TWI410820B - Method and system for evaluating an object - Google Patents

Abstract

A method, system and a computer program product for evaluating a object; the method includes: (i) obtaining an image of an area of the object; wherein the area comprises multiple arrays of repetitive structural elements that are at least partially surrounded by at least one group of non-repetitive regions; wherein non-repetitive regions that belong to a single group of non-repetitive regions are ideally identical to each other; wherein the non-repetitive regions are arranged in a repetitive manner; and (ii) providing an evaluation result in response to a comparison between image information of a first sub-area to image information of a second sub-area that is proximate to the first sub-area; wherein the first sub-area comprises a first array of repetitive structural elements and a first non-repetitive region; wherein the second sub-area comprises a second array of repetitive structural elements and a second non-repetitive region.

Description

Method and system for evaluating objects

The present invention generally relates to the field of automated inspection of articles such as wafers, masks or reticles for microfabrication, flat panel displays, micro-electromechanical (MEM) devices and the like.

In the past few decades, defect detection for detecting microfabrication defects has become a standard part of the micromachining manufacturing process especially for semiconductor wafers.

The various detection techniques that are most likely to find multiple types of defects are commonly used in multiple steps in a semiconductor manufacturing process. The economic benefits of testing have been very significant and it is generally believed that detection technology has made a significant contribution to the significant growth in the field of semiconductor wafer fabrication that emerged in the 1990s.

The detection system is applied to a large number of different applications, including monitoring of the marked program when a particular program step in the manufacturing process has an increased defect density that exceeds the normal expected level of the step; Circle wafers to solve the problem, the wafer is processed only with a subset of the manufacturing process steps to facilitate troubleshooting and diagnostics or to optimize a specific subset of program steps, and to optimize new manufacturing processes during program development To reduce or eliminate program-specific or system defect mechanisms.

Wafer inspection systems for patterned wafer inspection typically operate as described below. High-power microscopes, traditionally optical microscopes, or more recently SEM (Scanning Electron Microscope) or electron microscopes, set to be computer controlled to sequentially acquire objects An image, such as a wafer or reticle containing a plurality of integrated circuits arranged in dices, for micromachining, flat panel displays, microelectromechanical (MEM) devices, etc., during or after fabrication. Or double the reticle.

The image or comparison data acquired in this way is then compared to the reference material. A defect is found or detected at a difference between the reference image and the acquired image. The reference image may be derived from Computer Aided Design (CAD) data, such as is typically detected using a reticle or doubling mask, additionally or alternatively, the reference image may be only the immediately adjacent cell or wafer on the wafer. Or an image of a similar wafer being detected. The sensitivity of the defect detection program for small defects can be adjusted by adjusting image acquisition parameters such as primitive size, contrast, brightness, charging and bias conditions, and image processing parameters for comparing the acquired detected image and reference image. To control.

An object, such as a wafer, can include a repeating region that includes a number of repeating structural elements, such as a storage unit (such as static memory (SRAM), dynamic memory (DRAM), ferroelectric memory (FRAM), flash memory). The repeating region may also include a repeating structural element programmable logic unit, such as a programmable logic unit included in a programmable logic device (PLA), a programmable logic circuit (PLD). Other items such as MEM displays and flat panel displays may include repeating regions.

Typically, ideally identical structural elements (called cells) included in the same repeating region are compared to each other or to a so-called "golden cell". The two types of comparisons are called unit to unit comparisons.

The storage array is usually surrounded by non-repeating areas. These non-repetitive regions are typically compared to one another using so-called wafer versus wafer comparisons.

Comparing a wafer to a wafer involves comparing image information of one wafer with image information of another wafer. It is known in the art that wafers versus wafers are significantly less sensitive to defects due to their reduced sensitivity than units and wafers. Yuan comparison. The latter is superior to wafer-to-wafer comparisons due to program variations, color changes (when applying light field techniques and when localized transparent layers are placed on the cell), and optical image acquisition (and/or illumination). The process changes are less sensitive. These variations may include changes in radiation intensity, aberrations; focal length misalignment, sensor saturation, sensor array non-uniformity, misalignment, and the like.

