JP2002084026A - F2 laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a molecular fluorine (F2) laser having enhanced efficiency, which can select the beam and narrow the selected beam, and control the wavelength. SOLUTION: An F2-laser includes a discharge chamber filled with a gas mixture including molecular fluorine for generating a spectrum emission in a wavelength range between 157 nm and 158 nm including a primary beam and a secondary beam, multiple electrodes coupled with a power supply circuit for producing a pulsed discharge to energize the molecular fluorine, a resonator including the discharge chamber and an interferometric device for generating a laser beam having a bandwidth less than 1 pm, and a wavelength monitor coupled in a feedback loop with a processor for monitoring a spectrum distribution of the laser beam. The processor controls an interferometric spectrum of the interferometic device based on the monitored spectrum distribution such that sidebands within the spectrum distribution are substantially minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to molecular fluorine (F ₂ ).
It relates laser, in particular, improved efficiency, narrow linewidth of the bright line and the selected bright line selection, and a F ₂ laser with a wavelength control.

[0002]

2. Description of the Related Art Semiconductor manufacturers currently employ a KrF excimer laser system operating at about 248 nm, and about 19
It uses a deep ultraviolet (DUV) lithography tool based on the next generation ArF excimer laser system operating at 3 nm. Vacuum UV (VU
V) lithography may use an _{F 2} laser operating at about 157 nm.

[0003] The release of the _{F 2} laser about λ ₁ = 157.6
At least two characteristic emission lines of 29 nm and λ ₂ = 157.523 nm are included. Each emission line is approximately 15 pm (0.0
It has a natural linewidth of 15 nm).
The ratio of the intensities of the two bright lines is | (λ ₁ ) / | (λ ₂ ) = 7. V. N. Ishenko, S.M. A. Kotub
el, and A.I. M. Razher, SOV. Jour
n. QE-16,5 (Soviet Quantitative Electronics Journal, 1
6, 5) (1986). 1, _{F 2}
Spontaneous emission spe
ctrum) illustrates two closely spaced peaks described above.

[0004] As integrated circuit device technology has entered a sub-quarter regime, it requires fine optical lithography technology. In KrF and ArF excimer laser systems, their spontaneous emission spectra are broad (> 100
pm), line narrowing and tuning are required. Linewidth narrowing is most commonly achieved in such laser systems by using a wavelength selector consisting of one or more prisms and diffraction gratings (Littrow configuration).
n)). However, when the F ₂ laser operating at a wavelength of about 157 nm, the use of reflective diffraction grating is sometimes unsatisfactory because of the high oscillation threshold low reflectance at this wavelength. In this regard, a master oscillator-power amplifier design has been proposed by the two applicants of the present application (US patent application Ser. / 599,130), for example, using a diffraction grating and / or etalon, each preferably combined with a beam expander, to improve the power of the output beam and reduce the very narrow linewidth (<1 pm). Making it possible. F ₂ laser of tunability (tunabilit
y) is shown using a prism in the laser cavity. M. Kakehata, E .; Hashimoto,
F. Kannari, M .; Obara, Keio University Pro
c. See CLEO-90, 106 (1990). From narrowband F ₂ laser at a controlled wavelength 1
It is desirable to provide a 57 nm beam.

[0005] F ₂ laser is also the gas and all of the optical elements, characterized by a strong absorbent absorbing relatively high cavity loss due to scattering of oxygen and water vapor showing a (intracavity loss) in particular about 157 nm. Short wavelength (157 nm) has become a cause of high absorption and scattering losses of F ₂ laser (scattering loss), contrast,
For example, a KrF excimer laser operating at 248 nm does not experience such losses. Accordingly, it is recognized herein that it is advisable to take measures to optimize the resonator efficiency.

[0006]

Therefore, about 157 nm
One of the plurality of emission lines it is an object of the present invention to provide an F ₂ laser is effectively selected.

[0007] It is yet another object of the present invention to provide an F ₂ laser with an effective means for line narrowing the selected emission lines.

[0008] With bright line selection and narrowing of the selected bright line
In this case, the output wavelength is controlled by F ₂Provide laser
This is yet another object of the present invention.

[0009]

In view of these and other objects, a primary line and a secondary line are considered.
a discharge chamber filled with a gas mixture comprising molecular fluorine to generate a spectral emission comprising a number of closely spaced emission lines in a wavelength range between 157 nm and 158 nm including Includes a number of electrodes coupled to the power supply circuit for generating a pulsed discharge for applying a voltage to molecular fluorine, a discharge chamber, a transmissive interferometric device, and a pair of resonator reflectors. 1p
F ₂ laser including a resonator for generating a laser beam having a bandwidth of less than m are provided. This interferometer apparatus has a transmittance (tran) of a selected portion of the primary emission line in order to substantially suppress the secondary emission line and a non-selected portion of the primary emission line.
smissivity) is maximized, and the transmittance of the non-selected portions of the secondary emission line and the primary emission line is configured to be relatively low.
Thereby select and line narrowing a primary emission lines, F ₂ laser, narrow in order to provide a band VUV laser beams, self-propelled (free-running) narrower than the bandwidth of the F ₂ laser of primary emission lines Single wavelength laser with spectral bandwidth
It emits a beam.

[0010] Furthermore, 15 lines including a primary line and a secondary line are included.
A discharge chamber filled with a gas mixture containing molecular fluorine to generate a spectral emission containing a number of closely spaced emission lines within a wavelength range between 7 nm and 158 nm; Includes a number of electrodes for generating an applied pulsed discharge, and a resonator for generating a laser beam having a bandwidth of less than 1 pm, including a discharge chamber, a reflective interferometer device, and another resonant reflector. F ₂ laser is provided. This interferometer device maximizes the transmittance of the selected portion of the primary emission line to substantially suppress the secondary emission line and the non-selected portion of the primary emission line, and sets the non-selection of the secondary emission line and the primary emission line. The F ₂ laser is configured to have a relatively low transmittance with the selected portion, thereby selecting and narrowing the primary emission line, so that the F ₂ laser can emit a narrow band VUV.
To provide a laser beam, the free-running F ₂ laser 1
A single wavelength laser beam having a spectral bandwidth narrower than the bandwidth of the next emission line is emitted.

157 including a primary emission line and a secondary emission line
Numerous tight spacings in the wavelength range between nm and 158 nm
Molecular emission to produce a spectral emission containing
Discharge chamber filled with a gas mixture containing nitrogen
And a power supply circuit that is coupled to the power supply circuit and applies a voltage to molecular fluorine.
Numerous electrodes that generate a loose discharge, discharge chamber, transmission
1pm including the interferometer device and a pair of resonant reflectors
A resonator for generating a laser beam having a full bandwidth;
F including₂A laser is provided. This interferometer device has two
Maximize the transmittance of the primary emission line to almost suppress the secondary emission line
And the transmittance of the secondary emission line is made relatively low.
To select the primary emission line, and ₂The laser
Free-running F to provide a narrow band VUV laser beam
₂Units with a spectral bandwidth narrower than that of the laser
To emit a single wavelength laser beam.
You.

[0015] Furthermore, 15 including the primary emission line and the secondary emission line.
A discharge chamber filled with a gas mixture containing molecular fluorine for generating a spectral emission containing a number of closely spaced emission lines in a wavelength range between 7 nm and 158 nm; a plurality of electrodes for generating a pulse discharge is applied, a discharge chamber, the reflection-type interferometer device, and another F ₂ laser including a resonator for generating a laser beam having a bandwidth of less than 1pm comprises a resonant reflector Is provided. This interferometer device is configured to maximize the transmittance of the primary emission line and to make the transmittance of the secondary emission line relatively low in order to substantially suppress the secondary emission line, thereby selecting the primary emission line. , _{F 2} laser,
Free-running F to provide a narrow band VUV laser beam
It is intended to emit a single wavelength laser beam having a spectral bandwidth narrower than the bandwidth of the _two lasers.

157 including a primary emission line and a secondary emission line
a discharge chamber filled with a gas mixture containing molecular fluorine to produce a spectral emission containing a number of closely spaced emission lines in the wavelength range between 158 nm and 158 nm; A large number of electrodes for generating a pulsed discharge to be applied, and a discharge chamber, a transmission interferometer,
PTIC), and F ₂ laser including a resonator for generating a laser beam having a bandwidth of less than 1pm and a pair of resonant reflector is provided. This dispersive optical device has
Multiple emission lines, including primary and secondary emission lines, such that only the next emission line remains within the acceptance angle of the resonator and any other emission lines, including the second emission line, are distributed outside the acceptance angle of the resonator. It is arranged in a specific direction to disperse closely spaced emission lines. The interferometer device maximizes the transmittance of the selected portion of the primary emission line and substantially lowers the transmittance of the non-selected portion of the primary emission line in order to substantially suppress the unselected portion of the primary emission line. It is configured as follows. Distributed optical device and the interferometer apparatus thereby to select and line narrowing a primary emission lines, F ₂ laser, in order to provide a narrow-band VUV laser beam, the bandwidth of the free-running F ₂ laser of primary emission lines It is intended to emit a single wavelength laser beam having a narrower spectral bandwidth.

157 including a primary emission line and a secondary emission line
a discharge chamber filled with a gas mixture containing molecular fluorine to produce a spectral emission containing a number of closely spaced emission lines in the wavelength range between 158 nm and 158 nm; Generates a laser beam having a bandwidth of less than 1 pm, including a number of electrodes for generating an applied pulsed discharge, and a discharge chamber, reflective interferometer device, dispersive optics, and other resonant reflectors F ₂ laser including a resonator for is provided. The dispersive optical device includes a primary and a secondary emission line such that only the primary emission line remains within the acceptance angle of the resonator and any other emission lines, including the secondary emission line, are dispersed outside the acceptance angle of the resonator. Are arranged in a specific direction so as to disperse a large number of closely-spaced emission lines. The interferometer device maximizes the reflectance of the selected portion of the primary emission line to substantially suppress the non-selection portion of the primary emission line, and makes the reflectance of the non-selected portion of the primary emission line relatively low. Is composed of Distributed optical device and interferometer system to select and line narrowing it by the primary emission lines, F ₂ laser, a narrow-band VUV laser
To provide a beam, and is to emit a single wavelength laser beam having a narrow spectral bandwidth than the bandwidth of the primary emission lines of the free-running F ₂ laser.

157 including a primary emission line and a secondary emission line
a discharge chamber filled with a gas mixture containing molecular fluorine to produce a spectral emission containing a number of closely spaced emission lines in the wavelength range between 158 nm and 158 nm; a plurality of electrodes for generating a pulse discharge to be applied, and, the F ₂ laser including a resonator, a for generating a laser beam having a bandwidth of less than 1pm comprises a discharge chamber and the interferometer system Provided. This interferometer device is used to substantially suppress the secondary emission line and the non-selection part of the primary emission line as compared with the selected part of the primary emission line. is configured in such a relatively suppress a portion of the primary emission lines, thereby to select and line narrowing a primary emission lines, F ₂ laser, in order to provide a narrow-band VUV laser beam, the free-running F It is intended to emit a single wavelength laser beam having a spectral bandwidth narrower than the bandwidth of the primary emission line of the _two lasers.

In addition, 15 including the primary emission line and the secondary emission line
A discharge chamber filled with a gas mixture containing molecular fluorine to generate a spectral emission containing a number of closely spaced emission lines in a wavelength range between 7 nm and 158 nm; a plurality of electrodes for generating a pulse discharge to be applied, and, F ₂ laser including a resonator, a for generating a laser beam having a bandwidth of less than 1pm comprises a discharge chamber and the interferometer system is provided You. The interferometer device is configured to relatively suppress the secondary emission line to substantially suppress the secondary emission line as compared to the primary emission line, thereby selecting the primary emission line and causing the F ₂ laser to: in order to provide a narrow-band VUV laser beam, it is intended to emit a single wavelength laser beam having a narrow spectral bandwidth than the bandwidth of the free-running F ₂ laser.

