Patent Application
20250174960
The present disclosure relates to a line narrowing laser device and an electronic device manufacturing method.
Recently, in a semiconductor exposure apparatus, improvement in resolution has been desired for miniaturization and high integration of semiconductor integrated circuits. For this purpose, an exposure light source that outputs light having a shorter wavelength has been developed. For example, as a gas laser device for exposure, a KrF excimer laser device for outputting laser light having a wavelength of about 248 nm and an ArF excimer laser device for outputting laser light having a wavelength of about 193 nm are used.
The KrF excimer laser device and the ArF excimer laser device each have a large spectral line width of about 350 to 400 pm in natural oscillation light. Therefore, when a projection lens is formed of a material that transmits ultraviolet rays such as KrF laser light and ArF laser light, there is a case in which chromatic aberration occurs. As a result, the resolution may decrease. Then, a spectral line width of laser light output from the gas laser device needs to be line-narrowed to the extent that the chromatic aberration can be ignored. For this purpose, there is a case in which a line narrowing module (LNM) including a line narrowing element (etalon, grating, and the like) is provided in a laser resonator of the gas laser device to line-narrow a spectral line width. A gas laser device with a narrowed spectral line width is referred to as a line narrowing gas laser device.
A line narrowing laser device according to an aspect of the present disclosure includes a laser resonator including an output coupling mirror and a line narrowing module that includes a prism and a grating that has a reflection surface having a concave shape; a laser chamber including a pair of discharge electrodes, and arranged on an optical path of the laser resonator; a power source configured to apply, to the discharge electrodes, a high voltage pulse whose repetition frequency is variable; a wavefront adjuster including the output coupling mirror; a spectrum detector configured to measure a spectral line width of pulse laser light output from the output coupling mirror; and a processor configured to control the wavefront adjuster based on the measured spectral line width.
An electronic device manufacturing method according to an aspect of the present disclosure includes generating pulse laser light using a line narrowing laser device, outputting the pulse laser light to an exposure apparatus, and exposing a photosensitive substrate to the pulse laser light in the exposure apparatus to manufacture an electronic device. Here, the line narrowing laser device includes a laser resonator including an output coupling mirror and a line narrowing module that includes a prism and a grating that has reflection surface having a concave shape; a laser chamber including a pair of discharge electrodes, and arranged on an optical path of the laser resonator; a power source configured to apply, to the discharge electrodes, a high voltage pulse whose repetition frequency is variable; a wavefront adjuster including the output coupling mirror; a spectrum detector configured to measure a spectral line width of the pulse laser light output from the output coupling mirror; and a processor configured to control the wavefront adjuster based on the measured spectral line width.
Embodiments of the present disclosure will be described below merely as examples with reference to the accompanying drawings.
1. Comparative example
Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the contents of the present disclosure. Also, all configurations and operation described in the embodiments are not necessarily essential as configurations and operation of the present disclosure. Here, the same components are denoted by the same reference numeral, and duplicate description thereof is omitted.
The exposure system includes a laser device 1 and an exposure apparatus 100. The laser device 1 includes a laser control processor 30. The laser control processor 30 is a processing device including a memory 302 in which a control program is stored, and a central processing unit (CPU) 301 which executes the control program. The laser control processor 30 is specifically configured or programmed to perform various processes included in the present disclosure. The laser control processor 30 corresponds to the processor in the present disclosure. The laser device 1 corresponds to the line narrowing laser device in the present disclosure, and is configured to output pulse laser light toward the exposure apparatus 100.
The exposure apparatus 100 includes an illumination optical system 101, a projection optical system 102, and an exposure control processor 110.
The illumination optical system 101 illuminates a reticle pattern of a reticle (not shown) arranged on a reticle stage RT with the pulse laser light incident from the laser device 1.
The projection optical system 102 causes the pulse laser light transmitted through the reticle to be imaged as being reduced and projected on a workpiece (not shown) arranged on a workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer on which a resist film is applied.
