JPH1114324A - Pattern defect inspection method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method by which such an error is not judged as a defect even if there are deformation, strain of patterns and a positioning error between a standard pattern and an inspection object detecting pattern in a wiring board by applying a different inspection standard to patterns or respective layers in an inspection of a multilayer pattern on a multilayer wiring board to which a solder resist is applied. SOLUTION: Inspection object patterns are detected, and labeled with respective patterns mutually separated in the detected patterns, and a feature quantity of the labeled individual patterns is calculated, and a table relating this feature quantity to positions of the labeled patterns is made. Meanwhile, a pattern being a standard for these inspection object patterns is prepared, and a feature quantity of a standard pattern is also similarly calculated, and a table releated to coordinates is made. In a pattern inspection, feature quantities of nearby patterns equivalent to corresponding coordinates of the table are compared with each other, and feature quantites of the inspection object patterns and the standard pattern are compared with each other, and a defect is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting the presence or absence of a defect in a wiring board pattern, and is applicable to the inspection of general electronic circuit patterns. Board final product)
It is optimally designed for inspection of defects. Specifically, defect inspection of the exposed copper land. An object of the present invention is to provide a method and an apparatus suitable for inspecting a silk character or a silk line pattern for defects.

[0002]

2. Description of the Related Art As an inspection method of an electronic circuit pattern, a method of judging a difference between a reference pattern and an inspection target pattern as a defect is often used. A conventional method of inspecting a wiring board pattern after applying a solder resist is also this method. As shown in FIG. 1, first, a target pattern 1 is detected by a detector 10 and stored in an image storage device 12, which is used as a reference pattern. The stored image is stored as a multivalued image, for example, an image having 256 levels of density. Next, the pattern to be inspected is similarly detected, and the difference between the stored reference pattern signal 13 and the pattern signal 14 to be inspected is calculated by the difference circuit 15.
If there is a difference in the pattern, a large difference signal comes out from the difference circuit. When the difference signal is larger than a certain set value, this can be determined as a defect. This can be realized by a binarizing circuit 16 as a circuit.

[0003]

It is important to automate the appearance inspection of an electronic circuit pattern in order to improve the reliability of a product and save labor in the manufacturing process. In particular, in the manufacture of a printed wiring board, the final product, that is, the appearance inspection of the wiring board after applying the solder resist is generally performed by visual inspection. The wiring board has a green color of the solder resist 2 and a silk pattern 3 as shown in FIG.
, A light blue color of the wiring board base portion 4, and a copper metal color of the copper exposed portion 5 to form a complicated pattern. For this reason, automatic inspection is difficult, and there is no appearance inspection device with sufficient performance. However, with the increasing functionality and density of electronic devices, the demand for improved inspection quality has become more stringent, and it has become more difficult to secure skilled inspection personnel. It is mandatory.

As described above, in a conventional wiring board inspection apparatus after applying a solder resist, these multilayer patterns are collectively detected as a multivalued image. For this reason, each of the multilayer patterns can be inspected only by the same inspection standard. However, each multilayer pattern has a different inspection standard. That is, the copper exposed portion pattern is made with relatively high accuracy, and must not have a defect that hinders soldering. On the other hand, silk patterns are manufactured by silk screen printing, and the patterns are rough.
Functionally, there are not so strict inspection standards because they exist for human reference only. The required inspection method is for each of these layer patterns,
It must be a way to apply different test criteria.

Further, according to the conventional method, if the wiring board has a deformation or pattern distortion, or an alignment error between the reference pattern and the inspection object detection pattern, these are detected as defects.
Since these errors always occur in an actual wiring board, an inspection method that does not judge such errors as defects is required.

An object of the present invention is to provide a pattern inspection method capable of inspecting a multilayer pattern formed on a sample by using different inspection standards for each layer without mistaking a distortion or an alignment error of a wiring board as a defect. A method and a pattern detection device are provided.

[0007]

In order to achieve the above-mentioned object, the present invention provides a pattern defect inspection method which detects a pattern to be inspected by imaging the pattern to be inspected, and detects the pattern to be inspected. Labeling each pattern separated from each other, calculating a feature amount for each of the labeled patterns, and storing a feature amount calculated for each pattern and positional information of the pattern in advance in a reference pattern. And pattern information, and determining a defect of the inspection target pattern based on the comparison result.

Further, the pattern defect inspection apparatus includes an irradiating means for irradiating an inspection target substrate having a pattern with illumination light, an image detecting means for detecting an image of the pattern irradiated by the irradiating means, and an image detecting means. A feature amount calculating means for labeling the image of the pattern detected by the above, calculating a feature amount for each of the labeled patterns, and storing the calculated feature amount together with positional information of the pattern; Storage means for storing the obtained feature quantity and reference pattern position information, and comparing the feature quantity and position information of the pattern obtained by the feature quantity calculation means with the feature quantity and position information of the reference pattern stored in the storage means. Defect determining means for determining a defect in the pattern.

According to the present invention, there is provided a pattern defect inspection apparatus, comprising: an irradiating means for irradiating an inspection target substrate having a pattern with illumination light; and detecting the fluorescent light emitted from the inspection target substrate by the irradiating means. A fluorescent image detecting means for detecting a fluorescent image of the target substrate; a red light image detecting means for detecting a red light illuminated by the irradiating means and reflected by the test target substrate to detect a red light image of the test target substrate; A feature amount is calculated from each of the fluorescence image detected by the image detection unit and the red light image detected by the red light image detection unit, and the feature amount is compared with a previously stored feature amount of the reference pattern to be inspected. And a defect determining means for determining a defect of the substrate.

That is, according to the present invention, the dimensions of the pattern are measured, and the pattern is inspected by comparing it with the dimensions of the reference pattern. Therefore, the dimensions of the pattern can be directly inspected with high accuracy. At this time, this inspection can be executed regardless of the distortion / extension / contraction of the target pattern and the amount of positioning error.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for inspecting a pattern defect from a detected image according to the present invention will be described with reference to FIGS.

First, a first embodiment will be described with reference to FIG.

FIG. 2 shows the detected pattern to be inspected.
It is assumed that the target pattern 1 is as shown in FIG. The inspection is performed as follows.

First, the pattern 1 is subjected to a process called "labeling" by image processing. Labeling is a process for assigning numbers,... To each isolated pattern as shown in FIG.

Next, a labeled pattern,
,... Are calculated for each pattern. The feature amount is, for example, a pattern width Lxdi, a height Lyd, a pattern area Sdi, a pattern perimeter Cdi, a barycenter coordinate Mxdiydi, a second moment M2xdiydi, or the like (i
= 1, 2, 3,. . . I). Also, the representative coordinate position (X di, Y di) of each pattern is calculated. This is, for example, the upper left coordinate or barycentric coordinate of each pattern. A feature amount table 33 of the detection pattern as shown in FIG. 2C is created from the feature amounts obtained by these processes.

On the other hand, it is assumed that the pattern to be inspected includes a "reference pattern". The reference pattern is obtained by detecting a pattern created from design data or an actual pattern in advance. As shown in FIG. 2D, the labeling and the feature amount table 35 of the reference pattern (FIG. 2F) are similarly created for the reference pattern 18. The labeling numbers are ',', ', ...

From these two tables, the inspection is performed as follows.

The coordinate values (X di, Y di) of the detection pattern to be inspected are sequentially subtracted from the feature amount table of the detection pattern shown in FIG. 2C (i = 1, 2, 3,... I). The difference between these coordinate values (Xdi, Ydi) and the coordinate values (Xsj, Ysj) in the feature quantity table of the reference pattern of FIG. 2 (f), Xdi−Xsj = εx, Xdi−Ysj = εy Are sequentially obtained (j = 1, 2, 3,... J).

When | εx | ≦ E and | εy | ≦ E (E is a position error allowable constant), it is determined that both patterns are the corresponding patterns, and the feature amounts are compared. In the comparison of the feature amounts, when the difference between the feature amounts is larger than a certain reference value, it is determined that there is a difference between the two patterns, and output that there is a defect.

For example, when | Lxdi−Lxsi | ≧ ΔL and | Lydi−Lysi | ≧ ΔL, the size of the pattern is determined to be different, and the detected pattern is determined to be defective. ΔL is an inspection reference constant for the pattern width.

In the above description, the width and height of the pattern are taken as the characteristic amounts, but the area S and the perimeter C of the pattern can also be taken.

At these times, the pattern can be inspected similarly based on | C di−C si | ≧ ΔC or | S di−S si | ≧ ΔS. ΔC
Is an inspection reference constant for the perimeter and ΔS is an inspection reference constant for the area.

In the above, the width, area, and perimeter of each pattern are used as the inspection criteria. It may be.

