Silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness as well as preparation method and application of silicon nitride ceramic substrate

Abstract

The invention discloses a silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness as well as a preparation method and application of the silicon nitride ceramic substrate. According to the silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness, provided by the invention, through a carbon material assisted annealing treatment method and selection of a non-oxygen sintering aid, the thermal conductivity of the prepared silicon nitride ceramic substrate is 80W / (m.K)-91W / (m.K), and the fracture toughness is 7.43 MPa.m < 1 / 2 >-8.06 MPa.m < 1 / 2 >, so that the aim of improving the thermal conductivity and the mechanical property at the same time is fulfilled; the silicon nitride ceramic substrate prepared by the method has the advantages that the process flow of the silicon nitride ceramic substrate can be optimized, the yield of test preparation can be increased, and the substrate material required by a semiconductor device with high heat and strong mechanical motion can be produced.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon nitride ceramic substrates, and in particular to a silicon nitride ceramic substrate having high thermal conductivity and high fracture toughness, and a preparation method and application thereof. Background Art

[0002] In recent years, as semiconductor devices are widely used in 3C electronic products, aerospace, new energy vehicles and other fields, integrated circuit systems tend to operate at high power, high current and high intensity. Therefore, the substrate material of the chip needs to have good thermal conductivity and excellent mechanical properties to protect the normal operation of the device. At present, there are three main ceramic substrates on the market: aluminum oxide, aluminum nitride and silicon nitride. Among them, silicon nitride substrates stand out for their excellent comprehensive performance and have good compatibility with the third-generation semiconductor SiC.

[0003] However, most of the silicon nitride ceramic substrates currently prepared are difficult to have both high thermal conductivity and high fracture toughness, which limits their application. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above technical background and provide a silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness and a preparation method and application thereof.

[0005] The present invention provides a silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness. The thermal conductivity of the silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness is 80W / (m·K) to 91W / (m·K), and the fracture toughness is 7.43MPa·m 1 / 2 ~8.06MPa·m 1 / 2 .

[0006] The present invention also provides a method for preparing the above-mentioned silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness, which comprises: covering a carbon material on an initial silicon nitride ceramic substrate obtained by debinding and sintering and performing a high-temperature annealing treatment to obtain a silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness.

[0007] In some embodiments of the present invention, the following steps are included: using a non-oxide sintering aid to assist in preparing a tape-cast blank, then subjecting the tape-cast blank to a binder removal treatment to obtain a silicon nitride blank, then subjecting the silicon nitride blank to a sintering treatment to obtain a silicon nitride ceramic initial substrate, and then covering the silicon nitride ceramic initial substrate with a carbon material and performing a high-temperature annealing treatment to obtain a silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness.

[0008] In some embodiments of the present invention, the non-oxide sintering aid includes chloride and silicide, the chloride includes at least one of calcium chloride and aluminum chloride, and the silicide includes at least one of zirconium silicide, cerium silicide and hafnium silicide.

[0009] In some embodiments of the present invention, the debinding temperature of the cast blank is 600°C to 800°C, the holding time is 10h to 14h, the sintering atmosphere of the silicon nitride blank is a nitrogen atmosphere, the sintering temperature is 1700°C to 1900°C, and the holding time is 8h to 10h.

[0010] In some embodiments of the present invention, after the initial silicon nitride ceramic substrate is covered and buried with a carbon material, it is placed in a graphite crucible and subjected to a high temperature annealing treatment;

[0011] Preferably, the carbon material is selected from at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, and hard carbon, preferably graphite powder, more preferably natural graphite powder, the particle size of the graphite powder is 0.5 μm to 10 μm, and the carbon content is ≥99.9%;

[0012] Preferably, the mass of the carbon material is 10% to 50% of the mass of the initial silicon nitride ceramic substrate.

[0013] In some embodiments of the present invention, the conditions for high temperature annealing treatment include: heating to a temperature of 1000° C. to 1600° C. in a nitrogen atmosphere, and keeping the temperature for 10 h to 20 h for annealing.

[0014] In some embodiments of the present invention, the tape casting blank is prepared by the following method: silicon nitride powder, non-oxide sintering aid, dispersant and organic solvent are mixed and ball-milled to obtain a first slurry; the first slurry, binder and plasticizer are mixed and ball-milled to obtain a second slurry; after filtering out the grinding medium in the second slurry, an organosilicon defoamer is added, and vacuuming is performed to obtain a tape casting slurry; after the tape casting slurry is formed, a tape casting blank is obtained;

[0015] Preferably, the particle size distribution of silicon nitride powder is 0.3 μm to 0.5 μm;

[0016] Preferably, the mass of the non-oxide sintering aid is 5% to 10% of the mass of the silicon nitride powder;

[0017] Preferably, the ball milling medium in the first slurry is a 10 mm silicon nitride ball, the ball milling speed is 180 r / min to 200 r / min, and the ball milling time is 2 h to 6 h; the ball milling medium in the second slurry is a 3 mm silicon nitride ball, the ball milling speed is 80 r / min to 100 r / min, and the ball milling time is 2 h to 6 h;

[0018] Preferably, the viscosity of the casting slurry is 5000 Pa·s to 5200 Pa·s, and the thickness of the casting green blank is 400 μm to 600 μm.

[0019] In some embodiments of the present invention, the process further includes: after the high temperature annealing is completed, cooling, surface cleaning, drying and polishing are performed to obtain a silicon nitride ceramic substrate having both high thermal conductivity and high fracture toughness.

[0020] The present invention also provides an application of the silicon nitride ceramic substrate having both high thermal conductivity and high fracture toughness or the silicon nitride ceramic substrate having both high thermal conductivity and high fracture toughness prepared by the above preparation method in an electronic device substrate.

[0021] The present invention has the following beneficial effects.

[0022] The present invention provides a silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness, and a preparation method and application thereof. The silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness provided by the present invention improves both thermal conductivity and mechanical properties through annealing treatment method and selection of sintering aids, so that the thermal conductivity of the silicon nitride ceramic substrate is 80W / (m·K) to 91W / (m·K), and the fracture toughness is 7.43MPa·m 1 / 2 ~8.06MPa·m 1 / 2 While the comprehensive performance meets expectations, it helps to optimize the process flow of silicon nitride ceramic substrates, improve the yield rate of experimental preparation, and produce substrate materials required for semiconductor devices that meet high heat and strong mechanical movement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 The graph is a graph showing the amount of graphite powder applied and the performance of the silicon nitride ceramic substrate in Examples 1 to 5. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0026] The following specifically describes a silicon nitride ceramic substrate having high thermal conductivity and high fracture toughness, and a preparation method and application thereof provided by an embodiment of the present invention.

[0027] In the first aspect, the embodiment of the present invention provides a silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness. The thermal conductivity of the silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness is 80W / (m·K) to 91W / (m·K), and the fracture toughness is 7.43MPa·m 1 / 2 ~8.06MPa·m 1 / 2 .

[0028] Optionally, the silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness provided in an embodiment of the present invention has a thermal conductivity of 80W / (m·K), 81W / (m·K), 82W / (m·K), 83W / (m·K), 84W / (m·K), 85W / (m·K), 86W / (m·K), 87W / (m·K), 88W / (m·K), 89W / (m·K), 90W / (m·K), 91W / (m·K) and any other value between 80 and 91W / (m·K), and the fracture toughness can be 7.43MPa·m 1 / 2 、7.50MPa·m 1 / 2 、7.60MPa·m 1 / 2 、7.80MPa·m 1 / 2 、7.85MPa·m 1 / 2 、8.04MPa·m 1 / 2 、8.06MPa·m 1 / 2 and 7.43MPa·m 1 / 2 ~8.06MPa·m 1 / 2 Any other value in between.

[0029] The embodiment of the present invention provides a silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness. The silicon nitride ceramic substrate has both high thermal conductivity and high fracture toughness, and its thermal conductivity and mechanical properties are significantly better than those of silicon nitride ceramic substrates on the market. Its comprehensive performance is better and is more suitable for meeting the use requirements of semiconductor devices with high heat and strong mechanical movement.

