Optical pulse stretcher apparatus

Abstract

This invention discloses an optical pulse stretcher device, comprising: an hermetically sealed container including one or more walls defining an internal cavity, the internal cavity being maintained in a controlled environment during operation, at least one wall having one or more windows configured to allow passage of one or more of a pulsed beam and an stretched pulsed beam; an optical stretcher disposed within the internal cavity and configured to receive a pulsed beam and generate at least one stretched pulsed beam; and one or more actuating devices. Each actuating device is in communication with an optical element entity within the internal cavity and is included in an adjustment mechanism outside the hermetically sealed container. The adjustment mechanism enables adjustment of the physical properties of one or more of the optical elements in communication with the actuating device entity without disrupting the controlled environment within the internal cavity.

Description

Technical Field

[0001] The disclosed subject matter relates to an optical pulse stretcher apparatus in which optical elements within an internal cavity can be adjusted without disrupting a controlled environment within the internal cavity. Prior Art

[0002] A lithography apparatus is a machine that applies a desired pattern to a substrate (typically onto target portions of the substrate). For example, lithography apparatus can be used in the manufacture of integrated circuits (ICs). In this case, a patterning device (alternatively referred to as a mask or reticle) is used to create the circuit patterns to be formed on the individual layers of the IC. This pattern can be transferred to a target portion (e.g., a portion containing one or more dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically accomplished by imaging onto a layer of radiation-sensitive material (resist) disposed on the substrate. Typically, a single substrate will contain a network of adjacent target portions patterned sequentially. Known lithography apparatus include so-called steppers, which illuminate each target portion by exposing the entire pattern onto the target portion at once, and so-called scanners, which illuminate each target portion by scanning the pattern with a radiation beam in a given direction (the "scanning" direction), while simultaneously scanning the target portion parallel or antiparallel 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.

[0003] For example, a light (or laser) source can be used to generate illuminating radiation for illuminating a patterning device of a lithography apparatus. The laser source can include a high-power gas discharge laser system and an optical pulse stretcher configured to extend a pulse outputted by the high-power gas discharge laser system. Summary of the Invention

[0004] In some general aspects, an optical pulse stretcher apparatus includes: a hermetically sealed container including one or more walls defining an internal cavity, the internal cavity being maintained in a controlled environment during operation, at least one wall having one or more windows, each window 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 actuators. Each actuator is in physical communication with an optical element within the internal cavity and includes an adjustment mechanism external to the hermetically sealed container. The adjustment mechanism enables adjustment of one or more physical properties of the optical element in physical communication with the actuator without disrupting the controlled environment within the internal cavity.

[0005] Implementations may include one or more of the following features. For example, an adjustment mechanism that enables adjustment of one or more physical properties of an optical element may include 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. The adjustment mechanism that enables translation of the optical element along a direction may include enabling translation of the optical element within an adjustment range of ±3 millimeters (mm) and with a nominal positional accuracy of less than 300 micrometers (µm), and the adjustment mechanism that enables rotation of the optical element about a direction may include enabling rotation of the optical element within an adjustment range of ±5 degrees and with a nominal angular accuracy of less than 0.1 degrees.

[0006] The optical element physically connected to the actuator device may include a mirror, a concave mirror, a beam splitter, or a prism. The optical element physically connected to the actuator device may include an alignment device comprising a prism and a fluorescent screen arranged in a fixed relationship with each other. The optical pulse stretcher device may also include a viewport arranged in a wall of the hermetically sealed container relative to the fluorescent screen, such that the fluorescent screen is visible from outside the hermetically sealed container through the viewport. The actuator device physically connected to 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 either the pulsed light beam or the stretched pulsed light beam.

[0007] Each actuator may include a sleeve hermetically sealed within the wall of the container and a drive element configured to move relative to the sleeve, the drive element being in physical communication with the optical element. The sleeve may be positioned and secured within a hole in the wall of the container, and the drive element may include an adjustment mechanism at a first end and a shaped tip screwdriver at a second end, the shaped tip screwdriver sized to interact with a shaped socket, the shaped socket being in physical communication with the optical element. The shaped socket may include a tapered feedthrough feature configured to align the shaped tip screwdriver with the shaped socket. Rotation of the adjustment mechanism at the first end may translate the shaped tip screwdriver at the second end, thereby translating the shaped socket in physical communication with the optical element. The shaped tip screwdriver may be a hexagonal tip screwdriver, and the shaped socket may be a hexagonal socket. The interior of the sleeve can accommodate the adjustment mechanism, and the interface between the sleeve and the adjustment mechanism can be a threaded interface, such that rotation of the adjustment mechanism causes the adjustment mechanism to translate relative to the sleeve and causes the shaped-tip screwdriver to translate and rotate relative to the sleeve. The threaded interface can include rounded-tip threads on the interior of the sleeve that mate with rounded-tip threads on the exterior of the adjustment mechanism. The sleeve and the adjustment mechanism can each be made of a lead-free metal or lead-free metal alloy, and the interface can be lubricant-free. The threaded interface can include threads on the interior of the sleeve that mate with threads on the exterior of the adjustment mechanism, the threads having a pitch of 80 to 100 teeth per inch. The shaped-tip screwdriver can be resiliently engaged with the adjustment mechanism. The drive element can maintain physical communication with the optical element throughout its range of motion within the sleeve. When one or more pulsed light beams and stretched pulsed light beams are passed through the window, and when the pulsed light beams and stretched pulsed light beams are operated at a repetition rate greater than 500 Hz, greater than 1000 Hz, or greater than 3000 Hz, the adjustment mechanism can adjust one or more physical properties of an optical element physically connected to the actuator device.

[0008] The controlled environment may be purged with gas and maintained at a pressure greater than atmospheric pressure, or at a pressure of about 15 to 22 pounds per square inch (PSI).

[0009] The optical stretcher may include two or more stacked confocal optical pulse stretchers disposed within an internal cavity. A first of the stacked confocal optical pulse stretchers may include a first plurality of mirrors and may be configured to receive a portion of a pulsed beam and generate a first stretched pulsed beam by reflecting the portion of the pulsed beam at the first plurality of mirrors. A second of the stacked confocal optical pulse stretchers may include a second plurality of mirrors and may be configured to receive a portion of the first stretched pulsed beam and generate a second stretched pulsed beam by reflecting the portion of the first stretched pulsed beam at the second plurality of mirrors. The first plurality of mirrors and the second plurality of mirrors may include concave mirrors.

[0010] The optical element in physical communication with the actuator may include an optical element of an optical stretcher.

[0011] In other general aspects, a deep ultraviolet (DUV) light source includes an optical pulse stretcher apparatus. The optical pulse stretcher apparatus comprises: a hermetically sealed container including one or more walls defining an internal cavity, the internal cavity being maintained in a controlled environment during operation, at least one wall having one or more windows, each window 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 actuators. Each actuator is physically connected to an optical element within the internal cavity and includes an adjustment mechanism external to the hermetically sealed container. The adjustment mechanism enables adjustment of one or more physical properties of the optical element physically connected to the actuator without disrupting the controlled environment within the internal cavity. Simple diagram description

[0012] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and enable one skilled in the art to make and use the invention. One or more of the drawings may not be drawn to scale.

[0013] FIG1 is a block diagram of an optical pulse stretcher apparatus comprising an optical stretcher disposed within an interior cavity of a hermetically sealed container defined by a plurality of walls, and one or more through-wall adjusters or actuators configured to effect adjustment of optical elements within the interior cavity;

[0014] FIG2A is a perspective view of an embodiment of an actuator mounted to the wall of the container of FIG1 , the actuator including an adjustment mechanism located outside the interior cavity, and a screwdriver located within the interior cavity and engaging a region or portion of the optical element, the screwdriver being movable in an axial direction relative to a sleeve fixed within the wall;

[0015] Figure 2B is a side sectional view of the actuator of Figure 2A;

[0016] Figure 2C is a side sectional view of the actuator of Figure 2A mounted to the wall of the container of Figure 1;

[0017] Figure 2D is a cross-sectional view of the actuator of Figure 2C taken along plane 2D-2D;

[0018] Figure 2E is a cross-sectional view of the actuator of Figure 2C taken along plane 2E-2E;

[0019] Figure 3A is a perspective view of an embodiment of the sleeve within the actuator device of Figures 2A to 2E;

[0020] FIG3B is a perspective view of an embodiment of a drive element comprising a body including an adjustment mechanism at a first end and a screwdriver at a second end, the drive element extending axially along a central opening of a sleeve when installed in an actuator device;

[0021] Figure 3C is a detailed view 3C of the interface between the drive element and the sleeve of Figure 2C;

[0022] FIG4 is a block diagram of an embodiment of the optical pulse stretcher apparatus of FIG1 implemented in a pulsed light source configured to supply a light beam to a photolithography exposure apparatus for producing a circuit pattern on a target portion of a substrate (or wafer);

[0023] 5A is a block diagram of an embodiment of an optical pulse stretcher apparatus comprising a first optical pulse stretcher device and a second optical pulse stretcher device configured as a series of stacked optical pulse stretcher devices;

[0024] FIG5B is a block diagram of an embodiment of an optical arrangement within a second optical pulse stretcher device, the optical arrangement being configured to receive a first stretched pulsed beam from a first optical pulse stretcher device, split the first stretched pulsed beam into a plurality of portions, redirect the split portions into 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 beam that is directed to the first optical pulse stretcher device;

[0025] Figure 6A is a block diagram showing an embodiment of an actuator and associated alignment apparatus in a side cross-sectional view and when the alignment apparatus is outside the path of the light beam;

[0026] Figure 6B is a block diagram of an embodiment of the actuator and associated alignment apparatus of Figure 6A shown in side cross-sectional view and when the alignment apparatus is in the path of the light beam;

[0027] Figure 6C is a plan view viewed toward the wall of the container accommodating the alignment device when the alignment device is outside the path of the light beam (as in Figure 6A);

[0028] Figure 6D is a plan view of the alignment device when it is in the path of the light beam (as in Figure 6B) viewed toward the wall of the container housing the alignment device;

[0029] Figure 7 is a perspective view of an embodiment of an optical element, the optical element is adjusted using three actuators at three different points on the back of the optical element;

[0030] 8A to 8C illustrate side cross-sectional views through a mirror, one of a set of adapters, and one of the respective actuators of FIG. 7 ; wherein FIG. 8A illustrates a neutral position of an adjustment mechanism of the actuator, FIG. 8B illustrates a position in which the adjustment mechanism has been rotated relative to the position shown in FIG. 8A (e.g., clockwise when facing the wall outside the internal cavity), and FIG. 8C illustrates a position in which the adjustment mechanism has been rotated (e.g., counterclockwise when facing the wall from outside the internal cavity relative to the position shown in FIG. 8A ); and

[0031] 8D shows a cross-sectional view of the screwdriver and socket of the actuator of FIG. 8A , the view being taken along the XY plane of FIG. 8A . Implementation Method

[0032] Referring to FIG. 1 , an optical pulse stretcher apparatus 100 includes a hermetically sealed container 105 comprising one or more walls 106a, 106b, 106c, and 106d defining an interior cavity 107. Four walls 106a, 106b, 106c, and 106d are shown in the two-dimensional representation of FIG. However, container 105 may have any suitable three-dimensional shape, such as a rectangular prism, a cube, or a cylinder, and the number of walls 106a, 106b, 106c, and 106d may vary depending on the shape. During operation of the optical pulse stretcher apparatus 100, interior cavity 107 is maintained in a controlled environment. For example, interior cavity 107 may be formed by hermetically sealed walls 106a, 106b, 106c, and 106d. In this manner, interior cavity 107 may be maintained at a specific pressure (such as a pressure below or above atmospheric pressure) or at a specific humidity environment (such as low humidity). As another example, the internal cavity 107 can be configured as a purged environment (such as a nitrogen purged environment). In some embodiments, the internal cavity 107 is maintained at a pressure of approximately 4-8 pounds per square inch (psi) above atmospheric pressure. For example, if the internal cavity 107 is a purged environment, the pressure can be maintained at approximately 18-23 psi.

[0033] At least one wall 106d of the container 105 includes one or more windows 108, wherein each window 108 is configured to transmit one or more pulsed light beams 109. The pulsed light beams 109 can be either unstretched or stretched. An unstretched pulsed light beam is a light beam that has not yet been transmitted to or passed through the apparatus 100 and, therefore, has not been optically stretched by the apparatus 100. A stretched pulsed light beam is a light beam that has been at least partially stretched by passing through the apparatus 100.

[0034] The optical pulse stretcher apparatus 100 includes an optical stretcher 115 disposed within an internal cavity 107. The optical stretcher 115 is configured to receive an input pulse beam 116 and generate at least one stretched output pulse beam 117. The optical stretcher 115 includes a plurality of optical elements 120-i, where i is a set of numbers 1, 2, ..., I, and I is a number greater than 1. The optical pulse stretcher apparatus 100 may also include one or more other optical elements 125-k within the internal cavity 107, where k is a set of numbers 1, 2, ..., K, and K is a positive integer. Each of the optical elements 120-i and 125-k is configured to interact with a pulse beam (such as, for example, pulse beam 109, pulse beam 116, or pulse beam 117) within the internal cavity 107 at a certain point.

[0035] One or more of the optical elements 120-i, 125-k within the optical pulse stretcher apparatus 100 may need to be adjusted (e.g., aligned or modified in position or angle). For example, to ensure that the input pulsed beam 116 properly traverses the optical stretcher 115, one or more of the optical elements 120-i may need to be adjusted. Furthermore, such adjustments to the optical elements 120-i may occur during the interaction of the input pulsed beam 116 with the optical elements 120-i. As another example, the optical pulse stretcher apparatus 100 may include a beam observation device for locating the center of the pulsed beam within the apparatus 100. The beam observation device may be configured to translate into and out of the path of the pulsed beam within the apparatus 100, such that when out of the path, it does not obstruct or alter the pulsed beam during normal operation, but can be moved into the path to enable visualization of the pulsed beam for diagnostic purposes. This beam observation device may be considered to be an optical element 125-k that needs to be translated into and out of the path of the pulsed beam.

[0036] Apparatus 100 includes one or more through-wall adjusters or actuators 130-j, where j is the set of numbers 1, 2, ..., J, and J is a positive integer. Each actuator 130-j extends through a wall (such as wall 106d). In this manner, at one end, actuator 130-j is physically within interior cavity 107, while at the opposite end, actuator 130-j is external to interior cavity 107. Each actuator 130-j is associated with and physically communicates with an optical element 120-i, 125-k requiring adjustment at a given moment. Therefore, some of optical elements 120-i, 125-k may not be associated with an actuator 130-j. In FIG1 , optical element 120-1 is associated with actuator 130-1, optical element 120-1 is associated with actuator 130-2, optical element 125-1 is associated with actuator 130-3, and optical element 125-2 is associated with actuator 130-4. Although FIG1 shows four actuators 130-1, 130-2, 130-3, and 130-4, there may be fewer or more than four actuators 130-j. Each actuator 130-j includes a respective adjustment mechanism 131-j located outside of hermetically sealed container 105. Thus, actuator 130-1 includes adjustment mechanism 131-1; actuator 130-2 includes adjustment mechanism 131-2; actuator 130-3 includes adjustment mechanism 131-3; and actuator 130-4 includes adjustment mechanism 131-4.

[0037] The adjustment mechanism 131-j enables adjustment of one or more physical properties of the optical element (120-i or 125-k) in physical communication with the actuator 130-j without disrupting the controlled environment within the internal cavity 107. That is, the adjustment mechanism 130-j enables the associated optical element 120-i, 125-k to be adjusted without opening the hermetically sealed container 105.

[0038] During previous adjustment procedures that require opening the hermetically sealed container 105, the usability of the apparatus 100 is time-consuming and complex. For example, it can be challenging for a field service engineer to directly access the optical elements 120-i, 125-k for adjustment using these previous procedures. This is because the space within the internal cavity 107 is limited, and the geometric arrangement of the various optical elements 120-i, 125-k can make access difficult. Furthermore, when the container 105 is open (during these previous adjustment procedures), the pulsed beam 109 typically operates at a lower repetition rate, making it more difficult for the field service engineer to quickly and accurately perform the required adjustments on the optical elements 120-i, 125-k. Finally, because the container 105 is hermetically sealed and the internal cavity 107 can utilize a purge gas, additional time is required to remove the purge gas, open the container 105, perform the adjustment, reseal the container 105, and reintroduce the purge gas into the internal cavity 107.

[0039] In contrast, by using actuator 130-j (and adjustment mechanism 131-j), the time and complexity of servicing optical pulse stretcher device 100 is reduced because the steps of opening and then closing container 105 are not required. Furthermore, during adjustment of optical elements 120-i, 125-k, pulsed beam 109 received by optical pulse stretcher device 100 through window 108 can be generated at a high repetition rate. By using pulsed beam 109 at a high repetition rate during adjustment, faster and / or more precise adjustments can be performed because pulsed beam 109 can be more easily visualized as it interacts with optical elements 120-i, 125-k. This is particularly important when optical element 125-k comprises, for example, a fluorescent screen, which generates fluorescence when interacting with pulsed beam 109. By operating at a high repetition rate, the adjustment process can be adapted as the screen (of optical element 125-k) ages; for example, the repetition rate of pulsed beam 109 can be adjusted to account for this degradation, depending on the age of the screen. High repetition rates can be repetition rates greater than 50 Hz, greater than 100 Hz, greater than 500 Hz, greater than 1000 Hz, or greater than 3000 Hz. In some embodiments, high repetition rates extend up to 6 kHz. In some embodiments, high repetition rates are required by downstream output equipment (such as the photolithography exposure equipment 462 of FIG. 4 ). Furthermore, 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 access optical elements 120-i, 125-k (as described above). Furthermore, the optical elements 120-i, 125-k may be adjusted while in the controlled environment of the internal cavity 107, and if a purge gas is used, the optical elements 120-i, 125-k may be maintained while being adjusted.

[0040] Actuator 130-j is designed to operate within the controlled environment of internal cavity 107. For example, if a purge gas is used during operation of device 100, the portion of actuator 130-j within internal cavity 107 is compatible with the purge gas. Because of the use of a purge gas and controlled environment, actuator 130-j operates without the use of lubricants or friction-reducing materials, such as Teflon or lead metal. Furthermore, by avoiding the use of lubricants and friction-reducing materials, outgassing at actuator 130-j is reduced. Outgassing, which can occur due to light scattering from lubricants or friction-reducing materials, can degrade the performance or lifespan of optical elements 120-i, 125-k.

[0041] Because each actuator 130-j extends between the interior cavity 107 and the exterior of the container 105, where the actuator 130-j is in physical communication with the respective optical element 120-i, 125-k, the actuator 130-j also needs to provide a seal at the interface 132-j between the actuator 130-j and the wall to which it is mounted. For example, a first seal is formed at the interface 132-1 between the actuator 130-1 and the wall 106c; a second seal is formed at the interface 132-2 between the actuator 130-2 and the wall 106c; a third seal is formed at the interface 132-3 between the actuator 130-3 and the wall 106d; and a fourth seal is formed at the interface 132-4 between the actuator 130-4 and the wall 106d.

[0042] As mentioned above, each actuator 130-j is in physical communication with its respective optical element 120-i, 125-k within the internal cavity 107. To achieve this physical communication, each actuator 130-j includes a screwdriver 133-j that physically contacts an area or portion of the optical element 120-i, 125-k. Thus, in the example of FIG1 , actuator 130-1 includes screwdriver 133-1 that physically contacts an area or portion of optical element 120-1; actuator 130-2 includes screwdriver 133-2 that physically contacts an area or portion of optical element 120-1; actuator 130-3 includes screwdriver 133-3 that physically contacts an area or portion of optical element 125-1; and actuator 130-4 includes screwdriver 133-4 that physically contacts an area or portion of optical element 125-2. The screwdriver 133 - j may be a device capable of making and maintaining physical contact with an area or portion of the optical element 120 - i , 125 - k .

[0043] Referring to Figures 2A-2E , an embodiment 230-j of the actuator 130-j is shown. In Figures 2C-2E , the actuator 230-j is shown mounted to the wall 206 of a hermetically sealed container, such as the container 105. The actuator 230-j includes an adjustment mechanism 231-j that, when the actuator 230-j is mounted to the wall 206, is positioned outside the interior cavity 207 ( Figure 2C ). The actuator 230-j includes a screwdriver 233-j that, when the actuator 230-j is mounted to the wall 206, is positioned inside the interior cavity 207. As discussed above, the screwdriver 233-j engages (is in physical contact with) a region or portion of the optical element 120-i or 125-k within the container 105. In this way, the adjustment mechanism 231 - j can be accessed from outside the container 105 and the screwdriver 233 - j can be controlled (to thereby adjust the optical element) without requiring access to the internal cavity 207 .

[0044] Adjustment mechanism 231-j is part of drive element 235-j and is located at its first end. Drive element 235-j extends through central opening 345-j ( FIG. 3A ) of sleeve 234-j. Adjustment mechanism 231-j includes a rotation element 236-j that enables adjustment mechanism 231-j to rotate relative to sleeve 234-j. In this embodiment, rotation element 236-j is a shaped opening or recess (specifically, a hexagonal socket) defined at the end of adjustment mechanism 231-j, and adjustment mechanism 231-j is designed similar to a screw. When a suitably shaped drive element is inserted into shaped opening 236-j and then rotated, adjustment mechanism 231-j rotates. For example, if the formed opening 236-j is a hexagonal socket, a hex head screwdriver or an Allen wrench can be inserted into the hexagonal socket 236-j and then rotated to rotate the adjustment mechanism 231-j relative to the sleeve 234-j.

[0045] The drive element 235-j is configured to move relative to the sleeve 234-j along the axial direction Zj, while the sleeve 234-j is hermetically sealed within and secured to the wall 206 ( FIG. 2C ). The drive element 235-j includes a body 237-j that extends axially (i.e., along the axial direction Zj) along the central opening 345-j ( FIG. 3A ) of the sleeve 234-j and defines a translational direction applied to the screwdriver 233-j. The drive element 235-j includes the screwdriver 233-j at a second end. The drive element 235-j also includes a biasing device 238-j that is configured to bias the screwdriver 233-j in the positive Zj direction so that the screwdriver 233-j remains engaged with a region or portion of the optical element 120-i or 125-k when the screwdriver 233-j is adjusting the optical element 120-i or 125-k. Biasing device 238-j includes a biasing member 239-j (such as a spring) mounted within cavity 240-j of coupler 241-j. Cavity 240-j receives second end 242-j of body 237-j and base 243-j of screwdriver 233-j, with biasing member 239-j mounted between base 243-j and second end 242-j. Biasing member 239-j is biased in the positive Zj direction, urging base 243-j, and thus screwdriver 233-j, in the positive Zj direction. Due to this biasing function, screwdriver 233-j resiliently engages adjustment mechanism 231-j. Furthermore, drive element 235-j maintains physical communication with an optical element (such as optical elements 120-i and 125-k) throughout its range of motion relative to sleeve 234-j. The coupler 241 - j is secured to the second end 242 - j of the body 237 - j by means of a securing means 244 - j , such as a set screw.

[0046] FIG3A shows the sleeve 234-j separated from the other components of the actuator 230-j. The sleeve 234-j includes a cylindrical body 346-j defining a central opening 345-j. Both the body 346-j and the central opening 345-j extend along an axial direction Zj, with the central opening 345-j extending through the sleeve 234-j. The sleeve 234-j also includes a cylindrical flange 347-j extending from the body 346-j. As shown in FIG2C , the flange 347-j is configured to enable the sleeve 234-j to form a hermetic seal against the wall 206. Specifically, a seal is formed at the interface between the wall 206 and the radial surface of the flange 347-j, preventing leakage of substances between the interior cavity 207 and the exterior of the container 105. In this example, the seal is formed by a gasket 248-j sandwiched between the radial surface of the flange 347-j and the outer surface of the wall 206. When the flange 347-j and the wall 206 are pressed into each other (along the axial direction Zj), the gasket 248-j is compressed. For example, the body 346-j may include an external threaded surface 350-j (as shown in FIG. 3A ), and a threaded nut 249-j ( FIG. 2C ) disposed about the body 346-j may be rotated relative to 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 (at the gasket 248-j) prevents purge gas (such as nitrogen or N 2 gas) from escaping from the internal cavity 207 along the path between the sleeve 234-j and the wall 206.

[0047] In some embodiments, an additional seal can be formed between the sleeve 234-j and the drive element 235-j. To this end, the flange 347-j of the sleeve 234-j includes an externally threaded surface 351-j (as shown in FIG. 3A ) that mates with an internally threaded surface of the cap 252-j (as shown in FIG. 2A-2C ). A seal can be formed at the interface between the cap 252-j and the outwardly radially facing surface of the flange 347-j. Specifically, when the cap 252-j is screwed onto the flange 347-j, a screw thread seal is formed, and when the cap 252-j is tightened, an O-ring 253-j positioned at the interface between the outer radial surface of the flange 347-j and the cap 252-j is compressed, thereby forming a seal. Thus, this second or additional seal relies on the placement of the cap 252-j over the flange 347-j. Therefore, to access the adjustment mechanism 231-j, the cap 252-j must be removed.

[0048] FIG3B shows the drive element 235-j separated from the other components of the actuator 230-j. A biasing device 239-j is positioned between the second end 242-j of the body 237-j and the base 243-j of the screwdriver 233-j. The screwdriver 233-j extends along the axial direction Zj and includes a tip 353-j that physically contacts a region or portion of the optical element 120-i, 125-k. The base 243-j of the screwdriver 233-j has a generally cylindrical shape having a diameter smaller than that of the cavity 240-j and is movable within the cavity 240-j along the axial direction Zj. The tip 353-j of the screwdriver 233-j has a geometry that is complementary to the geometry of the region or portion of the optical element 120-i, 125-k with which it physically contacts. Thus, the tip 353-j is able to maintain frictional engagement with an area or portion of the optical element 120-i, 125-k. For example, the tip 353-j may be hexagonal in shape, and the area or portion of the optical element 120-i, 125-k in physical contact with the tip 353-j may be a hexagonal socket.

[0049] As shown in Figures 3B and 3C, the body 237-j includes a threaded outer surface 354-j. This threaded outer surface 354-j mates with a threaded inner surface 355-j of the central opening 345-j of the sleeve 234-j (as shown in Figure 3A). Thus, the interface between the body 237-j and the sleeve 234-j is a threaded interface. Because the sleeve 234-j is secured within the opening of the wall 206, when the cap 252-j is removed and the adjustment mechanism 231-j is engaged (such as by turning an internal hexagonal wrench inserted into the hexagonal socket 236-j), the entire body 237-i rotates relative to the sleeve 234-j, causing the body 237-i to translate relative to the sleeve 234-j (and relative to the wall 206) along the axial direction Zj. 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 a circular thread, the thread is formed by rolling the surface (surface 354-j or 355-j) with a die rather than cutting the thread on a machine. In some embodiments, the threads at surfaces 354-j and 355-j may have a small pitch, such as 80 to 100 teeth per inch.

[0050] Because the components of the sleeve 234-j and adjustment mechanism 231-j (such as the body 237-j, coupler 241-j, biasing device 239-j, and screwdriver 233-j) are at least partially located within the internal cavity 207 (which is a controlled environment), the sleeve and adjustment mechanism components are made of materials that do not react with any materials within the internal cavity 107 / 207. Furthermore, the components of the sleeve 234-j and adjustment mechanism 231-j that move relative to each other (such as the body 237-i) should be made of materials that enable relative motion while also ensuring that friction remains below an acceptable level. Furthermore, the interface between the body 237-j and sleeve 234-j (detailed in FIG. 3C ) needs to operate without the use of lubricants (i.e., the body 237-j needs to be able to move relative to the sleeve 234-j), which could disrupt the controlled environment within the internal cavity 107 / 207. Taking these factors into consideration, in some embodiments, the sleeve 234-j and the adjustment mechanism 231-j components can be made of lead-free metals or lead-free metal alloys. For example, the sleeve 234-j can be made of phosphor bronze (such as UNS C51000 or H04 temper). If the adjustment mechanism 231-j is a screw, it can be made of stainless steel, such as Type 303 stainless steel (UNS S30300).

[0051] Referring to FIG4 , embodiment 400 of optical pulse stretcher apparatus 100 is part of a pulsed light source 460. Light source 460 can be used as part of a lithography apparatus to supply a pulsed light beam 461 to a photolithography exposure apparatus 462 for producing circuit patterns on target portions of a substrate (or wafer). In some embodiments, light source 460 is a deep ultraviolet (DUV) light source, and light beam 461 has a wavelength within the DUV wavelength range, which may include, for example, wavelengths from about 100 nanometers (nm) to about 400 nm. As illustrated in FIG4 , light source 460 may be a dual-stage light source including a first stage 463A and a second stage 463B. First stage 463A may include a master oscillator (M0) that generates a first pulsed light beam 464, which is transmitted to second stage 463B via optical elements 465 including relay optics. The second stage 463B may include a power amplifier (PA) that receives the first pulsed beam 464 and optically amplifies the first pulsed beam 464 to form a second pulsed beam 466 that is directed to the optical pulse stretcher device 400.

[0052] First stage 463A may include, for example, an MO chamber module, wherein a discharge between electrodes (not shown) may induce a discharge in a laser gas to generate an inversion population of high-energy molecules, such as argon, krypton, or xenon, to produce relatively broadband radiation. This radiation is line-narrowed to a relatively narrow bandwidth and center wavelength selected in a line-narrowing module ("LNM") within first stage 463A. First stage 463A may also include an MO output coupler (MO OC), which may include a partially reflecting mirror that, together with a reflective grating in the LNM, forms an oscillator cavity in which first stage 463A oscillates to form first pulsed beam 464. First stage 463A may also include other components, such as a line-centering analysis module (LAM).

[0053] The optical element 465 may include a MO wavefront engineering box (WEB) for redirecting the first pulsed beam 464 toward the second platform 463B. The optical element 465 may also include, for example, a beam expansion optical element having, for example, a multi-prism beam expander (not shown) and coherence breaking, for example, in the form of an optical delay path (not shown).

[0054] Second stage 463B includes a PA chamber module, which also serves as an oscillator, for example, formed by injecting first pulsed beam 464, and output coupling optics, which can be redirected back through the gain medium in the PA chamber via a beam reverser. The output coupling optics can incorporate partially reflecting input / output couplers, a maximum reflective mirror for the nominal operating wavelength (which can be approximately 193 nm for ArF systems), and one or more prisms. Second stage 463B optically amplifies first pulsed beam 464 to form second pulsed beam 466.

[0055] Each of the MO chamber module (of the first stage 463A) and the PA chamber module (of the second stage 463B) can be part of a gas discharge light source, such as an excimer light source. In such light sources, the MO chamber module and the PA chamber module each contain a gas mixture comprising a combination of one or more noble gases (which may include argon, krypton, or xenon) as a gain medium and a reactive gas (which may include fluorine or chlorine). Thus, for example, the gain medium in each module may include argon fluoride (ArF), krypton fluoride (KrF), or xenon chloride (XeCl). If the gain medium includes ArF, the wavelength of the pulsed beam 461 is approximately 193 nm, and if the gain medium includes KrF, the wavelength of the pulsed beam 461 is approximately 248 nm. The size of the microelectronic features patterned on the wafer (in the photolithography exposure apparatus 462) depends on the wavelength of the pulsed beam 461, with lower wavelengths resulting in smaller minimum feature sizes.

[0056] The second pulsed beam 466 is input to the optical pulse stretcher apparatus 400 , where a copy of the second pulsed beam 466 is delayed and recombined to thereby reduce speckle in the pulsed beam 461 directed to the photolithography exposure apparatus 462 .

[0057] An example of a dual-stage light source 460 and an optical pulse stretcher device 400 is described in WO 2021 / 076658 published by applicant Cymer, LLC on April 22, 2021, the disclosure of which is incorporated herein by reference in its entirety.

[0058] In some embodiments, the optical pulse stretcher device 400 includes a single pulse stretcher. In other embodiments, the optical pulse stretcher device 400 includes multiple stages of pulse stretchers. For example, the pulse stretcher may include a plurality (at least two) of concave mirrors arranged relative to each other to form a confocal resonator. In some embodiments, as discussed in detail in WO 2021 / 076658, the optical pulse stretcher device 400 includes a first optical pulse stretcher device 400-1 and a second optical pulse stretcher device 400-2 configured as a series of stacked optical pulse stretcher devices. In these embodiments, the first optical pulse stretcher device 400-1 receives the second pulse beam 466 and delays and recombines a replica of the second pulse beam 466 to produce a first stretched pulse beam 418. This first stretched pulse beam 418 is then input to the second optical pulse stretcher device 400-2, which delays and recombines a replica of the first stretched pulse beam 418 to produce a second stretched pulse beam 419. This second stretched pulsed beam 419 is input to the first optical pulse stretcher device 400-1, where it is then redirected out as pulsed beam 461.

[0059] Optical pulse stretcher apparatus 400 includes a hermetically sealed container 405 comprising a plurality of walls 406a, 406b, 406c, 406d, 406e, 406f, 406g, and 406h, which together define an interior cavity containing the optical components or elements of devices 400-1 and 400-2. For simplicity, FIG4 shows a two-dimensional representation of container 405 having eight walls, but container 405 is three-dimensional and may include walls extending in other directions or parallel to the page. As with optical pulse stretcher apparatus 100, apparatus 400 includes one or more through-wall adjusters or actuators 430-j. FIG4 shows two actuators 430-1 and 430-2, where actuator 430-1 is associated with an optical element (not shown in FIG4 ) within a first optical pulse stretcher device 400-1, and actuator 430-2 is associated with an optical element (not shown in FIG4 ) within a second optical pulse stretcher device 400-2. The optical pulse stretcher apparatus 400 may include fewer than or more than two actuators 430-j, and each of the optical pulse stretcher devices 400-1 and 400-2 may include one or more respective actuators 430-j.

[0060] Each optical pulse stretcher device 400-1, 400-2 may include one or more optical pulse stretchers, wherein each optical pulse stretcher includes one or more confocal resonators. The confocal resonator includes reflective surfaces that generally face each other and are arranged relative to each other such that a pulsed beam (such as the second pulsed beam 466 or the first stretched pulsed beam 418) reflects back and forth in a region between the reflective surfaces.

[0061] Referring to FIG5A , an embodiment 500 of the optical pulse stretcher apparatus 400 is shown. The optical pulse stretcher apparatus 500 includes a first optical pulse stretcher device 500-1 and a second optical pulse stretcher device 500-2, which are configured as a series of stacked optical pulse stretcher devices. In these embodiments, the first optical pulse stretcher device 500-1 receives the second pulse beam 466 and delays and recombines a copy of the second pulse beam 466 to produce a first stretched pulse beam 518. This first stretched pulse beam 518 is then input to the second optical pulse stretcher device 500-2, which delays and recombines the copy of the first stretched pulse beam 518 to produce a second stretched pulse beam 519. This second stretched pulse beam 519 is input to the first optical pulse stretcher device 500-1, where it is then redirected out as the pulse beam 461.

[0062] The first optical pulse stretcher device 500-1 includes at least one optical pulse stretcher 503-1 within its internal cavity 507-1. The at least one optical pulse stretcher includes at least two opposing mirrors 502a, 502b that generate reflections therebetween and define a confocal resonator. For example, the optical pulse stretcher 503-1 may include a first single mirror 502a and a second single mirror 502b to generate two reflections of the delayed portion of the second pulsed light beam 466. As another example, the optical pulse stretcher 503-1 may include two first mirrors 502a and two second mirrors 502b that generate four reflections of the delayed portion of the second pulsed light beam 466. The mirrors 502a, 502b may be separated by a physical distance sufficiently large to achieve a desired optical delay. In some implementations, 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 approximately 30 nanoseconds (ns) to approximately 50 ns. Mirrors 502a and 502b can be circular and concave. Additionally, first optical pulse stretcher device 500-1 can include other optical elements. For example, beam splitter 504 is positioned in the path of second pulse beam 466 to split a portion of second pulse beam 466 toward optical pulse stretcher 503-1. A pair of beam splitters 504a and 504b can be positioned to split first stretched pulse beam 518 into second optical pulse stretcher device 500-2 and then recombine second stretched pulse beam 519 from second optical pulse stretcher device 500-2.

[0063] The second optical pulse stretcher device 500-2 includes one or more confocal optical pulse stretchers within its internal cavity 507-2. In the illustrated example, there are three confocal optical pulse stretchers 503-2i, 503-2ii, and 503-2iii. Each of the optical pulse stretchers 503-2i, 503-2ii, and 503-2iii includes at least two respective opposing mirrors 570-ai, 570-bi; 570-aii, 570-bii; and 570-aiii, 570-biii. Although two opposing mirrors are shown in each pulse stretcher 503-2i, 503-2ii, and 503-2iii, each pulse stretcher 503-2i, 503-2ii, and 503-2iii may include more than two opposing mirrors.

[0064] The second optical pulse stretcher device 500-2 also includes an optical arrangement 572 configured to receive the first stretched pulse beam 518, split the first stretched pulse beam 518 into a plurality of portions, redirect the split portions into one or more of the pulse stretchers 503-2i, 503-2ii, 503-2iii, and recombine the delayed split portions to form a second stretched pulse beam 519. Thus, the optical arrangement 572 includes one or more beam splitters and folding mirrors.

[0065] 5B , an embodiment 572B of the optical arrangement 572 is shown. The optical arrangement 572B includes three beam splitters 571i, 571ii, and 571iii positioned along the path of the first stretched pulsed beam 518, wherein each beam splitter 571i, 571ii, and 571iii is configured to extract a portion of the first stretched pulsed beam 518 and direct that portion into a respective confocal optical pulse stretcher 503-2i, 503-2ii, and 503-2iii. The optical arrangement 572B also includes two folding mirrors 504c and 505d configured to direct a second stretched pulsed beam 519 (formed by passing a portion of the first stretched pulsed beam 518 through each of the confocal optical pulse stretchers 503-2i, 503-2ii, and 503-2iii) back toward the first optical pulse stretcher device 500-1.

[0066] Referring again to FIG5A , optical pulse stretcher apparatus 500 includes a hermetically sealed container 505 comprising a plurality of walls 506a, 506b, 506c, 506d, 506e, 506f, 506g, and 506h, which together define an interior cavity that houses the optical components or elements of devices 500-1 and 500-2. For simplicity, FIG5A shows a two-dimensional representation of container 505 having eight walls, but container 505 is three-dimensional and may include walls extending in other directions or parallel to the page, and container 505 may include different segments connected together.

[0067] The optical pulse stretcher device 500 may also include optical elements 573a and 573b, which are used to align other optical components within the optical pulse stretcher device 500. In the example of FIG5A , optical element 573a is an alignment device configured to selectively interact with the first stretched pulsed beam 518, and optical element 573b is an alignment device configured to selectively interact with the second stretched pulsed beam 519. Additional alignment devices may be used at other locations along the path of the beam traveling through the optical pulse stretcher device 500. Alignment device 573a is used to visualize the first stretched pulsed beam 518, and alignment device 573b is used to visualize the second stretched pulsed beam 519. This visualization enables engineers to determine the path of the beams and make adjustments to other components within the device 500 to ensure alignment of the beams with the optical components. During normal operation of the device 500, the device 500 optically stretches the second pulsed beam 466 to form the pulsed beam 461. During normal operation of the apparatus 500, the alignment device 573a does not interact with the first stretched pulsed beam 518, and the alignment device 573b does not interact with the second stretched pulsed beam 519, as shown in FIG5A. On the other hand, during visualization operation, when visualization of the beam 518 is required, the alignment device 573a is moved and thereby inserted into the path of the beam 518, and when visualization of the beam 519 is required, the alignment device 573b is moved and thereby inserted into the path of the beam 519.

[0068] Similar to optical pulse stretcher device 100, apparatus 500 includes one or more through-wall adjusters or actuators 530-j. Actuators 530-1, 530-2, 530-3, 530-8, 530-9, and 530-10 are associated with mirrors 570-biii, 570-bii, 570-bi, 570-ai, 570-aii, and 570-aiii of optical pulse stretchers 503-2i, 503-2ii, and 503-2ii, respectively. Actuators 530-4 and 530-5 are associated with alignment devices 573a and 573b, respectively. Actuators 530-6 and 530-7 are associated with mirrors 502b and 502a, respectively, of optical pulse stretcher 503-1. Finally, at least one actuator 530-11 is associated with an optical element within optical arrangement 572. Actuators 530-1, 530-2, and 530-3 are installed as through-wall adjusters in wall 506a; actuators 530-4 and 530-5 are installed as through-wall adjusters in wall 506c; actuator 530-6 is installed as a through-wall adjuster in wall 506d; actuator 530-7 is installed as a through-wall adjuster in wall 506e; actuators 530-8, 530-9, and 530-10 are installed as through-wall adjusters in wall 506g; and actuator 530-11 is installed as a through-wall adjuster in wall 506h. The optical pulse stretcher apparatus 500 may include fewer than or more than eleven actuators 530-j, and each of the optical pulse stretcher apparatuses 500-1 and 500-2 may include one or more respective actuators 530-j.

[0069] Referring to FIG5B , there may be more than one actuator 530-11 mounted in the wall as a through-the-wall adjuster to provide access to one or more of the optical components within optical arrangement 572B. In this embodiment, two actuators 530-11 and 530-12 are mounted on wall 506h for controlling and adjusting respective mirrors 504c and 504d. Additionally, actuators 530-13, 530-14, and 530-15 are mounted (along different walls parallel to the page) to respective beam splitters 571i, 571ii, and 571iii. Actuators 530-11 and 530-12 can be mounted to respective folding mirrors 504c and 504d in a manner similar to that shown in FIG6A-6D or FIG7 . The actuators 530-13, 530-14, 530-15 may be configured relative to respective beam splitters 571i, 571ii, 571iii in a manner similar to that shown in Figure 7. Thus, as discussed below with respect to Figure 7, two actuators may be configured for each beam splitter 571i, 571ii, 571iii to provide both tip adjustment and tilt adjustment for each beam splitter 571i, 571ii, 571iii.

[0070] Referring to Figures 6A-6D , an embodiment of actuator 530-4 and associated alignment device 573a is shown in side cross-sectional views (Figures 6A and 6B) and in plan views looking toward wall 506c (Figures 6C and 6D). Figures 6A and 6C illustrate normal operation, while Figures 6B and 6D illustrate visualization operation. Specifically, in Figures 6A and 6C , alignment device 573a is outside the path of light beam 518, while in Figures 6B and 6D , alignment device 573a is placed in the path of light beam 518. Alignment device 573a includes a refractive element, such as a prism 574a, and a visualization device, such as a fluorescent screen 575a. An engineer can view fluorescent screen 575a through a viewport 576 located in wall 506c near the screen 575a. Viewport 576 is hermetically sealed to wall 506c and enables visualization of fluorescent screen 575a from outside container 505. Viewport 576 comprises a material transparent to light generated at fluorescent screen 575a. Fluorescent screen 575a is fixed relative to prism 574a, and thus, the screen and prism can move together under the control of actuator 530-4. Actuator 530-4 includes an adjustment mechanism 531-4 located outside interior cavity 507-1 and at one end of a drive element 535-4. The other end of drive element 535-4 includes a screwdriver 533-4, which physically engages alignment device 573a (e.g., with a wall of alignment device 573a). As adjustment mechanism 531-4 rotates, drive element 535-4 adjusts (e.g., translates along the Z-4 axis) relative to sleeve 534-4, which is fixed to wall 506c, thereby moving alignment device 573a between a non-interactive position in Figures 6A and 6C and an interactive position in Figures 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 toward fluorescent screen 575a, where the light causes the material within screen 575a to fluoresce. The resulting light 577 is visualized through viewport 576, as shown in Figure 6D. By visualizing light 577, an engineer can find the center of light beam 518 and, if necessary, preferably make adjustments to move the center of light beam 518.

[0071] Referring to FIG. 7 , as discussed above, the optical element capable of being adjusted by the actuator 130 - j can be a mirror, such as a concave mirror, or it 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 within an internal cavity 707 defined by a plurality of walls, with a portion of one wall 706 a shown in FIG. The concave mirror 780 can be an optical element 120 - i within the optical stretcher 115, such as any of the concave mirrors 570 - ai, 570 - ai, 570 bi, 570 bii, 570 biii within the first optical pulse stretcher device 500 - 1 ( FIG. 5A ), or any of the mirrors 502 a, 502 b within the second optical pulse stretcher device 500 - 2 ( FIG. 5A ). In other embodiments, the concave mirror 780 is a beam splitter, such as that shown in FIG. 5B .

[0072] Concave mirror surface 780 can be physically connected to three actuators 730-1, 730-2, and 730-3 at three different points 781-1, 781-2, and 781-3 on the rear surface 782 of mirror surface 780. Each actuator 730-1, 730-2, and 730-3 includes a respective drive element 735-1, 735-2, and 735-3 extending along direction Z 780. Drive elements 735-1, 735-2, and 735-3 include respective adjustment mechanisms 731-1, 731-2, and 731-3 outside of internal cavity 707 and respective screwdrivers 733-1, 733-2, and 733-3 inside internal cavity 707. Drive elements 735-1, 735-2, 735-3 translate along direction Z 780 relative to respective sleeves 734-1, 734-2, 734-3 secured within (and hermetically sealed within) wall 706a. To facilitate visualization of adjustment mechanisms 731-1, 731-2, 731-2, external caps (such as cap 252-j) are not shown in FIG7 . However, each adjustment mechanism 731-1, 731-2, 731-3 can be covered by a respective cap when not engaged for adjustment, as described above with reference to FIG2A-2E and as shown in FIG8A-8C (where cap 752-1 is shown covering adjustment mechanism 731-1).

[0073] In some embodiments, such as shown in FIG7 , each screwdriver 733-1, 733-2, 733-3 engages a respective adapter 783-1, 783-2, 783-3 rather than directly engaging points 781-1, 781-2, 781-3. On one side of mirror 780, each adapter 783-1, 783-2, 783-3 includes a respective socket (as shown in FIG8A ) for receiving a sphere 784-1, 784-2, 784-3 located at the respective point 781-1, 781-2, 781-3. Additionally, on the other side, each adapter 783-1, 783-2, 783-4 includes a socket (as shown in FIG8A through FIG8C ) shaped to complement the shape of the screwdriver 733-1, 733-2, 733-3. 8A to 8C , the operation of the actuator 730 - 1 is described below. The operations of the other actuators 730 - 2 and 730 - 3 are similar to those of the actuator 730 - 1 .

[0074] By contacting the mirror 780 at three points 781-1, 781-2, 781-3, the translation imparted at the respective screwdrivers 733-1, 733-2, 733-3, and thus to the respective points 781-1, 781-2, 781-3 of the rear surface 782 of the mirror 780, enables various adjustments to be made to the mirror 780. For example, by translating both screwdrivers 733-1 and 733-2 and leaving one screwdriver 733-3 stationary, it is possible to rotate the mirror 780 about the Y 780 direction, or by translating both screwdrivers 733-2 and 733-3 while leaving one screwdriver 733-1 stationary, it is possible to rotate the mirror 780 about the X 780 direction. On the other hand, translating all three screwdrivers 733-1, 733-2, 733-3 enables the entire mirror 780 to be translated along the Z 780 direction. Alternatively or additionally, it is possible to translate the mirror 780 along the X 780 direction or the Y 780 direction or to rotate the mirror 780 about the Z 780 direction by engaging the mirror 780 at points on other surfaces of the mirror 780.

[0075] Figures 8A-8C show side cross-sectional views through mirror 780, adapter 783-1, and respective actuators 730-1. As shown, screwdriver 733-1 is engaged within socket 785-1 of adapter 783-1, while ball 784-1 is nested between a cavity on rear surface 782 of mirror 780 and socket 786-1 of adapter 783-1. If the tip of screwdriver 733-1 is hexagonal (in XY cross-section), socket 785-1 is a complementary hexagonal socket, as shown in Figure 8D, a cross-section taken along the XY plane.

[0076] In FIG8A , a "neutral" position is shown. In FIG8B , adjustment mechanism 731-1 has been rotated relative to the position shown in FIG8A (e.g., clockwise when facing wall 706a from outside interior cavity 707). This clockwise rotation causes screwdriver 733-1 to translate along the +Z 780 direction. In FIG8C , adjustment mechanism 731-1 has been rotated relative to the position shown in FIG8A (e.g., counterclockwise when facing wall 706a from outside interior cavity 707). This counterclockwise rotation causes screwdriver 733-1 to translate along the -Z 780 direction. At the same time, screwdriver 733-1 remains engaged in socket 785-1 because it is biased along the +Z 780 direction by biasing device 738-1 (which may be designed similarly to biasing device 238-j discussed above). In one example, screwdriver 733-1 translates within a range of ±3 millimeters (mm) relative to its neutral position in FIG. 8A , and this translation results in a ±3 mm translation of a point on rear surface 782 of mirror 780. Adjustment of mirror 780 can be accomplished with an accuracy of less than 300 micrometers (µm). As discussed above, mirror 780 can be rotated, for example, by translating both screwdrivers 733-1 and 733-2 while leaving one screwdriver 733-3 stationary, thereby rotating mirror 780 about the Y 780 axis, or by translating both screwdrivers 733-2 and 733-3 while leaving one screwdriver 733-1 stationary, thereby rotating the mirror about the X 780 axis. Mirror 780 can be rotated within an adjustment range of ±5 degrees and with a nominal angular accuracy of less than 0.1 degrees.

[0077] When actuator 730-1 is installed in wall 706a, the tip of screwdriver 733-1 is guided into socket 785-1 by means of a tapered feature 786-1 formed into mounting member 787, with adapter 783-1 at least partially assembled within the mounting member. Tapered feature 786-1 is designed as a feedthrough and facilitates alignment between the tip of screwdriver 733-1 and socket 785-1. Furthermore, due to the biasing function performed by biasing device 738-1, screwdriver 733-1 resiliently engages adjustment mechanism 731-1. Furthermore, drive element 735-1 maintains physical communication with mirror 780 throughout its range of motion relative to sleeve 734-1, including the positions shown in Figures 8A through 8C.

[0078] While details of actuator 730-1 are shown in Figures 7 and 8A-8D , the operation of actuator 730-1 is similar to the other actuators discussed herein. Thus, actuator 530-j in Figure 5A can operate similarly to actuator 730-1. Furthermore, actuators 530-4 and 530-5 can also operate similarly to actuator 730-1, even if they are controlling something other than a mirror.

[0079] The embodiments can be further described using the following terms: 1. An optical pulse stretcher device comprising: A hermetically sealed container comprising one or more walls defining an interior cavity that is maintained in a controlled environment during operation, at least one wall having one or more windows, each window 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 a pulsed light beam and generate at least one stretched pulsed light beam; and One or more actuators, each actuator being physically connected to an optical element within the internal cavity and comprising an adjustment mechanism external to the hermetically sealed container, wherein the adjustment mechanism enables adjustment of one or more physical properties of the optical element physically connected to the actuator without disrupting the controlled environment within the internal cavity. 2. An optical pulse stretcher device as described in item 1, wherein the adjustment mechanism for adjusting one or more physical properties of the optical element includes an adjustment mechanism for achieving one or more of a translation of the optical element along any direction and a rotation of the optical element around any direction. 3. An optical pulse stretcher device as described in item 2, wherein the adjustment mechanism for achieving the translation of the optical element along a direction includes achieving the translation of the optical element within an adjustment range of ±3 millimeters (mm) and with a nominal position accuracy of less than 300 microns (µm), and the adjustment mechanism for achieving the rotation of the optical element around a direction includes achieving the rotation of the optical element within an adjustment range of ±5 degrees and with a nominal angular accuracy of less than 0.1 degrees. 4. An optical pulse stretcher device as described in item 1, wherein the optical element physically connected to the actuator device includes a mirror, a concave mirror, a beam splitter or a prism. 5. An optical pulse stretcher device as described in item 1, wherein the optical element physically connected to the actuator device includes an alignment device, the alignment device includes a prism and a fluorescent screen arranged in a fixed relationship with each other, and the optical pulse stretcher device further includes a viewing port arranged in a wall of the airtight sealed container relative to the fluorescent screen, so that the fluorescent screen can be seen from outside the airtight sealed container through the viewing port. 6. An optical pulse stretcher device as described in item 5, wherein the actuator physically connected to the alignment device is configured to translate the alignment device from a first position and a second position, wherein at the first position, the prism interacts with one or more of the pulse beam and the stretched pulse beam, and at the second position, the prism does not interact with any pulse beam or stretched pulse beam. 7. An optical pulse stretcher apparatus as claimed in claim 1, wherein each actuator comprises a sleeve hermetically sealed within a wall of the container and a drive element configured to move relative to the sleeve, the drive element being physically connected to the optical element. 8. An optical pulse stretcher device as described in item 7, wherein the sleeve is positioned and fixed in a hole in a wall of the container, and the drive element includes the adjustment mechanism located at a first end and a shaped tip screwdriver located at a second end, the shaped tip screwdriver being sized to interact with a shaped socket, which is physically connected to the optical element. 9. The optical pulse stretcher apparatus of clause 8, wherein the shaped socket comprises a tapered feedthrough feature configured to align the shaped tip screwdriver with the shaped socket. 10. An optical pulse stretcher device as described in item 8, wherein rotation of the adjustment mechanism at the first end causes the formed tip screwdriver at the second end to translate, thereby translating the formed socket that is physically connected to the optical element. 11. An optical pulse stretcher apparatus as in item 8, wherein the shaped tip screwdriver is a hexagonal tip screwdriver and the shaped socket is a hexagonal socket. 12. An optical pulse stretcher device as described in item 8, wherein the adjustment mechanism is received within one of the sleeves, and the interface between the sleeve and the adjustment mechanism is a threaded interface, so that rotation of the adjustment mechanism causes the adjustment mechanism to also translate relative to the sleeve, and causes the formed tip screwdriver to translate and rotate relative to the sleeve. 13. An optical pulse stretcher device as described in item 12, wherein the threaded interface includes a circular tip thread located on the interior of the sleeve, which cooperates with a circular tip thread on the exterior of one of the adjustment mechanisms. 14. An optical pulse stretcher device as described in item 12, wherein the sleeve and the adjustment mechanism are each made of lead-free metal or lead-free metal alloy, and the interface is free of lubricant. 15. An optical pulse stretcher device as described in item 12, wherein the threaded interface includes threads on the interior of the sleeve, which threads cooperate with threads on the exterior of the adjustment mechanism, and the threads have a pitch of 80 to 100 teeth per inch. 16. An optical pulse stretcher device as described in item 8, wherein the formed tip screwdriver is elastically engaged with the adjustment mechanism. 17. An optical pulse stretcher device as described in item 5, wherein the drive element remains physically connected to the optical element throughout the entire range of movement within the sleeve. 18. An optical pulse stretcher device as described in item 5, wherein when one or more pulse beams and stretched pulse beams are passed through the window, and when the pulse beams and stretched pulse beams are operated at a repetition rate greater than 500 Hz, greater than 1000 Hz or greater than 3000 Hz, the adjustment mechanism achieves adjustment of one or more physical properties of the optical element physically connected to the actuator device. 19. The optical pulse stretcher apparatus of clause 1, wherein the controlled environment is purged with gas and maintained at a pressure greater than atmospheric pressure, or at a pressure of about 15 to 22 pounds per square inch (PSI). 20. The optical pulse stretcher apparatus of clause 1, wherein the optical stretcher comprises two or more stacked confocal optical pulse stretchers disposed within the internal cavity, A first one of the stacked confocal optical pulse stretchers includes a first plurality of mirrors and is configured to receive a portion of the pulsed beam and generate a first stretched pulsed beam by reflecting the portion of the pulsed beam at the first plurality of mirrors; and A second one of the stacked confocal optical pulse stretchers includes a second plurality of mirrors and is configured to receive a portion of the first stretched pulse beam and generate a second stretched pulse beam by reflecting the portion of the first stretched pulse beam at 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 comprise concave mirrors. 22. An optical pulse stretcher device as described in item 1, wherein the optical element physically connected to the actuator device includes an optical element of the optical stretcher. 23. A deep ultraviolet (DUV) light source comprising: An optical pulse stretcher device comprising: A hermetically sealed container comprising one or more walls defining an interior cavity that is maintained in a controlled environment during operation, at least one wall having one or more windows, each window 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 a pulsed light beam and generate at least one stretched pulsed light beam; and One or more actuators, each actuator being physically connected to an optical element within the internal cavity and comprising an adjustment mechanism external to the hermetically sealed container, wherein the adjustment mechanism enables adjustment of one or more physical properties of the optical element physically connected to the actuator without disrupting the controlled environment within the internal cavity.

[0080] Other embodiments are within the scope of the following claims.

[0081] 100: Optical Pulse Stretcher Device 105: Airtight sealed container 106a: wall 106b: wall 106c: wall 106d: wall 107: Internal cavity 108: Window 109: Pulse Beam 115: Optical Expander 116: Input pulse beam 117: Output pulse beam 120-1: Optical components 120-2: Optical components 120-I: Optical components 125-1: Optical components 125-2: Optical components 125-K: Optical components 130-1: Motion Device 130-2: Motion Device 130-3: Motion Device 130-4: Motion Device 131-1: Adjustment mechanism 131-2: Adjustment mechanism 131-3: Adjustment mechanism 131-4: Adjustment mechanism 132-1: Interface 132-2: Interface 132-3: Interface 132-4: Interface 133-1: Screwdriver 133-2: Screwdriver 133-3: Screwdriver 133-4: Screwdriver 206:Wall 207: Internal cavity 230-j: Actuating device 231-j: Adjustment mechanism 233-j: Screwdriver 234-j: casing 235-j: driving element 236-j: Rotating element 237-j: Main body 238-j: Biasing equipment 239-j: Biasing device 240-j: Cavity 241-j: Coupler 242-j: Second end 243-j: base 244-j: Fixing device 248-j: Gasket 249-j: Threaded nut 252-j: cap 253-j: O-ring 345-j: Center opening 346-j: Cylindrical body 347-j: flange 350-j: External thread surface 351-j: External thread surface 353-j: cutting edge 354-j: threaded outer surface 355-j: threaded inner surface 400: Implementation Plan 400-1: First Optical Pulse Stretcher Device 400-2: Second optical pulse stretcher device 405: Airtight sealed container 406a: wall 406b: wall 406c: Wall 406d: wall 406e: Wall 406f: wall 406g: wall 406h: Wall 418: First stretched pulse beam 419: Second stretched pulse beam 430-2: Actuator 460: Light Source 461: Pulse Beam 462: Photolithography exposure equipment 463A: Level 1 463B: Second level 464: First Pulse Beam 465: Optical components 466: Second Pulse Beam 500: Implementation Plan 500-1: First Optical Pulse Stretcher Device 500-2: Second optical pulse stretcher device 502a: First single mirror 502b: Second single mirror 503-1: Optical Pulse Stretcher 503-2i: Optical Pulse Stretcher 503-2ii: Optical Pulse Stretcher 503-2iii: Optical Pulse Stretcher 504: Beam Splitter 504a: Beam splitter 504b: Beam splitter 504c: Folding mirror / mirror 504d: Folding mirror / mirror 505:Container 506a: wall 506b: wall 506c: Wall 506d: wall 506e: Wall 506f: wall 506g: wall 506h: wall 507-1: Internal cavity 507-2: Internal cavity 518: First stretched pulse beam 519: Second stretched pulse beam 530-1: Actuator 530-2: Actuator 530-3: Actuator 530-4: Actuator 530-5: Actuator 530-6: Actuator 530-7: Actuator 530-8: Actuator 530-9: Actuator 530-10: Actuator 530-11: Actuator 530-12: Actuator 530-13: Actuator 530-14: Actuator 530-15: Actuator 531-4: Adjustment mechanism 533-4: Screwdriver 534-4: Casing 535-4: Drive element 570-ai: Mirror 570-aii: Mirror 570-aiii: Mirror 570-bi: mirror 570-bii: Mirror 570-biii: Mirror 571i: Beam Splitter 571ii: Beam Splitter 571iii: Beam Splitter 572:Optical Configuration 572B: Optical Configuration 573a: Optical components 573b: Optical components 574a: Prism 575a: Screen 576: Viewport 577: Light 706a: Wall 707: Internal cavity 730-1: Actuator 730-2: Actuator 730-3: Actuator 731-1: Adjustment mechanism 731-2: Adjustment mechanism 731-3: Adjustment mechanism 733-1: Screwdriver 733-2: Screwdriver 733-3: Screwdriver 734-1: Casing 734-2: Casing 734-3: Casing 735-1: Drive element 735-2: Drive Components 735-3: Drive Components 738-1: Bias Equipment 752-1: Hat 780: Concave mirror / mirror 781-1: Point 781-2: Point 781-3: Point 782: rear surface 783-1: Adapter 783-2: Adapter 783-3: Adapter 784-1: Sphere 784-2: Sphere 784-3: Sphere 785-1: Socket 786-1: Socket 787:Mounting parts

Claims

1. An optical pulse stretcher device comprising: a hermetically-sealed container including one or more walls defining an internal cavity, the internal cavity being maintained in a controlled environment during operation, at least one wall having one or more windows configured to allow passage of one or more of a pulsed light beam and an 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 actuating devices, each actuating device communicating with a corresponding optical element entity of the optical stretcher, the optical element being disposed within the internal cavity, each of the actuating devices including an adjustment mechanism outside the hermetically-sealed container, wherein the adjustment mechanism adjusts the physical properties of one or more of the optical elements communicating with the actuating device entity without disrupting the controlled environment within the internal cavity.

2. The optical pulse stretcher device of claim 1, wherein the adjustment mechanism for adjusting one or more physical properties of the optical element includes an adjustment mechanism for translating the optical element along one of any directions and rotating the optical element about one of any directions.

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

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

5. The optical pulse stretcher device of claim 1, wherein the optical element in communication with the actuation device entity includes an alignment device comprising a prism and a fluorescent screen configured in a fixed relationship with each other, and the optical pulse stretcher device further includes a viewport disposed relative to the fluorescent screen in a wall of the hermetically sealed container, such that the fluorescent screen can be seen from outside the hermetically sealed container through the viewport.

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

7. The optical pulse stretcher device of claim 1, wherein each actuation device includes a sleeve hermetically sealed within a wall of the container and a drive element configured to move relative to the sleeve, the drive element being in physical communication with the optical element.

8. The optical pulse stretcher device of claim 7, wherein the sleeve is positioned and fixed within a bore in a wall of the container, and the drive element includes the adjustment mechanism at a first end and a shaped-tip driver at a second end, the shaped-tip driver being sized to interact with a shaped socket in communication with the optical element body.

9. The optical pulse stretcher device of claim 8, wherein the shaped socket includes a tapered feedthrough feature configured to align the shaped tip screwdriver with the shaped socket.

10. The optical pulse stretcher device of claim 8, wherein rotation of the adjustment mechanism at the first end causes the shaped tip screwdriver at the second end to translate, thereby translating the shaped socket communicating with the optical element body.

11. The optical pulse stretcher device of claim 8, wherein the shaped tip screwdriver is a hexagonal tip screwdriver and the shaped socket is a hexagonal socket.

12. The optical pulse stretcher device of claim 8, wherein the adjustment mechanism is internally received in one of the sleeves, and the interface between the sleeve and the adjustment mechanism is a threaded interface, such that rotation of the adjustment mechanism causes the adjustment mechanism to translate relative to the sleeve, and causes the shaped tip screwdriver to translate and rotate relative to the sleeve.

13. The optical pulse stretcher device of claim 12, wherein the threaded interface includes a round-tipped thread located inside the sleeve, the round-tipped thread engaging with a round-tipped thread outside one of the adjustment mechanisms.

14. The optical pulse stretcher device of claim 12, wherein the sleeve and the adjustment mechanism are each made of lead-free metal or lead-free metal alloy, and the interface is free of lubricant.

15. The optical pulse stretcher device of claim 12, wherein the threaded interface includes threads inside the sleeve that mate with threads outside the adjustment mechanism, the threads having a pitch of 80 to 100 teeth per inch.

16. The optical pulse stretcher device of claim 8, wherein the shaped tip screwdriver is elastically engaged with the adjustment mechanism.

17. The optical pulse stretcher device of claim 7, wherein the drive element remains in communication with the optical element body throughout the entire range of motion within the sleeve.

18. The optical pulse stretcher device of claim 5, wherein when one or more pulse beams and stretched pulse beams are passed through the window, and when the pulse beams and stretched pulse beams are operated at a repetition rate greater than 500 Hz, greater than 1000 Hz or greater than 3000 Hz, the adjustment mechanism adjusts one or more physical properties of the optical element in physical communication with the actuation device.

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

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

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

22. The optical pulse stretcher device of claim 1, wherein the optical element in communication with the actuation device entity includes one of the optical elements of the optical stretcher.

23. A deep ultraviolet (DUV) light source comprising: an optical pulse stretcher device comprising: a hermetically sealed container including one or more walls defining an internal cavity, the internal cavity being maintained in a controlled environment during operation, at least one wall having one or more windows configured to allow passage of one or more of a pulsed beam and an stretched pulsed beam; an optical stretcher disposed within the internal cavity and configured to receive a pulsed beam and generate at least one stretched pulsed beam; and one or more actuating devices, each actuating device communicating with a corresponding optical element entity of the optical stretcher, the optical element being disposed within the internal cavity, each of the actuating devices including an adjustment mechanism outside the hermetically sealed container, wherein the adjustment mechanism adjusts the physical properties of one or more of the optical elements communicating with the actuating device entity without disrupting the controlled environment within the internal cavity.

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