JPH0422443B2 - - Google Patents

Description

Detailed Description of the Invention [Summary of the Invention] The present invention provides a surface profile measuring device for measuring surface waviness or surface roughness on a sample to be measured or a sample to be processed. Processing) Laser light is irradiated onto the sample, the reflected light is incident on the top of the prism, and the amount of reflected light distributed from the top to the left and right sides of the prism is detected by a photodetector and a differential amplifier is used. The present invention relates to a surface shape measuring device which obtains a surface inclination by using a method, and obtains a height from this value.

[Industrial application field]

The present invention relates to a surface shape measuring device, and more particularly to a surface shape measuring device that uses an optical stylus to measure surface roughness, waviness, etc.

[Conventional technology]

In a magnetic disk device, a magnetic head is used to write and read information, and the flying height from the disk surface to the slider of the magnetic head is 0.2μ.
However, if there are undulations or rough irregularities on the surface of the disk, the slider on which the magnetic head is mounted may fall into the troughs of the undulations or ride on top of the undulations, making it impossible to extract the signal or causing the magnetic head to hit the disk. Generally, it is necessary to suppress the waviness or roughness of the surface of a magnetic disk to 0.05 μm or less. For this reason, it is necessary to measure the height (waviness and roughness) of the surface of the sample to be measured (processed), which is a magnetic disk carrier, and maintain it at a constant value. A stylus-type surface roughness meter has been known as a device for measuring the shape of a sample surface. This surface roughness meter can measure roughness with an accuracy of about 0.001 μm, but since it measures vertical movement with a needle with a radius of about 4 μm placed on the surface of the sample to be measured, it is not only a destructive test but also slows down the measurement speed. It has the disadvantage of being slow (about 10 seconds/mm).

Furthermore, examples of conventional optical non-contact measurement are shown in Professor DJ Whitehouse's special lecture materials (sponsored by the Japan Society of Precision Machinery Engineers, September 1960). A surface shape measuring device is known that detects the difference in spot diameter due to the deviation of the reflected wave by focusing on the spot.

This method can detect surface waviness and roughness with an accuracy of about 0.001 μm, and has the feature of being a non-destructive test, but it has the problem of short measurement length and slow measurement time.

[Problem that the invention seeks to solve]

The optical spot method mentioned above generally has a resolution of 1.6 μm.
There was a problem that the resolution was fixed and the resolution could not be adjusted. Furthermore, since the spot diameter is as small as 1.6 μmφ, the longer the measurement length, the more measurement points will be required. X
- If the Y stage has accuracy errors in the vertical direction due to vibrations, etc., the focus position will change, which not only requires increasing the accuracy of the stage, but also makes it difficult to block the vibrations of the drive system to an amplitude of 1 nm or less. There was also the problem that the measurement time was extremely slow, on the order of 3 mm/minute. In addition, the above-mentioned materials introduce a method of detecting the tilt of an object from the angle of reflection of light and detecting surface displacement, but the vibration of the object also poses a problem in achieving high accuracy. Ta.

[Means for solving problems]

The present invention was made in view of the above-mentioned drawbacks, and its purpose is to provide a surface profile measuring device that can perform non-contact surface profile inspection at high speed, has a long measurement length, and has variable measurement resolution. to do,
The means includes an X-Y direction moving stage on which a sample to be measured is placed, a parallel laser beam from a laser light source is reflected by one reflecting mirror surface of a pair of reflecting mirrors, and the reflected laser beam is directed to the stage. The surface to be measured of the mounted sample to be measured is irradiated with light, and the specularly reflected light from the surface to be measured is reflected by the other reflecting mirror surface of the pair of reflecting mirrors, as described below.
and an optical system that directs the light toward each apex of the second beam splitting prism, and an optical system that splits the light given by the optical system into two parts with the apex as a border in a direction corresponding to the first direction on the surface to be measured. 1 beam splitting prism, and a second beam splitting prism which is orthogonal to the first direction on the surface to be measured, and splits the light given by the optical system into
A second beam splitting prism splits the beam into two with the apex as the border in a direction corresponding to the direction of a first photodetector pair that detects the displacement of the beam according to the inclination in one direction; and the second beam splitting prism.
The first photodetector pair is arranged perpendicularly to the first photodetector pair, which receives each of the divided beams and detects the displacement of the beam according to the inclination of the measured surface in the second direction. a second photodetector pair and a differential sensor for obtaining tilt values in the first and second directions on the surface to be measured based on displacements of beams respectively detected by the first and second photodetector pairs; When the amplifying means and the surface to be measured are scanned in the X-Y direction, the position coordinates in the scanning direction are used as independent variables, and the slope values sequentially obtained by the differential amplifying means according to the scanning are used as dependent coefficients. , an arithmetic circuit that obtains a height distribution of the surface to be measured by independently integrating the dependent variable in the first and second directions with respect to the independent variable. achieved by.

