JPH0361122B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for performing an inspection by scanning an object to be inspected with a photoelectric conversion scanner and comparing the pattern width of a read pattern with a design reference value. A pattern width inspection method characterized in that a circular mask scan is performed based on a design reference value centered around the detected pattern edge to find intersections with the pattern, and defects are determined based on the number of intersections. Regarding equipment.

Conventionally, this type of equipment, for example, a photomask inspection equipment for printed circuit boards, or an IC
(Integrated Circuit) photomask inspection equipment, etc., detects the running direction of the pattern in order to inspect the pattern width, then determines the pattern edges and compares them to the design standard value based on the distance relationship between the pattern edges. An inspection method was used to make a comparative judgment. In this case, since it is difficult to inspect the pattern width of patterns with orientations other than horizontal and vertical, only patterns with angles of limited directions, such as 0°, 45°, 90°, and 135°, are tested. A method has been used in which the pattern edges are cut out, the distance between the pattern edges is examined separately for each angle, and the distance between the pattern edges is compared with the design reference value.
For this reason, it is difficult to inspect the vicinity where the direction of the pattern changes, and it has been impossible to inspect patterns in directions other than the limited directions.

In order to eliminate the above-mentioned defects, the present invention performs circular mask scanning centered on the point of the pattern edge, and performs defect determination based only on the number of intersections with the pattern, thereby reducing the pattern width regardless of the direction of the pattern. Inspection is possible.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing an edge detection mask for determining a pattern edge from a pattern scanned and read out by a photoelectric conversion scanner. The pattern edge detection mask 1 is scanned by the following method, and the theoretical formula ・(b+c+d+e+f+g+h+i)=1
...If the equation (1) (where the point on the pattern = "0") is satisfied, a pattern edge is detected.

FIG. 2 shows a principle diagram of pattern width inspection using the circular mask scanning proposed by the present invention. In the figure, numeral 3 indicates a binarized image of the pattern of the object to be scanned, read out by scanning with a photoelectric conversion scanner. For this binarized image,
The pattern edge detection mask 1 is scanned to detect pattern edges, and a circular mask 3 determined from design reference values is scanned around the position where the pattern edge was detected. 4 indicates the intersection with the pattern resulting from the circular mask scanning. In this way, for a pattern having a pattern width that satisfies the design standard value, the number of intersections obtained by performing circular mask scanning is always "2".

FIG. 3 is a diagram for explaining how defects are determined using a circular mask when the pattern width is less than the design standard value. When the circular mask 2 is scanned using the same method as described above, the pattern A new intersection point 5 with the pattern occurs at a location where the pattern does not satisfy the design standard value, and the number of intersection points becomes four. In this way, the circular mask is scanned to find the number of intersections with the pattern, and if the number is other than "2", it can be determined that there is a defect.

FIG. 4 is a diagram for explaining the method of performing the circular mask scanning and finding the intersection points with the pattern. This is a cutout image obtained by cutting out using a known method, and 3 indicates a pattern of the object to be inspected. When the pattern edge detection mask 1 satisfies equation (1), it is determined that a pattern edge has been detected, and the circular mask 2 is scanned to find the number of intersections with the pattern. Generally, the method of finding the number of intersections with this pattern circular mask is to sequentially scan the data of X ₁ , X ₂ , ...X ₃₂ and change the value from "1" to "0". A method is used in which the sum of the number of items and the number of items that change from "0" to "1" is counted.

FIG. 5 is a diagram for explaining a circuit that scans the circular mask and calculates the number of intersections with a pattern, as set forth in claim 3 of the present invention. X ₁ X ₂ ,…
..., X ₃₂ is used as input data, and when the Exclusive OR circuit 7 is used to calculate the Exclusive OR of two adjacent points, the output signal 8 has a value of "1" only at the intersection of the pattern and the circular mask, Otherwise, data that is "0" is output, and by adding this output signal using the adding circuit 9, the number of intersections between the circular mask and the pattern, 10, can be obtained, and as in the conventional case, There is no need to sequentially scan the data of X ₁ , X ₂ , . . . X ₃₂ , and speeding up is possible.

FIG. 6 shows a block diagram of a pattern width inspection apparatus constructed using the pattern width inspection method described above. In the figure, the pattern of the object to be inspected read out by scanning with the photoelectric conversion scanner 11 is converted into a binary image 13 by the binarization circuit 12, and as described above, by a generally known method, The image is cut out by the image cutout circuit 14.
A pattern edge detection circuit 15 that scans the pattern edge detection mask performs pattern edge detection on this cut-out image, and if a pattern edge is detected, a control signal 16 is output. This control signal controls the circular mask scanning circuit 17 so that circular mask scanning is performed only when pattern edges are detected. The mask dimensions for performing circular mask scanning are determined from the design standard values, and are preliminarily set as the mask selection signal 21.
The circular mask is set in the circular mask scanning circuit 17 and a circular mask determined based on design standards is selected. This circular mask scanning is performed, and the intersection point with the pattern is determined by the counter circuit 18 in the manner described above.
The defect determination circuit 19 determines whether the number of intersections with the pattern is "2" and, if it is "2" or less, sends a defect determination signal 20 indicating that the pattern width is less than the design reference value. Output.

That is, for example, when inspecting the pattern width of a photomask on a printed circuit board by comparing it with the design standard value, the pattern edge is detected, and then a circular mask scan is performed centered on the pattern edge to determine the number of intersections with the pattern. Defects can be determined by determining the direction of the pattern, unlike in the past, there is no need to detect the running direction of the pattern, and the only directions that can be inspected are patterns such as 0°, 45°, 90°, 135°, etc. There are no limitations, and pattern inspection facing any direction is possible.

Furthermore, if the circuit configuration shown in FIG. 5 is used to find the intersection between the circular mask and the pattern, when the circular mask scan is performed on the image cut out by a generally known method, The number of intersections with the pattern can be immediately determined, increasing speed.

[Brief explanation of drawings]

FIG. 1 shows a pattern edge detection mask,
Figure 2 is a diagram of the principle of pattern width inspection using a circular mask, and Figure 3 is an explanatory diagram of how a circular mask is used to determine defects when the pattern width to be inspected is less than the design standard value. Figure 4 is an explanatory diagram of a method of performing circular mask scanning to find the points of intersection with the pattern, and Figure 5 shows a circuit that performs circular mask scanning to find the number of intersections with the pattern. , FIG. 6 is a block diagram of a pattern width inspection device. In the figure, 1 is a pattern edge detection mask;
2 is a circular mask, 3 is a pattern of the object to be inspected, 4 is an intersection between the circular mask and the pattern, 5
is the intersection with the circular mask at the point where the pattern width does not satisfy the design standard value, 6 is the cutout image of the object to be inspected, 7 is the exclusive OR circuit, 8 is the output signal, 9 is the addition circuit, 10 is the number of intersections between the circular mask and the pattern, 11 is the photoelectric exchange scanner,
12 is a binarization circuit, 13 is a binarized image, 14 is
15 is a pattern edge detection circuit; 16 is a control signal; 17 is a circular mask scanning circuit; 18 is a counter circuit; 19 is a defect determination circuit;
Reference numeral 20 indicates a defect/judgment signal, and 21 indicates a mask selection signal.

Claims (1)

[Claims] 1. In a pattern width inspection method in which a pattern of an object to be inspected is scanned with a photoelectric conversion scanner and the pattern condition is inspected, it is determined whether the pattern width of the formed pattern satisfies a design standard value. In order to make a determination, pattern edges are detected from the pattern scanned and read out by the photoelectric conversion scanner, and a circular mask scan is performed based on the design standard value centered around the detected pattern edge, and the points of intersection with the pattern are determined. A pattern width inspection method characterized by determining defects by determining the number of defects. 2 Scanning the object to be inspected with a photoelectric conversion scanner and converting the read pattern into a binary image 2
a digitization circuit; a pattern edge detection circuit for determining a pattern edge from the binarized pattern;
a circular mask scanning circuit that performs circular mask scanning based on a design reference value with the detected edge position as the center; a counting circuit that performs the circular mask scanning to determine the number of intersections with a pattern; and the counting circuit. 1. A pattern inspection device comprising: a defect determination circuit that performs defect determination based on the number of intersections with a pattern determined by . 3. When scanning the circular mask and calculating the number of intersections with the pattern, a circuit is used to calculate the number of intersections with the pattern by calculating Exclusive OR of two adjacent points on the circular mask. A pattern width inspection device according to claim 2, characterized in that: