A method for metallizing a ceramic substrate and a ceramic copper clad substrate

Abstract

The application relates to the technical field of silicon nitride ceramic metallization, in particular to a ceramic substrate metallization method and a ceramic copper-clad substrate. The ceramic substrate metallization method comprises the following steps: adopting a magnetron sputtering method to sequentially deposit a TiN / Ti gradient transition layer and a Cu seed layer on the surface of a ceramic substrate to prepare a ceramic copper-clad substrate; the TiN / Ti gradient transition layer comprises a TiN transition layer and a Ti transition layer; the thickness of the TiN transition layer is 100-600 nm; and the thickness of the Ti transition layer is 100-200 nm. By controlling the nanometerization of the thickness of the TiN / Ti gradient transition layer, the problems that the existing silicon nitride ceramic substrate metallization method is still complex in preparation process, the interface bonding is poor due to the large interface stress between the metal and the ceramic, and the high thermal resistance of the multilayer interface can reduce the heat dissipation performance are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon nitride ceramic metallization, and in particular to a metallization method of a ceramic substrate and a ceramic copper-clad substrate. Background Art

[0002] With the continuous development of lightweight and integrated high-power electronic devices, heat dissipation has become a key technology that affects device performance and lifespan. In power modules, the heat dissipation substrate not only has to provide electrical connection and mechanical support functions, but also serves as an important heat dissipation channel. As a new type of heat dissipation material, ceramic substrates have excellent thermal conductivity, insulation, voltage resistance, and good thermal matching with chips. They are widely used as key materials for IGBT modules in new energy vehicles, high-speed railways, LED lighting and other fields. The full English name of IGBT module is Insulated Gate Bipolar Transistor Modules, and the Chinese name is Insulated Gate Bipolar Transistor Modules.

[0003] Before packaging a ceramic substrate, its surface must be metallized. This involves firmly adhering a metal conductive layer to the ceramic surface to achieve a connection between the ceramic and the metal. Metallization is the most critical step in the ceramic substrate manufacturing process, determining the device's packaging performance, manufacturing cost, and service life. However, the inherent difference in thermal expansion coefficients between ceramics and metals results in significant stress at the interface when the substrate is subjected to thermal cycling, leading to ceramic cracking or metal layer peeling, which in turn causes module failure. Therefore, implementing metallization with high interface bonding strength and thermal shock resistance on the ceramic surface is a key issue in overcoming its application bottleneck.

[0004] Silicon nitride ceramic substrates have excellent comprehensive properties such as high thermal conductivity, high mechanical properties, and high reliability, and are gradually becoming the most promising substrate material for high-power modules. After metallization, they can weld thicker oxygen-free copper and achieve higher reliability in IGBT modules for electric vehicles. However, the current thermal cycling resistance of silicon nitride ceramic copper-clad laminates cannot meet the requirements of electric vehicles to maintain performance after 3,000 thermal cycles under temperature conditions of -40°C to 250°C. Therefore, the development of new silicon nitride ceramic surface metallization technologies to provide strong interface bonding and high-temperature impact resistance is the key to manufacturing high-reliability and high-quality silicon nitride ceramic substrates.

[0005] Currently, the main methods for metallizing silicon nitride ceramic substrates are direct copper cladding and active metal brazing. While these methods offer a certain degree of reliability, existing methods still suffer from complex preparation processes, high metal-ceramic interface stress leading to poor interface bonding, and thick interfaces resulting in high thermal resistance. Summary of the Invention

[0006] In order to solve the problems of large metal-ceramic interface stress leading to poor interface bonding and thick interface leading to high thermal resistance in existing metallization methods of silicon nitride ceramic substrates, the present invention aims to provide a ceramic substrate metallization method and a ceramic copper-clad substrate.

[0007] To achieve the above objectives, the technical solutions of the present invention are as follows.

[0008] A first aspect of the present invention provides a method for metallizing a ceramic substrate, comprising the following steps:

[0009] A TiN / Ti gradient transition layer and a Cu seed layer are sequentially deposited on the surface of a ceramic substrate by magnetron sputtering to prepare a ceramic copper-clad substrate; the TiN / Ti gradient transition layer includes a TiN transition layer and a Ti transition layer; the thickness of the TiN transition layer is between 100nm and 600nm; the thickness of the Ti transition layer is between 100nm and 200nm.

