Method for surface direct metallization of diamond using platinum group metals and enhancing the bonding strength with non-wetting metals

Abstract

The application discloses a method for directly metallizing diamond surface by using platinum group metal and enhancing the bonding strength with non-wetting metal, and aims to solve the problems of poor adhesion and easy falling of non-wetting metal on diamond, and the need of subsequent annealing and other complicated steps for commonly used intermediate layers such as titanium and tungsten. The method for enhancing the bonding strength with non-wetting metal comprises the following steps: firstly, polishing a diamond sheet and then boiling the diamond sheet in aqua regia; secondly, placing the pretreated diamond sheet into an oxidizing acid solution and boiling the diamond sheet; thirdly, depositing or plating a platinum group metal layer on the diamond sheet by using a vacuum physical vapor deposition process or a wet plating process; and fourthly, depositing or plating a non-wetting metal layer on the surface of the metallized diamond sheet. The platinum group metal has the tendency of diffusing with diamond to form a dense solid solution, so that the surface metallization of the diamond can be directly completed by deposition, and the prepared diamond-platinum group metal structure has high bonding strength, low resistance and low thermal resistance.

Description

Technical Field

[0001] This invention belongs to the field of diamond metallization technology, specifically relating to a method for directly metallizing the surface of diamond using platinum group metals and enhancing the bonding strength with non-wetting metals. Background Technology

[0002] Diamond, as a representative third-generation semiconductor material, is increasingly widely used in high-power electronic devices. On the one hand, diamond's ultra-wide bandgap and high breakdown voltage make it suitable for developing power devices and high-energy detectors; on the other hand, the high heat flux of high-power electronic devices requires diamond, which has ultra-high thermal conductivity, to be used as a heat dissipation material.

[0003] In the fields of electronic devices and high-end thermal management, gold, silver, copper, and aluminum are often used as metal materials that come into direct contact with diamond. However, as non-wetting metals, gold, silver, copper, and aluminum have van der Waals contact with diamond, making it difficult for them to interpenetrate or bond with diamond. This results in poor adhesion and can easily lead to fatal problems such as interface detachment. To increase adhesion, diamond is usually metallized. Common diamond metallization methods in the industry typically use carbide-forming metals such as titanium or tungsten as an intermediate layer between the non-wetting metal and diamond, followed by high-temperature annealing to form titanium or tungsten carbides at the interface, thus enabling covalent bonding between diamond and the metal. However, the titanium carbide structure formed by titanium plating and annealing diamond is porous, which actually reduces adhesion. Furthermore, tungsten has poor adhesion to gold, and gold easily detaches from the tungsten.

[0004] Platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum), as transition metals, possess an incomplete d-shell electron configuration, resulting in high reactivity with carbon. They form a covalent contact with diamond and exhibit good miscibility with carbon at room temperature, readily forming solid solutions. Under high temperature and pressure, they can form carbides, and are generally used as heteroepitaxial substrates for diamond. Furthermore, platinum group metals widely exhibit isomorphic substitution among themselves, showing high miscibility with non-diamond-wetting metals such as gold, silver, copper, and aluminum. They also possess high chemical stability, excellent corrosion and oxidation resistance, and a long service life. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of poor adhesion and easy detachment of non-wetting metals (gold, silver, copper, aluminum, etc.) on diamond, and the need for cumbersome steps such as subsequent annealing for commonly used intermediate layers such as titanium and tungsten. Therefore, this invention provides a method for directly metallizing the surface of diamond using platinum group metals and enhancing the bonding strength with non-wetting metals.

[0006] The present invention utilizes platinum group metals to directly metallize the surface of diamond and enhance the bonding strength with non-wetting metals, and is implemented according to the following steps:

[0007] 1. Polish the diamond sheet, then boil it in aqua regia to remove residual impurities on the diamond surface, thus obtaining a pretreated diamond sheet.

[0008] 2. The pretreated diamond sheet is placed in an oxidizing acid solution, which is a mixture of concentrated sulfuric acid and concentrated nitric acid. It is boiled at 300-370°C for 1.5-2.5 hours. Then, it is ultrasonically cleaned with deionized water, acetone and alcohol in sequence to obtain a diamond sheet with ketone oxygen terminals.

[0009] 3. A platinum group metal layer with a thickness of 5-100 nm is deposited or coated on the surface of a diamond sheet with ketone oxygen terminals using vacuum physical vapor deposition or wet plating process to obtain a metallized diamond sheet.

