JPS62235511A - Surface condition inspecting apparatus - Google Patents

Abstract

PURPOSE:To enable quantitative evaluation per each range of surface condition of a specimen surface, by obtaining statistical quantities per each specified range by a reflecting condition of light from a specimen and inspecting the surface condition of the specimen based upon the statistical quantities. CONSTITUTION:A laser beam L emitted from a laser source 1 is turned into a linear polarized light by a polarized light beam splitter 2 and it is irradiated onto a surface 6 of a disk 5. A reflected beam of light R from the surface 6 is received by a light-receiving surface 8 of a bright point detector 7 after passing through the splitter 2. A signal VD issued out continuously from the detector 7 as it scans the surface 6 in this way, is given to a microcomputer 100 and stored in an address corresponding to a coordinate position on the surface 6 inside a memory 103. Upon completion of scanning of the surface 6, such statistical quantities representing surface roughness and the like are determined by calculation per each specified range on the surface (6). Then, a surface condition of the disk 5 is inspected on the basis of the statistical quantities per each specified range.

Description

[Detailed Description of the Invention] (Industrial Application Field) ゛This invention is a surface condition inspection method for inspecting the processing condition (roughness and flaws) of the surface of an object to be inspected, such as a master magnetic disk for a computer. Regarding equipment.

(Conventional technology and its problems) The quality of products such as magnetic disks and semiconductor wafers is greatly affected by the unevenness and flaws that exist on their surfaces. It is necessary to control the quality by inspecting the surface condition for machining corrosion. Various types of surface condition inspection devices have been proposed, but the most typical non-destructive inspection device is an optical inspection device, which has a configuration similar to that of the conventional example (Japanese Patent Publication No. 56-30495). Waveform diagrams are shown in FIGS. 9 and 10, respectively.

In FIG. 9, reflected light 1 obtained by irradiating light onto an object to be inspected (not shown) is received by a light receiver 51 and then filtered by an amplifier 52, as shown in FIG. 10(a). The received light signal becomes U. This received light signal U8 is passed through a high-pass filter 53 to become a signal Ub shown in FIG. 10(b).

This signal @Ub is given to the ground level detection circuit 54,
This ground level detection circuit generates a ground noise envelope signal (shown by a broken line in FIG. 10(b)) of the signal Ub.

The ground noise envelope signal is sent to the first and second discrimination circuits 55.
56, the first discriminator circuit 55 uses this ground noise inclusive signal as a threshold value to output the output signal U of the high-pass filter 53.

When the level of the signal U exceeds the ground noise envelope signal level, the defect detection signal @Uo (Fig. 10 (C
)). On the other hand, in the second discrimination circuit 56, the predetermined set value U is set. The ground noise envelope signal is discriminated using the ground noise envelope signal as a threshold value, and when the ground noise envelope signal exceeds the setting fliUo, a total defect signal U (FIG. 10(d)) is output.

However, such equipment can only qualitatively evaluate the presence or absence of defects and the overall state of roughness; instead, it is necessary to perform a stationary inspection to determine in what area and to what degree machining defects exist on the inspected object. The problem is that it is difficult.

(Objective of the Invention) The present invention is intended to overcome the above-mentioned problems in the prior art, and provides a surface condition inspection device that can quantitatively evaluate the surface condition of the surface of an object to be inspected for each region. The purpose is to

(Means for Achieving the Object) In order to achieve the above-mentioned object, the surface condition inspection apparatus according to the present invention includes: (1) a scanning mechanism that scans a light beam from a light source on the surface of the object to be inspected; a reflected light detection means that detects reflected light from the body surface and sequentially outputs a detection signal according to the state of the reflected light; means for obtaining a predetermined statistic a expressing the condition based on the detection signal, and is configured to inspect the surface condition of the object to be inspected based on the statistic in each section.

Of these, the reflected light detecting means (2) above may be constructed using a light receiving position detecting means that generates a light receiving position detection output according to the receiving position of the reflected light on the light receiving surface, as will be described in detail later. is most preferred.

(Embodiment) Structure and operation of A. FIG. 1 is a schematic block diagram of a surface condition inspection apparatus which is an embodiment of the present invention. The optical configuration and operation of this embodiment will be explained below with reference to FIG. 1.

