JP2006047206A - Combined microscope - Google Patents

Abstract

【Task】
The present invention makes it possible to acquire an internal X-ray image of a sample and to realize the function of an electron microscope.
[Solution]
The X-ray generator is shared with the electron beam generator by shielding the electron beam of the electron column 1 with the movable target 9 and generating X-rays. Thereby, since the irradiation X-ray and the irradiation electron beam to the sample are incident on the same axis, it is possible to observe both the sample internal information and the surface information in the same visual field. In addition, the element distribution image of the target region 15 can be overlaid and displayed on the X-ray image indicating the internal form information of the entire sample. Since the mechanical cutting means 10 is provided, it is also possible to display an electron beam image or the like inside the sample.
[Selection] Figure 3

Description

  The present invention relates to a microscope technique for observing or analyzing the surface state and composition distribution of a fine structure sample such as a living body or a semiconductor.

  A scanning electron microscope (SEM) that scans an electron beam on a sample to detect secondary electrons and reflected electrons from the sample and observes the surface form on the order of nanometers is used in various industrial fields. In addition, by incorporating an energy dispersive X-ray spectrometer (EDX) or wavelength dispersive X-ray spectrometer (WDX) into this, and examining the energy of X-rays excited by the incidence of an electron beam, Devices for measuring and observing elemental distribution are also commercialized.

When the target part exists in the sample or in the lower layer of the sample, an X-ray microscope using highly transmissive X-rays is required to measure the form and shape inside the sample and obtain information. Is suitable.
As an X-ray microscope, for example, a projection X-ray microscope is proposed in which a metal piece target is fixed to an electron column similar to an electron microscope and the inside of the sample cannot be observed from the surface due to an X-ray source diameter of several tens of nm. (See Patent Document 1).
In addition, microfocus X-ray fluoroscopy devices, microfocus X-ray CT devices, and the like have been put to practical use for inspection of fine parts such as electronic components, and the X-ray focal spot size in these devices is submicron (for example, 0.4 μm). ). Furthermore, X-rays have the advantage that they can be observed in the atmosphere.

As described above, X-ray microscopes and electron microscopes have played an important role in various industrial fields in recent years, and it is necessary to develop complex microscopes that integrate the functions and operability of these microscopes and that are more convenient. It is said that.
Until now, in the case where the optical system is shared between the laser microscope and the scanning microscope, it has been proposed to use the data on the surface roughness of the sample obtained by the laser microscope for observation with the scanning probe microscope. (See Patent Document 2).
However, there is no known composite microscope that can display information inside a sample simultaneously or in time series by combining an X-ray image and an electron beam image.
JP 2003-131000 A JP-A-7-198730

  The scanning electron microscope can acquire information in the vicinity of the sample surface in the nanometer order, but it is difficult to selectively acquire information in the sample (for example, mm order). When it is desired to acquire internal observation information, the sample is cut to expose the target portion and observed. At this time, generally, the target site at the time of cutting is searched with an optical microscope, sometimes with an electron microscope while being cut with another device, and then the sample is fixed to the electron microscope for observation. In some cases, the sample cutting site cannot be found well. In the worst case, a valuable target part may be damaged at the time of cutting.

  On the other hand, in the case of a projection X-ray microscope, the target is thinned to achieve an X-ray focal spot size of several tens of nanometers (20 to 200 nm). If the X-ray dose is increased to such an extent that it can be seen through, a problem that the target is damaged occurs. For example, a microfocus X-ray apparatus with a target thickness in the micron order is suitable for observing the inside of a sample on the order of mm, but the X-ray focal spot size is only about submicron.

Therefore, when observing the structure and composition (element) distribution of the target part in the nanometer order after accurately grasping the shape and position of the target part inside the sample, any single device can be used. It is difficult to use these devices in combination. However, since a plurality of devices are used, a series of operations takes time, and not only the workability is bad, but also depending on the sample, the surface state changes with time, or impurities (contamination) are generated during sample movement between devices. It is also possible that the original information cannot be obtained due to adhesion.
An object of the present invention is to provide a composite microscope capable of acquiring an internal X-ray image of a sample and realizing the function of an electron microscope.

  The composite microscope of the present invention includes a sample stage that supports a sample in a vacuum vessel, an X-ray generator that irradiates the sample with X-rays, an X-ray detector that detects X-rays transmitted through the sample, and a sample An electron column that can be scanned by irradiation with an electron beam, an electron detector that detects secondary electrons or reflected electrons generated from a sample irradiated with the electron beam, a display unit, and an X-ray detector An X-ray image control unit for processing signals to display an X-ray image on the display unit, an electron beam image control unit for processing signals from an electron detector to display an electron beam image on the display unit, and a sample And a detection signal processing unit for displaying the X-ray image and the electron beam image of the same portion simultaneously or in time series.

The composite microscope further includes an element analyzer that performs elemental analysis by detecting characteristic X-rays excited by electron beam irradiation, and the detection signal processing unit can display an element distribution image of the sample on the display unit. It is also possible.
The detection signal processing unit can also display an electron beam image on the X-ray fluoroscopic image or the X-ray tomographic image so as to be displayed on the display unit.
Furthermore, the detection signal processing unit may be configured to display an element distribution image on the X-ray fluoroscopic image or the X-ray tomographic image so as to be displayed on the display unit.

A metal plate that generates X-rays by electron beam irradiation can be detachably provided on the path of the electron beam irradiated from the electron column so that the electron column also serves as an X-ray generator.
Further, a sample cutting means may be provided in the vacuum container so that the inside of the sample is exposed to the outer surface.
As such a sample cutting means, a microtome, an ion gun for performing ion beam etching, a focused ion beam processing apparatus, or the like can be used.

As the X-ray generator, a microfocus X-ray tube having an X-ray focal spot size of 10 μm or less can be used.
The sample cutting means can control the sample cutting so that the surface designated based on the X-ray fluoroscopic image or the X-ray tomographic image is exposed.
In the present invention, the operating vacuum in the apparatus is suitably controlled at a low vacuum of 1 to 2,700 Pa.

According to the present invention, an X-ray image and an electron beam image can be displayed simultaneously or in time series.
If an element analyzer is further provided, characteristic X-rays excited by electron beam irradiation can be detected and elemental analysis can be performed.
If the X-ray image and the electron beam image are displayed in an overlapping manner, a contrast image between the original sample internal information and the surface information can be acquired.
If the elemental analysis image is displayed so as to overlap the X-ray image, the elemental analysis at the specified position can be performed.

If a metal plate for generating X-rays is detachably provided on the path of the electron beam irradiated from the electron column, the electron column can also serve as an X-ray generator.
If a sample cutting means is provided, it becomes possible to accurately extract a target site inside a large sample on the order of millimeters and obtain a structure and elemental analysis on the order of nanometers.
By providing the sample cutting means, the inside of the sample can be exposed to the outer surface, and an X-ray image and an electron beam image of the same internal portion that could not be obtained can be obtained simultaneously or in time series. .
If the X-ray detector is a microfocus X-ray tube having an X-ray focal spot size of 10 μm or less, finer observation can be performed.

X-ray images have the advantage of being able to be imaged in the atmosphere, but electron beam images require an evacuated environment.
If the operating vacuum of the apparatus of the present invention is set to a low vacuum of 1 to 2700 Pa, for example, internal information by X-rays and surface information by electron beams can be confirmed at the same time for a water-containing sample such as a living body. Become.

An embodiment of the present invention will be described.
1 to 3 are diagrams showing each operation of the apparatus. FIG. 1 is for X-ray image capturing, FIG. 2 is for electron beam image and element distribution image capturing, and FIG. 3 is an electron column and X-ray generation. It shows the case where the vessel is shared.

The apparatus will be described.
A sample stage 24 is provided in the chamber 23 to be evacuated, and the sample 14 is placed on the sample stage 24. The degree of vacuum in the chamber 23 is 1 to 2700 Pa.
As shown in FIG. 1, the X-ray generator 11 that irradiates the sample 14 with the X-ray 13 and the X-ray detector that detects the X-ray transmitted through the sample 14 are shown in FIG. 17 is arranged so as to be opposed, and the result of the X-ray detector 17 is sent to the detection signal processing unit 21 and displayed on the display unit 22.
Further, the sample stage 24 is a rotary type in order to take an X-ray tomographic (CT) image.

As shown in FIG. 2, as for electron beam imaging, an upper portion of a chamber 23 is provided with a cathode 2 for generating electrons, an anode 3 for extracting and accelerating electrons generated at the cathode 2, and an accelerated electron beam. And an electron lens barrel 1 having a scanning coil 6 for irradiating the sample with an electron beam and scanning the sample.
The electron beam 7 emitted from the electron column 1 is irradiated onto the sample 14, and the generated secondary electrons 26 are captured and detected by the secondary electron detector 18, processed by the detection signal processing unit 21, and then displayed. A scanning electron microscope image is displayed on the monitor of the unit 22.

