JP4785193B2 - Micro site analysis system using focused ion beam - Google Patents

Description

  The present invention relates to a micro site analysis apparatus, and more particularly to a micro site analysis apparatus using a focused ion beam.

  If it is possible to analyze the outer shell (surface) and inner core (inner) for fine particles of several microns or less, it is possible to clarify the origin of the fine particles and the subsequent modification history. It becomes. By using these pieces of information, it becomes possible to identify the generation source of particulates with a high environmental load and take measures to suppress the generation. Furthermore, since it is possible to trace back to the source, it becomes possible to clarify the responsibility of the emitter.

  However, it has been difficult to perform analysis by distinguishing the outer shell and inner core of fine particles having a size of several microns or less with a conventional composition analyzer or the like. For example, as a method for performing composition analysis of a minute part such as a fine particle or a wafer, there is a method of performing mass analysis of secondary ions emitted by irradiating a measured part with an ion beam. In this method, mass analysis of the portion irradiated with the ion beam is possible, but it was difficult to obtain internal information. For example, in order to obtain internal information, it is conceivable to perform mass analysis while digging down the measurement site using ion etching and analyze the change over time of the obtained information. However, in reality, the drilling speed is often not uniform between the surface and the inside, and eventually only a mixture of information on the surface and the inside can be obtained. Similar problems occur when ion etching and a surface analysis method such as Auger electron spectroscopy are used in combination.

  It is also conceivable to cut a fine part such as a fine particle and perform composition analysis on the cross section. For example, there is a technique in which fine particles are cut using a focused ion beam and secondary ions generated by irradiating the cross-section with the focused ion beam are subjected to mass analysis. At this time, in order to irradiate the cross section with a focused ion beam in order to generate secondary ions, the cross section needs to be directed toward the focused ion beam apparatus. Conventionally, in order to do this, in the example of Patent Document 1, for example, an opening is formed from a direction perpendicular to the sample, the stage on which the sample is placed is rotated eucentric 180 degrees, and the stage is tilted to further The cross section of the opening was directed to the focused ion beam device.

  As another method, for example, in the example of Patent Document 2, a micro sample is separated from a sample using a focused ion beam, a probe supported by a manipulator is connected to the micro sample, and the micro sample is operated by operating the probe. The sample was directed to a focused ion beam device.

  Furthermore, in the example of Non-Patent Document 1, using two focused ion beam devices arranged so that the respective lines of sight intersect perpendicularly, a sample is disposed at the intersection of the lines of sight, while fine particles are cut, and on the other hand The focused ion beam was irradiated to the cross section.

JP-A-11-213935 JP 2005-259707 A Tetsuo Sakamoto, Kazuaki Shibata, Kazunari Takanashi, Masanori Owari, Yoshimasa Nihei, "Structural Analysis of Coal Fly Ash Particles by means of Focused-Ion-Beam Time-of-Flight Mass Spectrometry", e-Journal of Surface Science and Nanotechnology, Vol . 2, 10 February 2004, pp. 45-51

  However, when searching for a target that is a processing target particle or positioning a processing site using a focused ion beam apparatus, a large amount of ions are irradiated to the target, so that damage to the target is large. That is, while the target is specified by the focused ion beam apparatus and the processing site is determined, the sputtering proceeds, and the smaller the particles, the faster the wear and the disappearance before analysis. . In addition, since organic substances and compounds on the outermost surface undergo degradation such as decomposition and segregation due to focused ion irradiation during search, there is also a problem that accurate information cannot be obtained even after subsequent mass spectrometry. It was.

  In the technique of Patent Document 1, it is necessary to greatly tilt the stage on which the sample is placed, and the rotation and tilt mechanism is complicated. Furthermore, in principle, it was impossible to irradiate a focused ion beam perpendicular to the cross section. In addition, in some analyzers such as a mass spectrometer, for example, a time-of-flight secondary ion mass spectrometer or the like, the analyzer inlet is perpendicular to the stage in order to efficiently draw ions into the analyzer. Some are preferred. However, in this prior art, the focused ion beam is irradiated with the stage tilted, and the focused ion beam and the scanning electron microscope are located in the vertical direction of the stage. It was impossible to combine with an analyzer. Furthermore, for a stage rotation mechanism on which a target of several microns or less is placed, a high degree of mechanical movement accuracy is required so that the target does not deviate from the field of view of the focused ion beam.

  Further, the technique of Patent Document 2 requires a probe supported by a manipulator, and when it becomes an ultrafine particle, it is very difficult to handle the probe, and such a probe that can be finely operated is not common and very It was expensive.

  Furthermore, in the technique of Non-Patent Document 1, two focused ion beam devices must be used, and the device is expensive.

  In view of such circumstances, the present invention can use a single focused ion beam device for cutting and secondary ion emission, and can analyze a cross section of a minute portion with high accuracy without unnecessarily altering a minute sample. It is an object of the present invention to provide a possible fine part analyzing apparatus.

  In order to achieve the above-described object of the present invention, a microscopic region analysis apparatus according to the present invention is disposed so as to have a sample stage on which a sample is placed and an oblique line of sight toward the sample stage, and is oblique to the sample stage. Focused ion beam device that can cut the target in the direction, and rotation that rotates the sample stage around the target center around the target so that the focused ion beam from the focused ion beam device can be irradiated onto the cut target cross section An electron beam device for searching for a target to be cut and observing a target whose center of rotation is rotated by a rotating unit, a correcting unit for correcting the position of the target observed by the electron beam device, and a focused ion beam device An analyzer for analyzing secondary ions emitted by a focused ion beam applied to a cross section of the target. Is shall.

  Here, the focused ion beam device may be arranged so that its line of sight is 45 degrees with respect to the surface normal of the sample stage.

  Further, the rotating means may be any means that rotates the sample position center so that the sample stage rotates 180 degrees.

  Further, the analyzer may be arranged so that its intake port is oriented in the vertical direction with respect to the sample stage.

  Further, the focused ion beam device irradiates the surface before cutting and the cross section after cutting of the target to emit secondary ions from the target, respectively, and the analyzing device irradiates the surface before cutting and after cutting. Any secondary ion may be used as long as it analyzes secondary ions from the cross section.

  In the micro site analysis apparatus of the present invention, since the target to be cut is searched using an electron beam apparatus, the micro sample is not unnecessarily altered. However, there is an advantage that each site can be analyzed accurately. In addition, by correcting the position of the target by using the electron beam device to observe the target that is rotating around the focus position, it is possible to accurately rotate the sample stage around the target center, There is also an advantage that a fine part analyzing apparatus can be realized at low cost without using a complicated mechanism.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic conceptual diagram for explaining the overall configuration of the microscopic region analysis apparatus of the present invention. Note that the sample particles in the figure are exaggerated and enlarged for convenience of explanation, but the actual sample particles are fine and accurately represent the magnitude relationship with the illustrated sample stage etc. is not. As shown in the figure, the fine region analyzing apparatus of the present invention mainly comprises a sample stage 1, a focused ion beam device 2, a rotating mechanism 3, an electron beam device 4, a correction unit 5, and an analyzing device 6. The sample stage 1 is a stage on which the sample is placed, and is preferably kept horizontal. Note that the target sample is not limited to a spherical object such as a fine particle, but may be a planar one such as a wafer, or any object as long as it is a target for mass analysis of a cross section. I do not care.

  As the focused ion beam device 2, a generally available device can be used. For example, an ion beam can be extracted from a liquid metal gallium ion source, focused, and irradiated to a sample with nanoscale accuracy. It is. Using this focused ion beam device 2, the target is cut. In the microscopic region analysis apparatus of the present invention, the focused ion beam device 2 is arranged so that the line of sight is oblique with respect to the sample stage 1. The focused ion beam apparatus 2 according to the present invention is only required to process the target so as to have a cross section cut obliquely by irradiating the target with the focused ion beam from an oblique direction. As described later, the focused ion beam device 2 is preferably arranged so that its line of sight is approximately 45 degrees with respect to the surface normal of the sample stage 1.

  The rotation mechanism 3 is composed of a motor or the like that rotates the sample stage 1, and is capable of centered rotation (eucentric operation) so as to horizontally rotate the sample stage 1 with a specific position as an axis. . This makes it possible to rotate the sample stage around a specific target in the sample placed on the sample stage 1. More specifically, the rotation mechanism 3 preferably has a degree of freedom in which the sample stage 1 has three axes of XYZ and a total of five axes of tilt and rotation, and these five axes can be controlled by a computer. good.

