Backscattered electron detection device and backscattered electron detection method

Abstract

The present invention provides a backscattered electron detection device and method capable of obtaining energy loss spectra with higher accuracy. [Solution] The backscattered electron detection device includes an irradiator that irradiates an object surface of a sample with electrons, a detector that detects at least a portion of the electrons reflected from the object surface, a voltage application unit that applies a voltage to the sample, and a correction unit that corrects a first electric field generated between the object surface of the sample to which the voltage is applied and the irradiator, and a second electric field generated between the object surface of the sample to which the voltage is applied and the detector.

Description

Technical Field

[0001] The present invention relates to a reflection electron detection device and a reflection electron detection method.

Background Art

[0002] As a method for obtaining information on the state of the sample surface, REELS (Reflection Electron Energy Loss Spectroscopy) has attracted attention (see, for example, Patent Document 1 and Patent Document 2). In REELS, an electron beam is irradiated onto a sample in a vacuum chamber, and the energy of the electrons reflected from the sample surface is analyzed. Specifically, it is analyzed how likely the electrons irradiated onto the sample surface are to lose energy and by how much, and an energy loss spectrum is generated. From this energy loss spectrum, the inelastic scattering process of the electron beam in the sample can be examined, and the chemical state of the sample surface can be evaluated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such REELS, it is difficult to generate an energy loss spectrum with high accuracy. Therefore, it is desirable to obtain an energy loss spectrum with higher accuracy using REELS.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a reflection electron detection device and a reflection electron detection method capable of obtaining an energy loss spectrum with higher accuracy.

Means for Solving the Problems

[0006] The above challenges will be addressed by the following means.

[0007] (1) A backscattered electron detection device, the backscattered electron detection device comprising: an irradiator for irradiating an object surface of a sample with electrons; a detector for detecting at least a portion of the electrons reflected from the object surface; a correction unit including a first plate-shaped electrode provided between the irradiator and the object surface and a second plate-shaped electrode provided between the detector and the object surface; the sample; and a voltage application unit for applying a voltage to the first plate-shaped electrode and the second plate-shaped electrode, wherein the correction unit corrects a first electric field generated between the object surface of the sample to which a voltage has been applied and the irradiator, and a second electric field generated between the object surface of the sample to which a voltage has been applied and the detector.

[0008] (2) The backscattered electron detection device according to (1) above, wherein the first plate-shaped electrode corrects the first electric field so that the electrons passing through the first electric field are directed toward the target surface, and the second plate-shaped electrode corrects the second electric field so that the electrons passing through the second electric field are directed toward the detector.

[0009] (3) The backscattered electron detection device according to (1) or (2) above, wherein the electrons emitted from the irradiator reach the target surface via a first passage provided in the first plate-shaped electrode, and the electrons reflected from the target surface reach the detector via a second passage provided in the second plate-shaped electrode.

[0010] (4) The backscattered electron detection device according to any one of (1) to (3) above, wherein the main surface of the first plate-shaped electrode faces the irradiator and the main surface of the second plate-shaped electrode faces the detector.

[0011] (5) The backscattered electron detection device according to (3) above, wherein the first passage is formed by an opening provided in the first plate-shaped electrode, and the second passage is formed by an opening provided in the second plate-shaped electrode.

[0012] (6) The backscattered electron detection device according to (3) above, wherein the first passage is formed by a slit provided in the first plate-shaped electrode, and the second passage is formed by a slit provided in the second plate-shaped electrode.

[0013] (7) The first plate-shaped electrode and the second plate-shaped electrode are connected to the backscattered electron detection device according to any of (1) to (6) above.

[0014] (8) The backscattered electron detection device according to any one of (1) to (6) above, wherein the first plate-shaped electrode and the second plate-shaped electrode are separated.

[0015] (9) A backscattered electron detection device comprising: an irradiator for irradiating an object surface of a sample with electrons; a detector for detecting at least a portion of the electrons reflected from the object surface; a correction unit for generating a first magnetic field between the irradiator and the object surface and a second magnetic field between the detector and the object surface; and a voltage application unit for applying a voltage to the sample, wherein the correction unit corrects a first electric field generated between the object surface of the sample to which a voltage has been applied and the irradiator, and a second electric field generated between the object surface of the sample to which a voltage has been applied and the detector.

[0016] (10) The backscattered electron detection device according to (9) above, wherein the first magnetic field acts to cancel out the component of the force acting on the electrons passing through the first electric field in a direction substantially perpendicular to the optical axis of the irradiator, and the second magnetic field acts to cancel out the component of the force acting on the electrons passing through the second electric field in a direction substantially perpendicular to the optical axis of the detector.

[0017] (11) The backscattered electron detection device according to any one of (1) to (10) above, wherein the irradiator and the detector are arranged in different directions relative to the target surface.

[0018] (12) The detector is a backscattered electron detector according to any of (1) to (11) above, which analyzes the energy of the detected electrons.

[0019] (13) A backscattered electron detection method comprising: applying a voltage to a sample; applying a voltage to a first plate-shaped electrode provided between the target surface of the sample and the irradiator to correct a first electric field generated between the target surface of the sample to which the voltage is applied and the irradiator; irradiating the target surface of the sample with electrons from the irradiator by passing the corrected first electric field through it; applying a voltage to a second plate-shaped electrode provided between the target surface and the detector to correct a second electric field generated between the target surface of the sample to which the voltage is applied and the detector; and detecting at least a portion of the electrons reflected from the target surface and passing through the corrected second electric field using the detector.

