Composite material

Abstract

To provide a composite material which enables precise processing.SOLUTION: At least a part of a cross section SA of a composite material 10 includes a first region S1 containing silicon, and a second region S2 which surrounds the whole circumference in the outside of the first region S1, is a single continuous region without through a grain boundary and contains silicon carbide.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a composite material containing silicon and silicon carbide.

Background Art

[0002] A composite material containing silicon and silicon carbide, also referred to as "SiSiC" etc., is known as a material having high corrosion resistance, heat resistance, etc. As described in Patent Document 1 below, the above composite material can be obtained, for example, by reaction sintering an aggregate composed of powdery carbon and silicon carbide while impregnating it with molten silicon.

[0003] The above composite material is relatively lightweight while having high rigidity and further having high thermal conductivity. For this reason, applications in various fields including semiconductor manufacturing equipment etc. are expected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As shown in the figures etc. in the above patent document, in the cross-section when cutting a composite material containing silicon and silicon carbide, there are a plurality of regions that are cross-sections of silicon carbide particles and regions containing silicon arranged in a matrix so as to fill the spaces between them. In conventional composite materials, it is known that the silicon carbide particles contained in the raw materials before firing hardly grow in size during the firing process. Therefore, the regions of the silicon carbide particles appearing in the above cross-section remain divided into a plurality while generally maintaining their original size, and relatively wide gaps are left between them. As a result, in the cross-section, the area of the silicon filling the gaps between the silicon carbide particles is relatively large.

[0006] In the composite material, the silicon part has a lower strength than the silicon carbide part. For this reason, in conventional composite materials, due to the relatively large area of silicon in the cross-section, there is a tendency to be over-machined during processing, and there has been a problem that it is difficult to perform precise processing as required in semiconductor manufacturing equipment and the like.

[0007] The present invention has been made in view of such problems, and an object thereof is to provide a composite material capable of performing precise processing.

Means for Solving the Problems

[0008] In order to solve the above problems, a composite material according to the present invention is a composite material containing silicon and silicon carbide, and in at least a part of a cross-section obtained by cutting the composite material along a plane, a first region containing silicon, and a first region A second region that surrounds the outside of the region over the entire circumference and is a single continuous region without intervening grain boundaries and contains silicon carbide is included.

[0009] In the cross-section of the composite material having such a configuration, at least in a part of the cross-section, the second region containing silicon carbide is arranged so as to surround the first region containing silicon over the entire circumference. Further, the second region surrounding the first region is a single continuous region without intervening grain boundaries. In the composite material having such a configuration, since the first region containing silicon is finely divided by the second region surrounding it, the ratio occupied by the first region in the cross-section is relatively small. The ratio of the first region, which is the part with low strength, is small, and "over-machining" during processing is suppressed, so that it becomes possible to perform more precise processing on the composite material than in the past.

[0010] In addition, the second region (silicon carbide) surrounding the first region is not a collection of a plurality of particles, but is a continuous single region without passing through grain boundaries. Since relatively high-strength silicon carbide is continuous, "excessive cutting" during processing is further suppressed. Also, an effect can be obtained in that particle detachment during processing is less likely to occur.

[0011] Incidentally, the "continuous single region" described above means to the extent that it is connected without passing through grain boundaries and becomes one, and does not indicate, for example, that the concentrations of various components are uniform throughout the region.

[0012] Also, in the composite material according to the present invention, it is also preferable that the ratio of the area occupied by the second region in the cross section is 70% or more. By setting the relatively high-strength second region to 70% or more, the workability of the composite material can be sufficiently improved.

[0013] Also, in the composite material according to the present invention, it is also preferable that the ratio of the area occupied by the second region in the cross section is 80% or more. By setting the relatively high-strength second region to 80% or more, the workability of the composite material can be further improved.

Effects of the Invention

[0014] According to the present invention, it is possible to provide a composite material capable of performing precise processing.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0016] Hereinafter, this embodiment will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same reference numerals are used for the same components in each drawing as much as possible, and duplicate descriptions are omitted.

[0017] The composite material 10 according to this embodiment is a solid material containing silicon and silicon carbide, and is also referred to as so-called "SiSiC" or the like. The composite material 10 is used, for example, as a material for components constituting a semiconductor manufacturing apparatus, but its specific use, final shape, etc. are not particularly limited.

