Encapsulation materials for flat optical devices

Abstract

To provide improved flat optical devices and encapsulation materials for the flat optical devices.SOLUTION: One or more embodiments include a substrate having a first arrangement of a first plurality of pillars formed thereon. The first arrangement of the first plurality of pillars includes pillars having a height h and a lateral distance d. The first arrangement of the first plurality of pillars includes a gap g corresponding to a distance between adjacent pillars of the first plurality of pillars. An aspect ratio of the gap g to the height h is between about 1:1 and about 1:20. A first adhesion-promoting material is disposed over the first arrangement of the first plurality of pillars. A first encapsulation layer is disposed over the first adhesion-promoting material. The first encapsulation layer fills the gap g between adjacent pillars of the first plurality of pillars. The first encapsulation layer includes a fluoropolymer.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001]

[0001] Embodiments of the present disclosure relate generally to optical devices. In particular, embodiments described herein relate to planar optical devices and encapsulation materials for planar optical devices. [Background technology]

[0002]

[0002] Planar optical devices include an array of posts with in-plane dimensions smaller than half the design wavelength of light and out-of-plane dimensions on the order of the design wavelength or larger. Planar optical devices can consist of a single layer or multiple layers of nanostructured posts. The posts of the planar optical device require encapsulation to act as a protective layer and as a spacer layer between successive layers of the multilayer array. However, in nanostructured planar optical devices, filling high aspect ratio apertures is often difficult, resulting in non-uniform gap filling. Furthermore, encapsulation of the posts increases the height of the posts and therefore the total thickness of the planar optical device. Increasing the total thickness of the planar optical device reduces the transmission efficiency and increases the complexity and cost of manufacturing. Therefore, what is needed in the art are improved planar optical devices and encapsulation materials for planar optical devices. Summary of the Invention

[0003] In one or more embodiments, an apparatus is provided that includes a substrate having a first array of a first plurality of pillars formed thereon. The first array of the first plurality of pillars includes pillars having a height, h, and a lateral distance, d. The first array of the first plurality of pillars includes a gap, g, that corresponds to a distance between adjacent pillars of the first plurality of pillars. An aspect ratio of the gap, g, to the height, h, is between about 1:1 and about 1:20. A first adhesion promoter is disposed over the first array of the first plurality of pillars. A first encapsulation layer is disposed over the first adhesion promoter. The first encapsulation layer fills the gap, g, between adjacent pillars of the first plurality of pillars. The first encapsulation layer includes a fluoropolymer.

[0004] In another embodiment, a method is provided that includes forming a first array of a first plurality of pillars on a surface of a substrate. The first array of the first plurality of pillars includes pillars having a height h, a lateral distance d, and a gap g corresponding to a distance between adjacent pillars of the first plurality of pillars. An aspect ratio of the gap g to the height h is between about 1:1 and about 1:20. The method includes disposing a first adhesion promoter material over the first array of the first plurality of pillars. The method includes disposing a first encapsulation layer over the first adhesion promoter material. The first encapsulation layer fills the gaps g between adjacent pillars of the first plurality of pillars. The first encapsulation layer includes a fluoropolymer.

[0005] In another embodiment, an apparatus is provided that includes a substrate having a first array of a first plurality of pillars formed thereon. The first array of the first plurality of pillars includes pillars having a first surface facing away from the substrate, one or more side surfaces facing adjacent pillars, and trenches formed between adjacent pillars. The apparatus includes a first adhesion promoter material disposed on the first surface and on the one or more side surfaces of the pillars. The first adhesion promoter material includes a fluorosilane. The apparatus includes a first encapsulation layer disposed on the first adhesion promoter material. The first encapsulation layer fills the trenches between adjacent pillars of the first plurality of pillars and includes an amorphous fluoropolymer. [Brief description of the drawings]

[0006]

[0006] So that the above-mentioned features of the present disclosure can be understood in detail, a specific description of the present disclosure briefly summarized above can be had by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings show only exemplary embodiments, and therefore should not be considered as limiting the scope of the present disclosure, as other equally effective embodiments may be permitted.

[0007] [Figure 1A] 1 is a schematic perspective view of a planar optical device according to one or more embodiments described herein. [Figure 1B-C]

[0008] 1B is a schematic cross-sectional view of a layer stack according to one or more embodiments described herein.

