JPS6367848B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern inspection device configured to self-diagnose a comparison/defect determination circuit as one component, and particularly relates to a mask inspection device equipped with a self-diagnosis function. be.

FIG. 1 shows a mask inspection apparatus according to the prior art.
In reality, it was extremely difficult to investigate the cause of poor performance or performance deterioration because there was no other suitable method of checking the performance of the device itself, such as using the pattern of .

That is, in the past, corresponding chip patterns on the mask 1 to be inspected were detected by the objective optical system 2,
2', pattern inspection device (integrated with binarization circuit)
3 and 3' are used to obtain two systems of time-series binary pattern data, and this time-series binary pattern data is processed by a comparison circuit 4 and a defect determination circuit 5 using a computer 6 to determine the presence or absence of defects in the mask pattern. That was what was being judged. Generally, on the mask 1 to be inspected, mask patterns such as IC chips are repeatedly arranged vertically and horizontally with the same pattern shape, but defects in the mask patterns occur not only during transfer but also during transportation. Figure 2 shows some examples of normal mask patterns and defective mask patterns. Generally speaking, since the probability that a defect with the same shape will occur in the same part of another mask pattern is almost zero, By comparing different mask patterns, defects can be detected from the differences.

By the way, conventional mask pattern defect detection is not just a matter of comparing corresponding bit data of binary pattern data using an exclusive OR gate, but a comparison of the mask patterns to be inspected. This is done while allowing a certain degree of positioning error or overlay error. A defect detection method that allows relative positioning errors or overlay errors is already known, and is disclosed, for example, in Japanese Patent Laid-Open No. 131469/1983. FIG. 3 shows the principle of such defect detection. Patterns 7 and 7' to be compared are aligned with a large overlay error, but if there is a pattern 8 that deviates from the tolerance range for a large overlay error, it is detected as defective. It is something that

The comparison/defect judgment circuit in mask inspection equipment that employs this defect detection method is not simple but has an extremely complex circuit configuration. It consists of a mechanical system and an optical system, and it is generally difficult to investigate the cause of defective or deteriorating inspection performance. Conventionally, the only way to confirm the performance of the device itself is to actually use the mask pattern on the mask to be inspected, and to check whether the cause of the poor or deteriorating performance lies in the electronic circuit system for comparison and defect determination. It was not easy to determine whether the problem existed in the optical system or the mechanical system, and as a result, the debugging and maintainability of the device was poor.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a pattern inspection device equipped with a self-diagnosis function that can at least ascertain whether or not the cause of defective or deteriorating inspection performance lies in the comparison/defect determination circuit system.

For this purpose, the present invention is constructed so that the function of the comparison/defect determination circuit is checked based on diagnostic pattern data appropriately created by a computer.

The present invention will be explained below with reference to FIGS. 4 and 5.

FIG. 4 shows the configuration of an example of a mask inspection apparatus according to the present invention, together with a mask to be inspected 1 and an illumination system 15. As shown in the figure, the points that are substantially different from those shown in FIG.
10', the binarized pattern data can be directly supplied to the comparison/defect determination circuit 9 for diagnosis via the changeover switches 12, 12'.
Normally, the changeover switches 11, 11', 12, 12' are provided as shown in the figure. Binarized pattern data obtained from the mask 1 is compared by a comparison/defect determination circuit 9 to perform defect determination processing. However, during debugging or maintenance of the device, the changeover switches 11, 11', 12, and 12' are switched as indicated by dotted lines, and the diagnostic binarized pattern data from the computer 6 is compared to perform defect determination processing. It is something that has become popular. The diagnostic binary pattern data does not necessarily need to be provided from the computer 6, but if the computer 6 already exists, it is more convenient to use it. The diagnostic binary pattern data given by the computer 6 may also be created off-line and stored in a storage device, but as will be described later, data obtained when diagnosing the optical system or mechanical system may be used. It is also possible to use In either case, the pattern memory 10,
Diagnostic binary pattern data is serially transferred to the comparison/defect determination circuit 9 via 10'.

