Systems and methods for real-time time-integral squared (TIS) and speckle contrast (SC) control in DUV lasers

Abstract

A light source apparatus includes a gas discharge stage configured to output a light beam and a time-integral squared (TIS) apparatus configured to receive a portion of the light beam and measure a TIS pulse width of the light beam in the time domain. The TIS apparatus is configured to calculate a speckle contrast (SC) of the light beam based on the measured TIS pulse width. The TIS pulse width is measured in real-time or near real-time. The calculated SC can be provided to a lithographic apparatus to reduce errors in a lithographic process. Advantageously the apparatus can measure the TIS pulse width in real-time, calculate the SC in real-time, adjust one or more parameters of the SC to control the SC, reduce errors in a lithographic process, perform diagnostics of the light source apparatus, and identify optimal maintenance planning of the light source apparatus.

Description

SYSTEMS AND METHODS FOR REAL-TIME TIME-INTEGRAL SQUARED (TIS) ANDCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Application No. 63 / 611,815, filed December 19, 2023, titled SYSTEMS AND METHODS FOR REAL-TIME TIME-INTEGRAL SQUARED (TIS) AND SPECKLE CONTRAST (SC) CONTROL IN DUV LASERS, which is incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to light source apparatuses, systems, and methods, for example, light source apparatuses, systems, and methods with a time -integral squared (TIS) apparatus for measuring and controlling a speckle contrast (SC) of a light beam.BACKGROUND

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern of a patterning device (e.g., a mask, a reticle) onto a layer of radiation-sensitive material (photoresist or, simply, “resist”) provided on a substrate.

[0004] To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which can be formed on the substrate. A lithographic apparatus, which uses deep ultraviolet (DUV) radiation, having a wavelength within the range 20-400 nm, for example 193 nm or 248 nm, maybe used to form features on a substrate.

[0005] A master oscillator power amplifier (MOPA) or a master oscillator power ring amplifier (MOPRA) is a two-stage optical resonator arrangement that produces a highly coherent amplified light beam. The performance of the MOPA or the MOPRA can depend critically on the master oscillator (MO), the power amplifier (PA), and / or the power ring amplifier (PRA). Electrodes of the MO, the PA, and / or the PRA surrounding a gas discharge medium and / or optical components of the MOPA or the MOPRA can degrade overtime, leading to reduced laser performance and required laser maintenance.

[0006] Speckle is a laser phenomenon caused by self-interference of coherent light, which can lead to random local illumination non-uniformity. Speckle contrast (SC) is a measurement of local illumination intensity variations across a speckle pattern. Non-uniformity in laser beam illumination can result in non-uniform patterning and lead to errors in a lithographic process. One parameter of SC is the timeintegral squared (TIS) pulse width of the laser beam. However, current systems do not monitor the TIS pulse width and, thus, do not measure the SC of the laser beam over time. Further, current systems do not control and / or optimize the SC overtime.SUMMARY

[0007] Accordingly, there is a need to develop a system that can measure the TIS pulse width in realtime or near real-time, calculate the SC in real-time or near real-time, and adjust one or more parameters of the SC to control the SC (e.g., in real-time). This novel approach can reduce errors in a lithographic process, perform diagnostics of the light source apparatus, and identify optimal maintenance planning of the light source apparatus.

[0008] In some embodiments, a light source apparatus can include a gas discharge stage and a time- integral squared (TIS) apparatus. In some embodiments, the gas discharge stage can be configured to output a light beam. In some embodiments, the gas discharge stage can include an optical amplifier including a chamber configured to house a gas discharge medium. In some embodiments, the gas discharge stage can include an energizing device configured to excite the gas discharge medium and generate the light beam. In some embodiments, the TIS apparatus can be configured to receive a portion of the light beam and measure a time -integral squared (TIS) pulse width of the light beam in the time domain. In some embodiments, the TIS apparatus can be further configured to calculate a speckle contrast (SC) of the light beam based on the measured TIS pulse width. In some embodiments, the TIS pulse width is measured in real-time or near real-time. In some embodiments, the calculated SC is provided to a lithographic apparatus to reduce errors in a lithographic process.

[0009] In some embodiments, the SC is calculated in real-time. In some embodiments, the SC is calculated in near real-time. In some embodiments, the SC is calculated within 1 ms. In some embodiments, the SC is calculated within a response time of one or more actuators of the light source apparatus.

[0010] In some embodiments, the SC is determined by the following equation:Sp ' eckle Contrastwhere TIS is the time-integral squared (TIS) pulse width in the time domain, is a wavelength of the light beam, c is the speed of light, BW is a bandwidth of the light beam, Abeam is a cross-sectional area of the light beam, and Q(nv is a beam divergence of the light beam.

[0011] In some embodiments, the TIS pulse width, the wavelength of the light beam, the bandwidth of the light beam, the cross-sectional area of the light beam, and / or the beam divergence of the light beam can be measured in real-time. In some embodiments, the TIS pulse width, the wavelength of the light beam, the bandwidth of the light beam, the cross-sectional area of the light beam, and the beam divergence of the light beam can be measured in near real-time.

[0012] In some embodiments, the bandwidth of the light beam is an E95 bandwidth corresponding to a spectral bandwidth of the light beam that contains 95% of the total pulse energy of the light beam.

[0013] In some embodiments, the light source apparatus can be configured to adjust the TIS pulse width based on the calculated SC, thereby decreasing critical dimension (CD) non -uniformity in the lithographic apparatus.

[0014] In some embodiments, the TIS pulse width can be measured in near real-time. In some embodiments, the TIS pulse width can be measured within a range of about 1 s to about 10 s. In some embodiments, the TIS pulse width can be measured in real-time. In some embodiments, the TIS pulse width can be measured within a range of about 10 ms to about 1 s. In some embodiments, the TIS pulse width can be measured in real-time within one millisecond. In some embodiments, the TIS pulse width can be measured in real-time within 0.1 ms.

[0015] In some embodiments, the TIS pulse width can be measured over time to perform diagnostics of the light source apparatus. In some embodiments, the TIS pulse width can be measured overtime to identify a performance trend of one or more optical components of the light source apparatus. In some embodiments, a correction can be made to the one or more optical components based on the identified performance trend.

[0016] In some embodiments, the TIS apparatus can include a sensor configured to measure a raw pulse signal of the light beam. In some embodiments, the TIS apparatus can further include a processor coupled to the sensor. In some embodiments, the processor can be configured to square the raw pulse signal and convert it to the time domain to measure the TIS pulse width. In some embodiments, the processor can be configured to calculate the SC based on the measured TIS pulse width.

[0017] In some embodiments, the light source apparatus can further include an optical pulse stretcher. In some embodiments, the optical pulse stretcher can be configured to adjust the TIS pulse width.

[0018] In some embodiments, the light source apparatus can further include a controller coupled to the TIS apparatus. In some embodiments, the controller can be configured to control the SC. In some embodiments, the controller can be configured to adjust one or more actuators of the light source apparatus corresponding to one or more parameters of the SC. In some embodiments, the controller can include a closed-loop feedback algorithm. In some embodiments, the closed-loop feedback algorithm can be configured to minimize the SC. In some embodiments, the closed-loop feedback algorithm can be configured to attain or maintain a desired SC. In some embodiments, the controller can be configured to conduct data mining and / or machine learning based on the TIS pulse width over time. In some embodiments, the data mining and / or machine learning can be used to identify optimal maintenance planning of the light source apparatus.

[0019] In some embodiments, the TIS apparatus can be an in-line passive apparatus and integrated into a beam path of the light beam.

[0020] In some embodiments, the light source apparatus can further include a database coupled to the TIS apparatus. In some embodiments, the database can be configured to store the TIS pulse width and SC over time. In some embodiments, the database can be integrated with pulse data of the light source apparatus.

[0021] In some embodiments, a time-integral squared (TIS) apparatus can include a sensor and a processor coupled to the sensor. In some embodiments, the TIS apparatus can be configured to calculate a speckle contrast (SC) of a light beam. In some embodiments, the sensor can be configured to measure a raw pulse signal of the light beam. In some embodiments, the processor can be configured to square the raw pulse signal and convert it to the time domain to measure a TIS pulse width of the light beam. In some embodiments, the TIS pulse width is measured in real-time or near real-time. In some embodiments, the measured TIS pulse width can be used to adjust one or more actuators or a control algorithm of a light source associated with the SC.

[0022] In some embodiments, the processor can be configured to calculate a SC of the light beam based on the measured TIS pulse width. In some embodiments, the SC can be calculated in real-time. In some embodiments, the SC can be calculated in near real-time.

[0023] In some embodiments, the TIS pulse width can be measured in real-time within one millisecond. In some embodiments, the TIS pulse width can be measured in real-time within 0.1 ms.

[0024] In some embodiments, the TIS apparatus can be an in-line passive apparatus and integrated into a beam path of the light beam.

[0025] In some embodiments, a method of measuring a speckle contrast (SC) of a light beam of a light source can include measuring a time-integral squared (TIS) pulse width of the light beam in the time domain. In some embodiments, the TIS pulse width is measured in real-time or near real-time. In some embodiments, the method can further include calculating a SC of the light beam based on the measured TIS pulse width. In some embodiments, the method can further include adjusting one or more parameters of the SC based on the calculated SC to reduce errors in a lithographic process.

