Optical apparatus, inspection apparatus, imagecapturing method, and program

Abstract

The objective of this invention is to image a sample with low noise. The optical system 20 guides the reflected light L2 generated by illuminating the sample 100 with illumination light L1 to the detector 50. The image processing unit 60 outputs an image (IMG) of the sample 100 based on the detection result of the reflected light L2 by the detector 50. The optical distance adjustment unit is capable of adjusting the optical distance between the sample 100 and the detector 50. The control unit 70 controls the optical distance adjustment unit in a manner that changes the optical distance between the detector 50 and the sample 100, and controls the image processing unit 60 in a manner that acquires images of the sample 100 multiple times based on the detection result of the detector 50. The image processing unit 60 acquires an image of the sample 100 based on the cumulative result of the multiple acquired images of the sample 100.

Description

[Technical Field]

[0001] This invention relates to an optical device, an inspection device, an imaging method, and a computer-readable medium storing a program. [Previous Technology]

[0002] With the miniaturization of semiconductor process nodes, the increasing sophistication of inspection of semiconductor wafers and photomasks has become a pressing need. For example, techniques for inspecting samples by photographing them to detect foreign matter in masks and other samples are well-known (Patent Document 1 and Patent Document 2). [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2022-161475. [Patent Document 2] Japanese Patent Application Publication No. 2023-117036. [Summary of the Invention]

[0004] [Problem to be solved by the invention] However, since the sample has even finer bumps and depressions than the pattern to be inspected, noise caused by the bumps and depressions will be captured when the sample is photographed.

[0005] As a reason for capturing noise caused by minute irregularities, it is believed that the following situations exist. That is, it is known that when the focal position of the optical system is shallower than the convex object, the image becomes brighter, and when the focal position of the optical system is deeper than the convex object, the image becomes darker; when the focal position of the optical system is shallower than the concave object, the image becomes darker, and when the focal position of the optical system is deeper than the concave object, the image becomes brighter; in view of this, it is believed that even minute irregularities on the sample will produce the same phenomenon.

[0006] Thus, when there are irregularities on the sample and the distance between these irregularities and the optical system differs from the position of the observed object, even minute irregularities will produce brightness noise in the sample image due to deviation from the focal point. This could lead to a deterioration in the precision of the inspection based on the sample image. Therefore, there is a need to reduce noise caused by the irregularities of the sample and to determine the method for photographing the sample.

[0007] [Means for Solving the Problem] The present invention is an optical device comprising: a detector for detecting light; an optical system for illuminating an object with illumination light and guiding secondary light generated by the illumination light illuminating the object to the detector; an image processing unit for outputting an image of the object in response to the detection result of the secondary light by the detector; an optical distance adjustment unit for adjusting the optical distance between the object and the detector; and a control unit for controlling the optical distance adjustment unit in a manner that changes the optical distance between the object and the detector, and controlling the image processing unit in a manner that acquires an image of the object multiple times based on the detection result of the detector; the image processing unit acquires the image of the object based on the cumulative result of the multiple acquired images of the object.

[0008] The present invention is an inspection device, which further comprises: the aforementioned optical device; and an inspection unit that inspects the aforementioned object based on the aforementioned image of the aforementioned object obtained by the aforementioned image processing unit.

[0009] The present invention is a shooting method performed in an optical device, the aforementioned optical device comprising: a detector for detecting light; an optical system for illuminating an object with the aforementioned illumination light and guiding secondary light generated by the illumination light illuminating the object to the aforementioned detector; and an optical distance adjustment unit capable of adjusting the optical distance between the object and the aforementioned detector; the aforementioned shooting method, in the aforementioned optical device, controls the aforementioned optical distance adjustment unit in a manner that changes the optical distance between the object and the aforementioned detector, and acquires images of the object multiple times based on the detection results of the aforementioned detector, and acquires an image of the object based on the cumulative result of the multiple acquired images of the object.

[0010] The present invention is a computer-readable medium storing a program, which is processed by a processing device configured as a computer and performs image processing in an optical device; the optical device includes: a detector for detecting light; an optical system for illuminating an object with illumination light and guiding secondary light generated by the illumination light illuminating the object to the detector; and an optical distance adjustment unit capable of adjusting the optical distance between the object and the detector; the computer-readable medium storing the program causes the processing device to perform the following processing: while controlling the optical distance adjustment unit in a manner that changes the optical distance between the object and the detector, acquiring images of the object multiple times based on the detection results of the detector; and acquiring an image of the object based on the cumulative result of the multiple images of the object acquired.

[0011] The present invention is an optical device comprising: a detector for detecting light; an optical system for illuminating an object with illumination light and guiding secondary light generated by the illumination light illuminating the object to the detector; an image processing unit for outputting an image of the object based on the detection result of the secondary light by the detector; a holding unit for holding the object; a driving unit for driving the holding unit; and a control unit for controlling the driving unit to change the optical distance between the object and the detector in a manner that includes a component in the thickness direction of the object and the moving holding unit, and controlling the image processing unit to acquire images of the object multiple times based on the detection result of the detector; the image processing unit acquires the image of the object based on the cumulative result of the multiple acquired images of the object.

[0012] The present invention is an optical device comprising: a detector for detecting light; an optical system for illuminating an object with illumination light and guiding secondary light generated by the illumination light illuminating the object to the detector; an image processing unit for outputting an image of the object in response to the detection result of the secondary light by the detector; and a control unit for controlling the optical system and the image processing unit to change at least one of the focal distances of the optical system on the object side or the detector side by changing the optical distance between the object and the detector, and to acquire images of the object multiple times based on the detection result of the detector; the image processing unit acquires the image of the object based on the accumulation result of the multiple acquired images of the object.

[0013] The present invention is an optical device comprising: a detector for detecting light; an optical system for illuminating an object with illumination light and guiding secondary light generated by the illumination light illuminating the object to the detector; an image processing unit for outputting an image of the object in response to the detection result of the secondary light by the detector; and a control unit for changing at least one of the relative position of the optical system relative to the object or the relative position of the optical system relative to the detector by changing the optical distance between the object and the detector, and for acquiring images of the object multiple times based on the detection result of the detector; the image processing unit acquires the image of the object based on the cumulative result of the multiple images of the object acquired.

[0014] The present invention is an optical device comprising: a detector for detecting light; an optical system for illuminating an object with illumination light and guiding secondary light generated by the illumination light illuminating the object to the detector; an image processing unit for outputting an image of the object in response to the detection result of the secondary light by the detector; an optical distance adjustment unit for adjusting the optical distance between the object and the detector; a detector driving unit for driving the detector; and a control unit for controlling the detector driving unit to change the optical distance between the object and the detector in a manner that includes a component in the thickness direction of the detector and the detector moves, and controlling the image processing unit to acquire images of the object multiple times based on the detection result of the detector; the image processing unit acquires the image of the object based on the cumulative result of the multiple acquired images of the object.

[0015] [Effect of the Invention] According to the present invention, it is possible to photograph samples with low noise.

Implementation Method

[0017] Hereinafter, the specific configuration of this embodiment will be described with reference to the drawings. The following description shows a preferred embodiment of the invention, and the scope of the invention is not limited to the following embodiments. In the following description, components with the same element symbols show substantially the same content.

[0018] [Embodiment 1] An optical device according to Embodiment 1 will be described. The optical device of this embodiment is configured as an optical device incorporated into an inspection device for a photomask, which is used in a semiconductor manufacturing process. The inspection device inspects for defects in a sample based on an image of the sample captured by the optical device.

[0019] FIG1 is a diagram showing an example of the configuration of the optical device in Embodiment 1. FIG2 is a diagram showing an example of the configuration of the inspection device in Embodiment 1. As shown in FIG2, the inspection unit 110 of the inspection device 1000 performs anomaly inspection of the sample 100 based on the image IMG of the sample 100 captured by the optical device 1, such as defect inspection.

[0020] The optical device 1 will be described below. As shown in FIG1, the optical device 1 includes a light source 10, an optical system 20, a stage 30, a drive mechanism 40, a detector 50, an image processing unit 60, and a control unit 70. In addition, the optical device 1 may also include other optical components.

[0021] Here, for ease of explanation of the optical device 1, an XYZ orthogonal coordinate system is used. The stage 31 is referred to as the XY plane, which is parallel to the X-axis and Y-axis directions; the stage 31 is the main surface of the stage 30, used to hold the sample 100. The direction orthogonal to the stage 31 is referred to as the Z-axis direction. For example, the +Z-axis direction is referred to as "upper" and the -Z-axis direction is referred to as "lower". In addition, "upper" and "lower" are used for ease of explanation and are not used to show the actual configuration direction of the optical device 1.

[0022] The light source 10 emits illumination light L1 toward the optical system 20. The light source 10 may also be a lamp source, an LED (light emitting diode) source, or a laser source, etc. The illumination light L1 may also be, for example, visible light, ultraviolet light, or EUV (extreme ultraviolet) light, etc.

[0023] The optical system 20 is composed of a beam splitter 21, an object lens 22 and a relay lens 23, and constitutes an imaging optical system; the imaging optical system illuminates the sample 100 placed on the stage 30 with the illumination light L1 emitted from the light source 10, and images the reflected light L2 from the sample 100 onto the detector 50.

[0024] The beam splitter 21 is, for example, a half mirror, which reflects about 1 / 2 of the illumination light L1 toward the objective lens 22. The objective lens 22 illuminates the target area of ​​the sample 100 placed on the stage surface of the stage 30 with the illumination light L1.

[0025] The reflected light L2 generated by illuminating the sample 100 with illumination light L1 is focused at the objective lens 22 and then incident on the beam splitter 21. The beam splitter 21 allows approximately half of the reflected light L2 to pass through. The reflected light L2 that has passed through the beam splitter 21 is focused at the relay lens 23 and then incident on the detector 50. In this way, the detector 50 acquires an image of the sample 100.

[0026] In the figures, representative optical elements included in the optical system 20 are shown for ease of explanation. However, the optical system 20 may also include various optical elements not shown, such as lenses, optical scanners, mirrors, filters, and beam splitters. Furthermore, the optical system 20 may also be a confocal optical system, for example. Additionally, in cases where short-wavelength light such as EUV light is used as the illumination light L1, the optical system 20 may also be a reflective optical system.

[0027] Furthermore, although the optical device 1 is described as an optical device with a bright field illumination mode in FIG1, the illumination mode of the optical device 1 is not limited to this.

[0028] Hereinafter, the reflected light L2 from the sample 100 will also be referred to as the secondary light generated by the sample 100 being illuminated by the illumination light L1. However, the secondary light is not limited to reflected light. The secondary light can also be various types of light generated by the sample 100 being illuminated by the illumination light L1, such as reflected light, scattered light, fluorescence, and transmitted light.

[0029] As explained above, the sample 100 is placed on the upper surface of the stage 30, i.e., the stage 31. Therefore, the thickness direction (also known as the height direction) of the sample 100 is the Z-axis direction. The sample 100 is a photomask or a semi-finished product in a semiconductor process; the photomask is formed by forming a fine pattern 102 on a flat member 101 such as a mask blank; the semi-finished product in the semiconductor process is formed by forming a device pattern on a wafer that is a flat member. The pattern 102 of the sample 100 is formed, for example, by a layer of opaque components deposited on the flat member 101 that is transparent to the illumination light L1, or the pattern 102 of the sample 100 is formed, for example, by depositing an absorber layer, which is mainly used to absorb the illumination light L1, on a multilayer, which is mainly used to reflect the illumination light L1.

