JPS62113349A - Electron beam energy analyzer - Google Patents

Abstract

PURPOSE:To make electron beam spectrums different in signal intensity each measurable with a detector of constant sensitivity, by adding an electron beam adsorber whose adsorption factor differs according to an incident position and a deflector both to an interval between a selector device of electron beams and the detector. CONSTITUTION:Electron beams 17 transmitting a sample are led into a spectrometer 9 and dispersed according to energy, and selected by a slit 13. Next, they are detected by a detector 14 and an energy spectrum is secured. At this time, at an interval between the slit 13 and the detector 14, there are provided with deflectors 20 and 21 to be deflected with output of the detector 14 and an electron beam absorber 22 whose adsorption factor differs according to an incident position. And, such as electron beam as being very large in a dynamic range is adsorbed by the adsorber 22 according to signal intensity, making it detectable in keeping sensitivity of the detector 14 constant as it is. Therefore, quantitative measurement is performable over the whole range of the signal intensity without entailing any alteration of measuring conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electron beam energy analyzer, and more particularly to an electron beam energy analyzer that facilitates the measurement of energy spectra.

(Prior art) When an electron beam energy analyzer irradiates a sample with an electron beam using an electron microscope or the like, the electron beam loses part of its energy due to interaction with the sample, but the energy of the electron beam that has passed through the sample is When analyzed, unique spectra are obtained depending on the elements that make up the sample, so this device performs elemental analysis by observing this energy loss spectrum.

FIG. 4 shows an energy analyzer in a conventional electron microscope, in which electrons 1! from an electron gun 1! i12 is irradiated onto the sample 4 through the focusing lens system 3, and the electron beam 2 transmitted through the sample 4 is guided to the spectrometer 9 via the objective lens 5, the intermediate lens 6, the projection lens 7, the entrance aperture 8, and the spectrometer 9.
In this spectrometer 9, the electron beam is dispersed according to energy and focused onto an exit slit 13 by an exit lens 12 to form a kind of band spectrum. 10a is a main power supply for supplying the main current to the main coil 11a of the spectrometer 9, and 10b is a sweep power supply for supplying the sweep 'R current to the energy sweep coil 11b. The spectrometer 9 performs an energy sweep using the sweep current from the sweep power supply 10b. An electron beam with a specific energy passes through the output slit 13 depending on the current value of the energy sweep coil 11b, and as the sweep current value changes, the energy of the electrons passing through the output slit 13 (direction is swept, so the energy 1M
An output signal of an energy spectrum is obtained on the detector 14 by the local current of the reference coil 11b. This output signal is input to a recorder 16 through an amplifier 15. on the other hand,
Since the sweep output from the sweep power supply 10b sweeps the recorder 16 in synchronization, an energy spectrum can be displayed. Fifth
The figure shows an example of the energy spectrum. is the so-called zero loss peak, which corresponds to the energy value of the input rJ1 electron beam with no energy loss, and Pl is the peak called the plasma loss peak, which is a peak caused by the interaction of Pn etc. with specific elements in the sample. be. The signal intensities of these peaks Pl and pn are significantly different, and their dynamic range is 107~
The number is as high as 108. Therefore, when the peak pn is amplified to the extent that it is easy to observe, the peaks P1 and Pl become saturated, and when the peak Pl is amplified to the extent that it is easy to observe, the peak Pn becomes almost unobservable.

In an electron beam energy analyzer, quantitatively measuring electron beam signals is essential for qualitative and quantitative analysis of energy spectra. Therefore, in order to eliminate the above-mentioned problems, each time the signal for subtracting the separation energy in the electron beam energy analyzer reaches a certain level, the amplification gain for amplifying the detection signal '- is automatically switched, making it suitable for observation. I'm trying to get a spectrum that looks like this.

(Problems to be Solved by the Invention) As mentioned above, when trying to detect a signal with an extremely large dynamic range using an amplification gain that corresponds to the signal size, the sensitivity of the detector may change during the measurement. It becomes necessary. However, since it takes a relatively long time for the electric circuit system to stabilize to a new sensitivity state, it is not possible to measure with high precision during this transitional stage.

The present invention has been made in view of the above points, and an object of the present invention is to use an electron beam energy analyzer that can measure signal groups with significantly different signal intensities without changing measurement conditions such as changing detector sensitivity. The goal is to provide the following.

(Means for Solving the Problems) The present invention, which solves the problems described in 11J1, includes a spectrometer that separates electron beams from a sample according to their energies, and a device for sweeping the energy of the spectrometer. means, a sorting means for sorting the electron beam separated by the spectrometer, a detection means for detecting the electrons sorted by the sorting means, and an amplification means for amplifying the output signal from the detection means. and display means for displaying an energy spectrum based on the output signal from the amplification means, which is swept in synchronization with the sweep of the spectrometer by the sweep means,
An electron beam absorber whose electron absorption rate differs depending on the incident position of the electron beam is disposed between the sorting means and the detector, and a deflector is disposed for deflecting the electron beam exiting the sorting means. As the spectrometer sweeps, the electrons emitted from the selection means enter different positions of the electron beam absorber Q4 t! L. The device is characterized in that it includes means for controlling the deflection by the deflector so that the deflection is controlled by the deflector.

