Method for adjusting charged particle beam device and charged particle beam device

Abstract

A light irradiation position adjustment method is a method for adjusting the irradiation position of first light, in a charged particle beam device including a particle beam source for irradiating a sample with a charged particle beam; a particle beam detector that detects the particle beam from the sample and generates a particle beam electrical signal; a light source that generates first light that irradiates the sample; a movable mechanism capable of moving the irradiation position of the first light; a photodetector that detects second light emitted from the sample via the irradiation of the first light and generates a photoelectric signal; a sample stage having a configuration on which a sample can be placed and moved; and a control device, wherein the light source irradiates an adjustment sample placed on the sample stage and including a reference structure with the first light, the photodetector detects the second light generated via the modulation of the first light by the reference structure and sends a photoelectric signal to the control device, the control device issues a command to change the irradiation position of the first light so as to pass through the reference structure, and, on the basis of the change in the photoelectric signal, adjusts the movable mechanism so that the irradiation position of the charged particle beam and the irradiation position of the first light match. Thus, the irradiation position of the charged particle beam and the irradiation position of the light can be accurately matched by a simple method.

Description

[Technical Field]

[0001] The present disclosure relates to a method for adjusting a charged particle beam device and the charged particle beam device. [Background technology]

[0002] When observing and analyzing a sample using a charged particle beam, it is known that the charging of the sample causes distortion of the secondary charged particle beam image and variations in brightness. To address this issue, there is a technology to control charging by irradiating the area irradiated with the charged particle beam with electromagnetic waves such as light.

[0003] Patent Document 1 discloses a technique for preventing charging by irradiating a charged particle beam simultaneously with irradiating a light beam.

[0004] Patent Document 2 discloses a charged particle beam device that determines whether the irradiation position of a primary charged particle beam and the irradiation position of light match based on the difference between a first observation image acquired when only a primary charged particle beam is irradiated and a second observation image acquired when light is irradiated in addition to the primary charged particle beam. Patent Document 2 also discloses that an adjustment sample used to identify the irradiation position of light has a grid-like pattern repeatedly arranged when viewed from above, and the pattern position coordinates can be recognized by marks, and that the adjustment is made to reduce the difference so that the irradiation position of the primary charged particle beam and the irradiation position of the light match.

[0005] Patent Document 3 discloses a method for adjusting the irradiation positions of a charged particle beam and a light beam.

[0006] Patent Document 4 discloses a method of displaying an area irradiated with ultraviolet light as a photoelectron image, and displaying the photoelectron image and the reflected electron image superimposed on a monitor.

[0007] Patent Document 5 discloses an optical height detection method in which a two-dimensional slit light is projected onto an object from diagonally above, the reflected light is detected, and the height of the object is detected by excluding the slit portion where the detection error is large. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-151483 [Patent Document 2] International Publication No. 2020 / 115876 [Patent Document 3] US Patent Application Publication No. 2018 / 0166247 [Patent Document 4] Japanese Patent Application Laid-Open No. 2009-004114 [Patent Document 5] Japanese Patent Application Laid-Open No. 2007-132836 Summary of the Invention [Problem to be solved by the invention]

[0009] In a device that irradiates light and a charged particle beam, it is necessary to adjust the light irradiation position relative to the charged particle beam irradiation position. For example, when removing charge from a sample by light irradiation, it is necessary to accurately align the charged particle beam irradiation area, where charging occurs, with the light irradiation area.

[0010] The present disclosure aims to accurately align the irradiation position of a charged particle beam and the irradiation position of light using a simple method. [Means for solving the problem]

[0011] A method for adjusting a light irradiation position according to one aspect of the present disclosure is a method for adjusting the irradiation position of the first light in a charged particle beam device including a particle beam source that irradiates a sample with a charged particle beam, a particle beam detector that detects the particle beam from the sample and generates a particle beam electrical signal, a light source that generates first light that irradiates the sample, a movable mechanism that can move the irradiation position of the first light, a photodetector that detects second light emitted from the sample in response to the irradiation of the first light and generates a photoelectric signal, a sample stage configured to allow the sample to be placed and moved, and a control device, in which the light source irradiates the first light onto an adjustment sample placed on the sample stage and including a reference structure, the photodetector detects the second light generated by modulation of the first light by the reference structure and sends a photoelectric signal to the control device, the control device issues a command to change the irradiation position of the first light so that it passes through the reference structure, and based on the change in the photoelectric signal, adjusts the movable mechanism so that the irradiation position of the charged particle beam and the irradiation position of the first light coincide with each other.

[0012] A charged particle beam device according to another aspect of the present disclosure is a charged particle beam device comprising: a particle beam source that irradiates a sample with a charged particle beam; a particle beam detector that detects the particle beam from the sample and generates a particle beam electrical signal; a light source that generates first light that irradiates the sample; a movable mechanism that can move the irradiation position of the first light; a photodetector that detects second light emitted from the sample in response to the irradiation of the first light and generates a photoelectric signal; a sample stage configured to allow the sample to be placed and moved; and a control device, wherein the light source irradiates the first light onto an adjustment sample placed on the sample stage and including a reference structure; the photodetector detects second light generated by modulation of the first light by the reference structure and sends a photoelectric signal to the control device; the control device issues a command to change the irradiation position of the first light so that it passes through the reference structure; and, based on the change in the photoelectric signal, adjusts the movable mechanism so that the irradiation position of the charged particle beam and the irradiation position of the first light coincide with each other. [Effects of the Invention]

[0013] According to the present disclosure, the irradiation position of the charged particle beam and the irradiation position of the light can be accurately aligned by a simple method. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram showing a charged particle beam device according to a first embodiment. [Figure 2] FIG. 1 is a diagram showing a light irradiation area on a sample. [Figure 3A] FIG. 2 is a cross-sectional view showing an example of the adjustment sample 6 of FIG. [Figure 3B] FIG. 3B is a top view showing the adjustment sample 6 of FIG. 3A. [Figure 3C] FIG. 3C is an enlarged view of an area 6p indicated by a dotted square in FIG. 3B. [Figure 3D] FIG. 3B is a cross-sectional view showing a modified example of the adjustment sample 6 of FIG. 3A. [Figure 4] FIG. 2 is a top view showing the overall structure of an adjustment sample used in Example 1. [Figure 5] FIG. 2 is a configuration diagram showing an example of a control system 5 in FIG. [Figure 6] 10 is a flowchart showing a method for adjusting a light irradiation position according to the first embodiment. [Figure 7A] FIG. 10 is a diagram illustrating an adjustment GUI according to the first embodiment. [Figure 7B] FIG. 10 is a diagram illustrating an adjustment GUI according to the first embodiment. [Figure 8A] 10 is a graph showing an example of mirror angle dependency of secondary light intensity in Example 1. [Figure 8B] 10 is a graph showing another example of mirror angle dependency of secondary light intensity in Example 1. [Figure 9A] FIG. 10 is a cross-sectional view showing an example of a reference structure used in Modification 1. [Figure 9B] 10 is a cross-sectional view showing another example of the reference structure used in Modification 1. FIG. [Figure 9C] 10 is a cross-sectional view showing another example of a reference structure used in Modification 1. FIG. [Figure 10] FIG. 10 is a cross-sectional view showing an example of a reference structure used in Modification 2. [Figure 11A] FIG. 11 is a cross-sectional view showing an example of a reference structure used in Modification 3. [Figure 11B] FIG. 11 is a cross-sectional view showing another example of the reference structure used in Modification 3. [Figure 12] 10 is a schematic diagram showing the influence of a change in the height of the sample in Example 2. FIG. [Figure 13] FIG. 10 is a schematic configuration diagram showing a charged particle beam device according to a second embodiment. [Figure 14A] FIG. 10 is a cross-sectional view showing an example of a sample for adjustment used in Example 2. [Figure 14B] FIG. 10 is a cross-sectional view showing another example of the adjustment sample used in Example 2. [Figure 15] 10 is a flowchart showing a method for calibrating a mirror angle according to a second embodiment. [Figure 16A] FIG. 10 is a diagram showing an example of a setting screen as a calibration GUI in the second embodiment. [Figure 16B] 10A and 10B are diagrams showing an example of the measurement value and adjustment result of the sample height in the calibration GUI of the second embodiment. [Figure 17] 10 is a flowchart showing a method for adjusting an irradiation position in the second embodiment. [Figure 18] 10 is a graph for explaining a method for determining a mirror angle in the second embodiment. [Figure 19] FIG. 10 is a configuration diagram showing a light irradiation system and a light detection system according to a third embodiment. [Figure 20A] FIG. 10 is a configuration diagram showing a light irradiation system and a light detection system according to a fourth embodiment. [Figure 20B] FIG. 10 is a configuration diagram showing a modified example of the optical system. [Figure 20C] FIG. 10 is a configuration diagram showing a modified example of the optical system. [Figure 21A] 20B is a graph showing a signal intensity X1 detected by the light receiving element 2b of FIG. 20A. [Figure 21B] 20B is a graph showing the signal intensity X2 detected by the light receiving element 2c of FIG. 20A. [Figure 21C] 20B is a graph showing an electrical signal X3 calculated by a signal processing unit 2d in FIG. 20A. [Figure 22] FIG. 10 is a top view showing an example of a sample for adjustment in Example 5. [Figure 23]13 is a flowchart showing an adjustment procedure for obtaining a coordinate transformation formula according to the fifth embodiment. [Figure 24] FIG. 13 is a diagram illustrating an example of a display GUI for an adjustment result according to the fifth embodiment. [Figure 25] FIG. 10 is a top view showing the relationship between the adjustment sample used in Example 6 and the light irradiation position. [Figure 26] 10 is a graph showing the signal intensity obtained in Example 6. [Figure 27A] 13A and 13B are diagrams illustrating a problem that occurs when the boundary line and the movable axis intersect obliquely in the sixth embodiment. [Figure 27B] 13 is a diagram illustrating a case in which the boundary line and the movable axis intersect at a right angle in the sixth embodiment. FIG. [Figure 28] 13 is a flowchart showing a method for adjusting a light irradiation position according to a sixth embodiment. [Figure 29] FIG. 20 is a diagram showing an adjustment GUI according to the sixth embodiment. [Figure 30] 13 is a diagram illustrating a method for adjusting the second adjustment axis in the sixth embodiment. FIG. [Figure 31] FIG. 20 is a diagram showing an adjustment GUI according to the sixth embodiment. [Figure 32A] 13 is a diagram illustrating the amount of secondary light before the light irradiation position is moved in Example 6. FIG. [Figure 32B] 32B is a diagram illustrating the amount of secondary light when the light irradiation position is moved from the position in FIG. 32A. FIG. [Figure 32C] 32A and 32B. FIG. 32B is a diagram illustrating the rate of change in the amount of secondary light between FIG. 32A and FIG. [Figure 33] 10 is a graph showing a rate of change in the amount of secondary light. [Figure 34A] FIG. 10 is a top view showing an example of a reference structure having boundary lines in two directions on a sample for adjustment. [Figure 34B] FIG. 10 is a top view showing another example of a reference structure having boundary lines in two directions on a sample for adjustment. [Figure 35] FIG. 13 is a top view showing a modified example of the adjustment sample that can be used in Example 6. [Figure 36A] 36 is a graph showing an electrical signal emitted from the reference structure 6a in FIG. 35 and detected by the light receiving element 2b. [Figure 36B]36 is a graph showing an electrical signal emitted from the reference structure 6m in FIG. 35 and detected by the light receiving element 2c. [Figure 36C] 10 is a graph showing an electrical signal calculated by a signal processing unit 2d. DETAILED DESCRIPTION OF THE INVENTION

[0015] The method for adjusting the light irradiation position in a charged particle beam device according to the present disclosure uses an adjustment sample including a reference structure that generates new light in response to light irradiation, a control device that controls the light irradiation position, and a photodetector that detects the light and generates an electrical signal, and the control device moves the light irradiation position so that it passes through the reference structure, and adjusts the light irradiation position relative to the charged particle beam irradiation position based on the change in the electrical signal.