[0026] In some embodiments, the method can further include measuring a wavelength ( ) of the light beam, a bandwidth (BW) of the light beam, a cross-sectional area (Abeam) of the light beam, and a beam divergence (Qdiv) of the light beam. In some embodiments, the method can further include performing diagnostics of the light source based on the measured TIS pulse width over time.

[0027] In some embodiments, the method can further include controlling the SC in real-time. In some embodiments, the method can further include controlling the SC in near real-time. In some embodiments, controlling the SC can include adjusting one or more actuators of the light source corresponding to one or more parameters of the SC. In some embodiments, controlling the SC can include adjusting a control algorithm of the light source corresponding to one or more parameters of the SC.

[0028] In some embodiments, a metrology and measurement apparatus can include an auto-shutter device, an optics metrology device, and a time -integral squared (TIS) apparatus. In some embodiments, the auto-shutter device can be configured to direct a portion of a light beam. In some embodiments, the optics metrology device can be configured to measure one or more parameters of the light beam. In some embodiments, the time-integral squared (TIS) apparatus can be configured to calculate a specklecontrast (SC) of the light beam based on a time-integral squared (TIS) pulse width of the light beam measured in the time domain. In some embodiments, the time-integral squared (TIS) pulse width can be measured in real-time or near real-time.

[0029] In some embodiments, the measured time-integral squared (TIS) pulse width can be used to adjust one or more actuators or a control algorithm of a light source associated with the speckle contrast (SC). In some embodiments, the calculated speckle contrast (SC) can be provided to a lithographic apparatus to reduce errors in a lithographic process. In some embodiments, the speckle contrast (SC) can be calculated in real-time or near real-time.

[0030] In some embodiments, the one or more parameters of the light beam can include a wavelength, a bandwidth, a cross-sectional area, abeam divergence, or a combination thereof. In some embodiments, the optics metrology device can include a beam sensor, a power sensor, a spectrometer, a beam expander, or a combination thereof.

[0031] In some embodiments, the auto-shutter device can include a beam splitter configured to passively isolate a portion of the light beam. In some embodiments, the auto-shutter device can include a modulator configured to direct the portion of the light beam at a specific time.

[0032] In some embodiments, the metrology and measurement apparatus can further include a database. In some embodiments, the database can be coupled to the optics metrology device, the timeintegral squared (TIS) apparatus, or both. In some embodiments, the database can be configured to store one or more measured values from the optics metrology device, the time-integral squared (TIS) apparatus, or both. In some embodiments, the one or more measured values can include a wavelength, a bandwidth, a cross-sectional area, a beam divergence, a TIS pulse width, a SC, or a combination thereof.

[0033] Implementations of any of the techniques described above may include a DUV light source, a system, a method, a process, a device, and / or an apparatus. The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

[0034] Further features and exemplary aspects of the embodiments, as well as the structure and operation of various embodiments, are described in detail below with reference to the accompanying drawings. It is noted that the embodiments are not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.BRIEF DESCRIPTION OF THE DRAWINGS / FIGURES

[0035] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the embodiments and, together with the description, further serve to explain the principles of the embodiments and to enable a person skilled in the relevant art(s) to make and use the embodiments.

[0036] FIG. 1A is a schematic illustration of a reflective lithographic apparatus, according to an exemplary embodiment.

[0037] FIG. IB is a schematic illustration of a transmissive lithographic apparatus, according to an exemplary embodiment.

[0038] FIG. 2 is a schematic illustration of a light source apparatus, according to an exemplary embodiment.

[0039] FIG. 3 is a schematic illustration of a metrology and measurement module shown in FIG. 2, according to an exemplary embodiment.

[0040] FIG. 4 is a schematic perspective illustration of a TIS apparatus, according to an exemplary embodiment.

[0041] FIG. 5 illustrates a flow diagram for the light source apparatus, according to an exemplary embodiment.

[0042] The features and exemplary aspects of the embodiments will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, generally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. Unless otherwise indicated, the drawings provided throughout the disclosure should not be interpreted as to-scale drawings.DETAILED DESCRIPTION

[0043] This specification discloses one or more embodiments that incorporate the features of this present invention. The disclosed embodiment(s) merely exemplify the present invention. The scope of the invention is not limited to the disclosed embodiment(s). The present invention is defined by the claims appended hereto.

[0044] The embodiment(s) described, and references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” “an exemplary embodiment,” etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is understood that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0045] Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “on,” “upper” and the like, may be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depictedin the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0046] The term “about” or “substantially” or “approximately” as used herein indicates the value of a given quantity that can vary based on a particular technology. Based on the particular technology, the term “about” or “substantially” or “approximately” can indicate a value of a given quantity that varies within, for example, 1-15% of the value (e.g., ±1%, ±2%, ±5%, ±10%, or ±15% of the value).

[0047] Numerical values, including endpoints of ranges, can be expressed herein as approximations preceded by the term “about,” “substantially,” “approximately,” or the like. In such cases, other embodiments include the particular numerical value. Regardless of whether a numerical value is expressed as an approximation, two embodiments are included in this disclosure: one expressed as an approximation, and another not expressed as an approximation. It will be further understood that an endpoint of each range is significant both in relation to another endpoint, and independently of another endpoint.

[0048] Embodiments of the disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the disclosure may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine - readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc.

[0049] The term “time -integral squared (TIS) pulse width” or “TIS pulse width” or “TIS value” as used herein indicates a time or duration of a laser pulse in the time domain (e.g., in nanoseconds) that encompasses the total energy of the laser pulse. The TIS pulse width is one parameter of the speckle contrast (SC) of a laser beam.

[0050] The term “speckle contrast (SC)” or “SC” or “SC value” as used herein indicates a numerical measurement of local illumination intensity variations across a speckle pattern. For example, the numerical measurement can be a difference in intensity between bright spots and dark spots of the speckle pattern, for example, for a particular area of the speckle pattern. In some embodiments, the SC can be defined as the standard deviation of the intensity variation divided by the mean intensity, ina range from 0 to 1 (e.g., a percentage). In some embodiments, the SC can be defined by the following equation:Speckle Contrast'where TIS is the TIS pulse width in the time domain, A is a wavelength of the light beam, c is the speed of light, BW is a bandwidth of the light beam, Abeam is a cross-sectional area of the light beam, and Q(nv is a beam divergence of the light beam.

[0051] The term “real-time” or “real time” as used herein indicates one or more operations or other processes that guarantee response times within a specified time with no delay. In some embodiments, real-time can include a timescale or response within one millisecond (ms). In some embodiments, realtime can include a timescale or response within 0.1 ms. In some embodiments, real-time can include a timescale or response within a reaction time or capability of one or more actuators of the light source apparatus (e.g., linear motor, servo motor, stepper, shutter, electro-optic modulator, acousto-optic modulator, etc.).

[0052] The term “near real-time” or “near real time” as used herein indicates one or more operations or other processes that guarantee response times within a specified time minus a processing time (e.g., electronic communication, automatic data processing) with no significant delays. Near real-time is slightly slower or delayed compared to real-time. In some embodiments, near real-time can include a timescale or response within a range of 10 ms to 100 ms. In some embodiments, near real-time can include a timescale or response within a range of 100 ms to 1 s. In some embodiments, near real-time can include a timescale or response within a range of 1 s to 10 s.

[0053] The term “E95 bandwidth” or “E95” as used herein indicates a spectral bandwidth of a light beam that contains 95% of the total pulse energy of the light beam.

[0054] The term “maintenance planning” as used herein indicates a planned or scheduled maintenance of one or more components of the light source, for example, including but not limited to, adjustment, recalibration, repair, replacement, and / or batch replacement of one or more components of the light source.

[0055] Before describing such embodiments in more detail, however, it is instructive to present an example environment in which embodiments of the present disclosure may be implemented.

[0056] Exemplary Lithographic System

[0057] FIGS. 1A and IB are schematic illustrations of a lithographic apparatus 100 and lithographic apparatus 100', respectively, in which embodiments of the present disclosure may be implemented. Lithographic apparatus 100 and lithographic apparatus 100' each include the following: an illumination system (illuminator) IL configured to condition a radiation beam B (for example, deep ultraviolet (DUV) radiation); a support structure (for example, a mask table) MT configured to support a patterning device (for example, a mask, a reticle, or a dynamic patterning device) MA and connected to a first positioner PM configured to accurately position the patterning device MA; and, a substrate table (forexample, a wafer table) WT configured to hold a substrate (for example, a photoresist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W. Lithographic apparatuses 100 and 100' also have a projection system PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion (for example, comprising one or more dies) C of the substrate W. In lithographic apparatus 100, the patterning device MA and the projection system PS are reflective. In lithographic apparatus 100', the patterning device MA and the projection system PS are transmissive.

[0058] The illumination system IL may include various types of optical components, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, for directing, shaping, or controlling the radiation beam B.