Although the unit has some advantages compared to the unit. It responds to the difference between the acquisition of image information of cells near the edge of the repeating region and the acquisition of image information of cells separated from the edges of the repeating region. Noting that due to the wider energy distribution of the radiation used to illuminate the area and the pattern information passing through the spatial frequency filter when illuminating structural elements near the edge of the array, the graphical information of a particular structural element may be surrounded by specific structural elements Object impact. Typically, such spatial frequency filters are configured to block interference lobes of an array of repeating structural elements. The non-repetitive region changes the position of the interfering lobes so that image information can pass through these spatial frequency filters.

Figure 1 shows a region 8 of a prior art wafer. The plurality of storage unit arrays 10-18 are surrounded by vertical slits (indicated by V) and horizontal seams (represented by "H slits" 20-30). During the commonly performed hybrid comparison process, the image information of the repeating structural elements within each array is compared to the image information of the repeating structural elements within the same array, while the image information of the vertical stitches is perpendicular to the vertical stitching of the other wafer. The image information is compared. This hybrid comparison process has the disadvantages of wafer versus wafer described above and the disadvantages of unit versus unit.

There is an increasing need for improved systems, methods, and computer program products that provide evaluable objects.

A method for evaluating an object, the method comprising: (i) obtaining an image of an area of the object; wherein the area comprises a plurality of arrays of repeating structural elements at least partially surrounded by at least one set of non-repetitive areas; The majority of the non-repetitive regions of a single set of non-repeating regions are desirably identical to each other; wherein the non-repetitive regions are arranged in a repeating manner; and (ii) the image information in response to the first sub-region and the second sub-region immediately adjacent to the first sub-region Providing an evaluation result between the image information; wherein the first sub-region includes the first array of repeating structural elements and the first non-repetitive region; wherein the second sub-region includes the second array of repeating structural elements and the second non- Repeat the area.

A system for evaluating an item; the system comprising: a storage unit configured to store an image of an area of the object; wherein the area comprises a plurality of arrays of repeating structural elements at least partially surrounded by at least one set of non-repetitive areas Wherein the plurality of non-repetitive regions belonging to a single set of non-repetitive regions are desirably identical to each other; wherein the non-repetitive regions are arranged in a repeating manner; and the processor configured to respond to the image information of the first sub-region and immediately adjacent to the first Providing an evaluation result between the image information of the second sub-region of the sub-region; wherein the first sub-region includes the first array of repeating structural elements and the first non-repetitive region; wherein the second sub-region includes the second array Repeating structural elements and second non-repetitive regions.

A computer program product comprising a computer usable medium having a computer readable program, wherein when executed on a computer, the computer can perform the following steps: receiving an image of an area of the object; wherein the area includes Repeating structural elements of the array, at least partially surrounded by at least one set of non-repetitive regions; most non-repetitive regions belonging to a single set of non-repetitive regions are desirably identical to each other; wherein the non-repetitive regions are arranged in a repeating manner; and responding to the first Image information of the sub-area and second of the first sub-area Providing an evaluation result between the image information of the sub-regions; wherein the first sub-region includes the first array of repeating structural elements and the first non-repetitive region; wherein the second sub-region includes the second array of repeating structural elements and Second non-repetitive area.

A method, system and computer program product for evaluating articles such as wafers, reticle or reticle for micromachining, flat panel displays, microelectromechanical (MEM) devices, etc., during or after manufacturing .

Sub-areas are defined in accordance with embodiments of the present invention. Each sub-region includes an array of repeating structural elements. The repeating array of structural elements is surrounded by at least one set of non-repetitive regions. Most of the non-repetitive regions belonging to a single set of non-repetitive regions are desirably identical to each other. The non-repeating regions are arranged in a repeating manner. The method, system, and computer program product take other comparisons in place of the wafer and the wafer. This comparison takes place between image information of a plurality of non-repetitive regions belonging to sub-regions that are immediately adjacent to one another (typically belonging to the same wafer). This type of comparison is more reliable due to less impact from program changes, color changes, or changes in image acquisition conditions.

According to an embodiment of the present invention, image information of one structural element replacing the repeating pattern array is compared with image information of another structural element of the same array of repeating structural elements, image information of the repeated structural elements of the first sub-area Image information comparison of corresponding repeating structural elements of the second sub-region. This comparison overcomes the comparison error caused by the comparison of the image information of the structural elements located near the edges of the repeating structural element array with the image information of the structural elements remote from the edges of the array of repeating structural elements.