[0020] (14) A backscattered electron detection method comprising: applying a voltage to a sample; generating a first magnetic field between the target surface of the sample and an irradiator to correct a first electric field generated between the target surface of the sample to which the voltage has been applied and the irradiator; irradiating the target surface of the sample with electrons from the irradiator by passing the corrected first electric field through it; generating a second magnetic field between the target surface and a detector to correct a second electric field generated between the target surface of the sample to which the voltage has been applied and the detector; and detecting at least a portion of the electrons reflected from the target surface and passing through the corrected second electric field using the detector.

[0021] (15) A backscattered electron detection device comprising: an irradiator for irradiating the target surface of a sample with electrons; a detector for detecting at least a portion of the electrons reflected from the target surface; a voltage application unit for applying a voltage to the sample; and a correction unit for correcting a first electric field generated between the target surface of the sample to which the voltage is applied and the irradiator, and a second electric field generated between the target surface of the sample to which the voltage is applied and the detector.

[0022] (16) Applying a voltage to a sample, correcting a first electric field generated between a target surface of the sample to which the voltage is applied and an irradiator, irradiating electrons from the irradiator through the corrected first electric field onto the target surface of the sample, correcting a second electric field generated between the target surface of the sample to which the voltage is applied and a detector, and detecting at least a part of the electrons reflected by the target surface using the detector.

Advantages of the Invention

[0023] In the reflection electron detection device and the reflection electron detection method according to the present invention, since a voltage is applied to the sample, a first electric field and a second electric field are formed around the sample. The first electric field accelerates electrons traveling from the irradiator toward the target surface, and the second electric field decelerates electrons traveling from the target surface toward the detector. As a result, the energy of the electrons irradiated onto the target surface can be made higher, and the energy of the electrons entering the detector can be made lower. Further, in this reflection electron detection device and the reflection electron detection method, the first electric field and the second electric field are corrected by the correction unit. Therefore, the trajectories of the electrons passing through the first electric field and the second electric field can be appropriately maintained. Thus, it becomes possible to obtain an energy loss spectrum with higher accuracy.

Brief Description of the Drawings

[0024] [Figure 1] It is a schematic diagram showing an example of the configuration of a reflection electron detection device according to a first embodiment of the present invention. [Figure 2] It is a perspective view showing an example of the configuration of the correction unit shown in FIG. 1. [Figure 3] It is a perspective view showing another example of the configuration of the correction unit shown in FIG. 1. [Figure 4] It is a flowchart showing an example of a method for detecting electrons by the reflection electron detection device shown in FIG. 1. [Figure 5] It is a diagram showing an example of the energy distribution of electrons emitted from a sample. [Figure 6]Figure 1 is a schematic diagram showing an example of the first and second electric fields corrected by the correction unit. [Figure 7] This is a schematic diagram showing an example of the first and second electric fields formed in a backscattered electron detection device according to a comparative example. [Figure 8] This is a schematic diagram showing an example of the configuration of a backscattered electron detection device according to the second embodiment. [Figure 9A] This figure shows the cross-sectional configuration along line AA shown in Figure 8. [Figure 9B] This figure shows the cross-sectional configuration along the BB line shown in Figure 8. [Figure 10] Figure 8 is a flowchart illustrating an example of an electron detection method using a backscattered electron detector. [Modes for carrying out the invention]

[0025] Embodiments of the present invention will be described in detail below with reference to the attached drawings. In the following drawings, the same reference numerals refer to the same components, and the size of each component in the drawings is represented in proportion to what is actually depicted for clarity and convenience of explanation. On the other hand, the embodiments described below are merely illustrative, and various modifications are possible from such embodiments.

[0026] In the following, "top" or "above" may include not only things that are directly above and in contact with the object, but also things that are above but not in contact with the object.

[0027] A singular noun refers to a component that includes multiple components unless the context clearly indicates otherwise. Furthermore, when a part is said to "include" or "have" a component, it does not exclude other components, but rather may include other components, unless otherwise specified.

[0028] Furthermore, the use of the term "the aforementioned," and similar demonstrative terms, can be singular or plural.

[0029] Unless explicitly stated otherwise, the steps constituting the method shall be performed in the appropriate order. This order is not necessarily limited to the order in which the steps are described. The use of all examples or illustrative terms (e.g., e.g.) is solely for illustrative purposes and is not limited by the scope of the claims, unless otherwise defined.

[0030] <First Embodiment> (Configuration of backscattered electron detector 1) Figure 1 shows an example of the schematic configuration of a backscattered electron detection device 1 according to the first embodiment of the present invention. The backscattered electron detection device 1 includes, for example, an irradiator 10, a detector 20, a voltage application unit 30, and a correction unit 40. The backscattered electron detection device 1 analyzes the state of the target surface 50S of a sample 50, for example, using REELS. Specifically, electrons are irradiated from the irradiator 10 onto the target surface 50S, and these electrons are reflected from the target surface 50S. The detector 20 detects the electrons reflected from the target surface 50S and analyzes the energy of the detected electrons. This allows an energy loss spectrum of the sample 50 to be obtained. The irradiator 10 and the detector 20 are grounded.

