A gallium nitride-diamond hetero-crystalline wafer and a preparation method thereof

Abstract

The present invention provides a gallium nitride-diamond hetero-crystalline wafer and a preparation method thereof. The crystalline wafer includes a diamond substrate, a tungsten disulfide thin film layer, and a gallium nitride epitaxial layer. The gallium nitride epitaxial layer includes an AlGaN buffer layer and a GaN functional layer. The AlGaN buffer layer is terminated with N atoms on the side close to the tungsten disulfide thin film layer. The present invention uses a tungsten disulfide (WS2) thin film as a lattice-matched nucleation layer, effectively solving the lattice mismatch problem between gallium nitride and the diamond substrate, reducing the thickness of the AlGaN buffer layer, and thus greatly reducing the thermal resistance between the GaN functional layer and the diamond substrate. This method can achieve mass production of large-size gallium nitride-diamond hetero-crystalline wafers, providing a material basis for high-power and high-density gallium nitride radio frequency devices.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor hetero-wafers, and particularly to a gallium nitride-diamond hetero-crystalline wafer and a preparation method thereof. Background Art

[0002] Gallium nitride (GaN), as a third-generation wide-bandgap semiconductor material, has excellent properties such as a large bandgap width, high thermal conductivity, high electron saturation drift velocity, and easy formation of hetero-structures. It is very suitable for developing high-frequency, high-power microwave, and millimeter-wave devices and circuits, and is the most ideal semiconductor material for developing microwave power devices in the past 20-odd years. With the continuous improvement of the crystal quality of epitaxial materials and the continuous improvement of device processes, the operating frequencies of microwave and millimeter-wave devices and circuits developed based on GaN-based materials are getting higher and higher, and the output power is getting larger and larger. However, with the development of GaN-based microwave power devices towards smaller sizes, larger output powers, and higher frequencies, the problem of "heat" has become increasingly prominent and has gradually become one of the most important problems restricting the improvement of the performance of such devices. Using diamond with high thermal conductivity as the substrate for high-frequency and high-power GaN-based devices can quickly diffuse the heat generated by the GaN device layer to the substrate layer and then to the package heat sink through the substrate layer, thus solving the problem of the rapid decline of power density with the increase of total power and frequency. The Defense Advanced Research Projects Agency of the United States found that GaN on diamond substrates can transmit power density at a lower channel temperature and is three times the efficiency of GaN radio frequency amplifiers on SiC substrates. Using diamond as the substrate material can increase the thermal conductivity of the device by 3-5 times, thus significantly reducing the cost, size, and power consumption of the device.

[0003] Currently, a variety of methods for preparing gallium nitride-diamond heterojunctions have been disclosed. US2006 / 0266280 discloses a method for integrating a wide-bandgap semiconductor material with a diamond substrate. In this method, a thick diamond film is epitaxially grown on the nucleation layer of the wide-bandgap material (such as gallium nitride) to form a heterojunction. CN110838438A discloses a method for integrating diamond and gallium nitride. In this method, the buffer layer of gallium nitride is directly thermally bonded to diamond to form a gallium nitride-diamond hetero-crystalline wafer. Adv. Mater. 2021, 2104564 discloses a method for binding gallium nitride and diamond at room temperature using a surface activation process. CN110690105A discloses a method for growing gallium nitride on a diamond substrate based on hexagonal boron nitride and aluminum nitride. In this method, a boron nitride transition layer is epitaxially grown on the diamond substrate. After patterning the boron nitride, aluminum nitride and gallium nitride are epitaxially grown to form a gallium nitride-diamond wafer.

[0004] For a gallium nitride-diamond hetero-crystalline wafer, reducing the thickness of the gallium nitride-diamond interface layer is the key to improving the vertical thermal conductivity. However, in the above methods, whether growing gallium nitride epitaxially on a diamond substrate or growing diamond epitaxially on a gallium nitride substrate, due to the problems of lattice mismatch and stress, a relatively thick lattice-matching layer and a relatively thick stress buffer layer are required between diamond and gallium nitride, which greatly affects the thermal conductivity between gallium nitride and diamond. While using the method of directly bonding gallium nitride and diamond, although the interface layer can currently be thinned to 1.5 nm, limited by the bonding process, only millimeter-sized fragmented samples can be made at present, and large-area wafer fabrication cannot be achieved. Summary of the Invention

[0005] To solve the above problems, the present invention proposes a gallium nitride-diamond hetero-crystalline wafer and its preparation method. By using a thin interface layer, the problem of lattice mismatch between gallium nitride and diamond substrates is effectively solved, and the thermal resistance between the gallium nitride epitaxial layer and the diamond substrate can be greatly reduced, providing a material basis for high-power and high-density gallium nitride radio frequency devices.

