Method for directly metallizing surface of diamond by using platinum group metal and enhancing bonding strength with non-infiltrating metal

Abstract

The invention discloses a method for directly metallizing the surface of diamond by using platinum group metal and enhancing the bonding strength with non-infiltrating metal, and aims to solve the problems that the non-infiltrating metal is poor in adhesive force on the diamond and easy to fall off, and common intermediate layers such as titanium and tungsten need tedious steps such as subsequent annealing. The method for enhancing the bonding strength with the non-infiltrating metal comprises the following steps: 1, polishing a diamond sheet, and then putting the diamond sheet into aqua regia for boiling treatment; 2, putting the pretreated diamond sheet into an oxidizing acid solution, and performing boiling treatment; 3, plating a platinum group metal layer on the diamond sheet by adopting a vacuum physical vapor deposition process or a wet plating process; and 4, depositing or plating a non-infiltrating metal layer on the surface of the metalized diamond sheet. According to the method, the surface metallization of the diamond can be completed through direct deposition by utilizing the tendency that the platinum group metal and the diamond are easily mutually diffused to form a compact solid solution, and the prepared diamond-platinum group metal structure has relatively high bonding strength and relatively low resistance and thermal resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of diamond metallization, and in particular relates to a method for directly metallizing the surface of diamond using platinum group metals and enhancing the bonding strength with non-wetting metals. Background Art

[0002] As a representative third-generation semiconductor material, diamond is increasingly being used in high-power electronic devices. On the one hand, diamond can be used to develop power devices and high-energy detectors due to its ultra-wide bandgap and high breakdown voltage. On the other hand, the high heat flux of high-power electronic devices requires the selection of diamond with ultra-high thermal conductivity as a heat dissipation material.

[0003] In the field of electronic devices and high-end thermal management, gold, silver, copper, aluminum, etc. are often used as metal materials that are in direct contact with diamond. However, as non-wetting metals, gold, silver, copper, aluminum, etc. are in van der Waals contact with diamond, and it is difficult for them to interpenetrate or bond with diamond. Therefore, the adhesion between them and diamond is poor, which can easily cause fatal problems such as detachment of the bonding interface. In order to increase the adhesion between the two, diamond usually needs to be metallized. The commonly used diamond metallization method in the industry usually uses carbon-forming metals such as titanium or tungsten as the intermediate layer between the non-wetting metal and diamond, and performs high-temperature annealing treatment to form titanium or tungsten carbide at the interface, so that diamond and metal are covalently bonded. However, the titanium carbide formed by titanium plating and annealing of diamond has a loose structure, and the adhesion is reduced. The adhesion between tungsten and gold is poor, and gold is easy to fall off on tungsten.

[0004] Platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, platinum) as transition metals have unsatisfied d-layer electrons, so they have high reactivity with carbon, and are in covalent contact with diamond. They have good mutual solubility with carbon at room temperature and are easy to form solid solutions. They can also form carbides under high temperature and high pressure, and are generally used as heteroepitaxial substrate materials for diamond. At the same time, platinum group metals widely have isomorphous substitution phenomenon with each other, and have high mutual solubility with gold, silver, copper, aluminum and other metals that are not wetted by diamond, and have high chemical stability, good corrosion resistance and oxidation resistance, and have a long service life. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that non-wetting metals (gold, silver, copper, aluminum, etc.) have poor adhesion on diamond and are easy to fall off, and that common intermediate layers such as titanium and tungsten require cumbersome steps such as subsequent annealing, thereby providing a method for directly metallizing the surface of diamond using platinum group metals and enhancing the bonding strength with non-wetting metals.

