Composite substrate and preparation method thereof

Abstract

The present invention relates to a composite substrate and a preparation method thereof. The composite substrate comprises a ceramic insulating layer, a thermally conductive medium layer and a copper substrate stacked in sequence. The thermally conductive medium layer comprises an adhesion layer, a thermally conductive copper layer and a bonding layer stacked in sequence. The adhesion layer is arranged adjacent to the ceramic insulating layer, and the bonding layer is arranged adjacent to the copper substrate. The material of the adhesion layer is at least one of Ti and CuO, and the material of the bonding layer is preferably metal In. The adhesion layer and the thermally conductive copper layer are sequentially deposited on the ceramic insulating layer using a magnetron sputtering process. The bonding layer and the copper substrate are pressure-bonded and sintered to obtain the composite substrate. The composite substrate combines the advantages of a metal copper substrate and a ceramic substrate, and has the characteristics of good heat dissipation performance, high insulation, high bonding strength, good thermal shock resistance, strong mechanical hardness and reasonable price.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor device packaging, and in particular to a composite substrate and a preparation method thereof. Background Art

[0002] With the rapid development of high-power, high-density power devices, heat dissipation from their substrates has become a critical factor affecting device lifespan, performance, and reliability. In electronic power devices, every 10°C increase in temperature on the package substrate reduces the device's effective lifespan by 30% to 50%. If heat rapidly accumulates within power electronic devices and cannot be dissipated promptly, the high temperature can cause thermal stress and fatigue between the chip and substrate, potentially even directly damaging the device. Therefore, effectively improving the thermal conductivity of the package substrate has become a pressing challenge and a technical bottleneck that urgently needs to be overcome in the development of power devices.

[0003] Nitride ceramic substrates are widely used in electronic device packaging, but their thermal conductivity is not as good as that of metal copper substrates, they are fragile and expensive, and the heat dissipation bottleneck of metal copper substrates lies in the low thermal conductivity of the insulation layer. Therefore, it is an urgent market need to overcome the shortcomings of copper substrates and nitride ceramic substrates, innovate the packaging substrate preparation process, and develop a new type of composite packaging substrate with high thermal conductivity, high insulation, high mechanical strength, good thermal shock resistance, matching the chip thermal expansion coefficient, and reasonable price. Summary of the Invention

[0004] In response to the technical problems existing in the prior art, the primary purpose of the present invention is to provide a composite substrate and a method for preparing the same. The composite substrate has the characteristics of good thermal conductivity and heat dissipation, high bonding strength, and good thermal shock resistance. The present invention adopts at least the following technical solutions:

[0005] On the one hand, the present invention provides a composite substrate, which includes a ceramic insulating layer, a thermal conductive medium layer and a copper substrate stacked in sequence, wherein the thermal conductive medium layer includes an adhesion layer, a thermal conductive copper layer and a bonding layer stacked in sequence, the adhesion layer is arranged adjacent to the ceramic insulating layer, and the bonding layer is arranged adjacent to the copper substrate.

[0006] Furthermore, the material of the adhesion layer is at least one of Ti and CuO.

[0007] Furthermore, when the material of the adhesion layer is Ti, its thickness is 110nm to 550nm. Preferably, the thickness of the Ti adhesion layer is 330nm.

[0008] When the material of the adhesion layer is CuO, the thickness thereof is 330 nm to 1100 nm. Preferably, the thickness of the CuO adhesion layer is 660 nm.

[0009] Furthermore, the material of the bonding layer is In.

[0010] Furthermore, the thickness of the bonding layer is 10 μm to 100 μm; preferably, the thickness of the bonding layer is 50 μm.

[0011] Furthermore, the thickness of the thermally conductive copper layer is 500 nm to 1500 nm.

[0012] Furthermore, the thickness of the copper substrate is 600 μm to 1000 μm; preferably, the thickness of the copper substrate is 800 μm.

