Pressure controlled spectral characteristic adjuster

Abstract

An apparatus includes a gas discharge system including a gas discharge chamber and configured to generate a light beam; and a spectral signature adjuster in optical communication with a precursor light beam generated by the gas discharge chamber. The spectral signature adjuster includes a body defining an interior maintained at a pressure below atmospheric pressure; at least one optical passage defined between the gas discharge chamber and the interior of the body, the optical passage being transparent to the precursor light beam; and an optical element set located within the interior, the optical element being configured to interact with the precursor light beam.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 62 / 824,525, filed on March 27, 2019, entitled “Pressure-Controlled Spectral Signature Adjuster,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The disclosed subject matter relates to a pressure controlled spectral signature modifier. Background Art

[0004] In semiconductor lithography (or photolithography), the manufacture of integrated circuits (ICs) requires the performance of a variety of physical and chemical processes on a semiconductor (e.g., silicon) substrate (also referred to as a wafer). A lithographic exposure device (also referred to as a scanner) is a machine that applies a desired pattern to a target area on a substrate. The substrate is irradiated with a beam of light generated by a light source. The wavelength of the beam is in the ultraviolet range, between visible light and X-rays, and thus has a wavelength between about 10 nanometers (nm) and about 400 nm. The wavelength of the beam may be in the deep ultraviolet (DUV) range, for example, where the wavelength may drop from about 100 nm to about 400 nm or in the extreme ultraviolet (EUV) range, where the wavelength is between about 10 nm and about 100 nm. These wavelength ranges are not exact, and there may be overlap between whether the light is considered DUV or EUV. Accurate knowledge of the spectral features or characteristics (e.g., bandwidth or wavelength) of the beam output from the light source and the ability to control these spectral features or characteristics are important. Summary of the invention

[0005] In some general aspects, a spectral signature adjuster includes a body defining an interior maintained at a pressure below atmospheric pressure; at least one optical pathway passing through the body, the optical pathway being transparent to a light beam having a wavelength in the ultraviolet range; a collection of optical elements located within the interior, the optical elements in the collection being configured to interact with the light beam, wherein the collection of optical elements includes one or more actuatable optical elements; and an actuation system located within the interior, the actuation system being in communication with the one or more actuatable optical elements and being configured to adjust physical aspects of the one or more actuatable optical elements.

[0006] Implementations may include one or more of the following features. For example, the spectral signature adjuster may include a vacuum port defined in a wall of the body, the vacuum port being in fluid communication with the interior and in fluid communication with a vacuum pump external to the spectral signature adjuster. The spectral signature adjuster may include a pressure sensor configured to measure pressure within the interior.

[0007] The optical element set may include a refractive element set and a diffractive element. Each refractive element may be a prism, and the diffractive element may be a grating. The refractive element set may include a set of four prisms.

[0008] The actuation system may include an actuator for each actuatable optical element, the actuator being configured to adjust a physical aspect of the actuatable optical element.

[0009] The spectral signature adjuster may further include an actuation interface defined in the body, the actuation interface being in communication with the actuation system and a control system external to the spectral signature adjuster.

[0010] The interior can be maintained at a pressure of 16 kilopascals (kPa) or less, 12 kPa or less, or 8 kPa or less. The interior can be maintained within an operating pressure of 400 Pascals (Pa) or within an operating pressure of 140 Pa or within an operating pressure of 20 Pa.

[0011] The interior may lack helium. The interior may include a purge gas. The purge gas may include nitrogen.

[0012] The body may include a purge port fluidly connecting the interior to a source of purge gas.

[0013] At least a portion of the body may be defined by a motion damping device that is physically coupled to a gas discharge body of the gas discharge chamber, and an optical pathway may extend through an interior of the motion damping device and through an optical port defined in the gas discharge body. The body may be hermetically sealed, and the interior of the motion damping device may be maintained at the same pressure as the interior of the body.

[0014] In other general aspects, an apparatus includes a gas discharge system including a gas discharge chamber and configured to generate a light beam; and a spectral signature adjuster in optical communication with a precursor light beam generated by the gas discharge chamber. The spectral signature adjuster includes a body defining an interior maintained at a pressure below atmospheric pressure; at least one optical passage defined between the gas discharge chamber and the interior of the body, the optical passage being transparent to the precursor light beam; and an optical element set located within the interior, the optical element being configured to interact with the precursor light beam.

[0015] Implementations may include one or more of the following features. For example, the device may include a control device that is in communication with the gas discharge system and the spectral signature adjuster. The device may include a pressure sensor that is configured to measure the pressure within the interior. The control device may include a pressure module that is in communication with the pressure sensor and is configured to receive the measured pressure and determine whether the measured pressure is within an acceptable pressure range. The device may also include a vacuum pump. The spectral signature adjuster may include a vacuum port that is defined in the body and is in fluid communication with the interior and the vacuum pump. The pressure module may be in communication with the vacuum pump and may be configured to control the operation of the vacuum pump based at least in part on a determination of the measured pressure.

[0016] The spectral signature adjuster may include an actuation system located within the interior, the actuation system communicating with one or more optical elements in the interior and configured to adjust physical aspects of the one or more optical elements to adjust one or more spectral signatures of the precursor light beam. The control device may include a spectral signature module communicating with the actuation system, the spectral signature module configured to receive an estimate of the one or more spectral signatures of the light beam and adjust a signal to the actuation system based on the received estimate.

[0017] The apparatus may further include a purge gas source in fluid communication with the interior. The control apparatus may include a purge gas module in communication with the purge gas source and configured to control the flow of the purge gas from the purge gas source into the interior.

[0018] The gas discharge system may include a first gas discharge stage including a gas discharge chamber configured to generate a seed beam from a precursor beam; and a second gas discharge stage configured to receive the seed beam and amplify the seed beam to produce a beam by the gas discharge system. The first gas discharge stage including the gas discharge chamber may house an energy source and may contain a gas mixture including a first gain medium; and the second gas discharge stage may include a gas discharge chamber housing the energy source and containing a gas mixture including a second gain medium.

[0019] The gas discharge chamber may house the energy source and contain a gas mixture including a first gain medium.

[0020] The interior may be maintained at a pressure equal to or lower than 16 kPa, equal to or lower than 12 kPa, or equal to or lower than 8 kPa.

[0021] The body may include a primary body housing a collection of optical elements, and a motion damping device located between the body and a gas discharge body of a gas discharge chamber, the interior of the motion damping device providing at least a portion of an optical pathway between the gas discharge chamber and the interior. The apparatus may include an optical window located between the motion damping device and the gas discharge chamber, the optical window providing an airtight isolation between the interior of the body and the gas discharge chamber. The interior of the motion damping device and the interior of the body may be fluidly open to each other such that the interior of the motion damping device and the interior of the body are at the same pressure.

[0022] In other general aspects, a method of controlling a spectral signature of a light beam includes: while operating a gas discharge system in a standby mode: injecting a purge gas into the interior of a body of a spectral signature adjuster; and pumping a substance out of the interior of the spectral signature adjuster body until the pressure inside the interior of the spectral signature adjuster body is below atmospheric pressure. The method includes: determining whether the pressure inside the interior of the spectral signature adjuster body is within an operating range of pressure; and if it is determined that the pressure inside the interior of the spectral signature adjuster body is within the operating range of pressure, switching from operating the gas discharge system in the standby mode to operating the gas discharge system in the output mode.

[0023] Implementations may include one or more of the following features. For example, the method may include: while operating the gas discharge system in an output mode: determining whether the pressure inside the interior of the spectral signature adjuster body is within an operating range of pressure; and if it is determined that the pressure inside the interior of the spectral signature adjuster body is outside the operating range of pressure, adjusting the pressure inside the spectral signature adjuster body. If it is determined that the pressure inside the interior of the spectral signature adjuster body is higher than the operating range of pressure, the method may include: adjusting the pressure inside the spectral signature adjuster body includes: pumping a substance out of the interior of the spectral signature adjuster body. Adjusting the pressure inside the spectral signature adjuster body may include opening the interior of the spectral signature adjuster body to the atmosphere in a controlled manner or stopping pumping a substance out of the interior of the spectral signature adjuster body.

[0024] The operating range of pressure may be centered around an operating pressure at or below 16 kPa, at or below 12 kPa, or at or below 8 kPa. The operating range of pressure may be 400 Pa, 140 Pa, or 20 Pa.