In the figure, a laser beam L irradiated from a laser light source 1 becomes linearly polarized light by a polarizing beam splitter 2, passes through a quarter-wave plate 3 and a focusing lens 4 having a focal length f, and exits from this lens 4 at a focal length f. The light is incident on the surface 6 of the disk 5, which is the object to be inspected, at the position . Then, the reflected light (reflected beam) R obtained by reflecting the Rade beam L on the disk surface 6 passes through the lens 4 and the 174-wave plate 3 again and enters the polarizing beam splitter 2 again.

Since the reflected light R at this point has passed through the 174-wave plate 3 twice, its polarization direction has been rotated by 90'' with respect to the irradiated laser beam L. Therefore,
The reflected light R passes through the polarizing beam splitter 2 as it is and is received by the light receiving surface 8 of the bright spot position detector 7.

By the way, in this case, the disk surface 6 is flat,
There are no defects or irregularities, and the disk surface 6 is a plane perpendicular to the direction of incidence of the laser beam L (hereinafter referred to as the "reference plane").
, the reflected light R is reflected in the same direction as the incident direction of the laser beam L, and passes through the polarizing beam splitter 2 after traveling in the opposite direction along the incident path of the laser beam L.
pass through. Then, as shown in FIG. 2, which is a partial diagram of FIG. 1, the reflected light R0 enters the reference position indicated by Xo on the light receiving surface 8 of the bright spot position detection B7 as a bright spot.

On the other hand, as shown in FIG.
2 and the reference surface 6a is θ, the reflected light R is reflected at a deflection angle of 2θ with respect to the incident laser beam. Then, the reflected light R after passing through the lens 4 becomes parallel to the incident laser beam L, but there is a polarization of ΔX−f−jan(2θ)−(1) with respect to the incident laser beam. It is causing the rank. Therefore, in this case, ! on the light receiving surface 8! The reflected light R will be incident at a position deviated by ΔX from the 1st level @x0. Therefore, by detecting this ΔX, it becomes possible to obtain the inclination angle θ from equation (1). In addition, since the inclination angle θ is minute in the case of minute bites or undulations on a precision machined surface, the approximate expression for the above equation (1) is Δx=f・2θ・
...(2) can be used.

In this way, the amount of deviation ΔX is determined by the inclination angle θ of the bite defect 21, etc.
Since m is a reflection of the amount of deviation ΔX, it is possible to determine the surface condition of the disk surface 6 based on this amount of deviation ΔX. At this time, in order to detect minute changes in the deviation mΔX as precisely as possible, the bright spot position detector 7 is
It is desirable to use a light-receiving surface whose light-receiving surface 8 is a continuous light-receiving surface. Therefore, in this embodiment, a sensor known as a semiconductor light spot position detector (hereinafter referred to as PSD) is used as the bright spot position detector 7. FIG. 3(a) shows the light-receiving surface 8 of the bright spot position detector 7 constructed using a one-dimensional PSD among such PSDs, and the light taken out from each of the electrodes X and Xb By taking the ratio of the current values, a signal corresponding to the deviation amount ΔX of the received bright spot SP is obtained at the signal level V in FIG. Bind and output. In this operation, since the light-receiving surface 8 is not a collection of discrete elements but has a continuous spread, the light-receiving position can be detected with high precision.

- to number - and Next, the scanning mechanism in this embodiment will be explained.

In this embodiment, when optically scanning the disk surface 6, the disk 5 is moved by the disk moving mechanism 30 shown in FIG. 1, and the optical system is kept fixed. In this disk moving mechanism 30, a motor 3 is attached to the end of the base 31.
3 is provided, and a feed screw 35 extending from this motor 33 causes the slide table 32 to be translated in the horizontal direction (X direction in the figure). This motor 3
3 is provided with an encoder 34 that detects the u-turn angle. Further, on this slide table 32, a motor 37 to which another encoder 36 is attached is fixed, and a disk holder (not shown) provided on the rotor of this motor 37 holds the disk 5 horizontally. The disk 5 is held in the α direction in the figure and rotated.

Therefore, for example, by driving the motor 37, the disk 5
If the other motor 33 is rotated by a predetermined angle each time the motor 33 rotates 360 degrees, the laser beam will be aligned with the disk surface 6.
will be scanned concentrically. Moreover, if the two motors 33 and 37 are rotated at the same time, the disk surface 6 will be scanned in a spiral manner. In this example, it is assumed that the former is the case. In this embodiment, such a disk moving mechanism 30 is used as a scanning mechanism, but the disk 5 is fixed and the front side of the laser beam L is moved by a rotating mirror, a vibrating mirror, etc. for scanning. Other scanning mechanisms may be used as appropriate.

