JPH04289409A - Substrate inspecting method - Google Patents

Abstract

PURPOSE:To make it possible to measure the sizes of irregularities highly accurately at high contrast even for a substrate comprising transparent material by selectively utilizing the polarization characteristics of pattern reflected light P and respective reflected lights S and N from the upper surface and the bottom surface of the substrate in response to the purpose. CONSTITUTION:Laser light 6 scanning a substrate 3A produces pattern reflection P, reflection S from the surface of the substrate, and reflection N from the bottom of the substrate. Each reflected light has the polarization characteristic. Most of the reflected light S is transmitted when the bearing angle is 0 deg., i.e., in P polarization. The amount of the reflected light S becomes the maximum value when the bearing angle is 90 deg., i.e., in S polarization, and the amount of the reflected light becomes the minimum value, conversely. Therefore, circular polarized laser light 6A is cast on the substrate 3A, and the S-polarization component of the reflected light is detected. Then, the sizes of the irregularities are obtained. In this way, the highly accurate measurement from which the effect of the reflected light N is removed can be performed. With the P-polarization component of the reflected light, the difference between the amounts of the reflected light S and the reflected light P becomes the maximum degree. Thus, the surface image having the high contrast, i.e., the planar image of the surface of the substrate 3A, can be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting the unevenness of the surface of a flat substrate. Moreover, specifically, it is a method for inspecting the wiring pattern of a printed wiring board.

As electronic components become smaller and their packaging density increases, it has become difficult to visually inspect them. Therefore, there is a need for a method for measuring the three-dimensional shape of an object in a non-contact manner.

For example, printed wiring boards with wiring patterns having widths and thicknesses of several micrometers to several tens of micrometers have been put into practical use. In terms of inspection reliability and inspection speed, visual inspection cannot compete with the visual inspection of such substrates.

[0004] Therefore, as a method for automatically inspecting the wiring pattern on the surface of a board without contact, an inspection method using a laser beam and the principle of triangulation has been adopted.

That is, this is a method of irradiating and scanning a printed wiring board with laser light and observing the reflected laser light to determine the dimensions of the irregularities on the board.

However, when the substrate to be inspected is made of a transparent material, for example, when the base material of a printed wiring board is transparent, there is a problem that errors occur in the measurement and inspection results.

Therefore, there is a need for an inspection method that can perform accurate inspection even when the substrate to be inspected includes a transparent member.

[0008]

2. Description of the Related Art Among the three-dimensional shapes of objects, film-like members and plate-like members are particularly thin, so visual inspection of the thickness is extremely difficult.

An example thereof is a printed wiring board on which electronic components are mounted and wired.

FIG. 8 is a perspective view illustrating a printed wiring board and its defects. That is, it is a substrate 3 in which a wiring pattern 2 is formed on a base material 1 by etching, printing, or the like.

Defects that occur in such printed wiring boards include defects 4 and disconnections in the wiring pattern 2, protrusions and protrusions 5, and the like.

However, the width and thickness h of the wiring pattern 2
1 is about several micrometers to several tens of micrometers, and it is difficult to discover by visual inspection.

(1) Inspection method using laser light FIG.
FIG. 2 is a block diagram illustrating a method for inspecting a substrate.

That is, the laser beam 6 is set at a predetermined angle θ.
The printed wiring board 3 is irradiated with the light, and the light is scanned in the scanning direction 12 as shown in the figure.

[0015] Then, the position of the laser beam reflected by the printed wiring board 3 is determined by PSD (POSITION SENSI).
TIV DETECTORS: Light spot position detection element)
7 to determine the thickness of the wiring pattern 2.

The laser beam reflected by the printed wiring board 3 is imaged on the PSD 7 by the imaging lens 8. Also,
A part of the reflected laser light is taken out to the camera 10 side by a half mirror 9, and its image is photographed.

(2) Inspection principle FIG. 10 is a diagram explaining the inspection principle. (a) is a view of FIG. 9 viewed from the left side, and (b) is a diagram showing the position of the laser beam focused on the PSD and camera. FIG.

