Light source device

Abstract

To provide a light source device that can improve the stability of a beam applied to a target material.SOLUTION: A light source device 100 comprises: a target holding part 110 which holds a target material 112 on its inner wall surface with a centrifugal force caused by rotation about a rotational axis; a seed laser SL which excites the target material 112 with a beam based on amplified light L12 amplified by an amplifier AM; and an optical switch SW or an element group EG exhibiting nonlinear optical effect provided between the amplifier AM and the target material 112. The optical switch SW or the element group EG suppresses a power component of in the amplified light L12 that is at a prescribed threshold value or below. The target material 112 generates plasma with a beam having suppressed power components.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a light source device. [Background technology]

[0002] Patent Document 1 describes a laser device that includes an amplifier arranged on the optical path of pulsed laser light, an optical shutter arranged on the optical path of pulsed laser light, and a controller that opens and closes the optical shutter.

[0003] Patent Document 2 describes a laser device that includes two or more amplifiers arranged on the optical path of pulsed laser light, and an optical isolator that is arranged between adjacent amplifiers on the optical path of the pulsed laser light and that suppresses the transmission of light traveling from the amplifiers to the side where a master oscillator is provided.

[0004] Patent document 3 describes a device comprising a cylindrically symmetric element having a surface coated with a target material for plasma formation, a system for outputting a train of laser beam pulses, and a pulse trimming unit for outputting trimmed pulses that interact with the target material to generate plasma. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-065804 [Patent Document 2] International Publication No. 2014 / 119199 [Patent Document 3] Patent No. 6968793 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide a light source device that can improve the stability of the light beam irradiated onto a target material. [Means for solving the problem]

[0007] The light source device according to the present disclosure includes a target holder that holds a target material on an inner wall surface by centrifugal force caused by rotation around a rotation axis, a laser that excites the target material with a beam of light based on amplified light amplified by an amplifier, and a switch or a group of elements exhibiting a nonlinear optical effect that is provided between the amplifier and the target material. The switch or the group of elements suppresses power components in the amplified light that are equal to or less than a predetermined threshold, and the target material generates plasma using the beam of light with the suppressed power components.

[0008] In the light source device, the switch may be in either a first state or a second state that suppresses propagation of the amplified light to the target material more than in the first state. The light source device may further include a control unit that switches the switch between the first state and the second state at a timing synchronized with a seed pulse.

[0009] In the light source device, the group of elements may include an element that converts the first wavelength of the input amplified light into a second wavelength, wherein the power of the transmitted light that passes through the element responds nonlinearly to the power of the amplified light, and a filter that is provided downstream of the element and suppresses propagation of the first wavelength component of the transmitted light to the target material. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to improve the stability of the light beam irradiated onto the target material. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view illustrating a light source device according to a first embodiment. [Figure 2] 3 is a perspective view illustrating a container serving as a target holding unit in the light source device according to the first embodiment. FIG. [Figure 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. FIG. [Figure 5] 1 is a block diagram illustrating a laser according to a first embodiment. [Figure 6] 1 is a graph showing the time waveform of each light beam in a laser. [Figure 7] 1 is a configuration diagram illustrating an inspection device equipped with a light source device according to a first embodiment. [Figure 8] FIG. 10 is a block diagram illustrating a laser according to a second embodiment. [Figure 9] 1 is a graph showing the time waveform of each light beam in a laser. [Figure 10] 10 is a graph comparing the output from the optical switch according to the first embodiment with the output from the optical element according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a specific configuration of this embodiment will be described with reference to the drawings. The following description shows a preferred embodiment of the present disclosure, and the scope of the present disclosure is not limited to the following embodiment. In the following description, parts with the same reference numerals indicate substantially the same content.

[0013] (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 inspection devices and exposure devices. The light source device may be provided integrally with the optical device, or may be disposed near the optical device as a separate entity. 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.

[0014] 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 holder. In the following embodiment 1, an example of a light source device will be described in which a liquid target material is held in a target holder including a container such as a crucible. However, the target holder may include a cylindrical drum or the like instead of a container such as a crucible. The drum may hold, for example, a solid target material. As another example, the light source device may use a tape-shaped target material or a target material that falls or is ejected in the form of droplets. In other words, the target holder is not necessarily required for the configuration of the light source device.