[0030] Stage 30 is a three-dimensional drive stage equipped with a drive mechanism 40. The control unit 70 controls the drive mechanism 40, thereby enabling stage 30 to be driven along the X-axis, Y-axis, and Z-axis respectively, and even to be driven to rotate around the axes. Stage 30 is an example of a holding part for holding the sample 100. The holding part is only used to hold and drive the sample 100, and can also be a configuration other than stage 30, such as a holder with an electrostatic chuck, a robot arm, etc. The driving method of stage 30, which is an example of a driving method for the holding part, will be described in detail later.

[0031] Detector 50 detects the reflected light L2 from the sample 100 imaged by optical system 20, thereby obtaining an image of sample 100. Detector 50 can also be a camera that can be applied to various shooting principles of TDI (Time Delay Integration) cameras, such as CCD (Charge Coupled Device) sensors and CMOS (Complementary Metal-Oxide Semiconductor) sensors.

[0032] Figure 3 is a schematic diagram showing the configuration of the detector 50. In the detector 50, N line sensors 51 are arranged in the X-axis direction at a predetermined pitch P in the light incident plane. Here, N is the number of line sensors 51 arranged in the X-axis direction, and is an integer greater than or equal to 2. Among each of the line sensors 51, a plurality of pixels are arranged in the Y-axis direction. Figure 3 shows an example where nine line sensors 51 are arranged in the X-axis direction, and nine pixels are arranged in the Y-axis direction among each of the line sensors 51. Furthermore, the number of line sensors arranged is only one example, but a plurality of line sensors other than nine can also be arranged. The number of pixels arranged is only one example, but a plurality of pixels other than nine can also be arranged.

[0033] In the inspection apparatus 1000 of this embodiment, the detector 50 and the image processing unit 60 are configured as a TDI camera, which is used to capture images of the sample 100. The detector 50 outputs the detection signal DAT, which is used to display the detection result of the reflected light L2, to the image processing unit 60.

[0034] The image processing unit 60 processes the detection signal DAT, thereby obtaining an image of the sample 100.

[0035] The control unit 70 provides a control signal CON1 to the drive mechanism 40, thereby driving the stage 30 in the desired direction and speed. Furthermore, the control unit 70 provides a control signal CON2 to the image processing unit 60, thereby controlling the image processing within the image processing unit 60. Thus, the control unit 70 can cause the image processing unit 60 to capture an image when the stage 30 moves to the desired position. This results in synchronization between the movement of the stage 30 and the image capturing sequence in the image processing unit 60.

[0036] Next, the relationship between the driving of the stage 30 in the optical device 1 and the imaging timing will be explained. In the optical device 1, the stage 30 is capable of reciprocating in the Z-axis direction, which is the thickness direction of the illumination light L1, with a predetermined period and a predetermined amplitude. In this way, the stage 30 (holding part) can be configured as an optical distance adjustment unit or optical distance adjustment mechanism to change the optical distance between the sample 100 and the detector 50 within a predetermined range.

[0037] Furthermore, the stage 30 system can reciprocate in the Z-axis direction while moving in both the X-axis and Y-axis directions, or one of them. In this embodiment, for the sake of simplicity, the stage 30 system is configured to reciprocate in the Z-axis direction while moving in the X-axis direction. In this way, specific positions of the sample 100 can be sequentially captured by the line sensors 51 of the detector 50.

[0038] In the inspection apparatus 1000, after a specific area of ​​the sample 100 is captured by the left-hand line sensor of two adjacent line sensors, the same specific area of ​​the sample 100 is captured by the right-hand sensor of the two adjacent line sensors. This sequence is repeated sequentially, so that the same specific area of ​​the sample 100 can be captured by each line sensor with a time difference.

[0039] In the optical device 1, the control unit 70 controls the console 30 and the image processing unit 60 in a manner that synchronizes the movement of the sample 100 in the X-axis direction with the shooting sequence. Thereby, each time the sample 100 moves to a predetermined distance ΔX in the X-axis direction and to a predetermined distance ΔZ in the Z-axis direction, the image processing unit 60 acquires an image of the sample 100.

[0040] The horizontal magnification of the image of the sample 100 projected onto the detector 50 is set to β by the optical system 20. By means of the control unit 70, the sample 100 is moved in the +X direction by the stage 30 to ΔX = P / β, thereby the position of a specific identical area of ​​the sample 100 in the Z-axis direction can be changed by the line sensor 51 and the image can be captured by time difference.

[0041] Furthermore, in the optical device 1, the stage 30 is moved back and forth in the Z-axis direction while being driven in the X-axis direction. That is, multiple images of the sample 100 are taken during one reciprocating motion of the stage 30 in the Z-axis direction.

[0042] Here, the number of shots taken during the period when the stage 30 reciprocates once along the Z-axis is q. Wherein, q is an integer greater than or equal to 2. At this time, during the period when the image of a specific position of the sample 100 (hereinafter referred to as the shooting target area) crosses the detector 50 in the X-axis direction, the stage 30 reciprocates at least once in the Z-axis direction. In this way, compared with a specific optical distance (which may be referred to as a predetermined optical distance) between focusing on the pattern 102 of the sample 100 and focusing on the detector 50, the shooting target area of ​​the sample 100 can be shot multiple times and continuously by a plurality of line sensors 51 in the range between the defocusing state on the positive side and the defocusing state on the negative side. In addition, the specific optical distance can also be determined according to the purpose of the optical device 1, for example, it can also be the optical distance when the illumination light L1 is focused on the area that becomes the shooting target of the sample 100 and the secondary light L2 is focused on the detector 50. Furthermore, the area of ​​the sample 100 that the illumination light L1 focuses on (i.e., the area that becomes the subject of the photograph of the sample 100) can also be determined according to the purpose of the optical device 1; the area of ​​the sample 100 that the illumination light L1 focuses on can be, for example: the transparent substrate layer (or multiple layers) of the sample 100; the pattern 102 (opaque layer or absorber layer) of the sample 100; the position of the sample 100 in the thickness direction between the pattern 102 (opaque layer or absorber layer) of the sample 100 and the transparent substrate layer (or multiple layers) of the sample 100; the position above the pattern 102 (in the direction away from the substrate); or the position slightly below the transparent substrate layer (or multiple layers) of the sample 100, etc.

[0043] As explained above, since the detector 50 and the image processing unit 60 constitute a TDI camera, multiple shooting results with different defocus states obtained by shooting the target area of ​​the sample 100 multiple times are accumulated.

[0044] In this way, even if the sample 100 has slight irregularities, the irregularities can offset the influence of noise during defocusing on the negative side and the influence of noise during defocusing on the positive side. As a result, noisy images can be reduced and an image of the sample 100 can be obtained.

[0045] A specific example is used to illustrate the relationship between the reciprocating movement of the sample 100 in the Z-axis direction and the imaging timing. Figure 4 is a diagram of an example of the movement of the display stage. In this example, the stage 30 reciprocates once during the period when the image of the object area OBJ of the sample 100 crosses the nine line sensors 51 of the detector 50 shown in Figure 3. In this case, the number of times q is captured during the period when the stage 30 reciprocates once in the Z-axis direction becomes 9.

[0046] In addition, the initial position of stage 30 is set to (X,Z)=(0,0), and the initial time is set to T0. Furthermore, stage 30 is driven in such a way that the Z-axis position at the initial shooting time during one reciprocating motion becomes the same as the Z-axis position at the final shooting time. Furthermore, in the following, to easily understand the reciprocating movement of stage 30, the initial position of the stage is set to 0, and the movement distance ΔZ is expressed as a phase in units of π / 4. That is, when k is set to an integer from 0 to q-1, the coordinate Zk of stage 30 in the timing Tk is expressed by the following formula: [Formula 1] Zk=k‧ΔZ=k‧2π / (q-1)=k‧π / 4 Furthermore, the coordinate Xk of the X-axis is expressed by the following formula: [Formula 2] Xk=k‧ΔX

[0047] That is, in the case where nine shots are taken during one reciprocating motion of stage 30 in the Z-axis direction, the coordinate system of stage 30 in shooting sequence T0 to shooting sequence T8 is as described below. Furthermore, the coordinates (X8, Z8) of stage 30 in shooting sequence T8 can also be used as the coordinates of the initial position (0, 0) relative to other different shooting target areas OJB in the sample 100. That is, shooting sequence T8 can also be used as the initial shooting sequence T0 relative to other different shooting target areas OJB in the sample 100, and the following movement of the coordinates of stage 30 can be repeated. (X0,Z0)=(0,0) (X1,Z1)=(ΔX, π / 4) (X2,Z2)=(2ΔX, π / 2) (X3,Z3)=(3ΔX, 3π / 4) (X4,Z4)=(4ΔX, π) (X5,Z5)=(5ΔX, 5π / 4) (X6,Z6)=(6ΔX, 3π / 2) (X7,Z7)=(7ΔX, 7π / 4) (X8,Z8)=(8ΔX, 2π) Furthermore, for example, if platform 30 moves along a sine wave with its initial position set to (X0,Z0)=(0,0) and its amplitude as A relative to the Z-axis coordinates, the coordinate system of platform 30 becomes as described below. (X0,Z0)=(0,0) (X1,Z1)=(ΔX, A‧Sin(π / 4))=(ΔX, A / √2) (X2,Z2)=(2ΔX, A‧Sin(π / 2))=(2ΔX, A) (X3,Z3)=(3ΔX, A‧Sin(3π / 4))=(3ΔX, A / √2) (X4,Z4)=(4ΔX, A‧Sin(π))=(4ΔX, 0) (X5,Z5)=(5ΔX, A‧Sin(5π / 4))=(5ΔX, -A / √2) (X6,Z6)=(6ΔX, A‧Sin(3π / 2))=(6ΔX, -A) (X7, Z7)=(7ΔX, A‧Sin(7π / 4))=(7ΔX, -A / √2) (X8,Z8)=(8ΔX, A‧Sin(2π))=(8ΔX, 0)

[0048] Figure 5 is a schematic diagram showing the process of photographing the target area OBJ of the sample 100. In Figure 5, as an example, nine rows of line sensors 51 are arranged in the X direction. Since the stage 30 is driven in each shooting sequence such that the image of the target area OBJ moves in the +X direction to the component of one line sensor, the target area OBJ is shifted (shifted) by one line segment in the +X direction in sequence. Since the detector 50 is configured as a sensor of the TDI camera, the charge of the line sensor obtained by photographing the target area OBJ in the previous shooting sequence is transferred to the adjacent line sensor 51 in the +X direction. Then, the target area OBJ is further photographed by the line sensor 51 with transferred charge, thereby further accumulating charge.

[0049] Furthermore, as explained above, since the stage 30 moves π / 4 sequentially along the Z-axis in each shooting sequence, the images of the subject area OBJ captured sequentially by the nine line sensors 51 accumulate shooting results under different defocus states. Additionally, the image captured by the ninth line sensor 51 may not accumulate because the Z-phase is the same as the initial position. In this case, images of the subject area OBJ captured sequentially by the eight line sensors 51 are accumulated.

[0050] Therefore, in this configuration, the following cycles are synchronized: the cycle of the stage 30 reciprocating once in the Z-axis direction; the cycle of accumulating the imaging results of a plurality of line sensors, that is, the cycle of accumulating a plurality of images of the same object area OBJ of the sample 100. For example, the cycle of accumulating the imaging results of a plurality of line sensors on the same object area OBJ of the sample 100 and obtaining an image of the object area OBJ (that is, the cycle of accumulating a plurality of images of the same object area OBJ of the sample 100) is an integer multiple of 1 or more of the cycle of the stage 30 reciprocating once in the Z-axis direction. That is, during one cycle of acquiring an image of the same object area OBJ of the sample 100, the stage 30 can reciprocate in the Z-axis direction to an integer multiple of 1, and the stage 30 can reciprocate at least once in the Z-axis direction. In addition, the images of the same shooting target area OBJ as the sample 100 can also accumulate at least the following images: (1) the image when the optical distance between the sample 100 and the detector 50 is a specific optical distance; (2) the image when the optical distance between the sample 100 and the detector 50 is longer than the specific optical distance by at least one change; (3) the image when the optical distance between the sample 100 and the detector 50 is shorter than the specific optical distance by an amount equal to at least one change in (2).

[0051] However, these descriptions are merely illustrative; images can also be accumulated when the reciprocation within a predetermined range of the stage 30 is "less than one reciprocation." That is, images accumulated from images of the same shooting object area OBJ as the sample 100 can also be used as images obtained when the stage 30 is "less than one reciprocation." For example, images can also be accumulated at a specific phase (optical distance within a desired range) and an image can be obtained. For example, an image can also be obtained by accumulating multiple images at a specific phase (optical distance within a desired range) specified by the user, such as when it conforms to frontal defocus.

[0052] Thus, according to the optical device 1, the sample is scanned and photographed by the TDI camera while being moved back and forth in a direction perpendicular to the scanning direction, thereby obtaining an image that accumulates the results of photographing the same subject area OBJ under different defocus conditions.

[0053] Therefore, even in cases where the sample 100 has unevenness that can become a source of noise, the influence of the unevenness on the image IMG can be eliminated because both the brightly illuminated and dimly illuminated images of the unevenness are accumulated. As a result, noise caused by the unevenness of the sample 100 in the image IMG can be reduced or even eliminated.

[0054] Therefore, in the inspection apparatus 1000, an image IMG with reduced or even eliminated noise can be used to inspect defects in the sample 100. As a result, according to the inspection apparatus 1000, the influence of noise can be suppressed, thereby improving the inspection precision.

[0055] [Embodiment 2] The optical device of Embodiment 2 will be described. Figure 6 is a schematic diagram showing an example of the configuration of the optical device of Embodiment 2. The optical device 2 is configured to replace the optical system 20 of Embodiment 1 with an optical system 80. The optical system 80 is configured to replace the objective lens 22 of the optical system 20 with an objective lens 82.

[0056] The objective lens 82 is configured to be able to adjust the focal position on the object side, i.e., the sample 100 side. For example, the objective lens 82 is configured as a zoom lens, which can use the change of focal distance of the illumination light L1 used to illuminate the sample 100. In this configuration, the control unit 70 provides a control signal CON3 to the optical system 80, thereby controlling the focal distance of the objective lens 82.

[0057] Furthermore, the objective lens 82 can also be configured in other ways as long as the focal position on the side of the sample 100 can be changed. For example, in the case where the objective lens 82 is a single-focal lens, the position of the objective lens 82 in the Z-axis direction can be changed, thereby changing the focal position of the objective lens 82 relative to the sample 100 in the Z-axis direction.

[0058] Figure 7 is a schematic diagram showing the change in focal distance when the objective lens 82 is configured as a variable focusing lens. As shown in Figure 7, by controlling the objective lens 82, the focal distance of the illumination light L1 can be appropriately changed.

[0059] Accordingly, in the optical device 2, instead of moving the stage 30 back and forth along the Z-axis, the focal position of the optical system 80 on the sample 100 side is moved back and forth along the Z-axis by means of the objective lens 82. In this way, similar to Embodiment 1, the optical distance between the sample 100 and the detector 50 can be changed in a back-and-forth manner within a predetermined range. Therefore, the objective lens 82 can be understood as constituting an optical distance adjustment unit or optical distance adjustment mechanism for changing the optical distance between the sample 100 and the detector 50 within a predetermined range.

[0060] In the above description, although it is explained that the focal position of the optical system on the sample 100 side is changed, the same effect can be obtained even if the focal position on the detector 50 side is changed. That is, the optical system 80 can also be configured such that the focal position of the reflected light L2 from the optical system 80 toward the detector 50 changes in the Z-axis direction. In this case, by moving the focal position of the optical system 80 on the detector 50 side along the Z-axis direction, the optical distance between the sample 100 and the detector 50 can be changed in a reciprocating manner within a predetermined range, just like in Embodiment 1. Furthermore, in the above description, although it is explained that the focal distance of the optical system is changed, the optical system can also be driven and its physical relative position with respect to the sample 100 can be changed, thereby obtaining the same effect. Furthermore, the optical system can also be driven and its physical relative position with respect to the detector 50 can be changed, thereby obtaining the same effect. Depending on the configuration of the optical system, the direction of the focal position change can correspond to the optical axis or it can be other than the Z-axis direction.

[0061] Furthermore, when the optical distance between the sample 100 and the detector 50 is changed, either the focal position on the sample 100 side or the focal position on the detector side of the optical system can be moved, or both can be moved. In addition, as long as the optical distance between the sample 100 and the detector 50 can be changed, other optical elements such as mirrors can be driven to replace the lens or used in conjunction with the lens.

[0062] Therefore, according to this configuration, even without moving the stage in the Z-axis direction, the sample 100 can be photographed in the same way as in Embodiment 1 by changing the optical distance between the sample 100 and the detector 50 through the optical system.

[0063] [Embodiment 3] The optical device of Embodiment 3 will be described. Figure 8 is a schematic diagram showing the configuration of the optical device of Embodiment 3. The optical device 3 is configured to have a detector drive unit 90 added to the optical device 1 of Embodiment 1.

[0064] The detector drive unit 90 is capable of driving the detector 50 in the Z-axis direction. The control unit 70 controls the drive of the detector 50 by the detector drive unit 90 via the control signal CON4. In this way, the detector 50 is moved in the Z-axis direction by moving the detection surface of the detector 50 within a predetermined range at the focal position on the side of the detector 50 including the optical system 20, thereby allowing the optical distance between the sample 100 and the detector 50 to vary within a predetermined range, similar to Embodiment 1. Therefore, the detector drive unit 90 can be understood as constituting an optical distance adjustment unit or optical distance adjustment mechanism for varying the optical distance between the sample 100 and the detector 50 within a predetermined range. The detector drive unit 90 can also move the detector 50 back and forth along a direction corresponding to the optical axis; depending on the configuration of the optical system, this direction can be the Z-axis or other axes.

[0065] Figure 9 is a schematic diagram showing the relationship between the detector 50 and the focal point on the side of the detector 50 of the optical system when the detector 50 is moved in the Z-axis direction. As shown in Figure 9, by moving the detector 50 in the Z-axis direction, the optical distance between the sample 100 and the detector 50 can be appropriately changed.

[0066] Thus, similar to optical device 1 and optical device 2, it is possible to capture images of the sample 100 that accumulate the shooting results in the focused state and the shooting results in the positive side defocused state and the negative side defocused state.

[0067] Therefore, according to this configuration, even without moving the stage in the Z-axis direction, the detector can be driven by the detector drive unit to photograph the sample in the same way as in Embodiment 1 and Embodiment 2.

[0068] [Other Embodiments] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the embodiments described above. Those skilled in the art will understand that various modifications can be made within the scope of the present invention, based on the structure and detailed description of the invention. Furthermore, each embodiment can be appropriately combined with other embodiments.

[0069] The same inspection section 110 as in Embodiment 1 can also be provided in the optical device of Embodiment 2 and Embodiment 3, and can be configured as an inspection device for inspecting defects of the sample 100.

[0070] The optical device described above can be integrated not only into an inspection device, but also into various devices that use the image IMG of the sample 100, such as a review device for displaying the image IMG of the sample 100.

[0071] In the review device for displaying the image IMG of the sample 100, images can also be accumulated at a specific phase (optical distance within a desired range) and images can be acquired, and images can be accumulated when the stage 30 has "returned less than once". For example, in the review device for displaying the image IMG of the sample 100, images obtained by accumulating a plurality of images that meet a specific phase (optical distance within a desired range) can also be acquired and displayed: the specific phase is a specific phase, such as when the image is in frontal or side defocus, based on the result of the specified acquisition unit specified by the user.

[0072] Furthermore, the control unit 70 can also switch between a first mode and a second mode. In the first mode, the control unit 70 controls the optical distance adjustment mechanism by varying the optical distance between the detector 50 and the target area OBJ, and causes the image processing unit 60 to acquire multiple images with different optical path lengths. In the second mode, the control unit 70 maintains a constant optical distance, and causes the image processing unit 60 to acquire multiple images of the target area OBJ at the same optical distance.

[0073] The control unit 70 can also switch between the first mode and the second mode based on the recipe for inspecting or reviewing the sample 100, the characteristics of the sample 100, or the characteristics of the pattern formed on the sample 100. Furthermore, the mode can also be switched based on a mode selection operation performed by the user. For example, in cases where the recipe aims to visualize noise caused by minute surface irregularities, the second mode can be selected. This allows identification of whether the sample 100 and / or the pattern of the sample 100 are sensitive to such noise. Conversely, the second mode can also be used when it is anticipated that the sample 100 and / or the pattern of the sample 100 will have low sensitivity to such noise. On the other hand, in cases where the sample 100 and / or the pattern has high sensitivity to such noise and the recipe aims to reduce or eliminate noise, the first mode can also be selected. Mode selection can also be performed via a graphical user interface (GUI) or by an automated system based on the determination process and / or the characteristics of the sample or pattern.

[0074] The optical system 20 described above is merely an example. Other configurations are possible as long as the illumination light L1 emitted from the light source 10 can illuminate the sample 100 held by the holding unit such as the stage 30, and the secondary light rays from the sample 100 can be imaged onto the detector 50. For example, in the case where the illumination light L1 is EUV light, the optical system 20 can be configured as a reflective optical system to guide the illumination light L1 toward the sample 100. Furthermore, a reflective optical system can also be used to guide the secondary light rays from the sample 100 toward the detector 50.

[0075] The term "optical distance adjustment mechanism" as used herein is not limited to a specific configuration, but includes any mechanical, optical, or electromechanical structure capable of adjusting the optical distance (optical path length) between an object (e.g., a sample) and a detector. For example, an optical distance adjustment mechanism may also include the following: a drive mechanism for moving a stage (holding part) or a sample; a drive mechanism for moving a detector; a lens configuration such as a variable lens that makes the focal position or focal distance variable; an optical system that uses an optical system to change the relative physical position between an optical component (lens, mirror, etc.) and an object or detector, a movable mirror, and / or a reflective component such as a prism to change the optical distance. In other words, any mechanism that substantially produces a change in optical distance can be considered an optical distance adjustment mechanism as long as it includes software-controlled elements and / or programmable optical components and achieves the desired functional effect of changing the optical distance between the object and the detector. Therefore, "optical distance adjustment mechanism" should be interpreted in a broad sense, encompassing all configurations that are functionally equivalent.

[0076] In other embodiments, the stage (holding unit) and / or detector may be configured such that the main surface of the object is tilted at a predetermined angle relative to a plane conjugate to the detection surface of the detector. In this configuration, due to the tilt, the optical distance between the object and the detector varies throughout the object. Furthermore, the control unit can also cause the image processing unit to change the relative position between the target area and the conjugate plane, thereby obtaining images of the target area at different optical path lengths. This change in relative position may also include a component in the direction orthogonal to the tilt axis in the main surface of the object. In this way, it is not necessary to reciprocate the object or the detector in the optical axis direction or the thickness direction of the object to obtain images at multiple optical distances. Thus, the configuration that changes the relative position between the conjugate plane and the target area OBJ by tilting the object surface can also be regarded as an example of the optical distance adjustment mechanism used here.

