JP5441856B2 - X-ray detection system - Google Patents

Description

  The present invention relates to an X-ray detection system, and more particularly to an X-ray detection system that analyzes a spectrum by imaging characteristic X-rays emitted from a sample as diffraction X-rays by a diffraction grating on an image sensor.

  When the sample is irradiated with a charged particle beam such as an electron beam, characteristic X-rays are generated from the sample. A technique for detecting the characteristic X-rays with a detector and measuring the composition of the sample is called energy dispersive X-ray spectroscopy. This technique utilizes the characteristic X-rays having the specific energy of the elements constituting the sample. The number of X-rays generated per unit time is counted for each X-ray energy to obtain information such as the elemental composition of the sample. Here, as a means for detecting X-rays, a semiconductor detection element using a semiconductor crystal such as silicon or germanium is generally used.

  On the other hand, when characteristic X-rays generated by irradiating a sample with a charged particle beam such as an electron beam are incident on the diffraction grating, the diffracted X-rays are separated. There is also a technique for detecting the diffracted X-rays with an X-ray CCD image sensor and imaging it.

  An apparatus for realizing this technique includes an electron beam irradiation unit that irradiates a sample with an electron beam, and an X-ray collection that collects characteristic X-rays emitted from the sample irradiated with the electron beam and guides them to a diffraction grating. An optical mirror, a diffraction grating that receives characteristic X-rays collected by the X-ray condenser mirror and generates diffracted X-rays, and an image sensor that detects diffracted X-rays generated by the diffraction grating. ing.

  This type of X-ray detection system is also described in Patent Document 1 below.

JP 2002-329473 A

  With the above X-ray detection system, when an electron beam is irradiated using a compound such as an oxide / nitrogen compound as a sample, light emission called cathode luminescence (CL), which has a wavelength different from that of the characteristic X-ray, is obtained in addition to the characteristic X-ray. May occur. Further, since it is a wavelength dispersion type spectrometer, there are complex peaks due to higher-order lines. Due to the presence of these cathodoluminescence and higher-order complex peaks, it is difficult to analyze the collected spectrum obtained by the image sensor.

  However, whether each peak of the sampled spectrum obtained by the image sensor is a diffracted X-ray (soft X-ray) to be measured or a composite peak of cathodoluminescence or higher-order rays is determined by the light reception result of the image sensor. Therefore, there is no system that can determine these.

  The present invention has been made in view of the above problems, and an object of the present invention is to obtain a sampled spectrum in a system in which a characteristic X-ray from a sample irradiated with an electron beam is diffracted by a diffraction grating and a spectrum is collected by an image sensor. It is to realize an X-ray detection system capable of providing information as to whether each peak is an X-ray to be measured or a composite peak of cathodoluminescence or higher order rays.

  That is, the present invention for solving the above problems is as described below.

  (1) The present invention includes an electron beam irradiation unit that irradiates a sample with an electron beam, a diffraction grating that receives characteristic X-rays emitted from the sample irradiated with the electron beam and generates diffraction X-rays, An image sensor that detects diffracted X-rays generated by the diffraction grating, and is disposed adjacent to the image sensor with the energy dispersion direction of the image of the diffracted X-rays as a measurement longitudinal direction. A scintillation counter for detection, and an analysis unit for analyzing the spectrum of the diffraction X-ray detected by the image sensor and analyzing the content of the peak of the spectrum by referring to the detection result of the scintillation counter. It is characterized by that.

  (2) In the present invention, in the above (1), the scintillation counter is configured to be movable in the measurement longitudinal direction, and in the period in which the diffracted X-ray is detected by the image sensor, the measurement longitudinal The diffraction X-ray is detected while moving in a direction.

  (3) The present invention is characterized in that, in the above (2), the scintillation counter has an energy setting range changed during movement in the measurement longitudinal direction.

  (4) The present invention is characterized in that, in the above (2), the scintillation counter repeatedly moves in the measurement longitudinal direction with the energy setting range set to a different state.

