JPH0754677B2 - X-ray analysis electron microscope - Google Patents

Description

TECHNICAL FIELD The present invention relates to an X-ray analysis electron microscope that performs analysis based on X-rays generated by electron beam irradiation.

[Prior Art] Conventionally, a characteristic X emitted from a point on a sample by focusing an electron beam on a desired point on the sample observed by an electron microscope or the like.
An apparatus is known in which a line is detected by a detector arranged near the sample, and an X-ray spectrum is displayed based on the detection signal.

[Problems to be Solved by the Invention] When X-rays emitted from a sample are spectrally analyzed by such an apparatus, the incident angle of the electron beam with which the sample is irradiated is selected to various values, but during measurement. Is held at the chosen value.

However, depending on the crystalline state of the sample and the angle of incidence of the electron beam on the crystalline sample (crystal plane), coherent bremsstrahlung or channeling radiation is generated, and the sample generates X-rays having specific energy. There are cases. FIG. 3 shows a situation in which coherent bremsstrahlung is generated when an electron beam EB is incident on a crystalline sample. In the figure, electron beams (electrons) incident on the crystal at a certain incident angle collide with the base paper in the crystal one after another with a constant period, and thus the electromagnetic wave (braking radiation) emitted by the collision has a phase correlation. And becomes a coherent electromagnetic wave. Therefore, X-rays (incorrect X-rays) having a specific energy irrelevant to the composition of the sample are generated,
For example, when an alloy sample of aluminum (Al) and silver (Ag) is analyzed, as shown in FIG. 4, the composition of the sample is between the characteristic X-ray peak A of Al and the characteristic X-ray peak B of Ag. The problem is that an unrelated false X-ray peak C is generated, and the accuracy and reproducibility of the quantitative analysis are significantly deteriorated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an X-ray analytical electron microscope capable of removing an incorrect peak by adding a simple configuration.

[Means for Solving Problems] An X-ray analysis electron microscope of the present invention is a focusing lens for focusing an electron beam on a sample surface, and a characteristic X-ray obtained by irradiating the sample with the electron beam. Detecting means for each energy or wavelength region, integrating means for integrating the detection signal obtained by the detecting means for each energy or wavelength region, and electrons on the sample during the integrating period by the integrating means. Means for periodically changing the electron beam incident angle over a predetermined angle range while fixing the radiation point, and means for obtaining an X-ray spectrum based on the output signal from the integrating means are provided. .

[Operation] In the present invention, a desired point on the sample is irradiated with an electron beam, and while the electron beam irradiation point is fixed, the electron beam incident angle at the point is periodically changed and emitted from the sample. The characteristic X-rays that are generated are detected, and the false peaks are removed.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is an apparatus configuration diagram for explaining a first embodiment of the present invention, and FIG. 2 is an apparatus configuration diagram for explaining a second embodiment of the present invention.

First, a first embodiment shown in FIG. 1 is an apparatus for performing X-ray analysis using an energy dispersive X-ray detector in a transmission electron microscope. In FIG. 1, 1 is an electron gun,
Reference numerals 2 and 3 are focusing lenses, 4a and 4b are deflection coils, 5 is a sample, 6 is an objective lens, 7 is an intermediate lens, 8 is a projection lens, 9 is a fluorescent plate, and 10, 11, 12, 13, and 14 are each lens. , A scanning unit of the deflection coil 4, 16 an irradiation angle control circuit, 17 an energy dispersive X-ray detector, and 18 an X-ray analyzer including a wave height analyzer.

In the transmission electron microscope configured as shown in FIG. 1, after the electron beam emitted from the electron gun 1 is focused by the focusing lenses 2 and 3 of the first and second stages controlled by the control units 7 and 8. , Is projected onto the sample 5. Electrons transmitted through the sample are lenses 7,8,
It is magnified by 9 and forms the final image on the fluorescent plate 9. When performing X-ray analysis of the sample surface using such a transmission electron microscope, the electron beam EB from the electron gun 1 is controlled by the control units 10 and 11, and the focusing lens 2 of the first stage and the focusing lens 2 of the second stage are controlled. It is focused by the lens 3. The focused electron beam is a deflection coil
After being deflected by 4a and 4b, it is incident on a desired point of the crystalline sample 5. Then, at this time, the X-rays excited by the electron beam and emitted from the sample are detected by the X-ray detector arranged near the sample. Here, when the deflection angle by the deflection coil 4a is θ,
The scanning unit 15 gives the relationship that the deflection angle by the deflection coil 4b becomes −2θ. When such a relationship is given to the deflection coils 4a and 4b, the electron beam passes through the same position on the optical axis for any θ, and the sample 5 is placed at that position. In addition, the scanning unit 15
The value of is repeatedly swept within the range of −3 ° ≦ θ ≦ 3 °. Therefore, the electron beam incident on the sample is repeatedly swept around the electron beam irradiation point on the sample so as to swing its head within an incident angle range of ± 3 °. Since the sweep repetition period is set sufficiently shorter than the measurement period in which X-ray analysis is performed, a large number of sweeps are performed within the measurement period.

