Method for growing diamond film based on aluminum nitride ceramic substrate, diamond film and application

Abstract

The invention belongs to the technical field of electronic devices, and discloses a method for growing a diamond film based on an aluminum nitride ceramic substrate, the diamond film and application. The method provided by the invention comprises the following steps: firstly, carrying out first surface ultrasonic treatment on an aluminum nitride ceramic substrate by adopting a hydrofluoric acid solution with a specific concentration to obtain a roughened aluminum nitride ceramic substrate; carrying out second surface ultrasonic treatment on the coarsened aluminum nitride ceramic substrate by adopting diamond micro-powder turbid liquid to obtain a seed crystal aluminum nitride ceramic substrate with high nucleation density on the surface; and finally, carrying out microwave plasma chemical vapor deposition and in-situ annealing treatment on the seed crystal aluminum nitride ceramic substrate, and growing on the aluminum nitride ceramic substrate to obtain the diamond film. The diamond film has low surface stress and good uniformity, has high bonding strength with the aluminum nitride ceramic substrate, is excellent in performance, can be well applied to preparation of microelectronic devices, and is excellent in application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic devices, and in particular relates to a method for growing a diamond film based on an aluminum nitride ceramic substrate, the diamond film and applications. Background Art

[0002] Aluminum nitride (AlN) ceramics have a simple crystal structure, short Al-N covalent bond length, high bond energy, good thermal conductivity, electrical insulation and mechanical properties, and have significant advantages in overall performance and cost. However, the thermal conductivity of AlN ceramics is low and decreases rapidly with increasing temperature, which gradually weakens its positive output effect in device thermal management under high-temperature working conditions. Therefore, improving the thermal properties of AlN ceramics has become the focus of current research.

[0003] Diamond is a typical carbon material and an allotrope of graphite. It has a completely different crystal structure from graphite. In the face-centered cubic structure of diamond, carbon atoms are arranged in sp 3 Hybridization forms stable covalent bonds, which makes diamond have excellent properties such as high hardness, high melting point, high thermal conductivity, low thermal expansion coefficient, excellent electrical insulation and good chemical stability. By depositing diamond film on the surface of AlN ceramics, not only the thermal properties of AlN ceramics are effectively improved, but the resulting composite layer structure also has excellent wear resistance and anti-penetration properties, which can be better used in electronics, machinery and other fields.

[0004] At present, the main method for preparing diamond film on the surface of AlN ceramics is chemical vapor deposition (CVD). In the CVD process, the main equipment used is hot wire chemical vapor deposition (HFCVD) device and microwave plasma chemical vapor deposition (MPCVD) device. In the process of depositing diamond film on AlN ceramic substrate by HFCVD, the metal wire is easy to evaporate at high temperature to produce metal atomic impurities, and the degree of dissociation of the hot wire to the gas during the deposition process is not high, the hydrogen atom content is low, and graphite is easy to co-exist during the growth process. The obtained diamond film contains more impurities and the quality is not ideal. Compared with HFCVD, the MPCVD device uses electrodeless discharge, and the plasma produced has almost no other impurities, which avoids the problem of electrodes and metal wires contaminating diamond crystals due to high-temperature evaporation. At the same time, it also overcomes the disadvantage that the metal wire is very sensitive to highly corrosive gases (high concentration of oxygen, halogen gases, etc.) during the deposition of diamond film by HFCVD. However, due to certain differences between AlN and diamond in properties such as lattice constant and thermal expansion coefficient, there are large and unevenly distributed residual stress and thermal stress in the resulting composite structure, which may cause the diamond film to fall off, crack, etc. The resulting diamond film also has the problem of unreasonable quality.

[0005] Therefore, it is of great significance to obtain a method capable of achieving high-quality diamond film deposition on AlN ceramics. Summary of the Invention

[0006] The first object of the present invention is to provide a method for growing diamond films on an aluminum nitride ceramic substrate. By using this method, diamond films can be well deposited on AlN ceramics to obtain a diamond film with low surface stress and good uniformity, and this diamond film has a high bonding strength with the aluminum nitride ceramic substrate, excellent performance, and can be well applied to the preparation of microelectronic devices, showing good application prospects.

[0007] The second object of the present invention is to provide a diamond film.

[0008] The third object of the present invention is to provide the application of the above method for growing diamond films on an aluminum nitride ceramic substrate and / or the diamond film in the preparation of microelectronic devices.

[0009] Specifically, the method for growing diamond films on an aluminum nitride ceramic substrate provided by the present invention specifically includes: S1. Take a hydrofluoric acid solution to perform first surface ultrasonic treatment and cleaning treatment on the aluminum nitride ceramic substrate to obtain a roughened aluminum nitride ceramic substrate; S2. Take a diamond micropowder suspension to perform second surface ultrasonic treatment on the first roughened aluminum nitride ceramic substrate to obtain a seed crystal aluminum nitride ceramic substrate; S3. Take the seed crystal aluminum nitride ceramic substrate to perform microwave plasma chemical vapor deposition and in-situ annealing treatment, and grow a diamond film on the seed crystal aluminum nitride ceramic substrate to obtain the diamond film; wherein, the concentration of the hydrofluoric acid solution is 0.05 - 0.08 wt%; the power of the first surface ultrasonic treatment is 1000 - 2000 W, and the time is 3 - 4 min.

[0010] Further, in step S1, the surface roughness of the aluminum nitride ceramic substrate is 5 - 10 nm, and the surface roughness of the roughened aluminum nitride ceramic substrate is 20 - 30 nm.

[0011] Further, in step S1, the cleaning treatment includes: sequentially taking acetone, ethanol, and deionized water to perform ultrasonic treatment on the roughened aluminum nitride ceramic substrate.

[0012] Further, in step S1, the power of the ultrasonic treatment is 100 - 200 W, and the time is 4 - 8 min.

[0013] Further, in step S2, the particle size of the diamond micropowder in the diamond micropowder suspension is 20 - 25 nm.

[0014] Further, in step S2, the solvent of the diamond micropowder suspension is acetone and / or ethanol.

[0015] Further, in step S2, based on the total mass of the diamond micropowder suspension, the concentration of the diamond micropowder is 0.1-3 wt%.

[0016] Further, in step S2, the power of the second surface ultrasonic treatment is 100-300 W, and the time is 10-15 min.

[0017] Further, in step S3, the microwave plasma chemical vapor deposition includes: placing the seed aluminum nitride ceramic substrate in an MPCVD reaction device, introducing reaction gases and auxiliary gases for deposition growth, and growing a diamond film on the seed aluminum nitride ceramic substrate.

[0018] Further, in step S3, the reaction gases include hydrogen and a carbon source gas, and the carbon source gas is selected from one or more of methane, propane, and ethylene.

[0019] Further, in step S3, based on the total volume of the reaction gases, the concentration of hydrogen is 95-98% (v / v), and the concentration of the carbon source gas is 2-5% (v / v).

[0020] Further, in step S3, the flow rate of the reaction gases is 250-750 sccm, and the flow rate of the auxiliary gas is 0.5-1.5 sccm.

[0021] Further, in step S3, the deposition temperature for the deposition growth is 700-950 °C, the deposition time is 4-60 h, the microwave power is 4000-5000 W, and the chamber pressure of the MPCVD reaction device is 100-200 Torr.

[0022] Further, in step S3, the annealing temperature for the in-situ annealing treatment is 500-700 °C, the holding time is 1-4 h, and the cooling time is 10-240 min.

[0023] The diamond film provided by the present invention is grown by the method for growing a diamond film based on an aluminum nitride ceramic substrate as described above.

[0024] The present invention also provides the application of the above method for growing a diamond film based on an aluminum nitride ceramic substrate and / or the diamond film in the preparation of microelectronic devices.

[0025] Beneficial effects:

[0026] In the method for growing diamond films on an aluminum nitride ceramic substrate provided by the present invention, first, a hydrofluoric acid solution with a specific concentration is used for the first surface ultrasonic treatment of the aluminum nitride ceramic substrate. Through the reactivity of hydrofluoric acid with AlN, while achieving roughening of the surface of the aluminum nitride ceramic substrate to obtain more surface defects, not only the surface properties of the aluminum nitride ceramic substrate are optimized to improve its chimeric ability for diamond micropowder, but also the formed surface state is conducive to the progress of microwave plasma chemical vapor deposition; then, a diamond micropowder suspension is used for the second surface ultrasonic treatment to obtain a seed crystal aluminum nitride ceramic substrate with a high nucleation density on the surface; using this seed crystal aluminum nitride ceramic substrate for microwave plasma chemical vapor deposition can achieve good deposition growth effects, thereby finally obtaining a diamond film with low surface stress and good uniformity, and this diamond film has a high bonding strength with the aluminum nitride ceramic substrate, excellent performance, can be well applied to the preparation of microelectronic devices, and has good application prospects. Description of the Drawings

[0027] Figure 1 SEM image of the diamond film provided in Example 1 of the present invention (scale bar is 10 μm);

[0028] Figure 2 SEM image of the diamond film provided in Example 4 of the present invention (scale bar is 10 μm);

[0029] Figure 3 SEM image of the diamond film provided in Example 5 of the present invention (scale bar is 10 μm);

[0030] Figure 4 SEM image of the diamond film provided in Example 6 of the present invention (scale bar is 10 μm);

[0031] Figure 5 One of the experimental result graphs of the residual stress test provided in the test example of the present invention;

[0032] Figure 6 Another experimental result graph of the residual stress test provided in the test example of the present invention;

[0033] Figure 7 Another experimental result graph of the residual stress test provided in the test example of the present invention;

[0034] Figure 8 Experimental result graph of the bonding strength test provided in the test example of the present invention (Example 1);

[0035] Figure 9 Experimental result graph of the bonding strength test provided in the test example of the present invention (Comparative Example 1);

[0036] Figure 10 Experimental result graph of the bonding strength test provided for the test example in the present invention (Comparative Example 2);

[0037] Figure 11 Experimental result graph of the bonding strength test provided for the test example in the present invention (Comparative Example 3). Detailed implementation manners

[0038] The method for growing diamond films on an aluminum nitride ceramic substrate provided by the present invention specifically includes: S1. Taking a hydrofluoric acid solution to perform first surface ultrasonic treatment and cleaning treatment on the aluminum nitride ceramic substrate to obtain a roughened aluminum nitride ceramic substrate; S2. Taking a diamond micropowder suspension to perform second surface ultrasonic treatment on the first roughened aluminum nitride ceramic substrate to obtain a seeded aluminum nitride ceramic substrate; S3. Taking the seeded aluminum nitride ceramic substrate to perform microwave plasma chemical vapor deposition and in-situ annealing treatment to grow diamond films on the seeded aluminum nitride ceramic substrate to obtain the diamond films.

[0039] In the present invention, in step S1, the concentration of the hydrofluoric acid solution is specifically 0.05 - 0.08 wt%, such as 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt% or any value between them; the power of the first surface ultrasonic treatment is specifically 1000 - 2000 W, such as 1000 W, 1250 W, 1500 W, 1800 W, 2000 W or any value between them; the time of the first surface ultrasonic treatment is specifically 3 - 4 min, such as 3 min, 3.2 min, 3.3 min, 3.5 min, 3.8 min, 4 min or any value between them.

[0040] In the present invention, in step S1, the surface roughness of the aluminum nitride ceramic substrate is preferably 5 - 10 nm, such as 5 nm, 5.8 nm, 6 nm, 6.3 nm, 7 nm, 7.4 nm, 8 nm, 8.1 nm, 8.2 nm, 8.5 nm, 9 nm, 10 nm or any value between them; the surface roughness of the roughened aluminum nitride ceramic substrate is preferably 20 - 30 nm, such as 20 nm, 21.8 nm, 24.3 nm, 25 nm, 26.7 nm, 28 nm, 29 nm, 30 nm or any value between them. At this time, using this roughened aluminum nitride ceramic substrate for subsequent second surface ultrasonic treatment, microwave plasma chemical vapor deposition and in-situ annealing treatment can prepare diamond films with higher quality.

[0041] In the present invention, in step S1, the cleaning treatment is to effectively remove unreacted hydrogen fluoride on the roughened aluminum nitride ceramic substrate. Those skilled in the art can make adaptive selections according to actual needs, and the present invention does not make special limitations.

[0042] In some specific embodiments, the cleaning treatment preferably includes: sequentially taking acetone, ethanol, and deionized water to perform ultrasonic treatment on the roughened aluminum nitride ceramic substrate. More specifically, the power of the ultrasonic treatment is preferably 100 - 200 W, such as 100 W, 1250 W, 150 W, 200 W, or any value therebetween; the time of the ultrasonic treatment is preferably 4 - 8 min, such as 4 min, 5 min, 6 min, 7 min, 8 min, or any value therebetween.

[0043] In the present invention, in step S2, the particle size of the diamond micropowder in the diamond micropowder suspension is preferably 20 - 25 nm, such as 20 nm, 21.5 nm, 23 nm, 24 nm, 25 nm, or any value therebetween. At this time, the diamond micropowder suspension can be better embedded on the surface of the roughened aluminum nitride ceramic substrate, thereby preparing a diamond film of higher quality.

[0044] In the present invention, in step S2, the solvent of the diamond micropowder suspension is a type of solvent commonly used in the existing preparation of diamond micropowder suspension. Those skilled in the art can make an adaptive selection according to actual needs, and the present invention does not make a special limitation. Specific examples thereof include but are not limited to: acetone and / or ethanol.

[0045] In some specific embodiments, in step S2, based on the total mass of the diamond micropowder suspension, the concentration of the diamond micropowder is preferably 0.1 - 3 wt%, such as 0.1 wt%, 0.35 wt%, 0.5 wt%, 0.9 wt%, 1 wt%, 1.8 wt%, 2 wt%, 3 wt%, or any value therebetween. At this time, the diamond micropowder suspension can better achieve the treatment effect on the first roughened aluminum nitride ceramic substrate, obtain a seed aluminum nitride ceramic substrate with a more ideal surface state, and ultimately realize the preparation of a high-quality diamond film.

