Sintered body and method for manufacturing sintered body

Abstract

The present invention provides a sintered body and a method for manufacturing a sintered body, the sintered body of an embodiment of the present invention includes boron carbide, includes a portion in which the volume ratio of grains having a grain size of greater than 30 μm and less than or equal to 60 μm with respect to the total grains is 50% to 70% when viewed from the surface, and the carbon content with respect to the total amount according to X-ray fluorescence analysis is 30% to 43% by weight.

Description

Technical Field

[0001] This embodiment relates to a sintered body with improved plasma etch resistance and components of a plasma processing apparatus including the sintered body. Background Technology

[0002] In a plasma processing apparatus, upper and lower electrodes are arranged inside a chamber, and semiconductor wafers, glass substrates, etc., are placed on the lower electrode. Operation is achieved by applying an electric current between the two electrodes. Electrons accelerated by the electric field between the upper and lower electrodes, electrons released from or heated by the electrodes, collide with ionized molecules of the process gas, thereby generating a plasma of the process gas. In this plasma, active species such as free radicals or ions can perform desired micro-processing on the surface of the object to be etched, for example, etching.

[0003] The manufacturing and design of microelectronic devices are becoming increasingly miniaturized, especially requiring higher dimensional accuracy and significantly higher power for plasma etching. Such plasma processing devices incorporate a focusing ring that is affected by the plasma.

[0004] As plasma power increases, it can lead to wavelength effects that cause standing waves and skin effects that concentrate the electric field at the center of the electrode surface. Consequently, the plasma distribution typically reaches its highest point at the center of the etched object and its lowest point at the edges, which can result in severe non-uniformity of the plasma distribution on the substrate and potentially reduce the quality of microelectronic devices.

[0005] By placing a focusing ring around the object to be etched, the surrounding electric field distribution can be affected, and the non-uniformity of the plasma distribution can be mitigated to some extent. However, compared to the plasma processing time, the etching rate of the focusing ring is relatively high, and the plasma distribution may be affected by etching. An improved scheme is needed to enhance the etching resistance and replacement cycle of such a focusing ring and achieve process efficiency.

[0006] As relevant prior art, there are "boron carbide materials" disclosed in Korean Patent No. 10-2262340 and "boron carbide sintered body and etching apparatus including the same" disclosed in Korean Patent No. 10-2020-0019068. Summary of the Invention

[0007] The problem the invention aims to solve

[0008] The purpose of this embodiment is to provide a sintered body and components therein that can guide a uniform plasma distribution for etched objects and have improved plasma etch resistance.

[0009] means for solving problems

[0010] To achieve the above objectives, the sintered body according to the embodiments may include boron carbide and includes a portion of grains with a grain size greater than 30 μm and less than or equal to 60 μm, which, when viewed from the surface, constitute 50% to 70% of the total grain size, and the carbon content relative to the total amount, as determined by X-ray fluorescence analysis, may be 30% to 43% by weight.

[0011] In one embodiment, the volume ratio of grains with a grain size of less than or equal to 10 μm relative to the total grain size can be from 0.01% to 1%.

[0012] In one embodiment, the volume ratio of grains with a grain size greater than 60 μm and less than or equal to 80 μm relative to the total grain size can be 12% to 20%.

[0013] In one embodiment, the average grain size can be from 30 μm to 70 μm.

[0014] In one embodiment, the content of boron and carbon can be 97% by weight or more.

[0015] In one embodiment, under plasma etching conditions of a chamber pressure of 100 mTorr, a plasma power of 800 W, an exposure time of 300 minutes, a CF4 gas flow rate of 50 sccm, an Ar gas flow rate of 100 sccm, and an O2 gas flow rate of 20 sccm in the chamber, the etching rate according to Formula 1 below can be 1.8% or less.

[0016] [Formula 1]

[0017] Etching rate = {(thickness before etching - thickness after etching) / (thickness after etching)} × 100%

[0018] In one embodiment, the thermal conductivity at 25°C can be above 23 W / mK and below 42 W / mK.

[0019] To achieve the above objectives, the method for manufacturing a sintered body according to this embodiment may include: a carbonization step, in which a molded body formed from a raw material composition is heat-treated at a temperature of 500°C to 1000°C; a first sintering step, in which, after the carbonization step, a heat treatment is performed at a temperature of 2100°C to 2300°C; and a second sintering step, in which, after the first sintering step, a heat treatment is performed at a temperature of 2200°C to 2320°C, wherein the raw material composition may contain boron carbide, carbonaceous substances, and sintering property modifiers.

