Cathodoluminescence observation method and cathodoluminescence device

Abstract

To provide a cathode luminescence observation method and a cathode luminescence device that are capable of performing low magnification observation while using a collecting mirror applicable to high magnification observation.SOLUTION: A cathode luminescence observation method includes a step of changing the distance between an observation surface of a sample and a focal point of a collecting mirror, and preparing for first data indicating a distribution in emission intensity of cathode luminescence within the observation surface for each distance, a step of identifying, from the first data, a distance at which the distribution in emission intensity within a field of view satisfies a predetermined relationship, and an emission region to be used for observation, a step of adjusting the positional relationship between the collecting mirror and the observation surface so as to match the identified distance and emission region, and a step of measuring the emission intensity of cathode luminescence in the emission region of the observation surface while focusing an electron beam on the observation surface after the adjustment of the positional relationship.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a cathodoluminescence observation method and a cathodoluminescence apparatus. [Background technology]

[0002] Cathodoluminescence devices are installed in, for example, scanning electron microscopes and can measure the physical properties of a sample in an extremely narrow field of view. In recent years, cathodoluminescence devices equipped with a focusing mirror for low-magnification observation in order to perform observation at a relatively low magnification have also become known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-031001 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, a cathodoluminescence apparatus equipped with a collector mirror for low-magnification observation cannot perform analysis in a very narrow field of view at high magnification, whereas a conventional cathodoluminescence apparatus equipped with a collector mirror primarily intended for high-magnification observation cannot perform analysis in a wide field of view at low magnification.

[0005] An object of the present disclosure is to provide a cathodoluminescence observation method and cathodoluminescence apparatus that are capable of performing low-magnification observation while using a collecting mirror that is applicable to high-magnification observation. [Means for solving the problem]

[0006] The cathode luminescence observation method disclosed herein includes the steps of: changing the distance between an observation surface of a sample and a focal point of a collecting mirror, and preparing first data indicating a distribution of cathode luminescence emission intensity within the observation surface for each distance; identifying, from the first data, a distance at which the distribution of the emission intensity within a field of view satisfies a predetermined relationship, and a light-emitting region to be used for observation; adjusting a positional relationship between the collecting mirror and the observation surface to match the identified distance and light-emitting region; and, after adjusting the positional relationship, measuring the cathode luminescence emission intensity in the light-emitting region of the observation surface while focusing an electron beam on the observation surface. Effect of the Invention

[0007] According to the present disclosure, low-magnification observation can be performed while using a collecting mirror that is adaptable to high-magnification observation. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a cathodoluminescence device according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram (part 1) showing the relationship between the sample, the focal point of the focusing mirror, and the focal point of the electron beam. [Diagram 3] FIG. 3 is a schematic diagram (part 2) showing the relationship between the sample, the focal point of the focusing mirror, and the focal point of the electron beam. [Figure 4] FIG. 4 shows a panchromatic image (part 1) obtained by cathodoluminescence observation. [Diagram 5] FIG. 5 shows a panchromatic image (part 2) obtained by cathodoluminescence observation. [Figure 6] FIG. 6 shows a panchromatic image (part 3) obtained by cathodoluminescence observation. [Figure 7] FIG. 7 shows a panchromatic image (part 4) obtained by cathodoluminescence observation. [Figure 8]FIG. 8 is a graph showing the distribution of luminescence intensity corresponding to FIG. [Figure 9] FIG. 9 is a graph showing the distribution of luminescence intensity corresponding to FIG. [Figure 10] FIG. 10 is a graph showing the distribution of luminescence intensity corresponding to FIG. [Figure 11] FIG. 11 is a graph showing the distribution of luminescence intensity corresponding to FIG. [Figure 12] FIG. 12 is a graph showing the average value of luminescence intensity along the X-axis. [Figure 13] FIG. 13 is a graph in which the graphs shown in FIG. 12 are normalized by their respective maximum values. [Figure 14] FIG. 14 is a graph showing the distribution of luminescence intensity in the identified luminescent region. [Figure 15] FIG. 15 shows a panchromatic image of the first sample (part 1). [Figure 16] FIG. 16 shows a panchromatic image of the first sample (part 2). [Figure 17] FIG. 17 shows a panchromatic image of the second sample (part 1). [Figure 18] FIG. 18 shows a panchromatic image of the second sample (part 2). [Figure 19] FIG. 19 is a diagram showing the functional configuration of a control unit in a first example of a cathodoluminescence observation method. [Figure 20] FIG. 20 is a flowchart (part 1) showing a first example of a cathodoluminescence observation method. [Figure 21] FIG. 21 is a flowchart (part 2) showing a first example of the cathodoluminescence observation method. [Figure 22] FIG. 22 is a flowchart showing a second example of the cathodoluminescence observation method. [Figure 23] FIG. 23 is a diagram (part 1) showing an example of a method for determining the average luminescence intensity. [Figure 24] FIG. 24 is a diagram (part 2) showing one example of a method for determining the average luminous intensity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described.

[0010] [1] A cathodoluminescence observation method according to one embodiment of the present disclosure includes the steps of: changing a distance between an observation surface of a sample and a focal point of a collecting mirror, and preparing first data indicating a distribution of cathodoluminescence emission intensity within the observation surface for each distance; identifying, from the first data, a distance at which the distribution of the emission intensity within a field of view satisfies a predetermined relationship, and a light-emitting region to be used for observation; adjusting a positional relationship between the collecting mirror and the observation surface to match the identified distance and light-emitting region; and, after adjusting the positional relationship, measuring the cathodoluminescence emission intensity in the light-emitting region on the observation surface while focusing an electron beam on the observation surface.

[0011] As described later, by intentionally shifting the observation surface from the focal point of the collecting mirror, it may be possible to perform observation using a region where the emission intensity is approximately uniform over a wide field of view. By preparing first data by changing the distance between the observation surface and the focal point of the collecting mirror, specifying the distance between the observation surface and the focal point of the collecting mirror and the emission region to be used for observation from the first data, and adjusting the positional relationship between the collecting mirror and the sample to match the specified distance and emission region, it is possible to perform low-magnification observation even if the collecting mirror is suitable for high-magnification observation.

[0012] [2] In [1], the step of preparing the first data may include a step of measuring a distribution of reference emission intensity of cathodoluminescence in the observation surface of the reference sample for each distance by using a reference sample different from the sample to be observed and changing the distance between the observation surface of the reference sample and the focal point of the collector mirror, and a step of recording the measured distribution of reference emission intensity in a database as the first data. In this case, the first data can be used even when the sample is replaced. Therefore, there is no need to perform observation to obtain the first data every time the sample is replaced, which reduces the burden on the user who is the observer.

[0013] [3] In [1], the step of preparing the first data may include a step of changing a distance between an observation surface of the sample to be observed and a focal point of the collector mirror, measuring a distribution of cathodoluminescence emission intensity in the observation surface of the sample for each distance, and a step of recording the measured distribution of emission intensity in a database as the first data. In this case, since the first data is prepared using the sample to be observed, it is easy to identify a distance and emission region suitable for the sample.

[0014] [4] In any one of [1] to [3], the predetermined relationship in the identifying step may include that the minimum value of the luminescence intensity in the luminescent region is 10% or more of the maximum value. According to actual observations by the present inventors, appropriate observations can be performed when the minimum value of the luminescence intensity is 10% or more of the maximum value.

[0015] [5] In any one of [1] to [4], the light-emitting region may include a square region with a side length of 200 μm. According to actual observations by the present inventors, appropriate observation can be performed when the light-emitting region includes a square region with a side length of 200 μm.

[0016] [6] In any one of [1] to [5], the distance between the observation surface and the focal point of the collecting mirror may be 300 μm or more. If the distance is 300 μm or more, it is easy to observe a light-emitting region including a square region with a side length of 200 μm.

[0017] [7] A cathodoluminescence apparatus according to another aspect of the present disclosure includes an observation unit and a control unit that controls the observation unit. The observation unit includes a sample holder that holds a sample, an electron beam source that irradiates the sample with an electron beam, a detector that detects cathodoluminescence light emitted by the sample, and a collecting mirror that collects the cathodoluminescence light on the detector. The control unit includes a recording unit that stores a database in which first data is recorded in accordance with a distance between an observation surface and a focal point of the collecting mirror, the first data indicating a distribution of cathodoluminescence emission intensity within the observation surface for each distance, an identification unit that identifies, from the first data, a distance at which the distribution of the emission intensity within a field of view satisfies a predetermined relationship and a light-emitting region to be used for observation, and an adjustment unit that adjusts the positional relationship between the collecting mirror and the observation surface to match the distance and the light-emitting region identified by the identification unit.

