Control device, light source device, control method, and program

Abstract

To provide a control device, a light source device, a control method, and a program capable of improving efficiency of operation and maintenance of the device.SOLUTION: The control unit 160 of the light source device 100 according to the present disclosure is a control device that determines a mode to be executed from among a plurality of modes. The plurality of modes include a first mode in which light-source device 100 illuminates sample 500 with illumination light L1 generated by irradiating molten target material 112 with a laser beam, and a second mode in which light-source device 100 changes target material 112 from a solid state to a molten state by irradiating at least one of target holder 110 of target material 112 and target material 112 in a solid state with a laser beam.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a control device, a light source device, a control method, and a program. [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 a rotation axis, and emits illumination light by irradiating the held target material with excitation light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-077007 [Patent Document 2] Japanese Patent Publication No. 2022-168463 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a control device, a light source device, a control method, and a program that can improve the efficiency of device operation and maintenance. [Means for solving the problem]

[0006] A control device according to the present disclosure is a control device for an optical device including a light source device that determines an execution mode from a plurality of modes, including a first mode in which the light source device illuminates an object with illumination light generated by irradiating a molten target material with a laser, and a second mode in which the light source device changes the target material from a solid state to a molten state by irradiating at least one of a holder for the target material or the target material in a solid state with a laser.

[0007] The control device according to the present disclosure is a control device for a light source device that determines an execution mode from among a plurality of modes, including a first mode in which light is generated by irradiating a molten target material with a laser, and a second mode in which the target material is changed from a solid state to a molten state by irradiating at least one of a holder for the target material or the target material in a solid state with a laser.

[0008] The peak power density of the laser in the second mode may be smaller than the peak power density of the laser in the first mode.

[0009] The laser irradiation state in the second mode may be in a defocused state compared to the laser irradiation state in the first mode.

[0010] The peak power of the laser in the second mode may be smaller than the peak power of the laser in the first mode.

[0011] The control device may switch the execution mode from the second mode to the first mode based on the fact that the position of the plasma generated by irradiating the laser matches a predetermined position when the execution mode is the second mode.

[0012] When the execution mode is the second mode, the control device may switch the execution mode from the second mode to the first mode based on the determination that the target material has melted.

[0013] The light source device may include a laser generator that outputs a laser in the first mode and a laser in the second mode, and the control device may control the laser generator according to the mode to be executed.

[0014] The light source device may include a first laser generator that outputs a laser in the first mode, a second laser generator that outputs a laser in the second mode, and an optical element through which the laser generated by the first laser generator and the laser generated by the second laser generator pass. The control device may control the first laser generator and the second laser generator according to the mode to be executed.

[0015] The light source device may include a holder configured to hold the molten target material by rotation, and the control device may cause the light source device to irradiate the laser beam onto the molten target material held by the holder when the execution mode is the first mode.

[0016] The optical device may include an adjusting unit that suppresses propagation of light generated from the light source device to the object, and the control unit may drive the adjusting unit when the execution mode is a second mode.

[0017] A light source device according to the present disclosure generates light by irradiating a molten target material with a laser, and includes a control unit that irradiates at least one of a target material holder and the target material in a solid state with a laser, thereby changing the target material from a solid state to a molten state.

[0018] The light source device may include the holding portion that holds the molten target material by rotating it.

[0019] The method for controlling an optical device according to the present disclosure includes a first step of illuminating an object with illumination light generated by irradiating a molten target material with a laser, a second step of changing the target material from a solid state to a molten state by irradiating at least one of a holder for the target material or the target material in a solid state with a laser, and a third step of switching between the first step and the second step.

[0020] The control method for a light source device according to the present disclosure includes a first step of generating light by irradiating a laser onto a molten target material, a second step of changing the target material from a solid state to a molten state by irradiating a laser onto at least one of a holder for the target material or the target material in a solid state, and a third step of switching between the first step and the second step.

[0021] The program according to the present disclosure causes an optical device to perform the following steps: a first step of illuminating an object with illumination light generated by irradiating a laser onto a molten target material; a second step of changing the target material from a solid state to a molten state by irradiating a laser onto at least one of a holder for the target material or the target material in a solid state; and a third step of switching between the first step and the second step.

[0022] The program according to the present disclosure causes a light source device to execute a first step of generating light by irradiating a laser onto a molten target material, a second step of changing the target material from a solid state to a molten state by irradiating a laser onto at least one of a holder for the target material or the target material in a solid state, and a third step of switching between the first step and the second step. [Effects of the Invention]

[0023] According to the present disclosure, the operation and maintenance of the device can be made more efficient. [Brief explanation of the drawings]

[0024] [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] 2 is a diagram illustrating a focus adjustment mechanism according to the first embodiment. FIG. [Figure 5] 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 6] FIG. 3 is a flowchart illustrating a method for controlling an operation mode according to the first embodiment. [Figure 7] 1 is a configuration diagram illustrating an inspection device equipped with a light source device according to a first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] 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.

[0026] (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.

[0027] 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, a tape-like structure, 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-like 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.

[0028] 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, and the driver 150B 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 be connected to other components. The controller 160 is a control device including one or more processors (processing devices). The processor is connected to a memory (not shown), and reads and executes a computer program from the memory to control the operations performed by the light source device 100. Details of this control will be described later.

[0029] As an example of a processor, one of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), an FPGA (Field-Programmable Gate Array), a DSP (Digital Signal Processor), and an ASIC (Application Specific Integrated Circuit) may be used, or multiple of these may be used in parallel.

[0030] The memory may be a volatile memory, a nonvolatile memory, or a combination thereof. The number of memories is not limited to one, and multiple memories may be provided. The volatile memory may be, for example, a random access memory (RAM) such as a dynamic random access memory (DRAM) or a static random access memory (SRAM). The nonvolatile memory may be, for example, a read only memory (ROM) such as a programmable random only memory (PROM) or an erasable programmable read only memory (EPROM), a flash memory, or a solid state drive (SSD).

[0031] The memory is used to store one or more instructions. Here, the one or more instructions are stored in the memory as a program. The processor can perform the processes described in the above embodiments by reading and executing the program from the memory.

[0032] The memory may be external to the processor or may be built into the processor. The memory may also include storage located away from the processor. In this case, the processor can access the memory via an I / O (Input / Output) interface.

[0033] As described above, one or more processors included in the light source device 100 execute one or more programs including instructions for causing a computer to execute the algorithms described with reference to the drawings. By executing the programs, the following information processing can be realized.

[0034] The target holder 110 holds a target material 112. The target holder 110 includes a container 111 such as a crucible. The container 111 can hold metal that has been heated from a solid state to a liquid state (i.e., melted). Hereinafter, the metal that has been melted will also be referred to as molten metal. The container 111 holds a 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.

[0035] 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.

[0036] 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.

[0037] 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 116A, and the outer surface of the cylindrical portion 114 is called the outer wall surface 116B. 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 the above as long as it can hold molten metal.

[0038] The target holder 110 supports the target material 112 on an inner wall surface 116A of the container 111 by centrifugal force. The inner wall surface 116A 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 116A may be connected to a groove 117.

[0039] In addition to the target holder 110, the light source device 100 may also include a heater 118 and a debris shield 119. By heating with the heater 118, a target material 112 such as molten metal can be formed in the container 111. The debris shield 119 is disposed at an opening 111a of the container 111 so as to cover the target material 112.

[0040] 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.

[0041] 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 focus adjustment mechanism 170. Note that the first optical member OP1 is not limited to the mirror 121 and the focus adjustment mechanism 170, as long as it is an optical member that irradiates the target material 112 with excitation light LR, and may also be a laser LS1 that generates the excitation light LR.

[0042] 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 incident angle tilted. By irradiating the excitation light LR at an inclined angle in this way, 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.

[0043] When the excitation light LR is irradiated from a direction perpendicular to the surface of the target material 112, debris scatters in all directions centered on the direction perpendicular to the surface. This can result in the debris adhering to the collector mirror 131 facing the irradiation position PS. On the other hand, when the excitation light LR is irradiated at an incident angle tilted toward the front of the irradiation position PS with respect to the direction of movement of the target holder 110, that is, when the excitation light LR is irradiated from a direction having an incident angle component tilted toward the front in a plane perpendicular to the rotation axis R, an angular velocity in the rotation direction of the container 111 is applied in the direction in which the debris scatters. Therefore, the debris can be further scattered in the reflection direction of the excitation light LR. In this way, the impact of debris on optical components such as the collector mirror 131 can be suppressed.

[0044] The mirror 121, for example, reflects the excitation light LR generated by the laser LS1 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. A condenser lens 122 (described later) in the focus adjustment mechanism 170 condenses the excitation light LR at the irradiation position PS of the target material 112.

[0045] The light source device 100 may include a laser LS1, which is a laser generator that generates excitation light LR. Alternatively, the light source device 100 may introduce excitation light LR from a laser LS1 that is installed outside the light source device 100 and separate from the light source device 100 into the light source device 100. The excitation light LR is, for example, laser light that includes IR light. The excitation light LR may irradiate the target material 112 under the control of the control unit 160 to start and stop oscillation. For example, the excitation light LR is reflected by a mirror 121 and focused by a focusing lens in the focus adjustment mechanism 170. As a result, the excitation light LR irradiates the target material 112.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 116A. 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.

[0051] The acquisition unit 140 may acquire surface positions of peripheral positions other than the irradiation position PS. The peripheral positions include portions of the inner wall surface 116A 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, 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 (the time of irradiation). The acquisition unit 140 acquires the surface position of the irradiation position PS by predicting the surface position of the irradiation position PS in this manner.

[0052] If the sensor 141 is placed at a position opposite the irradiation position PS so that the surface position at the irradiation position PS can be measured and acquired, there is a risk that it will be affected by debris. Furthermore, since plasma 127 is generated at the irradiation position PS, there is a risk that the surface position will not be acquired accurately. Therefore, the sensor 141 is placed so as 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 placed so as 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 placed so as to face a peripheral position other than position P1 as long as the influence of debris can be reduced.

[0053] Fig. 4 is a diagram illustrating the focus adjustment mechanism 170 in the light source device 100 according to embodiment 1. As shown in Fig. 4, the focus adjustment mechanism 170 includes a condenser lens 122 and a driver 150C. In Fig. 4, the driver 150C is connected to the condenser lens 122.

[0054] The condenser lens 122 condenses the excitation light LR reflected by the mirror 121 onto the irradiation position PS of the target material 112. The control unit 160 controls the driving unit 150C to move the condenser lens 122 either toward the front or rear of the laser optical path. This allows the laser output from the laser LS1 to be defocused, as described below.

[0055] 5 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. 5, 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.

[0056] The driving units 150A and 150C drive 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 150A performs beam scanning by changing the angle of the mirror 121 with respect 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.

[0057] 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.

[0058] 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.

[0059] The control of the control unit 160 in the present disclosure will be described below. The light source device 100 or an optical device including the light source device 100 (an example will be described later) executes an operation according to one of a plurality of operation modes under the control of the control unit 160. The control unit 160 can switch between, for example, a first mode operation and a second mode operation as the plurality of operation modes and cause the light source device 100 or the optical device to execute the operation. However, the plurality of operation modes may include operation modes other than the first mode and the second mode. The first mode is a mode in which the light source device 100 generates plasma by irradiating the molten target material 112 with excitation light LR from the laser LS1, thereby generating light. The generated light may be EUV light LE, and the generated light may be used as illumination light for illuminating an object (a sample 500 described later). The first mode is a mode in which the optical device illuminates an object (a sample 500 described later) by using light generated by irradiating the molten target material 112 with excitation light LR from the laser LS1 as illumination light. The details of this operation are as described above.

[0060] The second mode is a mode in which the light source device 100 irradiates at least one of the target holding unit 110 that holds the target material 112 or the solid target material 112 with a laser (hereinafter also referred to as a heating laser) from the laser LS1, thereby changing the target material 112 from a solid state to a molten state. In the second mode, the object irradiated with the heating laser from the laser LS1, i.e., the object directly heated by the heating laser (hereinafter also referred to as a heating object), may be the target material 112 or a part of the container 111, including the interior or outer periphery of the container 111. For example, when the container 111 rotates about the rotation axis R, the control unit 160 may control the laser LS1 to irradiate the heating laser with a position on the container 111 that is shifted in the rotation direction from the position where the target material 112 is held.

[0061] At this time, the control unit 160 may control the laser LS1 so that the peak power density of the heating laser in the second mode is smaller than the peak power density of the excitation light LR in the first mode. In the first mode, high-temperature plasma needs to be generated, so the peak power density of the laser needs to be large. However, in the second mode, it is only necessary to apply an amount of heat sufficient to melt the target material 112, so the peak power density of the laser can be smaller than in the first mode.

[0062] The control unit 160 can execute the following processes to adjust the peak power density of the laser output by the laser LS1 in the first mode and the second mode. Note that the control unit 160 may execute both (i) and (ii), or only one of them, as long as the peak power density of the heating laser in the second mode is smaller than the peak power density of the excitation light LR in the first mode.

[0063] (i) The control unit 160 may set the irradiation state of the heating laser on the target holder 110 in the second mode to a defocused state compared to the irradiation state of the excitation light LR on the target material 112 in the first mode. A defocused state refers to a state in which the laser is not focused on the target being irradiated. In other words, the spot diameter of the heating laser irradiated on the target being heated in the second mode is larger than the spot diameter of the excitation light LR irradiated on the target material 112 in the first mode. Furthermore, the distance between the focal point of the heating laser and the target being heated in the second mode is larger than the distance between the focal point of the excitation light LR and the target material 112 in the first mode. When switching from the first mode to the second mode, the control unit 160 controls the operation of the drive unit 150C shown in FIG. 4 to move the condenser lens 122 toward either the front or rear of the optical path. This allows the control unit 160 to move the focal position of the laser output by the laser LS1 and set the irradiation state of the heating laser in the second mode to a defocused state.

[0064] (ii) The control unit 160 may set the peak power of the heating laser in the second mode to be lower than the peak power of the excitation light LR for the target material 112 in the first mode. For example, the control unit 160 may set the relationship between the pulse width W1 of the excitation light LR in the first mode and the pulse width W2 of the heating laser in the second mode as W1 < W2, so that even when the pulse energy is substantially the same in both modes, the peak power of the heating laser in the second mode can be set to be lower than the peak power of the excitation light LR for the target material 112 in the first mode.

[0065] Note that assuming the peak power density is D, the peak power is PP, and the laser irradiation spot area is M, the relationship D = PP / M may hold. Therefore, the control unit 160 can make the peak power density in the first mode different from the peak power density in the second mode by controlling the peak power by the above method or controlling the laser irradiation spot area. When the laser irradiation spot area is small, the light is in a focused state, and when the laser irradiation spot area is large, the light is in an unfocused state (defocused state). Therefore, making the laser more defocused by the control of the control unit 160 may be synonymous with making the laser irradiation spot area larger.

[0066] <Light source control method> Next, referring to FIG. 6, a method for controlling the operation mode will be described. FIG. 6 is a flowchart illustrating a method for controlling the operation mode according to Embodiment 1. First, as shown in step S11, the control unit 160 sets the operation mode to the second mode. Next, as shown in step S12, the control unit 160 determines whether the optical device satisfies a predetermined condition set in advance. If the condition is not satisfied, the control unit 160 keeps the operation mode set to the second mode and executes the determination in step S12 again. If the condition is satisfied, the control unit 160 sets the operation mode to the first mode as shown in step S13.

[0067] If the control unit 160 determines that a predetermined condition different from the condition in step S12 is satisfied when the operation mode is set to the first mode, the control unit 160 may transition the operation mode to the second mode. Furthermore, if the control unit 160 determines that the optical device satisfies a certain condition when the operation mode is in the first mode or the second mode, the control unit 160 may transition the operation mode to a third mode that is neither the first mode nor the second mode.

[0068] Examples of the predetermined conditions in step S12 are shown below. The control unit 160 may switch the operation mode from the second mode to the first mode when the position of the plasma generated by irradiating the target material 112 with a heating laser coincides with a predetermined position (or may be based on the coincidence with the predetermined position). The predetermined position refers to a position where the optical path of the light L0 generated by the plasma faces a direction suitable for the application of the light L0 (for example, a position where the optical path faces a direction suitable for illuminating the sample 500, which is the target object, with the light L0), and is a position pre-stored in memory. When the sensor 141 observes the generated plasma 127 as a bright spot, the control unit 160 determines whether the observed bright spot coincides with the predetermined position.

[0069] As an example of the predetermined condition in step S12, the control unit 160 may switch the operation mode from the second mode to the first mode when it determines that the target material 112 has melted in the second mode (or based on the determination that the target material 112 has melted). For example, when the sensor 141 photographs the target material 112, the control unit 160 can determine whether the target material 112 has melted by analyzing the photographed image. When the brightness of the photographed image changes between the liquid state and the solid state of the target material 112, the control unit 160 may determine whether the target material 112 has melted by determining whether the brightness of the entire target material 112 or a predetermined region of the target material 112 in the photographed image is the same as the brightness of the target material 112 in the liquid state. The control unit 160 can make a similar determination not only based on the brightness but also on the hue and saturation of the photographed image.

[0070] Furthermore, a sensor (for example, a non-contact sensor) capable of measuring the temperature of the target material 112 or the target holder 110 may be provided inside the light source device 100. The control unit 160 determines that the target material 112 has melted when the temperature measured by the sensor is equal to or higher than a predetermined threshold value.

[0071] The control unit 160 may switch the operation mode from the second mode to the first mode when a predetermined switching condition is met. The predetermined switching condition may include, as described above, that the position of the plasma generated by irradiating the target material 112 with the heating laser coincides with a predetermined position. The predetermined switching condition may also include, as described above, that it is determined that the target material 112 has melted. The predetermined switching condition may also include that both the melting of the target material 112 has been determined and the position of the plasma generated by irradiating the target material 112 with the heating laser coincide with a predetermined position.

[0072] When the operation mode is switched from the second mode to the first mode, the control unit 160 can adjust the peak power density of the laser as described above.

[0073] <Optical equipment> Next, an optical device will be described, using an inspection device as an example of the optical device.

[0074] 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.

[0075] 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.

[0076] The light source device 100 generates illumination light L1. The illumination light L1 includes, for example, EUV light LE with a wavelength 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 include light other than EUV light.

[0077] In the light source device 100, a shutter 180 is provided near the location where the generated illumination light L1 is emitted. The shutter 180 is connected to a drive unit 150E, and its opening and closing are controlled in accordance with the operation of the drive unit 150E. The shutter 180 is provided in the optical path between the target material 112 and the sample 500, which is the object. Therefore, when the shutter 180 is in a closed state, light is not emitted from the light source device 100. On the other hand, when the shutter 180 is in an open state, light can be emitted from the light source device 100.

[0078] The control unit 160 controls the driving of the drive unit 150E, thereby controlling the opening and closing of the shutter 180. In the first mode, the control unit 160 opens the shutter 180, thereby allowing the illumination light L1 to illuminate the sample 500. On the other hand, in the second mode, the control unit 160 drives the shutter 180 to close it, thereby preventing the light from the light source device 100 from illuminating the sample 500. Therefore, even if light originating from the target material 112 is generated in the second mode, the control unit 160 can prevent the light from reaching the sample 500.

[0079] When the shutter 180 is in an open state, 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 a sample 500 such as an EUV mask and a detection surface 411 of the detector 410.

[0080] 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.

[0081] 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.

[0082] The sample 500 is placed on a stage 520. Here, a plane parallel to the upper surface 510 of the sample 500 is defined as the δε plane, and a direction perpendicular to the δε plane is defined as the ζ axis direction. The illumination light L1 is incident on the sample 500 from a direction tilted from the ζ axis direction. That is, the illumination light L1 is incident obliquely and illuminates the sample 500.

[0083] 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 δε plane. Furthermore, the drive unit 530 can perform focus adjustment by moving the stage 520 in the ζ-axis direction.

[0084] Illumination light L1 from light source device 100 illuminates an inspection area of ​​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 sample 500 from a direction tilted with respect to the ζ-axis direction. Light from sample 500 illuminated by illumination light L1 is incident on perforated concave mirror 310. In the following, light from sample 500 illuminated by illumination light L1 will be described as reflected light L2. Note that light incident on perforated concave mirror 310 from sample 500 is not limited to reflected light L2 and may include diffracted light, etc. The reflected light L2 reflected by sample 500 is incident on perforated concave mirror 310. A hole 311 is provided at the center of 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.

[0085] 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.

[0086] After passing through the convergence point IF2, the reflected light L2 diverges as it travels and enters the concave mirror 340. Therefore, 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 way, the inspection optical system 300 inspects the sample 500, which is the inspection target, using the light L1 extracted from the output optical system 130 of the light source device 100. In other words, 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] As described above, the control unit 160 determines one of a plurality of operation modes to be executed. For example, the control unit 160 can switch between a first mode in which the sample 500 is illuminated by irradiating the target material 112 with a laser and a second mode in which the target holder 110 is melted by irradiating the target material 112 with a laser. Therefore, the light source device 100 can execute the second mode under the control of the control unit 160 and then execute the first mode, thereby simplifying the process up to illuminating the target object and improving the efficiency of operation of the light source device 100. Furthermore, for example, even if the target material 112 is attached to the container 111, the attached target material 112 can be preheated in the second mode under the control of the control unit 160, thereby completing preparations for generating illumination light and improving the efficiency of maintenance of the light source device 100.

[0092] Furthermore, the control unit 160 may switch between opening and closing the shutter 180 in the first mode and the second mode. This makes it difficult for light originating from the target material 112 to reach the sample 500 even if light is generated in the second mode, thereby making it possible to suppress the occurrence of unexpected erroneous inspections.

[0093] The shutter 180 may be provided in the optical path up to the field of view 511 in the illumination optical system 200, instead of in the light source device 100. The control unit 160 of the light source device 100 or the control unit of the inspection device 1 controls the shutter 180, so that the opening and closing of the shutter 180 in the first mode and the second mode are controlled in the same manner as described above.

[0094] The shutter 180 is an example of an adjustment means for suppressing propagation of light generated from the light source device 100 to the sample 500, which is an object of interest. As an adjustment means other than the shutter 180, for example, an optical element such as a mirror or an actuator for changing the position and posture of a stage on which the sample 500 is placed may be provided in the inspection device 1. The control unit 160 drives the optical element or actuator in the second mode. As a result, even if light originating from the target material 112 is generated in the second mode, it is possible to suppress propagation of the light to the sample 500.

[0095] Furthermore, the control unit 160 may set the peak power density of the laser in the second mode to be smaller than that in the first mode. If the peak power density in the second mode is large, when the target material 112 that was once melted and then solidified is fixed to the target holder 110, plasma may be generated from the target holder 110, resulting in the emission of illumination light. However, by reducing the peak power density in the second mode, this phenomenon can be suppressed.

[0096] Furthermore, when the operation mode to be executed is the second mode, the control unit 160 may switch the operation mode to be executed from the second mode to the first mode when the position of the plasma generated by irradiating the target material 112 with the heating laser coincides with a predetermined position. This allows the control unit 160 to keep the operation mode in the second mode when the illumination light L1 is emitted at an angle unsuitable for inspection with respect to the sample 500, thereby obtaining stable inspection results.

[0097] Furthermore, when the control unit 160 determines that the target material 112 has melted in the second mode, the control unit 160 may switch the operation mode to be executed from the second mode to the first mode. This allows the control unit 160 to keep the mode in the second mode when the illumination light L1 is not being emitted to the sample 500, thereby making it possible to obtain stable inspection results.

[0098] (Embodiment 2) A light source device according to embodiment 2 will be described. In this embodiment, a light source device having a different configuration from the light source device according to embodiment 1 will be described.

[0099] The light source device may further include a laser generator (hereinafter also referred to as laser LS2) different from the laser LS1. The control unit 160 controls the laser LS1 to perform laser irradiation in the first mode according to the operation mode to be executed, and controls the laser LS2 to perform laser irradiation in the second mode. The location irradiated with the heating laser in the second mode is not limited to the target material 112 or its periphery. For example, the laser LS2 may heat the container 111 and melt the solid target material 112 by irradiating the bottom 113 of the container 111, the inner wall surface 116A on which the target material 112 is not held, or the outer wall surface 116B. The characteristics of the laser irradiated by the laser LS2 in the second mode are as described in the first embodiment.

[0100] The optical path from laser LS1 to target material 112 and the optical path from laser LS2 to container 111 may share a portion in common. For example, light source device 100 may be provided with a common optical element, such as a mirror 121 or a condenser lens 122, on both optical paths. The laser from laser LS1 and the laser from laser LS2 are output via a common optical element. However, the optical paths may not share a common optical element and may be non-overlapping.

[0101] (Embodiment 3) In the second mode of the first or second embodiment, the target holder 110 may not hold the target material 112. After the target material 112 reaches a temperature sufficient to melt it, the target holder 110 may hold the target material 112. Furthermore, the position at which the target holder 110 holds the target material 112 in the second mode of the first or second embodiment may be different from the position at which the target holder 110 holds the target material 112 in the first mode. After the target material 112 reaches a temperature sufficient to melt it, the target holder 110 may hold the target material 112 at the holding position in the first mode.

[0102] The program defining the operations executed by the control unit 160 of the light source device 100 includes instructions or software code that, when loaded into a computer, causes the computer to perform one or more functions described in the embodiments. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disk (DVD), Blu-ray (registered trademark) disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage devices. The program may also be transmitted on a transient computer-readable medium or communication medium. By way of example and not limitation, transient computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals. The transient computer-readable medium or communication medium may provide the program to the computer via a wired communication path, such as an electric wire or optical fiber, or via a wireless communication path.

[0103] Although the embodiments of the present disclosure have been described above, the present disclosure includes appropriate modifications that do not impair the objects and advantages thereof, and is not limited to the above-described embodiments. Furthermore, the configurations of Embodiments 1 to 3 may be combined as appropriate. [Explanation of symbols]

[0104] 1. Inspection equipment 100 Light source device 110 Target holder 111 Container 111a opening 112 Target material 113 Bottom 114 Cylindrical part 115 bottom 116A Inner wall 116B Exterior wall surface 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 170 Focus adjustment mechanism 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 BS beam spot FOV field of view L0 light L1 illumination light L2 reflected light LE EUV light LR excitation light LS1 Laser OP1 First optical member OP2 Second optical element P1 position PS irradiation position R rotation axis

Claims

1. A control device for an optical device including a light source device, which determines an execution mode from among a plurality of modes, The plurality of modes include a first mode in which the light source device illuminates an object with illumination light generated by irradiating a molten target material with a laser, and a second mode in which the light source device changes the target material from a solid state to a molten state by irradiating at least one of a holder for the target material or the target material in a solid state with a laser. Control device.

2. A control device for a light source device that determines a mode to be executed from a plurality of modes, The plurality of modes include a first mode in which light is generated by irradiating a molten target material with a laser, and a second mode in which the target material is changed from a solid state to a molten state by irradiating at least one of a holder for the target material or the target material in a solid state with a laser. Control device.

3. a peak power density of the laser in the second mode is less than a peak power density of the laser in the first mode; The control device according to claim 1 or 2.

4. The laser irradiation state in the second mode is in a defocused state compared to the laser irradiation state in the first mode. The control device according to claim 3 .

5. The peak power of the laser in the second mode is less than the peak power of the laser in the first mode. The control device according to claim 3 .

6. switching the execution mode from the second mode to the first mode based on the fact that the position of the plasma generated by the laser irradiation matches a predetermined position when the execution mode is the second mode; The control device according to claim 1 or 2.

7. when the execution mode is the second mode, the execution mode is switched from the second mode to the first mode based on the determination that the target material has melted; The control device according to claim 1 or 2.

8. the light source device includes a laser generator that outputs a laser in the first mode and a laser in the second mode, controlling the laser generator according to the mode to be executed; The control device according to claim 1 or 2.

9. The light source device is a first laser generator that outputs a laser in the first mode; a second laser generator that outputs a laser in the second mode; an optical element through which the laser generated by the first laser generator and the laser generated by the second laser generator pass, controlling the first laser generator and the second laser generator according to the execution mode; The control device according to claim 1 or 2.

10. the light source device includes a holding unit that rotates to hold the molten target material, When the execution mode is the first mode, the light source device is caused to irradiate the laser onto the molten target material held by the holding unit. The control device according to claim 1 or 2.

11. the optical device includes an adjustment means for suppressing propagation of light generated from the light source device to the object; driving the adjusting means when the execution mode is the second mode; The control device according to claim 1 .

12. A light source device that generates light by irradiating a molten target material with a laser, a control unit that irradiates a laser beam onto at least one of the target material holder and the target material in a solid state, and changes the target material from a solid state to a molten state; Light source device.

13. The holding unit holds the molten target material by rotating it. The light source device according to claim 12.

14. A first step of illuminating an object with illumination light generated by irradiating a molten target material with a laser; a second step of irradiating a laser beam onto at least one of a holder for the target material or the target material in a solid state, thereby changing the target material from a solid state to a molten state; a third step of switching between the first step and the second step. A method for controlling an optical device.

15. a first step of generating light by irradiating a molten target material with a laser; a second step of irradiating a laser beam onto at least one of a holder for the target material or the target material in a solid state, thereby changing the target material from a solid state to a molten state; a third step of switching between the first step and the second step. A method for controlling a light source device.

16. A first step of illuminating an object with illumination light generated by irradiating a molten target material with a laser; a second step of irradiating a laser beam onto at least one of a holder for the target material or the target material in a solid state, thereby changing the target material from a solid state to a molten state; a third step of switching between the first step and the second step; A program that causes an optical device to execute the above.

17. a first step of generating light by irradiating a molten target material with a laser; a second step of irradiating a laser beam onto at least one of a holder for the target material or the target material in a solid state, thereby changing the target material from a solid state to a molten state; a third step of switching between the first step and the second step; A program that causes a light source device to execute the above.

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