Scanning electron microscope and brightness adjustment method

Abstract

To enable objective and reproducible adjustment of a brightness distribution of an electronic image.SOLUTION: A histogram 78 of a standard sample is produced based on an electronic image. An offset of a detection signal is automatically adjusted such that a mid point Cx between an apex point P1a of a first peak and an apex point P2a of a second peak matches a standard mid point C0. Gain of the detection signal is then adjusted such that a distance Dx between an apex point P1b and an apex point P2b matches a standard distance D0.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a scanning electron microscope and a brightness adjustment method, and more particularly to adjusting the brightness distribution of an electron image. [Background technology]

[0002] Scanning electron microscopes are used in particle analysis. For example, an electron image (such as a backscattered electron image or a secondary electron image) is formed based on the detection signal obtained by two-dimensionally scanning an electron beam over a sample. The electron image is then binarized, and each particle contained in the sample is identified by analyzing the binarized electron image. Specifically, the number of particles, the size of each particle, and the shape of each particle are identified. A composition analysis based on X-ray spectroscopy is performed on each identified particle, and the elements that make up each particle are identified. The sample is, for example, a cleaning solution left over after cleaning a product, and each particle corresponds to a foreign particle.

[0003] Prior to particle analysis based on an electronic image, the brightness distribution (brightness histogram) of the electronic image is adjusted. Specifically, an offset adjustment is performed to adjust the offset of the detection signal, and a gain adjustment is performed to adjust the gain of the detection signal. The brightness distribution of the electronic image may also be adjusted for purposes other than particle analysis.

[0004] Patent Document 1 discloses a technology for automatically adjusting the luminance distribution of an electronic image by comparing the actual luminance distribution obtained from a real sample with multiple reference luminance distributions. Patent Document 1 does not describe automatic adjustment of the luminance distribution using a standard sample. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 4-328234 Summary of the Invention [Problem to be solved by the invention]

[0006] Manually adjusting the brightness distribution based on the electronic image of the sample being measured does not ensure sufficient objectivity and reproducibility, and sample analysis results will vary depending on the observer. It is desirable to automatically adjust the brightness distribution so that the actual brightness distribution approaches or matches the ideal brightness distribution.

[0007] An object of the present invention is to objectively adjust the brightness distribution of an electron image with good reproducibility, to provide a brightness adjustment technique for particle analysis based on electron images, or to maintain an appropriate brightness distribution of an electron image even if the state of a scanning electron microscope changes over time. [Means for solving the problem]

[0008] A scanning electron microscope according to the present invention includes an observation unit that irradiates an electron beam onto an observation region set across a first element region and a second element region in a standard specimen and detects electrons emitted from the observation region, a formation unit that forms an electron image of the observation region based on a detection signal generated by the detection of the electrons, and an adjustment unit that applies offset adjustment and gain adjustment to the detection signal or the electron image so that an actual brightness distribution of the electron image matches a standard brightness distribution, the first element region includes a first element, the second element region includes a second element, and a standard luminance distribution corresponding to a combination of the first element and the second element is used as the standard luminance distribution; The offset adjustment and the gain adjustment are performed by observing the standard sample prior to or during the observation of the actual sample.

[0009] A brightness adjustment method according to the present invention includes the steps of irradiating an observation region set across a first element region and a second element region in a standard specimen with an electron beam and detecting electrons emitted from the observation region, forming an electron image of the observation region based on a detection signal generated by the detection of the electrons, and applying offset adjustment and gain adjustment to the detection signal or the electron image so that an actual brightness distribution of the electron image matches a standard brightness distribution, the first element region includes a first element, the second element region includes a second element, and a standard luminance distribution corresponding to a combination of the first element and the second element is used as the standard luminance distribution;The offset adjustment and the gain adjustment are performed by observing the standard sample prior to or during the observation of the actual sample. [Effects of the Invention]

[0010] According to the present invention, it is possible to objectively adjust the brightness distribution of an electron image with good reproducibility. Alternatively, according to the present invention, it is possible to provide a brightness adjustment technique for particle analysis based on electron images. Alternatively, according to the present invention, it is possible to maintain an appropriate brightness distribution of an electron image even if the state of a scanning electron microscope changes over time. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a scanning electron microscope according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of a signal processing circuit. [Figure 3] FIG. 4 is a diagram illustrating information stored in a storage unit. [Figure 4] FIG. 2 is a diagram showing an example of a sample holder. [Figure 5] FIG. 1 is a diagram showing an example of a standard sample. [Figure 6] FIG. [Figure 7] 1A and 1B are explanatory diagrams showing a brightness adjustment method according to an embodiment. [Figure 8] 1 is a flowchart illustrating a brightness adjustment method according to an embodiment. [Figure 9] 1 is a flowchart showing the operation of a scanning electron microscope. [Figure 10] FIG. 10 is a diagram showing a standard sample table. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment will be described with reference to the drawings.

[0013] (1) Overview of the embodiment A scanning electron microscope according to an embodiment includes an observation unit, a formation unit, and an adjustment unit. The observation unit irradiates an observation region set across a first element region and a second element region in a standard sample with an electron beam and detects electrons emitted from the observation region. The formation unit forms an electron image of the observation region based on a detection signal generated by the detection of electrons. The adjustment unit applies offset adjustment and gain adjustment to the detection signal or the electron image so that the actual brightness distribution of the electron image matches the standard brightness distribution. The offset adjustment and the gain adjustment are performed by observing a standard sample prior to or during the observation of the actual sample.

[0014] According to the above configuration, an electron image of a standard sample is obtained, and offset and gain adjustments are performed so that its actual luminance distribution matches the standard luminance distribution. Therefore, the luminance distribution of the electron image can be adjusted objectively and with good reproducibility. If particle analysis is performed after offset and gain adjustments, the accuracy of particle analysis can be improved. Because offset and gain adjustments can be performed using the actual measurement results of the standard sample, the scanning electron microscope is less susceptible to changes in its condition over time.

[0015] Offset and gain adjustments may be applied to the detection signal. In this case, the adjustments are made to either the analog or digital detection signal. Offset and gain adjustments may also be applied to the electron image. By performing offset and gain adjustments sequentially or simultaneously, the actual brightness distribution of the electron image is optimized. The observation unit is a measurement unit that scans an electron beam over a sample and detects the electrons (backscattered electrons, secondary electrons, etc.) generated thereby. When performing offset and gain adjustments, the standard brightness distribution itself may be used, or multiple feature quantities representing the standard brightness distribution may be used. For example, if a product contains a foreign substance made of a specific material in its base material, one of the first and second elements is the base material element, and the other of the first and second elements is the foreign substance element. A standard brightness distribution is prepared for each combination of base material and foreign substance material. Standard brightness distributions corresponding to combinations of base material and multiple foreign substance materials may also be prepared.

[0016] In the embodiment, the adjustment unit performs offset adjustment and gain adjustment so that two actual peak positions identified from the actual luminance distribution match two standard peak positions representing the standard luminance distribution. With this configuration, the offset adjustment and gain adjustment can be performed quickly and easily. The standard luminance distribution can also be called a target luminance distribution.

[0017] In an embodiment, the adjustment unit includes an offset adjustment unit and a gain adjustment unit. The offset adjustment unit performs offset adjustment so that the midpoint between two actual peak positions coincides with the midpoint between two standard peak positions. The gain adjustment unit performs gain adjustment so that the interval between the two actual peak positions coincides with the interval between the two standard peak positions. Performing two-stage adjustment can avoid complicating the adjustment process.

[0018] In this embodiment, the offset adjustment is performed first, followed by the gain adjustment. If the gain adjustment is performed first, there is a high possibility that one peak (or part of the peak) will exceed the observation range and become invisible. If the offset adjustment is performed first, the possibility of such a problem occurring can be reduced.

[0019] The scanning electron microscope according to the embodiment includes a memory unit and a control unit. The memory unit stores coordinate information that identifies an observation area. The control unit executes control to align an electron beam irradiation area with the observation area based on the coordinate information. The irradiation area can be adjusted by moving a stage or deflecting the electron beam.

