JP2001148231A - Multiple charged particle detector, and scanning type transmission electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiple charged particle detector by which observation of specific element image in real time is made possible. SOLUTION: In a multiple charged particle detector arranged in orbit of electron beam that is transmitted through the sample, and that is separated by energy, the multiple charged particle detector is provided comprising not less than 2 scintillators, a shielding member that separates above scintillators, photoconductors equipped to above respective scintillators, and photoelectric multipliers equipped to the respective photoconductors above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting transmitted electrons obtained by scanning a sample, and more particularly to a multi-charged particle detector suitable for obtaining a specific element image of the sample, and using the same. The present invention relates to a scanning transmission electron microscope.

[0002]

2. Description of the Related Art A scanning transmission electron microscope is a kind of a scanning electron microscope, and is a kind of a transmission electron microscope that detects electrons transmitted through a sample instead of secondary electrons. These scanning transmission electron microscopes have attracted much attention recently because they have high contrast even at a relatively low accelerating voltage and can obtain ultrahigh-resolution images at the molecular and atomic levels.

A scanning transmission electron microscope generally includes a detector for detecting electrons transmitted through a sample with an opening angle within the convergence angle of an electron probe irradiating the sample, and a detector transmitting electrons through a wide opening angle. Two detectors for detecting electrons are provided. The former detector detects a bright-field image, and the latter detector detects a dark-field image. The former detector mainly detects transmitted electrons and inelastic scattered electrons,
It is elastic scattered electrons that are detected by the latter detector.

The inelastic scattered electrons can be separated in energy by an electron energy spectrometer, and the energy-separated inelastic scattered electrons are used, for example, for obtaining a specific element of a sample.

[0005]

FIG. 2 is an energy analysis spectrum of inelastic scattered electrons transmitted through a thin film sample. Absorption edge edges of electrons (core-loss electrons) whose energy is lost by exciting inner-shell electrons of a specific atom can be confirmed on a continuous gentle falling curve due to various multiple scatterings. In order to obtain a sample image based on a specific element, it is necessary to detect a change in the edge of the absorption edge on a continuous spectrum, and it is necessary to remove information on the continuous spectrum.

In order to remove this continuous spectrum (removal of a background signal), first, either an image based on electrons in the energy region not including the absorption edge edge or an image in the energy region including the absorption edge edge is first detected. And then
It has been practiced to change the intensity of an energy spectrometer provided downstream of the sample and detect the other image.

However, since one image is detected and then the other image is acquired, the observation time becomes enormous, and the problem that the time-varying sample state change cannot be observed in real time. is there.

An object of the present invention is to provide a multi-charged particle detector capable of observing a specific element image in real time, and a scanning transmission electron microscope using the same. .

[0009]

According to the present invention, there is provided a charged particle detector which passes through a sample and is disposed on the trajectory of an energy-separated electron beam. A scintillator, a shielding member that separates the two or more scintillators, a light guide provided in each of the two or more scintillators, and a multi-charged particle detector including a photomultiplier tube provided in each of the light guides. provide.

According to the present invention, in order to solve the above-mentioned problems, an electron source, a scanning deflector for scanning an electron beam emitted from the electron source on a sample, and an electron beam transmitted through the sample In the scanning transmission electron microscope equipped with an energy spectrometer that separates the energy, and a detector that detects electrons of specific energy separated by the energy spectrometer,
The detector includes at least two electron detection surfaces, and includes means for forming a distribution image of a specific element based on signals generated by core-loss electrons and non-core-loss electrons among the electrons obtained on the two electron detection surfaces. A scanning transmission electron microscope characterized by the following.

According to the above configuration, it is possible to simultaneously obtain electrons in the energy region not including the absorption edge and electrons in the energy region including the absorption edge by using at least two electron detection surfaces. Become.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a scanning transmission electron microscope (Scanning Transmission Electron Micro) employed in the embodiment of the present invention.
FIG. 2 is a diagram illustrating an outline of a scope (STEM). 1 is an electron gun, 2 is a convergent lens, 3 is a scanning coil, 4 is an objective lens, 5 is a sample, 6 is an annular electron detector for elastic scattering, 7 is an energy analyzer, 8 is an electron detector, and 9 is an electron detector. C for scanning image
RT and 10 are energy selection slits, and 11 is an electron beam.

The electron beam 1 generated and accelerated by the electron gun 1
1 is converged in a point shape by the converging lens 2, and then scanned in two directions by the scanning coil 3, further narrowed down to an extremely small spot by the objective lens 4, and irradiated onto the sample surface 5. Among the transmitted electron beams, elastic scattered electrons that do not lose energy scattered at a relatively wide angle are detected by the annular detector 6, and a scanning electron microscope image by the elastic scattered electrons is obtained. On the other hand, an energy loss (loss) electron beam (inelastic scattered electron) scattered at a small angle is selected as a specific energy electron by the energy spectroscope 7 and displayed on the CRT 9 as a specific energy loss image in synchronization with scanning. .

