Apparatus and method for generating multiple laser beams

Abstract

Apparatus and methods for generating multiple laser beams using multiple laser chambers. The relative timing of the beams is controllable so that they can, for example, be staggered, can overlap, or be prevented from overlapping, or can occur in rapid sequence. The beams can have different spectral and power characteristics, such as different wavelengths. A system is also disclosed in which at least one of the multiple laser chambers is configured to generate radiation of two different wavelengths.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 62 / 853,772, filed on May 29, 2019, entitled “APPARATUS FOR AND METHOD OF GENTIPLE LASER BEAMS,” and U.S. Application No. 62 / 978,515, filed on February 19, 2020, entitled “APPARATUS FOR AND METHOD OF GENERATING MULTIPLE LASER BEAMS,” both of which are incorporated herein by reference in their entirety.

[0003] This application also claims priority to U.S. Application No. 62 / 851,147, filed on May 22, 2019, entitled “CONTROL SYSTEM FOR A PLURALITY OF DEEP ULTRAVIOLET OPTICAL OSCILLATORS,” and U.S. Application No. 63 / 006,162, filed on April 7, 2020, entitled “CONTROL SYSTEM FOR A PLURALITY OF DEEP ULTRAVIOLET OPTICALOSCILLATORS,” both of which are also incorporated herein by reference in their entirety. Technical Field

[0004] The present disclosure relates to generating multiple laser beams for use in, for example, a lithographic apparatus. Background Art

[0005] The lithographic apparatus applies the desired pattern to a substrate such as a wafer of semiconductor material, typically to a target portion of the substrate. A pattern forming device, alternatively referred to as a mask or reticle, can be used to generate a circuit pattern to be formed on a single layer of a wafer. The transfer of the pattern is typically accomplished by imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. Typically, a single substrate will contain adjacent target portions that are patterned in succession.

[0006] The lithographic apparatus comprises a so-called stepper, in which each target portion is irradiated by exposing the entire pattern onto the target portion at once, and a so-called scanner, in which each target portion is irradiated by scanning the pattern by a radiation beam in a given direction (the "scanning" direction) and simultaneously scanning the substrate parallel or antiparallel to that direction. The pattern can also be transferred from the patterning device to the substrate by imprinting the pattern onto the substrate. In this document, for simplicity, both steppers and scanners will be referred to simply as scanners.

[0007] The light source used to illuminate the pattern and project it onto the substrate can be in any of a variety of configurations. Common deep ultraviolet excimer lasers used in lithography systems include the 248nm wavelength krypton fluoride (KrF) laser and the 193nm wavelength argon fluoride (ArF) laser. Typically, excimer lasers are designed to use a specific gas mixture. While small, slow adjustments to the wavelength can be easily made, rapidly changing the wavelength is not easy.

[0008] However, there may be situations where it is desirable to have the ability to change wavelengths. For example, in 3D NAND, memory capacity layers (tiers) are stacked on top of each other. The transition from 2D to 3D NAND architecture requires significant changes to the manufacturing process. In 3D NAND manufacturing, the challenges are mainly driven by etching and deposition processes with extreme aspect ratios (e.g., the ratio of the hole diameter to its depth). Creating complex 3D structures with ultra-high aspect ratio (HAR) features is very complex and requires extremely high precision, and ultimately process uniformity and repeatability for reliable high-volume manufacturing. In addition, as the height of the multi-layer stack increases, the difficulty of achieving consistent etching and deposition results at the top and bottom of the memory array also increases.

[0009] These considerations lead to the need for a greater depth of focus. The depth of focus (DOF) of photolithography is given by the relationship DOF = ±mλ / (NA) 2 Determine, where λ is the wavelength of the illuminating light, NA is the numerical aperture, and m is an actual factor that depends on the resist process. Because 3D NAND lithography has higher requirements for depth of focus, multiple exposure passes are sometimes performed on the wafer, with each pass using a different focal plane. One method involves changing the wafer stage height for each pass. Changing the wavelength is another way to achieve the same effect. The material that makes up the lens that focuses the laser radiation usually has some non-zero dispersion, so different wavelengths will focus at different depths. For this reason, it may be necessary to have the ability to quickly change the wavelength.

[0010] In addition to wavelength considerations, the use of higher doses of resist with KrF lasers leads to the need for KrF lasers with higher powers. For example, some applications may desire a KrF laser capable of delivering up to 120W of power.

[0011] Laser systems that can provide flexible wavelength switching and / or higher power irradiation are needed. Summary of the invention

[0012] In order to provide a basic understanding of the embodiments, a simplified overview of one or more embodiments is presented below. This overview is not an extensive overview of all contemplated embodiments, and is not intended to identify key or essential elements of all embodiments, nor is it intended to define the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to a more detailed description presented later.

[0013] According to one aspect of the embodiments, a laser system having two independent laser chambers or cavities is disclosed. Control of at least two wavelengths can be achieved using the two independent cavities. The beams can overlap in space or time to provide higher power than that provided by either beam independently. Putting two lasers into one platform does not increase the operating cost of the lower power process because only one cavity needs to be used at a time. By putting two lasers together with a scanner, the service range can be doubled if higher power is not required. This is not possible with a master power amplifier (MOPA) or similar two-chamber system.

[0014] According to another aspect of the embodiment, the system may include components for allowing a user to use either chamber alone for a low power process or to use both chambers in coordination for a high power process.

[0015] In accordance with another aspect of the embodiments, the relative firing times of the two chambers can be controlled such that the chambers can be fired simultaneously, or with a slight delay in firing of one chamber relative to firing of the other chamber, or the firing can be staggered to essentially double the effective repetitions used in the scanner.

[0016] According to another aspect of the embodiment, a gas discharge laser system is disclosed, the gas discharge laser system comprising a first laser chamber module adapted to generate a first beam of laser radiation having a first wavelength, a second laser chamber module adapted to generate a second beam of laser radiation having a second wavelength, the second wavelength being different from the first wavelength, and a beam combiner arranged to receive the first beam and the second beam and adapted to propagate the first beam and the second beam along a common output beam path. The first laser chamber module may include a first excimer laser chamber module. The first laser chamber module may include an ArF laser chamber module. The first excimer laser chamber module may include a KrF laser chamber module. The second laser chamber module may include a second excimer laser chamber module. The second laser chamber module may include an ArF laser chamber module. The second excimer laser chamber module may include a KrF laser chamber module. The gas discharge laser system may further include a third laser chamber module adapted to generate a third beam of laser radiation, and the beam combiner may be arranged to receive the third beam and propagate the third beam along the common output beam path.

[0017] The gas discharge laser system may further include a discharge timing circuit arranged to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module. The discharge timing circuit may be adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module, such that the first laser chamber module discharges at a first repetition rate and the second laser chamber module discharges at a second repetition rate, the second repetition rate being substantially the same as the first repetition rate and offset relative to the first repetition rate by half of the period of the first repetition rate. The discharge timing circuit may be adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module, such that the first laser chamber module and the second laser chamber module discharge at substantially the same repetition rate, and wherein the second laser chamber module discharges substantially immediately after the first laser chamber module completes discharge. The discharge timing circuit may be adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module, such that the first laser chamber module and the second laser chamber module discharge substantially simultaneously. The discharge timing circuit may be adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module, such that the first laser chamber module and the second laser chamber module do not discharge substantially simultaneously. The discharge timing circuit may be adapted to generate a common command for exciting both the first laser chamber module and the second laser chamber module.

[0018] The first laser chamber module may be adapted to fire without delay after a common command. The first laser chamber module may be adapted to fire with a delay after a common command. The second laser chamber module may be adapted to fire without delay after a common command. The second laser chamber module may be adapted to fire with a delay after a common command.

