JP2007327812A - Diameter measuring method, and diameter measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of measuring a diameter of a circular diskcapable of measuring the diameter by calculation by eliminating the effect of gravity in the measurement of circular disk such as a wafer etc., capable of measuring the true diameter in no gravity state, by correcting the essentially provided warpage even in the state of no external force into a flat face state a remaining warp of the circular disk provided even in a state of no external force into the correct circular flat disk is obtained by calculation. <P>SOLUTION: The diameter measurement method for calculating under the no gravity state is provided as follows: the reference deviation of the diameter of the reference circular disk approximated by the actual measurement disk being the measurement object supported in a prescribed state is previously calculated, then the diameter of the actual measurement circular disk is measured in the same prescribed supporting state, and the actual measurement diameter in no gravity state is calculated by correcting the actual measurement diameter with the reference deviation amount. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a diameter measuring method and apparatus for measuring the diameter of a disk-shaped body such as a silicon wafer in a non-contact manner.

  In recent years, with the miniaturization of design rules, etc., values such as flatness, deflection, and diameter of a disk-like body such as a silicon wafer (hereinafter referred to as a wafer) have been strictly controlled. For example, the allowable diameter value is 300 ± 0.2 mm for a 300 mm wafer, so diameter measurement is still performed using calipers. However, since measurement with calipers is a contact type, there is a possibility of damaging or contaminating the object to be measured, and recently, measurement with calipers has become the final process control as the measurement accuracy has become about several tens of μm. Not suitable for.

For this reason, a non-contact wafer diameter measuring device is currently being developed. As a non-contact measurement method of the wafer diameter, an irradiation optical system that irradiates measurement light to the outer peripheral portion of the wafer at the outer peripheral position of the wafer corresponding to the diameter of the disk-shaped object to be measured, A pair of light receiving optical systems for receiving measurement light irradiated from the irradiation optical system and partially blocked by the outer peripheral portion of the wafer, and calculating the diameter of the wafer based on an optical image by the light receiving optical system Non-contact diameter measuring devices are known as Patent Document 1 and Patent Document 2, for example.
The former measures the diameter by arranging the irradiation optical system and the receiving optical system in the direction perpendicular to the wafer surface, and the latter in the horizontal direction on the wafer surface. The measurement accuracy in this case is on the order of microns.
In the former, the wafer is rotated while the vicinity of the center of the wafer is fixed, and the position of the outer periphery of the wafer at each rotational position is measured to obtain the diameter.
Furthermore, in the latter, the center of the wafer is mechanically fixed, and the diameter is obtained by measuring the position by imaging the outer periphery.
JP-A-6-213620 JP 7-218228 A

As described above, the conventional technology is excellent in that the diameter of the wafer can be measured with high accuracy, but it measures the diameter including the change in diameter due to the influence of deflection based on the weight of the wafer itself. Therefore, it does not measure the true diameter of the wafer in the absence of gravity.
Furthermore, in the conventional method, the diameter including the influence of the warpage inherent to the wafer is observed. However, at the stage of wafer development, there is a case where it is necessary to measure the diameter of the wafer in a state where the warp is forcibly extended, that is, the wafer is chucked and extended on a flat stage.
The conventional diameter measuring apparatus cannot be used for measuring the diameter of a wafer in a state where such a warp is forcibly extended.

Therefore, the present invention has been made in view of the above circumstances, and its first object is to eliminate the influence of gravity in measuring the diameter of a disk-like body such as a wafer, and to make it true in the absence of gravity. It is an object to provide a diameter measuring method capable of measuring the diameter.
The second object of the present invention is to provide a diameter measuring method and apparatus capable of calculating the diameter of a disk-shaped body when the disk-shaped body is flattened by extending the warp originally provided in the absence of external force. It is to be.

