Visual inspection method and visual inspection apparatus

Abstract

To provide an appearance inspection method which can accurately perform an inspection with comparison between an inspection image and a reference image.SOLUTION: A visual inspection method for inspecting the appearance of an inspection object on the basis of an inspection image Pt obtained by imaging the inspection object includes the step of dividing the inspection object into multiple visual fields Fi, sequentially imaging each visual field, creating an inspection image with an imaging position of an alignment mark Mi set in the visual field as the reference from the photographed image imaged for each visual field and determining the quality of the inspection image. The divided visual field has an overlap region Vi in the adjacent visual field. The photographed image of a prescribed pattern in the overlap region is registered as an alignment mark used in the adjacent visual field. The inspection image is created with the imaging position of the registered alignment mark as the reference in the adjacent visual field.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an appearance inspection method and an appearance inspection apparatus for inspecting the appearance of an inspection object based on an inspection image obtained by imaging the inspection object.

Background Art

[0002] As a method for inspecting patterns formed on inspection objects such as semiconductor wafers and liquid crystal substrates, the inspection object is imaged by an imaging means, an inspection image is created from the obtained imaging image, and this inspection image and a reference image are compared to inspect for the presence or absence of defects (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the inspection object is divided into a plurality of fields of view, the imaging means is relatively moved with respect to the inspection object, and imaging is sequentially performed for each field of view, and an inspection image is created from the obtained imaging image, if the positioning accuracy of the imaging means is low, a deviation occurs in the position between the inspection image to be compared and the reference image, and the portion where the deviation occurs may be detected as a pseudo defect.

[0005] In order to prevent such misjudgment from occurring, it is conceivable to register an alignment mark for each field of view, cut out an inspection image from within the field of view of the imaging image based on the imaging position of the alignment mark, and compare the cut-out inspection image with the reference image for inspection.

[0006] However, the pattern formed on the object being inspected may change shape due to process variations. If the registered alignment marks change shape due to process variations, the alignment marks cannot be recognized. As a result, it was not possible to crop the inspection image at the correct position, and there was a problem in that inspection by comparing the inspection image with a reference image could not be performed accurately.

[0007] The present invention has been made in view of the above, and aims to provide a visual inspection method and a visual inspection apparatus that can accurately perform inspection by comparing an inspection image with a reference image. [Means for solving the problem]

[0008] The present invention provides a visual inspection method for inspecting the appearance of an object to be inspected based on an inspection image obtained by imaging the object to be inspected, comprising the steps of: dividing the object to be inspected into a plurality of fields of view and sequentially imaging each field of view; creating an inspection image of a predetermined range for each field of view from the images of the object to be inspected captured in each field of view, based on the imaging positions of alignment marks set within the field of view; and determining the quality of the inspection image for a predetermined area of ​​the inspection image created for each field of view, wherein the divided fields of view have overlapping regions in adjacent fields of view, and in the step of creating an inspection image, images of a predetermined pattern within the overlapping region are registered as alignment marks to be used in the adjacent field of view, and in the step of creating an inspection image to be performed in the adjacent field of view, the inspection image is created based on the imaging positions of the registered alignment marks.

[0009] The present invention provides an appearance inspection device for inspecting the appearance of an object to be inspected based on an inspection image obtained by imaging the object to be inspected and a reference image. The device comprises: an imaging means for dividing the object to be inspected into a plurality of fields of view and sequentially imaging each field of view; an inspection image creation means for creating an inspection image of a predetermined range for each field of view from the images of the object to be inspected captured in each field of view, based on the imaging positions of alignment marks set within the field of view; and a determination means for determining the quality of the inspection image based on the inspection image created for each field of view. The divided fields of view have overlapping regions in adjacent fields of view. The inspection image creation means registers images of a predetermined pattern within the overlapping region as alignment marks in the adjacent field of view. The inspection image creation means, when performed in the adjacent field of view, creates an inspection image based on the imaging positions of the registered alignment marks. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a visual inspection method and a visual inspection apparatus that can accurately perform inspections by comparing inspection images with reference images. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram showing the configuration of the visual inspection device in this embodiment. [Figure 2] Figure 2 is a diagram showing the inspection flow of the visual inspection method in this embodiment. [Figure 3] Figures 3(A) and 3(B) illustrate the method for creating inspection images in this embodiment. [Figure 4] Figure 4 shows an example of how to determine the quality of an inspection image. [Figure 5] Figure 5 shows an example of how to determine the quality of an inspection image. [Figure 6] Figures 6(A) and 6(B) illustrate a method for inspecting patterns formed on a semiconductor wafer. [Figure 7] Figures 7(A) and 7(B) illustrate a conventional method for creating examination images. [Figure 8] Figs. 8(A) and (B) are diagrams for explaining the process of creating a conventional inspection image.

Best Mode for Carrying Out the Invention

[0012] Before explaining the present invention, a method of dividing an object to be inspected into a plurality of fields of view, sequentially imaging each field of view while relatively moving an imaging means with respect to the object to be inspected, and creating an inspection image from the obtained imaging images will be explained.

[0013] Fig. 6 is a diagram illustrating a method of inspecting a pattern formed on a semiconductor wafer W. As shown in Fig. 6(A), a plurality of chips C having the same pattern are formed on the semiconductor wafer W.

[0014] Fig. 6(B) is an enlarged view of one chip C, and the chip C is divided into nine fields of view F i (i = 1 to 9) indicated by a broken line, and the imaging means is relatively moved with respect to the semiconductor wafer W, and imaging is sequentially performed for each field of view. In each field of view F i there are respectively alignment marks M i (i = 1 to 9) registered in advance, and an inspection image is created based on the imaging positions of the alignment marks M i from the imaging images captured for each field of view. Note that the alignment marks M i usually have unique patterns registered within each field of view F i . i

[0015] Fig. 7 is a diagram for explaining a method of creating an inspection image. As shown in Fig. 7(A), for each field of view F i a reference image P i of a predetermined range is registered in advance based on the position (x, y) of the alignment mark M S . Note that the reference image P S is for comparison with the inspection image in order to detect defects, and usually, an image selected as a representative from a plurality of non-defective images, an image generated by a non-defective product learning method, or the like is used.

[0016] Figure 7(B) shows the captured field of view F', depending on the positioning accuracy of the imaging means. i This diagram shows the state where the alignment mark M is misaligned. i The imaging position (x', y') is also shifted, therefore, alignment mark M i Based on the imaging position (x', y'), the field of view F' i From the acquired image, the examination image P t The extracted examination image P t and reference image P S A comparison is made with the correct position of the examination image P. t and reference image P S It is possible to perform tests by comparing them.

[0017] Figure 8 shows that the imaging means is scanned relative to the direction of arrow S, and the divided fields F1 to F3 are sequentially captured, resulting in the inspection image P t This is a diagram illustrating the process of creating [the product / service].

[0018] As shown in Figure 8(A), alignment marks M1 to M3 are pre-registered in each of the fields of view F1 to F3. Alignment marks M1 to M3 are selected from among the patterns within each field of view F1 to F3 that are easy to recognize and are unique.

[0019] In the initial field of view F1, the alignment mark M1 is searched for, and the imaging position of the recognized alignment mark M1 is used as the reference for the examination image P in field of view F1. t Create the following. Similarly, for the second and third fields F2-F3, search for alignment marks M2-M3 and, based on the imaging positions of the recognized alignment marks M2-M3, create the examination image P in fields F2-F3. t Create.

[0020] However, the pattern formed on the object being inspected may change shape due to process variations. For example, as shown in Figure 8(B), if foreign matter is attached to alignment mark M2 in field of view F2, the pattern shape will differ from the registered alignment mark M2, making it impossible to recognize alignment mark M2. Similarly, if the pattern shape of alignment mark M3 in field of view F3 changes (in the example shown in Figure 8(B), the linear pattern becomes thicker), the pattern shape will differ from the registered alignment mark M3, making it impossible to recognize alignment mark M3. Therefore, at the correct position, the inspection image P t Unable to extract, examination image P t and reference image P S It is not possible to perform accurate tests by comparing them.

[0021] This invention solves the above problem, and the inspection image P t and reference image P S The present invention provides a visual inspection method and a visual inspection apparatus that enable accurate inspection by comparison.

[0022] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. Furthermore, modifications can be made as appropriate without departing from the scope of achieving the effects of the present invention.

[0023] Figure 1 is a schematic diagram showing the configuration of an appearance inspection device 100 in one embodiment of the present invention.

[0024] As shown in Figure 1, the visual inspection apparatus 100 in this embodiment includes a stage 10 on which the object to be inspected W is placed, an imaging means 11 for imaging the object to be inspected W, an inspection image creation means 12 for creating an inspection image from the image of the object to be inspected W, a determination means 13 for determining whether the inspection image is good or bad by comparing the inspection image with a reference image, and a storage means 14 for storing the reference image, alignment marks, etc.