[0018] As will be described later, the composite material 10 is obtained by reactive sintering an molded body made of powdery carbon and silicon carbide while impregnating it with molten silicon. In this regard, it is the same as the conventional SiSiC. However, the composite material 10 according to this embodiment is different from the conventional SiSiC in the shape and distribution of each region appearing in the cross-section when cut.

[0019] The image shown in FIG. 1 is an image obtained by observing a cross-section SA that appears by cutting the composite material 10 along a plane with a scanning electron microscope (SEM). The range of the cross-section SA is 500 μm × 350 μm, and the magnification is 250 times. Each of the white regions scattered in the cross-section SA has been confirmed to be a region mainly containing silicon (Si). This region is also referred to as the "first region S1" hereinafter. Among the cross-section SA, the black region surrounding the first region S1 has been confirmed to be a region mainly containing silicon carbide (SiC). This region is also referred to as the "second region S2" hereinafter.

[0020] The first region S1 may be a region where silicon occupies 100%, or may be a region containing components other than silicon. Similarly, the second region S2 may be a region where silicon carbide occupies 100%, or may be a region containing components other than silicon carbide.

[0021] It has also been confirmed that there are scattered regions on the cross-section SA that do not correspond to either the first region S1 or the second region S2. Examples of such regions include regions containing carbon particles, which are one of the raw materials during molding.

[0022] FIG. 2 shows the distribution of the second region S2 in the cross-section SA. FIG. 2(A) shows the respective second regions S2 as black regions by performing image processing (binarization) on the cross-section SA of FIG. 1. FIG. 2(B) is a schematic redrawing after enlarging a part of FIG. 2(A).

[0023] As shown in FIGS. 2(A) and 2(B), in the cross-section SA of the composite material 10, there are a plurality of first regions S1, and these are arranged in a substantially uniform dispersion state while being separated from each other. At least a part of the first regions S1 is surrounded by the second region S2 from the outside and over the entire circumference. Also, in at least the range shown in FIG. 2(B) of the cross-section SA, the second region S2 is observed to be a single continuous region without passing through grain boundaries. That is, in the image obtained by observing at a magnification of 250 times or less as shown in FIG. 1, the presence of grain boundaries that divide the second region S2 shown in FIG. 2(B) into a plurality is not confirmed.

[0024] As will be described later, in this embodiment, during the production of the composite material 10, granulated powder with a higher sphericity and improved fluidity than in the past is used as a raw material. As a result of silicon carbide, carbon, etc. in the raw material being more evenly dispersed than in the past, grain growth of silicon carbide has occurred, and it is considered that the continuous second region S2 as shown in FIG. 2(B) has been formed.

[0025] The second region S2 that surrounds the first region S1 over the entire circumference from the outside is a single continuous region without passing through grain boundaries as described above, but it does not have to be a single continuous region over the entire cross-section SA shown in FIG. 1. For example, in the cross-section SA shown in FIG. 1, there may be a plurality of second regions S2 that are continuous without passing through grain boundaries, and these plurality of second regions S2 may be adjacent to each other through grain boundaries. In this case, it is sufficient if the first region S1 surrounded over the entire circumference exists inside at least one of the second regions S2.

[0026] In addition, the second region S2 is observed as a "single continuous region without passing through grain boundaries" as long as it is observed at a magnification of 250 times or less by a scanning electron microscope. When the second region S2 surrounding the entire circumference of the first region S1 is observed in detail at a magnification exceeding 250 times, grain boundaries or boundaries corresponding thereto that divide the second region S2 may be observed.

[0027] To compare with the composite material 10 having the above configuration, the composite material 11 according to the comparative example will be described. The image in FIG. 3(A) is an image obtained by observing a cross-section SB that appears by cutting the composite material 11 according to the comparative example along a plane with a scanning electron microscope (SEM). Similar to FIG. 1, the range of the cross-section SB is 500 μm × 350 μm, and the magnification of enlargement is 250 times. FIG. 3(B) is a schematic redrawing after enlarging a part of FIG. 3(A).

[0028] The region labeled "S11" in FIG. 3(B) is a region mainly containing silicon, similar to the first region S1 in FIG. 2(B). The region labeled "S12" in FIG. 3(B) is a region mainly containing silicon carbide, similar to the second region S2 in FIG. 2(B).

[0029] In the comparative example of FIG. 3, the region S12 (silicon carbide) exists as relatively large particles, and a plurality of such particles are present in the cross section SB. Among the plurality of regions S12, some are in contact with each other, but the regions S12 are separated from each other by grain boundaries. Further, due to the relatively large size of each region S12, the gap region S11 (silicon) is relatively wide and is distributed in a matrix form in the cross section SB. In a part of the cross section SB, there may also be a region S11 surrounded entirely by the region S12, but the surrounding region S12 is not a single region. That is, there may be a portion where a plurality of adjacent regions S12 (silicon carbide) via grain boundaries are arranged so as to surround the entire circumference of the region S11 (silicon).

[0030] As is clear when contrasted with the comparative example of FIG. 3, in the composite material 10 of the present embodiment shown in FIG. 2, the second region S2 is a continuous single region without passing through grain boundaries, and in this respect, it is different from the comparative example in that the second region S2 is surrounded entirely on the inside circumference.

[0031] In the composite material 10 having such a configuration, since the first region S1 containing silicon is finely divided by the second region S2 surrounding it, the ratio occupied by the first region S1 in the cross section SA is relatively small. As is generally known, the silicon contained in the first region S1 has a lower strength than the silicon carbide contained in the second region S2. In the composite material 10, the ratio of the first region S1, which is a portion with low strength, is small, and "excessive chipping" during processing is suppressed, so that more precise processing can be performed compared to the prior art.

[0032] Further, the second region S2 (silicon carbide) surrounding the first region S1 is not a collection of a plurality of particles, but is a continuous single region without passing through grain boundaries. Due to the continuity of the relatively high-strength silicon carbide, "excessive chipping" during processing is further suppressed. Also, an effect can be obtained in that the detachment of particles during processing is less likely to occur.

[0033] FIG. 4 shows the results of an experiment comparing the workability of the composite material 10 according to the present embodiment and the workability of the composite material 11 according to the comparative example.

[0034] In the table of FIG. 4, the "SiC area ratio" represents the percentage of the area of the region containing SiC (the first region S1 or region S12) in the cross section of each sample. In FIG. 4, for each of the present embodiment and the comparative example, the SiC area ratios in a plurality of cross sections of one sample are measured, and the obtained values are shown in a range. The image of each cross section to be measured is an image in a range of 500 μm × 350 μm as in FIG. 1, and the magnification is 250 times. The range of the cross section when measuring the SiC area ratio may be wider than the above.

[0035] In the composite material 10 according to the present embodiment, the SiC area ratio was measured in the range of 87.5% to 95.1%. In the composite material 11 according to the comparative example, the SiC area ratio was measured in the range of 66.2% to 79.1%.

[0036] When measuring the SiC area ratio, for the images of FIGS. 1 and 3 obtained by observation using a scanning electron microscope, only each second region S2 was extracted by performing binarization processing using image analysis software to create an image as shown in FIG. 2. Then, using the function of the above image analysis software, the ratio of the total area occupied by the second region S2, that is, the SiC area ratio, was calculated.

[0037] In the table of Fig. 4, the "processing depth" refers to the depth of the recess formed on the surface of each sample after sandblasting under the same conditions, which was measured with a gauge and the measurement results were expressed in units of mm. In the example of Fig. 4, for each of the present embodiment and the comparative example, sandblasting was performed on each of three locations in one sample, and the processing depth of each part was measured. The "average processing depth" shown in Fig. 4 is the average value of the above three processing depths. In the composite material 10 according to the present embodiment, the measured average processing depth was 2.89 mm. In the composite material 11 according to the comparative example, the measured average processing depth was 4.83 mm. Thus, in the composite material 10 according to the present embodiment, it was confirmed that the average processing depth was suppressed to be smaller than that of the comparative example, and it is a material that is more easily processed precisely.

[0038] Apart from the present embodiment shown in Fig. 1 and the like, the inventors created multiple types of composite materials 10 while changing the manufacturing conditions, and calculated the SiC area ratio and measured the average processing depth for each sample. According to the measurement, it was confirmed that if the ratio of the area occupied by the second region S2 in the cross-section SA is 70% or more, the average processing depth becomes smaller than before, and the workability is sufficiently improved. It was confirmed that the larger the ratio of the area occupied by the second region S2 in the cross-section SA, the smaller the average processing depth. When the ratio is 80% or more, the improvement in workability compared to the conventional case becomes remarkable. When the ratio is 90% or more (more preferably 95% or more), it was confirmed that the workability is further improved to such an extent that a fine and highly accurate structure required for semiconductor manufacturing equipment and the like can be formed extremely easily.

