Method for Adjusting Thermal Conductivity and Bending Strength of Silicon Nitride Substrate

Abstract

The present invention relates to a method for adjusting the physical properties of a silicon nitride substrate, and more specifically, includes a step of manufacturing a silicon nitride substrate and a step of adjusting the remaining amount of magnesium in the silicon nitride substrate. The thermal conductivity of the silicon nitride substrate is inversely proportional to the remaining amount of magnesium in the silicon nitride substrate, and the flexural strength of the silicon nitride substrate is proportional to the remaining amount of magnesium in the silicon nitride substrate.

Description

Technical Field

[0001] The present invention relates to a method for adjusting the physical properties of a silicon nitride substrate, and more particularly, to a method for adjusting the thermal conductivity and flexural strength of a silicon nitride substrate.

Background Art

[0002] Ceramic materials having high electrical insulation and thermal conductivity can be used as a heat medium for quickly transferring the heat generated by an element. Ceramic materials are used as substrates for elements for transportation equipment, substrates for high-integration electronic circuits, heat dissipation components for laser oscillation units, components of reaction vessels for semiconductor manufacturing equipment, and precision mechanical components.

[0003] In particular, ceramic substrates used for high-power elements are required to have high insulation, high breakdown voltage, high thermal conductivity, high strength, and low dielectric constant. Suitable ceramic substrates for these requirements include aluminum nitride substrates, alumina substrates, and silicon nitride substrates.

[0004] A silicon nitride (Si3N4) substrate has high strength (500 MPa to 800 MPa), high toughness (5 MPa·m to 8 MPa·m), and excellent thermal expansion coefficient compatibility with silicon (Si). Furthermore, the silicon nitride (Si3N4) substrate has high thermal conductivity (70 W / mK to 170 W / mK). That is, the silicon nitride (Si3N4) substrate is suitable as a material for next-generation high-power elements.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a method for adjusting the thermal conductivity of a silicon nitride substrate.

[0006] Another problem to be solved by the present invention is to provide a method for adjusting the flexural strength of a silicon nitride substrate.

Means for Solving the Problems

[0007] A method for adjusting the thermal conductivity of a silicon nitride substrate according to the concept of the present invention may include a step of manufacturing a silicon nitride substrate and a step of adjusting the remaining amount of magnesium in the silicon nitride substrate. The step of manufacturing the silicon nitride substrate includes a step of mixing silicon nitride powder, a ceramic additive containing magnesium oxide, and a solvent to form a slurry, a step of molding the slurry to form a sheet, a step of sandwiching at least one said sheet between a lower plate and an upper plate to form a laminated structure, a step of subjecting the laminated structure to a degreasing process, and a step of subjecting the laminated structure to a sintering process. The thermal conductivity of the silicon nitride substrate can be inversely proportional to the remaining amount of magnesium in the silicon nitride substrate.

[0008] A method for adjusting the flexural strength of a silicon nitride substrate according to another concept of the present invention may include a step of manufacturing a silicon nitride substrate and a step of adjusting the remaining amount of magnesium in the silicon nitride substrate. The step of manufacturing the silicon nitride substrate includes a step of mixing silicon nitride powder, a ceramic additive containing magnesium oxide, and a solvent to form a slurry, a step of molding the slurry to form a sheet, a step of sandwiching at least one said sheet between a lower plate and an upper plate to form a laminated structure, a step of subjecting the laminated structure to a degreasing process, and a step of subjecting the laminated structure to a sintering process. The flexural strength of the silicon nitride substrate can be proportional to the remaining amount of magnesium in the silicon nitride substrate.

Advantages of the Invention

[0009] The present invention has clarified that the most important factor determining the physical properties (thermal conductivity and flexural strength) of the finally manufactured silicon nitride substrate is the remaining amount of magnesium. The present invention can easily control the final remaining amount of magnesium by various and simple methods during the manufacturing process of the silicon nitride substrate. As a result, the present invention can be easily controlled so that the silicon nitride substrate has the desired physical properties (thermal conductivity and flexural strength).

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4a

Figure 4b

Figure 4c

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Modes for Carrying Out the Invention

[0011] To fully understand the configuration and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and can be embodied in various forms and various modifications can be made. However, it is provided by the description of the present embodiment to make the disclosure of the present invention complete and to fully inform those with ordinary knowledge in the technical field to which the present invention belongs of the scope of the invention.

[0012] In various embodiments of this specification, terms such as first, second, third, etc. are used to describe various components, but these components should not be limited by these terms. These terms are merely used to distinguish one component from another. The embodiments described and illustrated herein also include their complementary embodiments.

[0013] The terms used in this specification are for the purpose of describing embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless specifically stated otherwise in the text. The terms "comprises" and / or "comprising" mentioned in the specification do not exclude the presence or addition of one or more other components.

[0014] FIG. 1 is a flowchart for explaining a method of adjusting the thermal conductivity and / or flexural strength of a silicon nitride substrate according to an embodiment of the present invention.

[0015] Referring to FIG. 1, a method of adjusting the thermal conductivity and / or flexural strength of a silicon nitride substrate according to the present invention may include a step of manufacturing a silicon nitride substrate (S100) and a step of adjusting the remaining amount of magnesium in the silicon nitride substrate (S200).

[0016] In one embodiment of the present invention, the concentration of magnesium (Mg) in the silicon nitride substrate can be inversely proportional to the thermal conductivity of the silicon nitride substrate. In other words, the higher the concentration of magnesium (Mg) in the silicon nitride substrate, the lower the thermal conductivity may be. In one embodiment of the present invention, the concentration of magnesium (Mg) in the silicon nitride substrate can be proportional to the flexural strength of the silicon nitride substrate. In other words, the higher the concentration of magnesium (Mg) in the silicon nitride substrate, the higher the flexural strength may be.

[0017] As a conclusion, according to the present invention, by controlling the residual amount of magnesium (Mg) in the silicon nitride substrate, the thermal conductivity and / or bending strength of the silicon nitride substrate can be adjusted. Hereinafter, with reference to FIGS. 2 to 9, the step (S100) of manufacturing the silicon nitride substrate will be described in more detail.

[0018] FIG. 2 is a flowchart for explaining a method of manufacturing a silicon nitride substrate according to an embodiment of the present invention. Referring to FIG. 2, the method of manufacturing a silicon nitride substrate according to an embodiment of the present invention may include a first step (S110) of preparing a ceramic additive, a second step (S120) of mixing silicon nitride powder, a ceramic additive, and a solvent to form a slurry, a third step (S130) of molding the slurry in a tape casting process to form a sheet, a fourth step (S140) of laminating the sheets to perform a laminating process to form a laminated sheet, a fifth step (S150) of sandwiching the laminated sheet (SSH) between a lower plate and an upper plate to form a laminated structure, a sixth step (S160) of performing a debinding process on the laminated structure, and a seventh step (S170) of performing a sintering process on the laminated structure.

[0019] FIG. 3 is a schematic diagram for explaining the first step of FIG. 2.

[0020] Referring to FIGS. 2 and 3, a first ball (BA1) and a first mixture (MI1) can be provided in a first container (CON1). The first mixture (MI1) may include ceramic powder and a solvent. Specifically, the first ball (BA1) and the solvent can be placed in the first container (CON1). Ceramic powder can be added to the solvent. The first ball (BA1) may include ceramics such as zirconia. The solvent is an organic solvent and may include, for example, ethanol. The ceramic powder may include yttrium oxide (Y2O3) and magnesium oxide (MgO).

[0021] The first mixture (MI1) may be mixed in a mixing device so that the ceramic powder is uniformly mixed within the first mixture (MI1). The first ball (BA1) can physically assist in uniformly mixing the ceramic powder. Specifically, the powders of yttrium oxide and magnesium oxide may be uniformly mixed within the first mixture (MI1).

[0022] After the mixing is completed, the first ball (BA1) can be removed. The first mixture (MI1) can be dried to evaporate any solvents. As a result, a powdery ceramic additive (SA) can be obtained (S110). The ceramic additive (SA) may contain yttrium oxide (Y2O3) and magnesium oxide (MgO).

[0023] In one embodiment of the present invention, the ceramic additive (SA) may consist only of yttrium oxide (Y2O3) and magnesium oxide (MgO). In another embodiment of the present invention, the ceramic additive (SA) may further contain not only yttrium oxide (Y2O3) and magnesium oxide (MgO) but also a further oxide (for example, zirconium oxide).

[0024] The mass ratio of the yttrium oxide (Y2O3) to the ceramic additive (SA) may be 0.3 to 0.5. The mass ratio of the magnesium oxide (MgO) to the ceramic additive (SA) may be 0.5 to 0.7. The atomic ratio of magnesium (Mg) to yttrium (Y) in the ceramic additive (SA) may be 1 to 5. More specifically, the atomic ratio of magnesium (Mg) to yttrium (Y) may be 2 to 5. In other words, the number of magnesium atoms in the ceramic additive (SA) may be 1 to 5 times, more specifically, 2 to 5 times the number of yttrium atoms.

[0025] Figures 4a to 4c are schematic diagrams for explaining the second stage of Figure 2.

[0026] Referring to FIGS. 2 and 4a, a solvent (SV) and a second ball (BA2) can be provided in a second container (CON2). The solvent (SV) is an organic solvent and may include, for example, isopropyl alcohol and toluene. Isopropyl alcohol and toluene may be mixed at a volume ratio of 4:6. The second ball (BA2) may include silicon nitride.

[0027] Silicon nitride (Si3N4) powder (SNP), a ceramic additive (SA), and a dispersant (DIS) can be put into the solvent (SV) of the second container (CON2) to prepare a second mixture (MI2). The ceramic additive (SA) may be the one prepared in the previous first step (S110). As the dispersant (DIS), a commercially available dispersant (DIS) can be used, for example, BYK-111 can be used.

[0028] The solvent (SV) may have 40 Vol% to 60 Vol% with respect to the total volume of the second mixture (MI2). The silicon nitride powder (SNP) may have 15 Vol% to 25 Vol% with respect to the total volume of the second mixture (MI2). The ceramic additive (SA) may have 5 wt% to 10 wt% with respect to the mass of the second mixture (MI2). More specifically, the ceramic additive (SA) may have 5 wt% to 7 wt% with respect to the mass of the second mixture (MI2).

[0029] When the content of the ceramic additive (SA) in the second mixture (MI2) exceeds 10 wt%, the physical properties (e.g., thermal conductivity) of the manufactured silicon nitride substrate may be greatly reduced. Also, the purity of the silicon nitride substrate may decrease. Therefore, the input amount of the ceramic additive (SA) can be strictly limited to 5 wt% to 10 wt%, more preferably 5 wt% to 7 wt%.

[0030] A first ball milling process can be performed on the second mixture (MI2) to uniformly mix the second mixture (MI2). The second ball can physically assist in uniformly mixing the second mixture (MI2).

[0031] Specifically, the first ball milling process may include rotating a second container containing the second mixture (MI2) at a constant speed using a ball milling machine. While the second container is rotating, mechanical grinding and uniform mixing can be performed by the second balls in the second container. The rotation speed of the ball milling machine may be 100 rpm to 500 rpm.

[0032] Referring to FIGS. 2 and 4b, after the first ball milling process, a binder (BI) and a plasticizer (PL) can be added to the second mixture (MI2) to prepare a third mixture (MI3). The binder (BI) may include at least one of cellulose derivatives such as ethyl cellulose, methyl cellulose, nitrocellulose, carboxymethyl cellulose, resins such as polyvinyl alcohol, acrylic esters, methacrylic esters, polyvinyl butyral, and mixtures of the derivatives and the resins. For example, the binder (BI) may include polyvinyl butyral (PVB). The plasticizer (PL) may include dibutyl phthalate or dioctyl phthalate. The mass of the plasticizer (PL) added may be about 50% of the mass of the binder (BI) added. Further, a solvent can be further added to the second mixture (MI2).

[0033] A second ball milling process can be performed on the third mixture (MI3) to uniformly mix the third mixture (MI3). By uniformly mixing the third mixture (MI3) through the second ball milling process, a slurry (SL) can be formed (S120). The second ball milling process may be substantially the same as or similar to the aforementioned first ball milling process. Thereafter, the second ball can be removed.

