Patent Application
20170063024
The present disclosure relates to a laser system.
A laser annealing apparatus may apply a pulse laser beam on an amorphous silicon film formed on a substrate. The pulse laser beam may be emitted from a laser system such as an excimer laser system. The pulse laser beam may have a wavelength of ultraviolet light region. Such pulse laser beam may reform the amorphous silicon film to a poly silicon film. The poly-silicon film can be used to form thin film transistors (TFTs). The TFTs may be used in large-sized liquid crystal displays.
A laser system according to one aspect of the present disclosure may include: a first laser apparatus configured to emit a first pulse laser beam; a second laser apparatus configured to emit a second pulse laser beam; a timing detector; and a controller. The timing detector may be configured to detect a first passage timing at which the first pulse laser beam passes a first position and a second passage timing at which the second pulse laser beam passes a second position. The controller may be configured to control a first trigger timing for the first laser apparatus to emit the first pulse laser beam and a second trigger timing for the second laser apparatus to emit the second pulse laser beam based on the first passage timing and the second passage timing.
A laser system according to another aspect of the present disclosure may include: a first discharge-pumped laser apparatus configured to emit a first pulse laser beam; a second discharge-pumped laser apparatus configured to emit a second pulse laser beam; a timing detector; and a controller. The timing detector may be configured to detect a first timing of electric discharge occurred for emitting the first pulse laser beam from the first laser apparatus, and detect a second timing of electric discharge occurred for emitting the second pulse laser beam from the second laser apparatus. The controller may be configured to control a first trigger timing for the first laser apparatus to emit the first pulse laser beam and a second trigger timing for the second laser apparatus to emit the second pulse laser beam based on the first timing of electric discharge and the second timing of electric discharge.
A laser system according to still another aspect of the present disclosure may include: a first laser apparatus configured to emit a first pulse laser beam; a second laser apparatus configured to emit a second pulse laser beam; a timing detector; a first optical path length adjuster; a second optical path length adjuster; and a controller. The timing detector may be configured to detect a first passage timing at which the first pulse laser beam passes a first position and a second passage timing at which the second pulse laser beam passes a second position. The first optical path length adjuster may be provided between the first laser apparatus and the timing detector in an optical path of the first pulse laser beam. The second optical path length adjuster may be provided between the second laser apparatus and the timing detector in an optical path of the second pulse laser beam. The controller may be configured to control the first optical path length adjuster and the second optical path length adjuster based on the first passage timing and the second passage timing.
A laser system according to still another aspect of the present disclosure may include: a first discharge-pumped laser apparatus configured to emit a first pulse laser beam; a second discharge-pumped laser apparatus configured to emit a second pulse laser beam; a timing detector; a first optical path length adjuster; a second optical path length adjuster; and a controller. The timing detector may be configured to detect a first timing of electric discharge occurred for emitting the first pulse laser beam from the first laser apparatus, and detect a second timing of electric discharge occurred for emitting the second pulse laser beam from the second laser apparatus. The first optical path length adjuster may be provided in an optical path of the first pulse laser beam. The second optical path length adjuster may be provided in an optical path of the second pulse laser beam. The controller may be configured to control the first optical path length adjuster and the second optical path length adjuster based on the first timing of electric discharge and the second timing of electric discharge.
A laser system according to still another aspect of the present disclosure may include: a first laser apparatus configured to emit a first pulse laser beam; a second laser apparatus configured to emit a second pulse laser beam; and a controller. The controller may be configured to control a first trigger timing for the first laser apparatus to emit the first pulse laser beam and a second trigger timing for the second laser apparatus to emit the second pulse laser beam, such that a difference between a first emitting timing at which the first pulse laser beam is emitted from the laser system and a second emitting timing at which the second pulse laser beam is emitted from the laser system approaches a predetermined value.
A laser system according to still another aspect of the present disclosure may include: a first laser apparatus configured to emit a first pulse laser beam; a second laser apparatus configured to emit a second pulse laser beam; a first optical path length adjuster; a second optical path length adjuster; and a controller. The first optical path length adjuster may be provided in an optical path of the first pulse laser beam. The second optical path length adjuster may be provided in an optical path of the second pulse laser beam. The controller may be configured to control the first optical path length adjuster and the second optical path length adjuster, such that a difference between a first emitting timing at which the first pulse laser beam is emitted from the laser system and a second emitting timing at which the second pulse laser beam is emitted from the laser system approaches a predetermined value.
Exemplary embodiments of the present disclosure will be described below with reference to the appended drawings.
Contents
3.1 Plurality of Laser Apparatuses
3.2 Plurality of High-Reflective Mirrors
3.3 Plurality of Timing Detectors
3.4 Beam Combiner System
3.5 Laser System Controller
3.6 Exposure Apparatus
3.7 Configuration for Timing Control
3.8 Main Flow
3.9 Details of S50
4.1 Configuration
4.2 Main Flow
4.3 Details of S50a
4.4 Details of S70
5.1 Configuration
5.2 Main Flow
5.3 Details of S50b
6.1 Configuration
6.2 Main Flow
7.1 Laser Apparatus
7.2 Beam Combiner Including Fly Eye Lens
7.3 Beam Combiner Using Flat Mirrors
Embodiments of the present disclosure will be described below in detail with reference to the drawings. The embodiments described below may represent several examples of the present disclosure, and may not intend to limit the content of the present disclosure. Not all of the configurations and operations described in the embodiments are indispensable in the present disclosure. Identical reference symbols may be assigned to identical elements and redundant descriptions may be omitted.
A laser annealing apparatus may perform laser annealing by irradiating an amorphous silicon film on a glass substrate with a pulse laser beam. The pulse laser beam may be demanded to increase its energy per one pulse for decreasing lead time to manufacture larger and larger liquid crystal displays as in recent years. Increasing energy per one pulse may be achieved by combining pulse laser beams emitted from respective laser apparatuses to form a combined laser beam, which may be applied to the amorphous silicon film.
However, the pulse laser beams emitted from the respective laser apparatuses may lose stable synchronization in their emitting timings. This may change waveform of the combined pulse laser beams. Such change in the waveform of the combined pulse laser beam may affect electric characteristics of materials to be made by the laser annealing.
According one aspect of the present disclosure, a first passage timing and a second passage timing may be detected. The first passage timing may be the timing when a pulse laser beam emitted from a first laser apparatus passes a first position. The second passage timing may be the timing when another pulse laser beam emitted from a second laser apparatus passes a second position. The first passage timing and the second passage timing may be used for controlling a first trigger timing and a second trigger timing. The first trigger timing may be used for emitting the pulse laser beam from the first laser apparatus. The second trigger timing may be used for emitting the pulse laser beam from the second laser apparatus.
One or more terms used in the present disclosure are described below.
An “optical path axis” of a pulse laser beam may be a central axis of an optical path of the pulse laser beam.
The laser system 5 may include a plurality of laser apparatuses 2a to 2e, a plurality of high-reflective mirrors 30a to 30e and 31a to 31e, a plurality of timing detectors 32a to 32e, a beam combiner system 3, and a laser system controller 20.
3.1 Plurality of Laser Apparatuses
The plurality of laser apparatuses 2a to 2e may include a first laser apparatus 2a, a second laser apparatus 2b, a third laser apparatus 2c, a fourth laser apparatus 2d, and a fifth laser apparatus 2e.
Each of the first to fifth laser apparatuses 2a to 2e may be an excimer laser apparatus using laser medium such as XeF, XeCl, KrF, or MT. The first to fifth laser apparatuses 2a to 2e may have substantially the same configurations with each other. The first to fifth laser apparatuses 2a to 2e may receive first to fifth trigger signals, respectively, and emit first to fifth pulse laser beams 21 to 25, respectively. Each of the first to fifth pulse laser beams 21 to 25 may have a wavelength of an ultraviolet region.
3.2 Plurality of High-Reflective Mirrors
The number of the high-reflective mirrors 30a to 30e may correspond to the number of the laser apparatuses 2a to 2e. The number of the high-reflective mirrors 31a to 31e may correspond to the number of the laser apparatuses 2a to 2e.
The high-reflective mirrors 30a and 31a may be provided such that the first pulse laser beam 21 emitted from the first laser apparatus 2a may enter a first concave lens 3311 described later in incident optics 33.