[0015] 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 components 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 driver 150, and a controller 160. In FIG. 1, the driver 150A is connected to the mirror 121, the driver 150B is connected to the condenser lens 122, and the driver 150C is connected to the collector mirror 131. However, the driver does not necessarily need to be connected to all of these optical components. To avoid cluttering the diagram, the controller 160 is connected to only some components, but it may also be connected to other components.

[0016] 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 when irradiated with excitation light LR. The excitation light LR is, for example, laser light including IR (Infrared) light.

[0017] 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, which will become the target material 112, such as frozen xenon (Xe), on the surface of the drum.

[0018] The target material 112 may include molten metal. Note that 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 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 generates plasma 127 when irradiated with excitation light LR.

[0019] The vessel 111 has a rotation axis R and rotates around the rotation axis R. The vessel 111 has, for example, a cylindrical shape with one opening closed. The closed portion of the vessel 111 is called the bottom 113. The cylindrical portion of the vessel 111 is called the cylindrical portion 114. The inner surface of the bottom 113 is called the bottom surface 115. The inner surface of the cylindrical portion 114 is called the inner wall surface 116. A groove 117 may be formed at the joint between the bottom 113 and the cylindrical portion 114. The vessel 111 may have a shape other than those described above as long as it can hold molten metal.

[0020] 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, which is formed to surround the rotation axis R, may include a cylindrical portion that is at a constant distance from the rotation axis R, or may include a cone-shaped portion that widens outward as it approaches the top. For example, the cone-shaped portion of the inner wall surface 116 may be connected to a groove 117.

[0021] 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, at time t1, the target material 112 is positioned at position P1 facing the sensor 141, and at time t2, as the container 111 rotates, the target material 112 moves to the irradiation position PS. In this way, as the target holder 110 moves (i.e., rotates), the target holder 110 moves the target material 112 to the irradiation position PS where it is irradiated with the excitation light LR.

[0022] The input optical system 120 includes a first optical member OP1. The first optical member OP1 irradiates the target material 112 with 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 excitation light LR, and may also be a laser LS that generates the excitation light LR.

[0023] 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.

[0024] The light source device 100 may include a laser LS that generates excitation light LR. Alternatively, the light source device 100 may introduce 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, laser light including IR light. The excitation light LR may be irradiated onto the target material 112 by the control of oscillation and stopping by 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. The detailed configuration of the laser LS will be described later.

[0025] 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 also be a second collector mirror (not shown) that further reflects the light L0 reflected by the collector mirror 131.

[0026] 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 (Extreme ultraviolet lithography) 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.

[0027] 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 that is 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 that is actually measured by the sensor 141 at the irradiation position PS, or may predict the surface position at the irradiation position PS from surface positions that are actually measured by the sensor 141 at peripheral positions, as will be described later. Furthermore, the acquisition unit 140 may predict the surface position of the target material 112 taking into account the tilt and vibration of the target holder 110 with respect to the rotation axis.

[0028] The acquisition unit 140 may be a separate entity 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-segment PD (Photo Diode), or a TDI (Time Delay Integration) camera. The acquisition 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. This allows the other sensor to supplement phase information that is difficult for the sensor 141, such as a displacement meter, to acquire.

[0029] The acquisition 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 acquisition 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 acquisition 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 molten metal. The acquisition unit 140 may also acquire the surface position of the target material 112 based on the thickness of the molten metal from the inner wall surface 116. Note that, in the case where the target material 112 is solid metal fixed to a cylindrical drum, the acquisition unit 140 may acquire the surface position of the target material 112 based on the thickness of the solid metal surface from the upper surface (surface) of the drum, as well as the tilt or vibration amount of the drum.

[0030] The acquisition 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 acquisition 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 acquisition unit 140 predicts the surface position of the irradiation position PS from the surface position of a position before the irradiation position PS in the direction of movement of the target holding unit 110. At this time, by taking into account the movement speed (rotation speed) of the target holding unit 110, the surface position of the excitation light LR It is possible to predict the surface position at the irradiation position PS at the time when the light beam reaches the irradiation position PS (the irradiation time). In this way, the acquisition unit 140 predicts the surface position of the irradiation position PS, thereby acquiring the surface position of the irradiation position PS.

[0031] 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, but may be a position facing a peripheral position such as position P1. As shown in FIG. 4, the drive units 150A to 150C vary the position of the light convergence point of at least one of the first optical member OP1 and the second optical member OP2. The drive units 150A to 150C are, for example, actuators.

[0032] The driving units 150A and 150B drive the first optical member OP1 so as to change the irradiation direction of the excitation light LR. For example, if the first optical member OP1 is a mirror 121, the driving unit 150A performs beam scanning by swinging the angle of the mirror 121 relative to the excitation light LR. Specifically, the driving unit 150A 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.

[0033] If mirror 121 is a piezo steering mirror, driver 150A may include a drive mechanism provided on the piezo steering mirror. Also, if mirror 121 is a galvanometer mirror, polygon mirror, or the like, driver 150A may be a drive mechanism provided on the galvanometer mirror, polygon mirror, or the like. Note that if another actuator with a short response time and good controllability is available, driver 150A may also be that.

[0034] Plasma 127 is generated at the irradiation position PS where the excitation light LR irradiates the target material 112. The generated plasma 127 is observed as a bright spot. The driver 150A drives the mirror 121 to change the optical axis of the excitation light LR, thereby changing the position of the focal point. As a result, the driver 150A 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 driver 150A may change the position of the focal point in two axial directions on the surface of the target material 112 at the irradiation position PS.

[0035] Fig. 5 is a block diagram illustrating a laser LS according to embodiment 1. As shown in Fig. 5, the laser LS includes a seed laser SL, an optical amplifier AM, and an optical switch SW. In the laser LS, the seed laser SL, the optical amplifier AM, and the optical switch SW are arranged in this order from the front stage to the rear stage.

[0036] The seed laser SL outputs seed light L11 before being amplified by the optical amplifier AM under the control of the control unit 160. The optical amplifier AM amplifies the input seed light L11 and outputs amplified light L12. One or more optical amplifiers AM may be provided as needed. As will be described later, the optical switch SW suppresses power components (low power components) below a predetermined threshold in the amplified light L12 output from the optical amplifier AM, and outputs the pumping light LR in which the low power components have been suppressed to the target material 112. Note that in FIG. 5, the mirror 121 and the condenser lens 122 provided on the optical path of the pumping light LR are omitted from the illustration.

[0037] FIG. 6 is a graph showing the time waveforms of each light beam from the laser LS. In FIG. 6(a), the seed light L11 has pulse components at times t1, t2, and t3. Each pulse component is amplified by the optical amplifier AM. At this time, as shown in FIG. 6(b), the amplified light L12 contains a low-power component LO other than each pulse component. The low-power component LO is a component having a power below a predetermined threshold, e.g., a component below the power suitable for generating plasma from the target material 112. The optical switch SW is controlled by the control unit 160 to be in an on state at times t1, t2, and t3 when the pulse components are output (i.e., at timings synchronized with the seed pulses) to transmit light, but to be in an off state at other times to prevent light from passing through. In other words, the optical switch SW is controlled in synchronization with the times of the pulse components. As a result, the components of the amplified light L12 are transmitted at times t1, t2, t3 and during the switch drive time DT at each time, but are not transmitted at other times. Therefore, as shown in Figure 6(c), the amplified pulse components remain in the pump light LR, while the low-power components are suppressed. Note that the wavelength of the amplified light L12 is the same as the wavelength of the pump light LR.

[0038] The optical switch SW may be configured to transmit light when in an off state and not transmit light when in an on state. In the above example, the optical switch SW controls the transmission of the amplified light L12 by turning on and off, but this is not limiting. That is, the optical switch SW may be configured to switch between (1) a first state in which the amplified light L12 is diffracted or reflected at a predetermined angle toward the target material 112 and a second state in which the amplified light L12 is transmitted, absorbed, or diffracted or reflected at an angle different from the predetermined angle, or (2) a first state in which the polarization state of the amplified light L12 is changed and the amplified light L12 is propagated to the target material 112 via a polarizing plate or a polarizing beam splitter, and a second state in which the amplified light L12 is inhibited from propagating to the target material 112, by switching between an on state and an off state. All of these are examples of the optical switch SW taking one of two states: a first state in which the amplified light L12 is propagated to the target material 112 as excitation light LR, and a second state in which the propagation of the amplified light L12 to the target material 112 is suppressed compared to the first state.

[0039] <Optical equipment> Next, an optical device will be described, using an inspection device as an example of the optical device.

[0040] FIG. 7 is a configuration diagram illustrating an inspection apparatus 1 including a light source device 100 according to the first embodiment. As shown in FIG. 7, 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 the light source device 100. The inspection apparatus 1 is an apparatus that inspects a sample 500 for defects and the like using light L0 generated by the light source device 100 as illumination light L1. 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.

[0041] The illumination optical system 200 includes an ellipsoidal mirror 210, an ellipsoidal mirror 220, and a drop mirror 230. The inspection optical system 300 includes 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 form a Schwarzschild magnification optical system.

[0042] The light source device 100 generates illumination light L1. The illumination light L1 contains, for example, EUV light LE of 13.5 nm, which is the same as the exposure wavelength of the EUV mask that serves as the sample 500. Note that the illumination light L1 may contain 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 travels 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 convergent light. The convergence point IF1 is located at a position conjugate with an upper surface 510 of the sample 500, such as an EUV mask, and a detection surface 411 of the detector 410.

[0043] After passing through the convergence point IF1, the illumination light L1 travels while diverging 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, travels 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 converging light. The ellipsoidal mirror 220 then 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 toward the sample 500, causing the illumination light L1 to be incident on the sample 500.

[0044] The ellipsoidal mirror 220 focuses the illumination light L1 onto 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.

[0045] The sample 500 is placed on a stage 520. Here, a plane parallel to the top 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. The illumination light L1 is incident on the sample 500 from a direction tilted from the γ axis direction. That is, the illumination light L1 is incident obliquely and illuminates the sample 500.

[0046] 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.

[0047] Illumination light L1 from the light source device 100 illuminates an inspection area of ​​the sample 500. The inspection area illuminated by illumination light L1 is, for example, 0.5 mm square. Note that the inspection area is not limited to 0.5 mm square. Illumination light L1 is incident on the sample 500 from a direction tilted with respect to the γ-axis direction. Light from the sample 500 illuminated by illumination light L1 is incident on the perforated concave mirror 310. In the following, light from the sample 500 illuminated by illumination light L1 will be described as reflected light L2. Note that the light incident on the perforated concave mirror 310 from the sample 500 is not limited to reflected light L2 and may include diffracted light, etc. 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.

[0048] The reflected light L2 reflected by the perforated concave mirror 310 is incident on the convex mirror 320. The convex mirror 320 reflects the reflected light L2 reflected by the perforated concave mirror 310 toward the hole 311 in the perforated concave mirror 310. The reflected light L2 that passes 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 in the perforated concave mirror 310. The reflected light L2 that is incident on the plane mirror 330 is reflected by the plane mirror 330. The reflected light L2 reflected by the plane mirror 330 travels while being narrowed and is collected at a 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 IF2 is located at a position conjugate with the upper surface 510 of the sample 500 and the detection surface 411 of the detector 410.

[0049] After passing through the convergence point IF2, the reflected light L2 travels while diverging and is incident on the concave mirror 340. Therefore, the concave mirror 340 converts the reflected light L2 reflected by the plane mirror 330 as convergent light. convergence The reflected light L2 is incident as divergent light through 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 way, the inspection optical system 300 detects the reflected light L2 extracted from the output optical system 130 of the light source device 100. illumination The light L1 is used to inspect the sample 500. That is, the inspection optical system 300 collects reflected light L2 from the sample 500 illuminated by the illumination light L1, and guides the collected reflected light L2 to the detector 410.

[0050] 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 image sensors arranged in a line in one direction. The image sensors are, for example, CCDs (Charge Coupled Devices). Note that the image sensors are not limited to CCDs.

[0051] 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.

[0052] The reflected light L2 contains information about defects in the sample 500. The specularly reflected light of the illumination light L1 that is 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 device 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.

[0053] As described above, the inspection apparatus 1 of this embodiment includes the light source device 100 described above and an inspection optical system 300 that inspects an object to be inspected with the light L0 extracted from the output optical system 130. Note that while the inspection apparatus 1 has been described as an optical apparatus, the optical apparatus may also be an exposure apparatus. For example, an exposure apparatus includes the light source device 100 described above and an exposure optical system that exposes an object to 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 an exposure area on the object to be exposed.

[0054] As described above, the optical switch SW in the laser LS suppresses the low-power component in the excitation light LR irradiated onto the target material 112. This improves the stability of the excitation light LR and stabilizes the brightness of the generated plasma 127, allowing stable detection results to be obtained in the detector 410.

[0055] (Embodiment 2) A light source device according to embodiment 2 will be described. In this embodiment, a laser configuration different from that of the laser LS according to embodiment 1 will be described.

[0056] Fig. 8 is a block diagram illustrating a laser LS according to embodiment 2. As shown in Fig. 8, the laser LS includes a seed laser SL, an optical amplifier AM, an optical element CR, and a filter FI. The optical element CR and the filter FI are also referred to as an element group EG that exhibits a nonlinear optical effect. In the laser LS, the seed laser SL, the optical amplifier AM, the optical element CR, and the filter FI are arranged in this order from front to rear.

[0057] The seed laser SL and the optical amplifier AM are similar to those in the first embodiment and therefore will not be described here. The optical element CR is composed of a crystal exhibiting a nonlinear optical effect, and emits light with a wavelength different from that of the incident amplified light L12 by, for example, generating phenomena such as stimulated Raman scattering or harmonic generation. In other words, the power of the nonlinear light L13 transmitted through the optical element CR responds nonlinearly to the power of the amplified light L12. Stimulated Raman scattering occurs in crystals such as YVO4 and KGW, and harmonic generation occurs in crystals such as LBO, KTP, and BBO. The wavelength conversion efficiency between the incident light and the output light in the optical element CR depends on the power of the incident laser light. In the optical element CR, wavelength conversion is difficult during periods of low power in the incident light, but wavelength conversion is easy during periods of high power. Therefore, the optical element CR converts the wavelength of the high-power component of the amplified light L12 and outputs it, while outputting the low-power component of the amplified light L12 without converting its wavelength. Hereinafter, the wavelength before conversion by the optical element CR will be referred to as λ, and the wavelength after conversion will be referred to as λ'. The filter FI suppresses transmission of the light with wavelength λ in the nonlinear light L13 output by the optical element CR and transmits the light with wavelength λ', thereby outputting the pump light LR.

[0058] FIG. 9 is a graph showing the time waveforms of each light beam in the seed laser SL. In FIG. 9(a), the seed light L11 has pulse components at times t1, t2, and t3. As described in the first embodiment, each pulse component is amplified by the optical amplifier AM. As shown in FIG. 9(b), the amplified light L12 at this time includes a low-power component. The low-power component is a component having a power below a predetermined threshold, e.g., a component below the power suitable for converting the target material 112 into plasma. The optical element CR converts the wavelength of the amplified light L12 when a pulse component, which is a high-power component, is present, and outputs nonlinear light L13 in which the wavelength conversion is suppressed when a low-power component LO is present. The filter FI outputs the pump light LR so as to transmit the high-power component of the amplified light L12 with wavelength λ' and suppress transmission of the low-power component of the amplified light L12 with wavelength λ. Therefore, as shown in FIG. 9(c), the low-power component LO is suppressed in the pump light LR.

[0059] As described above, the optical element CR and the filter FI that perform wavelength conversion are provided in the laser LS. LS The filter FI can transmit the high-power component of the amplified light L12 having a wavelength λ' and suppress transmission of the low-power component of the amplified light L12 having a wavelength λ' while suppressing transmission of the other low-power components. This improves the stability of the excitation light LR and stabilizes the brightness of the generated plasma 127, thereby enabling stable detection results to be obtained at the detector 410. Furthermore, unlike the first embodiment, synchronization control of the optical element CR and the filter FI with the laser pulse by the control unit 160 is not required. This allows the laser LS to be designed with a simpler configuration. While the filter FI has been described above as transmitting the high-power component of the amplified light L12 having a wavelength λ' and suppressing transmission of the low-power component of the amplified light L12 having a wavelength λ, the function of the filter FI is not limited thereto. The filter FI may reflect the high-power component of the amplified light L12 having a wavelength λ' at a predetermined reflection angle, so that the reflected high-power component of the amplified light L12 propagates toward the target material 112 as the excitation light LR, while the low-power component of the amplified light L12 is transmitted or absorbed by the filter FI. This is also an example in which the filter FI suppresses propagation of the low-power component (first wavelength component) of the amplified light L12 to the target material 112.

[0060] Furthermore, when a low-power component is included in the vicinity of a high-power component in the amplified light L12 output from the optical amplifier AM, for example, when at least one of a low-power pre-pulse and a low-power post-pulse is included in the vicinity of the main pulse, it may be advantageous to use the optical element CR as in embodiment 2. This will be explained using FIG.

[0061] FIG. 10(a) shows the waveform of the amplified light L12. The amplified light L12 includes a pre-pulse S1, a main pulse S2, and a post-pulse S3 near times t1, t2, and t3. The pre-pulse S1 and the post-pulse S3 are located in the temporal vicinity of the main pulse S2. The power of the pre-pulse S1 and the post-pulse S3 is less than a threshold TH, which determines whether the power is high or low, and the power of the main pulse S2 is greater than the threshold TH. FIG. 10(b) shows the waveform of the amplified light L12 of FIG. 10(a) when the low-power component LO is suppressed using the optical switch SW according to the first embodiment. FIG. 10(c) shows the waveform of the amplified light L12 of FIG. 10(a) when the low-power component LO is suppressed using the optical element CR according to the second embodiment.

[0062] As shown in Figure 10(b), depending on the drive time DT of the optical switch SW, it may not be possible to remove pre-pulse and post-pulse components. There is a limit to how much the drive time DT of the optical switch SW can be shortened. Therefore, if at least one of the pre-pulse and post-pulse components occurs very close to the main pulse and this component is included in the switch drive time together with the main pulse, the optical switch SW may not be able to remove such low-energy components. On the other hand, as shown in Figure 10(c), the optical element CR can also suppress pre-pulses and post-pulses that are very close to the main pulse. This is because the optical element CR is a passive element and has a fast time response.

[0063] The optical switch SW, the optical element CR, and the filter FI may be provided downstream of the optical amplifier AM, and therefore the first optical member OP1 may include the optical switch SW, the first optical member OP1 may include the filter FI, or the first optical member OP1 may include the optical element CR and the filter FI.

[0064] 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. In addition, the configurations of embodiment 1 may be combined as appropriate. [Explanation of symbols]

[0065] 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 surface 117 Groove 118 Heater 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 Perforated 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 L 0 light L1 illumination light L2 reflected light LE EUV light LR excitation light LS Laser OP1 First optical member OP2 Second optical element P1 position PS irradiation position R rotation axis SL Seed Laser AM light amplifier SW Optical switch EG element group CR optical element FI filter

Claims

1. a target holder that holds the target material on an inner wall surface by centrifugal force caused by rotation around the rotation axis; a laser that excites the target material with a beam based on amplified light; a switch or a group of elements exhibiting a nonlinear optical effect provided between the amplifier and the target material, the switch or the element group suppresses power components in the amplified light that are equal to or less than a predetermined threshold; The target material generates plasma by the light beam with the power component suppressed. Light source device.

2. the switch is in either a first state or a second state that suppresses propagation of the amplified light to the target material compared to the first state; the light source device further includes a control unit that switches the switch between the first state and the second state at a timing synchronized with a seed pulse. The light source device according to claim 1 .

3. The element group includes: an element that converts a first wavelength of the input amplified light into a second wavelength, wherein the power of light transmitted through the element responds nonlinearly to the power of the amplified light; a filter provided downstream of the element and configured to suppress propagation of the first wavelength component of the transmitted light to the target material, The light source device according to claim 1 .

4. The amplified light includes a pre-pulse, a main pulse, and a post-pulse, the power of the pre-pulse and the post-pulse is less than a threshold that determines whether the power is high or low, and the power of the main pulse is greater than the threshold; the filter suppresses propagation of the pre-pulse and the post-pulse to the target material; The light source device according to claim 3 .

5. The optical fiber further includes a drive unit that varies a focusing position of the light beam with the suppressed power component relative to the target material, the driving unit varies the position of the light focusing point in two axial directions on the surface of the target material at an irradiation position where the light beam with the suppressed power component is irradiated. The light source device according to claim 1 .

6. The invention further comprises an acquisition unit for acquiring the surface position of the target material held and moved by the target holding unit, at an irradiation position where the light beam with the suppressed power component is irradiated, the driving unit varies a focusing position of the light beam, the power component of which is suppressed, with respect to the target material, based on the surface position acquired by the acquiring unit. The light source device according to claim 5 .

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