JP2001352116A - Laser device, aligner using the same, and exposing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized UV(ultra-violet) laser device which can generate stably UV rays having both sufficient output and low coherency as a light source of an aligner or the like, and is easy of maintenance, and the aligner. SOLUTION: A laser light generating part has a single wavelength oscillation laser, an optical modulator and a time division light branching means; and branches and outputs the optically modulated pulse light into each channel in order every single pulse. The optical amplifier has fiber optical amplifiers and amplifies and outputs each channel branched laser light. An output end of the optical amplifier is constituted by tying up fiber ends in a bundle having a desired number of fibers and a shape. The bundle output is subjected to wavelength conversion by a wavelength converting part provided with a cooler for cooling at least a part at -40 deg.C or lower, and an UV laser light having a desired wavelength is obtained. When the fiber bundle is set as one bundle, its output end diameter is at most 2 mm, and the wavelength converting part can be constituted by using a pair of nonlinear optical crystals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device, and more particularly to a semiconductor device, a liquid crystal display device, and an image pickup device (CCD).
And low-coherence UV light that can suppress the generation of speckles, like light sources for exposure equipment used in photolithography processes that manufacture micro devices such as thin-film magnetic heads. The present invention relates to a simple laser device and an exposure device using such a laser device.

[0002]

2. Description of the Related Art Along with advances in information equipment, semiconductor integrated circuits are required to have enhanced functions, an improved storage capacity, a reduced size, and the like. In order to increase the degree of integration, it is only necessary to reduce the size of each circuit pattern. However, the minimum pattern size of a circuit is generally determined by the performance of an exposure apparatus used in a manufacturing process.

An exposure apparatus using optical lithography optically reduces and projects a circuit pattern precisely drawn on a photomask onto a semiconductor wafer coated with a photoresist and transfers the circuit pattern. The minimum pattern dimension (resolution) R on the wafer at the time of exposure is expressed by the following equation (1) according to the wavelength λ of the light source used for projection by the exposure apparatus and the numerical aperture NA of the projection optical system. It is represented by the following equation (2).

R = K ・ λ / NA (1) DF = λ / 2 (NA) ² (2) As is clear from the above equation (1), the minimum pattern dimension R It can be seen that there are three directions for reducing the constant K: a direction to decrease the constant K, a direction to increase the numerical aperture NA, and a direction to decrease the wavelength λ of the light source to be projected.

Here, the constant K is a constant determined by the projection optical system and process, and usually takes a value of about 0.5 to 0.8. The method of reducing the constant K is called super-resolution in a broad sense. Until now, improvements in projection optical systems, modified projections, phase shift mask methods, etc. have been proposed and studied. However, there are disadvantages such as limitations on applicable patterns. On the other hand, the numerical aperture NA can be made smaller as the value of the numerical aperture NA becomes larger from the equation (1).
This also means that the focal depth becomes shallower, as is apparent from equation (2). For this reason, there is a limit in increasing the NA value, and usually about 0.5 to 0.6 is considered appropriate in consideration of both.

Therefore, the simplest and most effective method for reducing the minimum pattern size R is to reduce the wavelength λ of light used for exposure. Here, along with the realization of a shorter wavelength, there are some conditions that must be provided for producing a light source of the exposure apparatus. Hereinafter, these conditions will be described.

First, a light output of several watts is required.
This is necessary to keep the time required for exposure and transfer of the integrated circuit pattern short. Secondly, in the case of ultraviolet light having a wavelength of 300 nm or less, materials that can be used as a lens of an exposure apparatus are limited, and it becomes difficult to correct chromatic aberration. For this reason, the light source needs to be monochromatic, and the line width of the spectrum is required to be 1 pm or less.

Third, the temporal coherence (coherence) increases with the narrowing of the spectral line width. Therefore, if light having a narrow line width is irradiated as it is, an unnecessary interference pattern called speckle occurs. Therefore, in order to suppress the occurrence of speckle, it is necessary to reduce the spatial coherence of the light source.

Many developments have been made for shortening the wavelength of an exposure light source in order to satisfy these conditions and realize high resolution. The direction of shortening the wavelength that has been studied so far is mainly divided into the following two types. One is the development of excimer lasers whose laser oscillation wavelength itself is short, and the other is the development of short-wavelength exposure light sources that utilize the generation of harmonics from infrared or visible light lasers. is there.

[0010] Among them, a KrF excimer laser (wavelength 2
48 nm), and an exposure apparatus using an ArF excimer laser (wavelength: 193 nm) as a light source having a shorter wavelength is currently being developed. However, these excimer lasers are large, have high energy per pulse, and are liable to damage optical components, and use toxic fluorine gas, which makes laser maintenance complicated and expensive. There have been various problems.

As the latter method, there is a method of converting long-wavelength light (infrared light or visible light) into shorter-wavelength ultraviolet light by utilizing the second-order nonlinear optical effect of a nonlinear optical crystal. . For example, "Longitudinally diode pumped continuous
wave 3.5W green laser (LY Liu, M. Oka, W. Wiech
mann and S. Kubota, Optics Letters, vol. 19 (1994), p.
189) "discloses a laser light source for converting the wavelength of light from a semiconductor-excited solid-state laser. In this conventional example,
A method is described in which a 1064 nm laser beam emitted from an Nd: YAG laser is wavelength-converted by using a nonlinear optical crystal to generate a 266 nm light beam of a fourth harmonic. Note that a solid-state laser is a general term for a laser whose laser medium is solid. Therefore, in a broad sense, a semiconductor laser is also included in a solid-state laser.
d: Refers to a solid-state laser excited by light, such as a YAG laser or a ruby laser. Here, too, a distinction is made.

In an example in which a solid-state laser is used as a light source of an exposure apparatus, a laser light generating unit for generating a laser light;
There has been proposed an array laser in which a plurality of laser elements composed of a wavelength converter for converting the wavelength of light from the laser light generator to ultraviolet light are bundled in a matrix. For example, in Japanese Patent Application Laid-Open No. 8-334803, one laser element that generates ultraviolet light by converting light from a laser light generation unit provided with a semiconductor laser by a nonlinear optical crystal provided in a wavelength conversion unit is used. An example of an array laser which is bundled in a matrix form (for example, 10 × 10) and used as one ultraviolet light source is disclosed.

In the array laser configured as described above, by bundling a plurality of independent laser elements, it is possible to keep the optical output of each laser element low and to increase the optical output of the entire apparatus. it can. Therefore, the load on the nonlinear optical element can be reduced. However, on the other hand, since the individual laser elements are independent, when application to an exposure apparatus is considered, it is necessary to match the oscillation spectra of the entire laser element. For example, the oscillation spectrum line width of each laser element is 1p
Even if it is less than m, the difference between the wavelengths of the plurality of laser elements as a whole must not be 3 pm, but must be 1 pm or less in the entire width.

For this purpose, for example, in order to make each laser element autonomously emit a single longitudinal mode of the same wavelength,
It was necessary to adjust the resonator length of each laser element or insert a wavelength selection element into the resonator. However, these methods have problems such as that the adjustment is delicate, and that as the number of constituent laser elements increases, a complicated configuration is required to oscillate the whole at the same wavelength.

On the other hand, an injection seed method is well known as a method for actively converting a plurality of lasers to a single wavelength (for example, Solid-s by Walter Koechner).
tateLaser Engineering, 3rd Edition, Springer Serie
s in Optical Science, Vol.1, Springer-Verlag, ISBN
0-387-53756-2, p246-249). This is because the light from a single laser light source having a narrow oscillation spectrum line width is split into a plurality of laser elements, and this laser light is used as a guided wave to tune the oscillation wavelength of each laser element, and This is a method of narrowing the width. However, this method has a problem that the structure becomes complicated because an optical circuit for branching the seed light to each laser element and a tuning control unit for the oscillation wavelength are required.

Further, such an array laser can significantly reduce the size of the entire device as compared with a conventional excimer laser, but it is still difficult to reduce the output beam system of the entire array to several centimeters or less. there were. In addition, the array laser configured as described above is expensive because a wavelength conversion unit is required for each array, and it is expensive when a part of the laser elements forming the array is misaligned or when the optical element is configured. In order to adjust this laser element in case of damage to
Once the whole array is disassembled and this laser element is taken out,
There was a problem that it was necessary to reassemble the array after adjustment.

[0017]

SUMMARY OF THE INVENTION The present invention relates to the problems of the prior art described above, for example, the problem that arises when an excimer laser is used as an ultraviolet light source of an exposure apparatus. Problems, such as the use of a laser, the complexity of maintenance, and the cost, damage to a nonlinear optical crystal, and space, which can be considered when a harmonic of a solid-state laser such as an Nd: YAG laser is used as an ultraviolet light source of an exposure apparatus. Problems such as speckle generation due to the increase in dynamic coherence, and a tuning mechanism that can be considered when using an array laser in which multiple laser elements that generate ultraviolet light are bundled in a matrix as the ultraviolet light source of the exposure apparatus. This is made in consideration of problems such as the complexity of the structure, the difficulty in reducing the output beam diameter, and the complexity of maintenance.

That is, an object of the present invention is to stably generate a single-wavelength ultraviolet light having a sufficiently narrow band as an ultraviolet light output having a low spatial coherence as a light source of an exposure apparatus. An object of the present invention is to provide a compact and easy-to-handle laser device. Another object of the present invention is to provide a compact and highly flexible exposure apparatus using such a small and easily handled laser device as a light source.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser light generator for generating light of a single wavelength, at least one optical amplifier having a fiber optical amplifier for amplifying the generated laser light, and the optical amplifier. A wavelength conversion unit that converts the wavelength of the light amplified by the nonlinear optical crystal into ultraviolet light, and a cooling device that cools at least a part of the wavelength conversion unit to −40 ° C. or less. Achieved.

More specifically, the laser light generating section is provided with a narrow-band single-wavelength oscillation laser (for example, a DFB semiconductor laser), and this single-wavelength laser light is fed to a fiber optical amplifier (for example, erbium-doped). Amplifying by a fiber optical amplifier, and converting the output light from the fiber amplifier into ultraviolet light (for example, wavelength 193 nm) by a wavelength conversion unit using a nonlinear optical crystal. An object of the present invention is to provide a laser device that generates a single-wavelength ultraviolet light that has a compact configuration and is easy to handle.

In the present invention, the output of a single-wavelength oscillation laser (for example, a DFB semiconductor laser or a fiber laser) is branched by an optical branching unit. The light was split into a plurality of outputs by the light splitting means (for example, a splitter or the like), and thereafter, fibers were provided. By bundling the plurality of fibers, a laser device was formed. As the light branching means, any means may be used as long as the laser light generated by the single frequency laser is branched into a plurality of laser beams in parallel.

Further, by providing a delay means for preventing the light from being overlapped in time, light independent from each other can be obtained. As a suitable means for this purpose, a beam splitter for splitting a plurality of laser beams generated by a single-wavelength laser in parallel is provided, and fibers having different lengths are provided on the emission side of the beam splitter. As a preferable mode of the fibers having different lengths, for example, the length of each fiber is set so that the delay interval between the fibers at the fiber output end becomes substantially constant after the laser light branched in parallel passes through this fiber. It is to provide. In addition, as the optical branching means and the delaying means, a time division multiplexer (TD) for distributing light to respective optical paths at predetermined time intervals may be used.
The use of M) is one aspect of the present invention.

Next, as the plurality of fibers provided on the output side of the optical branching means, a plurality of fiber optical amplifiers (for example, an erbium-doped fiber optical amplifier or an yttrium-doped fiber optical amplifier) are provided, for example, in two stages. Is preferably provided in the amplification stage of the second stage.
Preferably, the fiber optical amplifier is configured using a large mode diameter fiber. By doing so, laser light with higher light intensity can be obtained. It is preferable to bundle a plurality of fiber optical amplifiers amplified by the fiber optical amplifier. It is to be noted that undoped fibers may be appropriately connected to the output terminals of the plurality of fiber optical amplifiers as needed.

The fiber output end is desirably provided by gradually expanding the core diameter of the fiber in a tapered shape toward the output end face. Further, it is preferable to provide a window member that transmits laser light at the fiber output end. With this configuration, the power density (light intensity per unit area) of the laser light at the fiber output end face can be reduced, and therefore, damage to the fiber output end can be suppressed.

According to the present invention, in a plurality of fibers provided on the incident side of the wavelength conversion unit, the output end of the fiber is adjusted to the configuration of the wavelength conversion unit, and an output group in which one or a plurality of fibers are bundled together. Or a plurality of output groups formed by dividing a plurality of fiber output ends into a plurality of groups and bundling each group. The wavelength converter generates harmonics of the fundamental wave using one or more sets of nonlinear optical crystals and outputs ultraviolet light (for example, ultraviolet light having a wavelength of 193 nm).
One set of wavelength converters can be made compact and economical, and multiple sets of wavelength converters can reduce the load per set. Can be realized.

When an optical amplifier is constructed using a plurality of fiber optical amplifiers, the output light from each fiber is monitored in order to suppress the variation in the ultraviolet light output due to the variation in the amplification factor of each fiber amplifier. It is desirable to provide fiber output control means for controlling the excitation intensity of each fiber optical amplifier. In addition, in order to stabilize the light wavelength of the ultraviolet light output at a specific wavelength, it is preferable to provide an oscillation wavelength control means for a single-wavelength oscillation laser using the frequency of a fundamental wave or a harmonic in a wavelength converter.

A light collecting optical element is provided on the incident side of the wavelength converter. The use form of the condensing optical element can be appropriately determined according to the output condition of the optical amplifier. For example, a condensing optical element is provided for each fiber output, and the output of an output group bundled in a bundle A use form such as disposing a light collecting optical element on the entire surface of the end portion is applicable.

By the way, as a configuration for outputting ultraviolet light, for example, a laser light generating section having a wavelength of 1.5 μm is used.
m, and at least one optical amplifier having a fiber optical amplifier for amplifying a fundamental wave having a wavelength of about 1.5 μm is provided as an optical amplifier.
Further, it is composed of a wavelength converter for generating an eighth harmonic of the amplified fundamental wave. With this configuration, it is possible to generate ultraviolet light having an output wavelength near 190 nm. The output light further defines the oscillation wavelength of the laser light generator (for example, 1.544 to 1.522 μm).
m), the wavelength can be 193 nm, which is the same wavelength as the ArF excimer laser.

As a configuration for obtaining the eighth harmonic, the second harmonic and the fourth harmonic of the fundamental wave are generated using the sum frequency generation (SFG) of the nonlinear optical crystal in combination with the wavelength conversion stage. Then, a sixth harmonic of the fundamental wave is generated by sum frequency generation, and the sixth harmonic and the second harmonic are generated by the sum frequency generation to generate an eighth harmonic of the fundamental wave. And the sum frequency generation of the second harmonic of the fundamental wave
A second harmonic of the third harmonic is generated, and a sixth harmonic of the fundamental wave is obtained by generating the second harmonic of the third harmonic. Further, the sixth harmonic and the second harmonic are eight times higher than the fundamental wave by generating the sum frequency. It is configured to generate harmonics. In these configurations, a BBO crystal is used for the generation of the eighth harmonic in the final stage. The BBO crystal is cooled to −40 ° C. or lower by a cooling device, and the absorption intensity near 193 nm is suppressed. 193n of BBO crystal by cooling
It is known that the absorption intensity in the vicinity of m decreases.
160746.

Further, according to an aspect of the laser apparatus of the present invention, an optical modulator for converting light from a light source (for example, a DFB semiconductor laser or the like) generating continuous light into pulsed light is provided.
Alternatively, an ultraviolet pulse laser beam can be obtained by pulsating a single-wavelength oscillation laser.

An illumination optical system which uses the laser device obtained as described above as a light source of a projection exposure apparatus, and further irradiates a mask on which a pattern to be projected is drawn with almost uniform intensity from the light source. And a projection objective optical system for projecting the pattern drawn on the mask onto the wafer, a projection exposure apparatus with easy maintenance can be obtained.

Further, a part of the fiber output amplified by the plurality of fiber optical amplifiers is divided and connected to a second fiber transmission system different from the first fiber transmission system to the illumination optical system of the exposure apparatus. Constructing an alignment system for detecting an alignment mark formed on a mask or a reference mark on a wafer stage is a preferred embodiment of an exposure apparatus using the laser apparatus of the present invention.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION A laser light source according to the present invention amplifies light of a single wavelength from a laser light generator by an optical amplifier, and converts the amplified light into ultraviolet light by a nonlinear optical crystal provided in a wavelength converter. By performing the conversion, it is possible to easily obtain ultraviolet light having a required spectral line width (for example, 1 pm or less) without using a complicated configuration.

Further, the laser light of a single wavelength is divided (or time-divided) into a plurality, the output light is amplified by a plurality of fiber optical amplifiers, and the amplified light is converted into ultraviolet light by a nonlinear optical crystal. With this configuration, it is intended to increase the laser light output of the entire light source while suppressing the peak power per pulse of the pulse light, and to supply ultraviolet light having low spatial coherence of light.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. First, a first embodiment of a laser device according to the present invention will be described with reference to FIG. The ultraviolet light generation device according to the present embodiment includes a laser light generation unit that includes a single wavelength oscillation laser 11 and generates a single wavelength laser light, and fiber optical amplifiers 13 and 1.
8 and 19, an optical amplifier for amplifying the light, optical branching means 14 and 16 for splitting the light into a plurality of parallel lights, fibers 15 and 17 having different lengths, and a non-linear optical crystal described later. And a wavelength converter that converts the wavelength of the converted light into a wavelength. The laser device generates the same output wavelength (193 nm) as the ArF excimer laser and has low spatial coherence.

In this embodiment, FIG. 1 shows an example of the configuration of a laser beam of a single wavelength output from a laser beam generator of a laser device according to the present invention until it is branched and amplified.
First, referring to FIG. 1, the laser light generating section is provided with a single-wavelength oscillation laser 11 for generating a single-wavelength laser light, and further includes splitters 14 and 16 serving as optical branching means. Fibers 15 and 17 of different lengths
And fiber optical amplifiers 18 and 19 are connected to the exit sides of the fibers 17 having different lengths, and a plurality of fiber optical amplifiers 18 and 19 are amplified in parallel.

The output end of the fiber optical amplifier 19 is bundled in a bundle, and the amplified laser light is incident on, for example, a wavelength converter (507 to 517, 550) shown in FIG. The fiber bundle output end 114 of the fiber optical amplifier 19 shown in FIG.
(A) and (b) correspond to the fiber bundle emission end 501 shown in FIG. This wavelength converter includes nonlinear optical crystals 507, 510, 514, 517 and the like, and converts a fundamental wave emitted from the fiber optical amplifier 19 into ultraviolet light. The wavelength converter according to the present invention will be described in detail as Embodiments 4 and 5 later in the embodiment of the present invention.

Hereinafter, the present embodiment will be described in more detail. As the single-wavelength oscillation laser 11 oscillating at a single wavelength shown in FIG. 1, for example, InGaAsP having an oscillation wavelength of 1.544 μm and a continuous wave output (hereinafter referred to as CW output) of 20 mW,
A DFB semiconductor laser is used. Here, a DFB semiconductor laser is a device in which a diffraction grating is formed in a semiconductor laser in place of a Fabry-Perot resonator having low longitudinal mode selectivity. Distributed feedback type (Distributed
Feedback: This is called a DFB laser. Since such a laser basically oscillates in a single longitudinal mode, its oscillation spectrum line width can be suppressed to 0.01 pm or less.

In order to fix the output wavelength of the laser device to a specific wavelength, a single-wavelength oscillation laser (Master Oscill
ator) is preferably provided with an oscillation wavelength control device for controlling the oscillation wavelength to a constant wavelength. Conversely, it is also preferable that the oscillation wavelength of the single-wavelength oscillation laser is positively changed by the oscillation wavelength control device so that its output wavelength can be adjusted. For example, when the laser apparatus of the present invention is applied to an exposure apparatus, according to the former, the occurrence or fluctuation of the aberration of the projection optical system due to wavelength fluctuation is prevented, and the image characteristics (such as image quality) during pattern transfer are prevented. Optical characteristics) do not change.

According to the latter, an altitude difference and a pressure difference between a manufacturing site where the exposure apparatus is assembled and adjusted and a place where the exposure apparatus is installed (delivery destination), and a difference in environment (atmosphere in a clean room), etc. Therefore, fluctuations in the imaging characteristics (such as aberrations) of the projection optical system caused by the deviation can be offset, and the time required for starting up the exposure apparatus at the delivery destination can be reduced. Furthermore, according to the latter, during the operation of the exposure apparatus, the illumination of the exposure illumination light, and aberrations of the projection optical system caused by changes in atmospheric pressure, projection magnification, and fluctuations in the focus position, etc., can be offset, and always The pattern image can be transferred onto the substrate in the best image forming state.

For example, when a DFB semiconductor laser is used as a single-wavelength oscillation laser, such oscillation wavelength control means can be achieved by controlling the temperature of the DFB semiconductor laser. The wavelength can be further stabilized to control the wavelength to be constant, or the output wavelength can be finely adjusted.

Usually, a DFB semiconductor laser or the like is provided on a heat sink, and these are housed in a housing. Therefore, in this example, the oscillation wavelength is adjusted by controlling the temperature using a temperature controller (for example, a Peltier element) provided on a heat sink attached to the single-wavelength oscillation laser (such as a DFB semiconductor laser) 11. Where DFB
In a semiconductor laser or the like, the temperature can be controlled in units of 0.001 ° C.

The oscillation wavelength of the DFB semiconductor laser has a temperature dependency of about 0.1 nm / ° C. For example, DF
When the temperature of the B semiconductor laser is changed by 1 ° C., the fundamental wave (1
544 nm), the wavelength changes by 0.1 nm.
In the eighth harmonic (193 nm), the wavelength is 0.0125 nm.
Will change. In the exposure apparatus, the wavelength of the exposure illumination light (pulse light) is set to ± 20 pm with respect to the center wavelength.
It is enough if the degree can be changed. Therefore, D
What is necessary is just to change the temperature of the FB semiconductor laser 11 by about ± 1.6 ° C.

As the monitor wavelength for feedback control when controlling the oscillation wavelength to a predetermined wavelength,
From the oscillation wavelength of the DFB semiconductor laser or the wavelength conversion output (2nd harmonic, 3rd harmonic, 4th harmonic, etc.) described below, the wavelength that gives the sensitivity necessary for performing the desired wavelength control and is the most easily monitored wavelength select. For example, as a single-wavelength oscillation laser, D with an oscillation wavelength of 1.51 to 1.59 μm
When an FB semiconductor laser is used, the third harmonic of the oscillation laser light has a wavelength of 503 nm to 530 nm, and this wavelength band corresponds to a wavelength range where absorption lines of iodine molecules are densely present. Precise oscillation wavelength control can be performed by selecting an appropriate absorption line of a molecule and locking to that wavelength.

The light output of the semiconductor laser is applied to an optical modulator 1 such as an electro-optical modulator or an acousto-optical modulator.
2 is used to convert CW light (continuous light) into pulsed light.
In the present configuration example, as an example, a case will be described in which the light modulation element 12 modulates pulse light with a pulse width of 1 ns and a repetition frequency of 100 kHz (pulse period of 10 μs). As a result of performing such light modulation, the light modulation element 1
2 has a peak output of 20 mW and an average output of 2 μW. Here, it is assumed that there is no loss due to the insertion of the optical modulation element 12. However, when the insertion loss is present, for example, when the loss is −3 dB, the peak output of the pulse light is 10 mW and the average output is 1 μW.

When an electro-optic modulator is used as the light modulator, an electrode having a chirp-corrected electrode structure such that the wavelength spread of the semiconductor laser output due to the chirp due to the change in refractive index with time is reduced. It is preferable to use an optical modulation element (for example, a two-electrode modulator). Further, by setting the repetition frequency to about 100 kHz or more, it is possible to prevent a decrease in amplification factor due to the influence of ASE (Amplified Spontaneous Emission) noise in a fiber optical amplifier described later. It is desirable that

The pulse light output obtained in this way is connected to an erbium (Er) -doped fiber optical amplifier (EDFA) 13 at the first stage to perform optical amplification of 35 dB (3162 times). At this time, the pulse light has a peak output of about 63
W, the average output is about 6.3 mW.

The output of the fiber amplifier 13 as the first-stage optical amplifier is first divided by a splitter 14 (a flat waveguide 1 × 4 splitter) as an optical branching means into a channel 4 to a channel 4.
Split into parallel outputs. Each output of channels 0 to 3 is
By connecting to fibers 15 having different lengths (only one of the channels 0 is shown in the figure), the light output from each fiber is given a delay corresponding to the fiber length to each output light. For example, in the present embodiment, it is assumed that the propagation speed of light in the fiber is 2 × 10 ⁸ m / s, and that the channels 0, 1, 2, and 3 are 0.1 m and 1 m respectively.
Connect fibers of 9.3m, 38.5m, 57.7m length. In this case, the light delay between adjacent channels at each fiber exit is 96 ns. Here, the fiber used for the purpose of delaying light in this way is called a delay fiber for convenience.

Next, the outputs of the four delay fibers are
The block is further divided into 32 outputs in parallel by 4 blocks of flat waveguide 1 × 32 splitter 16 (channels 0 to 3 in each block).
1) Divide into 128 channels in total. Then, the delay fibers 17 having different lengths are connected again to the channels 1 to 31 except the channel 0 in each block. For example, in this embodiment, channels 1 to 31 each have 0.6
A fiber having a length of × N meters (N is a channel number) is connected. As a result, a delay of 3 ns is given between adjacent channels in each block, and the output of channel 31 is 3 × 31 = 93 with respect to the output of channel 0 of each block.
An ns delay is provided.

On the other hand, a delay of 96 ns is provided between the first to fourth blocks by the delay fiber 15 at the time of input of each block as described above. Therefore, the channel 0 output of the second block has a delay of 96 ns with respect to the channel 0 output of the first block, and the delay with the channel 31 of the first block is 3 ns. This is the same between the second and third blocks and the third and fourth blocks. As a result, a total output of 12
At the output terminals of the eight channels, pulse light having a delay of 3 ns between adjacent channels is obtained. Although only channel 1 of the first block is shown in FIG. 1 and the description of other channels is omitted, other channels have the same configuration.

By the above branching and delay, a pulse light having a delay of 3 ns between adjacent channels can be obtained at the output terminals of a total of 128 channels. At this time, the optical pulse observed at each output terminal is an optical pulse. The same 100 kHz as the pulse modulated by the modulation element 12 (pulse period 10 μm)
s). Therefore, looking at the entire laser beam generator, 9.62 after generating 128 pulses at 3 ns intervals.
The repetition that the next pulse train is generated at intervals of μs is performed at 100 kHz. That is, the total output is 12
8 × 100 × 10 ³ = 1.28 × 10 ⁷ pulses / sec.

In this embodiment, an example has been described in which the number of divisions is set to 128 and a short delay fiber is used. For this reason, 9.62 .mu.
Although an interval where s does not emit light occurs, the number of divisions is increased,
Or by making the delay fiber longer and of the appropriate length, or by using a combination of these
It is also possible to make the pulse intervals completely equal. For example, when the number of pulse repetitions of the laser light incident on the splitter 14 is f [Hz] and the number of divisions is m, the length of each fiber is set so that the delay interval of each fiber is 1 / (f × m). It can also be achieved by setting.

Further, the number of divisions of at least one of the splitters 14 and 16 or the number of pulse repetitions f defined by the light modulating element 12 is adjusted so that the above-mentioned pulse intervals are completely equal, or the division is made. Both the number and the number of repetitions f may be adjusted. Therefore, each fiber length of the delay fibers 15 and 17 and the splitter 1
By adjusting at least one of the number of divisions 4 and 16 and the number of pulse repetitions f, not only pulse intervals can be set at equal intervals, but also the intervals can be set arbitrarily.

In order to change the fiber length after assembling the light sources, for example, the delay fibers 15 and 17 are required.
Are preferably bundled into a unit so that this unit can be replaced with another delay fiber unit having a different delay time between channels. Also, when changing the number of divisions of the splitters 14 and 16, it is preferable to prepare another splitter having a different number of divisions corresponding to each of the splitters 14 and 16 and to replace them. At this time, it is desirable that each unit of the delay fibers 15 and 17 is configured to be exchangeable according to the change in the number of divisions of the splitters 14 and 16.

In this embodiment, the oscillation timing of the light source (pulse light), that is, the repetition frequency f (pulse cycle) can be adjusted by controlling the timing of the drive voltage pulse applied to the light modulation element 12. . Further, when the output of the pulse light can fluctuate with the change of the oscillation timing, the magnitude of the driving voltage pulse applied to the light modulation element 12 is also adjusted at the same time to compensate for the output fluctuation. Good.

In this example, a fiber optical amplifier 18 is connected to each of the 128 delay fibers 17, and a fiber optical amplifier 19 is connected with a narrow band filter 113 interposed therebetween. The narrow band filter 113 is provided with the ASE generated by the fiber optical amplifiers 13 and 18, respectively.
By cutting the light and transmitting the output wavelength of the DFB semiconductor laser 11 (the wavelength width is about 1 pm or less), the wavelength width of the transmitted light is substantially narrowed. As a result, the ASE light is transmitted to the subsequent fiber optical amplifier (18 and 1).
9) to prevent the amplification gain of the laser light from being lowered. Here, the narrow band filter preferably has a transmission wavelength width of about 1 pm.
Since the wavelength width of light is about several tens of nm, the ASE light can be cut to such an extent that there is no practical problem even if a narrow band filter having a transmission wavelength width obtained at this time of about 100 pm is used.

