JP2003068835A - Vacuum chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum chuck in which planarity can be ensured when an adsorbed article is adsorbed without requiring any polishing work and adhesion of particles to the article is reduced. SOLUTION: A vacuum chuck 1 for vacuum adsorbing an article 10 comprises a planar body 2, a circumferential wall 3 for mounting the article provided at the circumferential fringe on one side of the body 2, a large number of protrusions 5 provided on the bottom part of a recess 4 surrounded by the circumferential wall 3 of the body 2 and supporting the article 10 at the substantially same height as the circumferential wall 3, and an opening 9 for exhausting air from the inside of the recess 4 formed in the bottom part thereof. The compositional material comprises a compact-bone ceramic sintered body having relative density of 99% or above and Young's modulus of 300 GPa or above, and the plate thickness at the part from the outer circumference of the body 2 to the inner circumference of the circumferential wall 3 and a part 50 mm on the inside of the inner circumference is set at 4 mm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the processing, measurement, and the like of an object such as a semiconductor substrate typified by a silicon wafer and other various substrates whose flatness is strictly required in the manufacturing process.
The present invention relates to a vacuum chuck used for transportation and processing.

[0002]

2. Description of the Related Art When processing, measuring, transporting, or processing semiconductor substrates such as silicon wafers typified by silicon, and other various substrates, a vacuum processing apparatus or the like is used as a method of adsorbing these adsorbed substances. If you are not in a low pressure environment,
A so-called vacuum adsorption method is generally adopted in which the lower surface side of the adsorbed material is evacuated and brought into close contact with the atmospheric pressure.

In a vacuum chuck for adsorbing an object to be adsorbed by such a vacuum adsorption method, when the contact area between the object to be adsorbed and the chuck is large, the object to be adsorbed is contaminated with contaminants such as particles from the vacuum chuck, There is a risk of significantly reducing the manufacturing yield. Further, if the vacuum chuck is made of a material having low rigidity, there is a risk that the object to be adsorbed may be deformed at the time of adsorption and the yield will be remarkably reduced. Therefore, a ceramic material having high rigidity and high purity has been conventionally used as a vacuum chuck. Further, in order to reduce the contact area between the vacuum chuck and the attracted object, a peripheral wall on which the attracted object is placed is provided on the outer periphery of the placement surface of the main body of the vacuum chuck,
A structure having a large number of supporting protrusions at the same height as the peripheral wall is adopted at the bottom of the recess surrounded by the peripheral wall (Japanese Patent Laid-Open No. 4-32).
3849).

[0004]

In the case of the vacuum chuck having such a structure, the diameter of the upper surface of the supporting protrusion needs to be about 0.2 mm in order to minimize the contact area between the upper surface of the supporting protrusion and the object to be adsorbed. However, since the rigidity of such a support projection having a small area is low, there is a problem in that it is deformed by vacuum suction and flatness cannot be maintained.

Further, since the peripheral wall is continuously formed, the peripheral wall portion inevitably has a higher rigidity than the portion of the vacuum chuck body where the supporting protrusions are formed, and when adsorbing an object to be adsorbed, The object to be adsorbed is 0.2 to 0.6μ at the peripheral wall.
There is a problem that the height of the object to be adsorbed rises and the flatness of the object to be adsorbed cannot be sufficiently maintained.

Further, in this type of vacuum chuck, when the object to be adsorbed is peeled off from the vacuum chuck, the object to be adsorbed is pushed up by the push-up rod, and therefore the vacuum chuck is formed with a hole for moving the push-up rod. An air inflow prevention wall for preventing the inflow of air from the hole is provided around the hole of the push-up rod. However, even when such an air inflow prevention wall is provided, the rigidity of that portion is determined by the supporting protrusion. There is also a problem that the flatness of the part tends to be higher than that of the part where the part is formed, and the flatness of the part cannot be maintained.

[0007] In order to solve such a problem, at present, a portion where the flatness is deteriorated by vacuum suction is slightly polished by hand to secure the flatness. The cost is huge and it is not realistic.

Further, since the vacuum chuck adsorbs a silicon wafer or the like that requires extremely high precision, it is required that the adhesion of particles to the object to be adsorbed is extremely small.

