JP2012209182A - Extreme ultraviolet light source apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent effluence of pollutants from a light emission port of an extreme ultraviolet light source apparatus to the side of an exposure machine.SOLUTION: EUV (extreme ultraviolet) light radiated from a high-temperature plasma P is collected to a focusing point F by an EUV condenser mirror 6, emitted from an EUV light emission port 7 and made incident on an exposure machine 30. A rotor (propeller) 8 to be rotated so as to intersect with the optical axis of the EUV light by a motor 9 is arranged between the condenser mirror 6 and the light emission port 7, and a rotary shaft 9a of the motor 9 is arranged on the outside of an optical path of extreme ultraviolet light. When extreme ultraviolet light is not emitted, the rotor 8 is allowed to pass between the condenser mirror 6 and the light emission port 7. When the extreme ultraviolet light is not emitted, the light emission port 7 is substantially shielded by the rotor 8, pollutants moving toward the light emission port 7 collide with the rotor 8 and the advancing direction of the pollutants is bent, so that the effluence of the pollutants is suppressed.

Description

  The present invention relates to an extreme ultraviolet light source device that emits extreme ultraviolet light, and more specifically, it is possible to prevent the outflow of contaminants from the extreme ultraviolet light source device to an exposure machine connected via a light exit port. The present invention relates to an extreme ultraviolet light source device.

As semiconductor integrated circuits are miniaturized and highly integrated, exposure light sources have become shorter in wavelength, and as a next-generation semiconductor exposure light source, in particular, extreme ultraviolet light with a wavelength of 13.5 nm (hereinafter referred to as EUV (Extreme Ultra Violet)). Development of an extreme ultraviolet light source device (hereinafter also referred to as an EUV light source device) that emits light) is underway.
FIG. 9 is a diagram for simply explaining the EUV light source device described in Patent Document 1. In FIG.
The EUV light source apparatus has a chamber 1 that is a container. In the chamber 1, there are a discharge part 1a in which a pair of disc-like discharge electrodes 2a, 2b constituting a plasma generation part is accommodated, a foil trap 5, an EUV collector mirror 6 which is a condenser optical means, and the like. And an EUV collector 1b to be accommodated.
Reference numeral 3 denotes a gas exhaust unit for exhausting the discharge unit 1a and the EUV condensing unit 1b to make the chamber 1 in 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.
14 is 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, 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 laser beam 17 is irradiated from the laser source 17a to the high temperature plasma raw material 14 transported to the upper discharge space. 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 light 17, pulse power is applied to the electrodes 2a and 2b from the power supply means 4 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 6 at a condensing point (also referred to as an intermediate condensing point) f of the condensing mirror 6, and is emitted from the EUV light exit port 7. Then, the light enters the exposure device 30 indicated by a dotted line connected via the EUV light exit 7.

Special table 2007-505460 gazette

In the chamber of the EUV light source device, substances that contaminate the inside of the exposure apparatus such as water and hydrocarbon (hydrocarbon) are drifting. For this reason, there is a possibility that the contaminants flow out to the exposure machine side from the light exit port connecting the EUV light source device and the exposure machine.
Since there is no glass material (glass) that transmits EUV light, a lid cannot be provided at the light exit in order to block outflow of contaminants. That is, in the EUV light source apparatus, it is an important problem to prevent the outflow of contaminants to the exposure machine side.
The present invention has been made based on the above, and it is an object of the present invention to realize an apparatus capable of preventing a contaminant from flowing out from the light exit of an extreme ultraviolet light source apparatus to the exposure machine side.

