Single crystal diamond aln template for gan power electronic devices and method of making same

Abstract

The application provides a single-crystal diamond AlN template for GaN power electronic devices and a preparation method thereof, and comprises the following steps: S1, growing a single-crystal epitaxial layer of iridium on an A-plane sapphire; S2, growing a single-crystal epitaxial layer of first cubic boron nitride on the single-crystal epitaxial layer of iridium; S3, growing a diamond film on the single-crystal epitaxial layer of cubic boron nitride; S4, growing a single-crystal epitaxial layer of second cubic boron nitride on the diamond film; S5, growing a single-crystal epitaxial layer of hexagonal boron nitride on the single-crystal epitaxial layer of second cubic boron nitride; and S6, growing a hexagonal aluminum nitride layer on the single-crystal epitaxial layer of hexagonal boron nitride. The single-crystal diamond AlN template allows a high-quality GaN epitaxial layer to be directly grown on the top of the diamond AlN template without any additional bonding or transferring steps, thereby reducing the cost.

Description

Technical Field

[0001] This invention relates to a single-crystal diamond AlN template for GaN power electronic devices and its preparation method, belonging to the field of GaN power electronic device preparation technology. Background Technology

[0002] Gallium nitride (GaN) is an inorganic compound, a direct-bandgap semiconductor, commonly used in light-emitting diodes (LEDs) since 1990. This compound has a wurtzite-like structure and is very hard. GaN has a wide bandgap of 3.4 eV, making it suitable for high-power, high-speed optoelectronic devices. For example, GaN can be used in violet laser diodes to generate violet (405nm) laser light without the need for a nonlinear semiconductor-pumped solid-state laser. GaN power electronic devices have attracted widespread attention in recent years due to their high power and high speed capabilities; however, the large amount of heat generated during operation negatively impacts device performance.

[0003] Diamond, with its exceptional thermal conductivity, is considered a solution for dissipating heat from gallium nitride (GaN) power electronic devices. However, while existing technologies have developed bonding methods to combine GaN device layers with diamond layers, these techniques typically offer higher thermal boundary resistances than bulk growth, requiring additional bonding or transfer steps and increasing costs. Summary of the Invention

[0004] This invention provides a single-crystal diamond AlN template for GaN power electronic devices and its preparation method, which can effectively solve the above-mentioned problems.

[0005] This invention is implemented as follows:

[0006] A method for preparing a single-crystal diamond AlN template includes the following steps:

[0007] S1, Iridium single-crystal epitaxy is grown on sapphire in plane A;

[0008] S2, growing a first cubic boron nitride single-crystal epitaxial layer on an iridium single-crystal epitaxial layer;

[0009] S3, diamond film is grown on the single-crystal epitaxy of cubic boron nitride;

[0010] S4, single-crystal epitaxy of second cubic boron nitride grown on a diamond film;

[0011] S5, grow a hexagonal boron nitride single crystal epitaxial layer on the second cubic boron nitride single crystal epitaxial layer;

[0012] S6, a hexagonal aluminum nitride layer is grown on a hexagonal boron nitride single crystal epitaxial layer.

[0013] As a further improvement, the growth in step S1 is performed using an electron beam evaporation method or a sputtering method; the deposition conditions for the electron beam evaporation method are: substrate temperature of 800-1000℃ and vacuum degree <10-9 Torr; the sputtering method is to sputter iridium using a DC bias sputtering gun, and the deposition conditions are: vacuum degree <5mTorr, substrate temperature of 800-1000℃, and a negative substrate bias voltage of 50-300V applied.

[0014] As a further improvement, the growth in step S2 is carried out by sputtering, and the deposition conditions are: the substrate temperature is fixed at 600-800℃, and a negative substrate bias voltage of 50-300V is applied.

[0015] As a further improvement, the growth in step S3 adopts microwave plasma enhanced chemical vapor deposition, specifically: deposition is performed on a substrate preheated to 700°C in a mixed hydrogen methane atmosphere, and then deposition is performed at a deposition temperature of 800-1100°C without applying a substrate bias voltage.

[0016] As a further improvement, the growth in step S4 is carried out by sputtering, with a negative substrate bias voltage of 50-300V applied and the substrate temperature fixed at 600-800℃.

[0017] As a further improvement, the growth in step S5 is performed by sputtering, the substrate temperature is fixed at 1000°C, and no substrate bias voltage is applied.

