JP7746124B2 - Scanning electron microscope and brightness adjustment method - Google Patents

Description

The present invention relates to a scanning electron microscope and a brightness adjustment method, and in particular to adjusting the brightness distribution of an electron image.

Scanning electron microscopes are used in particle analysis. For example, an electron image (such as a backscattered electron image or 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, and the shape of each particle are determined. A compositional analysis based on X-ray spectroscopy is then performed on each identified particle, and the elements that make up each particle are identified. The sample is, for example, the cleaning solution remaining after cleaning a product, and each particle corresponds to a foreign particle.

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.

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

Japanese Unexamined Patent Publication No. 4-328234

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 person performing the measurement. It is desirable to automatically adjust the brightness distribution so that the actual brightness distribution approaches or matches the ideal brightness distribution.

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

A scanning electron microscope according to the present invention includes an observation unit that 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 emerging 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 luminance distribution of the electron image matches a standard luminance distribution , wherein 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, and the offset adjustment and the gain adjustment are performed by observation of the standard sample prior to or during observation of a real sample.

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 sample with an electron beam and detecting electrons emerging 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, wherein the first element region includes a first element, the second element region includes a second element, a standard brightness distribution corresponding to a combination of the first element and the second element is used as the standard brightness distribution, and the offset adjustment and the gain adjustment are performed by observing the standard sample prior to or during observation of a real sample.

The present invention makes it possible to objectively adjust the brightness distribution of an electron image with good reproducibility. Alternatively, the present invention provides a brightness adjustment technique for particle analysis based on electron images. Alternatively, the present invention makes it possible to maintain an appropriate brightness distribution of an electron image even if the state of the scanning electron microscope changes over time.

1 is a block diagram showing a scanning electron microscope according to an embodiment. FIG. 2 is a block diagram showing an example of the configuration of a signal processing circuit. FIG. 4 is a diagram illustrating information stored in a storage unit. FIG. 2 is a diagram showing an example of a sample holder. FIG. 1 is a diagram showing an example of a standard sample. FIG. 1A and 1B are explanatory diagrams showing a brightness adjustment method according to an embodiment. 1 is a flowchart illustrating a brightness adjustment method according to an embodiment. 1 is a flowchart showing the operation of a scanning electron microscope. FIG. 10 is a diagram showing a standard sample table.

The following describes the embodiment with reference to the drawings.

(1) Overview of the embodiment A scanning electron microscope according to the embodiment has an observation unit, a formation unit, and an adjustment unit. The observation unit irradiates an observation area 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 area. The formation unit forms an electron image of the observation area based on a detection signal generated by detecting the 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 observation of the actual sample.

With the above configuration, an electronic image of a standard sample is obtained, and offset and gain adjustments are performed so that its actual brightness distribution matches the standard brightness distribution. This allows the brightness distribution of the electronic image to be adjusted objectively and with good reproducibility. If particle analysis is performed after offset and gain adjustments, the accuracy of the 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.

Offset and gain adjustments may be applied to the detection signal. In this case, the analog or digital detection signal is the subject of adjustment. 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 the electron beam over the 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 representative of the standard brightness distribution may be used. For example, if a product contains a foreign object 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 object element. A standard brightness distribution is prepared for each combination of base material and foreign object material. Standard brightness distributions corresponding to combinations of base material and multiple foreign object materials may also be prepared.

In an 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. This configuration allows offset adjustment and gain adjustment to be performed quickly and easily. The standard luminance distribution can also be referred to as a target luminance distribution.

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 avoids complicating the adjustment process.

In this embodiment, offset adjustment is performed first, followed by gain adjustment. If gain adjustment is performed first, there is a greater chance that one peak (or some of the peaks) will exceed the observation range and become invisible. If offset adjustment is performed first, the likelihood of such a problem occurring can be reduced.

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

A scanning electron microscope according to an embodiment has a sample holder. The sample holder has a plurality of actual sample holders that hold a plurality of actual samples, and a standard sample holder that holds 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, offset and gain adjustments can be performed quickly at any timing.

In this embodiment, offset and gain adjustments are performed by observing a standard sample prior to observing multiple real samples. Furthermore, offset and gain adjustments are performed by observing a standard sample midway through observing multiple real samples. There is a tendency for the average brightness of the electronic image to gradually decrease as the observation time increases. By performing offset and gain adjustments 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.

The brightness adjustment method according to the embodiment includes an observation step, a formation step, and an adjustment step. In the observation step, an electron beam is irradiated onto an observation region set across a first element region and a second element region in the standard sample, 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. Offset adjustment and gain adjustment are performed by observing a standard sample prior to or during observation of the actual sample. In the embodiment, all steps are performed automatically, but some steps may also be performed manually.

(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.

First, we will explain the observation unit. The observation unit 10 functions as the measurement unit. Specifically, the observation unit 10 has an electron tube 14. The electron tube 14 houses an electron gun, deflection lens, objective lens, etc. An electron beam 16 is generated by the electron gun.

A sample chamber 18 is provided at the bottom of the microscope tube 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 to the stage 22. The position and orientation of the sample holder 24 are changed by the stage 22. The sample holder 24 contains 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.

Multiple detectors are provided within the sample chamber 18. These include a backscattered electron detector, a secondary electron detector, an X-ray detector (spectrometer), and the like. In this embodiment, the detection signal output from the backscattered electron detector is used for particle analysis.

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

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 and is 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.

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. A variety of well-known methods can be used for particle analysis. The particle analysis results are displayed on a display (not shown).

