JP3462963B2 - Wafer processing equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer processing apparatus and, more particularly, to a wafer processing apparatus for placing a wafer on a susceptor, rotating the wafer and heating it with a heater.

[0002]

2. Description of the Related Art In order to deal with ULSI that is highly integrated, high uniformity and high precision are required, and the progress of increasing the diameter of the substrate is remarkable. Also in semiconductor devices, the conventional batch processing is shifting to single-wafer processing. This also applies to the epitaxial device and the CVD device.

The key point in single-wafer processing is throughput. In order to improve the throughput, it is essential to shorten the temperature raising and lowering time, the transfer time, and the high growth rate. Regarding the high growth rate, by rotating the wafer at a high speed of several hundreds of revolutions or more, the thickness of the boundary layer that contributes to the growth becomes thin, the vapor phase reaction is controlled, and the high growth rate becomes possible.

FIG. 1 shows an outline of such a wafer processing apparatus. In FIG. 1, the wafer processing apparatus is configured such that a reaction gas is introduced from a gas supply port 2 at an upper portion of a reaction chamber 1 through a rectifying plate 3, a wafer 6 is introduced from a wafer introduction section 4, and the wafer is placed on a susceptor 5 serving as a holding table. The wafer 6 is rotated around the rotating shaft 7 together with the susceptor 5, and the heater 6 mounted on the lower portion of the wafer 6 heats the wafer 6. The reaction gas is exhausted from the exhaust hole 9 provided in the lower part of the reaction chamber.

FIG. 2 shows a plan view (a) and sectional views (b) and (c) of the susceptor 5 holding the wafer 6.
A through hole 12 is formed in the center of the susceptor 5 so that heat from the heater 8 can pass to the back surface of the wafer 6. The susceptor 5 has a wafer mounting portion 11 for mounting the wafer 6, and the through hole 1 is provided in the wafer mounting portion 11.
A step portion 10 is formed on the outer edge of 2 and is formed into a perfect round counterbore.

When an orientation flat portion (hereinafter referred to as an orientation flat portion) 6a is formed on the wafer 6, an orientation flat mounting portion 11a having a shape corresponding to the orientation flat portion 6a is formed on the wafer mounting portion 11. There is.

[0007]

As shown in FIG. 2A, the conventional susceptor 5 has a step portion 10 (for example, a wafer having a counterbore diameter larger than the diameter of the wafer 6). A wafer mounting portion 11 (for example, a counterbore diameter: 151.5 ± 0.1 mm for a diameter of 150 ± 0.5 mm) and an inner diameter smaller than that of the wafer 6 (for example,
The diameter of the wafer was 150 ± 0.5 mm, and the inner diameter of the wafer mounting portion was 147.5 ± 0.1 mm.

Therefore, the wafer 6 and the susceptor 5 are
When is rotated, even if the center of rotation and the center of the susceptor 5 are made to coincide with each other, a gap is formed between the wafer 6 and the step portion 10, so that the wafer approaches each direction in each case. Therefore, the entire outer peripheral portion 6b of the wafer 6 does not contact the peripheral edge 10a of the step portion 10 uniformly, and the contact regions are unevenly distributed as shown in FIG.

On the other hand, the wafer 6 is heated by the lower heater 8, but the wafer outer peripheral portion 6b is indirectly heated via the wafer mounting portion 11.

Wafer mounting portion 11 and wafer outer peripheral portion 6b
If the contact area of the wafer is uniformly distributed over the entire outer peripheral portion 6b of the wafer, the amount of heat for compensating for the temperature decrease due to the heat capacity of the wafer mounting portion 11 is given to the susceptor 5 itself, so that the heater 8 passes through the through hole. The temperature difference between the central portion of the wafer 6 directly heated by the radiant heat passing through the wafer 6 and the outer peripheral portion 6b of the wafer can be eliminated, and the occurrence of slip can be suppressed.

However, if the contact area becomes non-uniform as described above, the amount of heat applied to the wafer outer peripheral portion 6b also becomes non-uniform, resulting in the problem that a large number of slips occur as shown in FIG.

In order to achieve a high growth rate, high-speed rotation is required. At this time, the wafer 6 vibrates during high-speed rotation due to the influence of rotational vibration and the like, and the counterbore-shaped step portion 10 of the susceptor 5 is used. There was also a problem in that the wafer 6 would come off further and the wafer 6 would be damaged.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer processing apparatus which solves the problems of the prior art, prevents the occurrence of slip, and prevents the wafer from jumping out of the susceptor and cracking.

