JP2903874B2 - Ion-excitation X-ray analyzer with focused ion beam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion-excited X-ray analyzer, and more particularly to a surface analyzer for preferentially detecting information on the composition of several atomic layers from the surface.

[0002]

2. Description of the Related Art Conventionally, a secondary ion mass spectrometer (SIMS) and a focused ion beam (FIB) are known as a measuring means having an ion beam irradiation system for scanning a finely focused ion beam on a sample. . When an electron beam is used as the irradiation system, a scanning electron microscope (SE
M), an X-ray microanalyzer (XMA), a transmission electron microscope (TEM) and the like are generally used. Here, the features of the prior art in which an X-ray semiconductor detector is arranged in the FIB which is considered to be closest to the present invention will be described. F
In the case of IB, ions are accelerated by an accelerating voltage of about 30 kV and are irradiated on the sample surface. In this case, the ions penetrate to a depth of several nm from the surface and sputter the surface atoms, and at the same time, generate secondary electrons, characteristic X-rays, and the like by interaction with the surface atoms. Since the penetration depth of ions is several nm, if the characteristic X-rays due to secondary excitation are ignored, FI
It is considered that X-ray analysis using B has more surface information than XMA or the like.

[0003]

The X-ray analysis by FIB is a measurement method which is sensitive to the surface composition as described above.
The conventional FIB uses an X-ray detector at 30 ° to the sample surface.
Since it was arranged at an appropriate position of 50 °, sufficient information sensitive to the surface composition could not be obtained. An object of the present invention is to provide a device capable of obtaining information more sensitive to the composition of the surface than before.

[0004]

According to the present invention, there is provided an ion beam irradiation system for scanning a narrowly focused ion beam on a sample,
In an ion excitation type X-ray analyzer having an X-ray detector for detecting characteristic X-rays generated from a sample surface due to ion bombardment, an X-ray detector is arranged in a direction of a critical angle of total reflection of X-rays in the sample. It is a configuration characterized by the following.

[0005]

The gist of the present invention is that, by placing an X-ray detector in a direction having the same extraction angle as the critical angle for total reflection, only the characteristic X-rays generated on the very surface of the sample are detected preferentially. It is in.

When an X-ray is incident on a substrate having an optically flat mirror surface at an angle lower than the total reflection critical angle of the substrate, a total reflection phenomenon occurs. This critical angle for total reflection φ _crit is expressed by the following equation.

Φ _crit ≒ 1.64 × 10 ⁻⁵ √ (ρ) · λ where λ is the wavelength of the incident X-ray and ρ is the density of the substrate.

FIG. 3 is an explanatory view showing a state in which incident ions have penetrated from the surface to a depth of several nm. FIB
Cases, the incident ion beam 1 enters to a depth A ₁ of a few nm from the surface 2a of the sample 2. The ions that have entered the sample excite atoms at a depth from A ₀ to A ₁ and excite characteristic X-rays. Characteristic X-rays are generated isotropically in all directions. Among them, X-rays generated in the A ₀ O direction parallel to the sample surface are refracted at point O by the principle of light beam regression, and the critical angle φ
Proceed in the direction OA ₀ 'of _crit . Surface deeper portion A ₁ characteristic X-rays generated in a direction parallel A ₁ O 'direction to the surface in the straight through the sample. Characteristic X-rays generated from A ₁ toward the surface A ₁ O direction travels refracted at point O in the direction OA ₁ 'direction of the large angle phi _crit + alpha than the critical angle phi _crit. Therefore, the characteristic X-rays detected by the X-ray detector placed in the critical angle φ _crit direction are only characteristic X-rays generated in the A ₀ O direction on the surface. The distance (several cm) from the sample to the X-ray detector is much larger than the irradiation range (several tens μm) of the ion beam, and the change in the extraction angle of the X-ray detector due to the movement of the incident point can be ignored. As described above, according to this method, only atoms existing on the very surface of the sample can be analyzed with high accuracy.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.

FIG. 2 is a schematic diagram showing one embodiment of an ion-excited X-ray analyzer using FIB according to the present invention, and FIG. 1 is an enlarged view of a main part. In this figure, in this embodiment, a FIB unit 3 for irradiating a finely focused ion beam 1 onto the surface of a sample 2 and observing an image, and generating a characteristic X-ray 4 through a slit 5 to determine the total reflection critical angle φ _{crit of the} sample. It comprises an X-ray detector 6 arranged so as to have the same take-out angle.

By performing the X-ray analysis as described above, it was possible to analyze only the atoms existing on the very surface of the sample with high accuracy.

As shown in FIG. 2, the FIB unit 3 includes a liquid metal ion source 7, an extractor 8, a current monitor 9,
Condenser lesbian 10, beam blanker 11, movable aperture 1
2. Stigmeter 13, objective lens 14, deflection electrode 1
5, the secondary electron detector 16 and the slit 5, which have the same configuration as that of the conventional device, and a description thereof will be omitted.

[0013]

As described above, according to the ion-excited X-ray analyzer using the FIB of the present invention, the detector is designed to detect only characteristic X-rays generated from atoms existing on the very surface of the sample. Since it is provided, it is optimal for surface analysis of a sample, and enables accurate measurement of the surface composition.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a main part of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of one embodiment of the present invention.

FIG. 3 is an explanatory view showing the principle of the present apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion beam 2 Sample surface 3 FIB part 4 Characteristic X-ray 5 Slit 6 X-ray detector 7 Liquid metal ion source 8 Extractor 9 Current monitor 10 Condenser lens 11 Beam blanker 12 Movable aperture 13 Stig meter 14 Objective lens 15 Deflection electrode 16 Secondary electron detector

Claims (1)

(57) [Claims] 1. An ion beam irradiation system for scanning a narrowly focused ion beam on a sample, an X-ray detector for detecting characteristic X-rays generated from the surface of the sample by ion bombardment, and detecting an X-ray on the sample. An ion-excited X-ray analyzer using a focused ion beam, wherein the X-ray detector is arranged in a direction of a critical angle of total reflection.