JPH1026507A - Method and apparatus for measurement of sheet thickness of board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the sheet thickness of a board in a noncontact manner and according to an in-line system even when an object to be measured is a board whose face has uneven parts by a method wherein the board is inserted between a pair of capacitance sensors provided with measuring electrodes which are mutually faced in parallel with conductive films and the capacitance of the sensors is detected. SOLUTION: A measuring apparatus 1 is constituted of one pair of capacitance sensors 2a, 2b which are provided with measuring electrodes and which are arranged and installed so as to be faced with each other. When a board 11 is inserted between the sensors 2a, 2b, electric charges are generated by the measuring electrodes at the sensors 2a, 2b on conductive films 6a, 6b formed on surfaces of the board 11 and on surfaces 6aa, 6ba which are faced with the measuring electrodes at the sensors 2a, 2b, and the sensors 2a, 2b measure capacitances Ca, Cb according to the electric charges. Distances d1 , d2 between the sensor 2a and the board 11 are obtained on the basis of the capacitances Ca, Cb, and a sheet thickness (t) is obtained on the basis of the distances d1 , d2 . The sheet thickness at the inside 7 of the board 11 can be obtained by subtracting the sheet thickness of the conductive films 6a, 6b from the sheet thickness (t).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the thickness of a substrate on which a conductive film is formed, in particular, the thickness of a substrate having an uneven surface in a non-contact manner. Things.

[0002]

2. Description of the Related Art At present, magnetic disks and magneto-optical disks are widely used as recording media, and the thickness of these disks is deeply related to their performance. For example, in the case of a magnetic disk, it is necessary to keep the thickness unevenness of one substrate within the specification for stabilizing the floating of the magnetic head, and to improve the yield of the magnetic disk, the thickness of each disk is increased. Must be managed. In the case of a magneto-optical disk, if the thickness of the disk varies greatly, the distance between the magnetic head for writing and the surface of the substrate changes, leading to a reduction in signal erasing efficiency. Therefore, variations in the thickness of the disk or the like, that is, variations in the thickness of the substrate, must be minimized.

In order to eliminate variations in board thickness,
That is, in order to improve the quality and yield of a recording medium or the like, it is necessary to accurately measure the thickness of the substrate. Currently, there are methods for measuring the thickness of a board, such as direct measurement with a micrometer or a vernier caliper, a method using ultrasonic waves, and irradiating a laser or the like from both the front and back sides of the board to calculate the thickness from information on the position of each side A method using a laser or the like is used.

[0004]

However, in direct measurement using a measuring instrument such as a micrometer or a caliper, the measuring surface of the measuring instrument must be brought into contact with the surface of the substrate.
For example, the surface of the object to be measured such as a magnetic disk or a magneto-optical disk that is in contact with the measuring instrument may be damaged,
Further, in this method, a so-called in-line type measurement in which the substrate is inspected while moving on the inspection line cannot be performed.

Further, in the method using ultrasonic waves, in order to prevent the reflection of ultrasonic waves at the boundary surface due to a large difference in intrinsic acoustic impedance, the ultrasonic sensor and the object to be measured are placed between the ultrasonic sensor and the object to be measured.
It is necessary to place a material whose specific acoustic impedance is not so different from those two, for example, water. Therefore, in this method, the surface of the object to be measured is contaminated with the substance.

In the measurement using a laser, non-contact and in-line measurement is possible, but one or both surfaces of the object to be measured are uneven due to the formation of pit holes such as a magneto-optical disk. In this case, the irradiated laser causes irregular reflection due to the unevenness, so that accurate data cannot be obtained. For this reason, it has not been possible to measure the thickness of a substrate, such as an optical disk, in which an uneven pattern is provided on the surface of the substrate in advance.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above problem. It is an object to provide a method and an apparatus.

[0008]

An object of the present invention is to provide a method for measuring the thickness of a substrate on which a conductive film is formed, the method comprising measuring a thickness of the substrate in parallel with the conductive film and larger than the total thickness of the substrate on which the conductive film is formed. At a predetermined interval, a pair of capacitance sensors having measurement electrodes facing each other is provided, and the substrate is inserted between the pair of capacitance sensors, and the pair of capacitance sensors The distance between the surface of the substrate and each of the paired capacitance sensors is calculated based on the detected capacitance, and the distance and the predetermined interval are used to calculate the distance between the paired capacitance sensors. The thickness of the substrate is measured.

That is, between a pair of capacitance sensors having measurement electrodes facing each other at a predetermined interval from each other,
By inserting the substrate on which the conductive film is formed, each capacitance sensor measures the capacitance according to the distance from the surface of the substrate to each capacitance sensor. The distance to the capacitance sensor can be measured, and the thickness of the substrate can be measured by subtracting this distance from the value of a predetermined interval provided with the pair of capacitance sensors. That is, by adopting such a method, the thickness of the substrate can be instantaneously measured in a non-contact manner, so that the surface of the substrate to be measured is not damaged or stained.

[0010] Another object of the present invention is to provide a method for measuring the thickness of a substrate on which a conductive film is formed, wherein a predetermined interval is set in parallel with the conductive film and larger than the total thickness of the substrate on which the conductive film is formed. Providing a pair of capacitance sensors having measurement electrodes facing each other, inserting the substrate between the pair of capacitance sensors, and providing the substrate and / or the pair of capacitance sensors. While moving the, the distance between the surface of the substrate and each of the pair of capacitance sensors is calculated by the capacitance detected by each of the pair of capacitance sensors, and the distance and the predetermined interval are calculated. Thus, the present invention solves the above problem by a method of measuring the thickness of the substrate, which comprises measuring the thickness unevenness of the substrate between the pair of capacitance sensors.

That is, between a pair of capacitance sensors having measurement electrodes facing each other at a predetermined distance from each other,
By inserting the substrate on which the conductive film is formed, the capacitance sensor measures the capacitance according to the distance from the surface of the substrate to each capacitance sensor. The distance to the capacitance sensor can be measured, and the thickness of the substrate can be measured by subtracting this distance from the value of a predetermined interval provided with the pair of capacitance sensors. Since the measurement is performed by such a method and while moving the substrate and / or the pair of capacitance sensors, it is possible to measure the thickness of a single substrate at a plurality of locations. That is, the thickness unevenness can be measured in a non-contact and in-line manner. At this time, the surface of the substrate to be measured is not damaged or stained, and furthermore, the production control of the substrate can be performed in such a simple process, and the quality and yield of the substrate can be improved. .

[0012] The above-described problem is also caused by a first electrode having a measurement electrode at a position facing one surface of a substrate having a conductive film.
And a second capacitance sensor having a measurement electrode is provided at a position facing the other surface of the substrate and at a position facing the first capacitance sensor. And a substrate thickness measuring device.

That is, when measuring the thickness of a substrate having a conductive film, a position opposed to one surface of the substrate is measured.
A first capacitance sensor having a measurement electrode is provided, and a second capacitance sensor having a measurement electrode is provided at a position facing the other surface of the substrate and at a position facing the first capacitance sensor. It is possible to measure the thickness of a substrate in a non-contact, in-line manner with only a very simple configuration of providing a capacitance sensor.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A substrate having a conductive film formed thereon is inserted between a pair of opposing capacitance sensors at a predetermined interval larger than the total thickness of the substrate. The pair of capacitance sensors measures the capacitance according to the distance between the surface of the substrate facing the capacitance sensor and the capacitance sensor. The value of this capacitance gives the distance between the surface of the substrate and each capacitance sensor, and subtracts the sum of this distance from the known spacing at which the capacitance sensor is provided to obtain the thickness of the substrate. Therefore, the thickness of the substrate can be measured in a non-contact manner, that is, without damaging or soiling the surface of the substrate to be measured.

Further, when an uneven pattern is formed on the surface of the substrate on which the conductive film is formed, the capacitance obtained from the capacitance sensor changes according to the uneven shape. If you calibrate according to the shape and calculate the distance between the surface of the board and the capacitance sensor,
The thickness and unevenness of the thickness of the substrate can be reliably measured without contact.

In addition, by using this method, measurement can be performed while moving the substrate, that is, in-line measurement is possible. At this time, if the pair of capacitance sensors are also moved at the same time, it is possible to measure the thickness unevenness two-dimensionally.

Furthermore, if a plurality of pairs of capacitance sensors are provided, it is possible to measure the thickness unevenness at a plurality of locations in a non-contact manner without moving the pair of capacitance sensors in the in-line measurement of the substrate. Can be. In the case where the thickness unevenness is measured two-dimensionally, the measurement time can be shortened by providing a plurality of pairs of capacitance sensors.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment according to the present invention. This measuring apparatus 1 has two capacitance sensors 2a, 2a, 2b, 2c having a known structure having measuring electrodes of areas Aa and Ab, respectively. 2b. These capacitance sensors 2a and 2b are arranged so as to face each other at a predetermined interval L and form a pair.

In this embodiment, the conductive films 6a and 6b are formed on both surfaces.
The substrate 11 on which (thickness is exaggerated in the figure) is measured, but the entire surface is flush.
That is, the surface of the substrate 11 has no irregularities, but irregularities are formed at the boundaries between the conductive films 6a and 6b and the inside 7 of the substrate. The conductive films 6a, 6
b is made of, for example, aluminum or a magnetic material, and the inside 7 of the substrate 11 is made of an insulator (derivative) such as glass or plastic in this embodiment. Note that this substrate 11
Are transported by a transport means (not shown) which does not hinder the installation of the capacitance sensors 2a and 2b, for example,
The substrate 11 is moved in a direction penetrating the paper surface by two thin belt conveyors or the like that support and transport both edges of the substrate 1.

The apparatus 1 for measuring the thickness of a substrate according to the present embodiment is configured as described above. Next, a method for measuring the thickness will be described.

When the substrate 11 is inserted between the capacitance sensors 2a and 2b of the measuring device 1 by a transport means (not shown), the measurement electrodes of the capacitance sensors 2a and 2b
Of the conductive films 6a and 6b formed on the surface of the substrate 11;
Surfaces 6aa, 6ba of the capacitance sensors 2a, 2b facing the measurement electrodes (indicated by two-dot chain lines in the figure)
Generates electric charges, and the capacitances Ca and C corresponding to the electric charges are generated.
b is measured by the capacitance sensors 6a and 6b. At this time, the capacitance C obtained by the capacitance sensor is the capacitance C
= K × A / d (1) K is the dielectric constant of the measurement area, A is the area of the measurement electrode of the capacitance sensor,
d is the distance between the surface of the substrate and the capacitance sensor.

[0023] Therefore, the capacitance sensor 2a detects the electrostatic capacitance Ca which is obtained by the area Aa / distance d ₁ of the dielectric constant Ka × measuring electrodes of the measuring area, the electrostatic capacitance sensor 2b is
An electrostatic capacitance Cb determined by a dielectric constant Kb of the measurement area × electrode area Ab / distance d ₂ is detected. Here, the dielectric constants Ka and Kb of the measurement area are the dielectric constants of the portions indicated by the alternate long and short dash lines in the figure, and in this embodiment, Ka = Kb, and this measurement is performed in the air. In
Ka and Kb are, of course, the dielectric constants of air. In this equation, Aa and Ab are the areas of the measurement electrodes of the capacitance sensors 2a and 2b as described above, and d ₁ is
It indicates the distance between the upper surface of the electrostatic capacitance sensor 2a and the substrate 11 (i.e. the upper surface of the conductive film 6a), similarly d ₂
Indicates the distance between the capacitance sensor 2b and the lower surface of the substrate 11 (that is, the lower surface of the conductive film 6b).

