AMB ceramic substrate preparation method based on magnetron sputtering

Abstract

The invention discloses a preparation method of an AMB substrate, which comprises the following specific preparation steps: placing a ceramic substrate in an ultrasonic cleaning machine for surface cleaning treatment, and then loading the ceramic substrate on a sample table of magnetron sputtering equipment; a magnetron sputtering process is adopted, multiple layers of titanium (Ti), copper (Cu) and silver (Ag) films are deposited in sequence, and the thickness of each layer is accurately controlled according to a preset proportion. Then, the surface of the deposited film is covered with a copper foil, a sample is placed in a vacuum heat treatment furnace, constant-temperature treatment is conducted at the set temperature, and the copper foil and the deposited film are tightly combined; the AMB substrate is prepared by adopting a magnetron sputtering technology. Compared with a traditional preparation process, nanoscale thickness control can be achieved in the thin film deposition process, and the size precision of an interface bonding layer is remarkably improved; and the process temperature is obviously reduced, and the interface reaction can be completed only by keeping the temperature at 700-800 DEG C, so that the thermal damage of the thermal cycle stress to the substrate material and the interface bonding layer is effectively reduced.

Description

Technical Field

[0001] The present invention relates to a method for preparing an AMB substrate based on magnetron sputtering. Background Art

[0002] As a high-performance electronic packaging material, the active metal brazing (AMB) substrate is widely used in fields such as power modules and LED packaging. The preparation of traditional AMB substrates mainly uses the brazing process. By adding an active brazing filler metal (such as an Ag-Cu-Ti alloy) between a ceramic substrate (such as Al2O3, AlN) and a metal layer (such as Cu), reliable connection between the ceramic and the metal can be achieved at high temperatures. However, in the traditional brazing process, it is difficult to precisely control the thickness of the brazing filler metal layer, and the process temperature is relatively high (usually higher than 850 °C), which is likely to cause thermal damage to the ceramic substrate; pores, cracks and other defects are easily generated during the process, reducing the product reliability. In recent years, due to its excellent thin film deposition performance, magnetron sputtering technology has been widely used in the field of electronic material preparation. This technology bombards the target material with high-energy particles, enabling the target atoms to be deposited on the substrate surface with nanoscale precision, and nanoscale thin film thickness control can be achieved; at the same time, the thin film has good composition uniformity and a relatively low process temperature, which can reduce thermal stress and has a high interfacial bonding strength. Therefore, developing a method for preparing an AMB substrate based on magnetron sputtering technology is of great significance for improving the performance and reliability of electronic packaging materials. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the difficulty in evenly coating the active metal paste on the surface of the substrate in the conventional AMB ceramic substrate manufacturing process, which greatly affects the performance of the metallized layer, and thus provides a method with extremely high control precision and simple process.

[0004] Since the brazing filler metal process temperature in the traditional brazing process is relatively high (usually higher than 850 °C), it is likely to cause thermal damage to the ceramic substrate; therefore, the film deposition method used in the present invention can also reduce the process. In summary, the AMB substrate preparation process in this patent can achieve the purpose of high-precision control and low process temperature.

[0005] The specific solution of the present invention is as follows: A method for preparing an AMB substrate based on magnetron sputtering, comprising the following steps: Step 1: Place the ceramic substrate in an ultrasonic cleaner for surface cleaning to remove surface impurities; Step 2: Load the sample cleaned in Step 1 onto the sample stage of the magnetron sputtering equipment, and deposit three layers of thin films of titanium, copper, and silver in sequence according to a certain ratio; Step 3: Cover the surface of the deposited film with a copper foil, apply uniform pressure using a special fixture, and then transfer the sample to a vacuum heat treatment furnace. Perform high-temperature treatment for a period of time to achieve interfacial bonding.

[0006] Further, in the above Step 1, the ceramic substrate material is materials such as silicon nitride (Si3N4), alumina (Al2O3), aluminum nitride (AlN), etc.

[0007] Further, in the above Step 2, the deposition temperature in the magnetron sputtering process is about 30 °C.

[0008] Further, in the above Step 2, the order of depositing the metal thin films is titanium, copper, and silver in sequence.

[0009] Further, in the above Step 2, the deposition rates of the three layers of titanium, copper, and silver thin films are 1 - 1.5 Å / S, 10 - 15 Å / S, and 20 - 30 Å / S in sequence.

[0010] Further, in the above Step 2, the thickness ratio of the three layers of titanium, copper, and silver thin films is 2:(20 - 30):(68 - 78).

[0011] Further, in the above Step 3, when using the fixture for treatment, cover an untreated ceramic spacer on the surface of the copper foil to achieve indirect contact between the pressure clamp and the copper foil and ensure uniform pressure distribution.

[0012] Further, in the above Step 3, the high-temperature treatment is carried out in a vacuum state and the programmed heating method is adopted: heat up to 700 °C - 800 °C at a rate of 6 °C / min - 8 °C / min and then hold for 2 h - 5 h.

[0013] Compared with the prior art, the present invention has the following beneficial effects.

[0014] The present invention uses magnetron sputtering technology to replace the traditional paste printing process, realizing the regulation of the thin film thickness with nanometer-level precision. Compared with the traditional coating process, this deposition method can improve the thickness uniformity of the metal layer, thus significantly optimizing the electrical properties and interfacial bonding strength of the metallized layer.

[0015] The active metal layer deposited by the present invention can be tightly bonded with the copper foil at a relatively low process temperature, solving the problem of thermal damage to the ceramic substrate caused by a relatively high process temperature. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments.

