JP2725469B2 - Micro defect detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro-defect detecting device, and more particularly, to a comparative inspection between printed wiring patterns.
The present invention relates to a micro-defect detection device that determines a signal level difference between patterns, determines a defect based on a magnitude relationship with a fixed threshold, and detects a micro-defect on a wiring pattern.

[0002]

2. Description of the Related Art Conventionally, detection of minute defects by a comparative inspection apparatus is performed by using an image obtained by scanning an object with a photoelectric conversion scanner and an image obtained by shifting the object by the repetition period of a wiring pattern. A method has been used in which, after accurate registration is performed, a difference image between the two is obtained, and a difference image whose output is larger than a certain threshold value is detected as a defect.

[0003]

However, in the above-mentioned conventional method, all the minute differences in the pattern edges of the wiring patterns to be compared are detected as defects. was there.

An object of the present invention is to provide a minute defect detecting apparatus which detects only minute defects in a pattern without being affected by a signal level difference at a pattern edge.

[0005]

According to the present invention, there is provided a micro-defect detecting apparatus, comprising: a photoelectric conversion scanner for scanning an object placed on an XY table; An A / D conversion circuit for converting the XY table into a signal, an image memory circuit for storing a digital image signal from the A / D conversion circuit, and the photoelectric conversion scanner after moving the XY table by a repetitive pattern on an object. Scanning circuit for performing fine position correction on the digital image signal output from the A / D conversion circuit with reference to the memory image signal read from the image memory circuit, and the correction output from the positioning circuit Means for calculating a difference between the corrected digital image signal and the memory image signal to generate a difference image; And wherein each of the memory image signal processed sequentially scans the edge detection operator, processing binding
The point where the absolute value of the result is equal to or more than a certain value is converted into a binary signal.
An edge detection circuit for obtaining an edge position from a logical sum, an edge labeling circuit for performing a labeling process for numbering an edge signal output from the edge detection circuit for each continuous area, and a label output from the edge labeling circuit configuration includes a mask generator circuit size of the region is taken more than a predetermined value in, and a micro-defect detection circuit extracts only minute defects from the difference image signal with a mask signal output from the mask generator Have been.

[0006]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In FIG. 1, first, an inspection object placed on an XY table 1 is scanned by a photoelectric conversion scanner 2, and the read image signal 3 is converted into a multi-level digital image signal by an A / D conversion circuit 4. And stored in the image memory circuit 7.

Next, the XY table 1 is moved by a fixed amount by the amount of the repetitive pattern on the object, and the same pattern as the pattern stored in the image memory circuit 7 is included in the XY table 1 in the same manner as the previous time. And A
The digital image signal 5 obtained from the / D conversion circuit 4 is input to a positioning circuit 6.

At the same time, the positioning circuit 6 reads the memory image signal 8 from the image memory circuit 7 and compares it with the digital image signal 5 input from the A / D conversion circuit 4 to perform fine position correction on the digital image signal 5. And outputs a corrected digital image signal 9.

The difference image calculation circuit 10 receives the corrected digital image signal 9 and the memory image signal 8, obtains a difference between the images, and outputs a difference image signal 11. Up to this point, this is the same as the case of the conventional defect detection by the comparative inspection. Conventionally, the difference image signal 11 that exceeds a certain threshold is output as a defect signal. In the present embodiment, the edge detection circuit 12, the edge labeling circuit 1
4. The mask generation circuit 16 and the minute defect detection circuit 18 do not output a defect signal corresponding to the pattern edge portion.

The edge detection circuit 12 receives the corrected digital image signal 9 and the memory image signal 8, and detects a 3 × 3 (dot) edge detection operator (dot for detecting an inclination) for each point of each image. The arithmetic processing) is sequentially scanned and processed, a point where the absolute value of the processing result is equal to or more than a certain value is set as an edge position, converted into a binary signal, and a logical OR of both is calculated and output as an edge signal 13.

The edge labeling circuit 14 examines the connection relation of each point of the image corresponding to the edge signal 13 input from the edge detection circuit 12, and performs a labeling process for assigning the same label number to a group of connected points as the same area. And outputs an edge label signal 15 with label numbers.

The mask generation circuit 16 includes an edge label signal 15 output from the edge labeling circuit
An area larger than a predetermined area is determined as an edge, and a mask signal 17 to be set as a non-inspection area is generated.
The microdefect detection circuit 18 performs a mask process on the difference image signal 11 using the mask signal 17 generated by the mask generation circuit 16 and outputs only a defect as a microdefect signal 19.

FIG. 2 is an image diagram for explaining a method up to generation of the mask signal 17 in the above embodiment.

FIGS. 2A and 2B show two input signals (corrected digital image signal 9 and memory image signal 8).
Are the edge images (hatched portions) corresponding to each edge signal obtained in the edge detection circuit 12 from A to B, A and B correspond to the respective pattern edges, and C is due to a defect in the printed wiring. FIG. 2C shows an edge image corresponding to the edge signal 13 output from the edge detection circuit 12, and is obtained by superposition (logical addition) of FIGS. 2A and 2B. FIG. 2D shows an edge label image subjected to labeling processing by the edge labeling circuit 14, and a number of numbers in the image indicate label numbers. The mask generation circuit 16 extracts only a signal having a large labeling area (for example, the label number “1” in FIG. 2D) from the edge label signal 15 corresponding to FIG. Is generated.

[0017]

As described above, the micro-defect detecting apparatus of the present invention detects a micro-defect only without being affected by variations in the pattern edge because the mask signal is generated and the signal at the pattern edge is removed. Therefore, there is an effect that a highly reliable comparative test can be efficiently performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is an image diagram illustrating a method for generating a mask signal in the present embodiment.

[Explanation of symbols]

 Reference Signs List 1 XY table 2 Photoelectric conversion scanner 3 Image signal 4 A / D conversion circuit 5 Digital image signal 6 Positioning circuit 7 Image memory circuit 8 Memory image signal 9 Corrected digital image signal 10 Difference image calculation circuit 11 Difference image signal 12 Edge detection circuit DESCRIPTION OF SYMBOLS 13 Edge signal 14 Edge labeling circuit 15 Edge label signal 16 Mask generation circuit 17 Mask signal 18 Micro defect detection circuit 19 Micro defect signal

Claims (1)

(57) [Claims] 1. A photoelectric conversion scanner for scanning an object placed on an XY table, an A / D conversion circuit for converting an image signal from the photoelectric conversion scanner into a multi-level digital image signal, An image memory circuit for storing the digital image signal from the / D conversion circuit; and moving the XY table by the number of repetitive patterns on the object, and then scanning the photoelectric conversion scanner to output from the A / D conversion circuit. A positioning circuit that performs fine position correction on the digital image signal by referring to the memory image signal read from the image memory circuit, and calculates a difference between the corrected digital image signal output from the positioning circuit and the memory image signal. A difference image calculating means for calculating and calculating a difference image; and detecting an edge of each of the corrected digital image signal and the memory image signal. Process by sequentially scanning outgoing operators
The point where the absolute value of the processing result is above a certain value is converted into a binary signal.
An edge detection circuit for obtaining an edge position from a logical sum of the two, an edge labeling circuit for performing a labeling process for numbering the edge signal output from the edge detection circuit for each continuous area, and an edge labeling circuit A mask generation circuit for extracting a label having an area size equal to or greater than a certain value in the output label; a micro defect detection circuit for extracting only a micro defect from the difference image signal with a mask signal output from the mask generation circuit; A microdefect detection device comprising: