JPH08162059A - Form observing device - Google Patents

Abstract

PURPOSE: To provide information for both the surface defect and internal defect forms of a sample and improve the working property and precision of the defect analysis by regulating the magnification and position of both images by an electron microscope and an optical microscope, and superposing both the images. CONSTITUTION: Images obtained by observing a defect on a sample 1 by an electron microscope 3 and an optical microscope 5 are stored in image memories 7, 8, respectively. The optical microscopic image stored in the image memory 8 is converted or worked by an image processing device 9 as occasion demands. Thereafter, the image data from the image memories 7, 8 are regulated in magnification by an image superposing device 10 so that the enlarging magnification in the electron microscope 3 and the optical microscope 5 are equal to each other. Further, both the images are regulated so that the positional relations of both the images are conformed to each other, and then superposed. Thus, the defect area of the sample 1 can be clearly known.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape observing apparatus for observing the surface shape and internal shape of a sample, particularly a 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 a relatively wide field of view is observed. Each has been used. In recent years, the control of defects and foreign substances that occur on a wafer during the manufacturing process of semiconductor devices typified by memory devices has become strict, and the size of defects to be noticed has also decreased due to the progress of pattern miniaturization accompanying the increase in the degree of integration. It's coming. Therefore, the proportion of observing the defect shape using an electron microscope has increased.

[0003]

However, when an electron microscope is used for the purpose of such defect analysis, there are the following problems. Acceleration voltage 1 commonly used
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 particles existing in a layer lower than the surface. On the other hand, with an optical microscope, although the resolution is inferior to that of an electron microscope, it may be possible to observe the shapes of objects and structures below the surface. This is the case, for example, for a defect or a foreign substance existing under an optically transparent film (such as a silicon oxide film used in a semiconductor manufacturing process). As described above, the device has been used properly according to the characteristics of each device, but in order to obtain an image with high resolution and an image with internal information, a monitor device or a photo shoot that displays the image obtained from each device A device was needed, and the task of comparing the two images was necessary.

The present invention has been made in order to solve the above-mentioned problems associated with the conventional example, and obtains a shape observing apparatus capable of obtaining an image of a defect shape including information on both the surface and the inside of the defect of a sample. The purpose is to

[0005]

A shape observing apparatus according to the present invention is a magnification observing apparatus for observing a defect on a sample with an electron microscope and an optical microscope so that the magnifications of images by the electron microscope and the optical microscope become equal. In addition, the image superimposing device is provided so that the positions of the images are adjusted so that the positional relationship between the images coincides with each other, and the images are superposed on the same display screen.

Further, there are further provided storage means for storing the images by the electron microscope and the optical microscope, respectively, and an image processing device for processing the images by the electron microscope or the optical microscope, which are stored in the storage means. The device is characterized by performing an image superimposing process of an image of either the electron microscope or the optical microscope stored in the storage means and the other image by the electron microscope or the optical microscope processed by the image processing device. It is what

Further, the image processing apparatus is characterized in that a characteristic portion of a defective area is extracted from the image obtained by the optical microscope, and only the area of the characteristic portion is colored or shaded.

Further, the image processing device is characterized in that the image obtained by the optical microscope is transformed in correspondence with the image obtained by the inclination of the electron microscope to generate a pseudo inclined image.

[0009]

In the shape observing device according to the present invention, the magnification is adjusted by the image superposing device so that the magnifications of the images by the electron microscope and the optical microscope become equal, and the position is adjusted so that the positional relationship between the two images may coincide. By adjusting and overlapping on the same display screen,
By utilizing the characteristics of both the electron microscope and optical microscope, it is possible to obtain an image of the defect shape that includes information on both the defect surface and inside of the sample, and improve the workability and accuracy of defect analysis. To do.

Further, the images obtained by the electron microscope and the optical microscope are respectively stored in the storage means, and the image processing device processes the images stored in the storage means by the electron microscope or the optical microscope to superimpose the images. By the device, by performing an image superimposing process of either one of the image of the electron microscope or the optical microscope stored in the storage means and the other image of the electron microscope or the optical microscope processed by the image processing device, Images of both the electron microscope and the optical microscope can be displayed on the same display screen, and the defect region or defect shape can be clearly displayed.

In the case where the outline of the defect shape is unclear by extracting the characteristic portion of the defective area from the image by the optical microscope and coloring or shading the area of the characteristic portion by the image processing apparatus. Even with this, it is possible to obtain an image in which the defective portion is highlighted and displayed so that the defective area can be clearly known.

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

[0013]

【Example】

Example 1. Hereinafter, the present invention will be described based on illustrated embodiments. 1 is a configuration diagram of a shape observation apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is a sample, 2 is a stage for mounting the sample 1, 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 defects on the sample 1 similarly to 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 is an image processing device for converting or processing the image stored in the image memory 8 by the optical microscope 5, and 10 is the same magnification of the image data from the image memories 7 and 8 in the electron microscope 3 and the optical microscope 5. The image superimposing device 11 superimposes the image data of the two images after adjusting the magnification and adjusting the positional relationship of the images of the two images to match each other.

Next, the operation of the above configuration will be described. For example, an image observed by the electron microscope 3 and an image observed by the optical microscope 5 for a defect on the sample 1 such as a semiconductor wafer during the manufacturing process are stored in the image memories 7 and 8, respectively. Of this,
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 superposing device 10 adjusts the magnification of the image data from the image memories 7 and 8 so that the electron microscope 3 and the optical microscope 5 have the same magnification. Further, adjustment is made so that the positional relationship between the images of the both is the same, and the image data of the both are superposed. At this time, it is necessary to change the setting of the magnifying power and adjust the positional relationship between the two images. These operations are performed by using the electron microscope image and the optical image displayed on the display device 11 connected to the image superposing device 10. This is performed through a pointing device (not shown) such as a mouse connected to the image superposing device 10 while observing the microscope image.

FIG. 2 is an explanatory view showing an example in which images are actually superposed using the shape observation apparatus having the above-mentioned configuration. 2A shows an electron microscope image (secondary electron image),
(B) is a schematic copy of an optical microscope image. These images were observed as defects of a sample 1 on a silicon substrate during a semiconductor manufacturing process by an electron microscope 3 and an optical microscope 5 shown in FIG. The image is an observation image of the same defect at the same position on the sample 1. Further, (c) is an image that has been subjected to image superimposition processing after the image superimposing device 10 has performed enlargement magnification and position adjustment of both images, and (d) is a line AA ′ line portion in (b). A cross section is shown. Further, in FIG. 2, 12 is a polycrystalline silicon film wiring on the silicon substrate 13, 14 is a defect in the electron microscope image, 15 is a foreign substance which becomes a nucleus of the defect in the optical microscope image, and 17 is a periphery of the foreign substance 15. The foreign matter 15 is visible interference fringes, and is embedded in the film of the silicon oxide film 16 formed on the polycrystalline silicon film wiring 12, as shown in FIG. 2D.

The defects caused by the foreign matter 15 as described above are
When observed by the electron microscope 3, as shown in FIG. 2A, only the outer shape of the defect 14 on the silicon oxide film 16 can be seen, and the presence or absence of the foreign substance 15 serving as a core and the silicon induced by the foreign substance 15 are observed. It is extremely difficult to determine the 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 foreign substance 15 at the bottom can be seen through the optically transparent silicon oxide film 16. further,
The portion where the film thickness of the silicon oxide film is nonuniform due to the foreign matter 15 can be seen as interference fringes 17. However, the contour of the defect 14 and the contour of the polycrystalline silicon film wiring 12 are unclear compared to the electron microscope image.

In the first embodiment, the sample 1 is replaced with the electron microscope 3
The image observed by (1) is stored in the image memory 7, and then the image observed by the optical microscope 5 (including the ITV camera 6) of the same defect 14 is stored in the image memory 8. In many cases, these two observed images have different magnifying powers, and the defect positions on the screen are also different, so that they cannot be superimposed as they are. Therefore,
The image data stored in the image memories 7 and 8 is processed by the image superposing device 10. Specifically, take the following steps. (1) Adjustment of magnification Magnification: A portion of each image that is known to have the same dimension, in this example, the distance between the lower ends of the two polycrystalline silicon film wirings 12 is measured, respectively, and the distances are made the same. Adjust the magnification of one image. (2) Position adjustment The center coordinates of the defect 14 and the foreign material 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 up for each pixel. In this case, adjustment may be made so as not to deteriorate the brightness, contrast, color tone, etc. 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 defect of the electron microscope 3, that is, the information of the lower portion of the sample cannot be obtained, and
The defect of the optical microscope 5, that is, the defect that the resolution of the image is low can be compensated for, and the characteristics of both can be utilized, and as shown in FIG. A clear outline of the crystalline silicon film wiring 12 can be obtained, and at the same time, the foreign material 15 in the silicon oxide film obtained by the optical microscope 5 and the nonuniform film thickness portion, that is, the interference fringes 17 can be observed at the same time. Further, the positional relationship among the defect 14, the foreign material 15, and the polycrystalline silicon film wiring 12 can be immediately known, and an image of the defect shape including information on both the defect surface and the inside of the sample can be obtained. This has the effect of greatly improving the workability and accuracy of defect analysis in wafers, which has become increasingly important in recent years.

Example 2. Next, the shape observation device according to the second embodiment will be described. FIG. 3 is an explanatory diagram of image superimposing processing corresponding to the first embodiment shown in FIG. The second embodiment has the same structure as that of the first embodiment shown in FIG. 1, and as shown in FIG.
Is unclear, for example, when the foreign matter 15 serving as a nucleus is small or absent, and the surface of the silicon oxide film 16 is gently swelled to have a mountain shape, the sample 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), the portion where the film thickness is nonuniform is an interference fringe (or an area with an interference color). Since it appears as, it is possible to know the existence of the defect.

That is, the image processing apparatus 9 extracts the interference fringe portion 17 in this optical microscope image, colors or adjusts the density of only this region, and superimposes it on the electron microscope image shown in FIG. 3A. 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 by the image processing device 9. The image superimposing apparatus 10 performs the image superimposing processing of the electron microscope image stored in the image memory 7 and the optical microscope image processed by the image processing apparatus 9 so as to process the image by The images of both the electron microscope and the optical microscope can be displayed on the same display screen, and the defect region or defect shape can be clearly displayed. Then, at that time, the image processing apparatus 10 extracts the characteristic portion of the defect area from the image obtained by the optical microscope and colors or shades only the area of the characteristic portion to make the outline of the defect shape unclear. Even in such a case, it is possible to obtain an image in which the defective portion can be clearly known by displaying the defective portion in an emphasized manner.

Example 3. Next, the shape observation device according to the third embodiment will be described. FIG. 4 is an explanatory diagram of image superimposing processing corresponding to the first embodiment shown in FIG. The third embodiment has the same configuration as that of the first embodiment shown in FIG. 1, and as shown in FIG. 4A, the stage 2 is tilted when observing the sample 1 with the electron microscope 3. It is intended for superimposing images when doing. In the case of observing with such an inclination, the shape of the defect 14 can be known more accurately, but in this case, in order to superimpose the optical microscope images shown in FIG. The optical microscope image may be deformed by 9 by an amount corresponding to the tilt angle of the stage 2 ', and the image processing device 9 may generate a pseudo tilt image as shown in FIG. By superimposing and displaying this image and the electron microscope image, the processed image shown in FIG. 4D can be obtained.

Therefore, according to the third embodiment, the image processing device 9 deforms the image obtained by the optical microscope 5 in accordance with the inclined image obtained by the electron microscope 3 to generate a pseudo inclined image, thereby inclining the sample. An image including information on the defect shape inside the sample can be displayed even on the tilted image obtained by the electron microscope 3, and an image can be obtained in which the defect shape 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 overlay processing device 1 are included.
0 is shown as a separate device, but these are
For example, the computer system may be integrated into one computer system, or a part or all of these may be incorporated in the electron microscope 3 and the optical microscope 5.
Further, although the image processing device 9 is provided only on the optical microscope 5 side of the image memory 8, it 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 superimposing device adjusts the magnifications of the images by the electron microscope and the optical microscope so that they are equal to each other, and the positional relationship between the two images is the same. By adjusting the position so that they overlap 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 the defect shape including information on both the defect surface and the inside of the sample, and the workability and accuracy of defect analysis can be improved. is there.

Further, the images by the electron microscope and the optical microscope are respectively stored in the storage means, and the image processing device processes the images by the electron microscope or the optical microscope stored in the storage means to superimpose the images. By performing an image superimposing process on the image of either one of the electron microscope or the optical microscope stored in the storage means and the other image by the electron microscope or the optical microscope processed by the image processing device by the aligning device. The images of both the electron microscope and the optical microscope can be displayed on the same display screen, and the defect region or defect shape can be clearly displayed.

In the case where the outline of the defect shape is unclear by extracting the characteristic part of the defect area from the image by the optical microscope and coloring or shading only the area of the characteristic part by the image processing apparatus. Even in this case, it is possible to obtain an image in which the defective area can be clearly known by displaying the defective portion in an emphasized manner.

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

[Brief description of 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 superimposing process according to the first embodiment of the present invention.

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

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

[Explanation of symbols]

1 sample, 3 electron microscope, 5 optical microscope, 7, 8
Image memory, 10 image superimposing device, 11 display device, 14 defects, 15 foreign matter, 17 interference fringes.

Claims (4)

[Claims] 1. An electron microscope and an optical microscope for observing defects on a sample are adjusted so that the magnifications of the images obtained by the electron microscope and the optical microscope are equal, and the positional relationship between the images is matched. A shape observing device comprising an image superimposing device whose position is adjusted and superposed on the same display screen. 2. The image superimposing apparatus further comprises storage means for respectively storing images by the electron microscope and optical microscope, and an image processing device for processing the images by the electron microscope or optical microscope stored in the storage means. The device is characterized by performing an image superimposing process of an image of either the electron microscope or the optical microscope stored in the storage means and the other image by the electron microscope or the optical microscope processed by the image processing device. The shape observation device according to claim 1. 3. The image processing apparatus according to claim 2, wherein a characteristic portion of a defective area is extracted from the image obtained by the optical microscope, and only the area of the characteristic portion is colored or shade-adjusted. Shape observation device. 4. The shape observation according to claim 2, wherein the image processing apparatus deforms the image by the optical microscope in correspondence with the tilt image by the electron microscope to generate a pseudo tilt image. apparatus.