[0018] As a further improvement, the growth in step S6 is performed using microwave plasma-enhanced chemical vapor deposition.

[0019] A single-crystal diamond AlN template prepared by the above method.

[0020] Application of the above-mentioned single-crystal diamond AlN template in GaN power electronic devices.

[0021] The beneficial effects of this invention are:

[0022] In the preparation of the single-crystal diamond AlN template of this invention, h-BN and c-BN layers are introduced between AlN and diamond, which facilitates a smooth transition of the crystal structure, thereby forming an ordered and continuous AlN epitaxial layer. The entire stack exhibits excellent adhesion and compatibility between different layers without disrupting the PVD vacuum, allowing for the direct growth of high-quality GaN epitaxial layers on top of the diamond AlN template without any additional bonding or transfer steps, thus reducing costs.

[0023] In the preparation of the single-crystal diamond AlN template in this invention, a diamond layer is used. The diamond layer has the highest thermal conductivity, which effectively releases the heat generated by gallium nitride power electronic devices and improves the performance of the devices.

[0024] In the preparation of the single-crystal diamond AlN template of the present invention, cubic boron nitride (c-BN) is introduced as a buffer layer on both the upper and lower surfaces of the diamond. The lattice constant of the c-BN layer is closer to that of diamond, which reduces the lattice mismatch between the substrate and the diamond layer, and between GaN and diamond. It can be used to produce large-area single-crystal diamonds with better quality and performance than traditional methods, and to develop high-quality gallium nitride epitaxy on large-area single-crystal diamonds, thereby improving the power of gallium nitride power electronic devices. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the growth of a single-crystal diamond AlN template provided in an embodiment of the present invention.

[0027] Figure 2 This is the X-ray diffraction pattern of the sample obtained in step S3 of Embodiment 1 of the present invention.

[0028] Figure 3 This is an atomic force microscope image of the sample obtained in step S3 of Embodiment 1 of the present invention.

[0029] Figure 4 This is a SEM image of the h-BN / c-BN / diamond / c-BN / Ir / A planar sapphire surface of the sample obtained in step S5 of Embodiment 1 of the present invention.

[0030] Figure 5 This is one of the XPS data graphs of the sample obtained in Example 1 of the present invention.

[0031] Figure 6 This is the second XPS data graph of the sample obtained in Example 1 of the present invention.

[0032] Figure 7 These are photographs (A), SEM images (B) taken from the center of the sample, and SEM images (C) taken from the edge of the sample, of the sample of Comparative Example 1 of this invention.

[0033] like Figure 8This is an X-ray diffraction (XRD) measurement pattern of the GaN / AlN / diamond heterostructure sample from Example 2 of this invention.

[0034] Figure 9 This is a transient region thermal reflectance (TDTR) measurement diagram of the sample in Embodiment 1 of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] like Figure 1 As shown, this invention provides a method for preparing a single-crystal diamond AlN template, comprising the following steps:

[0037] S1, growing a single crystal epitaxial layer of iridium (Ir) on A-plane sapphire;

[0038] S2, growing a first cubic boron nitride (c-BN) single crystal epitaxial layer on an iridium single crystal epitaxial layer;

[0039] S3, diamond film is grown on single-crystal epitaxy of cubic boron nitride (c-BN);

[0040] S4, Single-crystal epitaxy of second cubic boron nitride (c-BN) grown on a diamond film;

[0041] S5, grow a hexagonal boron nitride (h-BN) single crystal epitaxial layer on a second cubic boron nitride (c-BN) single crystal epitaxial layer;

[0042] S6, a hexagonal aluminum nitride (AlN) layer is grown on a hexagonal boron nitride single crystal (h-BN) epitaxial layer.

[0043] As a further improvement, the growth in step S1 is performed using electron beam evaporation or sputtering; the deposition conditions for the electron beam evaporation method are: substrate temperature of 800-1000℃ and vacuum degree <10. -9Torr; The sputtering method is to sputter iridium using a DC bias sputtering gun. The deposition conditions are: vacuum degree <5mTorr, substrate temperature 800-1000℃, and a negative substrate bias voltage of 50-300V, which helps to better form crystal nuclei on the sapphire substrate.

[0044] As a further improvement, the growth in step S2 is performed using sputtering. Since c-BN has a similar cubic crystal structure and lattice parameters, it can be grown on the iridium layer by sputtering deposition. A pure iridium target is used to grow c-BN, and a substrate bias voltage is applied. Applying a negative substrate bias voltage of 50-300V during deposition helps to form a cubic crystal structure, rather than hexagonal boron nitride. The substrate temperature is kept constant at 600-800℃ during deposition.

[0045] As a further improvement, the growth in step S3 employs microwave plasma-enhanced chemical vapor deposition (MPCVD). MPCVD involves deposition on a substrate preheated to 700°C in a mixed hydrogen-methane atmosphere, followed by deposition at a temperature of 800-1100°C. This method eliminates the need for a DC bias voltage on the substrate, producing large-area single-crystal diamond wafers with superior quality and performance compared to traditional methods, thus reducing production costs and complexity.

[0046] The lattice constants of iridium and diamond differ by 7.03%, with iridium having a lattice constant of [missing value]. The lattice constant of diamond is Because c-BN has The lattice constant of the c-BN layer is closer to that of diamond. Therefore, adding a c-BN intercalation layer as a buffer between the iridium and diamond layers can gradually match the lattice constant, reducing the lattice mismatch between the substrate and the diamond layer. Furthermore, a key issue with using iridium as the substrate in conventional methods is its higher coefficient of thermal expansion (CTE) compared to diamond, which can lead to structural defects and degrade the quality of the diamond film over time. In this embodiment, the CTE of c-BN is more similar to that of iridium than that of diamond, ensuring that the diamond film maintains its integrity and quality over time. This method provides a practical and effective way to produce large-area single-crystal diamond wafers with better quality and performance than conventional methods.

[0047] As a further improvement, the growth in step S4 is performed using sputtering. c-BN, due to its cubic crystal structure and similar lattice parameters, can be grown on the diamond layer via sputtering deposition. A pure boron target is used to grow c-BN on the diamond layer. During deposition, a negative substrate bias of 50-300V is used to form a cubic structure instead of hexagonal boron nitride. The substrate temperature is fixed at 600-800℃ during deposition.

[0048] As a further improvement, the growth in step S5 is performed by sputtering, the substrate temperature is fixed at 1000°C, and no substrate bias voltage is applied.

[0049] As a further improvement, the growth in step S6 employs microwave plasma-enhanced chemical vapor deposition. The microwave plasma-enhanced chemical vapor deposition method involves deposition on a substrate preheated to 700°C in a mixed hydrogen-methane atmosphere, followed by deposition at a deposition temperature of 800-1100°C, without the need to apply a DC bias voltage to the substrate.

[0050] The present invention also provides a single-crystal diamond AlN template prepared by the above method.

[0051] The present invention also provides an application of the above-mentioned single-crystal diamond AlN template in GaN power electronic devices.

[0052] Example 1

[0053] This invention provides a method for preparing a single-crystal diamond AlN template, comprising the following steps:

[0054] S1, Iridium single-crystal epitaxy is grown on sapphire in plane A; electron beam evaporation is used; deposition conditions are: substrate temperature 950℃, vacuum degree <10 -9 Torr.

[0055] S2, a first cubic boron nitride single crystal epitaxial layer is grown on an iridium single crystal epitaxial layer; the sputtering method is used, and the deposition conditions are: the substrate temperature is fixed at 800℃ and a negative substrate bias voltage of 200V is applied.

[0056] S3, diamond film is grown on a single crystal epitaxial layer of cubic boron nitride; microwave plasma enhanced chemical vapor deposition is used, specifically: deposition is performed on a substrate preheated to 700°C in a mixed hydrogen methane atmosphere, followed by deposition at a deposition temperature of 1100°C, without applying a substrate bias voltage.

[0057] S4, a second cubic boron nitride single crystal epitaxial growth is performed on a diamond film; a sputtering method is used, a negative substrate bias voltage of 150 is applied, and the substrate temperature is fixed at 600℃.

[0058] S5, a hexagonal boron nitride single crystal epitaxial layer is grown on the second cubic boron nitride single crystal epitaxial layer; the sputtering method is used, the substrate temperature is fixed at 1000℃, and no substrate bias voltage is applied.

[0059] S6, a hexagonal aluminum nitride layer is grown on a hexagonal boron nitride single crystal epitaxial layer using microwave plasma enhanced chemical vapor deposition. Specifically, deposition is performed on a substrate preheated to 700°C in a mixed hydrogen methane atmosphere, followed by deposition at a deposition temperature of 1100°C, without applying a substrate bias voltage.

