JP2014073919A - Method for manufacturing nitride-based ceramic substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a nitride-based ceramic substrate which does not require a thermal treatment step of reducing deformation after a sintering step, can suppress deformation after the sintering step, and can prevent sheet moldings laminated at sintering from being stuck to each other.SOLUTION: A separation layer is formed on one principal surface of a sheet molding so that its area is 95% or less of the area of the principal surface, and the sheet molding is sintered at 1,700-2,000°C in a state where a plurality of sheet moldings are superposed on each other through the separation layer to manufacture a nitride-based ceramic substrate.

Description

  The present invention relates to a method for manufacturing a nitride ceramic substrate.

  Silicon nitride substrates, aluminum nitride substrates and other nitride-based ceramic substrates are widely used as insulating members constituting ceramic circuit substrates on which power semiconductor modules such as IGBTs and power MOSFETs and other electronic components are mounted. Such a nitride-based ceramic substrate has a ceramic circuit substrate formed by bonding a metal plate (such as a metal circuit plate and a metal heat dissipation plate) to one or both main surfaces thereof. As a method for joining the nitride-based ceramic substrate and the metal plate, for example, an active metal method for joining via a brazing material and a so-called copper direct joining method for directly joining a copper plate are known.

  Here, normally, when manufacturing a nitride-based ceramic substrate, a raw material slurry mixed with silicon nitride powder, sintering aid powder, organic binder, solvent, etc. is formed into a sheet with a predetermined thickness by, for example, a doctor blade method. A plurality of the sheet compacts are stacked and sintered in a sintering furnace. In many cases, a separation layer containing boron nitride as a main raw material is formed on at least one main surface of the sheet molded body so that the sheet molded bodies do not adhere to each other during the sintering. And an example of the manufacturing method of the nitride-type ceramic substrate which concerns on formation of this isolation | separation layer is disclosed by following patent document 1 and 2. FIG.

Patent Document 1 states that “a ceramic green sheet is molded, and a release agent containing BN powder having an oxygen content of 3% by weight or less and an average particle size of 20 μm or less is formed on the surface as BN powder by a roll coater. After applying 3 to ³ mg / cm ² , stack multiple sheets, degrease, press the top and bottom surfaces of the laminate with a BN setter, and store in a sealed container made of the same material as the setter. And a method for producing a ceramic sintered body characterized by sintering, and a plate-like aluminum nitride sintered body having a flatness of 100 μm or less formed by the production method.

In addition, in Patent Document 2 relating to the application of the present applicant, "a plurality of silicon nitride sintered bodies are obtained by separating and then laminating and sintering a plurality of green sheets via a separating material, A silicon nitride substrate manufacturing method for obtaining a silicon nitride substrate from the silicon nitride sintered body, wherein the separating material has an oxygen content of 0.01 to 0.5% by weight, an average particle diameter of 4 to 20 μm, and a specific surface area of 20 m ^2. / G or less boron nitride (BN) powder, and the BN powder is applied to the surface of the green sheet at a coating amount of 0.05 to 1.4 mg / cm ² , ” And “in the silicon nitride substrate containing Si ₃ N ₄ as a main component, the coefficient of variation Cv indicating the distribution of B amount derived from BN remaining on the surface of the silicon nitride substrate is 1.0 or less, and the silicon nitride Waviness Wa of the substrate surface is 1.5 μm or less (However, the waviness is measured by using a surface roughness meter to measure the waviness center line waviness, and the arithmetic mean waviness Wa, that is, the arithmetic mean of the absolute value of the deviation from the mean value of the surface height. The measurement conditions are an evaluation length of 30 mm, a measurement speed of 0.3 mm / s, a cutoff value (λc) of 0.25 mm, a cutoff value (λf) of 8.0 mm), and a relative density of A silicon nitride substrate characterized by being 98% or more "is disclosed.

  However, as in Patent Document 1 or 2, when the separation layer is formed on the entire main surface of the sheet molded body, there is a problem that deformation such as warpage occurs in the obtained nitride-based ceramic substrate. Here, it is estimated that the reason why deformation occurs in the nitride-based ceramic substrate is as follows. That is, when the shrinkage ratio between the sheet molded body and the separation layer is compared, the shrinkage ratio of the separation layer mainly composed of boron nitride is small. And since the load is applied to each sheet molded body in the laminated state, the shrinkage of the sheet molded body is suppressed by the separation layer during sintering, and residual stress is generated in the nitride-based ceramic substrate after sintering. This residual stress is released when individual nitride ceramic substrates are separated from the nitride ceramic substrates laminated after sintering, or when heated in other processes after the sintering process. It is considered that deformation occurs in the physical ceramic substrate.

