Optical Pulse Stretching Device

Abstract

An optical pulse stretcher apparatus includes an enclosed container with one or more walls defining an internal cavity maintained in a controlled environment during operation, at least one wall having one or more windows each configured to pass one or more of a pulsed light beam and a stretched pulsed light beam, an optical stretcher disposed within the internal cavity and configured to receive the pulsed light beam and generate at least one stretched pulsed light beam, and one or more actuation devices, each in physical communication with an optical element within the internal cavity and including an adjustment mechanism external to the enclosed container, the adjustment mechanism enabling adjustment of one or more physical properties of an optical element in physical communication with the actuation device without disturbing the controlled environment within the internal cavity.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Application No. 63 / 325,972, entitled "OPTICAL PULSE STRETCHER APPARATUS," filed March 31, 2022, the entire contents of which are incorporated by reference herein.

[0002] The disclosed subject matter relates to an optical pulse stretcher apparatus that can adjust optical elements within an internal cavity without disturbing the controlled environment within the internal cavity. [Background technology]

[0003]

[0003] A lithographic apparatus is a machine that applies a desired pattern to a substrate, usually to a target portion of the substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A patterning device, also called a mask or reticle, can then be used to generate a circuit pattern that is to be formed in an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising part of one or several dies) on the substrate (e.g. a silicon wafer). The transfer of the pattern is typically done by imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will comprise a network of adjacent target portions, which are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern via a radiation beam in a predetermined direction (the "scan" direction) while synchronously scanning the target portion parallel or anti-parallel to this scan direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0004]

[0004] The light source (or laser source) can be used to generate illumination radiation for, for example, illuminating a patterning device of a lithographic apparatus. The laser source may comprise a high power gas discharge laser system and an optical pulse stretcher configured to lengthen pulses of the output of the high power gas discharge laser system. Summary of the Invention

[0005]

[0005] In some general aspects, an optical pulse stretcher apparatus includes an enclosed container with one or more walls defining an internal cavity maintained in a controlled environment during operation, at least one wall having one or more windows each configured to pass one or more of a pulsed light beam and a stretched pulsed light beam, an optical stretcher disposed within the internal cavity and configured to receive the pulsed light beam and generate at least one stretched pulsed light beam, and one or more actuation devices. Each actuation device is in physical communication with an optical element in the internal cavity and includes an adjustment mechanism external to the enclosed container. The adjustment mechanism allows adjustment of one or more physical properties of the optical element in physical communication with the actuation device without disturbing the controlled environment within the internal cavity.

[0006]

[0006] Embodiments may include one or more of the following features. For example, the adjustment mechanism enabling adjustment of one or more physical properties of the optical element may include an adjustment mechanism enabling one or more of translation of the optical element along any direction and rotation of the optical element about any direction. The adjustment mechanism enabling translation of the optical element along a direction may include enabling translation of the optical element with an adjustment range within ±3 millimeters (mm) and a nominal positional accuracy of less than 300 microns (μm), and the adjustment mechanism enabling rotation of the optical element about a direction may include enabling rotation of the optical element with an adjustment range within ±5 degrees and a nominal angular accuracy of less than 0.1 degrees.

[0007]

[0007] The optical element in physical communication with the actuation device may include a mirror, a concave mirror, a beam splitter, or a prism. The optical element in physical communication with the actuation device may include an alignment device with a prism and a fluorescent screen arranged in a fixed relationship relative to each other. The optical pulse stretcher device may also include a viewport arranged in a wall of the enclosed vessel relative to the fluorescent screen such that the fluorescent screen is visible from outside the enclosed vessel through the viewport. The actuation device in physical communication with the alignment device may be configured to translate the alignment device between a first position in which the prism interacts with one or more of the pulsed light beam and the stretched pulsed light beam, and a second position in which the prism does not interact with the pulsed light beam or the stretched pulsed light beam.

[0008]

[0008] Each actuation device may include a bushing sealed within a wall of the container and a drive element configured to move relative to the bushing and in physical communication with the optical element. The bushing may be positioned and fixed within a hole in the wall of the container, and the drive element may include an adjustment mechanism at a first end and a molded tip driver at a second end, the molded tip driver being sized to interact with a molded socket in physical communication with the optical element. The molded socket may include a conical feedthrough mechanism configured to align the molded tip driver with the molded socket. Rotation of the adjustment mechanism at the first end may translate the molded tip driver at the second end, thereby translating the molded socket in physical communication with the optical element. The molded tip driver may be a hexagonal tip driver and the molded socket may be a hexagonal socket. An interior of the bushing may house the adjustment mechanism, and the interface between the bushing and the adjustment mechanism may be a threaded interface where rotation of the adjustment mechanism also translates the adjustment mechanism relative to the bushing and translates and rotates the molded tip driver relative to the bushing. The threaded interface may include a round-tipped thread on the interior of the bushing that mates with a round-tipped thread on the exterior of the adjustment mechanism. The bushing and the adjustment mechanism may each be made of a lead-free metal or lead-free metal alloy, and the interface is lubricant-free. The threaded interface may include a thread on the interior of the bushing that mates with a round-tipped thread on the exterior of the adjustment mechanism, the thread having a pitch of 80 to 100 teeth per inch. The molded tip driver may be in elastic engagement with the adjustment mechanism. The drive element may remain in physical communication with the optical element over all of the range of motion within the bushing. The adjustment mechanism may enable adjustment of one or more physical properties of the optical element in physical communication with the actuation device while passing one or more pulsed light beams and the stretched pulsed light beam through the window, and while manipulating the pulsed light beams and the stretched pulsed light beam at a repetition rate of greater than 500 Hertz (Hz), 1000 Hz, or 3000 Hz.

[0009] The controlled environment may be gas purged and maintained at a pressure greater than atmospheric, or about 15 to 22 pounds per square inch (PSI).

[0010]

[0010] The optical stretcher may include two or more stacked confocal optical pulse stretchers disposed within the internal cavity. A first one of the stacked confocal optical pulse stretchers may comprise a first plurality of mirrors and may be configured to receive a portion of the pulsed optical beam and generate a first stretched pulsed optical beam by reflecting the portion of the pulsed optical beam off the first plurality of mirrors. A second one of the stacked confocal optical pulse stretchers may comprise a second plurality of mirrors and may be configured to receive a portion of the first stretched pulsed optical beam and generate a second stretched pulsed optical beam by reflecting the portion of the first stretched pulsed optical beam off the second plurality of mirrors. The first and second plurality of mirrors may include concave mirrors.

[0011]

[0011] The optical elements in physical communication with the actuation device may include optical elements of an optical stretcher.

[0012]

[0012] In another general aspect, a deep ultraviolet (DUV) light source includes an optical pulse stretcher apparatus. The optical pulse stretcher apparatus includes an enclosed vessel with one or more walls defining an internal cavity maintained in a controlled environment during operation, at least one wall having one or more windows each configured to pass one or more of a pulsed light beam and a stretched pulsed light beam, an optical stretcher disposed within the internal cavity and configured to receive the pulsed light beam and generate at least one stretched pulsed light beam, and one or more actuation devices. Each actuation device is in physical communication with an optical element in the internal cavity and includes an adjustment mechanism external to the enclosed vessel. The adjustment mechanism allows adjustment of one or more physical properties of the optical element in physical communication with the actuation device without disturbing the controlled environment in the internal cavity. [Brief description of the drawings]

[0013]

[0013] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the invention and, together with the description, serve to explain the principles of the invention and to enable one of ordinary skill in the relevant art to make and use the invention. One or more of the drawings may not be to scale.

[0014] [Figure 1]

[0014] A block diagram of an optical pulse stretcher apparatus comprising an optical stretcher disposed within an internal cavity of an enclosed container defined by a plurality of walls, and one or more through-wall adjusters or actuation devices configured to enable adjustment of optical elements within the internal cavity. [Figure 2A]

[0015] FIG. 2 is a perspective view of an example of an actuation device mounted to the wall of the container of FIG. 1, the actuation device comprising an adjustment mechanism positioned outside the internal cavity and a driver inside the internal cavity that engages with a region or portion of the optical element, the driver being axially movable relative to a bushing fixed in the wall. [Figure 2B]

[0016] 2B is a side cross-sectional view of the actuation device of FIG. 2A. [Figure 2C]

[0017] 2B is a side cross-sectional view of the actuation device of FIG. 2A attached to the wall of the container of FIG. 1. [Figure 2D]

[0018] 2D is a cross-sectional view of the actuation device of FIG. 2C in a 2D-2D plane. [Figure 2E]

[0019] 2E is a cross-sectional view of the actuation device of FIG. 2C taken along plane 2E-2E. [Figure 3A]

[0020] 2C is a perspective view of an embodiment of a bushing in the actuation device of FIGS. 2A to 2E. FIG. [Figure 3B]

[0021] FIG. 1 is a perspective view of an example of a drive element having a body with an adjustment mechanism at a first end and a driver at a second end, the drive element extending axially along a central opening of a bushing when mounted within an actuation device. [Figure 3C]

[0022] 3C is a detailed view of the interface between the drive element and the bushing of FIG. 2C. [Figure 4]

[0023] 2 is a block diagram of an embodiment of the optical pulse stretcher apparatus of FIG. 1 in an embodiment of a pulsed light source configured to provide a light beam to a photolithography exposure tool to generate a circuit pattern on a target portion of a substrate (or wafer). [Figure 5A]

[0024] 1 is a block diagram of an embodiment of an optical pulse stretcher apparatus in which a first optical pulse stretcher device and a second optical pulse stretcher device are arranged as a series of stacked optical pulse stretcher devices. [Figure 5B]

[0025] FIG. 1 is a block diagram of an example optical arrangement within a second optical pulse stretcher device, the optical arrangement configured to receive a first stretched pulsed light beam from the first optical pulse stretcher device, split the first stretched pulsed light beam into a plurality of portions, redirect the split portions to one or more of the pulse stretchers of the second optical pulse stretcher device, and recombine the delayed split portions to form a second stretched pulsed light beam directed to the first optical pulse stretcher device. [Figure 6A]

[0026] FIG. 2 is a block diagram of an embodiment in which the actuation device and associated alignment apparatus are shown in a cross-sectional side view, with the alignment apparatus out of the path of the light beam. [Figure 6B]

[0027] FIG. 6B is a block diagram of an embodiment in which the actuation device of FIG. 6A and associated alignment apparatus are shown in cross-sectional side view, with the alignment apparatus in the path of a light beam. [Figure 6C]

[0028] FIG. 6B is a plan view looking towards the wall of the enclosure housing the alignment device when the alignment device is out of the path of the light beam as in FIG. 6A. [Figure 6D]

[0029] FIG. 6C is a plan view looking towards the wall of a container housing the alignment device when the alignment device is in the path of the light beam as in FIG. 6B. [Figure 7]

[0030] FIG. 13 is a perspective view of an example of an optical element adjusted with three actuation devices at three different points on the rear surface of the optical element. [Figure 8A-8C]

[0031] 8A shows a side cross-sectional view of the mirror, one of the adapter sets, and one of the corresponding actuation devices of FIG. 7, with FIG. 8A showing a neutral position of the adjustment mechanism of the actuation device, FIG. 8B showing a position where the adjustment mechanism has been rotated relative to the position shown in FIG. 8A (e.g., clockwise when facing the outer wall of the internal cavity), and FIG. 8C showing a position where the adjustment mechanism has been rotated relative to the position shown in FIG. 8A (e.g., counterclockwise when facing the wall from outside the internal cavity). [Figure 8D]

[0032] 8B shows a cross-sectional view of the driver and socket of the actuation device of FIG. 8A along the XY plane of FIG. 8A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015]

[0033] Referring to FIG. 1, the optical pulse stretcher device 100 comprises a sealed container 105 with one or more walls 106a, 106b, 106c, 106d that define an internal cavity 107. In the two-dimensional representation of FIG. 1, four walls 106a, 106b, 106c, 106d are shown. However, the container 105 may be of any suitable three-dimensional shape, such as a rectangular parallelepiped, a cube, a cylinder, etc., and the number of walls 106a, 106b, 106c, 106d may vary depending on the shape. The internal cavity 107 is maintained in a controlled environment during operation of the optical pulse stretcher device 100. For example, the internal cavity 107 may be formed by the sealed walls 106a, 106b, 106c, 106d. Thus, the internal cavity 107 may be maintained at a particular pressure (such as a pressure below or above atmospheric pressure) or a particular humidity environment (such as low humidity). As another example, the internal cavity 107 may be configured as a purged environment (such as a nitrogen purged environment). In some embodiments, the internal cavity 107 may be maintained at a pressure between about 4 and 8 pounds per square inch (psi) above atmospheric pressure. For example, when the internal cavity 107 is a purged environment, the pressure may be maintained at about 18 to 23 psi.

[0016]

[0034] At least one wall 106d of the container 105 includes one or more windows 108, each configured to pass one or more pulsed light beams 109. The pulsed light beams 109 can be unstretched pulsed light beams or stretched pulsed light beams. An unstretched pulsed light beam is a light beam that has not entered or passed through the device 100 and thus has not yet been optically stretched by the device 100. A stretched pulsed light beam is a light beam that has been at least partially stretched by passing through the device 100.

[0017]

[0035] The optical pulse stretcher device 100 comprises an optical stretcher 115 disposed within the internal cavity 107. The optical stretcher 115 is configured to receive an input pulsed optical beam 116 and generate at least one stretched output pulsed optical beam 117. The optical stretcher 115 comprises a plurality of optical elements 120-i (where i is a set of numbers 1, 2, ... I, where I is a number greater than 1). The optical pulse stretcher device 100 may also comprise one or more other optical elements 125-k (where k is a set of numbers 1, 2, ... K, where K is a positive integer) within the internal cavity 107. Each of the optical elements 120-i and 125-k is configured to interact with a pulsed optical beam (e.g., pulsed optical beam 109, pulsed optical beam 116, or pulsed optical beam 117, etc.) at a point within the internal cavity 107.

[0018]

[0036] One or more of the optical elements 120-i, 125-k in the optical pulse stretcher device 100 may need to be adjusted (e.g., aligned or changed in position or angle). For example, one or more of the optical elements 120-i may need to be adjusted to ensure that the input pulsed light beam 116 properly traverses the optical stretcher 115. Furthermore, such adjustments of the optical elements 120-i may be made while the input pulsed light beam 116 is interacting with that optical element 120-i. As another example, the optical pulse stretcher device 100 may include a beam observation device that is used to locate the center of the pulsed light beam in the device 100. The beam observation device may be configured to translate in and out of the path of the pulsed light beam in the device 100, and while out of the path, it does not interfere with or alter the pulsed light beam during normal operation, but may be moved into the path to allow visualization of the pulsed light beam for diagnostic purposes. Such a beam observation device may be considered as an optical element 125-k that needs to be translated in and out of the path of the pulsed light beam.

[0019]

[0037] The apparatus 100 includes one or more through-wall adjusters or actuation devices 130-j (where j is a set of numbers 1, 2, ...J, where J is a positive integer). Each actuation device 130-j extends through a wall (such as wall 106d). Thus, at one end, the actuation device 130-j is physically within the internal cavity 107, and at the other opposite end, the actuation device 130-j is outside the internal cavity 107. Each actuation device 130-j is associated with and physically communicates with the optical element 120-i, 125-k that needs to be adjusted at a given time. Thus, some of the optical elements 120-i, 125-k may not be associated with an actuation device 130-j. In FIG. 1, the optical element 120-1 is associated with the actuation device 130-1, the optical element 120-I is associated with the actuation device 130-2, the optical element 125-1 is associated with the actuation device 130-3, and the optical element 125-2 is associated with the actuation device 130-4. Although four actuation devices 130-1, 130-2, 130-3, 130-4 are shown in FIG. 1, there may be fewer or more than four actuation devices 130-j. Each actuation device 130-j includes a corresponding adjustment mechanism 131-j outside the sealed container 105. Thus, the actuation device 130-1 includes the adjustment mechanism 131-1, the actuation device 130-2 includes the adjustment mechanism 131-2, the actuation device 130-3 includes the adjustment mechanism 131-3, and the actuation device 130-4 includes the adjustment mechanism 131-4.

[0020]

[0038] The adjustment mechanism 131-j allows for adjustment of one or more physical properties of an optical element (120-i or 125-k) in physical communication with the actuation device 130-j without disturbing the controlled environment within the internal cavity 107. That is, the adjustment mechanism 130-j allows for adjustment of the associated optical element 120-i, 125-k without requiring opening of the sealed container 105.

[0021]

[0039] Conventional adjustment procedures that require the opening of the sealed container 105 make servicing of the apparatus 100 time-consuming and complicated. For example, it may be difficult for a field service engineer to directly access the optical elements 120-i, 125-k to perform adjustments using these conventional procedures. This is because space within the internal cavity 107 is limited and the geometric arrangement of the various optical elements 120-i, 125-k may make access difficult. Also, while the container 105 is open (during these conventional adjustment procedures), the pulsed light beam 109 typically operates at a lower repetition rate, which makes it more difficult for a field service engineer to quickly and accurately perform the necessary adjustments to the optical elements 120-i, 125-k. Finally, because the container 105 is sealed and the internal cavity 107 may use purge gas, extra time is required to remove the purge gas, open the container 105, perform the adjustments, reclose the container 105, and reintroduce the purge gas into the internal cavity 107.

[0022]

[0040] In contrast, the use of the actuation device 130-j (and the adjustment mechanism 131-j) reduces the time and complexity of maintaining the optical pulse stretcher apparatus 100, since the procedure of opening the container 105 and then closing the container 105 is not necessary. Also, the pulsed light beam 109 that the optical pulse stretcher apparatus 100 receives through the window 108 can be generated at a high repetition rate during adjustment of the optical elements 120-i, 125-k. By using the pulsed light beam 109 at a high repetition rate during adjustment, it is easier to visualize the pulsed light beam 109 interacting with the optical elements 120-i, 125-k, and therefore faster and / or more accurate adjustments can be performed. This is particularly important when the optical elements 125-k include, for example, a fluorescent screen, which generates fluorescent light when interacting with the pulsed light beam 109. By operating at a high repetition rate, the adjustment process can be adapted as the phosphor screen (of the optical element 125-k) ages; for example, the repetition rate of the pulsed light beam 109 can be adjusted in response to the aging of the phosphor screen to accommodate this degradation. A high repetition rate can be a repetition rate of more than 50 Hertz (Hz), more than 100 Hz, more than 500 Hz, more than 1000 Hz, or more than 3000 Hz. In some embodiments, the high repetition rate is a rate up to 6 kilohertz (kHz). In some embodiments, the high repetition rate is a repetition rate required for a downstream output device (such as the repetition rate required for the photolithography exposure device 462 of FIG. 4). Furthermore, the optical elements 120-i, 125-k can be adjusted remotely by a field service engineer without requiring the field service engineer to directly and often awkwardly (as described above) access the optical elements 120-i, 125-k. Additionally, the optical elements 120-i, 125-k may be conditioned while within the controlled environment of the internal cavity 107, and if a purge gas is used, the purge gas may be maintained while the optical elements 120-i, 125-k are conditioned.

[0023]

[0041] The actuation device 130-j is designed to operate in the controlled environment of the internal cavity 107. For example, if a purge gas is used during operation of the apparatus 100, the inner portion of the internal cavity 107 of the actuation device 130-j is compatible with the purge gas. Because of the use of a purge gas and the controlled environment, the actuation device 130-j operates without the use of lubricants or friction-reducing materials, such as Teflon or lead-containing metals. Avoiding the use of lubricants and friction-reducing materials also reduces outgassing in the actuation device 130-j. Possible outgassing due to light scattering occurring in lubricants and friction-reducing materials can reduce the performance and life of the optical elements 120-i, 125-k.

[0024]

[0042] Because each actuation device 130-j extends between the interior cavity 107 where the actuation device 130-j is in physical communication with a corresponding optical element 120-i, 125-k and the outside of the container 105, the actuation device 130-j also needs to provide a seal at the interface 132-j between the actuation device 130-j and the wall to which it is attached. For example, a first seal is formed at the interface 132-1 between the actuation device 130-1 and the wall 106c, a second seal is formed at the interface 132-2 between the actuation device 130-2 and the wall 106c, a third seal is formed at the interface 132-3 between the actuation device 130-3 and the wall 106d, and a fourth seal is formed at the interface 132-4 between the actuation device 130-4 and the wall 106d.

[0025]

[0043] As mentioned above, each actuation device 130-j is in physical communication with its corresponding optical element 120-i, 125-k in the internal cavity 107. To enable this physical communication, each actuation device 130-j includes a driver 133-j in physical contact with a region or portion of the optical element 120-i, 125-k. Thus, in the example of FIG. 1, actuation device 130-1 includes a driver 133-1 in physical contact with a region or portion of the optical element 120-1, actuation device 130-2 includes a driver 133-2 in physical contact with a region or portion of the optical element 120-I, actuation device 130-3 includes a driver 133-3 in physical contact with a region or portion of the optical element 125-1, and actuation device 130-4 includes a driver 133-4 in physical contact with a region or portion of the optical element 125-2. The driver 133-j may be a device that can be brought into and maintained in physical contact with a region or portion of the optical element 120-i, 125-k.

[0026]

[0044] 2A-2E, an embodiment 230-j of the actuation device 130-j is shown. In Fig. 2C-2E, the actuation device 230-j is shown attached to a wall 206 of a closed container, such as the container 105. The actuation device 230-j includes an adjustment mechanism 231-j that is located outside the internal cavity 207 when the actuation device 230-j is attached to the wall 206 (Fig. 2C). The actuation device 230-j includes a driver 233-j that is inside the internal cavity 207 when the actuation device 230-j is attached to the wall 206. As discussed above, the driver 233-j engages (is in physical contact with) a region or portion of the optical element 120-i or 125-k in the container 105. In this manner, adjustment mechanism 231-j is accessible from outside of enclosure 105 and allows driver 233-j to be controlled (and thus the optical element to be adjusted) without having to access interior cavity 207.

[0027]

[0045] The adjustment mechanism 231-j is part of the drive element 235-j and is at its first end. The drive element 235-j extends through a central opening 345-j (FIG. 3A) of the bushing 234-j. The adjustment mechanism 231-j includes a rotation element 236-j that allows the adjustment mechanism 231-j to rotate relative to the bushing 234-j. In this embodiment, the rotation element 236-j is a shaped opening or recess (specifically, a hexagon socket) defined at the end of the adjustment mechanism 231-j, and the adjustment mechanism 231-j is designed like a screw. The adjustment mechanism 231-j rotates when a suitably shaped drive element is inserted into the shaped opening 236-j and rotated. For example, if the shaped opening 236-j is a hexagon socket, the adjustment mechanism 231-j can be rotated relative to the bushing 234-j by inserting a hexagon screw driver or an Allen wrench into the hexagon socket 236-j and rotating it.

[0028]

[0046] The driving element 235-j is configured to move along the axial direction Zj relative to the bushing 234-j, while the bushing 234-j is sealed and fixed within the wall 206 (FIG. 2C). The driving element 235-j includes a body 237-j that extends axially (i.e., along the axial direction Zj) along a central opening 345-j (FIG. 3A) of the bushing 234-j and determines the direction of translation applied to the driver 233-j. The driving element 235-j includes a driver 233-j at a second end. The driving element 235-j also includes a biasing device 238-j configured to bias the driver 233-j in the positive Zj direction so that the driver 233-j remains engaged with a region or portion of the optical element 120-i or 125-k while the driver 233-j adjusts the optical element 120-i or 125-k. The biasing device 238-j includes a biasing device 239-j (such as a spring) mounted in a cavity 240-j of the coupler 241-j. The cavity 240-j receives the second end 242-j of the body 237-j and the base 243-j of the driver 233-j, and the biasing device 239-j is mounted between the base 243-j and the second end 242-j. The biasing device 239-j is biased in the positive Zj direction to push the base 243-j, and thus the driver 233-j, in the positive Zj direction. This biasing function causes the driver 233-j to be in elastic engagement with the adjustment mechanism 231-j. Additionally, the drive element 235-j remains in physical communication with the optical elements (such as optical elements 120-i, 125-k) throughout the entire range of motion of the drive element 235-j relative to the bushing 234-j. The coupler 241-j is secured to the second end 242-j of the body 237-j by a fastening device 244-j, such as a set screw.