That is, the laser beam 6 irradiated onto the printed wiring board 3 is applied to the surface 1 of the base material 1 of the printed wiring board 3.
There is a laser beam S that is reflected by -s and a laser beam P that is reflected by the surface of the wiring pattern 2.

Furthermore, when the base material 1 is made of a transparent material, a part of the irradiated laser beam 6 passes through the base material 1 and is reflected by the bottom surface 1-d of the base material 1. However, there is a laser beam N emitted from the surface 1-s of the base material 1 again. Incidentally, this light N reflected from the bottom surface of the base material appears conspicuously when a wiring pattern or the like is also present on the bottom surface 1-d of the base material.

On the other hand, as shown in FIG. 10(a), if the thickness of the wiring pattern 2 is h1 and the thickness of the base material 1 is h2, even if the laser beam 6 is irradiated at the same angle θ, the reflected laser beam The positions of the lights P, S, and N are different, and can be perceived as a difference in the light spot position of the reflected laser light on the PSD 7.

FIG. 10(b) is a diagram showing the light spot position on the PSD 7, where the horizontal axis is time and the vertical axis is the light spot position. Note that since the laser beam scans at a constant speed, the time on the horizontal axis in the figure corresponds to the scanning position on the printed wiring board in the laser beam scanning direction.

As shown in the figure, in the reflected laser light from the printed wiring board 3, the wiring pattern reflected light P and the board surface reflected light S appear repeatedly, and a rectangular shape corresponding to the uneven dimensions on the printed wiring board 3 is formed. shows the trajectory of

That is, the difference h10 in position between the wiring pattern reflected light P and the base material surface reflected light S corresponds to the thickness h1 of the wiring pattern 2.

Note that the light N reflected from the bottom of the base material is reflected from the wiring pattern 2.
The difference h20 between the positions of the light S reflected on the surface of the base material and the light N reflected on the bottom surface of the base material is determined by the thickness h2 of the base material 1.
corresponds to

(3) Calculation of PSD and height FIGS. 9 and 1
As the PSD 7 shown in 0, any element (device) can be used as long as it can determine the position of a light spot.

[0026] Therefore, as an example of a PSD, a PSD composed of a semiconductor will be used and its operation will be explained.

FIG. 11 is a diagram explaining the PSD and signal processing. (a) is a diagram explaining the configuration of the PSD, and (b) is a diagram explaining the method of determining the light spot position and brightness from the output signal of the PSD. This is a block diagram.

That is, the P layer 13,
It is composed of three layers: an N layer 14 on the back surface and an I layer 15 in the middle. Then, electrodes 16 are provided at both ends of the P layer 13.
, 17 are provided to guide the output current to the terminals 18, 19. Further, the terminal 20 is a terminal that applies a bias to the N layer 14.

[0029] In PSD 7 like this (spot shape)
When the incident light 21 is irradiated, a photocurrent 22 that is photoelectrically converted,
23 is divided and output as output currents A and B from terminals 18 and 19. Note that since a charge proportional to the light energy is generated at a position irradiated with the incident light 21, the sum of the output currents A and B is proportional to the light energy.

Furthermore, since the P layer 13 has a uniform resistance value over the entire surface, the photocurrents 22 and 23 are outputted in inverse proportion to the distance from the irradiation position of the incident light 21 to the electrodes 16 and 17. They become output current A and output current B, respectively.

That is, the following equations (1) and (2) hold true. Brightness I=A+B
------(1) Light spot position H=(A-B)/
(A+B)---(2)

[0032] Therefore,
As shown in FIG. 11(b), a light spot position signal, that is, a height signal H and a brightness signal I
and can be obtained.

[0033]

However, when the base material 1 of the printed wiring board 3 is made of a transparent material, there is a problem in that errors occur in measuring the dimensions of the irregularities on the board 3 to be inspected.

That is, in the printed wiring board 3 in which the wiring pattern 2 is formed on the surface of the base material 1 made of a transparent material, the light N reflected from the bottom surface of the base material appears.

