JP2001158674A - Sintered compact of porous silicon carbide, method for producing the same, member for wafer-polishing device and table for wafer-polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sintered compact of a porous silicon carbide, extremely superior in soaking properties, thermal responsibility and dimensional stability. SOLUTION: This table 2 is usable for a wafer-polishing device 1, and is composed of base materials 11A and 11B made from the sintered compact of the porous silicon carbide. The sintered compact of the porous silicon carbide has open pores 23 present in a structure constituted of silicon carbide crystals 21 and 22. The average particle diameter of the silicon carbide crystals 21 and 22 is >=20 μm, the porosity and the thermal conductivity thereof are <=40% and >=80 W/m.K respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous silicon carbide sintered body, a method for manufacturing the same, a member for a wafer polishing apparatus, and a table for a wafer polishing apparatus.

[0002]

2. Description of the Related Art Conventionally, silicon carbide (SiC) has been known as a kind of non-oxide ceramic. Silicon carbide sintered body has thermal conductivity, heat resistance, thermal shock resistance, wear resistance, hardness,
It has suitable characteristics such as excellent oxidation resistance and corrosion resistance.

[0003] Therefore, the silicon carbide sintered body is exposed to abrasion-resistant materials such as mechanical seals and bearings, refractory materials for high-temperature furnaces, heat-resistant structural materials such as heat exchangers and combustion tubes, and acids and alkalis. It can be said that it is a widely usable material such as a corrosion-resistant material such as a pump part which is easily damaged. In recent years, there has been a movement to use a silicon carbide sintered body as a constituent material of a semiconductor manufacturing apparatus (for example, a wafer polishing apparatus, etc.), focusing on the above-described various properties, particularly, high thermal conductivity.

[0004] A wafer polishing apparatus refers to a lapping machine or a polishing machine for polishing a device formation surface of a semiconductor wafer. This apparatus includes a wafer top plate, a table made of a porous silicon carbide sintered body, and the like. Cooling water is circulated through a flow path provided in the table. A semiconductor wafer is attached to the holding surface of the wafer top plate using a thermoplastic wax. The semiconductor wafer held by the rotating pusher plate is pressed from above onto the polished surface of the table. As a result, the semiconductor wafer comes into sliding contact with the polishing surface, and one side surface of the wafer is uniformly polished. Then, the heat generated in the wafer at this time is conducted outside the apparatus by the cooling water circulating in the flow path after conducting in the table.

[0005]

Incidentally, the silicon carbide sintered body has a property of efficiently conducting heat, and thus has an advantage that temperature variation hardly occurs inside the sintered body. Accordingly, the sintered body is provided with high soaking properties and thermal responsiveness. Further, as a result of avoiding the generation of thermal stress and making the base material less likely to warp, the shape stability is improved.

Although the silicon carbide sintered body has a higher thermal conductivity than other ceramic sintered bodies,
The value of the thermal conductivity in the porous body is 10 W / m · K to 70
It was only about W / m · K. Therefore, in order to realize a porous silicon carbide sintered body having more excellent thermal uniformity, thermal responsiveness, and shape stability, it has been considered that further improvement in thermal conductivity is essential. Similarly, when this sintered body is used for the table, it has been considered that improvement in thermal conductivity is essential for realizing a large-diameter and high-quality wafer.

The present invention has been made in view of the above-mentioned problems, and a first object of the present invention is to provide a porous silicon carbide sintered body having extremely excellent heat uniformity, thermal response, and shape stability. It is in. A second object is to provide a method capable of reliably producing such a suitable sintered body. further,
A third object is to provide a member for a wafer polishing apparatus and a table for a wafer polishing apparatus which are suitable for manufacturing large-diameter and high-quality wafers.

[0008]

According to the first aspect of the present invention, there is provided a porous sintered body having open pores in a structure composed of silicon carbide crystals. The average particle size of the silicon carbide crystal is 20 μm
As described above, the porosity is 40% or less, and the thermal conductivity is 80 W / m · K.
The gist is the porous silicon carbide sintered body described above.

According to the second aspect of the present invention, in a porous sintered body having an open pore in a structure constituted by silicon carbide crystals, the silicon carbide crystals have an average particle size of 2%.
The gist of the present invention is a porous silicon carbide sintered body having a pore size of 0 μm to 100 μm, a porosity of 5% to 30%, and a thermal conductivity of 80 W / m · K or more.

A third aspect of the present invention is the method according to the first or second aspect, wherein fine silicon carbide crystals having an average particle size of 0.1 μm to 1.0 μm are included in an amount of 10% by volume to 50% by volume, and
Roughly silicon carbide crystals having an average particle size of 25 μm to 150 μm are included in 50% by volume to 90% by volume.

[0011] In the invention according to claim 4, open pores are present in a structure constituted by silicon carbide crystals,
A method for producing a porous silicon carbide sintered body having an average particle size of 20 μm or more, a porosity of 40% or less, and a thermal conductivity of 80 W / m · K or more, wherein the silicon carbide crystal has an average particle size of 5 μm or more.
10 parts by weight to 100 parts by weight of fine powder of α-type silicon carbide having an average particle size of 0.1 μm to 1.0 μm are blended with 100 parts by weight of coarse powder of α-type silicon carbide of μm to 100 μm. A step of uniformly mixing, a step of molding the mixture obtained in the above step into a predetermined shape to obtain a molded body, and a step of firing the molded body in a temperature range of 1700 ° C. to 2400 ° C. to obtain a sintered body. The gist of the present invention is a method for producing a porous silicon carbide sintered body.

According to a fifth aspect of the present invention, there is provided a member used in a wafer polishing apparatus, wherein the wafer polishing apparatus comprises the porous silicon carbide sintered body according to any one of the first to third aspects. The member is the gist.

According to a sixth aspect of the present invention, there is provided a table having a polishing surface on which a semiconductor wafer held on a holding surface of a wafer holding plate constituting a wafer polishing apparatus is slidably contacted. The substrates are joined together in a state where a plurality of the substrates made of the porous silicon carbide sintered body according to any one of the above are laminated, and a fluid flow path is provided at a joint interface of the substrates. The summary of the table for a wafer polishing apparatus is as follows.

The "action" of the present invention will be described below. According to the first to third aspects of the present invention, the average particle size of the silicon carbide crystal constituting the porous structure is set to a relatively large value of 20 μm or more. Since the efficiency of heat conduction inside the crystals is generally higher than the efficiency of heat conduction between crystals, the larger the average particle size, the higher the thermal conductivity. The fact that the porosity is set to a small value of 40% or less also contributes to an improvement in thermal conductivity. That is, when the porosity is reduced, the voids in the sintered body are reduced, so that heat is easily conducted.

[0015] For this reason, temperature variation is less likely to occur inside the sintered body as compared with a conventional porous body having a thermal conductivity value much lower than 80 W / m · K. As a result, extremely high heat uniformity and thermal responsiveness are imparted to the sintered body. Further, as a result that the generation of thermal stress is reliably avoided and the substrate is less likely to warp, extremely high shape stability is imparted to the sintered body.

In this case, the average particle size of the silicon carbide crystal is 20
If it is less than μm or the porosity exceeds 30%, it becomes difficult to set the thermal conductivity to a high value of 80 W / m · K or more. Therefore, it becomes impossible to sufficiently improve the heat uniformity, the thermal responsiveness, and the shape stability. In addition, the value of the thermal conductivity needs to be 80 W / m · K or more, more preferably 100 W / m or more, and particularly preferably 100 W / m · K to 180 W / m · K. preferable.

The average particle size of the silicon carbide crystal is 20 μm to 1 μm.
00 μm, preferably 30 μm to 90 μm.
μm, more preferably 40 μm to 70 μm
Most preferably, it is set to m. If the average particle size is too large, the number of voids increases, and the density of the sintered body may decrease.

The porosity of the open pores is preferably set to 5% to 30%, more preferably 10% to 25%, and most preferably 10% to 20%.

The sintered body has an average particle size of 0.1 μm or less.
50% by volume of a coarse silicon carbide crystal (hereinafter, referred to as coarse crystal) containing 10% by volume to 50% by volume of fine silicon carbide crystal (hereinafter, referred to as fine crystal) of 1.0 μm and having an average particle size of 25 μm to 65 μm. Preferably, it contains about 90% by volume.

As described above, in the case of a sintered body in which fine crystals and coarse crystals are contained at an appropriate ratio, the gaps formed between the coarse crystals are likely to be filled with the fine crystals, and the substantial voids are formed. The ratio becomes smaller. As a result, the thermal resistance of the sintered body is further reduced, and it is considered that this greatly contributes to the improvement of the thermal conductivity.

The average diameter of the fine crystals is 0.1 μm to 1.0 μm.
μm, often 0.1 μm to 0.9 μm
Is more preferably set to 0.1 μm to 0.7 μm.
Most preferably, it is set to μm. If an attempt is made to make the average particle size of the fine crystals extremely small, it is necessary to use expensive fine powder, which may lead to a rise in material costs. Conversely, if the average grain size of the fine crystals is too large, the voids formed between the coarse crystals cannot be sufficiently filled, and the thermal resistance of the sintered body may not be sufficiently reduced.