[0018] The recording unit, the specifying unit, and the adjusting unit control the observation unit, so that a user who is an observer can easily perform cathode luminescence observation at a low magnification and with a wide field of view.

[0019] [Details of the embodiment of the present disclosure] Hereinafter, the embodiments of the present disclosure will be described in detail, but the present disclosure is not limited thereto. In this specification and drawings, components having substantially the same functional configuration may be denoted by the same reference numerals to avoid redundant description. In the following description, an XYZ Cartesian coordinate system is used, but this coordinate system is defined for the purpose of explanation. In addition, when viewed from an arbitrary point, the -Z side may be referred to as the upper side, upper side, or top, and the +Z side may be referred to as the lower side, lower side, or bottom. In this disclosure, "planar view" refers to viewing an object from above, and "planar shape" refers to the shape of an object viewed from above.

[0020] (Configuration of cathode luminescence device) First, the configuration of a cathodoluminescence (CL) device according to an embodiment will be described. Fig. 1 is a block diagram showing a CL device according to an embodiment. The CL device 1 according to the embodiment has a control unit 10 and an observation unit 20. The control unit 10 controls the observation unit 20.

[0021] The control unit 10 is a computer and includes a bus 11, an input device 12, an output device 13, a storage device 14, a memory device 15, a processing unit 16, and an interface device 17. The input device 12, the output device 13, the storage device 14, the memory device 15, the processing unit 16, and the interface device 17 are connected to each other via the bus 11.

[0022] The input device 12 is a device for inputting various types of information and is realized, for example, by a keyboard, a pointing device, etc. The output device 13 is for outputting various types of information and is realized, for example, by a display, etc. The interface device 17 includes a local area network (LAN) card, etc., and is used for connecting to a network.

[0023] A control program for controlling the observation unit 20 is stored in the storage device 14. The memory device 15 reads out and stores the control program from the storage device 14 when the CL device 1 is started. The arithmetic processing device 16 then realizes various processes, as described below, in accordance with the control program stored in the memory device 15. The memory device 15 includes a database 18.

[0024] The observation unit 20 is provided in, for example, a scanning electron microscope (SEM). The observation unit 20 includes an electron beam source 21, a condenser mirror 22, a sample holder 23, and a detector 24. A sample is provided on the sample holder 23, and an electron beam is irradiated from the electron beam source 21 to the sample. The sample irradiated with the electron beam emits light by CL, and the light emitted from the sample is condensed on the detector 24 by the condenser mirror 22. The control unit 10 controls the electron beam source 21, the condenser mirror 22, and the sample holder 23, and the result of detection by the detector 24 is output to the control unit 10. As the condenser mirror 22, for example, a condenser mirror capable of observation at 10,000 times magnification is used.

[0025] (Principle of CL observation) Next, the principle of CL observation used in this embodiment will be described. Figures 2 and 3 are schematic diagrams showing the relationship between the sample, the focal point of the collector mirror, and the focal point of the electron beam. Figure 2 shows a state in which one focal point 22F of the collector mirror 22 is aligned with the observation surface 30A of the sample 30 held by the sample holder 23. Figure 3 shows a state in which the focal point 22F of the collector mirror 22 is shifted from the observation surface 30A of the sample 30 held by the sample holder 23.

[0026] 2 and 3, the collector mirror 22 has, for example, an elliptical mirror surface 22M. The two focal points of the collector mirror 22 are in a plane (reference plane 26) parallel to the XY plane, and the sample holder 23 is provided near one focal point 22F of the collector mirror 22, and the detector 24 is provided at the other focal point. The detector 24 is located on the +Y side of the sample holder 23. The collector mirror 22 has an opening 22A formed therein so that the observation surface 30A of the sample 30 can be irradiated with the electron beam 25 from outside in parallel to the Z-axis direction. The opening shape of the opening 22A may be, for example, a square shape with a side length of about 1 mm, or a circle with a diameter of about 1 mm.

[0027] 2, when the focal point 22F of the collector mirror 22 is aligned with the observation surface 30A and the electron beam 25 is irradiated at a position aligned with the focal point 22F of the collector mirror 22 in a plane parallel to the XY plane, the light generated by CL on the observation surface 30A reaches the detector 24. On the other hand, when the focal point 22F of the collector mirror 22 is aligned with the observation surface 30A and the electron beam 25 is irradiated at a position shifted from the focal point 22F of the collector mirror 22 in a plane parallel to the XY plane, the light generated by CL on the observation surface 30A is unlikely to reach the detector 24. For example, when the electron beam 25A in FIG. 2 is irradiated, the light generated by CL reaches the detector 24, but when the electron beam 25B or 25C is irradiated, the light generated by CL is unlikely to reach the detector 24.

[0028] In this manner, when the focal point 22F of the focusing mirror 22 is aligned with the observation surface 30A, a strong peak is obtained when the electron beam 25 is irradiated to a position aligned with the focal point 22F of the focusing mirror 22 in a plane parallel to the XY plane.

[0029] 3, when the electron beam 25 is irradiated in a state where the focal point 22F of the collector mirror 22 is shifted from the observation surface 30A in the Z-axis direction, the light generated by CL on the observation surface 30A that passes through the focal point 22F of the collector mirror 22 reaches the detector 24. Therefore, even if the electron beam 25 is irradiated at a position shifted from the focal point 22F of the collector mirror 22 in a plane parallel to the XY plane, the light generated by CL on the observation surface 30A can reach the detector 24. Note that, when the electron beam 25 is irradiated straight at a position aligned with the focal point 22F of the collector mirror 22 in a plane parallel to the XY plane, the light 27 generated by CL on the observation surface 30A passes through the opening 22A and does not reach the detector 24.

[0030] In this way, when the focal point 22F of the collecting mirror 22 is shifted in the Z-axis direction from the observation surface 30A, the light emission can be detected over a wide range in a plane parallel to the XY plane, although it is weaker than when the focal point 22F of the collecting mirror 22 is aligned with the observation surface 30A.

[0031] (Observation example) Next, an observation example using the above principle will be described. Figures 4 to 7 are diagrams showing panchromatic images (hereinafter referred to as panchromatic images) obtained by CL observation. The panchromatic images shown in Figures 4 to 7 are panchromatic images of a gallium nitride (GaN) layer epitaxially grown on a substrate. Figures 8 to 11 are graphs showing the distribution of emission intensity corresponding to Figures 4 to 7, respectively. Figures 4 and 8 show the panchromatic image and the distribution of emission intensity when the observation surface 30A coincides with the reference surface 26 (Z = 0 μm). Figures 5 and 9 show the panchromatic image and the distribution of emission intensity when the observation surface 30A is 100 μm away from the reference surface 26 in the Z-axis direction (Z = 100 μm). Figures 6 and 10 show the panchromatic image and the distribution of emission intensity when the observation surface 30A is 300 μm away from the reference surface 26 in the Z-axis direction (Z = 300 μm). Fig. 7 and Fig. 11 show the distribution of the panchromatic image and the luminescence intensity when the observation surface 30A is 500 μm away from the reference surface 26 in the Z-axis direction (Z=500 μm). Fig. 12 is a graph showing the average luminescence intensity in the X-axis direction. Fig. 13 is a graph normalized by the maximum value of the graph shown in Fig. 12.

[0032] 4 to 13, the smaller the deviation of the observation surface 30A from the reference plane 26 in the Z-axis direction, the higher the peak intensity, and as the deviation increases, the peak intensity decreases while the light-emitting region with a small difference in peak intensity becomes wider. This shows that even if the field of view to be observed is relatively wide, suitable CL light-emitting intensity can be obtained over the entire field of view by shifting the observation surface 30A from the reference plane 26 in the Z-axis direction.

[0033] For example, assume that a certain sample is observed in a field of view with a dimension of 400 μm in the Y-axis direction and a dimension of 320 μm in the X-axis direction. In this case, a light-emitting region within this dimension range in which the ratio of the minimum value to the maximum value of the light-emitting intensity is large and the minimum value is also large is identified from Figures 4 to 13. From such criteria, for example, light-emitting region 51 in Figures 6 and 10 can be identified. Figure 14 is a graph showing the distribution of light-emitting intensity in light-emitting region 51.

[0034] The inventor of the present application set the deviation of observation surface 30A from reference surface 26 to 300 μm and observed the first sample using light-emitting region 51, and obtained the panchromatic image shown in FIG. 15. FIG. 15 shows an observation of a field of view of 400 μm in the Y-axis direction and 320 μm in the X-axis direction at a low magnification of 300 times. As shown in FIG. 15, multiple defects 41 were observed within the field of view. Meanwhile, for reference, the deviation of observation surface 30A from reference surface 26 was set to 0 μm for the same field of view, and the first sample was observed using light-emitting region 52 in FIG. 4, which provides a strong peak intensity, and obtained the panchromatic image shown in FIG. 16. As shown in FIG. 16, the defect 41 observed in FIG. 15 was not observed, and only artifact 42 appeared. The first sample is a semiconductor substrate.

[0035] In addition, the inventor of the present application set the deviation amount of the observation surface 30A from the reference surface 26 to 100 μm and observed the second sample using the light-emitting region 53 in FIG. 5, and obtained the panchromatic image shown in FIG. 17. In FIG. 17, an area of ​​a field of view of 40 μm in the Y-axis direction and 32 μm in the X-axis direction was observed at a medium magnification of 3000 times. Thus, even when observed at a medium magnification, multiple defects were observed within the field of view as shown in FIG. 17. On the other hand, for reference, the deviation amount of the observation surface 30A from the reference surface 26 was set to 0 μm for the same field of view, and the second sample was observed using the light-emitting region 52 in FIG. 4, and obtained the panchromatic image shown in FIG. 18. As shown in FIG. 18, the defects observed in FIG. 17 were not observed. Thus, even when observed at a medium magnification of 3000 times using a high-magnification collecting mirror, by setting the deviation amount to 100 μm, it became possible to observe defects that could not be observed by normal high-magnification measurement. The second sample is a semiconductor epitaxial layer.

[0036] In this way, even when the field of view to be observed is relatively wide, it is possible to obtain a suitable CL emission intensity over the entire field of view and perform CL observation by shifting the observation surface 30A in the Z-axis direction from the reference surface 26. The size of the field of view is not particularly limited, but it is possible to perform CL observation of a light-emitting area including a square area with one side having a length of 200 μm, for example.

[0037] (First example of CL observation method) Next, a first example of a CL observation method using the CL device 1 will be described. In the first example, before an actual sample is analyzed, a reference sample is used to change the distance between the observation surface of the reference sample in the Z-axis direction and the focal point of the collector mirror 22, and first data indicating the distribution of CL emission intensity in the observation surface for each distance is acquired and stored in the database 18. That is, in the first example, the first data is prepared in advance in the database 18 using a reference sample. Note that it is preferable to use a reference sample such as a semiconductor epitaxial layer whose emission intensity is considered to be constant over the entire surface of the sample. Here, for example, 0 μm, 100 μm, 300 μm, 500 μm, and 1000 μm are used as the distance between the observation surface and the collector mirror. Then, when an actual sample is observed, the control unit 10 reads out the first data from the database 18 based on the control program stored in the storage device 14, and performs control based on the first data. FIG. 19 is a diagram showing the functional configuration of the control unit 10 in the first example of the CL observation method. FIGS. 20 and 21 are flowcharts showing the first example of the CL observation method. FIG. 20 shows a process flow for creating the first data, and FIG. 21 shows a process flow for performing observation using the first data.

[0038] As shown in Fig. 19, in terms of functional configuration, control unit 10 has recording unit 61, identification unit 62, and adjustment unit 63. Recording unit 61 stores database 18 in which first data is recorded. Identification unit 62 identifies, from the first data, a distance and a light-emitting region where the distribution of light-emitting intensity within the field of view satisfies a predetermined relationship, according to the dimensions of the field of view of the sample to be observed. Adjustment unit 63 adjusts the positional relationship between collecting mirror 22 and the sample to match the distance and light-emitting region identified by identification unit 62.