[0030] In the second aspect, an embodiment of the present invention also provides a method for preparing the above-mentioned silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness, which comprises: covering a carbon material on the silicon nitride ceramic initial substrate obtained by debinding and sintering and performing a high-temperature annealing treatment to obtain a silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness.

[0031] During the high-temperature sintering of silicon nitride ceramics, the raw material low-temperature phase α-Si3N4 will be transformed into the high-temperature phase β-Si3N4 through a phase transformation mechanism. However, during the sintering process, the sintering holding time has always been a difficult-to-control influencing factor. On the one hand, a slightly longer holding time will cause some grains to overgrow, which causes dislocation and aggregation at the grain boundaries, resulting in increased stress inside the crystal and reduced toughness of the silicon nitride ceramic substrate. On the other hand, a slightly shorter holding time will lead to fine grain growth, an increase in the number of grain boundaries, and low thermal conductivity. It is difficult to obtain a silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness by controlling the holding time.

[0032] In order to solve the above difficulties in the preparation process of silicon nitride ceramic substrates, an embodiment of the present invention provides a method for preparing a silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness, which includes: on the silicon nitride ceramic initial substrate obtained by debinding and sintering, a carbon material is covered for high-temperature annealing to obtain a silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness. In the above preparation method, the debinding treatment can remove organic matter and volatile substances in the cast blank to reduce pores and surface defects in the subsequent sintering process, thereby helping to improve the density and mechanical properties of the silicon nitride ceramic substrate. After debinding, the silicon nitride blank has a suitable size and improves the uniformity of the grain distribution inside the material, which helps the sintering process to further improve the density and mechanical strength of the substrate. After that, the carbon material is covered on the silicon nitride ceramic initial substrate for high-temperature annealing. As the temperature slowly increases, the carbon in the carbon material reacts with the oxygen remaining in the silicon nitride ceramic initial substrate to generate carbon dioxide, reduce the lattice oxygen content, and reduce oxygen vacancy defects. At the same time, the high temperature annealing mechanism will also promote the secondary growth of some grains, the grain boundary edges will become thinner, and the boundary dislocations and grain boundary defects will be reduced, thereby achieving the purpose of simultaneously improving the thermal conductivity and fracture toughness of the silicon nitride ceramic substrate.

[0033] In some optional embodiments, the steps include: using a non-oxide sintering aid to assist in preparing a tape-cast blank, then subjecting the tape-cast blank to a binder removal treatment to obtain a silicon nitride blank, then subjecting the silicon nitride blank to a sintering treatment to obtain a silicon nitride ceramic initial substrate, and then covering the silicon nitride ceramic initial substrate with a carbon material and performing a high-temperature annealing treatment to obtain a silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness.

[0034] In some optional embodiments, the non-oxide sintering aid includes: chloride and silicide, the chloride includes at least one of calcium chloride and aluminum chloride, and the silicide includes at least one of zirconium silicide, cerium silicide, and hafnium silicide.

[0035] Since silicon nitride molecules are composed of strong covalent bonds, it is usually necessary to add a sintering aid to promote the formation of a liquid phase and reduce the sintering temperature. At present, the preparation method of silicon nitride ceramic substrates mostly selects oxides such as MgO, Al2O3, Y2O3, La2O3 as sintering aids, which inevitably increases the content of lattice oxygen in silicon nitride, which will lead to aggravated phonon scattering and a decrease in the mean free path of phonons, thereby causing the thermal conductivity of the substrate to decrease. The preparation method of silicon nitride ceramic substrates provided in an embodiment of the present invention uses a non-oxide sintering aid to assist in the preparation of silicon nitride substrates. The non-oxide sintering aid can not only generate a liquid phase to promote the phase transition of silicon nitride, but also reduce the intake of oxygen content in the raw material, reduce the probability of oxygen vacancies in the finished substrate material, and improve the thermal conductivity to a certain extent.

[0036] In some optional embodiments, the debinding temperature of the cast blank is 600°C to 800°C, the holding time is 10h to 14h, the sintering atmosphere of the silicon nitride blank is a nitrogen atmosphere, the sintering temperature is 1700°C to 1900°C, and the holding time is 8h to 10h.

