Reinforced ruthenium-plated molybdenum sheet and preparation method thereof

Abstract

The invention discloses an enhanced ruthenium-plated molybdenum plate and a preparation method thereof, and belongs to the technical field of ruthenium-plated molybdenum plates. The preparation method comprises the following steps: plating a high-purity molybdenum plating layer with the thickness of 0.1-0.5 mu m on the surface of a molybdenum sheet in a vacuum sputtering manner in a magnetron sputtering manner to obtain a molybdenum-plated molybdenum sheet; the preparation method comprises the following steps: carrying out oxidation pickling and ion cleaning on a molybdenum-plated molybdenum sheet, and then depositing a ruthenium plating layer with the thickness of 0.5-1 mu m on the surface of the cleaned molybdenum-plated molybdenum sheet in a vapor deposition manner to obtain the enhanced ruthenium-plated molybdenum sheet. According to the preparation method, the requirement for the molybdenum plate base body is low, the rolled molybdenum plate which is not ground can be directly used, the ruthenium plating layer which is firmly attached and tightly combined is formed on the base body, and the enhanced ruthenium plating molybdenum plate is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of molybdenum sheets, and particularly to the technical field of ruthenium-plated molybdenum sheets. Background Art

[0002] Due to its excellent electrical and thermal conductivity, molybdenum sheets are widely used in the packaging and heat dissipation of power semiconductor devices. However, pure molybdenum sheets have poor corrosion resistance and are prone to oxidation at high temperatures, which affects their reliability during long-term use. On the other hand, ruthenium exhibits excellent corrosion resistance and oxidation resistance in high-temperature environments and has good electrical conductivity, making it suitable for electronic components and electrical contact materials and an ideal coating material. Plating ruthenium on the surface of molybdenum sheets can significantly improve their corrosion resistance, oxidation resistance, and electrical conductivity.

[0003] Traditional molybdenum sheet ruthenium plating processes include, for example, multi-layer electroless ruthenium plating or diffusion ruthenium infiltration after electroplating. Both of them have problems of insufficient bonding strength and uneven plating layers, and are prone to peeling off during application, with poor durability. At the same time, the processes of electroless plating and electroplating are relatively complex, with low production efficiency, and the plating solutions cause serious environmental pollution. Compared with electroless plating and electroplating, ruthenium plating by physical vapor deposition (PVD) method has many advantages such as lower process temperature, shorter process time, smaller deformation of molybdenum sheets, high production efficiency, and no environmental pollution.

[0004] However, directly using PVD to plate ruthenium makes it difficult to form an effective and reliable bond between the molybdenum substrate and the ruthenium coating, thus obtaining a ruthenium-plated molybdenum sheet with high peel strength. Summary of the Invention

[0005] Aiming at the defects of the prior art, the purpose of the present invention is to propose a strengthened ruthenium-plated molybdenum sheet and its preparation method.

[0006] The technical solution of the present invention is as follows: A preparation method of a strengthened ruthenium-plated molybdenum sheet, which includes: (1) Using high-purity molybdenum as a target, by means of magnetron sputtering, a high-purity molybdenum coating with a thickness of 0.1 - 0.5 μm is vacuum sputtered on the surface of the molybdenum sheet to obtain a molybdenum-coated molybdenum sheet; (2) Oxidizing and pickling the molybdenum-coated molybdenum sheet to obtain a pickled molybdenum-coated molybdenum sheet; (3) Ion cleaning and activation of the pickled molybdenum-coated molybdenum sheet by an improved anode layer ion source to obtain an activated molybdenum-coated molybdenum sheet, where the improved anode layer ion source is obtained by replacing the inner cathode and outer cathode materials of the ordinary anode layer ion source with high-purity molybdenum; (4) By means of vapor deposition, a ruthenium coating with a thickness of 0.5 - 1 μm is deposited on the surface of the activated molybdenum-coated molybdenum sheet to obtain the strengthened ruthenium-plated molybdenum sheet.

