JP2004111765A - Narrow-band laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a narrow-band laser device having stable spectrum characteristics. <P>SOLUTION: This narrow-band laser device comprises narrow-band optical devices (32, 33) for setting the wavelength of laser beams (21) as a narrow band, and further comprises a heat transfer preventing means, such as a heat insulator (38) or the like for preventing heat from transferring from at least one heat generation source out of a laser chamber (12), into which a laser medium is sealed; a drive means (36) for driving an air blower in the laser chamber (12); and a cooling pipe (39) for flowing a coolant to a heat exchanger (13) in the laser chamber (12), to the narrow-band optical devices (32, 33) or a narrow-band box (31) for enclosing the narrow-band optical devices (32, 33). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a narrow-band laser device having a narrow wavelength.
[0002]
[Prior art]
Conventionally, in a narrow-band laser device such as an excimer laser device in which the wavelength is narrow, a technology is known in which the temperature change of the narrow-band optical element and the gas around it is reduced to suppress wavefront disturbance. I have. (See, for example, Patent Document 1.) FIG. 15 shows an excimer laser device according to the related art disclosed in the publication, and the related art will be described below with reference to FIG.
[0003]
In FIG. 15, an excimer laser device 11 includes a laser chamber 12 in which a laser gas containing fluorine is sealed. Windows 17 and 19 for transmitting a laser beam 21 are respectively provided at front and rear portions of the laser chamber 12.
The main electrodes 14 and 15 are disposed inside the laser chamber 12 so as to be perpendicular to the plane of the drawing, and discharge is generated between the main electrodes 14 and 15 to excite a laser gas to generate a laser beam 21.
[0004]
The generated laser beam 21 is incident on the inside of the narrow-band box 31 attached to the rear of the laser chamber 12 (to the right in FIG. 15).
Inside the band narrowing box 31, for example, two prisms 32, 32 and a grating 33 are provided.
The laser beam 21 is expanded in beam width by the prisms 32 and 32, is diffracted by the diffraction surface 33A of the grating 33, and is turned back only at a predetermined center wavelength and a wavelength near the predetermined center wavelength. Thereby, the bandwidth of the laser light 21 is narrowed.
[0005]
The laser light 21 having the narrowed band is amplified between the main electrodes 14 and 15 while the reflection between the front mirror 16 and the grating 33 is repeated. Then, a part thereof partially transmits through the front mirror 16 and is emitted forward.
A beam splitter 22 is disposed in front, samples a part of the laser light 21, and monitors a center wavelength and a spectral line width by a wavelength measuring device 35.
[0006]
At least one of the grating 33 and the prisms 32, 32 is mounted on a rotatable rotary stage (not shown). The laser controller 29 outputs a command to the rotating stage based on the detection result of the wavelength measuring device 35, and performs control so that the center wavelength and the spectral line width of the laser light 21 become target values. This is called wavelength control.
In some cases, a mirror (not shown) is interposed between the grating 33, the prisms 32, 32, and the like, and the mirror is rotated by a rotary stage to perform wavelength control.
[0007]
At this time, the laser light 21 is irregularly reflected on the surfaces of optical elements such as the prisms 32 and 32 and the grating 33 inside the band narrowing box 31 or is absorbed by the optical element, so that the optical element, particularly the grating 33 is formed. The nearby temperature gradually rises. As a result, the refractive index of air in the vicinity of the diffraction surface 33A of the grating 33 becomes non-uniform, and the wavefront of the laser light 21 is disturbed, and the spectral characteristics and the beam profile become unstable.
[0008]
The spectral characteristics at this time refer to, for example, the center wavelength, the spectral line width, or the spectral purity. The spectral purity is one of the indices indicating the shape of the wavelength intensity distribution, and indicates a wavelength width in which, for example, 95% of the total energy of the laser light 21 falls.
[0009]
In order to prevent such disturbance of the wavefront, a purge gas ejection port 54 for ejecting a clean and low-reactivity purge gas such as nitrogen gas is provided inside the band narrowing box 31. The purge gas continuously ejected from the purge gas ejection port 54 is blown onto the back surface 33B of the grating 33 to cool the grating 33 heated by the laser light 21. The inside of the band narrowing box 31 is filled with a purge gas.
This prevents the temperature rise of the grating 33 and the instability of the wavefront due to the fluctuation of the gas near the diffraction surface 33A due to the laser light 21, thereby improving the beam profile and the spectral characteristics.
[0010]
Further, the purge gas is caused to flow in an air curtain shape in parallel with the diffraction surface 33A of the grating 33. As a result, heat on the diffraction surface 33A of the grating 33 is removed, thereby preventing the wavefront from becoming unstable (see, for example, Patent Document 2).
[0011]
[Patent Document 1]
Japanese Patent No. 2696285 (FIG. 1)
[Patent Document 2]
JP 2001-135883 A (FIGS. 6A to 6C)
[0012]
[Problems to be solved by the invention]
However, the conventional technique has the following problems.
That is, these conventional techniques are intended to prevent the temperature of the gas in the vicinity of the grating 33 from rising due to the irradiation of the laser beam 21. As a means, a purge gas is externally introduced and blown into the grating 33. I'm wearing it.
[0013]
FIG. 16 is a graph showing a change in the full width at half maximum (FWMH) of the spectrum waveform of the laser beam 21 in the conventional technique. In FIG. 16, the horizontal axis represents the time t elapsed from the time t0 when the oscillation of the excimer laser device 11 starts, and the vertical axis represents the change in the full width at half maximum of the spectrum waveform.
The three waveforms shown at the bottom of the graph show spectrum waveforms at times t0, t1, and t2, respectively. The horizontal axis is the wavelength λ, and the vertical axis is the light intensity for that wavelength.
As shown in FIG. 16, the full width at half maximum of the spectrum waveform gradually increases from time t0 to time t1. Then, the distance gradually becomes smaller between the time t1 and the time t2, and almost returns to the original state.
[0014]
In the prior art, the above method is used to avoid the temperature rise of the grating 33 and the instability of the spectrum shape due to the fluctuation of the gas near the diffraction surface 33A. Despite this, actually, as shown in FIG. 16, instability of the full width at half maximum of the spectrum waveform, that is, instability of the spectrum shape occurs. In particular, the tendency is remarkable immediately after the excimer laser device 11 is started.
Although only the full width at half maximum is shown in the graph shown in FIG. 16, it has been found that other spectral characteristics such as spectral purity also deteriorate.
[0015]
The present invention has been made in view of the above problem, and has as its object to provide a narrow-band laser device having a stable spectral characteristic.
[0016]
Means for Solving the Problems, Functions and Effects
As a result of the inventor's earnest research, the occurrence of the above-mentioned instability of the spectrum shape is caused by the heat from the heat source such as the laser chamber 12 arranged near the outside of the narrow-band narrowing box 31. 31 has been found to be caused by receiving it.
[0017]
FIG. 3 shows a plan view of the excimer laser device 11. In FIG. 3, a heat insulating material 38 is adhered around the laser chamber 12.
FIG. 14 is a graph showing the result of examining the change in the full width at half maximum of the spectral waveform of the laser beam 21 when the heat from the heat source is hardly transmitted to the band narrowing box 31 in this manner. In FIG. 14, the horizontal axis indicates the time t elapsed from the time t0 when the oscillation of the excimer laser device 11 starts, and the vertical axis indicates the change in the full width at half maximum of the spectrum waveform.
[0018]
As shown in FIG. 14, even when the time elapses from t0 to t2, the full width at half maximum of the spectrum waveform hardly changed. This is more apparent when compared with FIG. 16 in the prior art in which the heat insulating material 38 was not used. Although only the full width at half maximum is shown in the graph shown in FIG. 14, it has been found that other spectral characteristics such as spectral purity are also good.
That is, if the heat from the heat source outside the narrowing box 31 in which the narrowing optical components such as the prisms 32 and 32 and the grating 33 are housed is not transmitted to the narrowing box 31, the spectral waveform becomes Stability is improved.
[0019]
The mechanism of the cause of the change in the spectral characteristics as shown in FIG. 16 is not known in detail, but is presumed as follows.
That is, when the heat from the heat source is transmitted to the band-narrowing box 31 and the band-narrowing box 31 is heated, the band-narrowing box 31 is not necessarily heated uniformly, but may be heated unevenly. It is considered highly likely.
[0020]
FIG. 17 shows a model diagram of the temperature distribution in which the inside of the band narrowing box 31 is shown in a plan view. As shown in FIG. 17, it is considered that a high-temperature region 74 locally exists inside the band-narrowing box 31 due to heating from the heat source.
If the high-temperature region 74 exists near the grating 33 or the optical path, a temperature difference occurs between the gas in the vicinity of the high-temperature region 74 and the gas in a region other than the vicinity of the high-temperature region 74. The gas in the narrowing box 31 corresponds to air or a purge gas when the inside of the narrowing box 31 is purged.
As a result, the density distribution of the gas becomes non-uniform in some places. Furthermore, partial gas convection also occurs due to the temperature difference, which is considered to further make the gas density distribution non-uniform.
[0021]
FIG. 18 is a graph showing the lapse of time at the temperatures A, B, and C in the optical path in the model diagram shown in FIG. The vertical axis is temperature and the horizontal axis is time t. As shown in FIG. 17, each of the points A, B, and C has a different distance from the high-temperature region 74. Therefore, as shown in FIG. 18, the degree of temperature rise at each point is different (point C near the high temperature region 74 is fast, and point A far away is slow).
As a result, it is considered that a difference in gas density occurs between the points A, B, and C, and that convection generated by a temperature difference between the points A, B, and C also causes gas fluctuation. Therefore, it is considered that the gas density in the optical path of the laser light 21 becomes non-uniform, the wavefront of the laser light 21 passing through the optical path becomes unstable, and the beam profile and the spectral characteristics become unstable.
Such non-uniformity of the refractive index has a greater effect on the wavefront disturbance in the vicinity of the grating 33 where the beam width is widened.
[0022]
In addition, when the band-narrowing optical elements such as the grating 33 and the prisms 32 and 32 are heated from a lower heat source, the temperature becomes higher than the surroundings and the gas is locally heated, thereby reducing the refractive index nonuniformity. May bring.
Further, it is considered that not only gas but also optical elements such as the prisms 32 and 32 through which the laser light 21 passes are heated, and the refractive index may become non-uniform in the inside.
[0023]
FIG. 19 is a graph in which the change in the full width at half maximum of the spectrum waveform of the laser light 21 is made to correspond to the time axis t in FIG. 18, and is a model diagram of the change in the spectrum waveform shown in FIG. In FIG. 19, the horizontal axis represents the elapsed time t from the time t0 when the oscillation of the excimer laser device 11 starts, and the vertical axis represents the full width at half maximum of the spectrum waveform.
As shown in FIG. 19, the full width at half maximum of the spectrum waveform gradually increases from time t0 to time t1. Then, the distance gradually becomes smaller between the time t1 and the time t2, and almost returns to the original state.
[0024]
The reason why the full width at half maximum of the spectrum waveform increases from time t0 to time t1 is considered as follows.
The temperature rise characteristics in the narrowing box 31 caused by heat from a heat source outside the narrowing box 31 are different at points A, B, and C in FIG. 17, for example. In particular, since the temperature rise of the heat source starts at time t0 when the oscillation of the excimer laser device 11 starts, the difference in the temperature rise characteristics at the points A, B, and C until time t1 is particularly large. As a result, the temperature difference between the points A, B, and C increases. Therefore, it is considered that the density distribution of the gas between the points A, B, and C becomes non-uniform, and the fluctuation of the gas due to the convection caused by the temperature difference is also large.