[0020] In one embodiment, the raw material composition may be raw material particles obtained by spray drying a raw material slurry containing boron carbide, carbonaceous substances, sintering property modifiers, and solvents.

[0021] In one embodiment, the first sintering step and the second sintering step can be performed under a pressure of less than 0.2 MPa. The first sintering step can be performed for 0.5 hours to 2 hours, and the second sintering step can be performed for 1 hour to 3 hours.

[0022] To achieve the above objectives, the component according to this embodiment may include the sintered body and may be applied inside a plasma processing apparatus.

[0023] Invention Effects

[0024] The sintered body according to this embodiment can reduce the generation of impurity particles during plasma etching by reducing line defects caused by coarse grains, and can have excellent plasma etching resistance and can stably maintain plasma etching resistance. Attached Figure Description

[0025] Figure 1A To show a scanning electron microscope image of the sintered body surface of Example 1 before electrolytic etching in the experimental example, Figure 1B To show a scanning electron microscope image of the sintered body surface of Example 1 after electrolytic etching in the experimental example, Figure 1C In the scanning electron microscope image of the sintered body surface of Example 1 after electrolytic etching in the experimental example, identifiable grains are distinguished by color.

[0026] Figure 2A A photograph showing the state of the sample of Example 1 after plasma etching in the experimental example, Figure 2B A photograph showing the sample state of Comparative Example 1 after plasma etching in the experimental example.

[0027] Figure 3A The sintered body surface and component measurement locations of Example 1 before electrolytic etching are shown. Figure 3B The sintered body surface and component measurement locations of Example 1 after electrolytic etching are shown.

[0028] Figure 4A The surface state of Example 1 before plasma etching is shown. Figure 4B The surface state of Example 1 after plasma etching is shown.

[0029] Figure 5A The surface condition of Comparative Example 1 before plasma etching is shown. Figure 5B The surface condition of Comparative Example 1 after plasma etching is shown. Detailed Implementation

[0030] Hereinafter, one or more embodiments will be described in detail with reference to the accompanying drawings to enable those skilled in the art to readily implement the present invention. However, this embodiment can be implemented in many different forms and is not limited to the embodiments described in this specification. Throughout the specification, the same reference numerals are used to refer to the same or similar configurations.

[0031] In this specification, when a component is described as "including" another component, it means, unless otherwise stated, that other components are also included, rather than excluding other components.

[0032] In this specification, when describing a component as "connected" to another component, it includes not only the case of "direct connection" but also the case of "connection through other components".

[0033] In this specification, "B is located on A" means that B is located on A in direct contact with A or in the presence of other layers in between, and should not be interpreted as B being located on the surface of A in contact with A.

[0034] In this specification, the term "combination of..." included in the Markush-type description refers to a mixture or combination of one or more constituent elements selected from the group consisting of the constituent elements of the Markush-type description, thereby implying that the present invention includes one or more constituent elements selected from the group consisting of the said constituent elements.

[0035] In this specification, the reference to "A and / or B" means "A, B or A and B".

[0036] In this specification, unless otherwise specified, terms such as “first,” “second,” or “A,” “B” are used to distinguish the same terms from each other.

[0037] Unless otherwise specified, the use of the singular in this specification is to be interpreted as including the meaning of singular or plural as the context suggests.

[0038] sintered body

[0039] To achieve the stated objective, the sintered body according to the embodiments may include boron carbide and includes a portion comprising, when viewed from the surface, a portion of grains with a grain size greater than 30 μm and less than or equal to 60 μm relative to the total grain size, comprising 50% to 70% of the volume of such grains, and a carbon content relative to the total amount as determined by X-ray fluorescence analysis, which may be 30% to 43% by weight.

[0040] The boron carbide in the sintered body can essentially be B4C.

[0041] The sintered body is based on boron carbide, contains a specified amount of carbon in addition to boron carbide, and may also contain a portion of silicon or silicon carbide (Si). x C y (e.g., oxygen, boron oxide). The carbon and silicon carbide in the sintered body can exist in the form of secondary phases.

[0042] The sintered body may contain boron carbide grains, and the boron carbide grains may also be observed on the surface of the sintered body.

[0043] The sintered body can have a coarser average grain size than existing boron carbide sintered bodies.

