Photonic integrated circuits for nano-lithography and nano-imaging

Abstract

A photonic integrated circuit (PIC 200), an optical system comprising such PIC and a method of processing a sample using such PIC are presented. The PIC comprising a plurality of scanning waveguides (112) and plasmonic nanostructures (114) in a tip of each of the scanning waveguides. The tip of the scanning waveguide is a part of the scanning waveguide where light exists or enters the PIC when in operation.

Description

[0001] Photonic Integrated Circuits for Nano-Lithography and Nano-Imaging

[0002] Technical field

[0003] The present disclosure relates to photonic integrated circuits (PICs) for nanolithography and nano-imaging, optical systems including such PICs and a method of processing a sample in such optical system.

[0004] Background

[0005] Optical lithography systems are widely used to fabricate photonic structures (micro and nano) on small chips, while optical imaging systems are employed to magnify and observe details that are too small to be seen with the naked eye. The performance of such systems is fundamentally determined by the wavelength of the light used and the numerical aperture of the system. In essence, the minimum feature size that can be defined using optical lithography and the smallest detail that can be resolved using optical microscopy are governed by the spot size of the beam, which is dependent on the wavelength of the light.

[0006] In the field of optical lithography, maskless lithography has emerged as a cutting-edge approach that offers significant advantages over traditional mask-based methods. Unlike conventional optical lithography, which relies on masks to project patterns onto a substrate, maskless lithography directly writes or prints patterns using a focused light beam, eliminating the need for physical masks. This capability makes it particularly valuable for applications requiring rapid prototyping, customization, and high flexibility in pattern design.

[0007] Direct Laser Writing (DLW) and Digital Micro mirror Devices (DMD) are two prominent maskless lithography techniques. DLW uses a focused laser beam to create patterns with high precision, achieving resolutions as fine as 100 nm or even smaller with advanced techniques like multiphoton polymerization. On the other hand, DMD technology employs an array of micromirrors to project a pattern directly onto a photosensitive material, allowing for high-speed and versatile patterning. Recent advancements in maskless lithography also include electron beam lithography with maskless capabilities and focused ion beam (FIB) lithography, which extend the potential for high-resolution patterning.

[0008] In optical imaging, recent developments have greatly improved the ability to see tiny details, even beyond the limits of traditional microscopes. Super-resolution techniques, such as stimulated emission depletion microscopy (STED) and scanning near-field optical microscopy (SNOM) enable imaging at the nanoscale, surpassing the diffraction limit and achieving resolutions down to 10-50 nm. Techniques like lightsheet microscopy and multiphoton microscopy allow for fast, deep tissue imaging with minimal photodamage, making them ideal for live-cell studies. Additionally, the integration of machine learning and artificial intelligence is transforming image processing, pushing optical imaging into new frontiers, and providing unprecedented detail in both biological and material sciences.

[0009] However, these technologies have some major drawbacks: they take a long time to operate (writing time in lithography and acquisition time in imaging), and they require a complicated, specialized environment.

[0010] For example, maskless lithography, including techniques like DLW and electron beam lithography, offers flexibility and rapid prototyping but suffers from slower processing speeds, as these methods write patterns point-by-point or line-by-line, making them much slower compared to the simultaneous pattern projection of traditional mask-based systems. Additionally, these systems are often costly, with high initial investments and operational expenses due to the advanced lasers and electron beams required, and their scalability is limited, making them less practical for large-volume production.

[0011] Similarly, super-resolution microscopy, which surpasses the diffraction limit of light, encounters significant issues related to point-by-point imaging. Many superresolution techniques require sequential scanning or imaging, which is inherently slow and can be particularly time-consuming for large or complex samples, as each point must be individually captured and processed. Prolonged exposure during this process can also lead to photobleaching and phototoxicity, potentially damaging samples or reducing fluorescent signals.

[0012] These factors restrict the practicality of super-resolution techniques for high-throughput applications or long-term live sample imaging, presenting challenges for dynamic and efficient imaging tasks. Summary

[0013] A summary of aspects of certain examples disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects and / or a combination of aspects that may not be set forth.

[0014] The present disclosure aims to overcome the drawbacks identified in the background section.

[0015] According to an aspect of the present disclosure, a photonic integrated circuit, PIC is presented. The PIC may include a plurality of scanning waveguides. The PIC may further include plasmonic nanostructures in a tip of each of the scanning waveguides. The tip of the scanning waveguide may be a part of the scanning waveguide where light exists or enters the PIC when in operation.

[0016] In an embodiment, the PIC may include a first optical subsystem and a second optical subsystem. The first optical subsystem may include the plurality of scanning waveguides including the plasmonic nanostructures in the tip of each of the scanning waveguides. The second optical subsystem may define an optical path between each of the scanning waveguides and a light source. The second optical subsystem may include one or more of: a light source; an input waveguide; one or more beam splitters; one or more programmable circuits; a plurality of waveguides of different lengths; an output waveguide; and / or a light detector.

[0017] In an embodiment, the PIC may include an input waveguide arranged to receive light from a light source. The PIC may further include a programmable circuit optically connected to the input waveguide and optically connected to the plurality of scanning waveguides.

[0018] In an embodiment, the PIC may include a plurality of programmable circuits. The PIC may further include one or more beam splitters. Each of the plurality of programmable circuits may be optically connected to the input waveguide via one or more of the beam splitters. Each of the plurality of programmable circuits may be optically connected to a different plurality of scanning waveguides.

[0019] In an embodiment, the PIC may include the light source. In an embodiment, the PIC may include an input waveguide arranged to receive light from a light source. The PIC may further include an output waveguide arranged to output light to a light detector. The PIC may further include one or more beam splitters. The PIC may further include a plurality of waveguides of different lengths. Each of the plurality of waveguides of different lengths may be optically connected to the input waveguide via one or more of the beam splitters. Each of the plurality of waveguides of different lengths may be optically connected to the output waveguide via one or more of the beam splitters. Each of the plurality of waveguides of different lengths may be optically connected a different one of the plurality of scanning waveguides.

[0020] In an embodiment, the PIC may include the light source.

[0021] In an embodiment, the PIC may include the light detector.

[0022] In an embodiment, at least one of the plurality of waveguides of different lengths may be spiral shaped.

[0023] According to an aspect of the present disclosure, an optical system is presented. The optical system may include one or more PICs having one or more of the abovedescribed features.

[0024] In an embodiment, the optical system may be an optical lithography system. In an embodiment, the optical system may be an optical imaging system.

[0025] In an embodiment, the optical system may be a combined optical lithography and optical imaging system.

[0026] According to an aspect of the present disclosure, a method of processing a sample in an optical system having one or more of the above-described features is proposed. The method may include providing the sample to the optical system. The method may further include dividing an area of the sample into subareas. The method may further include projecting a plurality of light beams onto one of the subareas using a PIC having one or more of the above-described features.

[0027] In an embodiment, the method may further include receiving reflected or scattered light by a PIC having one or more of the above-described features.

[0028] Brief description of the Drawings Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbol indicate corresponding parts, in which:

[0029] Fig. 1A and Fig. 1B show two example embodiment of optical devices;

[0030] Fig. 2A and Fig. 2B show an example embodiment of a PIC for use in an optical lithography system;

[0031] Fig. 3A and Fig. 3B show an example embodiment of a PIC for use in an optical imaging system;

[0032] Fig. 4A, Fig. 4B and Fig. 4C are example embodiments of optical systems; and Fig. 5 shows the steps of a method of processing a sample in an optical system. The figures are intended for illustrative purposes only, and do not serve as restriction of the scope of the protection as laid down by the claims.

[0033] Detailed description

[0034] It will be readily understood that the components of the embodiments as generally described herein and illustrated in the appended figures could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of various embodiments, as represented in the figures, is not intended to limit the scope of the present disclosure but is merely representative of various embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0035] The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the present disclosure is, therefore, indicated by the appended claims rather than by this detailed description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

[0036] Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present disclosure should be or are in any single example of the present disclosure. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Thus, discussions of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same example.

[0037] Furthermore, the described features, advantages, and characteristics of the present disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the present disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the present disclosure. Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the indicated embodiment is included in at least one embodiment of the present disclosure. Thus, the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0038] To overcome the drawbacks identified in the background section, the present disclosure proposes a new approach to improve resolution by using on-chip optical waveguides integrated with plasmonic nanostructures that help in focusing the light more tightly, allowing to create and observe even smaller features of, e.g., a few tens of nanometers. The waveguides may act like a scanning probe and may be scaled up to perform multiple imaging or writing tasks simultaneously, which greatly speeds up the process. This combination of waveguides and nanostructures may lead to faster and more precise systems for imaging and lithography.

[0039] The present disclosure presents a design of a photonic integrated circuit (PIC) that incorporates on-chip waveguides integrated with plasmonic nanostructures. This design enables the creation of multiple scanning tips on a compact and miniaturized photonic platform. By integrating such PICs into the direct laser writing technique, a minimum feature may be achieved of a few tens of nanometers thanks to the plasmonic nanostructures.

[0040] The solution of the present disclosure may divide the area of an entire sample into multiple regions and perform one or both of lithography and imaging tasks across all regions parallelly using multiple waveguides, thereby improving scanning speed and efficiency.

[0041] In lithography systems, this setup allows to write on multiple areas of the sample simultaneously, leveraging the multiple waveguides embedded in the PICs. As a result, multiple devices may be patterned with feature sizes under a few tens of nanometers simultaneously, in the same time it would typically take to pattern a single device.

[0042] Similarly, in imaging systems, such PICs allows simultaneously collecting data from multiple areas of the sample, significantly reducing the acquisition time.

[0043] Fig. 1A and Fig. 1B illustrate two example embodiments of optical devices 100A, 100B including a first optical subsystem 110 implemented in a PIC 102A, 102B according to an aspect of the present disclosure. The optical device 100A, 100B may be configured for operation in an optical lithography system or for operation in an optical imaging system, depending on the implementation of a second optical subsystem 120, 124.

[0044] The first optical subsystem 110 implemented in PIC 102A, 102B includes a plurality of scanning waveguides 112. In Fig. 1A and Fig. 1B, four of such scanning waveguides 112 are shown, but there may be any other number of scanning waveguides 112 implemented in the PIC 102A, 102B. At the tip of each scanning waveguide 112, plasmonic nanostructures 114 focus the light tightly for projection onto an external sample.

[0045] The integration of multiple scanning waveguides 112 with plasmonic nanostructures 114 in its tip into PIC 102A, 102B enable to above mentioned parallel processing of a sample using highly focused light.

[0046] The PIC 102A of the present disclosure may include a second optical subsystem 120, such as shown in Fig. 1A. Alternatively, as shown in Fig. 1B, a second optical subsystem 124 may be external to the PIC 102B, with the scanning waveguides 112 being connected to the second optical subsystem 124 via intermediary optical connections 122. It is possible to include a part of the second optical subsystem 124 into the PIC 102B, while another part is implemented external to the PIC 102B (not shown).

[0047] Fig. 2A and Fig. 2B shows an example embodiment of a PIC 200 for use in an optical lithography system. Fig. 2A illustrates the optical subsystems within the PIC 200. Fig. 2B shows the same example embodiment of Fig. 2A, detailing optical elements within the PIC 200.

[0048] As shown in Fig. 2A, the PIC 200 may include one or more first optical subsystems 110; in this example four. In this example, the second optical subsystem 120 is implemented within the PIC 200, similar to PIC 102A of Fig. 1A.

[0049] Fig. 2B shows the same example embodiment of Fig. 2A, detailing the optical elements within the PIC 200. Also shown is an external sample 250, e.g., a wafer, which may be exposed to the focused light coming from the scanning waveguides 112 with plasmonic nanostructures 114. The dots 252 illustrate light projected onto the sample 250 during a photolithographic process.

[0050] The optical lithography solution of the present disclosure, such as shown in Fig.

[0051] 2A and Fig. 2B, may include the PIC 200 integrating the first optical system and a light source 202 to achieve high-efficiency, nanoscale fabrication. The PIC 200 may further include an input waveguide 204, multiple scanning waveguides 112 (output), one or more programmable circuits 208, and on-chip beam splitters 206, all on a compact photonic platform.

[0052] In operation, light is injected into the input waveguide 204, and the on-chip beam splitters 206 may distribute the light across an array of waveguides, i.e., the waveguides after light has been split by the on-chip beam splitters 206. The programmable circuit 208 controls the distribution of the light into the output scanning waveguides 112 of the respective programmable circuit 208, resulting in different patterns 252 on the sample 250, e.g., on a layer of photoresists material.

[0053] At the tip of each scanning waveguide 112, the plasmonic nanostructures 114 focus the light tightly, enabling feature sizes of, e.g., tens of nanometers. This approach allows for simultaneous exposure and fabrication of a sample 250, allowing, e.g., multiple semiconductor devices to be fabricated by the optical lithography machine using the PIC 200. The writing time for many of such fabricated devices can be substantially identical to that for a single device, making the solution of the present disclosure ideal for mass production.

[0054] As explained with Fig. 1B, although less preferred, one or more of the optical components may be realized external to the PIC 200. For example, one or more of the programmable circuits 208, one or more of the beam splitters 206, the array of waveguides defined by the beam splitters 206, the input waveguide 204 and / or the light source 202 may be external to the PIC 200. The PIC 200 may include further components, such as optical isolators, which are not shown in Fig. 2B.

[0055] Fig. 3A and Fig. 3B shows another example embodiment of a PIC 300 for use in an optical imaging system. Fig. 3A illustrates the optical subsystems within the PIC 300. Fig. 3B shows the same example embodiment of Fig. 3A, detailing optical elements within the PIC 300.

[0056] As shown in Fig. 3A, the PIC 300 may include one or more first optical subsystems 110; in this example one. In this example, the second optical subsystem 120 is implemented within the PIC 300, similar to PIC 102A of Fig. 1A.

[0057] Fig. 3B shows the same example embodiment of Fig. 3A, detailing the optical elements within the PIC 300. Also shown is an external sample 350, which may be exposed to the focused light coming from the scanning waveguides 112 with plasmonic nanostructures 114. The dots 352 illustrate light projected onto the sample 350 during an optical imaging process. The light may be reflected or scattered from the surface of the sample 350 and received by the first optical subsystem 110.

[0058] The optical imaging solution of the present disclosure, such as shown in Fig. 3A and Fig. 3B, may include a PIC 300 integrating the first optical subsystem 110 and waveguides of different lengths 308A, 308B, 308C, 308D, a light source 302, and a light detector 312. The PIC 300 may further include an input waveguide 304, an output waveguide 310, multiple scanning waveguides 112 with plasmonic nanostructures 114 in the tip of each scanning waveguide 112, and on-chip beam combiners / splitters 306 on a compact photonic platform.

[0059] In operation, light is injected into the input waveguide 304, and on-chip beam splitters 306 may split the light into an array of waveguides, i.e., the waveguides after light has been split by the on-chip beam splitters 306.

[0060] Different waveguides of the array may shine and collect the light at various locations, depicted by the dots 352, on the scanning sample 350. At the tip of each scanning waveguide 112, the plasmonic nanostructures 114 focus the light to a spot size, e.g., below a few tens nm, allowing for resolution of features smaller than, e.g., a few tens nm.

[0061] In an optical imaging system, the PIC 300 may also act like a combiner in reflection geometry, combining the reflected light from different scanning waveguides 112. The reflected light signal may be combined using the on-chip beam splitters 306 and send the detector 312 through the output waveguide 310.

[0062] There may be any plurality number of waveguides of different lengths implemented in the PIC 300, e.g., four of such waveguides 308A, 308B, 308C, 308D such as shown in Fig. 3B.

[0063] In a non-limiting embodiment, the differences in length of the waveguides 308A, 308B, 308C, 308D may be realized by forming these waveguides as spiral shaped waveguides, as shown in Fig. 3B. Other shapes may be used to realize the differences in length. Due to the different lengths of the waveguides 308A, 308B, 308C and 308D, the reflected light may be detected from specific scanning waveguides 112 at specific time stamps, as the light traveling through the shortest waveguide length would arrive earlier. The detected light intensities may be mapped at different times to the reflection of the scanning sample at different locations simultaneously and a full image of the sample 350 may thus be acquired.

[0064] An imaging system based on PICs 300 of the present disclosure may be implemented in different wavelength ranges, starting from visible to mid-infrared (mid-IR). Thanks to the progress made in integrated photonics, both the light source 302 and light detectors 312 may be integrated on the same chip 300, resulting in a more stable and compact imaging system.

[0065] As explained with Fig. 1B, although less preferred, one or more of the optical components may be realized external to the PIC 300. For example, one or more of the waveguides of different lengths 308A-D, one or more of the beam splitters 306, the array of waveguides defined by the beam splitters 306, the input waveguide 304, the light source 302, the output waveguide 310 and / or the light detector 312 may be external to the PIC 300. The PIC 300 may include further components, such as optical isolators, which are not shown in Fig. 3B.

[0066] The solution of the present disclosure thus allows dividing an area of a sample 250, 350 into small areas (or subareas) and processing these subareas in parallel using the optical device 100A, 100B, e.g., implemented as PIC 200 or PIC 300. Parallel processing allows for faster imaging in optical lithography processes and / or acquiring high-resolution images (near-field) and diffraction-limited images (far-field) with high scanning speed in optical imaging processes. An optical system may include one or more optical devices 100A, 100B. In Fig.

[0067] 4A an example of an optical lithography system 400A is illustrated, including one or more PICs 200 and further components 402A external to the PIC 200. In Fig. 4B an example of an optical imaging system 400B is illustrated, including one or more PICs 300 and further components 402B external to the PIC 300. In Fig. 4B an example of a combined optical lithography and optical imaging system 400B is illustrated, including one or more PICs 200, one or more PICs 300 and further components 402C external to the PICs 200, 300.

[0068] Fig. 5 shows an example process 500 of using the solution of the present disclosure. In step 502 a sample 250, 350 may be provided. In step 504, the area of the sample 250, 350 may be divided into subareas. In step 506, a plurality of light beams 252, 352 are projected onto a subarea using the optical device 100A, 100B, e.g., implemented as PIC 200 or PIC 300, of the present disclosure. Thus, multiple regions (subareas) of the sample can be parallelly processed, either for optical lithography or for optical imaging, or both.

[0069] In an optical imaging system, the method may further include receiving reflected light by the optical device 100A, 100B in step 508.

[0070] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope thereof.

Claims

CLAIMS1. A photonic integrated circuit, PIC (102A, 102B, 200, 300) comprising:a plurality of scanning waveguides (112); andplasmonic nanostructures (114) in a tip of each of the scanning waveguides (112),wherein the tip of the scanning waveguide (112) is a part of the scanning waveguide (112) where light exists or enters the PIC (102A, 102B, 200, 300) when in operation.

2. The PIC (100A, 200, 300) according to claim 1, comprising a first optical subsystem (110) and a second optical subsystem (120),wherein the first optical subsystem comprises the plurality of scanning waveguides (112) including the plasmonic nanostructures (114) in the tip of each of the scanning waveguides (112),wherein the second optical subsystem (120) defines an optical path between each of the scanning waveguides (112) and a light source (302),and wherein the second optical subsystem (120) comprises one or more of: a light source (202, 302);an input waveguide (204, 304);one or more beam splitters (206, 306);one or more programmable circuits (208);a plurality of waveguides of different lengths (308A, 308B, 308C, 308D); an output waveguide (310); anda light detector (312).

3. The PIC (200) according to claim 1, comprising:an input waveguide (204) arranged to receive light from a light source (202); and a programmable circuit (208) optically connected to the input waveguide (204) and optically connected to the plurality of scanning waveguides (112).

4. The PIC (200) according to claim 3, comprising:a plurality of programmable circuits (208); andone or more beam splitters (206),wherein each of the plurality of programmable circuits (208) is optically connected to the input waveguide (204) via one or more of the beam splitters (206), and wherein each of the plurality of programmable circuits (208) is optically connected to a different plurality of scanning waveguides (112).

5. The PIC (200) according to claim 3 or claim 4, wherein the PIC (200) comprises the light source (202).

6. The PIC (300) according to claim 1, comprising:an input waveguide (304) arranged to receive light from a light source (302); an output waveguide (310) arranged to output light to a light detector (312); one or more beam splitters (306); anda plurality of waveguides of different lengths (308A, 308B, 308C, 308D), wherein each of the plurality of waveguides of different lengths (308A, 308B, 308C, 308D) is optically connected to the input waveguide (304) via one or more of the beam splitters (306),wherein each of the plurality of waveguides of different lengths (308A, 308B, 308C, 308D) is optically connected to the output waveguide (310) via one or more of the beam splitters (306),and wherein each of the plurality of waveguides of different lengths (308A, 308B, 308C, 308D) is optically connected a different one of the plurality of scanning waveguides (112).

7. The PIC (300) according to claim 6, wherein the PIC (300) comprises the light source (302).

8. The PIC (300) according to claim 6 or claim 7, wherein the PIC (300) comprises the light detector (312).

9. The PIC (300) according to any one of the claims claim 6-8, wherein at least one of the plurality of waveguides of different lengths (308A, 308B, 308C, 308D) is spiral shaped.

10. An optical system (402A, 402B, 402C) comprising one or more photonic integrated circuits, PIC (102A, 102B, 200, 300), according to any one of the preceding claims.

11. The optical system (402A) according to claim 10, wherein the optical system (402A) is an optical lithography system.

12. The optical system (402B) according to claim 10, wherein the optical system (402A) is an optical imaging system.

13. The optical system (402C) according to claim 10, wherein the optical system (402A) is a combined optical lithography and optical imaging system.

14. A method of processing a sample (250, 350) in an optical system according to any one of the claims 10-13, the method comprising:providing (502) the sample (250, 350) to the optical system;dividing (504) an area of the sample (250, 350) into subareas;projecting (506) a plurality of light beams (252, 352) onto one of the subareas using a photonic integrated circuit, PIC (102A, 102B, 200, 300) according to any one of the claims 1-9.

15. The method according to claim 14, further comprising:receiving reflected or scattered light by the PIC (102A, 102B, 300) according to any one of the claims 1-2 or any on of the claims 6-9.

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