阅读说明：本技术 覆铜陶瓷基板 (Copper-clad ceramic substrate ) 是由 庄凯翔 许建强 许建中 邱国创 于 2020-01-15 设计创作，主要内容包括：此处提供的覆铜陶瓷基板包括：氮化物陶瓷基板；第一钝化层,包括掺杂其他金属的氧化铝或氧化硅,其他金属是钛、钒、铬、锰、铁、钴、镍、铜、或上述的组合,且铝或硅与其他金属的重量比例介于60:40至99.5:0.5之间；以及第一铜层,其中第一钝化层位于氮化物陶瓷基板的上表面与第一铜层之间。(The copper-clad ceramic substrate provided herein includes: a nitride ceramic substrate; a first passivation layer comprising alumina or silica doped with another metal, the other metal being titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or a combination thereof, and the weight ratio of aluminum or silicon to the other metal being between 60:40 and 99.5: 0.5; and a first copper layer, wherein the first passivation layer is located between the upper surface of the nitride ceramic substrate and the first copper layer.)

1. A copper-clad ceramic substrate, comprising:

a nitride ceramic substrate;

a first passivation layer comprising alumina or silica doped with another metal, the other metal being titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or a combination thereof, and the weight ratio of aluminum or silicon to the other metal being 60:40 to 99.5: 0.5; and

a first copper layer formed on the first copper layer,

wherein the first passivation layer is located between the upper surface of the nitride ceramic substrate and the first copper layer.

2. The copper-clad ceramic substrate according to claim 1, wherein the nitride ceramic substrate comprises an aluminum nitride ceramic substrate or a silicon nitride ceramic substrate.

3. The copper-clad ceramic substrate according to claim 1, wherein the nitride ceramic substrate has a thickness of 0.3mm to 1 mm.

4. The copper-clad ceramic substrate of claim 1, wherein the thickness of the first passivation layer is between 1 micron and 5 microns.

5. The copper-clad ceramic substrate of claim 1, wherein the thickness of the first passivation layer is between 1 micron and 2 microns.

6. The copper-clad ceramic substrate according to claim 1, wherein the thickness of the first copper layer is between 0.1mm and 0.3 mm.

7. The copper-clad ceramic substrate according to claim 1, further comprising:

a second passivation layer comprising alumina or silica doped with other metals, the other metals being titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or combinations thereof, and the weight ratio of aluminum or silicon to the other metals being between 60:40 and 99.5: 0.5; and

a second copper layer formed on the first copper layer,

wherein the second passivation layer is located between the lower surface of the nitride ceramic substrate and the second copper layer.

8. The copper-clad ceramic substrate of claim 7, wherein the thickness of the second passivation layer is between 1 micron and 5 microns.

9. The copper-clad ceramic substrate of claim 7, wherein the thickness of the second passivation layer is between 1 micron and 2 microns.

10. The copper-clad ceramic substrate according to claim 7, wherein the thickness of the second copper layer is between 0.1mm and 0.3 mm.

Technical Field

The present disclosure relates to a copper-clad ceramic substrate and a method for forming the same.

Background

With the rise of the electric vehicle market, the demand of the IGBT power module for controlling the output of the voltage and current of the motor engine increases, and with better acceleration performance, the voltage and current required by the power module are higher and higher (>1200V, >800A), and a technique of a copper-clad ceramic substrate for packaging the IGBT chip is also more and more important, and the copper-clad ceramic substrate needs to be capable of bearing high voltage and high current, and needs to have the characteristics of high structural strength, high thermal conductivity, high thermal cycle reliability and the like.

The copper-clad ceramic substrate is composed of a ceramic substrate, copper foils with a thickness of more than 0.1mm and bonded to each other at the upper and lower parts, and alumina (Al) as a common material for the middle ceramic substrate₂O₃) Zirconium oxide toughened alumina (ZTA), aluminum nitride (AlN), silicon nitride (Si)₃N₄) And the like, wherein the AlN ceramic has the advantages of optimal thermal conductivity (the thermal conductivity coefficient reaches 180W/m.K, the thermal conductivity coefficient of alumina is 30W/m.K), thermal expansion coefficient close to that of a wafer material such as silicon (Si), germanium (Ge) and the like. In addition, Si₃N₄Ceramics have both strength and thermal conductivity characteristics, and are ceramic substrate materials with high thermal cycling reliability.

The common Method for manufacturing Copper-clad ceramic substrates is Direct Bonded Copper bonding (Direct Bonded Copper Method), in which a Copper foil with a treated surface is covered on a ceramic substrate and heated to 1050-1080 ℃ in an inert atmosphere, so that the Copper oxide on the surface of the Copper foil is Bonded to the ceramic substrate.

When aluminum nitride is used as the ceramic substrate, an additional oxidation treatment is required to form a stable inert protective layer on the surface of the aluminum nitride ceramic substrate. However, the copper oxide reacts with the inert protective layer to generate gas, i.e., bubbles are formed at the interface of the copper foil and the ceramic substrate. The bubbles reduce the bonding strength, heat conduction and reliability of the copper foil and the ceramic substrate.

In view of the above, there is a need for a new copper-clad ceramic substrate to solve the above problems.

Disclosure of Invention

The copper-clad ceramic substrate provided by one embodiment of the disclosure comprises: a nitride ceramic substrate; a first passivation layer comprising alumina or silica doped with another metal, the other metal being titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or a combination thereof, and the weight ratio of aluminum or silicon to the other metal being between 60:40 and 99.5: 0.5; and a first copper layer, wherein the first passivation layer is located between the upper surface of the nitride ceramic substrate and the first copper layer.

In one embodiment, the nitride ceramic substrate comprises an aluminum nitride ceramic substrate or a silicon nitride ceramic substrate.

In one embodiment, the nitride ceramic substrate has a thickness of between 0.3mm and 1 mm.

In one embodiment, the thickness of the first passivation layer is between 1 and 5 microns.

In one embodiment, the thickness of the first passivation layer is between 1 and 2 microns.

In one embodiment, the thickness of the first copper layer is between 0.1mm and 0.3 mm.

In one embodiment, the copper-clad ceramic substrate further includes: a second passivation layer comprising alumina or silica doped with another metal, the other metal being titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or a combination thereof, and the weight ratio of aluminum or silicon to the other metal being between 60:40 and 99.5: 0.5; and a second copper layer, wherein the second passivation layer is located between the lower surface of the nitride ceramic substrate and the second copper layer.

In one embodiment, the thickness of the second passivation layer is between 1 and 5 microns.

In one embodiment, the thickness of the second passivation layer is between 1 and 2 microns.

In one embodiment, the thickness of the second copper layer is between 0.1mm and 0.3 mm.

Drawings

FIGS. 1-3 are schematic diagrams of a method of forming a copper-clad ceramic substrate according to an embodiment;

FIG. 4 is a schematic diagram of a copper-clad ceramic substrate according to an embodiment.

[ notation ] to show

11 nitride ceramic substrate

13 precursor layer

15 passivation layer

17 copper foil

Detailed Description

In one embodiment, a nitride such as aluminum nitride (AlN) or silicon nitride (Si) is provided₃N₄) And cleaning the surface of the nitride ceramic substrate 11, in one embodiment, the nitride ceramic baseThe thickness of the plate 11 is between 0.3mm and 1 mm. If the thickness of the nitride ceramic substrate 11 is too small, the substrate strength cannot resist the substrate fracture due to the thermal stress introduced after the bonding of the copper foil. If the thickness of the nitride ceramic substrate 11 is too large, the interface thermal resistance is too large, and the heat conduction perpendicular to the substrate side is not good, so that the heat of the IGBT wafer cannot be effectively conducted out, and the product characteristics are degraded. For example, the nitride ceramic substrate 11 may be alkali-washed and then the substrate surface neutralized with deionized water. Next, the surface of the nitride ceramic substrate 11 is dried, and precursor layers 13 containing titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or a combination thereof are formed on the upper surface and the lower surface of the nitride ceramic substrate 11, as shown in fig. 1. For example, the precursor layer 13 may be deposited, powdered, printed, sprayed, or coated.

Then, the nitride ceramic substrate 11 having the precursor layer 13 on the upper and lower surfaces thereof is heated to 1000 to 1300 ℃ for 0.1 to 6 hours, so that the precursor layer 13 is converted into the passivation layer 15, as shown in fig. 2. In one embodiment, the oxygen concentration of the environment of the step of heating the precursor layer 13 is between 100ppm and 1%. If the oxygen concentration is too low, the passivation element cannot produce the passivation effect. If the oxygen concentration is too high, the thickness of the passivation layer is too large. After the above steps, the passivation layer 15 formed on the upper and lower surfaces of the nitride ceramic substrate 11 includes aluminum oxide (when the nitride ceramic substrate 11 is aluminum nitride) or silicon oxide (when the nitride ceramic substrate 11 is silicon nitride) doped with titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or a combination thereof, and the doping element corresponds to the composition of the precursor layer 13. In the passivation layer 15, the weight ratio of aluminum or silicon to other doping metals (e.g., titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or combinations thereof) is between 60:40 and 99.5: 0.5. If the proportion of other doping elements is too low, the effect of the doping elements is not achieved. If the proportion of the other doping elements is too high, the passivation layer cannot be formed to provide the bond. In one embodiment, the thickness of the passivation layer 15 is between 1 micron and 5 microns. In another embodiment, the thickness of the passivation layer 15 is between 1 and 2 microns. If the thickness of the passivation layer 15 is too small, it is not effective to help the copper foil to adhere to the nitride ceramic substrate 11. If the thickness of the passivation layer 15 is too large, the bonding strength is lowered.

The surface of the copper foil 17 is then pre-oxidized to form pre-oxidized surfaces on the upper and lower surfaces of the copper foil 17. In one embodiment, the thickness of the copper foil 17 is between 0.1mm and 0.3 mm. Next, the nitride ceramic substrate 11 having the passivation layer 15 on the upper and lower surfaces thereof is placed between two pieces of pre-oxidation-treated copper foil 17 in an inert atmosphere (low oxygen concentration, such as 20ppm) and heated to 1050 to 1080 ℃, so that the copper foil 17 is bonded to the nitride ceramic substrate 11 via the passivation layer 15, as shown in fig. 3. Thus, the copper-clad ceramic substrate is obtained, and the copper-clad ceramic substrate has an excellent copper foil tension value (is less prone to delamination). It can be seen from the X-ray transmission photographs that the passivation layer 15 of alumina or silica doped with ti, v, cr, mn, fe, co, ni, cu, or combinations thereof has a significantly reduced size and number of bubbles after bonding compared to the passivation layer of pure alumina.

In another embodiment, the passivation layer 15 and the copper foil 17 may be formed on only one side of the nitride ceramic substrate 11, as shown in fig. 4.

The copper-clad ceramic substrate can be used as a circuit board in a high-power module to bear an IGBT wafer with high voltage and high current. The high power module may be used in an electric vehicle, a wind power generator, a power plant, or the like.

In order to make the aforementioned and other objects, features and advantages of the present disclosure more comprehensible, preferred embodiments accompanied with figures are described in detail below:

[ examples ]

Comparative example 1

The copper foil without oxygen copper was cut into 4.25 inches × 0.3mm size, and the upper and lower surfaces of the copper foil were polished with a #2500 abrasive belt, cleaned with ultrasonic waves, and then heated to 250 ℃ in the atmosphere for 30 minutes to pre-oxidize the surface of the copper foil. The treated copper foil was stored under vacuum for future use.