[0059] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA with respect to a reference frame, the design of at least one of the lithographic apparatuses 100 and 100', and other conditions, such as whether or not the patterning device MA is held in a vacuum environment. The support structure MT may use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. The support structure MT can be a frame or a table, for example, which can be fixed or movable, as required. By using sensors, the support structure MT can ensure that the patterning device MA is at a desired position, for example, with respect to the projection system PS.

[0060] The term “patterning device” MA should be broadly interpreted as referring to any device that can be used to impart a radiation beam B with a pattern in its cross-section, such as to create a pattern in the target portion C of the substrate W. The pattern imparted to the radiation beam B can correspond to a particular functional layer in a device being created in the target portion C to form an integrated circuit.

[0061] The patterning device MA may reflective (as in lithographic apparatus 100 of FIG. 1A) or transmissive (as in lithographic apparatus 100' of FIG. IB). Examples of patterning devices MA include reticles, masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase shift, or attenuated phase shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B which is reflected by a matrix of small mirrors.

[0062] The term “projection system” PS can encompass any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors, such as the use of an immersion liquid on the substrate W or the use of a vacuum. A vacuum environment can be used for DUV or electron beam radiation since other gases can absorb too much radiation or electrons. A vacuum environment can therefore be provided to the whole beam path with the aid of avacuum wall and vacuum pumps. In some aspects, a purged or inert environment can be used for DUV radiation (e.g., N2 gas purged environment). In some aspects, one or more modules along the DUV radiation beam path can maintained in a vacuum environment and / or a purged environment.

[0063] Lithographic apparatus 100 and / or lithographic apparatus 100' can be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such “multiple stage” machines, the additional substrate tables WT can be used in parallel, or preparatory steps can be carried out on one or more tables while one or more other substrate tables WT are being used for exposure. In some situations, the additional table may not be a substrate table WT.

[0064] The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g., water, so as to fdl a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure.

[0065] Referring to FIGS. 1A and IB, the illuminator IL receives a radiation beam from a radiation source SO. The radiation source SO and the lithographic apparatus 100, 100' can be separate physical entities, for example, when the radiation source SO is an excimer laser (e.g., master oscillator power amplifier (MO PA) or master oscillator power ring amplifier (MOPRA)). In such cases, the radiation source SO is not considered to form part of the lithographic apparatus 100 or 100', and the radiation beam B passes from the radiation source SO to the illuminator IL with the aid of a beam delivery system BD (in FIG. IB) including, for example, suitable directing mirrors and / or a beam expander. In other cases, the radiation source SO can be an integral part of the lithographic apparatus 100, 100', for example, when the radiation source SO is a mercury lamp. The radiation source SO and the illuminator IL, together with the beam delivery system BD, if required, can be referred to as a radiation system .

[0066] The illuminator IL can include an adjuster AD (in FIG. IB) for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and / or inner radial extent (commonly referred to as “n-outer” and “n-inner,” respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL can comprise various other components (in FIG. IB), such as an integrator IN and a condenser CO. The illuminator IL can be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross section.

[0067] Referring to FIG. 1A, the radiation beam B is incident on the patterning device (for example, mask) MA, which is held on the support structure (for example, mask table) MT, and is patterned by the patterning device MA. In lithographic apparatus 100, the radiation beam B is reflected from the patterning device (for example, mask) MA. After being reflected from the patterning device (for example, mask) MA, the radiation beam B passes through the projection system PS, which focuses theradiation beam B onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF2 (for example, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT can be moved accurately (for example, so as to position different target portions C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor IF1 can be used to accurately position the patterning device (for example, mask) MA with respect to the path of the radiation beam B. Patterning device (for example, mask) MA and substrate W can be aligned using first and second mask alignment marks Ml, M2 and first and second substrate alignment marks Pl, P2, respectively.

[0068] Referring to FIG. IB, the radiation beam B is incident on the patterning device (for example, mask) MA, which is held on the support structure (for example, mask table) MT, and is patterned by the patterning device MA. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system PS has a pupil conjugate PPU to an illumination system pupil IPU. Portions of radiation emanate from the intensity distribution at the illumination system pupil IPU and traverse a mask pattern MP without being affected by diffraction at the mask pattern MP and create an image MP' of the intensity distribution at the pupil conjugate PPU.

[0069] The projection system PS projects an image MP' of the mask pattern MP, where image MP' is formed by diffracted beams produced from the mask pattern MP by radiation from the intensity distribution, onto a photoresist layer coated on the substrate W. For example, the mask pattern MP may include an array of lines and spaces. A diffraction of radiation at the array and different from zeroth order diffraction generates diverted diffracted beams with a change of direction in a direction perpendicular to the lines. Undiffracted beams (i.e., so-called zeroth order diffracted beams) traverse the pattern without any change in propagation direction. The zeroth order diffracted beams traverse an upper lens or upper lens group U1 of the projection system PS, upstream of the pupil conjugate PPU of the projection system PS, to reach the pupil conjugate PPU. The portion of the intensity distribution in the plane of the pupil conjugate PPU and associated with the zeroth order diffracted beams is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IU. The aperture device PD, for example, is disposed at or substantially at a plane that includes the pupil conjugate PPU of the projection system PS.

[0070] The projection system PS is arranged to capture, by means of an upper lens or upper lens group U1 and a lower lens or lower lens group U2, not only the zeroth order diffracted beams, but also first- order or first- and higher-order diffracted beams (not shown). In some embodiments, dipole illumination for imaging line patterns extending in a direction perpendicular to a line may be used to utilize the resolution enhancement effect of dipole illumination. For example, first-order diffracted beams interfere with corresponding zeroth-order diffracted beams at the level of the wafer W to create an image MP' of the mask pattern (line pattern) MP at highest possible resolution and process window (i.e., usable depth of focus in combination with tolerable exposure dose deviations). In some embodiments, astigmatismaberration may be reduced by providing radiation poles (not shown) in opposite quadrants of the illumination system pupil IPU. For example, the illumination at the illumination system pupil IPU may use only two opposite illumination quadrants, sometimes referred to as BMW illumination, such that the remaining two quadrants are not used in the illumination but are configured to capture first -order diffracted beams. Further, in some embodiments, astigmatism aberration may be reduced by blocking the zeroth order beams in the pupil conjugate PPU of the projection system PS associated with radiation poles in opposite quadrants.

[0071] With the aid of the second positioner PW and position sensor IF (for example, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT can be moved accurately (for example, so as to position different target portions C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor (not shown in FIG. IB) can be used to accurately position the patterning device (mask) MA with respect to the path of the radiation beam B (for example, after mechanical retrieval from a mask library or during a scan).

[0072] In general, movement of the mask table MT can be realized with the aid of a long -stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT can be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT can be connected to a short-stroke actuator only or can be fixed. Patterning device (mask) MA and substrate W can be aligned using first and second mask alignment marks Ml, M2, and first and second substrate alignment marks Pl, P2, respectively. Although the substrate alignment marks (as illustrated) occupy dedicated target portions, they can be located in spaces between target portions (known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the pattern device (mask) MA, the mask alignment marks can be located between the dies.

[0073] Mask table MT and patterning device MA can be in a vacuum chamber V, where an in-vacuum robot IVR can be used to move patterning devices, such as a mask, in and out of vacuum chamber V. Alternatively, when mask table MT and patterning device MA are outside of the vacuum chamber V, an out-of-vacuum robot (not shown) can be used for various transportation operations, similar to the invacuum robot IVR. Both the in-vacuum robot IVR and out-of-vacuum robot need to be calibrated for a smooth transfer of any payload (e.g., mask) to a fixed kinematic mount of a transfer station.

[0074] The lithographic apparatus 100 and 100' can be used in at least one of the following modes:

[0075] 1. In step mode, the support structure (for example, mask table) MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam B is projected onto a target portion C at one time (i.e., a single static exposure). The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed.

[0076] 2. In scan mode, the support structure (for example, mask table) MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam B is projected ontoa target portion C (i.e., a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure (for example, mask table) MT can be determined by the (de- )magnification and image reversal characteristics of the projection system PS.

[0077] 3. In another mode, the support structure (for example, mask table) MT is kept substantially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam B is projected onto a target portion C. A pulsed radiation source SO can be employed and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes a programmable patterning device, such as a programmable mirror array.

[0078] Combinations and / or variations on the described modes of use or entirely different modes of use can also be employed.

[0079] In a further embodiment, lithographic apparatus 100 includes an extreme ultraviolet (EUV) source, which is configured to generate a beam of EUV radiation for EUV lithography. A relative vacuum, i.e. a small amount of gas (e.g. hydrogen) at a pressure well below atmospheric pressure, may be provided in the radiation source SO, in the illumination system IL, and / or in the projection system PS. The radiation source SO may be a laser produced plasma (LPP) source, a discharge produced plasma (DPP) source, a free electron laser (FEL), an excimer laser, a master oscillator power amplifier (MOPA), a master oscillator power ring amplifier (MOPRA), or any other radiation source that is capable of generating DUV radiation.

[0080] Exemplary Light Source Apparatus

[0081] As discussed above, a master oscillator power amplifier (MOPA) or a master oscillator power ring amplifier (MOPRA) is atwo-stage optical resonator arrangement. The master oscillator (MO) (e.g., first optical resonator stage) produces a highly coherent light beam. The power amplifier (PA) or the power ring amplifier (PRA) (e.g., second optical resonator stage) increases the optical power of the light beam while preserving the beam properties. The MO can include a gas discharge chamber, an optical coupler (OC), a linewidth narrowing module (LNM), and a line -center analysis module (LAM). The OC and the LNM can surround the gas discharge chamber to form an optical resonator. The MO can be optically coupled to a wavefront engineering box (WEB) to send the produced light beam to the PA or the PRA. The PA or the PRA can include a second gas discharge chamber, a second wavefront engineering box (WEB), and a beam reverser (BR). The WEB and the BR can surround the second gas discharge chamber to form a second optical resonator. For example, certain MOPAs and MOPRAs have been previously described in U.S. Patent No. 7,643,528, issued January 5, 2010, U.S. Patent No. 7,822,092, issued October 26, 2010, and U.S. Application No. 18 / 020,718, filed August 10, 2021, which are hereby incorporated by reference herein in their entireties.

[0082] Performance of the MOPA or the MOPRA can depend critically on the MO, the PA, and / or the PRA, for example, the optical windows and / or optical components of the MO, the PA, and / or the PRAthat output the light beam. An excimer laser utilizes an excimer (e.g., excited dimer) or an exciplex (e.g., excited complex) to output deep ultraviolet (DUV) radiation. An excimer is a short-lived homodimeric molecule formed from two species (e.g., Ar2, Kn. F2, Xe2). An exciplex is a heterodimeric molecule formed from more than two species (e.g., ArF, KrCl, KrF, XeBr, XeCl, XeF). Electrodes of the MO, the PA, and / or the PRA surrounding the gas discharge medium (e.g., F2, ArF, KrF, and / or XeF) and / or optical components of the MOPA or the MOPRA can degrade over time, leading to reduced laser performance and required laser maintenance.

[0083] Speckle is a laser phenomenon caused by self-interference of coherent light, which can lead to random local illumination non-uniformity. Speckle contrast (SC) is a numerical measurement of local illumination intensity variations across a speckle pattern, for example, difference in intensity between bright spots and dark spots for a particular area of the speckle pattern. SC is the standard deviation of the intensity variation divided by the mean intensity. SC can be defined by the following equation:Sp ' eckle Contrastwhere TIS is the time-integral squared (TIS) pulse width in the time domain, is a wavelength of the light beam, c is the speed of light, BW is a bandwidth of the light beam, Abeam is a cross-sectional area of the light beam, and Q(nv is a beam divergence of the light beam. Non-uniformity in laser beam illumination can result in non-uniform patterning and lead to errors in a lithographic process, for example, including but not limited to line-width roughness (LWR), line-edge roughness (LER), edgeplacement errors (EPE), critical dimension (CD) errors, critical dimension (CD) non-uniformity, etc.

[0084] One key parameter of SC is the time-integral squared (TIS) pulse width of the laser beam. The TIS pulse width is the time or duration of the laser pulse in the time domain that encompasses the total energy of the laser pulse. The TIS pulse width can be measured, along with other parameters of the light beam (e.g., wavelength, bandwidth, cross-sectional area, beam divergence), to calculate the SC of the light beam. Further, the TIS pulse width can be adjusted to change (e.g., reduce) the SC, for example, using an optical pulse stretcher. For example, since the SC is inversely proportional to the TIS pulse width, SC oc ^=, the optical pulse stretcher can increase the TIS pulse width (e.g., from 200 ns to 400 ns) to thereby reduce the SC.

[0085] However, current systems do not monitor the TIS pulse width and, thus, do not measure the SC of the laser beam over time. Further, current systems do not control and / or optimize the SC over time, for example, in real-time, to reduce errors in a lithographic process, perform diagnostics of the light source, increase laser stability, and / or identify optimal maintenance planning of the light source.

[0086] Embodiments of light source apparatuses, systems, and methods as discussed below can measure the TIS pulse width in real-time or near real-time, calculate the SC in real-time or near real-time, adjust one or more parameters of the SC (e.g., wavelength, bandwidth, cross-sectional area, beam divergence) to control the SC (e.g., in real-time), reduce errors in a lithographic process (e.g., LWR, LER, CD errors, CD non-uniformity, or a combination thereof), perform diagnostics of the light source apparatus, identify optimal maintenance planning of the light source apparatus, and increase the service lifetimes of the master oscillator, the power amplifier, and / or the power ring amplifier.

[0087] FIG. 2 illustrates light source apparatus 200, according to various exemplary embodiments. Light source apparatus 200 can be configured to provide a highly coherent and aligned light beam (e.g., light beam 250), for example, to a DUV lithographic apparatus (e.g., lithographic apparatus 100'). Light source apparatus 200 can be further configured to measure a TIS pulse width of light beam 250 and calculate a SC oflightbeam 250 in real-time or near real-time. Light source apparatus 200 can be further configured to adjust one or more parameters of the SC (e.g., wavelength, bandwidth, cross-sectional area, beam divergence, TIS pulse width) to control and / or optimize the SC (e.g., in real-time). Light source apparatus 200 can be further configured to reduce errors in a lithographic process (e.g., LWR, LER, CD errors, CD non-uniformity, or a combination thereof), perform diagnostics of light source apparatus 200, identify optimal maintenance planning of light source apparatus 200, and increase the service lifetimes of the master oscillator, the power amplifier, and / or the power ring amplifier of light source apparatus 200.

[0088] Although light source apparatus 200 is shown in FIG. 2 as a stand-alone apparatus and / or system, the embodiments of this disclosure can be used with other optical systems, such as, but not limited to, radiation source SO, lithographic apparatus 100, 100', and / or other optical systems. In some embodiments, light source apparatus 200 can provide an excimer laser beam (e.g., DUV radiation), for example, to a DUV lithographic apparatus. In some embodiments, light source apparatus 200 can be radiation source SO in lithographic apparatus 100, 100'. For example, DUV radiation beam B can be light beam 250. In some embodiments, light source apparatus 200 can be a MOPA or a MOPRA formed by MO subsystem 210 (e.g., first gas discharge stage) and PRA subsystem 230 (e.g., second gas discharge stage). As discussed above, for example, certain MOPAs and MOPRAs have been previously described in U.S. Patent No. 7,643,528, issued January 5, 2010, and U.S. Patent No. 7,822,092, issued October 26, 2010, and U.S. Application No. 18 / 020,718, filed August 10, 2021, which are hereby incorporated by reference herein in their entireties.

[0089] As shown in FIG. 2, light source apparatus 200 can include master oscillator (MO) subsystem 210, relay optics subsystem 220, power ring amplifier (PRA) subsystem 230, laser output subsystem 240, and controller 260. In some embodiments, light source apparatus 200 can be a pulsed laser source that produces a pulsed laser beam (e.g., light beam 250). In some embodiments, all of the above listed components can be housed in a three-dimensional (3D) frame. For example, the 3D frame can include a metal (e.g., aluminum, steel, etc.), a ceramic, and / or any other suitable rigid material.

[0090] MO subsystem 210 can be configured to output a highly coherent light beam (e.g., light beam 211). MO subsystem 210 can be further configured act as a solid state or gas discharge seed laser. MOsubsystem 210 can be further configured to output amplified spontaneous emission (ASE) and / or light beam 211. MO subsystem 210 can include linewidth narrowing module (LNM) 212, gas discharge chamber 214, optical coupler 216, and line-center analysis module (LAM) 218. As shown in FIG. 2, MO subsystem 210 generates ASE and / or a light beam in an optical cavity formed by LNM 212, gas discharge chamber 214, optical coupler 216, and LAM 218, indicated by the bidirectional arrows, and outputs light beam 211, indicated by the unidirectional arrow, as would be apparent to a person of ordinary skill in the art.

[0091] LNM 212 can be configured to control a linewidth of the generated light beam (e.g., light beam 211). In some embodiments, LNM 212 can include a reflective grating. In some embodiments, LNM 212 can include abeam expander (e.g., multi -prism beam expander) and an adjustable reflective grating (e.g., via a piezoelectric actuator) to reflect a selected (narrow) portion of the broader spectrum of light beam 211 back into gas discharge chamber 214 to amplify that selected portion, thereby tuning light beam 211 (e.g., adjusting wavelength and bandwidth).

[0092] Gas discharge chamber 214 can be configured to generate a seed laser and output a light beam (e.g., light beam 211). Gas discharge chamber 214 (e.g., MO chamber) can be further configured to receive electrical discharges (e.g., voltage pulses) between electrodes (e.g., via voltage control system 215a) thereby causing lasing gas discharges in a gas discharge medium (e.g., lasing gas, including F2, ArF, KrF, and / or XeF) to create an inverted population of high energy molecules (e.g., excited dimer, excited complex) to produce relatively broadband radiation (e.g., DUV radiation), for example, that may be linewidth narrowed to a relatively narrow bandwidth and tuned to a selected center wavelength (e.g., via LNM 212). Gas discharge chamber 214 can include voltage control system 215a and pressure control system 215b.

[0093] Voltage control system 215a can be configured to apply high voltage electrical pulses across electrodes in gas discharge chamber 214 to excite a gas discharge medium (e.g., F2, ArF, KrF, and / or XeF) to output ASE and / or light beam 211 (e.g., 193 nm). In some embodiments, voltage control system 215a can include a high voltage power supply (not shown), a voltage compression amplifier (not shown), a pulse energy monitor (not shown), and / or a controller (e.g., controller 260) for providing high voltage electrical pulses across the electrodes. For example, a voltage control system has been previously described in U.S. Patent No. 6,240,117, issued May 29, 2001, which is hereby incorporated by reference herein in its entirety.

[0094] Pressure control system 215b can be configured to control a concentration of the gas discharge medium (e.g., F2, ArF, KrF, and / or XeF) in gas discharge chamber 214. In some embodiments, pressure control system 215b can include a gas discharge line to provide one or more gas components (e.g., A , I<r2. F2, Xe2, ArF, KrCl, KrF, XeBr, XeCl, XeF, KrNe, etc.) of the gas discharge medium to gas discharge chamber 214. In some embodiments, pressure control system 215b can include a vacuum line to provide a negative pressure (e.g., draw out) to a portion of the gas discharge medium of gas discharge chamber 214, for example, during injection of one or more gas components. In some embodiments,pressure control system 215b can include one or more gas sources (not shown), one or more pressure regulators (not shown), a vacuum pump (not shown), and / or a controller (e.g., controller 260) for controlling a concentration of the gas discharge medium in gas discharge chamber 214. For example, a pressure control system has been previously described in U.S. Patent No. 6,240,117, issued May 29, 2001, which is hereby incorporated by reference herein in its entirety.

[0095] Optical coupler 216 can be configured to form, along with LNM 212 and gas discharge chamber 214, an optical cavity in which seed light (e.g., amplified spontaneous emission (ASE)) from gas discharge chamber 214 oscillates (reflects) back and forth to form a master oscillator (MO) and generate light beam 211. In some embodiments, optical coupler 216 can include a partially reflective mirror.

[0096] LAM 218 can be configured to analyze a line-center of light beam 211 and measure a wavelength of light beam 211. In some embodiments, LAM 218 can include an etalon spectrometer for fine wavelength measurements and a grating spectrometer for coarse wavelength measurements.

[0097] Relay optics subsystem 220 can be configured to redirect light beam 211 from MO subsystem210 toward PRA subsystem 230. Relay optics subsystem 220 can include wavefront engineering box (WEB) 222. In some embodiments, WEB 222 can include a beam expansion element (e.g., a multiprism beam expander) to adjust a cross-sectional area of light beam 211. In some embodiments, WEB 222 can include a coherence busting element (e.g., an optical delay path) to adjust (e.g., enlarge) a phase-space area of light beam 211. As shown in FIG. 2, relay optics subsystem 220 receives light beam211 from MO subsystem 210 and directs light beam 211 to PRA subsystem 230 for further amplification, indicated by the unidirectional arrows, as would be apparent to a person of ordinary skill in the art.

[0098] PRA subsystem 230 can be configured to amplify light beam 211 from MO subsystem 210 and output amplified light beam 231. PRA subsystem 230 can be further configured to maximize the nominal operating wavelength of light beam 211 for a selected gas discharge medium (e.g., 193 nm for ArF). PRA subsystem 230 can include second wavefront engineering box (WEB) 232, second gas discharge chamber 234, and beam reverser (BR) 236. As shown in FIG. 2, PRA subsystem 230 amplifies light beam 211 received from relay optics subsystem 220 in a second optical cavity formed by BR 236, second gas discharge chamber 234, and second WEB 232, indicated by the bidirectional arrows, and outputs amplified light beam 231, indicated by the unidirectional arrow, as would be apparent to a person of ordinary skill in the art.

[0099] Second WEB 232 can be configured to direct light beam 211 from MO subsystem 210 (via relay optics subsystem 220) toward second gas discharge chamber 234. Second WEB 232 can be further configured to form, along with second gas discharge chamber 234 and BR 236, a second optical cavity (gain medium) in which light beam 211 oscillates (reflects) back and forth to form a power ring amplifier (PRA) and generate amplified light beam 231. In some embodiments, second WEB 232 can include a partially reflective mirror. In some embodiments, second WEB 232 can include a beam expansion element (e.g., a multi-prism beam expander) to adjust a cross-sectional area of amplifiedlight beam 231. In some embodiments, second WEB 232 can include a coherence busting element (e.g., an optical delay path) to adjust (e.g., enlarge) a phase-space area of amplified light beam 231.

[0100] Second gas discharge chamber 234 can be configured to amplify light beam 211 and output an amplified light beam (e.g., amplified light beam 231). Second gas discharge chamber 234 (e.g., PRA chamber) can be further configured to receive electrical discharges (e.g., voltage pulses) between electrodes (e.g., via voltage control system 235a) thereby causing lasing gas discharges in a gas discharge medium (e.g., lasing gas, including F2, ArF, KrF, and / or XeF) to create an inverted population of high energy molecules (e.g., excited dimer, excited complex) to produce relatively broadband radiation (e.g., DUV radiation). Second gas discharge chamber 234 can include voltage control system 235a and pressure control system 235b.

[0101] Voltage control system 235a can be configured to apply high voltage electrical pulses across electrodes in second gas discharge chamber 234 to excite a gas discharge medium (e.g., F2, ArF, KrF, and / or XeF) to output amplified light beam 231 (e.g., 193 nm). In some embodiments, voltage control system 235a can include a high voltage power supply (not shown), a voltage compression amplifier (not shown), a pulse energy monitor (not shown), and / or a controller (e.g., controller 260) for providing high voltage electrical pulses across the electrodes. For example, a voltage control system has been previously described in U.S. Patent No. 6,240,117, issued May 29, 2001, which is hereby incorporated by reference herein in its entirety.

[0102] Pressure control system 235b can be configured to control a concentration of the gas discharge medium (e.g., F2, ArF, KrF, and / or XeF) in second gas discharge chamber 234. In some embodiments, pressure control system 235b can include a gas discharge line to provide one or more gas components (e.g., Ar2, Kr2, F2, Xe2, ArF, KrCl, KrF, XeBr, XeCl, XeF, KrNe, etc.) of the gas discharge medium to second gas discharge chamber 234. In some embodiments, pressure control system 235b can include a vacuum line to provide a negative pressure (e.g., draw out) to a portion of the gas discharge medium of second gas discharge chamber 234, for example, during injection of one or more gas components. In some embodiments, pressure control system 235b can include one or more gas sources (not shown), one or more pressure regulators (not shown), a vacuum pump (not shown), and / or a controller (e.g., controller 260) for controlling a concentration of the gas discharge medium in second gas discharge chamber 234. For example, a pressure control system has been previously described in U.S. Patent No. 6,240,117, issued May 29, 2001, which is hereby incorporated by reference herein in its entirety.

[0103] BR 236 can be configured to redirect light beam 211 and / or amplified light beam 231 back through the gain medium of second gas discharge chamber 234. In some embodiments, BR 236 can include an adjustable mirror.

[0104] Baser output subsystem 240 can be configured to measure one or more parameters of amplified light beam 231 from PRA subsystem 230. In some embodiments, laser output subsystem 240 can be an in-line passive apparatus and integrated into a beam path of amplified light beam 231 from PRA subsystem 230. Laser output subsystem 240 can include bandwidth analysis module (BAM) 242, opticalpulse stretcher (OPuS) 244, and metrology and measurement module 300. As shown in FIG. 2, laser output subsystem 240 receives amplified light beam 231 from PRA subsystem 230 and directs amplified light beam 231 through BAM 242, OPuS 244, and metrology and measurement module 300 for further analysis and / or modification (e.g., pulse stretching), indicated by the unidirectional arrows, and outputs light beam 250, indicated by the final unidirectional arrow, as would be apparent to a person of ordinary skill in the art.

[0105] BAM 242 can be configured to analyze a bandwidth of amplified light beam 231 from PRA subsystem 230. In some embodiments, BAM 242 can be configured to divert (e.g., pick -off) a portion of amplified light beam 231 for metrology purposes, for example, to measure a bandwidth and / or a pulse energy of amplified light beam 231.

[0106] OPuS 244 can be configured to control a pulse duration of amplified light beam 231. OPuS 244 can be further configured to adjust a TIS pulse width of light beam 250 (e.g., via pulse stretching amplified light beam 231 to increase a TIS pulse width and generate stretched light beam 245). In some embodiments, OPuS 244 can receive amplified light beam 231 and stretch amplified light beam 231 (e.g., increasing TIS pulse width) to generate stretched light beam 245.

[0107] Controller 260 can be configured to monitor and adjust one or more parameters (e.g., wavelength, bandwidth, cross-sectional area, beam divergence, TIS pulse width, SC, or a combination thereof) and / or one or more components of light source apparatus 200 (e.g., LNM 212, WEB 222, second WEB 232, OPuS 244, metrology and measurement module 300, etc.). Controller 260 can be further configured to control a SC of light beam 250. Controller 260 can be further configured to adjust one or more actuators of light source apparatus 200 (e.g., linear motor, servo motor, piezoelectric, stepper, shutter, electro-optic modulator, acousto-optic modulator, etc.) corresponding to one or more parameters of the SC (e.g., wavelength, bandwidth, cross-sectional area, beam divergence).