The gist of the present invention resides in that two or more detection surfaces of the electron detector 8 are provided. Hereinafter, a specific structure of the electron detector will be described in detail.

FIG. 3 is a diagram showing a case where two detection surfaces are provided. 21 is an energy-separated electron beam, 22
Is a scintillator, 23 is a light guide, 24 is a light shielding plate, 25
Is an O-ring for vacuum sealing, 26 is a glass fiber, 27
Is a photomultiplier tube, 28 is an amplifier circuit, 29 is an arithmetic circuit, 30
Is a vacuum flange, and 33 is an injection groove for a vacuum-resistant adhesive resin.

The transmitted electrons 21 dispersed in the vacuum by the energy analyzer 7 are separately detected as fluorescence by the two scintillators 22 divided by the light shielding plate 24, and the light guide 2 is vacuum-shielded by the vacuum seal 25.
It is led into the atmosphere by 3. Light guide 23 and light shielding plate 2
4 is adhered by a resin injection groove 33 for vacuum resistance and sealed by a flange 30 for vacuum.

According to such a configuration, the scintillator 22
It is possible to stably maintain the vacuum in the high vacuum region where the is disposed.

Further, the light is guided to a photomultiplier tube 27 by a glass fiber 26, is converted into an electric signal, and is amplified by an amplifier 28. Signals of electrons detected at a plurality of locations are processed by the arithmetic circuit 29.

FIG. 4 shows a scanning transmission electron microscope equipped with the multiple detector of the present invention. Reference numeral 31 denotes a scanning transmission electron microscope (STEM) without a mirror, 32 denotes a quadrupole magnetic lens, 7 denotes a sector electromagnet (energy analyzer), 34 denotes a second quadrupole magnetic lens, and 36 denotes a quadrupole magnetic lens. Represents a multiple detector (22 to 28 in FIG. 3).

Although the beam 21 transmitted through the sample by the STEM 31 is dispersed in energy by the sector magnetic field 7, the dispersion distance alone is short, and the multiple detector 36 may not be able to sufficiently detect electrons in different energy ranges. Therefore, it is necessary to converge on the multiple detector while expanding the dispersion of the sector magnetic field. In the present invention, a quadrupole lens 34 for zooming the dispersion is provided after the fan-shaped magnetic field, and the quadrupole lens 32 is provided before the fan-shaped magnetic field for the converging lens. According to such a configuration, it is possible to perform analysis based on high-resolution energy separation.

The transmitted electron beams 21 having different energies and having different variances are individually detected by a multiple detector 36, processed by an arithmetic circuit 29, and displayed on a CRT as an energy filter scanning electron microscope image.

In the STEM, it is necessary to focus the electron beam on a specific extremely small portion and analyze the energy at that location to identify the element. To meet this need, as shown in FIG. 5, the multiple detector 36 of the present invention is separated from the beam line 21 and a CCD (Charge-Couple) is provided behind it.
By providing the parallel detector 41 using a (d Device) element, an energy loss spectrum can be captured with high sensitivity.

For this purpose, the multiplex detector 36 has a mechanism that can be moved in a vacuum by an air drive cylinder 40. In addition, even when a beam having an energy width that is a multiple detector is selected, after observing the energy spectrum with the CCD parallel detector 41, confirming the energy position and energy window width of the core loss edge of the element to be examined, The multi-stage detector 36 is inserted into the beam line so that beams of different energies can be detected simultaneously.

The energy filter STEM according to the present invention
An image background processing method will be described with reference to FIG. As shown in FIG. 6A, consider a case in which a silicon nitride film (SiN) in silicon (Si) is used as a model, and a STEM mapping image of nitrogen is taken by scanning the sample with a focused electron beam. .

While the beam is scanning over Si (scanning beam positions: 1, 3), it is considered that the spectrum becomes as shown in FIG. 6B. When the beam reaches the second SiN layer, an energy loss value of 40, as shown in FIG.
At 0 eV, a K-shell edge of nitrogen appears.

Using the dual electron detector of this patent, while scanning the incident electron beam, the energy loss electrons A and B of about 400 eV are simultaneously detected, and their signal values,
When a scanning image is drawn at an A / B ratio, the ratio increases only in the SiN layer portion, and a bright portion appears on the CRT. This is S
This corresponds to a STEM distribution image of nitrogen in a TEM.

As described above, according to the apparatus of the embodiment of the present invention, when the intensity of the energy spectrometer is changed to acquire a Yualos electron image and a sample image based on a background signal, the specific element image including the image calculation time is included. Although it took several hundred minutes to obtain a specific element image, a specific element image can be obtained in an extremely short time.

Further, it is possible to observe the state of the sample, which changes every moment, in real time. Furthermore, when the intensity of the energy spectrometer is changed to acquire a Yualos image and a background image, there is a possibility that an error due to a change over time may occur in the observation conditions at the time of acquiring each image. Since both images could be acquired at the same time, such a problem could be solved.

In particular, when the energy of the electron beam incident on the sample is high, the adverse effects are more remarkable due to the deformation of the sample. However, in the apparatus according to the present invention, such adverse effects are suppressed. Was completed.

When a CCD is used as a detector, since the capacity of each pixel is small, when an excessive electron current is incident, a saturation phenomenon and a memory afterimage effect remain, a conversion unevenness between pixels occurs, and an error occurs in image calculation. However, according to the electronic detection by the scintillator of the apparatus of the embodiment of the present invention, there is no such adverse effect, so that a highly accurate energy filter image can be obtained.

[0031]

As described above, according to the structure of the present invention, it is possible to obtain a high-accuracy specific element distribution image, and it is possible to greatly reduce the analysis time.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a scanning electron microscope provided with an energy filter.

FIG. 2 is a diagram showing an example of an energy analysis spectrum.

FIG. 3 is a diagram showing the structure of a multiple detector according to the present invention.

FIG. 4 is a diagram showing a scanning transmission electron microscope with a multiple detector according to the present invention.

FIG. 5 is a diagram showing an embodiment of the present invention using a movable multiplex detector and a CCD parallel detector.

FIG. 6 is a diagram showing a background processing method of the energy filter STEM of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Converging lens, 3 ... Scanning coil, 4 ...
Objective lens, 5: sample, 6: annular electron detector for elastic scattering, 7: energy analyzer, 8: electron detector, 9: CRT for scanning image, 10: energy selection slit, 11 ...
Electron beam, 21 ... electron beam separated by energy,
22 scintillator, 23 light guide, 24 light shield plate,
25 vacuum seal, 26 glass fiber, 27 photomultiplier tube, 28 amplifier circuit, 29 arithmetic circuit, 30 vacuum flange, 31 scanning electron microscope (STE)
M), 32: a quadrupole magnetic lens for convergence, 33: a groove for injecting an adhesive resin for vacuum resistance, 34: a quadrupole magnetic lens for distributed zoom, 36: a multiple detector, 40: an air-driven cylinder, 41 ... Parallel detector using CCD element.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Tanaka 882, Omo, Oaza, Hitachinaka City, Ibaraki Pref. Within the Measuring Instruments Group of Hitachi, Ltd. 1 Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Kazuhiro Ueda 7-1-1 Omikacho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Takashi Aoyama Omikamachi, Hitachi City, Ibaraki Prefecture 7-1-1 1-1 F-term in Hitachi Research Laboratory, Hitachi, Ltd. (Reference) 5C033 NN03 NP06 SS07 SS08

Claims (10)

[Claims] 1. A charged particle detector which passes through a sample and is arranged on the trajectory of a charged particle beam separated by energy,
Two or more scintillators, a shielding member for separating between the two or more scintillators, a light guide provided in each of the two or more scintillators, and a photomultiplier provided in each of the light guides. Features a multi-charged particle detector. 2. The multi-charged particle detector according to claim 1, wherein each of the photomultiplier tubes includes an amplifier circuit provided in each of the photomultiplier tubes. 3. An electron source, a scanning deflector for scanning an electron beam emitted from the electron source on a sample, an energy spectroscope for separating the energy of the electron beam transmitted through the sample, and an energy spectroscope. In a scanning transmission electron microscope including a detector for detecting electrons having a specific energy separated, the detector includes at least two electron detection surfaces,
A scanning transmission electron microscope, comprising: means for forming a distribution image of a specific element based on signals generated by core-loss electrons and signals other than core-loss electrons among the electrons obtained on the two electron detection surfaces. 4. The scanning transmission electron microscope according to claim 3, wherein the detector includes two or more scintillators and a blocking member that separates each of the scintillators. 5. The scanning transmission electron microscope according to claim 4, wherein said two or more scintillators are arranged in a direction of separation of said energy spectrometer. 6. A scanning transmission electron microscope according to claim 3, wherein a quadrupole lens is disposed at an entrance and an exit of an electron beam of said two electron detection surfaces of said energy spectrometer. 7. The system according to claim 6, wherein the electron beam is converged by the quadrupole lens disposed at the entrance in conjunction with the expansion of the dispersion of the electron beam by the quadrupole lens disposed at the exit side. A scanning transmission electron microscope, characterized in that: 8. A means according to claim 3, wherein said means for generating an electric signal based on the electrons obtained at said two electron detection surfaces;
Means for dividing the two electric signals to form a relative distribution image at a specific energy. 9. The scanning transmission electron microscope according to claim 3, wherein said detector is formed so as to be able to be taken in and out of a position where said electron beam passes. 10. A scanning transmission electron microscope according to claim 9, further comprising a parallel detector using a CCD at a stage subsequent to said detector.