[0037] Optionally, the debinding temperature of the cast blank can be 600°C, 650°C, 700°C, 750°C, 800°C and any other value between 600°C and 800°C, the time can be 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h and any other value between 10h and 14h, the sintering temperature of the silicon nitride blank can be 1700°C, 1750°C, 1800°C, 1850°C, 1900°C and any other value between 1700°C and 1900°C, and the time can be 8h, 8.5h, 9h, 9.5h, 10h and any other value between 8h and 10h.

[0038] The embodiment of the present invention provides a method for preparing a silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness. During the sintering process of the silicon nitride blank, the sintering temperature is controlled at a temperature point between 1700°C and 1900°C for 8 hours to 10 hours. The appropriate holding time can promote the full phase transformation of α-Si3N4 and the crystal growth of β-Si3N4, and promote the bonding between powder particles. The shorter holding time in this article can avoid the grain growth caused by excessive sintering, making the grain growth relatively short, and paving the way for the subsequent high-temperature annealing treatment to make the grain grow again. In addition, controlling the sintering atmosphere can promote the phase transformation of Si3N4, and the N element therein can also promote the formation of liquid phase.

[0039] In some optional embodiments, after the initial silicon nitride ceramic substrate is covered and buried with a carbon material, it is placed in a graphite crucible for high-temperature annealing treatment;

[0040] Preferably, the carbon material is selected from at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, and hard carbon, preferably graphite powder, more preferably natural graphite powder, the particle size of the graphite powder is 0.5 μm to 10 μm, and the carbon content is ≥99.9%;

[0041] Preferably, the mass of the carbon material is 10% to 50% of the mass of the initial silicon nitride ceramic substrate.

[0042] Optionally, the mass of the carbon material may be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% of the mass of the initial silicon nitride ceramic substrate and any other value between 10% and 50%.

[0043] It is worth noting that the use of carbon material to cover and bury the silicon nitride ceramic initial substrate is to evenly spread the carbon material over the entire silicon nitride ceramic initial substrate. In the preparation process of the silicon nitride ceramic substrate provided by the embodiment of the present invention, the carbon material used is preferably graphite powder. On the one hand, the graphite powder is in a powder state and is easily spread on the surface of the silicon nitride ceramic initial substrate. On the other hand, the main component of the graphite powder is carbon element, which can react with the oxygen in the silicon nitride ceramic initial substrate without bringing other impurities, and it has a high ignition point and will not spontaneously combust at high temperatures. The oxygen content in the silicon nitride ceramic initial substrate will decrease with the increase in the amount of graphite powder, but too much graphite powder will also have an adverse effect. It is speculated that the possible reason is: too thick graphite powder is spread on the silicon nitride ceramic initial substrate, which is not conducive to the discharge of oxygen in the surface layer of the substrate and the secondary growth of grains. Excessive graphite powder consumption will cause a decrease in thermal conductivity and / or fracture toughness.

[0044] In some optional embodiments, the conditions for high temperature annealing treatment include: heating to a temperature of 1000° C. to 1600° C. in a nitrogen atmosphere, and keeping the temperature for 10 h to 20 h for annealing.

[0045] Optionally, the heating temperature may be 1000° C., 1050° C., 1100° C., 1150° C., 1200° C., 1250° C., 1300° C., 1350° C., 1400° C., 1450° C., 1500° C., 1550° C., 1600° C., and any other value between 1000° C. and 1600° C. The holding time may be 10 h, 10.5 h, 11 h, 11.5 h, 12 h, 12.5 h, 13 h, 13.5 h, 14 h, 14.5 h, 15 h, 15.5 h, 16 h, 16.5 h, 17 h, 17.5 h, 18 h, 18.5 h, 19 h, 19.5 h, 20 h, and any other value between 10 h and 20 h.

[0046] The embodiment of the present invention provides a method for preparing a silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness. The use of carbon material to cover and bury the initial silicon nitride ceramic substrate can completely isolate the residual oxygen in the annealing environment, so that the oxygen impurities in the initial silicon nitride ceramic substrate react with the carbon material, thereby reducing the lattice oxygen content on the surface of the silicon nitride ceramic. In addition, high-temperature annealing treatment can also promote the secondary growth of some grains, thereby reasonably controlling the grain size in the silicon nitride ceramic substrate, and achieving the purpose of simultaneously improving the thermal conductivity and fracture toughness of the silicon nitride ceramic substrate. The annealing temperature here is lower than the Si3N4 sintering phase transition temperature.

