JPH07243996A - X-ray microanalysis method - Google Patents

Abstract

PURPOSE:To provide an X-ray scanned micro-image having a resolution higher than that in the conventional method by scanning X-rays serving as a probe on a sample. CONSTITUTION:This device is constituted of a probe scanning mechanism 10 for scanning a conducting probe 1 along the sample face directly above the surface of a sample 2, an electron beam source 11 capable of focusing electrons in a range smaller than the width of the tip section of the probe 1, and a means measuring the diffracted X-rays 5 or photoelectrons 6 from the sample 2 by the characteristic X-rays 4 generated by an electron beam 3 radiated onto the probe 1. The X-ray analysis information from a region smaller than before can be collected while the surface of the sample 2 is observed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray microanalysis method for measuring various physical properties such as an atomic structure of a minute region of a substance.

[0002]

2. Description of the Related Art A conventional method for analyzing a minute area using an X-ray as a probe is, as shown in FIG. 101 is used to collect light in a very small area and X-ray analysis of this area is performed. Due to the limitation of the processing technology of the light collecting device, the size of the region capable of collecting X-rays is generally about several hundred nm when using the zone plate, and about several μ when using the oblique incidence mirror. In most cases, orbital synchrotron radiation is used as the X-ray source, and a monocrystalline diffractive plate is used for monochromatization. When an X-ray tube is used as the X-ray source, an X-ray filter made of a substance having an absorption edge between the Kα and Kβ rays of the characteristic X-rays in order to monochromate the characteristic X-rays. 103 may be arranged in a space through which X-rays pass. Since X-rays cannot be deflected by an electric field or a magnetic field, and the scale of an X-ray source is generally large and difficult to move, the sample position is selected by moving the sample itself.

[0003]

However, it is difficult for the conventional method to know to which position on the sample the obtained analytical information corresponds exactly. In addition, there is a problem in the resolution limit due to the limitation of the light collecting device.

[0004]

In order to solve the above problems, the present invention provides a probe scanning mechanism for scanning a conductive probe along the surface of a sample just above the surface of the sample, and the probe. An electron beam source capable of converging electrons in a range smaller than the width of the tip of the probe and a characteristic X-ray generated by the electron beam applied to the probe are used to measure diffracted X-rays from the sample or photoelectrons By doing so, information on the physical properties of the minute region of the sample is obtained.

[0005]

The present invention will be described with reference to FIG. In general, when a substance is irradiated with an electron beam having an energy of several tens of KeV, a characteristic X-ray that is peculiar to the type of atoms constituting the substance is generated. As shown in FIG. 3, characteristic X-rays 4 are also generated when the tip of the probe 1 is irradiated with the electron beam 3. When the tip of the probe is irradiated with an electron beam within 100 nm from the tip, the characteristic X-rays emitted above the probe 1 are absorbed by the probe 1 itself. The light is emitted from the probe toward the sample 2. Since the generated characteristic X-ray is a spherical wave and its intensity weakens in inverse proportion to the square of the distance from the generation center point, the intensity becomes 1/100 at the position of ten times the radius of the range irradiated with the electron beam. Become. Therefore, when the gap between the probe and the sample is 1 nm or less,
It can be considered that the diffracted X-rays 5 and the photoelectrons 6 excited by the characteristic X-rays mainly have information on the sample surface near the tip of the probe. At this time, if the range of the characteristic X-ray intensity up to 1/10 is defined as the position resolution, the resolution becomes about a dozen nm even when an electron beam source having a beam diameter of about several nm used in a normal scanning electron microscope is used. It is possible to realize a value that is about an order of magnitude smaller than the method.

[0006] The probe 1 is two-dimensionally scanned on the surface of the sample 2,
At the same time, if the electron beam 3 is also scanned so that its convergence point is always at the tip of the probe, a scanning X-ray microscope image can be obtained. This can be realized by synchronizing the scanning circuit 13 for scanning the probe and the electron beam scanning circuit 12 for scanning the electron beam. The relationship between the probe 1 and the sample 2 is so-called
Since it has the same configuration as that of the scanning probe microscope,
While scanning the probe, while controlling the gap between the probe and the sample so that the tunnel current flowing between the probe and the sample and / or the force acting between the probe and the sample are constant, By scanning, a scanning probe microscope image and a scanning X-ray microscope image can be simultaneously obtained.

It is also possible to obtain a scanning electron microscope image of a sample by scanning the electron beam independently of the movement of the probe and providing a secondary electron detector and / or a backscattered electron detector.
Although the scanning electron microscope image cannot be observed simultaneously with the scanning X-ray microscope image, there is an advantage that the measurement can be performed while confirming the state of the sample surface, the probe position, and the shape of the probe tip.

Various target metals are used in the X-ray tube, but among them, aluminum, zirconium, copper and molybdenum are often used and much data is accumulated. It is also known that tungsten can form a tip having an extremely small radius of curvature by electropolishing, and is the most suitable material as a probe material. For these reasons, it is desirable to use copper, molybdenum, or tungsten as the material of the probe.

In order to convert the characteristic X-rays generated by the structure according to the present invention into a monochromatic color, as shown in FIG. 3B, the characteristic X-rays of the characteristic X-rays generated by the probe at the tip of the probe 1 are changed to Kα rays. K
The filter substance 7 having an absorption edge between the β-ray and the electron beam may be vapor-deposited, and the electron beam may be applied to the uncoated portion of the substance. By doing so, X-ray spectroscopy can be performed efficiently using only Kα X-rays.

It is not desirable that the electron beam 3 directly strikes the surface of the sample 2, and it is desirable that the electron beam be incident parallel to the sample in order to hit the tip of the probe. However, in order to observe the scanning electron microscope image, the electron beam needs to enter the sample 2 at a certain angle. Therefore, it is appropriate that the angle between the incident direction of the electron beam and the sample surface is 30 degrees or less.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.
In this embodiment, the tip of the probe 1 is irradiated with the electron beam 3 obtained from the electron beam source 11. The characteristic X-rays 4 generated at this time hit the sample 2 and emit diffracted X-rays 5 and photoelectrons 6. These diffracted X-rays and photoelectrons are detected by the X-ray detector 2 respectively.
0 and detected by the energy analyzer 21.

A second embodiment of the present invention will be described with reference to FIG. In this embodiment, the probe scanning circuit 13 and the electron beam scanning circuit 12 operate in synchronization with each other, and the electron beam 3
Is always converged on the tip of the probe 1. The tungsten probe 1 serves as an X-ray source and a scanning tunneling microscope probe, and can simultaneously observe the scanning X-ray microscope image 16 and the scanning tunneling microscope image 15. The material of the probe 1 may be molybdenum, copper or other metal other than tungsten.

A third embodiment of the present invention will be shown with reference to FIG. In this embodiment, the atomic force microscope image 25 can be obtained instead of the scanning tunneling microscope image.
In general, a scanning probe microscope including a magnetic force microscope can be used in the present invention. Further, in this embodiment, the secondary electron detector 22 and the backscattered electron detector 23 are provided, and the X-ray microscope image 16 can be obtained while confirming the shape of the sample surface and the probe by the scanning electron microscope image 24. . In this embodiment, the electron beam scanning circuit 12 is provided with a probe scanning circuit 13 in order to obtain a secondary electron image or a backscattered electron image.
It is also possible to scan the electron beam 3 independently of. Further, the incident angle of the electron beam 3 can be changed from 0 degree to 30 degrees in order to detect the reflected electrons more efficiently and obtain information on the sample surface.

A fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, nickel is vapor-deposited on the tip of the probe 1 made of copper, and a part of the nickel is used as the opening 8 for the electron beam 3 to enter. Focusing the electron beam 3 on the opening enables X-ray spectroscopy using only Cu (Kα) rays.

[0015]

According to the present invention, it becomes possible to carry out X-ray analysis of local physical properties of a substance while confirming the sample surface.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a conventional local X-ray analysis method.

FIG. 3 is an explanatory view showing the operation of the present invention.

FIG. 4 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a third embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

1 ... Probe, 2 ... Sample, 3 ... Electron beam, 4 ... Characteristic X-ray, 5 ...
Diffracted X-rays, 6 ... Photoelectrons, 10 ... Probe scanning mechanism, 11 ... Electron beam source, 20 ... X-ray detector, 21 ... Energy analyzer.

Claims (7)

[Claims] 1. A probe scanning mechanism for scanning a conductive probe along the surface of a sample just above the surface of the sample, and an electron focusing device in a range smaller than the width of the tip of the probe. And a photoelectron excited by the characteristic X-ray from the sample by the characteristic X-ray generated by the electron beam applied to the tip of the probe. An X-ray microanalysis method characterized by obtaining physical property information of the microscopic region. 2. The probe according to claim 1, wherein the probe scanning circuit for driving the probe scanning mechanism is synchronized with an electron beam scanning circuit for irradiating the probe with the electron beam. Even during scanning, the electron beam is always focused on the tip of the probe,
An X-ray microanalysis method for obtaining a scanning X-ray microscope image by obtaining physical property information corresponding to the position of the probe on the surface of the sample. 3. The gap between the probe and the sample according to claim 2, wherein the tunnel current flowing between the probe and the sample or the force acting between the probe and the sample is constant. An X-ray microanalysis method for simultaneously obtaining a scanning probe microscope image and the scanning X-ray microscope image obtained by controlling 4. The method according to claim 1, 2 or 3, wherein the main elements constituting the probe are aluminum, zirconium,
X-ray microanalysis method that is copper, molybdenum, or tungsten. 5. The angle between the incident direction of the electron beam and the surface of the sample is 30 according to claim 1, 2, 3 or 4.
X-ray microanalysis, which is sub-degree. 6. The method according to claim 1, 2, 3, 4 or 5.
A filter substance made of an element having an absorption edge between the Kα line and the Kβ line of the characteristic X-rays of the main elements forming the probe is fixed to the surface of the tip of the probe, and the electron beam is absorbed. An X-ray microanalysis method of irradiating a portion of the probe where the filter substance is not fixed. 7. The X-ray microanalysis method according to claim 6, wherein copper and nickel, molybdenum and zirconium, or tungsten and hafnium are used as a combination of the material of the probe and the filter substance, respectively.