[0006] The method of using platinum group metals to directly metallize the surface of diamond and enhance the bonding strength with non-wetting metals is achieved by the following steps:

[0007] 1. Polishing the diamond sheet, boiling the polished diamond sheet in aqua regia to remove residual impurities on the diamond surface, and obtaining a pre-treated diamond sheet;

[0008] 2. Put the pretreated diamond sheet into an oxidizing acid solution, which is a mixture of concentrated sulfuric acid and concentrated nitric acid, and boil it at a temperature of 300-370°C for 1.5-2.5 hours. Then, ultrasonically clean it with deionized water, acetone, and alcohol in turn to obtain a diamond sheet with keto oxygen terminals.

[0009] 3. Depositing or coating a 5-100 nm thick platinum group metal layer on the surface of the diamond sheet with keto oxygen terminal by vacuum physical vapor deposition process or wet plating process to obtain a metallized diamond sheet;

[0010] Fourth, a non-wetting metal layer with a thickness of 5 to 100 nm is deposited or plated on the surface of the metallized diamond sheet using a vacuum physical vapor deposition process or a wet plating process, thereby completing a method of using platinum group metals to increase the bonding strength between diamond and non-wetting metal;

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

[0012] The present invention introduces a platinum group metal intermediate layer between the non-wetting metal and the diamond, and utilizes the tendency of the platinum group metal to diffuse with the diamond to form a dense solid solution, and the surface metallization of the diamond can be completed by direct deposition. At the same time, the presence of the oxygen terminal can form a complex covalently connected with the diamond in a COM structure. The combined effect of the two factors greatly increases the adhesion between the metal and the diamond, avoiding the cumbersome steps of subsequent annealing and diffusion bonding required for the traditional intermediate contact layer of titanium, tungsten, chromium, etc., simplifying the process, and the operation process is simple and reliable, which is convenient for large-scale promotion and application. The diamond-platinum group metal structure made by the present invention has high bonding strength, low electrical resistance and thermal resistance, and can be used as a diamond-based electrode contact in the field of electronic devices or a diamond-based heat conduction module structure in the field of heat dissipation. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0015] Figure 33D and 2D distribution diagrams of the electron differential density after adsorption and bonding of platinum on oxygen-terminated diamond in the present invention;

[0016] Figure 4 These are photos of diamond samples with a gold layer and a platinum + gold layer deposited on the diamond in Example 1;

[0017] Figure 5 This is an optical micrograph of the interface of a diamond sample having a gold layer and a platinum + gold layer deposited on the diamond in Example 1;

[0018] Figure 6 This is a photo of the diamond sample after being taped in Example 1;

[0019] Figure 7 This is an optical micrograph of the interface of the diamond sample after being taped in Example 1. DETAILED DESCRIPTION

[0020] Specific implementation method 1: In this implementation method, the method of using platinum group metals to directly metallize the surface of diamond and enhance the bonding strength with non-wetting metals is implemented according to the following steps:

[0021] 1. Polishing the diamond sheet, boiling the polished diamond sheet in aqua regia to remove residual impurities on the diamond surface, and obtaining a pre-treated diamond sheet;

[0022] 2. Put the pretreated diamond sheet into an oxidizing acid solution, which is a mixture of concentrated sulfuric acid and concentrated nitric acid, and boil it at a temperature of 300-370°C for 1.5-2.5 hours. Then, ultrasonically clean it with deionized water, acetone, and alcohol in turn to obtain a diamond sheet with keto oxygen terminals.

[0023] 3. Depositing or coating a 5-100 nm thick platinum group metal layer on the surface of the diamond sheet with keto oxygen terminal by vacuum physical vapor deposition process or wet plating process to obtain a metallized diamond sheet;

[0024] Fourth, a non-wetting metal layer with a thickness of 5 to 100 nm is deposited or plated on the surface of the metallized diamond sheet using a vacuum physical vapor deposition process or a wet plating process, thereby completing a method of using platinum group metals to increase the bonding strength between diamond and non-wetting metal;

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

[0026] In step three of this embodiment, when depositing a platinum group metal layer on the diamond sheet with oxygen terminations, full coverage or patterning can be performed.

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

[0028] Specific implementation method 2: The difference between this implementation method and specific implementation method 1 is that the surface roughness of the polished diamond sheet in step 1 is ≦10 nm.

