JP5599992B2 - Ionized laser device and extreme ultraviolet light source device - Google Patents

Description

  The present invention relates to an ionization laser device and an extreme ultraviolet light source device, and more particularly to an ionization laser device and an extreme ultraviolet light source device capable of outputting laser light having a plurality of wavelengths.

  Conventionally, as a method of ionizing atoms or molecules such as tin (Sn), germanium (Ge), or nickel (Ni) as a target, there is an ionization method disclosed in Non-Patent Document 1 shown below, for example. In this ionization method, for example, when Sn is ionized, gaseous Sn atoms are combined using a combined laser beam obtained by combining laser beams of a total of three wavelengths of 286.42 nm, 811.62 nm, and 823.67 nm. Ionized. The three-wavelength laser light is generated from, for example, laser light output from three sapphire lasers and harmonic light thereof.

Y. Liu, et. Al., “Laser ion source tests at the HRIBF on stable Sn, Ge and Ni isotopes”, Nucl. Instr. And Meth. B 243 (2006) 442-452

  However, Non-Patent Document 1 described above does not disclose the stabilization of the wavelength of the laser beam output from the three sapphire lasers. Usually, in order to stabilize the wavelength of the laser beam output from the laser device, the wavelength of the laser beam is measured using a wavelength meter, and the laser device is feedback-controlled so that the measured wavelength becomes a desired wavelength. .

  However, since the wavelength meter is a detector that measures the relative wavelength of the laser beam, the measured wavelength includes Doppler shift and other effects, and the wavelength of the laser beam output from the laser device is exactly as it is. Cannot be measured. For this reason, in the wavelength feedback control of the laser device using the wavelength detected by the wavelength meter, the wavelength of the laser beam irradiated to the target cannot be adjusted to the target wavelength with high accuracy. As a result, the wavelength of the laser beam Deviated from the desired wavelength, and the ionization efficiency of the target was reduced. In particular, when ionizing a target through an excited state, it is necessary to adjust the wavelength of the laser beam that excites the target and the wavelength of the laser beam that ionizes the excited target with high accuracy, but feedback control using a wavelength meter However, there is a problem that the ionization efficiency of the target is greatly reduced because sufficient accuracy cannot be obtained for wavelength control with respect to each laser beam.

  Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide an ionization laser device and an extreme ultraviolet light source device capable of ionizing a target with high ionization efficiency even when the target is ionized through an excited state. And

In order to achieve this object, an ionization laser apparatus according to the present invention is an ionization laser apparatus that outputs laser light for ionizing a target through one or more excitation states, and an excitation laser that excites the target. Excitation laser output means for outputting light, excitation absolute wavelength detection means for detecting the absolute wavelength of the excitation laser light, and ionization for outputting ionization laser light for ionizing the target excited by the excitation laser light Laser output means, ion quantity detection means for detecting the amount of atoms or molecules ionized by the ionization laser light, and the absolute wavelength of the excitation laser light detected by the excitation absolute wavelength detection means with adjusting the wavelength of the excitation of laser light by controlling the pump laser output means, said Lee And control means for adjusting the wavelength of the ionizing laser beam by controlling the laser output unit for the ionization based on the amount of the ionized atom or molecule that has been detected by the emission amount detecting means, and comprising the To do.

  An extreme ultraviolet light source device according to the present invention is a light source device that generates extreme ultraviolet light by irradiating a target with a laser beam, and a chamber in which extreme ultraviolet light is generated, and is supplied to the chamber. A target material, an EUV plasma generation laser light source that generates plasma by irradiating the target with an EUV plasma generation laser beam, and a condensing optical system that collects extreme ultraviolet light emitted from the plasma, An ionizing laser device that ionizes neutral particles by irradiating the plasma region with ionized laser light, and ionizing means that ionizes neutral particles contained in particles emitted from the plasma to form charged particles; In order to collect at least the charged particles ionized by the ionization means. And electric field forming means for forming an electric field on the magnetic field forming means or the chamber to form a, characterized by comprising any one of the ionizing laser device described above.

  According to the present invention, since the wavelength of the laser beam is adjusted to a desired wavelength based on the measured absolute wavelength, the deviation of the laser beam from the desired wavelength due to the Doppler effect or other factors is sufficiently reduced. It is possible. As a result, it is possible to improve the light absorption rate of the target and effectively give energy to the target. As a result, even when the target is ionized through an excited state, the ionization laser device and the extreme that can ionize the target with high ionization efficiency An ultraviolet light source device can be realized.

FIG. 1 is a conceptual diagram for explaining an ionization process of a target (Sn atom) according to Embodiment 1 of the present invention. FIG. 2 is a schematic diagram showing a schematic configuration of the ionization laser device according to Embodiment 1 of the present invention. FIG. 3 is a schematic diagram showing a configuration example of the ionization laser device according to Embodiment 1 of the present invention. FIG. 4 is a schematic diagram showing a specific example of the first to third lasers shown in FIG. FIG. 5A is a schematic diagram showing a specific example of the first / second laser galvatron according to the first embodiment of the present invention. FIG. 5B is a waveform diagram showing an example of an optogalvano signal output from the first / second laser galvatron in Embodiment 1 of the present invention. FIG. 5C is a diagram showing the relationship between the amount of optogalvano signal current and the wavelength of laser light in the first exemplary embodiment of the present invention. FIG. 6 is a flowchart showing an example of start-up operation of the ionization laser device according to Embodiment 1 of the present invention. FIG. 7 is a flowchart showing an example of steady operation of the ionization laser device according to the first embodiment of the present invention. FIG. 8 is a conceptual diagram for explaining an ionization process of a target (Sn atom) according to Modification 1-1 of Embodiment 1 of the present invention. FIG. 9 is a schematic diagram illustrating a configuration example of an ionization laser device according to Modification 1-1 of Embodiment 1 of the present invention. FIG. 10 is a flowchart showing an example of the startup operation of the ionization laser device according to Modification 1-1 of Embodiment 1 of the present invention. FIG. 11 is a flowchart showing an example of steady operation of the ionization laser device according to Modification 1-1 of Embodiment 1 of the present invention. FIG. 12 is a schematic diagram illustrating a specific example of a fluorescence detector according to Modification 1-2 of Embodiment 1 of the present invention. FIG. 13A is a schematic diagram illustrating a specific example of a light absorption detector according to Modification 1-3 of Embodiment 1 of the present invention. FIG. 13B is a waveform diagram showing an example of a light detection signal output from the light absorption detector according to Modification 1-3 of Embodiment 1 of the present invention. FIG. 13C shows the relationship between the maximum value of the photodetection signal and the wavelength of the laser beam in Modification 1-3 of Embodiment 1 of the present invention. FIG. 14 is a schematic diagram showing specific examples of first to third lasers according to Modification 1-4 of Embodiment 1 of the present invention. FIG. 15 is a schematic diagram showing a schematic configuration of an absolute wavelength detector according to Modification 1-5 of Embodiment 1 of the present invention. FIG. 16 is a schematic diagram showing a schematic configuration of an absolute wavelength detector according to Modification 1-6 of Embodiment 1 of the present invention. FIG. 17 is a schematic diagram showing a configuration example of the ionization laser device according to the second embodiment of the present invention. FIG. 18 is a schematic diagram for explaining the operating principle of the ionization laser device shown in FIG. FIG. 19 is a flowchart showing an example of start-up operation of the ionization laser device according to the second embodiment of the present invention. FIG. 20 is a flowchart showing an example of steady control operation of the ionization laser device according to the second embodiment of the present invention. FIG. 21 is a schematic cross-sectional view showing a schematic configuration of an EUV laser apparatus according to Embodiment 3 of the present invention. FIG. 22A is a schematic cross-sectional view showing a schematic configuration of an EUV laser apparatus according to Modification 3-1 of Embodiment 3 of the present invention. 22B is a cross-sectional view taken along line AA in FIG. 22A.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the following description, each drawing only schematically shows the shape, size, and positional relationship to the extent that the contents of the present invention can be understood. Therefore, the present invention is illustrated in each drawing. It is not limited to only the shape, size, and positional relationship. Moreover, in each figure, a part of hatching in a cross section is abbreviate | omitted for clarification of a structure. Furthermore, the numerical values exemplified below are merely preferred examples of the present invention, and therefore the present invention is not limited to the illustrated numerical values.

<Embodiment 1>
First, an ionization laser apparatus according to Embodiment 1 of the present invention will be described in detail with reference to the drawings. In the following description, the case where the ionization target is an Sn atom is taken as an example, but the present invention is not limited to this, and various atoms or molecules can be used as the ionization target.

FIG. 1 is a conceptual diagram for explaining an ionization process of a target (Sn atom) according to the first embodiment. As shown in FIG. 1, in the first embodiment, Sn atoms that are targets are ionized through a plurality of steps (three steps in the first embodiment). Specifically, first, gasified Sn atoms are irradiated with laser light LS1 having a wavelength λ ₁ (= 286.32 nm) (hereinafter referred to as first laser light) LS1. As a result, the Sn atoms absorb the first laser beam LS1, and the electrons in the ground state thereof transition from the orbit E0 (= 5p ^{2 3} P ₀ ) to the orbit E1 (= 5p6s ³ P ⁰ ₁ ) (step S1). ). In the following description, a state in which electrons are in the orbit E1 is referred to as a first eigenstate.

Subsequently, LS2 (hereinafter referred to as a second laser beam) of a laser beam having a wavelength λ ₂ (= 811.62 nm) is irradiated to the Sn atom in the first eigenstate. However, since the lifetime of the first eigenstate is as short as about 5 ns, the first laser beam LS1 is also irradiated onto the Sn atoms together with the second laser beam LS2. Thereby, the Sn atom in the first eigenstate absorbs the second laser light LS2, and the electrons in the orbit E1 transit to the orbit E2 (= 5p6p ³ P ₁ ) (step S2). In the following description, a state where electrons are in the orbit E2 is referred to as a second eigenstate.

Thereafter, in addition to the first laser beam LS1 and the second laser beam LS2, a wavelength λ ₃ (= 823.67 nm) corresponding to the remaining energy (eV) necessary for ionizing Sn atoms in the second eigenstate. LS3 (hereinafter referred to as third laser light) LS3 is irradiated (step S3). As a result, the Sn atom in the second eigenstate absorbs LS3, and the electrons in the orbit E2 (= 5p6p ³ P ₁ ) have an energy equal to or higher than the ionization potential (IP = 59233 cm ⁻¹ ). Jumps from the valence band to the conduction band (E3), and as a result, Sn atoms are ionized.

Here, in step S1, the band width (also referred to as line width) of the energy level corresponding to the orbit E1 is very narrow. Therefore, in order to increase the light absorption rate of electrons in the ground state with respect to the first laser light LS1 and efficiently excite Sn atoms from the ground state to the first eigenstate, the wavelength of the first laser light LS1 is changed to the ground state. It is necessary to accurately match the wavelength λ ₁ (= 286.32 nm: hereinafter referred to as the first target wavelength) corresponding to the energy level difference (band gap energy) between the first eigenstate and the first eigenstate.

Therefore, in the first embodiment, the absolute wavelength of the first laser light LS1 is obtained using a first absolute wavelength detector 110 (see FIG. 2) described later, and this absolute wavelength becomes the first target wavelength λ _1. The light source of the first laser light LS1 (first laser 102 (see FIG. 2) described later) is feedback-controlled. This allows intended to adjust accurately the actual wavelength of the first laser beam LS1 to the first target wavelength lambda _1.