In this embodiment, the dielectric constant Ka of the measurement area is
Since Kb and the areas Aa and Ab of the measurement electrodes are constant,
The distances d ₁ and d ₂ are determined by the obtained capacitances Ca and Cb.
Is obtained. In the present embodiment, since the capacitance sensors 2a and 2b are provided at a predetermined distance L from each other, if the obtained distances d ₁ and d ₂ are subtracted from L,
The plate thickness t is determined. That is, the plate thickness t is t = L− (d
₁ + d ₂ )... (2) When obtaining the thickness of the inside 7 of the substrate 11, the thickness of the conductive films 6a and 6b may be subtracted from the obtained thickness t.

Therefore, in this embodiment, the thickness t of the substrate 11 can be accurately measured without contact. Also, substrate 1
When the calculation for obtaining the thickness t of 1 is performed by a computer or the like, the thickness t of the substrate 11 is obtained instantaneously. Furthermore,
When the substrate 11 passes between the capacitance sensors 2a and 2b while moving, that is, in the in-line measurement, the thickness t of the substrate 11 (between the capacitance sensors 2a and 2b) is successively increased. Substrate 1
The thickness unevenness of No. 1 can be measured.

Next, a second embodiment of the present invention will be described with reference to FIG. 2. The same parts as those in the above embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

The measuring apparatus 1 of the present embodiment is the same as the above-described embodiment, except that the shape of the substrate 21 to be measured is different. In the substrate of this embodiment, conductive films 6a 'and 6b' (which are made of, for example, aluminum or a magnetic material as in the above embodiment) are formed on both surfaces of the substrate 21 as in the above embodiment. Unlike the above embodiment, the conductive films 6a 'and 6b' have an uneven pattern formed on the surface of the conductive films 6a 'and 6b' along the pattern of the unevenness of the inside 7 '. In the present embodiment, the plate thickness t 'of the substrate 21 is shown as the center of the conductive films 6a' and 6b 'where the uneven pattern is formed. The inside 7 'of the substrate 21 is made of an insulator (derivative) such as glass or plastic, as in the above embodiment.

When such a substrate 21 passes through the pair of capacitance sensors 2a, 2b, the conductive film 6 is applied to the measurement electrodes of the capacitance sensors 2a, 2b in the same manner as in the above embodiment.
Charges appear on the surfaces 6aa ′, 6ba ′ of the a ′, 6b ′,
The capacitance according to the charge is expressed by the capacitance sensors 2a, 2a
b measures. However, in this embodiment, the conductive film 6
Since an uneven pattern is formed on the surfaces of a ′ and 6b ′, the apparent surface area increases, that is, the surfaces 6aa ′ and 6aa ′ of the conductive films 6a ′ and 6b ′ of the present embodiment.
The area of 6ba 'is the same as that of the conductive films 6a and 6b of the first embodiment.
Are larger than the areas of the surfaces 6aa and 6ba of the first embodiment, the capacitance obtained by the capacitance sensors 2a and 2b is larger than the capacitance obtained in the first embodiment having no irregularities. Therefore, as in the present embodiment, the conductive films 6a 'and 6b'
If the surface has irregularities, the capacitance sensor 2a,
Substrate 21 and the electrostatic capacitance sensor 2a calculated by the equation (1) based on the electrostatic capacity obtained from 2b, the distance between 2b is the actual distance d ₁ ', d _2' is calculated shorter than.
However, since the increase in the capacitance is due to the pattern of the concavo-convex shape on the surface of the substrate 21, the capacitance obtained in advance from a substrate having a concavo-convex pattern similar to the substrate 21 to be measured, The relationship between the thickness of the substrate and the actually obtained thickness (for example, in a destructive inspection) is determined.
The distance d ₁ ′, d ₂ ′ is obtained by obtaining the value of the capacitance that has increased due to the presence of the uneven pattern, and calibrating the distance that has been determined short based on the increase in the capacitance.
Get. Accordingly, the plate thickness t ′ and the plate thickness unevenness of the substrate 21 in the present embodiment can be calculated from the equation (2) (where d ₁ is d).
'The, d ₂ to d _{2' 1} substitutes) can be determined accurately.

