Air gap packaging of nanostructured optical devices

Abstract

Embodiments described herein relate to encapsulated optical devices and methods of forming optical devices with controllable air gap encapsulation. In one embodiment, a plurality of openings are formed in a support layer around a plurality of optical device structures to create a high index contrast between the optical device structures, the support layer, and the openings. In another embodiment, a sacrificial material is disposed between the optical device structures and a subsequently disposed encapsulation layer is disposed on the optical device structures. The sacrificial material is removed, thereby forming a space defined by the encapsulation layer, the substrate, and each optical device structure. In yet another embodiment, an encapsulation layer is disposed over the optical device structures, thereby forming a space defined by the encapsulation layer, the substrate, and each optical device structure.

Description

background Technical Field

[0002] Embodiments of this disclosure generally relate to optical devices. More specifically, the embodiments described herein relate to packaged optical devices and methods for forming optical devices with controllable air gap packages. Background Technology

[0004] Nanostructured optical devices comprise arrangements of structures with in-plane dimensions less than half the design wavelength of light. For example, the structures can have submicron dimensions, such as nanometer-sized dimensions. Optical devices including waveguide combiners (such as augmented reality waveguides) or flat optical devices (such as metasurfaces) can consist of single or multiple layers of such structures. Optical devices incorporating such structures require encapsulation for mechanical protection. Encapsulation materials can also be used as spacers between successive layers of a multilayer arrangement of optical structures. Furthermore, the optical properties of the encapsulation material affect the performance of the optical device. For example, a high contrast between the refractive index of the material of the structure and the refractive index of the materials between the structures is desirable for improving the performance of the optical device. Air, with a refractive index of about 1.0, is a desirable material to be located between the structures to improve the optical properties of the optical device. Therefore, encapsulated optical devices and methods for forming optical devices with controllable air gap encapsulation are needed in the art. Summary of the Invention

[0005] In one embodiment, an optical device is provided. The optical device includes a plurality of optical device structures disposed in or on a substrate. Each optical device structure has a critical dimension of less than 2 micrometers corresponding to the width or diameter of its cross-section and a structural material having an optical device refractive index between about 1.7 and about 4.0. The plurality of optical device structures also include a support layer surrounding each of the plurality of optical device structures. The support layer includes a support material having a support layer refractive index of about 1.0 to 1.6. A plurality of openings are disposed through the support layer. Each of the plurality of openings is adjacent to two or more of the plurality of structures. The plurality of openings have a refractive index of about 1.0.

[0006] In another embodiment, a method is provided. The method includes disposing a support layer on a substrate and between a plurality of optical device structures. The support layer is coplanar with a first hard mask layer disposed on the plurality of optical device structures. The method further includes disposing a second hard mask layer over the support layer and the first hard mask layer, and disposing a resist layer over the second hard mask layer. The method further includes exposing a pattern in the resist layer. The pattern exposes a portion of the second hard mask layer, the pattern corresponding to an opening to be formed in the support layer. The method further includes etching the exposed portion of the second hard mask layer. The method further includes etching the exposed portion of the support layer to form an opening through the support layer. The method further includes removing the first hard mask layer and the second hard mask layer.

[0007] In another embodiment, a method is provided. The method includes disposing a sacrificial material on a substrate and between optical device structures of a plurality of optical device structures. The plurality of optical device structures include a critical dimension of less than 2 micrometers corresponding to the width or diameter of the cross-section of the optical device structure. The plurality of optical device structures include a structural material having an optical device refractive index between about 1.7 and about 4.0. The method further includes disposing an encapsulation layer over the plurality of optical device structures and the sacrificial material. The encapsulation layer includes an encapsulation material having an encapsulation refractive index of about 1.0 to about 1.6. The method further includes removing the sacrificial material using an etching process. The etching process includes etching the sacrificial material at a higher rate than that of the encapsulation layer, wherein the encapsulation layer, the substrate, and each optical device structure of the plurality of optical device structures define a space therebetween. The space has a refractive index of about 1.0.

[0008] In another embodiment, an optical device is provided. The optical device includes a plurality of optical device structures disposed in or on a substrate. The plurality of optical device structures include a critical dimension of less than 2 micrometers corresponding to the width or diameter of the cross-section of the optical device structure. The plurality of optical device structures include a structural material having an optical device refractive index between about 1.7 and about 4.0. The optical device further includes an encapsulation layer having an encapsulation refractive index of about 1.0 to about 1.6. The encapsulation layer includes a first portion of a first material. The first portion surrounds the top surface of the plurality of optical device structures. The first portion of the first material includes gaps defined between the first portions. The encapsulation layer further includes a second portion of a second material disposed at least in the gaps, wherein the encapsulation layer, the substrate, and each of the plurality of optical device structures define a space therebetween. The space has a refractive index of about 1.0.

[0009] In another embodiment, a method is provided. The method includes disposing a first portion of an encapsulation layer. The first portion of the encapsulation layer surrounds the top surface of a plurality of optical device structures. The plurality of optical device structures are disposed in or on a substrate and the plurality of optical device structures include a critical dimension of less than 2 micrometers corresponding to the width or diameter of the cross-section of the optical device structure. The plurality of optical device structures include a structural material having an optical device refractive index between about 1.7 and about 4.0. The first portion of the encapsulation layer includes a first material having a first refractive index of about 1.0 to about 1.6. The first portion of the encapsulation layer includes gaps defined between the first portions of the encapsulation layer. The method further includes disposing a second portion of the encapsulation layer at least in the gaps between the first portions of the encapsulation layer. The second portion includes a second material having a second refractive index of about 1.0 to about 1.6. The first and second portions, the substrate, and the plurality of optical device structures define a space therebetween, and this space has a refractive index of about 1.0. Attached Figure Description

[0010] To gain a more detailed understanding of the manner in which the features of this disclosure are described above, a more specific description of the disclosure briefly outlined above can be obtained by referring to the embodiments, some of which are illustrated in the accompanying drawings. However, it will be noted that the drawings illustrate only exemplary embodiments and are therefore not intended to limit the scope of the disclosure, and other equivalent embodiments are permissible.

[0011] Figure 1A This is a schematic top view of an optical device according to the embodiments described herein.

[0012] Figure 1B This is a schematic cross-sectional view of an optical device according to an embodiment described herein.

[0013] Figure 2 This is a flowchart of a method for forming an optical device according to the embodiments described herein.

[0014] Figures 3A to 3J This is a schematic perspective view of a substrate during operation of a method for forming an optical device according to an embodiment described herein.

[0015] Figure 4 This is a flowchart of a method for forming an optical device according to the embodiments described herein.

[0016] Figures 5A to 5E This is a schematic cross-sectional view of a substrate during operation of a method for forming an optical device according to an embodiment described herein.

[0017] Figure 6 This is a flowchart of a method for forming an optical device according to the embodiments described herein.

[0018] Figures 7A to 7C This is a schematic cross-sectional view of a substrate during operation of a method for forming an optical device according to an embodiment described herein.

[0019] For ease of understanding, the same reference numerals have been used to identify common elements in the figures where possible. It is contemplated that elements and features of one embodiment may be advantageously incorporated into other embodiments without further description. Detailed Implementation

[0020] Embodiments of this disclosure generally relate to optical devices. More specifically, the embodiments described herein relate to optical devices and methods of forming optical devices.

[0021] One embodiment includes multiple optical device structures disposed in or on a substrate. Each optical device structure has a critical dimension of less than 2 micrometers corresponding to the width or diameter of its cross-section. The multiple optical device structures include a structural material having an optical device refractive index between about 1.7 and about 4.0. The multiple optical device structures also include a support layer surrounding each of the multiple optical device structures. The support layer includes a support material having a support layer refractive index of about 1.0 to 1.6. Multiple openings are disposed through the support layer. Each of the multiple openings is adjacent to two or more of the multiple structures. The multiple openings have a refractive index of about 1.0. A refractive index contrast is created between the optical device structures, the support layer, and the openings.

[0022] In another embodiment, a sacrificial material is disposed between the optical device structures, and subsequently, an encapsulation layer is disposed on the optical device structures and the sacrificial material. The sacrificial material is removed, thereby forming a space defined by the encapsulation layer, the substrate, and each optical device structure. Therefore, there is a contrast between the refractive index of the structural material, the refractive index of the encapsulation material, and the refractive index of the space including air having a refractive index of 1.0.

[0023] In another embodiment, a first portion and a second portion of the encapsulation layer are disposed above the optical device structure, thereby forming a space defined by the encapsulation layer, the substrate, and each optical device structure. Therefore, there is a refractive index contrast between the space, the optical device structure, the encapsulation layer, and the substrate.

[0024] Figure 1A This is a schematic top view of the optical device 100 and Figure 1BThis is a schematic cross-section of the optical device 100. In some embodiments that can be combined with other embodiments described herein, the optical device 100 is a planar optical device, such as a metasurface. In other embodiments that can be combined with other embodiments described herein, the optical device 100 is a waveguide combiner, such as an augmented reality waveguide combiner. The embodiments described herein provide an optical device 100 comprising a plurality of optical device structures 102 disposed in or on a surface 103 of a substrate 104. In one embodiment that can be combined with other embodiments described herein, the plurality of optical device structures 102 are nanostructures having submicron dimensions (e.g., nanometer-sized dimensions). In another embodiment that can be combined with other embodiments described herein, the plurality of optical device structures 102 are subwavelength structures.