The basic invention according to the present application for achieving the above object is as described in claims 1 and 2.
As described above, in the diameter measuring method for measuring the diameter of the disk-shaped body by measuring the outer peripheral position of the disk-shaped body corresponding to the diameter of the disk-shaped body that is the conventional measurement target, The element of change could not be eliminated. On the other hand, in the invention described in claim 1, the reference change amount of the diameter caused by gravity when the reference disc body having the same condition as the actual measurement disc object to be measured is supported in a predetermined support state. Is calculated in advance.
Next, the actual diameter is measured when the actually measured disk-like body that is the object of measurement is actually supported in the same predetermined support state as when the reference change amount is calculated.
Such an actual diameter includes a diameter error corresponding to the reference change amount due to gravity.
Therefore, in the present invention, the actual diameter obtained by the actual measurement is corrected by the reference change amount. As a result, the diameter of the measured disk-like body in the weightless state can be calculated. Since the material of the disk-like body and the dimensional conditions are known, the standard change amount as described above can be applied to both-end support and single-end beam theory, and is known as the amount of deflection due to its own weight and the resulting change in diameter. The calculation method is extremely high. Therefore, the diameter of the measured disk-like body in the weightless state can be calculated with high accuracy by correcting the diameter using the reference change amount.

In order to achieve the second object, the present invention is a diameter measurement for measuring the diameter of the disk-shaped body by measuring the outer peripheral position of the disk-shaped body corresponding to the diameter of the disk-shaped body to be measured. In the method,
In addition to calculating in advance the deflection on the model when a disc-like body supported under a predetermined support state is applied to an appropriate model, the rate of change in the diameter of the disc-like body caused by the deflection on the model is calculated. Calculate in advance,
Measure the actual diameter and deflection of the measured disk when the measured disk is supported under gravity.
Based on the actual diameter and the rate of change of the diameter of the disk-shaped body corresponding to the deflection, a diameter measuring method characterized in that the diameter when the actual disk-shaped object to be measured is extended in a plane is calculated Has been. The concept of deflection includes a deflection distribution.
The change rate of the diameter of the disk-shaped body based on the above-described bending can be appropriately calculated by a known geometric calculation.
In addition, in this method, since a geometric calculation based on the deflection distribution is used, a flat disk-like body having no bending and warping can be obtained as a calculation method.

The measurement diameter is the surface of the disk-shaped body sandwiching the outer periphery of the disk-shaped body at the outer circumferential position of the disk-shaped body corresponding to the diameter of the disk-shaped body or the reference disk-shaped body to be measured. It is possible to measure with an irradiating optical system and a light receiving optical system arranged at right angles or parallel to each other.
Further, as an example of the predetermined support state, a disk-shaped body is supported at three points on the outer peripheral portion, that is, a three-point support is representative.

  Further, when the disk-like body is supported by the three-point support as described above, two of the three points that support the disk-like body are arranged in the vicinity of the diameter measuring points by the irradiation optical system and the light receiving optical system. Is desirable.

Further, when the measurement method according to claim 1 is regarded as an apparatus,
In a diameter measuring apparatus for measuring the diameter of the disk-shaped body by measuring the outer peripheral position of the disk-shaped body corresponding to the diameter of the disk-shaped body to be measured,
Means for supporting the actual disc-shaped object to be measured;
The reference change amount of the diameter caused by gravity when the reference disk-like object approximated to the actual measurement disk-like object to be measured is supported in a predetermined support state is calculated and held in advance, and the actual measurement object that is the measurement object By correcting the actual diameter when the disk is actually supported in the same predetermined support state as when calculating the reference change amount with the reference change amount, the diameter of the measured disk-like body in the weightless state is calculated. It is grasped as a diameter measuring device characterized by comprising a computer for calculation.
Specifically, the irradiation optical system and the light receiving optical system arranged at right angles or parallel to the surface of the disk-like body across the outer periphery of the disk-like body, and the reference change amount of the diameter caused by gravity calculated in advance. A configuration including a computer holding data is preferable.

Further, when the method according to claim 2 is regarded as an apparatus,
In a diameter measuring apparatus for measuring the diameter of the disk-shaped body by measuring the outer peripheral position of the disk-shaped body corresponding to the diameter of the disk-shaped body to be measured,
Means for supporting the actual disc-shaped object to be measured;
When the disc-like body supported under a predetermined supporting state is applied to an appropriate model, the deflection on the model is calculated and held in advance, and the diameter of the disc-like body generated by the deflection on the model is maintained. Calculate the rate of change in advance,
Based on the actual diameter of the actual disk and the rate of change of the diameter of the disk corresponding to the deflection when the actual disk is measured under gravity, the actual disk is measured A diameter measuring device characterized by calculating a diameter when stretched automatically is grasped.
Specifically, with the outer periphery of the disk-shaped body sandwiched between, the irradiation optical system and the light-receiving optical system disposed at right angles or in parallel with the surface of the disk-shaped body, and the surface of the disk-shaped body move The structure provided with the non-contact distance meter which measures the bending of a disk shaped body is preferable.

  As described above, according to the present invention, it is possible to accurately measure the diameter of a disk-like body in a weightless state, that is, in a state where there is no influence of gravity. Further, according to the present invention, it is possible to calculate the diameter of a flat disk-shaped body in which the warpage of a warped disk-shaped body is forcibly extended.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
1 is a plan view showing a state in which the wafer is supported at three points by the diameter measuring apparatus according to the first embodiment of the present invention, FIG. 2 is a side view of the measuring apparatus shown in FIG. 1, and FIG. FIG. 4 is a conceptual diagram showing the principle of diameter calculation in the apparatus shown in FIGS. 1 and 2, FIG. 4 is a side view showing the deflection of the wafer in the diameter measuring apparatus according to the second embodiment, and FIG. The conceptual diagram which shows the principle of the diameter measuring apparatus which concerns on this embodiment, FIG. 6 is a conceptual diagram for demonstrating the measuring object in this invention.

Hereinafter, a case where the diameter of a wafer is measured as an example of a disk-shaped body will be described as an example. The present invention can be similarly applied to disks other than wafers.
An object to be measured according to the present invention will be described with reference to FIG.
FIG. 6 shows three wafers U1, U1, U3 indicated by one central point. U1 represents a wafer without warping in the absence of gravity. In this case, the wafer U1 is perfectly flat as shown, and the diameter of the wafer U1 is D1.
On the other hand, the wafer U2 is also in a state where there is no gravity, but a wafer whose diameter is D2 because the warp is generated in the same shape (that is, the diameter) as the wafer U1 even in the state where there is no external force. Show. Therefore, D1> D2.
Further, U3 shows a wafer whose diameter is further reduced because the warpage caused by gravity is applied to the wafer U2 which has been warped as described above, in addition to the deformation caused by the warp. The diameter in this case is D3.
That is, D1>D2> D3
Note that U4 in the figure indicates a wafer that is bent due to the originally unwarped wafer U1 being placed in a gravity field and has a smaller diameter than the wafer U1.

In the present invention, there are a first embodiment and a second embodiment described below. In either case, the diameter of the wafer causing the deflection by supporting the wafer in the field of gravity is measured, and the measured value is measured. Is used to calculate the diameter of the wafer in any of the states shown in FIG.
For example, in the first embodiment described below, the diameter of a wafer such as U3 (or U4) placed in the gravity field is measured, and the diameter of the wafer such as U2 (or U1) is obtained by calculation. To do.
In the second embodiment, the diameter of a wafer such as U3 (or U4) placed in the gravity field is measured, and the diameter of the wafer stretched on a flat plate such as U1 is obtained by calculation. Is.
This figure shows the case where the wafer is supported at one central point for easy understanding, but in the actual embodiment described below, a disk-shaped wafer is supported at three points on the outer periphery. Note that the vertical direction of deflection occurs in the opposite direction to that of FIG.

[First Embodiment]
In the diameter measuring apparatus according to the first embodiment, when measuring the diameter of the wafer that is the actual measurement object, the wafer W is horizontally aligned by three pins P1, P2, and P3 as shown in FIGS. Point support. In this state, the position coordinates of the outer peripheral positions K1, K2 of the wafer corresponding to the diameter of the wafer W are measured.
The position coordinates of the outer peripheral positions K1 and K2 are perpendicular or parallel to the surface of the wafer W with the outer peripheral part of the wafer W sandwiched between the outer peripheral part of the wafer W corresponding to the diameter of the wafer W to be measured. It is measured by the irradiation optical system and the light receiving optical system arranged in the above. Such an optical diameter measuring method itself is the same as that described in Patent Document 1 or 2.

FIG. 2 shows a case where the optical axes of the irradiation optical system and the light receiving optical system are arranged perpendicular to the surface of the wafer W. That is, light sources LED1 and LED2, which are an example of an irradiation optical system having a vertical optical axis, are arranged below the positions corresponding to the outer peripheral positions K1 and K2 of the wafer W, and the optical axes are shared above the light sources LED1 and LED2. Light receiving portions S1 and S2 such as a CCD camera as an example of a light receiving optical system are provided. The light source and the light receiving unit are arranged so that the outer peripheral positions K1 and K2 of the wafer W cross the light beams from the light sources LED1 and LED2 to the light receiving units S1 and S2.
As a result, as shown in FIG. 3, images J1 and J2 in which the outer peripheral portions K1 and K2 of the wafer W are shown at the center are output from the light receiving portions S1 and S2 to the computer PC. The coordinates of the outermost peripheral part at the outer peripheral positions K1 and K2 in both the images J1 and J2 are coordinates corresponding to the diameter.
As described above, when the irradiation optical system and the light receiving optical system are arranged on the optical axis perpendicular to the surface of the wafer W, the position of the outermost peripheral portion in the horizontal section of the wafer is measured. On the other hand, when the irradiation optical system and the light receiving optical system are arranged on the optical axis in the direction along the surface of the wafer W, the position of the outermost peripheral portion in the vertical cross section of the wafer is measured.

As described above, when the wafer W is horizontally arranged and supported at three points, its own weight acts on the wafer W and bends downward, so that its diameter D is slightly larger than that in the weightless state. In the conventional diameter measuring method that adopts the actually measured diameter as it is, the error due to the weight of the wafer W cannot be avoided.
In order to solve this problem, in the first embodiment, in the diameter measuring method for measuring the diameter of the wafer by measuring the outer peripheral position of the upper wafer corresponding to the diameter of the wafer to be measured as described above, When a reference wafer approximated to the target actual measurement wafer is supported in the same predetermined support state as the actual measurement, the reference change in diameter caused by gravity is obtained in advance by calculation or actual measurement. The actual diameter of the actually measured wafer when actually supported in the same predetermined support state as when the reference change amount was calculated is measured, and the actual diameter is corrected by the reference change amount, thereby the actual disk is corrected. The diameter in the weightless state of the object is calculated.

Specifically, it is as follows.
Assuming that the positions of the pins P1 and P2 that support the wafer W are in the vicinity of the light receiving portions S1 and S2 that are the measurement portions of the wafer W, the wafer W is substantially supported by the two pins P1 and P2. It can be said. The pins P3 merely support the wafer W so as not to tilt.
In such a dynamic system, the disk-shaped wafer W is grasped as a simple model supported at both ends by the pins P1 and P2.
In this embodiment, for simplification of calculation as described above, a case where both ends of the wafer W are substantially supported at two points is taken as an example. However, the calculation may be complicated. For example, it should be pointed out that the present invention can be applied to the position of a pin constituting the apex of an equilateral triangle or any other support structure.

