JPH035020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron beam device capable of displaying electron channeling patterns.

[Prior Art] As shown in Fig. 1, if the electron beam is sequentially angularly scanned in the directions of θx and θy while the incident point P is fixed as the irradiation point of the electron beam on the sample S, the bragg condition is satisfied. Two lines parallel to the crystal plane are displayed on the display screen as the trajectory of the angle. Note that OL indicates an objective lens. An image consisting of a set of two lines like this is called an electron channeling pattern, and by analyzing this electron channeling pattern, we can understand the crystal surface habit, grain boundaries, and crystal orientation relationships between different phases. Observation of electron channeling patterns has recently become widespread because it allows us to know things like this.

Figure 2 shows a conventional device for observing electron channeling patterns. In the figure, 1 is an electron gun, and the electron beam EB from this electron gun 1 is focused by focusing lenses 2 and 3. After that, the light passes through the objective aperture 4 and enters the deflection system. The deflection system is the first one for scanning in the X (horizontal) and Y (vertical) directions.
A first stage scanning coil 5ax, 5ay, a second stage scanning coil 5bx, 5by for scanning in the X and Y directions, and a first stage disposed immediately outside the scanning coil 5ax, 5ay.
It consists of alignment coils 6bx, 6by arranged just outside of the stage alignment coils 6ax, 6ay and scanning coils 5bx, 5by. These alignment coils 6ax, 6ay, 6bx, 6
By can be supplied with deflection current from deflection power supplies 7ax, 7ay, 7bx, and 7by. The electron beam EB deflected by each scanning coil and alignment coil is irradiated onto a sample 10 through a dynamic focus lens 8 and an objective lens 9. 11X is a scanning signal generation circuit that generates a scanning signal in the X direction as shown in FIG. It's getting old. 11Y is a scanning signal generation circuit that generates a scanning signal in the Y direction as shown in FIG. It's getting old.
The X and Y direction scanning signals from the scanning signal generation circuits 11X and 11Y are sent to the scanning coil of the cathode ray tube CR.
It is also supplied to CRx and CRy, and the cathode ray tube CR is scanned in synchronization with the scanning of the electron beam EB. Moreover, the scanning signal generation circuits 11X, 11Y
These scanning signals are supplied to adder circuits 13X and 13Y via switches Sx and Sy, respectively. Signals from potentiometers 14X and 14Y are supplied to these adder circuits 13X and 13Y, respectively. The output signals of adder circuits 13X and 13Y are supplied to squaring circuits 15X and 15Y, respectively. The output signals of these square circuits 15X and 15Y are output from the adder circuit 1.
6, and the output signal of the adder circuit 16 is supplied to the dynamic focus lens 8 via a variable gain amplifier 17. In this dynamic focus lens 8, when Cs is the spherical aberration coefficient of the objective lens, the focal length F of the objective lens is apparently shifted by ΔF∝Cs(Xi ² +Yi ² )...(1) due to spherical aberration. This is to correct this shift by shifting the focal length by the amount given by equation (1) in synchronization with the scanning of the electron beam. 18
is a secondary electron detector, and the output signal from this detector 18 is supplied via an amplifier 19 to the grid CRg of the cathode ray tube CR.