[0046] In some specific embodiments, in step S2, the power of the second surface ultrasonic treatment is preferably 100 - 300 W, such as 100 W, 150 W, 200 W, 250 W, 300 W, or any value therebetween; the time is preferably 10 - 15 min, such as 10 min, 12.2 min, 13 min, 14.5 min, 15 min, or any value therebetween.

[0047] In the present invention, in step S3, the microwave plasma chemical vapor deposition specifically includes: placing the seeded aluminum nitride ceramic substrate in an MPCVD reaction device, introducing reaction gases and auxiliary gases for deposition growth, and growing a diamond film on the seeded aluminum nitride ceramic substrate. Among them, the reaction gases specifically include hydrogen and a carbon source gas, and specific examples of the carbon source gas include, but are not limited to, one or more of methane, propane, and ethylene.

[0048] In some specific embodiments, in the microwave plasma chemical vapor deposition, based on the total volume of the reaction gases, the concentration of hydrogen is preferably 95-98% (v / v), such as 95% (v / v), 95.3% (v / v), 96% (v / v), 96.7% (v / v), 97.1% (v / v), 98% (v / v), or any value between them; the concentration of the carbon source gas is preferably 2-5% (v / v), such as 2% (v / v), 2.3% (v / v), 2.8% (v / v), 3.1% (v / v), 3.4% (v / v), 4% (v / v), 5% (v / v), or any value between them.

[0049] In some specific embodiments, in the microwave plasma chemical vapor deposition, the flow rate of the reaction gases is preferably 250-750 sccm, such as 250 sccm, 290 sccm, 300 sccm, 450 sccm, 500 sccm, 600 sccm, 750 sccm, or any value between them; the flow rate of the auxiliary gas is preferably 0.5-1.5 sccm, such as 0.5 sccm, 0.8 sccm, 1.3 sccm, 1.5 sccm, or any value between them.

[0050] In some specific embodiments, in the microwave plasma chemical vapor deposition, the deposition temperature for the deposition growth is preferably 700-950 °C, such as 700 °C, 750 °C, 780 °C, 800 °C, 830 °C, 890 °C, 900 °C, 950 °C, or any value between them; the deposition time is preferably 4-60 h, such as 4 h, 4.8 h, 5 h, 5.6 h, 8 h, 10 h, 15 h, 20 h, 25 h, 30 h, 40 h, 50 h, 60 h, or any value between them; the microwave power is preferably 4000-5000 W, such as 4000 W, 4150 W, 4200 W, 4300 W, 4500 W, 5000 W, or any value between them; the chamber pressure of the MPCVD reaction device is preferably 100-200 Torr, such as 100 Torr, 125 Torr, 145 Torr, 160 Torr, 180 Torr, 200 Torr, or any value between them.

[0051] In the present invention, in step S3, the annealing temperature of the in-situ annealing treatment is preferably 500 to 700 °C, such as 500 °C, 520 °C, 540 °C, 580 °C, 600 °C, 650 °C, 700 °C or any value therebetween; the holding time is preferably 1 to 4 h, such as 1 h, 1.2 h, 1.4 h, 1.8 h, 2 h, 3.5 h, 4 h or any value therebetween; the cooling time is preferably 10 to 240 min, such as 10 min, 15 min, 20 min, 60 min, 120 min, 240 min or any value therebetween. At this time, the in-situ annealing treatment can effectively reduce the surface stress of the diamond film, thereby effectively improving the quality of the obtained diamond film.

[0052] The present invention also provides a diamond film, which is grown by the method for growing a diamond film on an aluminum nitride ceramic substrate as described above.

[0053] The present invention also provides the application of the method for growing a diamond film on an aluminum nitride ceramic substrate and / or the diamond film in the preparation of microelectronic devices.

[0054] The embodiments of the present invention are described in detail below. The examples of the embodiments are intended to explain the present invention and should not be construed as limiting the present invention. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For the reagents or instruments not specified in terms of the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0055] Example 1

[0056] This example is used to illustrate a method for growing a diamond film on an aluminum nitride ceramic substrate, which specifically includes:

[0057] S1. Take an AlN ceramic substrate with a thickness of 0.55 mm and place the growth surface facing upwards in a hydrofluoric acid solution with a concentration of 0.07 wt%, and perform the first surface ultrasonic treatment for 4 min at an ultrasonic power of 1000 W. Then, after thoroughly rinsing the surface of the AlN ceramic substrate with deionized water, successively perform ultrasonic treatment on the roughened aluminum nitride ceramic substrate with acetone, absolute ethanol and deionized water at an ultrasonic power of 200 W for 8 min, and thoroughly rinse the surface of the AlN ceramic substrate with deionized water after each ultrasonic treatment to obtain a roughened aluminum nitride ceramic substrate.

