JPH057817B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sample rotation device in a charged particle beam apparatus such as an electron microscope.

In many mechanical sample rotation and movement mechanisms incorporated in electron microscopes and the like, various inconveniences arise because the position of the sample irradiated by the electron beam does not coincide with the center of rotation when the sample is rotated. For example, a scanning electron microscope has the advantage of being able to obtain a clear image even if the surface of the observation sample is highly uneven, but in order to take full advantage of this advantage, it is necessary to move the sample surface in any direction with respect to the irradiated electron beam. It is necessary to be able to tilt the axis so that the portion corresponding to the shadow of the unevenness can be observed. In many cases, a sample device that changes the sample position has a fixed sample tilting direction in one direction, and therefore cannot tilt the sample as desired. FIG. 1 shows the configuration of such a conventional sample apparatus, in which a tilting mechanism 2 is attached to a side wall 1 of a sample chamber, and its tilting axis is fixed in the X direction. At the top of the tilting mechanism 2,
There is an XY movement mechanism 3, and a rotation mechanism 4 above it.
is mounted, and the observation sample 5 is attached to the rotation mechanism 4 via a holder. In order to tilt the sample surface in any direction with respect to the sample irradiation electron beam 6 using such sample placement, it is sufficient to operate the rotation mechanism 4 and the tilt mechanism 2 in combination, but the XY movement mechanism 3
If the rotation center of the rotation mechanism is shifted from the optical axis Z due to the operation of the rotation mechanism 4, there is a drawback that the field of view of the scanned image being observed is lost due to the operation of the rotation mechanism 4.

By the way, the sample rotation operation by the image observer is performed by turning a rotation knob attached to the operation panel left and right. At this time, it is not a problem for experts, but for beginners, it is important to know in which direction the rotation knob should be turned to rotate the field of view in the desired direction, and how far the rotation knob should be turned to achieve the desired field of view. I don't know if it will rotate by the amount.

The present invention has been made in view of these points, and its purpose is to provide a sample rotation device for a charged particle beam device that can reliably rotate the field of view by a desired amount in a desired direction without visual field deviation. It's about doing.

The sample rotation device in the charged particle beam apparatus of the present invention that achieves this objective includes an XY movement mechanism that moves the sample in two XY directions orthogonal to each other, a rotation mechanism placed on the XY movement mechanism, and a rotation mechanism that irradiates the sample. Immediately before the sample rotation operation in a sample rotation device in a charged particle beam device equipped with an electric XY movement means that electrically moves the field of view of an electron microscope image by deflecting the electron beam or the electron beam that passes through the sample. The states of the XY moving mechanism and the rotating mechanism are stored as initial signals, and the electron beam on the sample before rotation is determined based on the initial signal and a change signal indicating a change from the initial state of the rotating mechanism. visual field correction means for creating a control signal for moving the irradiation center of the electron beam in the direction of movement by an amount that the irradiation center moves based on sample rotation, and supplying the control signal to the electric XY moving means; and the rotation mechanism. The present invention is characterized by comprising means for displaying marks in the cathode ray screen indicative of the direction and amount of rotation of the field of view caused by the rotation operation, based on the output from the rotation operation means for supplying a rotation signal to the rotation operation means.