  (5) In the present invention, in the above (2), the scintillation counter is configured such that the energy setting range is changed during movement in the measurement longitudinal direction, and the scintillation counter is repeatedly moved with the energy setting range set to a different state. It is characterized by.

  (6) The present invention includes an electron beam irradiation unit that irradiates a sample with an electron beam, a diffraction grating that receives characteristic X-rays emitted from the sample irradiated with the electron beam and generates diffraction X-rays, An image sensor for detecting diffracted X-rays generated by the diffraction grating, and an energy dispersion direction of the image of the diffracted X-ray, which is disposed adjacent to the image sensor as a measurement longitudinal direction. The semiconductor radiation detector for detecting the spectrum of the laser beam and the spectrum of the diffracted X-ray detected by the image sensor are analyzed, and the content of the peak of the spectrum is analyzed by referring to the detection result of the semiconductor radiation detector And an analysis unit.

  (7) According to the present invention, in the above (6), the semiconductor radiation detector is configured to be movable in the measurement longitudinal direction, and in the period in which the image sensor detects the diffracted X-ray, The diffraction X-ray is detected while moving in the measurement longitudinal direction.

  According to these inventions, the following effects can be obtained.

  (1) In the present invention, a characteristic X-ray emitted from a sample is imaged on an image sensor as a diffracted X-ray by a diffraction grating, and the spectrum is analyzed to detect the diffracted X-ray in an energy setting range. The scintillation counter is arranged adjacent to the image sensor with the energy dispersion direction of the image of the diffracted X-ray as the measurement longitudinal direction, and the analysis unit analyzes the spectrum of the diffracted X-ray detected by the image sensor. The content of the peak of the spectrum is analyzed with reference to the detection result.

  As a result, in a system in which characteristic X-rays from a sample irradiated with an electron beam are diffracted by a diffraction grating and a spectrum is collected by an image sensor, each peak of the collected spectrum is a diffracted X-ray (soft X-ray) to be measured. It is possible to provide information on whether there is a cathodoluminescence or a complex peak of higher order lines.

  (2) In this invention, the scintillation counter is configured to be movable in the measurement longitudinal direction, and detects the diffracted X-ray while moving in the measurement longitudinal direction during the period in which the image sensor detects the diffracted X-ray. This makes it possible to collect information about the spectrum in accordance with the collection of the spectrum by the image sensor.

  (3) In the present invention, the scintillation counter changes the energy setting range during movement in the longitudinal direction of measurement, so that the accuracy of collecting information about the spectrum in accordance with the collection of the spectrum by the image sensor. It becomes possible to improve.

  (4) In the present invention, the scintillation counter moves information in the longitudinal direction of the measurement repeatedly with the energy setting range set to a different state, so that information about the spectrum is obtained in accordance with the collection of the spectrum by the image sensor. It will be possible to improve the accuracy of collection.

  (5) In this invention, the scintillation counter changes its energy setting range during movement in the longitudinal direction of measurement, and further, the energy setting range is set to a different state and repeatedly moved, whereby the spectrum is collected by the image sensor. The accuracy of collecting information about the spectrum can be improved.

  (6) In the present invention, in the X-ray detection system for analyzing the spectrum by forming the characteristic X-rays emitted from the sample as diffraction X-rays on the image sensor by the diffraction grating and analyzing the spectrum, at each energy dispersion position of the diffraction X-rays A semiconductor radiation detector that detects the spectrum is placed adjacent to the image sensor with the energy dispersion direction of the image of the diffracted X-ray as the measurement longitudinal direction, and the analysis unit analyzes the spectrum of the diffracted X-ray detected by the image sensor. At the same time, the spectrum peak content is analyzed with reference to the detection result of the semiconductor radiation detector.

  As a result, in a system in which characteristic X-rays from a sample irradiated with an electron beam are diffracted by a diffraction grating and a spectrum is collected by an image sensor, information about the spectrum is collected in accordance with the collection of the spectrum by the image sensor. It is possible to provide information on whether each peak of the collected spectrum is a diffracted X-ray or a composite peak of cathodoluminescence or higher order lines.

