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 Art

[0002] In Patent Document 1, for example, a front pin and a rear pin method have been proposed as a focusing control method.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Due to requirements for an optical device and the like, it is preferable that there are various variations for focusing control in the front pin and rear pin methods. Among such variations, in particular, an optical device and a focusing control method that can facilitate focusing are desired.

[0005] The present disclosure has been made to solve the above-described problems, and an object thereof is to provide an optical device and a focusing control method that can facilitate focusing.

Means for Solving the Problems

[0006] The optical apparatus according to this disclosure comprises: a first detection means provided at a front-pin position relative to a sample for detecting light from the sample; a second detection means provided at a rear-pin position relative to the sample for detecting the light from the sample; a control means for performing focus control based on the output result of the first detection means and the output result of the second detection means; and a shielding means for shielding at least the central region of the light beam of the light from the sample, wherein the first detection means and the second detection means receive at least a portion of the edge region of the light beam of the light from the sample.

[0007] The optical apparatus described above further includes 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 of the light beam of the first light, and the second detection means receives at least a portion of the end region of the light beam of the second light.

[0008] In the optical device described above, 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 described above, the optical distance from the separating means to the first shielding means and the optical distance from the separating means to the second shielding means may be different.

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

[0011] In the optical apparatus described above, the separation means includes a first separation means for separating a portion of the light from the sample into first light, and a second separation means for separating a portion of the light from the sample into second light, wherein the first separation means may be provided closer to the sample than the second separation means.

[0012] In the optical apparatus described above, the optical distance between the first separation means and the first shielding means may be equal to the optical distance between the second separation means and the second shielding means, and the optical distance between the first shielding means and the first detection means may be equal to the optical distance between the second shielding means and the second detection means.

[0013] The optical apparatus described above further includes a slit positioned 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 this disclosure comprises the steps of: providing a first detection means for detecting light from a sample at a front-pin position relative to the sample; providing a second detection means for detecting the light from the sample at a rear-pin position relative to the sample; shielding at least the central region of the light beam from the sample with a shielding means; receiving at least a portion of the edge region of the light beam with the first detection means and the second detection means; and performing focusing control based on the output result of the first detection means and the output result of the second detection means.

[0015] The above focusing control method further comprises a step of separating a portion of the light from the sample into a first light and a second light using separation means, and in the step of receiving light with the first detection means and the second detection means, the first detection means may receive at least a portion of the end region of the light beam of the first light, and the second detection means may receive at least a portion of the end region of 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 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.

[0017] In the focus adjustment control method, in the step of shielding by the shielding means, the optical distance from the separation means to the first shielding means and the optical distance from the separation means to the second shielding means may be different.

[0018] In the focus adjustment control method, in the step of shielding by the shielding means, the second shielding means may be provided between the focal position of the second light and the second detection means.

[0019] In the focus adjustment control method, in the separating step, the separating means includes a first separating means for separating a part of the light from the sample into first light and a second separating means for separating a part of the light from the sample into second light, and the first separating means may be provided closer to the sample side than the second separating means.

[0020] In the focus adjustment 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 detection means may be equal to the optical distance between the second shielding means and the second detection means.

[0021] [[ID=I6]]The focus adjustment control method further includes a step of disposing a slit in the optical path from the light source to the sample, and in the step of shielding by the shielding means, the shape of the shielding means may be set based on at least one of the direction and size of the slit.

Advantages of the Invention

[0022] According to the present disclosure, it is possible to provide an optical device and a focus adjustment control method that can facilitate focus adjustment.

Brief Description of the Drawings

[0023] [Figure 1] It is a configuration diagram illustrating an optical device according to Embodiment 1. [Figure 2] In the optical device according to Embodiment 1, it is a cross-sectional view illustrating the shape of a shielding means for shielding light. [Figure 3] In the optical device according to Embodiment 1, it is a cross-sectional view illustrating the shape of a shielding means for shielding light. [Figure 4] In the optical device according to Embodiment 1, it is a cross-sectional view illustrating the shape of a shielding means for shielding light. [Figure 5] In the optical device according to Embodiment 1, it is a flowchart diagram illustrating a focusing control method. [Figure 6] In the optical device according to the comparative example, it is a perspective view illustrating a slit. [Figure 7] In the optical device according to Embodiment 1, it is a perspective view illustrating a shielding means. [Figure 8] In the optical device according to the comparative example, it is a graph illustrating the light reception amounts of the first light and the second light respectively received by the first detection means and the second detection means. The horizontal axis represents the position of the sample surface from the focus, and the vertical axis represents the light reception amounts of the first light and the second light respectively received by the first detection means and the second detection means. [Figure 9] In the optical device according to the comparative example, it is a graph illustrating the change in the light reception amount calculated based on a predetermined formula from the light reception amounts of the first light and the second light respectively received by the first detection means and the second detection means. The horizontal axis represents the position of the sample surface from the focus, and the vertical axis represents the change in the light reception amount calculated based on the predetermined formula. [Figure 10] In the optical device according to Embodiment 1, it is a graph illustrating the light reception amounts of the first light and the second light respectively received by the first detection means and the second detection means. The horizontal axis represents the position of the sample surface from the focus, and the vertical axis represents the light reception amounts of the first light and the second light respectively received by the first detection means and the second detection means. [Figure 11] In the optical device according to Embodiment 1, it is a graph illustrating the change in the light reception amount calculated based on a predetermined formula from the light reception amounts of the first light and the second light respectively received by the first detection means and the second detection means. The horizontal axis represents the position of the sample surface from the focus, and the vertical axis represents the change in the light reception amount calculated based on the predetermined formula. [Figure 12] This is a diagram illustrating an optical device according to Embodiment 2. [Figure 13] This is a plan view illustrating a slit plate in the optical device according to Embodiment 2. [Figure 14] This is a plan view illustrating a slit plate in the optical device according to Embodiment 2. [Figure 15] This is a plan view illustrating a slit plate in the optical device according to Embodiment 2. [Figure 16] This is a cross-sectional view illustrating the shape of a shielding means for shielding the first light, including the slit light, in the optical device according to Embodiment 2. [Figure 17] This is a cross-sectional view illustrating the shape of a shielding means for shielding the first light, including the slit light, in the optical device according to Embodiment 2. [Figure 18] This is a cross-sectional view illustrating the shape of a shielding means for shielding the first light, including the slit light, in the optical device according to Embodiment 2. [Figure 19] This is a cross-sectional view illustrating the shape of a shielding means for shielding the first light, including the slit light, in the optical device according to Embodiment 2. [Figure 20] This is a cross-sectional view illustrating the shape of a shielding means for shielding the first light, including the slit light, in the optical device according to Embodiment 2. [Figure 21] This is a cross-sectional view illustrating the shape of a shielding means for shielding the first light, including the slit light, in the optical device according to Embodiment 2. [Figure 22] This is a diagram illustrating an optical device according to a modified example 3 of Embodiment 2. [Figure 23] This is a plan view illustrating a slit plate in an optical device according to a modified example 4 of Embodiment 2. [Modes for carrying out the invention]

[0024] The specific configuration of this embodiment will be described below with reference to the drawings. The following description illustrates preferred embodiments of the present disclosure, and the scope of the present disclosure is not limited to the following embodiments. In the following description, the same reference numerals indicate substantially the same components.

[0025] <Embodiment 1> The optical device and focus control method according to Embodiment 1 will now be described. The optical device is, for example, an inspection device for inspecting a sample. However, the optical device is not limited to an inspection device; for example, it may be an imaging device for imaging a sample.

[0026] <Optical equipment> Figure 1 is a diagram illustrating an optical device according to Embodiment 1. As shown in Figure 1, the optical device 1 comprises 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. In addition to these components, the optical device 1 may further comprise other components, or some of these components may be omitted.

[0027] The optical component 10 focuses the light L10 from the sample SMP. The optical component 10 is configured to guide the focused 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 component 10 includes an objective lens 11, a relay lens 12, and a separation means 13. In addition to these components, the optical component 10 may also include other components, or some of these components may be omitted, as long as it is configured to focus the light L10 from the sample SMP to the main detection means 40.

[0028] The objective lens 11 focuses the light L10 from the sample SMP. The objective lens 11 may convert the light L10 into parallel light. The light L10 that has passed through the objective lens 11 is incident on the relay lens 12. The relay lens 12 focuses the incident light L10 so that it is focused 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 principal optical axis C10 of the light L10. This causes the driving means 20 to position 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 detection means 40. Thus, 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. This allows the driving means 20 to move the objective lens 11 along the direction of the principal optical axis C10. The driving means 20 may also be attached to an optical member 10 other than the objective lens 11, as long as it can align the focal point of the optical member 10 with the sample surface and the light-receiving surface of the main detection means 40.

[0031] The separation means 13 may include mirrors 14 and 15. In addition to mirrors 14 and 15, the separation means 13 may also include other components. Mirror 14 separates a portion of light L10 from light L10. The portion of light L10 separated by mirror 14 is called light L20. The light L20 separated by mirror 14 is incident on mirror 15.

[0032] Mirror 15 transmits a portion of the light L20 and reflects a portion of the light L20. Mirror 15 includes, for example, a half-mirror. Note that mirror 15 may be other mirrors such as an unpolarized beam splitter. For example, mirror 15 transmits half of the light L20 and reflects the other half. The light L20 transmitted through mirror 15 is called the first light L21. The first light L21 transmitted through mirror 15 is incident on the first detection means 41. The optical axis of the first light L21 incident on the first detection means 41 is called the first optical axis C21. On the other hand, the light L20 reflected by mirror 15 is called the second light L22. The second light L22 reflected by mirror 15 is incident on the second detection means 42. The optical axis of the second light L22 incident on the second detection means 42 is called the second optical axis C22.

[0033] In this way, the separation means 13 separates a portion 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 positioned in front of the sample SMP. For example, the first detection means 41 is positioned in front of 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 positioned at a back-pin position with respect to the sample SMP. For example, the second detection means 42 is positioned at a back-pin position with respect to the position where light L10 (second light L22) is focused by the optical member 10, that is, optically behind the position where light L10 (second light L22) is focused. The second detection means 42 detects 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 means 30 receives output results from the first detection means 41 and the second detection means 42. Based on the output results of the first detection means 41 and the second detection means 42, the control means 30 performs focus adjustment control. Specifically, the control means 30 performs focus adjustment control by driving the driving means 20 to move the optical member 10 so that the light L10 forms an image on the main detection means 40. For example, if the front pin position and the back pin position are at the same distance from the focal position, the control means 30 moves the position of the optical member 10 using the driving means 20 so that the amount of light received by the first detection means 41 (first light L21) and the amount of light received by the second detection means 42 (second light L22) are equal. In this way, the control means 30 performs focus adjustment control.

[0037] The first shielding means 51 is positioned between the mirror 15 and the first detection means 41. That is, the first shielding means 51 is positioned optically forward of the focal point of the light beam of the first light L21. The first shielding means 51 shields at least the central region of the light beam of the first light L21 that has passed through the mirror 15. The second shielding means 52 is positioned between the mirror 15 and the second detection means 42. The second shielding means 52 may be positioned between the focal point of the light beam of the second light L22 and the second detection 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 separation means 13 (optical distance from the separation 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 separation means 13 (optical distance from the separation 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] Figures 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 Embodiment 1. In Figures 2 to 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 and one direction is defined as the β-axis direction. In Figures 2 to 4, the relationship between the first shielding means 51, the first light L21, and the first optical axis C21 is shown, but the relationship between the second shielding means 52, the second light L22, and the second optical axis C22 is similar.

[0039] As shown in Figure 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-sectional shape that includes the first optical axis C21 and extends in the α-axis direction. The first shielding means 51 separates the light beam of the first light L21 into two end regions ER divided in the β-axis direction. The first shielding means 51 shields the central region CR of the light beam of the first light L21 including the first optical axis C21, and transmits the end region ER in the +β-axis direction and the end region ER in the -β-axis direction of the first light L21.

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

[0041] As shown in Figure 4, when viewed from the direction of the first optical axis C21 of the first light beam L21, the first shielding means 51 may have a circular cross-section including the first optical axis C21. The first shielding means 51 may shield the central region CR of the first light beam L21 and transmit the peripheral end region ER of the first light beam L21. In Figures 2 to 4, rectangular and circular cross-sectional shapes are shown for the first shielding means 51, but it is not limited to these. The first shielding means 51 may have other cross-sectional shapes as long as it can shield the central region CR of the light beam of the first light beam L21 and transmit the end region ER of the light beam of the first light beam L21.

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

[0043] <Focus adjustment control method> Next, the focus control method in the optical device 1 according to this embodiment will be described. Figure 5 is a flowchart illustrating the focus control method in the optical device 1 according to Embodiment 1.

[0044] As shown in step S11 of Figure 5, the first detection means 41 is installed at the front pin position and the second detection means 42 is installed at the rear pin position. Specifically, the first detection means 41, which detects light L10 from the sample SMP, is installed at the front pin position relative to the sample SMP, and the second detection means 42, which detects light L10 from the sample SMP, is installed at the rear pin position relative to the sample SMP.

[0045] Next, as shown in step S12, at least the central region CR in the luminous 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 separated into a first light L21 and a second light L22 by the separation means 13. The first shielding means 51 shields the central region CR in the luminous beam of the first light L21, and the second shielding means 52 shields the central region CR in the luminous beam of the second light L21.

[0046] Next, as shown in step S13, at least a portion of the edge region ER in the luminous 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 portion of the edge region ER in the luminous beam of the first light L21, and the second detection means 42 receives at least a portion of the edge region ER in the luminous beam of the second light L22.

[0047] Next, as shown in step S14, focus adjustment 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 using the drive means 20 based on the output results of the first detection means 41 and the second detection means 42. In this way, focus adjustment control of the optical device 1 can be performed.

[0048] <Comparative Example and This Embodiment> Next, before describing the effects of this embodiment, we will describe a comparative example. Then, we will describe the effects of this embodiment 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] Figure 6 is a perspective view illustrating a slit 151 in an optical device 101 according to a comparative example. Figure 7 is a perspective view illustrating a first shielding means 51 in an optical device 1 according to Embodiment 1. Figure 6 shows the relationship between the slit 151 and the first detection means 41 at the front pin position, and the relationship between the slit and the second detection means 42 at the rear pin position is similar. Figure 7 shows the relationship between the first shielding means 51 and the first detection means 41 at the front pin position, and the relationship between the second shielding means 52 and the second detection means 42 at the rear pin position is similar.

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

[0051] Figure 8 is a graph illustrating the amount of light received by the first detection means 41 and the second detection means 42, respectively, in an optical apparatus 101 according to a comparative example. The horizontal axis indicates the position of the sample surface from the focal point, and the vertical axis indicates the amount of light received by the first detection means 41 and the second detection means 42, respectively. In the optical apparatus 101 of Figure 8, the first detection means 41 and the second detection means 42 are positioned at the same distance from each other, in front of and behind the focal point, respectively.

[0052] Figure 9 is a graph illustrating the change in the amount of light received in the optical apparatus 101 according to a comparative example, calculated based on a predetermined formula from the amount of light received by the first detection means 41 and the second detection means 42, respectively. 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 light received calculated based on the predetermined formula. The predetermined formula showing the change in the amount of light received D in Figure 9 is, for example, the following formula (1).

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

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

[0055] Figure 10 is a graph illustrating the amount of light received by the first detection means 41 and the second detection means 42, respectively, in the optical device 1 according to Embodiment 1. The horizontal axis indicates the position of the sample surface from the focal point, and the vertical axis indicates the amount of light received by the first detection means 41 and the second detection means 42, respectively. In the optical device 1 of Figure 10, the first detection means 41 and the second detection means 42 are positioned at the same distance from each other, in front of and behind the focal point.

[0056] Figure 11 is a graph illustrating the change in the amount of light received in the optical device 1 according to Embodiment 1, calculated by the first detection means 41 and the second detection means 42 based on a predetermined formula from the amount of light received by the first light L21 and the second light L22, respectively. 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 light received calculated based on the predetermined formula. The predetermined formula showing the change in the amount of light received D in Figure 11 is formula (1) described above. The slope in the profile of the change in the amount of light received shown in Figure 11 indicates the sensitivity to sensing the change in the amount of light received. As shown in Figure 11, in the optical device 1 of this embodiment, the sensitivity to the change in the amount of light received detected by the first detection means 41 and the second detection means 42 is, for example, 3.8 / μm. Therefore, the sensitivity to the change in the amount of light received detected by the optical device 1 of this embodiment is greater than the sensitivity to the change in the amount of light received detected by the optical device 101 of the comparative example.

[0057] In the case of the optical device 1 of this embodiment, which has a magnifying optical system that detects light L10 from a sample SMP by magnifying it to a magnitude greater than 100, even if the NA of the objective lens 11 in the optical element 10 is about 0.8, the NA of the light L10, first light L21, and second light L22 immediately before they enter the main detection means 40, first detection means 41, and second detection means 42 may be less than 0.008. In other words, the light beam immediately before it enters the main detection means 40, first detection means 41, and second detection means 42 is close to parallel light in the central region CR and has a slight inclination in the edge region ER. Therefore, the sensitivity to detect the focal position from changes in the amount of light detected using the central region CR, which is close to parallel light, is insensitive. On the other hand, the sensitivity to detect the focal position from changes in the amount of light detected using the edge region ER, which has more inclination than the central region CR, is sensitive. That is, since the amount of light detected changes greatly with even a small change in the position of the sample surface, the accuracy of detecting the focal position can be improved.

[0058] As shown in the comparative example optical device 101 in Figure 9, when the central region CR of the first light L21 and second light L22 transmitted through the slit 151 is used, the change in the amount of 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 small. In contrast, as shown in the optical device 1 of this embodiment in Figure 11, when the central region CR is shielded by the first shielding means 51 and the second shielding means 52 and the edge region ER is used, the change in the amount of 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 large.

[0059] Next, the effects of this embodiment will be described. In this embodiment, the optical device 1 is equipped with a first shielding means 51 and a second shielding means 52 that shield the central region CR in the light beams of the first light L21 and the second light L22 used for focusing. As a result, the first detection means 41 and the second detection means 42 can receive the edge region ER in the light beam of light L10 from the sample SMP. Therefore, the signal output change during the search for the focal position can be made steeper, making focusing easier.

[0060] The optical device 1 separates the light L10 from the sample SMP into a first light L21 and a second light L22 using a separation means 13. As a result, the first detection means 41 receives the edge region ER of the light beam of the first light L21, and the second detection means 42 receives the edge region ER of the light 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 thus 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] <Example 1> Next, a modified example 1 of this embodiment will be described. The mirror 14 has at least two reflection regions. The mirror 14 reflects a portion of the light beam L10 from the sample SMP in the first reflection region, and the remaining portion of the light beam L10 from the sample SMP in the second reflection region. The light reflected in the first reflection region is detected by the first detection means 41, and the light reflected in the second reflection region is detected by the second detection means 42. In this modified example, the mirror 14 can be said to be the separation means 13, and in this modified example, the mirror 15 that was provided in this embodiment may be omitted. When the light reflected in the first reflection region and detected by the first detection means 41 is called L211 (not shown), and the light reflected in the second reflection region and detected by the second detection means 42 is called L221 (not shown), a first shielding means 511 may be provided on the optical path of light L211, and a second shielding means 521 may be provided on the optical path of light L221. Furthermore, the positions in the optical path where the first shielding means 511 and the second shielding means 521 are provided may be different from each other. The first shielding means 511 may be provided in front of 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] <Modification 2> Next, a modified example 2 of Embodiment 1 will be described. In Modified Example 2, the separation means 13 is provided with a switching element 16 instead of a mirror 15. The switching element 16 may be switched at high speed so that light L10 (light L0) from the sample SMP is incident on each of the first detection means 41 and the second detection means 42. Such a switching element 16 is an example of a separation means 13 that separates a portion of the light L10 from the sample SMP into first light L21 and second light L22. Even with this configuration, the first detection means 41 and the second detection means 42 can receive the edge region ER in the light beam of light L10 (light L20) from the sample SMP. Therefore, the signal output change during the search for the focal position can be made steeper, making focusing easier.

[0063] <Embodiment 2> Next, the optical device 2 according to Embodiment 2 will be described. The optical device 2 of this embodiment is equipped with a slit in the optical path from the light source to the sample SMP. Figure 12 is a configuration diagram illustrating the optical device 2 according to Embodiment 2. Figures 13 to 15 are plan views illustrating the slit plate 62 in the optical device 2 according to Embodiment 2. As shown in Figures 12 to 15, the optical device 2 is equipped with a light source 60, a lens 61, a slit plate 62, and a mirror 63. The optical device 2 may further be equipped with other members such as polarizing plates.

[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 the lens 61. The illumination light L60 converted into parallel light is incident on the slit plate 62. The optical axis of the illumination light L60 is called the illumination optical axis C60. The slit plate 62 is positioned in the optical path from the light source 60 to the sample SMP. For example, the slit plate 62 is positioned between the lens 61 and the mirror 63. However, the slit plate 62 is not limited to being between the lens 61 and the mirror 63 as long as it is positioned in the optical path from the light source 60 to the sample SMP. For example, if 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 positioned 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 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. Thus, 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 direction in which the slit 70 extends is the same direction as the direction in which the pattern formed on the sample SMP extends, or a direction perpendicular to the direction in which the pattern extends. The pattern includes, for example, the pattern of a photomask. The direction in which the slit 70 extends is called the slit direction, and the direction in which the pattern extends is called the pattern direction.

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

[0068] As shown in Figure 15, the shape of the slit 70 may be a cross shape having two parts extending in directions inclined in the γ-axis direction and the δ-axis direction. In Figure 15, the two slit directions are inclined in the pattern direction. In this way, since there are two slit directions inclined in the pattern direction, the effects of diffraction due to the inclination cancel each other out, and the effect of diffraction of the illumination light L60 can be further reduced. Note that the two slit directions in the cross shape may be the γ-axis direction and the δ-axis direction. Furthermore, the two slit directions may be 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] The illumination light L60 passes through the slit 70 and the detection hole 80. The portion of the illumination light L60 that passes through the slit 70 is called the slit light L70, and the light that passes through the detection hole 80 is called the detection light L80. The illumination light L60 that passes through the slit plate 62 includes the slit light L70 and the detection light L80. A portion of the 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 focused 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, the light L10 from the sample SMP in this embodiment includes the illumination light L60 reflected by the sample SMP. In other words, the light L10 from the sample SMP includes the reflected light from the slit light L70 and the detection light L80 reflected by the sample SMP. The reflected light from the slit light L70 and the detection light L80 reflected by the sample SMP is also referred to as the slit light L70 and the detection light L80, respectively. 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, similar to Embodiment 1.

[0071] As described above, the optical device 2 of this embodiment has a magnifying optical system. Therefore, the light beam immediately before it enters the main detection means 40, the first detection means 41, and the second detection means 42 is close to parallel light. Furthermore, the separation means 13 is positioned so that the light beam of light L10 can be considered as parallel light. As a result, the separation means 13 separates the slit light L70 reflected by the sample SMP from the detection light L80 reflected by the sample SMP. The light L20 reflected by the mirror 14 in the separation means 13 includes the slit light L70.

[0072] Light L20 reflected by mirror 14 enters mirror 15 in separation means 13. The first light L21 transmitted through mirror 15 and the light L22 reflected by mirror 15 include slit light L70. In this way, separation means 13 separates slit light L70 into first light L21 and second light L22. Light L10 that is not reflected by mirror 14 and enters main detection means 40 includes detection light L80.

[0073] Figures 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. While Figures 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] As shown in Figure 16, if 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 beam of the slit light L70 into two end regions ER divided in the β-axis direction. The first shielding means 51 may shield the central region CR of the luminous beam of the slit light L70 including the first optical axis C21, and transmit the end region ER in the +β-axis direction and the end region ER in the -β-axis direction of the slit light L70.

[0075] As shown in Figure 17, if 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 the central region CR and the end region ER in the +β-axis direction of the luminous beam of the slit light L70 including the first optical axis C21, and transmit the 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 end region ER in the -β axis direction of the slit light beam L70, while allowing the end region ER on the +β axis direction side of the slit light L70 to pass through.

[0077] As shown in Figure 18, if the slit light L70 extends in a direction inclined in the α-axis direction and the β-axis direction, the first shielding means 51 may have a rectangular cross-sectional shape extending in a direction inclined in the α-axis direction and the β-axis direction. The first shielding means 51 may separate the light beam of the slit light L70 into two end regions ER divided in a direction perpendicular to the direction in which the slit light L70 extends (referred to as the slit light orthogonal direction). The first shielding means 51 may shield the central region CR of the light beam of the slit light L70 including the first optical axis C21, while transmitting the end regions ER at both ends of the slit light L70 in the slit light orthogonal direction.

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

[0079] As shown in Figure 19, if the slit light L70 extends in a direction inclined in 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 beam of the slit light L70 into two end regions ER divided in the β-axis direction. The first shielding means 51 may shield the central region CR of the luminous beam of the slit light L70 and transmit the end region ER in the +β-axis direction and the end region ER in the -β-axis direction of the slit light 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 slit light beam L70, while allowing the other end region ER in the β-axis direction to pass through.

[0081] As shown in Figure 20, if the slit light L70 has a cross shape with two parts (referred to as the first slit light L71 and the second slit light L72) extending in two mutually orthogonal directions (referred to as the first slit light direction and the second slit light direction) tilted in the α-axis direction and the β-axis direction, 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 light L71 into two end regions ER divided in a direction orthogonal to the first slit light direction (referred to as the first slit light orthogonal direction). The first shielding means 51 may shield the central region CR of the light beam of the first slit light L71 and transmit the end regions ER at both ends of the first slit light L71 in the first slit light orthogonal direction.

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

[0083] Furthermore, the first shielding means 51 may shield the 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, while allowing the other end region ER to pass through. Also, the first shielding means 51 may shield the 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, while allowing the other end region ER to pass through.

[0084] As shown in Figure 21, even when the slit light L70 has a cross shape with a first slit light L71 and a second slit light L72 extending in the first slit light direction and the second slit light direction, the first shielding means 51 may have a rectangular cross-sectional shape. The first shielding means 51 may separate the light beam of the slit light L70, including the first slit light L71 and the second slit light L72, into two end regions ER divided in the β-axis direction. The first shielding means 51 may shield the central region CR of the light beam of the slit light L70 and transmit the end region ER in the +β axis direction and the 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 and one end region ER in the β-axis direction of the slit light beam L70, while allowing the other end region ER to pass through.

[0086] Thus, 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 size of the slit 70. Therefore, the degree of freedom in designing the optical member 10 and the like can be improved. For example, it can also accommodate a slit direction designed based on the pattern direction, so the optical device 2 can accommodate various variations.

[0088] <Variation 3> Next, a modification 3 of Embodiment 2 will be described using Figure 22. Figure 22 is a configuration diagram illustrating an optical device according to modification 3 of Embodiment 2. In the optical device 2c of modification 3, the member that functions as the separation means 13 consists of a mirror 141 as the first separation means 131 and a mirror 142 as the second separation means 132. The slit plate 62 has a rectangular slit 70 and a detection hole 80 (see, for example, Figure 13). Mirror 141 reflects the slit light L71 that has been transmitted near the first short side of the slit 70 and reflected by the sample SMP, and mirror 142 reflects the slit light L72 that has been transmitted near the second short side of the slit 70 and 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 mirror 141 is detected by the first detection means 41, and the slit light L72 reflected by mirror 142 is detected by the second detection means 42. A first shielding means 51 is provided in the optical path of the slit light L71, and a second shielding means 52 is provided in the optical path of the slit light L72. Mirror 141, which is the first separation means 131, may be positioned closer to the sample SMP, i.e., optically further forward, than mirror 142, which is the second separation means 132. Furthermore, the optical distance (D11) between the first separation means 131, which is the mirror 141, and the first shielding means 51 may be equal to the optical distance (D12) between the second separation means 132, which is the mirror 142, and the second shielding means 52, and the optical distance (D21) between the first shielding means 51 and the first detection means 41 may be equal to the optical distance (D22) between the second shielding means 52 and the second detection means 42. By making these optical distances equal, the unit including the separation means, shielding means, and detection means can be made common for both optical L71 (for front pin) and optical L72 (for rear pin). Note that in modified example 3, the slit plate 62 may not be provided.

[0089] <Modification 4> In Modification 3, a slit plate 621, as shown in Figure 23, may be provided instead of the slit plate 62. Figure 23 is a plan view illustrating the slit plate 621 in the optical device according to Modification 4 of Embodiment 2. The slit plate 621 has slits 71, slit 72, and detection holes 80. The slits 71, slit 72, and detection holes 80 penetrate the surface of the slit plate 621. The slits 71 and slit 72 may be provided at positions opposite each other across the illumination optical axis C60 (for example, at positions point-symmetric with respect to the illumination optical axis C60). The slits 71 and slit 72 may have any shape and orientation as described in Figures 13 to 15. Illumination light L60 passes through the slits 71, slit 72, and detection holes 80. In this modified example, the portion of the illumination light L60 that passes through the slit 71 is also referred to as slit light L71, and the portion of the illumination light L60 that passes through the slit 72 is also referred to as slit light L72. Mirror 141 may reflect the slit light L71 reflected by the sample SMP, and mirror 142 may reflect the slit light L72 reflected by the sample SMP. A first shielding means 51 is provided in the optical path of the slit light L71 reflected by mirror 141, and the slit light L71 is detected by a first detection means 41. A second shielding means 52 is provided in the optical path of the slit light L72 reflected by mirror 142, and the slit light L72 is detected by a second detection means 42. Mirrors 141 and 142 may be positioned 180° apart across the principal optical axis C10.

[0090] While embodiments of this disclosure have been described above, this disclosure includes appropriate modifications that do not impair its purpose and advantages, and is not limited by the embodiments described above. Furthermore, appropriate omissions and combinations of the configurations of Embodiments 1 and 2, as well as Modifications 1, 2, 3, and 4, are also within the scope of the technical concept of this disclosure. 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 Miller 16 Switching elements 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 lenses 62, 621 Slit plate 63 Miller 70, 71, 72 Slits 80 detection holes 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 detection means is provided at a front pin position relative to the sample and detects light from the sample, A second detection means is provided at a rear pin position relative to the sample and detects the light from the sample, A control means that performs focus adjustment 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 the central region of the light beam from the sample, Equipped with, The first detection means and the second detection means receive at least a portion of the end region of the light beam of light from the sample, The system further comprises separation means for separating a portion of the light from the sample into first light and second light, The first detection means receives at least a portion of the end region of the light beam of the first light, The second detection means receives at least a portion of the end region of the light beam of the second light, The shielding means is, A first shielding means for shielding at least the central region of the luminous beam of the first light, A second shielding means for shielding at least the central region of the luminous beam of the second light, Includes, The separation means is A first separation means for separating a portion of the light from the sample into first light, The system includes a second separation means for separating a portion of the light from the sample into a second light, The first separation means is provided on the sample side of the second separation means, The optical distance between the first separating means and the first shielding means is equal to the optical distance between the second separating means and the second shielding means. The optical distance between the first shielding means and the first detection means is equal to the optical distance between the second shielding means and the second detection means. optical equipment.

2. The second shielding means is provided between the focal position of the second light and the second detection means, The optical apparatus according to claim 1.

3. The optical path from the light source to the sample further includes a slit, The shape of the shielding means is determined based on at least one of the orientation and size of the slit. The optical apparatus according to claim 1.

4. A first detection means is provided at a front pin position relative to the sample and detects light from the sample, A second detection means is provided at a rear pin position relative to the sample and detects the light from the sample, A control means that performs focus adjustment 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 the central region of the light beam from the sample, A slit is placed in the optical path from the light source to the sample, Equipped with, The first detection means and the second detection means receive at least a portion of the end region of the light beam of light from the sample, The shape of the shielding means is determined based on at least one of the orientation and size of the slit. optical equipment.

5. The system further comprises separation means for separating a portion of the light from the sample into first light and second light, The first detection means receives at least a portion of the end region of the light beam of the first light, The second detection means receives at least a portion of the end region of the light beam of the second light, The optical apparatus according to claim 4.

6. The shielding means is, A first shielding means for shielding at least the central region of the luminous beam of the first light, A second shielding means for shielding at least the central region of the luminous beam of the second light, including, The optical apparatus according to claim 5.

7. The optical distance from the separation means to the first shielding means and the optical distance from the separation means to the second shielding means are different. The optical apparatus according to claim 6.

8. The second shielding means is provided between the focal position of the second light and the second detection means, The optical apparatus according to claim 6 or 7.

9. The separation means is A first separation means for separating a portion of the light from the sample into first light, The system includes a second separation means for separating a portion of the light from the sample into a second light, The first separation means is provided on the sample side of the second separation means, The optical apparatus according to claim 6.

10. The steps include providing a first detection means for detecting light from a sample at a front pin position relative to the sample, and providing a second detection means for detecting the light from the sample at a rear pin position relative to the sample, The steps include: shielding at least the central region of the light beam from the sample with a shielding means; The steps include receiving light from at least a portion of the end region of the light beam using the first detection means and the second detection means, The steps include: performing focus control based on the output result of the first detection means and the output result of the second detection means; The steps include separating a portion of the light from the sample into first light and second light using separation means, Equipped with, In the step of receiving light with the first detection means and the second detection means, The first detection means receives at least a portion of the end region of the light beam of the first light, The second detection means receives at least a portion of the end region of the light beam of the second light, In the step of shielding with the shielding means, The shielding means is, A first shielding means that shields at least the central region of the luminous beam of the first light, A second shielding means that shields at least the central region of the luminous beam of the second light, Includes, In the separation step, The separation means is A first separation means for separating a portion of the light from the sample into first light, The system includes a second separation means for separating a portion of the light from the sample into a second light, The first separation means is provided on the sample side of the second separation means, In the separation step, The optical distance between the first separating means and the first shielding means is equal to the optical distance between the second separating means and the second shielding means. The optical distance between the first shielding means and the first detection means is equal to the optical distance between the second shielding means and the second detection means. Focusing control method.

11. In the step of shielding with the shielding means, The second shielding means is provided between the focal position of the second light and the second detection means, The focus control method according to claim 10.

12. The step further includes arranging a slit in the optical path from the light source to the sample, In the step of shielding with the shielding means, The shape of the shielding means is determined based on at least one of the orientation and size of the slit. The focus control method according to claim 10.

13. The steps include providing a first detection means for detecting light from a sample at a front pin position relative to the sample, and providing a second detection means for detecting the light from the sample at a rear pin position relative to the sample, The steps include: shielding at least the central region of the light beam from the sample with a shielding means; The steps include receiving light from at least a portion of the end region of the light beam using the first detection means and the second detection means, The steps include: performing focus control based on the output result of the first detection means and the output result of the second detection means; The steps include: placing a slit in the optical path from the light source to the sample; Equipped with, In the step of shielding with the shielding means, The shape of the shielding means is determined based on at least one of the orientation and size of the slit. Focusing control method.

14. The further step involves separating a portion of the light from the sample into first light and second light using separation means. In the step of receiving light with the first detection means and the second detection means, The first detection means receives at least a portion of the end region of the light beam of the first light, The second detection means receives at least a portion of the end region of the light beam of the second light, The focus control method according to claim 13.

15. In the step of shielding with the shielding means, The shielding means is, A first shielding means that shields at least the central region of the luminous beam of the first light, A second shielding means that shields at least the central region of the luminous beam of the second light, including, The focus control method according to claim 14.

16. In the step of shielding with the shielding means, The optical distance from the separation means to the first shielding means and the optical distance from the separation means to the second shielding means are different. The focus control method according to claim 15.

17. In the step of shielding with the shielding means, The second shielding means is provided between the focal position of the second light and the second detection means, The focus control method according to claim 15 or 16.

18. In the separation step, The separation means is A first separation means for separating a portion of the light from the sample into first light, The system includes a second separation means for separating a portion of the light from the sample into a second light, The first separation means is provided on the sample side of the second separation means, The focus control method according to claim 15.

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