[Effect]

The surface profile measuring device of the present invention irradiates a sample to be measured with laser light from a laser light source via a pair of reflecting mirrors, makes the reflected light enter the top of a beam splitting prism, and from the top, the left and right sides of the resolving prism A pair of photodetectors receives the displacement according to the incident displacement, and calculates this based on the difference output between the pair of photodetectors to detect height components such as waviness and roughness on the sample surface. This is what I did. Note that an example using a beam splitting prism and a pair of photodetectors is already known.

〔Example〕

Hereinafter, the surface profile measuring device of the present invention will be described in detail with reference to FIGS. 1 to 4. Fig. 1 is a schematic diagram of the surface profile measuring device of the present invention, and Fig. 2 is a characteristic diagram for explaining the beam splitting prism and a pair of photodetectors used in Fig. 1. It shows the output difference between a pair of photodetectors with respect to the amount of movement. Figure 3 is a schematic diagram of the lens system that changes the beam diameter of the laser beam, and Figure 4 shows the beam diameter and the observed surface height of the sample to be measured. FIG.

In FIG. 1, reference numeral 1 is a sample to be measured such as a magnetic disk, and an aluminum disk is ground and coated with magnetic particles. This sample to be measured is
A laser beam from a laser source 3 placed on an axially movable X-Y stage 2 and emitting a He-Ne (helium-neon) laser of, for example, about 5 mW passes through at least two reflecting mirrors in a triangular shape. The laser beam is made incident on one of the reflecting mirrors of the pair of reflecting mirrors or the reflecting prism 4 formed in the above, and the surface of the sample to be measured 1 is irradiated with the laser beam reflected by the reflecting mirror. The laser beam reflected by the sample to be measured is incident on the half mirror 7 via the other of the pair of reflecting mirrors 4 . The laser beam that has passed through the half mirror 7 is incident on the top (edge) 5a' of the beam splitting prism 5a in order to detect the surface inclination within the X-Z plane of the sample to be measured 1, and is detected by the displacement from the top to the left and right. Accordingly, the amount of light is applied to photodetectors 6a and 6b consisting of photomultipliers and the like arranged on the left and right sides of the beam splitting prism. The laser beam reflected by the half mirror 7 is directed to the top (edge) 5 of a beam splitting prism 5c for detecting the surface inclination in the Z-Y plane of the sample 1 to be measured.
c′, and the amount of light corresponding to the displacement from the top to the left and right is detected by the photodetector 6c, which is composed of Hol multipliers etc. arranged on the left and right sides of the beam splitting prism,
6d. At this time, if the height direction changes on the upper surface of the sample to be measured 1, the reflection direction of the reflected laser beam changes as shown by the broken line, and the incident position with respect to the tops of the beam splitting prisms 5a and 5c moves. If this amount of movement is d, the amount of light incident on the photodetectors 6a, 6b and 6c, 6d changes as the ratio of the laser beam being divided by the apexes 5a', 5c' changes. The outputs of the pair of photodetectors 6a, 6b and 6c, 6d are output by two sets of differential amplifiers 8a,
8b and an integrating circuit 9.
It is added to an arithmetic circuit 9 consisting of a and 9b. Note that an example using a beam splitting prism and a pair of photodetectors is also described in the aforementioned special lecture materials.

Figure 2 is a graph showing the relationship between the moving amount d of the laser beam incident on the top of the beam splitting prism and the difference output between the photodetectors 6a, 6b and 6c, 6d. Shows the state of being hit by a laser beam. The range in which this graph maintains linearity depends on the voltage applied to the photodetector, the intensity of the light source, etc.

The procedure for measuring with the above configuration is to first place a standard reference disk on the X-Y stage 2, and output the outputs from the photodetectors 6a, 6b and 6c, 6d to the differential amplifiers 8a, 8b. The beam splitting prism position is adjusted in advance so that the difference is zero, that is, the outputs of the differential amplifiers 8a and 8b are zero, and then the sample to be measured 1 is placed on the X-Y stage 2.
The coordinate system (x,
y, z) are determined as shown in FIG. Positional coordinates x _i (i=1, 2,
3...) for the photodetector 6a, 6b or 6c,
If the output difference of each of 6d is v _i (i=1, 2, 3...), then θ _i on the irradiated surface is xz, in the xy plane θ _i = d _i /2l=k/2lv _i ...( 1).

Here, d _i is the amount of movement of the laser beam on the beam splitting prism, k is the slope of the calibration line shown in FIG. 2, and l is the distance from the surface of the sample 1 to be measured to the beam splitting prisms 5a and 5c. Now, considering the xz plane in the x-axis direction, when θ is sufficiently small, θ _i ≒
Since tanθ _i =dz/dx, dz/dx _x=xi =k/2lv _i (2) The slope of the sample to be measured can be obtained. Each point of the position coordinates obtained in this way is integrated into the integrating circuit 9a,
If we integrate using 9b, we can find the height distribution on the xz plane. _In ^other words _{, z i =} 〓 ⁱ _{( dz /} dx) Δx _i =
x _i+1 −x _i, where c is an integral constant. Δx _i =Δx=const
In the end, z _i =k・Δx/2l 〓 ⁱ v _i +c ...(4) This calculation is performed by the integrating circuit 9a in the arithmetic circuit 9.
It will be held in Further, the surface inclination dz/dy in the yz plane of the sample 1 to be measured is detected by the beam splitting prism 5c and the photodetectors 6c and 6d, and the height is determined in the same manner as the above equations (2) to (4).

Another embodiment of the invention will be further explained with reference to FIG. That is, this shows a means for changing the resolution when measuring a sample to be measured, and a lens system 10 shown by a broken line is provided in the laser optical path between the laser source 3 and the pair of reflection mirrors 4. As shown in FIG. 3, this lens system 10 changes the diameter through which the laser beam passes through a pinhole 10a. If the diameter of the pinhole is increased, the diameter of the light spot on the sample becomes smaller, and a finer surface of the sample to be measured can be detected. In FIG. 3, in the optical path of the laser beam emitted from the laser source 3 shown by the solid line, which is not constricted by a pinhole, the laser beam incident on the sample is reflected by the beam splitting prism 5 through a pair of reflection mirrors 4.
The spot diameter when projected onto the top of a or 5b is the value shown by D ₁ , but the laser beam is focused through a lens system including a pinhole 10a and irradiated onto the sample 1 as shown by the broken line, and its reflection is The spot diameter of the laser beam incident on the beam splitting prism 5a or 5b is _D2 , and the relationship _D1 > _D2 holds. The beam diameter may be changed by changing the irradiation distance. FIG. 4 shows how the measurement resolution depends on the diameter of the laser beam incident on the surface to be measured when measuring the surface to be measured. Figure 4a shows the observation surface height (waviness) on the vertical axis when the diameter of the laser beam projected onto the sample surface is 0.5 mm, and time on the horizontal axis, and Figure 4b shows The diameter of the laser beam projected onto the sample surface is 0.1 mm, the vertical axis is the observation surface height (roughness), and the horizontal axis is time.If the laser spot diameter is made smaller, the sample surface becomes finer. structure can be detected. In a configuration without the lens system 10 described above, the spot diameter of the laser beam becomes relatively large, and only a surface structure with a gentle periodicity corresponding to this spot diameter can be measured. In other words, when the laser beam diameter is about 70μmφ, it is 140μm.
At 700 μm, surface roughness with a period of approximately 1.4 mm can be detected with an accuracy of 0.01 μm.

The feature of this device is that the sample 1 can be heated by 1 to 2 μm due to vibration etc.
The reflection angle of the laser beam does not change even if it moves up and down.
It was confirmed through actual measurements that a surface waviness sample accuracy of 0.01 μm could be obtained. This is because when the beam reflection angle at the sample surface is set to 2°, a vertical movement of about 2 μm corresponds to a beam position change of 0.07 μm at the top position of the light splitting prism, which is within the sample error. .

FIG. 5 shows another embodiment of the surface profile measuring device of the present invention. FIG. 6 is a waveform explanatory diagram of FIG. 5.
In FIG. 5, parts that are the same as those in FIG.
Outputs a, b and c, d of b, 6c, 6d, respectively
are added to differential amplifiers 8a and 8b via preamplifiers 8d, 8c and 8f and 8e, and summation amplifiers, that is, adder circuits 8g and 8h, add a+b.
and c+d, and the outputs are passed through logic circuits 8i and 8j such as gate circuits to integrator circuits 9a and 9.
Add to b. With this configuration, the sixth
As shown in Figure a, there is dust 1 on the surface 1a of the sample to be measured.
1 or scratch 12, the differential amplifier 8
The outputs of a and 8b are as shown in Figure 6b.
gives data regarding the slope of the adder circuit 8.
The output of g, 8h is the dust 11 as shown in Figure 6c.
Laser light incident on a sample to be measured that is scratched or scratched is scattered and the detection output level decreases. For this reason, the output that has become below a predetermined slice level 13 is taken out in advance, and a defect determination pulse 14 for detecting and determining defects such as dust and scratches is input into the integrating circuits 9a and 9b as shown in FIG. 6d. Do not perform measurements, etc.