[0077] In the embodiment described above, although the movement distance ΔZ of stage 30 is represented by phase, ΔZ can also be any fixed distance in the Z-axis direction. Furthermore, the movement distance during one reciprocating cycle of stage 30 can be a fixed value or a variable value. The movement in the Z-axis direction can also be along any waveform, such as a sine wave, a triangular wave, or a combination of these waveforms.

[0078] In the embodiments described above, although the hardware configuration of the optical device of the present invention is mainly described, it is not limited thereto. The optical device of the present invention can also be implemented by executing computer programs to perform arbitrary processing. These processes can also be implemented by executing programs on a computer that includes at least one processor (e.g., a microprocessor, CPU (Central Processing Unit), GPU (Graphics Processing Unit), MPU (Micro Processing Unit), DSP (Digital Signal Processor)). Specifically, it is sufficient to create one or more programs containing instruction sets and supply such programs to the computer, where the instruction sets are algorithms used to enable the computer to perform these signal transmission or signal reception processing.

[0079] Computer programs can be stored and supplied to a computer using various forms of non-transitory computer-readable medium. Non-transitory computer-readable medium includes tangible storage medium having various forms of physical form. Examples of non-transitory computer-readable media include: magnetic recording media (such as flexible disks, magnetic tapes, and hard disk drives), optical magnetic recording media (such as optical discs), CD-ROMs (Compact Disc Read Only Memory), CD-Rs (Compact Disc-Recordable), CD-RWs (Compact Disc ReWritable), and semiconductor memories (such as masked read only memory, PROMs (Programmable Read Only Memory), EPROMs (Erasable Programmable Read Only Memory), flash ROMs, and RAMs (Random Access Memory)). Furthermore, programs can also be supplied to the computer via various forms of transient computer-readable medium. Temporary computer-readable media includes electrical signals, optical signals, and electromagnetic waves. Temporary computer-readable media can supply programs to a computer via wired or wireless communication loops, such as electrical wires and fiber optic cables.

[0080] Hereinafter, an example of the configuration of a computer for implementing an optical device will be shown. Figure 10 is a diagram showing an example of the configuration of a computer for implementing an image processing unit and a control unit of an optical device. The image processing unit and the control unit of the optical device can be implemented by a computer 9000, such as a dedicated computer or a personal computer. However, the computer does not need to exist physically separately, and there can be multiple computers in the case of distributed processing. As shown in Figure 10, the computer 9000 includes, for example, a processor 9001, a ROM (Read Only Memory) 9002, a RAM 9003, a memory unit 9004, a communication interface 9005, and a user interface 9006.

[0081] The processor 9001, ROM 9002, RAM 9003, memory unit 9004, communication interface 9005, and user interface 9006 are connected to each other via bus 9007. Furthermore, descriptions of the OS (operating system) software used to operate the computer are omitted, but it can be appropriately imported into the computer 9000.

[0082] The ROM9002 is constructed, for example, by a non-volatile semiconductor memory device. The ROM9002 stores information such as various programs used in the computer 9000.

[0083] The memory unit 9004 is constructed using various memory devices, such as hard disks and / or solid-state drives (SSDs). Furthermore, the memory unit 9004 is not limited to a memory device integrated into the computer 9000; it can also be an external memory device of the computer 9000. External memory devices can also be cloud storage connected to the computer 9000 via various communication units, such as a network. The memory unit 9004 stores information such as various programs and data used in the computer 9000.

[0084] RAM9003 is constructed using volatile semiconductor memory devices, etc. The program and data used by processor 9001 are appropriately loaded into RAM9003 from one or both of ROM9002 and memory unit 9004.

[0085] The processor 9001 is configured with, for example, a CPU. Furthermore, the processor 9001 may include not only a CPU but also a GPU. GPUs are used for parallel, standardized processing, such as processing in neural networks, thereby increasing processing speed compared to CPUs. The processor 9001 appropriately performs various processes based on various programs stored in ROM 9002 or various programs and data stored in RAM 9003. Furthermore, the processor 9001 may also appropriately store the data generated by processing in RAM 9003 and / or memory 9004.

[0086] The communication interface 9005 is a communication network that connects the computer 9000 to the internet or intranet via various wired or wireless communication units. In this way, the computer 9000 can communicate with other devices, systems, and sensors connected to the communication network.

[0087] The user interface 9006 includes, for example, a display unit that provides information in a manner accessible to the user via a display device or the like; and a sound output unit that outputs sound. Furthermore, the user interface 9006 includes an input unit, such as a keyboard, mouse, and touch panel, which allows the user to input information into the computer 9000 through operation. Additionally, the user interface 9006 may also include sensors or other devices used to acquire information useful to the user.

[0088] Here, although the computer 9000 is described as a device, this description is merely illustrative. The computer 9000 may also be composed of a plurality of physically separate devices. Part of the plurality of devices may be a portable device, and other parts of the plurality of devices may be stationary devices.

[0089] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the embodiments described above. Those skilled in the art will understand that various modifications can be made within the scope of the present invention, based on the structure and detailed description of the invention. Furthermore, each embodiment can be appropriately combined with other embodiments.

[0090] Each diagram is a simple illustration used to depict one or more embodiments. Each diagram may not be associated with only one specific embodiment, but may also be associated with one or more other embodiments. As will be understood by those skilled in the art, in order to create, for example, an unspecified diagram or illustrated embodiment, the various features or steps described with reference to any diagram can be combined with features or steps shown in one or more other diagrams. For the purpose of illustrating an illustrative embodiment, not all features or steps shown in any diagram are necessarily required, and some features or steps may be omitted. The order of steps described in any diagram may also be appropriately changed. [Simplified Explanation of the Diagram]

[0016] [Figure 1] is a diagram showing an example of the configuration of the optical device in Embodiment 1. [Figure 2] is a diagram showing an example of the configuration of the inspection device in Embodiment 1. [Figure 3] is a diagram schematically showing the configuration of the detector. [Figure 4] is a diagram showing an example of the movement of the display stage. [Figure 5] is a diagram schematically showing the passage when photographing a specific area of ​​the sample. [Figure 6] is a diagram schematically showing an example of the configuration of the optical device in Embodiment 2. [Figure 7] is a diagram schematically showing the change of focal distance in the case where the object lens is configured as a zoom lens. [Figure 8] is a diagram schematically showing the configuration of the optical device in Embodiment 3. [Figure 9] is a diagram schematically showing the relationship between the detector and the focal point on the detector side of the optical system when the detector is moved in the Z-axis direction. [Figure 10] is a diagram showing an example of the configuration of the computer used to implement the optical device.