[0020] A scanning electron microscope according to an embodiment has a sample holder. The sample holder has a plurality of actual sample holders for holding a plurality of actual samples and a standard sample holder for holding a standard sample. The actual sample holders are arranged in a ring shape in the sample holder. The standard sample holder is surrounded by the actual sample holders in the sample holder. By adopting this configuration, the amount of movement of the stage carrying the sample holder can be reduced when adjusting the offset and gain. Alternatively, the offset and gain adjustments can be performed quickly at any timing.

[0021] In an embodiment, offset adjustment and gain adjustment are performed by observing a standard sample prior to observing multiple real samples. Furthermore, offset adjustment and gain adjustment are performed by observing a standard sample during the observation of multiple real samples. There is a tendency for the average brightness of an electronic image to gradually decrease as the observation time increases. By performing offset adjustment and gain adjustment intermittently, the decrease in brightness can be compensated for and the brightness distribution can be maintained appropriately. This increases the reliability of particle analysis results.

[0022] The brightness adjustment method according to the embodiment includes an observation step, a formation step, and an adjustment step. In the observation step, an observation region set across a first element region and a second element region in a standard sample is irradiated with an electron beam, and electrons emitted from the observation region are detected. In the formation step, an electron image of the observation region is formed based on a detection signal generated by detecting the electrons. In the adjustment step, offset adjustment and gain adjustment are applied to the detection signal or the electron image so that the actual brightness distribution of the electron image matches the standard brightness distribution. Prior to or during observation of the actual sample, offset adjustment and gain adjustment are performed by observing a standard sample. In the embodiment, all steps are performed automatically, but some steps may be performed manually.

[0023] (2) Details of the embodiment FIG. 1 shows a scanning electron microscope according to an embodiment. This scanning electron microscope has a function for performing particle analysis. For example, particle analysis is applied to foreign particles contained in cleaning water after product cleaning. In this case, the product may be an industrial product or a semiconductor product. The scanning electron microscope has an observation unit 10 and an arithmetic and control unit 12.

[0024] First, the observation unit will be described. The observation unit 10 functions as a measurement unit. Specifically, the observation unit 10 has an electron tube 14. The electron tube 14 houses an electron gun, a deflection lens, an objective lens, etc. An electron beam 16 is generated by the electron gun.

[0025] A sample chamber 18 is provided at the bottom of the microscope column 14. The sample chamber 18 is surrounded by a housing 20. A stage 22 is provided within the sample chamber 18, and a sample holder 24 is fixed onto the stage 22. The position and orientation of the sample holder 24 are changed by the stage 22. The sample holder 24 is equipped with an actual sample and a standard sample. The actual sample is the object to be measured, that is, the object to be analyzed. The standard sample is observed when adjusting the brightness distribution.

[0026] A plurality of detectors are provided in the sample chamber 18. These include a backscattered electron detector, a secondary electron detector, an X-ray detector (spectrometer), etc. In this embodiment, a detection signal output from the backscattered electron detector is used for particle analysis.

[0027] Next, the calculation control unit 12 will be described. As will be shown later in FIG. 2, the signal processing circuit 26 has an offset adjustment circuit, a gain adjustment circuit, and an A / D converter. In the embodiment, the offset adjustment and gain adjustment are applied to the analog detection signal. Of course, the offset adjustment and gain adjustment may also be applied to the digital detection signal. The offset adjustment and gain adjustment may also be applied to the electronic image, which will be described later. Whichever method is adopted, the luminance distribution of the electronic image can be adjusted as a result.

[0028] The image forming unit 28 forms an electronic image based on the detection signal (digital detection signal) output from the signal processing circuit 26. The electronic image is a two-dimensional image, also called an SEM image. When observing a standard sample, an electronic image of the standard sample is formed, and when observing a real sample, an electronic image of the real sample is formed.

