Method for producing silicon nitride powder for substrate manufacturing and silicon nitride powder produced thereby

Abstract

A method for manufacturing silicon nitride powder for manufacturing substrates is provided. The method for manufacturing silicon nitride powder for manufacturing substrates according to one embodiment of the present invention includes the steps of: manufacturing a mixed raw material powder containing metal silicon powder and crystal phase control powder; manufacturing the mixed raw material powder into granules having a predetermined particle size; nitriding the granules at a predetermined temperature within a range of 1200 to 1500°C while supplying nitrogen gas at a predetermined pressure; and pulverizing the nitrided granules. This makes it easy to realize the powder to have an α crystal phase at a desired level, and therefore, when realized as a substrate, a substrate having a dense density can be manufactured.

Description

Technical Field

[0001] The present invention relates to silicon nitride powder, and more particularly to a method for producing silicon nitride powder for substrate manufacturing and the silicon nitride powder produced thereby.

Background Art

[0002] Silicon nitride sintered bodies are excellent in abrasion resistance, heat resistance, low thermal expansion, thermal shock resistance, and corrosion resistance against metals, and have conventionally been used for various structural members such as gas turbine members, engine members, and steelmaking machine members. Further, since they have high insulation characteristics and good heat dissipation characteristics, they are used as electrical component materials such as ceramic substrates.

[0003] As a method for synthesizing silicon nitride powder for producing such a silicon nitride sintered body, an imide thermal decomposition method is known in which silicon tetrachloride and ammonia are reacted to form an imide intermediate, which is then thermally decomposed to obtain silicon nitride powder. The silicon nitride powder synthesized by this method is a powder having a relatively uniform particle size and an average particle diameter of 1 μm or less, and is an α-type silicon nitride powder having a high α conversion rate. α-type silicon nitride powder undergoes a phase transition from the α-type to the β-type during sintering by increasing the sintering temperature. As a result, for example, a dense sintered body having a relative density exceeding 99% can be obtained, and thus it is currently widely used. However, this method has the disadvantage that it requires expensive compounds as raw materials, the manufacturing process is very complicated, and it is disadvantageous in terms of manufacturing cost and time.

[0004] Therefore, as another method for producing silicon nitride powder, research on a direct nitridation method for producing silicon nitride powder by nitriding silicon solids to obtain agglomerates and then pulverizing them has continued. This method has the advantage of relatively low raw material costs. However, this method also has problems such as improving the purity of the obtained silicon nitride powder. That is, in this method, since the nitridation reaction proceeds gradually from the surface at a low temperature at which the silicon solid does not melt, it is known that it is advantageous to make the particle size of the silicon solid very small in advance. However, conversely, there is a risk of contamination with contaminants such as metallic substances that become impurities in the pulverization process of adjusting the particle size of the silicon solid, which is the raw material substance. In addition, when contaminated with contaminants, there are problems of increased man-hours, extended production time, and increased production costs due to the need to undergo acid washing for removing contaminants before nitridation.

[0005] Furthermore, silicon is likely to elute during the nitridation process. In this case, there is a risk that the thermal conductivity and mechanical strength of the substrate will rapidly decrease due to the melting and vaporization of silicon during sintering for substrate production.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been devised in consideration of the above points, and its object is to provide a method for producing silicon nitride powder suitable for producing a substrate having improved thermal conductivity and excellent mechanical strength when sintered onto a substrate, and silicon nitride powder produced using the same.

Means for Solving the Problems

[0007] The present invention has been devised in consideration of the above points, and includes a step of producing a mixed raw material powder containing silicon powder and crystal phase control powder, a step of mixing an organic binder with the mixed raw material powder to produce granules having a predetermined particle size, and a step of nitriding the granules at a predetermined temperature within the range of 1200 to 1500 °C while adding nitrogen gas at a predetermined pressure. Also provided is a method for manufacturing silicon nitride (Si3N4) powder for substrate production, including the step of pulverizing the nitrided granules.

