Light source device, inspection device, exposure device, light source control method, inspection method, and exposure method

Abstract

A light source device, an inspection device, an exposure device, a light source control method, an inspection method, and an exposure method are provided that are capable of improving the stability of light extracted from a light source. [Solution] The light source device 100 of the present disclosure comprises an input optical system 120 including a first optical member OP1 that irradiates excitation light LR onto a target material 112, an output optical system 130 including a second optical member OP2 that extracts light L0 generated by irradiating the target material 112 with the excitation light LR, a target holding unit 110 that holds the target material 112, an acquisition unit 140 that acquires the surface position of the target material 112, a drive unit 150 that changes the position of the focal point of at least one of the first optical member OP1 and the second optical member OP2, and a control unit 160 that drives the drive unit 150 based on the surface position.

Description

[Technical field]

[0001] The present disclosure relates to a light source device, an inspection device, an exposure device, a light source control method, an inspection method, and an exposure method. [Background technology]

[0002] Patent Document 1 describes a light source in which a target material is formed on the surface of a cylindrical member that rotates around a rotation axis, and the formed target material is irradiated with excitation light to emit illumination light.

[0003] Patent document 2 describes a light source that uses centrifugal force to hold a molten metal target material on the inner wall of a crucible that rotates around an axis of rotation, and emits illumination light by irradiating the held target material with excitation light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-077007 A [Patent Document 2] JP 2022-168463 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the light source device, the relative position between the light emitting point located near the surface of the target material and the optical member may fluctuate due to vibrations that occur when the target holder such as a cylindrical member or a crucible rotates, deformation of the structure itself, and the introduction of the target material into the target holder. This may result in a case where light cannot be stably extracted from the light source device.

[0006] The object of the present disclosure has been made to solve such problems, and is to provide a light source device, an inspection device, an exposure device, a light source control method, an inspection method, and an exposure method that can improve the stability of the light extracted from the light source device. [Means for solving the problem]

[0007] The light source device according to the present disclosure comprises an input optical system including a first optical member that irradiates a target material with excitation light, an output optical system including a second optical member that extracts light generated by irradiating the target material with the excitation light, a target holding unit that holds the target material, an acquisition unit that acquires a surface position of the target material, a driving unit that varies a position of a focal point of at least one of the first optical member and the second optical member, and a control unit that drives the driving unit based on the surface position.

[0008] In the light source device, the acquisition section may acquire the surface position as a relative position with respect to the second optical member.

[0009] In the light source device, the first optical member may irradiate the target material with the excitation light at an angle inclined from an axis perpendicular to a surface of the target material.

[0010] In the light source device, the target holding section may move the target material to an irradiation position where the excitation light is irradiated, in association with the movement of the target holding section.

[0011] In the above light source device, the acquisition unit may acquire the surface position at a peripheral position other than the irradiation position, and acquire the surface position at the irradiation position by predicting the surface position at the irradiation position from the acquired surface positions at the peripheral positions.

[0012] In the light source device described above, the target material may include molten metal, the target holder may include a container that contains the target material therein, and the target material may be supported on an inner wall surface of the container by centrifugal force.

[0013] In the light source device, the acquisition unit may acquire the surface position of the target material based on a distance from a sensor to a surface of the molten metal.

[0014] In the above light source device, the acquisition unit may predict the surface position of the irradiation position from the surface position at a position just before the irradiation position in the direction of the movement of the target holding unit, and the control unit may control the driving unit based on the predicted surface position.

[0015] In the above light source device, when the surface position fluctuates at a predetermined period, the acquisition unit may predict the surface position based on the period, and the control unit may control the driving unit based on the predicted surface position.

[0016] In the light source device, the first optical member may include a mirror that reflects the excitation light onto the target material.

[0017] In the light source device, the second optical member may include a collector mirror that reflects the generated light.

[0018] In the above light source device, the first optical member may include a mirror that reflects the excitation light to the target material, the second optical member may include a collector mirror that reflects the generated light, and the control unit may set a drive control amount of the first optical member greater than a drive control amount of the second optical member.

[0019] In the above light source device, the first optical member may include a focusing lens that focuses the excitation light, and the control unit may control the drive unit to move the focusing lens in a direction parallel to the optical axis of the excitation light to vary the position of the focusing point.

[0020] In the above light source device, the first optical member includes a mirror that reflects the excitation light onto the target material and a focusing lens that focuses the excitation light, and when the surface position is a predetermined surface position, the control unit controls the drive unit to vary the optical axis of the mirror to vary the position of the focusing point, and controls the drive unit to move the focusing lens in a direction parallel to the optical axis of the excitation light to vary the position of the focusing point, and when the surface position is not the predetermined surface position, the control unit controls the drive unit to vary the optical axis of the mirror to vary the position of the focusing point, and restricts movement of the focusing lens in a direction parallel to the optical axis of the excitation light.

[0021] In the light source device, the light may include EUV light.

[0022] An inspection apparatus according to the present disclosure includes the above-described light source device, and an inspection optical system that inspects an inspection object with the light extracted from the output optical system.

[0023] In the inspection apparatus, the control unit may drive the drive unit so that the light scans a visual field area on the inspection object.

[0024] In the above inspection device, the control unit may drive the drive unit so that scanning movement in a short-side direction component of a rectangular field of view area of ​​the inspection object remains within a certain range.

[0025] An exposure apparatus according to the present disclosure includes the light source device described above, and an exposure optical system that exposes an exposure target with the light extracted from the output optical system.

[0026] In the exposure apparatus, the control unit may drive the drive unit so that the light scans an exposure area on the exposure target.

[0027] The light source control method according to the present disclosure includes the steps of holding a target material in a target holding unit, acquiring a surface position of the target material in an acquisition unit, causing a control unit to vary a position of a focal point of at least one of a first optical member and a second optical member in a drive unit based on the surface position, irradiating excitation light onto the target material using an input optical system including the first optical member, and extracting light generated by irradiating the target material with the excitation light using an output optical system including the second optical member.

[0028] The inspection method according to the present disclosure includes a step of inspecting an object to be inspected with the light extracted by the above-described light source control method.

[0029] The exposure method according to the present disclosure includes a step of exposing an exposure target with the light extracted by the above-described light source control method. Effect of the Invention

[0030] According to the present disclosure, it is possible to provide a light source device, an inspection apparatus, an exposure apparatus, a light source control method, an inspection method, and an exposure method that can improve the stability of the light extracted from the light source device. [Brief description of the drawings]

[0031] [Figure 1] 1 is a cross-sectional view illustrating a light source device according to a first embodiment. [Diagram 2] 3 is a perspective view illustrating a container serving as a target holding portion in the light source device according to the first embodiment. FIG. [Diagram 3] 1 is a plan view illustrating a light source device according to a first embodiment. [Figure 4] 3 is a diagram illustrating an acquisition unit, a drive unit, and a control unit in the light source device according to the first embodiment. [Diagram 5] FIG. 2 is a schematic diagram illustrating the relationship between the displacement of the surface position of the target material and the movement of the bright spot in the light source device according to the first embodiment, as viewed from the direction of the rotation axis of the container. [Figure 6]FIG. 2 is a schematic diagram illustrating the relationship between the displacement of the surface position of the target material and the movement of the bright spot in the light source device according to the first embodiment, as viewed from a direction perpendicular to the rotation axis. [Figure 7] 4 is a schematic diagram illustrating a visual field area detected by a detector of an inspection device that detects light generated by the light source device according to the first embodiment. FIG. [Figure 8] FIG. 2 is a schematic diagram illustrating the cancellation of the displacement of the surface position using a mirror in the light source device according to the first embodiment, as viewed from the direction of the rotation axis of the container. [Figure 9] 4 is a schematic diagram illustrating the cancellation of the displacement of the surface position using a mirror in the light source device according to the first embodiment, as viewed from a direction perpendicular to the rotation axis. FIG. [Figure 10] 4 is a schematic diagram illustrating a visual field area detected by a detector of an inspection device that detects light generated by the light source device according to the first embodiment. FIG. [Figure 11] 4 is a flowchart illustrating a light source control method using the light source device according to the first embodiment. [Figure 12] 1 is a configuration diagram illustrating an inspection device equipped with a light source device according to a first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, a specific configuration of the present embodiment will be described with reference to the drawings. The following description shows a preferred embodiment of the present disclosure, and the scope of the present disclosure is not limited to the following embodiment. In the following description, parts with the same reference numerals indicate substantially the same contents.

[0033] (Embodiment 1) A light source device according to a first embodiment will be described. The light source device of this embodiment generates light such as illumination light and exposure light used in optical devices such as an inspection device and an exposure device. The light source device may be provided integrally with the optical device, or may be disposed near the optical device as a separate entity from the optical device. When the optical device is an inspection device, the light source device generates illumination light that illuminates an inspection object in the inspection device. When the optical device is an exposure device, the light source device generates exposure light that exposes an exposure object in the exposure device.

[0034] The light source device generates light such as illumination light and exposure light by irradiating excitation light onto a target material held in a target holding unit. In the following, an example of a light source device in which molten metal held in a container is used as a target material will be described. Note that the light source device is not limited to one in which the target material is molten metal held in a container, and may be one in which the target material is liquid metal in droplet form, solid metal fixed to a cylindrical drum, or the like.

[0035] FIG. 1 is a cross-sectional view illustrating a light source device 100 according to the first embodiment. FIG. 2 is a perspective view illustrating a container 111 as a target holder 110 in the light source device 100 according to the first embodiment. FIG. 3 is a plan view illustrating the light source device 100 according to the first embodiment. Some members are omitted in FIG. 3. As shown in FIGS. 1 to 3, the light source device 100 includes a target holder 110, an input optical system 120, an output optical system 130, an acquisition unit 140, a sensor 141, a driving unit 150, and a control unit 160. In FIG. 1, the driving unit 150 is connected to the mirror 121, the condenser lens 122, and the collector mirror 131, but it is not necessarily required to connect to all of these optical members. In addition, in order to avoid complication of the figure, the control unit 160 is connected to only some members, but may be connected to other members.

[0036] The target holding unit 110 holds a target material 112. The target holding unit 110 includes a container 111 such as a crucible. The container 111 can melt metal inside. The container 111 holds the target material 112 such as molten metal that generates plasma 127 by irradiation with excitation light LR. The excitation light LR is, for example, laser light including IR (Infrared) light.

[0037] The target holding unit 110 is not limited to the container 111, and may be a cylindrical drum. In this case, the target holding unit 110 holds the target material 112 by fixing a solid metal, such as xenon (Xe), which becomes the target material 112, on the surface of the drum.

[0038] The target material 112 may include a molten metal. The target material 112 is not limited to the molten metal held in the container 111, and may be a solid metal, liquid droplets, or the like, as long as it is a substance that generates plasma 127 when irradiated with the excitation light LR. The molten metal is, for example, melted tin (Sn) or lithium (Li), but is not limited to tin or lithium, as long as it is a substance that generates plasma 127 when irradiated with the excitation light LR.

[0039] The container 111 has a rotation axis R and rotates around the rotation axis R. The container 111 has, for example, a cylindrical shape with one opening closed. The closed part of the container 111 is called a bottom 113. The cylindrical part of the container 111 is called a cylindrical part 114. The inner surface of the bottom 113 is called a bottom surface 115. The inner surface of the cylindrical part 114 is called an inner wall surface 116. A groove 117 may be formed at the joint between the bottom 113 and the cylindrical part 114. The container 111 may have a shape other than the above as long as it can hold the molten metal.

[0040] The target holder 110 supports the target material 112 on an inner wall surface 116 of a container 111 by centrifugal force. The inner wall surface 116 formed to surround the rotation axis R may include a cylindrical portion having a constant distance from the rotation axis R, or may include a cone-shaped portion that widens outward as it approaches the upper part. For example, the cone-shaped portion of the inner wall surface 116 may be connected to a groove 117.

[0041] In addition to the target holding unit 110, the light source device 100 may also include a heater 118 and a debris shield 119. A target material 112 such as a molten metal can be formed in the container 111 by heating with the heater 118. The debris shield 119 is disposed at an opening 111a of the container 111 so as to cover the target material 112.

[0042] As the container 111 rotates about the rotation axis R, the target material 112 also rotates about the rotation axis R. As shown in Fig. 3, for example, the target material 112 located at position P1 facing the sensor 141 at time t1 moves to the irradiation position PS at time t2 as the container 111 rotates. In this way, the target holding unit 110 moves the target material 112 to the irradiation position PS where the excitation light LR is irradiated as the target holding unit 110 moves (i.e., rotates).

[0043] The input optical system 120 includes a first optical member OP1. The first optical member OP1 irradiates the target material 112 with the excitation light LR. The first optical member OP1 includes, for example, at least one of a mirror 121 and a condenser lens 122. Note that the first optical member OP1 is not limited to the mirror 121 and the condenser lens 122 as long as it is an optical member that irradiates the target material 112 with the excitation light LR, and may also be a laser LS that generates the excitation light LR.

[0044] The first optical member OP1 irradiates the target material 112 with the excitation light LR at an angle tilted from an axis perpendicular to the surface of the target material 112. Specifically, for example, the first optical member OP1 irradiates the surface of the irradiation position PS where the excitation light LR is irradiated with the excitation light LR at an inclined incident angle. By irradiating the excitation light LR at an inclined angle in this manner, it is possible to suppress the influence of debris on optical members including the collector mirror 131 and the like. The reason why the influence of debris on optical members such as the collector mirror 131 can be suppressed will be explained below.

[0045] When the excitation light LR is irradiated from a direction perpendicular to the surface of the target material 112, the debris scatters in all directions centered on the direction perpendicular to the surface. This may cause the debris to adhere to the collector mirror 131 facing the irradiation position PS. On the other hand, when the excitation light LR is irradiated on the surface of the irradiation position PS at an inclined incidence angle, the debris can be scattered in the reflection direction opposite to the incidence direction of the excitation light LR. This makes it possible to suppress the adhesion of the debris to the collector mirror 131. Furthermore, the excitation light LR is irradiated at an incidence angle inclined toward the front side of the irradiation position PS with respect to the direction of movement of the target holding unit 110. In other words, the excitation light LR is irradiated from a direction having a component of an incidence angle inclined toward the front side in a plane perpendicular to the rotation axis R. This adds an angular velocity in the rotation direction of the container 111 to the direction in which the debris scatters, so the debris can be further scattered in the reflection direction of the excitation light LR. In this way, the influence of the debris on optical members such as the collector mirror 131 can be suppressed.

[0046] The mirror 121 reflects, for example, the excitation light LR generated by the laser LS toward the irradiation position PS of the target material 112. The mirror 121 may include, for example, a mirror such as a piezo steering mirror. Note that the mirror 121 is not limited to a piezo steering mirror, and may include a galvanometer mirror, a polygon mirror, or the like, as long as it can reflect the excitation light LR toward the target material 112. The condenser lens 122 condenses the excitation light LR at the irradiation position PS of the target material 112.

[0047] The light source device 100 may include a laser LS that generates excitation light LR. On the other hand, the light source device 100 may introduce the excitation light LR from a laser LS that is installed outside the light source device 100 separately from the light source device 100 into the light source device 100. The excitation light LR is, for example, a laser light including IR light. The excitation light LR may irradiate the target material 112 by controlling the oscillation and stopping of the control unit 160. For example, the excitation light LR is reflected by a mirror 121 and condensed by a condenser lens 122. As a result, the excitation light LR irradiates the target material 112.

[0048] The output optical system 130 includes a second optical member OP2. The second optical member OP2 extracts the light L0 generated by irradiating the target material 112 with the excitation light LR from the light source device 100. The second optical member OP2 includes, for example, a collector mirror 131. Note that the second optical member OP2 is not limited to the collector mirror 131 as long as it is an optical member that extracts the light L0 generated by irradiating the target material 112 with the excitation light LR, and may be a second collector mirror (not shown) that further reflects the light L0 reflected by the collector mirror 131.

[0049] The collector mirror 131 reflects the light L0 generated from the target material 112 by irradiation with the excitation light LR. The collector mirror 131 reflects, for example, the EUV light LE generated by irradiation with the excitation light LR. That is, the light L0 may include the EUV light LE. The EUV light LE is generated from the plasma 127 generated by irradiating the target material 112 with the excitation light LR. The EUV light LE generated from the plasma 127 generated in the target material 112 is emitted as illumination light to an optical device such as an inspection device. Therefore, the illumination light includes the EUV light LE generated from the plasma 127.

[0050] The acquisition unit 140 acquires the surface position of the target material 112. The acquisition unit 140 is connected to a sensor 141, and acquires from the sensor 141 the surface position of the target material 112 actually measured by the sensor 141. The acquisition unit 140 acquires the surface position of the target material 112 at an irradiation position PS where the excitation light LR irradiates the target material 112. The acquisition unit 140 may acquire the surface position actually measured by the sensor 141 at the irradiation position PS, or may predict the surface position at the irradiation position PS from the surface positions actually measured by the sensor 141 at peripheral positions, as described later. The acquisition unit 140 may also predict the surface position of the target material 112 taking into consideration the inclination and vibration of the target holder 110 with respect to the rotation axis.

[0051] The acquiring unit 140 may be a separate body from the sensor 141, or may be integrated with the sensor 141. Specifically, the sensor 141 may include, for example, a displacement meter, a high-speed camera, a low-speed camera, a four-division PD (Photo Diode), and a TDI (Time Delay Integration) camera. The acquiring unit 140 may acquire the surface position of the target material 112 by combining the sensor 141 such as a displacement meter with another sensor, for example. This allows the other sensor to supplement phase information that is difficult for the sensor 141 such as a displacement meter to acquire.

[0052] The acquiring unit 140 may acquire the surface position of the target material 112 as a relative position with respect to the second optical member OP2. Specifically, the acquiring unit 140 may acquire the surface position of the target material 112 at the irradiation position PS as a relative position with respect to the second optical member OP2, or may acquire the surface position at a peripheral position as a relative position with respect to the second optical member OP2. The acquiring unit 140 may acquire the surface position of the target material 112 based on the distance from the sensor 141 to the surface of the liquid surface of the molten metal. The acquiring unit 140 may also acquire the surface position of the target material 112 based on the thickness of the liquid surface of the molten metal from the inner wall surface 116. Note that, in the case where the target material 112 is a solid metal fixed to a cylindrical drum, the acquiring unit 140 may acquire the surface position of the target material 112 based on the inclination or vibration amount of the drum in addition to the thickness of the surface of the solid metal from the upper surface (surface layer surface) of the drum.

[0053] The acquiring unit 140 may acquire surface positions of peripheral positions other than the irradiation position PS. The peripheral positions include parts of the inner wall surface 116 of the container 111 other than the irradiation position PS. The acquiring unit 140 may predict the surface position of the irradiation position PS from the surface positions of the peripheral positions acquired from the sensor 141. Specifically, the acquiring unit 140 predicts the surface position of the irradiation position PS from the surface position at a position before the irradiation position PS with respect to the movement direction of the target holding unit 110. At this time, by taking into consideration the movement speed (rotation speed) of the target holding unit 110, it is possible to predict the surface position at the irradiation position PS at the time when the excitation light reaches the irradiation position PS (time of irradiation). The acquiring unit 140 acquires the surface position of the irradiation position PS by predicting the surface position of the irradiation position PS in this way.

[0054] If the sensor 141 is arranged at a position opposite the irradiation position PS so that the surface position of the irradiation position PS can be actually measured and obtained, it may be affected by debris. In addition, since plasma 127 is generated at the irradiation position PS, there is a risk that the surface position cannot be obtained accurately. Therefore, the sensor 141 is arranged to face a peripheral position away from the irradiation position PS. This makes it possible to suppress the influence of debris and improve the measurement accuracy of the surface position. For example, the sensor 141 may be arranged to face a position P1 on the opposite side of the irradiation position PS with respect to the rotation axis R. Note that the sensor 141 may be arranged to face a peripheral position other than the position P1 as long as the influence of debris can be reduced.

[0055] 4 is a diagram illustrating the acquisition unit 140, the drive unit 150, and the control unit 160 in the light source device 100 according to the first embodiment. As described above, the position of the sensor 141 is not limited to a position facing the irradiation position PS, and may be a position facing a peripheral position such as position P1. As shown in FIG. 4, the drive unit 150 changes the position of the light focusing point of at least one of the first optical member OP1 and the second optical member OP2. The drive unit 150 is, for example, an actuator.

[0056] The driving unit 150 drives the first optical member OP1 so as to change the irradiation direction of the excitation light LR. For example, when the first optical member OP1 is a mirror 121, the driving unit 150 performs beam scanning by changing the angle of the mirror 121 with respect to the excitation light LR. Specifically, the driving unit 150 changes the reflecting surface of the mirror 121 so that the excitation light LR scans the surface of the target material 112 in a predetermined direction.

[0057] When mirror 121 is a piezo steering mirror, driving unit 150 may include a driving mechanism provided on the piezo steering mirror. When mirror 121 is a galvanometer mirror, a polygon mirror, or the like, driving unit 150 may be a driving mechanism provided on the galvanometer mirror, the polygon mirror, or the like. When another actuator with a short lead time and good controllability is available, driving unit 150 may be that.

[0058] At the irradiation position PS where the excitation light LR irradiates the target material 112, plasma 127 is generated. The generated plasma 127 is observed as a bright spot. The driving unit 150 varies the optical axis of the mirror 121 to vary the position of the focal point. As a result, the driving unit 150 moves the bright spot at high speed to perform beam shaping. Therefore, when the optical device is an inspection device, it is possible to improve the uniformity and availability on the detector of the inspection device. The driving unit 150 may vary the position of the focal point in two axial directions on the surface of the target material 112 at the irradiation position PS.

[0059] FIG. 5 is a schematic diagram illustrating the relationship between the displacement of the surface position of the target material 112 and the movement of the bright spot in the light source device 100 according to the first embodiment, as viewed from the direction of the rotation axis R of the container 111. FIG. 6 is a schematic diagram illustrating the relationship between the displacement of the surface position of the target material 112 and the movement of the bright spot in the light source device 100 according to the first embodiment, as viewed from a direction perpendicular to the rotation axis R. FIG. 7 is a schematic diagram illustrating the field of view FOV detected by the detector of the inspection device that detects the generated light L0 in the light source device 100 according to the first embodiment. Note that, although the displacement of the surface position of the target material 112 held in the container 111 is described here as an example, the same can be said when considering the surface position of the target material 112 held on the surface of a cylindrical drum.

[0060] As shown in Fig. 7, for convenience of explanation, one direction in the field of view FOV detected by the detector is the X-axis direction, and the other direction perpendicular to the one direction is the Y-axis direction. In this case, the Z-axis direction is the defocus direction of the beam spot BS. The defocus direction corresponds to the optical axis direction of the collector mirror 131. Figs. 5 and 6 show the relationship between the movement direction of the beam spot BS of the light L0 generated from the bright spot of the plasma 127 in the field of view FOV and the movement direction of the plasma 127 generated in the target material 112.

[0061] The displacement of the surface position of the target material 112 includes surface vibration caused by vibration due to rotation of the container 111 etc. propagating to the surface position, and displacement due to consumption or replenishment of the target material 112. In addition, when the target material is a solid such as frozen xenon, displacement due to roughness or unevenness of the target surface is also included.

[0062] 5 to 7, when the excitation light LR is incident obliquely on the surface position of the target material 112, as the surface position is displaced, the beam spot BS moves in a direction having components in the X-axis direction and the Y-axis direction on the viewing area FOV. In this way, the displacement of the bright spot in the direction perpendicular to the optical axis of the collector mirror 131 results in the displacement of the beam spot BS in the X-axis direction and the Y-axis direction on the viewing area FOV.

[0063] FIG. 8 is a schematic diagram illustrating the cancellation of the displacement of the surface position using the mirror 121 in the light source device 100 according to the first embodiment, as viewed from the direction of the rotation axis R of the container 111. FIG. 9 is a schematic diagram illustrating the cancellation of the displacement of the surface position using the mirror 121 in the light source device 100 according to the first embodiment, as viewed from the direction perpendicular to the rotation axis R. As shown in FIGS. 8 and 9, the reflective surface of the mirror 121 such as a steering mirror can be moved in accordance with the displacement of the surface position to cancel the displacement of the component perpendicular to the optical axis. Of the displacements of the surface position, the surface vibration is displaced at a high frequency. Therefore, a steering mirror that can be driven at a high frequency is suitable for canceling the surface vibration. The direction of the displacement of the surface position due to consumption and replenishment of the target material 112 is the same as the direction of the surface vibration described above. However, such a displacement due to consumption and replenishment of the target material 112 becomes a low-frequency displacement. Therefore, the driving unit 150 drives the first optical member OP1 at a low frequency.

[0064] FIG. 10 is a schematic diagram illustrating a field of view FOV detected by a detector of an inspection device that detects light generated in the light source device 100 according to the first embodiment. As shown in FIG. 10, the displacement of the bright spot in a direction parallel to the optical axis results in defocusing of the beam spot BS in the Z-axis direction. Therefore, the driving unit 150 moves the position of the condenser lens 122 in a direction parallel to the optical axis of the excitation light LR. As a result, the driving unit 150 varies the position of the condenser point of the excitation light LR. In this way, when the first optical member OP1 includes the condenser lens 122, the driving unit 150 moves the position of the condenser lens 122 in a direction parallel to the optical axis of the excitation light LR.

[0065] The driving unit 150 may drive the second optical member OP2 so as to change the extraction direction of the generated light L0. When the surface position of the target material 112 is displaced, the optical path of the light L0 generated from the target material 112 is displaced. Therefore, when the second optical member OP2 includes a collector mirror 131, the driving unit 150 performs beam scanning by changing the angle of the collector mirror 131 with respect to the light L0.

[0066] The control unit 160 drives the driving unit 150 based on the surface position of the target material 112 acquired by the acquisition unit 140. Here, the acquisition unit 140 acquires the surface position of the target material 112 as a relative position with respect to the second optical member OP2. When it is predicted that the surface position acquired as the relative position with respect to the second optical member OP2 will be displaced by a predetermined threshold or more, the control unit 160 controls the driving unit 150 so that the position of the light focusing point of at least one of the first optical member OP1 and the second optical member OP1 varies. Therefore, even if the surface position (the thickness of the target material 112 from the inner wall surface 116 and the drum surface) is displaced, the control unit 160 may limit the execution of the control of the driving unit 150 when the relative position does not displace by a predetermined threshold or more.

[0067] The control unit 160 calculates a control amount based on the surface position acquired by the acquisition unit 140. Then, the control unit 160 drives the driving unit 150 based on the calculated control amount. The control unit 160 may include, for example, a control board. For example, the control unit 160 controls the driving unit 150 so that the optical axis of the mirror 121 changes and the position of the light condensing point changes based on the calculated control amount. Furthermore, the control unit 160 controls the driving unit 150 so that the condensing lens 122 moves in a direction parallel to the optical axis of the excitation light LR and the position of the light condensing point changes based on the calculated control amount. Furthermore, the control unit 160 controls the driving unit 150 so that the optical axis of the collector mirror 131 changes and the optical axis of the generated light L0 changes based on the calculated control amount. The control unit 160 may drive the driving unit 150 so that the light L0 scans the field of view FOV of the inspection target of the inspection device.

[0068] For example, the control unit 160 drives the driving unit 150 so that the movement of the scan in the Y-axis direction component shown in FIG. 7, for example, 80% of the locus of the center of the beam spot BS, remains within the field of view FOV. The target control amount for this purpose can be determined in advance based on experimental results or simulation results. Specifically, the experiment or simulation is performed to determine how much the beam spot BS moves in the Y-axis direction due to the displacement of the surface position, and how much the beam spot BS moves in the Y-axis direction due to the driving of the optical member. The above 80% is an example. Also, 80% of the beam spot BS itself may remain within the field of view FOV. In this way, the control unit 160 drives the driving unit 150 so that the movement of the scan in the short side direction component of the rectangular field of view FOV of the inspection object remains within a certain range.

[0069] The control unit 160 may prioritize the control of the first optical member OP1 over the control of the second optical member OP2. For example, the control unit 160 may set the control amount of the first optical member OP1 to be greater than the control amount of the second optical member OP2. Furthermore, the control unit 160 may control the first optical member OP1 more times than the control amount of the second optical member OP2. This is because the first optical member OP1 is easier to control than the second optical member OP2, and has less effect on other optical members after being moved by the drive unit 150.

[0070] There are cases where the surface position of the target material 112 increases or decreases suddenly. For example, the surface position changes suddenly when the container 111 is refilled with the target material 112. In this case, the surface position increases or decreases to such an extent that not only the mirror 121 is moved but also the condenser lens 122 needs to be used to deal with defocusing. Therefore, the surface position in such a case where the surface position changes suddenly is set in advance as a predetermined surface position. Then, when the surface position of the target material 112 is at the predetermined surface position, the control unit 160 controls the driving unit 150 to move the optical axis of the mirror 121 to change the position of the condenser point, and controls the driving unit 150 to move the condenser lens 122 in a direction parallel to the optical axis of the excitation light LR to change the position of the condenser point.

[0071] When the acquisition unit 140 predicts the surface position of the irradiation position PS from the surface position at a position P1 before the irradiation position PS in the movement direction of the target holding unit 110, the control unit 160 calculates a control amount based on the predicted surface position. Then, the control unit 160 performs feedforward control of the driving unit 150 based on the calculated control amount.

[0072] Although the sensor 141 may actually measure the surface position of the irradiation position PS, and the control unit 160 may control the driving unit 150 based on the actually measured surface position, there may be cases where the control unit 160 is unable to transmit a control signal to the driving unit 150 or calculate a control amount in time for controlling the position of the focal point of the optical member that matches the irradiation timing of the excitation light LR. Therefore, the control unit 160 controls (e.g., feedforward control) the driving unit 150 based on the surface position of the irradiation position PS predicted from the surface position of position P1. To accommodate such an operation, the driving unit 150 may be designed to be capable of operating at several hundred Hz.

[0073] When the surface position varies with a predetermined period, the acquisition unit 140 may predict the surface position of the target material 112 based on the period, and the control unit 160 may control (e.g., feedforward control) the driving unit 150 based on the predicted surface position. The control unit 160 may calculate a control amount based on the period and feedforward control the driving unit 150. For example, when the variation in the surface position includes surface vibration that oscillates with a predetermined period, the control unit 160 calculates the period of the surface vibration. Then, the control unit 160 calculates a control amount based on the calculated period and feedforward controls the driving unit 150.

[0074] <Light source control method> Next, a light source control method using the light source device 100 will be described. Fig. 11 is a flow chart illustrating a light source control method using the light source device 100 according to the first embodiment. As shown in step S11 in Fig. 11, first, the target material 112 is held by the target holding unit 110. For example, the target material 112 such as a molten metal that generates plasma 127 by irradiation with excitation light LR is held in a container 111 such as a crucible.

[0075] Next, as shown in step S12, the surface position of the target material 112 is acquired by the acquisition unit 140. For example, the acquisition unit 140 may acquire the surface position at the irradiation position PS by predicting the surface position at the irradiation position PS from the surface positions at the peripheral positions actually measured by the sensor 141.

[0076] Next, as shown in step S13, the control unit 160 causes the driving unit 150 to vary the position of the focal point of at least one of the first optical member OP and the second optical member OP based on the surface position acquired by the acquisition unit 140. For example, the control unit 160 causes the control unit 160 to calculate the control amount for driving the first optical member OP1 and / or the second optical member OP2. Specifically, the control unit 160 causes the control unit 160 to calculate the control amount for driving the first optical member OP1 and / or the second optical member OP2 based on the surface position acquired by the acquisition unit 140. Then, the control unit 160 causes the driving unit 150 to vary the position of the focal point of at least one of the first optical member OP1 and the second optical member OP2. For example, when the first optical member OP1 includes a mirror 121, the control unit 160 controls the driving unit 150 to vary the optical axis of the mirror 121 to vary the position of the focal point. Furthermore, when the first optical member OP1 includes the condenser lens 122, the control unit 160 controls the driving unit 150 to move the condenser lens 122 in a direction parallel to the optical axis of the excitation light LR to vary the position of the focal point. Furthermore, when the second optical member OP2 includes the collector mirror 131, the control unit 160 controls the driving unit 150 to vary the optical axis of the collector mirror 131 based on the calculated control amount to vary the optical axis of the generated light L0.

[0077] Next, as shown in step S14, the target material 112 is irradiated with excitation light LR by the input optical system 120 including the first optical member OP1.

[0078] Next, as shown in step S15, the light L0 generated by irradiating the target material 112 with the excitation light LR is extracted by the output optical system 130 including the second optical member OP2. In this manner, by controlling the light source device 100, the light L0 to be used in the optical device can be extracted.

[0079] <Optical equipment> Next, an optical device will be described. In the following, an inspection device will be used as an example of the optical device.

[0080] FIG. 12 is a configuration diagram illustrating an inspection apparatus 1 including a light source device 100 according to the first embodiment. As shown in FIG. 12, the inspection apparatus 1 includes an illumination optical system 200, an inspection optical system 300, a detector 410, and an image processing unit 420. The inspection apparatus 1 may further include a light source device 100. The inspection apparatus 1 is an apparatus that uses light L0 generated by the light source device 100 as illumination light L1 to inspect defects and the like of a sample 500. The sample 500 is, for example, an EUV mask. The sample 500 is not limited to an EUV mask, and may be a semiconductor substrate or the like.

[0081] The illumination optical system 200 has an ellipsoidal mirror 210, an ellipsoidal mirror 220, and a drop-in mirror 230. The inspection optical system 300 has a concave mirror with a hole 310, a convex mirror 320, a plane mirror 330, and a concave mirror 340. The concave mirror with a hole 310 and the convex mirror 320 configure a Schwarzschild magnification optical system.

[0082] The light source device 100 generates illumination light L1. The illumination light L1 includes, for example, EUV light LE of 13.5 nm, which is the same as the exposure wavelength of the EUV mask that is the sample 500. The illumination light L1 may include light other than EUV light. The illumination light L1 generated from the light source device 100 is reflected by the ellipsoidal mirror 210. The illumination light L1 reflected by the ellipsoidal mirror 210 advances while being narrowed, and is collected at a convergence point IF1. Therefore, the ellipsoidal mirror 210 reflects the illumination light L1 generated from the light source device 100 as a convergent light. The convergence point IF1 is located at a position conjugate to the upper surface 510 of the sample 500 such as an EUV mask and the detection surface 411 of the detector 410.

[0083] After passing through the convergence point IF1, the illumination light L1 advances while expanding and is incident on a reflecting mirror such as the ellipsoidal mirror 220. Therefore, the illumination light L1 reflected by the ellipsoidal mirror 210 is incident on the ellipsoidal mirror 220 as divergent light via the convergence point IF1. The illumination light L1 incident on the ellipsoidal mirror 220 is reflected by the ellipsoidal mirror 220, advances while being narrowed, and is incident on the drop-in mirror 230. In other words, the ellipsoidal mirror 220 reflects the incident illumination light L1 as convergent light. Then, the ellipsoidal mirror 220 causes the illumination light L1 to be incident on the drop-in mirror 230. The drop-in mirror 230 is disposed directly above the EUV mask. The illumination light L1 incident on and reflected by the drop-in mirror 230 is incident on the sample 500. Therefore, the drop-in mirror 230 reflects the illumination light L1 reflected by the ellipsoidal mirror 220 to the sample 500, thereby causing the illumination light L1 to be incident on the sample 500.

[0084] The ellipsoidal mirror 220 focuses the illumination light L1 on the sample 500. The illumination optical system 200 is installed so that, when the illumination light L1 illuminates the sample 500, an image of the light source device 100 is formed on the upper surface 510 of the sample 500. Therefore, the illumination optical system 200 provides critical illumination. In this manner, the illumination optical system 200 illuminates the sample 500, such as an EUV mask, using critical illumination by the illumination light L1 generated by the light source device 100.

[0085] The sample 500 is placed on a stage 520. Here, a plane parallel to an upper surface 510 of the sample 500 is defined as an αβ plane, and a direction perpendicular to the αβ plane is defined as a γ axis direction. Illumination light L1 is incident on the sample 500 from a direction tilted from the γ axis direction. That is, illumination light L1 is incident obliquely to illuminate the sample 500.

[0086] The stage 520 is a three-dimensional drive stage having a drive unit 530. The drive unit 530 can illuminate a desired area of ​​the sample 500 by moving the stage 520 in the αβ plane. Furthermore, the drive unit 530 can perform focus adjustment by moving the stage 520 in the γ-axis direction.

[0087] The illumination light L1 from the light source device 100 illuminates an inspection area of ​​the sample 500. 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 illumination light L1 is incident on the sample 500 from a direction tilted with respect to the γ-axis direction. The light from the sample 500 illuminated by the illumination light L1 is incident on the perforated concave mirror 310. In the following, the light from the sample 500 illuminated by the illumination light L1 is described as reflected light L2. The light incident on the perforated concave mirror 310 from the sample 500 is not limited to the reflected light L2, and may include diffracted light and the like. The reflected light L2 reflected by the sample 500 is incident on the perforated concave mirror 310. A hole 311 is provided at the center of the perforated concave mirror 310. The perforated concave mirror 310 collects the reflected light L2 from the sample 500, and reflects the collected reflected light L2 as convergent light.

[0088] The reflected light L2 reflected by the concave mirror 310 with a hole is incident on the convex mirror 320. The convex mirror 320 reflects the reflected light L12 reflected by the concave mirror 310 with a hole toward the hole 311 of the concave mirror 310 with a hole. The reflected light L2 passing through the hole 311 is incident on the plane mirror 330. The plane mirror 330 causes the reflected light L2 reflected by the convex mirror 320 to be incident as convergent light through the hole 311 of the concave mirror 310 with a hole. The reflected light L2 incident on the plane mirror 330 is reflected by the plane mirror 330. The reflected light L2 reflected by the plane mirror 330 advances while being narrowed, and is collected at the convergence point IF2. Therefore, the plane mirror 330 reflects the incident reflected light L2 as convergent light. The convergence point IF2 is sometimes called an aperture stop. The convergence point IF 2 is located at a position conjugate with the upper surface 510 of the sample 500 and the detection surface 411 of the detector 410 .

[0089] After passing through the convergence point IF2, the reflected light L2 advances while diverging and enters the concave mirror 340. Thus, the reflected light L2 reflected by the plane mirror 330 as convergent light enters the concave mirror 340 as divergent light via the convergence point IF2. The concave mirror 340 reflects the incident reflected light L2 as convergent light toward the detector 410. The reflected light L2 reflected by the concave mirror 340 is detected by the detector 410. In this manner, the inspection optical system 300 inspects the sample 500, which is the inspection target, with the light L1 extracted from the output optical system 130 of the light source device 100. That is, the inspection optical system 300 collects the reflected light L2 from the sample 500 illuminated by the illumination light L1, and guides the collected reflected light L2 to the detector 410.

[0090] The detector 410 may include a TDI (Time Delay Integration) sensor. The detector 410 receives light from the sample 500 illuminated by the illumination light L1. The area on the sample 500 detected by the detector 410 is called a field of view 511. The detector 410 receives reflected light L2 from the field of view 511 illuminated by the illumination light L1. The field of view 511 may be included in the inspection area illuminated by the illumination light L1. The detector 410 acquires image data of the sample 500, such as an EUV mask. When the detector 410 includes a TDI sensor, the detector 410 includes a plurality of imaging elements arranged in a line in one direction. The imaging elements are, for example, CCDs (Charge Coupled Devices). Note that the imaging elements are not limited to CCDs.

[0091] The image data of the sample 500 acquired by the detector 410 is output to the image processing unit 420 and processed in the image processing unit 420. The image processing unit 420 may be, for example, an information processing device such as a server device or a personal computer.

[0092] The reflected light L2 contains information about defects in the sample 500. The specularly reflected light of the illumination light L1 incident on the sample 500 from a direction tilted with respect to the Z-axis direction is detected by the inspection optical system 300. If a defect exists in the sample 500, the defect is observed as a dark image. This observation method is called bright-field observation. Note that the inspection apparatus 1 may also cause the illumination light L1 to be incident on the sample 500 from the Z-axis direction and detected by the inspection optical system 300. If a defect exists in the sample 500, the defect is observed as a bright image. This observation method is called dark-field observation.

[0093] In this manner, the inspection apparatus 1 of the present embodiment includes the light source device 100 described above and the inspection optical system 300 that inspects the inspection object with the light L0 extracted from the output optical system 130. The inspection method using the inspection apparatus 1 includes a step of inspecting the inspection object with the light L0 extracted by the light source control method described above. Although the inspection apparatus 1 has been described as an optical apparatus, the optical apparatus may be an exposure apparatus. For example, the exposure apparatus includes the light source device 100 described above and an exposure optical system that exposes the exposure object with the light L0 extracted from the output optical system 130. The control unit 160 may drive the drive unit 150 so that the light L0 scans the exposure area on the exposure object. The exposure method using the exposure apparatus includes a step of exposing the exposure object with the light L0 extracted by the light source control method described above.

[0094] Next, the effects of this embodiment will be described. The light source device 100 of this embodiment drives the drive unit 150 with a control amount based on the surface position of the target material 112. As a result, the light source device 100 varies the position of the light condensing point of at least one of the first optical member OP1 and the second optical member OP2. Therefore, even if the surface position of the target material 112 varies due to vibration and consumption of the target material 112, the light condensing point varies following the variation, so that the stability of the light L0 extracted from the light source device 100 can be improved.

[0095] For example, the first optical member OP1 such as the mirror 121 may be originally introduced to improve uniformity availability on the detector 410 of the inspection device 1. Specifically, the mirror 121 of the first optical member OP1 scans the field of view FOV so that the illumination light L1 uniformly illuminates the field of view FOV. In this embodiment, such a first optical member OP1 is also used to cancel the displacement of the surface position. Therefore, this embodiment can appropriately deal with the positional fluctuation of the bright spot caused by the displacement of the surface position of the irradiation position PS due to the variation in the thickness of the target material 112, and can realize the stabilization of the intensity of the generated light L1 such as EUV light LE.

[0096] The acquiring unit 140 acquires the surface position of the target material 112 as a relative position with respect to the second optical member OP2, so that the accuracy of the surface position can be improved. In addition, the acquiring unit 140 acquires the surface positions of peripheral positions other than the irradiation position PS, and predicts the surface position of the irradiation position PS from the surface positions of the acquired peripheral positions. Specifically, the acquiring unit 140 predicts the surface position of the irradiation position PS from the surface position at a position before the irradiation position PS with respect to the direction of movement of the target holding unit 110. Therefore, the focusing point of the excitation light LR can be aligned with the surface position at the irradiation position in advance, so that the stability of the light L1 can be improved. Furthermore, the control unit 160 calculates a control amount based on the predicted surface position, and feed-forward controls the driving unit 150. This allows the focusing point to be changed in accordance with the displacement of the surface position.

[0097] The target holder 110 supports the target material 112 on the inner wall surface 116 by the centrifugal force of the rotating container 111. This makes it possible to make the surface position of the target material 112 uniform, thereby improving the stability of the light L1.

[0098] The control unit 160 may vary the position of the focal point by varying the optical axis of the mirror 121, or may vary the position of the focal point by moving the condenser lens 122 in a direction parallel to the optical axis of the excitation light LR. The control unit 160 may also vary the optical axis of the generated light L0 by varying the optical axis of the collector mirror 131. In this way, the control amount is calculated in response to the variation in the surface position, so that the stability of the light L0 can be improved.

[0099] 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-mentioned embodiments. In the embodiments of the present disclosure, the target holder 110 is a container 111 such as a crucible, but the target holder 110 is not limited to this, and may be one that holds the target material 112 on the surface of a cylindrical object, or one that holds the target material 112 with a tape-like object, etc. Furthermore, the configurations of the first embodiment may be combined as appropriate. [Explanation of symbols]

[0100] 1. Inspection equipment 100 Light source device 110 Target holder 111 Container 111a opening 112 Target material 113 Bottom 114 Cylindrical part 115 Bottom 116 Inner Wall 117 Groove 118 Heater 119 Debris Shield 120 Input Optical System 121 Mirror 122 Condenser Lens 127 Plasma 130 Output Optical System 131 Collector Mirror 140 Acquisition Department 141 Sensors 150 Drive unit 160 Control section 200 Illumination optical system 210 Ellipsoidal Mirror 220 Ellipsoidal Mirror 230 Drop-in mirror 300 Inspection Optical System 310 Holed concave mirror 311 holes 320 Convex mirror 330 plane mirror 340 concave mirror 410 Detector 411 Detection surface 420 Image Processing Unit 500 samples 510 Top surface 511 Field of view 520 Stage 530 Drive unit BS Beam Spot FOV field of view L0 light L1 illumination light L2 reflected light LE EUV light LR excitation light LS Laser OP1 First optical member OP2 Second optical member P1 position PS irradiation position R rotation axis

Claims

1. an input optical system including a first optical member that irradiates the target material with excitation light; an output optical system including a second optical member that extracts light generated by irradiating the target material with the excitation light; A target holder for holding the target material; An acquisition unit that acquires a surface position of the target material; a drive unit that changes a position of a light focusing point of at least one of the first optical member and the second optical member; A control unit that drives the drive unit based on the surface position; A light source device comprising:

2. the acquisition unit acquires the surface position as a relative position with respect to the second optical member. The light source device according to claim 1 .

3. The first optical member irradiates the target material with the excitation light at an angle inclined from an axis perpendicular to the surface of the target material. The light source device according to claim 1 .

4. The target holding unit moves the target material to an irradiation position where the excitation light is irradiated, in accordance with the movement of the target holding unit. The light source device according to claim 1 .

5. The acquisition unit is acquiring the surface positions at peripheral positions other than the irradiation position; acquiring the surface position of the irradiation position by predicting the surface position of the irradiation position from the acquired surface positions of the peripheral positions; The light source device according to claim 4 .

6. the target material comprises molten metal; the target holder includes a container for accommodating the target material therein, and supports the target material on an inner wall surface of the container by centrifugal force. The light source device according to claim 4 .

7. The acquisition unit acquires the surface position of the target material based on a distance from a sensor to a surface of the liquid surface of the molten metal. The light source device according to claim 6 .

8. the acquisition unit predicts the surface position of the irradiation position from the surface position at a position before the irradiation position with respect to the direction of the movement of the target holding unit; The control unit controls the drive unit based on the predicted surface position. The light source device according to claim 5 .

9. When the surface position varies with a predetermined period, the acquisition unit predicts the surface position based on the period, and the control unit controls the drive unit based on the predicted surface position. The light source device according to claim 1 .

10. The first optical member includes a mirror that reflects the excitation light to the target material. The light source device according to claim 1 .

11. The second optical member includes a collector mirror that reflects the generated light. The light source device according to claim 1 .

12. the first optical member includes a mirror that reflects the excitation light to the target material, the second optical member includes a collector mirror that reflects the generated light, the control unit sets a drive control amount of the first optical member to be greater than a drive control amount of the second optical member. The light source device according to claim 1 .

13. the first optical member includes a condenser lens that condenses the excitation light, the control unit controls the drive unit to move the condenser lens in a direction parallel to an optical axis of the excitation light to vary the position of the condensing point. The light source device according to claim 1 .

14. the first optical member includes a mirror that reflects the excitation light onto the target material and a condenser lens that condenses the excitation light, When the surface position is a predetermined surface position, the control unit Controlling the driving unit to vary the optical axis of the mirror to vary the position of the light-collecting point; controlling the driving unit to move the condenser lens in a direction parallel to an optical axis of the excitation light to vary the position of the condensing point; When the surface position is not a predetermined surface position, the control unit The driving unit is controlled so as to vary the optical axis of the mirror to vary the position of the focusing point, and the movement of the focusing lens is restricted in a direction parallel to the optical axis of the excitation light. The light source device according to claim 1 .

15. The light includes EUV light. The light source device according to claim 1 .

16. The light source device according to any one of claims 1 to 15, an inspection optical system that inspects an inspection object with the light extracted from the output optical system; An inspection device equipped with

17. The control unit drives the driving unit so that the light scans a visual field area of ​​the inspection object.

17. The inspection apparatus according to claim 16.

18. The control unit drives the driving unit so that a scan movement in a short side direction component of a rectangular field of view of the inspection object remains within a certain range.

17. The inspection apparatus according to claim 16.

19. The light source device according to any one of claims 1 to 15, an exposure optical system that exposes an exposure target with the light extracted from the output optical system; An exposure apparatus comprising:

20. The control unit drives the drive unit so that the light scans an exposure area on the exposure target.

20. The exposure apparatus according to claim 19.

21. Holding the target material with a target holder; acquiring a surface position of the target material by an acquisition unit; a step of causing a control unit to vary a position of a light focusing point of at least one of the first optical member and the second optical member based on the surface position; Irradiating the target material with excitation light using an input optical system including the first optical member; extracting light generated by irradiating the target material with the excitation light using an output optical system including the second optical member; A light source control method comprising:

22. An inspection method comprising the step of inspecting an inspection object with the light extracted by the light source control method according to claim 21.

23. 22. An exposure method comprising the step of exposing an exposure object with the light extracted by the light source control method according to claim 21.

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