  When a metal plate is bonded to the nitride-based ceramic substrate that has been deformed in this way, the metal plate follows the deformation of the nitride-based ceramic substrate, so that the plane of the surface of the metal plate on which the power semiconductor or the like is mounted The degree may decrease. In addition, when using a power module in which a power semiconductor is mounted on a ceramic circuit board in which a metal plate is bonded to this nitride-based ceramic substrate, nitriding is caused by the thermal stress generated by the cooling / heating cycle due to the start / stop of the power semiconductor, etc. There is a possibility that the metal plate is peeled off from the physical ceramic substrate.

  Therefore, in Patent Document 3 below, a silicon nitride raw material powder is formed into a sheet, and after this sheet molded body is sintered, a load of 0.5 to 6.0 kPa is applied in a state where a plurality of sheets are stacked, and 1550 to 1700 ° C. A technique for obtaining a silicon nitride substrate with a small deformation by heat treatment in JIS is disclosed.

Japanese Patent No. 3369819 JP 2011-178598 A JP 2009-215142 A

  According to the method for manufacturing a nitride-based ceramic substrate of Patent Document 3, a nitride-based ceramic substrate with reduced deformation compared to the methods for manufacturing the nitride-based ceramic substrate of Patent Documents 1 and 2 can be obtained. After the sintering process, it is necessary to separately perform a heat treatment process to reduce deformation, which is disadvantageous in terms of industrial production.

  An object of the present invention is a nitride system that does not require a heat treatment step to reduce deformation after the sintering step, can suppress deformation after the sintering step, and can prevent adhesion of the laminated sheet compacts during sintering. The object is to provide a method for manufacturing a ceramic substrate.

  In order to achieve the above object, one aspect of the present invention is a method for manufacturing a nitride-based ceramic substrate, wherein one main surface of the sheet molded body has an area of 95% or less of the area of the main surface. The separation layer is formed as described above, and the sheet compact is sintered at 1700 to 2000 ° C. in a state where a plurality of the sheet compacts are stacked via the separation layer.

In addition, it is preferable that a plurality of the separation layers are formed separately from each other on the main surface. In addition, the separation layer is preferably arranged in a dot shape on the main surface, and may be at least one of a substantially rectangular shape, a substantially circular shape, a substantially triangular shape, and a substantially elliptical shape. Furthermore, it is more preferable that the individual areas of the plurality of separation layers formed by separation are 0.004 to ⁴ mm ² .

  In addition, the height of the separation layer from the main surface is preferably 1 to 20 μm.

  According to the present invention, the object can be achieved.

It is process drawing of the manufacturing method of the nitride-type ceramic substrate concerning embodiment. It is a figure which shows the example of formation of the separation layer concerning embodiment. It is a figure which shows the example of formation of the separation layer concerning embodiment. It is a figure which shows the example of formation of the separation layer concerning embodiment. It is a figure which shows the example of formation of the separation layer concerning embodiment. It is a figure which shows the example of formation of the separation layer concerning embodiment. It is a figure explaining the measuring method of a deformation | transformation of a nitride-type ceramic substrate.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings. Hereinafter, a method for manufacturing a silicon nitride substrate as a nitride-based ceramic substrate will be described as an example. However, the present invention is not limited to this, and can be applied to an aluminum nitride substrate or other nitride ceramic substrate manufactured through a similar process.

  In the method for producing a nitride ceramic substrate according to the present embodiment, a separation layer is formed on one main surface of a sheet molded body so as to have an area of 95% or less of the area of the main surface. Are sintered at 1700 to 2000 ° C. in a state where a plurality of layers are stacked via the separation layer.