[0008] According to one embodiment of the present invention, the metallic silicon powder may be obtained by dry pulverizing polycrystalline metallic silicon scrap or single-crystalline silicon wafer scrap in order to minimize contamination by metallic impurities during pulverization.

[0009] Also, the metallic silicon powder may have a resistivity of 1 to 100 Ωcm.

[0010] Also, the polycrystalline metallic silicon scrap or single-crystalline silicon wafer scrap may have a purity of 99% or more.

[0011] Also, the metallic silicon powder may have an average particle size of 0.5 to 4 μm, the rare earth element-containing compound powder may have an average particle size of 0.1 to 1 μm, and the magnesium-containing compound powder may have an average particle size of 0.1 to 1 μm.

[0012] Also, the granules may have a D50 value of 100 μm or less, more preferably 20 to 55 μm.

[0013] Also, the rare earth element-containing compound is yttrium oxide, the magnesium-containing compound is magnesium oxide, and the yttrium oxide may be contained in the mixed raw material powder at 2 to 5 mol%, and the magnesium oxide may be contained at 2 to 10 mol%.

[0014] Also, the nitrogen gas may be applied at a pressure of 0.1 to 0.2 MPa during nitridation.

[0015] Also, during nitridation, it may be heated at a heating rate of 0.5 to 10 °C / min from 1000 °C or higher to a predetermined temperature.

[0016] Also, the present invention provides silicon nitride powder for substrate production, which is produced by the production method according to the present invention and contains 9% by weight or less of polycrystalline silicon.

[0017] According to one embodiment of the present invention, the weight ratio of the α-crystalline phase may be 0.7 or more with respect to the total weight of the α-crystalline phase and the β-crystalline phase.

[0018] The present invention also provides a composition for producing silicon nitride powder, in which a mixed raw material powder containing metal silicon powder and a crystal phase control powder containing a rare earth element-containing compound and a magnesium-containing compound is mixed with an organic binder and formed into granules having a predetermined particle size.

[0019] According to one embodiment of the present invention, the granules may have a D50 of 20 to 55 μm.

[0020] The present invention also provides a silicon nitride substrate which is produced by forming a slurry containing silicon nitride powder produced by the production method according to the present invention into a sheet shape and then sintering it, and which has a thermal conductivity of 70 W / mK or more and a three-point bending strength of 650 MPa or more.

Advantages of the Invention

[0021] The method for producing silicon nitride powder according to the present invention can easily embody the powder so as to have an α-crystalline phase at a target level, and thereby can produce a substrate having a dense density when embodied on the substrate. In addition, since a secondary phase can be formed uniformly within the grain boundaries of the substrate sintered using this, the thermal conductivity of the produced substrate can be further improved. In addition, in the case of the silicon nitride powder according to the present invention, the content of impurities is small or does not contain any impurities, and particularly does not contain eluted silicon, so it is suitable for producing a substrate excellent in thermal conductivity and mechanical strength.

Best Mode for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. The present invention can be embodied in various different forms and is not limited to the embodiments described herein.

[0023] A method for producing silicon nitride powder according to an embodiment of the present invention includes a step of producing a mixed raw material powder including metallic silicon powder, and a crystal phase control powder including a rare earth element-containing compound and a magnesium-containing compound; a step of mixing a solvent and an organic binder with the mixed raw material powder to form a slurry, and then spray-drying the slurry to produce granules having a predetermined particle size; a step of nitriding the granules at a predetermined temperature within a range of 1200 to 1500 °C while applying nitrogen gas at a predetermined pressure; and a step of pulverizing the nitrided granules.

[0024] First, the step of producing a mixed raw material powder including metallic silicon powder, and a crystal phase control powder including a rare earth element-containing compound and a magnesium-containing compound in the method for producing silicon nitride powder will be described.