[0029]

[0047] 3A shows the bushing 234-j separated from the other components of the actuation device 230-j. The bushing 234-j includes a cylindrical body 346-j defining a central opening 345-j, both of which extend along an axial direction Zj, with the central opening 345-j extending through the bushing 234-j. The bushing 234-j also includes a cylindrical flange 347-j extending from the body 346-j. The flange 347-j is configured to allow the bushing 234-j to be sealed to the wall 206, as shown in FIG. 2C. Specifically, a seal is formed at the interface between the wall 206 and a radial surface of the flange 347-j, which prevents leakage of material between the internal cavity 207 and the exterior of the container 105. In this example, the seal is formed from a gasket 248-j sandwiched between the radial surface of the flange 347-j and the exterior surface of the wall 206. The gasket 248-j is compressed when the flange 347-j and the wall 206 are pressed together (along the axial direction Zj). For example, the body 346-j may include an external threaded surface 350-j (shown in FIG. 3A), and a threaded nut 249-j (FIG. 2C) disposed around the body 346-j may rotate against the external threaded surface 350-j to press the wall 206 and the flange 347-j together, thereby compressing the gasket 248-j and engaging the seal. This seal (in the gasket 248-j) prevents the purge gas (such as nitrogen or N2 gas) from leaking from the internal cavity 207 along a path between the bushing 234-j and the wall 206.

[0030]

[0048] In some embodiments, an additional seal may be formed between the bushing 234-j and the driving element 235-j. To this end, the flange 347-j of the bushing 234-j includes an outer threaded surface 351-j (shown in FIG. 3A ) that mates with an inner threaded surface of the cap 252-j (shown in FIGS. 2A-2C ). The seal may be formed at the interface between the cap 252-j and the outward radial surface of the flange 347-j. Specifically, a threaded seal is formed when the cap 252-j is screwed onto the flange 347-j, and as the cap 252-j is tightened, an O-ring 253-j disposed at the interface between the outer radial surface of the flange 347-j and the cap 252-j is compressed to form the seal. This second or additional seal is therefore dependent on the placement of the cap 252-j on the flange 347-j. Thus, the cap 252-j must be removed to access the adjustment mechanism 231-j.

[0031]

[0049] 3B shows the driving element 235-j separated from the other components of the actuation device 230-j. The biasing device 239-j is between the second end 242-j of the body 237-j and the base 243-j of the driver 233-j. The driver 233-j extends along the axial direction Zj and has a tip 353-j that is in direct physical contact with a region or portion of the optical element 120-i, 125-k. The base 243-j of the driver 233-j has a generally cylindrical shape with a diameter smaller than the diameter of the cavity 240-j and can move along the axial direction Zj within the cavity 240-j. The tip 353-j of the driver 233-j has a geometric shape complementary to the geometric shape of the region or portion of the optical element 120-i, 125-k with which it is in physical contact. As such, the tip 353-j can maintain frictional engagement with a region or portion of the optical element 120-i, 125-k. For example, the tip 353-j can be hexagonal in shape and the region or portion of the optical element 120-i, 125-k in physical contact with the tip 353-j can be a hexagonal socket.

[0032]

[0050] As shown in Figures 3B and 3C, the body 237-j includes a threaded outer surface 354-j that mates with a threaded inner surface 355-j (shown in Figure 3A) of the central opening 345-j of the bushing 234-j. Thus, the interface between the body 237-j and the bushing 234-j is a threaded interface. Because the bushing 234-j is fixed within the opening in the wall 206, when the cap 252-j is removed and the adjustment mechanism 231-j is engaged (such as by turning an Allen wrench inserted into the hex socket 236-j), the entire body 237-i rotates relative to the bushing 234-j, which also translates the body 237-i along the axial direction Zj relative to the bushing 234-j (and the wall 206). The threads of the threaded outer surface 354-j and the threads of the threaded inner surface 355-j can be rounded rather than sharp. To obtain rounded threads, the threads are formed by rolling the surface (surface 354-j or 355-j) with a die rather than cutting the threads with a machine. In some embodiments, the threads of surfaces 354-j and 355-j can have a fine pitch, such as a pitch of 80 to 100 teeth per inch.

[0033]

[0051] The bushing 234-j and the components of the adjustment mechanism 231-j (such as the body 237-j, the coupler 241-j, the biasing device 239-j, and the driver 233-j) are at least partially located within the internal cavity 207, which is a controlled environment, and therefore are made of materials that do not react with any materials within the internal cavity 107 / 207. Additionally, the bushing 234-j and the components of the adjustment mechanism 231-j that move relative to each other (such as the body 237-i) must be made of materials that allow relative motion while ensuring that friction is kept below an acceptable level. Additionally, the interface between the body 237-j and the bushing 234-j (shown in detail in FIG. 3C) must operate without the use of lubricants that may interfere with the controlled environment within the internal cavity 107 / 207 (i.e., the body 237-j must be able to move relative to the bushing 234-j). Considering these factors, in some embodiments, the bushing 234-j and the components of the adjustment mechanism 231-j may be made of a lead-free metal or lead-free metal alloy. For example, the bushing 234-j may be made of phosphor bronze (such as UNS C51000 or H04 temper). If the adjustment mechanism 231-j is a screw, it may be made of stainless steel, such as stainless steel type 303 (UNS S30300).

[0034]

[0052] Referring to FIG. 4, the embodiment 400 of the optical pulse stretcher apparatus 100 is part of a pulsed light source 460. The light source 460 can be used as part of a lithography apparatus for providing a pulsed light beam 461 to a photolithography exposure apparatus 462 to generate a circuit pattern on a target portion of a substrate (or wafer). In some embodiments, the light source 460 is a deep ultraviolet (DUV) light source, and the light beam 461 has a wavelength in the DUV wavelength range, which may include wavelengths from about 100 nanometers (nm) to about 400 nm, for example. As shown in FIG. 4, the light source 460 may be a dual stage light source comprising a first stage 463A and a second stage 463B. The first stage 463A may comprise a master oscillator (MO) generating a first pulsed light beam 464, which is passed to the second stage 463B via an optical element 465 comprising a relay optical system. The second stage 463B may include a power amplifier (PA) that receives the first pulsed light beam 464 and optically amplifies the first pulsed light beam 464 to form a second pulsed light beam 466 that is directed to the optical pulse stretcher device 400.

[0035]

[0053] The first stage 463A may include, for example, an MO chamber module in which a lasing gas discharge is induced in a lasing gas by an electric discharge between electrodes (not shown) to generate a population inversion of energetic molecules, including, for example, argon, krypton, or xenon, to generate a relatively broadband radiation. This radiation is line narrowed to a relatively very narrow bandwidth and center wavelength selected in a line narrowing module ("LNM") in the first stage 463A. The first stage 463A may also include an MO output coupler (MO OC), which may include a partially reflective mirror that, together with a reflective grating in the LNM, forms an oscillator cavity in which the first stage 463A oscillates to form the first pulsed light beam 464. The first stage 463A may also include other components, such as a line center analysis module (LAM).

[0036]

[0054] The optical elements 465 may comprise an MO wavefront engineering box (WEB) that serves to redirect the first pulsed light beam 464 to the second stage 463B. The optical elements 465 may also include beam expanding optics, such as a multi-prism beam expander (not shown), and coherence breaking, such as in the form of an optical delay path (not shown).

[0037]

[0055] The second stage 463B comprises, for example, a PA chamber module, which is also an oscillator formed by the incidence of the first pulsed light beam 464, and output coupling optics, which may be redirected back through the gain medium in the PA chamber via a beam reverser. The output coupling optics may incorporate partially reflective input and output couplers, a maximum reflecting mirror for the nominal operating wavelength (which for an ArF system may be around 193 nm), and one or more prisms. The second stage 463B optically amplifies the first pulsed light beam 464 to form a second pulsed light beam 466.

[0038]

[0056] Each of the MO chamber module (of the first stage 463A) and the PA chamber module (of the second stage 463B) may be part of a gas discharge light source, such as an excimer light source. In such a light source, each of the MO chamber module and the PA chamber module includes a gas mixture including a combination of one or more noble gases, which may include argon, krypton, or xenon, and a reactive gas, which may include fluorine or chlorine, as a gain medium. Thus, for example, the gain medium of each module may include argon fluoride (ArF), krypton fluoride (KrF), or xenon chloride (XeCl). When the gain medium includes argon fluoride, the wavelength of the pulsed light beam 461 is about 193 nm, and when the gain medium includes krypton fluoride, the wavelength of the pulsed light beam 461 is about 248 nm. The size of the microelectronic features patterned on the wafer in the photolithography exposure device 462 depends on the wavelength of the pulsed light beam 461, the lower the wavelength, the smaller the minimum feature size.

[0039]

[0057] The second pulsed light beam 466 is input to the optical pulse stretcher device 400 where copies of the second pulsed light beam 466 are delayed and recombined to reduce speckle in the pulsed light beam 461 directed to the photolithography exposure device 462.

[0040]

[0058] Examples of the dual stage light source 460 and optical pulse stretcher apparatus 400 are described in WO2021 / 076658, published on April 22, 2021 by applicant Cymer, LLC, the disclosure of which is incorporated by reference in its entirety into this specification.

[0041]

[0059] In some embodiments, the optical pulse stretcher apparatus 400 comprises a single pulse stretcher. In other embodiments, the optical pulse stretcher apparatus 400 comprises a multi-stage pulse stretcher. For example, the pulse stretcher may comprise a plurality (at least two) concave mirrors arranged relative to each other to form a confocal resonator. In some embodiments, the optical pulse stretcher apparatus 400 comprises a first optical pulse stretcher device 400-1 and a second optical pulse stretcher device 400-2 arranged as a series of stacked optical pulse stretcher devices, as discussed in detail in WO2021 / 076658. In these embodiments, the first optical pulse stretcher device 400-1 receives the second pulsed light beam 466 and delays and recombines a copy of the second pulsed light beam 466 to generate the first stretched pulsed light beam 418. This first stretched pulsed light beam 418 is then input to a second optical pulse stretcher device 400-2 which delays and recombines copies of the first stretched pulsed light beam 418 to generate a second stretched pulsed light beam 419. This second stretched pulsed light beam 419 is input to the first optical pulse stretcher device 400-1 where it is redirected out as pulsed light beam 461.

[0042]

[0060] The optical pulse stretcher apparatus 400 comprises a sealed container 405 comprising a number of walls 406a, 406b, 406c, 406d, 406e, 406f, 406g, 406h that together define an internal cavity that houses the optical components or elements of the devices 400-1 and 400-2. For simplicity, FIG. 4 shows a two-dimensional rendering of the container 405 having eight walls, however, the container 405 may be three-dimensional and comprise walls that extend in other directions or parallel to the plane of the page. Similar to the optical pulse stretcher apparatus 100, the apparatus 400 comprises one or more through-wall adjusters or actuation devices 430-j. 4 shows two actuation devices 430-1 and 430-2, where actuation device 430-1 is associated with optical elements (not shown in FIG. 4) in a first optical pulse stretcher device 400-1 and actuation device 430-2 is associated with optical elements (not shown in FIG. 4) in a second optical pulse stretcher device 400-2. The optical pulse stretcher apparatus 400 may include fewer or more than two actuation devices 430-j, and each of the optical pulse stretcher devices 400-1, 400-2 may include one or more corresponding actuation devices 430-j.

[0043]

[0061] Each optical pulse stretcher device 400-1, 400-2 may comprise one or more optical pulse stretchers, each comprising one or more confocal resonators that comprise reflective surfaces generally facing each other and positioned relative to each other such that a pulsed light beam (such as the second pulsed light beam 466 or the first stretched pulsed light beam 418) is reflected back and forth in a region between the reflective surfaces.

[0044]

[0062] 5A, an embodiment 500 of the optical pulse stretcher apparatus 400 is shown. The optical pulse stretcher apparatus 500 comprises a first optical pulse stretcher device 500-1 and a second optical pulse stretcher device 500-2 arranged as a series of stacked optical pulse stretcher devices. In these embodiments, the first optical pulse stretcher device 500-1 receives the second pulsed light beam 466 and delays and recombines a copy of the second pulsed light beam 466 to generate a first stretched pulsed light beam 518. This first stretched pulsed light beam 518 is then input to the second optical pulse stretcher device 500-2, which delays and recombines a copy of the first stretched pulsed light beam 518 to generate a second stretched pulsed light beam 519. This second stretched pulsed light beam 519 is input to the first optical pulse stretcher device 500-1 where it is redirected out as the pulsed light beam 461.

[0045]

[0063] The first optical pulse stretcher device 500-1 comprises at least one optical pulse stretcher 503-1 in its internal cavity 507-1, comprising at least two opposing mirrors 502a, 502b that generate a reflected light between them and define a confocal resonator. For example, the optical pulse stretcher 503-1 may comprise a first single mirror 502a and a second single mirror 502b to generate two reflected lights of the delayed portion of the second pulsed light beam 466. As another example, the optical pulse stretcher 503-1 may comprise two first mirrors 502a and two second mirrors 502b to generate four reflected lights of the delayed portion of the second pulsed light beam 466. The mirrors 502a, 502b may be separated from each other by a physical distance large enough to allow for the desired optical delay. In some embodiments, the mirrors 502a, 502b are separated by a physical distance of, for example, about 1 meter (m) to about 3 m. Such a physical distance can provide an optical delay of about 30 nanoseconds (ns) to about 50 ns. The mirrors 502a, 502b can be circular and concave mirrors. The first optical pulse stretcher device 500-1 can also include other optical elements. For example, a beam splitter 504 is positioned on the path of the second pulsed light beam 466 to split a portion of the second pulsed light beam 466 toward the optical pulse stretcher 503-1. A pair of beam splitters 504a, 504b can be positioned to split the first stretched pulsed light beam 518 into the second optical pulse stretcher device 500-2 and then recombine the second stretched pulsed light beam 519 from the second optical pulse stretcher device 500-2.

[0046]

[0064] The second optical pulse stretcher device 500-2 comprises one or more confocal optical pulse stretchers in its internal cavity 507-2. In the illustrated example, there are three confocal optical pulse stretchers 503-2i, 503-2ii, 503-2iii. Each of the optical pulse stretchers 503-2i, 503-2ii, 503-2iii comprises at least two corresponding opposing mirrors 570-ai, 570-bi; 570-aii, 570-bii; 570-aiii, 570-biii. Although two opposing mirrors are shown for each pulse stretcher 503-2i, 503-2ii, 503-2iii, it is possible for each pulse stretcher 503-2i, 503-2ii, 503-2iii to comprise three or more opposing mirrors.

[0047]

[0065] The second optical pulse stretcher device 500-2 also comprises an optical arrangement 572 configured to receive the first stretched pulsed light beam 518, split the first stretched pulsed light beam 518 into a plurality of portions, redirect the split portions to one or more of the pulse stretchers 503-2i, 503-2ii, 503-2iii, and recombine the delayed split portions to form the second stretched pulsed light beam 519. Thus, the optical arrangement 572 comprises one or more beam splitters and folding mirrors.

[0048]

[0066] 5B, an embodiment 572B of the optical device 572 is shown. The optical device 572B comprises three beam splitters 571i, 571ii, 571iii arranged along the path of the first stretched pulsed light beam 518, each of which is configured to extract a portion of the first stretched pulsed light beam 518 and direct the portion to a corresponding confocal optical pulse stretcher 503-2i, 503-2ii, 503-2iii. The optical device 572B also comprises two folding mirrors 504c, 505d arranged to return the second stretched pulsed light beam 519 (formed by passing a portion of the first stretched pulsed light beam 518 through the confocal optical pulse stretchers 503-2i, 503-2ii, 503-2iii) to the first optical pulse stretcher device 500-1.

[0049]

[0067] Referring again to Figure 5A, optical pulse stretcher apparatus 500 comprises a sealed container 505 comprising a number of walls 506a, 506b, 506c, 506d, 506e, 506f, 506g, 506h that together define an interior cavity that houses the optical components or elements of devices 500-1 and 500-2. For simplicity, Figure 5A shows a two-dimensional rendering of container 505 having eight walls, however container 505 may be three-dimensional and may comprise walls that extend in other directions or parallel to the plane of the page, and container 505 may comprise different sections that are connected together.

[0050]

[0068] The optical pulse stretcher device 500 may also include optical elements 573a, 573b used to align other optical elements in the optical pulse stretcher device 500. In the example of FIG. 5A, optical element 573a is an alignment device configured to selectively interact with the first stretched pulsed light beam 518, and optical element 573b is an alignment device configured to selectively interact with the second stretched pulsed light beam 519. Additional alignment devices may be used elsewhere along the path of the light beam passing through the optical pulse stretcher device 500. Alignment device 573a is used to visualize the first stretched pulsed light beam 518, and alignment device 573b is used to visualize the second stretched pulsed light beam 519. These visualizations allow an engineer to determine the path of the light beam and adjust other components in the device 500 to ensure that the light beam is aligned with the optical elements. During normal operation of the apparatus 500, the apparatus 500 optically stretches the second pulsed light beam 466 to form the pulsed light beam 461. During normal operation of the apparatus 500, as shown in FIG. 5A, the alignment device 573a does not interact with the first stretched pulsed light beam 518, and the alignment device 573b does not interact with the second stretched pulsed light beam 519. Meanwhile, during visualization operations, when light beam 518 needs to be visualized, the alignment device 573a is moved to insert it into the path of light beam 518, and when light beam 519 needs to be visualized, the alignment device 573b is moved to insert it into the path of light beam 519.

[0051]

[0069] Similar to the optical pulse stretcher device 100, the device 500 includes one or more through-wall adjusters or actuation devices 530-j. Actuation devices 530-1, 530-2, 530-3, 530-8, 530-9, 530-10 are associated with mirrors 570-biii, 570-bii, 570-bi, 570-ai, 570-aii, 570-aiii of the optical pulse stretchers 503-2i, 503-2ii, 503-2iii, respectively. Actuation devices 530-4 and 530-5 are associated with alignment devices 573a and 573b, respectively. Actuation devices 530-6 and 530-7 are associated with mirrors 502b and 502a of the optical pulse stretcher 503-1, respectively. Finally, at least one actuation device 530-11 is associated with an optical element in optical arrangement 572. Actuation devices 530-1, 530-2, 530-3 are mounted as through-wall adjusters in wall 506a, actuation devices 530-4 and 530-5 are mounted as through-wall adjusters in wall 506c, actuation device 530-6 is mounted as through-wall adjuster in wall 506d, actuation device 530-7 is mounted as through-wall adjuster in wall 506e, actuation devices 530-8, 530-9, 530-10 are mounted as through-wall adjusters in wall 506g, and actuation device 530-11 is mounted as through-wall adjuster in wall 506h. The optical pulse stretcher apparatus 500 may comprise fewer or more than eleven actuation devices 530-j, and each of the optical pulse stretcher devices 500-1, 500-2 may comprise one or more corresponding actuation devices 530-j.

[0052]

[0070] Referring to FIG. 5B, there may be two or more actuation devices 530-11 mounted on the wall as through-wall adjusters to access one or more of the optical components in the optical arrangement 572B. In this embodiment, two actuation devices 530-11, 530-12 are mounted on the wall 506h for controlling and adjusting the corresponding mirrors 504c, 504d. In addition, actuation devices 530-13, 530-14, 530-15 are mounted on the corresponding beam splitters 571i, 571ii, 571iii (along another wall parallel to the paper). The actuation devices 530-11, 530-12 may be mounted on the corresponding folding mirrors 504c, 504d in a manner similar to that shown in FIG. 6A to FIG. 6D or as shown in FIG. 7. The actuation devices 530-13, 530-14, 530-15 may be positioned relative to the corresponding beam splitters 571i, 571ii, 571iii in a manner similar to that shown in Figure 7. Thus, as discussed below with respect to Figure 7, there may be two actuation devices positioned relative to each beam splitter 571i, 571ii, 571iii to provide both tip and tilt adjustment for each beam splitter 571i, 571ii, 571iii.

[0053]

[0071] 6A-6D, an embodiment of the actuation device 530-4 and associated alignment device 573a is shown in side cross-sectional view (FIGS. 6A and 6B) and in plan view looking towards the wall 506c (FIGS. 6C and 6D). FIGS. 6A and 6C show normal operation, while FIGS. 6B and 6D show visualization operation. Specifically, in FIGS. 6A and 6C, the alignment device 573a is out of the path of the light beam 518, while in FIGS. 6B and 6D, the alignment device 573a is placed in the path of the light beam 518. The alignment device 573a comprises a refractive element, such as a prism 574a, and a visualization device, such as a fluorescent screen 575a. An engineer can view the fluorescent screen 575a through a viewport 576 located in the wall 506c close to the fluorescent screen 575a. The viewport 576 is sealed to the wall 506c, allowing visualization of the fluorescent screen 575a from outside the container 505. The viewport 576 includes a material that transmits light generated by the fluorescent screen 575a. The fluorescent screen 575a is fixed relative to the prism 574a so that they are movable together under the control of the actuation device 530-4. The actuation device 530-4 is external to the internal cavity 507-1 and includes an adjustment mechanism 531-4 positioned at one end of the drive element 535-4. The other end of the drive element 535-4 includes a driver 533-4 that physically engages with the alignment device 573a (e.g., a wall of the alignment device 573a). As the adjustment mechanism 531-4 rotates, the drive element 535-4 is adjusted (e.g., translated along the Z-4 ​​axis) relative to a bushing 534-4 fixed to the wall 506c, thereby moving the alignment device 573a between the non-interacting position of FIGS. 6A and 6C and the interacting position of FIGS. 6B and 6D. When alignment device 573a is inserted into the path of light beam 518, a portion 518p of light beam 518 is redirected by prism 574a to fluorescent screen 575a, where the light causes material in screen 575a to fluoresce, as shown in FIG. 6D, and light 577 generated from the fluorescence is visible through viewport 576.By visualizing light 577, an engineer can better locate the center of light beam 518 and make adjustments to move the center of light beam 518 if necessary.

[0054]

[0072] With reference to FIG. 7, as discussed above, the optical element adjustable by the actuation device 130-j can be a mirror, such as a concave mirror, or can be another optical element, such as a beam splitter (as shown in FIG. 5B). For example, the optical element can be a concave mirror 780 in an internal cavity 707 defined by a number of walls, a portion of one wall 706a being shown in FIG. 7. The concave mirror 780 can be an optical element 120-i in the optical stretcher 115, such as any of the concave mirrors 570-ai, 570-aii, 570-aii, 570bi, 570bii, 570biii in the first optical pulse stretcher device 500-1 (FIG. 5A) or any of the mirrors 502a, 502b in the second optical pulse stretcher device 500-2 (FIG. 5A). In another embodiment, the concave mirror 780 is a beam splitter, such as that shown in FIG. 5B.

[0055]

[0073] The concave mirror 780 may be in physical communication with three actuation devices 730-1, 730-2, 730-3 at three different points 781-1, 781-2, 781-3 on the rear surface 782 of the mirror 780. Each actuation device 730-1, 730-2, 730-3 may be in physical communication with three actuation devices 730-1, 730-2, 730-3 in a direction Z 780 The drive elements 735-1, 735-2, 735-3 include corresponding adjustment mechanisms 731-1, 731-2, 731-3 outside the internal cavity 707 and corresponding drivers 733-1, 733-2, 733-3 inside the internal cavity 707. The drive elements 735-1, 735-2, 735-3 are oriented in a direction Z relative to corresponding bushings 734-1, 734-2, 734-3 fixed (sealed) within the wall 706a. 780In order to visualize adjustment mechanisms 731-1, 731-2, 731-3, external caps (such as cap 252-j) are not shown in FIG. 7. However, each adjustment mechanism 731-1, 731-2, 731-3 may be covered by a corresponding cap when not engaged for adjustment, as described above with reference to FIGS. 2A-2E and as shown in FIGS. 8A-8C (where cap 752-1 is shown covering adjustment mechanism 731-1).

[0056]

[0074] In some embodiments, such as that shown in FIG. 7, each driver 733-1, 733-2, 733-3 does not directly engage with the points 781-1, 781-2, 781-3, but rather engages with a corresponding adapter 783-1, 783-2, 783-3. On the side of the mirror 780, each adapter 783-1, 783-2, 783-3 has a corresponding socket (shown in FIG. 8A) for receiving a sphere 784-1, 784-2, 784-3 located at the corresponding point 781-1, 781-2, 781-3. Also, on the opposite side, each adapter 783-1, 783-2, 783-4 has a socket (shown in FIG. 8A to FIG. 8C) that is shaped to complement the shape of the driver 733-1, 733-2, 733-3. The operation of the actuation device 730-1 is illustrated below with reference to FIG. 8A to FIG. 8C. The operation of the other actuation devices 730-2 and 730-3 is similar to that of the actuation device 730-1.

[0057]

[0075] Contacting the mirror 780 at three points 781-1, 781-2, 781-3 allows various types of adjustment of the mirror 780 by translation transmitted to the corresponding drivers 733-1, 733-2, 733-3, which in turn are transmitted to the corresponding points 781-1, 781-2, 781-3 on the back surface 782 of the mirror 780. For example, by translating two of the drivers 733-1 and 733-2 and keeping one driver 733-3 stationary, the mirror 780 can be adjusted to Y 780The mirror 780 can be rotated around the X direction by translating the two drivers 733-2 and 733-3 while keeping one driver 733-1 stationary. 780 On the other hand, the three drivers 733-1, 733-2, and 733-3 are all moved in parallel to rotate the entire mirror 780 in the Z direction. 780 Alternatively or additionally, the mirror 780 can be translated along the X direction. 780 Direction or Y 780 Mirror 780 can be moved by translating it along the Z direction or by engaging mirror 780 at a point on another surface of mirror 780. 780 It is possible to rotate around a direction.

[0058]

[0076] 8A-8C show side cross-sectional views of a mirror 780, an adapter 783-1, and a corresponding actuation device 730-1. As shown, the driver 733-1 is engaged within a socket 785-1 of the adapter 783-1, while the sphere 784-1 is located between a cavity in the back surface 782 of the mirror 780 and a socket 786-1 of the adapter 783-1. If the tip of the driver 733-1 is hexagonal (in the XY cross section), then the socket 785-1 is a complementary hexagonal socket, as shown in the cross section along the XY plane in FIG. 8D.

[0059]

[0077] In Figure 8A, a "neutral" position is shown. In Figure 8B, adjustment mechanism 731-1 has been rotated (e.g., clockwise when facing wall 706a from outside interior cavity 707) relative to the position shown in Figure 8A. This clockwise rotation causes driver 733-1 to rotate in a +Z 780 In FIG. 8C, adjustment mechanism 731-1 has been rotated (e.g., counterclockwise when facing wall 706a from outside interior cavity 707) relative to the position shown in FIG. 8A. This counterclockwise rotation causes driver 733-1 to translate along the -Z 780 Meanwhile, the driver 733-1 is translated along the +Z direction by a biasing device 738-1 (which may be designed similarly to the biasing device 238-j discussed above).780 Since it is biased along the direction, it remains engaged with the socket 785-1. In one example, the driver 733-1 translates parallel within a range of ±3 millimeters (mm) with respect to the neutral position of FIG. 8A, and by this translation, the points on the back surface 782 of the mirror 780 can be translated parallel within a range of ±3 mm. The adjustment of the mirror 780 may be performed with an accuracy of less than 300 micrometers (μm). As discussed above, the mirror 780, for example, translates two of the drivers 733-1 and 733-2 and keeps one driver 733-3 stationary to rotate the mirror 780 780 about the Y 780 axis, or rotates the mirror about the X

[0060]

[0078] While installing the actuating device 730-1 within the wall 706a, the tip of the driver 733-1 is guided to the socket 785-1 through a conical feature 786-1 formed within a mount 787 to which the adapter 783-1 is at least partially attached. The conical feature 786-1 is designed as a feed-through to enable alignment between the tip of the driver 733-1 and the socket 785-1. Also, due to the biasing function executed by the biasing device 738-1, the driver 733-1 is elastically engaged with the adjustment mechanism 731-1. And the drive element 735-1 remains physically in communication with the mirror 780 within all operating ranges of the drive element 735-1 with respect to the bushing 734-1, including the positions shown from FIG. 8A to FIG. 8C.

[0061]

[0079] Details of actuation device 730-1 are shown in Figures 7 and 8A-8D, however, the operation of actuation device 730-1 is similar to other actuation devices discussed herein. Thus, actuation device 530-j of Figure 5A can operate similarly to actuation device 730-1. Additionally, actuation devices 530-4, 530-5 can operate similarly to actuation device 730-1, even though they control things other than mirrors.

[0062]

[0080] The embodiments can be further described using the following clauses. 1. A sealed container having one or more walls defining an interior cavity maintained in a controlled environment during operation, at least one wall having one or more windows each configured to pass one or more of a pulsed light beam and a stretched pulsed light beam; an optical stretcher disposed within the internal cavity and configured to receive the pulsed light beam and generate at least one stretched pulsed light beam; one or more actuation devices, each in physical communication with an optical element within the internal cavity and comprising an adjustment mechanism external to the enclosure, the adjustment mechanism enabling adjustment of one or more physical properties of the optical element in physical communication with the actuation device without disturbing the controlled environment within the internal cavity; An optical pulse stretcher device comprising: 2. The optical pulse stretcher apparatus of clause 1, wherein the adjustment mechanism that enables adjustment of one or more physical properties of the optical element includes an adjustment mechanism that enables one or more of translation of the optical element along any direction and rotation of the optical element about any direction. 3. The optical pulse stretcher apparatus of clause 2, wherein the adjustment mechanism that enables translation of the optical element along a certain direction includes enabling translation of the optical element with an adjustment range of within ±3 millimeters (mm) and a nominal positional accuracy of less than 300 microns (μm), and the adjustment mechanism that enables rotation of the optical element about a certain direction includes enabling rotation of the optical element with an adjustment range of within ±5 degrees and a nominal angular accuracy of less than 0.1 degree. 4. The optical pulse stretcher apparatus of clause 1, wherein the optical element in physical communication with the actuation device comprises a mirror, a concave mirror, a beam splitter, or a prism. 5. The optical pulse stretcher apparatus of clause 1, wherein the optical element in physical communication with the actuation device comprises an alignment apparatus comprising a prism and a fluorescent screen disposed in a fixed relationship relative to one another, and the optical pulse stretcher apparatus further comprises a viewport disposed in a wall of the enclosed vessel relative to the fluorescent screen such that the fluorescent screen is visible from outside the enclosed vessel through the viewport. 6. The optical pulse stretcher apparatus of clause 5, wherein an actuation device in physical communication with the alignment apparatus is configured to translate the alignment apparatus between a first position in which the prism interacts with one or more of the pulsed light beam and the stretched pulsed light beam and a second position in which the prism does not interact with the pulsed light beam or the stretched pulsed light beam. 7. An optical pulse stretcher apparatus according to clause 1, wherein each actuation device comprises a bushing sealed within a wall of the enclosure and a drive element configured to move relative to the bushing and in physical communication with the optical element. 8. The optical pulse stretcher apparatus of clause 7, wherein the bushing is positioned and secured within the hole in the wall of the container, and the drive element includes an adjustment mechanism at a first end and a molded tip driver at a second end, the molded tip driver being sized to interact with a molded socket in physical communication with the optical element. 9. The optical pulse stretcher apparatus of clause 8, wherein the molded socket comprises a conical feedthrough mechanism configured to align the molded tip driver with the molded socket. 10. The optical pulse stretcher apparatus of clause 8, wherein rotation of the adjustment mechanism at the first end translates a shaped tip driver at the second end, thereby translating a shaped socket in physical communication with the optical element. 11. The optical pulse stretcher apparatus of clause 8, wherein the shaped tip driver is a hexagonal tip driver and the shaped socket is a hexagonal socket. 12. The optical pulse stretcher apparatus of clause 8, wherein an interior of the bushing houses an adjustment mechanism and the interface between the bushing and the adjustment mechanism is a threaded interface such that rotation of the adjustment mechanism translates the adjustment mechanism relative to the bushing and translates and rotates the molded tip driver relative to the bushing. 13. The light pulse stretcher apparatus of clause 12, wherein the threaded interface comprises blunt threads on the interior of the bushing that mate with blunt threads on the exterior of the adjustment mechanism. 14. An optical pulse stretcher apparatus according to clause 12, wherein the bushing and the adjustment mechanism are each made of a lead-free metal or a lead-free metal alloy and the interfaces are free of lubricants. 15. The light pulse stretcher apparatus of clause 12, wherein the threaded interface comprises threads on the interior of the bushing that mate with threads on the exterior of the adjustment mechanism, the threads having a pitch of 80 to 100 teeth per inch. 16. The optical pulse stretcher apparatus of clause 8, wherein the shaped tip driver is in resilient engagement with the adjustment mechanism. 17. The optical pulse stretcher apparatus of clause 5, wherein the drive element remains in physical communication with the optical element throughout its entire range of motion within the bushing. 18. An optical pulse stretcher apparatus of clause 5, wherein the adjustment mechanism enables adjustment of one or more physical characteristics of an optical element in physical communication with the actuation device while passing one or more of the pulsed light beams and the stretched pulsed light beam through the window and while manipulating the pulsed light beams and the stretched pulsed light beams at repetition rates greater than 500 Hertz (Hz), 1000 Hz, or 3000 Hz. 19. The optical pulse stretcher apparatus of clause 1, wherein the controlled environment is gas purged and maintained at a pressure greater than atmospheric pressure, or about 15 to 22 pounds per square inch (PSI). 20. The optical stretcher includes two or more stacked confocal optical pulse stretchers disposed within an internal cavity; a first of the stacked confocal optical pulse stretchers includes a first plurality of mirrors and is configured to receive a portion of the pulsed light beam and generate a first stretched pulsed light beam by reflecting the portion of the pulsed light beam off the first plurality of mirrors; The optical pulse stretcher apparatus of clause 1, wherein a second one of the stacked confocal optical pulse stretchers comprises a second plurality of mirrors and is configured to receive a portion of the first stretched pulsed light beam and generate a second stretched pulsed light beam by reflecting a portion of the first stretched pulsed light beam off the second plurality of mirrors. 21. The optical pulse stretcher apparatus of clause 20, wherein the first plurality of mirrors and the second plurality of mirrors include concave mirrors. 22. The optical pulse stretcher apparatus of clause 1, wherein the optical element in physical communication with the actuation device comprises an optical element of an optical stretcher. 23. A sealed container having one or more walls defining an internal cavity maintained in a controlled environment during operation, at least one wall having one or more windows each configured to pass one or more of a pulsed light beam and a stretched pulsed light beam; an optical stretcher disposed within the internal cavity and configured to receive the pulsed light beam and generate at least one stretched pulsed light beam; one or more actuation devices, each in physical communication with an optical element within the internal cavity and comprising an adjustment mechanism external to the enclosure, the adjustment mechanism enabling adjustment of one or more physical properties of the optical element in physical communication with the actuation device without disturbing the controlled environment within the internal cavity; A deep ultraviolet (DUV) light source comprising an optical pulse stretcher apparatus having:

[0063]

[0081] Other embodiments are within the scope of the following claims.

Claims

1. a sealed container having one or more walls defining an internal cavity maintained at a controlled environment during operation, at least one wall having one or more windows each configured to pass one or more of the pulsed light beam and the stretched pulsed light beam; an optical stretcher disposed within the internal cavity and configured to receive the pulsed optical beam and generate at least one stretched pulsed optical beam; one or more actuation devices, each in physical communication with an optical element within the internal cavity and comprising an adjustment mechanism external to the enclosure, the adjustment mechanism enabling adjustment of one or more physical properties of the optical element in physical communication with the actuation device without disturbing the controlled environment within the internal cavity; An optical pulse stretcher device comprising:

2. 2. The optical pulse stretcher apparatus of claim 1 , wherein the adjustment mechanism that enables adjustment of one or more physical properties of the optical element comprises an adjustment mechanism that enables one or more of translation of the optical element along any direction and rotation of the optical element about any direction.

3. the adjustment mechanism enabling the translation of the optical element along a direction enables translation of the optical element with an adjustment range of within ±3 millimeters (mm) and a nominal positional accuracy of less than 300 microns (μm); 3. The optical pulse stretcher apparatus of claim 2, wherein the adjustment mechanism enabling the rotation of the optical element about a direction includes enabling the rotation of the optical element with an adjustment range within ±5 degrees and a nominal angular accuracy of less than 0.1 degrees.

4. 2. The optical pulse stretcher apparatus of claim 1, wherein the optical element in physical communication with the actuation device comprises a mirror, a concave mirror, a beam splitter, or a prism.

5. the optical element in physical communication with the actuation device comprises an alignment apparatus comprising a prism and a fluorescent screen disposed in a fixed relationship relative to one another; 2. The optical pulse stretcher apparatus of claim 1, further comprising a viewport disposed in a wall of the enclosed vessel relative to the fluorescent screen such that the fluorescent screen is visible from outside the enclosed vessel through the viewport.

6. 6. The optical pulse stretcher apparatus of claim 5, wherein the actuation device in physical communication with the alignment apparatus is configured to translate the alignment apparatus between a first position in which the prism interacts with one or more of the pulsed light beam and the stretched pulsed light beam and a second position in which the prism does not interact with the pulsed light beam or the stretched pulsed light beam.

7. 2. The optical pulse stretcher apparatus of claim 1, wherein each actuation device comprises a bushing sealed within a wall of the enclosure and a drive element configured to move relative to the bushing and in physical communication with the optical element.

8. The bushing is positioned and secured within an aperture in a wall of the container; the drive element comprises the adjustment mechanism at a first end and a molded tip driver at a second end; 8. The optical pulse stretcher apparatus of claim 7, wherein said shaped tip driver is sized to interface with a shaped socket in physical communication with said optical element.

9. 9. The optical pulse stretcher apparatus of claim 8, wherein the molded socket comprises a conical feedthrough mechanism configured to align the molded tip driver with the molded socket.

10. 9. The optical pulse stretcher apparatus of claim 8, wherein rotation of said adjustment mechanism at said first end translates said shaped tip driver at said second end, thereby translating said shaped socket in physical communication with said optical element.

11. the molded tip driver is a hex tip driver; 9. The optical pulse stretcher apparatus of claim 8, wherein said shaped socket is a hexagonal socket.

12. an interior of the bushing housing the adjustment mechanism; 9. The optical pulse stretcher apparatus of claim 8, wherein the interface between the bushing and the adjustment mechanism is a threaded interface, wherein rotation of the adjustment mechanism translates the adjustment mechanism relative to the bushing and translates and rotates the shaped tip driver relative to the bushing.

13. 13. The optical pulse stretcher device of claim 12, wherein said threaded interface comprises blunt threads on said interior of said bushing that mate with blunt threads on an exterior of said adjustment mechanism.

14. the bushing and the adjustment mechanism are each made of a lead-free metal or a lead-free metal alloy; 13. The optical pulse stretcher apparatus of claim 12, wherein the interface is free of lubricants.

15. the threaded interface comprising threads on the interior of the bushing that mate with threads on the exterior of the adjustment mechanism; 13. The optical pulse stretcher device of claim 12, wherein said thread has a pitch of 80 to 100 teeth per inch.

16. 9. The optical pulse stretcher apparatus of claim 8, wherein said shaped tip driver is in resilient engagement with said adjustment mechanism.

17. 6. The optical pulse stretcher apparatus of claim 5, wherein said drive element remains in physical communication with said optical element over the entire range of motion within said bushing.

18. 6. The optical pulse stretcher apparatus of claim 5, wherein the adjustment mechanism enables adjustment of one or more physical properties of the optical element in physical communication with the actuation device while passing one or more pulsed light beams and stretched pulsed light beams through the window and while manipulating the pulsed light beams and the stretched pulsed light beams at repetition rates greater than 500 Hertz (Hz), 1000 Hz, or 3000 Hz.

19. 2. The optical pulse stretcher apparatus of claim 1, wherein the controlled environment is gas purged and maintained at a pressure greater than atmospheric pressure, or about 15 to 22 pounds per square inch (PSI).

20. the optical stretcher includes two or more stacked confocal optical pulse stretchers disposed within the internal cavity; a first one of the stacked confocal optical pulse stretchers comprises a first plurality of mirrors and is configured to receive a portion of the pulsed light beam and generate a first stretched pulsed light beam by reflecting the portion of the pulsed light beam off of the first plurality of mirrors; 2. The optical pulse stretcher apparatus of claim 1 , wherein a second one of the stacked confocal optical pulse stretchers comprises a second plurality of mirrors and is configured to receive a portion of the first stretched pulsed light beam and generate a second stretched pulsed light beam by reflecting the portion of the first stretched pulsed light beam off of the second plurality of mirrors.

21. 21. The optical pulse stretcher apparatus of claim 20, wherein the first plurality of mirrors and the second plurality of mirrors comprise concave mirrors.

22. 2. The optical pulse stretcher apparatus of claim 1, wherein the optical elements in physical communication with the actuation device include optical elements of the optical stretcher.

23. a sealed container having one or more walls defining an internal cavity maintained at a controlled environment during operation, at least one wall having one or more windows each configured to pass one or more of the pulsed light beam and the stretched pulsed light beam; an optical stretcher disposed within the internal cavity and configured to receive the pulsed optical beam and generate at least one stretched pulsed optical beam; one or more actuation devices, each in physical communication with an optical element within the internal cavity and comprising an adjustment mechanism external to the enclosure, the adjustment mechanism enabling adjustment of one or more physical properties of the optical element in physical communication with the actuation device without disturbing the controlled environment within the internal cavity; A deep ultraviolet (DUV) light source comprising an optical pulse stretcher apparatus having:

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