JPH03231749A - Method for correcting pattern with converged ion beam device - Google Patents

Abstract

PURPOSE:To accurately correct even such defects as to remarkably deform a pattern by regulating the pattern width of a normal pattern for reference so that the pattern is made to coincide with the defective pattern. CONSTITUTION:A defective pattern is detected while observing secondary ion images. A secondary ion image contg. the defective pattern is inputted into a computer and subjected to image processing for removing a noise component and the outline of the pattern is extracted. The defective pattern 17 is compared with a reference pattern 16 as a normal pattern having the same shape as the defective pattern. A vacancy in the defective pattern is recognized as a white defect 18 and a part of the defective pattern protruding from the reference pattern as a black defect 19. Since the pattern width of the reference pattern is made equal to that of the defective pattern, the defects are exactly recognized and the accuracy of the correction can be enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to photomasks and reticles (
The present invention relates to an apparatus that uses a focused ion beam to repair a pattern defective part (hereinafter referred to as a white defect part) or a pattern surplus part (hereinafter referred to as a black defect part) of a mask (hereinafter simply referred to as a mask).

[Summary of the invention]

2. Description of the Related Art In recent years, as semiconductor devices (LSI) have become highly integrated, mask patterns necessary for their manufacture have become finer and more complex. As a result, the pattern is largely broken during mask manufacturing, and white defects occur.

Defects with mixed black defects may be created. In order to correct such defects into a normal pattern, the defective part is recognized by referring to the normal pattern.Generally, the line width on the mask differs depending on the position I on the mask, but this is not possible at present. is considered a normal pattern. In such a case, by matching the line width of the reference pattern to the pattern containing the defect, the defect can be properly recognized and the accuracy of correction can be improved.

[Conventional technology]

Find a normal pattern that is the same as the defective pattern, extract the outline of that pattern from the secondary ion image of the normal pattern, use it as a reference pattern, and compare the reference pattern and the defective pattern by performing image processing using a computer. By this, the defective part of the defective pattern is recognized and the defect is corrected.

[Problem to be solved by the invention]

However, even if the pattern is the same, the size of the pattern will differ during transfer depending on its position on the mask. Therefore, there are problems in that the pattern containing the defect and the normal pattern to be referenced do not completely match, leading to incorrect recognition of defective parts and poor correction accuracy.

[Failure to solve the problem]

The present invention has obtained the following means to solve the above problems.

That is, the pattern width is adjusted so that the reference normal pattern matches the defective pattern.

[Operation] The operation of the present invention will be explained based on FIG. 2. Figure 2 (A
) is a diagram comparing a pattern including a defect with a reference pattern. Here, since the reference pattern is larger, if the difference between the two patterns is directly calculated, unrelated portions such as the shaded area in FIG. 2(B) will be recognized as defects. Therefore, by matching the reference pattern to the pattern width of the pattern including the defect, the defect can be correctly recognized as shown in FIG. 2(C).

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 shows an overall configuration diagram of a focused ion beam device based on the present invention. Reference numeral 1 denotes an ion source which emits an ion beam 2. Reference numeral 3 denotes a scanning electrode which consists of X and Yt poles and scans the ion beam spot over a predetermined range within the xy plane.

Reference numeral 4 denotes an objective lens which forms an image of the spot of the ion beam 2 on the surface of the mask 8 which is the object to be irradiated.

Reference numeral 5 denotes a gas gun which sprays organic compound vapor 6 onto the white defect site of the mask 8, and simultaneously irradiates it with an ion beam while scanning, and applies a light-shielding film to correct the white defect. In addition, when repairing a black defective portion, the unnecessary adhering portion is irradiated with the ion beam 2 in a limited manner and removed by sputtering. 9 is an XY stage on which the mask 8 is placed and moves in the X or Y direction. A detector 10 detects the intensity of the secondary ions 7 ejected from the surface of the mask 8 by the ion beam 2. This planar distribution of secondary ion intensity corresponds to the pattern of the mask 8. 11 is an A/D converter which converts an analog quantity called secondary ion intensity into digital data.

