Metrology for improved duv laser alignment

Abstract

The light source apparatus includes a gas discharge stage, a sensing apparatus, an optical arrangement, an adjustment apparatus, and a control apparatus. The gas discharge stage includes an optical amplifier and a set of optical elements, the optical amplifier including a chamber of a gas discharge medium configured to sustain an output beam, the optical elements configured to form an optical resonator around the optical amplifier. The optical arrangement is configured to image light from a plurality of different object planes within the gas discharge stage onto the sensing apparatus. The adjustment apparatus is in physical communication with one or more optical components within the gas discharge stage and is configured to modify at least one geometric aspect of the optical components. The control apparatus is in communication with the sensing apparatus and the adjustment apparatus and provides a signal to the adjustment apparatus based on output from the sensing apparatus.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Application No. 62 / 953,115, filed December 23, 2019, entitled “METROLOGY FOR IMPROVING DUVLASER ALIGNMENT,” which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to the alignment of light source devices and systems, such as the alignment of light sources for lithography devices and systems. Background Technology

[0004] A photolithography apparatus is a machine configured to apply a desired pattern onto a substrate. Photolithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A photolithography apparatus can project a pattern from a patterning apparatus (e.g., a mask, a photomask) onto a layer of radiation-sensitive material (resist) disposed on a substrate.

[0005] To project patterns onto a substrate, photolithography equipment can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. Compared to photolithography equipment that uses deep ultraviolet (DUV) radiation with a wavelength of, for example, 193 nm, photolithography equipment that uses extreme ultraviolet (EUV) radiation with wavelengths in the range of 4 to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0006] A master oscillator power amplifier (MOPA) is a two-stage optical resonator arrangement that produces a highly coherent amplified beam. The performance of a MOPA depends primarily on the alignment of the master oscillator (MO). MO alignment can include the alignment of the gas discharge chamber, the alignment of the input / output optics, and the alignment of the spectral characterization tuner.

[0007] However, MO alignment can be time-consuming and requires several hours of manual maintenance. Furthermore, monitoring and adjusting MO alignment can suppress or block the beam output to equipment such as DUV lithography. Summary of the Invention

[0008] Therefore, it is necessary to reduce alignment time and the alignment variation of the master oscillator over time, and to monitor and dynamically control the quantifiable alignment error of the master oscillator.

[0009] In some embodiments, the light source device includes a gas discharge stage, a sensing device, an optical arrangement, an adjustment device, and a control device. The gas discharge stage includes an optical amplifier and a set of optical elements. The optical amplifier includes a chamber configured to hold a gas discharge medium, the gas discharge medium outputting a light beam, and the optical elements are configured to form optical resonators around the optical amplifier. The optical arrangement is configured to image light from multiple different object planes within the gas discharge stage onto the sensing device. The adjustment device physically communicates with one or more optical components within the gas discharge stage and is configured to modify at least one geometric aspect of the optical components. The control device communicates with the sensing device and the adjustment device. The control device is configured to provide a signal to the adjustment device based on an output from the sensing device.

[0010] In some embodiments, the chamber of the gas discharge stage includes a first optical port and a second optical port. In some embodiments, the set of optical elements includes an input / output optical element in optical communication with the first optical port and a spectral feature adjuster in optical communication with the second optical port. In some embodiments, the optical arrangement includes one or more focusing optical elements that can be adjusted along the optical path of the beam to select which object plane is imaged onto the sensing device.

[0011] In some embodiments, the sensing device includes a camera that senses a two-dimensional representation of a light beam received by the sensing device. In some embodiments, the camera includes a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) camera.

[0012] In some embodiments, the sensing device and optical arrangement are integrated within a three-dimensional frame that also houses the gas discharge stage. In some embodiments, the light source device further includes an illuminator configured to direct imaging light into the gas discharge stage.

[0013] In some embodiments, an imaging apparatus includes an illuminator, a sensing device, and an optical arrangement. The illuminator is configured to direct imaging light into a gas discharge stage from which the output beam is emitted. The sensing device is configured to receive the beam and / or imaging light. The optical arrangement is configured to image the beam and / or imaging light from multiple different object planes within the gas discharge stage onto the sensing device.

[0014] In some embodiments, the sensing device and optical arrangement are configured to receive amplified spontaneous emission (ASE) from a gas discharge stage for initial calibration. In some embodiments, the optical arrangement includes one or more focusing optics that are adjustable along the optical path of the beam to select which object plane is imaged onto the sensing device.

[0015] In some embodiments, the sensing device includes a camera that senses a two-dimensional representation of a light beam received by the sensing device. In some embodiments, the camera includes a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) camera.

[0016] In some embodiments, the imaging device is integrated within a three-dimensional frame that also houses the gas discharge stage.

[0017] In some embodiments, a method for aligning a gas discharge stage includes aligning both an imaging beam from an imaging device and amplified spontaneous emission (ASE) from a chamber with a first aperture of an input / output optics element and a second aperture of a spectral feature adjuster. The gas discharge stage outputs a light beam and includes a chamber having a first optical port and a second optical port, an input / output optics element in optical communication with the first optical port, and a spectral feature adjuster in optical communication with the second optical port. In some embodiments, the method further includes aligning the input / output optics element at the first aperture with the imaging beam. In some embodiments, the method further includes aligning the spectral feature adjuster and the chamber at the second aperture with the light beam.

[0018] In some embodiments, aligning the imaging beam and the ASE includes: using the ASE as a beacon to guide the imaging beam, which is aligned with the optical axis of the gas discharge stage, and coarsely adjusting the chamber along the optical axis of the gas discharge stage. In some embodiments, aligning the imaging beam and the ASE includes: adjusting the imaging beam using an optical arrangement to center the imaging beam on the first aperture and the second aperture.

[0019] In some embodiments, aligning the input / output optics at the first aperture includes: inserting a retroreflector into the imaging light and focusing the imaging light onto a sensing device to define a first alignment position. In some embodiments, aligning the input / output optics at the first aperture includes: removing the retroreflector and adjusting the input / output optics at the first aperture to align the back reflection of the imaging light onto the sensing device from a second alignment position to a first alignment position. In some embodiments, aligning the input / output optics at the first aperture includes: imaging the imaging light from the input / output optics onto the sensing device via a far-field back reflection at the first aperture.

[0020] In some embodiments, aligning the spectral feature adjuster and the chamber at the second aperture includes: contouring the beam at the first aperture and / or the second aperture onto the sensing device. In some embodiments, contouring the beam includes: measuring the vertical symmetry of the beam at the first aperture and adjusting the spectral feature adjuster at the second aperture using a tilt modulator (TAM). In some embodiments, measuring the vertical symmetry includes: imaging the near-field beam profile of the beam at the first aperture. In some embodiments, contouring the beam includes: measuring the horizontal symmetry of the beam at the first aperture and finely adjusting the chamber. In some embodiments, measuring the horizontal symmetry includes: imaging the near-field beam profile of the beam at the first aperture. In some embodiments, contouring the beam includes: measuring the horizontal symmetry of the beam at the second aperture and finely adjusting the chamber. In some embodiments, measuring the horizontal symmetry includes: imaging the near-field beam profile of the beam at the second aperture.

[0021] In some embodiments, alignment of the spectral feature adjuster and the chamber at the second aperture occurs simultaneously with the light beam used in the lithography apparatus.

[0022] Implementations of any of the above-described technologies may include EUV light sources, DUV light sources, systems, methods, processes, apparatuses, and / or devices. Details of one or more implementations are set forth in the accompanying drawings and the following description. Other features will be apparent from the specification, drawings, and claims.

[0023] Other features and exemplary aspects of the embodiments, as well as the structure and operation of each embodiment, are described in detail below with reference to the accompanying drawings. It should be noted that the embodiments are not limited to the specific embodiments described herein. The embodiments presented herein are for illustrative purposes only. Other embodiments will be apparent to those skilled in the art based on the teachings contained herein. Attached Figure Description

[0024] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate embodiments and, together with the description, further serve to explain the principles of the embodiments and enable those skilled in the art to make and use these embodiments.

[0025] Figure 1 This is a schematic diagram of a lithography apparatus according to an exemplary embodiment.

[0026] Figure 2 This is a schematic top view of a light source device according to an exemplary embodiment.

[0027] Figure 3 This is according to an exemplary embodiment. Figure 2 A schematic partial cross-sectional view of the gas discharge stage of the light source device shown.

[0028] Figure 4 This is according to an exemplary embodiment. Figure 2 A schematic partial cross-sectional view of the gas discharge stage of the light source device shown.

[0029] Figure 5 This is according to an exemplary embodiment. Figure 2 A schematic partial view of the light source device shown.

[0030] Figure 6 This is a schematic diagram of an imaging device according to an exemplary embodiment.

[0031] Figure 7 This is a schematic diagram of an imaging device according to an exemplary embodiment.

[0032] Figure 8 This is a schematic diagram of an imaging device according to an exemplary embodiment.

[0033] Figure 9 The illustration shows a flowchart for aligning a gas discharge stage according to an exemplary embodiment.

