JP2005268366A - Lpp type euv light source apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent components from pollution by reducing an area which may be exposed to air in order to perform maintenance, and to speed up processing such as vacuum suction at the time of restarting in an LPP type EUV light source apparatus. <P>SOLUTION: The LPP type EUV light source apparatus is constituted of a plurality of chambers such as a chamber provided with a target jet nozzle and a chamber provided with a converging optical system. Respective chambers are mutually connected by a passage which is opened/closed by a valve, and at the time of maintenance, only the vacuum chamber which is required to be opened is opened to air. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an LPP type EUV light source device used in an exposure apparatus or the like.

  LPP is known as a means for generating EUV light. LPP is an abbreviation for Laser Produced Plasma, which is obtained by condensing and irradiating laser light onto a liquid or gaseous target material ejected from the inside of a nozzle having a thin inner diameter, and irradiating the laser light into plasma. EUV light is emitted. The LPP type EUV light source device will be further described with reference to patent documents.

  In FIG. 1 of Patent Document 1, there is an apparatus for generating X-ray radiation or extreme ultraviolet radiation including an output laser beam 3 of a laser oscillator, a lens 13 for condensing the laser beam, and a nozzle 10 for injecting a target material. It is shown. The jet 17 of target material is jetted from the nozzle 10 and then changes to intermittent flow states 15 and 12 through a continuous flow state. On the other hand, the laser beam 3 collected by the lens 13 irradiates the target material, and the target material is turned into plasma at that position to emit EUV light. In addition, since EUV light is largely absorbed by gas, the nozzle 10, the laser light irradiation position 11 (EUV light generation region), and the like are arranged in a vacuum chamber. In Patent Document 1, in such an X-ray radiation or extreme ultraviolet radiation generator, the laser beam 3 is irradiated to a range where the jet 17 is in a continuous flow state, so that the laser is more reliably and easily obtained than in an intermittent flow state. It describes that the target can be irradiated with light.

  Patent Document 2 shows an example in which an EUV light source and an exposure apparatus are combined. In Patent Document 2, an EUV light source using charged particle storage ring radiation is used instead of the LPP type. However, in order to reduce EUV light absorption by gas, the optical path from the EUV light source to the exposure apparatus and the exposure atmosphere are high vacuum. This point must be maintained regardless of the type of EUV light source.

  FIG. 5 of Patent Document 2 shows an overall view of an EUV (X-ray) exposure apparatus. In this EUV exposure apparatus, EUV light emitted from the light source So reaches the exposure chamber 102 through the beam duct 103, and is irradiated onto the semiconductor wafer Wo through a mask Mo having an LSI circuit pattern.

The inside of the exposure chamber 102 is evacuated to a predetermined vacuum pressure by the exposure chamber exhaust line 104. Helium gas is supplied from the helium gas supply line while maintaining the degree of vacuum, and the reduced pressure atmosphere of the helium gas is maintained. . The helium gas plays a role of enabling convection necessary for heat dissipation of the mask Mo or the like, but it is necessary to create a reduced pressure atmosphere in order to suppress absorption of EUV light.
The beam duct 103 is maintained in an ultrahigh vacuum by a beam duct exhaust line 195. Further, the ultra-high vacuum atmosphere in the beam duct 103 and the reduced-pressure atmosphere in the exposure chamber 102 are blocked by the beryllium window 106.

  When such an exposure chamber is opened to the atmosphere for maintenance or the like, if the atmosphere enters the EUV light source side from the beryllium window 106 through the bypass line 108, the ultra-high vacuum of the beam duct is impaired. Therefore, when the exposure is resumed, it is necessary to restore the vacuum degree of the beam duct again by discharging the gas adhering to the inner wall of the beam duct by the vacuum pump of the exhaust line. This prolongs the restart time of the apparatus and brings about the problem of a reduction in exposure throughput.

  Patent Document 2 discloses an invention for solving this problem. As shown in FIG. 1 of Patent Document 2, when the exposure chamber 2 is opened to the atmosphere for maintenance or the like, the first shut-off valve 9 is closed. Thereby, the inside of the beam duct 3 between the shut-off valve 9 and the beryllium window 8 is maintained in a reduced-pressure helium atmosphere, and the inside of the beam duct on the EUV light source side is maintained in an ultrahigh vacuum atmosphere.