The implementation of C8 is the same as the theory.

Next, while performing such scanning, signals V are output one after another from the bright spot position detector 7 in FIG.

The processing will be explained. This signal VD is amplified by the preamplifier 41 shown in FIG. This bandpass filter 42 is for removing the DC component of the signal 0 and extracting the fluctuation component. The waveform of the signal va after passing through the bandpass filter 42 is shown in FIG. 4(a).
is shown.

On the other hand, the encode signal from the encoder 36 provided in the disk transfer mechanism 30 of FIG. Each time the angle Δα (not shown) is exceeded, the timing signal TS
is applied to the A/D converter 43. The A/D converter 43 A/D converts the input signal Va every time this timing M@TS is input, and outputs it to the microcomputer 100 at the next stage. Therefore, detection signals are given to the microcomputer 10o in the order corresponding to the scanning position on the disk surface 6.

Therefore, below, the operation of this microcomputer 100 will be explained with reference to the flowchart of FIG.

First, I10 circuit 1 of this microcomputer 100
01, it is determined whether or not the interrupt signal INT is applied from the timing circuit 44. This interrupt signal IN
T is a timing signal T to the A/D converter 43
Similar to S, this is a signal generated every time the rotation angle of the motor 37 exceeds a predetermined minute rotation angle. Therefore, on the same circumference, this signal I
NT will be given.

When this INT signal is input to the I10 circuit 101, the microcomputer 100 enters an interrupt state, and the A/
The signal from D converter 43 is captured and stored in memory 103 of FIG. Therefore, this I10 circuit 101 performs the same function as a sampling circuit or a gate circuit. Therefore, hereinafter, the data taken in from the A/D converter 43 in this manner will be referred to as sampling data, and each point on the disk surface 6 from which each sampling data was determined will be referred to as a sampling point.

In this way, the sampling data V as shown in FIG. This is an address corresponding to the coordinates.

This association is performed based on the encoded outputs of encoders 34 and 36. Therefore, when all the sampling data have been taken in, the sampling data has been found in a form that corresponds to the coordinates (ie, scanning positions) of each sampling point. Then, when the scanning of the disk surface 6 is completed and the data import is finished,
Next, we move on to calculation of statistics expressing the roughness of the disk surface 6.

By the way, in this invention, this statistical amount (exampled later) is calculated for each predetermined section on the surface of the object to be inspected, but in this embodiment, as shown in FIG. A region including a predetermined number (nllffi) of the sampling points P in the radial direction is defined as one section. Hereinafter, these sections will be referred to as A1. from the outer circumferential side of the disk 5. A2, . . . and these will be collectively referred to as section A.

Each of these wards rr! Regarding lA, the following can be considered as a statistical quantity that expresses the surface condition (roughness and flaws in this embodiment) within that section.

■ Integral of sampling data ■b in the interval (direct: f V, dx ■ Average value of the absolute value of sampling data V: IVb
l> Among these, the integral value can be approximated by the discrete phase of each sampling data, or a value close to the integral value of the page can be obtained using the trapezoidal formula or the like. moreover,
Considering that the above integral operation (■) is a type of averaging operation, the above (■) to (■) are calculated as the power average (including the negative power) of the amount obtained based on the sampler data (detection signal level) vb. This is an example of a response. However, the statistical quantity in this invention is not limited to the above-mentioned one, but may be any statistical path m that can express the state within the section. In the following, the case of calculating the RMS value (R) corresponding to the above item ``1S'' will be described.

Returning to FIG. 5, when all the sampling data have been stored, the sampling data for the sampling points belonging to section A1 in FIG. 6 is read from the memory 103 in FIG. (
ii Calculate and obtain R, .

For example, for sampling data as shown in section A1 in FIG. 7(a), the value shown in section A1 in FIG. 7(b) is determined as its RMS value Rrl.

Next, this RMSilR is compared with a threshold value R111 set in advance according to the allowable roughness limit (see FIGS. 5 and 7(b)), R<R.

If it is IS, we will directly move on to the calculation for the next interval A2, but if R≧
In the case of RTH, the coordinates indicating that section (for example, the coordinates of the center point of the section) are stored as defect coordinates, and then the calculation for the next section A2 is started.

Then, the calculation for the data in the final section is completed,
Similar processing is performed for other radial directions.

When the surface condition for each section is detected from all the data in this manner, the defect coordinates are displayed on the display 104 in FIG. 1, and an alarm is issued if necessary, thereby completing a series of processes.