Alumina substrates from Kyocera having dimensions of 4.25 inches by 0.635mm and a surface roughness of 0.6 to 0.8 microns. And putting the alumina substrate into 5% NaOH, carrying out ultrasonic oscillation for 3 minutes to wash the alumina substrate with alkali, putting the alumina substrate into deionized water, and carrying out ultrasonic oscillation for 3 minutes to neutralize the surface of the alumina washed with alkali. The alumina substrate was then spun to remove water and heated to 120 ℃ for 10 minutes to dry the alumina substrate. The steps can clean the upper surface and the lower surface of the alumina substrate.

The surface-cleaned alumina substrate was placed between two treated copper foils, and DBC process was performed at an oxygen concentration of 20ppm, and maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes, and 1056 ℃ for 5 minutes, respectively, at a temperature rise rate of 40 ℃/min. Thus, a copper foil/alumina substrate/copper foil copper-clad ceramic substrate with a copper foil tensile value of 66N/cm (ASTM D903) was obtained.

Comparative example 2

The copper foil was treated in the manner of comparative example 1. Aluminum nitride substrates available from Maruwa having dimensions of 4.25 inches by 0.635mm and a surface roughness of 0.2 to 0.8 microns. And putting the aluminum nitride substrate into 5% NaOH, carrying out ultrasonic oscillation for 3 minutes to wash the aluminum nitride substrate with alkali, and putting the aluminum nitride substrate into deionized water, carrying out ultrasonic oscillation for 3 minutes to neutralize the surface of the aluminum nitride after alkali washing. Then, the aluminum nitride substrate is rotated to remove water, and is heated to 120 ℃ and maintained for 10 minutes to dry the aluminum nitride substrate. The above steps can clean the upper surface and the lower surface of the aluminum nitride substrate.

The cleaned aluminum nitride substrate was preheated in the atmosphere for 560 minutes at 1100 ℃ and 360 minutes at 700 ℃ to form passivation layers of aluminum oxide on the upper and lower surfaces of the aluminum nitride substrate. The thickness of the passivation layer was 8 μm.

An aluminum nitride substrate having an aluminum oxide passivation layer on the upper and lower surfaces was placed between two pieces of treated copper foil, and DBC process was performed at an oxygen concentration of 20ppm, respectively maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes, and 1056 ℃ for 5 minutes, with a temperature rise rate of 40 ℃/minute. Thus, a copper clad ceramic substrate of copper foil/aluminum oxide passivation layer/aluminum nitride substrate/aluminum oxide passivation layer/copper foil can be obtained, wherein the copper foil tensile value is 44N/cm (the measurement standard is ASTM D903).

Comparative example 3

The copper foil was treated in the manner of comparative example 1, and the surface of the aluminum nitride substrate was cleaned in the manner of comparative example 2. The cleaned aluminum nitride substrate was preheated in the atmosphere for 560 minutes at 1020 ℃ and 360 minutes at 700 ℃ to form passivation layers of aluminum oxide on the top and bottom surfaces of the aluminum nitride substrate. The thickness of the passivation layer was 2 μm.

An aluminum nitride substrate having an aluminum oxide passivation layer on the upper and lower surfaces was placed between two pieces of treated copper foil, and DBC process was performed at an oxygen concentration of 20ppm, respectively maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes, and 1056 ℃ for 5 minutes, with a temperature rise rate of 40 ℃/minute. Thus, a copper clad ceramic substrate of copper foil/aluminum oxide passivation layer/aluminum nitride substrate/aluminum oxide passivation layer/copper foil can be obtained, wherein the copper foil tensile value is 34N/cm (the measurement standard is ASTM D903).

Comparative example 4

The copper foil was treated in the manner of comparative example 1, and the surface of the aluminum nitride substrate was cleaned in the manner of comparative example 2. Coating to form a 1 micron thick tin chloride layer (SnCl)₂) After cleaning, the aluminum nitride substrate with tin chloride layer on the upper and lower surfaces is preheated in the atmosphere, and maintained at 1100 deg.c for 560 min and 700 deg.c for 360 min to form tin-doped aluminum oxide passivation layer on the upper and lower surfaces. The thickness of the passivation layer was 8 μm, and the weight ratio of aluminum to tin in the passivation layer was 98:2 (measured by Energy Dispersive X-ray Spectroscopy (EDS)).