  By the way, the exposure chamber is not the only place that requires maintenance of the EUV exposure apparatus. In other words, the LPP type EUV light source has a condensing optical system that collects EUV light emitted from a plasma target and transmits it in the direction of an apparatus (such as an exposure apparatus) that uses the EUV light. This optical system also requires maintenance. Further, when a target material that has been jetted from a nozzle and irradiated with laser light to become high-temperature plasma adheres to the optical system, or a residue of the target material melted at a high temperature at the nozzle adheres to the optical system, EUV The light condensing operation becomes difficult. In this case as well, the vacuum chamber including the EUV light source must be opened to the atmosphere in order to replace the condensing optical system.

  Furthermore, since the target material that has been turned into plasma by laser irradiation collides with the nozzle at a high speed, if the nozzle is damaged, the target material adheres to the nozzle, or the nozzle deteriorates due to the high temperature of the plasma, the target The injection characteristics (injection amount, injection direction, stability in the injection direction, etc.) change, and there arises a problem that the EUV light generation amount decreases or becomes unstable. In this case as well, the vacuum chamber containing the EUV light source must be opened to the atmosphere for nozzle replacement.

  Here, Patent Document 3 shows a vacuum chamber structure necessary for an LPP type EUV light source. As shown in FIG. 5 of Patent Document 3, one end side of a target injection nozzle (capillary tube) 31 is connected to a tank 32 for containing water as a target, and water can be introduced into the nozzle 31. Multiple ends of the nozzle 31 protrude into the source space 33. The water travels in the direction of arrow 35 under high pressure, and is jetted in the form of water droplets 39 into the source space 33 through the nozzle 31 internal passage.

  The water droplet 39 is first jetted in the vacuum space 62, passes through the narrow tube 65 and reaches the source space 33, where it is irradiated with the laser beam 47 to be turned into plasma, and EUV light is generated. Here, if it is necessary to collect the EUV light, a condensing curved mirror or the like is installed in the generation source space 33. The inside of the vacuum space 62 is exhausted by the vacuum pump 63, and the inside of the generation source space 33 is exhausted by the vacuum pump 34. Since the gas generated by the evaporation of the water droplets 39 in the vacuum space 62 is exhausted by the vacuum pump 63, a high degree of vacuum inside the generation source space 33 can be easily maintained.

  The water after being irradiated with the laser beam 47 passes through the narrow tube 59 and reaches the vacuum space 53 and is exhausted by the vacuum pump 57. The heating element 70 serves to prevent water from freezing. This is because ice freezes and becomes an obstacle to the EUV generation operation.

Thus, by dividing the EUV generation source into a plurality of rooms communicating with each other and evacuating each room, it becomes easy to maintain and control the high degree of vacuum inside the generation source space 33 where the EUV light is generated.
JP 2000-509190 A (FIG. 1) Japanese Patent Laid-Open No. 7-270600 (FIG. 1) Japanese translation of PCT publication No. 2003-518731 (FIG. 5)

  However, when the EUV generation source is partitioned by a plurality of communicating rooms, a maintenance problem occurs. First, when a curved mirror for collecting EUV light is installed in the source space 33 shown in FIG. 5 of Patent Document 3, it is necessary to open the source space 33 to the atmosphere in order to replace the curved mirror. . Then, the vacuum spaces 62 and 53 are also opened to the atmosphere through the narrow tubes 65 and 59. However, originally, it is not necessary to open the atmosphere to a vacuum space other than the source space 33 only for exchanging the curved mirror. Nevertheless, when the air is released to the atmosphere, it must be evacuated again to return to a high vacuum state, and dust adhering to the inner wall surface of the vacuum space must be removed. Further, when a low-temperature material such as liquid xenon (Xe) is used for the target, it is necessary to cool the nozzle and the liquefier. However, when the air is released to the atmosphere, this cooling control is stopped, and the temperature of the liquefier must be raised to about room temperature in order to prevent condensation, so that a stable jet (droplet) of liquid Xe or the like is again ejected. There is also a problem that it takes time to start up. Further, when a molten metal material such as liquid tin is used as the target material, it is necessary to heat the nozzle and the heat exchanger. Since the heating control must be stopped when the atmosphere is released, a start-up time is still required to eject a stable jet (droplet) of liquid tin or the like again.

  In view of the above problems, the present invention reduces the range of destruction of the high vacuum atmosphere in the LPP type EUV light source device used for semiconductor exposure and the like, and simplifies the work up to the restart of the device. And it aims at shortening the working time.