[0007] In the above technical solution of the present invention, the magnetron sputtering adopted is a physical vapor deposition technology that can generate high-energy particle bombardment, and it can generate a dense and uniform thin film structure. Through the action of high-energy particles during the sputtering process of the present invention, the deposited molybdenum plating layer obtains a smaller grain size and a more refined grain structure, improves the surface condition of the molybdenum sheet itself, and also reduces the exposure of its surface defects, significantly improving the bonding ability between the molybdenum sheet and the ruthenium plating layer.

[0008] In the above technical solution, the oxidative pickling is to use a solvent with oxidation and acidity to perform surface treatment on the molybdenum-plated molybdenum sheet, which can chemically etch and activate the molybdenum-plated molybdenum sheet to a certain extent. Without over-etching the surface molybdenum thin film, it increases the surface roughness of the material, thereby increasing the bonding force between the subsequent ruthenium layer and the molybdenum thin film. At the same time, the oxidative pickling also cleans the molybdenum-plated molybdenum sheet to remove pollutants and oxides on its surface.

[0009] In the above technical solution, using an improved anode layer ion source for ion cleaning and activation can effectively avoid the problem of element pollution during the ion cleaning process with a large beam current and high-speed ions, activate the molybdenum-plated molybdenum sheet, and improve the production efficiency of the continuous production process.

[0010] According to some preferred embodiments of the present invention, the oxidative pickling includes: washing the molybdenum-plated molybdenum sheet with aqua regia, and then cleaning it with deionized water after washing.

[0011] According to some preferred embodiments of the present invention, the magnetron sputtering treatment is carried out under vacuum, the treatment temperature is 450°C - 550°C, and the deposition rate is 5 - 10 nm / min.

[0012] According to some preferred embodiments of the present invention, the sputtering gas pressure of the magnetron sputtering treatment is 0.1 - 0.6 Pa, and the sputtering power is 700 - 1300 W.

[0013] According to some preferred embodiments of the present invention, step (1) further includes: after the magnetron sputtering treatment, cooling the sputtered molybdenum sheet obtained in an inert gas cycle to 55 - 65°C to obtain the molybdenum-plated molybdenum sheet.

[0014] According to some preferred embodiments of the present invention, the vapor deposition treatment is carried out under vacuum, the treatment temperature is 150 - 250°C, and the deposition rate is 10 - 20 nm / min.

[0015] According to some preferred embodiments of the present invention, the vapor deposition treatment is carried out in a magnetron sputtering device, and its sputtering gas pressure is 0.1 - 0.5 Pa, and the sputtering power is 800 - 1200 W.

[0016] According to some preferred embodiments of the present invention, the rate of the improved anode layer ion source for ion cleaning activation is 150 - 650 mm / min, the pressure is 0.06 - 0.8 Pa, and the current is 0.3 - 2.0 A.

[0017] The above - mentioned preferred embodiments of the present invention increase the ion source current, thereby increasing the beam current of the anode layer ion source and enhancing the cleaning effect per unit time. At the same time, considering that under the condition of a large beam current, the anode layer ion source will exhibit a relatively serious cathode etching phenomenon, and the cathode material will also be mixed into the ion beam bombarding the sample surface, causing elemental contamination and affecting the overall performance of the material. The common solution will reduce the ion source beam current and add a transition section, resulting in problems such as an increase in equipment length and a decrease in production efficiency. On the other hand, in the technical solution of the present invention, the substrate material is high - purity molybdenum. A small amount of cathode material molybdenum mixed in the ion beam will not cause contamination of the raw materials. Moreover, molybdenum, as a metal with a high melting point and a low sputtering rate, can well replace the currently used stainless - steel cathode. Therefore, the present invention can increase the ion source beam current and the cleaning speed, reduce the equipment length, and improve the production efficiency without causing raw material contamination and adding a transition section.

[0018] The present invention further provides a reinforced ruthenium - plated molybdenum sheet prepared according to the above - mentioned preparation method.