According to another embodiment of the invention, the array of repeating elements is separated into an inner portion and an outer portion. The outer part can be positioned inside and around the repeating structure Between non-repeating regions of the array of components. The inner portion includes selected structural elements that are selected such that their image information is unaffected by the non-repetitive region and the image information of the structural elements of the outer portion may be affected by the non-repetitive region. The image information of the structural elements within the inner portion of the repeating structural element array is compared to the image information of other structural elements within the same inner portion. The image information of the structural elements within the outer portion of the array of repeating structural elements belonging to a particular sub-region is compared to the corresponding image information of the structural elements within the outer portion of another array of repeating structural elements belonging to another sub-region.

Terms such as "first" and "second" are used to arbitrarily distinguish between the elements described by the term unless otherwise stated. Therefore, these terms are not intended to indicate - the timing or other prioritization of the elements.

Unless otherwise stated, the term "corresponding structural element" means a structural element belonging to a different sub-area that is substantially positioned at the same location with respect to the boundaries of the sub-areas to which they belong.

The term "image information" means information used to describe information obtained during light collection of an image. This information usually includes one or more grayscale primitives, but this is not required. Note that image information can be obtained by using an imaging lens or a non-imaging lens. Image information can be digitally processed (eg by using a filter) before being compared to other image information.

Figure 2 shows two sub-areas in accordance with an embodiment of the present invention. The image information of the first sub-area is compared with the corresponding image information of the second sub-area. Figure 2 shows successive sub-regions. Note that the image information comparison can be made between sub-regions that are immediately adjacent to each other, even if the sub-regions are separated from each other. Referring to the embodiment depicted in FIG. 1, the sub-areas including the array 10 and the horizontal slits 20 can be compared to another sub-area including the array 18 and the horizontal slit 27. Note that the image information of the first sub-area can be compared with information representing a plurality of other sub-areas. This may include the information of the first sub-area with a plurality of other sub-areas The average (or other statistical or statistical correlation function) is compared.

If the expected change between these regions due to program changes is below a certain program change threshold, then the two sub-regions can be considered as being in close proximity. Additionally or alternatively, if the temporal change in color change, light image acquisition, and/or illumination process has a lower impact on the comparison process than a particular threshold, then the two sub-regions may be considered as being in close proximity. Each of these thresholds can be set by the user, the evaluation tool operator, or the item manufacturer in response to various parameters such as required sensitivity, required signal to noise ratio, desired detected defects, and the like. If the distance between these sub-regions does not exceed a small portion of the length (or width) of the wafer, then typically the sub-regions are considered to be in close proximity to each other.

Figure 4 illustrates a method 100 for evaluating an item in accordance with an embodiment of the present invention.

The method 100 begins at step 110 by obtaining an image of an area of an object; wherein the area includes a plurality of arrays of repeating structural elements at least partially surrounded by at least one set of non-repetitive areas. Most of the non-repetitive regions belonging to a single set of non-repetitive regions are desirably identical to each other. The non-repeating regions are arranged in a repeating manner.

Note that this area can be much smaller than a wafer, can include one or more dices, and the like.

Referring to the embodiment depicted in Figure 2, the array of repeating structural elements is array 10 and array 13. The non-repeating regions of the first set include horizontal slits 20, 23, and 26, while the second set of non-repeating regions include vertical slits (indicated by V).

Step 110 may include obtaining these images optically (including using electro-optics), obtaining image information representative of the images, and the like. An attention area, such as the image of area 8 of Figure 1, may involve capturing a multi-part image of area 8 and generating a composite image that includes portions of a plurality of independently optically acquired images. Also, note that optical collection of images may be required To be aligned. When each sub-area is aligned, alignment is usually easier (and less time spent). Note that the multi-part optically obtained images of the regions may partially overlap, thereby compensating for various misalignment problems associated with optical acquisition of the image. In addition, it is noted that the image of region 8 can be generated after acquiring a plurality of images of the region and processing the graphics (eg, by summing the images to average random noise). Those skilled in the art will appreciate that the image can be acquired by using monochromatic radiation, charged particle beams, broadband radiation, pulsed light sources, continuous light sources, and the like.

Step 110 is followed by step 130, which provides an evaluation result in response to a comparison between the image information of the first sub-area and the image information of the second sub-area immediately adjacent to the first sub-area. The first sub-region includes a repeating structural element of the first array and a first non-repetitive region. The second sub-region includes a repeating structural element of the second array and a second non-repetitive region. Note that each sub-region may include one or more portions of one or more non-repetitive regions.

