JPH06259816A - Method for measuring thickness of stamper - Google Patents

Abstract

PURPOSE:To exactly measure the thickness of a stamper with high precision by measuring the thickness of the stamper after the influence due to the inclination in the stamper being a subject to be measured is eliminated. CONSTITUTION:The stamper formed on a glass plate is set to a movable stage 7. Then, the movable stage 7 is moved and a measuring position is aligned. A laser displacement gage 1 and the laser displacement gage (measuring istrument) 1a are rotated around a central line 4, and a rotation angle where the displacement becomes maximum or minimum is obtained. The value of the displacement gage when the meter is rotated by 90 deg. from the rotation angle becomes a real value. The operation is performed by the laser displacement gages 1 and 1a independently, and the thickness of the stamper is obtained from these values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the thickness of a stamper for manufacturing a substrate for an optical recording medium.

[0002]

2. Description of the Related Art An optical recording medium is for recording / reproducing information by detecting the presence or absence of pits by the reflection of an irradiated laser beam. Therefore, in order to quickly record and reproduce desired information, the guide groove is required to quickly move the laser light to a predetermined place (high speed access). The width and depth of the guide groove vary depending on the laser beam diameter and control method, but in the case of an optical disk, the groove width is usually 0.8
The groove width is about 2.5 μm, the groove pitch is about 12 μm, and the groove depth is about 1000 to 3000 Å.

Such a fine concavo-convex pattern is transferred to the substrate by a nickel stamper which is a hard material. There are various methods such as an injection method and an extrusion molding method, but most of them use a stamper having a thickness of several tens μm to several hundreds μm.

A stamper having a thickness of several tens of μm to several hundreds of μm is manufactured as follows. A guide groove pattern is formed on the glass with a thickness of about 10 mm with resist or the like, and a nickel conductive film is formed on this surface by sputtering to a thickness of several thousand Å.
The film is formed to a degree. Electroforming is performed on this surface to change the nickel film thickness from several tens of μm to several hundreds of μm. This nickel is polished to a predetermined thickness and peeled from the glass to obtain a stamper. During this polishing, the thickness of the nickel stamper cannot be directly measured because it cannot be separated from the glass. Therefore, for example, a laser displacement meter was used to measure the polished surface side and the glass surface side of the stamper, and the thickness of the stamper was calculated from the difference.

[0005]

However, in the above conventional example, it was difficult to accurately measure the thickness of the nickel stamper. The reason for this is as follows.

The laser displacement meter irradiates an object to be measured 12 with incident light (irradiation light) 11 of laser light as shown in FIG.
The displacement of the object to be measured is measured from the position of the reflected light 13 on the light receiving surface of the light receiving sensor 14. Therefore, the unit vector of the traveling direction of the irradiation light

[0007]

[Outer 1]

And a plane including the light receiving surface (paper surface in FIG. 2)
A unit vector that is the normal vector of the DUT

[0009]

[Outside 2] Is the unit vector in the direction of travel of the irradiation light

[0010]

[Outside 3] If the relation of the following formula (I) is not always satisfied, accurate measurement cannot be performed.

[0011]

[Equation 1]

However, when nickel is sputtered and electroformed on glass, more or less stress is usually generated. As a result, the glass will be somewhat distorted. This distortion changes the direction of the normal vector of the surface to be measured, and as a result, the laser displacement meter value deviates from the true value.

The present invention has been made in order to remedy the above drawbacks of the prior art. A machine groove for rotating a measuring laser and a measuring instrument having a light receiving surface is provided, and the above (I) is provided.
The purpose is to measure the thickness of the stamper accurately and accurately by measuring the condition with the effect of the tilt of the stamper removed so that the formula is satisfied.

[0014]

That is, according to the present invention, when measuring the thickness of a stamper formed on a glass plate in a method of manufacturing a stamper, a portion irradiated with laser light and reflected light from an object to be measured are measured. In the method of measuring the thickness of the stamper by arranging laser displacement gauges on both sides of the stamper that measures the displacement of the measured object from the position where the reflected light is received, The stamper thickness measuring method is characterized in that the thickness of the stamper is measured in a state where the influence of the inclination of a certain stamper is eliminated.

In the present invention, a laser displacement meter having a laser light irradiation portion for measuring displacement and a reflected light receiving portion thereof detects a means for rotating about a central axis of symmetry and an inclination of an object to be measured. It is preferable that the laser displacement meter is rotated so that the inclination of the object to be measured does not affect the measurement.

The means for detecting the inclination of the object to be measured is
The means for detecting the distribution of the light receiving position when the laser displacement meter is rotated or the inclination of the object to be measured is a means for irradiating the object to be measured with a laser beam parallel to the central axis of rotation of the laser displacement meter. A means for receiving the reflected light, and a method for detecting the inclination of the object to be measured by the position of the received reflected light are preferable.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the embodiments shown in the drawings.

Example 1 FIG. 1 is an explanatory view showing one embodiment of a stamper thickness measuring method of the present invention. In FIG. 1, 1 is a laser displacement meter (measuring instrument), 2 is a nickel stamper, and 3 is a glass plate. The measuring instrument of the laser displacement meter of No. 1 has means capable of rotating about its center line 4. When the stamper that is the object to be measured has an inclination, the reflected light position 21 on the light receiving surface of the light receiving sensor 14 changes as shown in FIG. 3 when the laser displacement gauge measuring device 1 is rotated. In FIG. 3, 22
The positions of 22a and 22a are shown in FIG.