[0009] 1C is a schematic top view of a support post arrangement of a layer stack according to one or more embodiments described herein. [Fig. 1D-E]

[0010] D and E are exemplary structures of a fluoropolymer encapsulant according to one or more embodiments described herein. [Diagram 2]

[0011] 1 illustrates a method of forming a planar optical device according to one or more embodiments described herein. [Figure 3A-B]

[0012] 1A and 1B are schematic cross-sectional views of a substrate during a method of forming a planar optical device according to one or more embodiments described herein. [Figure 3C-D] 1C and 1D are schematic cross-sectional views of a substrate during a method of forming a planar optical device according to one or more embodiments described herein. [Figure 4]

[0013] A-D are exemplary structures of adhesion promoters according to one or more embodiments described herein.

[0008]

[0014] For ease of understanding, wherever possible, like reference numerals have been used to designate like elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009]

[0015] Embodiments described herein relate to planar optical devices and encapsulation materials for planar optical devices. One or more embodiments include a substrate having a first array of a first plurality of posts formed thereon. The first array of the first plurality of posts includes posts having a height h and a lateral distance d. The first array of the first plurality of posts includes a gap g corresponding to a distance between adjacent posts of the first plurality of posts. An aspect ratio of the gap g to the height h is between about 1:1 and about 1:20. A first adhesion promoter is disposed on the first array of the first plurality of posts. A first encapsulation layer is disposed on the first adhesion promoter. The first encapsulation layer fills the gap g between adjacent posts of the first plurality of posts. The first encapsulation layer includes a fluoropolymer.

[0010]

[0016] FIG. 1A is a schematic perspective view of a planar optical device 100 having at least one layer stack (stacked layers) 101A, 101B. FIG. 1B is a schematic cross-sectional view of the layer stack 101A. FIG. 1C is a schematic top view of the arrangement of the support posts 104 of the layer stack 101A. The planar optical device 100 includes at least one layer stack 101A, 101B. Although aspects of the apparatus and methods described herein may be described with reference to the layer stack 101A, it should be understood that aspects of the apparatus and methods described herein are equally applicable to the layer stack 101B. For clarity in the figures provided herein, reference numerals may be omitted for the arrangement of the layer stack 101B.

[0011]

[0017] In one or more embodiments that can be combined with other embodiments described herein, the planar optical device 100 is a single-layer stack planar optical device including a layer stack 101A. In other embodiments that can be combined with other embodiments described herein, the planar optical device 100 is a multi-stack optical device including a layer stack 101A and one or more layer stacks 101B. The layer stack 101A includes an array of a plurality of support posts 104A disposed on a surface of the substrate 102 and an encapsulation layer 106A. The encapsulation layer 106A includes a gap fill portion 108A and a cap portion 109A. In the illustrated embodiment of the multi-stack optical device, a first layer stack of the one or more layer stacks 101B is disposed on the layer stack 101A. In some other embodiments, the one or more layer stacks 101B are disposed on a second surface of the substrate 102 opposite the first surface. In other words, the layer stack 101A and the one or more layer stacks 101B are disposed on both sides of the substrate 102. In one or more embodiments that can be combined with other embodiments described herein, the first layer stack of the layer stacks 101B includes an array of multiple support posts 104B disposed on the cap portion 109A of the encapsulation layer 106A. In other embodiments that can be combined with other embodiments described herein, the array of multiple support posts 104B of the first layer stack of the layer stacks 101B is disposed on a spacer layer (not shown) disposed on the encapsulation layer 106A. In embodiments that include a spacer layer, the spacer layer is operable to provide support for the array of multiple support posts 104B and has a predetermined thickness (e.g., up to about 50 μm) depending on the optical function of the planar optical device 100. In one or more embodiments that can be combined with other embodiments described herein, the encapsulation layer 106A and the spacer layer are formed of different materials. In other embodiments, the cap portion 109A of the encapsulation layer 106A serves the same function as a spacer layer. In embodiments in which the encapsulation layer 106A functions as a spacer layer, the encapsulation layer 106A has a predetermined thickness depending on the optical function of the planar optical device 100.

