CN117756555B - A method for preparing a high-reliability aluminum nitride-coated aluminum substrate - Google Patents

Abstract

The invention relates to the field of semiconductors, in particular to a preparation method of a high-reliability aluminum nitride aluminum-coated substrate. The method carries out alkali treatment and accelerated aging treatment on the aluminum nitride ceramic to hydrolyze and convert the aluminum hydroxide on the surface layer of the aluminum nitride ceramic into a uniform aluminum oxide film layer. And then nitriding and sintering are carried out, and an aluminum oxynitride layer is formed on the surface of the aluminum nitride ceramic. And then placing the treated aluminum nitride ceramic in a forming die, and casting and sintering to obtain the high-reliability aluminum nitride coated substrate. The high-reliability aluminum nitride aluminum-coated substrate prepared by the method has the advantages of strong reliability, low thermal resistance, good heat resistance, ceramic strength enhancement and capability of meeting the packaging heat dissipation requirement.

Description

A method for preparing a high-reliability aluminum nitride-coated aluminum substrate

Technical Field

The invention relates to the field of semiconductors, and in particular to a method for preparing a high-reliability aluminum nitride-coated aluminum substrate.

Background Art

In recent years, IGBT high-power device modules have gradually come into people's attention. As an indispensable part of it, the performance of ceramic substrates has become one of the important performances of IGBT modules. Direct Bonding Copper (DBC) and Active Metal Brazing (AMB) are the two most common ceramic substrates on the market. They have high thermal conductivity, high mechanical strength, low expansion coefficient and other characteristics. However, as the working temperature continues to change, copper forms a large amount of residual stress at the ceramic substrate, resulting in cracks at the interface of the ceramic substrate. Compared with copper, the high plasticity and lower yield strength of aluminum can effectively buffer the thermal stress caused by the temperature change of the substrate, so that its interface reliability is enhanced to a certain extent. Direct Bonding Aluminum (DBA) is unique in the direction of high reliability, but under extreme working temperature conditions, the aluminum nitride coated aluminum substrate interface will also experience thermal fatigue after multiple hot and cold transitions, and the stress accumulates to form cracks at the ceramic interface.

In order to overcome the defects of the prior art, the present invention provides a method for preparing an aluminum nitride-coated aluminum substrate with high reliability.

Summary of the invention

The object of the present invention is to provide a method for preparing a high-reliability aluminum nitride-coated aluminum substrate to solve the problems in the prior art.

In order to solve the above technical problems, the present invention provides the following technical solutions:

A method for preparing a high-reliability aluminum nitride-coated aluminum substrate comprises the following steps:

Step 1: placing the aluminum nitride ceramic in a sodium hydroxide solution, taking it out after ultrasonic cleaning, and then placing it in 98-100% humidity and 120-140° C. for aging for 96-120 hours. After the reaction is completed, washing it with pure water and drying it to obtain pretreated aluminum nitride ceramic;

Step 2: In a nitrogen environment, the pretreated aluminum nitride ceramic is subjected to nitriding sintering, and after sintering, the ceramic is cooled in the furnace to form an aluminum nitride oxide layer on the surface;

Step 3: Place the aluminum nitride ceramic processed in step 2 in a molding mold, place a high-purity aluminum block at the upper end of the mold pouring port, and after clamping, pour and sinter at 660-950°C for 60-120 minutes. After sintering, cool with the furnace to form a metal aluminum layer on the surface, and then demold, cut, grind, and repair the plate to prepare a high-reliability aluminum nitride aluminum-clad substrate.

More optimally, in step 1, the concentration of the sodium hydroxide solution is 1-3 g/L.

More optimally, in step 1, the ultrasonic cleaning parameters are: temperature is 40-60°C, and time is 30-60s.

More optimally, in step 2, the nitriding sintering process parameters are: temperature of 1500-1800°C, time of 60-120min, and gas pressure of 1-5MPa.

More optimally, in step 2, the thickness of the aluminum oxynitride layer is 0.5-3.0 μm.

More optimally, in step three, during pouring and sintering, the vacuum degree is 0.001-0.01Pa.

Beneficial effects of the present invention:

The present invention provides a method for preparing a high-reliability aluminum nitride coated aluminum substrate, which is mainly prepared by an aluminum oxynitride layer on the surface of an aluminum nitride ceramic, and an alkaline treatment is performed on the surface of the aluminum nitride ceramic using a sodium hydroxide solution to accelerate the aging treatment, so that the surface aluminum hydroxide is hydrolyzed and converted into a uniform aluminum oxide film layer, and then a layer of aluminum oxynitride film is formed on the surface of the aluminum nitride ceramic by nitriding and sintering. The aluminum oxynitride layer generated on the surface of the aluminum nitride ceramic has high strength and high reliability in combination with the aluminum nitride ceramic. The thickness of the aluminum oxynitride layer is optimized and controlled, and the strength of the ceramic can be further enhanced under the heat dissipation conditions that meet the packaging requirements. The aluminum liquid is used for high-temperature direct infiltration molding, and a direct ceramic-coated aluminum interface can be directly formed, with lower thermal resistance and higher reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

FIG1 is a flow chart of a method for preparing a high-reliability aluminum nitride-coated aluminum substrate according to the present invention;

FIG2 is a schematic diagram of the interface structure layer of the high reliability aluminum nitride coated aluminum substrate according to Example 1 of the present invention;

FIG3 is a cross-sectional SEM image of a high reliability aluminum nitride coated aluminum substrate according to Example 5 of the present invention;

In Figure 2: 1-metal aluminum layer, 2-aluminum oxynitride layer, 3-aluminum nitride ceramic.

DETAILED DESCRIPTION

The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the present invention. Obviously, 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, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Source of raw materials:

Aluminum nitride ceramic, provided by Haigood Technology Co., Ltd., has a size of 138×190×0.635mm.

Example 1: Step 1: Place an aluminum nitride ceramic 3 having a size of 138×190×0.635 mm in a sodium hydroxide solution having a concentration of 3 g/L, and immerse it for 60 seconds under the conditions of a reaction temperature of 55°C and an ultrasonic frequency of 20 KHz. After taking it out, place it in an accelerated aging box with a humidity of 100% and keep it at 130°C for 96 hours. After the reaction is completed, wash it with pure water at 25°C and dry it to obtain a pretreated aluminum nitride ceramic;

Step 2: In a nitrogen environment, the pretreated aluminum nitride ceramic is heated to 1800°C at a heating rate of 10°C/min, and nitridation sintered for 120 minutes at a temperature of 1800°C and a gas pressure of 3.5MPa. After sintering, the ceramic is cooled in the furnace to form an aluminum nitride layer 2 with a thickness of 3μm on the surface;

Step three: Place the aluminum nitride ceramic treated in step two in a forming mold, and place a high-purity aluminum block with a mass of 62.5g after surface treatment to remove the oxide layer on the upper end of the mold pouring port; Place the clamped aluminum nitride coated aluminum sample in a vacuum brazing furnace, pour and sinter at 750°C for 120 minutes, and the sintering vacuum degree is 0.0026Pa. After sintering, cool with the furnace to form a metal aluminum layer 1 on the surface. Take out the product and demold it, cut and grind the aluminum overflow area on the edge of the aluminum nitride coated aluminum liner after demolding, and then use 800# and 1200# grinding liquids to repair the plate in turn to prepare a high-reliability aluminum nitride coated aluminum substrate.

Example 2: Step 1: Place an aluminum nitride ceramic 3 having a size of 138×190×0.635 mm in a sodium hydroxide solution having a concentration of 4 g/L, and immerse it for 60 seconds under the conditions of a reaction temperature of 52° C. and an ultrasonic frequency of 20 KHz. After taking it out, place it in an accelerated aging box with a humidity of 99.3% and keep it at 125° C. for 97 hours. After the reaction is completed, wash it with pure water at 25° C. and dry it to obtain a pretreated aluminum nitride ceramic;

Step 2: In a nitrogen environment, the pretreated aluminum nitride ceramic is heated to 1800°C at a heating rate of 10°C/min, and nitridation sintered for 120 minutes at a temperature of 1800°C and a gas pressure of 2.8 MPa. After sintering, the ceramic is cooled in the furnace to form an aluminum nitride layer 2 with a thickness of 2.8 μm on the surface;

