JPS60243951A - Axis alignment method in electron beam equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for aligning an axis in an electron beam device capable of displaying an electron channeling pattern.

1, when the electron beam irradiation point on the sample S is fixed at the incident point P, the required electron beam is
If the angle is sequentially scanned in the two directions of θy, two lines parallel to the crystal plane will be displayed on the display screen as angular loci that satisfy the Bragg condition. Note that OL indicates an objective lens.

An image made up of a collection of two lines like this is called an electron channeling pattern, and by analyzing this electron channeling pattern, we can understand things such as crystal surface habits, crystal grain boundaries, and crystal orientation relationships between different phases. Observation of this pattern has recently become widespread. +'+Cf As mentioned above, angular scanning is necessary to obtain this electron channeling pattern, but there is a device that performs angular scanning by scanning the front focal plane of the objective lens with an electron beam. ~', the focal length F is longer than ΔF<Cs (Xi 2 + Yi 2 ) due to the spherical aberration of the objective lens.
(1) (the error will shift. However, in equation (1) ×
1°Yi are horizontal and vertical scanning signals flowing to the deflection coil for locking the electron beam, and C3 is the spherical aberration coefficient of the objective lens. Therefore, when trying to obtain an electron channeling pattern in a minute area, a dynamic focus lens is provided near the objective lens and the amount or focal length given by equation (1) is synchronized with the scanning of the electron beam. However, in order to maximize the effect of correction by this dynamic focus lens, it is necessary to align the axes of the objective lens and the dynamic focus lens. Conventionally, this alignment is performed by mechanically moving a dynamic focus lens. By the way, when the excitation intensity of the objective lens is changed, the intensity of the deflection magnetic field by the lens changes, so alignment is required again, but as mentioned above, in the past, alignment was performed mechanically. Because of this, the mirror body had to be disassembled and aligned each time, which was extremely troublesome.

SUMMARY OF THE INVENTION An object of the present invention is to solve these conventional drawbacks and provide a method for alignment in an electron beam apparatus that can easily and accurately align an objective lens and a dynamic focus lens.

[Structure of the invention] In the present invention, the X direction and Y direction scanning signals are respectively XI.

Let Yi be, Xi and YI are placed on the X and Y direction deflectors.
The front focal plane of the objective lens is scanned by the electron beam, and a signal proportional to Xi2+Y12 is supplied to the dynamic focus lens located near the objective lens, thereby fixing the irradiation position of the electron beam on the sample. In this method, an electron beam is angularly scanned, and a detection signal accompanying the angular scanning is guided to a display means that is scanned in synchronization with the scanning to obtain an Elektron channeling pattern. The scanning signals X1 and Yl
C to scan the sample two-dimensionally, and when n is a number of 2 or more, X to the dynamic focus lens.
an alignment coil disposed in front of the objective lens so as to supply a signal of 1Tl+YII'l and, as a result, to observe the image displayed on the display means so that an unblurred image area is located at the center of the display means; The feature is that the deflection current of the beam is adjusted.

"Example] Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 2 shows an apparatus for carrying out the present invention. 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, and then The light passes through the aperture 4 and enters the deflection system. The deflection system includes a first stage scanning coil 5ax for scanning in the x (horizontal) and Y (vertical) directions;
! 5ay, and a second stage scanning coil 5bx for scanning in the X and Y directions.

5by and the first stage alignment coils 6ax and 5ay arranged outside the scanning coils 5ax and 5ay.
and a scanning coil 5bx, 5by (7) and a coil 6bx for the alignment member 1 located just outside.

It consists of 6by. These alignment carp /L/
6 a X, 6 a V, '6 b X,
6b y has deflection power supplies 7ax, 7ay, 7bx
, 7by can be supplied. The electron beam EB deflected by each scanning coil and alignment coil J passes through a dynamic focus lens 8 and an objective lens 9 and is irradiated onto the sample 1o. 11
X is a scanning signal generation circuit that generates a scanning signal in the X direction as shown in FIG.
The scanning signal from X is supplied to scanning coils 5ax and 5bx via a balance circuit 12X. 11Y is shown in Figure 3 (
This is a scanning signal generation circuit that generates a scanning signal in the Y-horn direction as shown in b), and the scanning signal from this scanning signal generation circuit 11Y is supplied to the scan-1 file 5ay and 5by via a balance circuit 12Y. . This scanning signal generation circuit 11
The X and Y direction scanning signals from X and 11Y are sent to the cathode ray tube 13.
The scanning beams 13X and 13V are also supplied to the cathode ray tube 13, and the cathode ray tube 13 is scanned in synchronization with the scanning of the electron beam EB. Moreover, the scanning signal generation circuits 11X and 11Y
The scanning signals of 2 East circuits 1/1 . It is supplied to X and 14Y. 2 East circuit 1
7! The output signals of IX and 1/IY are supplied to an adder circuit 15, and the output signal of the adder circuit 15 is supplied to the dynamic focus lens 8 via a variable gain amplifier 16. 17 is an excitation power source for the objective lens 9;
The output signal from the excitation power source 17 is supplied to the objective lens 9 via an adder circuit 18. The adder circuit 18 can be supplied with a current as shown in FIG. 21 is a secondary electron detector;
The output signal is supplied to the grid 13G of the cathode ray tube 13 via an amplifier 22 and an adder circuit 23. 24
．． X is a comparison circuit, and this comparison circuit 24X is supplied with the X direction scanning signal from the X direction scanning signal generation circuit 11X and the signal from the potentiometer 25X, and generates a matching pulse when both signals match. do.

Therefore, according to the output signal from the potentiometer 25X, the image shown in FIG.
＞A luminous line]× is displayed.

Similarly, 24Y is a comparison circuit, and this comparison circuit 24Y is supplied with the Y-direction scanning signal and the signal from the potentiometer 25Y, and generates a matching pulse 1j when both signals match. Therefore, on the screen of the negative 8-line tube 11, bright lines such as 1, indicated by 1-y in FIG. 4(a), are displayed superimposed on the image.

In such a configuration, first, the excitation of the focusing lens 3 is made strong, and then the balance circuit 10X is further applied.

10Y, as shown by the dotted line in Figure 2,
The electron beam EB is deflected using the center of the objective lens 9 as a deflection fulcrum, whereby the sample is scanned two-dimensionally (two-dimensionally) to obtain a normal scanned image.

When the output signal from the detector 21 obtained in conjunction with this scanning is supplied to the cathode ray tube 13 via the amplifier 22, a secondary electron image of the sample 10 is displayed on the cathode ray tube 13. Therefore, the objective lens 9 is focused so that a sharp image is displayed. Next, potentiometer 25X
, 25Y so that the intersection point U of the bright lines 1x, +-y displayed on the cathode ray tube 11 is located at the center of the screen of the cathode ray tube 11 as shown in FIG. 10 to align the image of a target object such as dust on the sample surface with the intersection point U. Therefore, the A-brar current as shown in FIG. 3(C) is generated from the A-brar power supply 19 to periodically change the focal length of the objective lens 9. As a result, the position of the image of the target object moves as if rotating C around the intersection U. Therefore, by adjusting the position of the objective diaphragm 4 so that the position of the image of the target does not move, the axis of the objective lens 9 can be set at a position corresponding to the center of the screen. Next, the axis of the objective lens 9 and the dynamic focus lens 8 are aligned. Now, for example, the distance between the objective lens 9 and the dynamic focus lens 8 is 11111 (Cd). , first turn off the switch 20 - C A - Bra power supply 19
After cutting off the supply of the wobbler current to the objective lens 9 so that a steady excitation signal from the excitation power supply 17 is supplied, the switch 3x is turned on.

Sy is closed and X and Y direction scanning signals are supplied to the 2 east circuits 14X and 1/IY. As a result of (a), when the X and Y direction scanning signals are Xi, Yi and J, respectively, the adder circuit 15 supplies the dynamic focus lens 8 with an excitation current proportional to X12-1-Yl2.

Now, for simplicity's sake, let's consider the case of Yl-0. Alignment 1 - Coil 6 a X , 6 a y, 6
b. The electron beam EB is scanned in the X direction centering on
The dynamic focus lens 8 includes an IC that changes the focal length in proportion to X i 2 as the dynamic focus lens 8 scans in the X direction.
Therefore, the focal point of the electron beam FB based on both lenses is a quadratic curve centered on the point C shown by the chain double-dashed line in FIG. 5(a) connecting the center of the objective lens 9 and the center of the dynamic focus lens 8 It changes as shown in R. Therefore, on the cathode ray color 13 screen, only the area MF at the edge of the screen is sharp and the other parts are blurred, and there are blurred areas around the sharp area F, as shown in Figure 4 (C). A vibratory rotating image is displayed. In Figure 4(C), D
-, D'' indicate the image of the vibrationally rotating target.

Therefore, as the amplification factor of the variable amplification factor amplifier 16 is increased, the large serrations of this sharp region 14F become narrower, and it becomes possible to identify the lifting point as well as the movement of the target object. It becomes even more intense. Therefore, the sample 10 is mechanically moved to move the image of the target object into the area ViF.

Therefore, the image of the target object is displayed on the A-shape without rotation. Therefore, the deflection power supplies 7ax, 7ay, 7bx, 7b
y to align the alignment coils 5ax and 6ay.

By adjusting the currents supplied to 6bx and 6by, this region ViF is covered so as to coincide with the intersection point U of the cathode ray tube 13, as shown in FIG. 4(e).