[0060] Example 2

[0061] Based on Example 1, a GaN layer was grown on a hexagonal aluminum nitride layer, with other operations remaining the same as in Example 1. The GaN layer was grown using microwave plasma-enhanced chemical vapor deposition. Specifically, deposition was performed on a substrate preheated to 700°C in a mixed hydrogen methane atmosphere, followed by deposition at a deposition temperature of 1100°C, without applying a substrate bias voltage.

[0062] Comparative Example 1

[0063] The difference from Example 1 is that steps S4 and S5 are omitted, while the other operations are the same as in Example 1.

[0064] The performance tests of the samples in Examples 1-2 and Comparative Example 1 are as follows: Figures 2 to 9 As shown.

[0065] like Figure 2 As shown, Figure 2 This is an X-ray diffraction (XRD) pattern of the sample obtained in step S3 of Embodiment 1 of the present invention, showing the crystallization peaks of the materials used to produce large-area single-crystal diamond wafers, including sapphire (1120), Ir (002), c-BN (200), and Ir (111). The position, intensity, and shape of each peak provide important information about the crystal structure and orientation of each material, which is crucial for determining the optimal growth conditions for the diamond layer and ensuring good alignment of the crystal structure of the diamond layer with the underlying substrate and buffer layer. A peak for sapphire (1120) was observed at 37.5 degrees, a peak for Ir (002) at 47.5 degrees, a peak for c-BN (200) at 43 degrees, and a peak for iridium (111) at 41.6 degrees. The presence of distinct peaks for each material indicates that the crystal structure of each layer is well aligned with the underlying layer, suggesting that the c-BN / Ir / sapphire structure can be successfully grown and used as a substrate for producing large-area single-crystal diamond wafers. In summary, the XRD data support the effectiveness of the method proposed in this invention, providing valuable information for optimizing the growth process and ensuring the quality and performance of the final diamond product.

[0066] like Figure 3The image shown is an atomic force microscopy (AFM) image of the sample obtained in step S3 of Embodiment 1 of this invention. The data in this image provides important information about the surface morphology and roughness of the cBN / Ir / sapphire structure used as a substrate for producing large-area single-crystal diamond wafers. The AFM data shows well-defined step flows on the surface of the cBN / Ir / sapphire structure, following a 7-degree cut of the A-plane sapphire substrate. Furthermore, the average surface roughness measured by AFM is 0.815 nm. These characteristics are important parameters for producing large-area single-crystal diamond wafers because they affect the quality and performance of the diamond layer. A smooth and uniform substrate surface is ideal because it minimizes defects and dislocations in the diamond layer, resulting in a higher quality and more reliable final product. The AFM data, including step flow and surface roughness measurements, supports the effectiveness of the method proposed in this invention and provides valuable information for optimizing the growth process and ensuring the quality and performance of the final diamond product.

[0067] like Figure 4 As shown, the SEM image of the h-BN / c-BN / diamond / c-BN / Ir / A planar sapphire surface of the sample obtained in step S5 of Embodiment 1 of this invention shows a smooth and uniform surface morphology without visible cracks or defects. This image confirms that the growth of each layer in the stack was successful and that the obtained surface is suitable for further growth of high-quality AlN epitaxial layers. A smooth surface is crucial for achieving good adhesion and crystal quality of subsequent layers, which is essential for the performance of the final device.

[0068] like Figure 5 The figure shown is one of the XPS data graphs of the sample obtained in Example 1 of this invention. This graph demonstrates the confirmed successful deposition of boron and nitride materials obtained from the AlN / h-BN / c-BN stack. The presence of the Al peak in the XPS spectrum also indicates the deposition of the aluminum nitride layer. The fact that the entire stack was grown monolithically without disrupting the PVD vacuum demonstrates the excellent adhesion and compatibility of the different layers in the stack. This is a significant achievement because it allows for the direct growth of high-quality GaN epitaxial layers on top of the AlN / h-BN / c-BN stack without any additional bonding or transfer steps. The XPS data confirms that the successful deposition of various layers is a key step in realizing high-performance GaN-based power electronic devices.