The high-reflective mirrors 30b and 31b may be provided such that the second pulse laser beam 22 emitted from the second laser apparatus 2b may enter a second concave lens 3312 described later in the incident optics 33.
The high-reflective mirrors 30c and 31c may be provided such that the third pulse laser beam 23 emitted from the third laser apparatus 2c may enter a third concave lens 3313 described later in the incident optics 33.
The high-reflective mirrors 30d and 31d may be provided such that the fourth pulse laser beam 24 emitted from the fourth laser apparatus 2d may enter a fourth concave lens 3314 described later in the incident optics 33.
The high-reflective mirrors 30e and 31e may be provided such that the fifth pulse laser beam 25 emitted from the fifth laser apparatus 2e may enter a fifth concave lens 3315 described later in the incident optics 33.
3.3 Plurality of Timing Detectors
The number of the timing detectors 32a to 32e may correspond to the number of the laser apparatuses 2a to 2e.
The timing detector 32a may include a beam splitter 35a and an optical sensor 36a. The beam splitter 35a may be provided in an optical path of the first pulse laser beam 21 from the first laser apparatus 2a to the incident optics 33 or a beam combiner 34. The beam splitter 35a may transmit the first pulse laser beam 21 at high transmittance to a first direction, and reflect a part of the first pulse laser beam 21 to a second direction.
The optical sensor 36a may include a photodiode or a photoelectric tube. The optical sensor 36a may be provided in an optical path of the first pulse laser beam 21 reflected by the beam splitter 35a to the above-mentioned second direction. The optical sensor 36a may be provided at a position where an optical path length from the beam splitter 35a to a light-receiving surface of the optical sensor 36a along the second direction is L. The optical path length may be a sum of at least one product of a refractive index of medium transmitting the light and a travelling distance of the light in the medium. The optical sensor 36a may receive a part of the first pulse laser beam 21.
The timing detector 32a may output a signal indicating a first passage timing at which the first pulse laser beam 21 passes a first position 21a. The first position 21a may correspond to, in the optical path of the first pulse laser beam 21 emitted from the beam splitter 35a to the first direction, a position where an optical path length from the beam splitter 35a is the above-mentioned L. The incident optics 33 or the beam combiner 34 may be positioned in the optical path of the first pulse laser beam 21 emitted from the beam splitter 35a to the first direction.
The timing detectors 32a to 32e may have substantially the same configurations with each other.
The timing detector 32b may output a signal indicating a second passage timing at which the second pulse laser beam 22 passes a second position 22a.
The timing detector 32c may output a signal indicating a third passage timing at which the third pulse laser beam 23 passes a third position 23a.
The timing detector 32d may output a signal indicating a fourth passage timing at which the fourth pulse laser beam 24 passes a fourth position 24a.
The timing detector 32e may output a signal indicating a fifth passage timing at which the fifth pulse laser beam 25 passes a fifth position 25a.
The first to fifth pulse laser beams 21 to 25 may be emitted from the laser system 5 at an emitting position 26a. Optical path lengths from the first to fifth positions to the emitting position 26a may be L1 to L5, respectively. The emitting position 26a, where the first to fifth pulse laser beams 21 to 25 are emitted from the laser system 5, may be located between the beam combiner system 3 and the exposure apparatus 4.
3.4 Beam Combiner System
The beam combiner system 3 may include the incident optics 33 and the beam combiner 34.
The incident optics 33 may include secondary light source optics 331 and condenser optics 332, being designed to constitute a Koehler illumination.
The secondary light source optics 331 may include first to fifth concave lenses 3311 to 3315.
The first concave lens 3311 may be provided between the timing detector 32a and the condenser optics 332 in the optical path of the first pulse laser beam 21 emitted from the first laser apparatus 2a. The first concave lens 3311 may transmit the first pulse laser beam 21, which has been emitted from the first laser apparatus 2a, toward the condenser optics 332. The first concave lens 3311 may expand beam width of the first pulse laser beam 21.
The first to fifth concave lenses 3311 to 3315 may have substantially the same configurations with each other.
The second concave lens 3312 may be provided in the optical path of the second pulse laser beam 22 emitted from the second laser apparatus 2b.
The third concave lens 3313 may be provided in the optical path of the third pulse laser beam 23 emitted from the third laser apparatus 2c.
The fourth concave lens 3314 may be provided in the optical path of the fourth pulse laser beam 24 emitted from the fourth laser apparatus 2d.
The fifth concave lens 3315 may be provided in the optical path of the fifth pulse laser beam 25 emitted from the fifth laser apparatus 2e.
The first to fifth pulse laser beams 21 to 25 entering the first to fifth concave lenses 3311 to 3315, respectively, may have substantially the same beam sizes and substantially the same beam divergences with each other.
Optical path axes of the first to fifth pulse laser beams 21 to 25 transmitted by the first to fifth concave lenses 3311 to 3315, respectively, may be substantially parallel to each other.
The condenser optics 332 may be provided such that, as explained below, the first to fifth pulse laser beams 21 to 25 may be made incident on substantially the same portion of a light-receiving surface of the beam combiner 34 at respective predetermined incident angles.
The condenser optics 332 may extend over the cross sections of the optical paths of the first to fifth pulse laser beams 21 to 25, at a position between the secondary light source optics 331 and the beam combiner 34. The condenser optics 332 may transmit the first to fifth pulse laser beams 21 to 25 toward the beam combiner 34. The condenser optics 332 may change respective directions of the optical path axes of the first to fifth pulse laser beams 21 to 25 to respective predetermined directions.
The condenser optics 332 may be provided such that a front-side focal plane of the condenser optics 332 substantially coincides with respective focal positions of the first to fifth concave lenses 3311 to 3315. The condenser optics 332 may thus collimate each of the first to fifth pulse laser beams 21 to 25 transmitted by the respective concave lenses 3311 to 3315, such that each of the beams has substantially parallel rays.
The condenser optics 332 may be provided such that a rear-side focal plane of the condenser optics 332 substantially coincides with the light-receiving surface of the beam combiner 34. Thus, the condenser optics 332 may make the first to fifth pulse laser beams 21 to 25 be incident on substantially the same portion of the beam combiner 34 at respective predetermined incident angles.
The beam combiner 34 may include a diffractive optical element (DOE). The diffractive optical element may be constituted by an ultraviolet-transmitting substrate, such as a synthetic quartz substrate or a calcium fluoride substrate, on which multiple grooves each having a predetermined shape are formed at a predetermined interval.
The first to fifth pulse laser beams 21 to 25, having been changed their directions of the optical path axes by the condenser optics 332 to the respective predetermined directions, may enter the beam combiner 34. The first to fifth pulse laser beams 21 to 25, which entered the beam combiner 34, may be emitted from the beam combiner 34 to directions substantially the same with each other. The above-mentioned respective predetermined directions may be designed such that the first to fifth pulse laser beams 21 to 25 are combined by the beam combiner 34. Such beam combiner 34 may be a diffractive optical element, for example, disclosed in U.S. Patent Application Publication No. 2009/0285076.
The first to fifth pulse laser beams 21 to 25 emitted from the beam combiner 34 may travel through substantially the same optical paths to enter the exposure apparatus 4.
The first to fifth pulse laser beams 21 to 25 may thus be combined by the beam combiner system 3 and emitted from the laser system 5. In the following description, a pulse laser beam formed by combining the first to fifth pulse laser beams 21 to 25 may be referred to as a “combined laser beam”. The combined laser beam may include the first to fifth pulse laser beams 21 to 25. The pulse energy of the combined laser beam may be approximately five times of the pulse energy of the pulse laser beam emitted from a single laser apparatus. “Combining” pulse laser beams may include emitting both a first pulse laser beam incident in a first direction and a second pulse laser beam incident in a second direction different from the first direction, to a third direction. The third direction may be substantially the same as one of the first and second directions or different from any one of the first and second directions. The first and second pulse laser beams emitted to the third direction may overlap with or be close to each other.
3.5 Laser System Controller
The laser system controller 20 may output the first to fifth trigger signals. The first to fifth trigger signals may be inputted to the first to fifth laser apparatuses 2a to 2e, respectively. The laser system controller 20 may receive the signals indicating the first to fifth passage timings outputted from the timing detectors 32a to 32e, respectively.