[0025] Optical device structure 102 has a critical dimension 106, for example, one of the width or diameter of optical device structure 102. In one embodiment that may be combined with other embodiments described herein, the critical dimension 106 is less than 2 micrometers (μm). In one embodiment that may be combined with other embodiments described herein, the critical dimension 106 is from about 100 nanometers (nm) to about 1000 nm. Various optical device structures include structural materials having an optical device refractive index between about 1.7 and about 4.0.

[0026] although Figure 1A and Figure 1B The optical device structure 102 is depicted as having a circular cross-section. The cross-section of the optical device structure 102 may have other shapes, including but not limited to rectangular, triangular, elliptical, regular polygonal, irregular polygonal, and / or irregularly shaped cross-sections. In some embodiments that can be combined with other embodiments described herein, the cross-section of the optical device structure 102 of the optical device 100 has a cross-section of a different shape. In other embodiments that can be combined with other embodiments described herein, the cross-section of the optical device structure 102 of the optical device 100 has a cross-section of substantially the same shape. In some embodiments that can be combined with other embodiments described herein, at least one of the critical dimensions 106 of the optical device structure 102 may differ from other critical dimensions 106 of the optical device structure 102. In other embodiments that can be combined with other embodiments described herein, the critical dimensions 106 of the optical device structure 102 are the same.

[0027] The substrate 104 may also be selected to transmit an appropriate amount of light of a desired wavelength or wavelength range, such as one or more wavelengths from about 100 μm to about 8000 μm. Without limitation, in some embodiments, the substrate 104 is configured such that the infrared to ultraviolet region of the transmission spectrum of the substrate 104 is greater than or equal to about 50% to about 100%. The substrate 104 may be formed of any suitable material, provided that the substrate 104 can sufficiently transmit light of the desired wavelength or wavelength range and can serve as adequate support for the optical device 100 described herein. In some embodiments that may be combined with other embodiments described herein, the material of the substrate 104 has a relatively low refractive index compared to the refractive index of the structural materials of the plurality of optical device structures 102. Substrate selection may include substrates of any suitable material, including but not limited to amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, silicon oxide, silicon carbide, polymers, or combinations thereof. In some embodiments that may be combined with other embodiments described herein, the substrate 104 comprises a transparent material. In one embodiment that may be combined with other embodiments described herein, the substrate 104 is transparent and has an absorption coefficient less than 0.001. Suitable examples may include oxides, sulfides, phosphides, tellurides, or combinations thereof. In one example, substrate 104 includes silicon (Si), silicon dioxide (SiO2), silicon nitride (SiN), germanium (Ge), silicon germanium (SiGe), InP, GaAs, GaN, fused silica, quartz, sapphire, or a high-refractive-index transparent material, such as high-refractive-index glass.

[0028] In one embodiment that may be combined with other embodiments described herein, the structural material of the optical device structure 102 includes a non-conductive material, such as a dielectric material. The dielectric material may include amorphous, polycrystalline, or crystalline materials. Examples of dielectric materials include, but are not limited to, silicon-containing materials, such as Si, silicon nitride (Si3N4), silicon oxynitride, or silicon dioxide. The silicon may be crystalline silicon, polycrystalline silicon, or amorphous silicon (a-Si). In another embodiment that may be combined with other embodiments described herein, the structural material of the optical device structure 102 includes, but is not limited to, materials containing titanium dioxide (TiO2), zinc oxide (ZnO), tin dioxide (SnO2), aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), cadmium stannate (Cd2SnO4), cadmium stannate (tin oxide) (CTO), zinc stannate (SnZnO3), tantalum oxide (Ta2O5), vanadium oxide (IV) (VO2O3), etc. xMaterials containing niobium oxide (Nb2O5) or niobium oxide (Nb2O5). In yet another embodiment, which may be combined with other embodiments described herein, the material of the optical device structure 102 includes a nanoimprint resist material. Examples of nanoimprint resist materials include, but are not limited to, at least one of the following: spin-on glass (SOG), flowable SOG, organic, inorganic, and mixed (organic and inorganic) nanoimprintable materials containing at least one of the following: silicon carbide (SiOC), TiO2, silicon dioxide (SiO2), vanadium oxide (IV) (VOC). x Materials, combinations thereof, or other suitable materials, including alumina (Al2O3), indium tin oxide (ITO), ZnO, tantalum oxide (Ta2O5), silicon nitride (Si3N4), titanium nitride (TiN), zirconium dioxide (ZrO2).

[0029] In one embodiment that may be combined with other embodiments described herein, the optical device structure 102 may be formed by one of the following: ion beam etching, reactive ion etching, electron beam (e-beam) etching, wet etching, nanoimprint lithography (NIL), or a combination thereof.

