A high thermal conductivity semiconductor package substrate and a method of manufacturing the same

Abstract

This invention discloses a high thermal conductivity semiconductor packaging substrate and its preparation method, relating to the field of electronic materials technology. The method includes the following steps: mixing composite aluminum nitride powder with a sintering aid, ball milling, drying, and pressing into shape; sintering under high temperature and high pressure in a nitrogen atmosphere to obtain an aluminum nitride ceramic substrate; washing and drying the aluminum nitride ceramic substrate; covering both sides of the aluminum nitride ceramic substrate with copper foil, laying active solder between the aluminum nitride ceramic substrate and the copper foil, and then connecting them by vacuum brazing to obtain the semiconductor packaging substrate; the composite aluminum nitride powder is composed of aluminum nitride powder and modified aluminum nitride powder in a mass ratio of (6~8):(2~4). The semiconductor packaging substrate prepared by this method has excellent interfacial compatibility, effectively reduces interfacial thermal stress, and has good thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of electronic materials technology, specifically to a high thermal conductivity semiconductor packaging substrate and its preparation method. Background Technology

[0002] As semiconductor devices rapidly develop towards high density, high power, and miniaturization, the heat generated during their operation increases dramatically, leading to increased device temperature, performance degradation, decreased reliability, and even failure. The semiconductor packaging substrate, as a key connecting carrier between the device and the heat dissipation system, has its thermal conductivity directly affecting the overall heat dissipation efficiency. Therefore, higher requirements are placed on the heat dissipation capabilities of the semiconductor packaging substrate.

[0003] In existing technologies, semiconductor packaging substrates often suffer from insufficient interfacial compatibility between materials. Regardless of whether the existing packaging substrates use ceramic-based materials or metal-based composite materials, there is a mismatch in the coefficient of thermal expansion between them and the active solder, copper foil, and other metal interconnect layers. This leads to weak interfacial bonding and increased thermal resistance, making it difficult for the substrate to dissipate heat efficiently. In fact, it may even cause failure risks such as interface cracking and delamination under high and low temperature cycling, thus reducing the reliability of semiconductor devices.

[0004] Therefore, solving the above problems and providing a high thermal conductivity semiconductor packaging substrate and its preparation method is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a high thermal conductivity semiconductor packaging substrate and its preparation method to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a high thermal conductivity semiconductor packaging substrate includes the following steps: Step 1: Mix composite aluminum nitride powder with a sintering aid, ball mill, dry, press into shape, and sinter under high temperature and high pressure in a nitrogen atmosphere to obtain an aluminum nitride ceramic substrate. Step 2: Wash and dry the aluminum nitride ceramic substrate; cover both sides of the aluminum nitride ceramic substrate with copper foil, lay active solder between the aluminum nitride ceramic substrate and the copper foil, and then connect them by vacuum brazing process to obtain a semiconductor packaging substrate.

[0007] In a more optimized manner, the composite aluminum nitride powder is composed of aluminum nitride powder and modified aluminum nitride powder in a mass ratio of (6~8):(2~4); The method for preparing the modified aluminum nitride powder is as follows: Step 1: Add aluminum nitride powder to deionized water and stir. Add ammonia water to adjust the pH to 10-11. Wash and dry to obtain pretreated aluminum nitride. Step 2: Heat-treat the pretreated aluminum nitride obtained in Step 1 in an air atmosphere at a temperature of 300~350℃ for 2~3 hours to obtain aluminum oxide-aluminum nitride powder. Step 3: Add the alumina-aluminum nitride powder obtained in Step 2 to anhydrous ethanol, stir, and then slowly add ethanolamine and zinc nitrate in sequence. Heat to 50~60℃, stir for 5~6 hours, filter and dry to obtain modified aluminum nitride powder.

[0008] In a more optimized manner, the mass ratio of aluminum nitride powder to deionized water in the raw materials for pretreated aluminum nitride is (1~3):(5~15). The raw materials for the modified aluminum nitride powder, by weight, are: 1-3 parts alumina-aluminum nitride powder, 35-45 parts anhydrous ethanol, 1-2 parts ethanolamine, and 2-4 parts zinc nitrate.

[0009] In a more optimized manner, the mass ratio of composite aluminum nitride powder to sintering aid in the raw materials of the aluminum nitride ceramic substrate is (8~12):(0.1~0.5).

[0010] More preferably, the sintering aid is composed of yttrium acetylacetonate and Sm2O3, with a mass ratio of yttrium acetylacetonate to Sm2O3 of (0.05~0.2):(0.05~0.3).

[0011] A more optimized method for preparing the active solder is as follows: copper powder, indium powder, zinc powder, titanium powder and nickel powder are mixed, vacuum ball milled, and then silver powder is added and stirred evenly to obtain the active solder.

[0012] In a more optimized manner, the raw materials of the active solder, by weight, are: 2-4 parts copper powder, 1-2 parts indium powder, 0.5-1 parts zinc powder, 0.4-0.8 parts titanium powder, 0.03-0.06 parts nickel powder, and 5-8 parts silver powder.

[0013] In a more optimized manner, during the high-temperature and high-pressure sintering process, the temperature is 1400~1600℃, the pressure is 1~3GPa, and the sintering time is 1~3h.

[0014] In a more optimized manner, the process parameters of the vacuum brazing process are: vacuum degree of 3×10⁻⁶. -4 ~5×10 -4 Pa, temperature is 800~1000℃.

[0015] A semiconductor packaging substrate prepared by a method for preparing a semiconductor packaging substrate with high thermal conductivity.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention uses a composite of aluminum nitride and modified aluminum nitride as the core intermediate layer material of a semiconductor packaging substrate, and combines it with a suitable composite sintering aid and active solder to achieve a tight bond between the intermediate layer and the outer copper foil, ultimately obtaining a packaging substrate with both high thermal conductivity and high thermal cycling resistance.

[0017] In the process of preparing the packaging substrate, one step is to introduce modified aluminum nitride, which involves constructing an alumina transition layer on the outer surface of aluminum nitride. On the one hand, since alumina itself has thermal conductivity, it can form a continuous thermal conduction path with aluminum nitride, while also filling the voids and defects on the surface of aluminum nitride, reducing heat conduction scattering loss, and thus improving heat conduction efficiency. On the other hand, the alumina transition layer can also introduce active groups on the surface of aluminum nitride, which can optimize the interface bonding between aluminum nitride and subsequent layers, avoid additional thermal resistance due to interface gaps, and thus effectively improve thermal conductivity. Secondly, the hydroxyl groups in ethanolamine bridge the alumina transition layer, and then the amino groups in ethanolamine and zinc nitrate are deposited in situ to form a zinc coating layer. Since the coefficient of thermal expansion of the zinc coating layer is between that of aluminum nitride and metal solder or copper foil, it can effectively reduce the interfacial thermal stress during thermal cycling, avoid stress cracking, and prevent the breakage of the heat conduction channel. At the same time, the zinc coating layer can also significantly improve the surface energy of aluminum nitride, improve the interfacial wettability between aluminum nitride and materials such as solder or resin, promote the efficient transfer of heat between different raw materials, thereby reducing the interfacial thermal resistance, improving the compatibility between aluminum nitride and other materials, and thus improving the thermal conductivity. Third, yttrium acetylacetonate (YA) and Sm2O3 are combined as sintering aids to synergistically improve the sintering density of composite aluminum nitride materials. Specifically, Y2O3 generated by the high-temperature decomposition of YA is reacted with Sm2O3 to form a low-melting-point Y-Sm-Al-O composite glass phase, which can fill the gaps between particles, promote sintering densification, and reduce the thermal conduction obstacles caused by pores. At the same time, the thermal expansion coefficient of this composite glass phase is between that of aluminum nitride and metal, which can buffer the difference in thermal expansion and reduce thermal stress concentration. Together with modified aluminum nitride, they can improve the thermal conductivity of the packaging substrate. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In the following embodiments, the parts are by weight. It should be noted that there are no special restrictions on the purchase manufacturers of all raw materials involved in this invention. Exemplary examples include: aluminum nitride (CAS: 24304-00-5, particle size 40nm), ethanolamine (CAS: 141-43-5), zinc nitrate (CAS: 13778-30-8), yttrium acetylacetone (CAS: 15554-47-9), Sm2O3 (CAS: 12060-58-1, purity 99.5%, particle size 50nm), and other reagents without special requirements are commercially available.