[0013] Furthermore, the ceramic insulating layer is an AlN ceramic insulating layer or an Al2O3 ceramic insulating layer, and its resistance value is greater than 3×10 11 Ω;

[0014] The thickness of the ceramic insulating layer is 180 μm to 500 μm.

[0015] Furthermore, when the area of ​​the composite substrate is 40 mm×40 mm, the average temperature rise / fall rate of the composite substrate per second at room temperature is 0.65 to 0.75° C.;

[0016] The bonding strength between the thermal conductive medium layer, the ceramic insulating layer and the copper substrate is greater than 1200N.

[0017] Another aspect of the present invention provides a method for preparing the composite substrate, comprising the following steps:

[0018] The adhesion layer is deposited on the surface of the ceramic insulating layer by using a magnetron sputtering process;

[0019] A thermally conductive copper layer is deposited on the surface of the adhesion layer using a magnetron sputtering process to form a laminated structure of ceramic insulation layer / adhesion layer / thermal conductive copper layer;

[0020] Placing a bonding sheet layer on the thermally conductive copper layer side of the laminated structure, placing a copper substrate on the bonding sheet layer, and performing pressure bonding;

[0021] Subsequently, high-temperature sintering is performed to form a composite substrate of ceramic insulation layer / adhesion layer / thermal conductive copper layer / bonding layer / copper substrate.

[0022] Furthermore, the high-temperature sintering temperature is 170° C. to 800° C., and the sintering time is 20 min to 60 min.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] The present invention combines the ceramic insulating layer and the copper substrate by providing an adhesive layer, a thermally conductive copper layer, and a bonding layer to form a composite substrate. The composite substrate has the characteristics of good thermal conductivity, high bonding strength, good thermal shock resistance, good insulation of the ceramic insulating layer, and low cost. Under the condition of a substrate area of ​​40mm×40mm, the composite substrate has an average temperature rise / fall of 0.65-0.75℃ per second at room temperature, and the resistance value of the ceramic insulating layer is greater than 3×10 11 Ω.

[0025] The preparation method of the composite substrate of the present invention adopts magnetron sputtering, pressure bonding and sintering processes, is green and environmentally friendly, simple and easy to operate, and is suitable for process promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of a composite substrate according to an embodiment of the present invention.

[0027] Figure 2 FIG. 4 is a schematic diagram of a preparation process of a composite substrate according to an embodiment of the present invention.

[0028] Figure 3 The figure is a flow chart of a method for preparing a composite substrate according to an embodiment of the present invention.

[0029] Figure 4 This is a temperature change curve diagram of the composite substrate during the heating / cooling process of Example 1 of the present invention.

[0030] Figure 5 FIG. 4 is a graph showing the IV characteristic of the ceramic insulating layer of the composite substrate according to Example 1 of the present invention.

[0031] Figure 6 1 is a curve diagram of parameter changes in a hot and cold cycle experiment of the composite substrate of Example 1 of the present invention. DETAILED DESCRIPTION

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without making creative work are all within the scope of protection of the present invention. The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, can be obtained from public commercial channels.

[0033] Spatially relative terms such as "below," "beneath," "below," "above," "upper," etc. are used in this specification to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures.

[0034] In addition, the use of terms such as "first," "second," and the like to describe various elements, layers, regions, sections, and the like is not intended to be limiting. The use of "having," "containing," "including," and "comprising" are open-ended terms that indicate the presence of stated elements or features, but do not exclude additional elements or features, unless the context clearly indicates otherwise.

[0035] In the present specification, the thickness refers to the direction from the copper substrate to the ceramic insulating layer.

[0036] The material of the bonding layer of the present invention is preferably metal In. Other metal materials suitable for bonding and sintering with the Cu substrate to form the composite substrate structure of the present invention all fall within the protection scope of the bonding layer material.

[0037] The material of the adhesion layer is preferably at least one of Ti and CuO. Other materials suitable for adhering to the surface of the ceramic insulating layer and capable of bonding and sintering with the Cu substrate to form the composite substrate structure of the present invention are all within the protection range of the adhesion layer.

[0038] The thermal conductive copper layer not only plays a role in heat conduction but also serves to connect the adhesion layer and the bonding layer.

[0039] Example 1

[0040] A composite substrate with a structure of Cu-In-Cu-Ti-AlN

[0041] like Figure 1 As shown, this embodiment of the present invention provides a Cu-In-Cu-Ti-AlN composite substrate, which comprises, from bottom to top, a copper substrate 1, a bonding layer 2, a thermally conductive copper layer 3, an adhesion layer 4, and an AlN ceramic insulating layer 5. The copper substrate 1 is 800 μm thick; the bonding layer is made of metallic In and has a thickness of 50 μm; the thermally conductive copper layer is 1365 nm thick; the adhesion layer 4 is made of metallic Ti and has a thickness of 330 nm; and the AlN ceramic insulating layer 5 is 380 μm thick. In this embodiment, the composite substrate has an area of ​​40 mm x 40 mm.

[0042] Example 2

[0043] A composite substrate with a structure of Cu-In-Cu-CuO-AlN

[0044] The composite substrate includes, from bottom to top, a copper substrate 1, a bonding layer 2, a thermally conductive copper layer 3, an adhesion layer 4, and an AlN ceramic insulating layer 5; wherein, the thickness of the copper substrate 1 is 800 μm; the material of the bonding layer is metal In, and its thickness is 50 μm; the thickness of the thermally conductive copper layer is 1365 nm; the material of the adhesion layer 4 is CuO, and its thickness is 660 nm; the thickness of the AlN ceramic insulating layer 5 is 380 μm.

[0045] Example 3

[0046] A composite substrate with a structure of Cu-In-Cu-CuO-Al2O3

[0047] The composite substrate includes, from bottom to top, a copper substrate 1, a bonding layer 2, a thermally conductive copper layer 3, an adhesion layer 4, and an AlN ceramic insulating layer 5; wherein, the thickness of the copper substrate 1 is 800 μm; the material of the bonding layer is metal In, and its thickness is 50 μm; the thickness of the thermally conductive copper layer is 1365 nm; the material of the adhesion layer 4 is CuO, and its thickness is 660 nm; the thickness of the Al2O3 ceramic insulating layer 5 is 380 μm.

[0048] Example 4

[0049] Preparation of a composite substrate with a structure of Cu-In-Cu-Ti-AlN

[0050] The following combination Figure 2 and Figure 3 The preparation method of the composite substrate is introduced, which includes the following steps:

[0051] Step S1: Ultrasonic cleaning of the copper substrate and the AlN ceramic insulating layer substrate in acetone: The copper substrate and the AlN ceramic insulating layer substrate are placed in acetone for ultrasonic cleaning for 15 minutes in sequence, wherein the acetone cleaning removes organic impurities; then the substrate is washed three times with deionized water and dried with nitrogen.

[0052] Step S2: Plating a titanium film layer on the first surface of the AlN ceramic insulating layer: Using a magnetron sputtering coating method, using a high-purity titanium target as a target source, and passing argon gas throughout the process, sputtering a titanium film layer with a thickness of 330 nm. The specific operation is as follows:

[0053] S2.1: Break vacuum and place sample: Introduce nitrogen to break vacuum, stick the AlN ceramic substrate on the mask with high-temperature resistant tape, place it in the vacuum chamber, and install high-purity titanium target and high-purity copper target.

[0054] S2.2: Vacuum to 5×10 -4 Pa, argon gas was introduced to 0.6 Pa with a gas flow rate of 25 sccm.

[0055] S2.3: Heating: Turn on the main switch of the heating power supply, heat to 100℃, keep warm for three minutes, continue to heat to 200℃, keep warm for three minutes, continue to heat to 300℃, keep warm for three minutes, and continue to heat to 350℃.