Claims

1. An optical device comprising: a detector for detecting light; an optical system for illuminating an object with illumination light and guiding secondary light generated by the illumination light illuminating the object to the detector; an image processing unit for outputting an image of the object based on the detection result of the secondary light by the detector; an optical distance adjustment unit capable of adjusting the optical distance between the object and the detector; and a control unit for controlling the optical distance adjustment unit in a manner that changes the optical distance between the object and the detector, and controlling the image processing unit in a manner that repeatedly acquires images of the same area of ​​the object based on the detection result of the detector; the image processing unit acquires an image of the area of ​​the object based on the cumulative result of the acquired multiple images of the object.

2. The optical device as described in claim 1, further comprising a holding part and a driving part as the aforementioned optical adjustment unit, wherein the holding part holds the aforementioned object, and the driving part drives the aforementioned holding part; the control part controls the aforementioned driving part in a manner that includes a component in the thickness direction of the aforementioned object and moves the aforementioned holding part, and causes the optical distance between the aforementioned object and the aforementioned detector to change.

3. The optical device as described in claim 1, wherein the aforementioned optical system is configured as the aforementioned optical distance adjustment unit; the aforementioned control unit changes at least one of the focal distances of the aforementioned optical system on the object side or the detector side by changing the optical distance between the aforementioned object and the aforementioned detector.

4. The optical device as described in claim 1, wherein the aforementioned optical system is configured as the aforementioned optical distance adjustment unit; the aforementioned control unit changes at least one of the relative position of the aforementioned optical system relative to the aforementioned object or the relative position of the aforementioned optical system relative to the aforementioned detector by changing the optical distance between the aforementioned object and the aforementioned detector.

5. The optical device as described in claim 1, further comprising: a detector drive unit configured as the aforementioned optical distance adjustment unit for driving the aforementioned detector; the aforementioned control unit controlling the aforementioned detector drive unit in a manner that includes a component in the thickness direction of the aforementioned detector and the aforementioned detector moves, and causing the optical distance between the aforementioned object and the aforementioned detector to change.

6. The optical device as described in any one of claims 3 to 5, further comprising: a holding part for holding the object; and a driving part for driving the holding part; the control part for controlling the driving part, thereby moving the holding part.

7. The optical device as described in claim 1, wherein the detector comprises: a plurality of sensors that detect the secondary light rays and are arranged in a predetermined direction orthogonal to the thickness direction of the detector; the control unit controls the drive unit to move the images of the object acquired by the plurality of sensors along the predetermined direction; and controls the image processing unit to acquire images of the same area of ​​the object acquired by each of the plurality of sensors as the plurality of images, and to acquire an image of the aforementioned area of ​​the object based on the cumulative result of the acquired plurality of images.

8. The optical device as described in claim 7, wherein the aforementioned control unit controls the aforementioned optical distance adjustment unit in two different ways: the optical distance between one of the two adjacent aforementioned sensors and the aforementioned same area of ​​the aforementioned object; and the optical distance between the other of the two adjacent aforementioned sensors and the aforementioned same area of ​​the aforementioned object.

9. The optical device described in any one of claims 1 to 5, wherein the aforementioned control unit controls the aforementioned optical distance adjustment unit in such a way that the optical distance between the aforementioned object and the aforementioned detector is repeated at least once within a predetermined range a predetermined number of times.

10. The optical device as described in claim 9, wherein the predetermined range includes: a predetermined optical distance, wherein the illumination light is focused onto the area of ​​the photographed object that is the object, and the secondary light is focused onto the detector.

11. The optical device as described in claim 10, wherein the aforementioned predetermined optical distance is the optical distance that is the center of the aforementioned predetermined range.

12. The optical apparatus as described in claim 9, wherein the image processing unit accumulates the image of the object during the period in which the optical distance between the object and the detector is repeated a predetermined number of times within the predetermined range.

13. An inspection apparatus comprising: an optical device as described in any one of claims 1 to 5; and an inspection unit that inspects the object based on the image of the object obtained by the image processing unit.

14. A method of taking a picture, performed in an optical device comprising: a detector for detecting light; an optical system for illuminating an object with illumination light and guiding secondary light generated by the illumination light illuminating the object to the detector; and an optical distance adjustment unit capable of adjusting the optical distance between the object and the detector; the method of taking a picture in the optical device, while controlling the optical distance adjustment unit in a manner that changes the optical distance between the object and the detector, acquiring images of the same area of ​​the object multiple times based on the detection results of the detector, and acquiring an image of the area of ​​the object based on the cumulative result of the multiple acquired images of the object.

15. A computer-readable medium storing a program, which is processed by a processing device configured as a computer and performing image capture processing in an optical device; the optical device comprising: a detector for detecting light; an optical system for illuminating an object with illumination light and guiding secondary light generated by the illumination light illuminating the object to the detector; and an optical distance adjustment unit capable of adjusting the optical distance between the object and the detector; the computer-readable medium storing the program causes the processing device to perform the following processing: while controlling the optical distance adjustment unit in a manner that changes the optical distance between the object and the detector, acquiring images of the same area of ​​the object multiple times based on the detection results of the detector; and acquiring an image of the aforementioned area of ​​the object based on the cumulative result of the multiple acquired images of the object.

Images