Figures 7a, b and 8 show other embodiments of the invention. FIG. 7 is a flowchart showing the manufacturing process of a conventional magnetic disk, and FIG. 7b is a flowchart showing the manufacturing process of the magnetic disk of the present invention. Figure 8 shows a system diagram when processing and measuring a workpiece (magnetic disk) using the surface profile measuring device of the present invention. The system is designed to conduct an inspection before adding value to the product.

That is, conventionally, in order to process and measure a sample to be measured (processed) such as a magnetic disk, the surface of the aluminum disk is ground 15 as shown in FIG. Coating 16 is performed, and in the next third step, the product is subjected to electrical writing, reading inspection and surface inspection 17, and if it is found to be defective, it is discarded 19 or undergoes processes such as re-grinding and re-coating. Good products are shipped as products 18. However, magnetic disks that are found to be defective are often discarded as is, and for this reason, a second disk with added value added by a coating film of magnetic particles is used.
The entire process is wasted. Therefore, in the present invention, the seventh
As shown in FIG. b, after polishing 15 of the aluminum disk, a surface inspection 17a is performed using the surface shape measuring device of the present invention, and defective products can be re-ground immediately, while good products can undergo the next third step of magnetic particles. The coating film 16 is applied, and the electrical inspection 17b is performed again. If the product is defective, it will be recoated, and if it is good, it will be shipped as product 19. Surface inspection is performed before the process that does not add value yet, resulting in a significant yield improvement, and grinding and surface inspection. Since these can be performed simultaneously, it is considered to be of great help in 100% inspection and in saving inspection time.

The above-described specific configuration is detailed in FIG.

In Figure 8, instead of processing and inspecting industrial products separately as described above, processing and inspection are performed simultaneously to save inspection time, constantly check the processing process, and improve yield. 20 is the sample 1 to be measured (processed) on the lathe.
is attached to the sample support stand 21. Reference numeral 22 denotes a grinding tool such as a cutting tool, which is used to finish the surface of a sample to be measured such as an aluminum disk.
Immediately after performing such processing, the surface is inspected with the sample 1 still attached. This inspection device 2
3 can use the above-mentioned surface profile measuring device shown in FIG. 1, but a commercially available non-contact surface roughness meter (Kosaka Institute HIPOS-ET10) or the like may also be used.

The output of the inspection device 23 is given to a signal processing circuit 24 to measure the magnetic disk, that is, the sample 1 to be measured in the radial and circumferential directions (only the X and Y directions are shown in FIG. 1, but measurement in the circumferential direction is also possible). Information on surface roughness and waviness is obtained as measurement data 25. A comparing circuit 27 compares this measurement data 25 with reference data 26 having predetermined roughness tolerances (level 1 and level 2). That is, when the signal level is lower than level 1, it is determined to be normal. If an abnormality appears in the surface roughness or waviness that exceeds the slice level, the control circuit 28 controls the drive circuit 2 depending on the degree of abnormality.
9 or the alarm generator 30, and the drive circuit 29 moves the position of the cutting edge of the tool (bite) 22 to cope with deterioration due to wear of the cutting edge of the cutting tool. Moreover, when level 2 is exceeded, the alarm generator 30 issues a tool exchange command and the tool 22 is exchanged (conversion may be performed automatically; for example, a plurality of cutting tools are rotated and brought into contact with the machined surface).

In this way, the cutting status can be checked at all times,
Tool replacement, which was conventionally done periodically without any solid reason, can now be done based on cutting data.

〔Effect of the invention〕

Since the present invention is constructed and operated as described above, the surface shape can be inspected at high speed in a non-contact manner, and the measurement length is long and the measurement resolution can be easily varied. Furthermore, the present invention has the feature that a surface shape measuring device capable of inspecting scratches, dust, etc. on the surface can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the surface shape measuring device of the present invention,
Figure 2 is a diagram showing the amount of movement of the top of the beam splitting prism versus the output difference of the photodetector, Figure 3 is a schematic diagram of the optical system for varying the measurement resolution, Figure 4 a,
b is a waveform diagram showing the relationship between the spot diameter and the observed surface height, FIG. 5 is a schematic diagram showing another embodiment of the surface shape measuring device of the present invention, and FIG. , a flaw detection waveform diagram, FIGS. 7a and 7b are magnetic disk manufacturing process diagrams, and FIG. 8 is a system diagram of a surface profile measuring apparatus showing still another embodiment of the present invention. 1... Sample to be measured, 2... X-Y stage, 3
...Laser source, 4...Pair of reflection mirrors, 5a,
5b...beam splitting prism, 5a', 5b'...top, 6a, 6b, 6c, 6d...photodetector, 7...
...Half mirror, 8...Amplifying means, 8a, 8b...
... Differential amplifier, 8c to 8f ... Preamplifier, 8
b, 8h...Addition circuit, 8i, 8j...Logic circuit, 9...Arithmetic circuit, 9a, 9b...Integrator circuit,
10... Lens system, 10a... Pinhole, 11
... Dust, 12 ... Scratch, 13 ... Slice level, 14 ... Defect determination pulse, 15 ... Grinding of aluminum disk, 16 ... Coating film of magnetic particles,
17... Inspection (electrical, surface), 17a... Surface inspection, 17b... Inspection (electrical), 18... Product,
19...Disposal, 20...Lathe, 21...Sample support stand, 22...Tool, 23...Inspection device, 24...
Signal processing circuit, 25...Measurement data, 26...Reference data, 27...Comparison circuit, 28...Control circuit, 29...Drive circuit, 30...Alarm device.

Claims (1)

[Claims] 1. An X-Y direction moving stage on which a sample to be measured is placed; a parallel laser beam from a laser light source is reflected by one reflecting mirror surface of a pair of reflecting mirrors, and the reflected laser beam is is irradiated onto the surface to be measured of the sample to be measured placed on the stage, and the specularly reflected light from the surface to be measured is reflected by the other reflecting mirror surface of the pair of reflecting mirrors to perform the first and second steps described below. Second
an optical system that directs the light toward each top of the beam splitting prism, and a first beam that splits the light given by the optical system into two in a direction corresponding to the first direction on the surface to be measured, with the top as the border. a splitting prism; a second beam splitting prism that splits the light provided by the optical system into two parts at the top in a direction corresponding to a second direction perpendicular to the first direction on the surface to be measured; and a first photodetector that receives each of the beams obtained by dividing into two by the first beam splitting prism and detects the displacement of the beam in the first direction on the surface to be measured according to the inclination. and the first beam splitting prism receives each of the beams obtained by dividing into two by the second beam splitting prism, and detects the displacement of the beam according to the inclination of the measured surface in the second direction. a second photodetector pair disposed perpendicularly to the photodetector pair; and a second photodetector pair arranged at right angles to the photodetector pair; and a differential amplifying means for obtaining a tilt value in a second direction; when the surface to be measured is scanned in the X-Y direction, position coordinates in the scanning direction are taken as independent variables; an arithmetic circuit that obtains the height distribution of the surface to be measured by independently integrating the dependent variable in the first and second directions with respect to the independent variable, using slope values sequentially obtained by the amplification means as dependent coefficients; A surface shape measuring device comprising: 2. A patent claim characterized in that a laser beam diameter adjusting means for adjusting the diameter of the laser beam from the laser light source is disposed in the optical system to adjust the diameter of the reflected light given to the beam splitting prism. The surface shape measuring device according to item 1. 3 sum output detection means for calculating the sum of the respective outputs of the first photodetector pair and the sum of the respective outputs of the second photodetector pair; 2. The surface shape measuring device according to claim 1, further comprising a defect determining means for determining defects on a sample to be measured. 4. The surface shape measuring device according to claim 1, wherein the pair of reflecting mirrors of the optical system are prisms. 5. An optical system of the surface shape measuring means is provided near the sample to be processed, and the processing tool for the sample to be processed is determined based on the output obtained by comparing the height distribution output obtained from the optical system and the photodetector with a standard reference level. The surface shape measuring device according to claim 1, characterized in that the surface shape measuring device is controlled. 6. An optical system of the surface shape measuring means is provided near the sample to be processed, and the height distribution output obtained from the optical system and the photodetector is compared with a standard reference level. The surface shape measuring device according to claim 1, characterized in that the device is configured to control an alarm means for notifying the time of replacement.