Optical apparatus, inspection apparatus, imaging method, and program

Abstract

To image a sample with low noise.SOLUTION: The optical system 20 guides reflection light L1 generated by irradiating the sample 100 with the illumination light L2 to the detector 50. The image processing unit 60 outputs an image IMG of the sample 100 according to the detection result of the reflection light L2 by the detector 50. The optical distance adjusting means can adjust the optical distance between the sample 100 and the detector 50. The control unit 70 controls the image processing unit 60 so as to acquire an image of the sample 100 a plurality of times based on the detection result of the detector 50 while controlling the optical distance adjusting means so as to change the optical distance between the detector 50 and the sample 100. The image processing unit 60 acquires an image of the sample 100 based on the integration result of the plurality of acquired images of the sample 100.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an optical device, an inspection device, an imaging method, and a program. [Background technology]

[0002] With the miniaturization of semiconductor process nodes, there is an urgent need for even higher sensitivity in the inspection of semiconductor wafers, photomasks, etc. For example, a technique for inspecting samples such as masks for foreign matter by imaging the sample is widely known (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-161475 [Patent Document 2] Japanese Patent Publication No. 2023-117036 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the sample may have irregularities that are finer than the pattern to be inspected, and therefore, when the sample is imaged, noise caused by the irregularities may be captured.

[0005] The reason why noise caused by minute irregularities is captured in the image is thought to be as follows: It is known that when the focal position of an optical system is shallow relative to a convex object, the image is bright, and when the focal position is deep, the image is dark, and when the focal position of an optical system is shallow relative to a concave object, the image is dark, and when the focal position is deep, the image is bright.It is thought that a similar phenomenon may occur with respect to minute irregularities on the sample.

[0006] As such, when unevenness exists on the sample at a different distance from the optical system than the target position, even if the unevenness is very small, deviation from the focal position will cause light and dark noise in the sample image. This can result in a decrease in the accuracy of inspections performed using sample images. Therefore, there is a need to establish a method for imaging samples while reducing the noise caused by the unevenness of the sample. [Means for solving the problem]

[0007] The optical device according to the present disclosure comprises a detector that detects light, an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector, an image processing unit that outputs an image of the object according to the detection result of the secondary light rays by the detector, an optical distance adjustment means that can adjust the optical distance between the object and the detector, and a control unit that controls the optical distance adjustment means so as to change the optical distance between the object and the detector, while controlling the image processing unit to acquire an image of the object multiple times based on the detection result by the detector, and the image processing unit acquires the image of the object based on the accumulation result of the multiple acquired images of the object.

[0008] The inspection device according to the present disclosure further includes the optical device described above, and an inspection unit that inspects the object based on the image of the object acquired by the image processing unit.

[0009] The imaging method according to the present disclosure is an optical device having a detector that detects light, an optical system that irradiates an object with illumination light and directs secondary light rays generated by irradiating the object with the illumination light to the detector, and an optical distance adjustment means that can adjust the optical distance between the object and the detector, wherein the optical distance adjustment means is controlled so that the optical distance between the object and the detector changes, and images of the object are acquired multiple times based on the detection results of the detector, and an image of the object is acquired based on the accumulation result of the multiple acquired images of the object.

[0010] The program disclosed herein causes a processing device configured as a computer that performs imaging processing in an optical device having a detector that detects light, an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector, and an optical distance adjustment means that can adjust the optical distance between the object and the detector to perform the following processing: acquiring images of the object multiple times based on the detection results of the detector while controlling the optical distance adjustment means so as to change the optical distance between the object and the detector; and acquiring an image of the object based on the accumulation result of the multiple acquired images of the object.

[0011] The optical device according to the present disclosure includes a detector that detects light, an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector, an image processing unit that outputs an image of the object according to the detection result of the secondary light rays by the detector, a holding unit that holds the object, a drive unit that drives the holding unit, and a control unit that controls the drive unit to move the holding unit including a component in the thickness direction of the object, thereby changing the optical distance between the object and the detector, and controls the image processing unit to acquire images of the object multiple times based on the detection result by the detector, and the image processing unit acquires the image of the object based on the accumulation result of the multiple acquired images of the object.

[0012] The optical device according to the present disclosure includes a detector that detects light, an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector, an image processing unit that outputs an image of the object according to the detection result of the secondary light rays by the detector, and a control unit that controls the optical system and the image processing unit to acquire an image of the object multiple times based on the detection result by the detector while changing at least one of the focal length on the object side or the detector side of the optical system so that the optical distance between the object and the detector changes, and the image processing unit acquires the image of the object based on the accumulation result of the acquired multiple images of the object.

[0013] The optical device according to the present disclosure includes a detector that detects light, an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector, an image processing unit that outputs an image of the object according to the detection result of the secondary light rays by the detector, and a control unit that controls the optical system and the image processing unit to acquire an image of the object multiple times based on the detection result by the detector while changing at least one of the relative position of the optical system with respect to the object or the relative position of the optical system with respect to the detector so that the optical distance between the object and the detector changes, and the image processing unit acquires the image of the object based on the accumulation result of the acquired multiple images of the object.