3.6 Exposure Apparatus
The exposure apparatus 4 may include an exposure apparatus controller 40, a high-reflective mirror 41, illumination optics 42, a mask 43, and transfer optics 44. The exposure apparatus 4 may apply the pulse laser beam, which is emitted from the laser system 5, to the irradiation object P according to a predetermined mask pattern.
The exposure apparatus controller 40 may perform control of moving a stage (not shown), which holds the irradiation object P, changing the irradiation objects P, or changing the masks 43. The exposure apparatus controller 40 may output the oscillation trigger signal to the laser system controller 20.
The high-reflective mirror 41 may be provided in an optical path of the pulse laser beam emitted from the laser system 5. The high-reflective mirror 41 may reflect the pulse laser beam emitted from the laser system 5 to make the pulse laser beam enter the illumination optics 42. The pulse laser beam entering the illumination optics 42 may have substantially parallel rays.
The illumination optics 42 may be provided between the high-reflective mirror 41 and the mask 43 in the optical path of the pulse laser beam emitted from the laser system 5. The illumination optics 42 may include a fly eye lens 421 and condenser optics 422, being designed to constitute a Koehler illumination.
The fly eye lens 421 may be provided between the high-reflective mirror 41 and the condenser optics 422 in the optical path of the pulse laser beam emitted from the laser system 5. The fly eye lens 421 may include a plurality of lenses arranged in a cross section of the pulse laser beam. The lenses may transmit respective parts of the pulse laser beam toward the condenser optics 422 to expand beam widths of the respective parts.
The condenser optics 422 may be provided between the fly eye lens 421 and the mask 43 in the optical path of the pulse laser beam emitted from the laser system 5. The condenser optics 422 may irradiate the mask 43 with the pulse laser beam emitted from the fly eye lens 421.
The condenser optics 422 may be provided such that a rear-side focal plane of the condenser optics 422 substantially coincides with a position of the mask 43. The condenser optics 422 may thus irradiate substantially the same portion of the mask 43 with the respective parts of the pulse laser beam transmitted by the respective lenses of the fly eye lens 421.
According to the above-mentioned configuration, the illumination optics 42 may reduce variation in light intensity distribution in a cross section of the pulse laser beam, with which the mask 43 is irradiated.
The mask 43 may have a rectangular slit. The shape of the slit may constitute the mask pattern of the mask 43. The mask pattern of the mask 43 may not be limited to have the rectangular shape. The mask pattern may have any desired shape.
The transfer optics 44 may be provided between the mask 43 and the irradiation object P in the optical path of the pulse laser beam emitted from the laser system 5. The transfer optics 44 may be provided such that an image of the mask 43 is transferred by the transfer optics 44 at a position substantially coinciding with a position where the irradiation object P shall be irradiated with the pulse laser beam. The transfer optics 44 may thus transfer the image of the mask pattern of the mask 43, irradiated with the pulse laser beam, to the irradiation object P.
The transfer optics 44 may include at least one convex lens. In another example, the transfer optics 44 may include a combination of a convex lens and a concave lens, or include a concave mirror. In still another example, the transfer optics 44 may include a cylindrical lens that transfers a lateral component of the image of the rectangular mask pattern to the irradiation object P.
The laser system 5 may thus emit the pulse laser beam having higher pulse energy than the pulse energy of the pulse laser beam emitted from the single laser apparatus. Consequently, the laser annealing apparatus 1 may efficiently give pulse energy to a large-sized irradiation object P. Thus, large-sized liquid crystal displays may be efficiently manufactured.
3.7 Configuration for Timing Control
The timer unit 20a and the delay circuit unit 20c may receive the oscillation trigger signal outputted from the exposure apparatus controller 40.
The delay circuit unit 20c may output the first to fifth trigger signals. The first to fifth trigger signals may be outputted at first to fifth trigger timings TR1 to TR5, delaying by respective predetermined delay times from the timing at which the delay circuit unit 20c received the oscillation trigger signal. The first to fifth laser apparatuses 2a to 2e may receive the first to fifth trigger signals, and emit the first to fifth pulse laser beams 21 to 25, respectively.
The timer unit 20a may receive signals indicating the first to fifth passage timings outputted from the timing detectors 32a to 32e. The signals indicating the first to fifth passage timings may indicate timings at which the first to fifth pulse laser beams 21 to 25 pass the first to fifth positions, respectively. The timer unit 20a may count clock signal after receiving the oscillation trigger signal until receiving each of the signals indicating the first to fifth passage timings. Count data obtained by counting the clock signal may be sent from the timer unit 20a to the processor 20b as the first to fifth passage timings TD1 to TD5.
The processor 20b may be configured to set the first to fifth trigger timings TR1 to TR5 based on the first to fifth passage timings TD1 to TD5, respectively. These trigger timings may be set such that differences between the emitting timings of the first to fifth pulse laser beams 21 to 25 from the laser system 5 approaches a predetermined value. The predetermined value may be substantially equal to 0.
As shown in
The timer unit 20a may receive the signals indicating the first to fifth passage timings to measure the first to fifth passage timings TD1 to TD5, respectively. The first to fifth passage timings TD1 to TD5 may be the timings at which the first to fifth pulse laser beams 21 to 25 pass the first to fifth positions, respectively.
The first to fifth emitting timings T1out to T5out at which the first to fifth pulse laser beams 21 to 25 are emitted from the laser system 5 may be calculated as follows:
T1out=TD1+L1/c
T2out=TD2+L2/c
T3out=TD3+L3/c
T4out=TD4+L4/c
T5out=TD5+L5/c
Here, L1 to L5 may correspond to the optical path lengths from the first to fifth positions 21a to 25a, respectively, to the position 26a where the laser beams are emitted from the laser system 5. Further, c may be the velocity of light in vacuum.
The processor 20b may update the first to fifth trigger timings TR1 to TR5 such that respective differences between the first to fifth emitting timings T1out to T5out approach a predetermined value. The predetermined value may be equal to 0.
Through the control described above with reference to
The number of the laser apparatuses in the laser system 5 may not be limited to five. It may be an integer equal to or more than two.
The oscillation trigger signal is not limited to be generated by the exposure apparatus controller 40, but may be generated by the laser system controller 20 at a predetermined repetition frequency.
3.8 Main Flow
First, at S20, the processor 20b may set the first to fifth trigger timings TR1 to TR5 to initial values TR1in to TR5in, respectively.
Next, at S50, the processor 20b may calculate the second to fifth emitting timings T2out to T5out at which the second to fifth pulse laser beams 22 to 25 are emitted from the laser system 5. The processor 20b may then calculate differences T12 to T15 between the second to fifth emitting timings T2out to T5out and respective target values of them. Details of this process will be described below with reference to
Next, at S60, the processor 20b may update the first to fifth trigger timings TR1 to TR5. The trigger timings TR1 to TR5 may be calculated as follows using the differences T12 to T15:
TR1=TR1
TR2=TR2−T12
TR3=TR3−T13
TR4=TR4−T14
TR5=TR5−T15
TR1 to TR5 in the right sides of the above-mentioned formulas may correspond to the trigger timings having been set, and TR1 to TR5 in the left sides of the above-mentioned formulas may correspond to the updated trigger timings.
Next, at S90, the processor 20b may determine whether the control on the trigger timings should be stopped. If the control should not be stopped (S90: NO), the processor 20b may return to the above-mentioned S50, and repeat the processes of S50 to S90. If the control should be stopped (S90: YES), the processor 20b may terminate the processing of this flowchart.
3.9 Details of S50
First, at S51, the processor 20b may set initial values for performing the processing of this flowchart as follows:
N=1
TD1sum
=TD2sum
=TD3sum
=TD4sum
=TD5sum
=0
Here, N may be a value of a counter. TD1sum to TD5sum may be accumulated values of TD1 to TD5 for calculating average values of TD1 to TD5, respectively.
Next, at S52, the processor 20b may determine whether the signals indicating the first to fifth passage timings have been inputted. This may be performed by determining whether the processor 20b has received the count data from the timer unit 20a. If the signals indicating the first to fifth passage timings have not been inputted (S52: NO), the processor 20b may standby until the signals are inputted. If the signals indicating the first to fifth passage timings have been inputted (S52: YES), the processor 20b may proceed to S53.
At S53, the processor 20b may read the first to fifth passage timings TD1 to TD5. The first to fifth passage timings TD1 to TD5 may correspond to the time periods from the timing at which the timer unit 20a receives the oscillation trigger signal until the respective timings at which the timer unit 20a receives the signals indicating the first to fifth passage timings.
Next, at S54, the processor 20b may update accumulated values TD1sum to TD5sum as follows:
TD1sum=TD1sum+TD1
TD2sum=TD2sum+TD2
TD3sum=TD3sum+TD3
TD4sum=TD4sum+TD4
TD5sum=TD5sum+TD5
TD1sum to TD5sum in the right sides of the above-mentioned formulas may correspond to the current accumulated values, and TD1sum to TD5sum in the left sides of the above-mentioned formulas may correspond to the updated accumulated values.
Next, at S55, the processor 20b may determine whether a value of the counter N is equal to or more than a predetermined value Nmax. The Nmax may be an integer determined in a range of 10 to 1000.
If the value of the counter N is not equal to or more than the predetermined value Nmax (S55: NO), the processor 20b may proceed to S56. At S56, the processor 20b may add 1 to the value of the counter N. The processor 20b may then return to the above-mentioned S52.
If the value of the counter N is equal to or more than the predetermined value Nmax (S55: YES), the processor 20b may proceed to S57.
At S57, the processor 20b may calculate average values TD1av to TD5av of the first to fifth passage timings TD1 to TD5, respectively, as follows:
TD1av=TD1sum/Nmax
TD2av=TD2sum/Nmax
TD3av=TD3sum/Nmax
TD4av=TD4sum/Nmax
TD5av=TD5sum/Nmax
Next, at S58, the processor 20b may calculate the first to fifth emitting timings T1out to T5out at which the first to fifth pulse laser beams 21 to 25, respectively, are emitted from the laser system 5.
T1out=TD1av+L1/c
T2out=TD2av+L2/c
T3out=TD3av+L3/c
T4out=TD4av+L4/c
T5out=TD5av+L5/c
Thus, by using the average values TD1av to TD5av of the first to fifth passage timings TD1 to TD5, respectively, stable control may be performed.
Next, at S59, the processor 20b may calculate differences T12 to T15 between the second to fifth emitting timings T2out to T5out and the respective target values of them as follows:
T12=T2out−T1out
T13=T3out−T1out
T14=T4out−T1out
T15=T5out−T1out
The target values of the second to fifth emitting timings T2out to T5out may be set to the same value with the first emitting timing T1out. The differences between the first to fifth emitting timings T1out to T5out may thus approach 0.
After S59, the processor 20b may terminate the processing of this flowchart and proceed to S60 of
According to the above-mentioned processing, the first to fifth pulse laser beams 21 to 25 may be emitted at substantially the same time at the emitting position of the laser system 5. The emitting timings of the first to fifth pulse laser beams 21 to 25 may thus coincide with each other, improving light intensity of the combined laser beam emitted from the laser system 5. A value of the light intensity may be obtained by dividing pulse energy with pulse width.
In the first embodiment, the timing detectors 32a to 32e are provided in the optical paths of the first to fifth pulse laser beams 21 to 25, respectively. However, the present disclosure is not limited to this. A memory may store required time periods from timings at which the first to fifth trigger signals are outputted by the laser system controller 20 until timings at which the first to fifth pulse laser beams 21 to 25, respectively, are emitted from the laser system 5. Based on the required time periods, the trigger timings may be controlled such that the differences between the emitting timings of the first to fifth pulse laser beams 21 to 25 from the laser system 5 approach a predetermined value.
As described below, the timing detectors 32a to 32e may be provided in the first to fifth laser apparatuses 2a to 2e, respectively. In that case, the first to fifth positions 21a to 25a may be set to the light-emitting positions of the pulse laser beams from the first to fifth laser apparatuses 2a to 2e, respectively.
4.1 Configuration
The pulse waveform measuring device 6 may include a beam splitter 61, focusing optics 62, and an optical sensor 63. The beam splitter 61 may be provided between the beam combiner system 3 and the exposure apparatus 4 in the optical path of the pulse laser beam. The beam splitter 61 may transmit the pulse laser beam at high transmittance to a first direction, and reflect a part of the pulse laser beam to a second direction. The focusing optics 62 may concentrate the pulse laser beam reflected by the beam splitter 61 to the second direction on a light-receiving surface of the optical sensor 63.
The optical sensor 63 may include a photodiode or a photoelectric tube. The optical sensor 63 may preferably include a biplanar photo tube. The optical sensor 63 may receive the pulse laser beam concentrated by the focusing optics 62. The optical sensor 63 may output data on a pulse waveform of the received pulse laser beam to the laser system controller 20.
According to this embodiment, the first to fifth emitting timings T1out to T5out, at which the first to fifth pulse laser beams 21 to 25 are emitted from the laser system 5, may sequentially shift by ΔT. By emitting the first to fifth pulse laser beams 21 to 25 sequentially shifting by ΔT from the laser system 5, a combined laser beam having a long pulse width may be generated. Further, by changing the value of ΔT, the pulse width of the combined laser beam may be changed.
4.2 Main Flow
First, at S20, the processor 20b may set the first to fifth trigger timings TR1 to TR5 to respective initial values TR1in to TR5in. The process at S20 may be substantially the same as the process at S20 described above with reference to
Next, at S30, the processor 20b may set a shift amount ΔT of the emitting timings T1out to T5out of the first to fifth pulse laser beams 21 to 25 from the laser system 5 to an initial value ΔTin.
Next, at S40, the processor 20b may read the target pulse width Dt. The target pulse width Dt may have been outputted from the exposure apparatus controller 40.
Next, at S50a, the processor 20b may calculate differences T12 to T15 between the second to fifth emitting timings T2out to T5out, at which the second to fifth pulse laser beams 22 to 25 are emitted from the laser system 5, and respective target values of them. Details of this process will be described below with reference to
Next, at S60, the processor 20b may update the first to fifth trigger timings TR1 to TR5. The process at S60 may be substantially the same as the process at S60 described above with reference to
Next, at S70, the processor 20b may correct the shift amount ΔT of the emitting timings of the first to fifth pulse laser beams 21 to 25 from the laser system 5. Details of this process will be described below with reference to
TIS=([∫I(t)dt]2)/(∫I(t)2dt)
Here, t may represent time. I(t) may represent light intensity at the time t. The symbol ∫ may represent integral.
Next, at S90, the processor 20b may determine whether the control on the trigger timings should be stopped. If the control should not be stopped (S90: NO), the processor 20b may return to the above-mentioned S50a, and repeat the processes of S50a to S90. If the control should be stopped (S90: YES), the processor 20b may terminate the processing of this flowchart.
4.3 Details of S50a
Target values to be set for calculating the differences T12 to T15 in S59a of
At S59a, the target values of the second to fifth emitting timings T2out to T5out may sequentially shift by ΔT from the first emitting timing T1out. The pulse width of the combined laser beam may thus be controlled.
The processing shown in
4.4 Details of S70
First, at S71, the processor 20b may set initial values for performing the processing of this flowchart as follows:
N=1
Dsum=0
Here, N may be a value of a counter. Dsum may be an accumulated value of pulse width D of the combined laser beam for calculating an average value of D.
Next, at S72, the processor 20b may determine whether the processor 20b has received data on the pulse waveform of the combined laser beam, in which the first to fifth pulse laser beams 21 to 25 are combined.
If the processor 20b has not received the data on the pulse waveform from the pulse waveform measuring device 6 (S72: NO), the processor 20b may standby until receiving the data on the pulse waveform. If the processor 20b has received the data on the pulse waveform from the pulse waveform measuring device 6 (S72: YES), the processor 20b may proceed to S73.
At S73, the processor 20b may calculate the pulse width D of the combined laser beam.
Next, at S74, the processor 20b may update the accumulated value Dsum as follows.
Dsum=Dsum+D
Dsum in the right side of the above-mentioned formula may correspond to the accumulated value having been calculated, and Dsum in the left side of the above-mentioned formula may correspond to the updated accumulated value.
Next, at S75, the processor 20b may determine whether a value of the counter N is equal to or more than a predetermined value Nmax. Nmax may be an integer determined in a range of 10 to 1000.
