JP2004306254A - Vacuum chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum chuck, having a high sucking force, able to prevent the dislocation and separation of a sucked body, having uniform sucking force as a whole, generating no distribution of sucking force, thereby, when the vacuum chuck is used as a polishing device, uniform polishing for the sucked body can be realized. <P>SOLUTION: This vacuum chuck is formed of porous ceramics, and the vacuum chuck includes: a sucker having a holding surface for sucking and holding a sucked body; and a sealant for sealing a region excluding the holding surface of the sucker and the sucking hole corresponding part. When the pore distribution of the sucker is measured by method of mercury penetration, the mean pore diameter is 10-40 μm, the percentage of pores having pore diameter 0.7 to 1.2 times as large as the mean pore diameter to the whole pore volume is 75% or more, the percentage of pores having pore diameter under 0.7 times as large as the mean pore diameter to the whole pore volume is 15% or less, and the percentage of pores having pore diameter 1.2 times or more as large as the mean pore diameter to the whole pore volume is 10% or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a vacuum chuck used to adsorb an object to be adsorbed such as a semiconductor wafer and perform, for example, a heating process, a grinding process, a polishing process, a CVD process, a PVD process such as a sputtering process, or the like. More specifically, the present invention particularly relates to a vacuum chuck suitably used for polishing a surface of a semiconductor wafer or the like.

Generally, when manufacturing a semiconductor product, a single-crystal silicon ingot is sliced thinly, and then its surface is ground, wrapped, and polished to obtain a mirror-polished silicon wafer.
The silicon wafer polishing step is an important step indispensable for manufacturing a precise semiconductor product (semiconductor chip). In such a silicon wafer polishing step, a wafer for fixing and polishing a silicon wafer is used. A polishing device is required. Therefore, various types of wafer polishing apparatuses have been conventionally proposed.

2. Description of the Related Art As a conventional wafer polishing apparatus, there has been used an apparatus which performs polishing by bonding a semiconductor wafer to a holding surface of a wafer holding jig using an adhesive (for example, see Patent Document 1).

FIG. 4 is a partially enlarged cross-sectional view schematically showing an example of the wafer polishing apparatus.
As shown in FIG. 4, in the wafer polishing apparatus 200, the semiconductor wafer 15 is held downward, the semiconductor wafer 15 is brought into contact with the polishing surface 225 a of the table 225, and the semiconductor wafer 15 is rotated. And a disc-shaped wafer holding jig 201 configured to polish the wafer, and a rotatable table 225 having a polishing surface 225a.

A pusher bar 224 is fixed to the center of the side opposite to the holding surface 221 of the wafer holding jig 201. The pusher bar 224 is connected to a driving unit (not shown). 224 and the wafer holding jig 201 rotate. The semiconductor wafer 15 is adhered and held via an adhesive layer made of thermoplastic wax or the like formed on the holding surface 221 of the wafer holding jig 201.

When polishing the semiconductor wafer 15, the wafer holding jig 201 and the table 225 are rotated, and then the wafer holding jig 201 or the table 225 is moved up and down to polish the semiconductor wafer 15 and the polishing surface 225 a of the table 225. The semiconductor wafer 15 is polished by bringing the semiconductor wafer 15 into sliding contact.

However, in such a wafer polishing apparatus 200, it is necessary to perform a step of attaching and detaching the semiconductor wafer 15, so that the number of steps is increased and the semiconductor wafer 15 may be damaged in these steps. There was a problem that there is. In addition, it is difficult to make the thickness of the adhesive layer interposed between the semiconductor wafer 15 and the holding surface 21 uniform, and there is a problem that the semiconductor wafer 15 is easily inclined.

Therefore, a polishing apparatus using a vacuum chuck that can easily attach and detach a semiconductor wafer has been proposed (for example, see Patent Document 2).
In the polishing apparatus using this vacuum chuck, since a porous body is used as an adsorbent for holding a semiconductor wafer, not only can the semiconductor wafer be easily detached, but also the semiconductor wafer and the holding surface of the adsorbent can be removed. Since there is no inclusion between them, there is an advantage that uniform polishing can be easily performed without tilting the semiconductor wafer.

However, in a conventional vacuum chuck using a porous body as an adsorbent, since the average pore diameter of the adsorbent is too small, it is difficult to evacuate and the adsorption power per unit area on the adsorption surface is weak. Therefore, in order to obtain a certain level of adsorption force, the thickness is reduced, or a bottomed hole or the like is formed inside the adsorbent, and the adsorbed body is sucked through the bottomed hole. Although it is inevitable, such an adsorbent has a problem in that the mechanical strength is low and cracks and warpage are easily generated.

In addition, the pore distribution is wide, and the ratio of pores having a small diameter is high, so that the adsorption force does not easily increase, and furthermore, the adsorption force varies depending on the location of the adsorption surface of the adsorbent, so that the adsorption force becomes non-uniform. When the object to be adsorbed is polished, various inconveniences such as an uneven polishing state occur.
On the other hand, if the average pore diameter of the adsorbent is increased, the evacuation becomes easier, so that the thickness can be increased. As a result, there is a problem that a polished surface in which pores are transferred to the object to be adsorbed is formed, a uniform polished surface is not formed, and the flatness of the polished surface of the object to be adsorbed is reduced.