[0025] The method may also include, before operating the gas discharge system in the standby mode, hermetically sealing the interior of the spectral signature adjuster body with a gas discharge cavity of the gas discharge system, the gas discharge cavity being optically connected to the interior of the spectral signature adjuster of the gas discharge system through an optical pathway. The gas discharge system may be operated in the output mode by directing the precursor beam between the gas discharge cavity and the interior of the spectral signature adjuster body so that the precursor beam interacts with an optical element within the interior of the spectral signature adjuster body. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a block diagram of a spectral signature adjuster including a body defining an interior having a controlled environment and housing an optical element configured to interact with a light beam;

[0027] Figure 2 is a diagram showing the communication between the inside of the spectral feature adjuster and the outside of the spectral feature adjuster Figure 1 A block diagram of an implementation of a spectral feature adjuster;

[0028] Figure 3 is a diagram showing details of the actuation system coupled to the optical element Figure 1 A block diagram of an implementation of a spectral feature adjuster;

[0029] Figure 4 is configured to interact with the precursor beam from the gas discharge system Figure 1 A block diagram of an implementation of a spectral feature adjuster;

[0030] Figure 5 is a diagram showing details of the optical path between the gas discharge system and the spectral characteristic adjuster Figure 4 A block diagram of an implementation of a spectral feature adjuster;

[0031] Figure 6 The invention shows the implementation of the optical path between the gas discharge system and the spectral characteristic adjuster and the implementation of the gas discharge system. Figure 4 and Figure 5 A block diagram of an implementation method of a spectrum characteristic adjuster;

[0032] Figure 7 is a diagram showing a two-stage implementation of a gas discharge system. Figures 4 to 6 A block diagram of an implementation method of a spectrum characteristic adjuster;

[0033] Figure 8 is a diagram showing a single-stage implementation of a gas discharge system. Figures 4 to 6 A block diagram of an implementation method of a spectrum characteristic adjuster;

[0034] Fig.9A yes Figures 1 to 6 A top view of an implementation method of a spectral feature adjuster;

[0035] Fig. 9B is a diagram showing how the beam behaves as Fig.9A Schematic diagram of the interaction of optical elements of a prism in a spectral characteristic adjuster;

[0036] Fig. 10A and Fig. 10B yes Fig.9A Top and bottom perspective views of a main body of a spectral signature adjuster;

[0037] Fig.11 is with Figures 1 to 8 A graph of a spectrum diagram of a light beam interacting with a spectral characteristic modulator; and

[0038] Fig.12 It is used to control Figures 1 to 8 Flow chart of the implementation of the process of spectral signature adjustment within the pressure regulator. DETAILED DESCRIPTION

[0039] refer to Figure 1 , the spectral feature adjuster 100 includes a body 102 defining an interior 104. The spectral feature adjuster 100 includes at least one optical passage 106 defined in the body 102, the optical passage 106 being configured to be transparent to a light beam 108 having a wavelength in the ultraviolet range. Thus, the optical passage 106 is transparent to a light beam 108 having a wavelength between about 10 nanometers (n) and about 400 nm. In some implementations in which the spectral feature adjuster 100 incorporates a deep ultraviolet (DUV) light source, the optical passage 106 is transparent to a light beam 108 having a wavelength in the DUV range (e.g., from about 100 nm to about 400 nm). The light beam 108 may be a light beam that emits light not in a continuous mode but in the form of light pulses.

[0040] The spectral feature adjuster 100 includes a set 100 of optical elements 110-i, where i is a positive integer. In this example, four optical elements 110-1, 110-2, 110-3, 110-4 (i=4) are shown, but the set 110 may include less than four or more than four optical elements 110-i. Each optical element 110-i in the set 110 is configured to optically interact with the light beam 108. This means that the light beam 108 is optically modified by the interaction with each optical element 110-i. Thus, for example, the light beam 108 may be refracted, reflected, deflected, diffracted, transmitted, expanded or contracted or amplified due to its interaction with one or more optical elements 110-i in the optical elements 110-i. Each optical element 110-i in the set may be different from other optical elements 110-i in the set. As an example, one or more optical elements in the optical element 110-i may be a refractive optical element such as a prism. As another example, one or more of the optical elements 110-i can be a reflective optical element such as a mirror or a beam splitter. At least one of the optical elements 110-i can be a diffractive optical element such as a grating. In operation, the light beam 108 is directed to the spectral characteristic adjuster 100 and the light beam 108 is adjusted based on how the light beam 108 optically interacts with the optical element 110-i. In this way, one or more spectral characteristics (such as bandwidth or wavelength) of the light beam 108 can be adjusted.

[0041] At least some of the optical elements 110-i are actuatable. Figure 1In the illustrated implementation, the optical elements 110-1, 110-2, 110-4 are actuatable. The actuatable optical elements 110-1, 110-2, 110-4 are physically adjustable in a manner such that their interaction with the light beam 108 can be modified. Adjustment of the actuatable optical elements 110-1, 110-2, or 110-4 can occur while the light beam 108 is interacting with the actuatable optical elements 110-1, 110-2, or 110-4 or while there is no interaction between the light beam 108 and the actuatable optical elements 110-1, 110-2, or 110-4. The actuatable optical elements 110-1, 110-2, 110-4 are physically adjustable in that one or more physical aspects of each of the actuatable optical elements 110-1, 110-2, 110-4 are adjustable. For example, the physical aspects of each of the actuatable optical elements 110-1, 110-2, 110-4 can be physically adjusted by being rotated, translated, vibrated, twisted, and / or warped. For example, the actuatable optical element 110-1 can be configured to rotate while the actuatable optical element 110-2 can be configured to translate. In other examples, a property such as a refractive index of the actuatable optical element 110-4 can be configured to be modulated. Moreover, different actuatable optical elements 110-1, 110-2, 110-4 can be physically adjusted in different ways.

[0042] The spectral feature adjuster 100 also includes an actuation system 120 housed within the interior 104. The actuation system 120 is in communication with one or more of the actuatable optical elements 110-1, 110-2, 110-4. As such, the actuation system 120 is configured to affect adjustment of physical aspects of the actuatable optical elements 110-1, 110-2, 110-4. The implementation of the optical element 110-i set 110 and the actuation system 120 is described in detail in detail below. Figure 3 and Fig.9A supply.

[0043] The environment within the interior 104 of the body 102 can be controlled to reduce damage that may occur to components exposed to the interior 104, such as the optical elements 110-i and the actuation system 120 in the set 110. Certain chemicals, elements, or mixtures can damage the optical elements 110-i or adversely affect how the light beam 108 interacts with the optical elements 110-i. As an example, oxygen can attenuate the light beam 108 while it is interacting with the optical elements 110-i in the set 110. While interacting with the light beam 108, oxygen can produce other unwanted chemicals, such as ozone, which can damage the optical elements 110-i and / or the actuation system 120. Other chemicals, elements, or mixtures can further heat up during operation of the spectral feature adjuster 100 (that is, while the light beam 108 interacts with the optical elements 110-i). When heated, some chemicals, elements, or mixtures can produce large changes in the refractive index of the path that the light beam 108 traverses within the interior 104, and this can produce undesirable thermal lensing effects. Ultimately, these problems lead to degradation in the operation of the spectral signature adjuster 100. Specifically, these problems lead to a decrease in the accuracy with which the spectral signature adjuster 100 controls or adjusts one or more spectral signatures of the light beam 108, and may also lead to degradation in other performance parameters such as the energy or power of the light beam 108.

[0044] As such, unwanted chemicals, elements, or mixtures are removed from the interior 104 during operation of the spectral signature adjuster 100 (that is, while the light beam 108 is interacting with one or more of the optical elements 110-i) or at other times. For example, another chemical (in the form of a gas) such as nitrogen or helium may be used to purge oxygen from the interior 104. However, the use of a purge gas may result in pressure and refractive index transients within the interior 104 because the purge gas flows through the path of the light beam 108. Such transients may result in transients in the spectral signature or performance parameters of the light beam 108. In order to reduce these transients and also reduce the amount or need for purge gas, the interior 104 is maintained at a pressure P below atmospheric pressure. ATM Pressure P I In fact, by maintaining a vacuum environment within the interior 104, the need to use helium as a purge gas may be eliminated.

[0045] It is also possible to maintain the interior 104 at a subatmospheric pressure P IThe density of any purge gas (such as nitrogen) used in the body 102 can be reduced. Additionally, the refractive index of the purge gas in the interior 104 is a function of the density, pressure, and temperature of the purge gas. Reducing the density and pressure of the purge gas in the interior 104 significantly reduces undesirable thermal lensing effects due to changes in the refractive index that occur with changes in the purge gas temperature. Reducing the purge gas density in the interior 104 also reduces the convective heat transfer rate from the optical components to the purge gas, thereby reducing the rate at which the temperature of the purge gas rises.

[0046] The pressure P of the interior 104 is controlled (e.g., by a control device, as discussed below) I , so that the pressure P I Maintain within the acceptable pressure range and also reduce the pressure P I fluctuations during operation of the spectral signature adjuster 100 .

[0047] To maintain the vacuum environment within the interior 104, as discussed below, the body 102 is designed to withstand a pressure differential between the interior 104 and an area outside the body 102. Additionally, as discussed below, the actuation system 120 is also designed to withstand a reduced pressure P within the interior 104. I Also, purge gas can still be used, although perhaps not as much purge gas is needed.

[0048] In some implementations, the pressure P in the interior 104 is I Maintain operating pressure P O The operating pressure is within the acceptable range ΔP. O The pressure outside the body 102 is about one atmosphere (atm), which is about 101 kPa (or about 760 Torr). In some implementations, the pressure P I Maintain an operating pressure of about 400Pa O , operating pressure P of 133Pa O Or 13Pa operating pressure P O within the range.