Also in step S2, the bandwidth of the energy level corresponding to orbit E2 is very narrow. For this reason, in order to increase the light absorptance of the electrons in the orbit E1 with respect to the second laser light LS2 and efficiently excite Sn atoms from the first eigenstate to the second eigenstate, the wavelength of the second laser light LS2 is changed. It is necessary to accurately match the wavelength λ ₂ (= 811.62 nm: hereinafter referred to as the second target wavelength) corresponding to the energy level difference between the first eigenstate and the second eigenstate.

Therefore in the first embodiment, the second absolute wavelength detector 210 to be described later absolute wavelength of the second laser beam LS2 determined using (see FIG. 2), as the absolute wavelength is the second target wavelength lambda ₂ The light source of the second laser beam LS2 (second laser 202 (see FIG. 2) described later) is feedback-controlled. This allows intended to adjust accurately the actual wavelength of the second laser beam LS2 to the second target wavelength lambda _2.

Note that in step S3, the bandwidth of the conductor (this is referred to as orbit E3), which is the electron transition destination when ionizing Sn atoms, is wider than that of orbits E1 and E2. However, in order to efficiently ionize Sn atoms in the second eigenstate, the wavelength of the third laser beam LS3 corresponds to the energy (eV) necessary to ionize Sn atoms in the second eigenstate. It is preferable to accurately match λ ₃ (= 823.67 nm: hereinafter referred to as the third target wavelength).

Therefore, in the first embodiment, the absolute wavelength of the third laser light LS3 is also obtained by using a third absolute wavelength detector 310 (see FIG. 2) described later, and this absolute wavelength becomes the third target wavelength λ _3. A light source of a third laser beam LS3 (a third laser 302 described later (see FIG. 2)) is feedback-controlled. Thereby, the actual wavelength of the third laser light LS3 can be adjusted to the third target wavelength λ3 with _high accuracy.

  As described above, by ionizing the target (Sn atom) through a plurality of excited states in the middle, it becomes possible to effectively give energy to the target using a laser beam having a low energy level of visible light, Efficient ionization of the target is possible.

  Next, an ionization laser apparatus capable of realizing the ionization process as described above will be described in detail with reference to the drawings. FIG. 2 is a schematic diagram showing a schematic configuration of the ionization laser device 1 according to the first embodiment. As shown in FIG. 2, the ionization laser device 1 controls the ionization laser 20 and the ionization laser 20 that output laser beams (first to third laser beams LS <b> 1 to LS <b> 3) including wavelength components of one band or more. And an ionization laser controller 10 for outputting the laser beam having a desired wavelength to the ionization laser 20 at a desired timing.

  The ionization laser 20 combines the laser beams output from the first to third laser devices 100 to 300 that output laser beams of different wavelengths and the first to third laser devices 100 to 300, respectively. And a multiplexing optical system 30 that outputs a laser beam LS.

The first to third laser devices 100 to 300 are output from the first to third lasers 102 to 302 that output the first to third laser beams LS1 to LS3 and the first to third lasers 102 to 302, respectively. The first to third absolute wavelength detectors 110 to 310 for detecting the absolute wavelengths of the first to third laser beams LS1 to LS3, and the first to third lasers 102 to 302 are output based on the detected absolute wavelengths. It includes first to third first to third controller 101-301 to the wavelength of the laser beam LS1~LS3 Komu fit to the first to third target wavelength lambda ₁ to [lambda] ₃ that, a. The first and second lasers 102 and 202 function as excitation laser output means for outputting the first and second laser beams LS1 and LS2 as excitation laser beams for exciting the target Tsn. On the other hand, the third laser 302 functions as an ionization laser output unit that outputs the third laser beam LS3 as an ionization laser beam for ionizing the target Tsn after excitation. The first and second absolute wavelength detectors 110 and 210 function as excitation absolute wavelength detection means for detecting the absolute wavelength of the excitation laser light (LS1, LS2), and the third absolute wavelength detector 310 includes It functions as an absolute wavelength detection means for ionization that detects the absolute wavelength of the laser beam for ionization (LS3). The first and second target wavelengths λ ₁ and λ ₂ are excitation wavelengths corresponding to energy for exciting the target to a predetermined eigenstate, and the third target wavelength λ ₃ is an ionization of the excited target. This is the ionization wavelength corresponding to the energy for the generation.

The first to third laser apparatuses 100 to 300 perform feedback control on the first to third lasers 102 to 302 based on the absolute wavelengths of the detected first to third laser lights LS1 to LS3, respectively. The wavelengths of the first to third laser beams LS1 to LS3 can be stably locked to the _first to third target wavelengths λ _{1 to} λ ₃ . The ionization laser controller 10 and the first to third controllers 101 to 301 are excitation laser output means based on the absolute wavelength of the excitation laser light (LS1, LS2) and the absolute wavelength of the ionization laser light (LS3). It functions as a control means for controlling certain first and second lasers 102 and 202 and a third laser 302 that is an ionization laser output means.

  The multiplexing optical system 30 is configured by appropriately using, for example, a diffraction grating, a half mirror, a dichroic mirror, a beam combiner, and the like, and as described above, the first to third laser devices 100 to 300 output from the first to third laser devices 100 to 300. The three laser beams LS1 to LS3 are combined to output a combined laser beam LS.

As described above, the ionization laser apparatus 1 according to the first embodiment has a laser beam having a wavelength (first to third target wavelengths λ _{1 to} λ ₃ ) corresponding to excitation energy or ionization energy given to the target (Sn atom) ( A plurality of laser devices (first to third laser devices 100 to 300) that output first to third laser beams LS1 to LS3) are used. For this reason, it is possible to adjust the wavelength of the laser beam output from each laser device (100 to 300) independently to the target wavelength with high accuracy. Moreover, in the ionization laser apparatus 1, adjustment to the target wavelength of each laser apparatus (100 to 300) is performed based on the absolute wavelength. For this reason, it is possible to effectively give energy to the target by improving the light absorptivity of the target. As a result, efficient ionization of the target becomes possible.

  Next, a more specific configuration example of the ionization laser device 1 shown in FIG. 2 will be described in detail with reference to the drawings. FIG. 3 is a schematic diagram showing a configuration example of the ionization laser apparatus 1A according to the first embodiment. As shown in FIG. 3, in the ionization laser apparatus 1 </ b> A, the first laser apparatus 100 includes a fluorescence detector 110 </ b> A as the first absolute wavelength detector 110. Further, the second / third laser device 200/300 includes first / second laser galvatrons 210A / 310A as second / third absolute wavelength detectors 210/310. Furthermore, the first to third laser devices 100 to 300 detect the wavelengths of the first to third laser beams LS1 to LS3 output from the first to third lasers 102 to 302, respectively. A total of 103 to 303 is provided. The first to third wavelength meters 103 to 303 only need to be able to detect the rough wavelengths of the first to third laser beams LS1 to LS3, and may be relative wavelengths. Among the wavelength meters, the first and second wavelength meters 103 and 203 function as excitation wavelength detecting means for detecting the wavelengths of the first and second laser lights LS1 and LS2 that are excitation laser lights, The wavelength meter 303 functions as an ionization wavelength meter that detects the wavelength of the third laser light LS3 that is an ionization laser beam.

FIG. 4 shows a specific example of the first to third lasers 102 to 302 shown in FIG. As shown in FIG. 4, the first laser 102 includes a narrow-band semiconductor laser 121 that outputs a narrow-band laser beam LS1a having a wavelength λ _1a (= 1145 nm) that is four times the first target wavelength λ ₁ . The Yb fiber amplifier 122 that amplifies the laser beam LS1a output from the narrow-band semiconductor laser 121, and the quadruple that generates the first laser beam LS1 that is a quarter wavelength of the amplified laser beam LS1a. And a wave generator 123. Therefore, the laser beam LS1a output from the narrow-band semiconductor laser 121 is amplified by the Yb fiber amplifier 122, converted to the first laser beam LS1 by the fourth harmonic generator 123, and then output. In this configuration, the wavelength control of the first laser light LS1 can be performed by controlling the substantial temperature of the narrow-band semiconductor laser 121.

  On the other hand, the second and third lasers 202 and 302 include narrow-band semiconductor lasers 221 and 321 and parametric oscillators 222 and 322, respectively, and a common Yb fiber laser 223. The Yb fiber laser 223 functions as a so-called optical pump that amplifies laser light. Therefore, the narrow-band laser light LS2a output from the narrow-band semiconductor laser 221 is input to the parametric oscillator 222 and amplified together with the laser light output from the Yb fiber laser 223, and then output as the second laser light LS2. Is done. Similarly, the narrow-band laser light LS3a output from the narrow-band semiconductor laser 321 is input to the parametric oscillator 322 and amplified together with the laser light output from the Yb fiber laser 223, and is then used as the third laser light LS3. Is output. In this configuration, the wavelength control of the second / third laser light LS2 / LS3 can be performed by controlling the substantial temperature of the narrow-band semiconductor laser 221/321.

  The narrow-band semiconductor lasers 121 to 321 are so-called seed light sources. The narrow-band semiconductor lasers 121 to 321 may be semiconductor lasers that pulsate and output laser light intermittently, or semiconductor lasers that continuously oscillate and output laser light. . Moreover, it is preferable that the 1st-3rd lasers 102-302 are comprised by the fiber laser which can be operated stably for a long time. Thereby, the ionization laser apparatus 1A that stably outputs laser light can be realized.

  Returning to FIG. In FIG. 3, a fluorescence detector 110A as a first absolute wavelength detector 110 is a so-called in-situ fluorescence detector disposed in a chamber (not shown) for ionization, and is emitted from a target (Sn atom). It is a detector that detects the intensity of the fluorescence. This fluorescence detector 110A can observe fluorescence emitted from an actual target (Sn atom).

Here, as described above, the lifetime in which the Sn atom maintains the first eigenstate is as short as about 5 ns. When electrons in the orbit E1 are de-excited and transit to the orbit ES1 (= 5p ^{2 3} P ₁ ), as shown in FIG. 1, a fluorescence CS having a wavelength λ _fluo (= 317.5 nm) is emitted. (Step SS1). Therefore, the ionization laser apparatus 1A shown in FIG. 3 obtains the absolute wavelength of the first laser light LS1 from the wavelength dependence of the light absorption rate of the electrons with respect to the first laser light LS1 by observing the fluorescence CS. That is, the wavelength dependency of the excitation efficiency of the electrons by the first laser light LS1 is obtained from the intensity of the fluorescence CS generated with respect to the irradiation of the first laser light LS1, and the wavelength at which this intensity reaches the maximum value is the absolute wavelength. As specified. In the following description, a state where electrons are in the orbit ES1 is referred to as an eigenstate after deexcitation.

Therefore, the first controller 101 controls the first laser 102 so that the intensity of the fluorescence CS detected by the fluorescence detector 110A takes the maximum value, and adjusts the wavelength of the first laser light LS1 to be output therefrom. in, Komu combined wavelength of the first laser beam LS1 to the first laser device 100 outputs the first target wavelength lambda _1. Further, the first controller 101, as the wavelength of the first laser beam LS1 maintains the first target wavelength lambda _1, the feedback control of the first laser 102. For example, when the first laser 102 is a semiconductor laser, the first controller 101 controls the substantial temperature to change the wavelength of the first laser light LS1 output from the first laser 102 to the first target wavelength λ. Set to ₁ . However, the present invention is not limited to this. For example, if the first laser 102 is another laser, the first controller 101 may directly control the resonator length, insert an etalon or a grating in the optical path, and determine the angle. by controlling it may be configured to wavelength of the first laser beam LS1 to the first laser 102 outputs as first Komu suit target wavelength lambda _1.

  On the other hand, the first / second laser galvatrons 210A / 310A as the second / third absolute wavelength detectors 210/310 are so-called optogalvanic discharge tubes and are enclosed in a discharge tube (follower cathode lamp). The absolute wavelength of the laser light is detected by irradiating the gas with laser light and detecting the amount of current depending on the spectral wavelength inherent to the gas generated thereby. The first / second laser galvatrons 210 </ b> A / 310 </ b> A are disposed, for example, at the front stage (or the rear stage) of the multiplexer 32/33 constituting the multiplexing optical system 30.

  Here, FIG. 5A shows a specific example of the first / second laser galvatron 210A / 310A according to the first embodiment. FIG. 5B shows an example of an optogalvano signal output from the first / second laser galvatron 210A / 310A, and FIG. 5C shows the relationship between the current amount of the optogalvano signal and the wavelength of the laser beam.

  As shown in FIG. 5A, the first / second laser galvatron 210A / 310A includes a rare gas-filled glass tube 212 filled with a rare gas, and an anode An and a cathode Ca disposed in the rare gas-filled glass tube 212. , And the following cathode cathode lamp 211. For example, helium (He) or argon (Ar) can be used as the rare gas sealed in the rare gas sealed glass tube 212. For the cathode Ca, for example, an Sn electrode made of the same material as the ionization target is used. A high voltage of several hundred to several thousand volts is applied to the anode An from the high-voltage power supply Hvs.

In this configuration, when a laser beam having a wavelength resonating with the absorption spectrum of atoms in the discharge plasma formed in the rare gas sealed glass tube 212 is incident, the discharge current flowing through the resistor R connected to the cathode Ca changes. Therefore, when the laser light (LS2 / LS3) passes through the rare gas filled glass tube 212 from the anode An side to the cathode Ca side, the resistance R connected to the cathode Ca has a laser beam as shown in FIG. 5B. An optogalvanic signal that changes according to the waveform and wavelength flows. The amount of current of the optogalvano signal depends on the wavelength of the laser light incident on the follow-cathode lamp 211 as shown in FIG. 5C. Therefore, the second / third controller 201/301 controls the second / third laser 202/302 so that the amount of current takes a maximum value, and the second / third laser light LS2 / LS3 output from the second / third laser 202/302. The wavelength of the second / third laser light LS2 / LS3 output from the second / third laser device 200/300 is adjusted to the second / third target wavelength λ ₂ / λ ₃ (the optimum ionization wavelength). ) Further, the second / third controller 201/301 is configured so that the wavelength of the second / third laser light LS2 / LS3 maintains the _second / third target wavelength λ ₂ / λ _3. 202/302 is feedback controlled. The wavelength control of the second / third laser 202/302 by the second / third controller 201/301 is the same as that of the first controller 101 described above. However, the atomic source is not limited to the follower cathode lamp 211 and may be the same atomic source as the target Tsn.

  Next, the operation of the ionization laser apparatus 1A according to the first embodiment will be described in detail with reference to the drawings. FIG. 6 is a flowchart showing an example of an operation at the time of startup of the ionization laser apparatus 1A according to the first embodiment (hereinafter referred to as startup operation). FIG. 7 is a flowchart showing an example of an operation at the time of steady control (hereinafter referred to as a steady operation) of the ionization laser apparatus 1A according to the first embodiment. In the following description, the first to third controllers 101 that control the first to third laser devices 100 to 300 under the operation of the ionization laser controller 10 that controls the ionization laser 20 and the control from the ionization laser controller 10. Description will be made by paying attention to the operations of .about.301.

As shown in FIG. 6, when the ionization laser controller 10 starts the start-up operation, the wavelength of the first laser 102 is roughly tuned to the first target wavelength λ ₁ (= 286.4 nm) (step S101). Specifically, under the control of the ionization laser controller 10, the first controller 101 causes the first laser 102 to start outputting the first laser light LS 1, and then the first wavelength meter 103 detects the first laser beam LS 1. wavelength of first laser beam LS1 is the first laser 102 is feedback controlled such that the first target wavelength lambda _1. Thus, in the coarse tuning step of the first laser 102, the first laser 102 is feedback-controlled based on the wavelength detected by the first wavelength meter 103. By keeping this is a coarse tuning prior to accurately tune the wavelengths of the first laser 102 to the first target wavelength lambda _1, it is possible to facilitate the time reduction and control during precise tuning.

Next, ionizing laser controller 10, to accurately tune the wavelength of the first laser 102 to a first target wavelength lambda ₁ (step S102). Specifically, under the control of the ionization laser controller 10, the first controller 101 changes the wavelength of the first laser light LS1 output from the first laser 102, and the fluorescence detected by the fluorescence detector 110A in this process. strength of the CS is to identify the wavelength at which the maximum value (first corresponding to the target wavelength lambda _1), feedback control of the first laser 102 as the wavelength Komu combined wavelength of the first laser beam LS1. Thus, in the tuning step of the first laser 102, so that the absolute wavelength of the first laser beam LS1 which is obtained from the intensity of the fluorescence CS detected by the fluorescence detector 110A is the first target wavelength lambda _1, the first laser 102 is feedback controlled. For this reason, it is possible to tune the wavelength of the first laser 102 to the first target wavelength λ ₁ more accurately.

Next, ionizing laser controller 10, the wavelength of the first laser 102 determines whether or not it is locked to the first target wavelength lambda ₁ (step S103), when it is not locked (No in step S103), step Returning to S102, the first controller 101 is again caused to perform feedback control of the first laser 102 using the fluorescence intensity detection result by the fluorescence detector 110A.

On the other hand, when the wavelength of the first laser 102 is locked to the first target wavelength λ ₁ (Yes in step S103), the ionization laser controller 10 next changes the wavelength of the second laser 202 to the second target wavelength λ _2. Coarse tuning is performed at (= 811.6 nm) (step S104). Specifically, under the control of the ionization laser controller 10, the second controller 201 causes the second laser 202 to start outputting the second laser light LS 2, and then the second wavelength meter 203 detects the second laser beam LS 2. wavelength of the laser beam LS2 is feedback-controls the second laser 202 such that the second target wavelength lambda _2. As described above, in the coarse tuning step of the second laser 202, the second laser 202 is feedback-controlled based on the wavelength detected by the second wavelength meter 203 as in the coarse tuning step of the first laser 102.

Next, the ionization laser controller 10 accurately tunes the wavelength of the second laser 202 to the second target wavelength λ ₂ (step S105). Specifically, under the control of the ionization laser controller 10, the second controller 201 changes the wavelength of the second laser LS2 output from the second laser 202, and the optogalvanoscope detected by the first laser galvatron 210A in this process. The wavelength (corresponding to the second target wavelength λ ₂ ) at which the signal value is maximum is specified, and the second laser 202 is feedback-controlled so that the wavelength of the second laser light LS 2 is matched with this wavelength. Thus, in the tuning step of the second laser 202, so that the absolute wavelength of the second laser beam LS2 obtained from Opto galvano signal detected by the first laser Galvatron 210A becomes the second target wavelength lambda _2, the second laser 202 is feedback controlled. Therefore, similarly to the tuning step of the first laser 102, it is possible to tune the wavelength of the second laser 202 to the second target wavelength λ ₂ more accurately.

Next, the ionization laser controller 10 determines whether or not the wavelength of the second laser 202 is locked to the second target wavelength λ ₂ (step S106). If not locked (No in step S106), step Returning to S105, the second controller 201 is again caused to perform feedback control of the second laser 202 using the optogalvano signal detected by the first laser galvatron 210A.

On the other hand, when the wavelength of the second laser 202 is locked to the second target wavelength λ ₂ (Yes in step S106), the ionization laser controller 10 next changes the wavelength of the third laser 302 to the third target wavelength λ _3. Coarse tuning (= 823.7 nm) is performed (step S107). Specifically, under the control of the ionization laser controller 10, the third controller 301 causes the third laser 302 to start outputting the third laser light LS 3, and subsequently the third wavelength meter 303 detects the third laser beam LS 3. feedback-controls the third laser 302 as the wavelength of the laser beam LS3 is third target wavelength lambda _3. Thus, in the coarse tuning step of the third laser 302, the third laser 302 is controlled based on the wavelength detected by the third wavelength meter 303, as in the coarse tuning step of the first / second laser 102/202. Feedback controlled.

Next, the ionization laser controller 10 accurately tunes the wavelength of the third laser 302 to the third target wavelength λ ₃ (step S108). Specifically, similarly to step S105, under the control of the ionization laser controller 10, the third controller 301 changes the wavelength of the third laser LS3 output from the third laser 302, and in this process, the second laser galvatron is changed. the value of the opto galvano signal 310A is detected by identifying the wavelength at which the maximum value (third corresponding to the target wavelength lambda _3), feeding back the third laser 302 so as to go combined wavelength of the third laser beam LS3 in this wavelength Control. This makes it possible to tune the wavelength of the third laser 302 to the third target wavelength λ ₃ more accurately, similarly to the tuning step of the first / second lasers 102/202.

Thereafter, ionizing laser controller 10, the wavelength of the third laser 302 determines whether or not it is locked to the third target wavelength lambda ₃ (step S109), when it is not locked (No in step S109), step S108 The third controller 301 is caused to execute feedback control of the third laser 302 again using the optogalvano signal detected by the second laser galvatron 310A. On the other hand, when the wavelength of the third laser 302 is locked to the third target wavelength lambda ₃ (Yes in step S109), ionizing laser controller 10 ends the start-up operation.

By performing the startup operation as described above, the wavelengths of the plurality of laser beams (first to third laser beams LS1 to LS3) output from the ionization laser device 1A are set in an appropriate order of the ionization process. It is possible to reliably adjust to a desired wavelength (first to third target wavelengths λ _{1 to} λ ₃ ). As a result, it becomes possible to easily and reliably match the wavelengths of all the laser beams to the target wavelengths.

When the wavelength of the first to third laser 102-302 by the raising operation is locked respectively to the first to third target wavelength lambda ₁ to [lambda] _3, ionizing laser device 1A, then, the first to third A steady operation is performed in which the laser beams LS1 to LS3 are constantly output at a stable wavelength.

In steady operation, the ionization laser controller 10 monitors the output wavelength of the first laser 102, that is, the wavelength of the first laser light LS1, as shown in FIG. 7 (step S111), and the output wavelength of the first laser 102 is the first wavelength. It is determined whether or not the target wavelength λ ₁ is locked (step S112). Specifically, whether the intensity of the fluorescence CS detected by the fluorescence detector 110A is substantially the same as the maximum value detected during the startup operation under the control of the ionization laser controller 10. detects whether, when the output wavelength of the first laser 102 if substantially unchanged value is determined to be locked to the first target wavelength lambda _1, is changed greatly, the intensity of the particular fluorescent CS if is greatly reduced, it is determined that the output wavelength of the first laser 102 is offset from the first target wavelength lambda _1. However, not limited thereto, for example, a wavelength that is detected by the first wavemeter 103, the first target wavelength lambda _1, or, locked the wavelength of the first laser 102 to the first target wavelength lambda ₁ in start-up operation It is detected whether or not it is equal to the wavelength detected immediately thereafter, and it is determined whether or not the output wavelength of the first laser 102 is locked to the first target wavelength λ ₁ based on the detection result. It can be deformed.

