JP2539530B2 - Sample image display - Google Patents

Description

The present invention relates to a sample image display device, and more particularly to a sample image display device used in an electron microscope, an optical microscope and the like.

[Conventional technology]

In a sample image display device such as an electron microscope, when a target shape image is moved to an arbitrary position in the visual field, the movement of the target shape image is generally performed by a human being, as described in, for example, JP-A-60-185350. Is specified by using a trackball or the like.

Incidentally, the prior art relating to the sample image display device is also described in JP-A-1-120752 in addition to the above-mentioned publication.

[Problems to be Solved by the Invention]

However, the technique described in Japanese Patent Laid-Open No. 60-185350 is to simply move a specified target shape image to a specified position on the screen. Even if a large number of objects similar in shape to the target moving object exist in the vicinity, or even if the target moving object is an object that is difficult to detect due to the influence of noise, etc., the target object can be easily In order to find the target object, instead of finding the target object, a shape object that is easier to find in the vicinity, that is, a shape object whose relative distance to the target object is known and which can be easily detected and specified is used as the detection object. No technology is disclosed for moving the target object, which should be originally moved, to the arbitrary position based on the position of the detection object and the relative distance.

On the other hand, in JP-A-1-120752, the wafer coordinate system does not immediately match the stage coordinate system even when the wafer is placed on the sample stage, and the target object on the wafer immediately after the magnification of the microscope is increased. Since an object cannot be caught in the field of view, two (or more) alignment marks are previously attached to a predetermined position on the wafer, the alignment mark is first found, and then the alignment mark on the wafer And a coordinate of the stage corresponding to the alignment mark coordinate, the displacement of both coordinate systems is obtained, and the technique of moving the stage based on this displacement amount to capture the target object in the visual field is disclosed. According to the position of the wafer,
A new step is required to attach a plurality of alignment marks in advance.

A first object of the present invention is that, in a sample image display device such as an electron microscope, when a target shape image is moved to a desired position in the visual field, a large number of objects similar in shape to the target moving object are present in the vicinity. However, or even if the target moving object is an object that is difficult to detect due to the influence of noise, etc., it is not necessary to additionally provide a plurality of alignment marks at a predetermined position on the sample, An object of the present invention is to provide an improved sample image display device unique to the present invention, which is capable of moving a target object to be originally moved to an arbitrary position.

Further, a second object of the present invention is to improve the stability of detection by detecting an object which has a large amount of features expressing a shape and whose position is easily determined only in relation to the first invention. It is to provide a sample image display device.

Furthermore, a third object of the present invention is to provide a method for registering a local shape in a sample image display device in which the amount of data to be stored is about the same as when directly detecting a moving object. .

Furthermore, a fourth object of the present invention is to use an area cursor to make it easier for the operator to intuitively understand the range of the registered partial image data, and to specify the target object. It is an object of the present invention to provide a method of registering a local shape in a sample image display device that can more easily perform the above.

[Means for solving the problem]

Therefore, the first purpose is to display means for displaying a sample image on a display screen, an image memory for storing the sample image, and a display screen of an arbitrary local shape in the sample image displayed on the display screen. In a sample image display device comprising means for obtaining a position at, and means for moving the field of view to an arbitrary position in the sample image based on the position information, a predesignated local shape is displayed on the display screen at an arbitrary position. When moving the field of view to the position of, instead of detecting the local shape to be moved, other at least one local shape that is easy to detect and specify, whose relative distance and direction to the local shape are known, is detected, This is achieved by providing means for moving the local shape to be originally moved to an arbitrary position based on the detected position of the local shape and the relative distance and direction.

Further, the second object is to detect the two or more local shapes that are easy to detect and specify, in relation to the first aspect of the invention, and to detect one or more high-reliable top positions among them. This is achieved by providing a means for moving a local shape to be originally moved to an arbitrary position based on information.

Still further, the third object is means for displaying a sample image on a display screen, an image memory for storing the sample image,
And means for designating an arbitrary position on the display screen,
By specifying the position of the local shape of the moving object and the position of at least one local shape that is easy to detect and specify by the means for specifying the position on the display screen, the specified easy to detect and easy to specify This is achieved by storing the partial image data centered on the position of the local shape and the distance from the center position to the position of the specified local shape of the moving object as registration data.

Furthermore, the fourth purpose is to display a sample image on a display screen, an image memory for storing the sample image,
A means for designating an arbitrary position on the display screen and a means for designating a partial area are provided, and the position of the local shape of the moving object is designated by the means for designating the position on the display screen, and at least one By specifying a local shape that is easy to detect and specify by the means for specifying the partial area on the display screen, the partial image data in the specified partial area and the specified moving object from the center position of the partial area are specified. This is achieved by storing the distance to the position of the local shape of as registration data.

[Action]

Therefore, according to the first aspect of the invention, in the sample image display device such as an electron microscope, when moving the object shape image to the arbitrary position in the visual field, a large number of objects similar in shape to the object to be moved are located nearby. Even if it exists, or if the target moving target is a target that is difficult to detect due to the influence of noise, etc., when moving the visual field of the local shape specified in advance to any position on the display screen, the moving target Instead of detecting the local shape that becomes, the at least one local shape whose relative distance and direction to the local shape are known and which can be detected and specified easily, and the position of the detected local shape, By providing means for moving the local shape to be originally moved to an arbitrary position on the basis of the relative distance and the direction, a plurality of alignment marks, particularly alignment marks, are set at a predetermined position on the sample. There is no need to attached to, may be viewing moving objects the object to be moved inherent to an arbitrary position.

Further, according to the second aspect of the invention, in relation to the first aspect of the invention, two or more easily detected and easily identified local shapes are detected, and among them, one or more high-reliable high-order local shapes are detected. Based on the position information of the position, the means to move the local shape that should be originally moved to an arbitrary position is provided, so that it is possible to detect by detecting an object that has many feature quantities that represent the shape and the position can be uniquely determined. The stability of can be increased.

Furthermore, according to the third aspect of the invention, the position of the local shape of the moving target and at least one position of the local shape that is easy to detect and specify are designated by means for designating the position on the display screen. Thus, only the partial image data centered on the position of the specified local shape that is easy to detect and specify and the distance from the center position to the position of the specified local shape of the movement target are saved as registration data. As a result, the amount of data to be stored can be about the same as when detecting a moving object directly.

Furthermore, in the fourth aspect of the present invention, the position of the local shape of the moving object is designated by means for designating the position on the display screen, and at least one local shape that is easy to detect and specify is displayed on the display screen. By specifying the partial area by means of specifying the partial area, the partial image data in the specified partial area and the distance from the center position of the partial area to the position of the specified local shape of the movement target are saved as registration data. According to the fourth aspect of the present invention, the use of the area cursor can make it easier for the operator to intuitively understand the range of the partial image data to be registered, and thus the target object can be more specified. It can be done easily.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to FIG.

In FIG. 1, an electron beam 2 emitted from an electron gun 1 is narrowed down by an objective lens 6 and irradiated on a sample 7. The objective lens 6 is excited by the objective lens power source 11. Further, the deflection signal generated by the deflection signal generator 14 can change the scanning range and scanning position on the sample by the computer 21, the deflection coil 5 is excited by the deflection amplifier 10, and the electron beam 2 on the sample 7 is excited. Two-dimensional scanning. In addition, the signal (secondary electron signal, reflected electron signal, etc.) generated by the electron beam 2 incident on the sample 7 is detected by the detector 12
Is converted into an electric signal by the A / D converter 15, and the analog signal is converted into a digital signal by the A / D converter 15.
Is stored. The contents of the image memory 16 are always converted from a digital signal to an analog signal by the D / A converter 17, added by the signal from the cursor signal generator 22 and by the adder 23, and an image display CRT (cathode ray tube). 19 luminance signals are applied to the grid. At this time, the A / D converter 15, the image memory 16, and the D / A converter 17 are A / D-converted and stored, and further D / A
A timing signal for converting and displaying an image is received from the deflection signal generator 14. Further, the image memory 16 is controlled by the computer 21 as to whether or not to store image data. The deflection coil 20 of the image display CRT 19 is excited by the deflection amplifier 18 based on the deflection signal of the deflection signal generator 14.

On the other hand, the stage 8 on which the sample 7 is placed is moved by the stage drive circuit 13, whereby the scanning position of the electron beam 2 on the sample 7 changes, and the field of view moves. In addition,
The same visual field movement can be performed by exciting the image shift coil 3 by the DC amplifier 9 and offsetting the scanning position of the electron beam 2 on the sample. The amount of movement of these visual field movements is controlled by the computer 21.

The signal of the cursor signal generator 22 changes according to the signal from the trackball 4 or the computer 21, and changes the display position of the cursor displayed on the image display CRT. The computer 21 can acquire the position information on the image display CRT 19 from the state of the cursor signal generator 22. Also,
The computer 21 can read all or part of the image data in the image memory 16, and by combining with the cursor position information, a part of the image data centered on the cursor position can be read from the corresponding position in the image memory. Can be read.

With the above-described configuration, the present invention performs the following processing. First, the procedure for registering the target image and the reference image will be described with reference to FIGS. 1 and 2.

First, a sample including a desired local shape is placed on the stage 8, and the electron beam 2 is irradiated to display an image on the CRT 19 for image display.

Next, the track hair 4 is used to manually align the crosshair cursor 26 with the local shape 24 that can be easily and uniquely identified in the displayed image (Fig. 2 (a)), and the computer
Give registration instructions to 21. The computer 21 acquires the cursor position information from the cursor signal generator 22 and saves it, and also reads some image data centered on the cursor position from the corresponding position on the image memory 16 and saves it as a reference image.

The above series of procedures is referred to as a standard image registration procedure.

Next, the trackball 4 is operated on the target local shape 25 on the same display image, the crosshair cursor 26 is aligned (FIG. 2B), and the computer 21 is instructed to register. After acquiring the cursor position information from the cursor signal generator 22, the computer 21 next uses the position information and the cursor position information of the reference image saved during the reference image registration procedure to determine the desired local shape. The relative distance between the reference image and the reference image is obtained and saved.

 Note that the above procedure is the target image registration procedure.

The above two procedures may be performed once at the beginning of the detection process.

Next, regarding the target local shape detection and movement processing,
This will be described with reference to FIGS. 1 and 3.

First, a sample to be measured or inspected is placed on the stage 8 and the electron beam 2 is irradiated to display an image on the CRT 19 for image display.

Next, the computer 21 is instructed to perform detection and movement processing. The computer 21 compares the reference image registered in advance with the image data in the image memory 16 and obtains the coordinates X, Y on the image display CRT where the reference image exists (FIG. 3 (a)). Further, from the coordinates X, Y and the relative distances Δx, Δy registered in advance, the movement amount for moving the target shape to the designated position is obtained by the following formula.

m _x = O _x − (X + Δx) m _y = O _y − (Y + Δy) where m _x and m _y are movement amounts in the x and y directions, and O _x and O _{y, respectively.}
Is the coordinates of the destination. Here, O _x and O _y may be registered at the time of registration work, or may be designated by using a crosshair cursor when the target shape is moved.

The calculated movement amount is sent to the stage drive circuit 13 or the image shift control circuit including the image shift coil 3 and the DC amplifier 9 as a visual field movement signal, and the visual field is moved to move the target shape to the designated position. (FIG. 3 (b)).

As described above, according to the present embodiment, the local shape that can be easily detected and uniquely identifies the position in the display image is detected, and the target shape is moved to the designated position based on the position information. This is particularly effective when there are a plurality of similar shapes in the same display image and the target shape is correctly moved to the designated position, as in the example of FIG.

In this embodiment, the detection in the case where there are a plurality of shapes similar to the target shape is taken up, but there is no target shape and there is no other similar shape, but it is difficult to detect it due to the influence of noise or the like. The same effect can be obtained for a target such as

Further, in the present embodiment, the target shape is moved to an arbitrary position, but if the position where the visual field does not move even if the observation magnification is changed is selected as the destination, the target shape is found at a low magnification and the magnification is increased. Observation can be done automatically. This effect is particularly effective when automatically measuring various characteristics of a fine shape on a sample, such as automatic measurement of a wafer in a semiconductor production line.

FIG. 4 is a diagram for explaining designation of a local shape by evaluation of detection reliability. The reliability of the detection is, for example, To use. In the figure, (a) is an example in which a cross-correlation function is calculated and plotted for each local shape, and here the local shape B has the highest detection reliability. Therefore, the local shape B is used to determine the position of the moving target E, the coordinates of the local shape B on the image are obtained, and the coordinates and the relative distance from the local shape B to the moving target E registered in advance are used. The position of the moving object E is determined, and according to this, the stability of detection can be increased by detecting the object that has many feature quantities that represent the shape and whose position is easily determined.

FIG. 5 shows a dimension measuring method. When the local shape A is a local shape that is easy to detect and specify, and the local shape B is the measurement target, the local shape A is first detected and the center coordinates of the local shape A and the local shape A registered in advance are used. The position of the local shape B is specified from the relative distances d _x and d _y to the position, then the local shape B is not moved and the scanning position of the electron beam on the sample is offset, and the measurement cursor is By moving to the position of the specified local shape B for measurement, it is possible to save the trouble of moving the local shape B, and the time required for dimension measurement can be shortened accordingly.

FIG. 6 shows a method of registering a local shape, and is an example in which two types of local shapes A and B are registered as easy-to-detect local shapes using a crosshair cursor.

First, the crosshair cursor is manually placed on the local shape A (FIG. 6 (a)), and a registration instruction is issued. Thereby,
The computer has the coordinates of the intersection of the crosshair cursors,
The image data in a partial area (dotted line area in the figure) of a predetermined size centered on the intersection is stored as partial image data. The same operation is performed for the local shape B (FIG. 6 (b)). As described above, two partial image data and coordinate values of two points on the image can be obtained.

Next, the crosshair cursor is aligned with the local shape C (FIG. 6 (c)) to be measured, and a registration instruction is issued. The computer obtains the distance between each point from the coordinates of the intersection of the crosshair cursor and the coordinates of two points on the image that have already been stored, and stores it as the relative distance from the measurement target to the local shapes A and B. According to this, the amount of data to be stored can be about the same as in the case of directly detecting the moving target.

FIGS. 7 (a) and 7 (b) show a method of registering a local shape using a crosshair cursor and an area cursor. The area cursor is used to specify a local shape that can be easily detected, and A crosshair cursor is used to specify the local shape. The area cursor moves with a trackball or the like so as to include a local shape that can be easily detected. The computer stores the image data in the area cursor as partial image data. Further, the relative distance is obtained from the center coordinates of the area cursor and the intersection coordinates of the crosshair cursor. According to this, the operator intuitively determines the range of the partial image data to be registered by using the area cursor. Therefore, the target object can be designated more easily. The size of the area cursor can be freely changed by giving an instruction to the computer.

〔The invention's effect〕

The present invention is as described above, and according to the present invention, in a sample image display device such as an electron microscope, in moving a target shape image to an arbitrary position in the visual field, an object having a shape similar to that of a target moving object is in the vicinity. Even if there are a large number of objects, or if the target moving object is an object that is difficult to detect due to the influence of noise, etc.,
At the time of moving the visual field to any position on the display screen, instead of detecting the local shape to be moved, at least one local shape whose relative distance and direction to the local shape are known and which can be easily detected and specified. By detecting the position of the detected local shape and moving the visual field of the local shape to be originally moved to an arbitrary position based on the relative distance and the direction. It is not necessary to additionally attach a plurality of marks for alignment to the position,
The target object to be originally moved can be moved to any position in the visual field.

Further, according to the present invention, two or more local shapes that are easily detected and easily specified are detected, and based on one or more position information with high detection reliability among them, the local shape that should be originally moved. By providing a means for moving to any position, it is possible to increase the stability of detection by detecting an object that has a large amount of features that express a shape and whose position is easily determined.

Furthermore, according to the present invention, by designating the position of the local shape of the moving target and the position of at least one local shape that is easy to detect and specify by the means for designating the position on the display screen, Saving by storing only partial image data centered on the position of the specified local shape that is easy to detect and specify and the distance from the center position to the position of the specified local shape of the movement target as registered data The amount of data to be processed is about the same as when directly detecting the moving object. Furthermore, according to the present invention, the position of the local shape of the moving object is designated by means for designating the position on the display screen, and at least one local shape that is easy to detect and specify is defined as a partial area on the display screen. By designating by the designating means, the partial image data in the designated partial region and the distance from the center position of the partial region to the position of the designated local shape of the moving object are stored as registration data. According to the present invention, the use of the area cursor allows the operator to intuitively understand the range of the partial image data to be registered, and thus the target object can be designated more easily.

It should be noted that Japanese Patent Laid-Open No. Sho 62-62 entitled "Analyzer using charged particle beam"
Although the technology described in the −229646 publication has been previously proposed,
The purpose of the technique described in the publication is to stably irradiate a beam on a sample position to be analyzed by X-ray for a long time. In other words, it is a measure against the problem that the analysis position moves due to the drift of the sample during observation, which makes accurate analysis difficult. Since the movement of the sample cannot be detected by spot-shaped beam irradiation, the drift of the sample is detected by using an image. The purpose of position detection using an image is to detect drift, and finally to correct the drift and track the analysis position.

On the other hand, the object of the present invention is to find a predetermined specific pattern from the observation visual field. When detecting a specific pattern, there are many problems to be solved in order to stabilize the detection, such as when there are a plurality of similar patterns or when the target to be detected is likely to deteriorate. The present invention is a proposal for solving the problem that occurs during such detection.

Further, the image signal selecting means described in JP-A-62-229646 is selected at a position different from the position to be subjected to X-ray analysis, so that the X-ray analysis position is obtained by electron beam irradiation for image acquisition. The purpose is to suppress the effect of contamination on the. In the examples, the bright spot marker Mp is not included and the image is moved to a position where the image contrast is relatively clear, but the position where the image contrast is clear is not always easy to detect in image processing. . This is because the image contrast is clear, but if there are patterns with similar shapes at multiple locations in the observation field of view, it is impossible to determine which shape should be originally detected, and detection is impossible.
This is the point proposed by the present invention.

As described above, the description about the image described in Japanese Patent Laid-Open No. 62-229646 has only an auxiliary meaning for accurately performing X-ray analysis of a specific position. The purpose is to stably detect a specific shape from the observation visual field.

On the other hand, the offset between the image and the analysis position in JP-A-62-229646 is temporary data as long as the analysis. This is because the analysis position changes for each analysis.

On the other hand, the present invention is based on the premise that a predetermined shape is repeatedly used under certain conditions. For example, a semiconductor inspection apparatus detects and inspects a specific shape for all dies on a wafer. Since wafers are inspected over multiple lots, the number of times the predetermined shape is used is considerable. Registering / storing the relationship between the partial image and the position to be observed is an extremely important function for the above-mentioned purpose of use, but it is not necessary in JP-A-62-229646.

[Brief description of drawings]

FIG. 1 is a block diagram of a scanning electron microscope showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of designation of a reference image and a target image using a crosshair cursor, and FIG. FIG. 4 is a conceptual diagram of the movement amount calculation at the time, FIG. 4 is a diagram illustrating designation of a local shape by evaluation of detection reliability, and FIG. FIG. 6 is a diagram for explaining a local shape registration method using a crosshair cursor, and FIG. 7 is a diagram for explaining a local shape registration method using both a region cursor and a crosshair cursor. 1 ... Electron gun, 2 ... Electron beam, 3 ... Image shift coil, 4 ... Trackball, 5 ... Deflection coil,
6 ... Objective lens, 7 ... Sample, 8 ... Stage, 9 ...
… Direct current amplifier, 10 …… Deflection amplifier, 11 …… Objective lens power supply, 12 …… Detector, 13 …… Stage drive circuit, 14 …… Deflection signal generator, 15 …… A / D converter, 16 …… Image memory, 1
7 …… D / A converter, 18 …… Deflection amplifier, 19 …… for image display
CRT, 20 …… deflecting coil, 21 …… computer, 22 ……
Cursor signal generator, 23 …… Adder, 24 …… Local shape that can be easily detected and uniquely identified in the displayed image, 25 …… Target local shape on the displayed image, 26 …… Crosshair cursor.

Claims (4)

(57) [Claims] 1. A means for displaying a sample image on a display screen, an image memory for storing the sample image, and a position on the display screen of an arbitrary local shape in the sample image displayed on the display screen. In the sample image display device, including means and means for moving the visual field to an arbitrary position in the sample image based on the position information, a visual field of a predesignated local shape is moved to an arbitrary position on the display screen. In this case, instead of detecting the local shape to be moved, at least one other easy-to-detect and easy-to-identify local shape whose relative distance and direction to the local shape are known is detected, and the detected local shape is detected. A sample image display device, comprising means for moving a local shape to be originally moved to an arbitrary position based on the position of the shape and the relative distance and direction. 2. The sample image display device according to claim 1,
Detects two or more local shapes that are easy to detect and specify,
A sample image display device comprising means for moving a local shape to be originally moved to an arbitrary position based on position information of one or more high-ranking ones of them having high detection reliability. 3. A means for displaying a sample image on a display screen, an image memory for storing the sample image, and means for designating an arbitrary position on the display screen, and a position of a local shape of a moving object. By specifying at least one position of the local shape that is easy to detect and specify by the means for specifying the position on the display screen, the position of the specified local shape that is easy to detect and specify is centered. A method of registering a local shape in a sample image display device, characterized in that the partial image data to be processed and the distance from the center position to the position of the specified local shape of the moving object are stored as registration data. 4. A means for displaying a sample image on a display screen, an image memory for storing the sample image, means for designating an arbitrary position on the display screen, and means for designating a partial area, The position of the local shape of the moving object is designated by means for designating the position on the display screen, and at least one local shape that is easy to detect and identify is designated by means for designating the partial area on the display screen. Thus, in the sample image display device, the partial image data in the specified partial area and the distance from the center position of the partial area to the position of the specified local shape of the moving object are stored as registration data. Local shape registration method.