[0069] like Figure 6The image shown is a second XRD data plot obtained from the sample of Example 1 of this invention. The XRD data plot of the AlN / h-BN / c-BN / diamond / c-BN / Ir / A planar sapphire sample confirms the successful growth of AlN on diamond. A sharp and strong AlN (002) peak appears at approximately 35 degrees, and a clear diamond (111) peak appears at approximately 42 degrees, clearly indicating that the AlN layer is epitaxially grown on the diamond substrate with high crystallinity. This is attributed to the introduction of h-BN and c-BN layers between AlN and diamond, which facilitates a smooth transition of the crystal structure, resulting in an ordered and continuous AlN epitaxial layer. The observation of Al, B, and N peaks in the XPS data further confirms the successful growth of AlN on the diamond / c-BN / Ir / A planar sapphire without disrupting the PVD vacuum, thus forming a monolithic structure. These results demonstrate the effectiveness of the novel method proposed in this invention, which allows for the growth of high-quality AlN epitaxy on diamond substrates for various applications in the field of power electronics.

[0070] like Figure 7 The image shown is a photograph (A), a SEM image (B) taken from the center of the sample, and a SEM image (C) taken from the edge of the sample, representing Comparative Example 1 of this invention. Figure 7 The photograph of the AlN template sample shows a circular wafer with a smooth surface and uniform color. SEM image taken from the center of the sample (…). Figure 7 B) shows a highly uniform and smooth surface, without obvious pinholes or defects, indicating a high-quality AlN template layer. In contrast, SEM images taken from the sample edge ( Figure 7 C) exhibits an amorphous morphology, which may be due to the lack of an h-BN / c-BN layer. During growth, the edges were blocked by the sample holder, preventing the deposition of the h-BN / c-BN layer and resulting in a lower-quality morphology.

[0071] like Figure 8 The image shows an X-ray diffraction (XRD) measurement pattern of the GaN / AlN / diamond heterostructure sample from Example 2 of this invention. The XRD data reveals clear and sharp peaks corresponding to the (002) planes of GaN and AlN, and the (111) plane of diamond. The presence of these peaks confirms the successful growth of high-quality GaN and AlN epitaxial layers on a diamond substrate. Furthermore, the sharp peaks in the diamond (111) plane indicate the high crystallinity and orientation of the diamond layer. These results demonstrate the effectiveness of the method described in this embodiment for growing high-quality GaN and AlN layers on a diamond substrate.

[0072] like Figure 9The image shown is a transient region thermal reflectance (TDTR) measurement graph of the sample from Example 1 of this invention. The TDTR method is a non-destructive technique that can accurately measure the thermal conductivity of thin films at high resolution. TDTR measurements show that the thermal conductivity of the diamond layer in Example 1 is 2265 W / (mK), significantly higher than that of other materials used in power electronics. This high thermal conductivity of the diamond layer in Example 1 makes it an excellent material for dissipating the heat generated by GaN power electrons.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a single-crystal diamond AlN template, characterized in that, Includes the following steps: S1, Iridium single-crystal epitaxy is grown on sapphire in plane A; the growth is performed using electron beam evaporation, and the deposition conditions for electron beam evaporation are: substrate temperature 800-1000℃, vacuum degree <10 -9 Torr; S2, a first cubic boron nitride single crystal epitaxial layer is grown on an iridium single crystal epitaxial layer; the growth is carried out by sputtering, and the deposition conditions are: the substrate temperature is fixed at 600-800 ℃, and a negative substrate bias voltage of 50-300 V is applied. S3, a diamond film is grown on a cubic boron nitride single crystal epitaxial layer; the growth is carried out by microwave plasma enhanced chemical vapor deposition, specifically: in a mixed hydrogen methane atmosphere, deposition is carried out on a substrate preheated to 700 °C, and then deposition is carried out at a deposition temperature of 800-1100 °C, without applying a substrate bias voltage. S4, a second cubic boron nitride single crystal epitaxial growth is performed on a diamond film; the growth is performed by sputtering, with a negative substrate bias voltage of 50-300V applied and the substrate temperature fixed at 600-800℃. S5, a hexagonal boron nitride single crystal epitaxial layer is grown on the second cubic boron nitride single crystal epitaxial layer; the growth is carried out by sputtering, the substrate temperature is fixed at 1000℃, and no substrate bias voltage is applied. S6, a hexagonal aluminum nitride layer is grown on a hexagonal boron nitride single crystal epitaxial layer using microwave plasma-enhanced chemical vapor deposition.

2. A single-crystal diamond AlN template prepared by the method of claim 1.

3. The application of the single-crystal diamond AlN template as described in claim 2 in GaN power electronic devices.

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