JPWO2018151294A1 - Silicon carbide member and member for semiconductor manufacturing equipment - Google Patents

Abstract

The silicon carbide member includes a β-type first silicon carbide crystal having a 3C crystal structure, and a second silicon carbide crystal having a crystal structure different from the first silicon carbide crystal. The silicon carbide member has a first surface, and a direction perpendicular to the first surface is defined as a first direction. The particles of the second silicon carbide crystal have a major axis extending along the first direction, and have an average length in the first direction of 100 μm or less. Such a silicon carbide member has excellent resistance to plasma and chemicals, and is suitable as a member for semiconductor devices such as a focus ring and a dummy wafer. [Selection] Fig. 6

Description

  The present disclosure relates to a silicon carbide member and a member for a semiconductor manufacturing apparatus.

  A silicon carbide material (CVD-SiC material) obtained by a chemical vapor deposition (CVD) method is used not only as a coating material but also as a single member of a CVD-SiC material as various members. A single CVD-SiC member is obtained, for example, by depositing silicon carbide (SiC) on the surface of a substrate by a CVD method, forming a film, and then removing the substrate. The CVD-SiC material is dense and high-purity as compared with the SiC material manufactured by the sintering method, and has excellent corrosion resistance, heat resistance, and strength characteristics. Therefore, the CVD-SiC material has been proposed as various members such as a heater for a semiconductor manufacturing apparatus, a focus ring used for an etching apparatus, a dummy wafer, a susceptor, a furnace core tube, a chemical resistant jig, and an analysis container. .

  The CVD-SiC material is mainly used inside a semiconductor manufacturing apparatus. Therefore, it is used as a free-standing film of high-purity SiC with the substrate used at the time of film formation removed. When a thick film of a CVD-SiC material is formed to be used as a self-supporting film, internal stress increases, and when a substrate is removed, a film of a CVD-SiC (hereinafter, simply referred to as a CVD-SiC film) such as a crack or a warp is formed. In some cases, deformation occurred. Patent Document 1 discloses that in a laminate in which three or more silicon carbide layers are laminated, the surface of each layer formed by CVD is flattened, and the warpage is suppressed by setting the thickness of each layer to 100 μm or less. ing.

  Further, SiC has a plurality of different crystal structures. For example, when the deposition rate is increased to efficiently obtain thick CVD-SiC, a plurality of silicon carbide crystals having different crystal structures are mixed.

JP-A-8-188468

  The silicon carbide member of the present disclosure includes a β-type first silicon carbide crystal having a 3C crystal structure, and a second silicon carbide crystal having a crystal structure different from the first silicon carbide crystal. The silicon carbide member has a first surface, and a direction perpendicular to the first surface is defined as a first direction. The particles of the second silicon carbide crystal have a major axis extending along the first direction and have an average length in the first direction of 100 μm or less.

  A member for a semiconductor manufacturing apparatus, a focus ring, and a dummy wafer according to the present disclosure include the above-described silicon carbide member.

It is a perspective view which shows typically a focus ring which is one of the examples of the member for semiconductor manufacturing apparatuses. It is a perspective view which shows typically the dummy wafer which is one of the examples of the member for semiconductor manufacturing apparatuses. FIG. 3 is a sectional view taken along line III-III of FIG. 1. FIG. 4 is an example of a cross-sectional view in which a broken line portion in FIG. 3 is enlarged. FIG. 4 is another example of a sectional view in which a broken line portion in FIG. 3 is enlarged. FIG. 4 is a cross-sectional view schematically showing one example of a microstructure of a silicon carbide member, in which a broken line portion in FIG. 3 is enlarged. FIG. 4 is a cross-sectional view schematically showing one example of a microstructure of a silicon carbide member, in which the vicinity of a first surface is enlarged. FIG. 7 is a cross-sectional view schematically illustrating another example of FIG. 6. It is sectional drawing which shows another example of the microstructure of a silicon carbide member typically.

  1 and 2 show an example of a member 1 for a semiconductor manufacturing apparatus using a silicon carbide material. FIG. 1 schematically shows a focus ring 1a, and FIG. 2 schematically shows a dummy wafer 1b. In a semiconductor manufacturing apparatus, in particular, a CVD (Chemical Vapor Deposition), a PVD (Physical Vapor Deposition), and a plasma etching apparatus, a wafer of Si or the like is subjected to plasma processing.

  The focus ring 1a is arranged on the outer periphery of the wafer. By processing the wafer using the focus ring 1a, the wafer can be processed more uniformly. Therefore, the focus ring 1a is required to have the same or similar resistivity as the wafer to be processed and high corrosion resistance to plasma. The corrosion resistance to plasma may be referred to as plasma resistance.

