Optical device and focusing control method

Abstract

To provide an optical device and a focusing control method capable of facilitating focusing.SOLUTION: An optical device 1 according to the present disclosure comprises: first detection means 41 that is provided at a front-focus position relative to a sample SMP, and detects light L10 from the sample SMP; second detection means 42 that is provided at a back-focus position relative to the sample SMP, and detects the light L10 from the sample SMP; control means 30 that performs focusing control based on the output results of the first detection means 41 and the second detection means 42; and shielding means 50 that shields at least a central region of a light flux of the light L10 from the sample SMP. The first detection means 41 and the second detection means 42 receive at least a part of an edge region of the light flux of the light L10 from the sample SMP.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an optical device and a focusing control method. [Background technology]

[0002] Patent Document 1 proposes, for example, a front-focus and back-focus method as a focusing control method. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7145030 Summary of the Invention [Problem to be solved by the invention]

[0004] In view of requirements for an optical device, it is preferable to have various variations for front-focus and rear-focus focusing control. Among such variations, an optical device and a focusing control method that can facilitate focusing are particularly desired.

[0005] The present disclosure has been made to solve the above-described problems, and aims to provide an optical device and a focusing control method that can facilitate focusing. [Means for solving the problem]

[0006] The optical device according to the present disclosure comprises a first detection means that is provided in a front-focus position relative to a sample and detects light from the sample, a second detection means that is provided in a back-focus position relative to the sample and detects the light from the sample, a control means that performs focusing control based on the output results of the first detection means and the second detection means, and a shielding means that shields at least a central region of the light beam from the sample, and the first detection means and the second detection means receive at least a portion of an end region of the light beam from the sample.

[0007] The optical device may further include a separation means for separating a portion of the light from the sample into a first light and a second light, wherein the first detection means receives at least a portion of the end region in the beam of the first light, and the second detection means receives at least a portion of the end region in the beam of the second light.

[0008] In the optical device, the shielding means may include a first shielding means that shields at least the central region of the light beam of the first light, and a second shielding means that shields at least the central region of the light beam of the second light.

[0009] In the optical device, the optical distance from the separating means to the first shielding means may be different from the optical distance from the separating means to the second shielding means.

[0010] In the optical device, the second shielding means may be provided between a focal position of the second light and the second detecting means.

[0011] In the optical device, the separating means may include a first separating means that separates a portion of the light from the sample into a first light, and a second separating means that separates a portion of the light from the sample into a second light, and the first separating means may be provided closer to the sample than the second separating means.

[0012] In the above optical device, the optical distance between the first separating means and the first shielding means may be equal to the optical distance between the second separating means and the second shielding means, and the optical distance between the first shielding means and the first detecting means may be equal to the optical distance between the second shielding means and the second detecting means.

[0013] The optical device may further include a slit arranged in the optical path from the light source to the sample, and the shape of the shielding means may be set based on at least one of the orientation and size of the slit.

[0014] The focusing control method according to the present disclosure comprises the steps of providing a first detection means for detecting light from a sample at a front-focus position relative to the sample and providing a second detection means for detecting the light from the sample at a back-focus position relative to the sample, shielding at least a central region of the light beam from the sample with a shielding means, receiving at least a portion of an end region of the light beam with the first detection means and the second detection means, and performing focusing control based on the output results of the first detection means and the second detection means.

[0015] The above-mentioned focusing control method may further include a step of separating a portion of the light from the sample into a first light and a second light by a separating means, and in the step of receiving the light by the first detecting means and the second detecting means, the first detecting means may receive at least a portion of the end region in the light beam of the first light, and the second detecting means may receive at least a portion of the end region in the light beam of the second light.

[0016] In the above-described focusing control method, in the step of shielding with the shielding means, the shielding means may include a first shielding means that shields at least the central region in the light beam of the first light, and a second shielding means that shields at least the central region in the light beam of the second light.

[0017] In the above focusing control method, in the step of shielding with the shielding means, an optical distance from the separating means to the first shielding means and an optical distance from the separating means to the second shielding means may be different.

[0018] In the above focusing control method, in the step of blocking with the blocking means, the second blocking means may be provided between a focal position of the second light and the second detecting means.

[0019] In the above focusing control method, in the separating step, the separating means may include a first separating means that separates a portion of the light from the sample into a first light, and a second separating means that separates a portion of the light from the sample into a second light, and the first separating means may be provided closer to the sample than the second separating means.

[0020] In the above-described focusing control method, in the separating step, the optical distance between the first separating means and the first shielding means may be equal to the optical distance between the second separating means and the second shielding means, and the optical distance between the first shielding means and the first detecting means may be equal to the optical distance between the second shielding means and the second detecting means.

[0021] The above-mentioned focusing control method may further include a step of placing a slit in the optical path from the light source to the sample, and in the step of shielding with the shielding means, the shape of the shielding means may be set based on at least one of the orientation and size of the slit. [Effects of the Invention]