FIG. 12 is a diagram illustrating the influence of light reflected from the bottom surface of the base material, and is a diagram showing the position of a light spot on the PSD. Note that the horizontal axis is time and position, and the vertical axis is the light spot position.

That is, if there is no wiring pattern on the surface irradiated with the laser beam, the reflected light becomes two light spots, the light S reflected from the surface of the base material and the light N reflected from the bottom surface of the base material, and is captured by the PSD.

Therefore, the output current due to the two light spots of the reflected lights S and N is output from the PSD, and the light spot position calculated from the ratio of the output currents is exactly between the two light spots of the reflected lights S and N. It will be calculated so that it exists in . By the way, the light spot position 2 detected by the PSD is indicated by a broken line in Figure 12.
6 is that.

The apparent light spot position 26 is determined by the ratio of the light S reflected from the surface of the base material to the light N reflected from the bottom surface of the base material. That is, the stronger the base material bottom surface reflected light N is, the more the apparent light spot position moves toward the base material bottom surface reflected light N side.

Therefore, the thickness h101 of the wiring pattern calculated from the output current of the PSD is the thickness h101 of the wiring pattern calculated from the output current of the PSD.
It increases by an error amount Δh from the value h10 when there is no h10.

From the above, equations (1) and (2)
Therefore, the following equations (3) to (6) hold true. 1) When the wiring pattern is irradiated with laser light
Brightness I=A+B=P
--------
-----(3) Light spot position H=(A-B)/
(A+B)=(A-B)/P
4)

2) When the base material part is irradiated with laser light Brightness I=A+B=S+N
---
(5) Light spot position H=(A-B)/(A+B
)=(A-B)/(S+N)---(6)

[0042]
In other words, when the wiring pattern is irradiated with laser light,
The brightness I and the light spot position H can be determined solely from the pattern reflected light P, but when the base material part is irradiated with laser light,
The brightness I and the light spot position H are determined depending not only on the light S reflected on the surface of the substrate but also on the light N reflected on the bottom surface of the substrate.

Therefore, in order to measure the unevenness dimension of the surface of the substrate to be inspected with high contrast and high accuracy, it is necessary to satisfy the following equations (7) and (8).

1) Conditions P≫(
S+N) ------(7)

2) High precision unevenness dimension measurement (height measurement) P
, S≫N ------(8)

[0046] The technical problem of the present invention is to solve the above-mentioned problems in substrate inspection, and to solve the problem even when the substrate is made of a transparent material.
The objective is to realize high-quality substrates by establishing an inspection method that enables high-contrast and highly accurate measurement of uneven dimensions.

[0047]

[Means for Solving the Problems] Fig. 1 is a diagram explaining the basic principle of the present invention, in which (a) is a perspective view of a substrate to be inspected and the irradiated laser beam, and (b) is a view of (a) from the left side. The view,
It is.

The present invention focuses on the fact that the pattern reflected light P, the substrate surface reflected light S, and the substrate bottom reflected light N have polarization characteristics, and selectively utilizes the polarized light depending on the purpose. There are characteristics.

(1) Inspection method using circularly polarized laser light, that is, the surface of the substrate 3A is irradiated and scanned with a laser beam 6 at a predetermined angle θ, and the laser beam reflected from the substrate 3A is detected from the position of the laser beam. When determining the irregularity dimension h1 of the surface of the substrate 3A and obtaining a planar image of the surface of the substrate 3A from the intensity of the reflected laser beam, a circularly polarized laser beam 6A is used as the laser beam 6 irradiated to the substrate 3A, and the reflected laser beam 6A is This is a substrate inspection method in which the S-polarized component of the laser beam is detected to determine the unevenness dimension h1 of the substrate 3A, and the P-polarized component is detected to obtain a planar image of the surface of the substrate 3A.

(2) Inspection method using linearly polarized laser light, that is, in (1) above, circularly polarized laser light 6A
Instead, this is a substrate inspection method using linearly polarized laser light 6B with an azimuth angle ψ of 45°.

[0051]

[Operation] Figure 2 is a diagram explaining the operation, (a) is a diagram showing the light spot position of the laser beam reflected on the substrate to be inspected, (b)
1 is a diagram showing polarization characteristics of laser light reflected by a substrate to be inspected.

(1) Inspection method using circularly polarized laser light As shown in FIG. 1(b), the laser light 6 irradiated and scanned on the substrate 3A is reflected in the same manner as in FIG. 10(a). That is, pattern reflected light P, base material surface reflected light S, and base material bottom surface reflected light N are obtained.

However, the reflected light has polarization characteristics, and the light S reflected from the surface of the substrate and the light N reflected from the bottom of the substrate exhibit particularly remarkable characteristics. That is, as shown in FIG. 2(b), the amount of reflected light changes depending on the azimuth angle ψ of the laser 6 irradiating the substrate 3A.

That is, the light S reflected from the surface of the base material is specularly reflected, and when the azimuth angle ψ is 0° (zero), that is, when the light is P-polarized, most of the light is transmitted. Further, when the azimuth angle ψ is 90°, that is, in the case of S-polarized light, the light S reflected from the surface of the base material becomes maximum, and conversely, the amount of light reflected from the bottom surface of the base material N becomes the minimum. Note that the pattern reflected light P is reflection from the metal surface, and the amount of reflected light hardly changes even if the azimuth angle ψ changes.

Therefore, by irradiating the substrate 3A with the circularly polarized laser beam 6A and detecting the S-polarized component of the reflected light to determine the unevenness dimension, measurement is performed that eliminates the influence of the light N reflected from the bottom of the substrate. It can be carried out.

Furthermore, in the P-polarized component of the reflected light, the difference in the amount of reflected light between the substrate surface reflected light S and the pattern reflected light P is the largest, resulting in a high contrast surface image, that is, the substrate 3A.
A planar image of the surface can be obtained.

That is, when measuring the unevenness dimension on the surface of the substrate 3A, it is possible to satisfy the equation (8),
In obtaining an image of the surface of the substrate 3A, the following equation (7) can be satisfied.

Note that the base material bottom surface reflected light N is a value obtained by excluding the amount of attenuation due to diffusion etc. of the light transmitted through the surface of the substrate, and the relationship between the base material surface reflected light S and the base material bottom surface reflected light N is is the following formula (
9) It can be shown as follows. S + N + attenuation = constant −−−−− (9)

[0059]
Incidentally, Fig. 2(a) shows the average light spot position 27, when the light spot position of the reflected laser beam is measured using a light spot position detection element.
28, and the average light spot position 28 measured by P-polarized light is offset from the position on the substrate surface, resulting in a measurement error that decreases by Δhb toward the bottom surface of the substrate. However, the average light spot position 27 measured by S-polarized light is
There is almost no offset Δha from the position of the base material surface,
Accurate measurements are possible.

(2) Inspection method using linearly polarized laser light With respect to the substrate to be measured 3A, the linearly polarized laser light 6B with an azimuth angle ψ of 45° has the same intensity as the P-polarized light component and the S-polarized light component. I have it.

Therefore, as in the case of circularly polarized light in (1) above, accurate unevenness dimension measurement can be performed by dividing and detecting the laser beam reflected from the substrate 3A into an S polarized light component and a P polarized light component. At the same time, it is possible to obtain images with high contrast.

Note that the azimuth angle ψ of linearly polarized light is not necessarily 45
It is not necessary that the angle is 0.degree., and it is sufficient that the S-polarized light and the P-polarized light components are included at the required intensity.

[0063]

EXAMPLES Next, examples will be used to explain how the method for inspecting a substrate according to the present invention can be practically implemented.

(1) Example-1 FIGS. 3 and 4 are diagrams explaining Example-1, with FIG. 3 specifically showing its configuration as a block diagram, and FIG. 4 a diagram explaining its operation. .