In addition, 15 including the primary emission line and the secondary emission line
A discharge chamber filled with a gas mixture containing molecular fluorine to generate a spectral emission containing a number of closely spaced emission lines in a wavelength range between 7 nm and 158 nm; 1 pm including a large number of electrodes for generating a pulse discharge to be applied, and a discharge chamber, an interferometer device, and a dispersive optical device
F ₂ laser is provided comprising a resonator for generating a laser beam having a bandwidth of less than. The dispersive optical device includes a primary and a secondary emission line such that only the primary emission line remains within the acceptance angle of the resonator and any other emission lines, including the secondary emission line, are dispersed outside the acceptance angle of the resonator. Are arranged in a specific direction so as to disperse a large number of closely-spaced emission lines. The interferometer device is configured to relatively suppress non-selected portions of the primary emission line in order to substantially suppress non-selected portions of the primary emission line. Distributed optical device and the interferometer apparatus thereby to select and line narrowing a primary emission lines, F ₂
Laser, in order to provide a narrow-band VUV laser beam, is intended to emit a single wavelength laser beam having a narrow spectral bandwidth than the bandwidth of the primary emission lines of the free-running F ₂ laser.

In addition, 15 including the primary emission line and the secondary emission line
A discharge chamber filled with a gas mixture containing molecular fluorine to generate a spectral emission containing a number of closely spaced emission lines in a wavelength range between 7 nm and 158 nm; a plurality of electrodes for generating a pulse discharge to be applied, and, the F ₂ laser including a resonator, a for generating a laser beam having a bandwidth of less than 1pm comprises a discharge chamber and the interferometer system Provided. The interferometer apparatus includes a secondary bright line and a non-selected primary bright line in order to substantially suppress the secondary bright line and the non-selected primary bright line compared to the selected primary bright line. The F ₂ laser is configured to relatively suppress, thereby selecting and narrowing the primary emission line,
In order to provide a narrow-band VUV laser system, and it is to emit a single wavelength laser beam having a narrow spectral bandwidth than the bandwidth of the primary emission lines of the free-running F ₂ laser. A wavelength monitor is coupled in a feedback loop to a processor for monitoring the spectral distribution of the laser beam. The processor controls the interferometric spectrum of the interferometer device based on the monitored spectral distribution such that sidebands in the spectral distribution are substantially minimized.

157 including a primary emission line and a secondary emission line
a discharge chamber filled with a gas mixture containing molecular fluorine to generate a spectral emission containing a number of closely spaced emission lines in the wavelength range between 158 nm and 158 nm; and a pulse discharge applying a voltage to the molecular fluorine. F ₂ including a number of electrodes coupled to the generating power supply circuit, and a resonator for generating a laser beam having a bandwidth of less than 1 pm including the discharge chamber and the interferometer device.
A laser is provided. This interferometer device has one secondary emission line
To substantially suppressed as compared with the following emission lines, configured to relatively suppress the secondary emission lines, thereby selecting the primary emission lines, F ₂ laser, in order to provide a narrow-band VUV laser beam it is intended to emit a single wavelength laser beam having a narrow spectral bandwidth than the bandwidth of the free-running F ₂ laser. A wavelength monitor is coupled in a feedback loop to a processor for monitoring the spectral distribution of the laser beam. The processor controls the interference spectrum of the interferometer device based on the monitored spectral distribution such that sidebands in the spectral distribution are substantially minimized.

Further, 15 lines including a primary line and a secondary line are included.
A discharge chamber filled with a gas mixture containing molecular fluorine to produce a spectral emission containing a number of closely spaced emission lines in a wavelength range between 7 nm and 158 nm; And a resonator for generating a laser beam having a bandwidth of less than 1 pm, including a discharge chamber, an interferometer device, and a dispersive optic device. F ₂ laser is provided. The dispersive optical device includes a primary and a secondary emission line such that only the primary emission line remains within the acceptance angle of the resonator and any other emission lines, including the secondary emission line, are dispersed outside the acceptance angle of the resonator. Are arranged in a particular direction to disperse a number of closely spaced emission lines, including: The interferometer device is configured to relatively suppress non-selected portions of the primary emission line in order to substantially suppress non-selected portions of the primary emission line. Distributed optical device and the interferometer apparatus thereby to select and line narrowing a primary emission lines, F ₂ laser, in order to provide a narrow-band VUV laser beam, the bandwidth of the free-running F ₂ laser of primary emission lines It is intended to emit a single wavelength laser beam having a narrower spectral bandwidth. A wavelength monitor is coupled in a feedback loop to a processor that monitors the spectral distribution of the laser beam. The processor is
The interference spectrum of the interferometer device is controlled based on the monitored spectral distribution so that sidebands in the spectral distribution are substantially minimized.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Priority) The present application is related to US Provisional Patent Application No. 60 / 212,18, filed on June 16, 2000.
Claims the benefit of No. 3 priority. (Incorporated by citation) The following is a list of citations of references,
Each of these may, in addition to the references cited in the priorities section above, disclose the following by reference in disclosing alternative embodiments of elements or features of the preferred embodiments that are not described in detail below. Of the preferred embodiments of the present invention. Reference is made to one or a combination of two or more of these references, resulting in variations of the preferred embodiment described in the following detailed description. Yet another patent,
Patent application and non-patent references are also cited within the written description, and are incorporated by reference into the preferred embodiments, which have exactly the same potency as that just described above for the following references. That is, U.S. patent application Ser.
No. 70, No. 09 / 447,882, No. 09/317,
No. 695, No. 09 / 574,921, No. 09/51
No. 2,417, No. 09 / 599,130, No. 09/6
No. 94,246, No. 09 / 712,877, No. 09 /
No. 738,849, No. 09 / 718,809, No. 09
No./733,874, No. 09 / 780,124, No. 0
Nos. 9 / 715,803, 60 / 212,301, 60 / 212,257, and 60 / 267,567, each of which are assigned to the same assignee as the present patent application, and U.S. Patent Nos. 6,154,470, 6,
No. 157,662, No. 6,219,368, No. 6,0
Nos. 28,879, 6,240,110 and 5,9
01,163 and E.I. Hecht, "Optics", Addison-Wesley, No. 8
-9 (1987); C. Driscoll edition,
"Handbook of Optics", McGra
w-Hill, pages 8-111 (1978), B
room, "Modes of a Laser Resonator Containing Filte
red Birefringent Plates), American Optical Society Magazine (J
Opt. Soc. Am.), 64, 447 (1974),
And all patents, patent applications and non-patent references mentioned in the background or specification of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 2, a schematic of an excimer or molecular fluorine laser system according to the preferred embodiment is shown. Suitable gas discharge laser systems, vacuum ultraviolet rays: a (VUV vacuuming ultraviolet) molecular fluorine (F ₂₎ for use with a lithography system VUV laser system, such as a laser system. For example, an alternative configuration of a laser system for use in other industrial applications, such as TFT annealing, photoablation and / or micromachining, meets the requirements of that application as shown in FIG. Configurations include those understood by those skilled in the art as being similar to and / or modified from the described system. For this purpose, alternative DUV or VUV laser systems and component configurations are disclosed in U.S. Patent Application Nos. 09 / 317,695, 09 / 130,277,
No. 09 / 244,554, No. 09 / 452,353
No., 09 / 512,417, 09 / 599,13
No. 0, 09/694, 246, 09/712, 8
No. 77, No. 09 / 574,921, No. 09/738,
No. 849, No. 09 / 718,809, No. 09/62
9,256, 09 / 712,367, 09/7
No. 71,366, No. 09 / 715,803, No. 09 /
No. 738,849, No. 60 / 202,564, No. 60
No. / 204,095, No. 09 / 741,465, No. 0
No. 9 / 574,921, No. 09 / 734,459, No. 09 / 741,465, No. 09 / 686,483,
Nos. 09 / 715,803 and 09 / 780,12
No. 4, and U.S. Patent Nos. 6,005,880, 6,0
No. 61,382, No. 6,020,723, No. 5,94
No. 6,337, 6,014,206, 6,15
No. 7,662, No. 6,154,470, No. 6,16
No. 0,831, No. 6,160,832, No. 5,55
9,816, 4,611,270, 5,76
Nos. 1,236, 6,212,214, 6,15
No. 4,470, and 6,157,662, each of which is assigned to the same assignee as the present application and incorporated herein by reference.

The system shown in FIG. 2 generally includes a solid pulsar module 104 and a gas treatment module 10.
6. A laser chamber 102 (or a heat exchanger and a chamber 102) having a pair of main discharge electrodes 103 connected to
Or a laser tube including a fan for circulating the gas mixture in the tube). Since the gas processing module 106 has a valve connection to the laser chamber 102, the halogen and buffer gas (es) and, optionally, gas additives are preferably in a premixed form.
form) (US patent application Ser. No. 09 / 513,025, assigned to the same assignee as the present application, and US Pat.
573 and 6,157,662, each of which is incorporated herein by reference).
The chamber is injected or filled. The solid pulser module 104 is powered by a high voltage power supply 108. Thyratron Pulsa Module (thyratron
pulser module) may be used instead. The laser chamber 102 is surrounded by an optical module 110 and an optical module 112 forming a resonator. Or optical modules 110 and 112 are controlled by the optical control module 114, or alternatively, especially KrF, as is preferable when ArF or F ₂ laser is used for optical lithography, narrow linewidth optical device (Line-narrowing optics) is an optical module 11
If it is included in one or both of 0, 112, it is controlled directly by the computer or processor 116.

A processor 116 for laser control receives various inputs and controls various operating parameters of the system. The diagnostic module 118 preferably includes a separate portion of the main beam 120 via optics for deflecting a small portion of the beam in the direction of the module 118, such as a beam splitter module 122. Receive and measure one or more parameters, such as pulse energy, average energy and / or power, and preferably wavelength. Beam 120
Is preferably the laser output to the imaging system (not shown) and, in particular, in the case of lithographic applications, ultimately the work piece (also not shown), which is output directly to the application process It may be done. The laser control computer 116 can communicate with the stepper / scanner computer, other control units 126, 128 and / or other external systems through the interface 124.

The laser chamber 102 contains a laser gas mixture and, in addition to a pair of main discharge electrodes 103, one or more preionization electrodes.
e) (not shown). Suitable main electrodes 103 are described in US patent application Ser. No. 09 / 453,670 for photolithography applications, assigned to the same assignee as the present application and incorporated herein by reference, but for example, If a narrow discharge width is not preferred, alternative configurations may be used. Other electrode configurations are described in U.S. Patent Nos. 5,729,565 and 4,860,300, each assigned to the same assignee as the present application, and alternative embodiments are all incorporated herein by reference. U.S. Pat. No. 4,691,32, which is incorporated herein by reference.
No. 2, No. 5,535,233, and No. 5,557,6
No. 29. Suitable preionization units are each present application and assigned to the same assignee US Patent Application No. 09 / 692,265 (KrF, ArF, is particularly suitable when the _{F 2} laser), 09 / 532,276 And alternative embodiments are described in U.S. Patent Nos. 5,337,330, 5,81
No. 8,865 and 5,991,324, and all of the above patents and patent applications are incorporated herein by reference.

The solid or thyratron pulsar module 104 and the high voltage power supply 108 are powered by compressed electrical pulses (co
Electrical energy during a mpressed electrical pulse is supplied to a pre-ionization electrode and a main electrode in the laser chamber 102 to energize the gas mixture. Suitable pulser modules and high voltage power supply components are each assigned to the same assignee as the present application and are incorporated by reference herein in US patent application Ser. No. 09 / 640,5.
No. 95, No. 60 / 198,058, No. 60/204,
Nos. 095, 09/432, 348 and 09/39
0,146, and U.S. Patent Nos. 6,005,880, 6,226,307 and 6,020,723. Other alternative pulsar modules are disclosed in US Pat. No. 5,985, each of which is incorporated herein by reference.
No. 2,800, No. 5,982,795, No. 5,94
No. 0,421, No. 5,914,974, No. 5,94
9,806, 5,936,988, 6,02
Nos. 8,872, 6,151,346 and 5,72
No. 9,562.

The laser cavity surrounding the laser chamber 102 containing the laser gas mixture preferably includes a line narrowing optic for a line narrowed excimer or molecular fluorine laser such as for photolithography. Are included, which may be undesirable if narrowing is not desired (such as in the case of TFT annealing), or narrowing may be performed in the front optical module 112, or may be external to the resonator. Spectral filter (spectral f
high reflectivity mirrors (hi) in the laser system if ilters are used or narrow line optics are placed in front of the HR mirrors to narrow the bandwidth of the output beam.
gh reflectivity mirror). According to a preferred embodiment herein, for example,
One or more dispersive prisms,
Birefringent plate or block and / or etalon or 09 / 715,80
15 such as an interferometer device, such as a device having a pair of opposed non-parallel plates as described in the '3 patent application.
Optics may be used to select one of a number of bright lines around 7 nm, in which case the same optic (s) or additional narrow line widths to narrow the selected bright line Chemical optical device (s) may be used. The total gas mixture pressure is lower than conventional systems, for example lower than 3 bar, to generate selected emission lines with a narrow bandwidth, such as 0.5 pm or less, without using additional line narrowing optics. (See US Patent Application Serial No. 60 / 212,301, assigned to the same assignee as the present application and incorporated herein by reference.)

The laser chamber 102 is sealed by a window that is transparent to the wavelength of the emitted laser radiation 120. This window may be a Brewster window and may be aligned at another angle, eg, 5 °, with respect to the optical path of the resonant beam. One of the windows may also serve to output couple the beam, and also serve as a highly reflective resonant reflector on the opposite side of the chamber 102 from which the beam is outcoupled. Sometimes.

After a portion of the output beam 120 passes through the output coupler of the optical module 112, the output portion deflects a portion of the beam toward the diagnostic module 118 or otherwise outputs the beam. A small portion of the combined beam is incident on a beam splitter module 122, which includes optics to cause the diagnostic module 118 to reach, while the main beam portion 120 is the output beam 1 of the laser system.
20 (US patent application Ser. No. 09 / 771,013, 09, assigned to the same assignee as the present invention).
Nos./598,552, and 09 / 712,877 and U.S. Pat. No. 4,611,270. Each of which is incorporated herein by reference.) Suitable optics include a beam splitter or other partially reflective surface optics. The optical device may also include a mirror or beam splitter as the second reflective optical device. More than one beam splitter and / or HR mirror and / or dichroic mirror
irror) may be used to direct a portion of the beam to components of the diagnostic module 118. Holographic beam sampler, transmission grating, partially transmissive reflection diff
raction grating, grism, prism or other refractive, dispersive and / or transmission optic (s) to separate small beam portions from main beam 120 for detection by diagnostic module 118 While the majority of the main beam 120 is made to reach the application process directly or via an imaging system or otherwise. These optics or additional optics can be used to separate atomic fluorine (at
It may be used to filter visible radiation, such as red emission from omic fluorine.

The output beam 120 is a beam splitter.
The reflected beam portion while passing through the module may be directed to the diagnostic module 118, and the main beam 120 may be reflected while a smaller portion is transmitted through the diagnostic module 118. The portion of the out-coupled beam that continues to pass through the beam splitter module is the output beam 120 of the laser, which is intended for industrial or laboratory applications such as imaging systems and workpieces for photolithographic applications. And propagate.

In particular, a molecular fluorine laser system and Ar
In the case of an F-laser system, an enclosure (not shown) preferably seals the beam path of beam 120, such as to keep the beam path unaffected by photoabsoroing species. A smaller enclosure is preferably between the chamber 102 and the optical modules 110 and 112, and the beam splitter 12
The beam path between 2 and the diagnostic module 118 is sealed. Suitable enclosures are described in U.S. patent application Ser. Nos. 09 / 598,552, 09 / 594,89, assigned to the same assignee as the present application and incorporated herein by reference.
No. 2, 09 / 727,600 and 09/131,
580 and U.S. Patent Nos. 6,219,368, 5,559,5, all of which are incorporated herein by reference.
No. 84, No. 5,221,823, No. 5,763,85
No. 5, No. 5,811,753 and No. 4,616,90
No. 8 explains this in detail.

The diagnostic module 118 preferably includes at least one energy detector. This detector measures the total energy of the beam portion that directly corresponds to the energy of the output beam 120 (US Pat. Nos. 4,611,270 and 6,212,214, which are incorporated herein by reference). reference). An optical arrangement, such as an optical attenuator, for example a plate or a coating, or other optical device is formed on or near the detector or beam splitter module 122 and the radiation incident on the detector (US patent application Ser. No. 09 / 172,80, each assigned to the same assignee as the present application and incorporated herein by reference).
No. 5, No. 09/741, 465, No. 09/712, 8
No. 77, 09/771, 013 and 09/77
1,366).

One of the other components of the diagnostic module 118
One preferably has a wavelength and / or a wavelength such as a monitor etalon or a grating spectrometer.
Or a bandwidth detection component (see FIGS. 5-6 of the present application).
And US patent application Ser. Nos. 09 / 416,344, 09 / 686,483, and 09 / 791,431, each assigned to the same assignee as the present invention.
And U.S. Pat. Nos. 4,905,243 and 5,979.
No. 8,391, No. 5,450,207, No. 4,92
No. 6,428, No. 5,748,346, No. 5,02
No. 5,445, No. 6,160,832, No. 6,16
See 0,831 and 5,978,394. All of the above wavelength and / or bandwidth detection and monitoring components are incorporated herein by reference. According to the preferred embodiment herein, the bandwidth is monitored and controlled in a feedback loop including a processor 116, an optics control module, and a gas processing module 106. The total pressure of the gas mixture in the laser tube 102 is controlled to a specific value to generate an output beam at a specific bandwidth.

Other components of the diagnostic module include US Pat. No. 6,243,405 and US patent application Ser. No. 09/842, each assigned to the same assignee as the present application and incorporated herein by reference. , No. 281 and 09/41
No. 8,052, including a pulse shape detector or an ASE detector, respectively, as described in further detail below.
Gas control and / or output beam energy stabilization, etc., or amplified spontaneous emission (ASE: am
ASE by monitoring the amount of plified spontaneous emission)
Ensure that stays below a predetermined level. For example, a beam alignment monitor (beam a) as described in US Pat. No. 6,014,206.
lignment monitor, or, for example, the beam profile monitor of US patent application Ser. No. 09 / 780,124, assigned to the same assignee as the present application.
r) may be present, where each of these patent documents is incorporated by reference in the description of this application.

Processor or control computer 116
Are the input or output parameters of the laser system and output beam, pulse shape, energy, ASE,
Energy stability, energy overshoot for burst mode operation, wavelength, spectral purity (sp
ectral purity) and / or some value in bandwidth. Processor 116 also controls the line narrowing module to tune wavelength and / or bandwidth or spectral purity, and controls the power and pulser modules 104 and 108 to preferably reduce the moving average pulse power or energy. Control so that the energy dose at a point on the workpiece is stabilized near a desired value. Further, the computer 11
6 controls a gas processing module 106 that includes gas supply valves connected to various gas sources. Still other functions of processor 116, such as providing overshoot control, energy stability control, and / or monitoring input energy to the discharge, are assigned to the same assignee as the present application and incorporated herein by reference. No. 09 / 588,561, which is incorporated herein by reference.

As shown in FIG.
Preferably, individually or in combination, the solid or thyratron pulsar module 104 and the HV power supply 10
8, gas processing module 106, optical module 110
And / or 112, in communication with the diagnostic module 118, and the interface 124. The laser cavity surrounding the laser chamber 102 containing the laser gas mixture contains an optical module 11 including line narrowing optics for a narrow line excimer or molecular fluorine laser.
0, which indicates whether narrowing is undesirable or
Or high reflectivity in the laser system if narrowing is performed at the front optics module 112 or a spectral filter external to the resonator is used to narrow the output beam width It may be replaced by a mirror or the like. Some variations of the line narrowing optics are described in detail below.

The laser gas mixture is initially filled into the laser chamber 102 in a process referred to in the present application as "new fill". In this procedure, the laser tube is evacuated of laser gas and contaminants and refilled with fresh gas of the ideal gas composition. The gas composition for a very stable excimer or molecular fluorine laser according to the preferred embodiment uses helium or neon or a mixture of helium and neon as the buffer gas, depending on the particular laser used. Suitable gas compositions are described in US Pat. Nos. 4,393,405, 6,157,162 and 4,977, each assigned to the same assignee as the present application and incorporated herein by reference. No. 573 and US patent application Ser. No. 09/5.
No. 13,025, No. 09 / 447,882, No. 09 /
418,052, and 09 / 588,561. The concentration of fluorine in the gas mixture is 0.00
It is in the range of 3% to 1.00%, preferably about 0.1%. Additional gas additives, such as noble gases or other gases, provide energy stability and overshoot control as described in the 09 / 513,025 application incorporated herein by reference. And / or may be added as an attenuator. Particularly, in the case of the F ₂ laser, it may xenon, the addition of krypton and / or argon is used. The concentration of xenon or argon in the mixture may range from 0.0001% to 0.1%. In the case of an ArF laser, 0.0
Addition of xenon or krypton having a concentration between 001% and 0.1% may be used. For a KrF laser, the addition of xenon or argon, also having a concentration between 0.0001% and 0.1%, may be used. The preferred embodiment of the present application specifically relates to using an F ₂ laser, but with ArF, KrF, and Xe
Several gas replenishment operations on the gas mixture composition of other systems such as Cl excimer lasers
hment action) is described, wherein the ideas described in this application can also be advantageously incorporated into these systems.

For each injection of the total gas volume in, for example, a 100 liter laser tube 102, for example, a buffer gas of 20 to 60 milliliters, or a rare gas-halide excimer laser Are mixed with a mixture of a halogen gas, a buffer gas and an active rare gas, for example 1 to 3
Halogen gas injection, including micro-halogen injection of milliliters of halogen gas, total pressure regulation and gas displacement procedures are preferably performed with vacuum pumps, valve networks and one or more gas compartments. May be performed using the gas processing module 106 including The gas treatment module 106 receives gas through gas lines connected to gas containers, tanks, cans, and / or bottles. Some suitable and alternative gassing and / or replenishing measures other than those specifically described in the present application (see below) are described in U.S. Pat. No. 4,977,497, assigned to the same assignee as the present application. No. 573, No. 6,212,
Nos. 214 and 5,396,514 and U.S. Patent Application Nos. 09 / 447,882, 09 / 418,052.
No., 09/734, 459, 09/513, 02
No. 5,09,588,561, and US Pat. Nos. 5,978,406, 6,014,398 and 6,028,880, all of which are incorporated herein by reference. Is incorporated by reference. Sources of xenon gas or other gas additives were mentioned above.
The '025 patent application may be included either inside or outside the laser system.

In some cases, the total pressure is adjusted in the form of gas release or the total pressure in the laser tube 102 is reduced. For example, when it is determined that the partial pressure of the halogen gas in the laser tube 102 is not desirable after the total pressure adjustment,
Following total pressure adjustment, gas composition adjustment (gas composition adju)
stment) is performed. The total pressure adjustment may also be performed after the gas refill operation, and may be performed in combination with adjusting the drive voltage to a smaller discharge than if the pressure adjustment were not performed in combination.

A gas displacement operation may be performed, which is described in Section 09, which is incorporated herein by reference.
As described in the / 734,459 patent application,
Depending on the amount of gas to be replaced, for example, any value from a few milliliters to 50 liters or more, but less than a new fill, a partial, mini, or macro gas replacement operation, or a partial fresh fill Sometimes called an operation. As an example, either directly or through an additional valve assembly that includes a small compartment to regulate the amount of gas injected (see the '459 patent application)
A gas line for injecting a premixed gas A containing 1% F ₂ : 99% other buffer gas such as Ne or He into the gas processing unit 106 connected to the laser tube 102; noble gas - halide excimer laser 1% noble gas in the case of: a separate gas line for injecting a premixed gas B containing 99% of the buffer gas may comprise, where F ₂ In the case of a laser, the premixed gas B is not used. In order to add or reduce the total pressure, i.e., to inject the buffer gas into the laser tube or to release part of the gas mixture in the tube, preferably with a halogen injection to maintain the halogen concentration Thus, another conduit may be used. That is, replenishing the concentration of fluorine in laser tube 102 by injecting premixed gas A (and premixed gas B in the case of a rare gas-halide excimer laser) into tube 102 via a valve assembly. Can be. Then, an amount of gas corresponding to the amount injected is released, and the total pressure can be maintained at the selected level. Additional gas lines and / or valves may be used to inject additional gas mixtures.
New filling, part and mini gas replacement and gas injection procedures,
Enhancement and normal micro-halogen injection, for example between 1 or less and 3 to 10 milliliters, and any and all other gas replenishment operations are performed by the gas processing unit 106 based on various inputs in the feedback loop. Initiated and controlled by processor 116 which controls the valve assembly of laser tube 102. These gas replacement procedures can be used in conjunction with a gas circulation loop and / or window replacement procedure to achieve a laser system with extended inspection intervals for both the gas mixture and the laser tube window. .

A general description of the linewidth narrowing features of an embodiment of a laser system used specifically in photolithography applications is provided herein, followed by:
To illustrate the variations and features used within the preferred embodiment of the present application to provide an output beam having high spectral purity or bandwidth (eg, less than 1 pm and preferably 0.6 pm or less). Patents and patent applications incorporated by reference in the description of this application are listed.
These exemplary embodiments may be used only to select the primary emission line λ ₁ , or may be used to provide emission line selection and provide additional emission line narrowing, or to provide the resonator with emission line selection. And additional optics for narrowing the selected bright line, and controlling (i.e., reducing) the total pressure may provide narrowing ( US patent application Ser. No. 60/21, assigned to the same assignee as the present application and incorporated herein by reference.
2,301). The bright line selection and line narrowing molecular fluorine laser resonator according to the preferred embodiment of the present application is described in further detail below with reference to FIG.

Exemplary line narrowing optics included in the optical module 110 include a beam expander, an etalon, or 09 / which is assigned to the same assignee as the present application and incorporated herein by reference. No. 715, 803 or No. 6
A pair of opposing non-planar reflective plates as described in the '0 / 280,398 patent application.
An apparatus having an ar reflection plate and a diffraction grating are included, and one or more dispersing prisms may alternatively be used, where the diffraction grating has a relatively higher degree of dispersion than the prism. ), But narrowband lasers such as those used with refractive or catadioptric photolithographic imaging systems generally exhibit somewhat lower efficiencies than the dispersing prism (s). As mentioned above, the front optics also have the numbers 09/715, 803, 09/09, each assigned to the same assignee as the present application and incorporated herein by reference.
No. 738,849 and 09 / 718,809 patent applications may include line narrowing optics as described in any of the patent applications.

Instead of having a retro-reflective grating in the rear optics module 110, the grating may be replaced by a high reflectivity mirror and a dispersive prism may result in lower dispersion. Yes, and interferometer devices such as beam expanders and devices with etalons or non-planar opposing plates may be used for line selection and linewidth narrowing, and alternatively in the rear optics module 110 In some cases, line narrowing or bright line selection may not be performed. When using an all-reflective imaging system, the laser uses the characteristic broadband bandwidth (ch) of the laser.
0.5 depending on the aracteristic broadband bandwidth)
It can be configured for semi-narrow band operation, such as having an output beam line width in excess of pm, such that it is provided by either an optical device or by reducing the total pressure in the laser tube. No additional narrowing of the bright line will be used.

The beam expander of the above exemplary line narrowing optics of optical module 110 preferably includes one or more prisms. The beam expander may include other beam expansion optics such as a lens assembly or a converging / diverging lens pair. The diffraction grating or high reflectivity mirror is preferably rotatable so that the wavelength reflected within the acceptance angle of the resonator can be selected or tuned. Also, alternatively, the diffraction grating, or other optical device (s), or the entire line narrowing module, may each be assigned to the same assignee as the present application and incorporated herein by reference. It may be pressure tuned as described in the 09 / 771,366 patent application and the 6,154,470 patent. Diffraction gratings can be used for both purposes to disperse the beam to achieve a narrow bandwidth, and preferably also to retroreflect the beam in the direction of the laser tube. Alternatively, a high reflectivity mirror is positioned after the diffraction grating to receive the reflection from the diffraction grating,
The beam may be reflected back in the direction of a Littman configuration diffraction grating, or the diffraction grating may be a transmission diffraction grating. One or more dispersive prisms may be used, and more than one etalon or other interferometer device may be used.

Depending on the type and degree of line narrowing and / or the desired selection and tuning, and the particular laser on which the line narrowing optics is to be installed, it is specifically described below in connection with FIG. Many alternative optical device configurations besides the ones can be used. For this purpose, US Pat. No. 4,399,5
No. 40, No. 4,905,243, No. 5,226,05
No. 5, No. 5,559,816, No. 5,659,419
No. 5,663,973, No. 5,761,236
No. 6,081,542, No. 6,061,382
No. 6,154,470, 5,946,337
No. 5,095,492, 5,684,822
No. 5,835,520, 5,852,627
No. 5,856,991, No. 5,898,725
No. 5,901,163, 5,917,849
No. 5,970,082, 5,404,366
No. 4,975,919, 5,142,543
No. 5,596,596, 5,802,094
No. 4,856,018, 5,970,082
No. 5,978,409, No. 5,999,318
No. 5,150,370 and 4,829,536
And German Patent DE 298 22090.3
And any of the patent applications referred to above and below in this application are referenced to obtain the line narrowing configuration used in the preferred laser system of this application, and these patents are referenced. The references are each incorporated herein by reference.

The optical module 112 preferably includes means for outcoupling the beam 120, such as a partially reflecting resonant reflector. Beam 120 is intra-reso
nator) may be output coupled in other ways, such as by a partially reflecting surface of a beam splitter or another optical element, in which case the optical module 112 would include a high reflectivity mirror. Optical device control module 11
4 preferably receives and interprets signals from the processor 116 and realigns, module 1
Control the optical modules 110 and 112, such as by initiating a gas pressure adjustment at 10, 112, or a reconfiguration procedure ('353,' 695, '277,' 554 referred to above).
And the '527 patent application).

The halogen concentration in the gas mixture is maintained constant during laser operation by a gas refill operation by refilling the amount of halogen in the laser tube for the preferred molecular fluorine laser of the present application. The gas is maintained at the same predetermined ratio as in laser tube 102 after a new fill procedure. In addition, gas injection operations such as μHI as understood from the '882 patent application referred to above are advantageously modified to a micro gas displacement procedure, so that the increase in energy of the output laser beam is reduced by the total pressure. Can be compensated for by reducing Further, the laser system is preferably configured to control the input drive voltage such that the energy of the output beam is at a predetermined desired energy. The drive voltage is preferably HV
_The gas treatment is maintained within a small range around _opt , while the gas treatment replenishes the gas and average pulse energy or by controlling the rate of gas flow through the laser tube 102 or the rate of gas flow, or the like. Operate to maintain energy exposure dose. Advantageously, according to the gas treatment described in the present application, the laser system comprises:
Achieves average pulse energy control and gas replenishment, extending the life of the gas mixture or time between new fills while allowing operation within a very small range near HV _opt (to the same assignee as the present application). US patent application Ser. No. 09/780, assigned to and incorporated by reference herein.
No. 120).

In all of the above and below embodiments, the materials used for the dispersive prism, the beam expander prism, the etalon or other interferometer device, the laser window and the output coupler are preferably molecular It is highly transmissive at wavelengths less than 200 nm, such as the 157 nm output emission wavelength of a fluorine laser. This material can also withstand long-term irradiation with ultraviolet light with minimal degradation. Examples of such materials are CaF ₂ , MgF ₂ , BaF ₂ , LiF and Sr
It is F _2, optionally fluorine-doped silica (Fluori
ne-doped quartz) may be used. Also, in all embodiments, many optical surfaces, especially prism optical surfaces, have anti-reflecting coatings on one or more optical surfaces to minimize reflection losses and extend their life.
ive coating) or not.

[0048] Further, the gas composition for the F ₂ laser of the above configuration, use helium, neon, or any mixture of helium and neon, as a buffer gas. The concentration of fluorine in the buffer gas is preferably 0.003%
To about 1.0%, preferably about 0.1%. However, if the total pressure is reduced to narrow the bandwidth, the fluorine concentration may be, for example, 1-7 mba regardless of the total pressure in the tube or the percentage concentration of halogen in the gas mixture.
r, more preferably between 0.1 and 3% so as to be maintained between about 3 and 5 mbar. To improve energy stability, burst control, and / or output energy of the laser beam, trace
Xenon and / or argon, and / or oxygen, and / or krypton and / or other gases (see the '025 application) may be used. The concentration of xenon, argon, oxygen, or krypton in the mixture will range from 0.0001% to 0.1%, and will suitably be well below 0.1%. Some alternative gas configurations, including trace gas additives, are disclosed in U.S. patent application Ser. No. 09 / 513,025 and U.S. Pat. 157,662.

A power amplifier can be placed after a line-narrowed oscillator, such as those described above, to increase the power of the beam output by the oscillator. Preferred features of the oscillator-amplifier setup are described in U.S. patent application Ser. Nos. 09 / 599,130 and 60 / 228,1 which are assigned to the same assignee as the present application and are hereby incorporated by reference.
No. 84. The amplifier is the discharge chamber 102
Or may be separate. Optical or electrical delays may be used to time the discharge at the amplifier with the time at which the light pulse arrives from the oscillator to the amplifier. In particular, in connection with the present invention, the molecular fluorine laser oscillator has an advantageous output coupler having a maximum transmission interference at λ ₁ and a minimum at λ ₂ , which is described below. This will be described in more detail. 157 nm
The beam is output from the output combiner and is incident on the amplifier of this embodiment to increase the power of the beam. That is, a very narrow bandwidth beam is achieved with high suppression of the secondary emission line λ ₂ and high power (at least a few watts to 10 watts or more). (Narrow Linewidth F ₂ Laser Oscillator) FIG.
Molecular fluorine (F) including a line narrowing module 50 having a prism beam expander 46 and an etalon 48 or interferometer device having non-planar, parallel, opposed plates.
₂ ) An outline of a preferred embodiment of a laser resonator device is shown. In the resonator device of the seventh embodiment, molecular fluorine, neon and / or
Or a discharge chamber 2 filled with a gas mixture comprising one or more buffer gases such as helium. A pair of main discharge electrodes 3a and 3b are inside the discharge chamber 2 and connected to a pulser circuit (not shown),
A voltage is applied to molecular fluorine. Discharge chamber 2 is preferably similar to chamber 102 described above with respect to FIG. One or more pre-ionization units are also in the discharge chamber (not shown, but see the above-referenced 09 / 692,265 patent application). Other aspects of the discharge chamber 2 can be found in the 09 / 453,670 patent application, otherwise as described above and / or as understood by those skilled in the art.

One window 40 of the configuration shown in FIG. 3 is a plano-parallel optical window that serves as an outcoupler. A partially reflecting mirror may alternatively be used separately from the chamber window 40 to output couple the beam. The window 40 serves the dual role of sealing the chamber 2 and coupling out the beam, reducing the number of optical surfaces in the resonator and thereby advantageously increasing efficiency. The window 40 is preferably aligned perpendicular to the optical axis, but at an angle such as 5 ° or Brewster's angle to achieve the desired reflectivity and transmittance characteristics and / or prevent parasitic oscillations.
le) or other selected angles.

A vacuum bellow 56 or similar device provides flexibility in terms of freedom of adjustment and a vacuum tight seal. Another window 44 is preferably a plano-convex lens, each of which is assigned to the same assignee as the present application and is incorporated by reference herein into US Pat. No. 6,061,382 and EP. Patent Application No. EP
It serves to compensate for wavefront curvature as described in 0095706 A1. Seal security is provided by seal 42.
Lens 44 may or may not be adjustable in direction. Lens 44 may be tilted slightly (about 5 degrees) from an angle perpendicular to the beam to suppress or avoid parasitic oscillations. Preferably, this lens 4
Reference numeral 4 denotes an anti-reflection coating.

The resonator of the F ₂ laser according to the preferred embodiment shown in FIG. 3 includes a bright line selection and / or line narrowing unit coupled to the chamber 2 via bellows 56 and seal 42. The beam is preferably expanded by one or more beam expansion prisms 46 to reduce beam divergence. Several prisms 46 may be used, and a converging divergence lens pair may be used.
(ng lens pair) or other means of beam expansion known to those skilled in the art.

A transmission etalon is preferably placed after the beam expander prism 46 and serves as a wavelength selector. Alternatively, interferometer devices having non-parallel opposing internal reflector plates, as described in more detail in 09 / 715,803 and 280,398, may be used. Finally, the highly reflective mirror 32 returns the beam through the resonator.

Since the line narrowing unit is in the enclosure 50 which is coupled to the laser chamber 2 using the bellows 56 and the seal 42, the line narrowing unit of the laser resonator is sealed from the outside air. An inert purge gas is preferably provided at the inlet and outlet ports 5
2, 54 through the enclosure 50. Vacuum port included or pump connected to port 5
An inert gas purge may not be used if connected via either 2 or 54 and enclosure 50 is maintained at a substantially low pressure at a low pressure. Methods of controlling the atmosphere within the enclosure include maintaining the enclosure under evacuated conditions using a pump or rapidly purging through the enclosure 50.
Flow the gas, or preferably first evacuate the enclosure and then flow the purge gas at a lower flow rate.
Followed by backfill of the purge gas after evacuation,
This procedure is repeated several times, for example 1 to 10 times, before the purge gas is drained at a low speed. For further details and alternative treatments for maintaining prepare the atmosphere of the enclosure, and is hereby incorporated by reference and assigned to the same assignee as the respective present application (F ₂ beam delivery path for the laser enclosure US Patent 6,219,36 (for diagnostic beam splitter module)
No. 8, and U.S. Patent Application Nos. 09 / 594,892 and 09 / 598,522.

The entire beam path between the chamber 2 and the highly reflective mirror 32 is preferably actually enclosed in an enclosure 50 which is preferably purged with nitrogen or some inert gas such as helium, argon, krypton or the like. You. High-purity nitrogen is preferably used for this purpose.

The pressure of the nitrogen gas or other inert gas in the enclosure 50 is adjustable, and the transmission spectrum of the interferometer device 48 can be adjusted by changing the pressure of the gas (eg, the present invention). U.S. patent application Ser. No. 09 / 771,3, relating to pressure regulation of a line narrowing unit including a diffraction grating and a beam expander, assigned to the same assignee as the application and incorporated herein by reference.
No. 66). The interferometer device 48 is enclosed in an inert gas-filled envelope (not shown), wherein the pressure in the envelope is controlled to control the transmission spectrum of the interferometer device 48. The transmission (transmissio
maximum n) is suitably, in a number of emission lines in the vicinity of 157nm, including the spontaneous emission spectrum of the free-running _{F 2} laser, the secondary emission lines around Suitably 157.52nm which is suppressed, 1
It is adjusted to match the maximum of the primary emission line at λ ₁ near 57.62 nm.

This pressure adjustment of the transmission spectrum of the interferometer device is illustrated in FIGS. 4 (a) to 4 (c). The interferometer device may alternatively be rotationally adjustable, or may be configured such that the gap spacing between opposing internal plates is adjustable. In FIG. 4B, the transmission spectrum of the interferometer device 48 is a periodic function of wavelength (peri
odic function). Each transmission peak (tr
the width of the interference peak) is approximately the free spectral range of the interferometer device 48 divided by its finesse, since the finesse is limited by the quality of the optical surface,
To minimize the width of the transmission peak, it is preferable to reduce the free spectral range as much as possible. The minimum free spectral range is determined by the specification that the peak adjacent to the center peak does not oscillate. Since the approximate natural bandwidth (see FIG. 4A) is between 0.6 pm and 1.0 pm, the optimal free spectral range is about 1.0 pm.
4 (a) to 4 (c) show the solid lines in FIG.
The selected emission line shown in FIG.
FIG. 4 (b) to FIG. 4 (c) show a second example of the laser output when the transmission spectrum deviates from the optimum state. 9 illustrates the occurrence of a peak. Pressure dependence of the transmission spectrum of etalon is 6,154,
This is described in the '470 patent. One way to change the pressure is to use a needle valve 52 shown in FIG.
Intake and emission of nitrogen (intake and
escape rate). The pressure is increased by closing outlet valve 54 and / or opening inlet valve 52, and vice versa.

A variant of this embodiment has the output coupler 40 as an independent optical element and a planar plane window (plano-plano wi).
ndow) having an output window of the chamber. This provides an opportunity to place the resonator optics on a mechanically stable structure separate from the chamber. However, this can increase optical losses and reduce the efficiency of the laser.

The laser oscillator described typically produces a lower output power compared to a free-running resonator. Therefore, in this embodiment, an amplifier (not shown, but refer to the 09 / 599,130 patent application) may be used.

The preferred material for all optical elements is CaF ₂ , but MgF ₂ , BaF ₂ , SrF ₂ or LiF can also be used. Interferometer device 48 is preferably 9
Film d having a reflectivity of 0% to 97%
It has an inner surface coated by an ielectric coating) and the outer surface is preferably anti-reflective coated. (Alternative Embodiment) Narrowing is preferably provided by an interferometer device such as an etalon, which acts as an output coupler or a high reflection resonant reflector. The interferometer device may also include a highly or partially reflective resonator mirror, as shown in the preferred embodiment.
flector mirror). Depending on the desired free spectral range and whether it is used as a resonant reflector in the reflection mode or in the transmission mode as shown in the embodiment of FIG. Or have a low finesse.

[0061] Alternative embodiments may be implemented using one or more apertures, preferably having dispersive elements such as prisms and, alternatively, diffraction gratings.
Opening, a prism is used for the bright line selection time to distribute the release of the F ₂ laser. Selected bright lines pass through the aperture, and unselected bright lines are blocked by the aperture.
Next, an interferometer device or prism is used to narrow the selected bright line.

The free spectral range (FS) of the interferometer device
The free spectral range (R) is approximately equal to the linewidth of the selected emission line of the free-running laser, but somewhat smaller, so that the output linewidth of the selected emission line becomes narrower. The FSR must not be much smaller than the free running line width to prevent sidebands from occurring in the adjacent interference order. If the FSR is too small, the outer peak of the transmission (or reflection) spectrum will overlap the selected bright line significantly. Allowing "parasitic" sidebands to resonate degrades beam quality. Prism 4 in resonator
Or if there is a dispersive element such as a prism (s) or diffraction grating, the selected emission line is narrowed by further reducing the width of the transmission (or reflection) maximum of the interferometer device. Thus, the sidebands are not suppressed, while the apertures are placed in the resonator to cut the sidebands, resulting in a narrow, high quality output beam.

The interferometer device 48 is configured to seal the discharge chamber 102 and as a window to eliminate the lossy optical interface of the additional optical window that seals the chamber 102, and is configured as a window. Reduce the dimensions of. The interferometer device is, in the illustrated embodiment, 09 /
The chamber 102 is sealed by bellows and O-rings, as shown in FIG. 4 of the '657 application.

As mentioned, the interferometer device may be housed in a jacket. In this embodiment, a gas inlet is preferably provided and one or more gases such as helium, neon, krypton, argon, nitrogen, other inert gases or other gases that do not absorb strongly around 157 nm are selected at a selected pressure. To enable filling of the jacket. The envelope may include means for measuring the pressure and / or temperature of the gas therein, wherein the pressure and / or temperature information is relayed to a processor 116 that controls the pressure and / or temperature. You may. The gas inlet may also be used to evacuate the envelope, including the gap between the plates of the interferometer device, to a low pressure, for example, using a mechanical pump.

The reflective inner surface of the plate of the interferometer device may be coated with a reflective film, or may be left uncoated. The spacers of the interferometer device are invar (registered trademark), zerodur,
Ultra low expansion material (ULE (registered trademark) glass) or quartz,
Alternatively, another material having a low coefficient of thermal expansion such that the temperature sensitivity of the gap thickness between the opposing inner plates is minimized may be included. This is advantageous because the transmission (or reflection) action of the interferometer device depends on the gap spacing.

The following illustrates a method of determining a suitable gap thickness estimate. The line width of the free-running _{F 2} laser is about 1pm or less, the wavelength is about 157 nm,
The FSR is about 0.4 cm ^-1 . This is because the gap between the plates (MgF ₂ , CaF ₂ , LiF ₂ , Ba)
When filled with a solid material having a refractive index of about 1.5 (such as F ₂ , SrF ₂ , crystalline quartz or fluorine-doped quartz), the etalon spacing is 8.3 m
m. A suitable interferometer device whose gap is filled with an inert gas such as nitrogen or helium will have a gap thickness on the order of about 12.5 mm. Both of these gap spacings are easily achievable.

As suggested above, a design consideration for an intracavity interferometer device is that the stability of the maximum and minimum transmission (or reflection) to changes in ambient conditions such as temperature is desirable. That is. For an inert gas such as nitrogen, the refractive index changes by about 300 ppm per bar of pressure. Thus, when the spacing between the reflective surfaces is about 12.5 mm, a frequency control within 10% of the FSR corresponds to a pressure control within 2 mbar of resolution. As discussed above, the reason for using helium, or alternatively nitrogen, argon or other inert gas or vacuum in the pressure regulated etalon 6, is mainly due to the strong presence of about 157 nm each in air. Air is not transparent at the 157 nm wavelength of interest due to the presence of absorbing oxygen, water vapor and carbon dioxide.

Further, the inner surface of the interferometer device is either coated with a partially reflective coating or not. In the latter case, the reflectivity of each surface is about 4-6%,
As a result, the maximum reflectance of the etalon is 16 to 24%.
Alternatively, the transmission interferometer (transmission int
As is preferred in the case of erferometric devices, the dielectric coating should be provided such that each surface exhibits a high reflectivity of greater than 50%, possibly 90% or more, for example up to 97% for high reflectivity. There is also. Similar considerations apply when a solid etalon is used.

Whether the interferometer device is used in transmission mode, as in the preferred embodiment shown in FIG. 3, or in reflection mode, such as an output coupler or a high reflection resonant reflector. However, the interferometer device may be used for both line selection and, at the same time, narrowing of the selected single line. The line selection is such that the transmission (or reflection) at the desired wavelength is maximized and the transmission (or reflection) at other non-selected wavelengths is at or near its minimum, with the FSR of the interferometer device and the maximum transmission (or reflection). Or reflection).

[0070] FSR of preferably interferometer apparatus used in the F ₂ laser of the present application can be prepared by the following method. The gas pressure to fill either the rear optics module 50 of FIG. 3 with the device inside or the envelope with only the device inside, and especially the pressure of the gas between the plates of the device, changes the gas pressure. The refractive index can be adjusted.
Alternatively, the spacing between the plates may be changed, for example using piezoelectric elements as spacers, or the device may be rotatable. Since the FSR depends on each of the refractive index of the gas, the angle at which the beam is incident on the device, and the spacing between the plates, the FSR can be adjusted by any of these methods. If the interferometer device is used in reflection mode as a resonant reflector, no rotational tuning option is possible. By adjusting the FSR of the device, the emission line selection aligns the maximum of the transmission (or reflection) spectrum of the device with the desired emission line to be selected, while free-running the minimum of the reflectance spectrum of the device. it can be carried out accurately by also be aligned in any unselected emission lines of F ₂ laser. The advantage of this configuration is simplicity, which is due to the choice of emission lines, with or without apertures, dispersion prisms, diffraction gratings,
Because no grism, birefringent plate, or other optical device is used (the prism 46 shown in FIG. 3 is preferably a beam expanding prism 46, but the prism 46
Note that one or both of these may be distributed to provide bright line selection). However, this system is inefficient in suppressing unwanted emission lines and can result in residual emission at such wavelengths.