[0034] Referring to FIGS. 2 and 4c, the slurry (SL) formed in the second ball milling process can be aged to remove volatile gases from the slurry (SL). While aging the slurry (SL), the slurry (SL) can be stirred using a stirrer (SIT). The aging can be performed for about 24 hours.

[0035] FIG. 5 is a schematic diagram for explaining the third stage of FIG. 2.

[0036] Referring to FIGS. 2 and 5, the slurry (SL) prepared in the second stage (S120) can be formed into a sheet (SH) by a tape casting process (S130). Specifically, in the tape casting process, the slurry (SL) can be poured onto a blade set at a constant dam height and applied onto a moving substrate film. The solvent can be volatilized from the slurry (SL) applied onto the substrate film, and then removed to obtain a sheet (SH) formed body. As the substrate film, a polymer tape such as a stainless steel tape, an oil paper tape, or a polyester can be used. For example, the slurry (SL) can be poured onto a doctor blade set at a dam height of about 0.3 mm and applied onto a substrate film moving at a predetermined speed (e.g., 0.1 m / min to 1 m / min). Thereafter, a drying process and a process of removing the substrate film are performed to obtain the sheet (SH).

[0037] The tape casting process can be carried out at 30°C to 80°C. The sheet (SH) formed in the tape casting process can be cut into an appropriate size. The thickness of the sheet (SH) may be 0.1 mm to 0.16 mm.

[0038] The sheet (SH) may have a size of M X N. Each of the M and N may be 60 mm to 300 mm, but is not particularly limited. That is, each of M and N can be changed according to the size of the target substrate.

[0039] Figure 6 is a schematic diagram for explaining the fourth step of Figure 2.

[0040] Referring to Figures 2 and 6, a plurality of sheets (SH) prepared in the third step (S130) can be laminated. A lamination process can be performed on the laminated sheets (SH) to form a laminated sheet (SSH) (S140). In one example, 3 to 5 sheets (SH) can be laminated to form a laminated sheet (SSH). The lamination process can be carried out at a pressure of about 10 MPa and a temperature of about 60°C.

[0041] The laminated sheet (SSH) can be pressurized. The pressurization process can use warm isostatic press (WIP). The pressurization process can be carried out at a pressure of about 30 MPa and a temperature of about 70°C. Finally, the thickness (TH) of the laminated sheet (SSH) may be 0.3 mm to 4 mm.

[0042] The laminated sheet (SSH) is formed by overlapping the sheets (SH), and the size of the laminated sheet (SSH) may also be substantially the same as the size of the sheet (SH). In other words, the laminated sheet (SSH) may have a size of M X N. Each of the M and N may be 60 mm to 300 mm.

[0043] Figure 7 is a schematic diagram for explaining the fifth step of Figure 2.

[0044] Referring to FIGS. 2 and 7, a laminated structure (SS) can be prepared. The laminated structure (SS) may include a lower plate (PLT1), an upper plate (PLT2), and a laminated sheet (SSH) interposed therebetween. Preparing the laminated structure (SS) may include sandwiching the laminated sheet (SSH) prepared in the fourth step (S140) between the lower plate (PLT1) and the upper plate (PLT2) (S150). In FIG. 7, an example is shown in which one laminated sheet (SSH) is interposed between the lower plate (PLT1) and the upper plate (PLT2), but the present invention is not limited thereto. For example, two or more laminated sheets (SSH) may be interposed between the lower plate (PLT1) and the upper plate (PLT2).

[0045] Before preparing the laminated structure (SS), boron nitride (BN) can be uniformly applied to the laminated sheet (SSH). The lower plate (PLT1) and the upper plate (PLT2) may contain boron nitride.

[0046] FIG. 8 is a schematic diagram for explaining the sixth step of FIG. 2.

[0047] Referring to FIGS. 2 and 8, a debinding process (Binder Burn Out, B.B.O.) can be performed on the laminated structure (SS) prepared in the fifth step (S150) (S160). As a result, all of the organic substances such as the binder, dispersant, and plasticizer in the laminated sheet (SSH) can be incinerated and removed. The debinding process can be performed at a temperature of about 600° C. for about 12 hours in an atmospheric furnace (AF). That is, the debinding process can be performed under the atmosphere (air).

[0048] FIG. 9 is a schematic diagram for explaining the seventh step of FIG. 2.

[0049] Referring to FIGS. 2 and 9, after the sixth stage (S160), a laminated structure (SS) can be provided within a crucible (CRU). Bedding powder (BNP) can be placed within the crucible (CRU), and the laminated structure (SS) may be embedded within the bedding powder (BNP). The bedding powder (BNP) may include boron nitride powder, silicon nitride powder, or a mixture thereof. When the bedding powder (BNP) includes a mixture of boron nitride powder and silicon nitride powder, the boron nitride powder and the silicon nitride powder may be mixed at a ratio of 1:1.

[0050] The crucible (CRU) can be heated to perform a sintering process on the laminated structure (SS) (S170). Thereby, the laminated sheet (SSH) can be sintered to form a silicon nitride substrate. The sintering process can be performed at a temperature of 1700°C to 2000°C. For example, the sintering process can be performed at a temperature of about 1900°C for about 6 hours. The sintering process can be performed in a nitrogen atmosphere. The sintered laminated sheet (SSH) can be obtained as a silicon nitride substrate.

[0051] FIG. 10 is a schematic diagram for explaining a method of adjusting the remaining amount of magnesium in a silicon nitride substrate according to an embodiment of the present invention.

[0052] Referring to FIGS. 1, 2, and 10, the step (S200) of adjusting the remaining amount of magnesium in the silicon nitride substrate may include at least one of a step (S210) of controlling the temperature of the sintering process (S170) in the manufacturing process of the silicon nitride substrate, a step (S220) of controlling the size of the sheet in the manufacturing process of the silicon nitride substrate, and a step (S230) of controlling the atomic ratio of magnesium (Mg) / yttrium (Y) in the ceramic additive in the manufacturing process of the silicon nitride substrate.

[0053] A step (S210) of controlling the temperature of a sintering step (S170) in a manufacturing process of a silicon nitride substrate will be described. The temperature of the sintering step (S170) described with reference to FIG. 9 can be adjusted to a temperature between 1700° C. and 2000° C. At this time, as the temperature of the sintering step increases, the volatilization amount (i.e., removal amount) of magnesium (Mg) in the laminated sheet (SSH) can increase. As the temperature of the sintering step increases, the remaining amount of magnesium (Mg) in the manufactured silicon nitride substrate can decrease. In other words, by controlling the temperature of the sintering step, the magnesium (Mg) in the manufactured silicon nitride substrate can be adjusted to a target concentration (i.e., remaining amount).

[0054] A step (S220) of controlling the size of a sheet (SH) or a laminated sheet (SSH) in a manufacturing process of a silicon nitride substrate will be described. By cutting the sheet (SH) described with reference to FIGS. 5 and 6, the size (M X N) of the sheet (SH) can be adjusted. At this time, as the size of the sheet (SH) increases, the volatilization amount (i.e., removal amount) of magnesium (Mg) in the subsequent sintering step can decrease. As the size of the sheet (SH) increases, the remaining amount of magnesium (Mg) in the manufactured silicon nitride substrate can increase. In other words, by controlling the size of the sheet (SH), the magnesium (Mg) in the manufactured silicon nitride substrate can be adjusted to a target concentration (i.e., remaining amount).

[0055] The step (S230) of controlling the atomic ratio of magnesium (Mg) / yttrium (Y) in the ceramic additive in the manufacturing process of the silicon nitride substrate will be described. The ceramic additive (SA) described with reference to FIGS. 3 and 4a may contain yttrium oxide (Y2O3) and magnesium oxide (MgO). As described above, the atomic ratio (Mg / Y) of magnesium (Mg) to yttrium (Y) in the ceramic additive (SA) may be 1 to 5, more specifically, 2 to 5. When manufacturing the ceramic additive (SA), by adjusting the ratio of the powder of yttrium oxide and the powder of magnesium oxide, the atomic ratio (Mg / Y) of the ceramic additive (SA) can be controlled within the range of 1 to 5, more specifically, 2 to 5.

