The present disclosure relates to an analysis system for analyzing an element contained in a sample.
By combining an electron microscope and an element analysis device, it is possible to obtain information on element species, element distribution, and the like of a site observed using the electron microscope. As the element analysis device, for example, an energy dispersive X-ray spectroscopy (EDS) device is used. As the electron microscope, for example, a scanning electron microscope (SEM) is used.
PTL 1 below discloses a technique of analyzing element distribution using EDS and further performing, by using a wavelength dispersive X-ray spectrometer (WDS), elemental analysis on each distribution region obtained as a result thereof.
NPL 1 below discloses an X-ray analyzer using a superconducting transition edge sensor (TES) having higher energy resolution than EDS.
A user may be keenly interested in knowing whether a sample contains a transition metal. In this case, the user does not want to miss even a small X-ray peak of the transition metal. However, compared with the TES, the EDS has low energy resolution and high measurement throughput, and thus there is a possibility that the peak of the transition metal is obscure in a coarse X-ray spectrum and information on the transition metal cannot be sufficiently identified from the X-ray spectrum.
Therefore, when the element cannot be sufficiently identified by using the EDS, it is conceivable to switch the measurement device to the TES to perform further analysis. However, since TES has high energy resolution but low throughput, there is a concern that the measurement throughput may decrease excessively when TES is excessively used.
In NPL 1, characteristics of the EDS and the TES are compared but the criteria for switching between both devices are not described. In PTL 1, an element distribution map is created using an EDS and then a WDS is used for each element phase, and it is not sufficiently considered to achieve both energy resolution and throughput between the EDS and the WDS. These literatures do not focus on spectrum information of the transition metal.
The present disclosure has been made in view of the above problems, and an object thereof is to reliably obtain spectrum information of a transition metal and to secure measurement throughput, in a case where a sample is analyzed using two or more element analysis devices having different energy resolution.
An analysis system according to the present disclosure analyzes a first X-ray of a sample by using a first element analysis device, and when a transition metal element is detected, analyzes a second X-ray of the sample by using a second element analysis device having higher energy resolution than the first element analysis device.
According to the analysis system of the present disclosure, in a case of analyzing a sample using two or more types of element analysis devices having different energy resolution, it is possible to secure measurement throughput and to reliably obtain spectrum information of a transition metal. Other problems, configurations, advantages, and the like of the present disclosure become apparent from the following description of embodiments.
The first element analysis device 11 is a device that analyzes an element contained in the sample 16, and can be implemented by, for example, an EDS device. The second element analysis device 12 is a device that analyzes an element contained in the sample 16, and has higher energy resolution than the first element analysis device 11. The second element analysis device 12 can be implemented by, for example, a TES device. The electron beam generation device 15 emits an electron beam 151 to the sample 16. The electron beam control device 14 controls the electron beam generation device 15. The sample 16 is, for example, a semiconductor substrate.
The electron beam generation device 15 condenses the electron beam 151 to a specific portion of the sample 16. Accordingly, a secondary particle 152 is generated from the sample 16. A detector 153 detects the secondary particle 152 and outputs a detection signal indicating an intensity thereof to the electron beam control device 14. The computer system 13 generates an observation image (SEM image) of the sample 16 by using the detection signal. The computer system 13 specifies, on the observation image, (a) a target portion 141 (target sample) to be subjected to element analysis and (b) a reference portion 142 (reference sample) for comparing the composition with the target portion 141.
Positions of the target portion 141 and the reference portion 142 may be designated by the user while viewing the observation image, or may be designated by the computer system 13 itself by searching for a specific shape pattern by an appropriate method such as template matching. For example, a position of a microparticle (for example, a foreign substance when the sample 16 is a semiconductor substrate) on the sample, a defect in a shape pattern, or the like can be specified as the target portion 141, and a position where the microparticle, the defect, and the like are not present can be specified as the reference portion 142.
The target portion 141 and the reference portion 142 may be located at different positions on the same sample, or the reference portion 142 may be designated on a reference sample different from the sample having the target portion 141. In either case, the target portion 141 is a target sample for performing elemental analysis, and the reference portion 142 is a reference sample serving as a comparison reference thereof.
The electron beam generation device 15 irradiates each of the target portion 141 and the reference portion 142 with the electron beam 151 over certain duration. The first element analysis device 11 acquires an X-ray 161 (first X-ray) emitted from the target portion 141 and the X-ray 161 (second X-ray) emitted from the reference portion 142.
The computer system 13 acquires data regarding a result obtained by the first element analysis device 11 detecting the X-ray 161, and acquires an energy spectrum (first energy spectrum) of the target portion 141 and an energy spectrum (second energy spectrum) of the reference portion 142 by using the data. The energy spectrum indicates a wavelength in energy (eV) on a horizontal axis and indicates the number (counts) of detected photons on a vertical axis.
By comparing the first energy spectrum with the second energy spectrum, the computer system 13 further determines whether to further perform the elemental analysis using the second element analysis device 12. A determination procedure will be described later in detail.
The first element analysis device 11 detects the X-ray 161 from each of the target portion 141 and the reference portion 142. The computer system 13 acquires the energy spectrum of the target portion 141 (S201: first energy spectrum) and the energy spectrum of the reference portion 142 (S202: second energy spectrum).
The computer system 13 compares the first energy spectrum with the second energy spectrum (S203), and extracts a feature from a region B on the energy spectrum (S204). An example of the region B will be described later.
When one or more features are extracted in the region B (S205: present), the computer system 13 further uses the second element analysis device 12 to analyze the element in the target portion 141 (S206). When no feature is extracted (S205: absent), the processing of the present flowchart ends without using the second element analysis device 12.
The computer system 13 can set, for example, a peripheral region of a characteristic X-ray of an assumed element species as the region B. In this example, with characteristic X-rays of carbon and oxygen (C-Kα line: 273 eV, O-Kα line: 525 eV) as a reference, an energy range of ±40 eV of the reference is set as the region B.
Instead, the computer system 13 may set an energy range, in which a significant difference occurs between the first energy spectrum 31 and the second energy spectrum 32, as the region B. In the example illustrated in
A case of using a difference between spectrums as an example of the feature in S204 and S205 is assumed. When the difference is equal to or greater than a threshold, the difference can be used as the feature of the energy spectrum of the target portion 141. However, in order to appropriately extract the difference, in an energy region where there is no difference in element composition between the target portion 141 and the reference portion 142, it is necessary that spectrum values (count values of the vertical axis) coincide with each other (the spectrum values may not be necessarily in strict coincidence, but are necessarily in coincidence such that at least the difference between the spectrums is less than a reference value). Accordingly, the computer system 13 adjusts one of the energy spectrums according to the following procedure such that the difference between the spectrums in a region (a region A in
The computer system 13 desirably sets, as the region A, an energy region (that is, an energy region other than the region B) from which the feature is not extracted, and adjusts one of the energy spectrums such that the difference between the energy spectrums in the region A is less than the reference value. Specifically, a scale of the count value (spectrum value) of each energy is adjusted by multiplying the count value by an appropriate coefficient so that the difference in the region A is less than the reference value. Accordingly, in the energy region (region A) in which there is no difference in element composition between the target portion 141 and the reference portion 142, the energy spectrums coincide with each other. That is, a difference in element composition is clearly indicated as a feature in the region B. Such processing of adjusting the difference between the energy spectrums in the region A to be less than the reference value is called processing of matching between spectrums.
When the target portion 141 is small, it is desirable to lower an acceleration voltage of the electron beam 151. On the other hand, in order to generate a target characteristic X-ray, energy of the electron beam 151 needs to be higher than energy of the characteristic X-ray. For example, when a transition metal is assumed as an element of the target portion 141, energy of a characteristic X-ray of the transition metal is 1.5 keV or less, and an acceleration voltage of the electron beam 151 may be 2.5 kV to 3 kV in consideration of generation efficiency of the X-ray. In this case, the generation efficiency of a characteristic X-ray of 2 keV or more is low, and an intensity of a continuous X-ray is dominant over an intensity of the characteristic X-ray. That is, a possibility that an energy region of 2 keV or more is set as the region B is low. Therefore, when a transition metal is assumed as the target portion 141, an energy region of 2 keV or more is suitable for the region A.
When a spectrum peak of O-Kα is shifted between the target portion 141 and the reference portion 142, a difference between the target portion 141 and the reference portion 142 in a spectrum tail region of the O-Kα line is reduced, and there is a possibility that a weak characteristic X-ray obscure in the tail region may be undetected. The same situation occurs in Si-Kα. Such a shift of the spectrum peak is caused by absorption of the Si-Kα line and the O-Kα line of the substrate by the target portion 141.
Therefore, the computer system 13 acquires the difference between the energy spectrum of the target portion 141 and the energy spectrum of the reference portion 142 after matching respective spectrum peaks of O-Kα and Si-Kα. Accordingly, it is possible to more reliably extract the difference between the energy spectrums in the tail region. Specifically, the computer system 13 adjusts one of the energy spectrums such that the difference between the spectrum peaks of O-Kα and Si-Kα is less than the reference value. That is, the scale of the count value is adjusted by multiplying the count value of each energy by an appropriate coefficient so that the difference between the spectrum peaks in the region B is less than the reference value.
After matching the spectrum peaks, the computer system 13 compares the spectrums 31 and 32 in an energy range excluding the peaks. In
Transition metal information may be important information for the user, and the user does not want to miss even traces of X-ray peak information of the transition metal. However, in a case where a minute sub-peak exists in the vicinity of a main peak as illustrated in
As an example in which a minute sub-peak is obscure as illustrated in
If one or more features are not extracted in S205, the computer system 13 further determines whether a feature of a transition metal is included in the first energy spectrum. The energy range for determining the presence or absence of the transition metal may be the region B or may be a region other than the region B. When the transition metal is contained, the processing proceeds to S206, and the transition metal is analyzed in detail using the second element analysis device 12. If no transition metal is contained, the processing proceeds to S701. Whether a transition metal is contained can be determined based on whether a spectrum peak corresponding to the transition metal (peak of Ni of 853 eV in
The computer system 13 determines whether the target portion 141 is an inorganic substance or an organic substance. In the embodiment, it is assumed that the user is interested in an inorganic substance, and thus the processing of the flowchart is ended when the target portion 141 is an organic substance. In case of an inorganic substance, the processing proceeds to S206, and the inorganic substance is analyzed in detail using the second element analysis device 12. The procedure of determining whether the target portion is an inorganic substance or an organic substance will be described below.
Thus, a difference in spectrum peak of the C-Kα line between the target portion 141 and the reference portion 142 is large when the target portion 141 is an organic substance, and is small when the target portion 141 is an inorganic substance. The computer system 13 can determine whether the target portion 141 is an organic substance or an inorganic substance based on the difference in S702. Specifically, it can be determined that the target portion 141 is an organic substance when the difference in spectrum peak in the vicinity of the C-Kα line between the target portion 141 and the reference portion 142 is equal to or greater than a threshold, and is an inorganic substance when the difference is smaller than the threshold.
The most significant difference in spectrum peak is presented when the acceleration voltage of the electron beam 151 is about (or equal to or less than) 1 kV as described with reference to
The determination of the organic substance and the inorganic substance is not necessarily performed using the difference in spectrum peak, and a feature equivalent to the difference may be used. For example, it is conceivable to compare spectrum area in the vicinity of the peak between the spectrums 31 and 32. In addition, similar features may be used.
In Embodiment 2, it is described that when there is no difference between the target portion 141 and the reference portion 142 (that is, when there is no feature of the energy spectrum, S205: absent), the processing proceeds to S701 to analyze the transition metal. Alternatively, when a transition metal is obtained at the time of acquiring the X-ray spectrum of the target portion 141, analysis using the second element analysis device 12 may be started. In Embodiment 3 of the present disclosure, a specific example thereof will be described. The configuration of the analysis system 1 is the same as that of Embodiment 1.
However, as described with reference to
The computer system 13 may switch between performing and not performing the flowchart of
The computer system 13 may switch between performing and not performing the flowchart of
In Embodiment 4, an element information amount of an analysis result that can be presented to the user can be increased (for example, not only the transition metal but also information on a heavy metal can be presented) by keeping the determination of second elemental analysis start up to inorganic/organic category determination.
A first elemental analysis setting button and a second elemental analysis setting button are provided on the GUI. When each button is pressed, corresponding pop up screens (lower portion of
The GUI further includes a field in which position information and particle (defect) code information output from an inspection device, which is different from the analysis system 1 and specifies a particle position, are described. In this field, for example, a file name describing a first elemental analysis result and a file name describing a second elemental analysis result (spectrum, element information, and the like) are described. Further, a “second elemental analysis execution” field is provided so as to be able to identify the sample 16 that is shifted to the analysis using the second element analysis device 12 among samples 16 analyzed using the first element analysis device 11, and “o” is assigned for the shifted sample 16.
When a first and second energy spectrum acquisition setting button is pressed, the computer system 13 displays the user interface described with reference to
The GUI further includes a field for setting conditions of first energy spectrum acquisition and second energy spectrum acquisition. The user selects spot analysis or area analysis in the first energy spectrum acquisition and the second energy spectrum acquisition.
The GUI further includes a field for selecting a method of matching between energy spectrums. The matching method can be selected from, for example, (a) a manual method in which a user selects a range, (b) 2 keV or more (the procedure described in
When the user presses a first elemental analysis execution button on the screen in
The GUI may display each energy spectrum. For example, the energy spectrum of the target portion 141, the energy spectrum of the reference portion 142, and the like can be displayed. The result of performing the matching processing and the process of the matching processing may be displayed.
The present disclosure is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above are described in detail to facilitate understanding of the present disclosure, and it is not necessary to include all of the configurations described. A part of one embodiment can be replaced with a configuration of another embodiment. A configuration of another embodiment can be added to a configuration of one embodiment. A part of a configuration of each embodiment may be deleted, added with a part of a configuration of another embodiment, or replaced with a part of a configuration of another embodiment.
Although it is described in Embodiment 2 that the acceleration voltage of the electron beam 151 is preferably about 1 kV, which is an example, other acceleration voltages may be used. The sub-peak of the transition metal shown in
In the embodiments described above, the position where the energy spectrum of the X-ray is acquired is specified by using the observation image of the sample 16 formed using the electron beam 151. In a case where the sample 16 is a semiconductor wafer as an example, the position of microparticles adhering to the sample surface (or the position of a defect in shape pattern) is specified based on the observation image and an element of the microparticles is specified by each element analysis device, whereby a failure cause and the like can be analyzed.
In the embodiments described above, the computer system 13 can be implemented by an arithmetic device such as a processor that executes a program in which the procedure of each flowchart is implemented, and a storage device that stores the program. Alternatively, the computer system 13 may be implemented by hardware such as a circuit device in which the same procedure is implemented, instead of the program.
Filing Document | Filing Date | Country | Kind |
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PCT/JP2022/012636 | 3/18/2022 | WO |