When the output wavelength of the DFB semiconductor laser 11 is positively changed, the narrow band filter may be replaced in accordance with the output wavelength. ± 20p
m) is preferably used. In a laser device applied to an exposure apparatus, the wavelength width is set to about 1 pm or less. In addition, the laser device of FIG. 1 is provided with three isolators 110, 111, and 112, which reduce the influence of return light.

With the above configuration, the output light from the generating section (the output end of the fiber optical amplifier 19) does not overlap with each other in time even though it is an extremely narrow band light. . Therefore, spatial coherence between channel outputs can be reduced.

In the above configuration, an example was described in which a DFB semiconductor laser was used as the single-wavelength oscillation laser 11 and the planar waveguide type splitters 14 and 16 were used as branching elements of the optical branching means. , DFB
As with the semiconductor laser, any laser having a narrow band in this wavelength region may be used. For example, an erbium (Er) -doped fiber laser can provide the same effect. Further, as the branching element of the light branching means, as in the case of the flat-plate waveguide splitter, any element may be used as long as it splits light in parallel. It works.

As described above, in the present embodiment, the output of the fiber 17 which is a delay fiber is further amplified by a single-stage or multi-stage EDFA (erbium-doped fiber optical amplifier, the same applies hereinafter). In this embodiment, as an example, an average output of about 50 μW for each channel in the laser light generating section and an average output of about 6.3 mW for the total of all channels are output by the two-stage EDFAs 18 and 19 for a total of 4 m.
An example in which amplification of 6 dB (40600 times) is performed is shown. In this case, the peak output is 2 at the output end of each channel.
0 kW, pulse width 1 ns, pulse repetition 100 kW
z, average power 2W, average power about 256W in all channels
Get.

Here, the planar waveguide type splitter 14,
Although the coupling loss at 16 is not taken into account, if there is such coupling loss, it is generated from the EDFA 19 by increasing the amplification gain of the fiber optical amplifier (for example, at least one of the EDFAs 18 and 19) by the loss. The output of the fundamental wave can be made the same as the above-described value (for example, the peak output is 20 kW). By changing the amplification gain of the fiber optical amplifier, the output of the fundamental wave can be made larger or smaller than the above-described value.

The wavelength 1.544, which is the output of this optical amplifier,
The μm single-wavelength pulse laser light is converted into an ultraviolet light pulse output having a narrow spectral line width by a wavelength conversion unit using a nonlinear optical crystal. An embodiment of the wavelength converter will be described later.

Next, a second embodiment of the laser device according to the present invention will be described with reference to FIG. The ultraviolet light generation device according to the present embodiment includes a laser light generation unit that generates a single-wavelength laser light, an optical amplifier that amplifies the light, and a wavelength conversion unit that wavelength-converts the amplified light. , The same output wavelength as the ArF excimer laser (193n
An ultraviolet laser device that generates laser light of m) and has low spatial coherence. The ultraviolet laser device according to the first embodiment of the present invention is a device in which an optical branching unit temporally splits and splits light (Time Division).
Multiplexer: TDM, 23), and the point that the laser light before entering the optical branching means is not amplified by the fiber optical amplifier. Of these, any configuration can be adopted before and after the optical branching means and the fiber optical amplifier.

In the first embodiment, the TD used in the second embodiment is used instead of the flat waveguide splitters (14, 16).
M (23) may be used, and in the second embodiment, TDM
A flat waveguide type splitter may be used instead of (23). An embodiment of the wavelength converter will be described later.

The last stage high peak output fiber optical amplifiers (19 in FIG. 1, FIG. 2)
In 25), in order to avoid an increase in the spectrum width of the amplified light due to the nonlinear effect in the fiber, the fiber mode diameter used in normal communication (5 to 6) is used.
It is desirable to use a large mode diameter fiber optic amplifier wider than [mu] m, for example 20-30 [mu] m.

FIG. 4 shows an example of the configuration of an optical amplifier using this large mode diameter fiber optical amplifier. In this optical amplifier 42 in which the fiber surrounded by the dotted square in FIG. 4 has a wide mode diameter, the semiconductor laser 4 for exciting the optical amplifier doped fiber having the wide mode diameter is used.
3 is coupled to a large mode diameter fiber corresponding to the diameter of a doped fiber for an optical amplifier, and the output of this semiconductor laser is wavelength-division multiplexed (Wavelength Division Multiplexer).
Multiplexer (WDM) 45 and 46 are used to input the doped fiber for the optical amplifier to excite the doped fiber.

This large mode diameter fiber (optical amplifier) 4
The laser light amplified in step 2 enters the wavelength converter 500,
Here, the wavelength is converted to ultraviolet laser light. Laser light (signal) to be amplified that propagates through this large mode diameter fiber
Is preferably a fundamental mode, which can be realized in a single mode or a multimode fiber having a low mode order by mainly selectively exciting the fundamental mode.

In particular, in FIG. 4, the semiconductor laser 43 and W
An optical polarization coupling element 44 is provided between the laser diode and the DM 45 so that laser beams output from two semiconductor lasers 43 whose polarization directions are orthogonal to each other can be combined. In this example, the polarization directions of the laser beams are orthogonalized by the optical polarization coupling element 44. However, the polarization directions may not be orthogonalized if a reduction in the efficiency of combining laser beams can be tolerated. Further, the effect of the return light is reduced by the isolator 404 provided on the incident side of the large mode fiber optical amplifier 42.

A narrow-band filter 403 is provided between the fiber optical amplifier 41 having a standard mode diameter and the large mode fiber optical amplifier 42 in order to remove ASE light generated from the fiber optical amplifier 42. ing. A semiconductor laser 401 for excitation is fiber-coupled to the fiber optical amplifier 41, and the output of the semiconductor laser 401 is input to the doped fiber for optical amplifier through the WDM 402, whereby the doped fiber is excited. You.

According to such a method, since the semiconductor laser 43 is coupled to the large mode diameter fiber, the coupling efficiency to the fiber is improved, and the output of the semiconductor laser can be used effectively. Further, by using a large mode diameter fiber having the same diameter, WDM45,
It is efficient because the loss at 46 can be reduced. In addition, the fiber optical amplifier 41 of the previous stage having a standard mode diameter
And the last stage fiber optical amplifier 4 having a wide mode diameter.
The connection with 2 is performed using a fiber whose mode diameter increases in a tapered shape.

Further, the final stage fiber optical amplifier (1)
In order to obtain a high output in 9 and 25), a double clad fiber 410 having a double fiber clad structure may be used instead of the large mode diameter fiber (42) in FIG. . One example of a cross-sectional view of the fiber 410 is shown in FIG. In this structure,
The core 411 is doped with ions that contribute to the amplification of the laser light, and the amplified laser light (signal) propagates through the core. First cladding 412 surrounding core
Is coupled with a semiconductor laser for excitation. The first cladding is multi-mode and has a large cross-sectional area, so that high-power excitation semiconductor laser light can be easily transmitted, and efficiently couples a multi-mode oscillation semiconductor laser.
The excitation light source can be used efficiently. A second clad 413 for forming a waveguide of the first clad is formed on the outer periphery of the first clad.

In the first and second embodiments, a quartz fiber or a silicate fiber can be used as the fiber optical amplifier. In addition, a fluoride fiber, for example, a ZBLAN fiber may be used. You may. In this fluoride-based fiber, the erbium doping concentration can be increased as compared with quartz or silicate-based fibers, so that the fiber length required for amplification can be shortened.

This fluoride-based fiber is desirably applied to the final stage fiber optical amplifiers (19, 25). The shortening of the fiber length reduces the spread of the wavelength width due to the nonlinear effect during propagation of the pulsed light into the fiber. For example, it is possible to obtain a light source in which the wavelength width required for the exposure apparatus is narrowed. In particular, the fact that this band narrowing light source can be used in an exposure apparatus having a projection optical system having a large numerical aperture is advantageous in designing and manufacturing a projection optical system, for example.

By the way, as described above, the output wavelength of the fiber optical amplifier having the cladding having the double structure is 1.51.
When using a thickness of ~ 1.59 µm, it is preferable to dope yttrium together with erbium as ions to be doped. This is because there is an effect of improving the pumping efficiency by the semiconductor laser. That is, when doping both erbium and yttrium, the strong absorption wavelength of yttrium extends around 915 to 975 nm, and a plurality of semiconductor lasers having different oscillation wavelengths at wavelengths near this are coupled by WDM to form the first semiconductor laser. By coupling to the cladding, the plurality of semiconductor lasers can be used as excitation light, so that a large excitation intensity can be realized. Further, for example, if a polarization coupling element is used as the optical coupling element 44 in FIG. 4, the outputs of the semiconductor lasers having different polarization directions can be coupled together, so that the excitation intensity can be further doubled.

As for the design of a doped fiber of a fiber optical amplifier, an apparatus (for example, an exposure apparatus) that operates at a predetermined fixed wavelength as in the present invention.
Then, the material is selected so that the gain of the fiber optical amplifier at a desired wavelength is increased. For example, in an ultraviolet laser device for obtaining the same output wavelength (193 to 194 nm) as an ArF excimer laser, if an optical amplifier fiber is used, a desired wavelength, for example, 1.548 μm
It is desirable to select a material that increases the gain at the time.

However, the communication fiber is designed to have a relatively flat gain in a wavelength region of several tens nm near 1.55 μm for wavelength division multiplexing communication. Therefore, for example, in a communication fiber having an erbium single-doped core as an excitation medium, a method of co-doping aluminum or phosphorus into a silica fiber is used to realize the flat gain characteristic. Therefore, in this type of fiber, the gain does not always increase at 1.548 μm. This is shown in FIG.

FIG. 6 shows the difference in the fluorescence intensity characteristics between the fibers by taking the wavelength on the horizontal axis and the fluorescence intensity on the vertical axis. Al / P Silica in the figure corresponds to the cable material for communication. On the other hand, if Silicate L22 shown in FIG. 6 is used, a higher gain can be obtained at 1.547 μm. Further, aluminum as a doping element shifts a peak around 1.55 μm to a longer wavelength side, and phosphorus has an effect to shift to a shorter wavelength side. Therefore, the gain can be increased near 1.547 μm by doping a small amount of phosphorus into the silicate L22.

On the other hand, when an optical amplifier fiber (for example, the double clad type fiber) having a core doped (co-doped) with both erbium and ytterbium is used, as shown in FIG. By adding a small amount of phosphorus to, a higher gain can be obtained around 1.547 μm. In FIG. 7, the horizontal axis represents wavelength, and the vertical axis represents gain per unit length. FIG. 7 shows the change in gain with respect to wavelength when the excitation intensity is changed and the population inversion density is changed. It is.

In the fiber optical amplifiers according to the first and second embodiments, since each fiber is an independent optical amplifier, the difference between the gains of the optical amplifiers causes variations in the optical output of each channel. Therefore, in the laser device of such a form, as shown in FIG. 8, for example, a part of the output is branched by the fiber optical amplifiers (41, 42) of each channel to monitor the light intensity, and The pumping semiconductor lasers (401, 4
It is desirable to provide fiber output control devices 405 and 406 that feedback-control the drive current of 3). In FIG. 8, a fiber output control device 405 for detecting the branch light from the fiber optical amplifier 41 controls the drive current of the semiconductor laser 401 connected to the fiber optical amplifier 41 based on the detected value, and A fiber output control device 406 for detecting the branched light from the optical amplifier 42 is connected to the semiconductor laser 4 connected to the large mode fiber optical amplifier 42 based on the detected value.
3 is controlled.

Further, as shown in FIG.
The light intensity in the wavelength conversion section 500 is monitored so that the light output from 0 becomes a predetermined light output, and the pumping semiconductor laser 40 as the entire fiber optical amplifier (41, 42) is monitored.
It is preferable to further include a fiber output control device 407 for feedback-controlling the drive currents 1 and 43 respectively. In FIG. 8, the fiber output control device 407
Controls the semiconductor lasers 401 and 43 independently of each other, but may control only one of the semiconductor lasers 401 and 43 based on the light intensity detected by the wavelength conversion unit 500. Further, the fiber output control device 407 branches the laser light in the middle of the wavelength converter 500 and detects the intensity thereof.
A part of the laser light output from the emission end of the laser beam may be branched and its intensity may be detected. In FIG. 8, FIG.
The other components that are the same as those described above are given the same numbers, and descriptions thereof are omitted.

With such a configuration, the amplification factor of the fiber optical amplifier of each channel is made constant for each amplification stage, so that a biased load is not applied between the fiber optical amplifiers and the entire fiber optical amplifier is uniform. Light intensity can be obtained. In addition, by monitoring the light intensity in the wavelength converter 500, a predetermined predetermined light intensity is fed back to each amplification stage, and a desired ultraviolet light output can be stably obtained.

The output ends of the final stage fiber optical amplifiers 19 and 25 in the first and second embodiments described above are bundled and formed into a required bundle shape (114, 2).
9). The number and shape of the bundles are determined according to the configuration of the wavelength conversion unit and the required shape of the light source. For example, this embodiment shows a case of a bundle having one circular cross section (114, 29, 501, etc.). At this time, since the clad diameter of each fiber is about 125 μm,
The diameter of the bundle at the output end in which 28 are bundled can be about 2 mm or less. The bundle can be formed using the output end of the final stage EDFA or YDFA as it is, but it is also possible to couple an undoped fiber to the final stage EDFA or YDFA and form the bundle at the output end. .

As shown in FIG. 9, at the output end 423 of each fiber 422 at the last stage in the optical amplifier,
It is preferable that the diameter of the core 421 in the fiber 422 is gradually increased in a tapered shape toward the output end, and the power density (light intensity per unit area) at the output end face 423 is reduced. At this time, the shape of the taper is such that the expansion of the core diameter increases sufficiently gently toward the output end face 423, and when the amplified laser light propagates through the tapered portion, the propagation transverse mode in the fiber is preserved. The setting is made such that the transverse mode excitation is sufficiently negligible (for example, about several mrad).

By setting as described above, the power density of light at the output end face 423 of the fiber can be reduced, and damage to the fiber output end caused by laser light, which is the most problematic in fiber damage, can be greatly suppressed. The effect is obtained. This effect is obtained when the power density of the laser light emitted from the output end of the fiber optical amplifier is higher (for example, as the light intensity is higher, the core diameter is smaller for the same power, or the number of channels for dividing the total power is smaller. A large effect can be obtained.

As shown in FIG. 10 (a), the laser beam is applied to the output end 434 of the fiber 432 at the final stage together with the increase in the core diameter or independently depending on the power density of the laser beam. Window member 43 of appropriate thickness to penetrate
It is preferable to dispose 3 closely. However, FIG.
In (a), the power density of the output light is reduced only by the window member 433 without increasing the diameter of the core 431 in the fiber.

Here, when there are a plurality of fiber outputs as in the first and second embodiments, in addition to the method shown in FIG. 10A in which a window member is provided for each fiber end, FIG.
As shown in (b), providing a common window member 443 at an output end 444 for each output group of each fiber optical amplifier 442 is also one example of the present embodiment. However, although the diameter of the core 441 in the fiber is not enlarged in FIG. 10B, the enlargement of the core diameter may be used together.

The number of a plurality of fiber optical amplifiers in which one window member 443 is provided in common may be arbitrary, for example, the last stage fiber optical amplifier 1 shown in FIG. 1 or FIG.
The total number of 9 or 25, that is, 128 lines may be used. In addition,
The material of the window member (433 or 443) is appropriately selected in consideration of the transmittance in the wavelength region of the fundamental laser beam and the adhesion to the fiber (for example, an optical glass material such as BK7 or a quartz material). For the close contact between the fiber and the window member, a method such as optical contact or fusion can be used.

With this configuration, the power density of the laser beam emitted from the window member becomes smaller than the power density in the fiber cores 431 and 441.
The effect of suppressing damage to the fiber output end by the laser beam can be obtained. By combining this with the expansion of the fiber core diameter at the output end, it is possible to solve the problem of damage to the fiber output end, which was a conventional problem.

In each of the above embodiments (FIGS. 1, 2, 4 and 8), the isolator 110, 111, 112, 26, 2
7, 404 etc. are inserted, and narrow band filters 113, 28, 403 are inserted in order to obtain good EDFA amplification characteristics. However, the location where the isolator or the narrow band filter is disposed or the number thereof is not limited to the above-described embodiment. It may be appropriately determined according to the situation, and at least one of the isolator and the narrow band filter may not be provided at all.

The narrow band filter only needs to have a high transmittance for only a desired single wavelength, and the transmission wavelength width of the filter is sufficiently less than 1 pm. By using a narrow band filter in this way, the ASE (Amplified Spontaneous Emitter) generated by the fiber amplifier can be used.
is reduced, and a decrease in the amplification factor of the fundamental wave output due to the ASE from the fiber optical amplifier at the preceding stage can be suppressed.

In the above embodiment, the light modulating element 12
Or, monitor the intensity of the pulse light cut out at 22 and adjust the magnitude of the drive voltage pulse applied to the light modulation element so that the intensity becomes constant for each pulse, thereby reducing the intensity of the pulse light. Feedback control may be performed.
Further, the laser light emitted from a large number of fiber optical amplifiers 19 or 25 is detected, and the delay time of the laser light in each channel and the oscillation interval of the laser light between the channels are monitored. The timing of the drive voltage pulse applied to the light modulation element is controlled so that
By controlling the DM 23, the oscillation timing of the laser light at the output end of the fiber bundle may be feedback-controlled. Alternatively, the wavelength of the ultraviolet light generated from the wavelength converter 500 may be detected, and the temperature of the single-wavelength oscillation laser 11 or 21 may be adjusted based on the detected value to perform feedback control of the wavelength of the ultraviolet light.

Further, the intensity fluctuation of the pulse light cut out by the light modulation element 12 or 22 is detected, and a plurality of fiber optical amplifiers (13, 18, 19, or 24,
The so-called feed-forward control for controlling the gain in at least one stage of 25) may be performed. Further, of the channels 0 to 127, the output (light intensity) of the channel having a short delay time, that is, the channel in which the pulse light is output earlier is detected, and the gain of the fiber optical amplifier (or the TDM 23) is determined based on the detected value. ), The output of the channel having a longer delay time than that of the channel, that is, the output of the channel in which the pulsed light is output with a delay may be subjected to feedforward control. In particular, in the first embodiment shown in FIG. 1, the output may be controlled not in units of channels but in units of blocks having 32 channels. For example, at least one output of the first block may be controlled. The output of one channel may be detected, and the output of the channel in the second block may be controlled based on the detected value.

A third embodiment of the ultraviolet laser device according to the present invention will be described with reference to FIG. The ultraviolet light generation device according to the present embodiment includes a laser light generation unit that includes a single wavelength oscillation laser 31 and generates a single wavelength laser light, an optical amplifier that includes fiber optical amplifiers 33 and 34 and amplifies incident light, and It is an object of the present invention to provide an ultraviolet laser device that includes a wavelength converter (not shown) that converts the wavelength of the amplified light, and generates a laser beam having the same output wavelength (193 nm) as an ArF excimer laser.

In this embodiment, the ultraviolet laser device shown in FIG. 3 includes a single-wavelength oscillation laser 31 for generating a single-wavelength laser beam, and the optical output of the single-wavelength oscillation laser 31 is a fiber optical amplifier. Amplified by 33,34. The output of the fiber optical amplifier 34 is, for example, as shown in FIG.
Wavelength conversion unit (507 to 517, 550) shown in FIG.
The amplified laser light is incident on the laser beam. The emission end of the fiber optical amplifier 34 in FIG. 3 corresponds to the fiber bundle emission end 501 shown in FIG. The wavelength conversion unit includes a set of nonlinear optical crystals 507, 510,
514, 517, etc., and an optical amplifier (31
To 36) are converted into ultraviolet light. The wavelength conversion section according to the present invention will be described in detail as Embodiments 4 and 5 later in the embodiment.

Hereinafter, the present embodiment will be described in more detail. As the single-wavelength oscillation laser 31 oscillating at a single wavelength shown in FIG.
An InGaAsP, DFB semiconductor laser having a W output of 30 mW is used. Since this laser basically oscillates in a single longitudinal mode, its oscillation spectral line width can be suppressed to 0.01 pm or less.

Light output (continuous light) of the semiconductor laser 31
Is converted into pulse light by a light modulation element 32 such as an electro-optic light modulation element or an acousto-optic light modulation element. In the present configuration example, as an example, a case where the light modulation element 32 modulates the pulse light into a pulse light having a pulse width of 1 ns and a repetition frequency of 100 kHz will be described. As a result of performing such light modulation, the peak output of the pulse light output from the light modulation element 32 is 30 mW, and the average output is 3 μW.

The output light pulsed in the same manner as in the first and second embodiments is amplified by a fiber optical amplifier having one or more stages of EDFA (erbium-doped fiber optical amplifier). In the present embodiment, as an example, a case has been described in which amplification is performed in a total of 58 dB (667000 times) by the two-stage fiber optical amplifiers 33 and 34. In this case, the fiber optical amplifier 3
The average output at the output terminal of No. 4 is 2W. This output end can be formed using the output end of the final stage fiber optical amplifier 34 as it is, but it is also possible to couple an undoped fiber to the final stage fiber optical amplifier 34. Further, in the present embodiment, a configuration example is shown in which isolators 35 and 36 are appropriately inserted into each connection portion in order to avoid the influence of return light.

The wavelength 1.544, which is the output of this optical amplifier,
The μm single-wavelength pulsed laser light is converted into an ultraviolet light pulse output having a narrow spectral line width by a wavelength converter (described later in detail) using a nonlinear optical crystal. In the optical amplifiers (31 to 36) according to the present embodiment, the output end is composed of one fiber optical amplifier 34.
A plurality of fiber optical amplifiers (33, 34) are prepared together with the plate waveguide type splitter (16) used in (FIG. 1) or the TDM (23) used in Embodiment 2, and the fiber optical amplifiers 34 are bundled. A fiber bundle may be formed. At this time, by adjusting the timing of the drive voltage pulse applied to the optical modulation element 32 provided in each of the plurality of optical amplifiers, the oscillation interval of the pulse light emitted from the plurality of optical amplifiers can be adjusted.
For example, as pulse light is emitted sequentially at equal time intervals,
It is preferable to shift the light emission timing for each optical amplifier. Also, in the present embodiment, the first and second embodiments are described.
Can be applied.

Next, an embodiment of the wavelength converter used in each of the first to third embodiments will be described. FIG.
FIGS. 1A and 1B show a configuration example of a wavelength converter according to the present invention as a fourth embodiment. This corresponds to the output end 501 of the fiber bundle (114 in the first embodiment, 29 in the second embodiment, etc.
At the output end of the single fiber (34). ), The fundamental wave with a wavelength of 1.544 μm is
The wavelength is converted into an eighth harmonic (harmonic) using a nonlinear optical crystal, and the wavelength is 193 nm, which is the same as that of the ArF excimer laser
1 shows a configuration example for generating ultraviolet light.

FIG. 11A shows a fundamental wave (wavelength 1.544).
μm) → second harmonic (wavelength 742 nm) → third harmonic (wavelength 51
5nm) → 6th harmonic (wavelength 257nm) → 8th harmonic (wavelength 1)
(93 nm).

In the first-stage wavelength converter 507, an LBO crystal is used to convert the generation of the second harmonic from the fundamental wave to the second harmonic. The wavelength converter (LBO crystal) 507 transmits a part of the fundamental wave without converting the wavelength, converts the wavelength of the fundamental wave to generate a second harmonic, and converts the fundamental wave and the second harmonic into a wave plate ( For example, a half wavelength and a half wavelength
A wavelength delay is given, and only the polarization of the fundamental wave is rotated by 90 degrees. The fundamental wave and the second harmonic wave enter the second-stage wavelength converter 510 through the lens 509, respectively. Where LB
The conversion from the fundamental wave to the second harmonic wave using the O crystal uses a method of adjusting the temperature of the LBO crystal, Non-Critical Phase Matching: NCPM, for phase matching for wavelength conversion. The NCPM does not cause an angle shift (Walk-off) between the fundamental wave and the second harmonic in the nonlinear optical crystal, so that conversion to the second harmonic wave can be performed with high efficiency.
This is advantageous because the beam is not deformed by -off.

The second-stage wavelength converter 510 generates the third harmonic (wavelength 515) from the second harmonic generated by the first-stage wavelength converter 507 and the fundamental wave transmitted without conversion by sum frequency generation.
nm). Although an LBO crystal is used as the wavelength conversion crystal, it is used in an NCPM having a different temperature from the wavelength conversion unit (LBO crystal) 507 in the first stage. Wavelength converter 51
The third harmonic obtained at 0 and the second harmonic transmitted without wavelength conversion are separated by a dichroic mirror 511,
The third harmonic reflected by the dichroic mirror 511 is
The light enters the third-stage wavelength converter 514 through the lens 513. The wavelength converter 514 is a β-BaB ₂ O ₄ (BBO) crystal, where the third harmonic is the sixth harmonic due to the generation of the second harmonic.
(Wavelength 257 nm).

The sixth harmonic obtained by the wavelength conversion unit 514 and the second harmonic transmitted through the dichroic mirror 511 and passed through the lens 512 are coaxially combined by the dichroic mirror 516, and are combined in the cooling device 550. 4 installed in
The light enters the wavelength conversion unit 517 in the first stage. Wavelength converter 517
A BBO crystal is used and cooled to −40 ° C. or lower, and an eighth harmonic (wavelength: 193 nm) is obtained by generating a sum frequency from the sixth harmonic and the second harmonic. Here, the reason for cooling the BBO crystal is to reduce the absorption at 193 nm. As the cooling device 550, for example, a cryostat or the like is preferably used.

In the present embodiment, the second-stage wavelength converter 5
The third harmonic and the second harmonic obtained in 10 are split by the dichroic mirror 511, and the sixth harmonic obtained in the third-stage wavelength converter 514 and the second harmonic are obtained in the second-stage wavelength converter 510. The second harmonic is combined with the dichroic mirror 516,
It was configured to be incident on the fourth-stage wavelength converter 517. Here, assuming that the characteristics of the dichroic mirror 511 are inverted, that is, the third harmonic wave is transmitted and the second harmonic wave is reflected, the third-stage wavelength converter 514 is the same as the second-stage wavelength converter 510. It may be arranged on the optical axis. At this time, the characteristics of the dichroic mirror 516 also need to be inverted. As described above, one of the sixth harmonic and the second harmonic passes through the branch optical path and the fourth-stage wavelength converter 517.
In the configuration in which the second and third harmonics are incident on the wavelength conversion unit 517 at the fourth stage, respectively.
12 can be arranged in different optical paths.

Since the sixth harmonic generated in the third-stage wavelength converter 514 has an elliptical cross-sectional shape due to the Walk-off phenomenon, good conversion efficiency is obtained in the fourth-stage wavelength converter 517. For this purpose, it is desirable to perform beam shaping of the sixth harmonic. Therefore, as in this embodiment, the condensing lens 51
By disposing the lenses 5 and 512 in separate optical paths, for example, a pair of cylindrical lenses can be used as the lens 515, and the beam shaping of the sixth harmonic can be easily performed. For this reason, it is possible to improve the overlap with the second harmonic wave in the fourth-stage wavelength conversion unit (BBO crystal) 517 and improve the conversion efficiency.

The configuration between the second-stage wavelength converter 510 and the fourth-stage wavelength converter 517 is not limited to that shown in FIG. Any configuration may be used as long as the optical path lengths of the sixth harmonic and the second harmonic are equal so that the second harmonic and the second harmonic enter simultaneously. Further, for example, the second-stage wavelength converter 510
The third and fourth wavelength conversion units 514 on the same optical axis as
The third-stage wavelength converter 514 converts only the third harmonic into a sixth harmonic by generating the second harmonic, and enters the fourth-stage wavelength converter 517 together with the second harmonic that is not wavelength-converted. The dichroic mirror 5
It is not necessary to use 11, 516.

FIG. 11B shows a fundamental wave (wavelength 1.544).
μm) → 2nd harmonic (wavelength 742 nm) → 4th harmonic (wavelength 38
6 nm) → 6th harmonic (wavelength 257 nm) → 8th harmonic (wavelength 1
(93 nm).

In the first-stage wavelength converter 518, an LBO crystal is used as the wavelength conversion crystal, and the LBO crystal is used in the NCPM to convert the wavelength of the fundamental wave to a second harmonic. The second harmonic generated from the first-stage wavelength converter 518 passes through the condenser lens 519 and passes through the second-stage wavelength converter 52.
Incident at 0.

In the second-stage wavelength converter 520, an LBO crystal is used as the wavelength conversion crystal, and the second harmonic generated by the first-stage wavelength converter 518 is converted into a fourth harmonic (wavelength). 515 nm). The fourth harmonic obtained by the wavelength converter 520 and the wavelength converter 5
The second harmonic transmitted through 20 is a dichroic mirror 5
The fourth harmonic reflected there is passed through a condenser lens 524 and reaches a dichroic mirror 525. On the other hand, the light transmitted through the dichroic mirror 521
The harmonic wave is rotated by 90 ° by the half-wave plate 522 and reaches the dichroic mirror 525 through the condenser lens 523, where it is coaxially synthesized with the fourth harmonic wave that has passed through the branch optical path. The light enters the third-stage wavelength converter 526.