  As described above, since the shrinkage rate between the separation layer and the sheet molded body is different, the shrinkage of the sheet molded body is suppressed by the separation layer during sintering, and as a result, residual stress is generated in the sintered silicon nitride substrate. . Therefore, the residual stress is released when the individual silicon nitride substrates are separated from the laminated silicon nitride substrates after sintering, or when the silicon nitride substrate is heated in another process after the sintering process. Deformation tends to occur. On the other hand, according to the configuration of the present embodiment, the area of the separation layer that inhibits the smooth shrinkage of the sheet molded body is required to prevent the sheet molded body from being fixed in the sintering process. The area of the main surface was 95% or less. This facilitates the shrinkage of the sheet compact during sintering, reduces the occurrence of residual stress in the obtained silicon nitride substrate, and suppresses deformation of the silicon nitride substrate obtained after sintering. There is no need to separately provide a process for correcting deformation after the ligation process. In addition, the sheet compacts are prevented from sticking to each other, and the individual silicon nitride substrates are easily separated from the stacked silicon nitride substrates.

FIG. 1 is a process diagram of a method for manufacturing a silicon nitride substrate according to an embodiment. In the raw material adjustment / mixing step (I) shown in FIG. 1, the raw material slurry is formed by adjusting the raw material of the silicon nitride substrate and mixing the raw materials. Here, the raw material slurry is silicon nitride raw material powder containing 0.1 to 6% by mass of magnesium oxide (MgO) as a sintering aid, and also yttrium oxide (Y ₂ O ₃ ) and erbium oxide as a sintering aid. At least one of (Er ₂ O ₃ ) is formed by mixing 2 to 10% by mass so that the total amount is 3 to 10% by mass and mixing with an organic binder or the like by a ball mill or the like. Moreover, as an organic binder, polyvinyl butyral, a methyl methacrylate resin, etc. can be used, for example, and 5-20 mass% is added.

  Next, in the forming step (II) shown in FIG. 1, the raw slurry is defoamed and then formed into a sheet having a predetermined thickness by a doctor blade method or the like. Although the plate | board thickness of the sheet molded object at this time can be suitably determined according to a use, it can be about 0.1-1.0 mm, for example.

  Next, in the separation layer forming step (III) shown in FIG. 1, one main surface of the sheet molded body formed in the forming step (II) has an area of 95% or less of the area of the main surface. A separation layer is formed. In the subsequent sintering step (IV), the separation layer is formed so that the sheet molded bodies are not fixed to each other when sintered in a state where a plurality of sheet molded bodies are laminated. The separation layer is formed, for example, by screen printing or spray coating by mixing boron nitride in a solvent.

  For example, a boron nitride paste for forming the separation layer by screen printing includes a boron nitride powder, an organic binder, and an organic solvent. As mixing ratios, it is preferable that the organic binder is 8.75 to 87.5 parts by mass and the organic solvent is 10 to 750 parts by mass with respect to 100 parts by mass of the boron nitride powder. Here, examples of the organic binder include polyvinyl butyral and ethyl cellulose. Examples of the organic solvent include ethanol, butanol, α-terpineol, and the like.

  An example of the separation layer 12 formed in the separation layer formation step (III) is shown in FIG. The shape of the separation layer 12 in this example is a rectangular shape having four sides separated by a predetermined distance from the outer edge of the sheet molded body 10, and the area thereof is 95% or less, preferably 80% or more of the main surface of the sheet molded body 10. It is. In addition, it is preferable that the height of the separation layer 12 from the main surface of the sheet molded body 10 is 1 to 20 μm so that the laminated sheet molded body 10 is not fixed during sintering (see FIGS. 3 to 3 below). The same applies to the separation layer of another example shown by 6). Furthermore, the shape of the separation layer 12 in the planar direction is not limited to FIG. 2, and may be a substantially circular shape or a polygonal shape that is 95% or less of the main surface of the sheet molded body 10.

  FIGS. 3A and 3B show examples of forming a separation layer in a preferable form. FIG. 3B is an enlarged plan view of a region J surrounded by a circle in FIG. Like the separation layer 12 shown in FIGS. 3A and 3B, a plurality of the separation layers 12 are formed separately from each other on the main surface of the sheet molded body 10. By making the total area smaller, the degree to which the shrinkage of the sheet compact is suppressed by the separation layer during sintering becomes lower, and the residual stress generated in the sintered silicon nitride substrate can be reduced.

Here, in the example of FIGS. 3A and 3B, dot-like (small area) separation layers 12 are formed in a plurality of grid patterns on one main surface of the sheet molded body 10. It should be noted that the shape of the separation layer 12 arranged in a dot shape in the planar direction is not limited to FIGS. 3 (a) and 3 (b). For example, shapes such as a substantially rectangular shape, a substantially circular shape, a substantially triangular shape, and a substantially elliptical shape can be appropriately determined. Moreover, it is good also as a polygon more than a pentagon. The area of the individual separation layers 12 in this case can be determined as appropriate as long as the total area of all the separation layers 12 is 95% or less of the area of the main surface of the sheet molded body 10. It is preferable that the thickness is 0.004 to ⁴ mm ² so that the ten pieces come into contact with each other and do not stick to each other. 3A and 3B, the total area of the individual separation layers 12 should be 80% or less and 20% or more of the area of the main surface of the sheet molded body 10. Is preferred.

  As described above, the total area of the plurality of separation layers 12 is 95% or less of the area of the main surface of the sheet molded body 10, and in FIGS. 3 (a) and 3 (b), the individual separation layers 12 are separated from each other. Is formed. For this reason, at the time of sintering, the degree to which the shrinkage of the sheet molded body is suppressed by the separation layer becomes lower, and the residual stress generated in the sintered silicon nitride substrate can be reduced. As a result, deformation of the obtained silicon nitride substrate is suppressed.

  In addition, the separation layer formed so as to be separated from each other on the main surface of the sheet molded body is not limited to the separation layers in FIGS. 3A and 3B, for example, FIGS. It can be set as the separation layer shown in FIG. In the example of FIG. 4, four separation layers 12 having a smaller area than the main surface are formed on one main surface of the sheet molded body 10. The total area of the four separation layers 12 is 95% or less of the area of the main surface of the sheet molded body 10. In the case of this example, the number of separation layers 12 is not limited to four, and may be five or more.

  In the example of FIG. 5, two separation layers 12 are formed in a region near the end of one main surface of the sheet molded body 10. The total area of the two separation layers 12 is 95% or less of the area of the main surface of the sheet molded body 10. In the case of this example, the number of separation layers 12 is not limited to two. For example, four separation layers 12 may be formed in regions near the upper, lower, left, and right ends of the sheet molded body 10 shown in FIG. Good.

  In the example of FIG. 6, the separation layer 12 is formed in a lattice shape on one main surface of the sheet molded body 10. The entire area of the grid-like separation layer 12 is 95% or less of the area of the main surface of the sheet molded body 10.

  In addition, also in the separation layer 12 shown by FIGS. 4-6, it is suitable that the height of the separation layer 12 from the main surface of the sheet molded object 10 shall be 1-20 micrometers. However, the height may be lowered if the total area of each separation layer 12 is increased. This is because as the total area of the separation layer 12 increases, the sheet molded bodies 10 are less likely to contact each other during sintering, and the sheet molded bodies are less likely to stick to each other. In any of the separation layers 12, the total area of the individual separation layers 12 is 95% or less of the main surface, preferably 80% or less, and the separation layers 12 are formed separately from each other. During sintering, the degree to which the shrinkage of the sheet compact is suppressed by the separation layer becomes lower, and the residual stress generated in the sintered silicon nitride substrate can be reduced. As a result, deformation of the obtained silicon nitride substrate is suppressed.

  In the sintering step (IV), the sheet compact is sintered at a temperature of 1700 to 2000 ° C. in a state where a plurality of sheet compacts are laminated via the separation layer in a sintering furnace to manufacture a silicon nitride substrate. At this time, it is preferable to sinter in a nitrogen pressurized atmosphere of 0.1 to 6.0 MPa. Moreover, it is preferable to sinter while applying a load of 10 to 200 Pa to the laminated sheet compact. In addition, after completion | finish of a sintering process (IV), each laminated | stacked nitride type ceramic substrate is isolate | separated and it is set as an individual silicon nitride substrate. Thereafter, the separation layer is removed from the surface of the silicon nitride substrate by blasting or the like.

  A silicon nitride substrate as a nitride-based ceramic substrate is manufactured through the above steps, but in addition to the exothermic peak temperature of the organic binder of the sheet molded body, measured by differential thermal analysis, before the sintering step (IV). The degreasing step of heating the separation layer and the sheet molded body at a temperature higher by 15 to 450 ° C. to remove the organic binder from the separation layer and the sheet molded body may be performed.

  Examples of the present invention will be specifically described below. The present invention is not limited to these examples.

  A silicon nitride substrate was manufactured based on the manufacturing method shown in FIG. 1, and the deformation amount and the sticking property of the obtained silicon nitride substrate were evaluated. Hereinafter, the production methods of Examples 1 to 7 and Comparative Examples 1 to 5, and the method for evaluating the amount of deformation and adhesion of the silicon nitride substrate will be described.

  In each of the examples and comparative examples, an average particle size of 0.8 μm, an oxygen content of 1%, an α conversion of 97% of silicon nitride powder of 92% by mass, an average particle size of 0.5 μm of magnesium oxide powder of 4% by mass and an average particle For a total of 100 parts by mass of 4% by mass of yttrium oxide powder having a diameter of 0.5 μm, 20 parts by mass of polyvinyl butyral as an organic binder, 5 parts by mass of di-2-ethylhexyl phthalate as a plasticizer, ethyl alcohol and 1- 150 parts by mass of a mixture of butyl alcohol was put in a container lined with resin, and mixed with a silicon nitride ball for 20 hours by a ball mill to prepare a raw material slurry. After adjusting the viscosity of the obtained slurry, it was formed into a sheet having a thickness of 0.4 mm by a doctor blade method. Then, this was cut | disconnected with the press apparatus and it was set as the sheet molded object. In each of the examples and the comparative examples, the dimension a of the sheet molded body 10 shown in FIGS. 2 and 3A and 2B was 150 mm, and the dimension c was 100 mm.

  To 100 parts by mass of hexagonal boron nitride powder (hereinafter sometimes referred to as BN powder), 10 parts by mass of polyvinyl butyral as an organic binder and 250 parts by mass of ethyl alcohol as an organic solvent are mixed for 1 hour. A powder slurry was prepared. In each example and comparative example, this BN powder slurry is printed on the main surface of the sheet molded body by screen printing, and a separation layer having a predetermined thickness is formed in the pattern shown in FIG. 2 or FIGS. 3 (a) and 3 (b). did. Then, it heated at 100 degreeC in air | atmosphere and the solvent in the separated layer 12 was removed. In addition, the separation layer 12 was formed with the patterns shown in FIGS. 3A and 3B and the dimensions b and d in Examples 1 and 2 and Comparative Example 1 in which the separation layer 12 was formed with the pattern shown in FIG. Table 1 shows the dimensions f and g (see FIG. 3B), the area of each separation layer, and the thickness of the separation layer in Examples 3 to 7 and Comparative Examples 2 to 5. In addition, about the area of each isolation | separation layer, it has displayed only about Examples 3-7 and Comparative Examples 2-5 which formed the isolation | separation layer of Fig.3 (a), (b). In the case of FIGS. 3A and 3B, the separation layers 12 are formed at an equal pitch, and further, in the plane direction from the separation layer 12 arranged on the outermost side to the outer edge of the sheet molded body. In addition, the separation layer 12 was arranged so that the distance e in the horizontal direction was substantially equally divided.

  In each of the examples and comparative examples, 10 sheet molded bodies on which the separation layer was formed were stacked with the surface on which the separation layer was formed as the upper surface, and placed on a boron nitride setter. Heated in air for hours and degreased.

  Next, while applying a load of 60 Pa to the laminated sheet molded body, sintering was performed at 1900 ° C. for 3 hours in a pressurized nitrogen atmosphere of 0.9 MPa, and nitriding of 10 laminated sheets was performed. A silicon substrate was obtained.

  Here, individual silicon nitride substrates were separated from the stacked silicon nitride substrates, and the evaluation of the adhesion between the silicon nitride substrates was confirmed as follows. The case where the silicon nitride substrate can be easily peeled without cracks or cracks (◯), and the case where the silicon nitride substrate can be peeled without cracks or cracks by applying an impact with a wooden hammer (△) ), The case where there was even one substrate in which the silicon nitride substrate was cracked or cracked when it was peeled off by applying an impact with a wooden hammer was determined as (x). Table 1 shows the results of evaluating the sticking property.

  Thereafter, a honing process is performed by injecting a slurry obtained by mixing alumina abrasive grains having an average particle diameter of 50 μm and water onto the separated silicon nitride substrate at a pressure of 0.2 MPa, and the length and width are 120 mm and 80 mm, respectively, and the thickness is 0.32 mm. A silicon nitride substrate was obtained.

  The deformation amount of the silicon nitride substrate obtained in each example and comparative example was confirmed with a three-dimensional laser measuring instrument (LT-8100 manufactured by Keyence) as follows. As shown in FIG. 7A, the surface of the silicon nitride substrate 1 placed on the surface plate 81 is irradiated with a laser 83, and scanning is performed in the direction of the arrow so that both ends A and B of the silicon nitride substrate are included. In FIG. 7A, the irradiation position of the laser 83 in the depth direction of the paper surface is set to a position of 10 mm from each end face of the silicon nitride substrate 1 and three points in the center as shown in FIG. The laser 83 is scanned along L1 to L3. Here, when the silicon nitride substrate 1 is deformed, it is often placed on the surface plate 81 in an inclined posture as shown in FIG. Therefore, as shown in FIG. 7C, the data measured so that the broken line C connecting both ends of the silicon nitride substrate 1 is horizontal is adjusted for each of the scanning lines L1 to L3. For example, in the case of the silicon nitride substrate 1 having the deformation illustrated in FIG. G and a distance H to a point F that is farthest from the lower side are obtained. For each of the scanning lines L1 to L3, a value obtained by dividing the value obtained by adding the distances G and H by the length I of the silicon nitride substrate 10 in the scanning direction is calculated, and the deformation amount per unit length (μm / mm) And an average value of the three values obtained for each of the scanning lines L1 to L3 is calculated as the deformation amount. Then, the deformation amounts of the 10 silicon nitride substrates obtained in each example and comparative example were obtained. The average value of the deformation amount of the 10 silicon nitride substrates is shown in Table 1 above.

  As shown in Table 1, in any of Examples 1 to 7, the deformation amount was less than 2 μm, and the result of sticking evaluation was also “◯” or “Δ”, and a substantially good silicon nitride substrate was obtained. On the other hand, in Comparative Examples 1, 3, and 5, the amount of deformation exceeds 2, and in Comparative Examples 2 and 4, the result of the sticking evaluation is x.

  Looking at these in detail, from Examples 1 and 2 and Comparative Example 1 in which the separation layer 12 was formed in the pattern shown in FIG. 2, the larger the area ratio on the main surface, the larger the deformation amount. It turns out that it becomes difficult to do. The area ratio on the main surface is Example 2 <Example 1 <Comparative Example 1, and the deformation amount is also Example 2 <Example 1 <Comparative Example 1. Is ×, Example 2 is Δ, and Example 1 is ○.

  Further, in Examples 3 to 7 and Comparative Examples 2 to 5 in which the separation layer 12 was formed in the pattern shown in FIGS. 3A and 3B, when Examples 3 to 6 and Comparative Examples 2 and 3 were compared, It can be seen that the amount of deformation tends to increase as the area of each separation layer increases. Further, when Examples 3 to 6 and Comparative Examples 2 and 3 are compared, it can be seen that the larger the area of each separation layer, the harder it becomes to adhere. Furthermore, when Example 7 and Comparative Examples 4 and 5 are compared, it can be seen that the amount of deformation increases as the height of the separation layer increases, but it becomes difficult to adhere.

  1 silicon nitride substrate, 10 sheet compact, 12 separation layer, 81 surface plate, 83 laser.

Claims (6)

A method of manufacturing a nitride-based ceramic substrate,
A separation layer is formed on one main surface of the sheet molded body so as to have an area of 95% or less of the area of the main surface,
A method for producing a nitride-based ceramic substrate, comprising sintering the sheet compact at 1700 to 2000 ° C in a state where a plurality of the sheet compacts are stacked via the separation layer.   The method for manufacturing a nitride-based ceramic substrate according to claim 1, wherein a plurality of the separation layers are formed separately from each other on the main surface.   The method for manufacturing a nitride-based ceramic substrate according to claim 2, wherein the separation layer is arranged in a dot shape on the main surface.   The method for manufacturing a nitride-based ceramic substrate according to claim 3, wherein the separation layer is at least one of a substantially rectangular shape, a substantially circular shape, a substantially triangular shape, and a substantially elliptical shape. The method for manufacturing a nitride-based ceramic substrate according to claim 4, wherein an area of the separation layer is 0.004 to 4 mm ² .   The method for producing a nitride-based ceramic substrate according to any one of claims 1 to 5, wherein a height of the separation layer from the main surface is 1 to 20 µm.

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