In FIG. 4, (a) is a sectional view of the substrate, (b) is a PMT output waveform diagram, (c) is a PSD output waveform diagram, and (d) is an output waveform diagram of the arithmetic circuit. In addition, the horizontal position of (a) and the waveform diagram (b) (c) (d
) are shown on the same scale as the horizontal position.

1) Configuration In this embodiment, a circularly polarized laser beam is used as the irradiation laser beam, and a polarizing beam splitter 36 is used to polarize the reflected laser beam.
, PMT (PHOTOMULTIPLIER) is used to measure the amount of light.
TUBE) 38, and PSD 7 is used to detect the position of the light spot.

Roughly dividing its configuration, it consists of a laser beam scanning system and a detection system that detects the reflected laser beam from the substrate 1a.

■ Laser beam scanning system The collimated laser beam from the laser light source 29 is
0 to make it linearly polarized light, and then use the λ/4 plate 31 to make it circularly polarized light. Furthermore, the circularly polarized laser beam is sent to a beam expander 32.
After that, the laser beam is magnified by the polygon scanner 33 to obtain a scanning laser beam.

Then, the scanning laser beam is passed through the scanning lens 3.
4 (for example, an fθ lens), and irradiates the substrate 3a through the reflection mirror 35 at a desired angle.

[0070] The substrate 3a also has an X-Y
It is placed on a stage and moves slightly in synchronization with the scanning of the laser beam. That is, by doing so, the entire surface of the substrate 3a is scanned with laser light.

(2) Detection system for reflected laser light The reflected laser light from the substrate 3a is detected by an optical system installed at a predetermined angle.

That is, the reflected laser light is transmitted through the imaging lens 8a.
to focus the light. Then, a polarizing beam splitter 36 is placed in front of the focal point to separate the reflected laser beam into S-polarized light and P-polarized light.

On the other hand, the P polarized light is transmitted through the cylindrical lens 3.
7, and a brightness signal, that is, a luminance signal a1 (PMT output signal a1) is obtained by the PMT 38.

On the other hand, the S-polarized light is
The SD 7 detects the light spot position and outputs the output signal A,
B is computed by the arithmetic circuit 24a to obtain an output b1. Note that the light shielding plate 39 placed in front of the PSD 7 is
Among the reflected laser beams a, the laser beams are arranged to spatially separate the light reflected from the bottom surface of the base material of the substrate 1a.

2) Operation As shown in FIG. 4(a), the base material 1a of the substrate 3a has a thickness h2, and the pattern 2a has a thickness h1. Therefore, the dimension of the irregularities on the surface of the substrate 3a is h1, and the surface image of the substrate 3a exhibits a striped pattern in which the pattern 2a appears repeatedly.

FIG. 4(b) shows the output waveform of the PMT 38, and the image of the pattern 2a can be obtained from its amplitude a. That is, there is a separate difference between the amount of P-polarized light reflected on the surface 1a-s of the base material 1a and the amount of P-polarized light reflected on the surface of the pattern 2a, and a PMT output with high contrast is obtained.

FIG. 4(c) shows the output waveform of the PSD 7, whose amplitude b is equal to the output signal A of the PSD 7.
, B (A-B).

[0078] The laser beam incident on the PSD 7 is S
It is polarized light, and therefore the influence of the laser light reflected from the bottom surfaces 1a-d of the substrate 3a is extremely small. In addition, the light shielding plate 3
9 is placed in front of the PSD 7, the light reflected from the bottom of the base material can be completely blocked. However, the light shielding plate 39 is not necessarily required.

FIG. 4(d) shows the output waveform of the arithmetic circuit 24a, and the amplitude of the waveform corresponds to the surface shape of the substrate 3a. That is, its amplitude h is PSD 7
Let the output signals of A and B be h=(A-B)/(A+B
), which corresponds to the thickness (height) h1 of the pattern 2a.

Incidentally, since the output signal of the arithmetic circuit 24a is calculated by capturing the light spot position of the S-polarized light by the PSD 7, highly accurate measurement results can be obtained.

