JP2010237200A - Method and device for observing specimen, and method and device for inspecting specimen using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for observing a specimen allowing a minute pattern to be observed. <P>SOLUTION: According to this method for observing a specimen, the pattern of the specimen is observed by using an electron beam. In this method, the electron beam is applied to the specimen to detect mirror electrons arising therefrom by the application of the electron beam, and an image of the specimen is generated from the detected mirror electrons. In a step of applying the electron beam, an electron beam is applied to the specimen with the landing energy LE of the electron beam adjusted so that applied electrons U-turn in a recess pattern to act as mirror electrons when the electron beam is applied thereto in a recess pattern with edges on both sides. A suitable condition therefor is LEA≤LE≤LEB+5[eV]. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sample observation method and apparatus for observing a pattern on a sample using an electron beam, and more particularly to a technique for observing a fine pattern using an electron beam having a low landing energy.

  In the manufacturing field of semiconductor devices and the like, a substrate-like sample (sample substrate) such as a wafer or a mask is observed. Sample observation is performed for sample inspection such as structural evaluation, enlarged observation, material evaluation, and confirmation of an electrical conduction state. In the inspection of the sample substrate, there are demands for high accuracy, high reliability, and high throughput. Therefore, it is desired to provide a sample observation technique that meets these requirements. Further, such sample observation technology and sample inspection technology are frequently used even during the device manufacturing process. The target sample is a semiconductor material, LSI, metal material, insulating material, or the like.

  Conventionally, when observing a pattern on a sample, an optical microscope or an electron beam observation apparatus is used. As a typical electron beam observation apparatus, a scanning electron microscope (SEM) is known. SEM enables observation at a high magnification by scanning an electron beam on a sample. An observation technique using SEM is disclosed in, for example, Patent Document 1.

  As an electron beam observation apparatus, an observation apparatus using a mapping projection optical system has also been proposed. Hereinafter, this type of observation apparatus is referred to as a mapping projection type observation apparatus. The projection projection observation apparatus irradiates a sample with an electron beam having a diameter larger than that of the SEM, and generates an image in a range corresponding to the diameter of the electron beam. Such an observation apparatus is disclosed in Patent Document 2, for example.

JP 2004-177446 A JP-A-11-108864

  By the way, recently, the pattern on the sample has become finer, and the pattern size (width, etc.) has reached 100 nm or less. For this reason, it is difficult to observe pattern shapes and pattern defects with conventional observation techniques.

  That is, in optical observation, the resolution is limited by the wavelength of light. When the pattern size is 100 nm or less, the pattern size becomes smaller than the wavelength of light, and as a result, sufficient resolution cannot be obtained and pattern defect detection becomes difficult.

On the other hand, in pattern observation and pattern defect inspection using SEM, the resolution can be increased by reducing the spot size of the electron beam. Therefore, even when the pattern size is 100 nm or less, the pattern can be observed and the pattern defect can be inspected. However, in order to observe a fine pattern, it is necessary to reduce the pixel size, and it takes an enormous amount of time for observation. For example, in order to detect a defect having a size of 50 nm, it is necessary to perform observation with a pixel size of about 10 nm. In this case, even if the inspection is performed at 200 MPPS (Mega pixel per second), it takes 1.4 hours per 1 cm ² . Therefore, it takes an enormous amount of time for one observation and is not practical.

  In addition, the mapping projection observation apparatus is configured to generate an image of a wide area by irradiating a sample with a large-diameter electron beam, thereby enabling observation in a shorter time than the SEM. However, when the pattern size is 100 nm or less, sufficient contrast cannot be obtained and the resolution is insufficient.

  More specifically, in the projection projection observation apparatus, the primary optical system irradiates the sample with an electron beam, and the secondary optical system generates an image of secondary electrons emitted from the sample. The imaging range (beam irradiation range) can be set to several tens of μm or more, and the observation time is short. However, the aberration of the secondary optical system cannot be sufficiently reduced, and it is not easy to realize the resolution required for observation of a pattern size of 100 nm or less.

  The present invention has been made under the above-described background, and an object thereof is to provide a technique that enables observation and inspection of a fine pattern on a sample.

  The sample observation method according to the first aspect of the present invention is a sample observation method for observing a pattern on a sample using an electron beam, and is generated by irradiating the sample with an electron beam and irradiating the electron beam. A step of detecting mirror electrons and a step of generating an image of a sample from the detected mirror electrons, and the step of irradiating the electron beam includes irradiating the concave pattern having edges on both sides with the electron beam. The sample is irradiated with the electron beam whose landing energy is adjusted so that the irradiated electrons are U-turned in the concave pattern to become mirror electrons.

  In the above configuration, the present invention pays attention to the characteristic of the mirror electron generation phenomenon that the mirror electrons are likely to be generated in the concave pattern because there are edges on both sides. The amount of mirror electrons generated in the concave pattern depends on the landing energy of the electron beam. Therefore, the landing energy is set so that the irradiation electrons efficiently become mirror electrons in the concave pattern. As will be described later, the landing energy is set to a considerably low value. Thereby, the resolution and contrast of the concave pattern can be increased, and a fine pattern can be observed.

  In the present invention, a mapping projection observation apparatus is preferably used. Thereby, a fine pattern can be observed in a short time.

  The landing energy may be set in a region where the mirror electrons and secondary emission electrons are mixed.

  Thereby, the landing energy can be appropriately set so that mirror electrons are generated in the pattern, and the contrast of the pattern can be increased.

  The landing energy may be set to LEA ≦ LE ≦ LEB + 5 eV. Here, LE is the landing energy of the electron beam, and LEA and LEB are the lowest landing energy and the highest landing energy in a region where the mirror electrons and secondary emission electrons are mixed.

  Thereby, the landing energy can be appropriately set so that mirror electrons are generated in the pattern, and the contrast of the pattern can be increased.

  The irradiation electrons may be incident on one edge of the concave pattern, bend toward the other edge in the vicinity of the one edge, and bend near the other edge to become mirror electrons.

  Thereby, it is possible to appropriately detect the mirror electrons by using the phenomenon that the mirror electrons are generated in the pattern, and to increase the contrast of the pattern.

  The irradiated electrons are incident toward one edge of the concave pattern, enter the concave pattern along a curved path passing through the vicinity of the one edge, and proceed without colliding with the bottom of the concave pattern. The direction may be changed to pass through the vicinity of the other edge of the concave pattern to become the mirror electrons.

  Thereby, it is possible to appropriately detect the mirror electrons by using the phenomenon that the mirror electrons are generated in the pattern, and to increase the contrast of the pattern.

  In the present invention, an aperture is disposed in a secondary optical system between the sample and the detector of the mirror electrons, and at least one of the size, position, and shape of the aperture is assigned to the mirror electrons passing through the aperture. It may be adjusted accordingly.

  Thereby, the contrast of the pattern can be increased. More specifically, the electrons detected from the sample include mirror electrons and secondary emission electrons. Secondary emission electrons spread over a wide range, while mirror electrons do not spread much. Therefore, by appropriately adjusting the aperture according to the mirror electrons, it is possible to reduce the secondary emission electrons passing through the aperture and relatively increase the detection amount of the mirror electrons. Therefore, the contrast of the pattern can be further increased.

  In the present invention, an image of the mirror electrons in the aperture may be generated, and the size of the aperture may be adjusted according to the size of the image. In the present invention, an image of the mirror electrons in the aperture may be generated, and the position of the aperture may be adjusted according to the position of the image. In the present invention, an image of the mirror electrons in the aperture may be generated, and the shape of the aperture may be adjusted according to the shape of the image.

  The present invention may be a sample inspection method, in which an image of the sample is generated from the mirror electrons by the sample observation method described above, and the pattern of the sample may be inspected using the image of the sample.

  Thereby, a fine pattern can be suitably inspected using the sample observation method of the present invention.

  The sample observation apparatus of the first aspect of the present invention detects a stage on which a sample having a pattern is placed, a primary optical system that irradiates the sample with an electron beam, and mirror electrons generated by the irradiation of the electron beam. A secondary optical system that generates an image of a sample from the detected mirror electrons, and the primary optical system is configured to irradiate a concave pattern having edges on both sides with the electron beam. The sample is irradiated with the electron beam whose landing energy is adjusted so that the irradiated electrons make U-turns in the concave pattern and become mirror electrons.

  In this configuration as well, as described above, the landing energy is adjusted so that mirror electrons are likely to be generated by paying attention to the phenomenon that mirror electrons are likely to be generated due to the concave pattern. Thereby, the resolution and contrast of the pattern image can be increased, and a fine pattern can be observed.

  The primary optical system may irradiate the electron beam having the landing energy set in a region where the mirror electrons and secondary emission electrons are mixed.

  Thereby, as described above, the landing energy can be set appropriately, and the contrast of the pattern can be increased.

  The landing energy may be set to LEA ≦ LE ≦ LEB + 5 eV. Here, LE is the landing energy of the electron beam, and LEA and LEB are the lowest landing energy and the highest landing energy in a region where the mirror electrons and secondary emission electrons are mixed.

  Thereby, as described above, the landing energy can be set appropriately, and the contrast of the pattern can be increased.

  The secondary optical system has an aperture arranged between the sample and the mirror electron detector, and at least one of the size, position, and shape of the aperture according to the mirror electrons passing through the aperture. You can adjust it.

  Thereby, as above-mentioned, an aperture can be adjusted appropriately according to mirror electrons. Secondary emission electrons passing through the aperture can be reduced, the detection amount of mirror electrons can be relatively increased, and the pattern contrast can be further increased.

  In the present invention, the secondary optical system may have an aperture, and the position of the aperture may be adjusted so that the center of intensity of the mirror electron coincides with the center of the aperture.

  As a result, mirror electrons can be detected well, and the amount of secondary emission electrons detected can be relatively reduced. Therefore, a high contrast image can be acquired.

  The secondary optical system may have an aperture, and the shape of the aperture may be an elliptical shape having a major axis in a direction corresponding to a longitudinal direction of the intensity distribution of the mirror electrons.

  In this configuration, an elliptical aperture is used according to the intensity distribution of the mirror electrons. Thereby, an image with high contrast can be acquired.

  The secondary optical system may have an aperture, the aperture may have a plurality of holes, and the plurality of holes may be arranged so as to surround the intensity center of the mirror electrons.

  In this configuration, the plurality of holes are appropriately arranged according to the scattering direction of the mirror electrons. Thereby, mirror electrons can be detected appropriately according to the application and properties.

  The secondary optical system may have an aperture, the aperture may have a plurality of holes, and one of the plurality of holes may be arranged so as to coincide with the intensity center of the mirror electron.

  Thereby, it is possible to appropriately observe an observation target having a characteristic in the scattering direction. Information useful for classification of observation objects can be obtained.

  The present invention may be a composite type sample observation apparatus, and may include a mapping projection observation apparatus and an SEM observation apparatus different from the mapping projection observation apparatus. The mapping projection observation apparatus may be the above-described sample observation apparatus. The mapping projection observation apparatus and the SEM observation apparatus may be provided in a chamber that accommodates a stage, and the stage is located between the observation position of the mapping projection observation apparatus and the observation position of the SEM observation apparatus. It may be movable.

  As a result, the mapping projection observation apparatus and the SEM observation apparatus are mounted in a common chamber. Therefore, observation using the two devices can be performed quickly and with high accuracy. For example, a pattern defect is detected by a mapping projection observation apparatus. The pattern defects are then reviewed in detail with SEM. Such a defect inspection can be performed quickly and with high accuracy.

  In the sample observation method according to the second aspect of the present invention, a sample placed on the same stage is observed by an optical microscope and an SEM type observation device different from the projection type observation device and the projection type observation device. A method for observing a composite sample for storing a positional relationship of optical centers of each of the three observation devices of the mapping projection observation device, the SEM observation device, and the optical microscope as coordinate data. The stage is moved between the three optical centers based on the data, and specific portions on the sample are individually observed by the three observation devices.

  More specifically, the sample observation method according to the second aspect of the present invention includes the following steps. (A) A region on which a sample having a specific pattern arrangement is placed on a stage capable of rotating in the XY plane, which is the sample placement surface, and moving in the X and Y directions, and including the specific pattern arrangement Adjusting the sample position on the stage so that the arrangement direction of the specific pattern is the X direction or the Y direction, and (b) by the sample observation method of the first aspect described above A mirror electronic image of a region including the specific pattern arrangement of the sample is obtained, the direction of the specific pattern arrangement is made to coincide with the X direction or the Y direction of the mirror electronic image, and the specific pattern is the mirror electron Adjusting the detection system of the mirror electrons so as to be in the center of the frame of the image; (c) observing a region including the specific pattern of the sample by SEM, and detecting the specific pattern of the sample; A step of adjusting the optical system of the SEM type observation apparatus so as to be at a predetermined center of the SEM image; (d) position coordinates of each stage after the adjustment in the steps (a), (b), and (c); Correlating each other and calculating at least one of the other two position coordinates from any one of these three position coordinates.

  Preferably, the step (a), the step (b), the step (c), and the step (d) are executed in this order.

  In the sample observation method of the second aspect of the present invention, each image obtained by sample observation using an optical microscope, sample observation using a mirror electron image, and sample observation using an SEM image corresponds to which position of the observation target sample. Can be associated with each other. Thereby, even when an observation target location specified by a certain method among the three observation methods is to be observed by another observation method, the observation target location can be specified quickly and accurately.

  According to the sample inspection method of the second aspect of the present invention, an image of the sample is generated from the mirror electrons by the sample observation method of the second aspect of the present invention, and the pattern of the sample is inspected using the image of the sample. Steps to do.

  The sample inspection method according to the second aspect of the present invention further includes (f) a step of performing SEM observation of a pattern defect portion determined by the pattern inspection in the step (e) to determine the authenticity of the defect. It can be set as an aspect.

  The sample inspection method according to the second aspect of the present invention further includes (g) a step of classifying the defect type of the pattern defect portion determined to be a true defect in the step (f). can do.

  The sample inspection method according to the second aspect of the present invention further includes (h) a coordinate file of a pattern defect portion determined as a true defect in the step (f), the optical microscope image, the mirror electronic image. And a step of associating and creating at least one image of the SEM image.

  According to the sample inspection method of the second aspect of the present invention, in addition to being able to suitably inspect a fine pattern, it is possible to determine the authenticity of a defect, classify a defect type, and specify a position in an observation image.

  The sample observation apparatus according to the second aspect of the present invention includes a mapping projection observation apparatus, a SEM observation apparatus different from the mapping projection observation apparatus, and an optical microscope, and the mapping projection observation apparatus includes: In the sample observation apparatus according to the first aspect of the present invention described above, the mapping projection observation apparatus, the SEM observation apparatus, and the optical microscope are provided in a chamber that houses the stage, and the stage includes the stage It is possible to move between the observation position of the mapping projection observation apparatus, the observation position of the SEM observation apparatus, and the observation position of the optical microscope.

  The sample observation apparatus according to the second aspect of the present invention stores the positional relationship of the optical centers of the projection projection observation apparatus, the SEM observation apparatus, and the optical microscope as coordinate data, and stores the stage as the 3 It is also possible to adopt a mode in which a control unit that can move between two optical centers is provided.

  Preferably, the stage is a stage that is movable in the X direction and the Y direction within the sample placement surface and is rotatable within the XY plane.

  Preferably, the detector provided in the secondary optical system of the mapping projection observation apparatus is configured to be capable of rotational adjustment in the XY plane which is an electron detection surface.

  Furthermore, it is preferable that an alignment unit that adjusts the position of the sample on the stage so that the arrangement direction of the specific pattern on the sample coincides with the X direction or the Y direction that is the moving direction of the stage is provided.

  The alignment unit performs the detection so that an arrangement direction of a specific pattern on the sample after the sample position adjustment matches an X direction or a Y direction of a frame of a mirror electronic image obtained by the mapping projection observation apparatus. Can be adjusted.

  In addition, the alignment unit is configured so that the observation image obtained by observing a specific pattern on the sample after the sample position adjustment by the SEM type observation device is positioned at the center of the SEM image. The optical system can be adjusted.

  The sample observation apparatus according to the second aspect of the present invention includes a gas supply unit that supplies a cleaning gas for removing contaminants attached to the surface of the sample, and a gas that guides the cleaning gas into the chamber. It is good also as an aspect provided with the introduction part.

  For example, the cleaning gas is a gas that exhibits a removing action by reacting with the contaminants or a gas that exhibits the removing action upon irradiation with the electron beam.

  In the sample observation apparatus according to the second aspect of the present invention, each image obtained by sample observation using an optical microscope, sample observation using a mirror electron image, and sample observation using an SEM image corresponds to which position of the observation target sample. Are associated with each other. Thereby, even when an observation target location specified by a certain method among the three observation methods is to be observed by another observation method, the observation target location can be specified quickly and accurately.

  The present invention may be a sample inspection apparatus provided with the sample observation apparatus according to the first or second aspect described above, and the inspection apparatus uses an image of the sample generated from the mirror electrons by the image processing unit. Used to inspect the pattern of the sample. Thereby, a fine pattern can be suitably inspected using the sample observation apparatus of the present invention.

  The image processing unit may include an arithmetic unit that performs SEM observation of a pattern defect portion determined by the pattern inspection to determine whether the defect is true or false.

  It is preferable that the calculation unit is capable of classifying defect types of defective pattern portions determined to be true defects.

  Further, the calculation unit can create a coordinate file of a pattern defect portion determined as a true defect in association with at least one of the optical microscope image, the mirror electronic image, and the SEM image. It is preferable.

  As described above, the present invention irradiates the sample to be observed with the electron beam whose landing energy is adjusted so that the irradiated electrons make U-turns in the concave pattern on the sample and become mirror electrons. Therefore, it is possible to provide a technique that enables observation and inspection of a fine pattern.

  Further, in the sample observation method and apparatus according to the second aspect of the present invention, each image obtained by sample observation using an optical microscope, sample observation using a mirror electron image, and sample observation using an SEM image indicates which position of the observation target sample. Therefore, even if an observation target location specified by one of the three observation methods is to be observed by another observation method, the observation target location is It becomes possible to specify quickly and accurately.

FIG. 1 is a diagram showing the relationship between landing energy and gradation when a sample is irradiated with an electron beam. FIG. 2 is a diagram illustrating a phenomenon in which mirror electrons and secondary emission electrons are generated in the transition region. FIG. 3 is a diagram showing the relationship between the landing energy and the gradation at the edge of the concavo-convex structure on the sample surface. FIG. 4 is a diagram illustrating an example of a concavo-convex structure of a pattern formed on a sample. FIG. 5 is a diagram illustrating a phenomenon in which mirror electrons are generated at the edge portion of the concavo-convex structure when the electron beam is irradiated. FIG. 6 is a diagram illustrating a phenomenon in which mirror electrons are generated at the edge portion of the concavo-convex structure when the electron beam is irradiated. FIG. 7 is a diagram illustrating a phenomenon in which mirror electrons are generated at the edge portion of the concavo-convex structure when the electron beam is irradiated. FIG. 8 is a diagram illustrating another example of the uneven structure of the pattern formed on the sample. FIG. 9 is a diagram showing the overall configuration of the sample inspection apparatus. FIG. 10 is a diagram showing a main part of the sample inspection apparatus. FIG. 11 is a diagram showing a main chamber, an electronic column, and an SEM, which are a part of the sample inspection apparatus. FIG. 12 is a diagram showing a configuration including an EB-CCD for measuring the signal intensity in the aperture. FIG. 13 is a diagram showing a conventional aperture as a reference example. FIG. 14 is a diagram showing an example of the shape of the aperture. FIG. 15 is a diagram illustrating an example of a configuration of an aperture member having a plurality of holes. FIG. 16 is a diagram illustrating an example of a configuration of an aperture member having a plurality of holes. FIG. 17 is a view showing an example of the configuration of an aperture member having four holes. FIG. 18 is a diagram showing an example of another configuration of an aperture member having four holes. FIG. 19 is a diagram showing a configuration example of a part of the sample observation apparatus according to the second aspect of the present invention. FIG. 20 is a diagram for explaining the basic concept of the sample observation method according to the second aspect of the present invention. FIG. 21 is a diagram for exemplifying a procedure for performing observation using the sample observation apparatus according to the second aspect of the present invention. FIG. 22 is a diagram for exemplifying the procedure for performing observation using the sample observation apparatus according to the second aspect of the present invention. FIG. 23A shows a sample on the stage at the start of OM observation. FIG. 23B shows the sample on the stage after alignment. FIG. 24 shows the extension or arrangement direction of the pattern on the sample after alignment is completed (FIG. 24A), the pixel arrangement direction of the sensor of the detector 70 before alignment (FIG. 24B), and It is a figure for demonstrating the mutual relationship of the pixel array direction (FIG.24 (c)) of the sensor of the detector 70 after alignment. FIG. 25 shows the extension or arrangement direction of the pattern on the sample after alignment of the detector (FIG. 25A), and the state of the mirror electron image of the alignment “+” pattern obtained by the detector before alignment. It is a figure for demonstrating notionally the mutual relationship of the mode (FIG.25 (c)) of the mirror electronic image of the said pattern obtained with the detector after alignment (FIG.25 (b)). FIG. 26 shows the extension or arrangement direction of the pattern on the sample after completion of the alignment of the detector 7 (FIG. 26A), and the mirror electron image of the alignment “+” pattern obtained by the aligned detector. The relationship between the state (FIG. 26B) and the state of the mirror electronic image of the alignment “+” pattern after the alignment of the center coordinates of the image frame (FIG. 26C) is conceptually illustrated. It is a figure for demonstrating. FIG. 27 is a diagram for conceptually explaining the configuration of an apparatus in which a sample cleaning function is added to the sample observation apparatus according to the second aspect of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In the present embodiment, a sample is observed using a mapping projection observation apparatus (an electron beam observation apparatus having a mapping projection optical system). This type of electron beam observation apparatus includes a primary optical system and a secondary optical system. The primary optical system irradiates a sample with an electron beam emitted from an electron gun, and generates electrons obtained from information such as the structure of the sample. The secondary optical system has a detector and generates an image of electrons generated by irradiation with an electron beam. In the projection type observation apparatus, a large-diameter electron beam is used, and a wide range of images can be obtained.

  When the sample is irradiated with an electron beam, a plurality of types of electrons are detected by the secondary optical system. The plural types of electrons are mirror electrons, secondary electrons, reflected electrons, and backscattered electrons. In this embodiment, a sample is observed mainly using the characteristics of mirror electrons. Mirror electrons are electrons that do not collide with the sample and bounce immediately before the sample. The mirror electron phenomenon is caused by the action of the electric field on the sample surface.

  In this embodiment, secondary electrons, reflected electrons, and backscattered electrons are referred to as secondary emission electrons. Even when these three types of electrons are mixed, the term secondary emission electrons is used. Of the secondary emission electrons, secondary electrons are typical. Therefore, secondary electrons may be described as representative of secondary emission electrons. For both mirror electrons and secondary emission electrons, expressions such as “emitted from the sample”, “reflected from the sample”, and “generated by electron beam irradiation” may be used.

  FIG. 1 shows the relationship between the landing energy LE and the gradation DN when the sample is irradiated with an electron beam. The landing energy LE is energy given to the electron beam irradiated on the sample. Assume that an acceleration voltage Vacc is applied to the electron gun and a retarding voltage Vrtd is applied to the sample. In this case, the landing energy LE is represented by the difference between the acceleration voltage and the retarding voltage (LE = Vacc−Vrtd).

  In FIG. 1, the gradation DN on the vertical axis represents the luminance in an image generated from electrons detected by the detector of the secondary optical system. That is, the gradation DN represents the number of detected electrons. As more electrons are detected, the gradation DN increases.

  FIG. 1 shows gradation characteristics in a small energy region near 0 [eV]. As shown in the figure, in a region where LE is greater than LEB (LEB <LE), the gradation DN shows a relatively small constant value. In a region where LE is equal to or lower than LEB and equal to or higher than LEA (LEA ≦ LE ≦ LEB), the gradation DN increases as LE decreases. In the region where LE is smaller than LEA (LE <LEA), the gradation DN shows a relatively large constant value.

  The gradation characteristics are related to the type of electrons detected. In the region of LEB <LE, almost all detected electrons are secondary emission electrons. This region can be called a secondary emission electron region. On the other hand, in the region of LE <LEA, almost all detected electrons are mirror electrons. This region can be called a mirror electron region. As shown in the figure, the gradation of the mirror electron region is larger than that of the secondary emission electron region. This is because the range of distribution of mirror electrons is smaller than that of secondary emission electrons. Since the distribution range is small, more electrons can reach the detector, and the gradation becomes large.

  The region of LEA ≦ LE ≦ LEB is a transition region from the secondary emission electron region to the mirror electron region (or vice versa). This region is a region where mirror electrons and secondary emission electrons are mixed, and can also be referred to as a mixed region. In the transition region (mixed region), the smaller the LE is, the more mirror electrons are generated and the gradation is increased.

  LEA and LEB mean the lowest landing energy and the highest landing energy in the transition region. Specific values of LEA and LEB will be described. According to the research results of the present inventors, LEA is −5 [eV] or more and LEB is 5 [eV] or less (that is, −5 [eV] ≦ LEA ≦ LEB ≦ 5 [eV]).

  The advantages of the transition area are as follows. In the mirror electron region (LE <LEA), all electrons generated by beam irradiation become mirror electrons. Therefore, regardless of the shape of the sample, all the detected electrons are mirror electrons, and the difference in gradation is reduced in both the concave and convex portions of the sample, and the S / N and contrast of the pattern and defect are reduced. Therefore, it may be difficult to use the mirror electron region for inspection. In contrast, in the transition region, mirror electrons are generated characteristically and specifically at the edge portion of the shape, and secondary emission electrons are generated at other portions. Therefore, the S / N and contrast of the edge can be increased. Therefore, the transition region is very effective when performing inspection. Hereinafter, this point will be described in detail.

  FIG. 2 shows the phenomenon of the above transition region. In FIG. 2, in the mirror electron region (LE <LEA), all electrons become mirror electrons without colliding with the sample. In contrast, in the transition region, some electrons collide with the sample, and the sample emits secondary electrons. As LE increases, the proportion of secondary electrons increases. Although not shown, when LE exceeds LEB, only secondary electrons are detected.

  Next, FIG. 3 shows the relationship between the landing energy LE and the gradation DN at the edge of the concavo-convex structure on the sample surface. The edge portions are portions where the height of the sample is changed at both ends of the concave portion. In FIG. 3, the dotted line indicates the gradation characteristic of the edge portion, and the solid line indicates the gradation characteristic of the other part. The characteristics of the other parts correspond to the characteristics of FIG.

  As shown in FIG. 3, the characteristic lines are different between the edge portion and other portions. The characteristic line of the edge portion is shifted in the direction in which the landing energy increases. That is, in the edge portion, the upper and lower limits of the transition region are large, and the upper limit of the transition region is LEB + 5 [eV]. Here, LEB is the upper limit of the transition region of the part other than the edge. The characteristic line shift occurs because the shape, structure, material, and the like are different between the edge portion and other portions. Then, due to the deviation of the characteristic line, a gradation difference ΔDN occurs between the edge portion and other portions.

  Next, the reason why the characteristics of the edge part are different from other parts as shown in FIG. 3 and the reason why the gradation difference ΔDN occurs will be examined.

FIG. 4 is an example of the concavo-convex structure of the sample, and shows a fine line / space cross section. For example, the convex portion is a line and the concave portion is a space. The line width and space width are 100 μm or less. In the shape of FIG. 4, the conductor (Si) has an uneven shape. An oxide film (SiO ₂ or the like) is formed on the top of the convex portion.

  FIG. 5 shows a phenomenon in which mirror electrons are generated at the edge of the concavo-convex structure when the structure of FIG. 4 is irradiated with an electron beam. In FIG. 5, a pattern of vertical stripes is formed. When the electron beam is irradiated, the irradiated electron changes its trajectory in the vicinity of one edge of the concave portion (groove), bends in the lateral direction, and proceeds toward the opposite edge of the groove. The irradiated electrons change their trajectory again near the opposite edge and return upward. Thus, the irradiated electrons become mirror electrons without colliding with the sample. The mirror electrons generated at the edge in this way can be called edge mirror electrons. Edge mirror electrons are generated symmetrically from the edges at both ends. FIG. 6 also shows the edge mirror electrons generated in the structure of FIG. 4 as in FIG. In FIG. 6, a horizontal stripe pattern is formed.

  FIG. 7 is another example of an electron trajectory in which irradiated electrons change to edge mirror electrons. In this example, irradiated electrons are incident toward one edge of the recess, enter the recess along a curved path passing through the vicinity of the one edge, and change the traveling direction without colliding with the bottom of the recess. , It passes through the vicinity of the other edge of the recess and becomes mirror electrons. Such mirror electrons are also edge mirror electrons. In the edge structure, each irradiation electron passes through the trajectory of FIG. 5 or FIG. 7 or an intermediate trajectory of FIG. 5 and FIG.

  Next, the reason why the electron trajectory tends to bend near the edge will be described. In the structure of FIG. 5, an oxide film is formed on the surface of the convex portion of the conductor. In this structure, the oxide film on the sample surface is negatively charged. And the electric potential of the conductor in a recessed part becomes relatively higher than the electric potential of an oxide film. Since the potential changes in the vicinity of the edge, the trajectory of the electrons is easily bent as described above, and as a result, edge mirror electrons are generated.

  In this embodiment mode, precharging is also preferable. Precharge is irradiation of an electron beam performed before sample observation. By precharging, the insulating region of the sample is negatively charged (in the example of FIG. 5 and the like, the oxide film on the sample surface is negatively charged). By performing the precharge, the potential of the insulating region is stabilized. As a result, edge mirror electrons are stably generated, and the characteristics shown in FIG. 3 are stably obtained. Therefore, sample observation can be performed satisfactorily and the accuracy of inspection using the sample observation result can be improved.

  The precharged electron beam may be irradiated using an electron optical system for sample observation. Alternatively, another electron gun may be provided for precharging.

FIG. 8 shows another example of the uneven structure of the sample. FIG. 8 is also a cross section of a line / space shape. In FIG. 8, a convex portion of an oxide film (SiO ₂ or the like) is formed on the Si surface. In such a structure, the equipotential surface is bent at the edges on both sides of the recess. The trajectory of irradiated electrons bends due to the bending of the equipotential surface. As a result, also in the structure of FIG. 8, the irradiated electrons pass through the trajectories shown in FIGS. 5 to 7 and become edge mirror electrons. Also in the structure of FIG. 8, precharge is suitably performed, and thereby the potential of the oxide film at the convex portion can be stabilized.

  Further, the concavo-convex structure may be formed only by the conductive material. Also in this case, an equipotential surface is formed along the unevenness. The equipotential surface is bent at the edges on both sides of the recess. The trajectory of the irradiated electrons is bent due to the bending of the equipotential surface. As a result, the irradiated electrons pass through the trajectory as described above and become edge mirror electrons.

  Even when the uneven surface is formed only of the conductive material, a natural oxide film exists on the surface of the conductive film. Therefore, it is preferable to perform precharging, which can stabilize the potential.

  As described in detail above, in the concave portion of the sample, electrons make a U-turn through the vicinity of both edges and become edge mirror electrons. For this reason, the edge mirror electrons are more likely to be generated than the mirror electrons at the normal site. As a result, as shown in FIG. 3, in the edge portion, the transition region spreads to the higher energy side than the portion other than the edge.

  Further, in the region, mirror electrons and secondary emission electrons are mixed. As described above, the secondary emission electrons are secondary electrons, reflected electrons, or backscattered electrons (or a mixture thereof). Secondary emission electrons are isotropically spread and emitted. Therefore, only a few percent of electrons reach the detector at the maximum. On the other hand, edge mirror electrons are generated by reflecting irradiated electrons as they are. Therefore, for edge mirror electrons, the transmittance (the arrival rate at the detector) is almost 100%. Therefore, high luminance (gradation) is obtained, and the gradation difference ΔDN from the surroundings becomes large.

  As described above, mirror electrons are easily generated at the edge portion, and the transmittance of the mirror electrons is large. As a result, as shown in FIG. 3, as the landing energy LE increases, the gradation characteristic line of the edge portion shifts, and a gradation difference ΔDN occurs between the edge portion and other portions.

  The present embodiment uses the above phenomenon to generate a pattern image with high resolution and high contrast. The concave structure described above corresponds to the concave pattern of the present invention. In the present embodiment, landing energy is set so that edge mirror electrons are efficiently generated in the concave pattern. As shown in the figure, the landing energy LE is set to a very low value as compared with the conventional general observation technique. By such energy setting, the gradation difference ΔDN between the pattern and the surroundings becomes large, and an image with high resolution and high contrast can be obtained.

  Specifically, the landing energy LE is set so that LEA ≦ LE ≦ LEB or LEA ≦ LE ≦ LEB + 5 [eV]. Thereby, the landing energy LE is set in a region where mirror electrons and secondary electrons are mixed.

  As described above, in the research result of the present invention, −5 [eV] ≦ LEA ≦ LEB ≦ 5 [eV]. For example, it is assumed that LEA = −5 [eV] and LEB = 5 [eV]. In this case, the landing energy LE is set to −5 [eV] ≦ LE ≦ 5 + 5 [eV] = 10 [eV]. More specifically, depending on the landing energy LE, the situation of the mixture of mirror electrons and secondary emission electrons changes, and the gradation difference also changes. It is considered that a great effect can be obtained by setting the landing energy LE in a region where the number of mirror electrons generated is relatively small.

  Next, a sample observation apparatus for realizing the sample observation method will be described. In the following description, a sample observation device is incorporated in a sample inspection device and used for inspection of a pattern defect of a sample. FIG. 9 shows the overall configuration of the sample inspection apparatus, and FIG. 10 shows the main part of the sample inspection apparatus.

  Referring to FIG. 9, the sample inspection apparatus 10 includes a sample carrier 12, a mini-environment 14, a load lock 16, a transfer chamber 18, a main chamber 22, an electronic column 24, and an image processing device 90. The mini-environment 14 is provided with a transfer robot in the atmosphere, a sample alignment device, a clean air supply mechanism, and the like. The transfer chamber 18 is provided with a transfer robot in vacuum.

  The main chamber 22 is provided with a stage 30 so as to move in the x direction, the y direction, and the θ (rotation) direction. An electrostatic chuck is installed on the stage 30. The sample itself is placed on the electrostatic chuck. Alternatively, the sample is held on the electrostatic chuck in a state where it is placed on a pallet or jig.

  The main chamber 22 is controlled by a vacuum control system 26 so that a vacuum state is maintained in the chamber. Further, the main chamber 22, the transfer chamber 18, and the load lock 16 are placed on a vibration isolation table 28, and are configured so that vibration from the floor is not transmitted.

  An electronic column 24 is installed in the main chamber 22. The electron column 24 includes an electron gun, a lens, wiring, and a field through, and further includes a detector 70 as shown. These configurations realize a primary optical system and a secondary optical system for mapping projection with an electron beam.

  The output signal of the detector 70 is sent to the image processing device 90 for processing. Both on-time signal processing and off-time signal processing are possible. On-time signal processing is performed during the inspection. When performing off-time signal processing, only an image is acquired and signal processing is performed later. Data processed by the image processing apparatus is stored in a recording medium such as a hard disk or a memory. Moreover, it is possible to display data on the monitor of the console as necessary. In order to perform such signal processing, system software 140 is provided. The system software 140 is realized by executing a program on a computer. An electron optical system control power supply 130 is provided to supply power to the electron column system. The main chamber 22 is provided with an optical microscope 110 and an SEM type inspection device (SEM) 120.

  In the sample inspection apparatus 10 in FIG. 9, a sample such as a wafer or a mask is transported from the sample carrier 12 (load port) to the mini-environment 14. In the mini environment 14, an alignment operation is performed.

  Next, the sample is transferred to the load lock 16 by a transfer robot in the atmosphere. The load lock 16 is exhausted from the atmosphere to a vacuum state by a vacuum pump. When the pressure becomes a certain value (for example, about 1 [Pa]) or less, the sample is transferred from the load lock 16 to the main chamber 22 by the transfer robot in vacuum arranged in the transfer chamber 18. The sample is held on an electrostatic chuck mechanism on the stage 30.

  In the main chamber 22, the sample is inspected. Here, the pattern of the sample is inspected using the sample observation method of the present invention described above. Further, as will be described later, an inspection is performed using the SEM 120. When the inspection is finished, the sample returns to the sample carrier 12 through the reverse path.

  Next, the main part of the sample inspection apparatus 10 will be described with reference to FIG. The configuration in FIG. 10 corresponds to the main chamber 22 and the electronic column 24 in FIG.

  In FIG. 10, a sample inspection apparatus 10 includes a primary optical system 40 that generates an electron beam, a stage 30 on which the sample 20 is installed, and a secondary optical system that generates images of secondary emission electrons and mirror electrons from the sample. 60, a detector 70 for detecting these electrons, and an image processing device 90 for processing a signal from the detector 70. The detector 70 is included in a part of the secondary optical system 60. Further, the sample inspection apparatus 10 includes a control unit 100 for controlling the entire apparatus. The control unit 100 corresponds to the system software 140 of FIG. Further, the sample inspection apparatus 10 is provided with an optical microscope 110 for alignment and an SEM 120 for review.

  The primary optical system 40 is configured to generate an electron beam and irradiate the sample 20. The primary optical system 40 includes an electron gun 41, lenses 42 and 45, apertures 43 and 44, an E × B filter 46, lenses 47, 49 and 50, and an aperture 48. An electron beam is generated by the electron gun 41. The lenses 42 and 45 and the apertures 43 and 44 adjust the shape of the electron beam and control the direction of the electron beam. In the E × B filter 46, the electron beam is affected by the Lorentz force due to the magnetic field and the electric field. The electron beam enters the E × B filter 46 from an oblique direction, is deflected vertically downward, and travels toward the sample 20. The lenses 47, 49, and 50 adjust the landing energy LE by controlling the direction of the electron beam and appropriately decelerating.

