Preparation method of high-heat-conductivity Ti coating on surface of CVD (Chemical Vapor Deposition) diamond

Abstract

The invention mainly provides a preparation method of a high-heat-conductivity Ti coating on the surface of a CVD diamond, which comprises the following steps: 1, pretreatment: sequentially carrying out ultrasonic acetone cleaning, ultrasonic acid pickling, ultrasonic deionized water rinsing and dehydration drying on a CVD diamond substrate; 2, ion implantation is carried out, specifically, the diamond substrate pretreated in the step 1 is placed in a vacuum chamber of ion implantation equipment, and ion implantation is carried out with Ti as a target material; 3, HiPIMS deposition, wherein the diamond substrate after ion implantation is moved to a magnetron sputtering vacuum chamber for Ti coating deposition; and 4, post-treatment is conducted, specifically, the diamond substrate deposited in the step 3 is taken out, ultrasonic alcohol cleaning is conducted, and drying and vacuum packaging are conducted. Through the synergistic effect of ion implantation and the HiPIMS technology, the Ti coating with high binding force and high heat conductivity is achieved on the surface of the CVD diamond, the problems that in a traditional metallization technology, the interface thermal resistance is high, the coating is loose, and environment pollution is caused are solved, and the method is particularly suitable for meeting the heat dissipation requirement of a high-power semiconductor device.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface modification of high thermal conductivity materials, and particularly relates to a method for preparing a Ti coating on the surface of CVD diamond by combining ion implantation and high-power pulsed magnetron sputtering (HiPIMS). Background Art

[0002] CVD diamond, that is, a polycrystalline diamond wafer prepared by chemical vapor deposition technology, has attracted much attention due to its excellent properties. With the rapid development of semiconductor technology, the power consumption and heat generation of chips have increased sharply. If the heat generated inside the circuit is not transferred out in time, the increase in working temperature will lead to a sharp decline in the stability and lifespan of electronic components. CVD diamond has excellent thermal conductivity and electrical properties, but due to its chemical inertness, it is difficult to directly connect with other materials such as chips. It is necessary to deposit a metal coating on the diamond surface to connect with other materials. This requires that the interfacial thermal conductance between the metal coating and CVD diamond is high enough and has a strong bonding force at the same time. Summary of the Invention

[0003] To solve the above problems, the present invention provides a method for preparing a high thermal conductivity Ti coating on the surface of CVD diamond, including the following steps: Step 1: Pretreatment, sequentially performing ultrasonic acetone cleaning, ultrasonic pickling, ultrasonic deionized water rinsing and dehydration drying on the CVD diamond substrate; Step 2: Ion implantation, placing the diamond substrate pretreated in Step 1 in the vacuum chamber of the ion implantation equipment, and performing ion implantation with Ti as the target; Step 3: HiPIMS deposition: Transferring the ion-implanted diamond substrate to the magnetron sputtering vacuum chamber for Ti coating deposition; Step 4: Post-treatment: Taking out the diamond substrate deposited in Step 3 after deposition, and performing ultrasonic alcohol cleaning, drying and vacuum packaging.

[0004] Furthermore, in Step 2, the vacuum degree of ion implantation is ≤1×10 -4 Pa, heated to 300 - 500 °C, and ion implantation is performed under the conditions of an ion implantation energy of 1 - 3 MeV, a beam current intensity of 1 - 100 mA, and a dose of 1.0×10¹ 6 ~1.0×10¹ 8 atoms / cm².

[0005] Furthermore, in Step 3, the vacuum degree of the HiPIMS deposition magnetron sputtering vacuum chamber is ≤1×10 - ³ Pa, heated to 100 - 300 °C, argon is introduced until the working pressure is 1.0 - 1.5 Pa, and the deposition is 200 - 300 nm.

[0006] Further, in step 3, HiPIMS deposition is carried out in a constant voltage mode of 800 V, with a pulse width of 50 - 100 μs, a frequency of 400 - 600 Hz, and a synchronous bias power supply of 100 - 300 V.

