JP2000149020A - Pattern alignment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain alignment of a pattern where no positioning mark has been set. SOLUTION: With regard to a master pattern, a land is defined as a positioning mark Fm, together with the coordinates of the center Cm of the land defined as the coordinates of the mark Fm and the pattern extending direction DI connected to the land defined as the direction of the mark Fm respectively. The area of a prescribed size existing at a position corresponding to the mark Fm is taken out of the image of a pattern to be measured. Then a land, having the same positioning mark and same direction as those of the master pattern within the said extracted area, is selected as a positioning mark Fp of the pattern to be measured, and the coordinates of the center Cp of this land is calculated as the coordinates of its positioning mark. Alignment is carried out between both positioning marks of the pattern to be measured and the master pattern, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern inspection method for inspecting a pattern formed on a green sheet or a film carrier, and more particularly, to an alignment method for aligning a master pattern with a pattern to be measured. .

[0002]

2. Description of the Related Art Conventionally, PGA (Pin Grid Array) has been known as a mounting technique suitable for a demand for increasing the number of pins of ICs and LSIs. In PGA, a ceramic substrate is used as a base of a package for attaching a chip, and wiring is performed to a lead wire extraction position. To make this ceramic substrate, a so-called green sheet made by kneading alumina powder with a liquid binder is used, and a paste containing a high melting point metal is screen-printed on the green sheet. By firing such a sheet, so-called simultaneous firing, in which the green sheet is sintered and the paste is metallized, is performed.

[0003] As another mounting technique, TAB is used.
(Tape Automated Bonding) is known. TAB method is a polyimide film carrier (TAB tape)
The copper foil pattern formed thereon is joined to the electrode of the IC chip to form an external lead. The copper foil pattern is formed by attaching a copper foil to a film with an adhesive and etching this.

In such a green sheet or film carrier, a pattern is visually inspected by a human using a microscope after the pattern is formed. However, visual inspection of fine patterns requires skill and
There was a problem of overworking the eyes. Therefore, as an alternative to the visual inspection, a technique has been proposed in which a pattern formed on a film carrier or the like is picked up by a TV camera and automatically inspected (for example, JP-A-6-273132 and JP-A-7-273132). No. 110863).

FIGS. 11 and 12 show Japanese Patent Application Laid-Open No. 6-273132.
FIG. 1 is a diagram for explaining a conventional inspection method for detecting a disconnection described in Japanese Patent Application Laid-Open Publication No. HEI 10-125, 1988. A master pattern created by imaging the pattern to be measured determined as a non-defective product is registered as a set of straight lines indicating pattern edges. The pattern to be measured is input as a set of edge data (edge coordinates) indicating a pattern edge extracted from a grayscale image obtained by capturing the pattern. Then, the extracted edge data n1, n2, n3.
.. and the line of the master pattern are associated. In order to perform this association, as shown in FIG. 11, the bisectors A2 'and A3' which divide the angles formed by the continuous straight lines A1 and A2, A2 and A3...
Ask for ...

The lines around the straight lines A1, A2, A3,... Of the master pattern are divided into areas respectively belonging to the straight lines A1, A2, A3,. .. Exist in each area are associated with the straight lines A1, A2, A3,... Of the master pattern to which the area belongs. . For example, in FIG. 11, the edge data n1 to n3 are associated with the straight line A1, and the data n4 to n6 are associated with the straight line A2. Next, the edge data of the pattern to be measured is compared with the master pattern to check whether the pattern to be measured is disconnected.

This inspection is realized by a labeling process for tracing the pattern edge by tracing the connected edge data n1 to n9 of the pattern to be measured, as shown in FIG. At this time, since the edge data is not connected at the disconnected portion due to the disconnection generated at the leading end of the pattern to be measured, there is no edge data corresponding to the straight lines A3 to A5 of the master pattern. Thus, the disconnection of the pattern to be measured can be detected.

FIG. 13 is a diagram for explaining a conventional inspection method for detecting a short circuit described in JP-A-6-273132. First, in the inspection area 20 in which the master pattern and the pattern to be measured are cut out to a predetermined size, the connected edge data of the pattern to be measured is tracked. Thereby, each edge data of the pattern to be measured is n1 to n
18 and are sequentially labeled. However, a master pattern Mb composed of two opposing straight lines as well as a master pattern Mb composed of two opposing straight lines indicating a pattern edge include:
Edge data n8 and n17 are not registered. Thus, a short circuit of the pattern to be measured can be detected.

FIG. 14 is a view for explaining a conventional inspection method for detecting a defect or a projection described in Japanese Patent Application Laid-Open No. Hei 7-10863. First, a perpendicular line perpendicular to the center line L is drawn, and the length between intersections where the perpendicular line intersects the straight lines A1 and A2 indicating the edges of the master pattern is determined in advance as the width W0 of the master pattern. Next, in an actual inspection, a distance between the edge data opposing the center line L of the master pattern is determined from the edge data n of the pattern to be measured. This is the width W of the pattern to be measured, and the loss or protrusion of the pattern to be measured is detected by comparing this with the width W0 of the master pattern.

However, in the pattern inspection apparatus using such an inspection method, there is a problem that the pattern inspection takes a long time because a detailed inspection is performed by software on the whole of the pattern to be measured by comparison with the master pattern. . Therefore, a pattern inspection apparatus capable of performing inspection in a short time has been proposed (for example, Japanese Patent Application No. 8-30280).
No. 7). In the pattern inspection apparatus described in Japanese Patent Application No. 8-302807, a defect candidate of a measured pattern is detected by hardware (primary inspection), and only a predetermined small area including the detected defect candidate is inspected by software. Secondary inspection), it is possible to inspect the defect of the pattern to be measured at a higher speed than before. By the way, in any of the above pattern inspection apparatuses, in order to compare a measured pattern captured by a camera with a master pattern,
It is necessary to align the master pattern and the pattern to be measured. This alignment has been performed by matching the position of a positioning mark provided in advance on the master pattern with the position of the corresponding positioning mark of the pattern to be measured.

[0011]

However, in the above-described alignment method, there is a problem that the position of the pattern to be measured cannot be aligned with the master pattern in which the positioning marks independent of other patterns are not provided. was there. The present invention has been made to solve the above-described problem, and has as its object to provide a positioning method capable of performing positioning even with a pattern in which positioning marks are not provided.

[0012]

According to a first aspect of the present invention, a land is used as a positioning mark, the center coordinates of the land are used as the coordinates of the positioning mark, and the direction in which a pattern connected to the land extends is defined by the positioning mark. A method of aligning a direction, in which an area of a predetermined size corresponding to the positioning mark of the master pattern is extracted from the image of the pattern to be measured, and within this area, the positioning mark of the master pattern and the above direction are aligned. Select the same land as the positioning mark of the pattern to be measured, calculate the center coordinates of the land as the coordinates of the positioning mark of the pattern to be measured in this positioning mark, and align the positions of the positioning marks of the pattern to be measured and the master pattern with each other. To align the master pattern and the pattern to be measured. Those were. Further, when there are a plurality of lands corresponding to the area, the center coordinates are calculated for each of the lands, and the calculated coordinates are used as the coordinates of the positioning mark of the master pattern. The closest land is adopted as a positioning mark of the pattern to be measured.

According to a third aspect of the present invention, a corner of a pattern is used as a positioning mark, a center coordinate of the corner is used as a coordinate of the positioning mark, and a direction in which a plurality of corner patterns extend is defined as a positioning mark. A region of a predetermined size at a position corresponding to the positioning mark of the master pattern from the image of the pattern to be measured, and the positioning mark of the master pattern and the direction Selects the corners of the same pattern as the positioning marks of the pattern to be measured, finds the center lines of a plurality of patterns forming the corners in the positioning marks, and determines the coordinates of the intersection of the center lines with the coordinates of the positioning marks of the pattern to be measured. By calculating the position of the positioning mark of the pattern to be measured and the master pattern. Data pattern is obtained to perform the alignment of the pattern to be measured. Claim 4
As described in, when there are a plurality of corresponding corners in the area, the coordinates of the intersection of the center line are calculated for each of these corners, and the calculated coordinates are most likely to be the coordinates of the positioning mark of the master pattern. The close angle is adopted as a positioning mark of the pattern to be measured.

At this time, in the method of claims 1 to 4,
The method of matching the positions of the positioning marks of the pattern to be measured and the master pattern is as follows. That is, after aligning the entire position of the master pattern and the measured pattern by aligning the positions of the positioning marks with respect to the entire area of the measured pattern and the master pattern, a plurality of divided areas are set in the measured pattern. At the same time, a plurality of divided areas corresponding to this are set in the master pattern, the coordinates of at least four positioning marks in the divided area of the pattern to be measured are determined, and the coordinates of at least four positioning marks corresponding to this are determined. The coordinate conversion formula between the pattern to be measured and the master pattern is determined from these coordinates in the corresponding divided area of the master pattern, and the master pattern and the measured pattern are converted by converting the divided area of the master pattern using the coordinate conversion formula. Pattern alignment is performed for each divided region. At this time, the positioning marks of claims 1 to 4 may be used as the positioning marks for the overall positioning, or the positioning marks of claims 1 to 4 may be used as the positioning marks for each divided area. It may be used for both the entire area and the divided area.
With the conventional alignment method, if there is local distortion such as expansion and contraction in the inspection work, even if the alignment with the master pattern is completed as a whole, local deviation from the master pattern occurs Therefore, this deviation may be detected as the above-mentioned defect candidate. In this case, even if the local distortion of the inspection work is within the allowable range, the secondary inspection is performed, so that there is a problem that an inspection time is required. On the other hand, according to the above-described method, if the local distortion of the inspection work is within the allowable range, the local distortion of the inspection work is absorbed by the alignment of each divided region by the coordinate conversion formula, and the master pattern is removed. The subtle displacement between the divided area of the target pattern and the divided area of the pattern to be measured can be corrected. Therefore, if the local distortion of the inspection work is within the allowable range, the distortion will not be detected as a defect candidate, and the secondary inspection due to the distortion will not be performed, thereby shortening the inspection time. can do. In addition, a deviation between the result of inputting the coordinates of the positioning mark of the pattern to be measured in the coordinate conversion formula and the coordinates of the corresponding positioning mark of the master pattern is obtained for each mark, and a positioning mark whose deviation is larger than a predetermined threshold value is determined. The accuracy of the coordinate conversion formula is determined by repeating the process of excluding both the pattern to be measured and the master pattern and obtaining the coordinate conversion formula again until all deviations are equal to or less than a predetermined threshold value, and determining the coordinate conversion formula. And high-accuracy positioning can be performed. When all the deviations are larger than the predetermined threshold value, the distortion of the divided area of the pattern to be measured is out of the allowable range, and it can be determined that the inspection work is defective. Also,
By setting each of the divided areas so that the left, right, top and bottom overlap with other divided areas, it is possible to determine whether or not the distortion at the boundary of each divided area is within an allowable range based on the deviation of a plurality of adjacent divided areas. it can.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] Next, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flowchart illustrating an inspection method according to a first embodiment of the present invention, and FIG. 2 is a block diagram of a pattern inspection apparatus used in the inspection method. In FIG. 2, 1 is a green sheet serving as an inspection work, and 2 is a green sheet 1.
Table, 3 is a line sensor camera for imaging the green sheet 1, 4 is a first image for performing a primary inspection for detecting a defect candidate of the pattern to be measured, and outputting address information indicating the position of the defect candidate. The processing device 5 uses the address information to determine a predetermined area including a defect candidate.
A second image processing device for obtaining an error between the pattern to be measured and the master pattern and performing a secondary inspection of the pattern to be measured, 6 is a host computer for controlling the entire device, and 7 is a display device for displaying inspection results. .

First, a master pattern created before the inspection will be described. Host computer 6
Reads out, by a magnetic disk device (not shown), design value data (hereinafter referred to as CAD data) of a green sheet created by a CAD (Computer Aided Design) system and written on, for example, a magnetic disk (step 101 in FIG. 1). Then, pattern edge data is extracted from the read CAD data. Edge data is
A set of pixels “1” indicating a pattern edge. Then, the area surrounded by the pixel “1” indicating the pattern edge is painted with “1”, and the pattern painted with this pixel “1” (the background other than the pattern is “0”) is used as the first reference to be inspected. (Step 10 in FIG. 1)
2).

As described above, in the present embodiment, in order to create an accurate master pattern, CAD data that has become a master in manufacturing the green sheet 1 is used. Next, the host computer 6 creates a second master pattern for detecting loss or disconnection and a third master pattern for detecting protrusions or short circuits from the first master pattern as follows (step 103 in FIG. 1). . FIG. 3 is a diagram for explaining a method of creating the second and third master patterns, and shows a part of the first master pattern.

First, as shown in FIG. 3A, the first master pattern is contracted in a direction perpendicular to its center line,
A second master pattern M1 is created. This is because opposing straight lines A1 and A1 indicating both edges of the first master pattern
4 (center line is L1) and the distance between A2 and A3 (center line is L2) are narrowed to narrow the first master pattern.

The accuracy of defect detection by the second master pattern M1 depends on how much the first master pattern is contracted. For example, when it is desired to recognize a defect when there is a defect exceeding 1/5 of the width of the first master pattern, the width of the second master pattern M1 is set to 3/5 of the width of the first master pattern. What is necessary is just to reduce it. It goes without saying that the detection accuracy may be determined in pixel units or actual dimensions. Thus, the second master pattern M1 for detecting loss or disconnection is created.

Subsequently, as shown in FIG. 3B, the first master pattern is expanded in a direction perpendicular to the center line to create a third master pattern M2. This corresponds to the opposite straight line A5 indicating both edges of the first master pattern.
And A8 (center line is L3), A6 and A7 (center line is L
4), A9 and A12 (center line is L5) and A10 and A1
1 (the center line is L6), and the first master pattern can be made thicker by widening the respective intervals.

However, the third master pattern M2 is actually
Is a master pattern M composed of straight lines A5 to A8.
a and a region (base portion where no pattern exists) sandwiched between two patterns generated by expanding the master pattern Mb including the straight lines A9 to A12.

The accuracy of defect detection by the third master pattern M2 is determined by how much the first master pattern is expanded. For example, when it is desired to recognize a defect when there is a defect exceeding 1/5 of the width of the first master pattern, the width of the third master pattern M2 is set to 7/5 of the width of the first master pattern. It should just be expanded as follows. The fact that the detection accuracy may be determined in pixel units or actual dimensions is the same as in the second master pattern. Thus, a third master pattern M2 for detecting a protrusion or a short circuit is created.

Next, the inspection of the pattern to be measured will be described. First, the green sheet 1 is imaged by the camera 3. Then, the first image processing device 4 digitizes the grayscale image output from the camera 3 and temporarily stores it in an internal image memory (not shown) (step 10).
4). Since the camera 3 is a line sensor in which pixels are arranged in the X direction, the XY table 2 or the camera 3 is moved in the Y direction (here, the table 2
2D image data is stored in the image memory.

Subsequently, the image processing apparatus 4 binarizes the grayscale image of the pattern to be measured stored in the image memory (step 105). The grayscale image data of the pattern to be measured includes the pattern and the other background (a base material such as a green sheet). However, since there is a density difference between the pattern and the background, the density value of the pattern and the background If a value between the density values is set as a threshold value, the pattern is converted to “1” and the background is converted to “0”. In this way, it is possible to obtain a pattern to be measured in which the pattern edge and the inside thereof are filled with the pixel “1”.

Next, the image processing device 4 aligns the entire binarized pattern to be measured with the entire master pattern (step 106). FIG. 4 is a diagram for explaining this alignment method. First, the image processing device 4
In the pattern to be measured P stored in the image memory,
At the time of creating the CAD data, three or more positioning marks a provided in advance are designated as shown in FIG.
In the first master pattern M sent from the host computer 6, the corresponding positioning marks b are designated as shown in FIG.

Then, for each of the pattern to be measured P and the master pattern M, the distances DXp and DXm between the two positioning marks arranged in the X direction are obtained. The distance between marks is the distance between the centers of gravity of two positioning marks.

Subsequently, an enlargement / reduction ratio (DXp / DXm) is calculated from the obtained distance between the marks, and the distance between the marks of the master pattern is made to match the distance between the marks of the pattern to be measured by the enlargement / reduction ratio. , The master pattern M is enlarged or reduced in all directions. Next, for each of the pattern P to be measured and the master pattern M ′ whose magnification / reduction has been corrected, the distance D between the two positioning marks arranged in the Y direction is determined.
Yp and DYm are obtained as shown in FIGS.

The relative speed between the line sensor camera 3 and the green sheet 1 (XY table 2) is adjusted so that the distance between marks of the pattern to be measured matches the distance between marks of the master pattern. Is imaged again.
The image resolution in the Y direction is determined by the pixel size of the camera 3 and the relative speed. Therefore, by changing the moving speed of the XY table 2 or the line sensor camera 3, the image resolution in the Y direction can be adjusted, and the distance between marks can be matched.

Next, based on the positioning mark positions of the pattern to be measured P ′ obtained by imaging in this manner and the positioning mark positions of the master pattern M ′ subjected to enlargement / reduction correction, FIG.
As shown in (e), the angle shift θ between the patterns P ′ and M ′ is obtained, and the master pattern M ′ is removed so that the angle shift is eliminated.
To rotate. Finally, the positions of the master pattern M ′ and the pattern to be measured P ′ are aligned so that the mark positions match each other.

In this way, for each of the pattern to be measured and the master pattern, the distance between the two positioning marks arranged in the X direction is obtained, and the master pattern is enlarged or reduced so that the obtained distance between the marks matches. For each of the measured pattern and the enlarged / reduced master pattern, the distance between the two positioning marks arranged in the Y direction is determined, and the relative speed between the line sensor camera and the measured pattern is determined so that the determined distance between the marks matches. Is adjusted, the pattern to be measured is imaged again, the angular deviation between the imaged measured pattern and the master pattern subjected to the enlargement / reduction correction is obtained, and the master pattern is rotated so as to eliminate the angular deviation. The position of the pattern and the pattern to be measured can be matched. As described above, in the present embodiment, the image resolution in the Y direction is adjusted by changing the capturing speed of the camera 3 with respect to the image resolution in the X direction determined by the number of pixels of the line sensor camera 3, and thereby the vertical ( The ratio of Y) to the width (X) can be 1: 1.

In an actual inspection, the ratio of length and width may not be completely 1: 1. For example, a pattern to be screen-printed on a green sheet may be printed in a state of being elongated depending on a printing direction. Therefore, in a pattern in which a good product has an elongation within an allowable range with respect to the standard, the ratio of length to width is not completely 1: 1. In the present embodiment, since the distance between marks in the Y direction is made to match by changing the capture speed of the camera 3, patterns to be measured having different vertical and horizontal scales within the allowable range can be made to match the master pattern. The position of the pattern can be automatically corrected for the change in the pattern position at the time.

Next, the image processing apparatus 4 performs positioning of the pattern to be measured and the master pattern for each divided region (step 107). FIG. 5 is a flowchart showing a positioning method for each divided area, and FIGS. 6 and 7 are diagrams for explaining this positioning method.

First, the image processing apparatus 4 sets a plurality of divided areas Em in the first master pattern M as shown in FIG. 6A, and sets a plurality of divided areas Ep corresponding thereto in FIG. Set in the pattern to be measured P as in b),
A single divided region Em is cut out from the master pattern M, and a corresponding divided region Ep is cut out from the pattern to be measured P (step 201 in FIG. 5). The position and size of each divided area are set in advance. Further, the size of each divided region may not be constant.