[0031] The irradiator 10 emits electrons along the optical axis 10A. The irradiator 10 includes, for example, an electron source, an electron accelerator, an electron deflector, and an electron lens. The electron source emits, for example, electrons of a predetermined energy. The electron accelerator imparts a predetermined amount of kinetic energy to the electrons emitted from the electron source. The electron deflector and electron lens adjust the direction of these kinetically energized electrons, focusing them toward the sample 50. The energy of the electrons emitted from the irradiator 10 is, for example, 0.1 keV to 30 keV.

[0032] Detector 20 detects electrons incident along the optical axis 20A. Detector 20 includes, for example, a deflection-dispersion energy analyzer. This energy analyzer is, for example, a magnetic field deflection type, an electrostatic deflection type, or a Wien filter type. Detector 20 is, for example, hemispherical, fan-shaped, or coaxial cylindrical. Detector 20 detects electrons using, for example, a channeltron or a multichannel plate. Detector 20 may also detect electrons using a scintillator and a photomultiplier tube. Detector 20 may include an amplifier.

[0033] The sample 50 is positioned, for example, at the intersection of the optical axis 10A of the irradiator 10 and the optical axis 20A of the detector 20. The optical axes 10A and 20A intersect at an angle of, for example, 60 to 120 degrees. The angle between the target surface 50S of the sample 50 and the optical axis 10A of the irradiator 10 is, for example, between 0 degrees and 90 degrees, and the angle between the target surface 50S of the sample 50 and the optical axis 20A of the detector 20 is, for example, between 0 degrees and 90 degrees. The sample 50 is positioned, for example, on a stage (not shown). The stage may move the target surface 50S of the sample 50 relative to the optical axes 10A and 20A. The stage may change the angle of the target surface 50S relative to each of the optical axes 10A and 20A. By changing the angle of the symmetric surface 50S with respect to the optical axis 10A and optical axis 20A, the incident angle of electrons on the symmetric surface 50S and the exit angle of electrons from the symmetric surface 50S can be changed. This makes it possible to obtain information about the state of the sample 50 from multiple angles. In the following, the direction parallel to the optical axis 10A may be referred to as the Z direction, the direction parallel to the optical axis 20A as the X direction, and the direction perpendicular to the optical axis 10A and optical axis 20A as the Y direction.

[0034] The voltage application unit 30 applies a predetermined positive voltage to the correction unit 40 and the sample 50, respectively. For example, the voltage application unit 30 applies a positive voltage of +1kV to +5kV to the correction unit 40 and the sample 50, respectively. The voltage application unit 30 includes, for example, a power supply. When a positive voltage is applied to the sample 50, a potential difference is created between the sample 50 and the irradiator 10 and the detector 20, respectively. This potential difference generates a first electric field between the target surface 50S and the irradiator 10 (first electric field EF1 in Figure 5, described later) and a second electric field between the target surface 50S and the detector 20 (second electric field EF2 in Figure 5, described later). The first electric field accelerates electrons traveling from the irradiator 10 through the first electric field toward the target surface 50S. The second electric field decelerates electrons traveling from the target surface 50S through the second electric field toward the detector 20. Therefore, compared to the case where no positive voltage is applied to the sample 50, the energy of the electrons irradiating the target surface 50S can be increased, and the energy of the electrons entering the detector 20 can be decreased. As will be described in detail later, this makes it possible to improve the accuracy of the energy loss spectrum obtained by the backscattered electron detector 1.

[0035] The voltage application unit 30 applies, for example, a positive voltage of the same magnitude to the correction unit 40 and the sample 50. As a result, the correction unit 40 and the sample 50 are at the same potential, and no large electric field is generated between them. The magnitude of the positive voltage applied to the correction unit 40 and the sample 50 only needs to be substantially the same, and may differ by, for example, about 1%.

[0036] The correction unit 40 is responsible for correcting the first and second electric fields. The correction unit 40 is composed of, for example, a first plate-shaped electrode 41 and a second plate-shaped electrode 42. The first plate-shaped electrode 41 is provided between the irradiator 10 and the target surface 50S. The second plate-shaped electrode 42 is provided between the detector 20 and the target surface 50S.

[0037] Figure 2 is a perspective view showing an example of the configuration of the correction unit 40. The main surfaces of the first plate-shaped electrode 41 and the second plate-shaped electrode 42 are, for example, rectangular in shape. The main surface of the first plate-shaped electrode 41 faces the irradiator 10. The first plate-shaped electrode 41 has a main surface parallel to the XY plane, for example. That is, the main surface of the first plate-shaped electrode 41 is positioned in a direction perpendicular to the optical axis 10A of the irradiator 10. As will be described in detail later, this corrects the first electric field between the target surface 50S and the irradiator 10 so that electrons emitted from the irradiator 10 are directed toward the target surface 50S along the optical axis 10A. The position and orientation of the first plate-shaped electrode 41 are, for example, fixed with respect to the irradiator 10.

[0038] The first plate-shaped electrode 41 is provided with, for example, a first passage 41P. The first passage 41P is, for example, an opening that penetrates the first plate-shaped electrode 41 in the Z-axis direction. Electrons emitted from the irradiator 10 pass through this first passage 41P and reach the target surface 50S. The first passage 41P is provided at a position corresponding to the optical axis 10A. The first passage 41P is, for example, provided in the center of the main surface of the first plate-shaped electrode 41 and has a circular planar shape.

[0039] The second plate-shaped electrode 42 is connected to, for example, the first plate-shaped electrode 41. For example, the first plate-shaped electrode 41 and the second plate-shaped electrode 42 are integrated. The first plate-shaped electrode 41 and the second plate-shaped electrode 42 are electrically connected. The main surface of the second plate-shaped electrode 42 faces the detector 20. The second plate-shaped electrode 42 has, for example, a main surface parallel to the YZ plane. That is, the main surface of the second plate-shaped electrode 42 is positioned in a direction perpendicular to the optical axis 20A of the detector 20. As will be described in detail later, this corrects the second electric field between the target surface 50S and the detector 20 so that electrons reflected from the target surface 50S are directed toward the detector 20 along the optical axis 20A. The position and orientation of the second plate-shaped electrode 42 are fixed with respect to the detector 20, for example.

[0040] The second plate-shaped electrode 42 is provided with, for example, a second passage 42P. The second passage 42P is, for example, an opening that penetrates the second plate-shaped electrode 42 in the X-axis direction. Electrons reflected from the target surface 50S of the sample 50 pass through this second passage 42P and are incident on the detector 20. The second passage 42P is provided at a position corresponding to the optical axis 20A. The second passage 42P is, for example, provided in the center of the main surface of the second plate-shaped electrode 42 and has a circular planar shape.

[0041] Figure 3 shows another example of the configuration of the first passage 41P and the second passage 42P. The first passage 41P and the second passage 42P may, for example, have a slit shape. The first passage 41P and the second passage 42P are each composed of slits parallel to the Y-axis direction. The shapes of the first passage 41P and the second passage 42P may be different from each other. By providing the first passage 41P and the second passage 42P with such slit shapes, the degree of freedom in aligning the optical axes 10A and 20A can be improved.

[0042] Sample 50 has, for example, a circular thin film shape. The thickness of sample 50 is, for example, 0.2 mm to 1.0 mm. Sample 50 is not particularly limited, but for example, it may be a semiconductor wafer. Sample 50 may be a metallic material or an insulating material deposited on a semiconductor wafer.

[0043] (Method for detecting electrons using backscattered electron detector 1) Figure 4 is a flowchart illustrating an example of an electron detection method using the backscattered electron detector 1. First, the backscattered electron detector 1 applies a predetermined positive voltage to the sample 50 (step S101). Next, the backscattered electron detector 1 applies a predetermined positive voltage to the first plate-shaped electrode 41 and the second plate-shaped electrode 42 (step S102). This corrects the first electric field between the target surface 50S and the irradiator 10, and the second electric field between the target surface 50S and the detector 20.

[0044] For example, the voltage application unit 30 applies a positive voltage to the sample 50, the first plate-shaped electrode 41, and the second plate-shaped electrode 42. The processing order of steps S101 and S102 may be reversed, or steps S101 and S102 may be performed simultaneously.

[0045] After applying a positive voltage to the sample 50, the first plate-shaped electrode 41, and the second plate-shaped electrode 42, the backscattered electron detection device 1 irradiates electrons from the irradiator 10 toward the target surface 50S of the sample 50 (step S103). The electrons emitted from the irradiator 10 pass through the corrected first electric field, travel along the optical axis 10A, and reach the target surface 50S.

[0046] At least some of the electrons that reach the target surface 50S are reflected near the target surface 50S. The electrons reflected near the target surface 50S pass through the corrected second electric field, travel along the optical axis 20A, and are detected by the detector 20. The detector 20 performs energy analysis on the detected electrons.

[0047] (Effects of the backscattered electron detector 1) In the backscattered electron detector 1 of this embodiment, a voltage is applied to the sample 50, so a first electric field and a second electric field are formed around the sample 50. The first electric field accelerates electrons traveling from the irradiator 10 toward the target surface 50S, and the second electric field decelerates electrons traveling from the target surface 50S toward the detector 20. This allows higher-energy electrons to be irradiated onto the target surface 50S, while also lowering the energy of the electrons entering the detector 20. Furthermore, the first and second electric fields around the sample 50 are corrected by the correction unit 40. Therefore, the trajectories of electrons passing through the first and second electric fields can be appropriately maintained. Thus, it is possible to obtain an energy loss spectrum with higher accuracy. The effects of this will be explained below.

[0048] In transmission-type EELS, thinning of the sample is necessary because electrons that have passed through the sample are detected. Furthermore, a support film of uniform thickness is required to support the sample. Compared to transmission-type EELS, REELS detects electrons reflected from the sample, eliminating the need for thinning. A support film of uniform thickness is also unnecessary. Therefore, REELS allows for simpler analysis of the sample surface condition compared to transmission-type EELS.

[0049] REELS measurements can utilize, for example, equipment for AES (Auger Electron Spectroscopy) measurements. AES involves irradiating the sample surface with electrons and analyzing the Auger electrons emitted from the sample surface.

