JPS6322012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an analytical electron microscope that does not have a scanning image observation function and is capable of performing X-ray analysis in a very small area while accurately confirming analysis points.

Conventionally, when performing X-ray analysis of extremely small regions of several hundred angstroms or less using an energy dispersive X-ray analyzer, it is extremely important to confirm field-of-view correspondence. We are checking. However, the resolution of scanning transmission images in devices equipped with normal thermionic electron guns is limited to 10 to 20 Å, and it is difficult to perform X-ray analysis at a desired point while checking ultrafine structures such as crystal lattice images of several Å. It cannot be done.

On the other hand, with a normal transmission electron microscope, it is easy to observe fine structures on the order of several angstroms, but when the electron beam is focused into a spot for analysis, the field of view on the fluorescent plate becomes significantly smaller. , it becomes impossible to observe the image and therefore confirm the field of view.

SUMMARY OF THE INVENTION In view of the above points, it is an object of the present invention to provide an apparatus that enables X-ray analysis of extremely small areas while confirming analysis points in a normal transmission electron microscope.

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and 1 is an electron gun that generates an electron beam. The electron beam emitted from this electron gun is focused by a first focusing lens 2 and a second focusing lens 3, and is irradiated onto a sample 4. The electron beam transmitted through the sample 4 is enlarged and imaged by an objective lens 5, and the image is further enlarged by an intermediate lens 6 and a projection lens 7 to form a final image on a fluorescent plate 8. Electron beam detectors 9 electrically insulated from each other are provided at the center of the fluorescent plate, and the amount of electrons flowing into the center of the fluorescent plate is detected. The signal from the detector 9 is sent to a switch signal generation circuit and used to generate a control signal for a switching circuit, which will be described later.

An energy dispersive X-ray detector (semiconductor detector) 11 is arranged near the sample 4, and
Detects X-rays generated from The output signal from this detector is appropriately amplified and then sent to the switching circuit 1.
2 to a processing circuit 13 for predetermined processing, and the output signal is sent to a display device or recording device 14 to obtain an X-ray spectrum. The switching circuit 12 is ON-OFF controlled by a signal from the switch signal generating circuit 10, and is turned ON/OFF.
It functions to send the output signal of the X-ray detector 11 to the signal processing circuit only in the state of . Reference numeral 15 denotes a variable current power supply for the second focusing lens 3, which functions to repeatedly vary the electron beam on the sample 4 between a spread state suitable for electron microscope image observation and a microspot state suitable for analysis. do.

In the above device, the second
When a current as shown in the figure is supplied to the second focusing lens 3, the size of the cross section of the electron beam on the sample 4 changes, and the observation field on the fluorescent plate 8 corresponds to each current as shown in Figure 3. As shown, it changes as →→→. Among these, the spot size is suitable for electron microscope image observation or micro analysis. A signal corresponding to the electron beam density is obtained from the detector 9, and the signal is stronger when the electron beam density is higher than when the electron beam density is higher. Therefore, only when the signal strength reaches the state shown in FIG. Only the detection signal of the X-rays generated from the sample is sent from the detector 11 to the signal processing circuit 13 during the test. Therefore, the display device 14 displays the X-ray spectrum of the extremely small sample area corresponding to the image located at the center on the fluorescent plate 8. The field of view search is performed in the state shown in FIG. 3, that is, in a state in which an image is projected onto the entire surface of the fluorescent plate, and the sample 4 is moved so that the desired sample area is located at the center of the fluorescent plate 8.

FIG. 4 is a diagram showing another embodiment of the present invention.
The same reference numerals as in the figure indicate the same parts. In this embodiment, the switching circuit 12 is controlled in synchronization with the variable excitation of the second focusing lens, and for this purpose a control signal is supplied to the switching circuit 12 from the variable power supply 15. . In this embodiment, since there is no electron beam detector in the center of the fluorescent plate, as shown at 8a in FIG.
It is convenient for finding the field of view by placing a mark in the center of the phosphor plate and moving the desired field of view within this mark.

With the configuration described in detail above, it is possible to set a desired point (area) as an X-ray analysis point while observing ultrafine structures using a normal transmission electron microscope image, and to use the scanning electron image observation function. The field of view of analysis points can be matched easily and with high precision using an electron microscope that does not have one, and furthermore, it has become possible to search for ultrafine structures in the field of view, which was previously impossible.

In the above embodiments, the variable current waveform of the focusing lens is not limited to that shown in FIG. Any waveform may be used as long as it switches to a spot state suitable for micro X-ray analysis. In addition, although the cross section of the electron beam was varied by the second focusing lens 3, due to the adjustment of the beam current and the size of the X-ray analysis point, the first focusing lens 2
Alternatively, the first focusing lens 2 and the second focusing lens 3 may be changed simultaneously.

Further, in the embodiment shown in FIG. 1, the detector 9 is provided at the center of the fluorescent plate 8, but the peripheral portion other than the center may be used as a detector. In this case, the switch signal generation circuit 1 is activated only when the detected current becomes zero.
0 emits a pulse signal to activate the switching circuit 12.
It goes without saying that it must be turned on.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of the present invention, and FIG.
Figures 3 and 3 are diagrams for explaining the device shown in Figure 1,
FIGS. 4 and 5 are schematic diagrams showing other embodiments of the present invention. 1: Electron gun, 2: First focusing lens, 3: Second focusing lens, 4: Sample, 5: Objective lens, 6: Intermediate lens, 7: Projection lens, 8: Fluorescent plate, 9: Electron beam detector, 10: Switch signal generation circuit, 11:
X-ray detector, 12: switching circuit, 13: signal processing circuit, 14: display device, 15: variable current power supply.

Claims (1)

[Claims] 1. A focusing lens for focusing the electron beam from the electron gun 1, which focuses the electron beam onto the sample 4.
a variable power source 1 that supplies an excitation current to the focusing lens so that the electron beam irradiated on the sample surface automatically alternates between a spread state and a spot state;
5. X generated from the sample by irradiation with the electron beam
An X-ray detector 11 that detects rays, a circuit 13 that processes the output signal of the X-ray detector, imaging lens systems 5, 6, and 7 that image the electrons that have passed through the sample, and a final image is projected. a fluorescent screen 8 disposed between the X-ray detector and the signal processing circuit, and the detector 1 during the period when the electron beam irradiated onto the sample is in a spot state;
The signal processing circuit 1 selectively outputs only the output signal of the signal processing circuit 1.
An analytical electron microscope characterized in that it is comprised of a circuit 12 for leading to a. 2. The analytical electron microscope according to claim 1, wherein the circuit 12 is controlled based on an output signal from an electron beam detector provided at the center of the fluorescent screen. 3. The analytical electron microscope according to claim 1, wherein the circuit 12 is controlled in synchronization with the variable power source.