Optical structure, method of manufacturing the same and optical system comprising the same

Abstract

The present disclosure provides an optical structure, a manufacturing method thereof, and an optical system comprising the same. The optical structure comprises an optical element and a plurality of protrusions. The optical element has a planarized upper surface. The protrusions are disposed on the planarized upper surface, wherein each protrusion independently has a sub-wavelength size. The optical structure provided by the present disclosure has the advantages of avoiding crosstalk interference, improving spatial resolution, overall sensitivity, noise ratio, and avoiding color mixing by disposing a super surface with a plurality of protrusions, thereby achieving better image quality. In addition, the isolation walls between light-emitting diodes can be omitted, thereby reducing the size of the device; since the optical multilayer film is not irradiated at a large angle, the blue shift problem can also be solved; and the fingerprint sensor can also generate a high-resolution image with higher contrast.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an optical structure, and in particular, to an optical structure having a metasurface. BACKGROUND

[0002] Various optical devices, such as complementary metal-oxide-semiconductor (CMOS) image sensors and optical fingerprint devices, have been developed. However, some problems can occur when a light source includes stray light. For example, a CMOS image sensor can be interfered by crosstalk, which reduces spatial resolution, overall sensitivity, and causes color mixing, resulting in image errors. If an optical multilayer film is used in an optical device, the optical multilayer film can generate a blue shift due to stray light being incident on the optical multilayer film at a large angle, which causes the wavelength of the stray light to shift toward blue light. In addition, an optical fingerprint device can generate a low-resolution image with low contrast due to the use of stray light.

[0003] Although the existing optical devices are sufficient to meet their intended purposes, they are not satisfactory in all aspects. As a result, there is a need for novel optical structures that can solve the above problems. SUMMARY

[0004] The present disclosure provides an optical structure that can collimate stray light. A metasurface is disposed on a planarized surface. The metasurface includes a pattern having a plurality of protrusions. When stray light passes through the metasurface, the metasurface can collimate the stray light. As a result, the stray light is incident on the optical device at 0 degrees. As a result, crosstalk in the CMOS image sensor can be avoided, thereby improving spatial resolution, enhancing overall sensitivity, and avoiding color mixing, and a better image quality is obtained. Since the optical multilayer film is not illuminated at a large angle, the problem of blue shift is also solved. The optical fingerprint device can also generate a higher-resolution image with higher contrast.

[0005] According to some embodiments of the present disclosure, an optical structure is provided. The optical structure includes an optical element and a plurality of protrusions. The optical element has a planarized upper surface. The protrusions are disposed on the planarized upper surface, wherein each protrusion independently has a sub-wavelength size.

[0006] According to some embodiments of the present disclosure, a method of manufacturing an optical structure is provided. The method includes providing an optical element having a planarized upper surface, and forming a plurality of protrusions on the planarized upper surface, wherein each protrusion independently has a sub-wavelength size.

[0007] According to some embodiments of the present disclosure, an optical system is provided. The optical system comprises a sensor, an optical element, and a plurality of protrusions. The optical element is disposed on the sensor. The optical element has a planarized upper surface. The protrusions are disposed on the planarized upper surface, wherein each of the protrusions independently has a sub-wavelength dimension.

[0008] Embodiments are illustrated by way of example with reference to the following drawings. BRIEF DESCRIPTION OF DRAWINGS

[0009] The present application can be more completely understood in consideration of the following detailed description in connection with the following drawings, in which:

[0010] Figure 1 According to some embodiments of the present disclosure, a method for fabricating an optical structure is disclosed, wherein a cross-sectional view of a step of the method is shown in FIG. 1.

[0011] Figure 2 According to some embodiments of the present disclosure, a method for fabricating an optical structure is disclosed, wherein a cross-sectional view of a step of the method is shown in FIG. 1.

[0012] Figure 3A According to some embodiments of the present disclosure, a method for fabricating an optical structure is disclosed, wherein a cross-sectional view of a step of the method is shown in FIG. 1.

[0013] Figure 3B According to some embodiments of the present disclosure, a method for fabricating an optical structure is disclosed, wherein a cross-sectional view of a step of the method is shown in FIG. 1.

[0014] Figure 4A According to some embodiments of the present disclosure, a method for fabricating an optical structure is disclosed, wherein a cross-sectional view of a step of the method is shown in FIG. 1.

[0015] Figure 4B According to some embodiments of the present disclosure, a method for fabricating an optical structure is disclosed, wherein a cross-sectional view of a step of the method is shown in FIG. 1.

[0016] Figure 5A According to some embodiments of the present disclosure, a method for fabricating an optical structure is disclosed, wherein a cross-sectional view of a step of the method is shown in FIG. 1.

[0017] Figure 5B According to some embodiments of the present disclosure, a method for fabricating an optical structure is disclosed, wherein a cross-sectional view of a step of the method is shown in FIG. 1.

[0018] Figure 6 According to some embodiments of the present disclosure, a method for fabricating an optical structure is disclosed, wherein a cross-sectional view of a step of the method is shown in FIG. 1.

[0019] Figure 7A According to some embodiments of the present disclosure, a top view of a plurality of protrusions is shown in FIG. 1.

[0020] Figure 7B is a top view of a plurality of protrusions according to some embodiments of the present disclosure;

[0021] Figure 7C is a top view of a plurality of protrusions according to some embodiments of the present disclosure;

[0022] Figure 7D is a top view of a plurality of protrusions according to some embodiments of the present disclosure;

[0023] Figure 8 is a schematic diagram of a metasurface and a module lens according to some embodiments of the present disclosure;

[0024] Figure 9A is a schematic diagram of a cross-section of a CMOS image sensor with a metasurface according to some embodiments of the present disclosure;

[0025] Figure 9B is a schematic diagram of a cross-section of a multi-layer film with a metasurface according to some embodiments of the present disclosure;

[0026] Figure 9C is a schematic diagram of a cross-section of a CMOS image sensor with a multi-layer film and a metasurface according to some embodiments of the present disclosure; and

[0027] Figure 9D is a schematic diagram of a cross-section of an optical fingerprint device with a metasurface according to some embodiments of the present disclosure.

[0028] Wherein, the reference signs are explained as follows:

[0029] 10A: mold

[0030] 10B: photomask

[0031] 50: light source

[0032] 100: optical structure

[0033] 102: optical element

[0034] 102A, 102C: CMOS image sensor

[0035] 102B: multi-layer film

[0036] 102D: fingerprint sensor

[0037] 102T: planarized upper surface

[0038] 104: material layer

[0039] 104', 104A, 104B, 104C, 104D: protrusion

[0040] 106A: resin layer

[0041] 106A': patterned resin layer

[0042] 106B: photoresist layer

[0043] 106B': patterned photoresist layer

[0044] 150: module lens

[0045] 200: substrate

[0046] 202: light emitting diode

[0047] 204: spacer

[0048] 206: filter layer

[0049] 208: microlens structure

[0050] 210, 310, 410: planar layer

[0051] 402: open hole structure

[0052] 404: transparent layer

[0053] C: center of protrusion (cylinder, cube, cuboid) / center of circumscribed circle of V-shaped antenna

[0054] D: distance between two adjacent centers

[0055] L: stray light

[0056] L1: first length of protrusion (cuboid)

[0057] L2: second length of protrusion (cuboid)

[0058] R: diameter of protrusion (cylinder)

[0059] S: circumscribed circle of protrusion (V-shaped antenna)

[0060] SL: side length of protrusion (cube)

[0061] SL1: first side length of protrusion (V-shaped antenna)

[0062] SL2: second side length of protrusion (V-shaped antenna)

[0063] SL3: third side length of protrusion (V-shaped antenna)

[0064] a: angle between third side lengths DETAILED DESCRIPTION

[0065] The optical structure of this disclosure is described in detail in the following description. In the following embodiments, numerous specific details and embodiments are set forth for illustrative purposes to provide a thorough understanding of this disclosure. Specific elements and configurations described in the following embodiments are set forth to clearly describe this disclosure. However, it will be apparent that the exemplary embodiments set forth herein are for illustrative purposes only, and the inventive concept can be embodied in various forms, and is not limited to those exemplary embodiments. Furthermore, the drawings of different embodiments may use similar and / or corresponding numbers to represent similar and / or corresponding elements in order to clearly describe this disclosure. However, the use of similar and / or corresponding numbers in the drawings of different embodiments does not imply any correlation between the different embodiments. Furthermore, in this specification, expressions such as "a first material layer disposed on / above a second material layer" may refer to direct contact between the first and second material layers, or it may refer to a non-contact state with one or more intermediate layers between the first and second material layers. In the above cases, the first material layer may not be in direct contact with the second material layer.

[0066] Furthermore, relative terms are used in this specification. For example, "lower," "bottom," "higher," or "top" are used to describe the position of one element relative to another. It should be understood that if the device is inverted, the "lower" element will become the "higher" element.

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should be understood that, in various cases, terms defined in common dictionaries should be interpreted as having a meaning consistent with the relative skill and context of this disclosure, and should not be interpreted in an idealized or overly formal manner unless so defined.

[0068] In this description, relative terms such as "down," "up," "horizontal," "vertical," "below," "above," "top," "bottom," etc., should be understood as referring to the orientation shown in the embodiment and related drawings. This relative use is for ease of explanation and does not imply that the described device must be manufactured or operated in a specific orientation. Furthermore, terms related to joining or connecting, such as "connection" or "interconnection," unless specifically defined, may indicate that two structures are in direct contact, or that two structures are not in direct contact but that another structure is disposed between them. Additionally, terms related to joining or connecting may also include embodiments where both structures are movable or both structures are fixed.

[0069] It should be understood that, although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers, sections, and / or portions, these elements, components, regions, layers, sections, and / or portions should not be limited by these terms. The terms are only used to distinguish one element, component, region, layer, section, or portion from another element, component, region, layer, section, or portion. Thus, a first element, component, region, layer, section, or portion discussed below could be termed a second element, component, region, layer, section, or portion without departing from the teachings of the present disclosure.

[0070] In the description, the terms "about," "approximately," "substantially," and the like are generally intended to refer to a range of values that fall within 20% of a given value, or within 10% of a given value, or within 5% of a given value, or within 3% of a given value, or within 2% of a given value, or within 1% of a given value, or within 0.5% of a given value. Where a given quantity is about a quantity, the meaning of about is implied even if not specifically stated.

[0071] According to some embodiments of the present disclosure, Figure 1 , Figure 2 , Figure 3A , Figure 3B , Figure 4A , Figure 4B , Figure 5A , Figure 5B and Figure 6 Cross-sectional schematic illustrations of different steps in a method of manufacturing an optical structure 100 are disclosed. Referring to Figure 1 , an optical element 102 is provided. As shown in Figure 1 , the optical element 102 has a planarized top surface 102T. In some embodiments, the optical element 102 further comprises an optical multilayer film.

[0072] Next, referring to Figure 2 , a material layer 104 is formed on the planarized top surface 102T. More specifically, the material layer 104 can be formed on the planarized top surface 102T by sputtering, spin coating, chemical vapor deposition (CVD), low pressure chemical vapor deposition (LPCVD), low temperature chemical vapor deposition (LTCVD), rapid thermal chemical vapor deposition (RTCVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), physical vapor deposition, molecular beam deposition, any other suitable process, or a combination thereof. The material of the material layer 104 comprises a dielectric material, such as titanium oxide, silicon nitride, silicon oxide, hydrogen silicide, or a combination thereof.

[0073] Next, the material layer 104 is patterned by a nanoimprint process to form a plurality of protrusions 104'. According to some embodiments of the present disclosure, Figure 3A , Figure 4A and Figure 5A A method of fabricating the optical structure 100 is disclosed. A resin layer 106A is formed on the material layer 104, as shown in Figure 3A More specifically, the resin layer 106A can be formed on the material layer 104 by sputtering, spin coating, chemical vapor deposition (CVD), low pressure chemical vapor deposition (LPCVD), low temperature chemical vapor deposition (LTCVD), rapid thermal chemical vapor deposition (RTCVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), physical vapor deposition, molecular beam deposition, any other suitable process, or a combination thereof.

[0074] In some embodiments, the material of the resin layer 106A includes a thermoplastic polymer or an ultraviolet light curable resin. The thermoplastic polymer can include polyethylene (PE), polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), nylon, polycarbonate (PC), polyurethane (PU), polytetrafluoroethylene (PTFE, also known as Teflon), polyethylene terephthalate (PET), or a combination thereof. The ultraviolet light curable resin can include epoxy acrylate, acrylated polyester, acrylated urethane, acrylated silicone, or a combination thereof.

[0075] Next, referring to Figure 4A , a mold 10A with a pattern is imprinted on the resin layer 106A. Thereafter, the resin layer 106A is cured by heating or ultraviolet light, depending on the material of the resin layer 106A.

[0076] Next, referring to Figure 5A , the mold 10A is removed, forming a patterned resin layer 106A'. The patterned resin layer 106A' serves as an etching mask for an etching process. Next, the material layer 104 can be etched by reactive ion etching, neutral beam etching, or other similar methods using a suitable etchant. Thereafter, a plurality of protrusions 104' corresponding to the pattern of the mold 10A are formed on the planarized upper surface 102T of the optical element 102, as shown in Figure 6 At this point, the fabrication of the super surface is complete. The nanoimprint process can have a higher process yield.

[0077] The material layer 104 can also be selectively patterned by a lithography process to form a plurality of protrusions 104'. According to some embodiments of the present disclosure, Figure 3B , Figure 4B and Figure 5B A method of fabricating the optical structure 100 is disclosed. A photoresist layer 106B is formed on the material layer 104, as shown in Figure 3B . More specifically, the photoresist layer 106B can be formed on the material layer 104 by sputtering, spin coating, chemical vapor deposition (CVD), low pressure chemical vapor deposition (LPCVD), low temperature chemical vapor deposition (LTCVD), rapid thermal chemical vapor deposition (RTCVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), physical vapor deposition, molecular beam deposition, any other suitable process, or a combination thereof.

[0078] The photoresist layer 106B includes a photoresist material that is sensitive to a radiation source. The photoresist material can be a positive or negative photoresist material, and the photoresist layer 106B can have a multi-layer structure. Further, the photoresist layer 106B can be implemented in a chemical amplification (CA) photoresist material. In one embodiment, a positive chemical amplification (CA) photoresist material includes a polymer material that is soluble in a developer after exposure to an acidic moiety. Alternatively, a negative chemical amplification (CA) photoresist material includes a polymer material that is insoluble in a developer after exposure to an acidic moiety.

[0079] Next, referring to Figure 4B , the photoresist layer 106B is exposed to a radiation source through a mask 10B having a pattern. In some embodiments, the radiation source can be ultraviolet (UV) radiation (i-line), deep ultraviolet (DUV) radiation, and / or extreme ultraviolet (EUV) radiation.

[0080] Next, referring to Figure 5B , a post-exposure bake and development are performed to remove portions of the photoresist layer 106B to form a patterned photoresist layer 106B'. The patterned photoresist layer 106B' serves as an etch mask for an etching process. Next, the material layer 104 can be etched using a suitable etchant by reactive ion etching, neutral beam etching, or other similar methods. Thereafter, a plurality of protrusions 104' corresponding to the pattern of the mask 10B are formed on the planarized upper surface 102T of the optical element 102, as shown in Figure 6 . At this point, the fabrication of the super surface is completed. Through the lithography process, the optical structure can have a high resolution of patterning and better process stability.

[0081] In embodiments where the optical element 102 is disposed above a CMOS image sensor, crosstalk interference caused by stray light can be avoided by disposing a metasurface with a plurality of protrusions. The metasurface can collimate the stray light such that the collimated stray light is illuminated on an undesired area, avoiding crosstalk interference, improving spatial resolution, overall sensitivity, noise ratio, and avoiding color mixing, and achieving better image quality. In addition, the isolation walls between light-emitting diodes can be omitted, thereby reducing the volume of the device.

[0082] In embodiments where the optical element 102 further comprises an optical multilayer film, the stray light is collimated by the metasurface such that the optical multilayer film is not illuminated at a large angle. As a result, the blue shift problem can be solved. Therefore, the metasurface can replace the blue glass used in the prior art to solve the blue shift problem.

[0083] In embodiments where the optical element 102 is disposed above a fingerprint sensor, the fingerprint sensor can generate a high-resolution image with higher contrast due to the collimation of stray light by the metasurface.

[0084] The plurality of protrusions 104’ can be cylinders, cubes, cuboids, or V-shaped antennas. Each protrusion 104’ can have a subwavelength dimension, which means that the dimension of each protrusion 104’ is smaller than the wavelength of the applied light source. The wavelength of the applied light source can be visible light or infrared light, for example, 630 nanometers, 850 nanometers, 940 nanometers, 1350 nanometers, or 1550 nanometers. In addition, there is a spacing between two adjacent protrusions 104’. It should be understood that the protrusion size and the spacing between two adjacent protrusions can control the incident light phase to be between 0 and 2π. Furthermore, the distribution (i.e., size distribution) of the plurality of protrusions 104’ controls the incident light phase to be between 0 and 2π.

[0085] Referring to Figure 7A , according to some embodiments of the present disclosure, a top view of the plurality of protrusions 104A is disclosed. Each protrusion 104A is a cylinder, which is circular from the top view. Each protrusion 104A independently has a diameter R from the top view. The diameter R is a subwavelength dimension. In some embodiments, the diameter R can be between 40 nanometers and 500 nanometers. Each protrusion 104A independently has a center C from the top view. In this embodiment, the center C is a point inside a circle, which is the same distance from every point on the circumference of the circle. There is a spacing D between two adjacent centers C. The spacing D can be between 100 nanometers and 1000 nanometers.

[0086] Figure 7BAccording to some embodiments of the disclosure, a top view of a plurality of protrusions 104B is disclosed. Each protrusion 104B is a cube, and appears as a square from the top view. Each protrusion 104B independently has a side length SL from the top view. The side length SL is a sub-wavelength dimension. In some embodiments, the side length SL can be between 40 nm and 500 nm. Each protrusion 104B independently has a center C from the top view. In this embodiment, the center C is a point inside the square such that any straight line passing through the point also passes through two points on opposite sides of the square edges that are the same distance from the center. There is a pitch D between two adjacent centers C. The pitch D can be between 100 nm and 1000 nm.

[0087] Figure 7C According to some embodiments of the disclosure, a top view of a plurality of protrusions 104C is disclosed. Each protrusion 104C is a cuboid, and appears as a rectangle from the top view. Each protrusion 104C independently has a first length LI and a second length L2 perpendicular to the first length LI from the top view. The first length LI and the second length L2 are sub-wavelength dimensions. In some embodiments, the first length LI can be between 40 nm and 500 nm, and the second length L2 can be between 40 nm and 500 nm. Each protrusion 104C independently has a center C from the top view. In this embodiment, the center C is a point inside the rectangle such that any straight line passing through the point also passes through two points on opposite sides of the rectangle edges that are the same distance from the center. There is a pitch D between two adjacent centers C. The pitch D can be between 100 nm and 1000 nm.

[0088] Figure 7D According to some embodiments of the disclosure, a top view of a plurality of protrusions 104D is disclosed. Each protrusion 104D is a V-shaped antenna, and appears as a V-shape from the top view. Each protrusion 104D independently has a first side length SL1, a second side length SL2, and a third side length SL3 from the top view. The first side length SL1 is adjacent to the second side length SL2, and the second side length SL2 is adjacent to the third side length SL3, that is, the second side length SL2 connects the first side length SL1 and the third side length SL3. The first side length SL1 is parallel to the third side length SL3. In some embodiments, the angle between the second side length SL2 and the first side length SL1 is an acute angle, and the angle between the second side length SL2 and the third side length SL3 is an obtuse angle. Alternatively, the angle between the second side length SL2 and the first side length SL1 is an obtuse angle, and the angle between the second side length SL2 and the third side length SL3 is an acute angle. In other embodiments, the second side length SL2 is the shortest distance between the first side length SL1 and the third side length SL3.

[0089] The first side length SL1, the second side length SL2, and the third side length SL3 are sub-wavelength dimensions. In some embodiments, the first side length SL1 can be between 40 nanometers and 500 nanometers, the second side length SL2 can be between 40 nanometers and 500 nanometers, and the third side length SL3 can be between 40 nanometers and 500 nanometers. Each protrusion 104D independently has a circumscribed circle S. The circumscribed circle S is a circle that passes through all vertices of the V-antenna. In this embodiment, the center C is the center of the circumscribed circle S of the V-antenna. The circumscribed circle S passes through all vertices of the largest triangle of the V-antenna. There is a spacing D between two adjacent centers C. The spacing D can be between 100 nanometers and 1000 nanometers. There is an angle a between the third side length SL3. The angle a is between 0 degrees and 180 degrees.

[0090] According to some embodiments of the present disclosure, Figure 8 A schematic diagram of a metasurface and a module lens 150 is disclosed. The module lens 150 is disposed between a light source 50 and an optical element 102 having a plurality of protrusions 104’ (i.e., a metasurface). The light source 50 includes a visible light source or an infrared light source. The infrared light source emits light having a wavelength of 850 nanometers, 940 nanometers, 1350 nanometers, or 1550 nanometers. The module lens 150 can focus stray light L from the light source 50 such that a majority of the stray light L can illuminate the optical element 102 and can be collimated by the metasurface, as shown. For example, the protrusions 104’ as collimators can collimate the stray light L having an angle between 0 degrees and 180 degrees to light having an angle of 0 degrees. Figure 8

[0091] According to some embodiments of the present disclosure, Figure 9A A cross-sectional schematic diagram of a CMOS image sensor 102A having a metasurface is disclosed. The CMOS image sensor 102A includes a substrate 200, a light emitting diode 202, a spacer 204, a filter layer 206, a microlens structure 208, a planarization layer 210, and a plurality of protrusions 104’.

[0092] The substrate 200 is a bulk semiconductor substrate, such as a semiconductor wafer. For example, the substrate 200 is a silicon wafer. The substrate 200 can include silicon or another elemental semiconductor material such as germanium. In some other embodiments, the substrate 200 includes a compound semiconductor. The compound semiconductor can include gallium arsenide, silicon carbide, indium arsenide, indium phosphide, another suitable material, or combinations thereof.

[0093] ​In some embodiments, the substrate 200 comprises a semiconductor-on-insulator (SOI) substrate. The semiconductor-on-insulator (SOI) substrate can be fabricated using a separation by implantation of oxygen (SIMOX) process, a wafer bonding process, another applicable method, or a combination thereof. In some embodiments, the substrate 200 is an undoped substrate.

[0094] Light emitting diodes 202 are disposed in the substrate 200. Spacers 204 are disposed between the light emitting diodes 202 to isolate the light emitting diodes 202. A filter layer 206 is disposed on the substrate 200. The filter layer 206 can be an organic filter or an inorganic filter. The filter layer 206 can comprise a plurality of sub-filters, each sub-filter corresponding to one light emitting diode 202. A microlens structure 208 is disposed on the filter layer 206.

[0095] A planar layer 210 is disposed on the microlens structure 208. The material of the planar layer 210 can comprise, but is not limited to, an organic transparent material, a dielectric material, a semiconductor material such as silicon, any other suitable transparent material, or a combination thereof. In some embodiments of the present disclosure, the dielectric material comprises silicon oxide, silicon nitride, silicon oxynitride, any other suitable dielectric material, or a combination thereof.

[0096] A plurality of protrusions 104’ is disposed on the planar layer 210. A module lens 150 is disposed between the light source 50 and the CMOS image sensor 102A. The module lens 150 can focus stray light L from the light source 50 such that a majority of the stray light L can be incident on the CMOS image sensor 102A and can be collimated by the metasurface, as shown in Figure 9A .

[0097] According to some embodiments of the present disclosure, Figure 9B A cross-sectional schematic view of a multilayer film 102B with a metasurface is disclosed. It is noted that the same or similar elements or layers are denoted by the same reference numerals. In some embodiments, for brevity, the same or similar elements or layers denoted by the same reference numerals have the same meaning and are not repeated.

