Gas purge system for a laser source

Abstract

A laser source includes a laser chamber configured to generate a first laser beam. The laser source also includes an optical system coupled to the laser chamber and configured to receive the first laser beam and output an output laser beam. The laser source also includes a gas purge system. According to some aspects, the gas purge system is configured to supply nitrogen gas into the optical system at a pressure lower than atmospheric pressure. According to some aspects, the gas purge system is configured to supply helium gas into the optical system.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Application No. 62 / 951,840, filed December 20, 2019, entitled “Low Pressure Gas Purge System for Laser Source”; and U.S. Application No. 63 / 022,023, filed May 8, 2020, entitled “Gas Purge Systems for Laser Source”, both of which are incorporated herein by reference in their entirety. Technical Field

[0003] This disclosure relates to systems and methods for providing a gas purging system in a laser source used, for example, in a photolithography apparatus and system. Background Technology

[0004] A photolithography apparatus is a machine that applies a desired pattern onto a substrate, typically onto a target portion of the substrate. Photolithography apparatuses can be used, for example, in the fabrication of integrated circuits (ICs). In this case, a patterning device (alternatively called a mask or stencil) is used to generate a circuit pattern to be formed on an individual layer of the formed IC. This pattern can be transferred onto a target portion (e.g., including portions, one or more dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is typically achieved by imaging onto a layer of radiation-sensitive material (photoresist, or simply "resist") disposed on the substrate. Typically, a single substrate will contain a network of continuously patterned adjacent target portions. Known photolithography apparatuses include so-called steppers, where each target portion is irradiated by exposing the entire pattern onto the target portion at once, and so-called scanners, where the pattern is scanned in a given direction ("scanning" direction) by a radiation beam, while simultaneously scanning the target portions parallel to or opposite to the scanning direction to irradiate each target portion. A pattern can also be transferred from a patterning device to a substrate by imprinting the pattern onto the substrate.

[0005] Laser sources can be used in conjunction with photolithography apparatuses to generate irradiation radiation for irradiating patterning devices, for example. Oxygen (O2) can be present in the optical path of the laser beam within the laser source. However, ozone (O3) generated by oxygen (O2) in the presence of a laser beam can be harmful to the optical components within the laser source. Summary of the Invention

[0006] Therefore, a gas purging system and a gas purging method are needed for laser sources.

[0007] This disclosure describes embodiments of low-pressure and other gas purging systems and methods.

[0008] One aspect of this disclosure provides a laser source including a laser chamber configured to generate a first laser beam. The laser source also includes an optical system coupled to the laser chamber and configured to receive and output the first laser beam. The laser source further includes a gas purging system configured to supply gas to the optical system at a pressure below atmospheric pressure.

[0009] In some examples, the gas purging system includes a gas supply pump configured to supply gas to the optical system at a pressure below atmospheric pressure. In some examples, the gas purging system also includes a second pump configured to substantially remove a second gas from the optical system.

[0010] In some examples, the gas includes nitrogen, and the second gas includes oxygen. In some examples, the pressure is between about 50 Torr and about 700 Torr.

[0011] In some examples, the optical system includes a first optical module and a second optical module. The gas purging system includes a first gas supply pump coupled to the first optical module to supply gas to the first optical module at a pressure below atmospheric pressure; and a second gas supply pump coupled to the second optical module to supply gas to the second optical module at a pressure below atmospheric pressure.

[0012] Another aspect of this disclosure provides a laser source including a laser chamber configured to generate a first laser beam. The laser source also includes an optical system coupled to the laser chamber and configured to receive the first laser beam and output a laser beam. The optical system includes a gas at a pressure below atmospheric pressure.

[0013] Another aspect of this disclosure provides a laser source comprising: a first laser chamber configured to generate a first laser beam and a second laser chamber configured to receive and amplify the first laser beam to generate a second laser beam. The laser source further includes a first optical system configured to direct the first laser beam toward the second laser chamber. The laser source also includes a second optical system configured to receive and guide the second laser beam as an output laser beam from the laser source. The laser source further includes a gas purging system configured to pump gas to the first and second optical systems at a pressure below atmospheric pressure.

[0014] In some examples, the gas purging system includes a gas supply pump configured to supply gas to a first optical system and a second optical system at a pressure below atmospheric pressure; and a second pump configured to substantially remove a second gas from the first optical system and the second optical system.

[0015] In some examples, the gas includes nitrogen, the pressure is between about 50 Torr and about 700 Torr, and the second gas is oxygen.

[0016] In some examples, the laser source also includes an optical module coupled to the first laser chamber. The optical module includes a second gas at a pressure below atmospheric pressure. In some examples, the second gas is oxygen.

[0017] Another aspect of this disclosure provides a photolithography apparatus including an irradiation system configured to modulate a radiation beam and a projection system configured to project a pattern imparted to the radiation beam onto a substrate. The irradiation system includes a laser source. The laser source includes a laser chamber configured to generate a first laser beam, and an optical system coupled to the laser chamber and configured to receive the first laser beam and output an output laser beam. The optical system may include nitrogen gas at a pressure below atmospheric pressure.

[0018] Another aspect of this disclosure provides an apparatus including a laser chamber configured to generate a first laser beam, and an optical system coupled to the laser chamber and configured to receive and output the first laser beam. The laser source also includes a gas purging system configured to supply gas to the optical system at a pressure below atmospheric pressure.

[0019] Alternatively or concurrently, this disclosure provides embodiments of helium purging systems.

[0020] One aspect of this disclosure provides a laser source including a laser chamber configured to generate a first laser beam. The laser source also includes an optical system coupled to the laser chamber and configured to receive and output the first laser beam. The laser source further includes a gas purging system configured to supply helium gas to the optical system.

[0021] In some examples, the gas purging system includes a gas supply pump configured to supply helium gas to the optical system. In some examples, the gas purging system also includes a second pump configured to substantially remove a second gas, wherein the gas is oxygen, from the optical system.

[0022] In some examples, the gas purging system includes a gas supply pump configured to supply helium to the optical system at a pressure below atmospheric pressure.

[0023] In some examples, the optical system includes a first optical module and a second optical module. The gas purging system includes a first gas supply pump coupled to the first optical module to supply helium to the first optical module; and a second gas supply pump coupled to the second optical module to supply helium to the second optical module.

[0024] Another aspect of this disclosure provides a laser source including a laser chamber configured to generate a first laser beam. The laser source also includes an optical system coupled to the laser chamber and configured to receive the first laser beam and output an output laser beam. The optical system includes helium gas.

[0025] Another aspect of this disclosure provides a laser source including a first laser chamber configured to generate a first laser beam and a second laser chamber configured to receive and amplify the first laser beam to generate a second laser beam. The laser source also includes a first optical system configured to direct the first laser beam toward the second laser chamber. The laser source further includes a second optical system configured to receive and guide the second laser beam as an output laser beam from the laser source. The laser source also includes a gas purging system configured to pump helium gas into the first and second optical systems.

[0026] Another aspect of this disclosure provides a photolithography apparatus including an irradiation system configured to modulate a radiation beam and a projection system configured to project a pattern imparted to the radiation beam onto a substrate. The irradiation system includes a laser source. The laser source includes a laser chamber configured to generate a first laser beam, and an optical system coupled to the laser chamber and configured to receive the first laser beam and output an output laser beam. The optical system may include helium gas.

[0027] Other features and the structure and operation of various embodiments are described in detail below with reference to the accompanying drawings. It should be noted that this disclosure is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to those skilled in the art based on the teachings contained herein. Attached Figure Description

[0028] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the principles of this disclosure and, together with the description, serve to explain the principles of embodiments of this disclosure and enable those skilled in the art to form and use embodiments of this disclosure.

[0029] Figure 1 This is a schematic diagram of a reflective lithography apparatus according to an exemplary embodiment.

[0030] Figure 2 This is a schematic diagram of a transmission lithography apparatus according to an exemplary embodiment.

[0031] Figure 3 This is a schematic diagram of a photolithography unit according to an exemplary embodiment.

[0032] Figure 4 The illustration shows a schematic diagram of a laser source with a purging system according to some embodiments of the present disclosure.

[0033] Figure 5 Another schematic diagram of a laser source having a low-pressure gas purging system according to some embodiments of the present disclosure is shown.

[0034] Figure 6 Another schematic diagram of a laser source with a helium purging system according to some embodiments of the present disclosure is shown.

[0035] The features of this disclosure will become more apparent when viewed in conjunction with the accompanying drawings, in which the same reference numerals identify corresponding elements throughout. In the drawings, unless otherwise indicated, the same reference numerals generally indicate the same, functionally similar, and / or structurally similar elements. Additionally, generally, the leftmost(s) of the reference numerals indicate the figure in which the reference numerals first appear. Unless otherwise indicated, the figures provided throughout this disclosure should not be construed as being drawn to scale. Detailed Implementation

[0036] This specification discloses one or more embodiments incorporating the features of the invention. The disclosed embodiments(s) are merely illustrative of the invention. The scope of this disclosure is not limited to the disclosed embodiments(s). The breadth and scope of this disclosure are defined by the appended claims and their equivalents.

[0037] The described embodiments and references to "an embodiment," "embodiment," "example embodiment," "exemplary embodiment," etc., in this specification indicate that the described embodiments may include specific features, structures, or characteristics, but not every embodiment necessarily includes such specific features, structures, or characteristics. Furthermore, such phrases do not necessarily refer to the same embodiment. Further, when a specific feature, structure, or characteristic is described in connection with an embodiment, it should be understood that, whether explicitly described or not, implementing such features, structures, or characteristics in conjunction with other embodiments is within the knowledge of those skilled in the art.

[0038] For ease of description, spatially relative terms such as “below,” “under,” “lower,” “above,” “on,” and “upper” are used herein to describe the relationship between an element or feature and another element(s) or feature(s) illustrated in the figures. In addition to the orientations depicted in the figures, spatially relative terms are intended to cover different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein will be interpreted accordingly.

[0039] As used herein, the term “about” indicates the value of a given quantity that can vary based on a particular technique. Based on a particular technique, the term “about” can indicate the value of a given quantity that varies within, for example, 10-30% of that value (e.g., ±10%, ±20%, or ±30% of that value).

[0040] However, it is beneficial to present example environments in which embodiments of this disclosure may be implemented before describing such embodiments in more detail.

