Light source device and optical device

Abstract

To provide a light source device and an optical device which can improve stability of light generated from a light source.SOLUTION: A light source device 100 includes: a target holding part 110 having a holding region for holding a target material TM for generating light L0 by giving excitation light LR thereto; a rotation shaft 120 for supporting the target holding part 110; and an axial rotation driving part 130 connected to the rotation shaft 120, and rotating the target holding part 110 around a central axis C of the rotation shaft 120 through the rotation shaft, wherein the target holding part 110 is rotated at a predetermined target rotation angular velocity, and the target holding part 110 has a mass such that a dangerous angular velocity in rotation becomes 85% or less of the target rotation angular velocity.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a light source device and an optical device. [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 light is emitted by irradiating the target material with excitation light.

[0003] Patent Document 2 describes a light source in which a molten metal target material is held by centrifugal force on the inner wall of a crucible that rotates around a rotation axis, and light is emitted by irradiating the target material with excitation light. [Prior art documents] [Patent documents]

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

[0005] Vibrations that occur when the structure rotates can cause the target irradiation position to change, making it difficult to extract light stably.

[0006] The present disclosure has been made in consideration of such problems, and provides a light source device and an optical device that can improve the stability of light generated from a light source. [Means for solving the problem]

[0007] A light source device according to one aspect of this embodiment includes a target holding portion having a holding area for holding a target material that generates light when excited by light, a rotation shaft for supporting the target holding portion, and a shaft rotation drive portion connected to the rotation shaft and rotating the target holding portion around the central axis of the rotation shaft via the rotation shaft, wherein the target holding portion is rotated at a predetermined target rotational angular velocity, and the target holding portion has a mass such that a critical angular velocity during rotation is 85% or less of the target rotational angular velocity.

[0008] In the above light source device, the target holding portion includes the holding area and a weight portion, and when one direction in the direction of the central axis is defined as one side and the direction opposite to the one side is defined as the other side, the holding area may be positioned on the one side of the weight portion and the weight portion may extend to the other side.

[0009] A light source device according to one aspect of this embodiment includes a target holding portion having a holding area that holds a target material that generates light when excited by light, a rotation shaft that supports the target holding portion, and a shaft rotation drive portion that is connected to the rotation shaft and rotates the target holding portion around a central axis of the rotation shaft via the rotation shaft, wherein the target holding portion includes the holding area and a weight portion, and when one direction in the direction of the central axis is defined as one side and the direction opposite to the one side is defined as the other side, the holding area is positioned on the one side of the weight portion and the weight portion extends to the other side.

[0010] In the above light source device, the target holding section includes a transport section that holds the target material in the holding area and transports it to an irradiation position, and a weight section having a portion that is provided on the shaft rotation drive section side rather than the joint portion between the transport section and the rotation shaft, and the transport section is detachable from the weight section and may be attached to the weight section when the excitation light is applied.

[0011] In the above light source device, the temperature in the process of fitting the rotating shaft into the weight portion may be lower than the temperature of the rotating shaft and the weight portion when the excitation light is applied to the target material, and the linear expansion coefficient of the weight portion may be smaller than the linear expansion coefficient of the rotating shaft, or the temperature in the process of fitting the rotating shaft into the weight portion may be higher than the temperature of the rotating shaft and the weight portion when the excitation light is applied to the target material, and the linear expansion coefficient of the weight portion may be greater than the linear expansion coefficient of the rotating shaft.

[0012] In the above light source device, the target material may be molten tin and the linear expansion coefficient of the weight portion may be smaller than the linear expansion coefficient of the rotating shaft, or the target material may be frozen xenon and the linear expansion coefficient of the weight portion may be larger than the linear expansion coefficient of the rotating shaft.

[0013] In the light source device described above, the weight portion may be joined to the rotation shaft by welding.

[0014] In the light source device described above, the weight portion may be bolted to a flange provided on the rotating shaft.

[0015] In the light source device described above, the target material may be a molten metal, and the transport section may hold the target material and transport it to the irradiation position by centrifugal force generated by rotation about the central axis.

[0016] In the above light source device, the target holding portion further includes a joining member that joins the conveying portion and the weight portion, the joining member being attached from the conveying portion toward the weight portion, the conveying portion being joined to the weight portion by the joining member and thereby rotating together with the weight portion, and the conveying portion may be removable from the rotating shaft when not joined by the joining member.

[0017] In the above light source device, the weight portion has a hole-shaped balance hole that adjusts the mass balance of the weight portion, and the transport portion may be attached to the weight portion after passing a test in a state where the transport portion is not attached to the weight portion.

[0018] The above light source device may further include a refill section that refills the molten metal into the conveying section so that a predetermined amount of the target material is retained in the conveying section, and the mass of the weight section may be determined based on the mass of the conveying section and the mass of the predetermined amount of the molten metal.

[0019] The above light source device may further include a vacuum chamber in which the conveying section is arranged, a weight casing in which at least a portion of the weight section is arranged, and a cooling section arranged between the conveying section and the weight section and configured to cool the target holding section.

[0020] The above light source device may further include an inlet formed in the cooling section for introducing a cooling gas toward a space between the cooling section and the conveying section, and an exhaust port formed in the weight casing for exhausting the cooling gas.

[0021] An inspection apparatus according to one aspect of this embodiment includes the light source device described above, and performs lithography or inspection based on the light generated from the target material. Effect of the Invention

[0022] According to the present disclosure, it is possible to provide a light source device and an optical device capable of improving the stability of the light from the light source. [Brief description of the drawings]

[0023] [Figure 1] 1 is a cross-sectional view illustrating a light source device according to a first embodiment. [Diagram 2]1 is a graph illustrating the amount of whirling from a central axis when a target holding part rotates around the central axis in a light source device of embodiment 1, where the horizontal axis indicates the rotation frequency of the target holding part and the vertical axis indicates the amount of whirling. [Diagram 3] 1 is a configuration diagram illustrating an inspection device equipped with a light source device according to a first embodiment. [Figure 4] 11 is a cross-sectional view illustrating a light source device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. The following description shows a preferred embodiment of the present disclosure, and the scope of the present disclosure is not limited to the following embodiment. In the following description, parts with the same reference numerals indicate substantially the same contents.

[0025] <Embodiment 1> A light source device according to a first embodiment will be described. The light source device of this embodiment generates light such as illumination light and exposure light used in optical devices such as an inspection device and an exposure device. The light source device may be provided integrally with the optical device, or may be disposed near the optical device as a separate entity from the optical device. When the optical device is an inspection device, the light source device generates illumination light that illuminates an inspection object in the inspection device. When the optical device is an exposure device, the light source device generates exposure light that exposes an exposure object in the exposure device.

[0026] The light source device generates light such as illumination light and exposure light by irradiating excitation light onto a target material held in a target holding section. Thus, the optical device performs lithography or inspection based on the light generated from the target material. In the following, as an example of a light source device, an example in which molten metal held in a container is used as the target material will be described. Note that the light source device is not limited to one in which the target material is molten metal held in a container, and may be one in which the target material is liquid metal in the form of droplets, solid metal fixed to a cylindrical drum, or the like.

[0027] <Light source device> FIG. 1 is a cross-sectional view illustrating a light source device 100 according to the first embodiment. In FIG. 1, hatching of some members is omitted so as not to make the drawing complicated. As shown in FIG. 1, the light source device 100 includes a target holding unit 110, a rotating shaft 120, and a shaft rotation driving unit 130. The light source device 100 may further include a refill unit 140, a vacuum chamber 150, a weight casing 160, an exhaust port 161, a cooling unit 170, an input optical system 180, and an output optical system 190. The light source device 100 may further include a driving member, a storage member, an optical member, and the like other than the above, or may omit some of the above driving members, storage members, optical members, and the like.

[0028] The target holding unit 110 holds the target material TM that generates light L0 when the excitation light LR is applied to the target material TM. The target holding unit 110 has a holding area for holding the target material TM. The target holding unit 110 includes a transport unit 111 and a weight unit 112. The transport unit 111 holds the target material TM and transports the target material TM to the irradiation position PS of the excitation light LR. The transport unit 111 includes a container 115 such as a crucible. Note that the transport unit 111 is not limited to the container 115 and may include a drum as long as the transport unit 111 can transport the target material TM to the irradiation position PS of the excitation light LR. The container 115 can melt metal inside. The container 115 can hold the target material TM such as molten metal that generates plasma when irradiated with the excitation light LR. The excitation light LR is, for example, laser light including IR (Infrared) light.

[0029] The target material TM may include molten metal. The target material TM is not limited to the molten metal held in the container 115, but may be a solid metal, liquid droplets, or the like, as long as it is a substance that generates plasma when irradiated with the excitation light LR. The molten metal is, for example, molten tin (Sn) or lithium (Li), but is not limited to tin or lithium, as long as it generates plasma when irradiated with the excitation light LR.

[0030] The transport unit 111 in the target holding unit 110 is not limited to the container 115, and may include a cylindrical drum. In this case, the target holding unit 110 holds the target material TM by fixing a solid metal, such as xenon (Xe), which becomes the target material TM, frozen on the surface of the drum. The area on the surface of the drum on which the solid metal is fixed in this manner may be the holding area for holding the target material TM.

[0031] The container 115 has, for example, a cylindrical shape with one opening closed. The closed part of the container 115 is referred to as the bottom. The cylindrical part of the container 115 is referred to as the cylindrical part. The inner surface of the bottom is referred to as the bottom surface. The inner surface of the cylindrical part is referred to as the inner wall surface. This inner wall surface may be a holding area for holding the target material TM. Note that the container 115 may include shapes other than those described above as long as it is capable of holding molten metal.

[0032] The target holder 110 has, for example, a hole formed along the central axis, or a cavity provided along the central axis. The target holder 110 is joined to the rotating shaft 120 inside the hole (cavity). For example, the target holder 110 may be joined to the rotating shaft 120 via a bolt. In this way, the target holder 110 is supported by the rotating shaft 120. The target holder 110 rotates around the central axis C of the rotating shaft 120.

[0033] Here, for convenience of explanation of the light source device 100, an XYZ orthogonal coordinate system is introduced. The direction along the central axis C of the rotation shaft 120 is the Z-axis direction, and the two directions perpendicular to the central axis C are the X-axis direction and the Y-axis direction, respectively. For example, the +Z-axis direction is called the upward direction, and the -Z-axis direction is called the downward direction. Also, the +Z-axis direction may be called the one side, and the -Z-axis direction may be called the other side. Therefore, one direction in the direction of the central axis C is one side, and the direction opposite to the one side is the other side. Note that the terms "upward" and "downward" are used for convenience of explanation of the light source device 100, and do not indicate the directions in which the actual light source device 100 is disposed.

[0034] As described above, the target holding unit 110 includes the transport unit 111 and the weight unit 112. The transport unit 111 includes a holding area. Thus, the target holding unit 110 includes a holding area and the weight unit 112. The holding area is disposed in the +Z axis direction of the weight unit 112. The weight unit 112 extends in the -Z axis direction. Thus, the target holding unit 110 includes the weight unit 112 on the -Z axis direction side of the transport unit 111. The weight unit 112 has a portion provided in the -Z axis direction from the joint portion between the transport unit 111 and the rotating shaft 120. The weight unit 112 may be provided on the -Z axis direction side from the joint portion between the transport unit 111 and the rotating shaft 120. For example, the weight unit 112 may be provided on the shaft rotation drive unit 130 side from the joint portion between the transport unit 111 and the rotating shaft 120.

[0035] The transport unit 111 is detachable from the weight unit 112. The transport unit 111 is attached to the weight unit 112 when the excitation light LR is applied to the target material TM. For example, the transport unit 111 is attached to the weight unit 112 after passing a predetermined test in a state in which the transport unit 111 is not attached to the weight unit 112. The predetermined test includes, for example, a test of the mass balance of the weight unit 112 and a vibration test.

[0036] The target holding unit 110 may further include a joining member 113 that joins the transport unit 111 and the weight unit 112. The transport unit 111 may be joined to the weight unit 112 by the joining member 113. The joining member 113 includes, for example, a bolt. The joining member 113 may be attached, for example, from the transport unit 111 toward the weight unit 112. Specifically, the joining member 113 may be attached from the bottom surface of the container 115 toward the weight unit 112.

[0037] The transport unit 111 is joined to the weight unit 112 by the joining member 113, and thereby rotates together with the weight unit 112 around the central axis C of the rotation shaft 120. When the transport unit 111 is a container 115 and the target material TM is molten metal, the transport unit 111 holds the target material TM by centrifugal force caused by the rotation about the central axis C of the rotation shaft 120, and transports the target material TM to the irradiation position PS. When the transport unit 111 is not joined to the weight unit 112 by the joining member 113, the transport unit 111 is detachable from the rotation shaft 120.

[0038] The weight portion 112 may include, for example, a cylindrical portion 112a, a disk portion 112b, and a cylindrical portion 112c, which are arranged from top to bottom along the Z-axis direction. The central axes of the cylindrical portion 112a, the disk portion 112b, and the cylindrical portion 112c are aligned. The cylindrical portion 112a, the disk portion 112b, and the cylindrical portion 112c may be integrated.

[0039] The diameter of the cylindrical portion 112a may be smaller than the diameter of the transport portion 111. The diameter of the cylindrical portion 112a may be smaller than the diameter of the disk portion 112b. The diameter of the disk portion 112b may be the same as the diameter of the cylindrical portion 112c. A hole is formed along the central axis of the cylindrical portion 112a and the disk portion 112b. The weight portion 112 is joined to the rotating shaft 120 inside the hole.

[0040] The cylindrical portion 112a is smaller than the diameter of the transport unit 111, and the diameters of the disk portion 112b and the cylindrical portion 112c. The cylindrical portion 112a is disposed between the transport unit 111 and the disk portion 112b and the cylindrical portion 112c. In this manner, the transport unit 111 having a larger diameter than the cylindrical portion 112a is disposed above the cylindrical portion 112a, and the disk portion 112b and the cylindrical portion 112c having a larger diameter than the cylindrical portion 112a are disposed below the cylindrical portion 112a, thereby improving the balance in the Z-axis direction and suppressing swinging rotation, etc. Alternatively, a temperature adjustment medium (for example, the cooling portion 170) can be disposed in the space outside the cylindrical portion 112a (the side away from the rotation axis 120), and a more suitable layout can be achieved for temperature control of the target holding portion 110.

[0041] Weight portion 112 may have a hole-shaped balance hole 114 for adjusting the balance of the mass of weight portion 112. Balance hole 114 is formed from the upper surface on the +Z axis direction side of disk portion 112b to the -Z axis direction side, and reaches cylindrical portion 112c.

[0042] The weight section 112 has a hollow cylindrical section 112c. This allows the mass of the section away from the rotating shaft 120 to be increased, and the effect of the balance adjustment by the balance hole 114 to be increased. The cylindrical section 112c may be arranged to surround the shaft rotation drive section 130. For example, the cylindrical section 112c may be arranged to surround a shaft rotation drive source such as a motor connected to the rotating shaft 120, which is the shaft rotation drive section 130. The cylindrical section 112c may be arranged to surround a gear connected to the rotating shaft 120, which is the shaft rotation drive section 130 (for example, a gear that transmits the driving force of a motor or the like connected to a rotating shaft different from the rotating shaft 120 to the rotating shaft 120). This allows the mass of the weight section 112 to be increased without increasing the length of the rotating shaft 120. Therefore, the amount of whirling of the rotating shaft 120 can be suppressed, and the balance of the target holder 110 can be improved.

[0043] The weight portion 112 may be joined to the rotating shaft 120 by shrink fitting or cooling fitting. This allows the weight portion 112 to be firmly joined to the rotating shaft 120. It is preferable to select materials for the weight portion 112 and the rotating shaft 120 so that the linear expansion coefficient of the weight portion 112 and the linear expansion coefficient of the rotating shaft 120 have the following relationship according to the relationship between the temperature T0 in the fitting process of the rotating shaft 120 to the weight portion 112 by shrink fitting or cooling fitting and the temperature T1 of the weight portion 112 and the rotating shaft 120 in the operation process of applying excitation light to the target material. That is, when the temperature T0 is lower than the temperature T1, it is preferable that the linear expansion coefficient of the weight portion 112 is smaller than the linear expansion coefficient of the rotating shaft 120. Also, when the temperature T0 is higher than the temperature T1, it is preferable that the linear expansion coefficient of the weight portion 112 is larger than the linear expansion coefficient of the rotating shaft 120. By selecting such materials, the weight portion 112 and the rotating shaft 120 can be maintained in a more firmly bonded state in the actual operation process of applying excitation light to the target material. For example, when the target material is molten tin (Sn), the actual operation process of applying excitation light to the target material is relatively high temperature, so it is preferable that the linear expansion coefficient of the weight portion 112 is smaller than that of the rotating shaft 120. When the target material is frozen xenon (Xe), the actual operation process of applying excitation light to the target material is relatively low temperature, so it is preferable that the linear expansion coefficient of the weight portion 112 is larger than that of the rotating shaft 120. By using the linear expansion coefficient as described above, the bond between the weight portion 112 and the rotating shaft 120 can be made stronger. Therefore, it is possible to suppress vibration during rotation of the target holder 110, and to stabilize the irradiation position PS of the excitation light LR. In addition, shrink fitting refers to a process in which the temperature of the weight portion 112 and the rotating shaft 120 is raised, the rotating shaft 120 is fitted into the hole in the weight portion 112 in an expanded state, and then cooled so that the rotating shaft 120 is fitted into the hole in the weight portion 112.In addition, cold fitting refers to lowering the temperature of the weight portion 112 and the rotating shaft 120, fitting the rotating shaft 120 into the hole in the weight portion 112 in a contracted state, and then heating (or returning the temperature) the rotating shaft 120 to fit into the hole in the weight portion 112.

[0044] The weight portion 112 may be joined to the rotating shaft 120 by welding. Also, the weight portion 112 may be bolted to a flange provided on the rotating shaft 120. With such a configuration, the joining between the weight portion 112 and the rotating shaft 120 can be made strong.

[0045] The axial rotation drive unit 130 is a gear or an axial rotation drive source such as a motor that is connected to the rotating shaft 120 and provides a rotational drive force to the rotating shaft 120. That is, as shown in the embodiment, when a motor is connected to the rotating shaft 120 and the axial rotation drive source such as a motor provides a drive force to the rotating shaft 120, the axial rotation drive unit is a axial rotation drive source such as a motor. Alternatively, when a gear is connected to the rotating shaft 120 and the drive force of a motor or the like connected to a rotating shaft different from the rotating shaft 120 is transmitted to the rotating shaft 120 via the gear, the axial rotation drive unit 130 is a gear connected to the rotating shaft 120.

[0046] 2 is a graph illustrating the amount of whirling from the central axis C when the target holding part 110 rotates around the central axis C in the light source device 100 according to the first embodiment, where the horizontal axis indicates the rotation frequency of the target holding part 110 and the vertical axis indicates the amount of whirling. The horizontal axis and the vertical axis each increase in the direction of the arrow.

[0047] 2 shows the cases where the mass M of the target holder 110 is mass M1 and mass M2, and where there is a target material TM (M1+TM and M2+TM) and there is no target material TM (M1 and M2). The relationship between the four masses M1, mass M1+TM, mass M2, and mass M2+TM is mass M2+TZ>mass M2>mass M1+TM>mass M1.

[0048] As shown in FIG. 2, each mass (mass M1, mass M1+TM, mass M2, mass M2+TM) has a frequency at which the amount of whirling peaks when the frequency is changed. The speed (angular speed) derived from the frequency at which the amount of whirling peaks is called the critical speed (critical angular speed) ωn=√(k / M). The larger the mass M, the smaller the critical speed ωn. Also, when the frequency exceeds the critical speed ωn, the larger the mass M, the smaller the amount of whirling. When there is a target material TM such as molten metal, the critical speed ωn becomes smaller, and the amount of whirling when the frequency exceeds the critical speed ωn also becomes smaller. This is thought to be due to the balancing effect of the liquid. Although not shown, when the diameter of the rotating shaft 120 is reduced, the amount of whirling when the frequency exceeds the critical speed ωn becomes larger.

[0049] In this embodiment, the target holding part 110 has a mass M such that the critical angular velocity ωn during rotation is 85% or less of a predetermined target rotational angular velocity ω0. The target rotational angular velocity ω0 is the angular velocity at which the target holding part 110 is rotated as a target.

[0050] The mass M of the target holder 110 is the mass in a state where the target material TM has not been charged into the target holder 110. The mass M of the target holder 110 may be the mass obtained by adding the mass of the target material TM in a state where the target material TM has been charged in an amount less than a predetermined target amount / the same as the predetermined target amount / or more than the predetermined target amount. Among these, if the mass M of the target holder 110 is set as the mass in a state where the target material TM has not been charged, the total mass of the rotating body when the target material TM is charged from this point will virtually increase due to the liquid amount of the target material TM. The rotation speed at which the amount of whirling becomes maximum is smaller than the critical angular velocity ωn=√(k / M) in a state where the target material TM has not been charged, and is preferably further smaller than the predetermined target rotation speed ω0.

[0051] Returning to FIG. 1, the rotating shaft 120 supports the target holding part 110. The rotating shaft 120 is, for example, a cylindrical rod shape extending in the Z-axis direction, and has a central axis C along the Z-axis direction. The rotating shaft 120 rotates around the central axis C by the rotational driving force of the shaft rotation driving part 130. As a result, the rotating shaft 120 rotates the target holding part 110. The linear expansion coefficient of the rotating shaft 120 is larger than the linear expansion coefficient of the weight part 112. Therefore, when the rotating shaft 120 is shrink-fitted to the weight part 112, the joining between the rotating shaft 120 and the weight part 112 can be strengthened.

[0052] The target holder 110 is rotated at a predetermined target rotational angular velocity ω0 via a rotating shaft. The rotating shaft 120 is rotated by a shaft rotation drive unit 130 connected to the rotating shaft 120. The shaft rotation drive unit 130 is, for example, a shaft rotation drive source such as a motor connected to the rotating shaft 120. Alternatively, the shaft rotation drive unit 130 may be a power transmission mechanism such as a gear connected to the rotating shaft 120, which transmits a driving force from another rotating shaft connected to a shaft rotation drive source such as a motor to the rotating shaft 120. The shaft rotation drive unit 130 is connected to the rotating shaft 120 and rotates the target holder 110 around the central axis C of the rotating shaft 120 via the rotating shaft 120. The shaft rotation drive unit 130 rotates the target holder 110 at a predetermined target rotational angular velocity ω0.

[0053] The refill unit 140 refills the transport unit 111 with molten metal so that a predetermined amount of target material TM is held in the transport unit 111. The refill unit 140 may supply the target material TM in a solid, liquid, gaseous, powdered, or other state to the transport unit 111, or may return the target material TM attached to a storage member such as a debris shield to the transport unit 11 to refill it. The mass of the weight unit 112 may be determined based on the mass of the transport unit 111 and the mass of the predetermined amount of molten metal.

[0054] The vacuum chamber 150 includes, for example, a housing, and the inside is depressurized. For example, the vacuum chamber 150 is evacuated by a vacuum pump. The transport unit 111 is arranged in the vacuum chamber 150. Note that the vacuum chamber 150 is not limited to the transport unit 111, and other parts of the target holding unit 110 may be arranged therein, and is not limited to the target holding unit 110, and other members of the light source device 100, such as the rotating shaft 120, the shaft rotation drive unit 130, and the refill unit 140, may be arranged therein.

[0055] The weight casing 160 includes, for example, a housing. At least a part of the weight part 112 is arranged in the weight casing 160. For example, the cylindrical part 112c of the weight part 112 is arranged in the weight casing 160. Note that the columnar part 112a and the disk part 111b may be arranged in the weight casing 160. The cylindrical part 112c of the weight part 112 rotates around the central axis C inside the weight casing 160.

[0056] The cooling unit 170 is disposed between the transport unit 111 and the weight unit 112, in a position close to the transport unit 111 and the cylindrical portion 112a. The cooling unit 170 includes, for example, a heat sink. The cooling unit 170 cools the target holding unit 110. The cooling unit 170 cools the target holding unit 110 by using, for example, a cooling gas. By disposing the cooling unit 170 in such a position, temperature control of the transport unit 111 and the rotating shaft 120 becomes easy, and vibration of the target holding unit 110 can be suppressed. The cooling gas is a gas introduced to increase the thermal conductivity between the cooling unit 170 such as a heat sink and the target holding unit 110, which is the object to be cooled.

[0057] The inlet 162 is formed in the cooling unit 170. The inlet 162 introduces the cooling gas used to cool the target holding unit 110 toward the transport unit 111. The exhaust port 161 is formed in the weight casing 160. The exhaust port 161 exhausts the cooling gas used to cool the target holding unit 110. The exhaust port 161 may be provided in the weight casing 160 at a position facing the cylindrical portion 112c. The cooling gas is introduced from the inlet 162, passes through the space between the cooling unit 170 and the transport unit 111, the space between the cooling unit 170 and the cylindrical portion 112a, and the space between the cooling unit 170 and the disk portion 112b, and is exhausted from the exhaust port 161 provided at a position facing the cylindrical portion 112c. The cooling gas follows such a path, and thus the temperature of the target holding unit 110 can be efficiently controlled.

[0058] The input optical system 180 irradiates the target material TM with the excitation light LR. The input optical system 180 may include a condenser lens 181. The input optical system 180 may include a laser that generates the excitation light LR, and a mirror that reflects the excitation light LR. Note that the input optical system 180 may include other optical members, not limited to the condenser lens 181, laser, mirror, etc., as long as the optical members irradiate the target material TM with the excitation light LR.

[0059] The input optical system 180 may irradiate the target material TM with the excitation light LR at an angle tilted from an axis perpendicular to the surface of the target material TM. Specifically, the input optical system 180 irradiates the surface of the irradiation position PS where the excitation light LR is irradiated with the excitation light LR at an inclined incident angle. By irradiating the excitation light LR at an inclined angle in this manner, the effect of debris on optical members including the collector mirror 191 and the like can be suppressed.

[0060] The output optical system 190 extracts the light L0 generated by irradiating the target material TM with the excitation light LR from the light source device 100. The output optical system 190 includes, for example, a collector mirror 191. Note that the output optical system 190 is not limited to the collector mirror 191 as long as it is an optical member that extracts the light L0 generated by irradiating the target material TM with the excitation light LR. In addition, the output optical system 190 may include a second collector mirror (not shown) that further reflects the light L0 reflected by the collector mirror 191.

[0061] The collector mirror 191 reflects the light L0 generated from the target material TM by irradiation with the excitation light LR. The collector mirror 191 reflects, for example, the EUV light LE generated by irradiation with the excitation light LR. That is, the light L0 may include the EUV light LE. The EUV light LE is generated from plasma generated by irradiating the target material TM with the excitation light LR. The EUV light LE generated from the plasma generated in the target material TM 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.

[0062] <Optical equipment> Next, an optical device will be described. In the following, an inspection device will be used as an example of the optical device. FIG. 3 is a configuration diagram illustrating an inspection device 1 equipped with a light source device 100 according to the first embodiment. As shown in FIG. 3, the inspection device 1 includes an illumination optical system 200, an inspection optical system 300, a detector 410, and an image processing unit 420. The inspection device 1 may further include the light source device 100. The inspection device 1 is a device that uses light L0 generated by the light source device 100 as illumination light L1 to inspect defects and the like of a sample 500. The sample 500 is, for example, an EUV mask. The sample 500 is not limited to an EUV mask, and may be a semiconductor substrate or the like.

[0063] The illumination optical system 200 has an ellipsoidal mirror 210, an ellipsoidal mirror 220, and a drop-in mirror 230. The inspection optical system 300 has a concave mirror with a hole 310, a convex mirror 320, a plane mirror 330, and a concave mirror 340. The concave mirror with a hole 310 and the convex mirror 320 configure a Schwarzschild magnification optical system.

[0064] The light source device 100 generates illumination light L1. The illumination light L1 includes, for example, EUV light LE of 13.5 nm, which is the same as the exposure wavelength of the EUV mask that is the sample 500. The illumination light L1 may include light other than EUV light. The illumination light L1 generated from the light source device 100 is reflected by the ellipsoidal mirror 210. The illumination light L1 reflected by the ellipsoidal mirror 210 advances while being narrowed, and is collected at a convergence point IF1. Therefore, the ellipsoidal mirror 210 reflects the illumination light L1 generated from the light source device 100 as a convergent light. The convergence point IF1 is located at a position conjugate to the upper surface 510 of the sample 500 such as an EUV mask and the detection surface 411 of the detector 410.

[0065] After passing through the convergence point IF1, the illumination light L1 advances while expanding and is incident on a reflecting mirror such as the ellipsoidal mirror 220. Therefore, the illumination light L1 reflected by the ellipsoidal mirror 210 is incident on the ellipsoidal mirror 220 as divergent light via the convergence point IF1. The illumination light L1 incident on the ellipsoidal mirror 220 is reflected by the ellipsoidal mirror 220, advances while being narrowed, and is incident on the drop-in mirror 230. In other words, the ellipsoidal mirror 220 reflects the incident illumination light L1 as convergent light. Then, the ellipsoidal mirror 220 causes the illumination light L1 to be incident on the drop-in mirror 230. The drop-in mirror 230 is disposed directly above the EUV mask. The illumination light L1 incident on and reflected by the drop-in mirror 230 is incident on the sample 500. Therefore, the drop-in mirror 230 reflects the illumination light L1 reflected by the ellipsoidal mirror 220 to the sample 500, thereby causing the illumination light L1 to be incident on the sample 500.

[0066] The ellipsoidal mirror 220 focuses the illumination light L1 on the sample 500. The illumination optical system 200 is installed so that, when the illumination light L1 illuminates the sample 500, an image of the light source device 100 is formed on the upper surface 510 of the sample 500. Therefore, the illumination optical system 200 provides critical illumination. In this manner, the illumination optical system 200 illuminates the sample 500, such as an EUV mask, using critical illumination by the illumination light L1 generated by the light source device 100.

[0067] The sample 500 is placed on a stage 520. Here, a plane parallel to an upper surface 510 of the sample 500 is defined as an αβ plane, and a direction perpendicular to the αβ plane is defined as a γ axis direction. Illumination light L1 is incident on the sample 500 from a direction tilted from the γ axis direction. That is, illumination light L1 is incident obliquely to illuminate the sample 500.

[0068] 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.

[0069] The illumination light L1 from the light source device 100 illuminates an inspection area of ​​the sample 500. The inspection area illuminated by the illumination light L1 is, for example, 0.5 mm square. The inspection area is not limited to 0.5 mm square. The illumination light L1 is incident on the sample 500 from a direction tilted with respect to the γ-axis direction. The light from the sample 500 illuminated by the illumination light L1 is incident on the perforated concave mirror 310. In the following, the light from the sample 500 illuminated by the illumination light L1 is described as reflected light L2. The light incident on the perforated concave mirror 310 from the sample 500 is not limited to the reflected light L2, and may include diffracted light and the like. The reflected light L2 reflected by the sample 500 is incident on the perforated concave mirror 310. A hole 311 is provided at the center of the perforated concave mirror 310. The perforated concave mirror 310 collects the reflected light L2 from the sample 500, and reflects the collected reflected light L2 as convergent light.

[0070] The reflected light L2 reflected by the concave mirror 310 with a hole is incident on the convex mirror 320. The convex mirror 320 reflects the reflected light L12 reflected by the concave mirror 310 with a hole toward the hole 311 of the concave mirror 310 with a hole. The reflected light L2 passing through the hole 311 is incident on the plane mirror 330. The plane mirror 330 causes the reflected light L2 reflected by the convex mirror 320 to be incident as convergent light through the hole 311 of the concave mirror 310 with a hole. The reflected light L2 incident on the plane mirror 330 is reflected by the plane mirror 330. The reflected light L2 reflected by the plane mirror 330 advances while being narrowed, and is collected at the convergence point IF2. Therefore, the plane mirror 330 reflects the incident reflected light L2 as convergent light. The convergence point IF2 is sometimes called an aperture stop. The focal point IF 2 is located at a position conjugate with the upper surface 510 of the sample 500 and the detection surface 411 of the detector 410 .

[0071] After passing through the convergence point IF2, the reflected light L2 advances while diverging and enters the concave mirror 340. Thus, the reflected light L2 reflected by the plane mirror 330 as convergent light enters the concave mirror 340 as divergent light via the convergence point IF2. The concave mirror 340 reflects the incident reflected light L2 as convergent light toward the detector 410. The reflected light L2 reflected by the concave mirror 340 is detected by the detector 410. In this manner, the inspection optical system 300 inspects the sample 500, which is the inspection target, with the light L1 extracted from the output optical system 190 of the light source device 100. That is, the inspection optical system 300 collects the reflected light L2 from the sample 500 illuminated by the illumination light L1, and guides the collected reflected light L2 to the detector 410.

[0072] The detector 410 may include a TDI (Time Delay Integration) sensor. The detector 410 receives light from the sample 500 illuminated by the illumination light L1. The area on the sample 500 detected by the detector 410 is called a field of view 511. The detector 410 receives reflected light L2 from the field of view 511 illuminated by the illumination light L1. The field of view 511 may be included in the inspection area illuminated by the illumination light L1. The detector 410 acquires image data of the sample 500, such as an EUV mask. When the detector 410 includes a TDI sensor, the detector 410 includes a plurality of imaging elements arranged in a line in one direction. The imaging elements are, for example, CCDs (Charge Coupled Devices). Note that the imaging elements are not limited to CCDs.

[0073] 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.

[0074] The reflected light L2 contains information about defects in the sample 500. The specularly reflected light of the illumination light L1 incident on the sample 500 from a direction tilted with respect to the Z-axis direction is detected by the inspection optical system 300. If a defect exists in the sample 500, the defect is observed as a dark image. This observation method is called bright-field observation. Note that the inspection apparatus 1 may also cause the illumination light L1 to be incident on the sample 500 from the Z-axis direction and detected by the inspection optical system 300. If a defect exists in the sample 500, the defect is observed as a bright image. This observation method is called dark-field observation.

[0075] In this manner, the inspection apparatus 1 of this embodiment includes the above-described light source device 100 and an inspection optical system 300 that inspects an object to be inspected with the light L0 extracted from the output optical system 190. Note that, although 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 above-described light source device 100 and an exposure optical system that exposes an object to light with the light L0 extracted from the output optical system 190.

[0076] Next, the effects of this embodiment will be described. In the light source device 100 of this embodiment, the target holding part 110 includes a weight part 112 on the axial rotation driving part 130 side. Therefore, it is possible to stabilize the rotation of the target holding part 110, and to improve the stability of the generated light L0.

[0077] Furthermore, by including the weight portion 112, the light source device 100 can reduce the amount of whirling of the target holding part 110 during rotation. This can improve the stability of the generated light L0. For example, since the light source device 100 includes the weight portion 112, it can reduce the critical angular velocity ωn during rotation of the target holding part 110, and can reduce the amount of whirling of the target holding part 110 during rotation.

[0078] Furthermore, the target holding unit 110 has a mass such that the critical angular velocity ωn during rotation is 85% or less of the target angular velocity ω0. This reduces the amount of whirling during rotation of the target holding unit 110. This improves the stability of the generated light L0.

[0079] The rotating shaft 120 is shrink-fitted to the weight portion 112. For example, the linear expansion coefficient of the rotating shaft 120 is set to be larger than the linear expansion coefficient of the weight portion 112. This makes it possible to strengthen the joint when the rotating shaft 120 is shrink-fitted to the weight portion 112 and reduce the amount of whirling during rotation of the target holding portion 110. Even if the temperature of the target holding portion 110 increases due to irradiation with the excitation light LR, the joint between the rotating shaft 120 and the target holding portion 110 can be strengthened by maintaining the relationship of the linear expansion coefficients described above.

[0080] Furthermore, the weight portion 112 can be further strengthened by joining the rotating shaft 120 to the weight portion 112 by welding and bolting with a flange. Shrink fitting, welding, and bolting may be performed independently or in combination.

[0081] The transport unit 111 is detachable from the weight unit 112. Therefore, it is possible to easily test the balance of the mass of the weight unit 112, etc., when the transport unit 111 is not attached to the weight unit 112. For example, adjustments can be easily made using the balance holes 114, and the adjustments of the weight unit 112 can be made more precise.

[0082] The transport unit 111 is attached to the weight unit 112 when the excitation light LR is applied after the weight unit 112 has passed a test such as a balance test. This allows the weight unit 112 to be adjusted using the balance hole 114, while facilitating the subsequent adjustment of the transport unit 111 itself. In this way, the target holding unit 110 can improve maintainability.

[0083] The refill unit 140 adjusts the amount of target material TM so that a predetermined amount of target material TM is held in the transport unit 111. This makes it possible to stabilize the rotation of the target holding unit 110 and improve vibration damping properties.

[0084] The light source device 100 includes a cooling section 170 such as a heat sink. For example, by discharging a cooling gas from an exhaust port 161, it is possible to suppress a decrease in the light source efficiency.

[0085] <Embodiment 2> Next, a light source device according to a second embodiment will be described. In the light source device of this embodiment, the target holding unit includes a drum. Fig. 4 is a cross-sectional view illustrating a light source device 101 according to the second embodiment. As shown in Fig. 4, in the light source device 100a of this embodiment, the target holding unit 110a has a drum 116 as a conveying unit 111a.

[0086] The drum 116 is cylindrical, and a target material TMa such as xenon (Xe) is frozen as a solid metal and fixed to the outer surface of the cylinder. The input optical system 180 irradiates the outer surface of the cylinder of the drum 116 with excitation light LR. In this manner, the target holder 110a of this embodiment holds the target material TMa that generates light L0 when excitation light LR is applied thereto.

[0087] According to this embodiment, even when the light source device 100a has a transport unit 111a such as a drum 116, it is possible to suppress vibration during rotation of the target holding unit 110a and improve the stability of the generated light L0. Other configurations, actions, and effects are included in the description of the first embodiment.

[0088] Although the embodiments of the present disclosure have been described above, the present disclosure includes appropriate modifications that do not impair the objects and advantages thereof, and is not limited to the above-mentioned embodiments. In addition, combinations of the configurations of the first and second embodiments are also within the scope of the technical idea of ​​the present disclosure. [Explanation of symbols]

[0089] 100, 100a light source device 110, 110a target holder 111, 111a Conveyor section 112 Weight section 112a Cylinder section 112b Disk part 112c cylindrical part 113 Joint materials 114 Balance Hole 115 Container 116 Drums 120 Rotational Axis 130 Axis Rotation Drive Unit 140 Refill section 150 Vacuum Chamber 160 Weight Casing 161 Exhaust port 162 Introduction 170 Cooling section 180 Input Optical System 181 Condenser Lens 190 Output Optical System 191 Collector Mirror 200 Illumination optical system 210 Ellipsoidal Mirror 220 Ellipsoidal Mirror 230 Drop-in mirror 300 Inspection Optical System 310 Holed concave mirror 311 holes 320 Convex mirror 330 plane mirror 340 concave mirror 410 Detector 411 Detection surface 420 Image Processing Unit 500 samples 510 Top surface 511 Field of view 520 Stage 530 Drive unit C center axis L0 light L1 illumination light L2 reflected light LE EUV light LR excitation light TM, TMa target material

Claims

1. a target holder having a holding area for holding a target material that generates light when excited by light; A rotation shaft supporting the target holder; a shaft rotation drive unit connected to the rotation shaft and configured to rotate the target holder around a central axis of the rotation shaft via the rotation shaft; Equipped with The target holder is rotated at a predetermined target rotational angular velocity, the target holder has a mass such that a critical angular velocity during rotation is 85% or less of the target rotation angular velocity; Light source device.

2. the target holding portion includes the holding area and a weight portion, When one direction in the direction of the central axis is defined as one side, and the opposite direction to the one side is defined as the other side, The holding area is disposed on the one side of the weight portion, The weight portion extends to the other side. The light source device according to claim 1 .

3. a target holder having a holding area for holding a target material that generates light when excited by light; A rotation shaft supporting the target holder; a shaft rotation drive unit connected to the rotation shaft and configured to rotate the target holder around a central axis of the rotation shaft via the rotation shaft; Equipped with the target holding portion includes the holding area and a weight portion, When one direction in the direction of the central axis is defined as one side, and the opposite direction to the one side is defined as the other side, The holding area is disposed on the one side of the weight portion, The weight portion extends to the other side. Light source device.

4. The target holder includes: a conveying unit that holds the target material in the holding area and conveys it to an irradiation position; a weight portion having a portion provided closer to the shaft rotation drive portion than a joint portion between the conveying portion and the rotating shaft; Including, The transport unit is detachable from the weight unit and is attached to the weight unit when the excitation light is applied.

4. The light source device according to claim 1.

5. the temperature in the process of fitting the rotating shaft into the weight portion is lower than the temperature of the rotating shaft and the weight portion when the excitation light is applied to the target material, and the linear expansion coefficient of the weight portion is smaller than the linear expansion coefficient of the rotating shaft, or the temperature in the process of fitting the rotating shaft into the weight portion is higher than the temperature of the rotating shaft and the weight portion when the excitation light is applied to the target material, and the linear expansion coefficient of the weight portion is larger than the linear expansion coefficient of the rotating shaft.

4. The light source device according to claim 2.

6. the target material is molten tin and the weight portion has a linear expansion coefficient smaller than the linear expansion coefficient of the rotating shaft, or the target material is frozen xenon and the weight portion has a linear expansion coefficient larger than the linear expansion coefficient of the rotating shaft; 4. The light source device according to claim 2.

7. The weight portion is joined to the rotating shaft by welding.

4. The light source device according to claim 2.

8. The weight portion is bolted to a flange provided on the rotating shaft.

4. The light source device according to claim 2.

9. the target material is a molten metal; The transport unit holds the target material by centrifugal force caused by rotation around the central axis and transports it to the irradiation position. The light source device according to claim 4 .

10. the target holding unit further includes a joining member that joins the transport unit and the weight unit, The joining member is attached from the conveying portion toward the weight portion, The conveying section is joined to the weight section by the joining member, and thereby rotates together with the weight section; When the conveying unit is not joined by the joining member, the conveying unit is detachable from the rotating shaft. The light source device according to claim 4 .

11. The weight portion has a hole-shaped balance hole for adjusting the balance of the mass of the weight portion, The transport unit is attached to the weight unit after passing a test in a state in which the transport unit is not attached to the weight unit. The light source device according to claim 10.

12. a refilling unit that refills the molten metal into the transport unit so that a predetermined amount of the target material is held in the transport unit; The mass of the weight portion is determined based on the mass of the conveying portion and the mass of the predetermined amount of the molten metal. The light source device according to claim 9 .

13. a vacuum chamber in which the transfer unit is disposed; A weight casing in which at least a portion of the weight portion is disposed; a cooling unit disposed between the transport unit and the weight unit and configured to cool the target holder; Further equipped with The light source device according to claim 4 .

14. an inlet formed in the cooling section for introducing a cooling gas toward a space between the cooling section and the transfer section; an exhaust port formed in the weight casing for exhausting the cooling gas; Further equipped with The light source device according to claim 13.

15. A light source device according to claim 1 or 3, An optical device that performs lithography or inspection based on the light generated from the target material.

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