JP3537894B2 - Shape observation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates samples, the shape observation equipment, particularly for observing the surface shape and internal shape of the sample such as a semiconductor wafer.

[0002]

2. Description of the Related Art Conventionally, for observing an object having an extremely fine structure represented by a semiconductor device, an electron microscope is used when high resolution is required, and an optical microscope is used when observing a relatively wide field of view. Each has been used. In recent years, the management of defects and foreign substances generated on wafers in the manufacturing process of semiconductor devices typified by memory elements has become strict, and the size of defects of interest has been reduced due to the progress of finer patterns with the increase in integration. It has become. For this reason, the rate of observing the defect shape using an electron microscope has been increasing.

[0003]

However, the use of an electron microscope for the purpose of such defect analysis has the following problems. Commonly used acceleration voltage 1
With a scanning secondary electron microscope of about kV, only information on the surface shape of the sample was obtained, and it was not possible to see the internal structure or the shape of defects or foreign substances present below the surface. On the other hand, the optical microscope may be capable of observing the shape of an object or structure below the surface although the resolution is lower than that of the electron microscope. This is the case, for example, for a defect or a foreign substance present below an optically transparent film (such as a silicon oxide film used in a semiconductor manufacturing process). As described above, each device has been used differently depending on the characteristics of each device.However, in order to obtain an image with high resolution and an image with internal information, a monitor device or a photographic device that projects the image obtained from each device is used. An apparatus was required, and an operation of comparing two images was required.

[0004] The present invention has been made to solve the problems according to the conventional example described above, the shape observation equipment which can obtain an image of the defect shape including a defect surface and information of the interior of both the sample The purpose is to get.

[0005]

SUMMARY OF THE INVENTION A shape observation apparatus according to the present invention comprises an electron microscope and an optical microscope for observing defects on a sample, and a magnification adjustment so that the magnifications of images obtained by the electron microscope and the optical microscope become equal. an image superimposition device for superimposing on the same display screen to position adjustment such that the position relation of both the images match as well as, the electron microscope
Storage for storing images by microscope and optical microscope
Means and the electron microscope stored in the storage means or
An image processing device for processing images by an optical microscope
In addition, the image superposition apparatus stores the data stored in the storage unit.
Image of either electron microscope or light microscope
And an electron microscope processed by the image processing apparatus or
Image superimposition processing with the other image by the optical microscope
And the image processing apparatus is controlled by the optical microscope.
Of the defect area in the image
Coloring or shading adjustment processing only in the area of
I do. Further, the image processing apparatus is provided with an electron microscope.
The image from the above optical microscope is changed to correspond to the tilt image
And generating a pseudo-tilt image.

[0006]

[0007]

[0008]

[0009]

[Action] In shape observation equipment according to the present invention, the image
Using a superposition device, adjust the magnification so that the magnifications of the images by the electron microscope and the optical microscope are equal, and adjust the position so that the positional relationship between the two images coincides, and superimpose them on the same display screen. By
Utilizing the characteristics of both electron microscopes and optical microscopes, it is possible to obtain images of defect shapes including information on both the defect surface and the inside of the sample, thereby improving the workability and accuracy of defect analysis. I do.

Further, the images obtained by the electron microscope and the optical microscope are respectively stored in storage means, and the images processed by the electron microscope or the optical microscope stored in the storage means are processed by the image processing device, so that the images are superimposed. By performing an image superimposition process between the image of one of the electron microscope or the optical microscope stored in the storage unit and the other image of the electron microscope or the optical microscope processed by the image processing device, An image of both an electron microscope and an optical microscope can be displayed on the same display screen, so that a defect area or a defect shape can be clearly displayed.

In the above image processing apparatus, a characteristic portion of a defect region is extracted from an image obtained by an optical microscope, and only the region of the characteristic portion is subjected to coloring or shading adjustment processing. Even in this case, it is possible to obtain an image in which the defective portion is highlighted and displayed so that the defective region can be clearly known.

Further, the image processing apparatus deforms the image obtained by the optical microscope in accordance with the tilted image obtained by the electron microscope to generate a pseudo tilted image. On the other hand, it is possible to display an image including information on the defect shape inside the sample, and to obtain an image from which the defect shape can be known more accurately.

[0013]

【Example】

Embodiment 1 FIG. Hereinafter, the present invention will be described based on illustrated embodiments. FIG. 1 is a configuration diagram of a shape observation device according to Embodiment 1 of the present invention. In FIG. 1, 1 is a sample, 2 is a stage on which the sample 1 is mounted, 2 'is a stage when tilted, 3 is an electron microscope for observing defects on the sample 1, 4 is a secondary electron detector, 5 is an optical microscope for observing a defect on the sample 1 like the electron microscope 3, 6 is an ITV camera, 7 and 8 are image memories for storing images observed by the electron microscope 3 and the optical microscope 5, respectively. Reference numeral 9 denotes an image processing apparatus for converting or processing an image stored in the image memory 8 by the optical microscope 5, and 10 makes image data from the image memories 7 and 8 equal in magnification between the electron microscope 3 and the optical microscope 5. After adjusting the magnification and adjusting the positional relationship between the two images so as to match each other, an image superimposing device 11 for superimposing the two image data is a display device.

Next, the operation of the above configuration will be described. For example, an image obtained by observing a defect on the sample 1 such as a semiconductor wafer during a manufacturing process by the electron microscope 3 and an image observed by the optical microscope 5 are stored in image memories 7 and 8, respectively. Of these,
The optical microscope image stored in the image memory 8 is converted or processed in the image processing device 9 as needed. afterwards,
The image superimposing device 10 adjusts the magnification of the image data from the image memories 7 and 8 so that the magnifications of the electron microscope 3 and the optical microscope 5 become equal. Further, the two images are adjusted so that the positional relationship between the two images coincides, and the two image data are superimposed. At this time, it is necessary to change the setting of the enlargement magnification and adjust the positional relationship between the two images. These operations are performed by using the electron microscope image displayed on the display device 11 connected to the image superimposing device 10 and the optical image. This is performed via a pointing device (not shown) such as a mouse connected to the image superposition apparatus 10 while viewing the microscope image.

FIG. 2 is an explanatory diagram showing an example in which images are actually superimposed using the shape observation apparatus having the above-described configuration. FIG. 2A shows an electron microscope image (secondary electron image).
(B) schematically shows optical microscope images. In these images, defects on the silicon substrate during the semiconductor manufacturing process as the sample 1 were observed by the electron microscope 3 and the optical microscope 5 shown in FIG. 5 is an image, which is an observation image of the same defect at the same position on the sample 1. (C) is an image that has been subjected to image superposition processing after the enlargement magnification and the position of both images have been adjusted by the image superposition apparatus 10, and (d) is an image taken along the line AA ′ in (b). 2 shows a cross section. Further, in FIG. 2, 12 is a polycrystalline silicon film wiring on a silicon substrate 13, 14 is a defect in an electron microscope image, 15 is a foreign substance serving as a nucleus of the defect in an optical microscope image, and 17 is a periphery of the foreign substance 15. This is a visible interference fringe, and the foreign matter 15 is buried in the silicon oxide film 16 formed on the polycrystalline silicon film wiring 12 as shown in FIG.

The defect caused by the foreign matter 15 as described above is
When observed by the electron microscope 3, as shown in FIG. 2A, only the outline of the defect 14 on the silicon oxide film 16 is visible, and the presence or absence of the foreign matter 15 serving as a nucleus and the silicon induced by the foreign matter 15 are observed. It is extremely difficult to determine a non-uniform portion of the oxide film 16. On the other hand, in the optical microscope image captured by the ITV camera 6 attached to the optical microscope 5, as shown in FIG. 2B, the lower foreign matter 15 can be seen through the optically transparent silicon oxide film 16. further,
The portion where the thickness of the silicon oxide film caused by the foreign matter 15 becomes uneven can be seen as interference fringes 17. However, the outline of the defect 14 and the outline of the polycrystalline silicon film wiring 12 are unclear as compared with the electron microscope image.