This digital data is taken into the computer 13, the mask pattern image is enlarged and reproduced, and displayed on the CRT 14. 12 is a scanning circuit and a computer 13
It receives the ion beam irradiation range and controls the scanning electrode 3. A CAD 15 is connected to the computer 13 by a communication line, and sends mask design data to the computer 13 when requested by the computer 13.

Next, an actual pattern correction method will be explained based on FIG. 2. First, the defect pattern is found while observing the secondary ion image. Next, the secondary ion image including the defective pattern imported into the computer 13 is subjected to image processing such as removal of noise components, and the outline of the pattern is extracted. The defective pattern is then compared with the reference pattern, which is the same normal pattern (Figure 2 (A)). Then, the difference between the two patterns is calculated, and the part where the defective pattern is missing more than the reference pattern is recognized as a white defective part, and the part where the defective pattern protrudes more than the reference pattern is recognized as a black defective part.

Here, the reference pattern includes a figure whose outline of the pattern is extracted from a secondary ion image of a normal pattern that is the same as a pattern containing a defect, or a figure that receives mask design data from CAD and uses that design data. Use shapes that create normal patterns.

Note that even for the same pattern, the size of the pattern differs during transfer depending on the position on the mask. Therefore, to improve accuracy, automatic magnification and width adjustment are performed by computer. Here, the method of magnification adjustment and width adjustment will be explained based on FIG. 3. Figure 3 shows the case of a pattern in which both the length on the pattern and the length of the base sandwiched between the pattern parts and the pattern part are required, and Figure 3 (A) shows the secondary pattern of the pattern including defects. ion statue,
FIG. 3(B) is the reference pattern. First, for a portion of the defect pattern in the X direction that does not include a defect, the length a on the pattern and the length b of the base sandwiched between the pattern portions are determined.

Next, the length ab' of the same portion in the reference pattern is determined. Next, adjust the magnification. The ratio (magnification) of the size of the defective pattern and the reference pattern is the size of the defective pattern.
a+b The size of the reference pattern becomes a'+b'.

From this, the length of the reference pattern is multiplied by (a+b)/(a'4-b') to match the size of the defective pattern. When this operation is possible in both the X and Y directions, the magnification is adjusted in each direction, and when it is only in one direction, the other direction is adjusted accordingly. However, if this magnification is above a certain value, it is treated as a defective part and no magnification adjustment is performed. Next, the lengths corresponding to the above portions a' and b' are determined for the reference pattern after zero magnification adjustment. If these lengths are a″ and b#, respectively, the difference in pattern width is a
It can be expressed as a'', b'-b, ((a-a'')+(b'-b))/2, etc.

The pattern width of the reference pattern is expanded according to the formula expressed above to match the pattern width of the defective pattern. When this operation is possible in both the X and Y directions, the width is adjusted in each direction, and when it is only in one direction, the width is adjusted in the other direction. However, if there is a difference in pattern width over a certain value, it is treated as a defective part and width alignment is not performed.

〔Effect of the invention〕

According to the present invention, even defects such as large pattern breaks can be corrected with high precision.

[Brief explanation of drawings]

Figure 1 is an overall configuration diagram of a focused ion beam device according to the present invention, and Figures 2 and 3 are diagrams of its operating principle.Ion source, ion beam, scanning electrode, objective lens, gas gun, organic compound vapor secondary Ion, mask, xy stage, detector, A/D converter, scanning circuit, computer, CRT, CAD, reference pattern, pattern including defects 18, white defect area 19, black defect area and above

Claims (1)

[Claims] an ion source that generates an ion beam; a scanning electrode that scans the ion beam; a gas gun that sprays organic compound vapor; a detector that detects secondary ions emitted from the mask pattern; In a focused ion beam device consisting of a computer that performs image processing based on secondary ion intensity and sets the ion beam irradiation position based on the data, in order to correct a defective pattern on the mask, a normal image corresponding to the defective pattern is detected. A pattern repair method comprising using a reference pattern, matching the reference pattern to the line width of a defective pattern, comparing both patterns to recognize a defective portion, and correcting the defect.