[0012]

[0018] The array of multiple pillars 104A, 104B includes pillars 104A, 104B having a height h and a lateral distance d. The height h of pillar 104A is defined as the distance from the surface of substrate 102 to cap portion 109A of encapsulation layer 106A. The height h of pillar 104B is defined as the distance from encapsulation layer 106A and / or a spacer layer (not shown) disposed on encapsulation layer 106A to cap portion 109B of encapsulation layer 106B. In some embodiments, the multiple pillars 104A, 104B may be four or more, for example, from 4 to about 10, depending on feature density and wafer size. 6 In some embodiments that can be combined with other embodiments described herein, the cross-section of the struts 104A, 104B is square and / or rectangular, and the lateral distance d of the struts 104A, 104B corresponds to the width of the struts 104A, 104B. In other embodiments that can be combined with other embodiments described herein, the cross-section of the struts 104A, 104B is circular, and the lateral distance d of the struts 104A, 104B corresponds to the diameter of the struts 104A, 104B. The gap g is the distance between adjacent ones of the struts 104A, 104B. In one or more embodiments, each of the arrays of the plurality of struts 104A, 104B has an aspect ratio (g:h) between about 1:1.5 and about 1:10. In other embodiments, the array of the plurality of struts 104A, 104B each has an aspect ratio (g:h) between about 1:1.5 and about 1:2.5. In yet other embodiments, the array of the plurality of struts 104A, 104B each has an aspect ratio (g:h) between about 1:1 and about 1:20.

[0013]

[0019] The lateral distance d and the gap g are less than half the operating wavelength. The operating wavelength corresponds to a wavelength or a range of wavelengths. In some embodiments, the wavelength or range of wavelengths includes one or more wavelengths from the UV range to the near infrared range (e.g., about 300 nm to about 1500 nm). Thus, for example, at a wavelength of 700 nm, the distance d and the gap g are less than 350 nm. In some embodiments, the gap g may be about 100 nm or less. In one or more embodiments that can be combined with other embodiments described herein, the lateral distance d of each strut of the plurality of struts 104A is substantially the same. In other embodiments that can be combined with other embodiments described herein, the lateral distance d of at least one strut is different from the lateral distance d of additional struts of the plurality of struts 104A. In one or more embodiments that can be combined with other embodiments described herein, the gap g of each adjacent strut of the plurality of struts 104A is substantially the same. In other embodiments that can be combined with other embodiments described herein, the gap g of at least one set of adjacent struts is different from the gap g of an additional set of adjacent struts of the plurality of struts 104A. In one or more embodiments that can be combined with other embodiments described herein, the lateral distance d of each adjacent strut of the plurality of struts 104A is greater than the gap g of each adjacent strut of the plurality of struts 104A. In some embodiments that can be combined with other embodiments described herein, the distance d is about 100 nm to about 300 nm, and the gap g is about 30 nm to about 100 nm. In some embodiments that can be combined with other embodiments described herein, the arrangement of the plurality of struts 104B corresponds to or otherwise matches the arrangement of the plurality of struts 104A. In other embodiments that can be combined with other embodiments described herein, the arrangement of the plurality of struts 104B does not correspond to the arrangement of the plurality of struts 104A.

[0014]

[0020] The substrate 102 may be selected to transmit light at the operating wavelength. In some non-limiting embodiments, the substrate 102 is configured to transmit approximately 50%, 60%, 70%, 80%, 90%, 95%, 99% or more of the UV range of the light spectrum. The substrate 102 may be formed of any suitable material, provided that it can adequately transmit light at the operating wavelength and function as a suitable support for at least the array of the plurality of pillars 104A and the encapsulation layer 106A. In some embodiments that can be combined with other embodiments described herein, the material of the substrate 102 has a relatively low refractive index compared to the refractive index of the material used for each of the pillars 104A, 104B. The substrate selection may include substrates of any suitable material, including, but not limited to, semiconductors, doped semiconductors, amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, silicon oxides, polymers, and combinations thereof. In some embodiments that can be combined with other embodiments described herein, the substrate 102 includes a transparent material. The substrate 102 is transparent with an absorption coefficient less than 0.001. Examples may include, but are not limited to, oxides, sulfides, phosphides, tellurides, and combinations thereof. In one example, the substrate 102 comprises a silica (SiO2)-containing material.

[0015]

[0021] The pillars 104A, 104B may include materials including, but not limited to, titanium dioxide (TiO2), zinc oxide (ZnO), tin dioxide (SnO2), aluminum doped zinc oxide (AZO), fluorine doped tin oxide (FTO), cadmium stannate (CTO), zinc stannate (SnZnO3), and silicon-containing materials. The silicon-containing materials may include at least one of silicon nitride (Si3N4) or amorphous silicon (a-Si)-containing materials. The pillars 104A, 104B may have a refractive index of about 1.8 or greater, such as from about 1.8 to about 6, such as from about 1.8 to about 5, such as from about 1.8 to about 4. The struts 104A, 104B may have an absorption coefficient of less than about 0.001, such as from about 0 to about 0.001, such as from about 0 to about 0.001, such as from about 0.00001 to about 0.001, such as from about 0.0001 to about 0.001.