[0039] The manufacturing method of the composite material 10 will be described. Hereinafter, points that are known as the manufacturing method of SiSiC will be appropriately simplified or omitted in the description.

[0040] First, weigh predetermined amounts of carbon powder and silicon carbide powder as raw materials, and disperse and mix them in pure water together with a binder and a dispersant to prepare a slurry. The obtained slurry is spray-dried using a spray dryer to prepare granulated powder containing carbon and silicon carbide.

[0041] At this time, by appropriately selecting the binder and the dispersant, the sphericity of the obtained granulated powder can be increased. The target sphericity value is preferably set to a higher value compared to the sphericity of the granulated powder used in conventional SiSiC materials.

[0042] The purpose of increasing the sphericity of the granulated powder is to give the granulated powder sufficient fluidity. The fluidity of the granulated powder is preferably increased to a level that would conventionally be considered excessive. Note that the fluidity of the granulated powder varies not only with the sphericity of the granulated powder but also with the size of the granulated powder. Therefore, for example, when spray-drying the slurry, it is preferable to control the size of the granulated powder by adjusting the flow rate of the supplied air to obtain granulated powder with optimal fluidity.

[0043] Thereafter, the obtained granulated powder is put into a predetermined mold, and a molded body is obtained by dry uniaxial compression molding. By increasing the fluidity of the granulated powder in advance as described above, the granulated powder is sufficiently densely filled in the mold. As a result, a molded body with a small pore diameter can be obtained.

[0044] Note that as the molding method, as long as it is a method capable of sufficiently densely filling the granulated powder with high fluidity, a method different from the above dry uniaxial compression press may be adopted. For example, molding may be performed using CIP (Cold Isostatic Pressing), or a method of shaping while laying powder using a 3D printer may also be used.

[0045] After the molding is completed, metallic silicon is placed on the obtained molded body and fired under reduced pressure. The molten silicon is impregnated into the molded body, and reaction sintering with the carbon powder is performed, whereby the composite material 10 shown in FIG. 1 and the like can be obtained.

[0046] In this embodiment, as described above, the fluidity of the granulated powder is enhanced more than before, and a molded body is obtained while being sufficiently densely filled in the mold. As a result, the reaction between silicon and carbon powder is carried out more uniformly throughout the material, so that a single second region S2 that is continuous over a relatively wide range as described above is considered to be formed.

[0047] When a composite material is formed by a conventional manufacturing method without sufficiently enhancing the fluidity of the granulated powder, a composite material having a cross-section similar to the comparative example in FIG. 3 is created. In creating the composite material 11 in FIG. 3, in order to make the structural difference from this embodiment more prominent, a molded body is created by casting molding.

[0048] Specifically, first, a predetermined amount of carbon powder and silicon carbide powder were weighed respectively, and dispersed and mixed in pure water together with a binder and a dispersant to prepare a slurry. Then, the obtained slurry was poured into a gypsum mold, and a molded body was obtained by casting molding. After the molding was completed, metallic silicon was placed on the obtained molded body and fired under reduced pressure.

[0049] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Those obtained by appropriately making design changes by those skilled in the art to these specific examples are also included in the scope of the present disclosure as long as they have the features of the present disclosure. Each element, its arrangement, conditions, shape, etc. included in each of the above-described specific examples are not limited to those illustrated and can be changed as appropriate. Each element included in each of the above-described specific examples can be combined as appropriate as long as no technical contradiction occurs.

Explanation of Reference Numerals

[0050] 10: Composite material SA: Cross-section S1: First region S2: Second region

Claims

Claim 1 A composite material containing silicon and silicon carbide, for a first image obtained by observing a range of 500 μm × 350 μm in a cross-section obtained by cutting the composite material along a plane at a magnification of 250 times using a scanning electron microscope, in a second image obtained by performing binarization processing using image analysis software, a first region containing the silicon, a single region that surrounds the outside of the first region over the entire circumference and is continuous without passing through grain boundaries, and contains the second region containing the silicon carbide, are included, the second region is the entire region excluding the first region in the second image, A composite material, characterized in that the ratio of the area occupied by the second region in the second image is 70% or more. Claim 2 The composite material according to claim 1, characterized in that the ratio of the area occupied by the second region in the second image is 80% or more.

Images