[0025] The metallic silicon powder as the main component of the raw material powder can be used without limitation in the case of metallic silicon powder capable of producing silicon nitride powder using a direct nitridation method. As an example, the metallic silicon powder may be polycrystalline metallic silicon scrap or single-crystalline silicon wafer scrap. The polycrystalline metallic silicon scrap may be a by-product of polycrystalline metallic silicon used for semiconductor process tools or solar panel manufacturing, and the single-crystalline silicon wafer scrap is also a by-product during the manufacture of silicon wafers. By using these scraps as the raw material powder, the manufacturing cost can be reduced.

[0026] In addition, the polycrystalline metallic silicon scrap or single-crystalline silicon wafer scrap may have a purity of 99% or more, which is more advantageous for ensuring the thermal conductivity and mechanical strength when sintering the silicon nitride powder produced thereby to manufacture a substrate.

[0027] In addition, the metallic silicon powder may have a resistivity of 1 to 100 Ω·cm, which is more advantageous for producing silicon nitride powder having the physical properties targeted by the present invention.

[0028] In addition, the metallic silicon powder used as the raw material powder may preferably be obtained by pulverizing polycrystalline metallic silicon scrap or single-crystalline silicon wafer scrap into a predetermined size. At this time, in order to prevent contaminants such as metallic impurities from being mixed into the raw material powder due to pulverization, dry pulverization methods can be used for the pulverization. Specifically, it can be pulverized into powder using dry pulverization methods such as a disk mill, a pin mill, or a jet mill. If contaminants are contained in the metallic silicon powder, there is a risk of an increase in manufacturing time and cost, and a cleaning process such as acid cleaning for removing the contaminants must be further performed. At this time, the average particle size of the pulverized metallic silicon powder may be 0.5 to 4 μm, more preferably 2 to 4 μm. If the average particle size is less than 0.5 μm, it is difficult to implement using a dry pulverization method, and there is a high risk of contaminants being mixed in due to non-pulverization, making it difficult to densify during sheet casting. Also, if the average particle size of the metallic silicon powder exceeds 4 μm, nitridation is not easy, so there may be parts that are not nitrided, making it difficult to densify the final substrate.

[0029] In addition, silicon nitride to be embodied has difficulties in self-diffusion, can be thermally decomposed at high temperatures, and has a limited sintering temperature. For these reasons, sintering onto a substrate or the like is not easy, it is difficult to embody a dense sintered body, and when producing silicon nitride powder by a direct nitridation method, it may be difficult to control the crystal phase. To solve such problems, remove impurities such as oxygen, and improve the physical properties of a substrate on which silicon nitride powder is sintered, a mixed raw material powder obtained by mixing a crystal phase control powder with metal silicon powder is used as the raw material powder. As an example, rare earth element-containing compounds, alkaline earth metal oxides, and combinations thereof can be used as the crystal phase control powder. Specifically, one or more selected from the group consisting of magnesium oxide (MgO), yttrium oxide (Y2O3), gadolinium oxide (Gd2O), holmium oxide (Ho2O3), erbium oxide (Er2O3), ytterbium oxide (Yb2O3), and dysprosium oxide (Dy2O3) can be used. However, in the present invention, in order to more easily control the crystal phase of silicon nitride powder, magnesium oxide and yttrium oxide are essentially contained in the crystal phase control powder, and when producing a substrate using the produced silicon nitride powder, there is an advantage that a higher density substrate with higher densification can be embodied, the amount of the residual grain boundary phase during sintering can be reduced, and the thermal conductivity can be further improved.

[0030] As an example, the yttrium oxide may be contained in the mixed raw material powder at 2 to 5 mol%, and the magnesium oxide may be contained at 2 to 10 mol%. If the yttrium oxide is less than 2 mol%, when the fabricated silicon nitride powder is sintered onto the substrate, it is difficult to fabricate a densified substrate, and it is difficult to capture oxygen in the grain boundary phase. Therefore, the amount of solid solution oxygen increases, the thermal conductivity of the sintered substrate decreases, and the mechanical strength may also decrease. Also, if the yttrium oxide exceeds 5 mol%, the grain boundary phase increases, and the thermal conductivity of the substrate obtained by sintering the fabricated silicon nitride powder may decrease, and the fracture toughness may decrease. Further, when the magnesium oxide is less than 2 mol%, both the thermal conductivity and the mechanical strength of the substrate obtained by sintering the fabricated silicon nitride powder are low, silicon may elute during nitridation, and it is difficult to manufacture a densified substrate. Also, if the magnesium oxide exceeds 10 mol%, the residual amount of magnesium in the grain boundary of the fabricated sintered substrate increases. Therefore, the thermal conductivity of the fabricated sintered substrate decreases, the sintering of the silicon nitride powder is not easy, and there is a problem that the fracture toughness decreases.

[0031] Further, for the rare earth element-containing compound powder, those having an average particle size of 0.1 to 1 μm and for the magnesium-containing compound powder, those having an average particle size of 0.1 to 1 μm can be used, which is more advantageous for achieving the object of the present invention.

[0032] Next, a step of mixing a solvent and an organic binder with the prepared mixed raw material powder to form a slurry and then spray-drying to produce granules having a predetermined particle size is performed.

[0033] Without immediately nitriding the mixed raw material powder, after producing granules having a predetermined particle size, a nitriding step described later is performed on the granules. As a result, the mixing uniformity of the mixed raw material powder can be enhanced, the crystal phase of the produced silicon nitride powder can be more easily controlled, the secondary phase of Si2Y2O5 in the grain boundary of the sintered substrate can be uniformly formed, and while further improving the thermal conductivity and mechanical strength of the sintered substrate, a silicon nitride powder having uniform characteristics that can improve the uniformity can be produced.

[0034] The granules may have a D50 value of 100 μm or less, more preferably 20 - 100 μm, even more preferably 20 - 55 μm, and still more preferably 20 - 40 μm. However, if the D50 exceeds 100 μm, the inflow of nitrogen gas into the granules is not smooth, so nitridation does not occur completely, and un-nitrided silicon melts and can elute outside the granules. When manufacturing a substrate using such silicon nitride powder, there is a risk that the eluted silicon can further elute outside the substrate during the production of the silicon nitride powder. Here, the D50 value means the value based on 50% volume measured using the laser diffraction scattering method.

[0035] Note that the granules can be obtained using the dry spraying method, and can be obtained using known conditions and apparatuses capable of performing the dry spraying method, and the present invention is not particularly limited thereto. Further, the mixed raw material powder is embodied as a slurry mixed with a solvent and an organic binder and then dry-sprayed. The solvent and the organic binder can be used without limitation in the case of the solvent and the organic binder used during slurrying in order to embody the ceramic powder into granules. As an example, the solvent preferably contains one or more selected from ethanol, methanol, isopropanol, distilled water, and acetone. Also, it is preferable to use a polyvinyl butyral (PVB)-based binder as the organic binder. Note that although the organic binder is contained during the production of the granules, if it is contained in a trace amount, a degreasing process may not be separately performed before the nitridation process described later.

[0036] Next, a step of performing nitridation treatment at a predetermined temperature within the range of 1200 - 1500 °C while adding nitrogen gas to the obtained granules at a predetermined pressure is carried out.

[0037] At this time, during the nitriding treatment, the nitrogen gas may be added at a pressure of 0.1 to 0.2 MPa, more preferably, it may be added at a pressure of 0.15 to 0.17 MPa. If the nitrogen gas pressure is less than 0.1 MPa, nitridation may not occur completely. Also, if the nitrogen gas pressure exceeds 0.2 MPa, a phenomenon of silicon elution occurs during the nitriding process. Further, during the nitriding treatment, it can be heated at a heating rate of 0.5 to 10 °C / min from 1000 °C or higher to a predetermined temperature. However, if the heating rate from 1000 °C or higher to the predetermined temperature is less than 0.5 °C / min, the sintering time can be excessively extended. Also, if the heating rate exceeds 10 °C / min, silicon elutes and it is difficult to manufacture a powder completely nitrided into silicon nitride.

[0038] Also, during the nitriding treatment, the temperature can be selected to be a predetermined temperature within the range of 1200 to 1500 °C. However, if the predetermined temperature is less than 1200 °C, nitridation may not occur uniformly. Also, if the predetermined temperature exceeds 1500 °C, a β-crystalline phase is rapidly formed. Thus, when manufacturing a substrate using such silicon nitride powder, densification is difficult. Also, nitridation can be performed for 30 minutes to 5 hours at the predetermined temperature, which is more advantageous for achieving the object of the present invention.

[0039] Next, a step of pulverizing the nitrided granules is performed.

[0040] A step of manufacturing silicon nitride powder using the nitrided granules, preferably, it can be by a dry method so as to prevent contamination during pulverization. As an example, it can be performed using an air jet mill.

[0041] Further, the present invention includes a silicon nitride powder for substrate manufacturing, which is manufactured by the manufacturing method according to the present invention and contains polycrystalline silicon derived from molten silicon of 8 wt% or less, preferably, 6 wt% or less, more preferably, 4 wt% or less, and still more preferably, 0 wt%. Thus, it is suitable for manufacturing a substrate with improved mechanical strength and thermal conductivity.

[0042] According to an embodiment of the present invention, the weight ratio of the α-crystalline phase may be 0.7 or more with respect to the total weight of the α-crystalline phase and the β-crystalline phase. However, if the weight ratio of the α-crystalline phase is less than 0.7 with respect to the total weight of the α-crystalline phase and the β-crystalline phase, it is difficult to improve the densification of the substrate sintered using silicon nitride powder, and it is difficult to improve the thermal conductivity and mechanical strength, especially the improvement of mechanical strength is difficult.

[0043] In addition, the silicon nitride powder can more uniformly form a secondary phase of Si2Y 2O5 in the grain boundary phase of the substrate sintered body embodied thereby, and thereby, a synergistic effect can be exhibited in improving the thermal conductivity of the substrate.

[0044] In addition, the silicon nitride powder may have an average particle size of 2 to 4 μm, which is more advantageous for embodying a substrate with improved mechanical strength and thermal conductivity.

[0045] In addition, the present invention is manufactured by sintering after forming a slurry containing silicon nitride powder produced by the manufacturing method according to the present invention into a sheet shape, and has a thermal conductivity of 70 W / mK or more, preferably 80 W / mK or more, more preferably 90 W / mK or more, and a three-point bending strength of 650 MPa or more, preferably 680 MPa or more, more preferably 700 MPa or more. The silicon nitride substrate is included. In addition, the silicon nitride substrate is excellent in uniformity, and after dividing the silicon nitride sintered body into 10 equal parts, the standard deviation of the thermal conductivity measured for each may be 5 W / mK or less, more preferably 3 W / mK or less, and the standard deviation of the three-point bending strength may be 25 MPa or less, more preferably 20 MPa or less. In addition, the silicon nitride substrate may have a sintered density of 3.0 g / cm 2 or more, and more preferably 3.2 g / cm 2 or more.

[0046] The silicon nitride substrate can be manufactured by a known method of sintering after forming a slurry containing silicon nitride powder into a sheet shape. As an example, the slurry can be formed into a sheet shape using the tape casting method.

[0047] In addition, the slurry may further contain a solvent and an organic binder. As the solvent, an organic solvent can be used to dissolve the organic binder and disperse the silicon nitride powder to adjust the viscosity. Substances capable of dissolving the organic binder can be used as the organic solvent. As an example, terpineol, dihydro terpineol (DHT), dihydro terpineol acetate (DHTA), butyl carbitol acetate (BCA), ethylene glycol, ethylene, isobutyl alcohol, methyl ethyl ketone, butyl carbitol, texanol (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate), ethylbenzene, isopropylbenzene, cyclohexanone, cyclopentanone, dimethyl sulfoxide, diethyl phthalate, toluene, mixtures thereof, etc. can be used. At this time, it is preferable to mix 50 to 100 parts by weight of the solvent with respect to 100 parts by weight of the silicon nitride powder. If the content of the solvent is less than 50 parts by weight, the viscosity of the slurry is high, making it difficult to perform tape casting and possibly difficult to adjust the coating thickness. If the content of the solvent exceeds 100 parts by weight, the viscosity of the slurry is too low, resulting in a long drying time and possibly difficult to adjust the coating thickness.

[0048] Also, it is preferable to mix 5 to 20 parts by weight of the organic binder with 100 parts by weight of the silicon nitride powder. Examples of the organic binder include cellulose derivatives such as ethyl cellulose, methyl cellulose, nitrocellulose, and carboxymethyl cellulose, or polymer resins such as polyvinyl alcohol, acrylate ester, methacrylate ester, and polyvinyl butyral. Considering forming a sheet-shaped molded body by the tape casting method, polyvinyl butyral can be used as the organic binder.

[0049] In addition, the slurry may further contain known substances contained in a slurry for forming a sheet, such as a dispersant and a plasticizer, and the present invention is not particularly limited thereto. The formed sheet may be sintered at a temperature of 1800 to 1900 ° C under a pressure of 0.5 to 1.0 MPa, which is more advantageous for realizing a high-quality silicon nitride substrate.

Mode for Carrying Out the Invention

[0050] The present invention will be described more specifically based on the following examples, but the following examples do not limit the scope of the present invention and should be understood as helping to understand the present invention.

[0051] <Example 1> Polycrystalline silicon scraps (purity 99.99%, resistivity 1 Ωcm) from semiconductor processing tools were dry-ground using a jet mill to prepare metallic silicon powder with an average particle size of 4 μm. To this, 2 mol% of yttrium oxide with an average particle size of 0.5 μm and 5 mol% of magnesium oxide with an average particle size of 0.5 μm were mixed to prepare mixed raw material powder. 100 parts by weight of the prepared mixed raw material powder was mixed with 80 parts by weight of ethanol as a solvent and 10 parts by weight of polyvinyl butyral as an organic binder to produce a slurry for granule production, and this was spray-dried using a thermal spraying device to produce granules with a D50 value of 20 μm. The produced granules were heat-treated at a nitrogen gas pressure of 0.15 MPa. Specifically, the heating rate was 5 °C / min up to 1000 °C and 0.5 °C / min from 1000 °C to 1400 °C, and then heat-treated at 1400 °C for 2 hours to obtain nitrided granules, which were ground using an air jet mill to obtain silicon nitride powder as shown in Table 1 below with an average particle size of 2 μm.

[0052] Thereafter, 5 parts by weight of polyvinyl butyral resin and 50 parts by weight of a solvent obtained by mixing toluene and ethanol at a ratio of 5:5 as a solvent were mixed, dissolved, and dispersed in 100 parts by weight of the obtained silicon nitride powder using a ball mill. Thereafter, the produced slurry was produced into a sheet using a normal tape casting method, and after being produced into a 170 μm sheet, 4 sheets of the produced sheet were cross-laminated, and then heat-treated at 1900 °C for 4 hours in a nitrogen atmosphere to produce a silicon nitride substrate as shown in Table 1.

[0053] <Comparative Example 1> Although produced in the same manner as in Example 1 without forming the mixed raw material powder into granules, silicon nitride powder was obtained, and thereby, a silicon nitride substrate as shown in Table 1 below was produced.

[0054] <Experimental Example 1> The following physical properties of the silicon nitride powder or silicon nitride substrate produced in Example 1 and Comparative Example 1 were evaluated, and the results are shown in Table 1 below.

[0055] 1. D50 The 50% volume reference value measured using the laser diffraction scattering method was defined as the D50 value.

[0056] 2. Sintering density The sintering density of the manufactured substrate was measured by the Archimedes method.