In order to solve the above problems, in the present invention, a rotating blade (propeller) is disposed between the collector mirror and the light exit of the extreme ultraviolet light source device, and the rotation axis thereof is disposed outside the optical path of the extreme ultraviolet light. . Then, the rotating blade is rotated, and when the extreme ultraviolet light is not emitted, the rotating blade is passed between the condenser mirror and the light exit port. While the rotary blade passes in front of the light emission port, the light emission port is substantially shielded by the rotary blade. In addition, since the rotor blades are rotated so as to intersect the optical axis of the EUV light, the contaminants that have traveled toward the light exit port collide with the rotor blades, and the traveling direction is bent, so Outflow is suppressed.
Here, the rotary blade also crosses the optical path of the extreme ultraviolet light collected by the condenser mirror. Therefore, the generation timing of the plasma that emits extreme ultraviolet light is synchronized with the rotation period of the rotating blade so that the extreme ultraviolet light does not interfere with the light exit, and no plasma is generated on the rotating blade. Sometimes it passes through the light exit before the light is incident.
That is, the present invention solves the above problems as follows.
(1) A container is provided with a plasma generation unit and a condensing mirror that collects extreme ultraviolet light emitted from the plasma generated in the plasma generation unit, and the container is focused by the condensing mirror. In the extreme ultraviolet light source device in which the extreme ultraviolet light is emitted and the light emission port connected to the second container (exposure machine) is formed, the light is emitted between the condenser mirror and the light emission port. A rotating blade that rotates in a plane that intersects the optical axis of the extreme ultraviolet light is disposed on the light incident side of the light exit port, and the condensing mirror collects the rotating shaft of the rotating means that rotates the rotating blade. It is placed outside the optical path of the shining extreme ultraviolet light.
(2) In the above (1), the extreme ultraviolet light source device is provided with a rotation control unit for controlling the rotation means, and the rotation control unit includes a period of plasma generation in the plasma generation unit, and the rotating blade. And the rotation of the rotor blades is controlled so that the rotor blades pass between the condenser mirror and the light exit port when the plasma is not generated.

In the present invention, a rotating blade that rotates in a plane intersecting the optical axis of the condenser mirror is disposed between the condenser mirror and the light exit opening and on the light incident side of the light exit opening. While the rotor blades pass in front of the light exit port, the light exit port can be substantially shielded and the outflow of contaminants can be suppressed. Further, the contaminant that has traveled toward the light exit port collides with the rotor blade, and the traveling direction thereof is bent. This can also suppress the outflow of pollutants.
Further, when the plasma is not generated, the rotation of the rotor blade is controlled so that the rotor blade passes between the condensing mirror and the light exit port, so that the rotor blade does not block extreme ultraviolet light. Will not drop.

It is a figure which shows schematic structure of the EUV light source device of this invention. It is a conceptual diagram of the rotary blade of the Example of this invention. It is an enlarged view of a rotor blade and the vicinity of a light exit. It is a figure explaining the relationship between the timing of EUV light generation, and operation | movement of a rotary blade. It is a figure which shows the positional relationship of a rotating shaft center and an optical path spot. It is a figure which shows the rotation position of a rotary blade. It is a figure which shows the relationship between the rotary blade rotational frequency f2 and the minimum rotary blade radius R. FIG. It is a figure which shows schematic structure at the time of applying this invention to the EUV light source device which is not provided with a discharge electrode. It is a figure explaining an EUV light source device.

FIG. 1 shows an outline of the configuration of the EUV light source apparatus of the present invention.
The configuration of the EUV light source apparatus is the same as that shown in FIG.
As described above, in the chamber 1 of the EUV light source device, the discharge part 1a in which a pair of disc-shaped discharge electrodes 2a, 2b and the like are accommodated, the foil trap 5 and the EUV collector mirror which is a condenser optical means. 6 and the like are provided. The chamber 1 is provided with a gas exhaust unit 3 for evacuating the chamber 1.
The disk-shaped electrodes 2a and 2b are separated from each other by a predetermined interval, and rotate around the rotation axes 16c and 16d by the rotation of the rotation motors 16a and 16b, respectively.
The high-temperature plasma raw material 14 is heated molten metal, for example, liquid tin, and is accommodated in a container 15, and the electrodes 2 a and 2 b each include a container 15 in which a part of the high-temperature plasma raw material 14 accommodates the high-temperature plasma raw material 14. It is arranged to be immersed in the inside.
The liquid high-temperature plasma raw material 14 is transported to the discharge space as the electrodes 2a and 2b rotate, and the high-temperature plasma raw material 14 is irradiated with the laser beam 17 from the laser source 17a. To do.

In a state where the high-temperature plasma raw material 14 is vaporized by the irradiation of the laser light 17, pulse power is applied to the electrodes 2a and 2b from the power supply means 4 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 emitted from the high temperature plasma P enters the EUV collector mirror 6 through the foil trap 5 and is collected by the EUV collector mirror 6 at a condensing point (intermediate condensing point) f of the collector mirror 6. Then, the light exits from the EUV light exit 7 and enters the exposure device 30 indicated by the dotted line connected to the EUV light source device via the EUV light exit 7.
The EUV collector mirror 6 is formed with a light reflecting surface 6a for reflecting EUV light having a wavelength of 13.5 nm emitted from the high temperature plasma P.
The EUV collector mirror 6 is composed of a plurality of light reflecting surfaces 6a arranged in a nested manner without contacting each other.
Each light reflecting surface 6a is formed by densely coating a metal such as Ru (ruthenium), Mo (molybdenum), Rh (rhodium) on the reflecting surface side of the base material having a smooth surface made of Ni (nickel) or the like. In this case, extreme ultraviolet light having an incident angle of 0 to 25 ° is reflected well. Each light reflecting surface 6a is configured such that the condensing points f coincide.

A rotating blade (propeller) 8 that rotates in a plane intersecting the optical axis of the EUV light is disposed between the EUV collector mirror 6 and the EUV light exit 7 and on the light incident side of the light exit 7. The
The rotary blade 8 is attached to a rotary shaft 9 a of a motor (rotating means) 9. When the motor 9 operates and the rotary shaft 9a rotates, the rotary blade 8 crosses the light incident side of the light exit 7.
The motor (rotating means) 9 and its rotating shaft 9a are arranged outside the optical path of the EUV light so as not to block the EUV light collected by the condensing mirror 6 and passing through the EUV light exit port 7.
FIG. 2 is a conceptual diagram of a rotor blade according to an embodiment of the present invention. This figure is a view of the rotor blades as viewed from the EUV collector mirror side. FIG. 10 (a) is a perspective view of the rotor blades, and FIGS. 9 (b) and (c) explain the relationship between the generation of plasma and the rotational position of the rotor blades. It is a figure to do.

Substances that contaminate the optical elements in the exposure machine, such as water and hydrocarbon (hydrocarbon), exist as gas (gas) in the chamber 1 and fly around the chamber 1 in all directions. A part of the light enters the exposure device 30 from the EUV light exit 7.
The rotary blade 8 is arranged on the light incident side of the EUV light exit 7 and rotates to prevent contaminants from entering the exposure device 30.

Here, the rotating blade 8 must not block the optical path during the emission of EUV light. As described above, in the EUV light source device, the plasma P that emits EUV light is formed by applying pulsed power from the power supply means 4. Therefore, EUV light is also emitted in a pulsed manner in accordance with the generation of the plasma P.
For this reason, as shown in FIGS. 2B and 2C, when the plasma P is formed and EUV light is emitted, the rotating blade 8 does not block the EUV light emission port 7 (FIG. 2C). ) When the plasma P is not generated and the EUV light is not emitted, the rotating blade 8 is rotated so that the rotating blade 8 closes the EUV light emission port 7 (FIG. 2B).

That is, the control unit 10 of the EUV light source apparatus controls the operation of the power supply means 4 and the laser source 17a to control the formation of plasma P, that is, the generation timing (cycle) of EUV light. In accordance with the formation of P (the generation timing (cycle) of EUV light), the operation of the motor 9 by the rotation control unit 11, that is, the rotation cycle of the rotary blade 8 is changed when plasma P is formed and EUV light is emitted. The rotor 8 is controlled so as not to block the EUV light exit 7.
The rotation control unit 11 is controlled by a synchronization control unit 10 a provided in the control unit 10. The synchronization control unit 10a outputs a synchronization signal to the rotation control unit 11 in order to synchronize the cycle of plasma generation in the plasma generation unit and the rotation cycle of the rotor blades. With this synchronization signal, the rotation control unit 11 causes the rotary blade 8 to pass between the condenser mirror 6 and the light exit port 7 when the plasma is not generated (when EUV light is not generated). Thus, the rotation of the rotor blade 8 is controlled.
Specifically, for example, by attaching an encoder to the motor 9 and feeding back the rotation signal of the motor 9 to the rotation control unit 11, the motor 9 is controlled to rotate in synchronization with the synchronization signal, or A sensor or the like is provided to detect the emission of EUV light, and the motor is rotated in synchronization with the emission of EUV light.

Hereinafter, a specific configuration example of the rotor blade will be described.
FIG. 3 shows an enlarged view of the vicinity of the rotor blade and the light exit port. FIG. 5A is a cross-sectional view of the vicinity of the light exit opening taken along a plane along the optical axis of the EUV light and the rotation axis of the motor 9, and FIG. 5B is a view of the rotary blade viewed from the EUV collector mirror 6 side. It is.
As shown in the figure, there are a plurality of rotor blades 8 attached to a rotating shaft 9 a of a motor 9.
As shown in FIG. 3A, the EUV light from the condenser mirror 6 is collected at the light exit 7 with an angle α with the optical axis. The light exit 7 is provided with an aperture having an opening diameter a. If the clearance between the rotor blade 8 and the aperture is t, and the axial length of the rotor blade 8 is d, the radius r of the optical path spot Ls traversed by the rotor blade 8 is r = a / 2 + (d + t) × tan α.
In this embodiment, α = 15 °, a = 4.4 mm, t = 1 mm, and d = 15 mm. Therefore, r is about 6.5 mm.

FIG. 4 is a diagram for explaining the relationship between the generation timing of EUV light and the operation of the rotating blades. FIGS. 4A to 4C show the rotating state of the rotating blade 8, and FIG. 4D shows the generation timing of EUV light. Indicates.
As shown in FIG. 4D, the EUV light is generated only for a time t1 in the operation of one pulse, and the time t2 until the emission of the next pulse is in a non-light emitting state.
During the EUV emission, the rotor blade 8 is prevented from reaching the optical path spot Ls, and during the EUV no light emission, the rotor blade 8 crosses the optical path spot Ls. The rotation frequency of the rotor blade 8 is f2, the diameter of the optical path spot is r, the radius of the navigation rotor blade 8 is R, and the width of the rotor blade 8 is w (see FIG. 4A).
4A shows the state of the rotor blade 8 at the light emission start time T1, and the angle θ1 (see FIG. 4B) that the rotor blade 8 advances during EUV light emission is θ1 = 2 × π × f2 × t1, EUV. The angle θ2 (see FIG. 4C) that the rotor blades advance during non-light emission is θ2 = 2 × π × f2 × t2.

The conditions for determining the shape of the rotor blade 8 will be described with reference to FIGS. 5 shows the positional relationship between the rotational axis center of the rotary blade 8 and the optical path spot Ls, and FIG. 6 shows the rotational position of the rotary blade.
First, θ2−θ4 ≧ 2 × β must be satisfied in order for the rotor blade 8 to completely cross the optical path spot Ls during no light emission. Here, θ4 is an angle at which the width w of the rotary blade 8 extends from the center of the rotary blade (axis) in the optical path spot Ls. Β is an angle shown in FIG. 5, and β = sin ⁻¹ (r / Δ).
When the distance (axis offset) between the optical axis and the rotation axis 9a is Δ, θ4 = w / Δ (radian). From this condition, the minimum shaft offset value Δ allowed for a certain rotation frequency f2 is determined. When this minimum axis offset is Δ1, the limit minimum radius of the rotor blade is R1 = Δ1 + r (condition 1).