[0034] The features and exemplary aspects of the embodiments will become more apparent from the following detailed description set forth in conjunction with the accompanying drawings, in which similar reference numerals consistently identify corresponding elements. In the drawings, similar reference numerals generally denote identical, functionally similar, and / or structurally similar elements. Additionally, typically, the leftmost(s) of the reference numerals identifies the drawing in which the reference numeral first appears. Unless otherwise stated, the drawings provided throughout this disclosure should not be construed as being drawn to scale. Detailed Implementation

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

[0036] The described embodiments and references to "an embodiment," "embodiment," "example embodiment," "exemplary embodiment," etc., in the specification indicate that the described embodiments may include specific features, structures, or characteristics, but each embodiment may not necessarily include those specific features, structures, or characteristics. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, it should be understood that the influence of such a feature, structure, or characteristic on other embodiments is within the knowledge of those skilled in the art, regardless of whether such other embodiments are explicitly described.

[0037] Spatial terms such as “below,” “under,” “down,” “above,” “above,” and “up” are used herein to describe the relationship of one element or feature to another element(s) or feature(s) shown in the figures. In addition to the orientations depicted in the figures, spatial relative terms are intended to cover different orientations of the device in use or operation. The device may be oriented in other ways (rotated 90 degrees or otherwise), and the spatial relative descriptors used herein shall be interpreted accordingly.

[0038] As used herein, the terms “about,” “substantially,” or “approximately” refer to the value of a given quantity that may vary based on a particular technique. Based on a particular technique, the terms “about,” “substantially,” or “approximately” may refer to the value of a given quantity that varies, for example, from 1 to 15% of the value (e.g., ±1%, ±2%, ±5%, ±10%, or ±15% of the value).

[0039] Embodiments of this disclosure 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 that can be read and executed by one or more processors. A machine-readable medium can include any mechanism for storing or transmitting information in a machine-readable (e.g., computing device) form. 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.). Furthermore, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are merely for convenience, and such actions are actually produced by the computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc.

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

[0041] Exemplary lithography system

[0042] Figure 1 A lithography system including a radiation source SO and a lithography apparatus LA is shown. The radiation source SO is configured to generate EUV and / or DUV radiation beams B and to provide the EUV and / or DUV radiation beams B to the lithography apparatus LA. The lithography apparatus LA includes an irradiation system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS, and a substrate stage WT configured to support a substrate W.

[0043] The irradiation system IL is configured to adjust the EUV and / or DUV radiation beam B before it is incident on the patterning device MA. Furthermore, the irradiation system IL may include a faceted field mirror assembly 10 and a faceted pupil mirror assembly 11. Together, the faceted field mirror assembly 10 and the faceted pupil mirror assembly 11 provide the EUV and / or DUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. In addition to or instead of the faceted field mirror assembly 10 and the faceted pupil mirror assembly 11, the irradiation system IL may include other mirrors or devices.

[0044] After being adjusted in this way, the EUV and / or DUV radiation beam B interacts with the patterning device MA (e.g., a transmissive mask for EUV, or a reflective mask for EUV). Due to this interaction, a patterned EUV and / or DUV radiation beam B' is generated. A projection system PS is configured to project the patterned EUV and / or DUV radiation beam B' onto a substrate W. For this purpose, the projection system PS may include a plurality of mirrors 13, 14 configured to project the patterned EUV and / or DUV radiation beam B' onto the substrate W held by a substrate stage WT. The projection system PS may apply a reduction factor to the patterned EUV and / or DUV radiation beam B' to form an image with features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS... Figure 1 The projection system PS is shown as having only two mirrors 13 and 14, but the projection system PS may include a different number of mirrors (e.g., six or eight mirrors).

[0045] The substrate W may include a pre-formed pattern. In this case, the photolithography apparatus LA aligns the image formed by the patterned EUV and / or DUV radiation beams B' with the pattern previously formed on the substrate W.

[0046] A relative vacuum can be provided in the radiation source SO, the irradiation system IL, and / or the projection system PS, i.e., a small amount of gas (e.g., hydrogen) at a pressure much lower than atmospheric pressure.

[0047] Exemplary light source device

[0048] As described above, the master oscillator power amplifier (MOPA) is a two-stage optical resonator arrangement. The master oscillator (MO) (e.g., the first optical resonator stage) generates a highly coherent beam (e.g., from a seed laser). The power amplifier (PA) (e.g., the second optical resonator stage) increases the optical power of the beam while preserving the beam characteristics. The MO may include a gas discharge chamber, input / output optics (e.g., an optical coupler (OC)), and a spectral characterization modulator (e.g., a linewidth narrowing module (LNM)). The input / output optics and the spectral characterization modulator may surround the gas discharge chamber to form an optical resonator.

[0049] The performance of MOPA depends primarily on the alignment of MO. MO alignment can include the alignment of the gas discharge chamber, the OC, and the LNM. Each of these alignments (e.g., chamber, OC, LNM, etc.) can lead to alignment errors and MO variations over time. However, MO alignment can be time-consuming and require several hours of manual maintenance (e.g., Synchronous Performance Maintenance (SPM)). Furthermore, initial alignment can be difficult (e.g., trial and error) if the chamber, OC, and LNM are largely misaligned (e.g., no initial reference point). Additionally, monitoring and adjusting MO alignment can suppress (e.g., block) the output beam (e.g., DUV beam) to, for example, DUV lithography equipment.

[0050] Imaging light (e.g., a visible laser beam) can be projected onto the chamber, OC, and LNM (e.g., sequentially or simultaneously) to illuminate and directly align the OC and / or LNM along the optical axis of the chamber (e.g., the first and second optical ports). Amplified spontaneous emission (ASE) from the gas discharge chamber can be used as a beacon (e.g., a reference point) to facilitate axial calibration (e.g., laser axis calibration) of the imaging light along the optical axis of the MO cavity (e.g., along the optical axes of the chamber, OC, and LNM). Additionally, the ASE can be used to initially align the chamber with the optical axis of the MO cavity (e.g., coarse alignment). Furthermore, sensing devices (e.g., a camera) can be used to visually survey different object planes within the MO (e.g., chamber ports, OC aperture, LNM aperture, etc.) and quantify any alignment errors (e.g., image comparison). For example, the sensing devices can survey the near-field (NF) and far-field (FF) regions of the imaging light on various object planes and apply adjustments (e.g., fine alignment) such as by beam profiles (e.g., horizontal symmetry, vertical symmetry, etc.).

[0051] The light source devices and systems described below can reduce the alignment time (e.g., SPM) of the master oscillator, reduce alignment variations of the master oscillator over time, and monitor and dynamically control quantifiable alignment errors of the master oscillator to provide, for example, a highly coherent beam to a DUV lithography apparatus.

[0052] Figures 2 to 5 A light source device 200 according to various exemplary embodiments is shown. Figure 2 This is a schematic top view of a light source device 200 according to an exemplary embodiment. Figure 3 and Figure 4 This is according to an exemplary embodiment. Figure 2 A schematic partial cross-sectional view of the gas discharge stage 220 of the light source device 200 shown. Figure 5 This is according to an exemplary embodiment. Figure 2 A schematic partial illustration of the light source device 200 shown.

[0053] Figure 2 A light source device 200 according to various exemplary embodiments is illustrated. The light source device 200 can be configured to monitor and dynamically control quantifiable alignment errors of a gas discharge stage 220 (e.g., MO), and, for example, provide a highly coherent and aligned light beam (e.g., beam 202, amplified beam 204) to a DUV lithography apparatus (e.g., LA). The light source device 200 can also be configured to reduce the alignment time of the gas discharge stage 220 (e.g., MO) and reduce alignment variations of the gas discharge stage 220 (e.g., MO) over time. While the light source device 200 in… Figure 2 While illustrated as a standalone device and / or system, embodiments of this disclosure can be used with other optical systems, such as, but not limited to, a radiation source SO, a lithography apparatus LA, and / or other optical systems. In some embodiments, the light source device 200 may be a radiation source SO in the lithography apparatus LA. For example, the EUV and / or DUV radiation beam B may be beam 202 and / or a magnified beam 204.

[0054] The light source device 200 may be a MOPA formed by a gas discharge stage 220 (e.g., MO) and a power loop amplifier (PRA) stage 280 (e.g., PA). The light source device 200 may include the gas discharge stage 220, a line analysis module (LAM) 230, a master oscillator wavefront engineering box (MoWEB) 240, a power loop amplifier (PRA) stage 280, a controller 290, and an imaging device 400 (e.g., a MO cavity alignment tool (MoCAT)). In some embodiments, all the components listed above may be housed within a three-dimensional (3D) frame 210. For example, the imaging device 400 may be integrated within the 3D frame 210, which also houses the gas discharge stage 220. In some embodiments, the 3D frame 210 may include metals (e.g., aluminum, steel, etc.), ceramics, and / or any other suitable rigid material.

[0055] Gas discharge stage 220 can be configured to output a highly coherent light beam (e.g., beam 202). Gas discharge stage 220 may include a first optical resonator element 254, a second optical resonator element 224, an input / output optics element 250 (e.g., OC), an optical amplifier 260, and a spectral feature adjuster 270 (e.g., LNM). In some embodiments, the input / output optics element 250 may include the first optical resonator element 254, and the spectral feature adjuster 270 may include the second optical resonator element 224. The first optical resonator 228 may be defined by the input / output optics element 250 (e.g., via the first optical resonator element 254) and the spectral feature adjuster 270 (e.g., via the second optical resonator element 224). The first optical resonator element 254 may be partially reflective (e.g., a partial mirror), and the second optical resonator element 224 may be reflective (e.g., a mirror or grating) to form the first optical resonator 228. The first optical resonator 228 can guide light generated by the optical amplifier 260 (e.g., amplified spontaneous emission (ASE) 201) to a fixed number of paths within the optical amplifier 260 to form a beam 202. In some embodiments, such as... Figure 2 As shown, the gas discharge stage 220 can output the beam 202 to the PRA stage 280, which is part of the MOPA arrangement.

[0056] PRA stage 280 can be configured to amplify beam 202 from gas discharge stage 220 via a multi-path arrangement and output amplified beam 204. PRA stage 280 may include a third optical resonator element 282, a power loop amplifier (PRA) 286, and a fourth optical resonator element 284. A second optical resonator 288 may be defined by the third optical resonator element 282 and the fourth optical resonator element 284. The third optical resonator element 282 may be partially reflective (e.g., a partial beam splitter), and the fourth optical resonator element 284 may be reflective (e.g., a mirror, prism, or beam inverter) to form the second optical resonator 288. The second optical resonator 288 may guide the beam 202 from gas discharge stage 220 into a fixed number of paths in PRA 286 to form the amplified beam 204. In some embodiments, PRA stage 280 may output the amplified beam 204 to a lithography apparatus, such as a lithography (LA) apparatus. For example, the magnified beam 204 can be an EUV and / or DUV radiation beam B from a radiation source SO in the lithography equipment LA.

[0057] like Figures 2 to 4As shown, optical amplifier 260 can be optically coupled to input / output optics 250 and spectral feature adjuster 270. Optical amplifier 260 can be configured to output ASE 201 and / or beam 202. In some embodiments, optical amplifier 260 can utilize ASE 201 as a beacon to guide the axial alignment of the optical axis of chamber 261 and / or the optical axis of gas discharge stage 220 (e.g., MO cavity). Optical amplifier 260 may include chamber 261, gas discharge medium 263, and chamber adjuster 265. Gas discharge medium 263 may be disposed within chamber 261, and chamber 261 may be disposed on chamber adjuster 265.

[0058] The chamber 261 can be configured to hold the gas discharge medium 263 within the first and second chamber optical ports 262a, 262b. The chamber 261 may include a first chamber optical port 262a and a second chamber optical port 262b opposite to the first chamber optical port 262a. In some embodiments, the first and second chamber optical ports 262a, 262b may form the optical axis of the chamber 261.

[0059] like Figure 3 As shown, the first chamber optical port 262a can optically communicate with the input / output optical element 250. The first chamber optical port 262a may include a first chamber wall 261a, a first chamber window 266a, and a first chamber aperture 264a. In some embodiments, such as Figure 3 As shown, the aperture 264a of the first chamber can be a rectangular opening.

[0060] like Figure 4 As shown, the second chamber optical port 262b can optically communicate with the spectral feature adjuster 270. The second chamber optical port 262b may include a second chamber wall 261b, a second chamber window 266b, and a second chamber aperture 264b. In some embodiments, such as Figure 4 As shown, the second chamber aperture 264b can be a rectangular opening. In some embodiments, the optical axis of chamber 261 passes through the first and second chamber apertures 264a and 264b.

[0061] The gas discharge medium 263 can be configured to output ASE 201 (e.g., 193 nm) and / or beam 202 (e.g., 193 nm). In some embodiments, the gas discharge medium 263 may include a gas for excimer laser generation (e.g., Ar2, Kr2, F2, Xe2, ArF, KrCl, KrF, XeBr, XeCl, XeF, etc.). For example, the gas discharge medium 263 may include ArF and is excited (e.g., by an applied voltage) from a surrounding electrode (not shown) in chamber 261, i.e., outputting ASE 201 (e.g., 193 nm) and / or beam 202 (e.g., 193 nm) through the first and second chamber optical ports 262a, 262b. In some embodiments, the gas discharge stage 220 may include a voltage power supply (not shown) configured to apply a high-voltage electrical pulse to an electrode (not shown) in chamber 261.

[0062] The chamber adjuster 265 can be configured to adjust the optical axis of the chamber 261 spatially (e.g., laterally, angularly, etc.) (e.g., along the first and second chamber optical ports 262a, 262b). Figure 2 As shown, a chamber adjuster 265 can be coupled to a chamber 261 and first and second chamber optical ports 262a, 262b. In some embodiments, the chamber adjuster 265 may have six degrees of freedom (e.g., 6-axis). For example, the chamber adjuster 265 may include one or more linear motors and / or actuators for providing adjustment of the optical axis of the chamber 261 in six degrees of freedom (e.g., forward / backward, up / down, left / right, yaw, pitch, roll). In some embodiments, the chamber adjuster 265 can laterally and angularly adjust the chamber 261 to align the optical axis of the chamber 261 (e.g., along the first and second chamber optical ports 262a, 262b) with the optical axis of the gas discharge stage 220 (e.g., an MO cavity). For example, as Figure 2 As shown, the optical axis of the gas discharge stage 220 (e.g., MO cavity) can be defined by the optical axes of the cavity 261 (e.g., along the first and second cavity optical ports 262a, 262b), the input / output optical element 250 (e.g., OC aperture 252), and the spectral feature adjuster 270 (e.g., LNM aperture 272).

[0063] Input / output optics 250 (e.g., OC) can be configured to optically communicate with the first chamber optical port 262a. In some embodiments, input / output optics 250 can be an optical coupler (OC) configured to partially reflect a light beam and form a first optical resonator 228. For example, an OC has been previously described in U.S. Patent No. 7,885,309, published February 8, 2011, which is incorporated herein by reference in its entirety. Figure 2 As shown, the input / output optical element 250 may include a first optical resonator element 254 to guide (e.g., reflect) light into the optical amplifier 260 and transmit light (e.g., beam 202, ASE 201) from the optical amplifier 260 out of the gas discharge stage 220 (e.g., MO cavity).

[0064] like Figure 3 As shown, the input / output optics 250 may include an OC aperture 252 and a first optical resonator element 254. The first optical resonator element 254 may be configured to be angularly adjusted (e.g., tilted and / or tilted) relative to the cavity 261 (e.g., the first cavity optical port 262a) in the vertical and / or horizontal directions to allow light passing through the OC aperture 252. In some embodiments, the OC aperture 252 may be a rectangular opening. In some embodiments, the alignment of the gas discharge stage 220 may be based on the alignment of the first cavity aperture 264a and the OC aperture 252. In some embodiments, the first optical resonator element 254 may be angularly adjusted (e.g., tilted and / or tilted) such that reflections from the input / output optics 250 are parallel to the optical axis of the gas discharge stage 220 (e.g., the MO cavity). In some embodiments, the first optical resonator element 254 may be an adjustable mirror (e.g., a partial reflector, beam splitter, etc.) capable of being angularly adjusted (e.g., tilted and / or tilted). In some embodiments, the OC aperture 252 may be fixed, and the first optical resonator element 254 may be adjustable. In some embodiments, the OC aperture 252 may be adjusted. For example, the OC aperture 252 may be spatially adjusted relative to the cavity 261 in the vertical and / or horizontal directions.

[0065] Spectral feature adjuster 270 (e.g., LNM) may be configured to optically communicate with the second chamber optical port 262b. In some embodiments, spectral feature adjuster 270 may be a line narrowing module (LNM) configured to provide spectral line narrowing to the beam. For example, an LNM has been previously described in U.S. Patent No. 8,126,027, published February 28, 2012, which is incorporated herein by reference in its entirety.

[0066] like Figure 2 As shown, the spectral feature adjuster 270 may include a second optical resonator element 224 to direct (e.g., beam 202, ASE 201) light from the optical amplifier 260 toward (e.g., reflect) the input / output optical element 250 back into the optical amplifier 260.

[0067] like Figure 4As shown, the spectral feature adjuster 270 may include an LNM aperture 272 and a tilt angle modulator (TAM) 274. The TAM 274 may be configured to angle the light passing through the LNM aperture 272 relative to the chamber 261 (e.g., the second chamber optical port 262b) in the vertical and / or horizontal directions. In some embodiments, the LNM aperture 272 may be a rectangular opening. In some embodiments, the alignment of the gas discharge stage 220 may be based on the alignment of the second chamber aperture 264b and the LNM aperture 272. In some embodiments, the TAM 274 may angle the spectral feature adjuster 270 (e.g., tilt and / or tilt) such that reflections from the spectral feature adjuster 270 are parallel to the optical axis of the gas discharge stage 220 (e.g., the MO cavity). In some embodiments, the TAM 274 may include an adjustable mirror (e.g., a partial reflector, a beam splitter, etc.) and / or an adjustable prism capable of angle adjustment (e.g., tilting and / or tilting). In some embodiments, the LNM aperture 272 may be fixed, while the TAM 274 may be adjustable. In some embodiments, the LNM aperture 272 may be adjusted. For example, the LNM aperture 272 may be spatially adjusted relative to the chamber 261 in the vertical and / or horizontal directions.