Subsequently, the image processing apparatus 4 specifies four or more preset positioning marks Fm in the divided area Em of the master pattern M as shown in FIG. Fp is designated in the corresponding divided area Ep of the pattern P to be measured as shown in FIG. 6D (step 202). In FIG. 6, the positioning marks Fm1, Fm2, Fm3, Fm
The positioning marks in the divided areas Ep corresponding to m4, Fm5, and Fm6 are Fp1, Fp2, Fp3, and Fp, respectively.
4, Fp5 and Fp6.

Here, a method of specifying the positioning marks Fm and Fp will be described with reference to FIG. As described above, the positioning mark Fm in each divided area Em of the master pattern M is used.
Is specified in advance. In the present embodiment, FIG.
As shown in (1), a circular land is set as the positioning mark Fm, and the coordinates of the center Cm of the land are set as the coordinates of the positioning mark Fm.

When creating the first master pattern M, the host computer 6 receives the X and Y coordinates of the center Cm of the land, the radius R of the land, and the lead from the land (the pattern connected to the land). The extension direction DI is stored. Such designation of the positioning mark Fm may be performed at four or more locations for each divided area Em of the master pattern M.

Next, as shown in FIG. 7B, the image processing apparatus 4 sets the mark Fm in the divided area Ep of the pattern P to be measured corresponding to the divided area Em of the master pattern M.
Is searched for a pattern that includes a point Cm 'having the same coordinates as the coordinates of. This pattern is the positioning mark Fp corresponding to the positioning mark Fm. Such a positioning mark Fp
May be specified for each positioning mark Fm.

Next, the image processing device 4 calculates the coordinates of each of the positioning marks Fp1 to Fp6 (step 20).
3). As with the positioning mark Fm, the positioning mark F
The coordinates of p are the coordinates of the center of the land. First, as shown in FIG. 7 (c), the image processing device 4
A straight line Sa that is tangent to the land of the positioning mark Fp is obtained from the straight lines perpendicular to the above. The intersection (contact point) of the straight line Sa and the land is defined as a first point Q1 for obtaining the center of the land.

Subsequently, the image processing device 4 sets the direction D
Among the straight lines perpendicular to I, a straight line Sb that maximizes the distance between land edges is obtained. The second and third points Q2 and Q3 for finding the center of the land at the intersection of the straight line Sb and the land
And Then, the image processing device 4 calculates the points Q1, Q2, Q
From the X and Y coordinates of No. 3, temporary X and Y coordinates of the center Cp of the land are calculated.

Next, as shown in FIG. 7D, the image processing device 4 performs a sector-shaped scan centering on the calculated Cp. Then, the image processing device 4 deletes, from the positioning mark Fp, the pixel “1” inside the fan and located farther from the center Cp than the above-mentioned stored value R. The scanning angle at this time is in a range of ± θ centered on the direction DI. Thus, the data of the lead portion of the positioning mark Fp is deleted, and only the land portion is extracted (FIG. 7).
(E)).

Finally, the image processing device 4 calculates the final X and Y coordinates of the center Cp from the extracted data of the land portion by, for example, the least square method. The above calculation may be performed for each of the positioning marks Fp1 to Fp6.

In the process described with reference to FIG. 7B, if there is no pattern including the point Cm ', the point C
In an area (window) of a predetermined size centered on m ', a land having a lead extending in the same direction as the above-mentioned direction DI is set as the positioning mark Fp. When a plurality of such lands exist, the coordinates of the center Cp are calculated for each of the lands by the above-described method, and the land whose calculated coordinates are closest to the coordinates of the point Cm ′ is adopted as the positioning mark Fp. I do.

Next, the image processing apparatus 4 calculates a coordinate conversion formula between the pattern to be measured and the master pattern by using the coordinates of the positioning marks Fm1 to Fm6 and the coordinates of the corresponding positioning marks Fp1 to Fp6. Is obtained by the least squares method (step 204 in FIG. 5). Xm = αXp + βYp + γ Ym = δXp + εYp + ζ (1)

In equation (1), Xm and Ym are the X and Y coordinates of the master pattern, Xp and Yp are the X and Y coordinates of the pattern to be measured, and α, β, γ, δ, ε, and ζ are constants. Next, the image processing device 4 performs positioning marks Fp1 to Fp6.
The coordinates Xm and Ym are calculated by substituting the coordinates of an arbitrary positioning mark among them, for example, the mark Fp1 into the coordinate conversion formula of Expression (1) as Xp and Yp. Then, a deviation between the coordinates of the positioning mark Fm1 corresponding to the positioning mark Fp1 substituted into the coordinate conversion formula and the calculated coordinates Xm, Ym is obtained for each X, Y coordinate. The calculation of such a deviation is performed for each positioning mark (step 205).

Subsequently, the image processing device 4 determines whether each of the calculated deviations is larger than a predetermined threshold value (Step 206). When all the deviations are equal to or smaller than the predetermined threshold value, it is determined that the distortion of the divided region Ep of the pattern to be measured is within the allowable range, and the derived coordinate conversion formula is appropriate, and this coordinate conversion formula is used. The coordinate conversion of the master pattern in the divided area Em is performed (Step 207).

