JPH1083782A - Scanning electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly move the stage of a scanning electron microscope while a specimen image is being observed. SOLUTION: An arrow 16 expressing the moving direction of the stage of scan type electron microscope is displayed in an image displaying device 12. The rotating angle 9 of the arrow 16 is calculated from the formula θ=θobj+θcoil+θstage+θrot, where θcoil is the mechanical rotating angle of a deflector, Gstage is the mechanical rotation of the coordinates for stage, θrot is the rotation in the scanning direction of the primary electron beam on the specimen generated by a deflection control power supply, and θobj is the rotation of the specimen image caused by the change in the exitation of the objective lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning electron microscope for detecting a secondary electron generated from a sample by irradiating a primary electron beam to obtain a scanned image of the sample.

[0002]

2. Description of the Related Art A scanning electron microscope uses a deflector to scan an electron beam, which is generated from an electron gun and is narrowed down, on a sample.
This is a device that forms a sample image by detecting secondary electrons generated from a sample by electron beam irradiation with a secondary electron detector and processing the detection signal in synchronization with electron beam scanning.

In this scanning electron microscope, when a primary electron beam scanned by a deflector passes through an objective lens arranged on the sample side of the deflector, the primary electron beam is rotated by the action of a magnetic field generated by the objective lens. Therefore, the scanning direction of the deflector and the scanning direction of the electron beam irradiated on the sample are different. This directly leads to rotation of the sample image, and the vertical and horizontal directions of the sample image viewed on the screen do not correspond to the stage coordinates. For this reason, the angle at which the primary electron beam is rotated by the excitation of the objective lens is calculated in advance, and the deflector is rotated and arranged by the calculated angle in the direction opposite to the direction rotated by the excitation of the objective lens. I have.

[0004]

In the above prior art, when the conditions such as the acceleration voltage of the electron beam are changed, the magnetic field of the objective lens for focusing on the sample also changes. Is not constant, and the sample image rotates. In addition, even when the height of the sample changes, the rotation angle changes for each sample because the magnetic field of the objective lens for focusing on the sample changes.
Therefore, usually, the vertical and horizontal directions of the sample image displayed on a display device such as a CRT are the coordinates of the stage (the moving direction of the stage).
It is difficult to smoothly perform an operation of immediately moving the stage while observing the sample image and moving a target portion located at a corner of the field of view to the center of the field of view.

Further, a scale or the like is displayed near the sample image in order to know the size on the sample image. However, when the sample is inclined, the actual size and the scale do not correspond. The present invention has been made in view of such problems of the related art, and has as its object to provide a scanning electron microscope that is easy to use when observing and analyzing a sample accompanied by a stage movement.

[0006]

According to the present invention, an arrow indicating a moving direction (moving axis) of a stage is displayed on an image display device for displaying a sample image. . The arrow indicating the direction of movement of the stage is realized by calculating the rotation angle of the sample image from conditions such as the acceleration voltage of the electron beam and the excitation current of the objective lens, and rotating and displaying the arrow by that rotation angle. can do. θ
When the XY stage above it is rotated by rotating the stage, when the deflector is mechanically rotated, or when the sample image is rotated by rotating the electron beam scanning direction of the deflector by the deflection control means. Also, by rotating the arrow corresponding to each, it is possible to display the accurate stage movement direction.

In addition, an arrow indicating the moving direction of the stage is displayed as a scale having a length corresponding to the magnification of the sample image, and this arrow is used as an index for knowing the size of a characteristic portion of the sample image. Can be. Moreover, by moving the arrow to an arbitrary position or setting an arbitrary length, the arrow can be used to directly know the size of the characteristic portion of the sample image. When the arrow is an obstacle to the observation of the sample image, it is hidden / displayed.
Switching of non-display may be enabled.

That is, the present invention provides an electron gun for generating an electron beam, an electron lens for narrowing down the electron beam and irradiating the electron beam on a sample, and a deflection for scanning the electron beam two-dimensionally on the sample. Detector, a detector for detecting a secondary signal generated from the sample by irradiation of the electron beam, display means for displaying the secondary signal detected by the detector as a sample image, and converting the sample to an electron beam. In contrast, a scanning electron microscope having a stage for moving, rotating, and tilting is characterized in that an arrow indicating a moving direction of the stage is displayed on a display means.