  The dummy wafer 1b is used as a substitute for the wafer when adjusting the conditions of the semiconductor manufacturing apparatus, cleaning, and the like. Like the focus ring 1a, the dummy wafer 1b is required to have the same or similar resistivity and high plasma resistance as the wafer to be processed.

  3 to 5 are sectional views taken along line III-III of the focus ring 1a shown in FIG. As shown in FIG. 3, the silicon carbide member has a first surface S1. The silicon carbide member is mainly exposed to the plasma on the first surface S1. 4 and 5 are cross-sectional views in which a part of FIG. 3 is enlarged. The microstructure differs between the example of FIG. 4 and the example of FIG. The silicon carbide material formed by the CVD method is generally composed of a columnar silicon carbide crystal 2 in which a crystal grows along a first arrow direction v as shown in FIG. 4 or FIG. The first direction is orthogonal to the first surface S1. Hereinafter, silicon carbide may be referred to as SiC, and a silicon carbide material formed by a CVD method may be referred to as a CVD-SiC material.

  The silicon carbide member may have any of the structures shown in FIGS. In FIGS. 4 and 5, the silicon carbide crystal 2 is schematically illustrated as a rectangle, so that the description shows that there is a cavity between the plurality of silicon carbide crystals 2. However, actual silicon carbide materials formed by CVD do not have such large cavities and are dense.

  There are many crystal polymorphs such as 3C, 4H, 6H and 15R in the crystal structure of silicon carbide. 3C, which is a zinc blende type structure, is also called β type, and 4H, 6H, 15R, etc. having other structures are called α type.

  Silicon carbide crystals having different crystal structures (crystal forms) have different resistances to plasma and chemicals. α-type silicon carbide crystals have relatively lower resistance to plasma and chemicals than β-type silicon carbide crystals. At the interface between silicon carbide crystals having different crystal forms, corrosion by plasma or a chemical solution easily progresses.

  For example, in a silicon carbide member in which α-type silicon carbide crystals have grown to form coarse particles, the coarse particles and their grain boundaries are portions having relatively low resistance to plasma and chemicals. When the surface of the silicon carbide member where the β-type silicon carbide crystal and the α-type silicon carbide crystal are mixed is exposed to plasma or a chemical solution, the α-type silicon carbide crystal and its grain boundaries are selectively etched. When α-type coarse grains are present, the unevenness of the etched surface becomes large, the surface becomes rough, and the surface roughness becomes large. As the surface roughness increases, the surface area exposed to the plasma or the chemical solution increases, and the corrosion easily proceeds. As described above, the presence of α-type coarse particles may deteriorate the resistance of the entire silicon carbide member to plasma and chemicals.

<First Embodiment>
As shown in FIG. 6, the silicon carbide member of the first embodiment has a β-type first silicon carbide crystal 2a having a 3C crystal structure and an α having a crystal structure different from the first silicon carbide crystal 2a. Second silicon carbide crystal 2b. Further, the silicon carbide member has a first surface S1, and the particles of first silicon carbide crystal 2a and the particles of second silicon carbide crystal 2b both have a first direction orthogonal to first surface S1. Has a major axis extending along. That the particles have a major axis extending along the first direction means that the major axis direction of the particles forms an angle of less than 45 ° with the first direction. That is, the particles of first silicon carbide crystal 2a and the particles of second silicon carbide crystal 2b have a shape in which the length in the first direction is longer than the length in the direction orthogonal to the first direction. The size of the particles of second silicon carbide crystal 2b is larger than the size of the particles of first silicon carbide crystal 2a. Particles of second silicon carbide crystal 2b have an average d1 of 100 μm or less, where d1 is the length in the first direction.

  The second SiC crystal 2b is α-type, and has lower resistance to plasma and chemicals than the β-type first SiC crystal 2a. Hereinafter, resistance to plasma and chemicals may be generally referred to as corrosion resistance. The particles of the second SiC crystal 2b having low corrosion resistance have a major axis extending along the first direction, and the average of the length d1 in the first direction is 100 μm or less, so that the second SiC crystal 2b The size and number of coarse grains are reduced. As a result, the area of the exposed portion of the second SiC crystal 2b, that is, the area of the second SiC crystal 2b exposed on the first surface S1, is reduced, and the corrosion resistance of the SiC member is improved. The average of d1 may be 50 μm or less, and may be 30 μm or less. By making d1 smaller, the area of the exposed portion of second SiC crystal 2b is further reduced, and the corrosion resistance of the SiC member is further improved.

  The first surface S1 is a surface formed in the final step of CVD, and is not a surface in contact with the base. The first surface S1 may be a processed surface that has been subjected to a polishing process or the like. Usually, the second SiC crystal 2b hardly exists on the surface in contact with the base. The second SiC crystal 2b grows from a nucleus generated during the deposition of CVD-SiC. Therefore, by observing the cross section of the CVD-SiC from which the base material has been removed, the surface on the side in contact with the base and the first surface S1 can be determined.

  The microstructure of the SiC member may be confirmed, for example, by observing the polished surface or cross section of the SiC member by backscatter electron diffraction (EBSD). The polished surface or cross section of the SiC member may be further wet-etched and observed with an optical microscope or a scanning electron microscope (SEM) to confirm the microstructure. As a method of wet etching, for example, a method of immersing the SiC member in molten NaOH or molten KOH may be used. The crystal structure of the SiC crystal may be confirmed by X-ray diffraction. Further, the local crystal structure (the crystal structure of each SiC particle) in the cross section of the SiC member may be confirmed by Electron BackScatter Diffraction (EBSD).

  The second SiC crystal 2b exists inside the SiC member and on the first surface S1. As shown in FIG. 7, the second SiC crystal 2b may have a portion exposed on the first surface S1 of the SiC member. Hereinafter, a portion where the second SiC crystal 2b is exposed on the first surface S1 of the SiC member may be simply referred to as an exposed portion of the second SiC crystal 2b. The average of the length d2 of the exposed portion of the second SiC crystal 2b may be 20 μm or less. When the average of d2, which is the length of the exposed portion of the second SiC crystal 2b, is set to 20 μm or less, it is possible to reduce a local decrease in resistance to plasma or a chemical solution on the first surface S1 of the SiC member. As a result, even if the SiC member is exposed to a plasma or a chemical solution, it is possible to reduce the occurrence of roughness and cracks on its surface, that is, the first surface S1. The average of d2 may be 10 μm or less, or even 5 μm or less. By making d2 smaller, the corrosion resistance of the SiC member is further improved.

  The length d2 of the exposed portion of the second SiC crystal 2b may be measured by measuring the length d2 of the exposed portion in a cross section perpendicular to the first surface S1, as shown in FIG. The number of measurements of d2 may be, for example, 10 and averaged. Alternatively, a diameter may be calculated by converting the area of the exposed portion of the second SiC crystal 2b into a circle, and the diameter may be set as d2.

Second Embodiment
The silicon carbide member of the second embodiment includes at least two silicon carbide layers 4 including first silicon carbide crystal 2a and second silicon carbide crystal 2b as shown in FIG. Two or three or more silicon carbide layers 4 may overlap in the first direction. The shapes of the particles of the first silicon carbide crystal 2a and the particles of the second silicon carbide crystal 2b of the second embodiment are the same as or similar to those of the first embodiment.

  The average thickness in the first direction of the SiC layer 4 may be 200 μm or less per layer. By setting the average thickness of SiC layer 4 to 200 μm or less, the size of second SiC crystal 2b can be reduced. By reducing the size of second SiC crystal 2b, the etching rate when the SiC member is exposed to plasma or a chemical can be made uniform. Also, the particles of the second SiC crystal 2b are less likely to be separated from the first surface S1, and the roughness of the first surface S1 due to etching can be reduced. The average thickness of the SiC layer 4 may be 50 μm or more.

  The different SiC layers 4 may have the same thickness or different thicknesses. The SiC member including two or more SiC layers 4 having different thicknesses includes the thinner SiC layer 4 at a position closer to the first surface S1 than the center in the first direction, and the first SiC layer 4 has a thickness smaller than the center in the first direction. A thick SiC layer 4 may be provided at a portion far from the surface S1.

  For example, the thickness of one SiC layer 4 can be determined by observing the cross section of the SiC member with a scanning electron microscope (SEM), measuring the thickness of one SiC layer 4 at three or more locations, and calculating the average value. Good. If the thickness of each SiC layer 4 is substantially equal, a value obtained by dividing the average value of the total thickness of the SiC members by the number of SiC layers 4 may be used as the average thickness of one SiC layer 4. .

  At the interface between adjacent SiC layers 4, an intervening layer 5 may be present as shown in FIG. 8.

  Due to the presence of the intervening layer 5, the second SiC crystal 2b existing in one SiC layer 4 and the second SiC crystal 2b existing in the other SiC layer 4 among the adjacent SiC layers 4 Becomes difficult to connect. That is, second SiC crystal 2b can be effectively interrupted at the interface between adjacent silicon carbide layers 4. Therefore, of the second SiC crystals 2b, two or more of the second SiC crystals 2b existing over the two or more silicon carbide layers 4, that is, projecting from the interface of the adjacent silicon carbide layer 4 or the intervening layer 5 The second SiC crystal 2b existing in the silicon carbide layer 4 can be reduced. The thickness of the intervening layer 5 may be, for example, not less than 1 μm and not more than 10 μm.

  Assuming that the number ratio of the second SiC crystals 2b existing over two or more SiC layers 4 among the second SiC crystals 2b included in the SiC member is N1, N1 may be 20% or less. If the second SiC crystal 2b is present over a plurality of SiC layers 4, it is likely to become coarse grains, and there is a concern that the corrosion resistance of the SiC member is reduced. By setting N1 to 20% or less, a decrease in the corrosion resistance of the SiC member can be reduced. The second SiC crystal 2b existing over two or more SiC layers 4 refers to one second continuous with two or more SiC layers 4 through an interface between adjacent SiC layers 4 or an intervening layer 5. It can also be referred to as SiC crystal 2b.

  Intervening layer 5 may include first SiC crystal 2a. Intervening layer 5 may be mainly composed of first SiC crystal 2a. The fact that the intervening layer 5 is mainly composed of the first SiC crystal 2a means that 90% or more of the SiC crystals constituting the intervening layer 5 are the first SiC crystal 2a.

  Intervening layer 5 may have a higher defect density than SiC layer 4. The defect density can be confirmed by mirror-finishing the cross section of the SiC member, wet-etching the mirror-finished cross section, and observing it with a scanning electron microscope (SEM) or the like.

  The intervening layer 5 may have an atomic ratio of silicon (Si) to carbon (C) (Si / C ratio) smaller than that of the SiC layer 4. If the Si / C ratio of the intervening layer 5 is smaller than that of the SiC layer 4, the α-type second SiC crystal 2b tends to undergo a phase transition to the β-type first SiC crystal 2a when forming the SiC layer 4. Become. As a result, the grain growth of second SiC crystal 2b in the vicinity of intermediate layer 5 can be effectively suppressed. In this case, the average of d1 of the particles of second SiC crystal 2b can be set to, for example, 50 μm or less. Note that the Si / C ratio of the SiC layer 4 is approximately 1.0, and may be, for example, 0.95 or more and 1.05 or less.

  Intervening layer 5 mainly composed of SiC may have a Si / C ratio of 0.90 or more and 0.999 or less.

  Intervening layer 5 may include at least one of an amorphous phase containing carbon as a main component and a crystalline phase. The intervening layer 5 may contain carbon (C) as a main component. The phrase “intervening layer 5 contains carbon as a main component” means that 90% or more of the elements constituting intervening layer 5 are carbon. In the SiC member having the intervening layer 5 containing carbon as a main component between the adjacent SiC layers 4, the grain growth of the second SiC crystal 2 b is more effective when forming the SiC layer 4. Is suppressed. As a result, the size and the number of the second SiC crystals 2b existing over two or more SiC layers 4, that is, the second SiC crystals 2b projecting from the intervening layer 5 and extending over the plurality of SiC layers 4 are further increased. Can be reduced.

  Also, the conductivity of carbon is higher than the conductivity of SiC. Therefore, when the SiC member having the intervening layer 5 containing carbon as a main component is used, for example, as a focus ring, charges accumulated in the wafer can be quickly released through the intervening layer 5 of the focus ring, and the processing efficiency of the wafer can be improved. Can be increased.

  The types and ratios of the elements constituting the SiC layer 4 and the intervening layer 5 can be confirmed by elemental analysis such as energy dispersive X-ray spectroscopy (EDS). It can also be confirmed by evaluating the crystal structure by backscatter electron diffraction (EBSD) or electron beam diffraction.

  Also in the second embodiment, the second SiC crystal 2b may be present inside the SiC member and on the first surface S1.

  The surface of the SiC layer 4, that is, the interface between the adjacent SiC layer 4 and the SiC layer 4, or the interface between the SiC layer 4 and the intervening layer 5, may have irregularities with a maximum height Rz of 20 μm or more. By setting the maximum height Rz of the surface of the SiC layer 4 to 20 μm or more, the structure of the interface between the SiC layers 4 or the structure of the interface between the SiC layer 4 and the intervening layer 5 becomes a structure having irregularities. The adhesion between the layers or between the SiC layer 4 and the intervening layer 5 can be improved. The maximum height Rz of the surface of the SiC layer 4 is determined by the line roughness of the interface between the SiC layer 4 and the SiC layer 4 or the interface between the SiC layer 4 and the intervening layer 5 in the cross section along the first direction of the SiC member. What is necessary is just to measure and calculate.

