A method for preparing a low interfacial thermal resistance gallium nitride / diamond material

Abstract

The application belongs to the technical field of semiconductor preparation, and discloses a preparation method of a gallium nitride / diamond material with low interface thermal resistance. S1, a polycrystalline diamond film is prepared, and then cutting, grinding and polishing are performed on the polycrystalline diamond film; S2, after the gallium nitride wafer and the diamond film prepared in step S1 are cleaned respectively, a silver-copper-titanium alloy dielectric layer is plated on the nitrogen surface of the gallium nitride and the single surface of the diamond film by using a magnetron sputtering technology; S3, the silver-copper-titanium alloy dielectric layer of the gallium nitride and the diamond film obtained in step S2 is etched by ICP, and an etching layer is obtained; after the etching is completed, cleaning and vacuum drying are performed, and the etching layer is ready for use; S4, the etching layer of the gallium nitride and the diamond film obtained in step S3 is placed in a face-to-face stacking mode as a bonding sample, and then direct current arc plasma heating is performed, and a target product is obtained. By means of the dielectric layer design and the unique bonding heating mode, the bonding strength of the gallium nitride and the diamond can be greatly improved, and the interface thermal resistance can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor fabrication technology, specifically relating to a method for preparing gallium nitride / diamond materials with low interfacial thermal resistance. Background Technology

[0002] Gallium nitride (GaN), as a third-generation semiconductor material, possesses characteristics such as a large bandgap, high breakdown electric field strength, high saturation electron velocity, and strong radiation resistance, making it the optimal choice for future high-power electronic devices and high-frequency microwave devices. With the continuous development of advanced communication technologies, heat dissipation in GaN HEMT devices and microwave RF devices has become the biggest bottleneck restricting the further development and application of GaN device technology. Heat dissipation capability is mainly reflected in the substrate material of the device. Existing SiC or Si heat dissipation substrate materials, due to their low thermal conductivity, affect the efficiency and lifespan of GaN devices. Diamond, with the highest known thermal conductivity (2000 W / mK) in nature and stable physical and chemical properties, can effectively extract heat from the hottest locations in GaN transistors, effectively solving the heat dissipation problem for improving GaN device performance.

[0003] Currently, the fabrication of diamond-based gallium nitride (GaN) devices mainly falls into two categories: bonding-based technology and GaN epitaxial layer-based diamond growth technology. GaN epitaxial layer-based diamond growth technology refers to the method of directly growing diamond on the back side of a GaN epitaxial layer. Patent CN106783998A discloses a high electron mobility GaN transistor based on a diamond substrate and its fabrication method. A bonding material is coated on the front side of a temporary carrier. A silicon carbide-based GaN wafer and the temporary carrier are then heat-bonded with their front sides facing each other. The silicon carbide substrate of the GaN wafer is then removed, and a dielectric layer and a polycrystalline diamond heat dissipation layer are grown on the surface of the GaN epitaxial layer. The wafer is then separated from the temporary carrier, ultimately obtaining a high electron mobility diamond-based GaN transistor. This patent overcomes the challenges of epitaxial technology and can effectively control the epitaxial growth of diamond from GaN. Patent CN 11389411 A describes a method for preparing diamond-based GaN materials with a diamond micropillar array. It employs an alternating arrangement of diamond and the original silicon substrate, along with a micropillar array structure, reducing lattice misalignment and distortion, increasing the thermal conductivity area, and significantly improving heat dissipation efficiency. Patent CN 114899099 A discloses an epitaxial method for growing gallium nitride high electron mobility transistors on a diamond substrate. This method involves sequentially growing an aluminum nitride high-resistivity layer, a buffer layer, an insertion layer, and an aluminum gallium oxide barrier layer via MOCVD, combined with a novel silicon carbide composite buffer layer, followed by high-temperature annealing and recrystallization. This addresses the challenges of controlling the crystal orientation and high defect density of the gallium nitride epitaxial layer on a diamond substrate under large mismatch conditions, thereby improving the crystal quality and electrical performance of gallium nitride transistors on diamond substrates.