[0030] Multiple optical device structures 102 are surrounded by a support layer 110. The support layer 110 provides mechanical support for the multiple optical device structures 102. The mechanical support of the multiple optical device structures 102 allows for the stacking of additional layers of optical device structures 102. The support layer 110 comprises a support material having a refractive index of about 1.0 to about 1.5. In one embodiment that can be combined with other embodiments described herein, the support material includes, but is not limited to, SiO2, low dielectric constant, SiOC, SiCONH, borophosphosilicate glass (BPSG), phosphosilicate glass (PSG), or Si3N4 material. The support layer 110 is disposed in gaps 114 between adjacent optical device structures 102. In some embodiments that can be combined with other embodiments described herein, two or more gaps 114 are different from each other. In other embodiments that can be combined with other embodiments described herein, the gaps 114 between the multiple optical device structures 102 are equal or substantially equal. The support layer 110 has a plurality of openings 112 disposed through the support layer 110. Each of the plurality of openings 112 has a critical dimension 108 corresponding to the width or diameter of the opening 112. The critical dimension 108 may be from about 0.1 nm to about 4000 nm. In some embodiments that may be combined with other embodiments described herein, at least one of the critical dimensions 108 of the opening 112 may be different from the critical dimensions of the other openings 112. In other embodiments that may be combined with other embodiments described herein, the critical dimension 108 of the opening 112 is the same. The support layer 110 surrounding the optical device structure 102 has a thickness 126. The thickness 126 may be from about 0.1 nm to about 1000 nm.

[0031] The support layer 110 has a support layer height 118. In one embodiment, which may be combined with other embodiments described herein, the plurality of optical device structures 102 have a structural height 116 coplanar with the support layer height 118. In another embodiment, which may be combined with other embodiments described herein, the structural height 116 is not equal to the support layer height 118. In one embodiment, which may be combined with other embodiments described herein, the support layer 110 may be disposed above the top surface 124 of the plurality of optical device structures 102. In another embodiment, which may be combined with other embodiments described herein, such as... Figure 1B As shown, the support layer 110 does not contact the top surface 124 of the plurality of optical device structures 102. In yet another embodiment, which may be combined with other embodiments described herein, the support layer 110 may be disposed above the top surface 124 of the plurality of optical device structures 102 and above the plurality of openings 112.

[0032] A large contrast in refractive index is desired between the structural materials of the multiple optical device structures 102 and the surrounding structures, including the substrate 104, the support material of the support layer 110, and the air in the multiple openings 112. Therefore, it is desirable to form the multiple openings 112, which include air with a refractive index of approximately 1.0, such that a refractive index contrast exists between the structural materials and the multiple openings 112. Increasing the contrast in refractive index of the materials forming the optical device 100 described herein allows for the use of materials with reduced thickness and a reduction in the thickness of the optical device 100.

[0033] Figure 2 Is formed as Figures 3A to 3J A flowchart of the method 200 of the optical device 100 shown. Figures 3A to 3J This is a schematic perspective view of a portion 301 of the substrate 104 during method 200. In one embodiment, which may be combined with other embodiments described herein, portion 301 may correspond to a portion or the entire surface of the substrate 104 of the optical device 100. In another embodiment, which may be combined with other embodiments described herein, portion 301 may correspond to a unit cell of the optical device 100.

[0034] At operation 201, such as Figures 3A to 3C As shown, a support layer 110 is disposed on the surface 103 of a substrate and between a plurality of optical device structures 102. The surface 103 of the substrate 104 has a plurality of optical device structures 102 disposed thereon. Prior to operation 201, a first hard mask layer 302 is disposed over each of the plurality of optical device structures 102. The support layer 110 may be deposited by one or more of the following processes: chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), multi-beam epitaxy (MBE), ion-beam-assisted deposition (IBAD), epitaxy, spin-on glass (SoG) or spin-on-coat (SoC) processing, or any other suitable processing. In one embodiment that may be combined with other embodiments described herein, at operation 201, as Figure 3B As shown, the support layer 110 is conformally fitted to the optical device structure 102. For example... Figure 3C As shown, the support layer 110 can be planarized such that the support layer 110 is coplanar with the first hard mask layer 302. The support layer 110 can be planarized by etching or chemical mechanical polishing (CMP).

[0035] At operation 202, such as Figure 3DAs shown, a second hard mask layer 304 is disposed above the support layer 110 and the first hard mask layer 302. In one embodiment, which may be combined with other embodiments described herein, the first hard mask layer 302 and the second hard mask layer 304 include hard mask materials, including but not limited to silicon nitride (SiN), SiO, low dielectric constants, SiOC, SiCONH, TaO, dielectrics, metal alloys (such as TiN), combinations thereof, or other suitable materials.