JP-A-11-320394 JP-A-2000-15573

The present invention has been made in view of the above problems, and has a high attraction force, a uniform attraction force as a whole, an improved attraction force distribution, and a use as a polishing apparatus. An object of the present invention is to provide a vacuum chuck that can realize uniform polishing of an adsorbent.

A vacuum chuck according to a first aspect of the present invention is made of a porous ceramic, and has an adsorbent body having a holding surface for adsorbing and holding an object to be adsorbed, and a surface excluding a holding surface of the adsorbent and a suction hole corresponding portion. And a sealing body for sealing substantially the entirety of the vacuum chuck,
When the pore distribution of the adsorbent was measured by a mercury intrusion method, the total pore volume of pores having an average pore diameter of 10 to 40 μm and having a pore diameter of 0.7 to 1.2 times the average pore diameter was measured. Is 75% or more, and the ratio of the pores having pore diameters smaller than 0.7 times the average pore diameter to the total pore volume is 15% or less, and 1.2 times the average pore diameter is 1.2% or less. The ratio of pores having a pore size exceeding the total pore volume to the total pore volume is 10% or less.

The vacuum chuck according to the second aspect of the present invention is made of porous ceramic, has a holding surface for adsorbing and holding the object to be sucked, and seals substantially the entire surface excluding the holding surface and the suction hole corresponding portion. A vacuum chuck comprising an adsorbent on which a sealing layer for stopping is formed,
When the pore distribution of the adsorbent was measured by a mercury intrusion method, the total pore volume of pores having an average pore diameter of 10 to 40 μm and having a pore diameter of 0.7 to 1.2 times the average pore diameter was measured. Is 75% or more, and the ratio of the pores having pore diameters smaller than 0.7 times the average pore diameter to the total pore volume is 15% or less, and 1.2 times the average pore diameter is 1.2% or less. The ratio of pores having a pore size exceeding the total pore volume to the total pore volume is 10% or less.

The vacuum chuck of the present invention has the above-described configuration, and the pore diameter of the adsorbent is set to an appropriate size, and there is almost no variation in the pore diameter. Is uniform throughout, and there is almost no distribution of adsorption force. When used as a polishing apparatus, phenomena such as transfer of pore distribution do not occur, and uniform polishing of the object to be adsorbed can be realized. it can.

First, the vacuum chuck of the first invention will be described.
A vacuum chuck according to a first aspect of the present invention is made of a porous ceramic, and has an adsorbent body having a holding surface for adsorbing and holding an object to be adsorbed, and a surface excluding a holding surface of the adsorbent and a suction hole corresponding portion. And a sealing body for sealing substantially the entirety of the vacuum chuck,
When the pore distribution of the adsorbent was measured by a mercury intrusion method, the total pore volume of pores having an average pore diameter of 10 to 40 μm and having a pore diameter of 0.7 to 1.2 times the average pore diameter was measured. Is 75% or more, and the ratio of the pores having pore diameters smaller than 0.7 times the average pore diameter to the total pore volume is 15% or less, and 1.2 times the average pore diameter is 1.2% or less. A vacuum chuck wherein a ratio of pores having a pore diameter exceeding the total pore volume is 10% or less.

A vacuum chuck according to a first aspect of the present invention includes an adsorbent made of porous ceramic and a sealing body.
The material of the adsorbent is not particularly limited, for example, nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, titanium nitride, silicon carbide, zirconium carbide, titanium carbide, tantalum carbide, carbide ceramics such as tungsten carbide, Oxide ceramics such as alumina, zirconia, cordierite, and mullite can be cited. Among these, they have high thermal conductivity, and include hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, hydrofluoric nitric acid, and sodium hydroxide. It is desirable to use silicon carbide which is excellent in chemical resistance to the silicon carbide. Note that a silicon-containing ceramic in which metal silicon is blended with the above ceramic, or a ceramic combined with silicon or a silicate compound can also be used.

In the vacuum chuck according to the first aspect of the present invention, when the pore distribution of the adsorbent is measured by a mercury intrusion method, the lower limit of the average pore diameter is 10 μm, and the upper limit is 40 μm. The lower limit of the average pore diameter is preferably 20 μm and the upper limit is 35 μm, more preferably the lower limit is 25 μm and the upper limit is 30 μm.
If the average pore diameter of the adsorbent is less than 10 μm, it becomes difficult to evacuate using the vacuum chuck of the present invention, and it is necessary to reduce the thickness of the adsorbent and sufficiently secure mechanical strength. You can't do that. On the other hand, if the average pore diameter exceeds 40 μm, the difference in adsorption power between the portion where the pores exist on the surface and the portion where the pores do not exist becomes large, and as a result, the polished surface in which the pores are transferred to the object to be adsorbed Are formed, a uniform polished surface is not formed, and the flatness of the polished surface of the object to be adsorbed is reduced.
The average pore diameter of the adsorbent may be measured by a conventionally known method such as a scanning electron microscope (SEM) in addition to the mercury intrusion method.

Further, in the vacuum chuck according to the first aspect of the present invention, the adsorbent has all pores (hereinafter, also referred to as main pores) having pore diameters of 0.7 to 1.2 times the average pore diameter. The ratio to the volume is 75% or more. That is, most of the adsorbent has pores having an average pore diameter of 10 to 40 μm, the peak of the pore diameter distribution is very sharp, and the variation in the pore diameter is small.
If the ratio of the main pores to the total pore volume is less than 75%, the pore diameter of the adsorbent greatly varies, and the adsorptive power of the adsorbent varies, for example, the vacuum of the present invention. If the chuck is used to grind the object to be polished or the like, a difference occurs in the attraction force, and the polished state of the object to be sucked is not uniform.
The ratio of the main pores to the total pore volume is preferably 80% or more, and more preferably 85% or more.

Further, in the adsorbent, the ratio of pores having a pore diameter of less than 0.7 times the average pore diameter (hereinafter, also referred to as micropores) to the total pore volume is 15% or less, and the average pore diameter is not more than 15%. The ratio of the pores having pore diameters exceeding 1.2 times the pore diameter (hereinafter also referred to as macropores) to the total pore volume is 10% or less. That is, in the adsorbent, pores smaller than the main pores (fine pores) and pores larger than the main pores (macropores) are substantially uniformly present.

When the ratio of the fine pores to the total pore volume exceeds 15%, for example, when the ratio of the main pores to the total pore volume is 75% or more but the average pore diameter is as small as about 10 μm, Since the ratio of the fine pores present in the substrate becomes high, and it becomes difficult to evacuate using the vacuum chuck of the present invention, it is necessary to reduce the thickness of the adsorbent and sufficiently secure mechanical strength. Can not be done. On the other hand, if the ratio of the macropores to the total pore volume exceeds 10%, for example, the ratio of the main pores to the total pore volume is 75% or more, but the average pore diameter is as large as about 40 μm. In addition, the ratio of the huge pores present in the adsorbent increases, and when the object to be adsorbed is polished using the vacuum chuck of the present invention, there is a partial difference in adsorption force. The condition is not uniform.
The ratio of the fine pores and the macropores to the total pore volume is preferably 10% or less and 5% or less, respectively.

In the vacuum chuck according to the first aspect of the present invention, the lower limit of the porosity of the adsorbent is preferably 20%, and the upper limit is preferably 50%. When the porosity is less than 20%, the suction force of the object to be sucked is weakened, and the object to be sucked moves or peels off when the object to be sucked is polished using the vacuum chuck of the present invention. There is. On the other hand, if the porosity exceeds 50%, the strength of the adsorbent decreases, and it is liable to be broken. To prevent this, it is necessary to increase the thickness of the adsorbent. And it becomes expensive.
The lower limit of the porosity is 25%, the upper limit is more preferably 45%, the lower limit is 30%, and the upper limit is even more preferably 40%.
The porosity can be measured by a conventionally known method such as a mercury intrusion method, an Archimedes method, and a measurement by a scanning electron microscope (SEM).

The lower limit of the average particle diameter of the adsorbent is preferably 30 μm, and the upper limit is preferably 70 μm. As described above, relatively large particles having an average particle size are desirable because, in general, the efficiency of heat conduction inside the particles is higher than the efficiency of heat conduction between particles. This is because the thermal conductivity is high and the pore diameter is easy to be uniform.

The shape of the adsorbent is not particularly limited, and may be a disk shape, or a shape in which a large-diameter disk and a small-diameter disk are integrally laminated. Further, the shape may be an elliptical plate shape in plan view, a rectangular parallelepiped shape or a cubic shape.

Although the mechanical strength of the adsorbent is not particularly limited, for example, in a three-point bending test based on JIS R 1601, it is desirably 20 MPa or more. If the pressure is less than 20 MPa, the adsorbent is likely to be warped or cracked.

The adsorbent preferably has a thermal conductivity of 50 W / m · K or more. For example, when a semiconductor wafer is polished by using the vacuum chuck of the present invention, the adsorbent is likely to be heated to a high temperature by frictional heat. For this reason, a material having a high thermal conductivity is preferable.

The thickness of the adsorbent is appropriately determined in consideration of the average pore diameter and the average porosity of the adsorbent, the thermal conductivity of constituent materials, and the like. For example, the adsorbent is made of silicon carbide. If it is, it is desirable that it is 5 to 60 mm. When the thickness of the adsorbent is less than 5 mm, the adsorbent becomes too thin with respect to its diameter, so that the adsorbent is likely to be warped, and the strength is reduced to be easily broken. On the other hand, if the thickness of the adsorbent exceeds 60 mm, the weight increases and the size of the vacuum chuck increases.

In the vacuum chuck according to the first aspect of the present invention, the adsorbent has a holding surface for adsorbing and holding the object to be adsorbed, and the shape of the holding surface usually depends on the shape of the adsorbent. However, only the holding surface may be formed in a specific shape. Further, the holding surface is desirably finished in a planar shape with high accuracy. A desirable upper limit of the flatness of the holding surface is 10 μm, and a more desirable upper limit is 5 μm.
When the flatness of the holding surface exceeds 10 μm, the flatness of the polished surface is reduced when the object to be sucked is polished.

In this specification, the flatness of the holding surface of the adsorbent refers to the height of the portion of the holding surface where pores are not formed and particles are present, and the highest point is plotted. (Distance) between the lower point and the lower point. Thereby, it is possible to evaluate the magnitude of the undulation of the holding surface. The reason for this definition is that the object to be adsorbed is supported by the portion of the holding surface where the particles are present. Because it is affected. Since the adsorbent is made of porous ceramic, the surface of the holding surface has a portion where particles exist and a portion where pores exist, as described above, and fine irregularities are formed due to this. However, the size of the unevenness can be evaluated by pore distribution and the like.
When the vacuum chuck of the first aspect of the present invention is used as a polishing apparatus, particularly a polishing apparatus for polishing the surface of a semiconductor wafer, the shape of the holding surface is desirably circular.

The size of the holding surface is not particularly limited, and the size is determined according to the size of the object to be sucked. For example, when the object to be sucked such as a semiconductor wafer is held, the holding of the object to be sucked is performed. It is desirable that the shape and dimensions are such that the outer edge of the object to be adsorbed is located 0.1 to 15 mm inside the outer edge of the surface. This is because the adsorption force is high and the adsorption force of the adsorbent is uniform overall, so that when used as a polishing apparatus, uniform polishing of the adsorbed object can be realized.

When the object to be adsorbed is adsorbed and held, when the object to be adsorbed is located outside the position 0.1 mm inside from the outer edge of the holding surface of the object to be adsorbed, If the distance between the outer edge of the body and the outer edge of the adsorbent is set to be smaller than 0.1 mm, the object to be adsorbed and the sealing body may be displaced in relation to the accuracy in mounting the semiconductor wafer. Easy to contact. For this reason, the semiconductor wafer may come into contact with the sealing body and rise during polishing.
In such a case, for example, when the vacuum chuck of the present invention is used as a semiconductor wafer polishing apparatus, the vicinity of the edge of the semiconductor wafer is excessively polished, and the polishing state becomes uneven.

On the other hand, when the object to be adsorbed is held such that the outer edge of the object to be adsorbed is positioned further inside than 15 mm from the outer edge of the holding surface of the object to be adsorbed, A large gap is left between them, so that a large amount of air is sucked in from the gap, and the suction force on the outer periphery of the object to be sucked is reduced and floated, so that the vicinity of the edge of the semiconductor wafer is also polished excessively. .

When the holding surface of the adsorbent is circular, the diameter is appropriately determined in consideration of the diameter of the semiconductor wafer or the like to be polished, and is preferably 100 to 330 mm.

The sealing body is provided to seal substantially the entire surface of the adsorbent body except for the holding surface, so that air does not leak from portions other than the holding surface of the adsorbent body. In addition, a suction part is provided in a part of the suction part. By suctioning the inside of the sealing body (the inside of the adsorbent) through the suction part, the inside of the adsorbent is depressurized and the object to be adsorbed can be adsorbed. It is supposed to be.

The material of the sealing body and the fixed base is not particularly limited, and may be a metal such as SUS, steel, or an aluminum alloy, or may be a ceramic such as silicon nitride, silicon carbide, or alumina. A dense body having the above mechanical strength is desirable. This is because it is necessary to have mechanical properties that can withstand reduced pressure (vacuum), and to eliminate air leakage from the sealing body.

FIG. 1A is a perspective view schematically showing an example of the vacuum chuck of the first invention, and FIG. 1B is a sectional view thereof.
As shown in FIG. 1, the vacuum chuck 10 includes an adsorbent 11 and a sealing body 12, and the above-described sealing body 12 in a form in which a cylindrical body is integrally formed on a disk. A disk-shaped adsorbent 11 is fixed inside the cylindrical body, and a fixed base 30 is provided below the vacuum chuck 10 having the above configuration.

Further, the sealing body 12 is fixed to the fixed base 30 using four bolts 31 arranged at equal intervals, and a suction hole 13 a communicating with the lower surface of the adsorbent 11 is formed in the center of the fixed base 30. The suction portion 13 is provided, and the air inside the adsorbent 11 can be sucked through the suction hole 13a. Note that the vacuum chuck 10 may include a rotation mechanism that enables rotation about the central axis of the suction unit 13.

After assembling the vacuum chuck 10, the suction unit 13 is connected to a vacuum pump or the like via an appropriate tubular member or the like, and air is sucked from the suction hole 13a to be placed on the holding surface 14 of the suction body 11. The placed semiconductor wafer 15 can be sucked and held.
Although no grooves or the like are formed in the adsorbent 11 shown in FIG. 1, grooves of various shapes are formed on the surface opposite to the holding surface 14 in order to increase the suction speed. Is also good.

Then, in a state where the polishing table having the polishing surface and the semiconductor wafer 15 adsorbed on the holding surface are parallel, the polishing table is rotated, the vacuum chuck 10 itself is rotated, or both are rotated, By bringing the both into contact, polishing of the surface of the semiconductor wafer 15 or the like can be performed. A roughened surface may be formed on the polishing table by attaching a polishing cloth, or a roughened surface may be formed using diamond abrasive grains or the like.

The shape of the sealing body 12 is not limited to the shape shown in FIG. 1. For example, a cavity may be formed on the entire surface of the adsorbent body 11 opposite to the holding surface 14. Further, a portion of the lower portion 12a of the sealing body which is in contact with the surface opposite to the holding surface 14 is formed thick, and a groove or a hole for guiding the air sucked into the suction hole to the suction hole is formed in that portion. You may.

The application of the vacuum chuck of the first present invention is not particularly limited, and as described above, the vacuum chuck may be used for performing a heating process, a grinding process, a polishing process, a CVD process, a PVD process such as a sputtering process, etc. Good.

As described above, when the pore distribution of the adsorbent is measured by the mercury intrusion method, the average diameter of the pores is 10 to 40 μm, and the average diameter of the pores is 0.7 to 1. The ratio of the pores having twice the pore diameter to the total pore volume is 75% or more, and the ratio of the pores having the pore diameters less than 0.7 times the average pore diameter to the total pore volume is 15%. The ratio of the pores having a pore diameter exceeding 1.2 times the average pore diameter to the total pore volume is 10% or less, and the pore diameter of the adsorbent is set to an appropriate size. Since there is almost no variation in the pore diameter, the suction power is high, the suction power is uniform as a whole, and the distribution of the suction power is almost non-existent. No phenomenon occurs, and uniform polishing of the adsorbed body can be realized. That.

Next, the method for manufacturing the vacuum chuck according to the first aspect of the present invention will be briefly described.
First, an adsorbent is manufactured.
To produce the adsorbent, a mixed composition containing at least a ceramic powder, a binder, and a dispersion medium is prepared.

It is desirable that the ceramic powder (coarse powder) has a certain degree of uniform particle size in advance so that the average particle size is small. If the average particle size of the ceramic powder has a large variation, the pore size of the adsorbent to be produced may vary. There is no particular limitation on the method of making the particle diameter of the ceramic powder uniform, and, for example, a known method such as a method of crushing, crushing, and sizing the ceramic powder after forming the ceramic powder into a compact having a high density or the like. Can be mentioned.
The ceramic powder is desirably adjusted so that the ratio of the ceramic powder having a particle diameter of 0.7 to 1.2 times the average particle diameter to all the ceramic powders is 75% or more.

The ceramic powder desirably uniformly mixes 10 to 100 parts by weight of a fine powder having an average particle diameter of 0.1 to 1.0 μm with 100 parts by weight of a coarse powder having an average particle diameter of 5 to 100 μm.
The binder is not particularly limited, and examples thereof include methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, polyethylene glycol, phenol resin, and epoxy resin.
Usually, the amount of the binder is preferably about 1 to 10 parts by weight based on 100 parts by weight of the ceramic powder.

The dispersion medium is not particularly limited, and examples thereof include an organic solvent such as benzene; an alcohol such as methanol; and water.
An appropriate amount of the dispersion medium is blended so that the viscosity of the mixed composition falls within a certain range.
These ceramic powder, binder and dispersion medium are mixed with an attritor or the like, then sufficiently kneaded with a kneader or the like, and then a granular powder is produced by a spray drying method or the like. Then, the granules are put into a mold and molded to produce a formed body.
The resulting form is degreased by heating to about 400 to 650 ° C. in an inert gas (argon) atmosphere to decompose and eliminate the binder and the like, leaving substantially ceramic powder alone.

Then, after the degreasing treatment is performed, the adsorbent is manufactured by sintering by heating to about 1400 to 2300 ° C. in an atmosphere of an inert gas such as nitrogen or argon, and sintering the ceramic powder.

The method for producing the adsorbent is not limited to the above-described method.For example, a ceramic powder whose particle diameter has been adjusted to some extent in advance, a metal silicon as a binder for binding the ceramic powder, a raw material including a binder, a dispersion medium solution, and the like may be used. By using the above-mentioned formed form using the above, the ceramic powder is combined with the metallic silicon by firing the formed form, and a method of manufacturing an adsorbent, and the binder of the mixed composition contains starch. And a method for producing an adsorbent using the starch-containing mixed composition.
Thereafter, the vacuum chuck is assembled by the method described with reference to FIG.

Next, the vacuum chuck according to the second aspect of the present invention will be described.
The vacuum chuck according to the second aspect of the present invention is made of porous ceramic, has a holding surface for sucking and holding the object to be sucked, and seals almost the entire surface except for the holding surface and the suction hole corresponding portion. A vacuum chuck configured to include an adsorbent on which a sealing layer for forming is formed,
When the pore distribution of the adsorbent was measured by a mercury intrusion method, the total pore volume of pores having an average pore diameter of 10 to 40 μm and having a pore diameter of 0.7 to 1.2 times the average pore diameter was measured. Is 75% or more, and the ratio of the pores having pore diameters smaller than 0.7 times the average pore diameter to the total pore volume is 15% or less, and 1.2 times the average pore diameter is 1.2% or less. The ratio of pores having a pore size exceeding the total pore volume to the total pore volume is 10% or less.

The adsorbent (porous ceramic) constituting the vacuum chuck of the second aspect of the present invention has a material, characteristics, etc., except that a sealing layer for sealing almost the entire surface excluding the holding surface is formed. Is similar to the adsorbent constituting the vacuum chuck according to the first aspect of the present invention, and therefore only the different points will be described.

FIG. 2A is a perspective view schematically showing one example of the vacuum chuck of the second invention, and FIG. 2B is a sectional view thereof. FIG. 3A is a perspective view schematically showing another example of the vacuum chuck according to the second invention, and FIG. 3B is a sectional view thereof.
As shown in FIGS. 2 and 3, the vacuum chuck 20 has a sealing layer 22 on the entire surface except for a portion corresponding to the holding surface 24 and the suction hole 23 (a suction hole corresponding portion) formed thereon. A fixing base 40 for supporting and fixing the adsorbent 22 formed of the formed adsorbent 21 and under which the sealing layer 22 is formed is provided. The adsorbent 21 has a shape in which an adsorbent upper portion 21b made of a disc having a smaller diameter is integrally formed on a lower adsorbent lower portion 21a made of a disc so as to share a central axis. In addition, through holes for fixing are formed at equal intervals in the lower part 21a of the adsorbent.

Then, the bolt 41 is inserted into the through hole of the lower part 21 a of the adsorbent and fixed to the fixed base 40, and the through hole of the adsorbent 22 is sealed by filling the inside of the through hole with the sealing agent 25. In the center of the fixed base 40, a suction part 23 having a suction hole 23a communicating with the lower surface of the adsorbent 21 is provided.
In the vacuum chuck 20, as in the case of the vacuum chuck 10, the semiconductor wafer 15 placed on the holding surface 24 of the suction body 21 is sucked and held by sucking air from the suction holes 23a. I can do it.

As shown in FIGS. 2 and 3, the sealing layer 22 is a liquid polymer, a raw material for forming a polymer, or a liquid polymer on the surface of the adsorbent body 21 other than the holding surface 24 and the suction hole corresponding portion 26. , By applying a glass composition or the like by coating or the like.
The sealing layer 22 may be an internal solidified layer 22 a formed by infiltrating and solidifying the raw material inside the adsorbent 21, and solidifying the raw material on the surface without penetrating the raw material into the adsorbent 21. The inner solidified layer 22a and the coating layer 22b formed by partially penetrating and solidifying the raw material inside the adsorbent 21 as shown in FIG. 2 may be used. Composite layer.
Further, as the sealing layer 22, two or more layers selected from the group consisting of the internal solidified layer 22a, the coating layer 22b, and the composite layer may be used in combination, for example, as shown in FIG. Alternatively, a coating layer 22b may be formed on the upper adsorbent 21b, and an internal solidified layer 22a may be formed on the lower adsorbent 21a.
By forming the sealing layer 22 in this manner, while preventing air from being sucked from a surface other than the holding surface 24, the air inside the adsorbent 21 through the suction hole 23a from the suction hole corresponding portion 26 is prevented. Can be sucked.

In addition, the sealing layer 22 may be omitted on the surface of the adsorbent 21 that is in contact with the fixed base 40 unless the side surface is a side surface. For example, a groove is formed on the surface of the adsorbent 21 opposite to the holding surface 24, It may be configured to be able to suck from that portion, and in addition to the suction hole corresponding portion, another opening is formed in the sealing layer 22 formed on the surface opposite to the holding surface 24, It may be configured to be able to suck from that part.

The shape of the adsorbent 21 is not limited to a shape in which disks having different diameters are integrally stacked as shown in FIGS. 2 and 3, and may be a disk as shown in FIG. Other shapes may be used.

The vacuum chuck 20 may include a rotation mechanism that enables rotation about the central axis of the suction unit.

The material of the fixed base 40 may be the same as that of the fixed base 30 described in the first invention. When a groove is formed on the surface opposite to the holding surface 24 of the adsorbent 21 or when an opening is formed in the sealing layer 22, naturally, the sucked air is A groove or a hole is formed to guide the fluid to the suction hole 23a.

The material forming the sealing layer 22 is not particularly limited, and includes, for example, resin, glass, metal, ceramic, and the like. However, resin is preferable because the sealing layer can be formed relatively easily. .

The resin may be a thermosetting resin or a thermoplastic resin. The thermosetting resin is not particularly limited, and examples thereof include an epoxy resin, a polyimide, a xylene resin, a polyurethane, a melamine resin, a phenol resin, an unsaturated polyester resin, and a urea resin. When these thermosetting resins are used, for example, a liquid resin before being polymerized may be applied and then cured by heating.

The thermoplastic resin is not particularly limited, and examples include ABS resin, AS resin, polyethylene, polypropylene, polyamide, polyamideimide, polyvinyl chloride, polystyrene, polymethyl methacrylate, and polyvinyl acetate. These thermoplastic resins are applied in a state of being dissolved in a solvent to form a material that becomes the sealing layer 22. Thereafter, the solvent may be scattered to be cured, and the viscosity may be reduced by heating to reduce the viscosity. The sealing layer 22 may be formed by press-fitting into a body.

Glass, metals, ceramics, and the like heat these materials to near their melting points to melt, lower their viscosity, and penetrate or press fit into the interior of the adsorbent.

In the sealing layer 22 near the holding surface of the adsorbent, it is preferable that the thickness of the internal solidified layer 22a be reduced and the thickness of the coating layer 22b be increased. The sealing layer 22 near the holding surface of the adsorbent is more preferably a coating layer 22b formed on the surface of the adsorbent. When the thickness of the internal solidified layer 22a is increased in the vicinity of the holding surface, it is estimated that the internal solidified layer in the vicinity of the holding surface expands due to polishing heat, swelling, and the like, and is likely to come into contact with the adherend. Because it is easy to become.
In the vicinity of the holding surface, the thickness of the internal solidified layer 22a is desirably 5 mm or less, and the thickness of the coating layer 22b is desirably 15 mm or less.

The vacuum chuck of the second present invention has a mean pore diameter of 10 to 40 μm when the pore distribution of the adsorbent is measured by a mercury intrusion method, similarly to the vacuum chuck of the first present invention. The ratio of the pores having a pore diameter of 0.7 to 1.2 times the total pore volume to the total pore volume is 75% or more, and the total fine pores having a pore diameter of less than 0.7 times the average pore diameter are smaller than 75%. The ratio with respect to the pore volume is 15% or less, the ratio of the pores having a pore size exceeding 1.2 times the average pore size with respect to the total pore volume is 10% or less, and the pore size of the adsorbent is: It is set to an appropriate size, has high adsorption power because there is almost no variation in pore diameter, and the adsorption power is uniform overall, and there is almost no distribution of adsorption power, and when used as a polishing device, In this method, there is no phenomenon such as transfer of pore distribution and uniform polishing of the adsorbed body. It can be realized.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
Α-type carbonization having an average particle diameter of 60 μm, in which the particle diameter is previously adjusted so that the ratio of silicon carbide powder having a particle diameter of 0.7 to 1.2 times the average particle diameter to all silicon carbide powders is 90% or more. 90% by weight of silicon powder and 10% by weight of α-type silicon carbide powder having an average particle diameter of 1 μm are wet-mixed, and 5 parts by weight of an organic binder (methyl cellulose) and 10 parts by weight of water are added to 100 parts by weight of the obtained mixture. After kneading by adding the parts by weight, spray drying was performed to obtain a granular powder.
The granular powder was placed in a mold and held at a pressure of 50 MPa for 5 minutes using a molding machine utilizing cold isostatic pressure (CIP) to produce a disk-shaped silicon carbide molded body.

Next, the silicon carbide compact was carried into a degreasing furnace and heated at 600 ° C. for 2 hours in an argon gas atmosphere to degrease the silicon carbide compact.

Next, the degreased silicon carbide molded body was fired at a temperature of 2200 ° C. to produce an adsorbent 11 made of a porous silicon carbide sintered body and having a diameter of 210 mm and a thickness of 10 mm.
Table 1 shows the porosity, pore distribution and average pore diameter measured by the mercury intrusion method as characteristics of the adsorbent.

Next, as shown in FIG. 1B, the obtained adsorbent body 11 was fixed to a sealing body, and the production of the vacuum chuck 10 was completed.

(Examples 2 to 4)
An adsorbent was manufactured in the same manner as in Example 1 except that silicon carbide powders having different average particle diameters were used and the characteristics of the adsorbent were as shown in Table 1. In addition, each silicon carbide powder is previously adjusted in particle diameter such that the ratio of silicon carbide powder having a particle diameter of 0.7 to 1.2 times the average particle diameter to the total silicon carbide powder is 75% or more. did.
Thereafter, a vacuum chuck was manufactured in the same manner as in Example 1 using each adsorbent.

(Example 5)
An adsorbent was manufactured in the same manner as in Example 1 except that silicon carbide powders having different average particle diameters were used and the shape and characteristics of the adsorbent were as shown in Table 1. The adsorbent 21 has a shape in which a lower adsorber lower portion 21a having a diameter of 240 mm and a thickness of 10 mm and an upper adsorbent portion 21b having a smaller diameter of 210 mm and a thickness of 10 mm are integrally formed as shown in FIG. And In addition, each silicon carbide powder is previously adjusted in particle diameter such that the ratio of silicon carbide powder having a particle diameter of 0.7 to 1.2 times the average particle diameter to the total silicon carbide powder is 75% or more. did.
Thereafter, a vacuum chuck 20 having a configuration as shown in FIG. 2 was manufactured using the adsorbent 21. In addition, the sealing layer 22 was formed by applying and drying the outer periphery and the bottom surface (excluding the portion corresponding to the suction hole) using an epoxy resin as a resin constituting the sealing layer 22. The thickness of the inner solidified layer 22a was 2 mm, and the thickness of the coating layer 22b was 2 mm.

(Example 6)
A vacuum chuck 20 having a configuration as shown in FIG. 3 was manufactured using the adsorbent 21 manufactured in the same manner as in Example 5.
When forming the sealing layer 22, an epoxy resin is applied to the outer periphery of the upper adsorbent 21b and dried to form a coating layer 22b having a thickness of 2 mm, and the outer periphery and the bottom surface (suction hole) of the lower adsorbent 21a are formed. An epoxy resin was applied, suctioned, and dried to form an internal solidified layer 22a having a thickness of 2 mm.

(Examples 7 to 16)
An adsorbent was manufactured in the same manner as in Example 1 except that silicon carbide powders having different average particle diameters and particle diameter variations were used, and the characteristics of the adsorbent were as shown in Table 1. . In addition, each silicon carbide powder is previously adjusted in particle diameter such that the ratio of silicon carbide powder having a particle diameter of 0.7 to 1.2 times the average particle diameter to the total silicon carbide powder is 75% or more. did.
Thereafter, a vacuum chuck was manufactured in the same manner as in Example 1 using each adsorbent.

(Comparative Examples 1 to 51)
An adsorbent was manufactured in the same manner as in Example 1 except that silicon carbide powders having different average particle diameters and different particle diameters were used and the characteristics of the adsorbent were as shown in Table 2. .
Thereafter, a vacuum chuck was manufactured in the same manner as in Example 1 using each adsorbent.

A semiconductor wafer having a diameter of 200 mm was placed on the vacuum chucks according to the examples and comparative examples, the semiconductor wafer was suctioned at a pressure of 10 KPa, and the semiconductor wafer was polished 10 times. Was evaluated for flatness. The polishing treatment was performed by bringing a vacuum chuck holding and holding a semiconductor wafer into contact with a table on which a rotating felt-shaped polishing cloth was attached. The number of rotations of the table was 1.2 s ^-1 .
The flatness of the polished surface was evaluated with a flatness measuring device (Nano Metro manufactured by Kuroda Seiko Co., Ltd.). The flatness of the polished surface is the difference (distance) between the highest point and the lowest point on the polished surface. Further, the pore distribution was measured by a mercury intrusion method using a pore distribution measuring apparatus (Autopore III 9420, manufactured by Shimadzu Corporation) in a range of pore diameters of 0.2 to 600 μm, and the average at that time was measured. The pore diameter was calculated as (4 V / A).
The evaluation results are shown in Tables 1 and 2 below.

As is clear from the results shown in Table 1, the adsorbent according to the example has an average pore diameter in the range of 10 to 40%, and has a pore diameter 0.7 to 1.2 times the average pore diameter. The ratio of the pores having to the total pore volume is 75% or more, and the ratio of the pores having a pore diameter less than 0.7 times the average pore diameter to the total pore volume is 15% or less. The ratio of the pores having a pore diameter exceeding 1.2 times the pore diameter to the total pore volume was 10% or less. Therefore, the flatness of the surface of the polished semiconductor wafer is extremely small at 0.3 μm or less, and the semiconductor wafer is polished with high accuracy and uniformity.

On the other hand, as is clear from the results shown in Table 2, the adsorbent according to the comparative example shows a particle size distribution outside the above range, and the flatness of the polished semiconductor wafer surface is 1.0 μm As described above, the flatness was greatly reduced, and uniform polishing could not be performed.

(A) is a perspective view schematically showing the vacuum chuck of the first invention, and (b) is a longitudinal sectional view thereof. (A) is a perspective view schematically showing an example of the vacuum chuck of the second invention, and (b) is a longitudinal sectional view thereof. (A) is a perspective view schematically showing another example of the vacuum chuck of the second invention, and (b) is a longitudinal sectional view thereof. It is the elements on larger scale which showed an example of the conventional wafer polishing apparatus typically.

Explanation of reference numerals

10, 20 Vacuum chuck 11, 21 Suction body 21a Suction body lower part 21b Suction body upper part 12 Sealing body 13, 23 Suction part 13a, 23a Suction hole 14, 24 Holding surface 15 Semiconductor wafer 22 Sealing layer 22a Internal solidified layer 22b Coating Layer 30, 40 Fixed base

Claims (4)

An adsorbent made of porous ceramic and having a holding surface for adsorbing and holding the to-be-adsorbed body, and a seal for sealing substantially the entire surface excluding the holding surface of the adsorbent and a suction hole corresponding portion. A vacuum chuck comprising a stationary body,
When the pore distribution of the adsorbent was measured by a mercury intrusion method, the average pore diameter was 10 to 40 μm, and the total pore volume of the pores having a pore diameter of 0.7 to 1.2 times the average pore diameter was measured. Is 75% or more,
A ratio of pores having a pore diameter of less than 0.7 times the average pore diameter to the total pore volume is 15% or less;
A vacuum chuck, wherein a ratio of pores having a pore diameter exceeding 1.2 times the average pore diameter to a total pore volume is 10% or less. A sealing layer made of porous ceramic, having a holding surface for sucking and holding the object to be sucked, and sealing almost the entire surface excluding the holding surface and the suction hole corresponding portion is formed. Vacuum chuck comprising an adsorbent,
When the pore distribution of the adsorbent was measured by a mercury intrusion method, the average pore diameter was 10 to 40 μm, and the total pore volume of the pores having a pore diameter of 0.7 to 1.2 times the average pore diameter was measured. Is 75% or more,
A ratio of pores having a pore diameter of less than 0.7 times the average pore diameter to the total pore volume is 15% or less;
A vacuum chuck, wherein a ratio of pores having a pore diameter exceeding 1.2 times the average pore diameter to a total pore volume is 10% or less. The vacuum chuck according to claim 1, wherein the sealing layer near the holding surface of the adsorbent is a coating layer formed on a surface of the adsorbent. The vacuum chuck according to any one of claims 1 to 3, wherein the porosity of the adsorbent is 20 to 50%.

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