An aluminum nitride substrate having a tin-doped aluminum oxide passivation layer on the upper surface and the lower surface was placed between two pieces of treated copper foil, and a DBC process was performed at an oxygen concentration of 20ppm, and maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes, and 1056 ℃ for 5 minutes, respectively, at a temperature rise rate of 40 ℃/minute. Thus, a copper foil/tin-doped aluminum oxide passivation layer/aluminum nitride substrate/tin-doped aluminum oxide passivation layer/copper foil copper-clad ceramic substrate with a copper foil tensile value of 30N/cm (ASTM D903) can be obtained.

Example 1

The copper foil was treated in the manner of comparative example 1, and the surface of the aluminum nitride substrate was cleaned in the manner of comparative example 2. Coating to form a 1 micron thick titanium oxide layer (TiO)₂) The cleaned aluminum nitride substrate with titanium oxide layer on the upper and lower surfaces is preheated at an oxygen concentration of 100ppm, and is maintained at 1100 ℃ for 560 minutes and 700 ℃ for 360 minutes, respectively, to form titanium-doped aluminum oxide passivation layers on the upper and lower surfaces of the aluminum nitride substrate. The thickness of the passivation layer was 2 μm, and the weight ratio of aluminum to titanium in the passivation layer was 90:10 (for EDS).

An aluminum nitride substrate having a titanium-doped aluminum oxide passivation layer on the upper surface and the lower surface was placed between two pieces of treated copper foil, and DBC process was performed at an oxygen concentration of 20ppm, respectively maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes, and 1056 ℃ for 5 minutes, with a temperature rise rate of 40 ℃/minute. Thus, a copper foil/titanium-doped aluminum oxide passivation layer/aluminum nitride substrate/titanium-doped aluminum oxide passivation layer/copper foil copper-clad ceramic substrate can be obtained, wherein the copper foil tensile value is 82N/cm (the measurement standard is ASTM D903).

Example 2

The copper foil was treated in the manner of comparative example 1, and the surface of the aluminum nitride substrate was cleaned in the manner of comparative example 2. Coating to form a 1 micron thick vanadium oxide layer (V)₂O₃) On the upper and lower surfaces of the cleaned aluminum nitride substrate, the aluminum nitride substrate with the vanadium oxide layer on the upper and lower surfaces is preheated under an oxygen concentration of 1%, and is respectively maintained at 1100 ℃ for 560 minutes and 700 ℃ for 360 minutes, so as to form vanadium-doped aluminum oxide passivation layers on the upper and lower surfaces of the aluminum nitride substrate. The thickness of the passivation layer was 4 μm, and the weight ratio of aluminum to vanadium in the passivation layer was 85:15 (amount)The test method is EDS).

An aluminum nitride substrate with a vanadium-doped aluminum oxide passivation layer on the upper surface and the lower surface is placed between two pieces of treated copper foil, and a DBC process is performed at an oxygen concentration of 20ppm, and maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes, and 1056 ℃ for 5 minutes, respectively, at a temperature rise rate of 40 ℃/minute. Thus, a copper foil/vanadium-doped aluminum oxide passivation layer/aluminum nitride substrate/vanadium-doped aluminum oxide passivation layer/copper foil copper-clad ceramic substrate can be obtained, wherein the copper foil tensile value is 81N/cm (the measurement standard is ASTM D903).

Example 3

The copper foil was treated in the manner of comparative example 1, and the surface of the aluminum nitride substrate was cleaned in the manner of comparative example 2. Coating to form a 1 micron thick chromium oxide layer (Cr)₂O₃) On the upper and lower surfaces of the cleaned aluminum nitride substrate, the aluminum nitride substrate having the chromium oxide layer thereon was preheated at an oxygen concentration of 500ppm, and maintained at 1100 ℃ for 560 minutes and 700 ℃ for 360 minutes, respectively, to form chromium-doped aluminum oxide passivation layers on the upper and lower surfaces of the aluminum nitride substrate. The thickness of the passivation layer was 3 μm, and the weight ratio of aluminum to chromium in the passivation layer was 92:8 (EDS method).

An aluminum nitride substrate having a chromium-doped aluminum oxide passivation layer on the upper surface and the lower surface was placed between two pieces of treated copper foil, and a DBC process was performed at an oxygen concentration of 20ppm, and maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes, and 1056 ℃ for 5 minutes, respectively, at a temperature rise rate of 40 ℃/minute. Thus, a copper foil/chromium-doped aluminum oxide passivation layer/aluminum nitride substrate/chromium-doped aluminum oxide passivation layer/copper foil copper-clad ceramic substrate can be obtained, wherein the copper foil tensile value is 79N/cm (the measurement standard is ASTM D903).

Example 4

The copper foil was treated in the manner of comparative example 1, and the surface of the aluminum nitride substrate was cleaned in the manner of comparative example 2. Coating to form a 1 micron thick manganese oxide layer (MnO)₂) On the upper and lower surfaces of the cleaned aluminum nitride substrate, the following steps are carried outThe aluminum nitride substrate having the manganese oxide layer on the upper and lower surfaces thereof was preheated at an oxygen concentration of 1% for 560 minutes at 1100 ℃ and 360 minutes at 700 ℃ to form manganese-doped aluminum oxide passivation layers on the upper and lower surfaces of the aluminum nitride substrate, respectively. The thickness of the passivation layer was 2 μm, and the weight ratio of aluminum to manganese in the passivation layer was 84:16 (EDS method).

An aluminum nitride substrate having manganese-doped aluminum oxide passivation layers on the upper surface and the lower surface was placed between two pieces of treated copper foil, and DBC process was performed at an oxygen concentration of 20ppm, respectively maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes, and 1056 ℃ for 5 minutes, with a temperature rise rate of 40 ℃/minute. Thus, a copper foil/manganese-doped aluminum oxide passivation layer/aluminum nitride substrate/manganese-doped aluminum oxide passivation layer/copper foil copper-clad ceramic substrate can be obtained, wherein the copper foil tensile value is 85N/cm (the measurement standard is ASTM D903).

Example 5

The copper foil was treated in the manner of comparative example 1, and the surface of the aluminum nitride substrate was cleaned in the manner of comparative example 2. Coating to form a 1 micron thick layer of iron oxide (Fe)₂O₃) The aluminum nitride substrate with the iron oxide layer on the upper surface and the lower surface thereof was preheated at an oxygen concentration of 500ppm, and maintained at 1100 ℃ for 560 minutes and 700 ℃ for 360 minutes, respectively, to form iron-doped aluminum oxide passivation layers on the upper surface and the lower surface of the aluminum nitride substrate. The thickness of the passivation layer was 2 μm, and the weight ratio of aluminum to iron in the passivation layer was 78:22 (EDS method).

An aluminum nitride substrate having iron-doped aluminum oxide passivation layers on the upper and lower surfaces was placed between two pieces of treated copper foil, and DBC process was performed at an oxygen concentration of 20ppm, respectively maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes, and 1056 ℃ for 5 minutes, with a temperature rise rate of 40 ℃/minute. Thus, a copper foil/iron-doped aluminum oxide passivation layer/aluminum nitride substrate/iron-doped aluminum oxide passivation layer/copper foil copper-clad ceramic substrate with a copper foil tensile value of 69N/cm (ASTM D903) can be obtained.

Example 6

The copper foil was treated in the manner of comparative example 1, and the surface of the aluminum nitride substrate was cleaned in the manner of comparative example 2. Coating and forming a nickel oxide layer (NiO) with the thickness of 1 micron on the upper surface and the lower surface of the cleaned aluminum nitride substrate, preheating the aluminum nitride substrate with the nickel oxide layer on the upper surface and the lower surface under the oxygen concentration of 1%, and respectively maintaining the temperature at 1100 ℃ for 560 minutes and 700 ℃ for 360 minutes to form a passivation layer of nickel-doped aluminum oxide on the upper surface and the lower surface of the aluminum nitride substrate. The thickness of the passivation layer was 4 μm, and the weight ratio of aluminum to nickel in the passivation layer was 80:20 (EDS method).

An aluminum nitride substrate having a nickel-doped aluminum oxide passivation layer on the upper surface and the lower surface was placed between two pieces of treated copper foil, and a DBC process was performed at an oxygen concentration of 20ppm, and maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes, and 1056 ℃ for 5 minutes, respectively, at a temperature rise rate of 40 ℃/min. Thus, a copper foil/nickel-doped aluminum oxide passivation layer/aluminum nitride substrate/nickel-doped aluminum oxide passivation layer/copper foil copper-clad ceramic substrate can be obtained, wherein the copper foil tensile value is 70N/cm (the measurement standard is ASTM D903).

Example 7

The copper foil was treated in the manner of comparative example 1, and the surface of the aluminum nitride substrate was cleaned in the manner of comparative example 2. Coating to form a 1 micron thick layer of cuprous oxide (Cu)₂O) on the upper and lower surfaces of the cleaned aluminum nitride substrate, and then preheating the aluminum nitride substrate having the cuprous oxide layer on the upper and lower surfaces at an oxygen concentration of 500ppm, respectively at 1100 ℃ for 560 minutes and 700 ℃ for 360 minutes, to form copper-doped aluminum oxide passivation layers on the upper and lower surfaces of the aluminum nitride substrate. The thickness of the passivation layer was 3 μm, and the weight ratio of aluminum to copper in the passivation layer was 65:35 (EDS method).

An aluminum nitride substrate having a copper-doped aluminum oxide passivation layer on the upper surface and the lower surface was placed between two pieces of treated copper foil, and a DBC process was performed at an oxygen concentration of 20ppm, respectively maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes, and 1056 ℃ for 5 minutes, with a temperature rise rate of 40 ℃/minute. Thus, a copper foil/copper-doped alumina passivation layer/aluminum nitride substrate/copper-doped alumina passivation layer/copper foil copper-clad ceramic substrate with a copper foil tensile value of 65N/cm (ASTM D903) can be obtained.

Example 8

The copper foil was treated in the manner of comparative example 1, and the surface of the aluminum nitride substrate was cleaned in the manner of comparative example 2. Physical vapor deposition of a titanium layer having a thickness of 100nm, a manganese layer having a thickness of 100nm, and a copper layer having a thickness of 100nm on the upper and lower surfaces of the cleaned aluminum nitride substrate, followed by preheating the aluminum nitride substrate having titanium, manganese, and copper layers on the upper and lower surfaces at an oxygen concentration of 500ppm, respectively at 1100 ℃ for 560 minutes and 700 ℃ for 360 minutes, to form passivation layers of aluminum oxide doped with titanium, manganese, and copper on the upper and lower surfaces of the aluminum nitride substrate. The thickness of the passivation layer was 3 μm, and the weight ratio of aluminum to titanium in the passivation layer was 90:10, the weight ratio of aluminum to manganese was 90:10, and the weight ratio of aluminum to copper was 90:10 (EDS method).

An aluminum nitride substrate with an aluminum oxide passivation layer doped with titanium, manganese and copper on the upper surface and the lower surface is placed between two pieces of treated copper foil, and a DBC process is performed under an oxygen concentration of 20ppm, and the aluminum nitride substrate is maintained at 700 ℃ for 5 minutes, 900 ℃ for 5 minutes and 1056 ℃ for 5 minutes respectively, and the temperature rise speed is 40 ℃/minute. Thus, a copper foil/titanium, manganese and copper doped alumina passivation layer/aluminum nitride substrate/titanium, manganese and copper doped alumina passivation layer/copper foil copper clad ceramic substrate can be obtained, wherein the copper foil tensile value is 85N/cm (the measurement standard is ASTM D903).

Although the present disclosure has been described with reference to a number of preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure, and therefore the scope of the disclosure should be limited only by the appended claims.