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the contents of the present disclosure are not limited to the embodiments described below, and various modifications are possible within the scope of the technical concept. Furthermore, corresponding parts in each drawing used to describe each embodiment described below will be designated by the same reference numerals, and duplicated explanations will be omitted. [Example]

[0017] In this example, we will explain an example in which charge generated on a sample by irradiation with a charged particle beam is removed by using charge generated by light irradiation. In this example, in order to deliver the charge generated by light to the charged area on the sample, an adjustment method is required to accurately align the light irradiation position with the electron beam irradiation position. However, the effect of light irradiation is not limited to charge removal. Other applications include, for example, measurement of absorption spectra and emission spectra, and shape observation using a microscope. In these cases, the adjustment method described in this example can be used to align the irradiation range of the charged particle beam with the observation range of light.

[0018] FIG. 1 is a schematic diagram showing the configuration of a charged particle beam device according to this embodiment.

[0019] The charged particle beam device is composed of a light irradiation system 1, a light detection system 2, an electron optical system 3, a sample stage system 4 (sample stage), and a control system 5 (control device). By using an adjustment sample 6, the light irradiation position relative to the electron irradiation position is adjusted.

[0020] The electron optical system 3 is configured to generate an SEM image and is composed of an electron beam source 3a (particle beam source), an electron beam condenser 3b, an electron beam detector 3c (particle beam detector), and an SEM image generator 3d. The electron beam emitted from the electron beam source 3a passes through the electron beam condenser 3b and is irradiated onto a point on a sample placed on a sample stage. Signal electrons emitted from the sample are converted into an electrical signal (particle beam electrical signal) by the electron beam detector 3c. The SEM image generator 3d generates an image by recording the generated electrical signal. Here, SEM is an abbreviation for Scanning Electron Microscope.

[0021] The sample stage system 4 is composed of a sample stage 4a on which a sample is placed, and a movable stage 4b ​​that moves the sample stage 4a. A sample is placed on the sample stage 4a, and its position can be changed by the movable stage 4b. In this figure, a sample for adjustment 6 is placed on the sample stage 4a. The sample for adjustment 6 has a reference structure 6a.

[0022] The light irradiation system 1 is composed of a light source 1a and a light irradiation position adjustment unit 1b. The light irradiation position adjustment unit 1b is composed of an optical element 1c and a movable stage 1d. The light source 1a is any light source having a wavelength ranging from X-rays to infrared, and may be a laser light source, an LED, a lamp, or the like. The wavelength may be fixed or a variable wavelength light source may be used. The light source 1a may also be a multicolor light source combining multiple light sources. Furthermore, the light source 1a may be a pulsed light source or a continuous wave light source. For example, when the light source 1a is used for the purpose of removing charge from a sample using light, it is necessary to excite charge in the sample, so it is desirable that the light source emits high-energy light, especially continuous light with a wavelength of 450 nm or less.

[0023] The light source 1a emits a light ray Ray1 toward the light irradiation position adjustment unit 1b. The optical element 1c of the light irradiation position adjustment unit 1b is a mirror. The movable stage 1d adjusts the angle of the optical element 1c so that the light ray Ray1 is irradiated at an appropriate position on the sample. Here, the light irradiation position adjustment unit 1b is a movable mechanism that can move the irradiation position of the light ray Ray1. Hereinafter, the position where the light ray Ray1 is irradiated will also be referred to as the "light irradiation position."

[0024] Furthermore, a lens or a prism can also be used as the optical element 1c. In this case, the position of the optical element 1c can be moved by a movable stage 1d to change the light irradiation position.

[0025] In this figure, ray Ray1 is incident obliquely via light irradiation position adjustment unit 1b so as not to affect the trajectory of the electron beam, and is then irradiated onto the sample. ray Ray1 may be irradiated as a parallel beam, or may be focused using a lens or curved mirror. However, the method of incidence is not limited to this. For example, a mirror with a hole through which the electron beam passes may be installed within electron optical system 3, and ray Ray1 may be incident parallel to the electron beam, and ray Ray1 may be irradiated perpendicularly onto the sample. Alternatively, ray Ray1 may be guided to the charged particle beam device via an optical fiber or the like. Either method is sufficient as long as ray Ray1 can be irradiated onto the sample.

[0026] When the light ray Ray1 is incident on the reference structure 6a, secondary light Ray2, which is light obtained by modulating the light ray Ray1, is generated. Here, modulated light refers to new light generated in response to the light ray Ray1, for example. Examples of secondary light Ray2 include diffracted light, fluorescent light, and scattered light. Alternatively, when a micromirror is used that selectively reflects light from the reference structure 6a only in a specific direction toward a detector (photodetector) provided in the optical detection system 2, the reflected light can also be considered to be new light generated from the reference structure 6a. Therefore, in this case, the reflected light (reflected light) can also be considered to be included in the secondary light.

[0027] However, the modulated light is not limited to the secondary light shown in the above example. For example, light attenuated by the reference structure 6a absorbing light is not new light emitted by the reference structure 6a and is therefore not secondary light, but can be considered a type of light modulated by the reference structure 6a. Therefore, such attenuated light can also be used to adjust the light irradiation position.

[0028] In this specification, the light irradiated onto the sample from the light source 1a is referred to as "first light." Furthermore, the light traveling from the sample to the photodetector, such as secondary light or attenuated light, is referred to as "second light."

[0029] The adjustment method based on light absorption will be described in detail in a modified example of the fourth embodiment.

[0030] In the following description, the case where the reference structure 6a emits secondary light will be described.

[0031] The photodetection system 2 detects the secondary light Ray2. The photodetection system 2 is composed of a photodetector that converts the energy of the secondary light Ray2 into an electrical signal (photoelectric signal). Although not described in this embodiment, an optical filter or lens may be additionally used to clearly detect the secondary light Ray2. The photodetector is an element that converts light into an electrical signal, and may be a CMOS or CCD camera, a photomultiplier tube, a silicon photomultiplier, a photodiode, or the like. Alternatively, as described in this embodiment, the secondary light may be detected by the electron beam detection unit 3c of the electron optical system 3. For example, an Everhart-Thornley detector (hereinafter referred to as an "ET detector") is a typical example of the electron beam detection unit 3c. The ET detector is composed of a photodetector, a scintillator, and a light guide. The secondary light Ray2 is converted into an electrical signal by either directly incident on the photodetector or by emitting fluorescence from the scintillator and detecting the fluorescence with the photodetector. Alternatively, the secondary light Ray2 may be incident on a light guide along the way, and then guided to the light receiving element.

[0032] Another detector is a Si photodiode, which is a semiconductor detector. Si photodiodes can detect both light and electrons, and therefore can be used in the light detection system 2. When the electron beam detection unit 3c is used as in this embodiment, the circuits and software for processing the electrical signals of the detector can be standardized, making this suitable for SEMs and electron beam lithography systems with SEM functions.

[0033] This configuration has the effect of making it possible to adjust the irradiation position without adding any mechanism or software to an existing charged particle beam device.

[0034] Alternatively, the light source 1a may modulate the output at frequency f, and the light detection system 2 may extract and detect only the component of frequency f, i.e., lock-in detection. By performing lock-in detection, it is possible to provide an adjustment method that is robust against disturbances such as light incident from outside the charged particle beam device.

[0035] Next, the principles of the light irradiation area and the adjustment method will be described.

[0036] FIG. 2 is a diagram showing the light irradiated area on the sample.

[0037] As shown in this figure, when laser light is incident on the sample at an angle, it irradiates an elliptical region 7a. The minor axis diameter of the elliptical region 7a is d, the major axis diameter is D, and the center position is (x, y). Furthermore, although details will be described later in this example, the reference structure 6a is adjusted by the sample stage system 4 so that its center is the irradiation position of the electron beam. The area where the elliptical region 7a and the reference structure 6a overlap is region 6aL, and secondary light is emitted from region 6aL.

[0038] In the following description, the spatial distribution is assumed to be such that the power density is high at the center of the elliptical region 7a and decreases with increasing distance from the center. For example, consider a Gaussian spatial distribution that occurs when a laser is used as the light source.

[0039] The amount of secondary light is determined by the area of ​​the region 6aL and the distance from the center of the elliptical region 7a. In particular, when the size of the reference structure 6a is smaller than the elliptical region 7a, the amount of secondary light is maximized when the center of the reference structure 6a coincides with the center of the elliptical region 7a. Therefore, by adjusting the light irradiation position (x, y) so that the amount of secondary light is maximized, the center of the reference structure 6a can be made to coincide with the light irradiation position.

[0040] The center of the reference structure 6a is adjusted in advance by the electron optical system 3 and the sample stage system 4 so that it coincides with the irradiation position of the electron beam. Therefore, by using the reference structure 6a according to the above principle, it is possible to accurately match the light irradiation position and the electron beam irradiation position. Note that while this embodiment shows an example in which the irradiation area is an ellipse, it can also be a perfect circle, i.e., d = D.

[0041] The central position (x, y) of the light can be adjusted by the movable part that moves the angle of the mirror. The movable part may have only one movable axis, but it is more preferable to have movable axes in two directions (H, V), since this allows the irradiation position to be set at any coordinate within the XY plane, that is, within the sample surface. For example, when the movable axis H is moved, the irradiation position moves to (x', y'). Similarly, when the movable axis V is moved, the irradiation position moves to (x'', y''). The range that the irradiation position can take when these movable axes (H, V) are moved to their maximum is hereinafter referred to as the movable range 7b of the irradiation position. The size of this in the H direction is R H , the size in the V direction is R V Let's say.

[0042] Next, an example of the adjustment sample 6 will be described.

[0043] FIG. 3A is a cross-sectional view showing an example of the adjustment sample 6 of FIG.

[0044] As shown in FIG. 3A, the adjustment sample 6 includes a flat substrate 6S and a reference structure 6a, which is an assembly of multiple fine protrusions provided in the center of the substrate 6S. The substrate 6S is formed of, for example, a Si substrate. The reference structure 6a is formed of multiple protrusions, each having a height of, for example, about 100 nm, and is made of, for example, Si. The reference structure 6a emits secondary light Ray2 in response to irradiation with light Ray1.

[0045] FIG. 3B is a top view showing the adjustment sample 6 of FIG. 3A.

[0046] 3B, the reference structure 6a has a circular shape and a cross-shaped center mark 6c is provided at the center of the reference structure 6a.

[0047] FIG. 3C is an enlarged view of the area 6p indicated by the dotted square in FIG. 3B.

[0048] In Figure 3C, region 6p of reference structure 6a has a structure in which multiple protrusions 6b are arranged at equal intervals vertically and horizontally. Each protrusion 6b is cylindrical. The diameter of each protrusion 6b is, for example, approximately 100 nm. The distance between adjacent protrusions 6b, i.e., period A, satisfies the following relational expression, where λ is the wavelength of light, n is the refractive index of the medium through which light enters the periodic structure, and d is the minor axis diameter of elliptical region 7a (Figure 2).

[0049] λ / n <A<d With this structure, there is a periodic structure of at least one period within the light irradiation area (elliptical area 7a), and the period A is greater than the wavelength λ, so the periodic structure acts as a diffraction grating. If the periodic structure is designed appropriately, diffracted light can be generated in the direction of the detector, and the diffracted light can be used as secondary light Ray2. Since diffracted light can be diffracted at a specific diffraction angle, secondary light Ray2 can be selectively emitted in the direction of the detector. This has the effect of ensuring that secondary light Ray2 can be detected reliably.

[0050] The refractive index n of the medium refers to the refractive index of the vacuum, n = 1, for example, when the adjustment sample is placed in a vacuum. The periodic structure is preferably made of Si, SiO2, or the like, which is resistant to deterioration due to exposure to ultraviolet light or electron beams or to the atmosphere. This is because it allows for stable long-term use.

[0051] FIG. 3D is a cross-sectional view showing a modified example of the adjustment sample 6 of FIG. 3A.

[0052] 3D, the reference structure 6a of the adjustment sample 6 is covered with a protective layer 6S'. The material of the protective layer 6S' may be any material that transmits the light ray Ray1, such as SiO2. In this case, the refractive index n of the medium is the refractive index of the protective layer 6S'.

[0053] In this way, the protective layer 6S' of the adjustment sample 6 can protect the reference structure 6a from foreign matter. Furthermore, cleaning the adjustment sample 6 by ultrasonic cleaning or the like does not damage the reference structure 6a, which has the effect of enabling the adjustment sample 6 to be used repeatedly.

[0054] The outer shape of the reference structure 6a may be any shape, but it is more preferable that the reference structure 6a have a shape that is rotationally symmetric about its center. This is because such a shape simplifies position adjustment because the amount of secondary light Ray2 emitted from the portion that overlaps with the light irradiation area (elliptical area 7a) increases monotonically with the distance from the center, regardless of the orientation of the reference structure 6a. For example, the outer shape of the reference structure 6a may be a perfect circle as shown in this embodiment. Alternatively, the reference structure 6a may have a shape that approximates a perfect circle with a polygon.

[0055] The center mark 6c is formed by removing a part of the protrusion 6b constituting the reference structure 6a so that the underlying Si substrate is exposed. Alternatively, the reference structure 6a may be formed without forming the protrusion 6b in the part to be the center mark 6c.

[0056] Alternatively, a protrusion having a shape different from that of the protrusion 6b may be disposed at the position of the center mark 6c. In this case, the material of the protrusion constituting the center mark 6c may be the same as that of the reference structure 6a, or may be a different material such as metal.

[0057] The center mark 6c is used to confirm the center of the reference structure 6a using an SEM image and to move the sample stage system 4. Therefore, the shape of the center mark 6c may be any shape as long as it can be confirmed in an SEM image, and may be circular, elliptical, L-shaped, rectangular, etc. The outer dimensions of the center mark 6c must be within the range of 10 nm to 1 mm, and should be within the field of view of the SEM. It is more desirable that the outer dimensions of the center mark 6c be smaller than the light irradiation diameter d. This is because a decrease in secondary light intensity due to the center mark 6c can be suppressed. Alternatively, if the size of the reference structure 6a is small enough to fit within an SEM image, i.e., on the order of a few μm, the center mark can be omitted because the center can be confirmed using the reference structure 6a itself as a marker.

[0058] FIG. 4 is a top view showing the overall structure of the adjustment sample used in this example.

[0059] The adjustment sample 6 shown in this figure has two reference structures: a reference structure 6a' for coarse adjustment and a reference structure 6a'' for fine adjustment.

[0060] The outer dimensions of the reference structure for coarse adjustment 6a' are larger than those of the reference structure for fine adjustment 6a'', making it suitable for roughly adjusting the light irradiation position. On the other hand, by making the outer dimensions of the reference structure for fine adjustment 6a'' smaller than the light irradiation diameter d (Figure 2), the amount of change in the secondary light intensity increases with respect to the deviation of the light irradiation position, allowing for more accurate adjustment of the light irradiation position. Note that when used for periodic fine adjustment of the light irradiation position, it is possible to use an adjustment sample without the reference structure for coarse adjustment 6a', since the deviation of the light irradiation position is expected to be small.

[0061] In this embodiment, both the coarse adjustment reference structure 6a' and the fine adjustment reference structure 6a'' have the same periodic structure. That is, both have a structure in which a plurality of protrusions 6b are arranged at similar intervals. In this way, the optical detection system 2 only needs to accommodate a single type of secondary light Ray2, which has the effect of simplifying the configuration of the optical system and facilitating the preparation of the adjustment sample 6.

[0062] Alternatively, the reference structure for coarse adjustment 6a' and the reference structure for fine adjustment 6a'' may be different types. For example, when a periodic structure is used, its dimensions cannot be made smaller than the period A. However, by using, for example, a phosphor, a smaller reference structure can be made, which is suitable for high-precision adjustment.

[0063] Next, the arrangement of the plurality of coarse adjustment reference structures 6a' and fine adjustment reference structures 6a'' will be described.

[0064] The coarse adjustment reference structure 6a' and the fine adjustment reference structure 6a'' need to have a large distance L between them so that the secondary light Ray2 emitted from the adjacent reference structure can be distinguished. Specifically, L>R. Here, R is the movable range R. H ,R V and the larger value. More preferably, taking into consideration the major axis diameter D of the elliptical region 7a (FIG. 2) that is the light irradiation region, L>R+D / 2. This arrangement has the effect of accurately adjusting the irradiation position without confusing it with the secondary optical signal of the adjacent reference structure.

[0065] Note that when reference structures emitting different types of secondary light Ray2 are placed adjacent to each other, the reference structures can be placed closer than the distance L. Here, different types of secondary light refer to, for example, secondary light of different wavelengths. Since fluorescence is light with a different wavelength from the incident light, it can be realized by combining a periodic structure that generates diffracted light with a phosphor, or by combining phosphors that emit light at different wavelengths. By changing the wavelength of the secondary light emitted from adjacent structures in this way, the secondary light from adjacent reference structures can be removed using a color filter or the like. Alternatively, when a reference structure having a periodic structure is placed adjacent to a reference structure whose polarization of the secondary light is different from that of the incident light, for example, when a phosphor or a scattering material is placed adjacent, the secondary light signals from the adjacent structures can be separated using a polarizer.

[0066] The sizes of the center mark 6c' of the reference structure for coarse adjustment 6a' and the center mark 6c'' of the reference structure for fine adjustment 6a'' may be enlarged or reduced to match the outer shape of each reference structure. However, when adjusting the position of the sample stage using an SEM image, it is preferable to use the same SEM magnification to achieve the same level of adjustment precision for the SEM image. Therefore, it is even more preferable to make the dimensions of the center mark 6c' for coarse adjustment the same as the dimensions of the center mark 6c'' for fine adjustment.

[0067] FIG. 5 is a configuration diagram showing an example of the control system 5 in FIG.

[0068] The control system 5 includes an SEM image processing unit 5a, a sample stage control unit 5b, a light control unit 5c, a display unit 5d, and a memory unit 5e. The SEM image processing unit 5a detects the center mark 6c of the reference structure 6a of the adjustment sample 6 shown in FIG. 3 based on the SEM image generated by the SEM image generation unit 3d. The sample stage control unit 5b moves the movable stage 4b ​​(FIG. 1) so that the center mark 6c of the reference structure 6a is located at the center of the SEM image. The light control unit 5c controls the mirror angle (H, V) based on the signal intensity of the secondary light Ray2 and adjusts the light irradiation position. The display unit 5d displays the SEM image and the adjustment results. The memory unit 5e records the adjusted mirror angle.

[0069] The basic operation of the method for adjusting the light irradiation position will be described with reference to FIGS. 6, 7A, 7B, 8A and 8B.

[0070] First, the user selects the adjustment sample 6 and reference structure 6a to be used (step S1). For example, as shown in FIG. 7A, the user can select from a list using a GUI (8a). The control device places the adjustment sample on the sample stage using a transfer arm or the like in accordance with the user's selection. Furthermore, the control device moves the sample stage to a position where the selected reference structure appears in the SEM image.

[0071] Next, while checking the SEM image, the stage is moved to the center of the mark (steps S2 to S3). The user selects a magnification using the GUI (8b) that allows the center mark to be confirmed. The control device automatically moves the sample stage using an algorithm such as pattern matching. Alternatively, while manually observing the SEM image 8c, the user sets the XY coordinates 8d of the sample stage so that the center mark of the reference structure is at the center of the image. Through these procedures (steps S1 to S3), the center of the electron beam irradiation range coincides with the center of the reference structure.

[0072] Next, the user sets the conditions for adjusting the light irradiation position (step S4). First, the user sets the output power of the irradiated laser (setting item 8e) to prevent the detector signal from saturating. Next, the user selects from a list the detector that will detect the secondary light Ray2 (setting item 8f). For example, in this embodiment, it is desirable to select the electron beam detection unit 3c that is located in a position where the secondary light Ray2 is most likely to be incident. Next, the user sets the mirror angle scan range (setting item 8g) for each of the two axes H and V. The scan range is the range over which the mirror angle is changed to search for the optimal mirror angle, and the start and end points of the scan can be set on the GUI, for example. Alternatively, a GUI configuration that allows the center and width of the range to be specified may be used, although this is not shown.

[0073] The user also selects which of the two axes, H or V, to adjust first using GUI (8h). The following explanation will use an example where axis H is selected to be adjusted first, but the same procedure can be used when axis V is selected to be adjusted first. In this case, the user can select the value to set for the angle of the non-selected axis, i.e., axis V, using GUI (8i). For example, the user can specify to use the center value of the scan range set by the user, or they can choose to set any value manually. Similarly, the user can use GUI (8j) to set the angle of the other axis, i.e., axis H, when adjusting axis V in the second stage of adjustment. For example, they can set it to use the optimal value obtained by adjusting axis H in the first stage of adjustment.

[0074] Next, when the user presses the start button, the control device starts irradiating light (step S5) and moves the angle of axis V (step S6). After that, while varying the value of axis H, the angle of axis H at which the magnitude of the electrical signal from the detector selected by the user is maximized is extracted (step S7). For example, the secondary light signal is recorded while varying the angle of axis H at regular intervals. At this time, the amount of secondary light increases when the light irradiation position passes through the reference structure. Therefore, when the secondary light intensity is plotted as a function of the mirror angle, a mountain-shaped function like that shown in Figure 8A is obtained. In other words, in Figure 8A, if the amount of secondary light is measured in the direction of axis H as shown in Figure 2, the amount of secondary light will form a curve with a prominent maximum value.

[0075] The results are displayed as the first scan results (graph 8k) in the adjustment results window as shown in Fig. 7B. The mirror angle with the maximum value is the adjusted mirror angle.

[0076] The method for determining the mirror angle at which the secondary light intensity is maximized can also be the gradient method, which is an algorithm also known as the steepest descent method, and has the advantage of enabling adjustment to be completed quickly because it can determine the maximum and minimum values ​​with a small number of trials.