[0039] In the process of acquiring the first data in the first example and storing it in database 18, first, as shown in Fig. 20, a reference sample is attached to sample holder 23, and the observation surface of the reference sample is aligned with the focal point of collector mirror 22 in the Z-axis direction (step S11). That is, in step S11, the distance between the observation surface of the reference sample and the focal point of collector mirror 22 in the Z-axis direction is set to 0 µm.

[0040] Next, while focusing the electron beam 25 on the observation surface of the reference sample, the electron beam 25 is scanned in a plane parallel to the XY plane to obtain the distribution of the CL emission intensity in the reference sample (step S12).

[0041] Next, the distribution of CL emission intensity obtained in step S12 is recorded in the database 18 of the recording unit 61 (step S13).

[0042] Next, it is determined whether the distribution of the CL emission intensity for all the predetermined distances has been completed (step S14). If the distribution of the CL emission intensity for all the predetermined distances has not been completed, the distance between the observation surface of the reference sample in the Z-axis direction and the focal point of the collector mirror 22 is changed (step S15).

[0043] After step S15, the process returns to step S12, and the processes from step S12 to step S15 are repeated until the distribution of the CL emission intensity for all the predetermined distances is completed.

[0044] When the distribution of CL emission intensity for all predetermined distances is completed, the process of storing the first data in the database 18 is completed.

[0045] In actual CL observation of a sample, after the sample to be observed is attached to the sample holder 23, the identifying unit 62 of the control unit 10 reads out the first data from the database 18 of the recording unit 61, as shown in FIG. 21 (step S16).

[0046] Next, the identifying unit 62 identifies, from the first data, a combination of the distance between the observation surface of the sample in the Z-axis direction and the focal point of the collecting mirror 22 and the light-emitting region, in which the distribution of the light-emitting intensity in the field of view satisfies a predetermined relationship, according to the dimensions of the field of view to be observed of the sample (step S17). For example, a process equivalent to identifying the combination of the distance of 300 μm and the light-emitting region 51 in the above observation example is performed. In this process, a combination in which the ratio of the minimum value to the maximum value of the light-emitting intensity is large within the field of view, and the minimum value is large is identified. The ratio of the minimum value to the maximum value of the light-emitting intensity is preferably 10% or more, more preferably 30% or more, even more preferably 50%, and particularly preferably 70% or more. According to actual observations by the inventors of the present application, appropriate observations can be performed even when the minimum value of the light-emitting intensity is 10% or more of the maximum value.

[0047] Next, the positional relationship between the observation surface of the sample and the focal point of the collector mirror 22 is adjusted according to the distance and light emission area specified by the adjustment unit 63 (step S18). For example, the sample holder 23 is moved in the Z-axis direction, and the collector mirror 22 is moved in a plane parallel to the XY plane.

[0048] Next, while the focal point of the electron beam 25 is adjusted to the observation surface of the sample, the electron beam 25 is scanned in a plane parallel to the XY plane, and the CL emission intensity in the light-emitting region of the observation surface is measured (step S19).

[0049] After measuring the CL emission intensity, the CL observation is terminated.

[0050] As described above, by intentionally shifting the observation surface from the focal point of the collector mirror 22, it may be possible to perform observation using a region where the emission intensity is approximately uniform over a wide field of view. In the first example, a reference sample is used, and conditions for this are prepared as first data, and the positional relationship between the collector mirror 22 and the sample is adjusted to match the distance between the observation surface and the focal point of the collector mirror 22 and the emission region according to the dimensions of the field of view. Therefore, even if the collector mirror 22 is suitable for high-magnification observation, low-magnification observation can be performed.

[0051] The first data stored in the database 18 can be used even when the sample is replaced. Therefore, it is not necessary to perform observation to obtain the first data every time the sample is replaced, which reduces the burden on the user who is the observer.

[0052] In particular, the recording unit 61, the specifying unit 62, and the adjusting unit 63 provided in the control unit 10 perform these controls, allowing the user, who is the observer, to easily perform CL observation with a wide field of view at a low magnification.

[0053] (Second example of CL observation method) Next, a second example of the CL observation method using the CL device 1 will be described. In the second example, a sample to be actually observed by CL is used, the distance between the observation surface of the sample in the Z-axis direction and the focal point of the collector mirror 22 is changed, and first data indicating the distribution of CL emission intensity in the observation surface for each distance is obtained and stored in the database 18. That is, in the second example, the first data is prepared using the sample to be observed. Then, the first data is read out from the database 18, and control based on the first data is performed. FIG. 22 is a flowchart showing the second example of the CL observation method.