In the first embodiment, the sample 1 is
Is stored in the image memory 7, and then an image of the same defect 14 observed by the optical microscope 5 (including the ITV camera 6) is stored in the image memory 8. In many cases, these two observation images have different magnifications, and furthermore, the defect positions on the screen are also different. Therefore,
The image data stored in the image memories 7 and 8 is processed by the image superposition device 10. Specifically, the following steps are taken. (1) Adjustment of enlargement magnification The distance between the lower ends of two polycrystalline silicon film wirings 12 which are known to be the same size in each image, in this example, are measured, and the distances are made equal. Adjust the magnification of one image. (2) Position Adjustment The center coordinates of the defect 14 and the foreign matter 15 in each image are obtained, and the coordinates of one image are adjusted so that these coordinates match. (3) Image superposition After the above processing, both image data are added for each pixel. In this case, adjustments may be made so as not to deteriorate the luminance, contrast, color tone, and the like when displayed on the display 11. After the above processing, the superimposed image is displayed on the display 11.

Therefore, according to the first embodiment, the drawback of the electron microscope 3, that is, information on the lower part of the sample cannot be obtained,
Both of the disadvantages of the optical microscope 5, that is, the disadvantage of low image resolution (resolution), can be compensated for and the characteristics of both can be utilized. As shown in FIG. A sharp outline of the crystalline silicon film wiring 12 can be obtained, and the foreign matter 15 in the silicon oxide film and a portion having a nonuniform film thickness, that is, interference fringes 17 can be simultaneously observed by the optical microscope 5. Further, the positional relationship between the defect 14, the foreign matter 15, and the polycrystalline silicon film wiring 12 can be immediately known, and an image of a defect shape including both information on the defect surface and inside of the sample can be obtained. This has the effect of greatly improving the workability and accuracy of defect analysis in a wafer, which has become increasingly important in recent years.

Embodiment 2 FIG. Next, a shape observation device according to a second embodiment will be described. FIG. 3 is an explanatory diagram of an image superimposing process corresponding to the first embodiment shown in FIG. The second embodiment has a configuration similar to that of the first embodiment shown in FIG. 1, and as shown in FIG.
Is obscure, for example, when the foreign matter 15 serving as a nucleus is small or absent, and the sample in which the surface of the silicon oxide film 16 is gently raised to form a mountain is observed. In the case of such a sample, FIG.
In the electron microscope image shown in (a), the outline of the defect 14 is unclear, but in the optical microscope image shown in FIG. 3 (b), a portion having a non-uniform film thickness is an interference fringe (or an area with an interference color). Because it appears, the existence of a defect can be known.

That is, the interference fringe portion 17 in the optical microscope image is extracted by the image processing device 9, only this region is colored or shaded, and superimposed on the electron microscope image shown in FIG. As a result, as shown in FIG. 3D, it is possible to obtain an image in which the defective area can be clearly known.

Therefore, according to the second embodiment, the images obtained by the electron microscope 3 and the optical microscope 5 are stored in the image memories 7 and 8 respectively, and the optical microscope 5 stored in the image memory 8 is stored by the image processing device 9. Is processed by the image superimposing device 10 to perform the image superimposing process on the electron microscope image stored in the image memory 7 and the optical microscope image processed by the image processing device 9. In addition, it is possible to display both images by the electron microscope and the optical microscope on the same display screen, so that the defect area or the defect shape can be clearly displayed. At this time, the image processing apparatus 10 extracts a characteristic portion of the defect region from the image obtained by the optical microscope, and performs coloring or shading adjustment processing only on the characteristic region, whereby the outline of the defect shape is unclear. Even in this case, it is possible to obtain an image in which a defective portion is highlighted and displayed so that the defective region can be clearly known.

Embodiment 3 FIG. Next, a shape observation device according to a third embodiment will be described. FIG. 4 is an explanatory diagram of an image superimposing process corresponding to the first embodiment shown in FIG. In the third embodiment, a configuration similar to that of the first embodiment shown in FIG. 1 is provided, and as shown in FIG. 4A, when the sample 1 is observed with the electron microscope 3, the stage 2 is tilted and observed. It is intended for superimposition of images at the time. When the observation is performed in such an inclined manner, the shape of the defect 14 can be more accurately known. In this case, however, in order to superimpose the optical microscope image shown in FIG. 9, the optical microscope image is deformed by an amount corresponding to the tilt angle of the stage 2 ′, and a pseudo tilt image as shown in FIG. By superimposing and displaying this image and the electron microscope image, an image after the processing shown in FIG. 4D can be obtained.

Therefore, according to the third embodiment, the image processing apparatus 9 deforms the image by the optical microscope 5 in correspondence with the tilt image by the electron microscope 3 to generate a pseudo tilt image, thereby tilting the sample. An image including information on the shape of a defect inside the sample can be displayed even on the tilted image obtained by the electron microscope 3 so that an image can be obtained in which the shape of the defect can be known more accurately.

In each of the embodiments described above, the image memories 7 and 8, the image processing device 9, and the superposition processing device 1
0 are shown as separate devices, but these are
For example, they may be integrated into one computer system, or some or all of them may be incorporated in the electron microscope 3 or the optical microscope 5.
Further, the image processing device 9 is provided only on the optical microscope 5 side of the image memory 8, but may be provided on the electron microscope 3 side of the image memory 7, or may be provided on both sides.

[0025]

As described above, according to the present invention , the image
Using a superposition device, adjust the magnification so that the magnifications of the images by the electron microscope and the optical microscope are equal, and adjust the position so that the positional relationship between the two images coincides, and superimpose them on the same display screen. By
Utilizing the characteristics of both the electron microscope and the optical microscope, it is possible to obtain an image of a defect shape including information on both the defect surface and the inside of the sample, thereby improving the workability and accuracy of the defect analysis. is there.

The images obtained by the electron microscope and the optical microscope are respectively stored in storage means, and the image processing apparatus processes the images obtained by the electron microscope or the optical microscope stored in the storage means. By performing an image superimposing process of an image of one of the electron microscope or the optical microscope stored in the storage unit and the other image of the electron microscope or the optical microscope processed by the image processing device, by a matching device. In addition, it is possible to display both images by the electron microscope and the optical microscope on the same display screen, so that the defect area or the defect shape can be clearly displayed.

The image processing apparatus extracts a characteristic portion of a defect area from an image obtained by an optical microscope, and performs coloring or shading adjustment processing only on the characteristic area, so that the outline of the defect shape is unclear. Even in this case, it is possible to obtain an image in which the defective portion is highlighted and displayed so that the defective region can be clearly known.

Further, the image processing apparatus deforms the image obtained by the optical microscope in accordance with the tilted image obtained by the electron microscope to generate a pseudo tilted image. On the other hand, it is possible to display an image including information on the shape of a defect inside the sample, and to obtain an image in which the shape of the defect can be more accurately known.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a shape observation device according to the present invention.

FIG. 2 is an explanatory diagram of an image superposition process according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of an image superposition process according to the second embodiment of the present invention.

FIG. 4 is an explanatory diagram of an image superimposing process according to a third embodiment of the present invention.

[Description of Signs] 1 sample, 3 electron microscope, 5 optical microscope, 7, 8
Image memory, 10 image superposition device, 11 display device, 14 defect, 15 foreign matter, 17 interference fringes.

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Claims (2)

(57) [Claims] 1. An electron microscope and an optical microscope for observing defects on a sample, and a magnification is adjusted so that magnifications of images obtained by the electron microscope and the optical microscope are equal, and a positional relationship between the images is matched. an image superimposition device for superimposing on the same display screen by positioning, the
Store images from electron microscope and optical microscope respectively
Storage means and an electron microscope stored in the storage means
Or an image processing device that processes images with an optical microscope
The image superimposing device is stored in the storage means.
Either electron microscope or optical microscope
Image and electron microscope processed by the above image processing device
Or the process of superimposing the image with the other image using the optical microscope.
And the image processing apparatus includes the optical microscope
Of the defect area in the image by
A shape observation apparatus characterized in that only a partial area is subjected to coloring or shading adjustment processing . 2. The image processing apparatus according to claim 1 , wherein
Images from the above optical microscope corresponding to the tilt image
Generating a pseudo-tilt image by deforming
The shape observation device according to claim 1 .