Note that the keyboard 105 in FIG. 1 is for inputting various data.

Although one embodiment of the present invention has been described above, this invention is not limited to the above embodiment, and for example, the following modifications are possible. ■ In the above embodiment, , a predetermined section fl in the radial direction of the disk surface 6
The statistical value was determined for each lA because the surface of the disk 7 is processed along the circumferential direction, so unevenness tends to occur in the radial direction, and it is important to detect this. However, the present invention is not limited to the case where statistics are determined for each section in the radial direction, but it is also possible to obtain predetermined sections in the circumferential direction of the disk 7.

Further, the above-mentioned section does not need to be a straight section, and may be a circular or arc-shaped section like the above-mentioned circumferential direction,
It may be a two-dimensional section.

■ In the above embodiment, a one-dimensional PS is used as the reflected light detection means.
D, but as shown in Figure 3(b), the two sets of electrodes (X, X) and (Y, Y,) were
(a) A two-dimensional PSD that is arranged in a perpendicular direction and performs two-dimensional bright spot position detection may be used. At this time, (V,,'') + VDb may be determined based on the outputs ■Da and VDb from each set, and this may be used as the detection output.

In addition, in PSD, the center of gravity position of the reflected light spot x 88 (
Since Fig. 8(a)) has the property of being detected as the offset position ΔX, for example, if there is harmless dust on the disk surface 6, the distribution of reflected light may be disrupted as shown in Fig. 8(b). Detection accuracy is also extremely high because the position of faith [x38] can also be detected. however,
The present invention is also applicable to cases where reflected light from an object to be inspected is captured using means other than PSD.

■ In the above embodiment, the correspondence between the photodetection signal and the scanning position is based on the encoded outputs of the encoders 34 and 36. In such cases, the distance between adjacent sampling points can be determined by dividing the total scanning distance by the number of sampling points, and it is also possible to associate the detection signal with the scanning position based on this. .

(2) The present invention can be used to inspect the surface condition of various objects to be inspected that cause light reflection, not only video disks, semiconductor wafers, aluminum drums, etc.

In addition, instead of surface roughness and defects as in the above examples,
When it is desired to know the distribution of dirt, it is also possible to detect an increase or decrease in reflected light due to dirt and apply the present invention to this. Furthermore, more detailed information can be obtained by directly outputting the distribution of the absolute values of the obtained statistics without using a threshold value.

(Effects of the Invention) As explained above, according to the present invention, statistics are obtained for each predetermined section from the reflection state of the reflected light from the object to be inspected, so the surface condition of the surface of the object to be inspected can be determined. It is possible to obtain a surface condition inspection device that can regularly evaluate each region.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, FIG. 2 is a partial diagram of the device shown in FIG. 1, FIG. 3 is a diagram showing the PSD light receiving surface, and FIG. FIG. 5 is a flowchart showing the operation of the embodiment; FIG. 6 is a diagram showing an example of setting sections on the disk surface; FIG. 7 is a diagram showing an example of RMS roughness detection. , Figure 8 shows P
Figures 9 and 10, which illustrate the characteristics of SD, are a configuration diagram of a conventional device and its waveform diagram, respectively. 1... Laser light source, 5... Disk, 7...
Bright spot position detector, 100... microcomputer,

Claims (3)

[Claims] (1) A surface condition inspection device that inspects the condition of the surface of the object to be inspected by irradiating the surface of the object to be inspected with a beam of light from a light source and detecting the reflected light from the surface of the object to be inspected, comprising: a scanning mechanism that scans a beam light on the surface of the object to be inspected; a reflected light detection means that detects reflected light from the surface of the object to be inspected and sequentially outputs a detection signal according to a reflection state of the reflected light; , means for determining, based on the detection signal, a predetermined statistic expressing the state of the surface within the section for each predetermined section on the surface of the object to be inspected, the statistic in each of the sections; A surface condition inspection device that inspects the surface condition of the object to be inspected based on. (2) The reflected light detection means includes a light receiving position detection means that has a light receiving surface that receives the reflected light and generates a light receiving position detection output according to the light receiving position of the reflected light on the light receiving surface, The surface according to claim 1, wherein the detection signal from the reflected light detection means is a signal indicating a value according to the amount of deviation of the light receiving position corresponding to the state of the surface of the object to be inspected. Condition inspection device. (3) The surface condition inspection device according to claim 1 or 2, wherein the statistical amount is an amount corresponding to a power average of amounts obtained based on the level of the detection signal.