[0010] The present invention achieves reliable connection between the silicon nitride ceramic substrate and the metallic copper by adding a TiN / Ti gradient transition layer between the ceramic substrate and the copper seed layer and controlling the thickness of the TiN / Ti gradient transition layer to nanometer size, thereby greatly improving the interface bonding strength and thermal cycling resistance of the silicon nitride ceramic copper-clad substrate. This solves the problems of the existing metallization method of silicon nitride ceramic substrate, such as complex preparation process, high stress at the metal-ceramic interface leading to poor interface bonding, and high thermal resistance of the multi-layer interface which reduces heat dissipation performance.

[0011] Preferably, the TiN transition layer has at least one layer, and the thickness of each TiN transition layer is 100nm to 200nm. The present invention solves the problem of interface bonding between silicon nitride ceramics and metals and how to reduce interface thermal resistance by nano-scaling the thickness of the intermediate layer.

[0012] Preferably, the TiN transition layer has at least two layers, and as the number of the TiN transition layers increases, the nitrogen content is controlled to gradually decrease from 40% to 45% during the deposition of the TiN transition layers.

[0013] The present invention prepares high-nitrogen-content TiN using 40%-45% nitrogen, then gradually reduces the nitrogen content in the TiN layer to transition from TiN to a pure Ti layer. This gradual reduction in nitrogen content in the TiN layer achieves the transition from TiN to Ti, addressing the interface bonding issues between silicon nitride ceramics and metals and reducing interfacial thermal resistance.

[0014] Preferably, the process of depositing the TiN transition layer also includes controlling the nitrogen content to be between 10% and 45%. The present invention adjusts the thickness of the TiN transition layer by controlling the nitrogen content and realizes the transition from TiN to Ti by gradually reducing the N content in the TiN layer.

[0015] Preferably, the method of depositing the TiN transition layer is:

[0016] Titanium target is used as target material, and the background vacuum degree is ≤5×10 -4 Pa, nitrogen is passed, the nitrogen content is 10% to 45%, the working pressure is controlled at 0.5Pa to 1.5Pa, the sputtering power is 2KW to 3KW, and the substrate bias is 50 to 70V; magnetron sputtering is performed to deposit a TiN transition layer on the surface of the ceramic substrate.

[0017] Preferably, the method of depositing the Ti transition layer is:

[0018] A titanium target is used as the target material, nitrogen is turned off, the working gas pressure is controlled to be 0.5Pa-1.5Pa, the sputtering power is 2KW-3KW, and the substrate bias is 50-70V; magnetron sputtering is performed to deposit a Ti transition layer on the surface of the Ti transition layer to form a TiN / Ti gradient transition layer.

[0019] Preferably, the method of depositing the Cu seed layer is:

[0020] A copper target is used as a target material, a working gas pressure is controlled at 0.5 Pa to 1.5 Pa, and a sputtering power is controlled at 2 KW to 3 KW; magnetron sputtering is performed to deposit a Cu seed layer on the surface of the TiN / Ti gradient transition layer.

[0021] Preferably, the thickness of the Cu seed layer is 5 μm to 10 μm. In the present invention, the thickness of the Cu seed layer can be selected according to actual needs.

[0022] Preferably, before depositing the TiN / Ti gradient transition layer, the process further includes: cleaning and drying the surface of the ceramic substrate; and performing glow sputtering cleaning on the ceramic substrate, thereby facilitating subsequent metallization treatment.

[0023] Preferably, the ceramic substrate is a silicon nitride ceramic substrate.

[0024] A second aspect of the present invention provides a ceramic copper-clad substrate, which is prepared by the metallization method of the ceramic substrate described in the first aspect.

[0025] Beneficial effects of the present invention:

[0026] 1. The present invention achieves reliable connection between the silicon nitride ceramic substrate and the metallic copper by adding a TiN / Ti gradient transition layer between the ceramic substrate and the copper seed layer and controlling the thickness of the TiN / Ti gradient transition layer to nanometer size, thereby significantly improving the interface bonding strength and thermal cycling resistance of the silicon nitride ceramic copper-clad substrate. This solves the problems of the existing metallization method of silicon nitride ceramic substrate, such as complex preparation process, high stress at the metal-ceramic interface leading to poor interface bonding, and high thermal resistance of the multi-layer interface which reduces heat dissipation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The X-ray diffraction patterns of the surface films of the ceramic copper-clad substrates prepared in Examples 1 to 3 are shown. (a) is the X-ray diffraction pattern of the surface film of the ceramic copper-clad substrate prepared in Example 1; (b) is the X-ray diffraction pattern of the surface film of the ceramic copper-clad substrate prepared in Example 2; and (c) is the X-ray diffraction pattern of the surface film of the ceramic copper-clad substrate prepared in Example 3.