[0016]

[0022] Utilizing the materials, dimensions, and processes described herein for the encapsulation layers 106A, 106B, including the gap filler 108A, 108B compositions corresponding to the gap g, provides a height h of the pillars 104A, 104B of about 1500 nm or less. In some embodiments that can be combined with other embodiments described herein, the height h of the pillars 104A, 104B is about 500 nm or less. In some embodiments that can be combined with other embodiments described herein, the height h of the pillars 104A, 104B is about 300 nm to about 1500 nm. Reducing the height h of the pillars 104A, 104B reduces the thicknesses 110A, 110B of the layer stacks 101A, 101B and the total thickness of the planar optical device 100. The reduced total thickness of the planar optical device 100 increases transmission efficiency due to impedance matching and device symmetry, and reduces manufacturing complexity and cost, compared to the bare optical device.

[0017]

[0023] In some embodiments, which may be combined with other embodiments described herein, the refractive index of the encapsulation layers 106A, 106B is about 1.0 to about 1.5, such as about 1.0 to about 1.45, such as about 1.0 to about 1.4, such as about 1.0 to about 1.3, such as about 1.0 to about 1.2, such as about 1.0 to about 1.1, alternatively about 1.3 to about 1.4, alternatively about 1.25 to about 1.35. In some embodiments, it may be desirable for the refractive index of the encapsulation layers 106A, 106B to approach the refractive index of air (e.g., 1.0) to match the performance of the optical device without the total encapsulant. In some embodiments, which may be combined with other embodiments described herein, the encapsulation layers 106A, 106B have an absorption coefficient of less than about 0.001. In some embodiments that can be combined with other embodiments described herein, the encapsulation layers 106A, 106B are hydrophobic to protect the pillars 104A from external factors (e.g., water, corrosion). In some embodiments that can be combined with other embodiments described herein, the encapsulation layers 106A, 106B are homogenous or uniform and substantially free of grain boundaries. In some embodiments that can be combined with other embodiments described herein, the encapsulation layers 106A, 106B form dense films (e.g., substantially free of voids and nominally porous). In some embodiments that can be combined with other embodiments described herein, the encapsulation layers 106A, 106B and the substrate 102 comprise substantially the same material.

[0018]

[0024] In some embodiments that can be combined with other embodiments described herein, the encapsulation layers 106A, 106B include one of a silica-containing material or a non-silica-containing material, such as a polymer-containing material, such as an organic fluoropolymer material. In some embodiments that can be combined with other embodiments described herein, the encapsulation layers 106A, 106B include an amorphous fluoropolymer. Amorphous fluoropolymers are highly optically transparent compared to semi-crystalline fluoropolymers. In some embodiments that can be combined with other embodiments described herein, the encapsulation layers 106A, 106B can be or include one of the fluoropolymers shown in Figures 1D-1E, such as poly[4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene] (Structure 107A) or perfluoro(3-butenyl vinyl ether) (PBVE) cyclopolymer (Structure 107B). With reference to structure 107A, the value of x can be from about 80 to about 12500, such as from about 120 to about 9000, such as from about 200 to about 5000, such as from about 500 to about 1000, such as about 870, and the value of y can be from about 80 to about 30000, such as from about 300 to about 15000, such as from about 300 to about 9000, such as from about 500 to about 1000, such as about 870. With reference to structure 107B, the value of n can be from about 30 to about 11,000, such as from about 50 to about 2,000, such as from about 100 to about 1,600, such as about 100, alternatively about 800, alternatively about 1,600. In other embodiments, the encapsulating layers 106A, 106B can be or include poly(tetrafluoroethylene-co-2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole). In some embodiments, which can be combined with other embodiments described herein, the encapsulating layers 106A, 106B can be or include a fluoropolymer having one or more crosslinkable alkoxysilane moieties.In some embodiments, which may be combined with other embodiments described herein, the encapsulation layers 106A, 106B may be or include other tetrafluoroethylene copolymers.In some other embodiments, which can be combined with other embodiments described herein, the encapsulation layers 106A, 106B are made of a C6 fluorocarbon, a perfluoropolyether poly-acrylate functional oligomer, 1H,1H,2H,2H-heptadecafluorodecyl methacrylate (HDFDMA), poly(tert-butyl methacrylate-co-glycidyl methacrylate), poly(2,2,3,3,4,4,4-heptafluorobutyl ... Poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate-co-glycidyl methacrylate), Poly(2,2,3,4,4,4-hexafluorobutyl acrylate), Poly(2,2,3,4,4,4-hexafluorobutyl methacrylate-co-glycidyl methacrylate), Poly(1,1,1,3,3,3-hexafluoroisopropyl acrylate), Poly(1,1,1,3,3,3-hexafluoroisopropyl methacrylate), Poly(1,1 ,1,3,3,3-hexafluoroisopropyl methacrylate-co-glycidyl methacrylate), poly(2,2,3,3,3-pentafluoropropyl acrylate), poly(2,2,3,3,3-pentafluoropropyl methacrylate), poly(2,2,3,3,3-pentafluoropropyl methacrylate-co-glycidyl methacrylate), poly(pentafluorostyrene), poly(pentafluorostyrene-co-glycidyl methacrylate), poly(pentafluorostyrene-co-glycidyl The polymer may be or include poly(2,2,3,3-tetrafluoropropyl acrylate), poly(2,2,3,3-tetrafluoropropyl methacrylate), poly(2,2,2-trifluoroethyl acrylate), poly(2,2,2-trifluoroethyl methacrylate-co-glycidyl methacrylate), poly(2,2,2-trifluoroethyl methacrylate-co-glycidyl methacrylate), other similar polymers, or combinations thereof.

[0019]

[0025] In one or more embodiments, the encapsulation layers 106A, 106B can be or include any fluoropolymer material having a refractive index less than about 1.5, such as from about 1 to about 1.5. In one or more embodiments, the encapsulation layers 106A, 106B include a material that is thermally stable up to about 250° C. In some embodiments, which can be combined with other embodiments described herein, the encapsulation layers 106A, 106B can be or include a fluorine-containing material, such as a metal fluoride, e.g., aluminum fluoride (AlF3) and magnesium fluoride (MgF2).

[0020]

[0026] Fluoropolymer-based encapsulation layers 106A, 106B may be advantageous for providing mechanical protection to the nano-posts of planar optical devices with low refractive index (e.g., refractive index less than about 1.5), high transparency (e.g., absorption coefficient less than about 0.001), and hydrophobicity (e.g., water contact angle of about 100° or more). As used herein, the contact angle measured at the solid-liquid interface is the angle between the surface of the liquid and the contact surface of the solid, and the contact angle ranges from 0° for complete wetting to a theoretical upper limit of 180° for insufficient wetting. In addition, fluoropolymer-based total encapsulation may be advantageous for protection of slanted diffraction gratings in waveguide combiners and flexible display technologies. Advantageously, fluoropolymer-based encapsulation layers 106A, 106B may improve the shelf life of planar optical devices. Advantageously, fluoropolymer-based encapsulation layers 106A, 106B, especially cap portions 109A, 109B, may provide mechanical support and spacing to multilayer planar optical devices. Beneficially, the fluoropolymer-based encapsulation layers 106A, 106B can be subjected to a further deposition process (e.g., atomic layer deposition) of a relatively high refractive index material (e.g., TiO2).Optical devices that can benefit from the present disclosure include lenses, beam deflectors, hologram generators, and diffusers.

[0021]

[0027] In some embodiments that can be combined with other embodiments described herein, the encapsulation layers 106A, 106B include a fluoropolymer-based aerogel material. The fluoropolymer-based aerogel material includes nanoscale porosity that provides voids to the encapsulation layers 106A, 106B. In one or more embodiments that can be combined with other embodiments described herein, the fluoropolymer-based aerogel material has a porosity that corresponds to about 95% or more, such as about 95% to about 99% nanoscale voids. The nanoscale porosity of the fluoropolymer-based aerogel material reduces the refractive index of the fluoropolymer. The reduced refractive index reduces the height h of the struts 104A, 104B. The fluoropolymer-based aerogel material is hydrophobic to protect the struts 104A from external factors. In yet other embodiments that can be combined with other embodiments described herein, the encapsulation layers 106A, 106B include a fluoropolymer-based mesoporous coating.