(Function) The present invention uses an electron beam absorber whose absorption rate is known at each part by an electron beam synchronized with a sweep power supply (-) which has an extremely large dynamic range and which is swept in accordance with the magnitude of energy. Since the absorption is carried out stepwise according to the signal strength, it is possible to quantitatively measure the entire range of signal strength.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, the same parts as in FIG. 2 are given the same reference numerals. 17 is an electron beam that has passed through the sample. Electrons 4017, which include a zero loss beak P + that has the energy of the incident electron beam without loss, a plasma loss beak P2, and a beak pn that has suffered an energy loss of a value specific to the element, pass through the spectrometer 9 through the Or exit slit 13. It is separated into an electron beam 19 and an electron beam 18 which is dispersed by a spectrometer 9 and blocked by an exit slit 13 . The electron beam 19 enters the detector 14, and the signal strength corresponding to the energy value is detected in synchronization with the deflection signal. The signal from the detector 14 is amplified by an amplifier 15 and then sent to the next stage. 24 is a clock oscillator that oscillates clock pulses and supplies the clock pulses to the 1 m power supply 10b. The sweep current 10b oscillates a sweep signal, causes the sweep current to flow through the sweep coil 11b, and sweeps the energy of the electrons passing through the output slit 13.

The clock oscillator 24 also provides clock pulses to the deflection power supply 23, and the deflection 7111!23 oscillates a deflection signal and provides the signal to the deflector 20.21. Each of the above-mentioned signals is as shown in FIG. The signal given to the deflector 20 is the third
A signal having a waveform as shown in FIG. 3C is applied to the deflector 21, and a signal with the opposite polarity to this signal is given to the deflector 21 to return the electron beam to the detector 14. To explain using the spectrum diagram shown in FIG. 5, for the zero loss beak P+ signal, α, which is a large deflection signal, is used for the plasma beak P? For β, p
For n, give δ. FIG. 2 shows the operation of the deflector based on this deflection signal. The structure of the electron beam absorber 22 is such that the thickness of the absorber changes as shown in the figure, and the absorption rate increases in proportion to the thickness. At the maximum deflection voltage, the electron beam takes the path indicated by α, the attenuation of the electron beam is maximum, and β, γ
The amount of attenuation decreases sequentially, and δ enters the detector 14 with zero attenuation.

Each attenuation is previously calibrated and known.

Here, the paths α, β+7+δ correspond to the potentials (or current values) of α, β, γ, and δ of the deflection signal in FIG. 3(C).

In this way, the electron beam emitted by the sweep current corresponding to the energy value is leaked by the deflection signal synchronized with the sweep current, undergoes a certain amount of absorption by the electron beam absorber, and is detected by a detector with a certain sensitivity. Then, a recording device (not shown) performs amplification according to the absorption amount of the electron beam absorber to restore the original signal strength and record the signal.

In this way, according to the present invention, a deflection signal is applied to the deflector in synchronization with the sweep current applied to the spectrometer, and the sensitivity of the detector is increased by causing the electron beam absorber to absorb according to the signal strength of the electron beam spectrum. It can be measured while keeping it constant.

Note that the above is just an example; for example, the deflection signal is not a stepped signal, but the magnitude of the deflection signal is changed according to the strength of the signal passing through the electron beam absorber and fed back to the deflector. Good too.

(Effects of the Invention) As described above in detail, according to the present invention, electron beam spectra with significantly different signal intensities can be accurately measured using a detector with constant sensitivity.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating an embodiment of the electron beam energy analyzer jd of the present invention, FIG. 2 is an explanatory diagram of the path according to the signal strength of the electron beam, and FIG. 3 is a diagram illustrating the timing of each borrowing. FIG. 4 is a block diagram of a conventional electron beam energy analyzer, and FIG. 5 is an example of an electron beam spectrum diagram. 1...Electron gun 2...Electron beam 3...Focusing lens system 4...Sample 5.6.7...Lens 8...Incidence aperture 9...Spectrometer 10
a Main power supply 101)...Pail power supply IQ 11a...
Main coil 11b...1 suspension coil 12...output lens 13...output slit 14...detector 1
5...Amplifier 16...Record g117...
・Trial transmission electron beam 18... Electron beam 19 that does not pass through the exit slit...
Electron beam passing through the exit slit 20.21...Deflector 22...Electron beam absorber 23...Deflection power source
24... Patent applicant for clock oscillation: JEOL Co., Ltd. Representative: Attorney: MW Ijima and 1 other person Figure 1 1]b sweep coil] 3. Output slit] 5,1!1B 17; diagram energy

Claims (1)

[Claims] A spectrometer that separates electron beams from a sample according to their energies, a means for sweeping the energy of the spectrometer, a sorting means for sorting the electron beams separated by the spectrometer, and a means for sorting the electron beams separated by the spectrometer. a detection means for detecting the sorted electrons, an amplification means for amplifying an output signal from the detection means, and an output from the amplification means that is swept in synchronization with the sweep of the spectrometer by the sweep means. and display means for displaying an energy spectrum based on a signal, in which an electron beam absorber whose electron absorption rate differs depending on the incident position of the electron beam is disposed between the sorting means and the detector. At the same time, a deflector is arranged to deflect the electron beam emitted from the sorting means, so that the electrons emitted from the sorting means are made to enter different positions of the electron beam absorber as the spectrometer sweeps. An electron beam energy analyzer comprising means for controlling deflection by the deflector.