[0056] As described above, the input amount of the ceramic additive (SA) in the slurry formation step (S120) can be strictly limited to 5 wt% to 7 wt%. Therefore, it is difficult to increase the input amount of the ceramic additive (SA) to increase the remaining amount of magnesium (Mg) in the silicon nitride substrate. However, by increasing the atomic ratio (Mg / Y) in the ceramic additive (SA), the remaining amount of magnesium (Mg) in the manufactured silicon nitride substrate can increase. In other words, by controlling the atomic ratio (Mg / Y) in the ceramic additive (SA), the magnesium (Mg) in the manufactured silicon nitride substrate can be adjusted to the target concentration (i.e., the remaining amount).

[0057] The sintered laminated sheet (SSH), that is, the manufactured silicon nitride substrate, may contain 99 wt% or more of SiN, but may also contain trace amounts of magnesium (Mg) and yttrium (Y) as impurities. The impurities magnesium (Mg) and yttrium (Y) may be residues derived from the aforementioned ceramic additive (SA).

[0058] The remaining amount (or concentration) of magnesium (Mg) in the silicon nitride substrate can affect the physical properties of the silicon nitride substrate (SNS). For example, the concentration of magnesium (Mg) in the silicon nitride substrate (SNS) can closely affect the thermal conductivity and bending strength of the silicon nitride substrate (SNS).

[0059] As described above, the thermal conductivity of the silicon nitride substrate can be inversely proportional to the remaining amount of magnesium (Mg) in the silicon nitride substrate. The bending strength of the silicon nitride substrate can be proportional to the remaining amount of magnesium (Mg) in the silicon nitride substrate. The remaining amount (or concentration) of magnesium in the silicon nitride substrate can be adjusted to 2,000 ppm to 20,000 ppm. At the remaining amount of magnesium, the thermal conductivity of the silicon nitride substrate can vary between 170 W / m·K and 70 W / m·K. At the remaining amount of magnesium, the bending strength of the silicon nitride substrate can vary between 750 MPa and 1000 MPa.

[0060] The silicon nitride substrate may have a size of M X N, where each of M and N may be 40 mm to 200 mm. In one embodiment of the present invention, the size of the silicon nitride substrate can be smaller than the size of the laminated sheet (SSH) by a sintering process.

[0061] Experimental Example A silicon nitride substrate was manufactured by the manufacturing method described in FIGS. 2 to 9 of the present invention. On the other hand, the temperature of the sintering step (S170) was changed to 1880 ° C, 1930 ° C, and 1980 ° C to prepare a first substrate (Experimental Example 1), a second substrate (Experimental Example 2), and a third substrate (Experimental Example 3), respectively. The remaining amount of magnesium in the first substrate, the second substrate, and the third substrate was measured. Also, the thermal conductivity and bending strength of the first substrate, the second substrate, and the third substrate were measured and shown in Table 1 below.

[0062]

Table 1

[0063] Referring to Table 1, it can be confirmed that as the temperature of the sintering process (S170) increases, the remaining amount of magnesium in the substrate decreases. That is, it was confirmed that by controlling the temperature of the sintering process (S170), the remaining amount of magnesium in the final silicon nitride substrate can be adjusted. It was confirmed that as the temperature of the sintering process (S170) increases, that is, as the remaining amount of magnesium decreases, the bending strength decreases. It was confirmed that as the temperature of the sintering process (S170) increases, that is, as the remaining amount of magnesium decreases, the thermal conductivity increases. In other words, it was confirmed that by adjusting the remaining amount of magnesium in the silicon nitride substrate, the physical properties (bending strength and thermal conductivity) of this can be controlled.

[0064] A silicon nitride substrate was manufactured by the manufacturing method described in FIGS. 2 to 9 of the present invention. On the other hand, the size (M X N) of the sheet was changed to 140 mm × 190 mm, 100 mm × 100 mm, and 40 mm × 40 mm, and a fourth substrate (Experimental Example 4), a fifth substrate (Experimental Example 5), and a sixth substrate (Experimental Example 6) were prepared respectively. The temperature of the sintering process was set to 2050°C. The remaining amount of magnesium in the fourth substrate, the fifth substrate, and the sixth substrate was measured. Also, the thermal conductivity and bending strength of the fourth substrate, the fifth substrate, and the sixth substrate were measured and shown in Table 2 below.

[0065]

Table 2

[0066] Referring to Table 2, it can be confirmed that the remaining amount of magnesium in the substrate decreases as the size of the sheet decreases. That is, it was confirmed that the remaining amount of magnesium in the final silicon nitride substrate can be adjusted by controlling the cut size of the sheet in the tape casting process. It was confirmed that the bending strength decreases as the size of the sheet decreases, that is, as the remaining amount of magnesium decreases. It was confirmed that the thermal conductivity increases as the size of the sheet decreases, that is, as the remaining amount of magnesium decreases. On the other hand, when comparing the fourth substrate (140 mm × 190 mm) with a large sheet size and the sixth substrate (40 mm × 40 mm) with a small size, it can be confirmed that even when manufacturing silicon nitride substrates under the same conditions, the difference in the remaining amount of magnesium is very large. For example, it can be confirmed that the remaining amount of magnesium in the fourth substrate is about four times larger than the remaining amount of magnesium in the sixth substrate. That is, it was confirmed that the control of the sheet size has a greater influence on the adjustment of the remaining amount of magnesium than the control of the temperature in the sintering process described above.

[0067] A silicon nitride substrate was manufactured by the manufacturing method described in FIGS. 2 to 9 of the present invention. On the other hand, the amount of ceramic additive input in the manufacturing process of the slurry and the atomic ratio of magnesium / yttrium (Mg / Y) in the ceramic additive were adjusted to be different, and the seventh substrate (Experimental Example 7), the eighth substrate (Experimental Example 8), and the ninth substrate (Experimental Example 9) were prepared. The remaining amount of magnesium in the seventh substrate, the eighth substrate, and the ninth substrate was measured.

[0068]

Table 3

[0069] Referring to Table 3, even when the ceramic additive is similarly introduced at 6 wt%, it can be confirmed that in Experimental Example 8 with a large Mg / Y atomic ratio, the actual Mg injection amount is even larger than that in Experimental Example 7. As a result, it was confirmed that the remaining amount of magnesium in the final silicon nitride substrate is even larger in the eighth substrate than in the seventh substrate. Experimental Example 9 involves introducing 7 wt% of the ceramic additive and setting the Mg / Y atomic ratio as high as 4.5. As a result, it can be confirmed that the actual Mg input amount is the highest at 1.88 wt%. Consequently, the remaining amount of magnesium in the final silicon nitride substrate was the largest in the ninth substrate. As a result, it can be confirmed that by adjusting the ratio of Mg / Y in the ceramic additive, the remaining amount of magnesium in the final substrate can be controlled.

[0070] Also, the thermal conductivities and flexural strengths of the seventh, eighth, and ninth substrates were measured and shown in Table 4 below.

[0071]

Table 4

[0072] Although the other manufacturing processes are carried out in the same manner, it can be confirmed that the seventh, eighth, and ninth substrates have different physical properties (flexural strength and thermal conductivity) even when only the input amount of the ceramic additive and the ratio of Mg / Y are different. In particular, it can be similarly confirmed that as the remaining amount of magnesium increases, the flexural strength increases and the thermal conductivity decreases. As a result, it was further confirmed that the core variable for adjusting the physical properties (flexural strength and thermal conductivity) of the silicon nitride substrate is the remaining amount of magnesium finally remaining.

[0073] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those of ordinary skill in the technical field to which the present invention pertains can understand that the present invention can be implemented in other specific forms without changing its technical idea and essential features. Therefore, it should be understood that all of the embodiments described above are exemplary and not restrictive.

Claims

1. A step of manufacturing a silicon nitride substrate; A step of adjusting the remaining amount of magnesium in the silicon nitride substrate; However, it includes: The step of manufacturing the silicon nitride substrate includes: Mixing silicon nitride powder, a ceramic additive containing magnesium oxide, and a solvent to form a slurry; Forming the slurry into a sheet; Sandwiching at least one of the sheets between a lower plate and an upper plate to form a laminated structure; Performing a degreasing process on the laminated structure; Performing a sintering process on the laminated structure; Including: The thermal conductivity of the silicon nitride substrate is inversely proportional to the remaining amount of magnesium in the silicon nitride substrate. A method for adjusting the thermal conductivity of a silicon nitride substrate.

