WO2018151294A1 - Silicon carbide member and member for semiconductor manufacturing device - Google Patents

Abstract

Provided is a silicon carbide member comprising a β-type first silicon carbide crystal having a 3C crystal structure and a second silicon carbide crystal having a crystal structure, which is different from that of the first silicon carbide crystal. The silicon carbide member has a first surface, and the direction orthogonal to the first surface is defined as a first direction. Particles of the second silicon carbide crystal have a major axis extending in the first direction and have an average length of 100 μm or less in the first direction. Such a silicon carbide member is highly resistant to plasma or liquid chemicals, and is suitably used as a member for a semiconductor device, such as a focus ring and a dummy wafer.

Description

Silicon carbide member and semiconductor manufacturing apparatus member

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 method (Chemical Vapor Deposition, CVD method) is used as a coating material, and a CVD-SiC material alone is used as various members. The single CVD-SiC member can be obtained, for example, by depositing silicon carbide (SiC) on the surface of the substrate by the 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 produced by the sintering method, and is excellent in corrosion resistance, heat resistance, and strength characteristics. For this reason, CVD-SiC materials have been proposed as various members such as heaters for semiconductor manufacturing equipment, focus rings used in etching equipment, dummy wafers, susceptors, furnace core tubes, chemical resistance jigs, and analytical containers. .

CVD-SiC materials are mainly used inside semiconductor manufacturing equipment. For this reason, it is used as a high-purity SiC free-standing film in a state in which the substrate used for film formation is removed. When a thick CVD-SiC material film is formed for use as a free-standing film, the internal stress increases, and the CVD-SiC film (hereinafter simply referred to as a CVD-SiC film) is cracked or warped when the substrate is removed. Deformation may occur. Patent Document 1 discloses that in a laminate in which three or more silicon carbide layers are stacked, 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.

Also, SiC has a plurality of different crystal structures. For example, when the film formation rate is increased in order 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 orthogonal to the first surface is defined as a first direction. The second silicon carbide crystal particles have a long diameter extending along the first direction, and an average length in the first direction is 100 μm or less.

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

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

1 and 2 are examples 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 semiconductor manufacturing apparatuses, particularly CVD (Chemical Vapor Deposition), PVD (Physical Vapor Deposition), and plasma etching apparatuses, wafers such as Si are plasma processed.

The focus ring 1a is disposed on the outer periphery of the wafer. By performing wafer processing using the focus ring 1a, the wafer can be processed more uniformly. For this reason, the focus ring 1a is required to have a resistivity equivalent to or similar to that of a wafer that is an object to be processed and a high corrosion resistance against plasma. Corrosion resistance to plasma is sometimes called plasma resistance.

The dummy wafer 1b is used as an alternative to a wafer when adjusting the conditions of a semiconductor manufacturing apparatus, cleaning, or the like. Similar to 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 cross-sectional views taken along the 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 exposed to the plasma primarily at the first surface S1. 4 and 5 are enlarged cross-sectional views of a part of FIG. The example of FIG. 4 and the example of FIG. As shown in FIG. 4 or FIG. 5, the silicon carbide material formed by the CVD method is generally constituted by columnar silicon carbide crystals 2 in which crystals grow along the arrow direction v that is the first direction. 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 structure of FIG. 4 and FIG. 4 and 5, since the silicon carbide crystal 2 is schematically described as a rectangle, there is a description that there are cavities between the plurality of silicon carbide crystals 2. However, the actual silicon carbide material formed by CVD does not have such a large cavity and is 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 with different crystal structures (crystal forms) have different resistance to plasma and chemicals. The α-type silicon carbide crystal has a relatively low resistance to plasma and chemicals compared to the β-type silicon carbide crystal. In addition, corrosion due to plasma or chemicals tends to proceed at the interface between silicon carbide crystals having different crystal forms.

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

<First Embodiment>
As shown in FIG. 6, the silicon carbide member of the first embodiment includes 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. Type second silicon carbide crystal 2b. The silicon carbide member has a first surface S1, and the first silicon carbide crystal 2a particles and the second silicon carbide crystal 2b particles both have a first direction perpendicular to the first surface S1. It has a long diameter extending along. That the particle has a major axis extending along the first direction means that the major axis direction of the particle forms an angle of less than 45 ° with respect to the first direction. That is, the particles of the first silicon carbide crystal 2a and the particles of the 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 second silicon carbide crystal 2b is larger than the size of the first silicon carbide crystal 2a. The particles of the second silicon carbide crystal 2b have an average of 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, the 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 long diameter extending along the first direction, and the average of the lengths 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 second SiC crystal 2b, that is, the area of second SiC crystal 2b exposed on 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 further 30 μm or less. By making d1 smaller, the area of the exposed portion of the second SiC crystal 2b is further reduced, and the corrosion resistance of the SiC member is further improved.

Note that the first surface S1 is a surface formed in the final step of CVD, and is not a surface in contact with the substrate. The first surface S1 may be a processed surface subjected to a polishing process or the like. Usually, the second SiC crystal 2b hardly exists on the surface in contact with the substrate. The second SiC crystal 2b grows from the 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 substrate can be discriminated from the first surface S1.

The microstructure of the SiC member may be confirmed by, for example, observing the polished surface or cross section of the SiC member by backscattered electron diffraction (Electron Back Scatter 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 wet etching method, for example, a method of immersing a 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. Moreover, you may confirm the local crystal structure in the cross section of a SiC member (crystal structure of each SiC particle) by backscattering electron diffraction (Electron | BackScatter | Diffraction, EBSD).

The second SiC crystal 2b is present inside the SiC member and on the first surface S1. As shown in FIG. 7, second SiC crystal 2 b may have a portion exposed on first surface S <b> 1 of the SiC member. Hereinafter, the 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 that is the length of the exposed portion of the second SiC crystal 2b is set to 20 μm or less, the local decrease in resistance to plasma or chemicals can be reduced on the first surface S1 of the SiC member. As a result, even if the SiC member is exposed to plasma or a chemical solution, it is possible to reduce the occurrence of roughness and cracks on the surface, that is, the first surface S1. The average of d2 may be 10 μm or less, and further 5 μm or less. By making d2 smaller, the corrosion resistance of the SiC member is further improved.

As shown in FIG. 7, the length d2 of the exposed portion in the cross section perpendicular to the first surface S1 may be measured as the length d2 of the exposed portion of the second SiC crystal 2b. The number of measurements of d2 is, for example, 10, and may be averaged. Moreover, the diameter which converted the area of the exposed part of the 2nd SiC crystal 2b into a circle is calculated, and it is good also considering the diameter as d2.

Second Embodiment
The silicon carbide member of the second embodiment includes at least two silicon carbide layers 4 including a first silicon carbide crystal 2a and a 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 the second SiC crystal 2b, the etching rate when the SiC member is exposed to plasma or chemicals can be made uniform. Further, the particles of the second SiC crystal 2b are not easily separated from the first surface S1, and the roughness of the first surface S1 due to etching can be reduced. The average thickness of SiC layer 4 may be 50 μm or more.

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 thin SiC layer 4 in a portion closer to the first surface S1 than the center in the first direction, and the first member is located in the first direction than the center in the first direction. A thick SiC layer 4 may be provided at a site far from the surface S1.

The thickness of one SiC layer 4 can be determined by, for example, observing the cross section of the SiC member with a scanning electron microscope (SEM) or the like, measuring the thickness of one SiC layer 4 at three locations, and taking the average value thereof. 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 layers of SiC layer 4 may be the average thickness of one SiC layer 4. .

An intervening layer 5 may exist at the interface between the adjacent SiC layer 4 and SiC layer 4 as shown in FIG.

