JP4761948B2 - Sintered silicon carbide and parts for semiconductor manufacturing equipment using the same - Google Patents

Description

The present invention is not extremely voids, have a smooth polished surface, related to the silicon carbide sintered body is high thermal conductivity, in particular, in the projection exposure apparatus, various precise processing apparatuses or various precision measuring device, a semiconductor wafer, The present invention relates to a member for a semiconductor manufacturing apparatus suitable for a substrate holding disk or a mirror capable of positioning and processing a substrate such as a mask and a reticle with high accuracy.

  Metal members such as stainless steel have been used for transporting and holding semiconductor wafers in the semiconductor manufacturing process, but in recent years, with the increase in the diameter of semiconductor wafers and the increase in circuit pattern density, suppression of deformation of the members, Suppression of metal contamination, maintenance of accuracy over a long period of time, and the like have been demanded, and ceramic members have come to be used in many cases in order to meet this demand.

Also, ceramic members are often used in mirrors used in precision optical equipment such as laser devices, substrate holding boards, and the like in order to avoid accuracy degradation due to thermal expansion.
In many cases, alumina, silicon nitride, cordierite, or silicon carbide is used for the ceramic member.

  In recent years, there has been a demand for a positioning device that is stable at high speed, high accuracy, and environmental changes. To satisfy this requirement, the stage top plate has a high Young's modulus to withstand the increase in force due to high speed, A silicon carbide sintered body having a high thermal conductivity and a high thermal expansion coefficient is being used so as to be resistant to changes.

Silicon carbide-based sintered bodies are attracting attention as a material having excellent mechanical properties, particularly low strength deterioration at high temperatures, and are being applied to various fields.
Such a silicon carbide based sintered body generally includes carbon and boron added to silicon carbide powder as a sintering aid, and after molding, 2000 to 2050 without pressure in an inert atmosphere such as Ar. It is obtained by firing at ° C.
The thermal conductivity of the silicon carbide sintered body thus obtained is at most about 60 to 80 W / (m · K).

Therefore, in Patent Document 1, a silicon carbide powder having an average particle size of 0.7 μm or less, boron or a compound powder thereof as a sintering aid is 0.1 to 0.5 mass%, and carbon powder is 1 to 10 mass. %
After being added and molded, normal pressure sintering at a temperature of 1900 to 2050 ° C. in an inert gas atmosphere, or a sintered body that has been sintered under normal pressure is further under a pressure of 98 MPa or more in an inert gas atmosphere and at normal pressure There has been proposed a method of obtaining a silicon carbide sintered body having a polishing surface with very few voids by performing HIP treatment at a temperature lower than the sintering temperature.

Further, in Patent Document 2, after forming a compound of boron or a compound thereof and carbon powder or a substance that generates carbon during sintering and a silicon carbide powder having an average particle size of 1 μm or less, water absorption is performed by firing at normal pressure. Produced a primary sintered body having a water absorption of 0.1% or less and a maximum diameter of free carbon contained of 10 μm or less. A method of obtaining a sintered material has been proposed, and a method in which hot isostatic pressure treatment is performed at a pressure of 75 MPa or more and at a temperature of 1700 to 2100 ° C. is proposed.
A mirror using this silicon carbide sintered body has been proposed.

Patent Document 3 discloses that silicon carbide powder having an average particle size of 0.7 μm or less, boron or a compound thereof as a sintering aid is 0.1 to 0.8 wt%, and carbon is 1 to 5 wt%. After adding, forming, and sintering under normal pressure in an inert gas atmosphere of 1900 to 2050 ° C., it is further subjected to hot isostatic pressure at a temperature lower than the sintering temperature under a pressure of 1000 kg / cm ² or more. Press (H
There has been proposed a method for producing a silicon carbide based sintered body characterized in that the surface of the HIP-treated body obtained by IP) treatment is polished with diamond abrasive grains having an average particle size of 2 μm or less.

Patent Document 4 discloses that 6H-type silicon carbide is the main component, contains at least free carbon and boron, the lattice constant of the silicon carbide crystal is 3.0802８０ or more on the a-axis, 15.105Å or more on the c-axis, and is sintered. Compound density is 2.8 g / cm ³ or more, thermal conductivity is 130 W / (m · K) or more, 6H-type silicon carbide is the main component, free carbon and boron are included, and compounds other than silicon In a proportion of not more than 10 mol%, the lattice constant of the silicon carbide crystal is not less than 3.0802Å on the a-axis, not less than 15.105Å on the c-axis, and the sintered body density is not less than 2.8 g / cm ³ , A rate of 130 W / (m · K) or more has been proposed.

  As a member that makes use of the characteristics of such a silicon carbide sintered body, in particular, it is frequently used for a substrate holding disk for attracting and holding or transporting a wafer or the like, a mirror used for positioning a stage or the like.