In the sintered body, the fine crystals are from 10% by volume to 5% by volume.
0% by volume, 15% to 40% by volume
It is more preferably contained, and 20% to 40% by volume
Most preferably, it is included. When the content ratio of the fine crystals is too small, it is difficult to secure a sufficient amount of the fine crystals to fill the voids formed between the coarse crystals, and the thermal resistance of the sintered body may not be reduced reliably. . Conversely, if the content ratio of the fine crystals is too large, the fine crystals filling the voids become rather surplus, and it is not possible to secure a coarse crystal which is originally necessary for improving the thermal conductivity. Therefore, the thermal resistance of the sintered body may be rather increased.

Further, the average grain size of the coarse crystals in the sintered body is preferably set to 25 μm to 150 μm.
It is more preferably set to 0 μm to 100 μm,
Most preferably, it is set to 60 μm to 80 μm.
If an attempt is made to reduce the average particle size of the coarse crystals to a very small value, the particle size difference from the fine particles becomes small, so that the effect of reducing the thermal resistance by mixing the fine crystals and the coarse crystals may not be expected. Conversely, if the average grain size of the coarse crystals is too large, individual voids formed between the coarse crystals will increase, so that even if there is a sufficient amount of fine crystals, the voids should be sufficiently filled. Becomes difficult. Therefore, there is a possibility that the thermal resistance of the sintered body cannot be sufficiently reduced.

[0024] In the sintered body, the coarse crystals are 50% by volume to 9%.
0% by volume, 60% to 85% by volume
More preferably, 60% to 80% by volume
Most preferably, it is included. When the content ratio of the coarse crystals is too small, the coarse crystals required to improve the thermal conductivity cannot be secured, and the thermal resistance of the sintered body may be rather increased. Conversely, if the content ratio of the coarse crystals is too large, the content ratio of the fine crystals becomes relatively small, and it becomes impossible to sufficiently fill the voids formed between the coarse crystals. Therefore, there is a possibility that the thermal resistance of the sintered body cannot be reduced reliably.

According to the fourth aspect of the present invention, the porous silicon carbide sintered body of the present invention comprises, as described above, a material preparation step, a molding step, in which a fine powder and a coarse powder are blended in a predetermined ratio and mixed. It is manufactured through a firing process.

In the material preparation step, the average particle size is 5
10 parts by weight to 100 parts by weight of fine powder of α-type silicon carbide having an average particle size of 0.1 μm to 1.0 μm are blended with 100 parts by weight of coarse powder of α-type silicon carbide of μm to 100 μm. Perform uniform mixing.

The average particle size of the α-type silicon carbide coarse powder is 5 μm.
m to 100 μm, and 15 μm to 7 μm.
It is more preferably set to 5 μm, and 25 μm to 6 μm.
Most preferably, it is set to 0 μm. When the average particle size of the α-type silicon carbide coarse powder is less than 5 μm, the effect of suppressing abnormal grain growth may be reduced. Conversely, if the average particle size of the α-type silicon carbide coarse powder exceeds 60 μm, the moldability may be deteriorated and the strength of the obtained porous body may be reduced.

The average particle size of the fine powder of α-type silicon carbide is 0.1 μm.
It is often set to 1 μm to 1.0 μm, and 0.1 μm
m to 0.8 μm, more preferably 0.
Most preferably, it is set to 2 μm to 0.5 μm.
If the average particle size of the fine powder of α-type silicon carbide is less than 0.1 μm, it becomes difficult to control the grain growth, and inevitably increases the material cost. Conversely, if the average particle size of the α-type silicon carbide fine powder exceeds 1.0 μm, the voids formed between the coarse crystals may be difficult to fill. In addition,
The reason why the α-type was selected as the fine powder is that the thermal conductivity tends to be somewhat higher because the crystal orientation is improved as compared with the β-type.

The amount of the fine powder is 10 parts by weight to 10 parts by weight.
The amount is preferably 0 parts by weight, more preferably 15 parts by weight to 65 parts by weight, and most preferably 20 parts by weight to 60 parts by weight. If the amount of the fine powder is too small, it is difficult to secure a sufficient amount of fine crystals to fill the voids formed between the coarse crystals, and the thermal resistance of the sintered body may not be sufficiently reduced. Further, in order to obtain a desired pore diameter of 20 μm or more, it is necessary to set the firing temperature to an extremely high temperature, which is disadvantageous in cost. Conversely, if the amount of the fine powder is too large, coarse crystals required to improve the thermal conductivity cannot be secured, and the thermal resistance of the sintered body may increase. Also, it becomes difficult to obtain a sintered body having excellent strength.