The image forming unit 28 and 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.

The information processing unit 32 is connected to a storage unit 40. The storage unit 40 is composed of semiconductor memory, a hard disk, etc. The information stored in the storage unit 40 will be explained later using Figure 3.

The histogram creation unit 34 creates a histogram (brightness histogram) of brightness distribution based on an electronic image of the standard sample. If the standard sample is composed of two materials (e.g., the product base material and the 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.

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

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 times during the sample observation. When observing multiple real samples sequentially, offset and gain adjustments using a standard sample may be performed between observations of two adjacent real samples. 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 times, the accuracy of particle analysis can be maintained or improved.

Figure 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.

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.

Figure 3 shows the information stored in the memory unit 40. In the example shown, the memory unit 40 stores observation area coordinate information 54, first standard brightness 56, second standard brightness 58, coefficient set 60, etc. The observation area coordinate information 54 is information that identifies the observation area set for the standard specimen, and the stage position and irradiation position are adjusted based on the observation area coordinate information 54.

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, or brightness axis, of the histogram, the first standard brightness 56 is the brightness (standard position) that is compared with the brightness at the apex of the first peak (first peak position), and the second standard brightness 58 is the 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. The representative position of each peak may be determined based on the average, center of gravity, etc. of each peak.

Coefficient set 60 consists of two coefficients, k1 and k2. Coefficient k1 determines the size of the increments during offset adjustment, and coefficient k2 determines the size of the increments during gain adjustment.

Figure 4 shows an example of a sample holder used in particle analysis. In the illustrated example, the sample holder 24 has a row of actual sample holders 62 and a standard sample holder 63 mounted on a base 64. The row of actual sample holders 62 is composed of six actual sample holders 62A arranged in a ring. The standard sample holder 63 is mounted in the center of the sample holder 24 and is surrounded by the six actual sample holders 62A.

Each actual sample holder 62A has a recess in which a circular sheet filter 66 is placed. The filter 66 is a member that captures particles in the cleaning solution. A ring 68 acting 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.

Figure 5 shows a standard sample 70. The lower part of Figure 5 (see A) shows the side of the standard sample 70, and the upper part of Figure 5 (see B) shows the top surface of the standard sample 70. Material 72 is composed of, for example, an element corresponding to the foreign matter. Material 72 has a cylindrical shape. Material 72 is composed of, for example, copper. A rectangular sheet 74 is attached to the top surface 72A of material 72. Sheet 74 is composed of an element corresponding to the product base material, for example, carbon. Sheet 74 may be composed of adhesive tape. Sheet 74 may also be made of thin metal flakes, resin film, etc. An observation area 76 is set on top surface 72A, spanning the surface of material 72 and the surface of sheet 74.

Figure 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 portion 76A, which belongs to the base material element region 200A, and the other half is portion 76B, which belongs to the foreign material element region 200B. Portions 76A and 76B have the same area.

Figure 7 shows a brightness adjustment method according to an embodiment. The histogram 78 shown in the upper part of Figure 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.

A standard intermediate position (standard intermediate brightness) C0 is identified as the intermediate position between the first standard position (first standard brightness) and the second standard position (second standard brightness). The standard intermediate position (standard intermediate brightness) C0 can also be referred to as the target intermediate position (target intermediate brightness). Furthermore, a standard interval (standard brightness difference) D0 is identified as the interval between the first standard position and the second standard position. The standard interval (standard brightness difference) D0 can also be referred to as the target interval (target brightness difference). The intermediate position can also be referred to as the center position.

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. The 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 standard midpoint position C0 described above.

The middle part of Figure 7 shows the histogram after offset adjustment. 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 so that the actual interval Dx matches the standard interval D0 (see reference numeral 86).

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

A variety of well-known techniques can be used to identify the multiple peaks contained in a histogram. For example, each peak may be identified by applying noise removal and smoothing to the histogram, and then performing two differentiation processes (inflection point extraction processes) on the histogram.

Figure 8 shows a flowchart of a brightness adjustment method according to an embodiment. A sample holder equipped with a standard sample and an actual 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.

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

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 number 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 number other than 2 is found as the number of peaks a predetermined number of times.

In S28, the actual middle position is determined from the two peak positions in the histogram, and the standard middle position is determined 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 the first difference. If the first difference is within the first tolerance range, S34 is executed; 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.

In S30, the actual interval is determined from the two peak positions 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.

By performing the above offset and gain adjustments, the histogram obtained from the standard sample approaches an ideal histogram. A threshold is then determined based on the histogram. For example, the midpoint between the first and second peaks is set as the threshold.

After offset and gain adjustments are completed, the actual sample is observed, thereby acquiring an electronic image of the actual sample. The electronic image is then binarized using the above threshold. Particle analysis is performed based on the binarized electronic 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 particle analysis methods can be used.

Figure 9 shows the operation of a 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 Figures 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 unobserved real samples remain, 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 considered to 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.

Figure 10 shows a standard sample table 88. The standard sample table 88 is used when multiple standard samples are selectively used. The standard sample table 88 is composed of multiple records 90 corresponding to multiple standard samples. Each record 90 includes a standard sample 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 other information 102 include acceleration voltage, irradiation current, observation magnification, etc.

The brightness adjustment method according to the embodiment allows the brightness distribution of an electron image to be adjusted objectively and with good reproducibility. In particular, because a standard sample is used, the brightness distribution of the electron image can be maintained at an appropriate level even if the condition of the scanning electron microscope changes over time.

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 (8)

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. 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. 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. 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: 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: 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. 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: 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: