Adjustable mounting apparatus for optical element

Abstract

An optical system is in a pulse stretcher of a deep ultraviolet light source. The optical system includes: an optical element configured, in operation, along a path of a light beam produced by the deep ultraviolet light source; and an adjustable mounting apparatus to which the optical element is located. The adjustable mounting apparatus includes: a passive alignment mount, and a drive mechanism coupled to the passive alignment mount, the drive mechanism including a wedge that is rotationally constrained.

Description

ADJUSTABLE MOUNTING APPARATUS FOR OPTICAL ELEMENTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Application No. 63 / 571,516, filed March 29, 2024, titled ADJUSTABLE MOUNTING APPARATUS FOR OPTICAL ELEMENT, which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The disclosed subject matter relates to an adjustable mounting apparatus for an optical element in an optical pulse stretcher apparatus of a deep ultraviolet light source.BACKGROUND

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, can be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (for example, comprising part of one or several dies) on a substrate (for example, a silicon wafer). Transfer of the pattern is typically by way of imaging onto a layer of radiation-sensitive material (resist) added to the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus includes so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so- called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the target portions parallel or anti-parallel to this scanning direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0004] A light (or laser) source can be used, for example, for generating spectral radiation for illuminating the patterning device with use of the lithographic apparatus. The laser source can include a high-power gas discharge laser system and an optical pulse stretcher configured to lengthen the pulse of the output of the high-power gas discharge laser system.SUMMARY

[0005] In some general aspects, an optical system is in a pulse stretcher of a deep ultraviolet light source. The optical system includes: an optical element configured, in operation, along a path of a light beam produced by the deep ultraviolet light source; and an adjustable mounting apparatus to which the optical element is located. The adjustable mounting apparatus includes: a passive alignmentmount, and a drive mechanism coupled to the passive alignment mount, the drive mechanism including a wedge that is rotationally constrained.

[0006] Implementations can include one or more of the following features. For example, the optical element can be a reflective optical element, a partially-reflecting beamsplitter, a diffractive optical element, or a refractive optical element. The passive alignment mount can include a kinematic mount or a pseudo-kinematic mount.

[0007] The passive alignment mount can include a kinematic mount. The kinematic mount can include: a flat plane, a groove, and a socket. The drive mechanism can include a first rounded tip touching the flat plane, a second rounded tip touching the groove, and a third rounded tip touching the socket. The first rounded tip touching the flat plane can provide five degrees of freedom, the second rounded tip touching the groove can provide four degrees of freedom, and the third rounded tip touching the socket can provide three degrees of freedom. The kinematic mount can include a first groove defined along a first axial direction, a second groove defined along a second axial direction, and a third groove defined along a third axial direction, each axial direction being distinct from the other two axial directions.

[0008] The passive alignment mount can be located and aligned to an optical element cell where the optical element is contained.

[0009] The drive mechanism can include a plurality of drive systems, each drive system associated with a contact element of the passive alignment mount. At least one of the drive systems can include: a pin including rounded tip at a first end and the wedge at a second end, the rounded tip touching one of the contact elements of the passive alignment mount; and a rod including a spherically-shaped tip constrained by the wedge of the pin. The optical system can further include a structure defining a plurality of cylindrical openings, with each cylindrical opening receiving either a pin or a rod. The structure can constrain and guide each pin and each rod received within its respective cylindrical opening. The translation of the rod along a first direction can cause the spherically-shaped tip of the rod to translate along the first direction, the spherically-shaped tip can interface with the wedge and can cause the pin to translate along a second direction that is distinct from the first direction. The second direction can be perpendicular to the first direction. The passive alignment mount can include a kinematic mount and the contact element of the kinematic mount can be one of a flat plane, a socket, or a groove. The rod of each drive system can be adjustable from outside an enclosure in which the optical element is contained.

[0010] The drive mechanism can include three drive systems, each drive system associated with a contact element of the passive alignment mount. One drive system can provide a linearly- constrained fixed point at a respective contact element, and the other two drive systems can be configured to move or translate the respective contact element.

[0011] The passive alignment mount can include a plurality of contact elements, each contact element can include or be made of hardened stainless steel. The drive mechanism can include aplurality of drive systems. Each drive system can be associated with a contact element of the passive alignment mount. At least two of the drive systems can include the wedge and a rounded tip. Both the wedge and the rounded tip can made of a hardened material with a hardness greater than or equal to 1400 Newtons / millimeter2(N / mm2). Both the wedge and the rounded tip can be made of a hardened material with a hardness greater than or equal to 2075 Newtons / millimeter2(N / mm2). The wedge and the rounded tip can be made of hardened stainless steel. Each wedge and each rounded tip can include a polished surface finish having a roughness of Ra 0.8 micrometers (Ra 32 micro inches, 35 RMS) or less. Each wedge and each rounded tip can include a polished surface finish having a roughness of Ra 0.4 micrometers (Ra 16 micro inches, 17.6 RMS) or better.

[0012] The adjustable mounting apparatus can lack lubricant.

[0013] The optical element can be a first optical element and the adjustable mounting apparatus can be a first adjustable mounting apparatus to which the first optical element is located. The first adjustable mounting apparatus can include a first kinematic mount and a first wedge adjustment mechanism coupled to the first kinematic mount. The optical system can further include a second optical element arranged relative to the first optical element and a second adjustable mounting apparatus to which the second optical element is located. The second adjustable mounting apparatus can include: a second kinematic mount, and a second wedge adjustment mechanism coupled to the second kinematic mount.

[0014] The wedge can include a flat surface at an end of a pin. The pin can extend along an axial pin direction and a normal of the flat surface extending between 20°-40° relative to the axial pin direction. The drive mechanism can include wings extending from the pin and adjacent to ends of the flat surface of the wedge. The wings can rotationally constrain the wedge.

[0015] The adjustable mounting apparatus can be configured to enable tilt adjustment in pitch and roll of the optical element.

[0016] In other general aspects, an optical system is inside a pulse stretcher of a deep ultraviolet light source. The optical system includes: a pair of fold mirrors configured, in operation, along a path of a light beam produced by the deep ultraviolet light source to direct the light beam from a first part of the pulse stretcher to a second part of the pulse stretcher; a pair of mirror cells mounted to a structure, each fold mirror being held stable in a respective mirror cell; and a pair of adjustable mounting apparatuses. Each mirror cell is positioned at a respective adjustable mounting apparatus. Each adjustable mounting apparatus includes a passive alignment mount associated with each mirror cell and a drive mechanism associated with each passive alignment mount. The drive mechanism includes a wedge that is rotationally constrained.

[0017] Implementations can include one or more of the following features. For example, the adjustable mounting apparatus can be configured to enable tilt adjustment in pitch and roll of the fold mirror held stable in the mirror cell positioned at the adjustable mounting apparatus.

[0018] In other general aspects, an optical element of a pulse stretcher is located at an adjustable mounting apparatus. The adjustable mounting apparatus is arranged inside a controlled environment of a pulse stretcher enclosure. The adjustable mounting apparatus includes: a cell to which the optical element is located; a passive alignment mount associated with the cell, and a drive mechanism coupled to the passive alignment mount. At least a part of the drive mechanism is controllable from outside the pulse stretcher enclosure. The drive mechanism includes a wedge that is rotationally constrained.

[0019] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.DRAWING DESCRIPTION

[0020] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable a person skilled in the relevant art(s) to make and use implementations described herein.

[0021] Fig. 1 is a schematic illustration of an optical system including an optical element located at an adjustable mounting apparatus that includes a passive alignment mount and a drive mechanism mechanically coupled to the passive alignment mount, the drive mechanism including a rotationally- constrained wedge;

[0022] Fig. 2 is a schematic illustration of an implementation of an adjustable mounting apparatus that includes a passive alignment mount having a plurality of contact elements and a drive mechanism having a plurality of drive systems, with each drive system associated with a respective contact element, at least two of the drive systems each include a respective rotationally-constrained wedge;

[0023] Fig. 3 A is a perspective view of an implementation of an adjustable mounting apparatus that includes a passive alignment mount having three contact elements and a drive mechanism having three drive systems, with each drive system associated with a respective contact element, at least two of the drive systems each include a respective rotationally-constrained wedge;

[0024] Fig. 3B is a perspective view of the passive alignment mount of Fig. 3A having three contact elements;

[0025] Fig. 4 is a side plan view of the adjustable mounting apparatus of Fig. 3 A;

[0026] Fig. 5 A is a cross-sectional view of the adjustable mounting apparatus of Fig. 4 taken along line 5A-5A;

[0027] Fig. 5B is a cross-sectional view of the adjustable mounting apparatus of Fig. 4 taken along line 5B-5B;

[0028] Fig. 6A is a side perspective view of an implementation of a pin that can be used in the drive mechanism of the adjustable mounting apparatus;

[0029] Fig. 6B is side plan view of the pin of Fig. 6A;

[0030] Fig. 6C is a side plan view of the pin of Fig. 6A;

[0031] Fig. 6D is a side cross-sectional view of the pin of Fig. 6A;

[0032] Fig. 7A is a side perspective view of an implementation of a rod that can be used in the drive mechanism of the adjustable mounting apparatus;

[0033] Fig. 7B is a side cross-sectional view of the rod of Fig. 7A;

[0034] Fig. 8 is a block diagram of an implementation of an optical pulse stretcher positioned at the output of a light source, the optical pulse stretcher receiving one or more optical systems;

[0035] Fig. 9A is a block diagram of an implementation of an optical pulse stretcher receiving one or more optical systems;

[0036] Fig. 9B is a block diagram of a portion of the optical pulse stretcher of Fig. 9A showing a set of mirrors, each mirror located at and controlled by an adjustable mounting apparatus; and

[0037] Fig. 10 is a perspective view of an implementation of an adjustable mounting apparatus that includes a passive alignment mount having three contact elements and a drive mechanism having three drive systems, with each drive system associated with a respective contact element, three of the drive systems each include a respective rotationally-constrained wedge.

[0038] The features of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, generally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. Unless otherwise indicated, the drawings provided throughout the disclosure should not be interpreted as to-scale drawings.DESCRIPTION

[0039] Referring to Fig. 1, an optical system 100 is arranged in an optical pulse stretcher 170 associated with a light source 160, which can be a deep ultraviolet light source. The optical system 100 includes an optical element 105 arranged or configured, when in operation, along a path of a light beam 162 produced by the light source 160. The light beam 162 can be a pulsed light beam that is input into the optical pulse stretcher 170 but has not interacted with any other optical elements within the optical pulse stretcher 170. Or, the light beam 162 can be a pulsed light beam that has already interacted with one or more other optical elements within the optical pulse stretcher 170. For clarity, other components such as the other optical elements are not shown in the optical pulse stretcher 170 in Fig. 1. Implementations of the optical pulse stretcher 170 are shown in Figs. 8, 9A, and 9B.

[0040] The optical pulse stretcher 170 is defined within a hermetically-sealed enclosure or housing 171 that includes one or more walls (depicted schematically as 172 in the two-dimensional representation of Fig. 1) that define an interior cavity 173. The housing 171 can be any suitable three- dimensional shape such as a rectangular prism, a cube, or a cylinder, and the number of walls 172 can vary depending on this shape. The interior cavity 173 is maintained, during operation of the optical pulse stretcher 170, as a controlled environment. For example, the interior cavity 173 can be formed by the hermetically sealed walls 172. In this way, the interior cavity 173 can be maintained at a particular pressure (such as a pressure below or above atmospheric pressure) or at a particular moisture level (such as low humidity environment). As another example, the interior cavity 173 can be configured as a gas purged environment (such as a nitrogen purged environment). In some implementations, the interior cavity 173 is maintained at a pressure that is about 4-8 pounds per square inch (psi) above atmospheric pressure. For example, if the interior cavity 173 is a gas purged environment, then the pressure can be maintained at about 18-23 psi. The optical pulse stretcher 170 is configured to receive an input pulsed light beam 161 and to generate at least one stretched output pulsed light beam 163.

[0041] There is a need to adjust (for example, to align or modify a position or angle of) the optical element 105 within the optical pulse stretcher 170. For example, in order to ensure that the light beam 162 is properly aligned with and traverses an optical element that is optically downstream of the optical system 100, the optical element 105 may need to be translated along one or more local axes or rotated about one or more local axes. The local coordinate system of the optical element 105 is given by X105, Y105, Z105. Moreover, such adjustment to the optical element 105 can occur while the light beam 162 is interacting with the optical element 105. To this end, the optical system 100 includes an adjustable mounting apparatus 110 to which the optical element 105 is located (such as fixed or constrained). The adjustable mounting apparatus 110 enables the alignment of the light beam 162 relative to an optical element downstream of the optical element 105. The adjustable mounting apparatus 110 includes a passive alignment mount 120 and a drive mechanism 130 mechanically coupled to the passive alignment mount 120. The passive alignment mount 120 receives the optical element 105 while the drive mechanism 130 imparts the mechanical constraint and / or motion to the passive alignment mount 120 and the optical element 105. The passive alignment mount 120 and the drive mechanism 130, in combination, provide a tip / tilt mechanism that enables the adjustment of the pitch and / or roll of the optical element 105 (relative to the X105 axis or the Y105 axis) without disrupting the controlled environment within the cavity 173. That is, the adjustable mounting apparatus 110 enables the optical element 105 to be adjusted without requiring the opening of the hermetically-sealed housing 171.

[0042] The adjustable mounting apparatus 110 fits into a small footprint (or volume) that is available within the cavity 173 of the optical pulse stretcher 170. The adjustable mounting apparatus 110 is designed with reduced friction at certain mechanical interfaces within the adjustable mountingapparatus 110. For example, the adjustable mounting apparatus 110 uses a set of materials at the mechanical interfaces that have reduced roughness to reduce the friction at these interfaces. As another example, the mechanical interfaces within the adjustable mounting apparatus 110 are designed in a manner that leads to a predictable motion at the interfaces. Because of these design updates, there is a reduced or eliminated need for a lubricant at the mechanical interfaces within the adjustable mounting apparatus 110. Lubricant within the cavity 173 is a contaminant and can degrade and spread within the cavity 173 and even outside the cavity 173 and into components of the light source 160. Thus, by eliminating the lubricant within the adjustable mounting apparatus 110, the cavity 173 is kept clean or cleaner, and there is a reduced chance of contaminating the light source 160.

[0043] The features of the adjustable mounting apparatus 110 that enable the reduced friction are described next. As mentioned, the adjustable mounting apparatus 110 includes the passive alignment mount 120 and the drive mechanism 130 mechanically coupled to the passive alignment mount 120. The drive mechanism 130 includes a wedge 135 that is a generally flat and rigid surface. The wedge 135 is rotationally constrained 136, as will be discussed in detail below. The rotational constraint 136 applied to the wedge 135 leads to predictable motion within the drive mechanism 130 and also between the drive mechanism 130 and the passive alignment mount 120.

[0044] The optical element 105 can be any element that is configured to optically interact with the light beam 162. For example, the optical element 105 can be a reflective optical element (such as a mirror), a partially-reflecting optical element (such as a beamsplitter), a diffractive optical element (such as a diffraction grating), or a refractive optical element (such as a prism).

[0045] As mentioned, the optical element 105 needs to be located in three dimensions (XIO5,YIO5,ZIO5), that is, distributed in a volume of space, and having three rotations specified and / or controlled. The passive alignment mount 120 can include or be a part of a kinematic mount or a pseudo-kinematic mount. The adjustable mounting apparatus 110 enables the orientation of the optical element 105 with respect to another body within the cavity 173 to a high degree of precision by providing precise mating features between the optical element (the passive alignment mount 120) and connecting elements of the drive mechanism 130, and precise distances between these features on the passive alignment mount 120 and the connecting elements of the drive mechanism 130.

[0046] In some implementations, such as shown in Fig. 2, an optical system 200 includes an adjustable mounting apparatus 210 that is designed with a passive alignment mount 220 and a drive mechanism 230. The optical system 200 also includes an optical element 205, which, as discussed above, can be any element that is configured to optically interact with a light beam 262 (similarly to the optical element 105). The passive alignment mount 220 includes a plurality of contact elements 220A, 220B, 220C and the drive mechanism 230 includes a plurality of drive systems 230A, 230B, 230C, with each drive system 230A, 230B, 230C associated with a respective and specific contact element 220A, 220B, 220C. The drive systems 230A and 230C each include a respective wedge 235Aand 235 C, and each wedge 235 A, 235 C is rotationally constrained 236A, 236C, as will be discussed in detail below.

[0047] In this implementation, three contact elements 220A, 220B, 220C and three drive systems 23 OA, 23 OB, 23 OC are shown but there could be fewer or more than three in other implementations. Moreover, while the schematic illustration of Fig. 2 is represented in two dimensions, that is, the X205, Z205 plane, it should be understood that the optical system 200 extends along three dimensions including along the Y205 axis into and out of the page. Thus, the contact elements 220A, 220B, 220C can be arranged, for example, in a spatial arrangement in the X205, Y205 plane as well as being able to extend along the Z205 axis. The drive systems 230A, 230B, 230C can also be arranged to extend along one or more of the X205, Y205, Z205 axes. Additionally, each contact element 220A, 220B, 220C is positioned at a location that is distinct from the other contact elements 220A, 220B, 220C so that none of the contact elements touch each other. Similarly, the extent of each drive system 230A, 230B, 230C is in a spatial location that does not intersect with or touch any of the other drive systems 230A, 230B, 230C.

[0048] As mentioned, the alignment mount 220 is “passive”, which means that when the contact elements 220A, 220B, 220C are engaged with the ends of the respective drive systems 230A, 230B, 230C, the correct alignment is attained. In some instances, the engagement of these mating features permanently controls the alignment.

[0049] The contact elements 220A, 220B, 220C of the passive alignment mount 220 and the drive systems 230A, 230B, 230C of the drive mechanism 230 can be micromachined. The contact elements 220A, 220B, 220C of the passive alignment mount 220 can be located and aligned to an optical element cell 221 at which the optical element 105 is contained. The contact elements 220A, 220B, 220C are fixed to the cell 221 so that a motion imparted to a particular contact element causes corresponding motion to be imparted to the cell 221 at the location of that contact element. Moreover, the drive systems 230A, 230B, 230C of the drive mechanism 230 can be constrained within a structure or body 231. That is, the structure 231 can define a plurality of openings 231A, 23 IB, 231C, with each opening 231A, 23 IB, 231C receiving at least a portion of a respective drive system 230A, 230B, 230C.

[0050] As mentioned above, the passive alignment mount 220 can include or be a part of a kinematic mount or a pseudo-kinematic mount. A kinematic mount is formed between the passive alignment mount 220 and the drive mechanism 230 to thereby create stiffness between the two bodies (the optical element 105 and the drive mechanism 230) in six, and only six, independent degrees of freedom (“DOFs”) or directions. Six DOFs are desired because the location of any object in space is defined by three orthogonal coordinates, and the attitude of the object is defined by three orthogonal rotations. A kinematic mount such as this has an advantage of being stiff, yet any strains or distortions in the drive mechanism 230 are not communicated to the passive alignment mount 220 (or to the optical element 105). Thus, any sensitive optical alignments of the optical element 105 are not alteredin the passive alignment mount 220 if the drive mechanism 230 undergoes deformation due to applied loads or bulk temperature changes.

[0051] In some implementations, it can be desirable to tailor a DOF based on the configuration of a “pseudo-kinematic” support or mount. “Pseudo-kinematic” means that although there may be many DOFs connecting at least two bodies (the optical element 105 and the drive mechanism 230), in a practical attachment scheme, the DOFs can be tailored such that only six DOFs have a relatively high stiffness, and substantially all other DOFs have a relatively low stiffness.

[0052] Thus, true “kinematic” support means only 6 stiff DOFs connecting two parts, and no other stiffness paths exist. “Pseudo-kinematic” means there are 6 DOFs with relatively high stiffness, and possibly many more with much lower stiffness (typically two to three orders of magnitude less). In some applications, it is desirable to have pseudo-kinematic DOFs with relatively low stiffness to be two to three orders of magnitude lower than DOFs with relatively high stiffness.

[0053] The materials of the passive alignment mount 220 and the drive mechanism 230 that form the kinematic (or pseudo-kinematic) mount provide polished surfaces with a finish having a roughness of Ra 0.8 micrometers (pm) or better. For example, the roughness may be approximately 0.8, 0.6, 0.5, 0.4, 0.3, 0.2 micrometers (pm) or less. Additionally, the materials of the passive alignment mount 220 and the drive mechanism 230 that form the kinematic (or pseudo-kinematic) mount can be made of hardened materials having a hardness that is greater than or equal to 1400 newtons / millimeter2(N / mm2). For example, the hardness may be approximately 1400, 1625, 1850, 2075, 2300, or greater than 2300 N / mm2. In one example, the material used for the passive alignment mount 220 and the drive mechanism 230 that form the kinematic (or pseudo -kinematic) mount is hardened stainless steel. Although the roughness average (Ra) is a useful average, there are various roughness profiles that could still have the same roughness average.

[0054] Because of these design updates noted above, there is eliminated need for a lubricant at the mechanical interfaces between respective contact elements 220A, 220B, 220C of the passive alignment mount 220 and the drive systems 230A, 230B, 230C of the drive mechanism 230. In this way, lubricant is eliminated within the adjustable mounting apparatus 210.

[0055] Referring to Figs. 3A, 3B, and 4, an optical system 300 is configured for use within the interior cavity 173 of the housing 171 and is a part of the optical pulse stretcher 170 (as shown in Fig. 1). The optical system 300 is therefore configured along the path of a light beam such as the light beam 162 of Fig. 1 or the light beam 262 of Fig. 2. The optical system 300 includes an optical element 305 (not visible in Figs. 3A and 3B but shown in Figs. 4, 5A, and 5B) contained or held by an optical element cell 321 and an adjustable mounting apparatus 310 that is designed based on the principles of the adjustable mounting apparatus 110 or 210.

[0056] The adjustable mounting apparatus 310 enables the alignment of the light beam 162 / 262 (Figs. 2 / 3) relative to an optical element downstream of the optical element 305 in the optical pulse stretcher 170. The adjustable mounting apparatus 310 includes a passive alignment mount 320 locatedand aligned to the optical element cell 321 at which the optical element 305 is contained. For example, the optical element 305 may be securely mechanically mounted onto the optical element cell 321. The adjustable mounting apparatus 310 includes a drive mechanism 330 mechanically coupled to the passive alignment mount 320, the drive mechanism 330 being constrained by a solid structure or body 331. The drive mechanism 330 imparts the mechanical constraint and / or motion to the passive alignment mount 320 and the optical element 305. In this way, the passive alignment mount 120 and the drive mechanism 330, in combination, provide a tip / tilt mechanism that enables the tip and / or tilt to the optical element 305 (relative to the X305 axis or the Y305 axis) without disrupting the controlled environment within the cavity 173 (Fig. 1) in which the optical system 300 is configured.

[0057] As discussed above, the optical element 305 can be a reflective optical element (such as a mirror), a partially-reflecting optical element (such as a beamsplitter), a diffractive optical element (such as a diffraction grating), or a refractive optical element (such as a prism). For an optical element 305 that relies on transmission through the optical element 305, the optical element cell 321 can include an opening 322 and the structure 331 can include an opening through which light can pass.

[0058] The passive alignment mount 320 includes three contact elements 320A, 320B, 320C and the drive mechanism 330 includes three drive systems 330A, 330B, 330C, with each drive system 330A, 330B, 330C associated with a respective and specific contact element 320A, 320B, 320C.

[0059] In addition to the passive alignment mount 320, which couples directly with the optical element cell 321, the adjustable mounting apparatus 310 includes a spring mounting apparatus 312 that includes a pair of spring element systems 313D, 313E that are fixed at a respective first end 314D, 314E to the passive alignment mount 320 and are fixed at a respective second end 315D, 315E to the optical element cell 321. In this way, the optical element cell 321 is held in a position relative to the passive alignment mount 320 but is able to be moved under control of the drive systems 330A, 330B, 330C and respective contact elements 320A, 320B, 320C.

[0060] The passive alignment mount 320 can be a part of a kinematic mount or a pseudo- kinematic mount. That is, a kinematic mount (or pseudo-kinematic mount) is formed between the passive alignment mount 320 and the drive mechanism 330 to thereby create stiffness between the two bodies (the optical element 305 and the drive mechanism 330) in six independent degrees of freedom (DOFs) or directions.

[0061] In this implementation, the kinematic mount includes the three contact elements 320A, 320B, 320C, which each have a distinct design. Fig. 3B shows an exploded view in which the contact elements 320A, 320B, 320C are shown separated from the optical element cell 321. The contact element 320A is a flat plane, the contact element 320B is socket (or a curved surface), and the contact element 320C is a groove. The contact element 320A is a flat surface at an end of a contact body, the flat surface extending in the X305, Y305 plane. The socket or curved surface of the contact element 320B tapers along the +Z305 direction into a contact body. The contact element 320C is a groove or linear indentation defined in a contact body.

[0062] Each drive system 330A and 330C includes a respective wedge 335A and 335C, and each wedge is rotationally constrained 336A and 336C, respectively (Figs. 5A and 5B), as will be discussed in detail below.

[0063] As mentioned previously, the alignment mount 320 is “passive”, which means that when the contact elements 320A, 320B, 320C are engaged with the ends of the respective drive systems 330A, 330B, 330C, the correct alignment can be attained by operation of the drive systems. In some instances, the engagement of these mating features permanently controls the alignment.

[0064] Referring also to Figs. 5A and 5B, the drive systems 330A, 330B, 330C of the drive mechanism 330 are constrained within the structure 331.

[0065] The drive system 330B (Fig. 5B) includes a pin 340B that extends through an opening 33 IB defined in the structure 331. The pin 340B includes a rounded tip 34 IB at a first end and the pin 340B is fixed in or to the structure 331 at a second end. The rounded tip 34 IB touches the contact element 320B, which is a socket as discussed above. Specifically, the tip 34 IB is seated within the socket of the contact element 320B. In this way, there are three rotational degrees of freedom at the interface between the rounded tip 341B and the contact element 320B.

[0066] The drive system 330A (Fig. 5A) includes a pin 340A that includes a rounded tip 341 A at a first end and the wedge 335A at a second end. The pin 340A extends through an opening 331A1 defined in the structure 331 and the pin 340A is biased in the -Z305 direction away from the contact element 320A with the use of a biasing device 344A (such as, for example, a spring). The drive system 330A also includes a rod 342A that extends through an opening 331A2 defined in the structure 331. The opening 331A2 intersects the opening 331A1 where the rod 342A interfaces with the pin 340A. The rod 342A includes a spherically-shaped tip 343A that contacts the wedge 335A of the pin 340A. The rod 342A is configured to linearly translate within the opening 331A2 along the X305 axis upon application of an external force and to provide a counter-bias to the pin 340A along the +Z305 direction to maintain contact between the rounded tip 341 A and the contact element 320A. The external force can be applied to the rod 342A at a location 346A and it can be applied from outside the structure 331 or even from outside the housing 171 in which the optical element 105 is contained (Fig. 1). Because the contact element 320A is a flat surface, there are three rotational degrees of freedom and two translational degrees of freedom at the interface between the rounded tip 341 A and the contact element 320A.

[0067] The tip 343A is constrained 336A by (and at) the wedge 335A of the pin 340A, which improves predictability in the motion between the rod 342A and the pin 340A. Specifically, the pin 340A also includes wings 345A (as shown more clearly in Figs. 6A-6D) that extend from the pin 340A at the second end, the wings 345A being adjacent to edges of the flat surface of the wedge 335A. The wings 345A act as a stop to reduce the translation of the tip 343A along the Y305 axis (the axis perpendicular to the X305 axis) and to reduce rotation of the wedge 335A and the pin 340A about the Z305 axis.

[0068] Translation of the rod 342A along the -X305 direction causes the tip 343A to translate along the -X305 direction. And, because the pin 340A is generally constrained to translate only along the Z305 axis, the tip 343A pushes the pin 340A at the interface with the wedge 335A along the +Z305 direction. The rounded tip 341 A touches the contact element 320A, which is a flat plane, as discussed above. The movement of the pin 340A along the +Z305 direction causes the tip 341 A to translate the contact element 320A along the +Z305 direction. Alternatively, translation of the rod 342A along the +X305 direction causes the tip 343A to translate along the +X305 direction. And, because the pin 340A is generally constrained to translate only along the Z305 axis and the pin 340A is biased away from the contact element 320A, the tip 343A releases the pin 340A at the interface with the wedge 335A along the -Z305 direction. The rounded tip 341 A remains in contact with or touching the contact element 320A as long as the tip 343A does not travel so far as to disengage with the wedge 335A. The movement of the pin 340A along the -Z305 direction causes the tip 341 A to translate the contact element 320A along the -Z305 direction.

[0069] The drive system 330C (Fig. 5B) includes a pin 340C that includes a rounded tip 341C at a first end and the wedge 335C at a second end. The pin 340C extends through an opening 331C1 defined in the structure 331 and the pin 340C is biased in the -Z305 direction away from the contact element 320C with the use of a biasing device 344C (such as, for example, a spring). The drive system 330C also includes a rod 342C that extends through an opening 331C2 defined in the structure 331. The opening 331C2 intersects the opening 331 Cl where the rod 342C interfaces with the pin 340C. The rod 342C includes a spherically-shaped tip 343C that contacts the wedge 335C of the pin 340C. The rod 342C is configured to linearly translate within the opening 331C2 along the X305 axis upon application of an external force and to provide a counter-bias to the pin 340C along the +Z305 direction to maintain contact between the rounded tip 341C and the contact element 320C. The external force can be applied to the rod 342C at a location 346C and it can be applied from outside the structure 331 or even from outside the housing 171 in which the optical element 105 is contained (Fig. 1). Because the contact element 320C is a linear groove, there are three rotational degrees of freedom and one translational degree of freedom at the interface between the rounded tip 341C and the contact element 320C. The translational degree of freedom is along the direction parallel with the direction of the groove.

[0070] The tip 343C of the rod 342C is constrained 336C by (and at) the wedge 335C of the pin 340C, which improves predictability in the motion between the rod 342C and the pin 340C. Specifically, the pin 340C also includes wings 345C (as shown more clearly in Figs. 6A-6D) that extend from the pin 340C at the second end, the wings 345C being adjacent to edges of the flat surface of the wedge 335C. The wings 345C act as a stop to reduce the translation of the tip 343C along the Y305 axis (the axis perpendicular to the X305 axis) and to reduce rotation of the wedge 335 C and the pin 340C about the Z305 axis relative to the rod 342C.

[0071] Translation of the rod 342C along the -X305 direction causes the tip 343 C to translate along the -X305 direction. And, because the pin 340C is generally constrained to translate only along the Z305 axis, the tip 343C pushes the pin 340C at the interface with the wedge 335C along the +Z305 direction. The rounded tip 341C touches the contact element 320C, which is a groove, as discussed above. The movement of the pin 340C along the +Z305 direction causes the tip 341C to translate the contact element 320C along the +Z305 direction. Alternatively, translation of the rod 342C along the +X305 direction causes the tip 343C to translate along the +X305 direction. And, because the pin 340C is generally constrained to translate only along the Z305 axis and the pin 340C is biased away from the contact element 320C, the tip 343C releases the pin 340C at the interface with the wedge 335C along the -Z305 direction. The rounded tip 341C remains in contact with or touching the contact element 320C as long as the tip 343C does not travel so far along the -X305 direction so as to disengage with the wedge 335C. The movement of the pin 340C along the -Z305 direction causes the tip 341C to translate the contact element 320C along the -Z305 direction.

[0072] Referring to Figs. 6A-6D, an example of a pin 640 that can be used as the pin 340A or the pin 340C is shown. The pin 640 is shown with a particular set of geometric dimensions, but the dimensions can be modified, depending on the placement of the pin 640 in the structure and the interaction of the pin 640 with its respective contact element. Each pin 640 includes a generally cylindrical-shaped body 647 that extends along an axial pin axis 640a, such axis 640a aligning with the Z305 axis of the mounting apparatus 110, 210, 310 when the pin 640 is operating as the drive mechanism 130, 230, 330. The pin 640 includes rounded tip 641 at the first end and the wedge 635 at the second end. The wedge 635 is a generally flat surface that is angled relative to the axis 640a. For example, a normal 635N of the flat surface of the wedge 635 can subtend an angle 9635 that is between 20°-40° of the axial pin axis 640a. The wedge 635 acts to constrain the tip of the rod as well as the pin 640 when the pin 640 operates in the drive mechanism 130, 230, 330 and the tip of the rod is contacting the wedge 635. To this end, the pin 640 includes wings 645i, 645ii that flank the ends of the flat surface of the wedge 635.

[0073] Referring to Figs. 7A and 7B, an example of a rod 742 that can be used as the rod 342A or the rod 342C is shown in Figs. 5A and 5B. The rod 742 includes a generally cylindrical-shaped body that extends along an axial rod axis 742a, such axis 742a aligning with the X305 axis of the mounting apparatus 110, 210, 310 when the rod 742 is operating as the drive mechanism 130, 230, 330. The rod 742 is a generally rigid body that can be made of a non-reactive material. The rod 742 includes a spherically-shaped tip 743 that, when the rod 742 operates in the drive mechanism 130, 230, 330, contacts the wedge 635 of the pin 640 (Figs. 6A-6D).

[0074] The wedge 635 of the pin 640 and the tip 743 of the rod 742 can be made of a hardened material, and can be made smooth enough to reduce friction at the interface between the tip 743 and the surface of the wedge 635. This improves the predictability in the motion of the pin 640 and eliminates or reduces the need for use of a lubricant at the interface. In some implementations, thewedge 635 and the tip 743 are made of a hardened material having a hardness greater than or equal to 1400 Newtons / millimeter2(N / mm2). In one implementation, the wedge 635 and the tip 743 are made of hardened stainless steel. In some implementations, the surface of the wedge 635 and the surface of the tip 743 are polished to have a roughness of Ra 0.8 micrometers (pm) or better. In various implementations of a mount, one or more contact elements or contact surfaces may be made of hardened stainless steel, or of another metallic material, or silicon dioxide, or of another glass material, or of sapphire, or of another mineral material. The value of Ra measures within a certain sampling length the arithmetic average of the peaks and valleys of the metal surface (the surface of the wedge 635 and the surface of the tip 743), including the deviations from the mean line. The surface roughness can be measured with a profdometer or laser scanner. The greater the deviations in the surface, the rougher the surface and if the Ra is small, the surface is smooth.

[0075] Referring to Fig. 8, an optical pulse stretcher 870 is configured relative to a light source 860. The optical pulse stretcher 870 is positioned at the output of the light source 860. The optical pulse stretcher 870 is designed in accordance with the design principles of the optical pulse stretcher 170, as will be discussed in more detail following the discussion relating to the other features of the light source 860 and the optical pulse stretcher 870.

[0076] The light source 860 can be used as a part of a lithographic apparatus to supply a pulsed light beam 863 to a photolithography exposure apparatus 850 for generating a circuit pattern on a target portion of a substrate (or wafer). In some implementations, the light source 860 is a deep ultraviolet (DUV) light source and the light beam 863 has a wavelength in the DUV wavelength range, which can include wavelengths from, for example, about 100 nanometers (nm) to about 400 nm. As illustrated in Fig. 8, the light source 860 can be a dual-stage light source that includes a first stage 864A and a second stage 864B. The first stage 864A can include a master oscillator (MO) that produces a first pulsed light beam 865, which is passed to the second stage 864B by way of optical elements 866 that includes relay optics. The second stage 864B can include a power amplifier (PA) that receives the first pulsed light beam 865 and optically amplifies the first pulsed light beam 865 to form a second pulsed light beam 867 that forms the input light beam 861 that is directed to the optical pulse stretcher 870.

[0077] The first stage 864A can include, for example, an MO chamber module, in which electrical discharges between electrodes (not shown) can cause lasing gas discharges in a lasing gas to create an inverted population of high energy molecules, such as including argon, krypton, or xenon to produce relatively broad band radiation. This radiation is line narrowed to a relatively very narrow bandwidth and center wavelength selected in a line narrowing module (‘LNM’) within the first stage 864A. The first stage 864A can also include an MO output coupler (MO OC), which can include a partially reflective mirror, forming, with a reflective grating in the LNM, an oscillator cavity in which the first stage 864A oscillates to form the first pulsed light beam 865. The first stage 864A can also include other components such as a line-center analysis module (LAM).

[0078] The optical elements 866 can include an MO wavefront engineering box (WEB) that serves to redirect the first pulsed light beam 865 toward the second stage 864B. The optical elements 866 can also include, for example, beam expansion optical elements with, for example, a multi prism beam expander (not shown) and coherence busting, for example, in the form of an optical delay path (not shown).

[0079] The second stage 864B includes a PA chamber module, which is also an oscillator, for example, formed by injection of the first pulsed light beam 865 and output coupling optics and can be redirected back through a gain medium in the PA chamber by way of a beam reverser. The output coupling optics can incorporate a partially reflective input / output coupler and a maximally reflective mirror for the nominal operating wavelength (which can be at around 193 nm for an ArF system) and one or more prisms. The second stage 864B optically amplifies the first pulsed light beam 865 to form the second pulsed light beam 867.

[0080] Each of the MO chamber module (of the first stage 864A) and the PA chamber module (of the second stage 864B) can be a 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, which includes a combination of one or more noble gases, which can include argon, krypton, or xenon, and a reactive gas, which can include fluorine or chlorine as the gain medium. Thus, for example, the gain medium in each module can include argon fluoride (ArF), krypton fluoride (KrF), or xenon chloride (XeCl). If the gain medium includes argon fluoride, then the wavelength of the pulsed light beam 861 is about 193 nm and if the gain medium includes krypton fluoride, then the wavelength of the pulsed light beam 861 is about 248 nm. The size of the microelectronic features patterned on the wafer (in the photolithography exposure apparatus 850 depends on the wavelength of the pulsed light beam 861, with a lower wavelength resulting in a smaller minimum feature size.

[0081] The second pulsed light beam 861 is an input light beam (like the input light beam 161) that is input to the optical pulse stretcher 870, where copies of the input light beam 861 are delayed and recombined to thereby reduce speckle in the pulsed output light beam 863 that is directed to the photolithography exposure apparatus 850.

[0082] Examples of a dual-stage light source 860 and an optical pulse stretcher 870 are described in WO 2021 / 076658, published on April 22, 2021 by applicant Cymer, LLC, the disclosure of which is incorporated herein by reference in its entirety.

[0083] In some implementations, the optical pulse stretcher 870 includes a single pulse stretcher. In other implementations, the optical pulse stretcher 870 includes several stages of pulse stretchers. For example, a pulse stretcher can include a plurality (at least two) of concave mirrors arranged relative to each other to form a confocal resonator. In some implementations, as discussed in detail in WO 2021 / 076658, the optical pulse stretcher 870 includes a first optical pulse stretcher device 870-1 and a second optical pulse stretcher device 870-2 arranged as a series of stacked optical pulse stretcherdevices. In these implementations, the first optical pulse stretcher device 870-1 receives the input pulsed light beam 861 and delays and recombines copies of the input pulsed light beam 861 to generate a first stretched pulsed light beam 818. This first stretched pulsed light beam 818 is then input to the second optical pulse stretcher device 870-2, which delays and recombines copies of the first stretched pulsed light beam 818 to generate a second stretched pulsed light beam 919. This second stretched pulsed light beam 919 is input to the first optical pulse stretcher device 870-1, where it is then redirected out as the pulsed light beam 863.

[0084] The optical pulse stretcher 870 includes a hermetically-sealed housing 871 that includes a plurality of walls 806a, 806b, 806c, 806d, 806e, 806f, 806g, 806h that together define the interior cavity 873 that houses optical components or elements of the devices 870-1 and 870-2. For simplicity, Fig. 8 shows a two-dimensional rendering of the housing 871 with eight walls but the housing 871 is three dimensional and can include walls that extend in other directions or parallel with the page or in geometric configurations other than what is shown.

[0085] The optical pulse stretcher 870 includes one or more through-wall adjusters or actuation devices 825-j . Two actuation devices 825-1 and 825-2 are shown in Fig. 8, with the actuation device 825-1 associated with an optical element (not shown in Fig. 8) within the first optical pulse stretcher device 870-1 and the actuation device 825-2 associated with an optical element (not shown in Fig. 8) within the second optical pulse stretcher device 870-2. The optical pulse stretcher 870 can include fewer than or more than two actuation devices 825-j and each of the optical pulse stretcher devices 870-1, 870-2 can include one or more respective actuation devices 825-j.

[0086] Each optical pulse stretcher device 870-1, 870-2 can include one or more optical pulse stretchers, with each optical pulse stretcher including one or more confocal resonators. A confocal resonator includes reflecting surfaces that generally face each other and are arranged relative to each other so that a pulsed light beam (such as the second pulsed light beam 861 or the first stretched pulsed light beam 818) is reflected back and forth in a region between the reflecting surfaces.

[0087] Referring to Fig. 9A, an implementation of an optical pulse stretcher 970 that is designed based on the principles of the optical pulse stretcher 170 of Fig. 1 and the optical pulse stretcher 870 of Fig. 8 is shown. The optical pulse stretcher 970 includes a first optical pulse stretcher device 970-1 and a second optical pulse stretcher device 970-2 arranged as a series of stacked optical pulse stretcher devices. In these implementations, the first optical pulse stretcher device 970-1 receives the second pulsed light beam 861, and delays and recombines copies of the second pulsed light beam 961 to generate a first stretched pulsed light beam 918. This first stretched pulsed light beam 918 is then input to the second optical pulse stretcher device 970-2, which delays and recombines copies of the first stretched pulsed light beam 918 to generate a second stretched pulsed light beam 919. This second stretched pulsed light beam 919 is returned to the first optical pulse stretcher device 970-1, where it is then redirected out as the pulsed light beam 963.

[0088] The first optical pulse stretcher device 970-1 includes, within its interior cavity 973-1, a least one optical pulse stretcher 903-1 that includes at least two opposing mirrors 902a, 902b that produce reflections between them and define a confocal resonator. For example, the optical pulse stretcher 903-1 can include a first single mirror 902a and a second single mirror 902b to produce two reflections of delayed portions of the second pulsed light beam 961. As another example, the optical pulse stretcher 903-1 can include two first mirrors 902a and two second mirrors 902b that produce four reflections of delayed portions of the second pulsed light beam 961. The mirrors 902a, 902b can be separated from each other by a large enough physical distance to enable the desired optical delays. In some implementations, the mirrors 902a, 902b are separated by a physical distance of, for example, about 1 meter (m) to about 3 m. Such physical distance can provide an optical delay of about 30 nanoseconds (ns) to about 50 ns. The mirrors 902a, 902b can be circular and concave mirrors. Additionally, the first optical pulse stretcher device 970-1 can include other optical elements. For example, a beam splitter 904 is positioned on the path of the second pulsed light beam 961 to split off a portion of the second pulsed light beam 961 toward the optical pulse stretcher 903-1. A pair of beam splitters 904a, 904b can be positioned to split off the first stretched pulsed light beam 918 to the second optical pulse stretcher device 970-2 and then recombine the second stretched pulsed light beam 919 from the second optical pulse stretcher device 970-2 to thereby form the output light beam 963.

[0089] The second optical pulse stretcher device 970-2 includes, within its interior cavity 973-2, one or more confocal optical pulse stretchers. In the example shown, there are three confocal optical pulse stretchers 903-2i, 903-2ii, 903-2iii. Each of the optical pulse stretchers 903-2i, 903-2ii, 903-2iii includes at least two respective opposing mirrors 970-ai, 970-bi; 970-aii, 970-bii; 970-aiii, 970-biii. Although two opposing mirrors are shown in each pulse stretcher 903 -2i, 903 -2ii, 903 -2iii, it is possible for each pulse stretcher 903-2i, 903-2ii, 803 -2iii to include more than two opposing mirrors.

[0090] The second optical pulse stretcher device 970-2 also includes an optical arrangement 974 that is configured to receive the first stretched pulsed light beam 918, split the first stretched pulsed light beam 918 into portions, redirect the split portions into one or more of the pulse stretchers 903 -2i, 903 -2ii, 903 -2iii, and recombine the split portions that have been delayed to form the second stretched pulsed light beam 919. The optical arrangement 974 therefore includes one or more beam splitters and fold mirrors.

[0091] Referring to Fig. 9B, an implementation 974B of the optical arrangement 974 is shown. The optical arrangement 974B includes three beamsplitters 975i, 975ii, 975iii placed along the path of the first stretched pulsed light beam 918, with each beamsplitter 975i, 975ii, 975iii configured to pick off a portion of the first stretched pulsed light beam 918 and direct that portion into the respective confocal optical pulse stretcher 903-2i, 903-2ii, 903-2iii. The optical arrangement 974B also include two fold mirrors 905c, 905d arranged to direct the second stretched pulsed light beam 919 (formedfrom passing the first stretched pulsed light beam 918 portions through each of the confocal optical pulse stretchers 903-2i, 903-2ii, 903-2iii) back toward the first optical pulse stretcher device 970-1.

[0092] Referring again to Fig. 9A, the optical pulse stretcher 970 includes a hermetically-sealed housing 971 that includes a plurality of walls 906a, 906b, 906c, 906d, 906e, 906f, 906g, 906h that together define the interior cavity 973 that houses optical components or elements of the devices 970- 1 and 970-2. For simplicity, Fig. 9A shows a two-dimensional rendering of the housing 971 with eight walls but the housing 971 is three dimensional and can include walls that extend in other directions or parallel with the page, the housing 971 can have a different geometry, and the housing 971 can include different sections that are connected together.

[0093] The optical pulse stretcher 970 can include other elements not shown. For example, the optical pulse stretcher 970 can include optical elements that are used for alignment of other optical elements within the optical pulse stretcher 970. Such an alignment apparatus can be configured to selectively interact with the first stretched pulsed light beam 918 and / or the second stretched pulsed light beam 919. Additional alignment apparatuses can be used at other locations along the path of the light beams that travel through the optical pulse stretcher 970. For example, an alignment apparatus can be used to visualize the first stretched pulsed light beam 918 and an alignment apparatus can be used to visualize the second stretched pulsed light beam 919.

[0094] The apparatus 970 includes one or more through-wall adjusters or actuation devices 925-j. Actuation devices 925-1, 925-2, 925-3, 925-4, 925-5, 925-6 are associated with, respectively, mirrors 970-biii, 970-bii, 970-bi, 970-ai, 970-aii, 970-aiii of the optical pulse stretchers 903-2i, 903-2ii, 903- 2iii. Actuation devices 925-7 and 925-8 are associated with, respectively, mirrors 902a and 902b of the optical pulse stretcher 903-1. Lastly, at least one actuation device 925-9 is associated with an optical element within the optical arrangement 974. The actuation devices 925-1, 925-2, 925-3 are mounted as through-wall adjusters in the wall 906a; the actuation device 925-7 is mounted as a through -wall adjuster in the wall 906d; the actuation device 925-8 is mounted as a through-wall adjuster in the wall 906e; the actuation devices 925-6, 925-7, 925-8 are mounted as through-wall adjusters in the wall 906g; and the actuation device 925-9 is mounted as a through-wall adjuster in the wall 906h. The optical pulse stretcher apparatus 970 can include fewer than or more than nine actuation devices 925-j and each of the optical pulse stretcher devices 970-1, 970-2 can include one or more respective actuation devices 925-j.

[0095] Referring to Fig. 9B, there can be more than one actuation device 925-9 mounted as a through-wall adjuster in a wall to access one or more of the optical components within the optical arrangement 974B. In this implementation, two actuation devices 925-9, 925-10 are mounted at wall 906h for control and adjustment of respective mirrors 905c, 905d.

[0096] Each mirror 905c, 905d can constitute an optical element such as the optical element 105, which needs to be adjusted. There is a need to adjust (for example, to align or modify a position or angle of) each mirror 905c, 905d within the optical pulse stretcher device 970-1 or 970-2. Forexample, in order to ensure that the light beam 918 is properly aligned with and traverses the mirror 905d that is optically downstream of the mirror 905c, the mirror 905c may need to be translated along one or more local axes or rotated about one or more local axes. Moreover, such adjustment to one or more of the mirrors 905c, 905d can occur while the light beam 918 or 919 is interacting with the mirror 905c, 905d. To this end, the mirror 905c is located at (such as fixed or constrained) and controlled by an adjustable mounting apparatus 910c and the mirror 905d is located at (such as fixed or constrained) and controlled by an adjustable mounting apparatus 910d. The adjustable mounting apparatus 910c enables the alignment of the light beam 918 relative to an optical element downstream of the mirror 905c and the adjustable mounting apparatus 910d enables the alignment of the light beam 919 relative to an optical element downstream of the mirror 905d. Each adjustable mounting apparatus 910c, 91 Od is designed with the principles of the adjustable mounting apparatus 110 and therefore includes a respective passive alignment mount 120 and a respective drive mechanism 130 mechanically coupled to the respective passive alignment mount 120. In some implementations, the adjustable mounting apparatus 910c can be designed like the adjustable mounting apparatus 210 or 310 and the adjustable mounting apparatus 910d can be designed like the adjustable mounting apparatus 210 or 310. In these implementations, the actuation device 925-9 can include a pair of actuation devices with each actuation device coupled to a respective drive system 330A or 330C within the drive mechanism 330 and the actuation device 925-10 can include a pair of actuation devices with each actuation device coupled to a respective drive system 330A or 330C within the drive mechanism 330. Moreover, each mirror 905c, 905d is held stable in a respective mirror cell 921c, 92 Id, with each mirror cell 921c, 92 Id being mounted to a structure (such as the structure 331) of the drive mechanism 330.

[0097] The operation of the adjustable mounting apparatus 910c, 91 Od is similar to the operation of the adjustable mounting apparatus 310 described above.

[0098] Other optical elements within the optical pulse stretcher 870 can be located at (such as fixed or constrained) and controlled by their respective adjustable mounting apparatuses that is designed like the adjustable mounting apparatus 110, 210, 310.

[0099] In other implementations, and with reference again to Figs. 3A and 3B, the passive alignment mount 320 can be a part of a kinematic mount or a pseudo-kinematic mount that includes three contact elements 320A’, 320B’, 320C’ that are a different design than the contact elements 320A, 320B, 320C. For example, in other implementations, each of the contact elements 320A’, 320B’, 320C’ is a groove or linear indentation defined in a contact body (similar to the contact element 320C.

[0100] In other implementations, and with reference again to Figs. 6A-6D, the pin 640 can have a shape other than cylindrical (in which its cross-sectional shape is circular). For example, the pin 640 can have a cross-sectional shape that is oval or polygonal. In other implementations, and with reference again to Figs. 7A and 7B, the rod 742 can have a shape other than cylindrical (in which itscross-sectional shape is circular). For example, the rod 742 can have a cross-sectional shape that is oval or polygonal.

[0101] With reference to Fig. 10, an implementation 1010 of the adjustable mounting apparatus 310 is shown. The adjustable mounting apparatus 1010 includes a passive alignment mount 1020 located and aligned to an optical element cell 1021 at which the optical element (not shown in Fig. 10 but can be any optical element 105) is contained in an opening 1022. The adjustable mounting apparatus 1010 includes a drive mechanism 1030 (which is partially shown) mechanically coupled to the passive alignment mount 1020, the drive mechanism 1030 being constrained by a solid structure or body (such as the body 331 of Fig. 3A). The drive mechanism 1030 imparts the mechanical constraint and / or motion to the passive alignment mount 1020 and the optical element. In this way, the passive alignment mount 1020 and the drive mechanism 1030, in combination, provide a tip / tilt mechanism that enables the tip and / or tilt to the optical element (relative to the Xwos axis or the Y wos axis) without disrupting the controlled environment within the cavity 173 (Fig. 1) in which the optical system 300 is configured.

[0102] The passive alignment mount 1020 includes three contact elements 1020A, 1020B, 1020C and the drive mechanism 1030 includes three drive systems 1030A, 1030B, 1030C (partially shown in Fig. 10), with each drive system 1030A, 1030B, 1030C associated with a respective and specific contact element 1020A, 1020B, 1020C.

[0103] The passive alignment mount 1020 is a part of a kinematic mount or a pseudo-kinematic mount. That is, a kinematic mount (or pseudo-kinematic mount) is formed between the passive alignment mount 1020 and the drive mechanism 1030 to thereby create stiffness between the two bodies (the optical element 105 and the drive mechanism 1030) in six independent degrees of freedom DOFs or directions.

[0104] In this implementation, the kinematic mount includes the three contact elements 1020A, 1020B, 1020C. The contact element 1020A is a first groove defined along a first axial direction 1023 A in a first contact body. The contact element 1020B is second groove defined along a second axial direction 1023B in a second contact body. And, the contact element 1020C is a third groove defined along a third axial direction 1023C in a third contact body. Each axial direction (such as 1023A) is distinct from the other two axial directions (such as 1023B, 1023C) and each axial direction lies in the Xwos, Ywos plane.

[0105] Each drive system 1030A, 1030B, 1030C includes a respective wedge 1035A, 1035B, 1035C, and each wedge is rotationally constrained 1036A, 1036B, and 1036C, respectively, as was discussed in detail above.

[0106] The implementations can be further described using the following clauses:1. An optical system in a pulse stretcher of a deep ultraviolet light source, the optical system comprising:an optical element configured, in operation, along a path of a light beam produced by the deep ultraviolet light source; and an adjustable mounting apparatus to which the optical element is located, the adjustable mounting apparatus comprising: a passive alignment mount, and a drive mechanism coupled to the passive alignment mount, the drive mechanism including a wedge that is rotationally constrained.2. The optical system of clause 1, wherein the optical element is a reflective optical element, a partially-reflecting beamsplitter, a diffractive optical element, or a refractive optical element.3. The optical system of clause 2, wherein the passive alignment mount comprises a kinematic mount or a pseudo-kinematic mount.4. The optical system of clause 1, wherein the passive alignment mount comprises a kinematic mount.5. The optical system of clause 4, wherein the kinematic mount comprises: a flat plane, a groove, and a socket.6. The optical system of clause 5, wherein the drive mechanism comprises a first rounded tip touching the flat plane, a second rounded tip touching the groove, and a third rounded tip touching the socket.7. The optical system of clause 5, wherein the first rounded tip touching the flat plane provides five degrees of freedom, the second rounded tip touching the groove provides four degrees of freedom, and the third rounded tip touching the socket provides three degrees of freedom.8. The optical system of clause 4, wherein the kinematic mount comprises a first groove defined along a first axial direction, a second groove defined along a second axial direction, and a third groove defined along a third axial direction, each axial direction being distinct from the other two axial directions.9. The optical system of clause 1, wherein the passive alignment mount is located and aligned to an optical element cell where the optical element is contained.10. The optical system of clause 1, wherein the drive mechanism comprises a plurality of drive systems, each drive system associated with a contact element of the passive alignment mount, wherein at least one of the drive systems comprises: a pin comprising rounded tip at a first end and the wedge at a second end, the rounded tip touching one of the contact elements of the passive alignment mount; and a rod comprising a spherically-shaped tip constrained by the wedge of the pin.11. The optical system of clause 10, further comprising a structure defining a plurality of cylindrical openings, with each cylindrical opening receiving either a pin or a rod, wherein the structure constrains and guides each pin and each rod received within its respective cylindrical opening.12. The optical system of clause 10, wherein the translation of the rod along a first direction causes the spherically-shaped tip of the rod to translate along the first direction, the spherically-shaped tip interfaces with the wedge and causes the pin to translate along a second direction that is distinct from the first direction.13. The optical system of clause 12, wherein the second direction is perpendicular to the first direction.14. The optical system of clause 10, wherein the passive alignment mount comprises a kinematic mount and the contact element of the kinematic mount is one of a flat plane, a socket, or a groove.15. The optical system of clause 10, wherein the rod of each drive system is adjustable from outside an enclosure in which the optical element is contained.16. The optical system of clause 1, wherein the drive mechanism comprises three drive systems, each drive system associated with a contact element of the passive alignment mount, wherein one drive system provides a linearly-constrained fixed point at a respective contact element, and the other two drive systems are configured to move the respective contact element.17. The optical system of clause 1, wherein the passive alignment mount includes a plurality of contact elements, each contact element comprising hardened stainless steel.18. The optical system of clause 17, wherein the drive mechanism comprises a plurality of drive systems, each drive system associated with a contact element of the passive alignment mount, at least two of the drive systems comprising the wedge and a rounded tip both made of a hardened material with a hardness greater than or equal to 1400 Newtons / millimeter2(N / mm2).19. The optical system of clause 17, wherein the drive mechanism comprises a plurality of drive systems, each drive system associated with a contact element of the passive alignment mount, at least two of the drive systems comprising the wedge and a rounded tip both made of a hardened material with a hardness greater than or equal to 2075 Newtons / millimeter2(N / mm2).20. The optical system of clause 19, wherein the wedge and the rounded tip are made of hardened stainless steel.21. The optical system of clause 19, wherein each wedge and each rounded tip includes a polished surface finish having a roughness of Ra 0.8 micrometers (Ra 32 micro inches, 35 RMS) or less.22. The optical system of clause 19, wherein each wedge and each rounded tip includes a polished surface finish having a roughness of Ra 0.4 micrometers (Ra 16 micro inches, 17.6 RMS) or better.23. The optical system of clause 1, wherein the adjustable mounting apparatus lacks lubricant.24. The optical system of clause 1, wherein the optical element is a first optical element and the adjustable mounting apparatus is a first adjustable mounting apparatus to which the first opticalelement is located, the first adjustable mounting apparatus comprising a first kinematic mount and a first wedge adjustment mechanism coupled to the first kinematic mount, and the optical system further comprises a second optical element arranged relative to the first optical element and a second adjustable mounting apparatus to which the second optical element is located, the second adjustable mounting apparatus comprising: a second kinematic mount, and a second wedge adjustment mechanism coupled to the second kinematic mount.25. The optical system of clause 1, wherein the wedge comprises a flat surface at an end of a pin, the pin extending along an axial pin direction and a normal of the flat surface extending between 20°-40° relative to the axial pin direction.26. The optical system of clause 25, wherein the drive mechanism includes wings extending from the pin and adjacent to ends of the flat surface of the wedge, the wings rotationally constraining the wedge.27. The optical system of clause 1, wherein the adjustable mounting apparatus is configured to enable tilt adjustment in pitch and roll of the optical element.28. An optical system inside a pulse stretcher of a deep ultraviolet light source, the optical system comprising: a pair of fold mirrors configured, in operation, along a path of a light beam produced by the deep ultraviolet light source to direct the light beam from a first part of the pulse stretcher to a second part of the pulse stretcher; a pair of mirror cells mounted to a structure, each fold mirror being held stable in a respective mirror cell; and a pair of adjustable mounting apparatuses, with each mirror cell positioned at a respective adjustable mounting apparatus, each adjustable mounting apparatus comprising a passive alignment mount associated with each mirror cell and a drive mechanism associated with each passive alignment mount, the drive mechanism including a wedge that is rotationally constrained.29. The optical system of clause 28, wherein the adjustable mounting apparatus is configured to enable tilt adjustment in pitch and roll of the fold mirror held stable in the mirror cell positioned at the adjustable mounting apparatus.30. An adjustable mounting apparatus to which an optical element of a pulse stretcher is located, the adjustable mounting apparatus arranged inside a controlled environment of a pulse stretcher enclosure, the adjustable mounting apparatus comprising: a cell to which the optical element is located; a passive alignment mount associated with the cell, and a drive mechanism coupled to the passive alignment mount, at least a part of the drive mechanism being controllable from outside the pulse stretcher enclosure, the drive mechanism including a wedge that is rotationally constrained.

[0107] Other implementations are within the scope of the following claims.

Claims

CLAIMS1. An optical system in a pulse stretcher of a deep ultraviolet light source, the optical system comprising: an optical element configured, in operation, along a path of a light beam produced by the deep ultraviolet light source; and an adjustable mounting apparatus to which the optical element is located, the adjustable mounting apparatus comprising: a passive alignment mount, and a drive mechanism coupled to the passive alignment mount, the drive mechanism including a wedge that is rotationally constrained.

2. The optical system of claim 1, wherein the optical element is a reflective optical element, a partially-reflecting beamsplitter, a diffractive optical element, or a refractive optical element.

3. The optical system of claim 2, wherein the passive alignment mount comprises a kinematic mount or a pseudo-kinematic mount.

4. The optical system of claim 1, wherein the passive alignment mount comprises a kinematic mount.

5. The optical system of claim 4, wherein the kinematic mount comprises: a flat plane, a groove, and a socket.

6. The optical system of claim 5, wherein the drive mechanism comprises a first rounded tip touching the flat plane, a second rounded tip touching the groove, and a third rounded tip touching the socket.

7. The optical system of claim 5, wherein the first rounded tip touching the flat plane provides five degrees of freedom, the second rounded tip touching the groove provides four degrees of freedom, and the third rounded tip touching the socket provides three degrees of freedom.

8. The optical system of claim 4, wherein the kinematic mount comprises a first groove defined along a first axial direction, a second groove defined along a second axial direction, and a third groove defined along a third axial direction, each axial direction being distinct from the other two axial directions.

9. The optical system of claim 1, wherein the passive alignment mount is located and aligned to an optical element cell where the optical element is contained.

10. The optical system of claim 1, wherein the drive mechanism comprises a plurality of drive systems, each drive system associated with a contact element of the passive alignment mount, wherein at least one of the drive systems comprises: a pin comprising rounded tip at a first end and the wedge at a second end, the rounded tip touching one of the contact elements of the passive alignment mount; and a rod comprising a spherically-shaped tip constrained by the wedge of the pin.

11. The optical system of claim 10, further comprising a structure defining a plurality of cylindrical openings, with each cylindrical opening receiving either a pin or a rod, wherein the structure constrains and guides each pin and each rod received within its respective cylindrical opening.

12. The optical system of claim 10, wherein the translation of the rod along a first direction causes the spherically-shaped tip of the rod to translate along the first direction, the spherically-shaped tip interfaces with the wedge and causes the pin to translate along a second direction that is distinct from the first direction.

13. The optical system of claim 12, wherein the second direction is perpendicular to the first direction.

14. The optical system of claim 10, wherein the passive alignment mount comprises a kinematic mount and the contact element of the kinematic mount is one of a flat plane, a socket, or a groove.

15. The optical system of claim 10, wherein the rod of each drive system is adjustable from outside an enclosure in which the optical element is contained.

16. The optical system of claim 1, wherein the drive mechanism comprises three drive systems, each drive system associated with a contact element of the passive alignment mount, wherein one drive system provides a linearly-constrained fixed point at a respective contact element, and the other two drive systems are configured to move the respective contact element.

17. The optical system of claim 1, wherein the passive alignment mount includes a plurality of contact elements, each contact element comprising hardened stainless steel.

18. The optical system of claim 17, wherein the drive mechanism comprises a plurality of drive systems, each drive system associated with a contact element of the passive alignment mount, at least two of the drive systems comprising the wedge and a rounded tip both made of a hardened material with a hardness greater than or equal to 1400 Newtons / millimeter2(N / mm2).

19. The optical system of claim 17, wherein the drive mechanism comprises a plurality of drive systems, each drive system associated with a contact element of the passive alignment mount, at least two of the drive systems comprising the wedge and a rounded tip both made of a hardened material with a hardness greater than or equal to 2075 Newtons / millimeter2(N / mm2).

20. The optical system of claim 19, wherein the wedge and the rounded tip are made of hardened stainless steel.

21. The optical system of claim 19, wherein each wedge and each rounded tip includes a polished surface finish having a roughness of Ra 0.8 micrometers (Ra 32 micro inches, 35 RMS) or less.

22. The optical system of claim 19, wherein each wedge and each rounded tip includes a polished surface finish having a roughness of Ra 0.4 micrometers (Ra 16 micro inches, 17.6 RMS) or better.

23. The optical system of claim 1, wherein the adjustable mounting apparatus lacks lubricant.

24. The optical system of claim 1, wherein the optical element is a first optical element and the adjustable mounting apparatus is a first adjustable mounting apparatus to which the first optical element is located, the first adjustable mounting apparatus comprising a first kinematic mount and a first wedge adjustment mechanism coupled to the first kinematic mount, and the optical system further comprises a second optical element arranged relative to the first optical element and a second adjustable mounting apparatus to which the second optical element is located, the second adjustable mounting apparatus comprising: a second kinematic mount, and a second wedge adjustment mechanism coupled to the second kinematic mount.

25. The optical system of claim 1, wherein the wedge comprises a flat surface at an end of a pin, the pin extending along an axial pin direction and a normal of the flat surface extending between 20°-40‘ relative to the axial pin direction.

26. The optical system of claim 25, wherein the drive mechanism includes wings extending from the pin and adjacent to ends of the flat surface of the wedge, the wings rotationally constraining the wedge.

27. The optical system of claim 1, wherein the adjustable mounting apparatus is configured to enable tilt adjustment in pitch and roll of the optical element.

28. An optical system inside a pulse stretcher of a deep ultraviolet light source, the optical system comprising: a pair of fold mirrors configured, in operation, along a path of a light beam produced by the deep ultraviolet light source to direct the light beam from a first part of the pulse stretcher to a second part of the pulse stretcher; a pair of mirror cells mounted to a structure, each fold mirror being held stable in a respective mirror cell; and a pair of adjustable mounting apparatuses, with each mirror cell positioned at a respective adjustable mounting apparatus, each adjustable mounting apparatus comprising a passive alignment mount associated with each mirror cell and a drive mechanism associated with each passive alignment mount, the drive mechanism including a wedge that is rotationally constrained.

29. The optical system of claim 28, wherein the adjustable mounting apparatus is configured to enable tilt adjustment in pitch and roll of the fold mirror held stable in the mirror cell positioned at the adjustable mounting apparatus.

30. An adjustable mounting apparatus to which an optical element of a pulse stretcher is located, the adjustable mounting apparatus arranged inside a controlled environment of a pulse stretcher enclosure, the adjustable mounting apparatus comprising: a cell to which the optical element is located; a passive alignment mount associated with the cell, and a drive mechanism coupled to the passive alignment mount, at least a part of the drive mechanism being controllable from outside the pulse stretcher enclosure, the drive mechanism including a wedge that is rotationally constrained.

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