JP2001185601A - Disk support device - Google Patents

Abstract

(57) [Problem] To provide a disk supporting device capable of minimizing the amount of vertical deformation of a disk when the disk is supported by three or more support portions. SOLUTION: This is a disk supporting device for supporting a disk 10 such as a Si semiconductor wafer having a Poisson's ratio in a range of 0 to 0.4999.
It has more than one support portion 11. In this disk support device, the center of the area occupied by the support portion 11 and the center of the disk are matched, and the disk 10 is placed on the support portion 11 in a horizontal posture. Assuming that the diameter of the disc 10 is D ₀ and the diameter of a circle r passing through each supporting portion 11 is D, the position where D / D ₀ is 0.6 or more and less than 0.7 with 0.677 as a center value. Each support 11 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk supporting device suitable for horizontally supporting a disk-shaped supporting object such as a Si semiconductor wafer.

[0002]

2. Description of the Related Art When a disk is supported from below by a transfer arm or the like, the position and number of supports provided on the transfer arm, the outer diameter (diameter) of the disk, the thickness of the disk, and the like depend on the disk. May bend beyond the permissible limits. For example, the outer diameter is several tens cm
When a circular plate made of Si (silicon) having a thickness of 1 mm or less is horizontally supported by three or more support portions that are upwardly convex,
Depending on the position and number of the support parts, a part of the disk (parts other than the support part) is greatly displaced in the vertical direction due to the weight of the disk, and as a result, the displacement amount of the entire disk (also referred to as its own weight displacement) May exceed the permissible limit.

In order to minimize the vertical displacement of the disk, the shape of the support, that is, the number of the support,
It became necessary to optimize the distance from the center of the disk to the support. When a geometric calculation is performed to find the optimum position of the support portion when there are three or more support portions, the position of the support portion described below is calculated.

Here, the diameter of the disc is D ₀ , the diameter of a circle passing through each support portion (sometimes referred to as a support position diameter in this specification) is D, and the number of support portions is in the circumferential direction of the disc. Assume that there is an infinite number (ie, circumferential support). Also, assuming that the weight in the outside and the outside of the circle, that is, the area inside and outside of the circle are equal to each other between the inside and outside of the circle passing through each supporting portion, the vertical displacement due to the weight of the disc is minimized, When the distance from the center of the plate to the support is geometrically determined, D = D ₀ / √2
= The 0.707D _0. For example, in the case of a disk having a diameter of 30 cm, by disposing the supporting portion at a position where the supporting position diameter becomes about 21.21 cm, the displacement of its own weight can be considerably reduced.

[0005]

However, according to the study of the present inventor, the position of the above-mentioned support part geometrically determined is such that it does not hit but does not come far away, and is not necessarily the most suitable. As described below, it has been found that a more optimal support position exists. Therefore, an object of the present invention is to provide a disk supporting device that can further reduce the vertical displacement of the entire disk when the disk is horizontally supported by three or more supporting portions. .

[0006]

SUMMARY OF THE INVENTION The present inventor has set forth the above-mentioned geometric calculation in order to determine the position where the own weight displacement becomes minimum when the disk is horizontally supported by three or more supporting portions. In place of the above, analysis by FEM (finite element method) was performed. The Poisson's ratio (ν) of the disk to be analyzed is [0], [0.2], [0.33], [0.42],
[0.4999]. The support forms were three-point support, four-point support, five-point support, and circumferential support (infinite point), which will be described later.

FIG. 1 shows a positional relationship between a disk 10 and a support portion 11 in the case of four equally-pointed supports as an example of a support form. Reference numeral 10a in the figure indicates the outer periphery of the disk 10.
The symbol r indicates a circle passing through each support 11. FIG. 2 is a perspective view showing a modified example of the FEM model of the disk 10 in the equidistant four-point support.