[0020] Example 1: A method for preparing a high thermal conductivity semiconductor packaging substrate, specifically including the following steps: I. Preparation of modified aluminum nitride powder: Step 1: Add 2 parts of aluminum nitride powder to 10 parts of deionized water and stir. Add ammonia water to adjust the pH to 11, wash and dry to obtain pretreated aluminum nitride. Step 2: The pretreated aluminum nitride obtained in Step 1 is subjected to heat treatment at 350°C in an air atmosphere for 2.5 hours to obtain aluminum oxide-aluminum nitride powder. Step 3: Add 2 parts of the alumina-aluminum nitride powder obtained in Step 2 to 40 parts of anhydrous ethanol, stir, and then slowly add 1.5 parts of ethanolamine and 3 parts of zinc nitrate in sequence. Heat to 55°C, stir for 5.5 hours, filter and dry to obtain modified aluminum nitride powder.

[0021] II. Preparation of active solder: Mix 3 parts copper powder, 1.5 parts indium powder, 0.7 parts zinc powder, 0.6 parts titanium powder and 0.04 parts nickel powder, vacuum ball mill, add 6.5 parts silver powder and continue stirring until uniform to obtain active solder.

[0022] III. Preparation of semiconductor packaging substrate: Step 1: Mix 7 parts aluminum nitride powder, 3 parts modified aluminum nitride powder, 0.1 parts yttrium acetylacetone and 0.2 parts Sm2O3 and ball mill for 15 hours at a speed of 300 r / min. Then dry and press into shape. Sinter in a nitrogen atmosphere at a temperature of 1500℃ and a pressure of 2 GPa for 2 hours to obtain an aluminum nitride ceramic substrate. Step 2: Wash and dry the aluminum nitride ceramic substrate; cover both sides of the aluminum nitride ceramic substrate with copper foil, and lay active solder between the aluminum nitride ceramic substrate and the copper foil. Then, connect them using a vacuum brazing process with a vacuum degree of 4×10⁻⁶. -4 A semiconductor packaging substrate was obtained by applying pressure at 900°C and setting the temperature at 900°C.

[0023] Example 2: A method for preparing a high thermal conductivity semiconductor packaging substrate, specifically including the following steps: I. Preparation of modified aluminum nitride powder: Step 1: Add 1 part aluminum nitride powder to 5 parts deionized water and stir. Add ammonia water to adjust the pH to 11. Wash and dry to obtain pretreated aluminum nitride. Step 2: Heat-treat the pretreated aluminum nitride obtained in Step 1 at 350°C in an air atmosphere for 2 hours to obtain aluminum oxide-aluminum nitride powder. Step 3: Add 1 part of the alumina-aluminum nitride powder obtained in Step 2 to 35 parts of anhydrous ethanol, stir, and then slowly add 1 part of ethanolamine and 2 parts of zinc nitrate in sequence. Heat to 50°C, stir for 5 hours, filter and dry to obtain modified aluminum nitride powder.

[0024] II. Preparation of active solder: Mix 2 parts copper powder, 1 part indium powder, 0.5 parts zinc powder, 0.4 parts titanium powder and 0.03 parts nickel powder, vacuum ball mill, add 5 parts silver powder and continue stirring until uniform to obtain active solder.

[0025] III. Preparation of semiconductor packaging substrate: Step 1: Mix 6 parts aluminum nitride powder, 2 parts modified aluminum nitride powder, 0.05 parts yttrium acetylacetone and 0.05 parts Sm2O3 and ball mill for 15 hours at a speed of 300 r / min. Then dry and press into shape. In a nitrogen atmosphere, set the temperature to 1400℃ and the pressure to 1 GPa, sinter for 1 hour to obtain aluminum nitride ceramic substrate. Step 2: Wash and dry the aluminum nitride ceramic substrate; cover both sides of the aluminum nitride ceramic substrate with copper foil, and lay active solder between the aluminum nitride ceramic substrate and the copper foil. Then, connect them using a vacuum brazing process with a vacuum degree of 3×10⁻⁶. -4 A semiconductor packaging substrate was obtained by applying pressure at 800°C and setting the temperature at 800°C.