[0010] IV. A non-wetting metal layer with a thickness of 5-100 nm is deposited or coated on the surface of a metallized diamond sheet using vacuum physical vapor deposition or wet plating processes, thereby completing the method of increasing the bonding strength between diamond and non-wetting metal using platinum group metals.

[0011] The platinum group metals mentioned in step three are ruthenium, rhodium, palladium, osmium, iridium, or platinum, and the non-wetting metals mentioned in step four are gold, silver, copper, or aluminum.

[0012] This invention introduces a platinum group metal (PGM) interlayer between a non-wetting metal and diamond. Leveraging the tendency of PGMs to readily interdiffused with diamond to form a dense solid solution, surface metallization of diamond can be achieved through direct deposition. Simultaneously, the presence of oxygen terminals enables the formation of a covalent complex with a COM structure between the diamond and the metal. The combined effect of these two factors significantly increases the adhesion between the metal and diamond, avoiding the cumbersome subsequent annealing and diffusion bonding steps required by traditional titanium, tungsten, and chromium interlayers. This simplifies the process, making it simple, reliable, and easy to scale up for widespread application. The diamond-PGM structure produced by this invention exhibits high bonding strength and low electrical and thermal resistance, making it suitable for use as diamond-based electrode contacts in electronic devices or as a diamond-based heat conduction module structure in heat dissipation applications. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the process flow for the present invention, which uses platinum group metals to directly metallize the surface of diamond and enhance the bonding strength with non-wetting metals.

[0014] Figure 2 This is a model diagram of the adsorption and bonding of platinum on oxygen-terminated diamond in this invention, showing that a CO-Pt complex covalent structure is formed between platinum, oxygen terminus, and diamond.

[0015] Figure 3These are the 3D and 2D distribution diagrams of the electron differential density after platinum adsorption and bonding on oxygen-terminated diamond in this invention.

[0016] Figure 4 These are photographs of diamond samples with gold and platinum + gold layers deposited on diamond, respectively, in Example 1.

[0017] Figure 5 These are optical micrographs of the interfaces of diamond samples with gold and platinum + gold layers deposited on diamond, respectively, in Example 1.

[0018] Figure 6 This is a photograph of the diamond sample after it was adhered with tape in Example 1;

[0019] Figure 7 This is an optical micrograph of the interface of the diamond sample after it was adhered with tape in Example 1. Detailed Implementation

[0020] Specific Implementation Method 1: This implementation method, which uses platinum group metals to directly metallize the surface of diamond and enhance the bonding strength with non-wetting metals, is achieved through the following steps:

[0021] 1. Polish the diamond sheet, then boil it in aqua regia to remove residual impurities on the diamond surface, thus obtaining a pretreated diamond sheet.

[0022] 2. The pretreated diamond sheet is placed in an oxidizing acid solution, which is a mixture of concentrated sulfuric acid and concentrated nitric acid. It is boiled at 300-370°C for 1.5-2.5 hours. Then, it is ultrasonically cleaned with deionized water, acetone and alcohol in sequence to obtain a diamond sheet with ketone oxygen terminals.

[0023] 3. A platinum group metal layer with a thickness of 5-100 nm is deposited or coated on the surface of a diamond sheet with ketone oxygen terminals using vacuum physical vapor deposition or wet plating process to obtain a metallized diamond sheet.

[0024] IV. A non-wetting metal layer with a thickness of 5-100 nm is deposited or coated on the surface of a metallized diamond sheet using vacuum physical vapor deposition or wet plating processes, thereby completing the method of increasing the bonding strength between diamond and non-wetting metal using platinum group metals.

[0025] The platinum group metals mentioned in step three are ruthenium, rhodium, palladium, osmium, iridium, or platinum, and the non-wetting metals mentioned in step four are gold, silver, copper, or aluminum.

[0026] In step three of this embodiment, when depositing a platinum group metal layer on a diamond sheet with oxygen terminals, the layer can be either fully covered or patterned.

[0027] The non-wetting metal-platinum group metal-diamond assembly obtained by using platinum group metals to increase the bonding strength between diamond and non-wetting metals can be used in heat conduction devices (modules) in electronic devices.

[0028] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the surface roughness of the polished diamond sheet in step one is ≤10nm.

[0029] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that, in step 1, the polished diamond sheet is placed in aqua regia and boiled at a temperature of 90℃~140℃ for 2 hours.

[0030] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the oxidizing acid solution in step two is composed of concentrated sulfuric acid with a mass concentration of 97% and concentrated nitric acid with a mass concentration of 95% in a volume ratio of 3:1 to 5:1.