2. The step of adjusting the remaining amount of magnesium in the silicon nitride substrate includes adjusting the temperature of the sintering process. The method for adjusting the thermal conductivity of a silicon nitride substrate according to Claim 1.

3. The temperature of the sintering process is adjusted to 1700°C to 2000°C, As the temperature of the sintering process increases, the remaining amount of magnesium in the silicon nitride substrate decreases. The method for adjusting the thermal conductivity of a silicon nitride substrate according to Claim 2.

4. The step of adjusting the remaining amount of magnesium in the silicon nitride substrate includes adjusting the size of the sheet. The method for adjusting the thermal conductivity of a silicon nitride substrate according to Claim 1.

5. The size of the sheet is adjusted to M X N, Each of M and N is 60 mm to 300 mm, As the size of the sheet increases, the remaining amount of magnesium in the silicon nitride substrate increases. The method for adjusting the thermal conductivity of a silicon nitride substrate according to Claim 4.

6. The ceramic additive includes yttrium oxide (Y ２ O ３ ) and magnesium oxide (MgO), and The step of adjusting the remaining amount of magnesium in the silicon nitride substrate includes adjusting the atomic ratio of magnesium (Mg) to yttrium (Y) in the ceramic additive. The method for adjusting the thermal conductivity of a silicon nitride substrate according to Claim 1.

7. The atomic ratio of magnesium (Mg) to yttrium (Y) in the ceramic additive is 2 to 5, As the atomic ratio increases, the remaining amount of magnesium in the silicon nitride substrate increases. The method for adjusting the thermal conductivity of a silicon nitride substrate according to Claim 6.

8. A step of manufacturing a silicon nitride substrate; A step of adjusting the remaining amount of magnesium in the silicon nitride substrate; although it includes the step of manufacturing the silicon nitride substrate comprises mixing silicon nitride powder, a ceramic additive containing magnesium oxide and a solvent to form a slurry; forming the slurry into a sheet; sandwiching at least one said sheet between a lower plate and an upper plate to form a laminated structure; performing a debinding process on the laminated structure; performing a sintering process on the laminated structure; including the flexural strength of the silicon nitride substrate is proportional to the remaining amount of magnesium in the silicon nitride substrate; A method for adjusting the flexural strength of a silicon nitride substrate.

9. The step of adjusting the remaining amount of magnesium in the silicon nitride substrate includes adjusting the temperature of the sintering process. The method for adjusting the flexural strength of a silicon nitride substrate according to claim 8.

10. The temperature of the sintering process is adjusted to 1700 °C to 2000 °C, and the remaining amount of magnesium in the silicon nitride substrate decreases as the temperature of the sintering process increases. The method for adjusting the flexural strength of a silicon nitride substrate according to claim 9.

11. The step of adjusting the remaining amount of magnesium in the silicon nitride substrate includes adjusting the size of the sheet. The method for adjusting the flexural strength of a silicon nitride substrate according to claim 8.

12. The size of the sheet is adjusted to M × N, where each of M and N is 60 mm to 300 mm, and the remaining amount of magnesium in the silicon nitride substrate increases as the size of the sheet increases. The method for adjusting the flexural strength of a silicon nitride substrate according to claim 11.

13. The ceramic additive includes yttrium oxide (Y ２ O ３ ) and magnesium oxide (MgO), and The step of adjusting the remaining amount of magnesium in the silicon nitride substrate includes adjusting the atomic ratio of magnesium (Mg) to yttrium (Y) in the ceramic additive. The method for adjusting the flexural strength of a silicon nitride substrate according to claim 8.

14. The atomic ratio of magnesium (Mg) to yttrium (Y) in the ceramic additive is 2 to 5, and the remaining amount of magnesium in the silicon nitride substrate increases as the atomic ratio increases. The method for adjusting the flexural strength of a silicon nitride substrate according to claim 13.

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