Further, θ5 ≧ 2 × β must be satisfied so that the rotor blade does not cross the optical path spot during light emission. Here, θ5 is an angle shown in FIG. 6 and is an angle obtained by subtracting the angle θ1 of the rotating blade during EUV emission and the width angle θ4 of the rotating blade from the interval angle θ3 of the rotating blade. That is, θ5 = θ3-θ1-θ4.
If the number of rotor blades is N, θ3 = 2π / N (radian). From these conditions, the minimum shaft offset value Δ allowed for a certain rotation frequency f2 is determined. Assuming that this minimum axis offset is Δ2, the limit minimum radius R2 of the rotor blade is Δ2 + r (condition 2).
The axis offset Δ must be greater than Δ1 and Δ2. If the axis offset Δ is determined, the minimum value of the rotor blade radius R is Δ + r as described above.

  FIG. 7 shows the relationship between the rotating blade rotation frequency f2 and the minimum rotating blade radius R. However, the EUV emission time t1 in one pulse operation was 1 μs, the EUV emission repetition frequency f1 was 20 kHz, the number N of rotating blades was 20, and the width w of the rotating blades was 10 mm. In FIG. 7, the limit minimum radius line R1 and the limit minimum radius line R2 correspond to the minimum axis offset Δ1 (condition 1) and the minimum axis offset Δ2 (condition 2), respectively. What the rotor blade radius R can take is the shaded area in FIG.

  If the repetition frequency of EUV light emission is f1, f1 and f2 × N must have a common divisor in order to synchronize the rotor blade so that it always crosses the optical path spot when there is no light emission. In this embodiment, since f1 = 20 kHz and N = 20, values that f2 can take are discrete values such as 2000 Hz, 1000 Hz, 500 Hz, and 200 Hz. As can be seen from FIG. 7, if the rotational frequency f2 is less than 1000 Hz, the rotor blade radius R must be increased, resulting in a larger apparatus. In this embodiment, the rotation frequency f2 = 1000 Hz and the blade radius R = 100 mm.

While the rotary blade 8 crosses the light exit port 7 while no light is emitted, the light exit port 7 is substantially shielded by the rotary blade 8. During this time, contaminants from the light source side to the exposure apparatus side are removed. Outflow is suppressed. It can be said that the larger the time ratio (shielding rate) at which the rotor 8 shields the light exit port 7, the higher the effect of suppressing the outflow of contaminants. The shielding rate is represented by θ4 / θ3, and in the present embodiment, the value is 34%.
Further, since the rotating blade 8 rotates so as to intersect the optical axis, the contaminant that has traveled toward the light exit 7 collides with the rotating blade 8, and the traveling direction thereof is bent, thereby causing contamination of the contaminant. There is also an effect that the outflow is suppressed. In the present embodiment, the time required for the rotor blade 8 to cross the light exit 7 is about 7.5 μs, and the length d = 15 mm in the optical axis direction of the rotor blade, so that it flies at a speed of about 2000 m / s or less. The incoming contaminant collides with the rotor blade 8 and does not flow out from the light exit 7. In the vicinity of the light exit, most of the contaminants are considered to be within this speed range, and the outflow to the exposure apparatus side is considerably suppressed.

In the above embodiment, the EUV light source device that emits EUV light by the discharge generated between the discharge electrodes has been described as an example. However, some EUV light source devices do not include a discharge electrode. Also, the present invention can be applied.
FIG. 8 shows an outline of a configuration in which the present invention is applied to an EUV light source apparatus that does not include a discharge electrode.
The EUV light source apparatus includes a chamber 1 that houses a condensing reflecting mirror 21 that is a condensing optical means. The condensing reflecting mirror 21 is formed with a light reflecting surface 21a for reflecting EUV light having a wavelength of 13.5 nm emitted from high-temperature plasma and condensing the light at a condensing point f.
The chamber 1 is provided with a gas exhaust unit 3 for making the chamber 1 in a vacuum state.

The EUV light source device includes a raw material supply unit 22 that drops (drops) and supplies a liquid or solid raw material M for generating high-temperature plasma on the light reflecting surface 21 a side of the condenser reflector 21. The raw material M is, for example, tin (Sn) or lithium (Li).
The EUV light source device includes a high-power laser device 23 that irradiates the raw material M supplied by the raw material supply means 22 with a laser beam with very high energy.
The raw material supply means 22 has a very high energy from the high-power laser device 23 through the laser incident window 23a to the high-temperature plasma raw material M supplied to the light reflecting surface 21a side of the condensing reflector 21. A laser beam is irradiated. As a result, the raw material M becomes high-temperature plasma and emits EUV light having a wavelength of 13.5 nm. The EUV light radiated from the high temperature plasma is reflected by the light reflecting surface 21a of the condensing reflecting mirror 21 and is condensed at the condensing point f. The condensed EUV light exits from the EUV light exit 7 and enters the exposure device 30 connected via the EUV exit 7.

  Then, the rotor blade (propeller) 8 described in the above embodiment is provided between the condenser reflector 21 and the EUV light exit 7 and on the light exit 7 side. The synchronization control unit 10 a of the control unit 10 generates a synchronization signal for synchronizing the dropping timing of the raw material M from the raw material supply means 22, the laser irradiation timing of the laser device 23, and the rotational speed of the rotary blade 8. As shown in FIG. 2, when the EUV light is emitted, the rotation control unit 11 does not emit the EUV light so that the rotating blade 8 does not block the EUV light emission port 7. At times, the rotor 8 is rotated so that the rotor 8 closes the EUV light exit 7.

DESCRIPTION OF SYMBOLS 1 Chamber 1a Discharge part 1b EUV condensing part 2a, 2b Discharge electrode 3 Gas exhaust unit 4 Electric power supply means 5 Foil trap 6 EUV condensing mirror 6a Light reflecting surface 7 EUV light emission port 8 Rotary blade (propeller)
9 Motor (Rotating means)
9a Rotating shaft 10 Control unit 10a Synchronous control unit 11 Rotation control unit 14 High temperature plasma raw material 15 Container 16a, 16b Rotating motor 16c, 16d Rotating shaft 17 Laser light 17a Laser source 21 Condensing reflecting mirror 21a Light reflecting surface 22 Raw material supplying means 23 Laser apparatus 30 Exposure machine M Raw material P Plasma

Claims (2)

The container includes a plasma generation unit and a condensing mirror that collects extreme ultraviolet light emitted from the plasma generated in the plasma generation unit, and the container includes extreme ultraviolet light collected by the condensing mirror. In the extreme ultraviolet light source device in which light is emitted and a light emission port connected to the second container is formed,
Between the condensing mirror and the light exit port, on the light incident side of the light exit port, a rotating blade rotating in a plane intersecting the optical axis of the extreme ultraviolet light is disposed,
The extreme ultraviolet light source device characterized in that a rotating shaft of a rotating means for rotating the rotating blade is disposed outside an optical path of extreme ultraviolet light collected by the condenser mirror. The extreme ultraviolet light source device further includes a rotation control unit that controls the rotating unit,
The rotation control unit synchronizes the generation period of the plasma in the plasma generation unit and the rotation period of the rotary blade, and when the plasma is not generated, the rotary blade is connected to the condenser mirror and the light exit port. The extreme ultraviolet light source device according to claim 1, wherein the rotation of the rotor blade is controlled so as to pass between the two.

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