Laser device and manufacturing method for electronic device

Abstract

To provide a laser device which can make the output energy large.SOLUTION: A laser device includes an oscillator which emits pulse-shaped seed light, a first amplifier which amplifies the seed light and emits first amplified light, a first pulse extender that extends the pulse width of the first amplified light, a beam splitter that divides the first amplified light with the extended pulse width into first split light and second split light with less energy than the first split light, a second amplifier that amplifies a portion of the second split light and emits a second amplified light, a second pulse stretcher that stretches the pulse width of the second amplified light, and a beam combiner that emits combined light that combines the first split light and the second amplified light whose pulse width has been stretched.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a laser device and a method for manufacturing an electronic device.

Background Art

[0002] In recent years, in semiconductor exposure apparatuses, as semiconductor integrated circuits have been miniaturized and highly integrated, an improvement in resolution has been demanded. For this reason, the wavelength of light emitted from an exposure light source has been shortened. For example, as a gas laser device for exposure, a KrF excimer laser device that outputs laser light with a wavelength of about 248 nm and an ArF excimer laser device that outputs laser light with a wavelength of about 193 nm are used.

[0003] The spectral linewidth of the spontaneous emission light of a KrF excimer laser device and an ArF excimer laser device is as wide as 350 to 400 pm. Therefore, when a projection lens is configured with a material that transmits ultraviolet light such as KrF and ArF laser light, chromatic aberration may occur. As a result, the resolution may decrease. Therefore, it is necessary to narrow the spectral linewidth of the laser light output from the gas laser device to such an extent that chromatic aberration can be ignored. Therefore, in the laser resonator of the gas laser device, a line narrowing module (LNM) including a line narrowing element (etalon, grating, etc.) may be provided to narrow the spectral linewidth. A gas laser device whose spectral linewidth is narrowed is called a line-narrowed gas laser device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] A laser device according to one aspect of the present disclosure includes an oscillator that emits pulsed seed light, a first amplifier that amplifies the seed light and emits first amplified light, a first pulse stretcher that stretches the pulse width of the first amplified light, a beam splitter that splits the first amplified light with the stretched pulse width into a first split light and a second split light having less energy than the first split light, a second amplifier that amplifies a part of the second split light and emits second amplified light, a second pulse stretcher that stretches the pulse width of the second amplified light, and a beam combiner that emits combined light obtained by combining the first split light and the second amplified light with the stretched pulse width.

[0006] A method for manufacturing an electronic device according to one aspect of the present disclosure includes generating laser light by a laser device including an oscillator that emits pulsed seed light, a first amplifier that amplifies the seed light and emits first amplified light, a first pulse stretcher that stretches the pulse width of the first amplified light, a beam splitter that splits the first amplified light with the stretched pulse width into a first split light and a second split light having less energy than the first split light, a second amplifier that amplifies a part of the second split light and emits second amplified light, a second pulse stretcher that stretches the pulse width of the second amplified light, and a beam combiner that emits combined light obtained by combining the first split light and the second amplified light with the stretched pulse width, outputting the laser light to an exposure device, and exposing the laser light onto a photosensitive substrate in the exposure device to manufacture an electronic device.

Brief Description of the Drawings

[0007] Some embodiments of the present disclosure will be described below by way of example only with reference to the accompanying drawings.

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[0008] <Content> 1. Comparative Example 1.1 Configuration of Exposure Device 200 1.2 Operation of Exposure Device 200 1.3 Configuration of Laser Device 100 1.3.1 First and Second Oscillators MO1 and MO2 1.3.2 First and Second Amplifiers PO1 and PO2 1.3.3 First and Second Pulse Stretchers PS1 and PS2 1.3.4 Others 1.4 Operation of Laser Device 100 1.4.1 First and Second Oscillators MO1 and MO2 1.4.2 First and Second Amplifiers PO1 and PO2 1.4.3 First and Second Pulse Stretchers PS1 and PS2 1.4.4 Others 1.5 Problems of the Comparative Example 2. Laser Device 100a for Branching the First Amplified Light Bpsa 2.1 Configuration 2.2 Operation 2.2.1 Timing Control 2.2.2 Energy control 2.3 Function 3. Laser device 100b for extending the pulse width of combined light Bpsa1 + Bpsb 3.1 Configuration 3.2 Operation 3.3 Function 4. Others 4.1 Control of applied voltage 4.2 Configuration of beam combiner COM 4.3 Supplementary explanation

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below are examples of the present disclosure and do not limit the content of the present disclosure. Also, not all of the configurations and operations described in the embodiments are essential as the configurations and operations of the present disclosure. Note that the same reference numerals are assigned to the same components, and duplicate descriptions are omitted.

[0010] 1. Comparative example FIG. 1 shows the configuration of an exposure system in a comparative example. The comparative example of the present disclosure is a form recognized by the applicant as being known only to the applicant and is not a known example recognized by the applicant.

[0011] The exposure system includes a laser device 100 and an exposure device 200. The laser device 100 is configured to output laser light B toward the exposure device 200.

[0012] 1.1 Configuration of exposure device 200 The exposure device 200 includes an illumination optical system 201 and a projection optical system 202. The illumination optical system 201 illuminates a reticle pattern (not shown) of a reticle disposed on a reticle stage RT with the laser light B incident from the laser device 100. The projection optical system 202 reduces and projects the laser light B that has passed through the reticle and forms an image on a workpiece (not shown) disposed on a workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with a resist film.

[0013] 1.2 Operation of Exposure Device 200 The exposure device 200 synchronizes the reticle stage RT and the workpiece table WT and moves them in parallel in opposite directions to each other. As a result, the workpiece is exposed with the laser light B reflecting the reticle pattern. Through such an exposure process, the reticle pattern is transferred onto the semiconductor wafer. Thereafter, an electronic device can be manufactured through a plurality of processes.

[0014] 1.3 Configuration of Laser Device 100 FIG. 2 shows the configuration of the laser device 100 according to the comparative example. The laser device 100 includes first and second oscillators MO1 and MO2, first and second amplifiers PO1 and PO2, first and second pulse stretchers PS1 and PS2, a beam combiner COM, and a processor 130.