[0044] In the sintered body, the volume ratio of grains with a grain size greater than 30 μm and less than or equal to 60 μm relative to the total grain size can be 50% to 70%, or 55% to 65%.

[0045] In the sintered body, the volume ratio of grains with a grain size of less than or equal to 10 μm relative to the total grain size can be from 0.01% to 1%, or from 0.01% to 0.81%.

[0046] In the sintered body, the volume ratio of grains with a grain size of less than or equal to 20 μm relative to the total grain size can be 2% to 14%, or 1% to 10%.

[0047] In the sintered body, the volume ratio of grains with a size greater than 60 μm and less than or equal to 80 μm relative to the total grain size can be 12% to 20%, or 14% to 18%.

[0048] In the sintered body, the volume ratio of grains with a grain size greater than 40 μm relative to the total grain size can be 44% to 65%, or 49% to 60%.

[0049] In the sintered body, the volume ratio of grains with a grain size greater than 70 μm relative to the total grain size can be 8% to 15%, or 9.1% to 13.7%.

[0050] The average grain size of the sintered body can be from 30 μm to 70 μm, or from 45 μm to 65 μm.

[0051] The grain size analysis of the sintered body can be performed by the method described in the following experimental examples, and can be based on observations on the surface.

[0052] Sintered bodies with such grain characteristics can reduce the generation of impurity particles during plasma etching by reducing line defects, can have excellent plasma etching resistance, and can help maintain plasma etching resistance.

[0053] Based on boron and carbon (B, C), the purity of the sintered body can be above 97%, above 99%, or above 99.2%.

[0054] The purity was evaluated based on the weight as determined by X-ray fluorescence analysis (XRF).

[0055] The carbon content of the sintered body, as determined by X-ray fluorescence analysis (XRF), can be from 30% to 43% by weight, or from 32% to 40% by weight. This carbon content can represent the case where carbon is added to the stoichiometric carbon content of boron carbide (B4C) (21.72% by weight). Alternatively, this could be due to a change in the bonding relationship of boron carbide during the sintering process, or due to the influence of carbonaceous substances added to the raw materials during manufacturing.

[0056] The boron content of the sintered body, as determined by X-ray fluorescence analysis, can be between 55% and 68% by weight, or between 56% and 66% by weight. As previously mentioned, such boron content may be due to the addition of more carbon, or it may be a result of the addition of carbonaceous substances to the raw materials during manufacturing.

[0057] In the sintered body, the oxygen content relative to the total amount, as determined by X-ray fluorescence analysis, can be from 0.1 wt% to 0.9 wt%, or from 0.3 wt% to 0.7 wt%.

[0058] In the sintered body, the silicon content relative to the total amount, as determined by X-ray fluorescence analysis, can be from 0.05 wt% to 0.5 wt%, or from 0.1 wt% to 0.4 wt%.

[0059] The sintered body, by having such other elemental contents, can play a positive role in densification.

[0060] The metallic impurity content of the sintered body can be below 400 ppm or below 200 ppm. The metallic impurities may include sodium, aluminum, calcium, iron, nickel, etc.

[0061] The flexural strength of the sintered body can be from 365 MPa to 547 MPa, or from 410 MPa to 502 MPa.

[0062] The Vickers hardness of the sintered body can be from 26.1 GPa to 39.1 GPa, or from 29.3 GPa to 35.9 GPa.

[0063] The compressive strength of the sintered body can be from 549 MPa to 823 MPa, or from 617 MPa to 755 MPa.

[0064] The elastic modulus of the sintered body can be from 308 GPa to 424 GPa, or from 347 GPa to 424 GPa.

[0065] The Poisson's ratio of the sintered body can be from 0.175 to 0.263, or from 0.197 to 0.241.

[0066] The thermal conductivity of the sintered body at 25°C can be above 23 W / mK and below 42 W / mK, and can be between 30 W / mK and 40 W / mK.

[0067] The coefficient of thermal expansion of the sintered body can be 3.34 × 10⁻⁶ at temperatures ranging from 25°C to 400°C. -6 / K to 5.02×10 -6 / K can be 3.76 × 10 -6 / K to 4.60×10 -6 / K.

[0068] The coefficient of thermal expansion of the sintered body at 400℃ to 800℃ can be 4.01×10⁻⁶. -6 / K to 6.02×10 -6 / K can be 4.52×10 -6 / K to 5.52×10 -6 / K.