In the above-mentioned material preparation step, a molding binder and a dispersion solvent are blended together with the two kinds of powders as required. Then, this is uniformly mixed and kneaded to appropriately adjust the viscosity, so that a raw material slurry is first obtained. As means for mixing the raw material slurry,
Vibration mill, attritor, ball mill, colloid mill,
There are high-speed mixers and the like. As a means for kneading the mixed raw material slurry, for example, there is a kneader or the like.

Examples of the molding binder include polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyethylene glycol, phenol resin, epoxy resin, acrylic resin and the like. It is preferable that the compounding ratio of the molding binder is generally in the range of 1 part by weight to 10 parts by weight based on 100 parts by weight of the total of the silicon carbide powder. If this ratio is less than 1 part by weight, the strength of the obtained molded article becomes insufficient, and the handleability deteriorates. Conversely, if the ratio exceeds 10 parts by weight, cracks are likely to occur in the molded body when the molding binder is removed by drying or the like, and the yield is deteriorated.

As a dispersion solvent, organic solvents such as benzene and cyclohexane, alcohols such as methanol, and water can be used. Next, silicon carbide granules are formed using the raw material slurry. As a method of granulating the silicon carbide powder, a conventional general-purpose technique such as a granulation method by spray drying (so-called spray drying method) can be used. That is, a method in which the raw material slurry is sprayed into a container maintained at a high temperature state, and the material slurry is rapidly dried is applicable.

Here, the water content of the granules is from 0.1% by weight to 2.% by weight.
It is preferably 0% by weight, more preferably 0.2% to 1.0% by weight. The reason is that when the moisture content of the granules is within the above range, the density of the molded body and the density of the sintered body are increased, and as a result, the thermal conductivity is increased. When the water content of the granules is less than 0.1% by weight, the density of the molded body and the density of the sintered body are not sufficiently increased, and the thermal conductivity is hardly increased. Conversely, if the moisture content of the granules exceeds 2.0% by weight, cracks may easily occur in the molded product during drying,
This leads to a decrease in yield.

In the subsequent molding step, granules made of the mixture obtained in the material preparation step are molded into a predetermined shape to produce a molded body. The molding pressure at that time is 1.0 t / c
m ^{2 to} 1.5 t / cm ² , and 1.1 t / c
More preferably, it is m ^{2 to} 1.4 t / cm ² . The reason is that the thermal conductivity increases as a result of the increase in the density of the molded body grooves and the density of the sintered body. Molding pressure is 1.0t / cm ²
If it is less than 3, the density of the compact and the density of the sintered compact do not become sufficiently high, and the thermal conductivity does not easily become high. Conversely, 1.5
When molding is performed at a pressure greater than t / cm ² , the density of the molded body can be sufficiently increased, but a dedicated press device is required, which results in a rise in equipment costs and difficulty in manufacturing. Become.

The density of the molded product is 2.0 g / cm ³
It is often set as above, especially 2.2 g / cm ³
It is preferably set to ~2.7g / cm ^3. The reason is that if the density of the compact is too low, the number of bonding portions between silicon carbide particles decreases. Therefore, the strength of the obtained porous body becomes low, and the handleability becomes poor. Conversely, if the density of the molded body is to be increased, a dedicated press device is required as described above, which results in an increase in equipment cost and difficulty in manufacturing.

In the subsequent firing step, the compact obtained by the molding step is heated at a temperature in the range of 1700 ° C. to 2400 ° C., preferably in the temperature range of 2000 ° C. to 2300 ° C.
It is particularly preferably fired in a temperature range of 2000 to 2300 ° C. to produce a sintered body.

If the firing temperature is too low, it is difficult to sufficiently develop a neck portion for connecting silicon carbide particles, and it may not be possible to achieve high thermal conductivity and high strength. Conversely, if the firing temperature is too high, the thermal decomposition of silicon carbide will start, resulting in a decrease in the strength of the sintered body. Moreover, as a result of an increase in the amount of heat energy to be applied to the firing furnace, there is a disadvantage in cost.

During firing, the inside of the firing furnace is filled with a gas atmosphere (for example, a non-oxidizing atmosphere or an inert atmosphere) comprising at least one selected from, for example, argon, helium, neon, nitrogen, hydrogen and carbon monoxide. ) Should be kept. At this time, the inside of the firing furnace may be in a vacuum state.

Further, at the time of firing, it is advantageous to suppress the volatilization of silicon carbide from the compact in order to promote the growth of the neck portion. As a method for suppressing the volatilization of silicon carbide from the compact, it is effective to charge the compact in a heat-resistant container capable of blocking the invasion of the outside air. As a material for forming the heat-resistant container, graphite or silicon carbide is preferable.

By performing each of the above steps, it is possible to reliably produce a porous silicon carbide sintered body having extremely excellent heat uniformity, thermal responsiveness and shape stability. According to the invention as set forth in claim 5, since the member is made of a porous silicon carbide sintered body having extremely excellent heat uniformity, thermal responsiveness, and shape stability, it is suitable for manufacturing a large-diameter, high-quality wafer. Becomes

According to the sixth aspect of the present invention, the semiconductor wafer comes into sliding contact with the polishing surface while rotating, so that one side surface of the semiconductor wafer is uniformly polished by the polishing surface. Since the above table is made of a porous silicon carbide sintered body having extremely excellent heat uniformity, heat responsiveness and shape stability,
The influence of heat or the like on the semiconductor wafer during polishing is minimized. Therefore, according to the table of the present invention, a large-diameter and high-quality wafer can be reliably manufactured.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a wafer polishing apparatus 1 according to an embodiment of the present invention will be described in detail with reference to FIGS.

FIG. 1 shows a wafer polishing apparatus 1 according to this embodiment.
Is schematically shown. The table 2 constituting the wafer polishing apparatus 1 has a disk shape. The upper surface of the table 2 is a polishing surface 2a for polishing the semiconductor wafer 5. A polishing cloth (not shown) is attached to the polishing surface 2a. The table 2 according to the present embodiment is directly and horizontally fixed to the upper end surface of the cylindrical rotating shaft 4 without using a cooling jacket. Therefore, when the rotation shaft 4 is driven to rotate, the table 2 rotates integrally with the rotation shaft 4.

As shown in FIG. 1, the wafer polishing apparatus 1 includes a plurality (two in FIG. 1 for convenience of illustration) of wafer holding plates 6. As a material for forming the plate 6, for example, a glass, a ceramic material such as alumina, a metal material such as stainless steel, or the like is employed. A pusher bar 7 is fixed to the center of one side surface (non-holding surface 6b) of each wafer holding plate 6. Each pusher bar 7 is located above the table 2 and is connected to driving means (not shown). Each pusher bar 7 horizontally supports each wafer holding plate 6. At this time, the holding surface 6
a is in a state facing the polishing surface 2a of the table 2. Further, each pusher bar 7 can not only rotate with the wafer holding plate 6 but also move up and down within a predetermined range. Instead of the method of moving the plate 6 up and down, a structure of moving the table 2 up and down may be adopted. The semiconductor wafer 5 is adhered to the holding surface 6a of the wafer holding plate 6 using, for example, thermoplastic wax. The semiconductor wafer 5 may be attracted to the holding surface 6a by evacuation or electrostatically. At this time, the polished surface 5a of the semiconductor wafer 5 needs to face the polished surface 2a of the table 2.

Next, the configuration of the table 2 will be described in detail. As shown in FIGS. 1 and 2, the table 2 of the present embodiment has two base materials 11 made of a porous silicon carbide sintered body.
A, 11B is a laminated ceramic structure. On the back surface of the upper base material 11A, a cooling water channel 1
Grooves 13 forming a part of 2 are formed in a predetermined pattern. The two substrates 11A and 11B are integrated by being joined to each other via the silver brazing material layer 14. As a result, the water channel 12 is formed at the joint interface between the substrates 11A and 11B. A through hole 15 is formed substantially at the center of the lower substrate 11B. These through holes 15
Is provided with a flow path 4 a provided in the rotating shaft 4 and the water passage 12.
And the communication.

The groove 13 forming a part of the water channel 12 is a ground groove formed by grinding the back surface of the upper substrate 11A after the raw processing and before firing. The depth of the groove 13 is 3
It is preferable that the width is set to about 10 mm and the width is set to about 20 mm.

Hereinafter, some examples which embody the present embodiment will be introduced. [Example 1] In the production of Example 1, as a starting material, a coarse powder of α-type silicon carbide having an average particle diameter of 30 µm (# 40
0) and α-type silicon carbide fine powder (GMF-15H2) having an average particle diameter of 0.3 μm. Then, 30 parts by weight of the fine powder was blended with 100 parts by weight of the coarse powder, and this was uniformly mixed.

After blending 5 parts by weight of polyvinyl alcohol and 50 parts by weight of water with respect to 100 parts by weight of this mixture, the mixture was mixed in a ball mill for 5 hours to obtain a uniform mixture. After drying the mixture for a predetermined time to remove a certain amount of water, an appropriate amount of the dried mixture was collected and granulated. At this time, the water content of the granules was adjusted to be about 0.8% by weight. Next, the granules of the mixture were molded using a metal mold at a pressing pressure of 1.3 t / cm ² . The obtained disk-shaped formed form (50 mmφ, 5 mm
The density of t) was 2.6 g / cm ³ .