[0029] Specific implementation method three: The difference between this implementation method and specific implementation method one or two is that in step one, the polished diamond sheet is placed in aqua regia and boiled at a temperature of 90° C. to 140° C. for 2 hours.

[0030] Specific embodiment 4: The difference between this embodiment and any one of specific embodiments 1 to 3 is that the oxidizing acid solution in step 2 is a mixture 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 mode 5: This implementation mode is different from specific implementation modes 1 to 4 in that the temperature of boiling at 350° C. for 2 hours is used in step 2.

[0032] In this embodiment, the surface of the diamond sheet is provided with keto oxygen terminals to enhance the hydrophilicity of the surface of the diamond wafer, which is beneficial to enhance the subsequent bonding force with the metal bonding layer.

[0033] Specific implementation method 6: The difference between this implementation method and any one of specific implementation methods 1 to 5 is that the ultrasonic cleaning in step 2 is performed in deionized water, acetone, and alcohol for 10 to 20 minutes respectively.

[0034] Specific implementation example 7: This implementation example is different from any one of specific implementation examples 1 to 6 in that the vacuum physical vapor deposition process described in step 3 and step 4 is a magnetron sputtering deposition process, an electron beam deposition process or a thermal evaporation process.

[0035] Specific implementation eight: This implementation is different from any one of specific implementations one to seven in that the wet plating process described in step three and step four is an electroplating process or a chemical plating process.

[0036] Specific embodiment 9: The difference between this embodiment and any one of specific embodiments 1 to 8 is that the thickness of the platinum group metal layer in step 3 is 15 nm to 35 nm.

[0037] Specific embodiment ten: This embodiment is different from any one of specific embodiments one to nine in that the thickness of the non-wetting metal layer in step four is 30 nm to 200 nm.

[0038] Embodiment 1: The method of using platinum group metals to directly metallize the surface of diamond and enhance the bonding strength with non-wetting metals in this embodiment is implemented according to the following steps:

[0039] 1. The polycrystalline diamond sheet is polished until the surface roughness reaches 10 nm, and the polished diamond sheet is placed in aqua regia and boiled at 100° C. for 2 hours to remove inorganic impurities such as metal and graphite to obtain a pre-treated diamond sheet;

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

[0041] 3. A platinum layer with a thickness of 30 nm is deposited on a diamond sheet with oxygen terminations by magnetron sputtering deposition process to obtain metallized diamond;

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

[0043] Figure 3 3D and 2D distribution diagrams of the electron difference density after platinum is adsorbed and bonded on oxygen-terminated diamond in the embodiment. It can be seen that a large amount of electron transfer occurs between platinum, oxygen terminals and diamond, indicating 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, and then placed 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 device is taken out to achieve bonding connection between the diamond and the silicon chip.

[0045] This embodiment is a heat conduction module structure, and its application scenario is the field of chip heat dissipation. Gold is often used as a bonding layer to connect diamond and silicon, but since gold and diamond are non-wetting and in van der Waals contact, the adhesion is poor. Using platinum, which can diffuse with diamond to form a dense solid solution, as a metallized intermediate layer can greatly increase the adhesion between diamond and non-wetting gold.

[0046] In this example, in order to demonstrate 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, and a tape adhesion peeling experiment was performed.

[0047] As attached Figure 4The diamond samples are shown as follows: Figure 5 This is an optical micrograph of the diamond sample interface. Figure 5 The diamond sample is attached after being taped. Figure 6 This is an optical micrograph of the interface of the diamond sample after tape bonding. It can be seen that the gold layer on the surface is 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] Embodiment 2: The method of using platinum group metals to directly metallize the surface of diamond and enhance the bonding strength with non-wetting metals in this embodiment is implemented according to the following steps:

[0049] 1. Polishing the single crystal diamond sheet until the surface roughness reaches 1 nm, and then boiling the polished diamond sheet in aqua regia at 140°C for 2 hours to remove inorganic impurities such as metal and graphite, thereby obtaining a pre-treated diamond sheet;

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

[0051] 3. A ruthenium intermediate layer with a thickness of 50 nm is deposited on a diamond sheet with keto oxygen terminations using an electron beam deposition process to obtain a diamond with direct surface metallization using a platinum group metal.