[0029] The particle analysis unit 30 performs particle analysis based on an electronic image of the actual sample. In this case, the electronic image of the actual sample is binarized using a threshold value, and individual particles are identified in the binarized electronic image, as well as the size and shape of each particle. Subsequently, composition analysis is performed by irradiating each particle with an electron beam. Furthermore, the amount of foreign matter is determined from the total particle area in the electronic image. Various well-known methods can be used for particle analysis. The particle analysis results are displayed on a display (not shown).

[0030] The image forming unit 28 and the particle analysis unit 30 may each be configured by a processor. The information processing unit 32 is configured by, for example, a CPU that executes a program. In FIG. 1, the multiple functions performed by the information processing unit 32 are represented by multiple blocks. The information processing unit 32 functions as a histogram creation unit 34, an offset adjustment unit 36, and a gain adjustment unit 38. The information processing unit 32 also functions as a control unit that controls the operation of the observation unit 10. The information processing unit 32 may function as the image forming unit 28 and the particle analysis unit 30.

[0031] A storage unit 40 is connected to the information processing unit 32. The storage unit 40 is configured by a semiconductor memory, a hard disk, etc. The information stored in the storage unit 40 will be explained later with reference to FIG.

[0032] The histogram creation unit 34 creates a histogram (brightness histogram) as a brightness distribution based on an electronic image of the standard sample. If the standard sample is composed of two materials (e.g., a product base material and a foreign material), two peaks will appear in the histogram of the standard sample. The histogram creation unit 34 repeatedly creates histograms during the offset adjustment process and the gain adjustment process.

[0033] The offset adjustment unit 36 ​​adjusts the offset of the detection signal. Normally, offset adjustment causes two peaks to move parallel along the horizontal axis of the histogram. The gain adjustment unit 38 adjusts the gain of the detection signal. Normally, gain adjustment changes the distance between the two peaks. Gain adjustment can also be called contrast adjustment.

[0034] Prior to observing a real sample, offset and gain adjustments are performed using a standard sample, and then offset and gain adjustments are performed using the standard sample at the necessary timing during the sample observation. When observing multiple real samples sequentially, offset and gain adjustments using the standard sample may be performed between two temporally adjacent real sample observations. Due to changes in the state of the electron gun and other reasons, the brightness distribution of the electron image gradually decreases as the observation time increases. By adjusting the brightness distribution at the necessary timing, the accuracy of particle analysis can be maintained or improved.

[0035] 2 shows an example configuration of the signal processing circuit 26. The signal processing circuit 26 has an offset adjustment circuit 42, a gain adjustment circuit 44, and an A / D converter 46. The order of these components may be reversed. An analog detection signal 48 and an offset adjustment signal 50 are input to the offset adjustment circuit 42. The offset adjustment circuit 42 adjusts the offset of the analog detection signal 48 based on the offset adjustment signal 50.

[0036] The gain adjustment circuit 44 receives the analog detection signal after offset adjustment, and also receives a gain adjustment signal 52. The gain adjustment circuit 44 adjusts the gain of the input analog detection signal based on the gain adjustment signal 52. The A / D converter 46 converts the analog detection signal output from the gain adjustment circuit 44 into a digital detection signal.

[0037] 3 shows information stored in the storage unit 40. In the example shown, the storage unit 40 stores observation area coordinate information 54, a first standard brightness 56, a second standard brightness 58, a coefficient set 60, etc. The observation area coordinate information 54 is information that specifies an observation area to be set for a standard specimen, and the stage position and irradiation position are adjusted based on the observation area coordinate information 54.

[0038] The histogram obtained from the standard sample includes a first peak corresponding to the first element and a second peak corresponding to the second element. The first element is either the product base material or the foreign material, and the second element is the other of the product base material and the foreign material. On the horizontal axis, i.e., the brightness axis, of the histogram, a first standard brightness 56 is a brightness (standard position) that is compared with the brightness at the apex of the first peak (first peak position), and a second standard brightness 58 is a brightness (standard position) that is compared with the brightness at the apex of the second peak (second peak position). While the standard brightness distribution itself may be stored in the memory unit 40, in this embodiment, two feature quantities that represent the standard brightness distribution, i.e., two standard brightnesses 56 and 58, are stored. A representative position of each peak may be determined based on the average, center of gravity, etc. of each peak.

[0039] The coefficient set 60 is made up of two coefficients k1 and k2. The coefficient k1 is a coefficient that defines the size of the increments during offset adjustment, and the coefficient k2 is a coefficient that defines the size of the increments during gain adjustment.

[0040] 4 shows an example of a sample holder used in particle analysis. In the illustrated example, the sample holder 24 has a real sample holder array 62 and a standard sample holder 63 provided on a base 64. The real sample holder array 62 is composed of six real sample holders 62A arranged in a ring. The standard sample holder 63 is provided in the center of the sample holder 24 and is surrounded by the six real sample holders 62A.

[0041] Each real sample holder 62A has a recess in which a filter 66 serving as a circular sheet is placed. The filter 66 is a member that captures particles in the cleaning solution. A ring 68 serving as a weight is placed in each recess to prevent the filter 66 from moving within the recess. A well-shaped depression is formed in the center of the standard sample holder 63, and a cylindrical standard sample 70 is inserted into it.

[0042] FIG. 5 shows a standard sample 70. The lower part of FIG. 5 (see A) shows a side view of the standard sample 70, and the upper part of FIG. 5 (see B) shows the top view of the standard sample 70. The material 72 is composed of, for example, an element corresponding to the foreign matter. The material 72 has a cylindrical shape. The material 72 is composed of, for example, copper. A rectangular sheet 74 is attached to the top surface 72A of the material 72. The sheet 74 is composed of an element corresponding to the product base material, for example, carbon. The sheet 74 may be composed of adhesive tape. A metal foil, a resin film, or the like may also be used as the sheet 74. An observation area 76 is set on the top surface 72A, spanning the surface of the material 72 and the surface of the sheet 74.

[0043] FIG. 6 shows an enlarged view of the observation region 76. The base material element region 200A is specifically a carbon region. The foreign material element region 200B is specifically a copper region. The observation region 76 is set across the base material element region 200A and the foreign material element region 200B. Half of the observation region 76 is a portion 76A that belongs to the base material element region 200A, and the other half of the observation region 76 is a portion 76B that belongs to the foreign material element region 200B. The portions 76A and 76B have the same area.

[0044] Fig. 7 shows a brightness adjustment method according to an embodiment. Histogram 78 shown in the upper part of Fig. 7 is a histogram created from an electronic image of a standard sample. The horizontal axis represents brightness I, and the vertical axis represents the number of pixels N.

[0045] A standard intermediate position (standard intermediate luminance) C0 is specified as the intermediate position between the first standard position (first standard luminance) and the second standard position (second standard luminance). The standard intermediate position (standard intermediate luminance) C0 can also be called a target intermediate position (target intermediate luminance). Furthermore, a standard interval (standard luminance difference) D0 is specified as the interval between the first standard position and the second standard position. The standard interval (standard luminance difference) D0 can also be called a target interval (target luminance difference). The intermediate position can also be called a center position.

[0046] The histogram 78 includes a first peak 80 and a second peak 82. For example, the first peak 80 is one of a base material element peak and a foreign material element peak, and the second peak 82 is the other of a base material element peak and a foreign material element peak. An actual midpoint position Cx is determined based on the apex position P1a of the first peak 80 and the apex position P2a of the second peak 82. An offset adjustment is performed (see reference numeral 84) so ​​that the actual midpoint position Cx coincides with the above-mentioned standard midpoint position C0.

[0047] The histogram after the offset adjustment is shown in the middle of Figure 7. The actual interval Dx is calculated as the difference between the apex position P1b of the first peak and the apex position P2b of the second peak. Gain adjustment is performed (see reference numeral 86) so that the actual interval Dx matches the standard interval D0.

[0048] The lower part of Fig. 7 shows a histogram after the offset adjustment and the gain adjustment. The actual interval Dx coincides with the standard interval D0. The apex position P1c of the first peak coincides with the first standard position, and the apex position P2c of the second peak coincides with the second standard position. Note that the gain adjustment may be performed while maintaining the state in which the actual middle position Cx coincides with the standard middle position C0. The offset adjustment may also be performed again after the gain adjustment.

[0049] The peaks in the histogram can be identified using various known techniques. For example, each peak may be identified by first performing noise removal and smoothing on the histogram and then performing two differentiation processes (inflection point extraction processes) on the histogram.

[0050] 8 shows a flowchart of a brightness adjustment method according to an embodiment. A sample holder equipped with a standard sample and a real sample is mounted on a stage. In S10, observation area coordinate information is referenced. In S12, two standard brightnesses (first standard brightness and second standard brightness) corresponding to the standard sample to be used are identified.

[0051] In S14, the stage position is controlled based on the observation area coordinate information. This determines the observation area as the actual irradiation area. In S16, an offset initial value is provided to the offset adjustment circuit, and a gain initial value is provided to the gain adjustment circuit. Various automatic adjustments such as autofocus may be performed at this stage.

[0052] In S18, an electron beam is irradiated onto the standard sample. Specifically, the electron beam is scanned across the entire observation area. An electron image (SEM image) is formed based on the detection signal obtained thereby. In S20, a histogram is created based on the electron image. In S22, the number of peaks contained in the histogram is counted. Typically, the number of peaks is 2. If the number of peaks is a value other than 2, the stage position is changed in S26. In other words, the observation area is changed so that the number of peaks becomes 2. Error processing may be performed when a value other than 2 is found as the number of peaks a predetermined number of times.

[0053] In S28, an actual middle position is identified from two peak positions in the histogram, and a standard middle position is identified from the first standard brightness (first standard position) and the second standard brightness (second standard position). The difference between the actual middle position and the standard middle position is calculated as a first difference. If the first difference is within a first tolerance range, S34 is executed, and if the first difference exceeds the first tolerance range, the offset is changed in S32. For example, the offset change amount is determined by multiplying the first difference by a coefficient k1. After the offset is changed, the steps from S18 onwards are executed again.

[0054] In S30, the actual interval is determined from the positions of two peaks in the histogram, and the standard interval is determined from the first standard brightness (first standard position) and the second standard brightness (second standard position). The difference between the actual interval and the standard interval is calculated as the second difference. If the second difference is within the second allowable range, this process ends. If the second difference exceeds the second allowable range, the gain is changed in S38. For example, the gain change amount is determined by multiplying the second difference by a coefficient k2. After the gain is changed, the steps from S18 onwards are executed again.

[0055] By adjusting the offset and gain as described above, the histogram obtained from the standard sample approaches an ideal histogram. Then, a threshold is determined based on the histogram. For example, the midpoint between the first and second peaks is set as the threshold.

[0056] After the offset adjustment and gain adjustment are completed, the actual sample is observed, thereby acquiring an electron image of the actual sample. The electron image is binarized using the above threshold. Particle analysis is performed based on the binarized electron image. When analyzing the composition of individual particles, an electron beam is irradiated onto each particle, and the spectrum of the characteristic X-rays generated thereby is analyzed. Various known methods can be used as particle analysis methods.

[0057] FIG. 9 shows the operation of the scanning electron microscope as a flowchart. In S40, the brightness distribution is adjusted using a standard sample. In this case, the brightness adjustment method shown in FIGS. 7 and 8 is executed. In S42, a real sample is observed, and particle analysis is applied to the resulting electron image. If it is determined in S44 that an unobserved real sample remains, it is determined in S46 whether a predetermined condition is met. For example, the predetermined condition is met when a certain amount of time has passed since the previous brightness distribution adjustment. Alternatively, the predetermined condition may be met when observation of one real sample is completed. If the predetermined condition is met, brightness distribution adjustment is performed again in S40. If it is determined in S44 that no unobserved real samples remain, this process ends.

[0058] FIG. 10 shows a standard specimen table 88. The standard specimen table 88 is used when multiple standard specimens are selectively used. The standard specimen table 88 is composed of multiple records 90 corresponding to multiple standard specimens. Each record 90 includes a standard specimen number 92, first element information 94, second element information 96, first standard brightness 98, and second standard brightness 100, and may further include other information 102 as needed. Examples of the other information 102 include acceleration voltage, irradiation current, and observation magnification.

[0059] According to the brightness adjustment method of the embodiment, the brightness distribution of an electron image can be adjusted objectively and with good reproducibility. In particular, since a standard sample is used, the brightness distribution of the electron image can be maintained at an appropriate level even if the state of the scanning electron microscope changes over time. [Explanation of symbols]

[0060] 10 observation unit, 12 calculation control unit, 22 stage, 24 sample holder, 26 signal processing circuit, 28 image formation unit, 30 particle analysis unit, 32 information processing unit, 34 histogram creation unit, 36 offset adjustment unit, 38 gain adjustment unit, 42 offset adjustment circuit, 44 gain adjustment circuit, 70 standard sample.

Claims

1. an observation unit that irradiates an electron beam onto an observation region set across a first element region and a second element region in the standard sample and detects electrons emitted from the observation region; a forming unit that forms an electron image of the observation area based on a detection signal generated by detecting the electrons; an adjustment unit that applies offset adjustment and gain adjustment to the detection signal or the electronic image so that the actual luminance distribution of the electronic image matches a standard luminance distribution; Including, the first element region includes a first element; the second element region includes a second element; a standard luminance distribution corresponding to a combination of the first element and the second element is used as the standard luminance distribution, the offset adjustment and the gain adjustment are performed by observing the standard sample prior to or during the observation of the real sample. A scanning electron microscope characterized by:

2. 2. The scanning electron microscope according to claim 1, the adjustment unit performs the offset adjustment and the gain adjustment so that two actual peak positions identified from the actual luminance distribution coincide with two standard peak positions representing the standard luminance distribution. A scanning electron microscope characterized by:

3. 3. The scanning electron microscope according to claim 2, The adjustment unit an offset adjustment unit that performs the offset adjustment so that a midpoint between the two actual peak positions coincides with a midpoint between the two standard peak positions; a gain adjustment unit that performs the gain adjustment so that the interval between the two actual peak positions matches the interval between the two standard peak positions; A scanning electron microscope comprising:

4. 4. The scanning electron microscope according to claim 3, The offset adjustment is performed first, followed by the gain adjustment. A scanning electron microscope characterized by:

5. 2. The scanning electron microscope according to claim 1, a storage unit that stores coordinate information that identifies the observation area; a control unit that aligns the irradiation area of ​​the electron beam with the observation area based on the coordinate information; A scanning electron microscope comprising:

6. 2. The scanning electron microscope according to claim 1, a sample holder having a plurality of actual sample holders for holding a plurality of actual samples and a standard sample holder for holding the standard sample; the plurality of actual sample holding portions are arranged in a ring shape in the sample holder; In the sample holder, the standard sample holder is surrounded by the plurality of actual sample holders. A scanning electron microscope characterized by:

7. 7. The scanning electron microscope according to claim 6, the offset adjustment and the gain adjustment are performed by observing the standard sample prior to observing the plurality of real samples; the offset adjustment and the gain adjustment are performed by observing the standard sample during the observation of the plurality of real samples. A scanning electron microscope characterized by:

8. irradiating an electron beam onto an observation region set across a first element region and a second element region in the standard sample, and detecting electrons emitted from the observation region; forming an electron image of the observation area based on a detection signal generated by detecting the electrons; applying offset and gain adjustments to the detection signal or the electronic image so that the actual luminance distribution of the electronic image matches a standard luminance distribution; Including, the first element region includes a first element; the second element region includes a second element; a standard luminance distribution corresponding to a combination of the first element and the second element is used as the standard luminance distribution, the offset adjustment and the gain adjustment are performed by observing the standard sample prior to or during the observation of the actual sample. A brightness adjustment method comprising:

Images