Patent Description:
In a known method of performing element analysis, a specimen is irradiated with a primary beam such as an electron beam or an X-ray, and X-rays emitted from the specimen are detected.

Energy-dispersive X-ray spectrometry, in which composition information about a specimen is acquired by irradiating the specimen with an electron beam in an electron microscope and detecting X-rays emitted from the specimen, is an example thereof. Energy-dispersive X-ray spectrometry uses the fact that characteristic X-rays have energy values that are unique to the elements constituting the specimen. On a spectrum of characteristic X-rays acquired by energy-dispersive X-ray spectrometry, element types contained in the specimen are determined from the energy values of the peaks, and the content of each element type is determined from the surface area of the corresponding peak.

Further, a method using a soft x-ray emission spectrometer (SXES), in which a diffraction grating is combined with a charge-coupled device (CCD) image sensor, is known as another example of the method described above. For example, in an analysis device disclosed in <CIT>, a specimen is irradiated with an electron beam, soft X-rays generated from the specimen are focused by a mirror and diffracted by the diffraction grating, the diffracted soft X-rays are received by the X-ray CCD image sensor, and thus a spectrum is acquired.

In the analysis device described above, the interval between adjacent points on the spectrum is determined by the pixel pitch of the CCD image sensor. Therefore, when the pixel pitch of the CCD image sensor is large relative to the energy resolution (wavelength resolution) of the X-rays in a spectroscopic element such as the diffraction grating, even assuming that the X-rays can be subjected to energy dispersion by the spectroscopic element at a high resolution, it may be impossible to reproduce the spectrum accurately.

<NPL> discloses a signal processing algorithm used to reformat spectroscopic data to correct for any rotation of the dispersion direction relative to a row of detectors.

According to a first aspect of the invention, there is provided an analysis device including:.

With this spectrum generation method, the interval between adjacent points on the spectrum can be reduced in comparison with a case where the divergent direction of the signal is parallel to the column direction of the detector, for example, and as a result, the resolution of the spectrum can be improved.

Embodiments of the invention are described in detail below with reference to the drawings. Note that the following embodiments do not unduly limit the scope of the invention as stated in the claims. In addition, all of the elements described below are not necessarily essential requirements of the invention.

First, an analysis device according to an embodiment of the invention will be described with reference to the figures. <FIG> is a diagram illustrating the configuration of an analysis device <NUM> according to an embodiment of the invention.

As illustrated in <FIG>, the analysis device <NUM> includes an electron beam emitting unit <NUM>, an X-ray focusing mirror <NUM>, a diffraction grating <NUM>, an X-ray detection device <NUM>, a display unit <NUM>, an operating unit <NUM>, a storage unit <NUM>, and a processing unit <NUM>.

The electron beam emitting unit <NUM> irradiates a specimen S with an electron beam. The electron beam emitting unit <NUM> includes an electron gun serving as an electron beam source, and an illumination-lens system for irradiating the specimen S with the electron beam emitted from the electron gun. The analysis device <NUM> may also function as a scanning electron microscope for acquiring a scanning electron microscope image (a SEM image).

In the analysis device <NUM>, an electrostatic deflection plate <NUM> is disposed above the specimen S. When the specimen S is irradiated with the electron beam, characteristic soft X-rays (also referred to simply as "X-rays" hereafter) are generated from the specimen S. In addition to the X-rays, backscattered electrons, secondary electrons, and so on are also generated from the specimen S. By disposing the electrostatic deflection plate <NUM>, the backscattered electrons, secondary electrons, and so on can be removed. Moreover, the potential applied to the electrostatic deflection plate <NUM> is variable, and by applying the potential in accordance with the accelerating voltage of the electron beam, background can be reduced.

The X-ray focusing mirror <NUM> focuses the X-rays emitted from the specimen S and guides the focused X-rays to the diffraction grating <NUM>. By focusing the X-rays using the X-ray focusing mirror <NUM>, the intensity of the X-rays entering the diffraction grating <NUM> can be increased. As a result, the measurement time can be reduced, and the S/N ratio of the spectrum can be improved.

The X-ray focusing mirror <NUM> is constituted by two mutually opposing mirrors, for example. The interval between the two mirrors is narrow on the specimen S side (the entrance side) and wide on the diffraction grating <NUM> side (the exit side). Thus, the dose of X-ray entering the diffraction grating <NUM> can be increased.

The diffraction grating <NUM> diffracts the X-rays that are generated by the specimen S when the specimen S is irradiated with the electron beam. When the X-rays enter the diffraction grating <NUM> at a specific angle, X-rays (diffracted X-rays) diffracted into respective energies (wavelengths) can be acquired. The diffraction grating <NUM> is an unequal interval diffraction grating, for example, in which grooves are formed at unequal intervals for the purpose of aberration correction. The diffraction grating <NUM> is configured such that when X-rays enter at a large entrance angle, the focus of the diffracted X-rays is formed on a detection plane <NUM> of an image sensor <NUM> rather than on the Rowland circle.

The X-ray detection device <NUM> is configured to include the image sensor <NUM> (an example of a detector) and a control device <NUM>.

The image sensor <NUM> detects the X-rays (diffracted X-rays) diffracted by the diffraction grating <NUM>. The image sensor <NUM> is highly sensitive to soft X-rays. The image sensor <NUM> is a charge-coupled device (CCD) image sensor, a complementary MOS (CMOS) image sensor, or the like, for example. The image sensor <NUM> is a back-illuminated CCD image sensor, for example. The image sensor <NUM> is positioned so that the detection plane <NUM> is aligned with an image plane of the diffracted X-rays.

<FIG> is a plan view schematically illustrating the detection plane <NUM> of the image sensor <NUM>.

As illustrated in <FIG>, the image sensor <NUM> includes detection regions <NUM> arranged in a plurality of rows and a plurality of columns. On a detection plane <NUM>, the detection regions <NUM> are arranged in a row direction C and a column direction D. The row direction C and the column direction D are orthogonal to each other. The row direction C is the direction in which the rows extend, and the column direction D is the direction in which the columns extend.

Hereafter, the number of detection regions <NUM> arranged in the row direction C will be set as M (where M is an integer of <NUM> or more), and the number of detection regions <NUM> arranged in the column direction D will be set as N (where N is an integer of <NUM> or more). In other words, the image sensor <NUM> includes M × N detection regions <NUM>. The number M of detection regions <NUM> arranged in the row direction C and the number N of detection regions <NUM> arranged in the column direction D may be the same or different.

Each detection region <NUM> corresponds to one pixel of a CCD image sensor, for example. Note that each detection region <NUM> may also be constituted by a plurality of adjacent pixels of the image sensor <NUM> (binning). The M × N detection regions <NUM> are each capable of independently detecting an X-ray diffracted by the diffraction grating <NUM>. The M × N detection regions <NUM> each output a detection signal. The detection signal includes information indicating the intensity of the X-ray detected in the detection region <NUM>.

On the detection plane <NUM> of the image sensor <NUM>, an energy dispersion direction A of the X-ray is a direction in which an X-ray incident on the detection plane <NUM> of the image sensor <NUM> disperses energy. Further, a divergent direction B of the X-ray is a direction in which an X-ray incident on the detection plane <NUM> of the image sensor <NUM> diffuses (a spreading direction). In the example illustrated in the figure, the energy dispersion direction A and the divergent direction B are orthogonal to each other.

The energy dispersion direction A is neither parallel nor perpendicular to the row direction C. Similarly, the divergent direction Bis neither parallel nor perpendicular to the column direction D. An angle θ formed by the divergent direction B of the X-ray and the column direction D satisfies the relationship of the following formula, for example. <MAT> where <NUM>° < θ < <NUM>°.

The control device <NUM> controls the image sensor <NUM> illustrated in <FIG>. The control device <NUM> supplies power to the image sensor <NUM>. Further, the control device <NUM> executes processing for transmitting an output signal from the image sensor <NUM> to the processing unit <NUM>. The control device <NUM> includes a cooling mechanism for cooling the image sensor <NUM> and thereby controls the temperature of the image sensor <NUM>.