In such a dynamic model, if known data such as the density, thickness, and diameter of the wafer to be supported is given, the amount of reduction of the diameter caused by the deflection at that time can be obtained in advance by a known calculation. is there.
Of course, the amount of diameter reduction due to the deflection based on the gravity of such a wafer is measured in advance by conducting an experiment in which a reference wafer approximated to the actual measurement wafer to be measured is supported in the same support state as the actual measurement. It is also possible to acquire by doing.
The amount of diameter reduction is the difference between the diameters D2 and D3 in FIG. 6 or the difference between the diameters D1 and D4. What is important is that the difference between the diameters D2 and D3 and the diameter unless the warp is extremely large, that is, the warp does not affect the dynamic system as a change in weight (or can be ignored). There is no significant difference between the difference between D1 and D4. Therefore, unless the warp is extremely large, the difference between the diameters D2 and D3 and the difference between the diameters D1 and D4 may be considered to be equal, and the reduction amount (U1− U4) may be obtained by calculation or actual measurement.
In this embodiment, the difference in diameter (reduction amount = D1−D4) is called a reference change amount of the diameter.
That is, in this embodiment, when the reference wafer approximated to the actual measurement wafer to be measured as described above is supported in the same supporting state as the actual measurement as described above, the reference change amount of the diameter caused by gravity is expressed as follows: Obtained in advance by calculation or actual measurement.

Next, in this embodiment, the actual diameter when the actually measured wafer that is the measurement target is actually supported in the same predetermined support state as when the reference change amount is calculated is measured. That is, when the actually measured wafer has a warp, the diameter D3 in FIG. 6 is actually measured. When the actually measured wafer has no warp, the diameter D4 is measured.
When the diameter D3 (or D4) reduced based on the gravity of the actually measured wafer W is acquired in this way, the actually measured diameter is corrected with the previously acquired reference change amount. The correction in this case is a simple addition.
In this way, in this embodiment, regardless of whether there is warp or not, the diameter in the gravity field on the measured wafer is corrected by the change amount of the diameter (reference change amount) with or without gravity. It does not matter how much the wafer is warped, and it can correct for changes due to the presence or absence of gravity.

In order to actually measure the diameter of the wafer W, it is necessary to actually measure the distance between the light receiving portions S1 and S2, that is, the distance of the camera constituting the light receiving portion. The position of such a camera is actually measured. That takes a lot of work. Therefore, the following measurement methods can be used.
This will be specifically described with reference to FIG.
An appropriate wafer W0 whose diameter D0 in the weightless state is known in advance is set at the measurement position as shown in FIG. 3, and data of the outer peripheral position at that time is collected so as not to bend. In order to eliminate the bending, a wafer close to a rigid body may be created and the outer peripheral position thereof may be measured. Note that the wafer W0 is used only for acquiring coordinates serving as a reference, and therefore the shape is not limited. For example, a scale with no deflection may be used. After that, the data of the outer peripheral part position in the wafer whose diameter is unknown to be measured is collected.
here,
XR Right outer periphery position when measuring actual wafer XL XL Left outer position when measuring actual wafer
D0 Diameter of reference wafer in zero gravity (known)
XR0 Right outer periphery position at the time of reference wafer measurement XL0 This is the left outer periphery position at the time of reference wafer measurement.
At this time, from the relationship of FIG.
D = D0 + (XR-XR0) + (XL-XL0)
If this is transformed,
D = XR-XL + D0- (XR0-XL0)
Here, since the above D0, XR0, and XL0 are known, the diameter D of the wafer W to be measured can be obtained by calculation if only XR and XL under the gravitational state are measured.

  In this embodiment, when the actually measured wafer includes a warp such as U3 in FIG. 6, only the diameter of the wafer including the warp such as U2 can be measured. It does not determine the diameter of a flat wafer without warping. In the second embodiment described below, the diameter of a flat wafer such as the wafer U1 is determined at once from the diameter of the wafer U3.

[Second Embodiment]
Also in the second embodiment to be described below, the diameter in the gravitational field is actually measured for the wafer W to be measured as in the first embodiment.
Therefore, the method for actually measuring the diameter in the field of gravity including the warp in the wafer W to be measured is the same as in the first embodiment, and the method shown in FIG. 3 is executed.
However, in the second embodiment, the amount of deflection in the wafer W is measured, and the diameter of the flat wafer is calculated from the actually measured diameter using this.

An example will be described with reference to FIGS.
In this embodiment, the amount of deflection dx of the wafer W on which gravity is applied in a state where both ends are supported as shown in FIG. 4 is measured. X represents a position. The amount of deflection can be measured by moving a non-contact distance meter E such as an electrostatic type shown in FIG. 2 along the surface of the wafer W as indicated by an arrow Y and measuring the distance at that time. is there.
As a simple example, a case where the deflection can be approximated by an arc model will be described. The maximum amount of deflection in this case is Δ as shown in FIG. Also, if the measured diameter of the wafer W to be measured is φ ′, the length of the arc forming the approximated arc of the wafer is R, and the center angle of the arc is 2θ,
Geometrically, φ ′ = 2Rsinθ
Δ = R−R cos θ
Since φ ′ and Δ are actually measured, the unknowns R and θ are calculated.
On the other hand, the length of the arc (diameter when the wafer W is extended into a flat plate shape) D is:
Since D = 2Rθ, D can be obtained by calculation using R and θ obtained above.

The method for obtaining more details will be described below.
That is, by moving the non-contact distance meter E, the deflection distribution of the wafer W in the arrow Y direction can be measured.
In general, it is known that in a simple both-end supported beam as shown in FIG. 4, if the deflection distribution is known, the amount of shrinkage due to beam deflection can be obtained by calculation. Therefore, the relationship between the deflection distribution in the various mechanical models as described above for the reference wafer and the shrinkage amount of the wafer diameter at that time is obtained in advance, and the ratio between the original diameter and the reduced diameter is obtained. For example, it is stored in advance as a database. At the time of actual measurement, the deflection distribution of the measurement target wafer W is measured, and the ratio between the stored original diameter and the reduced diameter corresponding to the measured deflection distribution is acquired. Thus, the original diameter of the measurement target wafer W, that is, the diameter of the wafer W stretched in a flat plate shape can be obtained by multiplying the measured diameter of the wafer by the above ratio.

As a modification, in the case of a wafer whose curvature is known to be negligible in advance, the following method can be employed.
That is, for example, using the finite element method or the differential element method, the gravity deflection can be obtained from the silicon shape (diameter and thickness), the elastic constant of the silicon wafer, the gravitational acceleration, and the three-point support position. . Due to gravity deflection, the apparent diameter of the wafer is reduced. The smaller value (d) can also be calculated by the above calculation, so if you calculate the values for typical wafer diameters and thicknesses in advance and hold them on a personal computer as a table, it is due to gravity deflection. The diameter Dflat of the wafer corrected for the decrease can be obtained.
Dflat = D + d
There are actual measurement and calculation as a method for calculating the gravitational deflection in advance.
In the case of calculation, specifically, it can be calculated by the method as described above.
The gravity deflection calculated in advance is stored in the computer PC.

Further, in the above embodiment, two cameras are used for the diameter measurement method. However, the rotation position is added to the wafer holder so that the edge position at an arbitrary position can be observed, and the measurement is performed in the embodiment. You may make it observe the edge of one place with one camera.
In addition to scanning in the XY direction of the XY stage, a wafer rotation drive mechanism may be provided.