Actually, the electrode diameter of the capacitance sensor is set to 0.
Using a measuring method of the present invention, a 6 mm-thick substrate 21 was used as in the present embodiment, and a substrate 21 having a concavo-convex pattern on both surfaces of the conductive films 6a 'and 6b' of the substrate was measured. Then, when the measured value was compared with the measured value of the thickness unevenness by the destructive inspection, the error was 0.2 μm or less. That is, this measurement method can measure the thickness unevenness with almost the same accuracy as the accuracy by the destructive inspection. In addition, when using an optical micro displacement meter to measure the thickness unevenness of the substrate 21 having the uneven pattern on both surfaces, the measured value shows a fluctuation of ± 50 μm or more and cannot be used for practical use. Was.

Next, a third embodiment of the present invention will be described with reference to FIG.
The same reference numerals are given to the same parts as in the above embodiment, and the detailed description thereof will be omitted.

The measuring apparatus 1 used in this embodiment is the same as the above-described embodiment, except that the shape of the substrate to be measured in this embodiment is different. In the above embodiment, the conductive film is formed on both surfaces of the substrate. In the present embodiment, the conductive film 6a ″ is formed only on one side of the substrate 31, in the drawing, above the substrate 31 (this is the same as in the above embodiment). Further, in the present embodiment, the portion other than the conductive film 6a ″ of the substrate 31, that is, the lower portion 7 ″ is an insulator (dielectric material) such as glass or plastic. The conductive film 6a ″ of the substrate 31 facing the capacitance sensor 2a has an uneven pattern on the surface similarly to the conductive film 6a ′ of the second embodiment, but has a lower portion. The lower surface of 7 "is formed flush with no irregularities.

The substrate 31 of this embodiment has a conductive film 6
Since a ″ is provided, the distance d ₁ ″ between the upper surface of the substrate 31 and the capacitance sensor 2a is measured in the same manner as in the second embodiment. That is, since the unevenness is formed on the surface facing the capacitance sensor 2a, the area of the surface 6aa ″ is larger than that without the unevenness, and therefore, the expression (1) is obtained from the capacitance obtained by the capacitance sensor 2a. Is shorter than the actual distance d ₁ ″, but the distance d between the upper surface of the substrate 31 and the capacitance sensor 2 a is calibrated by correcting the increase in capacitance due to the uneven pattern.
₁ "can be obtained.

On the other hand, although the conductive film is not formed on the lower surface of the substrate 31 as described above, the capacitance sensor 2b
Is used, the distance d ₂ ″ between the lower surface of the substrate 31 and the capacitance sensor ₂ b can be accurately obtained.
That is, by the measurement electrode of the capacitance sensor 2b,
In the lower portion 7 "made of an insulator, electrostatic induction occurs at a portion 7b" indicated by a three-dot chain line, so that charges corresponding to the electrostatic induction are generated. Accordingly, when the distance from the capacitance sensor 2b to the lower surface of the substrate 31 changes, the charge due to the electrostatic induction generated according to the distance changes. If the capacitance is calibrated, the distance d ₂ ″ between the capacitance sensor 2 b and the lower surface of the substrate 31 can be accurately obtained.

At this time, the upper surface 7a ″ of the lower portion 7 ″
(The mesh portion in FIG. 3)
It is considered that a charge opposite to the charge generated on the lower surface of the substrate 31 is generated. However, since the upper surface 7a ″ is in contact with the conductive film 6a ″, the charge is formed on the lower surface 6ab ″ of the conductive film 6a ″ so as to cancel the charge. Is thought to occur. Therefore, the lower 7 "
Does not have any effect on the capacitance obtained by the upper capacitance sensor 2a, therefore, based on the capacitance obtained from the capacitance sensor 2a, The distance d ₁ ″ is obtained.

Then, the thickness t ″ of the substrate 31 of this embodiment is
Are the capacitance sensors 2a, 2b
Distance d ₁ ″ and distance d ₂ ″ obtained above from the distance L
By pulling, i.e. the thickness t of the substrate 31 ', from the formula (2) (d ₁ provided that the d ₁ "and substitutes d _2" to d ₂₎
I get it. Therefore, also in this embodiment, as in the above-described embodiment, a non-contact and accurate plate thickness can be measured.

When a conductive film is formed only on one surface of the substrate, and when the substrate itself other than the conductive film is made of a conductor such as a metal, the conductive film is formed on the other surface of the substrate. It can be considered in the same manner as in the first and second embodiments in which the film is formed. That is, when there is no unevenness on the surface of the substrate, the thickness of the substrate can be accurately obtained in a non-contact manner by measuring the distance between each capacitance sensor and the surface of the substrate as in the first embodiment. When the surface of the substrate has irregularities, the distance between each capacitance sensor and the surface of the substrate is measured as in the second embodiment, and the substrate is calibrated by the irregularities. The thickness can be accurately measured without contact. Even in this case, when measuring the thickness of the substrate, the thickness unevenness can be accurately measured even in an in-line method in which the substrate moves.

While the above embodiment of the present invention has been described above, the present invention is, of course, not limited to this, and various modifications can be made based on the technical idea of the present invention.

For example, in the above embodiment, the thickness and the thickness unevenness were measured using a pair of capacitance sensors.
As shown in FIG.
When 1 moves in the direction of arrow F, if a plurality of pairs (three pairs in the figure) of capacitance sensors are arranged without being aligned in the direction of movement, the thicknesses of different portions of the substrate can be measured simultaneously.
Further, as shown in FIG. 4, one-dimensional thickness unevenness in the moving direction on the substrate may be measured, but the substrate and / or the pair of capacitance sensors are moved vertically, horizontally, and diagonally to May be measured two-dimensionally.

In the above embodiment, the shape of the substrate was not mentioned. However, the present invention is not limited to the rectangular substrate shown in FIG.
The thickness of 1 can also be measured in a non-contact manner.
In this case, the disk-shaped substrate 51 is moved in one direction, for example, as shown in FIG.
It is of course possible to carry out the measurement in the in-line method by transporting in the direction of arrow F ′ in
Can be rotated in the direction of arrow r to measure the concentric thickness and unevenness of the thickness. Further, when the disc-shaped substrate 51 is rotated, the pair of capacitance sensors 2a, 2b
Is moved in the radial direction of the disk, that is, in the direction indicated by the arrow G, whereby the thickness unevenness over the entire surface of the disk-shaped substrate 51 can be measured. At this time, for example, a plurality of pairs of capacitance sensors 2a and 2b to be moved
With this arrangement, the thickness unevenness over the entire surface of the substrate 51 can be measured in a shorter time.

Further, in the above embodiment, the conductive film is provided on the surface of the substrate. However, even when the conductive film is inside the substrate, that is, the calibration as described in the lower part 7 ″ of the third embodiment is performed downward. If the same is applied not only to the capacitance sensor 2b provided on the substrate but also to the capacitance sensor 2a provided on the upper part, the thickness and unevenness of the thickness of the substrate on which the conductive film is formed other than on the surface can be measured. That is, if the conductive film is provided inside the substrate, the influence of the measurement electrode of each capacitance sensor does not affect the capacitance detected by the other capacitance sensor. Therefore, the distance between the capacitance sensor and the surface of the substrate can be accurately obtained only by performing the calibration as described in the lower part 7 ″ of the third embodiment, that is, the thickness of the substrate can be accurately determined. Can get to In the above embodiment, a substrate having irregularities inside and on the surface has been described. However, it is needless to say that the thickness of a substrate having no irregularities can be measured.

