WO2013183471A1 - Appearance inspection device and appearance inspection method - Google Patents

Abstract

Provided is an appearance inspection device that can perform strict good-or-defective determination without being impacted by the unevenness of a formed film, while maintaining favorable examination resolution and short inspection takt time. More specifically, the following are provided: an examination pattern specifying section for specifying, as an examination-target pattern image, a partial region of image data acquired using an image acquisition section; a luminance information acquisition section for acquiring luminance information for each divided region in which examination-target pattern images are divided into a matrix shape; and a determination reference pattern registering section for registering a previously acquired examination-target pattern as a determination reference pattern. The appearance inspection device is characterized by being provided with the following: a luminance difference calculation section for comparing the determination reference pattern and an examination target pattern to be acquired next as a target of good-or-defective determination and thereby calculating the luminous information difference; a good-or-defective reference registration section for pre-registering in divided regions a good-or-defective determination reference value relating to luminance-information differences of divided regions calculated using the luminance difference calculation section; and a good-or-defective determination section for performing good-or-defective determination for the divided regions of the examination target pattern on the basis of the reference value of good-or-defective determination.

Description

Appearance inspection apparatus and appearance inspection method

The present invention continuously captures appearance images of a plurality of circuit patterns and transfer patterns formed on a substrate to be inspected, such as a semiconductor wafer, a photomask, and a printed circuit board, and inspects the quality of the pattern. The present invention relates to an inspection apparatus and an appearance inspection method.

A plurality of circuit patterns and transfer patterns formed in a matrix on a substrate such as a semiconductor wafer, photomask, or printed circuit board are visually inspected to determine whether the patterns are patterned in a predetermined state. Has been done. In this appearance inspection, the presence or absence of foreign matters contained in the pattern, chipping / peeling of the pattern, thinning / thickening of the pattern, etc. is inspected. As a specific visual inspection procedure, a pattern to be inspected is continuously imaged by an imaging camera, luminance information contained in an image acquired by imaging is extracted, and pass / fail judgment is performed based on the extracted luminance information It is carried out.

FIG. 8 is a plan view of a semiconductor wafer on which a plurality of patterns to be inspected are arranged.
FIG. 8 shows a state in which the semiconductor wafer Wz to be inspected is placed on the placement table 20. A plurality of chips Dz (n) (n = 1 to N) are patterned on the semiconductor wafer Wz. Further, the chips Dz (n) are in the order indicated by the broken-line arrows in the drawing, that is, the order of Dz (1), Dz (2), Dz (3), Dz (4), ..., Dz (N). Thus, the imaging is sequentially performed. The images of the chips Dz (1) to Dz (N) obtained by sequentially capturing images in the above order are further subdivided into a matrix, and luminance information is acquired for each subdivided divided area. The

FIG. 9 is an image diagram showing a divided region P (i, j) that is subdivided into a matrix with respect to the pattern of the chip Dz (n) picked up at the nth time. Here, n = 1 to N, i = 1 to I, and j = 1 to J (the same applies hereinafter). The first chip Dz (1) to the fourth chip Dz (4) schematically represent circuit patterns using patterns in which two figures such as “F” having different line densities are overlapped. Has been. Each of the chips Dz (1) to Dz (4) is subdivided into a matrix of I rows × J columns, and respective divided regions P (1, 1) to P (I, J) are set.

9, (a) shows a non-defective chip Dz (1), (b) shows a non-defective chip Dz (2) including the defective pattern B1, (c) shows a non-defective chip Dz (3), d) shows a defective chip Dz (4) including the defective pattern B2, and (e) shows a chip D0 as a non-defective model serving as a determination reference pattern.

In the chip Dz (1) illustrated in FIG. 9A, the luminance information Bz (1, i, j) of each divided region P (i, j) is acquired. The acquired luminance information B (1, i, j) is determined to be good or bad based on an allowable range associated with the luminance information B0 (i, j) of the chip D0 serving as a determination reference pattern.
The chip Dz (1) is a non-defective product if the luminance information B (1, 1, 1) to B (1, i, j) of each divided region P is within the allowable range associated with the luminance information B0. Is determined.

Since the chip Dz (2) shown in FIG. 9B includes the defective pattern B1, the luminance information B of the divided area P of the portion is out of the allowable range associated with the luminance information B0 of the chip D0. It is determined as a defective product.
The chip Dz (3) shown in FIG. 9C does not include a defective pattern, and the luminance information B of the divided area P in the portion is within the allowable range associated with the luminance information B0 of the chip D0. It is determined as a non-defective product.
Since the chip Dz (4) shown in FIG. 9D includes the defective pattern B2, the luminance information B of the divided area P of the portion is out of the allowable range associated with the luminance information B0 of the chip D0. It is determined as a defective product.

In the conventional inspection, in order to define the chip D0 serving as a determination reference pattern as a non-defective model, a plurality of non-defective products are selected from images acquired in the past, and the positions of the selected images are determined. The luminance information B of the corresponding divided area P is registered by averaging (for example, Patent Document 1).

In addition, along with the pattern to be inspected, the surrounding pattern is also acquired at the same time, the average data of the eight images around the inspection target pattern is set as a non-defective model, and compared with the central inspection target pattern. The technique which performs is proposed (for example, patent document 2).

Special Table 2003-156475 JP 2005-156475 A

The pattern formed on the substrate to be inspected is formed through a film forming process and a patterning process. At this time, the luminance information at the time of pattern inspection varies due to the influence of the film thickness change in the film forming process. In particular, the influence of the change of the film thickness in the spin coating for applying the photoresist is large, and the film thickness gradually changes from the center of the substrate to the peripheral part. Therefore, in the pattern inspection after exposure / development, the luminance information of the inspection target pattern gradually changes from the center of the substrate to the peripheral portion.

FIG. 10 is a plan view of another semiconductor wafer on which a plurality of patterns to be inspected are arranged. Unlike the embodiment shown in FIG. 8, the semiconductor wafer W is affected by a change in film thickness in the film forming process. For this reason, the semiconductor wafer W is gradually thinned from the center in the outer peripheral direction, and the film thickness gradually changes, and the part C1 with a slightly thin film, the part C2 with an average film thickness, and the part C3 with a slightly thick film However, it occurs several times concentrically.

However, in the case of the semiconductor wafer W including such a change in film thickness, in the form in which a non-defective product model is specified from images acquired in the past and a determination reference pattern for determining pass / fail is specified, the brightness of the acquired image In some cases, it is possible to make an erroneous determination that a good product is a defective product. In addition, in order to avoid such a phenomenon, if the allowable range for a non-defective product is widened, an erroneous determination that a defective product is a good product may be made.

On the other hand, in the case of the inspection form in which the inspection target image and the neighboring adjacent images are observed at a time and an average image is generated from the neighboring neighboring images and used as a reference pattern for the inspection, the following problems are involved. .
1) If the resolution of the imaging camera remains the same, the observation area expands at a time, so the observation magnification is low. Therefore, the resolution of the inspection target pattern is lowered.
2) To maintain the resolution of the pattern to be inspected, it is necessary to increase the resolution of the imaging camera or increase the number of imaging cameras, and the amount of image information handled increases accordingly. Therefore, the time required for one process is longer than before.

Therefore, the present invention provides an appearance inspection apparatus and an appearance inspection method capable of performing strict pass / fail judgment without being affected by unevenness of film formation while maintaining good inspection resolution and a short inspection tact.

In order to solve the above problems, the invention described in claim 1
In an appearance inspection apparatus that images and inspects the appearance of the pattern on a substrate on which a plurality of patterns are repeatedly patterned,
A mounting table for mounting the substrate;
A moving stage unit for moving the mounting table in a predetermined direction;
An illumination unit that emits light toward the substrate;
An imaging unit for imaging a pattern on the substrate;
An image acquisition unit that acquires, as image data, a pattern on the substrate imaged by the imaging unit;
Among the image data acquired by the image acquisition unit, an inspection pattern specifying unit that specifies at least a part of the region as an inspection target pattern image;
About the inspection target pattern image, a luminance information acquisition unit that acquires luminance information for each divided region divided into a matrix,
A determination reference pattern registration unit for registering the previously acquired inspection target pattern as a determination reference pattern;
A luminance difference calculation unit that compares the determination reference pattern with an inspection target pattern to be acquired next and is a target of pass / fail determination, and calculates a difference in luminance information for each of the divided regions corresponding to the position of the comparison pattern; ,
A pass / fail criterion registering unit that pre-registers, for each of the divided regions, a reference value for determining pass / fail for the difference in luminance information calculated for each of the divided regions calculated by the brightness difference calculating unit;
An appearance inspection apparatus comprising: a quality determination unit that performs quality determination for each of the divided regions of the inspection target pattern based on the quality determination reference value.

The invention described in claim 2
The reference value for the pass / fail judgment is:
A standard deviation set for each of the divided areas;
Multiplying the standard deviation by a multiplication factor;
An offset value that is added to a value obtained by multiplying the standard deviation by the magnification factor,
The appearance inspection apparatus according to claim 1, further comprising a determination reference parameter registration unit that registers the offset value, the magnification count, and a standard deviation set for each divided region.

The invention according to claim 3
The determination reference pattern as a first inspection target pattern,
Next, the second inspection target pattern is the inspection target pattern that is acquired next and is the target of pass / fail judgment,
Obtaining a third inspection target circuit pattern different from the two inspection target patterns;
In the luminance difference calculation unit,
A first luminance difference calculation unit for calculating a difference in luminance information between the first and second inspection target patterns;
A second luminance difference calculation unit for calculating a difference in luminance information between the first and third inspection target patterns;
In the pass / fail judgment section,
A first pass / fail determination unit that performs pass / fail determination on a difference in brightness information for each of the divided areas calculated by the first brightness difference calculation unit;
A second pass / fail determination unit that performs pass / fail determination on the difference in brightness information for each of the divided areas calculated by the second brightness difference calculation unit;
If one of the result of the first pass / fail determination unit and the result of the second pass / fail determination unit is a pass determination, the part is determined to be a passable product,
The integrated determination unit is provided, wherein if both the result of the first pass / fail determination unit and the result of the second pass / fail determination unit are determined to be defective, the part is determined to be a defective product. An appearance inspection apparatus according to claim 2.

The invention according to claim 4
4. The appearance inspection apparatus according to claim 1, wherein the inspection target pattern to be inspected is adjacent to the determination reference pattern.

The invention described in claim 5
5. The inspection target pattern is replaced with the determination reference pattern if the inspection target pattern to be inspected is determined to be a non-defective product in the quality determination unit. It is an appearance inspection device.

The invention described in claim 6
Acquire the first to third inspection target patterns immediately after the start of inspection,
In the luminance difference calculation unit,
The difference between the luminance information of the first and second inspection target patterns is the first difference,
The difference between the luminance information of the first and third inspection target patterns is the second difference,
In the pass / fail judgment unit,
A pass / fail determination is made for each of the first difference and the second difference,
Determined by the pass / fail determination unit,
The first inspection target pattern is registered as a non-defective product in the determination reference pattern registration unit if any one of the first difference and the second difference is determined to be good. 6. An appearance inspection apparatus according to any one of 1 to 5.

The invention described in claim 7
In an appearance inspection method for imaging and inspecting the appearance of the pattern on a substrate on which a plurality of patterns are repeatedly patterned,
A substrate mounting step for mounting the substrate on a mounting table;
A table moving step for moving the mounting table in a predetermined direction;
An illumination light irradiation step for irradiating light toward the substrate;
An imaging step of imaging a pattern on the substrate;
An image acquisition step of acquiring the pattern on the substrate imaged in the imaging step as image data;
An inspection pattern specifying step of specifying at least a part of the image data acquired in the image acquisition step as an inspection target pattern image;
For the inspection target pattern image, a luminance information acquisition step for acquiring luminance information for each divided region divided in a matrix,
A determination reference pattern registration step for registering the previously acquired inspection target pattern as a determination reference pattern,
A luminance difference calculation step of comparing the determination reference pattern with an inspection target pattern to be acquired next and being a pass / fail determination target, and calculating a difference in luminance information for each of the divided regions corresponding to the position;
A pass / fail criterion registration step of pre-registering, for each of the divided regions, a reference value for determining pass / fail for the difference in luminance information for each of the divided regions calculated by the brightness difference calculating unit;
An appearance inspection method comprising: a quality determination step for performing quality determination for each of the divided regions of the inspection target pattern based on the quality determination reference value.

