of tantalum foil. Specifically, the thickness of the tantalum foil layer 2 covering the upper surface of the bottom wall 11 can range from 0.2 mm to 0.3 mm, that is, the sum of the thickness of the multiple layers of tantalum foil on the upper surface of the bottom wall 11 can be 0.2 mm to 0.3 mm.

[0040] Alternatively, the inner peripheral surface of the side wall 12 of the graphite crucible body 1 may also be covered with a single layer of tantalum foil.

[0041] In some embodiments, the first bonding layer is an amorphous carbon material layer.

[0042] In some embodiments, the second adhesive layer is also an amorphous carbon material layer.

[0043] Furthermore, in some embodiments, the amorphous carbon material layer is formed by thermal decomposition and carbonization of an organic glue. Preferably, the organic glue is, for example, a photoresist whose main component is polyamic acid resin.

[0044] Specifically, in the manufacturing process of the composite crucible, an organic glue can be evenly coated on the inner circumference of the side wall 12 and the upper surface of the bottom wall 11 of the pre-made graphite crucible body, and then the cut tantalum foil is attached to the inner circumference of the side wall 12 and the upper surface of the bottom wall 11, and finally the graphite crucible body is placed in a vacuum annealing furnace for vacuum heating, so that the organic glue is pyrolyzed at high temperature and amorphous carbon is generated. Since amorphous carbon is consistent with the main material of the graphite crucible, the two can be tightly connected; and since carbon atoms will partially penetrate between tantalum atoms under high temperature, amorphous carbon can also be tightly connected with the tantalum foil, so that the tantalum foil is tightly attached to the inner circumference of the side wall 12 and the upper surface of the bottom wall 11 of the graphite crucible body.

[0045] Moreover, if the tantalum foil layer 2 includes multiple layers of tantalum foil, a layer of tantalum foil can be first attached to the inner circumferential surface of the side wall 12 of the graphite crucible body and the upper surface of the bottom wall 11, and then an organic glue is coated on the surface of the cut tantalum foil, and the tantalum foil coated with the organic glue is attached to the surface of the first layer of tantalum foil, and finally the graphite crucible body is placed in a vacuum annealing furnace for vacuum heating, so as to form multiple layers of tantalum foil on the inner surface of the graphite crucible body.

[0046] Based on the composite crucible proposed in this embodiment, this embodiment also provides a specific manufacturing process of the composite crucible, which specifically includes:

[0047] Step S1: cutting tantalum foil;

[0048] Specifically, the size of the cut tantalum foil is slightly smaller than the size of the bottom wall and the side wall of the graphite crucible body, so that the tantalum foil can just cover the bottom wall and the side wall of the graphite crucible body after the tantalum foil is heated and expanded; for example, if the graphite crucible body is cylindrical with an inner diameter of 110 mm and an inner height of 100 mm, the tantalum foil used to be attached to the inner circumference of the side wall is cut into a rectangle with a length of 345 mm and a width of 99 mm, and the tantalum foil used to be attached to the upper surface of the bottom wall is cut into a circle with a diameter of 109 mm;

[0049] Step S2: coating a viscous liquid photoresist on the upper surface of the bottom wall and the inner peripheral surface of the side wall, and evenly scraping with a scraper;

[0050] Specifically, the thickness of the photoresist is, for example, 0.3 mm;

[0051] Step S3: rolling the rectangular tantalum foil into a cylindrical shape and attaching it to the inner circumference of the side wall;

[0052] Step S4: attaching a circular tantalum foil to the upper surface of the bottom wall;

[0053] Step S5: Pressing the cylindrical pressing block into the graphite crucible body to press the tantalum foil on the side thereof and the tantalum foil below it;

[0054] Specifically, the cylindrical pressed block may be a graphite block;

[0055] Step S6: placing the graphite crucible body together with the cylindrical pressed block into a vacuum annealing furnace for vacuum heating;

[0056] Step S7: Cooling to room temperature to form a composite crucible, and taking out the cylindrical pressed block.

[0057] In some embodiments, the composite crucible further comprises a graphite crucible cover 3; the graphite crucible cover 3 is used to be detachably connected to the upper edge of the side wall, and the graphite crucible cover 3 can completely cover the upper edge of the side wall 12 to seal and close the growth chamber. Figure 1 As shown, the lower surface of the graphite crucible cover 3 is used to be fixedly connected to the seed crystal 4 so as to move upward and combine with the seed crystal 4 after the source powder is thermally sublimated.