[0036] At operation 203, such as Figure 3E As shown, a resist layer 306 is disposed above the second hard mask layer 304. In one embodiment, which may be combined with other embodiments described herein, the resist layer 306 is a three-layer stack comprising an organic planarization layer, an anti-reflective coating, and a photoresist layer. The organic planarization layer is disposed above the second hard mask layer 304, the anti-reflective coating is disposed above the organic planarization layer, and the photoresist layer is disposed above the anti-reflective coating.

[0037] At operation 204, such as Figure 3F As shown, pattern 308 is exposed in resist layer 306. Pattern 308 exposes the exposed portion 305 of the second hard mask layer 304. The exposed portion 305 can be accessed through pattern 308 formed in resist layer 306. In one embodiment, which can be combined with other embodiments described herein, pattern 308 is exposed using photolithography. In another embodiment, which can be combined with other embodiments described herein, resist layer 306 is imprinted in NIL processing. Pattern 308 corresponds to the pattern of two or more plurality of openings 112 that will be formed adjacent to optical device structure 102 in support layer 110.

[0038] At operation 205, the exposed portion 305 of the second hard mask layer 304 is etched. In one embodiment, which can be combined with other embodiments described herein, the resist layer 306 may be removed during operation 205 as the exposed portion 305 is etched. Figure 3G As shown, when the exposed portion 305 of the second hard mask layer 304 is removed, the exposed portion 310 of the support layer 110 is formed. In one embodiment, which can be combined with other embodiments described herein, the exposed portion 305 of the second hard mask layer 304 is removed via ashing, isotropic wet bench cleanstrip, reactive-ion-ech (RIE), or anisotropic stripping. The exposed portion 310 of the support layer 110 corresponds to a plurality of openings 112 in the optical device pattern of the support layer 110.

[0039] At operation 206, such as Figure 3H As shown, the exposed portion 310 of the support layer 110 is etched. The support layer 110 undergoes a wet etching process to form openings 312 of a plurality of openings 312. In one embodiment, which may be combined with other embodiments described herein, as the exposed portion 310 is etched, the resist layer 306 may be removed during operation 205. At operation 207, as... Figure 3I As shown, the second hard mask layer 304 and the first hard mask layer 302 are removed.

[0040] In one embodiment that can be combined with other embodiments described herein, such as Figure 3J As shown, the openings 312 of the plurality of openings 112 can be enlarged. Enlarging the openings 312 increases the critical size 108. The openings 312 are enlarged by at least one of wet etching or SRP processing. Enlarging the openings 312 improves the refractive index contrast between the openings 312 and the structural materials of the plurality of optical device structures 102. The openings 312 containing air have a refractive index of about 1.0 and the structural materials have a refractive index between about 1.7 and about 4.0. Therefore, there is a contrast in the refractive indices of the structural materials, the support material of the support layer 110, and the openings. In one embodiment, the contrast between the refractive index of the structural materials and the refractive index of the support materials is about 1.2 to about 3.8.

[0041] Figure 4 This is a flowchart of the method 400 for forming the optical device 500. Figures 5A to 5E This is a schematic cross-sectional view of a portion 501 of the substrate 104 during method 400. In one embodiment, which may be combined with other embodiments described herein, portion 501 may correspond to a portion or the entire surface of the substrate 104 of the optical device 500 having a plurality of optical device structures 102 formed thereon.

[0042] At operation 401, such as Figure 5A As shown, sacrificial material 502 is disposed on the surface 103 of substrate 104 and between the optical device structures 102. During operation 401, sacrificial material 502 is disposed in gaps 114. Gap 114 is disposed between each optical device structure 102. In some embodiments that can be combined with other embodiments described herein, two or more gaps 114 are different from each other. In other embodiments that can be combined with other embodiments described herein, two or more gaps 114 between the multiple optical device structures 102 are equal or substantially equal.

[0043] In one embodiment that can be combined with other embodiments described herein, the sacrificial material 502 is deposited via CVD, hot-wire CVD (HWCVD), PECVD, inductively coupled plasma CVD (ICPCVD), FCVD, ALD, MBE, PVD, SoG, SoC, or ion beam assisted deposition (IBAD). Multiple optical device structures 102 include structural materials having an optical device refractive index between about 1.7 and about 4.0. Multiple optical device structures 102 have a critical dimension 106 corresponding to the width or diameter of the cross-section of the optical device structure 102. In one embodiment that can be combined with other embodiments described herein, depending on the cross-section of the optical device structure 102, the critical dimension 106 is less than 2 μm and corresponds to the width or diameter of the optical device structure 102. In one embodiment that can be combined with other embodiments described herein, the critical dimension 106 is from about 100 nanometers (nm) to about 1000 nm.

[0044] At operation 402, such as Figure 5B As shown, an encapsulation layer 504 is disposed above a plurality of optical device structures 102 and a sacrificial material 502. The encapsulation layer 504 comprises an encapsulation material having an encapsulation refractive index between about 1.0 and about 1.6. The encapsulation layer 504 is a mechanically robust layer used to assist assembly and protect the optical device structures 102 from environmental exposure. Furthermore, the encapsulation layer 504 may improve the optical performance of the optical device 500 or other aspects of the optical device 500. Figure 5C As shown, in one embodiment that can be combined with other embodiments described herein, a plurality of openings 506 are formed to extend through the encapsulation layer 504 to the gap 114. The plurality of openings 506 provide openings for removing the sacrificial material 502.

[0045] At operation 403, such as Figure 5D As shown, sacrificial material 502 is selectively removed from gap 114 at a higher rate than that for removing encapsulation layer 504. In one embodiment, which may be combined with other embodiments described herein, the sacrificial material is removed by wet etching, isotropic wet stripping, RIE, or anisotropic stripping. In another embodiment, which may be combined with other embodiments described herein, the sacrificial material is removed via thermal annealing.

[0046] like Figure 5D and Figure 5E As shown, the encapsulation layer 504, the substrate 104, and each of the plurality of optical device structures 102 define a space 508. The space 508, including the air disposed therein, has a refractive index of approximately 1.0. Therefore, there is a contrast between the refractive index of the structural material, the refractive index of the encapsulation material, and the refractive index of air having a refractive index of 1.0. Figure 5E As shown, in an embodiment where the sacrificial material 502 is exposed to the etchant using multiple openings 506, the multiple openings 506 are filled with material after the sacrificial material 502 is removed.

[0047] In one embodiment that can be combined with other embodiments described herein, a second layer of the optical device structure 102 may be formed on the encapsulation layer 504 once the optical device structure 102 has been encapsulated by the encapsulation layer 504. For example, after the fabrication of an additional optical device structure, an additional optical device structure may be formed on the encapsulation layer 504, such that method 400 can be repeated to form a multilayer optical device 500.

[0048] Figure 6 This is a flowchart of a method 600 for forming an optical device 700. Figures 7A to 7C This is a schematic cross-sectional view of a portion 701 of the substrate 104 during method 600. In one embodiment, which may be combined with other embodiments described herein, portion 701 may correspond to a portion or the entire surface of the substrate 104 of the optical device 700 having a plurality of optical device structures 102 formed thereon.

[0049] At operation 601, such as Figure 7A As shown, a first portion 702 of an encapsulation layer 704 is disposed on the top surface 710 of a plurality of optical device structures 102. The first portion 702 of the encapsulation layer 704 surrounds the top surface 710 of the plurality of optical device structures 102. The first portion 702 of the encapsulation layer 704 comprises an encapsulation material having a first refractive index of about 1.0 to about 1.6. In one embodiment, which may be combined with other embodiments described herein, the first portion 702 is deposited using high-density plasma deposition. The first portion 702 of the encapsulation layer 704 may conform to the top surface 710 of the plurality of optical device structures 102.

[0050] The first portion 702 may include, but is not limited to, SiN, low dielectric constant, SiOC, SiCONH, SiO, PSG, BPSG, TaO, TiN materials, combinations thereof, or other suitable materials. The first portion 702 may be disposed via CVD, FCVD, ALD, MBE, PVD, SoG, SoC, epitaxy, or IBAD. Multiple optical device structures 102 are disposed on the surface 103 of the substrate 104. The multiple optical device structures 102 include structural materials having a refractive index between about 1.7 and about 4.0. In one embodiment that may be combined with other embodiments described herein, depending on the cross-section of the optical device structure 102, the critical dimension 106 is less than 2 μm and corresponds to the width or diameter of the optical device structure 102. In one embodiment that may be combined with other embodiments described herein, the critical dimension 106 is from about 100 nm to about 1000 nm. In some embodiments that may be combined with other embodiments described herein, a gap 114 is disposed between each optical device structure 102. A gap 712 is also disposed between adjacent first portions 702 of the encapsulation layer 704. In some embodiments that can be combined with other embodiments described herein, two or more gaps 114, 712 are different from each other. In other embodiments that can be combined with other embodiments described herein, two or more gaps 114, 712 between a plurality of optical device structures 102 are equal or substantially equal.

[0051] At operation 602, such as Figure 7B As shown, a second portion 706 of the encapsulation layer 704 is disposed at least in the gap 712 of the first portion 702 of the encapsulation layer 704. The second portion 706 of the encapsulation layer 704 includes an encapsulation material having a second refractive index of about 1.0 to about 1.6. In one embodiment, which may be combined with other embodiments described herein, the second portion 706 is deposited using atomic layer deposition. The encapsulation layer 704 including the first portion 702 and the second portion 706, the substrate 104, and each of the plurality of optical device structures 102 define a space 708. The space has a refractive index of about 1.0. Therefore, there is a contrast between the refractive index of the structural material, the first and second refractive indices of the encapsulation material, and the refractive index of the space 708.

[0052] like Figure 7C As shown, in one embodiment that can be combined with other embodiments described herein, the first portion 702 and the second portion 706 of the encapsulation layer 704 become coplanar with each other via chemical mechanical polishing (CMP) or refining through an RIE process. CMP or RIE processes can also thin the encapsulation layer 704.

[0053] In one embodiment that can be combined with other embodiments described herein, once the optical device structure 102 has been encapsulated by the encapsulation layer 704, a second layer of the optical device structure 102 may be formed on the encapsulation layer 704. For example, after fabricating an additional optical device structure, an additional optical device structure may be formed on the encapsulation layer 704, such that method 600 can be repeated to form a multilayer optical device 700.

[0054] In summary, this paper describes a packaged optical device and a method for forming an optical device with a controllable air gap package. In one embodiment, multiple openings are formed in a support layer around multiple optical device structures to create a high refractive index contrast between the optical device structures, the support layer, and the openings. In another embodiment, a sacrificial material is disposed between the optical device structures, and subsequently, a package layer is disposed on the optical device structures. The sacrificial material is removed, thereby forming a space defined by the package layer, the substrate, and each optical device structure. Thus, a high refractive index contrast is created between the space, the optical device structures, the package layer, and the substrate. In yet another embodiment, the package layer is disposed above the optical device structures, thereby forming a space defined by the package layer, the substrate, and each optical device structure. Thus, a high refractive index contrast is created between the space, the optical device structures, the package layer, and the substrate.

[0055] Although the foregoing provides examples of this disclosure, other and further examples of this disclosure may be devised without departing from the essential scope of this disclosure, and the scope of this disclosure is defined by the appended claims.

Claims

1. An optical device comprising: Multiple optical device structures are disposed in or on a substrate, each of the multiple optical device structures comprising: A critical dimension of less than 2 micrometers, the critical dimension corresponding to the width or diameter of the cross-section of each structure; as well as Structural material having an optical device refractive index between about 1.7 and about 4.0; as well as A support layer, surrounding each of the plurality of optical device structures, provides mechanical support for the plurality of optical device structures, the support layer comprising: A support material having a support layer refractive index of about 1.0 to about 1.5; and Multiple openings are provided through the support layer, each of the multiple openings being adjacent to two or more optical device structures, the multiple openings having a refractive index of about 1.

0.

2. The optical device according to claim 1, wherein the plurality of optical device structures have a structural height and the support layer has a support layer height, the support layer height being greater than the structural height.

3. The optical device according to claim 1, wherein the plurality of optical device structures have a structural height and the support layer has a support layer height, the support layer height being equal to the structural height.

4. The optical device according to claim 1, wherein the optical device structure comprises one or more of the following: titanium dioxide (TiO2), zinc oxide (ZnO), tin dioxide (SnO2), niobium oxide (Nb2O5), aluminum-doped zinc oxide, titanium nitride (TiN), zirconium dioxide (ZrO2), indium tin oxide, tantalum pentoxide (Ta2O5), fluorine-doped tin oxide, vanadium oxide (IV), aluminum oxide (Al2O3), cadmium stannate (Cd2SnO4), zinc stannate (SnZnO3), silicon, silicon nitride (Si3N4), silicon oxycarbonate (SiOC), silicon oxynitride (SiON), and silicon dioxide (SiO2).

5. A method for forming an optical device, comprising the following steps: A support layer is disposed on a substrate and between multiple optical device structures, the support layer being coplanar with a first hard mask layer disposed on the multiple optical device structures; A second hard mask layer is disposed above the support layer and the first hard mask layer; A resist layer is disposed above the second hard mask layer; The pattern in the resist layer is exposed, the pattern exposing an exposed portion of the second hard mask layer, the pattern corresponding to an opening to be formed in the support layer; Etch the exposed portion of the second hard mask layer; Etch the exposed portion of the support layer to form the opening through the support layer; as well as Remove the first hard mask layer and the second hard mask layer. The opening comprises air having a refractive index of about 1.0, the plurality of optical device structures comprise a structural material having an optical device refractive index between about 1.7 and about 4.0, and the support layer comprises a support material having a support layer refractive index of about 1.0 to about 1.

6.

6. The method according to claim 5, wherein the resist layer is a three-layer stack comprising an organic planarization layer, an anti-reflective coating, and a photoresist layer.