[0015] 1.3.1 First and Second Oscillators MO1 and MO2 The first and second oscillators MO1 and MO2 have the same configuration as each other. Each of the first and second oscillators MO1 and MO2 is a master oscillator including a laser chamber 10, a pair of discharge electrodes 11a and 11b, a narrowbanding module 14, and an output coupling mirror 15.

[0016] The narrowbanding module 14 and the output coupling mirror 15 constitute a laser resonator. The laser chamber 10 is arranged in the optical path of the laser resonator. Windows 10a and 10b are provided at both ends of the laser chamber 10. Inside the laser chamber 10, the discharge electrodes 11a and 11b are arranged. A pulse power supply 12 is connected to the discharge electrode 11a. The laser chamber 10 is filled with a laser gas containing, for example, argon gas or krypton gas as a rare gas, fluorine gas as a halogen gas, neon gas as a buffer gas, and the like.

[0017] The narrowband module 14 includes a prism 14b and a grating 14c. The prism 14b is disposed in the optical path of the light emitted from the window 10a. The grating 14c is disposed in the optical path of the light transmitted through the prism 14b. The output coupling mirror 15 is a partial reflection mirror and is disposed in the optical path of the light emitted from the window 10b.

[0018] 1.3.2 First and Second Amplifiers PO1 and PO2 The first amplifier PO1 is disposed in the optical path of the seed light B1 output from the first oscillator MO1, and the second amplifier PO2 is disposed in the optical path of the seed light B1 output from the second oscillator MO2. The first and second amplifiers PO1 and PO2 have the same configuration as each other. Each of the first and second amplifiers PO1 and PO2 is a power oscillator including a laser chamber 20, a pair of discharge electrodes 21a and 21b, a rear mirror 24, and an output coupling mirror 25.

[0019] Each of the rear mirror 24 and the output coupling mirror 25 is a partial reflection mirror. The reflectivity of the rear mirror 24 is set higher than the reflectivity of the output coupling mirror 25. The rear mirror 24 and the output coupling mirror 25 constitute a laser resonator. The laser chamber 20 is disposed in the optical path of the laser resonator. Windows 20a and 20b are provided at both ends of the laser chamber 20. Inside the laser chamber 20, the discharge electrodes 21a and 21b are disposed. A pulse power supply 22 is connected to the discharge electrode 21a. The same laser gas as in the laser chamber 10 is enclosed in the laser chamber 20.

[0020] The discharge directions between the discharge electrodes 11a and 11b and between the discharge electrodes 21a and 21b are the V direction or the -V direction. The output direction of the seed light B1 from the output coupling mirror 15 is the Z direction. The V direction and the Z direction are perpendicular to each other, and the directions perpendicular to both of them are the H direction and the -H direction.

[0021] 1.3.3 First and Second Pulse Stretchers PS1 and PS2 The first pulse stretcher PS1 is disposed in the optical path of the laser beam B2 output from the first amplifier PO1, and the second pulse stretcher PS2 is disposed in the optical path of the laser beam B2 output from the second amplifier PO2. The first and second pulse stretchers PS1 and PS2 have the same configuration as each other. Each of the first and second pulse stretchers PS1 and PS2 includes first to fourth concave mirrors 31 to 34 and a beam splitter 35. Each of the first to fourth concave mirrors 31 to 34 is a spherical mirror.

[0022] 1.3.4 Others High reflection mirrors 61 and 62 are disposed in the optical paths of the laser beams Bps1 and Bps2 output from the first and second pulse stretchers PS1 and PS2, respectively.

[0023] The beam combiner COM is disposed in a space including the optical paths of both the laser beams Bps1 and Bps2 reflected by the high reflection mirrors 61 and 62, respectively.

[0024] The processor 130 is a processing device including a memory 131 storing a control program and a CPU (central processing unit) 132 executing the control program. The processor 130 is specially configured or programmed to execute various processes included in the present disclosure.

[0025] 1.4 Operation of the laser device 100 1.4.1 The first and second oscillators MO1 and MO2 In each of the first and second oscillators MO1 and MO2, when a high voltage pulse generated by the pulse power supply 12 is applied to the discharge electrode 11a, a discharge occurs inside the laser chamber 10. Due to the energy of this discharge, the laser medium inside the laser chamber 10 is excited and transitions to a high energy level. When the excited laser medium then transitions to a low energy level, it emits light having a wavelength corresponding to the energy level difference. The light generated inside the laser chamber 10 is emitted to the outside of the laser chamber 10 through the windows 10a and 10b.

[0026] The light emitted from the window 10a of the laser chamber 10 is expanded in the beam width in the H direction by the prism 14b and then enters the grating 14c. The light incident on the grating 14c from the prism 14b is reflected by a plurality of grooves of the grating 14c and diffracted in a direction according to the wavelength of the light. The prism 14b reduces the beam width in the H direction of the diffracted light from the grating 14c and returns the light to the laser chamber 10 through the window 10a.

[0027] The output coupling mirror 15 transmits and outputs a part of the light emitted from the window 10b of the laser chamber 10, and reflects the other part and returns it to the inside of the laser chamber 10 through the window 10b.

[0028] In this way, the light emitted from the laser chamber 10 reciprocates between the narrowbanding module 14 and the output coupling mirror 15 and is amplified each time it passes through the discharge space inside the laser chamber 10. This light is narrowed each time it is reflected by the narrowbanding module 14. In this way, the laser-oscillated and narrowed light is output as the seed light B1 from the output coupling mirror 15.

[0029] 1.4.2 First and Second Amplifiers PO1 and PO2 In each of the first and second amplifiers PO1 and PO2, a high-voltage pulse generated by the pulse power supply 22 is applied to the discharge electrode 21a. The processor 130 transmits an oscillation trigger signal to the pulse power supply 22 from the time when it transmits an oscillation trigger signal to the pulse power supply 12 so that the timing when the seed light B1 enters the inside of the laser chamber 20 is synchronized with the timing when discharge occurs inside the laser chamber 20. The time until is set.

[0030] The seed light B1 reciprocates between the rear mirror 24 and the output coupling mirror 25 and is amplified each time it passes through the discharge space inside the laser chamber 20. The amplified laser light B2 is output from the output coupling mirror 25.

[0031] 1.4.3 First and second pulse stretchers PS1 and PS2 In each of the first and second pulse stretchers PS1 and PS2, the beam splitter 35 transmits a part of the laser beam B2 incident in the Z direction from the output coupling mirror 25 as the first output light in the Z direction, and reflects the other part in the V direction.

[0032] The first to fourth concave mirrors 31 to 34 sequentially reflect the laser beam B2 reflected in the V direction by the beam splitter 35, and make it incident on the beam splitter 35 in the V direction. At this time, the beam cross-section of the laser beam B2 incident on the beam splitter 35 in the Z direction forms an image on the beam splitter 35 at a 1:1 size by the first to fourth concave mirrors 31 to 34. The beam splitter 35 reflects a part of the laser beam B2 incident in the V direction from the fourth concave mirror 34 as the second output light in the Z direction, and transmits the other part in the V direction.

[0033] There is a time difference corresponding to the time for light to make one round in the delay optical path formed by the first to fourth concave mirrors 31 to 34 between the first output light and the second output light. By spatially overlapping the first output light and the second output light, laser beams Bps1 and Bps2 with an extended pulse width can be emitted.

[0034] By extending the pulse width of the laser beam, the generation of speckles on the surface of the semiconductor wafer exposed by the exposure apparatus 200 is suppressed. Speckles are bright and dark spots generated by interference when the laser beam is scattered to equalize the light intensity distribution of the laser beam. The intensity of the speckles is represented by the speckle contrast SC and can be calculated by the following formula. SC=(λ 2 / (A·Ω)+τ c / TIS) 1 / 2 Here, λ is the wavelength, A is the area of the beam cross-section, Ω is the beam divergence angle, τ c is the coherence time, and TIS is the pulse width calculated by the following formula. TIS = ([∫I(t)dt] 2 ) / (∫I(t) 2 dt) Here, t is time, and I(t) is the light intensity at time t.

[0035] 1.4.4 Others The high - reflection mirrors 61 and 62 reflect the laser lights Bps1 and Bps2 respectively toward the beam combiner COM. The beam combiner COM combines the laser lights Bps1 and Bps2 by bringing their optical paths close to each other and emits the combined light.

[0036] The processor 130 controls the applied voltages of the first and second oscillators MO1 and MO2 generated by the pulse power supply 12 and the applied voltages of the first and second amplifiers PO1 and PO2 generated by the pulse power supply 22 so that the energy of one pulse of the seed light B1 and the energy of one pulse of the laser light B2 respectively become desired values. Further, the processor 130 transmits an oscillation trigger signal to the pulse power supplies 12 and 22 so that the repetition frequency of the combined light output from the beam combiner COM becomes a desired value.

[0037] In order to improve the processing speed of the semiconductor wafer in the exposure apparatus 200, it is required to increase the output energy of the laser apparatus 100. As methods for increasing the output energy of the laser apparatus 100, a method of increasing the repetition frequency and a method of increasing the energy per pulse are conceivable. However, if the repetition frequency is increased, after one discharge, the next discharge may occur before the discharge products between the discharge electrodes 11a and 11b and between the discharge electrodes 21a and 21b are removed, and the discharge becomes unstable. Alternatively, if the rotation speed of a fan (not shown) is increased to remove the discharge products in a short time, the power consumption increases. Also, when the repetition frequency is increased, the influence of the acoustic wave becomes large and the light quality deteriorates. On the other hand, if the energy per pulse is increased, since the peak intensity becomes large, the optical element is likely to deteriorate due to two - photon absorption.

[0038] Therefore, the processor 130 alternately transmits oscillation trigger signals to the pulse power supplies 12 of the first and second oscillators MO1 and MO2. If the repetition frequency of each oscillation trigger signal of the first and second oscillators MO1 and MO2 is 6 kHz, the repetition frequency of the combined light can be 12 kHz. According to the configuration of the comparative example, compared with the case of laser oscillation at a repetition frequency of 12 kHz using one oscillator and one amplifier, the first and second oscillators MO1 and MO2 and the first and second amplifiers PO1 and PO2 each perform laser oscillation at a repetition frequency of 6 kHz, so the possibility of unstable discharge can be reduced. Also, according to the configuration of the comparative example, compared with the case of laser oscillation at a repetition frequency of 6 kHz using one oscillator and one amplifier, the energy of the laser light per unit time increases without increasing the peak intensity of the laser light, so the deterioration of the optical element is suppressed.

[0039] 1.5 Problems of the Comparative Example In the comparative example, the first and second oscillators MO1 and MO2 and the first and second amplifiers PO1 and PO2 are required. Since each of the first and second oscillators MO1 and MO2 includes the laser chamber 10 and the band narrowing module 14, there is a problem that the laser device 100 becomes expensive and the installation space becomes large.

[0040] 2. Laser Device 100a for Branching the First Amplified Light Bpsa 2.1 Configuration FIG. 3 schematically shows the configuration of the laser device 100a according to the first embodiment. The laser device 100a includes an oscillator MO, first and second amplifiers POa and POb, a beam splitter BS, first and second pulse stretchers PSa and PSb, a beam combiner COM, and a processor 130. Although FIG. 3 shows several high-reflection mirrors for changing the traveling direction of light, the traveling direction of light and the arrangement of the high-reflection mirrors are not limited to those shown.

[0041] The configurations of the oscillator MO, the first and second amplifiers POa and POb, the first and second pulse stretchers PSa and PSb, the beam combiner COM, and the processor 130 are the same as those of the first oscillator MO1, the first and second amplifiers PO1 and PO2, the first and second pulse stretchers PS1 and PS2, the beam combiner COM, and the processor 130 in the comparative example, respectively.

[0042] The oscillator MO emits pulsed seed light Bmo. The first amplifier POa is arranged in the optical path of the seed light Bmo, amplifies the seed light Bmo, and emits the first amplified light Bpoa. The first pulse stretcher PSa is arranged in the optical path of the first amplified light Bpoa, stretches the pulse width of the first amplified light Bpoa, and emits it as the first amplified light Bpsa.

[0043] The beam splitter BS is arranged in the optical path of the first amplified light Bpsa with an extended pulse width, and splits the first amplified light Bpsa into a first split light Bpsa1 and a second split light Bpsa2. The second split light Bpsa2 has less energy than the first split light Bpsa1. When the first split light Bpsa1 is the light transmitted through the beam splitter BS and the second split light Bpsa2 is the light reflected by the beam splitter BS, the transmittance of the beam splitter BS is desirably 80% or more and 96% or less.

[0044] The second amplifier POb is arranged in the optical path of the second split light Bpsa2, amplifies a part of the second split light Bpsa2, and emits the second amplified light Bpob. The second pulse stretcher PSb is arranged in the optical path of the second amplified light Bpob, stretches the pulse width of the second amplified light Bpob, and emits it as the second amplified light Bpsb.

[0045] The total optical path length of the delay optical paths included in the first pulse stretcher PSa and the total optical path length of the delay optical paths included in the second pulse stretcher PSb may be equal to each other. The number of stages of the delay optical paths included in the first pulse stretcher PSa and the number of stages of the delay optical paths included in the second pulse stretcher PSb may be equal to each other. When the first and second pulse stretchers PSa and PSb include delay optical paths with the same number of stages, the combination of the optical path lengths of the delay optical paths included in the first pulse stretcher PSa and the combination of the optical path lengths of the delay optical paths included in the second pulse stretcher PSb may be equal to each other. The equality of the optical path lengths of the delay optical paths is not limited to the case where they are exactly the same, but includes the case where the smaller one is 95% or more of the larger one.

[0046] The beam combiner COM is disposed in a space including the optical paths of both the first split light Bpsa1 and the second amplified light Bpsb with an extended pulse width. The beam combiner COM emits combined light Bpsa1 + Bpsb obtained by combining the optical paths of the first split light Bpsa1 and the second amplified light Bpsb with an extended pulse width by bringing them close to each other. The configuration of the beam combiner COM will be described later with reference to FIGS. 8 and 9.

[0047] Beam splitters with higher transmittance than reflectance are respectively disposed in the optical paths of the seed light Bmo, the first split light Bpsa1, the second amplified light Bpsb, and the combined light Bpsa1 + Bpsb. Energy sensors Emo, a first energy sensor Epoa, a second energy sensor Epob, and an energy sensor Ecom are respectively disposed in the optical paths of the light reflected by those beam splitters.

[0048] 2.2 Operation FIG. 4 is a time chart showing the oscillation trigger signals and the pulse time waveforms of the laser lights of the respective parts of the laser device 100a according to the first embodiment. The horizontal axis of FIG. 4 indicates time, and the vertical dashed lines in FIG. 4 indicate that the events on the same dashed line occur almost simultaneously.

[0049] 2.2.1 Timing Control Processor 130 outputs oscillation trigger signals Tmo, Tpoa, and Tpob to oscillator MO and first and second amplifiers POa and POb, respectively. Oscillator MO and first and second amplifiers POa and POb output seed light Bmo and first and second amplified lights Bpoa and Bpob, respectively, in response to oscillation trigger signals Tmo, Tpoa, and Tpob.

[0050] The time T1 from when processor 130 outputs oscillation trigger signal Tmo to oscillator MO until it outputs oscillation trigger signal Tpoa to first amplifier POa is set such that parameters such as the energy, energy stability, and spectral linewidth of first amplified light Bpoa are optimized.

[0051] The pulse time waveform of first amplified light Bpsa with an extended pulse width may include multiple peaks. The time interval between adjacent peaks may correspond to the time it takes for light to make one round trip in the delay optical path included in first pulse stretcher PSa. However, when first pulse stretcher PSa has a configuration in which multiple stages of delay optical paths are connected in series, since combinations of the number of round trips of each delay optical path become diverse, the pulse time waveform of first amplified light Bpsa becomes a complex waveform including more peaks. The same applies to the pulse time waveform of second amplified light Bpsb with an extended pulse width.

[0052] The ratio of the energies of first and second split lights Bpsa1 and Bpsa2 is determined by the transmittance of beam splitter BS.

[0053] The time T2 from when processor 130 outputs oscillation trigger signal Tpoa to first amplifier POa until it outputs oscillation trigger signal Tpob to second amplifier POb is set such that the pulse width of combined light Bpsa1 + Bpsb becomes as long as possible. From this perspective, processor 130 controls the amplification timing in second amplifier POb such that second amplifier POb amplifies a part included in the latter half of the pulse time waveform of second split light Bpsa2. Time T2 is longer than time T1.

[0054] 2.2.2 Energy Control The energy of the seed light Bmo is measured by the energy sensor Emo (see Fig. 3). The processor 130 controls the applied voltage HVmo of the oscillator MO based on the measurement result by the energy sensor Emo. Thereby, the energy of the seed light Bmo is controlled to be within an appropriate range as the seed light of the first amplifier POa.

[0055] Of the second split light Bpsa2 incident on the second amplifier POb, only the portion after the oscillation trigger signal Tpob is input to the second amplifier POb is used as the seed light of the second amplifier POb. The seed light of the second amplifier POb includes at least one peak portion included in the latter half of the pulse time waveform of the second split light Bpsa2. When the energy of the seed light of the second amplifier POb is made equal to that of the seed light Bmo of the first amplifier POa, the energy of the second split light Bpsa2 is larger than the energy of the seed light Bmo.

[0056] The pulse time waveform of the combined light Bpsa1 + Bpsb corresponds to the composite waveform of the first split light Bpsa1 and the second amplified light Bpsb and is controlled as follows. The energy of the first split light Bpsa1 and the energy of the second amplified light Bpsb are measured by the first and second energy sensors Epoa and Epob, respectively. The processor 130 controls the applied voltage HVpoa of the first amplifier POa based on the measurement result by the first energy sensor Epoa, and controls the applied voltage HVpob of the second amplifier POb based on the measurement result by the second energy sensor Epob. The control of the applied voltage based on the measurement result of the energy will be described later with reference to Fig. 7.