However, when silicon carbide sintered bodies are used as these members, the pores of the ceramic material itself remain on the polished surface on the surface of the sintered body, which is not sufficiently satisfactory in terms of surface smoothness and optical characteristics. It was.
This is mainly caused when pores remain at grain boundaries between crystal grains in the sintered body when the silicon carbide sintered body is made of polycrystalline ceramics.
For this reason, a member requiring a very smooth surface is formed by forming a silicon carbide film on the surface by a CVD (chemical vapor deposition) method and polishing the film.

For example, Patent Document 5 proposes an optical reflecting mirror in which a SiC film formed by a CVD method and an Al film are stacked on at least a surface to be a mirror portion of a silicon carbide ceramic substrate including SiC-Si ceramic. ing.
Japanese Patent Laid-Open No. 10-203870 JP 2001-247368 A Japanese Patent Laid-Open No. 11-147766 Japanese Patent No. 3157957 JP 2003-57419 A

  As a method for producing a silicon carbide sintered body, various production methods have been proposed as shown in Patent Documents 1 to 4, but various methods are used when used in semiconductor production apparatuses such as mirrors and substrate holding discs. Have a problem.

In Patent Document 1, 0.1 to 0.5% by mass of boron or its compound powder as a sintering aid and 1 to 10% by mass of carbon powder are added to silicon carbide powder having an average particle size of 0.7 μm or less. And then sintering under normal pressure at a temperature of 1900 to 2050 ° C. in an inert gas atmosphere, or further sintering a sintered body under normal pressure sintering under a pressure of 98 MPa or more in an inert gas atmosphere. A silicon carbide sintered body having a polishing surface with very few voids can be obtained by performing the HIP treatment at a temperature lower than the bonded temperature, but the void size of 10 μm is 100 or more per 1 mm ^2. When the bonded body is used as a member for a semiconductor manufacturing apparatus, particles on the sliding contact surface with the substrate become a problem in the substrate holding disk.
Further, in the case of a mirror, there is a problem that a desired reflectance cannot be obtained due to the presence of voids.

Further, in Patent Documents 2 to 4, it has been proposed to reduce voids by performing HIP treatment on the silicon carbide sintered body, but simply performing HIP treatment on the silicon carbide sintered body that has undergone primary sintering. However, it is difficult to use it for a substrate holder or a mirror. For example, in the case of a substrate holder, the voids in the portion on which the substrate is placed may not disappear sufficiently, and there are many on the surface of the substrate placement surface. In some cases, particles such as dust and dust enter into the voids unique to the crystalline ceramics, which are transferred to the wafer and deteriorate the mounting accuracy of the wafer.
That is, even if the HIP process is performed, the voids cannot be sufficiently reduced depending on the conditions, and SiC is often deposited on the surface by CVD or the like.
Further, in the case of a mirror, it is difficult for the void to diffuse the irradiation light and to obtain a high reflectance.
This is probably because the HIP treatment is performed as it is without controlling the crystal grain size in the primary sintering.

Further, Patent Document 5 proposes an optical reflecting mirror formed by depositing an Al film, but there are cases in which the reflectance is insufficient when the reflectance is 65% or more and less than 85%.
When compared with arithmetic average roughness (Ra), the arithmetic average roughness (Ra) of a conventional optical reflecting mirror using a silicon nitride-based sintered body as a base material is 1 nm or less, whereas silicon carbide is used as a base material. In some cases, the arithmetic average roughness (Ra) of the optical reflecting mirror reached several nm.
Moreover, when using SiC-Si ceramic in which Si is impregnated with SiC as the silicon carbide sintered body, lapping is performed before the deposition of the Al film, but there is a difference in hardness between SiC and Si. In some cases, Si was processed first, and SiC remained in a round shape.
In this case, the surface flatness is low, and the arithmetic average roughness (Ra) may reach a little less than 10 nm. Even if an Al film is deposited, the performance of the obtained optical reflection mirror may be insufficient. It was.

  As described above, the conventional silicon carbide sintered body has no silicon carbide sintered body that can simultaneously satisfy all of the characteristics such as high thermal conductivity, low thermal expansion, and extremely few voids. In this semiconductor manufacturing process, since exposure with higher precision is required, a silicon carbide sintered body that has solved the above-described problems has been desired.

The silicon carbide based sintered body of the present invention has a thermal conductivity at room temperature of 180 W / (m · K) or more, a linear expansion coefficient at room temperature of 2.6 × 10 ⁻⁶ / ° C. or less, and an average void diameter of 1.5 μm or less. , the maximum void diameter Ri der below 5 [mu] m, titanium or their compounds, or 200ppm in terms of titanium, and contains the following range 400 ppm, further _{WC, Si 3 N 4, VC} , a metal compound selected from TaC It is characterized by containing 10 mol% or less .

  Furthermore, the silicon carbide based sintered body of the present invention is characterized in that the thermal conductivity at 600 to 800 ° C. is 60 W / (m · K) or more.

  A member for a semiconductor manufacturing apparatus according to the present invention is a member for a semiconductor manufacturing apparatus formed of the silicon carbide sintered body, and is characterized in that at least a part thereof is provided with a mirror portion. .

  Further, in the member for a semiconductor manufacturing apparatus of the present invention, the mirror portion is made of a metal film deposited on the surface of the silicon carbide sintered body, and the wavelength of the mirror portion of the mirror portion including the metal film is from 400 nm to 400 nm. The regular reflectance at 700 nm is 85% or more.

  Furthermore, the regular reflectance at a wavelength of 400 nm to 700 nm in the silicon carbide sintered body in the mirror part excluding at least the metal film is 20% or more.

  Furthermore, the member for a semiconductor manufacturing apparatus of the present invention has a surface having an arithmetic average roughness (Ra) of the mirror part of the member for a semiconductor manufacturing apparatus using the silicon carbide sintered body of 1 nm or less. It is a feature.

  Next, a member for a semiconductor manufacturing apparatus according to the present invention is a member for a semiconductor manufacturing apparatus formed of the silicon carbide sintered body, and is used for a substrate holding board.

The silicon carbide sintered body of the present invention has a thermal conductivity of 180 W / (m · K) or more at room temperature, a linear expansion coefficient of 2.6 × 10 ⁻⁶ / ° C. or less at room temperature, and an average void diameter of 1.5 μm. A metal compound selected from WC, Si ₃ N ₄ , VC, and TaC , wherein the maximum void diameter is 5 μm or less , titanium or a compound thereof is contained in a range of 200 ppm or more and 400 ppm or less in terms of titanium. Because it contains 10 mol% or less , for example, the heat generated by exposure in the semiconductor manufacturing process is quickly diffused to eliminate the change in accuracy due to thermal expansion, and further, dust and dust do not enter the void, reducing the influence of particles. be able to.

  Moreover, since the heat conductivity in 600-800 degreeC is 60 W / (m * K) or more, it can transfer heat | fever rapidly also in a high temperature environment, for example, the use of the shaping | molding die used for lead-free glass molding Is preferred.

Further, by the present invention using the silicon carbide sintered body to the substrate holding plate, with high thermal conductivity, low coefficient of thermal expansion, and since it has voids fewer features, for example, when holding the foundation, Even when exposed to a beam such as exposure, heat is not locally accumulated, it is possible to dissipate heat to reduce shape deformation, maintain stable high accuracy, and there are few voids on the support surface in contact with the substrate. Can prevent particles and other contaminants.

  Embodiments of the present invention will be described below.

In the silicon carbide based sintered body of the present invention, the thermal conductivity of the silicon carbide based sintered body at room temperature is 180 W / (m · K) or more, the linear expansion coefficient at room temperature is 2.6 × 10 ⁻⁶ / ° C. or less, and the average The void diameter is 1.5 μm or less, and the maximum void diameter is 5 μm or less.

If the thermal conductivity is less than 180 W / (m · K), the heat dissipation will be poor, and heat will not be dissipated when heat is locally applied, and even if the thermal expansion coefficient is low, distortion will occur and accuracy will deteriorate. End up.
The heat dissipation is preferably good, and is preferably 180 W / (m · K) or more.
Furthermore, it is desirable that it is 200 W / (m · K) or more.
If it is 200 W / (m · K) or more, the thermal conductivity with other metal members is similar, which is preferable in terms of design.
In particular, since the thermal conductivity is close to that of aluminum, it is possible to obtain a member having a small difference in thermal conductivity even when an aluminum alloy film is formed on the upper surface of the substrate using the silicon carbide of the present invention. It becomes.

  The thermal conductivity at room temperature is a value measured at a measurement temperature in the range of 22 ° C. to 24 ° C., and the thermal conductivity measured at any set temperature within this temperature range is 180 W / (m -K) Indicates that it is greater than or equal to

Furthermore, even in an environment exceeding the room temperature, the thermal conductivity can be maintained at a high value, and for example, the thermal conductivity of 60 W / (m · K) or more can be maintained even in applications at 600 ° C. or higher.

The silicon carbide sintered body preferably has an average crystal grain size in the range of 3 to 10 μm.
The reason is that if it is less than 3 μm, the crystal particles in the silicon carbide sintered body are not sufficiently filled, and the mechanical properties of the sintered body are impaired.
In particular, the strength and rigidity are low.
In addition, if the average crystal grain size is larger than 10 μm, voids existing between the crystals may remain without being crushed, and it is preferably 10 μm or less.
Accordingly, the average crystal grain size is preferably in the range of 3 to 10 μm, and more preferably in the range of 3 to 7 μm.

The density of the silicon carbide based sintered body is 3.18 g / cm ³ or more, the Young's modulus can be 440 GPa or more, and the specific rigidity can be 135 GPa · cm ³ / g or more.
Therefore, when used as a member for a semiconductor manufacturing apparatus, it is possible to provide a member with extremely high accuracy and little deformation.

Moreover, it is important that the linear expansion coefficient is 2.6 × 10 ⁻⁶ / ° C. or less at room temperature no matter how high the thermal conductivity is, and it is a material suitable as a member for a semiconductor manufacturing apparatus in combination with the above heat dissipation. It becomes.
In addition, since the average void diameter is 1.5 μm or less and the maximum void diameter is 5 μm or less, even if the member is in direct contact with the wafer, the void is small and the generation of particles generated between silicon carbide crystals is suppressed. be able to.

  Next, a method for manufacturing the silicon carbide sintered body of the present invention will be described.

First, a raw material powder obtained by adding at least a boron compound powder and a carbon compound powder as additives to silicon carbide powder as a main component is obtained.
Next, the raw material powder is molded using various molding methods to obtain a molded body, and then the primary sintering is completed at a temperature at which silicon carbide particles are suppressed from growing, and primary sintering is performed. After obtaining the body, hot isostatic pressing (HIP) treatment is performed.

This will be described in more detail below.
Silicon carbide powder as the main component, boron carbide (B ₄ C), metal boron, etc. as boron compounds that form boron components as additives, carbon compounds that form carbon components such as carbon black, graphite, etc. A phenol resin or coal tar pitch that can generate carbon can be used.
The content of these additives depends on the amount of oxygen in the raw material powder, and it is necessary that 0.15 to 3 mol of boron and 1 to 5 mol of carbon remain with respect to 1 mol of oxygen in the silicon carbide raw material. It is.

These raw material powders are weighed at a predetermined ratio and mixed thoroughly by a mixing means such as a ball mill, and then a binder is added to the powder, and a known molding method such as press molding, extrusion molding, casting molding, cold A molded body is obtained by molding into a desired shape by isostatic pressing or the like.
In addition, when phenol resin etc. are added as an additive, carbon can be produced | generated by carrying out the calcination process in 600-800 degreeC in a non-oxidizing atmosphere, and thermally decomposing.

Next, in order to obtain high heat conduction, the molded body obtained as described above is subjected to primary sintering at a relatively low temperature of 1900 to 2100 ° C. in a vacuum or in an inert atmosphere such as Ar.
As a result, since the grain growth can be suppressed without increasing the activity by reducing the amount of heat at the time of primary sintering, it is possible to suppress the grain growth of the silicon carbide particles of the molded body, and the voids existing between the crystals are also small. can do.
When the primary sintering temperature is lower than 1900 ° C., the crystal does not sinter, and it becomes difficult to eliminate sufficient voids no matter how much the HIP treatment is performed thereafter.
On the other hand, when the temperature is higher than 2100 ° C., the crystals of the primary sintered body will be enlarged, so that when the HIP treatment is further performed, the crystals of the silicon carbide-based sintered body that are obtained no matter how low the temperature are processed. Large, void disappearance becomes difficult.
Furthermore, if the crystals are not sufficiently sintered, the bonding of the particles will be insufficient, and if this silicon carbide sintered body is used for a substrate holding disk, the grains will be shattered during blasting during the formation of protrusions. It is easy to cause chipping.
In addition, when the crystal is enlarged, a defective portion is generated at a time when one crystal is grain-removed, which is not preferable at the time of blasting when forming a protrusion.

Finally, the obtained primary sintered body is subjected to HIP treatment.
As a result, voids having a void diameter exceeding 5 μm can be almost eliminated while maintaining the size of the silicon carbide crystal substantially the same as the size at the end of the primary sintering.
In addition, it becomes possible to control the solid solution of an additive composed of a compound of boron or carbon or a cation in the additive into silicon carbide, and the grain growth of silicon carbide particles can be effectively suppressed.