[0108] Controller 260 can include a plurality of connections to various components of light source apparatus 200, for example, first connection 261 (e.g., electrically, mechanically, and / or optically coupled to MO subsystem 210, for example, LNM 212), second connection 262 (e.g., electrically, mechanically, and / or optically coupled to relay optics subsystem 220, for example, WEB 222), third connection 263 (e.g., electrically, mechanically, and / or optically coupled to PRA subsystem 230, for example, second WEB 232), fourth connection 264 (e.g., electrically, mechanically, and / or optically coupled to laser output subsystem 240, for example, OPuS 244), and fifth connection 265 (e.g., electrically, mechanically, and / or optically coupled to metrology and measurement module 300).

[0109] In some embodiments, controller 260 can include a closed-loop feedback algorithm configured to minimize the SC of light beam 250. For example, the closed-loop feedback algorithm can measure (e.g., in real-time) different parameters of the SC (e.g., wavelength, bandwidth, cross-sectional area, beam divergence, TIS pulse width), calculate the resulting SC value, and then automatically adjust (e.g., via adjustment of one or more actuators in light source apparatus 200) one or more of the measured parameters to minimize the SC value.

[0110] In some embodiments, controller 260 can include a closed-loop feedback algorithm configured to attain or maintain a desired SC of light beam 250. For example, the closed-loop feedback algorithm can measure (e.g., in real-time) different parameters of the SC (e.g., wavelength, bandwidth, cross- sectional area, beam divergence, TIS pulse width), calculate the resulting SC value, and then automatically adjust (e.g., via adjustment of one or more actuators in light source apparatus 200) one or more of the measured parameters to attain or maintain the desired SC value.[oni] In some embodiments, controller 260 can be configured to conduct data mining of measured TIS values and / or calculated SC values over time to identify optimal maintenance planning of light source apparatus 200. For example, the data mining can identify one or more performance trends (e.g., change over time) of one or more optical components (e.g., LNM 212, WEB 222, second WEB 232, OPuS 244, etc.) of light source apparatus 200 and schedule and / or make one or more corrections to the identified optical component(s) based on the identified performance trend(s).

[0112] In some embodiments, controller 260 can be configured to conduct machine learning of measured TIS values and / or calculated SC values over time to identify optimal maintenance planning of light source apparatus 200. For example, the machine learning can identify one or more performance trends (e.g., change over time) of one or more optical components (e.g., LNM 212, WEB 222, second WEB 232, OPuS 244, etc.) of light source apparatus 200 and schedule and / or make one or more corrections to the identified optical component(s) based on the identified performance trend(s). In some embodiments, the machine learning of controller 260 can include simulated annealing, gradient descent, finite difference, interpolation, population models, regression, parameter adaptation, supervised machine learning, unsupervised machine learning, neural networks, classification models, clustering, vector quantization, stochastic gradient descent, implicit updates, leaky averaging, momentum methods, adaptive gradient (AdaGrad), backpropagation, root mean square propagation (RMSProp), adaptive moment estimation (Adam), or a combination thereof.

[0113] Exemplary Metrology and Measurement Module

[0114] FIG. 3 illustrates metrology and measurement module 300, according to various exemplary embodiments. Metrology and measurement module 300 can be configured to passively measure one or more parameters of a light beam (e.g., wavelength, bandwidth, cross-sectional area, beam divergence, TIS pulse width, SC, or a combination thereof) in real-time or near real-time. Metrology and measurement module 300 can be further configured to communicate the measured one or more parameters of the light beam (e.g., wavelength, bandwidth, cross-sectional area, beam divergence, TIS pulse width, SC, or a combination thereof) to a controller, for example, to form a feedback loop (e.g., closed-loop feedback algorithm). Metrology and measurement module 300 can be further configured to monitor and store one or more parameters of the light beam (e.g., wavelength, bandwidth, cross- sectional area, beam divergence, TIS pulse width, SC, or a combination thereof) in a database (e.g., online database), for example, for data mining and / or machine learning applications. Although metrology and measurement module 300 is shown in FIG. 3 as a stand-alone apparatus and / or system,the embodiments of this disclosure can be used with other optical systems, such as, but not limited to, a radiation source, a lithographic apparatus, a light source apparatus, and / or other optical systems. In some embodiments, metrology and measurement module 300 can include an optics metrology device, an auto-shutter, and a TIS measurement device.

[0115] As shown in FIG. 3, metrology and measurement module 300 can include laser input 302, laser output 304, beam splitter 310, beam sensor 320, power sensor 330, database 350, and TIS apparatus 400. In some embodiments, metrology and measurement module 300 can receive laser input 302 (e.g., a stretched light beam), transmit laser output 304 (e.g., a light beam), and receive a portion of laser input 302 via beam splitter 310 (e.g., a dichroic mirror) for in-line passive measurement of one or more parameters of laser input 302 (e.g., wavelength, bandwidth, cross-sectional area, beam divergence, TIS pulse width, SC, or a combination thereof).

[0116] Beam splitter 310 can be configured to passively isolate a portion of laser input 302. In some aspects, beam splitter 310 can include an optical auto-shutter (e.g., electro-optic modulator) to investigate a portion of laser input 302 at a specific time. For example, the optical auto-shutter (e.g., with partially reflective mirror) can remain open until a measurement of laser input 302 is taken.

[0117] Beam sensor 320 can be configured to measure one or more parameters of laser input 302, for example, wavelength, bandwidth, cross-sectional area, and beam divergence of laser input 302 (e.g., a light beam). In some embodiments, beam sensor 320 can include one or more spectrometers (e.g., etalon spectrometer, grating spectrometer, etc.), one or more beam expanders (e.g., multi-prism beam expander, etc.), one or more photodetectors (e.g., photodiode, APD, CCD, CMOS, PMT, etc.), or a combination thereof to measure a wavelength (e.g., 193 nm), a bandwidth (e.g., E95 bandwidth), a cross-sectional area (e.g., 1 mm2), and a beam divergence (e.g., horizontal beam divergence, vertical beam divergence) of laser input 302 (e.g., a light beam). In some embodiments, metrology and measurement module 300 can include one or more optical components (e.g., mirrors, prisms, waveguides, optical fibers, etc.) to direct a portion of laser input 302 from beam splitter 310 to beam sensor 320.

[0118] Power sensor 330 can be configured to measure optical power of laser input 302. In some embodiments, power sensor 330 can measure a pulse energy of the light beam (e.g., E = PavgAt). In some embodiments, metrology and measurement module 300 can include one or more optical components (e.g., mirrors, prisms, waveguides, optical fibers, etc.) to direct a portion of laser input 302 from beam splitter 310 to power sensor 330.

[0119] Database 350 can be configured to store one or more measured values from beam sensor 320, power sensor 330, and / or TIS apparatus 400. Database 350 can be further configured to store TIS pulse width and SC values of laser input 302 over time. In some embodiments, database 350 can be integrated with pulse data of a light source apparatus (e.g., via a controller and / or power sensor 330). In some embodiments, database 350 can include an online database (e.g., remote server, cloud server, etc.) configured to aggregate measurement data from one or more light source apparatuses. For example, theremote server can perform data mining and / or machine learning on large amounts of data (e.g., big data) to identify one or more performance trend(s) and / or optimal maintenance planning. In some embodiments, database 350 can be in communication with the controller. In some embodiments, metrology and measurement module 300 can include one or more connections (e.g., electronic, wired, wireless, etc.) between beam sensor 320, power sensor 330, and / or TIS apparatus 400 and database 350 to transfer measured data to database 350.

[0120] TIS apparatus 400 can be configured to receive a portion of laser input 302 (e.g., a light beam) and measure a TIS pulse width of the laser input 302 in the time domain. TIS apparatus 400 can be further configured to calculate a SC of laser input 302 based on the measured TIS pulse width. In some embodiments, metrology and measurement module 300 can include one or more optical components (e.g., mirrors, prisms, waveguides, optical fibers, etc.) to direct a portion of laser input 302 from beam splitter 310 to TIS apparatus 400. In some embodiments, TIS apparatus 400 can be included with metrology and measurement module 300. In some embodiments, TIS apparatus 400 can be separate from metrology and measurement module 300, for example, after metrology and measurement module 300 or between an OPuS and metrology and measurement module 300.

[0121] In some embodiments, TIS apparatus 400 can measure the TIS pulse width in real-time or near real-time. For example, TIS apparatus 400 can measure the TIS pulse width in real-time within one millisecond. In some embodiments, the calculated SC can be provided (e.g., via a controller) to a lithographic apparatus to reduce errors in a lithographic process (e.g., reducing LWR, LER, CD errors, CD non-uniformity, or a combination thereof). In some embodiments, TIS apparatus 400 can calculate the SC in real-time or near real-time. For example, TIS apparatus 400 can calculate the SC in real-time within one millisecond. TIS apparatus 400 can include TIS actuator 420 and TIS processor 440.

[0122] TIS actuator 420 can be configured to adjust one or more components of TIS apparatus 400, for example, to adjust a position and / or rotation of TIS apparatus 400 relative to laser input 302. In some embodiments, TIS actuator 420 can include one or more actuators (e.g., linear, piezoelectric, tilt, rotational, etc.). TIS processor 440 can be configured to square a raw pulse signal of laser input 302 and convert it to the time domain to measure the TIS pulse width. TIS processor 440 can be further configured to calculate the SC based on the measured TIS pulse width. In some embodiments, TIS processor 440 can include one or more processors, microprocessors, microcontrollers, and / or ASICs, for example, to calculate the SC in real-time.

[0123] Exemplary TIS Apparatus

[0124] FIG. 4 illustrates time-integral squared (TIS) apparatus 400, according to various exemplary embodiments. TIS apparatus 400 can be configured to measure a TIS pulse width of a light beam and calculate a SC of the light beam based on the measured TIS pulse width. TIS apparatus 400 can be further configured to adjust one or more actuators or a control algorithm (e.g., via a controller) of light source apparatus associated with the SC of the light beam. Although TIS apparatus 400 is shown in FIG. 4 as a stand-alone apparatus and / or system, the embodiments of this disclosure can be used withother optical systems, such as, but not limited to, a radiation source, a lithographic apparatus, a light source apparatus, a metrology and measurement module, and / or other optical systems.

[0125] As shown in FIG. 4, TIS apparatus 400 can include TIS sensor 410, first connector 414, second connector 416, third connector 418, TIS actuator 420, and TIS processor 440. In some embodiments, TIS apparatus 400 can receive a portion of laser input (e.g., a light beam), measure a TIS pulse width, and calculate a SC of laser input. In some embodiments, TIS apparatus 400 can be in communication with beam sensor 320 and / or power sensor 330 of metrology and measurement module 300, for example, to receive measured values of wavelength, bandwidth, cross-sectional area, and beam divergence of laser input 302.

[0126] TIS sensor 410 can be configured to measure a raw pulse signal (e.g., voltage signal) of laser input 302. In some embodiments, TIS sensor 410 can include a photomultiplier tube (PMT). TIS sensor 410 can include a sensor assembly or body (e.g., PMT assembly) that is coupled to first connector 414, second connector 416, and third connector 418.

[0127] First connector 414 can be configured to supply high voltage to TIS sensor 410 (e.g., PMT). Second connector 416 (e.g., coaxial connector) can be coupled to TIS actuator 420 and configured to transfer control signals from TIS actuator 420 to TIS sensor 410. TIS actuator 420 can be configured to adjust one or more components of TIS sensor 410, for example, to adjust a position and / or rotation of TIS sensor 410 relative to laser input 302. In some embodiments, TIS actuator 420 can include one or more actuators (e.g., linear, piezoelectric, tilt, rotational, etc.).

[0128] Third connector 418 (e.g., coaxial connector) can be coupled to TIS processor 440 and configured to transfer measurement data (e.g., raw pulse signal) to TIS processor 440. TIS processor 440 can be configured to square a raw pulse signal of laser input 302 (e.g., a light beam) and convert it to the time domain to measure the TIS pulse width. TIS processor 440 can be further configured to calculate the SC based on the measured TIS pulse width. In some embodiments, TIS processor 440 can include one or more processors, microprocessors, microcontrollers, and / or ASICs, for example, to calculate the SC in real-time.

[0129] In some embodiments, TIS processor 440 can calculate the SC in real-time or near real-time. For example, TIS processor 440 can receive raw pulse signal from TIS sensor 410, square the raw pulse signal and convert it to the time domain to measure the TIS pulse width, receive measured values of wavelength, bandwidth, cross-sectional area, and beam divergence of laser input (e.g., via a beam sensor), and calculate the SC based on the measured values (e.g., in real-time).

[0130] In some embodiments, TIS processor 440 can calculate the SC based on the following equation:Speckle Contrast'where TIS is the TIS pulse width in the time domain, A is a wavelength of the light beam, c is the speed of light, BW is a bandwidth of the light beam, Abeam is a cross-sectional area of the light beam, and Q(nv is a beam divergence (vertical beam divergence multiplied by horizontal beam divergence, e.g., diw^div) °f the light beam. In some embodiments, the TIS pulse width, the wavelength (A) of the light beam, the bandwidth (BW) (e.g., E95 bandwidth) of the light beam, the cross-sectional area (Abeam) of the light beam, and the beam divergence ( div) of the light beam can be measured in real-time or near real-time, for example, via TIS apparatus 400 and the beam sensor.

[0131] In some embodiments, TIS apparatus 400 can measure a TIS pulse width of light beam, calculate a SC of the light beam (e.g., light beam 250), communicate the calculated SC value to controller 260, and controller 260 can adjust one or more parameters of SC (e.g., wavelength, bandwidth, cross-sectional area, beam divergence, TIS pulse width) to adjust (reduce) the SC value. For example, controller 260 can adjust OPuS 244 to pulse stretch the light beam (e.g., stretched light beam 245), thereby increasing the TIS pulse width and decreasing the SC value.

[0132] Exemplary Flow Diagram

[0133] FIG. 5 illustrates flow diagram 500 for light source apparatus, according to an exemplary embodiment. Flow diagram 500 can be configured to measure a TIS pulse width of a light beam and calculate a SC of the light beam in real-time or near real-time. Flow diagram 500 can be further configured to adjust one or more parameters of the SC (e.g., wavelength, bandwidth, cross-sectional area, beam divergence, TIS pulse width) to control and / or optimize the SC (e.g., in real-time). Flow diagram 500 can be further configured to reduce errors in a lithographic process (e.g., LWR, LER, CD errors, CD non-uniformity, or a combination thereof), perform diagnostics of a light source (e.g., a light source apparatus), identify optimal maintenance planning of the light source, and increase the service lifetime of the light source.

[0134] It is to be appreciated that not all operations in FIG. 5 are needed to perform the disclosure provided herein. Further, some of the operations may be performed simultaneously, sequentially, and / or in a different order than shown in FIG. 5. Flow diagram 500 shall be described with reference to FIGS. 2-4. However, flow diagram 500 is not limited to those example embodiments. Although flow diagram 500 is shown in FIG. 5 as a stand-alone method, the embodiments of this disclosure can be used with other apparatuses, systems, and / or methods, such as, but not limited to, a radiation source SO, a lithographic apparatus, a light source apparatus, a metrology and measurement module, a TIS apparatus, and / or other optical systems. In some embodiments, flow diagram 500 can be implemented by light source apparatus 200 shown in FIG. 2.

[0135] In operation 502, a TIS pulse width of a light beam of a light source (e.g., light source apparatus) can be measured in real-time or near real-time (e.g., via TIS apparatus 400).

[0136] In operation 504, a SC of the light beam can be calculated based on the measured TIS pulse width (e.g., via the TIS apparatus). In some embodiments, the SC can be calculated in real-time or near real-time.

[0137] In operation 506, one or more parameters of the SC can be adjusted (e.g., via a controller) based on the calculated SC. In some embodiments, the one or more parameters can include a wavelength of the light beam (e.g., 193 nm), a bandwidth of the light beam (e.g., E95 bandwidth), a cross-sectional area of the light beam (e.g., 1 mm2), a beam divergence of the light beam, a TIS pulse width of the light beam, or a combination thereof. In some embodiments, the one or more parameters can be adjusted by the controller, for example, via control signals to a LNM and / or an OPuS.

[0138] In operation 508, the SC can be controlled in real-time or near real-time. In some embodiments, the wavelength, the bandwidth, the cross-sectional area, the beam divergence, and the TIS pulse width can be measured in real-time (e.g., within 1 ms) or near real-time (e.g., within 1 s) via one or more components (e.g., TIS apparatus 400), an SC value can be calculated based on the measured parameters, the SC value can be sent to the controller, and the controller can adjust one or more parameters of the SC to control the SC synchronously with the measured parameters in real-time (e.g., within 1 ms) or near real-time (e.g., within 1 s).

[0139] In operation 510, optionally, diagnostics of the light source (e.g., a light source apparatus) can be performed based on the measured TIS pulse width over time. In some embodiments, the controller can monitor the measured TIS pulse width over time and / or the calculated SC over time to identify one or more performance trends of the light source, for example, decreasing TIS pulse width over time. In some embodiments, the controller can correct and / or schedule a planned maintenance of one or more components of the light source based on the identified performance trends.

[0140] In operation 512, optionally, one or more actuators (e.g., linear, piezoelectric, tilt, rotational, etc.) or a control algorithm (e.g., closed-loop feedback algorithm) corresponding to one or more parameters of the SC (e.g., wavelength, bandwidth, cross-sectional area, beam divergence, TIS pulse width, or a combination thereof) can be adjusted (e.g., via the controller). In some embodiments, the one or more actuators or the control algorithm can be adjusted in real-time (e.g., within 1 ms) or near real-time (e.g., within 1 s), thereby minimizing the SC over time and / or attaining or maintaining a desired SC over time.

[0141] Although specific reference may be made in this text to the use of the apparatus, system, and / or lithographic apparatus in the manufacture of ICs, it should be explicitly understood that such an apparatus, system, and / or lithographic apparatus described herein may have other possible applications, for example, it can be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, LCD panels, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “reticle,” “wafer,” or “die” herein may be considered as synonymous with the more general terms “mask,” “substrate,” and “target portion,” respectively.