[0004] In the currently reported diamond growth technology based on gallium nitride epitaxial layers, although the problems of stability and heat dissipation of diamond grown on GaN surface have been solved, the problem of high interfacial thermal resistance between diamond and GaN still exists. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing gallium nitride / diamond materials with low interfacial thermal resistance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a gallium nitride / diamond material with low interfacial thermal resistance, comprising the following steps:

[0008] S1. Prepare a polycrystalline diamond film, then cut, grind, and polish it. The shape and size of the diamond film after cutting are consistent with those of the gallium nitride wafer.

[0009] S2. After cleaning the gallium nitride wafer and the diamond film prepared in step S1, a silver-copper-titanium alloy dielectric layer is deposited on the nitrogen side of the gallium nitride and the single side of the diamond film using magnetron sputtering technology.

[0010] S3, the silver-copper-titanium alloy dielectric layer of gallium nitride and diamond film obtained in step S2 by ICP etching is used to obtain the etched layer; after etching, it is cleaned and vacuum dried for later use.

[0011] S4. The etched layers of gallium nitride and diamond film obtained in step S3 are stacked face to face as bonding samples, and then heated by DC arc plasma to obtain the target product.

[0012] Preferably, in step S1, the polycrystalline diamond film can be prepared using any existing technology, including but not limited to microwave plasma chemical vapor deposition: deposition temperature 850-870℃, deposition rate 4-8 μm / h; and the surface roughness Ra of the diamond film after grinding and polishing is 2-3 nm.

[0013] Preferably, in step S2, during magnetron sputtering, diamond and gallium nitride are placed adjacent to each other on the substrate, the substrate temperature is 200-300 ℃, and three metal targets (silver, copper, and titanium) are sputtered simultaneously. The sputtering power of the silver target is set to 60-100 W, the sputtering power of the copper target is set to 30-60 W, the sputtering power of the titanium target is set to 20-40 W, the argon gas flux is 10-25 sccm, the chamber pressure is 0.5-0.7 Pa, and the sputtering time is 3-9 min.

[0014] Preferably, in step S2, the sputtering rate should be maintained at 2-4 nm / min, and the thickness of the silver-copper-titanium alloy dielectric layer should be controlled at 20-36 nm. After sputtering, the gallium nitride and diamond films should be placed in a vacuum dish for later use to avoid excessive contact with air.

[0015] Preferably, in step S3, the ICP etching conditions are: ICP etching power 600-800 W, RF power 30-50 W, etching chlorine content 10-20 sccm, argon content 8-12 sccm, and etching pressure 2-4 Pa.

[0016] Preferably, in step S4, the parameters for DC arc plasma heating are: heating temperature 880-920 ℃, power supply 20-25 KW, argon content 7.5-8.0 slm, chamber pressure (inner chamber pressure of DC arc plasma equipment) 3.1-3.5 kPa, pipe pressure (pressure in the pipe connecting the vacuum system and DC arc plasma equipment) 14.50-15.50 kPa, holding for 10-15 min, then reducing the power supply at a rate of 1-2 KW / 5 min to achieve cooling, and when the temperature drops to 500-600 ℃, turning off the power supply and stopping the argon gas supply, and cooling the furnace to room temperature.

[0017] Preferably, in step S4, the DC arc plasma increases the Lorentz stabilizing magnetic field, and the bonded sample increases the Lorentz extending magnetic field; when the power is turned off, both the Lorentz stabilizing magnetic field and the Lorentz extending magnetic field are simultaneously turned off. Both the Lorentz stabilizing magnetic field and the Lorentz extending magnetic field are Lorentz magnetic fields, but the Lorentz stabilizing magnetic field is used to stabilize the DC arc plasma, while the Lorentz extending magnetic field is used to extend the DC arc plasma.

[0018] Ideally, the ratio of the magnetic field strength of the Lorentz stable magnetic field to the Lorentz extended magnetic field is 1: (0.1-0.3).

[0019] To better ensure that gallium nitride and diamond are not ablated by plasma, in step S4, the bonded sample is placed in a molybdenum holder and covered with a molybdenum cap.

[0020] To ensure uniform heating of the sample, in step S4, a distance of 30-40 cm is maintained between the bottom of the DC arc plasma and the top of the bonded sample.

[0021] The key to the implementation of this invention lies in:

[0022] (1) Inductively coupled plasma (ICP) etching of silver-copper-titanium alloy dielectric layer. After ICP etching, an etching layer will be formed on the surface of diamond and gallium nitride dielectric layer. Before DC arc plasma heating, the etching layers of gallium nitride and diamond film are stacked face to face as bonding samples, and the etching microstructures on diamond and gallium nitride are as consistent as possible to reduce the uneven thickness of bonding layer caused by capillary effect at the top of dielectric layer.