[0049] In order to maintain the pressure P in the interior 104 I Below atmospheric pressure P ATMThe optical passage 106 may include an optical window 107 formed in a wall of the body 102 and also enable the passage of the light beam 108. The optical window 107 is made of a material that is transparent to the wavelength of the light beam 108 and is also configured to withstand the pressure difference between the interior 104 and the exterior of the body 102. The optical window 107 may be made of a material that is capable of transmitting very high pulse energy laser pulses at very short wavelengths (such as a DUV wavelength of 193 nanometers (nm) or 248 nm) with minimal losses. For example, the optical window 107 may be a crystalline structure made of calcium fluoride (CaF2), magnesium fluoride (MgF2), or fused quartz. In some implementations (such as Figure 5 and Figure 6 In the implementation shown), the surface normal of the optical window is not parallel to the direction of the light beam 108 to prevent unwanted reflections of the light beam 108 from traveling along the path of the light beam 108.

[0050] refer to Figure 2 , the spectral feature adjuster 100 is implemented as a spectral feature adjuster 200. The spectral feature adjuster 200 includes a body 202 made of a solid non-reactive material that can withstand an internal pressure P I With external pressure P ATM The body 202 may be made in multiple parts that are hermetically sealed using suitable sealing devices such as O-rings or gaskets. The body 202 may be machined to allow communication between the exterior and the interior 104 through the body 202.

[0051] For example, communication can be achieved through a feedthrough or a vacuum port. Communication through the body 202 can be fluid-based (for gas to flow into or out of the interior 104). An example of fluid-based communication through the body 202 is a vacuum port for pumping substances out of the interior 104 or a port for passing a purge gas into the interior 104. Communication through the body 202 can be electromagnetic-based, for passing electromagnetic signals into and out of the interior 104. An example of electromagnetic-based communication through the body 202 is a feedthrough of a cable type suitable for transmitting electromagnetic signals. For example, a coaxial, multi-pin or power feedthrough can be located in the body 202. Communication through the body 202 can be mechanical-based. For example, a motion feedthrough can be used to provide precise repeatable motion or rough positioning. Communication through the body 202 can be thermal-based. For example, the body 202 can include one or more thermocouple feedthroughs, which are designed to transmit signals through the wall of the body 202 by means of thermocouple material pairs. Communication through the body 202 can be optically based. For example, body 202 may be fitted with one or more optical windows, such as optical window 107 , each of which is hermetically sealed and permits light to pass between interior 104 and an exterior of body 202 .

[0052] In some implementations, the body 202 is formed of a wall or structure made of stainless steel. Figure 2 Examples of communications through body 202 are discussed.

[0053] The body 202 is configured with a vacuum port 222 defined in a wall of the body 202. The vacuum port 222 is in fluid communication with the interior 104 and also in fluid communication with a vacuum pump 224 external to the body 202 of the spectral signature adjuster 200. The operation of the vacuum pump 224 is controlled by a pressure control module 226.

[0054] The body 202 also receives a pressure sensor 228 that is configured to measure the pressure P within the interior 104 of the body 202. I In some implementations, the pressure sensor 228 is mounted inside the interior 104 of the body 202, as shown at A. In other implementations, the pressure sensor 228 is mounted in a gas feedthrough to the vacuum pump 224, as shown at B. This arrangement of the pressure sensor 228 in the gas feedthrough to the vacuum pump 224 ensures that the pressure sensor 228 is more protected from reflections of the light beam 108 and stray radiation generated by the light beam 108. The pressure sensor 228 can be a light-based oxygen (O2) sensor, such as an optical dissolved oxygen sensor from Mettler Toledo.

[0055] The body 202 includes an actuation interface 229 that provides a feedthrough (that is, a hermetically sealed link or passage) for any communication between components of the actuation system 120 and the external spectral signature control module 232. This communication can be electrical or mechanical. Thus, the actuation interface 229 can include one or more hermetically sealed feedthroughs, each of which corresponds to a specific communication or to a communication with a specific component of the actuation system 120.

[0056] If a purge gas is used in the interior 104, the body 202 also includes a purge port 234 that provides a fluid path to a purge gas source 236. Under the control of a purge gas control module 238 (which may include one or more fluid control valves), the purge gas may be released into the interior 104 through the purge port 234. The purge gas may be any non-reactive gas, such as nitrogen (N2), neon (Ne), argon (Ar), or carbon dioxide (CO2). Moreover, because the interior 104 is maintained at a sub-atmospheric pressure, the use of an inert gas such as helium as a purge gas may be avoided.

[0057] refer to Figure 3In some implementations, the actuation system 120 is configured as an actuation system 320 that includes an actuator 320-i for each actuatable optical element 110-i, the actuator 320-i being configured to adjust a physical aspect of the actuatable optical element 110-i. For example, the actuation system 320 includes actuators 320-1, 320-2, and 320-4 that are coupled to the optical elements 110-1, 110-2, and 110-4, respectively. The link between the actuator 320-i and its corresponding optical element 110-i can be physical. For example, the optical element 110-1 can be mounted on a movable mount that serves as the actuator 320-1. Such a mount can be rotatable, translatable, or both rotatable and translatable. As another example, the optical element 110 - 2 may be mounted to a device that changes the shape of the optical element 110 - 2 , such as by bending.

[0058] refer to Figure 4 , the device 430 includes a spectral signature adjuster 400 configured to receive a precursor beam 408 generated by a gas discharge system 440. Similar to the spectral signature adjuster 100, the spectral signature adjuster 400 includes a body 402 defining an interior 404. The spectral signature adjuster 400 includes at least one optical passage 406 defined in the body 402, the optical passage 406 being configured to be transparent to the precursor beam 408 having a wavelength in the ultraviolet range. Thus, the optical passage 406 is transparent to a beam having a wavelength between about 10 nanometers (nm) and about 400 nm or in the DUV range (e.g., from about 100 nm to about 400 nm). The optical passage 406 can be adapted with an optical window 407 similar to the optical window 107.

[0059] The spectral feature adjuster 400 includes a set 410 of optical elements 410-i, where i is a positive integer. In this example, five optical elements 410-1, 410-2, 410-3, 410-4, 410-5 (that is, i=5) are shown, but the set 410 may include less than five or more than five optical elements 410-i. Each optical element 410-i in the set 410 is configured to optically interact with the precursor beam 408. This means that the precursor beam 408 is optically modified by the interaction with each optical element 410-i. Therefore, for example, the beam 408 may be refracted, reflected, deflected, diffracted, transmitted, expanded or contracted, or amplified due to its interaction with the optical element 410-i. Each optical element 410-i in the set may be different from the other optical elements 410-i in the set. As discussed above, one or more of the optical elements 410-i can be refractive optical elements such as prisms, reflective optical elements such as mirrors or beam splitters, and / or diffractive optical elements such as gratings. In operation, the precursor beam 408 is directed to the spectral feature adjuster 400, which adjusts the precursor beam 408 based on how the precursor beam 408 optically interacts with the optical elements 410-i. In this way, the spectral feature adjuster 400 modifies one or more spectral features (such as bandwidth or wavelength) of the precursor beam 408.

[0060] The gas discharge system 440 is configured to generate a light beam 432 from the precursor beam 408. The light beam 408 may be a light beam that emits light not in a continuous mode but in the form of optical pulses. Thus, the light beam 432 output from the gas discharge system 440 is also a pulsed light beam 432. The light beam 432 may be provided to an apparatus 444, such as a lithography exposure apparatus for patterning of the substrate W, or it may be subjected to other optical processing (such as optical amplification, coherence reduction, etc.) before being used in the apparatus.

[0061] refer to Figure 5 In some implementations, the device 430 is designed as a device 530, which includes a spectral feature adjuster 500 configured to receive a precursor beam 408 generated by a gas discharge system 540. The gas discharge system 540 includes a gas discharge body 541 defining a gas discharge chamber 542. The gas discharge system 540 may include Figure 5 Other components not shown, such as a second gas discharge body and chamber and beam modification optics. Gas discharge system 540 outputs beam 432 for use by lithographic exposure apparatus 444.

[0062] The spectral feature adjuster 500 includes a body 502, which includes a primary body 502A configured to accommodate a set 410 of optical elements 410-i. The body 502 includes a secondary body 502B, which is a motion damping device between the primary body 502A and a gas discharge body 541 defining a gas discharge chamber 542. Therefore, the interior 504 extends from the primary interior 504A (defined by the body 502A) and the secondary interior 504B (defined by the secondary body 502B). The interior 504B of the motion damping device 502B and the interior 504A of the primary body 502A are in fluid communication with each other, so that the interior 504B of the motion damping device 502B is at the same pressure (P I ). Light beam 408 passes through secondary interior 504B while traveling along optical pathway 506. Thus, interior 504B of motion damping device 502B provides at least a portion of optical pathway 506 between gas discharge chamber 542 and interior 504.

[0063] The optical pathway 506 includes an optical window 507 located between the motion damping device 502B and the gas discharge chamber 542. The interior of the secondary body 502B extends from the optical window to the interior 504. The optical window 507 provides a gas-tight separation between the interior 504 of the body 502 and the gas discharge chamber 542. In this implementation, the optical window 507 is fitted in the gas discharge body 541.

[0064] The motion damping device 502B can be any device that mechanically insulates the body 502 from the gas discharge body 541 so as to reduce or prevent vibrations in one of the bodies (such as the gas discharge body 541) from affecting the other of the bodies (such as the body 502). For example, vibrations in the gas discharge body 541 are damped by the motion damping device 502B and vibrations in the body 502 are damped by the motion damping device 502B. In some implementations, the motion damping device 502B is a bellows. The bellows can also provide compensation to balance thermal expansion and installation tolerances (e.g., height differences or angular offsets) between the body 502 and the gas discharge body 541.

[0065] The bellows 502B may be an edge-welded bellows 502B, which means that it is welded to the gas discharge body 541 to provide a gas-tight seal. I -P ATM ), so the bellows 502B can shrink or expand. Therefore, the wall of the bellows 502B needs to be configured to withstand this pressure difference.

[0066] like Figure 5As shown in the illustration, the optical window 507 can be cut and tilted in a special way so that when the light beam 408 interacts with the optical window 507, its normal N is not aligned with the path or axial direction D_408 of the light beam 408 (that is, not parallel).

[0067] Implementation 630 of apparatus 530 illustrates various aspects of control in Figure 6 In Figure 6 In the embodiment of the present invention, the spectral characteristic adjuster 600 is configured to receive the precursor beam 408 generated by the gas discharge system 640. Figure 5 Similar to the device 530 of FIG. 5 , the gas discharge system 640 includes a gas discharge body 641 defining a gas discharge chamber 642, and the spectral feature adjuster 600 includes a body 602, the body 602 includes a primary body 602A, the primary body 602A is configured to accommodate the optical element 410-i set 410. The body 602 includes a secondary body 602B, the secondary body 602B is a motion damping device between the primary body 602A and the gas discharge body 641. The interior of the motion damping device 602B sets at least a portion of the optical path 606 between the gas discharge chamber 642 and the interior 604. The gas discharge system 640 may include Figure 6 Other components not shown.

[0068] The device 630 includes a control device 650 in communication with the gas discharge system 640 and the spectral characteristic adjuster 600. The control device 650 includes various modules 626, 638, 631, 643 that are dedicated to controlling certain aspects of the device 630. Other modules (not shown) can be included in the control device 650 for controlling other aspects of the device 630. Moreover, each of the modules 626, 638, 631, 643 can be co-located or proximate to the aspect that is respectively controlled.

[0069] The control device 650 may include a light source control module 643 configured to communicate with one or more elements, components, or systems within the gas discharge system 640. The light source control module 643 may be placed closer to the gas discharge system 640 than other modules in the control device 650. For example, the light source control module 643 may include a power control submodule for controlling power to one or more elements, components, or systems within the gas discharge system 640. As another example, the light source control module 643 may include a fluid control submodule for controlling one or more gas components within the gas discharge chamber 642 or any other gas discharge chamber within the gas discharge system 640.

[0070] The control device 650 includes a pressure control module 626 that communicates with a vacuum pump 624 and a pressure sensor 628 in the interior 604. The vacuum pump 624 is in fluid communication with the interior 604 of the body 602 through a vacuum port 622 defined in the body 602. Thus, the operation of the vacuum pump 224 is based on the measured pressure P from the pressure sensor 628. I The pressure control module 626 is configured to receive the measured pressure P from the pressure sensor 628. I And determine the measured pressure P I Is the operating pressure P O As discussed above, the operating pressure P O Can be equal to or lower than about 16 kilopascals (kPa). In some implementations, the pressure P I Maintain operating pressure at about P O In other words, P I Keep in P O + / -200Pa. In other implementations, the pressure P I Maintain the operating pressure P O In the vicinity of about 140Pa; that is, P I Keep until P O + / -70Pa. In other implementations, the pressure P I Maintain the operating pressure P O In other words, P I Keep until P O + / -10Pa.

[0071] The control device 650 includes a spectral signature control module 631. The spectral signature control module 631 communicates with the actuation system 120 by way of an actuation interface 629, which provides communication through the body 602. In some implementations, the actuation interface 629 can be a single feedthrough that provides one or more interfaces for electromagnetic signals between the spectral signature control module 631 and the actuation system 120. In other implementations, the actuation interface 629 can include multiple feedthroughs (such as Fig.9A and Fig. 10B ), wherein each feedthrough provides an interface for electromagnetic signals between the spectral signature control module 631 and one of the actuators in the actuation system 120 (such as any of the actuators 320-i). Alternatively, the communication between the spectral signature control module 631 and the actuation system 120 may be wireless, in which case the actuation interface 629 is not required.

[0072] The spectral signature control module 631 sends one or more signals to the actuation system 120 to instruct the actuation system 120 to adjust or modify one or more optical elements 410-i, thereby adjusting at least one spectral signature (such as wavelength or bandwidth) of the precursor beam 408. The modification of the spectral signature of the precursor beam 408 also modifies the spectral signature of the beam 432 generated by the precursor beam 408. As discussed above, the beam 432 output from the gas discharge system 640 can be supplied to the photolithography exposure device 444, which uses the beam 432 to pattern a substrate. Therefore, the spectral signature control module 631 can communicate with the photolithography exposure device 444 to receive instructions regarding the desired spectral signature of the beam 432. A communication channel (which can be a wired channel or a wireless channel) can be provided between the spectral signature control module 631 and the photolithography exposure device 444. The information received by the spectral signature control module 631 from the photolithography exposure device 444 can include a request from the photolithography exposure device 444 to change one or more characteristics of the beam 432.

[0073] For example, lithographic exposure device 444 sets requirements for the value of one or more spectral characteristics of beam 432 in order to produce a desired patterning or lithographic result on a substrate. Depending on the patterning of the substrate, lithographic exposure device 444 requires a specific spectral characteristic or set of spectral characteristics from beam 432.

[0074] In one example, the lithographic exposure device 444 requires that each pulse of the light beam 432 has a spectral characteristic selected from a plurality of discrete spectral characteristics when used to pattern a substrate. It may be desirable that the wavelength of the light beam 432 changes between a set of discrete different values ​​on a pulse-to-pulse basis. This may mean that the wavelength changes for each adjacent consecutive pulse. Alternatively, the wavelength changes every other pulse (so that the wavelength remains at one discrete value for two consecutive pulses, and remains at another discrete value for two consecutive pulses, and so on).

[0075] For example, from the perspective of the lithographic exposure apparatus 444, changing the wavelength can produce valuable results. Specifically, chromatic aberration of the light beam 432 as it passes through the lithographic exposure apparatus 444 can result in a correlation between the wavelength of the light beam 432 and the position of the focal plane of the pulses of the light beam 432 at the substrate (along an axial direction that is orthogonal to the image plane of the substrate). Moreover, it may be desirable to change the focal plane of the light beam 432 as the light beam 432 interacts with or strikes the substrate. Thus, by changing the wavelength of the light beam 432, the focal plane of the light beam 432 at the substrate in the lithographic exposure apparatus 444 can be adjusted. In this example, the lithographic exposure apparatus 444 instructs the spectral feature control module 631 to adjust the wavelength in a manner desired for such patterning of the substrate.

[0076] The control device 650 may include a purge gas control module 638 configured to control one or more fluid control valves that adjust the amount of purge gas supplied from the purge gas source 636. The purge gas is supplied to the interior 604 by way of a purge port 634 that provides fluid communication into the interior 604 of the body 602. As discussed above, the purge gas may be any non-reactive gas, such as nitrogen (N2). Moreover, because the interior 604 is maintained at a sub-atmospheric pressure, the use of an inert gas such as helium as a purge gas may be avoided.

[0077] Although the purge port 634 is shown as being formed in the primary body 602A, alternatively, the purge port 634 may be disposed in the secondary body 602B (bellows).

[0078] The control device 650 and each of the modules (such as modules 626, 638, 631, 643) include one or more of the following: digital electronic circuit systems, computer hardware, firmware, and software. The control device 650 may include a memory, which may be a read-only memory and / or a random access memory. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including, for example, semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. The control device 650 and each of the modules (such as modules 626, 638, 631, 643) may also include one or more input devices (such as a keyboard, a touch screen, a microphone, a mouse, a handheld input device, etc.) and one or more output devices (such as a speaker or a monitor).

[0079] Each module in the control device 650 and modules (such as modules 626, 638, 631, 643) includes one or more programmable processors, and one or more computer program products embodied in a machine-readable storage device in a tangible manner for execution by the programmable processor. One or more programmable processors can each execute an instruction program to perform a desired function by operating on input data and generating appropriate outputs. Typically, the processor receives instructions and data from a memory. Any of the foregoing items can be supplemented or incorporated into a specially designed ASIC (application-specific integrated circuit).

[0080] Each module and each of the modules 626, 638, 631, 643 comprises a set of computer program products executed by one or more processors such as a processor. Moreover, any of the modules 626, 638, 631, 643 can access data stored in the memory. Each module 626, 638, 631, 643 can receive data from other components and then analyze the data as needed. Each module 626, 638, 631, 643 can communicate with one or more other modules.

[0081] Although the control device 650 (and modules 626, 638, 631, 643) are shown as boxes (where all of their components may be co-located), the control device 650 or any of the modules 626, 638, 631, 643 may be composed of components that are physically remote from each other. For example, the spectral feature control module 631 may be physically co-located with the body 602.

[0082] Any of the modules 626, 638, 631, and 643 may also be in communication with each other. In some implementations, the pressure control module 626 is in communication with the light source control module 643. For example, information may be provided from the pressure control module 626 to the light source control module 643. Such information may provide an indication of a failure of the vacuum pump 624 to the light source control module 643 so that the light source control module 643 may be quickly shut down or stopped. In other examples, the light source control module 643 may provide the pressure control module 626 with an operating pressure P O The spectral feature control module 631 may be directly connected to the light source control module 643. Moreover, the pressure control module 626 and the purge gas control module 638 may be directly connected to the spectral feature control module 631.

[0083] refer to Figure 7 , shows an implementation of the gas discharge system 640 as a two-stage gas discharge system 740. The two-stage gas discharge system 740 includes a first gas discharge stage 751 including a gas discharge body 641 defining a gas discharge chamber 642; and a second gas discharge stage 752. The gas discharge system 740 is used as a light source for generating a light beam 432 of optical pulses to the device 444.

[0084] The first gas discharge stage 751 acts as a master oscillator (MO), while the second gas discharge stage 752 acts as a power amplifier (PA). The MO 751 provides a seed beam 753 to the PA 752 by way of a power optical device set 754. The MO 751 typically includes a gain medium in which amplification occurs and an optical feedback mechanism such as an optical resonator. The PA 752 typically includes a gain medium in which amplification occurs when seeded with a seed laser beam 753 from the MO 751. If the PA 752 is designed as a regenerative ring resonator, it is described as a power ring amplifier (PRA), and in this case, the ring design can provide sufficient optical feedback. The spectral feature adjuster 600 receives the precursor beam 408 from the MO 751 to enable fine-tuning of spectral features, such as the central wavelength and bandwidth of the precursor beam 408, at relatively low output pulse energies. PA 752 receives seed beam 753 from MO 751 (through power optics 754) and amplifies seed beam 753 to produce amplified beam 732 to obtain the power required for output for lithography through lithography exposure device 444. Amplified beam 732 is guided through output optics set 755, which may include one or more pulse stretchers, optical shutters, or analysis modules, and the output of which is beam 432 guided to lithography exposure device 444.

[0085] The gas discharge chamber 642 of the MO 751 houses two elongated electrodes, a laser gas used as a gain medium, and a fan that circulates the gas between the electrodes. A laser resonator is formed between the spectral feature adjuster 600 on one side of the gas discharge chamber 642 and an output coupler 707 (such as a partially transmissive optical element) on the second side of the gas discharge chamber 642 to output a seed beam 753 to the PA 752.

[0086] PA 752 also includes a gas discharge chamber and, if PA 752 is a regenerative ring amplifier, a beam reflector or beam steering device that reflects the beam back into its gas discharge chamber to form a circulation path. The PA gas discharge chamber also includes its own pair of elongated electrodes, a laser gas that serves as a gain medium, and a fan for circulating the gas between the electrodes. The seed beam 753 is amplified by repeatedly passing through the gas discharge chamber of PA 752. PA 752 may include a beam modification optical system that provides a means for optically coupling in the seed beam 753 and optically coupling out a portion of the amplified radiation from PA 752 to form an amplified beam 732 (e.g., a partially reflecting mirror).

[0087] The laser gas used in the gas discharge chamber 642 of MO 751 and the gas discharge chamber of PA 752 may be any suitable gas for generating a laser beam near the desired wavelength and bandwidth. For example, the laser gas includes argon fluoride (ArF) emitting light at a wavelength of about 193 nm or krypton fluoride (KrF) emitting light at a wavelength of about 248 nm.

[0088] refer to Figure 8 , shows an implementation of the gas discharge system 640 as a single-stage gas discharge system 840. The single-stage gas discharge system 840 includes a gas discharge stage 851, which includes a gas discharge body 641 defining a gas discharge chamber 642. The gas discharge system 840 is used as a light source for generating a beam 432 of optical pulses to the device 444. The gas discharge chamber 642 contains two elongated electrodes, a laser gas used as a gain medium, and a fan that circulates the gas between the electrodes. A laser resonator is formed between a spectral feature adjuster 600 on one side of the gas discharge chamber 642 and an output coupler 807 (such as a partially transmissive optical element) on a second side of the gas discharge chamber 642 to output a beam 853. The laser gas used for the gas discharge chamber 642 can be any suitable gas for generating a laser beam near a desired wavelength and bandwidth. For example, the laser gas includes argon fluoride (ArF) emitting light at a wavelength of about 193 nm or krypton fluoride (KrF) emitting light at a wavelength of about 248 nm.

[0089] The gas discharge system 840 also includes an optics assembly 855 , which may include one or more pulse stretchers, optical shutters, or analysis modules, and the output of the output optics assembly 855 is the light beam 432 directed to the lithography exposure device 444 .

[0090] refer to Fig.9A , shows an implementation 900 of a spectral signature adjuster 100, which includes a body 902 defining an interior 904 that houses a set 910 of five optical elements 910-1, 910-2, 910-3, 910-3, 910-4, 910-5 (generally referred to as 910-i, where i can be 1, 2, 3, 4, or 5) and an actuation system 920. The actuation system 920 includes an actuator 920-1, 920-2, 920-3, 920-4, 920-5 (generally referred to as 920-i, where i can be 1, 2, 3, 4, or 5) for each respective actuatable optical element. Each optical element 910-i is arranged to interact with a light beam 108 that enters the interior 904 through an optical passage 906.

[0091] The set 910 of five optical elements includes a dispersive optical element 910-1, which may be a grating, and a beam expander consisting of refractive optical elements 910-2, 910-3, 910-4, 910-5, which may be prisms. The grating 910-1 may be a reflective grating designed to disperse and reflect the light beam 108. Thus, the grating 910-1 is made of a material suitable for interacting with the light beam 108 having a wavelength in the DUV range. Each of the prisms 910-2, 910-3, 910-4, 910-5 is a transmissive prism that is used to disperse and redirect the light beam 108 as it passes through the body of the prism. Each of the prisms 910-2, 910-3, 910-4, 910-5 may be made of a material that permits the transmission of the wavelength of the light beam 108, such as calcium fluoride.

[0092] Before impinging on the diffractive surface 911-1 of the grating 910-1, the light beam 108 enters the interior 904 through the optical pathway 906, then passes through the prism 910-5, then the prism 910-4, then the prism 910-3, and then the prism 910-2. As the light beam 108 passes through the prisms 910-5, 910-4, 910-3, 910-2 each time, the light beam 108 is optically magnified and redirected (refracted at a certain angle) toward the next optical component. Before returning through the optical pathway 906 and exiting the interior 904, the light beam 108 is diffracted and reflected back from the grating 910-1 through the prisms 910-2, prisms 910-3, prisms 910-4, and prisms 910-5. As the light beam 108 passes from the grating 910 - 1 through each of the successive prisms 910 - 2 , 910 - 3 , 910 - 4 , 910 - 5 , the light beam 108 is optically compressed as it travels toward the optical pathway 906 .

[0093] like Fig. 9B As shown, rotating a particular prism P (which may be any of prisms 910-2, 910-3, 910-4, 910-5) changes the angle of incidence of the light beam 108 impinging on the entry surface H(P) of the rotated prism P. The two local optical qualities of the light beam 108 passing through the rotated prism P (optical magnification OM(P) and beam refraction angle δ(P)) are the angle of incidence of the light beam 108 impinging on the entry surface H(P) of that rotated prism P. The optical magnification OM(P) of the light beam 108 passing through the prism P is the ratio of the lateral width Wo(P) of the light beam 108 leaving the prism P to the lateral width Wi(P) of the light beam 108 entering the prism P. Also, again referring to Fig.9A, changing the local optical magnification OM(P) of the light beam 108 at one or more of the prisms P causes the optical magnification OM of the light beam 108 to change overall, and changing the local beam refraction angle δ(P) through one or more of the prisms P causes the incident angle of the light beam 108 at the diffractive surface 911-1 of the grating 910-1 to change overall. The wavelength of the light beam 108 can be adjusted by changing the incident angle of the light beam 108 hitting the diffractive surface 911-1 of the grating 910-1, and the bandwidth of the light beam 108 can be adjusted by changing the optical magnification OM of the light beam 108.

[0094] The grating 910-1 can be a high blaze angle step grating, and the light beam 108 incident on the grating 910-1 will be reflected and diffracted at any incident angle that satisfies the grating equation. The grating equation provides a relationship between the spectral order of the grating 910-1, the diffraction wavelength (that is, the wavelength of the diffracted light beam), the angle of incidence of the light beam 108 onto the diffractive surface 911-1 of the grating 910-1, the exit angle of the light beam 108 diffracted from the diffractive surface 911-1 of the grating 910-1, the vertical divergence of the light beam 108 incident on the diffractive surface 911-1 of the grating 910-1, and the groove pitch of the diffractive surface 911-1 of the grating 910-1. If grating 910-1 is used so that the incident angle of light beam 108 onto grating 910-1 is equal to the exit angle of light beam 108 from grating 910-1, then grating 910-1 and prism set 910-2, 910-3, 910-4, 910-5 are considered to be arranged in a Littrow configuration and the wavelength of light beam 108 reflected from grating 910-1 is the Littrow wavelength.

[0095] Each actuator of actuators 920-1, 920-2, 920-3, 920-5 is connected to its corresponding optical element 910-1, 910-2, 910-3, 910-5. Each actuator 920-1, 920-2, 920-3, 920-5 is a mechanical device for moving or controlling the corresponding optical element. Actuators 920-2, 920-3, 920-5 receive energy from spectral feature control module 631 and convert the energy into a certain motion, which is imparted to the corresponding optical element. For example, actuators 920-2, 920-3, 920-5 can be any of a force device and a rotation stage for rotating the corresponding prism 910-2, 910-3, 910-5. Actuators 920-1, 920-2, 920-3, 920-5 may include, for example, motors such as linear stepper motors, rotary stepper motors, valves, pressure control devices, piezoelectric devices, hydraulic actuators, and voice coils. In this implementation, prism 910-4 remains stationary or is not physically coupled to the actuator. Actuator 920-1 may be a beam correction device configured to bend optical element 910-1 (which is a grating in this implementation).

[0096] Each of the prisms 910-2, 910-3, 910-4, 910-5 is a right angle prism through which the pulsed light beam 108 is transmitted. The propagation direction of the light beam 108 inside the interior 904 and through the prisms 910-2, 910-3, 910-4, 910-5 is in the XS-YS plane of the spectral feature adjuster 900. The prism 910-2 is physically coupled to the actuator 920-2, which causes the prism 910-2 to move about a Z direction parallel to the spectral feature adjuster 900. S The prism 910-3 is physically coupled to an actuator 920-3 which causes the prism 910-3 to rotate about a Z axis parallel to the spectral feature adjuster 900. S The axis about which the axis rotates.

[0097] Additionally, the prism 910-5 is physically coupled to an actuator 920-5, which is configured to move about a Z axis parallel to the spectral feature adjuster 900. S The actuator 920-5 may include a rotary stepper motor having a rotary shaft and a rotary plate fixed to the rotary shaft, and the prism 910-5 is fixed to the rotary plate. The rotary shaft and the rotary plate rotate about a direction parallel to the Z axis. S The axis of the prism 910-5 is rotated about its axis parallel to the Z axis. SThe prism axis rotates about the axis. The rotary stepper motor can be a direct drive stepper motor, which is a traditional electromagnetic motor with built-in stepper motor function for position control. In other implementations where higher motion resolution may be required, the stepper motor can use piezoelectric motor technology. The rotary stepper motor can be a rotary stage that is controlled by a motor controller using a variable frequency drive control method to provide rapid rotation of the prism 910-5.

[0098] In this implementation, if Fig.9A As shown and also as Fig. 10A and Fig. 10B As shown, each actuator 920-2, 920-3, 920-5 is in communication with the spectral signature control module 631 through a corresponding actuation interface 929-2, 929-3, 929-5, each actuation interface providing communication through the body 902. For example, wires from each actuator 920-2, 920-3, 920-5 pass through a hermetically sealed electrical feedthrough at a corresponding actuation interface 929-2, 929-3, 929-5. Alternatively, each actuator 920-2, 920-3, 920-5 can be in communication with the spectral signature control module 631 by means of a single actuation interface 929 providing a single communication through the body 902. All wires from each actuator 920-2, 920-3, 920-5 pass through a single hermetically sealed electrical feedthrough at the actuation interface 929.

[0099] Actuation interfaces 929-2, 929-3, 929-5 can provide wired connectivity required for controlling corresponding actuators 920-2, 920-3, 920-5. The connectivity includes both power signals and drive signals. The power signal may need to be sent through a dedicated airtight sealed electrical feedthrough to reduce noise that may interfere with the drive signal. One or more dedicated electrical feedthroughs for power signals can be configured with additional electrical insulation to further reduce noise interference at the drive signal. Moreover, the wired connectivity provided by the actuation interfaces 929-2, 929-3, 929-5 can be shielded from the effects of stray radiation generated by the light beam 108 that passes through the interior 904 and interacts with the optical element 910-i to avoid exhaustion of any insulated wire sheaths used for such transmission. For example, heavy stainless steel braided wire conduits can be used to provide wired connectivity from actuators 920-2, 920-3, 920-5 through corresponding actuation interfaces 929-2, 929-3, 929-5.

[0100] The actuator 920-1 is connected to an external control device 631-1 (which may be part of the spectral signature control module 631 if automated, or a human operator if manually controlled) via a mechanical actuation interface 929-1. The mechanical actuation interface 929-1 includes a mechanical feedthrough that implements a through-the-wall rotation mechanism for controlling the actuator 920-1.

[0101] refer to Fig.11 , the spectral characteristics of the light beam 108 controlled by any of the spectral characteristics adjusters 100, 200, 300, 400, 500, 600 discussed herein are any aspects or representations of the spectrum 1160 of the light beam 108. The spectrum 1160 may be referred to as an emission spectrum. The spectrum 1160 contains information about how the light energy, spectral intensity, or power of the light beam 108 is distributed over different wavelengths. The spectrum 1160 of the light beam 108 is depicted in the form of a chart or graph, where the spectral intensity 1161 (not necessarily with an absolute calibration) is plotted as a function of wavelength 1162 (or optical frequency, which is inversely proportional to wavelength).

[0102] One example of a spectral characteristic is bandwidth, which is a measure of the width 1163 of the spectrum 1160. This width 1163 may be given in terms of the wavelength or frequency of the laser. Any suitable mathematical construct (that is, metric) related to the details of the spectrum 1160 may be used to estimate a value that characterizes the bandwidth of the beam 108. For example, the full width of the spectrum at a fraction (X) of the maximum peak intensity of the spectrum 1160 (referred to as FWXM) is used to characterize the bandwidth of the beam 108. As another example, the width of the spectrum 1160 containing a fraction (Y) of the integrated spectral intensity (referred to as EY) may be used to characterize the bandwidth of the beam 108. Another example of a spectral characteristic is wavelength, which may be a wavelength value 1164 of the spectrum 1160 at a particular (such as maximum) spectral intensity.

[0103] refer to Fig.12 , a process 1270 for controlling the pressure within the spectral feature adjuster is performed. When discussing the process 1270, reference is made to the spectral feature adjuster 600, but the process 1270 can be applied by any of the spectral feature adjusters 100, 200, 300, 400, 500, or 600 described herein. The process 1270 can be performed by the control device 650.

[0104] After the gas discharge system 640 is ready to restart from a restart or standby mode, the process 1270 begins. In this case, the gas discharge system 640 is ready to operate but the spectral feature adjuster 600 is not yet ready to operate. In standby mode, the gas discharge system 640 is therefore waiting and ready to operate, and the light source control module 643 operates the gas discharge system 640 in standby mode (1271). For example, during standby mode, gas filling and purging are active, and fans are configured to continue to circulate gas between electrodes of any discharge chamber in the system 640. However, the gas discharge system 640 does not generate a beam 432 for use by the device 444 while in standby mode (thus, the electrodes do not provide energy to one or more laser gases in the discharge chamber of the gas discharge system 640).

[0105] After restarting the gas discharge system 640 (while the gas discharge system 640 is still in the standby mode 1271), the spectral signature adjuster 600 is not yet ready for operation. That is, the pressure within the interior 604 is not controlled and the purge gas is not used to purge the interior 604. Therefore, the spectral signature adjuster 600 is sealed, and the purge gas control module 638 operates the purge gas source 636 to inject a purge gas (such as N2) into the interior 604 (1272). The purge gas can be used to exhaust other unwanted gaseous components (such as oxygen) from the interior 604 of the body 602, which may have entered the interior 604 before restarting the gas discharge system 640.

[0106] The pressure control module 626 operates the vacuum pump 624 to pump the material out of the interior 604 (1273). The pressure control module 626 analyzes the measured pressure P from the pressure sensor 628, for example. I To determine the pressure P I Is the operating pressure P O within the operating range ΔP (1274).

[0107] If the pressure control module 626 determines that the pressure P I Not in operating pressure P O If the pressure control module 626 determines that the pressure P is within the operating range ΔP (1274), it continues to operate the vacuum pump 624 to pump the material out of the interior 604 (1273). I At operating pressure P O If the pressure control module 626 is within the operating range ΔP of (1274), the light source control module 643 switches from operating the gas discharge system 640 in the standby mode (1271) to operating the gas discharge system 640 in the output mode (1275). For example, the pressure control module 626 sends a signal to the light source control module 643 to instruct the light source control module 643 to start operating the gas discharge system 640 in the output mode.

[0108] Operation (1275) of the gas discharge system 640 in the output mode includes: generating the precursor beam 408; adjusting the spectral characteristics of the precursor beam 408 by interacting with the spectral characteristics adjuster 600; and forming the beam 432 from the precursor beam 408 for use by the device 444. During operation (1275) of the gas discharge system 640 in the output mode and because the precursor beam 408 is interacting with the optical element 410-i in the set 410 in the spectral characteristics adjuster 600, for the operating pressure P O The operating range ΔP of the spectral signature adjuster 600 requires maintaining the pressure within the interior 604 of the body 602. This is because the spectral characteristics of the precursor beam 408, such as bandwidth and wavelength, are directly affected or modified by changes in pressure within the interior 604 through which the precursor beam 408 passes.

[0109] The pressure control module 626 determines the pressure P within the interior 604 of the spectral signature adjuster body 602. I Is the operating pressure P0 outside the operating range ΔP (1276). For example, the pressure control module 626 compares the measured pressure P from the pressure sensor 628 to the measured pressure P I With operating pressure P O If the pressure control module 626 determines that the pressure P within the interior 604 I At operating pressure P O If the spectral characteristic adjuster body 602 is outside the operating range ΔP (1276), the pressure within the interior 604 of the spectral characteristic adjuster body 602 is adjusted (1277).

[0110] For example, if the pressure control module 626 determines that the pressure P within the interior 604 of the spectral signature adjuster body 602 I Greater than the operating pressure P O , the pressure control module 626 may send a signal to the vacuum pump 624 to pump the substance out of the interior 604 of the spectral signature adjuster body 602. As another example, if the pressure control module 626 determines that the pressure P within the interior 604 of the spectral signature adjuster body 602 is I Lower than the operating pressure P O If the operating range ΔP (1276) of the spectral signature adjuster body 602 is exceeded, the pressure control module 626 can send a signal to the vacuum pump 624 to stop pumping the substance out of the interior 604 of the spectral signature adjuster body 602. Alternatively, the pressure control module 626 can request the vacuum pump 624 or some other pump to open the interior 604 of the spectral signature adjuster body 602 to the atmosphere in a controlled manner so that the pressure P in the interior 604 is IAlternatively or additionally, the pressure control module 626 may send a signal to the purge gas control module 638 to input more purge gas into the interior 604 via the purge port 634 .

[0111] By controlling the pressure in the spectral signature adjuster 600 within an operating range in the standby mode (1274) and the output mode (1276), certain characteristics of the light beam 432 (such as the spectral signature or energy) can be maintained within an acceptable range.

[0112] Other implementations are within the scope of the following claims.

[0113] Further aspects of the invention are set out in the following numbered clauses.

[0114] 1. A spectral characteristic adjuster, comprising:

[0115] a body defining an interior maintained at a pressure below atmospheric pressure;

[0116] at least one optical passage through the body, the optical passage being transparent to light beams having wavelengths in the ultraviolet range;

[0117] an optical element collection located within the interior, the optical elements in the collection being configured to interact with the light beam, wherein the optical element collection includes one or more actuatable optical elements; and

[0118] An actuation system, located within the interior, is in communication with the one or more actuatable optical elements and is configured to adjust a physical aspect of the one or more actuatable optical elements.

[0119] 2. The spectral characteristic adjuster according to clause 1, further comprising:

[0120] A vacuum port is defined in a wall of the body, the vacuum port being in fluid communication with the interior and in fluid communication with a vacuum pump external to the spectral signature adjuster.

[0121] 3. The spectral characteristic adjuster according to clause 1, further comprising:

[0122] A pressure sensor is configured to measure pressure within the interior.

[0123] 4. The spectral characteristic adjuster according to clause 1, wherein the optical element set comprises: a refractive element set; and

[0124] Diffractive element.

[0125] 5. A spectral characteristic adjuster according to claim 4, wherein each refractive element is a prism and each diffractive element is a grating.

[0126] 6. A spectral characteristic adjuster according to clause 5, wherein the set of refractive elements comprises a set of four prisms.

[0127] 7. A spectral signature adjuster according to clause 1, wherein the actuation system comprises an actuator for each actuatable optical element, the actuator being configured to adjust a physical aspect of the actuatable optical element.

[0128] 8. The spectral characteristic adjuster according to clause 1, further comprising:

[0129] An actuation interface is defined in the main body, and the actuation interface is in communication with the actuation system and a control system external to the spectral characteristic adjuster.

[0130] 9. A spectral characteristic adjuster according to claim 1, wherein the interior is maintained at a pressure equal to or lower than 16 kilopascals (kPa), equal to or lower than 12 kPa, or equal to or lower than 8 kPa.

[0131] 10. The spectral characteristic adjuster according to clause 1, wherein the internal operating pressure is maintained within 400 Pascal (Pa), or within 140 Pa, or within 20 Pa.

[0132] 11. A spectral characteristic adjuster according to claim 1, wherein the interior is lacking in helium.

[0133] 12. The spectral characteristic adjuster of clause 1, wherein the interior includes a purge gas.

[0134] 13. The spectral signature adjuster of clause 12, wherein the purge gas comprises nitrogen.

[0135] 14. The spectral signature adjuster of clause 1, wherein the body includes a purge port that connects the interior to a purge gas source fluid.

[0136] 15. A spectral signature adjuster according to clause 1, wherein at least a portion of the body is defined by a motion damping device of a gas discharge body that is physically coupled to a gas discharge chamber, and the optical pathway extends through the interior of the motion damping device and through an optical port defined in the gas discharge body.

[0137] 16. A spectral signature adjuster according to clause 15, wherein the body is hermetically sealed and the interior of the motion damping device is maintained at the same pressure as the interior of the body.

[0138] 17. An apparatus comprising:

[0139] A gas discharge system comprising a gas discharge chamber and configured to generate a light beam; and a spectral characteristic adjuster in optical communication with a precursor light beam generated by the gas discharge chamber, the spectral characteristic adjuster comprising:

[0140] a body defining an interior maintained at a pressure below atmospheric pressure;

[0141] at least one optical passage defined between the gas discharge chamber and the interior of the body, the optical passage being transparent to the precursor beam; and

[0142] A collection of optical elements, located within the interior, are configured to interact with the precursor beam.

[0143] 18. The apparatus of clause 17, further comprising a control device in communication with the gas discharge system and the spectral characteristic adjuster.

[0144] 19. The apparatus according to clause 18, further comprising:

[0145] A pressure sensor is configured to measure pressure within the interior.

[0146] 20. The apparatus of clause 19, wherein the control device comprises a pressure module in communication with the pressure sensor and configured to receive the measured pressure and determine whether the measured pressure is within an acceptable pressure range.

[0147] 21. The device of clause 20, further comprising a vacuum pump, wherein the spectral signature adjuster comprises a vacuum port defined in the body, the vacuum port being in fluid communication with the interior and the vacuum pump.

[0148] 22. The apparatus of clause 21, wherein the pressure module is in communication with the vacuum pump and is configured to control operation of the vacuum pump based at least in part on the determination regarding the measured pressure.

[0149] 23. An apparatus according to claim 18, wherein the spectral characteristic adjuster includes an actuation system located within the interior, the actuation system being connected to one or more optical elements within the interior and configured to adjust physical aspects of the one or more optical elements to adjust one or more spectral characteristics of the precursor beam.

[0150] 24. An apparatus according to clause 23, wherein the control device includes a spectral signature module, which is in communication with the actuation system, and the spectral signature module is configured to receive an estimate of one or more spectral signatures of the light beam and adjust the signal to the actuation system based on the received estimate.

[0151] 25. The apparatus of clause 18, further comprising a purge gas source in fluid communication with the interior, wherein the control device comprises a purge gas module in communication with the purge gas source and configured to control a flow of purge gas from the purge gas source.

[0152] 26. The apparatus of clause 17, wherein the gas discharge system comprises:

[0153] a first gas discharge stage including a gas discharge chamber configured to generate a seed beam from a precursor beam; and

[0154] The second gas discharge stage is configured to receive the seed beam and amplify the seed beam so that a light beam is generated by the gas discharge system.

[0155] 27. The device according to clause 26, wherein

[0156] A first gas discharge stage including a gas discharge chamber houses an energy source and contains a gas mixture including a first gain medium; and

[0157] The second gas discharge stage includes a gas discharge chamber housing the energy source and containing a gas mixture including a second gain medium.

[0158] 28. The apparatus of clause 17, wherein the gas discharge chamber houses the energy source and contains a gas mixture including the first gain medium.

[0159] 29. The device of clause 17, wherein the interior is maintained at a pressure equal to or lower than 16 kPa, equal to or lower than 12 kPa, or equal to or lower than 8 kPa.

[0160] 30. An apparatus according to claim 17, wherein the body includes a primary body that houses a collection of optical elements; and a motion damping device that is located between the primary body and the gas discharge body of the gas discharge chamber, the interior of the motion damping device providing at least a portion of the optical path between the gas discharge chamber and the interior.

[0161] 31. The apparatus of clause 30, further comprising an optical window between the motion damping device and the gas discharge chamber, the optical window providing a gas-tight separation between the interior of the body and the gas discharge chamber.

[0162] 32. An apparatus according to clause 30, wherein an interior of the motion damping device and an interior of the body are fluidly open to each other such that the interior of the motion damping device is at the same pressure as the interior of the body.

[0163] 33. A method for controlling a spectral characteristic of a light beam, the method comprising:

[0164] While operating the gas discharge system in standby mode:

[0165] injecting a purge gas into the interior of the body of the spectral signature adjuster; and

[0166] pumping the substance out of the interior of the spectral signature adjuster body until the pressure within the interior of the spectral signature adjuster body is less than atmospheric pressure;

[0167] determining whether the pressure within the interior of the spectral signature adjuster body is within an operating range of pressure; and

[0168] If it is determined that the pressure within the interior of the spectral signature adjuster body is within the operating range of pressure, a switch is made from operating the gas discharge system in the standby mode to operating the gas discharge system in the output mode.

[0169] 34. The method of clause 33, further comprising: while operating the gas discharge system in the output mode:

[0170] determining whether the pressure inside the spectral signature adjuster body is within an operating range of pressure; and

[0171] If it is determined that the pressure inside the spectral signature adjuster body is outside the operating range of pressure, the pressure inside the spectral signature adjuster body is adjusted.

[0172] 35. A method according to clause 34, wherein if it is determined that the pressure inside the spectral signature adjuster body is higher than the operating range of pressure, adjusting the pressure inside the spectral signature adjuster body includes: pumping a substance out of the interior of the spectral signature adjuster body.

[0173] 36. A method according to clause 34, wherein if it is determined that the pressure inside the spectral characteristic adjuster body is lower than the operating range of pressure, adjusting the pressure inside the spectral characteristic adjuster body includes: opening the interior of the spectral characteristic adjuster body to the atmosphere in a controlled manner or stopping pumping matter out of the interior of the spectral characteristic adjuster body.

[0174] 37. The method of clause 33, wherein the operating range of pressure is centered around an operating pressure at or below 16 kPa, at or below 12 kPa, or at or below 8 kPa

[0175] 38. The method according to clause 33, wherein the operating range of pressure is 400Pa, 140Pa or 20Pa.

[0176] 39. The method according to clause 33 also includes: before operating the gas discharge system in standby mode, hermetically sealing the interior of the spectral characteristic adjuster body with the gas discharge cavity of the gas discharge system, and the gas discharge cavity is optically connected with the interior of the spectral characteristic adjuster of the gas discharge system through an optical path.

[0177] 40. A method according to clause 39, wherein operating the gas discharge system in an output mode includes: guiding a precursor beam between the gas discharge cavity and the interior of the spectral characteristic adjuster body so that the precursor beam interacts with an optical element within the interior of the spectral characteristic adjuster body.

Claims

1. A spectral characteristic adjuster, comprising: a body defining an interior maintained at a pressure below atmospheric pressure; at least one optical pathway through the body, the optical pathway being transparent to light beams having wavelengths in the ultraviolet range; a collection of optical elements located within the interior, the optical elements in the collection being configured to interact with the light beam, wherein the collection of optical elements includes one or more actuatable optical elements; as well as an actuation system located within the interior, the actuation system being in communication with the one or more actuatable optical elements and configured to adjust a physical aspect of the one or more actuatable optical elements, wherein the spectral characteristic adjuster is in communication with a control device, the control device is also in communication with a gas discharge system, the gas discharge system includes a gas discharge chamber and is configured to generate the light beam, The control device is configured to: determining whether the pressure within the interior of the body of the spectral signature adjuster is within an operating range of pressure; and If it is determined that the pressure within the interior of the body of the spectral signature adjuster is within the operating range of pressures, a switch is made from operating the gas discharge system in a standby mode to operating the gas discharge system in an output mode.

2. The spectral characteristic adjuster according to claim 1, wherein the optical element set comprises: A collection of refractive elements; as well as Diffractive element.

3. The spectral characteristic adjuster according to claim 2, wherein each refractive element is a prism and the diffraction element is a grating.

4. The spectral signature adjuster of claim 3, wherein the set of refractive elements comprises a set of four prisms.

5. The spectral signature adjuster of claim 1, wherein the actuation system comprises an actuator for each actuatable optical element, the actuator being configured to adjust a physical aspect of the actuatable optical element.

6. The spectral characteristic adjuster according to claim 1, further comprising: An actuation interface is defined in the main body, and the actuation interface is in communication with the actuation system and a control system external to the spectral characteristic adjuster.

7. The spectral characteristic adjuster of claim 1, wherein the interior is devoid of helium.

8. The spectral signature adjuster of claim 1, wherein the interior comprises a purge gas.

9. The spectral signature adjuster of claim 1, wherein the body includes a purge port connecting the interior to the purge gas source fluid.

10. A spectral feature adjuster according to claim 1, wherein at least a portion of the body is defined by a motion damping device of a gas discharge body that is physically coupled to the gas discharge chamber, and the optical pathway extends through the interior of the motion damping device and through an optical port defined in the gas discharge body.

11. A light source device, comprising: a gas discharge system including a gas discharge chamber and configured to generate a light beam; a spectral characteristic adjuster in optical communication with the precursor beam generated by the gas discharge chamber, the spectral characteristic adjuster comprising: a body defining an interior maintained at a pressure below atmospheric pressure; at least one optical pathway defined between the gas discharge chamber and the interior of the body, the optical pathway being transparent to the precursor beam; and a collection of optical elements located within the interior, the optical elements configured to interact with the precursor beam, and The control device is configured to: determining whether the pressure within the interior of the body of the spectral signature adjuster is within an operating range of pressure; and If it is determined that the pressure within the interior of the body of the spectral signature adjuster is within the operating range of pressures, a switch is made from operating the gas discharge system in a standby mode to operating the gas discharge system in an output mode.

12. The light source device of claim 11, further comprising a control device in communication with the gas discharge system and the spectral characteristic adjuster.

13. The light source device according to claim 12, further comprising: A pressure sensor is configured to measure pressure within the interior.

14. The light source device according to claim 12, wherein the spectral characteristic adjuster comprises an actuation system, wherein the actuation system is located within the interior, the actuation system is connected to one or more optical elements within the interior and is configured to adjust physical aspects of the one or more optical elements, thereby adjusting one or more spectral characteristics of the precursor light beam.

15. A light source device according to claim 14, wherein the control device includes a spectral feature module, which is connected to the actuation system, and the spectral feature module is configured to receive an estimate of one or more spectral features of the light beam and adjust the signal to the actuation system based on the received estimate.

16. The light source device according to claim 11, wherein the gas discharge system comprises: a first gas discharge stage including a gas discharge chamber configured to generate a seed beam from the precursor beam; as well as A second gas discharge stage is configured to receive the seed beam and amplify the seed beam to generate the beam from the gas discharge system.

17. The light source device according to claim 16, wherein: The first gas discharge stage including the gas discharge chamber houses an energy source and contains a gas mixture including a first gain medium; and The second gas discharge stage includes a gas discharge chamber housing an energy source and containing a gas mixture including a second gain medium.

18. The light source device of claim 11, wherein the gas discharge chamber houses an energy source and contains a gas mixture including a first gain medium.

19. The light source device according to claim 11, wherein the main body comprises: a primary body housing the collection of optical elements; and a motion damping device located between the primary body and a gas discharge body of the gas discharge chamber, the interior of the motion damping device providing at least a portion of the optical pathway between the gas discharge chamber and the interior.

20. The light source apparatus of claim 19, wherein the interior of the motion damping device and the interior of the body are fluidly open to each other such that the interior of the motion damping device is at the same pressure as the interior of the body.

21. A method for controlling a spectral characteristic of a light beam, the method comprising: While operating the gas discharge system in standby mode: injecting a purge gas into the interior of the body of the spectral signature adjuster; as well as pumping a substance out of the interior of the spectral signature modifier body until the pressure within the interior of the spectral signature modifier body is below atmospheric pressure; determining whether the pressure within the interior of the spectral signature adjuster body is within an operating range of pressures; and If it is determined that the pressure within the interior of the spectral signature adjuster body is within the operating range of pressures, a switch is made from operating the gas discharge system in the standby mode to operating the gas discharge system in an output mode.

22. The method according to claim 21, further comprising: While operating the gas discharge system in output mode: determining whether the pressure within the interior of the spectral signature adjuster body is within an operating range of pressures; and If it is determined that the pressure within the interior of the spectral signature adjuster body is outside of the operating range of pressure, the pressure within the interior of the spectral signature adjuster body is adjusted.

23. The method of claim 22, wherein if it is determined that the pressure within the interior of the spectral signature adjuster body is above the operating range of pressure, adjusting the pressure within the interior of the spectral signature adjuster body comprises: Pumping matter out of the interior of the spectral signature modifier body.

24. The method of claim 22, wherein if it is determined that the pressure within the interior of the spectral signature adjuster body is below the operating range of pressure, adjusting the pressure within the interior of the spectral signature adjuster body comprises: The interior of the spectral signature adjuster body is opened to the atmosphere in a controlled manner or pumping of material out of the interior of the spectral signature adjuster body is stopped.

25. The method of claim 21, further comprising: Before operating the gas discharge system in standby mode, the interior of the spectral characteristic adjuster body is hermetically sealed with a gas discharge cavity of the gas discharge system, and the gas discharge cavity is optically connected with the interior of the spectral characteristic adjuster of the gas discharge system through an optical path.

26. The method of claim 25, wherein operating the gas discharge system in an output mode comprises: A precursor beam is directed between the gas discharge cavity and the interior of the spectral signature adjuster body such that the precursor beam interacts with optical elements within the interior of the spectral signature adjuster body.

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