Method for manufacturing silicon nitride substrate and silicon nitride substrate manufactured thereby

Abstract

Provided is a method for manufacturing a silicon nitride substrate and a silicon nitride substrate manufactured thereby. The method for manufacturing a silicon nitride substrate according to an embodiment of the present invention includes a step of preparing a ceramic composition including a metal silicon powder and a crystal phase control powder containing a rare earth element-containing compound and a magnesium-containing compound; a step of manufacturing a sheet-shaped molded body using a slurry prepared by mixing the ceramic composition with a solvent and an organic binder; and a heat treatment step including a nitriding section in which heat treatment is performed at a first temperature in the range of 1300°C to 1500°C while applying nitrogen gas at a predetermined pressure to the molded body, and a sintering section in which heat treatment is performed at a second temperature in the range of 1700°C to 1900°C. According to this, compared to the past, it is possible to reduce the manufacturing time and man-hours, and thus it is suitable for mass production.

Description

TECHNICAL FIELD

[0001] The present invention relates to a manufacturing method of a silicon nitride substrate and a silicon nitride substrate manufactured thereby. BACKGROUND

[0002] The silicon nitride sintered body has excellent wear resistance, heat resistance, low thermal expansion, heat shock resistance, and corrosion resistance to metals, and thus has been used for various structural parts such as parts for gas turbines, parts for engines, mechanical parts for steelmaking, etc. In addition, due to its high insulation performance and good heat dissipation performance, it has been used as a material for electronic parts such as ceramic substrates, etc.

[0003] The silicon nitride substrate is generally manufactured by a two-step method of preparing a silicon nitride powder and then sintering the prepared silicon nitride powder. The reason for using this method is that, when nitriding and sintering are performed in a substrate form, it is difficult to achieve a substrate exhibiting uniform physical properties regardless of positions, and in order to solve this problem, a method of first manufacturing a silicon nitride powder in such a manner that it has uniform physical properties in a powder state and then manufacturing a substrate using the silicon nitride powder has been widely used.

[0004] However, the two-step method as described above requires cooling and pulverizing the nitrided body after nitriding and then forming it into a predetermined shape, and then sintering, and thus the manufacturing time is 50 hours or more, and the working hours can be increased.

[0005] Therefore, there is an urgent need to research a manufacturing method of a silicon nitride substrate that can significantly shorten the manufacturing time, can also reduce the working hours, and the silicon nitride substrate realized thereby has excellent thermal conductivity and mechanical strength, while exhibiting these physical properties uniformly at each position of the substrate.

[0006] PRIOR ART DOCUMENT

[0007] PATENT DOCUMENT

[0008] (Patent Document 1) Korean Patent Laid-Open Publication No. 10-1997-7000234 SUMMARY

[0009] TECHNICAL PROBLEM

[0010] The present invention has been developed in view of the above-described problems, and an object of the present invention is to provide a manufacturing method of a silicon nitride substrate and a silicon nitride substrate manufactured thereby, which can manufacture a silicon nitride substrate by reducing the manufacturing time and working hours with respect to the existing manufacturing method of a silicon nitride substrate, and the silicon nitride substrate realized thereby has excellent flatness, thermal conductivity, and mechanical strength, while exhibiting these physical properties uniformly at each position of the substrate.

[0011] SOLUTION TO THE PROBLEM

[0012] The present invention has been developed in view of the above-described problems, and provides a method of manufacturing a silicon nitride (Si3N4) substrate, the method of manufacturing a silicon nitride substrate including: a step of preparing a ceramic composition including a metal silicon powder, a crystal phase control powder including a rare earth element-containing compound and a magnesium-containing compound; a step of manufacturing a sheet-shaped molded body using a slurry prepared by mixing the ceramic composition with a solvent and an organic binder; and a heat treatment step including a nitriding section in which heat treatment is performed at a first temperature in the range of 1300°C to 1500°C while nitrogen gas is applied at a predetermined pressure to the molded body, and a sintering section in which heat treatment is performed at a second temperature in the range of 1700°C to 1900°C.

[0013] According to an embodiment of the present invention, the metal silicon powder can be prepared by dry milling of a polycrystalline metal silicon scrap or a single crystal silicon wafer scrap in order to minimize contamination by metal impurities during the milling process.

[0014] In addition, the metal silicon powder can have a resistivity of 1 Ω·㎝ to 100 Ω·㎝.

[0015] In addition, the polycrystalline metal silicon scrap or the single crystal silicon wafer scrap can have a purity of 99% or more.

[0016] In addition, the rare earth element-containing compound can be yttrium oxide, the magnesium-containing compound can be magnesium oxide, and the ceramic composition can include 2 mol% to 5 mol% of the yttrium oxide and 2 mol% to 10 mol% of the magnesium oxide.

[0017] Also, the metal silicon powder can have an average particle diameter of 0.5 μm to 4 μm, the rare earth element-containing compound powder can have an average particle diameter of 0.1 μm to 1 μm, and the magnesium-containing compound powder can have an average particle diameter of 0.1 μm to 1 μm.

[0018] In addition, the heat treatment step can be continuously performed from the nitriding section to the sintering section.

[0019] In addition, a section in which heat treatment is performed at a temperature lower than the first temperature or cooling to a temperature lower than the first temperature can not be included between the nitriding section and the sintering section.

[0020] In addition, in the heat treatment step, heat treatment can be performed at a temperature rise rate of 0.1°C / min to 2°C / min while nitrogen gas is applied at a pressure of 0.1 MPa to 0.2 MPa from 1000±20°C to the first temperature.

[0021] In addition, nitrogen gas can be applied at a pressure of 0.1 MPa to 0.2 MPa in the nitriding section, and the nitriding section can be performed for 2 hours to 10 hours.

[0022] In addition, the pressure of the nitrogen gas applied from the first temperature to 1700±20°C can be lower than the pressure of the nitrogen gas applied in the nitriding zone.

[0023] In addition, between the nitriding zone and the sintering zone, a first shrinkage zone in which the temperature is increased at a rate of 0.1 to 10.0°C / min while applying nitrogen gas at a pressure of 0.15 to 0.3 MPa from the first temperature to 1700±20°C, and a second shrinkage zone in which the temperature is increased at a rate of 1 to 10°C / min while applying nitrogen gas at a pressure of 0.8 to 0.98 MPa from 1700±20°C to the second temperature, can be further included.

[0024] In addition, the present application provides a silicon nitride substrate manufactured by the manufacturing method according to the present application, having a thermal conductivity of 75 W / mK or more and a three-point bending strength of 700 MPa or more.

[0025] Effects of the Invention

[0026] Compared to the prior art, the manufacturing method of the silicon nitride substrate according to the present application can reduce the manufacturing time and man-hours, and thus is suitable for mass production. In addition, by minimizing or preventing the phenomenon of silicon melting and dissolving during the nitriding process, the silicon nitride substrate realized has excellent mechanical strength. Furthermore, after entering the sintering zone while suppressing the rapid transition to the β phase, sintering is completed, and thus the transition to the β phase, the promotion of the growth of the β phase, and the uniform growth can be achieved, and thus the thermal conductivity is more improved. In addition, the thermal conductivity and the mechanical strength are uniform regardless of the position of the substrate, and the flatness is excellent, and thus a higher quality substrate can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A graph showing the change in temperature conditions over time in the heat treatment step included in an embodiment of the present application.

[0028] Figure 2 A schematic view showing the cross section of a stack of several shaped bodies before heat treatment (a) and after the nitriding process, the stack having changed due to movement or re-vacuuming, according to an embodiment of the present application.

[0029] REFERENCE NUMERALS

[0030] 1, 2: Shaped body

[0031] 10: Boron nitride plate

[0032] 100: Laminated body DETAILED DESCRIPTION

[0033] Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings so as to be easily carried out by those having ordinary skill in the art to which the present application pertains. The present application can be realized by a variety of different embodiments, and is not limited to the embodiments described in this specification.

[0034] The silicon nitride substrate according to an embodiment of the present application can be manufactured by a manufacturing method including a step of preparing a ceramic composition including a metal silicon powder, a crystal phase control powder including a rare earth element-containing compound and a magnesium-containing compound; a step of manufacturing a sheet-shaped molded body using a slurry prepared by mixing the ceramic composition with a solvent and an organic binder; and a heat treatment step including a nitriding interval in which heat treatment is performed at a first temperature in the range of 1300°C to 1500°C while applying nitrogen gas at a predetermined pressure to the molded body, and a sintering interval in which heat treatment is performed at a second temperature in the range of 1700°C to 1900°C.

[0035] First, the step of preparing a ceramic composition will be described.

[0036] The ceramic composition can be manufactured by mixing a ceramic composition including a metal silicon powder and a crystal phase control powder including a rare earth element-containing compound and a magnesium-containing compound.

[0037] As the raw material powder, the metal silicon powder as a main material can be used without limitation as long as it is a metal silicon powder that can be used to manufacture a silicon nitride powder by a direct nitriding method or a metal silicon powder that can be used to manufacture a silicon nitride molded body. For example, the metal silicon powder can be a polycrystalline metal silicon scrap or a single crystal silicon wafer scrap. The polycrystalline metal silicon scrap can be a by-product of polycrystalline metal silicon used to manufacture a jig for a semiconductor process or a solar cell panel, and the single crystal silicon wafer scrap is also a by-product generated in a silicon wafer manufacturing process, and thus the manufacturing cost can be reduced by using the scrap as a by-product as a raw material powder.

[0038] In addition, the purity of the polycrystalline metal silicon scrap or the single crystal silicon wafer scrap can be 99% or more, and thus the thermal conductivity and the mechanical strength of the manufactured silicon nitride substrate can be more favorably ensured.

[0039] In addition, the resistivity of the metal silicon powder can be 1Ω·㎝ to 100Ω·㎝, and thus the present application can more favorably manufacture a silicon nitride substrate having desired physical properties.

[0040] On the other hand, the metal silicon powder used as the raw material powder can be preferably a powder of a predetermined size obtained by pulverizing polycrystalline metal silicon waste or single crystal silicon wafer waste. At this time, in order to prevent contaminants such as metal impurities from being mixed into the raw material powder due to the pulverization, the pulverization can be performed using a dry pulverization method, and specifically, can be performed using a dry pulverization method such as a disc mill, a pin mill, a jet mill, or the like. If the metal silicon powder contains a contaminant, it can be necessary to further perform a cleaning process such as pickling in order to remove the contaminant, which can result in an increase in manufacturing time and cost. At this time, the average particle diameter of the metal silicon powder after the pulverization can be 0.5 to 4 μm, and more preferably, can be 2 to 4 μm. If the average particle diameter is less than 0.5 μm, it can be difficult to achieve the pulverization using a dry pulverization method, and the possibility of contamination due to fine pulverization increases, and densification at the time of sheet casting can become difficult. In addition, if the average particle diameter of the metal silicon powder exceeds 4 μm, it is not easy to nitride, and thus there can be a portion that is not nitrided, and it can be difficult to achieve densification of the final substrate.

[0041] On the other hand, silicon nitride, which is the material of the substrate to be achieved, is difficult to self-diffuse, and its sintering temperature is limited because it is thermally decomposed at a high temperature, and for these reasons, it is not easy to sinter into a substrate, and it is difficult to achieve a substrate that is overall uniformly nitrided, and thus, in order to solve the above-mentioned difficulties and improve the physical properties of the silicon nitride substrate by removing impurities such as oxygen, a ceramic composition in which a crystal phase control powder is mixed in the metal silicon powder is used as the raw material powder. For example, as the crystal phase control powder, a rare earth element-containing compound, an alkaline earth metal oxide, and a combination thereof can be used, and specifically, at least one 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 application, in order to more easily achieve sintering and crystal phase control of the silicon nitride substrate, it is necessary for the crystal phase control powder to contain magnesium oxide and yttrium oxide, and the above-mentioned magnesium oxide and yttrium oxide have the advantage of allowing the manufactured silicon nitride substrate to have a higher density that is more densified, and further improving the thermal conductivity coefficient by reducing the amount of residual grain boundary phase in sintering.

[0042] In addition, in order to improve the mechanical strength in correspondence with thermal stress or thermal shock of increasingly severe semiconductor manufacturing processes, the above-mentioned ceramic composition containing silicon can further contain a strength enhancement powder including at least one of iron oxide (Fe2O3) and titanium oxide (TiO2), and preferably, the strength enhancement powder can contain both iron oxide and titanium oxide.

[0043] In particular, the heat treatment step to be described below is implemented in one sintering furnace by a continuous heat treatment step instead of nitriding and sintering in separate furnaces, and a combination of magnesium oxide and yttrium oxide or a combination of magnesium oxide, yttrium oxide, iron oxide, and titanium oxide can be used to nitride the silicon metal powder into silicon nitride and sinter it. In other words, instead of nitriding and sintering in separate furnaces or cooling and sintering after nitriding in a one-step process, nitriding and sintering are implemented in one step after the silicon-containing ceramic composition is loaded into the furnace, and in this one-step process, densification of the sintered body in which the entire shaped body is uniformly nitrided without silicon dissolution can not be easily achieved, but the above-mentioned crystal control powder included in the ceramic composition or the strength-enhancing powder included together with the crystal control powder can be used to achieve a uniformly nitrided and densified sintered body. For this purpose, preferably, the ceramic composition can include 2 to 5 mol% of the above-mentioned yttrium oxide and 2 to 10 mol% (preferably, 4 to 8 mol%) of the above-mentioned magnesium oxide. In addition, when further containing iron oxide and titanium oxide, 0.1 to 3 mol% of iron oxide and 1 to 5 mol% of titanium oxide can be further included with respect to the total number of moles of the ceramic composition, whereby even if a nitriding-sintering one-step process is performed, it can have a more improved mechanical strength. If the content of yttrium oxide is less than 2 mol%, it is difficult to achieve a densified substrate when sintered into a substrate, and it is difficult to trap oxygen at the grain boundaries, whereby the amount of solid-solution oxygen increases, so that the thermal conductivity of the sintered substrate can be low, and the mechanical strength can also be reduced. In addition, if the content of yttrium oxide exceeds 5 mol%, the amount of grain boundary phase increases, so that the thermal conductivity and fracture toughness of the silicon nitride substrate to be achieved can be reduced. In addition, when the content of magnesium oxide is less than 2 mol%, both the thermal conductivity and the mechanical strength of the silicon nitride substrate to be achieved can be low, there is a possibility of silicon dissolution during nitriding, and it can be difficult to manufacture a densified substrate. In addition, if the content of magnesium oxide exceeds 10 mol%, the amount of residual magnesium at the grain boundaries increases when sintered, which can reduce the thermal conductivity of the substrate to be achieved, is not easy to sinter, and the fracture toughness is reduced. In addition, if the content of iron oxide is less than 0.1 mol% and / or the content of titanium oxide is less than 1 mol%, the improvement in mechanical strength can be very small. In addition, if the content of iron oxide exceeds 3 mol% and / or the content of titanium oxide exceeds 5 mol%, the mechanical strength of the sintered body is reduced.

[0044] In addition, preferably, the above-mentioned yttrium oxide and magnesium oxide in the composition can have a molar ratio of 1:1.5 to 1:2.0, whereby it can be more advantageous to achieve the purpose of the present application.

[0045] In addition, the above-mentioned rare earth element-containing compound powder can have an average particle diameter of 0.1 to 1 μm, and the magnesium-containing compound powder can have an average particle diameter of 0.1 to 1 μm, whereby it can be more advantageous to achieve the purpose of the present application.

[0046] Second, a step of manufacturing a sheet-shaped molded body by forming a slurry after mixing a solvent and an organic binder in the prepared ceramic composition is performed.

[0047] As the above solvent and organic binder, any known solvent and organic binder used in the manufacture of a ceramic substrate or a ceramic green sheet can be used without limitation. Specifically, the above solvent functions to adjust the viscosity by dissolving the organic binder and dispersing the ceramic composition, and examples thereof can include 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, cumene, cyclohexanone, cyclopentanone, dimethyl sulfoxide, diethyl phthalate, toluene, and a mixture thereof, etc. At this time, 50 to 100 parts by weight of the above solvent is preferably mixed with respect to 100 parts by weight of the ceramic composition. If the content of the above solvent is less than 50 parts by weight, the viscosity of the slurry is high, and it is difficult to manufacture a molded body, and in particular, it is difficult to adjust the thickness of the molded body. If the content of the above solvent exceeds 100 parts by weight, the viscosity of the slurry is too thin, the drying time is prolonged, and it can be difficult to adjust the thickness of the molded body.

[0048] In addition, the above organic binder functions to bind the ceramic composition in the prepared slurry into a predetermined shape. 5 to 20 parts by weight of the above organic binder is preferably mixed with respect to 100 parts by weight of the above ceramic composition. The above organic binder can be a cellulose derivative such as ethyl cellulose, methyl cellulose, nitro cellulose, or carboxyl cellulose, or a polymer resin such as polyvinyl alcohol, acrylate, methacrylate, or polyvinyl butyral, and polyvinyl butyral can be used as the above organic binder in consideration of the formation of a sheet-shaped molded body by a tape casting method.

[0049] On the other hand, the above slurry can further include known materials contained in a slurry for manufacturing a molded body using ceramics, such as a dispersant and a plasticizer, etc., and there is no particular limitation thereto in the present application.

[0050] The manufactured slurry can be manufactured in a sheet shape, and at this time, the slurry can be implemented as a molded body using a known molding method. For example, the slurry can be manufactured using a known method such as a tape casting method, but is not limited thereto.

[0051] Next, the prepared shaped body is subjected to a heat treatment step.

[0052] Referring to Figure 1 , the shaped body is subjected to a heat treatment step including a nitriding section (S3) of silicon nitride (Si3N4) after the shaped body is installed in a sintering furnace and a sintering section (S5) of sintering the nitrided shaped body, and the above heat treatment step can further include a temperature rising section (S1, S2) performed before the nitriding section (S3), a temperature rising section (S4) performed between the nitriding section (S3) and the sintering section (S5), and a cooling section (S6) performed after the sintering section (S5).

[0053] In the manufacturing process according to the present application, the nitriding process of nitriding the shaped body into a silicon nitride shaped body and the sintering process of sintering the nitrided shaped body into a substrate are simultaneously performed in one heat treatment step. Conventionally, a silicon nitride substrate is generally implemented using a two-step method, i.e., silicon powder is manufactured into silicon nitride powder, and then the silicon nitride powder is used again to manufacture a silicon nitride substrate. However, the two-step method requires an additional cooling process and a grinding process of the silicon nitride powder after the silicon nitride powder is manufactured until sintering, and thus takes a long time to manufacture and increases manufacturing costs, which is not suitable for mass production. Nevertheless, the reason for using the two-step method as described above is because, when nitriding is performed in a small-sized powder state, silicon nitride powder having more uniform characteristics can be easily manufactured, thereby facilitating the securing of a silicon nitride substrate having uniform characteristics.

[0054] In the present application, the two-step method that has been inevitably adopted in the past to implement a substrate having uniform characteristics is dispensed with, and a silicon nitride substrate is manufactured by simultaneously performing a nitriding process and a sintering process using a one-step method as a heat treatment step, and thus not only the manufacturing time is significantly shortened, but also a silicon nitride substrate having uniform characteristics can be implemented, thereby completing the present application.

[0055] The above heat treatment step can be continuously performed from the nitriding section to the sintering section without stopping the heat treatment. In addition, since the shaped body shaped into a substrate shape is nitrided and then sintered from the beginning, rather than being nitrided in a powder state, a section of performing heat treatment at a temperature lower than the first temperature or cooling to a temperature lower than the first temperature can not be included between the above nitriding section and the sintering section.