[0019] There is a certain transition layer between the molybdenum - plated layer and the molybdenum substrate of the reinforced ruthenium - plated molybdenum sheet, which mainly comes from the difference in crystal state caused by the difference in the preparation methods of the molybdenum - plated layer and the molybdenum substrate. There is a relatively clear boundary between the molybdenum - plated layer and the ruthenium - plated layer, without the appearance of a transition layer, and they are firmly combined, which conforms to the characteristics of non - wetting of molybdenum and ruthenium at low temperatures.

[0020] The preparation method of the present invention newly deposits a molybdenum - plated layer on the surface of the molybdenum sheet by magnetron sputtering, improves the surface state of the original matrix molybdenum sheet, fills the microscopic defects of the substrate to make it smoother, and forms a refined and dense molybdenum - plated layer, significantly improving the deposition conditions of the ruthenium - plated layer, enhancing the uniformity of the ruthenium - plated layer and the bonding ability with the molybdenum layer; The preparation method of the present invention has low requirements for the molybdenum sheet substrate and can directly use rolled molybdenum sheets for plating without grinding the molybdenum sheets. The preparation method of the present invention can form a ruthenium - plated layer that adheres firmly and combines tightly with the molybdenum sheet substrate, obtaining a reinforced ruthenium - plated molybdenum sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a display diagram of the peeling situation after the 3M tape peeling test for Example 1.

[0022] Figure 2 It is a display diagram of the peeling situation after the 3M tape peeling test for Comparative Example 1.

[0023] Figure 3 It is a diagram showing the peeling situation after the 3M tape peeling test for Comparative Example 2. Specific Embodiments

[0024] The present invention will be further described in detail through specific embodiments below, but it should not be understood that the scope of the present invention is limited to the following examples. Without departing from the above method idea of the present invention, various substitutions or changes made according to common general knowledge and conventional means in the art should be included within the scope of the present invention.

[0025] Example 1 The ruthenium - molybdenum coated wafer is prepared through the following steps: (1) Put a molybdenum wafer with a specification of φ30 mm×T1.4 mm into a cleaning kettle to remove the grease and organic contaminants on the surface, and then dry it to obtain a molybdenum wafer with a clean surface; (2) Put the molybdenum wafer with a clean surface into a magnetron sputtering device, pump high vacuum to form a vacuum system, then heat up the magnetron sputtering device to 500 °C to form a high - temperature system, carry out molybdenum deposition under the conditions of a sputtering pressure of 0.1 Pa and a sputtering power of 1000 W, with a deposition time of 60 min, and then cool down the gas in a nitrogen atmosphere to 60 °C by gas circulation to obtain a molybdenum wafer with a molybdenum coating thickness of 0.5 μm, that is, a molybdenum - coated molybdenum wafer; (3) Carry out oxidative pickling on the molybdenum - coated molybdenum wafer, then dry it and put it into a magnetron sputtering device to pump high vacuum to form a vacuum system. Heat up the magnetron sputtering device to 200 °C to form a high - temperature system, and then continuously carry out ion source cleaning and ruthenium deposition with a deposition time of 30 min. Cool down the gas in a nitrogen atmosphere to 60 °C by gas circulation to obtain a ruthenium - molybdenum coated wafer with a ruthenium layer thickness of 0.5 μm; among them, the specific process of oxidative pickling is: place the molybdenum - coated molybdenum wafer in aqua regia for 1 - 3 min, and then wash it with deionized water; the specific conditions of ion source cleaning are: cleaning pressure 0.2 Pa, cleaning current 2 A, cleaning speed 500 mm / min, and use a high - purity molybdenum ion source for cleaning; the specific conditions of ruthenium deposition are: sputtering pressure 0.2 Pa, sputtering power 1000 W.