<Production method>
A method for manufacturing the SiC member will be described. The CVD apparatus used for producing the SiC member of the present embodiment is not particularly limited to this. The CVD apparatus may include, for example, a vertical or horizontal batch type CVD chamber having a gas inlet and a gas outlet, and an electric heating means. In a CVD apparatus that heats using a high frequency, the substrate can be selectively heated. The high frequency used for heating may be, for example, not less than 3 kHz and not more than 100 kHz.

  The CVD method may be any method as long as a substrate is set in a CVD chamber, gases such as a source gas and a carrier gas are introduced into the CVD chamber, and a chemical vapor deposition (CVD) reaction is performed on the substrate.

  The source gas may be a gas containing carbon atoms and silicon atoms. As the gas containing a silicon atom, a gas having a structure in which one or more chlorine atoms are bonded to a silicon atom in a molecule may be used. Methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, or a mixed material of silicon chloride and a hydrocarbon gas may be used. By using these source gases, for example, CVD-SiC can be deposited at a high deposition rate of 0.1 mm / hour or more, and a SiC member can be efficiently produced.

  These source gases are mixed with a carrier gas such as hydrogen or argon at a predetermined ratio and introduced into the CVD chamber as a mixed gas. The mixing ratio between the source gas and the carrier gas may be, for example, three times or more and ten times or less the volume of the carrier gas with respect to the volume of the source gas. The carrier gas may be hydrogen. When hydrogen is used as a carrier gas, a dechlorination reaction from silicon atoms can be promoted.

  A gas containing a dopant atom may be further introduced into the CVD chamber. By introducing dopant atoms into CVD-SiC, the electrical resistivity of CVD-SiC can be reduced. As the dopant atom, nitrogen, boron, or the like may be used. Examples of the nitrogen-containing gas include nitrogen, ammonia, trimethylamine, and triethylamine. Examples of the boron-containing gas include boron trichloride, diborane, and the like. The ratio between the source gas and the gas containing the dopant atoms may be appropriately adjusted according to the desired electric resistivity. For example, the volume of the gas containing dopant atoms may be 0.01 times or more and 50 times or less the volume of the source gas. Hereinafter, a mixed gas of a source gas, a carrier gas, and a gas containing a dopant atom as needed is referred to as a mixed source gas.

  The reaction temperature of CVD may be, for example, 1200 ° C. or higher, and may be 1250 ° C. or higher. When the reaction temperature is lower than 1200 ° C., the deposition rate of CVD-SiC is significantly reduced, and the production efficiency is reduced. The reaction temperature may be, in particular, 1350 ° C. or higher, further 1350 ° C. or higher and 1500 ° C. or lower.

  The silicon carbide member having a microstructure as shown in FIG. 6 may be manufactured as follows.

(Step A)
The mixed raw material gas is introduced onto the substrate so that the pressure in the CVD chamber is about -98 kPa or more and -80 kPa or less with respect to the atmospheric pressure, and CVD-SiC having a thickness of 50 μm or more and 200 μm or less is deposited on the substrate. (SiC layer 4). The deposition rate of CVD-SiC and the introduction time of the mixed source gas may be appropriately adjusted.

(Step B)
In the step B, the flow rate of the source gas is set to 1/100 or more and 1/10 or less of the step A, and the mixed source gas is introduced onto the substrate, and the mixed gas is introduced onto the SiC layer 4 of the CVD-SiC formed in the step A. Further, CVD-SiC having a thickness of 1 μm or more and 10 μm or less is deposited. In order to adjust the introduction flow rate of the raw material gas, the introduction flow rate of the mixed raw material gas is made 1/100 or more and 1/10 or less, or the ratio of the raw material gas in the mixed raw material gas is made 1/100 or more and 1/10 or less. There are the following methods, and any of them may be used. The deposition rate of CVD-SiC and the introduction time of the mixed source gas may be appropriately adjusted.

  In this step B, since the source gas is in a dilute state, minute β-type first SiC crystals 2a having a 3C structure are easily generated, and the growth of α-type second SiC crystals 2b is suppressed. You.

  By alternately repeating the above steps A and B, a silicon carbide member having a microstructure as shown in FIG. 6 is obtained. At this time, the temperature of the base may be 1200 ° C. or higher and 1400 ° C. or lower. The number of repetitions of Step A and Step B may be appropriately adjusted according to the desired thickness of the silicon carbide member.

  The silicon carbide member having a microstructure as shown in FIG. 8 may be manufactured as follows.

(Step C)
In Step C, the flow rate of the source gas introduced is set to be smaller than 1/100 of Step A. This mixed raw material gas is introduced onto the substrate, and CVD-SiC is further deposited on the SiC layer 4 of CVD-SiC formed in the step A. In order to adjust the introduction flow rate of the source gas, there are a method in which the introduction flow rate of the mixed source gas is made smaller than 1/100 and a method in which the ratio of the source gas in the mixed source gas is made smaller than 1/100. You may. The introduction time of the mixed source gas in the step C may be, for example, 0.01 times or more and 4.0 times or less the time required for the step A.

  Also in this step C, the β-type first SiC crystal 2a having the 3C structure is easily generated. In the step C, since the source gas is particularly extremely diluted, the defect density of the first SiC crystal 2a to be formed increases, and the intervening layer 5 is formed. As a result, the growth of the α-type second SiC crystal 2b is further suppressed, and the coarsening of the second SiC crystal 2b can be more effectively suppressed. The existence of the intervening layer 5 having a high defect density can be confirmed by wet etching the cross section of the silicon carbide member.

  By alternately repeating the above steps A and C, a silicon carbide member having a microstructure as shown in FIG. 8 is obtained. At this time, the temperature of the base may be 1200 ° C. or higher and 1400 ° C. or lower. The number of repetitions of Step A and Step C may be appropriately adjusted according to the desired thickness of the silicon carbide member.

(Step D)
Further, in step D, the flow rate of the source gas introduced is set to 1/100 or more and 1/10 or less of step A, and the pressure in the CVD chamber is set to about -100 kPa or more and less than -98 kPa with respect to the atmospheric pressure. In the process D, Si is released from the SiC layer 4 of the CVD-SiC formed in the process A because the pressure in the CVD chamber is low. As a result, an intervening layer 5 having a lower Si / C ratio than the SiC layer 4 is formed. The introduction time of the mixed source gas in the step D may be, for example, 0.01 times or more and 4.0 times or less the time required for the step A.

  A silicon carbide member having a microstructure as shown in FIG. 8, wherein the Si / C ratio of the intervening layer 5 is smaller than the Si / C ratio of the SiC layer 4 by alternately repeating the above steps A and D. Is obtained. At this time, the temperature of the base may be 1200 ° C. or higher and 1400 ° C. or lower. The number of repetitions of Step A and Step D may be appropriately adjusted depending on the desired thickness of the silicon carbide member.

(Step E)
In step E, the pressure in the CVD chamber is set to about −100 kPa or more and less than −98 kPa with respect to the atmospheric pressure, and further, the introduction of the source gas and the carrier gas is stopped. In the step E, since the pressure in the CVD chamber is low and the source gas is not supplied, the desorption of Si from the SiC layer 4 of the CVD-SiC formed in the step A proceeds more. As a result, an intervening layer 5 containing carbon as a main component is formed. In the step E, the time for stopping the gas introduction may be, for example, 0.01 times or more and 4.0 times or less the time required for the step A.

  By repeating the above steps A and E alternately, a silicon carbide member having a microstructure as shown in FIG. 8 and in which the main component of the intervening layer 5 is carbon is obtained. At this time, the temperature of the base may be 1200 ° C. or higher and 1400 ° C. or lower. The number of repetitions of Step A and Step E may be appropriately adjusted according to the desired thickness of the silicon carbide member.

  As described above, by depositing CVD-SiC while periodically changing the introduction flow rate of the raw material gas and the pressure in the CVD chamber as necessary, the α-type can be obtained without removing the substrate and the CVD-SiC from the CVD chamber. A silicon carbide member having a small particle size of second SiC crystal 2b or a silicon carbide member having two or more silicon carbide layers 4 can be obtained. Therefore, the silicon carbide member of the present disclosure also has an advantage of being superior in production efficiency as compared with a conventional case where a stacked structure is formed through removal from a CVD chamber or processing.

  As a substrate on which CVD-SiC is deposited, for example, graphite may be used. Since the coefficient of thermal expansion of graphite is close to the coefficient of thermal expansion of silicon carbide, the use of graphite as a base can reduce deformation of the base and CVD-SiC formed on the surface of the base due to thermal stress.

  The coefficient of thermal expansion of graphite may be slightly larger than the coefficient of thermal expansion of CVD-SiC. When the substrate and the CVD-SiC are cooled to room temperature after the deposition of the CVD-SiC, if the coefficient of thermal expansion of graphite is slightly larger than the coefficient of thermal expansion of the CVD-SiC, the thermal stress generated in the CVD-SiC becomes a compressive stress. It becomes. When compressive stress is applied to CVD-SiC, cracks are less likely to occur in CVD-SiC.

  In silicon carbide members such as the focus ring 1a and the dummy wafer 1b, CVD-SiC is used as a self-solid (also referred to as a self-standing film). In a silicon carbide member used as a self-solid, it is necessary to remove the substrate from the formed CVD-SiC. A graphite substrate is easily removed from CVD-SiC by oxidation or grinding.

  In the silicon carbide member thus obtained, a cone-shaped structure 6 having low corrosion resistance as shown in FIG. 9 is not easily generated. Therefore, such a silicon carbide member is less likely to have a rough or cracked outer surface even when exposed to plasma or a chemical solution. Such a silicon carbide member may be used as a heater and a susceptor for a semiconductor manufacturing apparatus in addition to the focus ring 1a and the dummy wafer 1b shown in FIG. You may use as various members, such as a container.

  The silicon carbide member of the present disclosure includes not only the self-stereoscopic body with the substrate removed as described above, but also a composite member of a silicon carbide coating and a substrate.

  CVD-SiC was formed on a graphite substrate by a CVD method using methyltrichlorosilane, hydrogen, and nitrogen as raw materials.

  As the CVD apparatus, an apparatus of a system for heating a substrate by high-frequency induction heating was used. The high frequency was 60 kHz. A substrate support made of a graphite substrate and a heat insulating material was placed in the CVD chamber, and the temperature was raised while evacuating the CVD chamber. The temperature of the graphite substrate was 1400 ° C., and a mixed source gas of methyltrichlorosilane as a source gas, hydrogen as a carrier gas, and nitrogen as a dopant gas was introduced, and CVD-SiC was deposited on the graphite substrate. The volume ratio of nitrogen to methyltrichlorosilane was 5 times.

  In step A, the volume ratio of the carrier gas to the source gas was set to 5 times, and the pressure in the CVD chamber was set to -95 kPa with respect to the atmospheric pressure. At this time, the deposition rate of CVD-SiC was about 0.5 mm / hour.

  In step B, the volume ratio of the carrier gas to the source gas was set to 100 times, and the pressure in the CVD chamber was set to -95 kPa with respect to the atmospheric pressure. At this time, the deposition rate of CVD-SiC was about 0.06 mm / hour.

  In step D, the volume ratio of the carrier gas to the source gas was set to 100 times, and the pressure in the CVD chamber was set to -100 kPa with respect to the atmospheric pressure. At this time, the deposition rate of CVD-SiC was about 0.02 mm / hour.

  In step E, the supply of the mixed source gas of the source gas and the carrier gas was stopped while the evacuation of the inside of the CVD chamber was continued. The pressure in the CVD chamber was -100 kPa with respect to the atmospheric pressure.

  Sample No. In Steps 1 to 9, Step A and any one of Steps B to E were set as one set, and CVD-SiC was produced under the conditions shown in Table 1. Further, the sample No. In No. 10, after performing the step A for 20 minutes, the graphite substrate and the CVD-SiC deposited on the surface thereof were taken out of the CVD chamber, and the surface of the CVD-SiC was polished. Sample No. In No. 10, CVD-SiC was produced under the conditions shown in Table 1 by setting the process A and the polishing of the surface as one set.

  The graphite substrate was removed from the obtained sample by machining, and various evaluations were performed.

  The obtained sample No. 1 to 10 silicon carbide members were immersed in molten sodium hydroxide to etch the surface. Thereafter, the cross section of the silicon carbide member and the state of the etched surface were confirmed with a scanning electron microscope (SEM). The confirmed surface is the first surface, which is different from the surface exposed by removing the graphite substrate, that is, the surface of SiC formed at the beginning of CVD. Sample No. No clear SiC layer and its interface were seen in Nos. 1-3. Sample No. 4 to 10, a clear SiC layer and its interface were confirmed. The total thickness of each sample was measured with a micrometer. Further, the sample No. The thickness of one layer of 4 to 10 was measured using SEM. Table 1 shows the average value of the total thickness of each sample and the average value of the thickness of one silicon carbide layer. The sample No. 1 to 3 were regarded as one SiC layer as a whole.

  The crystal structure of the silicon carbide member was confirmed by X-ray diffraction (XRD). Sample No. Each of 1 to 10 contained a first SiC crystal having a β-type structure and a second SiC crystal having an α-type structure. In addition, the sample No. was measured by backscattered electron diffraction (EBSD). 1 to 10 all confirmed that the size of the second SiC crystal was larger than the size of the first SiC crystal on average. Table 1 shows the figure numbers corresponding to the microstructure of each sample.

  The length d1 of the second SiC crystal in the first direction and the length d2 of the exposed portion exposed on the first surface were measured using a SEM at a magnification of 200 to 500 times. Table 2 shows the average value of d1 and the average value of d2.

