Optical apparatus, inspection apparatus, imaging method, and program

Abstract

The sample is imaged with low noise. [Solution] The optical system 20 guides reflected light L2, generated by irradiating the sample 100, which is tilted with respect to a plane conjugate to the detection surface 50A of the detector 50, with illumination light L1, to the detector 50. The image processing unit 60 outputs an image of the sample 100 according to the reflected light L2 detection result at the detector 50. The optical distance adjustment means can adjust the optical distance between the detection surface 50A and the imaging target area OBJ of the sample 100. The control unit 70 sets the imaging target area OBJ to X on the main surface of the sample 100. S The image processing unit 60 is controlled to acquire multiple images of the image target area OBJ at multiple different optical distances while controlling the optical distance adjustment means so that the optical distance between the detection surface 50A and the imaging target area OBJ varies by including the axial component. The image processing unit 60 acquires an image IMG of the image target area OBJ based on the integration result of the multiple images.

Description

[Technical Field]

[0001] This disclosure relates to optical devices, inspection devices, imaging methods, and programs. [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, and other materials. For example, a technique that involves imaging the sample to inspect for foreign objects in samples such as masks 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 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, the sample may contain finer irregularities than the pattern being inspected, and as a result, noise caused by these irregularities may be captured when the sample is imaged.

[0005] The following are possible reasons why noise caused by minute irregularities is captured in the image: It is known that when the focal point of an optical system is shallow for a convex object, the image is bright, and when the focal point is deep, the image is dark. Similarly, when the focal point of an optical system is shallow for a concave object, the image is dark, and when the focal point is deep, the image is bright. It is possible that a similar phenomenon occurs with respect to minute irregularities on the sample.

[0006] Thus, if there are irregularities on the sample at a distance from the optical system that differs from the observation target position, even minute irregularities can cause brightness and darkness noise in the sample image due to the shift from the focal point. As a result, the accuracy of inspections performed using the sample image may deteriorate. Therefore, there is a need to establish a method for imaging the sample while reducing noise caused by the irregularities in the sample. [Means for solving the problem]

[0007] The optical apparatus according to this disclosure includes a detector that detects light incident on a detection surface; an optical system that irradiates an object with illumination light, which is positioned such that its main surface is inclined by a predetermined angle with respect to a surface conjugate to the detection surface, and guides secondary rays generated by the illumination light on the object to the detector; an image processing unit that outputs an image of the object according to the detection result of the secondary rays by the detector; an optical distance adjustment means that can adjust the optical distance between the detection surface and the object's imaging target area; and a control unit that controls the image processing unit to acquire a plurality of images of the imaging target area at a plurality of different optical distances, based on the detection result by the detector, while controlling the optical distance adjustment means so that the optical distance between the detection surface and the imaging target area varies by varying the relative position of the imaging target area with respect to the detection surface, which includes a component in the driving direction perpendicular to the axis of inclination on the main surface of the object; the image processing unit acquires an image of the imaging target area based on the integration result of the plurality of acquired images.

[0008] The inspection apparatus according to this disclosure comprises the optical apparatus described above and an inspection unit that inspects an object based on the image of the target area acquired by the image processing unit.

[0009] The imaging method according to the present disclosure includes a detector that detects light incident on a detection surface, an optical system that irradiates an object arranged such that a main surface is inclined by a predetermined angle with respect to a surface conjugate to the detection surface with illumination light, and guides secondary light generated by irradiating the object with the illumination light to the detector, and an optical distance adjustment unit that can adjust an optical distance between the detection surface and an imaging target region of the object. In the optical device, by varying a relative position of the imaging target region with respect to the detection surface including a component in a driving direction orthogonal to an axis of the inclination on the main surface of the object, while controlling the optical distance adjustment unit such that the optical distance between the detection surface and the imaging target region varies, based on a detection result of the secondary light by the detector, a plurality of images of the imaging target region at different optical distances are acquired, and an image of the imaging target region is acquired based on an integration result of the acquired plurality of images.

[0010] The program according to the present disclosure is configured as a processing device that functions as a computer that performs imaging processing in an optical device including a detector that detects light incident on a detection surface, an optical system that irradiates an object arranged such that a main surface is inclined by a predetermined angle with respect to a surface conjugate to the detection surface with illumination light, and guides secondary light generated by irradiating the object with the illumination light to the detector, and an optical distance adjustment unit that can adjust an optical distance between the detection surface and an imaging target region of the object, and causes the processing device to perform a process of acquiring a plurality of images of the imaging target region at different optical distances while controlling the optical distance adjustment unit such that the optical distance between the detection surface and the imaging target region varies by varying a relative position of the imaging target region with respect to the detection surface including a component in a driving direction orthogonal to an axis of the inclination on the main surface of the object based on a detection result of the secondary light by the detector, and a process of acquiring an image of the imaging target region based on an integration result of the acquired plurality of images.

Advantages of the Invention

[0011] According to the present disclosure, it is possible to perform imaging of a sample with low noise.

