JPH05285761A - Vacuum chuck - Google Patents

Abstract

PURPOSE:To provide a vacuum chuck which can prevent a deformation of a work owing to suction, and can maintain a clean chuck surface. CONSTITUTION:A chuck surface is formed of numerous spheres 6 or cut spheres 6 whose upper sides are cut and made into flat surfaces, which are arranged in one layer on the surface of a chuck base 1 and connected to the chuck base surface 2. Gaps between neighboring spheres 6 or cut spheres 6 form suction holes 8.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to vacuum chucks, and more particularly to chuck surfaces.

[0002]

2. Description of the Related Art A work having high compliance is deformed by a holding force when held by a chuck. A vacuum chuck or an electromagnetic chuck is widely used as a chuck for such a work. A vacuum chuck is used when processing a non-magnetic material such as a silicon wafer. The vacuum chuck has many suction holes,
The work can be supported with high accuracy.

The suction holes are classified into a pore type and a porous type. The pore type is a chuck face plate provided with a large number of pores. In the porous type, a plate obtained by sintering ceramic particles or the like with voids is attached to the surface of the chuck base.

[0004]

A vacuum chuck having a chuck surface of the fine pore type has the following problems.

The minimum hole diameter and pitch of the intake holes are limited in view of processing or economical reasons, and the practical minimum hole diameter is about 0.5 mm and the minimum hole pitch is about 10 mm. On the other hand, the suction hole portion has a stronger suction force than the other portions, and is largely recessed in a thin work such as a silicon wafer. Therefore, in the pore type in which the minimum hole diameter and the minimum hole pitch are limited, the deformation amount of the intake hole portion may become so large that it cannot be ignored in terms of processing accuracy. In such a case, since the portion of the intake hole is recessed, the amount of processing is smaller than that of other portions, and flat processing cannot be performed.

Further, in the vacuum type chuck whose chuck surface is the above-mentioned porous type, an extremely large number of minute suction holes are densely distributed over the entire chuck surface at a small pitch. Therefore, unlike the above-mentioned pore type, there is no large local deformation at the intake holes. However, there are the following problems.

When a work is processed in a state where particles or dust are sandwiched between the work surface and the chuck surface, the work rises at the portion where the particles are sandwiched, so that portion is processed more than other portions. Therefore, if there are particles, flat processing cannot be performed. For this reason, when fixing the work to the chuck surface,
The chuck surface needs to be clean. However, the edge of the opening of the suction hole on the chuck surface side is a sharp and irregularly shaped edge, and if particles adhere to the edges and become stuck, it is extremely difficult to remove the particles. Therefore, the chuck surface could not be cleaned to the extent that it does not affect the processing accuracy.

The present invention is intended to provide a vacuum chuck capable of preventing deformation of a work due to suction and maintaining a clean chuck surface.

[0009]

A vacuum chuck according to the present invention has a chuck surface which is arranged in a single layer on the surface of a chuck base and has a plurality of spheres bonded to the surface of the chuck base or a sphere having a flat upper surface. Has been formed.

Alumina is used as the material for the spheres or spheroids.
Ceramics such as zirconia, sialon, silicon carbide and glass, metals such as SUS and hard alloys, Teflon,
Hard resin such as vinyl chloride is used. The diameter of the sphere or spheroid is several tens of μm to several mm. It is desirable to arrange them in a close-packed state in which adjacent spheres or split spheres are in close contact with each other. The active metal method is used, for example, to bond the spheres or spheroids to the chuck base surface. In order to form a chuck surface for supporting a workpiece such as silicon by a sphere, the sphere is bonded to the surface of the chuck base, and then the upper surface of the adhered sphere is ground or polished to be flat. In the case of the spheroid, the area of the contact surface with the work becomes wider and the pitch between the contact surfaces of the adjacent spherules becomes smaller.

[0011]

The gap between adjacent spheres or split spheres forms an intake hole. Therefore, the intake hole pitch can be made significantly smaller than that of the conventional pore type.

In the case of a sphere, the opening edge of the intake hole is spherical and therefore smooth. Further, in the case of the spheroid, the opening edge of the intake hole has a regular smooth arc, and does not have a sharp irregular shape unlike the conventional porous type. Therefore, even if particles adhere to the edge of the opening, they are easily removed by suction from the intake holes.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows a part of the vacuum chuck of the present invention.

As shown in the drawing, a chuck base 1 of a vacuum chuck is fixed in a guide ring 3. The upper surface of the chuck base 1 is ground with high precision and has high flatness. An intake passage 5 is formed between the outer peripheral surface of the chuck base 1 and the inner peripheral surface of the guide ring 3.
The gap of the intake passage 5 is 0.3 mm. A vacuum pump (neither is shown) is connected to the intake passage 5 via a pipe.

Balls 6 made of alumina ceramics are arranged on the upper surface of the chuck base 1 in a close-packed state, and are joined via a joining layer 9. The ceramic balls 6 are processed with high precision by lapping. The tops of the ceramic balls 6 are manufactured so as to have the same height as the upper surface 4 of the guide ring 3 and form a chuck surface. The diameter of the ceramic balls 6 is 2 mm. The chuck base 1 and the ceramic balls 6 are joined by the active metal method.

The gap between the ceramic balls 6 and the ceramic balls 6 which are in contact with each other forms an intake hole 8.
The intake passage 5 communicates with the intake hole 8.

As a result of grinding a silicon wafer having a diameter of 150 mm and a thickness of 0.6 mm by using the vacuum chuck constructed as described above, there is no local deformation due to particle entrapment and the flatness is 0. It was 8 μm.

In the above embodiment, high precision ceramic balls were used. The embodiment shown in FIG. 2 shows a vacuum chuck in which a ceramic ball, which is not very accurate, is used.

In this embodiment, as shown in FIG. 1, the ceramic balls 6 are arranged on the upper surface 2 of the chuck base 1 and bonded, and then the upper surface 4 of the guide ring 3 and the tops of the ceramic balls 6 are ground. The ceramic balls 6 are split balls, and the upper surface 7 of the split balls is a chuck surface flush with the upper surface 4 of the guide ring 3. According to this embodiment, the upper surface 2 of the chuck base 1 and the ceramic ball 6 are joined to each other, whereby the ceramic ball 6
It is possible to obtain a chuck surface having high flatness even when the tops of the chucks are uneven.

[0020]

According to the present invention, since the gap between adjacent spheres or split spheres forms the intake hole, the intake hole diameter and the hole pitch can be remarkably reduced. Further, since the opening edge of the intake hole does not have a sharp and irregular shape, even if particles adhere to the opening edge, they are easily removed by suction from the intake hole. Therefore, since the work can be fixed to the clean chuck surface without deformation of the work, the work can be processed with high accuracy.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a part of a vacuum chuck according to an embodiment of the present invention.

FIG. 2 is a sectional view schematically showing an enlarged local portion of a vacuum chuck according to another embodiment of the present invention.

[Explanation of symbols]

 1 chuck base 2 upper surface of chuck base 3 guide ring 4 upper surface of guide ring 5 air passage 6 ceramic ball 7 upper surface of ceramic ball 8 intake hole 9 bonding layer

Claims (1)

[Claims] 1. A chuck surface is formed by a plurality of spheres arranged on the chuck base surface of a vacuum chuck in a single layer and joined to the chuck base surface or by a split sphere having a flat upper surface. Vacuum chuck to do.