[0022] According to the present disclosure, it is possible to provide an optical device and a focusing control method that can facilitate focusing. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a configuration diagram illustrating an optical device according to a first embodiment. [Figure 2] 3A and 3B are cross-sectional views illustrating the shape of a shielding means for shielding light in the optical device according to the first embodiment. [Figure 3] 3A and 3B are cross-sectional views illustrating the shape of a shielding means for shielding light in the optical device according to the first embodiment. [Figure 4] 3A and 3B are cross-sectional views illustrating the shape of a shielding means for shielding light in the optical device according to the first embodiment. [Figure 5] 4 is a flowchart illustrating a focusing control method in the optical device according to the first embodiment. FIG. [Figure 6] FIG. 10 is a perspective view illustrating a slit in an optical device according to a comparative example. [Figure 7] 3 is a perspective view illustrating a shielding means in the optical device according to the first embodiment. FIG. [Figure 8] 1 is a graph illustrating the amount of first light and second light received by the first detection means and the second detection means, respectively, in an optical device according to a comparative example, where the horizontal axis indicates the position of the sample surface from the focus, and the vertical axis indicates the amount of first light and second light received by the first detection means and the second detection means, respectively. [Figure 9] 1 is a graph illustrating the change in the amount of received light calculated based on a predetermined formula from the amount of first light and second light received by the first detection means and the second detection means, respectively, in an optical device according to a comparative example, in which the horizontal axis indicates the position of the sample surface from the focus, and the vertical axis indicates the change in the amount of received light calculated based on the predetermined formula. [Figure 10] 1 is a graph illustrating the amounts of first light and second light received by the first detection means and the second detection means, respectively, in an optical device according to embodiment 1, where the horizontal axis indicates the position of the sample surface from the focus, and the vertical axis indicates the amounts of first light and second light received by the first detection means and the second detection means, respectively. [Figure 11] 1 is a graph illustrating the change in the amount of received light calculated based on a predetermined formula from the amount of first light and second light received by the first detection means and the second detection means, respectively, in the optical device of embodiment 1, in which the horizontal axis indicates the position of the sample surface from the focus, and the vertical axis indicates the change in the amount of received light calculated based on the predetermined formula. [Figure 12] FIG. 10 is a configuration diagram illustrating an optical device according to a second embodiment. [Figure 13] 10 is a plan view illustrating an example of a slit plate in an optical device according to a second embodiment. FIG. [Figure 14] 10 is a plan view illustrating an example of a slit plate in an optical device according to a second embodiment. FIG. [Figure 15] 10 is a plan view illustrating an example of a slit plate in an optical device according to a second embodiment. FIG. [Figure 16] 10A and 10B are cross-sectional views illustrating the shape of a shielding means for shielding a first light including a slit light in an optical device according to a second embodiment. [Figure 17] 10A and 10B are cross-sectional views illustrating the shape of a shielding means for shielding a first light including a slit light in an optical device according to a second embodiment. [Figure 18] 10A and 10B are cross-sectional views illustrating the shape of a shielding means for shielding a first light including a slit light in an optical device according to a second embodiment. [Figure 19] 10A and 10B are cross-sectional views illustrating the shape of a shielding means for shielding a first light including a slit light in an optical device according to a second embodiment. [Figure 20] 10A and 10B are cross-sectional views illustrating the shape of a shielding means for shielding a first light including a slit light in an optical device according to a second embodiment. [Figure 21] 10A and 10B are cross-sectional views illustrating the shape of a shielding means for shielding a first light including a slit light in an optical device according to a second embodiment. [Figure 22] FIG. 10 is a configuration diagram illustrating an optical device according to a third modification of the second embodiment. [Figure 23] 10 is a plan view illustrating an example of a slit plate in an optical device according to a fourth modification of the second embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0024] 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.

[0025] <Embodiment 1> An optical device and a focusing control method according to embodiment 1 will be described. The optical device is, for example, an inspection device that inspects a sample. Note that the optical device is not limited to an inspection device, and may be, for example, an imaging device that images a sample.

[0026] <Optical equipment> Fig. 1 is a structural diagram illustrating an optical device according to embodiment 1. As shown in Fig. 1, the optical device 1 includes an optical member 10, a driving means 20, a control means 30, a main detection means 40, a first detection means 41, a second detection means 42, a first shielding means 51, and a second shielding means 52. The optical device 1 may include other components in addition to these components, or may omit some of these components.

[0027] The optical element 10 collects light L10 from the sample SMP. The optical element 10 is configured to guide the collected light L10 to the main detection means 40. The optical axis of the light L10 guided to the main detection means 40 is called the main optical axis C10. The optical element 10 includes an objective lens 11, a relay lens 12, and a separation means 13. Note that the optical element 10 may include other components in addition to these components, or some of these components may be omitted, as long as it is configured to collect light L10 from the sample SMP to the main detection means 40.

[0028] The objective lens 11 collects light L10 from the sample SMP. The objective lens 11 may convert the light L10 into parallel light. The light L10 that passes through the objective lens 11 is incident on the relay lens 12. The relay lens 12 collects the incident light L10 so that the light L10 is collected on the main detection means 40. The main detection means 40 receives the light L10. As a result, the main detection means 40 detects the light L10 from the sample SMP.

[0029] The driving means 20 drives the optical member 10 to move along the direction of the main optical axis C10 of the light L10. As a result, the driving means 20 positions the focal point of the optical member 10 on the sample surface of the sample SMP. The driving means 20 also moves the optical member 10 so that the light L10 from the sample SMP is focused on the light-receiving surface of the main detecting means 40. In this way, the optical system including the optical member 10 may constitute a confocal optical system.

[0030] The driving means 20 may be attached to the objective lens 11 of the optical member 10. In this way, the driving means 20 moves the objective lens 11 along the direction of the main optical axis C10. Note that the driving means 20 may be attached to an optical member 10 other than the objective lens 11, as long as the driving means 20 can adjust the focal point of the optical member 10 to the sample surface and the light receiving surface of the main detection means 40.

[0031] The separating means 13 may include mirrors 14 and 15. The separating means 13 may further include other members in addition to the mirrors 14 and 15. The mirror 14 separates a portion of the light L10 from the light L10. The portion of the light L10 separated by the mirror 14 is called light L20. The light L20 separated by the mirror 14 is incident on the mirror 15.

[0032] The mirror 15 transmits a portion of the light L20 and reflects a portion of the light L20. The mirror 15 includes, for example, a half mirror. Note that the mirror 15 may also be another mirror, such as a non-polarizing beam splitter. For example, the mirror 15 transmits half of the light L20 and reflects half of the light L20. The light L20 that passes through the mirror 15 is referred to as the first light L21. The first light L21 that passes through the mirror 15 is incident on the first detection means 41. The optical axis of the first light L21 that enters the first detection means 41 is referred to as the first optical axis C21. On the other hand, the light L20 that is reflected by the mirror 15 is referred to as the second light L22. The second light L22 that is reflected by the mirror 15 is incident on the second detection means 42. The optical axis of the second light L22 that enters the second detection means 42 is referred to as the second optical axis C22.