Thus, when the incident angle of the electron beam incident on the crystalline sample is continuously and repeatedly changed, in the X-ray spectrum obtained over a certain measurement period, the characteristic X-ray that does not depend on the electron beam incident angle is measured during the measurement period. During this period, the spectrum intensity increases, but the irregularity depending on the incident angle of the electron beam occurs only at the moment when the incident angle reaches a specific value, so the accumulation effect does not increase, and the spectrum is as shown in FIG. Almost all the peaks C due to the illegal X-rays are suppressed, and the peaks C due to the characteristic X-rays are included.

Next, a second embodiment shown in FIG. 2 is an apparatus for performing X-ray analysis using a wavelength dispersive X-ray spectrometer in a scanning electron microscope. In FIG. 2, 21 is an electron gun, 22,23
Is a focusing lens, 24 is a deflection coil, 25 is a sample, 26 is an objective lens, 27 and 28 are focusing lens control units, and 29 is a deflection coil 24.
Scanning unit, 30 an irradiation angle control circuit, 31 a dispersive crystal 32, X
A wavelength dispersive X-ray spectrometer including a line detector 33. Reference numeral 34 is a spectrum display device.

The electron beam EB from the electron gun 1 is focused by the first-stage focusing lens 22 and the second-stage focusing lens 23 controlled by the control units 27 and 28. The focused electron beam is deflected by the deflection coil 24, and then passes through the objective lens 26 and enters the crystalline sample 25 arranged at the focal position of the objective lens. And
At this time, the X-rays excited by the electron beam and emitted from the sample are detected by the X-ray detector 33 through the analysis crystal 32.
Here, the deflection coil 24 is controlled by the scanning unit 29, which scans the electron beam with the electron beam deflection angle θ set in the irradiation angle control circuit 30 and the sweep repetition period before the objective lens 26. The scanning is performed near the focal plane. Therefore, the incident angle of the electron beam incident on the sample through the objective lens 26 is repeatedly changed so as to swing its head around the electron beam irradiation point on the sample. At this time, the repetition cycle of the electron beam sweep is set to be a cycle sufficiently shorter than the wavelength sweep speed of the wavelength dispersive X-ray spectrometer.

As described above, by continuously and repeatedly changing the incident angle of the electron beam incident on the crystalline sample, the incident angle of a specific electron beam in the X-ray spectrum obtained by sweeping the wavelength over a certain measurement period. It is possible to stochastically reduce the generation of false X-rays due to coherent bremsstrahlung and channeling radiation. Therefore, the X-ray emitted from the sample at this time is transmitted through the dispersive crystal 32 to the X-ray detector.
If the X-ray spectrum is detected by 33, and the detected information is supplied to the spectrum display device 20 to display the X-ray spectrum, the X-ray spectrum is suppressed from the peak due to the incorrect X-ray, as in the case of the first embodiment. It becomes a thing.

[Advantages of the Invention] The present invention changes the electron beam incident angle periodically over a predetermined angle range while fixing the electron beam irradiation point on the sample, and obtains the characteristic obtained from the sample as X-ray energy at each energy or wavelength region. Since the X-ray spectrum is obtained based on the integrated signal for each time, the spectrum intensity of the characteristic X-ray generated from the element contained in the sample is an illegal X-ray generated only at a specific electron beam incident angle. It is possible to obtain an X-ray spectrum in which the peak due to the false X-rays is almost suppressed, which is greatly increased compared to the spectrum intensity of As a result, qualitative and quantitative analysis of the sample can be performed accurately even when the sample having crystallinity is irradiated with the electron beam.

[Brief description of drawings]

FIG. 1 is an apparatus configuration diagram for explaining a first embodiment of the present invention, FIG. 2 is an apparatus configuration diagram for explaining a second embodiment of the present invention, and FIGS. 3 and 4 are It is a figure for demonstrating a prior art example. 1: electron gun, 2, 3: focusing lens 4: deflection coil, 5: sample 6: objective lens 10, 11: focusing lens control unit 15: scanning unit, 16: irradiation angle control circuit 17: energy dispersive X-ray detection Instrument 18: X-ray analyzer

Claims (1)

[Claims] 1. A focusing lens for focusing an electron beam on a sample surface, a detection means for detecting a characteristic X-ray obtained by irradiating the sample with the electron beam for each energy or wavelength region, and the detection. Integrating means for integrating the detection signal obtained by the means for each energy or wavelength region, and the electron beam incident angle at a predetermined angle while the electron beam irradiation point on the sample is fixed during the integrating period by the integrating means. An X-ray analysis electron microscope comprising means for periodically changing over a range and means for obtaining an X-ray spectrum based on an output signal from the integrating means.