[0026] Example 2 The ruthenium - molybdenum coated wafer is prepared through the following steps: (1) Put a molybdenum wafer with a specification of φ30 mm*T1.4 mm into a cleaning kettle to remove the grease and organic contaminants on the surface, and then dry it to obtain a molybdenum wafer with a clean surface; (2) Place the molybdenum wafers with clean surfaces into a magnetron sputtering device, evacuate to a high vacuum to form a vacuum system. Then, heat the magnetron sputtering device to 500 °C to form a high-temperature system. Next, perform molybdenum deposition at a sputtering pressure of 0.1 Pa and a power of 1000 W for a deposition time of 60 min. After that, cool down the gas in a nitrogen atmosphere by circulating to 60 °C to obtain molybdenum wafers with a molybdenum coating thickness of 0.5 μm, that is, molybdenum-coated molybdenum wafers; (3) Perform oxidative pickling on the molybdenum-coated molybdenum wafers. After drying, place them into the magnetron sputtering device and evacuate to a high vacuum to form a vacuum system. Heat the magnetron sputtering device to 200 °C to form a high-temperature system. Then, continuously perform ion source cleaning and ruthenium deposition for a deposition time of 60 min. Cool down the gas in a nitrogen atmosphere by circulating to 60 °C to obtain ruthenium-coated molybdenum wafers with a ruthenium layer thickness of 1 μm. The specific process of oxidative pickling is as follows: Place the molybdenum-coated molybdenum wafers in aqua regia for 1 - 3 min, and then wash them with deionized water. The specific conditions for ion source cleaning are as follows: cleaning pressure 0.2 Pa, cleaning current 2 A, cleaning speed 500 mm / min, and use a high-purity molybdenum ion source for cleaning. The specific conditions for ruthenium deposition are as follows: sputtering pressure 0.2 Pa, sputtering power 1000 W.

[0027] Example 3 The ruthenium-coated molybdenum wafers are prepared through the following steps: (1) Place the molybdenum wafers with a specification of φ30 mm * T1.4 mm into a cleaning kettle to remove the grease and organic contaminants on the surface. Then, dry them to obtain molybdenum wafers with clean surfaces; (2) Place the molybdenum wafers with clean surfaces into a magnetron sputtering device, evacuate to a high vacuum to form a vacuum system. Then, heat the magnetron sputtering device to 500 °C to form a high-temperature system. Next, perform molybdenum deposition at a sputtering pressure of 0.1 Pa and a power of 1000 W for a deposition time of 10 min. After that, cool down the gas in a nitrogen atmosphere by circulating to 60 °C to obtain molybdenum wafers with a molybdenum coating thickness of 0.1 μm, that is, molybdenum-coated molybdenum wafers; (3) Perform oxidative pickling on the molybdenum-coated molybdenum wafers. After drying, place them into the magnetron sputtering device and evacuate to a high vacuum to form a vacuum system. Heat the magnetron sputtering device to 200 °C to form a high-temperature system. Then, continuously perform ion source cleaning and ruthenium deposition for a deposition time of 60 min. Cool down the gas in a nitrogen atmosphere by circulating to 60 °C to obtain ruthenium-coated molybdenum wafers with a ruthenium layer thickness of 1 μm. The specific process of oxidative pickling is as follows: Place the molybdenum-coated molybdenum wafers in aqua regia for 1 - 3 min, and then wash them with deionized water. The specific conditions for ion source cleaning are as follows: cleaning pressure 0.2 Pa, cleaning current 2 A, cleaning speed 500 mm / min, and use a high-purity molybdenum ion source for cleaning. The specific conditions for ruthenium deposition are as follows: sputtering pressure 0.2 Pa, sputtering power 1000 W.

[0028] The ruthenium-coated molybdenum wafers prepared in Examples 1-3 were respectively subjected to ruthenium coating adhesion test and 3M tape peeling test, and the results are shown in Table 1: Table 1 Test results of coating properties of Examples 1-3

[0029] Among them, the adhesion of the ruthenium coating was tested by the scratch method, and the process was as follows: Using a micro-scratch tester, a hard indenter diamond needle was used to scratch the surface of the coating under an increasing normal force (pressure) until the coating was damaged. The bonding strength was evaluated according to the critical load (N, Newton) when the coating ruptured.

[0030] The process of the 3M tape peeling test was as follows: Take a 3M tape of appropriate length and paste it on the coating of the specimen to be tested, press it firmly until there are no bubbles, pores, etc. between the tape and the coating. After 10 s, peel the tape with a force perpendicular to the coating direction, and observe whether there are phenomena such as tearing, film layer peeling off on the coating surface, and whether there is adhered ruthenium metal on the tape.

