JP2011076960A - Device for recognition of thin-film sample position in electron microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for recognition of a thin-film sample position in an electron microscope, allowing multi-axial stage movement to bring easily an objective thin film sample piece within an observation visual field. <P>SOLUTION: The device includes an electron beam source 21 for emitting an electron beam, an irradiation lens system 22 for regulating a current amount of the electron beam, a sample block 24 for holding a sample 23, a multi-axial stage 28 for operating the sample block 24, a control unit 31 for controlling the movement of the multi-axial stage 28, an image focusing lens system 25 for magnification and image forming of an electron transmitted through the sample 23, an alignment deflector for correcting an orbit of the electron beam, a control driver for controlling lenses of the lens system and the alignment deflector, a computer 30 for controlling the control unit 31, a means 26 for acquiring a magnification-image-focused image as digital information using a CCD camera, a means 33 for storing the digital information into the computer 30, and a means 32 for computing the digital information by the computer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thin film sample position recognition apparatus in an electron microscope, and more specifically, can irradiate a sample with an electron beam and acquire an image obtained by enlarging an image of transmission electrons transmitted through the sample by an imaging electron optical system, or an electron beam. One or more thin film sample pieces that belong to an electron microscope that can scan and irradiate the sample, detect secondary electrons, reflected electrons, and transmitted electrons generated from the sample, and can be imaged, and placed on the sample mesh The present invention relates to a technical field for automatically recognizing the position.

  In recent years, in addition to material manufacturers such as steel, there are increasing opportunities for electron microscopes to be used in fields such as semiconductors and flat panel displays (FPD). Material manufacturers mainly used in research and development, but in fields such as semiconductors and FPDs, in addition to research and development, product failure analysis, dimensional measurement (hereinafter referred to as observation), and analysis may be performed. Many. In product defect analysis and dimensional measurement, the sample to be observed is placed on a mesh support (hereinafter referred to as sample mesh). As a sample to be observed, a thin film sample is prepared using an FIB (focused ion beam apparatus) or the like.

  As shown in FIGS. 3 and 4, one or a plurality of the prepared sample thin films are manually or automatically placed on the sample mesh. FIG. 3 is a diagram illustrating a configuration example of a sample mesh. In the figure, reference numeral 10 denotes a sample mesh, which constitutes a placement unit on which a sample is placed. The diameter of the sample mesh 10 is about 3 mm. The inside is in a lattice shape using the lattice member 12. Reference numeral 11 denotes a unit region constituting this lattice, and a plurality of fine holes 11a are formed in the inside thereof as shown in the enlarged view. Reference numeral 16 denotes an attachment provided at the center of the sample mesh 10.

  FIG. 4 is a diagram showing a state in which a sample is placed on the sample mesh. The same components as those in FIG. 3 are denoted by the same reference numerals. In the figure, the thin film sample piece 1 is placed in a plurality of unit regions 11. The thin film sample piece 1 is installed at an arbitrary angle in a unit region 11 made of a grid member 12.

  A thin film sample piece processed by FIB or the like is often several μm on a side, and an operator must search from a sample mesh to observe with an electron microscope. To search for a thin film sample with an electron microscope, a low magnification (several hundred to several thousand times on the monitor) is used, or a scanning electron microscope (STEM) scanning function is provided. If it is an apparatus, it searches in the observation mode in the low magnification. When the thin film sample piece to be observed is found, the magnification is set to a high magnification and the desired observation or analysis is performed.

  However, a plurality of thin-film sample pieces installed on the sample mesh are often installed in a semiconductor or FPD factory as shown in FIG. This is because there are several tens of samples to be observed and analyzed in one day, and in some cases 100 or more. Thus, when there are a plurality of sample thin pieces on the sample mesh, the thin film sample piece is searched for with a low magnification for each thin film sample piece, and then the observation and analysis operations are repeated with the high magnification.

  As another method, all or a part of the thin film sample pieces initially set on the sample mesh are searched at a low magnification and stored for each thin film sample piece by using the memory function of the sample coordinates of the electron microscope. The position information of the thin film sample piece is stored in the memory of the computer. The operator automatically moves the sample stage to the coordinates of the thin film sample piece by calling the target thin film sample piece position from the memory when observing and analyzing.

  As a conventional device of this type, the magnification of the transmission electron microscope is set to the first magnification, the mesh is moved at this magnification to obtain an image of each field of view, and a large number of obtained image data are joined together. An image of the entire mesh area is acquired, an observation point to be observed at a higher second magnification is arbitrarily specified from an image of the entire observation area, and each specified observation point is automatically captured and displayed on the display. An apparatus is known (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2005-216645 (paragraphs 0051 to 0056, FIG. 7)

  Currently, the method of searching for the position of a thin film sample piece on a sample mesh with an electron microscope is generally a manual search method. As described above, in order to find the position of the thin film sample piece placed on the sample mesh, it is necessary to search for each thin film sample piece with a low magnification. The more it takes, the more time it takes. The operator aims to observe and analyze the thin film sample piece, not to find it. For this reason, a function for automatically searching for the positions of all thin film sample pieces in a short time is required.

  In recent years, the number of cases where a cross section of a semiconductor device is observed and analyzed with an electron microscope is increasing. In the case of semiconductor devices, precise measurement of the wiring width is often performed. As shown in FIG. 5, it is desired to perform precise length measurement with the silicon substrate portion positioned below the observation region. This is to make the area to be measured horizontal or vertical. If the area to be measured is slanted as shown in (a), an error in the number of pixels occurs. In the case of precise length measurement, the length is measured with the object to be measured horizontal or vertical as shown in FIG.

  However, as described above, in the thin film sample piece placed on the sample mesh, the silicon substrate portion is not necessarily the lower part of the observation region. This is because the rotation of the thin film sample piece cannot often be taken into account when the sample mesh is transferred from a thin film processing apparatus such as FIB. In particular, since thin film sample pieces to be observed and analyzed tend to increase as described above, it is not realistic to be aware of rotation for each thin film sample piece.

  Furthermore, when the thin film sample piece on the sample mesh is observed and analyzed with an electron microscope, the sample mesh is fixed to a dedicated sample holder. When fixing the sample mesh to the sample holder, it is not realistic to consider the rotation of the sample mesh. This is because the sample mesh has a diameter of about 3 mm and it is difficult for the operator to work while considering the rotation angle.

  In a scanning electron microscope or a scanning transmission electron microscope, it is possible to easily change the scanning direction of the electron beam electrically so that the silicon substrate is positioned below the observation region. However, an image cannot usually be rotated arbitrarily with a transmission electron microscope. Recently, a technique has been devised in which an image can be arbitrarily rotated and captured by rotating a CCD camera that acquires a transmission electron image. However, the operator must adjust the rotation angle of the CCD camera for each thin film sample piece, which is inconvenient.

  The present invention has been made in view of such problems, and the position of the thin film sample piece can be automatically stored in the memory of a computer, and the multi-axis stage can be moved easily so that the target thin film sample piece enters the observation field of view. An object of the present invention is to provide a thin film sample position recognition apparatus in an electron microscope.

In order to solve the above-described problems, the present invention has the following configuration.
(1) The invention described in claim 1 is an electron beam source that emits an electron beam, an irradiation lens system that adjusts the amount of current of the electron beam, a sample table that holds a sample, and a multi-axis that operates the sample table A stage, a control unit for controlling the movement of the multi-axis stage, an imaging lens system for enlarging and imaging electrons transmitted through the sample, an alignment deflector for correcting the trajectory of the electron beam, a lens of the lens system, A control driver for controlling the alignment deflector; a computer for controlling the control unit; means for acquiring an enlarged image as digital information using a CCD camera; means for storing the digital information in a computer; One or more thin film samples placed on a sample mesh from a low magnification image in an electron microscope having at least means for computing digital information with a computer It recognizes the piece position, and calculates and records the barycentric coordinates of the lamella strip.

  (2) In the invention according to claim 2, an electron microscope image of a sample mesh in which the thin film sample piece is not installed is registered in a computer in advance by magnification, and the electron microscope of the sample mesh in which the thin film sample piece is installed The image and the electron microscope image obtained at the same magnification as the electron microscope image of the sample mesh on which the thin film sample piece of the sample mesh on which the thin film sample piece is not installed are image-processed to calculate the position of the thin film sample piece It is characterized by that.

  (3) The invention according to claim 3 calculates the position of the center of gravity of the thin film sample piece and moves the multi-axis stage necessary for the thin film sample piece to enter the observation field of view from the barycentric coordinate information of the thin film sample piece. And a multi-axis stage is moved by an operator's instruction so that the instructed thin film sample piece enters the observation field of view.

  (4) In the invention described in claim 4, the position information and the image information at the time of recognition of the recognized thin film sample piece are displayed on the user interface as a list, and the thin film sample piece enters the observation visual field according to the operator's instruction. In addition, the multi-axis stage is automatically moved.

  (5) According to the invention described in claim 5, the operation of the electron microscope is registered in advance in the recipe, and the multi-axis stage movement is performed from the recognition of all the thin film sample piece positions in the electron microscope which can operate as registered. It is characterized by that.

  (6) In the invention described in claim 6, the electron microscope image A obtained by rotationally correcting the image of the thin film sample piece is registered in a computer in advance, and the multi-axis stage is set so that each thin piece sample piece enters the observation visual field. The rotation angle of the CCD camera that can move and rotate the high-magnification image B of the thin film sample piece and the image A by image processing so that the reference area of the thin film sample piece becomes horizontal is calculated, and the CCD camera rotates. It is characterized by.

  (7) The invention according to claim 7 is an electron microscope capable of acquiring a scanning secondary electron image, a scanning reflection electron image, and a scanning transmission image by using a deflector in an irradiation lens system for adjusting an electron beam current amount. Recognizing the position of one or a plurality of thin film sample pieces placed on the sample mesh by a low-magnification scanning image, calculating and recording the barycentric coordinates of the thin film sample pieces, and performing the operations of claims 2 to 5 The thin film sample piece rotation-corrected image A is registered in the computer in advance, and the multi-axis stage is automatically moved so that each thin film sample piece falls within the observation field of view. The image B and the image A are subjected to image processing to calculate a correction amount in the scanning direction of the electron beam so that the reference position of the thin film sample piece is horizontal, and the scanned image is rotated.

  (1) According to the first aspect of the present invention, a computer for controlling the control unit, means for acquiring an enlarged image as digital information using a CCD camera, and means for storing the digital information in the computer And an electron microscope having a means for computing the digital information by a computer, and automatically recognizing the position of one or more thin film sample pieces placed on the sample mesh from a low magnification image, and calculating the barycentric coordinates of the thin film sample pieces. It can be calculated and recorded automatically.

  (2) According to the invention of claim 2, an electron microscope image of a sample mesh in which a thin film sample piece is installed and a sample mesh in which a thin film sample piece of a sample mesh in which the thin film sample piece is not installed is installed The electron microscope image acquired at the same magnification as the electron microscope image can be image-processed, and the position of the thin film sample piece can be automatically calculated.

(3) According to the invention described in claim 3, it is possible to move the multi-axis stage so that the instructed thin film sample piece falls within the observation visual field.
(4) According to the invention described in claim 4, the position information and the recognized image information are displayed as a list on the user interface for the recognized thin film sample piece, and the thin film sample piece is within the observation field according to the operator's instruction. The multi-axis stage can be moved automatically to enter.

  (5) According to the invention described in claim 5, the operation of the electron microscope is registered in advance in the recipe, and in the electron microscope that can automatically operate as registered, all the thin film sample piece positions are recognized to be multiaxial. Stage movement can be performed automatically.

  (6) According to the invention described in claim 6, the electron microscope image A obtained by rotationally correcting the image of the thin film sample piece is registered in the computer in advance, and automatically, so that each thin film sample piece enters the observation field of view. The multi-axis stage is moved, and the rotation angle of the CCD camera that can rotate so that the reference area of the thin film sample piece is horizontal by image processing of the high magnification image B of the thin film sample piece and the image A is automatically calculated. it can.

  (7) According to the seventh aspect of the invention, the position of one or a plurality of thin film sample pieces placed on the sample mesh is automatically recognized by the low magnification scanning image, and the barycentric coordinates of the thin film sample pieces are automatically determined. The calculated and recorded image A corrected for rotation of the thin film sample piece is registered in the computer in advance, and the multi-axis stage automatically moves so that each thin film sample piece falls within the observation field of view. A correction amount in the scanning direction of the electron beam can be calculated by performing image processing on the high-magnification image B and the image A so that the reference position of the thin film sample piece is horizontal, and the scanned image can be rotated.

It is a block diagram which shows one Example of this invention. It is explanatory drawing of the direction identification of a sample mesh. It is a figure which shows the structural example of a sample mesh. It is a figure which shows the state which mounted the sample on the sample mesh. It is a figure which shows the observation area | region of a silicon substrate.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 20 is a transmission electron microscope (TEM). In the TEM 20, 21 is an electron gun as an electron beam source for emitting an electron beam, 22 is an irradiation electron optical system as an irradiation lens system for adjusting the amount of electron beam current, 24 is a sample stage for holding a sample, and 23 is The sample is placed on the sample table 24. Reference numeral 25 denotes an imaging electron optical system as an imaging lens for enlarging and imaging electrons transmitted through the sample. Reference numeral 26 denotes an image acquisition device as means for acquiring an image enlarged and imaged by the imaging electron optical system 25 as digital information using a CCD camera.

  Reference numeral 28 denotes a sample moving mechanism as a multi-axis stage for operating the sample stage 24. A computer 30 stores image data obtained by the image acquisition device 26 and performs various image processing. As the computer 30, for example, a personal computer (personal computer) is used. In the computer 30, 33 is a memory for storing the center of gravity of the image data in addition to the digital image data acquired by the image acquisition device 26, 34 is an image display mechanism for displaying the image data stored in the memory 33, and 32 is a memory An analysis unit 31 that reads and analyzes the image data stored in 33 is a sample position correction unit as a control unit that receives the output of the analysis unit 32 and corrects the position of the sample. The sample position correcting unit 31 gives a control signal to the sample moving mechanism 28.

Although not shown in the figure, an acceleration tube for accelerating the electron beam at high speed, an alignment deflector for correcting the trajectory of the electron beam, and a control driver for controlling the lens of the lens system and the alignment deflector are provided. ing. Then, the position of one or a plurality of thin film sample pieces placed on the sample mesh is automatically recognized from the low-magnification image, and the barycentric coordinates of the thin film sample pieces are automatically calculated and recorded. The operation of the apparatus configured as described above will be described as follows.
Example 1
Embodiment 1 will be described with reference to FIGS. 1, 2, 3, and 4. FIG. FIG. 2 is an explanatory diagram of the direction identification of the sample mesh, FIG. 3 is a diagram showing a configuration example of the sample mesh, and FIG. 4 is a diagram showing a state where the sample is placed on the sample mesh. Before carrying the sample mesh on which the thin film sample piece to be observed and analyzed is placed into the sample chamber of the electron microscope, the sample mesh on which the thin film sample piece is not installed (FIG. 3) and when searching for the thin film sample piece An image I acquired at a low magnification (several hundred times) is prepared and stored in the memory 33 of the computer 30.

  A normal transmission electron microscope projects and observes a transmission electron image on a fluorescent screen. However, in a transmission electron microscope capable of acquiring a transmission electron image with a CCD camera, the magnification is set to an extremely low magnification so that almost the entire area of the sample mesh 10 is covered. It can be taken into the computer 30 as digital information. If the entire area of the sample mesh 10 cannot be acquired, the image is divided and acquired and stored in the memory 33.

  Next, the thin film sample piece 1 carries the sample mesh (FIG. 4) onto the sample chamber of the electron microscope on the sample mesh 10. Here, the thin film sample piece 1 is prepared using a thin film processing apparatus such as FIB. Moreover, the produced thin film sample piece 1 is installed on the sample mesh 10 automatically or manually. The thin film sample piece 1 carried into the sample chamber acquires an image of the sample mesh 10 under the same observation conditions as the image I. This image is set as an image II. Here, when acquiring the images I and II, the multi-axis stage 28 that changes the position of the sample mesh 10 is set to the neutral position (reference position).

By performing pattern matching between the image I and the image II, the rotation angle of the image II with respect to the image I can be calculated. Since the sample mesh 10 is attached to a dedicated sample holder for an electron microscope, the mesh itself is rotating. The state of the image I is set as the basic position, and the rotation angle is calculated.

  By the way, the conventional pattern matching calculates the shift amount of the number of pixels in the X direction (the horizontal direction of the image) and the Y direction (the vertical direction of the image). Depending on the algorithm, the amount of deviation can be calculated with an accuracy of one pixel or less. However, pattern matching considering image rotation and enlargement / reduction has not been possible. However, in recent years, applications that take rotation and enlargement / reduction into account have begun to be marketed due to higher functions of computers and improvements in algorithms, so that the amount of rotation between the two images can be calculated quantitatively.

  When calculating the rotation amount by pattern matching, an accurate rotation angle cannot be calculated if the image is a lattice-like image like the sample mesh 10. Therefore, although depending on the type of the sample mesh, for example, as shown in FIG. 2, a region 16 having an asymmetrical shape provided in the center of the sample memory is provided, and a pattern matching reference portion is formed using this region 16. By doing so, the rotation angle can be calculated.

Next, the rotation angle calculated for the image II by the above-described method is rotated by image processing. This image is set as an image III. Next, the difference between the image I and the image III is calculated. This difference image is referred to as an image IV. Next, a difference image between image I and image IV is created by image processing, and this image is converted to image V.
And In the image V, in the image I and the image IV, pixels with almost the same gradation appear near the 0th gradation due to the difference and appear as black, and pixels with greatly different gradation appear as white as the degree of difference increases. That is, an aggregate of pixels expressed in a color other than black is a thin film sample piece candidate.

However, other than the thin film sample piece may appear other than black due to factors such as noise. Therefore, in order to reduce the error, a threshold value of luminance that is an aggregate of pixels to be thin film sample piece candidates is determined in advance and binarized to narrow down the thin film sample piece candidates. Furthermore, since the approximate size of the thin film sample piece can be known in advance, if the acquisition magnification of the image II is determined, the range of the number of pixels of the aggregate of candidate thin film sample pieces can be determined, and the thin film within that range can be determined. Sample specimen candidates are narrowed down to thin film specimens. An aggregate of pixels satisfying at least the above conditions is identified as a thin film sample piece.

  Next, one or a plurality of thin film sample piece coordinates on the identified sample mesh 10 are calculated. Each calculated thin film sample piece 1 is an aggregate of pixels as described above. The center of gravity (center) of the thin film sample piece 1 can be obtained by calculating the luminance center of gravity of the aggregate of pixels. The calculation of the luminance centroid is a general image processing method and can be easily performed. The center-of-gravity position is calculated for all of the calculated thin film sample pieces 1.

Since the images I and II are acquired at the neutral position of the multi-axis stage, the central portion of each image is an observation field of view when the multi-axis stage 28 performs high-magnification observation at the neutral position. Therefore, in the image III, the difference (number of pixels) between the center of the image and the gravity center position of each thin film sample piece 1 is calculated in both the X direction and the Y direction. Since the magnification at which the image is acquired is known, the distance between the observation visual field center position and each thin film sample piece 1 can be calculated from the number of pixels. However, depending on the electron optical system, the center of the visual field may change between the low magnification mode and the high magnification mode. In this case, the amount of change is known in advance, so the correction amount is stored in the memory 33 in advance and corrected. The distance between the observation field center and each thin film sample piece 1 is calculated.

  The calculated distance between the observation field center and each thin film sample piece 1 is stored in the memory 33 of the computer 30 together with the above-described image and distance, the calculated pseudonym of the thin film sample piece 1, and the like as a list on a user interface (UI) or the like. indicate. The kana of the thin film sample piece may be determined in advance.

  The operator selects the thin film sample piece 1 listed in the UI, so that the multi-axis stage automatically causes the thin film sample piece 1 to be observed according to the distance information between the calculated observation visual field center and each thin film sample piece 1. You can move to get inside. Here, in the list displayed on the UI, the binarized image of the corresponding thin film sample piece region or the image representing the shape of the thin film sample piece 1 extracted based on the binarized image is displayed at the same time. It can be determined whether the target thin film sample piece 1 is other than the erroneously detected thin film sample piece. Therefore, it is possible to determine whether or not the sample is a thin film sample piece before moving the multi-axis stage, and the multi-axis stage is not moved to a position where it is erroneously detected. Therefore, the operator can efficiently work.

According to this embodiment, the position of one or a plurality of thin film sample pieces placed on the sample mesh can be automatically recognized from the low-magnification image, and the barycentric coordinates of the thin film sample pieces can be automatically calculated and recorded.
(Example 2)
A second embodiment will be described with reference to FIGS. FIG. 5 is a view showing an observation region of the silicon substrate. In Example 2, the operation of the electron microscope, such as a recipe (procedure), is reserved in advance in Example 1, and in the electron microscope that can automatically operate as reserved, all the thin film sample piece positions are recognized from multiple axes. The stage is moved automatically.

  The sample holder on which the sample mesh 10 on which the thin film sample piece 1 is installed is fixed is manually or automatically carried into the electron microscope main body. After the sample mesh 10 is carried into the main body of the electron microscope, it automatically operates according to the plan registered in the recipe. In the case of an electron microscope having a function in which the sample mesh 10 can be automatically carried into the electron microscope, the sample mesh 10 can be operated by a recipe from the introduction of the sample mesh 10.

  The CCD camera can also be rotated by a recipe operation. FIG. 5 is a schematic diagram of a cross section of a MOS transistor, but the length measurement results are different between FIGS. 5 (a) and 5 (b). In particular, in recent years, semiconductors have been miniaturized, and the area to be measured has become smaller. Therefore, length measurement at high magnification is required, and length measurement errors are becoming severe.

The white region of the image V described in the first embodiment (the aggregate of the maximum gradation pixels since binarization is performed)
Since the thin film sample piece is shown, the approximate size of the thin film sample piece 1 can be calculated. The optimum observation magnification is automatically determined from the calculated size of the thin film sample piece 1, and a transmission electron image is acquired by a CCD camera after setting the observation magnification. This image is designated as an image VI. An image (referred to as image VII) acquired in a state in which the observation area in the thin film sample piece is corrected with the rotation angle of the CCD camera is registered in the memory 33 of the computer 30 in advance, and image VI and image VIII are subjected to pattern matching. Thus, the rotation amount of the image can be calculated. The rotation amount of the image calculated here is used as the rotation angle of the CCD camera, and the CCD camera is rotated. In addition to the recipe, the operator can instruct the operation of the above-described CCD camera rotation function from the above-described UI.

According to the second embodiment, an electron microscope image A in which the rotation corrected image of the thin film sample piece is registered in advance in the computer, and the multi-axis stage is automatically moved so that each thin film sample piece enters the observation field of view. The rotation angle of a CCD camera that can rotate so that the reference area of the thin film sample piece is horizontal can be automatically calculated by image processing the high-magnification image B of the thin film sample piece and the image A.
(Example 3)
Example 3 is an irradiation electron optical system for irradiating a sample with an electron beam emitted from an electron gun, and a deflector (not shown) that scans the electron beam into the irradiation electron optical system to irradiate the sample. , A control unit (not shown) for controlling electron beam scanning, a sample moving mechanism for moving the sample in the X direction (left and right direction), Y direction (up and down direction), and Z direction (height direction), and the sample orthogonally A sample tilt mechanism (not shown) capable of tilting with two axes, a sample moving mechanism, a control device for controlling the operation of the sample tilt mechanism, and secondary electrons generated by scanning the sample with an electron beam. A detector (not shown) for detecting reflected electrons and transmitted electrons, a unit (not shown) for imaging the detected signal in synchronization with the scanning signal, and means for storing the image signal in a memory of a computer or the like And fewer computers to analyze the image signal In the electron microscope that has at least, the position of the thin film sample piece placed on the sample mesh installed on the sample moving mechanism or the sample tilting mechanism is automatically recognized from the low magnification image, and when performing high magnification observation, The coordinates of the thin film sample piece are calculated and recorded so that the thin film sample piece enters the observation visual field, and the multi-axis stage moves so that the thin film sample piece enters the observation visual field.

  Hereinafter, Example 3 is demonstrated using FIGS. Before carrying the sample mesh 10 with the thin film sample piece 1 to be observed and analyzed into the sample chamber of the electron microscope, the thin film sample piece 1 with the sample mesh (FIG. 3) without the thin film sample piece 1 installed. An image I acquired at a low magnification (hundreds of times) when searching is prepared and stored in the memory 33 of the computer 30.

Next, the sample mesh (FIG. 4) in which the thin film sample piece 1 is placed on the sample mesh 10 is carried into the sample chamber of the electron microscope. Here, the thin film sample piece 1 is prepared using a thin film processing apparatus such as FIB. Moreover, the produced thin film sample piece 1 is mounted on the sample mesh 10 automatically or manually. The thin film sample piece 1 carried into the sample chamber is the sample mesh 1 under the same observation conditions as when the image I was acquired.
Acquire 0 images. This image is set as an image II.

When the images I and II are acquired, the multi-axis stage 28 that changes the position of the sample mesh 10 is set to the neutral position.
By performing pattern matching between the image I and the image II, the rotation angle of the image II with respect to the image I can be calculated. Since the sample mesh 10 is attached to a dedicated sample holder for an electron microscope, the mesh itself is rotating. The state of the image I is set as the basic position, and the rotation angle is calculated.

  By the way, the conventional pattern matching calculates the shift amount of the number of pixels in the X direction (the horizontal direction of the image) and the Y direction (the vertical direction of the image). Depending on the algorithm, the shift amount can be calculated with an accuracy of 1 pixel or less. However, pattern matching considering image rotation and enlargement / reduction has not been possible. However, in recent years, applications that take rotation and enlargement / reduction into account have begun to be marketed due to higher computer functions and improved algorithms, so that the amount of rotation between the two images can be calculated quantitatively.

  When calculating the rotation amount by pattern matching, an accurate rotation angle cannot be calculated if the image is a lattice-like image like a sample mesh. Therefore, depending on the type of the sample mesh, for example, as shown in FIG. 2, by using a region 16 having an asymmetrical shape provided at the center of the sample mesh 10 and using this region as a reference portion for pattern matching. The rotation angle can be calculated.

Next, the analysis unit 32 rotates the rotation angle calculated by the above-described method for the image II by image processing. This image is set as an image III. Then, the average luminance of the image I and the average luminance of the image III are calculated, and the difference between the two average luminances is calculated. This difference is added to either image I or image III to match the brightness of the entire image. Here, for the sake of explanation, the difference is added to the image III, and the image after the difference is added is referred to as an image IV.

The analysis unit 32 creates a difference image between the image I and the image IV by image processing, and sets this image as an image V. In the image V, pixels having substantially the same gradation in the images I and IV are in the vicinity of the 0th gradation due to the difference and appear as black, and a pixel having a greatly different gradation appears as white as the degree of the difference increases. That is, an aggregate of pixels expressed in a color other than black is a thin film sample piece candidate.

  However, other than the thin film sample piece may appear in other than black due to factors such as noise, in order to reduce the error, in advance to determine the threshold of luminance as a collection of pixels that are thin film sample piece candidates, Binarize to narrow down the thin film sample piece candidates. Further, since the approximate size of the thin film sample piece can be known in advance, if the image II acquisition magnification is determined, the range of the number of pixels of the aggregate of candidate pixels for the thin film sample piece 1 can be determined. Sample specimen candidates are narrowed down to thin film specimens. An aggregate of pixels satisfying at least the above conditions is identified as a thin film sample piece.

  Next, one or a plurality of thin film sample piece coordinates on the identified sample mesh 10 are calculated. Each calculated thin film sample piece is an aggregate of pixels as described above. By calculating the luminance centroid of the pixel aggregate, the centroid (center) of the thin film sample piece can be obtained. The calculation of the luminance gravity center is a general image processing method and can be easily performed. The center-of-gravity position is calculated for all of the calculated thin film sample pieces.

Since the images I and II are acquired at the neutral position of the multi-axis stage, the central portion of each image is an observation field for high-magnification observation at the time of the multi-axis stage neutral.
Therefore, in the image III, the difference (number of pixels) between the center of the image and the gravity center position of each thin film sample piece is calculated together with the X direction and the Y direction. Since the magnification at which the image is acquired is known, the distance between the observation visual field center position and each thin film sample piece can be calculated from the number of pixels. However, depending on the electron optical systems 2 and 5, the center of the visual field may change between the low magnification mode and the high magnification mode. In this case, the amount of change is known in advance, so the correction amount is stored in the memory 33 in advance. It correct | amends and calculates the distance of an observation visual field center and each thin film sample piece.

  The calculated distance between the observation visual field center and each thin film sample piece is stored in the memory 33 of the computer 30 together with the above-described image and distance, the calculated pseudonym of the thin film sample piece, and displayed as a list on the UI or the like. The kana of the thin film sample piece 1 may be defined in advance.

  The operator selects the thin film sample piece 1 listed on the UI, so that the multi-axis stage automatically moves the thin film sample piece within the observation field based on the calculated distance information between the observation field center and each thin film sample piece 1. Can move to enter. The list displayed on the UI simultaneously displays a binarized image of the corresponding thin film sample region or an image representing the shape of the thin film sample segment extracted based on the binarized image, so that the operator can display the target thin film sample. It is possible to determine whether the sample is a piece other than a falsely detected thin film sample piece. Therefore, it is possible to determine whether or not the sample is a thin film sample piece before moving the multi-axis stage, and the multi-axis stage is not moved to a position where it is erroneously detected. Therefore, the operator can efficiently work.

  The contents described above can also be implemented by the recipe operation described in the second embodiment. However, the rotation correction of the scanned image is performed by correcting the scanning direction of the electron beam using the electron beam scanning unit. In addition to the recipe, this rotation correction can be instructed by the operator from the UI as described in the second embodiment.

The effects of the present invention described above are listed as follows.
1) The position of the thin film sample piece can be automatically recognized. This is because by acquiring one or several low-magnification images, the position of the thin film sample piece can be automatically recognized by image processing.
2) The position of the thin film sample piece can be automatically stored in the computer, and the multi-axis stage can be easily moved so that the target thin film sample piece enters the observation field of view. This is because the position information of the thin film sample piece can be automatically recognized, and the multi-axis stage coordinates for the target thin film sample piece to enter the observation field can be calculated mathematically.
3) The rotation correction of the thin sample image can be automatically performed. This is because by registering the rotation-corrected image of the target thin film sample piece in the computer in advance, pattern matching is performed with the image before the rotation correction, and the amount of rotation of the image can be calculated.
4) The time for searching for the thin film sample piece can be shortened, and the OFF state of the objective lens at the time of low magnification can also be shortened. In order to search for a thin film sample piece, it is necessary to search at a low magnification. However, when a plurality of thin film sample pieces are placed on a sample mesh, it takes a very long time. Therefore, in the present invention, it is possible to search for a thin film sample piece by acquiring one or a plurality of low-magnification images, which can be completed in a short time. The low magnification mode is often realized by turning off the objective lens due to the characteristics of the electron optical system. If the low-magnification state is continued for a long time, the amount of temperature change of the objective lens increases, causing a focus drift and a magnification (length measurement) error after changing to the high-magnification mode. Therefore, the present invention is very effective.

20 Transmission electron microscope (TEM)
21 Electron gun 22 Irradiation electron optical system 23 Sample 24 Sample stage 25 Imaging electron optical system 26 Image acquisition device 28 Sample moving mechanism 30 Computer 31 Sample position correcting unit 32 Analyzing unit 33 Memory 34 Image display mechanism

Claims (7)

An electron beam source that emits an electron beam;
An irradiation lens system for adjusting the amount of electron beam current;
A sample stage for holding the sample;
A multi-axis stage for operating the sample stage;
A control unit for controlling the movement of the multi-axis stage;
An imaging lens system for enlarging and imaging electrons transmitted through the sample;
An alignment deflector that corrects the trajectory of the electron beam;
A control driver for controlling the lens and alignment deflector of the lens system;
A computer for controlling the control unit;
Means for acquiring a magnified image as digital information using a CCD camera;
Means for storing the digital information in a computer;
Means for computing the digital information by a computer;
In an electron microscope having at least
An apparatus for recognizing a thin film sample in an electron microscope, which recognizes the position of one or a plurality of thin film sample pieces placed on a sample mesh from a low-magnification image and calculates and records the barycentric coordinates of the thin film sample pieces.   An electron microscope image of a sample mesh in which the thin film sample piece is not installed is registered in a computer in advance by magnification, and an electron microscope image of the sample mesh in which the thin film sample piece is installed and the thin film sample piece is not installed 2. The electron according to claim 1, wherein the electron microscope image obtained at the same magnification as the electron microscope image of the sample mesh on which the thin film sample piece of the sample mesh is installed is image-processed to calculate the position of the thin film sample piece. Thin film sample position recognition device in a microscope.   The center of gravity position of the thin film sample piece is calculated, the amount of movement for moving the multi-axis stage necessary for the thin film sample piece to enter the observation field of view is calculated from the barycentric coordinate information of the thin film sample piece, and the operator's instruction 3. The apparatus for recognizing a thin film sample position in an electron microscope according to claim 1, wherein the multi-axis stage moves so that the designated thin film sample piece falls within the observation field.   For the recognized thin film sample piece, the position information and the image information at the time of recognition are displayed as a list on the user interface, and the multi-axis stage moves so that the thin film sample piece falls within the observation field of view according to an operator's instruction. The thin film sample position recognition apparatus in an electron microscope according to claim 3.   The operation of the electron microscope is registered in advance in a recipe, and the multi-axis stage movement is performed from recognition of all thin film sample piece positions in an electron microscope that can operate as registered. Thin film sample position recognition device in an electron microscope.   An electron microscope image A whose rotation-corrected image of the thin film sample piece is registered in a computer in advance, the multi-axis stage moves so that each thin film sample piece enters the observation field of view, and a high-magnification image B of the thin film sample piece 6. The rotation angle of a CCD camera that can be rotated so that the reference region of the thin film sample piece is horizontal by image processing of the image A and the image A, and the CCD camera rotates. The thin film sample position recognition apparatus in the electron microscope of Claim 1.   An electron microscope capable of acquiring a scanning secondary electron image, a scanning reflection electron image, and a scanning transmission image using a deflector in an irradiation lens system for adjusting the amount of electron beam current is placed on a sample mesh by a low-magnification scanning image. One or a plurality of thin film sample piece positions are recognized, and the barycentric coordinates of the thin film sample piece are calculated and recorded, and the operation of the second to fifth aspects is provided, and the rotation of the thin film sample piece is corrected. The image A is registered in advance in the computer, the multi-axis stage is automatically moved so that each thin film sample piece falls within the observation field, and the high magnification image B and the image A of the thin film sample piece are processed by image processing. An apparatus for recognizing a thin film sample position in an electron microscope, which calculates a correction amount in a scanning direction of an electron beam so that a reference position of a sample piece is horizontal, and rotates a scanned image.

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