Determined in step S112, if the output wavelength of the first laser 102 is not locked to the first target wavelength lambda ₁ (No in step S112), ionizing laser controller 10, the same procedure as step S102 of FIG. 6 The output wavelength of the first laser 102 is locked to the first target wavelength λ ₁ (step S113), and then the process returns to step S112 so that the output wavelength of the first laser 102 becomes the first target wavelength λ ₁ again. It is determined whether or not it is locked.

On the other hand, the determination in step S112 results, if the output wavelength of the first laser 102 is locked to the first target wavelength lambda ₁ (Yes in step S112), ionizing laser controller 10, then, the second laser 202 monitoring the output wavelength, i.e. the wavelength of the second laser beam LS2 (step S114), the output wavelength of the second laser 202 determines whether it is locked to the second target wavelength lambda ₂ (step S115). Specifically, under the control of the ionization laser controller 10, the second controller 201 is a value at which the current value of the optogalvano signal detected by the first laser galvatron 210 </ b> A is not substantially different from the maximum value detected during the start-up operation. If the current value is substantially unchanged, it is determined that the output wavelength of the second laser 202 is locked to the second target wavelength λ ₂ , and particularly when the output wavelength is greatly changed, If the current value of the opto galvanometer signal is greatly reduced, it is determined that the output wavelength of the second laser 202 is offset from the second target wavelength lambda _2. However, not limited to this, similarly to step S112, by using the second wavemeter 203, the output wavelength of the second laser 202 and determines whether it is locked to the second target wavelength lambda _2, various It can be deformed.

Determined in step S115, if the output wavelength of the second laser 202 is not locked to the second target wavelength lambda ₂ (No in step S115), ionizing laser controller 10, the same procedure as step S105 in FIG. 6 The output wavelength of the second laser 202 is locked to the second target wavelength λ ₂ (step S116), and then the process returns to step S115 so that the output wavelength of the second laser 202 becomes the second target wavelength λ ₂ again. It is determined whether or not it is locked.

On the other hand, if the result of determination in step S115 is that the output wavelength of the second laser 202 is locked to the second target wavelength λ ₂ (Yes in step S115), the ionization laser controller 10 then moves the third laser 302 monitoring the output wavelength, i.e. the third wavelength of the laser beam LS3 (step S117), it determines whether the output wavelength of the third laser 302 is locked to the third target wavelength lambda ₃ (step S118). A specific procedure example is the same as that in step S115.

Result of the determination in step S118, the case where the output wavelength of the third laser 302 is not locked to the third target wavelength lambda ₃ (No in step S118), ionizing laser controller 10, the same procedure as step S108 of FIG. 6 The wavelength of the third laser 302 is locked to the third target wavelength λ ₃ (step S119), and then the process returns to step S118, where the output wavelength of the third laser 302 is set to the third target wavelength λ ₃ again. Determine if it is locked.

On the other hand, the result of the determination in step S118, the case where the output wavelength of the third laser 302 is locked to the third target wavelength lambda ₃ (Yes in step S118), ionizing laser controller 10, the end of the steady-state operation is indicated It is determined whether or not (step S120), and when instructed (Yes in step S120), the steady operation is terminated. On the other hand, when the termination of the steady operation is not instructed (No in step S120), the ionization laser controller 10 returns to step S111 and repeats the same operation again.

By executing the steady operation as described above, any one of a plurality of laser beams (first to third laser beams LS1 to LS3) output from the ionization laser device 1A has a desired wavelength (first to third). When it deviates from the target wavelengths [lambda] _1- [lambda] ₃ ), it becomes possible to re-adjust the wavelength from the laser beam with the deviated wavelength. For this reason, when it is not necessary to adjust the wavelength of all the laser beams, it is possible to easily and appropriately lock all the laser beams to the desired wavelengths while omitting the trouble of adjusting the wavelengths of all the laser beams from the beginning. It becomes possible. As a result, an ionization laser device that can ionize a target with a high ionization rate even when using a plurality of laser beams can be realized.

(Modification 1-1)
Next, a modification of the ionization laser device according to the first embodiment will be described in detail with reference to the drawings. In Embodiment 1 mentioned above, the case where the target (Sn atom) was ionized through three steps S1-S3 was mentioned as an example. On the other hand, in the modified example 1-1 of the first embodiment, a case where the target (Sn atom) is ionized through two steps will be described as an example.

FIG. 8 is a conceptual diagram for explaining a target (Sn atom) ionization process according to Modification 1-1. As shown in FIG. 8, in Modification 1-1, first, as in the first embodiment, the first laser beam LS <b> 1 is irradiated to the target Sn atom, and electrons in the ground state are irradiated. Is shifted from the trajectory E0 (= 5p ^{2 3} P ₀ ) to the trajectory E1 (= 5p6s ³ P ⁰ ₁ ) (step S1). Thereby, the Sn atom becomes the first eigenstate.

Subsequently, in addition to the first laser beam LS1, a laser beam having a wavelength λ ₄ (= 408.8 nm) corresponding to the remaining energy (eV) necessary for directly ionizing Sn atoms in the first eigenstate ( Hereinafter, LS4 (referred to as a fourth laser beam) is irradiated (step S4). As a result, the Sn atoms absorb the fourth laser beam LS4, and the electrons in the orbit E1 (= 5p6s ³ P ⁰ ₁ ) have an energy equal to or higher than the ionization potential (IP = 59233 cm ⁻¹ ). Jumps out of the valence band to the conductor (E3), and as a result, Sn atoms are ionized. In the following description, the wavelength λ _{4 is referred} to as a fourth target wavelength.

  Next, an ionization laser apparatus capable of realizing the ionization process according to the modification 1-1 will be described in detail with reference to the drawings. FIG. 9 is a schematic diagram illustrating a configuration example of an ionization laser device 1A-1 according to Modification 1-1. As shown in FIG. 9, an ionization laser device 1A-1 includes a first laser device 100 that outputs a first laser beam LS1, a fourth laser device 400 that outputs a fourth laser beam LS4, and first and fourth lasers. And a combining optical system 30 that combines the laser beams output from the devices 100 and 400 and outputs the combined laser beams as the combined laser beam LSa.

Here, the first laser device 100 is the same as the first laser device 100 shown in FIG. The fourth laser device 400 includes a fourth laser 402 that outputs the fourth laser light LS4, a fourth wavelength meter 403 that detects the wavelength of the fourth laser light LS4 output from the fourth laser 402, and a fourth The third laser galvatron 410A as an absolute wavelength detector that detects the absolute wavelength of the laser beam LS4, and the wavelength of the fourth laser beam LS4 is based on the wavelength detected by the fourth wavelength meter 403 or the third laser galvatron 410A. 4 comprises a fourth controller 401 that a fourth laser 402 performs feedback control to lock the target wavelength lambda _4, a. Note that the fourth wavelength meter 403 only needs to be able to detect the approximate wavelength of the fourth laser light LS4, and may be a relative wavelength.

Further, the fourth laser 402, the fourth wavelength meter 403, and the third laser galvatron 410A in the fourth laser apparatus 400 are the same as those in the second / third laser apparatus 200/300. However, the fourth laser 402 is feedback-controlled by the fourth controller 401 to output a fourth laser beam LS4 fourth target wavelength lambda _4.

  Next, operation | movement of the ionization laser apparatus 1A-1 by this modification 1-1 is demonstrated in detail using drawing. FIG. 10 is a flowchart showing an example of the startup operation of the ionization laser device 1A-1 according to Modification 1-1. FIG. 11 is a flowchart showing an example of a steady operation of the ionization laser device 1A-1 according to Modification 1-1. In the following description, the operation of the ionization laser controller 10 for controlling the ionization laser 20-1 and the first / fourth for controlling the first / fourth laser devices 100/400 under the control from the ionization laser controller 10. Description will be made focusing on the operation of the controller 101/401.

As shown in FIG. 10, when the ionization laser controller 10 starts the start-up operation, the ionization laser controller 10 goes through a process similar to the process described using steps S101 to S103 in FIG. to lock the wavelength of the laser 102 to the first target wavelength lambda ₁ (step S101 to S103).

Through the process of steps S101 to S103, if the wavelength of the first laser 102 is locked to the first target wavelength lambda ₁ (Yes in step S103), then, ionizing laser controller 10, the wavelength of the fourth laser 402 Coarse tuning is performed to the fourth target wavelength λ ₄ (= 408.8 nm) (step S404). Specifically, under the control of the ionization laser controller 10, the fourth controller 401 causes the fourth laser 402 to start outputting the fourth laser light LS 4, and then the fourth wavelength meter 403 detects the fourth. feedback control of the fourth laser 402 as the wavelength of the laser beam LS4 become the fourth target wavelength lambda _4. As described above, in the coarse tuning step of the fourth laser 402, the fourth wavelength meter 403, based on the wavelength detected by the fourth wavelength meter 403, similarly to the steps S101 / S104 / S107 in FIG. The laser 402 is feedback controlled.

Next, ionizing laser controller 10, to accurately tune the wavelength of the fourth laser 402 to the fourth target wavelength lambda ₄ (step S405). Specifically, similarly to steps S105 / S108 in FIG. 6 in the first embodiment described above, the fourth controller 401 controls the fourth laser LS3 output by the fourth laser 402 under the control of the ionization laser controller 10. changing the wavelength to identify the wavelength value of the opto galvanometer signal third laser Galvatron 410A in this process is detected becomes the maximum value (4 corresponding to the target wavelength lambda _4), to the wavelength of the fourth laser beam LS4 The fourth laser 402 is feedback controlled so as to adjust the wavelength. This makes it possible to tune the fourth laser 402 to the fourth target wavelength λ ₄ more accurately, similarly to the tuning step of the first laser 102.

Thereafter, ionizing laser controller 10, the wavelength of the fourth laser 402 determines whether or not it is locked to the fourth target wavelength lambda ₄ (step S406), when it is not locked (No in step S406), step S405 Then, the fourth controller 401 is caused to execute feedback control of the fourth laser 402 again using the optogalvano signal detected by the third laser galvatron 410A. On the other hand, when the wavelength of the fourth laser 402 is locked to the fourth target wavelength lambda ₄ (Yes in step S406), ionizing laser controller 10 ends the start-up operation.

When the wavelengths of the first and fourth lasers 102 and 402 are locked to the first and fourth target wavelengths λ ₁ and λ ₄ by the start-up operation, the ionization laser device 1A-1 then has the first, A steady operation is performed in which the fourth laser beams LS1 and LS4 are constantly output at a stable wavelength.

As shown in FIG. 11, when the ionization laser controller 10 starts a steady operation, the ionization laser controller 10 goes through a process similar to the process described using steps S111 to S113 in FIG. wavelength of 102 to maintain the state of being locked to the first target wavelength lambda ₁ (step S111 to S113).

Determined in step S112, when the wavelength of the first laser 102 is locked to the first target wavelength lambda ₁ (Yes in step S112), then, ionizing laser controller 10, the output wavelength of the fourth laser 402, that monitors the fourth wavelength of the laser light LS4 (step S414), determines whether the wavelength of the fourth laser beam LS4 is locked to the fourth target wavelength lambda ₄ (step S415). Specifically, under the control of the ionization laser controller 10, the fourth controller 401 is a value at which the current value of the optogalvano signal detected by the third laser galvatron 410 </ b> A is not substantially different from the maximum value detected during the start-up operation. detecting whether a, when the wavelength of the fourth laser beam LS4 if substantially unchanged current value is determined to be locked to the fourth target wavelength lambda _4, has changed significantly, particularly If the current value of the opto galvanometer signal is greatly reduced, it is determined that the wavelength of the fourth laser beam LS4 is shifted from the fourth target wavelength lambda _4. Note that this embodiment is not limited thereto, for example, by using the fourth wavelength meter 403, such as the wavelength of the fourth laser beam LS4 determines whether it is locked to the fourth target wavelength lambda _4, various modifications are possible .

Determined in step S415, when the wavelength of the fourth laser beam LS4 is not locked to the fourth target wavelength lambda ₄ (No in step S415), ionizing laser controller 10, the same procedure as step S405 of FIG. 10 The wavelength of the fourth laser 402 is locked to the fourth target wavelength λ ₄ (step S416), and then the process returns to step S415, where the wavelength of the fourth laser light LS4 becomes the fourth target wavelength λ ₄ again. Determine if it is locked.

On the other hand, the result of the determination in step S415, when the wavelength of the fourth laser beam LS4 is locked to the fourth target wavelength lambda ₄ (Yes in step S415), ionizing laser controller 10, as in step S120 of FIG. 7 Then, it is determined whether or not the end of the steady operation is instructed (step S120). When the instruction is instructed (Yes in step S120), the steady operation is ended. On the other hand, when the termination of the steady operation is not instructed (No in step S120), the ionization laser controller 10 returns to step S111 and repeats the same operation again.

  By executing the steady operation as described above, an ionization laser device that can ionize a target at a high ionization rate even when a plurality of laser beams are used can be realized as in the first embodiment.

(Modification 1-2)
Next, a modification of the fluorescence detector as the absolute wavelength detector 110 in the first embodiment will be described in detail with reference to the drawings. In the first embodiment described above, so-called in-situ fluorescence arranged in a chamber (not shown) for ionizing the target (Sn atom) so that the fluorescence emitted from the actual target (Sn atom) can be observed. The detector 110A was used. On the other hand, in the present modified example 1-2, the target (Sn atom) is arranged independently of the target (Sn atom), not in the actual target (Sn atom) but in the preceding stage (or the subsequent stage) of the multiplexer 32 constituting the multiplexing optical system 30. ) Is used to detect the intensity of the fluorescence CS emitted by the same atom (Sn atom) as the irradiation of the first laser beam LS1.

  FIG. 12 is a schematic diagram illustrating a specific example of the fluorescence detector 110A-1 according to Modification 1-2. As shown in FIG. 12, the fluorescence detector 110 </ b> A- 1 has a vapor-sealed cell 111 having airtightness and the vapor (Sn vapor 113) of the same atom (Sn atom) as the target flows into the vapor-sealed cell 111. A steam generator 112 and a photodetector 119 that detects the intensity of the fluorescent CS generated in the steam-sealed cell 111 are provided.

  In this configuration, the vapor sealed cell 111 emits the light incident window 114 and the light exit window 115 for allowing the first laser light LS1 to pass through the vapor sealed cell 111 and the Sn vapor 113 in the vapor sealed cell 111. And a light extraction window 116 for taking out the fluorescent CS. Therefore, the first laser light LS1 incident from the light incident window 114 is irradiated to the Sn vapor 113 at a certain point (fluorescence generation point CSo) in the vapor sealed cell 111. Then, atoms in the Sn vapor 113 are excited by the first laser light LS1, and then de-excited. At the time of deexcitation, the fluorescence CS is emitted from the fluorescence generation point CSo of the Sn vapor 113. The optical image of the fluorescence generation point CSo is transferred to the image detection surface of the photodetector 119 by the transfer lens 117 disposed outside the light extraction window 116. The photodetector 119 detects the intensity of the fluorescence CS from the brightness of the transferred optical image of the fluorescence generation point CSo, and outputs the detection result to the first controller 101. Note that a background light blocking filter 118 that blocks light having a wavelength other than the wavelength of the fluorescence CS, for example, scattered light of the first laser light LS1 serving as background light, may be provided on the image detection surface of the photodetector 119. Thereby, it becomes possible to detect the intensity of the fluorescence CS more accurately.

(Modification 1-3)
Next, a modification of the absolute wavelength detector 210/310 in the first embodiment will be described in detail with reference to the drawings. In the above-described first embodiment, as the absolute wavelength detector 210/310, for the so-called optogalvanic spectroscopy, the absolute wavelength of the laser light (LS2 / LS3) is specified from the spectral wavelength specific to the gas enclosed in the follower cathode lamp 211. A discharge tube (first / second laser galvatron 210A / 310A) was used. On the other hand, in this modified example 1-3, the absorption amount of the laser beam is detected from the attenuation of the laser beam (LS2 / LS3) that has passed through the inside of the follow-cathode lamp in which a predetermined gas is sealed, and the absolute wavelength thereof is determined. The light absorption detector 210A-1 / 310A-1 to be specified is used.

  FIG. 13A is a schematic diagram illustrating a specific example of the light absorption detector 210A-1 / 310A-1 according to Modification 1-3. FIG. 13B shows an example of the light detection signal output from the light absorption detectors 210A-1 / 310A-1, and FIG. 13C shows the relationship between the maximum value of the light detection signal and the wavelength of the laser light.

  As shown in FIG. 13A, the light absorption detector 210A-1 / 310A-1 includes a rare gas-filled glass tube 212 filled with a rare gas and a rare gas, like the first / second laser galvatron 210A / 310A. It consists of a follower cathode lamp 211 including an anode An and a cathode Ca arranged in the sealed glass tube 212.

In this configuration, when a laser beam having a wavelength resonating with an absorption spectrum of atoms in the discharge plasma formed in the rare gas-filled glass tube 212 is incident, the laser beam is absorbed. Therefore, the laser beam (LS2 / LS3) incident on the rare gas sealed glass tube 212 is attenuated when passing from the anode An side to the cathode Ca side. As a result, as shown in FIG. 13B, the optical sensor 214 provided on the light output side of the follow-cathode lamp 211 detects a light detection signal that changes according to the waveform and wavelength of the laser light. The maximum value of the light detection signal (sensor light detection intensity) is attenuated depending on the wavelength of the laser light incident on the follow-cathode lamp 211 as shown in FIG. 13C. Therefore, the second / third laser 202/302 is controlled so that the sensor light detection intensity takes the minimum value, and the wavelength of the second / third laser light LS2 / LS3 to be output from the second / third laser 202/302 is adjusted. 2 / The wavelength of the second / third laser light LS2 / LS3 output from the third laser device 200/300 can be adjusted to the second / third target wavelength λ ₂ / λ ₃ (ionization optimum wavelength).

(Modification 1-4)
Next, modified examples of the first to third lasers 102 to 302 in the first embodiment will be described in detail with reference to the drawings. In the first embodiment described above, the first to third lasers 102 that amplify and output the laser light output from the narrow-band semiconductor laser 121/221/321 as the seed light source by the fiber amplifier (122/223). ~ 302 was used. On the other hand, in Modification 1-4, the first to third lasers 102-1 each including a narrow-band laser oscillator that oscillates using laser light output from a narrow-band semiconductor laser as a seed light source as seed light. ~ 302-1.

  FIG. 14 is a schematic diagram illustrating a specific example of the first to third lasers 102-1 to 302-1 according to Modification 1-4. As shown in FIG. 14, the first laser 102-1 includes a narrow-band semiconductor laser 121-1 that outputs narrow-band seeder light, a narrow-band laser oscillator 122-1 that oscillates with seeder light, and a narrow-band. A third harmonic wave generator 123-1 for generating a first laser beam LS1 having a wavelength of one third of the laser beam LS1b output from the laser beam generator 122-1. The second / third lasers 202-1 / 302-1 are oscillated by the seeder light and the second / third lasers 221-1 / 321-1, which output the narrowband seeder light. And a narrow-band laser oscillator 222-1 / 322-1 that outputs laser light LS2 / LS3. In addition, the first to third lasers 102-1 to 302-1 are output from the Nd: YVO4 laser 125-1 that outputs laser light of a predetermined wavelength and the Nd: YVO4 laser 125-1 as other configurations. A double wave generator 124-1 that outputs laser light having a half wavelength of the laser light as excitation light, and a narrowband laser that emits the excitation light output from the double wave generator 124-1. A reflecting mirror 126-1 that guides to the oscillator 122-1 / 2222-1 / 322-1, and a dichroic mirror 127-1 / 2277-1 / 327-1 that is a beam splitter.

  As in the case of a CW green laser, the second harmonic generator 124-1 and the YVO4 laser 125-1 are integrated. For example, the second harmonic generator 124- is included in the resonator of the YVO4 laser 125-1. 1 may be arranged. Further, for example, an Nd: YAG laser may be used instead of the YVO4 laser 125-1 which is a wavelength tunable excitation light source.

  The narrow band semiconductor laser 121-1/221-1/321-1 is a seed light source for wavelength selection and narrow band. Since this narrow-band semiconductor laser 121-1/221-1/321-1 does not require incident excitation light from the same optical axis as the YVO4 laser 125-1 that is an excitation light source, a dichroic mirror as shown in FIG. The pump light is not limited to the configuration in which the pump light is incident from the rear of 127-1/227-1/327-1, and the pump light is narrowed from another mirror that forms the resonator 121-1/221-1/321. -1 may be configured so as to be incident respectively. However, since the configuration shown in FIG. 14 is a configuration in which excitation light is incident from the same optical axis as that of the YVO4 laser 125-1, it is necessary to use the dichroic mirrors 127-1 / 227-1 / 327-1.

In this configuration, the seeder light output from the narrow-band semiconductor laser 121-1 of the first laser 102-1 passes through the dichroic mirror 127-1 and enters the narrow-band laser oscillator 122-1 that is a titanium sapphire laser. Entered. In addition, a part of the excitation light output from the second harmonic generator 124-1 is also input to the narrow-band laser oscillator 122-1. The narrow-band laser oscillator 122-1 oscillates with these seeder light and excitation light, thereby narrow-band laser light LS _{1 b} having a wavelength λ _1b (= 860 nm) that is three times the first target wavelength λ ₁ . Is output. The laser beam LS1b output from the narrow-band laser oscillator 122-1 is a first laser beam LS1 having a wavelength of 1/3 (first target wavelength λ ₁ = 286.3 nm) in the third harmonic generator 123-1. It is output after being converted to.

Also, the seeder light output from the narrow-band semiconductor lasers 221-1 / 321-1 of the second / third lasers 202-1 / 302-1 is transmitted through the dichroic mirrors 227-1 / 327-1 and narrowed. Input to the banded laser oscillator 222-1 / 322-1. In addition, a part of the excitation light output from the second harmonic generator 124-1 is also input to the narrow-band laser oscillator 222-1 / 322-1. The narrow-band laser oscillator 222-1/322-1 oscillates with these seeder light and pumping light, thereby the second / third laser light LS 2 / LS ₃ having the second / third target wavelengths λ ₂ / λ 3. Is output.

  The Nd: YVO4 laser 125-1 may be an Nd: YLF laser or an Nd: YAG laser, and the narrow band laser oscillator 122-1 / 2222-1 / 322-1 oscillates in a narrow band, for example. A Ti sapphire oscillator can be used. Further, the narrow-band semiconductor lasers 121-1 to 211-1 are semiconductor lasers that continuously oscillate and output laser light even if they are semiconductor lasers that intermittently output laser light by pulse oscillation. It may be. The first to third lasers 102-1 including an Nd: YVO4 laser 125-1, a second harmonic generator 124-1, a reflection mirror 126-1 and half mirrors 127-1 / 227-1 / 327-1. ˜302-1 may be formed in one or a semiconductor substrate that is appropriately divided as necessary. This makes it possible to reduce the size of the first to third lasers 102-1 to 302-1 and facilitate handling.

(Modification 1-5)
Further, when a narrow-band laser beam is used as the seed beam, the absolute wavelength of the laser beam can be obtained from a diffraction image formed by the laser beam and the reference beam. Hereinafter, this will be described in detail as modification 1-5 of the first embodiment with reference to the drawings.

FIG. 15 is a schematic diagram showing a schematic configuration of an absolute wavelength detector 110B / 210B / 310B according to Modification 1-5. In FIG. 15, illustrating the wavelength measurement target of the laser light (LS1 / LS2 / LS3) as a narrow-band oscillation line _{L 0.} As shown in FIG. 15, the absolute wavelength detector 110B / 210B / 310B includes a beam splitter 111B for multiplexing narrowband oscillation line _{L 0} and the reference light L having a predetermined wavelength, narrow band oscillation line _{L 0} and the reference light An incident slit st that narrows the combined light with L, a concave mirror 112B that reflects the combined light incident through the incident slit st and converts it into collimated light, a diffraction grating 113B that diffracts the collimated combined light, and diffraction A concave mirror 114B that forms a diffraction image of the combined light at a predetermined position, and a line sensor 115B that is provided at the predetermined position and reads the diffraction image of the combined light.

Therefore, the absolute wavelength of the narrow-band oscillation line L ₀ is obtained by obtaining the distance between the diffraction image K _{0 of} the narrow-band oscillation line L _{0 and} the diffraction image K of the reference light L read by the line sensor 115B. That is, it is possible to specify the absolute wavelength of the laser beam (LS1 / LS2 / LS3). The specified absolute wavelength is input to the first to third controllers 101 to 301, respectively.

(Modification 1-6)
Further, another example of the absolute wavelength detector when a narrow-band laser beam is used as seed light will be described in detail below as modification 1-6 of the first embodiment with reference to the drawings.

FIG. 16 is a schematic diagram showing a schematic configuration of an absolute wavelength detector 110C / 210C / 310C according to Modification 1-6. Also in FIG. 16 will be described wavelength measurement target of the laser light (LS1 / LS2 / LS3) as a narrow-band oscillation line _{L 0.} As shown in FIG. 16, the absolute wavelength detector 110C / 210C / 310C includes a beam splitter 111C for multiplexing and narrowband oscillation line _{L 0} and the reference light _{L 1} and _{L 2} of a predetermined wavelength, narrow band oscillation line L expanding the diffusion plate 112C, and the etalon 113C for selectively transmitting light of a specific wavelength among the diffused multiplexed light, the light transmitted through the etalon 113C to diffuse the combined light of the ₀ and the reference light L ₁ and L ₂ comprising a lens 114C for diameter, a line sensor 115C for reading the narrowband oscillation line L ₀ and the reference light L ₁ and the interference pattern L ₂ and is formed disposed in a predetermined position, the.

The light receiving surface of the line sensor 115C, the interference fringes _V 0 ~V ₂ ring is formed by a narrow-band oscillation line _{L 0} and the reference light _{L 1} and _{L 2.} Therefore, the interference fringes _{V 0} which narrowband oscillation line _{L 0} read by the line sensor 115C and the radius _{R 0,} of the interference fringes _{V 1} of the reference light _{L 1} having a radius _{R 1} and the reference light _{L 2} of the interference fringes _{V 2} from a radius _{R 2} Prefecture, absolute wavelength of the narrow band oscillation line _{L 0,} i.e. it is possible to identify the absolute wavelength of the laser beam (LS1 / LS2 / LS3). The specified absolute wavelength is input to the first to third controllers 101 to 301, respectively.

<Embodiment 2>
Next, an ionization laser apparatus according to Embodiment 2 of the present invention will be described in detail with reference to the drawings. In the following description, the case where the ionization target is Sn atoms is taken as an example, as in the first embodiment. Therefore, also in the second embodiment, the ionization process of the target (Sn atom) is the same as the process shown in FIG. However, the present invention is not limited to this, and various atoms or molecules can be used as an ionization target.

  FIG. 17 is a schematic diagram illustrating a configuration example of the ionization laser device 2 according to the second embodiment. As shown in FIG. 17, in the ionization laser device 2, as compared with the ionization laser device 1A (see FIG. 3) according to the first embodiment, the ionization laser 20 is replaced with an ionization laser 20A. In the ionization laser 20A, the second laser device 200 and the third laser device 300 in the ionization laser 20 are replaced with the second laser device 200A and the third laser device 300A, respectively. The second laser device 200 </ b> A and the third laser device 300 </ b> A are not illustrated in which ionization is actually performed instead of the first laser galvatron 210 </ b> A in the second laser device 200 and the second laser galvatron 310 </ b> A in the third laser device 300. An ionization detector 510 is provided for measuring the ionization amount of the target generated in the chamber. The ionization detector 510 is a so-called in-situ ionization detector, and is arranged in a chamber (not shown) for ionizing a target (Sn atom). However, the present invention is not limited to this, and instead of the ionization detector 510 that detects the ionization amount from the current generated by the ionized atoms, an ion detector that detects the ionization amount from the mass of the ionized atoms may be used.

  Next, the operation principle of the ionization laser device 2 shown in FIG. 17 will be described in detail with reference to the drawings. FIG. 18 is a schematic diagram for explaining the operation principle of the ionization laser device 2 shown in FIG. As shown in FIG. 18, the ionization laser 20A appropriately outputs the first laser light LS1, the second laser light LS2, and the third laser light LS3 under the control of the controller 10A. The controller 10A may be the first to third controllers 101 to 301 or the ionization laser controller 10.

  Laser light (LS1, LS2, LS3) output from the ionization laser 20A is condensed to a predetermined point in a chamber (not shown) by the condenser lens CLZ. However, at this time, if the laser beam (LS1, LS2, LS3) satisfies the irradiation density necessary for ionizing the target (Sn atom) Tsn, the condensing lens CLZ is not necessarily required, and the condensing shape is It doesn't have to be a point. For example, it may be a linear shape or a circular surface, and may have a shape and intensity distribution adapted to the neutral gas target distribution. The condensing lens CLZ is not a single lens shown in FIG. 18, but may be a lens group that reduces the aberration due to each wavelength of the laser light (LS1, LS2, LS3), and has the same effect as an aspherical lens. May be obtained. In the case of focusing on a specific point, a neutral gas (vapor) target (Sn atom) Tsn exists at the predetermined point. For this reason, for example, when the first laser beam LS1 is output to the ionization laser 20A in step S1 shown in FIG. 1, the fluorescence CS is emitted from the target Tsn. The fluorescence detector 110A disposed in the vicinity of the ionization chamber detects the intensity of the fluorescence CS and outputs the detection result to the controller 10A. The controller 10A adjusts the wavelength of the first laser light LS1 by controlling the ionization laser 20A so that the intensity of the fluorescence CS detected by the fluorescence detector 110A takes a maximum value.

  Further, for example, when the first and second laser beams LS1 and LS2 are output to the ionization laser 20A in step S2 shown in FIG. 1, Sn atoms excited by the first laser beam LS1 change the photons of the second laser beam LS2. By absorbing two (two-photon absorption), the target Tsn is ionized. The ionization detector 510 detects the amount (ionization amount) of the ionized target Tsn and outputs the detection result to the controller 10A. The controller 10A controls the ionization laser 20A to adjust the wavelength of the second laser light LS2 so that the ionization amount of the target Tsn detected by the ionization detector 510 takes a maximum value.

  Further, for example, when the first to third laser beams LS1 to LS3 are output to the ionization laser 20A in step S3 shown in FIG. 1, Sn atoms excited by the first laser beam LS1 are combined with photons of the second laser beam LS2. By absorbing the photons of the third laser beam LS3 one by one (two-photon absorption), the target is efficiently ionized. The ionization detector 510 detects the amount (ionization amount) of the ionized target Tsn and outputs the detection result to the controller 10A. The controller 10A adjusts the wavelength of the third laser light LS2 by controlling the ionization laser 20A so that the ionization amount of the target Tsn detected by the ionization detector 510 takes a maximum value.

  Next, the operation of the ionization laser device 2 according to the second embodiment will be described in detail with reference to the drawings. FIG. 19 is a flowchart showing an example of start-up operation of the ionization laser device 2 according to the second embodiment. FIG. 20 is a flowchart showing an example of steady control operation of the ionization laser device 2 according to the second embodiment. In the following description, the first to third laser devices 100, 200A, and 300A are controlled under the operation of the ionization laser controller 10 that controls the ionization laser 20A and the control from the ionization laser controller 10. Description will be made by paying attention to the operation of the controllers 101-301.

As shown in FIG. 19, when the ionization laser controller 10 starts the start-up operation, the ionization laser 20A is roughly tuned (step S201). Specifically, from the wavelengths detected by the first to third wavelength meters 103 to 303, the wavelengths of the first to third laser beams LS1 to LS3 output from the first to third lasers 102 to 302 are first set. ˜Coarse tuning to third target wavelengths λ ₁ to λ ₃ , respectively. Note that the coarse tuning to each target wavelength is similar to the process described above using steps S101, S104, and S107 in FIG. The coarse tuning of the ionization laser 20A in step S201 is repeated until this is completed (No in step S202).

  When the coarse tuning of the ionization laser 20A is completed (Yes in step S202), the ionization laser controller 10 then irradiates the first laser light LS1 to the target Tsn (step S203). As a result, a phenomenon occurs in which the target Tsn is excited to the first eigenstate and then de-excited in a chamber (not shown).

Next, ionizing laser controller 10 controls the first controller 101, tuning the wavelength of the first laser 102 to a first target wavelength lambda ₁ (step S204). This step S204 is repeated until the intensity of the fluorescence CS detected by the fluorescence detector 110A reaches the maximum value (No in step S205). For example, the first controller 101 changes the wavelength of the first laser light LS1 output from the first laser 102 in the vicinity of the roughly tuned wavelength, and from the intensity spectrum of the fluorescence CS detected by the fluorescence detector 110A in this process. The wavelength having the maximum intensity is specified, and the first laser 102 is adjusted to the state when the wavelength is output.

When the intensity of the fluorescence CS is the maximum value (Yes in step S205), then, ionizing laser controller 10 controls the second controller 201, tuning the wavelength of the second laser 202 to a second target wavelength lambda ₂ (Step S206). This step S206 is repeated until the ionization amount of the target Tsn detected by the ionization detector 510 reaches the maximum value (No in step S207). For example, the second controller 201 changes the wavelength of the second laser light LS2 output from the second laser 202 in the vicinity of the roughly tuned wavelength, and changes in the current value (wavelength detected by the ionization detector 510 in this process). The wavelength at which the current value becomes the maximum value is specified from the dependence), and the second laser 202 is adjusted to the state when the wavelength is output.

When the current value (ionization amount) reaches the maximum value (Yes in step S207), the ionization laser controller 10 next controls the third controller 301 to change the wavelength of the third laser 302 in the same manner as in step S206. Tuning is performed to the three target wavelengths λ ₃ (step S208). This step S208 is repeated until the ionization amount of the target Tsn detected by the ionization detector 510 reaches the maximum value (No in step S209). When the current value (ionization amount) reaches the maximum value (Yes in step S209), the ionization laser controller 10 completes the start-up operation.

By performing the startup operation as described above, the wavelengths of the plurality of laser beams (first to third laser beams LS1 to LS3) output from the ionization laser device 2 are ionized as in the first embodiment. It is possible to reliably adjust to a desired wavelength (first to third target wavelengths λ _{1 to} λ ₃ ) along an appropriate sequence of processes. As a result, it becomes possible to easily and reliably match the wavelengths of all the laser beams to the target wavelengths.

When the wavelength of the first to third laser 102-302 are locked respectively to the first to third target wavelength lambda ₁ to [lambda] ₃ by the raising operation, ionizing laser device 2, then, the first to third A steady operation is performed in which the laser beams LS1 to LS3 are constantly output at a stable wavelength.

  In the steady operation, as shown in FIG. 20, the ionization laser controller 10 monitors the ionization amount of the target Tsn from the current value of the ionization amount detected by the ionization detector 510 (step S211), and the ionization monitored thereby. It is determined whether or not the amount is larger than a preset threshold value or a value immediately after coarse tuning in step S201 in FIG. 19 (hereinafter referred to as a first threshold value) (step S212). As a result of the determination in step S212, when the ionization amount is larger than the first threshold (Yes in step S212), the ionization laser controller 10 proceeds to step S221.

On the other hand, when the ionization amount is less than or equal to the first threshold (No in step S212), the ionization laser controller 10 repeats the tuning control described in, for example, steps S206 to S209 in FIG. The wavelengths of the three lasers 202 and 302 are tuned to the second and third target wavelengths λ ₂ and λ ₃ , respectively (step S213).

  Thereafter, the ionization laser controller 10 determines again whether or not the ionization amount is larger than the first threshold value (step S214). If the ionization amount is larger than the first threshold value (Yes in step S214), the process proceeds to step S221.

On the other hand, if the ionization amount is not more than the first threshold value even after tuning in step S213 (No in step S214), the ionization laser controller 10 repeats the tuning control described in, for example, steps S204 to S205 in FIG. 19 once or more. in the step of the wavelength of the first laser 102 first tuned to the target wavelength lambda ₁ (step S215), the threshold or 19 intensity of the fluorescence CS is preset to detect fluorescence detector 110A when this is It is determined whether or not it is greater than the value immediately after the coarse tuning in S201 (hereinafter referred to as the second threshold) (step S216). As a result of the determination in step S216, when the intensity of the fluorescence CS is larger than the second threshold (Yes in step S216), the ionization laser controller 10 proceeds to step 221.

On the other hand, when the intensity of the fluorescence CS is equal to or smaller than the second threshold (No in step S216), the ionization laser controller 10 monitors the wavelengths of the first to third laser beams LS1 to LS3 output from the first to third lasers. Then, it is determined whether or not these wavelengths are locked to the _first to third target wavelengths λ _{1 to} λ ₃ (step S218).

As a result of the determination in step S218, when the wavelengths of the first to third laser beams LS1 to LS3 are locked to the _first to third target wavelengths λ _{1 to} λ ₃ (Yes in step S218), the ionization laser controller 10 Determines that the cause of the malfunction is due to other factors, and executes predetermined control (step S219). The predetermined control includes notification (warning or the like) to the operator of the ionization laser device 2 and power shutdown.

On the other hand, the result of the determination in step S218, when the wavelength of the first to third laser beam LS1~LS3 is not locked to the first to third target wavelength lambda ₁ to [lambda] _3, respectively (No in step S218), ionizing laser the controller 10, for example, by executing the start-up operation shown in FIG. 19 again, to tune the wavelength of the first to third laser 101-301 to the first to third target wavelength lambda ₁ to [lambda] _3, respectively (step S220 ). Thereafter, the ionization laser controller 10 determines whether or not an instruction to end the steady operation is input from, for example, an operator (step S221). If the end instruction is input (Yes in step S221), the steady operation is performed. Exit. On the other hand, when the end instruction is not input (No in step S221), the ionization laser controller 10 returns to step S211 and performs the same operation again.

By executing the steady operation as described above, any one of a plurality of laser beams (first to third laser beams LS1 to LS3) output from the ionization laser device 2 is also provided, as in the first embodiment. When it deviates from a desired wavelength (first to third target wavelengths λ _{1 to} λ ₃ ), it becomes possible to adjust the wavelength again from the laser beam having the shifted wavelength. For this reason, when it is not necessary to adjust the wavelength of all the laser beams, it is possible to easily and appropriately lock all the laser beams to the desired wavelengths while omitting the trouble of adjusting the wavelengths of all the laser beams from the beginning. It becomes possible. As a result, an ionization laser device that can ionize a target with a high ionization rate even when using a plurality of laser beams can be realized.

<Embodiment 3>
Next, an extreme ultraviolet light source device (EUV laser device) using the ionization laser device according to each embodiment described above will be described in detail with reference to the drawings. In the following description, the case of using the ionization laser device 2 according to the above-described second embodiment will be described as an example. However, the present invention is not limited to this, and the ionization laser according to the above-described first embodiment or a modification thereof. It goes without saying that a device can also be used.

  FIG. 21 is a schematic cross-sectional view showing a schematic configuration of the EUV laser apparatus 3 according to the third embodiment. As shown in FIG. 21, the EUV laser apparatus 3 includes an EUV generation chamber 40 that is a chamber for ionizing a target (Sn atom), an ionization laser 20A that constitutes the ionization laser apparatus 2, a fluorescence detector 110A, and ionization detection. And an electromagnetic coil 50A and 50B for forming a magnetic force line 51 for guiding the target Tsn that has been plasmatized or ionized in the EUV generation chamber 40 to the direction of discharge. For convenience of explanation, the ionization laser controller 10 in the ionization laser apparatus 2 is not shown, but the ionization laser controller 10 is also included in the EUV laser apparatus 3.

  The EUV generation chamber 40 includes optical windows 41, 42, and 43, and an exposure unit connection port 45 that guides EUV light (extreme ultraviolet light) generated in the EUV generation chamber 40 to an external exposure unit. From the optical window 41, EUV plasma generation laser light PLS for making the target Tsn in the EUV generation chamber 40 into plasma is incident. The EUV plasma generation laser light PLS is focused on the point (EUV light generation source F) where the gaseous (vapor) target Tsn in the EUV generation chamber 40 is concentrated. Therefore, EUV light is generated from the target Tsn irradiated with the EUV plasma generation laser light PLS at the EUV light generation point F.

  In the EUV generation chamber 40, an EUV light condensing mirror 44 for condensing the EUV light generated at the EUV light generation point F to the exposure machine connection port 45 is provided. Therefore, the EUV light generated at the EUV light generation point F is directly or after being reflected by the EUV light collecting mirror 44, and then guided from the exposure machine connection port 45 to an exposure machine (not shown).

  Normally, the target Tsn that has been plasmatized by the EUV plasma generation laser light PLS is guided away from the EUV light generation point F by the magnetic force lines 51 formed by the electromagnetic coils 50A and 50B, and is collected by the ionization detector 510. As a result, erosion due to the collision of Sn ions with the EUV collector mirror 44 disposed in the vicinity of the EUV light generation point F is prevented, and a decrease in reflectance due to this erosion is prevented. However, the atoms discharged by the magnetic field lines 51 are only charged atoms. Therefore, the target Tsn that has not been converted to plasma by the EUV plasma generation laser light PLS cannot be efficiently discharged using the magnetic force lines 51. The target Tsn that has not been turned into plasma becomes so-called debris and drifts in the EUV generation chamber 40. Some debris adheres to the EUV collector mirror 44 and reduces its reflectivity. This makes it impossible to efficiently collect and collect EUV light. Further, the reflectance of the EUV collector mirror 44 decreases according to the amount of debris attached. Each time EUV light is generated, the amount of adhesion increases and the reflectance decreases, so that EUV light cannot be stably guided to the exposure machine. Eventually, it becomes necessary to clean or replace the EUV collector mirror 44, which causes a decrease in throughput and an increase in running cost. In addition, debris adheres to the optical window and reduces the transmittance of light passing through the window, or flows into the exposure device via the exposure device connection port 45 to generate contamination, thus adversely affecting the entire EUV laser apparatus. Effect.

  Therefore, the EUV laser apparatus 3 according to the third embodiment uses the ionization laser apparatus 2 to reliably ionize most of the target Tsn. As a result, most of the target Tsn can be reliably collected, so that the occurrence of debris can be suppressed and debris adhesion to the EUV collector mirror 44 and diffusion in the apparatus can be prevented. As a result, efficient and stable generation of EUV light is possible.

Laser light (LS1 to LS3) used for ionization of the target Tsn is applied to the EUV light generation point F through the optical window 42 from the ionization laser 20A. Therefore, first, when the ionization laser 20A outputs the first laser beam LS1, the EUV light generation point F excites the Sn atoms as the target Tsn to the first eigenstate. Further, the Sn atom excited to the first eigenstate is immediately deexcited to the eigenstate after being deexcited as described above. At this time, fluorescent CS is emitted from the Sn atoms. The intensity of the fluorescence CS emitted from the Sn atoms at the EUV light generation point F is detected by the fluorescence detector 110 </ b> A through the optical window 43. Ionizing laser controller 10, not shown, based on the intensity of the fluorescence CS fluorescence detector 110A detects when this, as the wavelength of the first laser beam LS1 outputted by the ionizing laser 20A is a first target wavelength lambda ₁ In addition, the ionization laser 20A is feedback-controlled. Note that a specific example of this feedback control is the same as that of the above-described second embodiment, and thus detailed description thereof is omitted here.

Further, when locking the wavelength of the first laser beam LS1 to the first target wavelength lambda _1, ionizing laser controller 10 subsequently outputs the second laser beam LS2 in addition to the first laser beam LS1. At this time, two-photon absorption of the second laser light LS2 by Sn atoms excited to the first eigenstate occurs, and the Sn atoms are ionized. The ionized Sn atoms (target Tsn as debris) are guided to the ionization detector 510 arranged on the discharge trajectory of the ionized Sn atoms by the magnetic force lines 51. The ionization laser controller 10 causes the wavelength of the second laser light LS2 output from the ionization laser 20A to be the second target wavelength λ ₂ based on the current flowing through the ionized Sn atoms detected by the ionization detector 510. In addition, the ionization laser 20A is feedback-controlled. Note that a specific example of this feedback control is the same as that of the above-described second embodiment, and thus detailed description thereof is omitted here.

Subsequently, when the first and second laser beams LS1 and LS2 for locking the first and second, respectively to the target wavelength lambda ₁ and lambda _2, ionizing laser controller 10, followed by first and second laser beams LS1 and LS2 In addition, the third laser beam LS3 is output. As a result, Sn atoms excited to the first eigenstate are ionized by absorbing one photon of the second laser beam LS2 and one photon of the third laser beam LS3. As described above, the ionized Sn atoms are guided and collected by the magnetic force line 51 to the ionization detector 510 arranged at a position away from the EUV light generation point F. Accordingly, the ionization laser controller 10 determines that the wavelength of the third laser light LS3 output from the ionization laser 20A is the third target wavelength λ ₃ based on the current flowing through the ionized Sn atoms detected by the ionization detector 510. Thus, the ionization laser 20A is feedback-controlled. Note that a specific example of this feedback control is the same as that of the above-described second embodiment, and thus detailed description thereof is omitted here.

  With the configuration and operation as described above, in the third embodiment, the target Tsn that has not been converted to plasma is prevented from adhering to the EUV collector mirror 44 as so-called debris and diffusing in the apparatus, and most of the target Tsn. As a result, the EUV laser device 3 capable of generating EUV light efficiently and stably can be realized. In the third embodiment, the ionized target is discharged using the magnetic field formed by the electromagnetic coils 50A and 50B. However, the ionized target that is a charged particle can also be collected by an electric field. In this case, an electrode to which a high voltage can be applied may be arranged in the vicinity of the EUV light generation point so that the target ionized in the direction of the ionization detector can be discharged. The high voltage at this time may be a constant voltage or a pulse voltage synchronized with the irradiation of the ionized laser.

(Modification 3-1)
Next, a modified example 3-1 of the EUV laser apparatus 3 according to the third embodiment will be described in detail with reference to the drawings. In the above-described third embodiment, the so-called in-situ fluorescence detector 110A is used for detecting the excitation efficiency of the target Tsn by the first laser light LS1. On the other hand, in this modification 3-1, a so-called in-situ fluorescence detector 610 is used.

  22A and 22B are schematic cross-sectional views showing a schematic configuration of an EUV laser apparatus 3A according to the modification 3-1. 22B is a cross-sectional view taken along line AA in FIG. 22A. As shown in FIGS. 22A and 22B, in the EUV laser apparatus 3A, the fluorescence detector 110A is replaced by a so-called in-situ fluorescence detector 610 in the same configuration as the EUV laser apparatus 3 shown in FIG. . Accordingly, the optical window 42 for observing the fluorescence CS generated at the EUV light generation point F in the EUV generation chamber 40 generates EUV light from the direction perpendicular to the optical axis of the EUV plasma generation laser light PLS. The point F is replaced by an optical window 46 that enables observation.

  The fluorescence detector 610 has the same configuration as that of the fluorescence detector 110A-1 described with reference to FIG. 12 in Modification 1-2 of Embodiment 1, and includes a transfer lens 117, a background light blocking filter 118, and a photodetector. 119. However, since the fluorescence detector 610 according to Modification 3-1 is a so-called in-situ fluorescence detector, the vapor sealed cell 111 is replaced with the EUV generation chamber 40.

  In this configuration, the fluorescence CS emitted from the EUV light generation point F when the target Tsn excited by the first laser light LS1 is de-excited is transferred to the photodetector 119 by the transfer lens 117 disposed outside the optical window 46. Guided to the image detection surface. At this time, the transfer lens 117 limits the field of view and reduces background light. The photodetector 119 detects the intensity of the fluorescence CS guided from the EUV light generation point F, and outputs the detection result to the first controller 101. Note that a background light blocking filter 118 is provided on the detection surface of the photodetector 119 to block light having a wavelength other than the wavelength of the fluorescence CS, for example, background light from the plasma target Tsn. Thereby, it becomes possible to detect the intensity of the fluorescence CS more accurately. Since other configurations and operations are the same as those of the above-described third embodiment, the description of the operation is omitted here.

  With the configuration and operation as described above, in the present modification 3-1, the target Tsn that has not been converted to plasma adheres to the EUV collector mirror 44 as so-called debris and diffuses in the apparatus, as in the third embodiment. Therefore, the most part of the target Tsn is ionized and collected, so that the EUV laser apparatus 3A capable of generating EUV light efficiently and stably can be realized.

  In addition, the above-described embodiment and its modifications are merely examples for carrying out the present invention, and the present invention is not limited to these, and various modifications according to specifications and the like are within the scope of the present invention. Furthermore, it is obvious from the above description that various other embodiments are possible within the scope of the present invention. For example, it is needless to say that the modification examples illustrated as appropriate for each embodiment can be applied to other embodiments.

1, 1A, 1A-1, 2 ionization laser device 3, 3A EUV laser device 10 ionization laser controller 10A controller 20, 20A, 20-1 ionization laser 30 multiplexing optical system 32, 33 multiplexer 40 EUV generation chamber 41, 42, 43, 46 Optical window 44 EUV light collecting mirror 45 Exposure machine connection port 50A, 50B Electromagnetic coil 51 Magnetic field lines 100-400 First to fourth laser devices 101-401 First to fourth controllers 102-402 First to second 4th laser 102-1 to 302-1 1st to 3rd laser 103 to 403 1st to 4th wavelength meter 110 to 310 1st to 3rd absolute wavelength detector 110A, 110A-1, 610 Fluorescence detector 110B, 110C, 210B, 210C, 310B, 310C Absolute wavelength detector 111 Vapor filled cell 111B, 111C Beam splitter 112 Vapor generator 112B Concave mirror 112C Diffusion plate 113 Sn Vapor 113B Diffraction grating 113C Etalon 114 Light entrance window 114B Concave mirror 114C Lens 115 Light exit window 115B, 115C Line sensor 116 Light extraction window 117 Transfer lens 118 Background light blocking filter 119 Photodetector 121-321, 121-1 to 212-1 Narrow band semiconductor laser 122 Yb fiber amplifier 122-1 to 222-1 Narrow band laser oscillator 123 4th harmonic generator 123-1 3 Double wave generator 125-1 Nd: YVO4 laser 124-1 Double wave generator 126-1 Reflection mirror 127-1 to 277-1 Dichroic mirror 200A to 300A Second to third laser devices 210A to 410A First to second 3 Zagalvatron 210A-1, 310A-1 Optical absorption detector 211 Follow cathode lamp 212 Noble gas sealed glass tube 214 Optical sensor 222, 322 Parametric oscillator 223 Yb fiber laser 510 Ionization detector An Anode Ca Cathode CLZ Condensing lens CS Fluorescence CSo fluorogenic point E0, E1, E2, E3, ES1 trajectory F EUV light generation point Hvs high voltage source K reference light L diffraction image L of the diffraction image K ₀ narrowband oscillation line _{L 0 of,} L 1, _{L 2} reference light L ₀ Narrowband oscillation line LS, LSa Combined laser light LS1 to LS4 First to fourth laser light LS1a, LS1b, LS2a, LS3a Laser light PLS EUV plasma generation laser light R ₀ interference vortex V ₀ radius R ₁ interference vortex V ₁ radius R ₂ radius of interference vortex V ₂ Tsn target V ₀ narrowband oscillation line L ₀ interference vortex V ₁ reference light L ₁ interference vortex V ₂ reference light L ₂ interference vortex st incident slit

Claims (12)

An ionization laser device that outputs laser light for ionizing a target through one or more excited states,
Excitation laser output means for outputting excitation laser light for exciting the target;
An excitation absolute wavelength detecting means for detecting an absolute wavelength of the excitation laser beam;
An ionization laser output means for outputting an ionization laser beam for ionizing the target excited by the excitation laser beam;
Ion amount detecting means for detecting the amount of atoms or molecules ionized by the ionizing laser beam ;
The excitation laser output means is controlled based on the absolute wavelength of the excitation laser light detected by the excitation absolute wavelength detection means to adjust the wavelength of the excitation laser light, and the ion amount detection means Control means for adjusting the wavelength of the ionization laser light by controlling the ionization laser output means based on the amount of the ionized atoms or molecules detected in
An ionization laser device comprising: The control means adjusts the wavelength of the ionization laser light by controlling the ionization laser output means so that the amount of the ionized atoms or molecules detected by the ion quantity detection means becomes a maximum value. The ionization laser device according to claim 1. Excitation wavelength detecting means for detecting the wavelength of the excitation laser light;
Ionization wavelength detecting means for detecting the wavelength of the ionization laser beam;
With
The control means roughly tunes the wavelength of the excitation laser light to the first wavelength for excitation based on the wavelength of the excitation laser light detected by the excitation wavelength detection means, and then Based on the absolute wavelength of the excitation laser light detected by the wavelength detection means, the absolute wavelength of the excitation laser light is tuned to the first wavelength, and the ionization detection detected by the ionization wavelength detection means After the wavelength of the laser beam for ionization is roughly tuned to the second wavelength for ionization based on the wavelength of the laser beam, the amount of the ionized atoms or molecules detected by the ion amount detection means becomes the maximum value. The ionization laser apparatus according to claim 1 or 2 , wherein the ionization laser output means is controlled to tune the wavelength of the ionization laser light to the second wavelength. The excitation absolute wavelength detecting means detects the absolute wavelength of the excitation laser beam from the intensity of fluorescence emitted when the target excited by the excitation laser beam or the same kind of atom or molecule as the target is deexcited. The ionization laser apparatus as described in any one of Claims 1-3 characterized by including the fluorescence detector to perform. 4. The ionization according to claim 1 , wherein the excitation absolute wavelength detecting unit includes an optogalvanic spectral discharge tube that outputs an optogalvano signal corresponding to the wavelength of the incident laser beam. Laser device. The excitation absolute wavelength detecting means includes an atomic source of a target material that absorbs the laser light according to the wavelength of the incident laser light, an optical sensor that detects the laser light that has passed through the atomic source of the target material, The ionization laser apparatus according to claim 1 , further comprising a light absorption detector. The said excitation absolute wavelength detection means detects the absolute wavelength of the said laser beam based on the diffraction image which the incident laser beam and the reference beam of a predetermined wavelength form in a predetermined surface . 4. The ionization laser device according to any one of 3 . The said excitation absolute wavelength detection means detects the absolute wavelength of the said laser beam based on the interference fringe which the incident laser beam and the reference light of a predetermined wavelength form in a predetermined surface . 4. The ionization laser device according to any one of 3 . The ionization laser apparatus according to claim 1 , wherein the excitation laser output unit and the ionization laser output unit are fiber lasers using a semiconductor laser as a seed light source. The ionization laser apparatus according to claim 1 , wherein the excitation laser output unit and the ionization laser output unit are semiconductor lasers built in a semiconductor substrate. The target is a gaseous Sn atom,
Laser output unit for the ionization, the first ionization laser output means for outputting a first first ionization laser beam for exciting the target excited to an excited state to the second excited state by the excitation laser beam, the includes a second ionization laser output means for outputting the second the second ionization laser light to ionize the target in an excited state, and said control means, said first ionization and the excitation laser output means The wavelength of the first ionizing laser light output by the first ionizing laser output means based on the amount of the ionized atoms or molecules detected by the ion quantity detecting means when the laser output means for driving is driven And the excitation laser output means, the first ionization laser output means, and the second ionization laser output means were driven. Claims, characterized in that to adjust the wavelength of the second ionization laser beam output from the laser output unit for the second ionization based on the amount of the ionized atom or molecule that is detected by the ion detecting means in Item 11. The ionization laser device according to any one of Items 1 to 10 . A light source device that generates extreme ultraviolet light by irradiating a target with a laser beam,
A chamber in which extreme ultraviolet light is generated;
A target material supplied into the chamber;
A laser light source for generating EUV plasma that generates plasma by irradiating the target with laser light for generating EUV plasma;
A condensing optical system that condenses extreme ultraviolet light emitted from the plasma;
An ionizing laser device that ionizes neutral particles by irradiating the plasma region with ionized laser light, and ionizing means that ionizes neutral particles contained in particles emitted from the plasma to form charged particles; ,
At least a magnetic field forming means for forming a magnetic field in the chamber or an electric field forming means for forming an electric field in the chamber in order to collect charged particles ionized by the ionizing means;
An ionization laser device according to any one of claims 1 to 11 ,
An extreme ultraviolet light source device characterized by comprising:

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