Brief Description of the Drawings

[0012] [Figure 1] It is a diagram showing a configuration example of an optical device according to Embodiment 1. [Figure 2] It is a diagram showing a configuration example of an inspection device according to Embodiment 1. [Figure 3] It is a diagram schematically showing the configuration of a detector. [Figure 4] It is a diagram showing the variation of the optical distance between a sample and a line sensor. [Figure 5] It is a diagram schematically showing the imaging process of an imaging target area of a sample. [Figure 6] It is a flowchart showing the procedure of imaging processing in the optical device according to Embodiment 1. [Figure 7] It is a diagram schematically showing the imaging process of a sample in the optical device in Embodiment 2. [Figure 8] It is a flowchart showing the procedure of imaging processing in the optical device according to Embodiment 2. [Figure 9] It is a diagram showing a configuration example of a computer for realizing an optical device.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, the specific configuration of this embodiment will be described with reference to the drawings. The following description shows preferred embodiments of the present disclosure, and the scope of the present disclosure is not limited to the following embodiments. In the following description, those denoted by the same reference numerals indicate substantially the same content.

[0014] Embodiment 1 The optical device according to Embodiment 1 will be described. The optical device according to this embodiment is configured as an optical device incorporated in an inspection device for a photomask used in a semiconductor manufacturing process. The inspection device inspects defects of a sample based on an image of the sample captured by the optical device.

[0015] Figure 1 is a diagram showing an example configuration of an optical device according to Embodiment 1. Figure 2 is a diagram showing an example configuration of an inspection device according to Embodiment 1. As shown in Figure 2, the inspection unit 110 of the inspection device 1000 inspects the sample 100 for abnormalities, such as defects, based on the image of the sample 100 captured by the optical device 1.

[0016] The optical device 1 will now be described. As shown in Figure 1, 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. The optical device 1 may also include other optical components.

[0017] Here, for the sake of explaining the optical device 1, we introduce the XYZ Cartesian coordinate system. The optical system 20 focuses illumination light L1 onto the sample 100 held on the stage surface 31, which is the main surface of the stage 30. The optical axis AX of the focused illumination light L1 follows. L1 The direction is defined as the Z-axis direction. The plane perpendicular to the Z-axis direction is defined as the XY plane, the horizontal direction of the paper is defined as the X-axis direction, and the direction normal to the paper is defined as the Y-axis direction. For example, the +Z-axis direction is called upward, and the -Z-axis direction is called downward. Note that upward and downward are for the sake of explanation and do not indicate the actual orientation of the optical device 1.

[0018] The light source 10 emits illumination light L1 into the optical system 20. The light source 10 may be a lamp light source, an LED (Light Emitting Diode) light source, or a laser light source. The illumination light L1 may be, for example, visible light, ultraviolet light, or EUV (Extreme Ultraviolet) light.

[0019] 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 sample 100 placed on the stage 30 with illumination light L1 emitted from the light source 10, and guides the reflected light L2 from the sample 100 to the detector 50.

[0020] The beam splitter 21 is, for example, a half-mirror that reflects approximately half of the illumination light L1 toward the objective lens 22. The objective lens 22 focuses the illumination light L1 onto the sample 100 placed on the stage surface 31 of the stage 30.

[0021] The reflected light L2 generated when the illumination light L1 illuminates the sample 100 is focused by the objective lens 22 and then incident on the beam splitter 21. The beam splitter 21 transmits approximately half of the reflected light L2. The reflected light L2 that has passed through the beam splitter 21 is focused by the relay lens 23 and then incident on the detection surface 50A of the detector 50. As a result, an image of the sample 100 is formed on the detection surface 50A.

[0022] For the sake of explanation, the diagram shows typical optical elements included in the optical system 20, but the optical system 20 may also be equipped with various optical elements not shown, such as lenses, optical scanners, mirrors, filters, and beam splitters. Furthermore, for example, the optical system 20 may be a confocal optical system. Also, when using short-wavelength light such as EUV light as the illumination light L1, the optical system 20 may be a reflective optical system.

[0023] Furthermore, although Figure 1 describes the optical device 1 as a bright-field illumination optical device, the illumination method of the optical device 1 is not limited to this.

[0024] In the following, the reflected light L2 from sample 100 will also be referred to as secondary light produced when sample 100 is illuminated by illumination light L1. However, secondary light is not limited to reflected light. Secondary light may be various types of light, such as reflected light, scattered light, fluorescence, or transmitted light, produced when sample 100 is illuminated by illumination light L1.

[0025] The sample 100 is, for example, a photomask in which a fine pattern 102 is formed on a flat member 101 such as mask blanks, or a semi-finished product in a semiconductor process in which a device pattern is formed on a wafer which is a flat member. The pattern 102 of the sample 100 is formed, for example, by a layer of an opaque member laminated on a flat member 101 transparent to the illumination light L1, or by laminating an absorber layer mainly absorbing the illumination light L1 on a multilayer layer mainly reflecting the illumination light L1.

[0026] The stage 30 is a three-axis stage driven by a drive mechanism 40. The stage surface 31 of the stage 30 is provided so as to be inclined relative to the optical axis AX of the illumination light L1. L1 Thereby, the sample 100 is held so as to be inclined relative to the optical axis AX of the illumination light L1. In FIG. 1, the normal lines of the stage surface 31 and the sample surface 100A which is the main surface of the sample 100 are inclined relative to the optical axis AX of the illumination light L1 by a predetermined inclination angle θ in the counterclockwise direction with the Y-axis direction as the inclination axis. In other words, the stage surface 31 and the sample surface 100A are inclined relative to the surface 50B conjugate with the detection surface 50A of the detector 50, which is parallel to the X-Y plane perpendicular to the optical axis AX of the illumination light L1, by the inclination angle θ in the counterclockwise direction with the Y-axis direction as the inclination axis as shown in the figure. L1 に対して相対的に傾斜するように保持される。図1においては、ステージ面31及び試料100の主面である試料面100Aの法線は、照明光L1の光軸AX L1 に対して、Y軸方向を傾斜軸として、反時計回り方向に所定の傾斜角度θだけ相対的に傾斜している。換言すれば、ステージ面31及び試料面100Aは、図示するように、照明光L1の光軸AX L1 に垂直なX-Y平面と平行な、検出器50の検出面50Aと共役な面50Bに対して、Y軸方向を傾斜軸として、反時計回り方向に傾斜角度θだけ相対的に傾斜している。