[0052] In this embodiment, diamond with surface metallization using platinum group metals can be directly used as a Schottky electrode structure, and the application scenario is electronic devices. The commonly used Schottky contact electrode material for diamond is usually aluminum, but since aluminum and diamond are in non-wetting van der Waals contact, the adhesion is poor and easy to fall off, and aluminum has a low melting point and is easily burned by high current in power devices.

[0053] This embodiment uses ruthenium, a platinum group metal that can diffuse with diamond to form a dense solid solution, as a Schottky contact electrode, which can greatly improve the adhesion between diamond and the metal electrode. Platinum group metals have high chemical stability, good corrosion resistance, oxidation resistance and high melting point, and have a longer service life than non-wettable metal electrodes. Therefore, in the field of electronic devices, they can directly replace traditional non-wettable metal 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 by following the steps below:

1. Polishing the diamond sheet, boiling the polished diamond sheet in aqua regia to remove residual impurities on the diamond surface, and obtaining a pre-treated diamond sheet; 2. Put the pretreated diamond sheet into an oxidizing acid solution, which is a mixture of concentrated sulfuric acid and concentrated nitric acid, and boil it at a temperature of 300-370°C for 1.5-2.5 hours. Then, ultrasonically clean it with deionized water, acetone, and alcohol in turn to obtain a diamond sheet with keto oxygen terminals.

3. Depositing or coating a 5-100 nm thick platinum group metal layer on the surface of the diamond sheet with keto oxygen terminal by vacuum physical vapor deposition process or wet plating process to obtain a metallized diamond sheet; Fourth, a non-wetting metal layer with a thickness of 5 to 100 nm is deposited or plated on the surface of the metallized diamond sheet using a vacuum physical vapor deposition process or a wet plating process, thereby completing a method of using platinum group metals to increase the bonding strength between diamond and non-wetting metal; The platinum group metal described in step three is ruthenium, rhodium, palladium, osmium, iridium or platinum, and the non-wetting metal described in step four is gold, silver, copper or aluminum.

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

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

4. The method for directly metallizing the surface of diamond using platinum group metals and enhancing the bonding strength with non-wetting metals according to claim 1, characterized in that In step 2, 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 the surface of diamond using platinum group metals and enhancing the bonding strength with non-wetting metals according to claim 1, characterized in that In step 2, the mixture is boiled at 350° C. for 2 hours.

6. The method of using platinum group metals to directly metallize the surface of diamond and enhance the bonding strength with non-wetting metals according to claim 1, characterized in that The ultrasonic cleaning in step 2 is carried out in deionized water, acetone and alcohol for 10 to 20 minutes respectively.

7. The method of using platinum group metals to directly metallize the surface of diamond and enhance the bonding strength with non-wetting metals according to claim 1, characterized in that The vacuum physical vapor deposition process described in step three and step four is a magnetron sputtering deposition process, an electron beam deposition process or a thermal evaporation process.

8. The method of using platinum group metals to directly metallize the surface of diamond and enhance the bonding strength with non-wetting metals according to claim 1, characterized in that The wet plating process described in step 3 and step 4 is an electroplating process or a chemical plating process.

9. The method of using platinum group metals to directly metallize the surface of diamond and enhance the bonding strength with non-wetting metals according to claim 1, characterized in that In step 3, the thickness of the platinum group metal layer is 15 nm to 35 nm.

10. The method for directly metallizing the surface of diamond using platinum group metals and enhancing the bonding strength with non-wetting metals according to claim 1, characterized in that In step 4, the thickness of the non-wetting metal layer is 30 nm to 200 nm.

Images