[0098] A planar layer 310 is disposed on the multilayer film 102B. The material of the planar layer 310 can comprise, but is not limited to, an organic transparent material, a dielectric material, a semiconductor material such as silicon, any other suitable transparent material, or a combination thereof. In some embodiments of the present disclosure, the dielectric material comprises silicon oxide, silicon nitride, silicon oxynitride, any other suitable dielectric material, or a combination thereof.

[0099] A plurality of protrusions 104' is disposed on the flat layer 310. A module lens 150 is disposed between the light source 50 and the multilayer film 102B. The module lens 150 can focus stray light L from the light source 50 such that most of the stray light L can be irradiated on the multilayer film 102B and can be collimated by the metasurface, as shown in Figure 9B

[0100] According to some embodiments of the present disclosure, Figure 9C A cross-sectional schematic of a CMOS image sensor 102C with a multilayer film 102B and a metasurface is disclosed. It is to be noted that the same or similar elements or layers are denoted by the same reference numerals. In some embodiments, for brevity, the same or similar elements or layers denoted by the same reference numerals have the same meaning and are not repeated.

[0101] The CMOS image sensor 102C includes the CMOS image sensor 102A and the multilayer film 102B. The multilayer film 102B is disposed on the CMOS image sensor 102A. A module lens 150 is disposed between the light source 50 and the CMOS image sensor 102C. The module lens 150 can focus stray light L from the light source 50 such that most of the stray light L can be irradiated on the CMOS image sensor 102C and can be collimated by the metasurface, as shown in Figure 9C

[0102] According to some embodiments of the present disclosure, Figure 9D A cross-sectional schematic of a fingerprint sensor 102D with a metasurface is disclosed. It is to be noted that the same or similar elements or layers are denoted by the same reference numerals. In some embodiments, for brevity, the same or similar elements or layers denoted by the same reference numerals have the same meaning and are not repeated.

[0103] The fingerprint sensor 102D includes a substrate 200, a light-emitting diode 202, an aperture structure 402, a transparent layer 404, and a flat layer 410.

[0104] The aperture structure 402 includes a plurality of openings. The light-emitting diode 202 is disposed according to a pattern of the aperture structure 402. The aperture structure 402 can include an opaque material. The opaque material can include silver, aluminum, gold, copper, niobium, nickel, titanium, tungsten, an alloy thereof, or a mixed material thereof.

[0105] The transparent layer 404 is disposed on the aperture structure 402. A portion of the transparent layer 404 is disposed in the openings of the aperture structure 402. The flat layer 410 is disposed on the transparent layer 404. The materials of the transparent layer 404 and the flat layer 410 are similar to the material of the flat layer 310.

[0106] ​​The module lens 150 is disposed between the light source 50 and the fingerprint sensor 102D. The module lens 150 can focus stray light L from the light source 50 so that most of the stray light L can be irradiated on the fingerprint sensor 102D and can be collimated by the metasurface, as shown in Figure 9D

[0107] Compared with the prior art, the optical structure provided by the present disclosure has one or more of the following advantages:

[0108] (1) By providing a metasurface with a plurality of protrusions, crosstalk interference can be avoided, spatial resolution, overall sensitivity, noise ratio, and color mixing can be improved, and better image quality can be achieved. In addition, the isolation wall between light-emitting diodes can be omitted, thereby reducing the size of the device.

[0109] (2) Since the optical multilayer film is not irradiated at a large angle, the blue shift problem can also be solved.

[0110] (3) The fingerprint sensor can also produce high-resolution images with higher contrast.

[0111] Although the embodiments of the present disclosure and their advantages have been disclosed as above, it should be understood that those skilled in the art can make modifications, substitutions and refinements without departing from the spirit and scope of the present disclosure. In addition, the protection scope of the present disclosure is not limited to the processes, machines, manufactures, compositions of matter, devices, methods and steps in the specific embodiments described in the specification. Those skilled in the art can understand from the content of the embodiments of the present disclosure that the processes, machines, manufactures, compositions of matter, devices, methods and steps currently or in the future developed, as long as they can achieve substantially the same function or obtain substantially the same result as the embodiments described herein, can be used according to the embodiments of the present disclosure. Therefore, the protection scope of the present disclosure includes the above processes, machines, manufactures, compositions of matter, devices, methods and steps. In addition, the protection scope of the present disclosure shall be subject to the appended claims.​

Claims

1. An optical structure, comprising: an optical element having a planarized upper surface; and a plurality of protrusions disposed on the planarized upper surface, wherein each of the protrusions independently has a sub-wavelength dimension, wherein the protrusions have a size distribution that controls the phase of incident light to be between 0 and 2π, and the protrusions collimate incident light having an angle between 0 and 180 degrees to light having an angle of 0 degrees, wherein the protrusions comprise V-shaped antennas that are V-shaped when viewed from above, and each of the protrusions has a first side length, a second side length, and a third side length, the second side length connecting the first side length and the third side length, the first side length being parallel to the third side length, the second side length being the shortest distance between the first side length and the third side length, the first side length being between 40 nm and 500 nm, the second side length being between 40 nm and 500 nm, and the third side length being between 40 nm and 500 nm. The protrusions have a pitch between 100 nm and 1000 nm.

2. The optical structure of claim 1, wherein, The protrusions comprise titanium oxide, silicon nitride, silicon oxide, hydrogen silicide, or a combination thereof.

3. The optical structure of claim 1, wherein, The optical element further comprises an optical multilayer film.

4. The optical structure of claim 1, wherein, 5. A method of manufacturing an optical structure, comprising: providing an optical element having a planarized upper surface; and forming a plurality of protrusions on the planarized upper surface, wherein each of the protrusions independently has a sub-wavelength dimension, wherein the protrusions have a size distribution that controls the phase of incident light to be between 0 and 2π, and the protrusions collimate incident light having an angle between 0 and 180 degrees to light having an angle of 0 degrees, wherein the protrusions comprise V-shaped antennas that are V-shaped when viewed from above, and each of the protrusions has a first side length, a second side length, and a third side length, the second side length connecting the first side length and the third side length, the first side length being parallel to the third side length, the second side length being the shortest distance between the first side length and the third side length, the first side length being between 40 nm and 500 nm, the second side length being between 40 nm and 500 nm, and the third side length being between 40 nm and 500 nm. The step of forming a plurality of protrusions on the planarized upper surface comprises: forming a material layer on the planarized upper surface; 6. The method of fabricating an optical structure of claim 5, wherein, forming a resin layer on the material layer; patterning the resin layer by a nanoimprint process; and etching the material layer to form the protrusions. The step of forming a plurality of protrusions on the planarized upper surface comprises: forming a material layer on the planarized upper surface; 7. The method of fabricating an optical structure of claim 5, wherein, forming a photoresist layer on the material layer; patterning the photoresist layer by a lithography process; and etching the material layer to form the protrusions.

8. An optical system, comprising: a sensor; an optical element disposed on the sensor, the optical element having a planarized upper surface; and ​ ​ ​ a plurality of protrusions disposed on the planarized upper surface, wherein each of the protrusions independently has a sub-wavelength dimension, wherein the protrusions have a size distribution that controls the phase of incident light to be between 0 and 2π, and the protrusions collimate incident light having an angle between 0 degrees and 180 degrees into light having an angle of 0 degrees, wherein the protrusions comprise V-shaped antennas that are V-shaped when viewed from above, and each of the protrusions has a first side length, a second side length, and a third side length, the second side length connecting the first side length and the third side length, the first side length being parallel to the third side length, the second side length being the shortest distance between the first side length and the third side length, the first side length being between 40 nanometers and 500 nanometers, the second side length being between 40 nanometers and 500 nanometers, and the third side length being between 40 nanometers and 500 nanometers.

9. The optical system of claim 8, further comprising a light source disposed on the optical element, wherein the light source comprises a visible light source or an infrared light source, and the sensor comprises a complementary metal-oxide-semiconductor image sensor or a fingerprint sensor.

10. The optical system of claim 9, wherein, the infrared light source emits light having a wavelength of 850 nanometers, 940 nanometers, 1350 nanometers, or 1550 nanometers.

Images