JPH0343742B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sample moving device such as a scanning electron microscope, which moves a field of view by moving a sample.

[Prior Art] Recently, scanning electron microscopes have been used to observe large samples such as integrated circuit elements at low magnification. In such a case, if the field of view is moved by electromagnetic deflection, the electron beam will scan at a position quite far from the optical axis, resulting in large aberrations and making it impossible to obtain a high-quality image. Therefore, in this type of apparatus, the field of view is changed by moving the sample. Conventionally, this sample movement was
For example, as long as the button is pressed, the sample continues to move.
This was done by pressing a button so that the sample stopped when the button was released, but it is difficult for non-skilled operators to know when to release the button, making it difficult to obtain the desired field of view with a single button operation. . Therefore, the desired field of view is obtained after pressing the button several times, but since mechanically moving the sample takes time, it is difficult to obtain the desired field of view easily and in a short time. I couldn't do it.

Taking these points into consideration, marks can be displayed on the sample image display screen, and when this mark is moved to the desired position in the image on the screen, the image area indicated by the mark will be automatically displayed. A sample moving device, such as a scanning electron microscope, has been developed that moves the sample so that it is displayed in the center of the screen.

However, in such a device, if you try to select a field of view by moving the mark to the edge of the screen to follow the part of interest in the image, and then displaying the part that is not displayed on the screen beyond the edge of the screen, It was necessary to manually lower the magnification each time. Therefore, it was not possible to smoothly indicate the part of the image to be focused on using marks. Also, when I lowered the magnification, I lost sight of the part I was looking at.

[Object of the Invention] An object of the present invention is to solve these conventional drawbacks and provide a sample moving device such as a scanning electron microscope that can easily and quickly obtain a desired field of view. .

[Structure of the Invention] Therefore, the present invention provides a means for two-dimensionally scanning an electron beam on a sample, a display means for displaying a sample image based on the supply of a detection signal accompanying the scanning of the electron beam, and a means for two-dimensionally scanning an electron beam on a sample. a magnification switching means for switching the magnification by switching the scanning width of a line; a sample moving means for moving the sample; a means for displaying a mark serving as a mark of a portion of interest on the sample on the display means; and the mark. A scanning electron microscope or the like equipped with a means for arbitrarily moving the display position of the mark and a means for automatically moving the sample so that the position on the sample corresponding to the mark is displayed in the center of the screen. In the sample moving device, means for automatically lowering the magnification by controlling the magnification control means when the position of the mark is moved to the edge of the screen, and a means for automatically lowering the magnification by controlling the magnification control means when the position of the mark is moved to the edge of the screen, and The present invention is characterized by comprising a mark display position control means for controlling the mark display position to be maintained regardless of a decrease in the mark display position.

[Examples] Examples of the present invention will be described in detail below based on the drawings.
FIG. 1 is for showing the outline of one embodiment of the present invention. In the figure, 1 is an electron gun, and an electron beam 2 from the electron gun 1 is focused by a focusing lens 3 and irradiated onto a sample 4. . 5X and 5Y are deflection coils, and a sawtooth scanning signal is supplied from a scanning signal generation circuit 6 to these deflection coils 5X and 5Y via a magnification switching circuit 7. 8X and 8Y are amplifiers. The scanning signal from the scanning signal generation circuit 6 is transmitted to the cathode ray tube 9.
It is also supplied to the deflection coil S of the cathode ray tube 9.
is scanned synchronously with the electron beam 2. 10 is a secondary electron detector for detecting secondary electrons generated from the sample 4, and the output signal of this detector 10 is sent to the amplifier 1.
After being amplified in step 1, the signal is supplied to the cathode ray tube 9 as a brightness signal via a bright spot adding circuit 12. 13 is a sample stage on which the sample 4 is placed, and this sample stage is driven by pulse motors 14X, 1
4Y allows movement in the X (horizontal) direction and the Y (vertical) direction. A drive circuit 15 generates drive pulses for rotating the pulse motors 14X and 14Y. 16 is a control device for controlling the display of the bright spot and the drive of the motor, and this control device 16 includes a bright spot signal generation circuit 17;
Motor drive control circuit 18, up/down counter 19, register 20, comparator 21, 1/C circuit 2
It consists of 2. The bright spot signal generating circuit 17 is supplied with a signal synchronized with the scanning signal from the scanning signal generating circuit 6, generates a bright spot display pulse at a predetermined timing using the synchronization signal as a starting point, and uses this pulse to display the bright spot. It is supplied to the adder circuit 12. A control signal from the drive control circuit 18 is supplied to the drive circuit 15, and the drive control circuit 18 controls the amount of rotation of the motors 14X and 14Y by controlling the number of drive pulses generated by the drive circuit 15. An input device 23 is connected to the control device 16 in order to cause the control device 16 to perform the above-described control. This input device 23 inputs the bright spot to the cathode ray tube 9.
Push button switches 23a, 23b, 23c, 23d for moving up, down, left and right on the screen.
is provided. The input device is also equipped with a knob 23e for instructing the observation magnification and a set switch 23f for instructing to move the point on the sample corresponding to the bright spot onto the optical axis 24.

In such a configuration, first, the knob 23e of the input device 23 is operated to set the observation magnification to M.
As a result, a digital value representing the observation magnification value M is stored in the register 20. Since the signal corresponding to the value M from this register 20 is supplied to the magnification switching circuit 7, the peak value of the scanning signal from the scanning signal generating circuit 6 is switched to the value corresponding to the observation magnification M in this circuit 7. As a result of the scanning signal having such a peak value being supplied to the deflection coil, the electron beam 2
scans the sample 4 two-dimensionally. At this time, the cathode ray tube 9 receives an X (horizontal) direction scanning signal synchronized with this scanning from the scanning signal generation circuit 6 with a period T as shown in FIG.
is the number of horizontal scanning lines constituting one screen), a sample image with a magnification of M is displayed based on the signal from the secondary electron detector 10. When the push button switches 23a, 23b, etc. for moving the bright spot are not pressed, the count value of the up-down counter 19 is 0, so the bright spot signal generation circuit 1
7 is supplied with a signal representing 0 from the up-down counter 19, and the bright spot signal generating circuit 17 receives the vertical synchronizing signal at a timing delayed by T/2 from the k/2nd horizontal synchronizing signal as a reference. A bright spot display pulse shown in FIG. 2b is generated. Since this pulse is added to the image signal in the bright spot adding circuit 12, a bright spot _P0 is displayed at the center of the screen of the cathode ray tube 9, as shown in FIG. 3a. For example, if the operator presses the push button switch 23d for a unit time τ, the up-down counter 19 will count up by 10, and the numerical signal from this counter 19 will be supplied to the bright spot signal generation circuit 17. As shown in FIG. 2c, the point signal generation circuit 17 uses the k/2nd horizontal synchronizing signal as a reference to generate T/2+10T/240 (however, half of the horizontal length of the screen corresponds to 120). A bright spot display pulse is generated with a timing delayed by 1), and the bright spot moves by one step (i.e., 1/24) to the right of the screen, reaching _P1 in FIG. 3a.
Next, for example, if the push button switch 23c is pressed for a time of 3τ, the up/down counter 19 will be
In order to count down by 30, a signal corresponding to -20 is supplied from the counter 19 to the bright spot signal generation circuit 17. As a result, the bright spot display pulse is generated from the bright spot signal generation circuit 17 at a timing delayed by T/2-20T/240 from the k/2nd horizontal synchronizing signal as shown in FIG. 2d. , the bright spot is moved three steps to the left and displayed at position P ₂ in Figure 3a. Similarly, when the push button switch 23a or 23b is pressed, the count value of the other up-down counter (not shown) changes, and a bright spot display is generated from the bright spot signal generation circuit 17 based on this count value signal. The horizontal synchronization signal that is the starting point of the pulse changes, and the display position of the bright spot can be moved in the vertical direction. Therefore, the push button switches 23a, 23
b, 23c, and 23d, the bright spot is moved to the center of the screen where the bright spot is desired to be moved, for example, _P3 , by moving the sample. Then, when the set switch 23f is pressed, this switch 23
A signal instructing the drive control circuit 18 to supply a drive control signal is supplied from f. At this time, drive control circuit 1
8 is the signal Ux from the up-down counter 19
Since the signal Uy from the other up-down counter (not shown) representing the vertical position of the bright spot and the signal representing the observation magnification M from the register 20 are supplied, the motor 14 is activated based on these signals.
A control signal is supplied to the drive circuit 15 to generate drive pulses for rotating X and 14Y by angles AUx/M and AUy/M (where A is a proportionality constant), respectively. As a result, sample 4 is at the center of the screen (P ₀
position) to the bright spot P ₃ by the actual distance in the X and Y directions and placed on the optical axis 24, and the part of the image indicated by the bright spot P ₃ is automatically displayed in the center of the screen. be done. On the other hand, when the control signal is supplied from the drive control circuit 18, the signal from the switch 23f is supplied to the up-down counter 19 etc. after a slight delay time, and the up-down counter is cleared. Therefore, the signal supplied from the up-down counter 19 to the bright spot signal generation circuit 17 becomes 0, and the position of the bright spot displayed on the screen also changes to the central P ₀ position as the field of view moves as described above. Move to.

Furthermore, suppose that while observing this image, an area H of the image of interest is located at the edge of the screen. In such a case, when the operator moves the bright spot to the right side of the screen by operating the push button switch 23d, the count value of the up-down counter 19 increases, but the bright spot does not change as shown in FIG. If the count value reaches 100 by moving to the position _P4 indicated by the dotted line Q (not displayed on the screen) in a, the output value of the up-down counter 19 and the reference value corresponding to the position of the dotted line Q The comparator 21, which is making a comparison with 100, supplies a response signal to the 1/C circuit 22, which causes the circuit 22 to perform an operation. Since the 1/C circuit 22 is supplied with a signal corresponding to the magnification value M from the register 20, this operation changes the magnification value M by 1/
A signal corresponding to the numerical value M/C multiplied by C (C is 2, for example) is generated, and this multiplication value signal is newly stored in the register 20. Due to this change in signal value, the magnification switching circuit 7 increases the amplification factor of the scanning signal so that the observation magnification becomes M/C. As a result, the area H of interest is displayed more centrally on the screen of the cathode ray tube 9, as shown in FIG. 3b. On the other hand, since the output signal of the up-down counter 19 is also supplied to the 1/C circuit 22 (actually, the other 1/C circuit provided separately),
As a result of the calculation by the 1/C circuit 22, the circuit 22 outputs a value 100/C, which is the count value 100 of the up-down counter 19 multiplied by 1/C, and this value is newly set in the up-down counter 19. . Therefore, the bright point P ₄ is the point P ₅ in Fig. 3b.
, and the relative position with area H is displayed at the same point on the lower magnification screen. Therefore, if the switch 23d is further pressed for a time of 2τ, the count value of the up-down counter 19 becomes 100/C+20, and at this time, the output pulse from the bright spot signal generation circuit 17 becomes as shown in FIG. _P5 moves two steps to the right and becomes the bright spot in Figure 3b.
Becomes _P6 . If the position of this bright spot _P6 is the part of the image that you want to move to the center of the screen, press the set switch 23f here. As a result, as in the case described above, the drive control circuit 18 controls the bright spot _P6 and the center of the screen based on the signal corresponding to 100/C+20 from the up-down counter 19 and the signal corresponding to M/C from the register 20. The actual X with the point (P ₀ ) of
A drive control signal is sent to the drive circuit 15 to move the sample stage 13 by the directional distance. the result,
The drive circuit 15 supplies drive pulses to the motor 14X to rotate the motor 14X at an angle A(100/C+20)/
By rotating it by (M/C), the point on the sample at the position of the bright spot P ₆ is placed on the optical axis 24. While the sample 4 is being moved in this way, the set switch 2
The signal from 3f is supplied to the register 20, and the value stored in the register 20 is returned to a signal representing the magnification M given by the knob 23e. Therefore, the magnification switching circuit 7 is switched to set the observation magnification to M. Furthermore, after the drive control circuit 18 operates, a signal from the set switch 23f is supplied to the up-down counter 19, and the counter 19 is cleared.
The output of the counter 19 is set to 0. Therefore, bright spots
As P ₆ moves to the center of the screen, the part corresponding to the bright spot P ₆ moves to the center of the screen, and an image as shown in FIG. 3c is obtained.

In addition, in the above explanation, for the sake of simplicity, we have explained the case where the bright spot moves only in the A desired image is displayed by control.

Note that the present invention is not limited to the embodiments described above, and can be modified in many ways. For example, in the above-described embodiment, a bright spot is displayed as a landmark, but it is also possible to display a bright line movable in the horizontal and vertical directions, and use the intersection of these two bright lines as a mark. It's okay. Alternatively, a surrounding line of a certain size may be displayed as a mark, or an area of a certain size may be displayed with higher brightness or contrast than other parts to distinguish it from others. good.

[Effects] As described above, in the apparatus based on the present invention, when observing a sample image and moving the mark to the center of the field of view and following the part to be observed and moving the mark to the edge of the screen, the magnification is automatically adjusted. As a result, it becomes easier to track the part you want to observe.

Furthermore, at this time, the relative position of the mark and the sample image is maintained even on the screen after the magnification is lowered, so even if the sample has a low contrast, you will not lose sight of the part of the sample that you were paying attention to, making the field of view selection operation easy and It can be done smoothly.

[Brief explanation of drawings]

Fig. 1 is a diagram showing one embodiment of the present invention, Fig. 2 is a diagram showing output signals from each circuit shown in Fig. 1, and Fig. 3 is a diagram showing changes in display on a cathode ray tube screen. It is a figure for explaining. 1: Electron gun, 2: Electron beam, 3: Converging lens,
4: Sample, 5X, 5Y: Deflection coil, 6: Scanning signal generation circuit, 7: Magnification switching circuit, 8X, 8Y, 1
1: amplifier, 9: cathode ray tube, 10: secondary electron detector, 12: bright spot addition circuit, 13: sample stage,
14X, 14Y: pulse motor, 15: drive circuit, 16: control device, 17: bright spot signal generation circuit,
18: Drive control circuit, 19: Up/down counter, 20: Register, 21: Comparator, 22: 1/
C circuit, 23: input device, 23a, 23b, 23
c, 24d: push button switch, 23e: indicator knob, 23f: set switch, 24: optical axis.

Claims (1)

[Claims] 1. A means for two-dimensionally scanning an electron beam on a sample, a display means for displaying a sample image based on the supply of a detection signal accompanying the scanning of the electron beam, and a magnification by switching the scanning width of the electron beam. a magnification switching means for switching, a sample moving means for moving the sample, a means for displaying a mark serving as a mark of a portion of interest on the sample on the display means, and a means for arbitrarily moving the display position of the mark. In a sample moving device such as a scanning electron microscope, which is equipped with a means for automatically moving the sample so that the position on the sample corresponding to the mark is displayed in the center of the screen, the position of the mark is displayed. means for automatically reducing the magnification by controlling the magnification control means when the mark is moved to an edge of the screen, and a position of the mark relative to the sample image is maintained regardless of the decrease in the magnification; A sample moving device such as a scanning electron microscope, characterized in that it is equipped with a mark display position control means for controlling the position of a mark.