[0057] 3. Thermal conductivity and uniformity After preparing a total of 10 test pieces for the manufactured substrates by example and comparative example, the thermal conductivity was measured for them by the KSL1604 (ISO18755, ASTM E1461) method. Then, the average value and standard deviation of the measured values were calculated. The closer the standard deviation is to 0, the more uniform the thermal conductivity is.

[0058] 4. Three-point bending strength and uniformity After preparing a total of 10 test pieces for the manufactured substrates by example and comparative example, the three-point bending strength (S) of the manufactured substrate was measured by the KSL1590 (ISO14704) method. Then, the average value and standard deviation of the values calculated by substituting into the following formula were calculated. The closer the standard deviation of the three-point bending strength is to 0, the more uniform the three-point bending strength is.

[0059] [Formula] S = 3PL / (2bd 2 )

[0060] In the formula, P is the breaking load, L is the distance between points, b is the width of the beam, and d is the thickness of the beam.

[0061]

Table 1

[0062] As can be confirmed from Table 1, the silicon nitride substrate according to Example 1 is excellent in thermal conductivity and three-point bending strength compared to the silicon nitride substrate according to Comparative Example 1, and it can be seen that uniform characteristics are exhibited. This is presumably the result of granulation of the silicon nitride powder used in the production of the silicon nitride substrate and the resulting increase in nitridation uniformity.

[0063] <Examples 2 to 9> Although produced in the same manner as in Example 1, the content of components, the D50 value of granules, nitridation conditions, etc. in the mixed raw material powder were changed as shown in Table 2 or Table 3 below to obtain silicon nitride powder, and thereby, silicon nitride powder and silicon nitride substrates as shown in Table 2 or Table 3 below were produced.

[0064] <Experimental Example 2> The following physical properties were evaluated for the silicon nitride powder or silicon nitride substrates produced in Examples 1 to 9, and the results are shown in Table 2 or Table 3 below.

[0065] 1. Crystal phase The α and β crystal phases were quantified for the silicon nitride powder through XRD measurement, and the weight ratio of the α crystal phase was calculated by the following formula. Weight ratio of α crystal phase = α / (α + β)

[0066] 2. D67 The 50% volume reference value measured using the laser diffraction scattering method was taken as the D50 value.

[0067] 3. Sintered density The sintered density of the produced substrate was measured by the Archimedes method.

[0068] 4. Thermal conductivity For 10 substrates produced for each example, the thermal conductivity was measured by the KSL1604 (ISO18755, ASTM E1461) method, and the average value of the measured values was calculated.

[0069] 5. Three-point bending strength For 10 substrates manufactured for each example, the three-point bending strength (S) was measured by the KSL1590 (ISO14704) method, calculated by the following formula, and the average value of the calculated values was calculated.

[0070] [Formula] S = 3PL / (2bd 2 )

[0071] In the formula, P is the breaking load, L is the distance between points, b is the width of the beam, and d is the thickness of the beam.

[0072] [Table 2]

[0073] [Table 3]

[0074] As can be confirmed from Table 2 and Table 3, the examples are powders that are very suitable for improving the thermal conductivity and three-point bending strength of the substrates manufactured using silicon nitride powder obtained by nitriding after manufacturing the mixed raw material powder into granules of an appropriate size. However, as in Example 6, when the granule size is large, the content of silicon eluted from the silicon nitride powder is high, and in this case, it can be seen that it is insufficient to improve the mechanical strength and thermal conductivity of the manufactured substrate.

[0075] As described above, one embodiment of the present invention has been described. However, the idea of the present invention is not limited to the embodiments presented in this specification, and those skilled in the art who understand the idea of the present invention can easily propose other embodiments by adding, changing, deleting, adding, etc. of components within the scope of the same idea, and this can also be said to be within the scope of the idea of the present invention.