Although the present invention is as described above, the example shown in FIG. 4 is configured so that mechanical systems and optical systems can also be diagnosed. That is, instead of the mask 1 to be inspected, a standard mask with a pattern suitable for diagnosis is prepared, and this is used to detect the pattern detectors 13, 13', which are imagers such as CCDs and TV cameras.
After converting the optical image into an electrical signal, the binarization circuit 1
4, 14', and the computer 6 via the pattern memories 10, 10'. The computer 6 compares the two series of binarized pattern data,
By checking whether the detected original image has the desired pattern, it is possible to diagnose up to the binarization circuits 14 and 14'. In addition,
The changeover switches 11, 11', 12, and 12' are interlocked and may be operated manually, but they may also be controlled by the computer 6. Also,
The pattern memories 10 and 10' are generally composed mainly of high-speed shift registers and high-frequency clock oscillators, and normally function as serial-in/parallel-out type, but when diagnosing the comparison/defect judgment circuit 9, they function as parallel-in/parallel-out type. It functions as a serial output type. However, it is also possible to accommodate the pattern memories 10, 10' on the computer 6 side.

Finally, the binarized pattern data for diagnosing the comparison/defect determination circuit will be explained with reference to FIG.

FIGS. 5A, a-L, and 1 show 12 types of diagnostic binary pattern data, and logical "1" areas are shown as hatched areas. Of these, the one shown in FIG. 5A and the one shown in FIG. 5A are provided as a pair to the comparison/defect determination circuit 9. Fifth
The data shown in Figures B and b and onwards are similarly paired and serially transferred to the comparison/defect determination circuit 9, but the binary pattern data for diagnosis is not limited to these examples of pattern data, but is merely an assumed pattern. This shall be determined as appropriate. Furthermore, although the binarized pattern data in this example is shown as a 16×16 pixel matrix, it is of course not limited to this and can be appropriately determined as necessary. Each pair of binarized pattern data is sequentially applied to the comparison/defect determination circuit 9 from the left side to the right side and from the top side to the bottom side, and even if a predetermined alignment error is allowed, differences exceeding the If there is a defect, the comparison/defect determination circuit 9 can be diagnosed by determining that there is a defect. In the above explanation, an example was explained in which binary pattern data was used as the data to be compared and judged, but if the technical idea of the present invention is used, it is generally possible to make a similar diagnosis using multi-value pattern data. should be obvious.

As explained above, the present invention supplies diagnostic multilevel pattern data directly to the comparison/defect determination circuit, thereby determining whether or not the cause of defective or deteriorating inspection performance exists in the comparison/defect determination circuit system. This has the advantage that debugging can be easily performed at the final manufacturing stage, and maintenance can be easily performed at the actual use stage.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of an example of a conventional mask inspection device together with an object to be inspected;
The figure shows an example of a normal mask pattern and a defective mask pattern.
FIG. 4 is a diagram showing the configuration of an example of a mask inspection device according to the present invention together with an object to be inspected; FIG.
a, B, b, C, c, D, d, E, e, F, f,
G, g, H, h, I, i, J, j, K, k, L,
1 is a diagram showing an example of a pair of diagnostic binarized pattern data. 2, 2'...Objective optical system, 6...Computer, 9
... Comparison/defect determination circuit, 11, 11', 12, 1
2'...Selector switch, 13,13'...Pattern detector, 14,14'...Binarization circuit.

Claims (1)

[Claims] 1 Time-series multi-value pattern data corresponding to the two systems of inspected patterns, obtained from the object to be inspected via the objective optical system, pattern detector, and multi-value code circuit, are checked within a certain range by the comparison/defect determination circuit. A pattern inspection device is a pattern inspection device which compares patterns with the assistance of a computer while allowing alignment errors, and determines that one of the patterns to be inspected has a defect if there is a difference of more than a certain level. During normal pattern inspection, time-series multivalued pattern data corresponding to two systems of inspected patterns are transmitted, and during debugging or maintenance of the equipment itself, two-system time-series diagnosis is performed via pattern memory from a computer. The method is characterized by a configuration in which the multivalued pattern data for use is selected by a changeover switch means and then applied to a comparison/defect determination circuit.
A pattern inspection device equipped with a self-diagnosis function.