Method for producing aluminum nitride substrate

Abstract

To provide a method for producing an aluminum nitride substrate having a small surface pore diameter and high thermal conductivity.SOLUTION: A method for manufacturing a polycrystalline aluminum nitride substrate includes: a step (A) of providing a polycrystalline aluminum nitride substrate whose surface is to be polished, causing a plasma formed of nitrogen and argon to act on a first layer aluminum nitride film generated by reaction on the surface of the substrate by a magnetron sputtering apparatus, and filling a gap of a hole generated due to a defect of a crystal lattice on the surface of the substrate; a step (B) of removing the first layer aluminum nitride film on the substrate by a flattening method to leave a filling portion in the hole; a step (C) of sintering the substrate, the surface of which has been flattened, at a high temperature to enhance the adhesion density between the aluminum nitride film in the gap and the substrate; a step (D) of subjecting the substrate, the sintering of which has been completed, to hole-filling sputtering of a second layer aluminum nitride film at a slow sputtering rate; and a step (C) of removing the second layer aluminum nitride film on the substrate by a flattening method to form a second layer aluminum nitride film on the substrate. (E) leaving the filling portion in the hole to complete the manufacture of the substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing an aluminum nitride substrate having small surface pore diameters and high thermal conductivity, and more particularly to a method for reducing the surface pore diameters of a polycrystalline aluminum nitride substrate. [Background technology]

[0002] Aluminum nitride (AlN) ceramic substrates have the advantages of high heat dissipation, long life, low thermal resistance, and voltage resistance, and with the improvement of manufacturing technology and equipment, AlN ceramic substrates are widely used in the high-power application field of the LED industry, improving the performance and reliability of high-power lighting device products and extending their service life, making them an important development material for next-generation high-power devices. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Chinese Patent Application Publication No. 106431419 [Patent Document 2] Chinese Patent Application Publication No. 115460798B [Patent Document 3] Chinese Patent Application Publication No. 104428441B [Patent Document 4] Chinese Patent Application Publication No. 109867521A Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional high-power LED substrate materials are mainly made of aluminum oxide, which has low thermal conductivity, but because high-power LEDs and power semiconductor elements emit high amounts of heat energy, thermal shock tests for the products are also severe.

[0005] Aluminum nitride is a ceramic insulator with high thermal conductivity (polycrystalline thermal conductivity is approximately 70-210 W m -1 ·K -1 Due to its excellent thermal conductivity, aluminum nitride materials are widely used in the microelectronics field. With the improvement of manufacturing technology and process equipment, aluminum nitride ceramic substrates, which combine the advantages of low thermal resistance and voltage resistance, have become applicable to the high-power LED lighting industry, improving the performance and reliability of high-power lighting products.

[0006] To improve the reliability and added value of high-power devices, surface filling of aluminum nitride substrates with high thermal conductivity reduces surface defects, thereby increasing thermal conductivity and facilitating the development and application of semiconductor and electronic devices with increasingly finer processes. In response to these demands, a technology to optimize the surface defects of aluminum nitride substrates with high thermal conductivity was developed. Key technical issues include: (1) surface filling materials, including chemical purity and material type; (2) surface filling processes, including vacuum plating and monitoring; (3) filler fusion techniques to improve the bonding strength and density of the filler; and (4) surface optimization techniques, including grinding, rough grinding, and fine grinding. While the gaps in the substrate surface have a high positive correlation with the reflectivity of optical element reflective substrates, they also present a certain obstacle to the development and application of high-power semiconductor and electronic products, which require high heat dissipation and high insulation properties and require increasingly finer process precision.

[0007] The main methods for manufacturing aluminum nitride films include chemical vapor deposition (CVD), reactive molecular beam epitaxy (MBE), plasma-assisted chemical vapor deposition (PACVD), laser-assisted chemical vapor deposition (LCVD), metal-organic chemical vapor deposition (MOCVD), pulsed laser deposition (PLD), reactive magnetron sputtering (MRS), and ion implantation. In magnetron sputtering, ions in the plasma are accelerated and come into contact with a metal or inorganic compound target, releasing energetic target ions that scatter to the target element, increasing the kinetic energy of the coating molecules and improving the film's density and adhesion, shortening the process time and effectively increasing production capacity.

[0008] The heat dissipation substrates for high-power light-emitting devices have the problem of poor heat dissipation compared to substrates with low thermal conductivity such as glass, PET, and aluminum oxide ceramic. However, the use of expensive materials such as sapphire and silicon carbide increases manufacturing costs. When applying the above substrates to high-power light-emitting devices, it is difficult to simultaneously satisfy the requirements of high thermal conductivity, high insulation, ease of surface planarization, and cost.