Claims

1. Manufacturing a mixed raw material powder containing metallic silicon powder and a crystal phase control powder containing a rare earth element-containing compound and a magnesium-containing compound; Mixing the mixed raw material powder with an organic binder and manufacturing it into granules having a volume-based D50 value of 20 to 55 μm; Nitriding the granules at a predetermined temperature within the range of 1200 to 1500 °C while applying nitrogen gas at a predetermined pressure; A method for producing silicon nitride (Si ３ N ４ )) powder for substrate production, including the step of pulverizing the nitrided granules.

2. The method for manufacturing silicon nitride powder for substrate manufacturing according to claim 1, wherein the metallic silicon powder is obtained by dry-grinding polycrystalline metallic silicon scrap or single-crystalline silicon wafer scrap in order to minimize contamination with metallic impurities during grinding.

3. The method for manufacturing silicon nitride powder for substrate manufacturing according to claim 1, wherein the metallic silicon powder has a resistivity of 1 to 100 Ωcm.

4. The method for manufacturing silicon nitride powder for substrate manufacturing according to claim 2, wherein the polycrystalline metallic silicon scrap or single-crystalline silicon wafer scrap has a purity of 99% or more.

5. The method for manufacturing silicon nitride powder for substrate manufacturing according to claim 1, wherein the metallic silicon powder has an average particle size of 0.5 to 4 μm, the rare earth element-containing compound powder has an average particle size of 0.1 to 1 μm, and the magnesium-containing compound powder has an average particle size of 0.1 to 1 μm.

6. The rare earth element-containing compound is yttrium oxide, and the magnesium-containing compound is magnesium oxide. The method for manufacturing silicon nitride powder for substrate manufacturing according to claim 1, wherein the yttrium oxide is contained in the mixed raw material powder at 2 to 5 mol%, and the magnesium oxide is contained at 2 to 10 mol%.

7. During nitriding, it is heated at a heating rate of 0.5 to 10 °C / min from 1000 °C or higher to a predetermined temperature, and the nitrogen gas is applied at a pressure of 0.1 to 0.2 MPa. The substrate manufacturing Method for manufacturing silicon nitride powder.

8. Polycrystalline silicon is 0 wt%, the thermal conductivity measured by the following evaluation method in the silicon nitride substrate is 70 W / mK or higher, the standard deviation of the thermal conductivity is 5 W / mK or lower, the three-point bending strength is 650 MPa or higher, and the standard deviation of the three-point bending strength is 25 MPa or lower. Silicon nitride powder for substrate manufacturing. [Evaluation Method] A slurry obtained by mixing 5 parts by weight of polyvinyl butyral resin and 50 parts by weight of a solvent obtained by mixing toluene and ethanol in a volume ratio of 5:5 with respect to 100 parts by weight of silicon nitride powder is formed into a sheet by tape casting, and then heat-treated at 1900 ° C for 4 hours in a nitrogen atmosphere. For 10 samples obtained by dividing the produced silicon nitride substrate into 10 equal parts, the thermal conductivity is measured according to ISO18755, the three-point bending strength is measured according to ISO14704, and the standard deviations of the thermal conductivity and the three-point bending strength are measured for the 10 samples.

9. The silicon nitride powder for substrate production according to claim 8, wherein the weight ratio of the α-crystalline phase is 0.7 or more with respect to the total weight of the α-crystalline phase and the β-crystalline phase.

10. A composition for producing silicon nitride powder, comprising a mixed raw material powder containing metallic silicon powder, a crystal phase control powder containing a rare earth element-containing compound and a magnesium-containing compound, and granules mixed with an organic binder, wherein the granules have a D50 value on a volume basis of 20 to 55 μm.

11. A silicon nitride substrate which is a sintered sheet containing the silicon nitride powder according to claim 8, having a thermal conductivity of 70 W / mK or more according to ISO18755, a standard deviation of the thermal conductivity of 5 W / mK or less for 10 samples divided into 10 equal parts, a three-point bending strength of 650 MPa or more according to ISO14704, and a standard deviation of the three-point bending strength of 25 MPa or less for 10 samples divided into 10 equal parts.

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