[0026] Example 3: A method for preparing a high thermal conductivity semiconductor packaging substrate, specifically including the following steps: I. Preparation of modified aluminum nitride powder: Step 1: Add 3 parts of aluminum nitride powder to 15 parts of deionized water and stir. Add ammonia water to adjust the pH to 11, wash and dry to obtain pretreated aluminum nitride. Step 2: Heat-treat the pretreated aluminum nitride obtained in Step 1 at 350°C in an air atmosphere for 3 hours to obtain aluminum oxide-aluminum nitride powder. Step 3: Add 3 parts of the alumina-aluminum nitride powder obtained in Step 2 to 45 parts of anhydrous ethanol, stir, and then slowly add 2 parts of ethanolamine and 4 parts of zinc nitrate in sequence. Heat to 60°C, stir for 6 hours, filter and dry to obtain modified aluminum nitride powder.

[0027] II. Preparation of active solder: Mix 4 parts copper powder, 2 parts indium powder, 1 part zinc powder, 0.8 parts titanium powder and 0.06 parts nickel powder, vacuum ball mill, add 8 parts silver powder and continue stirring until uniform to obtain active solder.

[0028] III. Preparation of semiconductor packaging substrate: Step 1: Mix 8 parts aluminum nitride powder, 4 parts modified aluminum nitride powder, 0.2 parts yttrium acetylacetone and 0.3 parts Sm2O3, ball mill, dry, press into shape, and sinter in a nitrogen atmosphere at a temperature of 1600℃ and a pressure of 3GPa for 3 hours to obtain aluminum nitride ceramic substrate. Step 2: Wash and dry the aluminum nitride ceramic substrate; cover both sides of the aluminum nitride ceramic substrate with copper foil, and lay active solder between the aluminum nitride ceramic substrate and the copper foil. Then, connect them using a vacuum brazing process with a vacuum degree of 5×10⁻⁶. -4 Pa, at a temperature of 1000℃, brazing connects the three components into a single unit, resulting in a semiconductor packaging substrate.

[0029] Comparative Example 1: Based on Example 1, the composition of the modified aluminum nitride powder was adjusted, ethanolamine and zinc nitrate were not added, and all other steps remained the same as in Example 1. The specific steps are as follows: I. Preparation of modified aluminum nitride powder: Step 1: Add 2 parts of aluminum nitride powder to 10 parts of deionized water and stir. Add ammonia water to adjust the pH to 11, wash and dry to obtain pretreated aluminum nitride. Step 2: The pretreated aluminum nitride obtained in Step 1 is subjected to heat treatment at 350°C in an air atmosphere for 2.5 hours to obtain modified aluminum nitride powder.

[0030] II. Preparation of active solder: Mix 3 parts copper powder, 1.5 parts indium powder, 0.7 parts zinc powder, 0.6 parts titanium powder and 0.04 parts nickel powder, vacuum ball mill, add 6.5 parts silver powder and continue stirring until uniform to obtain active solder.

[0031] III. Preparation of semiconductor packaging substrate: Step 1: Mix 7 parts aluminum nitride powder, 2 parts modified aluminum nitride powder, 0.1 parts yttrium acetylacetone and 0.2 parts Sm2O3 and ball mill for 15 hours at a speed of 300 r / min. Then dry and press into shape. In a nitrogen atmosphere, set the temperature to 1500℃ and the pressure to 2 GPa, sinter for 2 hours to obtain aluminum nitride ceramic substrate. Step 2: Wash and dry the aluminum nitride ceramic substrate; cover both sides of the aluminum nitride ceramic substrate with copper foil, and lay active solder between the aluminum nitride ceramic substrate and the copper foil. Then, connect them using a vacuum brazing process with a vacuum degree of 4×10⁻⁶. -4 A semiconductor packaging substrate was obtained by applying pressure at 900°C and setting the temperature at 900°C.

[0032] Comparative Example 2: Based on Example 1, the modification process of the modified aluminum nitride powder was adjusted, and the alumina transition layer was not prepared. All other steps remained the same as in Example 1. The specific steps are as follows: I. Preparation of modified aluminum nitride: Add 2 parts of aluminum nitride powder to 40 parts of anhydrous ethanol, stir, then slowly add 1.5 parts of ethanolamine and 3 parts of zinc nitrate in sequence, heat to 55°C, stir for 5.5 hours, filter and dry to obtain modified aluminum nitride powder.

[0033] II. Preparation of active solder: Mix 3 parts copper powder, 1.5 parts indium powder, 0.7 parts zinc powder, 0.6 parts titanium powder and 0.04 parts nickel powder, vacuum ball mill, add 6.5 parts silver powder and continue stirring until uniform to obtain active solder.

[0034] III. Preparation of semiconductor packaging substrate: Step 1: Mix 7 parts aluminum nitride powder, 3 parts modified aluminum nitride powder, 0.1 parts yttrium acetylacetone and 0.2 parts Sm2O3 and ball mill for 15 hours at a speed of 300 r / min. Then dry and press into shape. In a nitrogen atmosphere, set the temperature to 1500℃ and the pressure to 2 GPa, sinter for 2 hours to obtain aluminum nitride ceramic substrate. Step 2: Wash and dry the aluminum nitride ceramic substrate; cover both sides of the aluminum nitride ceramic substrate with copper foil, and lay active solder between the aluminum nitride ceramic substrate and the copper foil. Then, connect them using a vacuum brazing process with a vacuum degree of 4×10⁻⁶. -4 A semiconductor packaging substrate was obtained by applying pressure at 900°C and setting the temperature at 900°C.

[0035] Comparative Example 3: Based on Example 1, a semiconductor packaging substrate was prepared using only aluminum nitride powder. The specific steps are as follows: 1. Preparation of active solder: Mix 3 parts copper powder, 1.5 parts indium powder, 0.7 parts zinc powder, 0.6 parts titanium powder and 0.04 parts nickel powder, vacuum ball mill, add 6.5 parts silver powder and continue stirring until uniform to obtain active solder.

[0036] II. Fabrication of semiconductor packaging substrates: Step 1: Mix 7 parts aluminum nitride powder, 0.1 parts yttrium acetylacetone and 0.2 parts Sm2O3 and ball mill for 15 hours at a speed of 300 r / min. Then dry and press into shape. Sinter in a nitrogen atmosphere at a temperature of 1500℃ and a pressure of 2 GPa for 2 hours to obtain aluminum nitride ceramic substrate. Step 2: Wash and dry the aluminum nitride ceramic substrate; cover both sides of the aluminum nitride ceramic substrate with copper foil, and lay active solder between the aluminum nitride ceramic substrate and the copper foil. Then, connect them using a vacuum brazing process with a vacuum degree of 4×10⁻⁶. -4A semiconductor packaging substrate was obtained by applying pressure at 900°C and setting the temperature at 900°C.

[0037] Comparative Example 4: Based on Example 1, only Sm2O3 was used as a sintering aid, and all other steps remained the same as in Example 1. The specific steps are as follows: I. Preparation of modified aluminum nitride powder: Step 1: Add 2 parts of aluminum nitride powder to 10 parts of deionized water and stir. Add ammonia water to adjust the pH to 11, wash and dry to obtain pretreated aluminum nitride. Step 2: The pretreated aluminum nitride obtained in Step 1 is subjected to heat treatment at 350°C in an air atmosphere for 2.5 hours to obtain aluminum oxide-aluminum nitride powder. Step 3: Add 2 parts of the alumina-aluminum nitride powder obtained in Step 2 to 40 parts of anhydrous ethanol, stir, and then slowly add 1.5 parts of ethanolamine and 3 parts of zinc nitrate in sequence. Heat to 55°C, stir for 5.5 hours, filter and dry to obtain modified aluminum nitride powder.

[0038] II. Preparation of active solder: Mix 3 parts copper powder, 1.5 parts indium powder, 0.7 parts zinc powder, 0.6 parts titanium powder and 0.04 parts nickel powder, vacuum ball mill, add 6.5 parts silver powder and continue stirring until uniform to obtain active solder.

[0039] III. Preparation of semiconductor packaging substrate: Step 1: Mix 7 parts aluminum nitride powder, 3 parts modified aluminum nitride powder and 0.2 parts Sm2O3 and ball mill for 15 hours at a speed of 300 r / min. Then dry and press into shape. In a nitrogen atmosphere, set the temperature to 1500℃ and the pressure to 2GPa, sinter for 2 hours to obtain aluminum nitride ceramic substrate. Step 2: Wash and dry the aluminum nitride ceramic substrate; cover both sides of the aluminum nitride ceramic substrate with copper foil, and lay active solder between the aluminum nitride ceramic substrate and the copper foil. Then, connect them using a vacuum brazing process with a vacuum degree of 4×10⁻⁶. -4 A semiconductor packaging substrate was obtained by applying pressure at 900°C and setting the temperature at 900°C.

[0040] Performance testing: The semiconductor packaging substrates prepared in Examples 1-3 and Comparative Examples 1-4 were tested for thermal conductivity and thermal cycle life. The specific test data are shown in the table below: Thermal conductivity test: The laser flash method is used. In a vacuum environment, the sample is heated instantaneously with a laser pulse. The temperature change curve of the back side over time is recorded by an infrared detector, and the thermal diffusivity is calculated. Combined with the sample density and specific heat capacity, the thermal conductivity is derived: thermal conductivity = thermal diffusivity × density × specific heat capacity. Heat resistance cycle count: A high and low temperature damp heat test chamber was used, with a heat cycle range of 50~300℃. The heating rate of the equipment was 5℃ / min and the cooling rate was 3℃ / min. The heat preservation stage (50℃ and 300℃) was maintained for 30 minutes. The total duration of a single cycle was 200 minutes. After every 50 cycles, the substrate was taken out and cooled to room temperature to observe the surface condition of the semiconductor packaging substrate.

[0041]

[0042] Conclusion: Comparing Examples 1-3, it can be seen that the thermal conductivity of the prepared semiconductor packaging substrates is all in the range of 94-96 [W·(m·K]. -1 Within the temperature range of 50~300℃, the number of heat-resistant cycles exceeded 1150, indicating that the prepared modified aluminum nitride powder can form a structurally complete alumina transition layer and a uniform zinc-based coating layer, and has good compatibility with subsequent sintering and brazing process parameters, significantly improving the thermal conductivity of the semiconductor packaging substrate.

[0043] Comparing Example 1 with Comparative Examples 1-4, it can be seen that: Comparative Example 1, lacking the addition of ethanolamine and zinc nitrate, cannot form a zinc coating layer, making it difficult to reduce interfacial thermal resistance and thus reduce thermal stress, ultimately resulting in a significant decrease in performance; Comparative Example 2, lacking an alumina transition layer, cannot combine with the subsequent zinc coating layer due to the lack of active sites on the aluminum nitride surface, thus failing to optimize interfacial thermal stress compatibility and wettability, leading to a decrease in thermal conductivity and thermal cycling count; Comparative Example 3 uses a single aluminum nitride powder, and due to the difference in its interfacial thermal expansion coefficient with the subsequent layers, the interfacial compatibility decreases, thereby reducing thermal conductivity; Comparative Example 4, using a single Sm2O3 as a sintering aid, cannot fill the small voids between particles, resulting in a decrease in sintering density, which in turn reduces interfacial interaction and thus reduces thermal conductivity. In summary, by establishing an alumina transition layer on the surface of aluminum nitride and then performing synergistic modification through zinc-based complexation coating via ethanolamine bridging, the inertness problem of pure aluminum nitride surface is solved, and the interfacial thermal stress adaptability and wettability are optimized through the zinc coating layer, effectively improving the thermal conductivity and thermal cycle resistance of semiconductor substrates.

