JP2841373B2 - Pattern inspection equipment - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an apparatus for inspecting a master pattern used for screen printing or photoengraving and a defect of a pattern formed by copying the master pattern, and more particularly The present invention relates to an apparatus for inspecting a pattern formed on a material having anisotropic shrinkage characteristics such as a vinyl sheet and a green sheet.

(Prior Art) Conventionally, in this type of pattern inspection, a pattern matching method is used in which a standard pattern is prepared in advance, the standard pattern and the pattern to be inspected are overlapped, and the difference is determined as a pattern defect. ing.

(Problems to be Solved by the Invention) In this pattern matching method, the positional relationship between pattern elements to be corresponded between a pattern to be inspected and a standard pattern is enlarged or enlarged based on a translation and a magnification common to a workpiece. It is assumed that there is a linear relationship with the reduction.

Therefore, for example, in a test for a work having anisotropic shrinkage, which has a shrinkage variation of about 1%, such as a green sheet, and the shrinkage ratio varies depending on the position and direction on the work, even if the pattern is acceptable, the pattern is defective. There is a drawback that it is determined that there is.

An object of the present invention is to provide a pattern inspection apparatus in which an allowable pattern within a certain range is not determined as a defect in an inspection for a work having anisotropic shrinkage characteristics.

(Means for Solving the Problems) In order to achieve the above object, a pattern inspection apparatus according to the present invention includes a one-dimensional CCD camera for imaging a work to be inspected, and the inspected object in a direction orthogonal to a direction of the one-dimensional CCD array. A moving table for sending a workpiece, a pre-processing unit for binarizing the output video signal of the one-dimensional CCD camera and removing noise included in the output video signal, and output data of the pre-processing unit for each scanning line Into a pattern width data string, a pattern width data memory storing a standard pattern width data string converted for each scanning line with respect to the standard pattern, and a pattern width data memory A window for setting a pattern width data string fitting search area for the scan line on the pattern width data memory based on the pattern width data string fitting result; In the fitting search area set by the window section, the pattern width data string of the work to be inspected is compared in order with the standard pattern width data string for each scanning line in the fitting search area, and If there is no standard pattern width data string within an allowable value for the pattern width data string, it is determined that the pattern width data string of the workpiece to be inspected cannot be associated, and such association is impossible. When a predetermined number or more of pattern width data strings of the work to be inspected are connected to each other, the pattern of the work to be inspected is determined to have a defect.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a pattern inspection apparatus according to the present invention.

The work 1 to be inspected is mounted on a moving table 2 and is sent in a direction orthogonal to an image sensor array of a one-dimensional CCD camera 3 for imaging the work 1.

The preprocessing unit 4 binarizes the output video signal of the one-dimensional CCD camera 3 by recognizing whether it is a pattern or a background based on a set threshold value, and performs noise removal of about one pixel.
Accordingly, the binary image data is sent to the pattern width measuring section 5. The pattern width data measuring section 5 sets the pattern width to the number of consecutive pixels corresponding to the pattern section on the binary image data for each scanning line, and determines the determination section 6 in the form of a pattern width data string.
Output to

On the other hand, the pattern width data memory 8 stores the pattern width data string of the entire scanning line area formed by the above-described method for the standard pattern. Pattern width data relating to the scanning line group is cut out by the window unit 7, and is similarly input to the determination unit 6.

The determination unit 6 compares the pattern width data string of the pattern to be inspected with the standard pattern width data string group to determine whether there is a pattern defect.

FIG. 2 is a diagram showing an example of a pattern for explaining the inspection principle in the present invention. FIG. 2A shows a standard pattern, and FIG. 2B shows a pattern to be inspected. For simplicity of description, this is an example in which the number of pixels of a one-dimensional CCD that performs a scanning function is 10, and the number of scanning lines in the entire inspection area is 10.

If the pattern portion is a figure shown by oblique lines in FIG. 2 (a), the pattern width data string formed for the standard pattern becomes FIG. 3 (a), which is stored in the pattern width data memory 8 in FIG. It is remembered.

The same applies to FIG. 2 (b), which is the pattern to be inspected. The pattern width data string is as shown in FIG. 3 (b), and each time the scanning of each scanning line l ′ _i (i = 1 to 10) is completed, the determination unit is completed. Is input to

The determination unit associates the pattern width data string l _i with the standard pattern and the pattern width data string lj to be inspected according to the following two rules.