The display unit <NUM> outputs an image generated by the processing unit <NUM>. The display unit <NUM> can be realized by a display such as a liquid crystal display (LCD), for example.

The operating unit <NUM> executes processing for converting instructions from a user into signals and transmitting the signals to the processing unit <NUM>. The operating unit <NUM> can be realized by an input device such as buttons, keys, a touch panel display, or a microphone, for example.

The storage unit <NUM> stores programs and data used by the processing unit <NUM> in various calculation processing and various control processing. The storage unit <NUM> is also used as a work area of the processing unit <NUM>. The storage unit <NUM> can be realized by a random access memory (RAM), a read only memory (ROM), a hard disk, and so on, for example.

The processing unit <NUM> performs processing for generating an X-ray spectrum based on the X-ray detection result acquired by the image sensor <NUM>. Further, the processing unit <NUM> executes control for displaying the generated spectrum on the display unit <NUM>. The functions of the processing unit <NUM> can be realized by executing a program using various processors (a central processing unit (CPU) or the like). The processing unit <NUM> includes a spectrum generation unit <NUM> and a display control unit <NUM>.

The spectrum generation unit <NUM> generates an X-ray spectrum based on X-ray detection result acquired by the image sensor <NUM>. The spectrum generation unit <NUM> performs processing for generating a spectrum (also referred to hereafter as a "row spectrum") for each row based on the detection signals relating to the detection regions <NUM> arranged in the row direction C, thereby generating a plurality of row spectra, and processing for generating an X-ray spectrum based on the plurality of row spectra. The processing performed by the spectrum generation unit <NUM> will be described in detail below.

The display control unit <NUM> executes control for displaying the spectrum generated by the spectrum generation unit <NUM> on the display unit <NUM>.

Next, a method employed in the analysis device <NUM> to generate an X-ray spectrum will be described. More specifically, first, a spectrum generation method employed in an analysis device according to a reference example will be described. Next, the spectrum generation method employed in the analysis device <NUM> will be described by comparing the method of the analysis device according to the reference example with the method of the analysis device <NUM>.

<FIG> is a plan view schematically illustrating a detection plane <NUM> of an image sensor <NUM> of the analysis device according to the reference example. Here, a case in which the image sensor <NUM> is a CCD image sensor having <NUM> × <NUM> pixels will be described. In other words, in the image sensor <NUM>, <NUM> detection regions <NUM> are arranged in the row direction C, and <NUM> detection regions <NUM> are arranged in the column direction D.

As illustrated in <FIG>, in the image sensor <NUM>, the energy dispersion direction A is parallel to the row direction C, and the divergent direction B is parallel to the column direction D.

<FIG> is a diagram illustrating the spectrum generation method employed in the analysis device according to the reference example.

In the analysis device according to the reference example, as illustrated in <FIG>, an X-ray spectrum S2 is generated by integrating the intensities of the X-rays detected by the plurality of detection regions <NUM> arranged in the column direction D.

In the analysis device according to the reference example, the column direction D is parallel to the divergent direction B of the X-ray, and therefore X-rays having the same energy (wavelength) are detected in the <NUM> detection regions <NUM> arranged in the same direction. Hence, the spectrum S2 is generated by integrating the intensities of the X-rays detected by the <NUM> detection regions <NUM> arranged in the column direction D.

On the spectrum S2, the horizontal axis expresses the energy (wavelength) of the X-ray. The energy of the X-ray corresponds to the position in the row direction C of the detection regions <NUM>. Further, on the spectrum S2, the vertical axis expresses the intensity of the X-ray. Thus, the spectrum S2 is represented by an energy axis that expresses the energy (wavelength) of the X-ray and is set as a horizontal axis, and an intensity axis that expresses the intensity of the X-ray and is set as a vertical axis. The number of points constituting the spectrum S2 matches the number of detection regions <NUM> arranged in the row direction C. Hence, the number of points constituting the spectrum S2 is <NUM>.

<FIG> is a diagram illustrating the spectrum generation method employed in the analysis device <NUM>. Differences with the analysis device according to the reference example will be described below, while description of similarities will be omitted.

As illustrated in <FIG>, in the analysis device <NUM>, the detection plane <NUM> of the image sensor <NUM> is acquired by rotating the image sensor <NUM> illustrated in <FIG> by the angle θ. Accordingly, the angle formed by the divergent direction B of the X-ray and the column direction D is the angle θ.

In the analysis device <NUM>, similarly to the analysis device according to the reference example, illustrated in <FIG>, <NUM> detection regions <NUM> are arranged in the row direction C and <NUM> detection regions <NUM> are arranged in the column direction D. In other words, the number M of detection regions <NUM> arranged in the row direction C = <NUM> and the number N of detection regions <NUM> arranged in the column direction D = <NUM>. Hence, the angle θ is θ = tan-<NUM> (<NUM>/<NUM>).

In the analysis device <NUM>, a row spectrum S4 is generated for each row so that <NUM> row spectra S4 are acquired. For example, first, on the first row, the row spectrum S4 of the first row is generated based on the intensities of the X-rays detected by the <NUM> detection regions <NUM> arranged in the row direction C. Next, on the second row, the row spectrum S4 of the second row is generated based on the intensities of the X-rays detected by the <NUM> detection regions <NUM> arranged in the row direction C. Similar processing is then performed from the third row onward. By repeating the processing for generating the row spectrum S4 from the first to the <NUM>th row in this manner, <NUM> row spectra S4 are acquired.

<FIG> is a diagram illustrating processing for correcting the energy axes of the row spectra S4.

The energy axes, i.e. the horizontal axes, of the <NUM> row spectra S4 deviate from each other. Therefore, the energy axes of the row spectra S4 are corrected based on peaks of the row spectra S4. More specifically, as illustrated in <FIG>, the energy axis of each row spectrum S4 is corrected so that positions of corresponding peaks on the <NUM> row spectra S4 have identical energy values.

Next, the <NUM> row spectra S4 having the corrected energy axes are formed into a single spectrum. For example, the points constituting the respective row spectra S4 of the <NUM> row spectra S4 are plotted on a single graph. In so doing, a spectrum S6 can be generated.

The spectrum S6 illustrated in <FIG> is constituted by <NUM> × <NUM> points, and the interval between adjacent points is <NUM>/<NUM> that of the spectrum S2 illustrated in <FIG>. In other words, the resolution of the energy axis of the spectrum S6 is <NUM> times greater than the resolution of the energy axis of the spectrum S2.

Cases in which one detection region <NUM> and one detection region <NUM> each form one pixel of the CCD image sensor were described above, but the above description applies likewise to a case in which the pixels constituting the CCD image sensor are binned.

For example, when <NUM> × <NUM> pixels form a single detection region <NUM>, the interval between adjacent points on the spectrum S6 generated by the analysis device <NUM> is <NUM>/<NUM> that of the spectrum S2 generated by the analysis device according to the reference example. In other words, the resolution of the energy axis of the spectrum S6 is <NUM> times greater than the resolution of the energy axis of the spectrum S2.

Next, the processing executed by the processing unit <NUM> of the analysis device <NUM> will be described. <FIG> is a flowchart illustrating an example of the processing executed by the processing unit <NUM> of the analysis device <NUM>.

In the analysis device <NUM>, when the specimen S is irradiated with an electron beam by the electron beam emitting unit <NUM>, X-rays are generated from the specimen S. The X-rays generated from the specimen S are focused by the X-ray focusing mirror <NUM> and then enter the diffraction grating <NUM>. The X-rays entering the diffraction grating <NUM> exit at exit angles corresponding to the energies (wavelengths) thereof and then enter the detection plane <NUM> of the image sensor <NUM>. The X-rays incident on the detection plane <NUM> are detected by the M × N detection regions <NUM>. Each of the M × N detection regions <NUM> outputs a detection signal. The detection signals output respectively from the M × N detection regions <NUM> are transmitted to the processing unit <NUM>.