[0027] The control unit 70 drives the stage 30 in the X-axis direction orthogonal to the Y-axis direction which is the inclination axis on the sample surface 100A, the Y-axis direction, and the Z-axis direction orthogonal to the X-axis direction and the Y-axis direction by controlling the drive mechanism 40. Note that the stage 30 may be driven in the Z-axis direction instead of the Z-axis direction according to the application. Further, the stage 30 may be driven to be rotatable around each of the three axes. S 軸方向と、Y軸方向と、X S 軸方向及びY軸方向に直交するZ S 軸方向と、にステージ30を駆動する。なお、ステージ30は、用途に応じて、Z S 軸方向ではなく、Z軸方向に駆動されてもよい。また、ステージ30は、3軸のそれぞれの周りに回転可能に駆動されてもよい。

[0028] Stage 30 is an example of a holding unit for holding the sample 100. Various holding mechanisms, such as a holder with an electrostatic chuck or a robot arm, may be used as Stage 30 or in place of Stage 30, as long as they hold the sample 100 and are driven in the same three-axis direction. The method for driving Stage 30 as an example of a method for driving the holding unit will be described in detail later.

[0029] The detector 50 acquires an image of the sample 100 by detecting the reflected light L2 from the sample 100, which is imaged onto the detection surface 50A via the optical system 20. The detector 50 may be a camera with various imaging principles applicable to TDI cameras such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor.

[0030] The detector 50 has multiple line sensors arranged in the X-axis direction on a detection surface 50A perpendicular to the Z-axis direction (thickness direction), with a predetermined pitch P within a width W. Each of the multiple line sensors has multiple pixels arranged in the Y-axis direction. Figure 3 is a schematic diagram showing the configuration of the detector 50. Figure 3 shows an example in which nine line sensors 51 to 59 are arranged in the X-axis direction, and nine pixels are arranged in the Y-axis direction on each of the line sensors 51 to 59. Note that the number of line sensors is just one example, and multiple line sensors other than nine may be arranged. The number of pixels is just one example, and multiple pixels other than nine may be arranged on a single line sensor.

[0031] In the optical device 1 according to this embodiment, the detector 50 and the image processing unit 60 constitute a TDI (Time Delay Integration) camera that captures an image of the sample 100. The detector 50 outputs a detection signal DAT, which indicates the detection result of reflected light L2, to the image processing unit 60.

[0032] The image processing unit 60 processes the detection signal DAT to integrate the images captured by line sensors 51 to 59 of the same area of ​​the sample 100, thereby acquiring an image of that area of ​​the sample 100.

[0033] The control unit 70 can drive the stage 30 in a desired direction and speed by providing a control signal CON1 to the drive mechanism 40. Furthermore, the control unit 70 can 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 perform imaging 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.

[0034] Next, the relationship between the drive of the stage 30 in the optical device 1 and the imaging timing will be explained. In the optical device 1, the X is tilted at an angle θ in the counterclockwise direction with respect to the detection surface 50A. S The stage 30 is driven with the axial direction as the driving direction, and while the sample 100 is moved, the same area of ​​the sample 100 is repeatedly imaged by line sensors 51 to 59 arranged on the detector 50. The tilt angle θ is assumed to be constant while the sample 100 is moved.

[0035] In this configuration, X S Since the sample 100 is moved with the axial direction as the driving direction, the optical distance between specific points on the sample 100 and line sensors 51-59 will differ.

[0036] As described above, in the optical device 1, the stage 30 and the drive mechanism 40 constitute an optical distance adjustment means that can adjust the optical distance between the detection surface 50A of the detector 50 and the imaging target area OBJ of the sample 100.

[0037] Figure 4 shows the variation in the optical distance between the sample and the line sensor. Figure 5 is a schematic diagram showing the imaging process of the target area of ​​the sample. Hereinafter, the same specific area of ​​the sample 100 imaged by each of the line sensors 51 to 59 of the detector 50 constituting the TDI camera will be referred to as the target imaging area OBJ. Below, the operation of the optical device 1 will be explained focusing on the specific target imaging area OBJ imaged by each of the line sensors 51 to 59 in the sample 100.

[0038] As shown in the diagram, the left line sensor of two adjacent line sensors is used to image the target area OBJ of sample 100, and then the right line sensor is used to image the target area OBJ of sample 100. As a result, the optical distance between each of the two adjacent line sensors and the target area OBJ will be different. By repeating this procedure sequentially, the target area OBJ of sample 100 can be imaged at different optical distances with a time difference using each line sensor.

[0039] The sample 100 is positioned such that the sample surface 100A is conjugate to the central line sensor 55 on the detection surface 50A. While maintaining this state, the stage 30 moves the sample 100 to the X S It moves along the axial direction. In other words, the central line sensor 55 will always image the sample 100 in the best focus state.