If the value of the counter N is not equal to or more than the predetermined value Nmax (S75: NO), the processor 20b may proceed to S76. At S76, the processor 20b may add 1 to the value of the counter N. The processor 20b may then return to the above-mentioned S72.
If the value of the counter N is equal to or more than the predetermined value Nmax (S75: YES), the processor 20b may proceed to S77.
At S77, the processor 20b may calculate an average value Dav of the pulse width D of the combined laser beam as follows.
Dav=Dsum/Nmax
Next, at S78, the processor 20b may calculate difference ΔD between the average value Dav of the pulse width D of the combined laser beam and the target pulse width Dt as follows.
ΔD=Dav−Dt
Next, at S79, the processor 20b may correct the shift amount ΔT of the first to fifth emitting timings T1out to T5out of the first to fifth pulse laser beams 21 to 25 from the laser system 5 as follows.
ΔT=ΔT−k·ΔD
Here, k may be an inverse of a value obtained by subtracting 1 from the number of the laser apparatuses. For example, in a case where five laser apparatuses 2a to 2e are used, k may equal to ¼. By correcting ΔT as described above, the pulse width of the combined laser beam may approach the target pulse width Dt.
After 579, the processor 20b may terminate the processing of this flowchart and proceed to S90 of
According to the above-mentioned processing, the first to fifth pulse laser beams 21 to 25 may be emitted at timings sequentially shifting by ΔT at the emitting position of the laser system 5. Such shift in the emitting timings of the first to fifth pulse laser beams 21 to 25 may enable the pulse width of the combined laser beam from the laser system 5 to be changed. Further, by performing feedback control on ΔT based on the target pulse width the pulse width of the combined laser beam may be stabilized.
5.1 Configuration
5.2 Main Flow
First, at S10, the processor 20b may read data on the target pulse waveform WT. The data on the target pulse waveform WT may have been received from the exposure apparatus controller 40.
Next, at S15, the processor 20b may calculate several target parameters based on the target pulse waveform WT. The target parameters to be calculated may be as follows: (1) Respective target values P1t to P5t of the pulse energy values of the first to fifth pulse laser beams; and (2) Respective target values ΔT12t to ΔT15t of the shift amounts of the emitting timings of the second to fifth pulse laser beams after the first pulse laser beam emitted from the laser system 5.
Preferably, these target parameters may be calculated such that the pulse waveform WS of the combined laser beam based on the target parameters approaches the target pulse waveform WT.
For example, the pulse waveform WS of the combined laser beam calculated by mutually superposing the pulse waveforms W1 to W5 of the pulse laser beams may be simulated based on the target values P1t to P5t of the pulse energy values of the first to fifth pulse laser beams 21 to 25 and the target values ΔT12t to ΔT15t of the shift amounts. An absolute value of difference between the pulse waveform WS and the target pulse waveform WT may then be integrated and the parameters may be calculated such that the integrated value ΔS1 may become minimum.
Next, at S20, the processor 20b may set the first to fifth trigger timings TR1 to TR5 to initial values TR1in to TR5in, respectively. The process at S20 may be substantially the same as the process at S20 described above with reference to
Next, at S50b, the processor 20b may calculate the differences T12 to T15 between the second to fifth emitting timings T2out to T5out, at which the second to fifth pulse laser beams 22 to 25 are emitted from the laser system 5, and respective target values of them. Details of this process will be described below with reference to
Next, at S60, the processor 20b may update the first to fifth trigger timings TR1 to TR5. The process at S60 may be substantially the same as the process at S60 described above with reference to
Next, at S80, the processor 20b may compare the pulse waveform WM of the combined laser beam, in which the first to fifth pulse laser beams 21 to 25 are combined, and the target pulse waveform WT to update the target parameters.
The updated target parameters may preferably be calculated such that the pulse waveform WM of the combined laser beam measured by the pulse waveform measuring device 6 approaches the target pulse waveform WT.
For example, an absolute value of difference between the measured pulse waveform WM and the target pulse waveform WT may be integrated and the parameters may be updated such that the integrated value ΔS2 may decrease. The pulse waveforms W1 to W5 of the respective pulse laser beams may be corrected such that the simulated pulse waveform WS and the measured pulse waveform WM are close to each other.
Next, at S90, the processor 20b may determine whether the control of the trigger timings and the pulse energy values should be stopped. If the control should not be stopped (S90: NO), the processor 20b may return to the above-mentioned S50b, and repeat the processes of S50b to S90. If the control should be stopped (S90: YES), the processor 20b may terminate the processing of this flowchart.
5.3 Details of 250b
Target values to be set for calculating the differences T12 to T15 in S59b of
At S59b, the target values of the second to fifth emitting timings T2out to T5out may shift by ΔT12t to ΔT15t, respectively, from the first emitting timing T1out.
As illustrated by broken lines in
As illustrated by broken lines in
As illustrated by broken lines in
As illustrated by broken lines in
As explained above, by setting the target values P1t to P5t of pulse energy values of the first to fifth pulse laser beams 21 to 25 and setting the target values ΔT12t to ΔT15t of the shift amounts of the timings, a combined laser beam having a desired pulse waveform may be generated.
6.1 Configuration
The number of the optical path length adjusters 7a to 7e may correspond to the number of the laser apparatuses 2a to 2e. The plurality of optical path length adjusters 7a to 7e may include first to fifth optical path length adjusters 7a to 7e.
The first optical path length adjuster 7a may be provided between the first laser apparatus 2a and the timing detector 32a in the optical path of the first pulse laser beam 21. The first optical path length adjuster 7a may make the first pulse laser beam 21 detour to change the optical path length of the first pulse laser beam 21. The first optical path length adjuster 7a may change the optical path length of the first pulse laser beam. 21 under control by the laser system controller 20.
The right-angle prism 71 may have a first surface 77a and a second surface 77b perpendicular to each other, each of which may be coated with a high-reflective film. The right-angle prism 71 may be held by a holder 77. The holder 77 may be fixed to the plate 74. The right-angle prism 71 may be provided in the optical path of the first pulse laser beam 21.
The two high-reflective mirrors 72 and 73 may be held by a holder 78 such that their reflective surfaces are perpendicular to each other. The holder 78 may be fixed to the plate 75. The plate 75 may be fixed to the uniaxial stage 76. The uniaxial stage 76 may be configured to move the two high-reflective mirrors 72 and 73 in a direction substantially parallel to the optical path axis of the first pulse laser beam 21 reflected by the first surface 77a of the right-angle prism 71.
The first pulse laser beam 21 reflected by the first surface 77a of the right-angle prism 71 may be reflected by the two high-reflective mirrors 72 and 73 and then be made incident on the second surface 77b of the right-angle prism 71. The first pulse laser beam 21 being incident on the second surface 77b of the right-angle prism 71 may emit from the second surface 77b of the right-angle prism 71 along an extension line of the optical path axis of the first pulse laser beam 21 incident on the first surface 77a of the right-angle prism 71.
The laser system controller 20 may drive a motor 79 of the uniaxial stage 76 to move the two high-reflective mirrors 72 and 73. Moving the two high-reflective mirrors 72 and 73 by a distance X may cause the optical path length of the first pulse laser beam 21 to be changed by 2×. By changing the optical path length, emitting timing of the first pulse laser beam 21 from the laser system 5 may be controlled.
The first to fifth optical path length adjusters 7a to 7e may have substantially the same configurations with each other.
The second optical path length adjuster 7b may change the optical path length of the second pulse laser beam 22 between the second laser apparatus 2b and the timing detector 32b.
The third optical path length adjuster 7c may change the optical path length of the third pulse laser beam 23 between the third laser apparatus 2c and the timing detector 32c.
The fourth optical path length adjuster 7d may change the optical path length of the fourth pulse laser beam 24 between the fourth laser apparatus 2d and the timing detector 32d.
The fifth optical path length adjuster 7e may change the optical path length of the fifth pulse laser beam 25 between the fifth laser apparatus 2e and the timing detector 32e.
6.2 Main Flow
At S20a, the processor 20b may set the optical path lengths AL1 to AL5 adjusted by the first to fifth optical path length adjusters 7a to 7e to initial values AL1in to AL5in, respectively.