[0014] The optical device according to the present disclosure includes a detector that detects light, an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector, an image processing unit that outputs an image of the object according to the detection result of the secondary light rays by the detector, an optical distance adjustment means that can adjust the optical distance between the object and the detector, a detector driving unit that drives the detector, and a control unit that controls the detector driving unit to move the detector including a component in the thickness direction of the detector, thereby controlling the image processing unit to acquire images of the object multiple times based on the detection result by the detector while changing the optical distance between the object and the detector, and the image processing unit acquires the image of the object based on the integration result of the multiple acquired images of the object. [Effects of the Invention]

[0015] According to the present disclosure, it is possible to image a sample with low noise. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 illustrates an example of a configuration of an optical device according to a first embodiment. [Figure 2] FIG. 1 illustrates an example of a configuration of an inspection device according to a first embodiment. [Figure 3] FIG. 2 is a diagram schematically illustrating the configuration of a detector. [Figure 4] FIG. 10 is a diagram illustrating an example of movement of a stage. [Figure 5] 1A to 1C are diagrams showing a schematic diagram of the process of imaging a specific region of a sample. [Figure 6] FIG. 10 is a diagram schematically illustrating a configuration of an optical device according to a second embodiment. [Figure 7] FIG. 10 is a diagram schematically showing a change in focal length when the objective lens is configured as a zoom lens. [Figure 8] FIG. 10 is a diagram schematically illustrating a configuration of an optical device according to a third embodiment. [Figure 9]10 is a diagram schematically showing the relationship between the detector and the focal point of the optical system on the detector side when the detector is moved in the Z-axis direction. FIG. [Figure 10] FIG. 10 is a diagram illustrating an example of the configuration of a computer for realizing the optical device. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, a specific configuration of this embodiment will be described with reference to the drawings. The following description shows a preferred embodiment of the present disclosure, and the scope of the present disclosure is not limited to the following embodiment. In the following description, parts with the same reference numerals indicate substantially the same content.

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

[0019] Fig. 1 is a diagram illustrating a configuration example of an optical device according to embodiment 1. Fig. 2 is a diagram illustrating a configuration example of an inspection device according to embodiment 1. As shown in Fig. 2, an inspection unit 110 of an inspection device 1000 inspects a sample 100 for abnormalities, such as defects, based on an image IMG of the sample 100 captured by the optical device 1.

[0020] The following describes the optical device 1. As shown in Fig. 1, the optical device 1 includes a light source 10, an optical system 20, a stage 30, a driving mechanism 40, a detector 50, an image processing unit 60, and a control unit 70. Note that the optical device 1 may include optical members other than these.

[0021] Here, for ease of explanation of the optical device 1, an XYZ Cartesian coordinate system will be introduced. The stage surface 31, which is the main surface of the stage 30 on which the sample 100 is placed, is defined as an XY plane parallel to the X-axis direction and the Y-axis direction. The direction perpendicular to the stage surface 31 is defined as the Z-axis direction. For example, the +Z-axis direction is referred to as the upward direction, and the -Z-axis direction is referred to as the downward direction. Note that the terms upward and downward are used for ease of explanation and do not indicate the actual orientation of the optical device 1.

[0022] The light source 10 emits illumination light L1 to the optical system 20. The light source 10 may be a lamp light source, an LED (Light Emitting Diode) light source, a laser light source, or the like. The illumination light L1 may be, for example, visible light, ultraviolet light, or EUV (Extreme Ultraviolet) light.

[0023] The optical system 20 consists of a beam splitter 21, an objective lens 22, and a relay lens 23, and constitutes an imaging optical system that irradiates the illumination light L1 emitted from the light source 10 onto a sample 100 placed on a stage 30 and forms an image of the reflected light L2 from the sample 100 on a detector 50.

[0024] The beam splitter 21 is, for example, a half mirror, and reflects approximately half of the illumination light L1 toward the objective lens 22. The objective lens 22 illuminates the illumination light L1 onto an imaging target area of ​​the sample 100 placed on the stage surface of the stage 30.

[0025] Reflected light L2 generated when illumination light L1 illuminates sample 100 is collected by objective lens 22 and then enters beam splitter 21. Beam splitter 21 transmits approximately half of the reflected light L2. Reflected light L2 that has passed through beam splitter 21 is collected by relay lens 23 and then enters detector 50. As a result, an image of sample 100 is formed on detector 50.

[0026] For ease of explanation, the figure shows representative optical elements included in the optical system 20, but the optical system 20 may be provided with various optical elements such as lenses, optical scanners, mirrors, filters, and beam splitters (not shown). Furthermore, for example, the optical system 20 may be a confocal optical system. Furthermore, when light with a short wavelength, such as EUV light, is used as the illumination light L1, the optical system 20 may be a reflective optical system.