As for element distribution image photography, in the chamber 23, in addition to the above-described devices, an X-ray for detecting characteristic X-rays 27 generated by irradiating the sample with the electron beam 7 emitted from the electron column 1 A detector 19 is provided. The detection signal of the X-ray detector 19 is also processed by the detection signal processing unit 21, and then an element distribution image is displayed on the display unit 22.
In addition, as shown in FIG. 3, a metal target 9 is detachably disposed immediately below the electron column 1 as an electron beam used in the electron column 1 as an X-ray generator. It can move in the vacuum of the chamber 23.
An X-ray detector 16 is disposed in the chamber 23 at a position facing the metal target 9 with the sample 14 interposed therebetween. The detection signal of the X-ray detection unit 16 is also processed only by the detection signal processing unit and displayed on the display unit 22.

The detection signal processing unit 21 and the display unit 22 are preferably shared by each measurement, but may be separately processed and displayed.
As for the sample cutting means, it is effective if the sample 14 is cut by the cutting means 10 such as a microtome to expose the surface 25 of the target portion 15. The cutting means is not limited to the mechanical cutting means, and may be means such as ion etching or FIB (focused ion beam processing apparatus). By providing these cutting means in the chamber 23, it is possible to prevent changes in the surface state over time and attachment of disturbing components (so-called contaminants) that occur when they are released into the atmosphere.

Next, each operation will be described.
FIG. 1 is a schematic diagram when an X-ray image is acquired in the embodiment. The electrons emitted from the electron generation source in the X-ray generator 11 are accelerated, collide with a metal target such as copper and generate X-rays 13 in the region 12, and the generated X-rays 13 are applied to the sample 14. Irradiated. X-ray generation is controlled by an X-ray generation control unit in the control unit 20.
The X-ray 13 transmitted through the sample 14 is detected by the X-ray detector 17, and an X-ray fluoroscopic image inside the sample is displayed on the monitor screen of the display unit 22 through the detection signal processing unit 21.

  Instead of the X-ray fluoroscopic image, the target stage 15 can be confirmed by acquiring internal information by rotating the sample stage 24 and capturing an X-ray tomographic (CT) image. The distance a in the depth direction from the surface of the target site can be grasped from the X-ray fluoroscopic image, and the distance b in the horizontal direction of the target site can be grasped from the X-ray CT image. The rotation of the sample stage 24 is controlled by a stage control unit in the control unit 20.

FIG. 2 is a schematic diagram when observing a surface state and an element distribution image with an electron beam in the same example.
The electron beam 7 emitted from the electron column 1 is irradiated on the sample, and the generated secondary electrons 26 are captured and detected by the secondary electron detector 18, processed by the detection signal processing unit 21, and then displayed on the display unit. A scanning electron microscope image is displayed on the monitor 22. The electron beam irradiation from the electron column 1 is controlled by an electron beam control unit in the control unit 20.
Here, the secondary electron detector 18 has been described as an example, but a configuration in which reflected electrons from the sample are detected by the reflected electron detector may be employed.

At this time, characteristic X-rays generated by being excited by the scanning electron beam 7 can be acquired by the X-ray spectrometer 19 to display an element distribution image.
Such a procedure is used when only the information on the surface of the sample 14 is to be acquired. However, when the target site 15 inside the sample is to be observed, the observation is not possible as it is. In that case, for example, the sample 14 can be cut by the cutting means 10 such as a microtome to expose the surface of the target portion 15. The operation of the cutting means 10 is controlled by a sample cutting control unit in the control unit 20.

  When the target portion of the sample is present inside the sample in the order of mm, for example, since the electron beam does not have internal permeability, only X-rays are an effective means for confirming the shape and position of the target portion 15 nondestructively. . The X-ray generator used here preferably has an X-ray focal spot size as small as possible. For example, a microfocus X-ray generator tube may be used. At present, micro-focus X-ray tubes are also commercially available at sub-micron level, so it is possible to confirm a considerable fine structure, but there is a demand for acquiring observation images and element distribution images with higher resolution. .

The sample cutting position can be determined from the aforementioned X-ray image shown in FIG. For example, the X-ray image is first acquired and displayed on the monitor of the display unit, and the cutting can be performed by automatically controlling the cutting means 10 by specifying (for example, clicking) the target portion. Further, even if automatic control is not performed, it is possible to perform manual cutting while viewing an electron beam image, a separately incorporated optical microscope image, or a displacement amount of a position sensor.
Thereby, the position of the target site 15 inside the sample can be accurately grasped, and the surface structure or element distribution image can be finely observed on the nanometer order.

FIG. 3 shows an X-ray generator shared by generating X-rays by shielding the electron beam of the electron column 1 with a target 9 in the embodiment. The attachment / detachment of the target is controlled by a target control unit in the control unit 20.
As shown in FIG. 3, when the target 9 is blocking the electron beam path, the electrons generated at the cathode 2 collide with the target to generate X-rays and irradiate the sample with the X-rays. X-rays that have passed through the sample are detected by the detection unit 16, processed by the detection signal processing unit 21, and then displayed on the display unit 22.
When obtaining the electron beam image at the position where the X-ray image is obtained, the target 9 is retracted to a position where the electron beam passage is not blocked.

  By sharing the electron column 1 with the X-ray generator, the irradiated X-ray and the irradiated electron beam on the sample are incident on the same axis, so that both the sample internal information and the surface information are observed in the same field of view. Can do. It is also possible to superimpose and display the element distribution image of the target region 15 on the X-ray image indicating the internal morphology information of the entire sample.

  After obtaining the X-ray image and the electron beam image, the target sample is cut by a mechanical cutting means to expose the inside of the sample to the outside, and the X-ray image or electron beam image inside the sample can be obtained by the above method. is there.

It is a schematic block diagram which shows one Example of this invention in the state at the time of X-ray image imaging | photography. It is a schematic block diagram which shows the same Example in the state at the time of electron beam image and element distribution image photography. It is a schematic block diagram which shows the same Example in the state at the time of sharing an electron column and an X-ray generator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electron barrel 2 Cathode 3 Anode 5, 8 Electromagnetic lens 6 Scanning coil 7 Scanning electron beam 9 Target 10 Mechanical cutting means 11 X-ray generator 12 Area 13 X-ray 14 Sample 15 Target part 16 Detector 17 X-ray detector 18 Secondary electron detection unit 19 X-ray spectrometer 21 Detection signal processing unit 22 Display unit 23 Chamber 24 Sample stage 25 Surface 26 Secondary electron

Claims (12)

A sample stage for supporting the sample in a vacuum vessel;
An X-ray generator for irradiating the sample with X-rays;
An X-ray detector for detecting X-rays transmitted through the sample;
An electron column that can be scanned by irradiating the sample with an electron beam;
An electron detector for detecting secondary electrons or reflected electrons generated from the sample irradiated with the electron beam;
A display unit;
An X-ray image control unit that processes a signal from the X-ray detector and displays an X-ray image on the display unit;
An electron beam image control unit that processes a signal from the electron detector and displays an electron beam image on the display unit;
A composite microscope comprising: a detection signal processing unit that displays an X-ray image and an electron beam image of the same portion of a sample simultaneously or in time series.   2. The element analyzer according to claim 1, further comprising an element analyzer for performing elemental analysis by detecting characteristic X-rays excited by electron beam irradiation, wherein the detection signal processing unit can also display an element distribution image of the sample on the display unit. Combined microscope.   The composite microscope according to claim 2, wherein the detection signal processing unit can superimpose an element distribution image on an X-ray fluoroscopic image or an X-ray tomographic image and display the superimposed image on the display unit.   The composite microscope according to claim 1, wherein the detection signal processing unit can superimpose an electron beam image on an X-ray fluoroscopic image or an X-ray tomographic image and display the image on the display unit.   Furthermore, the metal plate which generate | occur | produces an X-ray by electron beam irradiation is provided so that attachment or detachment is possible on the path | route of the electron beam irradiated from the said electron column, The said electron column serves as an X-ray generator. A composite microscope according to any one of the above.   The composite microscope according to any one of claims 1 to 5, wherein a sample cutting means is provided in the vacuum vessel so that the inside of the sample can be exposed to the outer surface.   The composite microscope according to claim 6, wherein the sample cutting means is a microtome.   7. The composite microscope according to claim 6, wherein the sample cutting means is an ion gun that performs ion beam etching.   The composite microscope according to claim 6, wherein the sample cutting means is an ion beam processing apparatus.   10. The composite microscope according to claim 1, wherein the X-ray generator is a microfocus X-ray tube having an X-ray focal spot size of 10 μm or less. 11.   The composite microscope according to any one of claims 6 to 10, wherein the sample cutting means controls the sample cutting so that a surface designated based on the X-ray fluoroscopic image or the X-ray tomographic image is exposed. The composite microscope according to any one of claims 1 to 11, wherein an operating vacuum degree in the apparatus is controlled at a low vacuum of 1 to 2,700 Pa.

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