The present invention has been made in view of the above circumstances, and it is possible to secure the flatness when adsorbing an adsorbent without polishing and to prevent particles from adhering to the adsorbent. An object is to provide a vacuum chuck with less adhesion.

[0010]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have used a dense and highly rigid ceramic having a Young's modulus of 300 GPa or more as a constituent material of a vacuum chuck. Moreover, they have found that it is effective to adjust the thickness of the peripheral wall of the vacuum chuck body and the air inflow prevention wall, and have completed the present invention.

That is, the present invention is a vacuum chuck for vacuum-adsorbing an object to be adsorbed, comprising a flat plate-shaped main body, and a peripheral wall provided on the peripheral edge of one surface of the main body and on which the object to be adsorbed is placed. A large number of supporting protrusions provided on the bottom of the recess surrounded by the peripheral wall of the main body and supporting the object to be adsorbed at substantially the same height as the peripheral wall, and provided on the bottom of the recess, A dense ceramics sintered body having a relative density of 99% or more and a Young's modulus of 300 GPa or more, which has an exhaust port for exhausting air, and from the outer periphery of the main body to the inner periphery of the peripheral wall and the inner periphery thereof. Provided is a vacuum chuck having a plate thickness of 4 mm or less in a portion up to 50 mm inside.

With such a structure, the rigidity of the main body of the vacuum chuck and the supporting protrusions is high, so that it is possible to prevent deformation of the supporting protrusions due to atmospheric pressure during vacuum adsorption.
In addition, the plate thickness of the part from the outer periphery of the main body to the predetermined distance is 4
Since the thickness is less than or equal to mm, the rigidity of the peripheral wall portion can be reduced. For this reason, the difference between the deformation amount of the support protrusion when vacuum suctioned and the deformation amount of the peripheral wall portion of the main body can be significantly reduced. The flatness can be maintained at 0.1 μm or less.

Further, the present invention is a vacuum chuck for vacuum-sucking an object to be adsorbed, comprising a flat plate-shaped main body, and a peripheral wall provided on the peripheral edge of one surface of the main body and on which the object to be adsorbed is placed.
Provided at the bottom of the recess surrounded by the peripheral wall of the main body,
A large number of supporting protrusions that support an object to be adsorbed at substantially the same height as the peripheral wall, an exhaust port provided at the bottom of the recess to exhaust the inside of the recess, and an object to be adsorbed provided at the bottom of the recess. A hole into which a push-up rod of an object is inserted; and an air inflow prevention wall that is provided around the hole to support an object to be adsorbed at substantially the same height as the peripheral wall and prevent the inflow of air from the hole. And has a relative density of 99% or more and a Young's modulus of 300 GPa or more, which is a dense ceramics sintered body, and from the hole to the outer periphery of the air inflow prevention wall and 50 mm outside the outer periphery. The thickness of the part is 4m
Provided is a vacuum chuck having a thickness of m or less.

Thus, the bottom of the recess is provided with a hole into which the stick for pushing up the object to be adsorbed is provided, and an air inflow prevention wall for supporting the substrate at substantially the same height as the peripheral wall is provided around the hole. In the same manner, the air inflow prevention wall portion is also more rigid and less likely to be deformed than the support protrusions, but the above configuration also reduces the air inflow prevention wall portion of the main body and causes vacuum suction. In this case, it is possible to increase the amount of deformation of this portion, and even when this portion deteriorates the flatness of the object to be adsorbed, it is possible to improve the flatness, for example,
It is possible to keep the flatness of the upper surface of the support protrusion and the upper surface of the air inflow prevention wall when adsorbing the object to be adsorbed to be as small as 0.1 μm or less.

When both the air inflow prevention wall portion and the peripheral wall portion deteriorate the flatness of the object to be adsorbed, the push-up rod of the object to be adsorbed is inserted after using the constituent materials as described above. From the hole to the outer periphery of the air inflow prevention wall and a portion 50 mm outside the outer periphery, and from the outer periphery of the main body to the inner periphery of the peripheral wall and a portion 50 mm inside the inner periphery. Both thickness of part is 4m
It may be m or less. As a result, the flatness of the upper surface of the support protrusion, the upper surface of the peripheral wall, and the upper surface of the air inflow prevention wall can be kept extremely small at 0.1 μm or less.

In the present invention, since high density ceramics having a relative density of 99% or more is used as a constituent material, the amount of discharged fine particles which cause pollution is extremely small. Therefore, transfer of particles from the vacuum chuck to the object to be adsorbed hardly occurs, and for example, the number of particles on the back surface of the object to be adsorbed can be kept extremely low at 10 particles / mm ² or less.

As the high-rigidity and high-density ceramics which are the constituent materials of the vacuum chuck, specifically, dense Si is used.
_C, can be mentioned _{Si 3 N 4, Al 2 O} 3 or the like.
Of these, SiC is particularly preferable because it is chemically stable and can be washed with hydrofluoric acid.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is a plan view showing a vacuum chuck according to an embodiment of the present invention, and FIG. 2 is a sectional view thereof. The vacuum chuck 1 is for adsorbing a semiconductor wafer, has a disk-shaped (flat plate) main body 2 made of ceramics, and has a wafer mounting surface 2
A peripheral wall 3 on which an object to be adsorbed is placed is provided on the outer periphery of a, and a large number of supporting projections 5 are provided at the same height as the peripheral wall 3 at the bottom of a recess 4 surrounded by the peripheral wall. The diameter of the tip of the support protrusion 5 is, for example, about 0.2 to 0.3 mmφ and is 4 to 5 m.
It is formed in about m pitches. However, in FIG. 1, for convenience,
The number of the support protrusions 5 is reduced and shown. Further, when the object to be adsorbed is peeled off from the vacuum chuck 1, the object to be adsorbed is pushed up by the three push-up bars 6, so that the body 2 is provided with three push-up bar holes 7 for moving the push-up bars 6. An air inflow prevention wall 8 for preventing the inflow of air from this hole is provided around the push-up rod hole 7. Further, at the center of the main body 2, there is provided an exhaust port 9 for exhausting the vacuum of the recess 4 to evacuate it.

As a constituent material of the vacuum chuck 1,
A highly rigid dense ceramic having a relative density of 99% or more and a Young's modulus of 300 GPa or more is used. Such dense and high-rigidity ceramics include SiC, Si ₃ N ₄ , and Al.
₂ O _{3 and the} like can be mentioned. Of these, SiC, which is chemically stable and can be washed with hydrofluoric acid, is particularly preferable. Here, the reason why the relative density is 99% or more is that
If it is less than 99%, many particles will be adsorbed on the pores of the ceramic surface, and when adsorbing an object to be adsorbed,
This is because the amount of particles transferred from the vacuum chuck 1 to the object to be adsorbed is large. Further, the Young's modulus is set to 300 GPa or more because if it is less than 300 GPa, the overall rigidity of the vacuum chuck 1 becomes low, and it becomes difficult to maintain the flatness of the whole object to be adsorbed.

In the present embodiment, the main body of the portion from the outer periphery 2b of the main body 2 shown in an enlarged view of the outer peripheral portion of FIG. 3 to the inner periphery of the peripheral wall 3 and a portion within 50 mm from the inner periphery. The plate thickness of No. 2 is 4 mm or less. Specifically, as shown in the AA cross section of FIG. 3, as shown in FIG. 4A, at least the outer periphery 2 b of the main body 2 to the peripheral wall 3 are shown.
The plate thickness of the portion up to the inner circumference of the plate is 4 mm or less, and FIG.
As shown in (b) of FIG. 4, the maximum thickness is 4 mm from the outer circumference 2 b of the main body 2 to the inner side of the inner circumference of the peripheral wall 3 by 50 mm.
It is configured as follows. That is, the portion of the main body 2 having a thickness of 4 mm or less is the portion from the outer periphery 2b of the main body 2 to the portion between (a) and (b) of FIG.

On the other hand, the main body 2 shown in an enlarged view of the main body 2 in FIG.
From the push-up rod hole 7 to the outer circumference of the air inflow prevention wall 8 and a portion 50 mm outside the outer circumference,
It is configured to be 4 mm or less. In addition, A- in FIG.
The A cross section is also substantially the same as in FIG.

Conventionally, as shown in FIG. 6, since the main body 2 has a uniform thickness, the peripheral wall 3 and the air inflow prevention wall 8 which are continuously formed are provided with the support projections 5 so as to have rigidity. It becomes relatively higher than the part where it is, as shown in FIG.
When the object to be adsorbed 10 such as a silicon wafer is adsorbed, the amount of compressive deformation of the support protrusions 5 is larger than that of the peripheral wall 3, so that the flatness of the object to be adsorbed 10 cannot be maintained with high accuracy. Also,
The same applies to the portion of the air inflow prevention wall 8.

On the other hand, in the case of FIG. 4 described above, as shown in FIG. 8, when the object to be adsorbed 10 is vacuum-adsorbed, the thickness in the vicinity of the peripheral wall 3 of the main body 2 is 4 mm or less due to the atmospheric pressure. The thin portion is relatively easily deformed, and as a result, the flatness of the object to be adsorbed 10 can be maintained with high accuracy. The same applies to the portion of the air inflow prevention wall 8.

In this case, the thickness is 4 mm as shown.
The following part is a relatively thin part, and the thickness of the other part of the main body 2 is in the range of 5 to 30 mm. The thickness of the relatively thin portion of the main body 2 is 4 mm or less is 4 m
If it exceeds m, the effect of lowering the rigidity of the peripheral wall 3 and the air inflow prevention wall 8 may be insufficient, and the rise of the object to be adsorbed may not be sufficiently eliminated. Further, as described above, the reason that the portion whose thickness is adjusted to 4 mm or less is set to be 50 mm inside from the inner circumference of the maximum peripheral wall 3 is that if the thickness is further increased, the peripheral wall 3 and the air inflow wall 8 are This is because the peripheral wall portion and the air inflow prevention wall portion are recessed without being able to support them even if they have rigidity.

As a method of forming the thin portion of the main body 2, as shown in FIG. 4, all the portions other than the thin portion of the main body 2 may be removed. Alternatively, as shown in FIG.
As shown in, the main body 2 may be cut out by processing to form a thin portion as the cutout portion 11.

The present invention is not limited to the above embodiment and can be variously modified. For example, in the above embodiment, the case where the push-up rod hole is formed is shown, but the case where it is not necessary may be provided. Further, the form of the thin portion of the main body is not limited to the above embodiment. Furthermore, the number of vacuum holes is not limited to one. Furthermore, in the above-described embodiment, a silicon wafer is assumed as the object to be adsorbed, and a disk-shaped vacuum chuck is used, but a non-disk-shaped object such as a rectangular object to be adhered such as a glass substrate of a liquid crystal display device may be used. Needless to say, it is applicable.

[0027]

EXAMPLES Examples of the present invention will be described below. In the vacuum chuck shown in FIG. 1, the constituent material is SiC having a relative density of 99.9% and a Young's modulus of 450 GPa,
The amount of deformation when a silicon wafer, which is an object to be adsorbed, was adsorbed was compared between the case where a portion having a thickness of 4 mm or less according to the present invention was formed in the main body and the case where a conventional thin portion was not formed. In addition, the number of particles on the back surface of the silicon wafer that is the object to be adsorbed was measured. As an example, as shown in FIG. 4, the outer periphery of the main body or the hole for the push-up bar has a thickness of 4 mm.
The following thin portions are formed (Examples 1 to 8),
As a comparative example, a thin portion was not formed in the outer peripheral portion of the main body and the hole for the push-up rod (Comparative Examples 1 and 2). The results are shown in Table 1.

In order to understand the influence of the material,
Low density silicon carbide (relative density 95%, Young's modulus 320
GPa) and low-rigidity mullite (relative density 99%, Young's modulus 220 GPa) were used to similarly measure the amount of deformation and the number of particles when a thin portion was formed within the scope of the present invention. The results are shown in Table 2.

[0029]

[Table 1]

[0030]

[Table 2]

As shown in Table 1, in each of Examples 1 to 8, the deformation amount of the silicon wafer, which is the object to be adsorbed, was 0.1 μm.
It was confirmed that the following high flatness was obtained. Also,
The number of particles was also 10 particles / mm ² or less. On the other hand, the conventional comparative example 1 in which a thin portion is not formed in the main body
In the case of 2, the deformation amount is 0.41 μm and 0.63 μm
m and sufficient flatness could not be obtained. As shown in Table 2, Comparative Examples 3 and 4 in which the shape and Young's modulus are within the range of the present invention, but the relative density of the constituent materials is lower than 99%.
Had sufficient flatness, but had many pores, and the particles existing in the pores were transferred to the wafer, and the number of particles exceeded 10 particles / mm ² . Further, although the shape and the relative density are within the range of the present invention, Comparative Examples 5 and 6 using the low-rigidity ceramics cannot maintain the desired flatness because the rigidity is low as a whole.

