JPH036616B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam deflection control device that enables observation in an electron microscope while keeping the field of view fixed during sample movement.

In an electron microscope, a sample is placed on a sample stage in a clean, evacuated sample chamber, and when an electron beam is projected onto the sample, the electrons emitted from the sample surface, transmitted through the sample, or absorbed by the sample are collected. Detection and observation of the surface or internal structure of the sample.

By the way, in a scanning electron microscope, there is a problem in that if the deflection angle of the electron beam that scans the sample surface becomes too large, deflection distortion occurs, so it is necessary to avoid increasing the deflection angle. The sample stage can not only be moved vertically, horizontally, and vertically by external operation, but also tilted or rotated so that the specimen can be observed. In addition to manual operation, the sample stage can be moved at a constant speed in the horizontal (X) direction and vertical (Y) direction using two step motors attached to the sides of the sample stage.
In the case of motor drive, it can be operated by operating a button provided on the outside.

By the way, when observing an electron microscope image, the sample is sometimes observed while moving the sample stage.In such cases, when using a conventional electron microscope, when the sample stage is moved within a plane by motor drive,
For beginners, the sample stage may not stop at the desired position depending on the movement speed or the timing of releasing the operation button, and the desired part of the sample cannot be observed unless the positioning operation is performed several times. There was a problem that I could not make observations as I wanted.

In view of the above points, the present invention is designed to deflect the electron beam by a deflection amount corresponding to the moving direction and moving speed of the sample stage while it is moving. By doing this, the observation field of view stops moving at the same time as the sample stop operation, making it easy to select the observation field of view.

The present invention will be explained below based on the drawings.

FIG. 1 is a block diagram of an electron beam deflection control device during movement of a sample stage in a scanning electron microscope. Inside the lens barrel 1 of the electron microscope,
Filament 11 and anode 1 constituting the electron gun
2, a condenser lens 13, a deflection coil 14 that deflects the electron beam generated from the electron gun, an objective lens 15, and a sample stage 16 on which the sample S is placed.
The sample stage 16 is motor-driven and has moving step motors 16a, 16.
b is attached. 2 is sample stage 16
An input circuit 3 includes operation buttons for moving the sample stage 16, and an input circuit 3 outputs step motor drive signals (X direction, Y direction, Z direction) for moving the sample stage 16 based on input signals from the input circuit 2. A control unit outputs a deflection control signal corresponding to the amount of movement of the stage 16; 4 is a step motor drive circuit that drives the step motors 16a and 16b of the sample stage 16 based on a drive signal output from the control unit 3; 5 is a control unit; a D/A converter 6 that converts the deflection control signal output from the section 3 into an analog signal;
7 corresponds to the scanning signal generated from the scanning signal generating circuit 6 and the sample stage movement amount output from the D/A converter 5. The output of the adder 7 is given to the deflection coil 14.

Next, the operation of the electron beam deflection control device according to the present invention will be explained with reference to FIG.

For convenience of explanation, an example will be described in which the sample stage 16 is moved in one direction (for example, in the X direction) by an external button operation.

FIG. 2A shows the temporal change in the moving speed of the sample stage 16. When the input circuit 2 (operation button) is operated at time A to start moving, the sample stage 16 receives the command from the control unit 3. As a result, the position of the sample stage 16 changes as shown in FIG. 2B. On the other hand, at this time, the control unit 3
A deflection control signal corresponding to the acceleration of the sample stage 16 is output from the D/A converter 5, and is converted into an analog signal by the D/A converter 5. This deflection control signal is sent to the adder 7
The signal is added to the scanning signal from the scanning signal generating circuit 6 and applied to the deflection coil 14. the result,
The electron beam gradually begins to be deflected in the direction opposite to the moving direction of the sample stage 16 at the deflection speed shown in FIG. Move little by little as shown in E.

Thereafter, at time B, when the acceleration of the sample stage 16 stops and the movement starts at a constant speed, the deflection speed based on the deflection control signal output from the control section 3 also becomes zero as shown in FIG. 2C, and the amount of deflection also decreases. D becomes constant as shown by b. At this time, the observation field also moves at a constant speed.

Thereafter, when the stop button is pressed at time C and a stop signal is output from the input circuit 2, the sample stage 16 enters deceleration operation as shown in FIG.
Along with this, the deflection speed also gradually decreases as shown in FIG. 2C, and the amount of deflection of the electron beam also gradually decreases as shown by C in FIG. 2D. During this time, the observation field does not move.

At time D, the movement of the sample stage 16 stops, and the amount of deflection of the electron beam also becomes zero.