[0058] S2. Place the roughened aluminum nitride ceramic substrate with the growth surface facing up in an anhydrous ethanol suspension of diamond micropowder (particle size of 20 nm) with a concentration of 1.0 wt%, and perform second surface ultrasonic treatment for 10 min at an ultrasonic power of 250 W to obtain a seed aluminum nitride ceramic substrate. Rinse it thoroughly with deionized water, and dry the obtained seed aluminum nitride ceramic substrate with nitrogen for standby.

[0059] S3. (1) Place the seed aluminum nitride ceramic substrate at the center of the substrate stage of a 6 kW / 2.45 GHz microwave plasma chemical vapor deposition system (Shenzhen Youpulai UP206), fix the substrate stage at a specified position in the cavity, close the cavity, reduce the cavity pressure to the background vacuum, introduce hydrogen at a flow rate of 500 sccm for cavity purging, and after purging, pump it to the background vacuum again.

[0060] (2) Raise the substrate stage to the specified position, introduce hydrogen to make the pressure in the cavity 6.5 Torr, turn on the microwave generator and adjust the microwave power to 4600 W. After introducing hydrogen until the pressure in the cavity reaches 20 Torr, the device switches from ignition to the heating stage. When the pressure in the cavity is 150 Torr by continuously introducing hydrogen, adjust the three-pin screw to minimize the reflected power.

[0061] (3) Introduce the reaction gas at a flow rate of 500 sccm and the auxiliary gas at a flow rate of 0.5 sccm, heat up the seed aluminum nitride ceramic substrate to 900 °C, and maintain the pressure in the cavity at 150 Torr. Deposit and grow on the seed aluminum nitride ceramic substrate for 20 h; among them, the reaction gas includes 96% (v / v) hydrogen and 4% (v / v) methane, and the auxiliary gas is oxygen.

[0062] (4) After the deposition and growth are completed, turn off all gases except hydrogen, keep the aluminum nitride ceramic substrate with the diamond film grown on it at 600 °C for 2 h, and then cool it evenly to room temperature within 120 min to complete the in-situ annealing treatment, obtaining a diamond film grown on the AlN ceramic substrate, and the thickness of this diamond film is 81.9 μm.

[0063] In step S1, the surface roughness Ra of the aluminum nitride ceramic substrate is measured to be 6.0 nm by a laser microscopy system. After the first surface ultrasonic treatment and cleaning treatment, the thickness of the roughened aluminum nitride ceramic substrate is 0.55 mm, and the surface roughness Ra is 24.3 nm.

[0064] Figure 1 This is the SEM image of the diamond film prepared in this example.

[0065] Example 2

[0066] The method for growing diamond films on an aluminum nitride ceramic substrate provided in this embodiment is basically the same as that in Embodiment 1. The difference lies in that in step S1, the concentration of the hydrofluoric acid solution is 0.05 wt%, and the time for ultrasonic treatment of the first surface is 4 min. Under the same other conditions, diamond films grown on the AlN ceramic substrate are obtained.

[0067] In step S1, the surface roughness Ra of the aluminum nitride ceramic substrate measured by a laser microscopy system is 9.5 nm. The thickness of the roughened aluminum nitride ceramic substrate obtained after the ultrasonic treatment and cleaning treatment of the first surface is 0.55 mm, and the surface roughness Ra is 35.8 nm. In step S4, the film thickness of the prepared diamond film is 85.1 μm.

[0068] Embodiment 3

[0069] The method for growing diamond films on an aluminum nitride ceramic substrate provided in this embodiment is basically the same as that in Embodiment 1. The difference lies in that in step S1(3), the concentration of the hydrofluoric acid solution is 0.05 wt%, and the time for ultrasonic treatment of the first surface is 3 min. Under the same other conditions, diamond films grown on the AlN ceramic substrate are obtained.

[0070] In step S1, the surface roughness Ra of the aluminum nitride ceramic substrate measured by a laser microscopy system is 6.5 nm. The thickness of the roughened aluminum nitride ceramic substrate obtained after the ultrasonic treatment and cleaning treatment of the first surface is 0.55 mm, and the surface roughness Ra is 7.1 nm. In step S4, the film thickness of the prepared diamond film is 76.7 μm.

[0071] Embodiment 4

[0072] The method for growing diamond films on an aluminum nitride ceramic substrate provided in this embodiment is basically the same as that in Embodiment 1. The difference lies in that in step S3(3), the deposition growth time is 4 h. Under the same other conditions, diamond films grown on the AlN ceramic substrate are obtained.

[0073] In step S1, the surface roughness Ra of the aluminum nitride ceramic substrate measured by a laser microscopy system is 8.0 nm. The thickness of the roughened aluminum nitride ceramic substrate obtained after the ultrasonic treatment and cleaning treatment of the first surface is 0.55 mm, and the surface roughness Ra is 24.1 nm. In step S4, the film thickness of the prepared diamond film is 10.2 μm.