In the third-stage wavelength conversion section 526, a BBO crystal is used as the wavelength conversion crystal. The fourth harmonic generated in the second-stage wavelength conversion section 520 and the wavelength conversion section 520 without wavelength conversion are used. A 6th harmonic (wavelength: 257 nm) is obtained from the 2nd harmonic that has passed through by generating a sum frequency. Wavelength converter 52
6 and the second harmonic transmitted through the wavelength converter 520 without wavelength conversion are separated by a dichroic mirror 527, and the second harmonic reflected here is converted into a half-wave plate 528. Then, the polarization direction is rotated by 90 °, and reaches the dichroic mirror 531 through the condenser lens 529. On the other hand, dichroic mirror 527
Passes through the condenser lens 530 and reaches the dichroic mirror 531, where it is coaxially synthesized with the second harmonic that has passed through the branch optical path, and is placed in the cooling device 551 in the four-stage The light enters the wavelength converter 532 of the eye. For example, a cryostat or the like is preferably used as the cooling device 551.

In the fourth-stage wavelength conversion section 532, a BBO crystal is used as the wavelength conversion crystal, and the sixth harmonic generated in the third-stage wavelength conversion section 526 and the wavelength conversion section 526 without wavelength conversion are used. And an 8th harmonic (wavelength: 193 nm) is obtained from the 2nd harmonic transmitted through. Where BBO
The crystals have been cooled to -40 ° C or less and have reduced absorption at 193 nm.

In this embodiment, dichroic mirrors (521 or 527) are arranged after the second and third stage wavelength converters 520 and 526, respectively, and the wavelength converters (520 or 526) are arranged. So that a pair of harmonics (2nd and 4th harmonics or 2nd and 6th harmonics) emitted from the optical path enter the next-stage wavelength converter (526 or 532) through different optical paths. Although the configuration is similar to that described with reference to FIG. 11A, the third-stage wavelength converter 526 may be arranged on the same optical axis as the other wavelength converters 518, 520, and 532.・ Mirrors 521, 5
It is not necessary to use 25, 527, 531 or the like.

In the present embodiment, the fourth and sixth harmonics generated by the second and third wavelength converters 520 and 526 have oval cross sections due to the walk-off phenomenon. . Therefore, in order to obtain good conversion efficiency in the third and fourth wavelength converters 526 and 532 using this beam as an input, the fourth harmonic wave and the sixth harmonic wave which are incident beams are required.
It is desirable to shape the beam shape of the harmonic wave so that the overlap with the second harmonic beam is good. By placing the condenser lenses 523 and 524 and 529 and 530 in separate optical paths as in this embodiment, for example, the lenses 524 and
A cylindrical lens pair can be used as 30, and beam shaping of the fourth harmonic and the sixth harmonic can be easily performed. Therefore, the third and fourth stage wavelength converters 526 and 532 have good overlap with the second harmonic, respectively, and can increase the conversion efficiency.

Note that the second and fourth harmonics generated from the second-stage wavelength converter 520 are simultaneously output from the third-stage wavelength converter 52.
It is only necessary that the optical path lengths of the second harmonic wave and the fourth harmonic wave be the same so as to be incident on the two wavelength converters 520, 5, and 5.
The configuration between 26 is not limited to FIG.
This is the same between the third-stage wavelength converter 526 and the fourth-stage wavelength converter 532.

FIGS. 12 (a) and 12 (b) correspond to FIGS.
The wavelength conversion efficiency at each stage for each channel and the average output of the eighth harmonic (wavelength 193 nm) obtained for each channel are shown for the wavelength converter shown in FIG. As described in the above embodiment, the output of the fundamental wave is the output terminal of each channel, and has a peak power of 20 kW, a pulse width of 1 ns, a pulse repetition frequency of 100 kHz, and an average output of 2 W. As a result, the average output of the eighth harmonic (wavelength 193 nm) per channel was 76.6 mW in the wavelength converter of FIG. 11A and 80.6 mW in the wavelength converter of FIG. 11B. Therefore, the average output from the bundle including all 128 channels is 9.8 W in FIG. 11A and 10.3 W in FIG. 11B, and any of the wavelength converters can be used as a light source for an exposure apparatus. It is possible to provide a sufficiently output ultraviolet light having a wavelength of 193 nm.

By constructing the wavelength converter as described in the fourth embodiment, the fundamental wave having a wavelength of 1.544 μm generated by the fundamental wave generator can be converted into the ultraviolet light having the wavelength of 193 nm. .

Next, another configuration example of the optical amplifier and the wavelength converter according to the present invention is shown in FIG. 13 as a fifth embodiment. In FIG. 13, the wavelength conversion unit has a plurality of parallel optical path configurations (square arrangement of four optical paths in the example of the figure), and according to this, the output terminals of a large number of fiber optical amplifiers 19 or 25 are formed into four bundles (output groups). While dividing the light, the condensing optical elements corresponding to the four fiber bundle output ends,
And an embodiment in which a wavelength converter is provided. In this example, FIG.
Alternatively, since it is assumed that the optical amplifier shown in FIG. 2 is used, 32 fiber optical amplifiers 19 or 25 are bundled in one fiber bundle. The bundle can be formed by using the EDFA output terminal of the final stage as it is, but it is also possible to couple an undoped fiber to the EDFA or the like of the final stage and form the bundle at the output terminal.

The fiber optical amplifier 19 or 25
In the case where a plurality of fiber bundles are formed by dividing the output end of the optical fiber into a plurality of fiber bundles, the output end of the large number (128 in this example) of adjacent fiber output The (fiber optical amplifier) is preferably configured to be bundled into different fiber bundles. For example, in the order in which laser light is emitted,
No. 0 for 8 fiber optical amplifiers (19 or 25)
No. 0 to 4, No. 127
, 124 are bundled as a first fiber bundle, and Nos. 1, 5, 9,.
, 125 fiber optical amplifiers are bundled as a second fiber bundle, and Nos. 3, 6, 10,.
6 are bundled as a third fiber bundle, and No. 4, 7, 11,..., 127 are bundled as a fourth fiber bundle. This makes it possible to equally divide the time interval of the pulse light incident on the wavelength converter (non-linear optical crystal) arranged corresponding to each fiber bundle.

Now, as shown in FIG. 13, the fundamental wave emitted from the output end 841 of the optical amplifier (FIG. 1 or FIG. 2) composed of four fiber bundles has four stages of wavelength converters 842 in this example. Wavelength conversion is performed at 843, 844, and 849, respectively. In this example, any of the wavelength converters (FIG. 11) described in the fourth embodiment can be used, but here, the wavelength converter shown in FIG. An example in which 1.544 μm) is converted into ultraviolet light having a wavelength of 193 nm by four-stage nonlinear optical crystals (518 to 532) will be described. For simplicity, the dichroic mirror is omitted, and nonlinear optical crystals are sequentially arranged. The fundamental wave of 1.544 μm (frequency ω) passes through the nonlinear optical crystals 842, 843, 844, and 849 from left to right in the figure, and is a second harmonic.
The wavelength is sequentially converted into a fourth harmonic, a sixth harmonic, and an eighth harmonic (wavelength: 193 nm) and output. Note that the nonlinear optical crystal 849 is installed in a cooling device (not shown),
Cooled below.

In FIG. 13, the fundamental wave (wavelength 1.544 μm) emitted from the output end 841 of the optical amplifier composed of four fiber bundles passes through the condenser lenses 845 provided corresponding to the four fiber bundles. Then, the light enters a wavelength converter (nonlinear optical crystal) 842, where a second harmonic is generated, which is twice the frequency ω of the fundamental wave, that is, a second harmonic having a frequency 2ω (wavelength 772 nm). The second harmonic generated by the wavelength converter 842 travels rightward and passes through the condenser lens 846 to enter the next wavelength converter (nonlinear optical crystal) 843. Here, the second harmonic generation is performed again, and the frequency 4ω (wavelength 386n) is twice the frequency 2ω of the incident wave (the second harmonic), that is, four times the fundamental wave.
m) is generated. The fourth harmonic generated by the wavelength converter 843 passes through the condenser lens 847 and enters the wavelength converter (non-linear optical crystal) 844 on the right, generates a sum frequency with the transmitted second harmonic and increases the frequency by six. Waves are generated.
Further, the transmitted second harmonic and sixth harmonic are collected by a condenser lens 848.
And enters the wavelength conversion unit 849, and an eighth harmonic (wavelength 193 nm) is generated by sum frequency generation.

In this embodiment, the nonlinear optical crystal used for the wavelength conversion is, for example, a wavelength conversion section 842.
The LBO crystal is used as a wavelength conversion crystal for converting a fundamental wave into a second harmonic in the wavelength conversion unit 843, the LBO crystal is used as a wavelength conversion crystal for converting a second harmonic to a fourth harmonic in the wavelength conversion unit 843, and the LBO crystal is used in the wavelength conversion unit 844.
BBO as a wavelength conversion crystal from harmonic and 4th harmonic to 6th harmonic
As the crystal, a BBO crystal is used as the wavelength conversion crystal from the second harmonic and the sixth harmonic to the eighth harmonic in the wavelength converter 849.

In this embodiment, the fundamental wave (wavelength 1.54
4 μm) → 2nd harmonic (wavelength 772 nm) → 4th harmonic (wavelength 3
86 nm) → sixth harmonic (wavelength: 257 nm) → eighth harmonic (wavelength: 193 nm) in this case, but this is shown in FIG.
This corresponds to a configuration in which a plurality of wavelength conversion units in FIG.
Therefore, FIG.
A configuration obtained by parallelizing a plurality of items (a) by the same method as in the present embodiment can be configured in the same manner as in the present embodiment.

Next, with reference to FIG. 14, a description will be given of a second example of the present embodiment regarding the coupling section between the optical amplifier and the wavelength conversion section. In this embodiment, the configuration of the wavelength conversion unit shown in FIG. 13 is a parallel configuration of five optical paths, and the output end of the fiber optical amplifier is divided into five to form five fiber bundles (output groups). Things. In this division, the output end of the fiber optical amplifier is not equally divided into five, and the output end 850 of a part (one fiber bundle in FIG. 13) of the five fiber bundles (output group) is a single or a small number of fiber optical amplifiers. Configure and others (Fig. 1
The fiber bundle output end 851 (four in 3) is a bundle of a plurality of fiber optical amplifiers equally divided so that the number of fiber optical amplifiers is the same.

These output lights are supplied to wavelength converters 852 to 852 provided for each output group (fiber bundle).
At 59, the light is converted into ultraviolet light of a predetermined wavelength and supplied to, for example, an exposure apparatus. The four-stage wavelength converters 852 to 859 are each composed of a plurality (five) of fiber bundles and the same number of wavelength converters, and the wavelength converters 852 to 859 are provided.
Condensing optical elements 855 to 8 arranged on the incident side of
Reference numeral 58 also includes the same number of condenser lenses as the fiber bundle. The wavelength conversion unit 859 is installed in a cooling device (not shown), and is cooled to -40 ° C or lower.

Here, when the ultraviolet laser device according to the present embodiment is applied to an exposure apparatus (FIG. 17 or FIG. 18), the fundamental waves generated from the output ends 851 of the four fiber bundles are converted by the wavelength converters (852 to 859). ), The wavelength is converted to ultraviolet light, and this ultraviolet light is irradiated on the reticle as illumination light for exposure through an illumination optical system. That is, the four fiber bundles are used as light sources for exposure. On the other hand, the light output generated from the output end 850 of the fiber bundle composed of a single or a small number of fiber optical amplifiers and converted into ultraviolet light is guided to an alignment system or a monitor system provided in the exposure apparatus. . That is, one fiber bundle (850) is used as an alignment light source or the like. The wavelength-converted ultraviolet light generated from the fiber bundle output end 850 is, for example, 4
The light is transmitted to an alignment system or the like by an undoped fiber coupled to the wavelength converter 859 of the stage.

In FIG. 14, the fundamental wave generated from the output end 851 of the four fiber bundles is converted into ultraviolet light and guided to the illumination optical system. However, the number of fiber bundles is one. May also be plural. Although one fiber bundle is used for alignment and monitoring, the number may be plural, and light emitted from the plural fiber bundles may be guided to different optical systems.

In this example, the light source for exposure and the light source for alignment are used.
Or, the light source used for monitoring or the like is the same, and the illumination light for exposure and the illumination light for alignment are obtained by splitting, amplifying, and wavelength-converting the output light of the same single-wavelength oscillation laser, and have the same wavelength. Ultraviolet light can be used.
For this reason, alignment or various types of monitoring can be performed through an optical system such as an illumination optical system or a projection optical system of the exposure apparatus.

Therefore, the design of the alignment optical system and the like is facilitated, and the configuration can be greatly simplified, or there is no need to provide a separate arrangement, and the exposure apparatus can be easily constructed. Since the irradiation of the exposure illumination light and the irradiation of the alignment illumination light or the like may not be performed simultaneously, for example, a shutter may be provided in the illumination light path, or a channel for distributing the pulse light by the TDM 23 may be selected. It is preferable to control the timing of the irradiation independently.

Further, in order to measure the focal position, projection magnification, aberration, telecentricity, etc. of the projection optical system, the aforementioned ultraviolet light for alignment and monitor can be used, and the measurement accuracy is improved. It becomes possible. The image forming plane of the projection optical system and the photosensitive substrate (wafer)
In the case of focusing, the use of light having the same wavelength as the exposure wavelength and focusing through a projection optical system can simultaneously improve the positioning accuracy.

By the way, according to the configuration of the present embodiment (FIGS. 13 and 14) as described above, the fiber output of the fiber optical amplifier is divided into a plurality of groups, and the input light to the nonlinear optical crystal is divided. Thereby, the incident power to the nonlinear optical crystal can be effectively reduced. Therefore, it is possible to solve problems such as output reduction and optical damage caused by light absorption and thermal effects in the nonlinear optical crystal. Note that the number of divisions (the number of fiber bundles) at the output end of the fiber optical amplifier is not limited to four or five, but may be two or more.

Next, in the ultraviolet light generating apparatus according to the present invention, the coupling part between the optical amplifier and the wavelength conversion part will be described in the sixth embodiment.
It will be described as. Here, the output end of the optical amplifier is formed by bundling the output end of the fiber optical amplifier as described in the first and second embodiments. At this time, the cladding diameter of each fiber optical amplifier was 125 μm.
Therefore, the diameter of the bundle at the output end where the 128 bundles are bundled can be set to about 2 mm or less.

Here, the number and shape of the bundles can be determined according to the configuration of the wavelength conversion unit and the required shape of the light source. For example, in the first and second embodiments, a bundle having one circular cross section is used. (114,
29, 501, etc.). At this time, if the output end of the fiber optical amplifier is formed on a flat surface as shown in FIG. 9 or FIG. 10, for example, the output end of the fiber bundle and the first-stage wavelength converter (non-linear optical (For example, a condenser lens 845 in FIG. 13)
Is provided and the light generated from the fiber bundle is condensed on the nonlinear optical crystal, so that the output light of the fiber optical amplifier can be effectively incident.

FIG. 15 shows another embodiment of the connecting portion according to the present invention. In FIG. 15, a fundamental wave is emitted from a fiber bundle output end 901 in which emission ends of a plurality of fiber optical amplifiers are bundled, and a lens 902 is provided for each fiber optical amplifier. Eye wavelength converter (non-linear optical crystal) 9
03 (for example, 50 in the fourth embodiment (FIG. 11)).
7, 518 etc.). In this embodiment, the diameter of the entire fiber bundle is 2 mm, the mode diameter of each fiber optical amplifier constituting the fiber bundle is 20 μm, and the wavelength conversion unit 9 in the first stage is set by an individual lens 902.
An example of focusing light at 03 will be described. Note that a pair of lenses 904 and 905 are disposed between the first-stage wavelength conversion unit 903 and the second-stage wavelength conversion unit 906, and light emitted from the wavelength conversion unit 903 emits light from the wavelength conversion unit. The light enters the wavelength conversion unit 906 under the same conditions as when the light enters the wavelength conversion unit 903.

In such an embodiment, the condensing lens is set so that each beam diameter in the nonlinear optical crystal has a desirable size (for example, about 200 μm in this embodiment) for obtaining the optimum harmonic conversion efficiency. A magnification of 902 (for example, about 10 times in this embodiment) is selected. Since each fiber output is condensed by an individual lens 902, the size (cross-sectional area) of the total luminous flux in the nonlinear crystal collected from all the fibers in the fiber bundle depends on the magnification of the condensing lens. Regardless of the diameter, the diameter is about the diameter of the fiber bundle itself. Therefore, the required size (cross section) of the wavelength conversion crystal
Is about the diameter of a fiber bundle, so that a small wavelength conversion crystal of about several mm square can be used, which is economical. Instead of providing the lens 902, the fiber output end face may be directly processed into a spherical or aspherical lens shape to have the function of a condensing optical element.

Next, another embodiment of the fiber output end in the coupling section between the optical amplifier and the wavelength conversion section is shown in FIG.
In the embodiment shown in FIGS. 16A and 16C, the condensing lens 902 shown in FIG. 15 is formed at the output end of each fiber 452, and this is bundled for each output group. An example is shown. In this example, fiber 4
A condensing optical element 453 is formed at the output end of each of the 52. The window member 433 provided at the fiber output end already described with reference to FIG. It has the function of a condensing optical element. With this configuration, it is possible to provide a light collecting function similar to that of FIG. 15 and to suppress damage to the fiber output end face.

FIG. 16B shows a plurality of fibers 4.
This is an embodiment in which a light-collecting optical element 463 is provided for each output group in which 62 are bundled. In this example, for example, the condenser lens 845 shown in FIG. 13 is formed at the output end of the fiber bundle, and the window member 443 already described with reference to FIG. This has a function of a condensing optical element.

Note that, instead of processing the fiber end or the output surface of the window member into a spherical or aspherical lens shape, the fiber end is formed using an ion exchange method such as a thermal ion exchange method or an electrolytic ion exchange method. Alternatively, when a glass window is used as a window member, the glass composition at the end of the glass window is partially changed by ion exchange, thereby giving a refractive index distribution equivalent to that of a lens, thereby providing a condensing optical function. It may be. In addition, FIG.
In (c), the diameters of the cores 451 and 461 in the fiber are not enlarged, but this enlargement of the core diameter can be used together.

The light is condensed on the second and subsequent wavelength converters (non-linear optical crystals) as in the case of the first stage, and the output can be performed by individual lenses for each fiber or for each bundle. However, the present embodiment describes a case where all outputs of the fiber bundle are condensed by a common set or one lens. By using a common lens in this way, the number of lenses used is reduced,
It is economical because the alignment of the lens becomes easy.

Since the output end of the wavelength conversion crystal (non-linear optical crystal) is located within the Rayleigh length of the beam condensed by the wavelength conversion crystal, the beam emitted from the wavelength conversion crystal is output from the wavelength conversion crystal. It becomes almost parallel light at the end. In this embodiment (FIG. 15), this emission beam is
4 and 905 show the case where light is condensed on the second-stage wavelength conversion crystal 906. Here, the focal length of the lens pair can be set to a magnification that provides a desirable beam diameter for obtaining optimum conversion efficiency in the second-stage wavelength converter 906. The condensing optical element (for example, 509 and 512 shown in FIG. 11A) for condensing the fundamental wave or its harmonic wave on the wavelength conversion crystal shown in FIG. 11 is constituted by one lens. It is also possible to form a single set of lenses as in this embodiment.

As described above, the fundamental wave generator (laser light generator and optical amplifier) is constituted by the structure shown in the first to third embodiments, and the wavelength converter is constituted by the structure shown in the fourth and fifth embodiments. In addition, by configuring the coupling section between the optical amplifier and the wavelength conversion section with the configuration shown in the sixth embodiment, an ultraviolet light output with an output wavelength of 193 nm or the like can be obtained.
These are the same wavelength as the oscillation wavelength of the ArF excimer laser.

In addition, the ultraviolet output light obtained in this manner is a pulse light emitted at intervals of about 3 ns when the fundamental wave generation unit according to the first embodiment is used, for example. The output light does not interfere with each other even though it is a single-wavelength ultraviolet light having a very narrow band without overlapping. Further, for example, in the case of using the fundamental wave generation unit according to the second embodiment, the obtained ultraviolet output light is pulsed light that is emitted at equal intervals of about 78 ns, and thus does not overlap with each other in time. Even though the single-wavelength ultraviolet light has a very narrow band, the individual output lights do not interfere with each other.

Further, in a solid-state ultraviolet laser array as disclosed in, for example, Japanese Patent Application Laid-Open No. 8-334803, a wavelength converter is provided for each parallelized fundamental wave laser (for each individual laser element). Necessary,
According to the present embodiment, since the fiber bundle diameter of the fundamental wave output is 2 mm or less even when all the channels are combined, it is possible to perform the wavelength conversion of all the channels with only one set of the wavelength converters. In addition, since the output end is a flexible fiber, it is possible to arrange the wavelength converter and other components such as a single-wavelength oscillation laser, a splitter, and a time division optical branching unit separately. Extremely high degree of freedom. Therefore, according to the present invention, it is possible to provide an inexpensive and compact ultraviolet laser device having a single wavelength and low spatial coherence.

Next, a description will be given of a seventh embodiment of the ultraviolet laser device according to the present invention. The ultraviolet laser device according to the present embodiment is characterized in that the ultraviolet laser device as described in the first to sixth embodiments is a light source for an exposure device.

Hereinafter, an embodiment of an exposure apparatus using an ultraviolet laser device according to the present invention will be described with reference to FIG. The exposure equipment used in the photolithography process is in principle the same as photolithography, and a circuit pattern precisely drawn on a photomask (reticle) is optically printed on a semiconductor wafer coated with photoresist. Transfer by reducing projection. The ultraviolet laser device 1261 according to the present invention is provided integrally with the entire exposure apparatus including the illumination optical system 1262, the projection optical system 1265, and the like. At this time, the ultraviolet laser device 1261 may be fixed to a mount supporting the illumination optical system 1262, or the ultraviolet laser device 1261 may be fixed to the mount alone. However, the ultraviolet laser device 1
It is preferable that a power supply and the like connected to the H.261 be separately provided.

Further, the ultraviolet laser device 1261 is divided into a first portion having a laser beam generator and an optical amplifier and a second portion having a wavelength converter.
The first portion may be fixed to a gantry different from the gantry while being fixed to the gantry integrally with the gantry. Further, all of the ultraviolet laser device 1261 may be arranged in a chamber accommodating the exposure apparatus main body, or a part of the ultraviolet laser device 1261, for example, a wavelength conversion unit is arranged in the chamber, and the remaining part is connected to the chamber. You may make it arrange | position to the outside integrally. The control system of the ultraviolet laser device 1261 may be housed in a control rack separately from the chamber, or a display unit (display), switches, and the like may be disposed outside the chamber integrally with the chamber, and the rest may be provided. You may arrange | position in a chamber.

According to the present invention, the ultraviolet light having a narrow band and low spatial coherence is supplied to the illumination optical system 1262.
Thus, the illuminance distribution is enlarged and projected so that the required illuminance distribution on the required projection plane becomes uniform, and is irradiated onto a quartz mask (quartz reticle) 1263 on which a circuit pattern of an integrated circuit is accurately drawn. The circuit pattern of the reticle 1263 corresponds to the projection optical system 1
The circuit pattern is projected on a semiconductor wafer (for example, a silicon wafer) 1266 coated with a photoresist after being reduced at a predetermined reduction magnification by 265, and the circuit pattern is imaged and transferred on the wafer.

The illumination optical system 1262 includes a reticle 1263.
A field stop that is arranged in a plane substantially conjugate to the pattern plane of the reticle 1263 and that defines an illumination area on the reticle 1263, on a predetermined plane in the illumination optical system 1262 that has a substantially Fourier transform relationship with the pattern plane of the reticle 1263. And a condenser lens that irradiates the reticle 1263 with ultraviolet light emitted from the aperture stop. At this time, in order to change the distribution of the amount of ultraviolet light on the predetermined surface, a plurality of aperture stops having at least one of shapes and sizes different from each other are provided on the turret, and a plurality of aperture stops selected according to the pattern of the reticle 1263 are provided. One of the aperture stops may be arranged in the optical path of the illumination optical system 1262.

An optical integrator (homogenizer) may be arranged between the wavelength conversion unit of the ultraviolet laser device 1261 and the field stop. When a fly-eye lens is used, the focal plane on the exit side is the pattern surface of the reticle 1263. And are arranged so as to have a relationship of almost Fourier transform,
When a rod integrator is used, the rod integrator may be arranged such that its emission surface is substantially conjugate with the pattern surface of the reticle 1263.

As the exposure start shutter of the exposure apparatus, the electro-optic modulator or the acousto-optic modulator (12, 22, 32) described in the first to third embodiments can be used. The electro-optic or acousto-optic modulator is switched from an off state, ie, a state in which no pulse is generated (internal loss is large), to an on state, ie, a state in which a pulse is generated (internal loss is reduced in a pulse). Start exposure.

It should be noted that the ultraviolet laser device 12 in this embodiment is
In the exposure apparatus having 61, it is not necessary to control the integrated amount of ultraviolet light on the wafer 1266 using a mechanical shutter, but for example, the output (power, center wavelength, wavelength width, etc.) of the ultraviolet laser device 1261 is controlled. When oscillating ultraviolet light for stabilization, to prevent the ultraviolet light from reaching the wafer 1266 and exposing the photoresist,
A shutter may be provided in the illumination optical path between the ultraviolet laser device 1261 and the wafer 1266, or the stage 1267 may be driven to retract the wafer 1266 from the ultraviolet light irradiation area.

The semiconductor wafer 1266 is
The circuit pattern is transferred to a different position on the semiconductor wafer by being placed on a stage 1267 having a 69 and moving the stage each time one exposure is completed. Such a stage driving and exposure method is called a step-and-repeat method. In addition to the stage driving and exposure methods, there is a step-and-scan method in which a driving mechanism is also provided on a support member 1264 that supports the reticle 1263, and scanning exposure is performed by synchronously moving the reticle and the semiconductor wafer. The ultraviolet laser device of the present invention can be applied to this method.

In an exposure apparatus that performs exposure with ultraviolet light, such as an exposure apparatus using an ultraviolet laser apparatus according to the present invention, usually, both the illumination optical system 1262 and the projection optical system 1265 have an all quartz lens configuration without color correction. It is. In particular, when the wavelength of the ultraviolet light is 200 nm or less, the projection optical system 12
At least one of the plurality of refractive optical elements constituting 65 may be made of fluorite, or a catadioptric optical system combining at least one reflective optical element (concave mirror, mirror, etc.) and a refractive optical element. May be used.

As described above, the exposure apparatus using the ultraviolet laser apparatus according to the present invention is smaller than other conventional methods (exposure apparatus using an excimer laser or a solid-state laser), and each element is Since it is configured by fiber connection, there is a high degree of freedom in the arrangement of each unit constituting the apparatus. FIG. 18 shows another embodiment utilizing the characteristics of the ultraviolet laser device according to the present invention.

This embodiment is different from Embodiments 1 to 5 in that the components of the laser light generator (single-wavelength laser, optical branching means, etc.) and the optical amplifier of the laser apparatus described in Embodiments 1 to 3 are used.
And the wavelength conversion section described in (1) is separately disposed to constitute an exposure apparatus. That is, while the wavelength conversion unit 1272 is mounted on the main body of the exposure apparatus, another part (laser light generation unit, optical amplifier, etc.) 1271 of the ultraviolet laser apparatus is separately provided outside the main body of the exposure apparatus, and Are connected by a connection fiber 1273 to form an ultraviolet laser device. Here, the connection fiber 1273 may be a fiber of the fiber optical amplifier itself (for example, the fiber bundle 114 in the first embodiment), an undoped fiber, or a combination thereof. Note that the portion of the exposure machine main body other than the ultraviolet laser device can be configured using the same device as in FIG.

By adopting such a configuration, the main components that generate heat, such as the semiconductor laser for excitation of the fiber optical amplifier, the power supply for driving the semiconductor laser, and the temperature controller, are disposed outside the exposure apparatus main body. Can be. Therefore, it is possible to suppress a problem caused by heat such that the alignment of the optical axis is out of order due to the influence of heat generated from the ultraviolet laser device as the exposure light source in the exposure device main body.

By the way, as shown in FIG.
The reticle stage 1264 holding the 263 is configured to be movable in the X and Y directions by the driving mechanism 1268 and to be able to rotate minutely. Also, the wafer stage 1
A reference mark plate FM is provided on the reference numeral 267, and this reference mark plate is used for, for example, baseline measurement described later. Further, in this example, an alignment system 1280 for detecting an alignment mark on the reticle 1263 and an off-axis alignment system 1281 provided separately from the projection optical system 1265 are provided.

The alignment system 1280 supplies the illuminating light for exposure or the illuminating light in the same wavelength range as the reticle 1263.
The above-mentioned alignment mark and the reference mark on the reference mark plate FM are radiated through the projection optical system 1265, and the light generated from both marks is received by an image pickup device (CCD) to detect the positional shift. Reticle 1
It is used for alignment of H.263, baseline measurement of the alignment system 1281, and the like.

Off-axis alignment system 128
1 irradiates an alignment mark on the semiconductor wafer 1266 with white light (broadband light) having a wavelength width of, for example, about 550 to 750 nm, and converts an image of an index mark and an image of the alignment mark provided therein into an image sensor. An image is formed on a (CCD) to detect a positional shift between the two marks.

Note that alignment systems 1280 and 1281
By detecting the reference marks on the reference mark plate FM, the base line amount of the alignment system 1281 can be measured from the detection result. Although the baseline measurement is performed before the exposure of the semiconductor wafer is started, the baseline measurement may be performed every time the semiconductor wafer is exchanged, or the base line measurement may be performed once in the exposure operation of a plurality of semiconductor wafers. Line measurement may be performed. However, baseline measurement is always performed after reticle replacement.