[0006] For this purpose, the present invention adopts the following technical solutions:

[0007] A gallium nitride-diamond hetero-crystalline wafer, as Figure 1 shown, the crystalline wafer includes a diamond substrate 1, a tungsten disulfide thin film layer 2, and a gallium nitride epitaxial layer 3; the gallium nitride epitaxial layer 3 includes an AlGaN buffer layer 31 and a GaN functional layer 32; the AlGaN buffer layer 31 is terminated by N atoms on the side close to the tungsten disulfide thin film layer.

[0008] Among them, the thickness of the tungsten disulfide thin film layer is 0.66 nm.

[0009] Among them, the diamond substrate is a single crystal or polycrystal of diamond, and its thickness is 0.1 - 1 mm.

[0010] Among them, the total thickness of the gallium nitride epitaxial layer is 100 - 1000 nm; the thickness of the AlGaN buffer layer is 10 - 100 nm; the thickness of the GaN functional layer is 900 - 990 nm.

[0011] The present invention also proposes a preparation method of a gallium nitride-diamond hetero-crystalline wafer, as Figure 2 shown, including the following steps:

[0012] 1) Polish and clean the diamond substrate until the surface average roughness is less than 1 nm;

[0013] 2) Grow a tungsten disulfide thin film layer with a certain thickness on the diamond substrate by chemical vapor deposition to obtain a diamond substrate / tungsten disulfide thin film layer structure;

[0014] 3) Place the diamond substrate / tungsten disulfide thin film layer structure in a metalorganic chemical vapor deposition equipment, and perform nitridation treatment on the surface of the tungsten disulfide thin film layer;

[0015] 4) Grow an AlGaN thin film layer at a low temperature on the surface of the tungsten disulfide thin film layer after nitridation treatment by metalorganic chemical vapor deposition method, and then grow a GaN functional layer at a high temperature on the AlGaN thin film layer to obtain a diamond substrate / tungsten disulfide thin film layer / gallium nitride epitaxial layer structure, that is, a gallium nitride-diamond heteroepitaxial wafer.

[0016] Among them, in the step 2), WO3 powder is used as the tungsten source, sulfur powder is used as the sulfur source, and a mixed gas of argon and hydrogen is used as the carrier gas to synthesize the tungsten disulfide thin film layer by chemical vapor deposition method; the heating temperature of the WO3 powder is 900-1100 °C, the heating temperature of the sulfur powder is 190-210 °C; the gas flow ratio of argon to hydrogen is 5:1; the temperature of the diamond substrate is 600-1000 °C; the thickness of the grown tungsten disulfide thin film layer is 0.66 nm.

[0017] Among them, in the step 3), NH3 is used to perform nitridation treatment on the surface of the tungsten disulfide thin film layer, the flow rate of NH3 is 800-1200 sccm, the air pressure is 600-800 Torr, and the treatment time is 5-10 min; the temperature of the diamond substrate is maintained at 600-700 °C.

[0018] Among them, in the step 4), trimethylgallium (TMGa) is used as the gallium source, trimethylaluminum (TMAl) is used as the aluminum source, and NH3 is used as the nitrogen source to grow a gallium nitride epitaxial layer on the surface of the tungsten disulfide thin film layer by metalorganic chemical vapor deposition method.

[0019] Among them, when growing the AlGaN thin film layer at a low temperature, the gas flow ratio of TMGa, TMAl and NH3 is kept at 1:3:900, the growth air pressure is 250-350 Torr, and the temperature of the diamond substrate is maintained at 600-700 °C

[0020] Among them, when growing the GaN functional layer at a high temperature, the gas flow ratio of TMGa and NH3 is kept at 1:100, the growth air pressure is 50-150 Torr, and the temperature of the diamond substrate is maintained at 1200-1400 °C.

[0021] Among them, the chemical vapor deposition equipment and the metalorganic chemical vapor deposition equipment are connected through a glove box, and the glove box is filled with argon or nitrogen; the diamond / tungsten disulfide thin film layer structure prepared by chemical vapor deposition is transferred to the metalorganic chemical vapor deposition equipment through the glove box, so as to avoid surface contamination caused by exposure to air.

[0022] The present invention provides a gallium nitride-diamond hetero-crystalline wafer and a preparation method thereof. A tungsten disulfide (WS2) thin film layer is used as a lattice-matched nucleation layer. Since the S atoms in WS2 can form van der Waals bonds and covalent bonds with metal atoms simultaneously, nitridation treatment is carried out on the surface of the tungsten disulfide thin film layer, and an AlGaN thin film layer is grown at a low temperature, so that the AlGaN buffer layer is terminated by N atoms on the side close to the tungsten disulfide thin film layer, which can ensure that the S atoms in WS2 and the N atoms in the AlGaN buffer layer form closer atomic bonds, can fully guide the lattice orientation of the GaN thin film growth, effectively solve the problems of lattice mismatch and stress between gallium nitride and the diamond substrate, and can greatly reduce the thermal resistance between the gallium nitride epitaxial layer and the diamond substrate; at the same time, by adopting the above preparation method, the crystal structure stability of the diamond substrate can be ensured, the production of large-area wafers can be realized, and a material basis is provided for high-power and high-density gallium nitride radio frequency devices. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of a gallium nitride-diamond hetero-crystalline wafer of the present invention.

[0024] Figure 2 It is a schematic flow diagram of a preparation method of a gallium nitride-diamond hetero-crystalline wafer of the present invention. Detailed Embodiments

[0025] In order to make the objectives, features, and advantages of the present invention clearer, the following further describes the specific embodiments of the present invention in more detail with reference to the accompanying drawings and embodiments. In the following description, many specific details are set forth to fully understand the present invention, but the present invention can be implemented in many other ways different from those described. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0026] Specific implementation of a gallium nitride-diamond hetero-crystalline wafer and a preparation method thereof according to the present invention is described as follows:

[0027] A gallium nitride-diamond hetero-crystalline wafer, as Figure 1 shown, the wafer includes a diamond substrate 1, a tungsten disulfide thin film layer 2, and a gallium nitride epitaxial layer 3; the gallium nitride epitaxial layer 3 includes an AlGaN buffer layer 31 and a GaN functional layer 32; the AlGaN buffer layer 31 is terminated by N atoms on the side close to the tungsten disulfide thin film layer.

[0028] Among them, the thickness of the tungsten disulfide thin film layer is 0.66 nm.

[0029] Among them, the diamond substrate is a diamond single crystal or polycrystal, and its thickness is 0.5 mm.

[0030] Among them, the total thickness of the gallium nitride epitaxial layer is 500 nm; the thickness of the AlGaN buffer layer is 50 nm; the thickness of the GaN functional layer is 950 nm.

[0031] The present invention also provides a method for preparing a gallium nitride-diamond hetero-crystalline wafer, as Figure 2 shown, comprising the following steps:

[0032] 1) Polish and clean the diamond substrate until the surface average roughness is less than 1 nm;

[0033] 2) Grow a tungsten disulfide thin film layer with a certain thickness on the diamond substrate by chemical vapor deposition to obtain a diamond substrate / tungsten disulfide thin film layer structure;

[0034] 3) Place the diamond substrate / tungsten disulfide thin film layer structure in an organometallic chemical vapor deposition equipment to nitride the surface of the tungsten disulfide thin film layer;

[0035] 4) Grow an AlGaN thin film layer at a low temperature on the surface of the nitrided tungsten disulfide thin film layer by organometallic chemical vapor deposition, and then grow a GaN functional layer at a high temperature on the AlGaN thin film layer to obtain a diamond substrate / tungsten disulfide thin film layer / gallium nitride epitaxial layer structure, that is, a gallium nitride-diamond hetero-crystalline wafer.

[0036] Among them, in the step 2), WO3 powder is used as the tungsten source, sulfur powder is used as the sulfur source, and a mixed gas of argon and hydrogen is used as the carrier gas to synthesize the tungsten disulfide thin film layer by chemical vapor deposition; the heating temperature of the WO3 powder is 1000 °C, the heating temperature of the sulfur powder is 200 °C; the gas flow ratio of argon to hydrogen is 5:1; the temperature of the diamond substrate is 800 °C; the thickness of the grown tungsten disulfide thin film layer is 0.65 nm.

[0037] Among them, in the step 3), NH3 is used to nitride the surface of the tungsten disulfide thin film layer, the flow rate of NH3 is 1000 sccm, the air pressure is 700 Torr, and the treatment time is 8 min; the temperature of the diamond substrate is maintained at 650 °C.

[0038] Among them, in the step 4), trimethylgallium (TMGa) is used as the gallium source, trimethylaluminum (TMAl) is used as the aluminum source, and NH3 is used as the nitrogen source to grow a gallium nitride epitaxial layer on the surface of the tungsten disulfide thin film layer by organometallic chemical vapor deposition.

[0039] Among them, when growing the AlGaN thin film layer at a low temperature, the gas flow ratio of TMGa, TMAl and NH3 is maintained at 1:3:900, the growth air pressure is 300 Torr, and the temperature of the diamond substrate is maintained at 650 °C

[0040] When growing the GaN functional layer at high temperature, the flow rate ratio of TMGa and NH3 gases is maintained at 1:100, the growth pressure is 100 Torr, and the temperature of the diamond substrate is maintained at 1300 °C.