[0028] Figure 2 This is a cross-sectional morphology of the TiN film in the ceramic copper-clad substrate prepared in Example 3.

[0029] Figure 3 The following are surface morphologies of the ceramic copper-clad substrates prepared in Examples 1 to 3 and Comparative Example 1 after 70 cycles of thermal cycling. (a) is a schematic diagram of the peeling of the transition layer system in Comparative Example 1 after thermal shock cycling; (b) is a schematic diagram of the peeling of the TiN / Ti gradient transition layer system in Example 1 after thermal shock cycling; (c) is a schematic diagram of the peeling of the TiN / Ti gradient transition layer system in Example 2 after thermal shock cycling; (d) is a schematic diagram of the peeling of the TiN / Ti gradient transition layer system in Example 3 after thermal shock cycling; (e) is a partial enlarged schematic diagram of the peeling interface in (a); (f) is a partial enlarged schematic diagram of the peeling interface in (d). In (e) and (f), 1, 2, 3, 4, and 5 represent different locations of the peeling interface, respectively. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0032] Currently, the main methods for metallizing silicon nitride ceramic substrates are direct copper cladding and active metal brazing. Direct copper cladding is called Direct Bond Copper (DBC). Active metal brazing is called Active Metal Brazing (AMB).

[0033] DBC technology refers to heating at a high temperature of 1000℃ or above in nitrogen containing oxygen, so that copper foil and ceramic substrate are firmly combined together through eutectic bonding, which has high bonding strength, can be welded with thick copper foil such as 100μm-600μm, and has good thermal conductivity and mechanical properties, and is widely used in IGBT module packaging of power devices. However, the preparation process of DBC substrate has high temperature, large stress at the interface of metal and ceramic, which limits the application of DBC substrate. Because micro-pores are easily generated between the ceramic and the copper layer, the heat shock resistance of the product is reduced, which becomes the bottleneck of the application of DBC substrate in high power density and high reliability device packaging. In addition, the eutectic temperature and oxygen content need to be strictly controlled during the preparation of DBC substrate, which requires high equipment and process control, resulting in high production cost.

[0034] AMB technology is a further development of DBC process technology, which mainly uses a small amount of active elements such as Ti and Zr in the solder to react with the ceramic to form a reaction layer on the surface of the ceramic, thereby improving the interfacial bonding strength between the ceramic and the metal. It is a widely used process for silicon nitride ceramic substrate. The silicon nitride substrate treated by AMB technology has high reliability. However, the cost of AMB method is high, there are few suitable active solders, and the composition of the solder and the process have a great influence on the welding quality. In practical application, the thickness of the intermediate layer determines the welding quality. When the thickness is too thin, the intermediate layer is easy to be discontinuous and have defects such as holes, which leads to poor bonding strength. When the thickness is too thick, the large residual stress in the film layer is easy to cause the substrate to crack, which reduces the bonding strength. Moreover, due to the high thermal resistance of the multi-layer interface, the tens to hundreds of microns thick intermediate layer in the AMB technology will reduce the heat dissipation performance to some extent.

[0035] Therefore, realizing the precise control of the thickness of the intermediate layer to nanometer is an effective way to solve the two key problems of the bonding of silicon nitride ceramic / metal interface and the reduction of interface thermal resistance.

[0036] In summary, although the silicon nitride substrate treated by the above metallization method has certain reliability, the existing metallization method of silicon nitride ceramic substrate still has the problems of complex preparation process, poor interface bonding due to large stress at the interface of metal and ceramic, and high thermal resistance of multi-layer interface which reduces the heat dissipation performance.

[0037] In order to solve the above problems, the present invention proposes a method for metallizing a silicon nitride copper-clad substrate based on high-power pulsed magnetron sputtering technology. By adding a TiN / Ti gradient transition layer between the ceramic substrate and the copper seed layer and controlling the thickness of the TiN / Ti gradient transition layer to nanometer size, a reliable connection between the silicon nitride ceramic substrate and the metallic copper is achieved, and the interface bonding strength and resistance to cold and hot cycles of the silicon nitride ceramic copper-clad substrate are greatly improved, so as to solve the problems of the existing metallization method of silicon nitride ceramic substrate still existing in the preparation process, the large stress at the metal-ceramic interface leading to poor interface bonding, and the high thermal resistance of the multi-layer interface which reduces the heat dissipation performance.

