JP3269524B2 - Electron energy loss spectrometer and spectral shift correction method therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electron energy loss spectrometer using a two-dimensional position detecting element and a method of correcting a spectrum shift thereof.

[0002]

2. Description of the Related Art In a transmission electron microscope, when an electron beam passes through a sample, an amount of energy loss corresponding to an element constituting the sample is received by interaction with the sample. Therefore, by analyzing the loss energy of the electron beam transmitted through the sample, information on the elements constituting the sample can be obtained. Electron energy loss spectroscopy (hereinafter EELS: Electron Energ
The y-loss spectroscopy) device is a device that performs elemental analysis of a sample by measuring the energy lost during transmission of the sample from the energy spectrum of the electron beam transmitted through the sample.

FIG. 6 is a diagram showing a configuration of a conventional EELS device.

[0004] The electron beam 104 transmitted through the sample 103 passes through an objective lens 105, an intermediate lens 106, and a projection lens 10.
7. Enter the electron energy analyzer through the entrance stop 108. Furthermore, the electron beam is applied to the magnetic field prism 109.
The energy is dispersed according to the energy, and the energy width of the electron beam taken in the exit slit 111 through the lens 110 is limited, and is detected by the CCD 112.

[0005] The CCD 112 is actually a two-dimensional position detecting element composed of a phosphor which emits fluorescence upon receiving an electron beam and a plurality of pixels such as a CCD which can measure the incident intensity for each detection position. In this case, the CCD 112 will be described. Although the fluorescence intensity actually detected by the CCD 112 is described as an electron beam intensity.

The electron beam intensity detected in the form of fluorescence at each pixel on the CCD 112 is stored in a memory corresponding to each pixel. Here, taking the sum of the electron beam intensities incident on the pixels in the same column having the same energy value,
A loss energy spectrum is obtained and the exit slit 11
By adjusting the width of 1, the width of the energy taken in can be arbitrarily adjusted.

By changing the intensity of the magnetic field in the magnetic field prism 109, the amount of energy per pixel of the CCD 112 can be adjusted.

FIG. 7A shows an electron beam intensity distribution on the CCD 112, and FIG. 7B shows an energy loss spectrum with the energy lost in the sample 103 taken along the vertical axis and the electron beam intensity taken along the horizontal axis. It is a figure showing an example. The energy loss spectrum shown in FIG. 7B is composed of a zero loss peak where the energy loss is around 0 and a peak caused by a constituent element of the sample.

[0009]

In a transmission electron microscope using the two-dimensional position detecting element constructed as described above, the loss energy is determined by the position of the incident pixel of the electron beam on the two-dimensional position detecting element. However, if the path of the electron beam shifts or vibrates due to the influence of an external electromagnetic field, the position of the incident pixel on the two-dimensional position detecting element also fluctuates, and the energy resolution of the spectrum is degraded.

FIG. 8 is a diagram showing a state in which the energy resolution of the spectrum is degraded. FIGS. 8A to 8D respectively show t = 0 ms to 2.5 ms and 2.5 ms to 5 m
s, 5 ms to 7.5 ms, 7.5 ms to 10 ms, continuous zero loss peaks measured every 2.5 ms,
FIG. 8E shows zero loss peaks from 0 ms to 10 ms. When a long-time spectrum is measured as shown in FIG. 8 (e), the path of the electron beam shifts due to the influence of the external electromagnetic field or the energy resolution of the spectrum deteriorates due to the influence of vibration.

In order to solve the above problem, it is conceivable that the measurement is performed in a short time in which the path of the electron beam is not affected by the shift or vibration due to the external electromagnetic field. The detection intensity does not reach the required intensity, and the reliability of the measurement decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and the energy resolution is deteriorated even if the path of the electron beam shifts or vibrates due to the external electromagnetic field. It is an object of the present invention to provide an electron energy loss spectrometer capable of measuring a spectrum for a long time and a method of correcting a spectrum shift thereof.

