JP2000338408A - Microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To multi-purposefully and efficiently detect an electron radiated by the radiation of an electron beam by analyzing the shape of a sample to be observed based on detection information obtained by detecting at least a secondary electron by a solid-state image pickup means. SOLUTION: The electron beam outputted from an electron gun 1 passes through the open hole of a CCD 6 after its spot diameter is adjusted by a diaphragm aperture 14 and a converging lens 15, and is radiated to the sample 16. The electron beam radiated to the sample 16 radiates the secondary electron and also is scattered on the surface of the sample 16. The radiated secondary electron and the scattered electron receive force by electric field and are pulled to the CCD 6 side, and made incident on the photosensitive surface of the CCD 6 opposed proximately to the sample 16. A detection signal made incident and detected is inputted in a computer 10 through a camera head 8 and a CCU 9, and processed and displayed as an output image corresponding to the radiated electron detected by the CCD 6 on a television monitor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microscope for irradiating an object with an electron beam or light, detecting and analyzing emitted electrons or scattered / reflected light, and reconstructing the shape of the object.

[0002]

2. Description of the Related Art Conventionally, a scanning electron microscope used for observing an object or the like which cannot be identified by an optical microscope has been known. The scanning electron microscope irradiates a sample while scanning an electron beam, detects the amount of secondary electrons emitted from the sample, and displays the detected secondary electrons in contrast. This scanning electron microscope utilizes the fact that the amount of secondary electrons emitted when irradiating a sample with an electron beam varies depending on the unevenness of the sample shape.

[0003]

However, the microscope described above reconstructs an image by detecting only the amount of secondary electrons emitted from the sample surface, and cannot perform sufficient observation. In addition, the secondary electron detector for detecting secondary electrons must be arranged at a position away from the sample so as not to hinder the irradiated electron beam, and the secondary electron detection efficiency is high. Did not.

Accordingly, an object of the present invention is to provide a microscope capable of efficiently detecting electrons emitted by irradiation with an electron beam in a multifaceted manner.

[0005]

A microscope according to the present invention comprises an electron beam generating means for outputting an electron beam irradiated to a sample to be observed in a vacuum, and a photosensitive surface between the electron beam generating means and the sample to be observed. A solid-state imaging device having an electron beam passage portion through which an electron beam output from the electron beam generation device passes, and disposed between the electron beam generation device and the solid-state imaging device. Deflection means for deflecting the electron beam to change the irradiation position of the electron beam on the sample to be observed, and at least secondary electrons among the electrons emitted from the sample to be observed by the irradiation of the electron beam are detected by the solid-state imaging means Analyzing means for analyzing the shape of the sample to be observed based on the detection information obtained thereby. Thus, by arranging the solid-state imaging means so as to face the sample, electrons emitted from the sample can be detected.

The microscope of the present invention has a light source for outputting irradiation light to be irradiated on the sample to be observed, and a photosensitive surface disposed between the light source and the sample to be observed, facing the sample to be observed. A solid-state imaging unit having an irradiation light passing / transmitting unit for transmitting or transmitting the output irradiation light, and a sample stage for mounting a sample to be observed that is movable relative to the solid-state imaging unit And analysis means for analyzing the shape of the sample to be observed based on information detected by the solid-state imaging means. Thus, by arranging the solid-state imaging means so as to face the sample, light scattered or reflected on the sample can be detected.

In the microscope of the present invention, the light source is
It may be characterized by outputting X-rays as irradiation light.
With such a configuration, scattered light from the inside of the sample can also be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings. In the respective drawings, the same elements are denoted by the same reference numerals, and overlapping description will be omitted.

FIG. 1 is a diagram showing a microscope according to the first embodiment. The microscope includes an electron gun 1 serving as an electron beam generating means, a deflecting means 2 provided near the trajectory of the electron beam, a sample stage 5 arranged on the trajectory of the output electron beam, and a sample on the sample stage 5. A solid-state imaging device (hereinafter, referred to as a “CC”) having an opening (an electron beam passage portion) and
D ”) 6 and the CC electrically connected to the CCD 6
A camera head 8 having a D drive circuit, and a camera control unit (hereinafter referred to as “C
9), a computer 10 for processing the detection signal obtained by the CCD 6, a first television monitor 11 for outputting an output image based on the detection signal obtained from the CCD 6, and a further output image signal. Computer 1
And a second television monitor 12 for processing and outputting at 0.

The configuration of the characteristic portion of the present embodiment will be described in detail.

The CCD 4 has the same configuration as that of the CCD disclosed in Japanese Patent Application Laid-Open No. 9-31837, and has an opening having a diameter of 200 μm in the center of the photosensitive surface. An aperture aperture 14 and a converging lens 15 are arranged on an electron beam orbit between the electron gun 1 and the CCD 6.
The diameter (spot diameter) of the cross section of the electron beam is adjusted so as to be incident on the opening 6.

A deflecting means 2 provided near the trajectory of the electron beam between the aperture aperture 14 and the CCD 6.
Comprises a deflection electrode 3 for applying a voltage to the electron beam and a deflection circuit 4 for controlling the applied voltage.
Is connected to the computer 10.

The sample stage 5 is a computer 1
The sample stage 5 is connected to a stage controller 13 which is controlled by 0 and the sample controller 5 can be moved in two types by the stage controller 13. The first is a movement in a direction orthogonal to the electron beam at a predetermined distance from the photosensitive surface of the CCD 6, and the second is a movement in an electron beam direction approaching or separating from the photosensitive surface of the CCD 6.

The CC whose photosensitive surface faces the sample stage 5
D6 is 5 mm between the photosensitive surface and the surface of the sample 16.
At a position indicated by the following, it is arranged so as to be parallel to the sample mounting surface of the sample stage 5, and is fixed to a ceramic package 7 supported by a support mechanism (not shown). Further, a voltage of 8 kV is applied between the sample stage 5 and the CCD 6 in a direction in which the CCD 6 becomes a high voltage, and an electric field is generated.

The components surrounded by the dotted line 17 in FIG. 1, that is, the electron gun 1, the aperture aperture 14, the deflection electrode 3, the CCD 6, and the sample stage 5 are housed in a vacuum vessel (not shown).

Next, the operation of the microscope according to the embodiment will be described. The electron beam output from the electron gun 1 has its spot diameter adjusted by the aperture aperture 14 and the converging lens 15, passes through the aperture of the CCD 6, and irradiates the sample 16. The electron beam applied to the sample 16 emits secondary electrons and scatters on the surface of the sample 16. Emitted secondary electrons and scattered electrons (hereinafter "secondary electrons" and "scattered electrons"
Are collectively referred to as “radiated electrons”), are pulled toward the CCD 6 by the force of the electric field, and are incident on the photosensitive surface of the CCD 6 opposed to the sample 16. A detection signal incident on the photosensitive surface of the CCD 6 and detected is input to the computer 10 through the camera head 8 and the CCU 9. The input detection signal is processed by the computer 10 and displayed on the first television monitor 11 as an output image corresponding to the emitted electrons detected by the CCD 6.

An output image corresponding to the emitted electrons detected by the CCD 6 will be specifically described with reference to FIGS. FIGS. 2 and 4 are partial views showing the state of the electron beam and the emitted electrons irradiated on the sample 16, and FIGS.
It is a figure showing an output image corresponding to emitted electrons detected at D6.

When the surface of the sample 16 is perpendicular to the electron beam, the emitted electrons spread almost uniformly from the point of incidence of the electron beam and enter the CCD 6 photosensitive surface (see FIG. 2). Note that this locus becomes parabolic because the CCD 6 and the sample stage 5
This is because an electric field is generated between them.

The output image 22 in this case is as shown in FIG. Referring to FIG. 3, the center + mark is a marker signal 21 indicating the center of the opening of the CCD 6. Also, a circle 23 of radius r ₁ surrounding the marker signal 21
Is the theoretical boundary that indicates the limit of secondary electron spread. The radius of the circle 23 is calculated from the energy of the secondary electrons emitted from the surface of the sample 16.

Hereinafter, this point will be described. The emitted electrons emitted from the sample 16 by the irradiation of the electron beam are spread and detected on the photosensitive surface of the CCD 6.
The spread on the photosensitive surface depends on the scattering direction of the emitted electrons and the initial velocity at the time of emission. That is, for the scattering direction, C
The closer to the parallel surface of the CD6 photosensitive surface and the greater the initial velocity, the greater the spread of emitted electrons detected on the CCD6 photosensitive surface. Therefore, secondary electrons when splashed in parallel with CCD6 photosensitive surface, is detected secondary electrons with the largest spread, which spread the limitations of secondary electrons, that is determined as a circle having a radius r _1. Specifically, 2k
When an electron beam having an energy of eV is incident on the surface of the sample 16, the distance between the CCD 6 photosensitive surface and the sample 16 is 5 m.
m, when the applied voltage is 8 kV, the secondary electrons have an energy over a width of several tens eV having a peak at several eV (up to 10 eV).
0 eV), which limits the spread of secondary electrons,
That is, the radius r _{1 of the} circle 23 is calculated to be 1.1 mm.

The use of the circle 23 enables more detailed analysis. For example, r ₁ ≦ 1.1 mm
By displaying the spatial distribution of the integral value I ₁ of the corresponding emission electron to the second television monitor 12, a sample image is obtained by only little secondary electrons. Also, the image due to the scattered electrons has an energy in which the scattered electrons are larger than the secondary electrons (about 2
keV), it is wider than the secondary electron image, and r
By displaying the spatial distribution of the integral value I ₂ corresponding emission electron to ₁ ≧ 1.1 mm, a sample image is obtained by only little scattered electrons. Furthermore, it is also possible to display the spatial distribution of I ₂ / (I ₁ + I ₂ ). In the conventional scanning electron microscope, an image is formed based on the total amount of secondary electrons emitted at each point on the sample surface. However, according to the present invention, the energy of the emitted electrons is selected as described above. Therefore, an image having a contrast different from that obtained by a conventional scanning electron microscope can be obtained, or an image which has not been seen can be seen.

Next, a case where the surface of the sample 16 is inclined with respect to the electron beam at the electron beam irradiation position will be described. In this case, radiated electrons are emitted almost uniformly around the normal to the surface of the inclined sample 16 (see FIG. 4). The output image 22 of the emitted electrons is as shown in FIG. From this detection result, the distance D ₁ between the center of gravity 24 of the image 22 of the emitted electrons and the center of the aperture can be obtained. From the obtained distance D ₁ and the distance D ₀ between the sample 16 and the photosensitive surface of the CCD 6, the electron beam is obtained. The average inclination angle of the surface of the sample 16 at the incident position is calculated. The irregularities on the surface of the sample 16 are as follows:
It can be considered that the distance is sufficiently smaller than the distance D ₀ between the sample 16 and the photosensitive surface of the CCD 6.

Next, reconstruction of the shape of the sample 16 will be described. When an instruction is given from the computer 10 to the deflecting circuit 4 and a voltage is applied to the deflecting electrode 3, the direction of the electron beam is changed, and the irradiation spot of the electron beam on the surface of the sample 16 can be changed. Under the control of the computer 10,
By sequentially changing the irradiation spot, the sample 16
An electron beam can be scanned on the surface, and a detection signal based on emitted electrons at each point on the sample 6 can be obtained. However, in this case, since the image 22 of the emitted electrons shifts from the center of the aperture according to the amount of deflection, it is necessary to correct the shift. By performing processing by the computer 10 based on the detection signals thus accumulated, the shape of the sample 16 in a predetermined region can be reconstructed.

In the microscope according to the first embodiment, since the electron beam passes through the aperture formed in the CCD 6, the range in which the electron beam can be scanned by the deflection electrode 3 is the range in which the electron beam can pass through the aperture. Within. To observe the sample 16 over a wider area, the computer 10
Then, an instruction may be given to the stage controller 13 to move the sample stage 5.

As described above, in the microscope of the first embodiment, since the CCD 6 is arranged so as to face the sample 16, not only the total amount of emitted electrons but also the density distribution of emitted electrons can be obtained. For this reason, more detailed observation can be performed.

In the microscope of the first embodiment, the CCD
6 Since the photosensitive surface is provided close to the sample 16,
Most of the emitted electrons can be detected. For this reason,
Accurate observation can be performed.

Next, a second embodiment of the present invention will be described. FIG. 6 is a diagram showing a microscope according to the second embodiment, and FIG.
FIG. 7 is a diagram showing a state of X-ray scattering when the microscope according to the second embodiment is used.

The microscope according to the second embodiment differs from the microscope according to the first embodiment in that X-rays are used instead of the electron beam irradiated on the sample 16. That is, a laser plasma X-ray source 31 is used in place of the electron gun 1, a zone plate 33 is arranged on an axis through which X-rays pass, and the X-rays are converged to irradiate the sample 16. Another difference from the microscope of the first embodiment is that in the microscope of the second embodiment, the aperture formed in the CCD 6 is about 300 μm, and there is no need for a vacuum vessel or deflecting means. It is not a component.

Next, the operation of the microscope according to the second embodiment will be described. The X-rays output from the laser plasma X-ray source 31 are converged to a size of about 0.1 μm in diameter by the stop aperture 32 and the zone plate 33, and the sample 1
6 is irradiated. The X-rays applied to the sample 16 are scattered as shown in FIG.
6 is detected. The subsequent process is the same as that of the first embodiment, and is displayed on the first television monitor 11 as an output image corresponding to the X-ray detected by the CCD 6.

By moving the sample stage 5 on which the sample 16 is placed by the stage controller 13,
X-rays can be scanned on the sample 16. Thus, the detection signal based on the scattered X-rays at each point of the sample 16 is accumulated, and the accumulated data is processed by the computer 10, so that the shape of the sample 16 can be reconstructed as in the first embodiment. .

As described above, also in the microscope of the second embodiment, since the CCD 6 is arranged close to the sample 16, X-rays scattered from the sample 16 can be detected efficiently, and the intensity distribution of the scattered X-rays can be improved. Is obtained. Further, in the microscope of the second embodiment, since the laser plasma X-ray source 31 is used as a light source, the sample 16
An additional effect is obtained that scattered X-rays not only from the surface but also from the inside of the sample 16 can be obtained.

Since the scattered X-rays scatter radially from the irradiation position (see FIG. 7), reconstruction of the sample 16 based on the output image is easier than in the microscope of the first embodiment.

Next, a third embodiment of the present invention will be described. FIG. 8 is a diagram showing a microscope according to the third embodiment, and FIG.
FIG. 9 is a diagram showing an image corresponding to the crystal structure of a sample 16 obtained by the microscope of the third embodiment.

The microscope according to the third embodiment has an X-ray source X
A sample tube 5 on which a sample 16 placed on the X-ray axis output from the X-ray tube 41 is mounted;
And a X-ray tube 41, a camera head 8 having a CCD drive circuit for driving the CCD 6, a CCU 9 for controlling the camera head 8, and a computer 10 for processing detection signals obtained by the CCD 6. When,
A television monitor 11 for outputting an output image based on a detection signal obtained from the CCD 6.

The configuration of the characteristic portion of the third embodiment will be described in detail. The CCD 6 has the photosensitive surface facing the sample 16, and the X-ray tube 41, which is the opposite surface of the photosensitive surface, has almost the same surface as the photosensitive surface. A shielding plate 42 having the same shape is provided to prevent a problem that X-rays from the X-ray tube 41 side pass through the CCD 6 and enter the photosensitive surface of the CCD 6. Also, the CCD 6 has 300
An opening of about μm is formed, and a collimator 43 for parallelizing X-rays guided to the opening is provided on the X-ray axis just before the opening.

Next, the operation of the microscope according to the third embodiment will be described. The X-ray output from the X-ray tube 41 is shaped into a parallel X-ray having a diameter of about 200 μm by the collimator 43, and is irradiated on the sample 16 through the aperture of the CCD 6.
When the sample 16 is irradiated with X-rays, the sample 16
Diffracted X-rays traveling toward the photosensitive surface are generated. This diffraction X
The line enters the photosensitive surface of the CCD 6 and is detected. A detection signal is input to the computer 10 through the camera head 8 and the CCU 9. The input detection signal is processed by the computer 10, and an image corresponding to the crystal structure is displayed on the television monitor 11 (see FIG. 9). Then, by analyzing this image, the crystal structure of the sample 16 can be obtained.

By giving an instruction from the computer 10 to the stage controller 13, the sample stage 5 can be moved and the X-ray irradiation spot can be changed. Thereby, the crystal structure at an arbitrary position of the sample 16 can be smoothly analyzed.

As described above, in the microscope according to the third embodiment, diffracted X-rays can be efficiently detected by disposing the CCD 6 so as to face the sample 16. Also,
In the microscope of the third embodiment, since the CCD 6 is used as a detector and is connected to the computer 10 via the camera head 8 and the CCU 9, the processing of the acquired detection signal can be performed smoothly by the computer 10. X
It is also easy to change the line irradiation position and obtain a detection signal.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments.

For example, the size of the aperture formed in the CCD, the distance between the CCD photosensitive surface and the sample, and the like may be changed according to the scattering angle of emitted electrons or scattered X-rays to be detected.

The X-ray generating means may use another X-ray source such as a gas puff source, or use a reflection type mirror such as an oblique incidence mirror or a Schwarzschild reflector for an X-ray lens for converging X-rays. May be used.

The solid-state imaging device used for detecting emitted electrons, scattered X-rays and the like may be a MOS-type fixed imaging device.

Further, in each of the above embodiments, the sample is irradiated with the electron beam or the X-ray vertically, but may be incident on the sample at a predetermined angle as needed.

In the second embodiment and the third embodiment,
Although an X-ray source is used as a light source, a microscope may be configured using a light source such as ultraviolet, visible, or infrared light.

Further, in the first and second embodiments, two television monitors are used, but one television monitor may be switched and used.

[0046]

According to the present invention, in a microscope for reconstructing the shape of a sample to be observed from the intensity of generated electrons, if only the total amount of secondary electrons or scattered electrons (radiated electrons) generated by the irradiated electron beam is obtained. Therefore, the density distribution can be detected, and the radiation electrons can be detected efficiently. For this reason, the accuracy of the microscope can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a microscope according to a first embodiment.

FIG. 2 is a partial view showing a state of an electron beam irradiated on a sample and electrons emitted along with the electron beam.

FIG. 3 is a diagram showing an output image corresponding to emitted electrons detected by a CCD.

FIG. 4 is a partial view showing the state of an electron beam irradiated on a sample and electrons emitted accordingly.

FIG. 5 is a diagram showing an output image corresponding to emitted electrons detected by a CCD.

FIG. 6 is a diagram illustrating a microscope according to a second embodiment.

FIG. 7 is a diagram showing a state of X-ray scattering.

FIG. 8 is a diagram illustrating a microscope according to a third embodiment.

FIG. 9 is a diagram showing an image corresponding to the crystal structure of a sample.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron gun, 2 ... Deflection means, 3 ... Deflection electrode, 4 ... Deflection circuit, 5 ... Sample stage, 6 ...
・ Solid-state imaging device, 7 ・ ・ ・ Ceramic package, 8 ・
..Camera head, 9 ... Camera control unit, 10 ... Computer, 11 ... First television monitor, 12 ... Second television monitor, 13 ... Stage controller, 14 ... Aperture Aperture, 15: converging lens, 21: marker signal, 22: image, 23
... Center of gravity of the image, 31 ... Laser plasma X-ray source,
32 ... aperture aperture, 33 ... zone plate, 41 ... X-ray tube, 42 ... shielding plate, 43 ...
Collimator.

Claims (3)

[Claims] 1. An electron beam generating means for outputting an electron beam irradiated to a sample to be observed in a vacuum, and a photosensitive surface facing the sample to be observed between the electron beam generating means and the sample to be observed. A solid-state imaging unit having an electron beam passing unit through which the electron beam output from the electron beam generation unit passes; and the solid-state imaging unit arranged between the electron beam generation unit and the solid-state imaging unit. A deflecting unit that deflects a line to change an irradiation position of the electron beam on the sample to be observed, and at least secondary electrons among electrons emitted from the sample to be observed by the irradiation of the electron beam are detected by the solid-state imaging unit. Analyzing means for analyzing the shape of the sample to be observed based on the detection information obtained by performing the measurement. 2. A light source for outputting irradiation light to irradiate a sample to be observed, and a photosensitive surface is arranged between the light source and the sample to be observed, facing the sample to be observed, and is output from the light source. Solid-state imaging means having an irradiation light passing / transmitting part for passing or transmitting the irradiated light, and a sample stage for mounting the sample to be observed, which is relatively movable with respect to the solid-state imaging means. And a analyzing means for analyzing a shape of the sample to be observed based on information detected by the solid-state imaging means. 3. The microscope according to claim 2, wherein said light source outputs X-rays as irradiation light.