[0041] Example lithography system

[0042] Figure 1 and Figure 2 These are schematic diagrams of lithography apparatus 100 and 100', respectively, in which embodiments of the present disclosure can be implemented. Lithography apparatus 100 and 100' each include: an irradiation system (irradiator) IL configured to modulate a radiation beam B (e.g., deep ultraviolet (DUV) radiation); a support structure (e.g., a mask stage) MT configured to support a patterning device (e.g., a mask, stencil, or dynamic patterning device) MA and connected to a first locator PM configured to accurately position the patterning device MA; and a substrate holder, such as a stage (e.g., a wafer stage) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second locator PW configured to accurately position the substrate W. Lithography apparatuses 100 and 100' also have a projection system PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion (e.g., including one or more dies) C of the substrate W. In the lithography apparatus 100, the patterning device MA and the projection system PS are reflective. In the lithography apparatus 100', the patterning device MA and the projection system PS are transmissive.

[0043] The irradiation system IL may include various types of optical components for guiding, shaping, or controlling the radiation beam B, such as refractive, reflective, reflective-refractive, magnetic, electromagnetic, electrostatic, or other types of optical components or any combination thereof.

[0044] The support structure MT holds the patterning device MA in a manner dependent on the orientation of the patterning device MA relative to the reference frame, the design of at least one of the lithography apparatuses 100 and 100', and other conditions such as whether the patterning device MA is held in a vacuum environment. The support structure MT can hold the patterning device MA using mechanical, vacuum, electrostatic, or other clamping techniques. The support structure MT can be, for example, a frame or stage, which can be fixed or movable as needed. By using sensors, the support structure MT can ensure that the patterning device MA is located at a desired position, for example, relative to the projection system PS.

[0045] The term "patterning device" MA should be interpreted broadly to refer to any device that can be used to impart a pattern to the radiation beam B in the cross-section of the radiation beam B, such as to generate a pattern in a target portion C of the substrate W. The pattern imparted to the radiation beam B may correspond to a specific functional layer generated in the target portion C of the device to form an integrated circuit.

[0046] The patterning device MA can be transmissive (e.g., located in...) Figure 2 In the photolithography apparatus 100') or reflective (such as located in Figure 1 (In the photolithography apparatus 100). Examples of patterning apparatus MA include photomasks, masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in photolithography and include mask types such as binary, alternating phase-shift, or attenuation 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 to reflect the incident radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B, which is reflected by the matrix of small mirrors.

[0047] The term "projection system" PS can encompass any type of projection system suitable for the exposure radiation used or for other factors such as the use of a liquid immersed on a substrate W or the use of a vacuum, including refractive, reflective, reflective-refractive, magnetic, electromagnetic, and electrostatic optical systems or any combination thereof. Therefore, a vacuum environment can be provided throughout the beam path by means of vacuum walls and vacuum pumps.

[0048] The lithography apparatus 100 and / or lithography apparatus 100' may be of the type having two (dual-stage) or more substrate stages WT (and / or two or more mask stages). In such "multi-stage" machines, additional substrate stages WT can be used in parallel, or preparation steps can be performed on one or more stages while one or more other substrate stages WT are used for exposure. In some cases, the additional stage may not be a substrate stage WT.

[0049] The lithography apparatus can also be of the type in which at least a portion of the substrate can be covered by a liquid (e.g., water) having a relatively high refractive index, thereby filling the space between the projection system and the substrate. Immersion liquids can also be applied to other spaces within the lithography apparatus, such as between the mask and the projection system. Immersion techniques for increasing the numerical aperture of a projection system are well known in the art. As used herein, the term "immersion" does not imply that structures such as the substrate must be submerged in the liquid, but only that the liquid is located between the projection system and the substrate during exposure.

[0050] Reference Figure 1 and Figure 2 The irradiator IL receives the radiation beam from the radiation source SO. The source SO and the lithography apparatus 100, 100' can be separate physical entities, for example, when the source SO is an excimer laser. In such cases, the source SO is not considered part of the lithography apparatus 100 or 100', and is integrated into the beam delivery system BD, which includes, for example, suitable directional mirrors and / or beam expanders. Figure 2 With the assistance of the lithography apparatus 100, 100', the radiation beam B is delivered from the source SO to the irradiator IL. In other cases, the source SO may be a component of the lithography apparatus 100, 100', for example, when the source SO is a mercury lamp. If desired, the source SO, the irradiator IL, and the beam delivery system BD may be referred to as the radiation system.

[0051] The irradiator IL may include a modulator AD for adjusting the angular intensity distribution of the radiation beam. Figure 2 (In the middle). Typically, at least the outer and / or inner radial ranges (often referred to as "σ-outer" and "σ-inner", respectively) of the intensity distribution in the pupil plane of the irradiator can be adjusted. Additionally, the irradiator IL may include various other components ( Figure 2 (In the middle), such as the integrator IN and the condenser CO. The irradiator IL can be used to adjust the radiation beam B to have the desired uniformity and intensity distribution in the cross section of the radiation beam B.

[0052] Reference Figure 1A radiation beam B is incident on a patterning device (e.g., a mask) MA held on a support structure (e.g., a mask stage) MT and patterned by the patterning device MA. In the lithography apparatus 100, the radiation beam B is reflected from the patterning device (e.g., the mask) MA. After being reflected from the patterning device (e.g., the mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. With the aid of a second positioner PW and a position sensor IF2 (e.g., an interferometer, a linear encoder, or a capacitive sensor), the substrate stage WT can be moved precisely (e.g., to position different target portions C in the path of the radiation beam B). Similarly, a first positioner PM and another position sensor IF1 can be used to accurately position the patterning device (e.g., the mask) MA relative to the path of the radiation beam B. Mask alignment marks M1, M2 and substrate alignment marks P1, P2 can be used to align the patterning device (e.g., the mask) MA and the substrate W.

[0053] Reference Figure 2 A radiation beam B is incident on a patterning device (e.g., a mask MA) held on a support structure (e.g., a mask stage MT) and patterned by the patterning device. After passing through the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system has a pupil conjugate PPU for the illumination system pupil IPU. The radiating portion is emitted from the intensity distribution at the illumination system pupil IPU and passes through the mask pattern unaffected by diffraction at the mask pattern, producing an image of the intensity distribution at the illumination system pupil IPU.

[0054] The projection system PS projects an image MP' of a mask pattern MP onto a photoresist layer coated on a substrate W, wherein the image MP' is formed by a diffracted beam generated by radiation from an intensity distribution according to the marked pattern MP. For example, the mask pattern MP may comprise an array of lines and spaces. Radiation diffraction at the array, distinct from zero-order diffraction, produces a deflected diffracted beam whose direction changes perpendicular to the lines. The undiffracted beam (i.e., the so-called zero-order diffracted beam) traverses the pattern without any change in propagation direction. The zero-order diffracted beam passes upstream of the pupil conjugate PPU of the projection system PS through the upper lens or upper lens group 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 associated with the zero-order diffracted beam is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. For example, an aperture device PD is disposed or substantially disposed in the plane comprising the pupil conjugate PPU of the projection system PS.

[0055] The projection system PS is arranged to capture not only the zeroth-order diffraction beam, but also the first-order diffraction beam, or first-order and higher-order diffraction beams (not shown), by means of a lens or lens group L. In some embodiments, dipole illumination for imaging a line pattern extending in a direction perpendicular to the line can be used to utilize the resolution enhancement effect of dipole illumination. For example, the first-order diffraction beam interferes with the corresponding zeroth-order diffraction beam at the level of the wafer W, thereby creating an image of the line pattern MP with the highest possible resolution and program window (i.e., the combination of available depth of focus and permissible exposure dose deviation).

[0056] With the aid of a second positioner PW and a position sensor IF (e.g., an interferometer, linear encoder, or capacitive sensor), the substrate stage WT can be moved precisely (e.g., to position different target portions C within the path of the radiation beam B). Similarly, the first positioner PM and another position sensor ( Figure 2 (Not shown) can be used to accurately position the mask MA relative to the path of the radiation beam B (e.g., after mechanical retrieval from the mask library or during scanning).

[0057] Typically, the movement of the mask stage MT can be achieved using a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) forming part of the first positioner PM. Similarly, the movement of the substrate stage WT can be achieved using a long-stroke module and a short-stroke module forming part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask stage MT can be connected only to the short-stroke actuator or can be fixed. The mask MA and substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks (as shown) occupy a dedicated target portion, the substrate alignment marks can be located in the space between the target portions (called kerf alignment marks). Similarly, when more than one die is provided on the mask MA, the mask alignment marks can be located between the dies.

[0058] The mask stage MT and patterning device MA can be located within a vacuum chamber V, where an in-vacuum robot IVR can be used to move patterning devices, such as masks, into and out of the vacuum chamber. Alternatively, when the mask stage MT and patterning device MA are outside the vacuum chamber, an external vacuum robot, similar to the in-vacuum robot IVR, can be used for various transport operations. Both the in-vacuum and external vacuum robots require calibration to smoothly transfer any payload (e.g., a mask) to a fixed kinematic base at the transfer station.

[0059] The photolithography apparatuses 100 and 100' can be used in at least one of the following modes:

[0060] 1. In step mode, the support structure (e.g., mask stage) MT and substrate stage WT remain substantially stationary while the entire pattern imparted to the radiation beam B is projected onto the target portion C in a single exposure (i.e., a single static exposure). The substrate stage WT then moves in the X and / or Y directions, allowing different target portions C to be exposed.

[0061] 2. In scanning mode, the support structure (e.g., mask stage) MT and the substrate stage WT are scanned synchronously, while the pattern applied to the radiation beam B is projected onto the target portion C (i.e., single dynamic exposure). The velocity and direction of the substrate stage WT relative to the support structure (e.g., mask stage) MT can be determined by the (de)magnification and image inversion characteristics of the projection system PS.

[0062] 3. In another mode, the support structure (e.g., mask stage) MT remains substantially stationary, thus holding the programmable patterning device, while the substrate stage WT is moved or scanned, and the pattern imparted to the radiation beam B is projected onto the target portion C. A pulsed radiation source SO can be used, and the programmable patterning device can be updated as needed after each movement of the substrate stage WT or between consecutive radiation pulses during scanning. This mode of operation can be readily applied to maskless lithography utilizing programmable patterning devices (e.g., programmable mirror arrays).

[0063] It is also possible to adopt a combination and / or variation of the described usage patterns or completely different usage patterns.

[0064] Exemplary photolithography unit

[0065] Figure 3 A lithography unit 300, sometimes also referred to as a lithocell or cluster, is shown. A lithography apparatus 100 or 100' may form part of the lithography unit 300. The lithography unit 300 may also include one or more devices for performing pre-exposure and post-exposure processing on a substrate. Typically, these devices include a spin coater SC for depositing photoresist (i.e., a "resist" layer), a developer DE for developing the exposed photoresist, a cooling plate CH, and a baking plate BK. A substrate handler or robot RO picks up a substrate from input / output ports I / O1, I / O2, moves the substrate between different processing devices, and delivers the substrate to a loading cassette LB of the lithography apparatus 100 or 100'. These devices, generally collectively referred to as a coating and developing system (track), are under the control of a coating and developing system control unit TCU, which is itself controlled by a supervisory control system SCS, which also controls the lithography apparatus via a lithography control unit LACU. Therefore, different devices can be operated to maximize throughput and processing efficiency.

[0066] Exemplary gas purging systems and methods

[0067] Figure 4 The illustration shows a schematic diagram of a laser source 400 with a gas purging system according to some embodiments of the present disclosure. In some aspects, the laser source 400 can be used as part of or other than the source SO of the lithography apparatus 100 or 100'. For example, the laser source 400 can be used to generate DUV radiation to be used in the lithography apparatus 100' or other DUV lithography apparatuses. Figure 4 As shown in the figure, the laser source 400 can generate a laser beam 407 for use in a photolithography apparatus.

[0068] According to some aspects, laser source 400 may include one or more laser chambers for generating a laser beam. For example, laser source 400 may include laser chamber 401 for generating laser beam 405. Although Figure 4 The figure illustrates a laser chamber 401, but aspects of this disclosure are not limited to this example, and the laser source 400 may include multiple laser chambers. Examples of dual-chamber laser sources are described below. Figure 5 and Figure 6 Let's have a discussion.

[0069] like Figure 4 As illustrated, the laser source 400 may also include an optical system 403. According to some examples, the optical system 403 is configured to receive a laser beam 405 and generate or direct a laser beam 407 away from the laser source 400. As discussed in more detail below, the optical system 403 may include one or more optical modules. As a non-limiting example, the optical system 403 may include one or more bellows, one or more tubes, one or more beam inverters, one or more bandwidth analysis modules, one or more optical pulse stretchers, one or more shutter modules, etc. It should be noted that aspects of this disclosure are not limited to these examples, and the optical system 403 may include more, fewer, or different modules and components. The optical system 403 may include any number of components, such as, but not limited to, lenses, mirrors, prisms, optical fibers, detectors, beam splitters, dispersive devices, etc.

[0070] According to some aspects, laser source 400 may include a gas purging system 408. Gas purging system 408 may be operatively coupled to optical system 403 and may be configured to supply gas to optical system 403. In optical system 403, ozone (O3) may be undesirably generated from oxygen (O2) in the presence of high-energy UV photons. Ozone may be harmful to the optical components of optical system 403. According to some examples, gas purging system 408 is configured to supply gas to optical system 403 to substantially remove oxygen from optical system 403. According to some aspects, the gas used by gas purging system 408 may include nitrogen (N2). In other words, gas purging system 408 may supply nitrogen to optical system 403 to substantially remove oxygen from optical system 403. Although nitrogen is used as an exemplary purging gas in some aspects of this disclosure, gas purging system 408 may use other suitable gases.

[0071] According to some examples, the gas purging system 408 can supply a purging gas (e.g., nitrogen) to the optical system 403 at a pressure of approximately atmospheric pressure. For example, the gas pressure provided by the gas purging system 408 can be approximately standard atmospheric pressure. For example, the gas pressure provided by the gas purging system 408 can be approximately 101,000 Pa to 102,000 Pa (e.g., equivalent to 758-765 mmHg). As a non-limiting example, the gas pressure provided by the gas purging system 408 can be approximately 101,325 Pa (e.g., equivalent to 760 mmHg). In other embodiments, various other pressures may be used.

[0072] However, in some examples, using a gas pressure of approximately atmospheric pressure as the purge gas at optical system 403 fails to meet certain optical specifications for optical system 403 (and / or laser source 400). For example, for high-power laser source 400 (e.g., but not limited to 60W, 90W, 120W, etc.), a gas pressure other than atmospheric pressure can produce more desirable optical performance. In some examples, a gas pressure of approximately atmospheric pressure at optical system 403 can cause high thermal transients. High thermal transients can lead to module failure. Thermal transients can increase with higher power lasers and / or module aging. Additionally, a gas pressure of approximately atmospheric pressure in optical system 403 can cause high instability in the spatial beam characteristics of the laser. For example, while vertical divergence is an exemplary parameter that is difficult to include, other parameters may also be affected by increased thermal lensing effects. Some examples of affected parameters are beam symmetry, beam profile mismatch, and, to some extent, beam pointing. While each parameter may have its own origin, some of these parameters are interrelated.

[0073] In some examples, the thermal transient originates from a purge gas (e.g., nitrogen) heated by the laser beam in the optical system 403. For example, nitrogen has a large temperature gradient in its refractive index. This large temperature gradient in the refractive index creates a large thermal lens for the laser beam.

[0074] According to some aspects of this disclosure, the gas purging system 408 is a low-pressure gas purging system configured to supply a purging gas (e.g., nitrogen) to the optical system 403 at a pressure below atmospheric pressure. By reducing the pressure of the purging gas, the density of the purging gas at the optical system 403 is reduced, and therefore, the amplitude of the thermal lens is also reduced. The density of the purging gas is proportional to its pressure. By reducing the pressure, the density of the purging gas is reduced, and thus the refractive index is reduced. Since the temperature gradient or change in refractive index is proportional to the density of the purging gas, thermal transients can theoretically be reduced.

[0075] According to some examples, the gas purging system 408 is configured to supply purge gas to the optical system 403 at a pressure below atmospheric pressure. For example, the pressure of the purge gas is below approximately standard atmospheric pressure. For example, the pressure of the purge gas may be less than approximately 760 Torr (e.g., approximately 760 mmHg). In some embodiments, the pressure of the purge gas may be between approximately 700 Torr and approximately 760 Torr. In some embodiments, the pressure of the purge gas is between approximately 600 Torr and approximately 700 Torr. In some embodiments, the pressure of the purge gas is between approximately 500 Torr and approximately 600 Torr. In some embodiments, the pressure of the purge gas is between approximately 400 Torr and approximately 500 Torr. In some embodiments, the pressure of the purge gas is between approximately 300 Torr and approximately 400 Torr. In some embodiments, the pressure of the purge gas is between approximately 200 Torr and approximately 300 Torr. In some embodiments, the pressure of the purge gas is between approximately 100 Torr and approximately 200 Torr. In some embodiments, the pressure of the purge gas is between approximately 10 Torr and approximately 100 Torr. In some embodiments, the pressure of the purge gas is between approximately 50 Torr and approximately 90 Torr. In some embodiments, the pressure of the purge gas is between about 1 Torr and about 10 Torr. It should be noted that these pressure values ​​are provided as examples, and other pressure values ​​less than atmospheric pressure may be used for the purge gas.

[0076] like Figure 4 As illustrated, the gas purging system 408 may include a gas supply pump 409, a pump 411, and a gas supply 417. In some aspects, the gas purging system 408 may be operatively coupled to the optical system 403 using one or more gas supply conduits 413 and one or more gas conduits 415.

[0077] For example, one or more gas supply conduits 413 are operatively coupled to a gas supply pump 409 to supply purge gas (e.g., nitrogen) from, for example, a gas supply 417 to the optical system 403. According to some examples, the gas supply conduit 413 may terminate at one or more gas inlets (not shown) at the optical system 403. According to some examples, the gas supply conduit 413 may be coupled to the gas supply pump 409 via one or more gas outlets (not shown). In some aspects, the gas supply pump 409 is configured to supply purge gas to the optical system 403 at a pressure below atmospheric pressure.

[0078] One or more gas conduits 415 are operatively coupled to pump 415 to remove gas (e.g., oxygen) from optical system 403. According to some examples, gas conduits 415 may terminate at one or more gas inlets (not shown) at pump 411. According to some examples, gas conduits 415 may be coupled to optical system 403 via one or more gas outlets (not shown). In some aspects, pump 411 may be configured to generate a negative pressure differential (e.g., a suction pump, etc.) and operatively coupled to optical system 403 to remove gas (e.g., oxygen) from optical system 403.

[0079] In some examples, the gas purging system 408 may include one or more sensors and a controller 412 to, for example, measure and / or control gas pressure. For example, the controller / sensor 412 may be configured to measure the pressure of the purge gas supplied by the gas purging system 408 to the optical system 403. For example, the controller / sensor 412 may be configured to measure the pressure of the purge gas at the gas supply pump 409, the optical system 403, the gas supply 417, the pump 411, the (multiple) conduits 413 and / or 415, and / or the (multiple) inlets and / or outlets associated with the (multiple) conduits 413 and / or 415. Additionally or alternatively, the controller / sensor 412 may be configured to control the gas supply pump 409, the gas supply 417, and / or the pump 411 based on, for example, the measured pressure and one or more pressure setpoints. Furthermore, the controller / sensor 412 may be configured to measure the pressure of the gas (e.g., oxygen) removed from the optical system 403. For example, the controller / sensor 412 may be configured to measure the pressure of gas (e.g., oxygen) removed from the optical system 403 at the pump 411, the conduit 415, and / or the inlet or outlet associated with the conduit 415.

[0080] In some examples, the control system 410 may be configured to control the gas supply pump 409 and / or pump 411, either alone or in combination with the controller sensor 412. According to some embodiments, the control system 410 may be configured to perform other operations within the laser source 400. For example, the control system 410 may control one or more gas sources (not shown) supplying gas to the laser chamber 401. As another example, the control system 410 may be connected to one or more temperature sensors in the laser chamber 401 to detect and / or control the gas temperature in the laser chamber 401.

[0081] In a non-limiting example, by using a gas purging system 408 as a low-pressure gas purging system, the terminal instability of vertical beam divergence in the optical system 403 can be reduced, for example, by a factor of five. The low-pressure gas purging system is configured to supply a purge gas (e.g., nitrogen) to the optical system 403 at a pressure below atmospheric pressure. As a non-limiting example, if the pressure of the purge gas (e.g., nitrogen) to the optical system 403 is reduced from about 760 Torr to about 100 Torr, the range of vertical divergence instability can be reduced from about 0.6 mrad (milliradians) to about 0.13 mrad. In some examples, 1 mrad can be a divergence (e.g., widening or broadening) of the laser beam when the diameter of the laser beam increases by 1 mm per 1 m of beam path. In another non-limiting example, for a high-power laser source 400 (e.g., but not limited to 90 W) using a gas purging system 408 as a low-pressure gas purging system, the duty cycle performance can vary from, for example, from about 20% to about 75%. It should be noted that these examples are provided as non-limiting examples, and other improvements can be observed in gas purging system 408 using a low-pressure gas purging system. In addition to directly improving beam divergence, embodiments of this disclosure can improve beam symmetry, profile mismatch, and / or laser linewidth stability.

[0082] Alternatively or additionally, according to some aspects of this disclosure, the gas purging system 408 may be a helium purging system configured to supply a purging gas (e.g., helium) to the optical system 403. In this exemplary embodiment, the gas purging system 408 is configured to supply helium as the purging gas to the optical system 403. In other words, helium can be used instead of nitrogen for purging to reduce and / or eliminate the thermal lensing effect that contributes to nitrogen, as discussed above. According to some examples, using helium as the purging gas can reduce and / or eliminate the thermal lensing effect due to the optical properties of helium, such as, but not limited to, the low (or ultra-low) temperature gradient of the refractive index associated with helium. In some examples, small volumes of helium can be used. In non-limiting examples, small volumes of helium, such as, but not limited to, a minimum volume of less than 1 standard liter per minute (slpm), can be used to maintain, for example, less than 20 parts per million (ppm) of oxygen in the optical system 403. This can be used compared to approximately 10 slpm of nitrogen. It should be noted that this volume of helium is provided as a non-limiting example, and other volumes of helium may be used.

[0083] According to some aspects of this disclosure, one or more gas supply conduits 413 are operatively coupled to a gas supply pump 409 to supply purge gas (e.g., helium) from, for example, a gas supply 417 to an optical system 403. The gas supply 417 may include a purge gas (e.g., helium). According to some examples, the gas supply conduit 413 may terminate at one or more gas inlets (not shown) at the optical system 403. According to some examples, the gas supply conduit 413 may be coupled to the gas supply pump 409 via one or more gas outlets (not shown). In some aspects, the gas supply pump 409 is configured to supply purge gas (e.g., helium) to the optical system 403. According to some aspects of this disclosure, a gas purging system 408 is configured to supply purge gas (e.g., helium) to the optical system 403 at approximately atmospheric pressure. Alternatively, the gas purging system 408 is configured to supply purge gas (e.g., helium) to the optical system 403 at a pressure less than or greater than atmospheric pressure.

[0084] One or more gas conduits 415 are operatively coupled to pump 415 to remove gas (e.g., oxygen) from optical system 403. According to some examples, gas conduits 415 may terminate at one or more gas inlets (not shown) at pump 411. According to some examples, gas conduits 415 may be coupled to optical system 403 via one or more gas outlets (not shown). In some aspects, pump 411 may be configured to generate a negative pressure differential (e.g., a suction pump, etc.) and operatively coupled to optical system 403 to remove gas (e.g., oxygen) from optical system 403.

[0085] In some examples, the gas purging system 408 may include one or more sensors and a controller 412 to, for example, measure and / or control gas pressure. For example, the controller / sensor 412 may be configured to measure the pressure of the purge gas (e.g., helium) supplied by the gas purging system 408 to the optical system 403. For example, the controller / sensor 412 may be configured to measure the pressure of the purge gas (e.g., helium) at the gas supply pump 409, the optical system 403, the gas supply 417, the pump 411, the (multiple) conduits 413 and / or 415, and / or the (multiple) inlets and / or outlets associated with the (multiple) conduits 413 and / or 415. Additionally or alternatively, the controller / sensor 412 may be configured to control the gas supply pump 409, the gas supply 417, and / or the pump 411 based on, for example, the measured pressure and one or more pressure setpoints. Furthermore, the controller / sensor 412 may be configured to measure the pressure of the gas (e.g., oxygen) removed from the optical system 403. For example, the controller / sensor 412 may be configured to measure the pressure of gas (e.g., oxygen) removed from the optical system 403 at the pump 411, the conduit 415, and / or the inlet or outlet associated with the conduit 415.

[0086] In some examples, the control system 410 may be configured to control the gas supply pump 409 and / or pump 411, either alone or in combination with the controller sensor 412. According to some embodiments, the control system 410 may be configured to perform other operations within the laser source 400. For example, the control system 410 may control one or more gas sources (not shown) supplying gas to the laser chamber 401. As another example, the control system 410 may be connected to one or more temperature sensors in the laser chamber 401 to detect and / or control the gas temperature in the laser chamber 401.

[0087] In a non-limiting example, by using a gas purging system 408 as a helium purging system, the terminal instability of vertical beam divergence in the optical system 403 can be reduced by, for example, five times. The helium purging system is configured to supply a purge gas (e.g., helium) to the optical system 403. As a non-limiting example, if the purge gas is helium, the vertical divergence instability range can be reduced from about 0.6 mrad to about 0.13 mrad. In another non-limiting example, for a high-power laser source 400 (e.g., but not limited to 90 W) using a gas purging system 408 as a helium purging system, the duty cycle performance can be changed from, for example, from about 20% to about 75%. It should be noted that these examples are provided as non-limiting examples, and other improvements can be seen in the gas purging system 408 using a helium purging system. In addition to directly improving beam divergence, embodiments of this disclosure can improve the differential emission time margin (dtMOPA) range, horizontal divergence, pointing stability, ultra-low beam stability, and / or laser bandwidth stability between the thermal lens, seed laser, and amplifier gain medium.

[0088] It should be noted that, although Figure 4 The diagram illustrates a gas supply pump 409, a pump 411, a gas supply 417, and two gas conduits 413 and 415, but aspects of this disclosure are not limited to these examples, and the gas purging system 408 may include any number of gas supplies, pumps, and gas conduits. Furthermore, the gas purging system 408 may be located inside, outside, or partially outside the laser source 400.

[0089] Figure 5 Another schematic diagram of a laser source 500 with a gas purging system according to some embodiments of the present disclosure is illustrated. In some aspects, the laser source 500 can be used as part of or other than the source SO of the lithography apparatus 100 or 100'. Alternatively or additionally, the laser source 500 can be used to generate DUV radiation for use in the lithography apparatus 100 or 100' or other DUV lithography apparatuses.

[0090] According to some sources, laser source 500 is Figure 4 An example of a laser source 400 illustrated in the figure. Figure 5As illustrated, laser source 500 may include a dual-chamber laser source. For example, laser source 500 may include a first laser chamber 503a and a second laser chamber 503b. In an exemplary embodiment, the first laser chamber 503a may include a master oscillator or a portion thereof. For example, laser source 500 may include a master oscillator, wherein the master oscillator includes the first laser chamber 503a. In this example, the second laser chamber 503b may include a power amplifier or a portion thereof. For example, laser source may include a power amplifier, wherein the power amplifier includes the second laser chamber 503b. Although some aspects of this disclosure are discussed with respect to dual-chamber laser sources, embodiments of this disclosure are not limited to these examples. Embodiments of this disclosure can be applied to laser sources having one chamber or laser sources having multiple laser chambers.

[0091] According to some embodiments, a first chamber 503a generates a first laser beam 509, which is guided to a second laser chamber 503b. The first laser beam 509 is amplified in the second laser chamber 503b to generate a second laser beam 511. The second laser beam 511 is guided to an optional optical pulse stretcher 510, an optional bellows 520e, and an optional shutter module 513. A third laser beam 515 is output from the shutter module 513 to a lithography apparatus (e.g., lithography apparatus 100 and / or 110').

[0092] According to some aspects, each laser chamber 503a and 503b contains a gas mixture. For example, in an excimer laser source, the first laser chamber 503a and the second laser chamber 503b may contain halogens, such as fluorine, as well as other gases, such as argon, neon, and other gases at different partial pressures that may add up to a total pressure. Laser chambers 503a and 503b may include other gases for generating and amplifying the laser beam. Laser chambers 503a and 503b may include the same or different gas mixtures.

[0093] In some aspects of this disclosure, laser source 500 may include (or may be coupled to) various suitable gas sources (not shown) to supply gas to laser chambers 503a and 503b. For example, a gas source (not shown) may be coupled to the first laser chamber 503a to provide a gas mixture for generating a first laser beam 509. Additionally, a gas source (not shown) may be coupled to the second laser chamber 503b to provide a gas mixture for generating a second laser beam 511. In some examples, gas sources may be coupled to laser chambers 503a and 503b respectively via valves (not shown). A control system (e.g., control system 540) may be used to control the valves for supplying gas from the gas sources to laser chambers 503a and 503b. In some aspects of this disclosure, the gas source for the first laser chamber 503a may contain a gas mixture including, but not limited to, fluorine, argon, and neon. According to some aspects, the gas source for the second laser chamber 503b may contain a mixture of argon, neon, and / or other gases, but without fluorine. However, other gas mixtures, such as those containing krypton, can be used in these gas sources.

[0094] As discussed above, the first laser chamber 503a is configured to generate a first laser beam 509. In some examples, the first laser beam 509 is configured to pass through a line narrowing module 501 before exiting the first laser chamber 503a. According to some aspects of this disclosure, the line narrowing module 501 is positioned and configured to select one or more center wavelengths around a narrowband wavelength. In some examples, the bandwidth of the narrowband may also be selected, for example, as narrow as possible. In some examples, the line narrowing module 501 may employ multiple center wavelength selection optics (e.g., dispersive optics), which may, depending on multiple physical parameters of the line narrowing module 501 and the optical parameters and performance capabilities of the wavelength selection optics used (e.g., dispersive optics), reflect light of the selected center wavelength and narrowed bandwidth back into an optical path, for example, a laser oscillating resonant chamber. In some examples, the line narrowing module 501 may include a reflection grating. The first laser chamber 503a, the line narrowing module 501, and the output coupler module (not shown) can be configured as an oscillator cavity for seed laser oscillation to form a laser beam 509.

[0095] After being generated by the first laser chamber 503a and passed through the line narrowing module 501 (and reflected within the line narrowing module 501), the first laser beam 509 is output from the first laser chamber 503a and directed to the second laser chamber 503b.

[0096] According to some examples, the laser source 500 may include one or more bellows 520a-520d connecting one or more modules of the laser source 500. For example, bellows 520a is coupled between the line narrowing module 501 and the first laser chamber 503a. In some examples, the line narrowing module 501 and the bellows 520a are coupled such that the gas pressure inside the line narrowing module 501 is the same as or similar to the gas pressure in the bellows 520a. Alternatively, the line narrowing module 501 and the bellows 520a are coupled such that the gas pressure inside the line narrowing module 501 is different from the gas pressure in the bellows 520a. In some examples, the line narrowing module 501 and / or the bellows 520a are coupled to a gas purging system (not shown), which is configured to supply a purging gas (e.g., nitrogen) to the line narrowing module 501 and / or the bellows 520a at a pressure of approximately atmospheric pressure. In other words, the gas purging system (not shown) is configured to supply purging gas to the line narrowing module 501 and / or the bellows 520a in conjunction with... Figure 4 The gas purging system 408 is used as a low-pressure gas purging system when operating under different gas pressures.