The processes at S30 to S50a may be substantially the same as those described with reference to
At S60a, the processor 20b may update the optical path lengths AL1 to AL5 adjusted by the first to fifth optical path length adjusters 7a to 7e. The optical path lengths AL1 to AL5 may be calculated as follows using the differences T12 to T15 between the second to fifth emitting timings T2out to T5out and the respective target values of them:
AL1=AL1
AL2=AL2−T12·c
AL3=AL3−T13·c
AL4=AL4−T14·c
AL5=AL5−T15·c
AL1 to AL5 in the right sides of the above-mentioned formulas may correspond to the optical path lengths having been set, and AL1 to AL5 in the left sides of the above-mentioned formulas may correspond to the updated optical path lengths.
The processes at S70 and S90 may be substantially the same as those described with reference to
In the configuration of the fourth embodiment, the first to fifth pulse laser beams 21 to 25 may be emitted at substantially the same time at the emitting position of the laser system 5. In other words, the first embodiment, in which the timings of the first to fifth trigger signals are controlled, may be modified to the configuration where the optical path lengths AL1 to AL5 are controlled so that the emitting timings from the laser system 5 coincide with each other.
In the configuration of the fourth embodiment, the pulse energy values of the first to fifth pulse laser beams 21 to 25 may be controlled. In other words, not only by controlling the optical path lengths AL1 to AL5, but also by controlling the pulse energy values, the pulse waveform of the combined laser beam emitted from the laser system 5 may become closer to the target pulse waveform.
The fourth embodiment includes the plurality of timing detectors 32a to 32e. However, the present disclosure is not limited to this. Emitting timings of the first to fifth pulse laser beams from the laser system 5, in which the optical path lengths AL1 to AL5 are set to respective predetermined values, may be stored in a memory. Based on the emitting timings, the optical path lengths AL1 to AL5 may be controlled so that the differences between the emitting timings of the first to fifth pulse laser beams from the laser system 5 approach predetermined values.
In the fourth embodiment, the optical path length adjusters 7a to 7e are provided in the optical paths between the first to fifth laser apparatuses and the corresponding timing detectors 32a to 32e. However, the present disclosure is not limited to this. For example, the optical path length adjusters 7a to 7e may be provided between the respective timing detectors 32a to 32e and the beam combiner system 3. In that case, the optical path lengths L1 to L5 from the first to fifth positions 21a to 25a to the emitting position 26a of the laser system may include the optical path lengths of the optical path length adjusters 7a to 7e, respectively.
7.1 Laser Apparatus
The master oscillator MO may include a laser chamber 10, a pair of electrodes 11a and 11b, a charger 12, and a pulse power module (PPM) 13. The master oscillator MO may further include a high-reflective mirror 14 and an output coupling mirror 15.
The laser chamber 10 may store laser gases constituting a laser medium, including a rare gas such as argon, krypton or xenon, a buffer gas such as neon or helium, and a halogen gas such as chlorine or fluorine. The pair of electrodes 11a and 11b may be provided in the laser chamber 10 as electrodes for exciting the laser medium by electric discharge. The laser chamber 10 may have an opening, sealed by an insulating member 29. The electrode 11a may be supported by the insulating member 29 and the electrode 11b may be supported by a return plate 10d. The return plate 10d may be electrically connected to an inner surface of the laser chamber 10 through electric wirings 10e and 10f described later. In the insulating member 29, conductive members 29a may be molded. The conductive members 29a may apply high-voltage, which is supplied by the pulse power module 13, to the electrode 11a.
The charger 12 may be a direct-current power source for charging a charge capacitor C0 of the pulse power module 13 at a predetermined voltage. The pulse power module 13 may include a switch 13a controlled by the laser controller 19. When the switch 13a turns ON, the pulse power module 13 may generate the pulsed high-voltage using electric energy in the charger 12. The high-voltage may be applied to the pair of electrodes 11a and 11b.
The high-voltage applied to the pair of electrodes 11a and 11b may cause dielectric breakdown and cause the electric discharge between the pair of electrodes 11a and 11b. Energy of the electric discharge may excite the laser medium in the laser chamber 10 to a high energy level. The excited laser medium may then change to a low energy level, where the laser medium generates light according to the difference of the energy levels.
The laser chamber 10 may have windows 10a and 10b at respective ends of the laser chamber 10. The light generated in the laser chamber 10 may be emitted from the laser chamber 10 through the windows 10a and 10b.
The high-reflective mirror 14 may reflect the light emitted from the window 10a of the laser chamber 10 at high reflectance to return the light to the laser chamber 10.
The output coupling mirror 15 may transmit to output a part of the light emitted from the window 10b of the laser chamber 10 and reflect to return another part of the light to the laser chamber 10.
The high-reflective mirror 14 and the output coupling mirror 15 may thus constitute an optical resonator. The light emitted from the laser chamber 10 may travel back and forth between the high-reflective mirror 14 and the output coupling mirror 15. The light may be amplified at every time to pass a laser gain region between the electrode 11a and the electrode 11b. The pulse laser beam of the amplified light may be emitted through the output coupling mirror 15.
The power amplifier PA may be provided in the optical path of the pulse laser beam emitted from the output coupling mirror 15 of the master oscillator MO. The power amplifier PA may include, as in the master oscillator MO, a laser chamber 10, a pair of electrodes 11a and 11b, a charger 12, and a pulse power module (PPM) 13. Configurations of these elements may be substantially the same as those in the master oscillator MO. The power amplifier PA does not have to include the high-reflective mirror 14 or the output coupling mirror 15. The pulse laser beam, which entered the power amplifier PA through the window 10a, may once pass the laser gain region between the electrode 11a and the electrode 11b, and then be emitted through the window 10b.
The pulse stretcher 16 may be provided in the optical path of the pulse laser beam emitted from the window 10b of the power amplifier PA. The pulse stretcher 16 may include a beam splitter 16a, and first to fourth concave mirrors 16b to 16e.
The pulse laser beam emitted from the power amplifier PA may be made incident on a first surface of the beam splitter 16a. The beam splitter 16a may transmit a part of the pulse laser beam incident on the first surface and reflect another part.
The first to fourth concave mirrors 16b to 16e may sequentially reflect the pulse laser beam reflected by the beam splitter 16a. The concave mirrors 16b to 16e may cause the pulse laser beam to be incident on a second surface of the beam splitter 16a opposite to the first surface. Here, the first to fourth concave mirrors 16b to 16e may be arranged such that an image of the pulse laser beam reflected by the first surface of the beam splitter 16a is transferred by the first to fourth concave mirrors 16b to 16e to the second surface of the beam splitter 16a at a magnification of 1 to 1. The beam splitter 16a may reflect at least a part of the pulse laser beam incident on the second surface. The pulse laser beam incident on the first surface and transmitted by the beam splitter 16a and the pulse laser beam incident on the second surface and reflected by the beam splitter 16a may be mutually superposed at substantially the same beam size and the same beam divergence.
There may be a time difference between the pulse laser beam which was incident on the first surface and was transmitted and the pulse laser beam which was incident on the second surface and was reflected. The time difference may correspond to the optical path length of a detour path formed by the first to fourth concave mirrors 16b to 16e. The pulse stretcher 16 may thus stretch the pulse width of the pulse laser beam.
The pulse energy measuring unit 17 may be provided in the optical path of the pulse laser beam emitted from the pulse stretcher 16. The pulse energy measuring unit 17 may include a beam splitter 17a, focusing optics 17b, and an optical sensor 17c.
The beam splitter 17a may transmit a part of the pulse laser beam, emitted from the pulse stretcher 16, at high transmittance toward the shutter 18. The beam splitter 17a may reflect another part of the pulse laser beam toward the focusing optics 17b. The focusing optics 17b may concentrate the light reflected by the beam splitter 17a on a light-receiving surface of the optical sensor 17c. The optical sensor 17c may detect the pulse energy of the pulse laser beam concentrated on the light-receiving surface and output data on the pulse energy to the laser controller 19.
The laser controller 19 may send and receive various signals to and from the laser system controller 20. The laser controller 19 may receive, for example, the first trigger signal or data on the target pulse energy from the laser system controller 20. The laser controller 19 may send a setting signal of the charging voltage to the charger 12 or an instruction signal of turning ON or OFF the switch to the pulse power module 13.