[0058] As another technical solution, this embodiment also provides a crystal growth device, which includes a heating furnace and the composite crucible as described above. The composite crucible is used to contain the seed crystal 4 and the source powder 5; the heating furnace is used to heat the composite crucible to thermally sublimate the source powder inside the composite crucible and grow a crystal on the seed crystal 4, thereby completing the crystal growth process. Specifically, the heating furnace can be an electromagnetic induction heating furnace.

[0059] Taking the heterogeneous growth of AlN crystals using SiC seed crystals as an example, the technicians used the above-mentioned crystal growth equipment to conduct experiments and obtained two-inch AlN crystals. In addition, the technicians also used X-ray diffraction to test the obtained AlN crystal samples. Specifically, Figure 2 As shown, the (0002) and (10-12) omega rocking curves of the AlN crystal sample have single-peak diffraction peaks with axial symmetry, indicating that the AlN crystal sample is a single crystal; and the half-peak widths of the (0002) and (10-12) curves are 722 arc seconds and 432 arc seconds, respectively, and the half-peak widths are small, indicating that the misalignment angles of adjacent lattices are small, which means that the lattice quality of the AlN crystal sample is good. It can be seen that the composite crucible and crystal growth device provided in this embodiment can process single crystals of good quality.

[0060] As described above, the composite crucible and crystal growth equipment provided in this embodiment can avoid contact between source powder and graphite material in the growth cavity by covering the upper surface of the bottom wall and the inner circumference of the side wall of the graphite crucible body with a tantalum foil layer, and can reduce the amount of tantalum material used, thereby reducing manufacturing costs. Moreover, since the tantalum foil is highly flexible and easy to deform, the tantalum foil is easy to cover on a surface of any shape, reducing the difficulty of processing, and is suitable for graphite crucible bodies of various sizes and shapes, and can directly modify existing graphite crucibles, further saving manufacturing costs.

[0061] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A composite crucible, used in crystal growth process; characterized in that: include: A graphite crucible body, comprising a bottom wall and a side wall, wherein the lower edge of the side wall is sealedly connected to the edge of the bottom wall to form a growth cavity together with the bottom wall for performing the crystal growth process; The tantalum foil layer comprises at least one layer of tantalum foil; at least one layer of the tantalum foil covers the upper surface of the bottom wall and the inner peripheral surface of the side wall to isolate the bottom wall and the side wall from the growth cavity.

2. The composite crucible according to claim 1, characterized in that: It also includes a first adhesive layer, which is located between the tantalum foil layer and the bottom wall and the side wall, and the first adhesive layer covers the upper surface of the bottom wall and the inner peripheral surface of the side wall; The first bonding layer is used to bond the tantalum foil layer to the upper surface of the bottom wall and the inner peripheral surface of the side wall.

3. The composite crucible according to claim 1, characterized in that: The tantalum foil layer comprises multiple layers of tantalum foil; The composite crucible further includes a second bonding layer located between two adjacent layers of the tantalum foils, and the second bonding layer is used for bonding the two adjacent layers of the tantalum foils.

4. The composite crucible according to claim 2, characterized in that: The first bonding layer is an amorphous carbon material layer.

5. The composite crucible according to claim 3, characterized in that: The second bonding layer is an amorphous carbon material layer.

6. The composite crucible according to claim 4 or 5, characterized in that: The amorphous carbon material layer is formed by thermal decomposition and carbonization of an organic glue.

7. The composite crucible according to claim 1, characterized in that: The thickness of the tantalum foil sheet in the tantalum foil layer covering the inner peripheral surface of the side wall is in the range of 0.05 mm to 0.1 mm.

8. The composite crucible according to claim 1, characterized in that: The thickness of the tantalum foil layer covering the upper surface of the bottom wall is in the range of 0.2 mm to 0.3 mm.

9. The composite crucible according to claim 1, characterized in that: It also includes a graphite crucible cover; the graphite crucible cover is used to be detachably connected to the upper edge of the side wall, and the graphite crucible cover can completely cover the upper edge of the side wall; the lower surface of the graphite crucible cover is used to be fixedly connected to the seed crystal.

10. A crystal growth device, characterized in that: Comprising a heating furnace and a composite crucible as claimed in any one of claims 1 to 9; The composite crucible is used to contain seed crystals and source powders; the heating furnace is used to heat the composite crucible so as to thermally sublimate the source powder inside the composite crucible and grow crystals on the seed crystals.

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