Gradient encapsulation of waveguide gratings

Abstract

The embodiments described herein relate to the gradient encapsulation of waveguide outcoupler gratings for controlling diffraction efficiency and directionality. A device comprises a first grating formed on a substrate, wherein the first grating has a plurality of first structures extending away from the substrate, and the first grating corresponds to an outcoupler. The device comprises a first encapsulating agent disposed in one or more gaps formed between adjacent first structures, wherein the filling ratio of the first encapsulating agent decreases along the first grating. Additionally, methods for manufacturing the device are described herein.

Description

Technology Field

[0001] The embodiments of the present disclosure generally relate to augmented reality waveguides. More specifically, the embodiments described herein relate to the gradient encapsulation of waveguide outcoupler gratings for controlling diffraction efficiency and directionality. Background Technology

[0002] Virtual reality is generally considered to be a computer-generated simulated environment that appears physically present to the user. Virtual reality experiences are created in 3D and can be viewed as head-mounted displays (HMDs), such as glasses or other wearable display devices, that have near-vision display panels as lenses to display a virtual reality environment that replaces the real environment.

[0003] However, while augmented reality enables an experience where users can still view their surroundings through the display lenses of glasses or other HMD devices, they can also view images of virtual objects generated for the display and appearing as part of the environment. Augmented reality can include virtual images, graphics, and videos that enhance or strengthen the environment experienced by the user, as well as any type of input such as audio and haptic inputs. As an emerging technology, augmented reality presents many challenges and design constraints.

[0004] One of these challenges is displaying virtual images overlaid on the surrounding environment. Augmented waveguide couplers are used to support the overlaying of images. The generated light is in-coupled into the augmented waveguide coupler, propagates through the augmented waveguide coupler, out-coupled from the augmented waveguide coupler, and overlaid on the surrounding environment. Light is coupled into and out of the augmented waveguide couplers using surface relief gratings. The diffraction efficiency and directionality of the out-coupled light may not be adequately controlled.

[0005] Therefore, what is needed in this technical field are improved waveguide couplers and manufacturing methods.

[0006] In one embodiment, a device is provided. The device comprises a first grid formed on a substrate, the first grid has a plurality of first structures extending away from the substrate, and the first grid corresponds to an outcoupler. The device comprises a first encapsulant disposed in one or more gaps formed between adjacent first structures, wherein the filling ratio of the first encapsulant decreases along the first grid.

[0007] In another embodiment, a device is provided. The device comprises a first grid formed on a substrate, the first grid has a plurality of first structures extending away from the substrate, and the first grid corresponds to an outcoupler. The device comprises a first encapsulating agent disposed in one or more first gaps formed between adjacent first structures, wherein the filling ratio of the first encapsulating agent decreases along the first grid. The device comprises a second grid formed on a substrate, the second grid has a plurality of second structures extending away from the substrate, and the second grid corresponds to an incoupler.

[0008] In another embodiment, a method is provided. The method comprises the step of forming a first grid on a substrate, wherein the first grid has a plurality of first structures extending away from the substrate, and the first grid corresponds to an outcoupler. The method comprises the step of forming a second grid on a substrate, wherein the second grid has a plurality of second structures extending away from the substrate, and the second grid corresponds to an incoupler. The method comprises the steps of depositing a first encapsulating agent on the first and second grids, curing the first encapsulating agent, and forming a patterned photoresist layer on the first and second grids. The method comprises the steps of etching the first encapsulating agent through the patterned photoresist layer—wherein the filling ratio of the first encapsulating agent decreases along the first grid—and depositing a global encapsulating agent on the first and second grids. Brief explanation of the drawing

[0009] In order to make the features cited above of the present disclosure understandable in detail, a more detailed description of the present disclosure, briefly summarized above, may be made with reference to embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings are merely illustrative of exemplary embodiments and should not be construed as limiting the scope thereof, and that other equally valid embodiments may be permitted.

[0010] FIG. 1a is a front perspective view of a waveguide coupler according to an embodiment.

[0011] FIG. 1b is a schematic cross-sectional view taken along the line (A-A') of FIG. 1a illustrating a waveguide coupler according to an embodiment.

[0012] FIG. 1c is a schematic cross-sectional view taken along the line (A-A') of FIG. 1a illustrating a waveguide coupler according to another embodiment.

[0013] FIG. 1d is a schematic cross-sectional view taken along the line (A-A') of FIG. 1a illustrating a waveguide coupler according to another embodiment.

[0014] FIG. 2 is a flowchart illustrating the operations of a method for encapsulating waveguide gratings according to an embodiment.

[0015] FIGS. 3a to 3j are schematic cross-sectional views of a waveguide coupler during manufacturing according to an example.

[0016] FIG. 4 is a flowchart illustrating the operations of a method for encapsulating waveguide gratings according to another embodiment.

[0017] FIGS. 5a to 5h are schematic cross-sectional views of a waveguide coupler during manufacturing according to another embodiment.

[0018] FIG. 6 is a flowchart illustrating the operations of a method for encapsulating waveguide gratings according to another embodiment.

[0019] FIGS. 7a to 7j are schematic cross-sectional views of a waveguide coupler during manufacturing according to another embodiment.

[0020] For ease of understanding, the same reference numbers have been used where possible to designate the same elements common to the drawings. It is considered that the elements and features of one embodiment may be advantageously incorporated into other embodiments without further mention. Specific details for implementing the invention

[0021] The embodiments described herein relate to the gradient encapsulation of waveguide outcoupler gratings for controlling diffraction efficiency and directionality. A device comprises a first grating formed on a substrate, wherein the first grating has a plurality of first structures extending away from the substrate, and the first grating corresponds to an outcoupler. The device comprises a first encapsulating agent disposed in one or more gaps formed between adjacent first structures, wherein the filling ratio of the first encapsulating agent decreases along the first grating. Additionally, methods for manufacturing the device are described herein.

[0022] FIG. 1a is a perspective front view of an exemplary waveguide coupler (100) (e.g., for augmented reality (AR) applications). It should be understood that the waveguide coupler (100) described below is an exemplary waveguide coupler that can be formed using the systems and methods described herein, and that the systems and methods of the present disclosure may be used to form or modify other optical devices and nanostructured optical devices, such as other waveguide couplers. For example, an optical device having more than three gratings, e.g., five or more gratings, may be formed. Alternatively, an optical device having fewer than three gratings, e.g., two gratings, may be formed. In another example, an optical device having gratings on two main planar sides may be formed. In yet another example, an optical device having more than one input coupler and more than one output coupler may be formed.

[0023] The waveguide coupler (100) comprises a first grating (110) corresponding to an incoupler, a second grating (120) corresponding to an outcoupler, and a third grating (130) between the incoupler and the outcoupler. In some embodiments, the waveguide coupler (100) may include one or more additional gratings. Here, the third grating (130) is an intermediate grating that expands the light between the first grating (110) and the second grating (120). It will be understood that the third grating (130) may be optional. In some embodiments, the first, second, and third gratings (110, 120, 130) are arranged to achieve substantial internal total reflection of light between the incoupler and the outcoupler.

[0024] FIG. 1b is a schematic cross-sectional view taken along the line (A-A') of FIG. 1a illustrating a waveguide coupler (100B) according to an embodiment. The waveguide coupler (100B) comprises a substrate (102). If the substrate (102) can adequately transmit light of a desired wavelength or wavelength range and can serve as a suitable support for the grating(s), the substrate (102) may be formed of any suitable material and may have any suitable thickness. In some embodiments, the material of the substrate (102) comprises one or more of silicon (Si), silicon dioxide (SiO2), silicon carbide (SiC), glass, plastic, polycarbonate, and sapphire-containing materials (but is not limited thereto). In some embodiments, the substrate (102) comprises doped glass. For example, the substrate (102) comprises glass doped with a heavy dopant such as lanthanum (La), zirconium (Zr), zinc (Zn), etc. The materials of the substrate (102) may additionally have rollable and flexible properties. In some embodiments, the materials of the substrate (102) comprise materials having a refractive index of about 1.5 to about 2.4 (but are not limited thereto). For example, the substrate (102) may be a doped high-refractive-index substrate having a refractive index of about 1.7 to about 2.4.

[0025] The waveguide coupler (100B) comprises a first grating (110) and a second grating (120) disposed on a substrate (102). In some embodiments, the first and second gratings (110, 120) may be disposed on one or more spacer layers (not shown) disposed on the substrate (102). In embodiments comprising a spacer layer, the spacer layer is operable to provide support for the first and second gratings (110, 120) and has a thickness and material according to the desired optical properties of the first and second gratings (110, 120). The first grating (110) comprises a plurality of structures (112) that extend over the substrate (102) and have gaps (114) formed between adjacent structures (112). Likewise, the second grid (120) includes a plurality of structures (122) that extend over the substrate (102) and have gaps (124) formed between the sidewalls (126) of adjacent structures (122). In some embodiments, the structures (112, 122) may be fins. In some embodiments, the structures (112, 122) may be disposed within the substrate (102). That is, the substrate (102) may be etched to form the structures (112, 122) disposed within it.

[0026] In some embodiments, the structures (112, 122) may be asymmetric (e.g., inclined or wedge-shaped). Here, the structures (112) are inclined oppositely to the structures (122). In some other embodiments, the structures (112, 122) may be inclined in the same direction. Here, the structures (112) are inclined to the left, while the structures (122) are inclined to the right. However, the orientation of the structures (112, 122) is not particularly limited to the illustrated embodiments. For example, the structures (112, 122) may be inclined oppositely to the described embodiments.

[0027] Here, the structures (122) are inclined at an angle (θ1) with respect to the surface normal (106), and the inclination angle (θ1) of each structure (122) is substantially the same. In other embodiments, the inclination angle (θ1) of one structure (122) may differ from the inclination angle (θ1) of another structure (122). In some embodiments, the inclination angle (θ1) may be about 30 degrees to about 60 degrees, for example, about 40 degrees to about 60 degrees, alternatively about 30 degrees to about 40 degrees, alternatively about 40 degrees to about 50 degrees, alternatively about 50 degrees to about 60 degrees, for example, about 50 degrees. In some embodiments, the inclination angle (θ1) may be about 0 degrees to about 30 degrees, for example, about 0 degrees to about 10 degrees, alternatively about 10 degrees to about 20 degrees, alternatively about 20 degrees to about 30 degrees. In some embodiments, the structures (122) may have an angle of inclination (θ1) equal to 0 with respect to the surface normal (106), and thus the structures (122) may be binary structures. Here, each structure (122) has a single part. In other embodiments, the structures (122) may have two or more parts having different angles of inclination with respect to the surface normal (106). In some embodiments, the material of the structures (122) is selected based on the desired depth and angle of inclination (θ1) of the structures (122).

[0028] The gaps (124) have a depth (D1) defined as the distance from the surface (104) of the substrate (102) to the top surface (128) of the structures (122) and a width (W1) defined as the distance between the side walls (126) of adjacent structures (122). Here, the depth (D1) of each gap (124) is substantially the same. In another embodiment, the depth (D1) of at least one gap (124) may differ from the depth (D1) of the other gaps (124). Here, the width (W1) of each gap (124) is substantially the same. In another embodiment, the width (W1) of at least one gap (124) may differ from the width (W1) of the other gaps (124).

[0029] In some embodiments, one or more of the structures (112, 122) may include structures having different geometric structures, such as angles of inclination or dimensions that are different from the angles of inclination or dimensions of other structures of the grid. Additionally, the angle of inclination of one individual structure within the plurality of structures (112, 122) may be different over the length or width of the grid.

[0030] The first and second lattices (110, 120) are independently silicon oxycarbide (SiOC) and titanium oxide (TiO₂). x ), TiO x Nanomaterials, niobium oxide (NbO xIt comprises at least one of ), niobium-germanium (Nb3Ge), silicon dioxide (SiO2), silicon carbonitride (SiOCN), vanadium (IV) oxide (VOx), aluminum oxide (Al2O3), indium tin oxide (ITO), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (Si3N4), silicon-rich Si3N4, hydrogen-doped Si3N4, boron-doped Si3N4, silicon carbonitrate (SiCN), titanium nitride (TiN), zirconium dioxide (ZrO2), germanium (Ge), gallium phosphide (GaP), polycrystalline diamond (PCD), nanocrystalline diamond (NCD), and doped diamond-containing materials. In some embodiments, the substrate (102) may be formed of any material contained in the first and second lattices (110, 120), and vice versa. In some embodiments, the substrate (102) and the first and second grids (110, 120) may be formed of the same material(s).

[0031] The first and second grids (110, 120) can be formed on the surface of the substrate (102) by any suitable process. For example, the first and second grids (110, 120) can be formed by one or more of the following processes: physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), fluid CVD (FCVD), atomic layer deposition (ALD), and spin-on processes.

[0032] In some embodiments, the material of the first and second gratings (110, 120) may have a refractive index of about 1.5 to about 2.65, for example about 1.5 to about 1.8, alternatively about 2.2 to about 2.65, alternatively about 1.8 to about 2.2, alternatively about 1.8 to about 2, alternatively about 2 to about 2.2, alternatively about 1.9 to about 2.1, for example about 1.9 to about 2.1, alternatively about 2 to about 2.1, for example about 2.

[0033] In some embodiments, the waveguide coupler (100B) may include a grid material layer (not shown) disposed between the substrate (102) and the structures (112, 122) of the first and second grids (110, 120). The grid material layer may be formed from any suitable materials and may be formed by any suitable process including the materials and processes used to form the first and second grids (110, 120) described above.

[0034] The waveguide coupler (100B) comprises a first encapsulating agent (140) disposed in the gaps (124) between the structures (122). In some embodiments, the first encapsulating agent (140) may have a refractive index contrast of about 0.2 or less, for example, about 0 to about 0.2, for example, about 0 to about 0.05, alternatively about 0.05 to about 0.1, alternatively about 0.1 to about 0.15, alternatively about 0.15 to about 0.2, alternatively about 0.1 or less, where the refractive index contrast is defined as the difference in refractive index between the first encapsulating agent (140) and the second grating (120).

[0035] In some embodiments, the first encapsulating agent (140) is about 1.6 to about 2.4, for example, about 1.7 to about 2.3, for example, about 1.8 to about 2.2, for example, about 1.8 to about 2, for example, about 1.9 to about 2, for example, about 1.95 to about 2, alternatively about 2 to about 2.2, for example, about 2 to about 2.1, for example, about 2 to about 2.05, for example, about 2, alternatively about 1.8 to about 1.85, alternatively about 1.85 to about 1.9, alternatively about 1.9 to about 1.95, alternatively about 1.95 to about 1.96, alternatively about 1.96 to about 1.97, alternatively about 1.97 to about 1.98, alternatively about 1.98 to about 1.99, alternatively It may have a refractive index of about 1.99 to about 2, alternatively about 2 to about 2.01, alternatively about 2.01 to about 2.02, alternatively about 2.02 to about 2.03, alternatively about 2.03 to about 2.04, alternatively about 2.04 to about 2.05, alternatively about 2.05 to about 2.1, alternatively about 2.1 to about 2.2, and alternatively about 1.95 to about 2.05.

[0036] In some embodiments, the first encapsulating agent (140) is polyimides, polyimide blends, metal-organic polyimide blends, metal oxides, metal nitrides, Al2O3, SiO2, TiO, TaO, AlN, SiN, SiO x N x It includes at least one of TiN, TaN, any of the materials forming the substrate (102), any of the materials forming the first and second lattices (110, 120), and any other suitable materials having refractive indices according to the ranges presented above. In some embodiments, the first encapsulating agent (140) comprises any material having suitable gap filling characteristics and a refractive index of about 1.8 to about 2.2.

[0037] The first encapsulating agent (140) has a height (H1) defined as the distance from the surface (104) of the substrate (102) to the top surface (142) of the encapsulating agent (140). The first encapsulating agent (140) has a filling ratio defined as the ratio of the height (H1) of the encapsulating agent (140) to the depth (D1) of the second grid (120). Here, the filling ratio decreases linearly from about 1 to about 0 along the second grid (120) from left to right. However, the profile of the first encapsulating agent (140) is not particularly limited to the illustrated embodiments. For example, in other embodiments, the filling ratio may decrease non-linearly (e.g., according to a power law function, an exponential function, or other polynomial function). In some embodiments, the filling ratio may generally decrease while including one or more sections in which the filling ratio is constant or even increases. In some embodiments, the filling rate may be reduced in steps (i.e., each gap (124) has a constant filling rate that is smaller than the previous gap (124) and larger than the next gap (124)). In some embodiments, the filling rate may be a combination of any of the gradients above.