7. The method of claim 5, wherein the step of disposing the support layer on the substrate and between the plurality of optical device structures further comprises the step of: etching the support layer to be coplanar with the first hard mask layer.

8. The method of claim 5, further comprising the step of: etching the opening to enlarge the width or diameter of the opening.

9. A method for forming an optical device, comprising the following steps: A sacrificial material is disposed on a substrate and between multiple optical device structures, the multiple optical device structures comprising: A critical dimension of less than 2 micrometers, the critical dimension corresponding to the width or diameter of the cross-section of the optical device structure; as well as Structural material having an optical device refractive index between about 1.7 and about 4.0; An encapsulation layer is disposed above the plurality of optical device structures and the sacrificial material. The encapsulation layer includes an encapsulation material having an encapsulation refractive index of about 1.0 to about 1.

6. The encapsulation layer may further include a plurality of openings disposed through the encapsulation layer for removal of the sacrificial material. as well as The sacrificial material is removed by etching, wherein: The encapsulation layer, the substrate, and each of the plurality of optical device structures define a space therebetween, the space having a refractive index of about 1.

0.

10. The method of claim 9, further comprising the step of: depositing material in the plurality of openings after the sacrificial material has been removed.

11. The method of claim 9, wherein the etching process further comprises the step of: using etching chemicals to etch the sacrificial material at a higher rate than that of the encapsulation layer.

12. An optical device comprising: Multiple optical device structures are disposed in or on a substrate, and the multiple optical device structures include: A critical dimension of less than 2 micrometers, the critical dimension corresponding to the width or diameter of the cross-section of the optical device structure; and A structural material having an optical device refractive index between about 1.7 and about 4.0; and Encapsulation layer, including: The encapsulation refractive index is approximately 1.0 to approximately 1.

6. A first portion of a first material, the first portion surrounding the top surface of the plurality of optical device structures, the first portion of the first material comprising: The gap defined between the first parts; and A second portion of the second material, wherein the second portion is at least disposed within the gap; wherein: The encapsulation layer, the substrate, and each of the plurality of optical device structures define a space therebetween, the space having a refractive index of approximately 1.

0. The first and second portions of the encapsulation layer are coplanar.

13. The optical device of claim 12, wherein a second plurality of optical device structures may be disposed on the encapsulation layer to produce a multilayer optical device.

14. The optical device according to claim 12, wherein the optical device structure comprises one or more of the following: titanium dioxide (TiO2), zinc oxide (ZnO), tin dioxide (SnO2), niobium oxide (Nb2O5), aluminum-doped zinc oxide, titanium nitride (TiN), zirconium dioxide (ZrO2), indium tin oxide, tantalum pentoxide (Ta2O5), fluorine-doped tin oxide, vanadium oxide (IV), aluminum oxide (Al2O3), cadmium stannate (Cd2SnO4), zinc stannate (SnZnO3), silicon, silicon nitride (Si3N4), silicon oxycarbide (SiOC), silicon oxynitride (SiON), and silicon dioxide (SiO2).

15. A method of forming an optical device, comprising the following steps: A first portion of an encapsulation layer is provided, the first portion of the encapsulation layer surrounding the top surface of a plurality of optical device structures, the plurality of optical devices being disposed in or on a substrate, the plurality of optical device structures comprising: A critical dimension of less than 2 micrometers, the critical dimension corresponding to the width or diameter of the cross-section of the optical device structure; and A structural material having an optical device refractive index between about 1.7 and about 4.0, the first portion of the encapsulation layer comprising: A first material having a first refractive index of about 1.0 to about 1.6; and A gap, the gap being defined between the first portions of the encapsulation layer; and A second portion of the encapsulation layer is disposed at least in the gap between the first portions of the encapsulation layer to fill the gap, the second portion comprising a second material having a second refractive index of about 1.0 to about 1.6, wherein: The first portion, the second portion, the substrate, and the plurality of optical device structures define a space therebetween, the space having a refractive index of approximately 1.0, and The first and second portions of the encapsulation layer are planarized by chemical mechanical polishing or reactive ion etching.

16. The method of claim 15, wherein the optical device structure comprises one or more of the following: titanium dioxide (TiO2), zinc oxide (ZnO), tin dioxide (SnO2), niobium oxide (Nb2O5), aluminum-doped zinc oxide, titanium nitride (TiN), zirconium dioxide (ZrO2), indium tin oxide, tantalum pentoxide (Ta2O5), fluorine-doped tin oxide, vanadium oxide (IV), aluminum oxide (Al2O3), cadmium stannate (Cd2SnO4), zinc stannate (SnZnO3), silicon, silicon nitride (Si3N4), silicon oxycarbide (SiOC), silicon oxynitride (SiON), and silicon dioxide (SiO2).

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