[0047] In some optional embodiments, the tape casting blank is prepared by the following method: silicon nitride powder, non-oxide sintering aid, dispersant and organic solvent are mixed and ball-milled to obtain a first slurry; the first slurry, binder and plasticizer are mixed and ball-milled to obtain a second slurry; after filtering out the grinding medium in the second slurry, an organosilicon defoamer is added, and vacuuming is performed to obtain a tape casting slurry; after the tape casting slurry is formed, a tape casting blank is obtained;

[0048] Preferably, the particle size distribution of silicon nitride powder is 0.3 μm to 0.5 μm;

[0049] Preferably, the mass of the non-oxide sintering aid is 5% to 10% of the mass of the silicon nitride powder;

[0050] Preferably, the ball milling medium in the first slurry is a 10 mm silicon nitride ball, the ball milling speed is 180 r / min to 200 r / min, and the ball milling time is 2 h to 6 h; the ball milling medium in the second slurry is a 3 mm silicon nitride ball, the ball milling speed is 80 r / min to 100 r / min, and the ball milling time is 2 h to 6 h;

[0051] Preferably, the viscosity of the casting slurry is 5000 Pa·s to 5200 Pa·s, and the thickness of the casting green blank is 400 μm to 600 μm.

[0052] Optionally, the particle size distribution of silicon nitride powder can be 0.3μm, 0.35μm, 0.4μm, 0.45μm, 0.5μm and any other value between 0.3μm and 0.5μm, the mass of non-oxide sintering aid is 5%, 6%, 7%, 8%, 9%, 10% and any other value between 5% and 10% of the mass of silicon nitride powder, and the thickness of silicon nitride blank can be 400μm, 450μm, 500μm, 550μm, 600μm and any other value between 400μm and 600μm.

[0053] The embodiment of the present invention provides a method for preparing a silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness. A non-oxide sintering aid is used to assist in preparing a tape-cast green blank. The non-oxide sintering aid does not contain oxygen. The non-oxide sintering aid can not only promote crystal transformation, but also reduce SiO2 to reduce the lattice oxygen content and reduce the grain boundary phase.

[0054] In some optional embodiments, the method further includes: cooling the silicon nitride substrate after high-temperature annealing, cleaning, drying and polishing the surface to obtain a silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness.

[0055] In a third aspect, an embodiment of the present invention further provides an application of the above-mentioned silicon nitride ceramic substrate having both high thermal conductivity and high fracture toughness or the silicon nitride ceramic substrate having both high thermal conductivity and high fracture toughness prepared by the above-mentioned preparation method in an electronic device substrate.

[0056] The present invention will be further described below in conjunction with the embodiments.

[0057] Example 1

[0058] A method for manufacturing a silicon nitride ceramic substrate having both high thermal conductivity and high fracture toughness comprises the following steps:

[0059] Step a. Mix 95g of silicon nitride powder (particle size of silicon nitride powder = 0.5μm), 2.5g of calcium chloride as a first sintering aid, 2.5g of hafnium silicide as a second sintering aid, 1g of triethyl phosphate as a dispersant, and 200g of an organic solvent (anhydrous ethanol: toluene = 1:1) and mill to obtain a first slurry. The milling medium is a 10mm silicon nitride ball, the milling speed is 200r / min, and the milling time is 2h.

[0060] Step b. Add 10 g of polyvinyl butyral (PVB) as a binder and 5 g of dioctyl phthalate (DOP) as a plasticizer to the first slurry obtained in step a, and continue to mix and treat by ball milling to obtain a second slurry, wherein the ball milling medium is replaced with 3 mm silicon nitride balls, the ball milling speed is 100 r / min, and the ball milling time is 2 h.