The arrows indicating the moving direction of the stage may be two arrows corresponding to a two-dimensional moving direction (moving axis) of the stage in a direction intersecting the optical axis, for example, X and Y directions. In the case where a rotating means for mechanically rotating the deflector around the optical axis is provided, the arrow indicating the moving direction of the stage is rotated in accordance with the rotation angle in conjunction with the rotation of the deflector by the rotating means. To do.

When a deflection control means for rotating the scanning direction of the electron beam by the deflector is provided, an arrow indicating the moving direction of the stage corresponds to the rotation angle in conjunction with the rotation of the scanning direction by the deflection control means. And rotate. The arrow indicating the moving direction of the stage is rotated in accordance with the rotation of the sample image by the magnetic field of the electron lens.

When the XY stage for moving the sample in the X and Y directions is mounted on the θ stage for rotating the sample, the XY stage corresponds to the rotation of the θ stage, that is, the rotation of the stage in the moving direction. Then, the arrow indicating the moving direction of the stage is rotated. The length of the arrow indicating the moving direction of the stage can be changed according to the magnification of the sample image, and a numerical value corresponding to the length of the arrow is displayed near the arrow according to the magnification of the sample image. be able to. The length of the arrow can be changed according to the inclination of the stage. Further, a numerical value corresponding to the length of the arrow can be displayed near the arrow according to the inclination of the stage.

When the arrow indicating the moving direction of the stage can be moved to an arbitrary position in the screen, the arrow can be moved to a characteristic portion of the sample and used as an index for knowing the size of the portion. If the arrow indicating the direction of movement of the stage can be made any length, the length of the arrow should be the same as the size of the characteristic part of the sample, and the length of the arrow displayed near the arrow at that time By reading the numerical value corresponding to, the size of the characteristic portion of the sample can be easily known.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram of a scanning electron microscope according to one embodiment of the present invention. Cathode 1
The cathode 1 by the voltage V1 applied between the
Is accelerated by an applied voltage V _acc applied between the cathode 1 and the acceleration electrode 4. The applied voltages V _acc and V 1 are applied by a high-voltage control power supply 19 controlled by the control CPU 21. The primary electron beam 2 is converged by the converging lens 5 controlled by the converging lens control power supply 13, and an unnecessary area is removed by the diaphragm 10. afterwards,
The sample 8 is narrowed down by the objective lens 6 controlled by the objective lens control power supply 20 and irradiated onto the sample 8. The sample 8 is two-dimensionally scanned by the two-stage deflector 7. The converging lens control power supply 13 and the objective lens control power supply 20 are controlled by a control CPU.
21. The deflection signal of the deflector 7 is controlled by a deflection control power supply 11 according to the observation magnification.

A secondary signal 14 such as secondary electrons generated from the sample 8 by the irradiation of the primary electron beam 2 is supplied to a secondary signal detector 9.
And stored in the image memory 24. CR
The image display device 12 such as T stores the stored image memory 24
Is displayed, an enlarged sample image 15 is displayed. Further, an arrow 16 indicating the moving direction of the stage with respect to the sample image 15 is displayed on the image display device 12. The sample 8 can be moved, rotated and tilted on the stage 1
7. The stage 17 is controlled for movement, rotation and tilt by a stage control unit 18.

An arrow 16 indicating the direction of movement of the stage 17
Corresponds to the X and Y coordinate axes of the stage 17 on the sample image 15, that is, the movement axis of the stage 17. An arrow 16 indicates that the coordinate system of the deflector 7 and the stage 17 is mechanically rotated around the optical axis or that the scanning direction of the primary electron beam 2 on the sample 8 is rotated by the deflection control power supply 11. The deflector 7 rotates in accordance with the rotation angle when the deflector 7 is controlled. Further, the arrow 16 rotates in accordance with the rotation angle on the sample image 15 calculated from the acceleration voltage V _acc from the high-voltage control power supply 19 and the excitation condition of the objective lens 6 from the objective lens control power supply 20. By rotating the arrows 16 correspondingly, the moving direction of the stage 17 corresponding to the coordinates of the stage 17 is displayed on the image display device 12.

Now, as shown in FIG. 2, it is assumed that the target portion 15a in the sample image 15 is displayed at the upper right corner in the sample image 15, and the operation of moving the target portion 15a to the center of the field of view is performed. Think. Conventionally, it is completely unknown how the image moves when the stage 17 is moved in which direction, so that the stage must be moved by trial and error. Therefore, conversely, the attention portion 15a may be moved out of the visual field by moving the stage to bring the attention portion 15 in the sample image 15 to the center of the visual field. However, according to the present invention, when the stage 17 is moved in the −X direction in FIG.
It is obvious at a glance that 5a moves toward the center of the visual field, and the operability is greatly improved.

Here, as shown in FIG. 2, by displaying a numerical value 22 near the arrow 16 corresponding to the length of the arrow 16 on the sample image 15 corresponding to the magnification of the sample image 15, The size of the arrow serves as an index for knowing the size of an arbitrary portion on the sample image 15. Alternatively, the length of the arrow 16 on the sample image 15 may be changed according to the magnification. At this time, the numerical value 22 indicates a value corresponding to the length of the arrow 16. Also, the arrow 16 can be moved to an arbitrary position, and by moving the arrow 16 so as to overlap the noted portion of the sample image 15, the size of the noted portion on the sample image 15 can be easily adjusted. You can know. Here, since the length of the arrow 16 can be arbitrarily changed, the distance between any two points on the sample image 15 can be measured. Furthermore, if display and non-display can be switched, it is possible to prevent the arrow from being displayed when the arrow is unnecessary or when obstructing image observation.

The tilt axis of the stage 17 is
7 is parallel to the X-axis direction, the arrow 16 representing the Y-axis is set to the numerical value 22 corresponding to the length. The numerical value 22 corresponding to the length, and the numerical value 22 corresponding to the lengths of both arrows in the cases other than the above, can be changed corresponding to the inclination angle of the stage 17, respectively. When the stage 17 is tilted, the sample image 15
You can know any size above. Here, the length of the arrow 16 may be changed according to the inclination angle of the stage 17.

FIG. 3 shows that the stage 17 is moved 30 degrees when the tilt axis of the stage 17 is parallel to the X-axis direction of the stage 17.
Numerical value 2 corresponding to the length of arrow 16 when tilted in degrees
2 represents an arrow when changing 2. As shown in the figure, the numerical value corresponding to the length of the file indicating the X-axis direction is the same as that in FIG. 2, but the numerical value corresponding to the length of the arrow indicating the Y-axis direction is changed.

FIG. 4 is a flowchart showing a procedure for displaying an arrow 16 indicating the moving direction of the stage 17 on the image display device 12. As shown in the figure, the control CPU 21 receives the mechanical rotation angle θ _coil of the deflector 7 in step 10, and receives the mechanical rotation angle θ _stage of the coordinates of the stage 17 in step 11. In step 12, the rotation angle _θobj of the primary electron beam 2 in the scanning direction by the magnetic field of the objective lens 6 is calculated.

The rotation angle θ _obj can be calculated by the following [Equation 1], where B (z) is the magnetic field distribution of the objective lens 6 on the optical axis z. Where e and m are the charge and mass of the electron, V _acc is the accelerating voltage, z _O and z
_I represents the coordinates of the object point and the image point on the optical axis z.

[0022]

(Equation 1)

In step 13, it is determined by the deflection control power supply 11 whether the scanning direction of the primary electron beam 2 is rotating, and if it is rotating, the rotation angle θ _rot is received in step 14. In step 15, the angle θ between the scanning direction of the primary electron beam 2 for scanning the sample 8 and the coordinate axis of the stage 17 is calculated. The rotation angle θ of the arrow 16 indicating the moving direction of the stage 17 can be calculated as in the following [Equation 2], with the direction in which the sample image 15 rotates counterclockwise being positive.

[0024]

In the step 16, the arrow 1 at the image magnification of the sample image 15 is set to θ = θ _obj + θ _coil + θ _stage + θ _rot
Calculate the length of 6. Further, in step 17, it is determined whether or not the stage 17 is tilted.
After recalculating the length of 6, the arrow 16 is displayed on the image display device 12 in step 19.

In order to display an arrow 16 indicating the moving direction of the stage 17 on the image display device 12, as shown in FIG.
It may be displayed in a window 2 (23b) different from the window 1 (23a) on which the sample image 15 is displayed,
If the mouse is available, move the pointer to arrow 16
May be displayed. In this way, the arrow 16 can be moved to an arbitrary position on the image display device 12.

[0026]

According to the present invention, since the moving direction of the stage is displayed on the screen displaying the sample image, the operation of moving the sample to a desired position while observing the sample image can be performed smoothly. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a scanning electron microscope according to the present invention.

FIG. 2 is a schematic diagram illustrating an example of an arrow indicating a moving direction of a stage.

FIG. 3 is a schematic diagram showing another example of an arrow indicating a moving direction of a stage.

FIG. 4 is a flowchart showing a procedure for displaying an arrow indicating a moving direction of a stage.

FIG. 5 is a schematic view showing an example for displaying an arrow indicating a moving direction of a stage.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cathode, 2 ... Primary electron beam, 3 ... Extraction electrode, 4 ... Acceleration electrode, 5 ... Focusing lens, 6 ... Objective lens, 7 ... Deflector,
8 sample, 9 secondary signal detector, 10 aperture, 11 deflection control power supply, 12 image display device, 13 convergent lens control power supply, 14 secondary signal, 15 sample image, 16 arrow, 1
7: stage, 18: stage controller, 19: high-voltage control power supply, 20: objective lens control power supply, 21: control CPU,
22 Numerical value, 23a Window 1, 23b Window 2, 24 Image memory

Claims (10)

[Claims] An electron gun for generating an electron beam, an electron lens for narrowing down the electron beam and irradiating the electron beam on a sample.
A deflector for two-dimensionally scanning the electron beam on the sample, a detector for detecting a secondary signal generated from the sample by irradiation of the electron beam, and a detector for detecting a secondary signal generated by the detector. In a scanning electron microscope including a display unit for displaying a next signal as a sample image, and a stage for moving, rotating, and tilting the sample with respect to the electron beam, a moving direction of the stage is displayed on the display unit. A scanning electron microscope displaying an arrow representing the following. 2. The scanning electron microscope according to claim 1, wherein the arrows indicating the moving direction of the stage are two arrows corresponding to a two-dimensional moving direction of the stage in a direction intersecting an optical axis. A scanning electron microscope characterized by the above-mentioned. 3. The scanning electron microscope according to claim 1, further comprising rotating means for mechanically rotating the deflector around an optical axis, wherein an arrow indicating a moving direction of the stage is determined by the rotating means. A scanning electron microscope, wherein the scanning electron microscope rotates in accordance with the rotation angle in conjunction with the rotation of the deflector. 4. The scanning electron microscope according to claim 1, further comprising: deflection control means for rotating a scanning direction of the electron beam by the deflector, wherein an arrow indicating a moving direction of the stage is:
A scanning electron microscope, wherein the scanning electron microscope rotates in accordance with the rotation angle in conjunction with the rotation in the scanning direction by the deflection control means. 5. The scanning electron microscope according to claim 1, wherein the arrow indicating the moving direction of the stage rotates in response to the rotation of the sample image by the magnetic field of the electron lens. Scanning electron microscope. 6. The scanning electron microscope according to claim 1, wherein the arrow indicating the moving direction of the stage rotates in accordance with the rotation of the stage in the moving direction. Scanning electron microscope. 7. The scanning electron microscope according to claim 1, wherein the arrow indicating the moving direction of the stage changes its length in accordance with the magnification of the sample image. Scanning electron microscope. 8. The scanning electron microscope according to claim 1, wherein a numerical value corresponding to the length of the arrow is provided in the vicinity of the arrow indicating the moving direction of the stage according to the magnification of the sample image. A scanning electron microscope characterized by displaying. 9. The scanning electron microscope according to claim 1, wherein an arrow indicating a moving direction of the stage changes in length in accordance with an inclination of the stage. Scanning electron microscope. 10. The scanning electron microscope according to claim 1, wherein a numerical value corresponding to the length of the arrow is provided in the vicinity of the arrow indicating the moving direction of the stage according to the inclination of the stage. A scanning electron microscope characterized by displaying.