The laser controller 19 may receive data on the pulse energy from the pulse energy measuring unit 17 and control the charging voltage of the charger 12 according to the data on the pulse energy. By controlling the charging voltage of the charger 12, the pulse energy of the laser beam may be controlled.
The laser controller 19 may further correct the timing of the trigger signal according to the charging voltage having been set, such that the electric discharge occurs at a predetermined constant timing from the oscillation trigger signal.
The shutter 18 may be provided in the optical path of the pulse laser beam transmitted by the beam splitter 17a of the pulse energy measuring unit 17. The laser controller 19 may control the shutter 18 to close in a period from the timing of starting laser oscillation until the timing when the difference between the pulse energy received from the pulse energy measuring unit 17 and the target pulse energy comes within an acceptable range. The laser controller 19 may control the shutter 18 to open when the difference between the pulse energy received from the pulse energy measuring unit 17 and the target pulse energy comes within the acceptable range. The signal outputted from the timing detector 32a in
The laser apparatus may not be limited to the excimer laser apparatus. A solid laser apparatus may be used. Such solid laser apparatus may emit third harmonic light having a wavelength of 355 nm or fourth harmonic light having a wavelength of 266 nm generated by a YAG laser.
The first laser apparatus 2a may include a timing detector 38, instead of the timing detector 32a shown in
The window 10c may transmit the light generated by the electric discharge between the pair of electrodes 11a and 11b. The focusing optics 38a may concentrate the light transmitted by the window 10c on a light-receiving surface of the optical sensor 38b. The optical sensor 38b may include a photodiode or a photoelectric tube. The optical sensor 38b may detect the light generated by the electric discharge between the pair of electrodes 11a and 11b and then send a signal indicating the timing of the electric discharge to the laser system controller 20. Consequently, the timing of the electric discharge in the laser chamber and the timing when the pulse laser beam passes the first position may substantially synchronize with each other.
The pulse power module 13 may include the charge capacitor C0, the switch 13a, a boosting transformer TC1, a plurality of magnetic switches Sr1 to Sr3, and a plurality of capacitors C1 to C3.
Each of the magnetic switches Sr1 to Sr3 may include a saturable reactor. Each of the magnetic switches Sr1 to Sr3 may be switched to a low impedance state when a time integral of the voltage across the magnetic switch becomes a predetermined value that depends on the characteristics of the magnetic switch.
In the charger 12, a charging voltage V may be set by the laser controller 19. The charger 12 may charge the charge capacitor C0 according to the charging voltage V having been set.
The switch 13a in the pulse power module 13 may receive the trigger signal from the laser controller 19. Upon receiving the trigger signal, the switch 13a may turn ON. When the switch 13a turns ON, electric current may flow from the charge capacitor C0 to a primary side of the transformer TC1.
The electric current through the primary side of the transformer TC1 in a first direction may cause induced current through a secondary side of the transformer TC1 in a second direction opposite to the first direction. The electric current through the secondary side of the transformer TC1 may allow the time integral of the voltage across the magnetic switch Sr1 to reach a threshold value.
When the time integral of the voltage across the magnetic switch Sr1 reaches the threshold value, the magnetic switch Sr1 may be closed due to magnetic saturation.
Closing the magnetic switch Sr1 may allow electric current to flow from the secondary side of the transformer TC1 to the capacitor C1 and to charge the capacitor C1.
As the capacitor C1 is charged, the magnetic switch Sr2 may be closed due to magnetic saturation.
Closing the magnetic switch Sr2 may allow electric current to flow from the capacitor C1 to the capacitor C2 and to charge the capacitor C2. Here, the electric current to charge the capacitor C2 may have a shorter pulse width than the electric current to charge the capacitor C1.
As the capacitor C2 is charged, the magnetic switch Sr3 may be closed due to magnetic saturation.
Closing the magnetic switch Sr3 may allow electric current to flow from the capacitor C2 to the capacitor C3 and to charge the capacitor C3. Here, the electric current to charge the capacitor C3 may have a shorter pulse width than the electric current to charge the capacitor C2.
The pulse width of the electric current may thus be compressed while the electric current flows from the capacitor C1 to the capacitor C2 and from the capacitor C2 to the capacitor C3, sequentially.
When the voltage across the capacitor C3 reaches a breakdown voltage of the laser gas, dielectric breakdown may occur in the laser gas between the pair of electrodes 11a and 11b. The laser gas may then be excited, and the pulse laser beam may be generated. As the switch 13a operates, discharging operation described above may be repeated and the pulse laser beam may be emitted in a predetermined repetition frequency. A current meter 39, which detects electric discharge current, may be used as the timing detector. The current meter 39 may be an electric current probe to detect the timing of electric discharge. The timing when the electric discharge occurs in the laser chamber and the timing when the pulse laser beam passes the first position may thus substantially synchronize with each other.
The pulse energy measuring unit 17 or the timing detector 38 to detect the timing of the electric discharge may be used instead of the timing detector 32a shown in FIG. 1. In that case, the first to fifth positions 21a to 25a may be the positions of each outlet of the pulse laser beam of the laser apparatus or the positions of each output coupling mirror 15 of the master oscillator, assuming that the first to fifth laser apparatuses have substantially the same configurations with each other.
7.2 Beam Combiner Including Fly Eye Lens
The fly eye lens 342a may be constituted by an ultraviolet-transmitting substrate, such as a synthetic quartz substrate or a calcium fluoride substrate, on which multiple concave or convex lenses are formed. The fly eye lens 342a may be provided at the position where the first to fifth pulse laser beams 21 to 25 emitted from the incident optics 33 overlap with each other. The lenses included in the fly eye lens 342a may be arranged in the cross section of a plurality of pulse laser beams including the first to fifth pulse laser beams 21 to 25. The lenses may transmit respective parts of the plurality of pulse laser beams toward the condenser optics 342b and expand beam widths of the respective parts. The fly eye lens 342a may thus form multiple point light sources as secondary light sources using the pulse laser beams. The fly eye lens 342a may include a set of cylindrical concave or convex lenses arranged in one direction and another set of cylindrical concave or convex lenses arranged in another direction perpendicular to the one direction.
The condenser optics 342b may include at least one convex lens. The condenser optics 342b may extend over the optical paths of the respective parts of the plurality of pulse laser beams expanded by the respective lenses of the fly eye lens 342a.
The fly eye lens 342a may be provided such that a front-side focal plane of the condenser optics 342b substantially coincides with respective focal positions of the fly eye lens 342a. The condenser optics 342b may thus collimate each of the parts of the plurality of pulse laser beams expanded by the respective lenses of the fly eye lens 342a, such that each of the parts has substantially parallel rays.
The condenser optics 342b may be provided such that a rear-side focal plane of the condenser optics 342b substantially coincides with a light-receiving surface of the fly eye lens 421 of the exposure apparatus 4. The condenser optics 342b may thus make the respective parts, expanded by the respective lenses of the fly eye lens 342a, enter substantially the same portion of the fly eye lens 421.
Consequently, the pulse laser beam in which the parts are overlapping with each other at the light-receiving surface of the fly eye lens 421 of the exposure apparatus 4 may have small variation in light intensity distribution in a cross section of the pulse laser beam.
7.3 Beam Combiner Using Flat Mirrors
The first right-angle prism 3371 may have a triangular prism shape whose base surface parallel to the paper surface has a right-angled triangular shape. The first right-angle prism 3371 may have two side-surfaces perpendicular to each other, each of which may be coated with a high-reflective film. The respective two side-surfaces of the first right-angle prism 3371 may constitute a first reflective surface 3371a and a second reflective surface 3371b.
The first right-angle prism 3371 may be arranged such that the first reflective surface 3371a of the first right-angle prism 3371 is parallel to a below-mentioned first reflective surface 3373a of the trapezoidal prism 3373. The first right-angle prism 3371 may be arranged such that the first reflective surface 3371a of the first right-angle prism 3371 intersects the optical path axis of the first pulse laser beam 21 at an angle of 45 degrees. The first right-angle prism 3371 may be arranged such that the second reflective surface 3371b of the first right-angle prism 3371 intersects the optical path axis of the second pulse laser beam 22 at an angle of 45 degrees.