[0069] The resistivity of the sintered body can be from 0.05 Ωcm to 2 Ωcm, or from 0.1 Ωcm to 1 Ωcm.

[0070] Sintered bodies with these characteristics can exhibit good reliability and durability when used as components of plasma processing devices, and can help maintain plasma etch resistance.

[0071] Under plasma etching conditions of a chamber pressure of 100 mTorr, a plasma power of 800 W, a plasma exposure time of 300 minutes, a CF4 gas flow rate of 50 sccm, an Ar gas flow rate of 100 sccm, and an O2 gas flow rate of 20 sccm, the etching rate of the sintered body according to Formula 1 below can be less than 1.8%.

[0072] [Formula 1]

[0073] Etching rate = {(thickness before etching - thickness after etching) / (thickness after etching)} × 100%

[0074] The etching rate of the sintered body can be less than 1.6% or less than 1.55%.

[0075] Because the sintered body has such plasma etch resistance and coarse grain characteristics, the generation of particles in the plasma processing can be suppressed to the greatest extent.

[0076] Based on the plasma etching conditions, the sintered body can have an etch rate that is reduced by more than 20% compared to the etch rate of silicon carbide prepared by chemical vapor deposition (CVD), and can have an etch rate that is reduced by more than 30%.

[0077] The relative density of the sintered body can be above 95% or above 97%, or below 99.9%. The sintered body can exhibit relatively large grain size while possessing excellent relative density.

[0078] part

[0079] To achieve the above objectives, the component according to this embodiment may include the sintered body and may be applied inside a plasma processing apparatus.

[0080] The component may include the sintered body on a portion of a surface that may be exposed to plasma, or it may include the sintered body on the entire surface.

[0081] The component may include the sintered body on its surface, and may also include other ceramic materials (silicon carbide, silicon, etc.) inside the surface.

[0082] The component can be one that affects the flow of plasma ions during plasma etching, such as a focusing ring. When the wafer is placed in a plasma processing apparatus, the focusing ring can be used as a support for supporting the edges of the wafer.

[0083] Since the component includes the sintered body, it can ensure good plasma etch resistance, reduce the frequency of component replacement, and effectively prevent the generation of particles that may have a negative impact on the yield.

[0084] Method for manufacturing sintered bodies

[0085] To achieve the above objectives, the method for manufacturing a sintered body according to this embodiment may include: a carbonization step in which a molded body formed from a raw material composition is heat-treated at a temperature of 500°C to 1000°C; a first sintering step in which, after the carbonization step, a heat treatment is performed at a temperature of 2100°C to 2300°C; and a second sintering step in which, after the first sintering step, a heat treatment is performed at a temperature of 2200°C to 2320°C.

[0086] The raw material composition can be raw material particles obtained by spray drying a raw material slurry containing boron carbide, carbonaceous substances, sintering property modifiers, and solvents.

[0087] The boron carbide in the raw material composition can be in powder form and can be a powder with a purity of more than 98% by weight of boron and carbon relative to the total powder content.

[0088] The carbonaceous material in the raw material composition can be in the form of a polymer resin or a carbonized polymer resin. For example, it can be a phenolic resin, polyvinyl alcohol resin, etc.

[0089] The sintering property improver of the raw material composition may include boron oxide, binder, etc., and the binder may include acrylic resin.

[0090] The solvent of the raw material composition may include water, alcohols, etc., and its content may be 60% to 80% by volume based on the total weight of the raw material slurry.

[0091] The raw material slurry can be prepared by a stirring process such as ball milling, and the ball milling process can be carried out for 5 to 20 hours using polymer balls or the like.

[0092] The formed body obtained in the carbonization step can be obtained by injecting raw material into a mold and applying pressure, or by applying cold isostatic pressing (CIP). In this case, the pressure can be from 100 MPa to 200 MPa.

[0093] A process to remove unwanted parts can be applied to the molded body during the carbonization step.

[0094] The heating process can continue for 10 to 15 hours until the heat treatment temperature of the first sintering step is reached.

[0095] The first sintering step can be carried out for 0.5 hours to 2 hours.

[0096] The heating process can continue for 2 to 5 hours until the heat treatment temperature of the second sintering step is reached.

[0097] The second sintering step can be carried out for 1 to 3 hours.

[0098] After the second sintering step, a cooling step can be performed to cool to room temperature, and the cooling step can last for 10 to 15 hours.

[0099] Through this sintering step, sintered bodies with relatively large grains can be manufactured, and good densification can be achieved.