Step three: Place the aluminum nitride ceramic treated in step two in a forming mold, and place a high-purity aluminum block with a mass of 68.3g after surface treatment to remove the oxide layer on the upper end of the mold pouring port; Place the clamped aluminum nitride coated aluminum sample in a vacuum brazing furnace, pour and sinter at 750°C for 120 minutes, and the sintering vacuum degree is 0.0035Pa. After sintering, cool with the furnace to form a metal aluminum layer 1 on the surface. Take out the product and demold it, cut and grind the aluminum overflow area on the edge of the aluminum nitride coated aluminum liner after demolding, and then use 800# and 1200# grinding liquids to repair the plate in turn to prepare a high-reliability aluminum nitride coated aluminum substrate.

Example 3: Step 1: Place an aluminum nitride ceramic 3 having a size of 138×190×0.635 mm in a sodium hydroxide solution having a concentration of 2.9 g/L, and immerse for 60 seconds under the conditions of a reaction temperature of 56°C and an ultrasonic frequency of 20 KHz. After taking it out, place it in an accelerated aging box with a humidity of 100% and keep it at 130°C for 93 hours. After the reaction is completed, wash it with pure water at 25°C and dry it to obtain a pretreated aluminum nitride ceramic;

Step 2: In a nitrogen environment, the pretreated aluminum nitride ceramic is heated to 1780°C at a heating rate of 10°C/min, and nitridation sintered for 120 minutes at a temperature of 1780°C and a gas pressure of 4.1MPa. After sintering, the ceramic is cooled in the furnace to form an aluminum nitride layer 2 with a thickness of 3.2μm on the surface;

Step three: Place the aluminum nitride ceramic treated in step two in a forming mold, and place a high-purity aluminum block with a mass of 65.7g after surface treatment to remove the oxide layer on the upper end of the mold pouring port; Place the clamped aluminum nitride coated aluminum sample in a vacuum brazing furnace, pour and sinter at 750°C for 120 minutes, and the sintering vacuum degree is 0.0053Pa. After sintering, cool with the furnace to form a metal aluminum layer 1 on the surface. Take out the product and demold it. Cut and grind the aluminum overflow area on the edge of the aluminum nitride coated aluminum liner after demolding, and then use 800# and 1200# grinding liquids to repair the plate in turn to prepare a high-reliability aluminum nitride coated aluminum substrate.

Example 4: Step 1: Place an aluminum nitride ceramic 3 having a size of 138×190×0.635 mm in a sodium hydroxide solution having a concentration of 3 g/L, and immerse it for 60 seconds under the conditions of a reaction temperature of 58°C and an ultrasonic frequency of 20 KHz. After taking it out, place it in an accelerated aging box with a humidity of 98.3%, and keep it at 120°C for 90 hours. After the reaction is completed, wash it with pure water at 25°C and dry it to obtain a pretreated aluminum nitride ceramic;

Step 2: In a nitrogen environment, the pretreated aluminum nitride ceramic is heated to 1750°C at a heating rate of 10°C/min, and nitridation sintered for 120 minutes at a temperature of 1750°C and a gas pressure of 4.8MPa. After sintering, the ceramic is cooled in the furnace to form an aluminum nitride layer 2 with a thickness of 3μm on the surface;

Step three: Place the aluminum nitride ceramic treated in step two in a forming mold, and place a high-purity aluminum block with a mass of 60.2g after surface treatment to remove the oxide layer on the upper end of the mold pouring port; Place the clamped aluminum nitride coated aluminum sample in a vacuum brazing furnace, pour and sinter at 745°C for 120min, and the sintering vacuum degree is 0.0033Pa. After sintering, cool with the furnace to form a metal aluminum layer 1 on the surface. Take out the product and demold it, cut and grind the aluminum overflow area on the edge of the aluminum nitride coated aluminum liner after demolding, and then use 800# and 1200# grinding liquids to repair the plate in turn to prepare a high-reliability aluminum nitride coated aluminum substrate.

Example 5: Step 1: Place an aluminum nitride ceramic 3 having a size of 138×190×0.635 mm in a sodium hydroxide solution having a concentration of 3 g/L, and immerse for 60 seconds under the conditions of a reaction temperature of 52°C and an ultrasonic frequency of 20 kHz. After taking it out, place it in an accelerated aging box with a humidity of 98.9% and keep it at 120°C for 90 hours. After the reaction is completed, wash it with pure water at 25°C and dry it to obtain a pretreated aluminum nitride ceramic;

Step 2: In a nitrogen environment, the pretreated aluminum nitride ceramic is heated to 1700°C at a heating rate of 10°C/min, and nitridation sintered for 120 minutes at a temperature of 1700°C and a gas pressure of 2.6MPa. After sintering, the ceramic is cooled in the furnace to form an aluminum nitride oxide layer 2 with a thickness of 1.3μm on the surface;

Step 3: Place the aluminum nitride ceramic treated in step 2 in a forming mold, and place a high-purity aluminum block with a mass of 66.1 g after surface treatment to remove the oxide layer on the upper end of the mold pouring port; place the clamped aluminum nitride aluminum-coated sample in a vacuum brazing furnace, pour and sinter at 780°C for 120 minutes, and the sintering vacuum degree is 0.0065 Pa. After sintering, cool with the furnace to form a metal aluminum layer 1 on the surface. After taking out the product, demold it, cut and grind the aluminum overflow area on the edge of the aluminum nitride aluminum-coated liner after demolding, and then use 800# and 1200# grinding liquids to repair the plate in turn to prepare a high-reliability aluminum nitride aluminum-coated substrate. The scanning electron microscope SEM image of the cross-sectional aluminum nitride oxide layer is shown in Figure 3 below.

Comparative Example 1: An aluminum nitride coated aluminum substrate was prepared using an untreated aluminum nitride ceramic sheet. The specific steps are as follows: an untreated aluminum nitride ceramic 3 was placed in a molding mold, and a high-purity aluminum block with a mass of 58.2 g after surface treatment to remove the oxide layer was placed on the upper end of the mold pouring port; the clamped aluminum nitride coated aluminum sample was placed in a vacuum brazing furnace, poured and sintered at 750°C for 120 minutes, and the sintering vacuum degree was 0.0026 Pa. After sintering, it was cooled in the furnace, and a metal aluminum layer 1 was formed on the surface. After the product was taken out, it was demolded, and the aluminum overflow area on the edge of the aluminum nitride coated aluminum liner after demolding was cut and ground, and then the plate was repaired with 800# and 1200# grinding liquids in turn to prepare an aluminum nitride coated aluminum substrate.

Comparative Example 2: An aluminum nitride coated aluminum substrate was prepared using an untreated aluminum nitride ceramic sheet. The specific steps are as follows: an untreated aluminum nitride ceramic 3 was placed in a molding mold, and a high-purity aluminum block with a mass of 65.3 g after surface treatment to remove the oxide layer was placed on the upper end of the mold pouring port; the clamped aluminum nitride coated aluminum sample was placed in a vacuum brazing furnace, poured and sintered at 750°C for 120 minutes, and the sintering vacuum degree was 0.0068 Pa. After sintering, it was cooled in the furnace, and a metal aluminum layer 1 was formed on the surface. After the product was taken out, it was demolded, and the aluminum overflow area on the edge of the aluminum nitride coated aluminum liner after demolding was cut and ground, and then the plate was repaired with 800# and 1200# grinding liquids in turn to prepare an aluminum nitride coated aluminum substrate.

Comparative Example 3: Unsurface-treated aluminum nitride ceramic sheets are used to prepare aluminum nitride-coated aluminum substrates. The specific steps are as follows: untreated aluminum nitride ceramics 3 are placed in a molding mold, and a high-purity aluminum block with a mass of 59.1 g after surface treatment to remove the oxide layer is placed on the upper end of the mold pouring port; the clamped aluminum nitride-coated aluminum sample is placed in a vacuum brazing furnace, poured and sintered at 750°C for 120 minutes, and the sintering vacuum degree is 0.0095 Pa. After sintering, it is cooled with the furnace, and a metal aluminum layer 1 is formed on the surface. After the product is taken out, it is demolded, and the aluminum overflow area on the edge of the aluminum nitride-coated aluminum liner after demolding is cut and ground, and then 800# and 1200# grinding liquids are used in turn to repair the plate to prepare a high-reliability aluminum nitride-coated aluminum substrate.

Detection test:

Bending strength test: The aluminum nitride coated aluminum substrate prepared by the present invention is used as the test product, and a sample with a size of 24.0mm*42.0mm is obtained after laser cutting. The sample is placed in a universal testing machine, and a bending strength test is performed using a three-point bending method. The sample is positioned between two lower rollers and an upper roller, and the upper roller is located in the middle of the span. The upper and lower rollers move relative to each other to cause the sample to bend and fracture, and the corresponding values are measured; the test values are shown in the following table.

Hot and cold cycle test: The aluminum nitride coated aluminum substrate prepared by the present invention is used as a sample, and ultrasonic nondestructive testing of the interface void rate is performed on the sample. A sample area with qualified void rate is selected for hot and cold cycle testing. The test range is -55°C-150°C, and the allowable temperature deviation range is ±2°C. Ultrasonic interface testing is performed on the sample after every 100 high and low temperature cycles. The test results are shown in the following table.

Bending strength/MPa Hot and cold cycle test Example 1 536 ≥3500 times Example 2 512 ≥3500 times Example 3 554 ≥3500 times Example 4 514 ≥3500 times Example 5 502 ≥3500 times Comparative Example 1 460 ≤2000 times Comparative Example 2 479 ≤2000 times Comparative Example 3 454 ≤2000 times

Conclusion: From the above experiments, it can be seen that the aluminum nitride ceramics have an aluminum nitride layer prepared by surface treatment and sintering, which can significantly improve the reliability of the bonding between the aluminum nitride and the aluminum layer. The number of hot and cold cycles is ≥3500 times, while that of the untreated sample is ≤2000 times. The interface reliability of the aluminum nitride-coated aluminum substrate is significantly improved.

It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process method article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process method article or device.

Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (5)

1. A method for preparing a high-reliability aluminum nitride coated aluminum substrate, characterized in that it comprises the following steps: Step 1: placing the aluminum nitride ceramic (3) in a sodium hydroxide solution with a concentration of 1-3 g/L, taking it out after ultrasonic cleaning, and then placing it in a 98-100% humidity and 120-140° C. for aging for 96-120 hours. After the reaction is completed, washing it with pure water and drying it to obtain a pretreated aluminum nitride ceramic; Step 2: In a nitrogen environment, the pretreated aluminum nitride ceramic is subjected to nitriding sintering, and after sintering, the ceramic is cooled in the furnace to form an aluminum nitride oxide layer (2) on the surface; the nitriding sintering process parameters are: temperature of 1500-1800° C., time of 60-120 min, and gas pressure of 1-5 MPa; Step 3: Place the aluminum nitride ceramic processed in step 2 in a molding mold, place a high-purity aluminum block at the upper end of the mold pouring port, and after clamping, pour and sinter at 660-950°C for 60-120 minutes. After sintering, cool in the furnace to form a metal aluminum layer (1) on the surface. Then, demold, cut, grind, and repair the plate to prepare a high-reliability aluminum nitride aluminum-clad substrate. 2. The method for preparing a high-reliability aluminum nitride-coated aluminum substrate according to claim 1 is characterized in that: in step 1, the ultrasonic cleaning parameters are: temperature is 40-60°C, and time is 30-60s. 3. The method for preparing a high-reliability aluminum nitride-coated aluminum substrate according to claim 1, characterized in that: in step 2, the thickness of the aluminum nitride oxide layer (2) is 0.5-3.0 μm. 4. The method for preparing a high-reliability aluminum nitride-coated aluminum substrate according to claim 1, characterized in that: in step 3, during pouring and sintering, the vacuum degree is 0.001-0.01 Pa. 5. A high-reliability aluminum nitride-coated aluminum substrate, characterized in that it is prepared according to the preparation method according to any one of claims 1-4.