FIG. 2E shows the moving distance of the origin of the observation field while the sample stage 16 moves.

What is important in the above deflection control is that when the moving speed of the sample stage 16 changes linearly between the acceleration period and the deceleration period as shown in Figure 2A, it is necessary to The point is that it is necessary to change the deflection control signal quadratically during the period.

FIG. 3 shows changes in the state of the observation field due to movement of the sample stage, and A shows the state when the stop button is pressed (time C in FIG. 2 A). B shows the state when the sample stage 16 is subsequently stopped (time D in FIG. 2A).
In the figure, 21 is the electron beam, 22 is the moving direction of the sample stage, 23 is the sample, N is the center of the scanning area (observation field of view), M is the intersection of the axis of the electron lens and the sample stage, and M' is at time C. Time D at point M on the sample
It shows the position in . As can be seen from this figure, after the sample stage 16 enters constant speed operation, no matter when you press the stop button, you can observe with the observation field at the time you pressed the stop button. The observation field of view does not change depending on the speed of movement,
Therefore, it is convenient for beginners to observe.

For convenience of explanation, the above embodiment describes the case where the sample stage moves only in the X direction, but the case where the sample stage moves in the Y direction and the case where it moves at a certain angle in the X and Y directions are exactly the same. be.

FIG. 4 is a block diagram when the electron beam deflection control device according to the present invention is applied to a transmission electron microscope, in which the same reference numerals as in FIG. 1 indicate the same components.

Inside the lens barrel 1, in addition to a filament 11, an anode 12, a condenser lens 13, and a deflection coil 14 that constitute an electron gun, there are a sample stage 17 on which a sample S is placed, an objective lens 18, and an intermediate lens 1.
9, a projection lens 20, and a fluorescent plate 21 are arranged, and the sample stage 17 can be moved by a step motor (not shown).
Similar to the embodiment shown in FIG. 1, when the input circuit 2 is operated to start or stop the movement of the sample stage 17, a drive signal is output from the control section 3.
The sample stage 17 is driven via the step motor drive circuit 4. As the sample stage 17 moves at an accelerated, constant speed, or decelerate, the control section 3 outputs a deflection control signal as shown in FIG. 2D, which is applied to the deflection coil 14. As a result, the electron beam is moved in the opposite direction to the moving direction of the sample stage 17, and when a stop signal is input from the input circuit 2, the amount of deflection is gradually reduced, and when the sample stage 17 stops, the amount of deflection is made zero. .

In this way, the observation field of view when the stop button is pressed from the outside can be observed even after the stop, so that the desired part of the sample can be reliably observed with a single movement operation. Note that the present invention is not limited to the apparatus of the above-mentioned embodiments; for example, the electron beam is not deflected when the sample stage starts moving, but is deflected in the moving direction by an amount corresponding to the moving speed only when the sample stage stops moving. It is possible to simplify the configuration of the device by deflecting the electron beam by only a certain amount. However, in this case, there are problems such as irregular movement of the observation field when the sample stage starts moving, and the need to cancel the deflection of the electron beam sometime after the sample stage stops. arise.

As explained above, in the present invention, the electron beam is deflected in the opposite direction to the moving direction while the sample is moving, and when the sample stops, the electron beam is returned to the axis. The observation field of view is fixed regardless of the timing of the stop operation or the moving speed of the sample, and even beginners can accurately stop sample movement with simple operations.

[Brief explanation of the drawing]

FIG. 1 is a block diagram when the electron beam deflection control device according to the present invention is applied to a scanning electron microscope.
Figure 2 is a diagram explaining the electron beam deflection control, in which A is the change in the speed of the sample stage, B is the position of the sample stage, C is the change in the electron beam deflection speed, D is the change in the amount of electron beam deflection, and H is the change in the electron beam deflection amount. are diagrams showing changes in distance from the starting point of view to the currently observed field of view, respectively.
FIG. 3 is a diagram illustrating movement of the observation field due to movement of the sample stage, and FIG. 4 is a block diagram when the electron beam deflection control device according to the present invention is applied to a transmission electron microscope. DESCRIPTION OF SYMBOLS 1... Lens barrel, 2... Input circuit, 3... Control part, 4... Step motor drive circuit, 5... D/A converter, 6...
Scanning signal generation circuit, 7...adder.

Claims (1)

[Claims] 1 Based on a stop signal instructing the stop of movement of the sample stage, the electron beam is deflected by approximately the same amount as the amount of movement of the sample stage to be moved thereafter, and the electron beam is irradiated when the stop signal is generated and when the stage is stopped. An electron beam deflection control device characterized in that the areas are made to substantially match each other.