The second right-angle prism 3372 may have a triangular prism shape whose base surface parallel to the paper surface has a right-angled triangular shape. The second right-angle prism 3372 may have two side-surfaces perpendicular to each other, each of which may be coated with a high-reflective film. The respective two side-surfaces of the second right-angle prism 3372 may constitute a first reflective surface 3372a and a second reflective surface 3372b.
The second right-angle prism 3372 may be arranged such that the first reflective surface 3372a of the second right-angle prism 3372 is substantially parallel to a below-mentioned second reflective surface 3373b of the trapezoidal prism 3373. The second right-angle prism 3372 may be arranged such that the first reflective surface 3372a of the second right-angle prism 3372 intersects the optical path axis of the fourth pulse laser beam 24 at an angle of 45 degrees. The second right-angle prism 3372 may be arranged such that the second reflective surface 3372b of the second right-angle prism 3372 intersects the optical path axis of the fifth pulse laser beam 25 at an angle of 45 degrees.
The trapezoidal prism 3373 may be made by an ultraviolet-transmitting material, such as synthetic quartz or calcium fluoride. The trapezoidal prism 3373 may have a quadrangular prism shape whose base surface parallel to the paper surface has a quadrangular shape. The base surface of the trapezoidal prism 3373 has a shape of isosceles trapezoid whose non-parallel and opposite sides are perpendicular to each other.
The trapezoidal prism 3373 may have two opposite side-surfaces which are non-parallel to each other, each of which may be coated with a high-reflective film. The respective two opposite side-surfaces which are non-parallel to each other may constitute the first reflective surface 3373a and the second reflective surface 3373b.
The trapezoidal prism 3373 may have the other two opposite side-surfaces which are parallel to each other, each of which may be coated with an anti-reflective film. The respective two opposite side-surfaces which are parallel to each other may constitute a first transmitting surface 3373c and a second transmitting surface 3373d.
The trapezoidal prism 3373 may be arranged such that the second transmitting surface 3373d of the trapezoidal prism 3373 is perpendicular to the optical path axis of the third pulse laser beam 23.
The first pulse laser beam 21 emitted from the first laser apparatus 2a may be reflected by the first reflective surface 3371a of the first right-angle prism 3371. The first pulse laser beam 21 may be reflected by the first reflective surface 3373a of the trapezoidal prism 3373 and then enter the light-receiving surface of the fly eye lens 421 at a right angle.
The second pulse laser beam 22 emitted from the second laser apparatus 2b may be reflected by the second reflective surface 3371b of the first right-angle prism 3371. The second pulse laser beam 22 may be reflected by the first reflective surface 3373a of the trapezoidal prism 3373 and then enter the light-receiving surface of the fly eye lens 421 at a right angle.
The third pulse laser beam 23 emitted from the third laser apparatus 2c may enter the second transmitting surface 3373d of the trapezoidal prism 3373 to travel inside the prism. The third pulse laser beam 23 incident on the trapezoidal prism 3373 may emit from the first transmitting surface 3373c and then enter the light-receiving surface of the fly eye lens 421 at a right angle.
The fourth pulse laser beam 24 emitted from the fourth laser apparatus 2d may be reflected by the first reflective surface 3372a of the second right-angle prism 3372. The fourth pulse laser beam 24 may be reflected by the second reflective surface 3373b of the trapezoidal prism 3373 and then enter the light-receiving surface of the fly eye lens 421 at a right angle.
The fifth pulse laser beam 25 emitted from the fifth laser apparatus 2e may be reflected by the second reflective surface 3372b of the second right-angle prism 3372. The fifth pulse laser beam 25 may be reflected by the second reflective surface 3373b of the trapezoidal prism 3373 and then enter the light-receiving surface of the fly eye lens 421 at a right angle.
The beam combiner 337 may thus align the first to fifth pulse laser beams 21 to 25 such that the optical path axes of them are substantially parallel to each other, before entering the pulse waveform measuring device 6. These pulse laser beams 21 to 25 may be partially reflected by the beam splitter 61, transmitted by the focusing optics 62, and then be made incident on the light-receiving surface of the optical sensor 63 provided at the focal position of the focusing optics 62. The pulse waveform measuring device 6 of this arrangement may measure the pulse waveform of the combined laser beam, even if the pulse laser beams of the combined laser beam are spaced apart from each other. The pulse laser beams 21 to 25 transmitted by the beam splitter 61 may enter the fly eye lens 421. Thus, the beam combiner 337 does not need to make the first to fifth pulse laser beams 21 to 25 overlap with each other.
If the pulse waveform does not need to be measured, the pulse waveform measuring device 6 may be omitted.
A controller, such as the laser system controller 20, in the above-mentioned embodiments may be constituted by a general-purpose control device, such as a computer or a programmable controller. For example, the controller may be constituted as described below.
The controller may include a processor 1000 and other elements connected to the processor 1000. Such elements may include a storage memory 1005, a user interface 1010, a parallel input/output (I/O) controller 1020, a serial I/O controller 1030, and an analog-to-digital (A/D) and digital-to-analog (D/A) converter 1040. The processor 1000 may include a central processing unit (CPU) 1001 and other elements connected to the CPU 1001 including a memory 1002, a timer 1003, and a graphics processing unit (GPU) 1004.
The processor 1000 may read out programs stored in the storage memory 1005. The processor 1000 may execute the read-out programs, read out data from the storage memory 1005 in accordance with the execution of the programs, or store data in the storage memory 1005.
The parallel I/O controller 1020 may be connected to devices 1021 to 102x communicable through parallel I/O ports. The parallel I/O controller 1020 may control communication using digital signals through the parallel I/O ports that is performed in the process where the processor 1000 executes programs.
The serial I/O controller 1030 may be connected to devices 1031 to 103x communicable through serial I/O ports. The serial I/O controller 1030 may control communication using digital signals through the serial I/O ports that is performed in the process where the processor 1000 executes programs.
The A/D and D/A converter 1040 may be connected to devices 1041 to 104x communicable through analog ports. The A/D and D/A converter 1040 may control communication using analog signals through the analog ports that is performed in the process where the processor 1000 executes programs.
The user interface 1010 may be configured to display progress of executing programs by the processor 1000 to an operator or to receive instructions by the operator to the processor 1000 to stop execution of the programs or to execute interruption processing.
The CPU 1001 of the processor 1000 may perform arithmetic processing of programs. In the process where the CPU 1001 executes programs, the memory 1002 may temporally store programs or temporally store data in the arithmetic process. The timer 1003 may measure time or elapsed time. The timer 1003 may output the time or the elapsed time to the CPU 1001 in accordance with the execution of the programs. When image data is inputted to the processor 1000, the GPU 1004 may process the image data in accordance with the execution of the programs and output the results to the CPU 1001.
The devices 1021 to 102x communicable through the parallel I/O ports, which are connected to the parallel I/O controller 1020, may be the first to fifth laser apparatuses 2a to 2e, the exposure apparatus controller 40, another controller, or the like, and may be used for sending or receiving the oscillation trigger signal or the signal indicating the passage timing.
The devices 1031 to 103x communicable through the serial I/O ports, which are connected to the serial I/O controller 1030, may be the first to fifth laser apparatuses 2a to 2e, the exposure apparatus controller 40, another controller, or the like, and may be used for sending or receiving data.
The devices 1041 to 104x communicable through the analog ports, which are connected to the A/D and D/A converter 1040, may be various sensors, such as the pulse waveform measuring device 6, or the like.
With the above-mentioned, configuration, the controller may be capable of achieving the operation illustrated in each of the embodiments.
The aforementioned descriptions are intended to be taken only as examples, and are not to be seen as limiting in any way. Accordingly, it will be clear to those skilled in the art that variations on the embodiments of the present disclosure may be made without departing from the scope of the appended claims.
The terms used in the present specification and in the entirety of the scope of the appended claims are to be interpreted as not being limiting. For example, wording such as “includes” or “is included” should be interpreted as not being limited to the item that is described as being included. Furthermore, “has” should be interpreted as not being limited to the item that is described as being had. Furthermore, the modifier “a” or “an” as used in the present specification and the scope of the appended claims should be interpreted as meaning “at least one” or “one or more”.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2014/065242 | Jun 2014 | US |
| Child | 15350277 | US |