[0068] LAM 230 can be configured to monitor the line center (e.g., center wavelength) of a beam (e.g., beam 202, imaging beam 206). LAM 230 can also be configured to monitor the energy of a beam (e.g., ASE 201, beam 202, imaging beam 206) for wavelength measurement. For example, LAMs have previously been described in U.S. Patent No. 7,885,309, published February 8, 2011, which is incorporated herein by reference in its entirety.

[0069] like Figure 2 As shown, LAM 230 can be optically coupled to gas discharge stage 220 and / or MoWEB 240. In some embodiments, LAM 230 can be disposed between gas discharge stage 220 and MoWEB 240. For example, as Figure 2 As shown, LAM 230 can be directly optically coupled to MoWEB 240 and optically coupled to gas discharge stage 220. In some embodiments, such as Figure 2 As shown, beam splitter 212 can be configured to direct ASE 201 and / or beam 202 toward PRA stage 280 and to direct ASE 201 and / or beam 202 toward imaging device 400. In some embodiments, such as Figure 2 As shown, beam splitter 212 can be configured to direct imaging light 206 from imaging device 400 toward gas discharge stage 220. In some embodiments, such as Figure 2As shown, the beam splitter 212 can be set in the MoWEB 240.

[0070] MoWEB 240 can be configured to provide beamforming to a light beam (e.g., beam 202, imaging beam 206). MoWEB 240 can also be configured to monitor the forward and / or backward propagation of the light beam (e.g., ASE 201, beam 202, imaging beam 206). For example, MoWEB was previously described in U.S. Patent No. 7,885,309, published February 8, 2011, which is incorporated herein by reference in its entirety. Figure 2 and Figure 4 As shown, MoWEB 240 can be optically coupled to LAM 230 and / or imaging device 400. In some embodiments, MoWEB 240 can be disposed between LAM 230 and imaging device 400. For example, as Figure 2 As shown, MoWEB 240 can be directly optically coupled to LAM 230 and directly optically coupled to imaging device 400. In some embodiments, LAM 230, MoWEB 240 and / or imaging device can be optically coupled to gas discharge stage 220 via a single optical arrangement.

[0071] The controller 290 can be configured to communicate with the input / output optics 250, the chamber adjuster 265, the spectral feature adjuster 270, and / or the imaging device 400. In some embodiments, the controller 290 can be configured to provide a first signal 292 to the input / output optics 250, a second signal 294 to the spectral feature adjuster 270, a third signal 296 to the chamber adjuster 265, and a fourth signal 298 to the imaging device 400. For example, as... Figure 5 As shown, the fourth signal 298 may include a first sub-signal 298a to the illuminator 410, a second sub-signal 298b to the optical arrangement 430, and a third sub-signal 298c to the sensing device 450 of the imaging device 400. In some embodiments, the controller 290 may be configured to provide signals (e.g., the first signal 292 and / or the second signal 294) to the input / output optics 250 and / or the spectral feature adjuster 270, and to adjust the input / output optics 250 (e.g., adjust the first optical resonator element 254) and / or the spectral feature adjuster 270 (e.g., adjust the TAM 274) based on the output from the imaging device 400 (e.g., a two-dimensional (2D) image comparison). For example, the output may come from the sensing device 450 along the third sub-signal 298c.

[0072] In some embodiments, the first optical resonator element 254, the chamber adjuster 265, and / or the TAM 274 may be in physical and / or electrical communication with the controller 290 (e.g., a first signal 292, a second signal 294, and / or a third signal 296). For example, the first optical resonator element 254, the chamber adjuster 265, and / or the TAM 274 may be adjusted by the controller 290 (e.g., laterally and / or angularly) to align the optical axis of the chamber 261 (e.g., along the first and second chamber optical ports 262a, 262b) with the optical axis of the gas discharge stage 220 (e.g., an MO cavity) defined by the input / output optical element 250 (e.g., OC aperture 252) and the spectral feature adjuster 270 (e.g., LNM aperture 272).

[0073] Exemplary imaging device

[0074] Figure 5 and Figure 6 An imaging device 400 according to various exemplary embodiments is shown. Figure 5 It is an example of an imaging device 400 according to an exemplary embodiment. Figure 2 A schematic partial illustration of the light source device 200 shown. Figure 6 This is an illustration of an imaging device 400 according to an exemplary embodiment.

[0075] Imaging device 400 can be configured to monitor and measure quantifiable alignment errors of gas discharge stage 220. Imaging device 400 can also be configured to reduce alignment time of gas discharge stage 220 and reduce alignment variations of gas discharge stage 220 over time. Although imaging device 400 in Figure 5 and Figure 6 While illustrated as a standalone device and / or system, embodiments of this disclosure can be used with other optical systems, such as, but not limited to, a radiation source SO, a lithography apparatus LA, a light source device 200, and / or other optical systems. In some embodiments, the imaging device 400 may be external to the 3D frame 210 of the light source device 200. For example, the imaging device 400 may be part of a separate external alignment and / or measurement tool.

[0076] Imaging device 400 may be a MoCavity Alignment Tool (MoCAT) for a gas discharge stage 220 (e.g., MO) of light source device 200. Imaging device 400 may include an illuminator 410, an optical arrangement 430, and a sensing device 450. In some embodiments, such as Figure 5 and Figure 6As shown, all the components listed above can be housed within a three-dimensional (3D) frame 402. For example, the 3D frame 402 may be 55 cm (length) × 25 cm (width) × 10 cm (depth). In some embodiments, the 3D frame 402 may comprise metal (e.g., aluminum, steel, etc.), ceramic, and / or any other suitable rigid material.

[0077] Illuminator 410 can be configured to direct imaging light 206 into gas discharge stage 220. Illuminator 410 may include illumination source 412, illumination 413, first optical element 414, second optical element 416, third optical element 418, beamforming aperture 420, and / or half-wave plate 422. In some embodiments, illumination source 412 may include a laser diode or light-emitting diode (LED) that outputs illumination 413. For example, illumination 413 may have a wavelength of about 400 nm to about 700 nm, such as 405 nm. In some embodiments, such as Figure 5 and Figure 6 As shown, the first optical element 414 may include collimating and / or focusing optics (e.g., collimator, focuser, etc.), and the second and third optical elements 416, 418 may include beam-forming optics (e.g., beam expander, telescope, etc.). In some embodiments, the beam-forming aperture 420 and / or the first polarizing optics 422 (e.g., half-wave plate) may be configured to adjust (e.g., define the beam diameter, define the beam polarization, etc.) the illumination 413 to form imaging light 206. Figure 5 and Figure 6 As shown, the illuminator 410 can be optically coupled to the optical arrangement 430 and directs the imaging light 206 toward the optical arrangement 430. In some embodiments, the illuminator 410 can direct a single optical pulse toward the gas discharge stage 220. For example, as Figure 5 As shown, the controller 290 can send a trigger to the irradiation source 412 via the first sub-signal 298a.

[0078] Optical arrangement 430 can be configured to image light (e.g., imaging light 206, ASE 201, and / or beam 202) from multiple different imaging lens positions 442 onto sensing device 450 (for imaging different object planes within gas discharge stage 220). Optical arrangement 430 may include a first beam steering optics 432 (e.g., an adjustable mirror), a first beam splitter 434 (e.g., a polarizing beam splitter), a second polarizing optics 436 (e.g., a quarter-wave plate), a second beam steering optics 438 (e.g., an adjustable mirror), an imaging lens 440, multiple imaging lens positions 442 for imaging different object planes in gas discharge stage 220, and a retractable retroreflector 470. First beam steering optics 432 can be configured to receive imaging light 206 from illuminator 410 and adjust (e.g., translate) along the optical axis (e.g., the Y-axis direction) of imaging light 206. The first beam splitter 434 may be configured to reflect the imaging light 206 from the first beam steering optics 432 and direct the imaging light 206, ASE 201, and / or beam 202 from the gas discharge stage 220 (e.g., from the object plane at the OC aperture 252, the first chamber aperture 264a, the second chamber aperture 264b, and / or the LNM aperture 272) toward the sensing device 450. The second beam steering optics 438 may be configured to adjust (e.g., tilt and / or rotate) the reflected imaging light 206, ASE 201, and / or beam 202. In some embodiments, the first and second beam steering optics 432, 438 may each include a linear motor and / or actuator providing adjustment (e.g., translation, tilt, rotation, etc.) and may be simultaneously adjusted to direct the imaging light 206 toward the gas discharge stage 220. For example, as... Figure 5 As shown, the controller 290 can send a signal to the optical arrangement 430 via a second sub-signal 298b to adjust the first and second beam-directing optics 432, 438. In some embodiments, the optical arrangement 430 may include one or more zoom lenses.