[0019]

[Outside 4] Is the position when the value of becomes maximum and minimum, from which the laser displacement meter (measuring device) 1 is rotated by 90 °,

[0020]

[Equation 2] When the above condition is satisfied, the position of the reflected light on the light receiving surface comes to the position of 23 in FIG. DUT (Stamper)
As for the distance between and, the value calculated from these 23 positions is the true value.

The actual thickness of the stamper is measured by the following procedure. First, the stamper formed on the glass plate is set on the moving stage 7. Next, the movable stage is moved to match the measurement location. The laser displacement gauges (measuring instruments) 1 and 1a are rotated about the center line 4 to find the rotation angle at which the displacement becomes maximum or minimum (the reflected light comes to the position 22 or 23 in FIG. 3). The true value is the value of the displacement meter when it is rotated 90 ° from the rotation angle. This operation is independently performed by the laser displacement meters 1 and 1a, and the stamper thickness is obtained from those values. After that, the stage is moved to the next measurement point and the above work is performed again.

Here, a laser displacement meter (LD-2510) manufactured by Keyence Corporation is used as one laser displacement meter, and a stage with a pulse motor (KS manufactured by Sigma Optical Co., Ltd., KS) is used.
LD-2500 manufactured by KEYENCE CORPORATION was used as the conversion calculator 5 which controls the rotation of the laser displacement meter (measuring device) No. 1 by rotation control at H-80PM).

Embodiment 2 As shown in FIG. 4, in addition to the displacement measuring laser 10 and the light receiving sensor 14, a tilt detecting laser 16 for detecting the direction of the normal vector of the object to be measured 12 and a tilt detecting light receiving. A device provided with the sensor 17 was used.

The laser light emitted from the laser 16 for detecting the tilt of the semiconductor laser with a collimator is the object to be measured 1
The two measurement points are illuminated. A unit vector indicating the traveling direction of the reflected light

[0025]

[Outside 5] Is the normal vector of the surface to be measured

[0026]

[Outside 6] , A unit vector indicating the traveling direction of the incident light

[0027]

[Outside 7] Then, the following expression (II) is satisfied.

[0028]

[Equation 3]

That is, the traveling direction of the reflected light is determined by the direction of the normal vector of the surface to be measured. Therefore, FIG.
In (a), a unit vector indicating the traveling direction of the tilt detection reflected light 20 for checking the direction of the surface to be measured

[0030]

[Outside 8] When the shaded reflected light 20 for tilt detection coincides with the incident light when shaded on a plane including the light receiving surface (the paper surface in FIG. 4A), the above formula (I) is established.

That is, as a light receiving sensor for detecting the reflected light 20 for tilt detection, for example, a vertical two-divided light receiving sensor 17 for tilt detection as shown in FIG. 4C is used, and the left and right (17A, 17B) thereof are used. When the laser displacement meter of the measuring instrument is rotated about the center line 4 and aligned so that the light amounts become equal, the above formula (1) is established. In FIG.
To obtain the installation location of the light receiving sensor 17 for tilt detection,
18 polarization beam splitters are used.

The method of measuring the thickness of the stamper is almost the same as that of the first embodiment.
The laser displacement meter of the measuring instrument of 1 is rotated so that the difference (17A-17B) of the light receiving sensors of 1 is 0. Therefore, compared with the first embodiment, there is an effect that the rotation time of the laser displacement meter of the measuring instrument 1 is significantly shortened and the measurement time is shortened.

[0033]

As described above, according to the present invention, the thickness of the stamper can be accurately measured by measuring the thickness of the stamper without the influence of the inclination of the stamper. There is.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a stamper thickness measuring method of the present invention.

[Fig.2] Principle diagram of displacement measurement

[Fig. 3] Position of reflected light when the laser displacement meter is rotated

FIG. 4 is an explanatory view showing another embodiment of the stamper thickness measuring method of the present invention.

[Explanation of symbols]

 1, 1a Laser displacement meter 2 Nickel stamper 3 Glass plate 4 Center axis 5 Displacement calculator 6 Displacement / thickness converter 7 Movable stage 10 Laser for displacement measurement (with collimator) 11 Incident light (irradiation light) 12, 12a DUT 13, 13a Reflected light 14 Light receiving sensor 15 Normal vector 16 of the surface to be measured 16 Tilt detection laser 17 Tilt detection light receiving sensor 18 Polarization beam splitter 19 Tilt detection incident light 20 Tilt detection reflected light 21 Reflected light trajectory

Claims (4)

[Claims] 1. When measuring the thickness of a stamper formed on a glass plate in the method of manufacturing a stamper, a portion for irradiating laser light and a portion for receiving reflected light from an object to be measured are arranged. , In the method of measuring the thickness of the stamper by arranging the laser displacement gauges on both sides of the stamper to measure the displacement of the measured object from the position where the reflected light is received, the effect of the inclination of the stamper that is the measured object is eliminated. A method for measuring the thickness of a stamper, which comprises measuring the thickness of the stamper with. 2. A laser displacement meter provided with a laser light irradiation portion for measuring displacement and a reflected light receiving portion thereof has means for rotating about a central axis of symmetry and means for detecting inclination of an object to be measured. The method for measuring the thickness of a stamper according to claim 1, wherein the laser displacement meter is rotated in such a position that the inclination of the object to be measured does not affect the measurement. 3. The stamper thickness measuring method according to claim 2, wherein the means for detecting the inclination of the object to be measured is a distribution of light receiving positions when the laser displacement meter is rotated. 4. The means for detecting the inclination of the object to be measured is means for irradiating the object to be measured with laser light parallel to the central axis of rotation of the laser displacement meter, and means for receiving the reflected light thereof.
The stamper thickness measuring method according to claim 2, wherein the inclination of the object to be measured is detected by the position of the received reflected light.