[0097] like Figure 5 As illustrated in the figure, and according to some aspects of this disclosure, a first laser beam 509 is directed by an optical system 505 to a second laser chamber 503b. According to some examples, the optical system 505 is coupled to the first laser chamber 503a using a bellows 520b, and to the second laser chamber 503b using a bellows 520c. The optical system 505 may include one or more optical modules. For example, the optical system 505 may include a wavelength metrology module (not shown). In some non-limiting examples, the wavelength metrology module may include a spectrometer for fine wavelength measurements and a coarser-resolution grating spectrometer. The wavelength metrology module may include other components.

[0098] The optical system 505 may also include one or more optical components for directing the laser beam 509 to the second laser chamber 503b. In some examples, these one or more optical components may include a first wavefront engineering box and a second wavefront engineering box (not shown). In some examples, the first wavefront engineering box receives the first laser beam 509 from the first laser chamber 503a and directs the first laser beam 509 to the second wavefront engineering box. The second wavefront engineering box directs the first laser beam 509 to the second laser chamber 503b. In some examples, the first wavefront engineering box may include, but is not limited to, components(s) for beam expansion via, for example, a prism beam expander and a coherence destroyer, in the form of an optical delay path. In some examples, the second wavefront engineering box may include a partially reflective input / output coupler and a maximum reflector for the nominal operating wavelength, as well as one or more prisms. In some examples, these one or more optical components for redirecting the first laser beam 509 may also include a tube for guiding the first laser beam 509.

[0099] In some examples, the optical system 505 may also include a bandwidth analysis module (not shown) as discussed below. It should be noted that although some exemplary modules / components have been discussed with respect to the optical system 505, aspects of this disclosure are not limited to these examples. The optical system 505 may include more, fewer, or different modules / components.

[0100] After the first laser beam 509 is directed to the second laser chamber 503b, the first laser beam 509 enters the second laser chamber 503b. In some aspects, the second laser chamber 503b may include a power amplifier or part of a power amplifier and is configured to amplify the first laser beam 509. According to some aspects, a beam inverter 507 is configured to receive the amplified laser beam and redirect the amplified laser beam back to the second laser chamber 503b. The beam inverter 507 and the second laser chamber 503b can be operatively coupled to each other using, for example, a bellows 520d.

[0101] According to some embodiments, the amplified laser beam 511 can be output from the second laser chamber 503b and pass through the bandwidth analysis module (not shown) of the optical system 505. The bandwidth analysis module can receive the second (amplified) laser beam 511 and pick up a portion for metrological purposes, such as measuring the output bandwidth and pulse energy.

[0102] A second laser beam 511 can be input to an optional optical pulse stretcher 510, wherein a copy of the second laser beam 511 can be delayed and recombined to, for example, reduce speckle. A third laser beam 515 is output from the optical pulse stretcher 510 and an optional shutter module 513 (e.g., an automatic shutter) to the lithography apparatus. In some examples, the optical pulse stretcher 510 is operatively coupled to the optical system 505 via a tube 521, and to the shutter module 513 using a bellows 520e.

[0103] According to some aspects of this disclosure, Figure 4 The optical system 403 of the laser source 400 may correspond to one or more of the following: optical system 505, beam reflector 507, optical pulse stretcher 510, shutter module 513, tube 521, and / or bellows 520b-520e. In some examples, one or more of the following: optical system 505, beam reflector 507, optical pulse stretcher 510, shutter module 513, tube 521, and / or bellows 520b-520e are coupled to a low-pressure gas purging system (e.g., when used as a low-pressure gas purging system). Figure 4 The low-pressure gas purging system 408 is configured to supply purging gas (e.g., nitrogen) at a gas pressure below atmospheric pressure to one or more of the optical system 505, beam reverser 507, optical pulse stretcher 510, shutter module 513, tube 521, and / or bellows 520b-520e.

[0104] According to some aspects of this disclosure, a low-pressure gas purging system (e.g., when used as a low-pressure gas purging system) Figure 4 The gas purging system 408 includes one or more gas supply pumps (e.g., gas supply pumps 531a and 531b), one or more pumps (e.g., pumps 533a and 533b), one or more gas conduits (e.g., gas conduits 532a-d, 534a and 534b), and one or more gas supplies (e.g., gas supply 535).

[0105] It should be noted that, although Figure 5 This is discussed in terms of multiple optical modules / systems coupled to the low-pressure gas purging system; however, aspects of this disclosure may include more, fewer, or other optical modules / systems coupled to the low-pressure gas purging system. Furthermore, Figure 5 A low-pressure gas purging system may include more or fewer pumps, gas supplies, and / or conduits.

[0106] According to some aspects, the line narrowing module 501, bellows 520a, first laser chamber 503a, and second laser chamber 503b are not coupled to a low-pressure gas purging system. For example, as discussed above, the gas purging system (not shown) for the line narrowing module 501 and bellows 520a is configured to supply purging gas to the line narrowing module 501 and / or bellows 520a at a gas pressure different from the gas pressure used by the low-pressure gas purging systems for the optical system 505, beam reverser 507, optical pulse stretcher 510, shutter module 513, tube 521, and / or bellows 520b-520e.

[0107] In some examples, beam reverser 507 is coupled to bellows 520d such that the gas pressure inside beam reverser 507 is the same as or similar to the gas pressure in bellows 520d. Alternatively, beam reverser 507 is coupled to bellows 520d such that the gas pressure inside beam reverser 507 is different from the gas pressure in bellows 520d. According to some aspects, beam reverser 507 and bellows 520d are operatively coupled to gas supply pump 531 (via gas supply conduit 532a) and pump 533a (via gas supply conduit 534a). Gas supply pump 531a (which is similar to...) Figure 4 The gas supply pump 409 can supply purge gas (e.g., nitrogen) from, for example, gas supply 535 to beam reverser 507 and bellows 520d at a pressure lower than or greater than atmospheric pressure (as described above regarding its use as a low-pressure gas purging system). Figure 4 The gas purging system 408 is discussed. Pump 533a (which is similar to...) Figure 4 The pump 411 is configured to substantially remove gas (e.g., oxygen) from the beam reverser 507 and bellows 520d (as described above regarding its use as a low-pressure gas purging system). Figure 4 The gas purging system 408 is discussed.

[0108] Although the air supply pump 531a is coupled to the beam reverser 507 and the pump 533a is coupled to the bellows 520d, aspects of this disclosure may include any combination of connections between the beam reverser 507 and / or the bellows 520d and the air supply pump 531a and the pump 533a.

[0109] In some examples, optical system 505, optical pulse stretcher 510, shutter module 513, bellows 520b, 520c, 520e, and tube 521 are coupled such that the gas pressure inside them is the same or similar. Alternatively, optical system 505, optical pulse stretcher 510, shutter module 513, bellows 520b, 520c, 520e, and tube 521 may be coupled such that the gas pressure inside them is different. According to some aspects of this disclosure, one or more air supply pumps 531b are operatively coupled to one or more of optical system 505, optical pulse stretcher 510, shutter module 513, bellows 520b, 520c, 520e, and tube 521. Air supply pump 531b (which is similar to Figure 4 The gas supply pump 409 can supply purge gas (e.g., nitrogen) from, for example, gas supply 535 to the optical system 505, the light pulse stretcher 510, the shutter module 513, the bellows 520b, 520c, 520e and the tube 521 (as described above regarding its use as a low-pressure gas purging system) at a pressure below atmospheric pressure. Figure 4 The gas purging system 408 is discussed.

[0110] In some examples, the air supply pump 531b can be coupled to the bellows 520c using the air supply conduit 532b. The air supply pump 531b can be coupled to the bellows 520d using the air supply conduit 532b. The air supply pump 531b can be coupled to the optical system 505 using the air supply conduit 532d. The air supply pump 531b can be coupled to the optical pulse stretcher 510 using the air supply conduit 532e. The air supply pump 531b can also be coupled to the tube 521, the bellows 520e, and / or the shutter module 513 using one or more conduits (not shown).

[0111] Pump 533b (which is similar to) Figure 4 The pump 411 is configured to substantially remove gas (e.g., oxygen) from one or more of the optical system 505, optical pulse stretcher 510, shutter module 513, bellows 520b, 520c, 520e, and tube 521 (as described above regarding its use as a low-pressure gas purging system). Figure 4 (As discussed in the gas purging system 408). In some examples, the pump 533b can be coupled to the optical pulse stretcher 510 using a gas conduit 534b.

[0112] As discussed above, any number of gas supply pumps 531, pump 533, gas supply 535 and / or conduits 532 and 534 can be used in the low-pressure gas purging system. Furthermore, any connection and / or any number of connections can be made between the low-pressure gas purging system and one or more of the optical system 505, beam reflector 507, optical pulse stretcher 510, shutter module 513, bellows 502b-e and tube 521.

[0113] In some examples, Figure 5 Low-pressure gas purging systems may include one or more sensors and controllers (e.g., similar to...) Figure 4 The controller / sensor 412 is configured to, for example, measure and / or control (multiple) gas pressures. One or more sensors and the controller may be part of and / or coupled to the control system 540. For example, the control system 540 may be configured to measure the pressure of a purge gas (e.g., nitrogen) supplied to one or more of the optical system 505, beam reflector 507, optical pulse stretcher 510, shutter module 513, bellows 502b-e, and tube 521. Alternatively or additionally, the control system 540 may be configured to measure the pressure of a gas (e.g., oxygen) removed from one or more of the optical system 505, beam reflector 507, optical pulse stretcher 510, shutter module 513, bellows 502b-e, and tube 521.

[0114] For example, the control system 540 may be configured to measure the pressure at one or more of the following: air supply pumps 531a and / or 531b; optical system 505; beam reverser 507; optical pulse stretcher 510; shutter module 513; bellows 502b-e and pipe 521; pumps 533a and / or 533b; gas supply 535 and / or conduits 532 and / or 534. Alternatively or additionally, the control system 540 may be configured to control air supply pumps 531a and / or 531b and / or pumps 533a and / or 533b based, for example, measured pressure(s) and one or more pressure setpoints.

[0115] According to some embodiments, the control system 540 may be configured to perform other operations within the laser source 500. For example, the control system 540 may control one or more gas sources (not shown) that supply gas to the laser chambers 503a and 503b. As another example, the control system 540 may be connected to one or more temperature sensors in the laser chambers 503a and 503b to detect and / or control the gas temperature in the laser chambers 503a and 503b.

[0116] Figure 6Another schematic diagram of a laser source 600 with a gas purging system according to some embodiments of the present disclosure is illustrated. In some aspects, the laser source 600 may be used as part of the source SO of the lithography apparatus 100 or 100' or as a laser source other than the source SO. Alternatively or additionally, the laser source 600 may be used to generate DUV radiation for use in the lithography apparatus 100 or 100' or other DUV lithography apparatuses.

[0117] According to some sources, laser source 600 is Figure 4 An example of a laser source 400 illustrated in the figure. Figure 6 As illustrated, laser source 600 may include a dual-chamber laser source. For example, laser source 600 may include a first laser chamber 603a and a second laser chamber 603b. In an exemplary embodiment, the first laser chamber 603a may include a master oscillator or a portion thereof. For example, laser source 600 may include a master oscillator, wherein the master oscillator includes the first laser chamber 603a. In this example, the second laser chamber 603b may include a power amplifier or a portion thereof. For example, laser source may include a power amplifier, wherein the power amplifier includes the second laser chamber 603b. Although some aspects of this disclosure are discussed with respect to dual-chamber laser sources, embodiments of this disclosure are not limited to these examples. Embodiments of this disclosure can be applied to laser sources having one chamber or laser sources having multiple laser chambers.

[0118] According to some embodiments, a first chamber 603a generates a first laser beam 609 that is directed to a second laser chamber 603b, where the first laser beam 609 is amplified to generate a second laser beam 611. The second laser beam 611 is directed to an optional optical pulse stretcher 610, an optional bellows 620e, and an optional shutter module 613. A third laser beam 615 is output from the shutter module 613 to a lithography apparatus (e.g., lithography apparatus 100 and / or 110').

[0119] Based on certain aspects, laser chambers 603a and 603b are respectively similar to those described above. Figure 5The laser chambers 503a and 503b are discussed. In some aspects of this disclosure, the laser source 600 may include (or may be coupled to) various suitable gas sources (not shown) to supply gas to the laser chambers 603a and 603b. For example, a gas source (not shown) may be coupled to the first laser chamber 603a to provide a gas mixture for generating a first laser beam 609. Additionally, a gas source (not shown) may be coupled to the second laser chamber 603b to provide a gas mixture for generating a second laser beam 611. In some examples, the gas sources may be coupled to the laser chambers 603a and 603b respectively via valves (not shown). A control system (e.g., control system 640) may be used to control the valves for supplying gas from the gas sources to the laser chambers 603a and 603b. In some aspects of this disclosure, the gas source for the first laser chamber 603a may comprise a gas mixture including, but not limited to, fluorine, argon, and neon. According to some aspects, the gas source for the second laser chamber 603b may contain a mixture of argon, neon, and / or other gases, but not fluorine. However, other gas mixtures, such as those including krypton, may be used in these gas sources.

[0120] As discussed above, the first laser chamber 603a is configured to generate a first laser beam 609. In some examples, the first laser beam 609 is configured to pass through a line narrowing module 601 before leaving the first laser chamber 603a. According to some aspects of this disclosure, the line narrowing module 601 is similar to... Figure 5 The line narrowing module 501. In some examples, the first laser chamber 603a, the line narrowing module 601, and the output coupler module (not shown) can be configured as an oscillator cavity for seed laser oscillation to form the laser beam 609.

[0121] After being generated by the first laser chamber 603a and passed through the line narrowing module 601 (and reflected within the line narrowing module 601), the first laser beam 609 is output from the first laser chamber 603a and directed to the second laser chamber 603b.

[0122] According to some examples, the laser source 600 may include one or more bellows 620 connecting one or more modules of the laser source 600. For example, bellows 620a is coupled between the line narrowing module 601 and the first laser chamber 603a. In some examples, the line narrowing module 601 is coupled to the bellows 620a such that the gas pressure inside the line narrowing module 601 is the same as or similar to the gas pressure in the bellows 620a. Alternatively, the line narrowing module 601 is coupled to the bellows 620a such that the gas pressure inside the line narrowing module 601 is different from the gas pressure in the bellows 620a. In some examples, the line narrowing module 601 and / or the bellows 620a are coupled to a gas purging system (not shown), which is configured to supply a purging gas (e.g., nitrogen) to the line narrowing module 601 and / or the bellows 620a at a pressure of approximately atmospheric pressure. In other words, the gas purging system (not shown) is configured to supply purging gas to the line narrowing module 601, and / or the bellows 620a, operating in accordance with the operation of the system when used as a helium purging system. Figure 4 The gas used in the gas purging system 408 is a different gas (e.g., helium) than nitrogen.

[0123] like Figure 6 As illustrated in the figure, and according to some aspects of this disclosure, a first laser beam 609 is directed by an optical system 605 to a second laser chamber 603b. According to some examples, the optical system 605 is coupled to the first laser chamber 603a using a bellows 620b, and to the second laser chamber 603b using a bellows 620c. The optical system 605 may be similar to... Figure 5 The optical system 505, and may include one or more such as those described above. Figure 5 The optical module under discussion.

[0124] The optical system 605 may also include one or more optical components for directing the laser beam 609 to the second laser chamber 603b. In some examples, these one or more optical components may include a first wavefront engineering box and a second wavefront engineering box (not shown). In some examples, the first wavefront engineering box receives the first laser beam 609 from the first laser chamber 603a and directs the first laser beam 609 to the second wavefront engineering box. The second wavefront engineering box directs the first laser beam 609 to the second laser chamber 603b. In some examples, the first wavefront engineering box may include, but is not limited to, components(s) for beam expansion via, for example, a prism beam expander and a coherence destroyer, in the form of an optical delay path. In some examples, the second wavefront engineering box may include a partially reflective input / output coupler and a maximum reflector for the nominal operating wavelength, as well as one or more prisms. In some examples, these one or more optical components for redirecting the first laser beam 609 may also include a tube for guiding the first laser beam 609.

[0125] In some examples, the optical system 605 may also include, as about Figure 5 The bandwidth analysis module discussed (not shown). It should be noted that although some exemplary modules / components have been discussed with respect to optical system 605, aspects of this disclosure are not limited to these examples. Optical system 605 may include more, fewer, or different modules / components.

[0126] After the first laser beam 609 is directed to the second laser chamber 603b, the first laser beam 609 enters the second laser chamber 603b. In some aspects, the second laser chamber 603b may include a power amplifier or part of a power amplifier and be configured to amplify the first laser beam 609. According to some aspects, a beam inverter 607 is configured to receive the amplified laser beam and redirect the amplified laser beam back to the second laser chamber 603b. The beam inverter 607 and the second laser chamber 603b may be operatively coupled to each other using, for example, a bellows 620d.

[0127] According to some embodiments, the amplified laser beam 611 can be output from the second laser chamber 603b and pass through the bandwidth analysis module (not shown) of the optical system 605. The bandwidth analysis module can receive the second (amplified) laser beam 611 and pick up a portion for metrological purposes, such as for measuring output bandwidth and pulse energy.

[0128] A second laser beam 611 can be input to an optional optical pulse stretcher 610, wherein a copy of the second laser beam 611 can be delayed and recombined to, for example, reduce speckle. A third laser beam 615 is output from the optical pulse stretcher 610 and an optional shutter module 613 (e.g., an automatic shutter) to the lithography apparatus. In some examples, the optical pulse stretcher 610 is operatively coupled to the optical system 605 via a tube 621, and to the shutter module 613 using a bellows 620e.

[0129] According to some aspects of this disclosure, Figure 4 The optical system 403 of the laser source 400 may correspond to one or more of the following: optical system 605, beam reflector 607, optical pulse stretcher 610, shutter module 613, tube 621, and / or bellows 620b-620e. In some examples, one or more of the following are coupled to a helium purging system (e.g., when used as a helium purging system): Figure 4The gas purging system 408. The helium purging system is configured to supply purging gas (e.g., helium) to one or more of the optical system 605, beam reverser 607, optical pulse stretcher 610, shutter module 613, tube 621 and / or bellows 620b-620e.

[0130] According to some aspects of this disclosure, a helium purging system (e.g., when used as a helium purging system) Figure 4 The gas purging system 408 includes one or more gas supply pumps (e.g., gas supply pumps 631a and 631b), one or more pumps (e.g., pumps 633a and 633b), one or more gas conduits (e.g., gas conduits 632a-d, 634a and 634b), and one or more gas supplies (e.g., gas supply 535).

[0131] It should be noted that, although Figure 6 This is discussed in terms of multiple optical modules / systems coupled to the low-pressure gas purging system; however, aspects of this disclosure may include more, fewer, or other optical modules / systems coupled to the low-pressure gas purging system. Furthermore, Figure 6 A helium purging system may include more or fewer pumps, gas supplies, and / or conduits.

[0132] According to some aspects, the line narrowing module 601, bellows 620a, first laser chamber 603a, and second laser chamber 603b are not coupled to a helium purging system. For example, as discussed above, the gas purging system (e.g., a nitrogen purging system - not shown) for the line narrowing module 601 and bellows 620a is configured to supply a nitrogen purging gas, different from the helium purging gas, to the line narrowing module 601 and / or bellows 620a. The helium purging system uses the helium purging gas for one or more of the optical system 605, beam reverser 607, optical pulse stretcher 610, shutter module 613, tube 621, and / or bellows 620b-620e.

[0133] In some examples, beam reverser 607 is coupled to bellows 620d such that the gas pressure inside beam reverser 607 is the same as or similar to the gas pressure in bellows 620d. Alternatively, beam reverser 607 and bellows 620d may be coupled such that the gas pressure inside beam reverser 607 is different from the gas pressure in bellows 620d. According to some aspects, beam reverser 607 and bellows 620d are operatively coupled to pump 633a (via gas conduit 634a) and gas supply pump 631 (via gas supply conduit 632a). Gas supply pump 631a (which is similar to...) Figure 4 The gas supply pump 409 can supply purge gas (e.g., helium) from, for example, gas supply 635 to bellows 620d and beam reverser 607. Pump 633a (which is similar to...) Figure 4 The pump 411 is configured to substantially remove gases (e.g., oxygen) from the beam reverser 607 and bellows 620d (as described above regarding its use as a helium purging system). Figure 4 The gas purging system 408 is discussed.

[0134] Although the air supply pump 631a is coupled to the bellows 620d and the pump 633a is coupled to the beam reverser 607, aspects of this disclosure may include any combination of connections between the beam reverser 607 and / or the bellows 620d and the air supply pump 631a and the pump 633a.

[0135] In some examples, optical system 605, optical pulse stretcher 610, shutter module 613, bellows 620b, 620c, 620e, and tube 621 are coupled such that the gas pressure inside them is the same or similar. Alternatively, optical system 605, optical pulse stretcher 610, shutter module 613, bellows 620b, 620c, 620e, and tube 621 may be coupled such that the gas pressure inside them is different. According to some aspects of this disclosure, one or more air supply pumps 631b are operatively coupled to one or more of optical system 605, optical pulse stretcher 610, shutter module 613, bellows 620b, 620c, 620e, and tube 621. Air supply pump 631b (which is similar to Figure 4 The gas supply pump 409 can supply purge gas (e.g., helium) from, for example, gas supply 635 to one or more of the optical system 605, optical pulse stretcher 610, shutter module 613, bellows 620b, 620c, 620e and tube 621 (as described above regarding when used as a helium purging system). Figure 4 The gas purging system 408 is discussed.

[0136] In some examples, the air supply pump 631b can be coupled to the bellows 620c using the air supply conduit 632b. The air supply pump 631b can be coupled to the bellows 620d using the air supply conduit 632b. The air supply pump 631b can be coupled to the optical system 605 using the air supply conduit 632d. The air supply pump 631b can be coupled to the optical pulse stretcher 610 using the air supply conduit 632e. The air supply pump 631b can also be coupled to the tube 621, the bellows 620e, and / or the shutter module 613 using one or more conduits (not shown).

[0137] Pump 633b (which is similar to...) Figure 4 The pump 411 is configured to substantially remove gas (e.g., oxygen) from one or more of the optical system 605, optical pulse stretcher 610, shutter module 613, bellows 620b, 620c, 620e, and tube 621 (as described above regarding its use as a helium purging system). Figure 4 (As discussed in the gas purging system 408). In some examples, the pump 633b can be coupled to the optical pulse stretcher 610 using a gas conduit 634b.

[0138] As discussed above, any number of gas supply pumps 631, pump 633, gas supply 635, and / or conduits 632 and 5634 can be used in the helium purging system. Furthermore, any connection and / or any number of connections can be made between the helium purging system and one or more of the optical system 605, beam reflector 607, optical pulse stretcher 610, shutter module 613, bellows 602b-e, and tube 621.

[0139] In some examples, Figure 6 A helium purging system may include one or more sensors and controllers (e.g., similar to...). Figure 4 The controller / sensor 412 is used to, for example, measure and / or control (multiple) gas pressures. One or more sensors and controllers may be part of and / or coupled to the control system 640. For example, the control system 640 may be configured to measure the pressure of a purge gas (e.g., helium) supplied to one or more of the optical system 605, beam reflector 607, optical pulse stretcher 610, shutter module 613, bellows 602b-e, and tube 621. Alternatively or additionally, the control system 640 may be configured to measure the pressure of a gas (e.g., oxygen) removed from one or more of the optical system 605, beam reflector 607, optical pulse stretcher 610, shutter module 613, bellows 602b-e, and tube 621.

[0140] For example, the control system 640 may be configured to measure the pressure at one or more of the following: air supply pumps 631a and / or 631b; optical system 605; beam reverser 607; optical pulse broadener 610; shutter module 613; bellows 602b-e and pipe 621; pumps 633a and / or 633b; gas supply 635 and / or conduits 632 and / or 634. Alternatively, the control system 640 may be configured to control air supply pumps 631a and / or 631b and / or pumps 633a and / or 633b based on, for example, the measured pressures and one or more pressure setpoints.

[0141] According to some embodiments, the control system 640 may be configured to perform other operations within the laser source 600. For example, the control system 640 may control one or more gas sources (not shown) that supply gas to the laser chambers 603a and 603b. As another example, the control system 640 may be connected to one or more temperature sensors in the laser chambers 603a and 603b to detect and / or control the gas temperature in the laser chambers 603a and 603b.

[0142] Some aspects of this disclosure (e.g., multiple control systems SCS, 410, 412, 540, and / or 640) can be implemented in hardware, firmware, software, or any combination thereof. Embodiments of this disclosure can also be implemented as instructions stored on a machine-readable medium, which can be read and executed by one or more processors. The machine-readable medium can include any mechanism for storing or transmitting information in a machine-readable form (e.g., a computing device). For example, a machine-readable medium can include read-only memory (ROM); random access memory (RAM); disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagation signals (e.g., carrier waves, infrared signals, digital signals, etc.) and other media. Further, firmware, software, routines, and / or instructions can be described herein as performing certain actions. However, it should be understood that such descriptions are merely for convenience, and such actions are actually generated by a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc.

[0143] While reference may be specifically made herein to the use of lithography apparatus in IC manufacturing, it should be understood that the lithography apparatus described herein may have other applications, such as fabricating integrated optical systems, guiding and detecting patterns for magnetic domain memory, flat panel displays, LCDs, thin-film magnetic heads, etc. Those skilled in the art will understand that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered synonymous with the more general terms “substrate” or “target portion,” respectively. Substrates mentioned herein may be processed before or after exposure in, for example, a tracking unit (typically a tool for coating a resist layer onto the substrate and developing 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. Furthermore, substrates may be processed more than once, for example to produce multilayer ICs; therefore, the term “substrate” as used herein may also refer to a substrate that already contains multiple processed layers.

[0144] It should be understood that the wording or terminology used herein is for descriptive rather than limiting purposes, and that the terminology or terminology used herein shall be interpreted by those skilled in the art based on the teachings herein.

[0145] As used herein, the term "substrate" describes a material on which a layer of material has been added. In some embodiments, the substrate itself may be patterned, and the material added on top of it may also be patterned, or may remain unpatterned.

[0146] The following examples are for illustrative purposes and not for limiting the embodiments of this disclosure. Other suitable modifications and adjustments to various conditions and parameters that are commonly encountered in the art and will be apparent to those skilled in the art(s) related to the art are within the spirit and scope of this disclosure.

[0147] While specific reference may be made herein to the use of the apparatus and / or system according to embodiments in IC manufacturing, it should be clearly understood that such apparatus and / or system have many other possible applications. For example, the apparatus and / or system can be used to manufacture integrated optical systems, guide and detection patterns for magnetic domain memory, LCD panels, thin-film magnetic heads, etc.

[0148] While specific embodiments of this disclosure have been described above, it should be understood that the embodiments may be practiced in ways other than those described. This description is not intended to limit the embodiments.

[0149] It should be understood that the Description of the Invention section, rather than the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more, but not all, exemplary embodiments as contemplated by the inventors(s), and are therefore not intended to limit this embodiment and the appended claims in any way.

[0150] The above descriptions have used functional building blocks to illustrate implementations of specified functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries can be defined by appropriately executing the specified functions and their relationships.

[0151] The above description of the specific embodiments so fully reveals the general nature of the embodiments that others can readily modify and / or debug them for various applications, such as the specific embodiments, by applying knowledge of the art without excessive experimentation or departing from the general concepts of this disclosure. Therefore, based on the teachings and guidance presented herein, such debugging and modifications are intended to fall within the meaning and scope of equivalents of the disclosed embodiments.

[0152] Other aspects of the invention are set forth in the following numbered clauses.

[0153] 1. A laser source, comprising:

[0154] A laser chamber is configured to generate a first laser beam;

[0155] An optical system, coupled to a laser cavity, is configured to receive a first laser beam and output an output laser beam; and

[0156] The gas purging system is configured to supply gas to the optical system at a pressure below atmospheric pressure.

[0157] 2. The laser source according to item 1, wherein the gas purging system comprises:

[0158] The gas supply pump is configured to supply gas to the optical system at a pressure lower than atmospheric pressure.

[0159] 3. The laser source according to clause 2, wherein the gas purging system further includes:

[0160] The second pump is configured to substantially remove the second gas from the optical system.

[0161] 4. The laser source according to clause 3, wherein the gas includes nitrogen and the second gas includes oxygen.

[0162] 5. The laser source according to clause 1, wherein the gas comprises nitrogen and the pressure is between about 50 Torr and about 700 Torr.

[0163] 6. The laser source according to item 1, wherein:

[0164] The optical system includes a first optical module and a second optical module; and

[0165] The gas purging system includes:

[0166] A first gas supply pump, coupled to a first optical module, supplies gas to the first optical module at a pressure below atmospheric pressure; and

[0167] A second gas pump is coupled to the second optical module to supply gas to the second optical module at a pressure lower than atmospheric pressure.

[0168] 7. A laser source, comprising:

[0169] A laser chamber is configured to generate a first laser beam; and

[0170] An optical system, coupled to the laser cavity, is configured to receive a first laser beam and output an output laser beam.

[0171] The optical system includes a gas at a pressure lower than atmospheric pressure.

[0172] 8. The laser source according to item 7 further includes:

[0173] The gas purging system is configured to supply gas to the optical system at a pressure below atmospheric pressure.

[0174] 9. The laser source according to item 8, wherein the gas purging system comprises:

[0175] A gas supply pump is configured to supply gas to the optical system at a pressure below atmospheric pressure; and

[0176] The second pump is configured to substantially remove the second gas from the optical system.

[0177] 10. The laser source according to paragraph 9, wherein the gas comprises nitrogen and the second gas comprises oxygen.

[0178] 11. The laser source according to clause 7, wherein the gas comprises nitrogen and the pressure is between about 50 Torr and about 700 Torr.

[0179] 12. The laser source according to item 7 further includes:

[0180] A second laser chamber is configured to at least indirectly receive the first laser beam and amplify the first laser beam to generate a second laser beam.

[0181] The optical system is configured to receive the second laser beam and output the laser beam.

[0182] 13. The laser source according to item 7 further includes:

[0183] An optical module is coupled to a laser chamber, wherein the optical module includes a second gas at a pressure of approximately atmospheric pressure.

[0184] 14. A laser source, comprising:

[0185] A first laser chamber is configured to generate a first laser beam;

[0186] The second laser chamber is configured to at least indirectly receive the first laser beam and amplify the first laser beam to generate the second laser beam;

[0187] A first optical system is configured to direct a first laser beam toward a second laser cavity;

[0188] A second optical system is configured to receive a second laser beam and guide the second laser beam as an output laser beam from a laser source; and

[0189] The gas purging system is configured to pump gas to the first and second optical systems at a pressure below atmospheric pressure.

[0190] 15. The laser source according to clause 14, wherein the gas purging system comprises:

[0191] An air supply pump is configured to supply gas to the first and second optical systems at a pressure below atmospheric pressure; and

[0192] The second pump is configured to substantially remove the second gas from the first optical system and the second optical system.

[0193] 16. The laser source according to clause 14, wherein the gas comprises nitrogen and the pressure is between about 50 Torr and about 700 Torr.

[0194] 17. The laser source according to clause 14 further includes:

[0195] An optical module is coupled to the first laser chamber, wherein the optical module includes a second gas at a pressure of approximately atmospheric pressure.

[0196] 18. The laser source according to clause 14 further includes:

[0197] The optical module is coupled to the second laser chamber.

[0198] The gas purging system is configured to pump the gas into the optical module at a pressure below atmospheric pressure.

[0199] 19. A photolithography apparatus, comprising:

[0200] The irradiation system is configured to adjust the radiation beam;

[0201] A projection system is configured to project a pattern assigned to the radiation beam onto a substrate.

[0202] The irradiation system includes a laser source, which includes:

[0203] A laser chamber is configured to generate a first laser beam; and

[0204] An optical system, coupled to the laser cavity, is configured to receive a first laser beam and output an output laser beam.

[0205] The optical system includes nitrogen gas at a pressure below atmospheric pressure.

[0206] 20. An apparatus comprising:

[0207] A laser chamber is configured to generate a first laser beam;

[0208] An optical system, coupled to a laser cavity, is configured to receive a first laser beam and output an output laser beam; and

[0209] The gas purging system is configured to supply gas to the optical system at a pressure below atmospheric pressure.

[0210] 21. A laser source, comprising:

[0211] A laser chamber is configured to generate a first laser beam;

[0212] An optical system, coupled to a laser cavity, is configured to receive a first laser beam and output an output laser beam; and

[0213] A gas purging system is configured to supply helium to the optical system.

[0214] 22. The laser source according to clause 21, wherein the gas purging system comprises:

[0215] A gas supply pump is configured to supply helium gas to the optical system.

[0216] 23. The laser source according to clause 22, wherein the gas purging system further comprises:

[0217] The second pump is configured to substantially remove the second gas from the optical system.

[0218] 24. The laser source according to clause 23, wherein the second gas includes oxygen.

[0219] 25. The laser source according to clause 21, wherein the gas purging system comprises:

[0220] The gas supply pump is configured to supply helium gas to the optical system at a pressure below atmospheric pressure.

[0221] 26. The laser source according to clause 21, wherein:

[0222] The optical system includes a first optical module and a second optical module; and

[0223] The gas purging system includes:

[0224] A first gas supply pump, coupled to a first optical module, supplies helium gas to the first optical module; and

[0225] A second gas supply pump is coupled to the second optical module to supply helium gas to the second optical module.

[0226] 27. A laser source, comprising:

[0227] A laser chamber is configured to generate a first laser beam; and

[0228] An optical system, coupled to the laser cavity, is configured to receive a first laser beam and output an output laser beam.

[0229] The optical system includes helium.

[0230] 28. The laser source according to clause 27 further includes:

[0231] A gas purging system is configured to supply helium to the optical system.

[0232] 29. The laser source according to clause 28, wherein the gas purging system comprises:

[0233] A gas supply pump is configured to supply helium gas to the optical system; and

[0234] The second pump is configured to substantially remove the second gas from the optical system.

[0235] 30. The laser source according to clause 29, wherein the second gas comprises oxygen.

[0236] 31. The laser source according to clause 27 further includes:

[0237] A second laser chamber is configured to at least indirectly receive the first laser beam and amplify the first laser beam to generate a second laser beam.

[0238] The optical system is configured to receive the second laser beam and output the laser beam.

[0239] 32. The laser source according to clause 27 further includes:

[0240] An optical module is coupled to a laser chamber, wherein the optical module includes a second gas at a pressure of approximately atmospheric pressure.

[0241] 33. A laser source, comprising:

[0242] A first laser chamber is configured to generate a first laser beam;

[0243] The second laser chamber is configured to at least indirectly receive the first laser beam and amplify the first laser beam to generate the second laser beam;

[0244] A first optical system is configured to direct a first laser beam toward a second laser cavity;

[0245] A second optical system is configured to receive a second laser beam and guide the second laser beam as an output laser beam from a laser source; and

[0246] A gas purging system is configured to pump helium gas into the first optical system and the second optical system.

[0247] 34. The laser source according to clause 33, wherein the gas purging system comprises:

[0248] A gas supply pump is configured to supply helium gas to the first optical system and the second optical system; and

[0249] The second pump is configured to substantially remove the second gas from the first optical system and the second optical system.

[0250] 35. The laser source according to clause 33 further includes:

[0251] The optical module is coupled to the second laser chamber.

[0252] The gas purging system is configured to pump helium gas to the optical module.

[0253] 36. A photolithography apparatus, comprising:

[0254] The irradiation system is configured to adjust the radiation beam;

[0255] The projection system is configured to project a pattern assigned to a radiation beam onto a substrate.

[0256] The irradiation system includes a laser source, which includes:

[0257] A laser chamber is configured to generate a first laser beam; and

[0258] An optical system, coupled to the laser cavity, is configured to receive a first laser beam and output an output laser beam.

[0259] The optical system includes helium.

[0260] 37. An apparatus comprising:

[0261] A laser chamber is configured to generate a first laser beam;

[0262] An optical system, coupled to a laser cavity, is configured to receive a first laser beam and output an output laser beam; and

[0263] A gas purging system is configured to supply helium to the optical system.

[0264] The breadth and scope of this disclosure should not be limited by any of the exemplary embodiments described above, but should be defined solely by the following claims and their equivalents.

Claims

1. A laser source, comprising: A laser chamber is configured to generate a first laser beam; An optical system is coupled to the laser cavity and configured to receive the first laser beam and output an output laser beam; as well as A gas purging system is configured to supply nitrogen or helium to the optical system at a pressure below atmospheric pressure.

2. The laser source according to claim 1, wherein the gas purging system comprises: A gas supply pump is configured to supply nitrogen or helium to the optical system at a pressure below atmospheric pressure.

3. The laser source according to claim 2, wherein the gas purging system further comprises: The second pump is configured to substantially remove oxygen from the optical system.

4. The laser source according to claim 1, wherein the pressure is between about 50 Torr and about 700 Torr.

5. The laser source according to claim 1, wherein: The optical system includes a first optical module and a second optical module; as well as The gas purging system includes: A first gas supply pump, coupled to the first optical module, supplies nitrogen or helium to the first optical module at a pressure below atmospheric pressure; as well as A second gas supply pump, coupled to the second optical module, supplies the nitrogen or helium gas to the second optical module at a pressure below atmospheric pressure.

6. A laser source, comprising: A laser chamber is configured to generate a first laser beam; An optical system is coupled to the laser cavity and configured to receive the first laser beam and output an output laser beam. The optical system includes nitrogen or helium gas at a pressure below atmospheric pressure.

7. The laser source according to claim 6, further comprising: A gas purging system is configured to supply nitrogen or helium to the optical system at a pressure below atmospheric pressure.

8. The laser source according to claim 7, wherein the gas purging system comprises: A gas supply pump is configured to supply nitrogen or helium to the optical system at a pressure below atmospheric pressure; as well as The second pump is configured to substantially remove oxygen from the optical system.

9. The laser source of claim 6, wherein the pressure is between about 50 Torr and about 700 Torr.

10. The laser source according to claim 6, further comprising: A second laser chamber is configured to at least indirectly receive the first laser beam and amplify the first laser beam to generate a second laser beam. The optical system is configured to receive the second laser beam and output the output laser beam.

11. The laser source according to claim 6, further comprising: An optical module is coupled to the laser chamber, wherein the optical module comprises oxygen at a pressure of approximately atmospheric pressure.

12. A laser source, comprising: A first laser chamber is configured to generate a first laser beam; A second laser chamber is configured to at least indirectly receive the first laser beam and amplify the first laser beam to generate a second laser beam. A first optical system is configured to direct the first laser beam toward the second laser cavity; A second optical system is configured to receive the second laser beam and guide the second laser beam as the output laser beam of the laser source; as well as A gas purging system is configured to pump nitrogen or helium gas to the first optical system and the second optical system at a pressure below atmospheric pressure.

13. The laser source according to claim 12, wherein the gas purging system comprises: A gas supply pump is configured to supply nitrogen or helium to the first optical system and the second optical system at a pressure lower than atmospheric pressure; as well as The second pump is configured to substantially remove oxygen from the first optical system and the second optical system.

14. The laser source of claim 12, wherein the pressure is between about 50 Torr and about 700 Torr.

15. The laser source according to claim 12, further comprising: An optical module is coupled to the first laser chamber, wherein the optical module comprises oxygen at a pressure of approximately atmospheric pressure.

16. The laser source according to claim 12, further comprising: The optical module is coupled to the second laser chamber. The gas purging system is configured to pump the nitrogen or helium gas into the optical module at a pressure below atmospheric pressure.

17. A photolithography apparatus, comprising: The irradiation system is configured to adjust the radiation beam; A projection system is configured to project a pattern assigned to the radiation beam onto a substrate. The irradiation system includes a laser source, which includes: A laser chamber is configured to generate a first laser beam; as well as An optical system is coupled to the laser cavity and configured to receive the first laser beam and output an output laser beam. The optical system includes nitrogen gas at a pressure below atmospheric pressure.

18. An optical device, comprising: A laser chamber is configured to generate a first laser beam; An optical system is coupled to the laser cavity and configured to receive the first laser beam and output an output laser beam; as well as A gas purging system is configured to supply nitrogen or helium to the optical system at a pressure below atmospheric pressure.

19. A photolithography apparatus, comprising: The irradiation system is configured to adjust the radiation beam; A projection system is configured to project a pattern assigned to the radiation beam onto a substrate. The irradiation system includes a laser source, which includes: A laser chamber is configured to generate a first laser beam; as well as An optical system is coupled to the laser cavity and configured to receive the first laser beam and output an output laser beam. The optical system includes helium gas at a pressure below atmospheric pressure.

20. A gas purging device for a laser source, the gas purging device comprising: An optical system is coupled to a laser chamber configured to generate a first laser beam, and the optical system is configured to receive the first laser beam and output an output laser beam. as well as A gas purging system is configured to supply nitrogen or helium to the optical system at a pressure below atmospheric pressure.

21. The gas purging apparatus according to claim 20, wherein the gas purging system comprises: A gas supply pump is configured to supply nitrogen or helium to the optical system at a pressure below atmospheric pressure; as well as The second pump is configured to substantially remove oxygen from the optical system.

22. A gas purging device for a laser source, the gas purging device comprising: A first optical system is configured to direct a first laser beam generated by a first laser chamber to a second laser chamber, the second laser chamber being configured to receive the first laser beam at least indirectly and amplify the first laser beam to generate a second laser beam. A second optical system is configured to receive the second laser beam and guide the second laser beam as an output laser beam. as well as A gas purging system is configured to pump nitrogen or helium gas to the first optical system and the second optical system at a pressure below atmospheric pressure.

23. The gas purging apparatus according to claim 22, wherein the gas purging system comprises: A gas supply pump is configured to supply nitrogen or helium to the first optical system and the second optical system at a pressure lower than atmospheric pressure; as well as The second pump is configured to substantially remove oxygen from the first optical system and the second optical system.

24. The gas purging apparatus according to claim 22, wherein the gas purging apparatus further comprises: An optical module is coupled to the first laser chamber, wherein the optical module comprises oxygen at a pressure of approximately atmospheric pressure.

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