[0071] In addition to molecular fluorine, the F ₂ laser gas mixture in the discharge chamber of the preferred embodiment further includes one or more other gases including at least one buffer gas, the buffer gas Is preferably helium, neon or a mixture of helium and neon. For example,
The discharge chamber 102 is initially 5% in 60 mbar Ne
F ₂ and the remaining He (balance He) (for example, 244)
And _{F 2} of 0mbar of He) or 3~5mbar, N
chamber and filled with a mixture of e and He.
2 is pressurized to 1-5 bar.

[0072] In either embodiment of the F ₂ laser of the present application, as the pulse duration is long, usually achievable spectral linewidth narrower. Each one of the laser beams in the cavity
For each roundtrip, spectral filtering of the beam (spec
tral filtering) occurs. For example, after each transmission (or reflection) from the preferred embodiment interferometer device 48 of FIG. 3, the intensity spectrum of the beam is the product of the transmission (or reflection) function of the device and the incident spectrum. The spectral width of the beam decreases approximately as the reciprocal of the square root of the number of round trips. In one embodiment, the pulse length of the molecular fluorine laser can be increased by using more neon as a buffer gas. The pulse can likewise be lengthened by lengthening the electrical pulse applied to the electrode 3.

The gas mixture is preferably optimized for pulse energy (gain) and pulse energy stability. Higher pressures and fluorine concentrations each generally achieve higher energy results, but also higher pulse energy fluctuations. The preferred device balances these considerations. About 3-5bar total pressure and 0.05% ~
Fluorine concentrations in the range of 0.2% are preferred.

As noted above, one or more
Opening is inserted into the resonator of any of the embodiments of the present application.
Sometimes. This aperture is used for the dispersion spectrum of the dispersion element.
Sideband and / or transmission through interferometer device 48 (or
射) Maximum and F₂Laser overlay with selected emission lines
It serves to cut the sidebands of the combination. (F with reduced line width₂Laser emission) FIGS. 4 (a) to 4
(C) has an etalon or non-parallel internal reflection surface
How an interferometer device, such as a device, is selected, e.g.
For example, F of the embodiment shown in FIGS. ₂About 157.62 of laser
Example of how to adjust the primary emission line of nm to narrow the line width
It is shown. FIG.₂About 15 of laser
The spontaneous emission spectrum of the primary emission line of 7.62 nm is shown as an example.
You. The transmission (or reflection) of the interferometer is shown in Fig. 4 (b).
As shown, it is a periodic function of wavelength. 4 (b)
The solid line indicates the first tuning setting (tuning configura) of the device.
) and the dashed line indicates the second tuning setting of the device.
are doing. The interferometer device is piezo-ellectrically
Or otherwise adjust the geometric gap spacing.
The angle of incidence of the beam on the reflective surface of the instrument
Adjustment and / or gap between the plates.
Adjust the pressure or other parameters in the
Tuning by adjusting the refractive index of the gas between the rates
Be tuned. One way to change the pressure is to use a needle valve
The nitrogen purge gas shown in FIG.
This is to control the inhalation and discharge of gas. For example,
By closing the force valve 54 and / or opening the inlet valve 52
Increase power and vice versa. Mentioned above
As shown, the interferometer device 48 of FIG.
Fixed pressure controlled separately from the pressure in the module 50
May be placed inside an existing envelope.

The width of each transmission peak is approximately the free spectral range of the interferometer device divided by its finesse,
This finesse is limited by the quality of the optical surface,
To minimize the width of the transmission peak, it is preferable to reduce the free spectral range as much as possible. The minimum free spectral range is determined by the specification that the peaks adjacent to the central peak generate almost no oscillation. FIG.
Since the approximate natural bandwidth of the emission peak illustrated in (a) is approximately 0.5 pm to 1.0 pm, the preferred optimal free spectral range is any range on the order of 1.0 pm. The solid lines shown in FIGS. 4 (b) and 4 (c) illustrate a preferred spectral alignment, where FIG.
(C) shows a single peak with a reduced line width. FIG.
The dashed lines in (b) and FIG. 4 (c) illustrate the undesirable spectral alignment, where the transmission spectrum of the interferometer device deviates from the optimum shown by the solid lines in FIGS. 4 (b)-(c). This is because two peaks, including the occurrence of the second peak in the laser output during the operation, are indicated by broken lines in FIG.

In an embodiment of the present application and with reference to FIG. 3, the interferometer device 48 is an etalon or the device 4
8 includes a non-parallel internal reflection plate. Also, the interferometer device 48 may alternatively be located on the other side of the chamber 2, i.e., on the output coupling side, and may be configured in a transmission mode, such as the configuration of the device 48 shown in FIG. . Also, the device 48 may be set in a reflective mode and may be arranged as a highly reflective or partially reflective (ie, output coupled) resonant reflector.

If the device 48 is constructed with non-parallel plates, the plates are preferably 09/715,
According to the disclosure in the '803 patent application, the gap spacing varies along the geometric extent of the plate. Because the beam passes through the dispersive element (s), such as the prism 46 of FIG. 3, the beam incident on the interferometer device is either geometrically arranged according to the wavelength in the beam or the beam profile Made to be placed along a cross section.

The gap spacing at the center of the plate of device 48 is determined by constructive interference of selected wavelengths.
It is like providing a nterference). Second, at off-center geometries at wavelengths representing sidebands when a normal etalon is used, the gap spacing is such as to provide destructive interference at that wavelength. Therefore, sidebands are thereby suppressed.

According to this embodiment, the FSR of the device 48 is such as to narrow the selected peak, with the sideband being transmitted (or reflected) if a normal etalon is used. ). Advantageously, without sidebands, a narrower peak is transmitted (or reflected) by device 48 than a normal etalon can transmit. As discussed above, it would be advantageous to have a molecular fluorine laser that emits a narrower bandwidth beam. (Wavelength and Bandwidth Monitoring Device) As understood from the above discussion, it is desirable to carefully control the center wavelength selected by the interferometer device 48 of FIG. 3 while suppressing sidebands. The wavelength / bandwidth monitor shown in FIG. 5 is advantageously used to monitor the spectral distribution of the beam emitted by a molecular fluorine laser, including selected and narrowed spectral emission lines. In this way, the transmission (or reflection) spectrum of the interferometer device 48 is not based on the information obtained by the wavelength monitoring device of FIG. It is controlled so as to be like the spectrum of the solid line.

FIG. 5 schematically illustrates a preferred design of a wavelength monitoring device for use in a molecular fluorine laser system, particularly one having an intracavity interferometer device, such as device 48 of FIG. A small portion of the output laser beam 13, which is coupled out by the output coupler 4 of the resonator including the discharge chamber 2 with the electrodes 3 as described above, is separated by a beam splitter 14 and by a mirror 16
It is directed to a spectrometer device 18, which is preferably a monitor etalon device. The wavelength monitoring device is preferably
Enclosure 22 for sealing the beam path from the resonator
Since the bellows 5 are used in this case, the atmosphere inside the enclosure 22 is purged, or the enclosure 22 is evacuated, so that photoabsorbing species enter the beam path. Is prevented.

The separated portion of the beam is preferably placed on the negative lens 1 before entering the monitoring etalon device 18.
7 is magnified. Alternatively, a light diffuser plate could be used instead of a negative lens, but in this case the intensity of light on the detector 20 may be significantly reduced. Alternatively, a beam expander may be used; in another embodiment, the beam is directly incident on the monitoring etalon device 18 without expansion. A positive lens 19 is disposed after the etalon 18 and forms an interference pattern on a linear diode array 20 disposed in the focal plane of the lens 19. The output 21 of the detector 20 is directed to a data acquisition device, which
Processor 116, as described in further detail below with respect to FIG.

The entire wavelength monitor is preferably purged with an inert gas, such as high purity nitrogen or other inert gas that does not absorb 157 nm, or is enclosed in an evacuated box 22 and contains a purge gas. It is desirable to avoid instability in the free range of the monitoring etalon device 18 due to fluctuations in the pressure of the etalon. Monitoring etalon device 1
8 may be located in a small enclosure 23, preferably evacuated or alternatively filled with an inert gas having a precisely controlled pressure. Such an enclosure 23 should have an optical window (not shown). In another embodiment, the entire box 22 is evacuated.

The spectral bandwidth and center wavelength information is preferably provided in a standard manner as understood from US Pat. No. 4,905,243 or other standard as understood by those skilled in the art. It is extracted from the interference pattern observed on the detector 20 in a manner. For example, KrF or Ar
In monitoring the wavelength of the F-laser, any method as understood by those skilled in the art may be used. (Closed Loop Control of Wavelength and / or Bandwidth) FIG. 6 schematically shows a closed cycle control loop.
Is exemplified. The output spectrum of the laser 30 is detected by the wavelength monitor 32. Data 33 is input to the central processing unit 34. This unit 34 determines whether the center wavelength and the "side-peak" are present. Based on these criteria, the pressure of the purge gas in the line narrowing module 31 is adjusted to increase or decrease through the control signal 35. Alternatively, the interferometer device 48 may be tuned as described above. This control loop is
, And acts to minimize the energy content of any sideband.

While illustrative drawings and specific embodiments of the present invention have been described and illustrated, it will be understood that the scope of the invention is not to be limited to the specific embodiments discussed herein. That is, the embodiments are to be considered illustrative rather than restrictive, and depart from the scope of the invention as set forth in the appended claims and equivalents by those skilled in the art. It should be understood that modifications may be made in these embodiments without departing from the invention.

Further, the method claims (me
In a thod claim, the steps are given in a selected order, but this is for printing convenience only and does not imply any particular order for performing the steps. That is, the steps may be performed in a wide variety of orders within the scope of these claims, unless a particular order is explicitly indicated or understood by one of ordinary skill in the art to be necessary. For example, in some method claims of the claims, the step of selecting one of the plurality of bright lines and narrowing the selected bright line includes the step of causing the beam to be narrow and / or a bright line selection element. , And out of the laser resonator.

[Brief description of the drawings]

FIG. 1 is a diagram showing an emission spectrum of an F ₂ laser without bright line selection or line narrowing.

2 is a diagram showing an outline of a F ₂ laser system according to a preferred embodiment.

3 is a diagram showing an outline of the cavity of the preferred embodiment line narrowing has been F ₂ laser according to Example.

4 (a) is a diagram illustrating the free-running spectrum of the emitted emission lines that are selected in the F ₂ laser. (B) is a figure which illustrates the transmission spectrum of an interferometer apparatus like an etalon in two tuning states of an interferometer apparatus. (C)
It generates a free-running emission lines of FIG. 4 (a), a diagram illustrating the output emission spectra of F ₂ laser including a cavity interferometer arrangement having a transmission spectrum shown in Figure 4 (b).

5 is a diagram illustrating an outline of a wavelength monitoring device F ₂ laser system according to a preferred embodiment.

6 is a diagram illustrating a closed loop wavelength control of F ₂ laser system according to a preferred embodiment.

[Description of sign]

 Reference Signs List 102 laser chamber 103 main discharge electrode 104 discharge circuit (solid pulser module) 106 gas processing module 108 high voltage power supply 110 rear optical module 112 front optical module 114 optical device control module 116 processor (Control computer) 118 ... Diagnostic module 120 ... Main laser beam 122 ... Beam splitter module 124 ... Interface 126 ... Stepper / scanner computer 128 ... Control unit

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Sergey V. Govolkov, United States, 33433, Boca Raton, Lacosta Drive 6315 Nambaem (72) Inventor Jurgen Kleinschmidt, Germany Weissenfels 06667, Rosa-Luxembourg Straße 18 (72) Inventor Peter Lokay, Germany Göttingen 37085 , Merkelstrasse 27 Yacht (72) Inventor Ube Stam Göttingen 37085, Germany, Heinholzbeek 29 F-term (reference) 5F071 AA06 HH02 HH07 JJ02 JJ05 5F072 AA06 HH02 JJ02 JJ05 KK06 KK08 MM08 RR05Y08

Claims (78)

[Claims] 1. An F ₂ laser for producing a spectral emission comprising a plurality of closely spaced emission lines in a wavelength range between 157 nm and 158 nm including a primary emission line and a secondary emission line. A discharge chamber filled with a gas mixture comprising: a plurality of electrodes coupled to a power supply circuit for generating a pulsed discharge for applying a voltage to the molecular fluorine; and generating a laser beam having a bandwidth of less than 1 pm. The transmission chamber, a transmission interferometer device,
A resonator comprising: a pair of resonant reflectors, wherein the interferometer device selects a portion of the primary emission line so as to substantially suppress the secondary emission line and a non-selected portion of the primary emission line. It is composed of the transmittance to maximize the secondary emission line transmittance of the non-selected portion of the primary emission lines to relatively low, providing the F ₂ laser, a narrow-band VUV laser beam thereby to a resonator for selecting and line narrowing the primary emission line to emit a single wavelength laser beam having a narrow spectral bandwidth than the bandwidth of the primary emission lines of the free-running F ₂ laser It comprises a _{F 2} laser. 2. The system of claim 1, wherein the resonator further includes a beam expander in front of the transmission interferometer to expand the beam and reduce divergence of the beam before entering the interferometer. Item 2. The laser according to Item 1. 3. The transmission interferometer device and the beam expander are located in a rear optical module of the resonator on the side of the discharge chamber opposite the side where the beam is outcoupled from the resonator. 3. The laser of claim 2, wherein said laser is applied. 4. The atmosphere in the rear optical module,
The material path is maintained substantially free of light absorbing about 157 nm, and the beam path between the rear optical module and the discharge chamber maintains the beam path substantially free of the material light absorbing about 157 nm. 4. The laser of claim 3, wherein the laser is sealed from ambient air. 5. The transmission interferometer apparatus of claim 1, wherein the transmission interferometer device is disposed in a rear optical module of the resonator on a side of the discharge chamber opposite the side from which the beam is coupled out. The laser as described. 6. The atmosphere in the rear optical module,
The material path is maintained substantially free of light absorbing about 157 nm, and the beam path between the rear optical module and the discharge chamber maintains the beam path substantially free of the material light absorbing about 157 nm. 6. The laser of claim 5, wherein the laser is sealed from ambient air. 7. The rear optical module is purged with the inert gas having a pressure controlled to control a refractive index of the inert gas to control an interference spectrum of the interferometer device. Item 7. A laser according to item 6. 8. The laser of claim 1, further comprising an amplifier for enhancing the energy of said laser beam. 9. The laser of claim 1, wherein one of said pair of resonant reflectors also seals said discharge chamber. 10. The method of claim 1, wherein a lens seals the discharge chamber as a window on the discharge chamber that transmits light exiting the discharge chamber and traveling along the light beam path toward the interferometer device. The laser as described. 11. The laser of claim 1, wherein said interferometer device comprises an etalon. 12. The interferometer device includes a pair of counter-reflective surfaces, wherein the first and second counter-reflective surfaces of the pair of counter-reflective surfaces are configured to reduce the primary purity to reduce spectral purity. The at least first counter-reflective surface is configured to have an optical distance that varies from one another over the incident beam cross-section, which serves to suppress outer portions of the emission lines.
A laser according to claim 1. 13. An F ₂ laser, comprising molecular fluorine that produces a spectral emission that includes a plurality of closely spaced emission lines in a wavelength range between 157 nm and 158 nm, including a primary emission line and a secondary emission line. A discharge chamber filled with a gas mixture; a plurality of electrodes coupled to a power supply circuit for generating a pulsed discharge for applying a voltage to the molecular fluorine; and for generating a laser beam having a bandwidth of less than 1 pm. The discharge chamber, the transmission interferometer device,
A resonator including a pair of resonant reflectors, wherein the interferometer device maximizes the transmittance of the primary emission line and compares the transmittance of the secondary emission line to substantially suppress the secondary emission line. is configured to target low, the F ₂ laser by it, narrowband VUV to provide a laser beam, a single-wavelength laser beam having a narrow spectral bandwidth than the bandwidth of the free-running F ₂ laser F ₂ laser and a resonator for selecting said primary emission lines to release. 14. The resonator further comprises a beam expander in front of the transmission interferometer device for expanding the beam and reducing divergence of the beam before entering the interferometer device. A laser according to claim 13. 15. The transmission interferometer device and the beam expander are located in the rear optical module of the resonator on the side of the discharge chamber opposite the side where the beam is coupled out of the resonator. 15. The laser of claim 14, wherein said laser is applied. 16. The atmosphere within the rear optical module is maintained substantially free of materials that absorb about 157 nm, and the beam path between the rear optical module and the discharge chamber is approximately about 157 nm. 16. The laser of claim 15, wherein the laser is sealed from ambient air to keep the material that absorbs 157 nm substantially free of light. 17. The apparatus of claim 13, wherein the transmission interferometer device is disposed in a rear optical module of the resonator on a side of the discharge chamber opposite the side at which the beam is outcoupled from the resonator. The laser as described. 18. The atmosphere in the rear optical module is maintained substantially free of materials that absorb about 157 nm, and the beam path between the rear optical module and the discharge chamber is approximately about 157 nm. 18. The laser of claim 17, wherein the laser is sealed from ambient air to keep the material that absorbs 157 nm substantially free of light. 19. The rear optical module is purged with an inert gas having a pressure controlled to control a refractive index of the inert gas to control an interference spectrum of the interferometer device. Item 19. The laser according to Item 18. 20. The laser of claim 13, further comprising an amplifier for enhancing the energy of the laser beam. 21. The laser of claim 13, wherein one of said pair of resonant reflectors also seals said discharge chamber. 22. The method according to claim 13, wherein a lens seals the discharge chamber as a window on the discharge chamber that transmits light exiting the discharge chamber along the light beam path toward the interferometer device. The laser as described. 23. The laser of claim 13, wherein the gas mixture is maintained at a pressure less than about 2 bar, such that the spectral bandwidth is narrower than if the gas mixture were maintained at a pressure of more than 2 bar. . 24. The gas mixture according to claim 19, wherein the spectral bandwidth is narrower than when the gas mixture is maintained at a pressure greater than 1.5 bar.
14. The laser of claim 13, wherein the laser is maintained at a lower pressure. 25. The laser of claim 13, wherein the gas mixture is maintained at a pressure of less than about 1 bar, such that the spectral bandwidth is narrower than if the gas mixture was maintained at a pressure of more than 1 bar. . 26. The laser of claim 13, wherein said interferometer device comprises an etalon. 27. The interferometer device includes a pair of counter-reflective surfaces, wherein the first and second of the pair of counter-reflective surfaces.
At least said first counter-reflective surface such that said counter-reflective surface has an optical distance varying from one another across the incident beam cross-section, serving to suppress outer portions of said first bright line to reduce spectral purity. 14. The laser according to claim 13, wherein 28. An F ₂ laser, comprising molecular fluorine that produces a spectral emission that includes a plurality of closely spaced emission lines in a wavelength range between 157 nm and 158 nm, including a primary emission line and a secondary emission line. A discharge chamber filled with a gas mixture; a plurality of electrodes coupled to a power supply circuit for generating a pulsed discharge for applying a voltage to the molecular fluorine; and for generating a laser beam having a bandwidth of less than 1 pm. A resonator including the discharge chamber, a transmission interferometer device, a dispersive optical device, and a pair of resonant reflectors, wherein the dispersive optical device is configured such that only the primary emission line has the resonance. The plurality of tight spacings, including the primary and secondary emission lines, such that any other emission lines, including the secondary emission lines, remain within the acceptance angle of the cavity and are dispersed outside the acceptance angle of the resonator. Min the emission line And the interferometer device maximizes the transmittance of a selected portion of the primary emission line to substantially suppress a non-selected portion of the primary emission line. is configured to relatively low permeability of the non-selected part of the next bright lines, the distributed optical devices and the interferometer apparatus is the F ₂ laser by it,
Free-running F to provide a narrow band VUV laser beam
F ₂ laser having a, a resonator for selecting and line narrowing the primary emission line to emit a single wavelength laser beam having a narrow spectral bandwidth than the bandwidth of the primary emission line ₂ laser . 29. The resonator further comprises a beam expander in front of the transmission interferometer device for expanding the beam before entering the interferometer device and reducing the divergence of the beam. A laser according to claim 28. 30. The transmission interferometer device and the beam expander are located in the rear optical module of the resonator on the side of the discharge chamber opposite the side where the beam is outcoupled from the resonator. 30. The laser according to claim 29, wherein 31. The atmosphere in the rear optical module is maintained substantially free of material that absorbs light of about 157 nm, and the beam path between the rear optical module and the discharge chamber has a beam path of about 157 nm. 31. The laser of claim 30, wherein the laser is sealed from ambient air to keep the material substantially free of light absorbing. 32. The transmission interferometer of claim 28, wherein the transmission interferometer device is located in a rear optical module of the resonator on a side of the discharge chamber opposite the side at which the beam is outcoupled from the resonator. The laser as described. 33. The atmosphere in the rear optical module is maintained substantially free of materials that absorb about 157 nm, and the beam path between the rear optical module and the discharge chamber is approximately 33. The laser of claim 32, wherein the laser is sealed from ambient air to keep the material that absorbs 157 nm substantially free. 34. The rear optics module is purged with an inert gas having a pressure controlled to control a refractive index of the inert gas to control an interferometer spectrum of the interferometer device. A laser according to claim 33. 35. The laser of claim 28, further comprising an amplifier that boosts the energy of the laser beam. 36. The laser of claim 28, wherein one of said pair of resonant reflectors also seals said discharge chamber. 37. A lens as in claim 28, wherein a lens seals the discharge chamber as a window on the discharge chamber that transmits light exiting the discharge chamber along the light beam path toward the interferometer device. The laser as described. 38. The laser of claim 28, wherein said interferometer device comprises an etalon. 39. The interferometer device includes a pair of counter-reflective surfaces, wherein the first and second counter-reflective surfaces of the pair of counter-reflective surfaces are configured to reduce the spectral purity of the primary emission line. 29. The laser of claim 28, wherein at least the first counter-reflective surface is configured to have an optical distance that varies from one another across the incident beam cross-section, which serves to suppress outer portions. 40. An F ₂ laser, comprising molecular fluorine that produces a spectral emission that includes a plurality of closely spaced emission lines in a wavelength range between 157 nm and 158 nm that includes a primary emission line and a secondary emission line. A discharge chamber filled with a gas mixture; a plurality of electrodes coupled to a power supply circuit for generating a pulsed discharge for applying a voltage to the molecular fluorine; and for generating a laser beam having a bandwidth of less than 1 pm. A resonator including the discharge chamber and an interferometer device, wherein the interferometer device deselects the secondary emission line and the primary emission line compared to a selected portion of the primary emission line. to substantially suppress section, the constructed a secondary emission lines and the unselected portions of the primary emission lines to relatively suppress, providing the F ₂ laser, a narrow-band VUV laser beam thereby Because the, the free-running _{F 2} laser 1
Selecting and narrowing the primary emission line to emit a single wavelength laser beam having a spectral bandwidth narrower than the bandwidth of the secondary emission line, wherein the resonator further enters the interferometer device F ₂ laser having a, a resonator including a front of the beam expander of the interferometer device to expand the beam prior to reduce the divergence of the beam. 41. The interferometer device is disposed in an optical module that is maintained substantially free of materials that absorb about 157 nm, and wherein a beam path between the optical module and the discharge chamber includes the beam path. 41. The laser of claim 40, wherein the laser is sealed from ambient air to keep the path substantially free of the material that absorbs about 157 nm. 42. The optical module is purged with the inert gas having a pressure controlled to control a refractive index of the inert gas to control an interference spectrum of the interferometer device. 42. The laser according to 41. 43. The laser according to claim 40, further comprising an amplifier for enhancing the energy of the laser beam. 44. The interferometer device includes a pair of counter-reflective surfaces, wherein the first and second counter-reflective surfaces of the pair of counter-reflective surfaces are configured to reduce the spectral purity.
41. The laser of claim 40, wherein at least the first counter-reflective surface is configured to have an optical distance that varies from one another across the incident beam cross-section, which serves to suppress outer portions of the emission line. 45. An F ₂ laser, comprising molecular fluorine that produces a spectral emission that includes a plurality of closely spaced emission lines in a wavelength range between 157 nm and 158 nm that includes a primary emission line and a secondary emission line. A discharge chamber filled with a gas mixture; a plurality of electrodes coupled to a power supply circuit for generating a pulsed discharge for applying a voltage to the molecular fluorine; and for generating a laser beam having a bandwidth of less than 1 pm. A resonator including the discharge chamber and an interferometer device, wherein the interferometer device relatively disperses the secondary emission line in order to substantially suppress the secondary emission line compared to the primary emission line. configured to suppress, whereby the F ₂ laser, in order to provide a narrow-band VUV laser beam, single wavelength les having a narrow spectral bandwidth than the bandwidth of the free-running F ₂ laser The primary emission line to emit a laser beam, wherein the resonator further increases the beam before entering the interferometer device to reduce the divergence of the beam. F ₂ laser having a, a resonator including a front of the beam expander of the total device. 46. The laser of claim 45, wherein the gas mixture is maintained at a pressure less than approximately 2 bar, such that the spectral bandwidth is narrower than if the gas mixture was maintained at a pressure greater than 2 bar. . 47. The method according to claim 47, wherein the gas mixture is approximately 1.5 bar so that the spectral bandwidth is narrower than if the gas mixture were maintained at a pressure greater than 1.5 bar.
46. The laser of claim 45, wherein the laser is maintained at a lower pressure. 48. The laser of claim 45, wherein the gas mixture is maintained at a pressure of less than about 1 bar, such that the spectral bandwidth is narrower than if the gas mixture were maintained at a pressure of more than 1 bar. . 49. The interferometer device is disposed in an optical module that is maintained substantially free of materials that absorb about 157 nm, and wherein a beam path between the optical module and the discharge chamber includes the beam path. Route about 157nm
46. The laser of claim 45, wherein the laser is sealed from ambient air to keep the material light absorbing. 50. The optical module is purged with an inert gas having a pressure controlled to control a refractive index of the inert gas to control an interference spectrum of the interferometer device. 49. The laser according to 49. 51. The laser of claim 45, further comprising an amplifier that enhances the energy of the laser beam. 52. The interferometer device includes a pair of counter-reflective surfaces, wherein the first and second counter-reflective surfaces of the pair of counter-reflective surfaces are outside of the first bright line to reduce spectral purity. 46. The laser of claim 45, wherein at least the first counter-reflective surface is configured to have an optical distance varying from one another across an incident beam cross-section that serves to suppress portions. 53. An F ₂ laser, comprising molecular fluorine that produces a spectral emission that includes a plurality of closely spaced emission lines in a wavelength range between 157 nm and 158 nm that includes a primary emission line and a secondary emission line. A discharge chamber filled with a gas mixture; a plurality of electrodes coupled to a power supply circuit for generating a pulsed discharge for applying a voltage to the molecular fluorine; and for generating a laser beam having a bandwidth of less than 1 pm. A resonator including the discharge chamber, the interferometer device, and the dispersive optical device, wherein the dispersive optical device is such that only the primary emission line remains within the light receiving angle of the resonator, The primary and secondary emission lines are dispersed so that any other emission line including the next emission line is dispersed outside the acceptance angle of the resonator.
Arranged in a specific direction to disperse the plurality of closely spaced emission lines including the secondary emission line, wherein the interferometer device substantially suppresses a non-selected portion of the primary emission line,
The non-selected portion of the primary emission lines are configured to relatively suppress the F ₂ laser the dispersive optical device and said interferometer device by it, in order to provide a narrow-band VUV laser beam, free-running F ₂ laser the primary emission line selection and line narrowing the primary emission line to emit a single wavelength laser beam having a narrow spectral bandwidth than the bandwidth of the, whereby the resonator is further , F ₂ laser having a, a resonator including a front of the beam expander of the interferometer device to reduce the divergence of the beam to expand the beam prior to entering the interferometer. 54. The interferometer device is maintained substantially free of material that absorbs about 157 nm, and the beam path between the optical module and the discharge chamber has a beam path that absorbs about 157 nm. 54. The laser of claim 53, wherein the laser is sealed from ambient air to keep the material substantially free of. 55. The optical module is purged with an inert gas having a pressure controlled to control a refractive index of the inert gas to control an interference spectrum of the interferometer device. 54. The laser according to 54. 56. The laser of claim 53, further comprising an amplifier that enhances the energy of the laser beam. 57. The interferometer device includes a pair of counter-reflective surfaces, wherein the first and second counter-reflective surfaces of the pair of counter-reflective surfaces are configured to reduce the spectral purity of the primary emission line. 54. The laser of claim 53, wherein at least the first counter-reflective surface is configured to have an optical distance varying from one another across an incident beam cross-section that serves to suppress outer portions. 58. An F ₂ laser, comprising molecular fluorine that produces a spectral emission that includes a plurality of closely spaced emission lines in a wavelength range between 157 nm and 158 nm, including a primary emission line and a secondary emission line. A discharge chamber filled with a gas mixture; a plurality of electrodes coupled to a power supply circuit for generating a pulsed discharge for applying a voltage to the molecular fluorine; and for generating a laser beam having a bandwidth of less than 1 pm. A resonator including the discharge chamber and an interferometer device, wherein the interferometer device deselects the secondary emission line and the primary emission line compared to a selected portion of the primary emission line. It is configured and the secondary emission lines and the unselected portions of the primary emission lines in order to substantially suppress a part to relatively suppress, providing the F ₂ laser, a narrow-band VUV laser beam thereby Because the, the free-running _{F 2} laser 1
A resonator for selecting and narrowing the primary emission line to emit a single wavelength laser beam having a spectral bandwidth narrower than a bandwidth of the secondary emission line; and a resonator coupled to a processor in a feedback loop, A wavelength monitoring device for monitoring a spectral distribution of a laser beam, wherein the processor determines the spectral distribution based on the monitored spectral distribution such that sidebands in the spectral distribution are substantially minimized. A wavelength monitoring device for controlling an interference spectrum of the interferometer device.
₂ lasers. 59. The wavelength monitoring device is disposed in a jacket that is maintained substantially free of materials that absorb about 157 nm, wherein a beam path between the jacket and the resonator is:
59. The laser of claim 58, wherein the laser is sealed from ambient air to maintain the beam path substantially free of the material that absorbs about 157 nm. 60. The laser of claim 58, wherein said bandwidth monitoring device includes a monitoring etalon device located within a jacket maintained by an atmosphere having a substantially constant refractive index. 61. The laser according to claim 60, wherein the envelope is evacuated. 62. The laser of claim 60, wherein the envelope is purged with an inert gas having a controlled pressure at a substantially constant pressure. 63. The wavelength monitoring device is disposed in a monitoring etalon device, a beam expanding optical device in front of the monitoring etalon device, an imaging optical device after the monitoring etalon device, and a focal plane of the imaging optical device. 59. The laser of claim 58, comprising: an array detector configured. 64. The laser of claim 58, wherein said wavelength monitoring device includes an optical device for filtering red light from said spectral distribution. 65. An F ₂ laser, comprising molecular fluorine that produces a spectral emission including a plurality of closely spaced emission lines in a wavelength range between 157 nm and 158 nm including a primary emission line and a secondary emission line. A discharge chamber filled with a gas mixture; a plurality of electrodes coupled to a power supply circuit for generating a pulsed discharge for applying a voltage to the molecular fluorine; and for generating a laser beam having a bandwidth of less than 1 pm. A resonator including the discharge chamber and an interferometer device, wherein the interferometer device relatively disperses the secondary emission line in order to substantially suppress the secondary emission line compared to the primary emission line. configured to suppress, whereby the F ₂ laser, in order to provide a narrow-band VUV laser beam, single wavelength les having a narrow spectral bandwidth than the bandwidth of the free-running F ₂ laser A resonator for selecting the primary emission line to emit a laser beam; and a wavelength monitoring device coupled to the processor in a feedback loop for monitoring a spectral distribution of the laser beam, wherein the wavelength monitoring device includes: A processor for controlling an interference spectrum of the interferometer device based on the monitored spectral distribution such that a sideband in the spectral distribution is substantially minimized.
₂ lasers. 66. The wavelength monitoring device is located in a jacket that is maintained substantially free of materials that absorb about 157 nm, and wherein a beam path between the jacket and the resonator is the beam path. 66. The laser of claim 65, wherein the laser is sealed from ambient air to maintain the path substantially free of the material that absorbs about 157 nm. 67. The laser of claim 65, wherein said bandwidth monitoring device comprises a monitoring etalon device located within a jacket maintained in an atmosphere having a substantially constant refractive index. 68. The laser of claim 67, wherein said envelope is evacuated. 69. The envelope is purged with an inert gas having a controlled pressure at a substantially constant pressure.
A laser according to claim 1. 70. The wavelength monitoring device includes a monitoring etalon device, a beam expanding optical device in front of the monitoring etalon device, an imaging optical device after the monitoring etalon device, and a focal plane of the imaging optical device. 65. The laser of claim 65, comprising: an array detector configured. 71. The laser of claim 65, wherein said wavelength monitoring device includes an optical device for filtering red light from said spectral distribution. 72. An F ₂ laser, comprising molecular fluorine that produces a spectral emission that includes a plurality of closely spaced emission lines in a wavelength range between 157 nm and 158 nm, including a primary emission line and a secondary emission line. A discharge chamber filled with a gas mixture; a plurality of electrodes coupled to a power supply circuit for generating a pulsed discharge for applying a voltage to the molecular fluorine; and for generating a laser beam having a bandwidth of less than 1 pm. A discharge chamber, an interferometer device, and a resonator including a dispersive optical device, wherein the dispersive optical device is such that only the primary emission line is within a light receiving angle of the resonator,
A particular direction to distribute the plurality of closely spaced emission lines, including the primary and secondary emission lines, such that any other emission lines, including the secondary emission lines, are distributed outside the acceptance angle of the resonator. Wherein the interferometer device is configured to relatively suppress the non-selected portion of the primary emission line so as to substantially suppress the non-selected portion of the primary emission line; the F ₂ laser device and the interferometer device by it, narrowband VUV to provide a laser beam, single wavelength having a narrow spectral bandwidth than the bandwidth of the primary emission lines of the free-running F ₂ laser laser·
A resonator for selecting and narrowing the primary emission line to emit a beam, and a wavelength monitoring device coupled to a processor in a feedback loop for monitoring the spectral distribution of the laser beam, A wavelength monitoring device that controls the interference spectrum of the interferometer device based on the monitored spectral distribution such that sidebands in the spectral distribution are substantially minimized. F
₂ lasers. 73. The wavelength monitoring device is located in a jacket maintained substantially free of material that absorbs about 157 nm, and wherein a beam path between the jacket and the resonator is the beam path. 73. The laser of claim 72, wherein the laser is sealed from ambient air to keep the path substantially free of the material that absorbs about 157 nm. 74. The laser of claim 72, wherein the bandwidth monitoring device includes a monitoring etalon device located within a jacket maintained in an atmosphere having a substantially constant refractive index. 75. The laser according to claim 73, wherein the envelope is evacuated. 76. The envelope is purged with an inert gas having a controlled pressure at a substantially constant pressure.
A laser according to claim 1. 77. The wavelength monitoring device is disposed on a monitoring etalon device, a beam expanding optical device in front of the monitoring etalon device, an imaging optical device after the monitoring etalon device, and a focal plane of the imaging optical device. 73. The laser of claim 72, comprising: an array detector configured. 78. The laser of claim 72, wherein said wavelength monitoring device includes an optical device for filtering red light from said spectral distribution.