[0031] Among them, there was no peeling phenomenon in the ruthenium coating of Example 1 as shown in the appendix Figure 1 shown.

[0032] Ruthenium-coated molybdenum wafers were prepared by the same process as in Examples 1-3, except that the process of magnetron sputtering molybdenum in step (2) was not carried out and the ruthenium plating process in step (3) was directly carried out to obtain ruthenium-coated molybdenum wafers without molybdenum coating. The same ruthenium coating adhesion test and 3M tape peeling test as in Examples 1-3 were carried out on them, and the results are shown in Table 2: Table 2 Test results of coating properties of Comparative Examples 1-3

[0033] Among them, a large amount of peeling phenomenon of the ruthenium coating occurred in Comparative Example 1 as shown in the appendix Figure 2 shown, and a partial peeling phenomenon of the ruthenium coating occurred in Comparative Example 2 as shown in the appendix Figure 3 shown.

[0034] The test results show that compared with the molybdenum wafers directly plated with ruthenium, the bonding strength between the ruthenium coating and the substrate in the ruthenium-coated molybdenum wafers obtained by adding a new molybdenum coating and then plating ruthenium in the present invention is significantly improved.

[0035] The above embodiments are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, improvements and refinements should also be regarded as within the protection scope of the present invention.

Claims

1. A preparation method of a ruthenium-plated molybdenum sheet, characterized in that, It includes: (1) Using high-purity molybdenum as a target, through magnetron sputtering treatment, a high-purity molybdenum coating with a thickness of 0.1 - 0.5 μm is deposited on the surface of the molybdenum sheet to obtain a molybdenum-coated molybdenum sheet; (2) Oxidizing and pickling the molybdenum-coated molybdenum sheet to obtain a pickled molybdenum-coated molybdenum sheet; (3) Ion cleaning and activation of the pickled molybdenum-coated molybdenum sheet by an improved anode layer ion source to obtain an activated molybdenum-coated molybdenum sheet. The improved anode layer ion source is obtained by replacing the inner cathode and outer cathode materials of the ordinary anode layer ion source with high-purity molybdenum; (4) Through vapor deposition treatment, a ruthenium coating with a thickness of 0.5 - 1 μm is deposited on the surface of the activated molybdenum-coated molybdenum sheet to obtain the enhanced ruthenium-coated molybdenum sheet.

2. The preparation method according to claim 1, wherein The oxidizing pickling includes: washing the molybdenum-coated molybdenum sheet with aqua regia, and then cleaning it with deionized water after washing.

3. The preparation method according to claim 1, wherein, The magnetron sputtering treatment is carried out under vacuum, the treatment temperature is 450°C - 550°C, and the deposition rate is 5 - 10 nm / min.

4. The preparation method according to claim 1, wherein The sputtering gas pressure of the magnetron sputtering treatment is 0.1 - 0.6 Pa, and the sputtering power is 700 - 1300 W.

5. The preparation method according to claim 1, characterized in that, Step (1) further includes: after the magnetron sputtering treatment, cooling the sputtered molybdenum sheet obtained in an inert gas atmosphere to 55 - 65°C to obtain the molybdenum-coated molybdenum sheet.

6. The preparation method according to claim 1, wherein The vapor deposition treatment is carried out under vacuum, the treatment temperature is 150 - 250°C, and the deposition rate is 10 - 20 nm / min.

7. The preparation method according to claim 1, characterized in that, The vapor deposition treatment is carried out in a magnetron sputtering device, the sputtering gas pressure is 0.1 - 0.5 Pa, and the sputtering power is 800 - 1200 W.

8. The preparation method according to claim 7, characterized in that, The rate of the ion cleaning and activation by the improved anode layer ion source is 150 - 650 mm / min, the pressure is 0.06 - 0.8 Pa, and the current is 0.3 - 2.0 A.

9. An enhanced ruthenium-coated molybdenum sheet prepared by the preparation method according to any one of claims 1 - 8.

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