[0054] 22, first, a sample is attached to the sample holder 23, and the observation surface of the sample is aligned with the focal point of the collector mirror 22 in the Z-axis direction (step S21). That is, in step S21, the distance between the observation surface of the reference sample and the focal point of the collector mirror 22 in the Z-axis direction is set to 0 μm.

[0055] Next, while the focus of the electron beam 25 is adjusted to the observation surface of the sample, the electron beam 25 is scanned in a plane parallel to the XY plane to obtain the distribution of the CL emission intensity in the sample (step S22).

[0056] Next, the distribution of CL luminescence intensity obtained in step S22 is recorded in the database 18 (step S23).

[0057] Next, it is determined whether the distribution of the CL emission intensity has been completed for all of the predetermined distances (step S24). If the distribution of the CL emission intensity for all of the predetermined distances has not been completed, the distance between the observation surface of the sample in the Z-axis direction and the focal point of the collector mirror 22 is changed (step S25).

[0058] After step S25, the process returns to step S22, and the processes from step S22 to step S25 are repeated until the distribution of the CL emission intensity for all the predetermined distances is completed.

[0059] When the distribution of the CL emission intensity for all the predetermined distances is completed, the process of acquiring the first data and storing it in the database 18 is completed. Next, the first data is read out from the database 18 (step S26).

[0060] Next, depending on the dimensions of the field of view to be observed of the sample, a combination of the distance between the observation surface of the sample in the Z-axis direction and the focus of the focusing mirror 22 and the light-emitting area, in which the distribution of light-emitting intensity within the field of view satisfies a predetermined relationship, is identified from the first data (step S27).

[0061] Next, the positional relationship between the observation surface of the sample and the focal point of the collector mirror 22 is adjusted according to the identified distance and light emission area (step S28).

[0062] Next, while the focal point of the electron beam 25 is adjusted to the observation surface of the sample, the electron beam 25 is scanned in a plane parallel to the XY plane, and the CL emission intensity in the field of view of the observation surface is measured (step S29).

[0063] After measuring the CL emission intensity, the CL observation is terminated.

[0064] In the second example, the first data is prepared using a sample to be observed, and the positional relationship between the collector mirror 22 and the sample is adjusted according to the size of the field of view so as to match the distance between the observation surface and the focal point of the collector mirror 22 and the light-emitting area. Therefore, as in the first example, even if the collector mirror 22 is suitable for high-magnification observation, low-magnification observation can be performed.

[0065] In particular, since the first data is prepared using the sample to be observed, it is easy to specify the distance and light-emitting area suitable for the sample. In addition, the user, who is the observer, can specify the distance and light-emitting area by himself / herself using the first data, thereby enabling CL observation of a wide field of view according to the user's own intention.

[0066] The collector mirror 22 may have a parabolic mirror surface instead of the elliptical mirror surface 22M.

[0067] In addition, when specifying the light-emitting region to be used in the actual observation, it is preferable to refer to the maximum and minimum values ​​of the light-emitting intensity within the range of the field of view, but the maximum value may become excessively large and the minimum value may become excessively small due to the influence of noise. Therefore, instead of simply using the maximum and minimum values, it is preferable to subdivide the light-emitting region into minute regions, set the average value of the light-emitting intensity in a plurality of minute regions including the minute region of interest as the average light-emitting intensity of the minute region of interest, and use the maximum and minimum values ​​of the average light-emitting intensity. Here, an example of a method for determining the average light-emitting intensity will be described. Figures 23 to 24 are diagrams showing an example of a method for determining the average light-emitting intensity.

[0068] 23, the light emitting region used to acquire the first data is divided into a plurality of minute regions 71. The size of the minute regions 71 is preferably 5% or less of the size of the field of view to be observed. When observing a field of view of 400 μm in the Y-axis direction and 320 μm in the X-axis direction, the size of the minute regions 71 in the Y-axis direction is preferably 20 μm or less and the size in the X-axis direction is preferably 16 μm or less.