[0019] The discharge timing circuit may be adapted to generate a first command for energizing the first laser chamber module and a second command for energizing the second laser chamber module. The first laser chamber module may be adapted to energize without delay after the first command. The first laser chamber module may be adapted to energize with a delay after the first command. The second laser chamber module may be adapted to energize without delay after the second command. The second laser chamber module may be adapted to energize with a delay after the command. The first laser chamber module may be energized at a first repetition rate, and the second laser chamber module may be energized at a second repetition rate, the second repetition rate being different from the first repetition rate. The discharge rate ratio of the first repetition rate to the second repetition rate may be a ratio of two integers, for example, 2:1 or 3:2.

[0020] The gas discharge laser system may further include a control system adapted to control both the first laser chamber module and the second laser chamber module. The gas discharge laser system may further include a gas supply system adapted to supply gas to both the first laser chamber module and the second laser chamber module. The gas discharge laser system may further include a first laser chamber metrology unit arranged to measure a parameter of a beam generated by the first laser chamber module. The gas discharge laser system may further include a second laser chamber metrology unit arranged to measure a parameter of a beam generated by the second laser chamber module. The gas discharge laser system may further include a combined beam metrology unit arranged to measure a parameter of a combination of a beam generated by the first laser chamber module and a beam generated by the second laser chamber module. The gas discharge laser system may further include a control unit arranged to receive an output from the first laser chamber metrology unit and configured to control a wavelength of the beam generated by the first laser chamber module based at least in part on the output of the first laser chamber metrology unit. The gas discharge laser system may further include a control unit arranged to receive an output from the second laser chamber metering unit and configured to control the wavelength of the beam generated by the second laser chamber module based at least in part on the output of the second laser chamber metering unit. The gas discharge laser system may further include a control unit arranged to receive an output from the combined beam metering unit and configured to control the spectrum of the combination of the beam generated by the first laser chamber module and the beam generated by the second laser chamber module based at least in part on the output of the combined beam metering unit. The gas discharge laser system may further include a first laser chamber line narrowing module arranged to receive the beam from the first laser chamber module and configured to narrow the bandwidth of the beam from the first laser chamber module. The gas discharge laser system may further include a second laser chamber line narrowing module arranged to receive the beam from the second laser chamber module and configured to narrow the bandwidth of the beam from the second laser chamber module. The gas discharge laser system may further include: a second laser chamber line narrowing module, arranged to receive the light beam from the second laser chamber module and configured to narrow the bandwidth of the light beam from the second laser chamber module; and a control unit, connected to the first laser chamber line narrowing module and the second laser chamber line narrowing module, and adapted to control the first laser chamber line narrowing module and the second laser chamber line narrowing module so that the first bandwidth is substantially the same as the second bandwidth. The gas discharge laser system may further include: a second laser chamber line narrowing module, arranged to receive the light beam from the second laser chamber module and configured to narrow the bandwidth of the light beam from the second laser chamber module; and a control unit, connected to the first laser chamber line narrowing module and the second laser chamber line narrowing module, and adapted to control the first laser chamber line narrowing module and the second laser chamber line narrowing module so that the first bandwidth is different from the second bandwidth.

[0021] According to another aspect of the embodiment, a lithographic apparatus is disclosed, the lithographic apparatus comprising: a first laser chamber module, the first laser chamber module being adapted to generate a first beam of laser radiation having a first wavelength; a second laser chamber module, the second laser chamber module being adapted to generate a second beam of laser radiation having a second wavelength, the second wavelength being different from the first wavelength; a beam combiner, arranged to receive the first beam and the second beam, and adapted to propagate the first beam and the second beam along a common output beam path; and a scanner, arranged to receive the first beam and the second beam, wherein the scanner is configured to provide instructions for adjusting the first wavelength and the second wavelength. The lithographic apparatus may further comprise a discharge timing circuit, the discharge timing circuit being arranged to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module. The discharge timing circuit may be adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module, so that the first laser chamber module and the second laser chamber module discharge at substantially the same repetition rate and 180 degrees out of phase with each other. The discharge timing circuit may be adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module, so that the first laser chamber module and the second laser chamber module discharge at substantially the same repetition rate, and the second laser chamber module discharges substantially immediately after the first laser chamber module completes the discharge. The discharge timing circuit may be adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module, so that the first laser chamber module and the second laser chamber module discharge substantially simultaneously. The discharge timing circuit may be adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module, so that the first laser chamber module and the second laser chamber module do not discharge substantially simultaneously. The lithographic apparatus may further include a control system adapted to control both the first laser chamber module and the second laser chamber module. The lithographic apparatus may further include a gas supply system adapted to supply gas to both the first laser chamber module and the second laser chamber module.

[0022] According to another aspect of the embodiment, a method for exposing a substrate in a lithographic apparatus is disclosed, the method comprising the steps of: receiving an indication of one or more target wavelengths from a scanner; in response to the indication, generating a first beam of laser radiation having a first wavelength using a first laser chamber module; in response to the indication, generating a second beam of laser radiation having a second wavelength using a second laser chamber module, the second wavelength being different from the first wavelength; causing the first beam and the second beam to propagate along a common output beam path; and using the first beam and the second beam in the scanner to expose the substrate to radiation having the first wavelength and radiation having the second wavelength in a single pass. The method may also include the steps of: controlling the relative timing of the steps of generating the first beam of laser radiation having the first wavelength and generating the second beam of laser radiation having the second wavelength, the second wavelength being different from the first wavelength. The steps of controlling the relative timing of the steps of generating the first beam of laser radiation having the first wavelength and generating the second beam of laser radiation having the second wavelength different from the first wavelength may include: generating the first beam of laser radiation and the second beam of laser radiation at substantially the same repetition rate and 180 degrees out of phase with each other. The step of controlling the relative timing of the steps of generating a first beam of laser radiation having a first wavelength and generating a second beam of laser radiation having a second wavelength different from the first wavelength may include generating the first beam of laser radiation and the second beam of laser radiation at substantially the same repetition rate, and generating the second beam substantially immediately after generating the first beam. The step of controlling the relative timing of the steps of generating the first beam of laser radiation having a first wavelength and generating the second beam of laser radiation having a second wavelength different from the first wavelength may include generating the first beam of laser radiation and the second beam of laser radiation substantially simultaneously. The step of controlling the relative timing of the steps of generating the first beam of laser radiation having a first wavelength and generating the second beam of laser radiation having a second wavelength different from the first wavelength may include generating the first beam of laser radiation and the second beam of laser radiation substantially simultaneously.

[0023] According to another aspect of the embodiment, a method of exposing a substrate in a lithographic apparatus is disclosed, the method comprising steps for: generating a first beam of laser radiation having a first wavelength for a first number of pulses using a first laser chamber module, and propagating pulses toward the substrate along an output beam path; and generating a second beam of laser radiation having a second wavelength for a second number of pulses using a second laser chamber module, and propagating pulses toward the substrate along the output beam path. The first wavelength may be substantially the same as the second wavelength. The first wavelength may be different from the second wavelength. The first number of pulses may be the same as the second number of pulses. The first number of pulses may be different from the second number of pulses. The first beam may have a first pulse energy, and the second beam may have a second pulse energy different from the first pulse energy. The method may further include the step of narrowing the bandwidth of the beam generated by the first laser chamber module. The method may further include the step of narrowing the bandwidth of the beam generated by the second laser chamber module. The method may further include the step of narrowing the bandwidth of the beam generated by the first laser chamber module by a first amount and narrowing the bandwidth of the beam generated by the second laser chamber module by a second amount, the second amount being different from the first amount. The method may further comprise the step of generating a command signal, wherein the step of generating the first beam of laser radiation and the step of generating the second beam of laser radiation are performed in response to the command signal. The method may further comprise the step of generating a first command signal and the step of generating a second command signal, wherein the step of generating the first beam of laser radiation is performed in response to the first command signal, and wherein the step of generating the second beam of laser radiation is performed in response to the second command signal.

