JP5373368B2 - X-ray analyzer using electron beam - Google Patents

Description

  The present invention relates to an X-ray analyzer that analyzes a sample by irradiating a sample surface with an electron beam and spectroscopically detecting characteristic X-rays generated from the sample.

  An electron probe microanalyzer (EPMA) is known as an X-ray analyzer that analyzes a sample by irradiating the surface of the sample with an electron beam and spectroscopically detecting characteristic X-rays generated from the sample. EPMA is generally a device equipped with a plurality of wavelength dispersive X-ray spectrometers (WDS), but an energy dispersive X-ray spectrometer (EDS). There are also many devices equipped with). Note that an X-ray spectrometer mainly mounted in a scanning electron microscope (SEM) or a transmission electron microscope (TEM) is an EDS.

  FIG. 8 is a block diagram showing a schematic configuration example of a conventional EPMA equipped with WDS and EDS. In FIG. 8, the electron beam EB emitted from the electron gun 1 disposed in the mirror body 100 is narrowed down by the focusing lens 2 and the objective lens 3 and irradiated onto the sample 4. A scanning coil 9 has a function of two-dimensionally scanning the electron beam EB and can change the irradiation position of the electron beam EB.

Reference numeral 8 denotes an irradiation current detector using the principle of the Faraday cup, which has a mechanism that can be inserted into and removed from the path of the electron beam EB. The hatched portion in FIG. 8 shows a state in which the current amount is detected by being inserted into the path of the electron beam EB. Since the irradiation current detector 8 has a beam shutter function, it also has a role of reducing beam damage of the sample 4 by preventing the sample 4 from being irradiated with the electron beam EB before starting the measurement.

  The EOS control system 11 controls the electron gun 1, the focusing lens 2, the objective lens 3, the scanning coil 9, and the irradiation current detector 8.

  10 is a gate valve for vacuum-separating the electron beam path above the objective lens 3 and the sample chamber in which the sample 4 is placed, and performs an opening / closing operation as shown by an arrow 10a. In order for the electron beam EB to reach the sample 5, the gate valve 10 must be in an open state.

  X-rays 5 generated from the sample 4 by irradiation with the electron beam EB are spectrally detected and detected by the WDS 6 and the EDS 7. The WDS 6 includes a spectroscopic crystal 12, a detector 13, and a WDS drive system 14, and control and signal capture are performed via a WDS measurement control system 15. In order to mount a plurality of WDSs, a plurality of sets having the same configuration as the WDS 6 are required.

  The EDS 7 performs control and signal capture via the EDS measurement control system 16. Normally, only one EDS 7 is installed per EPMA.

  The irradiation position (that is, the analysis point) of the electron beam EB on the sample 4 placed on the sample stage 17 is about several tens of mm in the horizontal direction by the XY movement mechanism 18 and about several mm in the height direction by the Z fine movement mechanism 19. It is movable in range. Further, the Z coarse movement mechanism 20 can change the height of the XY movement mechanism 18 and the Z fine movement mechanism 19 up and down as shown by an arrow 20a within a large range of about several tens of millimeters. Reference numeral 18 ′ shows a case where the height of the sample 4 is moved to a position where both the WDS and EDS cannot be analyzed by the Z coarse movement mechanism 20. The sample stage 17 is controlled by a sample stage control system 19.

  In addition, about the irradiation current detector 8, the gate valve 10, and the Z rough movement mechanism 20, there is also EPMA which is not equipped with these functions depending on the model.

  The EOS control system 11, WDS measurement control system 15, EDS measurement control system 16, and sample stage drive system 19 are connected to a measurement control device 22. The measurement control device 22 is a computer that controls each part necessary for measurement and takes in signals. An input device 23 such as a keyboard / mouse and a display device 24 such as a liquid crystal monitor are connected to the measurement control device 22.

In an actual device, an evacuation system, secondary electron / reflected electron signal detector, power supply, DA / AD converter, etc. for maintaining the electron beam passage and the sample chamber at a high vacuum of about 10 ⁻³ Pa are provided. Although configured, the illustration and description are omitted because they are not directly related to understanding the present invention.

  Next, the principle of X-ray detection in WDS and EDS will be described.