  (7) In the present invention, the semiconductor radiation detector is configured to be movable in the measurement longitudinal direction, and in the period in which the image sensor detects the diffracted X-rays, the semiconductor radiation detector moves the measurement X-rays while moving the diffraction X-rays. By detecting, information about the spectrum can be collected in accordance with the collection of the spectrum by the image sensor.

It is a block diagram which shows the structure of the X-ray detection system to which embodiment of this invention is applied. It is a block diagram which shows the structure of the X-ray detection system to which embodiment of this invention is applied. It is a block diagram which shows the structure of the principal part of the X-ray detection system to which embodiment of this invention is applied. It is explanatory drawing which shows the characteristic of the X-ray detection system to which embodiment of this invention is applied. It is explanatory drawing which shows the characteristic of the X-ray detection system to which embodiment of this invention is applied. It is explanatory drawing which shows the characteristic of the X-ray detection system to which embodiment of this invention is applied.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments (embodiments) for carrying out an image forming apparatus of the present invention will be described below in detail with reference to the drawings.

<First Embodiment>
First, the configuration of the X-ray detection system of the first embodiment will be described with reference to FIGS.

  In FIG. 1, known basic members for holding each part such as a lens barrel and a gantry, a mechanism part for holding a vacuum, etc. are omitted, and the arrangement of the characteristic parts of the embodiment is mainly shown. The X-ray detection system is shown in a perspective view. FIG. 2 shows the X-ray detection system in a state close to a block diagram. FIG. 3 shows an enlarged structure for detecting diffracted X-rays.

  The electron beam irradiation unit 10 is provided in a lens barrel portion of a scanning electron microscope and irradiates the sample 20 with an electron beam.

  The X-ray focusing mirror unit 30 focuses the characteristic X-rays emitted from the sample 20 by the two mirrors 34 a and 34 b and guides them to the diffraction grating 50. Here, by condensing with the X-ray condensing mirror unit 30, the intensity of the characteristic X-rays incident on the diffraction grating 50 can be increased, the measurement time can be shortened, and the S / N ratio of the spectrum can be improved. . Here, for the sake of explanation, the mirrors 34a and 34b are exposed, but the present invention is not limited to this, and a cylindrical structure such as a mirror external housing that integrally holds the mirrors 34a and 34b. The body may be present.

  The diffraction grating 50 receives characteristic X-rays collected by the X-ray condenser mirror unit 30 and generates diffracted X-rays having different diffraction states according to energy. This diffractive grating 50 is formed with unequally spaced grooves for aberration correction, and such unequally spaced diffractive gratings are nearly parallel to a large incident angle (diffraction grating surface (Y axis in FIG. 1)). When the light is incident at an angle, the focal point of the diffracted light is not formed on the Roland circle, but on a plane substantially perpendicular to the light beam (light receiving surface of the image sensor 60: XZ plane in FIG. 1)). In the first embodiment, the diffracted light is designed to be focused on a plane including the light receiving surface of the image sensor 60 and the adjacent scintillation counter 70.

  The image sensor 60 is an X-ray CCD camera or an X-ray CMOS camera having sensitivity to soft X-rays in order to detect diffracted X-rays. Desirably, it comprises a back-illuminated X-ray CCD camera. The position of the image sensor 60 is adjusted so that the light receiving surface thereof coincides with the image plane of diffracted X-rays.

  The scintillation counter 70 is disposed adjacent to the image sensor 60 with the energy dispersion direction of the image of the diffracted X-ray as the measurement longitudinal direction, and detects the diffracted X-ray in the energy setting range. The scintillation counter 70 is adjusted in position with the image sensor 60 so that the light receiving surface thereof coincides with the image plane of diffraction X-rays. In addition, the scintillation counter 70 is configured such that the detection element 72 can be moved in the measurement longitudinal direction (diffracted X-ray energy dispersion direction) by the drive mechanism 71.

  The analysis unit 80 is a waveform analyzer that analyzes the diffracted X-rays detected by the image sensor 60 and generates an energy distribution spectrum that means how many X-rays with a certain value of energy are detected. The analysis unit 80 has a function of referring to the detection result of the scintillation counter 70 and analyzing the content of the peak of the energy distribution spectrum.

  The display unit 90 is a display that visually displays an energy distribution spectrum that is an analysis result of the analysis unit 80 and various other information.

  The analysis unit 80 and the display unit 90 can also be configured by a computer device and a computer program that calculates an energy distribution spectrum.

  Further, the scintillation counter 70 has a function of detecting diffracted X-rays while moving in the measurement longitudinal direction during a period in which the image sensor 60 is detecting diffracted X-rays based on an instruction from the analysis unit 80. Further, the scintillation counter 70 has a function of changing the energy setting range by the analysis unit 80 when moving in the measurement longitudinal direction.

  Further, the scintillation counter 70 may be adjusted in position so that the diffracted X-rays from the diffraction grating 50 are reliably imaged, but a part of the diffracted X-rays imaged on the image sensor 60 is scintillation counter 70. The positional relationship may be such that it is incident on.

  Although not shown, the sample 20, the X-ray condensing mirror unit 30, the diffraction grating 50, the image sensor 60, and the scintillation counter 70 are provided in a spectroscope chamber evacuated by a vacuum pump, and are gate valves. It shall be attached to the lens barrel of a scanning electron microscope via.

  Further, details of the configuration of the diffraction grating 50 and its periphery in this X-ray detection system are described in Japanese Patent Application Laid-Open No. 2002-329473, to which the applicant of the present application separately applied. In addition, since a known system for processing the diffracted X-ray obtained by the image sensor 60 can be used, detailed description thereof is omitted.

  In the X-ray detection system as described above, the electron beam irradiating unit 10 irradiates the sample 20 with the electron beam, and causes the characteristic X-ray generated in the sample 20 to enter the diffraction grating 50. The diffraction grating 50 receives the characteristic X-rays collected by the X-ray focusing mirror unit 30 and generates diffracted X-rays having different diffraction states according to energy. The diffracted X-ray is subjected to exposure processing by the image sensor 60.

  In the exposure processing based on the above electron beam irradiation, a predetermined exposure time of several seconds to several tens of seconds is determined so that the image sensor 60 has a sufficient signal level.

  Then, the analysis unit 80 analyzes the output of the image sensor 60, generates an energy distribution spectrum that means how many X-rays of a certain value of energy are detected, and displays them on the display unit 90.

  On the other hand, the driving mechanism 71 obtains exposure time data or a movement instruction from the analysis unit 80, and a predetermined energy filter is applied to the detection element 72 of the scintillation counter 70 during the predetermined exposure time of several seconds to several tens of seconds. In the state, the energy dispersion direction moves one way or reciprocates one way.

  In this state, a part of the diffracted X-rays imaged on the image sensor 60 is input to the detection element 72 of the scintillation counter 70. The detection result of the detection element 72 is transmitted to the analysis unit 80.

  Here, as an energy filter, based on an instruction from the analysis unit 80, energy of soft X-rays, energy other than soft X-rays (more or less), energy of specific known rays other than soft X-rays, etc. Set to either. When the detection element 72 moves one reciprocating motion or more, different energy can be detected by setting different energy filters for each movement.

  Then, the analysis unit 80 analyzes the output of the image sensor 60 (FIG. 4A), and an energy distribution spectrum (FIG. 4B) that means how many X-rays with a certain value of energy are detected. Is generated and displayed on the display unit 90.

  In parallel with this, the analysis unit 80 refers to the detection result of the scintillation counter 70 and analyzes the content of the peak of the energy distribution spectrum.

  That is, the analysis unit 80 determines whether each peak of the energy distribution spectrum is caused by soft X-rays to be measured, or is affected by other components such as cathodoluminescence or higher order rays, Analyze to what extent the influence of the ingredients.

  FIG. 4C is a characteristic diagram schematically showing what kind of spectrum each peak of the energy distribution spectrum includes, and the horizontal axis on the front is the same as the horizontal axis of FIG. The depth direction represents the spectrum of each peak.

  In this case, based on the instruction from the analysis unit 80, the energy setting range of the detection element 72 of the scintillation counter 70 is the soft X-ray energy, the energy other than soft X-ray (more or less), and the identification other than the soft X-ray. The known element energy is set, and detection is performed while moving the detection element 72 one way or one reciprocation.

  Although the display in FIG. 4C differs depending on the energy setting range of the detection element 72 of the scintillation counter 70, each peak of the energy distribution spectrum is different even if it is at least one type of energy setting range. And the influence of the spectrum of the energy setting range of the scintillation counter 70 will become clear.

  In the above description, the energy setting range of the detection element 72 of the scintillation counter 70 is determined before the movement starts. However, during the movement of the detection element 72, an instruction from the analysis unit 80 is given. It is also possible to set or change the setting range of energy. In this case, for example, different settings can be made for each peak, and the spectrum analysis can be performed accurately, so that the electronic state distribution information can be obtained more accurately.

  In addition, an energy setting range is determined for the soft X-ray region light (FIG. 5B), and the soft X-ray region light and interference light are obtained by subtracting the soft X-ray region light and the entire XES. It is possible to separate soft X-rays and interference light as shown in FIG.

  In addition, the detection element 72 of the scintillation counter 70 is changed to a plurality of energy setting ranges, and each detection is performed by moving several times (several one-way movements or several reciprocal movements) within the exposure time. By doing so, as shown in FIG. 4D, the influence of each peak of the energy distribution spectrum and a plurality of spectra in the energy setting range of the scintillation counter 70 becomes clear. Here, the characteristic display in the spectral direction in FIG. 4 (d) increases each time detection with the energy setting range changed is increased. And in this case, it becomes clear whether it is influenced by some components such as cathodoluminescence and higher order lines.

  If a plurality of energy setting ranges are set for the obtained XES with known lines (known light # 1 to # 3 in FIG. 6), the second peak among the three peaks roughly divided in FIG. It can be seen that it is a composite peak.

  However, since it is performed within the exposure time, if the energy setting range of the scintillation counter 70 is increased, the detection time per setting may be shortened and the measurement accuracy may be reduced, so that it may be limited to the necessary energy setting range. desirable.

  As described above, according to the first embodiment, each peak of the energy distribution spectrum is a diffracted X-ray (soft X-ray) to be measured, or a composite peak of cathodoluminescence or higher order rays. It becomes possible to provide such information.

  That is, the possibility of misperception due to interference light is reduced in the energy distribution spectrum, and more accurate spectrum analysis is possible.

  Further, since the spectrum analysis can be performed accurately, the electronic state distribution information can be obtained more accurately.

  Furthermore, peak overlap, which is almost impossible with the image sensor 60 alone, can also be accurately separated from each spectrum shown in FIG.

  In the first embodiment, since the spectrum is detected by the scintillation counter 70 using the exposure time, the process can proceed in the same time as the conventional method.

Second Embodiment
In the configuration of the first embodiment described above, the scintillation counter 70 is replaced with a semiconductor radiation detector capable of scanning in the energy direction. In this case, the detection element 72 of the scintillation counter 70 is replaced with a semiconductor radiation detector. Other configurations and basic operations are the same as those in the first embodiment.

  In this case, the detection element 72 of the scintillation counter 70 is moved within the exposure time within a plurality of energy setting ranges in the first embodiment only by moving the semiconductor radiation detector by one in the energy dispersion direction of the image sensor 60 within the exposure time. The same or more data can be obtained as in the case where the detection is performed by moving several times.

  That is, only by moving the semiconductor radiation detector in the energy dispersion direction of the image sensor 60, as shown in FIG. 4D, each peak of the energy distribution spectrum and a plurality of spectra detected by the semiconductor radiation detector It becomes clear about the influence.

  In this case, depending on the measurable energy range of the semiconductor radiation detector, it becomes clear whether it is affected by several components such as cathodoluminescence and higher-order lines.

  As described above, according to the second embodiment, each peak of the energy distribution spectrum is a diffracted X-ray (soft X-ray) to be measured, or a composite peak of cathodoluminescence or higher-order rays. It becomes possible to provide such information. That is, the possibility of misperception due to interference light is reduced in the energy distribution spectrum, and more accurate spectrum analysis is possible.

  Further, since the spectrum analysis can be performed accurately, the electronic state distribution information can be obtained more accurately. Furthermore, peak overlap, which is almost impossible with the image sensor 60 alone, can also be accurately separated from each spectrum shown in FIG.

  In the second embodiment, since the spectrum detection is performed by moving the semiconductor radiation detector by one using the exposure time, it is possible to proceed with the process in the same time as the conventional method. Furthermore, in the semiconductor radiation detector according to the second embodiment, energy setting as in the first embodiment is unnecessary, so that it is not necessary to move the detection element many times, and highly accurate measurement and analysis are possible. become.

DESCRIPTION OF SYMBOLS 10 Electron beam irradiation part 20 Sample 30 X-ray condensing mirror part 40 X-ray condensing mirror adjustment part 50 Diffraction grating 60 Image sensor 70 Scintillation counter 71 Drive mechanism 72 Detection element 80 Analysis part 90 Display part

Claims (7)

An electron beam irradiation unit for irradiating the sample with an electron beam;
A diffraction grating that receives characteristic X-rays emitted from the sample irradiated with the electron beam and generates diffracted X-rays;
An image sensor for detecting diffracted X-rays generated by the diffraction grating;
A scintillation counter that is arranged adjacent to the image sensor with the energy dispersion direction of the image of the diffracted X-ray as a measurement longitudinal direction, and detects the diffracted X-ray in an energy setting range;
Analyzing the spectrum of the diffracted X-ray detected by the image sensor, referring to the detection result of the scintillation counter, and analyzing the content of the peak of the spectrum;
An X-ray detection system comprising: The scintillation counter is configured to be movable in the measurement longitudinal direction,
Detecting the diffracted X-ray while moving in the measurement longitudinal direction during a period in which the image sensor detects the diffracted X-ray;
The X-ray detection system according to claim 1. In the scintillation counter, the energy setting range is changed during movement in the measurement longitudinal direction.
The X-ray detection system according to claim 2. The scintillation counter moves repeatedly in the measurement longitudinal direction with the energy setting range set to a different state.
The X-ray detection system according to claim 2. In the scintillation counter, the energy setting range is changed during movement in the measurement longitudinal direction, and the scintillation counter is repeatedly moved with the energy setting range set to a different state.
The X-ray detection system according to claim 2. An electron beam irradiation unit for irradiating the sample with an electron beam;
A diffraction grating that receives characteristic X-rays emitted from the sample irradiated with the electron beam and generates diffracted X-rays;
An image sensor for detecting diffracted X-rays generated by the diffraction grating;
A semiconductor radiation detector that is arranged adjacent to the image sensor with the energy dispersion direction of the image of the diffracted X-ray as a measurement longitudinal direction and detects a spectrum at each energy dispersion position of the diffracted X-ray;
Analyzing the spectrum of the diffracted X-ray detected by the image sensor, referring to the detection result of the semiconductor radiation detector, and analyzing the content of the peak of the spectrum;
An X-ray detection system comprising: The semiconductor radiation detector is configured to be movable in the measurement longitudinal direction,
Detecting the diffracted X-ray while moving in the measurement longitudinal direction during a period in which the image sensor detects the diffracted X-ray;
The X-ray detection system according to claim 6.