JPS631700B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scanning electron microscope for observing magnetic domains.

In the process of developing magnetic materials, magnetic domains are observed using a scanning electron microscope. One method for observing magnetic domains is to examine changes in magnetic contrast. This is to examine changes or the presence or absence of changes in magnetic contrast by, for example, rotating a detector facing the sample surface around a magnetic domain, or conversely by rotating the sample itself.

To implement such a technique, the detector must be rotated around the sample, or the sample must be rotated. Therefore, a special and large-scale attached mechanism is required to rotate the detector, and
Another problem is that after taking a photo, the sample is rotated 180 degrees and taken again, which takes a long time. Furthermore, since the images to be compared and examined were not obtained at the same time, it is impossible to eliminate the influence of changes in the sample over time.

The present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide a scanning electron microscope that has a simple configuration and can examine the above-mentioned changes in magnetic contrast in a short time.

In order to achieve this object, the present invention provides a means for irradiating a finely focused electron beam onto a sample surface, a scanning means for two-dimensionally scanning the electron beam irradiation position on the sample surface in a horizontal direction and a vertical direction; In a scanning electron microscope equipped with a means for detecting a signal generated from a sample by electron beam irradiation and an image display means to which the output signal of the detection means is supplied as a brightness modulation signal, a magnetic field is generated and the A magnetic field generating means in which a sample is disposed, a switching excitation means for reversing the polarity of the magnetic field generated by the magnetic field generating means in synchronization with horizontal scanning by the scanning means, and a magnetic field generating means corresponding to each magnetic field polarity in the image display means. The present invention is characterized by providing means for displaying two sample images. Hereinafter, one embodiment of the present invention will be explained in detail using the drawings.

FIG. 1 is a diagram showing the configuration of an apparatus according to an embodiment of the present invention. A case is shown in which a change in the amount of reflected electron emission obtained is detected as a video signal. In the figure,
Reference numeral 3 denotes an oscillator that generates periodic pulses as shown in FIG. 2, and based on the output pulses, a horizontal scanning signal generating circuit 4 generates a sawtooth sample horizontal scanning signal as shown in FIG. is supplied to the horizontal deflection coil 5 for the electron beam 2. Further, the scanning signal generating circuit 4 generates a blanking signal as shown in FIG. 6 for each retrace scanning time, and this blanking signal is used as a brightness modulation signal for the cathode ray tube 7 via an adding circuit 6.

A horizontal deflection coil 8 for the electron beam scanning the screen of the cathode ray tube 7 is supplied with a sawtooth cathode ray tube horizontal scanning signal as shown in FIG. 4 from a second scanning signal generating circuit 9. The scanning signal generating circuit 9 generates a scanning signal having a period twice that of the output of the scanning signal generating circuit 4 based on the output of the scanning signal generating circuit 4.

On the other hand, the vertical deflection coil 10 for the irradiation electron beam 2 and the vertical deflection coil 11 of the cathode ray tube 7 are both supplied with a sawtooth vertical scanning signal from a vertical scanning signal generation circuit 12, and the period thereof is equal to that of the horizontal scanning signal. Since the magnification is several hundred times larger, two-dimensional scanning of the electron beam is performed on the sample surface and the cathode ray tube screen. The reflected electrons generated from the sample 1 are detected by a semiconductor detector 13, and are used as a brightness modulation signal for a cathode ray tube 7 via an amplifier 14 and an adder circuit 6.

Both ends of the sample 1 are fixed to both ends of a U-shaped magnetic core 15, so that the sample forms part of a magnetic path. An excitation coil 16 is wound around the core 15.
As shown in FIG. 5, a rectangular wave current whose polarity is reversed in synchronization with the output pulse of the oscillator 3 is supplied from the rectangular wave generation circuit 17, so that a ferromagnetic material sample such as silicon steel, for example, is Become magnetized.

FIGS. 7 and 8 show the relationship between electron beam scanning on a sample and on a cathode ray tube screen in the apparatus shown in FIG. 1. The trajectory of the electron beam horizontally scanning sample 1 is A1, B1, A2, B as shown in Figure 7.
2,... On the other hand, horizontal scanning on a cathode ray tube screen has A on the left half as shown in Figure 8.
1, A2, A3, ..., B1, B2, B on the right half
3,... Therefore, there are two sample scan images for the same viewing area on the left and right sides of the cathode ray tube screen, that is, image A formed by scanning lines A1, A2, A3,..., and image A formed by scanning lines B1, B2,... Images B formed by B3, . . . are displayed side by side.

At this time, as shown in FIG. 5, the excitation coil 16 is supplied with an excitation current whose polarity is reversed in synchronization with the horizontal scanning of the electron beam on the sample. It is inverted as (+), (-), (+), (-), . . . in synchronization with the horizontal scanning of the line. As a result, image A displayed on the cathode ray tube screen is a scanned image in which the direction of magnetization of the sample is, for example, (+), image B is a scanned image in which the direction of magnetization of the sample is (-), and image A , B are obtained at the same time. By comparing images A and B obtained simultaneously in this way, it becomes possible to immediately check whether the magnetic contrasts of images A and B are reversed or not. At that time, image A,
Since B is obtained at the same time, it is not affected by changes in the sample over time.

Incidentally, as the frequency of the oscillator 3 is gradually increased, changes in the magnetic domain structure in the sample depending on the frequency can also be observed.

Furthermore, the present invention is not limited to the embodiment shown in FIG. For example, instead of displaying the two sample images A and B on a single cathode ray tube screen, it is also easy to provide two cathode ray tubes and display the sample images A and B on their respective screens. Furthermore, magnetic domain observation can be performed even if secondary electrons are detected instead of reflected electrons.

As described above, according to the present invention, the magnetic field generating means in which a sample is disposed in the magnetic path, and the polarity of the magnetic field generated by the magnetic field generating means are reversed in synchronization with the horizontal scanning of the electron beam on the sample. It is possible to examine changes in magnetic contrast in a short time with a simple configuration in which the image display means is provided with switching excitation means for causing the magnetic field to change, and means for displaying two sample images corresponding to each magnetic field polarity.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an apparatus according to an embodiment of the present invention, FIGS. 2 to 6 are waveform diagrams for explaining the operation of the apparatus shown in FIG. 1, and FIGS. FIG. 3 is a diagram for explaining electron beam scanning on a screen. DESCRIPTION OF SYMBOLS 1...sample, 2...electron beam, 3...oscillator, 4...horizontal scanning signal generation circuit, 5, 8...horizontal deflection coil, 6...addition circuit, 7...braun tube, 9...second
scanning signal generation circuit, 10, 11... vertical deflection coil, 12... vertical scanning signal generation circuit, 13
...Semiconductor detector, 14...Amplifier, 15...Core, 1
6... Coil, 17... Rectangular wave generation circuit.

Claims (1)

[Claims] 1 means for irradiating a narrowly focused electron beam onto the sample surface; scanning means for two-dimensionally scanning the electron beam irradiation position on the sample surface in the horizontal and vertical directions;
In a scanning electron microscope equipped with a means for detecting a signal generated from a sample by electron beam irradiation and an image display means to which the output signal of the detection means is supplied as a brightness modulation signal, a magnetic field is generated and the A magnetic field generating means in which a sample is disposed, a switching excitation means for reversing the polarity of the magnetic field generated by the magnetic field generating means in synchronization with horizontal scanning by the scanning means, and a magnetic field generating means corresponding to each magnetic field polarity in the image display means. A scanning electron microscope characterized in that it is provided with means for displaying two sample images.