KR20170135105A - Manufacturing method of sheet-type silicon nitride subststrate - Google Patents

Abstract

The present invention relates to a method for manufacturing a sheet type silicon nitride substrate comprising the steps of: preparing ceramics raw materials including Si powder, Y_2O_3 powder and MgO powder; mixing the ceramics raw materials, a solvent, an organic binder, a dispersing agent and a plasticizer to form slurry; forming a sheet type molded product in a tape casting method using the slurry; laminating the molded products in a plurality of layers and performing compression to form a laminated sheet; degreasing the laminated sheet in an oxidizing atmosphere in order to minimize an amount of residual oxygen and carbon; nitriding the degreased laminated sheet; and sintering the nitrided laminated sheet. The present invention can manufacture the sheet type substrate with thin thickness at low costs using the tape casting method and perform degreasing treatment in the oxidizing atmosphere and performing nitriding treatment in an N_2 atmosphere to minimize the amount of residual oxygen and carbon, thereby enhancing mechanical properties, particularly fracture toughness, high temperature properties and thermal conductivity of a silicon nitride sintered body, obtaining high quality silicon nitride (Si_3N_4) sintered body via reaction sintering, and lowering shrinkage even after nitridation by the reaction sintering to manufacture elaborate shapes.

Description

[0001] The present invention relates to a sheet-type silicon nitride substrate,

The present invention is a sheet-like to the silicon nitride substrate according to the manufacturing method, and more particularly can be prepared using the tape casting of a sheet form of a thickness at a low cost, and the residual oxygen by degreasing in an oxidizing atmosphere, and nitriding treatment in N ₂ atmosphere And the amount of carbon can be minimized, thereby improving the mechanical properties, particularly fracture toughness and high temperature characteristics of the silicon nitride sintered body, and improving the thermal conductivity characteristics. Also, by reaction sintering, high quality silicon nitride (Si ₃ N ₄ ) a sintered body can be obtained, and a shrinkage rate is low even after the nitridation reaction by reactive sintering, so that a precise shape can be produced.

Ceramic materials with high electrical insulation and thermal conductivity have excellent functions as a heating medium for rapidly transmitting and diffusing generated heat of a device, and can be used as a substrate material for a transport device, a substrate material for a highly integrated electronic circuit, a heat sink for a laser oscillation part, Have been used as reaction vessel parts, precision machine parts, etc. of semiconductor manufacturing apparatuses. Particularly, ceramic heat sink plates for power devices with high output power, which have become increasingly important in recent industrial fields, are required to have high dielectric constant, withstand voltage, thermal conductivity, strength, toughness and low dielectric constant. has been required, the aluminum nitride (AlN), alumina (Al ₂ O _3), silicon nitride, a ceramic material suitable for this requirement (Si ₃ N _4), etc. have been studied.

Aluminum nitride (AlN) has been widely studied and commercialized as a high power ceramic heat sink plate material due to its high thermal conductivity (100 ~ 270 W / mK). However, due to the difference in thermal expansion coefficient between Si and low strength (250 ~ 450 MPa) 4.5 to 4.6 × 10 ^-6 / K, and Si: 2.6 × 10 ^-6 / K), resulting in poor reliability and short life span.

On the other hand, silicon nitride (Si ₃ N ₄ ) has high strength (500 to 800 MPa), high toughness (5 to 8 MPa · m ^1/2 ) and excellent thermal expansion coefficient matching with Si (2.7 to 3.4 × 10 ^-6 / K) (70 to 170 W / mK) comparable to aluminum nitride (AlN), and exhibits excellent heat-resistant fatigue properties compared to aluminum nitride (AlN), making it suitable as a material for next-generation high-output power devices.

However, silicon nitride (Si ₃ N ₄ ) is not yet commercially available as a radiator plate due to its low price competitiveness due to high cost of raw material powder.

Korean Patent Publication No. 10-1988-0000329

A problem to be solved by the present invention is to reduce the amount of residual oxygen and carbon by minimizing the amount of residual oxygen and nitriding in an N ₂ atmosphere by degreasing treatment in an oxidizing atmosphere, (Si ₃ N ₄ ) sintered body can be obtained through the reaction sintering, and the sintered body of silicon nitride (Si ₃ N ₄ ) can be obtained through the reaction sintering, and the sintered body of silicon nitride The present invention provides a method of manufacturing a sheet-like silicon nitride substrate which is capable of producing a sophisticated shape because the shrinkage rate is small even after the nitriding reaction by sintering.

The present invention provides a method for producing a ceramic slurry, comprising the steps of: preparing a ceramic raw material containing Si powder, Y ₂ O ₃ powder and MgO powder; mixing the ceramic raw material, solvent, organic binder, dispersant and plasticizer to form a slurry; A step of forming a molded article in the form of a sheet by using a tape casting method, a step of laminating the formed article to a plurality of layers and pressing to form a laminated sheet, A step of degreasing the laminated sheet, a step of nitriding the degreased laminated sheet, and a step of sintering the nitrided laminated sheet.

The Y ₂ O ₃ powder is preferably contained in the ceramic raw material in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the Si powder.

It is preferable that the MgO powder is contained in the ceramic raw material in an amount of 0.1 to 7 parts by weight based on 100 parts by weight of the Si powder.

The organic binder is preferably mixed with 5.5 to 9.5 parts by weight based on 100 parts by weight of the ceramic raw material.

The organic binder may comprise polyvinylbutyral.

The dispersant is preferably mixed in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of the ceramic raw material.

The dispersing agent may include a copolymer dispersing agent.

The plasticizer is preferably mixed in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the ceramic raw material.

The plasticizer may include dioctyl phthalate.

The degreasing treatment is preferably performed at 300 to 500 ° C to minimize the amount of residual oxygen and carbon.

The nitridation treatment is preferably performed in an N ₂ atmosphere at 1350 to 1500 ° C.

The sintering may include a reaction sintering performed in an N ₂ atmosphere at a pressure higher than normal pressure to suppress decomposition of the nitrided product into Si and N ₂ .

The sintering is preferably performed at a temperature of 1800 to 1950 캜.

The Si powder may be a scrap of Si or a powder in which a Si wafer is pulverized.

The Si powder preferably has a mean particle size of 0.5 to 20 mu m.

It is preferable that the molded article in the form of a sheet is formed to a thickness of 10 to 200 mu m and the laminated sheet is formed to a thickness of 0.5 to 20 mm.

The manufacturing method of the sheet-like silicon nitride substrate may further include a step of cutting the laminated sheet to a desired size before degreasing treatment.

According to the present invention, it is possible to produce a sheet having a thin thickness at low cost by using tape casting.

Further, according to the present invention, the amount of residual oxygen and carbon can be minimized by performing degreasing treatment in an oxidizing atmosphere and nitriding treatment in an N ₂ atmosphere, thereby improving mechanical properties, particularly fracture toughness and high temperature characteristics, of the silicon nitride sintered body And the thermal conductivity characteristics can be improved.

Further, according to the present invention, high-quality silicon nitride (Si ₃ N ₄ ) sintered body can be obtained through reaction sintering, and a shrinkage rate is small even after the nitridation reaction by reaction sintering, so that a precise shape can be produced.

Further, according to the present invention, it is possible to manufacture a sheet-type silicon nitride substrate of high purity which can be recycled and used at a low cost by using a scrap of Si discarded as a by-product of the manufacturing process or using a powder obtained by shattering a Si wafer, As a result, price competitiveness can be secured.

1 is a view showing a process according to an experimental example.
FIG. 2 is a graph showing the viscous behavior of the slurry according to the amount of PVB (polyvinylbutyral) added to the raw material of ceramics in Experimental Example 1. FIG.
3 is a graph showing the density of the laminated sheet according to the amount of PVB added to the raw material of ceramics in Experimental Example 1. FIG.
FIG. 4A is an optical microscope photograph of the surface of the laminated sheet when the laminated sheet is prepared by adjusting the addition amount of PVB relative to the raw material of the ceramics in Experimental Example 1 to 5.5%, FIG. 4B is a photograph showing the laminated sheet prepared by adjusting the amount of PVB added to the ceramic raw material to 7.5% And FIG. 4C is an optical microscope photograph of the surface of the green sheet when the laminated sheet is prepared with the amount of PVB added to the ceramic raw material being 9.5%.
5 is a graph showing a thermogravimetric analysis of a laminated sheet prepared by adjusting the amount of PVB added to the ceramic raw material to 7.5% in Experimental Example 1. FIG.
Fig. 6 is a graph showing a case where a laminated sheet is produced without mixing Y ₂ O ₃ powder and MgO powder according to Experimental Example 2, and the above laminated sheet is degreased in an oxidizing atmosphere and an inert atmosphere, respectively, and the residual oxygen amount is measured.
Fig. 7 is a graph showing a case where a laminated sheet was produced without mixing Y ₂ O ₃ powder and MgO powder according to Experimental Example 2, and the laminated sheet was degreased in an oxidizing atmosphere and an inert atmosphere, respectively, and the amount of carbon was measured.
8 is a graph showing the amount of residual oxygen present in a specimen by degreasing in an oxidizing atmosphere and an inert atmosphere at 400 DEG C according to Experimental Example 3 and nitriding treatment at temperatures of 1400 DEG C and 1450 DEG C, respectively.
9 is a graph showing the amount of carbon present in a specimen by degreasing in an oxidizing atmosphere and an inert atmosphere at 400 ° C according to Experimental Example 3 and nitriding at 1400 ° C and 1450 ° C, respectively.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not.

A method of manufacturing a sheet-like silicon nitride (Si ₃ N ₄ ) substrate according to a preferred embodiment of the present invention includes the steps of preparing a raw material for ceramics including Si powder, Y ₂ O ₃ powder and MgO powder, A step of forming a slurry by mixing an organic binder, a dispersant and a plasticizer; and a step of forming a molded article in the form of a sheet by molding by means of a tape casting method using the slurry, a step of laminating the molded article into a plurality of layers, Degreasing the laminated sheet in an oxidizing atmosphere to minimize the amount of residual oxygen and carbon, nitriding the degreased laminated sheet, and sintering the nitrided laminated sheet. .

The Y ₂ O ₃ powder is preferably contained in the ceramic raw material in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the Si powder.

It is preferable that the MgO powder is contained in the ceramic raw material in an amount of 0.1 to 7 parts by weight based on 100 parts by weight of the Si powder.

The organic binder is preferably mixed with 5.5 to 9.5 parts by weight based on 100 parts by weight of the ceramic raw material.

The organic binder may comprise polyvinylbutyral.

The dispersant is preferably mixed in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of the ceramic raw material.

The dispersing agent may include a copolymer dispersing agent.

The plasticizer is preferably mixed in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the ceramic raw material.

The plasticizer may include dioctyl phthalate.

The degreasing treatment is preferably performed at 300 to 500 ° C to minimize the amount of residual oxygen and carbon.

The nitridation treatment is preferably performed in an N ₂ atmosphere at 1350 to 1500 ° C.

The sintering may include a reaction sintering performed in an N ₂ atmosphere at a pressure higher than normal pressure to suppress decomposition of the nitrided product into Si and N ₂ .

The sintering is preferably performed at a temperature of 1800 to 1950 캜.

The Si powder may be a scrap of Si or a powder in which a Si wafer is pulverized.

The Si powder preferably has a mean particle size of 0.5 to 20 mu m.

It is preferable that the molded article in the form of a sheet is formed to a thickness of 10 to 200 mu m and the laminated sheet is formed to a thickness of 0.5 to 20 mm.

The manufacturing method of the sheet-like silicon nitride substrate may further include a step of cutting the laminated sheet to a desired size before degreasing treatment.

Hereinafter, a method for manufacturing a sheet-like silicon nitride substrate according to a preferred embodiment of the present invention will be described in more detail.

Silicon Nitride (Si ₃ N ₄ ) is excellent in high strength (500 to 800 MPa), toughness (5 to 8 MPa · m ^1/2 ) and thermal expansion coefficient matching with Si (2.7 to 3.4 × 10 ^-6 / K) It is capable of exhibiting a high thermal conductivity (70 ~ 170 W / mK) comparable to aluminum (AlN). It exhibits excellent heat-resistant fatigue characteristics compared to aluminum nitride (AlN) and is suitable for materials for next generation high-output power devices.

However, silicon nitride (Si ₃ N ₄ ) is not yet commercially available as a radiator plate due to its low price competitiveness due to high cost of raw material powder. In order to solve such a problem, a scrap of Si may be used as a high-purity Si powder obtained as a by-product of the manufacturing process, or a powder obtained by shattering a Si wafer may be used as a starting material when manufacturing the teeth or wafers for semiconductor processing.

A raw material for ceramics including Si powder, Y ₂ O ₃ powder and MgO powder is prepared for producing a high purity sheet-like silicon nitride substrate.

The Si powder may be a scrap of Si or a powder in which a Si wafer is pulverized. It is possible to recycle the resource by using scrap of Si discarded as a by-product of the manufacturing process or by using the crushed powder of the Si wafer, and it is possible to manufacture a sheet silicon nitride substrate of high purity at a low cost and to secure price competitiveness . The Si powder preferably has a mean particle size of 0.5 to 20 mu m.

The Y ₂ O ₃ powder is preferably contained in the ceramic raw material in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the Si powder. The Y ₂ O ₃ powder is preferably a powder having an average particle diameter of 0.5 to 20 μm.

It is preferable that the MgO powder is contained in the ceramic raw material in an amount of 0.1 to 7 parts by weight based on 100 parts by weight of the Si powder. The MgO powder is preferably a powder having an average particle diameter of 0.5 to 20 mu m.

The ceramic raw material, the solvent, the organic binder, the dispersant, and the plasticizer are mixed to form a slurry.

The organic binder is preferably mixed with 5.5 to 9.5 parts by weight based on 100 parts by weight of the ceramic raw material. Examples of the organic binder include cellulose derivatives such as ethyl cellulose, methyl cellulose, nitrocellulose, and carboxy cellulose, and resins such as polyvinyl alcohol, acrylic ester, methacrylic ester, and polyvinyl butyral And a mixture of the cellulose derivative and the resin may be used. As the organic binder, other generally known materials may be used. It is most preferable to use polyvinylbutyral as the organic binder in consideration of forming a sheet-shaped molded article by a tape casting method as described later.

As the solvent, an organic solvent may be used to dissolve the organic binder and disperse the ceramic raw material to adjust the viscosity. As the organic solvent, a material capable of dissolving the organic binder may be used. For example, terpineol, Dihydro terpineol (DHT), dihydro terpineol acetate (DHTA), butyl carbitol acetate (BCA), ethylene glycol, ethylene, isobutyl alcohol, methyl ethyl ketone, butyl Carbitol, texanol (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate), ethylbenzene, isopropylbenzene, cyclohexanone, cyclopentanone, dimethylsulfoxide, diethyl phthalate , Toluene, mixtures thereof, and the like. It is preferable that the solvent is mixed in an amount of 60 to 100 parts by weight based on 100 parts by weight of the ceramic raw material. If the content of the solvent is less than 60 parts by weight, the viscosity of the slurry may be too high to perform tape casting and it may be difficult to control the thickness of the coating. If the content of the solvent exceeds 100 parts by weight, It takes a long time to dry and it may be difficult to control the coating thickness.

The dispersant is preferably mixed in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of the ceramic raw material. The dispersing agent may include a copolymer dispersing agent.

The plasticizer is preferably mixed in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the ceramic raw material. The plasticizer may include dioctyl phthalate.

Various mixing methods such as a 3D mixer, ball milling, milling media, and a jet mill may be used. Hereinafter, the mixing process by the ball milling method will be specifically described as an example. The mixture is uniformly mixed while being mechanically pulverized by rotating at a constant speed using a ball milling machine containing raw materials including raw materials for ceramics, a solvent, an organic binder, a dispersant and a plasticizer. The ball used for ball milling may be a ball made of a ceramic such as zirconia. The balls may be all the same size or may be used together with balls having two or more sizes. The size of the balls, the milling time, and the rotation speed per minute of the ball miller are controlled so as to be mixed with the desired particle size while pulverizing. For example, the size of the balls may be set in the range of about 1 to 50 mm in consideration of the size of the particles, and the rotational speed of the ball miller may be set in the range of about 100 to 500 rpm. The ball milling is carried out for 1 to 48 hours in consideration of the target particle size and the like. By ball milling, the ceramic raw material is homogeneously mixed while being crushed into fine sized particles.

The above slurry is used to form a molded body (green sheet) in the form of a sheet by a tape casting method. The tape casting method is a method in which a ceramic slurry is prepared by mixing an aqueous or non-aqueous solvent with a binder, a plasticizer, a dispersant, and the like in an appropriate ratio, and then the slurry is poured into a doctor blade set at a predetermined dam height, The slurry is applied to a moving substrate film while controlling the thickness of the slurry to be applied to the substrate film on the blade, and then the solvent is volatilized and removed from the substrate film to obtain a tape-shaped molded article. The substrate film may be a stainless steel tape, oil paper tape, polymer tape such as polyester, or the like. For example, the slurry is poured into a doctor blade set at a dam height of 300 mu m and the slurry is applied while moving the substrate film at a predetermined speed (for example, 2.0 m / min) while controlling the thickness of the slurry applied to the film substrate with the blade And a step of removing the substrate film from the drying step. Among the methods for producing a molded article, the tape casting process is a low-cost process for manufacturing into a thin sheet form. The sheet-shaped formed article is preferably formed to a thickness of 10 to 200 mu m in consideration of the particle size of Si powder or the like, the thickness of a laminated sheet to be described later, and the like.

The formed body is laminated by a plurality of layers and pressed to form a laminated sheet. The laminated sheet is preferably formed to a thickness of 0.5 to 20 mm. For example, the table temperature of the stacking machine is set at 40 占 폚, and a plurality of sheet-shaped molded articles are stacked. Then, a pressure of 12 tons is applied for 10 seconds, and WIP (Warm Isostatic Press ) Equipment at 70 DEG C and 20 MPa for 10 minutes to produce a laminated sheet. The laminated sheet may be cut to a desired size before the degreasing treatment described later.

The laminated sheet is degreased in an oxidizing atmosphere to minimize the amount of residual oxygen and carbon. The degreasing treatment is preferably performed at 300 to 500 ° C to minimize the amount of residual oxygen and carbon. In order to obtain a silicon nitride sintered body of high density through the tape casting method, an organic material such as an organic binder, a dispersing agent and a plasticizer is added to prepare a uniform and highly laminated laminated sheet. The organic material contained in this laminated sheet is obtained by obtaining a high- It is preferable to be completely removed through the degreasing process.

The degreased laminated sheet is nitrided. The surface of the Si powder used as a raw material for ceramics generally contains SiO _{2. In} addition, oxygen may be introduced into slurry production, tape casting, degreasing, and the like. Thus, If the SiO ₂ film is formed on Si powder surface with a delay the nitrification reaction and leaving the residual Si, residual Si present in the silicon nitride sintered body as possible because they affect the mechanical properties, especially fracture toughness and high temperature properties of silicon nitride sintered SiO ₂ The nitrification rate must be increased. Further, the degreasing step may well not be made after the sintering of oxygen may degrade the thermal conductivity of a large amount even when employing silicon nitride (Si ₃ N ₄₎ in a substrate of silicon nitride (Si ₃ N ₄₎ crystal. In consideration of these points, the nitridation process is preferably performed in an N ₂ atmosphere at 1350 to 1500 ° C.

The nitrided laminated sheet is sintered. The sintering preferably includes reactive sintering. The sintering preferably includes a reaction sintering performed in an N ₂ atmosphere at a pressure higher than normal pressure (for example, 2 to 100 atm) to suppress decomposition of the nitrided product into Si and N ₂ . By reaction sintering may obtain a silicon nitride (Si ₃ N ₄₎ sintered body of high quality, the reaction sintering method is Si is reacted with a nitrogen gas and the method for obtaining a silicon nitride (Si ₃ N _4), the shrinkage after the nitrification reaction if the sintering reaction Small and precise shape can be manufactured. The sintering is preferably performed at a temperature of 1800 to 1950 캜.

Hereinafter, experimental examples according to the present invention will be specifically shown, and the present invention is not limited by the following experimental examples.

In this experimental example, a sheet type substrate (thick film substrate) for a heat radiator plate was manufactured through tape casting using a high purity Si powder as a starting material. The amount of residual oxygen and carbon is measured after changing the temperature and the atmospheric condition of the degreasing process and the amount of residual oxygen and carbon is measured even after the nitriding process following the degreasing process so that oxygen and carbon remaining in the degreasing process And the defatting conditions favorable to the properties of the final heat dissipation substrate were suggested. FIG. 1 shows a process chart according to an experimental example.

<Experimental Example 1>

Si powder, Y ₂ O ₃ powder and MgO powder were first mixed with a 3D mixer using a zirconia ball to prepare a raw material for ceramics. The 3D mixer used zirconia balls. The average particle size of the Si powder (Grade 4,> 98.9%, VESTA Si, USA) used in this experiment was about 3 μm and Y ₂ O ₃ powder (Grade B,> 99.9% MgO (> 99%, High Purity Chemical, Japan) having an average particle size of about 8 mu m was used. The ceramic raw material contains 97 wt% of Si powder, 5 wt% of Y ₂ O ₃ powder, and 2 wt% of MgO powder.

A solvent, an organic binder, a plasticizer and a dispersant were added to a ceramic raw material in which Si powder, Y ₂ O ₃ powder and MgO powder were mixed and ball milled for 24 hours . The organic binder was polyvinyl butyral (PVB) (BMSZ,> 97%, SEKISUI Chemical Co., LTD, Japan), and the organic binder used was a mixture of ethanol (EtOH) and toluene DOP (Dioctyl phthalate) (99%, SAMCHUN Chemical, Korea) was used as the plasticizer, and a copolymer type (DISPERBYK®-111, Altana, Germany) was used as the dispersant.

The ball milled product was aged for 24 hours to obtain a slurry.

The slurry was prepared by changing the content (P / B) of the organic binder (B) relative to the ceramic raw material (P) in the range of 5.5 to 9.5% in order to obtain an optimal sheet shaped green body. Table 1 below shows typical compositions when the content (P / B) of the organic binder (B) relative to the raw material (P) of the ceramic is 7.5%. The viscosity of the slurry was measured using a rotary rheometer (HAAKE MARS III). The measurement conditions were 0 - 200 min ^{- 1} per minute for 10 minutes at 25 ° C.

Ceramic raw material (wt%) Solvent (wt%) Dispersant (wt%) Organic binder (wt%) Plasticizer (wt%) 53.93 40.45 0.16 4.05
(P / B = 7.5%) 1.41

The viscous behavior of the slurry with respect to the amount of PVB added to the ceramics raw material (solid content) is shown in Fig.

Referring to FIG. 2, when the viscosity of the slurry was measured according to the addition amount of PVB as an organic binder, the viscosities of the slurries were found to be 2414, 616 and 406 cP (Shear rate = 100s ^-1 ). When the PVB content of the ceramics raw material was 5.5%, the center portion of the green sheet and the left and right side thickness variations were relatively large. When the PVB addition amount of the ceramic raw material was 9.5%, the thickness of the green sheet was too thin, It was ineffective when producing sheets.

Tape casting was performed by pouring the slurry into a doctor blade set at a height of a dam of 300 mu m and moving the substrate film at a speed of 2.0 m / min, performing a drying process at a temperature of 70 DEG C for 60 minutes, The substrate film was peeled off to finally obtain a sheet-shaped molded article (hereinafter referred to as a green sheet) having a thickness of 100 mu m.

The table temperature of the stacking machine was set at 40 DEG C, and a plurality of green sheets were stacked. Then, a pressure of 12 ton was applied for 10 seconds to form a thickness of 1 mm. WIP (Warm Isostatic Press) for 10 minutes at 70 ° C and 20 MPa. The result of the compression was cut to a size of 30 x 30 mm to obtain a laminated sheet.

The densities of the laminated sheets were determined by the dimensional measurement method, and the average density and the standard deviation were obtained from 10 samples for each content. The surface state of the laminated sheet was confirmed by using an optical microscope.

The thermogravimetric analysis of the laminated sheet was carried out by TG-DSC (SDT Q600). The rate of temperature increase was 10 ° C / min and the flow rate of the atmosphere control gas was 100 ml / min.

The density of the laminated sheet according to the amount of PVB added relative to the raw material of ceramics is shown in Fig.

3, the density values of the laminated sheets were 1.61, 1.63, and 1.62 g / cm 3, respectively, when the addition amounts of PVB were 5.5%, 7.5%, and 9.5%, respectively. . However, when PVB content of 5.5% was higher than that of the raw materials of ceramics, it was found that the density distribution was larger than other compositions, which is an adverse condition in the actual process.

Optical microscope photographs of the surface of the laminated sheet according to the addition amount of PVB relative to the raw material of ceramics are shown in Figs. 4A to 4C. FIG. 4A is an optical microscope photograph of the surface of the laminated sheet when the laminated sheet was prepared at a PVB addition amount of 5.5% relative to the raw material of the ceramics. FIG. And FIG. 4C is an optical microscope photograph of the surface of the laminated sheet when the laminated sheet is made to have the PVB content of 9.5% of the raw material of the ceramics.

