JPS6235618A - Defect detector - Google Patents

Abstract

PURPOSE:To detect the relative positions of a mask pattern and a foreign matter by a method wherein a dark vision illuminator and a transmitting illuminator are provided respectively on the main surface side and the backside of a product while an optical examination system which can simultaneously examine a transmitted image and dark vision is provided on the main surface side of product. CONSTITUTION:A dark vision illuminator 4 composed of a light source 2 and a lens 3 is arranged on the main surface side of mask 1 while a transmitting illuminator 7 composed of another light source 5 and another lens 6 is also arranged on the backside of mask 1. Besides, an optical examination system 10 composed of the other lens 8 and a television camera 9 is provided on the main surface side of mask 1. An image is formed of an image of pattern 13 illuminated as a black pattern by a transmitted image 12, a foreign matter 14 by a dark vision image 11 and a bright image of another foreign matter 15. In such a constitution, the dark vision image 11 and the transmitted image 12 can be visualized simultaneously in the same vision so that the relative positions of mask pattern and foreign matters may be detected accurately without fail.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a technique that is effective when applied to the inspection of defects such as foreign objects and scratches in transparent bodies having opaque patterns. It concerns techniques that are effective for use in inspections.

[Background technology]

In the photolithography process in semiconductor manufacturing, a pattern formed with chrome or the like on a transparent glass substrate is used as an original plate and is called a mask or reticle. ), this pattern is used as a semiconductor thin plate (wafer) made of silicon, etc.
The necessary circuit pattern is formed by transferring the pattern on top. If foreign matter is present on the mask during this pattern transfer, the foreign matter pattern will also be transferred, resulting in pattern defects. This is particularly problematic for reticles used in reduction aligners because all patterned chips are defective.

Therefore, it is necessary to confirm that there are no foreign substances before exposure. As a technique for observing foreign matter with good visibility, a method of detecting foreign matter by irradiating a laser is known, for example, as described in Japanese Patent Publication No. 5!1152626.

On the other hand, as a result of analyzing and considering the relationship between foreign matter in the mask and the circuit pattern formed by exposure, it is found that if the foreign matter is present in the circuit pattern part of the mask, the circuit pattern part is an area that is shielded from light, so the foreign matter is Even if such particles are present, they do not cause any abnormality in the circuit pattern formed on the wafer. Therefore, a mask in which foreign particles are distributed on the circuit pattern in each square is considered to be defective, and a cleaning process to remove the foreign particles is performed. The inventors have found that the plain text can be used as is without having to be re-sent, and that this plain text improves productivity.

[Purpose of the invention]

An object of the present invention is to provide a defect inspection device that can detect the position of a defect in a transparent body having an opaque pattern by clarifying the relationship with the position of the opaque pattern.

Another object of the present invention is to provide a defect inspection device that can reduce the number of man-hours in manufacturing semiconductor devices.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, the defect inspection device of the present invention detects a dark field image by dark field illumination and simultaneously detects a transmitted image by transmitted illumination when inspecting foreign substances on a mask, so that it is possible to detect a dark field image by dark field illumination and a transmitted image by transmitted illumination. Since shiny foreign objects can be detected accurately and reliably, the presence or absence of foreign objects and the relationship between the mask pattern and the foreign object position can be detected with high precision, making it easy to determine whether or not the mask can be used as an exposure mask even if foreign objects are present. can be done. Therefore, if the mask has a distribution of foreign matter that does not pose a problem even if there is foreign matter on the mask, 1. Since the mask can be used for exposure without any processing, the number of man-hours is reduced compared to the method used by Barai, which cleans all masks that are determined to be defective due to foreign substances, and it is possible to reduce the manufacturing cost of semiconductor devices. .

〔Example〕

FIG. 1 is a schematic diagram showing the principle of a defect inspection apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a circuit pattern and a foreign matter pattern within the same field of view.

In the defect inspection apparatus of this embodiment, as shown in FIG. A field illumination 4 is provided, and a mask 1 is provided.
A transmitted illumination 7 consisting of a light source 5 and a lens 6 is provided on the back side of the .

Further, this defect inspection apparatus is provided with an optical observation system 10 consisting of a lens 8 and a television camera 9 on the main surface side of the mask 1, and a dark field image 11 by the dark field illumination 4 and the transmitted image. The transmitted image 12 by the illumination 7 can be detected at the same time.

The mask 1 has a circuit pattern 13 made of, for example, a chromium film formed on its main surface.

In this embodiment, for example, a pattern 13 consisting of the letter A of the alphabet is provided. The region of this pattern 13 is an opaque region through which no light passes. In the figure, opaque areas are cross-hatched. In addition, in this embodiment, as shown in FIG. )15 will be explained.

In such a defect inspection apparatus, the field of view (image) by the television camera 9 is displayed as an image as shown in FIG. That is, the foreign matter 14, 15 on the mask 1 is projected by the dark-field illumination 4 as a point-shaped dark-field image 11 that shines due to diffuse reflection on its surface. However, as shown in FIG. 3, in the observation system using the dark field illumination 4, the pattern 13 is formed of an extremely thin layer, so the pattern 13 is As shown by the two-dot chain line,
It is not actually shown.