[0057] Alternatively, the pulse time waveform of the combined light Bpsa1 + Bpsb may be measured by the energy sensor Ecom. The processor 130 calculates the energy of the first part included in the first half H1 of the pulse time waveform of the combined light Bpsa1 + Bpsb and the energy of the second part included in the second half H2, and controls the applied voltage HVpoa of the first amplifier POa based on the energy of the first part and controls the applied voltage HVpob of the second amplifier POb based on the energy of the second part.

[0058] The first split light Bpsa1 and the second amplified light Bpsb may have equivalent energy. Thus, the energy difference between the first split light Bpsa1 and the second amplified light Bpsb may be smaller than the energy difference between the first and second split lights Bpsa1 and Bpsa2. Also, since the first split light Bpsa1 is generated by branching from the first amplified light Bpsa, the energy of the first amplified light Bpsa may be greater than the energy of the second amplified light Bpsb.

[0059] 2.3 Operation (1) According to the first embodiment, the laser device 100a includes the following components. (a) An oscillator MO that emits pulsed seed light Bmo, (b) A first amplifier POa that amplifies the seed light Bmo and emits first amplified light Bpoa, (c) A first pulse stretcher PSa that extends the pulse width of the first amplified light Bpoa, (d) A beam splitter BS that splits the first amplified light Bpsa with an extended pulse width into a first split light Bpsa1 and a second split light Bpsa2 having less energy than the first split light Bpsa1, (e) A second amplifier POb that amplifies a part of the second split light Bpsa2 and emits second amplified light Bpob, (f) A second pulse stretcher PSb that extends the pulse width of the second amplified light Bpob, (g) A beam combiner COM that emits combined light Bpsa1 + Bpsb obtained by combining the first split light Bpsa1 and the second amplified light Bpsb with an extended pulse width.

[0060] When splitting the seed light Bmo output from the oscillator MO and injecting it into two amplifiers, in order to make the split seed light Bmo the required amount of light in each of the two amplifiers, it is necessary to double the output energy of the oscillator MO, which may shorten the life of the oscillator MO. According to the first embodiment, since the first amplified light Bpsa is split at a stage subsequent to the first amplifier POa, even if there is one oscillator MO, it is possible to obtain a second split light Bpsa2 with a sufficient amount of light as the seed light for the second amplifier POb while suppressing the load on the oscillator MO. Since there is one oscillator MO and only one each of the laser chamber 10 and the narrowbanding module 14 is required, it is possible to suppress the laser device 100a from becoming expensive or occupying a large installation space. Also, since the first amplified light Bpsa is split at a stage subsequent to the first pulse stretcher PSa, the peak intensity of the first amplified light Bpsa incident on the beam splitter BS can be reduced, suppressing the deterioration of optical elements such as the beam splitter BS.

[0061] (2) According to the first embodiment, the laser device 100a further includes a processor 130. The processor 130 controls the amplification timing in the second amplifier POb so that the second amplifier POb amplifies a part included in the latter half of the pulse time waveform of the second split light Bpsa2.

[0062] According to this, since a part of the second split light Bpsa2, which is included in the latter half of the pulse time waveform of the second split light Bpsa2, is amplified to obtain the second amplified light Bpsb, the pulse width of the combined light Bpsa1 + Bpsb can be increased when combined with the first split light Bpsa1. And by increasing the pulse width, the speckle contrast SC can be reduced.

[0063] (3) According to the first embodiment, the energy difference between the first split light Bpsa1 and the second amplified light Bpsb with an extended pulse width is smaller than the energy difference between the first and second split lights Bpsa1 and Bpsa2.

[0064] According to this, the difference in energy between the first half and the second half of the combined light Bpsa1 + Bpsb can be reduced.

[0065] (4) According to the first embodiment, the laser device 100a includes a processor 130. The processor 130 is configured to output an oscillation trigger signal Tmo, Tpoa, and Tpob to the oscillator MO, the first amplifier POa, and the second amplifier POb, respectively. The time T1 from when the oscillation trigger signal Tmo is output to the oscillator MO until when the oscillation trigger signal Tpoa is output to the first amplifier POa is shorter than the time T2 from when the oscillation trigger signal Tpoa is output to the first amplifier POa until when the oscillation trigger signal Tpob is output to the second amplifier POb.

[0066] According to this, by shifting the amplification timings in the first and second amplifiers POa and POb, the pulse width of the combined light Bpsa1 + Bpsb can be increased when the first split light Bpsa1 and the second amplified light Bpsb are combined.

[0067] (5) According to the first embodiment, the energy of the second split light Bpsa2 is greater than the energy of the seed light Bmo.

[0068] According to this, since the energy of the second split light Bpsa2 is large, a sufficient amount of light can be obtained by using a part of the second split light Bpsa2 as the seed light of the second amplifier POb.

[0069] (6) According to the first embodiment, the laser device 100a includes a first energy sensor Epoa that measures the energy of the first split light Bpsa1, a second energy sensor Epob that measures the energy of the second amplified light Bpsb with an extended pulse width, and a processor 130. The processor 130 controls the applied voltage HVpoa of the first amplifier POa based on the measurement result by the first energy sensor Epoa, and controls the applied voltage HVpob of the second amplifier POb based on the measurement result by the second energy sensor Epob.

[0070] According to this, by separately measuring the first split light Bpsa1 and the second amplified light Bpsb, and independently controlling the applied voltages HVpoa and HVpob of the first and second amplifiers POa and POb, the pulse time waveform of the combined light Bpsa1 + Bpsb can be accurately controlled, and sufficient energy stability can be achieved. Also, the dose amount indicating the energy of the laser light irradiated to one location on the semiconductor wafer can be stabilized.

[0071] (7) According to the first embodiment, the laser device 100a includes an energy sensor Ecom that measures the pulse time waveform of the combined light Bpsa1 + Bpsb, and a processor 130. The processor 130 calculates the energy of the first portion included in the first half H1 of the pulse time waveform and the energy of the second portion included in the second half H2 of the pulse time waveform, controls the applied voltage HVpoa of the first amplifier POa based on the energy of the first portion, and controls the applied voltage HVpob of the second amplifier POb based on the energy of the second portion.