[0044] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a high thermal conductivity semiconductor packaging substrate, characterized in that: The process includes the following steps: Step 1: Mix the composite aluminum nitride powder with a sintering aid, ball mill, dry, press into shape, and sinter under high temperature and high pressure in a nitrogen atmosphere to obtain an aluminum nitride ceramic substrate; Step 2: Wash and dry the aluminum nitride ceramic substrate; cover both sides of the aluminum nitride ceramic substrate with copper foil, lay active solder between the aluminum nitride ceramic substrate and the copper foil, and then connect them by vacuum brazing process to obtain a semiconductor packaging substrate.

2. The method for preparing a high thermal conductivity semiconductor packaging substrate according to claim 1, characterized in that: The composite aluminum nitride powder is composed of aluminum nitride powder and modified aluminum nitride powder in a mass ratio of (6~8):(2~4); The method for preparing the modified aluminum nitride powder is as follows: Step 1: Add aluminum nitride powder to deionized water and stir. Add ammonia water to adjust the pH to 10-11. Wash and dry to obtain pretreated aluminum nitride. Step 2: Heat-treat the pretreated aluminum nitride obtained in Step 1 in an air atmosphere at a temperature of 300~350℃ for 2~3 hours to obtain aluminum oxide-aluminum nitride powder. Step 3: Add the alumina-aluminum nitride powder obtained in Step 2 to anhydrous ethanol, stir, and then slowly add ethanolamine and zinc nitrate in sequence. Heat to 50~60℃, stir for 5~6 hours, filter and dry to obtain modified aluminum nitride powder.

3. The method for preparing a high thermal conductivity semiconductor packaging substrate according to claim 2, characterized in that: In the raw materials for the pretreated aluminum nitride, the mass ratio of aluminum nitride powder to deionized water is (1~3):(5~15). The raw materials for the modified aluminum nitride powder, by weight, are: 1-3 parts alumina-aluminum nitride powder, 35-45 parts anhydrous ethanol, 1-2 parts ethanolamine, and 2-4 parts zinc nitrate.

4. The method for preparing a high thermal conductivity semiconductor packaging substrate according to claim 1, characterized in that: In the raw materials of the aluminum nitride ceramic substrate, the mass ratio of composite aluminum nitride powder to sintering aid is (8~12):(0.1~0.5).

5. The method for preparing a high thermal conductivity semiconductor packaging substrate according to claim 1, characterized in that: The sintering aid is composed of yttrium acetylacetonate and Sm2O3, with a mass ratio of yttrium acetylacetonate to Sm2O3 of (0.05~0.2):(0.05~0.3).

6. The method for preparing a high thermal conductivity semiconductor packaging substrate according to claim 1, characterized in that: The method for preparing the active solder is as follows: copper powder, indium powder, zinc powder, titanium powder and nickel powder are mixed, vacuum ball milled, and then silver powder is added and stirred evenly to obtain the active solder.

7. The method for preparing a high thermal conductivity semiconductor packaging substrate according to claim 6, characterized in that: The active solder contains, by weight, 2-4 parts copper powder, 1-2 parts indium powder, 0.5-1 parts zinc powder, 0.4-0.8 parts titanium powder, 0.03-0.06 parts nickel powder, and 5-8 parts silver powder.

8. The method for preparing a high thermal conductivity semiconductor packaging substrate according to claim 1, characterized in that: During the high-temperature and high-pressure sintering process, the temperature is 1400~1600℃, the pressure is 1~3GPa, and the sintering time is 1~3h.

9. The method for preparing a high thermal conductivity semiconductor packaging substrate according to claim 1, characterized in that: The process parameters for the vacuum brazing process are: vacuum degree 3×10 -4 ~5×10 -4 Pa, temperature is 800~1000℃.

10. A semiconductor packaging substrate prepared by a method for preparing a high thermal conductivity semiconductor packaging substrate according to any one of claims 1 to 9.

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