[0023] (2) DC arc plasma heating can improve the uniformity of the bonding between gallium nitride and diamond without damaging the gallium nitride conductive layer and the diamond bonding surface, thus ensuring the bonding quality, improving the bonding strength between diamond and gallium nitride, and reducing the interface thermal resistance.

[0024] Beneficial effects:

[0025] (1) Diamond is the best heat sink material among heat dissipation materials, which can meet the heat dissipation requirements of semiconductor devices. This invention can greatly improve the bonding strength between gallium nitride and diamond and reduce the interface thermal resistance through dielectric layer design and unique bonding heating method.

[0026] (2) The gallium nitride / diamond prepared by the present invention can be used as a semiconductor device material, which solves the problems of poor heat dissipation and low thermal conductivity of gallium nitride itself. Attached Figure Description

[0027] Figure 1 : A schematic diagram of the preparation method of the present invention. Detailed Implementation

[0028] To make the present invention clearer and more explicit, the present invention will be further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0029] Example 1

[0030] A method for preparing a gallium nitride / diamond material with low interfacial thermal resistance, comprising the following steps:

[0031] (1) Preparation of polycrystalline diamond film by microwave plasma chemical vapor deposition: 2-inch single-crystal silicon was used as the deposition substrate material, and a heteroepitaxial CVD polycrystalline film was grown. The main deposition parameters included: deposition temperature 860 ℃, methane / hydrogen = 300 / 15 (flow ratio), power supply 3900 W, deposition rate 5 μm / h, and deposition time 500 h. Subsequently, hydrogen fluoride was used to remove the silicon substrate to obtain a 2.0 mm thick polycrystalline diamond film, such as... Figure 1As shown in (a); then the polycrystalline diamond film is cut (the shape and size of the diamond film after cutting are consistent with the gallium nitride wafer), ground, and polished (until the surface roughness Ra is 2 nm);

[0032] (2) After cleaning the gallium nitride and the diamond film prepared in step S1, a silver-copper-titanium alloy dielectric layer is deposited on the nitrogen side of the gallium nitride and the single side of the diamond film using magnetron sputtering technology: the gallium nitride and diamond are placed in a magnetron sputtering apparatus and the vacuum is evacuated to 2×10⁻⁶. -4 Below Pa, diamond and gallium nitride (GaN) films were placed adjacent to each other on a substrate at a substrate temperature of 200 °C. Three metal targets—silver, copper, and titanium—were sputtered simultaneously. The sputtering power was set to 80 W for the silver target, 40 W for the copper target, and 20 W for the titanium target. The argon gas flux was 10 sccm, the chamber pressure was 0.5 Pa, the sputtering rate was 3 nm / min, and the sputtering time was 9 min. After sputtering, the GaN and diamond film samples were promptly placed in a vacuum dish for later use to avoid excessive contact with air. Figure 1 As shown in (c) and (d);

[0033] (3) The silver-copper-titanium alloy dielectric layer on the diamond and gallium nitride surfaces was etched using inductively coupled plasma (ICP) etching. The dielectric layer was etched according to the ICP etching program: ICP power was 600 W, RF power was 30 W, chlorine content was 10 sccm, argon content was 8 sccm, etching pressure was 2 Pa, and AZ4620 photoresist was used. After etching, an etched layer was obtained, consisting of several uniformly arranged frustums. The shape and number of frustums on the diamond and gallium nitride etched layers were basically consistent. After cleaning the photoresist, the layers were transferred to a vacuum drying oven at 200 °C for later use. Figure 1 As shown in (e) and (f);