In the firing step, primary sintering is performed in a vacuum atmosphere at a temperature of 1900 to 2100 ° C., and HIP treatment is performed in an inert gas atmosphere at a temperature of 1800 to 2000 ° C. and 180 MPa or higher to obtain a silicon carbide-based sintered material. The average void diameter of the body can be 1.5 μm or less and the maximum void diameter can be 5 μm or less. When used as a substrate holding disk or a mirror as a member of a semiconductor or liquid crystal manufacturing apparatus, between silicon carbide crystals Generation of the generated particles can be suppressed.
When the temperature of the HIP process is lower than 1800 ° C., the densification is not promoted because the temperature is lower than the temperature at which the primary sintered body is formed.
Furthermore, it is preferable to set the temperature of HIP treatment at a temperature lower than 100 ° C. below the temperature of primary sintering, and if this temperature range is reached, the pressure can be increased when the crystal is softened. Easily disappear.
On the other hand, when the temperature is higher than 2000 ° C., the temperature range is higher than the temperature of primary sintering, so that the crystal growth is promoted and voids hardly disappear, and the regular reflectance becomes low when used as a mirror. Cheap.
At the same time, by setting the inert gas atmosphere to 180 MPa or more, voids existing between the silicon carbide particles are crushed, and the voids are more likely to disappear.

  More preferably, the primary sintering temperature is fired in a vacuum atmosphere of 1950 to 2050 ° C., and the HIP treatment temperature is 1850 to 1950 ° C. and an inert gas atmosphere of 190 MPa or more.

Moreover, it is preferable to add titanium compounds, such as TiC, TiN, and TiO, as an additive in the range of 200 ppm or more and 400 ppm or less in terms of titanium.
If it is less than 200 ppm, the thermal conductivity of the obtained sintered body is 180 W / (m · K) or higher, and the thermal conductivity at 600 to 800 ° C. cannot be 60 W / (m · K) or higher. If it exceeds 400 ppm, these metal compounds are liable to be dissolved in silicon carbide crystals, and the strength and rigidity of the silicon carbide based sintered body are deteriorated.
Moreover, it becomes easy to produce | generate a boron and compound which are other sintering auxiliary agents, and sinterability will be inhibited, and influences, such as a density not going up, will come out.

In addition, as a metal compound to be added, WC, Si ₃ N ₄ , AlN, VC, TaC, ZrO ₂ or the like may be added, and the amount in that case is based on the amount of silicon carbide powder. It is preferable that it is 10 mol% or less.
This is because when the amount exceeds 10 mol%, the metal compound is liable to be dissolved in the silicon carbide crystal.

The average particle size of the silicon carbide powder in the raw material powder is preferably 0.1 to 1 μm.
This is appropriate because it can be fired at the primary sintering temperature without impairing the properties of low-temperature easy sintering. In particular, if the powder is larger than 1 μm, the properties of low-temperature easy sintering are impaired and sintering at low temperatures becomes impossible.
Further, if the powder is larger than 1 μm, the crystal grain size becomes large when the silicon carbide sintered body is obtained, so that the strength is impaired.
Since it is difficult to obtain a silicon carbide powder having an average particle size smaller than 0.1 μm, the average particle size of the silicon carbide powder in the raw material powder is preferably in the range of 0.1 to 1 μm, preferably 0.8. It may be in the range of 1 to 0.7 μm, and more preferably in the range of 0.1 to 0.5 μm.

  Further, in the silicon carbide sintered body, the boron compound is 0.2% by mass or more and 1.5% by mass or less in terms of boron, and the carbon compound is 1% by mass or more and 3% by mass in terms of carbon. It is preferable to add so that it may become the following ranges.

The addition amount of these additives depends on the amount of oxygen in the raw material powder, and requires 1 to 5 mol of carbon and 0.15 to 3 mol of boron with respect to 1 mol of oxygen in the silicon carbide raw material. It is desirable to add such an amount that the carbon content is about 1 to 3% by mass and the boron is about 0.2 to 1.5% by mass.
Further, the amount of Na is less than that of a silicon carbide sintered body of an Al-based auxiliary material having a liquid phase, and even if it comes into direct contact with the wafer, it does not cause contamination.
If carbon or boron is a sintering aid, there is an effect of easily eliminating voids.

Furthermore, it is preferable that the apparent density of the primary sintered body is 3.10 to 3.17 g / cm ³ and the crystal grain size is ³ to 10 μm.
By adjusting the apparent density within this range, voids disappear in the HIP process more effectively, and if it is less than 3.10 g / cm ³ , sintering does not proceed and 3.17 g / cm 3. ^When it is larger than ³ , the crystal tends to enlarge.
For this reason, if the apparent density is controlled within this range in the primary sintering, an appropriate HIP process can be performed.
When the crystal grain size is less than 3 μm, sufficient sintering is not performed and the strength and rigidity are low. On the other hand, when the crystal grain size exceeds 10 μm, the crystal is enlarged and the void cannot sufficiently reduce the void.

In order to set the apparent density of the primary sintered body to 3.10 to 3.17 g / cm ³ and the crystal grain size to ³ to 10 μm, the temperature of the primary sintering is 1900 to 2100 ° C. as described above. do it.

The apparent density is measured by a method in accordance with JIS R 1634, and the average crystal grain size is measured by using an SEM photograph taken 10,000 times, and arbitrarily drawing a straight line.
The distance on the straight line is divided by the number of crystal grains on the straight line.

  The silicon carbide sintered body thus obtained is finished into a desired shape after HIP processing, and subjected to various processing such as grinding processing and lapping processing, blast processing, polishing processing, etc., to produce a semiconductor wafer, a liquid crystal substrate It can be suitably used as a member for a semiconductor manufacturing apparatus such as a transporting and holding member, a stage position measuring mirror in an exposure apparatus, a precision optical instrument mirror and the like.

  Here, the member for semiconductor manufacturing apparatuses which has a mirror part which uses the silicon carbide sintered body of this invention is demonstrated.

  FIG. 1 is a perspective view showing a semiconductor manufacturing apparatus member 6 using a silicon carbide sintered body according to the present invention and provided with a mirror portion 6a.

  The substrate 5 constituting the semiconductor manufacturing apparatus member 6 has a quadrangular prism shape, and includes a mirror portion 6a on at least one side corresponding to a side surface of a plate (not shown) on which the substrate 5 is installed. 6a is a device for receiving and reflecting light and calculating the position from the light reflection speed to determine the distance position.

By using the silicon carbide sintered body as the base 5 as the member 6 for a semiconductor manufacturing apparatus having the mirror portion 6a, the surface to be the mirror portion 6a is flattened to have a flatness of 0.1 μm or less by lapping or polishing. The surface roughness (Ra) can be finished to 1 nm or less, and the average void diameter of the surface can be 1.5 μm or less, and the maximum void diameter can be 5 μm or less.
Conventionally, a SiC film was deposited by CVD or the like, and after filling the voids, the film was ground and polished to obtain a smooth surface. In the present invention, the silicon carbide sintered body itself forming the substrate 5 is used. However, since the voids that reduce the reflectance are extremely small and few, it is possible to form the mirror portion 6a having a high reflectance by directly depositing a metal film typified by aluminum.

The mirror portion 6a is made of a metal film, and Al, Ag, Pt, etc. deposited by vapor deposition or sputtering can be used as the metal film.
Furthermore, if necessary, a surface film in which one or more low refractive index films and one or more high refractive index films are alternately laminated in the film forming direction on an Al metal film is deposited or sputtered. It may be formed.

Thereby, this mirror part 6a becomes regular reflection rate in wavelength 400nm -700nm 85% or more, and when light, such as a laser which is irradiation light, is irradiated to mirror part 6a, without deteriorating the energy of irradiation light The sensitivity of receiving reflected light can be maintained.
In particular, the diffuse reflectance with respect to the irradiation light of the He—Ne laser is close to 0%, and the reflectance of the reflected light depends on the regular reflectance.
This is because the surface of the sintered body has very few voids, so that the irradiation light does not affect the voids.
Furthermore, the regular reflectance at a wavelength of 633 nm is preferably 95% or more.
The regular reflectance is a value of the entire mirror portion 6a, and is a value of a silicon carbide sintered body constituting the metal film formed on the surface and the base 5 formed on the lower surface thereof.

Further, the thickness of the metal film is preferably in the range of 0.1 to 0.3 μm. If the film thickness is less than 0.1 μm, the influence of coloration of the substrate 5 is greatly generated, and the reflectance may be lowered. is there.
On the contrary, when the film thickness is larger than 0.3 μm, the surface unevenness is affected by the surface irregularities, and the regular reflectance is lost.

Furthermore, it is preferable that the regular reflectance in the wavelength 400nm-700nm of the surface of the silicon carbide sintered body in the mirror part 6a among the base | substrates 5 is 20% or more.
This is because even when a metal film is deposited on the mirror portion 6a, a high regular reflectance can be obtained without impairing the reflectance of the metal film itself.
The regular reflectance is a value on the surface of the silicon carbide sintered body constituting the substrate 5 constituting the mirror portion 6a, that is, the surface of the substrate 5 immediately below the metal film.

Moreover, it is preferable that the arithmetic mean roughness (Ra) of the base body 5 made of a silicon carbide sintered body constituting the mirror portion 6a has a surface of 1 nm or less.
This is because when the arithmetic average roughness (Ra) is larger than 1 nm, the reflected light is scattered and the regular reflectance when the metal film is applied is impaired, and a desired regular reflectance of 85% or more is obtained. This is because it becomes difficult.