[0040] In the optical device 1, the control unit 70 controls X S The drive mechanism 40 and the image processing unit 60 are controlled so that the movement of the sample 100 along the axial direction is synchronized with the imaging timing T1 to T9 of the line sensors 51 to 59. As a result, the sample 100 moves along the X S Along the axial direction, the drive pitch ΔX corresponds to the array pitch P of line sensors 51-59. S Each time it moves, one of the line sensors 51-59 acquires an image of the target area OBJ. This will be explained in detail below.

[0041] The imaging target area OBJ is first imaged by the line sensor 51 at timing T1. At this time, the optical distance D between the imaging target area OBJ and the line sensor 51 is at its longest, resulting in a negative defocus state.

[0042] After that, Stage 30 is X S Pitch ΔX in the axial direction S It moves in increments. Accordingly, the imaging target area OBJ is sequentially imaged by line sensors 52 to 54 at timings T2 to T4. During this time, the optical distance D between the imaging target area OBJ and line sensors 52 to 54 decreases by ΔZ while maintaining a negative defocus state.

[0043] Next, the imaging target area OBJ is imaged by the central line sensor 55 at timing T5. At this time, the optical distance D between the imaging target area OBJ and the line sensor 55 is the optical distance corresponding to the best focus state, as described above.

[0044] After that, Stage 30 is X S Pitch ΔX along the axial direction S It moves in increments. Accordingly, the imaging target area OBJ is sequentially imaged by line sensors 56 to 58 at timings T6 to T8. During this time, the optical distance D between the imaging target area OBJ and line sensors 52 to 54 decreases by ΔZ while maintaining a positive defocus state.

[0045] Furthermore, Stage 30 is X S Pitch ΔX along the axial direction S When the area moves by that much, the imaging target area OBJ is imaged by the line sensor 59 at timing T9. At this time, the optical distance D between the imaging target area OBJ and the line sensor 59 becomes the shortest possible, resulting in a positive defocus state.

[0046] Here, the optical distance corresponding to the best focus state is also referred to as the predetermined optical distance. The optical distance corresponding to a negative defocus state is also referred to as the first optical distance. The optical distance corresponding to a positive defocus state is also referred to as the second optical distance.

[0047] Therefore, Stage 30 is X S 8ΔX along the axial direction S While only the line sensors 51-59 are driven, nine images of the target area OBJ are acquired, each with a different focus state. Since detector 50 is configured as a sensor for the TDI camera, the charge of the line sensor that captured the target area OBJ in the previous imaging timing is transferred to the line sensor to its right in the diagram. Then, the target area OBJ is further imaged by the line sensor to which the charge has been transferred, and the charge is further accumulated.

[0048] Furthermore, since the detector 50 is configured as a sensor for the TDI camera, a line sensor adjacent to a line sensor that has captured an image of the target area OBJ1 at a given time may capture an image of another target area OBJ2 adjacent to the target area OBJ1 at that time.

[0049] The image processing unit 60 integrates the nine images of the target area OBJ acquired by the line sensors 51 to 59 to obtain an image IMG of the target area OBJ.

[0050] For the sake of simplicity, this explanation describes a case where the target area OBJ is captured under nine different focus conditions, including the best focus state. However, this is merely an example. The target area OBJ may be captured under any number of different focus conditions other than the nine including the best focus state, and the image IMG of the target area OBJ may be generated by integrating the results of these captures.

[0051] Furthermore, the line sensor that acquires the image in the best-focus state among multiple line sensors is not limited to the central line sensor, but may be any line sensor at any position other than the line sensors at both ends and the central line sensor.

[0052] The detector 50 may have a number of line sensors arranged in a continuous line equal to the number of focus states used to image the target area OBJ. Alternatively, any number of line sensors may be arranged on the detector 50, and the same number of line sensors as the number of focus states used to image the target area OBJ may be selected from the arranged line sensors and used for imaging.

[0053] The tilt angle θ of stage 30 may be an angle experimentally obtained that is sufficient to remove noise caused by minute irregularities. Alternatively, the angle at which the signal-to-noise ratio (SNR), defined as the ratio of the signal intensity from the detected defect to the signal intensity from the noise caused by minute irregularities, is maximized may be experimentally selected and used as the tilt angle θ of stage 30. Note that these methods for setting the tilt angle θ are merely examples, and it may be set appropriately according to the characteristics of the sample 100. For example, there are cases where it is desirable to observe the thickness direction of sample 100, such as when the pattern 102 of sample 100 consists of an absorber layer formed on a multilayer. In this case, the tilt angle θ may be set so that the focus range encompasses the thickness of the sample 100 to be observed. That is, if the number of imaging cycles is n and the thickness of the object to be observed is T, then the focus variation range R = (n-1)ΔX S The inclination angle θ may be set such that sinθ is greater than T / cosθ.

[0054] Next, the imaging procedure in the optical device 1 will be described. Figure 6 is a flowchart showing the imaging procedure in the optical device according to Embodiment 1. In the following, the control unit 70 controls each part of the optical device to perform imaging of the sample 100.

[0055] Step S1 The control unit 70 controls the drive mechanism 40 to move the imaging target area OBJ to the initial position for measurement. In the example above, X at timing T1 corresponding to imaging by the line sensor 51S =0 represents the initial position.

[0056] Step S2 The target area OBJ is imaged using one of the line sensors 51 to 59 corresponding to the position of the target area OBJ.

[0057] Step S3 The control unit 70 determines whether imaging of the target area OBJ has been completed at all positions corresponding to each of the line sensors 51 to 59.

[0058] Step S4 If imaging of the target area OBJ at all positions has not been completed, the control unit 70 controls the drive mechanism 40 to X S Pitch ΔX along the axial direction S Move only that. Then, return the process to step S2.

[0059] Step S5 When imaging of the target area OBJ at all positions is complete, the control unit 70 commands the image processing unit 60 to complete the imaging process. The image processing unit 60 then accumulates the imaging results from nine imaging sessions of the target area OBJ to obtain an image IMG of the target area OBJ.

[0060] As explained above, with this configuration, even if minute irregularities exist on the sample 100, the effects of noise during defocusing on the negative side and the effects of noise during defocusing on the positive side can be canceled out. As a result, an image of the sample 100 can be acquired while reducing the effects of noise.

[0061] Therefore, the inspection device 1000 can inspect defects in the sample 100 using an image IMG from which noise has been reduced or removed. As a result, the inspection device 1000 can improve inspection accuracy by suppressing the effects of noise.

[0062] Furthermore, according to this configuration, Stage 30 is ZS There is no need to move in the axial or Z-axis direction, X S Since movement is limited to the axial direction, the structure and operation of the stage 30 and the drive mechanism 40 can be simplified.

[0063] Embodiment 2 In the above embodiment, sample 100 is X S In the previous description, the imaging target area OBJ was imaged by line sensors 51-59 while the device was driven along the axial direction. In contrast, this embodiment describes a method in which the optical device 1 efficiently performs imaging while moving the imaging target area OBJ on the sample 100 in the Y-axis direction as well.

[0064] Figure 7 schematically shows the imaging process of the sample in the optical device in Embodiment 2. In Figure 7, multiple imaging target areas OBJ provided on the sample 100 are X S Arranged along the axial direction, X S A region with the axial direction as the longitudinal direction is called a stripe. In this example, eight stripes ST1 to ST8 are arranged consecutively from the -Y side to the +Y side. Figure 7 shows an example in which multiple imaging target regions OBJ are set within stripe ST1, as indicated by the dashed lines. Optical device 1 scans sample 100 X S By driving along the axial direction, images of each target area OBJ of each stripe can be acquired.

[0065] Here, we consider the case where stripe imaging is performed sequentially from stripe ST1 to stripe ST8. First, stage 30 is X S Imaging is performed by driving the sensor in the forward direction, from the negative side to the positive side along the axial direction. In this case, when imaging of stripe ST1 is completed, sample 100 will be X S It is currently in a state where it has moved towards the positive side in the axial direction.

[0066] In this state, the stage 30 is driven to the negative side of the Y-axis by the dimension ΔY of the imaging target area OBJ. This allows the target stripe to be switched from stripe ST1 to stripe ST2.

[0067] Then, sample 100 is X S The imaging is performed by driving the device in the opposite direction, from the positive side to the negative side along the axial direction. In this case, when the imaging of stripe ST2 is completed, sample 100 will be X S It is in a state where it has moved to the negative side in the axial direction.

[0068] Subsequently, stage 30 is driven by a pitch ΔY in the negative direction of the Y axis, and then X S By switching the axial drive to either the forward or reverse direction during imaging, it is possible to alternately and repeatedly perform forward imaging of stripe ST1 (stripes ST3, ST5, ST7) and reverse imaging of stripe ST2 (stripes ST4, ST6, ST8). This allows for efficient imaging of stripes ST1 to ST8 without unnecessarily driving stage 30.

[0069] Next, the imaging procedure for multiple stripes will be described. Figure 8 is a flowchart of the imaging procedure in the optical device according to Embodiment 2. In the following, the control unit 70 controls each part of the optical device to image the sample 100. Figure 8 assumes the case in which stripes ST1 to ST8 are imaged in order as described above.

[0070] Step S11 The control unit 70 sets the initial driving direction of the sample 100 as X S Set either the forward or reverse direction along the axial axis. Also, drive the stage 30 to the initial position for imaging. In this example, the stage 30 is driven to the imaging start position of stripe ST1.

[0071] Step S12 In the set driving direction, the target area OBJ within the stripe is imaged according to the processing procedure shown in Figure 6 in Embodiment 1, and an image IMG is obtained.

[0072] Step S13 The control unit 70 determines whether or not there are any stripes that have not yet been imaged.

[0073] Step S14 If there are any stripes that have not yet been imaged, the control unit 70 controls the drive mechanism 40 to move the sample 100 by a pitch ΔY towards the negative side in the Y-axis direction. As a result, the stripe to be imaged moves to the adjacent stripe on the +ΔY side of the sample 100 by a pitch ΔY.

[0074] Step S15 The control unit 70 controls the X of the stage 30. S The direction of drive along the axial direction is reversed. That is, if the drive direction of the sample 100 in step S12 was forward, the drive direction is switched to the reverse direction. On the other hand, if the drive direction of the sample 100 in step S12 was reverse, the drive direction is switched to the forward direction. Then, the process is returned to step S12.

[0075] Step S16 If there are no stripes that have not yet been imaged, that is, if imaging has been completed for all stripes, the control unit 70 instructs the image processing unit 60 to complete the imaging process. As a result, the image processing unit 60 combines the eight images IMG acquired for stripes ST1 to ST8 to obtain an image of the sample 100.

[0076] In the imaging method described above, after imaging one stripe is completed, the sample 100 can be moved by one pitch in the Y direction to continue imaging adjacent stripes. This eliminates the need to drive the stage 30 to the starting position when starting imaging of each stripe. Therefore, a wide area of ​​the sample 100 can be imaged efficiently in a short time.

[0077] While this example describes imaging eight stripes, it goes without saying that the number of stripes to be imaged can be any number other than eight.

[0078] Furthermore, when imaging multiple stripes, the imaging method is not limited to alternating between imaging in the forward direction and imaging in the reverse direction. For example, imaging in the forward direction or in the reverse direction may be performed two or more times consecutively. Alternatively, imaging of multiple stripes may be performed using only imaging in the forward direction or only imaging in the reverse direction.

[0079] Other embodiments Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be made as can be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0080] In Figures 1 and 2, the detection surface 50A is perpendicular to the Z-axis direction, which is the vertical direction of the paper, and the sample surface 100A and the stage surface 31 are inclined with respect to the XY plane. However, this does not mean that the sample 100 and the stage 30 are inclined relative to the optical system 20 and the detector 50. In other words, in the above embodiment, it is sufficient that the sample surface 100A and the stage surface 31 are inclined relative to the surface 50B which is conjugate to the detection surface 50A, with the optical system 20 in between. Therefore, the sample 100 and the stage 30 may be inclined relative to the optical system 20 and the detector 50, or the optical system 20 and the detector 50 may be inclined relative to the sample 100 and the stage 30. Furthermore, the design and arrangement of the optical elements may be adjusted, for example, by distorting the optical distance from the sample 100 and the stage 30 to the detection surface 50A of the detector 50, so that the sample 100 and the stage 30 are inclined relative to the surface 50B which is conjugate to the detection surface 50A of the detector 50.

[0081] The control unit 70 may appropriately switch between a mode in which the sample 100 and the stage 30 are positioned so as to be inclined to a plane conjugate to the detection surface 50A of the detector 50 (first mode) and a mode in which the sample 100 and the stage 30 are positioned parallel to a plane conjugate to the detection surface 50A of the detector 50 (second mode) by controlling the optical distance adjustment means composed of the stage 30 and the drive mechanism 40. In the first mode, as described above, the control unit 70 controls the relative position of the imaging target area OBJ with respect to the detection surface 50A of the detector 50, X S In the second mode, the control unit 70 varies the optical distance between the detection surface 50A and the imaging target area OBJ by varying the axial component, causing the image processing unit 60 to acquire multiple images of the imaging target area OBJ at multiple different optical distances. The image processing unit 60 then acquires an image of the imaging target area OBJ based on the integration result of the acquired multiple images. In the second mode, the control unit 70 varies the relative position of the imaging target area OBJ with respect to the detection surface 50A while keeping the optical distance between the detection surface 50A of the detector 50 and the imaging target area OBJ approximately constant, causing the image processing unit 60 to acquire multiple images of the imaging target area OBJ at approximately constant optical distances. The image processing unit 60 then acquires an image of the imaging target area OBJ based on the integration result of the acquired multiple images. The control unit 70 may switch between the first mode and the second mode by controlling the optical distance adjustment means, or in addition to this, by controlling a drive unit different from the drive mechanism 40 that is connected to at least one of the detector 50, stage 30, and optical member.

[0082] The control unit 70 may switch between the first mode and the second mode depending on the inspection or review recipe for the sample 100, or the characteristics of the sample 100 or the characteristics of the pattern of the sample 100. For example, the control unit 70 may set a second mode when the recipe requires the visualization of noise caused by minute irregularities in the sample 100. This allows the control unit 70 to determine whether the sample 100 is susceptible to noise caused by minute irregularities. It also allows the control unit 70 to determine whether a predetermined pattern of the sample 100 is susceptible to noise caused by minute irregularities. Furthermore, the control unit 70 may set a second mode when, for example, the sample 100 or the pattern of the sample 100 has characteristics that make it less susceptible to noise caused by minute irregularities. Moreover, the control unit 70 may set a first mode when, for example, the sample 100 or the pattern of the sample 100 has characteristics that make it susceptible to noise caused by minute irregularities, and the recipe requires the removal of noise.

[0083] Furthermore, by arranging the sample 100 and stage 30 so as to be inclined to a plane conjugate to the detection surface 50A of the detector 50, it is conceivable that the distance of each unit pixel on the sample 100 of the detector 50 will change. In other words, it is conceivable that the distance of each unit pixel on the sample 100 of the detector 50 in the first mode and the distance of each unit pixel on the sample 100 of the detector 50 in the second mode will be different from each other. Therefore, in the first mode, the control unit 70 may set the movement speed of the stage 30, the frame rate and line rate of the detector 50, etc., in accordance with the change in the distance of each unit pixel on the sample 100 due to the inclination at the inclination angle θ. This makes it possible to suppress the effect of the change in the distance of each unit pixel on the sample 100 and to acquire images in the first mode with the same sensitivity as in the second mode.

[0084] The optical apparatus according to the above-described embodiment may be incorporated not only into an inspection apparatus, but also into various other devices that use an image of the sample 100, such as a review apparatus that displays an image of the sample 100.

[0085] In a review device that displays an image of sample 100, images may be accumulated when the stage 30 is driven within an arbitrary range, such as by integrating images at a specific focus state (a desired range of optical distances). For example, a review device that displays an image of sample 100 may acquire and display an image obtained by integrating multiple images at specific focus states (a desired range of optical distances), such as when the image is defocused on the positive side, which are identified based on the results of a specification acquisition means that accepts specifications from the user.

[0086] The optical system 20 described above is merely an example, and other configurations are possible as long as illumination light L1 emitted from the light source 10 is irradiated onto the sample 100 held by the stage 30 or other holding means, and secondary rays from the sample 100 are 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. Alternatively, secondary rays from the sample 100 may be guided to the detector 50 by the reflective optical system. The reflective optical system may include plane mirrors, aspherical mirrors such as ellipsoidal mirrors, Schwarzschild optical systems, etc.

[0087] In the embodiments described above, the optical device according to the disclosure has been described primarily as a hardware configuration, but it is not limited thereto. It is also possible to realize the optical device according to the disclosure by having a computer execute a computer program to perform any processing. These processing may be realized by having a computer, which includes at least one processor (e.g., a microprocessor, CPU, GPU, MPU, or DSP (Digital Signal Processor)), execute a program. Specifically, one or more programs containing a set of instructions for causing a computer to perform algorithms related to these transmission signal processing or reception signal processing can be created and supplied to the computer.

[0088] Computer programs 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 recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / Ws, and semiconductor memory (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, and RAMs (random access memory)). Programs may also be supplied to a computer using various types of transient computer-readable media. Examples of transient computer-readable media include electrical signals, optical signals, and electromagnetic waves. Transitory computer-readable media can be supplied to a computer via wired communication channels such as electric wires and optical fibers, or via wireless communication channels.

[0089] The following shows an example of a computer configuration for realizing an optical device. Figure 10 shows an example of a computer configuration for realizing the image processing unit and control unit of an optical device. The image processing unit and control unit of an 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; there may be multiple computers when performing distributed processing. As shown in Figure 10, the computer 9000 has, for example, a processor 9001, ROM (Read Only Memory) 9002, RAM (Random Access Memory) 9003, a storage unit 9004, a communication interface 9005, and a user interface 9006.

[0090] The processor 9001, ROM 9002, RAM 9003, memory unit 9004, communication interface 9005, and user interface 9006 are interconnected via bus 9007, enabling them to communicate with each other. While the operating system software necessary to run the computer is not described here, it will be implemented in the computer 9000 as appropriate.

[0091] ROM is composed of, for example, non-volatile semiconductor memory devices. ROM 9002 stores information such as various programs used by the computer 9000.

[0092] The storage unit 9004 is composed of various storage devices, such as hard disks and solid-state disks. Furthermore, the storage unit 9004 is not limited to storage devices installed in the computer 9000, but may also be external storage devices. External storage devices may include various communication means, such as cloud storage connected to the computer 9000 via a network. The storage unit 9004 stores information such as various programs and data used by the computer 9000.

[0093] RAM 9003 is composed of volatile semiconductor memory devices. Programs and data used by the processor 9001 are loaded into RAM 9003 as needed from either ROM 9002 or memory unit 9004, or both.

[0094] The processor 9001 may be composed of, for example, a CPU (Central Processing Unit). Alternatively, the processor 9001 may include not only a CPU but also a GPU (Graphics Processing Unit). A GPU is suitable for parallel processing of routine tasks, and by applying it to, for example, neural network processing, it is possible to improve processing speed compared to a CPU. The processor 9001 executes various processes as appropriate, based on various programs stored in the ROM 9002 or various programs and data held in the RAM 9003. The processor 9001 may also store the data generated by the processing in the RAM 9003 or the storage unit 9004 as appropriate.

[0095] 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 or wireless communication means. This allows the computer 9000 to communicate with other devices, systems, and sensors connected to the communication network.

[0096] The user interface 9006 includes, for example, a display unit that provides information so that the user can perceive it, such as through a display device, and an audio output unit that provides audio. The user interface 9006 also includes an input unit that allows the user to input information into the computer 9000 through user operation, such as a keyboard, mouse, and touch panel. Furthermore, the user interface 9006 may include devices such as sensors that acquire information useful to the user.

[0097] Here, the computer 9000 is described as a single device, but this is merely an example. The computer 9000 may consist of multiple physically separate devices. Some of these devices may be portable, while others may be stationary.

[0098] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be made as can be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0099] Each drawing is merely illustrative to illustrate one or more embodiments. Each drawing may be associated with one or more other embodiments rather than with only one specific embodiment. As those skilled in the art will understand, 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, for example, to create embodiments not explicitly shown or described. Not all features or steps shown in any one drawing to illustrate an exemplary embodiment are necessarily required, and some features or steps may be omitted. The order of steps shown in any of the drawings may be changed as appropriate. [Explanation of symbols]

[0100] 1~3 Optical device 10 light source 20 Optical system 21 Beam Splitter 22 Objective lenses 23 Relay Lens 30 stages 31 Stages 40 Drive mechanism 50 detectors 50A detection surface 50B Conjugate surface to the detection surface 51-59 Line Sensor 60 Image Processing Unit 70 Control Unit 100 samples 100A Sample surface 101 Flat plate member 102 patterns 110 Inspection Department 1000 inspection devices 9000 Computers 9001 Processor 9002 ROM 9003 RAM 9004 Storage section 9005 Communication Interface 9006 User Interface 9007 Bus CON1, CON2 control signals DAT detection signal L1 illumination light L2 reflected light OBJ imaging target area

Claims

1. A detector that detects light incident on the detection surface, An optical system that irradiates illumination light onto an object positioned such that its principal surface is inclined by a predetermined angle with respect to a conjugate surface to the detection surface, and guides the secondary light rays generated by the illumination light on the object to the detector, An image processing unit outputs an image of the object in accordance with the detection result of the secondary light ray by the detector, An optical distance adjustment means capable of adjusting the optical distance between the detection surface and the imaging target area of ​​the object, The system includes a control unit that controls the image processing unit to acquire multiple images of the image target at multiple different optical distances based on the detection result of the detector, while controlling the optical distance adjustment means so that the optical distance between the detection surface and the image target area changes by varying the relative position of the image target area with respect to the detection surface, including a component in the driving direction perpendicular to the axis of inclination on the main surface of the object, The image processing unit acquires an image of the target area based on the integration result of the acquired plurality of images. optical equipment.