[0009] Among prior art patents, for example, Patent Document 1 below discloses a method for manufacturing an aluminum nitride ceramic substrate with high thermal conductivity for high-power microelectronic devices. The method for manufacturing an aluminum nitride substrate with high thermal conductivity includes a material blending step (1) in which high-purity aluminum nitride powder is obtained, combined with yttrium oxide as a sintering aid, and uniformly mixed in an organic solvent and additives; a production step (2) in which a green body is obtained using a doctor blade and uniform pressure technology; a debinding step (3) in which debinding is performed in a hydrogen / nitrogen mixed atmosphere; and a sintering step (4) in which the debinding green body is sintered under atmospheric pressure. The method for manufacturing a polycrystalline aluminum nitride substrate with high thermal conductivity disclosed in the above patent document primarily involves modification by blending during the initial manufacturing process of the aluminum nitride substrate. These adjustments, from adjusting the ratio of sintering agent to optimizing the atmosphere during powder compaction, adhesive removal, and sintering, enable the production of an aluminum nitride substrate with high thermal conductivity. However, the subsequent optimization of hole processing is not performed on the surface of the polycrystalline ceramic substrate. During the sintering process, defects in the crystal lattice are likely to cause gaps, reducing the strength and thermal conductivity of the substrate and the flatness of the substrate surface, which directly affects the efficiency of the development of high-power semiconductor processes and the application of optical reflecting mirrors. Therefore, while maintaining high thermal conductivity, optimizing the filling of holes on the surface of the aluminum nitride substrate is also an important point to increase the added value of the product in terms of application.

[0010] In the partial manufacturing process of power electronic components, conductive circuits must be fabricated on both sides of a ceramic substrate. To ensure electrical continuity between the circuits on both sides, holes are drilled in the ceramic substrate and then filled with a metal conductive paste or directly electroplated copper, achieving electrical continuity between the upper and lower metal circuits. Many patents for metallization and hole filling on ceramic surfaces have been developed by creating conductive holes and then filling them with highly conductive metal pillars. Previous patent documents, such as Patent Document 2 listed below, disclose a method for filling holes in ceramic substrates. This method is related to the processing of semiconductor power devices and addresses the problem of the tendency for bubbles and holes to form during the metal circuit filling process in micro-conductive holes in ceramic substrates, resulting in low electroplating efficiency. However, this method is only applicable to conductive metals during the filling process and is primarily used in the metallization processing of substrates. The optimization of surface flatness of aluminum nitride substrates according to the present invention is different because it is based on the same material for hole filling applications, and aluminum nitride is an insulator, so surface hole filling cannot be performed using electroplating methods.

[0011] III-V materials are often difficult to grow or deposit off a substrate without forming crystal defects or cracks. For many applications, such as high-power power supplies, LEDs, or integrated circuits, preventing defects during the production of sensitive III-V thin films is extremely challenging. Previous patent documents, such as Patent Document 3 listed below, disclose methods for forming aluminum nitride buffer layers and active layers by physical vapor deposition. These methods are primarily optimized using a PVD manufacturing method, depositing thin films onto the aluminum nitride buffer layer on the surface of one or more substrates simultaneously in one or more chambers, and producing aluminum nitride film buffer layers with high crystal orientation. When applied to heterogeneous crystal growth between substrates such as sapphire or silicon crystal and III-nitride layers, defects caused by differences in the nature and crystal lattice of the materials are widespread, resulting in poor quality in subsequent processes. However, since the main use of the aluminum nitride film produced on the aluminum nitride substrate is to repair gaps in holes on the surface of the aluminum nitride substrate, in the present invention, there is no need to improve the crystal orientation, the parameters for sputtering the aluminum nitride film can be set simply, and there is no need to perform complex heat treatments and plating layer production processes in multiple chambers.

[0012] Previous patent documents, such as Patent Document 4 listed below, disclose a method for secondary modification and densification of ceramic oxide thin films. This method involves subjecting an incompletely densified ceramic oxide substrate to a second-phase solution treatment to fill gaps using capillary action and introducing a low-temperature sintering aid to modify the gap boundary of the incompletely densified ceramic oxide thin film, followed by secondary sintering to densify the thin film and improve its performance. This method for producing dense ceramic oxide thin films is primarily used in solid oxide fuel cells to stabilize the separator between the ceramic oxide-based electrolyte and the porous anode, thereby inhibiting high-temperature reactions between the electrolyte material and the anode material. In this method, the pores of the ceramic are primarily filled using capillary action, and secondary sintering is performed using a low-temperature sintering aid to enhance the densification of the thin film. The above-mentioned method introduces a low-temperature sintering aid through capillary action. The process involves immersion in a modifying solution, circulating immersion, and drying 2 to 5 times, each time taking 2 to 8 hours. A secondary sintering process fills the pores on the surface of the thin film. While this method effectively improves the densification of the thin film, the heat treatment process is time-consuming and complicated, and the thin film surface is prone to loss of flatness, making it primarily applicable to non-planar objects. In this invention, since the surface of the aluminum nitride substrate is a planar substrate, reactive magnetron sputtering film thinning technology is used. When high-energy target ions used in sputtering contact the surface of the polycrystalline aluminum nitride substrate, a dense aluminum nitride film is formed. Furthermore, high-temperature sintering and surface grinding and / or polishing processes are combined to simultaneously fill the pores on the surface of the aluminum nitride substrate and slightly increase its thermal conductivity and bending resistance.

[0013] Therefore, the industry currently needs a method for producing polycrystalline aluminum nitride substrates with small surface pores and high thermal conductivity. Substrates that simultaneously satisfy high thermal conductivity, high insulation, small surface pores, and low porosity are needed, and a method is needed to produce substrates with high heat dissipation and high insulation capabilities and low porosity using a simple process, which will not only be beneficial for the development of miniaturization processes for high-power electronic devices, but also potentially be applicable to products such as optical devices and high-power semiconductor chips that require high heat dissipation in the future.

[0014] Therefore, the present inventors believed that the above drawbacks could be improved, and as a result of extensive research, they came up with the proposal of the present invention, which effectively improves the above problems through rational design.

[0015] The present invention was made in consideration of the above circumstances, and aims to solve the above-mentioned problems. That is, a primary object of the present invention is to provide a method for manufacturing an aluminum nitride substrate having small surface pores and high thermal conductivity. The method of the present invention includes steps such as surface grinding of the polycrystalline aluminum nitride substrate, polishing, high-temperature sintering, two polishing steps, and hole filling with a two-layer deposition of an aluminum nitride film, thereby producing a polycrystalline aluminum nitride substrate having small surface pores with high heat dissipation and low cost.

[0016] To enhance the application value of aluminum nitride substrates and meet requirements for high thermal conductivity, high insulation, surface flatness, ease of processing, and low cost, a method for manufacturing aluminum nitride substrates with small surface pores and high thermal conductivity has been developed. The substrate is made of polycrystalline aluminum nitride, the surface of which is pre-polished. A first layer of aluminum nitride film is applied to fill surface defects on the aluminum nitride substrate, followed by high-temperature sintering to enhance the adhesion density of the hole-filling process. After grinding and / or polishing, a second layer of aluminum nitride film is applied to the substrate. The second surface hole-filling process is then performed, followed by a second grinding and / or polishing process to complete the process. This method allows for the simpler and faster production of aluminum nitride substrates with high thermal conductivity, high insulation, and small surface pores, making them suitable for use in optical elements requiring high heat dissipation, and meeting the process development needs of high-power semiconductor electronic products. [Means for solving the problem]

[0017] In order to solve the above problems, one aspect of the present invention is a method for producing an aluminum nitride substrate having small surface pore diameters and high thermal conductivity, which comprises the steps of: providing a polycrystalline aluminum nitride substrate having a polished surface; applying plasma formed by an aluminum target, nitrogen, and argon using a magnetron sputtering device to a first-layer aluminum nitride film formed by reaction on the surface of the substrate, thereby filling gaps caused by defects in the crystal lattice on the surface of the substrate; and removing the first-layer aluminum nitride film from the aluminum nitride substrate by a planarization method such as thinning, grinding, and / or polishing. The method includes the steps of: (B) leaving the filled portions in the holes; (C) sintering the aluminum nitride substrate after the surface planarization has been completed at a high temperature to strengthen the adhesion between the aluminum nitride film in the gaps and the substrate; (D) sputtering the sintered aluminum nitride substrate at a slow sputtering rate to fill the holes with a second layer of aluminum nitride film; and (E) removing the second layer of aluminum nitride film from the aluminum nitride substrate by a planarization method such as thinning or grinding and / or polishing, leaving the filled portions in the holes, thereby completing the production of an aluminum nitride substrate with small surface pore diameters and high thermal conductivity.

[0018] In the manufacturing method according to the present invention, the polycrystalline aluminum nitride substrate in step (A) is manufactured by a doctor blade method or a high-temperature sintering cutting and forming method. The thermal conductivity of the surface-polished polycrystalline aluminum nitride substrate is 170 W m -1 ·K -1 The average roughness (Ra) of the center line is in the range of 20 nm to 30 nm.

[0019] In addition, the manufacturing method according to the present invention further includes, before step (A), step (1) of cleaning the polycrystalline aluminum nitride substrate whose surface is to be polished by combining wiping paper with one of solvents selected from acetone, alcohol, and isopropanol to remove dirt, and step (2) of removing organic matter and moisture remaining on the surface of the polycrystalline aluminum nitride substrate by oxygen ion plasma, the oxygen ion plasma being generated by reactive ion etching (RIE) or inductively coupled plasma etching (ICP), the source gas of the oxygen ion plasma being a mixed gas of oxygen and argon, the ratio of the mixed gas of oxygen and argon being in the range of 20% to 30%, and the process time being about 1 minute.

[0020] In addition, in the manufacturing method according to the present invention, the magnetron sputtering device in step (A) is a DC direct current sputtering device or an RF magnetron sputtering device, the thickness of the aluminum nitride film formed in the first layer is in the range of 6 μm to 12 μm, and the defects in the surface crystal lattice that are filled are gaps of holes less than 20 μm.

[0021] In the manufacturing method according to the present invention, the surface thinning and grinding and / or polishing method in step (B) is a chemical mechanical grinding method or a physical mechanical grinding method, and the thickness of the aluminum nitride film after the surface thinning and grinding and / or polishing is in the range of 6 μm to 12 μm.