[0056] S2.4: Sputtering Ti film: Open the target baffle, adjust the RF power to 80W, set the sample rotation table speed to 25, perform pre-sputtering, and observe whether it is glowing. After pre-sputtering, open the sample baffle and perform sputtering. The sputtering rate is 180nm / 60min, the sputtering time is 110min, and the coating thickness is 330nm to form a Ti-AlN composite layer.

[0057] S2.5: End of sputtering titanium film layer: After the titanium film sputtering is completed, close the sample stage baffle, stop the sample stage rotation, and close the target material baffle.

[0058] Step S3: Copper film is plated on the surface of the Ti film of the Ti-AlN composite layer: A copper film with a thickness of 1365 nm is sputtered on the surface of the titanium film of the sputtered Ti-AlN composite layer by magnetron sputtering. The specific operation is as follows:

[0059] S3.1: Continue with the previous steps, without removing the sample. The vacuum chamber is in a high vacuum environment and proceed to the next step, copper film plating. Adjust the target position DC power supply power to 80mAx383V=30.64W.

[0060] S3.2: Turn on the sample turntable, adjust the speed to 25, adjust the gate valve to make the sputtering intensity stronger, keep the temperature at 350℃ unchanged, and keep the gas flow rate at 25sccm unchanged.

[0061] S3.3: Open the baffle and start sputtering. The copper film plating rate is 105nm / 10min. The copper film is plated twice. The first plating is 10 minutes without taking it out. After two hours, it is plated again for 120 minutes. The total copper film thickness is 1365nm.

[0062] S3.4: After sputtering is completed, break the vacuum and take out the Cu-Ti-AlN composite layer sample.

[0063] Step S4: placing an indium sheet and a copper substrate on the surface of the Cu layer of the Cu-Ti-AlN composite layer, and pressure-bonding the Cu-Ti-AlN composite layer to the indium sheet and the copper substrate. The specific operation is as follows:

[0064] The Cu-Ti-AlN composite layer is placed at the bottom, the indium layer is in the middle, and the copper substrate is placed on the platform. A sheet press is used to pressure bond them at a pressure of 2 MPa for 5 minutes to obtain a Cu-In-Cu-Ti-AlN composite layer.

[0065] Step S5: High-temperature sintering of the Cu-In-Cu-Ti-AlN composite layer: Place the composite layer on a ceramic ark with the AlN side at the bottom and the copper substrate side at the top, using two ceramic arks to hold it down. Gently advance the composite layer into a high-temperature tube furnace, purging and purging the furnace three times to ensure air-free sintering. Argon gas is introduced throughout the sintering process at a gas flow rate of 400 sccm. The temperature is raised to 170°C, with the starting temperature set at 25°C. The heating time is 17 minutes, and the temperature is maintained for 30 minutes. This yields the Cu-In-Cu-Ti-AlN composite substrate of Example 1.

[0066] The above structure is used as a Cu-In-Cu-Ti-AlN composite substrate to test its performance. The temperature change curve of the composite substrate during the heating / cooling process is shown in the figure below. Figure 4 As shown, analyzing its temperature change curve, it can be seen that during the heating process, the composite substrate only needs 60 seconds to heat up from 41.7°C to 85.0°C, roughly reaching the temperature stability value, with an average temperature increase of 0.72°C per second. The heat conduction speed is very fast and there is no heat deposition. During the cooling process, the temperature drops from 80.8°C to 37.2°C in the first 60 seconds, with an average temperature drop of 0.73°C per second, while it takes 60 seconds to cool from 37.2°C to 27.2°C, indicating that the composite substrate has a fast heat dissipation speed, but the heat dissipation speed is obviously slow in the last minute. This is due to the contact between the composite substrate and the desktop, which results in no obvious heat dissipation and heat deposition.

[0067] The composite substrate is placed on a probe station and the current-voltage on the ceramic insulating layer is measured at different voltages. Figure 5 The IV characteristic curve of the ceramic insulation layer is shown. From the IV curve, it can be seen that when the voltage is 30V, the current is 9×10 -11 A, calculated by Ohm's law, the resistance value at this time is 3.3×10 11 Ω, which exceeds the maximum test range of the probe station.

[0068] like Figure 6 As shown in the figure, the parameter change curve of the hot and cold cycle experiment of the novel composite substrate with the structure of Cu-In-Cu-Ti-AlN in Example 1 of the present invention is shown. Frequent temperature fluctuations may cause delamination of the Cu sheet and the AlN ceramic, and finally cause failure of the substrate. The hot and cold cycle test can be used to detect the ability of the composite substrate to withstand instantaneous changes in high and low temperatures in the working environment. The high and low temperatures in the working environment are simulated using a heating platform and a refrigerator temperature respectively. The heating platform is heated to 80°C each time, and the refrigerator temperature is 0°C. The hot and cold cycle experiment is carried out in this temperature range. The specific operation is as follows:

[0069] First, the new composite substrate with the structure of Cu-In-Cu-Ti-AlN in Example 1 of the present invention was placed on a heating platform and heated at room temperature of 25°C for 5 minutes, and then the heated composite substrate was quickly placed in a refrigerator for 5 minutes. This was counted as one cycle. After 10 cycles, it was observed that the composite substrate did not split and there were no cracks at the interface between the upper layers of the substrate.

[0070] The bonding strength between the layers in the composite substrate was tested, and it was found that the bonding strength between the thermal conductive medium layer, the ceramic insulating layer and the copper substrate was greater than 1200N.

[0071] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A composite substrate comprising a ceramic insulating layer, a thermally conductive medium layer and a copper substrate stacked in sequence, characterized in that: The thermal conductive medium layer includes an adhesive layer, a thermal conductive copper layer and a bonding layer stacked in sequence, the adhesive layer is adjacent to the ceramic insulating layer, and the bonding layer is adjacent to the copper substrate; The material of the adhesion layer is at least one of Ti and CuO. When the material of the adhesion layer is Ti, the thickness thereof is 110 nm to 550 nm. When the material of the adhesion layer is CuO, the thickness thereof is 330 nm to 1100 nm. The material of the bonding layer is In, and the thickness of the bonding layer is 10 μm to 100 μm; The thickness of the thermal conductive copper layer is 500nm~1500nm; the thickness of the copper substrate is 600μm~1000μm; The ceramic insulating layer is an AlN ceramic insulating layer or an Al2O3 ceramic insulating layer, and its resistance value is greater than 3×10 11 Ω; the thickness of the ceramic insulating layer is 180μm~500μm; In an area of ​​40mm×40mm, the composite substrate has an average temperature rise / fall rate of 0.65~0.75℃ per second at room temperature; The bonding strength between the thermal conductive medium layer, the ceramic insulating layer and the copper substrate is greater than 1200N.

2. The composite substrate according to claim 1, characterized in that When the material of the adhesion layer is Ti, the thickness of the Ti adhesion layer is 330 nm.

3. The composite substrate according to claim 1, characterized in that When the material of the adhesion layer is CuO, the thickness of the CuO adhesion layer is 660 nm.

4. The composite substrate according to any one of claims 1 to 3, characterized in that: The thickness of the bonding layer is 50 μm.

5. The composite substrate according to any one of claims 1 to 3, characterized in that: The copper substrate has a thickness of 800 μm.

6. A method for preparing a composite substrate according to any one of claims 1 to 5, characterized in that: The following steps are involved: The adhesion layer is deposited on the surface of the ceramic insulating layer by using a magnetron sputtering process; A thermally conductive copper layer is deposited on the surface of the adhesion layer using a magnetron sputtering process to form a laminated structure of ceramic insulation layer / adhesion layer / thermal conductive copper layer; Placing a bonding sheet layer on the thermally conductive copper layer side of the laminated structure, placing a copper substrate on the bonding sheet layer, and performing pressure bonding; Subsequently, high-temperature sintering is performed to form a composite substrate of ceramic insulation layer / adhesion layer / thermal conductive copper layer / bonding layer / copper substrate.

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