[0079] Imaging lens 440 may include a linear motor and / or actuator that provides adjustment (e.g., translation) of imaging lens 440 toward sensing device 450 along the optical axis (e.g., Y-axis direction) of imaging light 206, ASE 201, and / or beam 202. In some embodiments, such as Figure 5 and Figure 6As shown, the imaging lens 440 can be adjusted to the imaging lens position 442 along the optical path of the imaging light 206 and / or beam 202 and / or ASE 201 to select which object plane is imaged onto the sensing device 450. For example, the imaging lens(s) for imaging different object planes in the gas discharge stage 220 can image the object planes of the OC aperture 252, the first chamber aperture 264a, the second chamber aperture 264b, and / or the LNM aperture 272. The retractable retroreflector 470 can be configured to reflect the imaging light 206 back to its source (e.g., the first beam splitter 434) with minimal scattering (e.g., the wavefront is directly reflected back). In some embodiments, the retractable retroreflector 470 may include a corner reflector (e.g., a corner cube reflector), a cat's eye reflector, or a phase conjugate mirror. In some embodiments, before the retractable retroreflector 470 is inserted into the imaging light 206, the first and second beam-directing optics 432, 438 may be adjusted to guide the imaging light 206 along the optical axis of the gas discharge stage 220 (e.g., an MO cavity) to define a reference alignment position (e.g., a reference alignment position for OC aperture 252 alignment). In some embodiments, the retractable retroreflector 470 may be inserted into the imaging light 206 to focus the reflected imaging light 206 onto the sensing device 450 to define a first alignment position.

[0080] Sensing device 450 may be configured to receive imaging light 206, ASE 201, and / or beam 202 based on the position of imaging lens 440 at (e.g., corresponding to the object plane at OC aperture 252, first chamber aperture 264a, second chamber aperture 264b, and / or LNM aperture 272). Sensing device 450 may include camera 452 and camera neutral density (ND) filter 454. In some embodiments, camera ND filter 454 may include one or more wavelength filters. In some embodiments, camera 452 may sense a two-dimensional (2D) representation of imaging light 206, ASE 201, and / or beam 202. In some embodiments, camera 452 may include a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) camera. For example, camera 452 may include a thin-film back-illuminated CCD camera and / or a thin-film back-illuminated CMOS camera. In some embodiments, the sensing device 450 can monitor and / or measure the 2D beam profile of the imaging light 206, ASE 201, and / or beam 202. For example, as Figure 5 As shown, the controller 290 can receive the detected image from the sensing device 450 via the third sub-signal 298c.

[0081] In some embodiments, the optical arrangement 430 and the sensing device 450 may be configured to receive the ASE 201 from the gas discharge stage 220 for initial calibration. For example, the ASE 201 may be used as a beacon to guide the imaging light 206 aligned with the optical axis of the chamber 261, and to adjust (e.g., coarsely) the chamber 261 along the optical axis of the imaging light 206 (e.g., via the chamber adjuster 265). In some embodiments, both the imaging light 206 from the imaging device 400 and the ASE 201 from the chamber 261 may be aligned along the OC aperture 252 and the LNM aperture 272. For example, the imaging light 206 may be adjusted via the optical arrangement 430 to center the imaging light 206 on the OC aperture 252 and / or the LNM aperture 272.

[0082] In some embodiments, the input / output optics 250 (e.g., OC) can be aligned with the imaging light 206. For example, the optical arrangement 430 can be adjusted so that the imaging light 206 is focused onto the input / output optics 250 (e.g., onto the OC aperture 252). In some embodiments, a retractable retroreflector 470 can be inserted into the imaging light 206 to define a first alignment position (e.g., an XY digital image position). In some embodiments, the retractable retroreflector 470 can be removed from the imaging light 206, and the input / output optics 250 can be adjusted so that the imaging light 206 is focused from a second alignment position (e.g., an XY digital image position) onto the sensing device 450 from the first alignment position (e.g., an XY digital image position). For example, the far-field (FF) back reflection of the imaging light 206 from the input / output optics 250 (e.g., OC) can be imaged onto the sensing device 450 and adjusted (e.g., via the first optical resonator element 254) until (e.g., iteratively) the first and second alignment positions coincide (e.g., the same XY digital image positions).

[0083] In some embodiments, the spectral feature adjuster 270 (e.g., LNM) and chamber 261 can be aligned with beam 202 and / or ASE 201. For example, the beam profile of beam 202 at OC aperture 252 and / or LNM aperture 272 can be focused onto sensing device 450. In some embodiments, the vertical symmetry of beam 202 at OC aperture 252 can be measured using sensing device 450, and the spectral feature adjuster 270 (e.g., LNM) can be adjusted via TAM 274 to align the beam 202 reflected from the spectral feature adjuster 270 (e.g., LNM) with the optical axis of gas discharge stage 220 (e.g., MO cavity). For example, the near-field (NF) beam profile of beam 202 at OC aperture 252 can be imaged by sensing device 450. In some embodiments, the horizontal symmetry of the beam 202 at the OC aperture 252 can be measured using the sensing device 450, and the chamber 261 can be adjusted by the chamber adjuster 265 to align the beam 202 with the OC aperture 252. For example, the near-field (NF) beam profile of the beam 202 at the OC aperture 252 can be imaged by the sensing device 450. In some embodiments, the horizontal symmetry of the beam 202 at the LNM aperture 272 can be measured using the sensing device 450, and the chamber 261 can be adjusted by the chamber adjuster 265 to align the beam 202 with the LNM aperture 272. For example, the near-field (NF) beam profile of the beam 202 at the LNM aperture 272 can be imaged by the sensing device 450. In some embodiments, the alignment of the spectral feature adjuster 270 (e.g., LNM) and the chamber 261 with the beam 202 can occur simultaneously with the beam 202 used in the photolithography apparatus. For example, alignment can occur simultaneously with the beam 202 and / or the amplified beam 204 used in the radiation source SO of the lithography equipment LA.

[0084] Additional exemplary imaging device

[0085] Figure 7 and Figure 8 Imaging devices 400', 400" according to various exemplary embodiments are shown. Figure 7 An imaging device 400' with an optical arrangement 430' is shown, the optical arrangement 430' having a beam optical branch 460 configured to receive a beam 202 and / or ASE 201 and transmit it toward a sensing device 450'. Figure 8An imaging device 400" with an optical arrangement 430" is shown. The optical arrangement 430" has a beam optical branch 460" and a sensing device 450" having a first sensing device 450a configured to receive imaging light 206 and / or ASE 201 and a second sensing device 450b configured to receive beam 202 and / or ASE 201. In some embodiments, the first and second sensing devices 450a, 450b may be combined into a single sensing device (e.g., a single camera).

[0086] Figure 7 An imaging device 400' according to an exemplary embodiment is shown. Figure 5 and Figure 6 The embodiment of the imaging device 400 shown is similar to Figure 7 Embodiments of the imaging device 400' shown may be similar. Similar reference numerals are used to indicate... Figure 5 and Figure 6 Similar features of the embodiment of the imaging device 400 shown and Figure 7 Similar features to embodiments of the imaging device 400' shown. Figure 5 and Figure 6 The embodiment of the imaging device 400 shown is similar to Figure 7 The main difference between the embodiments of the imaging device 400' shown is that the imaging device 400' includes an optical arrangement 430' with a beam optical branch 460 configured to receive the beam 202 and transmit it toward the sensing device 450', rather than... Figure 5 and Figure 6 The optical arrangement 430 and sensing device 450 are shown.

[0087] Although the imaging device 400' is in Figure 7 While illustrated as a standalone device and / or system, embodiments of this disclosure can be used with other optical systems, such as, but not limited to, a radiation source SO, a lithography apparatus LA, a light source device 200, an imaging device 400, and / or other optical systems. In some embodiments, the imaging device 400' may be external to the 3D frame 210 of the light source device 200. For example, the imaging device 400' may be part of a separate external alignment and / or measurement tool.

[0088] like Figure 7 As shown, an exemplary aspect of the imaging device 400' is an optical arrangement 430' having a beam optical branch 460 configured to receive beam 202 and / or ASE 201. In some embodiments, the beam optical branch 460 may isolate beam 202 and / or ASE 201 and direct beam 202 and / or ASE 201 toward a sensing device 450' separated from the imaging light 206. For example, as Figure 7 As shown, the beam optics branch 460 may include coated optics configured to reflect a beam 202 and / or ASE 201 (e.g., a gas discharge medium 263 for ArF) at a specific wavelength (e.g., 193 nm).

[0089] The beam optics branch 460 may include a first DUV dielectric mirror 462, a DUV neutral density (ND) filter 464, a first DUV mirror 466, and a second DUV dielectric mirror 468. The first DUV dielectric mirror 462 may be configured to receive beam 202 and / or ASE 201 from the gas discharge stage 220, and reflect beam 202 (e.g., 193 nm) and / or ASE 201, and transmit imaging light 206 (e.g., 405 nm) and / or ASE 201. The first DUV dielectric mirror 462 may reflect beam 202 and / or ASE 201 toward the DUV ND filter 464 and the first DUV mirror 466. The first DUV mirror 466 may be configured to reflect beam 202 (e.g., 193 nm) and may include a UV fused silica or BK7 window. In some embodiments, the first DUV reflector 466 may be a window (e.g., a UV fused silica or BK7 window) configured to reflect the beam 202 (e.g., 193 nm) and reduce the intensity of the beam 202 (e.g., by a factor of 100:1). The second DUV dielectric reflector 468 may be configured to reflect the beam 202 and / or ASE 201 toward the sensing device 450' and transmit the imaging light 206 (e.g., 405 nm). Figure 7 As shown, for clarity, the imaging light 206 from the illuminator 410 in the optical arrangement 430' is omitted. The sensing device 450' is configured to receive only the beam 202 and / or ASE 201 for a specific measurement (e.g., beam contouring). In some embodiments, the first and second beam steering optics 432, 438, the first and second DUV medium reflectors 462, 468, and / or the first DUV reflector 466, similar to the optical arrangement 430, may each include a linear motor and / or actuator that provides adjustment (e.g., translation, tilt, rotation, etc.) and may be simultaneously adjusted to guide the beam 202 and / or ASE 201 toward the sensing device 450'.