[0142] Although specific reference may have been made above to the use of aspects in the context of optical lithography, it will be appreciated that aspects may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[0143] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by those skilled in relevant art(s) in light of the teachings herein.

[0144] The term “substrate” as used herein describes a material onto which material layers are added. In some aspects, the substrate itself may be patterned and materials added on top of it may also be patterned, or may remain without patterning. The substrate referred to herein may be processed, before or after exposure, for example, in a track unit (e.g., a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology unit, and / or an inspection unit. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example, to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0145] The following examples are illustrative, but not limiting, of the aspects of this disclosure. Other suitable modifications and adaptations of the variety of conditions and parameters normally encountered in the field, and which would be apparent to those skilled in the relevant art(s), are within the spirit and scope of the disclosure.

[0146] While specific aspects have been described above, it will be appreciated that the aspects may be practiced otherwise than as described. The description is not intended to limit the scope of the claims.

[0147] It is to be appreciated that the Detailed Description section, and not 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 aspects as contemplated by the inventor(s), and thus, are not intended to limit the aspects and the appended claims in any way.

[0148] The aspects have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

[0149] The foregoing description of the specific aspects will so fully reveal the general nature of the aspects that others can, by applying knowledge within the skill of the art, readily modify and / or adapt for various applications such specific aspects, without undue experimentation, without departing from the general concept of the aspects. Therefore, such adaptations and modifications are intended to bewithin the meaning and range of equivalents of the disclosed aspects, based on the teaching and guidance presented herein.

[0150] The breadth and scope of the aspects should not be limited by any of the above -described exemplary aspects, but should be defined only in accordance with the following claims and their equivalents.

Claims

CLAIMS1. A light source apparatus comprising: a gas discharge stage configured to output a light beam, the gas discharge stage comprising: an optical amplifier comprising a chamber configured to house a gas discharge medium; and an energizing device configured to excite the gas discharge medium and generate the light beam; and a time-integral squared (TIS) apparatus configured to: receive a portion of the light beam and measure a time-integral squared (TIS) pulse width of the light beam in the time domain, and calculate a speckle contrast (SC) of the light beam based on the measured time-integral squared (TIS) pulse width, wherein the time-integral squared (TIS) pulse width is measured in real-time or near real-time, and wherein the calculated speckle contrast (SC) is provided to a lithographic apparatus to reduce errors in a lithographic process.

2. The light source apparatus of claim 1, wherein the speckle contrast (SC) is calculated in realtime or near real-time.

3. The light source apparatus of claim 1, wherein the speckle contrast (SC) is determined by the following equation:Sp ' eckle Contrastwhere TIS is the time-integral squared (TIS) pulse width in the time domain, A is a wavelength of the light beam, c is the speed of light, BW is a bandwidth of the light beam, Abeam is a cross-sectional area of the light beam, and Q(nv is a beam divergence of the light beam.

4. The light source apparatus of claim 3, wherein the time-integral squared (TIS) pulse width, the wavelength of the light beam, the bandwidth of the light beam, the cross-sectional area of the light beam, and / or the beam divergence of the light beam are measured in real-time or near real-time.

5. The light source apparatus of claim 3, wherein the bandwidth of the light beam is an E95 bandwidth corresponding to a spectral bandwidth of the light beam that contains 95% of the total pulse energy of the light beam.

6. The light source apparatus of claim 1, wherein the light source apparatus is configured to adjust the time-integral squared (TIS) pulse width based on the calculated speckle contrast (SC), thereby decreasing critical dimension (CD) non -uniformity in the lithographic apparatus.

7. The light source apparatus of claim 1, wherein the time-integral squared (TIS) pulse width is measured in real-time within one millisecond.

8. The light source apparatus of claim 1, wherein the time-integral squared (TIS) pulse width is measured over time to perform diagnostics of the light source apparatus.

9. The light source apparatus of claim 8, wherein: the time-integral squared (TIS) pulse width is measured over time to identify a performance trend of one or more optical components of the light source apparatus, and a correction is made to the one or more optical components based on the identified performance trend.

10. The light source apparatus of claim 1, wherein the time-integral squared (TIS) apparatus comprises: a sensor configured to measure a raw pulse signal of the light beam; and a processor coupled to the sensor and configured to square the raw pulse signal and convert it to the time domain to measure the time-integral squared (TIS) pulse width.

11. The light source apparatus of claim 10, wherein the processor is configured to calculate the speckle contrast (SC) based on the measured time-integral squared (TIS) pulse width.

12. The light source apparatus of claim 1, further comprising an optical pulse stretcher configured to adjust the time-integral squared (TIS) pulse width.

13. The light source apparatus of claim 1, further comprising a controller coupled to the timeintegral squared (TIS) apparatus and configured to control the speckle contrast (SC).

14. The light source apparatus of claim 13, wherein the controller is configured to adjust one or more actuators of the light source apparatus corresponding to one or more parameters of the speckle contrast (SC).

15. The light source apparatus of claim 13, wherein the controller comprises a closed-loop feedback algorithm configured to minimize the speckle contrast (SC).

16. The light source apparatus of claim 13, wherein the controller comprises a closed-loop feedback algorithm configured to attain or maintain a desired speckle contrast (SC).

17. The light source apparatus of claim 13, wherein the controller is configured to conduct data mining and / or machine learning based on the time-integral squared (TIS) pulse width overtime to identify optimal maintenance planning of the light source apparatus.

18. The light source apparatus of claim 1, wherein the time-integral squared (TIS) apparatus is an in-line passive apparatus and integrated into a beam path of the light beam.

19. The light source apparatus of claim 1, further comprising a database coupled to the timeintegral squared (TIS) apparatus and configured to store the time-integral squared (TIS) pulse width and speckle contrast (SC) overtime.

20. The light source apparatus of claim 19, wherein the database is integrated with pulse data of the light source apparatus.

21. A time-integral squared (TIS) apparatus configured to calculate a speckle contrast (SC) of a light beam, the time-integral squared (TIS) apparatus comprising: a sensor configured to measure a raw pulse signal of the light beam; and a processor coupled to the sensor and configured to square the raw pulse signal and convert it to the time domain to measure a time-integral squared (TIS) pulse width of the light beam, wherein the time-integral squared (TIS) pulse width is measured in real-time or near real-time, and wherein the measured time-integral squared (TIS) pulse width is used to adjust one or more actuators or a control algorithm of a light source associated with the speckle contrast (SC).

22. The time-integral squared (TIS) apparatus of claim 21, wherein the processor is configured to calculate a speckle contrast (SC) of the light beam based on the measured time-integral squared (TIS) pulse width.

23. The time-integral squared (TIS) apparatus of claim 22, wherein the speckle contrast (SC) is calculated in real-time or near real-time.

24. The time-integral squared (TIS) apparatus of claim 21, wherein the time-integral squared (TIS) pulse width is measured in real-time within one millisecond.

25. The time-integral squared (TIS) apparatus of claim 21, wherein the time-integral squared (TIS) apparatus is an in-line passive apparatus and integrated into a beam path of the light beam.

26. A metrology and measurement apparatus comprising: an auto-shutter device configured to direct a portion of a light beam; an optics metrology device configured to measure one or more parameters of the light beam; and a time-integral squared (TIS) apparatus configured to calculate a speckle contrast (SC) of the light beam based on a time-integral squared (TIS) pulse width of the light beam measured in the time domain, wherein the time-integral squared (TIS) pulse width is measured in real-time or near real-time, and wherein the measured time-integral squared (TIS) pulse width is used to adjust one or more actuators or a control algorithm of a light source associated with the speckle contrast (SC).

27. The metrology and measurement apparatus of claim 26, wherein the calculated speckle contrast (SC) is provided to a lithographic apparatus to reduce errors in a lithographic process.

28. The metrology and measurement apparatus of claim 26, wherein the speckle contrast (SC) is calculated in real-time or near real-time.

29. The metrology and measurement apparatus of claim 26, wherein the one or more parameters of the light beam comprises a wavelength, a bandwidth, a cross-sectional area, a beam divergence, or a combination thereof.

30. The metrology and measurement apparatus of claim 26, wherein the optics metrology device comprises a beam sensor, a power sensor, a spectrometer, a beam expander, or a combination thereof.

31. The metrology and measurement apparatus of claim 26, wherein the auto-shutter device comprises a beam splitter configured to passively isolate a portion of the light beam.

32. The metrology and measurement apparatus of claim 26, wherein the auto-shutter device comprises a modulator configured to direct the portion of the light beam at a specific time.

33. The metrology and measurement apparatus of claim 26, further comprising a database coupled to the optics metrology device, the time-integral squared (TIS) apparatus, or both, the database configured to store one or more measured values from the optics metrology device, the time-integral squared (TIS) apparatus, or both.

34. The metrology and measurement apparatus of claim 33, wherein the one or more measured values comprises a wavelength, a bandwidth, a cross-sectional area, a beam divergence, a TIS pulse width, a SC, or a combination thereof.

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