[0007] Further, in step 1, ultrasonic cleaning with acetone is carried out for ≥ 10 minutes, ultrasonic pickling is carried out for ≥ 15 minutes, ultrasonic rinsing with deionized water is carried out for ≥ 30 minutes, and the ultrasonic pickling uses a mixed solution of concentrated sulfuric acid and hydrogen peroxide.

[0008] Further, in step 2, the ion implantation energy is 2 MeV, the beam current intensity is 50 mA, and the dose is 1.0×10¹ 7 atoms / cm².

[0009] Further, the HiPIMS pulse width is 75 μs, the pulse frequency is 500 Hz, and the pulse timing of the bias power supply is completely synchronized with that of the HiPIMS power supply.

[0010] Further, in step 3, the thickness of the Ti coating is 250 - 300 nm.

[0011] Therefore, the beneficial effect of the present invention is that through the synergistic effect of ion implantation and HiPIMS technology, a Ti coating with high bonding strength and high thermal conductivity is realized on the surface of CVD diamond, solving problems such as high interfacial thermal resistance, loose coating, and environmental pollution in traditional metallization processes, and is particularly suitable for the heat dissipation requirements of high-power semiconductor devices. Brief Description of the Drawings

[0012] Figure 1 It is the process flow chart of the present invention.

[0013] Figure 2 It is the cross-sectional microstructure morphology diagram of the Ti coating obtained on the surface of CVD diamond in Example 1 of the present invention.

[0014] Figure 3 It is the surface microstructure morphology diagram of the Ti coating obtained on the surface of CVD diamond in Example 1 of the present invention.

[0015] Figure 4 It is the SRIM simulation result diagram of ion implantation in Example 1 of the present invention. Detailed Description of the Embodiment

[0016] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, reference can be made to the drawings and embodiments to further illustrate the technical solutions of the present invention. It should be understood that the embodiments described herein are only used to explain the technical solutions or principles of the present invention, and are not used to limit the protection scope of the present invention. Embodiment

[0017] This embodiment includes the following steps: Step 1: Ultrasonically clean the CVD diamond substrate with acetone, ultrasonically pickle it, ultrasonically rinse it with deionized water, and dehydrate and dry it. The three cleaning steps are carried out for 10 min, 15 min, and 30 min respectively; Step 2: Place the diamond substrate processed in Step 1 in the vacuum chamber of the ion implantation equipment, install the Ti target, adjust the background vacuum degree of the vacuum chamber of the ion implantation equipment to 8×10 -5 Pa and heat it to 400 °C. Turn on the ion implantation source, adjust the ion implantation energy to 2 MeV, adjust the ion beam current intensity to 50 mA, and the ion implantation dose is 1.0×10 17 atoms / cm 2 , open the baffle. When the ion implantation dose reaches the preset value, close the baffle, turn off the ion source, and wait until the workpiece temperature drops below 100 °C, then turn off the vacuum system; Step 3: Place the workpiece processed in Step 2 into the magnetron sputtering vacuum chamber, adjust the background vacuum degree of the magnetron sputtering vacuum chamber to 5×10 -4 Pa and heat it to 200 °C, and introduce argon to the working pressure of 0.5 Pa; the bias power supply is a DC pulse power supply, and its pulse properties should be synchronized with the HiPIMS power supply. The bias voltage is set to 200 V; turn on the magnetron Ti target source, set the constant voltage mode to 800 V, keep the pulse width set at 75 μs unchanged, and keep the pulse frequency set at 500 Hz unchanged for a total of 10 min. The total thickness of the Ti coating is 300 nm; Step 4: After Step 3 runs for 10 min, turn off all power supplies and the introduction of argon. Wait until the temperature of the magnetron sputtering vacuum chamber drops below 100 °C, then turn off the vacuum system; Step 5: After taking out the workpiece, ultrasonically clean it with alcohol for 30 min, dry it and put it into a vacuum bag for proper storage. Embodiment

[0018] This embodiment includes the following steps: Step 1: Ultrasonically clean the CVD diamond substrate with acetone, ultrasonically pickle it, ultrasonically rinse it with deionized water, and dehydrate and dry it. The three cleaning steps are carried out for 10 min, 15 min, and 30 min respectively; Step 2: Place the diamond substrate processed in Step 1 in the vacuum chamber of the ion implantation equipment, install the Ti target, adjust the background vacuum degree of the vacuum chamber of the ion implantation equipment to 8×10 -5 Pa and heat it to 400 °C. Turn on the ion implantation source, adjust the ion implantation energy to 2 MeV, adjust the ion beam current intensity to 50 mA, and the ion implantation dose is 1.0×10 17 atoms / cm 2, open the baffle. When the ion implantation dosage reaches the preset value, close the baffle, turn off the ion source, and turn off the vacuum system after the workpiece temperature drops below 100°C; Step 3: Place the workpiece processed in Step 2 into the magnetron sputtering vacuum chamber, and adjust the background vacuum degree of the magnetron sputtering vacuum chamber to 5×10 -4 Pa and heat it to 200°C, and introduce argon to the working pressure of 0.5 Pa; the bias power supply is a DC pulse power supply, and its pulse attributes should be synchronized with the HiPIMS power supply. The bias voltage is set to 200 V; turn on the magnetron Ti target source, set the constant voltage mode to 800 V, keep the pulse width set at 100 μs unchanged, and keep the pulse frequency set at 300 Hz unchanged for a total of 10 min. The total thickness of the Ti coating is 250 nm; Step 4: After running for 10 min in Step 3, turn off all power supplies and the argon gas supply. After the temperature of the magnetron sputtering vacuum chamber drops below 100°C, turn off the vacuum system; Step 5: Take out the workpiece and perform ultrasonic alcohol cleaning for 30 min. After drying, put it into a vacuum bag for proper storage. Example

[0019] This example includes the following steps: Step 1: Perform ultrasonic acetone cleaning, ultrasonic pickling, ultrasonic deionized water rinsing, and dehydration drying on the CVD diamond substrate in sequence. The three cleaning steps are carried out for 10 min, 15 min, and 30 min respectively; Step 2: Place the diamond substrate processed in Step 1 into the vacuum chamber of the ion implantation equipment, install the Ti target, and adjust the background vacuum degree of the ion implantation equipment vacuum chamber to 8×10 -5 Pa and heat it to 400°C, turn on the ion implantation source, adjust the ion implantation energy to 2 MeV, adjust the ion beam current intensity to 50 mA, and the ion implantation dosage is 1.0×10 17 atoms / cm 2 , open the baffle. When the ion implantation dosage reaches the preset value, close the baffle, turn off the ion source, and turn off the vacuum system after the workpiece temperature drops below 100°C; Step 3: Place the workpiece processed in Step 2 into the magnetron sputtering vacuum chamber, and adjust the background vacuum degree of the magnetron sputtering vacuum chamber to 5×10 -4 Pa and heat it to 200°C, and introduce argon to the working pressure of 0.5 Pa; the bias power supply is a DC pulse power supply, and its pulse attributes should be synchronized with the HiPIMS power supply. The bias voltage is set to 150 V; turn on the magnetron Ti target source, set the constant voltage mode to 800 V, keep the pulse width set at 75 μs unchanged, and keep the pulse frequency set at 500 Hz unchanged for a total of 10 min. The total thickness of the Ti coating is 280 nm.

[0020] Step 4: After step 3 runs for 10 minutes, turn off all power supplies and the argon gas supply. Wait until the temperature of the magnetron sputtering vacuum chamber drops below 100°C, and then turn off the vacuum system. Step 5: After taking out the workpiece, perform ultrasonic alcohol cleaning for 30 minutes. After drying, put it into a vacuum bag and store it properly.

[0021] For the technical solution proposed by the present invention, since metal Ti and CVD diamond have completely different crystal structures and chemical properties, the Ti coating deposited on the diamond surface by general coating preparation techniques has the problem of low bonding strength. By ion implanting Ti ions with the same composition as the coating, the diamond surface has the same elements as the Ti coating, changing the bonding mode between the two and enhancing the bonding strength between the Ti coating and CVD diamond.

[0022] Secondly, the heat conduction mechanisms in metal Ti and CVD diamond are different. In metal Ti, heat is mainly conducted through the movement of free electrons, while in diamond, heat is mainly conducted through lattice vibration. Different heat conduction mechanisms result in a relatively high interfacial thermal resistance between the Ti coating and CVD diamond. By means of ion implantation, a carbide layer with a composition, structure, and properties between the two is introduced between the Ti coating and CVD diamond, which is beneficial to improving the heat conduction efficiency and reducing the interfacial thermal resistance.

[0023] Furthermore, traditional coating preparation techniques such as electroplating and DC magnetron sputtering may encounter problems such as large environmental pollution, poor coating bonding strength, and uneven coating. The HiPIMS technology used in the present invention is used to prepare the Ti coating. By increasing the plasma density and energy through megawatt-level instantaneous power, the coating density and the film-substrate bonding strength are improved, which helps to improve the overall performance.

[0024] 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 principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a high thermal conductivity Ti coating on a CVD diamond surface, characterized in that: The following steps are involved: Step 1: Pretreatment, the CVD diamond substrate is sequentially subjected to ultrasonic acetone cleaning, ultrasonic acid cleaning, ultrasonic deionized water rinsing and dehydration and drying; Step 2: ion implantation, placing the diamond substrate pretreated in step 1 in a vacuum chamber of an ion implantation device, and performing ion implantation using Ti as a target; Step 3: HiPIMS deposition, transferring the diamond substrate after ion implantation to a magnetron sputtering vacuum chamber for Ti coating deposition; Step 4: Post-treatment: After the deposition is completed, the diamond substrate deposited in step 3 is taken out, and ultrasonic alcohol cleaning, drying and vacuum packaging are performed.

2. The preparation method according to claim 1, characterized in that: The vacuum degree of ion implantation in step 2 is ≤1×10 -4 Pa, heated to 300~500℃, ion implantation energy 1~3 MeV, beam intensity 1~100 mA, dose 1.0×10¹ 6 ~1.0×10¹ 8 Ion implantation is performed at 100 atoms / cm².

3. The preparation method according to claim 1, characterized in that: In step 3, the vacuum degree of the HiPIMS deposition magnetron sputtering vacuum chamber is ≤ 1×10 - ³ Pa, heated to 100~300℃, introduced argon gas to a working pressure of 1.0~1.5 Pa, and deposited 200~300 nm.

4. The preparation method according to claim 3, characterized in that: In step 3, the HiPIMS deposition adopts a constant voltage mode of 800 V, a pulse width of 50-100 μs, a frequency of 400-600 Hz and a synchronous bias power supply of 100-300 V.

5. The preparation method according to claim 1, characterized in that: In the step 1, the ultrasonic acetone cleaning is performed for ≥10 minutes, the ultrasonic acid cleaning is performed for ≥15 minutes, and the ultrasonic deionized water rinsing is performed for ≥30 minutes. The ultrasonic acid cleaning uses a mixed solution of concentrated sulfuric acid and hydrogen peroxide.

6. The preparation method according to claim 2, characterized in that: In step 2, the ion implantation energy is 2 MeV, the beam intensity is 50 mA, and the dose is 1.0×10¹ 7 atoms / cm².

7. The preparation method according to claim 4, characterized in that: The HiPIMS pulse width is 75 μs, the pulse frequency is 500 Hz, and the pulse timing of the bias power supply is fully synchronized with the HiPIMS power supply.

8. The preparation method according to claim 1, characterized in that: The thickness of the Ti coating in step 3 is 250-300 nm.

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