[0090] Figure 8 An imaging device 400 according to an exemplary embodiment is shown. Figure 7 The embodiment of the imaging device 400' shown is similar to Figure 8 The embodiment of the imaging device 400 shown can be similar. Similar reference numerals are used to indicate... Figure 7 Similar features of the embodiment of the imaging device 400' shown and Figure 8Similar features to an embodiment of the imaging device 400 shown. Figure 7 The embodiment of the imaging device 400' shown is similar to Figure 8 The main difference between the embodiments of the imaging device 400" shown is that the imaging device 400" includes an optical arrangement 430" having a beam optical branch 460', which is configured to receive the beam 202 and transmit the beam 202 toward the sensing device 450" rather than Figure 7 The optical arrangement 430' shown, and the imaging device 400" includes a sensing device 450" having a first sensing device 450a configured to receive imaging light 206 and / or ASE 201 and a second sensing device 450b configured to receive light beam 202 and / or ASE 201, rather than Figure 7 The sensing device 450' shown is illustrated. In some embodiments, the first and second sensing devices 450a and 450b can be combined into a single sensing device (e.g., a single camera). In some embodiments, the first and second sensing devices 450a and 450b can be two separate, independent sensing devices, each with an independent camera.

[0091] Although the imaging device is 400" Figure 8 While illustrated as a standalone device and / or system, embodiments of this disclosure can be used with other optical systems, such as, but not limited to, a radiation source SO, a lithography apparatus LA, a light source device 200, an imaging device 400, an imaging device 400', and / or other optical systems. In some embodiments, the imaging device 400" may be external to the 3D frame 210 of the light source device 200. For example, the imaging device 400" may be part of a separate external alignment and / or measurement tool.

[0092] like Figure 8 As shown, an exemplary aspect of the imaging device 400" is an optical arrangement 430" having a first imaging lens 440a and a second imaging lens 440b configured to receive imaging light 206 and / or ASE 201, and a beam optical branch 460' configured to receive beam 202 and / or ASE 201. In some embodiments, the beam optical branch 460' may isolate beam 202 and / or ASE 201 and guide beam 202 and / or ASE 201 toward a sensing device 450" separate from the imaging light 206. For example, as Figure 8 As shown, the beam optical branch 460' may include coated optical elements configured to reflect a beam 202 and / or ASE 201 (e.g., a gas discharge medium 263 for ArF) at a specific wavelength (e.g., 193 nm).

[0093] The optical arrangement 430" may include a first imaging lens 440a,(multiple) first imaging lens positions 442a, a beam block 444, a second imaging lens 440b,(multiple) second imaging lens positions 442b, and a beam optical branch 460'. Similar to the imaging lens 440, the first and second imaging lenses 440a and 440b may each include a linear motor and / or actuator, which respectively provide adjustment (e.g., translation) of the first and second imaging lenses 440a and 440b along the optical axis (e.g., Y-axis direction) of the imaging beam 206 and / or ASE 201 and the optical axis (e.g., Y-axis direction) of the beam 202 and / or ASE 201 toward the sensing device 450". In some embodiments, such as Figure 8 As shown, the first imaging lens 440a can be adjusted to the imaging lens position 442a along the optical path of imaging light 206 and / or ASE 201 to select which object plane to image onto the first sensing device 450a. For example, the imaging lens position 442a(s) for imaging different object planes in the gas discharge stage 220 can image the object planes of the OC aperture 252, the first chamber aperture 264a, the second chamber aperture 264b, and / or the LNM aperture 272. In some embodiments, such as Figure 8 As shown, the second imaging lens 440b can be adjusted to the imaging lens position 442b along the optical path of beam 202 and / or ASE 201 to select which object plane is imaged onto the second sensing device 450b. For example, the imaging lens position 442b(s) used to image different object planes in the gas discharge stage 220 can image the object planes of the OC aperture 252, the first chamber aperture 264a, the second chamber aperture 264b, and / or the LNM aperture 272.

[0094] The beam optics branch 460' may include a first DUV dielectric mirror 462 and a DUV neutral density (ND) filter 464. The first DUV dielectric mirror 462 may be configured to receive beam 202 and / or ASE 201 from the gas discharge stage 220, and reflect beam 202 (e.g., 193 nm) and / or ASE 201, and transmit imaging light 206 (e.g., 405 nm) and / or ASE 201. The first DUV dielectric mirror 462 may reflect beam 202 and / or ASE 201 toward the DUV ND filter 464 and the second imaging lens 440b. The second sensing device 450b is configured to receive only beam 202 and / or ASE 201 for specific measurements (e.g., beam contouring). In some embodiments, similar to the first beam steering optics 432 of the optical arrangement 430, the first DUV medium reflector 462 may include a linear motor and / or actuator that provides adjustment (e.g., translation, tilting, rotation, etc.) and may be adjusted to guide the beam 202 and / or ASE201 toward the second sensing device 450b.

[0095] like Figure 8 As shown, an exemplary aspect of the imaging device 400" is a sensing device 450" having a first sensing device 450a configured to receive imaging light 206 (and / or ASE 201) and a second sensing device 450b configured to receive light beam 202 (and / or ASE 201). In some embodiments, the first sensing device 450a may be configured to receive imaging light 206 and / or ASE 201 and optimized for far-field (FF) detection of imaging light 206 (e.g., 405 nm). For example, imaging lens positions 442a may be used for far-field (FF) contouring of imaging light 206 reflected from input / output optics 250 (e.g., OC). In some embodiments, the second sensing device 450b may be configured to receive light beam 202 and / or ASE 201. 201 and optimize the near-field (NF) contouring of the beam 202 (e.g., 193 nm). For example, the imaging lens position 442b can be used for near-field (NF) contouring of the beam 202 at the OC aperture 252, the first chamber aperture 264a, the second chamber aperture 264b and / or the LNM aperture 272.

[0096] The first sensing device 450a may be configured to receive imaging light 206 based on the position of the first imaging lens 440a corresponding to the object plane of the first imaging lens(s) position 442a (e.g., the object plane of the OC aperture 252, the first chamber aperture 264a, the second chamber aperture 264b, and / or the LNM aperture 272). The first sensing device 450a may include a first camera 452a and a first camera neutral density (ND) filter 454a. The first camera 452a may be configured to measure imaging light 206 and / or ASE 201. For example, the first camera 452a may be optimized to detect visible wavelengths (e.g., 405 nm). In some embodiments, the first camera 452a may sense a two-dimensional (2D) representation of imaging light 206 and / or ASE 201. In some embodiments, the first camera 452a may include a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) camera. For example, the first camera 452a may include a thin-film back-illuminated CCD camera and / or a thin-film back-illuminated CMOS camera. In some embodiments, the first sensing device 450a may monitor and / or measure the 2D beam profile of the imaging light 206 and / or ASE 201, such as the far-field (FF) 2D beam profile. In some embodiments, the first camera ND filter 454a may include one or more wavelength filters.

[0097] The second sensing device 450b may be configured to receive the light beam 202 based on the position of the second imaging lens 440b corresponding to the object plane of the second imaging lens(s) position 442b (e.g., the object plane of the OC aperture 252, the first chamber aperture 264a, the second chamber aperture 264b, and / or the LNM aperture 272). The second sensing device 450b may include a second camera 452b and a second camera neutral density (ND) filter 454b. The second camera 452b may be configured to measure the light beam 202 and / or the ASE 201. For example, the second camera 452b may be optimized to detect a DUV wavelength (e.g., 193 nm). In some embodiments, the second camera 452b may sense a two-dimensional (2D) representation of the light beam 202 and / or the ASE 201. In some embodiments, the second camera 452b may include a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) camera. For example, the second camera 452b may include a thin-film back-illuminated CCD camera and / or a thin-film back-illuminated CMOS camera. In some embodiments, the second sensing device 450b may monitor and / or measure the 2D beam profile of the beam 202 and / or ASE 201, such as the near-field (NF) 2D beam profile. In some embodiments, the second camera ND filter 454b may include one or more wavelength filters.

[0098] Exemplary flowchart

[0099] Figure 9 A flowchart 900 for aligning a gas discharge stage 220 according to one embodiment is shown. It should be understood that it is not necessary... Figure 9 All steps in the document are used to perform the disclosure provided herein. Furthermore, some of the steps may be simultaneous, sequential, and / or combined with... Figure 9 The different execution orders shown are illustrated. (Refer to...) Figures 2 to 5 Flowchart 900 is described. However, flowchart 900 is not limited to these exemplary embodiments.

[0100] In step 902, as Figure 3 and Figure 5 As illustrated in the example, both the imaging light 206 from the imaging device 400 and the ASE 201 from the chamber 261 can be aligned with the OC aperture 252 of the input / output optics 250 (e.g., OC). In some embodiments, aligning both the imaging light 206 and the ASE 201 includes using the ASE 201 as a beacon to guide the imaging light 206, which is aligned with the optical axis of the gas discharge stage 220, and adjusting (e.g., coarsely) the chamber 261 along the optical axis of the gas discharge stage 220. For example, the imaging device 400 (e.g., first and second beam steering optics 432, 438) can guide the imaging light 206 onto the OC aperture 252 and image the ASE 201 onto the sensing device 450, and via the chamber adjuster 265 ( Figure 2 (As shown in the diagram) Adjust chamber 261 until the images of OC aperture 252 and ASE 201 overlap. In some embodiments, aligning both imaging light 206 and ASE 201 includes adjusting imaging light 206 using optical arrangement 430 to center imaging light 206 on OC aperture 252. For example, first and second beam steering optics 432, 438 may be adjusted (e.g., translated, tilted, rotated, etc.) until imaging light 206 is centered on OC aperture 252 (e.g., a rectangular opening) and detected by sensing device 450 at appropriate imaging lens position 442 (e.g., the object plane of OC aperture 252). In some embodiments, the deviation of the centroid of imaging light 206 from the center of OC aperture 252 may be less than ±0.1 mM.

[0101] In step 904, as Figure 4 and Figure 5As illustrated in the example, both the imaging light 206 from the imaging device 400 and the ASE 201 from the chamber 261 can be aligned with the LNM aperture 272 of the spectral feature adjuster 270 (e.g., LNM). In some embodiments, aligning both the imaging light 206 and the ASE 201 includes: using the ASE 201 as a beacon to guide the imaging light 206, which is aligned with the optical axis of the chamber 261, and adjusting (e.g., coarsely) the chamber 261 along the optical axis of the imaging light 206. For example, the imaging device 400 can guide the imaging light 206 onto the LNM aperture 272 and image the ASE 201 onto the sensing device 450, and via the chamber adjuster 265 ( Figure 2 (As shown in the diagram) Adjust chamber 261 until the images of LNM aperture 272 and ASE 201 overlap. In some embodiments, aligning both imaging light 206 and ASE 201 includes adjusting imaging light 206 using optical arrangement 430 to center imaging light 206 on LNM aperture 272. For example, first and second beam steering optics 432, 438 may be adjusted (e.g., translated, tilted, rotated, etc.) until imaging light 206 is centered on LNM aperture 272 (e.g., a rectangular opening) and detected by sensing device 450 at appropriate imaging lens position 442 (e.g., the object plane of LNM aperture 272). In some embodiments, the deviation of the centroid of imaging light 206 from the center of LNM aperture 272 may be less than ±0.1 mM.

[0102] In step 906, as Figure 3 and Figure 5As illustrated in the examples, an input / output optics element 250 (e.g., OC) can be aligned with an imaging beam 206. In some embodiments, aligning the input / output optics element 250 (e.g., OC) includes inserting a retractable retroreflector 470 into the imaging beam 206 and focusing the imaging beam 206 onto the sensing device 450 to define a first alignment position (e.g., an XY digital image position). In some embodiments, aligning the input / output optics element 250 (e.g., OC) includes removing the retractable retroreflector 470 from the imaging beam 206 and adjusting a first optical resonator element 254 until the far-field (FF) profile of the imaging beam 206 is translated from a second alignment position (e.g., an XY digital image position) on the sensing device 450 to the first alignment position (e.g., an XY digital image position). For example, sensing device 450 can image the far-field (FF) back reflection of imaging light 206 from input / output optics 250 (e.g., OC) onto sensing device 450, and first optical resonator element 254 can (e.g., angularly) adjust input / output optics 250 (e.g., OC) until the images at the first and second alignment positions overlap. In some embodiments, the deviation of the centroid of the reflected imaging light 206 from input / output optics 250 (e.g., OC) from the first alignment position (e.g., XY digital image position) defined using a retractable retroreflector 470 can be less than ±1 pixel (e.g., less than about 25 μrad angular error).

[0103] In step 908, as Figures 2 to 5 As illustrated in the example, the spectral feature adjuster 270 (e.g., LNM) and chamber 261 can be aligned with the beam 202. In some embodiments, aligning the spectral feature adjuster 270 (e.g., LNM) and chamber 261 includes conforming the beam 202 at the OC aperture 252 onto the sensing device 450. For example, the vertical symmetry of the beam 202 at the OC aperture 252 can be measured (e.g., imaging the near-field (NF) beam profile of the beam 202 at the OC aperture 252), and the spectral feature adjuster 270 (e.g., LNM) can be adjusted using the TAM 274 until any vertical asymmetry is reduced (e.g., the beam 202 is vertically symmetrical at the OC aperture 252). In some embodiments, the quantifiable alignment error of the vertical symmetry of the beam 202 at the OC aperture 252 can be less than approximately ±50 μrad (angle) error.

[0104] In some embodiments, aligning the spectral feature adjuster 270 (e.g., LNM) and the chamber 261 includes conforming the beam 202 at the OC aperture 252 onto the sensing device 450. For example, the horizontal symmetry of the beam 202 at the OC aperture 252 can be measured (e.g., imaging the near-field (NF) beam profile of the beam 202 at the OC aperture 252), and the chamber adjuster 265 ( Figure 2 As shown, chamber 261 is adjusted (e.g., finely) until any horizontal asymmetry is reduced (e.g., beam 202 is horizontally symmetrical at OC aperture 252). In some embodiments, the quantifiable alignment error of the horizontal symmetry of beam 202 at OC aperture 252 may be less than about ±50 μM (lateral) error and less than about ±50 μrad (angular) error.

[0105] In some embodiments, aligning the spectral feature adjuster 270 (e.g., LNM) and the chamber 261 includes conforming the beam 202 at the LNM aperture 272 onto the sensing device 450. For example, the horizontal symmetry of the beam 202 at the LNM aperture 272 can be measured (e.g., imaging the near-field (NF) beam profile of the beam 202 at the LNM aperture 272), and the chamber adjuster 265 (in Figure 2 (As shown in the figure) Adjust (e.g., fine) the chamber 261 until any horizontal asymmetry is reduced (e.g., the beam 202 at the LNM aperture 272 is horizontally symmetrical). In some embodiments, the quantifiable alignment error of the horizontal symmetry of the beam 202 at the LNM aperture 272 may be less than about ±50 μM (lateral) error and less than about ±50 μrad (angular) error.

[0106] In some embodiments, the alignment of the spectral feature adjuster 270 (e.g., LNM) and the chamber 261 with the beam 202 can occur simultaneously with the beam 202 used in the lithography apparatus. For example, the alignment can occur simultaneously with the beam 202 and / or the amplified beam 204 used in the radiation source SO of the lithography apparatus LA.

[0107] While specific references may be made herein to the use of lithography equipment in IC manufacturing, it should be understood that the lithography equipment described herein may have other applications, such as manufacturing 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. The substrate referred to herein may be processed before or after exposure in, for example, a track cell (a tool typically used to apply a resist layer to the substrate and develop the exposed resist), a measurement cell, or an inspection cell. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Furthermore, a substrate may be processed more than once, for example, to produce a multilayer IC; therefore, the term “substrate” as used herein may also refer to a substrate that already contains multiple processed layers.

[0108] While the embodiments have been specifically referenced above in the context of photolithography, it should be understood that the embodiments can be used in other applications, such as imprint lithography, and are not limited to photolithography where the context permits. In imprint lithography, the morphology in the patterning apparatus defines a pattern created on a substrate. The morphology of the patterning apparatus can be pressed into a resist layer provided to the substrate, and then the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. After the resist has been cured, the patterning apparatus is removed from the resist to leave a pattern therein.

[0109] It should be understood that the wording or terminology used herein is for descriptive rather than limiting purposes, and therefore the terminology or terminology used herein should be interpreted by those skilled in the art based on the teachings herein.

[0110] 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 thereon may also be patterned, or may remain unpatterned.

[0111] Implementations can be carried out in hardware, firmware, software, or any combination thereof. Implementations can also be implemented as instructions stored on a machine-readable medium that can be read and executed by one or more processors. Machine-readable media can include any mechanism for storing or transmitting information in a machine-readable form (e.g., a computing device). For example, machine-readable media 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, etc. Furthermore, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are merely for convenience, and such actions are actually produced by the computing device, processor, controller, or other device executing the firmware, software, routines, and / or instructions.

[0112] The following examples are illustrative and not restrictive of embodiments of this disclosure. Other suitable modifications and adaptations to various conditions and parameters that are commonly encountered in the art and will be apparent to those skilled in the art are within the spirit and scope of this disclosure.

[0113] While specific references may be made herein to the use of devices and / or systems in IC manufacturing, it should be clearly understood that such devices and / or systems have many other possible applications. For example, they may be employed in the manufacture of integrated optical systems, guiding and detection patterns for magnetic domain memories, LCD panels, thin-film magnetic heads, and so on. Those skilled in the art will understand that, in the context of such alternative applications, any use of the terms “mask,” “wafer,” or “die” herein should be considered to be replaced by the more general terms “mask,” “substrate,” and “target portion,” respectively.

[0114] While specific embodiments have been described above, it should be understood that embodiments may be practiced in ways other than those described. This description is not intended to limit the invention.

[0115] It should be understood that the "Detailed Description" section, rather than the "Summary" and "Abstract" sections, is intended to be used to interpret the claims. The "Summary" and "Abstract" sections may set forth one or more, but not all, exemplary embodiments contemplated by the inventors, and are therefore not intended to limit the embodiments and the appended claims in any way.

[0116] The embodiments have been described above using functional building blocks that illustrate the implementation of specific functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries can be defined as long as the specified functions and their relationships are properly performed.

[0117] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments that others can readily modify and / or adapt various applications of such specific embodiments by applying knowledge within the art without departing from the general concept of the embodiments, without excessive experimentation. Therefore, based on the teachings and guidance presented herein, such adaptations and modifications are intended to be within the equivalent meaning and scope of the disclosed embodiments.

[0118] Other aspects of the invention are set forth in the following numbered clauses.

[0119] 1. A light source device, comprising:

[0120] Gas discharge stage, including:

[0121] An optical amplifier, comprising a chamber configured to hold a gas discharge medium, the gas discharge medium outputting a light beam; and

[0122] A set of optical elements is configured to form an optical resonator around an optical amplifier;

[0123] Sensing devices;

[0124] The optical arrangement is configured to image light from multiple different object planes within the gas discharge stage onto a sensing device.

[0125] Adjustment equipment, which is in physical communication with one or more optical components within a gas discharge stage, and configured to modify at least one geometric aspect of the optical components; and

[0126] The control device communicates with the sensing device and the adjustment device, and is configured to provide signals to the adjustment device based on the output from the sensing device.

[0127] 2. The light source device according to Clause 1, wherein the chamber of the gas discharge stage includes a first optical port and a second optical port.

[0128] 3. The light source apparatus according to Clause 1, wherein one set of optical elements comprises:

[0129] Input / output optical elements, the input / output optical elements optically communicating with the first optical port; and

[0130] Spectral feature adjuster, which communicates optically with the second optical port.

[0131] 4. The light source device according to Clause 1, wherein the optical arrangement includes one or more focusing optical elements, the one or more focusing optical elements being adjustable along the optical path of the beam to select which object plane is imaged onto the sensing device.

[0132] 5. The light source device according to Clause 1, wherein the sensing device includes a camera that senses a two-dimensional representation of a light beam received by the sensing device.

[0133] 6. The light source device according to Clause 5, wherein the camera includes a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) camera.

[0134] 7. The light source device according to Clause 1, wherein the sensing device and optical arrangement are integrated within a three-dimensional frame that also houses the gas discharge stage.

[0135] 8. The light source apparatus according to Clause 1 further includes an illuminator configured to direct imaging light into a gas discharge stage.

[0136] 9. An imaging device, comprising:

[0137] An illuminator is configured to direct imaging light into a gas discharge stage of the output beam;

[0138] Sensing devices are configured to receive light beams and / or imaging light; and

[0139] The optical arrangement is configured to image light beams and / or imaging light from multiple different object planes within the gas discharge stage onto a sensing device.

[0140] 10. The imaging apparatus according to Clause 9, wherein the sensing device and optical arrangement are configured to receive amplified spontaneous emission (ASE) from a gas discharge stage for initial calibration.

[0141] 11. The imaging apparatus according to Clause 9, wherein the optical arrangement includes one or more focusing optical elements, the one or more focusing optical elements being adjustable along the optical path of the beam to select which object plane is imaged onto the sensing apparatus.

[0142] 12. The imaging apparatus according to Clause 9, wherein the sensing device includes a camera that senses a two-dimensional representation of a light beam received by the sensing device.

[0143] 13. Imaging apparatus according to Clause 12, wherein the camera includes a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) camera.

[0144] 14. The imaging apparatus according to Clause 9, wherein the imaging apparatus is integrated within a three-dimensional frame that also houses the gas discharge stage.

[0145] 15. A method for aligning a gas discharge stage, the gas discharge stage outputting a beam, and comprising a chamber having a first optical port and a second optical port, an input / output optical element in optical communication with the first optical port, and a spectral feature adjuster in optical communication with the second optical port, the method comprising:

[0146] Align the imaging light from the imaging device and the amplified spontaneous emission (ASE) from the chamber with the following:

[0147] The first aperture of the input / output optical element; and

[0148] The second aperture of the spectral feature adjuster;

[0149] Align the input / output optics at the first aperture with the imaging light; and

[0150] The spectral feature adjuster and chamber at the second aperture are aligned with the beam.

[0151] 16. The method according to Clause 15, wherein aligning both the imaging beam and the ASE comprises: using the ASE as a beacon to guide the imaging beam aligned with the optical axis of the gas discharge stage, and coarsely adjusting the chamber along the optical axis of the gas discharge stage.

[0152] 17. The method according to Clause 15, wherein aligning both the imaging light and the ASE comprises: adjusting the imaging light using an optical arrangement to center the imaging light on the first aperture and the second aperture.

[0153] 18. The method according to Clause 15, wherein aligning the input / output optical element at the first aperture comprises: inserting a retroreflector into the imaging light and focusing the imaging light onto the sensing device to define a first alignment position.

[0154] 19. The method according to Clause 18, wherein aligning the input / output optics at the first aperture comprises: removing the retroreflector and adjusting the input / output optics at the first aperture to align the imaging light to the back reflection on the sensing device from the second alignment position to the first alignment position.

[0155] 20. The method according to Clause 18, wherein aligning the input / output optics at the first aperture comprises: imaging imaging light from the input / output optics at the first aperture onto a sensing device via far-field back reflection.

[0156] 21. The method according to Clause 15, wherein aligning the spectral feature adjuster and the chamber at the second aperture includes: conforming the beam at the first aperture and / or the second aperture to the sensing device.

[0157] 22. The method according to Clause 21, wherein shaping the beam comprises: measuring the vertical symmetry of the beam at a first aperture, and adjusting the spectral feature adjuster at a second aperture using a tilt modulator (TAM).

[0158] 23. The method according to Clause 22, wherein measuring vertical symmetry includes: imaging the near-field beam profile of the beam at the first aperture.

[0159] 24. The method according to Clause 21, wherein shaping the beam comprises: measuring the horizontal symmetry of the beam at the first aperture and finely adjusting the chamber.

[0160] 25. The method according to Clause 24, wherein measuring horizontal symmetry includes: imaging the near-field beam profile of the beam at a first aperture.

[0161] 26. The method according to Clause 21, wherein shaping the beam comprises: measuring the horizontal symmetry of the beam at the second aperture and finely adjusting the chamber.

[0162] 27. The method according to Clause 26, wherein measuring horizontal symmetry includes: imaging the near-field beam profile of the beam at the second aperture.

[0163] 28. The method according to Clause 15, wherein the alignment of the spectral feature adjuster and the chamber at the second aperture occurs simultaneously with the beam used in the lithography apparatus.

[0164] The breadth and scope of the embodiments should not be limited by any of the exemplary embodiments described above, but should be limited only by the appended claims and their equivalents.

Claims

1. A light source apparatus, comprising: a gas discharge stage, comprising: an optical amplifier, comprising a chamber configured to hold a gas discharge medium, the gas discharge medium outputting a light beam; and a set of optical elements configured to form an optical resonator around the optical amplifier; a sensing apparatus; an optical arrangement configured to image light from a plurality of different object planes within the gas discharge stage onto the sensing apparatus, wherein the optical arrangement comprises one or more focusing optical elements that are adjustable along an optical path of the light beam to thereby select which object plane is imaged onto the sensing apparatus; an adjustment apparatus in physical communication with one or more optical components within the gas discharge stage and configured to modify at least one geometric aspect of the optical components; and a control apparatus in communication with the sensing apparatus and the adjustment apparatus, the control apparatus configured to provide a signal to the adjustment apparatus based on output from the sensing apparatus.

2. The light source apparatus of claim 1, wherein the chamber of the gas discharge stage comprises a first optical port and a second optical port.

3. The light source apparatus of claim 1, wherein the set of optical elements comprises: an input / output optical element in optical communication with a first optical port; and a spectral feature adjuster in optical communication with a second optical port.

4. The light source apparatus of claim 1, wherein the sensing apparatus comprises a camera that senses a two-dimensional representation of the light beam received by the sensing apparatus.

5. The light source apparatus of claim 4, wherein the camera comprises a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) camera.

6. The light source apparatus of claim 1, wherein the sensing apparatus and the optical arrangement are integrated within a three-dimensional frame that also houses the gas discharge stage.

7. The light source apparatus of claim 1, further comprising an illuminator configured to direct imaging light into the gas discharge stage.

8. An imaging apparatus, comprising: an illuminator configured to direct imaging light into a gas discharge stage that outputs a light beam, the illuminator being distinct from the gas discharge stage; a sensing apparatus; and an optical arrangement configured to selectively image the light beam and the imaging light from a plurality of different object planes within the gas discharge stage onto the sensing apparatus, wherein the optical arrangement comprises one or more focusing optical elements that are adjustable along an optical path of the light beam to thereby select which object plane is imaged onto the sensing apparatus.

9. The imaging apparatus of claim 8, wherein the sensing apparatus and the optical arrangement are configured to receive amplified spontaneous emission (ASE) from the gas discharge stage for initial calibration. ​ ​ 10. The imaging device of claim 8, wherein the sensing device comprises a camera that senses a two-dimensional representation of the light beam received by the sensing device.

11. The imaging device of claim 10, wherein the camera comprises a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) camera.

12. The imaging device of claim 8, wherein the imaging device is integrated within a three-dimensional frame that also houses the gas discharge stage.

Images