[0050] Figure 5 shows an example of the energy distribution of electrons emitted from a sample. The vertical axis represents the number of electrons emitted, and the horizontal axis represents the energy of the electrons emitted from the sample. Upward movement on the vertical axis indicates a larger number of electrons, and rightward movement on the horizontal axis indicates higher electron energy. In AES measurement, the sample is irradiated with electrons of 10 keV or higher, and Auger electrons of approximately 2 keV or lower are detected. On the other hand, REELS detects backscattered electrons, which have the same energy as the irradiated electrons, i.e., zero-loss scattered electrons. In REELS measurement, the higher the energy of the irradiated electrons, the less secondary electrons that cause noise are mixed in, and the better the signal-to-noise ratio (SNR). There are two reasons for this: First, the higher the energy of the irradiated electrons, the less secondary electrons are generated. Second, the higher the energy of the irradiated electrons, the higher the energy of the zero-loss scattered electrons, and the wider the difference between the energy range of the electrons used in REELS measurement and the peak energy range of secondary electrons.

[0051] Furthermore, in AES and REELS systems, the over-voltage ratio, expressed by the following equation (1), is important.

[0052]

number

[0053] Theoretically, when U > 1, a substance can be excited by irradiated electrons, but in practice, spectral measurement becomes possible when U = 2 to 20. Furthermore, a high signal-to-noise ratio is often obtained when U = 10. From the perspective of this overpotential ratio, the higher the energy of the irradiated electrons, the more accurate the measurement becomes.

[0054] However, AES measurements do not require the detection of electrons in such high energy ranges. Therefore, when attempting to apply an AES measurement device to REELS measurements, the detector's detectable electron energy range is limited, making it difficult to irradiate the sample with high-energy electrons and thus hindering the improvement of the accuracy of the resulting energy loss spectrum.

[0055] In contrast, in the backscattered electron detector 1, a positive voltage is applied to the sample 50, so a first electric field (first electric field EF1 in Figure 6, described later) is formed between the target surface 50S of the sample 50 and the irradiator 10, and a second electric field (second electric field EF2 in Figure 6, described later) is formed between the target surface 50S and the detector 20.

[0056] Figure 6 shows the equipotential lines of the first electric field EF1 and the second electric field EF2, respectively. Here, a first plate-shaped electrode 41 is provided between the irradiator 10 and the target surface 50S, and a second plate-shaped electrode 42 is provided between the detector 20 and the target surface 50S. As a result, the direction of the first electric field EF1 is corrected in a direction parallel to the optical axis 10A of the irradiator 10, and the direction of the second electric field EF2 is corrected in a direction parallel to the optical axis 20A of the detector 20. This will be explained below.

[0057] Figure 7 shows an example of the configuration of a backscattered electron detector 1000 according to a comparative example. This backscattered electron detector 1000 does not have a correction unit (for example, the correction unit 40 in Figure 6). In this respect, the backscattered electron detector 1000 differs from the backscattered electron detector 1. In this backscattered electron detector 1000, when a positive voltage is applied to the sample 50, an electric field is formed along the target surface 50S. Since the irradiator 10 and the detector 20 are arranged in directions where their optical axes intersect, the electric field EF formed near the target surface 50S is deviated from the direction parallel to at least one of the optical axes 10A and 20A. Electrons passing through such an electric field EF are deflected, causing distortion in the electron trajectory. In other words, the electron trajectory deviates from the optical axes of the irradiator and the detector.

[0058] For example, the deflection function of the irradiator 10 can return electrons reflected from the target surface 50S to the direction of the optical axis 20A. However, this method changes the angle of the irradiating electrons. Also, electrons reflected from the target surface 50S have various energy values ​​(see Figure 5). When these electrons with various energy values ​​pass through the electric field EF, the deflection angle differs depending on the energy value, which may cause a bias in the energy values ​​of the electrons incident on the detector 20. Therefore, this may significantly reduce the accuracy of the energy loss spectrum.

[0059] In contrast, in the backscattered electron detection device 1 shown in Figure 6, the first electric field EF1 is corrected by the first plate-shaped electrode 41, and the second electric field EF2 is corrected by the second plate-shaped electrode 42. Since the main surface of the first plate-shaped electrode 41 is positioned perpendicular to the optical axis 10A, the first electric field EF1 between the irradiator 10 and the first plate-shaped electrode 41 is formed parallel to the optical axis 10A. Since the main surface of the second plate-shaped electrode 42 is positioned perpendicular to the optical axis 20A, the second electric field EF2 between the detector 20 and the second plate-shaped electrode 42 is formed parallel to the optical axis 20A.

[0060] The backscattered electron detector 1, with its first and second electric fields EF1 and EF2 corrected in this manner, operates as follows. For example, the voltage application unit 30 applies a positive voltage of +3kV to the first plate electrode 41, the second plate electrode 42, and the sample 50, respectively. When the irradiator 10 emits electrons at, for example, 1keV, the electrons passing through the first electric field EF1 are accelerated toward the target surface 50S. Near the first plate electrode 41, the electrons emitted from the irradiator 10 reach, for example, about 4keV. At this time, since the first electric field EF1 is corrected in a direction parallel to the optical axis 10A of the irradiator 10, the electrons travel along a trajectory along the optical axis 10A with almost no deflection. Since no strong electric field is formed between the first plate electrode 41 and the sample 50 at the same potential, the electrons reach the target surface 50S via the first passage 41P while maintaining an energy of about 4keV. Furthermore, the electron lens of the irradiator 10 may be adjusted according to the magnitude of the positive voltage applied to the first plate-shaped electrode 41, the second plate-shaped electrode 42, and the sample 50. This allows electrons to be irradiated onto the target surface 50S while taking into account the focusing effect caused by the first electric field EF1.

[0061] When electrons reach the target surface 50S of the sample 50, they undergo various physical processes in the vicinity of the target surface 50S and are emitted from the target surface 50S. The electrons emitted from the target surface 50S are, for example, secondary electrons and backscattered electrons (see Figure 5), and have various energy values. Backscattered electrons include zero-loss scattered electrons. Since no strong electric field is formed between the second plate electrode 42 and the sample 50, which are at the same potential, for example, some of the electrons emitted from the target surface 50S pass through the second passage 42P while maintaining their energy value. When the electrons that have passed through the second passage 42P pass through the second electric field EF2, they are decelerated to about 1 keV and reach the detector 20. At this time, since the second electric field EF2 is corrected to be parallel to the optical axis 20A of the detector 20, the electrons travel along a trajectory along the optical axis 20A with almost no deflection. For example, electrons with an energy of 3 keV or less cannot travel through the second electric field EF2. In other words, the second electric field EF2 also has a filtering function that removes electrons below a predetermined energy value.

[0062] In this way, the backscattered electron detector 1 increases the energy of electrons emitted from the irradiator 10 from 1 keV to approximately 4 keV before they reach the target surface 50S of the sample 50, while simultaneously reducing the energy of electrons reflected from the target surface 50S to approximately 1 keV before they are incident on the detector 20. At the same time, the first plate-shaped electrode 41 and the second plate-shaped electrode 42 maintain the electron trajectories along the optical axis 10A of the irradiator 10 and the optical axis 20A of the detector 20. Therefore, it becomes possible to obtain an energy loss spectrum with higher accuracy.

[0063] The following describes a backscattered electron detection device 1 according to another embodiment. To avoid repetition of the explanation, detailed descriptions of configurations similar to those of the backscattered electron detection device 1 of the first embodiment will be omitted.

[0064] <Second Embodiment> Figures 8, 9A, and 9B show an example of the configuration of the backscattered electron detection device 2 according to the second embodiment. Figure 8 shows an example of the schematic configuration of the backscattered electron detection device 2, Figure 9A shows a cross-sectional configuration along line AA shown in Figure 8, and Figure 9B shows a cross-sectional configuration along line BB shown in Figure 8. This backscattered electron detection device 2 has a correction unit 60 instead of the correction unit 40 (Figure 1). In the backscattered electron detection device 2, a magnetic field is generated by the correction unit 60, and the first electric field and the second electric field are corrected by this magnetic field. Except for this point, the backscattered electron detection device 1 according to the second embodiment has the same configuration as the backscattered electron detection device 1 described in the first embodiment above.

[0065] The correction unit 60 includes, for example, a first yoke 61, a first coil 62, a second yoke 63, and a second coil 64. For example, the first coil 62 is located near the first yoke 61, and the second coil 64 is located near the second yoke 63.

[0066] When current flows through the first coil 62, a first magnetic field MF1 is formed. The direction of the first magnetic field MF1 is, for example, one direction in the Y direction. The magnitude of the current flowing through the first coil 62 is adjusted according to the energy of the electrons irradiated from the irradiator 10. This first magnetic field MF1 acts on electrons passing through the first electric field.

[0067] When current flows through the second coil 64, a second magnetic field MF2 is formed. The direction of the second magnetic field MF2 is, for example, the same as the direction of the first magnetic field MF1. The magnitude of the current flowing through the second coil 64 is adjusted according to the energy of the electrons detected by the detector 20. This second magnetic field MF2 acts on electrons passing through the second electric field.

[0068] Figure 10 is a flowchart illustrating an example of an electron detection method using the backscattered electron detector 2. First, the backscattered electron detector 2 applies a predetermined positive voltage to the sample 50 (step S201). Next, the backscattered electron detector 2 forms a first magnetic field MF1 and a second magnetic field MF2 (step S202). This corrects the first electric field between the target surface 50S and the irradiator 10, and the second electric field between the target surface 50S and the detector 20.

[0069] The first magnetic field MF1 and the second magnetic field MF2 are formed, for example, by passing current through the first coil 62 and the second coil 64. The order of processing steps S201 and S202 may be reversed, and the processing of steps S201 and S202 may be performed simultaneously.

[0070] After forming the first magnetic field MF1 and the second magnetic field MF2, the backscattered electron detector 2 irradiates electrons from the irradiator 10 toward the target surface 50S of the sample 50 (step S203). The electrons emitted from the irradiator 10 pass through the corrected first electric field, travel along the optical axis 10A, and reach the target surface 50S.