Therefore, although it is possible to confirm the foreign object using the observation system using the dark field illumination 4, it is not possible to confirm the positional relationship between the foreign object and the pattern 13.
(visual recognition) is not possible. On the other hand, in this embodiment, in addition to the observation system using the dark field illumination 4, as shown in FIG. In the observation system using the transmitted illumination 7, as shown in FIG. 6, both the pattern 13 and the transmitted image 12 of the foreign object 15 located outside the pattern 13 can be seen as black. However, the transmitted image of a minute foreign object cannot be observed due to the wraparound of light or the like. In addition,
As a matter of course, the foreign object 1 located on the pattern 13
4 cannot be confirmed because the pattern 13 is opaque.

However, this observation system using the transmitted illumination 7 is limited to the pattern 13.
The transmitted image 12 can be clearly seen as a black area through which no light passes. In addition, the observation system using the transmitted illumination 7 and the observation system using the dark field illumination 4 have respective images (dark field image 11
．． This does not interfere with the transmitted image 12). Therefore, as shown in FIG. 2, the images in the defect inspection apparatus according to the present invention include an image of a pattern 13 shown as a black pattern in a transmitted image 12, and a foreign object (foreign object on the pattern) 14 in a dark field image. The dark-field image 11 of the foreign substance (non-pattern foreign substance) 15 on the transmitted image 12, which is a black image, can be clearly observed because it is formed by the shining image of the foreign substance (non-pattern foreign substance) 15. The foreign matter (pattern foreign matter) 14 located on the transparent area also forms a shining dark-field image 11, so that it can be reliably visually recognized.

Such a defect inspection device can detect the positional correlation between a foreign object and a circuit pattern with high precision.

As a result, mask 1 whose foreign material distribution is unsuitable for mask 1
Alternatively, the mask 1 in which the distribution of foreign matter does not impair the function of the mask 1 can be determined with high precision. Foreign matter that does not impair the function of the mask 1 (foreign matter on the pattern) 14
A certain mask 1 is directly subjected to the next process, and a mask 1 whose foreign material distribution is unsuitable as a mask 1 is sent to the cleaning process again to be cleaned.

The selection, use, and cleaning of masks that fully perform the mask function and masks that do not perform the mask function saves man-hours in semiconductor device manufacturing by omitting the cleaning of masks that do not need to be cleaned even if there are foreign substances. Improved productivity by reducing costs.

Cost reduction can be achieved.

〔effect〕

(1) Since the defect inspection apparatus of the present invention can simultaneously visually recognize a dark field image and a transmitted image within the same field of view, it is possible to accurately and reliably detect the positional correlation between the mask pattern and the foreign matter.

(2) According to (1) above, the defect inspection device of the present invention not only confirms the presence or absence of foreign matter, but also foreign matter located at a position where the foreign matter impairs the mask function (foreign matter located on the pattern).
The effect is that it is possible to detect with high precision whether or not it is.

(3) According to the above (2), according to the defect inspection apparatus of the present invention, re-cleaning is performed only on masks whose foreign matter impairs the mask function, and masks with foreign matter that do not impair the mask function are subjected to the next exposure. Since it can be used in a process, it is possible to reduce the number of man-hours for manufacturing a semiconductor device, thereby achieving an effect of improving productivity.

(4) According to (1) to (3) above, according to the present invention, the positional correlation between a pattern and a foreign object can be detected with high precision, and the use of a mask is determined based on this detection result. By doing so, a synergistic effect can be obtained in that manufacturing costs can be reduced by reducing the number of man-hours for manufacturing semiconductor devices.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. For example, the present invention can also be applied to the detection of defects other than foreign matter such as scratches, and the same effects as those of the previous embodiment can be obtained. Further, by utilizing the characteristic that the defect inspection apparatus of the present invention has a dark field image as a shining image and a transmitted image as a dark image, it is possible to detect whether a defect is on the front surface or the back surface of the object to be detected. Further, in the defect inspection apparatus of the present invention, if the detection of the foreign object position is automated, the number of steps for manufacturing a semiconductor device can be further reduced.

[Application field]

In the above explanation, the invention made by the present inventor was mainly applied to the technology for detecting the positional correlation between a mask pattern and a foreign object, which is the background field of application, but the invention is not limited to this, and for example, The present invention can also be applied to detecting the presence or absence of defects such as foreign matter adhesion or scratches on displays, such as liquid crystal panels, and detecting their positions.

At least, the present invention can be applied to a technique for detecting defects such as foreign matter on the front and back surfaces of a transparent body having an opaque portion.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the principle of a defect inspection device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing a circuit pattern and a foreign object pattern within the same field of view, and Fig. 3 is a diagram using dark field illumination. FIG. 4 is a schematic diagram showing the optical system, FIG. 4 is a schematic diagram also showing a dark field image, FIG. 5 is a schematic diagram showing the optical system using transmitted illumination, and FIG. 6 is a schematic diagram similarly showing a transmitted image. ■...Mask, 2...Light source, 3...Lens, 4...
・Dark field illumination (5... light source, 6... lens, 7...
... Transmitted illumination, 8... Lens, 9... Television camera, 10... Optical observation system, 11... Dark field image, 12
...Transmission image, 13...Pattern, 14...Foreign object (
Foreign matter on the pattern), 15...Foreign matter (foreign matter outside the pattern)
.

Claims (1)

[Claims] 1. An apparatus for detecting defects in a transparent article having a partially opaque area, which includes dark field illumination provided on the main surface side of the article, and transmitted illumination provided on the back side of the article. and an optical observation system capable of simultaneously observing the transmitted image and the dark field image of the article.