  In the present specification, the “centered position rotation” is not necessarily limited to the one that performs the eucentric operation as described above. For example, a specific target in the sample is previously placed on the sample table before the rotation. If a mechanism that can be moved and arranged at the center of rotation is provided, the center of rotation of the sample stage may be set as the focus position, and the center may be rotated. Even with this configuration, an operation similar to the eucentric operation is possible.

  FIG. 2 is a diagram showing a state in which the sample stage 1 is rotated 180 degrees by the rotation mechanism 3 and the cross section of the target is directed toward the focused ion beam device 2 in the microscopic region analysis apparatus of the present invention. Thus, by rotating the sample stage 1 by the rotation mechanism 3, the focused ion beam from the focused ion beam device 2 can be irradiated onto the cut cross section of the target.

  Here, the angle of the line of sight of the focused ion beam apparatus 2 with respect to the sample stage 1 will be described more specifically. For example, when the line of sight of the focused ion beam device 2 is arranged so as to be 60 degrees with respect to the surface normal of the sample stage 1, the target is cut at an angle of 60 degrees. If the cross section of the target is turned 180 degrees toward the focused ion beam device, the incident angle of the focused ion beam on the cross section becomes 60 degrees. Even in this state, it is of course possible to analyze a fine part, but since the beam diameter becomes an ellipse, the resolution in the surface direction is also reduced, which may hinder more accurate analysis. Therefore, the focused ion beam device 2 is arranged so that the line of sight of the focused ion beam device 2 is 45 degrees with respect to the surface normal of the sample stage 1. As a result, the target is cut at an angle of 45 degrees, and when the sample stage 1 is rotated 180 degrees and the cross section of the target is directed toward the focused ion beam device, the incident angle of the focused ion beam on the cross section is 0 degree, that is, The beam can be incident perpendicular to the cross section. Therefore, since the beam diameter becomes a perfect circle, the resolution in the surface direction is increased, and more accurate analysis is possible. Also, it is not always necessary to rotate the sample stage 1 by 180 degrees, but for the same reason as described above, the focused ion beam can be irradiated perpendicularly to the cross section of the target by rotating it by 180 degrees. More preferable.

  As the electron beam device 4, a generally available device can be used. For example, a device that can generate an electron beam by accelerating thermoelectrons generated from a filament by an electric field or a high electric field at the tip of a heated needle. The device etc. which emits electrons by multiplying. In the microscopic region analysis apparatus of the present invention, the electron beam device 4 is used to search for a specific target to be subjected to cross-section processing in the sample placed on the sample stage 1. Thereby, it becomes possible to search for a fine sample in a non-destructive manner, and it is possible to prevent the fine sample from being unnecessarily altered. The electron beam device 4 may be arranged at any position as long as the target can be searched and the state during rotation can be observed. However, in consideration of the fact that the cut surface of the target can be confirmed from the front, the device layout, and the like, It is only necessary that the electron beam device 4 is disposed at a position facing the focused ion beam device 2 centering on 1 so that the line of sight of the electron beam device 4 is 45 degrees with respect to the surface normal of the sample stage.

  Here, the rotation mechanism 3 does not have high mechanical drive accuracy to such an extent that the rotation mechanism 3 continues to capture and rotate around an object having a size of several microns or less. For this reason, even if the focus position center rotation is performed, there is a high possibility that the target is actually out of the field of view of the focused ion beam device 2. Therefore, the electron beam device 4 continues to observe the target placed on the sample stage 1 even while the focus position is rotated by the rotation mechanism 3. Thereby, since the position shift of the target can be detected, the position of the target can be corrected using the correction unit 5 described later.

  The correction unit 5 corrects the position of the target observed by the electron beam device 4. In addition, correcting the position of the target not only corrects by moving the position of the target itself, but also corrects the position of the target observed by moving the field of view of the electron beam device or the focused ion beam device. Is also included. While the target is being rotated around the focus position, for example, the focused ion beam device 2 or the electron is corrected by beam shift correction or the like so that the target is arranged at substantially the center of the visual field of the focused ion beam device 2 or the electron beam device 4. The line of sight of the beam device 4 is corrected. Specifically, the line of sight can be adjusted at the nano level by bending a focused ion beam or electron beam using an electric field. The correction unit 5 shifts the beam by voltage control or the like manually by visual observation or automatically by pattern recognition based on the information of the target observed by the electron beam device 4 and the focused ion beam. The line of sight of the apparatus 2 is corrected, and the electron beam apparatus 4 continues to capture a fine target. As described above, the correction unit 5 compensates the limit of the mechanical accuracy of the rotation mechanism 3 by nano-level adjustment by beam shift of the focused ion beam device 2 or the electron beam device 4. Therefore, since it is not necessary to perform mechanical control and adjustment of the rotation mechanism with high accuracy, the analysis device can be realized at a lower cost than an apparatus using a high-accuracy probe or the like.

  The analysis device 6 is a device for analyzing secondary ions emitted from the focused ion beam device 2 by the focused ion beam irradiated onto the cross section of the target. Specifically, for example, an Auger electron spectrometer, a secondary ion mass spectrometer (SIMS), a time-of-flight secondary ion mass spectrometer (TOF-SIMS), a quadrupole mass spectrometer, etc. Apparatus. Furthermore, the ionization analyzer disclosed in Japanese Patent Application No. 2006-161691 by the applicant of the present application is also applicable. However, the analyzer used in the microscopic region analyzer of the present invention is not limited to these, and any analyzer that can be developed or developed in the future is applicable as long as it can perform surface analysis of a substance by ion analysis. .

  Here, since the analyzer 6 captures and analyzes secondary ions emitted by the focused ion beam, the analyzer 6 is preferably arranged so as to be perpendicular to the sample stage 1. . More specifically, in the case of a device that uses an electric field to draw ions into the intake port of the analyzer, such as a time-of-flight secondary ion mass spectrometer, the intake port should be oriented perpendicular to the sample stage. Preferably they are arranged. If the intake port is not oriented in the vertical direction, the generated ions cannot be taken straight into the analyzer, but hit the inner surface of the intake port, which is usually cylindrical, and this effectively prevents ions from being drawn into the analyzer. End up. For this reason, the analyzer used in the present invention is arranged so that the intake port of the analyzer is oriented in the vertical direction with respect to the sample stage in order to efficiently draw the generated ions into the analyzer.

  Now, the procedure for analyzing fine particles using the fine part analyzing apparatus of the present invention configured as described above will be described below with reference to actually taken photographs. FIG. 3 is a photograph of a state in which fine particles have been searched, identified, cut, and rotated using the microscopic region analysis apparatus of the present invention. 3A shows a state in which particles are being searched for by the electron beam device 4, FIG. 3B shows a state in which a target is specified, and FIG. 3C shows that cutting processing has been started by the focused ion beam device 2. FIG. 3 (d) shows a state in which the cutting of the target is completed, FIG. 3 (e) shows a state in which the sample stage is rotated around the focus position so as to rotate 180 degrees, and FIG. 3 (f) shows a focused ion. The state where the cross section of the target was observed with the beam apparatus 2 is each represented. Note that, in the fine region analyzing apparatus of the present invention, specifically, the focused ion beam device 2 and the electron beam device 4 are arranged so as to face each other with the sample table 1 as the center, and the respective line of sight is the surface normal of the sample table. What was arrange | positioned so that it might become 45 degree | times was used. The fine particles actually analyzed shown in the photograph are spherical particles having a diameter of about 4.7 microns.

  As an analysis procedure, first, sample particles are placed on the sample stage 1. Sample particles are ultrafine particles of about several microns, and not only one particle is placed, but a large number of particles are placed as an aggregate. Then, a sample fine particle is searched using the electron beam device 4 (FIG. 3A), and one fine particle as an appropriate target is specified (FIG. 3B). Note that the field of view of the electron beam device 4 may be widened at the time of search, and when a specific target is determined to some extent, the field of view is narrowed and the target is expanded to specify one particle. Next, the XY coordinates of the target are obtained from the electron beam apparatus 4, and the line of sight of the focused ion beam apparatus 2 is directed to the target using this information. Note that the target may be specified after first matching the line of sight of the electron beam device 4 and the focused ion beam device 2. That is, a characteristic location other than the target fine particles is found from the sample, and the focused ion beam device 2 and the electron beam device 4 are observed so that this location becomes a reference, and the height of the sample stage (Z axis) and each The beam shift amount of the beam device is adjusted in advance so that the field of view of each beam device matches, and then the electron beam device 4 observes the target so that the target enters the field of view. They may be translated (XY axis movement) while the positional relationship is fixed.

  When it is necessary to analyze the outer shell of the target, a focused ion beam is irradiated toward the outer shell so that secondary ions are emitted from the outer shell. As a result, secondary ions are released from the outer shell of the target and analyzed by the analyzer 6. This analysis result includes information about the outer shell of the target.

  Next, in order to cut the target, the target is irradiated with a focused ion beam from the focused ion beam device 2 (FIG. 3C). In the case of spherical particles, the target can be analyzed from the outer shell to the center position by cutting so as to pass through the approximate center of the sphere. The cross section of the target thus cut is directed toward the electron beam device 4 (FIGS. 3D and 1). From this state, the sample stage 1 is rotated by 180 degrees by using the rotation mechanism 3 to rotate around the target position around the target (FIGS. 3E and 2). At this time, the target is observed with the electron beam device 4 and the sample stage 1 is rotated while correcting the position so that the target is at the center of the field of view of the electron beam device 4. Absent. When the target is rotated 180 degrees, the cross section of the target faces the focused ion beam device 2 (FIG. 3 (f)). Then, a focused ion beam device 2 irradiates the target cross section with a focused ion beam, and secondary ions emitted from the cross section are analyzed by the analyzer 6. This analysis result contains information about the inner core of the target. In addition, it is also possible to analyze continuously from the outside to the center of the cross section of the target, thereby making it possible to clarify the origin of the generation of fine particles and the subsequent modification history.

  As described above, in the fine region analyzing apparatus of the present invention, the focused ion beam apparatus is used only for cutting the target and emitting the secondary ions, and the electron beam apparatus is used for searching for the target and observing the rotating target. Since it is used, analysis can be performed with high accuracy without changing the target unnecessarily. For this reason, it is possible to analyze not only the inorganic composition but also the organic composition by distinguishing the surface and the inside even for a fine part having a size of several microns or less.

  Note that the microscopic region analysis apparatus of the present invention is not limited to the illustrated examples described above, and it is needless to say that various modifications can be made without departing from the scope of the present invention.

FIG. 1 is a schematic diagram for explaining the overall configuration of the microscopic region analysis apparatus of the present invention. FIG. 2 is a schematic diagram for explaining a state in which the sample stage of the microscopic region analyzing apparatus of the present invention is rotated 180 degrees and the cross section of the target is directed toward the focused ion beam apparatus. FIG. 3 is a photograph of a state in which fine particles have been searched, identified, cut, and rotated using the microscopic region analysis apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample stand 2 Focused ion beam apparatus 3 Rotation mechanism 4 Electron beam apparatus 5 Correction | amendment part 6 Analyzer

Claims (2)

A micro site analysis device for analyzing a cross section of a sample, the device comprising:
A sample stage on which the sample is placed;
A focused ion beam device arranged to have a line of sight of 45 degrees with respect to the surface normal of the sample stage, and capable of cutting a target in an oblique direction with respect to the sample stage;
Rotating means for rotating the sample position around the target so as to rotate the sample stage 180 degrees around the target in order to irradiate the section of the cut target with the focused ion beam from the focused ion beam device;
The position is opposed to the focused ion beam apparatus with the sample stage as the center, and is arranged so as to have a line of sight of 45 degrees with respect to the surface normal of the sample stage. An electron beam device for observing a target whose center of rotation is rotating;
Correction means for correcting the position of the target observed by the electron beam device;
A time-of-flight mass spectrometer for analyzing secondary ions emitted from a focused ion beam irradiated on a cross-section of a target from the focused ion beam device , which is arranged so that an intake port faces a direction perpendicular to the sample stage When,
A micro site analysis apparatus comprising: The fine site analysis apparatus according to claim 1, wherein the focused ion beam device irradiates a focused ion beam on a surface before cutting of the target and a cross section after cutting in order to emit secondary ions from the target, The time-of-flight mass spectrometer analyzes a secondary ion from a surface before cutting and a cross-section after cutting, respectively.