[0013]

[0014]

SUMMARY OF THE INVENTION The electronic energy of the present invention
The loss spectroscopy method is an electron energy loss spectroscopy method for detecting a spectrum of an electron beam transmitted through a sample. A two-dimensional position detecting element, a second two-dimensional position detecting element for correcting the incidence of the zero loss peak of the electron beam, and the first
Two-dimensional position detecting element and second two-dimensional position detecting element
A first method for storing the detection value of each pixel in
Memory and a second memory, performing measurement in a short time a plurality of times, and performing the second measurement in each of the plurality of measurements.
For each of the detected values in the memory, the address at which the spectral intensity of the electron beam is maximized is detected, and these addresses are
Address is a predetermined address for the peak value and
The address is moved so that the address of the first memory is moved in the same manner as the second memory.
The detection value of the first memory scan matches identified as the detection value for the same energy value, characterized in that the measurement result of a long time by integrating the detected values at each measurement.

[0015]

The electron energy loss spectrometer of the present invention
Is an electron energy loss spectrometer for detecting a spectrum of an electron beam transmitted through a sample, wherein the first for detecting the spectrum of the electron beam is constituted by a plurality of pixels.
A two-dimensional position detecting element, and a second two-dimensional position detecting element for correction Zeroro Speak of the electron beam, which is composed of a plurality of pixels are arranged in a position to be incident, the first
One two-dimensional position detecting element and a second two-dimensional position detecting element
A first storing the detection value of each pixel in the child
And a control device for determining the detection result of the spectrum of the electron beam based on the detection results by the first and second two-dimensional position detecting elements, wherein the control device performs for each detected value of the second memory in each measurement in a short time made the spectral intensity of the electron beam detects each address having the maximum this
These addresses are predefined for peak values
The address is moved to become the address, and the second
Row address movement of said first memory like the memory
The detection value of the first memory having the same address is identified as the detection value for the same energy value, and the detection result in each measurement is integrated to obtain the measurement result over a long time. It is characterized by doing.

[0017]

[0018]

[Operation] In the present invention configured as described above, the detected spectrum value is shifted and integrated in accordance with the shift of the zero loss peak at which the spectrum intensity of the electron beam becomes maximum. If the path of the electron beam shifts or vibrates due to the influence of the external electromagnetic field, the zero loss peak also shifts, and the shifted spectrum detection value is added accordingly, so that the energy resolution does not deteriorate .

[0020]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. In this embodiment, E shown as a conventional example in FIG.
The CCDs 112 of the ELS device are two CCDs 1 and 2, and memories 12 and 1 for storing detection values of the CCDs 1 and 2 are provided.
3. A control device 14 for correcting the detection value from the stored contents of each memory and a display device 15 for displaying the correction result are provided. In addition, the sample 3, the electron beam 4, the objective lens 5, the intermediate lens 6, the intermediate lens 6, the projection lens 7, the entrance diaphragm 8, the magnetic field prism 10, and the exit slit 11 shown in FIG. , Objective lens 1
05, intermediate lens 106, projection lens 107, entrance stop 108, magnetic field prism 110, and exit slit 111
The description is omitted because it is the same as.

FIG. 2 and FIG.
FIG. 4 is a diagram for explaining a light receiving state of No. 2 in which the traveling direction of the electron beam 4 is drawn in a direction from the top to the bottom of the paper.

In this embodiment, a CCD 2 for drift correction is provided beside the CCD 1 for spectrum detection. The CCD 2 for drift correction is provided so that the zero loss peak falls on the light receiving surface.

In the example shown in FIG. 1, the case where the zero loss spectrum is incident on each of the CCDs 1 and 2 is shown.
In the example shown in FIG. 7, a state is shown in which the zero loss spectrum does not enter the CCD 1 for spectrum detection and enters only the CCD 2. As shown in FIGS. 1 and 2, a correction CCD 2 is provided so as to follow the zero loss peak.

The reason why the zero loss spectrum does not enter or exit the light receiving surface of the spectrum detecting CCD 1 as described above is due to the fact that the degree of dispersion changes depending on the excitation value of the magnetic field prism 9. For example, if the CCD is 1024
When the energy detectable per pixel is 0.5 eV, the detectable energy width is limited to 512 eV. 600 eV
If you want to see the energy lost peak of C
The energy range incident on the CD is 150 eV to 650 e
V, etc., and a zero loss peak does not enter.