[0061] Step c. Filter the second slurry obtained in step b with a sieve to remove the silicon nitride balls, add 5g of organic silicon defoamer, and evacuate to 10 -1 Pa, and maintain for 30 min until the viscosity of the slurry reaches 5000 Pa·s, and the casting slurry is obtained.

[0062] Step d. The casting slurry obtained in step c is formed by a casting machine, and the conveyor belt speed of the casting machine is set to 4 cm / min, the scraper height is 1.0 mm, and the drying temperatures of the three temperature zones are 35°C, 45°C, and 55°C, respectively, to obtain a casting blank with a thickness of 0.5 mm.

[0063] Step e. The tape-cast blank obtained in step d is subjected to a binder removal treatment to obtain a silicon nitride blank, and the silicon nitride blank is subjected to a sintering treatment to obtain an initial silicon nitride ceramic substrate. The binder removal temperature is 600° C., the holding time is 12 hours, the sintering atmosphere is a nitrogen atmosphere, the sintering temperature is 1900° C., and the holding time is 8 hours.

[0064] Step f. Covering the silicon nitride ceramic initial substrate obtained in step e with a thin layer of graphite powder, the amount of graphite powder is 2.7 g, and then placing the silicon nitride ceramic initial substrate with the surface evenly covered with graphite powder on a graphite crucible, annealing in an annealing furnace in a nitrogen atmosphere, heating to 1400°C, keeping temperature for 10 hours, then reducing to 300°C at 2°C / min to 3°C / min, and then naturally cooling to room temperature.

[0065] Step g. After cleaning, drying and polishing the surface of the annealed silicon nitride ceramic initial substrate obtained in step f, the final silicon nitride ceramic substrate material is obtained. The thermal conductivity is measured to be 80 W / (m·K) and the fracture toughness is 7.43±0.21 MPa·m 1 / 2 .

[0066] The preparation steps of the silicon nitride blanks in Examples 2 to 5 and Comparative Examples 1 to 7 are the same as those in Example 1. The raw material composition, sintering mechanism and annealing mechanism parameters of the silicon nitride blanks are shown in Table 1. Table 1 shows the process parameters and test results of the examples and comparative examples.

[0067] Table 1

[0068]

[0069]

[0070] Combining Table 1 and Figure 1 It can be seen from Examples 1 to 5 that, in the annealing mechanism, a thin layer of graphite powder is coated on the surface of the silicon nitride ceramic initial substrate, and the carbon in the graphite powder reacts with the residual oxygen in the crystal phase of the silicon nitride ceramic initial substrate to generate carbon dioxide. The elimination of lattice oxygen further reduces vacancy defects, which is more conducive to improving the crystal structure. The comprehensive performance of the prepared silicon nitride ceramic substrate is the best in Example 3.

[0071] Compared with Example 1, during the preparation of the silicon nitride ceramic substrate provided by Comparative Example 1, a thin layer of graphite powder was not coated on the surface of the silicon nitride ceramic initial substrate. Although annealing treatment was also performed, the purpose of simultaneously improving thermal conductivity and fracture toughness could not be achieved.

[0072] In the sintering process of the silicon nitride blanks in Comparative Examples 2 to 6, the holding time is too short to allow the crystals to grow fully. If the holding time is extended, the thermal conductivity and fracture toughness of the silicon nitride ceramic substrate cannot be balanced. This may be because the extension of the holding time will cause the substrate grains to grow rapidly and unevenly, and thus the performance of the final silicon nitride ceramic substrate cannot be balanced or effectively controlled. Therefore, the sintering holding time of the silicon nitride blank is preferably 8h to 10h.

[0073] Compared with Example 1 and Comparative Example 7, in Example 1, a non-oxygen sintering aid is selected, which reduces the oxygen content intake in the raw materials, reduces the probability of oxygen vacancies in the crystal phase, and improves the thermal conductivity to a certain extent.

[0074] In summary, the silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness provided by the embodiment of the present invention improves the thermal conductivity and mechanical properties at the same time through the annealing treatment method and the selection of sintering aids, so that the comprehensive performance of the prepared silicon nitride ceramic substrate reaches the expected. While helping to optimize the process flow of silicon nitride ceramic substrates, it improves the yield of experimental preparation and produces substrate materials required for semiconductor devices that meet high heat and strong mechanical movement.

