JP7626009B2 - Discharge plasma generating unit and light source device equipped with same - Google Patents

Description

The present invention relates to a discharge plasma generating unit that generates discharge plasma, and a light source device equipped with the same.

In recent years, as semiconductor integrated circuits become finer and more highly integrated, the wavelength of light used for exposure is becoming shorter. As a next-generation semiconductor exposure light source, development is underway of an extreme ultraviolet light source device (hereinafter also referred to as an EUV light source device) that emits extreme ultraviolet light with a wavelength of 13.5 nm (hereinafter also referred to as EUV light).

There are several known methods for generating EUV light (EUV radiation) in an EUV light source device. One of these methods involves heating and exciting extreme ultraviolet emitting species (hereinafter also referred to as EUV emitting species) to generate plasma, and extracting the EUV light from the plasma.
EUV light source devices employing such a method are divided into an LPP (Laser Produced Plasma) type and a DPP (Discharge Produced Plasma) type depending on the plasma generation method.

DPP type EUV light source devices apply a high voltage to a gap between electrodes to which a discharge gas containing EUV radiating species (gas-phase plasma raw material) is supplied, generating high-density plasma through discharge, and utilize the extreme ultraviolet light emitted from the plasma.
As a DPP method, for example, as described in Patent Document 1, a method has been proposed in which a liquid phase plasma raw material (e.g., tin (Sn) or lithium (Li)) is supplied to the surface of an electrode that generates a discharge, the raw material is irradiated with an energy beam such as a laser beam to vaporize the raw material, and then plasma is generated by discharge. Such a method is sometimes called an LDP (Laser Assisted Discharge Produced Plasma) method.
On the other hand, an LPP type EUV light source device irradiates a target material with laser light, and excites the target material to generate plasma.

The EUV light source device is used as a light source device for a lithography apparatus in semiconductor device manufacturing. Alternatively, the EUV light source device is used as a light source device for an inspection apparatus for masks used in lithography. In other words, the EUV light source device is used as a light source device for other optical system devices (utilization devices) that utilize EUV light.

JP 2017-219698 A

In the LDP method using a liquid-phase plasma raw material, the liquid-phase plasma raw material is supplied to the surfaces of a pair of electrodes that generate a discharge. In order to generate EUV light appropriately, it is important to appropriately set the distance between each electrode and the amount of plasma raw material supplied to the surface of each electrode.
On the other hand, the electrode body may be scraped off when plasma is generated. When the electrode shape changes in this way, maintenance work, including replacement of the electrode, is performed.

For example, when adjusting the positional relationship of each component, such as the arrangement between electrodes or the arrangement of a supply source that supplies liquid-phase plasma raw material to the surface of each electrode, the maintenance may take a long time. In addition, since the light source device is stopped during maintenance, an increase in maintenance time may limit the operating time of other optical devices that use EUV light.
For this reason, there is a demand for technology that makes it possible to easily maintain an apparatus that generates plasma from a liquid-phase plasma raw material.

In view of the above circumstances, the object of the present invention is to provide a discharge plasma generation unit that can facilitate the maintenance of an apparatus that generates plasma from liquid-phase plasma raw material, and a light source device equipped with the same.

In order to achieve the above object, a discharge plasma generating unit according to one embodiment of the present invention comprises a pair of discharge electrodes, a pair of containers, and a support member.
Each of the pair of discharge electrodes is formed in a disk shape.
Each of the pair of containers is capable of containing plasma raw material in a liquid phase.
The support member rotatably supports the pair of discharge electrodes so that the peripheral portions of the pair of discharge electrodes face each other with a space between them, and supports the pair of containers so that the plasma raw material is supplied to each of the pair of discharge electrodes.

In this discharge plasma generation unit, a pair of disk-shaped discharge electrodes and a pair of containers that hold plasma raw material in a liquid phase are supported by a support member. Each discharge electrode is supported rotatably and positioned so that their peripheral edges face each other with a space between them. Each container is positioned so as to supply plasma raw material to each discharge electrode. This makes it possible to attach and detach each discharge electrode and container as a unit while they are properly positioned, making it easier to maintain the device that generates plasma from liquid-phase plasma raw material.

The container may have a storage section that opens upward and stores liquid-phase plasma raw material. In this case, the support member may support the pair of containers such that at least a portion of the discharge electrode is inserted into the storage section from above the corresponding container.

This makes it possible to easily supply plasma raw material to each discharge electrode.

The discharge plasma generating unit may further include a pair of thickness adjustment parts that adjust the thickness of the plasma raw material attached to the pair of discharge electrodes inserted into the storage parts of the pair of containers. In this case, the support member may support the pair of thickness adjustment parts in correspondence with the pair of discharge electrodes.

This makes it possible to adjust the supply of plasma raw material, enabling plasma to be generated under appropriate conditions.

The discharge plasma generating unit may further include a pair of rotary drive units that rotate the pair of discharge electrodes around their respective central axes. In this case, the support member may support the pair of discharge electrodes via the pair of rotary drive units.

This makes it possible to attach and detach the rotary drive unit together with the discharge electrode and container, which can shorten the time required for maintenance work, for example.

The support member may be configured as a lid that covers an opening provided in the outer wall of the vacuum chamber from the outside, and may support the pair of discharge electrodes and the pair of containers so that they fit within the vacuum chamber.

This allows the entire discharge plasma unit to be attached and detached from outside the vacuum chamber, making it easier to perform tasks such as replacing the discharge plasma unit.

The support member may have a second positioning portion that is guided by a first positioning portion provided in the vacuum chamber.

This makes it possible to mount the discharge plasma unit in the correct position relative to the vacuum chamber.

A plasma raw material layer made of the plasma raw material may be formed on at least a portion of the discharge electrode.

This makes it possible to achieve light emission of appropriate intensity from the initial stage of operation when the discharge plasma unit is actually operated.

The plasma raw material may contain tin. In this case, the material of the discharge electrode may be tungsten.

Even if the plasma raw material is tin and the discharge electrode is made of tungsten, which has low wettability with respect to tin, providing a plasma raw material layer makes it possible to achieve light emission of appropriate intensity from the initial stage of operation.

The plasma raw material layer may be formed at least on the peripheral portion of the discharge electrode.

This allows the discharge plasma unit to operate reliably from the initial stage of operation.

The area of the plasma raw material layer formed in the peripheral portion may be 80% or more of the area of the peripheral portion.

This makes it possible to achieve the desired light emission intensity from the initial stage of operation when the discharge plasma unit is actually operated.

A light source device according to one aspect of the present invention includes a housing, a discharge plasma generating unit, a beam irradiating unit, a power supply unit, and a raw material supply unit.
The discharge plasma generation unit is a unit that is removably attached to the housing, and includes a pair of discharge electrodes, each of which is configured in a disk shape, a pair of containers, each of which can hold plasma raw material in a liquid phase, and a support member that rotatably supports the pair of discharge electrodes so that the peripheral portions of the pair of discharge electrodes face each other with a space between them, and supports the pair of containers so that the plasma raw material is supplied to each of the pair of discharge electrodes.
The beam irradiation unit irradiates the discharge electrode with an energy beam that vaporizes the plasma raw material supplied to the discharge electrode.
The power supply unit supplies discharge power for generating a discharge plasma to the pair of discharge electrodes.
The raw material supply unit supplies the plasma raw material to the pair of containers.

The present invention makes it possible to facilitate the maintenance of an apparatus that generates plasma from liquid-phase plasma raw material.

1 is a schematic diagram for explaining an overview of a discharge plasma generating unit according to one embodiment of the present invention; FIG. 2 is a perspective view showing a configuration example of a discharge plasma generating unit. FIG. 3 is a cross-sectional view of the discharge plasma generating unit shown in FIG. 2 . FIG. 2 is a perspective view showing an example of the configuration of a fixing substrate on which a discharge plasma generating unit is mounted. FIG. 2 is a cross-sectional view showing a state in which the discharge plasma generating unit is mounted on a fixing substrate. 2 is a schematic diagram showing a configuration example of a discharge electrode mounted in a discharge plasma generating unit. FIG. 1 is a schematic cross-sectional view showing the configuration of an EUV light source device equipped with a discharge plasma generating unit.

The following describes an embodiment of the present invention with reference to the drawings.

