阅读说明：本技术 用于光学计量的高亮度照明源 (High brightness illumination source for optical metrology ) 是由 A·玛纳森 A·希尔 O·巴沙尔 A·阿布拉莫夫 于 2020-04-16 设计创作，主要内容包括：本发明涉及一种照明源,其可包含两个或更多个输入光源、集光器,及光束均匀器、散斑减少器或任何数目个输出光纤的任何组合,以提供所选择的照明光展量(etendue)。所述集光器可包含一或多个透镜以将来自所述两个或更多个输入光源的照明组合成照明光束,其中来自所述两个或更多个输入光源的所述照明占据所述集光器的输入孔径的不同部分。所述光束均匀器可包含用于接收所述照明光束的第一非圆形核心光纤、第二非圆形核心光纤,及用于将所述照明光束的远场分布从所述第一非圆形核心光纤中继到所述第二非圆形核心光纤的输入面的一或多个耦合透镜,以提供具有均匀近场及远场分布的输出光。(The present invention relates to an illumination source that may include two or more input light sources, a light collector, and any combination of a beam homogenizer, a speckle reducer, or any number of output optical fibers to provide a selected etendue (etendue) of illumination. The light collector may include one or more lenses to combine illumination from the two or more input light sources into an illumination beam, wherein the illumination from the two or more input light sources occupies different portions of an input aperture of the light collector. The beam homogenizer may include a first non-circular core optical fiber for receiving the illumination beam, a second non-circular core optical fiber, and one or more coupling lenses for relaying the far field distribution of the illumination beam from the first non-circular core optical fiber to an input face of the second non-circular core optical fiber to provide output light having uniform near field and far field distributions.)

1. An illumination source, comprising:

two or more input light sources; and

a light collector including one or more lenses to combine illumination from the two or more input light sources into an illumination beam, wherein the illumination from the two or more input light sources occupies different portions of an input aperture of the light collector; and

a beam homogenizer, comprising:

a first non-circular core optical fiber, wherein the first optical fiber receives the illumination beam;

a second non-circular core fiber; and

one or more coupling lenses for relaying a far field distribution of the illumination beam from the first non-circular core fiber to an input face of the second non-circular core fiber, wherein a near field output distribution and a far field output distribution of the illumination beam from the second non-circular core fiber are uniform within a selected tolerance.

2. The illumination source of claim 1, wherein the light collector combines the light from the two or more input light sources into a common etendue.

3. The illumination source of claim 1, further comprising:

two or more collimating lenses for collimating the light from the two or more input light sources, wherein the light collector receives the light from the two or more input light sources from the two or more collimating lenses.

4. The illumination source of claim 1, wherein a core of at least one of the first non-circular core fiber or the second non-circular core fiber has a shape of a regular hexagon, a rectangle, or a square.

5. The illumination source of claim 1, further comprising:

two or more output optical fibers having different etendue; and

a fiber coupler configured to selectively couple the illumination beam into a selected output fiber of the two or more output fibers to provide the illumination beam in a selected etendue.

6. The illumination source of claim 1, further comprising:

one or more additional beam homogenizers, wherein the two or more output fibers comprise:

the beam homogenizer, and the one or more additional beam homogenizers.

7. The illumination source of claim 1, wherein at least one of the two or more input light sources comprises:

a coherent light source.

8. The illumination source of claim 7, wherein the coherent light beam comprises:

a laser source.

9. The illumination source of claim 7, wherein the laser source comprises:

a supercontinuum laser source.

10. The illumination source of claim 7, further comprising:

a speckle reducer comprising at least one phase change optical element to produce a plurality of decorrelated distributions of the illumination beam over a selected time frame to mitigate speckle in the illumination beam.

11. The illumination source of claim 10, wherein the speckle reducer comprises:

a movable diffuser.

12. The illumination source of claim 10, wherein the speckle reducer comprises:

a translatable mirror configured to vary a position of the illumination beam on an input face of the first non-circular core fiber.

13. The illumination source of claim 12, wherein the translatable mirror overscans the illumination beam across the input face of the first optical fiber.

14. The illumination source of claim 1, wherein at least one of the two or more light sources comprises:

a non-coherent light source.

15. The illumination source of claim 14, wherein the non-coherent light source comprises:

at least one of a laser sustained plasma source or a lamp source.

16. The illumination source of claim 1, further comprising:

at least one of a tunable spectral filter or a tunable intensity filter.

17. An illumination source, comprising:

two or more input light sources; and

a light collector including one or more lenses to combine illumination from the two or more input light sources into an illumination beam, wherein the illumination from the two or more input light sources occupies different portions of an input aperture of the light collector;

two or more output optical fibers having different etendue; and

a fiber coupler configured to selectively couple the illumination beam into a selected output fiber of the two or more output fibers to provide the illumination beam in a selected etendue.

18. The illumination source of claim 17, wherein at least one of the two or more output optical fibers comprises:

a beam homogenizer, comprising:

a first non-circular core fiber, wherein the first fiber receives the illumination beam from the fiber coupler;

a second non-circular core fiber; and

one or more coupling lenses for relaying a far field distribution of the illumination beam from the first non-circular core fiber to an input face of the second non-circular core fiber, wherein a near field output distribution and a far field output distribution of the illumination beam from the second non-circular core fiber are uniform within a selected tolerance.

19. The illumination source of claim 18, wherein the first non-circular core optical fiber and the second non-circular core optical fiber have a common core size.

20. The illumination source of claim 17, wherein at least one of the two or more input light sources comprises:

a coherent light source.

21. The illumination source of claim 20, wherein the coherent light source comprises:

a laser source.

22. The illumination source of claim 21, wherein the laser source comprises:

a supercontinuum laser source.

23. The illumination source of claim 20, further comprising:

a speckle reducer comprising at least one phase change optical element to produce a plurality of decorrelated distributions of the illumination beam over a selected time frame to mitigate speckle in the illumination beam.

24. The illumination source of claim 23, wherein the speckle reducer comprises:

a movable diffuser.

25. The illumination source of claim 23, wherein the speckle reducer comprises:

a translatable mirror configured to vary a position of the illumination beam on an input face of the selected output optical fiber.

26. The illumination source of claim 25, wherein the translatable mirror overscans the illumination beam across an input face of the selected output optical fiber.

27. The illumination source of claim 17, wherein at least one of the two or more input light sources comprises:

a non-coherent light source.

28. The illumination source of claim 27, wherein the non-coherent light source comprises:

at least one of a laser sustained plasma source or a lamp source.

29. The illumination source of claim 17, further comprising:

at least one of a tunable spectral filter or a tunable intensity filter.

30. The illumination source of claim 17, further comprising:

at least one tunable edge filter.

31. The illumination source of claim 17, further comprising:

a beam homogenizer, comprising:

a first non-circular core optical fiber, wherein the first optical fiber receives the illumination beam from the light collector;

a second non-circular core fiber; and

one or more coupling lenses for relaying a far field distribution of the illumination beam from the first non-circular core fiber to an input face of the second non-circular core fiber, wherein a near field output distribution and a far field output distribution of the illumination beam from the second non-circular core fiber are uniform within a selected tolerance, wherein the fiber coupler receives the illumination beam from the beam homogenizer.

32. A metrology system, comprising:

two or more input light sources; and

a light collector including one or more lenses to combine illumination from the two or more input light sources into an illumination beam, wherein the illumination from the two or more input light sources occupies different portions of an input aperture of the light collector;

one or more illumination optics for directing the illumination beam to a sample; and

one or more collection optics for directing radiation emitted by the sample in response to the illumination beam to a detector.

33. The metrology system of claim 32, wherein the light collector combines the light from the two or more input light sources into a common etendue.

34. The metering system of claim 32, further comprising:

two or more output optical fibers having different core sizes; and

a fiber coupler configured to selectively couple the illumination beam into a selected output fiber of the two or more output fibers to provide the illumination beam in a selected etendue.

35. The metrology system of claim 32, wherein the illumination source further comprises:

two or more collimating lenses for collimating the light from the two or more input light sources, wherein the light collector receives the light from the two or more input light sources from the two or more collimating lenses.

36. The metering system of claim 32, further comprising:

a beam homogenizer, comprising:

a first non-circular core optical fiber, wherein the first optical fiber receives the illumination beam from the light collector;

a second non-circular core fiber; and

one or more coupling lenses for relaying a far field distribution of the illumination beam from the first non-circular core fiber to an input face of the second non-circular core fiber, wherein a near field output distribution and a far field output distribution of the illumination beam from the second non-circular core fiber are uniform within a selected tolerance, wherein the one or more illumination optics receive the illumination beam from the beam homogenizer.

37. The metrology system of claim 32, wherein at least one of the two or more input light sources comprises:

a coherent light source.

38. The metrology system of claim 37, wherein the coherent light source comprises:

a laser source.

39. The metrology system of claim 38, wherein the laser source comprises:

a supercontinuum laser source.

40. The metering system of claim 37, further comprising:

a speckle reducer comprising at least one phase change optical element to produce a plurality of decorrelated distributions of the illumination beam over a selected time frame to mitigate speckle in the illumination beam.

41. The metrology system of claim 40, wherein the speckle reducer comprises:

at least one of a movable diffuser or a translatable mirror.

42. The metrology system of claim 32, wherein at least one of the two or more input light sources comprises:

a non-coherent light source.

43. The metrology system of claim 42, wherein the non-coherent light source comprises:

at least one of a laser sustained plasma source or a lamp source.

44. The metering system of claim 32, further comprising:

at least one of a tunable spectral filter or a tunable intensity filter.

45. The metrology system of claim 32, wherein the metrology system comprises:

a superposition metrology system.

46. The metrology system of claim 45, wherein the overlay metrology system comprises:

an imaging overlay metrology system, wherein the one or more collection optics provide an image of the sample on the detector based on the radiation emitted by the sample.

47. The metrology system of claim 45, wherein the overlay metrology system comprises:

a scatterometry overlay metrology system, wherein the one or more collection optics provide a pupil image associated with an angular distribution of radiation emitted by the sample.

48. A beam homogenizer, comprising:

a first non-circular core optical fiber, wherein the first optical fiber receives an illumination beam;

a second non-circular core fiber; and

one or more coupling lenses for relaying a far field distribution of the illumination beam from the first non-circular core fiber to an input face of the second non-circular core fiber, wherein a near field output distribution and a far field output distribution of the illumination beam from the second non-circular core fiber are uniform within a selected tolerance.

49. The beam homogenizer of claim 48, wherein the first non-circular core fiber homogenizes the spatial distribution of the illumination beam at the output face of the first non-circular core fiber within a selected tolerance with respect to the spatial distribution of the illumination beam at the input face of the first non-circular core fiber.

50. The beam homogenizer of claim 49, wherein the second non-circular core fiber homogenizes the spatial distribution of the illumination beam at an output face of the second non-circular core fiber within a selected tolerance with respect to the spatial distribution of the illumination beam at the input face of the second non-circular core fiber.

51. The beam homogenizer of claim 48, wherein the far field distribution comprises:

an angular distribution of the illumination beam at an output face of the first non-circular core fiber.

52. The beam homogenizer of claim 48, wherein a core of at least one of the first non-circular core fiber or the second non-circular core fiber has a shape of a regular hexagon, a rectangle, or a square.

Technical Field

The present disclosure relates generally to illumination sources for optical metrology systems, and more particularly, to high brightness illumination sources based on multiple coherent input beams.

Background

The illumination source brightness or radiance is related to the radiated power per solid angle from the source and the spatial extent of the source. In a given optical system, effective source brightness control associated with light captured and directed through the system can control the intensity of light provided as output. Thus, in the context of optical metrology, illumination source brightness limits the intensity of light on a sample and thus limits the possible measurement throughput at a given sensitivity. Thus, increasing the brightness of the illumination source may enable increased sampling rates, increased sensitivity per measurement, or a combination of both. However, the method of increasing the source brightness must be balanced against the increase in cost, system complexity, and system reliability. Accordingly, it is desirable to develop systems and methods for providing efficient high brightness illumination.

Disclosure of Invention

In accordance with one or more illustrative embodiments of the present disclosure, an illumination source is disclosed. In one illustrative embodiment, the illumination source includes two or more input light sources. In another illustrative embodiment, the illumination source includes a light collector including one or more lenses to combine illumination from the two or more input light sources into an illumination beam, wherein the illumination from the two or more input light sources occupies different portions of an input aperture of the light collector. In another illustrative embodiment, the illumination source includes a beam homogenizer. In one illustrative embodiment, the beam homogenizer includes a first non-circular core optical fiber to receive the illumination beam. In another illustrative embodiment, the beam homogenizer includes a second non-circular core fiber. In another illustrative embodiment, the beam homogenizer includes one or more coupling lenses to relay a far field distribution of the illumination beam from the first non-circular core fiber to an input face of the second non-circular core fiber, wherein a near field output distribution and a far field output distribution of the illumination beam from the second non-circular core fiber are uniform within a selected tolerance.

In accordance with one or more illustrative embodiments of the present disclosure, an illumination source is disclosed. In one illustrative embodiment, the illumination source includes two or more input light sources. In another illustrative embodiment, the illumination source includes a light collector including one or more lenses to combine illumination from the two or more input light sources into an illumination beam, wherein the illumination from the two or more input light sources occupies different portions of an input aperture of the light collector. In another illustrative embodiment, the illumination source includes two or more output optical fibers having different etendue. In another illustrative embodiment, the illumination source includes a fiber optic coupler configured to selectively couple the illumination beam into a selected output fiber of the two or more output fibers to provide the illumination beam at a selected etendue.

In accordance with one or more illustrative embodiments of the present disclosure, a metrology system is disclosed. In one illustrative embodiment, the metrology system comprises two or more input light sources. In another illustrative embodiment, the metrology system includes a light collector including one or more lenses to combine illumination from the two or more input light sources into an illumination beam, wherein the illumination from the two or more input light sources occupies different portions of an input aperture of the light collector. In another illustrative embodiment, the metrology system includes one or more illumination optics to direct the illumination beam to a sample. In another illustrative embodiment, the metrology system includes one or more collection optics to direct radiation emitted by the sample in response to the illumination beam to a detector.

According to one or more illustrative embodiments of the present disclosure, a beam homogenizer is disclosed. In one illustrative embodiment, the beam homogenizer includes a first non-circular core fiber to receive an illumination beam. In another illustrative embodiment, the beam homogenizer includes a second non-circular core fiber. In another illustrative embodiment, the beam homogenizer includes one or more coupling lenses to relay a far field distribution of the illumination beam from the first non-circular core fiber to an input face of the second non-circular core fiber, wherein a near field output distribution and a far field output distribution of the illumination beam from the second non-circular core fiber are uniform within a selected tolerance.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the invention. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the general description, serve to explain the principles of the invention.

Drawings

Many advantages of the present disclosure can be better understood by those skilled in the art by reference to the following drawings, in which:

fig. 1 is a block diagram of a high brightness illumination system in accordance with one or more embodiments of the present disclosure;

fig. 2 is a conceptual diagram of an illumination source including a light collector to combine input light from two or more input light sources into a single source illumination beam, in accordance with one or more embodiments of the present disclosure;

fig. 3 is a conceptual diagram of a beam homogenizer, according to one or more embodiments of the present disclosure;

fig. 4A is a cross-sectional view of a non-circular core optical fiber having a square core in accordance with one or more embodiments of the present disclosure;

fig. 4B is a cross-sectional view of a non-circular core optical fiber having a hexagonal core in accordance with one or more embodiments of the present disclosure;

fig. 5A is a conceptual diagram of a speckle reducer including a movable diffuser in accordance with one or more embodiments of the present disclosure;

FIG. 5B is a conceptual diagram of a speckle reducer including controllable mirrors to position a source illumination beam at various locations on an input face of an optical fiber, according to one or more embodiments of the present disclosure;

fig. 5C is a conceptual diagram of etendue switching by selectively directing a source illumination beam 104 into a first selected optical fiber to provide a selected system etendue, in accordance with one or more embodiments of the present disclosure;

fig. 5D is a conceptual diagram of etendue switching by selectively directing a source illumination beam 104 into a second selected optical fiber to provide a selected system etendue, in accordance with one or more embodiments of the present disclosure;

fig. 6 is a conceptual diagram of one or more filters according to one or more embodiments of the present disclosure;

fig. 7 is a conceptual diagram of an illumination system configured to provide high brightness coherent illumination in accordance with one or more embodiments of the present disclosure; and

fig. 8 is a conceptual diagram of an optical metrology tool including a high intensity illumination system in accordance with one or more embodiments of the present disclosure.

Detailed Description

Reference will now be made in detail to the disclosed subject matter as illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with respect to certain embodiments and specific features thereof. The embodiments set forth herein are considered to be illustrative and not restrictive. It will be readily apparent to persons of ordinary skill in the art that various changes and modifications in form and detail may be made therein without departing from the spirit and scope of the disclosure.

Embodiments of the present disclosure relate to systems and methods for providing high brightness illumination by combining multiple coherent illumination sources into a single output distribution. Additional embodiments of the present disclosure relate to providing a combined output distribution into a selected etendue such that the combined source is compatible with an optical system, such as (but not limited to) an optical metrology system. Furthermore, although it has been recognized that optical metrology and optical inspection may be technical terms in the fields such as semiconductor manufacturing and metrology, the terms optical metrology and optical metrology tool are used herein to generally describe any optical system suitable for, but not limited to, sample characterization and defect inspection.

The illumination source brightness seriously affects the design and performance of the optical metrology system. The illumination source brightness or radiance is related to the radiated power per solid angle from the source and the spatial extent of the source. Furthermore, the radiance on the sample is limited by the radiance of the source.

It is generally desirable to provide a high brightness illumination source to provide efficient and flexible use of light from the source. Accordingly, the design of an optical system (e.g., a metrology system) that may utilize an illumination source may incorporate tradeoffs between desired optical invariants of the system, overall system cost, and desired performance metrics (e.g., sensitivity and throughput based on the brightness of the available sources). For example, an illumination source with a fixed brightness may constrain the optical design, which requires tradeoffs in performance metrics (such as (but not limited to) the illumination area on the sample), sensitivity, and measurement throughput. As another example, increasing the illumination source brightness for a system with a fixed etendue or optically invariant may enable increased sensitivity and/or measured flux without further modification of the system.

The brightness of the illumination source can generally be increased by increasing the radiated power from the illumination source or by reducing any combination of the solid angle of emission or spatial extent (e.g., etendue) of the source. Each of these factors may be constrained by technical and/or design limitations of the associated system. For example, the optical invariants of the system may constrain the possible solid angles of emission and/or the spatial extent of the illumination source based on desired radiance properties on the sample. In some applications, such as (but not limited to) imaging overlay metrology, it may be desirable to limit or reduce the Numerical Aperture (NA) of the illumination on the sample to improve accuracy. However, limiting the numerical aperture may correspondingly limit the spatial extent of the illumination source from which light may be collected and thus limit the effective brightness of the source.

It is therefore generally desirable to increase the source brightness by increasing the radiant power within a selected or constrained etendue. However, directly increasing the radiant power of a given illumination source often faces technical challenges and requires high cost in exchange for some gain in brightness. For example, increasing the laser pumping power can increase the radiant power of a non-coherent source (e.g., a plasma-based source), but increasing the laser pumping power also increases the plasma size (e.g., increases the spatial extent of the source) and thus provides a limited increase in source brightness. As another example, increasing the pump power of a coherent laser source (e.g., a supercontinuum laser source) may increase the radiation power, but this may negatively impact the gain material lifetime and may result in an inefficient and expensive sub-linear photon per dollar brightness increase.

In some embodiments of the present disclosure, the illumination source combines a plurality of coherent laser sources into a selected etendue to provide a high brightness output beam. In this regard, the brightness of the common output may be related to the sum of the input sources. For example, the outputs of multiple lasers may be directed to a common collection optic that combines the light into a single source beam. In this regard, the output of each laser may occupy a different portion of the input numerical aperture of the collection optics and the combined source beam will include the sum of the input laser sources.

Additional embodiments relate to beam homogenizers for providing uniform output distribution in both the near field and the far field. For example, the beam homogenizer may eliminate non-uniformities of the combined source beam associated with the plurality of input lasers described above to produce an output beam that is uniform in both the near field and the far field within selected tolerances. However, it should be recognized herein that a beam homogenizer in accordance with embodiments of the present invention may be adapted to provide a uniform output based on a variety of input sources including, but not limited to, a single source or a combination of multiple sources.

In some embodiments of the present disclosure, the beam homogenizer includes two optical fibers having a non-circular shaped core (e.g., non-circular core fibers). In this regard, the output of the first non-circular core fiber may be spatially uniform in the near field, but may lack far field uniformity (e.g., angular uniformity). Both near field uniformity and far field uniformity may be obtained by mapping the far field distribution (e.g., corresponding to the angular distribution) of a first non-circular core fiber onto the input face of a second non-circular core fiber.

Additional embodiments relate to mitigating speckle associated with coherent laser sources. Speckle reduction can be achieved by generating multiple de-correlated speckle distributions over a correlation time frame, such as (but not limited to) the integration time of the detector. Speckle reduction may be achieved, for example, by moving (e.g., rotating) the diffuser plate. By way of another example, speckle reduction can be achieved by scanning light over an input face of a multimode optical fiber to provide a varying speckle profile at the output of the optical fiber. In some embodiments, light from a coherent illumination source may be scanned onto the input face of the non-circular core fiber of the beam homogenizer, as described herein.

Additional embodiments of the present disclosure are directed to providing illumination having a selected etendue. In this regard, the output from the illumination source may be matched to the etendue of an optical system, such as, but not limited to, an optical metrology system. For example, light from a source having a relatively low etendue, such as (but not limited to) a laser source, may be efficiently coupled to a relatively large etendue associated with a selected illumination mode (e.g., illumination field size and numerical aperture) of an optical system.

Additional embodiments of the present disclosure relate to switching or otherwise controlling the amount of illumination etendue of a high-brightness illumination source according to the present disclosure. For example, the amount of illumination etendue may be selected or otherwise switched based on the core size and/or numerical aperture of the optical fibers in the source. Furthermore, the illumination source may include a plurality of output optical fibers having different core sizes and/or numerical apertures, such that the amount of illumination etendue may be controlled by selecting the core size and/or numerical aperture of the output optical fiber. In some embodiments, the output fiber that provides the selected etendue may include a beam homogenizer with one or more non-circular core fibers, as disclosed herein.

Additional embodiments of the present disclosure relate to controlling the spectral shape and intensity of the output distribution of a high-brightness illumination source. For example, a series of tunable high-pass and low-pass spectral edge filters can quickly tune the spectral bandwidth of the output light. Further, the tunable intensity filter may provide output light having a selected intensity.

Referring now to fig. 1-8, a system and method for providing high brightness illumination will be described in more detail.

Fig. 1 is a block diagram of a high brightness illumination system 100 in accordance with one or more embodiments of the present disclosure.

In one embodiment, the illumination system 100 includes an illumination source 102 to produce a source illumination beam 104. The illumination system 100 may further include additional components to modify or otherwise control the spatial, temporal, and/or spectral characteristics of the source illumination beam 104. In another embodiment, the illumination system 100 includes one or more filters 106 to control the intensity and/or spectral content of the source illumination beam 104. In another embodiment, the illumination system 100 includes a speckle reducer 108 to mitigate speckle associated with the coherent source illumination beam 104. In another embodiment, the illumination system 100 includes a beam homogenizer 110 to provide a uniform illumination beam 112 having a uniform spatial distribution in both the near field and the far field. For example, the beam homogenizer 110 may mitigate the presence of hot spots or other irregularities in the spatial or angular profile of the light from the illumination source 102.

In another embodiment, the illumination system 100 includes a controller 114 communicatively coupled to at least one of the illumination source 102, the filter 106, the speckle reducer 108, or the beam homogenizer 110. In this regard, the controller 114 may provide one or more signals to one or more components of the illumination system 100, including but not limited to the illumination source 102, the filter 106, the speckle reducer 108, or the beam homogenizer 110, to direct or otherwise control various aspects of the source illumination beam 104 or the uniform illumination beam 112.

In another embodiment, the controller 114 includes one or more processors 116. In another embodiment, the one or more processors 116 are configured to execute a set of program instructions that are stored in the memory medium 118 or memory. Further, the controller 114 may include one or more modules containing one or more program instructions stored in a memory medium 118 that are executable by the processor 116. The processor 116 of the controller 114 may include any processing element known in the art. To this extent, the processor 116 can comprise any microprocessor-type device configured to execute algorithms and/or instructions. In one embodiment, the processor 116 may be comprised of a desktop computer, a mainframe computer system, a workstation, a graphics computer, a parallel processor, or any other computer system (e.g., networked computers) configured to execute a program configured to operate the lighting system 100, as described in this disclosure. It is further recognized that the term "processor" may be broadly defined to encompass any device having one or more processing elements that execute program instructions from the non-transitory memory medium 118.

The memory medium 118 may comprise any storage medium known in the art suitable for storing program instructions executable by the associated processor 116. For example, the memory medium 118 may include a non-transitory memory medium. As additional examples, the memory medium 118 may include, but is not limited to, read-only memory, random access memory, magnetic or optical memory devices (e.g., disks), magnetic tape, solid state drives, and the like. It should further be noted that the memory medium 118 may be housed in a common controller housing with the processor 116. In one embodiment, the memory medium 118 may be remotely located relative to the physical location of the processor 116 and the controller 114. For example, the processor 116 of the controller 114 may access a remote memory (e.g., a server) accessible over a network (e.g., the Internet, an intranet, and the like). Accordingly, the foregoing description should not be construed as limiting, but merely as illustrative of the present invention.

It is recognized herein that the steps described in this disclosure may be performed by the controller 114. Further, the controller 114 may be formed of a single component or a plurality of components. It should further be noted herein that the various components of the controller 114 may be housed in a common enclosure or within multiple enclosures. In this manner, any controller or combination of controllers may be packaged separately as a module suitable for integration into the lighting system 100.

The illumination source 102 may include any type of light source known in the art. Further, the illumination source 102 may have any selected spectral content.

In one embodiment, the illumination source 102 includes one or more coherent light sources, such as (but not limited to) one or more laser sources. In this regard, the illumination source 102 may generate a source illumination beam 104 having a high coherence (e.g., high spatial coherence and/or temporal coherence). For example, the illumination source 102 may include one or more broadband lasers, such as, but not limited to, one or more supercontinuum lasers or white light lasers. By way of another example, the illumination source 102 may include one or more narrow band lasers. By way of another example, the illumination source 102 may include one or more tunable lasers to provide a source illumination beam 104 having a tunable spectral intensity. Further, the coherent illumination source 102 may be based on any type of technology or product design. For example, the illumination source 102 may include, but is not limited to, any combination of one or more fiber lasers, one or more diode lasers, or one or more gas lasers.

In another embodiment, the illumination source 102 includes one or more low coherence sources to provide a source illumination beam 104 having low or partial coherence (e.g., low or partial spatial coherence and/or temporal coherence). For example, the illumination source 102 may include one or more Light Emitting Diodes (LEDs). By way of another example, the illumination source 102 may include a Laser Sustained Plasma (LSP) source, such as, but not limited to, a LSP lamp, LSP bulb, or LSP chamber suitable to contain one or more elements that may emit broadband illumination when excited into a plasma state by a laser source. By way of another example, the illumination source 102 may include a lamp source, such as, but not limited to, an arc lamp, a discharge lamp, an electrodeless lamp, or the like.

Further, the illumination source 102 may include any combination of light sources. In one embodiment, illumination source 102 includes one or more super-continuous laser sources for providing broadband illumination and one or more partially co-tuned high brightness LEDs for supplementing gaps in the spectrum of the one or more super-continuous laser sources.

The illumination source 102 may further provide light having any selected temporal characteristics. In one embodiment, the illumination source 102 includes one or more continuous wave sources to provide a continuous wave source illumination beam 104. In another embodiment, the illumination source 102 includes one or more pulsed sources to provide a pulsed or otherwise modulated source illumination beam 104. For example, the illumination source 102 may include one or more mode-locked lasers, one or more Q-switched lasers, or the like.

The illumination source 102 may include or otherwise be formed from any number of input light sources. In one embodiment, the illumination source 102 includes a single light source to produce the source illumination beam 104. In another embodiment, the illumination source 102 combines light generated by multiple input light sources (such as, but not limited to, multiple laser sources) into a single output light beam. In this regard, light from multiple input light sources may be combined into a common etendue to provide high brightness illumination.

In some embodiments, the illumination source 102 generates a source illumination beam 104 by combining light from multiple input light sources. Fig. 2 is a conceptual diagram of an illumination source 102, the illumination source 102 including a light collector 202 to combine input light 204 from two or more input light sources 206 into a single source illumination beam 104, in accordance with one or more embodiments of the present disclosure. For example, the light collector 202 may include one or more optical components, such as, but not limited to, a lens or beam splitter, suitable for receiving input light 204 from a plurality of input light sources 206 and producing the combined source illumination beam 104. Thus, the power in the source illumination beam 104 may be the sum of the power input to the light source 206.

The illumination system 100 may include any number of input light sources 206 arranged in any selected distribution with respect to the light collector 202. In one embodiment, the illumination system 100 includes a plurality of input light sources 206 having output optics (e.g., output fibers, output mirrors, or the like) arranged in a 2D array pattern (e.g., a 2D grid pattern). For example, the output optics of the plurality of input light sources 206 may be arranged in a rectangular array, a triangular array, a hexagonal array, or the like. In another embodiment, the illumination system 100 includes a plurality of input light sources 206 arranged in a random or pseudo-random distribution.

The input light sources 206 may be arranged in any configuration to provide the input light 204 within the input aperture of the light collector 202. In one embodiment, as illustrated in fig. 2, the input light source 206 is arranged to provide the input light 204 within a dedicated portion of the input numerical aperture of the light collector 202. For example, as illustrated in fig. 2, the light collector 202 may receive collimated input light 204 from each input source 206 within a dedicated portion of an input aperture of the light collector 202. Further, the illumination system 100 may include one or more collimating lenses 208 to collimate the input light 204 from the input light source 206. In another embodiment, although not shown, the input light 204 from the input light source 206 may be superimposed within the input numerical aperture of the light collector 202. For example, the output fibers of the fiber-based input light source 206 may be arranged in a bundle such that the input light 204 of the input light 204 emanating from the output fibers may be superimposed.

Each of the input light sources 206 may have any selected spectral or power characteristics. In this regard, the spectrum of the source illumination beam 104 may be controlled based on the spectrum of the input light sources 206, and the power of the source illumination beam 104 may be controlled based on the number and power of the input light sources 206. In one embodiment, the illumination system 100 includes a plurality of input light sources 206 having substantially similar spectra and/or powers. In another embodiment, the plurality of input light sources 206 may have different spectra and/or powers.

It should be understood, however, that fig. 2 and the associated description are for illustration only and should not be construed as limiting. Specifically, the illumination source 102 may include any number of components to combine light from multiple sources into a single source illumination beam 104 using any technique known in the art. In one embodiment, illumination source 102 combines input light from two input sources having orthogonal polarizations with a polarizing beam splitter to produce source illumination beam 104. In another embodiment, the illumination source 102 uses one or more dichroic beam splitters to combine input light from two or more input sources with a substantially non-overlapping spectrum. In another embodiment, the illumination source 102 spatially or angularly encapsulates input light from two or more input light sources into a selected etendue, which may be (but is not necessarily) greater than that of any of the input light sources.

Referring now to fig. 3 through 4B, beam homogenizer 110 will be described in more detail. Fig. 3 is a conceptual diagram of a beam homogenizer 110 in accordance with one or more embodiments of the present disclosure. Uniform illumination may be beneficial for many applications including, but not limited to, optical metrology. However, not all illumination sources have a sufficiently uniform spatial or angular output profile. For example, the source illumination beam 104 from an extended illumination source or a combined illumination source (e.g., as illustrated in fig. 2) may have a non-uniform spatial or angular profile, which may result in non-uniformities in the near field or the far field. As another example, a source illumination beam 104 formed from multiple input laser sources (e.g., input light source 206) having different spectra may exhibit spatially varying spectral characteristics. Thus, beam homogenizer 110 may provide a uniform illumination beam 112 having uniform spatial and spectral distribution in the near field and in the far field.

In one embodiment, beam homogenizer 110 includes at least two non-circular core fibers and coupling optics for relaying light between the non-circular core fibers to provide a uniform illumination beam 112 that is uniform in both the near field and the far field. For example, fig. 3 illustrates a beam homogenizer 110 having a first non-circular core fiber 302a and a second non-circular core fiber 302b and coupling optics 304 for relaying light exiting the first non-circular core fiber 302a to the second non-circular core fiber 302b in accordance with one or more embodiments of the present disclosure.

It should be recognized herein that a single non-circular core fiber 302 may improve the spatial uniformity of the output distribution of light at the output face relative to the input distribution of light at the input face. In this regard, the single non-circular core fiber 302 may operate as a near-field beam homogenizer. However, it may be the case that a single non-circular core fiber 302 is unable to homogenize the far-field distribution of light, such that even though the near-field distribution near the output face is spatially uniform, the far-field distribution may exhibit hot spots or other irregularities. In other words, a single non-circular core fiber 302 can homogenize the spatial distribution of light at the output face relative to the spatial distribution of light at the input face, but not necessarily the angular distribution of light exiting the fiber relative to the angular distribution of light entering the fiber.

In one embodiment, as illustrated in fig. 3, the beam homogenizer 110 may include coupling optics 304 to relay the far field distribution (e.g., angular distribution) of the output of the first non-circular core fiber 302a to the input face of the second non-circular core fiber 302 b. The far-field distribution corresponds to the angular distribution of light from the first non-circular core fiber 302a and thus may represent the far-field output distribution of the first non-circular core fiber 302a, which may exhibit the non-uniformities described above. Thus, relaying this far-field distribution to the input face of the second non-circular core fiber 302b implements two points. First, any non-uniformity of the far field distribution may be mitigated by the second non-circular core fiber 302 b. Accordingly, the near-field spatial distribution of the uniform illumination beam 112 from the second non-circular core fiber 302b may be uniform (e.g., within a selected tolerance). Second, a uniform spatial distribution in the near field at the output of the first non-circular core fiber 302a may be converted to a uniform angular distribution into the second non-circular core fiber 302 b. Thus, the angular or far field distribution of the uniform illumination beam 112 from the second non-circular core fiber 302b may also be uniform (e.g., within a selected tolerance).

The beam homogenizer 110 may comprise a non-circular core fiber (e.g., the first non-circular core fiber 302a or the second non-circular core fiber 302b) having a core of any size or shape suitable for homogenizing the output light relative to the input light. It should further be recognized herein that the etendue of beam homogenizer 110 (and thus possibly the entire illumination system 100) may be fixed by the overall core size. Thus, it may be the case that design requirements associated with the wavelength and/or etendue of the optical system may limit the overall core size and thus the characteristics of the non-circular core fiber (e.g., the first non-circular core fiber 302a or the second non-circular core fiber 302b) in the beam homogenizer 110.

In one embodiment, at least one non-circular core fiber in beam homogenizer 110 comprises a single multimode core at one or several operating wavelengths of illumination source 102. For example, the multimode non-circular core may have a non-circular cross-sectional shape in a plane perpendicular to the length of the optical fiber. For example, the multimode, non-circular core may comprise a polygonal cross-sectional shape having any number of straight sides. By way of another example, the multi-mode non-circular core may include a cross-sectional shape having one or more curved sides.

Fig. 4A and 4B are cross-sectional views of a non-circular core fiber according to one or more embodiments of the present disclosure. In particular, fig. 4A is a cross-sectional view of a non-circular core optical fiber 302 having a square core 402, while fig. 4B is a cross-sectional view of a non-circular core optical fiber 302 having a hexagonal core 402 (e.g., a regular hexagonal core 402). It should be understood, however, that the examples of square and hexagonal cores illustrated in fig. 4A and 4B are for illustration only and should not be construed as limiting. Further, the non-circular core fiber 302 may comprise a single multimode core having any selected core size. For example, the non-circular core fiber 302 may have, but is not limited to, a square core (e.g., as illustrated in FIG. 4A) with 0.4mm sides to provide 0.22NA, 0.2mm sides to provide smaller NA, and 0.6mm sides to provide higher NA.

It should be recognized herein that a bundle of closely packed waveguides (e.g., a bundle of individual rods, multi-core optical fibers, or the like) arranged in a non-circular array may provide beam homogenization in a manner similar to that described herein with respect to a single non-circular core optical fiber. In another embodiment, at least one non-circular core fiber in beam homogenizer 110 is a multicore fiber having a core with a cross-sectional shape that includes a close-packed array or bundle of non-circular features. In another embodiment, at least one non-circular core fiber in beam homogenizer 110 includes a single multimode core at an operating wavelength having a non-circular cross-sectional shape that is otherwise suitable for close packing or deployment into a close packing array (e.g., rectangular, hexagonal, or the like). In this regard, the core shape may mimic a bundle of closely packed non-circular waveguides, but may operate as a single core multimode optical fiber of different size dimensions (e.g., for providing a desired etendue). For example, a beam homogenizer 110 suitable for use with wavelengths extending into the ultraviolet spectral range (e.g., suitable for integration with an optical metrology system) may include, but does not necessarily include, at least one single-core multimode optical fiber having a non-circular cross-sectional shape.

The non-circular core fiber 302 (e.g., the first non-circular core fiber 302a or the second non-circular core fiber 302b) may be formed of any material or combination of materials by any process known in the art. For example, core 402 and/or cladding 404 may be formed from any material including, but not limited to, glass, polymer, or crystalline material.

It may be the case that the efficacy of the uniformity may be affected by various factors such as, but not limited to, the length of the fiber, the shape of the non-circular core, or the size of the non-circular core. For example, increasing the length of the fiber generally (but not necessarily) linearly increases the performance of beam homogenizer 110.

Referring now to fig. 5A and 5B, the speckle reducer 108 will be discussed in more detail. Where illumination source 102 provides a spatially coherent uniform illumination beam 112, it may be desirable to provide speckle reducer 108 to produce multiple decorrelated speckle distributions over a selected time frame. For example, it may be desirable to provide multiple decorrelated speckle distributions over the integration time of a detector of an optical metrology system. In this regard, speckle associated with the spatially coherent source illumination beam 104 may not appear as noise on the detector.

Speckle reducer 108 may include any number of components suitable for implementing any speckle reduction technique known in the art.

Fig. 5A is a conceptual diagram of the speckle reducer 108 including a movable diffuser 502, according to one or more embodiments of the present disclosure. The diffuser 502 may comprise any type of material that randomly or pseudo-randomly scatters or spatially modifies the phase of incident light. For example, the diffuser 502 may include, but is not limited to, a ground glass plate, a pseudo-randomly etched plate, or the like. In one embodiment, the speckle reducer 108 includes a translator 504 to move the diffuser 502 at a rate sufficient to provide a plurality of decorrelated speckle distributions over a selected time frame. For example, the translator 504 may include, but is not limited to, a rotary stage for rotating the diffuser 502 or a translation stage for linearly translating the diffuser 502.

Fig. 5B is a conceptual diagram of the speckle reducer 108, the speckle reducer 108 including controllable mirrors 506 to position the source illumination beam 104 at various locations on the input face of the optical fiber 508, according to one or more embodiments of the present disclosure. It should be recognized herein that the speckle distribution of light emanating from an optical fiber depends on the particular path of many wavefronts propagating through the fiber. Thus, the output speckle distribution can be varied by temporally modifying various aspects of the optical path, including (but not limited to) the input angle or position of the fiber.

In one embodiment, as illustrated in fig. 5B, the speckle reducer 108 includes a translator 510 to modify the position of the controllable mirror 506 to scan the source illumination beam 104 over the input face of the optical fiber 508 or otherwise vary the input angle or position of the source illumination beam 104 over the input face of the optical fiber 508. Further, the controllable mirror 506 may (but need not) be controlled by the controller 114. Controllable mirror 506 may comprise any type of movable or deformable mirror known in the art. For example, the controllable mirror 506 may comprise a galvanometer. By way of another example, the controllable mirror 506 may comprise a resonant scanner. By way of another example, controllable mirror 506 may include a mirror attached to one or more rotating or translating stages.

Further, the controllable mirror 506 may scan or otherwise direct the source illumination beam 104 over any selected portion of the core (e.g., core 402) of the optical fiber 508. In one embodiment, the controllable mirror 506 overfills the core of the optical fiber 508 by scanning or otherwise directing the source illumination beam 104 over an area larger than the core of the optical fiber 508. In another embodiment, the controllable mirror 506 underfills the core of the optical fiber 508 by scanning or otherwise directing the source illumination beam 104 over an area smaller than the core of the optical fiber 508. In another embodiment, the controllable mirror 506 scans or otherwise directs the source illumination beam 104 over an area matching the core of the optical fiber 508.

In another embodiment, the speckle reducer 108 includes one or more optical elements 512 to control the spatial size of the source illumination beam 104. For example, as illustrated in fig. 5A, the optical element 512 may expand and/or collimate the source illumination beam 104 on the diffuser 502 to a selected size based on the size of various structures on the diffuser 502 to provide scattering and/or phase modification. As another example, the optical element 512 may expand and/or collimate the source illumination beam 104 on the translator 504. Further, the optical element 512 may focus the source illumination beam 104 to a desired spot size suitable for coupling with any subsequent components, such as, but not limited to, the first non-circular core fiber 302a of the beam homogenizer 110. For example, the speckle reducer 108 may provide the source illumination beam 104 into a selected etendue (e.g., associated with a core size of the optical fiber 508) using the scattered source illumination beam 104 of the diffuser 502 in fig. 5A or the translator 504 in fig. 5B.

The optical fibers 508 may comprise any type of optical fiber known in the art. In one embodiment, the speckle reducer 108 includes a dedicated optical fiber 508. In another embodiment, the optical fiber 508 may correspond to the first non-circular core fiber 302a of the beam homogenizer 110. In this regard, the speckle reducer 108 may direct the source illumination beam 104 into the beam homogenizer 110. In some embodiments, the speckle reducer 108 does not include the optical fiber 508, but provides multiple de-correlated speckle distributions of the source illumination beam 104 in any selected plane.

Furthermore, as previously described herein, the optical fiber may be characterized as having an inherent etendue based on the core size and Numerical Aperture (NA) of the optical fiber. However, it should be recognized that the effective NA of the fiber can be adjusted to some extent by underfilling the fiber. Thus, the etendue of the illumination system 100 providing illumination through the optical fibers may be controlled or otherwise defined by the etendue of the optical fibers. In some embodiments, the illumination system 100 includes two or more output optical fibers having different etendue (e.g., different core sizes and/or different numerical apertures) and a fiber coupler for directing illumination (e.g., the source illumination beam 104) into selected output optical fibers to provide a selected system etendue (e.g., a selected illumination etendue).

Fig. 5C and 5D are conceptual diagrams of etendue switching by selectively directing a source illumination beam 104 into a selected optical fiber to provide a selected system etendue, in accordance with one or more embodiments of the present disclosure. In one embodiment, the illumination system 100 may include a plurality of output fibers 514 (e.g., output fibers 514a, 514b in fig. 5C) having different core sizes and/or numerical apertures. For example, output fiber 514a may include a core 516a having a first size or NA and output fiber 514b may include a second core 516b having a second size or NA. In another embodiment, the illumination system 100 includes a fiber coupler 518 to direct light into a selected output fiber 514 to provide a selected system etendue.

The fiber coupler 518 may comprise any type of fiber coupler known in the art. In one embodiment, as illustrated in fig. 5C and 5D, the fiber coupler 518 may include a translatable mirror 520 (e.g., a galvanometer or the like) and associated translator 522 and one or more coupling optical elements 524 (e.g., lenses). For example, the fiber coupler 518 may include the controllable mirror 506 of the speckle reducer 108. In another embodiment, although not shown, the fiber coupler 518 may include one or more translation devices to position the selected output fiber 514 in the beam path of the source illumination beam 104. The fiber coupler 518 may also be configured to adjust the NA of the output fiber 514, and thus the system etendue, by controlling the NA used to couple light into the selected output fiber 514.

Furthermore, output fiber 514 may comprise any type of fiber. In one embodiment, the illumination system 100 includes a plurality of beam homogenizers 110, which include optical fibers having different core sizes and/or numerical apertures to provide different etendue. In this case, the fiber coupler 518 (e.g., the controllable mirror 506 of the speckle reducer 108 illustrated in fig. 5B, or the like) can select a particular beam homogenizer 110 to provide a selected etendue of illumination suitable for coupling into any external system (e.g., an optical metrology system, or the like). In another embodiment, the illumination system 100 includes any number of selected output optical fibers 514 as the final system element to provide the selected etendue of the illumination.

Further, although not shown in the figures, any external component or system to which the illumination system 100 may provide illumination (such as an optical metrology system or the like) may have one or more elements suitable for receiving output from any of the selected output optical fibers 514. For example, if the light from the output fibers 514 can be distinguished based on spectral content, polarization, or the like, the external system may include one or more beam splitters to direct the light from each of the output fibers 514 to a common beam path. By way of another example, the external system may include a fiber coupler as described in the context of fig. 5C to selectively receive light from the selected output fiber 514 and direct the light along a defined path.

Referring now to fig. 6, fig. 6 is a conceptual diagram of one or more filters 106 according to one or more embodiments of the present disclosure. In one embodiment, at least one of the one or more filters 106 is communicatively coupled with the controller 114 such that the controller 114 can control various characteristics of the source illumination beam 104.

In one embodiment, the one or more filters 106 include at least one tunable intensity filter 602 to selectively control the intensity of the source illumination beam 104. For example, tunable intensity filter 602 may include a position-varying neutral density filter (e.g., a gradient filter or the like). In this regard, the intensity of source illumination beam 104 may be controlled (e.g., by translator 604) by adjusting the position of tunable intensity filter 602 relative to source illumination beam 104. For example, as illustrated in fig. 6, tunable intensity filter 602 may include a circular gradient filter such that the intensity of source illumination beam 104 passing through tunable intensity filter 602 may be selected by rotating the circular gradient filter to a selected position. By way of another example, although not shown in the figures, tunable intensity filter 602 may include a linear gradient filter such that the intensity of source illumination beam 104 passing through tunable intensity filter 602 may be selected by translating the linear gradient filter to a selected location using one or more translation stages.

In another embodiment, the one or more filters 106 include at least one tunable spectral filter (e.g., a tunable high pass filter, a tunable low pass filter, a tunable band pass filter, or a tunable notch filter) to selectively control the spectral characteristics of the source illumination beam 104. For example, the tunable spectral filter may include one or more position variation filters, such as (but not limited to) one or more tunable edge filters, where the cutoff wavelength may be tuned based on the position or angle of the source illumination beam 104. For example, as illustrated in fig. 6, the one or more filters 106 may include a circularly tunable high-pass filter 606 and a circularly tunable low-pass filter 608, where the high-pass and low-pass cutoff wavelengths may be selected by rotating the respective filters. In this regard, the spectral characteristics (e.g., center wavelength, bandwidth, spectral transmittance value, or the like) of the source illumination beam 104 may be quickly tuned (e.g., by the translator 610) by modifying the position of the tunable high-pass filter 606 and/or the tunable low-pass filter 608 relative to the source illumination beam 104.

It should be understood, however, that the filter 106 and associated description illustrated in fig. 6 are for illustration only and should not be construed as limiting. Specifically, the illumination system 100 may include any type or combination of intensity and/or spectrum controllers known in the art. Further, in some embodiments, although not shown in the figures, the source illumination beam 104 may be translated (e.g., using a beam scanner or the like) to a selected location on any of the filters (e.g., tunable intensity filter 602, tunable high pass filter 606, and/or tunable low pass filter 608) to provide tuning.

Referring now to fig. 7 and 8, the integration of the various components of the lighting system 100 and the integration of the lighting system 100 into external systems is described in more detail.

In general, the various components of the illumination system 100 illustrated in fig. 1 (e.g., the illumination source 102, the filter 106, the speckle reducer 108, and/or the beam homogenizer 110) may be adapted to provide any combination and sequential integration of a uniform illumination beam 112 having selected characteristics. Furthermore, in some embodiments, the lighting system 100 includes a subset of the components illustrated in fig. 1.

For example, fig. 7 is a conceptual diagram of an illumination system 100 configured to provide high brightness illumination in accordance with one or more embodiments of the present disclosure. In one embodiment, the illumination system 100 includes an illumination source 102 configured as illustrated in FIG. 2, a filter 106 configured as illustrated in FIG. 6, a speckle reducer 108 configured as illustrated in FIG. 5B, and a beam homogenizer 110 configured as illustrated in FIG. 3. For example, the illumination source 102 may include a light collector 202 to collect illumination from multiple coherent laser sources (e.g., a supercontinuum laser source, a narrow band laser source, a partially coherent LED source, or the like) into a common etendue to provide a high brightness source illumination beam 104. The filter 106 may include a tunable intensity filter 602 and one or more tunable spectral filters (e.g., a tunable high pass filter 606 and a tunable low pass filter 608) to provide the source illumination beam 104 with selected intensity and spectral characteristics. The speckle reducer 108 can then include a controllable mirror 506 to scan the source illumination beam 104 across the input face of the beam homogenizer 110 (e.g., the first non-circular core fiber 302 a). Accordingly, speckle reducer 108 can simultaneously mitigate speckle associated with coherent input light source 206 and provide coupling of source illumination beam 104 into beam homogenizer 110. It should be recognized herein that the source illumination beam 104 formed by the plurality of input light sources 206 may exhibit substantial non-uniformity (e.g., hot spots and the like). Accordingly, beam homogenizer 110 may provide a uniform illumination beam 112 having a uniform distribution in both the near field and the far field (e.g., within a selected tolerance). In addition, the etendue of illumination system 100 may be controlled by the core size of the optical fiber (e.g., second non-circular core optical fiber 302b) in beam homogenizer 110. Thus, the combination of the collector 202, the filter 106, the speckle reducer 108, and the beam homogenizer 110 can provide a high brightness tunable coherent illumination source based on combining multiple input light sources 206 into a selected etendue.

It should be understood, however, that the example embodiment and associated description in fig. 7 are for illustration only and should not be construed as limiting. Rather, the lighting system 100 may be formed of any combination of components in any selected order. For example, the order of the filter 106, speckle reducer 108, and/or beam homogenizer 110 may be advantageously modified. Moreover, not all components need be included in each configuration. For example, the speckle reducer 108 may not be needed, particularly in applications where a partial or low coherence illumination source 102 is used. As another example, it may be the case that filter 106 or one or more components thereof are not needed for a particular application.

In some embodiments, the individual components provided herein as part of the illumination system 100 may be provided separately as independent components. For example, beam homogenizer 110 may be provided as a standalone device suitable for use with a variety of input light sources.

In some embodiments, the lighting system 100 may be integrated into one or more external systems. For example, the illumination system 100 may provide a uniform high brightness uniform illumination beam 112 suitable for use in an optical metrology system.

Fig. 8 is a conceptual diagram of an optical metrology tool 800 including a high intensity illumination system 100 in accordance with one or more embodiments of the present disclosure. The optical metrology tool 800 may be configured as any type of metrology tool known in the art including, but not limited to, an imaging metrology tool for generating one or more images of the sample 802 or a scatterometry metrology tool for analyzing scattering and/or diffraction of light from the sample 802. Further, the metrology tool may be used in any application including, but not limited to, metrology for characterizing one or more aspects of a fabricated structure (such as an overlay metrology tool or the like) or an inspection tool for detecting defects on patterned or unpatterned samples.

In one embodiment, optical metrology tool 800 includes illumination system 100 to produce a uniform illumination beam 112 having a high brightness in a selected etendue suitable for integration with optical metrology tool 800. For example, the lighting system 100 may (but need not) be configured as illustrated in fig. 7. Furthermore, uniform illumination beam 112 can have any spectral width. In one embodiment, the illumination system 100 provides broadband coherent illumination (e.g., based on multiple supercontinuum laser sources).

In another embodiment, the optical metrology tool 800 directs the uniform illumination beam 112 from the illumination system 100 to the sample 802 as an illumination beam 804 via an illumination path 806. The illumination path 806 may include one or more optical components suitable for modifying and/or adjusting the illumination beam 804 and directing the illumination beam 804 to the sample 802. For example, the illumination path 806 may include (but does not necessarily include) one or more lenses 808 (e.g., for collimating the illumination beam 804, the relay pupil, and/or the field plane, or the like) or one or more beam control elements 810 to modify the illumination beam 804. For example, beam control element 810 may include, but is not limited to, one or more polarizers, one or more filters, one or more beam splitters, one or more diffusers, one or more homogenizers, one or more apodizers, one or more beam shapers, or one or more mirrors (e.g., static mirrors, translatable mirrors, scanning mirrors, or the like). In another embodiment, the optical metrology tool 800 includes an objective lens 812 to focus the illumination beam 804 onto the sample 802 (e.g., a superimposed target having superimposed target elements positioned on two or more layers of the sample 802). In another embodiment, the sample 802 is disposed on a sample stage 814 adapted to hold the sample 802 and further configured to position the sample 802 relative to the illumination beam 804.

In another embodiment, the optical metrology tool 800 includes one or more detectors 816 configured to capture radiation (e.g., sample radiation 818) emitted from the sample 802 (e.g., an overlay target on the sample 802) through the collection optics path 820 and generate one or more overlay signals indicative of an overlay of two or more layers of the sample 802. The collection path 820 may include a plurality of optical elements to direct and/or modify the illumination collected by the objective 812, including, but not limited to, one or more lenses 822 or one or more beam steering elements 824 to modify the sample radiation 818. For example, beam steering element 824 may include, but is not limited to, one or more filters, one or more polarizers, one or more beam stops, or one or more beam splitters.

Detector 816 can receive any distribution of sample radiation 818 suitable for a particular application. For example, the detector 816 may receive an image of the sample 802 provided by an element (e.g., the objective lens 812, one or more lenses 822, or the like) in the collection light path 820. By way of another example, detector 816 can receive radiation that is reflected or scattered from sample 802 (e.g., via specular reflection, diffuse reflection, and the like). By way of another example, detector 816 can receive radiation (e.g., luminescence associated with absorption of illumination beam 804, and the like) generated by sample 802. By way of another example, detector 816 can receive one or more diffraction orders of radiation from sample 802 (e.g., 0 th order diffraction, 1 st order diffraction, 2 nd order diffraction, and the like). In this regard, the detector 816 can receive a pupil plane image associated with the angular distribution of sample radiation 818 in response to the illumination beam 804.

The illumination path 806 and the collection path 820 of the optical metrology tool 800 may be oriented in various configurations suitable for illuminating the sample 802 with the illumination beam 804 and collecting radiation emitted from the sample 802 in response to the incident illumination beam 804. For example, as illustrated in fig. 8, the illumination system 100 may include a beam splitter 826 oriented such that the objective lens 812 may simultaneously direct the illumination beam 804 to the sample 802 and collect radiation emitted from the sample 802. As another example, the illumination path 806 and the collection path 820 may contain non-overlapping optical paths.

The subject matter described herein sometimes illustrates different components contained within, or connected with, other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. Conceptually, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Thus, any two components herein combined to achieve a particular functionality can be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "connected," or "coupled," to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "couplable," to each other to achieve the desired functionality. Specific examples of "couplable" include, but are not limited to, physically interactable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interactable and/or logically interacting components.

It is believed that the present invention and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages. The form described is merely illustrative and it is the intention of the appended claims to encompass and include such changes. Furthermore, it is to be understood that the invention is defined by the appended claims.