[0041] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A gallium nitride-diamond hetero-crystalline wafer, characterized in that, The heterogeneous crystalline wafer includes a diamond substrate, a tungsten disulfide thin film layer, and a gallium nitride epitaxial layer; the gallium nitride epitaxial layer includes an AlGaN buffer layer and a GaN functional layer; nitridation treatment is performed on the surface of the tungsten disulfide thin film layer, and the AlGaN buffer layer is N-atom terminated on the side close to the tungsten disulfide thin film layer; The S atoms of the tungsten disulfide thin film layer and the N atoms in the AlGaN buffer layer form atomic bonds, and can simultaneously form van der Waals bonds and covalent bonds of metal atoms; Using WO3 powder as the tungsten source, sulfur powder as the sulfur source, and a mixed gas of argon and hydrogen as the carrier gas, a tungsten disulfide thin film layer is synthesized by chemical vapor deposition; the heating temperature of the WO3 powder is 900-1100 °C, the heating temperature of the sulfur powder is 190-210 °C; the gas flow ratio of argon to hydrogen is 5:1; the temperature of the diamond substrate is 600-1000 °C; the thickness of the tungsten disulfide thin film layer is 0.66 nm; NH3 is used to perform nitridation treatment on the surface of the tungsten disulfide thin film layer, the flow rate of NH3 is 800-1200 sccm, the air pressure is 600-800 Torr, and the treatment time is 5-10 min; the temperature of the diamond substrate is maintained at 600-700 °C.

2. The gallium nitride-diamond heterogeneous crystal wafer according to claim 1, wherein The diamond substrate is a diamond single crystal or polycrystal, and its thickness is 0.1-1 mm.

3. The gallium nitride-diamond heterogeneous crystal wafer according to claim 1, characterized in that The total thickness of the gallium nitride epitaxial layer is 100-1000 nm; the thickness of the AlGaN buffer layer is 10-100 nm; the thickness of the GaN functional layer is 900-990 nm.

4. A method for preparing a gallium nitride-diamond hetero-crystalline wafer, characterized in that, It includes the following steps: 1) Polish and clean the diamond substrate until the surface average roughness is less than 1 nm; 2) Grow a tungsten disulfide thin film layer with a thickness of 0.66 nm on the diamond substrate by chemical vapor deposition to obtain a diamond substrate / tungsten disulfide thin film layer structure; 3) Place the diamond substrate / tungsten disulfide thin film layer structure in an organometallic chemical vapor deposition equipment to perform nitridation treatment on the surface of the tungsten disulfide thin film layer; 4) Grow an AlGaN thin film layer at a low temperature on the surface of the tungsten disulfide thin film layer after nitridation treatment by organometallic chemical vapor deposition, and then grow a GaN functional layer at a high temperature on the AlGaN thin film layer to obtain a diamond substrate / tungsten disulfide thin film layer / gallium nitride epitaxial layer structure, that is, a gallium nitride-diamond heterogeneous crystalline wafer.

5. The preparation method of a gallium nitride-diamond hetero-crystalline wafer according to claim 4, wherein, In step 2), WO3 powder is used as the tungsten source, sulfur powder is used as the sulfur source, and a mixed gas of argon and hydrogen is used as the carrier gas, and a tungsten disulfide thin film layer is synthesized by chemical vapor deposition; the heating temperature of the WO3 powder is 900-1100 °C, the heating temperature of the sulfur powder is 190-210 °C; the gas flow ratio of argon to hydrogen is 5:1; the temperature of the diamond substrate is 600-1000 °C; the thickness of the grown tungsten disulfide thin film layer is 0.66 nm.

6. The preparation method of a gallium nitride-diamond hetero-crystalline wafer according to claim 4, wherein In step 3), the surface of the tungsten disulfide thin film layer is nitrided with NH3. The flow rate of NH3 is 800-1200 sccm, the gas pressure is 600-800 Torr, and the treatment time is 5-10 min. The temperature of the diamond substrate is maintained at 600-700 °C.

7. The preparation method of a gallium nitride-diamond hetero-crystalline wafer according to claim 4, characterized in that, In step 4), TMGa is used as the gallium source, TMAl is used as the aluminum source, and NH3 is used as the nitrogen source. A gallium nitride epitaxial layer is grown on the surface of the tungsten disulfide thin film layer by metalorganic chemical vapor deposition.

8. The preparation method of a gallium nitride-diamond hetero-crystalline wafer according to claim 4 or 7, characterized in that, When growing the low-temperature AlGaN thin film layer, the gas flow rate ratio of TMGa, TMAl, and NH3 is maintained at 1:3:900, and the growth gas pressure is 250-350 Torr. The temperature of the diamond substrate is maintained at 600-700 °C.

9. The preparation method of a gallium nitride-diamond hetero-crystalline wafer according to claim 4 or 7, characterized in that, When growing the high-temperature GaN functional layer, the gas flow rate ratio of TMGa and NH3 is maintained at 1:100, and the growth gas pressure is 50-150 Torr. The temperature of the diamond substrate is maintained at 1200-1400 °C.

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