4A to 4C, several agglomerates were found in the laminated sheet prepared by adjusting the addition amount of PVB to 5.5% of the raw materials of the ceramics, and cracks were observed in the laminated sheet prepared by adjusting the addition amount of PVB to 9.5% of the raw materials of the ceramics . The surface state of the laminated sheet prepared with 7.5% PVB added to the raw material of ceramics was superior to that of the other compositions. Even when the viscosity and density characteristics were taken into account, the PVB addition amount to the ceramics raw material was 7.5% Respectively.

FIG. 5 shows the result of thermogravimetric analysis of the laminated sheet prepared by adjusting the addition amount of PVB relative to the raw material of ceramics to 7.5%.

5, in both the oxidizing atmosphere (see FIG. 5 (a) and FIG. 5 (b) in the case of the N ₂ atmosphere) , Which is thought to be due to the decomposition of organic matter at this temperature. In the oxidizing atmosphere, the weight decreased to 450 ℃ and then increased again. In contrast, in the inactive atmosphere, the weight did not increase even after 300 ° C, and the behavior gradually decreased. This is because the reaction rate of oxygen and Si increases in the oxidizing atmosphere, so that a considerable amount of SiO ₂ film is formed on the surface of the Si powder. Therefore, it is considered that the weight increase occurs. In the inert atmosphere, do.

<Experimental Example 2>

Si powder was prepared as a raw material for ceramics. The 3D mixer used zirconia balls. The Si powder (Grade 4,> 98.9%, VESTA Si Co., USA) used in this experiment had an average particle size of about 3 μm.

A solvent, an organic binder, a plasticizer and a dispersant were added to the Si powder and ball milled for 24 hours. The organic binder was polyvinyl butyral (PVB) (BMSZ,> 97%, SEKISUI Chemical Co., LTD, Japan), and the organic binder used was a mixture of ethanol (EtOH) and toluene DOP (Dioctyl phthalate) (99%, SAMCHUN Chemical, Korea) was used as the plasticizer, and a copolymer type (DISPERBYK®-111, Altana, Germany) was used as the dispersant.

The ball milled product was aged for 24 hours to obtain a slurry.

The slurry was prepared under the condition that the content (P / B) of the organic binder (B) relative to the Si powder (P) was 7.5% in order to obtain an optimal sheet-shaped molded article (green sheet). The composition is shown in Table 2 below when the content (P / B) of the organic binder (B) relative to the Si powder (P) is 7.5%.

Si powder (wt%) Solvent (wt%) Dispersant (wt%) Organic binder (wt%) Plasticizer (wt%) 53.93 40.45 0.16 4.05
(P / B = 7.5%) 1.41

Tape casting was performed by pouring the slurry into a doctor blade set at a height of a dam of 300 mu m and moving the substrate film at a speed of 2.0 m / min, performing a drying process at a temperature of 70 DEG C for 60 minutes, The substrate film was peeled off to finally obtain a sheet-shaped molded article (hereinafter referred to as a green sheet) having a thickness of 100 mu m.

The table temperature of the stacking machine was set at 40 DEG C, and a plurality of green sheets were stacked. Then, a pressure of 12 ton was applied for 10 seconds to form a thickness of 1 mm. WIP (Warm Isostatic Press) for 10 minutes at 70 ° C and 20 MPa. The result of the compression was cut to a size of 30 x 30 mm to obtain a laminated sheet.

The laminated sheet was subjected to a debinding process. N / O elemental analyzer (HORIBA EMGA-920) and C / S elemental analyzer (LECO CS230) were used to quantitatively analyze the amount of residual oxygen and carbon after degreasing under various conditions. The degreasing in the oxidizing atmosphere proceeded in a box-type electric furnace, and the degassing in an inert atmosphere proceeded in a tubular electric furnace. The N ₂ gas used for the inert atmosphere was purity grade 5N, and the flow rate was fixed at a rate of 1 L / min.

In order to investigate the effects of degreasing process conditions on residual oxygen and carbon content, the degreasing conditions were varied in the range of 300 ~ 700 ℃. The pure Si powder was subjected to a heat treatment (degreasing treatment) in an oxidizing atmosphere and the residual oxygen amount was measured. The residual oxygen amount was indicated by a dotted line in Fig. 6 (see Fig. 6C) )). The residual oxygen amount at room temperature corresponds to about 1.0 wt% of the residual oxygen amount formed during the production of the raw Si powder. As the heat treatment temperature increased, the residual oxygen content increased continuously, and about 3.0 wt% was detected at the maximum heat treatment temperature of 700 ° C.

In the case of producing a laminated sheet without mixing the Y ₂ O ₃ powder and the MgO powder in this Experimental Example, since the measurement results may be ambiguous to clearly distinguish the residual oxygen and the amount of carbon in the degreasing process, The sheets were subjected to a degreasing treatment in an oxidizing atmosphere and an inert atmosphere, respectively, and the residual oxygen amount and the carbon amount were analyzed. The results for residual oxygen amount are shown in Fig. 6, and the results for the carbon amount are shown in Fig. 6 (a) shows the case of performing the degreasing process in the oxidizing atmosphere, (b) shows the case of performing the degreasing process in the inert atmosphere, and FIG. 7 (a) (B) is for the case where the degreasing process is carried out in an inert atmosphere.

