JP6176138B2 - Debris reduction device - Google Patents

Description

  The present invention relates to a debris reduction device that protects a condenser mirror and the like from debris emitted from high-temperature plasma that is an extreme ultraviolet light source.

  As semiconductor integrated circuits are miniaturized and highly integrated, exposure light sources have been shortened, and as a next-generation semiconductor exposure light source, particularly extreme ultraviolet light (hereinafter referred to as EUV (Extreme Ultra Violet) light having a wavelength of 13.5 nm). Development of an extreme ultraviolet light source device (hereinafter also referred to as an EUV light source device) that emits light is also in progress.

There are several known methods for generating EUV light in an EUV light source device. One of them is a method of generating high-temperature plasma by heating and exciting extreme ultraviolet light radiation species (hereinafter referred to as EUV radiation species). There is a method for extracting EUV light from this high-temperature plasma.
EUV light source devices adopting such a method are roughly classified into LPP (Laser Produced Plasma) type EUV light source devices and DPP (Discharge Produced Plasma) type EUV light source devices, depending on the high temperature plasma generation method. It is done.

[DPP EUV light source device]
FIG. 6 is a diagram for simply explaining the DPP-type EUV light source device described in Patent Document 1. In FIG.
The EUV light source apparatus has a chamber 1 that is a discharge vessel. In the chamber 1, an EUV condensing unit that houses a discharge unit 1 a that houses a pair of disc-shaped discharge electrodes 2 a and 2 b, a foil trap 5, an EUV condensing mirror 9 that is a condensing optical means, and the like. Part 1b.
1c is a gas exhaust unit for exhausting the discharge part 1a and the EUV condensing part 1b to make the inside of the chamber 1 into a vacuum state.
2a and 2b are disk-shaped electrodes. The electrodes 2a and 2b are separated from each other by a predetermined interval, and rotate about the rotation shafts 16c and 16d by the rotation of the rotary motors 16a and 16b, respectively.
Reference numeral 14 denotes a high-temperature plasma raw material that emits EUV light having a wavelength of 13.5 nm. The high-temperature plasma raw material 14 is heated molten metal, for example, liquid tin (Sn), and is accommodated in the container 15.

The electrodes 2a and 2b are arranged so that a part of the electrodes 2a and 2b is immersed in a container 15 that accommodates the high temperature plasma raw material 14. The liquid high-temperature plasma raw material 14 placed on the surfaces of the electrodes 2a and 2b is transported to the discharge space as the electrodes 2a and 2b rotate. The high temperature plasma raw material 14 transported to the discharge space is irradiated with laser light 17 from a laser source 17a. The high temperature plasma raw material 14 irradiated with the laser beam 17 is vaporized.
In a state where the high temperature plasma raw material 14 is vaporized by the irradiation of the laser beam 17, pulse power is applied to the electrodes 2a and 2b from the power supply means 3 to start pulse discharge between the electrodes 2a and 2b. A plasma P is formed by the high temperature plasma raw material 14. When the plasma is heated and excited by a large current flowing at the time of discharge, the EUV is emitted from the high temperature plasma P.
The EUV light radiated from the high temperature plasma P is collected by the EUV collector mirror 9 at a condensing point (also referred to as an intermediate condensing point) f of the condensing mirror 9, and is emitted from the EUV light extraction unit 8 to the EUV light source device. The light enters the exposure device 40 indicated by the connected dotted line.

  The EUV collector mirror 9 generally has a structure in which a plurality of thin concave mirrors are arranged in a nested manner with high accuracy. The shape of the reflecting surface of each concave mirror is, for example, a spheroidal shape, a rotating paraboloid shape, or a Walter shape, and each concave mirror is a rotating body shape. Here, the Walter shape is a concave shape in which the light incident surface is composed of a rotation hyperboloid and a rotation ellipsoid, or a rotation hyperboloid and a rotation paraboloid in order from the light incidence side.

[LPP EUV light source device]
FIG. 7 is a diagram for simply explaining an LPP type EUV light source apparatus.
The LPP type EUV light source apparatus has a light source chamber 1. The light source chamber 1 is provided with a raw material supply unit 10 and a raw material supply nozzle 20 for supplying a raw material (high temperature plasma raw material) that is an EUV radiation species. From the raw material supply nozzle 20, for example, droplet-shaped tin (Sn) is released as a raw material.
The inside of the light source chamber 1 is maintained in a vacuum state by a gas exhaust unit 1c constituted by a vacuum pump or the like.

A laser beam (laser beam) 22 from an excitation laser beam generator 21 which is a laser beam irradiation unit is introduced into the chamber 10 through a laser beam incident window 23 while being collected by a laser beam focusing unit 24. The raw material (for example, droplet-shaped tin) emitted from the raw material supply nozzle 20 is irradiated through a laser beam passage hole 25 provided at a substantially central portion of the EUV collector mirror 9. The excitation laser beam generation device 21 used here is, for example, a pulse laser device with a repetition frequency of several kHz, and a carbon dioxide (CO ₂ ) laser, a YAG laser, or the like is used.

  The raw material supplied from the raw material supply nozzle 20 is heated and excited by irradiation with the laser light 22 to become high temperature plasma, and EUV light is emitted from this high temperature plasma. The emitted EUV light is reflected by the EUV collector mirror 9 toward the EUV light extraction unit, is collected at the condensing point (intermediate condensing point) of the EUV collector mirror, and is emitted from the EUV light extraction unit 8. Then, the light enters the exposure device 40 indicated by a dotted line connected to the EUV light source device.

Here, the EUV collector mirror 9 is a spherical reflecting mirror coated with, for example, a multilayer film of molybdenum and silicon. Depending on the arrangement of the excitation laser light generation device 21 and the laser light incident window 23, the laser light The passage hole 25 may not be required.
Further, the laser beam 22 for generating high temperature plasma may reach the EUV light extraction unit as stray light. Therefore, a spectral purity filter (not shown) that transmits EUV light and does not transmit laser light 22 may be disposed in front of the EUV light extraction unit (on the high-temperature plasma side).
[Debris reduction device (foil trap)]
In the EUV light source device described above, various debris is generated from the high temperature plasma P. This is caused by, for example, debris such as metal powder generated by sputtering of the metal (for example, a pair of disc-shaped discharge electrodes 2a and 2b) in contact with the high temperature plasma P or Sn which is the high temperature plasma raw material 14. To debris.
These debris obtains large kinetic energy through the process of plasma contraction and expansion. That is, debris generated from the high temperature plasma P is ions or neutral atoms that move at high speed, and such debris hits the EUV collector mirror 9 to scrape the reflective surface or deposit on the reflective surface. , Reducing the reflectivity of EUV light.

  Therefore, in the EUV light source device, in order to prevent damage to the EUV collector mirror 9 between the discharge part 1a and the EUV collector mirror 9 accommodated in the EUV light collector 1b, a debris reduction device: (Hereinafter also referred to as DMT). For example, a foil trap 5 is used as the DMT. The foil trap 5 functions to capture debris as described above and allow only EUV light to pass through.

An example of the foil trap is shown in Patent Literature 2 and Patent Literature 3, and is described as “Foil Trap” in Patent Literature 3.
FIG. 8 shows a schematic configuration of a foil trap as disclosed in Patent Document 2.
The foil trap 5 is composed of a plurality of thin films (foil) or thin flat plates (plates) (hereinafter referred to as radial centers) radially arranged around the central axis of the foil trap 5 (in FIG. 8, coincident with the optical axis of EUV light). The thin film and the flat plate are collectively referred to as “foil 5a”), a concentric outer ring 5c that supports the plurality of foils 5a, and a ring-shaped support body of the central column 5b.
The foil 5a is arranged and supported so that its plane is parallel to the optical axis of the EUV light. Therefore, when the foil trap 5 is viewed from the extreme ultraviolet light source (high temperature plasma) side, only the thickness of the foil 5a can be seen except for the support portion of the central support column 5b and the outer ring 5c. Therefore, most of the EUV light from the high temperature plasma P can pass through the foil trap 5.

  On the other hand, the plurality of foils 5a of the foil trap 5 function to increase the pressure by decreasing the conductance of the portion by finely dividing the arranged space. Therefore, the speed of debris from the high temperature plasma P decreases because the collision probability increases in a region where the pressure is increased by the foil trap 5. Some debris with reduced velocity is captured by the foil or foil support.

In the DPP EUV light source device, light on the optical axis (light emitted from the high-temperature plasma P at an angle of 0 ° (radiation angle is 0 °)) or a concave mirror located on the innermost side of the EUV collector mirror The light incident on the EUV mirror at an incident angle smaller than the angle at which light can be reflected (hereinafter also referred to as the minimum incident angle) is not used for the exposure, but is preferably not present. For this reason, there is no problem even if the central column 5c exists, and the central column 5b may actively shield the light. The central column 5b has a cone shape because it has a shape that blocks light having a minimum incident angle determined by the configuration of the EUV collector mirror. Therefore, hereinafter, the central support column is also referred to as a cone.
In addition, since the foil trap 5 is arrange | positioned near high temperature plasma, the heat load received is also large. Therefore, the foil 5a and the cone 5b constituting the foil trap 5 are formed of a high heat resistant material such as molybdenum (Mo), for example.

  The above-described foil trap is often employed mainly for DPP type EUV light source devices. In the case of an LPP type EUV light source device, the collision direction to the EUV collector mirror is controlled by controlling the debris traveling direction by a magnetic field, or the debris adhering to the EUV collector mirror is removed by a cleaning gas such as hydrogen gas. doing. However, as shown in FIG. 7, a foil trap as described above may be disposed between the high temperature plasma and the EUV collector mirror. That is, the foil trap can be employed not only in the DPP type EUV light source device but also in the LPP type EUV light source device.

[Rotating foil trap, fixed foil trap]
In recent years, as described in Patent Document 4, two foil traps are provided in series, and one foil trap is rotated.
FIG. 9 shows a schematic configuration. In the example shown in FIG. 9, the foil trap closer to the high temperature plasma P has a function of rotating. Hereinafter, the foil trap having the rotating function is also referred to as a rotary foil trap, and the non-rotating fixed foil trap is also referred to as a fixed foil trap.

In the rotary foil trap 4, a cone 4 b (center column) is connected coaxially with a rotation shaft of a rotation mechanism (not shown). When the rotating shaft of the rotating mechanism rotates, the rotary foil trap 4 rotates around the rotating shaft of the cone 4b.
Each foil 4a of the rotary foil trap 4 is fixed to the cone 4b by, for example, brazing using a gold solder, and each foil 4a extends radially around the rotation axis of the cone 4b. Since the rotary foil trap 4 only needs to be fixed to the cone 4b, the outer ring as shown in FIG. 8 need not be provided.

  The rotary foil trap 4 captures debris flying from the plasma P when a plurality of foils 4a rotate around the rotation axis of the cone 4b. For example, debris caused by Sn, which is a high-temperature plasma raw material, is captured by each foil 4a of the rotary foil trap 4 or deflected so that the traveling direction is different from the EUV collector 9 side. That is, accumulation of debris on each concave mirror of the EUV collector mirror 9 is suppressed by using the rotary foil trap 4.

  The fixed foil trap 5 captures debris that travels at a high speed that could not be captured by the rotary foil trap 4. Since the debris collision probability increases in the region where the pressure is increased by the fixed foil trap 5, the speed of the debris moving at a high speed decreases. Some debris with reduced speed is captured by the foil 5a or the support of the foil 5a. That is, sputtering by high-speed debris of each concave mirror of the EUV collector mirror 9 is suppressed by using the fixed foil trap 5. If necessary, the cone 5b of the fixed foil trap 5 may also be cooled.

  In the example shown in FIG. 9, since the rotary foil trap faces the high temperature plasma, the rotary foil trap 4 is heated by the high temperature plasma P or heated by debris colliding. Therefore, the heat load received by the rotary foil trap 4 is high. Therefore, the rotary foil trap 4 normally cools the cone 4b by providing a cooling pipe inside the cone 4b and flowing a coolant such as water through the cooling pipe. Since the foil 4a is directly fixed to the cone 4b by brazing or the like, it is thermally connected to the cone 4b. Therefore, by cooling the cone 4b, the foil is also cooled.

Although each foil 4a of the rotary foil trap 4 is cooled, the temperature of each foil 4a is higher than 250 ° C., which is the melting point of tin (Sn), which is a high-temperature plasma raw material.
Therefore, the debris caused by Sn trapped in the foil is eventually liquefied and moved radially along each foil by the centrifugal force generated by the rotation of the rotary foil trap and detached from the outer periphery of each foil. become.

The liquefied debris that is separated from each foil 4a of the rotary foil trap 4 by centrifugal force is scattered undesirably, contaminating the inside of the chamber, or depositing a part of EUV emitted from the high temperature plasma at a position where it is shielded from light. In order to avoid this problem, as shown in Patent Document 5, a cover member that surrounds the rotary foil trap is provided on the outer periphery of the rotary foil trap 4.
FIG. 10 shows a rotary foil trap provided with a cover member. The cover member 11 captures and collects liquefied debris (debris caused by Sn) detached from the outer edge of the rotary foil trap 4. The collected debris is discharged from the debris discharge port 11a. Therefore, debris does not adhere to an undesired portion in the chamber.
The cover member 11 has openings 11b and 11c, and the size of the openings 11b and 11c is a condensing range (condensing angle) of an EUV collector mirror located at the rear stage of the DMT (on the EUV emission side of the DMT). ) Is set to a size that does not block the radiation of EUV light from the high-temperature plasma P that travels inside. That is, since the cover member 11 is provided outside the condensing range (condensing angle) by the EUV collector mirror 9, EUV condensed by the EUV collector mirror 9 is shielded by the cover member 11 described above. There is no.

Special table 2007-505460 gazette JP-T-2002-504746 Special table 2004-214656 gazette Special table 2012-513653 gazette International Publication No. 2010/072429

As the input power to the high temperature plasma increases, the heat load applied to the foil trap also increases. In particular, overheating of the cover member 11 disposed so as to surround the rotary foil trap 4 (hereinafter also referred to as “Rotary Foil Trap: RFT”) becomes a problem.
As described above, the cover member 11 is for collecting debris (tin) ejected by the centrifugal force of RFT and discharging it out of the foil trap. The above-described cover member 11 is heated by the heater 12 as shown in FIG. 10 in order to melt tin from the captured RFT, and the temperature is always kept above the melting point of tin. Therefore, as shown in FIG. 10, the debris (tin) captured inside the cover member 11 is liquefied and moves along the inner surface of the cover member, and the debris (tin) discharge port 11a (hereinafter, tin discharge) It is also discharged from the outlet).

  During EUV light emission (while high temperature plasma is being generated), the cover member 11 is also subjected to a thermal load from the high temperature plasma, so the heater heating power is weakened to adjust the temperature of the cover member. However, as the input power to the plasma increases and the thermal load from the high temperature plasma to the cover member 11 increases, even if the heater heating is completely stopped, the temperature of the cover member 11 becomes a temperature equal to or higher than the melting point of tin. Adjustment becomes impossible.

It is known that the cover member is made of, for example, stainless steel, and reacts with tin when the temperature rises to form (Fe, Cr) Sn _{2 —} crystal having a high melting point. When this is formed at the tin discharge port of the cover member 11, the tin discharge port is closed and tin is deposited inside the cover member. The deposited tin eventually comes into contact with the rotating RFT, and may damage the RFT and the RFT drive mechanism that rotates the RFT (not shown).

On the other hand, when the cover member 11 is overheated, the cover member 11 is deformed by thermal expansion. The set temperature range of the temperature of the cover member 11 by heating the heater is set to, for example, about 300 to 400 ° C. in consideration of the melting point of tin. The influence of the thermal expansion of the cover member 11 in this temperature range is taken into consideration at the time of design. However, when the temperature of the cover member 11 exceeds this temperature range, the distance between the cover member 11 and the RFT is further increased, and the conductance is increased. Change. Specifically, it has been confirmed by simulation that the gas pressure decreases and the debris reduction effect deteriorates.
Therefore, overheating of the cover member 11 must be avoided. For this purpose, it is conceivable to provide a cooling mechanism for cooling the cover member 11. As the cooling mechanism, for example, a structure in which a pipe through which the refrigerant passes is brought into contact with the cover member and heat is exchanged between the cover member 11 and the refrigerant is employed.
However, water cannot be used as a coolant to cool the cover member 11 so that the temperature of the cover member 11 is maintained above the melting point of tin. A method of cooling by circulating gas as a refrigerant in the pipe is also conceivable, but it is not easy because heat exchange efficiency is low and space is limited.
The present invention solves the above problems, the purpose of the present invention is to prevent the cover member surrounding the rotary foil trap from overheating, thereby suppressing the reaction between tin and the cover member, Further, the thermal expansion of the cover member is reduced to suppress the pressure drop inside the cover member.

In the EUV light source device described above, the high temperature plasma and the debris reduction device are disposed with a space therebetween, and a thermal load is applied to the rotary foil trap of the debris reduction device, its cover member, and the like by radiation from the high temperature plasma. Therefore, the light that travels in the light collection range of the light collecting mirror is a region outside the light collection range of the EUV light collecting mirror disposed in the subsequent stage of the debris reduction device, and between the high temperature plasma and the cover member. A shielding member that has an opening to pass through and shields radiation from the plasma from reaching the cover member is disposed. Thereby, the thermal load added to the said cover member can be suppressed.
Here, the shielding member is heated, and the cover member and the like are secondarily heated by radiation from the heated shielding member. Therefore, a heat shielding member is provided between the shielding member and the cover member. Thereby, the radiation from the said shielding member can be interrupted and the heat input to a cover member can be prevented.
That is, in the present invention, the above problem is solved as follows.
(1) Arranged between a plasma and a condensing mirror that collects light emitted from the plasma, and provided with a plurality of foils extending radially from a main axis, the light passes through but debris from the plasma is captured. A debris reduction apparatus comprising a foil trap that surrounds the foil trap and a cover member that is disposed outside the light collection range of the light collecting mirror, and the light collecting is provided between the plasma and the cover member. A shielding member is provided that has an opening through which light traveling in the light collection range of the mirror passes and shields radiation from the plasma from reaching the cover member, and between the shielding member and the cover member, A heat shielding member for suppressing heat radiation from the shielding member to the cover member is provided.
(2) In the above (1), the material of the shielding member is molybdenum, tungsten, and molybdenum or an alloy containing tungsten.
(3) In said (1) and (2), the said shielding member is electrically connected with the vacuum vessel in which the debris reduction apparatus main body or the debris reduction apparatus is accommodated.
(4) In the above (1), (2), and (3), the shielding member includes a groove and / or a projection for guiding tin emitted from the plasma and deposited on the shielding member to form droplets.
(5) In the above (1), (2), (3), and (4), the surface area on the debris reducing device side of the shielding member is larger than the surface area on the plasma side.

In the present invention, the following effects can be obtained.
(1) By providing a shielding member between the plasma and the cover member that covers the outer periphery of the rotating foil trap, the cover member can be prevented from being overheated by radiation from the plasma. Further, by providing a heat shielding member between the shielding member and the cover member, heat input to the cover member due to radiation from the heated shielding member is prevented, and the cover member is secondarily overheated. Can be prevented.
As a result, the reaction between tin and the cover member can be suppressed, and the thermal expansion of the cover member is reduced, so that the pressure drop inside the cover member is also suppressed.
(2) When the shielding member is formed of molybdenum, tungsten, and a refractory metal of molybdenum or an alloy containing tungsten, even if the cover member is exposed to high temperature due to radiation from plasma, problems such as melting Can prevent it from happening.
(3) When a potential difference is generated between the shielding member and the cover member, a discharge is generated there. The inside of the cover member and the foil trap is particularly susceptible to discharge because the gas pressure is high to prevent debris. If a discharge occurs here, debris is generated secondarily by sputtering and must be avoided. Therefore, the shielding member is composed of a conductive member such as a refractory metal as described above, and the shielding member is set to the ground potential, and is set to the same potential as the chamber and the debris reduction member body that are set to the ground potential. , Discharge between these can be prevented.
(4) Tin that is emitted together with light from the plasma accumulates on the shielding member. The deposited tin melts when the shielding member reaches a temperature equal to or higher than the melting point of tin due to radiation from the plasma. Eventually, the tin that has become droplets travels along the surface of the shielding member due to gravity and collects at the bottom of the shielding member, but the shielding member is provided with grooves and protrusions to guide the tin that has become droplets. Thus, it is possible to prevent the tin droplet from blocking the condensing range of the EUV collector mirror or falling into the foil trap.
(5) The shielding member is overheated by the radiation from the plasma and becomes a high temperature, and secondary heat radiation by the radiation from the shielding member may reach the plasma generation unit. Therefore, by providing irregularities on the debris reducing device side of the shielding member closest to the plasma and making the surface area larger than the plasma side, radiation emitted to the plasma side can be reduced. In addition, although the radiation to the debris reduction apparatus side will increase correspondingly, the radiation to the cover member can be reduced by providing a heat shielding member between the shielding member and the cover member.

It is a figure which shows schematic structure figure of the debris reduction apparatus (DMT) of the Example of this invention. It is a figure which shows the other Example of this invention which provided two or more heat shielding members. It is a figure which shows the modification of a debris reduction apparatus provided with a heat shielding member. It is a figure which shows the modification (1) of a shielding member. It is a figure which shows the modification (2) of a shielding member. It is a figure for demonstrating briefly the EUV light source device of a DPP system. It is a figure for demonstrating briefly the LPP type EUV light source device. It is a figure which shows schematic structure of a foil trap. It is a figure which shows the structure at the time of providing two foil traps in series and using one foil trap as a rotary foil trap. It is a figure which shows the rotary foil trap which provided the cover member.

  FIG. 1 shows a schematic configuration diagram of a debris reduction device (hereinafter also referred to as DMT) of an embodiment of the present invention. The DMT main body of the present embodiment is composed of a rotary foil trap (hereinafter also referred to as RFT) 4, a cover member 11 surrounding the rotary foil trap (hereinafter also referred to as RFT), and a fixed foil trap (not shown) disposed on the EUV emission side of RFT4. . Note that the fixed foil trap may be omitted as appropriate.

The cover member 11 has the openings 11b and 11c as described above, and the size of the openings 11b and 11c is the condensing range of the EUV collector mirror located at the rear stage of the DMT (the EUV emission side of the DMT). The size is set so as not to block the radiation of EUV light from the high-temperature plasma P traveling in the (condensing angle).
Temperature sensors 12a for sensing the temperature of the cover member 11 are provided at various locations outside the cover member 11 (for ease of understanding, only one temperature sensor 12a is shown in FIG. 1). The temperature information signal of the cover member 11 sent from the temperature sensor 12a is input to the temperature control unit 12b. The temperature control unit 12b that has received the temperature information signal adjusts the heater 12 that heats the cover member 11 so that the temperature of the cover member 11 surrounding the RFT 4 is equal to or higher than the melting point of tin.

  In the DMT (debris reduction device) of the present invention, a shielding member 6 is provided between the high temperature plasma P and the cover member 11 to shield radiation (thermal radiation) from the high temperature plasma P from reaching the cover member 11. Provided. The shielding member 6 is made of molybdenum, tungsten, and an alloy containing molybdenum or tungsten, and has an opening 6a. The size of the opening 6a shields the radiation of EUV light from the high-temperature plasma P that travels within the condensing range (condensing angle) of the EUV condensing mirror located at the subsequent stage of the DMT (on the EUV emission side of the DMT). The size is not set.

  As described above, the cover member 11 is disposed outside the condensing range of the EUV condensing mirror located at the rear stage of the DMT. Therefore, the shielding member 6 of the present invention is located between the high temperature plasma P and the cover member 11, and the solid angle when the shielding member 6 is viewed from the plasma P is the cover from the plasma P without the shielding member 6. It is larger than the solid angle when the member 11 is viewed. Thus, the radiation from the plasma P is blocked by the shielding member 6 without directly reaching the cover member 11.

Here, since the shielding member 6 receives radiation from the high temperature plasma P and becomes high temperature, the cover member 11 is disposed behind the shielding member 6 (on the side opposite to the surface facing the high temperature plasma P of the shielding member 6). Then, the cover member 11 is secondarily heated by the radiation from the shielding member 6 that has become high temperature, and is overheated.
In order to suppress the influence of such secondary heating from the shielding member 6, in this embodiment, the thermal shielding is provided between the shielding member 6 and the cover member 11 that are directly exposed to radiation from the high temperature plasma P. The member 7 is arranged. Similar to the shielding member 6, the thermal shielding member 7 can be made of molybdenum, tungsten, and any of molybdenum or an alloy containing tungsten.

Similar to the shielding member 6, the thermal shielding member 7 has an opening 7a, and the opening 7a, like the opening 6a, is a condensing range of the EUV collector mirror located at the rear stage of the DMT (DUV EUV emission side). The size is set so as not to block the radiation of EUV light from the high-temperature plasma P traveling in (condensing angle). In addition, since the heat shielding member 7 is disposed at the subsequent stage of the shielding member 6, the size of the opening 7 a of the heat shielding member 7 is larger than the size of the opening 6 a of the shielding member 6.
Since the heat shielding member 7 is disposed relatively close to the shielding member 6, the heat shielding member 7 on the surface side facing the back surface (the surface opposite to the surface facing the high temperature plasma P) of the shielding member 6. Most of the heat radiation from the shielding member 6 heated by receiving radiation from the high temperature plasma P is incident on the surface.

However, compared with the energy of radiation from the high temperature plasma P received by the first shielding member 6, the energy of the heat radiation emitted from the shielding member 6 heated by the radiation from the high temperature plasma P is small. Therefore, by providing the heat shielding member 7 as shown in FIG. 1, the heat radiation reaching the cover member 11 can be mitigated.
When a potential difference is generated between the shielding member 6, the heat shielding member 7, and the cover member 11, a discharge is generated there. Since the cover member 11 and the foil trap 4 have a high gas pressure to prevent debris, discharge is particularly likely to occur. If a discharge occurs here, debris is generated secondarily by sputtering and must be avoided.
Therefore, as shown in FIG. 1, it is desirable to set the shielding member 6 and the thermal shielding member 7 to the ground potential. Since the cover member 11 and the debris reducing device main body, the chamber (vacuum container) in which these are housed, are normally grounded and at ground potential, the shielding member 6 and the heat shielding member 7 are housed in the above debris reducing device main body. By connecting them electrically to a chamber and setting them to the ground potential, they can be set to the same potential, and discharge between them can be prevented.

As described above, in this embodiment, since the shielding member 6 is provided between the plasma P and the cover member 11 covering the outer periphery of the rotating foil trap 4, the cover member 11 is overheated by the radiation from the plasma P. Can be prevented. In addition, since the heat shielding member 7 is disposed between the shielding member 6 and the cover member 11, even if the shielding member 6 reaches a high temperature, heat radiation reaching the cover member 11 from the shielding member 6 can be reduced. it can.
For this reason, it can prevent that the cover member 11 is overheated by the radiation | emission from the plasma P, and can suppress reaction with tin and the cover member 11. FIG.
Further, since the thermal expansion of the cover member 11 is also reduced, as described above, the cover member 11 is deformed by the thermal expansion, the distance between the cover member 11 and the RFT 4 is further widened, the gas pressure is reduced, and debris is reduced. It is possible to prevent the problem that the effect is deteriorated.

  FIG. 2 shows another embodiment of the present invention. The DMT in this embodiment is provided with a plurality of heat shielding members. As described above, since the shielding member 6 receives the radiation from the high temperature plasma P and becomes high temperature, the member located behind the shielding member 6 is secondarily heated by the radiation from the shielding member 6 that has become high temperature. And may overheat. In order to suppress the influence of such secondary heating from the shielding member 6, in the present embodiment, there are a plurality of gaps between the shielding member 6 and the cover member 11 that are directly exposed to radiation from the high temperature plasma P. The heat shielding members 71 and 72 are arranged. Other configurations are the same as those shown in FIG. 1, and the same components are denoted by the same reference numerals.

Both heat shielding members 71 and 72 have an opening 7a. Since the heat shielding members 71 and 72 are arranged at the subsequent stage of the shielding member 6, the size of the opening 7 a of the heat shielding member 71 is larger than the size of the opening 6 a of the shielding member 6, and the opening of the heat shielding member 72. The size of the portion 7 a is larger than the size of the opening 7 a of the heat shielding member 72.
Further, since the heat shielding member 71 is disposed relatively close to the shielding member 6, the heat shielding member on the surface side facing the back surface (the surface opposite to the surface facing the high temperature plasma P) of the shielding member 6. Most of the heat radiation from the shielding member 6 is incident on the surface 71, and similarly, the heat shielding member 72 is disposed relatively close to the heat shielding member 71. , Most of the heat radiation from the heat shielding member 71 is incident.

  However, compared with the energy of the radiation from the high-temperature plasma P received by the shielding member 6, the energy of the thermal radiation emitted from the shielding member 6 is small. Further, the energy of heat radiation emitted from the heat shielding member 71 is smaller than the energy of heat radiation from the shielding member 6 received by the heat shielding member 71. Therefore, in comparison with the DMT of the present invention shown in FIG. 1, in the case of the DMT having the plurality of heat shielding members 71 and 72 shown in FIG. 2, the heat radiation reaching the cover member 11 can be further alleviated.

FIG. 3 is a view showing a modification of the debris reduction device (DMT) provided with a heat shielding member.
In FIG. 3, the heater, the temperature sensor, the temperature control unit, and the like that heat the cover member 11 are omitted.
In the embodiment shown in FIG. 3, the shielding member 6 and the thermal shielding member 73 are provided in the DMT, and the thermal shielding member 73 facing the cover member 11 is enlarged so as to surround almost the entire cover member 11. It is.
By configuring the heat shielding member 73 as described above, the secondary radiation emitted from the surface of the heat shielding member 73 facing the cover member 11 is incident relatively uniformly over the entire cover member 11. To do. Therefore, it is possible to reduce the local high temperature portion in the cover member 11 heated by the radiation from the heat shielding member 73. That is, it is possible to suppress the occurrence of thermal deformation of the cover member 11 due to the local high temperature portion.

Here, since the cover member 11 of the present invention shown in the above embodiment surrounds the RFT 4 that is a rotating body, the outer shape viewed from the direction facing the high temperature plasma P side is circular. Therefore, the shielding member 6 and the heat shielding members 7, 71, 72 of the present invention are plate-like, and the shape seen from the above direction can be a simple annular shape. Further, as described above, the annular shield member 6, the heat shield members 7, 71, 72 and the openings 6a, 7a provided in the heat shield member 73 are disposed between the high temperature plasma P and the DMT. In this case, the EUV radiation from the high-temperature plasma P traveling in the condensing range (condensing angle) of the EUV condensing mirror located at the subsequent stage of the DMT is set to a size that does not block the EUV radiation.
The shielding member 6 and the thermal shielding members 7, 71, 72, 73 of the present invention are of a size that does not shield EUV radiation from the high-temperature plasma P that travels within the condensing range (condensing angle) of the EUV collector mirror. If the openings 6a and 7a set to be secured, it is not always necessary to form an annular shape.

In FIG. 4, the modification of the structure of the shielding member of this invention is shown. 4A shows a view of the shielding member 6 viewed from the plasma P side, and FIG. 4B is a cross-sectional view taken along line AA in FIG. 4A.
In the present embodiment, grooves and / or protrusions for guiding tin are provided on the surface of the shielding member 6 facing the high temperature plasma P.
FIG. 4 shows an example of the structure, and the outer periphery of the opening 6a set to a size that does not block the EUV radiation from the high-temperature plasma P that travels within the condensing range (condensing angle) of the EUV collector mirror. The case where the groove part 6b is provided in the part is shown.

Part of debris (tin) from the high temperature plasma P is deposited on the entire surface of the shielding member 6 facing the high temperature plasma P. Due to the radiation from the high temperature plasma P, the temperature of the shielding member 6 easily reaches the melting point of tin or more, and the tin deposited on the shielding member surface is melted. Although tin that has become droplets due to gravity moves downward, as shown in FIG. 4, by providing the groove 6b on the surface, tin that has become droplets does not cross the opening 6a. be able to. In addition, a protrusion may be provided instead of the groove 6b, or both the groove and the protrusion may be provided. In short, a channel for preventing droplets of tin from crossing the opening 6a is provided in the opening 6a. What is necessary is just to form in a periphery.
In addition, the protrusion part 6c is provided in the lower part of the shielding member 6 shown in FIG. The debris (tin) deposited and liquefied on the surface of the shielding member 6 moves downward through the surface of the shielding member 6, the groove 6b, etc., but as shown in FIG. By providing 6c, the liquefied debris collects in the said protrusion part 6c, and falls below it.
For this reason, the liquefied debris can be collected and collected in one place, and debris can be easily collected.

In FIG. 5, the modification of the structure of the shielding member 6 of this invention is shown. As described above, the secondary heating to the cover member 11 due to radiation from the first shielding member 6 is performed by the heat shielding member (the heat shielding member 7 in FIG. 1, the heat shielding members 71 and 72 in FIG. 3 can be avoided by introducing a heat shielding member 73) surrounding the entire cover member. However, the radiation from the shielding member 6 extends not only to the cover member side but also to structural members such as electrodes that generate high-temperature plasma P, and may cause a drift in the EUV emission point.
The shielding member 6 shown in FIG. 5 has a concavo-convex portion 6d formed on the surface facing the debris reduction device (DMT) in order to cope with such a problem. 5A is a view of the shielding member 6 viewed from the plasma P side, FIG. 5B is a cross-sectional view taken along the line BB in FIG. 5C, and FIG. 5C is the DMT side of the shielding member 6. It is the figure seen from the (cover member side).

  As shown in FIG. 5, an uneven part 6d is formed on the surface of the shielding member 6 facing the DMT (the surface facing the cover member 11), and the surface area of the surface is increased, so that the shielding member 6 moves toward the plasma P side. Relative radiation can be reduced. Although the radiation to the cover member side is relatively increased, as described above, by arranging the heat shielding member between the shielding member 6 and the cover member 11 shown in FIG. 5, the secondary due to the radiation to the shielding member 6 is achieved. The influence on the cover member 11 such as heating can be reduced.

DESCRIPTION OF SYMBOLS 1 Chamber 1a Discharge part 1b EUV condensing part 1c Gas exhaust unit 2a, 2b Discharge electrode 3 Power supply means 4 Rotary foil trap (RFT)
4a, foil 4b, central strut 5, foil trap 6, shielding member 6a, opening 6b, groove 6c, protrusion 6d, uneven portion 7, thermal shielding member 71, thermal shielding member 72, thermal shielding member 73, thermal shielding member 7a, opening 8 EUV light extraction part 9, EUV light collection Mirror 10 Raw material supply unit 11 Cover member 11a Debris (tin) discharge ports 11b and 11c Opening 12 Heater 12a Temperature sensor 12b Temperature control unit 14 High-temperature plasma raw material 15 Containers 16a and 16b Rotating motors 16c and 16d Rotating shaft
17 Laser light 17a Laser source 20 Raw material supply nozzle 21 Laser light generator for excitation 22 Laser light 23 Laser light incident window 24 Laser light condensing means 40 Exposure machine P Plasma

Claims (5)

A foil trap disposed between a plasma and a condensing mirror that collects light emitted from the plasma, and includes a plurality of foils extending radially from a main axis, and the light passes therethrough but traps debris from the plasma. And a debris reduction device comprising a cover member that surrounds the foil trap and is disposed outside the light collection range of the light collecting mirror.
A shielding member that has an opening through which light traveling in the light collection range of the light collecting mirror passes between the plasma and the cover member, and shields radiation from the plasma from reaching the cover member. A debris reduction device, wherein a thermal shielding member that suppresses thermal radiation from the shielding member to the cover member is provided between the shielding member and the cover member. The debris reduction device according to claim 1, wherein the material of the shielding member is molybdenum, tungsten, or an alloy containing molybdenum or tungsten. 3. The debris reduction according to claim 1, wherein the shielding member is electrically connected to a debris reduction device main body or a vacuum container in which the debris reduction device is housed. apparatus. The said shielding member is equipped with the groove | channel and / or processus | protrusion for guide | inducing the tin emitted from plasma and deposited on the shielding member, and became the droplet form, It is characterized by the above-mentioned. Debris reduction apparatus as described. 5. The debris reduction device according to claim 1, wherein a surface area of the shielding member on a debris reduction device side is larger than a surface area on a plasma side.

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