As described above, according to the present invention,
It is possible to obtain the flatness when adsorbing an adsorbent without polishing, and to obtain a vacuum chuck in which particles are less attached to the adsorbent.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing a vacuum chuck according to an embodiment of the present invention.

FIG. 3 is an enlarged view showing an outer peripheral portion of the main body of the vacuum chuck according to the embodiment of the present invention.

FIG. 4 is a partial cross-sectional view showing an enlarged main part of the vacuum chuck according to the embodiment of the present invention.

FIG. 5 is an enlarged view showing a hole for a push-up rod of a main body in the vacuum chuck according to the embodiment of the present invention.

FIG. 6 is a partial cross-sectional view of a conventional vacuum chuck.

FIG. 7 is a sectional view showing a state in which an object to be adsorbed is adsorbed by a conventional vacuum chuck.

FIG. 8 is a cross-sectional view showing a state in which an object to be adsorbed is adsorbed by the vacuum chuck according to the embodiment of the present invention.

FIG. 9 is a partial cross-sectional view showing an enlarged main part of a vacuum chuck according to another embodiment of the present invention.

[Explanation of symbols]

1; Vacuum chuck 2; body 2a; mounting surface of the main body 2b; outer periphery of the main body 3; peripheral wall 4; recess 5, 5a, 5b; supporting protrusions 6; Push-up bar 7; Hole for push-up rod 8; Air inflow prevention wall 9; exhaust port 10: Object to be adsorbed 11; notch

Continued front page    (72) Inventor Motohiro Umezu             2-4 Daisaku, Sakura City, Chiba Prefecture Pacific Ocean             Inside Cement Co., Ltd. (72) Inventor Hisao Sato             2-16 Shibadaimon, Minato-ku, Tokyo Stock market             Company Japan Ceratech Tokyo Branch F term (reference) 5F031 CA02 CA05 GA08 GA32 HA02                       HA07 HA08 HA10 HA13 HA14                       HA33 PA26

Claims (3)

[Claims] 1. A vacuum chuck for vacuum-adsorbing an object to be adsorbed, comprising: a flat plate-shaped main body; a peripheral wall provided on the peripheral edge of one surface of the main body and on which the object to be adsorbed is placed; Provided at the bottom of the recess surrounded by the peripheral wall,
It has a large number of supporting protrusions that support an object to be adsorbed at substantially the same height as the peripheral wall, and an exhaust port that is provided at the bottom of the recess and exhausts the inside of the recess. %, Young's modulus is 300
It is composed of a dense ceramics sintered body of GPa or more, from the outer periphery of the main body to the inner periphery of the peripheral wall and 5 from the inner periphery.
A vacuum chuck having a plate thickness of 4 mm or less at a portion between 0 mm inside. 2. A vacuum chuck for vacuum-adsorbing an object to be adsorbed, comprising: a flat plate-shaped main body, a peripheral wall provided on the periphery of one surface of the main body, on which the object to be adsorbed is placed, Provided at the bottom of the recess surrounded by the peripheral wall,
A large number of supporting protrusions that support the object to be adsorbed at substantially the same height as the peripheral wall, an exhaust port provided in the bottom of the recess to exhaust the inside of the recess, and an object to be adsorbed provided in the bottom of the recess. A hole into which a push-up rod of an object is inserted; and an air inflow prevention wall that is provided around the hole and supports an object to be adsorbed at substantially the same height as the peripheral wall, and that prevents the inflow of air from the hole. Has a relative density of 99% or more and a Young's modulus of 300.
A vacuum chuck comprising a dense ceramics sintered body of GPa or more and having a plate thickness of 4 mm or less from the hole to the outer periphery of the air inflow prevention wall and a portion 50 mm outside the outer periphery. . 3. The vacuum chuck according to claim 2, wherein the plate thickness of the portion from the outer periphery of the main body to the inner periphery of the peripheral wall and a portion 50 mm inside the inner periphery is 4 mm or less. .