[0022]

[0028] In one or more embodiments that may be combined with other embodiments described herein, the gap filling portion 108A and the cap portion 109A are formed of the same material such that the encapsulation layer 106A has a uniform refractive index. In other embodiments, the gap filling portion 108A and the cap portion 109A are formed of different materials having the same or different refractive indexes. In some embodiments, the refractive index of the gap filling portion 108A is greater than the refractive index of the cap portion 109A. In other embodiments, the refractive index of the gap filling portion 108A is less than the refractive index of the cap portion 109A. In some embodiments, the reduced height h of the pillars 104A can be used when the refractive index of the encapsulation layer 106A has a reduced value in the gap filling portion 108A, the cap portion 109A, or both.

[0023]

[0029] FIG 2 is a diagram of a method 200 for forming the planar optical device 100 shown in FIGS. 3A-3D. In operation 201, an array of posts 104A is formed on a surface of a substrate 102. In one or more embodiments that may be combined with other embodiments described herein, forming the array of posts 104A includes disposing a post material 301 on the surface of the substrate 102 and removing a portion of the post material 301 to form a trench 302. The trench 302 corresponds to the gap g between the posts 104A (including the gap portion 108A of the planar optical device 100), the remaining portion of the post material 301 corresponds to the lateral distance d, and the thickness of the post material 301 corresponds to the height h.

[0024]

[0030] In operation 202, an adhesion promoter 304 is disposed on the plurality of pillars 104A. The adhesion promoter 304 primes the pillars 104A to improve flowability of the encapsulation layer 306A to fill the trench 302. In some embodiments that may be combined with other embodiments described herein, the adhesion promoter 304 comprises a material having a hydrophobic tail group. In such embodiments, bonding of the adhesion promoter 304 to the exposed surfaces of the plurality of pillars 104A leaves the hydrophobic tail groups exposed to improve the surface flowability and gap filling of the encapsulation layer 306A, resulting in a substantially void-free gap filling. In some embodiments that may be combined with other embodiments described herein, the adhesion promoter 304 comprises a fluorosilane material. In some embodiments that can be combined with other embodiments described herein, the adhesion promoter 304 can include one of the materials shown in Figures 4A-4D, such as trichloro(1H,1H,2H,2H-perfluorooctyl)-silane (structure 400A), 1H,1H,2H,2H-perfluorooctyltriethoxysilane (structure 400B), 1H,1H,2H,2H-perfluorodecyltriethoxysilane (structure 400C), or trichloro(3,3,3-trifluoropropyl)-silane (structure 400D). In one or more embodiments that can be combined with other embodiments described herein, the adhesion promoter 304 is conformally disposed on the support posts 104A. In one or more embodiments that can be combined with other embodiments described herein, the adhesion promoter 304 is a monolayer. In some embodiments, the monolayer has a thickness of about 1 nm to about 10 nm. In some embodiments, the exposed surface of the planar optical device 100 is cleaned with a suitable cleaning solution, such as isopropyl alcohol, before the adhesion promoter 304 is disposed thereon. In some embodiments, the adhesion promoter 304 can be deposited by spin coating. In one or more embodiments that can be combined with other embodiments described herein, during the deposition process, the substrate 102 is rotated about the central axis 103 of the substrate 102. In some embodiments, the substrate 102 is rotated at about 200 rpm or more, such as about 500 rpm or more.In some embodiments that can be combined with other embodiments described herein, after deposition of the adhesion promoter 304, the planar optical device 100 is heated and / or maintained at an elevated temperature. In some embodiments, the elevated temperature is higher than room temperature, such as about 23° C. or higher, such as about 50° C. or higher, such as about 80° C. or higher, such as about 110° C. or higher. In some embodiments that can be combined with other embodiments described herein, the spin-coating and heating operations are repeated two or more times. In some embodiments that can be combined with other embodiments described herein, the adhesion promoter 304 is sonicated after heating.

[0025]