[0017] Figure 1 This is the laser confocal microscopy morphological characterization diagram of the deposited thin film in Example 1 of the present invention.

[0018] Figure 2 This is the laser confocal microscopy morphological characterization diagram of the co-fired interface of the deposited thin film - copper foil in Example 1 of the present invention.

[0019] Figure 3 This is the laser confocal microscopy morphological characterization diagram of the deposited thin film in Example 2 of the present invention.

[0020] Figure 4 This is the laser confocal microscopy morphological characterization diagram of the co-fired interface of the deposited thin film - copper foil in Example 2 of the present invention. Detailed implementation manners Example 1

[0021] This example includes the following steps: Step 1: Place the alumina (Al2O3) ceramic substrate in an ultrasonic cleaner for surface cleaning to remove surface impurities; Step 2: Load the cleaned sample onto the sample stage of a magnetron sputtering device, and deposit three layers of titanium, copper, and silver thin films successively with thicknesses of 80 nm, 800 nm, and 2000 nm; the deposition rates are 1.5 Å / S, 12.9 Å / S, and 25 Å / S respectively; Step 3: Use copper foil as the intermediate layer, stack and assemble the deposited thin film and the untreated ceramic substrate, and apply uniform pressure through a special fixture to ensure interface contact. Place the assembled sample in the vacuum furnace cavity, evacuate to about 1×10 -2 Pa. Adopt a programmed temperature control method, heat to 750 °C at a constant heating rate of 6 °C / min, and keep the temperature constant at this temperature for 2 hours for heat treatment.

[0022] Figure 1 This is the surface morphology diagram of the metal thin film prepared in Example 1 of the present invention.

[0023] Figure 2 This is the laser confocal microscopy morphology diagram of the co-fired interface of the deposited thin film - copper foil in Example 1 of the present invention. By peeling the interface between the tightly bonded thin film and copper foil, an obvious interlocking structure can be observed between the metal thin film and copper foil, indicating that significant mutual diffusion or mechanical interlocking has occurred at the interface between the two. Example 2

[0024] This example includes the following steps: Step 1: Place the aluminum nitride (AlN) ceramic substrate in an ultrasonic cleaner for surface cleaning to remove surface impurities; Step 2: Load the cleaned sample onto the sample stage of the magnetron sputtering equipment, and deposit three layers of titanium, copper, and silver thin films in sequence with thicknesses of 80 nm, 1000 nm, and 1800 nm; the deposition rates are 1.5 Å / S, 14.8 Å / S, and 22.9 Å / S respectively; Step 3: Use copper foil as the intermediate layer, stack and assemble the deposited thin film with the untreated ceramic substrate, and apply uniform pressure through a special fixture to ensure interface contact. Place the assembled sample in the vacuum furnace chamber, evacuate to about 1×10 -2 Pa. Adopt a program-controlled temperature method, heat it to 700 °C at a constant heating rate of 6 °C / min, and keep it at a constant temperature for 2.5 hours at this temperature for heat treatment.

[0025] Figure 3 This is the surface morphology diagram of the metal thin film prepared in Example 2 of the present invention.

[0026] Figure 4 This is the laser confocal microscope morphology diagram of the co-fired interface of the deposited thin film - copper foil in Example 2 of the present invention. By peeling the interface between the tightly bonded thin film and copper foil, it can be observed that an obvious interlocking structure has formed between the metal thin film and copper foil, indicating that significant mutual diffusion or mechanical interlocking has occurred at the interface between the two.

Claims

1. A method for preparing an AMB substrate using magnetron sputtering technology, characterized in that, It includes the following steps: Step 1: Place the ceramic substrate in an ultrasonic cleaner for surface cleaning to remove surface impurities; Step 2: Load the sample cleaned in Step 1 onto the sample stage of a magnetron sputtering device, and deposit three layers of thin films of titanium, copper, and silver in sequence according to a certain ratio; Step 3: Cover the surface of the deposited thin film with copper foil, apply uniform pressure using a special fixture, and then transfer the sample to a vacuum heat treatment furnace. High-temperature treatment is carried out for a period of time to achieve interfacial bonding.

2. The method for preparing an AMB substrate according to claim 1, wherein The ceramic substrate materials used are materials such as silicon nitride (Si3N4), alumina (Al2O3), and aluminum nitride (AlN).

3. The method for preparing an AMB substrate according to claim 1, wherein, The deposition temperature during the magnetron sputtering process is about 30 °C.

4. The method for preparing an AMB substrate according to claim 1, wherein, The order of depositing the metal thin films is titanium, copper, and silver in sequence.

5. The method for preparing an AMB substrate according to claim 1, wherein The deposition rates of the three layers of thin films of titanium, copper, and silver are 1.5 Å / S, 8 Å / S, and 20 Å / S respectively.

6. The method for preparing an AMB substrate according to claim 1, wherein, The thickness ratio of the three layers of thin films of titanium, copper, and silver is 2:(20 - 30):(68 - 78).

7. The method for preparing an AMB substrate according to claim 1, wherein, Cover an untreated ceramic spacer on the surface of the copper foil to achieve indirect contact between the pressure clamp and the copper foil and ensure uniform pressure distribution.

8. The method for preparing an AMB substrate according to claim 1, wherein, The high-temperature treatment is carried out in a vacuum state and the programmed heating method is adopted: heat up to 700 °C - 800 °C at a rate of 6 °C / min - 8 °C / min and then hold for 2 - 5 h.

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