Subsequently, by grinding the bottom surface of the molded body to become the upper base material 11A later, a groove 13 having a depth of 5 mm and a width of 10 mm was formed on almost the entire bottom surface. Next, the formed body was charged in a crucible and fired using a Tamman type firing furnace. The firing was performed in an argon gas atmosphere at 1 atm. During firing, the maximum temperature is 2200 ° C. at a rate of 10 ° C./min.
And then kept at that temperature for 4 hours.

Base material 1 made of porous silicon carbide sintered body obtained
The open pores of 1A and 11B had a porosity of 20%, a thermal conductivity of 130 W / m · K, and a density of 2.5 g / cm ³ .
The average particle size of the silicon carbide crystals was 30 μm. Specifically, fine crystals having an average particle size of 1.0 μm
80% by volume of coarse crystals containing and having an average particle size of 40 μm
Included. For reference, FIG. 4C shows a graph of the particle size distribution in the sintered body of Example 1.

Subsequently, after performing a facing process by a conventionally known method, two substrates 11A, 11A are formed using a silver brazing material.
B was joined and integrated. Further, by polishing the surface of the upper substrate 11A, the table 2 having a polished surface 2a having a surface roughness suitable for polishing the semiconductor wafer 5 was finally completed.

The table 2 of Example 1 thus obtained is set in the above-mentioned various polishing apparatuses 1, and the semiconductor wafers 5 of various sizes are polished while the cooling water W is constantly circulated in the water channel 12. Was. When the semiconductor wafer 5 obtained through polishing by various polishing apparatuses 1 was observed, the wafer 5 was not damaged irrespective of the wafer size. Also, there was no occurrence of a large warp in the wafer 5. That is, table 2 of the present embodiment
In the case of using, a very large diameter and high quality semiconductor wafer 5
Was obtained.

FIG. 3 is a cross-sectional view conceptually showing an enlarged table 2 of the first embodiment. The porous silicon carbide sintered body composing the table 2 includes fine crystals 21 and coarse crystals 2.
And 2. The voids formed between the coarse crystals 22 are:
It is almost filled with the fine crystal 21. Therefore,
It can be understood that the substantial void ratio, that is, the porosity of the open pores 23 is considerably small. [Example 2] In the production of Example 2, the average particle diameter was 35%.
A coarse powder (# 360) of α-type silicon carbide having a thickness of μm was used, and 30 parts by weight of the fine powder was mixed with 100 parts by weight of the coarse powder, and the mixture was uniformly mixed. Other conditions were basically the same as in Example 1.

As a result, the porosity of the open pores of the obtained porous silicon carbide sintered bodies 11A and 11B was 17%,
Thermal conductivity is 145W / mK, density is 2.55g / cm
^{Was 3} . The average particle size of the silicon carbide crystal is 36 μm.
Met. Specifically, it contained 20% by volume of fine crystals having an average particle size of 1.0 μm and 80% by volume of coarse crystals having an average particle size of 45 μm. In addition, for reference, FIG.
2 shows a graph of the particle size distribution in the sintered body of Example 2.

After completing the table 2 in the same procedure as in the first embodiment, the table 2 was set in the above-mentioned various polishing apparatuses 1 and the semiconductor wafers 5 of various sizes were polished. Excellent results were obtained. Example 3 In the preparation of Example 3, the average particle diameter was 57%.
A .mu.m coarse powder of .alpha.-type silicon carbide (# 240) was used, and 30 parts by weight of the fine powder were blended with 100 parts by weight of the coarse powder, and were uniformly mixed. Other conditions were basically the same as in Example 1.

As a result, the porosity of the open pores of the obtained porous silicon carbide sintered bodies 11A and 11B was 15%,
Thermal conductivity is 150 W / m · K, density is 2.6 g / cm ³
Met. The average particle size of the silicon carbide crystals was 65 μm. Specifically, it contained 20% by volume of fine crystals having an average particle size of 1.0 μm and 80% by volume of coarse crystals having an average particle size of 80 μm. FIG. 4A shows a graph of the particle size distribution of the sintered body of Example 3 for reference.

After completing the table 2 in the same procedure as in the first embodiment, the table 2 was set in the various polishing apparatuses 1 described above, and the semiconductor wafers 5 of various sizes were polished. Excellent results were obtained. [Comparative Example] In the production of the comparative example, the average particle diameter was 10 μm.
Was used, and 45 parts by weight of a fine powder of α-type silicon carbide having an average particle diameter of 0.7 μm was blended with 100 parts by weight of the coarse powder and uniformly mixed. . Other conditions were basically the same as in Example 1.