[0038] The technical solution of the present invention is further described below by means of specific examples. In the following examples, the methods described are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0039] In the following examples, the purity of the Ti target and the Cu target is 99.99%; the purity of the argon gas and the nitrogen gas is 99.999%.

[0040] Example 1

[0041] A method for metallizing a ceramic substrate is to deposit a high nitrogen content TiN / Ti gradient transition layer on the surface of a silicon nitride substrate using magnetron sputtering technology. The specific method includes the following steps:

[0042] Step 1, cleaning of the silicon nitride substrate: soak the silicon nitride substrate in anhydrous ethanol, ultrasonicate it in acetone and anhydrous ethanol in sequence for 10 to 15 minutes, and dry it.

[0043] Step 2: Glow cleaning: Install the dried silicon nitride substrate on the workpiece turntable in the vacuum chamber of the magnetron sputtering equipment, and install the Ti target and Cu target on the corresponding target positions. Then evacuate the vacuum chamber of the magnetron sputtering equipment to a pressure of ≤5×10 -4 After 100 Pa, argon gas is introduced to control the gas pressure to 0.5 Pa to 1.5 Pa, a bias voltage of -200 V to -500 V is applied to the silicon nitride substrate, and then glow cleaning is performed in a magnetron sputtering chamber for 30 min to 45 min.

[0044] Step 3, depositing a high nitrogen content TiN transition layer on the surface of the silicon nitride substrate: introduce argon and nitrogen with a purity of not less than 99.9%, a nitrogen content of 45%, a substrate bias of 60V, an operating pressure of 0.8Pa, and a sputtering power of 2.5KW, and then deposit a 150nm high nitrogen content TiN transition layer on the surface of the silicon nitride substrate.

[0045] Step 4: Depositing Ti layer on TiN transition layer: turn off nitrogen, working pressure 0.5 Pa, substrate bias 60 V, sputtering power 2.5 KW, deposit 200 nm Ti layer on high nitrogen content TiN transition layer.

[0046] Step 5: Depositing Cu seed layer on high nitrogen content TiN / Ti gradient transition layer: turn on Cu target, working pressure 0.5 Pa, Cu target sputtering power 3 KW, deposit 8 μm Cu seed layer on high nitrogen content TiN / Ti gradient transition layer, to prepare ceramic copper clad substrate with strong interface bonding.

[0047] To facilitate subsequent thermal shock cycle test, cut the metal Cu foil and ultrasonically clean it in acetone and anhydrous ethanol solution for 10 min, then dry and cover thick copper on the Cu seed layer of the ceramic copper clad substrate; the purpose of covering thick copper is to test thermal cycle stability in thermal shock test. The thick copper is a metal Cu foil with a thickness of 100 μm-600 μm. Then perform cold and hot cycle test in the temperature range of -10 ℃-150 ℃.

[0048] Example 2

[0049] A method for metallizing ceramic substrate, which is to deposit multi-layer TiN / Ti transition layer on the surface of silicon nitride substrate by using magnetron sputtering technology, and the specific method comprises the following steps:

[0050] Step 1: Clean the silicon nitride ceramic plate: immerse the silicon nitride substrate in anhydrous ethanol, then ultrasonically clean it in acetone and anhydrous ethanol for 10 min-15 min, and dry.

[0051] Step 2: Perform glow cleaning: install the dried silicon nitride substrate on the workpiece turret in the vacuum chamber of the magnetron sputtering equipment, and install the Ti target and Cu target on the corresponding target positions. Then pump the magnetron sputtering vacuum chamber to a pressure of ≤5×10 -4 Pa, introduce argon, control the pressure to be 0.5 Pa-1.5 Pa, apply a bias of -200 V--500 V to the silicon nitride substrate, and then perform glow cleaning in the magnetron sputtering chamber for 30 min-45 min.