FIG. 5 is a schematic diagram for explaining the principle of the WDS equipped in the EPMA. It is denoted by the common reference numerals to those performing Figure 8 the same or similar operations. In the X-ray spectrometer shown in FIG. 5, the diffractive surface center C of the spectral crystal 12 moves on a straight line SC that is inclined from the X-ray generation point S by the X-ray extraction angle α with respect to the horizontal plane. This is called a crystal straight X-ray spectrometer. In this type of X-ray spectrometer, the X-ray generation point S, the diffraction surface center C of the spectroscopic crystal 12, and the slit center F of the X-ray detector 13 are always on the circumference of a Roland circle RC having a constant radius R. The slit center position F of the X-ray detector 13 and the center Q of the Roland circle are moved so that the lengths of the line segment SC and the line segment CF are always equal. The crystal lattice plane of the spectroscopic crystal 12 is such that the diffractive surface of the spectroscopic crystal 12 that is curved with a curvature 2R around the point D is always directed to the center Q of the Roland circle. The length of the line segment SC is the spectral position L, and the X-ray incident angle to the diffraction surface center C (the angle formed between the straight line C1 passing through the diffraction surface center C and circumscribing the Roland circle RC) is θ.
L = 2R × sin θ (1)
It is. On the other hand, the diffraction condition of X-rays incident on the spectral crystal is expressed by the following equation (2) from the Bragg condition, where X is the wavelength of the X-ray and d is the surface spacing of the spectral crystal.
2d × sin θ = n × λ (2)
Here, n is a diffraction order and a positive integer. A diffraction line in which n is 2 or more is generally referred to as a high-order diffraction line (hereinafter sometimes abbreviated as “high-order line”).
From the equations (1) and (2), the following equation (3) is derived.
L = (2R / 2d) × n × λ (3)
By measuring the spectral position L, the wavelength λ of the diffracted characteristic X-ray can be known. Since the characteristic X-ray has an element-specific wavelength, the element contained in the sample can be identified from the wavelength λ. Further, the concentration of the element contained in the sample can be known from the intensity of the measured characteristic X-ray.

  In FIG. 5, the analysis point S is the only point that satisfies the Bragg condition. However, in an actual apparatus, the peak of the spectrum obtained by the distortion of the diffraction surface of the spectroscopic crystal 12 has a broadening (represented by a half-value width). If the tolerance is in accordance with the size of the spread and the spectral position L, X-rays generated at a position deviating from the analysis point S can reach the X-ray detector 13 in both the horizontal and height directions. Is possible. The half width of the spectrum varies greatly depending on the type of spectral crystal. The allowable range deviating from the analysis point S varies depending on the analysis purpose and the required analysis accuracy, but in the case of WDS, it may be considered to be usually several μm to several tens of μm. In the case of a long-wavelength X-ray spectroscopic crystal (a spectroscopic element having a superlattice structure that is not actually a crystal is generally used), it is about several hundreds of μm.

  Next, EDS will be described. FIG. 6 is a diagram showing the X-ray detection principle of EDS using a PIN semiconductor in which lithium (Li) is doped in silicon (Si) for X-ray detection. In FIG. 6, when X-rays generated from a sample enter a PIN semiconductor, a number of ion pairs corresponding to the energy of the X-ray quanta is generated. Due to the bias voltage applied to the semiconductor, the generated ion pair is separated to generate an avalanche, and an electric pulse signal having a magnitude proportional to energy is taken out. The pulse signal is integrated for each channel for each energy range by a multi-channel analyzer (not shown) according to the magnitude. An X-ray spectrum can be obtained by displaying the accumulated data as a graph with the channel (energy) on the horizontal axis and the count value (integrated value) on the vertical axis.

  Unlike EDS, EDS does not depend on a geometrical focusing method, and in principle, X-rays from either direction can be detected. However, in the case of an EDS mounted on an EPMA or the like, for example, an aperture may be provided in front of the detector in order to limit the total amount of X-ray quanta incident on the detector. FIG. 7 shows an example of such an EDS detector. In FIG. 7, 30 is a semiconductor X-ray detector, 31 is a protective cylinder such as the X-ray detector 30, 32 is a heat conductive material for cooling the X-ray detector 30, and 33 is a thin plate such as beryllium. Numeral 34 is an incident X-ray limiting aperture plate, 34a, 34b, and 34c are aperture holes having different aperture diameters, and 35 is a rotation instruction for changing the aperture diameter of the aperture hole by rotating the incident X-ray limiting aperture plate 34. It is a stick.

  The X-ray 5 generated from the analysis point S passes through the aperture 34 (in the case of FIG. 7), the X-ray passage hole 31a, and the window 33 and enters the X-ray detector 30. That is, the aperture hole provided in the incident X-ray limiting aperture plate 34 also functions as a collimator according to the aperture diameter of the aperture hole and the distance from the aperture hole to the X-ray detection surface. Therefore, even when using EDS, there is an allowable range that deviates from the analysis point S. However, the range is an order of magnitude wider than that in the case of WDS, and is usually about several millimeters.

  However, some apparatuses are equipped with a sample stage having a function of raising and lowering the sample height within a range of 10 mm or more. In such an apparatus, even an EDS may not be analyzed.

In Japanese Patent Application Laid-Open No. 2006-78424 of Patent Document 1, in a scanning electron microscope equipped with an EDS, it is determined whether the height of a sample is at a predetermined position. A technique for notifying an operator is disclosed.

JP 2006-78424 A

  The technique disclosed in Japanese Patent Application Laid-Open No. 2006-78424 of Patent Document 1 is that the height of the sample with respect to the X-ray spectrometer (only EDS is shown in the examples) is within a predetermined position range. It is only determined. However, as described above, in EPMA, many devices equipped with WDS and EDS are used at the same time. The principle of X-ray detection differs between WDS and EDS. Further, even within the same WDS and EDS, there is a great difference in the mechanical structure of the device to which the detector is attached, so that there is a large difference in the allowable range that deviates from the analysis point S. The size of the allowable range varies depending on the analysis mode. Therefore, when determining whether or not the analysis can be performed correctly when actually performing the analysis, the operator carefully considers which X-ray spectrometer is used and in which analysis mode the analysis is performed. Must.

  The present invention has been made to solve the above-described problems, and an object of the present invention is a state in which an X-ray analyzer mounted simultaneously with WDS and EDS can perform analysis correctly in consideration of an analysis mode. It is to notify the operator of the result of the determination in an easy-to-understand manner.

In order to solve the above problem, the invention according to claim 1
An X-ray analyzer that performs elemental analysis by irradiating a sample with a finely focused electron beam and detecting characteristic X-rays generated from the sample surface,
Means for irradiating a thinly focused electron beam to an arbitrary position on the sample;
Means for moving the sample position in a direction perpendicular to and parallel to the electron beam irradiation direction;
In an X-ray analyzer equipped with a wavelength dispersive X-ray spectrometer and an energy dispersive X-ray spectrometer,
According to each analysis mode of point analysis, line analysis, and surface analysis, each of the wavelength dispersive X-ray spectrometer and the energy dispersive X-ray spectrometer is analyzed using each X-ray spectrometer. A database that stores the setting conditions that must be met in order for the
An analysis mode specifying means for the operator to specify which analysis mode is selected from point analysis, line analysis and surface analysis;
With collecting the setting state of the check item of the predetermined said X-ray analysis apparatus for analyzing mode specified by the analyzing mode designating means, the said wavelength-dispersive X-ray spectrometer energy dispersive X It reads the setting conditions to analysis by the line spectrometer meet to properly performed from the database, and determines the set-state determining means for determining the set state of being collected meets the setting condition by collection means,
Notification means for notifying an operator of the determination result by the setting state determination means for the wavelength dispersive X-ray spectrometer and the energy dispersive X-ray spectrometer;
It is characterized by providing.

According to a second aspect of the present invention, the setting state determination unit is configured so that the setting state satisfies the setting condition separately for each of the wavelength dispersive X-ray spectrometer and the energy dispersive X-ray spectrometer. It is characterized by determining whether or not.

  In the invention according to claim 3, the notification means determines whether the setting state satisfies the setting condition for each of the wavelength dispersive X-ray spectrometer and the energy dispersive X-ray spectrometer. Is notified by switching between lighting and extinguishing of the lamp.