[0069] Next, an assembly region 72 is determined in which 25 microregions 71 including the microregion 71 of interest (microregion 71A in FIG. 24) at its center are assembled, and the average value of the luminescence intensity in the assembly region 72 is calculated and this is set as the average luminescence intensity of the microregion 71 of interest. Then, the average luminescence intensity is calculated for all microregions 71 for which an assembly region 72 can be determined, that is, for the microregions 71 within region 73 in FIG. 24.

[0070] When identifying the luminescent region to be used in actual observation, the maximum and minimum values ​​of the average luminescent intensity are used, so that a more preferable luminescent region can be identified with the influence of noise suppressed.

[0071] Although the embodiments have been described in detail above, the present disclosure is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the claims. [Explanation of symbols]

[0072] 1. Cathodoluminescence equipment 10 Control section 11 Bus 12 Input Devices 13 Output Devices 14 Storage device 15 Memory Devices 16 Processing Unit 17 Interface Device 18 Database 20 Observation Section 21 Electron beam source 22 Condenser mirror 22A opening 22F focus 22M Elliptical Mirror 23 Sample Holder 24 Detector 25, 25A, 25B, 25C electron beam 26 Reference plane 27 light 30 Samples 30A Observation surface 41 Defects 42 Artifacts 51, 52, 53 Light-emitting area 61 Recording Section 62 Specific part 63 Adjustment section 71, 71A Micro area 72 Gathering area 73 areas S11, S12, S13, S14, S15, S16, S17, S18, S19, S21, S22, S23, S24, S25, S26, S27, S28, S29 steps

Claims

1. a step of changing a distance between an observation surface of a sample and a focal point of a collector mirror, and preparing first data indicating a distribution of emission intensity of cathodoluminescence in the observation surface for each distance; specifying a distance at which the distribution of the luminescence intensity in a field of view satisfies a predetermined relationship and a luminescence region to be used for observation from the first data; adjusting a positional relationship between the collector mirror and the observation surface to match the identified distance and light emitting area; measuring a cathodoluminescence intensity in the light-emitting region on the observation surface while focusing the electron beam on the observation surface after adjusting the positional relationship; The cathode luminescence observation method includes the steps of:

2. The step of preparing the first data includes: a step of measuring a distribution of reference emission intensity of cathodoluminescence in the observation surface of the reference sample for each distance by using a reference sample different from the sample to be observed and changing a distance between the observation surface of the reference sample and the focal point of the collecting mirror; recording the measured distribution of the reference luminescence intensity as the first data in a database; The cathodoluminescence observation method according to claim 1 , comprising:

3. The step of preparing the first data includes: a step of changing a distance between an observation surface of the sample to be observed and a focal point of the collecting mirror, and measuring a distribution of emission intensity of cathodoluminescence within the observation surface of the sample for each distance; recording the measured distribution of the emission intensities in a database as the first data; The cathodoluminescence observation method according to claim 1 , comprising:

4. 4. The cathodoluminescence observation method according to claim 1, wherein the predetermined relationship in the specifying step includes a condition that a minimum value of the luminescence intensity in the luminescent region is 10% or more of a maximum value.

5. 4. The cathodoluminescence observation method according to claim 1, wherein the light-emitting region includes a square region with a side length of 200 μm.

6. 4. The cathodoluminescence observation method according to claim 1, wherein the distance between the observation surface and the focal point of the collector mirror is 300 μm or more.

7. An observation unit; A control unit that controls the observation unit; having The observation unit includes: A sample holder for holding a sample; an electron beam source for irradiating the sample with an electron beam; A detector for detecting cathodoluminescence light emitted by the sample; a focusing mirror that focuses the cathodoluminescence light onto the detector; having The control unit is a recording unit for storing a database in which first data indicating a distribution of the emission intensity of cathode luminescence in the observation surface for each distance between the observation surface and a focal point of the collecting mirror is recorded according to the distance; an identification unit that identifies a distance at which the distribution of the emission intensity in a field of view satisfies a predetermined relationship and a light-emitting region to be used for observation from the first data; an adjustment unit that adjusts a positional relationship between the collecting mirror and the observation surface so as to conform to the distance and the light emitting area specified by the specification unit; and A cathodoluminescence device comprising:

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