[0027] Furthermore, in FIG. 1, the optical device 1 has been described as an optical device of a bright field illumination type, but the illumination type 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 a secondary light ray generated when the sample 100 is illuminated with the illumination light L1. However, the secondary light ray is not limited to reflected light. The secondary light ray may be any of various light rays generated when the sample 100 is illuminated with the illumination light L1, such as reflected light, scattered light, fluorescent light, or transmitted light.

[0029] As described above, the sample 100 is placed on the stage surface 31, which is the upper surface of the stage 30. Therefore, the thickness direction (which may also be called the height direction) of the sample 100 is the Z-axis direction. The sample 100 is, for example, a photomask in which a fine pattern 102 is formed on a flat plate member 101 such as a mask blank, or a semi-finished product in a semiconductor process in which a device pattern is formed on a flat plate member, such as a wafer. The pattern 102 of the sample 100 is formed, for example, by a layer of an opaque member laminated on the flat plate member 101 that is transparent to the illumination light L1, or by laminating an absorber layer that mainly absorbs the illumination light L1 on a multilayer layer that mainly reflects the illumination light L1.

[0030] The stage 30 is a three-dimensional drive stage provided with a drive mechanism 40. The control unit 70 controls the drive mechanism 40, so that the stage 30 is driven along each of the X-axis, Y-axis, and Z-axis, or further rotates around the axes. The stage 30 is an example of a holder that holds the sample 100. The holder may be configured other than the stage 30, such as a holder with an electrostatic chuck or a robot arm, as long as it can be driven while holding the sample 100. A method for driving the stage 30, which is an example of a method for driving the holder, will be described in detail later.

[0031] The detector 50 acquires an image of the sample 100 by detecting reflected light L2 from the sample 100 that is imaged via the optical system 20. The detector 50 may be a camera based on various imaging principles that are applicable to TDI cameras, such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor.

[0032] FIG. 3 is a diagram schematically illustrating the configuration of the detector 50. The detector 50 has N line sensors 51 arranged at a predetermined pitch P in the X-axis direction on the surface onto which light is incident. Here, N is an integer equal to or greater than 2, which is the number of line sensors 51 arranged in the X-axis direction. Each line sensor 51 has a plurality of pixels arranged in the Y-axis direction. FIG. 3 illustrates an example in which nine line sensors 51 are arranged in the X-axis direction, and each line sensor 51 has nine pixels arranged in the Y-axis direction. Note that the number of line sensors arranged is merely an example, and a number of line sensors other than nine may be arranged. The number of pixels arranged is merely an example, and a number of pixels other than nine may be arranged.

[0033] In the inspection device 1 according to this embodiment, the detector 50 and the image processing unit 60 are configured as a TDI (Time Delay Integration) camera that captures an image of the sample 100. The detector 50 outputs a detection signal DAT indicating 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 to obtain an image of the sample 100.

[0035] The control unit 70 can drive the stage 30 in a desired direction and at a desired speed by providing a control signal CON1 to the drive mechanism 40. The control unit 70 can also control the imaging process in the image processing unit 60 by providing a control signal CON2 to the image processing unit 60. This allows the control unit 70 to cause the image processing unit 60 to capture an image when the stage 30 moves to a desired position. As a result, the movement of the stage 30 and the imaging timing in the image processing unit 60 can be synchronized.

[0036] Next, we will explain the relationship between the driving of the stage 30 and the imaging timing in the optical device 1. In the optical device 1, the stage 30 can perform reciprocating motion at a predetermined cycle and a predetermined amplitude in the optical axis direction of the illumination light L1, i.e., in the Z-axis direction which is the thickness direction of the sample 100. As a result, the stage 30 can be understood to constitute an optical distance adjustment means which changes the optical distance between the sample 100 and the detector 50 within a predetermined range.

[0037] Furthermore, the stage 30 can move in either or both of the X-axis and Y-axis directions while reciprocating in the Z-axis direction. In this embodiment, for the sake of simplicity, it is assumed that the stage 30 moves in the X-axis direction while reciprocating in the Z-axis direction. This allows each of the line sensors 51 of the detector 50 to sequentially capture images of specific positions on the sample 100.

[0038] In the inspection device 1, the left line sensor of two adjacent line sensors images a specific area of ​​the sample 100, and then the right line sensor images the same specific area of ​​the sample 100. By repeating this procedure sequentially, the same specific area of ​​the sample 100 can be imaged by each line sensor at different times.

[0039] In the optical device 1, the control unit 70 controls the stage 30 and the image processing unit 60 so that the movement of the sample 100 in the X-axis direction is synchronized with the timing of imaging. As a result, the image processing unit 60 acquires an image of the sample 100 every time the sample 100 moves by a predetermined pitch ΔX in the X-axis direction and a predetermined pitch ΔZ in the Z-axis direction.