According to the method for producing a silicon carbide sintered body, primary sintering is terminated at a temperature at which the silicon carbide particles are suppressed from growing, and then hot isostatic pressing (HIP) treatment is performed. Since the sintering is performed, voids can be eliminated while maintaining the size of the silicon carbide crystal substantially the same as the size at the end of the primary sintering, and the crystal grain size is reduced. In this case, since the voids existing between the crystals can be reduced during the primary sintering, the average crystal grain size is 2 to 10 μm, the average void diameter is 1.5 μm or less, and the maximum void diameter is 5 μm or less. A dense and high thermal conductivity silicon carbide based sintered body can be obtained.
Moreover, when the crystal grains are formed small, the surface can have an arithmetic average roughness (Ra) of 1 nm or less, and when used as a mirror used in a semiconductor manufacturing process, it is stable even when irradiated with light rays. A smooth mirror part with little shape deformation due to heat can be formed, and it can be suitably used as a highly accurate positioning mirror.
And since the void which reduces regular reflectance is very small and few, the mirror which has high reflectance can be provided by depositing metal films, such as aluminum.
In addition, since the arithmetic average roughness (Ra) has a surface of 1 nm or less, an extremely smooth surface can be obtained only by polishing without performing expensive CVD in production, and a highly accurate mirror is provided. Can do.

  Next, a substrate holding plate which is a member for a semiconductor manufacturing apparatus using the silicon carbide sintered body of the present invention will be described.

  2A and 2B show a substrate holding plate using the silicon carbide sintered body according to the present invention, in which FIG. 2A is a perspective view thereof, and FIG. 2B is an enlarged sectional view of a part of the substrate holding plate.

  The substrate holder 1 of the present invention comprises a flat substrate 4 made of the above-mentioned silicon carbide sintered body, and a plurality of protrusions are formed on the surface thereof, and each protrusion contacts the liquid crystal substrate 7. It is comprised from the support surface 2 which supports this, and the non-support surface 3 lowered from the support surface 2.

The flat plate-like body is a disk-shaped or quadrangular plate shape, and is not limited to the shape.
Further, the shape of the support surface 2 may be a circle or a square, and preferably a circular shape because chipping hardly occurs during blasting.

In the manufacturing method of the substrate holding disk 1 of the present invention, the obtained silicon carbide sintered body is finished into a desired shape, the base 4 is formed into a desired plate-like body by grinding, and then the lapping or polishing surface is formed. The substrate holding disk 1 can be manufactured by forming the support surface 2 and the non-support surface 3 by finishing and then blasting.
Furthermore, by further finishing the support surface 2 of the substrate holder 1 with high accuracy by lapping and polishing, the substrate holder 1 with few voids can be obtained.

Moreover, the support surface 2 with very few particles can be obtained by making the support surface 2 into a surface whose arithmetic mean roughness (Ra) is 1 nm or less.
The preferable specific rigidity of the substrate holder 1 may be 135 GPa · cm ³ / g or more, and these can be satisfied with the above-described silicon carbide sintered body.

And if it is the board | substrate holding | maintenance board | substrate 1 using the silicon carbide sintered body of this invention, the heat | fever which generate | occur | produced by exposure of the semiconductor manufacturing process will be spread | diffused quickly, the accuracy change by thermal expansion will be lost, and also dust and dust will be collected. It is possible to provide the substrate holding plate 1 that is not affected by particles without entering the void.
Furthermore, an extremely smooth surface can be obtained only by polishing without performing expensive CVD.

In addition, the semiconductor manufacturing apparatus member 6 of the present invention may be one in which the substrate holding plate 1 is provided with the mirror portion 6a. Usually, the member serving as a base for fixing the substrate holding plate 1, the mirror portion 6a and the substrate. There is no problem even if the holding plate 1 is formed as a single unit.
When this shape is adopted, positioning can be ensured, which is suitable for exposure apparatus parts and inspection apparatus parts having higher precision positioning.

  Examples of the present invention will be described below.

Example 1
As raw material powder, TiC is added to silicon carbide powder having an average crystal grain size of 0.8 μm as shown in Table 1 in terms of titanium, B ₄ C is 0.8% by mass in terms of boron, and 2% of carbon. It adjusted so that it might become mass%.
Silicon carbide powder having an average particle size of 0.5 μm was used.

Then, a disk-shaped molded body having a diameter of 10 mm and a thickness of 5 mm, a prismatic molded body having a length of 3 mm × 3 mm and a length of 16 mm were prepared, and primary sintering was performed at the temperatures shown in Table 1, and further shown in the same table. HIP treatment was performed at temperature and pressure.
Finally, the surface of the obtained silicon carbide sintered body was ground and lapped with a tin plate using 2 μm free diamond abrasive grains as a final finish to obtain a sample for evaluation.

The apparent density of the primary sintered body was measured in accordance with JIS C 2141, and the average crystal grain size of the primary sintered body was arbitrarily measured using a SEM photograph taken at a magnification of 10,000. The distance on the straight line was divided by the number of crystal grains on the straight line.