[0031] In operation 203, an encapsulation layer 306A corresponding to the encapsulation layer 106A is disposed on the pillars 104A. Disposing the encapsulation layer 306A may include, but is not limited to, spin coating, dip coating, spray coating, vapor drawing, or aerosolization. A gap-filling portion 308A of the encapsulation layer 306A is disposed in the trenches 302 corresponding to the gaps g of the pillars 104A. In some embodiments, the flow and gap-filling of the gap-filling portion 308A is improved by disposing an adhesion promoter 304 on the plurality of pillars 104A before disposing the encapsulation layer 306A. After applying the adhesion promoter 304 to the exposed surfaces of the plurality of pillars 104A, the contact angle of the encapsulation layer 306A on the coating surface of the plurality of pillars 104A is reduced to about 40° or less, such as about 30° or less, such as 20° or less. The cap portion 309A of the encapsulation layer 306A is disposed on and above the plurality of posts 104A and on the gap-fill portion 308A. In some embodiments, the thickness of the cap portion 309A can be varied by adjusting the solution concentration of the encapsulation material. In some embodiments, the solution concentration of the encapsulation material can be about 0.1% v / v to about 10% v / v, such as about 1% v / v to about 5% v / v, such as about 3% v / v. In one or more embodiments that can be combined with other embodiments described herein, the cap portion 309A of the encapsulation layer 306A has a thickness of about 50 nm or more, such as about 50 nm to about 1 cm, such as about 50 nm to about 1 mm, such as about 50 nm to about 100 μm, such as about 50 nm to about 10 μm. In other embodiments that can be combined with other embodiments described herein, the cap portion 309A of the encapsulation layer 306A has a thickness of about 1 μm or less, such as about 50 nm to about 1 μm. In one or more embodiments that can be combined with other embodiments described herein, during the deposition process, the substrate 102 is rotated about the central axis 103 of the substrate 102. In some embodiments, the substrate 102 is rotated at about 1000 rpm or more, such as about 2000 rpm or more, alternatively about 500 rpm to about 6000 rpm.In some embodiments, which may be combined with other embodiments described herein, after deposition of the encapsulation layer 306A, the planar optical device 100 is heated and / or maintained at an elevated temperature (e.g., up to about 275° C. or higher) to facilitate curing of the encapsulation layer 306A. In other embodiments, the encapsulation layer 306A can be cured in air without heating.

[0026]

[0032] Operations 201-203 form a single layer stack planar optical device 100 including layer stack 101A. In operation 204, at least operations 201-203 are repeated at least once to form a multi-stack optical device having layer stack 101A and at least one layer stack 101B. Layer stack 101B includes at least encapsulation layer 306A, an array of multiple support posts 104B, and encapsulation layer 306B. The array of multiple support posts 104B formed via operation 201 is disposed on one of encapsulation layers 306A, and a spacer layer (not shown) is disposed on encapsulation layer 306A.

[0027]

[0033] In summary, the embodiments described herein provide a planar optical device and a method for forming a planar optical device. One or more embodiments of the optical device are single-layer stack planar optical devices including one layer stack. The layer stack includes a first array of a first plurality of posts disposed on a surface of a substrate and a first encapsulation layer. Another embodiment of the optical device is a multi-layer stack optical device including a first layer stack and a second layer stack formed thereon. A second layer stack of the one or more layer stacks is disposed on the first layer stack. The second layer stack includes a second array of a second plurality of posts disposed on one of the first encapsulation layer and a spacer layer disposed on the first encapsulation layer. The materials, dimensions, and processes described herein of the encapsulation layer and the corresponding composition of the gap provide a height h of the posts of about 1500 nm or less, for example about 300 nm to about 1500 nm, for example about 300 nm to about 500 nm. Reducing the height h of the pillars reduces the thickness of the layer stack and reduces the overall thickness of the planar optical device, which, compared to bare optical devices, provides higher transmission efficiency due to impedance matching and device symmetry, and reduces manufacturing complexity and cost.

[0028]

[0034] While the foregoing is directed to embodiments of the present disclosure, other and additional embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the claims that follow.

Claims

1. 1. A substrate having a first array of a first plurality of pillars formed thereon, the first array of the first plurality of pillars comprising: a support post having a height h and a lateral distance d; and a gap g corresponding to a distance between adjacent columns of the first plurality of columns, the gap g having an aspect ratio of the gap g to the height h being between about 1:1 and about 1:20; The substrate comprising: a first adhesion promoter disposed on a first array of the first plurality of struts; a first encapsulation layer disposed on the first adhesion promoter, the first encapsulation layer filling the gaps g between adjacent struts of the first plurality of struts, the first encapsulation layer comprising a fluoropolymer; An apparatus comprising:

2. The device of claim 1 , wherein the first encapsulation layer comprises an amorphous fluoropolymer.

3. 2. The device of claim 1, wherein the first encapsulation layer comprises at least one of poly(4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene) or perfluoro(3-butenyl vinyl ether) (PBVE) cyclopolymer.