In the present embodiment, the wavelength converter shown in FIG. 14 is used as the wavelength converter connected to the ultraviolet laser device (fundamental wave generator) 1271. That is, the wavelength converter 1272 into which the fundamental wave generated from the four fiber bundle output terminals 851 is incident and the wavelength converter 1279 into which the fundamental wave generated from the fiber bundle output terminal 850 is incident are separated. The wavelength conversion unit 1279 is provided integrally with a gantry holding the alignment system 1280. The wavelength conversion unit 1279 is provided integrally with a gantry holding the illumination optical system 1262. At this time, the connection fiber 1278 is coupled to the fiber bundle output end 850 to guide the fundamental wave to the wavelength converter 1279. Accordingly, it is not necessary to separately prepare a light source for the alignment system 1280, and the reference mark can be detected using illumination light having the same wavelength as the illumination light for exposure, thereby enabling highly accurate mark detection.

In this embodiment, the illumination light having the same wavelength as the exposure illumination light is guided to the alignment system 1280.
A wavelength longer than the wavelength (for example, 193 nm) of the exposure illumination light may be guided to the alignment system 1280 or 1281 or the like. That is, of the three stages of wavelength converters shown in FIG. 14, for example, the pulse light emitted from the second stage wavelength converter 853 may be guided to the alignment system by the connection fiber. In addition, a part of the pulse light emitted from the first-stage wavelength conversion unit 852 is branched, and the remaining pulse light is wavelength-converted by the second-stage wavelength conversion unit 853.
Two pulse lights having different wavelengths respectively emitted from the two wavelength converters 852 and 853 may be guided to the alignment system.

The exposure apparatus shown in FIG. 18 has a single-wavelength oscillation laser,
The oscillation wavelength of the DFB semiconductor laser, that is, the reticle 1263 is adjusted by adjusting the temperature using a temperature controller (for example, a Peltier element) provided on a heat sink on which the B semiconductor laser (such as 11 in FIG. 1) is mounted. Is provided with a wavelength control device 1274 for controlling the wavelength of the ultraviolet laser light (exposure illumination light) applied to the substrate. Wavelength control device 127
Reference numeral 4 controls the temperature of the DFB semiconductor laser in units of 0.001 ° C. to stabilize the center wavelength of the ultraviolet laser light and adjust the optical characteristics (aberration, focal position, projection magnification, etc.) of the projection optical system 1265. And so on. Thereby, the wavelength stability of the ultraviolet laser light during the exposure operation of the semiconductor wafer can be improved, and the irradiation of the ultraviolet laser light, and the optical characteristics of the projection optical system 1265 that fluctuate due to a change in the atmospheric pressure and the like can be improved. It can be easily adjusted.

Further, the exposure apparatus shown in FIG. 18 has a light modulation element (FIG. 1) for converting continuous light generated from a single-wavelength oscillation laser (such as a DFB semiconductor laser) into pulsed light in a fundamental wave generation section 1271. A pulse control unit 1275 for applying a drive voltage pulse to the semiconductor wafer 1266, and a pulse necessary to expose the photoresist during circuit pattern transfer according to the sensitivity characteristics of the photoresist applied to the semiconductor wafer 1266. The exposure control unit 1276 controls the oscillation timing and the magnitude of the control pulse output from the pulse control unit 1275 in accordance with the number of pulses, and the control unit 1277 controls the entire exposure apparatus. Are provided.

The control unit 1277 exposes information (not shown) for reading a semiconductor wafer or an identification symbol (such as a bar code) attached to a cassette holding the semiconductor wafer, or exposes information on the sensitivity characteristics of the photoresist input by the operator. The exposure control unit 1276 calculates the number of exposure pulses required for pattern transfer based on the input information. Further, the exposure control unit 1276 controls the trigger pulse control unit 1275 based on the number of exposure pulses and the intensity of the pulse light determined according to the number of exposure pulses, and oscillates the control pulse applied to the light modulation element and the magnitude of the control pulse. Adjust the length. This controls the start and end of the exposure, and the intensity of the pulse light irradiated on the semiconductor wafer 1266, and the integrated light amount given to the photoresist by the irradiation of the plurality of pulse lights is adjusted to an appropriate exposure amount corresponding to the sensitivity. Controlled.

Here, when the laser device shown in FIG. 1 or FIG. 2 is used as the fundamental wave generation section 1271 in this example, one pulse light cut out by the light modulation element is divided into a plurality (128). However, in this example, the divided 12
Eight pulse lights may be used as one pulse to perform exposure amount control in units of this pulse, or the divided 128 pulse lights may be used as one pulse to perform exposure amount control. Good. When the latter exposure amount control is performed, the gain of the fiber optical amplifier in the fundamental wave generation unit 1271 is adjusted instead of the control of the light modulation element by the pulse control unit 1275, and the pulse on the semiconductor wafer is adjusted. The light intensity may be controlled, or the two controls may be used in combination.

The exposure apparatus shown in FIG. 18 is capable of selectively exposing a semiconductor wafer by switching between a step-and-repeat method and a step-and-scan method. In the step-and-repeat method, the illumination optical system 126 is configured such that the entire circuit pattern on the reticle 1263 is irradiated with the illumination light for exposure.
The field stop (reticle blind) in 2 is driven to adjust the size of the opening and the like. On the other hand, in the step-and-scan method, the irradiation area of the exposure illumination light within the circular projection field of view of the projection optical system 1265 is limited to a rectangular slit shape extending along a direction orthogonal to the scanning direction of the reticle 1263. Adjust the aperture of the field stop. Therefore,
In the step-and-scan method, the reticle 1263
Since only a part of the upper circuit pattern is illuminated, the entire circuit pattern is scanned and exposed on a semiconductor wafer, so that the projection is synchronized with the relative movement of the reticle 1263 with respect to the exposure illumination light. The semiconductor wafer 1266 is moved relative to the exposure illumination light at a speed ratio corresponding to the projection magnification of the optical system 1265.

By the way, in the exposure amount control at the time of the scanning exposure, at least one of the pulse repetition frequency f defined by the light modulation element and the inter-channel delay time defined by the TDM 23 shown in FIG. 2 is adjusted. Then, a plurality of pulse lights are oscillated at equal time intervals from the fundamental wave generator 1271 during the scanning exposure. Further, in accordance with the sensitivity characteristics of the photoresist, the intensity of the pulse light on the semiconductor wafer, the scanning speed of the semiconductor wafer, the oscillation interval (frequency) of the pulse light, and the pulse light in the scanning direction of the semiconductor wafer (that is, the irradiation area thereof) ) Is adjusted, and the integrated light amount of the plurality of pulsed lights irradiated while each point on the semiconductor wafer crosses the irradiation area is controlled to an appropriate exposure amount. At this time, in consideration of throughput, other control parameters, that is, pulse light intensity, oscillation frequency, and irradiation area, are controlled in the exposure amount control so that the scanning speed of the semiconductor wafer is almost maintained at the maximum speed of the wafer stage 1267. It is preferable to adjust at least one of the widths.

When scanning exposure is performed by using the laser apparatus shown in FIG. 1 or FIG. 2, in the exposure amount control, the 128 divided pulsed lights are oscillated at equal time intervals as one pulse each as described above. Preferably. However, the oscillation interval of the divided 128 pulse lights is adjusted according to the scanning speed of the semiconductor wafer, and the 128 pulse lights can be regarded as one pulse, that is, the 128 pulse lights are irradiated. If the distance that the semiconductor wafer moves during this time does not cause a decrease in the exposure control accuracy,
The exposure amount control may be performed with 28 pulsed lights as one pulse.

It is preferable that the surface of the fiber (including the fiber optical amplifier and the like) used in the above-described embodiment is covered with Teflon (registered trademark). It is desirable that the coating with Teflon be performed on all the fibers. In particular, the fibers disposed in the chamber accommodating the exposure apparatus main body are coated with Teflon. This is because foreign matter (including fibers and the like) generated from the fiber may become a substance that contaminates the exposure apparatus, and constitutes an illumination optical system, a projection optical system, an alignment optical system, and the like generated due to the contaminant. To prevent fogging of optical elements, fluctuations in transmittance (reflectance) and optical characteristics (including aberrations) of these optical systems, or fluctuations in illuminance on a reticle or a semiconductor wafer and distribution thereof. It becomes possible. Instead of coating with Teflon, the fibers arranged in the chamber may be collectively stored in a stainless steel housing.

In the semiconductor device, a step of designing its function and performance, a step of manufacturing a reticle based on this design step, a step of manufacturing a wafer from a silicon material, and a step of forming a reticle pattern on the wafer using the above-described exposure apparatus. , A device assembling step (including a dicing step, a bonding step, and a package step), and an inspection step. In addition, the above-described exposure apparatus can be used not only for manufacturing semiconductor elements, but also for example, for a liquid crystal display, an image pickup element (eg,
Etc.), a thin-film magnetic head, a reticle, and the like.

Further, the illumination optical system and the projection optical system composed of a plurality of optical elements are incorporated in the main body of the exposure apparatus for optical adjustment, and a reticle stage and a wafer stage composed of a number of mechanical parts are mounted on the main body of the exposure apparatus. The exposure apparatus according to the present embodiment can be manufactured by connecting wires and pipes, and performing overall adjustment (electrical adjustment, operation confirmation, and the like).

In the above-described exposure apparatus, the ultraviolet laser apparatus 1261 is attached to the exposure apparatus main body, or a part of the ultraviolet laser apparatus 1261 (laser light generating section and optical amplifier, etc.) arranged outside the exposure apparatus main body and the main body. A fiber is connected to a wavelength conversion unit disposed in the inside, and an optical axis alignment between the ultraviolet laser device 1261 (wavelength conversion unit) and the illumination optical system 1262 is performed. It is desirable that the exposure apparatus be manufactured in a clean room in which the temperature, the degree of cleanliness, and the like are controlled.

[0173]

As described above, according to the present invention,
It is possible to provide an ultraviolet laser device that is compact, has a high degree of freedom in equipment arrangement, is easy to maintain, hardly causes damage to the nonlinear optical crystal, and generates ultraviolet light with low spatial coherence.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a laser light generator and an optical amplifier according to a first embodiment of an ultraviolet laser device according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a laser light generator and an optical amplifier according to a second embodiment of the ultraviolet laser device according to the present invention.

FIG. 3 is an explanatory diagram showing a configuration of a laser light generator and an optical amplifier according to a third embodiment of the ultraviolet laser device according to the present invention.

FIG. 4 is an explanatory diagram showing a configuration of an optical amplifier according to another embodiment of the ultraviolet laser device according to the present invention.

FIG. 5 is a cross-sectional view of a double clad fiber optical amplifier.

FIG. 6 is a characteristic diagram showing a relationship between wavelength and gain by an element doped into an erbium-doped fiber optical amplifier.

FIG. 7 is a characteristic diagram showing a change in gain with respect to pumping intensity in a fiber optical amplifier in which erbium and yttrium are co-doped.

FIG. 8 is a configuration diagram showing a configuration of a fiber output control unit of the ultraviolet laser device according to the present invention.

FIG. 9 is a side view illustrating an enlarged state of a fiber core at an output end of the fiber optical amplifier.

FIG. 10 is a side view showing an example of an output end of the fiber optical amplifier.

FIG. 11 is an explanatory diagram illustrating a configuration of a wavelength conversion unit according to a fourth embodiment of the ultraviolet laser device according to the present invention.

FIG. 12 is a table showing the conversion efficiency of the wavelength converter according to the present invention.

FIG. 13 is an explanatory diagram illustrating a configuration of a wavelength conversion unit according to a fifth embodiment of the ultraviolet laser device according to the present invention.

FIG. 14 is an explanatory diagram illustrating an example of a wavelength conversion unit input unit according to a sixth embodiment of the ultraviolet laser device according to the present invention.

FIG. 15 is an explanatory diagram showing another embodiment of the wavelength converter input section of the ultraviolet laser device according to the present invention.

FIG. 16 is an explanatory diagram showing another embodiment of the wavelength converter input section of the ultraviolet laser device according to the present invention.

FIG. 17 is an explanatory view showing a configuration example of an exposure apparatus according to the present invention.

FIG. 18 is an explanatory view showing another configuration example of the exposure apparatus according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Light source, single wavelength oscillation laser (DFB semiconductor laser, fiber laser, etc.) 12 ... Optical modulator 14, 16 ... Splitter (optical branching means) 13 ... Fiber optical amplifier 15, 17 ... Fibers with different lengths (delay) Means, delay fiber) 18: fiber optical amplifier (first fiber optical amplifier) 19: fiber optical amplifier (second fiber optical amplifier) 114: fiber output end (fiber bundle output end) 21: light source, single wavelength oscillation laser ( DFB semiconductor laser, fiber laser, etc.) 22: optical modulator 23: time-division optical branching means (TDM, optical branching means, delay means) 24: fiber optical amplifier (first fiber optical amplifier) 25: fiber optical amplifier (second) Fiber optical amplifier) 29 ... Fiber output end (fiber bundle output end) DESCRIPTION OF SYMBOLS 1 ... Light source, single wavelength oscillation laser (DFB semiconductor laser, fiber laser, etc.) 32 ... Optical modulator 33 ... Fiber optical amplifier (first fiber optical amplifier) 34 ... Fiber optical amplifier (second fiber optical amplifier) 41 ... Fiber Optical amplifier (first fiber optical amplifier) 42 ... Fiber optical amplifier (second fiber optical amplifier) 405, 406, 407 ... Fiber output control devices 421, 341, 441, 451, 461 ... Cores 423, 434, 444, 454, 464: Fiber output end surface 433, 443 (453, 463): Window member 453, 463: Lens 501: Fiber output end (fiber bundle output end) 507, 510, 513, 514, 517, 518, 5
20, 526, 532: Non-linear optical crystal 550, 551: Cooling device 841: Fiber output end (fiber bundle output end) 842, 843, 844, 849: Non-linear optical crystal 901: Fiber output end (fiber bundle output end) 902, 904, 905: Lens 903, 906: Nonlinear optical crystal 1261: Laser device 1262: Illumination optical system 1263: Mask (reticle) 1265: Projection optical system 1266: Wafer 1268, 1269: Driving mechanism (driving device) 1271: Laser device 1272 … Wavelength converter 1273 transmission system (first fiber) 1277 control device (adjustment device) 1278 transmission system (second fiber) 1279 wavelength converter 1280, 1281 alignment system

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01S 3/042 H01S 5/12 5F073 3/10 H01L 21/30 515B 5/12 H01S 3/04 LF term (Ref.) AB28 BA09 EA02 EA12 GA03 GA12

Claims (60)