[0014]

In order to achieve the above object, the wafer processing apparatus of the present invention places a wafer on a susceptor, rotates the wafer around a rotating shaft, and heats it with a heating source such as a heater or a lamp. In the wafer processing apparatus for processing by, the susceptor has a wafer mounting portion for mounting and holding the wafer, the wafer mounting portion of the through hole formed to apply the heat of the heater to the wafer. Having a step portion extended from the outer edge, the peripheral portion of the step portion is formed by a plurality of arcs of different diameters,
One of the plurality of arcs has a diameter substantially equal to the diameter of the wafer.

Further, it is preferable that any one of the plurality of arcs has a diameter substantially equal to the diameter of the wafer and the center of the arc is displaced from the axial center position of the rotary shaft. Characterize.

Further, preferably, the step portion is formed in a counterbore shape.

Further, preferably, the step portion is formed by a plurality of projecting portions which are erected intermittently, and the peripheral portion of the step portion connects the erected surfaces of the plurality of projecting portions. Formed.

Further, the peripheral portion of the step portion is formed by two first arcs and second arcs having different diameters.

The diameter of the first circular arc is the same as the maximum diameter value obtained by adding the tolerance to the center value of the standard values of the diameters of a plurality of wafers to be processed, and the diameter of the second circular arc is the same as the maximum diameter value . It is larger than the diameter of one arc.

The center position of the first circular arc is displaced from the axial center position of the rotary shaft.

The wafer mounting portion has an orientation flat mounting portion for mounting the orientation flat portion of the wafer, and the center position of the first circular arc is displaced from the axial center position of the rotating shaft. To position.

Further, the center position of the first arc, the position and the direction opposite to the orientation flat mounting portion with respect to the axial center position of the rotary shaft, located offset from the axis position of the rotary shaft.

Further, the distance between the axial position of the rotary shaft and the center position of the first circular arc is equal to the distance between the center of gravity of the wafer having an orientation flat portion and the central position of the wafer.

The center position of the second arc is concentric with the center position of the through hole.

Further, the first arc has an arc length that is less than or equal to the arc length of the semicircle.

In addition, a projection that projects in the thickness direction of the wafer is formed in at least a partial region of the periphery of the step.

Further, the protrusion has a thickness of 2 mm.
Has more than double the height.

The operation of the present invention described above will be described.

The peripheral portion of the step portion is formed by a plurality of arcs. The stepped portion may be formed in a counterbore shape, or may be formed by a plurality of protruding portions that are intermittently erected.

When the susceptor on which the wafer is placed is rotated about the rotation axis, the wafer receives centrifugal force and moves so as to approach the peripheral edge of the step. By making one of the plurality of arcs an arc having a diameter substantially equal to the diameter of the wafer, the wafer is subjected to centrifugal force and finally fits into the arc having an approximately equal diameter.

These facts are due to the fact that any one of the plurality of arcs has a diameter substantially equal to the diameter of the wafer and the center of rotation of the arc is displaced from the axial center position of the rotary shaft. It can certainly be realized.

For example, an example in which the peripheral portion of the step portion is formed by the first circular arc and the second circular arc will be described.

Since the diameter of the second circular arc is larger than the diameter of the wafer, the wafer is partially surrounded by the second arc.
It makes a rolling motion to revolve while contacting an arc. While the rolling motion is repeated, the peripheral edge of the wafer, which receives the centrifugal force, fits into the first arc, and while repeating the rotation, the wafer can be stopped by the frictional force with the peripheral portion.

Further, the orientation flat portion is formed on the wafer, and the center of gravity of the wafer is located in the direction opposite to the orientation of the orientation flat portion with respect to the center position of the wafer, so that the wafer rotates while contacting the first arc. In time, the center of gravity comes to be located at a stable position passing through the axial center O, and as a result, the orientation flat portion comes to be located at the orientation flat placement portion.

In this case, by setting the distance between the axial center position O and the center position of the first circular arc so as to match the distance between the center position of the wafer 6 having the orientation flat portion and the center of gravity position, the first circular arc is formed. It becomes possible to easily position the orientation flat portion on the orientation flat placement portion by passing the rotation in the above-mentioned less number of times.

Further, since the projections projecting in the thickness direction of the wafer 6 are formed on the peripheral edge of the step portion, when the wafer revolves around while contacting the peripheral edge, the wafer should come off from the step portion. Can be prevented.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings.

The schematic structure of the semiconductor device of this embodiment is as follows.
As shown in FIG. 7, except for the susceptor 105, it is almost the same as the wafer processing apparatus for high speed rotation growth shown in FIG.
In FIG. 7, the reaction gas is introduced from the gas supply port 2 in the upper part of the reaction chamber 1 through the flow straightening plate 3, and the wafer 6 placed on the susceptor 5 serving as a holding table from the wafer introduction part is rotated by the rotating shaft for each susceptor 5. Wafer 6 by rotating it around 7
It is adapted to be heated by a heater 8 installed below the. The susceptor 105 is made of a carbon material, a silicon compound, or a composite material thereof. Although a heater is used as a heating source of this device, a lamp is not limited to this.

Next, the susceptor 105 in this embodiment will be described in detail with reference to FIGS. 5 and 6.

FIG. 5 shows the susceptor 11 after high speed rotation.
5 shows a state in which the wafer 6 is placed. The axis position of the rotary shaft 7 is O. FIG. 5A is a plan view of the susceptor 105, and FIGS. 5B, 5C, and 5D are each shown in FIG.
It is sectional drawing seen from the line OA, OB, and OC in FIG.

As shown in FIG. 5, the susceptor 105 has a wafer mounting portion 111 formed in a counterbored shape for mounting and holding the wafer 6, and the wafer mounting portion 111 receives the heat of the heater 8 from the wafer. 6 has a step portion 110 at the outer edge of a through hole 112 formed so as to contact the first hole 6 and a peripheral edge portion 110a of the step portion 110 has two different first arcs 115 and second
And arc 116.

The center position 114 (X mark) of the first arc 115
Passes through the axial center position O of the rotary shaft 7 and the orientation flat placement portion 111.
It is located on a straight line AOC that bisects a and is displaced from the axial center position O in the direction opposite to the orientation flat placement portion 111a.

The first arc 115 is an arc having a diameter substantially equal to the diameter of the wafer 6 and is not larger than a semicircle. The diameter of the first circular arc 115 is set equal to the maximum diameter value obtained by adding the diameter tolerance to the center value of the diameter of the group of wafers 6 to be processed.

When the wafer 6 has the orientation flat portion 6a, the axial center position O and the center position 1 of the first arc 115 are set.
It is desirable that the distance to 14 be set so as to match the distance between the center position and the center of gravity of the wafer 6 having the orientation flat portion 6a. Thereby, as described later, the orientation flat portion 6a can be easily located on the orientation flat placement portion 111a.

The second arc 116 is the axial center position O of the rotary shaft 7.
Is an arc having a diameter that is sufficiently larger than the diameter of the wafer 6 with the center at.

The through hole 112 has a diameter smaller than the diameter of the wafer 6 with the center position 114 of the first arc 115 as the center.

As shown in FIG. 5A, the wafer placing portion 111 is provided with an orientation flat placing portion 111a extending from the peripheral edge portion 110a toward the center O so that the orientation flat portion 6a of the wafer 6 can be placed. Has been formed. Further, on both sides of the orientation flat placement portion 111a, the second edge from the outer edge of the through hole 112 is
A region 111b reaching the arc 116 is formed.

The first arc 115 and the second arc 116 intersect at two points 110b and 110b on the peripheral edge 110a. A virtual circular arc portion obtained by virtually extending the first circular arc 115 is indicated by reference numeral 115a. A ring region 111b having the same width is formed between the first circular arc 115 and the virtual circular arc portion 115a and the outer edge of the through hole 112. Further, the orientation flat placement portion 11a also has an orientation flat region 111c formed between the outer edge of the through hole 112 and the width of the ring region 111b.

Further, as shown in FIGS. 5 (a) and 5 (d),
Intersections 110b, 1 at the periphery 110a of the step 110
At a position near 10b and an intermediate position between the intersections 110b and 110b, the thickness of the wafer 6 is reduced by 2 in the thickness direction of the wafer 6.
Protrusions 117, 117, 117 having a height of twice or more are formed. The depth of the step portion 110 shown in the cross section of the OA and OB portions in FIGS. 5B and 5C is approximately the same as the thickness of the wafer 6. The number and height of the protrusions 117 are not limited to this example, and can be appropriately selected.

Next, the operation of this embodiment will be described.

Initially, the wafer 6 is placed so that the center of the wafer 6 substantially coincides with the axial center position O. In this case, in the wafer 6, the orientation flat portion 6a is located at the orientation flat mounting portion 1
It is placed at a position unrelated to the position of 11a.

When the susceptor 105 on which the wafer 6 is placed is rotated around the rotary shaft 7, the wafer 6 receives centrifugal force and moves so as to approach the peripheral edge 110 a of the step portion 110. Since the diameter of the second arc 116 is sufficiently larger than the diameter of the wafer 6 and the center position is at the axial center position O, the wafer 6 partially has the peripheral edge of the second arc 116.
Make a rolling motion so that it revolves around while touching. While the rolling motion is repeated, the peripheral edge of the wafer 6 which receives the centrifugal force reaches the intersection 110b between the first circular arc 115 and the second circular arc 116 and fits into the first circular arc 115.
The diameter of the first circular arc 115 is substantially the same as the diameter of the wafer 6 and is set equal to the maximum diameter value in consideration of the diameter tolerance of the wafer 6 to be processed. If it fits in one circular arc 115, it will only rotate without revolving.

In this way, the wafer 6 rotates about its peripheral edge in contact with the first arc 115. Further, since the orientation flat portion 6a is formed on the wafer 6 and the center of gravity of the wafer 6 is located in the direction opposite to the orientation position of the orientation flat portion 6a with respect to the center position of the wafer 6, the wafer 6 is
While rotating around the circular arc 115, a stable position is obtained at a position where the center of gravity is on the straight line OC. As a result,
The orientation flat portion 6a is located in the orientation flat placement portion 111a or the orientation flat area 111c.

In the above description, while the wafer 6 rotates in the first circular arc 115, the orientation flat portion 6a comes to be positioned on the orientation flat mounting portion 111a, but the wafer 6 becomes the second circular arc 116. By rotating while revolving and rotating while being in contact with each other, the orientation flat portion 6 does not repeat its rotation when it fits in the first arc 115.
It is also possible for a to be located on the orientation flat mounting portion 111a.

Further, at the peripheral edge 110a of the stepped portion 110, the positions near the intersections 110b and 110b and the intersection 110
Since protrusions 117, 117, 117 that protrude in the thickness direction of the wafer 6 are formed at intermediate positions between the wafers 110b and 110b, when the wafer 6 revolves while contacting the peripheral edge 110a, the step 110 causes the wafer 6 to rotate. It can be prevented from coming off and popping out. As a result, in order to achieve a high growth rate, even if the wafer 6 is rotated at a high speed, it is possible to eliminate the risk of the wafer 6 being damaged by being ejected from the step 110 of the susceptor 5.

Next, a specific example of this embodiment will be described.

As the wafer 6, both the conventional example and the present invention have a diameter of 150 mm and a thickness of 625 μm, and the diameter tolerance is ±.
A 0.2 mm Si wafer was used.

In the susceptor 105 shown in FIG. 7, the height of the wafer placing portion 111 and the orientation flat placing portion 111a is 1 mm, the diameter of the through hole 112 at the center of the susceptor 105 is 148 mm, and the susceptor 105 has the meat. Thickness is 1.
The peripheral edge 110a of the stepped portion 110 has a diameter of 152 mm with the axial center position O of the rotary shaft 7 as the center.
From the arc 116 and the axial center position O, the orientation flat mounting portion 110a
Position 1 offset by 1 mm on the straight line OC in the direction opposite to
Centering 14 and taking into account the diameter tolerance of the wafer 7
The first circular arc 115 is a 120 ° fan-shaped arc line-symmetric with respect to a straight line OC having a radius of 5.1 mm. Furthermore, the protrusions 117, 117, 117 having a width of 3 mm, a depth of 1.5 mm, and a height of 1 mm along the first arc 115 at the intersection of the peripheral edge 110a and the straight line OC, and at the edge portion opened 60 ° to the left and right with respect to the straight line OC. Are formed.

With the wafer 6 placed on these susceptors 105, the wafer 6 is rotated at 2000 rpm to rotate the wafer 6 at 11 rpm.
Heated at 50 ° C. for 5 minutes. As a result, in the susceptor 5 of the conventional example, a large number of slips of maximum 7 mm were generated as shown in FIG. It was
Also, the wafer 6 that frequently occurs in the conventional susceptor 5
With respect to the jumping of No., the susceptor 105 of the present invention has no problem.

Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 6 is a conceptual diagram of the susceptor 205. The susceptor 115 shown in FIG. 5 has the concave wafer-deposited wafer mounting portion 110, but the wafer mounting portion 210 of the susceptor 205 shown in FIG. 6 is not concavely recessed. .

The susceptor 205 has a disk 201 on which the wafer 6 is placed, and the disk 201 rotates around the rotary shaft 7 as in the case shown in FIG. On the disk 201, a contour line 210 having the same shape as the peripheral edge 110a of the wafer mounting portion 110 shown in FIG. 5 is formed. The contour line 210 is a first arc 210a corresponding to the first arc 115 and a second arc 210b corresponding to the second arc 116.
It consists of and. On the disk 201 , the first arc 2
A plurality of protrusions 220 and 221 are provided, each of which has three protrusions 220 and 221 arranged so as to circumscribe the 10a and the second arc 210b. That is, the plurality of protrusions 220 and 221 are
It is erected so that the contour line 210 is formed by connecting the erected surfaces 220a and 221a. The heights of the protrusions 220 and 221 are formed by protrusions that are twice as thick as the thickness of the wafer 6.

Specifically, the wafer mounting portion 210 of the susceptor 205 shown in FIG. 6 has a protrusion 221 circumscribing a second circular arc 211b having a diameter of 152 mm centered on the axial center position O of the rotary shaft 7, and a shaft 221. From the center position O to the orientation flat mounting portion 210a
Centering on a position 114 deviated by 1 mm in the direction opposite to, and a projection 220 circumscribing a first arc 211a of 120 ° which is line-symmetrical to a line OC having a radius of 75.1 mm which takes the diameter tolerance of the wafer into consideration. Have These protrusions 2
Widths of 20 and 221 are 3 mm, depth is 1.5 mm, and height is 2 m.
It has a shape of m.

The susceptor 205 is set to 2000 in the state where the wafer 6 is placed, as in the example of the above-described embodiment.
The wafer 6 was heated at 1150 ° C. for 5 minutes while rotating at rpm. As a result, like the susceptor 105, the slip length was as short as 1 to 2 mm, and the number was small. In addition, there was no flight of the wafer 6.

Although the embodiments of the present invention have been described above, in the above description, the wafer 6 has the orientation flat portion 6a and the wafer mounting portion has the orientation flat mounting portion. However, in the present invention, the wafer mounting portion does not necessarily have to have the orientation flat mounting portion,
It is possible to process the wafer 6 that does not have the orientation flat portion 6a. In this case, the second step of the wafer loading section
As shown in FIG. 5 or 6, the arc is not straightly cut for the orientation flat placement portion, and the second arc is formed as a continuous arc. Even in this case, by setting the center position of the first circular arc so as to be displaced from the axial center position O, the wafer 6 receives a centrifugal force as the susceptor rotates, and the wafer finally fits into the first circular arc. It will be crowded.

[0066]

As described above, according to the configuration of the present invention, the peripheral portion of the step portion of the wafer mounting portion is formed by a plurality of arcs having different diameters, and one of the plurality of arcs is formed. Since the arc has a diameter approximately equal to the diameter of the wafer,
Wafers can be fitted into arcs of approximately equal diameter.

Further, any one of the plurality of circular arcs has a diameter substantially equal to the diameter of the wafer, and the center of rotation of the circular arc is displaced from the axial center position of the rotation axis of the susceptor. It is possible to receive force and securely fit into the arc.

As a result, the contact area between the wafer mounting portion and the outer peripheral portion of the wafer can be uniformly distributed over the entire outer peripheral portion of the wafer, so that the occurrence of slip can be suppressed.

The wafer mounting portion has an orientation flat mounting portion for mounting the orientation flat portion of the wafer, and the center position of the first circular arc is displaced from the axial position of the rotation axis of the susceptor. Therefore, the orientation flat portion of the wafer can be surely moved to the position of the orientation flat placement portion, and the occurrence of slip can be suppressed even for the wafer having the orientation flat portion.

Further, since the projections that project in the thickness direction of the wafer are formed on the peripheral portion of the step portion, when the wafer revolves while contacting the peripheral portion, it is possible to prevent the wafer from jumping out of the step portion. Can be prevented. As a result, even when the wafer is rotated at a high speed in order to achieve the growth rate, it is possible to prevent the wafer from vibrating during the high speed rotation and coming off from the stepped portion of the wafer mounting portion and jumping to damage the wafer.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a conventional wafer processing apparatus.

FIG. 2 is a plan view (a) showing a wafer mounting portion of a conventional susceptor and sectional views (b) and (C) showing arrangements of a susceptor, a wafer and a heater as seen from lines OA and OB.

FIG. 3 is a plan view showing a connection region (shaded portion) between the wafer and the susceptor when the wafer is placed on the conventional susceptor shown in FIG. 2 and rotated at high speed.

FIG. 4 is a diagram showing a situation of slips generated on a wafer which is heated at a high speed by using the conventional susceptor shown in FIG.

FIG. 5 is a plan view (a) showing a state of the susceptor and the wafer after the susceptor is rotated at a high speed in one embodiment of the present invention and an arrangement of the susceptor, the wafer and the heater as seen from lines OA, OB and OC. Sectional views (b), (c),
(D).

FIG. 6 is a plan view (a) showing a state of the susceptor and the wafer after the susceptor is rotated at a high speed according to another embodiment of the present invention and an arrangement of the susceptor, the wafer and the heater as seen from lines OA, OB and OC. Sectional views (b), (c),
(D).

FIG. 7 is a sectional view showing a schematic configuration of a wafer processing apparatus of the present invention.

[Explanation of symbols]

1 reaction chamber 2 Reaction gas supply port 3 current plate 4 Wafer inlet 5 Conventional susceptor 6 Waha 6a Orifla part of Waha 7 rotation axis 8 heater 9 exhaust port 110 Wafer mount 110a orientation flat mounting part 112 through hole 115 First arc 116 second arc 117 protrusion 201 disk 210 Wafer mount 210a orientation flat mounting part 211 contour 211a first arc 211b Second arc 220, 221 protrusion 220a, 221a Standing surface of protrusion

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Claims (13)

(57) [Claims] 1. A wafer processing apparatus in which a wafer is placed on a susceptor and rotated around a rotation axis and heated by a heating source such as a heater or a lamp for processing, wherein the susceptor is for holding and holding the wafer. The wafer mounting portion has a step portion extending from the outer edge of a through hole formed so as to apply the heat of the heating source to the wafer, and the peripheral edge portion of the step portion is A wafer processing apparatus, which is formed by a plurality of arcs having different diameters, and one of the plurality of arcs has a diameter substantially equal to the diameter of the wafer. 2. An arc of any one of the plurality of arcs,
2. The wafer processing apparatus according to claim 1, wherein the wafer has a diameter substantially equal to the diameter of the wafer, and the center of the circular arc is displaced from the axial center position of the rotary shaft. 3. The wafer processing apparatus according to claim 1, wherein the step portion is formed in a counterbore shape. 4. The step portion is formed by a plurality of projecting portions that are intermittently erected, and the peripheral edge portion of the step portion is formed by connecting upright surfaces of the plurality of projecting portions. The wafer processing apparatus according to claim 1, wherein the wafer processing apparatus is a wafer processing apparatus. 5. The peripheral portion of the stepped portion has two different diameters of the first portion.
The wafer processing apparatus according to claim 1, wherein the wafer processing apparatus is formed by an arc and a second arc. 6. The diameter of the first arc is the same as the maximum diameter value obtained by adding a tolerance to the center value of the standard values of the diameters of a plurality of wafers to be processed, and the diameter of the second arc is the first diameter. 1
The wafer processing apparatus according to claim 5, wherein the diameter is larger than the diameter of the arc. 7. The semiconductor device according to claim 5, wherein the center position of the first arc is displaced from the axial center position of the rotary shaft. 8. The wafer mounting portion has an orientation flat mounting portion for mounting an orientation flat portion of the wafer, and a center position of the first arc is displaced from an axial center position of the rotating shaft. The semiconductor device according to claim 5, wherein the semiconductor device is located. 9. The center position of the first circular arc is located in a direction opposite to the position of the orientation flat mounting portion with respect to the axial center position of the rotating shaft, and is displaced from the axial center position of the rotating shaft. The semiconductor device according to claim 8. 10. The wafer processing apparatus according to claim 5, wherein the center position of the first arc is concentric with the center position of the through hole. 11. The wafer processing apparatus according to claim 5, wherein the first circular arc has an arc length equal to or less than a semicircular arc length. 12. The wafer processing apparatus according to claim 1, wherein a protrusion that protrudes in the thickness direction of the wafer is formed in at least a partial region of the periphery of the step. 13. The wafer processing apparatus according to claim 12 , wherein the protrusion has a height that is at least twice the thickness of the wafer with respect to the surface on which the wafer is placed.