  In order to solve the above-described problem, an EUV light source apparatus according to one aspect of the present invention includes a first vacuum chamber in which a nozzle for injecting an LPP target material is disposed, and a first vacuum for evacuating the first vacuum chamber. A pump, a first valve that opens and closes a passage that connects the first vacuum chamber and the first vacuum pump, a laser oscillator that outputs laser light for irradiating the LPP target material, and a first vacuum chamber And a second vacuum chamber installed in the direction of travel of the LPP target material ejected from the nozzle, which is generated when the LPP target material is turned into plasma upon irradiation with laser light emitted from the laser oscillator. A second vacuum chamber in which a condensing optical system for condensing the EUV light is disposed, and a second vacuum chamber for evacuating the second vacuum chamber. Comprising the flop, a second valve for opening and closing the passage connecting the second vacuum chamber and a second vacuum pump, and a third valve the first and second vacuum chamber to open and close the passage communicating.

  According to the present invention, in an LPP type EUV light source device partitioned into at least two or more communicating chambers that perform functions such as target material injection, target material laser light irradiation, residual target removal, etc. A gate valve is provided in the passage, and means for evacuating each chamber individually is provided. That is, since the vacuum of each chamber is controlled independently, even during maintenance, only the chamber that requires maintenance is opened to the atmosphere, and the vacuum of the chamber that does not perform maintenance (may be slightly low vacuum). Can be maintained. Therefore, it is possible to simplify the work up to the startup of the LPP type EUV apparatus, shorten the time required for the work, and improve the throughput.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram showing an LPP type EUV light source apparatus according to an embodiment of the present invention. The LPP type EUV light source device includes a first vacuum chamber 1, a second vacuum chamber 5, and a laser light source (laser oscillator) 11 disposed outside the vacuum chamber.

  The first vacuum chamber 1 is a chamber (liquid Xe injection chamber) in which liquid xenon (Xe), which is an LPP target material, is injected. The liquid Xe injection chamber 1 is provided with a cooler 2 that cools the target material and a nozzle 3 that is connected to the cooler 2 and jets the target material. The liquid Xe ejection chamber 1 is connected to a vacuum pump through a pipe 4 provided with a gate valve 4a, and the inside thereof is evacuated by the vacuum pump.

  The second vacuum chamber 5 is a chamber (laser irradiation chamber) in which EUV light is generated by irradiating the target material with laser light. In the laser irradiation chamber 5, a window 6 that transmits a laser beam 12 emitted from a laser light source 11, a curved mirror 7 that collects the generated EUV light, and an optical path tube 8 that transmits the collected EUV light. And are provided. The laser irradiation chamber 5 is connected to a vacuum pump through a pipe 9 provided with a gate valve 9a, and the inside is evacuated by the vacuum pump.

The liquid Xe ejection chamber 1 and the laser irradiation chamber 5 communicate with each other via a pipe 10 provided with a gate valve 10a.
The target Xe 13 ejected from the nozzle 3 in the liquid Xe ejection chamber 1 is irradiated with the laser beam 12 in the laser irradiation chamber 5, and is converted into plasma to generate EUV light 14. The EUV light 14 is collected by the curved mirror 7 and transmitted to an exposure apparatus (not shown) via the optical path tube 8.

Next, the operation at the time of maintenance of the LPP type EUV light source apparatus according to this embodiment will be described.
As described above, the liquid Xe ejection chamber 1 and the laser irradiation chamber 5 communicate with each other via a tube 10 (preferably a thin tube), and this tube 10 is connected to the gate valve 10a as necessary. Blocked. The liquid Xe ejection chamber 1 and the laser irradiation chamber 5 are provided with pipes 4 and 9 communicating with a vacuum pump, respectively, and these pipes are individually sealed by the gate valves 4a and 9a as necessary. .

When exchanging the condenser mirror, the tube 10 connecting the chambers and the tube 9 leading to the vacuum pump of the laser irradiation chamber 5 are respectively sealed by the gate valves 10a and 9a. Then, N ₂ gas or clean air is introduced only into the laser irradiation chamber 5 using a purge gas introduction mechanism (not shown), and then the atmosphere is released to replace the condensing mirror.

  During this maintenance work, a vacuum (somewhat low vacuum may be sufficient) in the liquid Xe irradiation chamber 1 can be maintained. Further, by maintaining the vacuum in the liquid Xe irradiation chamber 1 and continuously operating the cooler 2, the temperature of the nozzle 3 can be maintained at a temperature suitable for jet injection, etc. Becomes unnecessary, and the startup time of the EUV light source can be shortened. Furthermore, by maintaining the vacuum in the liquid Xe irradiation chamber 1 and continuing the operation of the cooler 2, it becomes possible to continue ejecting a jet (droplet) from the nozzle. As a result, the jet (droplet) Since it takes no time to generate / stabilize the (let)), EUV light can be generated immediately after the maintenance is completed. Moreover, by continuing to eject, there is a possibility of troubles accompanying stoppage or ejection of the jet (droplet), for example, the ejected target material 13 deviates from the laser irradiation position (position where the EUV light 14 was generated). The possibility etc. can be reduced. In addition, even when droplet ejection is stopped, by maintaining the temperature above the solidification temperature of the target, there is no problem that the nozzle is clogged by the frozen or solidified target, and the droplet injection can be stably operated. The transition goes smoothly.

Similarly, when replacing the nozzle, the tube 10 connecting the chambers and the tube 4 leading to the vacuum pump of the liquid Xe injection chamber 1 are respectively sealed by the gate valves 10a and 4a, and a purge gas introduction mechanism (not shown) is provided. After introducing N ₂ gas or clean air, only this chamber is opened to the atmosphere and the nozzle is replaced. Thereby, when the nozzle is replaced, the condensing mirror is not exposed to the atmosphere, so that the cleanliness of the reflecting surface can be maintained.

  As disclosed in Patent Document 3, even when three or more vacuum chambers communicate with each other, only the chamber in which the maintenance parts are installed is opened to the atmosphere by using a gate valve in the same manner. Maintenance may be performed.

  In the present embodiment described above, the insides of the first and second vacuum chambers are evacuated using different vacuum pumps, but the first vacuum chamber evacuation vacuum pump and the second vacuum chamber evacuation. It is also possible to use a single vacuum pump. For example, while the first vacuum chamber is open to the atmosphere for maintenance, the gate valve between the first vacuum chamber and the second vacuum chamber is closed, and the inside of the second vacuum chamber is evacuated by an exhaust vacuum pump. Keep doing. Alternatively, at that time, the gate valve between the second vacuum chamber and the vacuum pump is closed to maintain the vacuum in the second vacuum chamber. In addition, when the maintenance is completed and the first vacuum chamber is brought into a vacuum state again, the gate valve between the second vacuum chamber and the vacuum pump is closed to temporarily evacuate and exhaust only the first vacuum chamber. The vacuum is drawn with a vacuum pump. Next, when the degree of vacuum in the first vacuum chamber and the second vacuum chamber becomes substantially equal, the gate valve between the second vacuum chamber and the vacuum pump is opened, and both chambers are evacuated simultaneously. Alternatively, a gate valve between the first vacuum chamber and the second vacuum chamber may be opened, and both chambers may be evacuated simultaneously. In this way, maintenance inside the chamber in the LPP type EUV apparatus can be performed efficiently.

  The present invention can be used in an LPP type EUV apparatus used in an exposure apparatus or the like.

It is a schematic diagram which shows the structure of the LPP type EUV apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st vacuum chamber (liquid Xe injection chamber), 2 ... Cooler, 3 ... Nozzle 4, 9, 10 ... Pipe, 4a, 9a, 10a ... Gate valve, 5 ... 2nd vacuum chamber (laser irradiation chamber) , 6 ... window, 8 ... light path tube, 7 ... curved mirror, 11 ... laser light source (laser oscillator), 12 ... laser beam, 13 ... target material (liquid xenon), 14 ... EUV light

Claims (2)

A first vacuum chamber in which a nozzle for injecting LPP target material is disposed;
A first vacuum pump for evacuating the first vacuum chamber;
A first valve for opening and closing a passage connecting the first vacuum chamber and the first vacuum pump;
A laser oscillator that outputs laser light for irradiating the LPP target material;
A second vacuum chamber that communicates with the first vacuum chamber and is disposed in a traveling direction of the LPP target material ejected from the nozzle, wherein the LPP target material is emitted from the laser oscillator. A second vacuum chamber in which a condensing optical system for condensing EUV light generated by turning into plasma upon receiving light irradiation is disposed;
A second vacuum pump for evacuating the second vacuum chamber;
A second valve for opening and closing a passage connecting the second vacuum chamber and the second vacuum pump;
A third valve for opening and closing a passage communicating with the first and second vacuum chambers;
An LPP type EUV light source device comprising: A first vacuum chamber in which a nozzle for injecting LPP target material is disposed;
A laser oscillator that outputs laser light for irradiating the LPP target material;
A second vacuum chamber that communicates with the first vacuum chamber and is disposed in a traveling direction of the LPP target material ejected from the nozzle, wherein the LPP target material is emitted from the laser oscillator. A second vacuum chamber in which a condensing optical system for condensing EUV light generated by turning into plasma upon receiving light irradiation is disposed;
A vacuum pump for evacuating the first and second vacuum chambers;
A first valve for opening and closing a passage connecting the first vacuum chamber and the vacuum pump;
A second valve for opening and closing a passage connecting the second vacuum chamber and the vacuum pump;
A third valve for opening and closing a passage communicating with the first and second vacuum chambers;
An LPP type EUV light source device comprising:

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