[0034] (4) The etched layers of gallium nitride and diamond films obtained in step S3 are stacked face-to-face as bonding samples in a molybdenum holder, covered with a molybdenum cap, and the frustums on the diamond and gallium nitride films are made to correspond as closely as possible. They are then bonded using DC arc plasma heating. Figure 1As shown in (g): A 30 cm distance is maintained between the bottom of the DC arc plasma and the top of the bonded sample. A Lorentz stabilizing magnetic field is added to the outer periphery of the DC arc plasma, and a Lorentz extending magnetic field is added to the outer periphery of the bonded sample. The heating temperature is 890 ℃, the power supply is 21 KW, the magnetic field strength ratio of the Lorentz stabilizing magnetic field to the Lorentz extending magnetic field is 1 / 0.2, the argon content is 7.5 slm, the chamber pressure is 3.1 kPa, the pipe pressure is 14.50 kPa, and the temperature is maintained for 10 min. Then, the power supply is reduced at a rate of 1 KW / 5 min to achieve cooling. When the temperature drops to 550 ℃, the power supply, the Lorentz stabilizing magnetic field and the Lorentz extending magnetic field are turned off, and the argon gas supply is stopped. The furnace is then cooled to room temperature to obtain gallium nitride / diamond semiconductor material, as shown in the figure. Figure 1 As shown in (i).

[0035] Example 2

[0036] A method for preparing a gallium nitride / diamond material with low interfacial thermal resistance, comprising the following steps:

[0037] (1) Preparation of polycrystalline diamond film by microwave plasma chemical vapor deposition: 2-inch single-crystal silicon was used as the deposition substrate material, and a CVD polycrystalline film was grown heteroepitaxially. The main deposition parameters included: deposition temperature 870 ℃, methane / hydrogen = 300 / 15 (flow ratio), power supply 3900 W, deposition rate 7 μm / h, and deposition time 400 h. Subsequently, hydrogen fluoride was used to remove the silicon substrate to obtain a 2.08 mm thick polycrystalline diamond film, such as... Figure 1 As shown in (a); then the polycrystalline diamond film is cut (the shape and size of the diamond film after cutting are consistent with the gallium nitride wafer), ground, and polished (until the surface roughness Ra is 3 nm);

[0038] (2) After cleaning the gallium nitride and the diamond film prepared in step S1, a silver-copper-titanium alloy dielectric layer is deposited on the nitrogen side of the gallium nitride and the single side of the diamond film using magnetron sputtering technology: the gallium nitride and diamond are placed in a magnetron sputtering apparatus and the vacuum is evacuated to 2×10⁻⁶. -4 Below Pa, diamond and gallium nitride (GaN) films were placed adjacent to each other on a substrate at a substrate temperature of 300 °C. Three metal targets—silver, copper, and titanium—were sputtered simultaneously. The sputtering power was set to 90 W for the silver target, 30 W for the copper target, and 30 W for the titanium target. The argon gas flux was 15 sccm, the chamber pressure was 0.6 Pa, the sputtering rate was 4 nm / min, and the sputtering time was 8 min. After sputtering, the GaN and diamond film samples were promptly placed in a vacuum dish for later use to avoid excessive contact with air. Figure 1 As shown in (c) and (d);

[0039] (3) The silver-copper-titanium alloy dielectric layer on the diamond and gallium nitride surfaces was etched using inductively coupled plasma (ICP) etching. The dielectric layer was etched according to the ICP etching program: ICP power was 700 W, RF power was 40 W, chlorine content was 15 sccm, argon content was 10 sccm, etching pressure was 3 Pa, and AZ4620 photoresist was used. After etching, an etched layer was obtained, consisting of several uniformly arranged frustums. The shape and number of frustums on the diamond and gallium nitride etched layers were basically consistent. After cleaning the photoresist, the layers were then transferred to a vacuum drying oven at 200 °C for later use. Figure 1 As shown in (e) and (f);

[0040] (4) The etched layers of gallium nitride and diamond films obtained in step S3 are stacked face-to-face as bonding samples in a molybdenum holder, covered with a molybdenum cap, and the frustums on the diamond and gallium nitride films are made to correspond as closely as possible. They are then bonded using DC arc plasma heating. Figure 1 As shown in (g): A 40 cm distance is maintained between the bottom of the DC arc plasma and the top of the bonded sample. A Lorentz stabilizing magnetic field is added to the outer periphery of the DC arc plasma, and a Lorentz extending magnetic field is added to the outer periphery of the bonded sample. The heating temperature is 900 ℃, the power supply is 22 KW, the magnetic field strength ratio of the Lorentz stabilizing magnetic field to the Lorentz extending magnetic field is 1 / 0.2, the argon content is 7.7 slm, the chamber pressure is 3.3 kPa, the pipe pressure is 14.70 kPa, and the temperature is maintained for 13 min. Then, the power supply is reduced at a rate of 1 KW / 5 min to achieve cooling. When the temperature drops to 600 ℃, the power supply, the Lorentz stabilizing magnetic field and the Lorentz extending magnetic field are turned off, and the argon gas supply is stopped. The furnace is then cooled to room temperature to obtain gallium nitride / diamond semiconductor material, as shown in the figure. Figure 1 As shown in (i).

Claims

1. A method for producing a low interfacial thermal resistance gallium nitride / diamond material, characterized by, The preparation steps are as follows: S1, prepare a polycrystalline diamond film, and then cut, grind and polish it, the shape and size of the diamond film after cutting are consistent with those of the gallium nitride wafer; S2, after the gallium nitride wafer and the diamond film prepared in step S1 are cleaned respectively, a silver-copper-titanium alloy dielectric layer is plated on a single side of the gallium nitride and a single side of the diamond film by using a magnetron sputtering technology; S3, ICP etching is performed on the silver-copper-titanium alloy dielectric layer of the gallium nitride and the diamond film obtained in step S2 to obtain an etching layer; after etching, cleaning and vacuum drying are performed for standby; S4, the etching layer of the gallium nitride and the diamond film obtained in step S3 is placed face to face as a bonding sample, and then direct current arc plasma heating is performed to obtain a target product; In step S2, the diamond and the gallium nitride are placed adjacent to each other on a substrate during magnetron sputtering, the substrate temperature is 200-300℃, the three metal targets of silver, copper and titanium are sputtered at the same time, the silver target sputtering target power is set to 60-100W, the copper target sputtering target power is set to 30-60W, the titanium target sputtering target power is set to 20-40W, the argon flux is 10-25sccm, the chamber pressure is 0.5-0.7Pa, and the sputtering time is 3-9min; In step S3, the ICP etching conditions are as follows: ICP etching power 600-800W, radio frequency power 30-50W, etching chlorine content 10-20sccm, argon content 8-12sccm, and etching pressure 2-4Pa.

2. The method of claim 1, wherein the low interfacial thermal resistance gallium nitride / diamond material is prepared by: In step S1, the polycrystalline diamond film is prepared by using a microwave plasma chemical vapor deposition method, the deposition temperature is 850-870℃, and the deposition rate is 4-8μm / h; after grinding and polishing, the surface roughness Ra of the diamond film is 2-3nm.

3. The method of claim 1, wherein the low interfacial thermal resistance gallium nitride / diamond material is prepared by the steps of: In step S2, the sputtering rate should be ensured to be 2-4nm / min, and the thickness of the silver-copper-titanium alloy dielectric layer is controlled to be 20-36nm; after sputtering, the gallium nitride and the diamond film are placed in a vacuum dish in time for standby. ​ 4. The method of claim 1, wherein the low interfacial thermal resistance gallium nitride / diamond material is prepared by the steps of: In step S4, the parameters of direct current arc plasma heating are as follows: heating temperature 880-920℃, power 20-25KW, argon content 7.5-8.0slm, chamber pressure 3.1-3.5kPa, pipeline pressure 14.50-15.50kPa, heat preservation time 10-15min, then the power is reduced at a speed of 1-2KW / 5min to achieve cooling, and when the temperature is cooled to 500-600℃, the power is turned off and the argon is stopped, and the furnace is cooled to room temperature. ​ 5. The method of claim 4, wherein the low interfacial thermal resistance gallium nitride / diamond material is prepared by: In step S4, the direct current arc plasma increases the Lorentz stable magnetic field, and the bonding sample increases the Lorentz extended magnetic field; when the power is turned off, the Lorentz stable magnetic field and the Lorentz extended magnetic field are also turned off.

6. The method of claim 5, wherein the low interfacial thermal resistance gallium nitride / diamond material is prepared by: The magnetic field intensity ratio of the Lorentz stable magnetic field to the Lorentz extended magnetic field is 1:(0.1-0.3).

7. The method of claim 1 or 4, wherein the low interfacial thermal resistance gallium nitride / diamond material is prepared by the steps of: In step S4, the bonding sample is placed in a molybdenum holder and covered with a molybdenum cover. ​ 8. The method of claim 1 or 4, wherein the low interfacial thermal resistance gallium nitride / diamond material is prepared by the steps of: In step S4, the distance between the bottom of the direct current arc plasma and the top of the bonding sample is kept at 30-40cm. ​

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