If all the deviations are larger than the predetermined threshold value, it is determined that the distortion of the divided region Ep of the pattern to be measured is out of the allowable range, and that the green sheet 1 to be inspected is defective (step). 208). On the other hand, when the deviation smaller than the threshold value and the deviation larger than the threshold value coexist, the image processing device 4 excludes the positioning mark whose deviation is larger than the threshold value, for example, the mark Fp6 and the corresponding positioning mark Fm6. After that (step 209), the coordinate conversion equation of equation (1) is obtained again from the coordinates of the remaining positioning marks Fm1 to Fm5 and Fp1 to Fp5 (step 204).

Steps 204 to 206, 2 as described above
Steps 08 and 209 are repeated until each deviation becomes equal to or less than a predetermined threshold value. In this manner, the coordinate conversion equation of equation (1) is determined, and the conversion of the master pattern in step 207 can be performed. The use of a coordinate transformation equation such as equation (1) means that a so-called affine transformation is performed, whereby the divided areas Em and E
The displacement of p can be corrected.

Note that the second and third master patterns correspond to the first master pattern.
Since the master pattern is created from the first master pattern, the alignment of the first to third master patterns with the pattern to be measured may be performed once using the first master pattern.

Further, in order to obtain the coordinate conversion equation of equation (1), at least three positioning marks are required for each of the master pattern and the pattern to be measured. However, since the accuracy of the coordinate conversion formula deteriorates with every three points, specify the positioning marks of at least four points and exclude the positioning marks whose deviation is larger than the threshold from the derivation of the coordinate conversion formula. ing. Therefore, even if the positioning marks are three points each for both the master pattern and the pattern to be measured, if each deviation does not become less than the threshold value, it is not possible to obtain the coordinate conversion formula by setting the positioning marks two points at a time. Also in this case, it is determined that the green sheet 1 to be inspected is defective.

Next, the image processing apparatus 4 compares the divided area of the pattern to be measured with the corresponding divided areas of the second and third master patterns and performs the primary inspection of the pattern to be measured (step S1). 108). FIG. 8 is a diagram for explaining this inspection method.

First, as shown in FIG. 8A, the divided area Ep of the pattern P to be measured is compared with the corresponding divided area Em of the second master pattern M1 whose position has been corrected by the coordinate conversion formula. However, what is actually compared is the pattern NP obtained by logically inverting the pattern P to be measured and the second master pattern M1. In other words, in the example of FIG. 8A, the portion other than the pattern NP indicated by the satin finish is the pattern P to be measured.

Pattern NP and second master pattern M1
Is obtained, the result of the logical product differs depending on whether the pattern P to be measured has a defect or a disconnection. For example, when the pattern to be measured P has “1” as its value and the master pattern M1 has “1”, if the pattern to be measured P has no loss or disconnection, the pattern NP and the master pattern M1 Since there is no overlap, the result of the logical product is “0”.

On the other hand, if there is a defect in the pattern to be measured P as shown in FIG. 8A, the pattern NP and the master pattern M1 overlap at this portion, and the result of the logical product is "1".
Becomes This is the same when the pattern to be measured has a disconnection. In this way, it is possible to detect loss or disconnection of the pattern to be measured. Then, the image processing device 4
Stores the position where the result of the logical product becomes “1” and is recognized as a defect candidate.

Subsequently, as shown in FIG. 8B, the divided area Ep of the pattern P to be measured and the third master pattern M2
Is compared with the corresponding divided region Em whose position has been corrected by the above coordinate conversion formula. Similarly to the above, when the logical product of the measured patterns Pa and Pb and the third master pattern M2 is obtained, the result of the logical product differs depending on whether the measured patterns Pa and Pb have a protrusion or a short circuit. That is, when there is no protrusion or short circuit in the patterns Pa and Pb to be measured, the result of the logical product is “0”.

On the other hand, when the pattern Pa to be measured has a protrusion as shown in FIG. 8B, the pattern Pa to be measured overlaps the master pattern M2 at this portion, and the result of the logical product is "1". . Similarly, if the patterns Pa and Pb to be measured are short-circuited, the result of the logical product is “1”. Thus, a protrusion or a short circuit of the pattern to be measured can be detected. Then, the image processing device 4 stores the position where the result of the logical product becomes “1” and is recognized as a defect candidate.

In FIGS. 3 and 8, the master patterns M1 and M2 are shown as having a value "1" not only for the edge but also for the inside, but the inside is "1".
When the master patterns M1 and M2 are created by the host computer 6, only the edges are used, and the image processing device 4 that receives the master patterns M1 and M2 sets the inside of the edges to "1". It may be painted out.

After performing such a primary inspection, the image processing apparatus 4 outputs the stored position of the defect candidate as address information. The second image processing device 5 performs processing when a defect candidate is detected by the first image processing device 4 (step 1).
09) For a region of a predetermined size smaller than the divided region centered on the defect candidate at the position indicated by the address information, the measured pattern is compared with the first master pattern to determine an error, thereby obtaining an error. A secondary inspection of the pattern is performed (step 110). The inspection method is the same as the above-described conventional method shown in FIGS.