[0022] In the manufacturing method according to the present invention, in step (C), the aluminum nitride substrate after the first grinding and / or polishing is subjected to a bonding and densification process by high-temperature sintering in a nitrogen atmosphere at atmospheric pressure. The temperature is in the range of 1750°C to 1850°C for 2 to 4 hours, which strengthens the bonding densification between the first-layer aluminum nitride film and the substrate, thereby maintaining the high thermal conductivity and bending strength of the substrate.

[0023] In the manufacturing method according to the present invention, in step (D), the sintered aluminum nitride substrate is used to fill holes in the thin film of the second-layer aluminum nitride film at a slow sputtering rate, thereby increasing its density and adhesion to the substrate.

[0024] In step (E), the second-layer aluminum nitride film of the aluminum nitride substrate is removed by thinning or planarization such as grinding and / or polishing, leaving the filled portions in the holes, thereby completing the production of a polycrystalline aluminum nitride substrate with small surface pore diameters and high thermal conductivity.

[0025] The method for filling surface pit defects in a polycrystalline aluminum nitride substrate according to the present invention utilizes reactive magnetron sputtering technology to produce an amorphous silicon aluminum nitride film on an aluminum nitride substrate with surface pit defects. Plasma is generated by controlling the nitrogen and argon concentrations to a specific ratio, and then contacted with an aluminum target to generate aluminum nitride, which is then scattered onto the surface of the polished polycrystalline aluminum nitride substrate. This aluminum nitride film effectively fills the pit defects on the surface of the polycrystalline aluminum nitride substrate. Next, grinding and / or polishing is used to remove the aluminum nitride film outside the surface pits, leaving only the aluminum nitride that fills the pit defects, effectively improving the surface flatness of the polycrystalline aluminum nitride substrate and reducing the surface pore size of the substrate. A high-temperature sintering heat treatment is also used to increase the density of the pit-filling on the aluminum nitride surface and maintain the thermal conductivity and bending strength of the substrate. The two-layer aluminum nitride film filling process is combined with grinding and / or polishing to fill many pit defects on the surface of the aluminum nitride substrate, which had diameters of less than about 20 μm before processing, to less than about 5 μm. The use of different sputtering parameters in combination not only increases the filling rate of the surface of the aluminum nitride substrate, but also enhances the density of the filling of the aluminum nitride film.

[0026] By reducing the surface pore size of the polycrystalline aluminum nitride substrate, the application value of the product can be effectively increased, making it more suitable for use in high-power reflective light-emitting substrates. In addition, the thin aluminum nitride substrate can better meet the requirements for developing integrated circuits with finer surfaces.

[0027] Other features of the present invention will become apparent from the description of this specification and the accompanying drawings. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a flowchart illustrating a method for manufacturing an aluminum nitride substrate having small surface pore diameters and high thermal conductivity according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram showing a method for manufacturing an aluminum nitride substrate having small surface pore diameters and high thermal conductivity according to an embodiment of the present invention. FIG. [Figure 3] FIG. 2 is an analytical diagram showing the ground surface of a polycrystalline aluminum nitride substrate observed with a high-magnification optical microscope according to an embodiment of the present invention. [Figure 4] FIG. 2 is a cross-sectional analysis diagram of a first aluminum nitride film sputtered onto a polycrystalline aluminum nitride substrate, observed with a high-magnification optical microscope according to an embodiment of the present invention. [Figure 5] FIG. 2 is a surface analysis diagram of a first-layer aluminum nitride film that has been sputtered and ground, observed with a high-magnification optical microscope according to an embodiment of the present invention. [Figure 6] FIG. 2 is a surface analysis diagram of an aluminum nitride substrate in which holes have been filled with a first-layer aluminum nitride film and which has been heated and sintered, observed with a high-magnification optical microscope according to an embodiment of the present invention. [Figure 7] FIG. 2 is a surface analysis diagram of a substrate showing aluminum nitride after the holes of the second-layer aluminum nitride film have been filled, observed with a high-magnification optical microscope according to an embodiment of the present invention. [Figure 8]FIG. 1 is a comparative diagram showing, from left to right, an aluminum nitride substrate in which hole filling has not been completed, an aluminum nitride substrate in which hole filling with a first-layer aluminum nitride film and grinding has been completed, and an aluminum nitride substrate in which hole filling with a second-layer aluminum nitride film and grinding has been completed, as observed with an electron microscope according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The following describes in detail the embodiments of the present invention, but the present invention is not limited to these, and various modifications are possible within the scope of the description. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0030] The method for manufacturing a polycrystalline aluminum nitride substrate with small surface pores and high thermal conductivity according to the present invention uses reactive magnetron sputtering technology. When high-energy sputtering target ions contact the surface of the polycrystalline aluminum nitride substrate, a dense first-layer aluminum nitride film is generated and used to fill the microscopic pit defects on the surface of the polycrystalline aluminum nitride substrate. Next, the aluminum nitride film on the outer surfaces of the substrate holes is removed by grinding and / or polishing, leaving aluminum nitride that fills the pit defects and improving surface flatness. High-temperature sintering is then performed to improve the adhesion between the aluminum nitride film filling the pit defects and the aluminum nitride substrate itself. After the sintered aluminum nitride substrate is subjected to a second-layer aluminum nitride film filling process with a slower sputtering rate, the aluminum nitride coating layer on the surface of the aluminum nitride substrate is then removed, leaving a thin aluminum nitride film filling the surface pit defects. The surface of the aluminum nitride substrate is filled with two layers of aluminum nitride films with different plating rates and then processed through a high-temperature sintering process, which repairs the original hole defects to a certain extent. Furthermore, two grinding and / or polishing processes are carried out to completely fill the minute hole defects on the surface of the aluminum nitride substrate, while maintaining high flatness, high thermal conductivity, and high bending strength. This makes the aluminum nitride substrate advantageous for improving the reflective efficiency of high-power optical coated reflective substrates, increasing their applicability and added value.

[0031] 1 is a flowchart showing a method for manufacturing an aluminum nitride substrate having small surface pores and high thermal conductivity according to one embodiment of the present invention. As shown in the figure, the method for manufacturing a polycrystalline aluminum nitride substrate having small surface pores and high thermal conductivity includes the steps of: providing a polycrystalline aluminum nitride substrate having a polished surface; applying plasma formed from nitrogen and argon to an aluminum target in a magnetron sputtering device to rapidly form a first layer of aluminum nitride film on the surface of the substrate, thereby filling gaps in holes caused by crystal lattice defects on the surface of the substrate; and removing the first layer of aluminum nitride film in step (A) by a thinning and polishing method, leaving the filled portions in the holes and planarizing the surface. The method includes the steps of (B) S102 forming an aluminum nitride substrate, (C) S103 sintering the planarized aluminum nitride substrate at a high temperature to strengthen the adhesion between the aluminum nitride film in the gaps and the substrate, (D) S104 filling sputtering of a second layer of aluminum nitride film at a slow sputtering rate on the sintered and densified aluminum nitride substrate, and (E) S105 removing the second layer of aluminum nitride film from the aluminum nitride substrate by thinning or planarization such as grinding and / or polishing, leaving the filled portions in the holes. Figure 2 is a schematic diagram illustrating a method for manufacturing an aluminum nitride substrate with small surface pores and high thermal conductivity according to one embodiment of the present invention. As shown in the figure, the aluminum nitride surface pit-filled substrate manufactured by the present invention includes a polycrystalline aluminum nitride substrate 100, a pit defect 200 in the aluminum nitride substrate, a second layer of low-plating-rate pit-filling aluminum nitride film 300, and a first layer of high-plating-rate pit-filling aluminum nitride film 400.

[0032] The method further includes, before step (A), step (1) of wiping the polycrystalline aluminum nitride substrate, the surface of which has been polished, with one solvent selected from acetone, alcohol, and isopropanol to remove dirt, and step (2) of removing organic residues and moisture on the surface of the polycrystalline aluminum nitride substrate with oxygen ion plasma. [Example]