(2) Embodiment 2 FIGS. 5 and 6 are diagrams for explaining Embodiment 2, with FIG. 5 specifically showing its configuration as a block diagram, and FIG. 6 showing the function of the beam splitting plate. There is.

In FIG. 6, (a) is a perspective view of the beam splitting plate and the PMT, and (b) is a view of (a) viewed from the left side.

The difference between this example and Example-1 is that the P used as the light spot position detection element in Example-1
In place of SD 7, beam splitting plate 40 and PMT 41
, PMT 42 is used.

That is, the beam splitting plate 40 and the PMT 4
1 and PMT 42 to detect the light spot position of the reflected laser beam. This configuration is disclosed and explained in detail in Japanese Patent Application Laid-Open No. 1-295105.

Incidentally, the operation of the beam splitting plate 40, PMT 41, and PMT 42 as a light spot position detecting device will be explained below with reference to FIG.

The beam splitting plate 40 is provided with a mirror section 43 and a transmitting section 44 so as to divide its surface into two.The mirror section 43 reflects the laser beam, and the transmitting section 44 transmits the laser beam.

On the other hand, the beam spot 48 of the laser beam 6a is arranged so as to be irradiated on the boundary between the mirror section 43 and the transmission section 44, and usually half of the beam spot 48 is placed on the mirror section 43 side, and the rest is placed on the mirror section 43 side. Half of the light is arranged so as to be irradiated onto the transparent section 44 side.

Therefore, when the beam spot 48 of the laser beam 6a moves to the mirror section 43 side or the transmitting section 44 side, the amount of the laser beam reflected by the mirror section 43 and the amount of the laser beam passing through the transmitting section 44 become different. The ratio of

Therefore, by capturing the laser beam reflected by the mirror section 43 with the PMT 41 and capturing the laser beam transmitted through the transmitting section 44 with the PMT 42,
Output signals A' and B' can be obtained according to the amount of light.

Note that the output signals A' and B' are
Corresponding to the output signals A and B of PSD 7 of No. 1, by performing the same calculation as in Example 1, that is, (A'-B')/(A'+B'), in the calculation circuit 24b shown in FIG.
A calculation output signal b2 corresponding to the thickness of the pattern 2a on the substrate 3a can be obtained.

Incidentally, in this Example-2 as well, since the P-polarized light and the S-polarized light of the laser beam reflected by the substrate 3a are detected separately, the same excellent detection characteristics as in Example-1 can be obtained. .

(3) Embodiment 3 FIG. 7 is a diagram for explaining Embodiment 3, and shows its configuration in a block diagram.

This embodiment differs from Embodiment 1 in that a half mirror 45 and analyzers 46 and 47 are used instead of the polarization beam splitter 36 used as a polarization separation element in Embodiment 1. The only point is that there is.

That is, the reflected laser beam reflected by the substrate 3a and focused by the imaging lens 8a is divided into two parts by the half mirror 45.
The analyzer 46 extracts the P polarized light from one laser beam, and the S polarized light is extracted from the other laser beam by the analyzer 47.

By the way, PMT 38 and PSD
7. The operation of the arithmetic circuit 24a is the same as in Example-1.

(4) Other Examples In Examples 1 to 3, a circularly polarized laser beam was used as the laser beam to irradiate the substrate to be inspected 3a, but instead of the λ/4 plate 31, Using a λ/2 plate, the substrate 3a
Alternatively, a linearly polarized laser beam having an azimuth angle of 45° may be irradiated.

[0097] The detection system for reflected laser light is as described in Example-
The configurations of Examples 1 to 3 can be used as they are.

Note that the linearly polarized laser beam irradiated onto the substrate 3a does not necessarily have to have an azimuth angle of 45°;
P polarized component and S of the laser beam irradiated to the substrate 3a
There is no problem as long as the polarized light component has the desired intensity. For example, the angle may be selected/determined within a range of about 30° to 60°.