[0031] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that step 2 involves boiling at 350°C for 2 hours.

[0032] This embodiment incorporates ketone oxygen terminals on the surface of the diamond wafer to enhance its hydrophilicity, thereby improving its adhesion to the subsequent metal bonding layer.

[0033] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the ultrasonic cleaning described in step two involves ultrasonic cleaning in deionized water, acetone, and alcohol for 10 to 20 minutes respectively.

[0034] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the vacuum physical vapor deposition process described in steps Three and Four is a magnetron sputtering deposition process, an electron beam deposition process, or a thermal evaporation process.

[0035] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the wet plating process described in Steps Three and Four is an electroplating process or a chemical plating process.

[0036] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the thickness of the platinum group metal layer in step three is 15nm to 35nm.

[0037] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the thickness of the non-wetting metal layer in step 4 is 30nm to 200nm.

[0038] Example 1: This example describes a method for directly metallizing diamond with platinum group metals and enhancing the bond strength with non-wetting metals, implemented according to the following steps:

[0039] 1. Polish the polycrystalline diamond sheet until the surface roughness reaches 10nm. After polishing, the diamond sheet is placed in aqua regia and boiled at 100℃ for 2 hours to remove inorganic impurities such as metal and graphite, and a pretreated diamond sheet is obtained.

[0040] 2. The pretreated diamond sheet is placed in an oxidizing acid solution, which is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1. The solution is boiled at 350°C for 2 hours and then ultrasonically cleaned in deionized water, acetone and alcohol for 15 minutes each to obtain a diamond sheet with oxygen terminals.

[0041] 3. A 30 nm thick platinum layer was deposited on an oxygen-terminated diamond wafer using a magnetron sputtering deposition process to obtain metallized diamond.

[0042] IV. A gold layer with a thickness of 70 nm is deposited on a metallized diamond wafer using a magnetron sputtering deposition process. The gold layer is located on a platinum layer, thereby completing the method of using platinum group metals to increase the bonding strength between diamond and non-wetting metal.

[0043] Figure 3 The following are 3D and 2D electron differential density distribution diagrams after platinum adsorbs and bonds on oxygen-terminated diamond in the example. It can be seen that a large number of electrons are transferred between platinum, oxygen terminal and diamond, which means that they have formed bonds with each other.

[0044] In this embodiment, a polycrystalline diamond with platinum and gold deposited on its surface is aligned and pre-bonded with another silicon chip with gold deposited on its surface. The chip is then transferred into a bonding device and kept within a certain pressure (0.5-30 MPa) and temperature (20-300°C) range for 10-30 minutes. After natural cooling, the chip is removed, thus achieving the bonding connection between the diamond and the silicon chip.

[0045] This embodiment describes a heat conduction module structure, applicable to chip heat dissipation. Gold is commonly used as a bonding layer to connect diamond and silicon, but because gold and diamond are non-wetting and have van der Waals contact, the adhesion is poor. Using platinum, which can interdiffused with diamond to form a dense solid solution, as a metallization intermediate layer can greatly increase the adhesion between diamond and non-wetting gold.

[0046] This embodiment demonstrates the difference in adhesion between diamond and platinum and gold. A 30nm platinum layer was deposited on half of the surface of a diamond, and then a 70nm gold layer was deposited on the entire surface. An adhesive tape adhesion and detachment experiment was then conducted.

[0047] As attached Figure 4The images show diamond samples with gold and platinum + gold deposits, respectively. Figure 5 Optical micrographs of the interface of the diamond sample are attached. Figure 5 For diamond samples after being adhered with tape, attached Figure 6 This is an optical micrograph of the interface of a diamond sample after it has been adhered with tape. It can be seen that the gold layer on the surface has been completely peeled off, indicating poor adhesion, while the platinum layer is still attached to the diamond, indicating that there is extremely high adhesion between platinum and diamond.

[0048] Example 2: This example describes a method for directly metallizing diamond with platinum group metals and enhancing the bond strength with non-wetting metals, implemented according to the following steps:

[0049] 1. Polish the single-crystal diamond sheet until the surface roughness reaches 1nm. After polishing, the diamond sheet is placed in aqua regia and boiled at 140℃ for 2 hours to remove inorganic impurities such as metal and graphite, and a pretreated diamond sheet is obtained.

[0050] 2. The pretreated diamond sheet is placed in an oxidizing acid solution, which is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 5:1. The solution is boiled at 350°C for 2 hours and then ultrasonically cleaned in deionized water, acetone and alcohol for 15 minutes each to obtain a diamond sheet with ketone oxygen terminals.