[0072] According to this, information necessary to independently control the applied voltages HVpoa and HVpob of the first and second amplifiers POa and POb can be obtained with one energy sensor Ecom. Thereby, the pulse time waveform of the combined light Bpsa1 + Bpsb can be accurately controlled, and sufficient energy stability can be achieved. Also, the dose amount can be stabilized.

[0073] (8) According to the first embodiment, the energy of the first amplified light Bpsa with an extended pulse width is larger than the energy of the second amplified light Bpsb with an extended pulse width.

[0074] According to this, since the energy of the first amplified light Bpsa is large, the first split light Bpsa1 obtained by splitting the first amplified light Bpsa can have a sufficient light amount as a part of the combined light Bpsa1 + Bpsb.

[0075] (9) According to the first embodiment, the first split light Bpsa1 is the light transmitted through the beam splitter BS, the second split light Bpsa2 is the light reflected by the beam splitter BS, and the transmittance of the beam splitter BS is 80% or more and 96% or less.

[0076] According to this, the first split light Bpsa1 can be made to have a sufficient light amount as a part of the combined light Bpsa1 + Bpsb, and a part of the second split light Bpsa2 can be made to have a sufficient light amount as the seed light of the second amplifier POb.

[0077] (10) According to the first embodiment, the optical path lengths of the delay optical paths included in the first and second pulse stretchers PSa and PSb are equal to each other.

[0078] According to this, the pulse time widths of the first split light Bpsa1 and the second amplified light Bpsb can be made equal.

[0079] (11) According to the first embodiment, each of the first and second pulse stretchers PSa and PSb includes delay optical paths having two or more equal stages to each other.

[0080] According to this, the speckle contrasts SC of the first split light Bpsa1 and the second amplified light Bpsb can be made equal.

[0081] (12) According to the first embodiment, the combination of the optical path lengths of the delay optical paths included in the first pulse stretcher PSa is equal to the combination of the optical path lengths of the delay optical paths included in the second pulse stretcher PSb.

[0082] According to this, the pulse time widths and the speckle contrasts SC of the first split light Bpsa1 and the second amplified light Bpsb can be made equal.

[0083] (13) According to the first embodiment, the beam combiner COM combines the first split light Bpsa1 and the second amplified light Bpsb with an extended pulse width by bringing their optical paths close to each other, and emits the combined light Bpsa1 + Bpsb.

[0084] According to this, even if the wavelengths and polarization directions of the first split light Bpsa1 and the second amplified light Bpsb are the same, the combined light Bpsa1 + Bpsb can be generated.

[0085] In other respects, the first embodiment is the same as the comparative example.

[0086] 3. Laser device 100b for extending the pulse width of the combined light Bpsa1 + Bpsb 3.1 Configuration FIG. 5 schematically shows the configuration of the laser device 100b according to the second embodiment. The laser device 100b includes a third pulse stretcher PSc disposed in the optical path of the combined light Bpsa1 + Bpsb. The third pulse stretcher PSc extends the pulse width of the combined light Bpsa1 + Bpsb and emits it as combined light Bpsc.

[0087] In the second embodiment, since the third pulse stretcher PSc is added, it is desirable that the number of stages of the delay optical paths of the first and second pulse stretchers PSa and PSb be as small as possible with 1 as the lower limit. By including the additional necessary number of stages of delay optical paths in the third pulse stretcher PSc other than the delay optical paths of the first and second pulse stretchers PSa and PSb, the number of delay optical paths included in the laser device 100b can be reduced. Therefore, it is desirable that the number of stages of the delay optical paths included in each of the first and second pulse stretchers PSa and PSb be equal to or less than the number of stages of the delay optical paths included in the third pulse stretcher PSc. Also, it is desirable that the number of stages of the delay optical paths included in the first and second pulse stretchers PSa and PSb be equal to each other. Furthermore, it is desirable that the difference in the optical path lengths of the first and second pulse stretchers PSa and PSb be smaller than either the difference in the optical path lengths of the first and third pulse stretchers PSa and PSc or the difference in the optical path lengths of the second and third pulse stretchers PSb and PSc.

[0088] It is desirable that the optical path length of each of the first and second pulse stretchers PSa and PSb is longer than the optical path length of the delay optical path included in the third pulse stretcher PSc. When the third pulse stretcher PSc includes a multi-stage delay optical path, it is desirable that the optical path length of each of the first and second pulse stretchers PSa and PSb is longer than the optical path length of the longest delay optical path among the delay optical paths included in the third pulse stretcher PSc.

[0089] 3.2 Operation FIG. 6 is a time chart showing the oscillation trigger signal and the pulse time waveform of the laser light of each part of the laser device 100b according to the second embodiment. Since the optical path length of the first pulse stretcher PSa is longer than the optical path length of the third pulse stretcher PSc, the time T3 for the first amplified light Bpoa to make one round of the delay optical path included in the first pulse stretcher PSa is longer than the time T4 for the combined light Bpsa1 + Bpsb to make one round of the delay optical path included in the third pulse stretcher PSc.

[0090] Since the optical path lengths of the first and second pulse stretchers PSa and PSb are long, the processor 130 can make the time T2 from when the oscillation trigger signal Tpoa is output to the first amplifier POa until when the oscillation trigger signal Tpob is output to the second amplifier POb long. It is desirable that the time T2 is longer than the time T3.

[0091] 3.3 Function (14) According to the second embodiment, the laser device 100b further includes a third pulse stretcher PSc that extends the pulse width of the combined light Bpsa1 + Bpsb in addition to the components of the laser device 100a.

[0092] According to this, instead of adding the third pulse stretcher PSc, the optical path length and the number of stages of each of the first and second pulse stretchers PSa and PSb can be reduced. Therefore, the total optical path length and the total number of stages of the first, second, and third pulse stretchers PSa, PSb, and PSc can be reduced.

[0093] (15) According to the second embodiment, each of the first and second pulse stretchers PSa and PSb includes a delay optical path having a number of stages equal to or less than the number of stages of the delay optical path included in the third pulse stretcher PSc.

[0094] According to this, since the number of stages of the delay optical path of each of the first and second pulse stretchers PSa and PSb is further reduced, the total number of stages of the delay optical paths of the first, second, and third pulse stretchers PSa, PSb, and PSc can be reduced.

[0095] (16) According to the second embodiment, each of the first and second pulse stretchers PSa and PSb includes a delay optical path having the same number of stages as each other.

[0096] According to this, the speckle contrast SC of the first split light Bpsa1 and the second amplified light Bpsb can be made equal.

[0097] (17) According to the second embodiment, the difference in optical path length between the first and second pulse stretchers PSa and PSb is smaller than either the difference in optical path length between the first and third pulse stretchers PSa and PSc or the difference in optical path length between the second and third pulse stretchers PSb and PSc.

[0098] The configuration of the first pulse stretcher PSa suitable for combination with the third pulse stretcher PSc is considered to be also suitable as the configuration of the second pulse stretcher PSb. By reducing the difference in optical path length between the first and second pulse stretchers PSa and PSb, the pulse time waveforms of both the first split light Bpsa1 and the second amplified light Bpsb with the pulse width extended can be made into ideal waveforms.

[0099] (18) According to the second embodiment, each of the optical path length of the first pulse stretcher PSa and the optical path length of the second pulse stretcher PSb is longer than the optical path length of the third pulse stretcher PSc.

[0100] According to this, the time difference between the first split light Bpsa1 and the second amplified light Bpsb can be increased, and the pulse width of the combined light Bpsa1 + Bpsb can be increased.

[0101] (19) According to the second embodiment, the laser device 100b includes a processor 130. The processor 130 is configured to output oscillation trigger signals Tpoa and Tpob to the first and second amplifiers POa and POb, respectively. The time T2 from when the oscillation trigger signal Tpoa is output to the first amplifier POa until when the oscillation trigger signal Tpob is output to the second amplifier POb is longer than the time T3 for the first amplified light Bpoa to travel one round through the delay optical path included in the first pulse stretcher PSa.

[0102] According to this, by greatly shifting the amplification timings in the first and second amplifiers POa and POb, the pulse width of the combined light Bpsa1 + Bpsb can be increased when the first split light Bpsa1 and the second amplified light Bpsb are combined.

[0103] In other respects, the second embodiment is the same as the first embodiment.

[0104] 4. Others 4.1 Control of Applied Voltage FIG. 7 is a flowchart of the control of the applied voltage executed by the processor 130 in the first and second embodiments. In FIG. 7, the following five controls are collectively described as the control of the applied voltage HV based on the energy E of the laser light. (a) Control of the applied voltage HVmo of the oscillator MO based on the energy of the seed light Bmo measured by the energy sensor Emo (b) Control of the applied voltage HVpoa of the first amplifier POa based on the energy of the first split light Bpsa1 measured by the first energy sensor Epoa (c) Control of the applied voltage HVpob of the second amplifier POb based on the energy of the second amplified light Bpob measured by the second energy sensor Epob (d) Control of the applied voltage HVpoa of the first amplifier POa based on the energy of the first part of the combined light Bpsa1 + Bpsb measured by the energy sensor Ecom (e) Control of the applied voltage HVpob of the second amplifier POb based on the energy of the second part of the combined light Bpsa1 + Bpsb measured by the energy sensor Ecom

[0105] In S1, the processor 130 obtains the result of measuring the energy E of the laser light while changing the applied voltage HV, and calculates the slope k of the energy E with respect to the applied voltage HV. This calculation is performed at regular intervals.

[0106] In S2, the processor 130 outputs an oscillation trigger signal to output one pulse of laser light.

[0107] In S3, the processor 130 obtains the measurement result of the energy E of the laser light and calculates the difference ΔE from the target value.

[0108] In S4, the processor 130 calculates the correction amount ΔHV of the applied voltage HV by the following formula. ΔHV = ΔE / k

[0109] In S5, the processor 130 corrects the applied voltage HV of the next pulse using the correction amount ΔHV.

[0110] After S5, the processor 130 returns the process to S2. In this way, the applied voltage HV is controlled so that the energy E of the laser light approaches the target value.

[0111] 4.2 Configuration of the beam combiner COM FIG. 8 shows a first configuration example of the beam combiner COM used in the first and second embodiments. The beam combiner COM according to the first configuration example includes a prism mirror 51 coated with a high reflection film 511.

[0112] The first split light Bpsa1 and the second amplified light Bpsb enter the beam combiner COM through optical paths perpendicular to each other. The high-reflection surface coated with the high-reflection film 511 is inclined at 45 degrees with respect to both the first split light Bpsa1 and the second amplified light Bpsb. The high-reflection surface of the prism mirror 51 and another surface form a ridge line 510 at an angle of 45 degrees or less. The second amplified light Bpsb does not enter the prism mirror 51 and passes through a position as close as possible to the ridge line 510 of the prism mirror 51. The first split light Bpsa1 is incident on a position as close as possible to the ridge line 510 of the high-reflection surface and is reflected in a direction parallel to the second amplified light Bpsb. Thereby, the first split light Bpsa1 and the second amplified light Bpsb can be brought close to each other.

[0113] FIG. 9 shows a second configuration example of the beam combiner COM used in the first and second embodiments. The beam combiner COM according to the second configuration example has a configuration in which a high-reflection film 521 is coated on a part of a planar substrate 52 that is transparent to the second amplified light Bpsb, and an antireflection film is coated on another part.

[0114] The first split light Bpsa1 and the second amplified light Bpsb enter the planar substrate 52 through optical paths perpendicular to each other. The high-reflection surface coated with the high-reflection film 521 is inclined at 45 degrees with respect to both the first split light Bpsa1 and the second amplified light Bpsb. The second amplified light Bpsb passes through a position as close as possible to the boundary between the part coated with the antireflection film and the part coated with the high-reflection film 521. The first split light Bpsa1 is incident on a position as close as possible to the boundary between the part coated with the high-reflection film 521 and the part coated with the antireflection film and is reflected in a direction parallel to the second amplified light Bpsb. Thereby, the first split light Bpsa1 and the second amplified light Bpsb can be brought close to each other.