[0056] On the other hand, as Figure 2As shown in part (a) of FIG. 1, the sheet-shaped molded body can be subjected to the heat treatment step in a state of a laminate 100 in which a plurality of the molded bodies 1, 2 are stacked. For example, the heat treatment step can be performed in a state in which two or more sheet-shaped molded bodies are stacked. At this time, the heat treatment step can be performed in a state in which the laminate 100 is arranged between boron nitride plates 10. In addition, a release agent such as boron nitride powder can be interposed between the stacked molded bodies 1, 2 to minimize or prevent adhesion between the molded bodies 1, 2 after the heat treatment. As described above, from the viewpoint of productivity, it is inevitable to perform the heat treatment step on a plurality of the molded bodies in a stacked state at one time. However, if the heat treatment is interrupted between the nitriding process and the sintering process during the heat treatment step on the plurality of the molded bodies, for example, due to movement of the laminate caused by change of the furnace and / or due to reasons such as release of vacuum or re-vacuum in the furnace, it is not possible to completely maintain the state of the laminate stacked before the heat treatment due to vibration occurring during the movement of the laminate or air pressure change at the time of re-vacuum, and the like, as shown in part (b) of FIG. 1. In addition, as shown in part (c) of FIG. 1, a part or the entire molded body is randomly moved in the horizontal direction so that the side end of the laminate 100 is zigzagged, which can cause a bending phenomenon in which the end portion of the molded body 1, 2 is bent. In addition, the bending phenomenon can cause an increase in defect rate such as reduction in bending strength, reduction in flatness, and the like. Therefore, when the heat treatment step is continuously performed without movement of the molded body due to change of the furnace and in a state in which the vacuum is not released and re-vacuumed after the furnace is evacuated, not only is the manufacturing time shortened, but there is also an advantage in that problems such as the bending phenomenon or reduction in bending strength and flatness of the end portion of the silicon nitride substrate are minimized or prevented after the heat treatment step. Figure 2 As shown in part (b) of FIG. 1, a part or the entire molded body is randomly moved in the horizontal direction so that the side end of the laminate 100 is zigzagged, which can cause a bending phenomenon in which the end portion of the molded body 1, 2 is bent. In addition, the bending phenomenon can cause an increase in defect rate such as reduction in bending strength, reduction in flatness, and the like. Therefore, when the heat treatment step is continuously performed without movement of the molded body due to change of the furnace and in a state in which the vacuum is not released and re-vacuumed after the furnace is evacuated, not only is the manufacturing time shortened, but there is also an advantage in that problems such as the bending phenomenon or reduction in bending strength and flatness of the end portion of the silicon nitride substrate are minimized or prevented after the heat treatment step.

[0057] The heat treatment step will be described in detail as follows, that is, the prepared molded body is installed in a furnace, and then the heat treatment can be performed at a predetermined temperature increasing rate or at a different temperature increasing rate until a nitriding zone (S3). At this time, a debinding process can be performed to remove organic compounds such as organic binders and the like in the molded body. However, if the content of the organic binder is low, the debinding can be omitted.

[0058] Specifically, in the debinding process, after the prepared shaped body is installed in a debinding furnace, the debinding can be performed by heating from a heat treatment starting temperature to 900°C at a predetermined temperature increasing rate or at different temperature increasing rates. In addition, the debinding process can be performed in a known atmosphere, for example, in an atmospheric atmosphere and / or a nitrogen atmosphere, and the specific atmosphere can be appropriately selected in consideration of the type and content of the organic binder used, etc. However, in consideration of the composition of the shaped body, the type and content of the organic binder, etc., it is preferable that the debinding be performed in an atmospheric atmosphere in a temperature range from the heat treatment starting temperature to 450°C and in a nitrogen atmosphere in a temperature range from 450°C to 900°C, whereby it is possible to facilitate the minimization or complete removal of carbon components remaining in the shaped body after the debinding process. The heat treatment starting temperature can be room temperature, for example, 20°C to 25°C. In addition, in the above heat treatment, the temperature can be increased to 450°C at a rate of 2°C / min to 8°C / min, and from 450°C to 900°C at a rate of 2°C / min to 8°C / min, and the temperature increasing rate from 450°C and the temperature increasing rate from 450°C to 900°C can be the same or different.

[0059] In addition, after the above debinding process is performed, the shaped body that has undergone the debinding process can also be subjected to a secondary debinding at 900°C to 1000°C. At this time, in the range from 900°C to 1000°C, the temperature is increased at a rate of 1°C / min to 10°C / min, more preferably at a low rate of 1°C / min to 3°C / min, and the pressure is 0.1 MPa to 0.2 MPa, more preferably 0.14 MPa to 0.17 MPa.

[0060] After that, according to a preferred embodiment of the present application, from a predetermined temperature (T1) to a first temperature (T2), specifically, while nitrogen gas is applied at a predetermined pressure from a temperature of 1000 ± 20°C to the first temperature (T2), the temperature can be increased at a relatively slow rate, specifically, while the nitrogen gas is applied at a pressure of 0.1 to 0.2 MPa, more preferably at a pressure of 0.14 to 0.18 MPa. In addition, the temperature can be increased at a rate of 0.1°C / min to 2.0°C / min, more preferably at a rate of 0.5°C / min to 1.0°C / min. If the nitrogen gas pressure is less than 0.1 MPa, even if the nitriding range (S3) is passed, the shaped body can not be completely nitrided, and thus there can be a portion that is not nitrided. In addition, if the nitrogen gas pressure exceeds 0.2 MPa, a phenomenon of silicon elution can occur, and the thermal conductivity and mechanical strength of the substrate can be reduced. In addition, if the temperature increasing rate from 1000 ± 20°C to the first temperature is less than 0.1°C / min, the time required for the heat treatment step can be excessively long. In addition, if the temperature increasing rate exceeds 2.0°C / min, silicon elution occurs, and thus it is difficult to manufacture a substrate that is completely nitrided to silicon nitride.

[0061] Meanwhile, after the molding body is loaded into a furnace, for example, until a temperature of 800°C or less, there is no limitation on the temperature increasing rate, and a temperature increasing condition applied when nitriding a general silicon substrate or silicon powder can be used, for example, the temperature can be increased at a rate of 4°C / min to 30°C / min. In addition, in this range, the temperature can be increased under an inert gas or nitrogen atmosphere.

[0062] Then, after continuously heating to increase the temperature to the first temperature (T2), a nitriding process corresponding to a nitriding range (S3) in which heat treatment is performed at the first temperature (T2) while applying nitrogen gas at a predetermined pressure is performed. The above first temperature (T2) can be a predetermined temperature in the range of 1300°C to 1500°C, and preferably, can be in the range of 1400°C to 1500°C. If the first temperature (T2) is less than 1300°C, nitriding can not be uniformly achieved. In addition, if the first temperature (T2) exceeds 1500°C, a β crystal phase is rapidly formed, and thus it is difficult to densify the substrate.

[0063] In addition, the pressure of the nitrogen gas applied in the nitriding range (S3) can be 0.1 MPa to 0.2 MPa, and more preferably, can be 0.14 MPa to 0.18 MPa. If the nitrogen gas pressure is less than 0.1 MPa, nitriding can not occur completely, and thus there can be a portion that is not nitrided. In addition, if the nitrogen gas pressure exceeds 0.2 MPa, a phenomenon in which silicon is dissolved can occur during nitriding, and the thermal conductivity and mechanical strength of the substrate can be reduced. In addition, the nitriding process can be performed for 2 hours to 10 hours, and more preferably, can be performed for 1 hour to 4 hours. On the other hand, the time of the nitriding process can be appropriately adjusted according to the first temperature (T2).

[0064] In addition, according to an embodiment of the present application, the pressure of the nitrogen gas applied from the above 1000±20°C to the above first temperature can be lower than the pressure of the nitrogen gas applied in the nitriding range, and thus nitriding can be more uniformly achieved, and a substrate having excellent appearance and mechanical strength can be advantageously achieved.

[0065] Further, after the nitriding process, heat treatment can be performed at a predetermined temperature increase rate until a second temperature (T3) at which the sintering process is performed. At this time, according to a preferred embodiment of the present application, the temperature can be increased at a slower rate while nitrogen is applied at a predetermined pressure from the first temperature (T2) to the second temperature (T3), and specifically, the temperature can be increased at a rate of 0.1°C / min to 10.0°C / min while nitrogen is applied at a pressure of 0.1 MPa to 1.0 MPa. If the nitrogen pressure is less than 0.1 MPa, it can be difficult to suppress the decomposition of silicon nitride. In addition, if the nitrogen pressure exceeds 1.0 MPa, problems can occur in the pressure resistance of the furnace. In addition, if the temperature is increased at a rate of less than 0.1°C / min from the first temperature (T2), the time required for the heat treatment step can be excessively long. In addition, when the temperature increase rate exceeds 10.0°C / min, rapid transition to the β phase occurs, thereby making it difficult to control the crystal, such as non-uniform growth of the β phase crystal, and the resulting substrate can be difficult to have the required physical properties.

[0066] According to an embodiment of the present application, the temperature increase interval from the first temperature (T2) to the second temperature (T3) can be divided into two intervals, thereby making it possible to manufacture a substrate having more excellent physical properties.

[0067] Specifically, between the above-described nitriding interval and the sintering interval, a first shrinkage interval in which the temperature is increased at a rate of 0.1°C / min to 10.0°C / min while nitrogen is applied at a pressure of 0.15 MPa to 0.3 MPa from the first temperature (T2) to 1700±20°C, and a second shrinkage interval in which the temperature is increased at a rate of 1°C / min to 10°C / min while nitrogen is applied at a pressure of 0.8 MPa to 0.98 MPa from 1700±20°C to the second temperature (T3) can be further included.

[0068] At this time, the nitrogen pressure in the first shrinkage interval can be 0.15 MPa to 0.3 MPa, and the nitrogen pressure in the second shrinkage interval can be 0.8 MPa to 0.9 MPa. In addition, the temperature increase rate of the first shrinkage interval can be 0.1°C / min to 10°C / min, and more preferably, can be 0.1°C / min to 2°C / min. In addition, in the second shrinkage interval, the temperature can be increased at a rate of 1°C / min to 10°C / min, and more preferably, at a rate of 1°C / min to 5°C / min, thereby easily achieving the object of the present application.

[0069] Next, the sintering process performed after reaching the second temperature (T3) will be described.

[0070] The above-mentioned second temperature (T3) can be selected in the range of 1700°C to 1900°C. If the temperature is lower than 1700°C, the shaped body can not be sufficiently densified. In addition, if the temperature exceeds 1900°C, there can be a problem of excessive growth and / or uneven growth of the particles, and the mechanical strength of the substrate realized can be reduced.

[0071] At this time, the sintering time can be adjusted according to the range of the above-mentioned second temperature (T3), and if the second temperature (T3) is lower, sintering can be performed for a longer time, and conversely, if the second temperature (T3) is higher, sintering can be performed for a shorter time than the sintering time under low temperature conditions. For example, the above-mentioned sintering can be performed for 2 hours to 10 hours, and more preferably, for 4 hours to 8 hours, whereby it can be advantageous to achieve the object of the present application.

[0072] In addition, the above-mentioned sintering process can also be performed under a nitrogen atmosphere, and the nitrogen pressure at this time can be the atmosphere condition employed when sintering the silicon nitride shaped body, for example, the nitrogen can be applied at a pressure of 0.1 MPa or more, more preferably, at a pressure of 0.9 MPa to 1.0 MPa, and even more preferably, at a pressure of 0.9 MPa to 0.98 MPa, whereby it can be more advantageous to achieve a high-quality silicon nitride substrate.

[0073] The substrate of the sintering section (S5) that has undergone the heat treatment step can then be further subjected to a cooling section (S6), and the above-mentioned cooling section (S6) can employ the usual cooling condition after sintering of the silicon nitride substrate, and there is no particular limitation thereto in the present application.

[0074] On the other hand, the thermal conductivity of the silicon nitride substrate realized by the above-mentioned production method can be 75 W / mK or more, preferably 80 W / mK or more, and more preferably 90 W / mK or more, and the three-point bending strength can be 650 MPa or more, preferably 680 MPa or more, and more preferably 700 MPa or more, and further preferably 750 MPa or more.

[0075] In addition, when the silicon content of the substrate is preferably 6% by weight or less, more preferably 4% by weight or less, and even more preferably 0% by weight, the substrate can have improved mechanical strength and thermal conductivity.

[0076] The present application will be described in more detail by the following examples, but the following examples should not be construed as limiting the scope of the present application, but as being helpful in understanding the present application.

[0077] <Example 1>

[0078] A polysilicon waste material (purity: 99.99%, resistivity: 1 Ω-cm) from a jig for semiconductor process was dry-pulverized using an airflow pulverizer to produce a metal silicon powder having an average particle diameter of 4 μm. Among them, 3 mol% of yttria having an average particle diameter of 0.5 μm and 5 mol% of magnesium oxide having an average particle diameter of 0.5 μm were mixed to prepare a ceramic composition. A slurry for manufacturing a substrate was prepared by mixing 100 parts by weight of the prepared ceramic composition with 80 parts by weight of ethanol as a solvent and 10 parts by weight of polyvinyl butyral as an organic binder, and a sheet-shaped molded body was manufactured using a tape casting method. Then, four of the manufactured molded bodies were laminated and installed in a furnace, and heat-treated under a nitrogen atmosphere, specifically, warmed up to 900°C at a temperature increasing rate of 5°C / min under a pressure of 0.15 MPa, and from 900°C to 1000°C at a temperature increasing rate of 1.2°C / min. Then, warmed up to 1460°C as a first temperature at a temperature increasing rate of 0.5°C / min under a nitrogen pressure of 0.15 MPa, and heat-treated at 1460°C as the first temperature under a nitrogen pressure of 0.17 MPa for 2 hours, thereby obtaining a nitrided substrate. Thereafter, warmed up to 1700°C at a temperature increasing rate of 1°C / min under a nitrogen pressure of 0.2 MPa, and from 1700°C to 1850°C as a second temperature at a temperature increasing rate of 4°C / min under a nitrogen pressure of 0.9 MPa, and sintered at 1850°C and 0.9 MPa for 5 hours, thereby manufacturing a silicon nitride substrate having a final thickness of 170 μm.

[0079] <Examples 2 to 12 and Comparative Examples 1 to 4>

[0080] Except for changing the first temperature, the second temperature, the nitriding zone pressure, the yttria content, and the magnesium oxide content, the silicon nitride substrates shown in Tables 1 to 3 below were manufactured in the same manner as in Example 1 above.

[0081] <Experimental Examples>

[0082] The following physical properties of the silicon nitride substrates manufactured in Examples 1 to 12 and Comparative Examples 1 to 4 were evaluated, and the results are shown in Tables 1 to 3 below.

[0083] 1. Three-point bending strength evaluation

[0084] The three-point bending strength was measured for the silicon nitride substrates manufactured according to the examples and the comparative examples as follows, i.e., two support points 20 mm apart were supported on a sample using an AGS-1000D (Shimadzu Corporation, Japan) as a universal testing machine in accordance with the international standard ASTM C 1161-02C (Standard Test Method for Flexural Strength of Advanced Ceramics at Ambient Temperatures), and a load was applied on the middle point thereof by a crosshead moving at a speed of 1 mm per minute. Once the maximum load at which the sample was broken was measured, the bending strength was calculated by the following Formula 1.

[0085] [Formula 1]

[0086] Bending strength (σ) = 3 x P x L / 2 x w x t2

[0087] In the above Formula 1, P denotes the maximum load, L denotes the sample length, w denotes the sample width, and t denotes the sample thickness.

[0088] 2. Thermal conductivity measurement

[0089] In order to measure the thermal conductivity for the silicon nitride substrates manufactured according to the examples and the comparative examples in accordance with the international standard ASTM E1461 (Standard Method for Thermal Diffusivity Measurement by Flash Method), a sample having a thickness of about 500 μm was manufactured into a 10 mm x 10 mm square, the thermal diffusivity was measured by a flash method (laser flash instrument, NETZCH, Germany), and was calculated by the following Formula 2.

[0090] [Formula 2]

[0091] Thermal conductivity (k) = α x p x Cp

[0092] In the above Formula 2, α denotes the thermal diffusivity (mm 2 / S), p denotes the density (g / cm 3 ), and Cp denotes the heat capacity (J / (kg K)).

[0093] 3. Post-sintering surface state evaluation

[0094] For the silicon nitride substrates manufactured according to the examples and the comparative examples, the post-sintering surface state was evaluated using a method of confirming the reaction degree of a sintered body by a phenomenon in which silicon is not completely nitrided but is melted and dissolved, (however, since a sample through which the phenomenon of dissolution occurs cannot manufacture a sample capable of measuring the thermal conductivity and the three-point bending strength, physical properties cannot be measured).

[0095] Table 1

[0096]

[0097]

[0098] Table 2

[0099]

[0100] Table 3

[0101]

[0102] As apparent from Tables 1 to 3, Examples 1 to 3, Example 5, Example 7 and Example 9, which satisfy the first temperature, the second temperature, the pressure in the nitriding zone, the content of yttria and the content of magnesia according to the present application, can achieve excellent mechanical strength and thermal conductivity and good surface state at the same time, as compared with Examples 4, 6, 8, 10 to 12 and Comparative Examples 1 to 4, which do not satisfy any of them.

[0103] The present application has been described above with reference to one embodiment thereof, but the gist of the present application is not limited to the embodiment described in the present specification, and those skilled in the art can easily propose other embodiments by adding, modifying, deleting, increasing, etc. of the constituent elements within the scope of the gist, and these belong to the scope of the gist of the present application.

Claims

1. A method for manufacturing a silicon nitride substrate, characterized in that, include: The step of preparing a ceramic composition comprising metallic silicon powder, a rare earth element compound containing yttrium oxide in a molar ratio of 1:1.5 to 2.0, and a phase-controlling powder containing a magnesium compound, wherein the magnesium compound is magnesium oxide; The step of manufacturing a sheet-like molded body using a slurry prepared by mixing the above-described ceramic composition with a solvent and an organic binder; and The heat treatment includes a nitriding zone in which nitrogen gas is applied to the molded body at a pressure of 0.14 to 0.18 MPa while heat treatment is performed at a first temperature in the range of 1300°C to 1500°C; a first shrinkage zone in which the temperature is raised from the first temperature to 1700±20°C at a nitrogen pressure of 0.15 to 0.30 MPa at a rate of 0.1 to 10.0°C / min; and a sintering zone in which heat treatment is performed at a second temperature in the range of 1700°C to 1900°C. In the heat treatment step described above, nitrogen gas is applied at a pressure of 0.14 to 0.18 MPa from 1000±20°C to the first temperature, while the temperature is increased at a rate of 0.5 to 1°C / minute.

2. The method for manufacturing a silicon nitride substrate according to claim 1, characterized in that, The aforementioned metallic silicon powder is produced by dry grinding of polycrystalline metallic silicon waste or monocrystalline silicon wafer waste in order to minimize contamination from metallic impurities during the grinding process.

3. The method for manufacturing a silicon nitride substrate according to claim 1, characterized in that, The resistivity of the aforementioned metallic silicon powder ranges from 1 Ω·cm to 100 Ω·cm.

4. The method for manufacturing a silicon nitride substrate according to claim 2, characterized in that, The purity of the aforementioned polycrystalline silicon waste or monocrystalline silicon wafer waste is above 99%.

5. The method for manufacturing a silicon nitride substrate according to claim 1, characterized in that, The average particle size of the aforementioned metallic silicon powder is 0.5 μm to 4 μm, the average particle size of the rare earth element compound powder is 0.1 μm to 1 μm, and the average particle size of the magnesium compound powder is 0.1 μm to 1 μm.

6. The method for manufacturing a silicon nitride substrate according to claim 1, characterized in that, The ceramic composition comprises 2 mol% to 5 mol% of the above-mentioned yttrium oxide and 2 mol% to 10 mol% of the above-mentioned magnesium oxide.

7. The method for manufacturing a silicon nitride substrate according to claim 1, characterized in that, The above heat treatment steps are performed continuously from the nitriding zone to the sintering zone.

8. The method for manufacturing a silicon nitride substrate according to claim 1, characterized in that, The above nitriding interval is carried out for 2 to 10 hours.

9. The method for manufacturing a silicon nitride substrate according to claim 1, characterized in that, The pressure of nitrogen applied from 1000±20℃ to the first temperature is lower than the pressure of nitrogen applied in the nitriding range.

10. The method for manufacturing a silicon nitride substrate according to claim 1, characterized in that, Between the first shrinkage zone and the sintering zone, there is also a second shrinkage zone where nitrogen is applied at a pressure of 0.80 MPa to 0.98 MPa while the temperature is increased at a rate of 1°C / min to 10°C / min, from 1700±20°C to the second temperature.

11. The method for manufacturing a silicon nitride substrate according to claim 1, characterized in that, The above heat treatment steps are performed by stacking multiple sheet-like molded bodies.

12. A silicon nitride substrate, characterized in that, Manufactured by the manufacturing method according to any one of claims 1 to 11, the thermal conductivity is 75 W / mK or higher, and the three-point bending strength is 700 MPa or higher.

Images