4. The device of claim 1 , wherein the first encapsulation layer comprises a tetrafluoroethylene copolymer.

5. The apparatus of claim 1 , wherein the first adhesion promoter comprises a fluorosilane.

6. 2. The apparatus of claim 1, wherein the first adhesion promoter comprises at least one of trichloro(1H,1H,2H,2H-perfluorooctyl)-silane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, or trichloro(3,3,3-trifluoropropyl)-silane.

7. The device of claim 1 , wherein the first adhesion promoter comprises a hydrophobic tail group.

8. 10. The device of claim 1, wherein the first encapsulation layer has a contact angle with the first adhesion promoter material of about 40 degrees or less.

9. a second array of a second plurality of pillars formed on the first encapsulation layer, a support post having a height h and a lateral distance d; and A gap g corresponding to the distance between adjacent columns of the second plurality of columns. a second array of the second plurality of struts, the second array comprising: an aspect ratio of the gap g to the height h between about 1:1 and about 1:20; a second adhesion promoter disposed on a second array of the second plurality of struts; a second encapsulation layer disposed on the second adhesion promoter, the second encapsulation layer filling the gaps g between adjacent struts of the second plurality of struts, the second encapsulation layer comprising a fluoropolymer; The apparatus of claim 1 further comprising:

10. forming a first array of a first plurality of pillars on a surface of a substrate, the first array of the first plurality of pillars comprising: a support post having a height h and a lateral distance d; and a gap g corresponding to a distance between adjacent columns of the first plurality of columns, the gap g having an aspect ratio of the gap g to the height h being between about 1:1 and about 1:20; forming a first array of the first plurality of struts, the first array comprising: disposing a first adhesion promoter material on a first array of the first plurality of struts; disposing a first encapsulation layer over the first adhesion promoter material, the first encapsulation layer filling the gaps g between adjacent struts of the first plurality of struts, the first encapsulation layer comprising a fluoropolymer; The method includes:

11. depositing the first adhesion promoter material by spin coating; baking the first adhesion promoter at an elevated temperature; Repeating the spin coating and baking operations two or more times. The method of claim 10 further comprising:

12. The method of claim 11 , wherein the first adhesion promoter is conformally deposited.

13. The method of claim 10 , further comprising depositing the first encapsulation layer by at least one of spin coating, dip coating, spray coating, or vapor drawing.

14. forming a second array of a second plurality of pillars on a surface of the first encapsulation layer, the second array of the second plurality of pillars comprising: a support post having a height h and a lateral distance d; and a gap g corresponding to a distance between adjacent columns of the second plurality of columns, the gap g having an aspect ratio of the gap g to the height h being between about 1:1 and about 1:20; forming a second array of the second plurality of struts, the second array comprising: disposing a second adhesion promoter on a second array of the second plurality of struts; disposing a second encapsulation layer over the second adhesion promoter material, the second encapsulation layer filling the gaps g between adjacent struts of the second plurality of struts, the second encapsulation layer comprising a fluoropolymer; The method of claim 10 further comprising:

15. The method of claim 10 , further comprising disposing a cap portion of the first encapsulation layer over the first plurality of pillars.

16. 1. A substrate having a first array of a first plurality of pillars formed thereon, the first array of the first plurality of pillars comprising: a post having a first surface facing away from the substrate and one or more side surfaces facing an adjacent post; and A trench formed between adjacent columns The substrate comprising: a first adhesion promoter disposed on the first surface and on the one or more side surfaces of the strut, the first adhesion promoter comprising a fluorosilane; a first encapsulation layer disposed over the first adhesion promoter material, the first encapsulation layer filling the trenches between adjacent pillars of the first plurality of pillars, the first encapsulation layer comprising an amorphous fluoropolymer; An apparatus comprising:

17. 17. The device of claim 16, wherein the first encapsulation layer comprises at least one of poly(4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene) or perfluoro(3-butenyl vinyl ether) (PBVE) cyclopolymer.

18. 17. The apparatus of claim 16, wherein the first adhesion promoter comprises at least one of trichloro(1H,1H,2H,2H-perfluorooctyl)-silane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, or trichloro(3,3,3-trifluoropropyl)-silane.

19. 17. The apparatus of claim 16, wherein the pillars have a height h, the trench has a width corresponding to a distance between adjacent pillars of the first plurality of pillars, and an aspect ratio of the trench width to the height h is between about 1:1 and about 1:

20.

20. The apparatus of claim 16 , wherein a cap portion of the first encapsulation layer is disposed over the first surface of the first plurality of posts.

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