[0074] Figure 2 This is the SEM image of the diamond film prepared in this embodiment. From Figure 1 and 2 The comparison of the shown results shows that with the increase of the deposition time, the grain size in the diamond film becomes larger.

[0075] Example 5

[0076] The method for growing diamond films on an aluminum nitride ceramic substrate provided in this example is basically the same as that in Example 1. The difference is that in step S3(3), the deposition growth time is 40 h, and other conditions are the same, obtaining diamond films grown on the AlN ceramic substrate.

[0077] In step S1, the surface roughness Ra of the aluminum nitride ceramic substrate measured by a laser microscopy system is 8.0 nm. The thickness of the roughened aluminum nitride ceramic substrate obtained after the first surface ultrasonic treatment and cleaning treatment is 0.55 mm, and the surface roughness Ra is 24.2 nm; in step S4, the film thickness of the prepared diamond film is 54.8 μm.

[0078] Figure 3 This is the SEM image of the diamond film prepared in this example. From Figure 1 and 3 The comparison of the shown results shows that as the deposition time increases, the grain size in the diamond film becomes larger.

[0079] Example 6

[0080] The method for growing diamond films on an aluminum nitride ceramic substrate provided in this example is basically the same as that in Example 1. The difference is that in step S3(3), the deposition growth time is 60 h, and other conditions are the same, obtaining diamond films grown on the AlN ceramic substrate.

[0081] In step S1, the surface roughness Ra of the aluminum nitride ceramic substrate measured by a laser microscopy system is 8.0 nm. The thickness of the roughened aluminum nitride ceramic substrate obtained after the first surface ultrasonic treatment and cleaning treatment is 0.55 mm, and the surface roughness Ra is 24.2 nm; in step S4, the film thickness of the prepared diamond film is 233.6 μm.

[0082] Figure 4 This is the SEM image of the diamond film prepared in this example. From Figure 3 and 4 The comparison of the shown results shows that when the deposition growth time is greater than or equal to 40 h, the grain size in the diamond film changes little, that is, the grain size growth tends to be saturated.

[0083] Example 7

[0084] The method for growing diamond films on an aluminum nitride ceramic substrate provided in this example is basically the same as that in Example 1. The difference is that in step S3(4), the cooling time of the in-situ annealing treatment is 10 min, and other conditions are the same, obtaining diamond films grown on the AlN ceramic substrate.

[0085] In step S1, the surface roughness Ra of the aluminum nitride ceramic substrate measured by a laser microscopy system is 8.0 nm. After the first surface ultrasonic treatment and cleaning treatment, the thickness of the roughened aluminum nitride ceramic substrate is 0.55 mm, and the surface roughness Ra is 24.0 nm. In step S4, the film thickness of the prepared diamond film is 82.0 μm.

[0086] Example 8

[0087] The method for growing diamond film on an aluminum nitride ceramic substrate provided in this example is basically the same as that in Example 1, except that in step S3(4), the cooling time of the in-situ annealing treatment is 20 min, and other conditions are the same, to obtain a diamond film grown on the AlN ceramic substrate.

[0088] In step S1, the surface roughness Ra of the aluminum nitride ceramic substrate measured by a laser microscopy system is 8.0 nm. After the first surface ultrasonic treatment and cleaning treatment, the thickness of the roughened aluminum nitride ceramic substrate is 0.55 mm, and the surface roughness Ra is 24.1 nm. In step S4, the film thickness of the prepared diamond film is 81.2 μm.

[0089] Example 9

[0090] The method for growing diamond film on an aluminum nitride ceramic substrate provided in this example is basically the same as that in Example 1, except that in step S3(4), the cooling time of the in-situ annealing treatment is 60 min, and other conditions are the same, to obtain a diamond film grown on the AlN ceramic substrate.

[0091] In step S1, the surface roughness Ra of the aluminum nitride ceramic substrate measured by a laser microscopy system is 8.0 nm. After the first surface ultrasonic treatment and cleaning treatment, the thickness of the roughened aluminum nitride ceramic substrate is 0.55 mm, and the surface roughness Ra is 24.3 nm. In step S4, the film thickness of the prepared diamond film is 81.5 μm.

[0092] Comparative Example 1

[0093] The method for growing diamond film on an aluminum nitride ceramic substrate provided in this comparative example is basically the same as that in Example 1, except that in step S1, the concentration of the hydrofluoric acid solution is 0.12 wt%, and the time of the first surface ultrasonic treatment is 4 min, and other conditions are the same, to obtain a diamond film grown on the AlN ceramic substrate.