The exposure control processor 110 is a processing device including a memory 112 in which the control program is stored and a CPU 111 which executes the control program. The exposure control processor 110 is specifically configured or programmed to perform various processes included in the present disclosure. The exposure control processor 110 performs overall control of the exposure apparatus 100 and transmits and receives various data and various signals to and from the laser control processor 30.
The exposure control processor 110 transmits setting data of a target spectral line width and a target pulse energy, and a trigger signal to the laser control processor 30. The laser control processor 30 controls the laser device 1 in accordance with these data and signals.
The exposure control processor 110 synchronously translates the reticle stage RT and the workpiece table WT in opposite directions to each other. Thus, the workpiece is exposed to the pulse laser light reflecting the reticle pattern.
By 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.
The wavefront adjuster 15a includes an output coupling mirror, and the output coupling mirror and the line narrowing module 14 configure a laser resonator. The laser chamber 10 is arranged on the optical path of the laser resonator. Windows 10a, 10b are arranged at both ends of the laser chamber 10. The discharge electrode 11a and a discharge electrode (not shown) paired with the discharge electrode 11a are arranged inside the laser chamber 10. The discharge electrode (not shown) is positioned so as to overlap with the discharge electrode 11a in the V-axis direction perpendicular to the paper surface. The V-axis direction corresponds to the first direction in the present disclosure. The laser chamber 10 is filled with a laser gas containing, for example, an argon gas or a krypton gas as a rare gas, a fluorine gas as a halogen gas, a neon gas as a buffer gas, and the like.
The power source 12 includes a switch 13 and is connected to the discharge electrode 11a and a charger (not shown).
The line narrowing module 14 includes a plurality of prisms 14a, 14b and a grating 14c. The prisms 14a, 14b are arranged in this order on the optical path of the light output from the window 10a. The surfaces of the prisms 14a, 14b on and from which the light is incident and output are both parallel to the V axis.
The grating 14c is arranged on the optical path of the light having transmitted through the prisms 14a, 14b. The direction of the grooves of the grating 14c is parallel to the V axis.
The wavefront adjuster 15a includes a cylindrical convex lens 15b and a cylindrical concave lens 15c.
The cylindrical convex lens 15b is a cylindrical plano-convex lens including a flat surface on which a partial reflection film is formed and a convex surface on the opposite side to the flat surface. The focal axis of the cylindrical convex lens 15b is parallel to the V axis.
The cylindrical concave lens 15c is a cylindrical plano-concave lens including a flat surface and a concave surface on the opposite side to the flat surface. The focal axis of the cylindrical concave lens 15c is parallel to the V axis. The cylindrical concave lens 15c is supported by a linear stage 15d. The linear stage 15d includes an actuator (not shown) that moves the cylindrical concave lens 15c along the optical path of the laser resonator, and a driver (not shown) that drives the actuator in accordance with a control signal from the laser control processor 30.
The convex surface of the cylindrical convex lens 15b and the concave surface of the cylindrical concave lens 15c face each other. The flat surface of the cylindrical convex lens 15b configures an output coupling mirror, and the convex surface of the cylindrical convex lens 15b and the cylindrical concave lens 15c configuring the wavefront adjuster 15a are located between the output coupling mirror and the laser chamber 10.
Although the flat surface of the cylindrical convex lens 15b configures the output coupling mirror, the cylindrical convex lens and the output coupling mirror may be configured by separate optical components. That is, the wavefront adjuster 15a may include, instead of the cylindrical convex lens 15b, an output coupling mirror configured by a planar substrate or a wedge substrate and having a partial reflection film, and a cylindrical convex lens located between the output coupling mirror and the laser chamber 10 without having a partial reflection film.
The monitor module 16 is located on the optical path of the pulse laser light output from the output coupling mirror included in the wavefront adjuster 15a. The monitor module 16 includes beam splitters 16a, 16b, an energy detector 16c, and a spectrum detector 16d.
The beam splitter 16a is located on the optical path of the pulse laser light output from the output coupling mirror. The beam splitter 16a is configured to transmit a part of the pulse laser light toward the exposure apparatus 100 at high transmittance and to reflect other parts thereof. The beam splitter 16b is located on the optical path of the pulse laser light reflected by the beam splitter 16a. The energy detector 16c is located on the optical path of the pulse laser light reflected by the beam splitter 16b. The spectrum detector 16d is located on the optical path of the pulse laser light transmitted through the beam splitter 16b. The spectrum detector 16d includes an etalon (not shown) and a light distribution sensor (not shown).
The laser control processor 30 transmits setting data of an application voltage to be applied to the discharge electrode 11a to the power source 12 based on the setting data of the target pulse energy received from the exposure control processor 110. The laser control processor 30 transmits a control signal to the linear stage 15d included in the wavefront adjuster 15a based on the setting data of the target spectral line width setting data received from the exposure control processor 110. Further, the laser control processor 30 transmits, to the switch 13 included in the power source 12, an oscillation trigger signal based on the trigger signal 1 received from the exposure control processor 110.
The switch 13 is turned on when the oscillation trigger signal is received from the laser control processor 30. When the switch 13 is turned on, the power source 12 generates a high voltage pulse from the electric energy charged in a charger (not shown), and applies the high voltage pulse to the discharge electrode 11a.
When a high voltage pulse is applied to the discharge electrode 11a, discharge occurs inside the laser chamber 10. The laser medium in the laser chamber 10 is excited by the energy of the discharge and shifts to a high energy level. When the excited laser medium then shifts to a low energy level, light having a wavelength corresponding to the difference between the energy levels is emitted.
The light generated in the laser chamber 10 is output to the outside of the laser chamber 10 through the windows 10a, 10b. The beam width of the light output through the window 10a of the laser chamber 10 is expanded by the prisms 14a, 14b, and then the light is incident on the grating 14c.
The light incident on the grating 14c from the prisms 14a, 14b is reflected by a plurality of grooves of the grating 14c and is diffracted in a direction corresponding to the wavelength of the light.
The prisms 14a, 14b reduce the beam width of the diffracted light from the grating 14c and return the light to the laser chamber 10 through the window 10a.
The output coupling mirror included in the wavefront adjuster 15a transmits and outputs a part of the light output through the window 10b of the laser chamber 10, and reflects the other part back into the laser chamber 10 through the window 10b.
In this way, the light output from the laser chamber 10 reciprocates between the line narrowing module 14 and the output coupling mirror, and is amplified each time the light passes through the discharge space in the laser chamber 10. The light is line narrowed each time being turned back in the line narrowing module 14. Thus, the light having undergone laser oscillation and line narrowing is output as pulse laser light from the output coupling mirror. The repetition frequency of the pulse laser light is the same as the repetition frequency of the high voltage pulse applied to the discharge electrode 11a, and the repetition frequency changes in accordance with the repetition frequency of the trigger signal received from the exposure apparatus 100.
The energy detector 16c detects the pulse energy of the pulse laser light and outputs the data of the pulse energy to the laser control processor 30. The data of the pulse energy is used by the laser control processor 30 to perform feedback control of the setting data of the application voltage to be applied to the discharge electrode 11a.
In the spectrum detector 16d, an interference fringe formed by the etalon (not shown) is measured by the light distribution sensor (not shown), and a fringe waveform indicating a light intensity distribution of the interference fringe is generated.
When the trigger signal from the exposure control processor 110 is paused, the laser device 1 pauses the burst oscillation. Thereafter, in accordance with the trigger signal from the exposure control processor 110, the laser device 1 performs the burst oscillation again. A period between the first burst oscillation and the subsequent second burst oscillation is referred to as a “pause period”.
The period in which the burst oscillation is performed corresponds, for example, to the period in which exposure of one exposure area of a semiconductor wafer is performed in the exposure apparatus 100. The pause period corresponds, for example, to the period in which the imaging position of a reticle pattern is moved from one exposure area to another in the exposure apparatus 100 or the period in which the semiconductor wafer is replaced.