  The invention described in claim 4 is characterized in that the lamp is a pseudo lamp displayed on a window of a computer provided in the X-ray analyzer.

  The invention according to claim 5 further includes item-by-item notification means for notifying an operator of a result of determination as to whether or not the setting state satisfies the setting condition for each confirmation item. .

  According to the present invention, in an X-ray analyzer mounted simultaneously with WDS and EDS, it is determined whether the analysis can be performed correctly in consideration of the analysis mode, and the result of the determination is easily understood by the operator. You can be notified. In addition, since it can be determined whether or not the analysis can be performed correctly by the X-ray spectrometer to be used for the analysis before the analysis is started, it is possible to prevent waste that the operator notices a defect after the analysis is started and performs the analysis again.

  Embodiments of the present invention will be described below with reference to the drawings. However, the technical scope of the present invention is not limited by this illustration. In each figure, the same reference numerals are given to those performing the same or similar operations, and detailed description is not repeated.

  FIG. 1 is a block diagram showing a schematic configuration example for carrying out the present invention, taking an EPMA equipped with a WDS and an EDS as an example. Elements that perform the same or similar operations as those of the conventional EPMA shown in FIG. In addition to the configuration of the conventional EPMA, the EPMA for carrying out the present invention includes a database 25 storing data used in the present invention and a program 26 storing means for implementing the present invention. In the configuration shown in FIG. 1, the program 26 is stored in the measurement control device 22, but may be configured in a control device different from the measurement control device 22.

  The database 25 should be filled in order to perform analysis using each X-ray spectrometer for each of WDS and EDS depending on the analysis mode of point analysis, line analysis, and surface analysis. Stores setting conditions.

FIG. 9 is a block diagram for explaining the function of the program 26. The program 26 includes a specification unit 26a (analysis mode specifying means) for the operator to specify which analysis mode is selected from point analysis, line analysis, and surface analysis, and confirmation items for EPMA that are determined in advance. A collecting unit 26b (collecting means) that collects a setting state of the data, and reading out setting conditions that should be satisfied in order to appropriately perform analysis by WDS and EDS for the specified analysis mode, and the current setting state Includes a determination unit 26c (determination unit) that determines whether or not the setting condition is satisfied, and a notification unit 26 d (notification unit) that notifies the operator of the determination result about WDS and EDS.

  First, confirmation items of EPMA will be described. FIG. 3 is an example of a window displayed on the display device 24, for example. FIG. 3A shows an example of displaying a case where point analysis is performed by WDS. The confirmation items include whether an acceleration voltage is applied to the electron gun 1 (ON), the irradiation current detector 8 is drawn from the electron beam passage (OUT), or a gate valve. 10 is open (OPEN), the image shift function is not used (OFF), or the analysis point height of the sample 4 supported by the sample stage Is within ± 1 mm with respect to a predetermined position (11 mm in this apparatus example), the scanning coil 9 is not in an operating state (probe scanning is turned off), or the like. A circle on the left side of each confirmation item is a display lamp that indicates the suitability of each confirmation item. In the point analysis mode, scanning with an electron beam is not performed, and in FIG. 3A, the item of scanning image magnification is displayed lightly.

  In addition, about the irradiation current detector 8, the gate valve 10, and the Z rough movement mechanism 20, there is also EPMA which is not equipped with these functions depending on the model. In the model, of course, those functions do not enter the confirmation items.

  Next, an example of how the operator specifies which analysis mode to perform analysis, point analysis, line analysis, and area analysis, and whether the current setting state satisfies the setting conditions stored in the database An example of a method for notifying the operator of the determination result will be described with reference to FIG.

  First, an example of how the operator designates the analysis mode will be described. FIG. 4 is an example of a window displayed on the display device 24, for example. In FIG. 4, reference numerals 42, 43, 44 and 45 are radio buttons. When the operator clicks any of the buttons 42 or 43 in the WDS column with the mouse, either point analysis or line / surface analysis is selected. For EDS, either radio button 44 or 45 is selected. In FIG. 4, the selected radio button is indicated by ◎ (double circle).