The spectrum generation unit <NUM> generates N row spectra S4 by generating a row spectrum S4 for each row based on the detection signals from the M detection regions <NUM> arranged in the row direction C (S100).

Next, the spectrum generation unit <NUM> generates the spectrum S6 based on the N row spectra S4 (S102).

In the processing for generating the spectrum S6, first, the energy axes of the N row spectra S4 are corrected based on the respective peaks of the N row spectra S4. More specifically, the energy axis of each row spectrum S4 is corrected so that positions of corresponding peaks on the N row spectra S4 have identical energy values.

Next, the spectrum generation unit <NUM> generates the spectrum S6 based on the N row spectra S4 having the corrected energy axes. For example, the points constituting the respective row spectra S4 of the N row spectra S4 are plotted on a single graph. In so doing, the spectrum S6 can be generated.

Next, the display control unit <NUM> executes control for displaying the spectrum generated by the spectrum generation unit <NUM> on the display unit <NUM> (S104). As a result, the spectrum S6 is displayed on the display unit <NUM>.

The analysis device <NUM> exhibits the following actions and effects, for example.

In the analysis device <NUM>, the image sensor <NUM> includes the detection regions <NUM> arranged in a plurality of rows and a plurality of columns, and the divergent direction B of an X-ray incident on the image sensor <NUM> is neither parallel nor perpendicular to the column direction D. Further, the spectrum generation unit <NUM> performs processing for acquiring the plurality of row spectra S4 by generating the row spectrum S4 for each row based on the detection signals relating to the detection regions <NUM> arranged in the row direction C, and processing for generating the spectrum S6 based on the plurality of row spectra S4. With the analysis device <NUM>, therefore, the interval between adjacent points on the spectrum can be reduced in comparison with a case where the divergent direction B of the X-ray is parallel to the column direction D, for example, and as a result, the resolution of the spectrum can be improved.

Further, with the analysis device <NUM>, the resolution of the spectrum can be improved, and therefore effective filter processing can be executed on the spectrum. When the number of points constituting the peaks of the spectrum is small, for example, filter processing using a low-pass filter or the like cannot be performed effectively.

In the analysis device <NUM>, when N denotes the number of detection regions <NUM> arranged in the column direction D, the angle θ formed by the divergent direction B of the X-ray and the column direction D is θ = tan-<NUM> (<NUM>/N). With the analysis device <NUM>, therefore, the interval between adjacent points can be set at <NUM>/N compared to that of a case in which the divergent direction B of the X-ray is parallel to the column direction D, for example. In other words, the resolution of the energy axis of the spectrum can be set at a multiple of N.

In the analysis device <NUM>, the energy axes of the plurality of row spectra S4 are corrected based on the respective peaks of the plurality of row spectra S4, and the spectrum S6 is generated based on the plurality of row spectra S4 having the corrected energy axes. With the analysis device <NUM>, therefore, the resolution of the spectrum S6 can be improved.

Furthermore, even if the angle formed by the divergent direction B of the X-ray and the column direction D deviates, for example, the energy axes of the plurality of row spectra S4 are corrected based on the respective peaks of the plurality of row spectra S4, and therefore the deviation in the angle can be corrected.

The spectrum generation method employed in the analysis device <NUM> has the following features, for example.

The spectrum generation method employed in the analysis device <NUM> includes the steps of acquiring the plurality of row spectra S4 by generating the row spectrum S4 for each row based on the detection signals relating to the detection regions <NUM> arranged in the row direction C, and generating the spectrum S6 based on the plurality of row spectra S4. Further, the image sensor <NUM> includes the detection regions <NUM> arranged in a plurality of rows and a plurality of columns, and the divergent direction B of an X-ray incident on the image sensor <NUM> is neither parallel nor perpendicular to the column direction D of the image sensor <NUM>. Hence, in comparison with a case where the divergent direction B of the X-ray is parallel to the column direction D, for example, the interval between adjacent points on the spectrum can be reduced, and as a result, the resolution of the spectrum can be improved.