  In the primary optical system 40 of the mapping projection optical system, the E × B filter 46 is particularly important. The primary electron beam angle can be determined by adjusting the electric field and magnetic field conditions of the E × B filter 46. For example, the condition of the E × B filter 46 is set so that the primary electron beam and the secondary electron beam are incident on the sample 20 substantially perpendicularly.

  The primary optical system 40 may irradiate not only an electron beam for imaging but also an electron beam for precharging. Alternatively, an electron gun or the like for precharging may be provided.

  The stage 30 is a structure for mounting the sample 20 as described above. The stage 30 is movable in the xy direction (horizontal direction) and the θ direction (rotation direction on a horizontal plane). Further, the stage 30 may be movable in the z direction (vertical direction) as necessary. A sample fixing mechanism such as an electrostatic chuck is provided on the surface of the stage 30.

  The secondary optical system 60 is configured to guide the electrons reflected from the sample 20 to the detector 70. As already described, mirror electrons and secondary emission electrons are guided to the detector 70. The secondary optical system 60 includes lenses 61 and 63, an aperture 62, an aligner 64, and a detector 70. The electrons are reflected from the sample 20 and pass through the objective lens 50, the lens 49, the aperture 48, the lens 47 and the E × B filter 46 again. Then, the electrons are guided to the secondary optical system 60. In the secondary optical system 60, the electrons pass through the lens 61, the aperture 62, and the lens 63, are adjusted by the aligner 64, and are detected by the detector 70.

  The aperture 62 has a role of defining the transmittance and aberration of the secondary system. In the present embodiment, the size, position, and shape of the aperture 62 can be adjusted. In order to perform this adjustment, an aperture adjustment mechanism 200 is provided. Aperture adjustment is performed to increase the contrast of the sample pattern in the observation image. The aperture adjustment will be described later.

  The detector 70 is configured to detect electrons guided by the secondary optical system 60. The detector 70 has a plurality of pixels on the detection surface. Various two-dimensional sensors can be applied to the detector 70. For example, a CCD (Charge Coupled Device) and a TDI (Time Delay Integration) -CCD may be applied to the detector 70. These are sensors that detect signals after converting electrons to light. Therefore, means such as photoelectric conversion are necessary. Thus, electrons are converted into light using photoelectric conversion or scintillator.

  Further, EB-TDI may be applied to the detector 70. EB-TDI does not require a photoelectric conversion mechanism and a light transmission mechanism. Electrons enter the EB-TDI sensor surface directly. Therefore, there is no deterioration in resolution, and a high MTF (Modulation Transfer Function) and contrast can be obtained. The detector 70 may be an EB-CCD.

  The control unit 100 is configured by a computer and controls the entire sample inspection apparatus 10. The control unit 100 corresponds to the system software 140 in FIG.

  The control unit 100 controls the primary optical system 40 including the electron gun 41 to adjust the landing energy LE. In the present embodiment, as described above, the landing energy LE is set so that edge mirror electrons are efficiently generated in the pattern of the sample 20. In addition, the control unit 100 controls the primary optical system 40 and the secondary optical system 60 to control and adjust the trajectory of electrons from the electron gun 41 to the detector 70. More specifically, the electron trajectory is controlled so that the electron beam passes through a predetermined appropriate trajectory from the electron gun 41 to the sample 20, and further, the electron from the sample 20 passes through the predetermined proper trajectory to the detector 70. . Further, as will be described in detail later, the control unit 100 controls the aperture adjustment mechanism 200 to perform aperture adjustment.

  In addition, the control unit 100 controls the image processing device 90 to process a signal from the detector 70 to generate an image of the pattern of the sample 20. Furthermore, the control unit 100 is configured to process an image generated by the image processing apparatus 90 and perform determination regarding a pattern defect.

  The configuration of each part of the sample inspection apparatus 10 has been described above. Next, the operation of the sample inspection apparatus 10 will be described.

  The sample inspection apparatus 10 moves the stage 30 in the horizontal direction while irradiating the sample 20 with the electron beam, detects electrons from the sample 20 by the detector 70, and generates an image of the sample 20 from the detection signal. The electron beam is emitted from the electron gun 41, guided to the primary optical system 40, and irradiated on the sample 20. In the incident process, the direction of the electron beam is changed by the E × B filter 46. In the present embodiment, the inspection is performed by the mapping projection method. Therefore, an electron beam having a large diameter is used so as to irradiate a relatively wide range of the sample.

  The landing energy LE of the electron beam is set so that edge mirror electrons are likely to be generated at the edge of the pattern, as described in the above description of the sample observation method. Specifically, the landing energy LE is set to LEA ≦ LE ≦ LEB + 5 [eV]. LEA and LEB are the lower limit and upper limit of the transition region in FIG. 1, and are, for example, −5 [eV] and 5 [eV].

  Therefore, edge mirror electrons are generated when the pattern of the sample 20 is irradiated with the electron beam. More specifically, some of the electron beams are irradiated near the edge of the pattern. Such an electron near the edge passes through the trajectory illustrated in FIGS. 5 to 7 and becomes an edge mirror electron.

  Electrons generated in the sample 20 are guided to the detector 70 by the secondary optical system 60. Then, an electron image is generated on the detection surface of the detector 70. In the sample 20, normal mirror electrons can be generated in addition to the edge mirror electrons by the electron beam irradiation. In addition to the mirror electrons, secondary emission electrons are also generated. Therefore, an image of these types of electrons is formed on the detector 70.

  The detector 70 detects electrons and sends a detection signal to the image processing device 90. In the image processing apparatus 90, the detection signal is processed to generate an image of the sample 20. Here, in the present embodiment, the landing energy LE is appropriately set, and many edge mirror electrons reach the detector 70. That is, the number of detected edge mirror electrons is larger than that of other types of electrons. Edge mirror electrons are generated at the edge of the pattern of the sample 20. Therefore, in the image of the sample 20, the gradation (brightness) of the pattern is increased. Then, the gradation difference from other parts increases. Therefore, the contrast of the pattern is increased.

  The control unit 100 determines a pattern defect using such an image of the sample 20. The controller 100 may determine the presence or absence of a pattern defect, may detect the position of the defect, and may further determine the type of defect. Further, the sample inspection apparatus 10 of the present embodiment may inspect not only pattern defects but also foreign matters. In this case, the control unit 100 may process the image of the sample 20 and determine the presence or absence of foreign matter. In addition, other tests may be performed.

  The defect determination process may be “die to die”. This process compares the two die images of sample 20. More specifically, images of two dies obtained sequentially are compared. When the patterns of the two dies are different, the control unit 100 determines that there is a defect.

  The defect determination process may be a “die to any die”. In this case, an image of a specific die is obtained from the sample 20 and is held as a determination criterion. Then, the image of the criterion die is compared with the images of many other dies in order. Also in this case, when the die patterns are different, the control unit 100 determines that there is a defect.

  Further, the defect determination process may be a “die to database”. In this case, the die image is compared with registered data such as design data. The design data is, for example, CAD data. When the die image is different from the registered data, the control unit 100 determines that there is a defect.

  The defect determination process may determine a cell defect. In this case, instead of the die image described above, the cell image is processed. The defect determination process may be “cell to cell”, “cell to any cell”, or “cell to database”.

  In this way, the control unit 100 performs defect determination. The defect determination result may be displayed on a monitor or recorded on a recording medium. Further, the defect determination result may be used by the SEM 120 in the next stage, as will be described below.

“About a configuration with both a mapping projection inspection device and an SEM”
FIG. 11 is a part of the sample inspection apparatus 10, and particularly shows the main chamber 22, the electron column 24, and the SEM 120. The electronic column 24 and the main chamber 22 constitute a mapping projection observation apparatus. Therefore, the sample inspection apparatus according to the present embodiment constitutes a composite observation apparatus that includes both the mapping projection observation apparatus and the SEM observation apparatus.

  As shown in FIG. 11, in the present embodiment, the stage 30 is movable, and in particular, is movable between the observation position of the electronic column 24 (mapping projection observation apparatus) and the observation position of the SEM 120. . With such a configuration, observation and inspection can be performed quickly and with high accuracy when both the mapping method and the SEM are used. For example, a pattern defect is detected by a mapping projection observation apparatus, and then the pattern defect is reviewed in detail by an SEM. Hereinafter, this feature will be described in more detail.

  According to the configuration of FIG. 11, both the electron column 24 and the SEM 120 are used while the sample 20 is mounted on the same stage 30. Therefore, when the sample 20 (stage 30) moves between the electron column 24 and the SEM 120, the coordinate relationship is uniquely determined. This is advantageous when specifying a predetermined portion of a pattern or specifying a pattern defect portion. Two inspection apparatuses can easily identify the same part with high accuracy. For example, the defect location is specified by the electronic column 24. This defective part is quickly positioned by the SEM 120.

  Suppose that the above composite configuration is not applied. For example, assume that the mapping optical inspection device and the SEM are arranged separately in separate vacuum chambers. It is necessary to move the sample between the separated devices, and it is necessary to place the sample on separate stages. Therefore, it is necessary for the two apparatuses to perform sample alignment separately, which takes time. Further, when the samples are aligned separately, the specific error at the same position is 5 to 10 [μm].

  On the other hand, in the present embodiment, as shown in FIG. 11, the sample 20 is placed on the same stage 30 in the same chamber 22 in two types of inspection. Even when the stage 30 moves between the mapping type electronic column 24 and the SEM 120, the same position can be specified with high accuracy. For example, the position can be specified with an accuracy of 1 [μm] or less.

  Such high-precision identification is very advantageous in the following cases. First, the sample 20 is inspected by a mapping method, and patterns and pattern defects are inspected. Then, identification of the detected defect and detailed observation (review) are performed by the SEM 120. Since an accurate position can be specified, not only the presence / absence of a defect (pseudo detection if there is no defect) can be determined, but also the detailed observation of the size and shape of the defect can be performed at high speed.

  As described above, if the defect detection electronic column 24 and the review SEM inspection apparatus 120 are provided separately, it takes a lot of time to specify the defect position. Such a problem is solved by this embodiment.

  As described above, in the present embodiment, an ultra-fine pattern is inspected with high sensitivity using a pattern by a mapping optical method and an imaging condition of a pattern defect. Further, a mapping optical type electron column 24 and an SEM type inspection device 120 are mounted in the same chamber 22. Thereby, in particular, inspection of ultra-fine patterns of 100 [nm] or less and pattern determination and classification can be performed very efficiently and at high speed.

Aperture adjustment
Next, aperture adjustment, which is another feature of the present embodiment, will be described.

  First, an outline of aperture adjustment will be described. In the aperture adjustment, the size, position, and shape of the aperture 62 of the secondary optical system 60 are adjusted to match the mirror electrons that pass through the aperture 62. In this sense, the aperture 62 of the present embodiment can be called a variable aperture (or an adjustment aperture or the like). The adjustment target is to make the spot (profile) of the mirror electrons at the height of the aperture 62 coincide with the hole of the aperture 62 as much as possible. However, in practice, it is difficult to completely match the mirror electron spot and the aperture 62. Therefore, in practice, the aperture 62 may be adjusted to be somewhat wider than the mirror electron spot.

  By adjusting the aperture 62 in this way, the contrast of the pattern in the image can be increased. More specifically, the electrons detected from the sample include mirror electrons and secondary emission electrons. As already described, secondary emission electrons spread over a wide range, while mirror electrons do not spread much. Therefore, by appropriately adjusting the aperture 62 according to the mirror electrons, it is possible to reduce the secondary emission electrons passing through the aperture 62 and relatively increase the detection amount of the mirror electrons. Therefore, the contrast of the pattern in the image can be further increased.

  The aperture 62 is adjusted by the aperture adjustment mechanism 200. Specifically, a plurality of types of apertures 62 may be provided. The plurality of types of apertures 62 are different in size and shape. The plurality of types of apertures 62 may be integrally formed or may be separate members. The aperture adjustment mechanism 200 can switch the aperture 62 used for observation on the optical axis. Then, under the control of the control unit 100, the aperture adjustment mechanism 200 selects the aperture 62 corresponding to the mirror electron from the plurality of types of apertures 62 and arranges it on the optical axis. Further, the aperture adjustment mechanism 200 adjusts the position of the aperture 62 according to the mirror electrons. Thus, the size, shape, and position of the aperture 62 are suitably adjusted.

  Within the scope of the present invention, the position of the aperture 62 may also include a position in a direction along the axis of the secondary optical system 60. Therefore, the aperture adjustment mechanism 200 may optimize the aperture position not only by moving the aperture 62 in the horizontal direction (XY direction) but also in the optical axis direction (Z direction). Further, the position of the aperture 62 may include a position in the rotation direction, that is, an aperture angle. The aperture adjustment mechanism 200 may rotate the aperture 62 on a horizontal plane, and the center of rotation may be the axis of the secondary optical system 60.

  In order to adjust the aperture, it is effective to use an image of mirror electrons in the aperture. This mirror electron image represents the above-mentioned mirror electron spot. Therefore, the aperture 62 is adjusted so as to match the mirror electron image in the aperture.

  In order to measure the mirror electron image at the aperture, a detector such as an EB-CCD is preferably added to the height of the aperture. Alternatively, it is preferable to arrange the aperture 62 and the detector 70 (FIG. 10) at an optically conjugate position. Thereby, a mirror electron image in the aperture 62 is obtained by the detector 70.

  The outline of the aperture adjustment has been described above. Next, the aperture adjustment will be described in more detail using a specific example.

(Aperture position adjustment)
In pattern observation, it is important to efficiently acquire a mirror signal from a pattern. The position of the aperture 62 is very important because it defines the transmittance and aberration of the signal. Secondary electrons are emitted from the sample surface in a wide angle range according to the cosine law, and reach a wide area uniformly in the aperture. Therefore, secondary electrons are insensitive to the position of the aperture 62. On the other hand, in the case of mirror electrons, the reflection angle on the sample surface is approximately the same as the incident angle of the primary electron beam. Therefore, the mirror electrons show a small spread and reach the aperture 62 with a small beam diameter. For example, the spreading region of mirror electrons is 1/20 or less of the spreading region of secondary electrons. Therefore, the mirror electrons are very sensitive to the position of the aperture 62. The spreading region of the mirror electrons in the aperture is usually a region of φ10 to 100 [μm]. Therefore, it is very advantageous and important to obtain the position where the mirror electron intensity is the highest and to arrange the center position of the aperture 62 at the obtained position.

  In order to realize the installation of the aperture 62 at such an appropriate position, the aperture adjustment mechanism 200 moves the aperture 62 in the x and y directions with an accuracy of about 1 [μm] in the vacuum of the electronic column 24. Move. The signal intensity is measured while moving the aperture 62. The brightness of the image may be determined as the signal strength. The evaluation value is, for example, the sum of luminance. Then, the position having the highest signal intensity is obtained, and the center of the aperture 62 is set at the obtained coordinate position.

  In the above, the aperture 62 has been moved in the xy direction. Within the scope of the present invention, the aperture 62 may be rotated by the aperture adjustment mechanism 20 to adjust the angle of the aperture 62. And an angle may be set based on the measurement result of signal strength. The angle is a position in the rotational direction. Therefore, the angle of the aperture is also included in the aperture position in the present invention. The rotation axis of the aperture 62 may be the axis of the secondary optical system 60. First, the adjustment in the xy direction described above may be performed, and the aperture center may be adjusted to a position where the signal intensity is the highest. Then, the aperture 62 may be rotated by a predetermined small angle, and the aperture 62 may be adjusted to an angle at which the signal intensity is highest.

  Further, an aperture or the like may be configured so that the position of the aperture 62 can be adjusted not only in the x and y directions but also in the z axis direction. The z-axis direction is the axial direction of the secondary optical system 60. In this case, the aperture 62 may be moved also in the z-axis direction, the signal strength may be measured, and the aperture 62 may be adjusted to a position where the signal strength is highest, and this configuration is also advantageous. The aperture 62 is preferably installed at a position where the mirror electrons are most narrowed. Thereby, the aberration of the mirror electrons can be reduced and the secondary emission electrons can be reduced very effectively. Therefore, higher S / N can be obtained.

(Configuration of signal strength measurement)
Here, a more preferable configuration for signal strength measurement will be described.

  FIG. 12 is a modification of the sample inspection apparatus of FIG. In FIG. 12, the configuration of the secondary optical system 60a is different from the secondary optical system 60 of FIG. 10, and specifically, an EB-CCD 65 is provided at the height of the aperture. The aperture 62 and the EB-CCD 65 are installed on an XY stage 66 that is an integral holding member having openings 67 and 68. Since the XY stage 66 is provided with openings 67 and 68, mirror electrons and secondary emission secondary electrons can reach the aperture 62 or the EB-CCD 65.

  The XY stage 66 moves the aperture 62 and the EB-CCD 65 to perform position control and positioning thereof. Thereby, the aperture 62 and the EB-CCD 65 are switched, and the current absorption of the aperture 62 and the image acquisition of the EB-CCD 65 are performed independently. The XY stage 66 is driven by the aperture adjustment mechanism 200 (the XY stage 66 may be a part of the aperture adjustment mechanism 200).

  When the secondary optical system 60a having such a configuration is used, first, the EB-CCD 65 is used to detect the spot shape of the electron beam and its center position. The image processing device 90 or another configuration may process the detection signal of the EB-CCD 65 to generate an image. The control unit 100 may obtain the spot shape and the center position of the mirror electrons from the detection signal image. As described above, the brightness of the mirror electrons is greater than the brightness of the secondary emission electrons. Therefore, the spot of the mirror electrons becomes brighter than the surrounding secondary emission electron portion. Therefore, for example, a region having a luminance of a predetermined value or more is specified as a mirror electron spot (profile). Further, for example, a region surrounded by an edge from the image is detected as a spot of mirror electrons. Then, the control unit 100 controls the XY stage 66 and arranges the hole center of the aperture 62 at the center position of the detected spot.

  As described above, in this embodiment, the EB-CCD 65 is used very advantageously. Since two-dimensional information of the beam can be known and the number of electrons incident on the detector 70 can be obtained, quantitative signal strength evaluation can be performed. The position of the aperture 62 can be directly adjusted using such measurement results. Thereby, the aperture can be positioned with high accuracy, the aberration of the electronic image is reduced, and the uniformity is improved. Further, the transmittance uniformity is improved, and an electronic image with high resolution and uniform gradation can be acquired.

  Further, the configuration of FIG. 12 can eliminate the work of measuring the signal intensity while moving the aperture 62 little by little. Therefore, it is effective for shortening the measurement time.

  Further, the configuration of FIG. 12 is suitably used not only for aperture adjustment but also for spot shape adjustment. The controller 100 adjusts the voltages of the stigmeter, the lenses 61 and 63, and the aligner 64 so that the spot shape is as close to a circle as possible and is minimized. With respect to this point, conventionally, the spot shape and astigmatism in the aperture 62 cannot be directly adjusted. Such direct adjustment is possible in the present embodiment, and astigmatism can be corrected with high accuracy.

  In the configuration of FIG. 12, the EB-CCD 65 is provided as a detector. However, other types of detectors may be provided.

  In FIG. 12, a beam image at the aperture 62 is obtained by adding the EB-CCD 65. However, similar beam images can be obtained with other configurations. Specifically, the aperture 62 is arranged so that the positional relationship between the aperture 62 and the detection surface of the detector 70 is optically conjugate in the z direction. This configuration is also very advantageous. As a result, an image of the beam in the aperture 62 is formed on the detection surface of the detector 70. Therefore, the beam profile in the aperture 62 can be observed using the detector 70, and a mirror electron image of the aperture 62 is obtained. Moreover, the EB-CCD 65 may not be provided.

  In addition, in the above description, the measurement result is used for adjusting the aperture position. The control unit 100 may suitably use the measurement result for the adjustment of the aperture size and aperture shape described below.

(Adjustment of aperture size and aperture shape)
The size of the aperture 62 (aperture diameter) is also important in the present embodiment. Since the signal region of the mirror electrons is small as described above, the effective size is about 10 to 200 [μm]. Further, the aperture size is preferably 10 to 100% larger than the beam diameter.

  In this regard, an electron image is formed by mirror electrons and secondary emission electrons. By setting the aperture size, the ratio of mirror electrons can be further increased. Thereby, the contrast of mirror electrons can be increased, that is, the contrast of the pattern can be increased.

  More specifically, when the aperture hole is made smaller, the secondary emission electrons decrease in inverse proportion to the aperture area. Therefore, the gradation of the normal part becomes small. However, the mirror electronic signal does not change, and the gradation of the pattern does not change. Therefore, the contrast of the pattern can be increased as much as the surrounding gradation is reduced, and a higher S / N can be obtained.

  The same principle holds for the aperture shape. It is preferable to match the aperture shape with the spot shape (profile) of the mirror electrons in the aperture 62. Thereby, the secondary emission electrons passing through the aperture 62 can be reduced without changing the mirror electron signal. Accordingly, the contrast of the pattern can be increased and a higher S / N can be obtained.

  The signal measurement described above may also be performed in the adjustment of the aperture size and shape. The signal measurement may be repeated while changing the aperture size and shape little by little. Preferably, the spot of the mirror electrons in the aperture 62 is measured using the configuration of FIG. Alternatively, a spot image is acquired by the detector 70 by setting the positional relationship between the detector 70 and the aperture 62 to a conjugate relationship. Thereby, the aperture size and shape can be adjusted easily and quickly.

  As explained above, mirror electrons are very sensitive to aperture size and shape. Therefore, proper selection of the aperture size and shape is very important for obtaining a high S / N.

(About aperture variations)
Next, the variation of the aperture suitably applied to this Embodiment is demonstrated with reference to FIGS.

  In FIG. 10 and the like, the aperture 62 is represented by a simple line. However, the actual aperture 62 is a member (part) having a hole. Generally, the member is sometimes referred to as an aperture, and the hole is sometimes referred to as an aperture. In the following description of aperture variations, the member is referred to as an aperture member in order to distinguish the member (part) from its hole. And the hole of a member is called an aperture hole. As another identification method, the aperture member may be called an NA aperture or the like.

  In FIGS. 13 to 18, the symbols 62 a to 62 d are aperture members. Reference numerals 169, 69, 69a, and 69b denote aperture holes. The aperture shape generally means the shape of the aperture hole. The aperture size and position are also specifically the size and position of the aperture hole. Here, the aperture member and the aperture hole are distinguished from each other. However, the aperture member and the aperture hole may be simply referred to as an aperture according to a general expression in the entire specification.

  FIG. 13 is a reference example and shows a conventional aperture hole 169. As shown in FIG. 13, conventionally, a circular aperture hole 169 has been installed at a fixed position. Therefore, the appropriate aperture size and shape as described above cannot be selected. On the other hand, the sample inspection apparatus 10 according to the present embodiment is configured to adjust the aperture by moving the aperture two-dimensionally or three-dimensionally.

  FIG. 14 shows an example of the aperture shape. In FIG. 14, the aperture hole 69 is elliptical. This hole shape is set to match the intensity distribution of the mirror electron signal. In this example, the measurement result of the intensity distribution of the mirror electrons in the aperture member 62 has an elliptical shape in which the intensity distribution is long in the y direction. Here, the y direction is a direction deflected by the E × B filter 46. The y direction coincides with the direction of the optical axis of the primary electron beam. The cause of the elliptical shape in the y direction is considered to be a deflection component in the E × B filter 46. Therefore, in order to efficiently capture mirror electrons, an aperture shape having a long axis in the y direction is very advantageous.

  Thereby, it is possible to increase the yield of mirror electrons as compared with the conventional case and obtain a higher S / N (for example, × 2 or more). For example, the intensity distribution of the secondary electron beam is 100 [μm] in the y direction and 50 [μm] in the x direction (these values are full widths at half maximum). The elliptical aperture hole 69 is selected in the range of plus 10 to 100% with respect to the secondary electron beam diameter. For example, the aperture hole 69 may be selected so that the aperture size is 150 [μm] in the y direction and 75 [μm] in the x direction.

  Next, the configuration of the aperture member having a plurality of aperture holes will be described with reference to FIGS. 15 to 18. Here, a plurality of aperture holes function as one aperture.

  FIG. 15 shows an example of the configuration of an aperture member 62a having a plurality of aperture holes 69a. In FIG. 15, the aperture member 62a has two circular aperture holes 69a. In this example, the two holes are arranged at positions shifted in the ± y directions with reference to the intensity center of the mirror electrons. The amount of deviation is, for example, about 50 [μm]. This configuration can capture both scattered + y side and -y side mirror electrons. Therefore, this configuration can increase the difference in signal amount between the scattered mirror electron signal and the background secondary emission electrons, and can obtain a high S / N ratio. Explaining this reason, in the case of secondary emission electrons, the amount scattered in the scattering direction is limited to a small amount. Therefore, the background can be reduced and the S / N can be relatively improved.

  FIG. 16 shows an example of the configuration of an aperture member 62a having four aperture holes 69a. In FIG. 16, four circular aperture holes 69a are arranged symmetrically with respect to the x-axis and the y-axis. That is, the two aperture holes 69a are disposed on the x-axis, the two aperture holes 69a are disposed on the y-axis, and the four aperture holes 69a are located at the same distance from the center (origin). In other words, the four aperture holes 69a are arranged at equal intervals around the origin. More simply, the four aperture holes 69a are arranged in a diamond shape. Thereby, even when there are mirror electrons scattered in both the x direction and the y direction, electrons can be acquired with a high S / N.

  FIG. 17 shows an aperture member 62c having four aperture holes 69a. The configuration of FIG. 17 is an example different from the configuration of FIG. In FIG. 17, four circular aperture holes 69a are arranged in the first to fourth quadrants in the xy plane, respectively. Also in this example, the four aperture holes 69a are disposed symmetrically with respect to the x-axis and the y-axis, and are disposed at an equal distance from the center (origin). In other words, the four aperture holes 69a are arranged at equal intervals around the origin. Also in the aperture member 62c having such a shape, the aperture hole 69a can be provided at a position where the signal intensity of the mirror electrons becomes high, and a high S / N signal can be acquired.

  As shown in FIGS. 16 and 17, the number of aperture holes 69a may be the same and their arrangement may be different. Thereby, the appropriate aperture members 62b and 62c according to a use can be used. And it becomes possible to acquire high S / N about each use.

  FIG. 18 is a view showing an example of the configuration of an aperture member 62d having eight aperture holes 69b. As shown in FIG. 18, the number of aperture holes 69 d may be more than four. In the aperture member 62d shown in FIG. 18, a plurality of aperture holes 69b are arranged at equal intervals on the circumference around the center of intensity of the mirror electrons. This configuration is advantageous when there is a mirror electron that specifically scatters strongly at the position of the aperture hole 69b somewhere on the circumference. Appropriate capture of such mirror electrons is possible.

  Further, in FIGS. 15 to 18, regarding the relationship between the intensity center of the mirror electron signal and the aperture holes 69 a and 69 b, the aperture position is deviated from the intensity center. However, the present invention is not limited to this, and the aperture position may coincide with the intensity center. That is, one aperture hole may be installed so as to coincide with the mirror electron intensity center. In this case, the other aperture holes capture scattered mirror electrons. These electrons are included in the electron image together with the mirror electrons at the intensity center. Such a composite image is obtained by the detector 70. In this way, a composite image of strong mirror electrons and specifically scattered mirror electrons can be acquired. Therefore, a high S / N can be obtained, and an observation target having a characteristic in the scattering direction can be detected effectively. In addition, the characteristics of the scattering direction can be used for classification of observation objects.

(Aperture adjustment according to landing energy)
Furthermore, according to the present embodiment, an appropriate aperture hole shape and size can be selected for the landing energy LE to be used. This choice also provides a very advantageous effect. The intensity distribution of the mirror electrons changes with the landing energy LE. Therefore, the inspection apparatus of the present embodiment may be configured to select an aperture size and shape according to the landing energy LE to be used. This makes it possible to adjust the aperture according to the intensity distribution, which is very advantageous.

  For example, consider a case where mirror electrons have an elliptical intensity distribution that is long in the y direction. Assume that imaging or inspection is performed under two different conditions. For example, in the first imaging / inspection condition, it is assumed that the landing energy is the first value, that is, LE = 3 [eV]. In the second imaging / inspection condition, the landing energy is a second value, that is, LE = 2 [eV]. Here, when the landing energy LE decreases, the mirror electron intensity distribution increases at the aperture height. The aperture size and shape are preferably selected so as to adapt to such distribution changes.

  For example, when the first landing energy is used, an elliptic aperture hole 69 of 100 [μm] in the y direction and 50 [μm] in the x direction may be selected. When the second landing energy is used, the mirror electron intensity distribution becomes about twice as large. Therefore, an elliptic aperture hole 69 of 200 [μm] in the y direction and 100 [μm] in the x direction may be used. In this way, mirror electrons can be detected very effectively.

(Aperture adjustment mechanism)
Lastly, the description of the aperture adjustment mechanism will be supplemented. In the present embodiment, a plurality of apertures (aperture members) may be integrated. That is, a plurality of aperture holes may be provided in one aperture member. The plurality of aperture holes may have different shapes and sizes. In this case, the aperture adjustment mechanism switches the aperture hole by moving the aperture member, and adjusts the aperture shape and the aperture size.

  Another example is a configuration in which the apertures are not integrated. That is, a plurality of aperture members are provided, and each aperture member has an aperture hole. In the plurality of aperture members, at least one of the hole size and the hole shape is different. In this case, the aperture adjustment mechanism adjusts the aperture shape and the aperture size by selecting and switching the aperture member.

  The above two configurations may be combined. For example, one aperture member is prepared for each type of aperture shape. Each aperture member has a plurality of aperture holes having the same shape and different sizes. Conversely, one aperture member is prepared for each aperture size. In this case, each aperture member may have a plurality of aperture holes having the same size and different shapes.

  The aperture adjustment mechanism 200 may have any configuration for moving and switching the aperture. The aperture may be moved and switched using the XY stage shown in the example of FIG. The aperture may be moved and switched by a linear motor. In addition, the aperture may be supported by a rotation support member, and a normal rotary motor may move the aperture or switch the aperture.

  The aperture adjustment according to the present embodiment has been described in detail above. The above aperture could be changed in size, position and shape. The present invention is not limited to such a configuration. Within the scope of the present invention, at least one of size, position and shape may be adjusted.

  In the above description, the aperture setting can be changed at any time. However, within the scope of the present invention, the aperture setting may be fixed after adjustment. In this case, the aperture size, position and shape may first be adjusted and determined according to the principles described above. Then, the determined aperture specification may be used fixedly. For example, the elliptical aperture described above may be used continuously.

  Below, the composite sample observation method and sample observation apparatus devised on the basis of the sample observation method and sample observation apparatus of the 1st aspect demonstrated so far are demonstrated. Note that the sample observation method and the sample observation apparatus of the second aspect are common in the configuration and effects of the sample observation method or the sample observation apparatus of the first aspect described above. Therefore, repeated description is omitted in the following description.

  FIG. 19 is a diagram showing a configuration example of a part of the sample observation apparatus according to the second aspect of the present invention. Since the configuration other than the configuration shown in this figure has already been described with reference to FIGS. 9, 10, 12, and the like, description thereof will be omitted. As shown in this figure, an electronic column 24 of a projection projection observation apparatus having a primary beam system 40 and a secondary beam system 60 is provided in a main chamber 22 that houses a stage 30 on which a sample 20 having a pattern is placed. An SEM 120 and an optical microscope 110 are provided. Further, the stage 30 is configured to be movable between these three observation devices so that any position on the sample 20 can be observed by each of the electron column 24, the SEM 120, and the optical microscope 110.

  The stage 30 provided in the main chamber 22 has a so-called XY stage 30a and a rotary stage 30b, and can move the sample 20 in the X direction and the Y direction in the XY plane as a sample mounting surface. The stage 20 can also be rotated in the XY plane.

Detector 70 provided in the upper portion of the secondary beam system 60 of the image projection observation apparatus receives a signal from the control unit 100, X _d direction and Y in the electron detection surface (X _d Y _d surface) It is configured to be able to rotate in the _d direction and the electron detection plane.

  In the composite type sample observation apparatus having such a configuration, a specific portion of the same sample is observed or a pattern is inspected by three types of observation apparatuses, ie, a projection projection observation apparatus, an SEM observation apparatus, and an optical microscope. can do.

  If a composite observation is to be performed using these three types of observation apparatuses individually, it is necessary to move the observation target sample from the stage of one apparatus to the stage of another apparatus. Such sample movement is performed. It is necessary to re-specify the location specified in the previous observation with another device, which is troublesome and the reproducibility must be as low as about 10 μm at the most. There is also a problem from the viewpoint.

  For example, it is assumed that the presence of an abnormal part that seems to be a pattern defect is confirmed by analyzing a mirror electronic image, and the position of the abnormal part on the sample is specified. When it is determined by SEM observation whether or not this defective pattern portion is a true defect, the sample is transferred from the stage of the projection projection observation apparatus to the stage of the SEM observation apparatus, and the mirror electronic image has already been obtained. SEM observation is performed by searching for a position on the sample where there is a pattern defect portion specified in the analysis. However, if the position cannot be accurately reproduced, a wrong place may be observed, or if the pattern defective portion is extremely small, the abnormality of the pattern may not be confirmed.

  On the other hand, if it is set as the structure of the composite type sample observation apparatus as mentioned above, in principle, the same place on a sample can be observed with a different kind of apparatus. Since the drive control of the stage on which the sample is placed can be performed with an accuracy of 1 μm or more (an error of 1 μm or less), it is possible to easily and quickly specify a highly accurate observation position at the submicron level. In addition, by observing the specific position with an SEM, it is possible to easily determine the authenticity of the defect, determine the defect type, and the like.

  In order to specify the observation position with such high accuracy, for example, a storage unit is provided in the control unit 100, and the optical centers of the optical microscope, the mapping projection observation device, and the SEM observation device are provided. Is stored as coordinate data, and the stage can be moved between these three optical centers based on the coordinate data.

For example, the sample 20 having a specific pattern arrangement is placed on the stage 30, and a region including the specific pattern arrangement is observed with the optical microscope 110. At this time, the stage 30 is moved so that a specific pattern as a reference comes to the optical center of the optical microscope, and the coordinates of the optical center position of the optical microscope are determined from the amount of stage movement at that time. Assume that the optical center position coordinates of the optical microscope thus determined are (x _o , y _o ).

Next, the stage is moved to the observation position of the mapping projection observation apparatus, and the stage 30 is further moved so that the above-described reference specific pattern is at the optical center of the projection projection observation apparatus. Then, the coordinates of the optical center position of the mapping projection observation apparatus are determined from the amount of movement of the stage. It is assumed that the optical center position coordinates of the mapping projection observation apparatus thus determined are (x _t , y _t ).

Subsequently, the stage is moved to the observation position of the SEM type observation apparatus, and further, the stage 30 is moved so that the above-described reference specific pattern comes to the optical center of the SEM type observation apparatus. Then, the coordinates of the optical center position of the SEM type observation apparatus are determined from the moving amount of the stage. Assume that the optical center position coordinates of the SEM type observation apparatus determined in this way are (x _s , y _s ). When these operations are performed, the positional relationship between the optical centers of the three observation devices, ie, the optical microscope, the mapping projection observation device, and the SEM observation device, is obtained as coordinate data. Since these coordinate data are obtained from the movement amount of the stage, they actually correspond to the coordinate data indicating the position of the stage 30 in the main chamber 22.

If the positional relationship between the optical centers of the observation devices is clarified, if the location on the sample specified by the optical microscope observation is (x _o , _yo ), the same location is mapped projection type observation device The sample may be moved to (x _t , y _t ) when observing with, and the sample may be moved to (x _s , y _s ) when observing with the SEM type observation apparatus. In addition, since such switching processing is executed instantaneously in the control unit 100, highly accurate alignment can be performed quickly.

  The sample observation apparatus according to the second aspect of the present invention includes an alignment unit that adjusts the sample position on the stage so that the arrangement direction of the specific pattern on the sample coincides with the X direction or the Y direction, which is the moving direction of the stage. May be provided. Such an alignment part can be provided in the control part 100, for example.

  In addition, the alignment unit includes a detector so that the arrangement direction of the specific pattern on the sample after the sample position adjustment matches the X direction or the Y direction of the frame of the mirror electronic image obtained by the projection projection observation apparatus. A function of adjusting 70 can be provided.

  Further, the alignment unit includes an optical system of the SEM type observation device so that an observation image obtained by observing a specific pattern on the sample after the sample position adjustment with the SEM type observation device is positioned at the center of the SEM image. It is possible to provide a function for adjusting the.

  Next, a procedure for performing observation using the above-described composite type sample observation apparatus will be described.

  FIG. 20 is a diagram for explaining the basic concept of the sample observation method according to the second aspect of the present invention. This sample observation method is different from the mapping projection type observation device and the mapping projection type observation device. A composite type sample observation method for observing a sample placed on the same stage by an SEM type observation device and an optical microscope, which is a mapping projection type observation device, an SEM type observation device, and an optical microscope. The positional relationship between the optical centers of the observation devices is stored as coordinate data, and based on the coordinate data, the stage is moved between the three optical centers, and a specific location on the sample is individually observed with the three observation devices. It is possible to do.

  FIG. 21 and FIG. 22 are diagrams for illustrating the procedure when performing observation using the sample observation apparatus according to the second aspect of the present invention by way of example, and these sample observation methods will be described below. Comprises the following steps.

  That is, in the sample observation method according to the second aspect of the present invention, a sample having a specific pattern arrangement is placed on a stage that can rotate in the XY plane as a sample placement surface and move in the X and Y directions. (A) adjusting the sample position on the stage so that the region including the arrangement of the specific pattern is observed with an optical microscope and the arrangement direction of the specific pattern is the X direction or the Y direction. And obtaining the mirror electronic image of the region including the arrangement of the specific pattern of the sample by the method already described as the sample observation method of the first aspect of the present invention, and determining the direction of the arrangement of the specific pattern of the mirror electronic image. A step (b) of adjusting a mirror electron detection system so as to match the X direction or the Y direction and the specific pattern comes to the center of the frame of the mirror electron image; and a specific pattern of the sample A step (c) of adjusting the optical system of the SEM type observation apparatus so that a specific pattern of the sample comes to a predetermined center of the SEM image, and the steps (a) and ( b) step (d), which associates the position coordinates of each stage after the adjustment in step (c) with each other, and calculates at least one of the other two position coordinates from any one of these three position coordinates; It has.

  In the mode shown in FIGS. 21 and 22, the above-described step (a), step (b), step (c), and step (d) are executed in this order.

  Referring to FIG. 21, first, a sample having a pattern to be observed is placed on the stage 30 and observation is started (S101). Next, the position of the sample 20 on the stage 30 is confirmed by the optical microscope (OM) 110 (S102), it is determined whether or not the sample position on the stage is appropriate (S103), and if necessary (S103) : No), the sample position is adjusted by the rotary stage 30b (S104).

  FIG. 23A shows the sample 20 on the stage 30 at the start of OM observation. In addition to the line and space pattern extending in the vertical and horizontal directions (X direction or Y direction), the sample 20 is used for alignment in a direction parallel or perpendicular to the extending direction of the line and space pattern. As shown, three “+” patterns are arranged.

In the sample in this state, the alignment direction of the “+” pattern for alignment is shifted by θ _{s from} the moving direction of the XY stage 30a (here, the Y direction). In such a mounted state, alignment (alignment) is not easy and accuracy is lowered even if the same part is observed with another projection apparatus such as a mapping projection type observation apparatus and an SEM type observation apparatus. Therefore, the rotation stage 30b is rotated counterclockwise by θ _s so that the direction of the pattern on the sample matches the movement direction of the XY stage 30a.

  FIG. 23B shows the sample 20 on the stage 30 after the alignment, and the alignment accuracy can be, for example, 1/100 to 1 / 100,000 radians (rad).

In this state, for example, paying attention to the center of the three “+” patterns in FIG. 23B, the stage position is adjusted so that the “+” pattern is positioned at the optical center of the optical microscope. Then, the coordinates (x _o , _yo ) of the optical center position of the optical microscope are obtained from the stage position after the position adjustment.

  Such alignment of the sample position may be performed by image processing such as pattern matching. The alignment accuracy when using image processing can be 1/10 to 1/100 pixels (Px). In addition, such image processing may be performed, for example, by causing the image processing apparatus 90 to process an OM image obtained by the optical microscope 110, and an alignment provided in the control unit 100 based on the image processing result. The stage may be adjusted by the unit.

Next, the mapping optical system detector 70 is adjusted. Specifically, the pixel arrangement direction of the sensor of the detector 70 is confirmed (S105), and it is determined whether or not the pixel arrangement direction of the sensor matches the moving direction (X direction or Y direction) of the stage 30 (S106). ) If necessary (S106: No), θ _t adjustment of the detector 70 is performed (S107).

  FIG. 24 shows the extension or arrangement direction of the pattern on the sample after the alignment is completed in the above procedure (FIG. 24A), the pixel arrangement direction of the sensor of the detector 70 before alignment (FIG. 24B). And FIG. 24 is a diagram for explaining a mutual relationship in the pixel arrangement direction (FIG. 24C) of the sensor of the detector 70 after alignment.

It is assumed that m × n pixels of p _{11 to} p _mn are provided on the electron detection surface 71 of the sensor of the detector 70. At this time, in the state before the alignment of the detector 70, the pixel arrangement directions (for example, p _{11 to} p _1m and p _{11 to} p _m1 ) do not coincide with the pattern extending direction, and the pixel arrangement direction. Is inclined by θ _t with respect to the alignment direction of the “+” pattern for alignment (FIG. 24B).

In this state, it is determined that the rotation angle θ _t of the mapping optical system detector is inappropriate (S106: No), θ _t adjustment of the detector 70 is executed, and the pixel arrangement direction is changed to “+” for alignment. The pattern is made to coincide with the pattern arrangement direction (FIG. 24C).

  FIG. 25 shows the mirror electronic image of the alignment “+” pattern obtained by the extension or arrangement direction of the pattern on the sample after alignment of the detector 70 (FIG. 25A) and the detector before alignment. FIG. 25B is a diagram for conceptually explaining the mutual relationship between the state of FIG. 25B and the state of the mirror electron image of the pattern obtained by the detector after alignment (FIG. 25C). is there.

In the mirror electronic image obtained by the detector before alignment (FIG. 24B), the arrangement direction of the pixels of the detector is inclined by θ _t with respect to the pattern extending direction. The arrangement direction is also tilted by θ _{t with} respect to the moving direction of the stage (here, the Y direction) (FIG. 25B).

  On the other hand, in the mirror electronic image obtained by the aligned detector (FIG. 24C), the arrangement direction of the pixels of the detector is made coincident with the arrangement direction of the pattern. It coincides with the moving direction of the stage (here, the Y direction) (FIG. 25C).

As described above, the sample positions are already aligned with high accuracy of about 1/100 to 1/10000 radians (rad). In this state, the stage is moved in the Y direction, and a mirror electronic image of the pattern is acquired in synchronization therewith, and the rotation angle of the detector is brought into a state where the mirror electronic image is the best (for example, a state where the contrast is maximized). θ _t is adjusted. The accuracy of alignment of such a detector can be set to, for example, 1/100 to 1 / 100,000 radians (rad) similarly to the sample position adjustment.

  As described above, a special alignment pattern (including marks) may be used for the alignment described above. For example, a line and space pattern provided on the sample of the above example. May be used together for alignment.

Next, following the above-described θ _t adjustment of the detector, the optical system of the projection type observation apparatus is adjusted so that the “+” pattern or mark used in the sample position alignment is at the center of the frame of the mirror electronic image. I do.

Specifically, after the θ _t adjustment of the detector is completed, the center coordinates of the image frame of the mirror electronic image are confirmed (S108). Since the mirror electronic image is a two-dimensional continuous image, the continuous image can be divided into frames by image processing. For example, the frame division of the mirror electronic image can be performed so that 1000 × 1000 Px, 2000 × 2000 Px, 4000 × 4000 Px, or the like is one frame.

  FIG. 26 shows the mirror electron image of the alignment “+” pattern obtained by the extension or arrangement direction (FIG. 26A) of the pattern on the sample after the alignment of the detector 70 and the aligned detector. And the state of the mirror electronic image of the alignment “+” pattern after the alignment of the center coordinates of the image frame (FIG. 26C) is conceptually illustrated. It is a figure for demonstrating.

  In the example shown in FIG. 26B, the three “+” patterns for alignment are displayed in the first, third, and fifth image frames. The center of these patterns is the image frame. Is off center. In such a state, it is determined that the center coordinates of the image frame are inappropriate (S109: No), the xy coordinates of the image frame are adjusted (S110), and the appropriate state as shown in FIG. Are aligned as follows.

  The adjustment of the center position of the image frame in the X direction can be performed by fine adjustment of the optical system of the projection type observation apparatus. In this case, adjustment with an accuracy of about 1/10 Px to 10 Px is possible.

  In addition, the adjustment of the center position of the image frame in the Y direction can be performed by finely adjusting the optical system of the projection type observation apparatus in the same manner as the adjustment in the X direction, but by changing the position of the frame division Is also possible. The latter adjustment can be easily performed by changing parameters input to the image processing apparatus 90.

With such an alignment, pay attention to the center of the three “+” patterns used in the sample position adjustment so that the “+” pattern is positioned at the optical center of the projection type observation apparatus. Adjust the position. Then, the coordinates (x _t , y _t ) of the optical center position of the mapping projection observation apparatus are obtained from the stage position.

Subsequently, an area including at least the center of the three “+” patterns is observed with an SEM, and it is confirmed that the center “+” pattern is located at a substantially central position in the SEM observation image. That is, it is confirmed that the central “+” pattern is at the optical center position of the SEM type observation apparatus (S111). Then, the coordinates (x _s , y _s ) of the optical center of the SEM type observation apparatus are obtained from the position of the stage at this time, and the mutual coordinates of the optical center of the optical microscope and the mapping projection type observation apparatus that have already been obtained are obtained. The coordinate data as the positional relationship is stored (S112).

Note that the relationship between the optical center position (x _s , y _s ) of the SEM type observation apparatus and the positions (x _o , _yo ) and (x _t , y _t ) of other optical centers is determined with higher accuracy. In this case, the optical system of the SEM type observation apparatus may be adjusted so that the central “+” pattern of the above three “+” patterns is at the center of the SEM observation image.

  In this case, as shown in FIG. 22, following the above-described step S111, the relationship between the coordinates of the optical center of the SEM and the coordinates of the optical center of the optical microscope and the mapping projection observation apparatus is obtained with a desired high accuracy. (S113), and if it is determined that it is insufficient (S113: No), the above-mentioned SEM optical center adjustment is executed (S114).

  Such an optical system can be adjusted by adjusting an electromagnetic lens (deflector). When a deflector having more than 8 poles is used, the deflection angle control can be performed with high accuracy of about 1/1000 to 1 / 100,000 rad.

  The sample observation apparatus according to the second aspect of the present invention can also be used as an inspection apparatus. For example, a pattern on the sample can be inspected based on the mirror electronic image by the image processing unit provided in the sample observation apparatus having the above-described configuration.

  Such a sample inspection apparatus may have a configuration in which a calculation unit is provided in the image processing unit, and the defect authenticity determination is performed by SEM observation of the pattern defect portion determined by the pattern inspection.

  Moreover, you may make it perform the classification | category of the defect type of the pattern defect location determined to be a real defect using the said calculating part.

  Further, the coordinate file of the pattern defect portion determined to be a true defect is created by using the arithmetic unit in association with at least one of the optical microscope image, the mirror electronic image, and the SEM image. Also good.

  In addition to such an embodiment, a sample observation apparatus having a sample cleaning function can be provided.

  FIG. 27 is a diagram for conceptually explaining the configuration of the apparatus in which the sample cleaning function is added to the sample observation apparatus according to the second aspect of the present invention described above. This apparatus is attached to the surface of the sample 20. A gas supply unit 150 that supplies a cleaning gas for removing contaminants and a gas introduction unit 160 that guides the cleaning gas into the main chamber 22 are provided. The working gas is ejected from the nozzle 180 provided at the tip of the gas introduction section 160 toward the surface of the sample.

  In general, when SEM observation is performed, contaminants such as carbon adhere to the sample surface. Such contaminants are originally irrelevant to the sample to be observed, but such contaminants may become false defects having a specific shape due to electron beam irradiation or the like. Therefore, in the sample observation apparatus shown in FIG. 27, a cleaning gas is introduced into the main chamber 22 and SEM observation is performed, or an electron beam irradiation system provided in the projection projection observation apparatus is used. Thus, the contaminants can be removed.

  As the cleaning gas, it is possible to use a gas that exhibits a removing action by reacting with contaminants or a gas that exhibits the removing action upon irradiation with the electron beam.

For example, SEM observation is performed in a state where oxygen gas, a mixed gas of oxygen and argon, or a fluorine-based gas such as SF ₆ is introduced into the main chamber 22. Contaminants adhere to the sample during SEM observation, but such contaminants react with the gas introduced into the main chamber 22 to sublimate gas (for example, CO gas or CO ₂ gas). To be removed from the sample surface.

In addition to this, for example, after performing SEM observation, it is also possible to perform cleaning over a wide range by irradiating a surface beam on the sample from the electron beam irradiation system of the projection type observation apparatus. When the irradiation area of the surface beam on the sample is, for example, 200 × 200 μm ² , the cleaning of the area range of 100 × 100 mm ² can be completed in about 30 minutes by moving the stage at a speed of 30 mm / s. .

  The embodiment of the present invention has been described above. According to the present invention, by appropriately adjusting the landing energy, the contrast of the fine pattern of the sample can be increased, and therefore the fine pattern can be observed.

  In particular, the present invention focuses on the characteristic of the mirror electron generation phenomenon that mirror electrons are likely to be generated in the concave pattern due to the edges on both sides. Such characteristics have not been used for pattern observation in the past. The amount of mirror electrons generated in the concave pattern depends on the landing energy of the electron beam. Therefore, the landing energy is set so that the irradiation electrons efficiently become mirror electrons in the concave pattern. Thereby, the resolution and contrast of the concave pattern can be increased, and a fine pattern can be observed.

  The technique of the present invention sets the landing energy to a fairly low value. Therefore, the observation technique of the present invention may be called a low landing energy technique.

  In the present invention, the above-mentioned low landing energy technique is applied to a projection type observation apparatus. Thereby, a fine pattern can be observed in a short time.

  In addition, specifically, the low landing energy may be set in a transition region in which mirror electrons and secondary emission electrons are mixed. Further, the landing energy LE may be set to LEA ≦ LE ≦ LEB + 5 eV. By such setting, mirror electrons are easily generated in the pattern portion, and the contrast of the pattern in the image can be increased.

  Further, in the present invention, as described in detail above, the size, position, and shape of the aperture are suitably adjusted, whereby the contrast of the pattern in the image can be further increased.

  In the present invention, the mapping projection observation apparatus and the SEM are provided in the same chamber, and the same stage is used to constitute a composite observation apparatus. As a result, when two types of inspection are continuously performed, the positioning time is shortened and the positioning accuracy is greatly increased. Therefore, quick and highly accurate observation is possible.

  Furthermore, in the sample observation method and apparatus according to the second aspect of the present invention, each image obtained by sample observation using an optical microscope, sample observation using a mirror electron image, and sample observation using an SEM image is at which position of the observation target sample. Therefore, even if an observation target location specified by one of the three observation methods is to be observed by another observation method, the observation target location is It becomes possible to specify quickly and accurately.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and it goes without saying that those skilled in the art can modify the above-described embodiments within the scope of the present invention.

  As described above, the sample observation technique according to the present invention is useful in the inspection of a semiconductor wafer or mask.

DESCRIPTION OF SYMBOLS 10 Sample inspection apparatus 12 Sample carrier 14 Mini-environment 16 Load lock 18 Transfer chamber 20 Sample 22 Main chamber 24 Electronic column 26 Vacuum control system 28 Vibration isolator 30 Stage 40 Primary optical system 41 Electron gun 42, 45, 47, 49 , 50, 61, 63 Lens 43, 44, 48, 62 Aperture 60, 60a Secondary optical system 64 Aligner 65 EB-CCD
66 XY stage 67, 68 Aperture 69, 69a, 69b, 169 Aperture hole 70 Detector 90 Image processing apparatus 100 Control unit 110 Optical microscope 120 SEM
130 Electro-optical system control power supply 140 System software 150 Gas supply device 160 Gas introduction unit 170 Flow rate adjustment unit 180 Nozzle 200 Aperture adjustment mechanism

Claims (39)

A sample observation method for observing a pattern on a sample using an electron beam,
Irradiating the sample with an electron beam;
Detecting mirror electrons generated by irradiation of the electron beam;
Generating an image of the sample from the detected mirror electrons,
In the step of irradiating the electron beam, the landing energy is adjusted so that when the electron beam is irradiated to a concave pattern having edges on both sides, the irradiated electron makes a U-turn in the concave pattern to become a mirror electron. A sample observation method comprising irradiating the sample with the electron beam.   The sample observation method according to claim 1, wherein the landing energy is set in a region where the mirror electrons and secondary emission electrons are mixed. The landing energy is
LEA ≦ LE ≦ LEB + 5 eV,
Here, LE is the landing energy of the electron beam, and LEA and LEB are the lowest landing energy and the highest landing energy in a region where the mirror electrons and secondary emission electrons are mixed. The sample observation method described in 1.   The irradiation electrons are incident toward one edge of the concave pattern, bend toward the other edge in the vicinity of the one edge, and bend near the other edge to become mirror electrons. The sample observation method according to any one of claims 1 to 3.   The irradiated electrons are incident toward one edge of the concave pattern, enter the concave pattern along a curved path passing through the vicinity of the one edge, and proceed without colliding with the bottom of the concave pattern. The sample observation method according to claim 1, wherein the sample is changed in direction and passes through the vicinity of the other edge of the concave pattern to become the mirror electrons.   An aperture is arranged in a secondary optical system between the sample and the detector of the mirror electrons, and at least one of the size, position and shape of the aperture is adjusted according to the mirror electrons passing through the aperture. The sample observation method according to any one of claims 1 to 5, wherein:   The sample observation method according to claim 6, wherein an image of the mirror electrons in the aperture is generated, and the size of the aperture is adjusted according to the size of the image.   The sample observation method according to claim 6, wherein an image of the mirror electrons in the aperture is generated, and the position of the aperture is adjusted according to the position of the image.   The sample observation method according to claim 6, wherein an image of the mirror electrons in the aperture is generated, and the shape of the aperture is adjusted according to the shape of the image.   A sample inspection comprising: generating an image of the sample from the mirror electrons by the sample observation method according to claim 1; and inspecting the pattern of the sample using the image of the sample. Method. A composite type sample observation method for observing a sample placed on the same stage by an optical microscope and an SEM type observation device different from the mapping projection type observation device and the mapping projection type observation device,
The positional relationship of the optical centers of the three observation devices of the mapping projection observation device, the SEM observation device, and the optical microscope is stored as coordinate data, and the stage is moved to the three optical centers based on the coordinate data. A composite type sample observing method characterized in that a specific portion on the sample is individually observed with the three observation devices by moving between the two. A composite-type sample observation method comprising the following steps.
(A) A region on which a sample having a specific pattern arrangement is placed on a stage capable of rotating in the XY plane, which is the sample placement surface, and moving in the X and Y directions, and including the specific pattern arrangement Adjusting the sample position on the stage so that the arrangement direction of the specific pattern is the X direction or the Y direction by observing the sample with an optical microscope:
(B) A mirror electronic image of a region including a specific pattern arrangement of the sample is obtained by the sample observation method according to any one of claims 1 to 9, and the direction of the specific pattern arrangement is changed to the mirror. Adjusting the mirror electron detection system so that it coincides with the X or Y direction of the electronic image and the specific pattern is in the center of the frame of the mirror electronic image;
(C) SEM observation of an area including the specific pattern of the sample, and adjusting the optical system of the SEM type observation apparatus so that the specific pattern of the sample is at a predetermined center of the SEM image:
(D) The position coordinates of each stage after the adjustment in step (a), step (b), and step (c) are associated with each other, and from one of these three position coordinates to the other two position coordinates Calculating at least one of:   The composite sample observation method according to claim 12, wherein the step (a), the step (b), the step (c), and the step (d) are performed in this order. A sample inspection method comprising the following steps.
(E) A step of generating an image of the sample from the mirror electrons by the sample observation method according to any one of claims 11 to 13 and inspecting a pattern of the sample using the image of the sample: The sample inspection method according to claim 14, further comprising the following steps.
(F) A step of performing SEM observation of the pattern defect portion determined by the pattern inspection in the step (e) to determine the authenticity of the defect: The sample inspection method according to claim 15, further comprising the following steps.
(G) A step of classifying the defect type of the pattern defect portion determined as a true defect in the step (f): The sample inspection method according to claim 15 or 16, further comprising the following steps.
(H) A coordinate file of a pattern defect determined as a true defect in the step (f) is created in association with at least one of the optical microscope image, the mirror electronic image, and the SEM image. Step: A stage on which a sample having a pattern is placed;
A primary optical system for irradiating the sample with an electron beam;
A secondary optical system for detecting mirror electrons generated by irradiation of the electron beam;
An image processing unit that generates an image of a sample from the detected mirror electrons,
In the primary optical system, the landing energy is adjusted so that when the electron beam is irradiated onto a concave pattern having edges on both sides, the irradiated electron makes a U-turn in the concave pattern and becomes a mirror electron. A sample observation apparatus irradiating the sample with a beam.   19. The sample observation apparatus according to claim 18, wherein the primary optical system irradiates the electron beam having the landing energy set in a region where the mirror electrons and secondary emission electrons are mixed. The landing energy is
LEA ≦ LE ≦ LEB + 5 eV,
Here, LE is the landing energy of the electron beam, and LEA and LEB are the lowest landing energy and the highest landing energy in a region where the mirror electrons and secondary emission electrons are mixed. The sample observation apparatus according to 1.   The secondary optical system has at least one of an aperture disposed between the sample and the detector of the mirror electrons, and the size, position, and shape of the aperture according to the mirror electrons passing through the aperture. The sample observation apparatus according to any one of claims 18 to 20, further comprising an aperture adjustment mechanism for adjusting the aperture.   21. The any one of claims 18 to 20, wherein the secondary optical system has an aperture, and the position of the aperture is adjusted so that the center of intensity of the mirror electron coincides with the center of the aperture. The sample observation apparatus according to item 1.   The secondary optical system has an aperture, and the shape of the aperture is an elliptical shape having a major axis in a direction corresponding to a longitudinal direction of the intensity distribution of the mirror electrons. The sample observation device according to any one of the above.   The secondary optical system has an aperture, the aperture has a plurality of holes, and the plurality of holes are arranged so as to surround the center of intensity of the mirror electrons. The sample observation device according to any one of 20.   The secondary optical system has an aperture, the aperture has a plurality of holes, and one of the plurality of holes is arranged so as to coincide with the intensity center of the mirror electron. Item 21. The sample observation apparatus according to any one of Items 18 to 20. A mapping projection observation apparatus, and an SEM observation apparatus different from the mapping projection observation apparatus;
The mapping projection observation device is the sample observation device according to any one of claims 18 to 20,
The mapping projection observation apparatus and the SEM observation apparatus are provided in a chamber that accommodates the stage, and the stage is between an observation position of the mapping projection observation apparatus and an observation position of the SEM observation apparatus. A composite type sample observation apparatus characterized by being movable. A mapping projection observation apparatus, a SEM observation apparatus different from the mapping projection observation apparatus, and an optical microscope,
The mapping projection observation apparatus is the sample observation apparatus according to any one of claims 18 to 25,
The mapping projection observation apparatus, the SEM observation apparatus, and the optical microscope are provided in a chamber that accommodates the stage, and the stage includes an observation position of the mapping projection observation apparatus and an observation of the SEM observation apparatus. A composite type sample observation apparatus, which is movable between a position and an observation position of the optical microscope.   A control unit that stores the positional relationship between the optical centers of the mapping projection observation apparatus, the SEM observation apparatus, and the optical microscope as coordinate data, and that enables the stage to move between the three optical centers. 28. The composite sample observation apparatus according to claim 27, wherein:   29. The composite sample observation apparatus according to claim 28, wherein the stage is a stage that is movable in the X direction and the Y direction within the sample placement surface and is rotatable within the XY plane.   30. The composite type according to claim 29, wherein the detector provided in the secondary optical system of the mapping projection type observation apparatus is configured to be capable of rotational adjustment in the XY plane which is an electron detection surface. Sample observation equipment.   An alignment unit that adjusts a sample position on the stage so that an arrangement direction of a specific pattern on the sample coincides with an X direction or a Y direction, which is a moving direction of the stage, is provided. 29. A composite type sample observation apparatus according to 29.   The alignment unit performs the detection so that an arrangement direction of a specific pattern on the sample after the sample position adjustment matches an X direction or a Y direction of a frame of a mirror electronic image obtained by the mapping projection observation apparatus. 32. The composite sample observation apparatus according to claim 31, wherein a vessel is adjusted.   The alignment unit is configured so that an observation image obtained by observing a specific pattern on the sample after the sample position adjustment with the SEM type observation device is positioned in the center of the SEM image. The composite sample observation apparatus according to claim 32, wherein the system is adjusted.   34. A gas supply unit that supplies a cleaning gas for removing contaminants attached to the surface of the sample, and a gas introduction unit that guides the cleaning gas into the chamber. The composite type sample observation apparatus according to any one of the above.   35. The composite type sample observation apparatus according to claim 34, wherein the cleaning gas is a gas that reacts with the contaminant and exhibits a removing action, or a gas that exhibits the removing action upon irradiation with the electron beam.   36. The sample observation device according to any one of claims 18 to 35, wherein the image processing unit inspects a pattern of the sample using an image of the sample generated from the mirror electrons. Sample inspection device.   37. The sample inspection apparatus according to claim 36, wherein the image processing unit includes a calculation unit that performs SEM observation of a pattern defect portion determined by the pattern inspection to determine whether the defect is true or false.   38. The sample inspection apparatus according to claim 37, wherein the calculation unit is capable of classifying defect types of pattern defect portions determined to be true defects.   The calculation unit can create a coordinate file of a pattern defect portion determined as a true defect in association with at least one of the optical microscope image, the mirror electronic image, and the SEM image. 38. The sample inspection apparatus according to 38.