[0051] 3. A ruthenium intermediate layer with a thickness of 50 nm was deposited on a diamond wafer with ketone oxygen terminals using electron beam deposition, resulting in diamond with direct surface metallization using platinum group metals.

[0052] In this embodiment, diamond surface-metallized with platinum group metals can be directly used as a Schottky electrode structure, applicable to electronic devices. The commonly used Schottky contact electrode material for diamond is usually aluminum, but because aluminum and diamond have a non-wetting van der Waals contact, the adhesion is poor and it is easy to detach. Furthermore, aluminum has a low melting point and is easily burned out by high current in power devices.

[0053] This embodiment uses ruthenium, a platinum group metal that can interdiffusion with diamond to form a dense solid solution, as a Schottky contact electrode. This can greatly improve the adhesion between diamond and the metal electrode. In addition, platinum group metals have high chemical stability, excellent corrosion resistance, oxidation resistance and high melting point. Compared with non-wetting metal electrodes, they have a longer service life. Therefore, in the field of electronic devices, they can directly replace traditional non-wetting aluminum as a Schottky contact electrode, without the need to deposit other metals outside the platinum group metal layer.

Claims

1. A method for directly metallizing the surface of diamond using platinum group metals and enhancing the bonding strength with non-wetting metals, characterized in that... This method is implemented according to the following steps:

1. Polish the diamond sheet, then boil it in aqua regia to remove residual impurities on the diamond surface, thus obtaining a pretreated diamond sheet.

2. The pretreated diamond sheet is placed in an oxidizing acid solution, which is a mixture of concentrated sulfuric acid and concentrated nitric acid. It is boiled at 300~370℃ for 1.5~2.5 hours. Then, it is ultrasonically cleaned with deionized water, acetone and alcohol in sequence to obtain diamond sheet with ketone oxygen terminals.

3. A platinum group metal layer with a thickness of 15~35nm is deposited or coated on the surface of a diamond sheet with ketone oxygen terminals using vacuum physical vapor deposition or wet plating process. The ketone oxygen terminals are covalently linked to the platinum group metal through a COM structure complex to obtain a metallized diamond sheet. IV. A non-wetting metal layer with a thickness of 5-100 nm is deposited or coated on the surface of a metallized diamond sheet using vacuum physical vapor deposition or wet plating, thereby completing the method of increasing the bonding strength between diamond and non-wetting metal using platinum group metals. The platinum group metals mentioned in step three are ruthenium, rhodium, palladium, osmium, iridium, or platinum, and the non-wetting metals mentioned in step four are gold, silver, copper, or aluminum.

2. The method for directly metallizing diamond with platinum group metals and enhancing the bonding strength with non-wetting metals according to claim 1, characterized in that... The surface roughness of the polished diamond sheet in step one is ≤10nm.

3. The method for directly metallizing diamond with platinum group metals and enhancing the bonding strength with non-wetting metals according to claim 1, characterized in that... After polishing in step one, the diamond sheet is placed in aqua regia and boiled at a temperature of 90℃~140℃ for 2 hours.

4. The method for directly metallizing diamond with platinum group metals and enhancing the bonding strength with non-wetting metals according to claim 1, characterized in that... In step two, the oxidizing acid solution is prepared by mixing concentrated sulfuric acid with a mass concentration of 97% and concentrated nitric acid with a mass concentration of 95% in a volume ratio of 3:1 to 5:

1.

5. The method for directly metallizing diamond with platinum group metals and enhancing the bonding strength with non-wetting metals according to claim 1, characterized in that... In step two, boil at 350℃ for 2 hours.

6. The method for directly metallizing diamond with platinum group metals and enhancing the bonding strength with non-wetting metals according to claim 1, characterized in that... The ultrasonic cleaning described in step two involves sequentially ultrasonicating in deionized water, acetone, and alcohol for 10-20 minutes each.

7. The method for directly metallizing diamond with platinum group metals and enhancing the bonding strength with non-wetting metals according to claim 1, characterized in that... The vacuum physical vapor deposition process described in steps three and four is magnetron sputtering deposition, electron beam deposition, or thermal evaporation.

8. The method for directly metallizing diamond with platinum group metals and enhancing the bonding strength with non-wetting metals according to claim 1, characterized in that... The wet plating process described in steps three and four is either an electroplating process or a chemical plating process.

9. The method for directly metallizing diamond with platinum group metals and enhancing the bonding strength with non-wetting metals according to claim 1, characterized in that... In step four, the thickness of the non-wetting metal layer is 30nm~100nm.

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