  The proportion N1 of the second SiC crystal existing over two or more silicon carbide layers was evaluated using a cross-sectional photograph of an SEM. The magnification of the photograph was 200 to 500 times. The total number of second SiC crystals and the number of second SiC crystals existing over two or more silicon carbide layers were counted, and the ratio was calculated.

  The presence or absence of the intervening layer and the maximum height Rz of the line roughness of the SiC layer were evaluated using SEM cross-sectional photographs. The ratio between Si and C in the intervening layer was evaluated by energy dispersive X-ray spectroscopy (EDS). Table 2 shows the results. The sample No. Nos. 1 to 3 were not evaluated for N1, Rz, and the intervening layer because the whole was one SiC layer.

For the plasma etching test, an RIE type etching apparatus was used. The first surface of each test piece was polished to have the same surface roughness. A test piece of each sample was placed in the etching chamber of the etching apparatus, and the first surface of each test piece was subjected to etching treatment. In the etching treatment, a CF ₄ gas was introduced into the etching chamber, and a high frequency of 13.56 MHz was introduced at an output of 0.8 W / cm ² to generate plasma. The processing time was 4 hours. As an evaluation of the resistance to plasma, the arithmetic average roughness Ra of the etched surface of the sample after the etching treatment was measured using an atomic force microscope (AFM). In addition, the etched surface was visually observed and observed with an SEM to confirm the presence or absence of cracks. The results are shown in Table 2.

  Sample No. Nos. 1 to 9 have no noticeable roughness on the etched surface where the length d1 of the second SiC crystal in the first direction is 100 μm or less, have a small Ra of 410 nm or less, and have high corrosion resistance to plasma. I was Sample No. Sample No. 9 showed cracks along the interface of the SiC layer not on the etched surface but on the side surfaces. In Nos. 1 to 8, no crack occurred. On the other hand, sample No. In Sample No. 10, d1 was as large as 250 μm, and the second SiC crystal was grown in grain size. Roughness was conspicuous on the etched surface, and Ra was as large as 550 nm. In addition, cracks occurred at the grain boundaries between the first SiC crystal and the second SiC crystal exposed on the etched surface.

1: Member for semiconductor manufacturing apparatus 1a: Focus ring 1b: Dummy wafer 2a: First silicon carbide crystal 2b: Second silicon carbide crystal 4: Silicon carbide layer 5: Intermediate layer 6: Conical structure S1: First surface

Claims (14)

A β-type first silicon carbide crystal having a crystal structure of 3C, and a second silicon carbide crystal having a crystal structure different from the first silicon carbide crystal;
When having a first surface and a direction orthogonal to the first surface is defined as a first direction,
The silicon carbide member, wherein the particles of the second silicon carbide crystal have a major axis extending in the first direction and have an average length in the first direction of 100 μm or less.   2. The silicon carbide member according to claim 1, wherein an average length of said second silicon carbide crystal in said first direction is 50 μm or less. 3. The second silicon carbide crystal has an exposed portion exposed on the first surface,
The silicon carbide member according to claim 1, wherein an average length of the exposed portion is 20 μm or less. At least two silicon carbide layers including the first silicon carbide crystal and the second silicon carbide crystal,
The silicon carbide member according to any one of claims 1 to 3, wherein the silicon carbide layer overlaps in the first direction. Having an intervening layer between the silicon carbide layers,
The silicon carbide member according to claim 4, wherein the intervening layer has an atomic ratio of silicon (Si) to carbon (C) (Si / C) smaller than that of the silicon carbide layer.   The silicon carbide member according to claim 5, wherein the intervening layer includes a first silicon carbide crystal.   The silicon carbide member according to claim 5, wherein the intervening layer contains at least one of an amorphous phase mainly containing carbon and a crystal phase mainly containing carbon.   The silicon carbide member according to any one of claims 4 to 7, wherein the silicon carbide layer has an average thickness of 200 µm or less.   The silicon carbide member according to claim 8, wherein the silicon carbide layer has an average thickness of 50 μm or more.   The carbonization according to any one of claims 4 to 9, wherein, among the second silicon carbide crystals, a number ratio of the second silicon carbide crystals existing over two or more of the silicon carbide layers is 20% or less. Silicon member.   The silicon carbide member according to any one of claims 4 to 10, wherein, in a cross section along the first direction, a surface of the silicon carbide layer has irregularities with a line roughness of a maximum height Rz ≥ 20 µm.   A member for a semiconductor manufacturing apparatus, comprising the silicon carbide member according to claim 1.   A focus ring comprising the silicon carbide member according to claim 1.   A dummy wafer comprising the silicon carbide member according to claim 1.

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