Optical system, illumination system and light system

Abstract

An optical system is provided that can reduce noise, comprising a first optical system, a second optical system, and a third optical system. The first optical system divides an input beam into first light and second light. The second optical system comprises a concave reflective surface that reflects the first light. The third optical system directs at least one of the first light reflected from the second optical system and the second light reflected from the first optical system to an output optical path of the third optical system.

Description

TECHNICAL FIELD

[0001] The present invention relates to an optical system. BACKGROUND

[0002] For illumination systems of lithography, non-complex or complex illumination patterns can be required to illuminate a target surface. However, non-complex or complex illumination patterns are affected by speckle noise generated by interference between different parts of the illumination pattern, especially when a coherent source is used to generate the pattern. This noise degrades the quality of the lithography process and can produce errors. SUMMARY

[0003] An optical system based on an aspect of the present invention includes a first optical system that divides an input beam of light into first light and second light, a second optical system that includes a concave reflective surface that reflects the first light, and a third optical system that directs at least one of the first light reflected from the second optical system and the second light reflected from the first optical system to an output optical path of the third optical system.

[0004] An optical system based on another aspect of the present invention includes a time delay system, wherein the time delay system generates a set of fine beams with reduced speckle from a coherent input illumination source, a first fine beam array and a second fine beam array, wherein the first fine beam array and the second fine beam array steer and shape the set of fine beams to achieve an illumination pattern at a target plane.

[0005] An optical system based on another aspect of the present invention includes a beam splitter that divides an input beam of light into first light and second light and directs the first light and the second light to different directions, an intermediate optical component that includes a refractive surface that refracts the first light and a concave mirror that reflects the first light from the refractive surface, and a beam combiner that directs the first light and the second light from the concave mirror to the same direction, wherein the first light from the concave mirror to the beam combiner passes through the refractive surface.

[0006] An optical system based on another aspect of the present invention includes a beam splitter that divides an input beam of light into first light and second light and directs the first light and the second light to different directions, an intermediate optical component that includes a first reflective surface that reflects the first light from the beam splitter and has a concave shape, and a second reflective surface that reflects the first light beam from the first reflective surface and directs the first light beam to the first reflective surface, and a beam combiner that directs the first light and the second light from the second reflective surface to the same direction, wherein the first light from the second reflective surface to the beam combiner passes through the first reflective surface. BRIEF DESCRIPTION OF DRAWINGS

[0007] Various embodiments of the invention are disclosed in the following detailed description and accompanying drawings.

[0008] Figure 1 This is a diagram illustrating an embodiment of a system for photolithography using an irradiation system with an optical delay system.

[0009] Figure 2A This is a diagram illustrating an embodiment of an optical delay system.

[0010] Figure 2B This is a diagram illustrating an embodiment of the output pattern at the target plane for an optical delay system.

[0011] Figure 3 This is a diagram illustrating an embodiment of the delay system.

[0012] Figure 4 This is a diagram illustrating an embodiment of an optical delay system.

[0013] Figure 5A This is a diagram illustrating an example embodiment of a system for irradiation.

[0014] Figure 5B This is a diagram illustrating an embodiment of a system for irradiation.

[0015] Figure 5C This is a diagram illustrating an embodiment of a system for irradiation.

[0016] Figure 5D This is a diagram illustrating an embodiment of a system for irradiation.

[0017] Figure 5E It is shown by Figure 5D A diagram showing the beam shape obtained from an embodiment of the system used for irradiation.

[0018] Figure 5F It indicates arrival Figure 5D A diagram showing the simulated phase of each beam of the second array in an embodiment of the system for illumination.

[0019] Figure 6 This is a diagram illustrating an embodiment of a time delay system using folded solid-state optics.

[0020] Figure 7 This is a diagram illustrating an embodiment of the delay element.

[0021] Explanation of icon numbers

[0022] 100: Pulse source;

[0023] 102: Irradiation system;

[0024] 104: Target plane;

[0025] 106: projection lens;

[0026] 108: wafer;

[0027] 200, 360, 400: input beam;

[0028] 202, 208, 214, 219, 300, 310, 320, 330, 340, 350, 402, 408, 414, 419, 602, 612, 624, 702, 710: beamsplitter;

[0029] 204, 210, 216, 404, 410, 416, 704: lens;

[0030] 206, 212, 218, 222, 406, 412, 418: curved reflector;

[0031] 220, 420: polarization relay;

[0032] 222, 422: polarization beamsplitter;

[0033] 302, 304, 316, 318: optical element;

[0034] 304, 306, 312, 314, 322, 324, 332, 334, 342, 344, 706, 708: mirror;

[0035] 370: output beam;

[0036] 500, 520, 540, 560: time delay system;

[0037] 502, 564, 566: element;

[0038] 504: collector;

[0039] 506, FE1: first fly's eye array;

[0040] 508, FE2: second fly's eye array;

[0041] 510, 530, 550, 570: condenser;

[0042] 512, 532, 552, 572: reticle shutter;

[0043] 522: near field beam shaper;

[0044] 524, 526, 528, 544, 546, 548: beamlet steering optics;

[0045] 542: far field beam shaper;

[0046] 604, 608, 610, 614, 616, 618, 620, 700: optical beams;

[0047] 606, 622: solid catadioptric lens. DETAILED DESCRIPTION

[0048] The disclosure can be implemented in numerous ways, including as a process; an apparatus; a system; a composition of matter; a computer program product (which can be implemented on a computer- readable storage medium) and / or a processor, such as a processor configured to

[0049] Generally, the order of the steps of the disclosed processes can be altered within the scope of the disclosure. Unless otherwise specified, an element, e.g., a processor or memory, described as being configured to perform a task can be implemented as a general component that is temporarily configured to perform the task at a given time or a specific component that is manufactured to perform the task. As used herein, the term 'processor' refers to one or more devices, circuits, and or processing cores configured to process data, such as computer program instructions.

[0050] The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present disclosure. Figure 1 A detailed description of one or more embodiments of the disclosure is provided below along with accompanying figures that illustrate the principles of the disclosure. The disclosure is described in connection with such embodiments, but the The scope of the disclosure is limited only by the claims and encompasses many alternatives, modifications and equivalents. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. These details are provided for the purpose of example and the present disclosure can be practiced according to the claims without some or all of these specific details. In some instances, conventional or other well-known structures and materials are not described in detail in order to avoid unnecessarily obscuring the present disclosure.

[0051] An optical delay system is disclosed.

[0052] In some embodiments, the optical delay system includes a beam splitter, an intermediate optical piece, and a beam combiner. The beam splitter divides an input beam into first light and second light, and directs the first light and the second light in different directions. The intermediate optical piece includes a refractive surface that refracts the first light and a concave mirror that reflects the first light from the refractive surface. The beam combiner directs the first light and the second light from the concave mirror in the same direction, where the first light from the concave mirror to the beam combiner passes through the refractive surface.

[0053] In some embodiments, the optical delay system includes a beam splitter, an intermediate optical component, and a beam combiner. The beam splitter divides an input beam into first light and second light, and directs the first light and the second light in different directions. The beam splitter can direct the first light and the second light in the same direction. The intermediate optical component includes a first reflective surface that reflects the first light from the beam splitter and has a concave shape, and a second reflective surface that reflects a first light beam from the first reflective surface and directs the first light beam to the first reflective surface. The beam combiner directs the first light and the second light from the second reflective surface in the same direction, where the first light from the second reflective surface to the beam combiner passes through the first reflective surface. The beam combiner can direct the first light and the second light in different directions.

[0054] In some embodiments, the optical or temporal delay system includes a plurality of arms that are traversed such that each of the set of fine beams traverses a different arrangement of the plurality of arms in order to reduce temporal coherence between each of the set of fine beams output by the temporal delay system. In some embodiments, the temporal delay system includes a plurality of temporal delay arms, where the optical path in an arm of the plurality of temporal delay arms is folded. In various embodiments, the optical path in the arm is substantially in glass (e.g., an index of refraction of approximately 1.5) or any other appropriate location above the index of refraction of air. In some embodiments, the optical path in the arm is substantially in air. In some embodiments, the optical path is folded N times. In various embodiments, N is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or greater, or any other appropriate value.

[0055] In some embodiments, the optical system includes: a first optical system that divides an input beam into first light and second light; a second optical system that includes a concave reflective surface that reflects the first light; and a third optical system that directs at least one of the first light reflected from the second optical system and the second light reflected from the first optical system to an output optical path of the third optical system.

[0056] In some embodiments, the second optical system includes a refractive component disposed between the first optical system and the concave mirror. In some embodiments, the refractive component is disposed between the concave mirror and the third optical system. In some embodiments, the refractive component has a back focal point located substantially on the concave reflective surface. In some embodiments, the second optical system includes a reflective surface that reflects the first light from the concave reflective surface, and wherein the concave reflective surface reflects the first light from the reflective surface of the second optical system. In some embodiments, the system further comprises a refractive component disposed between the concave reflective surface and the reflective surface. In some embodiments, the concave reflective surface and the reflective surface are formed on the refractive component. In some embodiments, the reflective surface has a concave shape. In some embodiments, the reflective surface has a convex shape. In some embodiments, the concave reflective surface faces a beam path of the second light between the first optical system and the third optical system. In some embodiments, the first light from the third optical system and the second light from the third optical system pass through different locations. In some embodiments, the system further comprises a fourth optical system including a concave reflective surface that reflects the first light from the third optical system. In some embodiments, an optical axis of the second optical system and an optical axis of the fourth optical system are eccentric to each other. In some embodiments, the third optical system divides the first light from the second optical system into third light and fourth light. In some embodiments, the system further comprises a fifth optical system disposed on an output path of the third optical system.

[0057] In some embodiments, an optical system includes a temporal delay system and a first array of beamlets and a second array of beamlets. The temporal delay system produces a set of beamlets with reduced speckle from a source of coherent input illumination. The first array of beamlets and the second array of beamlets divert and shape the set of beamlets to achieve an illumination pattern at a target plane. In various embodiments, the first array of beamlets or the second array of beamlets includes one or more of: a reflective surface, a refractive surface, a diffractive element, a hologram, and / or a metasurface, or any other suitable element. In some embodiments, the illumination pattern includes an array of beamlets. In various embodiments, the array includes one of: a square array, a rectangular array, an array having an overall shape of a ring, an array having an overall shape of a dipole, or an array having an overall shape of a quadrupole, or any other suitable geometry. In some embodiments, the temporal delay system includes a plurality of arms that are traversed such that each beamlet in the set of beamlets traverses a different permutation of the plurality of arms in order to reduce temporal coherence between each beamlet in the set of beamlets output by the temporal delay system. In some embodiments, the source of coherent input illumination includes a pulsed laser. In some embodiments, the system is configured to position a reticle at the target plane. In some embodiments, the system is configured to project an image of the reticle on a wafer.

[0058] In some embodiments, a time delay system includes: a beam splitter that divides an input beam into first light and second light and directs the first light and the second light into different directions; an intermediate optical component that includes a refractive surface that refracts the first light and a concave mirror that reflects the first light from the refractive surface; and a beam combiner that directs the first light and the second light from the concave mirror into the same direction, where the first light from the concave mirror to the beam combiner passes through the refractive surface.

[0059] In some embodiments, a time delay system includes: a beam splitter that divides an input beam into first light and second light and directs the first light and the second light into different directions; an intermediate optical component that includes a first reflective surface that reflects the first light from the beam splitter and has a concave shape and a second reflective surface that reflects the first light beam from the first reflective surface and directs the first light beam to the first reflective surface; and a beam combiner that directs the first light and the second light from the second reflective surface into the same direction, where the first light from the second reflective surface to the beam combiner passes through the first reflective surface.

[0060] In some embodiments, a time delay system includes a set of beam splitters and arm optics of different sizes. In some embodiments, the system includes a near-field beam shaper to shape a set of beamlets output by the time delay system. In some embodiments, the system includes a far-field beam shaper to shape a set of beamlets output by the time delay system. In some embodiments, the time delay system includes a plurality of time delay arms, where the optical path in the arms of the plurality of time delay arms is folded. In some embodiments, the optical path in the arms is substantially in glass. In some embodiments, the optical path in the arms is substantially in air. In some embodiments, the optical path is folded N times.

[0061] In some embodiments, an optical system includes: a beam splitter that divides an input beam into first light and second light and directs the first light and the second light into different directions; an intermediate optical component that includes a refractive surface that refracts the first light and a concave mirror that reflects the first light from the refractive surface; and a beam combiner that directs the first light and the second light from the concave mirror into the same direction, where the first light from the concave mirror to the beam combiner passes through the refractive surface. In some embodiments, a time delay system includes a set of beam splitters and arm optics of different sizes. In some embodiments, the system includes a near-field beam shaper to shape a set of beamlets output by the time delay system. In some embodiments, the system includes a far-field beam shaper to shape a set of beamlets output by the time delay system. In some embodiments, the time delay system includes a plurality of time delay arms, where the optical path in the arms of the plurality of time delay arms is folded. In some embodiments, the optical path in the arms is substantially in glass. In some embodiments, the optical path in the arms is substantially in air. In some embodiments, the optical path is folded N times.

[0062] In some embodiments, the optical system includes: a beam splitter that divides an input beam into first light and second light and directs the first light and the second light to different directions; an intermediate optical piece that includes a refractive surface that refracts the first light and a concave mirror that reflects the first light from the refractive surface; and a beam combiner that directs the first light and the second light from the concave mirror to the same direction, where the first light from the concave mirror to the beam combiner passes through the refractive surface. In some embodiments, the intermediate optical piece includes an optical axis, and where the first light entering the intermediate optical piece is decentered from the optical axis. In some embodiments, a midpoint between a beam division point at the beam splitter and a beam passing point of the second light on a beam combining surface of the beam combiner is decentered from the optical axis of the intermediate optical piece. In some embodiments, the system further includes a second intermediate optical piece that includes a refractive surface that refracts the first light and the second light from the beam combiner, and a concave mirror that reflects the first light and the second light from the refractive surface. In some embodiments, a first spacing between the refractive surface of the intermediate optical piece and the concave mirror of the intermediate optical piece is less than a second spacing between the refractive surface of the second intermediate optical piece and the concave mirror of the second intermediate optical piece.

[0063] In some embodiments, the optical system includes: a beam splitter that divides an input beam into first light and second light and directs the first light and the second light to different directions; an intermediate optical piece that includes a first reflective surface that reflects the first light from the beam splitter and has a concave shape, and a second reflective surface that reflects the first light beam from the first reflective surface and directs the first light beam to the first reflective surface; and a beam combiner that directs the first light and the second light from the second reflective surface to the same direction, where the first light from the second reflective surface to the beam combiner passes through the first reflective surface.

[0064] In various embodiments, each provides an optical system element. In various embodiments, each optical system element is disposed to achieve its function (e.g., to provide an optical time delay).

[0065] Figure 1 FIG. 1 is an example of a system that illustrates using an illumination system with an optical delay system for lithography. In the illustrated example, the system includes a pulse source 100, an illumination system 102, a target plane 104, a projection lens 106, and a wafer 108. The pulse source 100 (e.g., a pulsed laser source) generates light for illuminating a target in the target plane 104 in order to project an image of the target on the wafer 108 using the projection lens 106 (e.g., an image of a reticle at the target plane is projected onto the wafer to perform lithography). The light generated by the pulse source 100 is processed using the illumination system 102 to produce a plurality of light beams with a low degree of speckle by reducing coherence between the plurality of light beams.

[0066] The illumination system 102 is designed to work with the pulsed source 100, which is a laser source that provides very coherent pulsed light beams. The coherent pulsed light beams are almost single mode, have very narrow bandwidth, and are almost transform limited - meaning the pulse length is almost as short as physics will allow, or the coherence length is approximately equal to the pulse length.

[0067] The optical delay system of the illumination system splits the light beam into 2 N copies, shifts each copy so that the copies are spaced apart by an axial distance (or time). In some embodiments, the time is longer than the coherence length (or time). In some embodiments, the delay is slightly shorter than the coherence length to obtain a spot that is partially reduced so that the overall pulse train length is not too long. The problem with long pulse trains is that they produce a blurred image in the scanning system. The optical or time delay system also displaces each light beam laterally (e.g., perpendicular to the direction of propagation) so that the light beams can be repositioned at desired locations in the illumination pupil by beam shaping optics. The beam shaping optics does two things: 1) the beam shaping optics takes the spatially separated light beams and directs them to the desired locations in the illumination pupil, and 2) the beam shaping optics shapes each light beam so that it provides the desired irradiance distribution at the target plane 104. The desired pupil distribution is a set of points that are selected to improve the lithography process. The points can be placed in a ring, equally spaced within a disc or annulus, clustered together in two smaller discs (dipoles), or anywhere else. The desired irradiance distribution is typically uniform over some rectangular area, but in principle can be anything. The optical delay system can be combined with a light source that provides pulsed or non-pulsed (continuous) light beams.

[0068] Optical delay system with Dyson-type repeaters

[0069] The problem of providing 2 N time delayed light beams that are parallel but regularly spaced in position (to reduce the temporal coherence of the source) is solved by using a Dyson type system consisting of one lens and one mirror to relay the light beams between the N+l beam splitters. The delayed light beams from the different arms are combined in different combinations and produce a set of light beams that are less temporally coherent at the target surface. The delayed light beams are also each spatially displaced in different combinations to produce a pattern at the target surface.

[0070] The system begins with an array of 50% beam splitters that send half of each beam to N delay arms. In some embodiments, the beam splitters do not have 50% transmission and reflection. In this case, some measures must be taken to equalize the beam power. One method is to modify the reflective coating of the Doyen mirror, or to place an attenuating filter somewhere in the Doyen (between the beam splitter and the lens, or between the lens and the mirror). In this disclosure, the delay arm contains one lens and one mirror (placed at the back focal plane of the lens), including what we call here a Doyen relay and shown below. The position of the optical axis of the Doyen relay relative to the axis of the light beam entering the relay determines the position at its output, so the position is chosen to produce a displacement of the output beam. This displacement can be produced out of our page plane, so that the final array of spots can be any desired shape - most likely, a rectangular array is needed as shown below. In some embodiments, the Doyen relay is referred to as an intra-mirror relay.

[0071] Figure 2A is a diagram illustrating an embodiment of an optical delay system. In some embodiments, Figure 2A The optical delay system of is used to implement an optical delay system of an illumination system (e.g., Figure 1 The optical delay system of is used to implement an optical delay system of an illumination system (e.g., In the illustrated example, the optical delay system receives an input beam 200 from a laser source (e.g., a pulsed laser source). The input beam 200 is partially reflected (e.g., first reflected rays) and partially transmitted (e.g., first transmitted rays) by a beam splitter 202. The first reflected rays are focused by a lens 204 onto a curved reflector 206 (e.g., in the form of a Doyen lens configuration, such that the incoming light rays are parallel to the incoming rays but exit in opposite directions) and reflected back (e.g., first reflected back rays) and through the lens 204 parallel to the incoming first reflected rays (e.g., first exit rays). In some embodiments, the first reflected rays and the first reflected back rays form a slight angle. In various embodiments, the lens 204, the lens 210, and / or the lens 216 have positive optical power. In various embodiments, the curved reflector 206, the curved reflector 218, and or the curved reflector 222 have a concave shaped reflective surface. In some embodiments, the lens 204 and the curved reflector 206 are arranged along a common optical axis. In some embodiments, the common optical axis is decentered from a virtual ridge line of a beam splitting surface of the beam splitter 202. The first transmitted rays can not be focused onto the curved reflector 206, in other words, the spot formed on the curved reflector 206 by the lens 204 can be spread to have a larger area.

[0072] The first exit ray is partially reflected (e.g., a second reflected ray) and partially transmitted (e.g., a second transmitted ray) by beamsplitter 208. The first transmitted ray also transmits to beamsplitter 208, enters beamsplitter 208 orthogonally to the first exit ray, and is partially reflected (e.g., propagates parallel to the second transmitted ray and will travel similarly to the second transmitted ray) and partially transmitted (e.g., propagates parallel to the second reflected ray and will travel similarly to the second reflected ray).

[0073] The second transmitted ray is focused by lens 210 onto curved reflector 222 (e.g., in the form of a Dyson lens configuration, such that the incoming light rays are parallel to the incoming ray but exit in the opposite direction) and reflected back (e.g., a second reflected back ray) and through lens 210 parallel to the incoming first exit ray (e.g., a second exit ray). The second transmitted ray can not be focused onto curved reflector 212, in other words, the spot formed by lens 210 on curved reflector 212 can be spread to have a larger area.

[0074] The second exit ray is partially reflected (e.g., a third reflected ray) and partially transmitted (e.g., a third transmitted ray) by beamsplitter 214. The second reflected ray also transmits to beamsplitter 214, enters beamsplitter 214 orthogonally to the second exit ray, and is partially reflected (e.g., propagates parallel to the third transmitted ray and will travel similarly to the third transmitted ray) and partially transmitted (e.g., propagates parallel to the third reflected ray and will travel similarly to the third reflected ray).

[0075] The third transmitted ray is focused by lens 216 onto curved reflector 218 (e.g., in the form of a Dyson lens configuration, such that the incoming light rays are parallel to the incoming ray but exit in the opposite direction) and reflected back (e.g., a third reflected back ray) and through lens 216 parallel to the incoming first exit ray (e.g., a third exit ray). The third transmitted ray can not be focused onto curved reflector 218, in other words, the spot formed by lens 216 on curved reflector 218 can be spread to have a larger area.

[0076] The third exit ray is partially reflected (e.g., a fourth reflected ray) and partially transmitted (e.g., a fourth transmitted ray) by beamsplitter 219. The third reflected ray also transmits to beamsplitter 219, enters beamsplitter 219 orthogonally to the third exit ray, and is partially reflected (e.g., propagates parallel to the fourth transmitted ray and will travel similarly to the fourth transmitted ray) and partially transmitted (e.g., propagates parallel to the fourth reflected ray and will travel similarly to the fourth reflected ray).

[0077] The fourth transmitted ray enters polarization relay 220, which produces a counter-propagating parallel beam of opposite polarization reflected by polarization beamsplitter 222 to produce a final exit beam parallel to the original input beam 200. In addition, the fourth reflected beam transmits through polarization beamsplitter 222 to become a final exit beam also parallel to the original input beam 200.

[0078] In some embodiments, polarization relay 220, which can be another Dyson, doubles the number of spots, but produces them in orthogonal polarizations (which can generally be linear, circular, or elliptical, but most likely s- and p-polarizations, since this can be easily implemented with a half-wave plate and a PBS as the final beamsplitter).

[0079] Figure 2B is a diagram illustrating an embodiment of an output pattern at a target plane for an optical delay system. In some embodiments, the optical delay system of Figure 2A produces the output pattern of Figure 2B .

[0080] Figure 3 is a diagram illustrating an embodiment of a delay system. In some embodiments, the optical delay system of Figure 3 is used to implement an optical delay system for an illumination system (e.g., the illumination system 102 of Figure 1 ). In the illustrated example, in this system, there are five delay paths, with the last delay path used to separate s- and p-polarizations. This produces 2 5 = 32 relatively incoherent pulses that arrive at different angles at the output of the system. To produce the different angles, one of the mirrors in each arm is tilted and the result is observed at the pupil of the illumination system. The delay system produces parallel but positionally separated beams. This approach: 1) produces parallel beams with lateral separation; 2) uses fewer optics (e.g., is cheaper to manufacture and more efficient); and is easier to align with smaller tilts of the mirrors of each channel.

[0081] Input beam 360 passes through its original path to output beam 370. A portion of input beam 360 is also reflected along one or more delay paths using beamsplitter 300. For example, a portion of input beam 360 is reflected toward mirror 304 and mirror 306. In some embodiments, optical element 302 and optical element 304 are used to adjust the beam as it returns to the original path of input beam 360.

[0082] The return beam is reflected by beamsplitter 310 along the original path of input beam 360 and transmitted along a second delay arm toward mirror 312 and mirror 314 before returning to the original path of input beam 360. In some embodiments, optical element 316 and optical element 318 are used to adjust the beam as it returns to the original path of input beam 360.

[0083] The return beam is reflected by beamsplitter 320 along the original path of input beam 360 and transmitted along a third delay arm toward mirror 322 and mirror 324 before returning to the original path of input beam 360.

[0084] The return beam is reflected by beamsplitter 330 along the original path of input beam 360 and transmitted along a fourth delay arm toward mirror 332 and mirror 334 before returning to the original path of input beam 360.

[0085] The return beam is reflected by beamsplitter 340 along the original path of input beam 360 and transmitted along a fifth delay arm toward mirror 342 and mirror 344. After mirror 344, the beam passes through a 1 / 2 waveplate to change the polarization of the beam before being combined into the original path of input beam 360 by beamsplitter 350.

[0086] The primary technical impact of this embodiment is improved speckle reduction and cost reduction (e.g., due to simplification of optics). These impacts equate to increased competitive advantage and profitability of the delay system.

[0087] Dyson delay system with incrementally larger beamsplitters

[0088] The problem of increased complexity of the Dyson relay needed to reduce aberrations of the shorter path delay is solved by using smaller beamsplitters for the shorter path and larger beamsplitters for the longer path. The basic problem is that when the Dyson has a large beam displacement compared to its length, the aberrations become large. Using smaller beamsplitters reduces the field size and makes the lenses simpler. The system is performed substantially as in Figure 2A with the exception of the size of the beamsplitters, and thus the field of view and possibly the size of the Dyson relay, increasing from first to last as shown in Figure 4 In some embodiments, a time delay system with a Dyson relay includes a set of beamsplitters and arm optics of different sizes (e.g., progressing from smaller size beamsplitters to larger size beamsplitters).

[0089] Figure 4 is a diagram showing an embodiment of an optical delay system. In some embodiments, the optical delay system of Figure 4 is used to implement an illumination system (e.g., the illumination system of Figure 1optical delay system of an illumination system 102). In the illustrated example, the optical delay system receives an input beam 400 from a laser source (e.g., a pulsed laser source). The input beam 400 is partially reflected (e.g., a first reflected ray) and partially transmitted (e.g., a first transmitted ray) by a beamsplitter 402. The first reflected ray is focused by a lens 404 onto a curved reflector 406 (e.g., in the form of a Dyson lens configuration, such that the incoming light rays exit parallel to the incoming rays but in opposite directions) and reflected back (e.g., a first reflected back ray) and through the lens 404 parallel to the incoming first reflected ray (e.g., a first exiting ray).

[0090] The first exiting ray is partially reflected (e.g., a second reflected ray) and partially transmitted (e.g., a second transmitted ray) by a beamsplitter 408. The first transmitted ray is also transmitted to the beamsplitter 408, enters the beamsplitter 408 orthogonal to the first exiting ray, and is partially reflected (e.g., propagates parallel to the second transmitted ray and will travel similarly to the second transmitted ray) and partially transmitted (e.g., propagates parallel to the second reflected ray and will travel similarly to the second reflected ray).

[0091] The second transmitted ray is focused by a lens 410 onto a curved reflector 412 (e.g., in the form of a Dyson lens configuration, such that the incoming light rays exit parallel to the incoming rays but in opposite directions) and reflected back (e.g., a second reflected back ray) and through the lens 410 parallel to the incoming first exiting ray (e.g., a second exiting ray).

[0092] The second exiting ray is partially reflected (e.g., a third reflected ray) and partially transmitted (e.g., a third transmitted ray) by a beamsplitter 414. The second reflected ray is also transmitted to the beamsplitter 414, enters the beamsplitter 414 orthogonal to the second exiting ray, and is partially reflected (e.g., propagates parallel to the third transmitted ray and will travel similarly to the third transmitted ray) and partially transmitted (e.g., propagates parallel to the third reflected ray and will travel similarly to the third reflected ray).

[0093] The third transmitted ray is focused by a lens 416 onto a curved reflector 418 (e.g., in the form of a Dyson lens configuration, such that the incoming light rays exit parallel to the incoming rays but in opposite directions) and reflected back (e.g., a third reflected back ray) and through the lens 416 parallel to the incoming first exiting ray (e.g., a third exiting ray).

[0094] A third exiting ray is partially reflected (e.g., fourth reflected ray) and partially transmitted (e.g., fourth transmitted ray) by beamsplitter 419. The third reflected ray also transmits to beamsplitter 419, enters beamsplitter 419 orthogonally to the third exiting ray, and is partially reflected (e.g., propagates parallel to the fourth transmitted ray and will travel similarly to the fourth transmitted ray) and partially transmitted (e.g., propagates parallel to the fourth reflected ray and will travel similarly to the fourth reflected ray).

[0095] The fourth transmitted ray enters polarization relay 420, which produces counter-propagating parallel beams of opposite polarization that are reflected by polarization beamsplitter 422 to produce a final exiting beam that is parallel to the initial input beam 400. In addition, the fourth reflected beam transmits through polarization beamsplitter 422 to become a final exiting beam that is also parallel to the initial input beam 400.

[0096] In some embodiments, polarization relay 420, which can be another Dyson, doubles the number of spots, but produces them in orthogonal polarization (which can generally be linear, circular, or elliptical, but most likely s- and p-polarization, as this can be readily implemented with a half-wave plate and PBS as the last beamsplitter).

[0097] As the complexity of the Dyson relay (e.g., number of elements and aspheres) must increase as the field of view increases (relative to its length), this embodiment makes it possible to reduce the field of view of the first Dyson, and thus the complexity. The longer Dysons located farther along the path have larger beamsplitters to accommodate the increased array of spots, which are preferably accommodated by longer lens systems.

[0098] In addition to the advantages of our prior art, this embodiment further reduces the cost of the optics by simplifying the shortest Dyson system.

[0099] The main technical impacts of the system are improved speckle reduction and cost reduction (by simplifying the optics and alignment procedures). These impacts are equivalent to increasing the competitive advantage and profitability of the system.

[0100] Spot reduction by spatially distributed time-delayed light beams

[0101] Figure 5A is a diagram showing an example embodiment of a system for illumination. In the example shown, the problem of utilizing a time delay system to minimize speckle while maintaining uniform average illumination in partially coherent projection is solved by shaping the beam of the time delay system 500 (TDS) and distributing the beam to separate locations in the illumination pupil to minimize spatial coherence as well as temporal coherence.

[0102] The method used in the system uses an element 502 (e.g., a diffractive optical element or a diffuser) to diffract / guide the light (after collection by a collector 504) into a first fly’s eye array (FE1 506) which then forms an image of the element 502 in the elements of a second fly’s eye array (FE2 508). The second fly’s eye then projects the image of the elements of the first fly’s eye into a condenser 510 which then produces an overlapping image of the first fly’s eye array (FE1 506) elements on a reticle blind (RB) 512 which then relays the image through another set of optics to a spatial light modulator. Since the RB 512 is conjugate to the spatial light modulator, in this description, the remaining optics are not necessary. Diffractive optical elements or diffusers are disclosed in U.S. Patent No. 5,850,300, the disclosure of which is hereby incorporated by reference. Spatial light modulators are disclosed in U.S. Patent No. 10,120,283, the disclosure of which is hereby incorporated by reference. The spatial light modulator is conjugate to the reticle blind plane. The spatial light modulator can replace the reticle blind. In some embodiments, there can be a lens that relays the image of the reticle blind to the spatial light modulator.

[0103] The problem solved here is that in this system, the field at FE2 is correlated between the FE2 elements because the element 502 illuminates all points in the pupil with all parts of the input beam that exit the time-delay system 500.

[0104] In some embodiments, the time-delay system 500 includes Figure 2A optical delay system. For the time-delay system 500, the output beams are all parallel, but each path creates a beam with a unique position via each of the placed mirror + lens relay. Each of these beams is directed to a desired position in the illumination pupil such that spatial coherence is minimized.

[0105] Figure 5B is a diagram showing an embodiment of a system for illumination. In the example shown, a spatially multiplexed time-delay system 520 processes an input beam to produce a plurality of output beams directed toward a near-field beam shaper 522. One of the key points for the embodiment depicted above is that there is a beamlet steering optic 524, a beamlet steering optic 526 (first fly’s eye array FE1), a beamlet steering optic 528 (second fly’s eye array FE2), and a condenser 530. These components steer each beamlet to a desired position in the pupil. The figure depicts a set of beams that are uniformly distributed, but in principle, the beam steering can place the beams in any arrangement, e.g., dipole, quadrupole, or annular.

[0106] One of the key issues that must be addressed is how to achieve low spatial coherence while also producing a uniform distribution at the reticle blind 532 (RB). In some embodiments, this issue is addressed by placing each different time-delayed beam in a separate location in the pupil. In some embodiments, the system first uses an aspheric beamlet shaping optic (e.g., a near-field beam transformer) to convert the circular Gaussian beam exiting the spatially multiplexed time-delay system 520 into a square top-hat beam (e.g., a flat irradiance distribution), and then fully and uniformly illuminate a single FE1 element. The FE1 element comprises an array of lenslets, each of which corresponds to a beamlet as output from the shaping optic. With a fully illuminated FE1 element, the RB illumination will also be uniform.

[0107] Figure 5C is a diagram showing an embodiment of a system for illumination. In the example shown, a spatially multiplexed time-delay system 540 processes an input beam to produce a plurality of output beams directed toward a far-field beam shaper 542. One of the key points for the embodiment depicted above is that there is a beamlet steering optic 544, a beamlet steering optic 546 (a first fly-eye array FE1), a beamlet steering optic 548 (a second fly-eye array FE2), and a condenser 550. These components steer each beamlet to a desired location in the pupil. The figure depicts a set of uniformly distributed beams, but in principle the beam steering can place the beams in any arrangement, such as a dipole, quadrupole, or annulus.

[0108] One of the key issues that must be addressed is how to achieve low spatial coherence while also producing a uniform distribution at the reticle blind 552 (RB).

[0109] This embodiment provides a reduced speckle by reducing spatial coherence while maintaining the ability to provide uniform illumination at the reticle blind.

[0110] Figure 5D is a diagram showing an embodiment of a system for illumination. In the example shown, the system is a spatially multiplexed time-delay system 540 that processes an input beam to produce a plurality of output beams directed toward a far-field beam shaper 542. One of the key points for the embodiment depicted above is that there is a beamlet steering optic 544, a beamlet steering optic 546 (a first fly-eye array FE1), a beamlet steering optic 548 (a second fly-eye array FE2), and a condenser 550. These components steer each beamlet to a desired location in the pupil. The figure depicts a set of uniformly distributed beams, but in principle the beam steering can place the beams in any arrangement, such as a dipole, quadrupole, or annulus. Figure 5B and Figure 5CThe method employed is a simplification and improvement. For each beam (or thin beam), there are two beam-shaping elements (element 564 and element 566). Arrays (element 564 and element 566) are used for beam steering and shaping, and in combination, to reposition the beam leaving the time delay system (TDS) 560 to the desired position at the mask curtain (RB) 572. To achieve this, the first array (element 564) imparts deflection to each beam, and elements of the second array (element 566), positioned to receive the beam, remove the deflection (or redirect the beam to the focusing optics (fly eye 568 and condenser 570)). The deflection of elements 564 and 566 can be achieved by tilting the refractive surface (containing a linear phase component) toward the hologram or metasurface or by using a tilted reflective surface.

[0111] The array's second function is beam shaping. This differs from... Figure 5B and Figure 5C The method employed here involves using individual elements to shape the beam. In this case, each element of the first array (element 564) is curved (in its reflective or refracting surface, or in the phase of the hologram or metasurface) to produce a beam with the desired shape (or close to the desired shape) at the second array (element 566). The shaping effect of the first array (element 564) can be aided by spatially varying the transmission amplitude and phase, which can be achieved by spatially altering transmission or reflection (e.g., by adjusting through a thin-film coating) or by changing the diffraction efficiency of the hologram or metasurface. Furthermore, transmission variations can be achieved using individual elements placed close to the first elements. In addition to redirecting the beam, the second array elements (element 566) can further refine the beam shape by reshaping the phase (through surface shaping or hologram / metasurface phase) and / or reshaping the amplitude.

[0112] Additionally, there is another array (fly eye 568) that images the first array element (element 564) to a position that allows the condenser lens (condenser 570) to overlap the beam at the target plane of RB 572.

[0113] In some embodiments, beam shaping of the first array (element 564) is achieved through a hyperbolic surface described by the following equation:

[0114]

[0115] Where ex and cy are the two principal curvatures, and kx and ky are the principal cone constants. For the square beam optimization system, such that cx = cy and kx = ky, the following is obtained with values ​​of cx = 19.1 / mm and kx = -31980. Figure 5E The beam shape in the image, where the wavelength is 760 nanometers and the radius of the Gaussian beam is 0.5 millimeters (axis in millimeters).

[0116] Figure 5F The simulated phase of each beam reaching the second array (element 566) is plotted (by simulation). The second array element (element 566) then acts to flatten the irradiance (above) and the following phase. The system uses a diffractive element for both arrays (element 564 and element 566), where there is no transmissive variation in the first element (element 564), and both the phase and amplitude are flattened in the second (element 566).

[0117] In various embodiments, the beam steering places the light beams in any desired arrangement, e.g., with a general shape that is square, rectangular, dipole, quadrupole, or annular.

[0118] Figure 6 is a diagram showing an embodiment of a time delay system using folded solid optics. In Figure 2A and Figure 3 each of the delay arms is progressively longer. In Figure 2A for example, each Dyson relay is approximately half the length of each of the delay lengths. If the shortest delay length is, for example, 20 mm, and there are 8 delay arms, then the shortest arm length is 10 mm and the longest is 10 mm * 2 8 = 5.12 meters. This is quite long. The system can simply fold back and forth, but Figure 6 the configuration in

[0119] In the illustrated example, light beam 604 enters beamsplitter 602 and splits into light beam 604 and light beam 608. Solid catadioptric lens 606 is used to fold light beam 604 and relay light beam 604 to the next beamsplitter (e.g., beamsplitter 612) of the time delay system (TDS). Solid catadioptric lens 606 includes a first surface having transmissive regions and reflective regions. The transmissive regions refract the light beam into the optic where the light beam makes five reflections (e.g., exiting light beam 610) before being refracted again toward the conjugate position. The next beamsplitter (beamsplitter 612) of the time delay system has two input light beams (e.g., light beam 608 and light beam 610) that are split and sent to solid catadioptric lens 622 and the next beamsplitter (e.g., beamsplitter 624). Light beam 608 splits into light beam 614 directed toward solid catadioptric lens 622 and light beam 616 directed toward beamsplitter 624. Light beam 610 splits into light beam 620 directed toward solid catadioptric lens 622 and light beam 618 directed toward beamsplitter 624.

[0120] In this approach, the two extra folds mean that the delay arm is 1 / 3 the length of the Dyson. The fact is that the path in glass (which typically has a refractive index of about 1.5) provides another factor of 1.5. The result is a total length reduction of 4.5x for the time delay circuit. Figure 2A

[0121] Other embodiments include:

[0122] • Different refraction and reflection at a single surface encounter discontinuous or aspheric surfaces of different curvatures

[0123] • Free surfaces that correct for astigmatism

[0124] • Transmission regions in the second surface that allow the beam to reflect at independently tiltable mirrors, which can be useful for aligning / adjusting the TDS

[0125] • Even more folds - it is conceivable to increase the number of reflections at the expense of the field of view. In such cases, the total length reduction is (m+1)*1.5 / 2, where m is the number of reflections.

[0126] The benefit of this embodiment over the more conventional approach of folding the path with just plane mirrors is that the monolithic design requires much fewer parts and is relatively easy to align.

[0127] Overall, while the individual elements can be more expensive, a much lower cost TDS should result - especially in cases where a large number (n>5) of delay arms are required.

[0128] Figure 7 is a diagram showing an embodiment of a delay element. In some embodiments, Figure 7 the delay element in Figure 2A or Figure 4 ​of the delay arm. There is an additional beam path that does not reach the delay arm that propagates directly through beamsplitter 702 and beamsplitter 710 (not shown). The beam is then refracted by lens 704 and reflected by mirror 706 to mirror 708. The beam is reflected back to mirror 706 using mirror 708. The beam is again reflected by mirror 706 to mirror 708 and back to mirror 706 before being refracted again by lens 704. The beam exits the delay arm by rejoining the original beam using beamsplitter 710. Mirror 706 now has three reflections of the beam instead of just one. The additional mirror (mirror 708) provides an additional fold, further reducing the physical space of the optical path. With this design, the two surfaces of lens 704 and the surfaces of each mirror (mirror 706 and mirror 708) can be independent design constraints. In some embodiments, mirror 706 comprises a concave mirror. In some embodiments, mirror 708 comprises a convex mirror. In some embodiments, mirror 706 and mirror 708 are arranged along a common optical axis. In some embodiments, the common optical axis is decentered from the virtual ridge line of the beamsplitter surfaces of beamsplitter 702 and beamsplitter 710. In some embodiments, the common optical axis is centered on the virtual ridge line of the beamsplitter surfaces of beamsplitter 702 and beamsplitter 710. Figure 7 In embodiments, lens 704 is optional. In some embodiments, mirror 706 and mirror 708 are used to construct the delay element.

[0129] In some embodiments, the lens can be replaced with lens segments instead of an annulus due to the propagation being in a plane. The large mirror (mirror 706) can also be split into segments, increasing the number of free parameters available. Alignment will become progressively difficult, and for most systems, alignment should be avoided.

[0130] In some embodiments, additional lens / mirror sets can be nested to further compact the system, but will also increase the difficulty and complexity of manufacturing and alignment.

[0131] Additional embodiments can include: 1) a Mangin mirror; and 2) a freeform surface.

[0132] While the foregoing embodiments have been described in some detail for purposes of clarity and understanding, the application is not limited to the details provided. There are many alternative ways of implementing the application. The disclosed embodiments are illustrative and not restrictive.

Claims

1. An optical system comprising: a first optical system that splits an input beam into first light and second light and directs the first light and the second light into different directions; a second optical system different from the first optical system and including a concave reflective surface that reflects the first light; and a third optical system different from the first optical system and the second optical system, wherein the first light reflected from the second optical system enters the third optical system from a first direction without passing through the first optical system, the second light from the first optical system enters the third optical system from a second direction different from the first direction, and the third optical system directs the first light and the second light to an output optical path of the third optical system.

2. The optical system of claim 1, wherein the second optical system includes a refractive component disposed between the first optical system and the concave mirror.

3. The optical system of claim 2, wherein the refractive component is disposed between the concave mirror and the third optical system.

4. The optical system of claim 2 or 3, wherein the refractive component has a back focal point located substantially on the concave reflective surface.

5. The optical system of claim 1 or 2, wherein the second optical system includes a reflective surface that reflects the first light from the concave reflective surface, and wherein the concave reflective surface reflects the first light from the reflective surface of the second optical system.

6. The optical system of claim 5, further comprising a refractive component disposed between the concave reflective surface and the reflective surface.

7. The optical system of claim 6, wherein the concave reflective surface and the reflective surface are formed on the refractive component.

8. The optical system of claim 5, wherein the reflective surface has a concave shape.

9. The optical system of claim 5, wherein the reflective surface has a convex shape.

10. The optical system of one of claims 1-3, wherein the concave reflective surface faces a beam path of the second light between the first optical system and the third optical system.

11. The optical system of any one of claims 1-3, wherein the first light from the third optical system and the second light from the third optical system pass through different locations.

12. The optical system of any one of claims 1-3, further comprising a fourth optical system including a concave reflective surface that reflects the first light from the third optical system.

13. The optical system of claim 12, wherein an optical axis of the second optical system and an optical axis of the fourth optical system are decentered from each other.

14. The optical system of claim 12, wherein the third optical system splits the first light from the second optical system into third light and fourth light. ​ 15. The optical system of claim 14, further comprising a fifth optical system disposed on the output path of the third optical system.

16. An optical system comprising: a beam splitter that divides an input beam into first and second light and directs the first and second light to different directions; an intermediate optical component that includes a refractive surface that refracts the first light and a concave mirror that reflects the first light from the refractive surface; and a beam combiner that directs the first and second light from the concave mirror to the same direction, wherein the first light from the concave mirror enters the beam combiner from a first direction without passing through the beam splitter and passes through the refractive surface.

17. The optical system of claim 16, wherein the intermediate optical component includes an optical axis, and wherein the first light entering the intermediate optical component is decentered from the optical axis.

18. The optical system of claim 17, wherein a midpoint between a beam division point at the beam splitter and a beam passing point of the second light on a beam combining surface of the beam combiner is decentered from the optical axis of the intermediate optical component.

19. The optical system of claim 16 or 17, further comprising a second intermediate optical component that includes a refractive surface that refracts the first and second light from the beam combiner and a concave mirror that reflects the first and second light from the refractive surface.

20. The optical system of claim 19, wherein a first separation between the refractive surface of the intermediate optical component and the concave mirror of the intermediate optical component is less than a second separation between the refractive surface of the second intermediate optical component and the concave mirror of the second intermediate optical component.

21. An optical system comprising: a beam splitter that divides an input beam into first and second light and directs the first and second light to different directions; an intermediate optical component that includes a first reflective surface that reflects the first light from the beam splitter and has a concave shape, and a second reflective surface that reflects the first light beam from the first reflective surface and directs the first light beam to the first reflective surface; and a beam combiner that the first light from the second reflective surface enters from a first direction without passing through the beam splitter, the second light enters the beam combiner from a second direction different from the first direction, and the beam combiner directs the first and second light from the second reflective surface to the same direction, wherein the first light from the second reflective surface to the beam combiner passes through the first reflective surface.

22. An illumination system comprising: a first optical element that divides an input beam into first and second light and directs the first and second light to different directions; a second optical element that directs the first and second light to the same direction, wherein the first light from the first optical element enters the second optical element from a first direction without passing through the beam splitter and passes through the first optical element. ​ a second optical element, the first light and the second light entering the second optical element from different directions, wherein the second optical element combines a portion of the first light with a portion of the second light to output third light in a first direction, and combines a portion of the first light with a portion of the second light to output fourth light in a second direction different from the first direction; a third optical element, the third light and the fourth light entering the third optical element from different directions, wherein the third optical element combines a portion of the third light with a portion of the fourth light to output fifth light; and a fly eye, the fifth light entering the fly eye.

23. The illumination system of claim 22, wherein the first optical element is configured so that neither of the first light and the second light enters the first optical element from the direction in which the input beam enters the first optical element, and the second optical element is configured so that neither of the third light and the fourth light enters the second optical element from the direction in which the first light enters the second optical element, and from the direction in which the second light enters the second optical element.

24. The illumination system of claim 22, wherein a length of a first path through which the first light travels is different from a length of a second path through which the second light travels, the first path is between the first optical element and the second optical element, and the second path is between the first optical element and the second optical element.

25. An optical system, comprising: a light source; the illumination system of any one of claims 22 to 24, wherein the illumination system illuminates a target with light from the light source; a projection lens, which projects an image of the target. ​ ​

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