Conveniently, step 130 includes at least one of steps 132, 134, and 136.

Step 132 includes comparing the image information of the first sub-region with the image information of the second sub-region, wherein the first sub-region includes a storage unit of the first array and a first non-repetitive region including the first slit. The second sub-region includes a second array of storage units and a second non-repeating region including a second slit. Figure 2 provides an embodiment of the sub-areas.

Step 134 includes comparing image information of corresponding structural elements of different sub-regions. Each structural element is tied at substantially the same position relative to the boundary of the sub-region comprising the structural element. Step 134 includes, for example: (i) image information of repeating structural elements belonging to the first sub-area and located not near the edge of their array, and corresponding structural elements of the second sub-area located not near the edge of the other array Comparison, and (ii) the first sub-area The image information of the structural elements of the non-overlapping region is compared to the corresponding structural elements of another non-overlapping region of the second sub-region.

Step 136 includes comparing image information of structural elements proximate the edges of the first array with image information of corresponding elements proximate to corresponding edges of the second array. Note that step 134 can be considered to include step 136, but this is not required.

Figure 3 shows two sub-areas in accordance with an embodiment of the present invention.

Figure 3 shows that each of the arrays 10 and 13 is divided into inner portions (10 (1) and 13 (1), respectively) and outer portions (10 (2) and 13 (2), respectively). The outer region includes structural elements whose image information is affected by one or more non-repetitive regions surrounding their array (at least greater than a particular threshold). The internal area consists of structural elements whose image information is unaffected by the non-repetitive area (or affects below a certain threshold). Note that the threshold can represent the balance between the features of the cell versus the cell and the features of the subregion compared to the subregion.

Figure 5 illustrates a method 200 in accordance with an embodiment of the present invention.

The method 200 begins at step 110 with obtaining an image of an area of an object; wherein the area includes a plurality of arrays of repeating structural elements that are at least partially surrounded by at least one set of non-repetitive regions; wherein the single set is non-repeating Most of the non-repetitive regions of the repeating region are desirably identical to each other; wherein the non-repetitive regions are arranged in a repeating manner.

Step 110 is followed by steps 144 and 146. These steps can be performed in parallel with each other, but for simplicity of explanation, FIG. 5 shows step 146 after step 144.

Step 144 includes comparing image information of the first repeating element contained in the outer portion of the first array of repeating structural elements to image information of the corresponding repeating element contained in the outer portion of the repeating structural element of the second array Compared. The first array belongs to the first sub-area and the second array belongs to the second sub-area. The first and second sub-regions are in close proximity to each other.

Step 146 includes comparing image information of the first repeating element contained in the inner portion of the repeating structural element of the first array with image information of another repeating element included in the inner portion of the repeating structural element of the first array Comparison.

Step 146 is followed by step 148, which provides an evaluation result in response to at least one of steps 144 and 146.

Figure 6 shows a system 300 in accordance with an embodiment of the present invention.

System 300 includes a storage unit 320, a processor 310, and an image acquisition unit 330. System 300 can optically obtain images of regions or receive images (or information representing such images) from a detection tool that includes an image acquisition unit.

The storage unit 320 is configured to store an image of an area of the object. The region includes a plurality of arrays of repeating structural elements at least partially surrounded by at least one set of non-repetitive regions; wherein the plurality of non-repetitive regions belonging to a single set of non-repetitive regions are desirably identical to each other; wherein the non-repetitive regions are arranged in a repeating manner .

The processor 310 is configured to provide an evaluation result by comparing the image information of the first sub-area with the image information of the second sub-area adjacent to the first sub-area; wherein the first sub-area includes a repetition of the first sub-area a structural element and a first non-repetitive region; wherein the second sub-region comprises a repeating structural element of the second array and a second non-repetitive region.

Conveniently, the processor 310 is configured to compare image information of the first sub-area with image information of the second sub-area; wherein the first sub-area comprises a first array of storage units and includes a first slot a first non-repetitive area; wherein the second sub-area includes a second array of storage units and includes a second non-repetitive region of the second slit.

Conveniently, the processor 310 is configured to compare image information of different structural elements of different sub-regions, wherein each structural element is tied at substantially the same position relative to a boundary of a sub-region comprising the structural element .