The above processing of steps 107 to 110 is repeated until there are no unexamined divided areas (step 11).
1), for each divided area. The logical product processing of the measured pattern and the second and third master patterns can be realized by hardware, and only the predetermined area including the detected defect candidate is compared with the measured pattern requiring a long processing time and the first master pattern. Since the inspection is performed, the pattern to be measured can be inspected at a high speed.

However, when there is a local distortion such as expansion and contraction in the green sheet 1, the conventional pattern inspection method causes a local deviation from the master pattern, and this deviation is detected as a defect candidate. Therefore, even if the local distortion of the green sheet 1 is within the allowable range, the secondary inspection is performed, and the inspection time is reduced.

On the other hand, in the present embodiment, if the local distortion of the green sheet 1 is within the allowable range (that is, the deviation is equal to or less than the threshold value), the alignment of each divided area by the coordinate conversion formula is performed. As a result, local distortion of the green sheet 1 is absorbed, and this distortion is not detected as a defect candidate.

In FIG. 6A and FIG. 6B, there is no overlap between the divided areas, but the actual divided areas are set so that the left, right, top, and bottom overlap with other divided areas. This is to check the connection between the divided areas.
Further, in the present embodiment, the inspection of the next divided area is performed after the inspection of one divided area is completed. However, if a plurality of divided areas are inspected in parallel, it is impossible to perform a higher-speed inspection. Needless to say.

[Second Embodiment] Next, a second embodiment of the present invention will be described in detail with reference to the drawings. Also in the present embodiment, the configurations of the inspection method and the pattern inspection apparatus are the same as those of the first embodiment, and
What is different from the above is the processing of step 202 and step 203 in the alignment method for each divided area described with reference to FIG. Thus, only the processing of steps 202 and 203 will be described.

FIGS. 9 and 10 are flow charts showing a method of aligning the pattern to be measured and the master pattern for each divided area in the present embodiment. Step 20
2, the image processing apparatus 4 sets the positioning marks F set in advance in the divided areas Em of the master pattern M.
As shown in FIG. 9C, four or more points m are designated, and the corresponding positioning marks Fp are designated in the corresponding divided areas Ep of the pattern P to be measured as shown in FIG. 9D (step 202 in FIG. 5). ).

As in the first embodiment, the positioning mark Fm in each divided area Em of the master pattern M is specified in advance. In this embodiment, as shown in FIGS. 10 (a), 10 (b), and 10 (c), corners of a pattern formed by two or more patterns intersecting at right angles are set as positioning marks Fm. The coordinates of the center Cm of the corner of this pattern are used as the coordinates of the positioning mark Fm.

Then, when creating the first master pattern M, the host computer 6 sets the X and Y coordinates of the center Cm of the corner of this pattern and the direction DI (D
I1 to DI9) are stored. Such designation of the positioning mark Fm may be performed at four or more locations for each divided area Em of the master pattern M.

Next, the image processing apparatus 4 determines, from the divided area Ep of the pattern P to be measured corresponding to the divided area Em of the master pattern M, a predetermined center having a point Cm ′ having the same coordinates as the coordinates of the positioning mark Fm. Area of size (window)
Cut out WI. Then, the image processing device 4 searches for a pattern in the window WI that extends in the same direction as the direction DI of the positioning mark Fm. This pattern is the positioning mark Fp corresponding to the positioning mark Fm.

For example, for the positioning mark Fm as shown in FIG. 10A, a pattern as shown in FIG. 10D extending in the direction of DI1, DI2 becomes the positioning mark Fp. Such designation of the positioning mark Fp may be performed for each positioning mark Fm.

Next, the image processing device 4 calculates the coordinates of each of the positioning marks Fp1 to Fp6 (step 20 in FIG. 5).
3). As with the positioning mark Fm, the positioning mark F
The coordinates of p are the coordinates of the center Cp of the corner of the pattern. Then, the image processing device 4, as shown in FIG.
The center lines La and Lb of each pattern of the positioning mark Fp are obtained, and the intersection of these center lines La and Lb is set as the center Cp. Thus, the X and Y coordinates of the center Cp can be calculated.

In the process described with reference to FIG. 10D, if there are a plurality of corresponding corners, the coordinates of the center Cp are calculated for each of these angles by the above-described method, and the calculated coordinates are set to the point Cm. The pattern closest to the coordinate 'may be adopted as the positioning mark Fp. As described above, effects similar to those of the first embodiment can be obtained.

In the first and second embodiments, the lands or the corners of the pattern are used as positioning marks for positioning each divided area. However, these may be used as positioning marks for overall positioning. , May be used for both the whole and divided regions.