Referring to FIG. 6, residual oxygen amount was found to be about 2.9 wt% at room temperature, regardless of the oxidizing atmosphere or the inert atmosphere. The organic binder (PVB, (C ₈ H ₁₄ O ₂ ) _n ) and the oxygen contained in the plasticizer (DOP, C ₆ H ₄ (COOC ₈ H ₁₇ ) ₂ ). The minimum residual oxygen amount was observed at about 400 ° C regardless of the atmosphere. In the oxidizing atmosphere, as the degreasing temperature was increased, the residual oxygen amount was increased to the same amount as that of the pure Si powder (see (c) in FIG. 6). In the inert atmosphere, no significant change was observed despite the increase of the degreasing temperature.

Referring to FIG. 7, the amount of residual carbon at room temperature is about 6.5 wt% as a result of analyzing the amount of residual carbon, which appears to be due to the carbon contained in the organic binder and the plasticizer. Regardless of the oxidizing atmosphere or the inert atmosphere, the amount of residual carbon was abruptly decreased in the process of raising the temperature to about 400 ° C, and there was no significant change even when the degreasing temperature was increased. However, the absolute amount of residual carbon was different according to the atmosphere. In the case of oxidizing atmosphere, about 0.024 wt% was detected at 500 ° C., while in the inert atmosphere, about 0.242 wt% was detected at about 10 times higher at the same temperature .

<Experimental Example 3>

Si powder, Y ₂ O ₃ powder and MgO powder were first mixed with a 3D mixer using a zirconia ball to prepare a raw material for ceramics. The 3D mixer used zirconia balls. The average particle size of the Si powder (Grade 4,> 98.9%, VESTA Si, USA) used in this experiment was about 3 μm and Y ₂ O ₃ powder (Grade B,> 99.9% MgO (> 99%, High Purity Chemical, Japan) having an average particle size of about 8 mu m was used. The ceramic raw material contains 97 wt% of Si powder, 5 wt% of Y ₂ O ₃ powder, and 2 wt% of MgO powder.

A solvent, an organic binder, a plasticizer and a dispersant were added to a ceramic raw material in which Si powder, Y ₂ O ₃ powder and MgO powder were mixed and ball milled for 24 hours . The organic binder was polyvinyl butyral (PVB) (BMSZ,> 97%, SEKISUI Chemical Co., LTD, Japan), and the organic binder used was a mixture of ethanol (EtOH) and toluene DOP (Dioctyl phthalate) (99%, SAMCHUN Chemical, Korea) was used as the plasticizer, and a copolymer type (DISPERBYK®-111, Altana, Germany) was used as the dispersant.

The ball milled product was aged for 24 hours to obtain a slurry.

The slurry was prepared by changing the content (P / B) of the organic binder (B) relative to the raw material (P) of ceramics in the condition of 7.5% in order to obtain an optimal sheet shaped green body (green sheet). The composition is shown in Table 3 below when the content (P / B) of the organic binder (B) relative to the raw material (P) of ceramics is 7.5%.

Ceramic raw material (wt%) Solvent (wt%) Dispersant (wt%) Organic binder (wt%) Plasticizer (wt%) 53.93 40.45 0.16 4.05
(P / B = 7.5%) 1.41

Tape casting was performed by pouring the slurry into a doctor blade set at a height of a dam of 300 mu m and moving the substrate film at a speed of 2.0 m / min, performing a drying process at a temperature of 70 DEG C for 60 minutes, The substrate film was peeled off to finally obtain a sheet-shaped molded article (hereinafter referred to as a green sheet) having a thickness of 100 mu m.

The table temperature of the stacking machine was set at 40 DEG C, and a plurality of green sheets were stacked. Then, a pressure of 12 ton was applied for 10 seconds to form a thickness of 1 mm, and WIP (Warm Isostatic Press) for 10 minutes at 70 ° C and 20 MPa. The result of the compression was cut to a size of 30 x 30 mm to obtain a laminated sheet.

The laminated sheet was subjected to a debinding process. N / O elemental analyzer (HORIBA EMGA-920) and C / S elemental analyzer (LECO CS230) were used to quantitatively analyze the amount of residual oxygen and carbon after degreasing under various conditions. The degreasing in the oxidizing atmosphere proceeded in a box-type electric furnace, and the degassing in an inert atmosphere proceeded in a tubular electric furnace. The N ₂ gas used for the inert atmosphere was purity grade 5N, and the flow rate was fixed at a rate of 1 L / min.

Nitriding was performed on the degreased laminated sheet. The nitriding treatment was carried out at 1400 DEG C and 1450 DEG C for 4 hours, respectively, followed by cooling to room temperature. After the nitriding treatment, the residual oxygen and carbon contents were analyzed by using N / O element analyzer and C / S element analyzer. For analysis of α-Si ₃ N ₄ , β-Si ₃ N ₄ and Si, X-ray diffraction analysis was performed.

In order to optimize the degreasing process conditions considering the nitriding process, it is degreased in an oxidizing atmosphere and an inert atmosphere at 400 ° C. and nitriding is carried out at a temperature of 1400 ° C. and 1450 ° C. for 4 hours to measure the amount of residual oxygen and carbon present in the sample FIG. 8 shows the residual oxygen amount, and FIG. 9 shows the carbon amount. FIGS. 8 and 9A show the case of performing the degreasing process in the oxidizing atmosphere and the nitriding treatment in the N ₂ atmosphere, FIG. 8B shows the case of performing the degreasing process in the inert atmosphere and nitriding in the N ₂ atmosphere Lt; / RTI &gt;

As can be seen from FIGS. 8 and 9, the residual oxygen and carbon present after the degreasing process were all reduced while proceeding with the nitriding process. In the case of residual oxygen, the residual oxygen amount of the specimen degreased in the oxidizing atmosphere was larger than the residual oxygen amount of the degreased specimen in the inert atmosphere, but it was abruptly decreased in the nitriding treatment temperature range. After the nitriding treatment, The residual oxygen content of the specimen was less than the residual oxygen content of the degreased specimen in the inert atmosphere. In the case of residual carbon, the amount of residual carbon in the degreased specimen in the oxidizing atmosphere was much smaller than the amount of residual carbon in the degreased specimen in the inert atmosphere, and this difference remained in the nitriding temperature range. The amount of residual carbon in the degreased specimen was not detectable by the C / S analyzer, indicating that it was significantly less than the amount of residual carbon of 0.108 wt% in the degreased specimen in an inert atmosphere.

10 is a graph showing an X-ray diffraction (XRD) pattern of a specimen subjected to degreasing in an oxidizing atmosphere and an inert atmosphere at 400 ° C and nitriding treatment at 1400 ° C for 4 hours. 10 (a) is for a case where a degreasing process is performed in an oxidizing atmosphere and nitriding is performed in an N ₂ atmosphere, (b) is a case where a degreasing process is performed in an inert atmosphere, and nitriding is performed in an N ₂ atmosphere .

Referring to FIG. 10, in each of the samples degreased in an oxidizing atmosphere and an inert atmosphere, similar α-Si ₃ N ₄ and β-Si ₃ N ₄ It is judged that the atmosphere of the degreasing step is not related to the phase change rate.

When the sheet-type Si ₃ N ₄ substrate is manufactured through the tape casting process, the degreasing of the laminated sheet is carried out in an oxidizing atmosphere of about 400 ° C. in consideration of the residual oxygen amount and the amount of carbon, Is effective in minimizing the amount of residual oxygen and carbon which may affect the thermal and mechanical properties in the future.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, This is possible.

Claims (12)

Preparing a ceramic raw material including Si powder, Y ₂ O ₃ powder and MgO powder;
Mixing the ceramic raw material, the solvent, the organic binder, the dispersant, and the plasticizer to form a slurry;
Forming a shaped body in a sheet form by molding the slurry using a tape casting method;
Laminating the formed body into a plurality of layers and pressing them to form a laminated sheet;
Degreasing the laminated sheet in an oxidizing atmosphere to minimize the amount of residual oxygen and carbon;
Nitriding the degreased laminated sheet; And
And sintering the nitrided laminated sheet.
The method of claim 1 wherein said Y ₂ O ₃ powder is 0.1 to 10 parts by weight relative to the Si powder containing 100 parts by weight of the ceramic raw material,
Wherein the MgO powder is contained in the ceramic raw material in an amount of 0.1 to 7 parts by weight based on 100 parts by weight of the Si powder.
The method according to claim 1, wherein the organic binder is mixed in an amount of 5.5 to 9.5 parts by weight based on 100 parts by weight of the ceramic raw material.
4. The method of claim 3, wherein the organic binder comprises polyvinylbutyral.
The method of claim 1, wherein the dispersant is mixed in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of the ceramic raw material,
Wherein the dispersing agent comprises a dispersing agent of a copolymer type.
The method of claim 1, wherein the plasticizer is mixed in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the ceramic raw material,
Wherein the plasticizer comprises dioctyl phthalate. &Lt; RTI ID = 0.0 &gt; 21. &lt; / RTI &gt;
The method according to claim 1, wherein the degreasing treatment is performed at 300 to 500 ° C to minimize the amount of residual oxygen and carbon.
The method of manufacturing a sheet-like silicon nitride substrate according to claim 1, wherein the nitriding treatment is performed in an N ₂ atmosphere at 1350 to 1500 ° C.
The process for producing a sheet-like silicon nitride substrate according to claim 1, wherein the sintering comprises reaction and sintering performed in an N ₂ atmosphere at a pressure higher than normal pressure in order to suppress decomposition of the nitrided product into Si and N ₂ Way.
The method according to claim 9, wherein the sintering is performed at a temperature of 1800 to 1950 캜.
The method according to claim 1, wherein the Si powder is a Si powder scrap or a Si wafer powder,
Wherein the Si powder is a powder having an average particle diameter of 0.5 to 20 占 퐉.
The sheet-shaped molded article according to claim 1, wherein the sheet-shaped molded article has a thickness of 10 to 200 탆,
The laminated sheet is formed to a thickness of 0.5 to 20 mm,
Further comprising the step of cutting the laminated sheet to a desired size before degreasing treatment.

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