[0077] Note that when the light irradiation diameter d is small relative to the size of the reference structure 6a, the curve does not have a mountain-like curve as shown in FIG. 8A, but a step-function curve as shown in FIG. 8B (a curve having a range in which the amount of secondary light is approximately constant and at a maximum value with respect to changes in the axis H). Furthermore, when the power density in the light irradiation region (elliptical region 7a) has a spatially uniform distribution, i.e., a flat-top spatial distribution, the curve also has a step-function curve as shown in FIG. 8B. In these cases, when the mirror angles at which the secondary light intensity decreases to half of its maximum value are H0 and H1, the optimal value of the mirror angle can be found as the center of the peak, as in (H0 + H1) / 2.

[0078] The algorithm for extracting the optimal mirror angle from the data shown in Figures 8A and 8B is not limited to the method using the maximum value or the method using the peak center as described above. Any algorithm can be used as long as it provides the optimal value based on the mirror angle dependency of the signal amount output by the optical detection system. For example, a method of fitting to a Gaussian function or a machine learning model can be used. Multiple algorithms may be implemented in the control device. The control device may automatically determine and select which algorithm to use, or the user may be able to select it on a GUI.

[0079] Next, the control device adjusts the other adjustment axis, i.e., axis V, using the same procedure (steps S8 to S9), and the second scan result (graph 8l) is displayed. The window in Figure 7B also displays the adjustment conditions, such as the laser power and the detector used, in column 8m.

[0080] The user can make adjustments by performing the adjustment procedure of steps S1 to S9 using the coarse adjustment reference structure and then the fine adjustment reference structure. If the mirror scanning position is significantly misaligned during adjustment, the light will not hit the reference structure, making it impossible to extract the mirror angle that maximizes the secondary light intensity. However, by first performing adjustment using the large coarse adjustment reference structure, the irradiation position can be roughly adjusted.

[0081] Furthermore, by having a fine adjustment reference structure on a single adjustment sample whose dimensions are smaller than the light irradiation diameter, it is possible to quickly switch between coarse adjustment and fine adjustment without changing the sample, thereby achieving the effect of adjusting the irradiation position with high precision.

[0082] After the fine adjustment is complete, the setting values ​​of the movable axes H and V are saved in the memory unit 5e (Figure 5). It is desirable to save all information used for the setting, such as the detector used for the setting and the H and V ranges. The results can be saved automatically, or the user can save them manually after checking the results. This procedure records the setting values ​​of the mirror angles that accurately align the electron beam irradiation position and the light irradiation position, and can be recalled later. Note that if the deviation between the electron beam and light irradiation positions is small, the coarse adjustment procedure can be omitted and fine adjustment can be performed from the beginning.

[0083] The adjustment method according to this embodiment uses an adjustment sample including a reference structure that generates secondary light in response to irradiation with light, a control device that controls the light irradiation position, and a photodetector that detects the secondary light and generates an electrical signal. The control device sequentially moves the light irradiation position in two directions so that it passes through the reference structure, thereby maximizing the amount of secondary light generated, thereby achieving the effect of accurately adjusting the light irradiation position relative to the electron beam irradiation position.

[0084] The adjustment method according to the present embodiment can also be applied to removing charge on a sample caused by irradiation with a charged particle beam. By accurately matching the light irradiation position with the charged particle beam irradiation position, the charge generated by light irradiation can be efficiently injected into the charged region, thereby improving the effect of removing charge.

[0085] The reference structure used in this embodiment is not limited to the periodic structure shown in FIG. 3, and various structures that emit secondary light Ray2 can be used.

[0086] The following description will be given using modified examples 1 to 3 of the reference structure.

[0087] [Reference structure variation 1] In Modification 1, an example in which a phosphor is used as the reference structure will be described.

[0088] The phosphor may be any material that emits light of different wavelengths depending on the light source. For example, it may be a material having a luminescence center, such as YAG, or a semiconductor, such as GaN. Alternatively, materials with microstructures, such as quantum dots, nanowires, or quantum wells, may be used. The emission wavelength may be any wavelength, for example, from ultraviolet to infrared. However, when an ET detector is used as the secondary light detector, it is preferable to use the same emission wavelength as the scintillator, since this allows for the use of a wavelength range with high detection sensitivity. From another perspective, it is preferable to use a wavelength range in which the light-receiving element constituting the ET detector is highly sensitive. Using a phosphor as the reference structure allows for the use of light of a different wavelength from the incident light as the secondary light. Therefore, by using a color filter or a dichroic mirror, the secondary light can be clearly detected without being affected by the incident light or reflected light.

[0089] FIG. 9A is a cross-sectional view showing an example of a reference structure used in Modification 1. FIG.

[0090] In FIG. 9A, the adjustment sample 6 has a reference structure 6a of a phosphor.

[0091] The reference structure 6a may have a flat structure, but the amount of secondary optical signal can be increased by changing the structure.

[0092] A method for increasing the secondary light will be described below.

[0093] FIG. 9B is a cross-sectional view showing another example of the reference structure used in Modification 1. As shown in FIG.

[0094] In this figure, a fine structure such as a SiO2 uneven structure 6d is formed on the surface of the substrate (made of Si) of the adjustment sample 6, and the surface of the uneven structure 6d is covered with a phosphor. With this configuration, light that is trapped within the sample due to total internal reflection can be extracted from the adjustment sample 6. This results in an increase in the amount of secondary light. Note that light is trapped by total reflection that occurs at the interface between the phosphor and air.

[0095] FIG. 9C is a top view showing another example of the reference structure used in Modification 1. FIG.

[0096] In this figure, the phosphor is provided to form an optical resonator structure. A microscopic optical resonator used as the reference structure 6a shown in this figure is, for example, an H1-type photonic crystal resonator 6e. However, the optical resonator structure is not limited to this, and a Fabry-Perot resonator or a microdisk resonator may also be used. These optical resonators can enhance the amount of light emitted, thereby increasing the amount of secondary light.

[0097] As shown in FIGS. 9B and 9C, adding an optical structure to the phosphor increases the amount of secondary light that can be detected, thereby providing the effect of enabling the secondary light to be clearly detected.

[0098] [Reference structure variation 2] In the second modification, a scatterer is used as the reference structure.

[0099] FIG. 10 is a cross-sectional view showing an example of a reference structure used in this modification.

[0100] The scatterer 6f is a structure that emits light of the same wavelength in an angular range in response to incident light. The angular range of scattering is determined by the surface roughness R of the scatterer 6f. zThe angle is determined by, and it is desirable to use a structure in which the photodetector is included in the angle range, because this allows the secondary light to be clearly detected. Since the secondary light emitted from the scatterer 6f is emitted in various directions, using the scatterer 6f as a reference structure has the effect of being compatible with many types of charged particle beam devices with different detector positions.

[0101] In this modification, the scatterer 6f has been described as having a roughened surface, but is not limited to this. For example, a scatterer in which titanium oxide is dispersed in a resin or the like, a scatterer using a polyester film with many flat voids inside, or a scatterer using a diffusing material such as barium sulfate can be used.

[0102] [Reference structure variation 3] In this modification, a modification in which a micromirror is used as the reference structure will be described.

[0103] FIG. 11A is a cross-sectional view showing an example of a reference structure used in this modification.

[0104] In this figure, the adjustment sample 6 has a micromirror reference structure 6g.

[0105] The surface of the micromirror is a mirror, and the light reflected by the micromirror is treated as secondary light. The mirror surface is tilted at an angle α with respect to the substrate surface of the adjustment sample 6, i.e., the XY plane. If the angle of incidence of the incident light with respect to the XY plane is β, then the angle of the light reflected by the micromirror is γ = β - α. On the other hand, the light specularly reflected from the outside of the reference structure 6g (the substrate surface of the adjustment sample 6) travels in the opposite direction to the incident light, i.e., in the direction of angle -β, with the normal to the substrate surface of the adjustment sample 6 as the axis of symmetry. Therefore, the detector can detect only the light reflected by the micromirror. The micromirror may be made of a metal with high reflectivity in the wavelength range of the incident light, or a dielectric multilayer film mirror.

[0106] When a micromirror is used as the reference structure 6g, all of the light reflected by the micromirror is directed toward the detector, which has the effect of efficiently obtaining a clear secondary optical signal. In addition, the surface of the micromirror may be curved. For example, if the surface is parabolic, light can be detected even more efficiently by placing the detector at the focal position of the parabolic surface.

[0107] FIG. 11B is a cross-sectional view showing another example of the reference structure used in this modification.

[0108] In this figure, the adjustment sample 6 has a reference structure 6h in which a plurality of mirrors are arranged in an array.

[0109] The reference structure 6h can increase the angle α without changing the thickness, making it easier to separate the specularly reflected light from the light directed in the direction of angle -β, allowing for clear detection of changes in the amount of secondary light.

[0110] Furthermore, the reference structure 6g (micromirror) may be a MEMS mirror, and the angle α may be controlled by an external control signal. Such a movable mechanism makes it possible to vary the angle of the generated secondary light, so that detectors at different positions can be adapted to many different types of charged particle beam devices. [Example]

[0111] This embodiment is different from the first embodiment mainly in that the sample stage system of the charged particle beam instrument has a sample height sensor.

[0112] First, the problem will be explained using FIG.

[0113] FIG. 12 is a schematic diagram showing the influence of a change in the height of the sample in this embodiment.

[0114] As shown in this figure, when light is incident obliquely at an angle β to avoid the trajectory of the electron beam, if the height of the sample 9 changes by dz, the light irradiation position moves by a distance dz tanβ on the surface of the sample 9. Therefore, the light irradiation position must also be adjusted in accordance with the change in the height of the sample 9.

[0115] FIG. 13 is a schematic diagram showing the configuration of the charged particle beam device of this embodiment.

[0116] The charged particle beam device shown in this figure differs from the first embodiment (FIG. 1) in that it has a height sensor 4c.

[0117] The height sensor 4c measures the height of the sample. By calibrating the mirror angle to an optimal angle according to the output value of the height sensor 4c, the light irradiation position can be adjusted for samples of any height.

[0118] FIG. 14A is a cross-sectional view showing an example of the adjustment sample used in this example.

[0119] The adjustment samples 6i, 6i', and 6i'' shown in this figure are used for calibration. The adjustment samples 6i, 6i', and 6i'' each have a substrate with a different thickness, allowing adjustment at different heights.

[0120] FIG. 14B is a cross-sectional view showing another example of the adjustment sample used in this example.

[0121] The adjustment sample 6j shown in this figure has portions with different thicknesses, and a reference structure 6a is provided in each portion.

[0122] In the following explanation, Fig. 14A will be used as an example, but the same procedure can be used when using a sample such as that shown in Fig. 14B. Also, Figs. 14A and 14B show examples of samples with only three different heights, but it goes without saying that samples with even more heights may be used.

[0123] The height sensor is preferably an optical lever type height sensor or a laser interferometer, as these can measure height with high accuracy, but the measurement method is not limited to these, and a ToF (Time of Flight) type height sensor or a mechanical height measurement may also be used. An example of the configuration of a height sensor is described in Patent Document 5.

[0124] Next, the procedure for calibrating the mirror angle will be described.

[0125] FIG. 15 is a flowchart showing a method for calibrating the mirror angle.

[0126] FIG. 16A is a diagram showing an example of a setting screen, which is an operation GUI.

[0127] FIG. 16B is an operation GUI showing an example of the measurement value and adjustment result of the sample height.

[0128] First, the user inputs the setting items (8b, 8e, 8f, 8g, 8h, 8i, 8j) for adjusting the light irradiation position (step S10). The setting items are the same as those in the first embodiment, and therefore a description thereof will be omitted.

[0129] Next, when the user presses the start button, the control device automatically uses a transfer arm or the like to place the sample for adjustment on the sample stage (step S11).

[0130] Next, the control device performs SEM photography without irradiating light (step S12). Then, the stage is moved so that the center mark is captured in the center of the SEM image (step S13). The movement to the center can be performed automatically using an algorithm such as pattern matching, as described in the first embodiment. Alternatively, as described in the first embodiment, the configuration may be such that manual adjustment can be performed by user input.

[0131] Next, the control device adjusts the mirror angles H and V as described in the first embodiment (step S14).

[0132] Next, the control device moves the sample stage to a flat area where there is no reference structure (step S15). Then, the height sensor measures the sample height (step S16). By measuring the height on the flat area, there is an advantage that the height can be measured accurately without being affected by the reference structure.

[0133] Next, the measurement device associates the measurement value of the sample height with the adjustment result (H, V) and stores them in the storage unit 5e (step S17). More preferably, conditions such as the laser output and the detector used during the adjustment are also stored at the same time.

[0134] Next, the control device uses a transfer arm or the like to remove the sample for adjustment from the sample stage (step S18).

[0135] Next, the control device returns to step S12 and performs adjustment using an adjustment sample of another height. When adjustment has been completed for all adjustment samples, the adjustment process ends.

[0136] When the above steps are completed, a table of optimal values ​​for mirror angles (H, V) according to the height sensor values ​​is created and displayed in table 8n.

[0137] If the movable stage 4b ​​also has a movable axis in the height direction (Z direction), instead of using samples of different heights, a table can be created that associates the height sensor value with the mirror angle value by changing the height of the movable stage 4b.

[0138] FIG. 17 is a flowchart showing a method for adjusting the irradiation position in the second embodiment.

[0139] Using this figure, we will explain how to automatically adjust the irradiation position depending on the height of the sample.

[0140] First, the user places the sample to be irradiated with the charged particle beam and light on the sample stage (step S20). Here, the sample refers to the sample to be observed, for example, when the charged particle beam device is an SEM. At this time, the height of the sample does not need to be known.

[0141] Next, the control device measures the height of the sample using a height sensor (step S21).

[0142] Finally, the control device sets the values ​​of the movable axes H and V by interpolating or extrapolating based on the table 8n (FIG. 16B) (step S22).

[0143] Figure 18 is a graph of Table 8n in Figure 16B. The horizontal axis represents the sample height, and the vertical axis represents the optimum value of the mirror angle.

[0144] While FIG. 18 only shows an example for the movable axis H, the same adjustment can be made for the movable axis V. The points shown on the graph in this figure are the values ​​determined in steps S10 to S17, and the curve is the line connecting these points. If the sample height is z1, the optimal mirror angle h1 is determined as the value of curve L1 for sample height z1. In other words, the optimal mirror angle can be calculated using curve L1 obtained by interpolation. Alternatively, if the sample height is outside the range of table 8n, it can be determined by extrapolating based on data points within the range.

[0145] The adjustment method according to this embodiment can automatically adjust the light irradiation position in conjunction with the height sensor, thereby enabling the electron beam irradiation position and the light irradiation position to be accurately aligned regardless of the sample height, even when the light is incident on the sample at an angle. [Example]

[0146] This embodiment is different from the first embodiment mainly in that a photodetector is installed on the path of the incident light.

[0147] 19 is a configuration diagram showing only the light irradiation system and the light detection system. The other device configurations are the same as those in the first embodiment, and therefore the description will be omitted.

[0148] In this figure, the light irradiation system 1 has a branching section 1e on the path of the incident light. A beam splitter can be used as the branching section 1e.

[0149] When ray Ray1 (incident light) is irradiated onto reference structure 6a of adjustment sample 6, secondary light Ray2 is generated. Secondary light Ray2 also travels in the exact opposite direction (180 degrees) to ray Ray1, and reaches branching unit 1e. Secondary light Ray2 then splits into a ray that passes through branching unit 1e and travels straight, and ray Ray3 that is reflected by branching unit 1e. Light detection system 2 detects ray Ray3 (secondary light).

[0150] By configuring the system to detect the secondary light returning from the adjustment sample 6 in this manner, the light irradiation system 1 and the light detection system 2 can be integrated, which makes the system more compact and makes it easier to install in a charged particle beam device.

[0151] When a phosphor is used as the reference structure, a dichroic mirror can be used in the branching section 1e. Dichroic mirrors are classified into short-pass and long-pass types. Short-pass types have the characteristic of allowing light with wavelengths shorter than a certain wavelength to travel straight and reflecting light with longer wavelengths. On the other hand, long-pass dichroic mirrors have the characteristic of allowing light with wavelengths longer than a certain wavelength to travel straight and reflecting light with shorter wavelengths.

[0152] In the configuration of this embodiment, the fluorescence returning from the sample is reflected by the branching section. Because the phosphor is a material that receives energy from incident light and generates light with lower energy, i.e., longer wavelength, than the incident light, a short-pass type dichroic mirror that reflects longer wavelength light is suitable. However, if the positions of the light source and the optical detection system are reversed, a long-pass type that allows the longer wavelength fluorescence to travel in a straight line is more suitable. The use of a dichroic mirror allows the optical path to be switched according to wavelength, allowing more secondary light to be incident on the detector than when a beam splitter is used, resulting in clearer detection of the secondary light.

[0153] A polarizing beam splitter can also be used in the splitter 1e. In this case, the polarization of the secondary light must be different from the polarization of the incident light, and this can be applied, for example, when a scattering body or a fluorescent body is used as the reference structure. By using a polarizing beam splitter, the optical path can be switched depending on the polarization. When a non-polarizing beam splitter is used, part of the secondary light signal travels straight through the beam splitter. Therefore, when a polarizing beam splitter is used, more secondary light can be reflected and incident on the detector. This has the effect of enabling clearer detection of the secondary light. [Example]

[0154] This embodiment is different from the first embodiment mainly in that a photodetector is installed on the path of the specularly reflected light.

[0155] 20A is a configuration diagram showing only the light irradiation system and the light detection system. The other device configurations are the same as those in Example 1, so a description thereof will be omitted.

[0156] In this figure, the light detection system 2 has a branching section 2a, two light receiving elements 2b and 2c, and a signal processing section 2d.

[0157] The splitter 2a splits the specularly reflected light into reflected light Ray1' and secondary light Ray3'. The secondary light Ray3' is detected by the light receiving element 2b. The split reflected light Ray1' is detected by the light receiving element 2c. When a phosphor is used as the reference structure 6a, a dichroic mirror or a polarizing beam splitter can be used as described in Example 3. When a scattering body is used as the reference structure 6a, a polarizing beam splitter can be used as described in Example 3.

[0158] Next, the changes in the signal intensities X1 and X2 of the light receiving elements 2b and 2c when the light irradiation position is adjusted will be described.

[0159] FIG. 21A is a graph showing the signal intensity X1 detected by the light receiving element 2b in FIG. 20A.

[0160] FIG. 21B is a graph showing the signal intensity X2 detected by the light receiving element 2c of FIG. 20A.

[0161] As explained in the first embodiment, when the light irradiation position is moved so that it passes through the reference structure, the signal intensity X1 of the secondary light becomes an upwardly convex curve F1 (FIG. 21A).

[0162] On the other hand, when secondary light is generated, part of the irradiated light energy is converted into secondary light, and the intensity of the resulting reflected light decreases (Figure 21B). Therefore, when the light irradiation position is moved so that it passes through the reference structure, the intensity of the reflected light becomes a downward convex curve F2.

[0163] FIG. 21C is a graph showing the electrical signal X3 calculated by the signal processing unit 2d in FIG. 20A.

[0164] The signal processing unit 2d receives the intensity X1 of the secondary light and the intensity X2 of the reflected light, divides them, and calculates a new electrical signal X3 = X1 / X2, which is output to the control system. The resulting curve F3 is steeper than the curves F1 and F2 (FIG. 21C). Therefore, when the adjustment described in Example 1 is performed using the curve F3 as the input signal, the signal changes significantly, which enables robust adjustment of the irradiation position without being affected by noise, etc.

[0165] The arithmetic processing performed by the signal processor 2d is not limited to division. For example, subtraction may be performed instead of division, or an exponential function or a logarithmic function may be used.

[0166] Furthermore, when a light irradiation system that irradiates light obliquely is used, it is desirable to provide a beam damper that terminates the optical path to prevent specularly reflected light from escaping the device or from being diffused inside the device and damaging internal components. In the configuration of the optical detection system according to this embodiment, by providing a detector on the path of specularly reflected light, a beam damper is not required, the configuration is simplified, and the secondary light can be detected more clearly.

[0167] [Modification of optical system] FIG. 20B is a configuration diagram showing a modified example of the optical system.

[0168] The light irradiation system is the same as that in FIG. 20A, and therefore a description thereof will be omitted.

[0169] In this modification, the light receiving element 2b uses the electron beam detection unit 3c described in the first embodiment. In this case, the branching unit 2a of the optical detection system 2 can be omitted, and the light receiving element 2c can be placed directly on the reflected light path. However, if a fluorescent material or a scattering material is used as the reference structure 6a, in addition to the reflected light, fluorescent light or scattered light may also be incident on the light receiving element 2c. Therefore, the light ray Ray1' is detected via an optical element 2a' that removes secondary light. This is desirable because it allows selective detection of only the reflected light. A color filter or polarizer can be used for the optical element 2a'.

[0170] [Modification of the reference structure] FIG. 20C is a configuration diagram showing a modified example of the optical system.

[0171] The reference structure 6a shown in this figure is made of a light absorber, which absorbs the light ray Ray1 and produces attenuated light as reflected light Ray1'.

[0172] The reference structure 6a is made of a material or structure that absorbs the light ray Ray1. Examples of materials that can absorb the light ray Ray1 include, but are not limited to, amorphous carbon and graphite. Alternatively, a microstructure that does not reflect light may be used. An example of a microstructure that can be used is a needle-shaped structure (black silicon) that is generated when silicon is plasma etched.

[0173] In this modified example, secondary light Ray2 is not generated. The irradiation position can be adjusted using only the reflected light Ray1' attenuated by the reference structure 6a. The light detection system 2 is composed of a single detector. The types of detectors that can be used are as described in the first embodiment.

[0174] When the mirror angle position is changed using the method described in Example 1, the amount of reflected light Ray1' decreases when the light irradiation position coincides with the reference structure 6a. This is similar to the downwardly convex curve F2 shown in FIG. 21B. Therefore, the control device can adjust the light irradiation position by determining the mirror angle that gives the minimum value of curve F2. Since light absorbers can absorb light over a wide range of wavelengths, using a light absorber for the reference structure 6a has the effect of enabling adjustment even when the light source emits light of multiple wavelengths. [Example]

[0175] This embodiment differs from the first embodiment mainly in that an adjustment sample is used in which the position of the center mark of the reference structure is shifted from the center coordinates of the original reference structure.

[0176] First, we will explain the issues using charged particle beam devices, particularly SEM, as an example.

[0177] SEMs have an image shift function that uses an electron beam deflector to move the SEM observation range over a range of several tens of micrometers or more without moving the sample stage. This means that there are cases where a position far from the light irradiation position adjusted using an adjustment sample is observed. Therefore, it is necessary to set the light irradiation position to any coordinate within the XY plane in accordance with the movement of the electron beam irradiation position.

[0178] To set the irradiation position at any coordinate on the XY plane, it is necessary to obtain a transformation formula that gives the mirror angle (H,V) from the desired light irradiation position (x,y) on the XY plane. In other words, it is necessary to obtain a coordinate transformation formula from XY space to HV space.

[0179] More specifically, the coordinate transformation formula is expressed by the following formulas (1) and (2).

[0180] H = AHX·X + AHY·Y + H0 …(1) V = AVX·X + AVY·Y + V0 …(2) It is determined by six coefficients (AHX, AHY, AVX, AVY, H0, V0).

[0181] In this embodiment, the conversion equations are expressed as linear equations such as equations (1) and (2), but the conversion equations are not limited to these. For example, when light is condensed through a lens, if the change in the irradiation position is curved relative to the mirror angle, a conversion equation may be created taking into account higher-order terms, such as second- or third-order terms. When a conversion equation taking into account higher-order terms is used, the curvature caused by the lens can also be taken into account, which has the effect of enabling accurate adjustment of the irradiation position even in cases where it is desired to adjust the irradiation range over a wide range such that curvature occurs when a lens is included in the optical system.

[0182] 22 is a top view showing an example of an adjustment sample used to obtain the coordinate transformation formula. The other device configurations are the same as in Example 1, so the explanation will be omitted.

[0183] As shown in this figure, an adjustment sample 6 having three reference structures 6k1, 6k2, and 6k3 is used. This is because there are six coefficients to be determined. The reference structures 6k1, 6k2, and 6k3 each have a center mark 6c for detecting the center by SEM observation. The structures, dimensions, etc. of the adjustment sample 6 and the reference structures 6k1, 6k2, and 6k3 are the same as those described in Example 1, so explanations will be omitted.

[0184] Each of the reference structures 6k1, 6k2, and 6k3 is positioned such that the position of the center mark 6c is shifted from the reference. For example, the reference structure 6k1 is shifted by Q1 (dx1, dy1) from the position of the center mark 6c. Similarly, the reference structures 6k2 and 6k3 are located at positions Q2 (dx2, dy2) and Q3 (dx3, dy3), respectively, with the center mark 6c as the origin. The coordinates of Q1 to Q3 may be selected arbitrarily, but since six coefficients must be determined, the vectors Q1Q2 and Q1Q3 must be linearly independent. In other words, when Q1 to Q3 are plotted on the XY plane, Q3 must not be on the straight line Q1-Q2.

[0185] FIG. 23 is a flowchart showing the adjustment procedure for obtaining the coordinate transformation formula.

[0186] First, the user sets the conditions for adjusting the light irradiation position (step S30). An example of the GUI of the setting screen may be the same as that shown in Fig. 16A, and therefore a description thereof will be omitted.

[0187] Next, the control device uses a transfer arm or the like to transfer the sample for adjustment to the sample stage (step S31).

[0188] Next, the control device performs SEM photography without irradiating light (step S32). Then, the sample stage is moved to the center mark position of the reference structure 6k1 (step S33). The control device acquires an SEM image and, using an algorithm such as pattern matching, moves the sample stage so that the center mark is located at the center of the SEM image. In the case of an SEM with an image shift function, the image shift is moved to the origin before imaging.

[0189] Next, the control device adjusts the irradiation position in the same manner as in the first embodiment (step S34).

[0190] Next, the control device records the adjustment result (H1, V1) in association with the deviation Q1 from the center mark (step S35).

[0191] Next, the control device moves the sample stage to the positions of the reference structures 6k2 and 6k3, and sequentially performs steps S32 to S35. The adjustment results (H2, V2) and (H3, V3) are recorded in association with Q2 and Q3, respectively.

[0192] Next, the control device calculates the conversion coefficients (step S36).

[0193] The control device obtains simultaneous equations by substituting the adjustment results into the above equations (1) and (2). For example, the simultaneous equations obtained by substituting the results into the above equation (1) are expressed as the following equations (3), (4), and (5).

[0194] H1=AHX·X1+AHY·Y1+H0 …(3) H2=AHX·X2+AHY·Y2+H0 …(4) H3=AHX·X3+AHY·Y3+H0 …(5) Since there are three degrees of freedom, the simultaneous equations (3), (4) and (5) can be solved, and the control device can determine the coefficients AHX, AHY and H0.

[0195] Similarly, the control device can obtain the coefficients AVX, AVY, and V0 by solving the simultaneous equations obtained by substituting them into the above equation (2). Note that although an example using three reference structures has been described in this embodiment, the optimum coefficients may be numerically calculated using four or more reference structures. Using more reference structures has the effect of enabling the coefficients to be determined with higher accuracy.

[0196] Finally, the control device stores the conversion coefficients, i.e., the coefficients AHX, AHY, H0, AVX, AVY, and V0, in the storage unit 5e (FIG. 5). More preferably, the sample height may also be measured as in the second embodiment, and the conversion coefficients may be stored in association with the sample height.

[0197] FIG. 24 is a diagram showing an example of a GUI for displaying the adjustment results.

[0198] The adjustment conditions are displayed in column 8m. The adjustment conditions are, for example, the laser power, the selected detector, etc. The measurement results for each reference structure 6k1, 6k2, 6k3 are displayed in column 8n'. The conversion factors are displayed in column 8p.

[0199] A method for adjusting the light irradiation position to any coordinate (x, y) on the sample using the calculated coefficients will be explained.

[0200] By substituting (x, y) into the above equations (1) and (2), the mirror angles Hxy and Vxy to be set are calculated by the following equations (6) and (7).

[0201] Hxy = AHX x + AHY y + H0 …(6) Vxy = AVX x + AVY y + V0 … (7) As in this embodiment, by adjusting the light irradiation position using a reference structure that is shifted by (x, y) based on the central marker, the effect is achieved that the light irradiation position relative to the irradiation position of the charged particle beam can be set arbitrarily. [Example]

[0202] This embodiment is different from the first embodiment mainly in that adjustment is made to the boundary line of the reference structure.

[0203] The principle will be explained with reference to Figures 25 and 26.

[0204] FIG. 25 shows an example of the structure of the adjustment sample used in this example.

[0205] In this figure, a semicircular reference structure 6a is provided on the right half of a wafer that is the adjustment sample 6. The reference structure 6a has a boundary line B1 that passes through the center of the adjustment sample.

[0206] The sample stage is adjusted in advance so that the electron beam irradiation position is on the boundary line B1. In this state, by adjusting the light irradiation position relative to the boundary line B1, the electron beam irradiation position and the light irradiation position can be adjusted so that they are on the same boundary line B1.

[0207] The boundary line refers to the line located at the boundary between the inside of the reference structure (the area where the reference structure is provided) and the outside (the area where the reference structure is not provided). For example, when the reference structure is configured with a periodic structure that emits diffracted light as described in Example 1, the part with the periodic structure is the inside, and the part without the periodic structure is the outside. The boundary between them is defined as the boundary line. Note that, as described in Modification Example 6, if there are different types of reference structures, the boundary line may also be the boundary line between those reference structures. In either case, it is sufficient that the amount of electrical signal generated in the detector changes before and after crossing the boundary line. For example, it is sufficient that the amount, wavelength, angular distribution, etc. of the generated secondary light changes.

[0208] The control device moves in a direction such that the laser irradiation position intersects with the boundary line B1. For example, Figure 25 shows a case in which, when the adjustment axis H is moved, it is controlled to move from the outside of the reference structure (elliptical region 7a), across the boundary line (elliptical region 7a'), and to the inside (elliptical region 7a'').

[0209] 26 is a plot of the change in the secondary light signal intensity as a function of the mirror angle, with the horizontal axis representing the value of axis H or axis V and the vertical axis representing the intensity of the secondary light.

[0210] When the irradiation position is outside the reference structure (elliptical region 7a), no secondary light is generated, but when the light irradiation region overlaps the boundary line, a secondary light signal begins to be detected. Because the amount of secondary light is the amount of light emitted from within the region 6aL where the reference structure and the light irradiation region overlap, the signal amount increases monotonically while the light irradiation region overlaps the boundary line. On the other hand, when the light irradiation region is completely within the reference structure, the amount of secondary light becomes constant.

[0211] In this way, when the adjustment axis is moved so as to intersect with the boundary line, the signal amount changes significantly at the position of the intersection, which has the effect of enabling reliable coarse adjustment even when the irradiation position is significantly displaced.

[0212] An example of an algorithm for adjusting the irradiation position based on such changes in the amount of secondary light will be described below. However, the algorithm is not limited to the one described here. Any data processing method that inputs a signal waveform and outputs the center position may be used, and Modification 4 will be described separately as an example of a different algorithm. Furthermore, the device may be equipped with multiple algorithms. The optimal algorithm may be automatically selected by the control device, or may be input by the user.

[0213] The specific principle of the algorithm of this embodiment will now be described.

[0214] When the center of the light irradiation area is on the boundary line (elliptical area 7a'), exactly half of the light irradiation area overlaps with the reference structure, resulting in half the maximum amount of secondary light generated. More specifically, when the minimum value in FIG. 26 is m and the maximum value is M, the amount of secondary light generated is (m + M) / 2. Hereinafter, (m + M) / 2 is referred to as the target value It. Note that It does not have to be exactly (m + M) / 2. A value of approximately (m + M) / 2 ± 0.2 ensures sufficient light irradiation of the electron beam irradiation area. Setting a tolerance range for the target value in this way has the effect of making the secondary light signal more robust against noise. The tolerance range may use the above guideline, or if high-precision adjustment is required, the user may specify a smaller value. Furthermore, if coarse adjustment is the purpose, a larger tolerance range is acceptable.

[0215] By utilizing this feature, the irradiation position can be adjusted by adjusting the mirror angle so that the amount of secondary light reaches the target value It.

[0216] The irradiation position can be adjusted more accurately if the boundary line B1 intersects the adjustment axis H at a right angle. The reason for this will be explained with reference to Figures 27A and 27B.

[0217] FIG. 27A is a diagram emphasizing the deviation of the irradiation position that occurs when the movable axis H and the boundary line B1 intersect obliquely.

[0218] The irradiation range of the electron beam is 6n, and the light irradiation position after adjustment of the movable axis H is 7a. The boundary line B1 is assumed to be parallel to the y-axis.

[0219] In this case, only the position perpendicular to the boundary line B1 (y-axis), i.e., the x-coordinate, can be adjusted using the boundary line B1; there is no sensitivity in the boundary line B1 direction. Therefore, the light irradiation position (elliptical region 7a) and the electron beam irradiation position 6n are shifted in the direction of the boundary line B1 (y-axis). However, since the H-axis and V-axis are tilted relative to the x-axis and y-axis, adjustment is performed with both the movable axis H and the movable axis V shifted.

[0220] FIG. 27B is a diagram showing a case where the adjustment specimen is rotated so that the boundary line B1 intersects with the movable axis H at a right angle.

[0221] 27A, the irradiation position is shifted in the direction of boundary line B1, but it can be accurately adjusted in the direction perpendicular to boundary line B1 (H-axis direction). Although the specific procedure will be explained later, it is also possible to accurately align the light irradiation position with the electron beam irradiation position by adjusting the V-axis with the H-axis fixed in the same way.

[0222] As described above, by making the adjustment axis and the boundary line intersect at right angles, the irradiation position can be adjusted accurately.