[0033] In this way, the splitting means 13 splits a part of the light L10 from the sample SMP into the first light L21 and the second light L22.

[0034] The first detection means 41 is provided at a front-focus position with respect to the sample SMP. For example, the first detection means 41 is provided at a front-focus position with respect to the position where the light L10 (first light L21) is focused by the optical member 10, that is, optically forward of the position where the light L10 (first light L21) is focused. The first detection means 41 detects the light L10 from the sample SMP. Specifically, the first detection means 41 detects the first light L21 that has passed through the mirror 15 in the separation means 13. The first detection means 41 outputs the detection result to the control means 30.

[0035] The second detection means 42 is provided at a back-focus position relative to the sample SMP. For example, the second detection means 42 is provided at a back-focus position relative to the position where the light L10 (second light L22) is focused by the optical member 10, that is, optically behind the position where the light L10 (second light L22) is focused. The second detection means 42 detects the light L10 from the sample SMP. Specifically, the second detection means 42 detects the second light L22 reflected by the mirror 15 in the separation means 13. The second detection means 42 outputs the detection result to the control means 30.

[0036] The control unit 30 receives output results from the first detection unit 41 and the second detection unit 42. The control unit 30 then performs focusing control based on the output results from the first detection unit 41 and the second detection unit 42. Specifically, the control unit 30 performs focusing control by driving the drive unit 20, which moves the optical member 10 so that the light L10 forms an image on the main detection unit 40. For example, when the front focus position and the back focus position are at the same distance from the focal position, the control unit 30 causes the drive unit 20 to move the position of the optical member 10 so that the amount of received light of the first light L21 detected by the first detection unit 41 and the amount of received light of the second light L22 detected by the second detection unit 42 become equal. In this way, the control unit 30 performs focusing control.

[0037] The first shielding means 51 is disposed between the mirror 15 and the first detecting means 41. That is, the first shielding means 51 is disposed optically forward of the focal position of the beam of the first light L21. The first shielding means 51 shields at least the central region of the beam of the first light L21 that has passed through the mirror 15. The second shielding means 52 is disposed between the mirror 15 and the second detecting means 42. The second shielding means 52 may be disposed between the focal position of the beam of the second light L22 and the second detecting means 42. That is, the position where the first shielding means 51 is provided on the optical path of the first light L21 separated by the separating means 13 (the optical distance from the separating means 13 to the first shielding means 51) and the position where the second shielding means 52 is provided on the optical path of the second light L22 separated by the separating means 13 (the optical distance from the separating means 13 to the second shielding means 52) may be different from each other. The second shielding means 52 shields at least the central region of the light beam of the second light L22 reflected by the mirror 15.

[0038] 2 to 4 are cross-sectional views illustrating the shape of the first shielding means 51 that shields the first light L21 in the optical device 1 according to the first embodiment. In Fig. 2 to Fig. 4, one direction perpendicular to the first optical axis C21 is defined as the α-axis direction, and the other direction perpendicular to the first optical axis C21 is defined as the β-axis direction. Note that while Fig. 2 to Fig. 4 show the relationship between the first shielding means 51, the first light L21, and the first optical axis C21, the relationship between the second shielding means 52, the second light L22, and the second optical axis C22 is similar.

[0039] 2, the first shielding means 51 may have a rectangular cross section when viewed from the direction of the first optical axis C21 of the first light L21. Specifically, for example, the first shielding means 51 may have a rectangular cross section that includes the first optical axis C21 and extends in the α-axis direction. The first shielding means 51 separates the light flux of the first light L21 into two end regions ER separated in the β-axis direction. The first shielding means 51 shields a central region CR of the light flux of the first light L21 that includes the first optical axis C21, and transmits the first light L21 through an end region ER in the +β-axis direction and an end region ER in the −β-axis direction.

[0040] 3, the first shielding means 51 may have a rectangular cross section when viewed from the direction of the first optical axis C21 of the first light L21. Specifically, for example, the first shielding means 51 may have a rectangular cross section that includes the first optical axis C21 and extends in the α-axis direction. The first shielding means 51 shields a central region CR of the light flux of the first light L21 that includes the first optical axis C21 and an end region ER in the +β-axis direction, and transmits an end region ER on the −β-axis side of the first light L21. Alternatively, the first shielding means 51 may shield a central region CR of the light flux of the first light L21 that includes the first optical axis C21 and an end region ER in the −β-axis direction, and transmit an end region ER on the +β-axis side of the first light L21.

[0041] As shown in Fig. 4, when viewed from the direction of the first optical axis C21 of the first light L21, the first shielding means 51 may have a circular cross section that includes the first optical axis C21. The first shielding means 51 may shield a central region CR of the first light L21 and transmit an edge region ER on the periphery of the first light L21. Although Figs. 2 to 4 show rectangular and circular cross-sectional shapes of the first shielding means 51, these shapes are not limiting. The first shielding means 51 may have another cross-sectional shape as long as it can shield the central region CR of the luminous flux of the first light L21 and transmit the edge region ER of the luminous flux of the first light L21.

[0042] In this way, the first detecting means 41 and the second light detecting unit receive at least a part of the edge region ER in the beam of light L10 from the sample SMP. Specifically, the first detecting means 41 receives at least a part of the edge region ER in the beam of first light L21. The second detecting means 42 receives at least a part of the edge region ER in the beam of second light L22.

[0043] <Focus control method> Next, a description will be given of a focusing control method in the optical device 1 according to this embodiment. Fig. 5 is a flow chart illustrating a focusing control method in the optical device 1 according to the first embodiment.

[0044] 5, the first detecting means 41 is placed in a front-focus position, and the second detecting means 42 is placed in a back-focus position. Specifically, the first detecting means 41 that detects the light L10 from the sample SMP is placed in a front-focus position with respect to the sample SMP, and the second detecting means 42 that detects the light L10 from the sample SMP is placed in a back-focus position with respect to the sample SMP.

[0045] Next, as shown in step S12, at least a central region CR in the beam of light L10 is shielded by the first shielding means 51 and the second shielding means 52. Specifically, a portion of the light L10 from the sample SMP is split into a first light L21 and a second light L22 by the splitting means 13. The first shielding means 51 shields the central region CR in the beam of the first light L21, and the second shielding means 52 shields the central region CR in the beam of the second light L21.

[0046] Next, as shown in step S13, at least a part of the end region ER in the light beam of light L10 is received by the first detection means 41 and the second detection means 42. Specifically, the first detection means 41 receives at least a part of the end region ER in the light beam of the first light L21, and the second detection means 42 receives at least a part of the end region ER in the light beam of the second light L22.

[0047] Next, as shown in step S14, focusing control is performed based on the output results of the first detection means 41 and the second detection means 42. Specifically, the control means 30 moves the position of the optical member 10 by the driving means 20 based on the output results of the first detection means 41 and the second detection means 42. In this manner, focusing control of the optical device 1 can be performed.

[0048] <Comparative Example and This Embodiment> Next, before describing the effects of this embodiment, a comparative example will be described. After that, the effects of this embodiment will be described in comparison with the comparative example. This will make the effects of this embodiment clearer. Note that the comparative example is also included within the scope of the technical concept of this embodiment.

[0049] Fig. 6 is a perspective view illustrating the slit 151 in the optical device 101 according to the comparative example. Fig. 7 is a perspective view illustrating the first shielding means 51 in the optical device 1 according to the first embodiment. Fig. 6 shows the relationship between the slit 151 and the first detection means 41 at the front focus position, but the relationship between the slit and the second detection means 42 at the back focus position is also similar. Fig. 7 shows the relationship between the first shielding means 51 and the first detection means 41 at the front focus position, but the relationship between the second shielding means 52 and the second detection means 42 at the back focus position is also similar.

[0050] As shown in Fig. 6, in the optical device 101 of the comparative example, the slit 151 transmits a central region CR of the beam of first light L21 from the sample SMP. Therefore, the first detection means 41 receives the central region CR of the beam of first light L21. On the other hand, as shown in Fig. 7, in the optical device 1 of this embodiment, the first shielding means 51 shields the central region CR of the beam of first light L21 from the sample SMP. Therefore, the first detection means 41 receives an edge region ER of the beam of first light L21.

[0051] 8 is a graph illustrating the amounts of the first light L21 and the second light L22 received by the first detecting means 41 and the second detecting means 42, respectively, in an optical device 101 according to a comparative example, where the horizontal axis indicates the position of the sample surface from the focal point, and the vertical axis indicates the amounts of the first light L21 and the second light L22 received by the first detecting means 41 and the second detecting means 42, respectively. In the optical device 101 of FIG. 8, the first detecting means 41 and the second detecting means 42 are disposed in front of and behind the focal point, respectively, at equal distances apart.

[0052] 9 is a graph illustrating the change in the amount of received light calculated based on a predetermined formula from the amounts of first light L21 and second light L22 received by the first detection means 41 and the second detection means 42, respectively, in the optical device 101 according to the comparative example, where the horizontal axis represents the position of the sample surface from the focal point, and the vertical axis represents the change in the amount of received light calculated based on the predetermined formula. The predetermined formula showing the change D in the amount of received light in FIG. 9 is, for example, the following formula (1).

[0053] D=(AB) / (A+B) (1)

[0054] Here, A indicates the amount of first light L21 received by the first detecting means 41, and B indicates the amount of second light L22 received by the second detecting means 42. The slope of the profile of the change in the amount of received light shown in Fig. 9 indicates the sensitivity to detect the change in the amount of received light. As shown in Fig. 9, in the optical device 101 of the comparative example, the sensitivity to the change in the amount of received light detected by the first detecting means 41 and the second detecting means 42 is, for example, 1.12 / μm.

[0055] 10 is a graph illustrating the amounts of the first light L21 and the second light L22 received by the first detecting means 41 and the second detecting means 42, respectively, in the optical device 1 according to embodiment 1, where the horizontal axis indicates the position of the sample surface from the focal point, and the vertical axis indicates the amounts of the first light L21 and the second light L22 received by the first detecting means 41 and the second detecting means 42, respectively. In the optical device 1 of FIG. 10, the first detecting means 41 and the second detecting means 42 are disposed in front of and behind the focal point, respectively, at equal distances apart.

[0056] FIG. 11 is a graph illustrating the change in the amount of received light calculated based on a predetermined formula from the amounts of the first light L21 and the second light L22 received by the first detecting means 41 and the second detecting means 42, respectively, in the optical device 1 according to the first embodiment. The horizontal axis indicates the position of the sample surface from the focal point, and the vertical axis indicates the change in the amount of received light calculated based on the predetermined formula. The predetermined formula representing the change D in the amount of received light in FIG. 11 is the above-described formula (1). The slope of the profile of the change in the amount of received light shown in FIG. 11 indicates the sensitivity to detect the change in the amount of received light. As shown in FIG. 11, the sensitivity of the change in the amount of received light detected by the first detecting means 41 and the second detecting means 42 in the optical device 1 according to this embodiment is, for example, 3.8 / μm. Therefore, the sensitivity of the change in the amount of received light detected by the optical device 1 according to this embodiment is greater than the sensitivity of the change in the amount of received light detected by the optical device 101 of the comparative example.

[0057] In the optical device 1 of this embodiment, which has a magnifying optical system that detects light L10 from the sample SMP at a magnification of more than 100 times, even if the objective lens 11 in the optical element 10 has an NA of approximately 0.8, the NAs of the light L10, first light L21, and second light L22 immediately before entering the main detection means 40, first detection means 41, and second detection means 42 may be smaller than 0.008. That is, the light beams immediately before entering the main detection means 40, first detection means 41, and second detection means 42 are nearly parallel in the central region CR and have a slight inclination in the edge regions ER. Therefore, the sensitivity of detecting the focal position from changes in the amount of received light detected using the central region CR, which is nearly parallel, is low. On the other hand, the sensitivity of detecting the focal position from changes in the amount of received light detected using the edge regions ER, which are more inclined than the central region CR, is high. That is, because the amount of received light changes significantly with a small change in the position of the sample surface, the accuracy of detecting the focal position can be improved.

[0058] As in the optical device 101 of the comparative example shown in FIG. 9, when the central region CR of the first light L21 and the second light L22 transmitted through the slit 151 is used, the change in the amount of received light detected by the first detection means 41 and the second detection means 42 is small. Therefore, the slope of the profile is small, and the sensitivity for detecting the focal position is low. In contrast, as in the optical device 1 of this embodiment shown in FIG. 11, when the edge region ER is used by shielding the central region CR with the first shielding means 51 and the second shielding means 52, the change in the amount of received light detected by the first detection means 41 and the second detection means 42 is large. Therefore, the slope of the profile is large, and the sensitivity for detecting the focal position is high.

[0059] Next, the effects of this embodiment will be described. In this embodiment, the optical device 1 is provided with a first shielding means 51 and a second shielding means 52 that shield a central region CR in the beams of the first light L21 and the second light L22 used for focusing. This allows the first detecting means 41 and the second detecting means 42 to receive an edge region ER in the beam of the light L10 from the sample SMP. This makes it possible to make a steep change in signal output when searching for the focal position, making focusing easier.

[0060] The optical device 1 separates light L10 from the sample SMP into first light L21 and second light L22 using the separation means 13. As a result, the first detection means 41 receives an end region ER in the beam of the first light L21, and the second detection means 42 receives an end region ER in the beam of the second light L22. Therefore, the first light L21 and the second light L22 detected by the first detection means 41 and the second detection means 42 can be separated, and therefore the sensitivity of the first light L21 and the second light L22 detected by the first detection means 41 and the second detection means 42 can be improved.

[0061] <Variation 1> Next, a first modification of this embodiment will be described. The mirror 14 has at least two reflective regions. The mirror 14 reflects a portion of the light beam L10 from the sample SMP at the first reflective region and reflects the remaining portion of the light beam L10 from the sample SMP at the second reflective region. The light reflected at the first reflective region is detected by the first detection means 41, and the light reflected at the second reflective region is detected by the second detection means 42. In this modification, the mirror 14 can be said to be the separation means 13. In this modification, the mirror 15 provided in this embodiment may be omitted. When the light reflected at the first reflective region and detected by the first detection means 41 is referred to as L211 (not shown), and the light reflected at the second reflective region and detected by the second detection means 42 is referred to as L221 (not shown), a first shielding means 511 may be provided on the optical path of the light L211, and a second shielding means 521 may be provided on the optical path of the light L221. In this case, the first shielding means 511 and the second shielding means 521 may be provided at different positions on the optical path. The first shielding means 511 may be provided before the focal position of the light L211 formed by the mirror 14 (separation means), and the second shielding means 521 may be provided between the focal position of the light L221 formed by the mirror 14 (separation means) and the second detection means.

[0062] <Variation 2> Next, a second modification of the first embodiment will be described. In the second modification, a switching element 16 is provided as the separating means 13 instead of the mirror 15. The switching element 16 may be switched at high speed so that the light L10 (light L0) from the sample SMP is incident on each of the first detecting means 41 and the second detecting means 42. Such a switching element 16 is an example of the separating means 13 that separates a portion of the light L10 from the sample SMP into the first light L21 and the second light L22. Even with this configuration, the first detecting means 41 and the second detecting means 42 can receive the end region ER of the light beam of the light L10 (light L20) from the sample SMP. This makes it possible to make the change in signal output steeper when searching for the focal position, facilitating focusing.

[0063] <Embodiment 2> Next, an optical device 2 according to a second embodiment will be described. The optical device 2 according to this embodiment includes a slit in the optical path from the light source to the sample SMP. FIG. 12 is a structural diagram illustrating the optical device 2 according to the second embodiment. FIGS. 13 to 15 are plan views illustrating the slit plate 62 in the optical device 2 according to the second embodiment. As shown in FIGS. 12 to 15, the optical device 2 includes a light source 60, a lens 61, a slit plate 62, and a mirror 63. The optical device 2 may further include other components such as a polarizing plate.

[0064] The light source 60 generates illumination light L60. The illumination light L60 emitted from the light source 60 is converted into parallel light by a lens 61. The parallel illumination light L60 is incident on a slit plate 62. The optical axis of the illumination light L60 is referred to as an illumination optical axis C60. The slit plate 62 is disposed in the optical path from the light source 60 to the sample SMP. For example, the slit plate 62 is disposed between the lens 61 and the mirror 63. Note that the location of the slit plate 62 is not limited to between the lens 61 and the mirror 63, as long as it is disposed in the optical path from the light source 60 to the sample SMP. For example, when the illumination light L60 from the light source 60 illuminates the sample SMP without passing through the objective lens 11, the slit plate 62 may be disposed at a predetermined position between the light source 60 and the sample SMP.

[0065] As shown in Figures 13 to 15, the slit plate 62 has a plate surface perpendicular to the illumination optical axis C60. In Figures 13 to 15, one direction perpendicular to the illumination optical axis C60 is defined as the γ-axis direction, and the other direction perpendicular to the illumination optical axis C60 and the one direction is defined as the δ-axis direction. The slit plate 62 has a slit 70 and a detection hole 80. The slit 70 and the detection hole 80 penetrate the plate surface of the slit plate 62. In this way, the optical device 2 further includes a slit 70 arranged in the optical path from the light source 60 to the sample SMP.

[0066] As shown in Figures 13 and 14, the slit 70 may have a portion extending in one direction perpendicular to the illumination optical axis C60. Specifically, as shown in Figure 13, the slit 70 may have a shape extending in the γ-axis direction. In Figure 13, the extension direction of the slit 70 is the same as the extension direction of the pattern formed on the sample SMP, or a direction perpendicular to the extension direction of the pattern. The pattern includes, for example, a photomask pattern. The extension direction of the slit 70 is called the slit direction, and the extension direction of the pattern is called the pattern direction.

[0067] As shown in FIG. 14, the slit direction of the slit 70 may be tilted in the γ-axis direction and the δ-axis direction. In FIG. 14, the slit direction is tilted toward the pattern direction. When the slit direction is parallel to the pattern direction or perpendicular to the pattern direction, the illumination light L60 may be diffracted by the pattern. Such diffraction of the illumination light L60 changes the intensity of the light L10 from the sample SMP, which may affect focusing. Therefore, by tilting the slit direction toward the pattern direction, diffraction by the pattern can be reduced.

[0068] As shown in FIG. 15, the shape of the slit 70 may be a cross shape having two portions extending in directions inclined toward the γ-axis and δ-axis directions. In FIG. 15, the two slit directions are inclined toward the pattern direction. In this way, since there are two slit directions inclined toward the pattern direction, the effects of diffraction due to the inclination can be canceled out, and the effects of diffraction of the illumination light L60 can be further reduced. Note that the two slit directions in the cross shape may be in the γ-axis and δ-axis directions. Furthermore, the two slit directions may be in the pattern direction and a direction perpendicular to the pattern direction. This makes it possible to detect the effects of diffraction in each direction.

[0069] Illumination light L60 passes through the slit 70 and the detection hole 80. The portion of illumination light L60 that passes through the slit 70 is called slit light L70, and the light that passes through the detection hole 80 is called detection light L80. Illumination light L60 that passes through the slit plate 62 includes slit light L70 and detection light L80. A portion of illumination light L60 that passes through the slit plate 62 is reflected by the mirror 63.

[0070] The mirror 63 includes, for example, a half mirror. The illumination light L60 reflected by the mirror 63 is collected by the objective lens 11 and illuminates the sample SMP. The illumination light L60 that illuminates the sample SMP is reflected by the sample SMP. Therefore, in this embodiment, the light L10 from the sample SMP includes the illumination light L60 reflected by the sample SMP. In other words, the light L10 from the sample SMP includes the slit light L70 and the detection light L80 reflected by the sample SMP. The reflected light of the slit light L70 and the detection light L80 reflected by the sample SMP are also referred to as the slit light L70 and the detection light L80, respectively. As in the first embodiment, the light L10 from the sample SMP is detected by the main detection means 40, the first detection means 41, and the second detection means 42 via the objective lens 11 and the relay lens 12.

[0071] As described above, the optical device 2 of this embodiment has a magnifying optical system. Therefore, the light beams immediately before entering the main detection means 40, the first detection means 41, and the second detection means 42 are nearly parallel. Furthermore, the separation means 13 is disposed at a position where the light beam of light L10 can be considered parallel. As a result, the separation means 13 separates the slit light beam L70 reflected by the sample SMP from the detection light beam L80 reflected by the sample SMP. The light L20 reflected by the mirror 14 in the separation means 13 includes the slit light beam L70.

[0072] The light L20 reflected by the mirror 14 is incident on the mirror 15 in the separating means 13. The first light L21 transmitted through the mirror 15 and the light L22 reflected by the mirror 15 contain the slit light L70. In this way, the separating means 13 separates the slit light L70 into the first light L21 and the second light L22. The light L10 that is not reflected by the mirror 14 and is incident on the main detecting means 40 contains the detection light L80.

[0073] 16 to 21 are cross-sectional views illustrating the shape of the first shielding means 51 that shields the first light L21 including the slit light L70 in the optical device 2 according to embodiment 2. Note that while Figs. 16 to 21 show the relationship between the first shielding means 51, the slit light L70, and the first optical axis C21, the relationship between the second shielding means 52, the slit light L70, and the second optical axis C22 is similar.

[0074] 16, when the slit light L70 extends in the α-axis direction, the first shielding means 51 may have a rectangular cross-sectional shape extending in the α-axis direction. The first shielding means 51 may separate the luminous flux of the slit light L70 into two end regions ER divided in the β-axis direction. The first shielding means 51 may shield a central region CR of the luminous flux of the slit light L70 including the first optical axis C21, and transmit an end region ER in the +β-axis direction and an end region ER in the −β-axis direction of the slit light L70.

[0075] 17, when the slit light L70 extends in the α-axis direction, the first shielding means 51 may have a rectangular cross-sectional shape extending in the α-axis direction. The first shielding means 51 may shield a central region CR of the luminous flux of the slit light L70 including the first optical axis C21 and an end region ER in the +β-axis direction, and may transmit an end region ER on the −β-axis side of the slit light L70.

[0076] The first shielding means 51 may shield the central region CR and the edge region ER in the −β-axis direction of the luminous flux of the slit light L70, and transmit the edge region ER on the +β-axis side of the slit light L70.

[0077] 18, when the slit beam L70 extends in a direction inclined toward the α-axis and β-axis directions, the first shielding means 51 may have a rectangular cross-sectional shape extending in a direction inclined toward the α-axis and β-axis directions. The first shielding means 51 may separate the luminous flux of the slit beam L70 into two end regions ER separated in a direction perpendicular to the direction in which the slit beam L70 extends (referred to as the slit beam perpendicular direction). The first shielding means 51 may shield a central region CR of the luminous flux of the slit beam L70 including the first optical axis C21, and may transmit end regions ER at both ends of the slit beam L70 in the slit beam perpendicular direction.