Among the obtained silicon carbide sintered bodies, the thermal conductivity was measured by a laser flash method at a room temperature of 23 ° C. and 700 ° C. using a disk-shaped sample having a diameter of 10 mm and a thickness of 5 mm, and at 3 mm × 3 mm. Using a prismatic sample with a length of 16 mm, the coefficient of thermal expansion is in the range of 0 ° C. to 50 ° C. with a temperature increase of 1 ° C./min by laser interferometry using a laser thermal dilatometer LIX-1 type manufactured by Vacuum Riko. Then, the data of room temperature (23 ° C.) measured in helium was measured as the coefficient of thermal expansion.
In addition, the average void diameter and the maximum void diameter were obtained using a disk-shaped sample having a diameter of 10 mm and a thickness of 5 mm, and an image of a metallurgical microscope was captured with a CCD camera using a Nireco LUZEX-FS, and magnification was obtained using image analysis. Measured by quantifying at 200 times, and using a disk-shaped sample having a diameter of 10 mm and a thickness of 5 mm, the regular reflectance is a value at a wavelength of 633 nm of a He-Ne laser using a spectrophotometer U-4000 manufactured by Hitachi, Ltd. As measured.

  Table 1 shows the results.

    From Table 1, it was found that the sample (No. 27) which was not subjected to HIP treatment in the production method had a very large average void diameter of 7.9 μm and a maximum void diameter of 26 μm.

Of the samples subjected to HIP treatment, the sample (No. 2) having a primary sintering temperature of less than 1900 ° C. has a large average void diameter of 2.6 μm and a maximum void diameter of 14.6 μm. I understood.
On the other hand, it was found that the sample (No. 23 ) exceeding 2100 ° C. had a large average void diameter of 2.6 μm and a maximum void diameter of 7.6 μm.

It was found that the sample (No. 3) having an HIP treatment temperature of less than 1800 ° C. had a large average void diameter of 1.9 μm and a maximum void diameter of 14.3 μm.
On the other hand, it was found that the sample (No. 11 ) having a HIP treatment temperature exceeding 2000 ° C. had a large average void diameter of 2.9 μm and a maximum void diameter of 8.4 μm.

In addition, it was found that the samples (No. 1, 12 ) having an amount of titanium of less than 200 ppm have low thermal conductivity at room temperature and high temperature.

  Further, the coefficient of linear expansion is a value that depends on the amount of boron and carbon added to the raw material powder without any significant difference among the samples.

  On the other hand, by setting the primary sintering temperature to 1900-2100 ° C. and the HIP treatment temperature to 1800-2000 ° C., the average void diameter and the maximum void diameter can be made extremely small, and the regular reflectance is also 20%. I was able to get the above.

It is a perspective view which shows the mirror which is a member for semiconductor manufacturing apparatuses which concerns on this invention. The board | substrate holding board which is a member for semiconductor manufacturing apparatuses which concerns on this invention is shown, (a) is the perspective view, (b) is sectional drawing to which the one part was expanded.

DESCRIPTION OF SYMBOLS 1 ... Substrate holding | maintenance board 2 ... Support surface 3 ... Non-support surface 4, 5 ... Base | substrate 6 ... Member 6a for semiconductor manufacturing apparatuses ... Mirror part 7 ... Liquid crystal substrate

Claims (7)

Thermal conductivity of 180W / (m · K) or more at room temperature, linear expansion coefficient of 2.6 × ^{10 -6} / ℃ or less at room temperature, an average void diameter of 1.5μm or less, the maximum void diameter Ri der less 5μm , Containing titanium or a compound thereof in a range of 200 ppm or more and 400 ppm or less in terms of titanium, and further containing 10 mol% or less of a metal compound selected from WC, Si ₃ N ₄ , VC and TaC. A silicon carbide sintered body. 2. The silicon carbide based sintered body according to claim 1 , wherein the thermal conductivity at 600 to 800 ° C. is 60 W / (m · K) or more. A member for a semiconductor manufacturing apparatus formed of the silicon carbide based sintered body according to claim 1 , wherein at least a part thereof is provided with a mirror portion. The mirror unit according to claim 3 in which a metal film that is deposited on the surface of the silicon carbide sintered body, and specular reflectance at a wavelength 400nm~700nm of the mirror section is equal to or less than 85% The member for semiconductor manufacturing apparatuses as described in 2. Member for a semiconductor manufacturing apparatus according to claim 3 or 4 at least specular reflectance at a wavelength 400nm~700nm silicon carbide sintered body of the mirror unit is characterized in that 20% or more. The member for a semiconductor manufacturing apparatus according to claim 3 , wherein the arithmetic average roughness (Ra) has a surface of 1 nm or less. A member for a semiconductor manufacturing apparatus, which is a member for a semiconductor manufacturing apparatus formed of the silicon carbide based sintered body according to claim 1 , wherein the member is used for a substrate holder.

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