Further, if the area of the measuring electrode of the capacitance sensor is reduced, the number of points of the thickness for judging the thickness unevenness can be increased, so that the thickness unevenness can be measured in a finer range. .

[0042]

The method and apparatus for measuring the thickness of a substrate according to the present invention described above have the following effects.

With a simple configuration in which a pair of capacitance sensors is provided, the thickness of a substrate having a conductive film can be measured in a non-contact, accurate, and instantaneous manner. Therefore, the surface of the substrate to be measured is not damaged or stained. This measuring method can also be used in an in-line method in which a substrate is inspected on a measuring line.

Further, if the thickness measurement of this method is used, the thickness of the substrate can be measured at a plurality of positions on the substrate by moving the substrate and / or the pair of capacitance sensors. Since the thickness unevenness can be measured, the quality of the substrate and the yield of the substrate can be improved. In addition, production management can be performed with simple processes.

[Brief description of the drawings]

FIG. 1 is a front view of a board thickness measuring apparatus showing a board thickness measuring method according to a first embodiment of the present invention.

FIG. 2 is a front view of a main part of a board thickness measuring apparatus showing a board thickness measuring method according to a second embodiment of the present invention.

FIG. 3 is a front view of a main part of a board thickness measuring apparatus showing a board thickness measuring method according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a first modified example of the present invention.

FIG. 5 is a diagram showing a second modification of the present invention.

[Explanation of symbols]

2a, 2b ... Capacitance sensor, 6a, 6a ', 6
a ", 6b, 6b '... conductive film, 11, 21, 31 ...
_{Substrate, d 1, d 1 ',} d 1 ", d 2, d 2', d 2" ...
... distance between the capacitance sensor and the surface of the substrate, L ... distance between the capacitance sensors, t, t ', t "... plate thickness of the substrate.

Claims (6)

[Claims] 1. A method for measuring a thickness of a substrate on which a conductive film is formed, comprising: a step of measuring a thickness of a substrate in parallel with the conductive film and at a predetermined interval larger than a total thickness of the substrate on which the conductive film is formed; Providing a pair of capacitance sensors having opposed measurement electrodes, inserting the substrate between the pair of capacitance sensors, and detecting the capacitance detected by each of the pair of capacitance sensors. Calculating a distance between the surface of the substrate and each of the pair of capacitance sensors; and measuring a thickness of the substrate between the pair of capacitance sensors from the distance and the predetermined interval. A method for measuring the thickness of a substrate. 2. The method according to claim 1, wherein the substrate is a substrate having an uneven pattern on both sides or one side. 3. The method according to claim 1, wherein said conductive film is provided on a surface of said substrate. 4. A method for measuring the thickness of a substrate on which a conductive film is formed, comprising: a step of measuring a thickness of a substrate parallel to the conductive film and at a predetermined interval larger than a total thickness of the substrate on which the conductive film is formed; Providing a pair of capacitance sensors having opposed measurement electrodes, inserting the substrate between the pair of capacitance sensors, while moving the substrate and / or the pair of capacitance sensors, Based on the capacitance detected by each of the pair of capacitance sensors, a distance between the surface of the substrate and each of the pair of capacitance sensors is calculated. From the distance and the predetermined interval, A method of measuring the thickness of a substrate, comprising measuring unevenness in the thickness of the substrate between capacitance sensors. 5. The method according to claim 4, wherein a plurality of said pair of capacitance sensors are provided. 6. A first capacitance sensor having a measurement electrode is provided at a position facing one surface of a substrate having a conductive film, and a first capacitance sensor having a measurement electrode is provided at a position facing the other surface of the substrate.
A second capacitance sensor having a measurement electrode is provided at a position facing the capacitance sensor.