FIG. 1 is a schematic diagram for explaining an overview of a discharge plasma generating unit according to an embodiment of the present invention.
The discharge plasma generation unit 1 is a unit that generates a discharge plasma (hereinafter, referred to as plasma P) by the LDP method. In this embodiment, the discharge plasma generation unit 1 is configured to generate plasma P that emits EUV light, and is mounted on and used in an EUV light source device 2. Therefore, the discharge plasma generation unit 1 functions as a source head that serves as a light source of EUV light in the EUV light source device 2, and generates plasma P in a vacuum chamber provided in the EUV light source device 2.
The discharge plasma generating unit 1 has a pair of discharge electrodes (EA, EB), a pair of containers (CA, CB), a pair of skimmers (SKA, SKB), and a unit substrate 20.

The pair of discharge electrodes EA, EB are each formed in a disk shape.
The discharge electrodes EA, EB are disposed such that the peripheral portions 10 of the electrodes face each other with a space therebetween. Here, the peripheral portions 10 of the discharge electrodes EA, EB are portions that form the periphery of the disk-shaped electrodes. In FIG. 1 , the peripheral portions 10 are strip-shaped end faces 11 provided on the periphery of each electrode.
The discharge electrodes EA and EB are each configured to be rotatable, and each electrode is connected to a drive mechanism (not shown) such as a motor.
The discharge electrodes EA, EB are made of a high melting point metal such as tungsten, molybdenum, or tantalum.

Each of the pair of containers CA, CB is a container (vessel) capable of containing plasma raw material in a liquid phase state.
The plasma raw material is a liquid phase raw material that generates a discharge plasma, and typically a liquid metal is used. In this embodiment, the containers CA and CB contain plasma raw materials SA and SB, which are made of liquid phase tin. The type of plasma raw material is not limited, and lithium, for example, may be used.
The containers CA and CB are made of a conductive material, so that the container CA is electrically connected to the plasma raw material SA, and the container CB is electrically connected to the plasma raw material SB.

1, the lower side of a discharge electrode EA is partially immersed in the plasma raw material SA stored in a container CA, and the lower side of a discharge electrode EB is partially immersed in the plasma raw material SB stored in a container CB.
As described above, the discharge electrodes EA, EB are configured to be rotatable. The liquid-phase plasma raw materials SA, SB adhering to the discharge electrodes EA, EB are transported to the discharge region D where plasma P is generated as the discharge electrodes EA, EB rotate.

The pair of skimmers SKA, SKB adjust the thickness of the plasma raw materials SA, SB adhering to the discharge electrodes EA, EB to a predetermined thickness.
The skimmer SKA is disposed corresponding to the discharge electrode EA, and adjusts the thickness of the plasma raw materials SA adhering to the discharge electrode EA before they are transported to the discharge region D. The skimmer SKB is disposed corresponding to the discharge electrode EB, and adjusts the thickness of the plasma raw materials SB adhering to the discharge electrode EB before they are transported to the discharge region D. This makes it possible to control the amounts of the plasma raw materials SA and SB supplied to the discharge region D.
In this embodiment, the skimmers SKA and SKB correspond to a pair of thickness adjustment units.

The unit substrate 20 is a support member that integrally supports each part that constitutes the discharge plasma generating unit 1 .
In the discharge plasma generation unit 1, a pair of discharge electrodes EA, EB are rotatably supported by a unit substrate 20 so that peripheral portions 10 of the pair of discharge electrodes EA, EB face each other with a space therebetween. In addition, the unit substrate 20 supports a pair of containers CA, CB so that plasma raw materials SA, SB are supplied to the pair of discharge electrodes EA, EB, respectively.
This makes it possible to integrally support the pair of discharge electrodes EA, EB and the pair of containers CA, CB in an arrangement that enables a discharge to be generated between the discharge electrodes EA, EB and a plasma raw material to be supplied to the discharge region D where the discharge occurs.
The unit substrate 20 also supports skimmers SKA, SKB arranged corresponding to the discharge electrodes EA, EB, and a motor for rotating the discharge electrodes EA, EB.

1, the unit substrate 20 is illustrated in a schematic manner by a rectangular region surrounding the pair of discharge electrodes EA, EB, the pair of containers CA, CB, and the pair of skimmers SKA, SKB. The specific configuration of the unit substrate 20 will be described in detail later.
In this embodiment, the unit substrate 20 corresponds to a support member.

The EUV light source device 2 on which the discharge plasma generation unit 1 is mounted is also provided with a plasma raw material supply unit 50, a pulsed power supply unit 56, and a laser source 57.

The plasma raw material supply unit 50 supplies plasma raw materials SA and SB to a pair of containers CA and CB. The plasma raw material supply unit 50 has a reservoir that stores the plasma raw material, for example, liquid metal (tin in this case) in a liquid phase. The plasma raw materials SA and SB are supplied in a liquid phase from this reservoir to each of the containers CA and CB.
In this embodiment, the plasma raw material supply unit 50 corresponds to a raw material supply unit.

The pulsed power supply unit 56 supplies discharge power for generating a discharge plasma to the pair of discharge electrodes EA, EB. In the present embodiment, the pulsed power supply unit 56 is connected to the containers CA, CB, and supplies pulsed power between the containers CA, CB.
As described above, the containers CA, CB are made of a conductive material, and the plasma raw materials SA, SB, which are made of tin, are also conductive materials. Furthermore, the discharge electrodes EA, EB are each partially immersed in the plasma raw materials SA, SB. Therefore, the pulsed power supplied to the containers CA, CB is supplied to the discharge electrodes EA, EB, respectively, via the plasma raw materials SA, SB.
In this embodiment, the pulsed power supply unit 56 corresponds to a power supply unit.

The laser source 57 irradiates the discharge electrode with an energy beam that vaporizes the plasma raw material supplied thereto. In this example, the peripheral portion 10 (the end face of the electrode) of the discharge electrode EA on the right side of the drawing is irradiated with an energy beam (laser beam LB) that vaporizes the plasma raw material SA.
In this embodiment, the laser source 57 corresponds to a beam irradiation unit.

1, a laser beam LB from a laser source 57 is irradiated onto the plasma raw material SA which has adhered to the discharge electrode EA and been transported to the discharge region D. The plasma raw material SA irradiated with the laser beam LB is vaporized and enters a gas phase state.
At this time, pulsed power is supplied to the containers CA, CB from the pulsed power supply unit 56. This pulsed power is supplied to the discharge electrodes EA, EB, respectively, as described above, and a discharge is generated between the discharge electrodes EA, EB.
This discharge heats and excites the gas-phase plasma raw material SA in the discharge region D with the current, generating plasma P, from which EUV light is emitted.

In this way, the source head (discharge plasma generation unit 1) that generates plasma P from liquid-phase plasma raw material includes various elements (discharge electrodes (EA, EB), containers (CA, CB), skimmers (SKA, SKB), etc.) for handling the liquid-phase plasma raw material. In order to properly generate plasma P, it is necessary to adjust and arrange these elements so that they have a predetermined positional relationship.
For example, the task of adjusting these elements one by one while attaching them to the EUV light source device 2 is not easy and requires a certain degree of skill. Also, if each element is attached individually, the task may take a long time. Also, it takes time to connect the other elements.

Therefore, the present inventors have invented a discharge plasma generation unit 1 that can be handled as a whole by using a unit substrate 20. That is, the inventors have invented a discharge plasma generation unit 1 in which a number of elements, such as the discharge electrodes EA, EB, containers CA, CB, the plasma raw materials SA, SB contained in each container CA, CB, skimmers SKA, SKB that adjust the thickness of the plasma raw materials SA, SB attached to each discharge electrode EA, EB, and motors MA, MB (see FIG. 2, etc.) for rotating the discharge electrodes EA, EB, are assembled onto a single unit substrate 20 to form a unit, and which can be attached to an EUV light source device 2.
This eliminates the need to adjust each element one by one, making it possible to facilitate maintenance of the EUV light source device 2.
A specific example of the configuration of the discharge plasma generating unit 1 will be described below.

Fig. 2 is a perspective view showing a configuration example of the discharge plasma generating unit 1. Fig. 3 is a cross-sectional view of the discharge plasma generating unit 1 shown in Fig. 2. Fig. 3 shows a cross section of the discharge plasma generating unit 1 taken along line AA shown in Fig. 2A.
As described above, the discharge plasma generating unit 1 has the discharge electrodes EA, EB, the containers CA, CB, the skimmers SKA, SKB, and the unit substrate 20. The discharge plasma generating unit 1 also has a pair of motors MA, MB.

First, the unit board 20 will be described.
The unit substrate 20 is a flange-shaped structure having a circular planar shape. In this embodiment, the unit substrate 20 is configured as a lid that covers, from the outside, an opening 33 (see FIGS. 4 and 5, etc.) provided in the outer wall of the vacuum chamber of the EUV light source device 2. The unit substrate 20 also supports a pair of discharge electrodes EA, EB and a pair of containers CA, CB so that they are contained within the vacuum chamber.
Therefore, the unit substrate 20 is attached from the outside to the outer wall of the vacuum chamber and functions as part of the outer wall of the vacuum chamber, as well as a support member for arranging the discharge electrodes EA, EB and the containers CA, CB within the vacuum chamber.

In the following, the vertical direction is referred to as the Z direction, and the horizontal plane perpendicular to the Z direction is referred to as the XY plane. Here, the unit substrate 20 is disposed along the XZ plane. Line AA shown in FIG. 2A is a line parallel to the X direction. The cross-sectional view shown in FIG. 3 represents a cross section of the unit substrate 20 cut along the XY plane.

When the unit substrate 20 is mounted on the EUV light source device 2, the side facing the inside of the EUV light source device 2 is described as the inner side of the unit substrate 20, and the opposite side is described as the outer side of the unit substrate 20. FIG. 2A is a perspective view showing the inner side of the unit substrate 20, and FIG. 2B is a perspective view showing the outer side of the unit substrate 20.

The unit substrate 20 has a disk-shaped substrate body 21 , a connection portion 22 , and a recess 23 .
The substrate body 21 is the main body of the unit substrate 20. Annular cutouts are formed on the inner and outer peripheral portions of the substrate body 21. The portions formed between the inner and outer cutouts and protruding in the radial direction become the connection portions 22. The connection portions 22 are connected to the outer wall of the EUV light source device 2 and fixed by screws or the like.
The recess 23 is a circular groove formed inside the substrate body 21. The central axis of the recess 23 is set to coincide with the central axis of the substrate body 21. Therefore, the substrate body 21 can be said to be a thin cylindrical member with one end closed.
The annular portion surrounding the recess 23 becomes the insertion portion 24 to be inserted into an opening 33 provided in the outer wall of the vacuum chamber. A unit side positioning portion 25 is formed in the cutout (the cutout on the inner side of the substrate body 21) that forms the connection portion 22 and the insertion portion 24. The unit side positioning portion 25 will be described later.

2A and 3 , in the discharge plasma generating unit 1, the discharge electrodes EA, EB and the containers CA, CB are arranged inside the recess 23, i.e., in the recessed portion inside the substrate body 21. The diameter and depth of the recess 23 may be appropriately set so that each element of the discharge plasma generating unit 1 can be arranged therein. In addition, the recess 23 does not necessarily have to be a circular groove, and may be, for example, an elliptical or rectangular recess 23.

The pair of discharge electrodes EA, EB are disk-shaped members. Typically, conductive members having the same shape and size are used as the respective discharge electrodes EA, EB.
The discharge electrodes EA, EB reach a high temperature due to the heat of the plasma P, etc. In order to reduce deformation, deterioration, wear, etc. even in such a high-temperature state, the discharge electrodes EA, EB are made of a high-melting point metal such as tungsten.

In this embodiment, a band-shaped end face 11 having a certain width is formed on the periphery of the discharge electrodes EA, EB. Furthermore, in the discharge electrodes EA, EB, the substantially circular main surfaces connected to the end faces 11 become side faces 12 of the discharge electrodes EA, EB. Of these, in this embodiment, the end faces 11 formed on the periphery of the discharge electrodes EA, EB become the peripheral portions 10 of the discharge electrodes EA, EB.
Note that an electrode having a sharpened periphery may be used instead of forming the end face 11. In this case, the outer peripheral portion of the side surface 12 of the discharge electrodes EA, EB (for example, a region having a width of about 10% of the radius of the electrode from the periphery of the side surface 12) becomes the peripheral portion 10.

2 and 3, the discharge electrodes EA, EB are arranged to fit into a recess 23 formed inside the unit substrate 20. The discharge electrodes EA, EB are arranged side by side such that their peripheral edges 10 face each other with a space therebetween and their Z-direction positions (horizontal positions) are the same. For example, the horizontal position of the center of each electrode is set to the same horizontal position as the center of the circular recess 23.
Here, when the inside of the unit substrate 20 is viewed from the front, the discharge electrode EA is disposed on the right side, and the discharge electrode EB is disposed on the left side.

The pair of motors MA, MB rotate the pair of discharge electrodes EA, EB around their respective central axes. In this embodiment, the motors MA, MB correspond to a pair of rotation drive units.
The motor MA has a rotating shaft JA, and the motor MB has a rotating shaft JB.
The motors MA, MB are disposed outside the unit substrate 20 , and the rotation shafts JA, JB of the motors MA, MB extend from the outside of the unit substrate 20 through the substrate body 21 to a recess 23 on the inside of the unit substrate 20 .

In this embodiment, the unit substrate 20 supports a pair of discharge electrodes EA, EB via a pair of motors MA, MB. Specifically, by supporting the rotating shafts JA, JB of the motors MA, MB, the discharge electrodes EA, EB connected to the rotating shafts JA, JB are supported as follows:

The discharge electrode EA is connected to the rotating shaft JA so that the central axis of the discharge electrode EA coincides with the central axis of the rotating shaft JA. Thus, the discharge electrode EA rotates around the central axis of the discharge electrode EA as the motor MA (rotating shaft JA) rotates.
Further, the discharge electrode EB is connected to the rotating shaft JB so that the central axis of the discharge electrode EB coincides with the central axis of the rotating shaft JB. Therefore, the discharge electrode EB rotates around the central axis of the discharge electrode EB as the motor MB (rotating shaft JB) rotates.

The unit substrate 20 is provided with seal members PA and PB for receiving the rotating shafts JA and JB.
The seal member PA is disposed in a through hole provided in the substrate body 21 through which the rotating shaft JA passes, seals the gap between the rotating shaft JA and the substrate body 21, and rotatably supports the rotating shaft JA.
The seal member PB is disposed in a through hole provided in the substrate body 21 through which the rotating shaft JB passes, seals the gap between the rotating shaft JB and the substrate body 21, and rotatably supports the rotating shaft JB.
The seal members PA and PB may be, for example, mechanical seals. By using the seal members PA and PB, when the unit substrate 20 is attached to a chamber 54 (see FIG. 7 ) of the EUV light source device 2 described below, it becomes possible to rotatably support the rotation shafts JA and JB while maintaining a reduced pressure atmosphere in the chamber 54.

The positions (through holes) at which the rotation axes JA, JB are installed are set so that the peripheral portions 10 of the discharge electrodes EA, EB face each other and are spaced apart. At this time, the discharge region D where the plasma P is generated is located in the gap between the discharge electrodes EA, EB where the peripheral portions 10 of the discharge electrodes EA, EB are closest to each other.
In the example shown in FIGS. 2 and 3, the discharge region D is formed so as to overlap with the central axis of the unit substrate 20 (substrate body 21).

In addition, the central axes of the discharge electrodes EA, EB are not parallel to each other. Specifically, as shown in Fig. 3, the rotation axes JA, JB are arranged such that the distance between the rotation axes JA, JB as viewed in the vertical direction (Z direction) is narrower on the outside where the motors MA, MB are provided and wider on the inside where the discharge electrodes EA, EB are provided.
Furthermore, the discharge electrode used as the anode (here, the discharge electrode EB) is retreated to the side where the motor is provided (the side of the bottom surface 26 of the recess 23) relative to the discharge electrode used as the cathode (here, the discharge electrode EA).

This arrangement makes it possible to bring the peripheral portions 10 of the discharge electrodes EA, EB closer to each other on the side where they face each other (opposing surface side), while moving the side opposite the opposing surface side of the discharge electrodes EA, EB out of the irradiation path of the laser beam LB. Furthermore, it becomes possible to irradiate the end surface 11 of the discharge electrode EA, which is the cathode, with the laser beam LB without blocking the laser beam LB with the discharge electrode EB, which is the anode. In other words, it becomes possible to easily irradiate the laser beam LB to the peripheral portion 10 of the discharge electrode EA near the discharge region D.

The pair of containers CA, CB are configured as liquid containers that contain plasma raw material in a liquid state. Each of the containers CA, CB has a container body 15 and a container portion 16.
The container body 15 is the main body of the containers CA, CB, and is made of a material (such as stainless steel) capable of containing the plasma raw material in a liquid phase state.
The storage section 16 is open upward and stores the liquid phase plasma raw material. Specifically, the storage section 16 is a concave structure formed in each container body 15 so as to be capable of storing a liquid.

2A , in this embodiment, a slit-shaped storage portion 16 into which a disk-shaped discharge electrode can be inserted is provided in a container body 15. The container body 15 also has a pair of side walls 17 that face each other with the storage portion 16 in between.
Here, the container body 15 is configured so that the planar shape of the side wall portion 17 when viewed from the Y direction is substantially semicircular, and is disposed so that the apex of the semicircle of the side wall portion 17 is at its lowest position. The storage portion 16 provided in the container body 15 also has a planar shape that is substantially semicircular when viewed from the Y direction. A step is provided above the container body 15, and one upper end of the container body 15 is lower than the other upper end when viewed from the Y direction.

As described above, the storage section 16 of the container CA stores the liquid-phase plasma raw material SA to be supplied to the discharge electrode EA. The storage section 16 of the container CB stores the liquid-phase plasma raw material SB to be supplied to the discharge electrode EB.

Here, container CA is placed so that the lower part of discharge electrode EA is inserted into storage section 16 that stores plasma raw material SA. Also, container CB is placed so that the lower part of discharge electrode EB is inserted into storage section 16 that stores plasma raw material SB. Specifically, as shown in FIG. 3, container CA and container CB are attached to bottom surface 26 of recess 23 of unit substrate 20 by mounting member 18.

Thus, in this embodiment, the pair of containers CA, CB are supported by the unit substrate 20 such that at least a portion of the discharge electrodes EA, EB is inserted into the accommodation portion 16 from above the corresponding containers CA, CB.
This makes it possible to easily supply the plasma raw materials SA, SB stored in the respective containers CA, CB by directly attaching them to the discharge electrodes EA, EB.

The containers CA, CB are positioned so that the lower part of the upper end of the container body 15 faces the peripheral parts 10 of the discharge electrodes EA, EB. This exposes the opposing parts of the discharge electrodes EA, EB, making it possible to properly position the peripheral parts 10 facing each other.

The liquid-phase plasma raw materials SA, SB are supplied to each of the storage sections 16 of the containers CA, CB by the plasma raw material supply section 50 described with reference to Fig. 1. The plasma raw material supply section 50 is attached to each of the containers CA, CB when the discharge plasma generation unit 1 is attached to the EUV light source device 2.
The container body 15 is provided with, for example, a supply port and a recovery port that communicate with the storage unit 16. The plasma raw material supply unit 50 is connected to the supply port and the recovery port, and supplies liquid phase plasma raw material from the supply port to the storage unit 16 and recovers the plasma raw material from the recovery port inside the storage unit 16. By circulating the plasma raw material in this manner, it becomes possible to precisely control the temperature and purity of the plasma raw material.
The containers CA, CB may each be provided with a heating mechanism such as a heater for maintaining the plasma raw materials SA, SB in a liquid phase state.

The pair of skimmers SKA, SKB adjust the thickness of the plasma raw materials SA, SB that adhere to the pair of discharge electrodes EA, EB inserted into the storage compartments 16 of the pair of containers CA, CB. That is, the skimmer SKA adjusts the thickness of the plasma raw materials SA that adhere to the discharge electrode EA, and the skimmer SKB adjusts the thickness of the plasma raw materials SB that adhere to the discharge electrode EB.

Specifically, the skimmers SKA, SKB adjust the thickness of the plasma raw materials SA, SB that are attached to the discharge electrodes EA, EB to a predetermined thickness.
The skimmers SKA and SKB are, for example, channel-shaped members formed with a U-shaped recess 28. The skimmers SKA and SKB are arranged so that the recess 28 sandwiches the peripheral portions 10 of the discharge electrodes EA and EB, i.e., so that the recess 28 passes through the peripheral portions 10 and the vicinity of the peripheral portions 10 of the discharge electrodes EA and EB.

In this case, the gap between the skimmers SKA, SKB and the surfaces of the discharge electrodes EA, EB determines the thickness of the plasma raw materials SA, SB that adhere to the discharge electrodes EA, EB. Therefore, for example, by appropriately setting the distance between the recesses 28 of the skimmers SKA, SKB and the peripheral portions 10 (end faces 11 of the electrodes) of the discharge electrodes EA, EB, it is possible to adjust the thickness of the plasma raw materials that adhere to the peripheral portions 10 to a predetermined thickness.

In this embodiment, the unit substrate 20 supports a pair of skimmers SKA, SKB corresponding to the pair of discharge electrodes EA, EB.
Specifically, skimmers SKA, SKB are positioned so that the thickness of the plasma raw materials SA, SB can be adjusted before the discharge electrodes EA, EB rotate and the plasma raw materials SA, SB are transported to the discharge region D.

The skimmer SKA is disposed in an area of the discharge electrode EA that is not surrounded by the container CA and on the side that does not face the discharge electrode EB.
The skimmer SKB is disposed in a region of the discharge electrode EB that is not surrounded by the container CB and on the side that does not face the discharge electrode EA.
2A, the left side of the discharge electrode EA and the right side of the discharge electrode EB are arranged to face each other. Thus, the skimmer SKA is arranged to the right of the discharge electrode EA that is not inserted into the container CA, and the skimmer SKB is arranged to the left of the discharge electrode EB that is not inserted into the container CB.

3, the side of each skimmer SKA, SKB not facing the discharge electrodes EA, EB (the side opposite to the recess 28 ) is supported by, for example, an annular insertion part 24 surrounding the recess 23 of the unit substrate 20. In this case, each skimmer SKA, SKB may be configured so that the distance between the recess 28 and the peripheral part 10 is adjustable. This makes it possible to precisely control the thickness of the plasma raw material transported to the discharge region D.

Figure 4 is a perspective view showing an example of the configuration of a fixing substrate on which the discharge plasma generation unit 1 is mounted. Figure 4A is a perspective view of the fixing substrate 30 on which the discharge plasma generation unit 1 is not mounted, and Figure 4B is a perspective view showing the positional relationship when the discharge plasma generation unit 1 is mounted on the fixing substrate 30. Figure 5 is a cross-sectional view showing the state in which the discharge plasma generation unit 1 is mounted on the fixing substrate 30.

The fixing substrate 30 is a member on which the discharge plasma generating unit 1 is attached, and constitutes the outer wall of a chamber 54 which is a vacuum chamber provided in the EUV light source device 2 .
The fixing substrate 30 is a plate-shaped member and is made of, for example, stainless steel, etc. The fixing substrate 30 has an outer wall surface 31 that is the outside of the chamber 54, an inner wall surface 32 that is the inside of the chamber 54, an opening 33, and a plurality of apparatus-side positioning portions 34.

The opening 33 is a circular through hole provided in the fixing substrate 30. The shape and size of the opening 33 are set so that it can be blocked by the unit substrate 20 (substrate body 21) of the discharge plasma generating unit 1.

5, an annular cutout is provided on the outer wall surface 31 side of the opening 33. The diameter of this cutout is set to be larger than the diameter of the insertion portion 24 of the unit substrate 20 and smaller than the diameter of the connection portion 22 of the unit substrate 20. Therefore, the insertion portion 24 of the unit substrate 20 is fitted into the cutout of the opening 33. The depth of the cutout of the opening 33 with respect to the outer wall surface 31 is set so that, for example, the connection portion 22 of the unit substrate 20 comes into contact with the outer wall surface 31 of the fixing substrate 30.
The diameter of the opening 33 on the inner wall surface 32 side of the fixing substrate 30 is set to be approximately the same as the diameter of the recess 23 of the unit substrate 20 .

The apparatus-side positioning portions 34 are provided on the outer wall surface 31 so as to surround the opening 33. In this embodiment, three apparatus-side positioning portions 34 are provided. Each apparatus-side positioning portion 34 has a structure that protrudes, for example, in a pin-like shape from the outer wall surface 31, and is disposed at equal intervals on a circumference surrounding the opening 33.
In this embodiment, the apparatus-side positioning portion 34 corresponds to a first positioning portion provided on the outer wall of the vacuum chamber.

2A , a plurality of unit-side positioning portions 25 are formed on the unit substrate 20. In this embodiment, three unit-side positioning portions 25 are provided corresponding to the three apparatus-side positioning portions 34 provided on the fixing substrate 30. Each apparatus-side positioning portion 34 has, for example, a concave groove whose cross-sectional shape is an isosceles triangle.
In this embodiment, the unit side positioning portion 25 corresponds to a second positioning portion.

When the apparatus-side positioning portion 34 and the unit-side positioning portion 25 are pressed into contact with each other, they function as a guide mechanism in which one guides the other.
When mounting the discharge plasma generation unit 1 (unit substrate) on the fixing substrate 30, the discharge plasma generation unit 1 is attached to a predetermined position on the fixing substrate 30 by abutting the protruding portion of the device side positioning portion 34 against the concave groove of the unit side positioning portion 25 described above.

In this manner, the unit substrate 20 is provided with the unit-side positioning portion 25 that is guided by the apparatus-side positioning portion 34 provided on the outer wall (fixing substrate 30) of the vacuum chamber. This makes it possible to mount the discharge plasma generation unit 1 on the EUV light source device 2 with high precision.
The number, arrangement, shape, etc. of the device side positioning parts 34 and the unit side positioning parts 25 are not limited, and any positioning mechanism capable of positioning the fixing substrate 30 and the unit substrate 20 may be used, for example.

As shown in Figure 5, the discharge plasma generation unit 1, which consists of the discharge electrodes EA, EB, motors MA, MB, containers CA, CB, skimmers SKA, SKB, and a unit substrate 20 to which they are integrally attached, is attached from the outside to the fixing substrate 30.
Furthermore, the fixing substrate 30 on which the discharge plasma generating unit 1 is mounted is attached to the wall of the chamber 54 so as to be able to maintain the reduced pressure atmosphere in the chamber 54, as shown in FIG.

In FIG. 5, the sealing structure between the wall of the chamber 54 and the fixing substrate 30 is omitted. Also, the sealing structure between the fixing substrate 30 and the discharge plasma generating unit 1 (unit substrate 20) is omitted. For example, a known structure capable of maintaining the reduced pressure atmosphere in the chamber 54 may be used as the sealing structure.

In this way, the discharge plasma generating unit 1 (source head mechanism) of the present invention has an integrated modular structure in which the discharge electrodes EA, EB, motors MA, MB, containers CA, CB, and skimmers SKA, SKB are attached to a unit substrate 20.
In the discharge plasma generation unit 1, for example, the arrangement of the discharge electrodes EA, EB, the positions of the skimmers SKA, SKB, the positional relationship between the discharge electrode EA and the container CA, and the positional relationship between the discharge electrode EB and the container CB are adjusted to be in a predetermined arrangement.
Furthermore, the discharge plasma generating unit 1 can be attached to an EUV light source device 2 via a fixing substrate 30 as shown in FIGS.

By using such a structure, for example, when performing maintenance such as replacing the discharge electrodes, it is possible to easily replace the entire discharge plasma generation unit 1. This eliminates the need to attach the various elements required for plasma generation one by one to the EUV light source device 2 while adjusting them each time so that they are in a specified positional relationship. As a result, maintenance work becomes much easier and it is possible to shorten the work time.

Furthermore, it becomes possible to quickly connect other elements (the above-mentioned pulsed power supply unit 56, plasma raw material supply unit 50, and lines for supplying power to motors MA and MB (see FIG. 7)) to the source head mechanism.
5 and other figures, the motors MA, MB are disposed outside the EUV light source device 2 (outside the chamber 54). This makes it easy to inspect the motors MA, MB during maintenance work. Furthermore, when cooling of the motors MA, MB is required, a cooling mechanism for cooling the motors MA, MB can be easily installed.

[Discharge electrode with plasma raw material layer formed]
The present inventor verified the operation of generating EUV light by mounting the discharge plasma generating unit 1 on the EUV light source device 2. This verification revealed that when using the discharge plasma generating unit 1 equipped with unused discharge electrodes EA, EB to which no plasma raw material is attached, it is not always possible to obtain EUV light of sufficient intensity at the beginning of operation.

The inventors' investigation revealed that when unused discharge electrodes EA, EB are used, liquid-phase tin (plasma raw materials SA, SB) does not adhere sufficiently to the discharge electrodes EA, EB, and the amount of liquid-phase plasma raw material supplied to the discharge region D is insufficient.

The reason why the amount of plasma raw materials SA, SB adhering to the discharge electrodes EA, EB is small is that the plasma raw materials SA, SB have low wettability to the discharge electrodes EA, EB. For example, if tungsten is used as the material for the discharge electrodes EA, EB, it is thought that the amount of plasma raw materials SA, SB adhering to unused or barely used discharge electrodes EA, EB will be small due to the low wettability between the tungsten that makes up the discharge electrodes EA, EB and the tin that is the plasma raw material SA, SB.

The intensity of the EUV light gradually improves as the EUV light source device 2 continues to operate. However, approximately five hours of discharge operation between the discharge electrodes EA, EB was required to obtain the desired EUV light intensity. In this case, the discharge electrodes EA, EB are exposed to the plasma P until the EUV light source device 2 is able to perform the specified operation, and a certain degree of wear occurs to the discharge electrodes EA, EB.

Figure 6 is a schematic diagram showing an example of the configuration of the discharge electrodes mounted on the discharge plasma generating unit 1. Figure 6 shows a schematic perspective view of the discharge electrodes E (EA, EB) mounted on the discharge plasma generating unit 1.

To solve the above problems, the inventors have invented a configuration in which a layer of plasma raw material (plasma raw material layer) is provided in advance on the surfaces of the discharge electrodes EA, EB mounted on the discharge plasma generating unit 1, as shown in Figure 6. In other words, a plasma raw material layer made of plasma raw materials SA, SB is formed on at least a portion of the discharge electrodes EA, EB.

The area where the plasma raw material layer is formed includes the portion that is transported to the discharge region D of the discharge electrodes EA, EB. This makes it possible to generate EUV light of sufficient intensity, for example, even immediately after the discharge plasma generation unit 1 is installed. In addition, there is no need to perform a long break-in period to obtain the desired EUV light intensity, and wear on the discharge electrodes EA, EB can be reduced.

In this embodiment, a tin layer 40 (tin film) is formed as the plasma raw material layer.
One method for forming the tin layer 40 is to use a discharge. The discharge used to form the tin layer 40 is a discharge that is generated with weaker power than the discharge that generates the plasma P. As described above, in the EUV light source device 2, when the operation of generating EUV light continues, the intensity of the EUV light gradually increases. This is because a tin layer of sufficient thickness is formed on the surfaces of the discharge electrodes EA, EB exposed to the discharge that generates the plasma P.
The present inventors have found that a tin layer 40 is formed on the electrode surface even when using a discharge generated with a weaker power than the discharge that generates the plasma P. Utilizing this fact, a tin layer 40 is formed in advance on the surfaces of the discharge electrodes EA, EB.

When the tin layer 40 is formed using an electric discharge, the tin layer 40 is formed in the vicinity of the area exposed to the electric discharge. Therefore, by generating an electric discharge so as to include the area where the tin layer 40 is to be formed, it is possible to form the tin layer 40 at a desired position.
For example, the discharge electrode to be treated is supported so as to be rotatable, and the discharge electrode is rotated with a portion of the discharge electrode immersed in liquid tin. An auxiliary electrode for generating a weak discharge is disposed near the discharge electrode. Then, while the discharge electrode is rotating, a weak discharge is generated between the discharge electrode and the auxiliary electrode. As a result, a tin layer 40 is formed around the portion exposed to the discharge during the rotation.
In addition, the method for forming the plasma raw material layer is not limited, and any method capable of forming a plasma raw material layer on the surface of the discharge electrode may be used.

In this embodiment, the tin layer 40, which is the plasma raw material layer, is formed at least on the peripheral portion 10 of the discharge electrodes EA, EB. As described above, the peripheral portion 10 of the discharge electrodes EA, EB is the portion where the discharge electrodes EA, EB are closest to each other, and is the portion that passes through the discharge region D where the plasma P is generated. Therefore, by forming the tin layer 40 at least on the peripheral portion 10 of the discharge electrodes EA, EB, it is possible to stably supply the plasma raw material (tin layer 40) to the discharge region D.

6, a tin layer 40 is formed on the end face 11 that is the peripheral portion 10 of the discharge electrode E. This makes it possible for the discharge plasma generating unit 1 equipped with the discharge electrode E to supply a sufficient amount of plasma raw material (tin layer 40) to the discharge region D from the time of initial operation. As a result, it becomes possible to stably emit EUV light with sufficient intensity.
6, the tin layer 40 is also formed on the outer periphery of the side surface 12 of the discharge electrode E. By forming the tin layer 40 on the side surface 12 of the discharge electrode E in this manner, an effect of cooling the discharge electrode E exposed to the plasma P and an effect of reducing friction with the skimmer and reducing the load on the motor are exerted.

In this way, when unused or lightly used discharge electrodes EA, EB are used, a tin layer 40 is formed in advance on at least a portion of the discharge electrodes EA, EB.

The process of forming the tin layer 40 on the discharge electrodes EA, EB is performed, for example, with the discharge electrodes EA, EB attached to the discharge plasma generating unit 1. In this case, for example, the discharge plasma generating unit 1 is connected to a vacuum chamber for performing a weak discharge. Then, the tin layer 40 is formed by applying a weak discharge generated using an auxiliary electrode to each of the discharge electrodes EA, EB. When the tin layer 40 is formed with the electrodes attached to the discharge plasma generating unit 1, it becomes possible to adjust the positions of the skimmers SKA, SKB, etc.
Also, the discharge electrodes EA, EB on which the tin layer 40 has been formed in advance may be mounted on the discharge plasma generating unit 1. In this case, it becomes possible to treat each of the discharge electrodes EA, EB individually, and it becomes possible to configure, for example, a compact device for forming the tin layer 40.

The inventor mounted the discharge electrodes EA, EB, on which the tin layer 40 had been formed in advance, on the discharge plasma generation unit 1, and attached the unit to the EUV light source device 2. After that, when the EUV light source device 2 was operated, it was demonstrated that EUV light of sufficient intensity could be obtained even in the early stages of operation of the EUV light source device 2.

The inventors also investigated the relationship between the area of the plasma raw material layer (tin layer 40) in the peripheral portion 10 and the intensity of the EUV light. As a result, it was found that when the area of the plasma raw material layer formed in the peripheral portion 10 is 80% or more of the area of the peripheral portion 10, the intensity of the EUV light becomes the desired value. Therefore, it is preferable to set the area of the plasma raw material layer formed in the peripheral portion 10 to 80% or more of the area of the peripheral portion 10. This makes it possible to generate EUV light with the desired intensity from the initial operation of the EUV light source device 2.

The area of the plasma raw material layer is not limited to the above example. For example, even if a plasma raw material layer that is less than 80% of the area of the peripheral portion 10 is formed, it is possible to generate EUV light with a sufficiently high intensity, making it possible to sufficiently shorten the time for break-in operation, etc.

As described above, in the discharge plasma generation unit 1 according to this embodiment, a pair of disk-shaped discharge electrodes EA, EB and a pair of containers CA, CB that contain plasma raw materials SA, SB in a liquid phase are supported by the unit substrate 20. Each discharge electrode EA, EB is supported rotatably and positioned so that their peripheral edges face each other with a space between them. Each container CA, CB is positioned so as to supply plasma raw materials SA, SB to each discharge electrode EA, EB. This makes it possible to attach and detach each discharge electrode EA, EB and containers CA, CB as a whole while they are properly positioned, making it possible to facilitate maintenance of the EUV light source device 2 that generates plasma P from liquid phase plasma raw materials.

The main components of the mechanism that generates plasma P using the LDP method and extracts EUV light from the plasma P include a set of discharge electrodes, a container (plasma raw material), a skimmer, a motor, etc. In the light source device, by properly arranging these elements so that they are in a predetermined positional relationship with each other, it becomes possible to extract EUV light of the desired intensity in the desired direction.

However, attaching these elements to the light source device one by one while adjusting them to achieve the desired positional relationships is not an easy task and requires a certain level of skill. In addition, connecting them to other elements (for example, the mechanism for supplying power to the discharge electrodes EA, EB, the mechanism for supplying power to the motors MA, MB, the mechanism for supplying plasma raw materials SA, SB to the containers CA, CB, etc.) also takes time, which can increase the time required for maintenance work.

In contrast, in the discharge plasma generation unit 1 according to this embodiment, the unit substrate 20 supports the discharge electrodes EA, EB and the containers CA, CB integrally so that they are in the correct positional relationship. In addition, the unit substrate 20 also supports the motors MA, MB and the skimmers SKA, SKB. This makes it possible to attach the numerous elements required to extract EUV light from the plasma P integrally to the EUV light source device 2 while maintaining a predetermined positional relationship.

In addition, because the position of each element on the unit substrate 20 is predetermined, it is possible to easily connect each element included in the discharge plasma generation unit 1 to the other elements that make up the EUV light source device 2. This makes it possible to significantly reduce the work time required for maintenance and shorten the downtime of the EUV light source device 2.

Furthermore, a plasma raw material layer is formed in advance on the discharge electrodes EA, EB mounted on the discharge plasma generating unit 1. As a result, for example, when the EUV light source device 2 is operated after replacing the discharge plasma generating unit 1, it becomes possible to generate EUV light with sufficient intensity even in the early stages of operation. This further shortens the actual downtime, making it possible to operate the device efficiently.

[EUV light source device]
An example of the basic configuration and operation of the EUV light source device 2 will be described.
Fig. 7 is a schematic cross-sectional view showing the configuration of an EUV light source device 2 equipped with a discharge plasma generation unit 1. Fig. 7 shows a cross section taken horizontally inside a chamber and inside a connected chamber of an extreme ultraviolet light source device (EUV light source device 2). Note that an LDP type EUV light source device is taken as an example here.
In the following description, in order to facilitate understanding of the EUV light source device, some elements already described above will be described again with new reference numerals.

The EUV light source device 2 emits extreme ultraviolet light (EUV light). The wavelength of this extreme ultraviolet light is, for example, 13.5 nm. The EUV light corresponds to one embodiment of radiation according to the present invention.
The EUV light source device 2 irradiates liquid-phase plasma raw materials SA, SB supplied to the surfaces of a pair of discharge electrodes EA, EB, which generate a discharge, with an energy beam such as a laser beam LB, thereby vaporizing the plasma raw materials SA, SB. Thereafter, a plasma P is generated by discharge in a discharge region D between the discharge electrodes EA, EB. EUV light is emitted from the plasma P.

The EUV light source device 2 can be used, for example, as a light source device for a lithography apparatus in semiconductor device manufacturing, or as a light source device for an inspection apparatus for a mask used in lithography.
For example, when the EUV light source device 2 is used as a light source device for a mask inspection device, a portion of the EUV light emitted from the plasma P is extracted and guided to the mask inspection device.
The mask inspection device performs mask blank inspection or pattern inspection using the EUV light emitted from the EUV light source device 2 as inspection light. By using EUV light, it is possible to support 5 nm to 7 nm processes. The EUV light extracted from the EUV light source device 2 is regulated by an opening (not shown) provided in the heat shield 65 in FIG. 7.

As shown in FIG. 7, the EUV light source device 2 has a light source unit 52 and a debris trap unit 53 .
The light source section 52 generates EUV light based on the LDP method. Here, the light source section 52 is configured using the discharge plasma generation unit 1 described above.
The debris trap 53 is a debris mitigation device that traps debris that is scattered together with the EUV light emitted from the light source 52. Debris generated by the light source 52 and debris captured by the debris trap 53 are stored in a debris storage unit (not shown) located below the debris trap 53.

The light source unit 52 includes a chamber 54 that isolates the plasma P generated inside from the outside. The chamber 54 forms a plasma generation chamber that houses the light source unit 52 that generates the plasma P.
In the present embodiment, the chamber 54 is an example of a housing for the light source device.
The chamber 54 is a rigid vacuum housing made, for example, of metal, and its interior is maintained at a reduced pressure of a predetermined pressure or less by a vacuum pump (not shown) in order to effectively generate discharges for heating and exciting the plasma raw materials SA, SB and to suppress attenuation of the EUV light.

The discharge plasma generation unit 1 described with reference to Figures 2 and 3 is attached to the chamber 54 of the light source section 52. Therefore, a pair of discharge electrodes EA, EB, a container CA in which liquid-phase plasma raw material SA is stored, and a container CB in which liquid-phase plasma raw material SB is stored are arranged inside the chamber 54. In addition, motors MA, MB are arranged outside the chamber 54.
In addition, the skimmers SKA and SKB are omitted from FIG.

As shown in FIG. 7, the EUV light source device 2 further includes a control unit 55 , a pulsed power supply unit 56 , a laser source (energy beam irradiation device) 57 , and a movable mirror 58 .
The control unit 55 , the pulsed power supply unit 56 , the laser source 57 and the movable mirror 58 are installed outside the chamber 54 .
The control unit 55 controls the operation of each unit of the EUV light source device 2. For example, the control unit 55 controls the rotational drive of the motors MA, MB to rotate the discharge electrodes EA, EB at a predetermined rotation speed. The control unit 55 also controls the operation of the pulsed power supply unit 56, the irradiation timing of the laser beam LB from the laser source 57, etc.

Two power supply lines QA, QB extending from the pulsed power supply unit 56 pass through feedthroughs FA, FB and are connected to containers CA, CB arranged inside the chamber 54, respectively.
The feedthroughs FA and FB are sealing members that are embedded in the walls of the chamber 54 to maintain the reduced pressure atmosphere within the chamber 54 .
The containers CA, CB are made of a conductive material, and the plasma raw materials SA, SB contained inside the containers CA, CB are also made of a conductive material such as tin.
The lower portions of the discharge electrodes EA, EB are immersed in the plasma raw materials SA, SB contained inside each container CA, CB. Therefore, when pulsed power is supplied from the pulsed power supply unit 56 to the containers CA, CB, the pulsed power is supplied to the discharge electrodes EA, EB via the plasma raw materials SA, SB, respectively.

The pulsed power supply unit 56 generates a discharge in the discharge region D by supplying pulsed power to the discharge electrodes EA, EB.
The plasma raw materials SA, SB are transported to the discharge region D based on the rotation of the discharge electrodes EA, EB, and are heated and excited by the current flowing between the discharge electrodes EA, EB during discharge, generating a plasma P that emits EUV light.

The laser source 57 irradiates an energy beam onto the plasma raw material SA attached to the discharge electrode EA transported to the discharge region D, thereby vaporizing the plasma raw material SA. The laser source 57 is, for example, a Nd:YVO ₄ (Neodymium-doped Yttrium Orthovanadate) laser device.
At this time, the laser source 57 emits a laser beam LB in the infrared region with a wavelength of 1064 nm. However, the energy beam irradiation device may be a device that emits an energy beam other than the laser beam LB, so long as it is capable of vaporizing the plasma raw material SA.

The laser beam LB emitted from the laser source 57 is guided to the movable mirror 58 via a focusing means including, for example, a focusing lens 59. The focusing means adjusts the spot diameter of the laser beam LB at the laser beam irradiation position on the discharge electrode EA. The focusing lens 59 and the movable mirror 58 are disposed outside the chamber 54.

The laser beam LB focused by the focusing lens 59 is reflected by the movable mirror 58, passes through a transparent window 60 provided in the side wall 54a of the chamber 54, and is irradiated onto the peripheral portion of the discharge electrode EA near the discharge region D. By adjusting the position of the movable mirror 58, the irradiation position of the laser beam LB on the discharge electrode EA is adjusted.

In order to facilitate irradiation of the peripheral portion of the discharge electrode EA near the discharge region D with the laser beam LB, the axes of the discharge electrodes EA, EB are not parallel.
The distance between the rotating shafts JA, JB is narrower on the motor MA, MB side and wider on the discharge electrode EA, EB side.
This allows the opposing surfaces of the discharge electrodes EA, EB to be brought closer together while the side opposite the opposing surfaces of the discharge electrodes EA, EB is moved away from the irradiation path of the laser beam LB, making it easier to irradiate the laser beam LB to the peripheral portion of the discharge electrode EA near the discharge region D.

The discharge electrode EB is disposed between the discharge electrode EA and the movable mirror 58 .
The laser beam LB reflected by the movable mirror 58 passes near the outer circumferential surface of the discharge electrode EB, and then reaches the outer circumferential surface of the discharge electrode EA.
At this time, the discharge electrode EB is retracted further toward the motor MB side (to the left in FIG. 7) than the discharge electrode EA so that the laser beam LB is not blocked by the discharge electrode EB.
The liquid-phase plasma raw material SA attached to the outer peripheral surface of the discharge electrode EA near the discharge region D is vaporized by irradiation with the laser beam LB and supplied to the discharge region D as gas-phase plasma raw material SA.

In order to generate plasma P in the discharge region D (to convert the gas-phase plasma raw material SA into plasma), the pulsed power supply unit 56 supplies power to the discharge electrodes EA, EB.
When the gas-phase plasma raw material SA is supplied to the discharge region D by irradiation with the laser beam LB, a discharge is generated between the discharge electrodes EA, EB in the discharge region D.
When a discharge occurs between the discharge electrodes EA, EB, the gas-phase plasma material SA in the discharge region D is heated and excited by the electric current, generating a plasma P. The EUV light radiated from the generated plasma P passes through a first window 61, which is a through-hole provided in the side wall 54b of the chamber 54, and enters the debris trap 53.

The debris trap 53 has a connection chamber 62 arranged on the side wall 54b of the chamber 54. The connection chamber 62 is a rigid body, for example a vacuum housing made of metal, and like the chamber 54, its interior is maintained at a reduced pressure below a predetermined pressure to suppress attenuation of the EUV light. The connection chamber 62 is connected between the chamber 54 and the utilization device 90 (for example a lithography device or a mask inspection device).

The internal space of the connecting chamber 62 communicates with the chamber 54 via the first window 61. The connecting chamber 62 has a second window 63 as a light extraction part that introduces the EUV light incident from the first window 61 to the utilization device 90. The second window 63 is a through hole of a predetermined shape formed in a side wall 62a of the connecting chamber 62.
The EUV light emitted from the plasma P in the discharge region D is introduced into the utilization device 90 through the first window 61 and the second window 63 .

On the other hand, debris is dispersed from the plasma P in various directions at high speed together with the EUV light.
The debris includes tin particles which are the plasma raw materials SA, SB, and material particles of the discharge electrodes EA, EB which are sputtered as the plasma P is generated.
These debris acquire large kinetic energy through the contraction and expansion processes of the plasma P. That is, the debris generated from the plasma P includes ions, neutral particles, and electrons that move at high speeds.
If such debris reaches utilization device 90, it may damage or contaminate the reflective coatings of optical elements within utilization device 90, reducing performance.

Therefore, in order to prevent the debris from entering the utilization device 90, a debris trap 53 for trapping the debris is provided in the connection chamber 62.
7, a rotary foil trap 64 having a plurality of foils and actively colliding the plurality of foils with debris by rotating is disposed as the debris trap unit 53. The rotary foil trap 64 is disposed inside the connection chamber 62 on the optical path of the EUV light traveling from the connection chamber 62 to the utilization device 90.
A fixed foil trap in which the positions of a plurality of foils are fixed may be arranged instead of the rotating foil trap 64. Alternatively, both the rotating foil trap 64 and the fixed foil trap may be provided.

<Other embodiments>
The present invention is not limited to the above-described embodiment, and various other embodiments can be realized.

The discharge plasma generating unit 1 described with reference to FIG. 5 etc. is configured as a unit that is attached to the chamber 54 from the outside. It is not limited to this, and it is also possible to configure the entire discharge plasma generating unit 1 to be placed inside the chamber 54, for example. In this case, a tray-shaped substrate or the like may be used as the unit substrate that supports the discharge electrode and the container. Besides this, the shape of the discharge plasma generating unit 1 is not limited.

A configuration has been described above in which the discharge plasma generating unit 1 includes skimmers SKA and SKB. The skimmers SKA and SKB do not necessarily have to be provided in the discharge plasma generating unit 1. For example, the skimmers SKA and SKB may be attached directly to the EUV light source device 2. Also, the skimmers SKA and SKB may not be provided, and the containers CA and CB may have the function of a skimmer.

The above describes a configuration in which the motors MA and MB are included in the discharge plasma generating unit 1. The motors MA and MB do not necessarily need to be provided in the discharge plasma generating unit 1. For example, a configuration in which the motor body is later attached to the rotating shafts JA and JB is also possible. Also, instead of a configuration in which the discharge electrodes are directly connected to the motors, the discharge electrodes may be rotated via a drive mechanism using gears, pulleys, etc. In this case, the motor is connected as the power source for the drive mechanism.

In the above, a configuration has been described in which the discharge electrodes EA, EB are inserted into the containers CA, CB, and the plasma raw materials SA, SB are supplied to the discharge electrodes EA, EB. The method of supplying the plasma raw materials from the containers CA, CB to the discharge electrodes EA, EB is not limited. For example, a configuration may be used in which the plasma raw materials are supplied by contacting the plasma raw materials taken out of the containers with the peripheral portions 10 of each electrode. Alternatively, a configuration may be used in which the plasma raw materials are dripped onto the surface of each electrode.

In this disclosure, in order to facilitate understanding of the explanation, the words "approximately", "almost", "approximately", etc. are used as appropriate. However, there is no clear difference between using the words "approximately", "almost", "approximately", etc. and not using them.
In other words, in the present disclosure, concepts that define shape, size, positional relationship, state, and the like, such as "center,""central,""uniform,""equal,""same,""orthogonal,""parallel,""symmetric,""extending,""axialdirection,""cylindrical,""cylindrical,""ring-shaped," and "annular," are concepts that include "substantially central,""substantiallycentral,""substantiallyuniform,""substantiallyequal,""substantially the same,""substantiallyorthogonal,""substantiallyparallel,""substantiallysymmetric,""substantiallyextending,""substantially axial direction,""substantiallycylindrical,""substantiallycylindrical,""substantiallyring-shaped,""substantiallyannular," and the like.
For example, this includes states that are included within a specified range (e.g., a range of ±10%) based on standards such as "perfectly centered,""perfectlycentral,""perfectlyuniform,""perfectlyequal,""perfectly the same,""perfectlyorthogonal,""perfectlyparallel,""perfectlysymmetrical,""perfectlyextended,""perfectlyaxial,""perfectlycylindrical,""perfectlycylindrical,""perfectlyring-shaped,""perfectlyannular," etc.
Therefore, even if the words "approximately", "almost", "roughly", etc. are not added, the concept may be included that can be expressed by adding "approximately", "almost", "approximately", etc. Conversely, a state expressed by adding "approximately", "almost", "approximately", etc. does not necessarily exclude a perfect state.

In this disclosure, expressions using "more than", such as "greater than A" and "smaller than A", are expressions that comprehensively include both concepts that include equivalent to A and concepts that do not include equivalent to A. For example, "greater than A" is not limited to cases that do not include equivalent to A, but also includes "A or greater". Furthermore, "smaller than A" is not limited to "less than A" but also includes "A or less".
When implementing the present invention, specific settings and the like may be appropriately adopted from the concepts included in "greater than A" and "smaller than A" so as to achieve the effects described above.

It is also possible to combine at least two of the characteristic features of the present invention described above. In other words, the various characteristic features described in each embodiment may be combined in any way, without distinction between the embodiments. Furthermore, the various effects described above are merely examples and are not limiting, and other effects may be achieved.

REFERENCE SIGNS LIST 1...Discharge plasma generation unit 2...EUV light source device EA, EB...Discharge electrode 10...Periphery CA, CB...Container 16...Storage section SA, SB...Plasma raw material MA, MB...Motor 20...Unit substrate 25...Unit side positioning section SKA, SKB...Skimmer 30...Fixing substrate 33...Opening 34...Device side positioning section 40...Tin layer

Claims (11)

A pair of discharge electrodes each having a disk shape;
A pair of containers each capable of housing a plasma raw material in a liquid phase;
a support member that rotatably supports the pair of discharge electrodes so that peripheral portions of the pair of discharge electrodes face each other with a space therebetween, and supports the pair of containers so that the plasma raw material is supplied to each of the pair of discharge electrodes,
The support member is
a member configured as a lid that closes an opening provided in an outer wall of a vacuum chamber from the outside, and that supports the pair of discharge electrodes and the pair of containers so as to be accommodated within the vacuum chamber,
a support surface facing the inside of the vacuum chamber, and an insert protruding annularly from the support surface and inserted into an outer wall of the vacuum chamber;
a discharge plasma generation unit that supports the pair of discharge electrodes and the pair of containers so that the pair of discharge electrodes and the pair of containers are contained in an area surrounded by the insertion portion when viewed from a first direction perpendicular to the support surface, and at least a portion of the pair of discharge electrodes and the pair of containers are contained in an area from the support surface to the tips of the insertion portion when viewed from a second direction perpendicular to the first direction. The discharge plasma generating unit according to claim 1,
the container has a storage section that opens upward and stores liquid-phase plasma raw material;
The support member supports the pair of containers such that at least a part of the discharge electrode is inserted into the accommodation part from above the corresponding container. The discharge plasma generating unit according to claim 2,
Further, a pair of thickness adjusting units are provided for adjusting the thickness of the plasma raw material adhered to the pair of discharge electrodes inserted into the storage portions of the pair of containers,
The support member supports the pair of thickness adjusting parts corresponding to the pair of discharge electrodes. The discharge plasma generating unit according to claim 3,
The pair of thickness adjusting parts are connected to the insertion part of the support member from an inner circumferential side. A discharge plasma generating unit according to any one of claims 1 to 3,
Further, a pair of rotary drive units are provided to rotate the pair of discharge electrodes around their respective central axes,
The support member supports the pair of discharge electrodes via the pair of rotation drive parts. A discharge plasma generating unit according to any one of claims 1 to 5,
The support member has a second positioning portion guided by a first positioning portion provided in the vacuum chamber. A discharge plasma generating unit according to any one of claims 1 to 6,
a plasma raw material layer made of the plasma raw material is formed on at least a part of the discharge electrode. The discharge plasma generating unit according to claim 7,
The plasma raw material contains tin,
The discharge electrode is made of tungsten. The discharge plasma generating unit according to claim 7,
the plasma raw material layer is formed at least on the peripheral portion of the discharge electrode. The discharge plasma generating unit according to claim 7,
an area of the plasma raw material layer formed in the peripheral portion being 80% or more of an area of the peripheral portion. A housing and
A unit that is detachably attached to the housing,
A pair of discharge electrodes each having a disk shape;
A pair of containers each capable of housing a plasma raw material in a liquid phase;
a support member that rotatably supports the pair of discharge electrodes so that peripheral portions of the pair of discharge electrodes face each other with a space therebetween, and supports the pair of containers so that the plasma raw material is supplied to each of the pair of discharge electrodes; and
a beam irradiation unit that irradiates an energy beam that vaporizes the plasma raw material supplied to the discharge electrode;
a power supply unit that supplies discharge power to generate a discharge plasma to the pair of discharge electrodes;
a raw material supply unit for supplying the plasma raw material to the pair of containers,
The support member is
a member configured as a lid that closes an opening provided in an outer wall of a vacuum chamber from the outside, and that supports the pair of discharge electrodes and the pair of containers so as to be accommodated within the vacuum chamber,
a support surface facing the inside of the vacuum chamber, and an insert protruding annularly from the support surface and inserted into an outer wall of the vacuum chamber;
a light source device that supports the pair of discharge electrodes and the pair of containers such that the pair of discharge electrodes and the pair of containers are contained in an area surrounded by the insertion portion when viewed from a first direction perpendicular to the support surface, and at least a portion of the pair of discharge electrodes and the pair of containers are contained in an area from the support surface to the tip of the insertion portion when viewed from a second direction perpendicular to the first direction.

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