[0078] The first shielding means 51 may shield the central region CR of the light flux of the slit light L70 and one end region ER of the slit light L70 in the direction perpendicular to the slit light, and transmit the other end region ER.

[0079] 19, when the slit light beam L70 extends in a direction inclined toward the α-axis direction and the β-axis direction, the first shielding means 51 may have a rectangular cross-sectional shape extending in the α-axis direction. The first shielding means 51 may separate the luminous flux of the slit light beam L70 into two end regions ER separated in the β-axis direction. The first shielding means 51 may shield a central region CR of the luminous flux of the slit light beam L70 and transmit an end region ER in the +β-axis direction and an end region ER in the −β-axis direction of the slit light beam L70.

[0080] The first shielding means 51 may shield the central region CR and one end region ER in the β-axis direction of the luminous flux of the slit light L70, and transmit the other end region ER in the β-axis direction.

[0081] 20 , in the case where the slit beam L70 has a cross shape having two portions (referred to as the first slit beam L71 and the second slit beam L72) extending in two mutually orthogonal directions (referred to as the first slit beam direction and the second slit beam direction) tilted toward the α-axis and β-axis directions, the first shielding means 51 may have a cross-shaped cross section. Specifically, the first shielding means 51 may separate the light beam of the first slit beam L71 into two end regions ER separated in a direction orthogonal to the first slit beam direction (referred to as the first slit beam orthogonal direction). The first shielding means 51 may shield a central region CR of the light beam of the first slit beam L71 and transmit end regions ER at both ends of the first slit beam L71 in the first slit beam orthogonal direction.

[0082] The first shielding means 51 may also separate the second slit light beam L72 into two end regions ER separated in a direction perpendicular to the second slit light direction (referred to as the second slit light perpendicular direction).The first shielding means 51 may then shield a central region CR of the second slit light beam L72 and transmit end regions ER on both ends of the second slit light beam L72 in the second slit light perpendicular direction.

[0083] The first shielding means 51 may shield a central region CR of the light beam of the first slit light L71 and one end region ER of the first slit light L71 in the direction perpendicular to the first slit light, and may transmit the other end region ER. The first shielding means 51 may also shield a central region CR of the light beam of the second slit light L72 and one end region ER of the second slit light L72 in the direction perpendicular to the second slit light, and may transmit the other end region ER.

[0084] 21 , even when the slit light L70 has a cross shape including a first slit light L71 and a second slit light L72 extending in the first and second slit light directions, the first shielding means 51 may have a rectangular cross-sectional shape. The first shielding means 51 may separate the luminous flux of the slit light L70 including the first slit light L71 and the second slit light L72 into two end regions ER separated in the β-axis direction. The first shielding means 51 may shield a central region CR of the luminous flux of the slit light L70 and transmit an end region ER in the +β-axis direction and an end region ER in the −β-axis direction of the slit light L70.

[0085] The first shielding means 51 may shield the central region CR of the luminous flux of the slit light L70 and one end region ER in the β-axis direction, and transmit the other end region ER.

[0086] In this way, the shapes of the first shielding means 51 and the second shielding means 52 are set based on at least one of the orientation and size of the slit 70. The first shielding means 51 shields at least the central region CR of the slit light L70 contained in the first light L21. The second shielding means 52 shields at least the central region CR of the slit light L70 contained in the second light L22.

[0087] According to this embodiment, in the optical device 2, the shapes of the first shielding means 51 and the second shielding means 52 are set based on at least one of the orientation and the size of the slit 70. This improves the degree of freedom in designing the optical member 10, etc. For example, since it is possible to accommodate a slit direction designed based on the pattern orientation, the optical device 2 can accommodate a wide variety of variations.

[0088] <Variation 3> Next, a third modification of the second embodiment will be described with reference to FIG. 22. FIG. 22 is a structural diagram illustrating an optical device according to the third modification of the second embodiment. In an optical device 2c of the third modification, the components functioning as the aforementioned separating means 13 include a mirror 141 as the first separating means 131 and a mirror 142 as the second separating means 132. The slit plate 62 has a rectangular slit 70 and a detection hole 80 (see, for example, FIG. 13). The mirror 141 reflects the slit light L71 that has passed through the vicinity of the first short side of the slit 70 and is reflected by the sample SMP, and the mirror 142 reflects the slit light L72 that has passed through the vicinity of the second short side of the slit 70 and is reflected by the sample SMP. The first short side and the second short side are opposite sides of the slit 70. The slit light L71 reflected by the mirror 141 is detected by the first detecting means 41, and the slit light L72 reflected by the mirror 142 is detected by the second detecting means 42. A first shielding means 51 is provided on the optical path of the slit light L71, and a second shielding means 52 is provided on the optical path of the slit light L72. The mirror 141 as the first separating means 131 may be provided closer to the sample SMP than the mirror 142 as the second separating means 132, i.e., optically further forward. Furthermore, the optical distance (D11) between the mirror 141, which is the first separating means 131, and the first shielding means 51 may be equal to the optical distance (D12) between the mirror 142, which is the second separating means 132, and the second shielding means 52, and the optical distance (D21) between the first shielding means 51 and the first detecting means 41 may be equal to the optical distance (D22) between the second shielding means 52 and the second detecting means 42. By making these optical distances equal, a unit including the separating means, the shielding means, and the detecting means can be used in common for the light L71 (for front focus) and the light L72 (for back focus). Note that in the third modification, the slit plate 62 does not have to be provided.

[0089] <Variation 4> In Modification 3, a slit plate 621 shown in FIG. 23 may be provided instead of the slit plate 62. FIG. 23 is a plan view illustrating the slit plate 621 in an optical device according to Modification 4 of Embodiment 2. The slit plate 621 has a slit 71, a slit 72, and a detection hole 80. The slits 71, 72, and the detection hole 80 penetrate the plate surface of the slit plate 621. The slits 71 and 72 may be provided at positions facing each other across the illumination optical axis C60 (for example, positions point-symmetric with respect to the illumination optical axis C60). The slits 71 and 72 may have any of the shapes and directions described with reference to FIGS. 13 to 15. The illumination light L60 passes through the slits 71, 72, and the detection hole 80. In this modification, the portion of illumination light L60 that passes through slit 71 is referred to as slit light L71, and the portion of illumination light L60 that passes through slit 72 is referred to as slit light L72. Mirror 141 may reflect slit light L71 reflected by sample SMP, and mirror 142 may reflect slit light L72 reflected by sample SMP. First shielding means 51 is provided on the optical path of slit light L71 reflected by mirror 141, and slit light L71 is detected by first detection means 41. Second shielding means 52 is provided on the optical path of slit light L72 reflected by mirror 142, and slit light L72 is detected by second detection means 42. Mirrors 141 and 142 may be provided at positions 180° apart across main optical axis C10.

[0090] Although the embodiments of the present disclosure have been described above, the present disclosure includes appropriate modifications that do not impair the objects and advantages thereof, and is not limited to the above-described embodiments. Furthermore, appropriate omissions and combinations of the configurations of Embodiments 1 and 2 and Modifications 1, 2, 3, and 4 are also within the scope of the technical concept of the present disclosure. Furthermore, the following configurations are also within the scope of the technical concept of the embodiments. [Explanation of symbols]

[0091] 1, 2, 2c, 2d optical equipment 10 Optical components 11 Objective Lens 12 Relay Lens 13 Separation means 14, 15, 141, 142 Mirror 16 Switching element 20 Driving means 30 Control Means 40 Main detection means 41 First detection means 42 Second detection means 50 Shielding means 51 First shielding means 52 Second shielding means 60 light source 61 Lens 62, 621 Slit plate 63 Mirror 70, 71, 72 Slits 80 detection hole 101 Optical equipment 131 First separation means 132 Second separation means 151 Slit C10 Main optical axis C21 1st optical axis C22 2nd optical axis C60 illumination optical axis CR central area ER end area L10 light L20 light L21 1st light L22 2nd light L60 illumination light L70, L71, L72 slit light L80 detection light SMP sample

Claims

1. a first detecting means provided at a front-focus position relative to the sample and configured to detect light from the sample; a second detecting means provided at a rear focus position relative to the sample and detecting the light from the sample; a control means for performing focusing control based on the output result of the first detection means and the output result of the second detection means; a shielding means for shielding at least a central region of the light beam from the sample; Equipped with the first detecting means and the second detecting means receive at least a portion of an end region of the beam of light from the sample; optical equipment.

2. further comprising a splitting means for splitting a portion of the light from the sample into a first light and a second light, the first detecting means receives at least a part of the end region of the light beam of the first light, the second detecting means receives at least a part of the end region of the light beam of the second light; 10. The optical device of claim 1.

3. The shielding means is a first shielding means for shielding at least the central region of the light beam of the first light; a second shielding means for shielding at least the central region of the light beam of the second light; Including, 3. The optical device according to claim 2.

4. an optical distance from the separating means to the first shielding means and an optical distance from the separating means to the second shielding means are different; 4. The optical device according to claim 3.

5. the second shielding means is provided between a focal position of the second light and the second detecting means.

5. An optical device according to claim 3 or 4.

6. The separating means a first separating means for separating a portion of the light from the sample into a first light; a second separating means for separating a portion of the light from the sample into a second light, the first separating means is provided closer to the sample than the second separating means; 4. The optical device according to claim 3.

7. an optical distance between the first separating means and the first shielding means is equal to an optical distance between the second separating means and the second shielding means; The optical distance between the first shielding means and the first detecting means is equal to the optical distance between the second shielding means and the second detecting means.

7. The optical device according to claim 6.

8. further comprising a slit disposed in a light path from a light source to the sample; The shape of the shielding means is set based on at least one of the orientation and size of the slit.

10. The optical device of claim 1.

9. providing a first detecting means for detecting light from a sample at a front-focus position relative to the sample, and a second detecting means for detecting the light from the sample at a back-focus position relative to the sample; a step of blocking at least a central region of the beam of light from the sample with a blocking means; receiving at least a portion of an end region of the light beam by the first detecting means and the second detecting means; performing focusing control based on the output result of the first detection means and the output result of the second detection means; A focusing control method comprising:

10. further comprising a step of separating a portion of the light from the sample into a first light and a second light by a separating means; In the step of receiving light by the first detecting means and the second detecting means, the first detecting means receives at least a part of the end region of the light beam of the first light, the second detecting means receives at least a part of the end region of the light beam of the second light; The focusing control method according to claim 9.

11. In the step of shielding with the shielding means, The shielding means is a first shielding means for shielding at least the central region of the light beam of the first light; a second shielding means for shielding at least the central region of the light beam of the second light; Including, The focusing control method according to claim 10.

12. In the step of shielding with the shielding means, an optical distance from the separating means to the first shielding means and an optical distance from the separating means to the second shielding means are different; The focusing control method according to claim 11.

13. In the step of shielding with the shielding means, the second shielding means is provided between a focal position of the second light and the second detecting means.

13. The focusing control method according to claim 11 or 12.

14. In the separating step, The separating means a first separating means for separating a portion of the light from the sample into a first light; a second separating means for separating a portion of the light from the sample into a second light, the first separating means is provided closer to the sample than the second separating means; The focusing control method according to claim 11.

15. In the separating step, an optical distance between the first separating means and the first shielding means is equal to an optical distance between the second separating means and the second shielding means; The optical distance between the first shielding means and the first detecting means is equal to the optical distance between the second shielding means and the second detecting means.

15. The focusing control method according to claim 14.

16. further comprising the step of placing a slit in a light path from a light source to the sample; In the step of shielding with the shielding means, The shape of the shielding means is set based on at least one of the orientation and size of the slit. The focusing control method according to claim 9.

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