[0024] The following describes in detail other features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention with reference to the accompanying drawings. Note that the present invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Based on the teachings contained herein, other embodiments will be apparent to those skilled in the relevant art. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated herein and constitute a part of the specification, serve to illustrate the invention and, together with the description, further serve to explain the principles of the invention and to enable those skilled in the relevant art to make and use the invention.

[0026] Figure 1 is a functional block diagram of a conventional two-chamber laser system.

[0027] Figure 2 Yes, you can Figure 1 Functional block diagram of a conventional pulse power circuit used in a system.

[0028] Figure 3 is a functional block diagram of a two-chamber laser system according to an aspect of an embodiment.

[0029] Figure 4 is a diagram of possible relative discharge timings in two laser chambers according to an aspect of an embodiment.

[0030] Figure 5 is a diagram of another possible relative discharge timing in two laser chambers according to an aspect of an embodiment.

[0031] Figure 6 is a diagram of a line narrowing module such as may be advantageously used in accordance with an aspect of an embodiment.

[0032] Figure 7 is a conceptual diagram of an output spectrum such as may be generated according to an aspect of an embodiment.

[0033] The features and advantages of the present invention will become more apparent from the detailed description below in conjunction with the accompanying drawings, in which the same reference numerals always identify corresponding elements. In the accompanying drawings, similar reference numerals generally indicate identical, functionally similar and / or structurally similar elements. DETAILED DESCRIPTION

[0034] Being able to avoid the need for additional exposure strokes will benefit wafer productivity. Being able to increase the amount of power delivered to the wafer beyond the limits of what a single laser can provide would also be beneficial. In theory, this can be achieved by using two lasers with superimposed beams connected to a scanner, allowing multi-wavelength exposure to be completed in a single stroke. Since a single KrF laser has maximum power, higher power can be achieved by connecting two lasers to a single scanner. However, using two independent lasers takes up additional floor space in the manufacturing facility and requires doubling the laser subsystems (e.g., gas handling, power distribution, accessories, and mechanical structures). An efficient way to generate multiple laser beams is needed without completely duplicating all components of the entire laser system.

[0035] This specification discloses one or more embodiments that incorporate features of the present invention. The disclosed (multiple) embodiments are merely illustrative of the present invention. The scope of the present invention is not limited to the disclosed embodiments. The present invention is defined by the appended claims.

[0036] The described embodiment(s) and references in the specification to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiment(s) may include certain features, structures, or characteristics, but each embodiment may not necessarily include the certain features, structures, or characteristics. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a certain feature, structure, or characteristic is described in conjunction with an embodiment, it should be understood that it is within the knowledge of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0037] Before describing the embodiments in further detail, it is helpful to present an example environment in which embodiments of the invention may be implemented. Figure 1 1 is a functional block diagram of a conventional two-chamber laser system 10. In this embodiment, a laser beam is provided at an input port of a photolithography machine 12, such as a stepper or scanner machine. The main components of the laser system 10 can be mounted below a substrate 14, on which the scanner 12 is mounted, as shown. The laser system 10 includes a beam delivery unit 16, which provides a closed beam path for delivering the laser beam to the input port of the scanner 12. The particular light source system shown includes a master oscillator 18 and a power amplifier 20, and is a type of laser system known as a master oscillator power amplifier or MOPA system. The laser system 10 also includes various components for controlling the spectral characteristics of the pulses, shaping the pulses, etc., which are generally represented as optical devices 22 and optical devices 24. Additional details of the arrangement and operation of such a laser system can be found, for example, in U.S. Patent No. 7,079,564, entitled "Control System for a Two Chamber GasDischarge Laser", published on July 18, 2006, the entire contents of which are incorporated herein by reference.

[0038] The master oscillator 18 and the power amplifier 20 each include two elongated electrodes, a laser gas, a fan for circulating the gas between the electrodes, and a water-cooled finned heat exchanger. The master oscillator 18 generates a first laser beam, which is double-pass amplified by the power amplifier 20 to generate a laser beam such as Figure 1 The output laser beam is shown by the arrow.

[0039] Steering Figure 2, a pulse power circuit is shown, which includes, for example, a high voltage resonant power supply 30, a commutator module 32, a compression head module 34, and a laser chamber module 36. The high voltage resonant power supply module 30 converts three-phase normal power station power into a high DC voltage. The commutator module 32 and the compression head module 34 compress and amplify the power from the resonant power supply module 30 to generate pulses with a desired discharge voltage across the electrodes in the laser chamber module 36. Additional details on the operation of the circuit system can be found in U.S. Patent No. 7,002,443, entitled "Method and Apparatus for Cooling Magnetic Circuit Elements," issued on February 21, 2006, the entire contents of which are incorporated herein by reference.

[0040] Light sources used in advanced lithography typically require sources with narrow spectral bandwidths to support the necessary uniformity of critical dimensions printed on the substrate (CD uniformity or CDU). However, this also limits the process window available to chipmakers in high-NA systems with a small depth of focus. The challenge for contact layers in particular is the reduction in process window area as feature size decreases.

[0041] A technique called focused drilling technology supports a larger process window in the patterning of contact layers and via layers. Focused drilling requires a wide spectrum bandwidth tuning capability and the necessary supporting metrology and control capabilities to provide chip manufacturers with greater process tolerance. A spectrum tuning method called RELAX. See I. Lalovic et al. "RELAX: Resolution Enhancement by Laser-spectrum Adjusted Exposure" (Optical Microlithography VXIII, Proc. of SPIE Vol 5754, 2005), the contents of which are incorporated herein by reference.

[0042] As mentioned above, depth of focus is a function of wavelength. DOF is particularly important for 3D NAND. In this technology, the photoresist applied is very thick, on the order of 1 to 15 μm, which greatly exceeds the typical DOF of a scanner system. Current manufacturing requires a two-step process in which the wafer is sent through with the focus set a few microns below the bottom of the structure, and then a second pass is made with the focus set a certain distance higher (e.g., in the range of about 1 μm to about 4 μm).

[0043] According to one aspect of the embodiment, by exposing the wafer to two different wavelength beams generated by two separate laser cavities during a single exposure, the need to subject the wafer to multiple passes is avoided. Thus, the depth of the focal plane can be adjusted on a shot-to-shot basis, thereby achieving multiple wavelengths of illumination in one pass for each target portion of the substrate.

[0044] exist Figure 3 In the arrangement shown, the first resonant charger 40 provides electrical energy to the first commutator 42 and the second commutator 44. The first commutator 42 provides pulses to the first compression head 46. The second commutator 44 provides pulses to the second compression head 48. The first compression head 46 induces a discharge in the first laser chamber module 50. The second compression head 48 induces a discharge in the second laser chamber module 52. In addition, Figure 3 , optical devices for conditioning the laser beam, such as first and second line narrowing modules 54, 56, first and second optical couplers 58, 60, and first and second stabilization modules 62, 64 are shown. The beam generated by the laser chamber module is line narrowed to produce a bandwidth much smaller than the natural bandwidth of the gas discharge system. The control circuit 70 can control the first and second line narrowing modules 54, 56 so that the bandwidth and wavelength of the beams generated by the first laser chamber module 50 and the second laser chamber module 52 can be different from each other.

[0045] Various triggering arrangements may be employed. For example, one trigger may be used to fire both chambers, with or without a delay between the timing of the trigger and the discharge of one or both of the chambers. Alternatively, the triggers may be generated separately, i.e., by separate circuitry, so that the two chambers will have different voltage / energy commands.

[0046] Various system components such as gas handling systems, control systems, interfaces, power distribution systems, cooling water systems, power supplies for chamber filters and blowers, and beam path purge systems that may be used in common by the first laser chamber module 50 and the second laser chamber module 52 are also generally indicated at 68. Thus, in the arrangement shown, the two laser chambers may share the use of these components and it is not necessary for them to have two of each.