[0223] If the movable axis H and boundary line B1 are not oriented at a right angle, the angle can be adjusted by rotating the adjustment sample, as explained above. Alternatively, if the mirror has two or more movable axes, the scanning direction of the light irradiation position itself can be adjusted by linking these axes.

[0224] Next, a procedure for adjusting the irradiation position in a two-dimensional plane by applying this principle will be described with reference to FIGS. 28, 29, 30 and 31. FIG.

[0225] FIG. 28 is a flowchart of the adjustment.

[0226] FIG. 29 shows an example of a GUI for inputting setting items in this embodiment.

[0227] FIG. 30 is a diagram showing the installation direction of the adjustment sample when adjusting the adjustment axis V.

[0228] FIG. 31 shows an example of a GUI for displaying the adjustment results of this embodiment.

[0229] First, the user sets the adjustment conditions (step S40). The setting items (8e, 8f, 8g, 8h) are the same as in Example 1, so their explanation will be omitted. Details of the other setting items (8q) will be explained in the relevant sections below. Note that in this example, an example will be explained in which the H-axis is selected as the first axis to be adjusted in setting item 8h, but the same adjustment can be achieved by first adjusting the V-axis and then adjusting the H-axis later.

[0230] When the user issues an instruction to start adjustment by operating the GUI or the like, the control device automatically transports the adjustment sample to the sample chamber and rotates the adjustment sample so that the boundary line of the reference structure is perpendicular to the adjustment axis H (step S41). At this time, the angle of the adjustment axis H is specified by the user in setting item 8q. Alternatively, if the mirror is fixed to the device and the angle is fixed, this setting item may be omitted and a fixed value may be used.

[0231] Next, the control device moves the stage so that the boundary line B1 is at the center of the SEM image (step S42). Alternatively, the user may manually move the stage while viewing the SEM image.

[0232] Next, the control device starts irradiating light at the specified power (step S43), and records the maximum value M and minimum value m of the secondary light intensity while scanning the angle H. Alternatively, measurements may be taken at only two points, the lower and upper limits of the scanning range, and the larger value may be used as the maximum value M and the smaller value as the minimum value m. Also, in this embodiment, an example is shown in which the movement range of the angle H is specified by the user in setting item 8q, but the entire movable range of the mirror may be used without requiring user input.

[0233] The control device calculates (m+M) / 2 from the measured value and sets the target value It. The results are displayed in the columns 8r, 8s, and 8t in FIG. 31 (step S44).

[0234] Next, the control device adjusts the mirror angle H so that the secondary light intensity becomes the target value It (step S45). The adjustment can be performed by repeating the adjustment of the mirror angle until the error between the target value and the measured value becomes equal to or less than a specified value. The repetition algorithm can be the bisection method or Newton's method.

[0235] The user can use setting item 8q to set the error rate at which the process will end and the maximum number of iterations. Here, the error rate E is defined as E = |(IN - It) / It|, where IN is the secondary light intensity after N adjustments.

[0236] The control device terminates the adjustment when the error rate E falls below a specified value. Alternatively, the control device also terminates the adjustment when the number of adjustment repetitions N exceeds a value specified by the user. When the number of repetitions exceeds an upper limit, the control device may abnormally terminate the adjustment by skipping the subsequent steps, or may continue the adjustment by using the mirror angle with the lowest error rate E. Alternatively, the control device may display a dialog screen to confirm with the user whether to continue the adjustment.

[0237] The final number of adjustment iterations, error rate, mirror angle after adjustment, and angle dependence of secondary light intensity are displayed in Graph 8k. Alternatively, all or part of the results can be saved as a log file without being displayed on the screen.

[0238] Next, as shown in FIG. 30, the control device rotates the adjustment specimen so that the boundary line is perpendicular to the V axis, and moves the specimen stage so that the center of the SEM field of view is again on the boundary line (steps S46 to S47).

[0239] Finally, the control device adjusts the angle V so that the amount of secondary light reaches the target value using the same procedure as for the H axis (step S48). Note that since the target value It has already been calculated in step S44, it is not necessary to reset the target value before adjusting the V axis, but this can also be done again. If the procedure of calculating the target value It again after step S47 is followed, an effect is achieved in that accurate adjustment is possible even when the amount of secondary light depends on the incident direction of light.

[0240] As described above, by rotating the adjustment sample and sequentially adjusting the boundary line in two directions, it is possible to reliably perform coarse adjustment even when the light irradiation position is significantly deviated from the boundary line.

[0241] It is also possible to achieve more reliable and accurate adjustment by combining the adjustments of this embodiment and Example 1. For example, if the light irradiation position is significantly deviated from the diameter of the circle of the reference structure used in Example 1, coarse adjustment may not be possible using the method of Example 1. In that case, coarse adjustment can be first performed using the method of this embodiment, and then adjustment can be performed again using the method of Example 1, thereby ensuring reliable coarse and fine adjustment.

[0242] [Variation 4] Modification 4 is a modification of the algorithm that performs adjustment by maximizing the rate of change of the secondary light amount.

[0243] 32A, 32B, and 32C are diagrams illustrating the rate of change in the amount of secondary light when the mirror angle H is changed from H0 to H1.

[0244] FIG. 33 is a graph showing an example in which the rate of change of the secondary light amount is plotted as a function of the mirror angle H.

[0245] First, when the mirror angle is H0, the amount of secondary light generated is determined by the area overlapping with the reference structure, and the signal amount is I0. Similarly, when the mirror angle is moved to H1, the amount of secondary light generated is I1.

[0246] Here, the signal increase I1-I0 when the mirror angle is changed from H0 to H1 is the difference between Figures 32A and 32B, and therefore corresponds to the amount of secondary light emitted from region 6aD in Figure 32C. As explained in Example 1, a light source such as a laser has a spatial distribution in which the illuminance is highest at the center, so the signal increase I1-I0 is greatest when region 6aD intersects the center of the irradiation region.

[0247] If the rate of change of the secondary light intensity is defined as (I1 - I0) / (H1 - H0), taking into account the change in the mirror angle, the rate of change becomes a mountain-shaped function as shown in Figure 33. The maximum value is reached when region 6aD passes through the center of the irradiation position. In other words, by adjusting the mirror to a position where the rate of change is maximum, it is possible to align the laser irradiation position with the boundary line of the reference structure.

[0248] By using an algorithm that maximizes the rate of change in this way, the procedure of maximizing and minimizing the amount of secondary light at the start of adjustment (step S44) can be omitted, which has the effect of shortening the adjustment time.

[0249] Furthermore, since an algorithm for finding the maximum value can be used instead of an algorithm that repeatedly adjusts the amount of secondary light so that it matches the target value, the adjustment can be completed with a small number of repetitions by using a gradient method or the like.

[0250] [Variation 5] In Modification 5, an example of the configuration of a reference structure for performing adjustments in a charged particle beam device that does not have a sample rotation mechanism will be described.

[0251] 34A and 34B show examples of the structure of the adjustment sample used in this modification.

[0252] The adjustment sample 6 of this modified example has a structure in which one-fourth of the wafer is made up of the reference structure 6a, and has both a horizontal boundary line LH and a vertical boundary line LV.

[0253] The procedure for adjusting the irradiation position using the adjustment sample in this modified example will be described with reference to the flowchart in FIG.

[0254] First, the user sets conditions (step S40) and issues an adjustment start command to the apparatus. In this modified example, an example will be described in which the user sets the H-axis adjustment to be performed first.

[0255] The control device moves the sample stage so that the irradiation position of the electron beam is on the boundary line LV (step S42). This modification is significantly different in that the step of rotating the sample (step S41) is unnecessary. However, because the boundary line LV is only long enough to reach the center of the wafer, to ensure reliable adjustment, it is necessary to adjust the stage so that the irradiation position of the electron beam is at 6pH near the center of the boundary line LV. After moving the stage, the control device adjusts the H axis (steps S43 to S45). The movement range of the light irradiation position at this time is, for example, from position 7aH to position 7aH'.

[0256] Next, the V-axis is adjusted. Since the reference structure of this embodiment additionally has a horizontal boundary line LH, the specimen rotation step S46 is not necessary. However, as with the H-axis adjustment, the boundary line LH only extends to the center of the wafer, so the specimen stage is adjusted so that the electron beam irradiation position is 6 pV near the center of the boundary line (step S47). Finally, the V-axis is adjusted (step S48). The range of movement of the light irradiation position at this time is, for example, from position 7 aV to position 7 aV'.

[0257] The structure that can be used in this modification is not limited to this structure. For example, a square reference structure may be placed at the center of the wafer and its boundary line may be used.

[0258] Furthermore, if the orientation of the movable axes H and V is oblique to the x- and y-axes due to the arrangement of the adjustment mechanism, it is possible to achieve higher precision adjustment by preparing the adjustment sample so that the boundary lines LV and LH intersect at right angles to the movable axes H and V, as shown in Figure 34B. In either case, at least two or more non-parallel boundary lines are required.

[0259] In this way, by using a reference structure having boundary lines in multiple directions on the adjustment sample itself, the procedure of rotating the adjustment sample can be omitted, thereby achieving the effect of shortening the adjustment time. In addition, since a mechanism for rotating the adjustment sample is no longer necessary, the device configuration can be simplified.

[0260] 34A and 34B, the lower left area is unused, so it is also possible to place an additional circular reference structure as described in Example 1. By having reference structures with multiple structures in this way, it becomes possible to use different structures for different purposes, such as using a coarse adjustment reference structure that allows for reliable adjustment during coarse adjustment, and a fine adjustment reference structure that requires fewer stage movements during fine adjustment and allows for faster adjustment during fine adjustment.

[0261] [Variation 6] In Modification 6, an example of adjustment using a boundary line between two different reference structures will be described.

[0262] The structure of the sample will be explained using FIG.

[0263] In this figure, as in FIG. 25, there is a reference structure 6a on the right half of the adjustment sample, which is made of GaN that emits blue light as an example. In this modified example, in addition to this, there is a GaAs reference structure that emits infrared light on the left side. Note that although this modified example uses a combination of GaN and GaAs as an example, other combinations of fluorescent materials may also be used. Alternatively, different types of reference structures may be combined; for example, the right side may have a periodic structure that generates diffracted light, and the left side may have a fluorescent material. In either case, it is sufficient to combine reference structures that emit different amounts of electrical signals.

[0264] When using this modified example, the detection optical system can be the optical system described in Example 4. Fluorescence emitted from the sample is separated by a dichroic mirror. If the dichroic mirror is a long-pass type, the light emitted from reference structure 6a is received by light-receiving element 2b, and the light emitted from reference structure 6m is received by light-receiving element 2c.

[0265] FIG. 36A plots the signal waveform F1 output from the light receiving element 2b, and FIG. 36B plots the signal waveform F2 output from the light receiving element 2c.

[0266] When the light irradiation position is elliptical region 7a, GaAs emits light, so a secondary optical signal is detected by light-receiving element 2c but not by light-receiving element 2b. On the other hand, when the light irradiation position is elliptical region 7a', GaN emits light, so only light-receiving element 2b detects secondary light. Therefore, waveforms F1 and F2 show opposite position dependencies.

[0267] FIG. 36C is a plot of the signal output by the signal processing unit 2d as described in the fourth embodiment.

[0268] The signal processing unit 2d outputs a value obtained by dividing the output signal of the light receiving element 2b by the output signal of the light receiving element 2c, for example. As already explained in the fourth embodiment, such a waveform F3 exhibits a steeper characteristic than the waveforms F1 and F2 obtained from a single detector, which has the effect of enabling more robust adjustment.

[0269] Preferred embodiments of the present disclosure will be summarized below.

[0270] The reference structure has a periodic structure, and the period of the periodic structure is λ / n or more, where λ is the wavelength of the first light and n is the refractive index of the medium into which the first light is incident, and is smaller than the irradiation diameter of the first light.

[0271] The reference structure is made of a material that emits fluorescence in response to the first light.

[0272] The reference structure is made of a material or structure that generates scattered light in response to the first light.

[0273] The reference structure is composed of a mirror surface that is adjusted to an angle such that the reflected light is emitted in the direction of the photodetector.

[0274] The reference structure has a straight boundary line that intersects the movable axis of the movable mechanism at a right angle.

[0275] The reference structure has a plurality of non-parallel boundaries.

[0276] The irradiation position of the first light is two-dimensionally adjustable.

[0277] The particle beam detector has a function of detecting light.

[0278] The adjustment sample has a plurality of structures, and the distance between adjacent structures is greater than the movable range of the irradiation position.

[0279] The adjustment samples have structures of different sizes, and the movable mechanisms are adjusted in descending order of size of the structures.

[0280] The charged particle beam device further includes a height sensor that measures the height of the sample, the sample for adjustment has portions of different heights, and the irradiation position of the first light at the height of the sample is calibrated by adjusting the movable mechanism.

[0281] The periodic structure is two-dimensional.

[0282] The movable mechanism is adjusted so that the intensity of the second light detected by the photodetector is maximized.

[0283] The movable mechanism is adjusted so that the intensity of the second light detected by the photodetector is half of the maximum value.

[0284] The movable mechanism is adjusted so that the rate of change of the intensity of the second light detected by the photodetector is maximized.

[0285] The second light includes reflected light and secondary light, and an electrical signal derived from the reflected light and secondary light is used to adjust the movable mechanism.

[0286] The adjustment sample has a marker for detecting its center using an image obtained by irradiating it with a charged particle beam, and the center of the reference structure of the adjustment sample is positioned at a position shifted from the center of the marker, and the reference structure is used to adjust the movable mechanism.

[0287] The first light is irradiated onto the sample from a different direction than the charged particle beam, which allows the light to be irradiated onto the sample without interfering with the irradiation path of the charged particle beam, and also eliminates the need for components such as lenses or prisms to make the light parallel to the charged particle beam.

[0288] The control device moves the irradiation position of the first light so that it passes through the boundary line of the reference structure.

[0289] The reference structure has a straight boundary line, and the straight boundary line is perpendicular to the direction in which the irradiation position of the first light is moved by the movable mechanism.

[0290] The reference structure has a plurality of non-parallel boundary lines.

[0291] The control device adjusts the movable mechanism to a position where the signal amount becomes (M+m) / 2, where M is the maximum value of the signal amount when the irradiation position of the first light passes through the boundary line of the reference structure and m is the minimum value of the signal amount.

[0292] The control device adjusts the movable mechanism to a position where the rate of change in the signal amount is maximum when the irradiation position of the first light passes through the boundary line of the reference structure.

[0293] The control device moves the irradiation position of the first light so that it passes through the boundary line of the reference structure.

[0294] The present disclosure is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present disclosure, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment or modification, and it is also possible to add the configuration of another embodiment or modification to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0295] 1: light irradiation system, 1a: light source, 1b: light irradiation position adjustment unit, 1c: optical element, 1d: movable stage, 2: light detection system, 3: electron optical system, 4: sample stage system, 5: control system, 6: sample for adjustment, 6a: reference structure, 7a: elliptical area, 7b: movable range of irradiation position, 9: sample.

Claims

1. A particle beam source that irradiates a sample with a charged particle beam; a particle beam detector that detects particle beams from the sample and generates particle beam electrical signals; a light source that generates a first light to irradiate the sample; a movable mechanism capable of moving an irradiation position of the first light; a photodetector that detects second light emitted from the sample in response to irradiation with the first light and generates a photoelectric signal; a sample stage configured to allow the sample to be placed and moved; a control device; and a method for adjusting the irradiation position of the first light in a charged particle beam device including the charged particle beam device, the method comprising: the light source irradiates the first light onto an adjustment sample placed on the sample stage, the adjustment sample including a reference structure; the photodetector detects the second light generated by the modulation of the first light by the reference structure and sends the photoelectric signal to the control device; the control device issues a command to change the irradiation position of the first light so that the first light passes through the reference structure based on the intensity of the second light, and adjusts the movable mechanism based on a change in the photoelectric signal so that the irradiation position of the charged particle beam and the irradiation position of the first light coincide with each other; the reference structure has a periodic structure, a period of the periodic structure is λ / n or more and smaller than an irradiation diameter of the first light, where λ is a wavelength of the first light and n is a refractive index of a medium into which the first light is incident.

2. A particle beam source that irradiates a sample with a charged particle beam; a particle beam detector that detects particle beams from the sample and generates particle beam electrical signals; a light source that generates a first light to irradiate the sample; a movable mechanism capable of moving an irradiation position of the first light; a photodetector that detects second light emitted from the sample in response to irradiation with the first light and generates a photoelectric signal; a sample stage configured to allow the sample to be placed and moved; a control device; and a method for adjusting the irradiation position of the first light in a charged particle beam device including the charged particle beam device, the method comprising: the light source irradiates the first light onto an adjustment sample placed on the sample stage, the adjustment sample including a reference structure; the photodetector detects the second light generated by the modulation of the first light by the reference structure and sends the photoelectric signal to the control device; the control device issues a command to change the irradiation position of the first light so that the first light passes through the reference structure based on the intensity of the second light, and adjusts the movable mechanism based on a change in the photoelectric signal so that the irradiation position of the charged particle beam and the irradiation position of the first light coincide with each other; The method for adjusting a light irradiation position, wherein the reference structure is made of a material that emits fluorescence in response to the first light.

3. The adjustment method according to claim 1 or 2, wherein the reference structure is made of a material or structure that generates scattered light in response to the first light.

4. 3. The adjustment method according to claim 1, wherein the reference structure is configured by a mirror surface adjusted to an inclination such that reflected light is emitted in the direction of the photodetector.

5. The adjusting method according to claim 1 , wherein the irradiation position of the first light is two-dimensionally adjustable.

6. The adjusting method according to claim 1 or 2, wherein the particle beam detector has a function of detecting light.

7. The adjustment sample has a plurality of structures, The adjustment method according to claim 1 , wherein a distance between the adjacent structures is greater than a movable range of the irradiation position.

8. The preparation sample has structures of different sizes, The adjustment method according to claim 1 or 2, wherein the adjustment of the movable mechanism is performed in descending order of size of the structures.

9. the charged particle beam device further includes a height sensor that measures the height of the sample; The adjustment sample has portions of different heights, The adjustment method according to claim 1 or 2, wherein the adjustment of the movable mechanism calibrates the irradiation position of the first light at the height of the sample.

10. The method of claim 1 , wherein the periodic structure is two-dimensional.

11. The adjusting method according to claim 1 or 2, wherein the adjustment of the movable mechanism is performed so that the intensity of the second light detected by the photodetector is maximized.

12. the second light includes reflected light and secondary light, The adjusting method according to claim 1 or 2, wherein the adjustment of the movable mechanism is performed using an electrical signal derived from the reflected light and the secondary light.

13. the adjustment sample has a marker for detecting a center from an image obtained by irradiating the charged particle beam, the center of the reference structure of the adjustment sample is disposed at a position shifted from the center of the marker; The adjustment method according to claim 1 or 2, wherein the movable mechanism is adjusted using the reference structure.

14. The adjusting method according to claim 1 , wherein the first light is irradiated onto the sample from a direction different from that of the charged particle beam.

15. a particle beam source that irradiates a sample with a charged particle beam; a particle beam detector that detects particle beams from the sample and generates particle beam electrical signals; a light source that generates a first light to irradiate the sample; a movable mechanism capable of moving an irradiation position of the first light; a photodetector that detects second light emitted from the sample in response to irradiation with the first light and generates a photoelectric signal; a sample stage configured to allow the sample to be placed and moved; A charged particle beam device comprising: the light source irradiates the first light onto an adjustment sample placed on the sample stage, the adjustment sample including a reference structure; the photodetector detects the second light generated by the modulation of the first light by the reference structure and sends the photoelectric signal to the control device; the control device issues a command to change the irradiation position of the first light so that the first light passes through the reference structure based on the intensity of the second light, and adjusts the movable mechanism based on a change in the photoelectric signal so that the irradiation position of the charged particle beam and the irradiation position of the first light coincide with each other; the reference structure has a periodic structure, a period of the periodic structure is λ / n or more, and is smaller than an irradiation diameter of the first light, where λ is a wavelength of the first light and n is a refractive index of a medium into which the first light is incident.

16. The charged particle beam device according to claim 15 , wherein the first light is irradiated onto the sample from a direction different from that of the charged particle beam.

17. The charged particle beam device according to claim 15 , wherein the irradiation position of the first light is two-dimensionally adjustable.

18. The charged particle beam device according to claim 15 , wherein the particle beam detector has a function of detecting light.

19. Further comprising a height sensor for measuring the height of the sample; The adjustment sample has portions of different heights, The charged particle beam device according to claim 15 , wherein the adjustment of the movable mechanism calibrates the irradiation position of the first light at the height of the sample.

20. The charged particle beam device according to claim 15 , wherein the adjustment of the movable mechanism is performed so that the intensity of the second light detected by the photodetector is maximized.

21. the second light includes reflected light and secondary light, The charged particle beam device according to claim 15 , wherein the adjustment of the movable mechanism is performed using an electrical signal derived from the reflected light and the secondary light.

22. The adjustment method according to claim 1 or 2, wherein the control device moves the irradiation position of the first light so that the irradiation position passes through a boundary line between an area where the reference structure is provided and an area other than the area.

23. The adjusting method according to claim 22 , wherein the boundary line is a straight line and intersects at a right angle with a direction in which the movable mechanism moves the irradiation position of the first light.

24. The adjustment method according to claim 22 , wherein a plurality of the boundary lines are provided and are non-parallel to each other.

25. 23. The adjustment method according to claim 22, wherein the control device adjusts the movable mechanism to a position where the signal amount becomes (M+m) / 2, where M is a maximum value of the signal amount when the irradiation position of the first light passes through the boundary line, and m is a minimum value of the signal amount.

26. The adjusting method according to claim 22 , wherein the control device adjusts the movable mechanism to a position where a rate of change in signal amount when the irradiation position of the first light passes through the boundary line is maximized.

27. The charged particle beam device according to claim 15 , wherein the control device moves the irradiation position of the first light so that the irradiation position passes through a boundary line between an area where the reference structure is provided and an area other than the area.

28. 16. The charged particle beam device according to claim 15, wherein the control device adjusts the movable mechanism to a position where the signal amount becomes (M+m) / 2 when the irradiation position of the first light passes through a boundary line between an area where the reference structure is provided and another area, where M is a maximum value of the signal amount and m is a minimum value of the signal amount.

29. 16. The charged particle beam device according to claim 15, wherein the control device adjusts the movable mechanism to a position where a rate of change in signal amount when the irradiation position of the first light passes through a boundary line between an area where the reference structure is provided and another area is maximized.

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