According to the method described above, the inspection reference (ΔL, ΔC, ΔC) having a size independent of the size of the position error ε
S, etc.), and the pattern can be inspected.
By changing the size of the inspection reference constants ΔL, ΔC, ΔS, etc., a precise inspection can be performed, and a coarse inspection can also be performed.

When there is an extra pattern defect 19 as shown in FIG. 2A, there is no reference pattern corresponding to the coordinates, so that this can be determined as a defect. Since the allowable value E of the position error ε is allowed up to a half of the arrangement pitch of the pattern, the inspection can be executed under the condition that the position tolerance is very large.

Next, a second embodiment of the pattern defect inspection according to the present invention will be described with reference to FIG.

An object pattern 1 shown in FIG. 3 is a pattern of a final product of the printed wiring board (after applying a solder resist and after forming a silk pattern). In the case where this pattern is to be inspected, a patent application Hei 8-4466 is used for pattern detection.
5 (March 1, 1996) can be applied.

An embodiment of extracting a copper pattern exposed portion (land portion) and a silk pattern from a detected image of a printed wiring board after applying a solder resist using this detection method will be described below.

FIG. 3 shows an ultraviolet curing type solder resist 2.
This is an example of extracting a copper exposed portion applicable to a wiring board to which is applied. FIG. 3 uses an image F detected by the fluorescence detection method and an image R obtained by illuminating with a red light and detecting a pattern. Since the ultraviolet-curable solder resist generates fluorescence, the detection by fluorescence causes the resist portion to appear bright and the other portions to appear dark. Also, the silk pattern 3 appears bright. In the red light illumination detection pattern R, the copper exposed portion 5 and the silk pattern 3 appear bright, and the others appear dark. Next, the detected image is set to “1” for the “bright” part.
It is assumed that an image in which the “dark” portion is converted to “0” is handled.

By the resist partial erasure process 21, the process of leaving the red light detection pattern "1" only in the "0" portion of the fluorescence detection pattern and performing the process of setting the other portions to "0" is performed. It is possible to obtain a pattern C of only the copper exposed portion 5 without 3 (portion indicated by a thick solid line in “copper exposed pattern c” in FIG. 3). As a result, a copper pattern 5 not covered with the solder resist 2 is obtained. By performing labeling of the image C and tabulation 33, the copper exposed portion (the land portion 7, the copper appearance 8, and other copper exposed defect portions) can be inspected by the method described in the first embodiment.

Next, a third embodiment of the pattern defect inspection according to the present invention will be described with reference to FIG.

FIG. 4 shows a silk pattern 3 applicable to a wiring board coated with a UV-curable solder resist.
This is an embodiment of extracting the. Silk pattern extraction processing 22
As a result, only in the "1" portion of the fluorescence detection pattern F,
By performing a process of leaving “1” in the red light detection pattern R and “0” in other portions, the silk pattern 3
Only the pattern S can be obtained. Using the image S, a tabulation 34 is performed, and the silk pattern 3 can be inspected according to the first embodiment.

Further, a fourth embodiment of the present invention will be described with reference to FIG.

FIG. 5 shows an embodiment applicable to a wiring board coated with a thermosetting solder resist. As the detection of the target pattern 1, the fluorescence detection pattern F and the red light detection pattern R are used as in the above embodiment. In the case of a thermosetting solder resist, the resist portion appears dark, so the silk pattern 3 appears bright in the detection pattern F based on fluorescence, and the other portions appear dark. On the other hand, in the red light illumination detection pattern R, the exposed portion 5 of the copper and the silk pattern 3 appear bright, and the others appear dark.

By the silk pattern erasing process 23, only the "1" portion of the silk detection pattern 3 by fluorescence is
By performing a process of setting “1” of the red light detection pattern R to “0” and leaving the image of the other portion as it is,
It is possible to obtain a pattern C having only the copper exposed portion without the silk pattern 3. A tabulation 33 'is performed using the image C, and the copper exposed portion 5 (the land portion 7, the copper appearance 8, and other copper exposed defect portions) can be inspected by the method described in the first embodiment.

A fifth embodiment of the present invention will be described with reference to FIG.

FIG. 6 shows an embodiment applicable to a thermosetting type solder resist coated wiring board. A method for extracting the silk pattern 3 from the fluorescence detection pattern F will be described. In this case, since only the silk pattern 3 of the fluorescence detection pattern F is brightly exposed, the silk pattern 3 is directly changed to the pattern S by setting the bright portion of the fluorescence detection pattern F to “1” and the others to “0”. Can be extracted. Using this image S, tabulation 34 'is performed, and the silk pattern 3 can be inspected by the method described in the first embodiment.

As described above, after detecting the target pattern 1, the copper exposed portion 5 and the silk pattern 3 could be separated and extracted. The reason for this is to apply different inspection criteria. That is, the copper exposed portion 5 is a portion to which the lead of the electronic component is to be soldered later and requires precise dimensional accuracy. Therefore, the inspection is performed according to an inspection standard for performing a high-accuracy dimensional inspection.

The silk pattern 3 has no role in performing an electrical function, and is simply used by an operator for reference. Therefore, the accuracy of the pattern need not be high. In addition, since the silk pattern itself is made by printing, the accuracy is poor. Therefore, the inspection is performed according to the appropriate inspection standard. in this way,
By separating and extracting both patterns, it is possible to realize a plurality of types of patterns having different accuracies by using one inspection apparatus with an optimal inspection standard.

FIG. 7 shows an embodiment of an inspection apparatus for realizing the pattern inspection method described in the present invention.

The detectors F and R of the target pattern 1 are connected to an optical system as shown in FIG.
It is assumed that the same part of the target pattern 1 is detected by using the mirror 24. The detector F detects the target pattern 1 illuminated by short-wavelength light such as violet light by fluorescence. As the detector, a TV camera or a linear image sensor is usually used, but detection by laser beam spot scanning can be used in some cases. Although omitted in FIG. 7, the illumination unit of the optical system includes an illumination unit that illuminates the target pattern with short-wavelength light such as violet light or ultraviolet light, and an illumination unit that illuminates the target pattern with red light obliquely. Have.

The detection signal 25 output from the detector F is A /
The signal passes through the D converter 27 and has, for example, a 256-level multi-tone signal F
Is converted to Next, the signal passes through the binarization circuit 28, and becomes an image signal F1 whose brightness is "1" or "0". Similarly, a binary signal R1 is obtained from the detector R. Or later,
As shown in the embodiments described so far, the process for extracting the copper exposed portion 5 and the silk pattern 3 from the two signals F1 and R1 is performed, and the image signal S of only silk is obtained.

In the case of an ultraviolet curing resist, the silk pattern 3 is extracted by the silk pattern extracting circuit 29. By executing the logical operation shown in the third embodiment from the signal F1 and the signal R1, the silk pattern signal S
Can be obtained.

In the case of a thermosetting solder resist, the signal F1 becomes the silk pattern signal S as shown in the fifth embodiment.

In the case of an ultraviolet curable resist, the exposed copper portion 5
Can be extracted as an image signal C from the signal F1 and the signal R1 by executing the logical operation shown in the second embodiment.
This is performed by the copper exposed portion extraction circuit 30.

In the case of a thermosetting resist, the exposed copper portion 5 can be extracted as an image signal C from the signal F1 and the signal R1 by executing the logical operation shown in the fourth embodiment. This is performed by the copper exposed portion extraction circuit 30.

As described above, when the silk pattern 3 and the copper exposed portion 5 are extracted as the image signal S and the image signal C, respectively, they are passed to the labeling circuits 31 and 31 '. The feature amounts of the labeled signals S1 and C1 are calculated by the feature amount extraction circuits 32 and 32 'as described above. The calculated features are stored in the computer PC1.
To generate feature amount tables 33 and 34 including coordinates and feature amounts.

On the other hand, the standard pattern is a computer PC
2, a pattern is developed from the CAD data, and a table 35 of feature amounts corresponding to the detected copper exposure pattern and the silk pattern is created. These tables are compared and a defect inspection is performed as described in the first embodiment. Note that the labeling and feature extraction processing are general image processing techniques, and are also commercially available as circuits.

[0049]

As described above, according to the present invention, a defect can be minutely detected by measuring the dimension of a pattern. At this time, since the comparison between the detection pattern and the reference pattern is performed by comparing the dimensions of the patterns at the corresponding positions, the detection pattern and the reference pattern are hardly affected by a dimensional error or a positioning error of the wiring board. In addition, in a sample in which various patterns are formed in a laminated structure, the patterns of each layer are separated and extracted and then inspected. Therefore, it is possible to perform the inspection with an inspection standard suitable for the inspection standard of the pattern of each layer. it can. As described above, it is possible to inspect an object which has not been able to be automatically inspected in the past, so that the effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a block diagram of an inspection apparatus configuration showing a conventional inspection method.

FIG. 2 is a diagram showing a processing flow of a feature value comparison inspection method according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a flow of processing of a land inspection method according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a processing flow of a silk part separation processing example which is a third embodiment of the present invention.

FIG. 5 is a diagram showing a processing flow of an example of a copper exposed portion separation processing according to a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a processing flow of a silk part separation processing example according to a fifth embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a pattern inspection apparatus according to the present invention.

[Explanation of symbols]

1 ... target pattern, 2 ... solder resist pattern, 3 ...
Silk pattern, 4 ... Substrate part, 9 ... Lens, 10 ... Detector, 29 ... Silk pattern extraction circuit, 30 ... Copper exposed part extraction circuit, 31, 31 '... Labeling circuit, 32, 32'
… Feature extraction circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masato Sasada 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref.

Claims (10)

[Claims] An image of a pattern to be inspected is detected to detect the pattern to be inspected, and a label is attached to each of the detected patterns to be inspected that are separated from each other. A feature amount is calculated, the feature amount calculated for each pattern and the position information of the pattern are compared with the feature amount and position information of a reference pattern stored in advance, and a defect of the inspection target pattern is determined based on the comparison result. A pattern defect inspection method, characterized in that: 2. The method according to claim 1, wherein the feature quantity includes at least one of a pattern dimension, an area, a perimeter, a center of gravity, a second moment, an Nth order, and a square of the area / perimeter. The pattern defect inspection method according to claim 1, wherein: 3. The pattern defect inspection method according to claim 1, wherein the pattern to be inspected is a pattern of a printed wiring board to which a solder resist is applied. 4. Detecting the pattern to be inspected,
The printed wiring board coated with the solder resist is illuminated with short-wavelength light such as violet light, and the first image is obtained by detecting the fluorescence generated from the solder resist portion and the silk print pattern,
The printed wiring board is illuminated with red light, and the printed wiring board illuminated with the red light is imaged to obtain a second image in which a copper exposed portion and a silk print pattern are revealed, and the first image and the second image are obtained. 2. The pattern defect inspection method according to claim 1, wherein the method is performed by extracting a copper exposed portion and a silk print pattern from the second image. 5. Detecting the pattern to be inspected,
Ignore the red detection image in the bright part of the fluorescence detection image,
2. The pattern defect inspection method according to claim 1, wherein the inspection is performed by extracting a copper exposed portion while leaving a red detection image only in a dark portion of the fluorescence detection image. 6. Detecting the pattern to be inspected,
2. The pattern defect inspection according to claim 1, wherein a red detection image is left in a bright portion of the fluorescence detection image and a silk pattern is extracted by ignoring the red detection image in a dark portion of the fluorescence detection image. Method. 7. Detecting the pattern to be inspected,
2. The pattern defect inspection method according to claim 1, wherein the method is performed by extracting a silk pattern from a bright portion of the fluorescence detection image. 8. An irradiating unit for irradiating an inspection target substrate having a pattern with illumination light, an image detecting unit for detecting an image of the pattern illuminated by the irradiating unit, and an image detecting unit detecting the image detected by the image detecting unit. A feature amount calculating means for labeling an image of a pattern, calculating a feature amount for each of the labeled patterns, and storing the calculated feature amount together with position information of the pattern; and a feature amount of a reference pattern calculated in advance. Storage means for storing an amount and position information of the reference pattern, and the characteristic amount and position information of the reference pattern stored in the storage means, the characteristic amount and position information of the pattern obtained by the characteristic amount calculation means. A pattern defect inspection device comprising: a defect determining unit that compares and determines a defect of the pattern. 9. An irradiating means for irradiating an inspection target substrate having a pattern with illumination light, and detecting fluorescence emitted from said inspection target substrate by being radiated by said irradiating means to detect a fluorescent image of said inspection target substrate. A fluorescent light image detecting means, a red light image detecting means for detecting a red light irradiated by the irradiating means and reflected by the test target substrate to detect a red light image of the test target substrate, and the fluorescent image detecting means A feature amount is calculated from each of the detected fluorescence image and the red light image detected by the red light image detection means, and the feature amount is compared with a previously stored feature amount of a reference pattern, and the inspection object is calculated. A pattern defect inspection apparatus comprising: a defect determination unit that determines a defect of a substrate. 10. The illumination device according to claim 8, wherein said illuminating means has a first irradiating unit for irradiating violet light or ultraviolet light and a second irradiating unit for irradiating red light. Pattern defect inspection equipment.