[0071]

According to the present invention, as described in claim 1, an area of a predetermined size at a position corresponding to the positioning mark of the master pattern is extracted from the image of the pattern to be measured, and Select the land with the same direction as the positioning mark of the master pattern as the positioning mark of the pattern to be measured, and calculate the center coordinates of the land as the coordinates of the positioning mark of the pattern to be measured in this positioning mark. By aligning the positions of the positioning marks, the master pattern and the pattern to be measured can be aligned. Therefore, since the lands can be used as the positioning marks, positioning can be performed even for a pattern in which positioning marks independent of other patterns are not provided.

According to a third aspect of the present invention, an area of a predetermined size at a position corresponding to the positioning mark of the master pattern is extracted from the image of the pattern to be measured, and is located within this area. Select the corner of the pattern having the same direction as the positioning mark of the pattern to be measured, find the center lines of the plurality of patterns making angles at the positioning mark, and determine the coordinates of the intersection of the center lines with the positioning mark of the pattern to be measured. , And the positions of the positioning marks of the measured pattern and the master pattern are aligned with each other, whereby the master pattern and the measured pattern can be aligned.
Therefore, since the corners of the pattern can be used as the positioning marks, positioning can be performed even for a pattern in which positioning marks independent of other patterns are not provided.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an inspection method according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a pattern inspection apparatus.

FIG. 3 is a diagram for explaining a method of creating second and third master patterns.

FIG. 4 is a diagram for explaining a method of aligning the pattern to be measured and the master pattern as a whole;

FIG. 5 is a flowchart illustrating a method for aligning a pattern to be measured and a master pattern for each divided region.

FIG. 6 is a diagram for explaining a method of aligning a pattern to be measured and a master pattern for each divided region.

FIG. 7 is a diagram for explaining a method of aligning a pattern to be measured and a master pattern for each divided region.

FIG. 8 is a diagram for explaining a primary inspection method based on comparison with second and third master patterns.

FIG. 9 is a flowchart illustrating a method of aligning a pattern to be measured and a master pattern for each divided region according to the second embodiment of the present invention.

FIG. 10 is a flowchart illustrating a method of aligning a pattern to be measured and a master pattern for each divided region according to the second embodiment of the present invention.

FIG. 11 is a diagram for explaining a conventional inspection method for detecting disconnection.

FIG. 12 is a diagram for explaining a conventional inspection method for detecting disconnection.

FIG. 13 is a view for explaining a conventional inspection method for detecting a short circuit.

FIG. 14 is a view for explaining a conventional inspection method for detecting a defect or a protrusion.

DESCRIPTION OF SYMBOLS 1 ... Green sheet, 2 ... XY table, 3 ... Line sensor camera, 4 ... First image processing device, 5 ... Second image processing device, 6 ... Host computer, 7 ... Display device .

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5B057 AA03 BA02 CA02 CA08 CA12 CA16 CB02 CB06 CB12 CB16 CC01 CD02 CD03 CD05 DA07 DB02 DB05 DB09 DC03 DC08 DC32 5F031 CA20 JA04 JA38 JA50

Claims (4)

[Claims] In a pattern inspection method for inspecting a pattern to be measured by comparing an image of a pattern to be measured by a camera with an image of a pattern to be measured, the land is used as a positioning mark, and the center coordinates of the land are determined. This is a positioning method in which the coordinates of the positioning mark are set, and the direction in which the pattern connected to the land extends is the direction of the positioning mark. Then, a land within this area and having the same direction as the positioning mark of the master pattern is selected as the positioning mark of the pattern to be measured, and the center coordinates of the land are calculated as the coordinates of the positioning mark of the pattern to be measured. , The measured pattern and the master pattern By aligning the mark determined, the alignment method of pattern, characterized by aligning the master pattern and the pattern to be measured. 2. The pattern alignment method according to claim 1, wherein when there are a plurality of corresponding lands in the area,
A pattern alignment method, wherein the center coordinates are calculated for each of the lands, and the land whose calculated coordinates are closest to the coordinates of the positioning marks of the master pattern is adopted as the positioning marks of the pattern to be measured. 3. A pattern inspection method for inspecting a measured pattern by comparing an image of a reference master pattern with an image of the measured pattern captured by a camera, wherein a corner of the pattern is used as a positioning mark, and a center of the corner is determined. A positioning method in which the coordinates are set as the coordinates of the positioning mark, and the direction in which the plurality of corner patterns extend is the direction of the positioning mark, wherein a predetermined position corresponding to the positioning mark of the master pattern is determined from the image of the pattern to be measured. An area having a size is taken out, and a corner of the pattern in the same direction as the positioning mark of the master pattern in this area is selected as a positioning mark of the pattern to be measured. Find each line, and set the coordinates of the intersection of this center line to the positioning mark of the pattern to be measured. A position of the master pattern and the pattern to be measured by calculating the coordinates of the target pattern and the position of the positioning mark of the master pattern. 4. The pattern alignment method according to claim 3, wherein, when a plurality of corresponding corners exist in the area, coordinates of an intersection of the center line are calculated for each of the corners,
A pattern alignment method characterized in that an angle whose calculated coordinates are closest to the coordinates of a positioning mark of a master pattern is adopted as a positioning mark of a pattern to be measured.