[0115] 4.3 Supplementary The above description is intended as an illustration only and not a limitation. Accordingly, it will be apparent to those skilled in the art that changes may be made to the embodiments of the present disclosure without departing from the scope of the claims. It will also be apparent to those skilled in the art that the embodiments of the present disclosure may be used in combination.

[0116] The terms used throughout this specification and the claims should be construed as “non-limiting” terms unless otherwise specified. For example, terms such as “including,” “having,” “comprising,” “containing,” etc. should be construed as not excluding the presence of components other than those described. Also, the modifier “one” should be construed to mean “at least one” or “one or more.” Also, the term “at least one of A, B, and C” should be construed as “A,” “B,” “C,” “A + B,” “A + C,” “B + C,” or “A + B + C.” Furthermore, it should be construed to include combinations with things other than “A,” “B,” and “C.”

Claims

1. An oscillator that emits pulsed seed light, A first amplifier that amplifies the seed light and emits first amplified light, A first pulse stretcher that stretches the pulse width of the first amplified light, A beam splitter that splits the first amplified light with its pulse width stretched into a first split light and a second split light having less energy than the first split light, A second amplifier that amplifies a part of the second split light and emits second amplified light, A second pulse stretcher that stretches the pulse width of the second amplified light, A beam combiner that emits combined light obtained by combining the first split light and the second amplified light with its pulse width stretched, A laser device comprising the above.

2. The laser device according to Claim 1, Further comprising a processor, The processor controls the amplification timing in the second amplifier so that the second amplifier amplifies the part included in the latter half of the pulse time waveform of the second split light. Laser device.

3. The laser device according to Claim 2, The energy difference between the first split light and the second amplified light with its pulse width stretched is smaller than the energy difference between the first and second split lights. Laser device.

4. The laser device according to Claim 1, Further comprising a processor, The processor is configured to output oscillation trigger signals to the oscillator and the first and second amplifiers respectively, and the time from when the oscillation trigger signal is output to the oscillator to when the oscillation trigger signal is output to the first amplifier is shorter than the time from when the oscillation trigger signal is output to the first amplifier to when the oscillation trigger signal is output to the second amplifier. Laser device.

5. The laser device according to Claim 1, The energy of the second split light is greater than the energy of the seed light. Laser device.

6. The laser device according to Claim 1, A first energy sensor that measures the energy of the first split light, A second energy sensor that measures the energy of the second amplified light with its pulse width stretched, A processor, Further comprising, The processor controls the applied voltage of the first amplifier based on the measurement result by the first energy sensor, and controls the applied voltage of the second amplifier based on the measurement result by the second energy sensor. Laser device.

7. The laser device according to claim 1, an energy sensor that measures the pulse time waveform of the combined light, a processor, further comprising, the processor calculates the energy of a first portion included in the first half of the pulse time waveform and the energy of a second portion included in the second half of the pulse time waveform, controls the applied voltage of the first amplifier based on the energy of the first portion, and controls the applied voltage of the second amplifier based on the energy of the second portion. Laser device.

8. The laser device according to claim 1, the energy of the first amplified light with an extended pulse width is greater than the energy of the second amplified light with an extended pulse width Laser device.

9. The laser device according to claim 1, the first split light is the light transmitted through the beam splitter, the second split light is the light reflected by the beam splitter, the transmittance of the beam splitter is 80% or more and 96% or less Laser device.

10. The laser device according to claim 1, the optical path lengths of the delay optical paths included in the first and second pulse stretchers are equal to each other Laser device.

11. The laser device according to claim 1, each of the first and second pulse stretchers includes two or more delay optical paths with equal stages to each other Laser device.

12. The laser device according to claim 11, the combination of the optical path lengths of the delay optical paths included in the first pulse stretcher is equal to the combination of the optical path lengths of the delay optical paths included in the second pulse stretcher Laser device.

13. The laser device according to claim 1, the beam combiner combines the optical paths of the first split light and the second amplified light with an extended pulse width to emit the combined light by bringing them close to each other Laser device.

14. The laser device according to claim 1, a third pulse stretcher that extends the pulse width of the combined light Laser device further comprising.

15. The laser device according to claim 14, each of the first and second pulse stretchers includes a number of delay optical paths equal to or less than the number of stages of the delay optical paths included in the third pulse stretcher Laser device.

16. The laser device according to claim 15, each of the first and second pulse stretchers includes the same number of delay optical paths as each other Laser device.

17. The laser device according to claim 14, The difference in the optical path lengths of the first and second pulse stretchers is smaller than either the difference in the optical path lengths of the first and third pulse stretchers or the difference in the optical path lengths of the second and third pulse stretchers. Laser device.

18. The laser device according to claim 14, Each of the optical path length of the first pulse stretcher and the optical path length of the second pulse stretcher is longer than the optical path length of the third pulse stretcher. Laser device.

19. The laser device according to claim 14, Further comprising a processor, The processor is configured to output an oscillation trigger signal to each of the first and second amplifiers, and the time from when the oscillation trigger signal is output to the first amplifier until when the oscillation trigger signal is output to the second amplifier is longer than the time for the first amplified light to make one round of the delay optical path included in the first pulse stretcher. Laser device.

20. A method for manufacturing an electronic device, comprising: An oscillator that emits pulsed seed light; A first amplifier that amplifies the seed light and emits first amplified light; A first pulse stretcher that stretches the pulse width of the first amplified light; A beam splitter that splits the first amplified light with an extended pulse width into a first split light and a second split light having less energy than the first split light; A second amplifier that amplifies a part of the second split light and emits second amplified light; A second pulse stretcher that stretches the pulse width of the second amplified light; A beam combiner that emits combined light obtained by combining the first split light and the second amplified light with an extended pulse width; Generating laser light by a laser device including the above components, Outputting the laser light to an exposure device, Exposing the laser light onto a photosensitive substrate in the exposure device to manufacture the electronic device. A method for manufacturing an electronic device including the above steps.

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