[0094] In step S1, the surface roughness Ra of the aluminum nitride ceramic substrate measured by a laser microscopy system is 6.1. After the first surface ultrasonic treatment and cleaning treatment, the thickness of the roughened aluminum nitride ceramic substrate is 0.48 mm, and the surface roughness Ra is 125.1 nm. In step S4, the film thickness of the prepared diamond film is 15.3 μm.

[0095] Comparative Example 2

[0096] The method for growing a diamond film on an aluminum nitride ceramic substrate provided in this comparative example is basically the same as that in Example 1, except that in step S1, the time of the first surface ultrasonic treatment is 10 s, and other conditions are the same, and a diamond film grown on an AlN ceramic substrate is obtained.

[0097] In step S1, the surface roughness Ra of the aluminum nitride ceramic substrate measured by a laser microscopy system is 6.1. After the first surface ultrasonic treatment and cleaning treatment, the thickness of the roughened aluminum nitride ceramic substrate is 0.55 mm, and the surface roughness Ra is 2.1 nm. In step S4, the film thickness of the prepared diamond film is 34.2 μm.

[0098] Comparative Example 3

[0099] This comparative example provides a method for growing a diamond film on an aluminum nitride ceramic substrate, which specifically includes:

[0100] S1. Take an AlN ceramic substrate with a thickness of 0.55 mm (surface roughness is 23.9 nm), and ultrasonically treat the AlN ceramic substrate with acetone, sewage ethanol, and deionized water in turn at an ultrasonic power of 1000 W for 10 min, and after each ultrasonic treatment is completed, the surface of the AlN ceramic substrate is thoroughly rinsed with deionized water to obtain a clean aluminum nitride ceramic substrate.

[0101] S2. Place the clean aluminum nitride ceramic substrate with the growth surface facing up in an anhydrous ethanol suspension of diamond micropowder with a concentration of 2.5 wt% (particle size is 20 nm), and perform a second surface ultrasonic treatment for 12 min at an ultrasonic power of 600 W to obtain a seed crystal aluminum nitride ceramic substrate. The seed crystal aluminum nitride ceramic substrate is thoroughly rinsed with deionized water and dried with nitrogen for standby.

[0102] S3. (1) Place the seed crystal aluminum nitride ceramic substrate at the center of the substrate stage of a 6 kW / 2.45 GHz microwave plasma chemical vapor deposition system (Shenzhen Youpulai UP206), fix the substrate stage at a specified position in the cavity, close the cavity, reduce the cavity pressure to the background vacuum, introduce hydrogen for cavity purging at a flow rate of 500 sccm, and after the purging is completed, pump it to the background vacuum again.

[0103] (2) The substrate stage rises to the designated position, hydrogen is introduced to make the pressure in the cavity 6.5 Torr, the microwave generator is turned on and the microwave power is adjusted to 4600 W. After hydrogen is introduced until the pressure in the cavity reaches 20 Torr, the equipment switches from the starting-up stage to the heating stage. When hydrogen is continuously introduced to make the pressure in the cavity 150 Torr, the three-pin screw is adjusted to minimize the reflected power.

[0104] (3) The reaction gas is introduced at a flow rate of 500 sccm, and the auxiliary gas is introduced at a flow rate of 0.5 sccm. The seeded aluminum nitride ceramic substrate is heated to 900 °C, and the pressure in the cavity is maintained at 150 Torr. Deposition growth is carried out on the seeded aluminum nitride ceramic substrate for 20 h; among them, the reaction gas includes 96% (v / v) hydrogen and 4% (v / v) methane, and the auxiliary gas is oxygen.

[0105] (4) After the deposition growth is completed, all gases except hydrogen are turned off. The aluminum nitride ceramic substrate with the diamond film grown on it is kept at 600 °C for 2 h, and then cooled uniformly to room temperature within 120 min to complete the in-situ annealing treatment, obtaining the diamond film grown on the AlN ceramic substrate, and the thickness of this diamond film is 40 μm.

[0106] Test Example

[0107] This test example is used to illustrate the relevant properties of the diamond films provided in the above examples and comparative examples. The specific tests include:

[0108] 1. Test of residual stress: The Raman spectrometer is used to test 5 identical positions on each diamond film. The results are as Figures 5 - 7 shown.

[0109] From Figures 5 - 7 the test results shown, compared with Comparative Examples 1-3, the surface stress state of the diamond films prepared by the methods provided in Examples 1-9 of the present invention is more uniform, and has lower surface residual stress.

[0110] 2. Test of thermal conductivity: Referring to the method provided in GB / T 39862-2021, the thermal conductivity of the composite structure including the diamond film and the aluminum nitride ceramic substrate is tested. The results are shown in Table 1.

[0111] Table 1.

[0112]

[0113]

[0114] As can be seen from the test results shown in Table 1, compared with the original aluminum nitride ceramic substrate, the growth and deposition of diamond films on the aluminum nitride ceramic substrate in Examples 1-9 of the present invention can effectively improve the thermal conductivity.