The above disk was made of a thin shell element, and for each of the above-mentioned support modes, the amount of vertical displacement of each part of the disk due to the weight of the disk when the support position diameter D was changed was determined. When the disc is arranged on the XY plane and the Z direction positive is up, the negative is down and the support point position is Z = 0, the displacement amount is Z
The amount of displacement in the direction (vertical direction) was calculated and represented in a graph.
The graph plot points are "periphery A", "belly Amax", "center", "belly Bmax", "peripheral B", and "full deformation (whole deformation)" defined below.

Outer circumference A: The intersection of the "line connecting the center of the support points adjacent to each other and the center of the disk" and the outer circumference of the disk. Antinode Amax: a point between the outer periphery A and the center, when the displacement in the Z direction is larger than the outer periphery A and the center, the maximum displacement point. Center: The center point of the disk and also the center of the area occupied by each support point. Outer circumference B: Intersection of the "line connecting the support point and the center of the disk" with the outer circumference of the disk. Antinode Bmax: a point between the outer periphery B and the center, when the displacement in the Z direction is larger than the outer periphery B and the center, the maximum displacement point. Overall deformation: the difference between the maximum and minimum values in the Z direction after the own weight deformation.

FIG. 3 shows the results obtained based on the above analysis method.
20 to FIG. The following Tables 1, 2, and 3 summarize the relationship between the minimum displacement position, the maximum displacement position, and the support mode read from the graphs in the drawings. Table 4 shows the D / D ₀ value that minimizes the total deformation for each Poisson's ratio and support type. Each of the graphs in FIGS. 3 to 20 is a dimensionless display on both the horizontal axis and the vertical axis, and the horizontal axis is (dimensionless support position diameter) = (support position diameter D) / (disc outer diameter D ₀ ). (Z-dimensional dimensionless position) = (Displacement Z) / (Center 1)
The displacement amount Z ₀ ) when the point is supported is shown.

The displacement of the disc's own weight changes depending on the outer diameter, the thickness, the Young's modulus, the Poisson's ratio, and the density of the disc. But,
When the support position diameter and the vertical displacement (Z direction position) are made dimensionless, the relationship between the support position and the displacement does not change even if the outer diameter, the plate thickness, the Young's modulus, and the density of the disk change.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

[Table 4]

As can be seen from FIGS. 3 to 20 and Tables 1 to 3, the deformed shape of the disk changes variously depending on the number of support portions and the diameter of the support position. There is an optimal position where That is, D
When the support portion was provided at a position where / D ₀ was 0.6 or more and less than 0.7, the amount of vertical displacement could take the minimum value in each support mode. In addition, a supporting form in which a convex shape appears upward by the number of the supporting portions, for example, FIGS.
In the case of the deformation mode of the FEM model shown in FIG.

In particular, in the case of equidistant support of three or four support portions, a support position where the outer peripheral point B is at the same height as the support portion, that is, FIGS. 3, 4, 6, 7, and 10, it was found that the overall deformation was minimized when the support portion was provided at the support position where the curve representing the "outer circumference B" in the vertical direction = zero in FIG.

It can be said that equidistant three-point support is preferable in terms of the contact state of the support portion with the disk, that is, that the disk has a good seat. However, three-point support has a difference in the displacement between the outer circumference A and the outer circumference B described above. Extremely large, the overall deformation is also large. For this reason,
In order to reduce the amount of deformation, it is recommended to use evenly distributed four-point supports. Note that there is a large difference between the displacement amount in the case of equidistant three-point support and the displacement amount in the case of equidistant four-point support. Since the difference is small, four-point support is sufficient for practical use.

When the number of the supporting portions is 5 or more and the circumferential support is included, as shown in FIGS. 5, 8, 9, 12, and 17 to 20, the height of the center of the disk is When the support portion is provided at a position having a height equivalent to the outer periphery point A, the total deformation takes a substantially minimum value.

When the number of support portions is 3 or 4, as shown in FIGS. 3, 4, 6, 7, 10, 11, and 13 to 16, the height of the center of the disk is By providing the support portion at a position where is equal to or higher than the outer periphery point A and the height of the center is equal to or lower than the support portion, the total deformation can be reduced.

When the number of the support portions is 5 or more and includes the circumferential support, as shown in FIG. 5, FIG. 8, FIG. 9, FIG. 12, FIG. The total deformation can be reduced by providing the support portion at a position that is equal to or higher than the center of the above and the height of the support portion is equal to or higher than the outer peripheral point B.

Regarding the Poisson's ratio, even if the Poisson's ratio changes in the range of 0 to 0.4999, FIG.
As shown in FIG. 20 or Table 4, the magnitude of the weight displacement of the disc is small in relation to the support position, and D / D ₀ is 0.6 or more and 0.7 or less at any of the support positions. Since the overall deformation can take the minimum value at the support position smaller than the above, the substantial influence by the Poisson's ratio can be neglected.

Therefore, the disk supporting apparatus of the present invention for achieving the above object has three or more supporting portions at equally-spaced positions in the circumferential direction of the disk to be supported. A disk supporting device that makes a center correspond to the center of the disk and places the disk on the support in a horizontal posture, wherein the diameter of the disk is D ₀ , and the diameter of a circle passing through each support is when the diameter was D, D / D ₀ is 0.6 or more, characterized by providing the supporting portion in a position less than 0.7.

In the present invention, regarding the Poisson's ratio,
It has been confirmed that a Poisson's ratio of 0 to 0.4999, which was analyzed by the present inventor, at least meets the purpose of the present invention. The present invention includes providing the disk as a Si semiconductor wafer and providing the support portions at three or four positions in the circumferential direction of the disk. When the number of the support portions is three or four, by adopting a support form in which a convex shape appears upward by the number of the support portions, it is possible to reduce the vertical displacement. Further, by providing the support at a position where the outer periphery of the disk (point B of the outer periphery) on the extension of the support is at the same height as the support, vertical displacement can be minimized.

Further, when the number of support portions is 5 or more and circumferential support is included, by providing the support portions at a position where the height of the center of the disk is equivalent to the height of the outer periphery point A, the entire deformation is achieved. Is almost minimized. When the number of the support portions is 3 or 4, the support portion is provided at a position where the height of the center of the disk is equal to or more than the outer peripheral point A and the height of the center is equal to or less than the support portion. Thereby, the total deformation can be reduced.

When the number of support portions is 5 or more and includes circumferential support, the height of the support portions is equal to or higher than the center of the disk, and the height of the support portions is equal to the outer peripheral point B. By providing the support portion at a position higher than that, the total deformation can be reduced.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below.
Will be explained. The disk supporting device 20 shown in FIG.
(Supporting object) Si semiconductor wafer as an example of 10
A body 21 on which the disc 10 is mounted,
Four upwardly projecting support portions formed on the upper surface of the body 21
11 and the disk 10 is placed on the support 11 in a horizontal posture.
I try to put it on. The disk 10 is dense throughout.
Poisson's ratio is uniform
(Represented by ν) is close to the Poisson's ratio of a Si semiconductor wafer
The value is 0.42. The diameter D of this disk 10₀Is an example
Φ300mm, thickness = 0.775mm, Young's modulus
E = 10890 (kgf / mm²), Density ρ = 2.3
8 × 10^-Ten(Kgf · sec^Two/ Mm^Four ).

The four supporting portions 11 are arranged in the circumferential direction of the disk 10,
That is, the diameter of the circle r passing through the support portion 11 at the position divided by four in the circumferential direction of the circle r passing through the support portion 11, that is, the support position diameter D is D / D _{0 according} to the analysis result described above.
Is set to 0.6 or more and less than 0.7.

More specifically, the Poisson's ratio of the disk 10 is set to 0.
In the case of equidistant four-point support at 42, according to the above-described analysis results, as can be seen from FIG. 11 and Table 3, the optimal position of the support part 11 is D / D ₀ = 0.677, that is, D = 203.
1 mm, and the displacement Z in that case was 0.011 mm. On the other hand, the current product has D = 246 mm, and the displacement Z of the entire wafer is 0.067 mm. That is, according to the embodiment of the present invention, the displacement amount is reduced to about one sixth of the current product. When the optimum position is geometrically obtained, D = D ₀ /√2=0.707 D ₀ = 212.1 mm
Therefore, the diameter of the support position becomes larger than that of the above embodiment, and the displacement amount becomes larger.

FIGS. 3 to 20 have been analyzed on the assumption that the support portions 11 are equally distributed in the circumferential direction of the disk without any dimension. , Due to the fact that the support part comes into surface contact with the disk to some extent, it is not possible to have strictly equal support, and the support position is somewhat wider than the theoretical equal support point Will be. Therefore, in order to examine the change in vertical displacement when the support point is shifted in the circumferential direction, the position of the support portion is shifted in the circumferential direction from the equidistant support point as shown in FIG. The relationship with the direction displacement was analyzed. The results are shown in FIGS. 23 and 24. In each case, four points are equidistantly supported (θ = 45 °).

In FIG. 23 and FIG. 24, the outer circumference 0 °: 4 equally distributed support points θ = 45 ° when viewed from the center of the disk.
And a point on the outer circumference in the 0 ° direction. Belly 0max: A point on the line connecting the outer circumference 0 ° and the center.
If the displacement in the Z direction is larger than ° and the center, the maximum displacement point. Center: The center point of the disk. Outer circumference 45 °: A point on the outer circumference in the 45 ° direction when the four equally spaced support points are 45 ° when viewed from the center of the disk. Antinode 45max: A point on the line connecting the outer circumference 45 ° and the center, and when the Z direction displacement is larger than the outer circumference 45 ° and the center, the maximum displacement point. Outer circumference 90 °: A point on the outer circumference in the 90 ° direction when the four equally-supported support points are 45 ° when viewed from the center of the disk. Antinode 90max: A point on the line connecting the outer periphery 90 ° and the center, and when the Z direction displacement is larger than the outer periphery 90 ° and the center, the maximum displacement point. Overall deformation: the difference between the maximum and minimum values in the Z direction after the own weight deformation.

As shown in FIG. 23, D / D ₀ is 0.
In the case of No. 9, if the angle is within a range of 5 ° on both sides centered on θ = 45 °, the displacement in the vertical direction is substantially the same even if θ is changed. Sensitivity increases rapidly). Further, as shown in FIG. 24, when D / D ₀ is 0.68, both sides of θ = 45 ° are out of the range of 2.5 ° (θ = 42.5 ° and 47.5 °). And the vertical displacement suddenly increases, and the tendency is D
/ D ₀ was observed in the range of 0.6 to 0.7. In consideration of these, the equal distribution support referred to in the present invention,
A range of ± 2.5 ° in the circumferential direction is set around a theoretically equidistant support point in a strict sense.

In carrying out the present invention, it goes without saying that the components constituting the present invention, such as the size and material of the disk and the form of the support portion, can be appropriately modified and carried out. For example, the disk may be a fixed density disk other than a semiconductor wafer, or may be a partially processed semiconductor wafer.

[0034]

According to the present invention, since the position of the supporting portion for supporting the disk can be optimized, the vertical displacement of the disk can be minimized.

[Brief description of the drawings]

FIG. 1 is a plan view showing a disk and a support part in the case of equally-distributed four-point support.

FIG. 2 is a perspective view showing an FEM model of a disk in the finite element method.

FIG. 3 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0.2 and equidistant three-point support is used.

FIG. 4 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0.2 and the equidistant four-point support is used.

FIG. 5 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0.2 and the case is circumferentially supported.

FIG. 6 is a graph showing a relationship between a support position diameter and a vertical displacement in the case of a Poisson's ratio of 0.33 and equidistant three-point support.

FIG. 7 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0.33 and the equidistant four-point support is used.

FIG. 8 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0.33 and the equidistant 5-point support is used.

FIG. 9 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0.33 and the case is circumferentially supported.