Therefore, from time t0 to time t1, the wavefront of the laser beam 21 passing through the optical path is also unstable, and the instability of the beam profile, the spectral characteristics, and the like is increased, so that the full width at half maximum of the spectrum waveform is increased.
[0025]
Thereafter, when the time t1 has elapsed, the temperature rises at the points A, B, and C begin to ease, and the temperature eventually saturates so as to converge to a certain temperature, and the temperature difference between the points A, B, and C decreases. This indicates that the temperature non-uniformity near the optical path inside the band narrowing box 31 is reduced.
Thus, after time t1, the instability of the wavefront of the laser light 21 passing through the optical path also gradually decreases. As a result, it is considered that the beam profile and the spectral characteristics become stable, and the full width at half maximum of the spectral waveform approaches a predetermined target value.
[0026]
On the other hand, FIG. 20 shows temperature changes at points A, B, and C when the heat insulating material 38 is attached around the laser chamber 12 as shown in FIG. The horizontal axis indicates the time t elapsed from the time t0 when the oscillation of the excimer laser device 11 starts, and the vertical axis indicates the change in the full width at half maximum of the spectrum waveform.
As shown in FIG. 20, by making it difficult for the heat from the heat source to be transmitted to the band-narrowing box 31, the high-temperature region 74 caused by the external heat source in the model diagram shown in FIG. 17 becomes very small. As a result, the temperature difference between the points A, B, and C becomes very small, and shows substantially the same temperature change.
[0027]
FIG. 21 is a graph in which the change in the full width at half maximum of the spectral waveform of the laser light 21 is made to correspond to the time axis t in FIG. 20, and is a model diagram in FIG. As shown in FIG. 21, the full width at half maximum of the spectrum waveform hardly changes even when the time elapses from t0 to t2.
That is, as shown in FIG. 20, the degree of temperature rise at each of the points A, B, and C is substantially the same, so that the difference in gas density between the points A, B, and C becomes small. Further, since the temperature difference between the points A, B, and C is small, the convection between the points A, B, and C is small, and it is considered that the fluctuation of the gas hardly occurs. As a result, the instability of the wavefront of the laser light 21 passing through the optical path is reduced, and the beam profile and the spectral characteristics are stabilized. Therefore, it is considered that the full width at half maximum of the spectral waveform is close to a predetermined target value.
[0028]
Conventionally, only the effect of heating by the laser beam 21 passing through the optical path is considered, and the effect of heating on the band-narrowing box 31 by heat transmitted from an external heat source has not been considered. Therefore, even if the purge gas is blown to the grating 33 as in the related art, the fluctuation of the spectral characteristics occurs.
As described above, the present invention provides a narrow-band laser device having stable spectral characteristics by preventing heat from an external heat source from being transmitted to the optical path of the narrow-band optical element or the laser beam 21. .
[0029]
That is, in order to achieve the above object, the present invention
In a narrow-band laser device having a narrow-band optical element for narrowing the wavelength of laser light,
At least one of the band-narrowing optical element and the optical path of the laser beam is provided with a heat transfer preventing unit for preventing heat from being transmitted from a heat source.
Accordingly, in the optical path of the laser light near the band-narrowing optical element, non-uniform refractive index caused by non-uniform heating due to heat transmitted from the heat source is less likely to occur, and wavefront disturbance is reduced.
[0030]
The invention also includes a band-narrowing box surrounding the band-narrowing optical element.
When the band-narrowing optical element is inside the band-narrowing box, the non-uniform refractive index caused by the non-uniform heating described above is likely to occur. Therefore, the effect of the present invention is high.
[0031]
Further, the present invention is a heat insulating means for blocking heat, wherein the heat transfer preventing means is provided between the band-narrowing optical element and a heat source.
This makes it difficult for the narrow-band optical element and the optical path in the vicinity thereof to be warmed, and for the refractive index to be non-uniform due to non-uniform heating due to heat transmitted from the heat source.
[0032]
Further, in the present invention, the heat insulating means is installed near a band narrowing box. Thereby, no matter where the heat source is located, it is possible to reliably prevent the heat from being transmitted to the band narrowing box.
[0033]
In the present invention, the heat insulating means is provided near a heat source.
Thus, for example, even when the band-narrowing optical element is present at a plurality of locations, it is not necessary to increase the number of heat insulating units.
[0034]
In the present invention, the heat insulating means is a heat insulating material.
The heat insulating material is inexpensive and easy to handle, and has a large heat insulating effect.
[0035]
Further, according to the present invention, the heat insulating means is a pipe through which a refrigerant flows.
Thereby, the heat insulation effect is large, and the heat can be more reliably prevented from being transmitted to the band-narrowing optical element.
[0036]
In the present invention, the temperature of the refrigerant is controlled to be substantially constant.
Thereby, the heat insulation effect is large, and the heat can be more reliably prevented from being transmitted to the band-narrowing optical element.
[0037]
Further, according to the present invention, the heat insulating means is a vacuum container having a vacuum inside.
Thereby, the heat insulation effect is large, and the heat can be more reliably prevented from being transmitted to the band-narrowing optical element.
[0038]
Further, in the present invention, the heat insulating means is a hollow container in which a constant temperature gas having a substantially constant temperature flows.
Thereby, the heat insulation effect is large, and the heat can be more reliably prevented from being transmitted to the band-narrowing optical element.
[0039]
Also, in the present invention, the heat transfer preventing means prevents the flow of air passing around the heat source from reaching the band-narrowing optical element or the band-narrowing box.
Thereby, the air warmed by the heat source rarely reaches the band-narrowing optical element, and the band-narrowing optical element is hardly heated.
[0040]
Further, the present invention is the heat insulating material, wherein the heat transfer preventing means is arranged so as to prevent a flow of air passing around the heat source from reaching the band-narrowing optical element or the band-narrowing box.
The heat insulating material is inexpensive and easy to handle, and has a large heat insulating effect.
[0041]
Further, in the present invention, the heat transfer preventing means passes around the heat source after the flow of the air passes around the narrow band optical element or the narrow band box.
Thereby, heat is less carried by the flow of air, and the band-narrowing optical element is less likely to be heated.
[0042]
Further, according to the present invention, the heat transfer preventing means includes a driving means for driving a blower inside the laser chamber, and at least one of a cooling pipe for flowing a refrigerant to a heat exchanger inside the laser chamber, and a narrow band optical element. On the other hand, it is arranged on the opposite side with respect to the laser chamber in which the laser medium is sealed.
As a result, the distance from the cooling pipe or the driving means, which is a heat source, to the band-narrowing optical element becomes longer, so that heat is hardly transmitted.
[0043]
Further, according to the present invention, the heat source is at least one of a laser chamber in which a laser medium is sealed, a driving unit for driving a blower inside the laser chamber, and a cooling pipe for flowing a refrigerant to a heat exchanger inside the laser chamber. .
These heat sources generate a particularly large amount of heat, and have a great effect of reducing the disturbance of the wavefront by preventing heat transfer to the band-narrowing optical element.
[0044]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, a first embodiment will be described. FIG. 1 is a plan view of a narrow-band excimer laser device 11 (hereinafter, referred to as an excimer laser device 11) shown as an example of a narrow-band laser device according to the first embodiment, and FIG. is there. 1 and 2, an excimer laser device 11 includes a laser chamber 12 in which a laser gas containing fluorine is sealed.
[0045]
Windows 17 and 19 for transmitting a laser beam 21 are provided at the front (right side in FIG. 1) and rear of the laser chamber 12 at Brewster angles with respect to the longitudinal direction of the laser chamber 12, respectively. .
[0046]
At the front and rear of the laser chamber 12, cavity plates 40, 40 are installed substantially parallel to each other. The cavity plates 40 are connected by three invar rods 41 extending along the longitudinal direction of the laser chamber 12. The cavity plates 40, 40 and the laser chamber 12 are connected by bellows 55, 55, respectively. The cavity plates 40, 40 are provided with through holes (not shown) through which the laser light 21 passes.
[0047]
The main electrodes 14 and 15 are disposed inside the laser chamber 12 so as to face each other, and a main discharge is generated between the main electrodes 14 and 15 to excite a laser gas to generate a laser beam 21.
The generated laser light 21 is incident on the inside of the narrow-band box 31 fixed to the cavity plate 40 on the rear side of the laser chamber 12.
[0048]
Inside the band narrowing box 31, for example, two prisms 32, 32 and a grating 33 are provided. The grating 33 is mounted on a rotary stage 56 for performing the wavelength control. 65 is a holder for supporting the prism 32.
The laser beam 21 is expanded in beam width by the prisms 32 and 32, is diffracted by the diffraction surface 33A of the grating 33, and is turned back only at a predetermined center wavelength and a wavelength near the predetermined center wavelength. Thereby, the wavelength of the laser light 21 is narrowed.
[0049]
As shown in FIG. 1, the narrow band box 31 is provided with a purge gas inlet 57 for introducing a low-reactivity and clean purge gas and a purge gas outlet 58 for discharging the purge gas. As indicated by an arrow 59, a purge gas is continuously introduced from the purge gas introduction port 57, and the inside of the band narrowing box 31 is always filled with the purge gas.
As the purge gas, for example, nitrogen is suitable, but other than that, an inert gas may be used.
[0050]
The laser light 21 having the narrowed band is amplified between the main electrodes 14 and 15 while the reflection between the front mirror 16 and the grating 33 is repeated. Then, a part thereof partially transmits through the front mirror 16 and is emitted forward.
[0051]
As shown in FIG. 2, a blower such as a once-through fan 24 and a heat exchanger 13 are provided inside the laser chamber 12. The once-through fan 24 sends fresh laser gas between the main electrodes 14 and 15, and circulates the gas heated by the main discharge to the heat exchanger 13 to cool it.
Cooling pipes 39, 39 are connected to the heat exchanger 13 and reach the outside of the laser chamber 12, and cool the laser gas by flowing a coolant such as cooling water into the inside.
[0052]
A motor 36 for driving the cross-flow fan 24 is provided on the side wall of the laser chamber 12. The output of the motor 36 is transmitted by the magnetic coupling 37 to the once-through fan 24 inside the laser chamber 12.
[0053]
For example, a sheet-like heat insulating material 38 is attached to at least one outer wall surface of the band narrowing box 31. The heat insulating material 38 prevents heat generated from the motor 36, the cooling pipe 39 of the heat exchanger 13, and the like from being transmitted to the band narrowing box 31, thereby preventing the internal temperature from rising unevenly.
As the heat insulating material 38, a material that does not generate dust or generate organic substances is preferable, and for example, Teflon (registered trademark) is preferable. Other examples of the heat insulating material 38 include a foaming agent, polyurethane, and silicone rubber.
[0054]
In the above embodiment, the heat insulating material 38 is stuck to the outer wall of the band-narrowing box 31. However, for example, the heat insulating material 38 that does not emit impurities when irradiated with the laser beam 21 may be used. Alternatively, it may be attached to the inner wall of the band narrowing box 31. At this time, since the laser beam 21 of the excimer laser device 11 is an ultraviolet ray, the reactivity is high, and care must be taken in selecting the material of the heat insulating material 38 that does not emit impurities. Further, even when the band narrowing laser device is a fluorine molecular laser device, further attention is required because the laser light is ultraviolet light having a shorter wavelength.
Alternatively, the band-narrowing box 31 may be formed using a material having heat insulating properties, for example, ceramics or the like.
[0055]
As described above, according to the first embodiment, the heat insulating material 38 is arranged around the narrow band optical element such as the grating 33 and the prism 32. Thus, the optical path of the band-narrowing optical element and the laser beam 21 is less likely to be unevenly heated, and the refractive index of the gas in the optical path is less likely to be uneven. Therefore, disturbance of the wavefront of the laser light 21 is small, and the beam profile and spectral characteristics are less likely to be unstable.
[0056]
Next, another configuration example according to the first embodiment will be described.
FIG. 3 is a plan view of the excimer laser device 11, and FIG. As shown in FIGS. 3 and 4, a heat insulating material 38 is attached around the laser chamber 12. Further, a heat insulating material 38 is fixed between the motor 36 and the cooling pipe 39 and the band narrowing box 31 by means not shown.
[0057]
In the excimer laser device 11, the laser chamber 12 is the largest heat source. Therefore, heat generated from the surface of the laser chamber 12 may be transmitted to the band-narrowing box 31 to increase the internal temperature.
In order to prevent this, a heat insulating material 38 is stuck around the laser chamber 12 to prevent heat from being transmitted to the band-narrowing box 31.
[0058]
As described above, the motor 36 and the cooling pipe 39 are also heat sources. Therefore, in order to prevent heat from being transmitted from these to the band narrowing box 31 and to heat the inside thereof, a heat insulating material 38 is fixed between the motor 36 and the cooling pipe 39 and the band narrowing box 31. ing.
Alternatively, although not shown, a heat insulating material 38 may be wound around the motor 36 or a heat insulating material 38 may be wound around the cooling pipe 39.
[0059]
That is, the heat insulating material 38 is arranged between the heat source of the excimer laser device 11 and the band narrowing box 31 to prevent heat from being transmitted from these heat sources to the band narrowing box 31. Thereby, the inside of the band narrowing box 31 is less likely to be unevenly heated by the heat transmitted from the heat source. Therefore, the optical paths of the band-narrowing optical elements 31 and 32 and the laser beam 21 are less likely to be unevenly heated, and local refractive index in the optical path is less likely to be uneven, so that the wavefront is also less likely to be disturbed.
[0060]
In the above description, the heat insulating material 38 has been described as being adhered to the laser chamber 12 in close contact with the laser chamber 12. However, the present invention is not limited to this, and the heat insulating material 38 is separated from the outer wall of the laser chamber 12 and fixed by other fixing means. May be.
At this time, as shown in FIG. 3, a heat insulating material 38 may be attached to the cavity plate 40 in order to cut off heat transmitted from the laser chamber 12 to the band narrowing box 31. Further, the cavity plate 40 may be made of a ceramic or the like having a strong heat insulating property.
[0061]
In the case where there is another heat source, the position of the heat insulating material 38 is not limited to the above description, and may be appropriately attached.
Furthermore, it is described that the heat insulating material 38 is arranged between all the heat sources and the band narrowing box 31. Only a heat insulation measure may be taken.
[0062]
Further, instead of the heat insulating material 38, a metal having good heat conductivity such as copper or aluminum may be disposed between the heat source and the band narrowing box 31. Thereby, the heat generated from the heat source spreads in the metal, and heats the band narrowing box 31 more uniformly. That is, the metal serves as a heat equalizing plate, and prevents a local high temperature region 74 from being generated inside the band narrowing box 31.
As a result, the temperature gradient of the gas in the optical path is reduced, the non-uniformity of the refractive index is reduced, and the disturbance of the wavefront is reduced.
[0063]
Next, a second embodiment will be described.
FIG. 5 shows a plan view of the excimer laser device 11 according to the second embodiment, and FIG. 6 shows a front view. As shown in FIGS. 5 and 6, constant temperature water pipes 42 are in contact with upper and lower outer walls of the band narrowing box 31. Constant temperature water (see arrow 60) having substantially the same temperature is always flowing inside the constant temperature water pipe 42.
Alternatively, the hot water pipe 42 may be in contact with another outer wall of the band-narrowing box 31 or may surround the band-narrowing box 31.
[0064]
A temperature control means 68 such as a heater or a cooler and a temperature sensor 69 are provided in a part of the constant temperature water pipe 42, and a temperature control controller 70 controls the temperature based on a signal from the temperature sensor 69. By controlling the operation of the means 68, the temperature of the constant temperature water flowing through the constant temperature water pipe 42 is kept substantially constant. A pump 77 circulates constant temperature water.
[0065]
Thus, the constant-temperature water blocks heat generated from the laser chamber 12, the motor 36, and the cooling pipe 39, which is a heat source, from reaching the band-narrowing box 31.
As a result, a local high-temperature region 74 is less likely to be generated inside the band narrowing box 31, and the temperature gradient of the gas in the optical path is reduced. That is, the nonuniformity of the refractive index is reduced, and the disturbance of the wavefront is reduced.
[0066]
Instead of making the constant temperature water pipe 42 contact with the narrow band box 31, the narrow band box 31 may be surrounded by a hollow water jacket, and constant temperature water may flow inside the water jacket. Alternatively, the wall of the band-narrowing box 31 may have a double structure, and constant-temperature water may flow through the inside of the box.
Further, the constant temperature water pipe 42 does not surround the entire periphery of the band narrowing box 31, but the constant temperature water pipe 42 is interposed between the band narrowing box 31 and the heat source as the heat insulating material 38 in FIG. You may do so.
[0067]
Next, another configuration example of the excimer laser device 11 according to the second embodiment will be described. FIG. 7 is a front view of the excimer laser device 11. As shown in FIG. 7, a hollow water jacket 43 is covered around the laser chamber 12, the motor 36, and the cooling pipe 39, and constant temperature water having substantially the same temperature is always flowed therein. .
Thus, heat generated from heat sources such as the laser chamber 12, the motor 36, and the cooling pipe 39 is absorbed by the constant temperature water in the water jacket 43 and is not transmitted to the band narrowing box 31.
[0068]
As a result, a local high-temperature region 74 is less likely to be generated inside the band narrowing box 31, and the temperature gradient of the gas in the optical path is reduced. That is, the nonuniformity of the refractive index is reduced, and the disturbance of the wavefront is reduced.
Furthermore, since the heat generated from the heat source is taken away by the constant temperature water, the temperature rise in the narrow band box 31 itself is small. Therefore, the nonuniformity of the temperature distribution in the optical path is reduced, and the disturbance of the wavefront is further reduced.
[0069]
Incidentally, the wall surfaces of the laser chamber 12, the motor 36, and the cooling pipe 39 may have a hollow double structure, and constant-temperature water may flow through the inside.
In addition, although the description has been made with reference to the constant temperature water, it is not always necessary to precisely control the temperature, and any water may be used as long as the temperature is substantially constant or changes gradually. For example, tap water can be used. The constant temperature water may be circulated or disposable. Further, a heat medium may be used instead of water.
[0070]
Next, a third embodiment will be described.
FIG. 8 shows a front view of an excimer laser device 11 according to the third embodiment. In FIG. 8, the outside of the band narrowing box 31 is surrounded by a vacuum jacket 44 whose inside is hollow at a vacuum or low pressure.
[0071]
Thereby, the vacuum jacket 44 has a vacuum heat insulating function like a thermos bottle, and the heat transfer from the outside to the inside of the band narrowing box 31 is extremely small. As a result, the manner in which heat is transmitted from the external heat source to the band-narrowing box 31 becomes gentle, and the local high-temperature region 74 is unlikely to be generated inside the band-narrowing box 31. That is, the temperature gradient of the gas in the optical path is reduced, the non-uniformity of the refractive index is reduced, and the disturbance of the wavefront is reduced.
[0072]
Note that the vacuum jacket 44 may not be provided around the entire area of the band narrowing box 31 but may be interposed between the box and the heat source. Further, heat sources such as the laser chamber 12, the motor 36, and the cooling pipe 39 may be surrounded by the vacuum jacket 44.
Instead of enclosing the outside of the narrow-band box 31 and the heat source with the vacuum jacket 44, the walls of the narrow-band box 31 and the heat source may have a double structure and the inside may be evacuated.
[0073]
Next, a fourth embodiment will be described.
FIG. 9 shows a front view of an excimer laser device 11 according to the fourth embodiment. In FIG. 9, the outside of the band narrowing box 31 is surrounded by a hollow air jacket 45. The illustration of the purge gas inlet 57 and the purge gas outlet 58 is omitted.
[0074]
The air jacket 45 is provided with a gas inlet 46 for introducing a constant-temperature gas (see arrow 62) having a substantially constant temperature and a gas outlet 47 for discharging the constant-temperature gas.
A constant temperature gas pipe 78 for flowing a constant temperature gas is connected to the gas introduction port 46 and the gas discharge port 47, and the constant temperature gas pipe 78 is connected to a temperature control means 71 such as a heater or a cooler. I have. 79 is a blower for circulating a constant temperature gas. The temperature control controller 73 controls the operation of the temperature control means 71 based on a signal from the temperature sensor 72 attached to the constant temperature gas pipe 78 so that the gas flowing through the constant temperature gas pipes 78 and 78 is converted into a constant temperature gas. Adjust the temperature so that
[0075]
By continuously flowing the constant temperature gas through the air jacket 45, heat generated from the heat source is cut off by the air jacket 45 before being transmitted to the narrow band box 31, and is discharged together with the constant temperature gas. Thus, it is possible to prevent the temperature of the band-narrowing box 31 from rising non-uniformly and to reduce the disturbance of the wavefront.
Further, since the heat generated from the heat source is taken away by the constant temperature gas, the temperature inside the band narrowing box 31 is lowered, and the disturbance of the wavefront is further reduced.
[0076]
As the constant temperature gas, air, nitrogen, or the like is preferable.
At this time, it is preferable that the gas flows so as to pass uniformly around the band-narrowing box 31 so that a stagnant portion is not formed as much as possible in the flow of the constant temperature gas. For example, as shown in FIG. 10, an appropriate partition plate 48 may be provided inside the air jacket 45 so that the constant temperature gas spirally flows around the narrow band box 31.
Alternatively, an air curtain-like flow of a constant-temperature gas may be generated between the motor 36 or the cooling pipe 39, which is a heat source, and the narrow band box 31.
[0077]
Further, the laser chamber 12, the motor 36, the cooling pipe 39, and the like, which are heat sources, are surrounded by an air jacket 45, or the air jacket 45 is disposed between the heat source and the narrow band box 31, and the inside thereof is kept at a constant temperature. Gas may be allowed to flow.
[0078]
In the above embodiment, the temperature of the constant temperature gas is controlled to be substantially constant. However, it is not always necessary to perform the temperature control, and the temperature is controlled to be substantially constant or to change gradually. Any gas may be used. For example, air in a clean room may be used as it is.
[0079]
Next, a fifth embodiment will be described.
FIG. 11 shows a front view of an excimer laser device 11 according to the fifth embodiment. In FIG. 11, the excimer laser device 11 includes a laser cover 49 that surrounds the laser chamber 12 and the band-narrowing box 31.
Although not shown in the first to fourth embodiments, the laser cover 49 is provided.
[0080]
An exhaust fan 52 and an exhaust pipe 53 for exhausting air inside the laser cover 49 and exhausting the air to a not-shown exhaust duct in a clean room where the excimer laser device 11 is installed are provided below the laser cover 49. . This is to prevent impurities and dust from accumulating inside the laser cover 49 and adversely affecting the excimer laser device 11, for example.
An opening 51 into which the filter 50 is inserted is provided above the laser cover 49, and air enters the inside of the laser cover 49 through the opening 51.
[0081]
At this time, the air that has entered the inside of the laser cover 49 from the opening 51 passes through the periphery of the laser chamber 12, as shown by an arrow 64, and then is guided to the exhaust fan 52. When such heated air passes near the band-narrowing box 31, the band-narrowing box 31 is heated.
In order to prevent this, in the present embodiment, a heat insulating material 66 is disposed between the laser chamber 12 and the band-narrowing box 31 to block the flow of hot air.
[0082]
At this time, the heat insulating material 66 reaches the upper part of the laser cover 49 in the vertical direction, and is fixed to the cavity plate 40 as an example. Although not shown, the laser beam reaches the laser cover 49 also in the lateral direction of the band narrowing box 31.
This makes it difficult for the flow of hot air to reach the band-narrowing box 31, so that a local high-temperature region 74 is unlikely to be generated inside the band-narrowing box 31, and the temperature gradient of the gas in the optical path is reduced. That is, the nonuniformity of the refractive index is reduced, and the disturbance of the wavefront is reduced.
[0083]
Next, a sixth embodiment will be described.
FIG. 12 shows a front view of an excimer laser device 11 according to the sixth embodiment. In FIG. 12, the excimer laser device 11 includes a laser cover 49 surrounding the laser chamber 12 and the band-narrowing box 31.
An opening 51 into which the filter 50 is inserted is attached to the upper part of the laser cover 49 behind the band narrowing box 31. Further, an exhaust fan 52 and an exhaust pipe 53 are additionally provided in a lower front part of the laser cover 49.
[0084]
As shown by an arrow 64, the air flow enters the inside of the laser cover 49 from the opening 51 through the filter 50, passes around the band-narrowing box 31, and flows to the front of the excimer laser device 11. . After being heated around the laser chamber 12, the air is exhausted from the exhaust fan 52 through the exhaust pipe 53.
That is, since air is taken in from the opening 51 near the band-narrowing box 31, the air passing around the band-narrowing box 31 is not heated by the heat source.
This makes it difficult for local high-temperature regions 74 to be generated inside the band-narrowing box 31 and reduces the temperature gradient of the gas in the optical path. That is, the nonuniformity of the refractive index is reduced, and the disturbance of the wavefront is reduced.
[0085]
Next, a seventh embodiment will be described.
FIG. 13 shows a front view of an excimer laser device 11 according to the seventh embodiment. In FIG. 13, a motor 36 for driving the once-through fan 24 and cooling pipes 39 and 39 of the heat exchanger 13 are provided on a side surface of the laser chamber 12 opposite to the band narrowing box 31.
[0086]
By doing so, the motor 36 and the cooling pipe 39, which are heat sources, move away from the band narrowing box 31, so that the heat received by the band narrowing box 31 is reduced.
This makes it difficult for local high-temperature regions 74 to be generated inside the band-narrowing box 31 and reduces the temperature gradient of the gas in the optical path. That is, the nonuniformity of the refractive index is reduced, and the disturbance of the wavefront is reduced.
[0087]
Note that the means for blocking the flow of heat between the band-narrowing box 31 and the heat source, as in the above embodiments, is not limited to being used alone, and may be used in combination. Good.
Furthermore, it is more effective to use a cooling means for cooling the band-narrowing optical element as described in the related art or a cooling means for cooling the inside of the band-narrowing box 31.
[0088]
Although only the case where the band-narrowing optical element is located behind the laser chamber 12 has been described, also in the case where the band-narrowing optical element is located at the front, front, and rear, similarly, heat generated from the heat source is applied to the band-narrowing optical element. You just need to keep it from being transmitted.
Furthermore, the case where the band-narrowing optical element is inside the band-narrowing box 31 has been described, but the present invention is not limited to this. Even when the band-narrowing box 31 is not provided or the band-narrowing optical element is located outside the band-narrowing box 31, the wavefront can be prevented from being disturbed by preventing heat transfer from the heat source.
[0089]
Although the above description has been made by taking an excimer laser device as an example, the present invention can be similarly applied to general laser devices that narrow the band of other wavelengths, such as a fluorine molecular laser device.
Also, the grating 33 has been described as the band-narrowing optical element, but, for example, an etalon may be used. Further, the present invention can be applied to a single-line element not only in a narrow band in a narrow sense, but also in a case where a wavelength is made into a single line using a dispersion prism in a fluorine molecular laser device or the like.
That is, the present invention can be applied to all laser devices that limit the spectral characteristics of the laser beam 21 in a free oscillation (free-run) state. Call.
[0090]
Although the case where wavelength control is performed has been described, a narrow-band laser device in which the position is adjusted so as to oscillate at a predetermined target wavelength at the time of assembling the narrow-band optical element, and thereafter wavelength control is not performed is described. Can also be applied.
In such a band-narrowing laser device, when the inside of the band-narrowing box 31 is heated, the holder 65 supporting the band-narrowing optical element may be distorted, and the spectral characteristic may deviate from a predetermined target value. . On the other hand, by applying the present invention, the distortion of the holder 65 and the like is reduced, and it is possible to always keep the spectrum characteristic within an allowable range from the target value without performing wavelength control.
[0091]
The heat insulating means such as the heat insulating material also has a function of preventing the inside of the band narrowing box 31, the band narrowing element, and the optical path of the laser beam 21 from being rapidly heated to increase the temperature. As a result, the temperature distribution inside the band-narrowing box 31 gradually changes. Therefore, by performing wavelength control, a large change in the full width at half maximum of the spectrum waveform is prevented.
Furthermore, such a heat insulating means also prevents the temperature rise in the inside of the band narrowing box 31, the band narrowing element, and the optical path of the laser beam 21 itself. As a result, the temperatures at the points A, B, and C do not rise so much, so that the refractive index does not easily become uneven due to the temperature distribution, and the wavefront does not easily disturb.
[Brief description of the drawings]
FIG. 1 is a plan view of an excimer laser device according to a first embodiment.
FIG. 2 is a front view of the excimer laser device according to the first embodiment.
FIG. 3 is a plan view of the excimer laser device according to the first embodiment.
FIG. 4 is a front view of the excimer laser device according to the first embodiment.
FIG. 5 is a plan view of an excimer laser device according to a second embodiment.
FIG. 6 is a front view of an excimer laser device according to a second embodiment.
FIG. 7 is a front view of an excimer laser device according to a second embodiment.
FIG. 8 is a front view of an excimer laser device according to a third embodiment.
FIG. 9 is a front view of an excimer laser device according to a fourth embodiment.
FIG. 10 is an explanatory diagram near the band narrowing box.
FIG. 11 is a front view of an excimer laser device according to a fifth embodiment.
FIG. 12 is a front view of an excimer laser device according to a sixth embodiment.
FIG. 13 is a front view of an excimer laser device according to a seventh embodiment.
FIG. 14 is a graph showing a change in full width at half maximum of the wavelength of laser light.
FIG. 15 is an explanatory diagram of an excimer laser device according to a conventional technique.
FIG. 16 is a graph showing a change in full width at half maximum of the wavelength of laser light according to the related art.
FIG. 17 is a model diagram of a temperature distribution, showing the inside of the narrowing box in a plan view.
FIG. 18 is a graph showing the time lapse of temperature at each point in the optical path.
FIG. 19 is a graph showing a change in full width at half maximum of a spectrum waveform of laser light.
FIG. 20 is a graph showing the time lapse of temperature at each point in the optical path.
FIG. 21 is a graph showing a change in full width at half maximum of a spectrum waveform of laser light.
[Explanation of symbols]
11: Excimer laser device, 12: Laser chamber, 13: Heat exchanger, 14: Main electrode (anode), 15: Main electrode, 16: Front mirror, 17: Front window, 19: Rear window, 20: Laser optical axis , 21: laser beam, 22: beam splitter, 24: cross-flow fan, 29: laser controller, 31: narrow band box, 32: prism, 33: grating, 35: wavelength measuring device, 36: motor, 37: magnetic cup Ring, 38: heat insulating material, 39: cooling pipe, 40: cavity plate, 41: invar rod, 42: constant temperature water pipe, 43: water jacket, 44: vacuum jacket, 45: air jacket, 46: gas inlet, 47 : Gas outlet, 48: partition plate, 49: laser cover, 50: filter, 51: opening, 52: exhaust Fan, 53: exhaust pipe, 54: purge gas outlet, 55: bellows, 56: rotary stage, 57: purge gas inlet, 58: purge gas outlet, 59: purge gas flow, 60: constant temperature water, 61: hollow part, 62 : Constant temperature gas, 64: air, 65: holder, 66: heat insulating material, 68: temperature control means, 69: temperature sensor, 70: temperature control controller, 71: temperature control means, 72: temperature sensor, 73: temperature control controller 74: high temperature area, 77: pump, 78: constant temperature gas pipe, 79: blower.

Claims (15)

In a narrow-band laser device including a narrow-band optical element (32, 33) for narrowing the wavelength of a laser beam (21),
A narrow band, characterized by comprising a heat transfer preventing means for preventing heat from being transmitted from a heat source to at least one of the optical path of the narrow band optical element (32, 33) and the laser beam (21). Laser device. The narrow-band laser device according to claim 1, further comprising a narrow-band box (31) surrounding the narrow-band optical element (32, 33). The heat transfer preventing means is a heat insulating means for blocking heat, which is provided between the band-narrowing optical element (32, 33) and a heat source. Narrow band laser device. 4. The narrow-band laser device according to claim 3, wherein the heat insulating means is installed near a narrow-band box (31). 5. The narrow-band laser device according to claim 3, wherein the heat insulating means is provided near a heat source. The laser device according to any of claims 3 to 5, wherein the heat insulating means is a heat insulating material (38). The narrow-band laser device according to any one of claims 3 to 5, wherein the heat insulating means is a pipe (42) or a hollow container through which the refrigerant (60) flows. The narrow-band laser device according to claim 7, wherein the temperature of the refrigerant (60) is controlled to be substantially constant. The laser device according to any one of claims 3 to 5, wherein the heat insulating means is a vacuum container (44) having a vacuum inside. The narrow-band laser device according to any one of claims 3 to 5, wherein the heat insulating means is a hollow container (45) in which a constant temperature gas (62) having a substantially constant temperature flows. The heat transfer preventing means is a means for preventing a flow of air passing around the heat source from reaching the band-narrowing optical element (32, 33) or the band-narrowing box (31). 3. The narrow-band laser device according to claim 1. The heat transfer preventing means is a heat insulating material arranged to prevent a flow of air passing around the heat source from reaching the band-narrowing optical element (32, 33) or the band-narrowing box (31). The narrow-band laser device according to claim 11, wherein: The heat transfer preventing means is arranged to allow the air flow to pass around the heat source after passing around the band-narrowing optical element (32, 33) or the band-narrowing box (31). The narrow-band laser device according to claim 11, wherein: The heat transfer preventing means is at least one of a driving means (36) for driving a blower inside the laser chamber (12) and a cooling pipe (39) for flowing a refrigerant to a heat exchanger (13) inside the laser chamber (12). The narrowing optical element according to claim 1, wherein one of the narrowing optical elements is disposed on the opposite side of a laser chamber enclosing a laser medium with respect to the narrowing optical element. Banded laser device. The heat generation source supplies a refrigerant to a laser chamber (12) enclosing a laser medium, a driving unit (36) for driving a blower inside the laser chamber (12), and a heat exchanger (13) inside the laser chamber (12). 15. The narrow-band laser device according to claim 1, wherein at least one of the flowing cooling pipes (39) is provided.

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