[0033] A single-sided polished polycrystalline aluminum nitride substrate is provided, with a thermal conductivity of 182 Wm -1 .K -1 The average roughness (Ra) of the center line of the polished surface is 25 nm. First, the surface is wiped clean with isopropanol. Figure 3 is an analytical diagram showing the ground surface of a polycrystalline aluminum nitride substrate observed with a high-magnification optical microscope according to one embodiment of the present invention. As shown in the figure, many hole defects with diameters ranging from 15 μm to 20 μm are observed on the polished surface. The surface of the polycrystalline aluminum nitride substrate is first cleaned with oxygen ion plasma for 1 minute to remove organic residues and moisture from the surface, and then placed in a high-vacuum magnetron sputtering chamber and set at a vacuum of 5×10 as the process environment. -8 Under conditions of less than 1000 torr, a 1.5 kW process power was used to generate plasma formed with 16 sccm of nitrogen and 48 sccm of argon, and high-energy ions were then generated from an aluminum target and scattered onto the surface of a polycrystalline aluminum nitride substrate, reactively forming a first-layer aluminum nitride film to fill the surface holes. The process took 60 minutes. Figure 4 shows a cross-sectional analysis of the first-layer aluminum nitride film sputtered onto a polycrystalline aluminum nitride substrate, observed with a high-magnification optical microscope according to one embodiment of the present invention. The coating thickness after measurement was approximately 11.3 μm. After the aluminum nitride film had filled the surface holes, the polycrystalline aluminum nitride substrate was subjected to surface thinning and grinding and / or polishing. The process conditions were as follows: first, CMP80 (primarily a nanometer-level polishing solution with a particle size of approximately 80 nm) was used at a rotation speed of 50 rpm, a temperature of 20°C, and a processing pressure of 2.5 kg / cm. 2 Then, the wafer was polished for 30 minutes under the conditions of CMP20 (mainly a nanometer-level polishing solution with a particle size of approximately 20 nm) at a rotation speed of 30 rpm, a temperature of 20°C, and a processing pressure of 2 kg / cm. 2The substrate was polished for 10 minutes under the conditions of 100°C to remove the aluminum nitride film on the surface, leaving the aluminum nitride plating in the holes. Figure 5 is a surface analysis diagram of the first-layer aluminum nitride film sputtered and ground, observed with a high-magnification optical microscope according to one embodiment of the present invention. As shown in the figure, after observation, it was found that the aluminum nitride film had filled the hole defects on the surface of the polycrystalline aluminum nitride substrate, and the diameter of most of the filled holes was measured to be less than 12 μm. The polycrystalline aluminum nitride substrate, after the hole defects had been filled and planarized with the first-layer aluminum nitride film, was subjected to a 1850 o The aluminum nitride substrate was sintered for 2 hours at a temperature of 0.5 C to strengthen the adhesion between the coating layer inside the hole and the substrate, and then cooled down by natural furnace cooling. Table 1 shows the aluminum nitride substrate with the hole filled with the first aluminum nitride film according to an embodiment of the present invention. The thermal conductivity and bending resistance strength after high-temperature sintering were measured and were 186 W m -1 ·K -1 and 439 MPa, all of which were slightly improved compared to before sintering. After sintering, the aluminum nitride substrate was first wiped clean with isopropanol and then observed under a high-magnification optical microscope. Figure 6 shows a surface analysis diagram of an aluminum nitride substrate, after heating and sintering, in accordance with an embodiment of the present invention, after filling with a first-layer aluminum nitride film, as observed under a high-magnification optical microscope. As shown in the figure, the edges of the large holes, which were originally deeply shaded, are now smooth after filling with the aluminum nitride film. Next, the surface of the polycrystalline aluminum nitride substrate is cleaned for 1 minute using oxygen ion plasma to remove organic residues and moisture from the surface. It is then placed in a high-vacuum magnetron sputtering chamber, and the process conditions are a vacuum of 5×10 -8In an environment below torr, an aluminum nitride film is reactively generated using a plasma formed with 20 sccm of nitrogen and 42 sccm of argon at a process power of 1.2 kW and an aluminum target, and then scattered onto the surface of the polycrystalline aluminum nitride substrate. The process lasts for 40 minutes. As shown in the measured values, the filled aluminum nitride film is approximately 8.3 μm. After filling the surface pit defects, the surface of the polycrystalline aluminum nitride substrate is thinned and ground and / or polished. The process conditions are as follows: first, a CMP80 (mainly a nanometer-level polishing solution with a particle size of approximately 80 nm) is used at a rotation speed of 50 rpm, a temperature of 20°C, and a processing pressure of 2.5 kg / cm. 2 After polishing for 25 minutes under the conditions, the sample was polished using CMP20 (mainly a nanometer-level polishing solution with a particle size of approximately 20 nm) at a rotation speed of 30 rpm, a temperature of 20°C, and a processing pressure of 2 kg / cm. 2 The substrate was polished for 10 minutes under these conditions to remove the aluminum nitride film on the surface, leaving the aluminum nitride plating in the holes. Figure 7 is a surface analysis diagram of a substrate, observed with a high-magnification optical microscope, showing the aluminum nitride film after the second-layer aluminum nitride film had been filled, according to one embodiment of the present invention. As shown in the figure, when the large holes on the substrate surface were filled with the aluminum nitride film, the edge shape of the hole became smooth, and the interior of the hole showed the appearance after being filled with the aluminum nitride film. Measurement of the substrate surface revealed that the diameter of most of the hole defects was less than 5 μm. The differences in the process of filling the gaps in the holes on the surface of a polycrystalline aluminum nitride substrate using this method were observed with an electron microscope (see Figure 8). [Example]

[0034] A single-sided polished polycrystalline aluminum nitride substrate is provided, with a thermal conductivity of 178 W m -1 ·K -1 The average roughness (Ra) of the polished surface is 29 nm. First, the surface is wiped clean with isopropanol. Then, the surface of the polycrystalline aluminum nitride substrate is cleaned with oxygen ion plasma for 1 minute to remove organic residues and moisture, and then it is placed in a high-vacuum magnetron sputtering system. The process conditions are a vacuum of 5×10-8 In a sub-torr environment, an aluminum nitride film was generated by reaction between a plasma formed with 18 sccm of nitrogen and 42 sccm of argon at a process power of 1.5 kW and an aluminum target, and then scattered onto the surface of the polycrystalline aluminum nitride substrate. The process lasted 60 minutes, and the thickness of the aluminum nitride coating after measurement was approximately 11.9 μm. After the aluminum nitride film had filled the surface pit defects, the polycrystalline aluminum nitride substrate surface was thinned and ground and / or polished. The process conditions were as follows: first, a rotation speed of 50 rpm was used with CMP80 (mainly a nanometer-level polishing solution with a particle size of approximately 80 nm), a temperature of 20°C, and a processing pressure of 2.5 kg / cm. 2 After polishing for 30 minutes under the conditions, the sample was polished using CMP20 (mainly a nanometer-level polishing solution with a particle size of approximately 20 nm) at a rotation speed of 30 rpm, a temperature of 20°C, and a processing pressure of 2 kg / cm. 2 The substrate was polished for 20 minutes under these conditions to remove the aluminum nitride film on the surface, leaving the aluminum nitride plating in the holes. After observation, it was found that the aluminum nitride film had filled the surface hole defects of the polycrystalline aluminum nitride substrate, and the diameter of most of the filled holes was measured to be less than 10 μm. The polycrystalline aluminum nitride substrate, after the hole defects had been filled and planarized with the first layer aluminum nitride film, was polished in a nitrogen atmosphere at 1750 o After sintering was completed, the temperature was lowered by natural furnace cooling. As shown in Table 1, the thermal conductivity and bending strength of the aluminum nitride substrate after high-temperature sintering were measured and found to be 185 W·m -1 ·K -1 and 434 MPa, all of which are slightly improved compared to before sintering. Next, the sintered polycrystalline aluminum nitride substrate is fabricated by filling the holes with a second layer of aluminum nitride film. First, the surface is wiped clean with isopropanol, then placed in an oxygen ion plasma chamber and cleaned with oxygen ion plasma for 1 minute to remove organic residues and moisture from the surface. Next, it is placed in a high-vacuum magnetron sputtering chamber and processed under a vacuum of 5 x 10 -8In an environment below torr, an aluminum nitride film is reactively generated using a plasma formed with 16 sccm of nitrogen and 40 sccm of argon at a process power of 1.2 kW and an aluminum target, and then scattered onto the surface of the polycrystalline aluminum nitride substrate. The process lasts for 40 minutes. Measurements show that the filled aluminum nitride film is approximately 6.1 μm thick. After filling the surface pit defects, the polycrystalline aluminum nitride substrate is then thinned and ground and / or polished. The process conditions are as follows: first, a CMP80 (mainly a nanometer-level polishing solution with a particle size of approximately 80 nm) is used at a rotation speed of 50 rpm, a temperature of 20°C, and a processing pressure of 2.5 kg / cm. 2 After polishing for 15 minutes under these conditions, the wafer was polished using CMP20 (mainly a nanometer-level polishing solution with a particle size of approximately 20 nm) at a rotation speed of 30 rpm, a temperature of 20°C, and a processing pressure of 2 kg / cm. 2 The substrate is polished for 10 minutes under these conditions to remove the aluminum nitride film on the surface, leaving the aluminum nitride plating in the holes. Observation under a high-magnification optical microscope reveals that the aluminum nitride film has filled the hole defects on the surface of the polycrystalline aluminum nitride substrate, and when the diameter of the hole defects is measured after filling, most are less than 7 μm.

[0035] Table 1 shows the aluminum nitride substrate in which the holes have been filled with the first layer aluminum nitride film according to an embodiment of the present invention. Measurement results show that the thermal conductivity and bending resistance strength are all slightly improved after high-temperature sintering. [Table 1]

[0036] The present invention first uses a polycrystalline aluminum nitride substrate to fill two layers of thin films and polish them twice, effectively reducing the size of holes caused by crystal lattice defects in the polycrystalline ceramic and improving the flatness of the substrate. To ensure both timeliness and reliability in filling holes on the surface of the aluminum nitride substrate, a two-stage aluminum nitride film sputtering filling method is used. This prevents the problem of a single long sputtering step resulting in an excessively thick film, which reduces adhesion to the substrate and increases the likelihood of plating layer peeling. To ensure timeliness, the first-layer aluminum nitride film sputtering process quickly fills the holes with the aluminum nitride film at a high plating rate, and an additional high-temperature sintering step enhances adhesion and density of the first-layer aluminum nitride film when filling the holes in the substrate. In contrast, the sputtering process for the second aluminum nitride film is modified to a slower sputtering rate, resulting in a denser aluminum nitride film filling method, enhancing the density and compactness of the aluminum nitride substrate after surface filling. After surface filling, all substrates have the excess aluminum nitride film plating layer removed from outside the surface hole, reducing the depth difference between the filled hole and the substrate surface. After hole filling, the polycrystalline aluminum nitride substrate has higher thermal conductivity than glass and polymer substrates. After hole filling, the polycrystalline aluminum nitride substrate has higher thermal conductivity than glass and polymer substrates. It offers better cost performance than high-thermal-conductivity single-crystal ceramic substrates. It also has better insulation properties than metal substrates. The improved substrate surface flatness further enhances its application as a reflective substrate for high-power light-emitting devices, achieving competitive advantages of high thermal conductivity, high reflectivity, and low cost. Furthermore, since the hole diameter on the substrate surface is reduced after filling, it is more suitable for the development of thin insulating circuit boards that are being miniaturized in high-power electronic products, thereby increasing the added value of products and further expanding the fields of future application.

[0037] The present invention can be embodied in various other forms without departing from its spirit or main characteristics. Therefore, the above-described embodiments are merely illustrative in all respects and should not be interpreted as limiting. The scope of the present invention is defined by the claims and is not limited to the text of the specification. Furthermore, all modifications and variations within the equivalent range of the claims are within the scope of the present invention. [Explanation of symbols]

[0038] S101~S105 Process 100 Polycrystalline aluminum nitride substrate 200 Hole defects in aluminum nitride substrate 300 Low plating rate second layer hole filling aluminum nitride film 400 High plating rate first layer hole filling aluminum nitride film

Claims

1. a step (A) of providing a polycrystalline aluminum nitride substrate having a polished surface, and applying plasma formed from an aluminum target, nitrogen, and argon by a magnetron sputtering device to a first layer aluminum nitride film produced by reaction on the surface of the substrate, thereby filling gaps caused by defects in the crystal lattice on the surface of the substrate; a step (B) of thinning and polishing the first aluminum nitride film of the step (A) to leave a filled portion in the hole and form an aluminum nitride substrate having a flat surface; a step (C) of sintering the aluminum nitride substrate having a flattened surface at a high temperature to strengthen the adhesion between the first aluminum nitride film in the gaps of the holes and the substrate; a step (D) of forming a second layer aluminum nitride film on the high-temperature sintered aluminum nitride substrate to complete a second surface filling step; and step (E) of removing the second-layer aluminum nitride film of step (D) by a thinning and polishing method, leaving the filled portions in the holes, thereby forming an aluminum nitride substrate having small surface pore diameters and high thermal conductivity.

2. 2. The method for producing an aluminum nitride substrate according to claim 1, wherein the polycrystalline aluminum nitride substrate having a polished surface in step (A) is produced by a doctor blade method or a high-temperature sintering cutting and forming method.

3. The thermal conductivity of the polycrystalline aluminum nitride substrate whose surface has been polished in step (A) is 170 W·m -１ ・K -１ 2. The method for manufacturing an aluminum nitride substrate according to claim 1, wherein the average roughness (Ra) of the center line is in the range of 20 nm to 30 nm.

4. Before step (A), (1) a step of wiping the polished surface of the polycrystalline aluminum nitride substrate with one solvent selected from acetone, alcohol, and isopropanol to remove surface contamination; and (2) removing organic residues and moisture on the surface of the polycrystalline aluminum nitride substrate using oxygen ion plasma, the oxygen ion plasma being generated by reactive ion etching (RIE) or inductively coupled plasma etching (ICP).

5. The manufacturing conditions of the first aluminum nitride film in step (A) are a degree of vacuum of 5×10 －８ 2. The method for producing an aluminum nitride substrate according to claim 1, wherein a plasma formed of 16 to 20 sccm of nitrogen and 40 to 48 sccm of argon is reacted with an aluminum target at a process power of 1.5 kW in an environment of less than 1000 MPa (torr), the process time is in the range of 30 to 90 minutes, and the thickness of the first layer aluminum nitride film scattered on the surface of the polycrystalline aluminum nitride substrate after the aluminum nitride film is formed is in the range of 6 μm to 12 μm.

6. 2. The method for producing an aluminum nitride substrate according to claim 1, wherein the surface thinning and grinding and / or polishing method in step (B) or step (E) is a chemical mechanical grinding method or a physical mechanical grinding method.

7. The surface thinning and grinding and / or polishing process conditions in step (B) or step (E) are as follows: first, CMP80, using a nanometer-level polishing solution with a particle size of approximately 80 nm, at a rotation speed of 40 to 60 rpm, a temperature of 20°C, and a processing pressure of 2.5 kg / cm ２ Polishing is performed for 10 to 60 minutes at 20 to 40 rpm, at a temperature of 20°C, and with a processing pressure of 2 kg / cm using a polishing solution of CMP20, mainly nanometer-level particles of about 20 nm. ２ 2. The method for producing an aluminum nitride substrate according to claim 1, wherein the aluminum nitride film on the surface of the substrate is removed by polishing the substrate with a polishing agent at 0.50 for 10 to 60 minutes.

8. The high-temperature sintering environment in step (C) is a nitrogen atmosphere at a sintering temperature of 1750 ｏ C. to 1850 ｏ C. The method for producing an aluminum nitride substrate according to claim 1, wherein the temperature is maintained for 2 to 4 hours and the temperature is lowered by natural furnace cooling.

9. The conditions for producing the second layer aluminum nitride film in step (D) are a degree of vacuum of 5×10 －８ 2. The method for producing an aluminum nitride substrate according to claim 1, wherein a plasma formed of 16 to 20 sccm of nitrogen and 40 to 42 sccm of argon is reacted with an aluminum target at a process power of 1.0 to 1.2 kW in an environment of less than 1000 MPa (torr), the process time is 30 to 60 minutes, and the thickness of the second-layer aluminum nitride film scattered on the surface of the polycrystalline aluminum nitride substrate after the aluminum nitride film is formed is in the range of 5 μm to 10 μm.

Images