FIG. 10 is a graph showing the relationship between the support position diameter and the vertical displacement in the case of a Poisson's ratio of 0.42 and equidistant three-point support.

FIG. 11 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0.42 and the equidistant four-point support is used.

FIG. 12 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0.42 and the case is circumferentially supported.

FIG. 13 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0 and equidistant three-point support is used.

FIG. 14 is a graph showing the relationship between the support position diameter and the vertical displacement in the case of a Poisson's ratio of 0.4999 and equidistant three-point support.

FIG. 15 is a graph showing the relationship between the support position diameter and the vertical displacement in the case of a Poisson's ratio of 0 and equidistant four-point support.

FIG. 16 is a graph showing the relationship between the support position diameter and the vertical displacement in the case of a Poisson's ratio of 0.4999 and equidistant four-point support.

FIG. 17 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0 and the equidistant 5-point support is used.

FIG. 18 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0.4999 and the equidistant 5-point support is used.

FIG. 19 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0 and the case is circumferentially supported.

FIG. 20 is a graph showing the relationship between the support position diameter and the vertical displacement when the Poisson's ratio is 0.4999 and the case is circumferentially supported.

FIG. 21 is a plan view of a disk supporting device according to an embodiment of the present invention.

FIG. 22 is a plan view showing the support point angle θ and the support position diameter when the support points are shifted in the circumferential direction of the disk.

FIG. 23 is a graph showing a change in vertical displacement when a support point having a support position diameter of 0.90 is changed in the circumferential direction of the disk.

FIG. 24 is a graph showing a change in vertical displacement when a support point having a support position diameter of 0.68 is changed in the circumferential direction of the disk.

[Explanation of symbols]

 10: disk 10a: outer periphery of disk 11: support

Claims (7)

[Claims] 1. A disk to be supported having three or more support portions at equally spaced positions in the circumferential direction, wherein the center of an area occupied by these support portions and the center of the disk correspond to each other, and a disc supporting device to put the plate in a horizontal posture on the supporting portion, the diameter of the disc D _0, when the diameter of the circle passing through the support portions and the D, D / D ₀ is 0. A disk supporting device, wherein the supporting portion is provided at a position of 6 or more and less than 0.7. 2. A disk supporting apparatus according to claim 1, wherein said disk is a Si semiconductor wafer, and said supporting portions are provided at three or four positions in a circumferential direction of said disk. 3. A disk to be supported having three or more support portions at equal positions in the circumferential direction of the disk, wherein the center of the area occupied by these support portions and the center of the disk correspond to each other, and A disk supporting device for placing a plate on the supporting portion in a horizontal posture, wherein when the number of the supporting portions is three or four, the outer circumference of the disk (point B of the outer circumference) on the extension of the supporting point is the support. A disk support device, wherein the support portion is provided at a position having a height equivalent to that of the support portion. 4. A disk to be supported having three or more supporting portions at equal positions in the circumferential direction of the disk, wherein the center of the area occupied by these supporting portions and the center of the disk correspond to each other, and A disk support device for placing a plate on the support portion in a horizontal posture, wherein the disk support device has a support form in which a convex shape appears upward by the number of the support portions. 5. When the number of said support portions is 5 or more and includes circumferential support, the height of the center of said disk is equal to the outer circumference of the disk (outer circumference point A) on the extension of the midpoint between said support portions. 5. The disk supporting device according to claim 4, wherein the supporting portion is provided at a position where the height is the same. 6. When the number of the support portions is three or four, the height of the center of the disk is equal to or greater than the outer periphery of the disk on the extension of the midpoint between the support portions (outer periphery A point). The disk support device according to claim 4, wherein the support portion is provided at a position where the height of the center is equal to or less than the height of the support portion. 7. When the number of the support portions is 5 or more and includes circumferential support, the height of the support portions is equal to or higher than the center of the disk, and the height of the support portions is 5. The disk support device according to claim 4, wherein the support portion is provided at a position which is equal to or greater than the outer circumference of the disk (point B) on the extension of the support portion.