JPH071684B2 - Electron beam intensity measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electron beam intensity measuring device for measuring electron beam intensity in an electron beam device such as an electron microscope using a two-dimensional sensor.

[Conventional technology]

Conventionally, structural analysis of a sample is performed by acquiring an X-ray or electron beam diffraction image of the sample. In this structural analysis, attention has been focused only on the information on the position of the diffraction spot, but recently, by measuring the intensity of each diffraction spot and obtaining this quantitative information, the crystal structure of the sample was constructed. I have come to know what each element is doing. There are the following two types of electron beam intensity measuring devices for that purpose.

One uses photographic film as electron beam intensity recording material,
This is a device that measures the electron beam intensity from the degree of blackening, and the other is a device that measures the electron beam intensity using a scintillator and a photomultiplier tube (PMT), or an ammeter.

[Problems to be Solved by the Invention]

However, in an apparatus in which a photographic film is used as an electron beam intensity recording material and the electron beam intensity is measured from its blackening degree, the relationship between the blackening degree of the photographic film and the electron beam intensity is as shown in FIG. The characteristic range is linear and the usable range is at most 2 × 10 ^-11 to 2 × 10 ^-10.
(Coulomb / cm ² ) is only about one digit, and it varies greatly depending on the type of developing solution and the film development conditions such as development temperature, as shown by characteristics A, B, and C, and even linear Since it is not perfect, it was difficult to measure the electron beam intensity accurately from the degree of blackening. for that reason,
For example, even when trying to obtain an electron beam diffraction image as in the case of X-ray diffraction imaging, the electron beam intensity range in electron beam diffraction is 2.
It couldn't be covered with film because it reached about 5 to 3 digits.

In a device that measures the electron beam intensity using a scintillator and a photomultiplier tube (PMT) or an ammeter, the scintillator or ammeter cannot store the electron beam and the electron microscope has a two-dimensional distribution. It was necessary to scan an electron microscope image for the measurement of the electron beam intensity distribution of, and as a result, the electron beam intensity distribution at the same time could not be measured.

The present invention is intended to solve the above-mentioned problems, and it is possible to obtain a wide dynamic range, to accurately measure an electron beam intensity value, and to obtain an intensity distribution of a two-dimensional electron beam image at the same time. It is an object of the present invention to provide an electron beam intensity measuring device capable of detecting.

[Means for Solving the Problems]

To this end, the present invention provides means for irradiating a two-dimensional sensor with an electron beam, means for scanning and exciting the two-dimensional sensor, light detecting means for detecting light emitted from the two-dimensional sensor, and the detecting means. Means for converting the signal from the above into a signal representing an incident electron beam intensity value corresponding to the detected intensity of the emitted light based on the relationship between the detected intensity of the emitted light and the incident electron beam intensity stored in advance. It features an electron beam intensity measuring device.

[Action]

The present invention irradiates a two-dimensional sensor with an electron beam to accumulate energy, detects the emitted light from the two-dimensional sensor generated by excitation such as light irradiation, and detects the detected intensity values of the emitted light stored in advance. By measuring the incident electron beam intensity from the emitted light intensity based on the relationship with the incident electron beam intensity value, it is possible to measure the electron beam intensity with excellent linearity and a wide dynamic range.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

In recent years, a two-dimensional sensor composed of a stimulable phosphor sheet or the like that accumulates irradiation electron beam energy when irradiated with an electron beam and then emits the accumulated energy as light by being excited by light irradiation or heating. Was developed, and one applied to an electron microscope has been proposed (Japanese Patent Laid-Open No. 61-517).
38, JP-A-61-93539, etc.). This two-dimensional sensor can temporarily store at least part of its energy when it is exposed to an electron beam, and can detect at least part of the accumulated energy by light, electricity, sound, etc. when it is excited from the outside. It consists of a material that has the ability to release in various forms.
Specifically, as this two-dimensional sensor, for example, JP-A-55-1 is used.
2429, 55-116340, 55-163472, 56-11395
No. 56-104645 and the like are particularly preferably used for the stimulable phosphor sheet. That is, when a certain kind of phosphor is irradiated with radiation such as an electron beam, a part of the energy of this radiation is accumulated in the phosphor, and then when the phosphor is irradiated with excitation light such as visible light, it is accumulated. The phosphor exhibits fluorescence (stimulated luminescence) according to energy. A phosphor having such a property is called a storage phosphor. The stimulable phosphor sheet is a sheet-shaped recording material made of the above stimulable phosphor, and generally comprises a support and a stimulable phosphor layer laminated on the support. The stimulable phosphor layer is formed by dispersing the stimulable phosphor in an appropriate binder. When the stimulable phosphor layer is self-supporting,
As such, it can serve as a stimulable phosphor sheet. An example of the stimulable phosphor for forming this stimulable phosphor sheet is described in detail in JP-A-61-93539.

Further, as the above-mentioned two-dimensional sensor, for example, Japanese Examined Patent Publication No.
No. 55-47720 and the like can be used. This thermal phosphor sheet mainly absorbs radiation energy accumulated by the action of heat,
It is a sheet-shaped recording material made of a phosphor (thermophosphor) that emits as a thermophosphor.

When the relation between the incident electron dose and the output signal intensity was investigated for such a two-dimensional sensor, the relation as shown in Fig. 3 was obtained, and the relation was about 10 ^-15 to 10 ^-9 (coulomb / cm ² ). It was found that the linearity was maintained over a wide range.

The present invention focuses on the fact that the characteristic as shown in FIG. 3 can be obtained by using the two-dimensional sensor in this way, and the electron beam intensity is measured by utilizing this characteristic.

As can be seen from the characteristics shown in FIG. 3, since the linearity is satisfied between the incident electron beam and the output signal intensity for 6 digits or more, the two-dimensional sensor that has accumulated energy by electron beam exposure is irradiated with light or heated. It is possible to accurately measure the irradiation electron beam from the emission intensity when excited by.

FIG. 1 is a diagram showing an embodiment of an electron beam intensity measuring apparatus utilizing the characteristics of FIG. 3, 1 is an electron microscope, 2 is a camera room,
3 is an electron gun, 4 is an electron beam, 5 is a converging lens, 6 is a sample,
7 is an objective lens, 8 is a magnifying lens, 9a is a stimulable phosphor sheet being imaged, 9b is a stimulable phosphor sheet being read, 10 is a carrier, 11 is a laser light source, 12 is a laser beam, and 13 is a galvanometer. A mirror, 14 is an erasing light source, 15 is a PMT, 16 is an amplifier, 17 is a processor, 26 is a display, and 27 is a console.

In the figure, a stimulable phosphor sheet is provided below the electron microscope 1.
A camera room 2 in which a transporting machine 10 for transporting 9a, 9b and 9a, 9b is installed is attached. Further, a reading unit is incorporated in the camera room 2. This is a part for reading out the electron beam intensity from the two-dimensional sensor 9b which has finished photographing, and the laser beam 12 generated from the laser light source 11 is scanned and irradiated by the galvano mirror 13 onto the two-dimensional sensor 9b. The light generated in proportion to the accumulated electron beam intensity is measured with the PMT15, and the amplifier 1
It is sent to the processor 17 through 6 and detected as an electric signal. A memory is provided inside (or outside) of the processor 17, and this memory stores the output signal intensity of the detector of the emitted light and the stimulable phosphor sheet, which are obtained based on the measurement performed in advance. The relationship with the incident electron beam intensity value (electron dose) as shown in FIG. 3 is recorded as a table. The processor 17 is capable of designating an address in the table by a signal representing the intensity of the emitted light from the PMT 15 and reading a signal representing the sensor incident electron beam intensity value (electron dose) corresponding to the address.

Next, the operation will be described. The electron beam 4 from the electron gun 3
Is converged by the converging lens 5 and irradiated on the sample 6, and an electron beam image is formed by the objective lens 7. This electron beam image is projected on the stimulable phosphor sheet 9a by the magnifying lens 8 and photographed. The stimulable phosphor sheet on which the image of the electron microscope is taken is conveyed to the reading section by the conveying machine 10, the signal intensity distribution is read, and the signal is processed by the processor 17.
That is, when a signal representing each intensity value of the emitted light is sent to the processor 17, the processor 17 specifies the address of the conversion table stored in the memory on the basis of this signal to determine each intensity value of the emitted light. The signal represented is converted into a signal representing the incident electron beam intensity value of the stimulable phosphor sheet corresponding to each intensity value. After that, stronger light is emitted from the erasing light source 14,
After the afterimage is erased, the carrier machine 10 sends the image again to the exposure position for re-exposure. In this way, the electron beam intensity is two-dimensionally and quantitatively read, and the read value is displayed on the display 26. In this embodiment, the reading unit for the stimulable phosphor sheet is shown in the camera room 2, but the reading unit for the stimulable phosphor sheet may be separated from the camera chamber 2. When a thermal phosphor sheet is used instead of the stimulable phosphor sheet, a heating type excitation means may be used instead of the light irradiation excitation means.

Further, in the above-described embodiment, the relation shown in FIG. 3 is stored in the form of a conversion table, but it is stored in the form of a conversion formula, and the processor calculates this formula to store the incident electron beam intensity of the sensor. You may make it calculate a value.

Furthermore, in the above-described embodiment, the intensity of the sensor incident electron beam has been limited to the calculation, but the sensor incident current value may be measured as follows. That is, conventionally, an ammeter was used to determine the exposure amount, but the conventional ammeter lacks sensitivity for imaging using the high-sensitivity sensor using the above-mentioned stimulable phosphor. Will end up. Therefore, the above-described embodiment may be developed and described with reference to FIG. Incidentally, in FIG. 2, the same components as those in FIG. 1 are designated by the same reference numerals.