5 parts by weight of polyvinyl alcohol and 50 parts by weight of water were blended with 100 parts by weight of this mixture, followed by mixing in a ball mill for 5 hours to obtain a uniform mixture. After drying the mixture for a predetermined time to remove a certain amount of water, an appropriate amount of the dried mixture was collected and granulated. Next, the granules of the mixture were molded at a pressing pressure of 0.6 t / cm ² using a metal stamping die. The density of the obtained disc-shaped green compact was 2.0 g / cm ³ .

Subsequently, by grinding the bottom surface of the molded body to become the upper base material 11A later, a groove 13 having a depth of 5 mm and a width of 10 mm was formed in almost the entire bottom surface. Next, the green compact was charged into a graphite crucible capable of shutting off outside air, and was fired using a Tamman-type firing furnace. The firing was performed in an argon gas atmosphere at 1 atm. Further, at the time of firing, heating was performed at a heating rate of 10 ° C./min to the maximum temperature of 1700 ° C., and thereafter, the temperature was maintained for 4 hours.

As a result, the porosity of the open pores of the obtained porous silicon carbide sintered bodies 11A and 11B was 38%,
Thermal conductivity was 50 W / m · K and density was 2.0 g / cm ³ . The average particle size of the silicon carbide crystals was 10 μm.

Therefore, according to the above-described embodiments of the present embodiment, the following effects can be obtained. (1) In each of the sintered porous silicon carbide bodies constituting the table 2 of each embodiment, the average particle diameter of the silicon carbide crystals is 20 μm.
m-100 μm, porosity 5% -30%, thermal conductivity 8
0 W / m · K or more.

In each of these sintered bodies, a fine crystal having an average particle size of 0.1 μm to 1.0 μm is formed in an amount of 10% by volume to 5% by volume.
It contains 0% by volume and 50% to 90% by volume of coarse crystals having an average particle size of 25 μm to 65 μm.

Therefore, the value of the thermal conductivity is 100 W / m · K
, And the table 2 is provided with extremely high thermal conductivity. For this reason, temperature variation is less likely to occur inside the sintered body than in the conventional product. As a result, extremely high heat uniformity and thermal responsiveness are imparted to the sintered body. In addition, the occurrence of thermal stress is reliably avoided, and the substrates 11A and 11B are less likely to warp, so that extremely high shape stability is imparted to the sintered body. As a result, the diameter and quality of the wafer 5 can be reliably increased.

(2) In the case of this table 2, the base material 11
The cooling water W can flow through the water channel 12 existing at the joint interface between the A and the 11B. Therefore, the heat generated during polishing of the semiconductor wafer 5 can be directly and efficiently released from the table 2 and the temperature can be finely controlled. Therefore, as compared with the conventional apparatus in which the table 2 is placed on the cooling jacket to perform indirect cooling, the temperature variation in the table 2 is extremely small, and the heat uniformity and the thermal response are remarkably improved. Therefore, according to this apparatus 1, the wafer 5 is less likely to be adversely affected by heat, and it is possible to cope with an increase in the diameter of the wafer 5. Moreover, the wafer 5
Can be polished with high accuracy, so that it is possible to cope with high quality.

The embodiment of the present invention may be modified as follows. The base materials 11A and 11B may be joined using a metal-based joining material represented by a brazing material, or may be joined using an adhesive made of a resin (for example, an epoxy resin).

The base materials 11A and 11B do not necessarily have to be joined via the brazing material layer 14. For example, instead of omitting the brazing material layer 14, the base materials 11A and 11B
B may be integrated by fastening a bolt and a nut.

Table 2 of the embodiment having a two-layer structure
Alternatively, the present invention may be embodied in a table having a three-layer structure. Of course, a stacked structure of four or more layers may be used. The groove 13 may be formed only on the upper substrate 11A, or may be formed only on the lower substrate 11B,
Alternatively, it may be formed on both base materials 11A and 11B.

In using the table 2 of the present embodiment, a liquid other than water may be circulated in the water channel 12.
Further, a gas may be circulated. The porous silicon carbide sintered body of the present invention may be used for the table 2 in a wafer polishing apparatus, or may be used for a member other than the table (such as a wafer top plate). Of course, the present invention is not limited to being used as a constituent material of a semiconductor manufacturing apparatus typified by the wafer polishing apparatus table 2 and the like. For example, the sintered body may be used as a radiator of an electronic component mounting substrate. In addition, the sintered body is used for wear-resistant materials such as mechanical seals and bearings, refractory materials for high-temperature furnaces, heat-resistant structural materials such as heat exchangers and combustion tubes, and corrosion-resistant materials such as pump parts. Of course, it is also possible.

Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiments are listed below together with their effects. (1) according to claim 4, when performing the step of obtaining a molded body by molding the mixture into a predetermined shape, setting the molding pressure to ^{1.0t / cm 2 ~1.5t / cm 2} . Therefore, according to the invention described in the technical idea 1, it is possible to sufficiently improve the thermal conductivity while avoiding an increase in equipment cost and difficulty in manufacturing.

(2) The method according to the fourth aspect, wherein the granules are produced from the mixture, and when the granules are formed into a predetermined shape to obtain the compact, the moisture content of the granules is reduced to 0.1% by weight. Set to ~ 2.0% by weight. Therefore,
According to the invention described in the technical idea 2, it is possible to sufficiently improve the thermal conductivity while avoiding a decrease in the yield.

[0071]

As described in detail above, according to the first to third aspects of the present invention, it is possible to provide a porous silicon carbide sintered body having extremely excellent heat uniformity, thermal responsiveness and shape stability. Can be.

According to the fourth aspect of the present invention, it is possible to provide a method for reliably producing such a suitable sintered body. According to the fifth aspect of the present invention, it is possible to provide a member for a wafer polishing apparatus suitable for manufacturing a large-diameter and high-quality wafer.

According to the sixth aspect of the present invention, a large-diameter
A table for a wafer polishing apparatus suitable for manufacturing a high quality wafer can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a wafer polishing apparatus according to an embodiment of the invention.

FIG. 2 is an enlarged sectional view of a main part of a table used in the wafer polishing apparatus.

FIG. 3 is a sectional view conceptually showing the table in an enlarged scale.

FIGS. 4 (a), (b), and (c) are graphs showing a particle size distribution in a porous silicon carbide sintered body constituting the table.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer grinding | polishing apparatus, 2 ... Table for wafer polishing apparatuses which are a kind of ceramic structures, 2a ... Polishing surface, 5 ... Semiconductor wafer, 6 ... Wafer holding plate, 6a ... Holding surface,
11A, 11B: base material, 12: cooling water channel as a fluid flow path, 21: fine silicon carbide crystals, 22: coarse silicon carbide crystals, 23: open pores.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/304 622 C04B 35/56 101P F-term (Reference) 3C058 AA09 CB01 CB10 4G001 BA22 BB22 BC13 BC52 BD03 BD12 BE02 BE22 BE33 4G019 FA13

Claims (6)

[Claims] 1. A porous sintered body in which open pores are present in a structure constituted by silicon carbide crystals, wherein said silicon carbide crystals have an average particle size of at least 20 μm and a porosity of 40%.
Hereinafter, a porous silicon carbide sintered body having a thermal conductivity of 80 W / m · K or more. 2. A porous sintered body in which open pores are present in a structure composed of silicon carbide crystals, wherein said silicon carbide crystals have an average particle size of 20 μm to 100 μm and a porosity of 5% to 30%. And a porous silicon carbide sintered body having a thermal conductivity of 80 W / m · K or more. 3. The composition according to claim 1, wherein the fine silicon carbide crystal has an average particle size of 0.1 μm to 1.0 μm in an amount of 10% by volume to 50% by volume, and
2. The composition according to claim 1, wherein said silicon carbide crystal has an average particle size of 25 to 150 [mu] m in an amount of 50 to 90% by volume.
Or the porous silicon carbide sintered body according to 2. 4. An open pore is present in a structure composed of silicon carbide crystals, the silicon carbide crystals have an average particle size of 20 μm or more, a porosity of 30% or less, and a thermal conductivity of 80% or less.
A method for producing a porous silicon carbide sintered body having a particle size of not less than W / m · K, comprising a coarse powder of α-type silicon carbide having an average particle size of 5 μm to 100 μm.
The average particle size is 0.1 μm to 1.0 μm with respect to 00 parts by weight.
A step of mixing 10 parts by weight to 100 parts by weight of the fine powder of α-type silicon carbide and uniformly mixing the mixture, a step of forming the mixture obtained in the step into a predetermined shape to obtain a molded body,
And a step of firing the molded body at a temperature in the range of 1700 ° C. to 2400 ° C. to obtain a sintered body. 5. A member for use in a wafer polishing apparatus, comprising the porous silicon carbide sintered body according to any one of claims 1 to 3. 6. A table having a polishing surface on which a semiconductor wafer held on a holding surface of a wafer holding plate constituting a wafer polishing apparatus is slidably contacted. Each of the substrates is joined in a state where a plurality of substrates made of the porous silicon carbide sintered body are laminated, and a table for a wafer polishing apparatus in which a fluid flow path is provided at a joint interface between the substrates. .