2. The optical distance adjustment means further comprises a holding unit for holding the object and a drive unit for driving the holding unit, The control unit controls the drive unit to drive the holding unit along the drive direction, thereby varying the optical distance between the detection surface and the imaging target area. The optical apparatus according to claim 1.

3. The detector comprises a plurality of sensors for detecting the secondary light ray, which are arranged in a predetermined direction perpendicular to the thickness direction of the detector on the detection surface. The control unit, The drive unit is controlled so that the image of the target area acquired by the plurality of sensors moves along the predetermined direction. The image processing unit is controlled so that each of the multiple sensors acquires an image of the target area as one of the multiple images. The optical apparatus according to claim 2.

4. The control unit controls the optical distance adjustment means such that the optical distance between one of the two adjacent sensors and the imaging target area is different from the optical distance between the other of the two adjacent sensors and the imaging target area. The optical apparatus according to claim 3.

5. The control unit controls the optical distance adjustment means so that the optical distance between the detection surface and the imaging target area varies within a predetermined range. The optical apparatus according to claim 1 or 2.

6. The predetermined range includes a predetermined optical distance at which the illumination light focuses on the imaging target area and the secondary light ray focuses on the detection surface. The optical apparatus according to claim 5.

7. The predetermined range includes the predetermined optical distance, a first optical distance shorter than the predetermined optical distance, and a second optical distance longer than the predetermined optical distance. The image processing unit acquires the image of the target area by integrating the image when the optical distance between the detection surface and the target area is the predetermined optical distance, the image when the optical distance is the first optical distance, and the image when the optical distance is the second optical distance. The optical apparatus according to claim 5.

8. The predetermined optical distance is the optical distance that lies at the center of the predetermined range. The optical apparatus according to claim 5.

9. The control unit controls the optical distance adjustment means so that the optical distance between the detection surface and the imaging target region increases or decreases monotonically while acquiring the plurality of images of the imaging target region. The optical apparatus according to claim 1 or 2.

10. The image processing unit acquires images of the multiple target areas for imaging for each of the multiple stripes arranged in the direction of the axis of inclination, in which the multiple target areas for imaging are arranged in the driving direction. The control unit controls the optical distance adjustment means such that, for two adjacent stripes among the plurality of stripes, the monotonically increasing and monotonically decreasing optical distances between the detection surface and the imaging target area are opposite in each case. The optical apparatus according to claim 9.

11. The image processing unit acquires images of the multiple target areas for imaging, for each of the multiple stripes arranged in the direction of the axis of inclination, wherein the multiple target areas for imaging are arranged in the driving direction and the direction of the axis of inclination. The optical apparatus according to claim 2.

12. The control unit controls the drive unit so that the direction of movement of the object is opposite for two adjacent stripes among the plurality of stripes. The optical apparatus according to claim 11.

13. The control unit controls the drive unit, When imaging the plurality of imaging target regions of the first stripe among the plurality of stripes, the object is driven in a first direction along the driving direction, By driving the object along the direction of the axis of the inclination, the object to be imaged by the detector is changed from the first stripe to the second stripe adjacent to the first stripe. When imaging the plurality of target areas of the second stripe, the target object is driven in a second direction opposite to the first direction. The optical apparatus according to claim 12.

14. The optical apparatus according to claim 1 or 2, The system includes an inspection unit that inspects an object based on the image of the target area acquired by the image processing unit, Inspection device.

15. An optical device comprising: a detector for detecting light incident on a detection surface; an optical system for irradiating an object with illumination light, which is positioned such that its main surface is inclined by a predetermined angle with respect to a surface conjugate to the detection surface, and guiding the secondary rays generated by the illumination light on the object to the detector; and optical distance adjustment means for adjusting the optical distance between the detection surface and the imaging target area of ​​the object, By varying the relative position of the imaging target area with respect to the detection surface, including a component in the driving direction perpendicular to the axis of inclination on the main surface of the object, the optical distance adjustment means is controlled so that the optical distance between the detection surface and the imaging target area varies, and based on the detection result of the secondary ray by the detector, multiple images of the imaging target area at multiple different optical distances are acquired. Based on the integration result of the acquired plurality of images, an image of the target imaging region is acquired. Imaging method.

16. A processing unit configured as a computer performs imaging processing in an optical device having a detector that detects light incident on a detection surface, an optical system that irradiates an object with illumination light, which is positioned so that its main surface is inclined by a predetermined angle with respect to a surface conjugate to the detection surface, and guides the secondary rays generated by the illumination light on the object to the detector, and optical distance adjustment means that can adjust the optical distance between the detection surface and the imaging target area of ​​the object, A process of acquiring multiple images of the imaging target region at multiple different optical distances based on the detection result of the secondary ray by the detector, while controlling the optical distance adjustment means so that the optical distance between the detection surface and the imaging target region changes by varying the relative position of the imaging target region with respect to the detection surface, including a component in the driving direction perpendicular to the axis of inclination on the main surface of the object, The process involves acquiring an image of the target imaging region based on the integration result of the acquired multiple images. program.

Images