In the conventional device with such a configuration, in order to utilize the correction effect of the dynamic focus lens and observe the electron channeling pattern in an extremely small area, first, the deflection power source 7ax,
Each deflection coil 6ax, 6 from 7ay, 7bx, 7by
Adjust the deflection current supplied to ay, 6bx, 6by,
The axis of the dynamic focus lens 8 and the axis of the objective lens 9 are aligned. After that, for example, a mesh is set as the sample 10, and the excitation intensity of the focusing lens 3 and the switch circuits 12X and 12Y are adjusted to generate an electron beam as shown by the dotted line in FIG.
The EB is deflected using the center of the objective lens 9 as a deflection fulcrum, whereby the sample 10 is two-dimensionally scanned to obtain a normal scanned image. As a result, a mesh image as shown in FIG. 4a is obtained on the screen of the cathode ray tube CR. Therefore, after moving the sample 10 so that the intersection of the grid lines constituting this mesh is located at the center of the screen, the excitation intensity of the focusing lens 3 is switched and the switch circuits 12X, 12
A scanning signal is supplied to the scanning coils 5ax and 5ay via Y, so that the electron beam EB scans the front focal plane S of the objective lens 9, as shown by the thin line in FIG. As a result, the electron beam EB is angularly scanned while being irradiated onto a narrow area on the sample 10. Therefore, an image as shown in FIG. 4 is displayed on the cathode ray tube CR. In FIG. 4b and FIG. 4c, which will be described later, ``A'' indicates the grid lines forming the mesh. Therefore, if the switches Sx and Sy are closed, the X and Y direction scanning signal generation circuits 11X and 1
From 1Y, scanning signals as shown in FIGS. 3a and 3b are supplied to adder circuits 13X and 13Y, respectively. Since the adder circuits 13X and 13Y are supplied with signals corresponding to the values a and b from the potentiometers 14X and 14Y, respectively, the output signals of the square circuits 15X and 15Y are (Xi-a) ² and ( Yi−b) will be proportional to ² . Therefore, a signal K{(Xi-a) ² +(Yi-b) ² } is supplied to the dynamic focus lens 8 via the variable gain amplifier 17, where K is a proportionality constant. Therefore, the movement of the irradiation area of the electron beam EB due to the spherical aberration of the objective lens is corrected, although not completely, and the image displayed on the cathode ray tube CR becomes as shown in FIG. 4c. As is clear from this figure, it is generally not possible to perfectly align the axes of the dynamic focus lens 8 and objective lens 9, so the center point Q (not actually displayed) when the electron beam EB is locked is takes various positions off the center of the screen. On the other hand, since the center point of correction by the dynamic focus lens 8 is located at a position corresponding to the phase values a and b, in the initial state, the center point of locking and the center point of correction generally do not coincide; Even if the amplification factor of the variable amplification factor amplifier 17 is increased as it is, the correction by the dynamic focus lens 8 cannot be effectively performed. Therefore,
The outputs of the potentiometers 14X and 14Y are adjusted so that the center of correction where K{(Xi-a) ² +(Yi-b) ² } becomes 0 coincides with the locking center Q.

[Problems to be Solved by the Invention] However, in this adjustment in the conventional device, the amplification factor of the variable amplification factor amplifier 17 is increased each time the outputs of the potentiometers 14X, 14Y are changed, and thereby the image obtained is From the uneven brightness shown in Figure 4 (d) to the uniform brightness shown in Figure 4 (e), it was necessary to repeat trial and error, and the adjustment required time and skill. .

SUMMARY OF THE INVENTION An object of the present invention is to solve these conventional drawbacks and provide an electron beam apparatus that can perform the above adjustment simply and in a short time.

[Configuration of the Invention] The X-direction and Y-direction scanning signals of the present invention are Xi,
When Yi, Xi,
Yi is supplied to scan the front focal plane of the objective lens with an electron beam, and a dynamic focus lens placed near the objective lens contains phase values a and b (Xi - a) ² + (Yi-b) ² is supplied to correct the movement of the electron beam irradiation position based on the spherical aberration of the objective lens, the electron beam travels in an angle, and the detection signal accompanying the angular scan is applied to the scan. In a device configured to display an electron channeling pattern by guiding it to a display means that is synchronously scanned, as the phase values a and b are adjusted, the electron channeling pattern corresponds to the values of a and b on the screen of the display means. The apparatus is characterized by comprising means for displaying a mark at a position.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 5 is for showing one embodiment of the present invention, and in FIG. 5, the same components as in FIG. 2 are given the same numbers. Unlike the prior art, the output signals of the potentiometers 14X, 14Y are supplied to comparison circuits 20X, 20Y, respectively. The comparison circuits 20X and 20Y each have the
Direction and Y direction scanning signal generation circuits 11X, 11Y
Further scanning signals are also supplied. The output signals of the comparison circuits 14X and 14Y are supplied to the addition circuit 21. The output signal of the amplifier 19 is also supplied to the adder circuit 21 . The output signal of the adder circuit 21 is supplied to the grid CRg of the cathode ray tube CR.

In such a configuration, the scanning signal generation circuit 1
1X and 11Y are supplied with scanning signals as shown in FIG. 3a and b, and these comparison circuits 20
X, 20Y are potentiometers 14X, 14Y
A coincidence pulse is generated when the output signal value of and the X and Y direction scanning signal values match. This coincidence pulse is added to the image signal from the secondary electron detector 20 in the adder circuit 19, and is added to the grid of the cathode ray tube CR.
CRg, Lx and Ly are placed on the screen of the cathode ray tube CR at positions corresponding to the output signal values a and b of the potentiometers 14X and 14Y in Fig. 6.
Bright lines as shown are displayed superimposed on the image. Therefore, the switches Sx and Sy are closed, and the signals from the X and Y direction scanning signal generation circuits 11X and 11Y are
Addition circuits 13X and 13 add scanning signals as shown in FIG.
If it is supplied to Y, a signal of K{(Xi-a) ² +(Yi-b) ² } is supplied to the dynamic focus lens 8 via the variable amplification factor amplifier 17, where K is a proportionality constant. Therefore, an image similar to the image shown in FIG. 4C can be displayed on the cathode ray tube 10.
So, once this screen is obtained, adjust the output signals of potentiometers 14X and 14Y to
As shown by the dotted line in the figure, the intersection point U of the bright lines is made to coincide with the locking center point Q. As a result, at the locking center point Q, the correction signal value supplied to the dynamic focus lens 9 is 0.
The spherical aberration of the objective lens 8 is corrected using this rocking center as the correction center. Therefore, by increasing the amplification factor of the variable amplification factor amplifier 17, an image with uniform brightness similar to the image shown in FIG. 4e can be obtained. Adjustment can be completed in this way, so when the sample is replaced with the sample to be observed, the center of correction by the dynamic focus lens 8 is aligned with the center point of locking, so that the Locking can be performed with the electron beam irradiated only in a narrow area, and an electron channeling pattern in an extremely small area can be displayed on the cathode ray tube 10.

[Effects of the Invention] As is clear from the above description, according to the apparatus based on the present invention, adjustment for aligning the center of correction by the dynamic focus lens with the center of locking can be easily and quickly performed. This makes it possible to improve the operability of this type of electron beam device.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of a device for obtaining an electron channeling pattern, FIG. 2 is a diagram illustrating a conventional device, and FIG.
The figures are diagrams for illustrating output signals from each circuit of the apparatus shown in Figures 2 and 5, Figure 4 is a diagram for explaining the display image of a conventional cathode ray tube, and Figure 5
The figure is a diagram for explaining one embodiment of the present invention. FIG. 6 is a diagram for explaining the operation of the device of one embodiment. 1: Electron gun, EB: Electron beam, 2, 3: Focusing lens, 4: Objective aperture, 5ax, 5ay, 5bx, 5by:
Scanning coil, 6ax, 6ay, 6bx, 6by: Alignment coil, 7ax, 7ay, 7bx, 7by: Deflection power supply, 8: Dynamic focus lens,
9: Objective lens, 10: Sample, 11X, 11Y:
Scanning signal generation circuit, 12X, 12Y: switch circuit, CR: cathode ray tube, Sx, Sy: switch, 13
X, 13Y, 16, 21: addition circuit, 14X, 1
4Y: potentiometer, 15X, 15Y: square circuit, 17: variable gain amplifier, 18: secondary electron detector, 19: amplifier, 20X, 20Y: comparison circuit.

Claims (1)

[Claims] 1 When the X-direction and Y-direction scanning signals are Xi and Yi, respectively, the X- and Y-direction electron beam deflectors have Xi and Yi.
The front focal plane of the objective lens is scanned by an electron beam, and the phase value a,
A correction signal of (Xi-a) ² + (Yi-b) ² including In a device configured to display an electron channeling pattern by guiding a detection signal associated with angular scanning to a display means scanned in synchronization with the scan, the screen of the display means changes as the phase values a and b are adjusted. An electron beam apparatus comprising means for displaying a mark at a position corresponding to the above values of a and b.