Referring back to
In S1, the laser control processor 30 receives the target spectral line width from the exposure apparatus 100.
In S2, the laser control processor 30 calculates the spectral line width based on data of the fringe waveform output from the spectrum detector 16d.
Specifically, the laser control processor 30 extracts a part of the fringe waveform corresponding to the free spectral range of the etalon. The extracted part of the waveform shows the relationship between the distance from the center of concentric circles constituting the interference fringes and the light intensity. Next, the laser control processor 30 acquires a spectral waveform by performing coordinate conversion of the waveform into the relationship between the wavelength and the light intensity. The laser control processor 30 calculates the spectral line width based on the spectral waveform. The spectral line width may be the full width at half maximum or an index called E95.
Referring back to
In S4, the laser control processor 30 transmits a control signal to the wavefront adjuster 15a based on the difference ΔΔλ. Thus, feedback control is performed on the spectral line width of the pulse laser light.
In S5, the laser control processor 30 determines whether or not to terminate the control of the spectral line width. For example, in a case in which the burst oscillation for outputting the pulse laser light at a constant repetition frequency and the pause period starts, the control of the spectral line width is terminated. When the control of the spectral line width is to be terminated (S5: YES), the laser control processor 30 ends processing of the present flowchart. When the control of the spectral line width is not to be terminated (S5: NO), the laser control processor 30 returns processing to S1 and repeats the above-described operation.
When the pulse laser light is generated in the laser device 1, an acoustic wave is generated in the laser chamber 10. The acoustic wave is a compression wave of the gas, and when the acoustic wave reaches the optical path of the laser resonator in the laser chamber 10, a refractive index distribution is generated on the optical path due to a density distribution of the gas. Due to the refractive index distribution on the optical path, the wavefront of the light directed toward the line narrowing module 14 changes and the spectral line width of the pulse laser light changes. Since the relationship between the timing at which the acoustic wave reaches the optical path and the timing at which the light passes therethrough depends on the repetition frequency of the pulse laser light, it is considered that the spectral line width of the pulse laser light changes when the repetition frequency of the pulse laser light is changed.
Although feedback control is performed on the spectral line width using the wavefront adjuster 15a as described with reference to
The repetition frequency of the pulse laser light is changed, for example, in the following cases:
Embodiments described below relate to suppressing a variation of the spectral line width when the repetition frequency of pulse laser light is changed.
The grating 14c includes a plurality of grooves and ridge lines parallel to the V axis, and the grooves and ridge lines are arranged in an alternating manner in a direction perpendicular to the V axis. A curved surface including these ridge lines, that is, a surface of the grating 14c that can be formed when all the grooves of the grating 14c are filled is defined as the reflection surface 14h of the grating 14c. The reflection surface 14h may be a part of a cylindrical shape curved in a plane perpendicular to the V axis, and the radius of the cylindrical shape is defined as a radius of curvature R_Grating. The radius of curvature R_Grating of the reflection surface 14h can be calculated from the measurement result obtained by measuring, by a wavefront measurement instrument (not shown), the wavefront of the light diffracted by the grating 14c and directed toward the prism 14b. As the wavefront measurement instrument, GPI-XP manufactured by Zygo Corporation (U.S.) can be used.
A beam magnification ratio M of the prisms 14a, 14b is given by the following expression, where the beam width in the direction perpendicular to the V axis of the light incident on the prism 14a from the laser chamber 10 is w1, and the beam width in the direction perpendicular to the V axis of the light incident on the grating 14c from the prism 14b is w2.
M=w2/w1
2.2 g Parameter g_Grating of Grating 14c
Let θ be the angle of incidence of the light incident on the grating 14c from the prism 14b. Let L be the optical path length between principal points of the grating 14c and the wavefront adjuster 15a (see
g_Grating=1−(L×M2)/(R_Grating×cos θ)
When the reflection surface 14h is concave, the g parameter g_Grating is smaller than 1. For example, when the optical path length L between the principal points of the grating 14c and the wavefront adjuster 15a is 1×103 mm, the beam magnification ratio M of the prisms 14a, 14b is 40 times, the reflection surface 14h is a concave surface having the radius of curvature R_Grating of 1×107 mm, and the incident angle θ of the light incident on the grating 14c from the prism 14b is 70 degrees, the g parameter g_Grating is about 0.53.
When the reflection surface 14h is a convex surface, the g parameter g_Grating is larger than 1.
2.3 g Parameter g_EFM of Wavefront Adjuster 15a
First, a combined focal length f_EFM of the wavefront adjuster 15a on the optical path entering the wavefront adjuster 15a from the laser chamber 10 and returning to the laser chamber 10 after being reflected by the partial reflection film 15e of the cylindrical convex lens 15b is calculated. A combined focal length f_EFM1 from the laser chamber 10 to the partial reflection film 15e is as follows.
f_EFM1=(f1×f2)/(f1+f2−d)
A combined focal length f_EFM2 from the partial reflection film 15e to the laser chamber 10 is the same as the combined focal length f_EFM1.
f_EFM2=f_EFM1
The combined focal length f_EFM of the wavefront adjuster 15a is as follows.
f_EFM=(f_EFM1×f_EFM1)/(f_EFM1+f_EFM1+δ1−δ2)
δ1 is the distance between the cylindrical concave lens 15c and the image-side principal point, and is calculated by the following expression.
δ1=f_EFM1×d/f2
δ2 is the distance between the cylindrical convex lens 15b and the object-side principal point, and is calculated by the following expression.
δ2=f_EFM1×d/f1
The g parameter g_EFM of the wavefront adjuster 15a is calculated as follows.
g_EFM=1−L/(2×f_EFM)
When the focal length f2 of the cylindrical convex lens 15b is smaller than the sum of the absolute value of the focal length f1 of the cylindrical concave lens 15c and the distance d between the principal points of the cylindrical concave lens 15c and the cylindrical convex lens 15b, the g parameter g_EFM is smaller than 1. For example, when the optical path length L between the principal points of the grating 14c and the wavefront adjuster 15a is 1×103 mm, the focal length f1 is −70 mm, the focal length f2 is 74 mm, and the distance d is 6 mm, the g parameter g_EFM is about 0.58.
When the focal length f2 is larger than the sum of the absolute value of the focal length f1 and the distance d, the g-parameter g_EFM is larger than 1.
In the comparative example, since the reflection surface of the grating 14c is planar, the g parameter g_Grating of the grating 14c is 1. When the g parameter g_EFM of the wavefront adjuster 15a is changed with the g parameter g_Grating fixed to 1, the spectral line width of the pulse laser light is changed.
In the first embodiment, the reflection surface of the grating 14c has a concave shape, and the g parameter g_Grating of the grating 14c is smaller than 1. When the g parameter g_Grating is smaller than 1, the interval between the contour lines of the spectral line width becomes wider. That is, the spectral line width is more stable when the g parameter g_EFM of the wavefront adjuster 15a is changed. It is considered that the stability of the spectral line width when the refractive index distribution is generated on the optical path of the laser resonator by the acoustic wave is also increased.
In
According to the first embodiment, the variation of the spectral line width when the repetition frequency of the pulse laser light is changed is suppressed, and the stability of the spectral line width is improved.
Since the variation width of the spectral line width decreases as the g parameter g_Grating decreases, it is desirable that the g parameter g_Grating is small.
However, the pulse energy has a peak when the g parameter g_Grating is equal to or larger than 0.4 and smaller than 0.5, and the pulse energy becomes low even when the g parameter g_Grating is larger or smaller than the range. The pulse energy when the g parameter g_Grating is 0.2 is approximately the same as the pulse energy when the g parameter g_Grating is 1. When the g parameter g_Grating becomes smaller than 0.2 or equal to or larger than 1.0, the ratio of the light entering the wavefront adjuster 15a among the light diffracted by the grating 14c decreases, and it is considered that the pulse energy is decreased due to leakage to the outside of the laser resonator. Therefore, the g parameter g_Grating is preferably equal to or larger than 0.2 and smaller than 1.0, and more preferably equal to or larger than 0.4 and smaller than 0.5.