The top view which shows the state which supported three points | pieces with the diameter measuring apparatus which concerns on 1st Embodiment of this invention. The side view of the measuring apparatus shown in FIG. The conceptual diagram which shows the principle of the diameter calculation in the apparatus shown in FIG.1 and FIG.2. The side view which shows the bending of the wafer in the diameter measuring apparatus which concerns on 2nd Embodiment. The conceptual diagram which shows the principle of the diameter measuring apparatus which concerns on 2nd Embodiment. The conceptual diagram for demonstrating the measuring object in this invention.

Explanation of symbols

S1, S2 ... Light receiving parts LED1, LED2 ... Light sources K1, K2 ... Peripheral positions P1, P2, P3 ... Pins U1, U2, U3, W, W0 ... Wafer E ... Non-contact distance meter J1, J2 ... Image

Claims (7)

In a diameter measuring method for measuring the diameter of the disk-shaped body by measuring the outer peripheral position of the disk-shaped body corresponding to the diameter of the disk-shaped body to be measured,
Calculate in advance a reference change in diameter caused by gravity when a reference disk similar to the actual disk that is the object to be measured is supported in a predetermined support state.
Measure the actual diameter when the actual disk-shaped object to be measured is actually supported in the same predetermined support state as when the above-mentioned reference variation was calculated,
A diameter measuring method, wherein the actual diameter is corrected with the reference change amount to calculate the diameter of the measured disk-like body in a weightless state. In a diameter measuring method for measuring the diameter of the disk-shaped body by measuring the outer peripheral position of the disk-shaped body corresponding to the diameter of the disk-shaped body to be measured,
In addition to calculating in advance the deflection on the model when a disc-like body supported under a predetermined support state is applied to an appropriate model, the rate of change in the diameter of the disc-like body caused by the deflection on the model is calculated. Calculate in advance,
Measure the actual diameter and deflection of the measured disk when the measured disk is supported under gravity.
A diameter measuring method, comprising: calculating a diameter when a measured disk-like object to be measured is extended in a plane on the basis of the actual diameter and the rate of change of the diameter of the disk-like object corresponding to the deflection.   The diameter is perpendicular to the surface of the disk-like body with the outer circumference of the disk-like body sandwiched between the outer circumference of the disk-like body corresponding to the diameter of the disk-like body to be measured or the reference disk-like body. 3. The diameter measuring method according to claim 1, wherein the diameter is measured by an irradiation optical system and a light receiving optical system arranged in parallel.   3. The diameter measuring method according to claim 1, wherein the predetermined support state supports the disk-like body at three points on the outer peripheral portion thereof.   The diameter measuring method according to claim 4, wherein two of the three points supporting the disc-like body are arranged in the vicinity of a diameter measuring point by the irradiation optical system and the light receiving optical system. In a diameter measuring apparatus for measuring the diameter of the disk-shaped body by measuring the outer peripheral position of the disk-shaped body corresponding to the diameter of the disk-shaped body to be measured,
Means for supporting the actual disc-shaped object to be measured;
The reference change amount of the diameter caused by gravity when the reference disk-like object approximated to the actual measurement disk-like object to be measured is supported in a predetermined support state is calculated and held in advance, and the actual measurement object that is the measurement object By correcting the actual diameter when the disk is actually supported in the same predetermined support state as when calculating the reference change amount with the reference change amount, the diameter of the measured disk-like body in the weightless state is calculated. A diameter measuring apparatus comprising: a computer for computing. In a diameter measuring apparatus for measuring the diameter of the disk-shaped body by measuring the outer peripheral position of the disk-shaped body corresponding to the diameter of the disk-shaped body to be measured,
Means for supporting the actual disc-shaped object to be measured;
When the disc-like body supported under a predetermined supporting state is applied to an appropriate model, the deflection on the model is calculated and held in advance, and the diameter of the disc-like body generated by the deflection on the model is maintained. Calculate the rate of change in advance,
Based on the actual diameter of the actual disk and the rate of change of the diameter of the disk corresponding to the deflection when the actual disk is measured under gravity, the actual disk is measured A diameter measuring device for calculating a diameter when stretched automatically.

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