A typical energy loss spectrum is shown in FIG.
As shown in (2), the zero loss peak has the maximum intensity. Since the zero-loss peak has a long spectral drift period,
For example, in the case of a short-time measurement of about 2.5 ms, there is almost no influence from the spectrum drift.

This embodiment focuses on the characteristics of the zero loss peak as described above, and detects the detected value of the CCD 1 for spectrum detection in accordance with the detection state of the CCD 2 for correction to which the zero loss peak is incident. Is corrected, thereby preventing the path of the electron beam from shifting or vibrating under the influence of the external electromagnetic field, thereby preventing the energy resolution from deteriorating.

Next, the operation in the long-time measurement of this embodiment will be described.

The detected values of the CCD 1 and the CCD 2 are stored in the memories 12 and 13 via the control device 14, respectively. The controller 14 recognizes the data detected by the CCDs 1 and 2 in the same time zone (at the same time) in association with each other, and shifts the detection value of the CCD 1 in accordance with the shift of the zero loss peak detected by the CCD 2. I do. More specifically, the spectrum intensities measured in a short time by each of the CCDs 1 and 2 are stored in the memories 12 and 13, the address having the maximum value in the memory 13 is determined, and the value (count) of the address is peaked. Move to an address that is predetermined for the value. Similarly, the count around the peak value is moved to around the peak value address. Then, the strength of each address after the movement is integrated. The same address movement as that of the memory 13 is performed on the memory 12, and the result is output to a display device 15 such as a CRT or a printer.

FIG. 4 is a diagram showing a detection state of a zero loss spectrum according to the present embodiment. FIGS. 4A to 4D show time t = 0 ms to 2.5 ms, 2.5 ms to 5 ms, and 5 ms.
2.5 continuous from 7.5 ms, 7.5 ms to 10 ms
FIG. 4E shows a zero-loss peak measured every ms.
Indicates a zero loss peak of 0 ms to 10 ms obtained by integrating them. 4 (b) to 4 (d), the solid line actually shows the detected value by the CCD 2, and the broken line
3 shows the result of performing the above-mentioned address movement performed in step S3. As shown by the dashed line, the path of the electron beam shifts under the influence of the external electromagnetic field, and the peak position of the spectrum gradually moves accordingly.However, the resolution is not reduced by performing the address movement. Absent.

The controller 14 performs the same address movement as that of the memory 13 with respect to the memory 12 for storing the detected value of the CCD 1 for spectrum detection. In spectrum detection for measuring a time spectrum, degradation of resolution does not occur.

As described above, the period in which the spectrum of the zero loss peak occurs is 10 ms or more, so that the influence of the vibration of the spectrum of the zero loss peak can be reduced.

Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram showing a main configuration of the second embodiment of the present invention.

In this embodiment, the zero loss peak is very far from the window for spectrum measurement and does not come out of the magnetic field prism.

This embodiment is different from the first embodiment in that the exit window of the magnetic field prism 9 is widened, and a CCD 14 for drift correction is installed in front of the exit slit 11 and the lens 10. Other configurations are the same as those of the embodiment shown in FIG.

The arrangement according to the present invention is effective even when the path of the electron beam deviates from the normal route as shown by the broken line in the figure.

In each of the embodiments described above, the detection value of the CCD 1 (CCD 13) for detecting the spectrum and the CCD 2 (CCD 13) for correcting the zero loss peak to enter.
Although it has been described that the memories 12 and 13 for respectively storing the detection values of 14) are provided independently, these may be realized by dividing the area in one memory.

Further, a CCD for correction may be combined with a moving mechanism, and moved to a position where the zero loss peak is incident by the moving mechanism, and then the spectrum detection described in each of the above embodiments may be performed.

Further, it has been described that two CCDs are provided. However, when detecting a spectrum near the zero loss peak or when using a CCD having a large number of pixels, one CCD is used.
The spectrum detection shown in each of the above embodiments can be performed by one CCD, and such a configuration may be adopted.