[0075] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A silicon nitride ceramic substrate having both high thermal conductivity and high fracture toughness, characterized in that: The silicon nitride ceramic substrate having both high thermal conductivity and high fracture toughness has a thermal conductivity of 80W / (m·K) to 91W / (m·K) and a fracture toughness of 7.43MPa·m 1 / 2 ~8.06MPa·m 1 / 2 .

2. A method for preparing a silicon nitride ceramic substrate having both high thermal conductivity and high fracture toughness according to claim 1, characterized in that: It includes: A carbon material is covered on the initial silicon nitride ceramic substrate obtained by debinding and sintering and subjected to high-temperature annealing treatment to obtain a silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness.

3. The preparation method according to claim 2, characterized in that: The following steps are involved: A non-oxide sintering aid is used to assist in preparing a tape-cast blank, which is then subjected to a binder removal treatment to obtain a silicon nitride blank, which is then subjected to a sintering treatment to obtain a silicon nitride ceramic initial substrate, and then the silicon nitride ceramic initial substrate is covered with a carbon material and subjected to a high-temperature annealing treatment to obtain a silicon nitride ceramic substrate with both high thermal conductivity and high fracture toughness.

4. The preparation method according to claim 3, characterized in that: The non-oxide sintering aid includes chloride and silicide. The chloride includes at least one of calcium chloride and aluminum chloride. The silicide includes at least one of zirconium silicide, cerium silicide and hafnium silicide.

5. The preparation method according to claim 3, characterized in that: The debinding temperature of the cast blank is 600°C to 800°C, and the holding time is 10h to 14h. The sintering atmosphere of the silicon nitride blank is a nitrogen atmosphere, the sintering temperature is 1700°C to 1900°C, and the holding time is 8h to 10h.

6. The preparation method according to claim 3, characterized in that: After covering and burying the initial silicon nitride ceramic substrate with the carbon material, the substrate is placed in a graphite crucible for high temperature annealing treatment; Preferably, the carbon material is selected from at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, and hard carbon, preferably graphite powder, more preferably natural graphite powder, the graphite powder has a particle size of 0.5 μm to 10 μm, and a carbon content of ≥99.9%; Preferably, the mass of the carbon material is 10% to 50% of the mass of the initial silicon nitride ceramic substrate.

7. The preparation method according to claim 6, characterized in that: The conditions of the high temperature annealing treatment include: heating to a temperature of 1000° C. to 1600° C. in a nitrogen atmosphere, and keeping the temperature for 10 h to 20 h for annealing.

8. The preparation method according to claim 3, characterized in that: The tape casting blank is prepared by the following method: silicon nitride powder, non-oxide sintering aid, dispersant and organic solvent are mixed and ball-milled to obtain a first slurry; the first slurry, binder and plasticizer are mixed and ball-milled to obtain a second slurry; after filtering out the grinding medium in the second slurry, an organic silicon defoamer is added, and vacuuming is performed to obtain a tape casting slurry; after the tape casting slurry is formed, a tape casting blank is obtained; Preferably, the particle size distribution of the silicon nitride powder is 0.3 μm to 0.5 μm; Preferably, the mass of the non-oxide sintering aid is 5% to 10% of the mass of the silicon nitride powder; Preferably, the ball milling medium in the first slurry is a 10 mm silicon nitride ball, the ball milling speed is 180 r / min to 200 r / min, and the ball milling time is 2 h to 6 h; the ball milling medium in the second slurry is a 3 mm silicon nitride ball, the ball milling speed is 80 r / min to 100 r / min, and the ball milling time is 2 h to 6 h; Preferably, the viscosity of the casting slurry is 5000 Pa·s to 5200 Pa·s, and the thickness of the casting green blank is 400 μm to 600 μm.

9. The preparation method according to claim 3, characterized in that: Also includes: After high-temperature annealing, the substrate is cooled, cleaned, dried and polished to obtain a silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness.

10. Use of the silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness according to claim 1 or the silicon nitride ceramic substrate with high thermal conductivity and high fracture toughness prepared by the preparation method according to any one of claims 2 to 9 in electronic device substrates.

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