Due to the presence of the intervening layer 5, the second SiC crystal 2 b existing in one SiC layer 4 and the second SiC crystal 2 b existing in the other SiC layer 4 among the adjacent SiC layers 4. However, it becomes difficult to connect. That is, second SiC crystal 2 b can be effectively interrupted at the interface between adjacent silicon carbide layer 4 and silicon carbide layer 4. Therefore, two or more of the second SiC crystals 2b projecting from the second SiC crystal 2b existing across the two or more silicon carbide layers 4, that is, 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, 1 μm or more and 10 μm or less.

When 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. When the second SiC crystal 2b exists over a plurality of SiC layers 4, there is a concern that the particles are likely to be coarse and reduce the corrosion resistance of the SiC member. By making N1 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 the two or more SiC layers 4 through the interface between the adjacent SiC layers 4 or the intervening layer 5. It can also be said to be the SiC crystal 2b.

The intervening layer 5 may include the 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 composing the intervening layer 5 are the first SiC crystal 2a.

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

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

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

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

Also, the conductivity of carbon is higher than that of SiC. Therefore, when an SiC member having an intervening layer 5 containing carbon as a main component is used as, for example, a focus ring, charges accumulated on the wafer can be quickly released through the intervening layer 5 of the focus ring, and the wafer processing efficiency is increased. 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 backscattered electron diffraction (Electron BackScatter 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 having 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 is made a structure having irregularities, and the SiC layer 4 The adhesion 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 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>
The manufacturing method of the SiC member will be described. The CVD apparatus used for producing the SiC member of this embodiment is not particularly limited to this. The CVD apparatus may include, for example, a vertical or horizontal batch type CVD chamber having gas inlets and outlets, and an electric heating means. In a CVD apparatus that heats using a high frequency, the substrate can be selectively heated. The frequency of the high frequency used for heating may be, for example, 3 kHz or more and 100 kHz or less.

The CVD method may be any method in which a substrate is set in the CVD chamber, a gas such as a source gas or a carrier gas is 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 the molecule may be used. Methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, a mixed raw material of silicon chloride and hydrocarbon gas, or the like 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 an SiC member can be produced efficiently.

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 of the source gas and the carrier gas may be, for example, 3 to 10 times 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, the dechlorination reaction from silicon atoms can be promoted.

Further, a gas containing dopant atoms may be introduced into the CVD chamber. By introducing dopant atoms into the CVD-SiC, the electrical resistivity of the CVD-SiC can be reduced. Nitrogen or boron may be used as the dopant atom. Examples of the nitrogen-containing gas include nitrogen, ammonia, trimethylamine, and triethylamine. Examples of the boron-containing gas include boron trichloride and diborane. The ratio between the source gas and the gas containing dopant atoms may be adjusted as appropriate according to the desired electrical resistivity. For example, the volume of the gas containing dopant atoms may be 0.01 to 50 times the volume of the source gas. Hereinafter, a mixed gas of a raw material gas, a carrier gas, and a gas containing dopant atoms as necessary is generally referred to as a mixed raw material gas.

The reaction temperature of CVD may be 1200 ° C. or higher, for example, and may be 1250 ° C. or higher. When the reaction temperature is less than 1200 ° C., the deposition rate of CVD-SiC is remarkably lowered, and the production efficiency is lowered. The reaction temperature may be particularly 1350 ° C. or higher, more preferably 1350 ° C. or higher and 1500 ° C. or lower.

A silicon carbide member having a microstructure as shown in FIG. 6 may be produced as follows.

(Process A)
The mixed source 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 adjusted as appropriate.

(Process B)
In the process B, the flow rate of the source gas is set to 1/100 or more and 1/10 or less that in the process A, the mixed source gas is introduced onto the substrate, and the CVD-SiC SiC layer 4 formed in the process A is formed. 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, a method of setting the introduction flow rate of the mixed raw material gas to 1/100 or more and 1/10 or less, or the ratio of the raw material gas in the mixed raw material gas is 1/100 or more, 1/10 There are the following methods, any of which may be used. The deposition rate of CVD-SiC and the introduction time of the mixed source gas may be adjusted as appropriate.

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

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 substrate temperature may be 1200 ° C. or higher and 1400 ° C. or lower. Moreover, what is necessary is just to adjust the repetition frequency of the process A and the process B suitably according to the thickness of the desired silicon carbide member.

A silicon carbide member having a microstructure as shown in FIG. 8 may be produced as follows.

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

Also in this step C, the β-type first SiC crystal 2a having a 3C structure is easily generated. In the process C, since the source gas is particularly in a very dilute state, the defect density of the first SiC crystal 2a to be formed is increased, 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. Presence 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 substrate temperature may be 1200 ° C. or higher and 1400 ° C. or lower. Moreover, what is necessary is just to adjust the frequency | count of repetition of the process A and the process C suitably according to the thickness of the desired silicon carbide member.

(Process D)
Further, in the step D, the introduction flow rate of the source gas is set to 1/100 or more and 1/10 or less, 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, since the pressure in the CVD chamber is low, Si is detached from the CVD-SiC SiC layer 4 formed in the process A. As a result, the intervening layer 5 having a Si / C ratio lower than that of the SiC layer 4 is formed. The introduction time of the mixed material gas in the process D may be, for example, 0.01 times or more and 4.0 times or less the time required for the process A.

The silicon carbide member having the microstructure as shown in FIG. 8 and having the Si / C ratio of the intervening layer 5 smaller than the Si / C ratio of the SiC layer 4 by alternately repeating the steps A and D described above. Is obtained. At this time, the substrate temperature may be 1200 ° C. or higher and 1400 ° C. or lower. Moreover, what is necessary is just to adjust the repetition frequency of the process A and the process D suitably according to the thickness of the desired silicon carbide member.

(Process 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 atmospheric pressure, and the introduction of the source gas and the carrier gas is stopped. In the process E, the pressure in the CVD chamber is low and the source gas is not supplied, so that the detachment of Si further proceeds from the CVD-SiC SiC layer 4 formed in the process A. As a result, the intervening layer 5 containing carbon as a main component is formed. In the process E, the time for stopping the gas introduction may be 0.01 times or more and 4.0 times or less of the time required for the process A, for example.

By alternately repeating the above steps A and E, 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 substrate temperature may be 1200 ° C. or higher and 1400 ° C. or lower. Moreover, what is necessary is just to adjust the frequency | count of repetition of the process A and the process E suitably according to the thickness of the desired silicon carbide member.

In this manner, by depositing CVD-SiC while periodically changing the flow rate of the source gas and, if necessary, the pressure in the CVD chamber, 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 diameter of the 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 that the production efficiency is excellent as compared with a case where a laminated structure is formed through removal from the CVD chamber and processing as in the related art.

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

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

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

In the silicon carbide member thus obtained, a cone-like structure 6 having low corrosion resistance as shown in FIG. 9 is unlikely to occur. Therefore, even when such a silicon carbide member is exposed to plasma or chemicals, the outer surface is less rough and cracks are not generated. 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-solid body from which the substrate is removed as described above, but also a composite member of a silicon carbide coating and the substrate.

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

The CVD apparatus used was a system that heats the substrate by high-frequency induction heating. The frequency of 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 set to 1400 ° C., 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 atmospheric pressure. At this time, the deposition rate of CVD-SiC was approximately 0.5 mm / hour.

In step B, the volume ratio of the carrier gas to the source gas was 100 times, and the pressure in the CVD chamber was −95 kPa with respect to atmospheric pressure. At this time, the deposition rate of CVD-SiC was approximately 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 approximately 0.02 mm / hour.

In step E, the supply of the raw material gas mixed with the raw material gas and the carrier gas was stopped while the vacuum exhaust in the CVD chamber was continued. The pressure in the CVD chamber was −100 kPa with respect to atmospheric pressure.

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

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

Obtained sample No. The surface was etched by immersing 1 to 10 silicon carbide members in molten sodium hydroxide. 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 initial stage of CVD. Sample No. A clear SiC layer and its interface were not seen in 1-3. Sample No. In 4 to 10, a clear SiC layer and its interface could be confirmed. The total thickness of each sample was measured with a micrometer. 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. Sample No. 1-3 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 included 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 determined by backscattered electron diffraction (EBSD). In all of 1 to 10, it was confirmed that the size of the second SiC crystal was on average larger than the size of the first SiC crystal. Table numbers corresponding to the microstructure of each sample are shown in Table 1.

The length d1 in the first direction of the second SiC crystal 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 ratio N1 of the crystal existing over two or more silicon carbide layers in the second SiC crystal was evaluated using a cross-sectional photograph of 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 an intervening layer and the maximum height Rz of the line roughness of the SiC layer were evaluated using SEM cross-sectional photographs. The ratio of Si and C in the intervening layer was evaluated by energy dispersive X-ray spectroscopy (EDS). The results are shown in Table 2. Sample No. Since 1 to 3 as a whole is one SiC layer, N1, Rz and the intervening layer were not evaluated.

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 etched. In the etching process, 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 treatment time was 4 hours. As an evaluation of 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). Moreover, the etched surface was observed visually and by SEM to confirm the presence or absence of cracks. The results are shown in Table 2.

Sample No. In Nos. 1 to 9, there is no noticeable roughness on the etched surface where the length d1 in the first direction of the second SiC crystal is 100 μm or less, Ra is as small as 410 nm or less, and it has high corrosion resistance to plasma. It was. Sample No. In No. 9, cracks along the interface of the SiC layer were observed on the side surface instead of the etched surface. In 1 to 8, no crack occurred. On the other hand, sample No. In No. 10, d1 was as large as 250 μm, and the second SiC crystal was grain-grown. 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.

DESCRIPTION OF SYMBOLS 1: Member for semiconductor manufacturing apparatuses 1a: Focus ring 1b: Dummy wafer 2a: 1st silicon carbide crystal 2b: 2nd silicon carbide crystal 4: Silicon carbide layer 5: Intervening layer 6: Cone-like structure S1: First surface

Claims (14)

1. 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 the first surface and the direction perpendicular to the first surface as the first direction,
   The particles of the second silicon carbide crystal have a major axis extending along the first direction, and an average length in the first direction is 100 μm or less.
2. The silicon carbide member according to claim 1, wherein an average length of the second silicon carbide crystals in the 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 or 2, wherein the average length of the exposed portions is 20 µm or less.
4. Comprising at least two silicon carbide layers comprising 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 the first direction.
5. 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 (Si / C) of silicon (Si) to carbon (C) smaller than that of the silicon carbide layer.
6. The silicon carbide member according to claim 5, wherein the intervening layer includes a first silicon carbide crystal.
7. The silicon carbide member according to claim 5, wherein the intervening layer includes at least one of an amorphous phase mainly composed of carbon and a crystal phase mainly composed of carbon.
8. 8. The silicon carbide member according to claim 4, wherein an average thickness of the silicon carbide layer is 200 μm or less.
9. The silicon carbide member according to claim 8, wherein an average thickness of the silicon carbide layer is 50 μm or more.
10. The carbonization according to any one of claims 4 to 9, wherein a number ratio of the second silicon carbide crystals existing over two or more silicon carbide layers in the second silicon carbide crystals is 20% or less. Silicon member.
11. The silicon carbide member according to any one of claims 4 to 10, wherein a surface of the silicon carbide layer has irregularities having a maximum height Rz ≧ 20 μm as a line roughness in a cross section along the first direction.
12. A member for a semiconductor manufacturing apparatus, comprising the silicon carbide member according to any one of claims 1 to 11.
13. A focus ring including the silicon carbide member according to any one of claims 1 to 11.
14. A dummy wafer comprising the silicon carbide member according to any one of claims 1 to 11.

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