[0038] In some embodiments, the filling ratio may have a maximum value of less than 1 (i.e., the encapsulant (140) is below the top surface (128)), for example, about 0.5 to about 1, for example, about 0.6 to about 1, for example, about 0.7 to about 1, for example, about 0.8 to about 1, for example, about 0.9 to about 1, alternatively about 0.8 to about 0.9, alternatively about 0.7 to about 0.8, alternatively about 0.6 to about 0.7, alternatively about 0.5 to about 0.6.

[0039] In some embodiments, the filling ratio may have a minimum value greater than 0 (i.e., the encapsulating agent (140) is present along the entire surface (104) of the second grid (120), for example, about 0 to about 0.5, for example, about 0 to about 0.4, for example, about 0 to about 0.3, for example, about 0 to about 0.2, for example, about 0 to about 0.1, alternatively about 0.1 to about 0.2, alternatively about 0.2 to about 0.3, alternatively about 0.3 to about 0.4, or alternatively about 0.4 to about 0.5.

[0040] In some embodiments, the filling ratio may be in the range of about 0 to about 1, for example, about 0.1 to about 1, for example, about 0.2 to about 1, for example, about 0.3 to about 1, for example, about 0.4 to about 1, for example, about 0.5 to about 1, for example, about 0.6 to about 1, for example, about 0.7 to about 1, for example, about 0.8 to about 1, for example, about 0.9 to about 1, alternatively about 0 to about 0.9, for example, about 0 to about 0.8, for example, about 0 to about 0.7, for example, about 0 to about 0.6, for example, about 0 to about 0.5, for example, about 0 to about 0.4, for example, about 0 to about 0.3, for example, about 0 to about 0.2, for example, about 0 to about 0.1.

[0041] The encapsulating agent gradients described herein enable control over the diffraction efficiency along the second grating (120). A low non-refractive index difference of the encapsulating agent (140) (e.g., about 0.2 or less) reduces the diffraction efficiency compared to unencapsulated gratings (i.e., gratings without the encapsulating agent (140)). Unencapsulated gratings may have air in contact with the surface (104) (i.e., refractive index 1) or may contain a global encapsulating agent having a low refractive index (e.g., a non-refractive index difference greater than about 0.2). In some embodiments, the diffraction efficiency of the second grating (120) may be about 2.5% or less, alternatively about 1% to about 50%, for example about 1% to about 40%, for example about 1% to about 30%, for example about 1% to about 20%, for example about 1% to about 10%, for example about 1% to about 5%, for example about 1% to about 2.5%, alternatively about 2.5% to about 5%, alternatively about 5% to about 10%, alternatively about 10% to about 20%, alternatively about 20% to about 30%, alternatively about 30% to about 40%, alternatively about 40% to about 50%.

[0042] In addition to reducing diffraction efficiency, the encapsulating gradients described herein control diffraction efficiency along the second grid (120). In some embodiments, as the filling ratio increases, the diffraction efficiency decreases. For example, as illustrated herein, the left end of the second grid (120) having the maximum filling ratio (i.e., 1) has the lowest diffraction efficiency (i.e., about 1% to about 5%), and the right end of the second grid (120) having the lowest filling ratio (i.e., 0) has the highest diffraction efficiency (i.e., about 40% to about 50%). However, the orientation of the second grid (120) is not particularly limited to the illustrated embodiments. For example, the orientation may be such that the filling ratio of the second grid (120) decreases from right to left.

[0043] Conventional devices use shallow depth gratings to reduce diffraction efficiency; however, shallow depth gratings limit directionality. The encapsulation gradients described herein can outcouple light at low efficiencies without reducing grating depth. Thus, the encapsulation gradients described herein can enable full-range tuning of diffraction efficiency while maintaining directionality toward the user across the entire surface of the second grating (120). In one or more embodiments, the advantages described above compared to conventional devices may be the result of combining asymmetric structures (122) and encapsulation gradients.

[0044] The waveguide coupler (100B) comprises a global encapsulator (150) on the first and second gratings (110, 120) and the first encapsulator (140). In some embodiments, the global encapsulator (150) may have a refractive index lower than that of the first and second gratings (110, 120) and the first encapsulator (140). In some embodiments, the refractive index of the global encapsulator (150) may be about 1 to about 1.7, for example, about 1.2 to about 1.5. In some embodiments, the global encapsulator (150) may have an absorption coefficient of less than about 0.001.

[0045] The global encapsulator (150) may be formed from any suitable transparent material including (but not limited to) silica-containing materials such as polymer-containing materials, for example fluoropolymer materials, and non-silica-containing materials. In some embodiments, the global encapsulator (150) may be formed from low-k dielectric films such as silicon dioxide (SiO2) or carbon and nitride-doped silicon oxide (SiCON) or silicon carbon nitride (SiCN). In some embodiments, the global encapsulator (150) may include fluorine-containing materials such as aluminum fluoride (AlF3) and magnesium fluoride (MgF2).

[0046] FIG. 1c is a schematic cross-sectional view taken along line (A-A') of FIG. 1a illustrating a waveguide coupler (100C) according to another embodiment. The waveguide coupler (100C) is similar to the waveguide coupler (100B) in most aspects, and the above description of the waveguide coupler (100B) may be incorporated herein without limitation.