[0040]

The effect obtained by the present invention is that the effect of the shift of the spectrum and the vibration due to the external electromagnetic field can be eliminated. Conventionally, even if an electron beam having an energy width of about 0.5 eV is incident, the path of the electron beam is shifted by an external electromagnetic field, and the energy width is observed to be, for example, about 1 eV. In this case, the shift in the path of the electron beam due to the influence of the external electromagnetic field, or in the case of vibration, the spectrum detection value shifted according to the shift of the zero-loss peak is integrated to increase the energy width, that is, decrease the energy resolution. Has the effect of being able to suppress

[0041]

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram for explaining a light receiving state of CCDs 1 and 2 in FIG.

FIG. 3 is a diagram for explaining a light receiving state of CCDs 1 and 2 in FIG. 1;

FIG. 4 is a diagram showing a detection state of a zero-loss spectrum according to the embodiment shown in FIG. 1;
0 ms to 2.5 ms, 2.5 ms to 5 ms, 5 ms to
2.5ms continuous 7.5ms, 7.5ms to 10ms
A zero loss peak measured for each s is shown, and (e) shows a zero loss peak of 0 ms to 10 ms obtained by integrating them.

FIG. 5 is a block diagram showing a main configuration of a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of an EELS device.

7A shows the electron beam intensity distribution on the CCD 112 shown in FIG. 6, and FIG. 7B shows the energy loss obtained by taking the energy lost in the sample 103 on the vertical axis and taking the electron beam intensity on the horizontal axis. It is a figure showing an example of a spectrum.

FIG. 8 is a diagram showing a state in which the energy resolution of a spectrum is degraded;
s to 2.5 ms, 2.5 ms to 5 ms, 5 ms to 7.5
ms, 7.5 ms to 10 ms, continuous zero-loss peaks measured every 2.5 ms, and (e) is 0 ms to 1 ms.
It shows a zero-loss peak at 0 ms.

[Explanation of symbols]

 1, 2 CCD 3 sample 4 electron beam 5 objective lens 6 intermediate lens 7 projection lens 8 entrance stop 9 magnetic field prism 10 lens 11 emission slit 12, 13 memory 14 control device 15 display device

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01J 49/44 H01J 37/26

Claims (2)

(57) [Claims] 1. An electron energy loss spectroscopy method for detecting a spectrum of an electron beam transmitted through a sample, comprising: a first two-dimensional position detecting element for detecting a spectrum of the electron beam as a two-dimensional position detecting element constituted by a plurality of pixels. A two-dimensional position detecting element , a second two-dimensional position detecting element for correcting incidence of the zero-loss peak of the electron beam , the first two-dimensional position detecting element, and a second two-dimensional position
Stores the detection value of each pixel in the detection element
A first memory and a second memory that perform measurement in a short time a plurality of times, and for each detection value of the second memory in each of the measurements performed a plurality of times, the spectrum intensity of the electron beam is reduced. The largest a
Detecting a dress each of these addresses peak value
Address so that it is a predetermined address for
Perform dress movement, the second memory as well as the address of the first memory
Is moved, and the first memory having the same address is detected.
An electron energy loss spectroscopy method comprising identifying output values as detection values for the same energy value, and integrating the detection values in each measurement to obtain a measurement result over a long period of time. 2. An electron energy loss spectrometer for detecting a spectrum of an electron beam transmitted through a sample, comprising: a first two-dimensional position detecting element for detecting a spectrum of the electron beam, the device being constituted by a plurality of pixels; A second two-dimensional position detecting element for correction, which is arranged at a position where the zero loss peak of the electron beam constituted by the pixels is incident, and the first two-dimensional position detecting element and the second two-dimensional position
Stores the detection value of each pixel in the detection element
A first memory and a second memory, and a control device for determining a detection result of the spectrum of the electron beam based on a detection result by the first and second two-dimensional position detection elements, wherein the control device includes: for each detected value of the second memory in each measurement in a short time is performed a plurality of times, the spectral intensity of the electron beam detects each address having the maximum set these addresses beforehand for the peak value Is
The address is moved so that the address becomes the same as the address of the first memory, similarly to the second memory.
Is moved, and the first memory having the same address is detected.
An electron energy loss spectrometer characterized by identifying output values as detection values for the same energy value, and integrating the detection values in each measurement to obtain a measurement result over a long period of time.