FIG. 2 is a schematic diagram showing an embodiment of the present invention, and the same reference numerals as in FIG. 1 represent the same components. In Figure 2, sample 5
is irradiated by a narrowly focused electron beam 6, and the irradiation position changes depending on the deflection signals supplied to the deflection coils 7X, 7Y. Deflection coil 7X, 7
Since the scanning signal from the scanning circuit 8 is supplied to Y via the magnification circuit 9 and the addition circuit 10, the sample 5
A certain area is two-dimensionally scanned by the electron beam, and its width is changed by operating a magnification circuit 9 consisting of a variable amplifier. The output of the scanning circuit 8 is also supplied to the deflection coils 12X and 12Y of the cathode ray tube 11, and the output of the detector 13 which detects the secondary electron signal emitted from the sample 5 as the brightness modulation signal of the cathode ray tube 11 is supplied to the deflection coils 12X and 12Y of the cathode ray tube 11. Since the light is supplied through the amplifier 14, a brightness modulated scanning image is displayed on the screen of the cathode ray tube 11. In the figure, 15 and 16 indicate (pulse) motors for moving in the X direction and moving in the Y direction, respectively.
Reference numerals 17 and 18 indicate (pulse) motors for driving the rotating mechanism 4 and the tilting mechanism 2, respectively. These motors are controlled based on control signals from the central control circuit 19, and drive control for each motor is performed by the X movement knob 20, Y movement knob 21, tilt knob 22, and rotation knob connected to the central control circuit 19. This is done by operating the knob 23. Regarding the rotary knob 23, a switching circuit 24 is provided between it and the central control circuit 19, and the switching circuit 24 converts the rotation signal related to the visual field rotation control given from the rotary knob 23 in response to the input signal from the set circuit 26. It is configured to apply the signal to the bright line display circuit 25 or the central control circuit 19. The bright line display circuit 25 controls the cathode ray tube 11 based on signals from the scanning circuit 8 and the rotary knob 23, as shown in FIG.
This is to generate a signal for displaying a bright line 27 representing the amount and direction of rotation of the field of view by the rotation knob 23 on the screen. In such a configuration,
When the sample 5 is rotated by the rotation mechanism 4, the field of view displayed on the cathode ray tube screen is rotated, and the center of rotation is moved by operating the XY movement mechanism 3. Therefore, the XY coordinates indicated by the XY sample moving mechanism 3 in a state where the center of this field of view rotation coincides with the center of the cathode ray tube screen are defined as the coordinate origin (0,0).

The visual field rotation operation using the apparatus shown in FIG. 2 is performed in the following steps.

(a) First, the rotation mechanism 4 and the tilting mechanism 2 are kept in the standard state, that is, the rotation angle φ = 0 and the tilt angle θ = 0, and from this initial state, the desired field of view is obtained on the cathode ray tube screen. Operate the XY movement mechanism 3. If the coordinates at this time are (X ₁ , Y ₁ ), the distance r from the origin is r=√2 ₁ +2 ₁ .

(b) Next, operate the rotation knob 23 to determine the desired visual field rotation direction and rotation amount φ ₀ . At this time, since the set circuit 26 has not yet been operated, the rotation signal from the rotation knob 26 is transmitted to the bright line display circuit 25.
The actual sample rotation is not performed. The bright line display circuit 25 displays a bright line 27 on the cathode ray tube screen, as shown in FIG. can be used as a guide for operating the rotary knob 23.

(c) Next, operate the set circuit 26 to set the hold circuit 2
Switch the signal output at 4 and turn the rotary knob 2.
The rotation signal from 3 is input to the central control circuit 19 instead of the brightness display circuit 25. As a result, the bright line 27 disappears from the screen of the cathode ray tube 11, and at the same time, a control signal based on the rotation signal input to the central control circuit 19 is given to the motor 17, and the rotation mechanism 4 moves the sample 5 to the origin of the XY coordinates. Rotate by an angle φ ₀ around . Due to this rotation, the coordinate position of the sample 5 also changes, and FIG. 4 shows this state. In Figure 4, the coordinate position before sample rotation is S ₀
(X ₁ , Y ₁ ), and the coordinate position when rotated by a minute angle φ ₀ is S ₁ (X ₁ +ΔX, Y ₁ +ΔY),
Change in X direction ΔX and Y when moving from S ₀ to S ₁
The direction change ΔY is expressed as follows.

ΔX=-r・φ ₀・sinφ ₀ ΔY=r・φ ₀・conφ ₀ In order to correct the sample movement based on such sample rotation, the central control circuit 19 calculates the movement component in the above equation and calculates its inverse A correction deflection signal is applied to the adder circuit 10 such that the field of view is shifted in the direction. The adder circuit 10 adds these correction deflection signals to the X and Y scanning signals to move the scanning center of the electron beam that scans the sample 5 by ΔX in the X direction and by ΔY in the Y direction.
Field shift on the cathode ray tube screen is prevented.

By the way, if the angle φ ₀ is not small or if the sample 5 is tilted by the tilting mechanism 2 and the initial state is different from the above operation example, it is possible to prevent the field of view from shifting by using geometric considerations instead of Fig. 4. The central control circuit 19 pre-programs a program for calculating the deflection components for the
All you have to do is store it in your memory.

FIG. 5 shows an embodiment in which the present invention is applied to a transmission electron microscope, and the same symbols as those used in FIG. 2 represent the same components. In FIG. 5, 28 indicates a fluorescent screen placed further below the imaging lens system (not shown) placed below the thin film sample 5, and 29 and 30 indicate deflection screens placed above and below the sample 5. The coil is shown. Deflection currents having intensities at a constant ratio are supplied to the coils 29 and 30 from a deflection power source 31, and by adjusting the output of the deflection power source 31, the path of the electron beam irradiating the sample is changed, for example, as shown by the broken line in the figure. It is possible to move the field of view of the electron microscope image formed on the fluorescent screen by moving the fluorescent screen. Further, the cathode ray tube 11 is for receiving a rotation signal from the rotation knob 23 into a bright line display circuit 32 and displaying bright lines representing the direction and amount of rotation of the field of view of a transmission electron microscope image formed on a fluorescent screen. . The operation of the apparatus of FIG. 5 is substantially the same as that of the apparatus of FIG. 2, except that the method of electrical field movement is slightly different.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments shown in FIGS. 2 and 5. For example, if the control to prevent deviation of the field of view is performed only by using the deflection device, the influence of deflection distortion will gradually increase. It's okay. Furthermore, the present invention can be easily applied to devices other than electron microscopes, such as X-ray microanalyzers and ion microanalyzers, which have the function of displaying image information about a sample using a charged particle beam. .

As explained above, in the present invention, the irradiation center of the electron beam on the sample before rotation is determined based on the sample rotation based on the change signal indicating the change from the initial state of the rotation mechanism and the initial signal. visual field correcting means for creating a control signal for moving the irradiation center of the electron beam in the direction of the movement by the amount of movement and supplying it to the electric XY moving means; Since a means for displaying marks indicating the direction and amount of rotation of the sample is provided, the observer can simply indicate the desired direction and amount of rotation using the marks, without causing visual field shifts due to rotation of the sample. Since it is possible to reliably observe an image in a desired rotational state, the rotation operation of the sample by the observer can be significantly improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the structure of a conventional sample device, Fig. 2 is a schematic diagram showing an embodiment of the device of the present invention, and Figs. 3 and 4 are schematic diagrams for explaining the operation of the device shown in Fig. 2. , FIG. 5 is a schematic diagram showing another embodiment of the present invention. 1...Sample chamber side wall, 2...Tilt mechanism, 3...
XY movement mechanism, 4...Rotation mechanism, 5...Sample, 6
...Electron beam, 7X, 7Y...Deflection coil, 8...
Scanning circuit, 9... Magnification circuit, 10... Addition circuit,
11...Cathode ray tube, 12X, 12Y...Deflection coil, 13...Detector, 14...Amplifier, 15,1
6, 17, 18...Motor, 19...Central control circuit, 20...X movement knob, 21...Y movement knob, 22...Tilt knob, 23...Rotation knob,
24...Switching circuit, 25...Bright line display circuit, 26
...Set circuit, 27... Bright line, 28... Fluorescent screen, 29, 30... Deflection coil, 31... Deflection power supply, 32... Bright line display circuit.

Claims (1)

[Claims] 1. An XY moving mechanism that moves the sample in two mutually orthogonal X and Y directions, a rotating mechanism placed on the XY moving mechanism, and a rotating mechanism that deflects the electron beam that irradiates the sample or the electron beam that passes through the sample. In a sample rotation device in a charged particle beam apparatus equipped with an electric XY movement means for electrically moving the field of view of an electron microscope image, the states of the XY movement mechanism and rotation mechanism immediately before the sample rotation operation are stored as an initial signal. and based on a change signal indicating a change from the initial state of the rotation mechanism and the initial signal, the direction of the movement is determined by the amount by which the irradiation center of the electron beam on the sample before rotation moves based on the rotation of the sample. Cathode rays are generated by the output from the visual field correction means that creates a control signal for moving the irradiation center of the electron beam and supplies it to the electric XY moving means, and the rotation operation means that supplies a rotation signal to the rotation mechanism. 1. A sample rotation device for a charged particle beam apparatus, comprising means for displaying marks on a screen that indicate the direction and amount of rotation of a field of view caused by a rotation operation.