[Claims] 1. A laser light generating section having a single-wavelength oscillation laser for generating a single-wavelength laser light within a wavelength range from an infrared region to a visible region, and a laser light generated by the laser light generating portion. An optical amplifier having a fiber optical amplifier for amplification; a wavelength conversion unit for converting the wavelength of the amplified laser light into ultraviolet light using a nonlinear optical crystal; and cooling at least a part of the wavelength conversion unit to −40 ° C. or less. A laser device comprising a cooling device and generating ultraviolet light of a single wavelength. 2. The single wavelength oscillation laser according to claim 1, further comprising an oscillation wavelength control means for controlling an oscillation wavelength of the generated laser light to a constant wavelength.
3. The laser device according to claim 1. 3. The laser device according to claim 1, further comprising an optical branching unit that branches a laser beam generated from the single-wavelength oscillation laser into a plurality of laser beams. 4. The splitter has a splitter for splitting a plurality of laser beams generated from the single-wavelength oscillation laser in parallel, and fibers having different lengths are provided on the emission side of the splitter. The laser device according to claim 3, wherein: 5. The length of each of the fibers having different lengths is determined so that the delay interval between the parallel-branched laser lights at the output ends of these fibers is substantially constant. The laser device according to claim 4, wherein 6. The respective lengths of the fibers having different lengths are defined as follows: the mutual delay interval of the parallel-branched laser beams at the output ends of the fibers is determined by the repetition frequency of the laser beam incident on the splitter and the repetition frequency of the laser beams. The laser device according to claim 5, wherein the laser device is determined so as to be a reciprocal of a product of the number of optical paths branched in parallel by the splitter. 7. The laser device according to claim 3, wherein the light splitting means has a time division multiplexer. 8. The output end of the optical amplifier provided on the incident side of the wavelength converter, wherein the core of the fiber output end is formed by expanding in a tapered shape toward the fiber output end face. Item 1
The laser device according to any one of claims 1 to 7. 9. An output end of the optical amplifier provided on an incident side of the wavelength converter, a window member through which the laser light amplified by the optical amplifier is transmitted is provided. The laser device according to claim 1. 10. The laser device according to claim 1, wherein the optical amplifier includes an erbium-doped fiber optical amplifier. 11. The laser device according to claim 1, wherein the optical amplifier has a fiber optical amplifier doped with both erbium and yttrium. 12. The optical amplifier according to claim 1, wherein the optical amplifier includes a plurality of fiber optical amplifiers for amplifying the plurality of branched lights branched by the optical branching unit. 3. The laser device according to claim 1. 13. The optical amplifier according to claim 1, wherein the output of the ultraviolet light has a predetermined optical output, or each of the optical outputs amplified by the plurality of fiber optical amplifiers has a predetermined optical output. 13. The laser device according to claim 12, further comprising fiber output control means for controlling the excitation intensity of each of the plurality of fiber optical amplifiers. 14. An output end of the optical amplifier provided on the incident side of the wavelength conversion unit, the output end being constituted by an output group in which a plurality of fiber output ends are bundled into one or a plurality of fiber output ends. 14. The laser device according to claim 12, wherein the laser device is divided into a plurality of groups, and is configured by a plurality of output groups formed by bundling the groups. 15. A first output group formed by one fiber output end or a bundle of a small number of fiber output ends, and a fiber output end of the first output group. A second output group formed by bundling the remaining fiber output ends except for the above, or by dividing the remaining fiber output ends into a plurality of groups substantially equally, and bundling and forming each group. The laser device according to claim 14, comprising: 16. An output group forming an output end of the optical amplifier provided on the incident side of the wavelength conversion unit, each of the output groups has a window member that transmits a laser beam amplified by the optical amplifier. The laser device according to claim 14 or claim 15, wherein 17. The laser device according to claim 14, wherein the wavelength converter is provided for each output group of the optical amplifier. 18. A light-collecting optical element according to claim 1, further comprising a condensing optical element for converging laser light emitted from said optical amplifier to a non-linear optical crystal of said wavelength converter and for making said non-linear optical crystal incident. The laser device according to claim 1. 19. The laser device according to claim 18, wherein said condensing optical element is provided for each output group of said optical amplifier. 20. The laser device according to claim 19, wherein the condensing optical element is a lens, and is integrally provided on an entire output end of an output group of the optical amplifier. 21. The laser device according to claim 18, wherein said condensing optical element is provided at each of a plurality of fiber output ends of said optical amplifier. 22. The laser device according to claim 21, wherein the condensing optical element is provided by using a plurality of fiber output ends of the optical amplifier as lenses. 23. The laser light generator, wherein the wavelength is 1.5.
a wavelength of about 1.5 μm, and the wavelength converter outputs the fundamental wave of about 1.5 μm output from the optical amplifier as 8th harmonic or 10th harmonic of ultraviolet light. The laser device according to any one of claims 1 to 22, wherein the laser device is generated. 24. The single wavelength oscillation laser according to claim 1, wherein
a DFB semiconductor laser or a fiber laser having an oscillation wavelength in the range of μm to 1.59 μm, wherein the wavelength conversion unit has a generation wavelength of 189 nm to 199 nm.
24. The laser device according to claim 23, wherein the laser device generates an 8th harmonic within the range. 25. The single-wavelength oscillation laser according to claim 1, wherein
A laser beam having an oscillation wavelength within a range of 4 μm to 1.552 μm; and the wavelength conversion unit generates an eight-fold harmonic within a range of 193 nm to 194 nm whose generation wavelength is substantially the same as the oscillation wavelength of the ArF excimer laser. The laser device according to claim 23, wherein the laser device generates a wave. 26. The wavelength conversion section, comprising: a first harmonic that generates an eighth harmonic of the fundamental wave by generating a sum frequency from a second harmonic of the fundamental wave and a sixth harmonic of the fundamental wave. 26. The device according to claim 23, further comprising a non-linear optical crystal, wherein the first non-linear optical crystal is installed in the cooling device and is cooled to -40C or lower. Laser device. 27. A wavelength conversion section comprising: a second nonlinear optical crystal that generates a second harmonic by generating a second harmonic from the fundamental wave; and a second nonlinear optical crystal that generates a second harmonic of the second harmonic. Wave 4
A third nonlinear optical crystal for generating a second harmonic, and a fourth harmonic for generating a sixth harmonic of the fundamental wave by sum frequency generation from a second harmonic of the fundamental wave and a fourth harmonic of the fundamental wave. 27. The laser device according to claim 26, further comprising a nonlinear optical crystal. 28. The method according to claim 28, wherein the first nonlinear optical crystal is β-Ba
B ₂ O ₄ (BBO) crystal, wherein the second nonlinear optical crystal is LiB ₃ O ₅ (LBO) crystal, BBO crystal, CeLiB ₆ O ₁₀ (CLBO) crystal,
Li ₂ B ₄ O ₇ (LB ₄ ) crystal, LiNbO ₃ crystal, KNb
O ₃ crystal, LiNbO ₃ quasi phase matching crystal, LiTaO ₃
A quasi phase matching crystal or a GdYCOB crystal, wherein the third nonlinear optical crystal is a BBO crystal, an LBO crystal,
KH ₂ PO ₄ (KDP) crystal, GdYCOB crystal, LiN
bO ₃ quasi-phase matched crystal, LiTaO ₃ quasi-phase matched crystal, a LB ₄ crystal or CLBO crystal, laser apparatus of claim 27, wherein the fourth non-linear optical crystal is characterized in that it is a BBO crystal. 29. The wavelength conversion section comprising: a second nonlinear optical crystal that generates a second harmonic from the fundamental wave by generating a second harmonic; and a sum frequency generation of the fundamental wave and the second harmonic. A third nonlinear optical crystal for generating a third harmonic of the fundamental wave, and a fourth nonlinear optical crystal for generating a sixth harmonic of the fundamental wave by a second harmonic of the third harmonic of the fundamental wave 27. The laser device according to claim 26, comprising: 30. The method according to claim 30, wherein the first nonlinear optical crystal is β-Ba
B ₂ O ₄ (BBO) crystal, wherein the second nonlinear optical crystal is LiB ₃ O ₅ (LBO) crystal, BBO crystal, CeLiB ₆ O ₁₀ (CLBO) crystal,
Li ₂ B ₄ O ₇ (LB ₄ ) crystal, LiNbO ₃ crystal, KNb
O ₃ crystal, LiNbO ₃ quasi phase matching crystal, LiTaO ₃
The quasi phase matching crystal or GdYCOB crystal, the third nonlinear optical crystal is a BBO crystal, and the fourth nonlinear optical crystal is a BBO crystal, an LB ₄ crystal or a CLBO crystal. 3. The laser device according to claim 1. 31. An exposure apparatus using the laser device according to any one of claims 1 to 30 as a light source. 32. An illumination optical system for irradiating ultraviolet light emitted from the laser device onto a mask, and projection optics for projecting transmitted light or reflected light from the mask onto a substrate to form a pattern image of the mask. The exposure apparatus according to claim 31, further comprising a system. 33. A laser device, wherein the output end of the optical amplifier divides a plurality of fiber output ends into a plurality of groups and includes a plurality of output groups formed by bundling the groups. 33. The exposure apparatus according to claim 31, wherein ultraviolet light output corresponding to at least one of the output groups is used as a light source for alignment. 34. A projection optical system for projecting a pattern image of a mask onto a substrate, and an ultraviolet light emitted from the laser device is converted into a mark pattern arranged on the object plane or image plane side of the projection optical system. The exposure apparatus according to any one of claims 31 to 33, further comprising a pattern detection system for irradiation. 35. An exposure apparatus for transferring a pattern image of a mask onto a substrate, comprising: a laser device for emitting a laser beam of a single wavelength within a wavelength range from an infrared region to a visible region; 1 optical fiber amplifier; optical branching means for splitting the amplified laser light into a plurality of light beams; second fiber optical amplifiers for respectively amplifying the plurality of split light beams; and light emitted from the second fiber optical amplifier. A light source having a wavelength converting means for converting the laser light into ultraviolet light, a cooling device for cooling at least a part of the wavelength converting means to -40 ° C. or lower, and transmitting the laser light emitted from the light source to an exposure apparatus. An exposure apparatus comprising: 36. The exposure apparatus according to claim 35, wherein the light source has optical means for reducing coherence of the plurality of branched lights. 37. A light source that generates continuous light within a wavelength range from an infrared region to a visible region, an optical modulator that converts the continuous light into pulse light, and a first fiber optical amplifier that amplifies the pulse light. A second fiber optical amplifier for amplifying the amplified pulse light, a wavelength converter for converting the wavelength of the pulse light amplified by the second fiber optical amplifier to ultraviolet light, and at least a part of the wavelength converter. A laser device comprising: a cooling device that cools the temperature to 40 ° C. or lower. 38. A fiber optical amplifier further comprising an optical branching means on at least one of the first and second fiber optical amplifiers on the incident side, wherein the pulse light divided by the optical branching means is arranged at a subsequent stage. 38. The laser device according to claim 37, wherein the laser beam is incident on the laser beam. 39. The apparatus according to claim 38, further comprising delay means for delaying each of the plurality of divided pulse lights and inputting the delayed light to a fiber optical amplifier disposed downstream of the light splitter. Laser device. 40. The apparatus according to claim 37, wherein the second fiber optical amplifier is a large mode diameter fiber.
10. The laser device according to claim 9. 41. The first and second fiber optical amplifiers each include a quartz fiber, a silicate-based fiber,
The laser device according to any one of claims 37 to 40, wherein the laser device is any one of a fiber and a fluoride fiber. 42. The second fiber optical amplifier is a ZBL
The fiber is an AN fiber.
2. The laser device according to 1. 43. The apparatus according to claim 37, further comprising at least one third fiber optical amplifier disposed between the first and second fiber optical amplifiers. Laser device. 44. An illumination optical system comprising the laser device according to claim 37, wherein the illumination optical system irradiates a pulse light amplified by the second fiber optical amplifier to a mask, and the pulse light. An adjustment device for adjusting at least one of oscillation, intensity, and wavelength of light. 45. The exposure apparatus according to claim 44, wherein the adjusting device has a first controller that controls the oscillation and magnitude of a control pulse applied to the optical modulator. 46. The apparatus according to claim 44, wherein the adjusting device has a second controller for controlling a gain of at least one of the first and second fiber optical amplifiers.
3. The exposure apparatus according to claim 1. 47. The adjustment device according to claim 44, wherein the adjustment device has a third controller for controlling a temperature of the light source.
47. The exposure apparatus according to any one of -46. 48. The apparatus according to claim 44, further comprising an alignment system for detecting a mark formed on said mask, and a transmission system for guiding at least a part of said amplified pulsed light to said alignment system. 48. The exposure apparatus according to any one of items 47 to 47. 49. The exposure apparatus according to claim 48, wherein the transmission system has first and second fibers for guiding the amplified pulse light to the illumination optical system and the alignment system, respectively. . 50. A plurality of said wavelength converters, wherein a first wavelength converter of said plurality of wavelength converters is provided between said second fiber optical amplifier and said first fiber, or between said first fiber and said first fiber. 50. The exposure apparatus according to claim 49, wherein the exposure apparatus is provided between the exposure apparatus and an illumination optical system. 51. The first wavelength conversion unit is provided between the first fiber and the illumination optical system, and is held integrally with at least a part of the illumination optical system. Item 51. The exposure apparatus according to Item 50. 52. A second wavelength converter among the plurality of wavelength converters is provided between the second fiber optical amplifier and the second fiber, or between the second fiber and the alignment system. 50. The method of claim 50, wherein
Or the exposure apparatus according to 51. 53. The apparatus according to claim 52, wherein the second wavelength converter is provided between the second fiber and the alignment system, and is held integrally with at least a part of the alignment system. 3. The exposure apparatus according to claim 1. 54. A projection optical system for projecting at least a part of a pattern formed on the mask onto a substrate, and a projection magnification of the projection optical system for scanning and exposing the whole of the pattern onto the substrate. The exposure apparatus according to any one of claims 44 to 53, further comprising a driving device that synchronously moves the mask and the substrate at a speed ratio substantially corresponding thereto. 55. Converting the continuous light in the infrared or visible range emitted from the light source into pulsed light, amplifying the pulsed light a plurality of times with a plurality of fiber optical amplifiers, and at least partially reducing the temperature to −40 ° C. or lower. An exposure method, wherein a wavelength of the amplified pulse light is converted into ultraviolet light by a cooled wavelength conversion unit, the ultraviolet light is irradiated onto a mask, and a substrate is exposed to the pulse light via the mask. 56. irradiating at least a part of the ultraviolet light on a mark on the mask prior to exposing the substrate,
The exposure method according to claim 55, wherein position information of the mark is detected. 57. The apparatus according to claim 55, wherein the wavelength of the ultraviolet light is controlled by adjusting the temperature of the light source.
7. The exposure method according to 6. 58. An apparatus for controlling the intensity of the ultraviolet light by controlling at least one of an optical modulator for converting the continuous light into the pulse light and the plurality of fiber optical amplifiers. 58. The exposure method according to any one of items 55 to 57. 59. The exposure method according to claim 58, wherein a repetition frequency of the pulse light defined by the light modulator is controlled to adjust an oscillation interval of the ultraviolet light. 60. A time divider which is arranged between the optical modulator and one of the plurality of fiber optical amplifiers and time-divides the pulse light into a plurality of light beams to control the oscillation interval of the ultraviolet light. The exposure method according to claim 58 or 59, wherein the exposure is performed.