[0100] The sintered body obtained through the second sintering step can be further shaped.

[0101] In the first sintering step, a specified heating rate can be applied until the heat treatment temperature is reached. The heating rate can be from 1°C / min to 10°C / min, or from 2°C / min to 5°C / min.

[0102] In the second sintering step, a specified heating rate can be applied until the heat treatment temperature is reached. The heating rate can be from 0.1°C / min to 5°C / min, or from 0.2°C / min to 1°C / min.

[0103] In the cooling step following the second sintering step, a specified cooling rate can be applied, which can be from -10°C / min to -1°C / min, or from -5°C / min to -2°C / min.

[0104] The first sintering step and the second sintering step can be carried out at a pressure below 0.2 MPa, at substantially atmospheric pressure (0.101 MPa), or at a pressure above 0.05 MPa.

[0105] The present invention will be described in more detail below through specific embodiments. These embodiments are merely examples to aid in understanding the invention, and the scope of the invention is not limited thereto.

[0106] Example 1 - Manufacturing of Sintered Body

[0107] A raw material slurry was prepared by mixing 14 parts by volume of boron carbide powder from China Abrasive and 70 parts by volume of ethanol solvent, relative to a total volume of 100 parts by volume. The mixture of the powder and solvent was then combined with 19.2 parts by weight of phenolic resin and 2 parts by weight of acrylic binder, relative to a total volume of 100 parts by weight. The raw material slurry was spray-dried through a nozzle to obtain raw material particles, which were then loaded into a mold to obtain a molded body. The molded body was heat-treated at 800°C to perform a carbonization step. Then, the temperature was increased to 2200°C at a rate of 3°C / min, followed by a first sintering step of heat treatment at 2200°C for 1 hour. Then, the temperature was increased to 2300°C at a rate of 0.5°C / min, followed by a second sintering step of heat treatment at 2300°C for 2 hours. Finally, a cooling step was performed to room temperature (25°C) at a rate of 3°C / min, thereby preparing a sintered body.

[0108] Comparative Example 1 - Silicon carbide prepared by chemical vapor deposition

[0109] Silicon carbide prepared by KNJ using chemical vapor deposition (CVD) was prepared.

[0110] Experimental Example - Grain and Composition Analysis of Sintered Bodies by Electrolytic Etching

[0111] The sintered body prepared in Example 1 was subjected to electrolytic etching in a 2% (v / v) KOH solution at a flow rate of 12 sccm to 20 sccm for 5 seconds and a voltage of 40 V to 51 V, followed by ultrasonic cleaning for 20 minutes. Random micro-regions on the surface before and after electrolytic etching were photographed using a scanning electron microscope (SEM) at magnifications of 500x to 1000x. The volume ratio of each grain size was analyzed, and the composition of a subset of locations (A, B, C, D, E, F) before and after electrolytic etching was analyzed. The results are shown in... Figures 1A to 1C , Figures 3A to 3B Tables 1, 2, and 3, etc.

[0112] Table 1

[0113] Less than or equal to 10 0.81 Greater than 10 and less than or equal to 20 10.14 Greater than 20 and less than or equal to 30 12.89 Greater than 30 and less than or equal to 40 21.79 Greater than 40 and less than or equal to 50 16.63 Greater than 50 and less than or equal to 60 21.02 Greater than 60 and less than or equal to 70 5.30 Greater than 70 and less than or equal to 80 11.42

[0114] Table 2

[0115]

[0116] Table 3

[0117]

[0118]

[0119] Figure 1A The surface of the sintered body of Example 1 before electrolytic etching is shown. Figure 1B The surface of the sintered body of Example 1 after electrolytic etching is shown. Figure 1C The image shows identifiable grains distinguished by color on the surface of the sintered body of Example 1 after electrolytic etching.

[0120] Figure 3A The sintered body surface and component measurement locations of Example 1 before electrolytic etching are shown. Figure 3B The sintered body surface and component measurement locations of Example 1 after electrolytic etching are shown.

[0121] Refer to Table 1 and Figures 1A to 1C It can be confirmed that in the sintered body of Example 1, coarse grains of tens of micrometers are uniformly distributed, and there are almost no grains smaller than 10 μm.

[0122] Refer to Tables 2 and 3 and Figures 3A to 3BIn the sintered body of Example 1, not only boron carbide, but also silicon carbide, glassy carbon, etc., can be identified on the surface before and after electrolytic etching.

[0123] Experimental Example - X-ray Fluorescence Analysis (XRF)

[0124] The sintered body samples of Example 1 and Comparative Example 1 were analyzed by X-ray fluorescence spectroscopy (XRF) using a ZSX Primus instrument from Rigaku Corporation, Japan. The results are shown in Table 4.

[0125] Table 4

[0126]

[0127]

[0128] As can be seen from Table 4, the sintered body of Example 1 contains approximately 60.91% by weight boron and 38.35% by weight carbon, and also contains some oxygen, silicon, etc.

[0129] Experimental Example - Plasma Etching Rate Measurement

[0130] The plasma etch rate of the sintered body samples of Example 1 and Comparative Example 1 was measured under the following conditions, and the results are shown in Tables 4 and 5. Figures 4A to 4B and Figures 5A to 5B wait.

[0131] plasma etching conditions

[0132] Chamber pressure: 100 mTorr, plasma power: 800 W, exposure time: 300 minutes, CF4 gas flow rate: 50 sccm, Ar gas flow rate: 100 sccm, O2 gas flow rate: 20 sccm

[0133] Figure 4A The surface state of Example 1 before plasma etching is shown. Figure 4B The surface state of Example 1 after plasma etching is shown.

[0134] Figure 5A The surface condition of Comparative Example 1 before plasma etching is shown. Figure 5B The surface condition of Comparative Example 1 after plasma etching is shown.

[0135] Table 5

[0136]

[0137]

[0138] *Etching rate: {(thickness before etching - thickness after etching) / (thickness after etching)} × 100%

[0139] Referring to Table 5, it can be confirmed that the plasma etch resistance of Example 1 is superior to that of silicon carbide manufactured by CVD.

[0140] The preferred embodiments of the present invention have been described in detail above, but the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art based on the basic concepts of the present invention as defined in the appended claims also fall within the scope of the present invention.

Claims

1. A sintered body, wherein, The sintered body includes boron carbide. This includes the portion where, when viewed from the surface, the volume ratio of grains with a grain size greater than 30 μm and less than or equal to 60 μm relative to the total grain size is 50% to 70%. The volume percentage of grains with a size greater than 60 μm and less than or equal to 80 μm relative to the total grain size is 12% to 20%. The carbon content relative to the total amount, based on X-ray fluorescence analysis, ranges from 30% to 43% by weight. The average grain size is 30 μm to 70 μm, and the boron and carbon content is over 97% by weight. The compressive strength of the sintered body is between 549 MPa and 823 MPa. Under plasma etching conditions of a chamber pressure of 100 mTorr, a plasma power of 800 W, an exposure time of 300 minutes, a CF4 gas flow rate of 50 sccm, an Ar gas flow rate of 100 sccm, and an O2 gas flow rate of 20 sccm, the etching rate according to Equation 1 is less than 1.8%. Formula 1 Etching rate = {(thickness before etching - thickness after etching) / (thickness after etching)} × 100%.

2. The sintered body according to claim 1, wherein, The volume percentage of grains with a size of 10 μm or less relative to the total grain size is 0.01% to 1%.

3. The sintered body according to claim 1, wherein, The thermal conductivity at 25℃ is above 23W / mK and below 42W / mK.

4. A method for preparing the sintered body according to claim 1, wherein, include: The carbonization step involves heat-treating the molded body, formed from the raw material composition, at a temperature of 500°C to 1000°C. The first sintering step involves heat treatment at a temperature of 2100°C to 2300°C after the carbonization step. The second sintering step is performed after the first sintering step, with heat treatment at a temperature of 2200°C to 2320°C. In the first sintering step, the heating rate is 1°C / min to 10°C / min until the heat treatment temperature is reached. In the second sintering step, the heating rate is 0.1°C / min to 5°C / min until the heat treatment temperature is reached. The raw material composition includes boron carbide, a phenolic resin as a carbon-based substance, and a sintering property improver.

5. The method for manufacturing a sintered body according to claim 4, wherein, The raw material composition is raw material particles obtained by spray drying a raw material slurry containing boron carbide, carbonaceous substances, sintering property improvers and solvents.

6. The method for manufacturing a sintered body according to claim 4, wherein, The first sintering step and the second sintering step are performed under a pressure below 0.2 MPa. The first sintering step is performed for 0.5 to 2 hours. The second sintering step is carried out for 1 to 3 hours.

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