[0047] Figure 3 The arrangement also includes a control circuit 70 and a scanner interface, where the control circuit 70 is capable of operating the two lasers with independent energies, controlling the relative excitation time, bandwidth and wavelength, and the scanner interface is capable of dividing the energy / pulse commands between the two lasers.

[0048] The beam from the first laser chamber module 50 and the beam from the second laser chamber module 52 are combined by a beam combiner 66. One way to achieve the combination of the beams from the two lasers in a single pass is to transmit them through a rotating prism. In one embodiment, the first laser chamber module 50 generates laser radiation having a first wavelength, and the second laser chamber module 52 generates laser radiation having a second wavelength different from the first wavelength. Thus, the two chambers cooperate to produce radiation of different wavelengths with different focal planes on the wafer and operating at different depths.

[0049] Figure 3 Also shown is a first metrology unit 72 , which is arranged to measure parameters of the light beam generated by the first laser chamber module 50 , including the wavelength. Figure 3 The arrangement shown also includes a second metrology unit 74, which is arranged to measure parameters of the beam generated by the second laser chamber module 52, including wavelength. A third metrology unit 76 is arranged to measure parameters of the combined beam, including wavelength, i.e., the combination of the beam of the first laser chamber module and the beam of the second chamber module. It will be appreciated that sometimes the combined beam may be only the beam from one of the laser chambers if the other chamber is not excited. The metrology units provide their measurements to the control circuit 70. The metrology units as shown can independently measure the light from the two laser chamber modules and the wavelength of the combined beam. The control unit 70 can use the measurements to control the wavelength of the beam generated by each laser chamber module.

[0050] The excitation of the two chambers can be interleaved to effectively double the repetition rate. Figure 4 The top timing diagram shows possible firing timings for the first laser chamber module 50, and the middle timing diagram shows possible firing timings for the second laser chamber module 52. The beams from the two lasers can be combined to achieve an effective repetition rate that is twice the repetition rate of either of the two lasers, as shown in the bottom timing diagram. As described above, the beam paths of multiple lasers can be combined using any of a variety of arrangements.

[0051] The excitation sequence of two (or more) laser chamber modules can be set to any of a variety of patterns. For example, the sequence can be set so that the chambers are alternately excited shot-by-shot. Alternatively, the sequence can be set so that a first laser chamber module is excited for a first number of shots and then a second chamber is excited for a second number of shots, wherein the first number and the second number may be equal or unequal. These sequences can be employed with laser chamber modules that generate light of the same wavelength or different wavelengths. In addition, laser chamber modules that generate light having two different wavelengths can be excited at substantially different repetition rates to produce spectra having different energy contents in each of the two wavelength beams. For example, the second discharge rate can be an integer multiple of the first discharge rate, such that the discharge rates can be, for example, a ratio of 2:1. The relationship between the first discharge rate and the second discharge rate can also be a ratio of two integers, such as 3:2.

[0052] Reference now Figure 5 , the time difference Δt between the excitation of the two lasers can be set to essentially any value, including zero (assuming the optics can withstand double the instantaneous power level) or so small that the two pulses do not occur simultaneously but instead occur one after the other (i.e., during the same exposure), thereby doubling the effective dose, as shown. The top timing diagram shows a possible excitation timing for the first laser chamber module 50, and the middle timing diagram shows a possible excitation timing for the second laser chamber module 52. Thus, the beams from the two lasers can be generated one after the other as shown to combine to achieve an effective dose that is twice the dose of either of the two lasers shown in the bottom timing diagram.

[0053] According to another aspect of the embodiment, both chambers operate simultaneously, but if the end user requires lower power, only one or the other of the chambers may be used. The chambers may be alternated for single chamber operation to balance the wear of the chambers and maximize life.

[0054] It should be noted that in some cases, the power of two lasers firing simultaneously may damage the system optics. In this case, it may be beneficial to include control circuitry to prevent simultaneous firing. However, the lasers can be fired one after the other to achieve a higher dose per interval without damaging the optics.

[0055] According to another aspect of the embodiment, Figure 3One or both of the line narrowing modules 54 and 56 shown can be configured to produce two wavelengths, i.e., two colors of output. The wavelengths can be the peak separations about the center wavelength. In the case where both line narrowing modules are configured to produce two wavelengths in this manner, the peak separations can be the same or different. Using such an arrangement, up to four wavelengths can be produced.

[0056] like Figure 6 As shown, it can be used as Figure 3 The line narrowing module 80 of one or both of the line narrowing modules 54 and 56 may include prisms 82, 84 and 86 (which together form a prismatic beam expander), a mirror 90 with an actuator 92, and a grating 96. The angle of the beam incident on the grating 96 determines the wavelength of the laser. Therefore, adjusting this angle affects the wavelength adjustment of the laser. By actuating the prism (dithering) or the splitting mirror 90 or the splitting grating 96, a double peak spectrum can be generated in the line narrowing module 80 on a pulse-to-pulse basis.

[0057] Figure 7 An example output spectrum is shown for the case where two line narrowing modules are configured for two color outputs. The x-axis is wavelength in arbitrary units and the y-axis is intensity in arbitrary units. Peaks 100 and 102 are produced by the first laser chamber module 50 and peaks 110 and 112 are produced by the second laser chamber module 52. These four wavelength spectra can be used to expose thicker photoresists and can be used as an alternative (or supplement) to meet higher power requirements.

[0058] The lasers can be fired in a "tic-toc" mode, where first one laser fires, then the other laser fires, then the first fired laser fires again, and so on, with the same interval between fires; or the lasers can be fired in a "stutter" mode, where the interval between two laser fires is less than half the interval between successive fires of the same laser.

[0059] As described above, the beam from the first laser chamber module 50 and the beam from the second laser chamber module 52 can be combined by the beam combiner 66. If they have different wavelengths, another way to combine the two beams is to use a dichroic mirror. The dichroic mirror works in such a way that one wavelength (short range) is transmitted and the other wavelength is reflected. Another technique for combining two laser beams having the same or different wavelengths involves the use of a pick-off mirror. Another arrangement for combining the two beams includes a mirror having a reflective coating 130 applied to a portion of the mirror. One laser beam can be reflected by the reflective coating while the other laser beam propagates through a portion of the mirror without the coating. Yet another arrangement for combining the two beams includes causing the beams to strike the mirror, wherein the mirror is in a first position where one beam propagates in a direction of use and the second beam propagates in another direction, and then moving the mirror to a second position (e.g., by rotation) so that only the second beam propagates in the direction of use. The same effect can be achieved by holding the mirror stationary and dithering the direction of propagation of one or both of the beams.

[0060] The above description uses two laser chambers as a specific example, but it is apparent that more than two chambers may be used, with one or more chambers being configured to generate laser radiation having multiple frequencies.

[0061] A single system with two laser chambers and shared auxiliary systems can be more compact than two complete laser systems, can have lower operating costs than a 60 W or lower MOPA laser, can provide more accurate wavelength control than can be achieved by dithering the wavelength on a single laser, and can allow high repetition rates, which in turn provides the potential for better dose control.

[0062] It is also possible that more than two laser chamber modules exist and are in use or available for use. For example, a MOPA / MOPA chamber pair could be incorporated into the system to provide higher repetition rates or powers. (Similarly, a dual "MOPRA" chamber pair could be incorporated into the system where the power amplifier includes some optical recycling through the gain medium. MOPA / MOPRA pairs are also contemplated.) These chambers can be made physically compact because the lower repetition rates of each chamber can be used independently.

[0063] It should be understood that the "Detailed Description" section, rather than the "Summary" and "Abstract" sections, is intended to be used to interpret the claims. The "Summary" and "Abstract" sections may set forth one or more but not all exemplary embodiments of the present invention contemplated by the inventors, and therefore, are not intended to limit the present invention and the appended claims in any way.

[0064] The present invention has been described above with the help of functional building blocks that illustrate the implementation of specific functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries may be defined as long as the specified functions and their relationships are appropriately performed.

[0065] The above description of the specific embodiments will reveal the general nature of the invention so fully that others can easily modify and / or adapt the various applications of these specific embodiments by applying the knowledge within the art without departing from the general concept of the invention without undue experimentation. Therefore, based on the teachings and guidance presented herein, such adaptations and modifications are intended to be within the meaning and scope of the equivalents of the disclosed embodiments. It should be understood that the wording or terminology herein is for the purpose of description rather than limitation, so that the terms or wording of this specification will be interpreted by those skilled in the art based on the teachings and guidance.

[0066] Further aspects of the invention are set out in the following numbered clauses.

[0067] 1. A gas discharge laser system, comprising:

[0068] a first laser chamber module adapted to generate a first beam of laser radiation having a first wavelength;

[0069] a second laser chamber module adapted to generate a second beam of laser radiation having a second wavelength, the second wavelength being different from the first wavelength; and

[0070] A beam combiner is arranged to receive the first beam and the second beam and is adapted to propagate the first beam and the second beam along a common output beam path.

[0071] 2. The gas discharge laser system of clause 1, wherein the first laser chamber module comprises a first excimer laser chamber module.

[0072] 3. The gas discharge laser system of clause 2, wherein the first excimer laser chamber module comprises an ArF laser chamber module.

[0073] 4. The gas discharge laser system of clause 2, wherein the first excimer laser chamber module comprises a KrF laser chamber module.

[0074] 5. The gas discharge laser system according to any one of clauses 1 to 4, wherein the second laser chamber module comprises a second excimer laser chamber module.

[0075] 6. The gas discharge laser system according to clause 5, wherein the second excimer laser chamber module is an ArF laser chamber module.

[0076] 7. The gas discharge laser system according to clause 5, wherein the second excimer laser chamber module is a KrF laser chamber module.

[0077] 8. The gas discharge laser system according to clause 1, further comprising a third laser chamber module adapted to generate a third beam of laser radiation, and wherein the beam combiner is arranged to receive the third beam and is adapted to propagate the third beam along a common output beam path.

[0078] 9. The gas discharge laser system of clause 1, further comprising a discharge timing circuit arranged to control a relative discharge timing of the first laser chamber module with respect to the second laser chamber module.

[0079] 10. A gas discharge laser system according to clause 9, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module such that the first laser chamber module discharges at a first repetition rate and the second laser chamber module discharges at a second repetition rate, the second repetition rate being substantially the same as the first repetition rate and being offset relative to the first repetition rate by half a period of the first repetition rate.

[0080] 11. A gas discharge laser system according to clause 9, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module such that the first laser chamber module and the second laser chamber module discharge at substantially the same repetition rate, and wherein the second laser chamber module discharges substantially immediately after the first laser chamber module completes discharge.

[0081] 12. The gas discharge laser system of clause 9, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module discharge substantially simultaneously.

[0082] 13. The gas discharge laser system of clause 9, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module do not discharge substantially simultaneously.

[0083] 14. The gas discharge laser system of clause 9, wherein the discharge timing circuit is adapted to generate a common command for energizing both the first laser chamber module and the second laser chamber module.

[0084] 15. A gas discharge laser system according to clause 14, wherein the first laser chamber module is adapted to fire without delay after a common command.

[0085] 16. A gas discharge laser system according to clause 14, wherein the first laser chamber module is adapted to fire with a delay after a common command.

[0086] 17. A gas discharge laser system according to any of clauses 14, 15 and 16, wherein the second laser chamber module is adapted to fire without delay after the common command.

[0087] 18. A gas discharge laser system according to any of clauses 14, 15 and 16, wherein the second laser chamber module is adapted to fire with a delay after the common command.

[0088] 19. The gas discharge laser system of clause 9, wherein the discharge timing circuit is adapted to generate a first command for energizing the first laser chamber module and a second command for energizing the second laser chamber module.

[0089] 20. The gas discharge laser system according to clause 19, wherein the first laser chamber module is adapted to fire without delay after the first command.

[0090] 21. The gas discharge laser system according to clause 19, wherein the first laser chamber module is adapted to fire with a delay after the first command.

[0091] 22. A gas discharge laser system according to any of clauses 19, 20 and 21, wherein the second laser chamber module is adapted to fire without delay after the second command.

[0092] 23. A gas discharge laser system according to any of clauses 19, 20 and 21, wherein the second laser chamber module is adapted to fire with a delay after a command.

[0093] 24. The gas discharge laser system of clause 1, wherein the first laser chamber module is excited at a first repetition rate and the second laser chamber module is excited at a second repetition rate, the second repetition rate being different from the first repetition rate.

[0094] 25. A gas discharge laser system according to clause 24, wherein the ratio of the discharge rate of the first repetition rate to the second repetition rate is a ratio of two integers.

[0095] 26. A gas discharge laser according to clause 25, wherein the ratio of the two integers is 2:1.

[0096] 27. A gas discharge laser according to clause 25, wherein the ratio of the two integers is 3:2.

[0097] 28. The gas discharge laser system of clause 1, further comprising a control system adapted to control both the first laser chamber module and the second laser chamber module.

[0098] 29. The gas discharge laser system according to clause 1, further comprising a gas supply system adapted to supply gas to both the first laser chamber module and the second laser chamber module.

[0099] 30. The gas discharge laser system according to clause 1, further comprising a first laser chamber metrology unit arranged to measure a parameter of the beam generated by the first laser chamber module.

[0100] 31. A gas discharge laser system according to clause 1 or 30, further comprising a second laser chamber metrology unit arranged to measure a parameter of the beam generated by the second laser chamber module.

[0101] 32. A gas discharge laser system according to any of clauses 1, 30 or 31, further comprising a combined beam metrology unit arranged to measure a parameter of a combination of the beam generated by the first laser chamber module and the beam generated by the second laser chamber module.

[0102] 33. The gas discharge laser system according to clause 30, further comprising a control unit arranged to receive the output from the first laser chamber metrology unit and configured to control the wavelength of the light beam generated by the first laser chamber module based at least in part on the output of the first laser chamber metrology unit.

[0103] 34. A gas discharge laser system according to clause 30 or 33, further comprising a control unit arranged to receive the output from the second laser chamber metrology unit and configured to control the wavelength of the light beam generated by the second laser chamber module based at least in part on the output of the second laser chamber metrology unit.

[0104] 35. A gas discharge laser system according to clause 32, further comprising a control unit arranged to receive the output of the combined beam metering unit and configured to control a spectrum of a combination of the beam generated by the first laser chamber module and the beam generated by the second laser chamber module based at least in part on the output of the combined beam metering unit.

[0105] 36. The gas discharge laser system of clause 1, further comprising a first laser chamber line narrowing module arranged to receive the light beam from the first laser chamber module and configured to narrow a bandwidth of the light beam from the first laser chamber module.

[0106] 37. The gas discharge laser system according to clause 36, further comprising a second laser chamber line narrowing module arranged to receive the light beam from the second laser chamber module and configured to narrow the bandwidth of the light beam from the second laser chamber module.

[0107] 38. A gas discharge laser system according to clause 36, further comprising:

[0108] a second laser chamber line narrowing module arranged to receive the light beam from the second laser chamber module and configured to narrow the bandwidth of the light beam from the second laser chamber module, and

[0109] A control unit is connected to the first laser chamber line narrowing module and the second laser chamber line narrowing module and is adapted to control the first laser chamber line narrowing module and the second laser chamber line narrowing module so that the first bandwidth is substantially the same as the second bandwidth.

[0110] 39. A gas discharge laser system according to clause 36, further comprising:

[0111] a second laser chamber line narrowing module arranged to receive the light beam from the second laser chamber module and configured to narrow the bandwidth of the light beam from the second laser chamber module, and

[0112] A control unit is connected to the first laser chamber line narrowing module and the second laser chamber line narrowing module and is adapted to control the first laser chamber line narrowing module and the second laser chamber line narrowing module so that the first bandwidth is different from the second bandwidth.

[0113] 40. A lithographic apparatus comprising:

[0114] a first laser chamber module adapted to generate a first beam of laser radiation having a first wavelength;

[0115] a second laser chamber module adapted to generate a second beam of laser radiation having a second wavelength, the first wavelength being different from the first wavelength;

[0116] a beam combiner arranged to receive the first beam and the second beam and adapted to propagate the first beam and the second beam along a common output beam path; and

[0117] A scanner is arranged to receive the first beam and the second beam, wherein the scanner is configured to provide instructions for adjusting the first wavelength and the second wavelength.

[0118] 41. The lithographic apparatus according to clause 40, further comprising a discharge timing circuit arranged to control a relative discharge timing of the first laser chamber module with respect to the second laser chamber module.

[0119] 42. A lithographic apparatus according to clause 41, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module discharge at substantially the same repetition rate and 180 degrees out of phase with each other.

[0120] 43. A lithographic apparatus according to clause 41, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module, such that the first laser chamber module and the second laser chamber module discharge at substantially the same repetition rate, and wherein the second laser chamber module discharges substantially immediately after the first laser chamber module completes discharge.

[0121] 44. The lithographic apparatus according to clause 41, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module are discharged substantially simultaneously.

[0122] 45. The lithographic apparatus according to clause 41, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module are not discharged substantially simultaneously.

[0123] 46. ​​The lithographic apparatus according to clause 40, further comprising a control system adapted to control both the first laser chamber module and the second laser chamber module.

[0124] 47. The lithographic apparatus according to clause 40, further comprising a gas supply system adapted to supply gas to both the first laser chamber module and the second laser chamber module.

[0125] 48. A method for exposing a substrate in a lithographic apparatus, the method comprising the following steps:

[0126] receiving an indication of one or more target wavelengths from a scanner;

[0127] In response to the indication, generating a first beam of laser radiation having a first wavelength using a first laser chamber module;

[0128] In response to the indication, generating, using a second laser chamber module, a second beam of laser radiation having a second wavelength different from the first wavelength;

[0129] causing the first beam and the second beam to propagate along a common output beam path; and

[0130] The first beam and the second beam are used in a scanner to expose the substrate to radiation having a first wavelength and radiation having a second wavelength in a single pass.

[0131] 49. The method of clause 48, further comprising the step of controlling the relative timing of the steps of generating a first beam of laser radiation having a first wavelength and generating a second beam of laser radiation having a second wavelength, the second wavelength being different from the first wavelength.

[0132] 50. A method according to claim 49, wherein the step of controlling the relative timing of the step of generating a first beam of laser radiation having a first wavelength and the step of generating a second beam of laser radiation having a second wavelength different from the first wavelength includes: generating the first beam of laser radiation and the second beam of laser radiation at substantially the same repetition rate and 180 degrees out of phase with each other.

[0133] 51. A method according to claim 49, wherein the step of controlling the relative timing of the steps of generating a first beam of laser radiation having a first wavelength and generating a second beam of laser radiation having a second wavelength different from the first wavelength includes: generating the first beam of laser radiation and the second beam of laser radiation at substantially the same repetition rate, and generating the second beam immediately after generating the first beam.

[0134] 52. A method according to clause 49, wherein the step of controlling the relative timing of the steps of generating a first beam of laser radiation having a first wavelength and generating a second beam of laser radiation having a second wavelength different from the first wavelength includes: generating the first beam of laser radiation and the second beam of laser radiation substantially simultaneously.

[0135] 53. A method according to clause 49, wherein the step of controlling the relative timing of the steps of generating a first beam of laser radiation having a first wavelength and generating a second beam of laser radiation having a second wavelength different from the first wavelength includes: generating the first beam of laser radiation and the second beam of laser radiation substantially simultaneously.

[0136] 54. A method for exposing a substrate in a lithographic apparatus, the method comprising the following steps:

[0137] generating a first beam of laser radiation having a first wavelength for a first number of pulses using a first laser chamber module and propagating the pulses along an output beam path toward the substrate; and

[0138] A second beam of laser radiation having a second wavelength is generated using a second laser chamber module for a second number of pulses, and the pulses are propagated along an output beam path toward the substrate.

[0139] 55. The method of clause 54, wherein the first wavelength is substantially the same as the second wavelength.

[0140] 56. The method of clause 54, wherein the first wavelength is different from the second wavelength.

[0141] 57. A method according to any one of clauses 54 to 56, wherein the first number of pulses is the same as the second number of pulses.

[0142] 58. A method according to any of clauses 54 to 56, wherein the first number of pulses is different from the second number of pulses.

[0143] 59. The method of any of clauses 54 to 58, wherein the first beam has a first pulse energy and the second beam has a second pulse energy different from the first pulse energy.

[0144] 60. The method of any of clauses 54 to 59, further comprising the step of narrowing the bandwidth of the optical beam generated by the first laser chamber module.

[0145] 61. The method of any of clauses 54 to 59, further comprising the step of narrowing the bandwidth of the light beam generated by the second laser chamber module.

[0146] 62. The method of clause 54, further comprising the step of narrowing the bandwidth of the beam generated by the first laser chamber module by a first amount and narrowing the bandwidth of the beam generated by the second laser chamber module by a second amount, the second amount being different than the first amount.

[0147] 63. The method of clause 54, further comprising the step of generating a command signal, wherein the steps of generating the first beam of laser radiation and generating the second beam of laser radiation are performed in response to the command signal.

[0148] 64. The method according to clause 54 further includes the step of generating a first command signal and the step of generating a second command signal, and wherein the step of generating a first beam of laser radiation is performed in response to the first command signal, and wherein the step of generating a second beam of laser radiation is performed in response to the second command signal.

[0149] 65. A gas discharge laser system comprising:

[0150] a first laser chamber module adapted to generate a first beam of laser radiation having a first spectrum with a first wavelength and a second wavelength different from the first wavelength;

[0151] a second laser chamber module adapted to generate a second beam of laser radiation having a second spectrum, the second spectrum having a third wavelength and a fourth wavelength, the third wavelength being different from the first wavelength and the second wavelength, the fourth wavelength being different from the first wavelength, the second wavelength, and the third wavelength; and

[0152] A beam combiner is arranged to receive the first beam and the second beam and is adapted to propagate the first beam and the second beam along a common output beam path.

[0153] 66. The gas discharge laser system of clause 65, further comprising a discharge timing circuit arranged to control a relative discharge timing of the first laser chamber module with respect to the second laser chamber module.

[0154] 67. A gas discharge laser system according to clause 66, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module such that the first laser chamber module discharges at a first repetition rate and the second laser chamber module discharges at a second repetition rate, the second repetition rate being substantially the same as the first repetition rate and being offset relative to the first repetition rate by half a period of the first repetition rate.

[0155] 68. A gas discharge laser system according to clause 66, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module relative to the second laser chamber module, such that the first laser chamber module and the second laser chamber module discharge at substantially the same repetition rate, and wherein the second laser chamber module discharges substantially immediately after the first laser chamber module completes discharge.

[0156] 69. The gas discharge laser system of clause 66, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module discharge substantially simultaneously.

[0157] 70. The gas discharge laser system of clause 65, wherein the first laser chamber module comprises a first laser chamber line narrowing module configured to cause the first laser chamber module to generate a first beam of laser radiation having a first spectrum.

[0158] 71. The gas discharge laser system of clause 70, wherein the second laser chamber module comprises a second laser chamber line narrowing module configured to cause the second laser chamber module to generate a second beam of laser radiation having a second spectrum.

[0159] 72. A method for exposing a substrate in a lithographic apparatus, the method comprising the following steps:

[0160] generating, using a first laser chamber module, a first beam of laser radiation having a first wavelength and a second wavelength;

[0161] generating a second beam of laser radiation having a third wavelength and a fourth wavelength, the first wavelength, the second wavelength, the third wavelength and the fourth wavelength being different from one another;

[0162] causing the first beam and the second beam to propagate along a common output beam path; and

[0163] The first beam and the second beam are used in a scanner to expose the substrate to radiation having a first wavelength and radiation having a second wavelength in a single pass.

[0164] 73. The method of clause 72, further comprising the step of controlling the relative timing of the steps of generating the first beam of laser radiation and the second beam of laser radiation.

[0165] 74. A method according to clause 73, wherein the step of controlling the relative timing of the step of generating the first beam of laser radiation and the second beam of laser radiation comprises: generating the first beam of laser radiation and the second beam of laser radiation at substantially the same repetition rate and 180 degrees out of phase with each other.

[0166] 75. A method according to clause 73, wherein the step of controlling the relative timing of the step of generating a first beam of laser radiation and a second beam of laser radiation comprises: generating the first beam of laser radiation and the second beam of laser radiation at substantially the same repetition rate, and generating the second beam immediately after generating the first beam.

[0167] 76. The method of clause 73, wherein the step of controlling the relative timing of the steps of generating the first beam of laser radiation and the second beam of laser radiation comprises generating the first beam of laser radiation and the second beam of laser radiation substantially simultaneously.

[0168] Other implementations are within the scope of the claims.

Claims

1. A gas discharge laser system, comprising: a first laser chamber module adapted to generate a first beam of laser radiation having a first wavelength; a second laser chamber module adapted to generate a second beam of laser radiation having a second wavelength, the second wavelength being different from the first wavelength; as well as a beam combiner arranged to receive the first beam and the second beam and adapted to propagate the first beam and the second beam along a common output beam path, wherein the beam combiner is configured to propagate the first beam and the second beam to a scanner to expose a substrate to radiation having the first wavelength and radiation having the second wavelength in a single pass, wherein the gas discharge laser system is configured to receive instructions for adjusting the first wavelength and the second wavelength through a scanner interface.

2. The gas discharge laser system of claim 1, wherein the first laser chamber module comprises a first excimer laser chamber module.

3. The gas discharge laser system of claim 2, wherein the first excimer laser chamber module comprises an ArF laser chamber module.

4. The gas discharge laser system of claim 2, wherein the first excimer laser chamber module comprises a KrF laser chamber module.

5. The gas discharge laser system of claim 1, wherein the second laser chamber module comprises a second excimer laser chamber module.

6. The gas discharge laser system of claim 5, wherein the second excimer laser chamber module is an ArF laser chamber module.

7. The gas discharge laser system of claim 1 , further comprising a third laser chamber module adapted to generate a third beam of laser radiation, and wherein the beam combiner is arranged to receive the third beam and is adapted to propagate the third beam along the common output beam path.

8. The gas discharge laser system of claim 1, further comprising a discharge timing circuit arranged to control a relative discharge timing of the first laser chamber module with respect to the second laser chamber module.

9. The gas discharge laser system of claim 8, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module discharges at a first repetition rate and the second laser chamber module discharges at a second repetition rate, the second repetition rate being substantially the same as the first repetition rate and being offset relative to the first repetition rate by half a period of the first repetition rate.

10. The gas discharge laser system of claim 8, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module discharge at substantially the same repetition rate, and wherein the second laser chamber module discharges substantially immediately after the first laser chamber module completes discharge.

11. The gas discharge laser system of claim 8, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module discharge substantially simultaneously.

12. The gas discharge laser system of claim 8, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module do not discharge substantially simultaneously.

13. The gas discharge laser system of claim 8, wherein the discharge timing circuit is adapted to generate a common command for energizing both the first laser chamber module and the second laser chamber module.

14. The gas discharge laser system of claim 13, wherein the first laser chamber module is adapted to fire without delay after the common command.

15. The gas discharge laser system of claim 13, wherein the first laser chamber module is adapted to fire with a delay after the common command.

16. The gas discharge laser system of claim 8, wherein the discharge timing circuit is adapted to generate a first command for energizing the first laser chamber module and a second command for energizing the second laser chamber module.

17. The gas discharge laser system of claim 16, wherein the first laser chamber module is adapted to fire without delay after the first command.

18. The gas discharge laser system of claim 16, wherein the first laser chamber module is adapted to fire with a delay after the first command.

19. The gas discharge laser system of claim 17, wherein the second laser chamber module is adapted to fire with a delay after the command.

20. The gas discharge laser system of claim 1, wherein the first laser chamber module is fired at a first repetition rate and the second laser chamber module is fired at a second repetition rate, the second repetition rate being different from the first repetition rate.

21. The gas discharge laser system of claim 1, further comprising a gas supply system adapted to supply gas to both the first laser chamber module and the second laser chamber module.

22. The gas discharge laser system of claim 1, further comprising a first laser chamber metrology unit arranged to measure a parameter of a beam generated by the first laser chamber module.

23. The gas discharge laser system of claim 1, further comprising a combined beam metrology unit arranged to measure a parameter of a combination of the beam generated by the first laser chamber module and the beam generated by the second laser chamber module.

24. The gas discharge laser system of claim 23, further comprising a control unit arranged to receive the output of the combined beam metrology unit and configured to control a spectrum of a combination of the beam generated by the first laser chamber module and the beam generated by the second laser chamber module based at least in part on the output of the combined beam metrology unit.

25. The gas discharge laser system of claim 1, further comprising a first laser chamber line narrowing module disposed to receive the light beam from the first laser chamber module and configured to narrow a bandwidth of the light beam from the first laser chamber module.

26. The gas discharge laser system of claim 25, further comprising: a second laser chamber line narrowing module arranged to receive the light beam from the second laser chamber module and configured to narrow the bandwidth of the light beam from the second laser chamber module, and A control unit is connected to the first laser chamber line narrowing module and the second laser chamber line narrowing module and is adapted to control the first laser chamber line narrowing module and the second laser chamber line narrowing module so that the first bandwidth is substantially the same as the second bandwidth.

27. The gas discharge laser system of claim 25, further comprising: a second laser chamber line narrowing module arranged to receive the light beam from the second laser chamber module and configured to narrow the bandwidth of the light beam from the second laser chamber module, and A control unit is connected to the first laser chamber line narrowing module and the second laser chamber line narrowing module and is adapted to control the first laser chamber line narrowing module and the second laser chamber line narrowing module so that the first bandwidth is different from the second bandwidth.

28. A lithographic apparatus comprising: a first laser chamber module adapted to generate a first beam of laser radiation having a first wavelength; a second laser chamber module adapted to generate a second beam of laser radiation having a second wavelength, the second wavelength being different from the first wavelength; a beam combiner arranged to receive the first beam and the second beam and adapted to propagate the first beam and the second beam along a common output beam path; as well as A scanner is arranged to receive the first beam and the second beam to expose a substrate to radiation having the first wavelength and radiation having the second wavelength in a single pass, wherein the scanner is configured to provide instructions for adjusting the first wavelength and the second wavelength.

29. The lithographic apparatus of claim 28, further comprising a discharge timing circuit arranged to control a relative discharge timing of the first laser chamber module with respect to the second laser chamber module.

30. The lithographic apparatus of claim 29, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module are discharged substantially simultaneously.

31. The lithographic apparatus of claim 29, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module are not discharged substantially simultaneously.

32. The lithographic apparatus of claim 28, further comprising a gas supply system adapted to supply gas to both the first laser chamber module and the second laser chamber module.

33. A method of exposing a substrate in a lithographic apparatus, the method comprising the steps of: receiving an indication of one or more target wavelengths from a scanner; In response to the indication, generating a first beam of laser radiation having a first wavelength using a first laser chamber module; In response to the indication, generating, using a second laser chamber module, a second beam of laser radiation having a second wavelength different from the first wavelength; causing the first beam and the second beam to propagate along a common output beam path; as well as The first beam and the second beam are used in the scanner to expose the substrate to radiation having the first wavelength and radiation having the second wavelength in a single pass, wherein the scanner is configured to provide instructions for adjusting the first wavelength and the second wavelength.

34. The method of claim 33, further comprising the step of controlling the relative timing of the steps of generating the first beam of laser radiation having the first wavelength and generating the second beam of laser radiation having the second wavelength, the second wavelength being different from the first wavelength.

35. The method of claim 34, wherein the step of controlling the relative timing of the steps of generating the first beam of laser radiation having the first wavelength and generating the second beam of laser radiation having the second wavelength different from the first wavelength comprises: The first beam of laser radiation and the second beam of laser radiation are generated at substantially the same repetition rate and 180 degrees out of phase with each other.

36. The method of claim 34, wherein the step of controlling the relative timing of the steps of generating the first beam of laser radiation having the first wavelength and generating the second beam of laser radiation having the second wavelength different from the first wavelength comprises: The first beam of laser radiation and the second beam of laser radiation are generated at substantially the same repetition rate, and the second beam is generated substantially immediately after the first beam is generated.

37. The method of claim 34, wherein the step of controlling the relative timing of the steps of generating the first beam of laser radiation having the first wavelength and generating the second beam of laser radiation having the second wavelength different from the first wavelength comprises: The first beam of laser radiation and the second beam of laser radiation are generated substantially simultaneously.

38. The method of claim 34, wherein the step of controlling the relative timing of the steps of generating the first beam of laser radiation having the first wavelength and generating the second beam of laser radiation having the second wavelength different from the first wavelength comprises: The first beam of laser radiation and the second beam of laser radiation are generated substantially simultaneously.

39. A method of exposing a substrate in a lithographic apparatus, the method comprising the steps of: generating a first beam of laser radiation having a first wavelength for a first number of pulses using a first laser chamber module and propagating the pulses along an output beam path toward the substrate; as well as generating a second beam of laser radiation having a second wavelength for a second number of pulses using a second laser chamber module and propagating the pulses along the output beam path toward the substrate; The first beam and the second beam are propagated to a scanner to expose the substrate to radiation having the first wavelength and radiation having the second wavelength in a single pass, wherein the scanner is configured to provide instructions for adjusting the first wavelength and the second wavelength.

40. The method of claim 39, wherein the first wavelength is substantially the same as the second wavelength.

41. The method of claim 39, wherein the first wavelength is different from the second wavelength.

42. The method of claim 41, wherein the first number of pulses is the same as the second number of pulses.

43. The method of claim 41, wherein the first number of pulses is different from the second number of pulses.

44. The method of claim 39, wherein the first beam has a first pulse energy and the second beam has a second pulse energy, the second pulse energy being different from the first pulse energy.

45. The method of claim 39, further comprising the step of narrowing the bandwidth of the optical beam generated by the first laser chamber module.

46. ​​The method of claim 39, further comprising the step of narrowing a bandwidth of a beam generated by the first laser chamber module by a first amount, and narrowing a bandwidth of a beam generated by the second laser chamber module by a second amount, the second amount being different than the first amount.

47. The method of claim 39, further comprising the step of generating a first command signal and the step of generating a second command signal, and wherein the step of generating a first beam of laser radiation is performed in response to the first command signal, and wherein the step of generating a second beam of laser radiation is performed in response to the second command signal.

48. A gas discharge laser system comprising: a first laser chamber module adapted to generate a first beam of laser radiation having a first spectrum, the first spectrum having a first wavelength and a second wavelength, the second wavelength being different from the first wavelength; a second laser chamber module adapted to generate a second beam of laser radiation having a second spectrum, the second spectrum having a third wavelength and a fourth wavelength, the third wavelength being different from the first wavelength and the second wavelength, the fourth wavelength being different from the first wavelength, the second wavelength and the third wavelength; as well as a beam combiner arranged to receive the first beam and the second beam and adapted to propagate the first beam and the second beam along a common output beam path, wherein the beam combiner is configured to propagate the first beam and the second beam to a scanner to expose a substrate to radiation having the first spectrum and radiation having the second spectrum in a single pass, wherein the gas discharge laser system is configured to receive instructions for adjusting the first wavelength and the second wavelength through a scanner interface.

49. The gas discharge laser system of claim 48, further comprising a discharge timing circuit arranged to control a relative discharge timing of the first laser chamber module with respect to the second laser chamber module.

50. The gas discharge laser system of claim 49, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module discharge at substantially the same repetition rate, and wherein the second laser chamber module discharges substantially immediately after the first laser chamber module completes discharge.

51. The gas discharge laser system of claim 49, wherein the discharge timing circuit is adapted to control the relative discharge timing of the first laser chamber module with respect to the second laser chamber module such that the first laser chamber module and the second laser chamber module discharge substantially simultaneously.

52. The gas discharge laser system of claim 48, wherein the first laser chamber module comprises a first laser chamber line narrowing module configured to cause the first laser chamber module to generate the first beam of laser radiation having the first spectrum.

53. The gas discharge laser system of claim 52, wherein the second laser chamber module comprises a second laser chamber line narrowing module configured to cause the second laser chamber module to generate the second beam of laser radiation having the second spectrum.

54. A method of exposing a substrate in a lithographic apparatus, the method comprising the steps of: generating, using a first laser chamber module, a first beam of laser radiation having a first wavelength and a second wavelength; generating a second beam of laser radiation having a third wavelength and a fourth wavelength, the first wavelength, the second wavelength, the third wavelength and the fourth wavelength being different from one another; causing the first beam and the second beam to propagate along a common output beam path; as well as The first beam and the second beam are used in a scanner to expose the substrate to radiation having the first wavelength and radiation having the second wavelength in a single pass, the scanner being configured to provide instructions for adjusting the first wavelength and the second wavelength.

55. The method of claim 54, further comprising the step of controlling the relative timing of the steps of generating the first beam of laser radiation and the second beam of laser radiation.

56. The method of claim 55, wherein the step of controlling the relative timing of the steps of generating the first beam of laser radiation and the second beam of laser radiation comprises: The first beam of laser radiation and the second beam of laser radiation are generated substantially simultaneously.

57. A gas discharge laser system comprising: a beam combiner arranged to receive a first beam having a first wavelength from a first source and a second beam having a second wavelength from a second source, and the beam combiner is adapted to propagate the first beam and the second beam along a common output beam path; a discharge timing circuit arranged to control the relative discharge timing of said first source with respect to said second source, wherein the beam combiner is configured to propagate the first beam and the second beam to a scanner to expose a substrate to radiation having the first wavelength and radiation having the second wavelength in a single pass, wherein the gas discharge laser system is configured to receive instructions for adjusting the first wavelength and the second wavelength through a scanner interface.

58. The gas discharge laser system of claim 57, wherein the discharge timing circuit is adapted to control the relative discharge timing in the first source with respect to the second source such that the first source discharges at a first repetition rate and the second source discharges at a second repetition rate, the second repetition rate being substantially the same as the first repetition rate and being offset relative to the first repetition rate by half a period of the first repetition rate.

59. The gas discharge laser system of claim 57, wherein the discharge timing circuit is adapted to control the relative discharge timing in the first source with respect to the second source such that the first source and the second source discharge at substantially the same repetition rate, and wherein the second source discharges substantially immediately after the first source completes discharge.

60. The gas discharge laser system of claim 57, wherein the discharge timing circuit is adapted to control the relative discharge timing in the first source with respect to the second source such that the first source and the second source discharge substantially simultaneously.

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