[0052] Step 3: Depositing two layers of TiN transition layer on the surface of silicon nitride substrate: introduce argon and nitrogen with a purity of not less than 99.9%, nitrogen content 45%, substrate bias 60 V, working pressure 0.8 Pa, sputtering power 2.5 KW, deposit 100 nm high nitrogen content TiN transition layer on the surface of silicon nitride substrate; reduce the nitrogen content to 20%, substrate bias 60 V, working pressure 0.6 Pa, sputtering power 2.5 KW, deposit 100 nm low nitrogen content TiN transition layer.

[0053] Step 4, depositing a Ti layer on the two TiN transition layers: turn off the nitrogen, set the working pressure to 0.5 Pa, the substrate bias to 60 V, and the sputtering power to 2.5 KW, and deposit a 200 nm Ti layer on the two TiN transition layers.

[0054] Step 5, depositing a Cu seed layer on the multilayer TiN / Ti transition layer: turning on the Cu target, the working gas pressure is 0.5 Pa, the Cu target sputtering power is 2.5 KW, and a Cu seed layer with a thickness of 8 μm is deposited on the multilayer TiN / Ti transition layer to prepare a ceramic copper-clad substrate with strong interface bonding.

[0055] To facilitate subsequent thermal shock cycling experiments, the cut Cu foil was ultrasonically cleaned in acetone and anhydrous ethanol for 10 minutes each. After drying, thick copper was applied to the Cu seed layer of the ceramic Cu-clad substrate. The purpose of the thick copper coating was to conduct thermal shock experiments to verify thermal cycling stability. The thick copper foil, with a thickness of 100μm to 600μm, was then subjected to thermal cycling experiments within a temperature range of -10°C to 150°C.

[0056] Example 3

[0057] A method for metallizing a ceramic substrate is to deposit a multilayer TiN / Ti transition layer on the surface of a silicon nitride substrate using magnetron sputtering technology. The specific method includes the following steps:

[0058] Step 1: Cleaning the silicon nitride ceramic plate: ultrasonically clean the silicon nitride substrate with acetone, anhydrous ethanol, and deionized water for 10 minutes in sequence, and then dry it.

[0059] Step 2: Glow cleaning: Install the dried silicon nitride substrate on the workpiece turntable in the vacuum chamber of the magnetron sputtering equipment, and install the Ti target and Cu target on the corresponding target positions. Then evacuate the vacuum chamber of the magnetron sputtering equipment to a pressure below 5×10 -4 After 100 Pa, argon gas is introduced to control the gas pressure to 0.5 Pa to 1.5 Pa, a bias voltage of -200 V to -500 V is applied to the silicon nitride substrate, and then glow cleaning is performed in a magnetron sputtering chamber for 30 min to 45 min.

[0060] Step 3: Deposit a multilayer TiN transition layer on the surface of the silicon nitride substrate: deposit a TiN base layer on the silicon nitride substrate with a sputtering power of 3 kW, a substrate bias of 70 V, a nitrogen content of 45%, a deposition thickness of 100 nm, and a background vacuum of no more than 5 × 10 -4 Pa, working pressure 1.0-1.5Pa; then the nitrogen content is reduced to 35%, the working pressure is 1.0Pa, and a TiN transition layer with a thickness of 150nm is deposited; finally, the nitrogen content is reduced to 10%, the working pressure is 0.3Pa, and a low nitrogen content TiN transition layer with a thickness of 200nm is deposited.

[0061] Step 4, depositing a Ti layer on the multi-layer TiN transition layer: turn off the nitrogen, control the gas pressure to 1.5 Pa, deposit Ti on the transition layer, sputtering power 3KW, substrate bias 70V, and deposit the Ti layer to a thickness of 200nm.

[0062] Step 5: depositing a Cu seed layer on the multilayer TiN / Ti transition layer: turning on the Cu target, controlling the gas pressure to 1.5 Pa, the Cu target sputtering power to 3 kW, and depositing a Cu seed layer with a thickness of 10 μm to prepare a ceramic copper-clad substrate with strong interface bonding.

[0063] Comparative Example 1

[0064] A method for metallizing a ceramic substrate is to deposit a Ti transition layer on the surface of a silicon nitride substrate using magnetron sputtering technology. The specific method includes the following steps:

[0065] Step 1: Cleaning the silicon nitride ceramic plate: ultrasonically clean the silicon nitride substrate with acetone, anhydrous ethanol, and deionized water for 10 minutes in sequence, and then dry it.