The invention according to claim 8 provides:
The reference value for the pass / fail judgment is:
A standard deviation set for each of the divided areas;
Multiplying the standard deviation by a multiplication factor;
An offset value that is added to a value obtained by multiplying the standard deviation by the magnification factor,
8. The appearance inspection method according to claim 7, further comprising a determination criterion parameter registration step of registering the offset value, the magnification count, and a standard deviation set for each divided region. .

The invention according to claim 9 is:
The determination reference pattern as a first inspection target pattern,
Next, the second inspection target pattern is the inspection target pattern that is acquired next and is the target of pass / fail judgment,
Obtaining a third test target circuit pattern different from the two different test target patterns;
In the luminance difference calculation step,
A first luminance difference calculating step for calculating a difference in luminance information between the first and second inspection target patterns;
A second luminance difference calculating step for calculating a difference between luminance information of the first and third inspection target patterns;
In the pass / fail judgment step,
A first pass / fail judgment step for performing pass / fail judgment on the difference of the brightness information for each of the divided areas calculated in the first brightness difference calculating step;
A second pass / fail determination step for determining pass / fail with respect to the difference in brightness information for each of the divided areas calculated in the second brightness difference calculating step;
If any one of the result of the first pass / fail determination step and the result of the second pass / fail determination step is a pass determination, the portion is determined to be a passable product,
The system further comprises an overall determination step in which if both the result of the first pass / fail determination step and the result of the second pass / fail determination step are determined to be defective, the part is determined to be a defective product. The visual inspection method according to claim 7 or claim 8.

The invention according to claim 10 is:
10. The appearance inspection method according to claim 7, wherein the inspection target pattern to be inspected is adjacent to the determination reference pattern.

The invention according to claim 11
11. The inspection target pattern is replaced with the determination reference pattern if the inspection target pattern to be inspected is determined to be non-defective in the pass / fail determination step. This is an appearance inspection method.

The invention according to claim 12
Acquire the first to third inspection target patterns immediately after the start of inspection,
In the luminance difference calculation step,
The difference between the luminance information of the first and second inspection target patterns is the first difference,
The difference between the luminance information of the first and third inspection target patterns is the second difference,
In the pass / fail judgment step,
A pass / fail determination is made for each of the first difference and the second difference,
Determined in the pass / fail determination step,
The registration of the determination reference pattern registration step is performed when one of the first difference and the second difference is determined to be good, and the first inspection target pattern is determined as non-defective. The visual inspection method according to any one of 7 to 11.

By using the appearance inspection apparatus and the appearance inspection method according to the present invention, it is possible to perform strict pass / fail judgment without being affected by unevenness of film formation while maintaining good inspection resolution and short inspection tact.

The conceptual diagram which shows an example of the form which embodies this invention The conceptual diagram which shows the mode of the imaging in an example of the form which embodies this invention The conceptual diagram which shows the division area of the acquisition image in an example of the form which embodies this invention The image acquisition flowchart in an example of the form which embodies the present invention The quality determination flowchart in an example of the embodiment embodying the present invention The quality determination flowchart in another example of the embodiment embodying the present invention The quality determination flowchart in yet another example of the embodiment embodying the present invention A plan view of a semiconductor wafer on which a plurality of patterns to be inspected are arranged The image figure which shows the division area P subdivided in the matrix form about the pattern of the imaged chip | tip D Plan view of another semiconductor wafer on which a plurality of patterns to be inspected are arranged

DESCRIPTION OF EMBODIMENTS Embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram showing an example of a form for embodying the present invention, in which a perspective view of an apparatus used for acquiring an image and a block diagram of a configuration necessary for an appearance inspection by acquiring an image are combined. Are listed.
In FIG. 1, the three axes of the orthogonal coordinate system are X, Y, and Z, the XY plane is the horizontal plane, and the Z direction is the vertical direction. In particular, in the Z direction, the direction of the arrow is represented as the top, and the opposite direction is represented as the bottom.

The appearance inspection apparatus 1 according to the present invention includes a placement table 20, a moving stage unit 2, an illumination unit 3, an imaging unit 4, an image acquisition unit 5, an inspection pattern specifying unit 6, and a luminance information acquisition unit 7. And a determination reference pattern registration unit 8, a luminance difference calculation unit 9, a quality reference registration unit 10, and a quality determination unit 11.

The mounting table 20 is for mounting the substrate W to be inspected, and has a flat surface in the XY direction. The mounting table 20 has grooves and pores formed in a portion where a substrate to be inspected is mounted. Further, the grooves and pores are connected to a vacuum source and a compressed air source via an open / close valve.

The moving stage unit 2 moves the mounting table 20 to an arbitrary position on the XY plane. The moving stage unit 2 includes an X-axis slider 21 and a Y-axis slider 22. The X-axis slider 21 is mounted on the apparatus frame 1F, moves at a predetermined speed in the X direction, and can be stopped at an arbitrary position. The Y-axis slider 22 is mounted on the X-axis slider 21, moves at a predetermined speed in the Y direction, and can be stopped at an arbitrary position. The mounting table 20 is mounted on the Y-axis slider 22. Therefore, the moving stage unit 2 can move the mounting table 20 at a predetermined speed alone or in conjunction with each other in the X direction and the Y direction, and can stand still at an arbitrary position.

The illumination unit 3 irradiates light toward the substrate W to be inspected, and includes a light source unit 31. The light source unit 31 is attached to the lens barrel 40, and the light 32 emitted from the light source unit 31 is reflected by the half mirror 41 incorporated in the lens barrel 40, passes through the objective lens 44a, and irradiates the substrate W. Is done. The light source unit 31 can be exemplified by using strobe illumination as a specific example. The strobe illumination is configured to repeat light emission at predetermined feed pitches in cooperation with the movement of the X-axis slider 21 and the Y-axis slider 22 of the moving stage unit 2. In addition, the light source part 31 is not restricted to the form directly attached to the lens-barrel 40, The thing of the form light-guided using a light guide from the light source installed in another place may be sufficient.

The imaging unit 4 images a pattern on the substrate W to be inspected, and includes a lens barrel 40, a half mirror 41, an objective lens 44a, and an imaging camera 45.
The imaging camera 45 is configured to include a light receiving element 46, and among the light 35 irradiated to the substrate W, the light 42 reflected by the observation region V on the substrate W is an objective lens 42 a, a half mirror 41, An image that passes through the lens barrel 43 and is irradiated on the light receiving element 46 is output to the outside as image data.
Specifically, imaging is performed simultaneously with the light emission of the strobe illumination, and image data is output. At this time, since the light emission time of the strobe illumination is very short, even an image captured during movement is captured in a state like a still image.

The image acquisition unit 5 acquires a pattern included in the observation region V on the substrate W imaged by the light receiving element 46 of the imaging camera 45 as image data.
Specifically, the image acquisition unit 5 can be configured using a device called a so-called image processing apparatus. Examples of the image processing apparatus include a unit type having an image processing function and a type using a board called an image processing board incorporated in a personal computer or a workstation.

Since the appearance inspection apparatus 1 according to the present invention is configured as described above, continuous imaging is performed while moving the mounting table 20 on which the substrate W to be inspected is placed at a predetermined speed, and the inspection object is inspected. Image data corresponding to the pattern can be acquired. Further, the acquired image data is judged as good or bad as described later.

Note that when the pattern on the substrate W is continuously imaged, the position of the pattern (chip D) patterned on the actual substrate W varies, and the moving speed of the moving stage unit 2 varies. To do. Therefore, even if the same part is intended to be imaged every time, it may be acquired in a slightly shifted state. Therefore, the range of the observation region V imaged by the imaging unit 5 is set to be slightly wider than the range in which the pattern (chip D) necessary for actual inspection can be observed.

FIG. 2 is a conceptual diagram showing a state of imaging in an example of a form embodying the present invention.
In FIG. 2, the first camera D (1) to the fourth chip among the N chips D (N) arranged on the substrate W while the imaging camera 45 moves relatively in the direction indicated by the arrow Vs. A state in which chips D (4) are sequentially imaged is shown. At the time shown in FIG. 2, the imaging camera 45 is imaging the third chip D (3). Further, at this time, although optical components such as a lens are not shown, the range of the observation region V set slightly wider than the chip D (3) is projected onto the light receiving element 46.

The inspection pattern specifying unit 6 specifies at least a part of the image data acquired by the image acquisition unit 5 as an inspection target pattern image.
Specifically, the inspection pattern specifying unit 6 is configured by using a device called an image processing apparatus similar to the image acquiring unit 5, and specifying necessary for appearance inspection from the image data acquired by the image acquiring unit 5. The inspection pattern is extracted.
If it demonstrates using FIG. 2, the area | region corresponding to the 3rd chip | tip D (3) included in the area | region of the whole observation area | region V will be specified as a test object pattern image. The processing to be specified is performed based on the alignment position of the periphery of each chip D (n), the peripheral pattern, and the relative position of the internal pattern, and the corresponding positions of the patterns to be compared in the processing described later are Make sure they are aligned.

In this way, the entire region of the observation region V and each chip D (n) are identified by extracting a necessary pattern, for example, by trimming unnecessary peripheral portions of the acquired image data, It can be used for comparison processing and luminance difference processing described later.

The luminance information acquisition unit 7 finely divides the image specified as the inspection target pattern image into a matrix, and acquires luminance information for each divided area P. Each of the divided areas P is, for example, a minute area corresponding to each of the light receiving elements 46 of the imaging camera 45, or a group of several light receiving elements (100 × 100 or 1000 × 1000) or the like.

FIG. 3 is a conceptual diagram showing divided areas of an acquired image in an example of a form embodying the present invention. In FIG. 3, the first chip D (1) to the fourth chip D (4) on the substrate W, which is the specified pattern image to be inspected, are divided into a matrix-like divided region P of I rows × J columns. The state of the arrangement of the subdivided individual divided areas P (i, j) is shown. Note that i = 1 to I and j = 1 to J (hereinafter the same).

Also, the luminance information about P (i, j) for each divided area of the nth chip D (n) is expressed as luminance information B (n, i, j). The luminance information B (n, i, j) is determined by an output signal from the imaging camera 45 and is expressed by, for example, a value by an 8-bit signal (tone data from black: 0 to white: 255).

The determination reference pattern registration unit A registers the previously acquired inspection target pattern as a determination reference pattern. Specifically, the first inspection target pattern of the substrate to be inspected is set, the pattern inspected immediately before in the flow of sequential inspection, or the flow of sequential inspection Among them, the pattern determined to be non-defective is set last (in other words, immediately before).
For example, the luminance information B (n−1, i, j) of the “n−1” th chip D (n−1) immediately before the nth chip D (n) is stored in the determination reference pattern registration unit A. Register.

The luminance difference calculation unit 8 compares a determination reference pattern with an inspection target pattern that is acquired next and is a target of pass / fail determination, and calculates a difference in luminance information for each divided region corresponding to each position. is there.
Specifically, the luminance information B (n, i, j) of the nth chip D (n) and the luminance of the “n−1” th chip D (n−1) registered as the determination reference pattern. A difference def (n, i, j) from the information B (n-1, i, j) is calculated using the following equation.

The pass / fail criterion registration unit B registers in advance a pass / fail judgment reference value for the difference in brightness information for each divided coordinate calculated by the brightness difference calculation unit for each divided region.
Specifically, when the luminance information B is acquired as a value by an 8-bit signal (tone data from black: 0 to white: 255), the reference value for pass / fail judgment is ± 5 in a certain range of divided areas. The reference values for pass / fail judgment are set individually such that the reference value for pass / fail judgment is ± 10 in the divided areas of another range, and the reference value for pass / fail judgment is ± 20 in the divided areas of another range.

Table 1 shows an example of the pass / fail criterion table for the chip D (n) of the type K.
A criterion def0 (i, j) is defined for each divided region P (i, j).

For example, if the criterion def0 (i, j) corresponding to P (i, j) is defined as “20”, “10”, “5”, the luminance difference of the divided region P (i, j) is If it is “within ± 20”, “within ± 10”, or “within ± 5”, it means that it can be determined as a non-defective product.
The data table of this determination criterion def0 (i, j) is registered in advance in association with the product information of the chip D.

The determination reference data table may be in the form exemplified above, but it is more preferable to do the following.
The criterion def0 (i, j), which is a criterion value for pass / fail judgment, is not a fixed value but a value represented by Equation (2).

At this time, the standard deviation σ (i, j), magnification factor b, and offset value a set for each divided region P (i, j) are used.

The standard deviation σ (i, j) set for each divided region P (i, j) is calculated from the distribution of luminance information of the pattern image to be inspected acquired from a plurality of chips that are known to be non-defective in advance.
The magnification factors a and b are set according to the following procedure. A chip having a defect to be detected and a good chip are prepared in advance. As an initial value, the offset value a = 0.
1) Find the last magnification factor b (= b1) that does not miss the defect to be detected.
2) On the other hand, a magnification factor b (= b2) is calculated, which is the last minute that the non-defective product does not become defective.
3) The intermediate value between b1 and b2 is set as the sensitivity.
The above-determined a and b are inspected, and if over-detection does not occur, this value is adopted, and if over-detection occurs, the value of a is increased to 1) to 3) above. To implement.

Each criterion parameter thus set: standard deviation σ (i, j), magnification factor b, offset value a set for each divided region P (i, j), and formula for calculating the criterion value Based on (2), pass / fail determination is performed. In this pass / fail judgment, if def (i, j) is within a range of ± {a + b · σ (i, j)}, that is, if Formula (3) is satisfied, it is judged as a non-defective product.

In this way, the criterion def0 (i, j) is not a fixed value,
Standard deviation σ (i, j) for each divided region derived from a plurality of non-defective samples,
It can be quickly set using two parameters a and b determined by the person in charge of inspection.
By doing so, it is possible to perform inspection within a wide allowable range for a portion with originally large variation, and to perform inspection with a narrow allowable range for a portion with originally small variation.

Furthermore, it is possible to respond quickly when it becomes necessary to change the reference value of the pass / fail judgment determined at the beginning while repeating the inspection. That is, if a defective product appears to be a non-defective product, the standard deviation σ (i, j), magnification factor b, and offset value a set for each divided region are included again including the image of the pattern. Can be re-determined.

By doing so, even if a film formation unevenness that was not anticipated was caused and a false detection was detected, the inspection conditions were reset to the optimum one, and a strict pass / fail judgment was made without being affected by the film formation unevenness. You can do it. In addition, it is not necessary to manually set the pass / fail judgment reference value for each divided area, so that it can be quickly reset and operated.
In addition, it is preferable to set these values for each inspection type as determination criterion parameters.

The pass / fail judgment unit 9 performs pass / fail judgment for each divided region of the inspection target pattern based on the pass / fail judgment reference value.
Specifically, when the reference value for pass / fail judgment is set to “5” in a certain area, the difference in luminance information of the corresponding divided areas between the previous image data and the subsequent image data is “ If it is “within ± 5”, the product is judged as non-defective, otherwise it is judged as defective. Alternatively, as described above, the quality determination is performed as a non-defective product if Equation (3) is satisfied, and as a defective product if it is not considered.

Since the appearance inspection apparatus 1 according to the present invention has the above-described configuration, it is possible to perform pass / fail determination from the difference between the image data acquired first and the image data acquired later.
The result of the pass / fail judgment is displayed on an information display provided in the appearance inspection apparatus 1, stored in a data collection unit, or transmitted to a host computer connected to the appearance inspection apparatus 1 through a communication line. The information display is configured using a so-called display monitor such as a liquid crystal display. The data collection unit is configured using an information recording medium such as a memory or a hard disk.

The appearance inspection method according to the present invention can be carried out by performing an image acquisition flow and a quality determination flow after image acquisition described below.
[Image acquisition flow]
FIG. 4 is an image acquisition flowchart in an example of a form embodying the present invention.
FIG. 4 shows a series of steps for acquiring image data of each inspection target pattern for each step in order to inspect a plurality of inspection target patterns arranged on the substrate W.

First, the substrate W to be inspected is placed on the placement table 20 of the appearance inspection apparatus 1 (s1: substrate placement step).
Next, pre-registered inspection conditions and the like are read (s2), moved to a reference mark reading position formed on the substrate W, and an alignment operation is performed (s3).

Subsequently, the mounting table 20 is moved to the movement start position in the first row (s4), the moving stage unit 2 is moved at a predetermined speed, and the movement of the mounting table 20 is started (s5: table moving step). .
While moving the mounting table 20, the current position information of the mounting table 20 is acquired from the X-axis position detector and the Y-axis position detector of the moving stage unit 2 (s6).

Based on the acquired current position information of the mounting table 20, it is determined whether or not it is a position where the imaging camera 45 should image the substrate W (s 7). If the current position of the mounting table 20 is a position where the imaging camera 45 should image the substrate W, strobe illumination is emitted toward the substrate W (s8: illumination light irradiation step), and at the same time, it is reflected from the substrate W. The captured light is imaged by the imaging camera 45 (s9: imaging step).

The image data captured by the imaging camera 45 will be described in detail later, but an image is acquired and a pass / fail judgment is made (s10).

While continuing the movement of the mounting table 20, it is determined based on the current position information whether or not one line of imaging has been completed (s21). If it is determined that the imaging of the first row has been completed, the movement of the moving stage unit 2 is stopped (s22). On the other hand, if it is determined in step s21 that the imaging in the first row has not been completed, steps s8 to s21 are repeated.

Next, after the above step s22, it is determined whether or not the imaging of all the columns is completed on the substrate W (s23). If it is determined that all the imaging is completed, the substrate W is taken out from the mounting table 20 (s24). . On the other hand, if it is determined in step s23 that the imaging of all the rows has not been completed, the placement table 20 is moved to the measurement start position of the next row (s4), and the steps necessary for the series of image acquisition ( Repeat s4 to s23).

[Flow of pass / fail judgment after image acquisition]
FIG. 5 is a pass / fail judgment flowchart in an example of a form embodying the present invention.
In FIG. 5, a series of steps for continuously determining pass / fail based on the image data acquired in step s10 is shown in detail for each step.

First, the pattern on the substrate W imaged in the imaging step (s9) is acquired as image data (s105: image acquisition step).
Next, at least a part of the acquired image data is specified as an inspection target pattern image (s106: inspection pattern specifying step). In this step, a so-called trimming process (also referred to as a crop process) is performed to remove unnecessary portions outside the area necessary for the inspection. Alternatively, processing for extracting and specifying the inspection target pattern included in the image data is performed based on positioning reference marks arranged in and around the inspection target pattern.

The inspection target pattern image identified in step s106 is divided into a matrix and luminance information is acquired for each divided region (s107: luminance information acquisition step).
In this step s107, for example, the nth chip D (n) on the substrate W is subdivided into I-row × J-column matrix-like divided areas to define individual divided areas P (i, j). The luminance information B (n, i, j) is acquired for each divided region P (i, j).
The acquired luminance information B (n, i, j) is stored in a temporary storage memory in the image processing unit or stored in a data recording medium connected to the image processing unit.

When the n-th chip D (n) is inspected, the inspection target pattern (that is, the (n−1) -th chip D (n−1)) acquired immediately before the inspection target pattern is used as the determination reference pattern. (S10A: determination reference pattern registration step).

The luminance information B (n, i, j) of the nth chip D (n) and the luminance information B (n−1) of the “n−1” th chip D (n−1) as the determination reference pattern. , I, j) is calculated (s108: luminance difference calculation step).

In addition, the pass / fail judgment standard def0 (n, i, j), which is the pass / fail judgment standard, is registered in advance (s10B: pass / fail standard registration step).

Then, the luminance difference def (n, i, j) calculated in step s108 is compared with a pass / fail judgment criterion def0 (n, i, j), and each divided region P (i, j) of the nth chip D (n) is compared. J) is judged for pass / fail (s109: pass / fail judgment step).

Then, the luminance information B (n, i, j) of the nth chip D (n) is updated and registered as a determination reference pattern used for the next (n + 1) th inspection (s110).

In the embodiment according to the above-described appearance inspection method, the determination for registering the offset value, the magnification factor, and the standard deviation set for each divided region is performed in the same manner as in the aspect related to the appearance inspection apparatus described above. Preferably, the method further includes a reference parameter registration step. By doing so, it is possible to perform a strict quality determination without being affected by film formation unevenness. In addition, it is not necessary to manually set the pass / fail judgment reference value for each divided area, so that it can be quickly reset and operated.

[Second form]
When the previous inspection target pattern is a non-defective product and the subsequent inspection target pattern is a defective product, the subsequent inspection target pattern is determined as a defective product. However, even if the subsequent pattern to be inspected is a non-defective product, if the determination is made based on the difference, the quality determination cannot be performed correctly. Therefore, the determination reference pattern is set as the first inspection target pattern, the inspection target pattern to be acquired and passed next is set as the second inspection target pattern, and is different from these two inspection target patterns. A third circuit pattern to be inspected is acquired. Then, the following two-step determination is performed so that the pass / fail determination can be performed correctly.

The appearance inspection apparatus 1B according to the present invention has the same apparatus configuration as the appearance inspection apparatus 1 described above, includes a first luminance difference calculation unit 7A and a second luminance difference calculation unit 7B, and replaces the pass / fail determination unit 9. The pass / fail judgment unit 9B is included.

The first luminance difference calculation unit 7A has the same configuration as the luminance difference calculation unit 7 of the appearance inspection apparatus 1, but when inspecting the nth chip D (n), the n−1th as described above. The difference def (n, i, j) of luminance information is calculated in comparison with the chip D (n−1).
The second luminance difference calculation unit 7B has the same configuration as the luminance difference calculation unit 7 of the appearance inspection apparatus 1, but when inspecting the nth chip D (n), the second luminance difference calculation unit 7B The difference def (n + 1, i, j) of the luminance information is calculated by comparing with the (n + 1) th chip D (n + 1).

The pass / fail determination unit 9B further includes a first pass / fail determination unit 9A, a second pass / fail determination unit 9B, and an overall determination unit 5C.
The first pass / fail judgment unit 9A compares the brightness information difference def (n, i, j) with the pass / fail judgment criterion def0 (n, i, j) to make a pass / fail judgment, and the first pass / fail result is determined. Output as judgment result.
The second pass / fail judgment unit 9B compares the brightness information difference def (n + 1, i, j) with the pass / fail judgment criterion def0 (n, i, j) to make a pass / fail judgment, and the result of the pass / fail judgment is the second pass / fail. Output as judgment result.
The overall determination unit 9C determines that the part is “non-defective” if either the result of the first pass / fail determination unit or the result of the second pass / fail determination unit is “good”.
If both the result of the first pass / fail determination unit and the result of the second pass / fail determination unit are “defective” determination, the part is determined to be “defective”.

When inspecting the nth chip D (n), the appearance inspection apparatus 1B according to the present invention not only compares with the image of the n−1th chip D (n−1) as described above, but also adds n + 1. The determination is made in consideration of the comparison result with the image of the second chip D (n + 1).

FIG. 6 is a pass / fail judgment flow chart in another example of a form embodying the present invention.
FIG. 6 shows a pass / fail judgment flow for the appearance inspection method corresponding to the appearance inspection apparatus 1B according to the present invention. Steps s105 to s108 are the same as the appearance inspection method corresponding to the appearance inspection apparatus 1 shown in FIG.

After step s108, a pass / fail judgment is made (s109B: first pass / fail judgment step). If it is a defective product, the judgment reference pattern is updated (s110), and the next (n + 1) th image is displayed. Obtaining (s125), specifying the inspection pattern (s126), obtaining the luminance information B (n + 1, i, j) (s127), and calculating the luminance difference def (n + 1, i, j) (s128).

Thereafter, a pass / fail judgment is performed on the luminance difference def (n + 1, i, j) (s129: second pass / fail judgment step). If def (n + 1, i, j) is within the judgment criteria, the nth chip D ( n) is determined as non-defective (s131). On the other hand, if def (n + 1, i, j) is not within the criterion, the nth chip D (n) is determined as a defective product (s132).

Since the appearance inspection apparatus 1B and the appearance inspection method according to the present invention are configured as described above, the chip D (n-1) is a good product, D (n) is a defective product, and D (n + 1) is a good product. Even if the inspection target pattern is acquired, it is possible to correctly determine the quality of each.

[Third embodiment]
In the appearance inspection apparatuses 1 and 1B and the appearance inspection method according to the present invention, the acquired inspection target pattern is preferably a pattern arranged at an adjacent position. If it does so, image data can be acquired at a fixed interval by making the illumination strobe light at a predetermined interval while moving the mounting table at a predetermined speed. By adjusting this interval to the processing tact of the appearance inspection apparatuses 1 and 1B, the inspection can be performed with the shortest processing tact.

[Fourth form]
While the inspection is performed by the appearance inspection apparatuses 1 and 1B and the appearance inspection method according to the present invention, defective products may exist continuously.
In such a case, in the above-described form, the “defective product” next to the “defective product” is determined as a defective product.
There is a possibility that a “defective product” after a “defective product” is determined as a “defective product”.

Therefore, it is preferable that the inspection target pattern determined as a non-defective product at the end (in other words, immediately before) is registered as a determination reference pattern.
Specifically, when it is determined as “defective”, the pattern is not updated as the determination reference pattern, and the inspection target pattern determined as “non-defective” immediately before is maintained as the determination reference pattern.
By doing so, even if defective products are continuously present, the defective product can be correctly determined as “defective” as compared with the determination reference pattern registered in advance as non-defective products.

[Fifth embodiment]
When performing the inspection in the first to fourth embodiments, it is necessary to first determine whether or not the first chip of the substrate to be inspected is a non-defective product.
FIG. 7 is a pass / fail judgment flow chart in still another example of the embodiment embodying the present invention, and shows a specific procedure for first judging whether or not the first chip of the substrate to be inspected is a non-defective product. ing.

First, the first to third inspection target patterns immediately after the start of inspection are acquired.
Then, in the luminance difference calculation unit,
The difference between the luminance information of the first and second inspection target patterns is the first difference,
The difference between the luminance information of the first and third inspection target patterns is calculated as the second difference.

In particular,
An image of the first chip D (1) immediately after the start of inspection is acquired (s305), and then an image of the second chip D (2) is acquired (s315), and the third chip D ( The image of 3) is acquired (s325).
After acquiring the image of the first chip D (1), the inspection pattern is specified (s306), and the luminance information B (1) is acquired (s307).
After acquiring the image of the second chip D (2), the inspection pattern is specified (s316), and the luminance information B (2) is acquired (s317).
After acquiring the image of the third chip D (3), the inspection pattern is specified (s326), and the luminance information B (3) is acquired (s327).
Then, the luminance difference between the inspection target patterns of the first chip D (1) and the second chip D (2) is calculated as the first difference def (1-2) (s318).
Further, the luminance difference between the inspection target patterns of the first chip D (1) and the third chip D (3) is calculated as the second difference def (1-3) (s328).

Subsequently, the pass / fail determination is performed on the first difference def (f1-2) and the second difference def (1-3), and if any of the pass / fail determination results of the first difference and the second difference is a pass / fail determination, The first inspection target pattern is registered as a non-defective product in the determination reference pattern registration unit.

In particular,
A pass / fail determination is made for the first difference def (1-2) (s319), and if it is determined as “defective product”, a pass / fail determination is made for the second difference def (1-3) (s329).
If any of step s319 and step 329 is determined as “non-defective”, the chip D (1) as the first inspection target pattern is determined as non-defective (s331) and registered in the determination reference pattern registration unit. To do.

If both step s319 and step 329 are determined as “defective products”, the chip D (1) as the first pattern is determined as a defective product (s332).
In this case, when subsequently inspecting, it is unclear whether the next second pattern is a good product or a defective product. Therefore, an image of the fourth chip D (4) is subsequently acquired, and the same processing as described above is performed, and the second and third inspection patterns, and the second and fourth inspection patterns are obtained. Comparison is made, each difference is calculated, and pass / fail judgment is performed. By doing so, appearance inspection can be started without preparing a good product model as in the prior art.

Alternatively, in a form different from the fifth form, in addition to obtaining the first to third inspection patterns, further obtaining a fourth pattern, the first inspection pattern and the first An appearance inspection apparatus and method in which the quality is determined based on the difference in luminance information of the second to fourth inspection patterns may be used. Then, there is non-regular film formation unevenness in the peripheral portion of the substrate to be inspected, and it is not possible to determine whether the first pattern is a non-defective product by simply comparing the first to third inspection patterns. Even in a case where it is determined as “defective product”, it is more preferable that the non-defective product can be correctly determined as “defective product” by adding the fourth pattern.

[Example]
As the imaging camera 45, a camera in which a 1-inch size light receiving element 46 having 2352 × 1728 effective vertical and horizontal effective pixels is incorporated is used.
As the strobe illumination, a xenon flash lamp having a rated output of 40 W and a half width of about 1 usec is used.
Since a plurality of objective lenses can be attached, an appropriate objective lens is selected according to the defect to be detected.
For example,
The objective lens 44 has a magnification of 1 ×
Observation field of view: length: 16.46 mm × width: 12.1 mm
Pixel size is 7μm
The objective lens 44 has a magnification of 10 times.
Observation field of view: length: 1.65 mm × width: 1.21 mm
Pixel size is 0.7μm
It becomes.

DESCRIPTION OF SYMBOLS 1 Appearance inspection apparatus 1B Appearance inspection apparatus 2 Moving stage part 3 Illumination part 4 Imaging part 5 Image acquisition part 6 Inspection pattern specific | specification part 7 Luminance information acquisition part 8 Luminance difference calculation part 9 Pass / fail judgment part 9B Pass / fail judgment part A Registration of judgment reference pattern Part B Pass / fail standard registration part W Substrate to be inspected V Imaging area 20 Placement table 21 X-axis slider 22 Y-axis slider 23 θ-axis table 31 Light source part 32 Released light 41 Half mirror 42 Reflected light 43 Lens tube 44 Objective lens 45 Imaging camera 46 Light receiving element

Claims (12)

1. In an appearance inspection apparatus that images and inspects the appearance of the pattern on a substrate on which a plurality of patterns are repeatedly patterned,
   A mounting table for mounting the substrate;
   A moving stage unit for moving the mounting table in a predetermined direction;
   An illumination unit that emits light toward the substrate;
   An imaging unit for imaging a pattern on the substrate;
   An image acquisition unit that acquires, as image data, a pattern on the substrate imaged by the imaging unit;
   Among the image data acquired by the image acquisition unit, an inspection pattern specifying unit that specifies at least a part of the region as an inspection target pattern image;
   About the inspection target pattern image, a luminance information acquisition unit that acquires luminance information for each divided region divided into a matrix,
   A determination reference pattern registration unit for registering the previously acquired inspection target pattern as a determination reference pattern;
   A luminance difference calculation unit that compares the determination reference pattern with an inspection target pattern to be acquired next and is a target of pass / fail determination, and calculates a difference in luminance information for each of the divided regions corresponding to the position of the comparison pattern; ,
   A pass / fail criterion registering unit that pre-registers, for each of the divided regions, a reference value for determining pass / fail for the difference in luminance information calculated for each of the divided regions calculated by the brightness difference calculating unit;
   An appearance inspection apparatus comprising: a quality determination unit that performs quality determination for each of the divided regions of the inspection target pattern based on the quality determination reference value.
2. The reference value for the pass / fail judgment is:
   A standard deviation set for each of the divided areas;
   Multiplying the standard deviation by a multiplication factor;
   An offset value that is added to a value obtained by multiplying the standard deviation by the magnification factor,
   The visual inspection apparatus according to claim 1, further comprising a determination criterion parameter registration unit that registers the offset value, the magnification count, and a standard deviation set for each divided region.
3. The determination reference pattern as a first inspection target pattern,
   Next, the second inspection target pattern is the inspection target pattern that is acquired next and is the target of pass / fail judgment,
   Obtaining a third inspection target circuit pattern different from the two inspection target patterns;
   In the luminance difference calculation unit,
   A first luminance difference calculation unit for calculating a difference in luminance information between the first and second inspection target patterns;
   A second luminance difference calculation unit for calculating a difference in luminance information between the first and third inspection target patterns;
   In the pass / fail judgment section,
   A first pass / fail determination unit that performs pass / fail determination on a difference in brightness information for each of the divided areas calculated by the first brightness difference calculation unit;
   A second pass / fail determination unit that performs pass / fail determination on the difference in brightness information for each of the divided areas calculated by the second brightness difference calculation unit;
   If one of the result of the first pass / fail determination unit and the result of the second pass / fail determination unit is a pass determination, the part is determined to be a passable product,
   The integrated determination unit is provided, wherein if both the result of the first pass / fail determination unit and the result of the second pass / fail determination unit are determined to be defective, the part is determined to be a defective product. The appearance inspection apparatus according to claim 2.
4. The appearance inspection apparatus according to claim 1, wherein the inspection target pattern to be inspected is adjacent to the determination reference pattern.
5. 5. The inspection target pattern is replaced with the determination reference pattern if the inspection target pattern to be inspected is determined to be a non-defective product in the quality determination unit. Appearance inspection device.
6. Acquire the first to third inspection target patterns immediately after the start of inspection,
   In the luminance difference calculation unit,
   The difference between the luminance information of the first and second inspection target patterns is the first difference,
   The difference between the luminance information of the first and third inspection target patterns is the second difference,
   In the pass / fail judgment unit,
   A pass / fail determination is made for each of the first difference and the second difference,
   Determined by the pass / fail determination unit,
   The first inspection target pattern is registered as a non-defective product in the determination reference pattern registration unit if any one of the first difference and the second difference is determined to be good. The visual inspection apparatus according to any one of 1 to 5.
   
7. In an appearance inspection method for imaging and inspecting the appearance of the pattern on a substrate on which a plurality of patterns are repeatedly patterned,
   A substrate mounting step for mounting the substrate on a mounting table;
   A table moving step for moving the mounting table in a predetermined direction;
   An illumination light irradiation step for irradiating light toward the substrate;
   An imaging step of imaging a pattern on the substrate;
   An image acquisition step of acquiring the pattern on the substrate imaged in the imaging step as image data;
   An inspection pattern specifying step of specifying at least a part of the image data acquired in the image acquisition step as an inspection target pattern image;
   For the inspection target pattern image, a luminance information acquisition step for acquiring luminance information for each divided region divided in a matrix,
   A determination reference pattern registration step for registering the previously acquired inspection target pattern as a determination reference pattern,
   A luminance difference calculation step of comparing the determination reference pattern with an inspection target pattern to be acquired next and being a pass / fail determination target, and calculating a difference in luminance information for each of the divided regions corresponding to the position;
   A pass / fail criterion registration step of pre-registering, for each of the divided regions, a reference value for determining pass / fail for the difference in luminance information for each of the divided regions calculated by the brightness difference calculating unit;
   An appearance inspection method comprising: a quality determination step for performing quality determination for each of the divided regions of the inspection target pattern based on the quality determination reference value.
8. The reference value for the pass / fail judgment is:
   A standard deviation set for each of the divided areas;
   Multiplying the standard deviation by a multiplication factor;
   An offset value that is added to a value obtained by multiplying the standard deviation by the magnification factor,
   The visual inspection method according to claim 7, further comprising a determination criterion parameter registration step of registering the offset value, the magnification count, and a standard deviation set for each divided region.
9. The determination reference pattern as a first inspection target pattern,
   Next, the second inspection target pattern is the inspection target pattern that is acquired next and is the target of pass / fail judgment,
   Obtaining a third test target circuit pattern different from the two different test target patterns;
   In the luminance difference calculation step,
   A first luminance difference calculating step for calculating a difference in luminance information between the first and second inspection target patterns;
   A second luminance difference calculating step for calculating a difference between luminance information of the first and third inspection target patterns;
   In the pass / fail judgment step,
   A first pass / fail judgment step for performing pass / fail judgment on the difference of the brightness information for each of the divided areas calculated in the first brightness difference calculating step;
   A second pass / fail determination step for determining pass / fail with respect to the difference in brightness information for each of the divided areas calculated in the second brightness difference calculating step;
   If any one of the result of the first pass / fail determination step and the result of the second pass / fail determination step is a pass determination, the portion is determined to be a passable product,
   The system further comprises an overall determination step in which if both the result of the first pass / fail determination step and the result of the second pass / fail determination step are determined to be defective, the part is determined to be a defective product. Item 7. The appearance inspection method according to item 7 or item 8.
10. 10. The appearance inspection method according to claim 7, wherein the inspection target pattern to be inspected is adjacent to the determination reference pattern.
11. 11. The inspection target pattern is replaced with the determination reference pattern if the inspection target pattern to be inspected is determined to be non-defective in the pass / fail determination step. Appearance inspection method.
12. Acquire the first to third inspection target patterns immediately after the start of inspection,
    In the luminance difference calculation step,
    The difference between the luminance information of the first and second inspection target patterns is the first difference,
    The difference between the luminance information of the first and third inspection target patterns is the second difference,
    In the pass / fail judgment step,
    A pass / fail determination is made for each of the first difference and the second difference,
    Determined in the pass / fail determination step,
    The registration of the determination reference pattern registration step is performed when one of the first difference and the second difference is determined to be good, and the first inspection target pattern is determined as non-defective. The appearance inspection method according to any one of 7 to 11.

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