In this state, the focal point of the electron beam FB based on the dynamic focus lens '8 and the objective lens 9 is the electron beam EB.
5(b) as shown by the quadratic curve R-, the position on the sample corresponding to the center of the screen (indicated by arrow E) is located at - of axis C. It will be in the next. The electron beam EB is connected to an alignment coil ('3ax, 6ay).

The objective lens 9 is aligned along the axis C by 6bx and 6by.
As a result, the axis of the objective lens 9 and the axis of the dynamic focus lens 8 can be aligned. Therefore, after the focusing lens 3 is weakly excited, the balance circuits 12X and 12Y are adjusted so that the focusing point of the electron beam FB is placed on the front focal plane S of the objective lens 9, as shown by the thin line J in FIG. Make sure the positions are the same. Therefore, while a signal proportional to Xi2+Yi2 is supplied to the dynamic focus lens 8, a scanning signal Xi is applied to each scanning coil.

When Yi is supplied, the axes of the dynamic focus lens 8 and the objective lens 9 are aligned, so the spread of the electron beam irradiation point due to the spherical aberration of the objective lens is corrected with high precision by the dynamic focus lens, and it is extremely small. It is possible to display an electron channeling pattern by irradiating only the desired area with an electron beam.

In the above embodiment, the signal supplied to the dynamic focus lens is used to align the axes of the dynamic focus lens and the objective lens, and the signal supplied to the dynamic focus lens is used to obtain the electron channeling pattern. For example, X and Y
Alternatively, a signal obtained by multiplying the scanning signal in the direction to the third power may be added and supplied.

In addition, in the two consecutive embodiments, the intersection of two bright lines was used as a mark to indicate the position of the screen.
It may be a bright spot, or it may be a dot with a color that allows it to be identified, such as a portion of a black image.

[Effects] As is clear from the above explanation, in the method based on the present invention, the axis of the objective lens and the axis of the dynamic focus lens can be easily and accurately aligned.
When the dynamic focus lens is used to correct the spread of the electron beam irradiation point due to the spherical aberration of the objective lens during angular scanning of the electron beam, its effect can be fully exhibited. Therefore, an electro-edge funneling pattern can be displayed by scanning the angle of the electron beam while irradiating only an extremely small area with the electron beam.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining scanning of an electron beam to obtain an electron channeling pattern, FIG. 2 is a diagram for showing an example of an apparatus for implementing the present invention, and FIG. 3 is a diagram for explaining scanning of an electron beam to obtain an electron channeling pattern. FIG. 4 is a diagram illustrating the output signals of each circuit element of the embodiment shown in FIG. FIG. 5 is an optical diagram for explaining the present invention in detail. 1: Electron gun, 2, 3: Focusing lens, /4: Aperture, 5ax
, 5ay, 5bx, 5bV: scanning coil, 6ax, 6
ay, 6bx, 6by near alignment coil, 7ax
, 7ay, 7bx, 7by: &i direction electric power source 8° dynamic lens, 9: objective lens, 10: sample,
11X, 11Y: Scanning signal generation circuit, 12X, 12Y:
Balanced circuit, 13 cathode ray tubes, 1/1. X, 14. Y: square circuit, 15, 18.23: addition circuit, 16: variable gain amplifier, 17: excitation power supply, 19: 4-bra power supply, 20
: switch, 21 primary electron detector, 22: amplifier 24
X, 24Y: Comparison circuit, 25X, 25Y: Potentiometer, C: Synthesis axis of objective lens and dynamometer lens, EEB: Electron beam, [-X, lj/: Bright line, U: Intersection of bright lines, D, D- , D": Image of target object, "
: Arrow, S: Front focal plane. Figure 3 □ (Lee---------□□ ■ m ″'>ryFigure 4 (a) Figure 4 (b)

Claims (1)

[Claims] When the X-direction and Y-direction scanning signals are Xi and Yi, respectively, Xi and Yi are supplied to the X- and Y-direction deflectors to scan the front focal plane of the objective lens with an electron beam and to place the electron beam in the vicinity of the objective lens. By supplying a signal proportional to Xi 2 + '1'i 2 to the dynamic focus lens, the irradiation position of the electron beam on the sample is fixed and the electron beam is angularly scanned, and the detection signal accompanying the angular scanning is In this method, the scanning signals Xi and Yi are supplied to the X and Y direction deflectors respectively to scan the sample two-dimensionally; When is a number of 2 or more, the dynamic focus lens has X1rl+
A signal Y1'' is supplied to the alignment coil disposed in front of the objective lens so that the image displayed on the display means is observed and the unblurred image area is located at the center of the display means. A method for aligning an axis in an electron beam device, characterized in that the deflection current is adjusted.