JPH0566118A - Wiring pattern inspecting device - Google Patents

Abstract

PURPOSE:To highly precisely measure thickness and waviness information by providing a second converging means with the principal point being conformed to the posterior focus position of a first converging means, and providing at least two optical position detecting means in the posterior focus position and in the front and rear of it. CONSTITUTION:In a wiring pattern inspecting device, the collimated laser beam from a laser generating device 5 is expanded by a laser expander 6, entered to a polygonal scanner 8, throttled by a scanning lens 9, and emitted to a substrate 13 to be inspected at a determined angle. The reflected light is imaged on a semiconductor position detecting element(PSD) 34 by a first converging lens 31 and a second converging lens 32. The light is divided there into two and converged on a second PSD 35. It is important here to place the PSD 34 on an imaging surface (the rear focus position of the lens 32) and the PSD 35 in a place other than this point. The outputs of the PSD 34, 35 are passed through amplifiers 35a, 35b, 40a, 40b, the imaging position is calculated in first and second height arithmetic circuits 36, 41 to determine the height, and information such as waviness and brightness is successively determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring pattern inspection device for inspecting a wiring pattern by optical means.

In recent years, as the density and size of electronic parts have increased, it has been strongly desired to measure the three-dimensional shape of an object in a non-contact manner. The density of printed circuit boards is also being increased, and the width and thickness of tens of μm to several μm are being achieved. The visual inspection of such a fine wiring pattern cannot be handled by the visual inspection because of the reliability and speed of the inspection. Therefore, it is desired to be able to inspect a fine wiring pattern quickly with high reliability.

[0003]

2. Description of the Related Art FIG. 8 is a block diagram of a conventional wiring pattern inspection apparatus. In FIG. 8, a wiring pattern inspection device 1
Are roughly classified into a laser scanning optical system 2, a light detection system 3, and
And a processing circuit system 4.

The laser scanning optical system 2 includes a laser generator 5, a beam expander 6, a pair of reflecting mirrors 7a,
7b, a polygon scanner 8, a scan lens 9, a reflection mirror 10 and the like. Further, the light detection system 3 includes an imaging lens 11, a semiconductor light position detection element (PS
D) 12. Reference numeral 13 denotes a substrate to be inspected which is inspected by the wiring pattern inspecting apparatus 1. Above the substrate to be inspected 13, for example, the wiring pattern 1
4 are formed.

In the processing circuit system 4, signals A and B from the PSD 12 are sent to a height calculation circuit 17 and a brightness calculation circuit 18 via amplifiers 15 and 16, respectively. The height data calculated by the height calculation circuit 17 is stored in the image memory 19, and the brightness data calculated by the brightness calculation circuit 18 is stored in the image memory 20.

The wiring pattern inspection apparatus 1 as described above is
The collimated laser light emitted from the laser generator 5 is expanded by the beam expander 6 and is reflected by the reflecting mirrors 7a, 7a.
It is incident on the polygon scanner 8 via b. As a result, the collimated laser light becomes scanning light for scanning a predetermined range. This scanning light is focused by a scan lens 9 such as an fθ lens, and is applied to the substrate 13 to be inspected via a reflection mirror 10.

The reflected light reflected by the substrate 13 to be inspected is condensed by the imaging lens 11 and imaged on the PSD 12. PS
The position is detected by D12, and the processing circuit system 4 detects the height and shading of the substrate 13 to be inspected by the output signal. The PSD 12 is used to increase the inspection speed (data processing rate: several). 10 M pixels / second) can be realized. With the wiring pattern inspection apparatus 1 having the above-described configuration, it is possible to measure a chip, a protrusion, a disconnection, a dent, or the like that has occurred in the inspected substrate 13 and the wiring pattern 14 with an accuracy of several tens of μm.

By the way, some of the substrates 13 to be inspected have glossiness and waviness. For example, the substrate 13 to be inspected
When a printed board is used as a printed board, there is a board in which wiring patterns are formed of thin films are laminated in multiple layers, and undulation occurs at a laminated portion of the pattern.

Here, FIG. 9 shows a view for explaining the reflection of the substrate to be inspected having the undulation. In FIG. 9, the reflection of the laser light applied to the waviness-free portion of the substrate 13 to be inspected (FIG. 9A) and the reflection when it is applied to the waviness portion (FIG. 9B), The light receiving position is different. Therefore, when measuring the thickness of the wiring pattern, as shown in FIG.
As shown in (C), it is necessary to distinguish height changes due to undulations from height changes due to changes in the thickness of the wiring pattern.

[0010]

Problems to be Solved by the Invention FIGS.
The figure for demonstrating the conventional inspection of the to-be-tested substrate is shown. FIG. 10 shows the case of the height change, and FIG. 11 shows the case of the swelling state.

In FIG. 10, when the height of X changes on the measurement surface of the substrate 13 to be inspected, the position of the light spot after condensing by the imaging lens 11 changes by the position of x on the imaging surface by the PSD 12. Occurs. Further, in FIG. 11, when the height does not change on the measurement surface and undulation occurs, the position of light on the image forming surface of the PSD 12 does not change. Therefore, the thickness change due to the height change can be measured without depending on the undulation.

However, in the above case, although it is possible to measure the height change, there is a problem that it is not possible to determine whether or not the undulation occurs.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide an apparatus for assembling a wiring pattern, which measures not only information on the thickness of the wiring pattern but also undulation information with high accuracy. ..

[0014]

SUMMARY OF THE INVENTION The above problem is that the substrate to be inspected on which a wiring pattern is formed is irradiated with a laser beam by a laser beam irradiating means, and the reflected light from the substrate to be inspected is
In the wiring pattern inspecting device for inspecting the wiring pattern by detecting through the light collecting means of the second light collecting means, the second light collecting means is provided with its principal point aligned with the back focus position of the first light collecting means. A first and second light position detecting means provided at least at any two positions of the back focus position of the second light converging means and three positions before and after the back focus position; By the output signals from the first and second optical position detecting means,
A processing means for calculating the height, brightness, and undulation of the measurement target portion of the inspected substrate can be solved.

[0015]

As described above, the second focusing means is provided so that the principal points coincide with the back focal point of the first focusing means, and the back focusing position of the second focusing means and the positions before and after it. The first and second optical position detecting means are provided at at least two positions.

For example, when one light position detecting means is provided at the back focal position of the second light collecting means, the height change due to the wiring pattern of the substrate to be inspected as shown in FIG. It can be measured by a change in the position of the detecting means. The waviness of the substrate to be inspected can be calculated by the signal from the optical position detecting means and the signal from another optical position detecting means.

As a result, not only the thickness information of the wiring pattern of the substrate to be inspected but also the undulation information can be measured with high accuracy.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of an embodiment of the present invention.
The same components as those in FIG. 8 are designated by the same reference numerals.

In FIG. 1, a wiring pattern inspection apparatus 1
Is a laser scanning optical system 2, a light detection system 3, and a processing means 3.
It is composed of 0.

The laser scanning optical system 2 includes a laser generator 5, a beam expander 6, a pair of reflecting mirrors 7a,
7b, a polygon scanner 8, a scan lens 9, a reflection mirror 10 and the like.

The light detection system 3 is a first light condensing means, which is a first
Condensing lens 31, second condensing lens 32 which is the second condensing means, half mirror (or beam splitter) 3
3, and first and second semiconductor position detecting elements (PSD) 34 and 35 which are first and second optical position detecting means. The 2nd condensing lens 32 is arrange | positioned so that a principal point may correspond to the back focus position of the 1st condensing lens 31. It should be noted that the first and second condenser lenses 31 and 32 may use a large number of combined lenses.

Although not shown, the first and second PSDs 34 and 35 are provided with a stage that moves in the optical axis direction of the reflected light. For example, the second PSD 35 has a second condenser lens 32.
The first PSD 34 is provided at a rear focus position after being deflected by the half mirror 33. For example, the first PSD 34 is provided at a position behind the rear focus of the second condenser lens 32 with the half mirror 33 interposed.

Reference numeral 13 is a substrate to be inspected on which a wiring pattern 14 is formed.
Moved in Y direction.

The processing means 30 includes A _{1 of} the second PSD 35.
The output signals from the point B _{1 and the} point B ₁ are transmitted through the amplifiers 35a and 35b to the first height calculation circuit 36 and the brightness calculation circuit 37.
Entered in. Then, the brightness data from the brightness calculation circuit 37 is stored in the first image memory 38, and the height data from the first height calculation circuit 36 is input to the swell amount calculation circuit 39.