[0066] Step 2: Glow cleaning: Install the dried silicon nitride substrate on the workpiece turntable in the vacuum chamber of the magnetron sputtering equipment, and install the Ti target and Cu target on the corresponding target positions. Then evacuate the vacuum chamber of the magnetron sputtering equipment to a pressure below 5×10 -4 After 100 Pa, argon gas is introduced to control the gas pressure to 0.5 Pa to 1.5 Pa, a bias voltage of -200 V to -500 V is applied to the silicon nitride substrate, and then glow cleaning is performed in a magnetron sputtering chamber for 30 min to 45 min.

[0067] Step 3: Deposit a Ti transition layer on the surface of the silicon nitride substrate: Keep the nitrogen closed and the background vacuum no higher than 5×10 - 4 Pa, controlled gas pressure 1.5Pa, deposited Ti transition layer on the surface of silicon nitride substrate, sputtering power 3KW, substrate bias 70V, the deposited Ti layer thickness is 200nm.

[0068] Step 4, depositing a Cu seed layer on the Ti transition layer: turning on the Cu target, controlling the gas pressure to 1.5 Pa, the Cu target sputtering power to 3 kW, and depositing a Cu seed layer with a thickness of 10 μm to prepare a ceramic copper-clad substrate with strong interface bonding.

[0069] To facilitate subsequent thermal shock cycling experiments, the cut Cu foil was ultrasonically cleaned in acetone and anhydrous ethanol for 10 minutes each. After drying, thick copper was applied to the Cu seed layer of the ceramic Cu-clad substrate. The purpose of the thick copper coating was to conduct thermal shock experiments to verify thermal cycling stability. The thick copper foil, with a thickness of 100μm to 600μm, was then subjected to thermal cycling experiments within a temperature range of -10°C to 150°C.

[0070] Table 1 Magnetron sputtering conditions of TiN transition layer

[0071]

[0072] Table 2 Thickness of different sputtered layers

[0073]

[0074]

[0075] Test 1: X-ray diffraction analysis.

[0076] The surface films of the ceramic copper-clad substrates prepared in Examples 1 to 3 were analyzed by X-ray diffraction. Figure 1 .

[0077] Figure 1 The X-ray diffraction patterns of the surface films of the ceramic copper-clad substrates prepared in Examples 1 to 3 are shown. (a) is the X-ray diffraction pattern of the surface film of the ceramic copper-clad substrate prepared in Example 1; (b) is the X-ray diffraction pattern of the surface film of the ceramic copper-clad substrate prepared in Example 2; and (c) is the X-ray diffraction pattern of the surface film of the ceramic copper-clad substrate prepared in Example 3.

[0078] Depend on Figure 1 The results show that the surface films of the ceramic copper-clad substrates prepared in Examples 1 to 3 all contain Si3N4, Ti2N, Ti3N4, Ti, Cu3Ti and Cu.

[0079] Test 2: Cross-sectional morphology analysis.

[0080] The cross-sectional morphology of the TiN film in the ceramic copper-clad substrate prepared in Example 3 was analyzed. Figure 2 . Figure 2 This is a cross-sectional morphology of the TiN film in the ceramic copper-clad substrate prepared in Example 3.

[0081] There is no obvious difference in the cross-sectional morphology of Example 1 and Example 2 from that of Example 3.

[0082] Depend on Figure 2The results show that the TiN film deposited in Example 3 has a dense structure and fine grain structure. There is no gap between the film and the silicon nitride substrate, and the surface of the film does not show any undulations. There are no defects such as holes at the interface.

[0083] Test 3: Thermal shock cycle experiment.

[0084] The ceramic copper-clad substrate prepared in Example 3 was subjected to a hot and cold cycle test in the temperature range of -10°C to 150°C, and the peeling condition after 70 cycles of hot and cold cycles was observed. The results are shown in FIG. Figure 3 .

[0085] Table 3 Compositions at different locations of the peeling interface in Comparative Example 1 (at.%)

[0086] element 1 2 3 4 5 Si 0.04 0.32 89.46 96.86 96.17 Ti 0.79 0.00 10.54 0.23 0.52 Cr 11.30 2.09 0.00 0.00 0.00 Cu 87.87 97.60 0.00 2.91 3.32

[0087] Table 4 Compositions at different locations of the peeling interface in Example 3 (at.%)

[0088] element 1 2 3 4 5 Si 99.69 99.66 93.99 96.37 0.42 Ti 0.34 0.00 2.26 0.00 0.00 Cr 0.00 0.06 0.50 0.00 1.04 Cu 0.00 0.28 3.26 3.63 98.54

[0089] Figure 3 The following are surface morphologies of the ceramic copper-clad substrates prepared in Examples 1 to 3 and Comparative Example 1 after 70 cycles of thermal cycling. (a) is a schematic diagram of the peeling of the transition layer system in Comparative Example 1 after thermal shock cycling; (b) is a schematic diagram of the peeling of the TiN / Ti gradient transition layer system in Example 1 after thermal shock cycling; (c) is a schematic diagram of the peeling of the TiN / Ti gradient transition layer system in Example 2 after thermal shock cycling; (d) is a schematic diagram of the peeling of the TiN / Ti gradient transition layer system in Example 3 after thermal shock cycling; (e) is a partial enlarged schematic diagram of the peeling interface in (a); (f) is a partial enlarged schematic diagram of the peeling interface in (d). In (e) and (f), 1, 2, 3, 4, and 5 represent different locations of the peeling interface, respectively.

[0090] Depend on Figure 3 The results show that the thermal fatigue performance of the TiN / Ti gradient transition layer system in Examples 1 to 3 is better than that of the pure Ti system in Comparative Example 1, and the thermal fatigue performance of the TiN / Ti gradient transition layer system in Example 3 is the best.

[0091] According to the composition analysis of different positions of the peeling interface in Tables 3 and 4, it can be seen that the peeling interface is between the transition layer and the Si3N4 substrate, which proves that the core of enhancing the ceramic metallization bonding strength in Example 3 lies in improving the bonding strength between the TiN / Ti gradient transition layer and the Si3N4 substrate, and at the same time verifies the superiority of the TiN / Ti gradient transition layer.

[0092] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for metallizing a ceramic substrate, characterized in that: The following steps are involved: A TiN / Ti gradient transition layer and a Cu seed layer were sequentially deposited on the surface of a ceramic substrate by magnetron sputtering to prepare a ceramic copper-clad substrate. The TiN / Ti gradient transition layer only includes a TiN transition layer and a Ti transition layer; the thickness of the Ti transition layer is 100nm to 200nm; The TiN transition layer has at least two layers, and the thickness of each TiN transition layer is 100nm to 200nm. As the number of TiN transition layers increases, the nitrogen content is controlled to gradually decrease from 40% to 45% during the deposition of the TiN transition layer.

2. The method for metallizing a ceramic substrate according to claim 1, wherein: The method for depositing the TiN transition layer is: Titanium target is used as target material, and the background vacuum degree is ≤5×10 -4 Pa, pass nitrogen, the nitrogen content is 10% to 45%, control the working pressure to 0.5Pa to 1.5Pa, the sputtering power is 2KW to 3KW, and the substrate bias is 50 to 70V; magnetron sputtering is performed to deposit a TiN transition layer on the surface of the ceramic substrate.

3. The method for metallizing a ceramic substrate according to claim 1, wherein: The method for depositing the Ti transition layer is: A titanium target is used as the target material, nitrogen is turned off, the working gas pressure is controlled to be 0.5Pa-1.5Pa, the sputtering power is 2KW-3KW, and the substrate bias is 50-70V; magnetron sputtering is performed to deposit a Ti transition layer on the surface of the TiN transition layer to form a TiN / Ti gradient transition layer.

4. The method for metallizing a ceramic substrate according to claim 1, wherein: The method for depositing the Cu seed layer is: A copper target is used as a target material, a working gas pressure is controlled at 0.5 Pa to 1.5 Pa, and a sputtering power is controlled at 2 KW to 3 KW; magnetron sputtering is performed to deposit a Cu seed layer on the surface of the TiN / Ti gradient transition layer.

5. The method for metallizing a ceramic substrate according to claim 1, wherein: The thickness of the Cu seed layer is 5 μm to 10 μm.

6. The method for metallizing a ceramic substrate according to claim 1, wherein: Before depositing the TiN / Ti gradient transition layer, the method further includes: cleaning and drying the surface of the ceramic substrate; and performing glow sputtering cleaning on the ceramic substrate.

7. The method for metallizing a ceramic substrate according to claim 1, wherein: The ceramic substrate is a silicon nitride ceramic substrate.

8. A ceramic copper-clad substrate, characterized in that: The ceramic substrate is prepared by the metallization method according to claim 1.

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