US-12625097-B2 - X-ray spectrum analysis apparatus and method

US12625097B2US 12625097 B2US12625097 B2US 12625097B2US-12625097-B2

Abstract

A soft X-ray measurement device detects a characteristic X-ray emitted from a sample including a primary element and a secondary element. An X-ray spectrum generated by a spectrum generator includes a waveform of interest which is an intrinsic waveform of the primary element, caused by transition of electrons from a valence band to an inner shell in the primary element. A secondary element analyzer calculates quantitative information of the secondary element through analysis of the waveform of interest.

Inventors

Takanori Murano
Shogo Koshiya
Masami Terauchi

Assignees

JEOL LTD.
TOHOKU UNIVERSITY

Dates

Publication Date: 20260512
Application Date: 20220317
Priority Date: 20210322

Claims (7)

1 . An X-ray spectrum analysis apparatus comprising: a generator that generates a first X-ray spectrum comprising a waveform of interest which is an intrinsic waveform of a primary element, caused by transition of electrons from a valence band to an inner shell in the primary element, based on a detection signal acquired through detection of a characteristic X-ray emitted from a sample comprising the primary element and a secondary element; and an analyzer that acquires quantitative information of the secondary element by comparing the waveform of interest with a reference waveform, determining an amount of shift as a result of the comparison between the waveform of interest and the reference waveform, and calculating the quantitative information of the secondary element based on the amount of shift, wherein the reference waveform is a waveform included in a second X-ray spectrum generated based on a detection signal acquired through detection of a characteristic X-ray emitted from a reference sample, and is an intrinsic waveform of the primary element in the reference sample, caused by transition of electrons from the valence band to the inner shell in the primary element, the reference sample does not include the secondary element, each of the first X-ray spectrum and the second X-ray spectrum is a spectrum of a soft X-ray having an energy of less than 100 eV, and a content ratio of the secondary element in the sample is 1% or less.
2 . The X-ray spectrum analysis apparatus according to claim 1 , wherein the analyzer comprises: a storage which stores the reference waveform; a comparator which compares the waveform of interest with the reference waveform; and a calculator which calculates the quantitative information of the secondary element based on a result of comparison by the comparator.
3 . The X-ray spectrum analysis apparatus according to claim 2 , wherein the calculator calculates a content of the secondary element as the quantitative information of the secondary element based on the result of comparison, according to a calibration curve which is generated in advance.
4 . The X-ray spectrum analysis apparatus according to claim 1 , wherein the generator generates a plurality of X-ray spectra corresponding to a plurality of positions in the sample, the analyzer calculates a plurality of quantitative information of the secondary element through analysis of a plurality of waveforms of interest comprised in the plurality of X-ray spectra, and the X-ray spectrum analysis apparatus further comprises a map generator that generates a secondary element map based on the plurality of quantitative information.
5 . The X-ray spectrum analysis apparatus according to claim 4 , further comprising: a sample image generator that generates a sample image representing the sample; and a combined image generator that generates a combined image by combining the secondary element map and the sample image.
6 . An X-ray spectrum analysis method for analyzing a first X-ray spectrum comprising a waveform of interest, wherein the first X-ray spectrum is generated based on a detection signal acquired through detection of a characteristic X-ray emitted from a sample comprising a primary element which is known and a secondary element which is known, the waveform of interest is an intrinsic waveform of the primary element, caused by transition of electrons from a valence band to an inner shell in the primary element, a form of the waveform of interest changes according to a content of the secondary element in the sample, and p 1 the X-ray spectrum analysis method comprises: comparing the waveform of interest with a reference waveform; determining an amount of shift as a result of the comparison between the waveform of interest and the reference waveform; and calculating the content of the secondary element based on the amount of shift, wherein the reference waveform is a waveform included in a second X-ray spectrum generated based on a detection signal acquired through detection of a characteristic X-ray emitted from a reference sample, and is an intrinsic waveform of the primary element in the reference sample, caused by transition of electrons from the valence band to the inner shell in the primary element, the reference sample does not include the secondary element, each of the first X-ray spectrum and the second X-ray spectrum is a spectrum of a soft X-ray having an energy of less than 100 eV, and a content ratio of the secondary element in the sample is 1% or less.
7 . A non-transitory recording medium storing a program executed by an information processing device, the program, when executed, causing the information processing device to execute a process comprising: generating a first X-ray spectrum comprising a waveform of interest which is an intrinsic waveform of a primary element, caused by transition of electrons from a valence band to an inner shell in the primary element, based on a detection signal acquired through detection of a characteristic X-ray emitted from a sample including the primary element and a secondary element; and generating quantitative information of the secondary element by comparing the waveform of interest with a reference waveform, determining an amount of shift as a result of the comparison between the waveform of interest and the reference waveform, and calculating the quantitative information of the secondary element based on the amount of shift, wherein the reference waveform is a waveform included in a second X-ray spectrum generated based on a detection signal acquired through detection of a characteristic X-ray emitted from a reference sample, and is an intrinsic waveform of the primary element in the reference sample, caused by transition of electrons from the valence band to the inner shell in the primary element, the reference sample does not include the secondary element, each of the first X-ray spectrum and the second X-ray spectrum is a spectrum of a soft X-ray having an energy of less than 100 eV, and a content ratio of the secondary element in the sample is 1% or less.

Description

CROSS REFERENCE TO RELATED APPLICATION This application claims priority to Japanese Patent Application No. 2021-047329 filed Mar. 22, 2021, the disclosure of which is hereby incorporated by reference in its entirety. BACKGROUND OF THE INVENTION Field of the Invention The present disclosure relates to an X-ray spectrum analysis apparatus and method, and in particular to analysis of a characteristic X-ray spectrum acquired from a sample which includes a primary element and a secondary element. Description of Related Art In recent years, an apparatus which measures a characteristic X-ray belonging to a soft X-ray region having an energy lower than a few hundreds of eV's has attracted attention. By observing and analyzing a spectrum of the characteristic X-ray, a state of a valence band in a particular element in a sample, such as, for example, a form of chemical bonding between atoms, can be analyzed. For example, a soft X-ray spectrometer is provided in a scanning electron microscope (SEM), an electron probe microanalyzer (EPMA), or the like. Document 1 (Terauchi et al., Chemical State Analysis with Soft-X-ray Emission Spectroscopy Based on SEM, Surface Science, Vol. 36, No. 4, pp. 184-188, 2015) discloses a scanning electron microscope with a soft X-ray spectrometer, and discloses a plurality of soft X-ray spectra acquired from a plurality of samples having different compositions. While Document 1 mentions a deviation among the plurality of soft X-ray spectra, Document 1 does not disclose a method of quantitatively analyzing a secondary element in the sample based on a signal acquired from a primary element in the sample. Document 2 (JP 2012-255689 A) and Document 3 (JP 2001-305081 A) disclose a method of quantitatively analyzing a minute-quantity element, but do not disclose a method of quantitatively analyzing a secondary element in the sample based on a signal acquired from a primary element in the sample. When a primary element dominantly exists in a sample and a minute quantity of a secondary element (for example, an additive or an impurity) also exists in the sample, even if detection of a characteristic X-ray emitted from the secondary element is attempted, a signal intensity that can be acquired is not sufficient. Even if the characteristic X-ray spectrum of the secondary element is observed, a result of quantitative analysis based on such a characteristic X-ray spectrum would include a large error. On the other hand, when an illumination current for an electron beam to be illuminated onto the sample is increased in order to increase the intensity of the characteristic X-ray emitted from the secondary element, a problem of damages of the sample tends to occur more easily. In order to improve the signal-to-noise (S/N) ratio, a configuration may be considered in which a signal accumulation time is elongated. In this case, however, a measurement time would consequently be elongated. It would be very convenient if the signal acquired from the primary element, included in the sample in a large quantity, can be utilized or referred to, for the quantitative analysis of the secondary element, but no such measurement method has been realized. SUMMARY OF THE INVENTION An advantage of the present disclosure lies in provision of an X-ray spectrum analysis apparatus and method which can acquire quantitative information of the secondary element with high precision, when a sample includes the primary element and the secondary element. Alternatively, an advantage of the present disclosure lies in realization of a novel measurement method which allows calculation of the quantitative information of the secondary element based on the signal acquired from the primary element. According to one aspect of the present disclosure, there is provided an X-ray spectrum analysis apparatus comprising: a generator that generates an X-ray spectrum including a waveform of interest which is an intrinsic waveform of a primary element, caused by transition of electrons from a valence band to an inner shell in the primary element, based on a detection signal acquired through detection of a characteristic X-ray emitted from a sample including the primary element and a secondary element; and an analyzer that generates quantitative information of the secondary element through analysis of the waveform of interest. According to another aspect of the present disclosure, there is provided an X-ray spectrum analysis method for analyzing an X-ray spectrum including a waveform of interest, wherein the X-ray spectrum is generated based on a detection signal acquired through detection of a characteristic X-ray emitted from a sample including a primary element which is known and a secondary element which is known, the waveform of interest is an intrinsic waveform of the primary element, caused by transition of electrons from a valence band to an inner shell in the primary element, a form of the waveform of interest changes according to a content of