JPH05285762A - Vacuum chuck and its manufacture - Google Patents

Abstract

PURPOSE:To provide a vacuum chuck which can prevent a deformation of a work owing to a suction, and can maintain a clean chuck surface, and furthermore, can form a chuck surface of a high accuracy of flatness. CONSTITUTION:A plane 17 is arranged in one layer connecting to the chuck base surface 12 of a vacuum chuck, and a chuck surface is formed of numerous cut spheres 16 contacting each other. The chuck surface is formed of numerous cut spheres 16, and gaps between neighboring cut spheres 16 are made into suction holes 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum chuck and its manufacturing method.

[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 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 be too large 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 the 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 at a small pitch over the entire chuck surface. 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 provides a vacuum chuck capable of preventing deformation of a work due to suction, maintaining a clean chuck surface, and capable of forming a chuck surface having a highly accurate flatness, and a manufacturing method thereof. Is what you are trying to do.

[0009]

In the vacuum chuck of the present invention, a flat surface portion is arranged in one layer so as to contact the surface of the chuck base of the vacuum chuck, and the chuck surface is formed by a large number of joined spheres. There is.

The first method of manufacturing a vacuum chuck of the present invention comprises the following steps.

(A) Arranging a large number of spheres in a single layer in a holding frame whose bottom surface serves as a reference surface. (B) Fixing the spheres in the holding frame with a bonding agent. (C) Sphere tops on the bottom surface. Flat surface processing in parallel to make blast balls (d) Heat bonding or melting with a solvent to take out the blast balls from the holding frame (e) The flat surface of many spheres is the chuck base surface of the vacuum chuck. Arranged in a single layer on the surface of the chuck base so as to be in contact with the surface of the chuck base. (F) Bonding the spheroids to the surface of the chuck base. ing.

(A) Arranging a large number of spheres in one layer in a holding frame whose bottom surface serves as a reference surface (b) fixing the spheres in the holding frame with a first bonding agent (c) sphere top (2) Turn the holding frame holding the blast balls upside down and place it on the chuck base of the vacuum chuck, and bond the blast balls to the surface of the chuck base with the second bonding agent. (E) Remove the holding frame from the split spheres bonded to the surface of the chuck base by melting only the first bonding agent by heating or melting with a solvent. The material of the spheres is alumina, zirconia, sialon,
Ceramics such as silicon carbide, metals such as SUS and hard alloys, and hard resins such as Teflon and vinyl chloride are used. The diameter of the sphere is several tens of μm to several mm. The holding frame is made of metal such as steel, and the bottom surface is processed by surface grinding with high precision so that the flatness is 1 μm or less. As a bonding agent for fixing the spheres to the holding frame, yellow wax (softening temperature is about 80 ° C.) that can be melted at a relatively low temperature is used. The top of the sphere is processed by surface grinding or polishing with the bottom surface of the holding frame as a reference surface. When arranging the spheres on the upper surface of the chuck base, it is desirable to arrange the spheres in a closest packed state. The surface of the chuck base is processed with high accuracy like the bottom surface of the holding frame. An active metal method or the like is used to join the spheroid to the surface of the chuck base.

In the second method of manufacturing a vacuum chuck,
The second bonding agent has higher bonding strength than the first bonding agent and is higher than the melting temperature of the first bonding agent or the first bonding agent.
Must be one that does not dissolve in the solvent of the bonding agent. As the second bonding agent, for example, a thermosetting epoxy resin that is sintered at about 200 ° C., or an active metal method that is bonded at a high temperature of 800 ° C. or higher is used. In addition, if the holding frame holding the spheroid is turned over and placed on the chuck base surface,
The flat part of the sphere is in contact with the surface of the chuck base of the vacuum chuck.

[0014]

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

Since the opening edge of the intake hole is spherical, it is smooth 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.

Further, since the spheres are flattened and the heights of the split spheres are made uniform, the chuck surface is a highly accurate flat surface. Further, since the flat portion of the sphere is bonded to the chuck base, the contact area between the sphere and the chuck base is wide, the spheres are stably arranged, and high bonding strength is obtained.

[0017]

EXAMPLE FIG. 1 schematically shows a state in which a large number of balls 6 are densely arranged inside a holding frame 1. The balls 6 are made of alumina ceramics and have a diameter of 1 mm. The bottom surface 2 of the holding frame 1 is surface-ground to have a flatness of 1 μm.
It is finished below. The ball housing portion 3 of the holding frame 1 has a square shape when viewed from above. Since the depth of the ball housing portion 3 is shallower than the diameter of the ball 6, the ball 6 projects from the top surface 4 of the holding frame 1.

As described above, the balls 6 are placed in the ball housing portion 3.
The molten yellow wax 8 is injected into the ball housing portion 3 in the state of arranging. As shown in FIG. 2, the yellow wax 8 fills the gaps between the balls 6 and solidifies. The solidified yellow wax 8 holds the ball 6 with a force capable of withstanding the grinding processing force.

Next, the ball top is ground parallel to the bottom surface 2 of the holding frame 1 to make the ball 6 a sphere. The processing accuracy is about the same as the flatness of the bottom surface 2 of the holding frame 1.

When the processing of the balls 6 is completed, the holding frame 1 containing the spheroids is heated to about 100 ° C. to melt the yellow wax 8. Then, the spheroid is taken out from the holding frame 1 in a state where the yellow wax 8 is melted. The taken out spheres are washed by ultrasonic cleaning using an organic solvent such as acetone, and the attached yellow wax 8 is washed off.

Next, as shown in FIG.
The flat surface portion 17 of 6 is the chuck base surface 1 of the vacuum chuck.
One layer is arranged in the closest packing state on the chuck base surface 12 so as to be in contact with 2. Then, the spheroid 16 is bonded to the chuck base surface 12 by the active metal method.

3 and 4 show a part of the vacuum chuck obtained as described above. The chuck base 11 is fixed inside the guide ring 13. The upper surface 12 of the chuck base 11 is ground with high precision, and has high precision flatness. An intake passage 15 is formed between the outer peripheral surface of the chuck base 11 and the inner peripheral surface of the guide ring 13. The gap of the intake passage 15 is 0.3 mm.
A vacuum pump (neither is shown) is connected to the intake passage 15 via a pipe. The spheroid 16 is bonded to the chuck base surface 12 via a bonding layer 18. The top of the spheroid 16 is manufactured to have the same height as the upper surface 14 of the guide ring 13 and forms a chuck surface. A gap between the sphere-shaped spheres 16 and the sphere-shaped spheres 16 that are in contact with each other forms an intake hole 20, and the intake passage 15 communicates with the intake hole 20.

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 having the above-mentioned structure, there is no local deformation due to pinching by particles and the flatness is 0. It was 8 μm.

[0024]

In the vacuum chuck of the present invention, since the gap between the adjacent spheres forms the intake hole, the intake hole diameter and the hole pitch can be significantly reduced. Further, since the opening edge of the intake hole does not have a sharp irregular shape, even if particles adhere to the opening edge, they are easily removed by suction from the intake hole. Further, since the spheres are flattened and the heights of the split spheres are made uniform, the chuck surface is a highly accurate flat surface. 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. Further, since the flat portion of the sphere is bonded to the chuck base, the contact area between the sphere and the chuck base is wide, the spheres are stably arranged, and high bonding strength is obtained.

In the vacuum chuck manufacturing method of the present invention,
Since all the spheroids that form the chuck surface are collectively processed, a highly accurate vacuum chuck can be efficiently manufactured. In particular, in the second manufacturing method, since the spheroidal body is bonded to the surface of the chuck base while being held by the holding frame, it is possible to manufacture a more accurate vacuum chuck.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view schematically showing a state in which a large number of balls are densely arranged in a holding frame in the method of the present invention.

FIG. 2 is an enlarged vertical sectional view schematically showing a state in which a large number of balls are fixed in a holding frame.

FIG. 3 is a vertical cross-sectional view showing a part of the vacuum chuck of the present invention.

FIG. 4 is a vertical cross-sectional view schematically showing an enlarged part of the vacuum chuck shown in FIG.

[Explanation of symbols]

 1 Holding Frame 2 Bottom of Holding Frame 3 Ball Housing 4 Top of Holding Frame 6 Ball 8 Yellow Wax 11 Chuck Base 12 Top of Chuck Base 13 Guide Ring 14 Top of Guide Ring 15 Ventilation Path 16 Split Sphere 17 Plane of Split Sphere 18 Bonding Layer 20 air intake

Claims (3)

[Claims] 1. A vacuum chuck, wherein a flat portion is arranged in one layer so as to contact a surface of a chuck base of the vacuum chuck, and a chuck surface is formed by a large number of joined spheres. 2. A method of manufacturing a vacuum chuck comprising the following steps. (A) Place a large number of spheres in the holding frame whose bottom surface is the reference surface.
Arrange in layers (b) Fix the spheres inside the holding frame with a bonding agent (c) Plane the top of the sphere parallel to the bottom surface to make spheres (d) Melt the bonding agent by heating or use a solvent Dissolve and take out the spheres from the holding frame. (E) Arrange the spheres in a single layer on the surface of the chuck base so that the flat surfaces of the many spheres are in contact with the chuck base surface. Bonding to the chuck base surface 3. A method of manufacturing a vacuum chuck comprising the following steps. (A) Place a large number of spheres in the holding frame whose bottom surface is the reference surface.
Arrange in layers (b) Fix the spheres in the holding frame with the first bonding agent (c) Plane the top of the spheres parallel to the bottom to make spheroids (d) Hold the spheroids The holding frame is turned over and placed on the chuck base of the vacuum chuck, and the split spheres are bonded to the surface of the chuck base with the second bonding agent. (E) Only the first bonding agent is melted by heating or melted with a solvent to make the chuck base. Removing the holding frame from the sphere ball bonded to the surface