0099

[Effects of the Invention] As described above, according to the substrate inspection method according to the present invention, even if the substrate is made of a transparent material,
It utilizes the difference between the polarization characteristics of the light reflected on the surface and the polarization characteristics of the light transmitted through the substrate and reflected at the bottom surface.
The uneven state of the substrate surface can be measured and inspected with high accuracy. Furthermore, it becomes possible to capture an image of the substrate surface with high contrast.

As a result, the substrate to be inspected can be inspected with high precision, and a high quality substrate can be realized.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the basic principle of the present invention, (a) is a perspective view of a substrate to be inspected and the irradiated laser beam, (b) is (a)
This is a view from the left side.

FIG. 2 is a diagram illustrating the operation, (a) is a diagram showing the light spot position of the laser beam reflected by the substrate to be inspected, (b) is a diagram showing the polarization characteristics of the laser beam reflected by the substrate to be inspected, It is.

FIG. 3 is a diagram illustrating Example 1, particularly showing its configuration as a block diagram.

FIG. 4 is a diagram for explaining Example-1, particularly for explaining the operation. (a) is a cross-sectional view of the board, (b) is a PMT output waveform diagram, (c) is a PSD output waveform diagram, and (d) is a diagram of the PSD output waveform.
) is the output waveform diagram of the arithmetic circuit. Further, the horizontal position in (a) and the horizontal position in the waveform diagrams (b), (c), and (d) are shown on the same scale.

FIG. 5 is a diagram illustrating Example 2, particularly showing its configuration as a block diagram.

FIG. 6 is a diagram explaining Example 2, particularly showing the function of the beam splitting plate. In addition, (a) is the beam splitting plate and P
A perspective view of the MT, (b) is a view of (a) seen from the left side.

FIG. 7 is a diagram for explaining Example 3, and shows its configuration in a block diagram.

FIG. 8 is a perspective view illustrating a printed wiring board and its defects.

FIG. 9 is a block diagram illustrating a method for inspecting a substrate.

10A and 10B are diagrams illustrating the inspection principle, in which (a) is a diagram seen from the left side of FIG. 9, and (b) is a diagram showing the position of the laser beam focused on the PSD and camera.

FIG. 11 is a diagram explaining PSD and signal processing, (a)
2 is a diagram illustrating the configuration of the PSD, and FIG. 3(b) is a block diagram illustrating a method for determining the light spot position and brightness from the output signal of the PSD.

[Fig. 12] A diagram illustrating the influence of light reflected from the bottom surface of the base material.
It is a figure which shows the light spot position on D. Note that the horizontal axis is time and position, and the vertical axis is the light spot position.

[Explanation of symbols]

1, 1A, 1a Base material 1
-s, 1A-s, 1a-s Base material surface 1-d, 1A-d, 1a-d Base material bottom surface 2, 2A, 2a (wiring) Pattern 3, 3A
(Printed wiring) board 6, 6a
Laser light 6A
Circularly polarized laser beam 6B
Linearly polarized laser beam with an azimuth angle of 7 PSD (
POSITION SENSITIV DETECT
R.S.)

Claims (2)

[Claims] Claim 1: A method for inspecting the uneven state of the surface of a substrate (3A), the method comprising
The surface of A) is irradiated and scanned with a laser beam (6), and the substrate (3A) is scanned from the position of the laser beam reflected by the substrate (3A).
When determining the unevenness dimension (h1) of the surface and obtaining a planar image of the surface of the substrate (3A) from the intensity of the reflected laser beam, a circularly polarized laser beam is used as the laser beam (6) to irradiate the substrate (3A). (6A), detect the S-polarized component of the reflected laser beam to determine the unevenness dimension (h1) of the substrate (3A), and detect the P-polarized component to obtain a planar image of the surface of the substrate (3A). A board inspection method characterized by the following. 2. The substrate inspection method according to claim 1, using a linearly polarized laser beam (6B) with an azimuth angle (ψ) of 45° in place of the circularly polarized laser beam (6A); A board inspection method characterized by: