Systems and methods for imaging using speckle-free illumination

Abstract

A lighting system is disclosed. The illumination system may include a narrowband illumination source. The illumination system may include an illumination path that includes one or more illumination optics. The illumination system may include a quantum dot assembly within the illumination path, the quantum dot assembly including a quantum dot layer disposed on a substrate, wherein the quantum dot assembly is configured to receive a narrowband illumination beam from the narrowband illumination source and emit a converted illumination beam having a spectral range wider than the narrowband illumination beam. The illumination system may include where the one or more illumination optics are configured to direct illumination from the quantum dot assembly to a sample disposed on a sample stage.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 449,319, filed Mar. 2, 2023, under 35 U.S.C. § 119(e), the entire content of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to high-brightness laser illumination, and more particularly, to using high-brightness laser illumination without speckle noise for an illumination system in an imaging system. Background Art

[0004] Imaging and metrology systems use illumination to image a sample surface. Illumination for imaging a sample (such as a semiconductor wafer) is typically generated from one or more laser sources. However, laser illumination is typically susceptible to speckle noise caused by the interference of coherent light. The presence of speckle noise makes it difficult or impossible to obtain an accurate image and / or measurement of a given sample. Obtaining speckle-free illumination is crucial for imaging. Current methods for generating speckle-free illumination include using multi-diode arrays, polarization multiplexing methods, and time multiplexing methods. Each of these current methods has drawbacks. Multi-diode arrays require very large diode arrays, polarization multiplexing is not always feasible, and time multiplexing methods are not suitable for short pulses of illumination. Accordingly, it is desirable to overcome the drawbacks of prior methods to mitigate the presence of speckles in inspection and / or metrology systems. Summary of the Invention

[0005] Disclosed is an illumination system. In an embodiment, the illumination system includes a narrowband illumination source. In an embodiment, the illumination system includes an illumination path that includes one or more illumination optics. In an embodiment, the illumination system includes a quantum dot assembly positioned within the illumination path, the quantum dot assembly including a quantum dot layer disposed on a substrate, wherein the quantum dot assembly is configured to receive a narrowband illumination beam from the narrowband illumination source and emit a converted illumination beam having a spectral range wider than the narrowband illumination beam. In an embodiment, the illumination system includes wherein the one or more illumination optics are configured to direct illumination from the quantum dot assembly to a sample disposed on a sample stage.

[0006] Disclose an optical characterization system. In an embodiment, the characterization system includes an illumination subsystem. In an embodiment, the illumination subsystem includes a narrowband illumination source. In an embodiment, the illumination subsystem includes an illumination path that includes one or more illumination optical devices. In an embodiment, the characterization system includes a quantum dot assembly positioned within the illumination path, the quantum dot assembly including a quantum dot layer disposed on a substrate, wherein the quantum dot assembly is configured to receive a narrowband illumination beam from the narrowband illumination source and emit a converted illumination beam having a spectral range wider than the narrowband illumination beam. In an embodiment, the one or more illumination optical devices are configured to direct illumination from the quantum dot assembly to a sample disposed on a sample stage. In an embodiment, the characterization system includes a detector. In an embodiment, the characterization system includes a photon collection subsystem configured to collect illumination from the same illumination and project the illumination onto the detector.

[0007] Disclose a method. In an embodiment, the method includes the steps of: generating a narrowband illumination beam. In an embodiment, the method includes the step of: directing the narrowband illumination beam along an illumination path that includes one or more illumination optical devices. In an embodiment, the method includes the steps of: using a quantum dot assembly positioned within the illumination path to convert the narrowband illumination beam into a converted illumination beam, wherein the quantum dot assembly includes a quantum dot layer disposed on a substrate. In an embodiment, the method includes the steps of: directing the converted illumination beam from the quantum dot assembly to a sample disposed on a sample stage. In an embodiment, the method includes the steps of: projecting illumination from the sample onto a detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Those skilled in the art can better understand many advantages of the present disclosure by referring to the accompanying drawings.

[0009] Figure 1A Simplified schematic diagram illustrating an illumination system according to one or more embodiments of the present disclosure having a quantum dot assembly disposed between two sets of illumination optical devices.

[0010] Figure 1B Conceptual diagram illustrating a quantum dot assembly according to one or more embodiments of the present disclosure.

[0011] Figure 1C Conceptual diagram illustrating a quantum dot assembly according to one or more embodiments of the present disclosure including a dichroic coating deposited on a front surface of a substrate.

[0012] Figure 1D Conceptual diagram illustrating a quantum dot assembly according to one or more embodiments of the present disclosure including a dichroic coating deposited on a back surface of a substrate.

[0013] Figure 2 Simplified schematic illustration of an illumination system according to one or more embodiments of the present disclosure having a quantum dot assembly disposed at the output of a narrowband illumination source.

[0014] Figure 3 Simplified schematic illustration of an illumination system according to one or more embodiments of the present disclosure having a reflective quantum dot assembly.

[0015] Figure 4A Block diagram of an optical characterization system incorporating a quantum dot-based illumination system according to one or more embodiments of the present disclosure.

[0016] Figure 4B Block diagram of a brightfield optical characterization system incorporating a quantum dot-based illumination system according to one or more embodiments of the present disclosure.

[0017] Figure 4C Block diagram of a transmission-based optical characterization system incorporating a quantum dot-based illumination system according to one or more embodiments of the present disclosure.

[0018] Figure 5 Flowchart illustrating a method of generating speckle-free high-brightness illumination according to one or more embodiments of the present disclosure. Detailed Description

[0019] Reference will now be made in detail to the disclosed subject matter, which is illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with respect to specific embodiments and their specific features. The embodiments set forth herein are to be considered illustrative and not restrictive. Those skilled in the art will readily appreciate that various changes and modifications in form and detail can be made without departing from the spirit and scope of the present disclosure.

[0020] Figures 1A to 3 An illumination system is described that is equipped with a quantum dot assembly to narrowband the illumination to prevent the generation of speckle noise within the optical system. Embodiments of the present disclosure are directed to eliminating speckle within a narrowband (e.g., laser) illumination system using a quantum dot array. For example, within the illumination system of an optical characterization system (e.g., an inspection system or an imaging-based metrology system), the quantum dot array can be advantageously positioned within the illumination arm of the optical characterization system and between the narrowband illumination source and the sample.

[0021] Embodiments of the present disclosure implement quantum dots to perform color conversion of laser illumination from an illumination source in a manner that broadens the spectrum of the illumination. Due to the broadening of the spectrum of the imaging illumination, the presence of speckle noise within the optical system can be reduced or eliminated.

[0022] Figures 1A to 1BDescribe a lighting system 100 for narrowband illumination broadening according to one or more embodiments of the present disclosure. In an embodiment, the lighting system 100 includes a quantum dot assembly 102 configured to broaden the spectral range of incident illumination 110 from a narrowband illumination source 104 (such as a laser source).

[0023] As Figure 1B shown, the quantum dot assembly 102 may include a quantum dot layer 103 disposed on a substrate 105. The quantum dot assembly 102 may be positioned within the illumination path 106 of the lighting system 100. The quantum dot layer 103 may be disposed on any type of substrate 105. For example, the quantum dot layer 103 may be disposed on a transparent substrate. In this case, the transparent quantum dot assembly 102 can be used in settings where transmission through the quantum dot assembly 102 is required. The transparent substrate 105 may include, but is not limited to, glass. As another example, the quantum dot layer 103 may be disposed on a reflective substrate. In this case, the reflective quantum dot assembly 102 can be used in settings where reflection from the quantum dot assembly 102 is required. The reflective substrate 105 may include, but is not limited to, a mirror.

[0024] As Figures 1C to 1D shown, in an embodiment, one or more surfaces of the transparent substrate 105 may be coated with a dichroic coating 107. The dichroic coating 107 may allow the narrowband illumination 110 from the illumination source 104 to pass through the substrate 105 but reflect other illumination wavelengths. For example, the dichroic coating 107 may be selected such that it transmits the narrowband illumination 110 from the illumination source 104 but reflects the converted illumination 112. The dichroic coating 107 may retro-reflect any converted illumination 112b traveling back towards the narrowband source 104 to redirect the illumination back to the sample 108. The converted illumination 112a emitted in the desired direction continues unobstructed. The dichroic coating 107 will reduce the amount of lost illumination and improve the efficiency of the lighting system 100. For example, as Figure 1C shown, the dichroic coating 107 may be deposited on the front surface of the substrate 105 before depositing the quantum dot layer 103. As another example, as Figure 1D shown, the dichroic coating 107 may be deposited on the back surface of the substrate 105. The quantum dot layer 103 may be formed by dispersing a selected amount of quantum dots in a polymer medium and coating the substrate / dichroic coating structure with the polymer medium. For example, a selected amount of quantum dots may be dissolved in a solution and cured in a polymer layer on the substrate / dichroic coating structure.

[0025] The quantum dot assembly 102 can be used as a passive element within the lighting system 100 to modify the incident illumination beam 110. The quantum dot assembly 102 can simultaneously convert the incident light into a desired center wavelength and broaden the spectrum of the light. Utilizing the broadened spectrum can eliminate or reduce speckle noise in the optics.

[0026] The narrowband illumination source 104 can include any light source capable of generating a narrowband illumination beam 110. For example, the narrowband illumination source 104 can include, but is not limited to, one or more lasers. For example, the one or more lasers can include one or more continuous wave (CW) lasers and / or one or more pulsed lasers.

[0027] In an embodiment, the quantum dot assembly 102 can be positioned downstream of the narrowband illumination source 104. In this way, the quantum dot assembly 102 can be configured to receive the narrowband illumination beam 110. After receiving the narrowband illumination beam 110, the quantum dot assembly 102 can convert the narrowband illumination beam 110 into a converted illumination beam 112. The converted illumination beam 112 can have a spectral range wider than the initial narrowband illumination beam 110 and be shifted relative to the initial narrowband illumination. It should be noted here that the converted illumination beam 112 can have spectral characteristics similar to those of a light emitting diode (LED). The converted illumination beam 112 can include any number of light wavelengths (e.g., red, green, blue). It should be noted that the color of the converted illumination beam 112 can depend on the type of quantum dot assembly 102 used in the illumination system 100 and the spectral content of the initial illumination beam 110. For example, the quantum dot assembly 102 can convert an incident blue laser beam into a royal blue-green laser beam or a red laser beam having a spectral range wider than the initial beam. As another example, the quantum dot assembly 102 can convert an incident green laser into a longer wavelength green laser beam or a red laser beam having a spectral range wider than the initial beam. As another example, the quantum dot assembly 102 can convert an incident red (or amber) laser beam into a longer wavelength red laser having a spectral range wider than the initial beam. It should be understood that the examples of color conversion are for illustration only and should not be construed as limiting the scope of the present disclosure.

[0028] In an embodiment, the illumination system 100 includes an illumination path 106 having one or more illumination optics 114a, 114b. In an embodiment, the illumination optics 114a, 114b can direct the narrowband illumination beam 110 from the narrowband illumination source 104 to the quantum dot assembly 102 and direct the converted illumination beam 112 from the quantum dot assembly 102 to a sample 108 disposed on a sample stage 109. The illumination optics 114a, 114b can include, but are not limited to, projection optics or homogenizer optics.

[0029] In an embodiment, as Figure 1A shown, the quantum dot assembly 102 can be positioned between two or more illumination optics 114a, 114b in a transmission configuration. For example, this configuration can be accomplished using a quantum dot assembly 102 that is at least partially transparent. For example, the quantum dot layer 103 of the quantum dot assembly 102 can be disposed on a transparent glass substrate 105.

[0030] Figure 2Describe the quantum dot assembly 102 disposed at the output of the narrowband illumination source 104. For example, the quantum dot assembly 102 can be transparent and positioned between the narrowband illumination source 104 and the illumination optics 114.

[0031] Figure 3 Describe an illumination system having a reflective quantum dot assembly 102 in accordance with one or more embodiments of the present disclosure. In an embodiment, the illumination optics 114a, 114b can be positioned at an angle to each other in a reflective configuration between a first illumination optic 114a and a second illumination optic 114b. For example, this configuration can be accomplished using a quantum dot assembly 102 that is at least partially reflective. For example, the quantum dot layer 103 of the quantum dot assembly 102 can be disposed on a reflective substrate 105.

[0032] Note that Figures 1A to 3 the examples depicted in should not be construed as limiting the scope of the present disclosure, but are for illustrative purposes only. Rather, it should be understood that the position of the quantum dot assembly 102 can vary significantly and can be positioned relative to the other components of the illumination system in any number of ways. As a non-limiting example, the quantum dot assembly 102 can be positioned near the narrowband illumination source 104 and / or after some of the illumination optics 114a, 114b. The position of the quantum dot assembly 102 can be specified by the design considerations of the illumination system 100. For example, the quantum dot assembly 102 can be positioned after a single illumination optic.

[0033] Figures 4A to 4C Describe various optical characterization system configurations incorporated into the illumination system 100 of the present disclosure. Note that Figures 4A to 4C the description of is for illustrative purposes only and should not be construed as limiting the scope of the present disclosure.

[0034] Figure 4A Describe a block diagram depicting an optical characterization system 400 incorporated into the illumination system 100 in accordance with one or more embodiments of the present disclosure. In an embodiment, the optical characterization system 400 includes an illumination subsystem 100 equipped with a quantum dot assembly 102. The illumination subsystem 100 should be construed to include all of the embodiments and features discussed with reference to the illumination system 100 of FIGS. 1 - 3.

[0035] In an embodiment, the optical characterization system 400 can include a photon collection subsystem 402 and a detector 404. The photon collection subsystem 402 can collect illumination 406 from the sample 108 and project the illumination 406 onto the detector 404. For example, this collected illumination 406 can be used for inspection and / or metrology of the sample 108. Note that converting the narrowband illumination beam 110 into a converted illumination beam 112 can reduce speckle noise at the detector 404 due to the broader spectral range of the converted illumination beam 112 relative to the input beam 110, which reduces the presence of interfering artifacts within the system 400.

[0036] Figure 4B The description depicts a block diagram of an optical characterization system 420 incorporated in a bright-field configuration of an illumination system 100 in accordance with one or more embodiments of the present disclosure. In an embodiment, the optical characterization system 410 includes an illumination subsystem 100 equipped with a quantum dot assembly 102. The illumination subsystem 100 should be interpreted to include all implementations and features discussed with reference to the illumination system 100 of FIGS. 1-4A. In an embodiment, the optical characterization system 410 includes a mirror 407 and a beam splitter 409 to couple the converted illumination beam 112 to the sample 108. In this regard, the mirror 407 directs the converted illumination 112 to the beam splitter 409. The beam splitter 409, in turn, directs the converted illumination 112 to the sample 108. In additional and / or alternative embodiments, the quantum dot assembly 102 may be integrated within the mirror 407. The beam splitter 409 may transmit illumination from the sample 108 along a light collection path to a light collection subsystem 402 and a detector 404. The light collection subsystem 402 may collect the illumination 406 from the sample 108 and project the illumination 406 onto the detector 404. For example, this collected illumination 406 may be used for inspection and / or metrology of the sample 108.

[0037] Figure 4C The description depicts a block diagram of an optical characterization system 420 incorporated in a transmission configuration of an illumination system 100 in accordance with one or more embodiments of the present disclosure. In an embodiment, the optical characterization system 420 includes an illumination subsystem 100 equipped with a quantum dot assembly 102. The illumination subsystem 100 should be interpreted to include all implementations and features discussed with reference to the illumination system 100 of FIGS. 1-4B. In an embodiment, the illumination source 104 and the illumination subsystem 100 are positioned on an opposite side (e.g., below the sample) of the sample 108 from the light collection subsystem 402 and the detector 404 (e.g., above the sample). In this regard, the converted illumination 112 is transmitted through the sample 108. The light collection subsystem 402, in turn, may collect the illumination 406 transmitted through the sample 108 and project the illumination 406 onto the detector 404.

[0038] Figure 5 The description depicts a flowchart of a method 500 for speckle-free high-brightness illumination in accordance with one or more embodiments of the present disclosure. The applicant reminds that the implementations and enabling technologies described in the context of the illumination system 100 and / or the characterization system 400 above should be interpreted to extend to the method 500. However, it should be further noted that the method 500 is not limited to the architecture of the illumination system 100 and / or the narrowband characterization system 400.

[0039] In an embodiment, method 500 includes step 502: generating a narrowband illumination beam. For example, the narrowband illumination beam may be generated by one or more narrowband illumination sources. The narrowband illumination source may include one or more lasers.

[0040] In an embodiment, method 500 includes step 504: guiding the narrowband illumination beam along an illumination path that includes one or more illumination optics. The one or more illumination optics may include one or more projection optics or homogenizer optics.

[0041] In an embodiment, method 500 includes step 506: converting the narrowband illumination beam into a converted illumination beam using a quantum dot assembly positioned within the illumination path, where the quantum dot assembly includes a quantum dot layer disposed on a substrate. The converted illumination beam may have a spectral range wider than the input narrowband illumination beam. The wider spectral range may reduce spectral noise at the detector. The converted illumination beam may include at least one of red, green, or blue light.

[0042] In an embodiment, method 500 includes step 508: directing the converted illumination beam from the quantum dot assembly to a sample disposed on a sample stage. For example, the converted illumination beam may (but need not) be directed to the sample by one or more illumination optics.

[0043] In an embodiment, method 500 includes step 510: projecting the illumination from the sample onto a detector. This may allow inspection or metrology on the sample.

[0044] The subject matter described herein sometimes illustrates different components that are included within or connected to other components. It should be understood that these depicted architectures are for illustrative purposes only, and in fact, many other architectures that achieve the same functionality may be implemented. In a conceptual sense, any arrangement of components that achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Thus, regardless of the architecture or intermediate components, any two components that are combined herein to achieve a particular functionality can be considered to be “associated” with each other such that the desired functionality is achieved. Similarly, any two components so associated can also be considered to be “connected” or “coupled” to each other to achieve the desired functionality, and any two components that can be so associated can also be considered to be “couplable” to each other to achieve the desired functionality. Specific examples of “couplable” include, but are not limited to, components that can physically interact and / or physically interact and / or can wirelessly interact and / or wirelessly interact and / or can logically interact and / or logically interact.

[0045] It is believed that the present disclosure and many of its attendant advantages will be understood from the foregoing description, and it should be understood that various changes may be made in the form, structure and arrangement of the components without departing from the disclosed subject matter or sacrificing all of its material advantages. The described forms are for purposes of illustration only, and the appended claims are intended to cover and embrace these changes. In addition, it should be understood that the present disclosure is defined by the appended claims.

Claims

1. A lighting system, comprising: A narrowband lighting source; A lighting path that includes one or more lighting optics; And A quantum dot assembly positioned within the lighting path, the quantum dot assembly including a quantum dot layer disposed on a substrate, wherein the quantum dot assembly is configured to receive a narrowband illumination beam from the narrowband lighting source and emit a converted illumination beam having a spectral range wider than the narrowband illumination beam, Wherein the one or more lighting optics are configured to direct illumination from the quantum dot assembly to a sample disposed on a sample stage.

2. The lighting system according to claim 1, wherein the wider spectral range of the converted illumination beam reduces speckle noise at a detector.

3. The lighting system according to claim 1, wherein the narrowband lighting source includes one or more lasers.

4. The lighting system according to claim 1, wherein the quantum dot layer is disposed on a transparent substrate.

5. The lighting system according to claim 4, further comprising a dichroic coating deposited on a surface of the transparent substrate.

6. The lighting system according to claim 1, wherein the quantum dot layer is disposed on a reflective substrate.

7. The lighting system according to claim 1, wherein the quantum dot assembly is transparent and positioned between two or more lighting optics.

8. The lighting system according to claim 7, wherein the two or more lighting optics include two or more projection optics or homogenizer optics.

9. The lighting system according to claim 1, wherein the quantum dot assembly is transparent and positioned between the narrowband lighting source and the one or more lighting optics.

10. The lighting system according to claim 1, wherein the quantum dot assembly is reflective and positioned between a first lighting optic and a second lighting optic.

11. The lighting system according to claim 1, wherein the lighting system is integrated within at least one of an inspection system or a metrology system.

12. An optical characterization system, comprising: An illumination subsystem, comprising: A narrowband lighting source; A lighting path that includes one or more lighting optics; and A quantum dot assembly positioned within the lighting path, the quantum dot assembly including a quantum dot layer disposed on a substrate, wherein the quantum dot assembly is configured to receive a narrowband illumination beam from the narrowband lighting source and emit a converted illumination beam having a spectral range wider than the narrowband illumination beam; Wherein the one or more lighting optics are configured to direct illumination from the quantum dot assembly to a sample disposed on a sample stage; A detector; and A light collection subsystem configured to collect illumination from the sample and project the illumination onto the detector.

13. The optical characterization system according to claim 12, wherein the wider spectral range of the converted illumination beam reduces speckle noise at the detector.

14. The optical characterization system according to claim 12, wherein the narrowband lighting source includes one or more lasers.

15. The optical characterization system according to claim 12, wherein the quantum dot layer is disposed on a transparent substrate.

16. The optical characterization system according to claim 15, further comprising a dichroic coating deposited on the surface of the transparent substrate.

17. The optical characterization system according to claim 12, wherein the quantum dot layer is disposed on a reflective substrate.

18. The optical characterization system according to claim 12, wherein the quantum dot assembly is transparent and positioned between two or more illumination optical devices.

19. The optical characterization system according to claim 12, wherein the quantum dot assembly is transparent and positioned between the narrowband illumination source and the one or more illumination optical devices.

20. The optical characterization system according to claim 12, wherein the quantum dot assembly is reflective and positioned between two or more illumination optical devices.

21. The optical characterization system according to claim 12, wherein the optical characterization system is configured as an inspection system or a metrology system.

22. A method, comprising: generating a narrowband illumination beam; guiding the narrowband illumination beam along an illumination path including one or more illumination optical devices; using a quantum dot assembly positioned within the illumination path to convert the narrowband illumination beam into a converted illumination beam, wherein the quantum dot assembly includes a quantum dot layer disposed on a substrate; guiding the converted illumination beam from the quantum dot assembly to a sample disposed on a sample stage; and projecting the illumination from the sample onto a detector.

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