(1) According to the first embodiment, the laser device 1a includes the laser resonator, the laser chamber 10, the power source 12, the wavefront adjuster 15a, the spectrum detector 16d, and the laser control processor 30.
The laser resonator includes the output coupling mirror configured of the flat surface of the cylindrical convex lens 15b and the line narrowing module 14, the line narrowing module 14 includes the prisms 14a, 14b and the grating 14c, and the reflection surface 14h of the grating 14c has a concave shape.
The laser chamber 10 includes the discharge electrode 11a and the discharge electrode paired therewith, and is arranged on the optical path of the laser resonator.
The power source 12 is configured to apply a high voltage pulse to the discharge electrode 11a, and the repetition frequency of the high voltage pulse is variable.
The wavefront adjuster 15a includes the output coupling mirror.
The spectrum detector 16d generates a fringe waveform to measure the spectral line width of the pulse laser light output from the output coupling mirror and reflected by the beam splitter 16a.
The laser control processor 30 controls the wavefront adjuster 15a based on the measured spectral line width.
Accordingly, since the reflection surface 14h has a concave shape, the variation of the spectral line width due to change in the repetition frequency of the pulse laser light is suppressed, and the spectral line width is stabilized.
(2) According to the first embodiment, the value of g_Grating calculated by the expression g_Grating=1−(L×M2)/(R_Grating×cos θ) is equal to or larger than 0.2 and smaller than 1.0, where the radius of curvature of the reflection surface 14h of the grating 14c is R_Grating, the incident angle of the light incident on the grating 14c from the prisms 14a, 14b is 0, the optical path length from the principal point of the grating 14c to the principal point of the wavefront adjuster 15a is L, and the beam magnification ratio by the prisms 14a, 14b is M.
Accordingly, the spectral line width can be stabilized, and decrease in the pulse energy can be suppressed.
(3) According to the first embodiment, the value of g_Grating is equal to or larger than 0.4 and smaller than 0.5.
Accordingly, it is possible to stabilize the spectral line width and obtain high pulse energy.
(4) According to the first embodiment, the laser control processor 30 controls the wavefront adjuster 15a such that g_EFM calculated by the expression g_EFM=1−L/(2×f_EFM) is larger than the value of g_Grating, where the combined focal length of the wavefront adjuster 15a is f_EFM.
Accordingly, the target spectral line width can be realized by increasing the g parameter g_EFM of the wavefront adjuster 15a by the amount of decreasing the g parameter g_Grating of the grating 14c.
(5) According to the first embodiment, the laser control processor 30 is configured to control the wavefront adjuster 15a such that the spectral line width measured using the spectrum detector 16d is equal to or larger than 0.15 pm and equal to or smaller than 0.5 pm, and the g parameter g_Grating of the grating 14c is equal to or larger than 0.2 and smaller than 1.0.
Accordingly, the spectral line width is set to be equal to or larger than 0.15 pm and equal to or smaller than 0.5 pm, and the g parameter g_Grating of the grating 14c is set to be equal to or larger than 0.2 and smaller than 1.0, so that the spectral line width is stabilized and decrease in the pulse energy can be suppressed.
(6) According to the first embodiment, the grating 14c includes the plurality of grooves in the direction of the V axis, and the reflection surface 14h has a concave shape curved in a plane perpendicular to the V-axis direction.
Accordingly, the spectral line width can be stabilized by adjusting the wavefront shape in the plane perpendicular to the V-axis direction.
(7) According to the first embodiment, the surface of the prism 14a in and from which the light reciprocating in the laser resonator is incident and output and the surface of the prism 14b in and from which the light is incident and output are parallel to the V-axis direction.
Accordingly, by causing the light to be incident on the grating 14c while expanding the beam width in the plane perpendicular to the V-axis direction by the prisms 14a, 14b, the spectral line width can be narrowed.