On the other hand, points A ₂ and B _{2 of} the first PSD 34
The output signal from the point is output to the second via the amplifiers 40a and 40b.
Is input to the height calculation circuit 41. The height data from the second height calculation circuit 41 is input by the waviness amount calculation circuit 39. The waviness amount calculation circuit 39 calculates the waviness amount based on the height data from the first and second height calculation circuits 36 and 41, and together with the height data, the second image memory 4
Memory to 2.

The wiring pattern inspection apparatus 1 as described above is for expanding the collimated laser light from the laser generator 5 by the beam expander 6 and making it enter the polygon scanner 8 to scan the light. This scanning light is narrowed down by a scanning lens (for example, fθ lens) 9 to be inspected substrate 1
Irradiate 3 with a predetermined angle. The reflected light from the inspected substrate 13 is imaged on the image plane of the first PSD 34 by the first condenser lens 31 and the second condenser lens 32. At this time, the light is split into two by the half mirror 33 and the other one
The two lights are collected on the second PSD 35. The respective positions of the first and second PSDs 34 and 35 can be freely selected by the stage moving in the optical axis direction of the reflected light.

Therefore, the first PSD 34 is adjusted to the image forming position of light, and the second PSD 35 is displaced from the image forming position. Therefore, in this embodiment, the first PSD 34
Is installed on the image forming surface (the rear focal position of the second condenser lens 32), and it is important that the second PSD 35 is installed on a position other than the image forming surface. First and second PSD3 respectively
The outputs of the amplifiers 4, 35 are amplifiers 35a, 35b, 40a, 4
0b, the first and second height arithmetic circuits 36, 41
Then, the respective image forming positions are calculated.

Measurement value H ₁ (= 1 of the first height calculation circuit 36
a (A ₁ −B ₁ ) / (A ₁ + B ₁ ), a is an amplifier 35
a, 35b, 40a, 40b) and the measured value H ₂ (= a (A ₂ −B ₂ ) / (A
₂ + B ₂ )) is input to the waviness amount calculation circuit 39.
Then, the light spot position and the amount of waviness are calculated (described later).
This value is stored in the second image memory 42.

The brightness I of the measurement target (wiring pattern 14) on the substrate 13 to be inspected is calculated by the brightness calculation circuit 37 (I = a (A ₁ + B ₁ )), and the first image memory 38 is obtained.
Stored in. It should be noted that although the collection of the brightness information is shown in FIG. 1 as being calculated from the signal from the second PSD 35, it may be calculated from the signal from the first PSD 34.

This makes it possible to measure the brightness, thickness and undulation information of the wiring pattern 14 of the substrate 13 to be inspected with high accuracy.

Next, the calculation of the amount of waviness will be described in detail with reference to FIGS.

2A and 2B are views for explaining an image due to height change and undulation in FIG. 1, FIG. 2A shows a case of height change, and FIG. 2B shows a case of undulation.

In FIG. 2 (A), first, when a height change occurs, in this configuration, the measurement surface and the first condenser lens 3 are arranged.
Since the focal planes of 1 and 1 are the same, the reflected light is x on the x axis.
Considering the case of moving only _one , as shown in FIG.
All light parallel to the optical axis is focused on the back focus. Therefore, x
_The position change corresponding to ₁ corresponds to the angle θ ₁ formed with the optical axis. Therefore, the relationship between x ₁ and θ ₁ is θ ₁ = A · x ₁ (1) and is proportional. However, A is the first condenser lens 31.
Is a constant determined by.

This light is condensed by the next _second condenser lens 32 at the back focal position f ₂ of the _second condenser lens 32. Here, the Z-axis is taken with the origin of the position of the principal point of the second condenser lens 32, the focal position is Z ₂ (position of the first PSD 34), and Z ₁ and Z ₃ (first 2 PSD
Take either Z ₁ or Z ₃ at the position of 35. The X axis is parallel to the x axis and is opposite to the x axis. In this case, the light movement of x ₁ on the x-axis on the Z _1, Z _2, Z ₃ is, X _1,
It appears as X ₂ and X _3, and the light is most condensed on Z ₂ . Therefore, the relationship between X and Z is X _n = Z _n tan θ ₁ (n = 1,2,3) (2). As a result, according to the equations (1) and (2), a certain Z
If the X position at the position can be measured, the position change (height change) x ₁ of the light on the measurement surface can be obtained. next,
Consider when swells occur. In FIG. 2 (B),
When the measurement surface is inclined by α / 2, the optical axis of α changes.
This inclination has an angle of β when passing through the first and second condenser lenses 31 and 32. The relationship between β and α is β = B · f ₁ · α / f ₂ (3). Here, B is a constant. In case of swell, Z ₂
It can be seen that no change occurs above. However, it appears at an angle β when moving back and forth from the position of Z ₂ . Therefore, in order to measure the waviness, it is necessary to measure the waviness amount by using the position information of the Z position other than Z ₂ .

Here, FIG. 3 shows a diagram for explaining the movement of the laser beam in FIG. FIG. 3A shows the case of height change, and FIG. 3B shows the case of undulation.

In FIG. 3A, when the height changes, when the x ₁ position changes from the optical axis center on the measurement surface, Z = Z ₁ ,
The imaging positions at Z ₂ and Z ₃ are X ₁ , X ₂ and X _{3 respectively.}
And match on a straight line as shown in FIG. The slope of this straight line is a value determined by the equation (1), for example, X
_{If 2} can be measured, the slope can be obtained from the equation (2). That is, the movement of the beam on the PSD due to only the height change is sufficient if the position of at least one PSD among the plurality of PSDs can be measured. However, the influence of swell may actually be mixed, and using one of arbitrary PSDs cannot measure the swell. That is, by measuring the light imaging position at Z = Z ₂ which is not affected by the undulation, the light imaging position at the second PSD 35 (no undulation)
Can be calculated. If this calculated value and the measured value actually obtained (measurement other than Z ₂ ) match, it is due to only the height change.

Further, in FIG. 3B, a case where undulation occurs will be examined. Therefore, consider the case where the image forming position of light at Z = Z ₂ is X ₂ . When undulation occurs on the measurement object, the beam image formation position at Z = Z ₁ and Z ₃ forms an image at a position different from the calculated value calculated by the equation (2). In the figure, they are X ₁₀ and X ₃₀ . Therefore, the calculated value X
The difference between the measured value and the measured value X ₀₀ corresponds to the swell.

Δ ₁ = X ₁ = X ₁₀ (4) Δ ₂ = X ₂ −X ₂ = 0 (5) Δ ₃ = X ₃ −X ₃₀ (6) These values have undulations. Is Δ ₂ = 0, Δ ₁ ,
Δ ₃ does not become 0. Therefore, in order to measure the change in the position of the light on the measurement surface and the measurement of the waviness, one calculated value at Z = Z ₂ and one measured value at other positions (Z = Z ₁ , Z ₃ ). It would be good if it could be measured. However, if there is no swell, Δ ₁ = Δ ₂ = Δ ₃ = 0.

Here, the relationship between the height change and the swell is shown in FIG.
The graph shown is shown. In FIG. 4, the second axis is the horizontal axis
The lens 32 shows the distance from the principal point, and the vertical axis shows PSD measurement.
The measurement position in the plane X-axis direction is shown. As shown in Figure 4, the swell
If there is not, it passes through origin 0 and tilts θ₁And the straight line (solid line)
It Therefore, if only the position of Z is accurately known, Z ₂
The image formation position at an arbitrary Z can be calculated from the measured value at.
It's a ridge because the first PSD 34 sits in the focal plane.
This is because it is not affected by

When undulation occurs, the straight line shown by the broken line in the figure is obtained. This straight line inclines according to the amount of undulation β with the point (Z ₂ , X ₂ ) as the center of rotation.

Next, FIG. 5 shows a block diagram for calculating the amount of waviness of the waviness amount calculation circuit. In the waviness amount calculation circuit 39 in FIG. 5, the calculated value H ₂ from the second height calculation circuit 41 is calculated.
Accordingly, the image forming position H ₁ in the case where there is no waviness in the second PSD 35 is calculated from the above equation (2). Then, the difference between the calculated value H ₁₀ of the first height calculation circuit 36 and the image forming position H ₁ due to the signals A ₁ and B ₁ of the second PSD 35 is the waviness amount Δ.
It is calculated as ₁ (= H ₁ −H ₁₀ ) (see FIG. 4).

As a result, the presence or absence of undulation is determined by the first and second
It can be determined by the PSDs 34 and 35.

Next, FIG. 6 shows a swell amount calculation block different from that of FIG. 5, and FIG. 7 shows a diagram for explaining the determination method of FIG. In this case, the first and second PSD3
4, 35 are arranged before and after the rear focus position f ₂ of the second condenser lens 32, and are not arranged at the rear focus position f ₂ .

In FIG. 6, the first and second PSD3
The first and second height calculation circuits 36 and 41 calculate the heights according to the output signals from the sensors 4 and 35, and the measured values H ₁ and H ₃ in _one scan are once stored in the memory. Then, in the second scan, the same height calculation is performed to obtain the respective measured values H ₁₀ and H ₃₀ , and the respective measured values are compared to obtain a comparison value Δ ₁ (= H ₁ −
H ₁₀ ) and Δ ₃ (H ₃ −H ₃₀ ) are calculated. This comparison value Δ
_The amount of waviness is determined from ₁ and Δ ₃ .

For example, as shown in FIG. 7, when the signs of Δ ₁ and Δ _{3 at} the first time and the second time are different, it is caused by undulation, and the amount of undulation is calculated from the variation.
When the signs of Δ ₁ and Δ _{3 at} the third time and the fourth time are the same, it is due to the height change, and the change amount of the height is calculated.

Then, by repeating this,
The thickness and swell information of the wiring pattern can be measured with high accuracy.

[0047]

As described above, according to the present invention, the second focusing means is provided so that the principal points coincide with the rear focus position of the first focusing means, and the rear focus of the second focusing means is provided. By providing the first and second optical position detection means at at least two positions, the position and the positions before and after the position, it is possible to highly accurately inspect not only the brightness and thickness information of the wiring pattern but also the undulation information. You can

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram for explaining image formation due to height and undulation in FIG.

FIG. 3 is a diagram for explaining the movement of the laser beam in FIG.

FIG. 4 is a graph showing the relationship between height change and undulation.

FIG. 5 is a block diagram of calculating a waviness amount of a waviness amount calculation circuit.

FIG. 6 is a block diagram of undulation amount calculation different from FIG.

FIG. 7 is a diagram for explaining the determination method of FIG.

FIG. 8 is a configuration diagram of a conventional wiring pattern inspection device.

FIG. 9 is a diagram for explaining reflection of a substrate to be inspected in which undulation occurs.

FIG. 10 is a diagram for explaining a conventional inspection of a substrate to be inspected.

FIG. 11 is a diagram for explaining a conventional inspection of a substrate to be inspected.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wiring pattern inspection device 2 Laser scanning optical system 3 Photodetection system 13 Inspected substrate 14 Wiring pattern 30 Processing means 31 First condensing lens 32 Second condensing lens 33 Half mirror 34 First PSD 35 Second PSD 36 First height calculation circuit 37 Brightness calculation circuit 39 Waviness amount calculation circuit 41 Second height calculation circuit

Claims (3)

[Claims] 1. A substrate to be inspected (13) on which a wiring pattern (14) is formed is irradiated with laser light by a laser beam irradiating means (2), and reflected light from the substrate to be inspected (13) is emitted.
A wiring pattern inspecting device for inspecting the wiring pattern (14) by detecting through the first light collecting means (31), wherein a principal point coincides with a back focal position of the first light collecting means (31). Second condensing means (32) provided so as to provide at least any two positions of the back focal position of the second condensing means (32) and three positions before and after the rear focal position. First and second optical position detecting means (3
4, 35) and the output signals from the first and second light position detecting means (34, 35), the height, brightness and undulation of the measurement target portion of the inspected substrate (13) are calculated. Processing means (3
0), and a wiring pattern inspecting device comprising: 2. The processing means (30) calculates a height of the measurement target portion based on an output signal from the first optical position detection means (34), and a first height calculation circuit (36) and A second height calculation circuit (B) having a brightness calculation circuit (37) for calculating the brightness and calculating the height of the measurement target portion based on the output signal from the second light position detection means (35) ( 41), and a waviness amount calculation circuit (39) for calculating the waviness of the measurement target portion based on output signals from the first and second height calculation circuits (36, 41). Claim 1
The wiring pattern inspection device described. 3. The waviness amount calculation circuit (39) is one of the first and second height calculation circuits (36, 41).
3. The wiring pattern inspection apparatus according to claim 2, wherein height data at the time of measurement is memorized, and presence or absence of undulation is determined by comparison with height data at the time of next measurement.