In the analysis device <NUM> described above, a case in which the angle θ formed by the divergent direction B of the X-ray and the column direction D satisfies θ = tan-<NUM> (<NUM>/N) was described, but as long as the divergent direction B of the X-ray is neither parallel nor perpendicular to the column direction D, there are no particular limitations on the angle θ.

<FIG> is a diagram illustrating a spectrum generation method employed in an analysis device according to a second modified example. Differences with the example of the above analysis device <NUM> will be described below, while description of similarities will be omitted.

In the analysis device <NUM> according to the above embodiment, the detection plane <NUM> of the image sensor <NUM> is rotated so that the divergent direction B of the X-ray is neither parallel nor perpendicular to the column direction D.

In the second modified example, meanwhile, as illustrated in <FIG>, the divergent direction B of the X-ray and the column direction D are set to be neither parallel nor perpendicular by bending the X-rays diffracted by the diffraction grating <NUM> (see <FIG>).

For example, when the diffraction grating <NUM> is an irregular interval diffraction grating, in which grooves are formed at irregular intervals for the purpose of aberration correction, the divergent direction B of the diffracted X-rays can be bent. In so doing, the divergent direction B and the column direction D can be set so as to be neither parallel nor perpendicular in a similar manner to a case in which the detection plane <NUM> of the image sensor <NUM> is rotated.

Hence, with the analysis device according to the second modified example, similar actions and effects to those of the analysis device <NUM> described above can be achieved.

Note that the invention is not limited to the embodiments described above, and various modifications may be applied within the scope of the invention.

For example, in the embodiments described above, as illustrated in <FIG>, the X-rays generated by the specimen S are diffracted by the diffraction grating <NUM>, but the spectroscopic element that diffracts the X-rays generated by the specimen S is not limited thereto, and a spectroscopic element capable of continuous energy dispersion of the X-rays may be used instead. A zone plate or the like, for example, may be cited as this type of spectroscopic element.

Further, in the embodiments described above, the specimen S is irradiated with an electron beam, but X-rays may be generated from the specimen S by irradiating the specimen S with a primary beam other than an electron beam. An X-ray beam, an ultraviolet beam, or the like may be cited as other types of primary beams.

The invention includes configurations that are substantially the same (for example in function and method) as the configurations described in the embodiments. The invention also includes configurations in which non-essential elements described in the embodiments are replaced by other elements. The invention further includes configurations obtained by adding known art to the configurations described in the embodiments.

Claim 1:
An analysis device (<NUM>) comprising:
a spectroscopic element (<NUM>) that diffracts a signal generated by a specimen (S);
a detector (<NUM>) that detects the signal diffracted by the spectroscopic element (<NUM>); and
a spectrum generation unit (<NUM>) that generates a spectrum of the signal based on a detection result by the detector (<NUM>), the spectrum being represented by a horizontal axis that expresses an energy of the signal, and a vertical axis that expresses an intensity of the signal,
the detector (<NUM>) including detection regions arranged in a plurality of rows and a plurality of columns,
a divergent direction of the signal incident on the detector being neither parallel nor perpendicular to a column direction of the detector,
the divergent direction of the signal and an energy dispersion direction of the signal being orthogonal to each other, and
the spectrum generation unit (<NUM>) performing:
processing for acquiring a plurality of row spectra by generating a row spectrum (S4) represented by a horizontal axis that expresses an energy of the signal and a vertical axis that expresses an intensity of the signal for each of the plurality of rows based on a result of detection of the signal in the detection regions arranged in a row direction of the detector (<NUM>); and
processing for generating a spectrum of the signal (S6) based on the plurality of row spectra (S4) having peaks of identical energy values,
characterized in that, in the processing for generating the spectrum (S6) of the signal:
energy axes of the plurality of row spectra (S4) are corrected by matching positions of the peaks having identical energy values, and
the spectrum of the signal (S6) is generated based on the plurality of row spectra having the corrected energy axes.