(8) According to the first embodiment, the wavefront adjuster 15a includes the cylindrical convex lens 15b having the focal axis F2 parallel to the V-axis direction and the cylindrical concave lens 15c having the focal axis F1 parallel to the V-axis direction.
Accordingly, the spectral line width can be controlled by adjusting the wavefront shape in the plane perpendicular to the V-axis direction.
(9) According to the first embodiment, the wavefront adjuster 15a includes the cylindrical convex lens 15b, the cylindrical concave lens 15c, and the linear stage 15d. The cylindrical convex lens 15b includes the flat surface configuring the output coupling mirror and the convex surface located between the flat surface and the laser chamber 10. The cylindrical concave lens 15c is located on the optical path between the cylindrical convex lens 15b and the laser chamber 10. The linear stage 15d moves the cylindrical concave lens 15c.
Accordingly, since the cylindrical concave lens 15c is moved, the spectral line width can be controlled by adjusting the wavefront without changing the resonator length.
(10) According to the first embodiment, the line narrowing module 14 includes the grating bending mechanism including the holder 14d for adjusting the curvature of the grating 14c, the expansion portion 14e, and the support portions 14f, 14g.
Accordingly, the curvature of the reflection surface 14h of the grating 14c can be adjusted to an appropriate value.
In other respects, the first embodiment is similar to the comparative example.
The master oscillator MO includes the laser chamber 10, the discharge electrode 11a, the line narrowing module 14, and the wavefront adjuster 15a. These configurations are similar to the corresponding configurations in the first embodiment, and the reflection surface of the grating 14c included in the line narrowing module 14 has a concave shape.
The high reflection mirrors 31, 32 are arranged on the optical path of pulse laser light B1 output from the master oscillator MO. Each of the high reflection mirrors 31, 32 is configured such that the position and posture thereof can be changed by an actuator (not shown). The high reflection mirrors 31, 32 configure a beam steering unit for adjusting an incident position and an incident direction of the pulse laser light B1 on the power oscillator PO.
The power oscillator PO is arranged on the optical path of the pulse laser light B1 that has passed through the beam steering unit. The power oscillator PO includes a laser chamber 20, a discharge electrode 21a and a discharge electrode 21b paired therewith, a rear mirror 24, and an output coupling mirror 25.
The rear mirror 24 is made of a material that transmits the pulse laser light B1, and one surface thereof is coated with a partial reflection film. The same applies to the output coupling mirror 25. Here, the reflectance of the rear mirror 24 is set higher than the reflectance of the output coupling mirror 25. The rear mirror 24 and the output coupling mirror 25 configure a laser resonator. The laser chamber 20 is arranged on the optical path of the laser resonator. Windows 20a, 20b are arranged at both ends of the laser chamber 20.
In other respects, the above-described components of the power oscillator PO are similar to the corresponding components of the master oscillator MO.
The monitor module 16 is arranged on the optical path of pulse laser light B2 output from the output coupling mirror 25. The configuration of the monitor module 16 is similar to the corresponding configuration in the first embodiment. In
The laser control processor 30 receives setting data of a first target pulse energy of the pulse laser light B2 output from the power oscillator PO from the exposure control processor 110.
The laser control processor 30 further sets a second target pulse energy of the pulse laser light B1 output from the master oscillator MO.
The laser control processor 30 transmits the setting data of the application voltage to each of the power sources of the master oscillator MO and the power oscillator PO based on the first and second target pulse energies.
The laser control processor 30 transmits the first and second oscillation trigger signals based on the trigger signal received from the exposure control processor 110 to the switches included in the respective power sources of the master oscillator MO and the power oscillator PO.
The operation of the master oscillator MO is similar to the operation of the laser device 1a in the first embodiment.
When receiving the second oscillation trigger signal from the laser control processor 30, the power source included in the power oscillator PO generates a high voltage pulse and applies the high voltage pulse to the discharge electrode 21a.
The delay time of the second oscillation trigger signal to the power source included in the power oscillator PO with respect to the first oscillation trigger signal to the power source included in the master oscillator MO is set so that the timing at which discharge occurs in the laser chamber 20 is synchronized with the timing at which the pulse laser light B1 output from the master oscillator MO enters the laser chamber 20.
The pulse laser light B1 reciprocates between the rear mirror 24 and the output coupling mirror 25, and is amplified each time the pulse laser light B1 passes through the discharge space in the laser chamber 20. The amplified pulse laser light B2 is output from the output coupling mirror 25.
According to the second embodiment, by amplifying the pulse laser light B1 output from the master oscillator MO, it is possible to output the pulse laser light B2 having a higher pulse energy toward the exposure apparatus 100.
The spectral line width of the pulse laser light B2 depends on the spectral line width of the pulse laser light B1. By making the reflection surface of the grating 14c concave, the spectral line width of the pulse laser light B2 can be stabilized.
In other respects, the second embodiment is similar to the first embodiment.
The power oscillator PO includes the laser chamber 20, high reflection mirrors 26a to 26c, an output coupling mirror 27, and a high reflection mirror 33. The configuration of the laser chamber 20, the windows 20a, 20b provided therein, and the pair of discharge electrodes 21a, 21b are similar to the corresponding configuration in the second embodiment.
The output coupling mirror 27 and the high reflection mirror 26a are arranged outside the laser chamber 20 and in the vicinity of the window 20a. The high reflection mirrors 26b, 26c are arranged outside the laser chamber 20 and in the vicinity of the window 20b. At the discharge space inside the laser chamber 20, the optical path from the high reflection mirror 26a to the high reflection mirror 26b intersects with the optical path from the high reflection mirror 26c to the output coupling mirror 27. The laser resonator configured of the high reflection mirrors 26a to 26c and the output coupling mirror 27 is referred to as a ring resonator.
The pulse laser light B1 output from the master oscillator MO is reflected by the high reflection mirrors 31, 32, 33 in this order, and incident on the output coupling mirror 27 from the outside of the laser resonator of the power oscillator PO substantially in the −H direction. The pulse laser light B1 that enters the laser resonator through the output coupling mirror 27 is reflected by the high reflection mirrors 26a, 26b, 26c in this order, amplified when passing through the discharge space, and incident on the output coupling mirror 27 in the Z direction from the inside of the resonator.
A part of the pulse laser light B1 incident on the output coupling mirror 27 in the Z direction is reflected substantially in the −H direction, reflected again by the high reflection mirrors 26a, 26b, 26c, and amplified. Another part of the pulse laser light B1 incident on the output coupling mirror 27 in the Z direction is transmitted and output toward the exposure apparatus 100 as the pulse laser light B2.
According to the third embodiment, since return light from the power oscillator PO directed toward the master oscillator MO is unlikely to occur, the master oscillator MO can be stably operated.
In other respects, the third embodiment is similar to the second embodiment.
The description above is intended to be illustrative and the present disclosure is not limited thereto. Therefore, it would be obvious to those skilled in the art that various modifications to the embodiments of the present disclosure would be possible without departing from the spirit and the scope of the appended claims. Further, it would be also obvious to those skilled in the art that the embodiments of the present disclosure would be appropriately combined.
The terms used throughout the present specification and the appended claims should be interpreted as non-limiting terms unless clearly described. For example, terms such as “comprise”, “include”, “have”, and “contain” should not be interpreted to be exclusive of other structural elements. Further, indefinite articles “a/an” described in the present specification and the appended claims should be interpreted to mean “at least one” or “one or more.” Further, “at least one of A, B, and C” should be interpreted to mean any of A, B, C, A+B, A+C, B+C, and A+B+C as well as to include combinations of any thereof and any other than A, B, and C.
The present application claims the benefit of International Application No. PCT/JP2022/033143, filed on Sep. 2, 2022, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/033143 | Sep 2022 | WO |
| Child | 19040321 | US |
