JP2024061093A - Monitor device, and monitor method - Google Patents

Abstract

To provide a monitor device and a monitor method that can monitor a change in a position of optical members consisting of an optical system.SOLUTION: A monitor device 30 according to the present disclosure is the monitor device 30 that monitors an inspection device 1 including: an illumination optical system 10 that illuminates an EUV mask 50, using critical illumination by illumination light L1 generated by a light source LS; and a detection optical system 20 that converges reflection light L2 from the EUV mask 50 illuminated by the illumination light L1, and guides the converged reflection light L2 to a detector 25. The monitor device comprises: a guide light introduction unit 31 that introduces guide light LG to the detection optical system 20 from between the detector 25 and the detection optical system 20; and a sensor 33 that detects, in the illumination optical system 10, the guide light LG introduced to the illumination optical system 10 via the detection optical system 20.SELECTED DRAWING: Figure 1

Description

This disclosure relates to a monitoring device and a monitoring method.

For example, in the inspection device described in Patent Document 1, when inspecting a lithography mask (hereinafter referred to as an EUV mask) using EUV (Extreme Ultra Violet) light, an illumination optical system that provides critical illumination is used to ensure the brightness of the illumination light. Critical illumination is a method of illuminating so that an image of the light source is formed on the top surface of the EUV mask, and is an optical system that can provide high-brightness illumination.

JP 2018-163075 A

The positions of optical components such as ellipsoidal mirrors that make up the illumination optical system may change over time due to changes in temperature, air pressure, etc. In such cases, deviations will occur in the optical adjustment of the optical path of the illumination light, etc. However, when making optical adjustments while monitoring illumination light such as EUV light, it is difficult to find out which optical components have changed in position.

The purpose of this disclosure is to solve these problems and to provide a monitoring device and a monitoring method that can monitor changes in the positions of optical components that make up an optical system.

The monitoring device according to the present disclosure is a monitoring device for monitoring an optical device including an illumination optical system that illuminates a sample using critical illumination by illumination light generated by a light source, and a detection optical system that collects light from the sample illuminated by the illumination light and guides the collected light to a detector, and includes a guide light introduction section that introduces guide light into the detection optical system from between the detector and the detection optical system, and a sensor that detects the guide light introduced into the illumination optical system via the detection optical system in the illumination optical system.

The monitor device according to the present disclosure is a monitor device for monitoring an optical device including an illumination optical system that illuminates a sample using critical illumination by illumination light generated by a light source, and a detection optical system that collects light from the sample illuminated by the illumination light and guides the collected light to a detector, and includes a guide light introduction section that introduces guide light into the detection optical system from between the detector and the detection optical system, a drive section that moves a stage on which the sample and a guide light mirror that reflects the guide light are placed side by side between a first position where the illumination light and the guide light are incident on the sample and a second position where the guide light is incident on the guide light mirror, and an interference measurement section that is inserted into the optical path of the guide light between the guide light introduction section and the detection optical system when the stage is positioned at the second position, and the interference measurement section detects a change in the optical axis of the guide light due to interference between the guide light before being introduced into the detection optical system and the guide light reflected by the guide light mirror.

The monitoring method according to the present disclosure is a monitoring method for an optical device including an illumination optical system that illuminates a sample using critical illumination by illumination light generated by a light source, and a detection optical system that collects light from the sample illuminated by the illumination light and guides the collected light to a detector, and includes the steps of causing a guide light introduction section to introduce guide light into the detection optical system from between the detector and the detection optical system, and causing a sensor to detect, in the illumination optical system, the guide light introduced into the illumination optical system via the detection optical system.

The monitoring method according to the present disclosure is a monitoring method for monitoring an optical device including an illumination optical system that illuminates a sample using critical illumination by illumination light generated by a light source, and a detection optical system that collects light from the sample illuminated by the illumination light and guides the collected light to a detector, and includes the steps of: having a guide light introduction section introduce guide light into the detection optical system from between the detector and the detection optical system; moving a stage on which the sample and a guide light mirror that reflects the guide light are placed side by side from a first position where the illumination light and the guide light are incident on the sample to a second position where the guide light is incident on the guide light mirror; when the stage is located at the second position, inserting an interference measurement section into the optical path of the guide light between the guide light introduction section and the detection optical system; and having the interference measurement section detect a change in the optical axis of the guide light due to interference between the guide light before being introduced into the detection optical system and the guide light reflected by the guide light mirror.

The present invention provides a monitoring device and a monitoring method that can monitor changes in the position of optical members that make up an optical system.

FIG. 1 is a configuration diagram illustrating an inspection device and a monitor device according to a first embodiment. 3A and 3B are diagrams illustrating a guide light introducing section according to the first embodiment. 3A and 3B are diagrams illustrating a guide light introducing section according to the first embodiment; 1 is a cross-sectional view illustrating an aperture stop according to a first embodiment. 5A and 5B are diagrams illustrating an example of an extraction mirror that extracts guide light according to the first embodiment. 5A and 5B are diagrams illustrating an example of an extraction mirror that extracts guide light according to the first embodiment. FIG. 4 is a flow chart illustrating a monitoring method according to the first embodiment. FIG. 11 is a configuration diagram illustrating an inspection device and a monitor device according to a second embodiment. FIG. 11 is a configuration diagram illustrating an inspection device and a monitor device according to a third embodiment. FIG. 13 is a configuration diagram illustrating an inspection device and a monitor device according to a fourth embodiment. FIG. 13 is a diagram illustrating an interferometer in a monitoring device according to a fourth embodiment. FIG. 10 is a flow chart illustrating a monitoring method according to a fourth embodiment. FIG. 13 is a flowchart illustrating a monitoring method according to another example of the fourth embodiment.

The specific configuration of this embodiment will be described below 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 similar content.

(Embodiment 1)
A monitoring device according to a first embodiment will be described. The monitoring device of this embodiment monitors an optical device. The optical device includes a device that inspects, processes, measures, etc. a sample using illumination light. For example, the optical device is an inspection device that inspects an inspection target, and an exposure device that exposes an exposure target. In the following, an inspection device will be used as an example of the optical device. Therefore, the sample is the inspection target.

<Configuration of the inspection device>
Fig. 1 is a configuration diagram illustrating an inspection apparatus and a monitor apparatus according to the first embodiment. As shown in Fig. 1, the inspection apparatus 1 includes an illumination optical system 10, a detection optical system 20, a detector 25, and a processing unit 40. The inspection apparatus 1 may further include a light source LS. The inspection apparatus 1 is an apparatus that uses illumination light L1 generated by the light source LS to inspect an object for defects and the like. The object to be inspected is, for example, an EUV mask 50. The object to be inspected is not limited to an EUV mask 50, and may be a semiconductor substrate or the like.

The illumination optical system 10 has an ellipsoidal mirror 11, an ellipsoidal mirror 12, and a drop mirror 13. The detection optical system 20 has a concave mirror with a hole 21, a convex mirror 22, a plane mirror 23, and a concave mirror 24. The concave mirror with a hole 21 and the convex mirror 22 form a Schwarzschild magnification optical system.

The light source LS generates illumination light L1. The illumination light L1 contains, for example, EUV light of 13.5 nm, which is the same as the exposure wavelength of the EUV mask 50 to be inspected. Note that the illumination light L1 may contain light other than EUV light. The illumination light L1 generated from the light source LS is reflected by the ellipsoidal mirror 11. The illumination light L1 reflected by the ellipsoidal mirror 11 advances while being narrowed, and is collected at the condensing point IF1. Thus, the ellipsoidal mirror 11 reflects the illumination light L1 generated from the light source LS as converging light. The condensing point IF1 is a position conjugate with the upper surface 51 of the EUV mask 50 and the detection surface 26 of the detector 25.

After passing through the focusing point IF1, the illumination light L1 advances while expanding and is incident on a reflecting mirror such as the ellipsoidal mirror 12. Therefore, the illumination light L1 reflected by the ellipsoidal mirror 11 is incident on the ellipsoidal mirror 12 as divergent light via the intermediate focusing point IF1. The illumination light L1 incident on the ellipsoidal mirror 12 is reflected by the ellipsoidal mirror 12, advances while being narrowed, and is incident on the drop mirror 13. In other words, the ellipsoidal mirror 12 reflects the incident illumination light L1 as convergent light. The ellipsoidal mirror 12 then causes the illumination light L1 to be incident on the drop mirror 13. The drop mirror 13 is disposed directly above the EUV mask 50. The illumination light L1 incident on and reflected by the drop mirror 13 is incident on the EUV mask 50. Therefore, the drop mirror 13 reflects the illumination light L1 reflected by the ellipsoidal mirror 12 to the EUV mask 50, thereby causing the illumination light L1 to be incident on the EUV mask 50.

The ellipsoidal mirror 12 focuses the illumination light L1 onto the EUV mask 50. The illumination optical system 10 is set up so that when the illumination light L1 illuminates the EUV mask 50, an image of the light source LS is formed on the upper surface 51 of the EUV mask 50. Therefore, the illumination optical system 10 provides critical illumination. In this way, the illumination optical system 10 illuminates the inspection object using critical illumination by the illumination light L1 generated by the light source LS.

The EUV mask 50 is placed on a stage 52. Here, a plane parallel to the top surface 51 of the EUV mask 50 is defined as the XY plane, and a direction perpendicular to the XY plane is defined as the Z axis direction. Illumination light L1 is incident on the EUV mask 50 from a direction tilted from the Z axis direction. In other words, illumination light L11 is incident obliquely and illuminates the EUV mask 50.

The stage 52 is an XYZ driven stage having a drive unit 53. The drive unit 53 can illuminate a desired area of the EUV mask 50 by moving the stage 52 in the X-axis direction and the Y-axis direction. Furthermore, the drive unit 53 can perform focus adjustment by moving the stage 52 in the Z-axis direction.

The illumination light L1 from the light source LS illuminates the inspection area of the EUV mask 50. The inspection area illuminated by the illumination light L1 is, for example, 0.5 mm square. The inspection area is not limited to 0.5 mm square. The light from the EUV mask 50 illuminated by the illumination light L1 is incident on the perforated concave mirror 21. In the following, the light from the EUV mask 50 illuminated by the illumination light L1 is described as reflected light L2. The light incident on the perforated concave mirror 21 from the EUV mask 50 is not limited to the reflected light L2, and may include diffracted light, etc. The reflected light L2 reflected by the EUV mask 50 is incident on the perforated concave mirror 21. A hole 21h is provided at the center of the perforated concave mirror 21. The perforated concave mirror 21 collects the reflected light L2 from the EUV mask 50 and reflects the collected reflected light L2 as convergent light.

The reflected light L12 reflected by the concave mirror 21 with a hole is incident on the convex mirror 22. The convex mirror 22 reflects the reflected light L12 reflected by the concave mirror 21 with a hole toward the hole 21h of the concave mirror 21 with a hole. The reflected light L12 that passes through the hole 21h is incident on the plane mirror 23. The plane mirror 23 causes the reflected light L2 reflected by the convex mirror 22 to be incident as convergent light through the hole 21h of the concave mirror 21 with a hole. The reflected light L2 that is incident on the plane mirror 23 is reflected by the plane mirror 23. The reflected light L2 reflected by the plane mirror 23 advances while being narrowed, and is converged at the focusing point IF2. Therefore, the plane mirror 23 reflects the reflected light L2 that is incident on it as convergent light. The focusing point IF2 is sometimes called an aperture stop. The focal point IF2 is a position conjugate with the upper surface 51 of the EUV mask 50 and the detection surface 26 of the detector 25.

After passing through the focal point IF2, the reflected light L2 diverges as it travels and enters the concave mirror 24. Thus, the reflected light L2 reflected by the plane mirror 23 as converging light enters the concave mirror 24 as diverging light via the focal point IF2. The concave mirror 24 reflects the incident reflected light L2 as converging light toward the detector 25. The reflected light L2 reflected by the concave mirror 24 is detected by the detector 25. In this way, the detection optical system 20 collects the reflected light L2 from the object to be inspected illuminated by the illumination light L11, and guides the collected reflected light L2 to the detector 25.

The detector 25 may include a TDI (Time Delay Integration) sensor. The detector 25 acquires image data of the EUV mask 50 to be inspected. The detector 25 may include a plurality of imaging elements arranged in a line in one direction. Linear image data captured by the plurality of imaging elements arranged in a line is called one-dimensional image data or one frame. The detector 25 acquires a plurality of one-dimensional image data by scanning in a direction perpendicular to the one direction. The imaging element is, for example, a CCD (Charge Coupled Device). Note that the imaging element is not limited to a CCD.

The reflected light L2 contains information such as defects in the EUV mask 50. The specularly reflected light of the illumination light L1 that is incident on the EUV mask 50 from a direction tilted with respect to the Z-axis direction is detected by the detection optical system 20. If there is a defect in the EUV mask 50, the defect is observed as a dark image. This observation method is called bright-field observation. Multiple one-dimensional image data of the EUV mask 50 acquired by the detector 25 are output to the processing unit 40 and processed into two-dimensional image data. The processing unit 40 includes, for example, an information processing device such as a server device or a personal computer.

<Monitor device>
Next, the monitor device 30 of this embodiment will be described. The monitor device 30 has a guide light introduction section 31, a take-out mirror 32, a sensor 33, a take-out mirror 34, and a sensor 35. The guide light introduction section 31 is disposed near the detector 25. The guide light introduction section 31 introduces the guide light LG into the detection optical system 20 from between the detector 25 and the detection optical system 20. Specifically, the guide light introduction section 31 irradiates the guide light LG onto the concave mirror 24. The guide light LG is, for example, visible light. Note that the guide light LG is not limited to visible light, and may be IR (Infra Red) light, EUV light, or the like.

2 and 3 are diagrams illustrating the guide light introduction section 31 according to the first embodiment. As shown in FIG. 2, the guide light introduction section 31 may include a folding mirror 36. The guide light introduction section 31 reflects the guide light LG emitted from the optical fiber 37 to the concave mirror 24. As a result, the guide light introduction section 31 introduces the guide light LG into the detection optical system 20. For example, the emission point of the guide light LG emitted from the optical fiber 37 is in a position conjugate with the detection surface 26 of the detector 25. Note that the guide light introduction section 31 is not limited to the folding mirror 36, and may further include a lens 38 as shown in FIG. 3, as long as it can introduce the guide light LG into the detection optical system 20. For example, the lens 38 is a meniscus lens, which can reduce the NA. The guide light introduction section 31 may also be an optical fiber 37 that directly emits the guide light LG to the detection optical system 20.

The positions of the illumination light L1 and reflected light L2 used in the inspection are preferably based on the detection optical system 20 side. Therefore, the guide light LG is introduced from the detection optical system 20 side. Also, in order to prevent the guide light LG from being detected by the detector 25, the guide light LG is introduced into the detection optical system 20 from outside the field of view of the detector 25 at the detection surface 26 of the detector 25. Also, the guide light LG is introduced from a position conjugate with the detection surface 26. By emitting the guide light LG from a position conjugate with the image plane of the illumination optical system 10 and using it as a reference for adjusting the illumination optical system 10, the adjustment of the illumination optical system 10 can be made more accurate.

The guide light introduction section 31 may have a driving section such as an actuator. The guide light introduction section 31 can move the introduction position of the guide light LG by the driving section. It is desirable that the guide light LG is focused at a position conjugate with the detection surface 26. Note that the guide light LG does not have to be focused at a position conjugate with the detection surface 26. For example, the guide light LG may be focused on the same plane as mirrors such as the ellipsoidal mirrors 11 and 12.

The guide light LG introduced from the guide light introduction section 31 is reflected by the concave mirror 24. The guide light LG reflected by the concave mirror 24 travels while being narrowed, and is focused at the focusing point IF2.

Figure 4 is a cross-sectional view illustrating an aperture stop according to the first embodiment. As shown in Figure 4, the light emitted from the image plane is collected at the condensing point IF2 which becomes the aperture stop. The aperture stop is relayed. At the condensing point IF2 which becomes the aperture stop and at a position conjugate with the condensing point IF2, the direction of the guide light LG is set so that the guide light LG coincides (intersects) with the optical axis of the reflected light L2. Then, the NA of the guide light LG is set so that the NA is larger than the NA of the reflected light L2 determined at the condensing point IF2, etc. Therefore, at the aperture stop (condensing point IF2), the cross-sectional area of the reflected light L2 perpendicular to the optical axis of the reflected light L2 is smaller than the cross-sectional area of the guide light LG perpendicular to the optical axis of the guide light LG.

After passing through the focal point IF2, the guide light LG expands as it travels and is incident on the plane mirror 23. The guide light LG that is incident on the plane mirror 23 is reflected by the plane mirror 23. The guide light LG that is reflected by the plane mirror 23 is reflected by the convex mirror 22 and is incident on the concave mirror 21 with a hole. The guide light LG that is incident on the concave mirror 21 with a hole is reflected by the concave mirror 21 with a hole and is incident on the EUV mask 50 as convergent light.

The guide light LG reflected by the EUV mask 50 travels while expanding, and is incident on the drop-in mirror 13. The guide light LG incident on the drop-in mirror 13 is reflected by the drop-in mirror 13 and is incident on the ellipsoidal mirror 12. The guide light LG incident on the ellipsoidal mirror 12 is reflected by the ellipsoidal mirror 12 and is incident on the ellipsoidal mirror 11 via the focusing point IF1. The guide light LG incident on the ellipsoidal mirror 11 is reflected by the ellipsoidal mirror 11 and reaches the light source LS.

The extraction mirror 32 is disposed between the focusing point IF1 and the ellipsoidal mirror 12. The extraction mirror 32 extracts the guide light LG between the focusing point IF1 and the ellipsoidal mirror 12. Figures 5 and 6 are diagrams illustrating the extraction mirrors 32 and 34 that extract the guide light LG according to the first embodiment.

As shown in FIG. 5, the extraction mirrors 32 and 34 are arranged on three peripheries of the illumination light L1 in a cross section perpendicular to the optical axis of the illumination light L1. By extracting the guide light LG with the three extraction mirrors 32 and 34, it is possible to detect a three-dimensional positional deviation of the optical axis. As shown in FIG. 6, the extraction mirrors 32 and 34 may be arranged on the periphery at four locations, or at five or more locations. It is preferable that the extraction mirrors 32 and 34 are arranged on the periphery of the illumination light L1 with a mutual offset as viewed from the optical axis. This makes it possible to suppress blocking of the guide light LG by the extraction mirror 32.

As shown in Figures 5 and 6, the extraction mirror 32 is positioned to extract a portion of the illumination light L1 used for inspection that is outside the NA. In other words, the extraction mirror 32 extracts the guide light LG that is outside the cross section of the illumination light L1 that is perpendicular to the optical axis of the illumination light L1. Specifically, the extraction mirror 32 reflects the portion of the illumination light L1 used for inspection that is outside the NA. The guide light LG reflected by the extraction mirror 32 is incident on the sensor 33. The extraction mirror 32 may be a half mirror or a beam splitter, or may be an opaque mirror.

The sensor 33 detects the guide light LG introduced into the illumination optical system 10 via the detection optical system 20 in the illumination optical system 10. That is, the sensor 33 detects the guide light LG introduced into the detection optical system 20 in a part of the optical path of the guide light LG in the illumination optical system 10. For example, the sensor 33 detects a change in the optical axis of the guide light LG extracted by the extraction mirror 32 at a position conjugate with the detection surface 26 of the detector 25. Specifically, the sensor 33 is disposed at a position conjugate with the focusing point IF1. The sensor 35 is a photodiode (hereinafter referred to as PD), a position detection sensor (hereinafter referred to as PSD), a two-dimensional sensor, or the like. For example, when the ellipsoidal mirror 12 is misaligned, the sensor 33 detects a change in the optical axis of the guide light LG.

The extraction mirror 34 is disposed between the light source LS and the ellipsoidal mirror 11. The extraction mirror 34 extracts the guide light LG between the light source LS and the ellipsoidal mirror 11. The extraction mirror 34 is disposed to extract a portion of the illumination light L1 used for the inspection outside the NA, similar to the extraction mirror 32. That is, the extraction mirror 34 extracts the guide light LG that is outside the cross section of the illumination light L1 that is perpendicular to the optical axis of the illumination light L1. Specifically, the extraction mirror 34 reflects the portion of the illumination light L1 used for the inspection outside the NA. The guide light LG reflected by the extraction mirror 34 is incident on the sensor 35. The extraction mirror 34 may be a half mirror or a beam splitter, or may be an opaque mirror.

The sensor 35 detects the guide light LG introduced into the illumination optical system 10 via the detection optical system 20 in the illumination optical system 10. That is, the sensor 35 detects the guide light LG introduced into the detection optical system 20 in a part of the optical path of the guide light LG in the illumination optical system 10. For example, the sensor 35 detects a change in the optical axis of the guide light LG extracted by the extraction mirror 34 at a position conjugate with the detection surface 26 of the detector 25. Specifically, the sensor 35 is disposed at a position conjugate with the light emitting point of the light source LS. The sensor 35 is, like the sensor 33, for example, a PD, a PSD, a two-dimensional sensor, etc. For example, when a positional deviation occurs in the ellipsoidal mirror 11, the sensor 35 detects a change in the optical axis of the guide light LG.

Sensors 33 and 35 monitor the focusing state of the guide light LG. The illumination optical system 10, including the position of the ellipsoidal mirror 11, is adjusted so that the focusing state of the guide light LG detected by the sensors 33 and 35 is constant. Since the guide light LG is introduced into the detection optical system 20 and illumination optical system 10 from outside the field of view, it can be constantly monitored even during inspection.

Next, a monitoring method for the inspection device 1 will be described. FIG. 7 is a flow chart illustrating a monitoring method according to the first embodiment. As shown in step S11 of FIG. 7, the guide light LG is introduced into the detection optical system 20. Specifically, in the inspection device 1 equipped with the illumination optical system 10 and the detection optical system 20, the guide light introduction section 31 is caused to introduce the guide light LG into the detection optical system 20 from between the detector 25 and the detection optical system 20.

Next, as shown in step S12 of FIG. 7, the guide light LG is detected in the illumination optical system 10. Specifically, the sensors 33 and 35 are caused to detect the guide light LG introduced into the illumination optical system 10 via the detection optical system 20 in the illumination optical system 10.

In step S12, in which the guide light LG is detected in the illumination optical system 10, the guide light LG may be extracted by an extraction mirror 32 between the focusing point IF1 and the ellipsoidal mirror 12. Then, the change in the optical axis of the guide light LG extracted by the extraction mirror 32 may be detected by a sensor 33 at a position conjugate with the detection surface 26 of the detector 25.

In addition, in step S12 of detecting the guide light LG in the illumination optical system 10, the guide light LG may be extracted by an extraction mirror 34 between the light source LS and the ellipsoidal mirror 11. Then, a change in the optical axis of the guide light LG extracted by the extraction mirror 32 may be detected by a sensor 35 at a position conjugate with the detection surface 26 of the detector 25. When the guide light LG is extracted by the extraction mirrors 32 and 34, a portion of the guide light LG outside the cross section of the illumination light L1 perpendicular to the optical axis of the illumination light L1 may be extracted.

Next, the effects of this embodiment will be described. The inspection device 1 of this embodiment introduces guide light LG into the detection optical system 20, and the introduced guide light LG is extracted by the illumination optical system 10. Therefore, based on the guide light LG extracted by the illumination optical system 10, it is possible to monitor changes in the position of each optical member constituting the illumination optical system 10 and the detection optical system 20. This makes it possible to adjust the optical axes of the illumination light L1 and the reflected light L2 in the illumination optical system 10 and the detection optical system 20 with high precision.

In addition, the guide light LG is introduced from outside the field of view of the detector 25. This makes it possible to adjust the position of the optical component using the guide light LG even during inspection using the illumination light L1.

Furthermore, at the aperture stop, the cross-sectional area of the reflected light L2 perpendicular to the optical axis of the reflected light L2 is smaller than the cross-sectional area of the guide light LG perpendicular to the optical axis of the guide light LG. Therefore, the extraction mirrors 32 and 34 can extract the guide light LG from a portion outside the cross section of the illumination light L1 perpendicular to the optical axis of the illumination light L1. This makes it possible to adjust the position of the optical components using the guide light LG without affecting the illumination light L1, even during inspection using the illumination light L1.

(Embodiment 2)
Next, a monitor device according to the second embodiment will be described. The monitor device of this embodiment extracts the guide light LG near the ellipsoidal mirrors 11 and 12. FIG. 8 is a configuration diagram illustrating an inspection device and a monitor device according to the second embodiment. As shown in FIG. 8, in the inspection device 2 of the second embodiment, the monitor device 30a has a sensor 33a near the ellipsoidal mirror 12. The sensor 33a is disposed, for example, on the periphery of the ellipsoidal mirror 12. Specifically, the sensor 33a is disposed so as to detect a portion outside the NA of the illumination light L1 used for inspection. The sensor 33a detects a change in the optical axis of the guide light near the ellipsoidal mirror 12.

In addition, in the inspection device 2, the monitor device 30a has a sensor 35a near the ellipsoidal mirror 11. The sensor 35a is arranged, for example, on the periphery of the ellipsoidal mirror 11. Specifically, the sensor 35a is arranged so as to detect a portion outside the NA of the illumination light L1 used for the inspection. The sensor 35a detects a change in the optical axis of the guide light near the ellipsoidal mirror 11.

In the monitoring method of this embodiment, in step S12 in which the guide light LG is detected in the illumination optical system 10, a change in the optical axis of the guide light LG is detected near the ellipsoidal mirror 12. Also, in step S12 in which the guide light LG is detected in the illumination optical system 10, a change in the optical axis of the guide light LG is detected near the ellipsoidal mirror 11.

According to this embodiment, the monitor device 30a places sensors 33a and 35a near the peripheries of the ellipsoidal mirrors 11 and 12, and adjusts the illumination optical system 10 so that the guide light LG is focused in a constant state. Since the monitor device 30a detects the guide light LG near the ellipsoidal mirrors 11 and 12, it can detect changes in the positions of the ellipsoidal mirrors 11 and 12 with high accuracy. Other configurations and effects are included in the description of embodiment 1.

(Embodiment 3)
Next, a monitor device according to a third embodiment will be described. In the monitor device 30a according to the second embodiment, the sensors 33a and 35a are disposed on the ellipsoidal mirrors 11 and 12. Therefore, the detection accuracy of the change in the position of the guide light LG in the optical axis direction may be reduced. Therefore, the monitor device according to the present embodiment detects the change in the position between the optical members in the optical axis direction of the guide light LG with high accuracy.

Figure 9 is a configuration diagram illustrating an inspection device and a monitor device according to embodiment 3. As shown in Figure 9, in the inspection device 3 of this embodiment, the monitor device 30b includes a measurement unit 60 in addition to the above-mentioned sensors 33a and 35a. The measurement unit 60 includes a beam emission unit 61, a beam mirror 62, an interference measurement unit 63, a beam emission unit 64, a beam mirror 65, and an interference measurement unit 66.

The measurement unit 60 measures the change in the distance between the ellipsoidal mirror 12 and the drop-in mirror 13. For example, the beam emission unit 61 and the interference measurement unit 63 are fixed to the drop-in mirror 13 or a support base for the drop-in mirror 13. The beam mirror 62 is fixed to the ellipsoidal mirror 12 or a support base for the ellipsoidal mirror 12.

The positional relationship between the beam emitting unit 61 and the interference measuring unit 63 and the beam mirror 62 may be reversed. That is, the beam emitting unit 61 and the interference measuring unit 63 may be fixed to the ellipsoidal mirror 12 or a support base for the ellipsoidal mirror 12, and the beam mirror 62 may be fixed to the drop-in mirror 13 or a support base for the drop-in mirror 13.

The beam emitting unit 61 emits a beam for interference measurement. The beam includes, for example, visible light. The beam emitting unit 61 may generate and emit a beam for interference measurement, or may receive and reflect a beam for interference measurement to emit a beam for interference measurement. The beam mirror 62 reflects the beam emitted by the beam emitting unit 61. The interference measurement unit 63 measures the change in the distance between the ellipsoidal mirror 12 and the drop-in mirror 13 due to interference between the beam emitted by the beam emitting unit 61 and the beam reflected by the beam mirror 62.

The measurement unit 60 also measures the change in the distance between the ellipsoidal mirror 11 and the ellipsoidal mirror 12. For example, the beam emission unit 64 and the interference measurement unit 66 are fixed to the ellipsoidal mirror 12 or a support base for the ellipsoidal mirror 12. The beam mirror 62 is fixed to the ellipsoidal mirror 11 or a support base for the ellipsoidal mirror 11.

The positional relationship between the beam emitting unit 64 and the interference measuring unit 66 and the beam mirror 65 may be reversed. That is, the beam emitting unit 64 and the interference measuring unit 66 may be fixed to the ellipsoidal mirror 11 or the support base of the ellipsoidal mirror 11, and the beam mirror 65 may be fixed to the ellipsoidal mirror 12 or the support base of the ellipsoidal mirror 12.

The beam emitting unit 64 emits a beam for interference measurement. The beam emitting unit 64 may generate and emit a beam for interference measurement, or may receive and reflect a beam for interference measurement to emit a beam for interference measurement. The beam mirror 65 reflects the beam emitted by the beam emitting unit 64. The interference measurement unit 66 measures the change in the distance between the ellipsoidal mirror 11 and the ellipsoidal mirror 12 by interference between the beam emitted by the beam emitting unit 64 and the beam reflected by the beam mirror 65.

The monitoring method of this embodiment may further include a step of having the measurement unit 60 measure the change in the distance between the ellipsoidal mirror 12 and the drop-in mirror. The measuring step includes the following steps. That is, the beam emission unit 61 emits a beam, the beam is reflected by the beam mirror 62, and the interference measurement unit 63 measures the change in the distance between the ellipsoidal mirror 12 and the drop-in mirror due to interference between the beam emitted by the beam emission unit 61 and the beam reflected by the beam mirror 62.

The monitoring method of this embodiment may further include a step of having the measurement unit 60 measure the change in the distance between the ellipsoidal mirror 11 and the ellipsoidal mirror 12. The measuring step includes the following steps. That is, the beam emission unit 64 emits a beam, the beam is reflected by the beam mirror 65, and the interference measurement unit 66 measures the change in the distance between the ellipsoidal mirror 11 and the ellipsoidal mirror 12 due to interference between the beam emitted by the beam emission unit 64 and the beam reflected by the beam mirror 65.

Next, the effects of this embodiment will be described. The sensors 33a and 35a can detect position changes in a direction perpendicular to the optical axis of the guide light LG with high accuracy. On the other hand, it may be difficult for the sensors 33a and 35a to detect position changes in a direction parallel to the optical axis of the guide light LG with high accuracy. Even in such cases, according to this embodiment, the measurement unit 60 can detect position changes in a direction parallel to the optical axis of the guide light LG with high accuracy, so that the optical members of the illumination optical system 10 can be adjusted with high accuracy. Other configurations and effects are included in the description of embodiments 1 and 2.

(Embodiment 4)
Next, a monitoring device according to embodiment 4 will be described. The monitoring device of this embodiment includes an interference measurement unit between the guide light introducing unit 31 and the detection optical system 20. The interference measurement unit of this embodiment detects a change in the position of each optical member of the detection optical system 20 by causing interference of the guide light LG.

Figure 10 is a configuration diagram illustrating an inspection device and a monitor device according to embodiment 4. As shown in Figure 10, in the inspection device 4 of this embodiment, the monitor device 30c includes a guide light introducing section 31, an interference measuring section 70, a guide light mirror 75, and a drive section 53 for a stage 52.

The guide light mirror 75 is disposed on the stage 52. For example, the guide light mirror 75 and the EUV mask 50 are disposed side by side on the stage 52. The guide light mirror 75 reflects the guide light LG introduced from the guide light introduction part 31 to the detection optical system 20.

The driving unit 53 moves the stage 52 between the first position and the second position. The driving unit 53 moves the stage 52 in the XY plane, thereby moving the stage 52 from the first position to the second position, or from the second position to the first position.

The first position is a position where the EUV mask 50 to be inspected is placed below the drop-in mirror 13. The first position is a position where the illumination light L1 and the guide light LG are incident on the EUV mask 50. When the stage 52 is positioned at the first position, the interference measurement unit 70 is removed from the optical path of the guide light LG between the guide light introduction unit 31 and the detection optical system 20. Therefore, the monitor device 30c detects the guide light LG using sensors 33 and 35, etc.

The second position is a position where the guide light mirror 75 is disposed below the drop-in mirror 13. The second position is a position where the guide light LG is incident on the guide light mirror 75. When the stage 52 is positioned at the second position, the interference measurement unit 70 is inserted into the optical path of the guide light LG between the guide light introduction unit 31 and the detection optical system 20. At the second position, the interference measurement unit 70 detects a change in the optical axis of the guide light LG due to interference between the guide light LG before it is introduced into the detection optical system 20 and the guide light LG reflected by the guide light mirror 75.

Figure 11 is a diagram illustrating an example of an interference measurement unit 70 in a monitor device 30c according to embodiment 4. As shown in Figure 11, the interference measurement unit 70 has a mirror 71, a lens 72, a mirror 73, and a sensor 74. The mirror 71 is, for example, a half mirror, a beam splitter, or the like, and reflects a part of the guide light LG emitted from the guide light introduction unit 31 and transmits a part of it. The guide light LG reflected by the mirror 71 is reflected by the mirror 73 via the lens 72. The guide light LG reflected by the mirror 73 is incident on the mirror 71 via the lens 72. A part of the guide light LG incident on the mirror 71 transmits through the mirror 71 and is incident on a sensor 74 such as a two-dimensional sensor.

On the other hand, the guide light LG emitted from the guide light introduction section 31 that passes through the mirror 71 enters the detection optical system 20. The guide light LG that enters the detection optical system 20 is reflected by the guide light mirror 75 via the detection optical system 20, and enters the mirror 71 via the detection optical system 20. A portion of the guide light LG that enters the mirror 71 is reflected by the mirror 71 and enters the sensor 74.

The sensor 74 detects interference between the guide light LG before it is introduced into the detection optical system 20 and the guide light LG reflected by the guide light mirror 75 via the detection optical system 20. The sensor 74 then detects a change in the optical axis of the guide light LG from, for example, a change in interference fringes.

Next, a monitoring method for monitoring the optical device of this embodiment will be described. FIG. 12 is a flow chart illustrating a monitoring method according to the fourth embodiment. As shown in step S21 of FIG. 12, the guide light LG is introduced into the detection optical system 20. For example, the guide light introduction section 31 is caused to introduce the guide light LG into the detection optical system 20 from between the detector 25 and the detection optical system 20.

Next, as shown in step S22, the stage 52 is moved to the second position. Specifically, the stage 52 on which the EUV mask 50 and the guide light mirror 75 are placed side by side is moved from the first position to the second position. The first position is the position where the illumination light L1 and the guide light LG are incident on the EUV mask 50. The second position is the position where the guide light LG is incident on the guide light mirror 75.

Next, as shown in step S23, the interference measurement unit 70 is inserted. Specifically, when the stage 52 is positioned at the second position, the interference measurement unit 70 is inserted into the optical path of the guide light LG between the guide light introduction unit 31 and the detection optical system 20.

Next, as shown in step S24, the guide light LG is detected by the interference measurement unit 70. Specifically, the interference measurement unit 70 detects a change in the optical axis of the guide light LG due to interference between the guide light LG before it is introduced into the detection optical system 20 and the guide light LG reflected by the guide light mirror 75. In this way, it is possible to monitor the change in the position of the optical members that make up the optical system.

Figure 13 is a flow chart illustrating a monitoring method according to another example of embodiment 4. As shown in Figure 13, steps S25 to S27 may be further included after the above-mentioned steps S21 to S24. That is, as shown in step S25, the stage 52 is moved from the second position to the first position.

Next, as shown in step S26, the interference measurement unit 70 is removed from the optical path of the guide light LG. Specifically, the interference measurement unit 70 is removed from the optical path of the guide light LG between the guide light introduction unit 31 and the detection optical system 20.

Next, as shown in step S27, the guide light LG introduced into the illumination optical system 10 via the detection optical system 20 is detected in the illumination optical system 10 by the sensors 33 and 35. In this way, the change in the position of the optical members that make up the optical system may be monitored.

Next, the effects of this embodiment will be described. The monitor device 30c of this embodiment detects changes in the optical axis of the guide light LG due to interference between the guide light LG before it is introduced into the detection optical system 20 and the guide light LG reflected by the guide light mirror via the detection optical system 20. Therefore, the position of each optical component of the detection optical system 20 can be adjusted with high accuracy.

In addition, by combining the detection of changes in the optical axis of the guide light LG by the interference measurement unit 70 with the detection of changes in the optical axis of the guide light LG by the sensors 33 and 35, etc., it is possible to detect changes in the positions of the optical members of the entire optical system with high accuracy. Other configurations and effects are included in the description of embodiments 1 to 3.

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, the configurations of embodiments 1 to 4 may be combined as appropriate.

The monitor devices 30 to 30c may also be connected to the processing unit 40, and the processing unit 40 may control the monitor devices 30 to 30c. In this case, some or all of the processing of the monitor devices 30 to 30c described above may be executed by a computer program.

A computer program includes instructions (or software code) that, when loaded into a computer, causes the computer to perform one or more functions described in the embodiments. The program may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray (registered trademark) disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The program may be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, a transitory computer-readable medium or communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

The technical concept of the embodiment also includes the following monitor program that causes a computer to execute the monitoring method of the embodiment.

an illumination optical system that illuminates a sample using critical illumination by illumination light generated by a light source;
a detection optical system that collects light from the sample illuminated by the illumination light and guides the collected light to a detector;
A monitor program for an optical device comprising:
a guide light introduction section that introduces a guide light into the detection optical system from between the detector and the detection optical system;
a sensor is caused to detect, in the illumination optical system, the guide light introduced into the illumination optical system via the detection optical system;
A monitor program that causes a computer to do the following:

Reference Signs List 1, 2, 3, 4 Inspection apparatus 10 Illumination optical system 11 Ellipsoidal mirror 12 Ellipsoidal mirror 13 Drop-in mirror 20 Detection optical system 21 Holed concave mirror 21h Hole 22 Convex mirror 23 Plane mirror 24 Concave mirror 25 Detector 26 Detection surface 30, 30a, 30b, 30c Monitor device 31 Guide light introduction section 32 Extraction mirror 33, 33a Sensor 34 Extraction mirror 35, 35a Sensor 36 Folding mirror 37 Optical fiber 38 Lens 40 Processing section 50 EUV mask 51 Upper surface 52 Stage 53 Driving section 60 Measurement section 61 Beam emission section 62 Beam mirror 63 Interference measurement section 64 Beam emission section 65 Beam mirror 66 Interference measurement section 70 Interference measurement section 71 Mirror 72 Lens 73 Mirror 74 Sensor 75 Guide light mirror IF1 Focus point IF2 Converging point L1 Illumination light L2 Reflected light LG Guide light LS Light source

Claims (24)

an illumination optical system that illuminates a sample using critical illumination by illumination light generated by a light source;
a detection optical system that collects light from the sample illuminated by the illumination light and guides the collected light to a detector;
A monitor device for monitoring an optical device comprising:
a guide light introducing section that introduces a guide light into the detection optical system from between the detector and the detection optical system;
a sensor that detects, in the illumination optical system, the guide light introduced into the illumination optical system via the detection optical system;
A monitor device comprising: The detection optical system includes:
a concave mirror with a hole that collects the light from the sample and reflects the collected light as convergent light;
a convex mirror that reflects the light reflected by the perforated concave mirror;
a plane mirror that causes the light reflected by the convex mirror to enter as the convergent light through a hole in the perforated concave mirror;
the light reflected by the plane mirror as the convergent light is incident as a divergent light via an aperture stop, and a concave mirror which reflects the incident light as the convergent light to the detector;
having
In the aperture stop, a cross-sectional area of the light perpendicular to an optical axis of the light is smaller than a cross-sectional area of the guide light perpendicular to the optical axis of the guide light.
2. The monitor device according to claim 1. The illumination optical system includes:
a first ellipsoidal mirror that reflects the illumination light generated from the light source as convergent light;
the illumination light reflected by the first ellipsoidal mirror is incident as divergent light via a light-converging point on a second ellipsoidal mirror, the second ellipsoidal mirror reflecting the incident illumination light as the convergent light;
a drop mirror that reflects the illumination light reflected by the second ellipsoidal mirror toward the sample, thereby causing the illumination light to be incident on the sample;
having
2. The monitor device according to claim 1. a mirror for extracting the guide light between the light collecting point and the second ellipsoidal mirror,
The sensor detects a change in the optical axis of the guide light extracted by the extraction mirror at a position conjugate with a detection surface of the detector.
4. The monitor device according to claim 3. a mirror for extracting the guide light between the light source and the first ellipsoidal mirror,
The sensor detects a change in the optical axis of the guide light extracted by the extraction mirror at a position conjugate with a detection surface of the detector.
4. The monitor device according to claim 3. the extraction mirror extracts the guide light in a portion outside a cross section of the illumination light perpendicular to an optical axis of the illumination light.
6. The monitor device according to claim 4 or 5. The sensor detects a change in the optical axis of the guide light in the vicinity of the second ellipsoidal mirror.
4. The monitor device according to claim 3. The sensor detects a change in the optical axis of the guide light in the vicinity of the first ellipsoidal mirror.
4. The monitor device according to claim 3. a measuring unit that measures a change in the distance between the second ellipsoidal mirror and the drop-in mirror;
The measurement unit is
a beam emitting unit that emits a beam;
a beam mirror that reflects the beam;
an interference measuring unit that measures a change in the distance based on interference between the beam emitted by the beam emitting unit and the beam reflected by the beam mirror;
having
8. The monitor device according to claim 7. a measurement unit that measures a change in a distance between the first ellipsoidal mirror and the second ellipsoidal mirror,
The measurement unit is
a beam emitting unit that emits a beam;
a beam mirror that reflects the beam;
an interference measuring unit that measures a change in the distance based on interference between the beam emitted by the beam emitting unit and the beam reflected by the beam mirror;
having
9. The monitor device according to claim 8. an illumination optical system that illuminates a sample using critical illumination by illumination light generated by a light source;
a detection optical system that collects light from the sample illuminated by the illumination light and guides the collected light to a detector;
A monitor device for monitoring an optical device comprising:
a guide light introducing section that introduces a guide light into the detection optical system from between the detector and the detection optical system;
a drive unit that moves a stage, on which the sample and a guide light mirror that reflects the guide light are placed side by side, between a first position where the illumination light and the guide light are incident on the sample and a second position where the guide light is incident on the guide light mirror;
an interference measurement unit that is inserted into an optical path of the guide light between the guide light introduction unit and the detection optical system when the stage is located at the second position;
Equipped with
the interference measurement unit detects a change in the optical axis of the guide light due to interference between the guide light before being introduced into the detection optical system and the guide light reflected by the guide light mirror.
Monitor device. a sensor that detects, in the illumination optical system, the guide light introduced into the illumination optical system via the detection optical system;
When the stage is located at the first position, the interference measurement unit is removed from the optical path of the guide light between the guide light introduction unit and the detection optical system.
12. The monitor device of claim 11. an illumination optical system that illuminates a sample using critical illumination by illumination light generated by a light source;
a detection optical system that collects light from the sample illuminated by the illumination light and guides the collected light to a detector;
A method for monitoring an optical device comprising:
A step of causing a guide light introducing unit to introduce a guide light into the detection optical system from between the detector and the detection optical system;
a step of causing a sensor to detect, in the illumination optical system, the guide light introduced into the illumination optical system via the detection optical system;
A monitoring method comprising: The detection optical system includes:
a concave mirror with a hole that collects the light from the sample and reflects the collected light as convergent light;
a convex mirror that reflects the light reflected by the perforated concave mirror;
a plane mirror that causes the light reflected by the convex mirror to enter as the convergent light through a hole in the perforated concave mirror;
the light reflected by the plane mirror as the convergent light is incident as a divergent light via an aperture stop, and a concave mirror which reflects the incident light as the convergent light to the detector;
having
In the aperture stop, a cross-sectional area of the light perpendicular to an optical axis of the light is smaller than a cross-sectional area of the guide light perpendicular to the optical axis of the guide light.
The monitoring method according to claim 13. The illumination optical system includes:
a first ellipsoidal mirror that reflects the illumination light generated from the light source as convergent light;
the illumination light reflected by the first ellipsoidal mirror is incident as divergent light via a light-converging point on a second ellipsoidal mirror, the second ellipsoidal mirror reflecting the incident illumination light as the convergent light;
a drop mirror that reflects the illumination light reflected by the second ellipsoidal mirror toward the sample, thereby causing the illumination light to be incident on the sample;
having
The monitoring method according to claim 13. In the step of detecting the guide light in the illumination optical system,
extracting the guide light by an extraction mirror between the light collecting point and the second ellipsoidal mirror;
a sensor that detects a change in the optical axis of the guide light extracted by the extraction mirror at a position conjugate with a detection surface of the detector;
16. The monitoring method of claim 15. In the step of detecting the guide light in the illumination optical system,
extracting the guide light by an extraction mirror between the light source and the first ellipsoidal mirror;
a sensor that detects a change in the optical axis of the guide light extracted by the extraction mirror at a position conjugate with a detection surface of the detector;
16. The monitoring method of claim 15. When the guide light is extracted by the extraction mirror, a portion of the guide light that is outside a cross section of the illumination light that is perpendicular to an optical axis of the illumination light is extracted.
18. A monitoring method according to claim 16 or 17. In the step of detecting the guide light in the illumination optical system,
detecting a change in the optical axis of the guide light in the vicinity of the second ellipsoidal mirror;
16. The monitoring method of claim 15. In the step of detecting the guide light in the illumination optical system,
detecting a change in the optical axis of the guide light in the vicinity of the first ellipsoidal mirror;
16. The monitoring method of claim 15. a step of measuring a change in a distance between the second ellipsoidal mirror and the drop-in mirror,
The step of measuring includes:
A beam is emitted from the beam emission section,
reflecting the beam on a beam mirror;
causing an interference measuring unit to measure a change in the distance due to interference between the beam emitted by the beam emitting unit and the beam reflected by the beam mirror;
20. The monitoring method of claim 19. a step of measuring a change in a distance between the first ellipsoidal mirror and the second ellipsoidal mirror,
The step of measuring includes:
A beam is emitted from the beam emission section,
reflecting the beam on a beam mirror;
causing an interference measuring unit to measure a change in the distance due to interference between the beam emitted by the beam emitting unit and the beam reflected by the beam mirror;
21. The monitoring method of claim 20. an illumination optical system that illuminates a sample using critical illumination by illumination light generated by a light source;
a detection optical system that collects light from the sample illuminated by the illumination light and guides the collected light to a detector;
A monitoring method for monitoring an optical device comprising:
A step of causing a guide light introducing unit to introduce a guide light into the detection optical system from between the detector and the detection optical system;
moving a stage on which the sample and a guide light mirror that reflects the guide light are placed side by side from a first position where the illumination light and the guide light are incident on the sample to a second position where the guide light is incident on the guide light mirror;
When the stage is located at the second position, an interference measurement unit is inserted into an optical path of the guide light between the guide light introduction unit and the detection optical system;
a step of causing the interference measurement unit to detect a change in the optical axis of the guide light due to interference between the guide light before being introduced into the detection optical system and the guide light reflected by the guide light mirror;
A monitoring method comprising: moving the stage from the second position to the first position;
removing the interference measurement unit from an optical path of the guide light between the guide light introduction unit and the detection optical system;
a step of causing a sensor to detect, in the illumination optical system, the guide light introduced into the illumination optical system via the detection optical system;
Further equipped with
24. The monitoring method of claim 23.

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