[0025] The imaging means 11 moves the stage 10 relative to the imaging means 11, and sequentially images the object under inspection W for each of the multiple divided fields of view. For example, if the object under inspection W is a semiconductor wafer, as shown in Figures 6(A) and (B), the imaging means 11 is used to image each of the multiple divided fields of view F for each chip C on which the same pattern is formed. i Moving sequentially directly below, bring chip C into view F. i Images are taken sequentially for each step.

[0026] Figure 2 is a diagram showing the inspection flow of the visual inspection method in this embodiment.

[0027] First, the object W to be inspected, placed on stage 10, is globally aligned (step S100). If the object W to be inspected is a semiconductor wafer, global alignment is performed for each chip C.

[0028] Next, the imaging means 11 is positioned in the divided field of view F i Of these, it moves relative to the leading field of view F1 (step S101).

[0029] Next, the object W to be examined, which is located within the leading field of view F1, is imaged (step S102).

[0030] Next, from the captured image of the object W being examined, the examination image P within the field of view F1 is determined based on the alignment marks set within the field of view F1. t Create (step S103).

[0031] Next, the examination image P created in visual field F1. t And, a reference image P pre-registered within the field of view F1 S By comparing it with the examination image P t Determine whether it is good or bad (Step S104). Inspection image P t The determination of whether it is good or bad is, for example, based on the examination image P t and reference image P S By comparing the two, if the difference in brightness values ​​of each pixel is within a preset range, it is determined to be a good pattern; otherwise, it is determined to be a defective pattern.

[0032] And all fields of view F i Determine whether the examination is complete (step S105), and if not, proceed to the adjacent field of view F i Steps S101 to S104 are repeated until completed, at which point the test is terminated.

[0033] Next, referring to Figure 3, the inspection image P, which is a characteristic of this embodiment, is shown. t This explains how to create it.

[0034] Figure 3 shows that the imaging means 11 is scanned relative to the direction of arrow S, and the divided fields F1 to F3 are sequentially captured, and the inspection image P is produced. t This diagram shows the steps (S103) for creating [the object].

[0035] As shown in Figure 3(A), the divided fields F1 to F3 have overlapping regions V1 and V2 in adjacent fields (F1 and F2; F2 and F3), respectively. Here, the overlapping regions V1 and V2 do not necessarily have to be the same size.

[0036] First, in the initial field of view F1, the alignment mark M1 is searched for, and the imaging position of the recognized alignment mark M1 is used as the reference for the examination image P in field of view F1. t This is created. Note that the alignment mark M1 is pre-registered in the storage means 14.

[0037] In the leading field of view F1, the examination image P t At the same time, the captured image of a predetermined pattern within the overlap region V1 with the adjacent field of view F2 is registered in the storage means 14 as the alignment mark M2 to be used in the adjacent field of view F2. The pattern of the alignment mark M2 is a pattern located in a preset position and range within the overlap region V1. The position and range of the pattern are registered in the storage means 14 in advance.

[0038] In the adjacent field of view F2, the alignment mark M2 registered within the overlapping region V1 with field of view F1 is searched for, and the imaging position of the recognized alignment mark M2 is used as the reference for the examination image P. t At the same time, the captured image of a predetermined pattern within the overlapping region V2 with the adjacent field of view F3 is registered in the storage means 14 as the alignment mark M3 to be used in the adjacent field of view F3.

[0039] Similarly, in the adjacent field of view F3, the alignment mark M3 registered within the overlapping region V2 with field of view F2 is searched for, and the imaging position of the recognized alignment mark M3 is used as the reference for the examination image P. t Create.

[0040] As described above, the pattern formed on the object W under inspection may change in shape due to process variations. For example, as shown in Figure 3(B), foreign matter may adhere to the alignment mark M2 in the field of view F2, or the pattern shape of the alignment mark M3 in the field of view F3 may change.

[0041] Thus, even if the pattern shape of alignment marks M2 and M3 changes due to process variations, the altered pattern is registered in the previous fields F1 and F2 as the alignment marks M2 and M3 used in the adjacent fields F2 and F3. Therefore, the registered alignment marks M2 and M3 can be easily recognized in fields F2 and F3. As a result, the inspection image P is displayed in the correct position. t Because it is possible to extract the image P t and reference image P S This allows for accurate testing through comparison.

[0042] Thus, according to this embodiment, adjacent fields of view F i Overlapping region V i A set of overlapping regions V i The captured image of a predetermined pattern within is transferred to the adjacent field of view F i Alignment mark M used in iRegistered as, adjacent field of view F i So, I registered the alignment mark M i Based on the imaging position, the examination image P t By creating the alignment mark M i Even if the pattern shape changes due to process variations, the inspection image P t and reference image P S This makes it possible to perform accurate tests by comparing them.

[0043] Although the present invention has been described above with reference to preferred embodiments, this description is not limiting, and various modifications are, of course, possible. For example, in the above embodiment, the inspection image P t and reference image P S By comparing it with the examination image P t The quality of the inspection image P was determined, but it is not limited to this. For example, as shown in Figure 4, the quality of the inspection image P t If there is a periodic repeating pattern D within it, adjacent repeating patterns D may be compared to detect defective patterns mixed in with good patterns. Alternatively, as shown in Figure 5, inspection image P t The pixel information (luminance, etc.) of a predetermined region Q within the image may be compared with a preset threshold, and any area exceeding this threshold may be detected as a defective area.

[0044] Furthermore, in the above embodiment, field of view F i Each time, sequentially, according to the inspection flow (steps S101-S104) shown in Figure 2, the inspection image P t The quality was judged, but the field of view F i Each time, sequentially, imaging of the object W to be examined and the examination image P t After creating (steps S102~S103), all fields of view F i In the examination image P t and reference image P S By comparing it with the examination image P t You may determine whether it is good or bad (step S104).

[0045] Furthermore, in the above embodiment, the chip C formed on the semiconductor wafer is divided into multiple fields of view Fi Each time, the examination image P t and reference image P S By comparing it with the examination image P t The quality of the chip was determined, but for areas spanning two or more chips C, the area was divided into multiple fields of view F. i Each time, the examination image P t and reference image P S By comparing it with the examination image P t You may judge whether it is good or bad.

[0046] Furthermore, although the above embodiment described an example of inspecting a pattern formed on a semiconductor wafer as the object to be inspected W, the method is not limited to this and can also be applied to methods of inspecting patterns formed on liquid crystal substrates, circuit boards, etc. [Explanation of symbols]

[0047] 10 stages 11. Imaging means 12. Inspection image creation method 13 Judgment means 14 Memory means 100 Visual Inspection Device F i field of view M i Alignment marks P S Reference image P t Examination images V i Overlap area

Claims

1. An appearance inspection method for inspecting the appearance of an object to be inspected based on an inspection image obtained by capturing an image of the object to be inspected, The steps include dividing the object to be inspected into multiple fields of view and sequentially imaging each of the fields of view, From the images of the object to be inspected captured for each field of view, a step is made to create an inspection image of a predetermined range for each field of view, based on the imaging position of the alignment mark set within the field of view. The steps include determining the quality of a predetermined region of the inspection image created for each field of view, and determining whether the image is good or bad. Includes, The divided fields of view have overlapping regions in adjacent fields of view. An appearance inspection method comprising the steps of creating the inspection image, registering an image of a predetermined pattern within the overlap area as an alignment mark to be used in the adjacent field of view, and creating the inspection image performed in the adjacent field of view, using the imaging position of the registered alignment mark as a reference.

2. The visual inspection method according to claim 1, wherein the step of determining whether the inspection image is good or bad is to compare the inspection image created for each field of view with a reference image of a predetermined range that has been registered in advance for each field of view, and determine whether the inspection image is good or bad.

3. The visual inspection method according to claim 1, wherein in the step of creating the inspection image, the predetermined pattern within the overlap region is a pattern located at a predetermined position and range within the overlap region.

4. The visual inspection method according to claim 1, wherein in the step of creating the inspection image performed in the field of view that is initially captured, the inspection image is created based on the imaging position of a pre-registered alignment mark within the field of view.

5. An appearance inspection device that inspects the appearance of an object to be inspected based on an inspection image obtained by imaging the object to be inspected and a reference image, The imaging means divides the object to be inspected into multiple fields of view and sequentially images each field of view, An inspection image creation means creates an inspection image of a predetermined range for each field of view, based on the imaging position of an alignment mark set within the field of view, from the image of the object to be inspected captured for each field of view. A determination means for determining the quality of the inspection image based on the inspection image created for each field of view. Equipped with, The divided fields of view have overlapping regions in adjacent fields of view. An appearance inspection device comprising: an inspection image creation means that registers an image of a predetermined pattern within the overlap region as an alignment mark in the adjacent field of view; and an inspection image creation means that operates in the adjacent field of view that creates the inspection image based on the imaging position of the registered alignment mark.

6. The appearance inspection apparatus according to claim 5, wherein the determination means compares the inspection image created for each field of view with a reference image of a predetermined range that has been registered in advance for each field of view, and determines whether the inspection image is good or bad.

Images