  Next, a method example for notifying the operator of the determination result will be described. Reference numerals 40 and 41 in the column of setting conditions are display lamps for displaying whether WDS and EDS satisfy the setting conditions. The indicator lamp lights up when the setting conditions are satisfied. ● (black circle) indicates that the lamp is on, and ○ (white circle) indicates that it is off.

  In FIG. 4, the analysis mode of line analysis and area analysis is set to one radio button, but it may be possible to select the analysis mode by dividing into three points: a point, a line, and a surface.

  Hereinafter, an example of a procedure for carrying out the present invention will be described with reference to the flowchart shown in FIG. The procedure of FIG. 2 is automatically executed by the measurement control device 22 including the program 26 except for the analysis mode designation.

  In step S1, the setting states of predetermined confirmation items of EPMA are collected (monitored).

  In step S2, for each of WDS and EDS, it is confirmed which mode of point analysis, line analysis, and surface analysis is designated by the operator. The operation for designating the analysis mode from the window shown in FIG. 4 by the operator can occur at any time during the execution of the program 26, and is not particularly shown in the flowchart.

  In step 3, it is determined whether or not analysis conditions suitable for measurement are set in the WDS for the designated analysis mode, and the process proceeds to step S4. If it is determined that it is suitable for the WDS measurement, the process proceeds from step S4 to step S5, and the WDS and EDS display lamps are turned on. If it is determined that the measurement is not suitable for the WDS measurement, the process proceeds from step S4 to step S7, and the WDS display lamp is turned off.

  In step S8, as shown in FIG. 3A, the suitability for each confirmation item is displayed. The indicator lamp lights up when the setting conditions are satisfied for each confirmation item. ● (black circle) indicates that the lamp is on, and ○ (white circle) indicates that it is off. The state shown in FIG. 3A indicates that the image shift is not OFF. In FIG. 4, when the point analysis mode is designated and the operator wants to know the cause when the WDS display lamp is turned off, the user can look at the window shown in FIG.

  In step S9, it is determined whether or not analysis conditions suitable for measurement are set by EDS for the designated analysis mode, and the process proceeds to step S10. When it is determined that it is suitable for the measurement of EDS, the process proceeds from step S10 to step S11, and the display lamp of EDS is turned on.

  If it is determined that the measurement is not suitable for the EDS measurement, the process proceeds from step S10 to step S12, and the display lamp of the EDS is turned off.

  In step S13, as shown in FIG. 3B, the suitability for each confirmation item is displayed. The indicator lamp lights up when the setting conditions are satisfied for each confirmation item. ● (black circle) indicates that the lamp is on, and ○ (white circle) indicates that it is off. The state shown in FIG. 3B indicates that the stage height is not within ± 1 mm with respect to the predetermined position.

The process proceeds from step S5, step S11, or step S13 to step S6.
Unless an operation for ending execution of the program 26 is performed, the process returns from step S6 to step S1, and a series of processes after step S1 is continued.

  In the flow chart of FIG. 2, the suitability for each confirmation item is displayed for WDS and EDS. However, the suitability for WDS and EDS as shown in FIG. 4 may be displayed. However, it is possible to quickly know the cause when the display lamp is turned off by displaying the suitability for each confirmation item. Therefore, the display of suitability for each confirmation item is more effective for an operator who is not familiar with analysis.

  Further, in the above-described method example of notifying the determination result to the operator, an example in which the pseudo lamp displayed on the window of the display device is used has been described. However, the actual lamp may be turned on / off.

  As described in the description of the background art, the setting condition when performing measurement by EDS is generally looser than that of WDS. For this reason, when it is determined that the WDS is suitable for the measurement, the EDS is also suitable for the measurement. In step S5, the display lamps are turned on for both the WDS and the EDS. If a specific condition for the EDS that is different from the specific WDS is added, step S5 may be deleted to make a determination independent of the WDS.

As described above, according to the present invention, in the X-ray analyzer (EPMA) mounted simultaneously with WDS and EDS, it is determined whether or not the analysis can be performed correctly in consideration of the analysis mode, The result of the determination can be notified to the operator in an easy-to-understand manner.