(Rule 1) Immediately before inspection pattern width data string l ' _i-1
Let l _m 'be a standard pattern width data string associated with the pattern width data string l ′ _i to be inspected, and lj (m′−α + 1 ≦ j
≦ m ′ + α + 1).

(Convention 2) Data strings l _i and lj to be associated
Are compared in order from the beginning, and if all the differences are equal to or smaller than β, it is determined that the association has been made.

The allowable widths α and β in the above-mentioned rules are set based on the degree of variation in shrinkage of the target work and the required inspection performance. Also, regarding the rule 1, the window unit 7 in FIG.
Means the range to set the data area taken out from the pattern width data memory 8.

The determination unit 6 associates a pattern width data string for each input scanning line l 'with each other, and determines that there is a data string that cannot be associated with γ or more continuous γ lines, and determines that the defect is a defect.

Specifically, it is assumed that α = 2, β = 1, and γ = 2, and a determination is made when the standard pattern width data string is as shown in FIG. 3 (a) and the pattern width data string is as shown in FIG. 3 (b). The operation of the unit will be described in more detail.

Pattern width data strings l'1 to l 'of the pattern to be inspected
6, the result of the association according to the above-mentioned rules is indicated by an arrow in the figure.

Paying attention to the association regarding l ₇ ′, since the data string on the standard pattern side associated with l ′ 6 is l 5, fitting of the pattern width data string l ′ 7 of the pattern to be inspected associated with rule 1 is performed. The search area is limited to l4 to l8 as shown by the bold frame in FIG. 9A, but none of these data strings satisfies the rule 2 between l'6 and l'6 It is determined that the association is impossible. Similarly, it is impossible to associate l′ 7, so two (=
.gamma.) It is impossible to make the correspondence continuously, and it is determined that there is a pattern defect. This corresponds to the detection of a defect indicated by in the pattern diagram shown in FIG. 2 (b). Conversely, a small difference and a portion which is erroneously recognized as a defect by the conventional pattern matching method due to anisotropic shrinkage is not regarded as a defect.

(Effects of the Invention) As described above, the determination apparatus according to the present invention converts two-dimensional pattern data into a pattern width data string, compares the standard pattern with the pattern width data string of the pattern to be inspected, and detects a minute difference. The comparison result is determined according to an allowable algorithm.

Therefore, if the difference is within a predetermined value, there is an effect that a pattern inspection for a work having anisotropic shrinkage characteristics can be performed without determining that the work is a pattern defect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a pattern inspection apparatus according to the present invention, FIG. 2 is a view showing an example of a pattern,
FIG. 3 is a diagram showing an example of a pattern width data string. 1. Workpiece to be inspected 2. Moving table 3. One-dimensional CCD camera 4. Preprocessing unit 5. Pattern width measurement unit 6. Judgment unit 7. Window unit 8. Pattern width data Memory 9: Fit search area for l'7

Claims (1)

(57) [Claims] 1. A one-dimensional CCD camera for imaging a work to be inspected, a moving table for feeding the work to be inspected in a direction orthogonal to a direction of the one-dimensional CCD array, and a binary signal output from the one-dimensional CCD camera A pre-processing unit for performing noise reduction and noise removal included in the output video signal; a pattern width-side constant unit for converting output data of the pre-processing unit into a pattern width data string for each scanning line; On the other hand, the pattern width data memory storing the standard pattern width data string converted for each scanning line, and the pattern width data memory based on the result of applying the pattern width data string of the scanning line up to immediately before. A window for setting a pattern width data string fitting search area for the line, and a pattern of the workpiece to be inspected in the fitting search area set by the window. The pattern width data string is sequentially compared with the standard pattern width data string for each scanning line in the fitting search area, and the standard pattern width data string within an allowable value for the pattern width data string of the work to be inspected is When there is no, it is determined that the pattern width data string of the work to be inspected cannot be correlated, and when the pattern width data string of the work to be inspected that cannot be correlated continues for a predetermined number or more, the A pattern inspection apparatus, comprising: a determination unit that determines that a pattern of a work to be inspected has a defect.