Conveniently, the processor 310 is configured to compare image information of structural elements proximate the edges of the repeating structural elements of the first array with image information of corresponding elements proximate to corresponding edges of the second array.

Conveniently, the processor 310 is configured to map image information of the first repeating element included in the outer portion of the repeating structural element of the first array with corresponding repeats in the outer portion of the repeating structural element included in the second array The image information of the component is compared.

Conveniently, the processor 310 is configured to image information of the first repeating element contained in the inner portion of the repeating structural element of the first array with another one of the inner portions of the repeating structural element included in the first array The image information of the repeating components is compared.

Suitably, a computer program product is provided. The computer includes a computer readable program, wherein the computer readable program, when executed on a computer, causes the computer to perform the steps of: receiving an image of an area of the object; wherein the area includes at least partially at least partially a plurality of arrays of repeating structural elements surrounded by a set of non-overlapping regions; wherein the plurality of non-repetitive regions belonging to a single set of non-overlapping regions are desirably identical to each other; wherein the non-repetitive regions are arranged in a repeating manner; and responsive to the first sub-region Providing an evaluation result between the image information and image information of the second sub-area adjacent to the first sub-region; wherein the first sub-region includes the first array of repeating structural elements and the first non-repetitive region; wherein The two sub-regions include a repeating structural element of the second array and a second non-repetitive region.

Conveniently, the computer program product enables the computer to compare the image information of the first sub-area with the image information of the second sub-area; wherein the first sub-area includes the first array of storage units and the first slot a non-repetitive region; wherein the second sub-region includes a second array of storage units and a second non-repetitive region including a second slit.

Conveniently, the computer program product enables the computer to compare image information of different structural elements of different sub-areas; wherein each structural element is tied at substantially the same position relative to the boundary of the sub-area including the structural element.

Conveniently, the computer program product enables the computer to compare image information of structural elements near the edges of the repeating structural elements of the first array with image information of corresponding elements adjacent the corresponding edges of the repeating structural elements of the second array.

Conveniently, the computer program product causes the computer to image information of the first repeating element included in the outer portion of the repeating structural element of the first array with corresponding repeating elements included in the outer portion of the repeating structural element of the second array The image information is compared.

Conveniently, the computer program product causes the computer to image information of the first repeating element included in the inner portion of the repeating structural element of the first array with another repeat included in the inner portion of the repeating structural element of the first array The image information of the component is compared.

Note that while the above text relates to the comparison between image information of structural elements of two sub-regions, multiple comparisons between structural elements of more than two different sub-regions may be implemented. For example, if there is a difference between the image information of two ideally identical structural elements of the two sub-regions, at least one additional comparison can be made to determine the two ideally identical corresponding structural elements to be compared. Which structural component is defective.

Further noting that the method, system and computer program product can be targeted The comparison between the image information of the area and the image information of the "gold" sub-area is appropriately corrected. Therefore, the image information of the first sub-area can be compared with the image information of the second sub-area.

A person skilled in the art will readily appreciate that various modifications and variations can be applied to the embodiments of the invention as described above without departing from the scope of the invention as defined by the appended claims.

8‧‧‧ Wafer area

10-18‧‧‧Storage unit array

20-30‧‧‧ horizontal seam

30‧‧‧First subregion

40‧‧‧Second subregion

10(1), 13(1) ‧‧‧

10(2), 13(2) ‧ ‧ outer parts

In order to understand the present invention and to explain how it is actually implemented, the embodiments will be described with reference to the accompanying drawings, by way of non-limiting embodiments, in which: FIG. 1 shows an area of a wafer; FIG. 2 shows an implementation according to the present invention. Two sub-regions of the mode; Figure 3 shows two sub-regions according to another embodiment of the invention; Figure 4 shows a method according to an embodiment of the invention; Figure 5 shows another method according to the invention A method of an embodiment; and a sixth diagram illustrates a system in accordance with an embodiment of the present invention.

Claims (4)

A method for evaluating an object, the method comprising the steps of: obtaining an image of a region of the object; wherein the region comprises a plurality of arrays of repeating structural elements at least partially surrounded by at least one set of non-repetitive regions; The plurality of non-repetitive regions belonging to a single group of non-repetitive regions are desirably identical to each other; wherein the non-repetitive regions are arranged in a repeating manner; and image information in response to a first sub-region and a first portion adjacent to the first sub-region Providing an evaluation result between the image information of the two sub-regions, wherein the first sub-region includes a first array of repeating structural elements and a first non-repetitive region; wherein the second sub-region includes a a second array of repeating structural elements and a second non-overlapping region, wherein the comparing comprises at least one of: a first array of storage units and an image information including a first non-repetitive region including a first slit and a Comparison between two image information of the image information of the second array storage unit and a second non-repetitive area including a second slit, not of different sub-areas Comparison of image information of structural elements, wherein each structural element is tied at substantially the same position relative to a boundary of a sub-area comprising the structural element, adjacent to an edge of the repeating structural element of the first array A comparison between the image information of the component and the image information of the image information of the corresponding component of a corresponding edge of the repeating structural component of the second array is included in an outer portion of the repeating structural component of the first array a comparison between image information of a first repeating element and image information of image information of a corresponding repeating element included in an outer portion of the repeating structural element of the second array, Image information of a first repeating element in an inner portion of the repeating structural element of the first array and image information of another repeating element included in the inner portion of the repeating structural element of the first array A comparison between two image information. A system for evaluating an object, the system comprising: a storage unit configured to store an image of an area of the object; wherein the area includes at least partially surrounded by at least one set of non-repetitive areas Repeating structural elements of a plurality of arrays; wherein the plurality of non-repetitive regions belonging to a single set of non-repetitive regions are desirably identical to each other; wherein the non-repetitive regions are arranged in a repeating manner; and a processor configured for use in the processor Providing an evaluation result in response to comparison between image information of a first sub-area and image information of a second sub-area adjacent to the first sub-area; wherein the first sub-area includes a first array a repeating structural element and a first non-repetitive region; wherein the second sub-region comprises a second array of repeating structural elements and a second non-repetitive region, wherein the comparing comprises at least one of: a first array of storage units And image information including a first non-repeating area having a first slit and a second array storage unit and a second non-repeating including a second slit Comparison of image information between two image information of a domain, comparison of image information of different structural elements of different sub-regions; wherein each structural component is tied to a boundary with respect to a sub-region including the structural component At substantially the same position, image information of structural elements near an edge of the repeating structural element of the first array and a corresponding one of the repeating structural elements of the second array Comparing the two image information of the image information of the corresponding component of the edge, the image information of a first repeating component included in an outer portion of the repeating structural component of the first array is included in the second array Comparing between two image information of image information of a corresponding repeating structural element in an outer portion of the repeating structural element, a first repeating element in an inner portion of the repeating structural element of the first array A comparison between image information and two image information of image information of another repeating structural element contained in the inner portion of the repeating structural element of the first array. A system as claimed in claim 2, comprising an image acquisition unit configured to optically obtain an image of the area of the object. A computer program product comprising a computer usable medium having a computer readable program, wherein when executed on a computer, the computer can perform the following steps: receiving an area of the object An image; the region comprising a plurality of arrays of repeating structural elements at least partially surrounded by at least one set of non-overlapping regions; wherein the plurality of non-repetitive regions belonging to a single set of non-overlapping regions are desirably identical to each other; And the non-repeating regions are arranged in a repeated manner; and an evaluation result is provided by comparing the image information of the first sub-region with the image information of a second sub-region immediately adjacent to the first sub-region; The first sub-region includes a first array of repeating structural elements and a first non-repetitive region; wherein the second sub-region includes a second array of repeating structural elements and a second non-repetitive region; wherein the comparing comprises at least the following One: Image information of a first array storage unit and a first non-repetitive area including a first slit and image information of a second array storage unit and a second non-repetitive area including a second slit Comparison of image information, comparison of image information of different structural elements of different sub-areas; wherein each structural element is tied at substantially the same position relative to a boundary of a sub-area including the structural element, Comparison between image information of structural elements of one edge of the first array of repeating structural elements and image information of image information of a corresponding element of a corresponding edge of the repeating structural element of the second array, including Image information of a first repeating element in an outer portion of the repeating structural element of the first array and image information of a corresponding repeating structural element included in an outer portion of the repeating structural element of the second array Comparing the two image information, the image information of a first repeating element in an inner portion of the repeating structural element of the first array and the weight contained in the first array Comparison between the two image information of another repeating structural information elements of the inner portion of the structural element.