[0071] Electrons that reach the target surface 50S are reflected near the target surface 50S. The electrons reflected near the target surface 50S pass through the corrected second electric field, travel along the optical axis 20A, and are detected by the detector 20. The detector 20 performs energy analysis on the detected electrons.

[0072] In this backscattered electron detector 2, similar to the backscattered electron detector 1, a voltage is applied to the sample 50, so a first electric field and a second electric field are formed around the sample 50. The first electric field accelerates electrons traveling from the irradiator 10 toward the target surface 50S, and the second electric field decelerates electrons traveling from the target surface 50S toward the detector 20. This allows for irradiating the target surface 50S with electrons of higher energy, while simultaneously lowering the energy of the electrons entering the detector 20.

[0073] Furthermore, the first and second electric fields are corrected by the correction unit 60. Specifically, the first magnetic field MF1 acts to cancel out the component of the force acting on electrons passing through the first electric field in a direction approximately perpendicular to the optical axis 10A, and the second magnetic field MF2 acts to cancel out the component of the force acting on electrons passing through the second electric field in a direction approximately perpendicular to the optical axis 20A. Therefore, the trajectories of electrons passing through the first and second electric fields can be appropriately maintained. Thus, it becomes possible to obtain an energy loss spectrum with higher accuracy. Here, the direction approximately perpendicular to the optical axes 10A and 20A can be any direction within the range in which the effects of the first magnetic field MF1 and the second magnetic field MF2 are exerted. Specifically, the direction approximately perpendicular to the optical axis 10A may be within the range of 80 to 100 degrees, within the range of 85 to 95 degrees, or 90 degrees with respect to the optical axis 10A.

[0074] Furthermore, the backscattered electron detector 2 eliminates the need to install electrodes or other components around the sample 50. This makes it possible to reduce the working distance (WD) between the irradiator 10 and the detector 20 and the sample 50.

[0075] The configurations of the backscattered electron detection devices 1 and 2 described above are merely the main configurations explained in order to illustrate the features of the embodiments described above, and are not limited to the above configurations, but can be modified in various ways within the scope of the claims. Furthermore, they do not preclude the configurations that are generally found in backscattered electron detection devices.

[0076] For example, the backscattered electron detectors 1 and 2 may include multiple detectors. For instance, some of the multiple detectors may be used to create a Scanning Electron Microscope (SEM) image of the target surface 50S of the sample 50. The creation of an SEM image facilitates observation of the field of view to be analyzed and selection of an appropriate field of view region.

[0077] Furthermore, at least one of the first plate-shaped electrode 41 and the second plate-shaped electrode 42 may be composed of multiple plate-shaped electrodes.

[0078] Furthermore, the first plate-shaped electrode 41 and the second plate-shaped electrode 42 may be separated from each other. In this case, the first plate-shaped electrode 41 and the second plate-shaped electrode 42 may, for example, be configured as separate components, and their respective positions can be freely adjusted. The first plate-shaped electrode 41 and the second plate-shaped electrode 42 may, for example, be electrically isolated.

[0079] Furthermore, although the first embodiment described above illustrates an example in which the correction unit 40 has a first plate-shaped electrode 41 and a second plate-shaped electrode 42, the electrodes included in the correction unit 40 may have shapes other than plate shapes, for example, they may have a block shape or a prismatic shape. The correction unit 40 may also have electrodes of different shapes from each other.

[0080] Furthermore, the voltage application unit 30 may apply voltage between the sample 50 and the first plate-shaped electrode 41, and between the sample 50 and the second plate-shaped electrode 42, respectively.

[0081] Furthermore, the correction unit 60 only needs to have a configuration capable of forming a first magnetic field MF1 and a second magnetic field MF2. For example, the correction unit 60 may be composed of members other than a coil and a yoke.

[0082] Furthermore, although the first and second embodiments described above illustrate how electrodes or a magnetic field are used to correct the first and second electric fields, other configurations may also be used to correct the first and second electric fields.

[0083] The backscattered electron detection device of the present invention also includes backscattered electron detection devices according to the following modified examples 1 and 2.

[0084] The backscattered electron detection device according to Modification 1 includes an irradiator that irradiates electrons onto a target surface of a sample, a detector that detects at least a portion of the electrons reflected from the target surface, a correction unit including a first plate-shaped electrode provided between the irradiator and the target surface and a second plate-shaped electrode provided between the detector and the target surface, the sample, and a voltage application unit that applies a voltage to the first plate-shaped electrode and the second plate-shaped electrode.

[0085] The backscattered electron detection device according to the modified example 2 includes an irradiator that irradiates electrons onto a target surface of a sample, a detector that detects at least a portion of the electrons reflected from the target surface, a correction unit that generates a first magnetic field between the target surface and the irradiator and a second magnetic field between the target surface and the detector, and a voltage application unit that applies a voltage to the sample. [Explanation of Symbols]

[0086] 1,2 Reflected electron detection device, 10 irradiator, 10A optical axis, 20 detectors, 20A optical axis, 30 Voltage application section, 40,60 correction units, 41 First plate-shaped electrode, 41P 1st passage, 42 Second plate-shaped electrode, 42P 2nd passage, 50 samples, 50S target surface, 61 First York, 62 First coil, 63 Second York, 64. Second coil.

Claims

1. A backscattered electron detection device, The aforementioned backscattered electron detection device is An irradiator that irradiates the target surface of the sample with electrons, A detector for detecting at least a portion of the electrons reflected from the surface of the object, A correction unit including a first plate-shaped electrode provided between the irradiator and the target surface, and a second plate-shaped electrode provided between the detector and the target surface, The sample and a voltage application unit that applies voltage to the first plate-shaped electrode and the second plate-shaped electrode. Equipped with, The correction unit is a backscattered electron detection device that corrects a first electric field generated between the target surface of the sample to which a voltage is applied and the irradiator, and a second electric field generated between the target surface of the sample to which a voltage is applied and the detector.

2. The first plate-shaped electrode corrects the first electric field so that the electrons passing through the first electric field are directed toward the target surface. The backscattered electron detection device according to claim 1, wherein the second plate-shaped electrode corrects the second electric field so that the electrons passing through the second electric field are directed toward the detector.

3. The electrons emitted from the irradiator reach the target surface via the first passage provided in the first plate-shaped electrode. The backscattered electron detection device according to claim 1, wherein the electrons reflected from the target surface reach the detector via a second passage provided in the second plate-shaped electrode.

4. The main surface of the first plate-shaped electrode faces the irradiator, The backscattered electron detection device according to claim 1, wherein the main surface of the second plate-shaped electrode faces the detector.

5. The first passage is formed by an opening provided in the first plate-shaped electrode, The backscattered electron detection device according to claim 3, wherein the second passage is formed by an opening provided in the second plate-shaped electrode.

6. The first passage is formed by a slit provided in the first plate-shaped electrode, The backscattered electron detection device according to claim 3, wherein the second passage is provided by a slit in the second plate-shaped electrode.

7. The backscattered electron detection device according to claim 1, wherein the first plate-shaped electrode and the second plate-shaped electrode are connected.

8. The backscattered electron detection device according to claim 1, wherein the first plate-shaped electrode and the second plate-shaped electrode are separated.

9. A backscattered electron detection device, The aforementioned backscattered electron detection device is An irradiator that irradiates the target surface of the sample with electrons, A detector for detecting at least a portion of the electrons reflected from the surface of the object, A correction unit that generates a first magnetic field between the irradiator and the target surface, and generates a second magnetic field between the detector and the target surface, A voltage application unit that applies voltage to the sample and Equipped with, The correction unit is a backscattered electron detection device that corrects a first electric field generated between the target surface of the sample to which a voltage is applied and the irradiator, and a second electric field generated between the target surface of the sample to which a voltage is applied and the detector.

10. The first magnetic field acts to cancel out the component of the force acting on the electrons passing through the first electric field in a direction substantially perpendicular to the optical axis of the irradiator, The backscattered electron detection device according to claim 9, wherein the second magnetic field acts to cancel out the component of the force acting on the electrons passing through the second electric field in a direction substantially perpendicular to the optical axis of the detector.

11. The backscattered electron detection device according to claim 1 or 9, wherein the irradiator and the detector are arranged in different directions relative to the target surface.

12. The backscattered electron detector according to claim 1 or 9, wherein the detector analyzes the energy of the detected electrons.

13. Applying voltage to the sample, A voltage is applied to a first plate-shaped electrode provided between the target surface of the sample and the irradiator to correct the first electric field generated between the target surface of the sample to which the voltage is applied and the irradiator. The process involves irradiating the target surface of the sample with electrons by passing the corrected first electric field from the irradiator, A voltage is applied to a second plate-shaped electrode provided between the target surface and the detector to correct the second electric field generated between the target surface of the sample to which the voltage is applied and the detector. To detect, using the detector, at least a portion of the electrons that have been reflected from the target surface and passed through the corrected second electric field. A method for detecting backscattered electrons, including the method described above.

14. Applying voltage to the sample, A first magnetic field is generated between the target surface of the sample and the irradiator, and the first electric field generated between the target surface of the sample to which a voltage is applied and the irradiator is corrected. The process involves irradiating the target surface of the sample with electrons by passing the corrected first electric field from the irradiator, A second magnetic field is generated between the target surface and the detector, and the second electric field generated between the target surface of the sample to which a voltage is applied and the detector is corrected. To detect, using the detector, at least a portion of the electrons that have been reflected from the target surface and passed through the corrected second electric field. A method for detecting backscattered electrons, including the method described above.

15. An irradiator that irradiates the target surface of the sample with electrons, A detector for detecting at least a portion of the electrons reflected from the surface of the object, A voltage application unit for applying a voltage to the sample, A correction unit for correcting a first electric field generated between the target surface of the sample to which a voltage is applied and the irradiator, and a second electric field generated between the target surface of the sample to which a voltage is applied and the detector. A backscattered electron detection device equipped with the following features.

16. Applying voltage to the sample, To correct the first electric field generated between the target surface of the sample to which the voltage is applied and the irradiator, The process involves irradiating the target surface of the sample with electrons by passing the corrected first electric field from the irradiator, To correct the second electric field generated between the target surface of the sample to which the voltage is applied and the detector, To detect, using the detector, at least a portion of the electrons that have been reflected from the target surface and passed through the corrected second electric field. A method for detecting backscattered electrons, including the method described above.

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