JP7156935B2 - Silica porous material for vacuum chuck - Google Patents

Description

TECHNICAL FIELD The present invention relates to a porous silica material used for a vacuum attachment chuck that adsorbs and supports an object by suction.

Conventionally, an object is attracted to the absorption surface by air suction, and a shadow of the object is created by illuminating the object from the back side. Vacuum chucks for machining, machining, etc. are known. In such a vacuum chuck, a member having optical transparency and fluid permeability is used for the adsorption surface. For example, the applicant of the present application has proposed a silica porous body for a vacuum chuck made of a sintered body of silica particles in Patent Document 1 as a member having such light and fluid permeability.

This porous silica material for a vacuum chuck utilizes the fact that the porous silica material does not easily transmit light, and has an average particle diameter of 5 μm to 300 μm and a particle distribution width within ±50% of the average particle diameter. It is formed from a sintered body of silica particles in. Further, this silica porous material has a pore diameter of 1 μm to 100 μm, a porosity of 5% to 45%, and an apparent density of 2.1 g/cm ³ or more, and the average diameter of the pores in the cross section is equal to that of the silica particles in the cross section. 1/12 or more and 3/4 or less of the average particle diameter of .

JP 2013-121888 A

In porous silica, it is generally necessary to increase the particle size in order to increase the light transmittance. However, there is a problem that the flatness is deteriorated. Conversely, if the particle size is made small in order to obtain the necessary strength, there is a problem that the light transmittance is lowered and sufficient properties cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made on the basis of such problems, and aims to provide a silica porous body for a vacuum chuck that can obtain high light transmittance and increase the flatness of the adsorption surface. aim.

The porous silica material for a vacuum chuck of the present invention is used for a chuck plate of a vacuum chuck that adsorbs and supports an object, and is made of a porous sintered body of silica particles having a particle size of 30 μm or more and 100 μm or less. , a support having an average pore diameter of 10 μm or more and 15 μm or less, and a porous sintered body of silica particles having a particle size of 1 μm or more and 40 μm or less joined to the side of the support that adsorbs an object, and a surface layer portion having an average pore size of 3 μm or more and 7 μm or less, and the average particle size of the silica particles in the support portion is 10 μm or more larger than the average particle size of the silica particles in the surface layer portion.

According to the porous silica material for a vacuum chuck of the present invention, since it is provided with a support portion made of a porous sintered body of silica particles having a particle size of 30 μm or more and 100 μm or less, chucking is performed while maintaining high light transmittance. Strength as a plate can be obtained. In addition, since the surface layer portion made of a porous sintered body of silica particles having a particle size of 1 μm or more and 40 μm or less is joined to the side of the support portion that adsorbs the object, the adsorption surface that adsorbs the object can be increased in strength and the flatness can be improved. Therefore, it is possible to form a chuck plate having high light transmittance and high flatness of the chucking surface.

Furthermore, if the thickness of the support is 3 mm or more and 5 mm or less, and the thickness of the surface layer is 0.5 mm or more and 1 mm or less, or the particle distribution width of the silica particles in the support is 20 μm or less, and the silica in the surface layer is A higher effect can be obtained by setting the particle distribution width of the particles to 30 μm or less.

1 is a diagram showing the configuration of a silica porous body for a vacuum chuck according to an embodiment of the present invention; FIG. FIG. 4 is a characteristic diagram showing the difference in light transmittance due to the difference in pore diameter of porous silica.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of a silica porous body 10 for vacuum chuck according to this embodiment. This porous silica material 10 for vacuum chuck is used for a chuck plate of a vacuum chuck that sucks and supports an object such as a flat member by suction. and a surface layer portion 12 disposed on the side for attracting an object. The surface layer portion 12 is preferably in direct contact with the support portion 11, and more preferably joined. The surface of the surface layer portion 12, that is, the surface opposite to the support portion 11, is a flat attracting surface that attracts an object. The support body part 11 and the surface layer part 12 are plate-shaped, for example, disc-shaped, have air permeability and translucency, and are each composed of a porous sintered body of silica particles having different particle diameters. .

The support portion 11 is made of a porous sintered body of silica particles having a particle size of 30 μm to 100 μm, and an average pore diameter of 10 μm to 15 μm. The surface layer portion 12 is made of a porous sintered body of silica particles having a particle diameter of 1 μm or more and 40 μm or less, and has an average pore diameter of 3 μm or more and 7 μm or less. The average particle size of the silica particles of the support portion 11 is configured to be larger than the average particle size of the silica particles of the surface layer portion 12 by 10 μm or more. The particle size and average particle size are values derived by a laser diffraction/scattering method. The average pore diameter is a value derived by mercury porosimetry.

By configuring in this way, the support portion 11 having a large grain size can provide strength as a chuck plate while maintaining high light transmittance, and the surface layer portion 12 having a small grain size can achieve the target The flatness of the chuck plate is improved by increasing the strength of the chucking surface that chucks the object, and the flatness of about 5 μm required for the chuck plate can be obtained.

The particle diameter of the silica particles used for producing the support body portion 11 is set to 30 μm or more and 100 μm or less. This is because if the thickness is smaller than 30 μm, the light transmittance cannot be sufficiently increased, and if the thickness is larger than 100 μm, the strength is greatly reduced and the shape cannot be maintained. The particle size of the silica particles used for producing the surface layer portion 12 is set to 1 μm or more and 40 μm or less. If it is smaller than 1 μm, cracks are likely to occur during sintering, and if it is larger than 40 μm, it is difficult to obtain sufficient flatness.

Further, the particle distribution width of the silica particles used for producing the support body portion 11 is preferably 30 μm or less, and the particle distribution width of the silica particles used for producing the surface layer portion 12 is preferably 20 μm or less. This is because cracking during sintering can be prevented by classifying to narrow the particle distribution width. For example, the particle size of the silica particles used for producing the support body portion 11 is preferably 70 μm or more and 100 μm or less, and the particle size of the silica particles used for producing the surface layer portion 12 is preferably 20 μm or more and 40 μm or less. preferable.

The reason why the average pore diameter of the support portion 11 is 10 μm or more is that the light transmittance can be further increased, and the reason that it is 15 μm or less is that the support layer has the necessary strength. The reason why the average pore diameter of the surface layer portion 12 is 7 μm or less is that the flatness can be increased. FIG. 2 shows the difference in light transmittance due to the difference in pore diameter of the silica porous material. As shown in FIG. 2, it can be seen that the larger the average pore diameter, the higher the light transmittance. In addition, the flatness tends to increase as the average pore diameter decreases, and the flatness is about 40 μm when the average pore diameter is 15 μm, whereas the flatness is about 5 μm when the average pore diameter is 7 μm. degree is obtained.

The thickness of the support portion 11 is preferably 3 mm or more and 5 mm or less, and the thickness of the surface layer portion 12 is preferably 0.5 mm or more and 1 mm or less. This is because if the thickness of the support portion 11 is less than 3 mm, it is difficult to obtain sufficient strength as a chuck plate, and if it is greater than 5 mm, the light transmittance is reduced. This is because if the thickness of the surface layer portion 12 is less than 0.5 mm, the surface layer cannot be uniformly formed, and if it is greater than 1 mm, the light transmittance is lowered.

This silica porous body 10 for vacuum chuck can be manufactured, for example, as follows. First, for example, the spherical silica forming the support portion 11 and the surface layer portion 12 is classified so as to have the above-described particle size and average particle size, mixed with a binder and cast into a mold at about 15°C to 50°C. It is gelled by leaving it at a predetermined temperature for about 3 to 12 hours. Next, for example, the gel is released from the mold and baked by holding at a predetermined temperature of about 1300° C. to 1350° C. for about 10 to 15 hours to form the support portion 11 and the surface layer portion 12 .

Subsequently, the obtained support portion 11 and surface layer portion 12 are processed, if necessary, washed, and then joined. For example, tetraethyl orthosilicate (TEOS), ultrapure water, hydrochloric acid, and propylene glycol are mixed, and a sol whose pH is adjusted with ammonia is applied between the support 11 and the surface layer 12, dried, Gel and bake. The firing temperature is preferably 1200° C. to 1350° C., for example. This is because if the temperature is lower than 1200° C., the bonding may be weak and peeling may occur, and if the temperature is higher than 1350° C., the silica glass will devitrify. In addition, silica particles may be mixed into the gel in the same amount at the time of joining.

As described above, according to the present embodiment, since the support portion is made of a porous sintered body of silica particles having a particle size of 30 μm or more and 100 μm or less, it can be used as a chuck plate while maintaining high light transmittance. strength can be obtained. In addition, since the surface layer portion made of a porous sintered body of silica particles having a particle size of 1 μm or more and 40 μm or less is joined to the side of the support portion that adsorbs the object, the adsorption surface that adsorbs the object can be increased in strength and the flatness can be improved. Therefore, it is possible to form a chuck plate having high light transmittance and high flatness of the chucking surface.
The average particle size of the silica particles in the support must be 10 µm or more larger than the average particle size of the silica particles in the surface layer. If the difference in average particle size between the two is less than 10 μm, or if the size relationship is reversed, the effect of the present invention having a two-layer structure cannot be obtained.

Furthermore, if the thickness of the support is 3 mm or more and 5 mm or less, and the thickness of the surface layer is 0.5 mm or more and 1 mm or less, or the particle distribution width of the silica particles in the support is 20 μm or less, and the silica in the surface layer is A higher effect can be obtained by setting the particle distribution width of the particles to 30 μm or less.

(Example 1)
First, spherical silica is classified to adjust the particle size and average particle size, mixed with a binder, cast into a mold, allowed to stand at 25° C. for 12 hours to gel, then released from the mold, and heated at 1350° C. for 12 hours. By holding and sintering, a disk-shaped support body portion 11 and a surface layer portion 12 were formed. The particle size of the spherical silica forming the support portion 11 was set to 30 μm or more and 100 μm or less, and the average particle size was set to about 70 μm. The particle size of the silica particles forming the surface layer portion 12 was set to 20 μm or more and 40 μm or less, and the average particle size was set to about 30 μm. The average pore diameter of the obtained support portion 11 was about 15 μm, and the average pore diameter of the surface layer portion 12 was about 7 μm. The thickness of the support portion 11 was set to 5 mm, and the thickness of the surface layer portion 12 was set to 0.5 mm.

Next, the surface of the obtained surface layer portion 12 was subjected to planarization processing, and the flatness was measured by three-dimensional measurement. As a result, the flatness was about 5 μm. Subsequently, the support portion 11 and the surface layer portion 12 thus obtained were washed and joined to manufacture the silica porous body 10 for a vacuum chuck. The bonding was performed by mixing TEOS, ultrapure water, 0.1 mol/l hydrochloric acid, and propylene glycol in a weight ratio of TEOS: ultrapure water:hydrochloric acid:propylene glycol=11.7:9:1:3, followed by bonding with ammonia. A sol adjusted to pH 4.5 to 5.0 was applied between the support portion 11 and the surface layer portion 12, dried, gelled, and fired at 1200.degree.

When the total transmittance of the obtained porous silica material 10 for vacuum chuck was measured using an integrating sphere, the transmittance of light from 400 nm to 750 nm was 7%.

(Comparative Examples 1 and 2)
As Comparative Example 1, a silica porous body was produced in the same manner as the support portion 11 of Example 1. The thickness was set to 5.5 mm. As Comparative Example 2, a silica porous body was produced in the same manner as the surface layer body 12 of Example 1. The thickness was also 5.5 mm. Also for Comparative Examples 1 and 2, surface exposure processing was performed, and flatness and light transmittance were measured in the same manner as in Example 1. As a result, the flatness of Comparative Example 1 was about 40 μm. Moreover, the light transmittance of Comparative Example 2 was 3%. That is, according to Example 1, it was found that the flatness of the chucking surface could be 5 μm or less, which is required for a chuck plate, and the light transmittance could be increased.

In Example 1, since the strength of the support was emphasized and the thickness was increased, the light transmittance was smaller than that in FIG.
If the thickness of the support portion 11 is reduced to about 3 mm, the light transmittance is further increased.

Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and various modifications are possible. For example, in the above embodiments, each component was specifically described, but it may be modified, and other components may be provided.

It can be used for a vacuum chuck that sucks and supports an object such as a semiconductor wafer by sucking air.

DESCRIPTION OF SYMBOLS 10... Silica porous body for vacuum chucks, 11... Support body part, 12... Surface layer part

Claims (3)

A silica porous material for a vacuum chuck, which is used for a chuck plate of a vacuum chuck that adsorbs and supports an object,
a support portion made of a porous sintered body of silica particles having a particle diameter of 30 μm or more and 100 μm or less and having an average pore diameter of 10 μm or more and 15 μm or less;
A surface layer disposed on the side of the support that adsorbs the object, made of a porous sintered body of silica particles having a particle diameter of 1 μm or more and 40 μm or less, and having an average pore diameter of 3 μm or more and 7 μm or less. and
A silica porous body for a vacuum chuck, wherein an average particle size of silica particles in the support portion is larger than an average particle size of silica particles in the surface layer portion by 10 μm or more. 2. The porous silica material for a vacuum chuck according to claim 1, wherein the thickness of said support portion is 3 mm or more and 5 mm or less, and the thickness of said surface layer portion is 0.5 mm or more and 1 mm or less. 3. The vacuum chuck according to claim 1, wherein the silica particles in the support portion have a particle distribution width of 30 μm or less, and the silica particles in the surface layer portion have a particle distribution width of 20 μm or less. Silica porous body.

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