The block diagram which shows the example of schematic structure of EPMA carrying WDS and EDS which implement this invention. The flowchart for demonstrating an example of the procedure which implements this invention. The example of a display of the window which displays the suitability by confirmation item in this invention. An example of the window for demonstrating the example of a method of specifying analysis mode, and the example of a method of notifying an operator of a determination result. The schematic diagram for demonstrating the principle of WDS with which EPMA is equipped. The figure for demonstrating the principle of the X-ray detection of EDS which uses a PIN type semiconductor for X-ray detection. The figure which shows the example of EDS which provides an aperture stop in front of the semiconductor detector. The block diagram which shows the schematic structural example of the conventional EPMA carrying WDS and EDS. The block diagram for demonstrating the function of the program in which the means which implements this invention was stored.

Explanation of symbols

(Common reference numerals are used for the same or similar operations.)
EB ... Electron beam, S ... Analysis point, 1 ... Electron gun, 2 ... Focusing lens, 3 ... Objective lens, 4 ... Sample, 5 ... Characteristic X-ray, 6 ... Wavelength dispersive X-ray spectrometer (WDS), 7 ... Energy dispersive X-ray spectrometer (EDS), 8 ... Irradiation current detector, 9 ... Scan coil, 10 ... Gate valve, 11 ... EOS control system, 12 ... Spectral crystal, 13 ... X-ray detector, 14 ... WDS drive 15 ... EDS measurement control system, 16 ... EDS measurement control system, 17 ... Sample stage, 18 ... XY movement mechanism, 19 ... Z fine movement mechanism, 20 ... Z coarse movement mechanism, 21 ... Sample stage control system, 22 ... Measurement Control device, 23 ... input device, 24 ... display device, 25 ... database, 26 ... program, 26a ... designating unit, 26b ... collecting unit, 26c ... determining unit, 26d ... notifying unit, 30 ... semiconductor X-ray detector, 31 ... Protection cylinder, 31a ... X-ray passage hole, 32 ... Conductive material, 33 ... window, 34 ... incident X-ray limiting aperture plate, 34a, 34b, 34c ... throttle hole, 35 ... rotary support rod, 40, 41 ... display lamp, 42, 43, 44, 45 ... radio buttons

Claims (5)

An X-ray analyzer that performs elemental analysis by irradiating a sample with a finely focused electron beam and detecting characteristic X-rays generated from the sample surface,
Means for irradiating a thinly focused electron beam to an arbitrary position on the sample;
Means for moving the sample position in a direction perpendicular to and parallel to the electron beam irradiation direction;
In an X-ray analyzer equipped with a wavelength dispersive X-ray spectrometer and an energy dispersive X-ray spectrometer,
According to each analysis mode of point analysis, line analysis, and surface analysis, each of the wavelength dispersive X-ray spectrometer and the energy dispersive X-ray spectrometer is analyzed using each X-ray spectrometer. A database that stores the setting conditions that must be met in order for the
An analysis mode specifying means for the operator to specify which analysis mode is selected from point analysis, line analysis and surface analysis;
With collecting the setting state of the check item of the predetermined said X-ray analysis apparatus for analyzing mode specified by the analyzing mode designating means, the said wavelength-dispersive X-ray spectrometer energy dispersive X and read, collected been determined set-state determining means for determining said setting condition satisfies the setting condition setting conditions to analysis by the line spectrometer meet to properly performed from the database,
Notification means for notifying an operator of the determination result by the setting state determination means for the wavelength dispersive X-ray spectrometer and the energy dispersive X-ray spectrometer;
An X-ray analysis apparatus comprising: The setting state determination means determines whether the setting state satisfies the setting condition separately for each of the wavelength dispersion X-ray spectrometer and the energy dispersion X-ray spectrometer. The X-ray analyzer according to claim 1, wherein The notification means determines whether or not the setting state satisfies the setting condition for each of the wavelength dispersive X-ray spectrometer and the energy dispersive X-ray spectrometer by switching the lamp on and off. The X-ray analysis apparatus according to claim 1, wherein notification is made. The X-ray analysis apparatus according to claim 1, wherein the lamp is a pseudo lamp displayed on a window of a computer provided in the X-ray analysis apparatus. The X-ray analyzer according to claim 1, further comprising item-by-item notification means for notifying an operator of a result of determination as to whether or not the setting state satisfies the setting condition for each confirmation item. .

Images