[0040] The lateral magnification of the image of the sample 100 projected onto the detector 50 by the optical system 20 is denoted by β. By performing an image capture each time the stage 30 moves the sample 100 in the +X direction by ΔX=P / β under the control of the control unit 70, the same specific region of the sample 100 can be imaged by each of the line sensors 51 at different positions in the Z-axis direction with a time difference.

[0041] Furthermore, in the optical device 1, the stage 30 is driven in the X-axis direction while being reciprocated in the Z-axis direction. That is, while the stage 30 makes one reciprocating movement in the Z-axis direction, images of the sample 100 are captured multiple times.

[0042] Here, the number of times imaging is performed while the stage 30 makes one reciprocating movement along the Z-axis direction is defined as q, where q is an integer equal to or greater than 2. At this time, by making the stage 30 reciprocate at least once in the Z-axis direction while an image of a specific position on the sample 100 (hereinafter referred to as the imaging target area) crosses the detector 50 in the X-axis direction, the imaging target area of ​​the sample 100 can be continuously imaged multiple times by the multiple line sensors 51 in a range between a positive defocus state and a negative defocus state relative to a specific optical distance (which may be referred to as a predetermined optical distance) at which the pattern 102 on the sample 100 is focused on the detector 50. The specific optical distance may be determined depending on the application of the optical device 1, and may be, for example, the optical distance at which the illumination light L1 is focused within the imaging target area of ​​the sample 100 and the secondary light ray L2 is focused on the detector 50. Furthermore, the area of ​​the sample 100 on which the illumination light L1 is focused (i.e., the area of ​​the sample 100 to be imaged) may be determined according to the application of the optical device 1, and may be, for example, the transparent substrate layer (or multilayer layer) of the sample 100, the pattern 102 (opaque layer or absorber layer) of the sample 100, or the thickness-wise position of the sample 100 between the pattern 102 (opaque layer or absorber layer) of the sample 100 and the transparent substrate layer (or multilayer layer) of the sample 100.

[0043] As described above, the detector 50 and the image processing unit 60 constitute a TDI camera, and multiple imaging results obtained by imaging the imaging target area of ​​the sample 100 multiple times under different focus conditions are accumulated.

[0044] This allows the influence of noise when the irregularities are negatively defocused to be offset by the influence of noise when the irregularities are positively defocused, even if the sample 100 has minute irregularities. As a result, an image of the sample 100 can be acquired while reducing the influence of noise.

[0045] The relationship between the reciprocating motion of the sample 100 in the Z-axis direction and the timing of imaging will be described using a specific example. Figure 4 is a diagram showing an example of stage movement. In this example, a case will be described in which the stage 30 makes one reciprocating motion while the image of the imaging target region OBJ of the sample 100 traverses the nine line sensors 51 of the detector 50 shown in Figure 3. In this case, the number of times q that imaging is performed while the stage 30 makes one reciprocating motion in the Z-axis direction is 9.

[0046] The initial position of the stage 30 is (X, Z) = (0, 0), and the initial time is T0. The stage 30 is driven so that the Z-axis position at the first image capture and the Z-axis position at the last image capture during one reciprocation are the same. In the following, to facilitate understanding of the reciprocating movement of the stage 30, the initial position of the stage is represented as 0, and the movement pitch ΔZ is represented as a phase in units of π / 4. In other words, when k is an integer between 0 and q-1, the coordinate Zk of the stage 30 in the Z-axis direction at timing Tk is expressed by the following equation: Z k =k·ΔZ=k·2π / (q-1)=k·π / 4 [1] The coordinate Xk in the X-axis direction is expressed by the following equation. X k =k ΔX [2]

[0047] That is, when nine images are captured while the stage 30 makes one round trip in the Z-axis direction, the coordinates of the stage 30 at the imaging timings T0 to T8 are as follows: The coordinates (X8, Z8) of the stage 30 at the imaging timing T8 may be set to the coordinates of the initial position (0, 0) for another different imaging target region OBJ of the sample 100. That is, the imaging timing T8 may be set to the first imaging timing T0 for another different imaging target region OBJ of the sample 100, and the following movement of the coordinates of the stage 30 may 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 the stage 30 has an initial position (X0, Z0) = (0, 0) and moves along a sine wave with an amplitude of A for the coordinate in the Z-axis direction, the coordinates of the stage 30 will be as follows: (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] FIG. 5 shows the imaged area OBJ of the sample 100. of5 is a diagram schematically illustrating the process of imaging. In FIG. 5, as an example, nine lines of line sensors 51 are arranged in the X direction. At each imaging timing, the stage 30 is driven so that the image of the imaging target area OBJ moves in the +X direction by the distance of one line sensor, so that the imaging target area OBJ sequentially shifts one line at a time in the +X direction. Because the detector 50 is configured as a TDI camera sensor, the charge of the line sensor that captured the imaging target area OBJ at the previous imaging timing is transferred to the adjacent line sensor 51 in the +X direction. Then, as the line sensor 51 to which the charge has been transferred further captures an image of the imaging target area OBJ, further charge is accumulated.

[0049] Furthermore, as described above, because the stage 30 moves by π / 4 along the Z-axis direction at each imaging timing, imaging results in different focus states are integrated into the images of the imaging target area OBJ imaged sequentially by the nine line sensors 51. Note that the image imaged by the ninth line sensor 51 does not need to be integrated because its Z phase is the same as that of the initial position. In this case, the images of the imaging target area OBJ imaged sequentially by the eight line sensors 51 are integrated.

[0050] Therefore, in this configuration, the period during which the stage 30 makes one reciprocating movement in the Z-axis direction is synchronized with the period during which the imaging results of the multiple line sensors are integrated, i.e., the period during which multiple images are acquired to be integrated as an image of the same imaging target region OBJ of the sample 100. For example, the period during which the imaging results of the multiple line sensors for the same imaging target region OBJ of the sample 100 are integrated to acquire an image of that imaging target region OBJ (i.e., the period during which multiple images are acquired to be integrated as an image of the same imaging target region OBJ of the sample 100) is an integer multiple of one or more of the period during which the stage 30 makes one reciprocating movement in the Z-axis direction. In other words, the stage 30 may be reciprocated in the Z-axis direction one or more integer times, or at least once, during one period during which multiple images are acquired to be integrated as an image of the same imaging target region OBJ of the sample 100. Furthermore, as images of the same imaging target area OBJ of the sample 100, at least (1) an image when the optical distance between the sample 100 and the detector 50 is a specific optical distance, (2) an 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 amount, and (3) an image when the optical distance between the sample 100 and the detector 50 is shorter than the specific optical distance by at least one change amount equal to the change amount in (2).

[0051] However, these explanations are merely examples, and images obtained when the stage 30 makes "less than one round trip" within a predetermined range may be accumulated. In other words, the images accumulated as images of the same imaging target region OBJ of the sample 100 may be images obtained when the stage 30 makes "less than one round trip." For example, an image may be acquired by accumulating images at a specific phase (a desired range of optical distance). For example, an image may be acquired by accumulating multiple images obtained when the stage 30 makes a specific phase (a desired range of optical distance) designated by the user, such as during positive defocus.

[0052] In this way, with the optical device 1, the sample is scanned and imaged with the TDI camera while being moved back and forth in a direction perpendicular to the scanning direction, thereby obtaining an image that is the sum of the results of imaging the same imaging target area OBJ under different focus conditions.

[0053] Therefore, even if there are uneven portions on the sample 100 that are a source of noise, the images of the uneven portions that appear bright and the images of the uneven portions that appear dark are integrated, so the influence of the uneven portions on the image IMG can be canceled out. As a result, noise in the image IMG that is caused by the unevenness of the sample 100 can be reduced or removed.

[0054] Therefore, the inspection device 1000 can use the image IMG in which noise has been reduced or removed to inspect defects in the sample 100. As a result, the inspection device 1000 can improve inspection accuracy by suppressing the influence of noise.

[0055] Embodiment 2 An optical device according to a second embodiment will be described. Fig. 6 is a diagram schematically illustrating the configuration of the optical device according to the second embodiment. The optical device 2 has a configuration in which the optical system 20 according to the first embodiment is replaced with an optical system 80. The optical system 80 has a configuration in which the objective lens 22 of the optical system 20 is replaced with an objective lens 82.

[0056] The objective lens 82 is configured as a lens that can adjust the focal position on the objective side, i.e., the side of the sample 100. For example, the objective lens 82 is configured as a zoom lens that can change the focal length of the illumination light L1 that illuminates the sample 100. In this configuration, the control unit 70 can control the focal length of the objective lens 82 by providing a control signal CON3 to the optical system 80.

[0057] The objective lens 82 may have other configurations as long as the focal position on the side of the sample 100 can be changed. For example, if the objective lens 82 is a single focal lens, the focal position of the objective lens 82 relative to the sample 100 can be changed in the Z-axis direction by changing the position of the objective lens 82 in the Z-axis direction.

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

[0059] As a result, in the optical device 2, instead of moving the stage 30 back and forth along the Z-axis direction, the focal position on the sample 100 side of the optical system 80 is moved along the Z-axis direction by the objective lens 82, thereby making it possible to change the optical distance between the sample 100 and the detector 50 so that it moves back and forth within a predetermined range, as in embodiment 1. As a result, the objective lens 82 can be understood to constitute an optical distance adjustment means that changes the optical distance between the sample 100 and the detector 50 within a predetermined range.

[0060] Although the above description has been given assuming that the focal position of the optical system on the sample 100 side is changed, the same effect can be achieved by changing the focal position on the detector 50 side. That is, the optical system 80 may be configured so that the focal position of the reflected light L2 traveling from the optical system 80 toward the detector 50 can be changed 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 so as to move back and forth within a predetermined range, as in the first embodiment. Furthermore, although the above description has been given assuming that the focal length of the optical system is changed, the same effect can be achieved by driving the optical system to change the physical position of the optical system relative to the object 100. Furthermore, the same effect can be achieved by driving the optical system to change the physical position of the optical system relative to the detector 100.