[0047] In contrast to the waveguide coupler (100B), the waveguide coupler (100C) comprises a first encapsulating agent (140) on the first grid (110) in addition to the second grid (120). The first encapsulating agent (140) is placed in the gaps (114) between the sidewalls (116) of adjacent structures (112). Here, the first encapsulating agent (140) on the first grid (110) has a top surface (144) that is higher in plane than the top surface (142) of the first encapsulating agent (140) on the second grid (120). In some embodiments, the top surface (144) may be non-plane. In some embodiments, the top surface (144) may be on or below the top surface (142). Here, the top surface (144) is higher than the top surface (118) of the structures (112) so that the filling ratio of the gaps (114) is constant and equal to 1. However, the profile of the first encapsulating agent (140) on the first grid (110) is not particularly limited to the illustrated embodiments. For example, the filling ratio may be less than 1. In these embodiments, the filling ratio may vary along the first grid (110).

[0048] The waveguide coupler (100C) includes a global encapsulation agent (150). Here, the global encapsulation agent (150) is in contact with the uppermost surface (144) of the first encapsulation agent (140) on the first grid (110).

[0049] FIG. 1d is a schematic cross-sectional view taken along the line (A-A') of FIG. 1a illustrating a waveguide coupler (100D) according to another embodiment. The waveguide coupler (100D) is similar in most aspects to the waveguide couplers (100B and / or 100C), and the above description of the waveguide couplers (100B, 100C) may be incorporated herein without limitation.

[0050] In contrast to waveguide couplers (100B, 100C), the waveguide coupler (100D) has two-sided gratings, wherein the two-sided gratings are defined as being on planar sides opposite each other of the substrate (102). Here, the first grating (110) is placed on the rear surface (108) of the substrate (102) opposite to the front surface (104) on which the second grating (120) is placed. The waveguide coupler (100D) includes a second encapsulating agent (146) on the first and second gratings (110, 120) on the rear surface (108). The second encapsulating agent (146) is placed in the gaps (114) between the sidewalls (116) of adjacent structures (112) of the first grating (110). The second encapsulating agent (146) has a surface (148) facing away from the rear surface (108) of the substrate (102). The second encapsulating agent (146) may be the same as or different from the first encapsulating agent (140), and the above description of the first encapsulating agent (140) may be incorporated herein without limitation.

[0051] Here, the second encapsulating agent (146) covers the back surface (108) on the first and second grids (110, 120). However, the second encapsulating agent (146) is not specifically limited to the illustrated embodiment. For example, the second encapsulating agent (146) may cover only the back surface (108) on the first grid (110). In some other embodiments, the second encapsulating agent (146) may be omitted.

[0052] The waveguide coupler (100D) includes a global encapsulator (150). Here, the global encapsulator (150) is in contact with the surface (148) of the second encapsulator (146) on the first and second grids (110, 120).

[0053] FIG. 2 is a flowchart illustrating the operations of a method (200) for encapsulating waveguide gratings according to an embodiment. FIG. 3a through 3j are schematic cross-sectional views of a waveguide coupler (100B) during manufacturing according to an embodiment.

[0054] Referring to FIGS. 2 and FIGS. 3a, in step (202), the method (200) includes the step of forming a first grid (110) corresponding to an incoupler and a second grid (120) corresponding to an outcoupler. The first and second grids (110, 120) may be formed using any of the materials and processes described above.

[0055] Referring to FIGS. 2 and FIGS. 3b, in step (204), the method (200) includes the step of depositing a first encapsulating agent (140) on first and second grids (110, 120). The first encapsulating agent (140) is deposited on the surface (104) of the substrate (102), on the gaps (114, 124), on the structures (112), and along the sidewalls (126) and top surfaces (128) of the structures (122). The first encapsulating agent (140) may be formed by any suitable process. For example, the first encapsulating agent (140) may be formed by one or more of PVD, CVD, PECVD, FCVD, ALD, and spin-on processes.

[0056] Referring to FIGS. 2 and FIGS. 3b, in step (206), the method (200) includes the step of curing the first encapsulating agent (140). In some embodiments, the first encapsulating agent (140) may be cured by heat, pressure, chemical treatment, or any other suitable curing technique.

[0057] Referring to FIGS. 2 and FIGS. 3c, in step (208), the method (200) includes the step of depositing a first hardmask layer (162) on a cured first encapsulating agent (140). The first hardmask layer (162) comprises at least one of titanium nitride, silicon nitride, and silicon carbide. The first hardmask layer (162) may be formed by any suitable process. For example, the first hardmask layer (162) may be formed by one or more of PVD, CVD, PECVD, FCVD, ALD, and spin-on processes.

[0058] Referring to FIGS. 2 and FIGS. 3d, in step (210), the method (200) includes the step of forming a second hard mask layer (164) patterned on a first hard mask layer (162). The patterned second hard mask layer (164) is placed on the second grid (120) but not on the first grid (110). Thus, the patterned second hard mask layer (164) can be used as an etching mask for etching the first hard mask layer (162) on the first grid (110). The patterned second hard mask layer (164) comprises at least one of a positive or negative tone photoresist, a metal-containing hard mask, a carbon-containing hard mask, an organic planarization layer (OPL), and other suitable hard mask materials. The patterned second hard mask layer (164) can be formed by any suitable process. For example, the patterned second hard mask layer (164) can be formed by one or more of PVD, CVD, PECVD, FCVD, ALD, and spin-on processes.

[0059] Referring to FIGS. 2 and FIGS. 3e, in step (212), the method (200) includes the step of removing a first hard mask layer (162) on a first grid (110). The first hard mask layer (162) may be removed by an etching process having etching selectivity for the first hard mask layer (162) relative to a patterned second hard mask layer (164). Thus, the first hard mask layer (162) may be removed from the first grid (110) without affecting the patterned second hard mask layer (164) and / or the first hard mask layer (162) on the second grid (120). The etching process may include at least one of wet etching, dry etching, reactive ion etching, and plasma etching.

[0060] Referring to FIGS. 2 and FIGS. 3f, in step (214), the method (200) includes the step of etching the first encapsulating agent (140) on the first grid (110). The first hard mask layer (162) on the second grid (120) may be used as an etching mask for etching the first encapsulating agent (140) on the first grid (110). The first encapsulating agent (140) may be removed by an etching process having etching selectivity for the first encapsulating agent (140) relative to either the patterned second hard mask layer (164) or the first hard mask layer (162). Thus, the first encapsulating agent (140) may be removed from the first grid (110) without affecting the first encapsulating agent (140) on the second grid (120). The etching process may include at least one of wet etching, dry etching, reactive ion etching, and plasma etching.

[0061] Referring to FIG. 2 and FIG. 3g, in step (216), the method (200) includes the step of removing a first hard mask layer (162) on a second grid (120). The first hard mask layer (162) may be removed from the second grid (120) to prepare an encapsulating agent (140) on the second grid (120) for a subsequent etching step. The first hard mask layer (162) may be removed by at least one of stripping, wet etching, dry etching, reactive ion etching, and plasma etching.

[0062] Referring to FIGS. 2 and FIGS. 3h, in step (218), the method (200) includes the step of forming a patterned photoresist layer (166) on the first and second grids (110, 120). In some embodiments, the patterned photoresist layer (166) may be formed by any suitable lithography process (e.g., a gray-scale lithography process using scanning gray tone exposure in which the dose is increased while scanning across the waveguide coupler (100B) from the first grid (110) to the second grid (120). The gray-scale lithography process may include the step of blanket-depositing a photoresist material on the first and second grids (110, 120). Here, the photoresist material is in contact with the first encapsulating agent (140) on the second grid (120) and the first grid (110). In some embodiments, the photoresist material may include photosensitive polymer-containing materials (but is not limited thereto).

[0063] Subsequently, the exposure of the photoresist material may include the step of forming a potential pattern within it using a gradient of exposure dose along the photoresist material. In some embodiments, the potential pattern may include any one-dimensional, two-dimensional, or three-dimensional shape created in the photoresist material using lithography or laser ablation (but is not limited thereto). In some embodiments, the potential pattern may be graded. The shape of the potential pattern may determine the profile of the first encapsulator (140). After forming the potential pattern, the photoresist material may be developed to form the patterned photoresist layer (166) shown in FIG. 3h. The photoresist material may be a positive tone photoresist so that the exposed areas of the photoresist material are removed during development. In some embodiments, the step of developing the photoresist material may include the step of performing a lithography process, such as photolithography or digital lithography, or the step of performing laser ablation.

[0064] Here, the patterned photoresist layer (166) has a thickness (T1) measured over the first encapsulating agent (140) that decreases linearly along the first and second grids (110, 120). However, the profile of the patterned photoresist layer (166) is not particularly limited to the illustrated embodiment. For example, the profile may decrease non-linearly (e.g. according to a power law function, an exponential function, or other polynomial function), the profile may decrease while generally including one or more sections where the profile is constant or even increasing, the profile may decrease stepwise, or the profile may be a combination of any of the above profiles. The profile of the patterned photoresist layer (166) may be transferred to the first encapsulating agent (140) during subsequent etching.

[0065] Referring to FIGS. 2 and FIGS. 3i, in step (220), the method (200) includes the step of etching the patterned photoresist layer (166) and the first encapsulating agent (140). Here, the etching process exposes portions of the sidewalls (126) and the top surfaces (128) of the structures (122). The etching process may include any suitable directional or non-directional etching process. In some embodiments, the profile of the patterned photoresist layer (166) may be transferred to the first encapsulating agent (140) by an isotropic etching process. The isotropic etching process may have etching selectivity for the patterned photoresist layer (166) and the first encapsulator (140) relative to the structures (122) so that the first encapsulator (140) can be etched without affecting the underlying structures (122). Here, the patterned photoresist layer (166) and the first encapsulator (140) are removed at substantially the same rate so that the profile of the etched first encapsulator (140) substantially matches the profile of the patterned photoresist layer (166). In some other embodiments, the profile of the etched first encapsulator (140) may differ from the profile of the patterned photoresist layer (166) depending on differences in etching rate or etching selectivity.

[0066] In some embodiments, directional etching may be used with or without a gradient formed in the patterned photoresist layer (166). In some embodiments, the top surface (142) of the etched first encapsulator (140) may be perpendicular to the sidewalls (126) of the structures (122). In some embodiments, the etching process may form a step reduction in the etched first encapsulator (140) such that the top surface (142) between adjacent structures (122) is substantially parallel to the surface (104) of the substrate (102).

[0067] In some embodiments, the etching process may include a cyclic etching process using one or more proximity masks. In some embodiments, the etching may be uniform. In some other embodiments, the etching may be optional. In some embodiments, a single etching chemistry may be used. In some other embodiments, two or more different etching chemistrys may be used.

[0068] Referring to FIGS. 2 and FIGS. 3j, in step (222), the method (200) includes the step of depositing a global encapsulator (150) on first and second grids (110, 120). The global encapsulator (150) is deposited on the surface (104) of the substrate (102), on the gaps (114), on the structures (112), on the etched first encapsulator (140), and along the exposed sidewalls (126) and top surfaces (128) of the structures (122). The global encapsulator (150) may be formed by any suitable process. For example, the global encapsulator (150) may be formed by one or more of PVD, CVD, PECVD, FCVD, ALD, and spin-on processes.

[0069] FIG. 4 is a flowchart illustrating the operations of a method (400) for encapsulating waveguide gratings according to an embodiment. FIG. 5a through 5h are schematic cross-sectional views of a waveguide coupler (100C) during manufacturing according to an embodiment.

[0070] Referring to FIGS. 4 and 5a, in step (402), the method (400) includes the step of forming a first grid (110) corresponding to an incoupler and the step of forming a second grid (120) corresponding to an outcoupler. Referring to FIGS. 4 and 5b, in step (404), the method (400) includes the step of depositing a first encapsulating agent (140) on the first and second grids (110, 120). Referring to FIGS. 4 and 5b, in step (406), the method (400) includes the step of curing the first encapsulating agent (140). Referring to FIGS. 4 and 5c, in step (408), the method (400) includes the step of depositing a first hard mask layer (172) on the cured first encapsulating agent (140). Steps (402 to 408) are similar to steps (202 to 208) of method (200).

[0071] Referring to FIGS. 4 and 5d, in step (410), the method (400) includes the step of forming a second hard mask layer (174) patterned on a first hard mask layer (172). Step (410) is similar to step (210) of the method (200), except that the patterned second hard mask layer (174) is placed on the first grid (110) but not on the second grid (120). Thus, the patterned second hard mask layer (174) can be used as an etching mask for etching the first hard mask layer (172) on the second grid (120).

[0072] Referring to FIGS. 4 and FIGS. 5e, in step (412), the method (400) includes the step of removing the first hard mask layer (172) on the second grid (120). Step (412) is similar to step (216) of the method (200), except that the first hard mask layer (172) remains in a state placed on the first grid (110).

[0073] Referring to FIGS. 4 and 5f, in step (414), the method (400) includes the step of forming a patterned photoresist layer (176) on first and second grids (110, 120). Step (414) is similar to step (218) of the method (200), except that the photoresist material comes into contact with a first hard mask layer (172) on the first grid (110) and a first encapsulating agent (140) on the second grid (120). After forming a potential pattern, the photoresist material can be developed to form the patterned photoresist layer (176) shown in FIG. 5f.

[0074] Referring to FIGS. 4 and 5g, in step (416), the method (400) includes the step of etching the patterned photoresist layer (176) and the first encapsulating agent (140). Step (416) is similar to step (220) of the method (200), except that the first hard mask layer (172) remaining on the first grid (110) is used as an etching mask to etch the first encapsulating agent (140) on the second grid (120) without affecting the first encapsulating agent (140) on the first grid (110).

[0075] Referring to FIGS. 4 and FIGS. 5h, in step (418), the method (400) includes the step of depositing a global encapsulator (150) on the first and second grids (110, 120). Step (418) is similar to step (222) of the method (200), except that the global encapsulator (150) is placed on the uppermost surface (144) of the first encapsulator (140) on the first grid (110).

[0076] FIG. 6 is a flowchart illustrating the operations of a method (600) for encapsulating waveguide gratings according to an embodiment. FIG. 7a through 7j are schematic cross-sectional views of a waveguide coupler (100D) during manufacturing according to an embodiment.

[0077] Referring to FIGS. 6 and FIGS. 7a, in step (602), the method (600) includes forming a first grid (110) corresponding to an incoupler on the back surface (108) of the substrate (102) and a second grid (120) corresponding to an outcoupler on the front surface (104) facing away from the back surface (108) of the substrate (102). Step (602) is similar to step (202) of the method (200), except that the first grid (110) is formed on the back surface (108) of the substrate (102).

[0078] Referring to FIGS. 6 and FIGS. 7b, in step (604), the method (600) includes the step of depositing a first encapsulating agent (140) on the front surface (104). Step (604) is similar to step (204) of the method (200), except that the first encapsulating agent (140) is deposited on the surface (104) of the substrate (102), in the gaps (124), and along the sidewalls (126) and top surfaces (128) of the structures (122).

[0079] Referring to FIGS. 6 and FIGS. 7b, in step (606), the method (600) optionally includes the step of depositing a second encapsulating agent (146) on the back surface (108). The second encapsulating agent (146) is deposited on the back surface (108) of the substrate (102), on the gaps (114), and on the structures (112). The second encapsulating agent (146) has a surface (148) facing away from the back surface (108) of the substrate (102). The second encapsulating agent (146) can be formed by any suitable process. For example, the second encapsulating agent (146) can be formed by one or more of PVD, CVD, PECVD, FCVD, ALD, and spin-on processes.

[0080] Referring to FIGS. 6 and FIGS. 7b, in step (608), the method (600) includes the step of curing the first encapsulating agent (140) and the optional second encapsulating agent (146). Step (608) is similar to step (206) of the method (200), except that the curing process can be applied to the front (104) and back (108) of the substrate (102).

[0081] Referring to FIGS. 6 and 7c, in step (610), the method (600) includes the step of depositing a first hard mask layer (182) on a cured first encapsulating agent (140) on the front surface (104). Referring to FIGS. 6 and 7d, in step (612), the method (600) includes the step of forming a patterned second hard mask layer (184) on the first hard mask layer (182) on the front surface (104). Referring to FIGS. 6 and 7e, in step (614), the method (600) includes the step of removing the first hard mask layer (182) on the first grid (110) on the front surface (104). Referring to FIGS. 6 and 7f, in step (616), the method (600) includes the step of etching the first encapsulating agent (140) on the first grid (110) on the front surface (104). Referring to FIGS. 6 and 7g, in step (618), the method (600) includes the step of removing the first hard mask layer (182) on the second grid (120) on the front surface (104). Referring to FIGS. 6 and 7h, in step (620), the method (600) includes the step of forming a patterned photoresist layer (186) on the first and second grids (110, 120) on the front surface (104). Referring to FIGS. 6 and 7i, in step (622), the method (600) includes the step of etching the patterned photoresist layer (186) and the first encapsulating agent (140) on the front surface (104). Steps (610 to 622) are similar to steps (208 to 220) of the method (200), except that the waveguide coupler (100D) has a first grid (110) on the back surface (108).

[0082] Referring to FIGS. 6 and 7j, in step (624), the method (600) includes the step of depositing a global encapsulator (150) on first and second grids (110, 120) on the front (104) and back (108). Step (624) is similar to step (222) of the method (200), except that the global encapsulator (150) is placed on the front (104) and back (108). The global encapsulator (150) is placed on the surface (148) of the second encapsulator (146) on the first and second grids (110, 120).

[0083] Although the foregoing relates to examples of the present disclosure, other and additional examples of the present disclosure may be devised without departing from the basic scope of the present disclosure, the scope of which is determined by the following claims.

Claims

Claim 1 A waveguide coupler comprising: a first grating disposed on the surface of a substrate ― said first grating has a plurality of first structures extending away from said substrate, said plurality of first structures are inclined in a first direction at an angle of inclination with respect to the normal of the surface of said substrate, said first grating corresponds to an outcoupler ―; and a first encapsulant disposed in one or more gaps formed between adjacent first structures, said first encapsulant having a filling ratio that decreases along said first grating in the first direction, said first encapsulant having a refractive index contrast greater than 0 and less than or equal to 0.2 with respect to said first grating. Claim 2 delete Claim 3 In claim 1, the first encapsulating agent is a waveguide coupler having a refractive index of 1.8 to 2.

2. Claim 4 In claim 1, the first encapsulating agent comprises one or more of polyimides, polyimide blends, or metal-organic polyimide blends, a waveguide coupler. Claim 5 A waveguide coupler according to claim 1, wherein the filling ratio of the first encapsulating agent is in the range of 0 to 1. Claim 6 In claim 1, the waveguide coupler in which the filling ratio decreases linearly. Claim 7 In claim 1, the waveguide coupler in which the filling ratio is gradually reduced. Claim 8 In claim 1, the waveguide coupler in which the filling ratio decreases non-linearly. Claim 9 A waveguide coupler according to claim 1, further comprising a second grid formed on the substrate, wherein the second grid has a plurality of second structures extending far from the substrate, and the second grid corresponds to an incoupler. Claim 10 A waveguide coupler comprising: a first grid of the waveguide coupler disposed on a substrate — the first grid has a plurality of first structures extending away from the substrate, and the first grid corresponds to an outcoupler —; a first encapsulating agent disposed in one or more first gaps formed between adjacent first structures — the filling ratio of the first encapsulating agent decreases along the first grid in the direction from a first structure on one side of the first grid to another first structure on the opposite side of the first grid —; and a second grid of the waveguide coupler disposed on the substrate — the second grid has a plurality of second structures extending away from the substrate, and the second grid corresponds to an incoupler —. Claim 11 In paragraph 10, the first encapsulating agent is disposed in one or more second gaps formed between adjacent second structures, a waveguide coupler. Claim 12 In item 10, the first and second grids are waveguide couplers formed on the front surface of the substrate. Claim 13 A waveguide coupler according to claim 10, wherein the first grid is formed on the front surface of the substrate and the second grid is formed on the rear surface of the substrate facing opposite to the front surface. Claim 14 A waveguide coupler according to claim 13, further comprising a second encapsulating agent disposed on the rear surface of the substrate, wherein the second encapsulating agent is disposed in one or more second gaps formed between adjacent second structures. Claim 15 A method for encapsulating a waveguide coupler, comprising the steps of: placing a first grid of the waveguide coupler on a substrate ― the first grid has a plurality of first structures extending far from the substrate, and the first grid corresponds to an outcoupler ―; placing a second grid of the waveguide coupler on the substrate ― the second grid has a plurality of second structures extending far from the substrate, and the second grid corresponds to an incoupler ―; depositing a first encapsulating agent on the first and second grids; curing the first encapsulating agent; forming a patterned photoresist layer on the first and second grids; etching the first encapsulating agent through the patterned photoresist layer ― the filling ratio of the first encapsulating agent decreases along the first grid ―; and depositing a global encapsulating agent on the first and second grids. Claim 16 A method for encapsulating a waveguide coupler according to claim 15, further comprising the steps of: depositing a first hardmask layer on the hardened first encapsulating agent; and forming a patterned second hardmask layer on the first hardmask layer. Claim 17 A method for encapsulating a waveguide coupler according to claim 16, further comprising: a step of removing the first hard mask layer on the first grid; and a step of etching the first encapsulating agent on the first grid using either the patterned second hard mask layer or the first hard mask layer as an etching mask. Claim 18 A method for encapsulating a waveguide coupler, wherein the step of forming the patterned photoresist layer comprises the step of performing a gray-scale lithography process. Claim 19 A method for encapsulating a waveguide coupler according to claim 15, wherein the step of etching the first encapsulating agent through the patterned photoresist layer comprises the step of transferring the profile of the patterned photoresist layer to the first encapsulating agent. Claim 20 A method for encapsulating a waveguide coupler according to claim 15, wherein the first grid is formed on the front surface of the substrate, the first encapsulating agent is deposited on the front surface, the second grid is formed on the rear surface of the substrate facing opposite to the front surface, and the method further comprises the step of depositing a second encapsulating agent on the rear surface. Claim 21 A method for encapsulating a waveguide coupler, wherein the first encapsulating agent has a difference in non-refractive index greater than 0 and less than or equal to 0.2 with respect to the first grid.

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