In FIG. 2, reference numeral 18 is a second stimulable phosphor sheet for measuring a current value. The second storage phosphor sheet 18 is attached to the shaft 19
By rotating around the stimulable phosphor sheet 18
Can be inserted and removed on the optical axis of the electron beam. Reference numeral 20 is a second PMT, 21 is a second amplifier, 22 is an excitation light source, 23 is an electron beam shutter deflector, 24 is a blanking signal generator, and 25 is a second erasing light source.

In such a configuration, first, a blanking signal generator 24 sends a blanking signal to the deflector 23 under the control of the processor 17 so that the sample is not irradiated with the electron beam. Then, the stimulable phosphor sheet 9a is arranged outside the optical axis. Therefore, light from the erasing light source 25 is applied to the stimulable phosphor sheet 18 in a state where the stimulable phosphor sheet 18 is erected as shown by the solid line in the figure to erase the afterimage on the stimulable phosphor sheet 18. Next, after arranging the stimulable phosphor sheet 18 on the optical axis as shown by the dotted line in the figure, the blanking signal generator 27 stops the sending of the blanking signal for a predetermined time t to store the stimulable phosphor sheet. Seat 18 for a certain time t
Only the electron beam carrying the sample image is irradiated. Then, the electron beam is blanked, and the stimulable phosphor sheet 18 is placed again in the upright position. Therefore, the excitation light source 22 is caused to emit light, and the light from this light source 22 is detected by the PMT 20. The signal from the PTM20 is sent to the processor 17 via the amplifier 21, and this signal is converted into a signal V representing the electron beam intensity corresponding to the intensity of the emitted light by the processor 17 as in the case of the embodiment shown in FIG. To be converted. The processor 17 further calculates V / t using the signal representing the exposure time t. This value represents the average value of the electron beam current value projected on the stimulable phosphor sheet 18,
This value is displayed by the display 27 under the control of the processor 17.
Is displayed in. By looking at this displayed value, the operator can accurately know the average value of the electron beam current value at the time of the extremely weak main shooting, and by doing so, the stimulable phosphor sheet 9a is placed directly below the optical axis to perform the main shooting. In this case, the exposure time can be set appropriately.

〔The invention's effect〕

As described above, the present invention pays attention to the fact that the emission intensity and the exposure electron beam intensity at the time of reading the electron beam image of the two-dimensional sensor have an excellent linear relationship (proportional relationship) over an extremely wide range, and utilize this characteristic. This makes it possible to measure the electron beam intensity at the time of exposure from the emission intensity of the two-dimensional sensor, which has a wide dynamic range and enables accurate measurement. Therefore, even if the electron beam diffraction range and the electron beam intensity range such as the absorption spectrum when the material is irradiated with the electron beam are wide, which were not possible with the conventional photographic film, the two-dimensional sensor is used for recording and quantitative determination. Therefore, it is possible to read out with high accuracy, and it is extremely effective when applied to structural analysis and the like. Further, since the two-dimensional sensor is a storage type detector, it becomes possible to measure the electron beam intensity at the same time in a two-dimensional electron beam image.

[Brief description of drawings]

FIG. 1 is a diagram for explaining one embodiment of an electron beam intensity measuring device according to the present invention, FIG. 2 is a diagram for explaining another embodiment of the present invention, and FIG. 3 is a stimulable phosphor sheet. Showing the relationship between the incident electron dose and the output signal intensity, and FIG. 4 is a view showing the relationship between the incident electron dose and the degree of blackening in the photographic film. 1 ... Electron microscope, 2 ... Camera room, 3 ... Electron gun, 4
...... Electron beam, 5 ...... Convergent lens, 6 …… Sample, 7 …… Objective lens, 8 …… Magnifying lens, 9 a …… Storing phosphor sheet during imaging, 9 b …… Storing phosphor during reading Sheet, 10 ...
… Conveyor, 11 …… Laser light source, 12 …… Laser light, 13 ……
Galvanometer mirror, 14, 25 …… Erase light source, 15, 20 …… PM
T, 16, 21 ... Amplifier, 17 ... Processor, 22 ... Excitation light source, 23 ... Blanking deflector, 4 ... Blanking signal generator, 26 ... Display, 27 ... Operating console.

Front page continuation (72) Inventor Yoshiaki Harada 3-1-2 Musashino, Akishima-shi, Tokyo JEOL Ltd. (56) Reference JP-A-61-138443 (JP, A)

Claims (2)

[Claims] 1. A means for irradiating a two-dimensional sensor with an electron beam,
The means for scanning and exciting the two-dimensional sensor, the light detecting means for detecting the light emitted from the two-dimensional sensor, and the detection intensity of the emitted light and the incident electron beam intensity in which the signal from the detecting means is stored in advance. An electron beam intensity measuring device comprising means for converting into a signal representing an incident electron beam intensity value corresponding to the detected intensity of the emitted light based on the relationship. 2. The two-dimensional sensor, after emitting light by excitation,
The electron beam intensity measuring device according to claim 1, wherein the afterimage is erased by irradiation with light from an erasing light source.