[0115] 3. Test of bonding strength: Referring to the method provided in the "German VDI3198 Standard", the film-substrate bonding force was tested by a FALCON 500 Vickers microhardness tester produced by INNOVATEST. The load application method was continuous loading. The cone angle of the diamond indenter was 136°15′, the applied load was 5 kgf, and the duration was 15 s. The indentation morphology was observed using a microscope to test the bonding strength between the diamond film and the aluminum nitride ceramic substrate. The results are as Figures 8 - 11 shown.

[0116] As Figures 8 - 11 can be seen from the test results shown, compared with Comparative Examples 1-3, the diamond film provided in Example 1 of the present invention and the aluminum nitride ceramic substrate have excellent bonding strength, and the overall structural performance is more stable.

[0117] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principle and purpose of the present invention.

Claims

1. A method for growing a diamond film based on an aluminum nitride ceramic substrate, characterized in that: The method comprises: S1, taking a hydrofluoric acid solution to perform a first surface ultrasonic treatment and a cleaning treatment on an aluminum nitride ceramic substrate to obtain a roughened aluminum nitride ceramic substrate; S2, taking a diamond micropowder suspension to perform a second surface ultrasonic treatment on the first roughened aluminum nitride ceramic substrate to obtain a seeded aluminum nitride ceramic substrate; S3, taking the seeded aluminum nitride ceramic substrate to perform microwave plasma chemical vapor deposition and in-situ annealing treatment, growing a diamond film on the seeded aluminum nitride ceramic substrate to obtain the diamond film; Wherein, the concentration of the hydrofluoric acid solution is 0.05-0.08wt%; the power of the first surface ultrasonic treatment is 1000-2000W, and the time is 3-4min.

2. The method for growing a diamond film on an aluminum nitride ceramic substrate according to claim 1, characterized in that: In step S1, the surface roughness of the aluminum nitride ceramic substrate is 5 to 10 nm; Optionally, the surface roughness of the roughened aluminum nitride ceramic substrate is 6-40 nm.

3. The method for growing a diamond film on an aluminum nitride ceramic substrate according to claim 1, characterized in that: In step S1, the cleaning process includes: taking acetone, ethanol and deionized water in sequence to perform ultrasonic treatment on the roughened aluminum nitride ceramic substrate; Optionally, the power of the ultrasonic treatment is 100-200 W, and the time is 4-8 min.

4. The method for growing a diamond film on an aluminum nitride ceramic substrate according to claim 1, characterized in that: In step S2, the particle size of the diamond powder in the diamond powder suspension is 20-25 nm; Optionally, the solvent of the diamond micropowder suspension is acetone and / or ethanol; Optionally, based on the total mass of the diamond powder suspension, the concentration of the diamond powder is 0.1-3 wt %.

5. The method for growing a diamond film based on an aluminum nitride ceramic substrate according to claim 1, characterized in that: In step S2, the power of the second surface ultrasonic treatment is 100-300W, and the time is 10-15 minutes.

6. The method for growing a diamond film based on an aluminum nitride ceramic substrate according to claim 1, characterized in that: In step S3, the microwave plasma chemical vapor deposition includes: taking the seed crystal aluminum nitride ceramic substrate into an MPCVD reaction device, introducing reaction gas and auxiliary gas for deposition growth, and growing a diamond film on the seed crystal aluminum nitride ceramic substrate.

7. The method for growing a diamond film based on an aluminum nitride ceramic substrate according to claim 6, characterized in that: In step S3, the reaction gas includes hydrogen and a carbon source gas, and the carbon source gas is selected from one or more of methane, propane and ethylene; Optionally, based on the total volume of the reaction gas, the concentration of the hydrogen gas is 95-98% (v / v), and the concentration of the carbon source gas is 2-5% (v / v); Optionally, the flow rate of the reaction gas is 250 to 750 sccm, and the flow rate of the auxiliary gas is 0.5 to 1.5 sccm; Optionally, the deposition temperature of the deposition growth is 700-950° C., the deposition time is 4-60 h, the microwave power is 4000-5000 W, and the cavity pressure of the MPCVD reaction device is 100-200 Torr.

8. The method for growing a diamond film based on an aluminum nitride ceramic substrate according to claim 1, characterized in that: In step S3, the annealing temperature of the in-situ annealing treatment is 500-700° C., the holding time is 1-4 hours, and the cooling time is 10-240 minutes.

9. A diamond film, characterized in that: The diamond film is grown by the method for growing a diamond film based on an aluminum nitride ceramic substrate as described in any one of claims 1 to 8.

10. The method for growing a diamond film based on an aluminum nitride ceramic substrate as claimed in any one of claims 1 to 8 and / or the use of the diamond film as claimed in claim 9 in the preparation of microelectronic devices.

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