[0061] Furthermore, when changing the optical distance between the sample 100 and the detector 50, either the focal position on the sample 100 side of the optical system or the focal position on the detector side may be moved, or both may be moved. Furthermore, if the optical distance between the sample 100 and the detector 50 can be changed, other optical elements such as mirrors may be driven instead of or in addition to the lenses.

[0062] Therefore, with this configuration, the sample can be imaged in the same way as in embodiment 1 by changing the optical distance between the sample 100 and the detector 50 in the optical system without moving the stage in the Z-axis direction.

[0063] Embodiment 3 An optical device according to a third embodiment will be described. Fig. 8 is a diagram schematically illustrating the configuration of the optical device according to the third embodiment. The optical device 3 has a configuration in which a detector driving unit 90 is added to the optical device 1 according to the first embodiment.

[0064] The detector driving unit 90 can drive the detector 50 in the Z-axis direction. The control unit 70 controls the driving of the detector 50 by the detector driving unit 90 using a control signal CON4. As a result, by moving the detector 50 back and forth in the Z-axis direction so that the detection surface of the detector 50 moves within a predetermined range including the focal position on the detector 50 side of the optical system 20, the optical distance between the sample 100 and the detector 50 can be changed within a predetermined range, as in the first embodiment. As a result, the detector driving unit 90 can be understood to constitute an optical distance adjustment means that changes the optical distance between the sample 100 and the detector 50 within a predetermined range.

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

[0066] This makes it possible to capture an image of the sample 100 by integrating the imaging results in a focused state, the imaging results in a defocused state on the positive side, and the imaging results in a defocused state on the negative side, similar to the optical devices 1 and 2.

[0067] Therefore, according to this configuration, the sample can be imaged in the same way as in the first and second embodiments by driving the detector with the detector driving unit, without moving the stage in the Z-axis direction.

[0068] Other embodiments Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0069] It goes without saying that an inspection device for inspecting defects in the sample 100 can be configured by providing the optical devices according to the second and third embodiments with the inspection unit 110 in the same manner as in the first embodiment.

[0070] The optical device according to the above-described embodiment may be incorporated not only into an inspection device but also into various devices that use an image IMG of the sample 100, such as a review device that displays an image IMG of the sample 100.

[0071] In a review device that displays an image IMG of the sample 100, images when the stage 30 makes "less than one round trip" may be accumulated, such as by accumulating images at a specific phase (a desired range of optical distance) to acquire an image. For example, a review device that displays an image IMG of the sample 100 may acquire and display an image that is an accumulation of multiple images at a specific phase (a desired range of optical distance), such as at a positive defocus, specified based on the result of a designation acquisition means that accepts designation from a user.

[0072] The optical system 20 described above is merely an example, and other configurations may be used as long as the illumination light L1 emitted from the light source 10 can be irradiated onto the sample 100 held by the stage 30 or other holding means, and secondary light rays from the sample 100 can be imaged on the detector 50. For example, if the illumination light L1 is EUV light, the optical system 20 may be configured as a reflective optical system to guide the illumination light L1 to the sample 100. Furthermore, the secondary light rays from the sample 100 may be guided to the detector 50 by a reflective optical system.

[0073] In the above-described embodiment, the movement pitch ΔZ of the stage 30 is expressed as a phase, but ΔZ may be any constant distance in the Z-axis direction. Furthermore, the movement pitch during one reciprocation of the stage 30 may be a constant value or a variable value. The movement in the Z-axis direction may be performed according to any waveform, such as a sine wave, a triangular wave, or a waveform that is a combination of these.

[0074] In the above-described embodiments, the optical device according to the present disclosure has been described primarily as a hardware configuration, but this is not limiting. The optical device according to the present disclosure can also be realized by having a computer execute a computer program to perform any desired processing. These processes may be realized by having a computer including at least one processor (e.g., a microprocessor, a CPU, a GPU, an MPU, or a DSP (Digital Signal Processor)) execute the program. Specifically, one or more programs including instructions for causing a computer to perform these algorithms related to transmission signal processing or reception signal processing may be created, and the programs may be supplied to the computer.

[0075] A computer program can be stored and supplied to a computer using various types of non-transitory computer-readable media. Non-transitory computer-readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic storage media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical storage media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / Ws, and semiconductor memories (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, and RAMs (Random Access Memory)). The program may also be supplied to a computer by various types of transitory computer-readable media. Examples of transitory computer-readable media include electrical signals, optical signals, and electromagnetic waves. The transitory computer-readable media can supply the program to a computer via a wired communication path such as an electric wire or optical fiber, or via a wireless communication path.

[0076] An example of the configuration of a computer for realizing the optical device is shown below. FIG. 10 is a diagram showing an example of the configuration of a computer for realizing the image processing unit and control unit of the optical device. The image processing unit and control unit of the optical device can be realized by a computer 9000 such as a dedicated computer or a personal computer (PC). However, the computer does not need to be physically single, and may be multiple when performing distributed processing. As shown in FIG. 10, the computer 9000 has, for example, a processor 9001, a ROM (Read Only Memory) 9002, a RAM (Random Access Memory) 9003, a storage unit 9004, a communication interface 9005, and a user interface 9006.

[0077] The processor 9001, ROM 9002, RAM 9003, storage unit 9004, communication interface 9005, and user interface 9006 are connected to each other so as to be able to communicate with each other via a bus 9007. Note that although explanation of OS software for operating the computer is omitted, it is also installed in the computer 9000 as appropriate.

[0078] The ROM is configured by, for example, a nonvolatile semiconductor memory device, etc. The ROM 9002 stores information such as various programs used by the computer 9000.

[0079] The storage unit 9004 is configured by various storage devices such as a hard disk, a solid state disk, etc. Furthermore, the storage unit 9004 is not limited to a storage device installed in the computer 9000, but may be a storage device external to the computer 9000. The external storage device may be a cloud storage connected to the computer 9000 via various communication means, for example, a network. The storage unit 9004 stores information such as various programs and data used by the computer 9000.

[0080] The RAM 9003 is configured by a volatile semiconductor memory device, etc. Programs, data, and other information used by the processor 9001 are loaded into the RAM 9003 from one or both of the ROM 9002 and the storage unit 9004 as appropriate.

[0081] The processor 9001 may be configured with, for example, a CPU (Central Processing Unit). The processor 9001 may also include not only a CPU but also a GPU (Graphics Processing Unit). A GPU is suitable for performing routine processing in parallel, and when applied to processing in a neural network, for example, it can improve processing speed compared to a CPU. The processor 9001 executes various processes based on various programs stored in the ROM 9002 or various programs and data held in the RAM 9003, as appropriate. The processor 9001 may also store data generated by processing in the RAM 9003 or the storage unit 9004, as appropriate.

[0082] The communication interface 9005 is an interface that connects the computer 9000 to a communication network such as the Internet or an intranet via various wired communication means or wireless communication means, etc. This allows the computer 9000 to communicate with other devices, systems, sensors, etc. that are connected to the communication network.

[0083] The user interface 9006 includes, for example, a display unit that provides information so that the user can recognize it using a display device or the like, and an audio output unit that outputs audio. The user interface 9006 also includes an input unit that allows the user to input information to the computer 9000 by operating a keyboard, mouse, touch panel, or the like. The user interface 9006 may also include devices such as sensors that obtain information useful to the user.

[0084] Although the computer 9000 has been described as a single device here, this is merely an example. The computer 9000 may be configured as multiple physically separated devices. Some of the multiple devices may be portable devices, and other devices may be stationary devices.

[0085] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0086] Each drawing is merely an example for describing one or more embodiments. Each drawing may relate not only to one particular embodiment, but also to one or more other embodiments. As will be understood by those skilled in the art, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings to create, for example, an embodiment not explicitly shown or described. Not all features or steps shown in any one drawing are necessary to describe an exemplary embodiment, and some features or steps may be omitted. The order of steps described in any drawing may be changed as appropriate. [Explanation of symbols]

[0087] 1~3 Optical device 10 light source 20, 80 optical system 21 Beam splitter 22, 82 objective lenses 23 Relay Lens 30 stages 31 Stage surface 40 Drive mechanism 50 detectors 51 Line sensor 60 Image processing section 70 Control Unit 90 Detector driver 100 samples 101 Flat plate member 102 patterns 110 Inspection Department 1000 Inspection Equipment 9000 computers 9001 processor 9002 ROM 9003 RAM 9004 Storage section 9005 Communication Interface 9006 User Interface 9007 Bus CON1~CON4 control signals DAT detection signal L1 illumination light L2 reflected light OBJ Image capture area

Claims

1. a detector for detecting light; an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector; an image processing unit that outputs an image of the object in accordance with a detection result of the secondary light beam by the detector; an optical distance adjusting means capable of adjusting the optical distance between the object and the detector; a control unit that controls the image processing unit to acquire images of the object multiple times based on the detection result by the detector while controlling the optical distance adjustment means so as to change the optical distance between the object and the detector, the image processing unit acquires the image of the object based on an integration result of the acquired multiple images of the object. optical equipment.

2. The optical distance adjusting means further includes a holding unit that holds the object and a driving unit that drives the holding unit, the control unit controls the drive unit to move the holding unit, including a component in a thickness direction of the object, thereby changing the optical distance between the object and the detector. The optical device according to claim 1 .

3. the optical system is configured as the optical distance adjustment means, the control unit changes at least one of a focal length of the optical system on the object side or the detector side so as to change an optical distance between the object and the detector; 10. The optical device of claim 1.

4. the optical system is configured as the optical distance adjustment means, the control unit changes at least one of a relative position of the optical system with respect to the object and a relative position of the optical system with respect to the detector so that an optical distance between the object and the detector changes.

10. The optical device of claim 1.

5. a detector driving unit that drives the detector and constitutes the optical distance adjusting means; the control unit controls the detector driving unit so that the detector moves including a component in a thickness direction of the detector, thereby changing the optical distance between the object and the detector.

10. The optical device of claim 1.

6. a holding unit that holds the object; a drive unit that drives the holding unit, The control unit controls the drive unit to move the holding unit.

6. An optical device according to any one of claims 3 to 5.

7. the detector includes a plurality of sensors that detect the secondary light beam and are arranged in a predetermined direction perpendicular to a thickness direction of the detector; The control unit controlling the drive unit to drive the holding unit so that the images of the object acquired by the plurality of sensors move along the predetermined direction; acquiring images of the same region of the object as the plurality of images by each of the plurality of sensors, and controlling the image processing unit to acquire images of the same position of the object based on an integration result of the acquired plurality of images.

3. The optical device according to claim 2.

8. the control unit controls the optical distance adjustment means so that an optical distance between one of the two adjacent sensors and the same region of the object is different from an optical distance between the other of the two adjacent sensors and the same region of the object.

8. The optical device according to claim 7.

9. the control unit controls the optical distance adjustment means so that the optical distance between the object and the detector reciprocates within a predetermined range at least once or a predetermined number of times.

6. An optical device according to any one of claims 1 to 5.

10. the predetermined range includes a predetermined optical distance at which the illumination light is focused within an area of ​​the object to be imaged and the secondary light beam is focused onto the detector; 10. The optical device according to claim 9.

11. the predetermined optical distance is an optical distance at the center of the predetermined range; 11. The optical device according to claim 10.

12. the image processing unit integrates the images of the object acquired while the optical distance between the object and the detector reciprocates within the predetermined range the predetermined number of times; 10. The optical device according to claim 9.

13. An optical device according to any one of claims 1 to 5; an inspection unit that inspects the object based on the image of the object acquired by the image processing unit, Inspection equipment.

14. An optical device having a detector that detects light, an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector, and optical distance adjustment means that can adjust the optical distance between the object and the detector, acquiring an image of the object multiple times based on the detection result of the detector while controlling the optical distance adjustment means so that the optical distance between the object and the detector changes; acquiring an image of the object based on an integration result of the acquired multiple images of the object; Imaging method.

15. a processing device configured as a computer that performs imaging processing in an optical device having a detector that detects light, an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector, and an optical distance adjustment means that can adjust the optical distance between the object and the detector, a process of acquiring an image of the object multiple times based on a detection result by the detector while controlling the optical distance adjustment means so as to change the optical distance between the object and the detector; and performing a process of acquiring an image of the object based on an integration result of the acquired multiple images of the object. program.

16. a detector for detecting light; an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector; an image processing unit that outputs an image of the object in accordance with a detection result of the secondary light beam by the detector; a holding unit that holds the object; a drive unit that drives the holding unit; a control unit that controls the drive unit so that the holding unit moves while including a component in the thickness direction of the object, and controls the image processing unit so that an image of the object is acquired multiple times based on the detection result by the detector while changing the optical distance between the object and the detector, the image processing unit acquires the image of the object based on an integration result of the acquired multiple images of the object. optical equipment.

17. a detector for detecting light; an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector; an image processing unit that outputs an image of the object in accordance with a detection result of the secondary light beam by the detector; a control unit that controls the optical system and the image processing unit to acquire an image of the object multiple times based on the detection result by the detector while changing at least one of a focal length of the optical system on the object side or the detector side so that an optical distance between the object and the detector changes; the image processing unit acquires the image of the object based on an integration result of the acquired multiple images of the object. optical equipment.

18. a detector for detecting light; an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector; an image processing unit that outputs an image of the object in accordance with a detection result of the secondary light beam by the detector; a control unit that controls the optical system and the image processing unit to acquire an image of the object multiple times based on the detection result by the detector while changing at least one of a relative position of the optical system with respect to the object and a relative position of the optical system with respect to the detector so that an optical distance between the object and the detector changes; the image processing unit acquires the image of the object based on an integration result of the acquired multiple images of the object. optical equipment.

19. a detector for detecting light; an optical system that irradiates an object with illumination light and guides secondary light rays generated by irradiating the object with the illumination light to the detector; an image processing unit that outputs an image of the object in accordance with a detection result of the secondary light beam by the detector; an optical distance adjusting means capable of adjusting the optical distance between the object and the detector; a detector driving unit that drives the detector; a control unit that controls the detector drive unit so that the detector moves including a component in the thickness direction of the detector, and controls the image processing unit so that an image of the object is acquired multiple times based on the detection result of the detector while changing the optical distance between the object and the detector, the image processing unit acquires the image of the object based on an integration result of the acquired multiple images of the object. optical equipment.

Images