Method of manufacturing optical elements with binary and blazed grating structures

Abstract

A method is provided for forming optical elements with different optical element structures in a single element material layer. The method includes forming a patterned hard mask over an element material layer deposited on a top surface of a substrate, and patterning a first region of the element material layer to form a first plurality of optical features. The method also includes depositing a dielectric layer over the patterned hard mask, and selectively etching the dielectric layer and the element material layer to form a second plurality of optical features in a second region of the element material layer. The first plurality of optical features may be a binary grating structure, and the second plurality of optical features may be a blazed grating structure.

Description

Technical Field

[0001] The embodiments of this disclosure generally relate to optical elements for augmented, virtual, and mixed reality. More specifically, the embodiments described herein relate to an optical element and a method of forming an optical element having a binary and blazed grating structure. Background Technology

[0002] Optical elements can be used to manipulate the propagation of light using structures formed on a substrate. The optical elements comprise structural arrangements with in-plane dimensions smaller than half the designed wavelength of light. These structures have submicron critical dimensions, such as nanometer-sized dimensions, to alter the propagation of light by manipulating photons, thereby inducing local phase discontinuities (i.e., sudden changes in phase over distances smaller than the wavelength of light). In addition to having submicron critical dimensions, it is also desirable for different segments of the optical elements, particularly on the same surface, to have different structures, such as binary gratings and angled or blazed gratings.

[0003] However, forming optical elements with different optical structures can be challenging. Therefore, there is a need in the art for an optical element and a method for forming optical elements with different optical element structures. Summary of the Invention

[0004] Embodiments of this disclosure relate to optical elements including optical element films and methods of forming optical element films for said optical elements. Specifically, the embodiments described herein provide optical elements comprising blazed and binary structures on the same element material layer.

[0005] In one embodiment, a method for forming an optical element is provided. The method includes forming a patterned hard mask over an element material layer deposited on a top surface of a substrate. A first portion of the patterned hard mask exposes a first region of the element material layer, and a second portion of the patterned hard mask exposes a second region of the element material layer. The method also includes: patterning the first region of the element material layer to form a first plurality of optical features in the first region of the element material layer; depositing a dielectric layer over the patterned hard mask and the element material layer; selectively etching the dielectric layer and the element material layer to form a second plurality of optical features in the second region of the element material layer; and removing the remaining portion of the dielectric layer deposited on the element material layer. The first plurality of optical features may be a binary structure, and the second plurality of optical features may be a blazed structure.

[0006] In one embodiment, a method of forming an optical element is provided. The method includes positioning a substrate in a processing chamber, the substrate including an element material layer deposited over a top surface of the substrate; and forming a patterned hard mask over the element material layer. A first portion of the patterned hard mask exposes a first region of the element material layer, and a second portion of the patterned hard mask exposes a second region of the element material layer. The method also includes forming a first photoresist layer over the patterned hard mask, the first region of the element material layer being exposed by the first photoresist; and etching the first region of the element material layer to form a first plurality of optical features in the element material layer. The method further includes: depositing a dielectric layer over the first and second regions of the element material layer exposed by the patterned hard mask; depositing a second photoresist over the patterned hard mask; and patterning the dielectric layer deposited over the second region of the element material layer to form a plurality of dielectric structures over the second region of the element material layer. The second photoresist exposes the dielectric layer deposited over the second region of the element material layer. The method continues to etch the plurality of dielectric structures and the second region of the element material layer to form a second plurality of optical features in the second region of the element material layer; and removes the remaining portion of the dielectric layer above the second photoresist layer and the first region of the element material layer.

[0007] In another embodiment, an optical element is provided. The optical element includes a substrate on which an element material layer is disposed; and a first grating region formed in the top surface of the element material layer. The first grating region is formed on a first portion of the element material layer and includes a plurality of binary grating structures, the top surfaces of which are substantially parallel to the top surface of the substrate, and the sidewalls are substantially perpendicular to the top surface of the substrate. The optical element also includes a second grating region formed in the top surface of the element material layer on a second portion of the element material layer. The second grating region includes a plurality of blazed grating structures. Attached Figure Description

[0008] To gain a more detailed understanding of the features described above, a more specific description of the present disclosure can be provided with reference to the embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only exemplary embodiments of the present disclosure and should not be construed as limiting its scope; other equally effective embodiments are permissible.

[0009] Figure 1This is a perspective front view of an optical element according to certain embodiments.

[0010] Figure 2 A schematic cross-sectional view of an optical element according to certain embodiments is illustrated.

[0011] Figure 3 The illustration shows a flowchart of a method for forming an optical element film according to certain embodiments.

[0012] Figures 4A to 4K The illustration depicts, according to certain embodiments, the process of... Figure 3 A schematic cross-sectional view of the optical element of the method.

[0013] To facilitate understanding, the same element symbols are used where possible to represent common components across the figures. It is conceivable that components and features of one embodiment may be beneficially incorporated into other embodiments without further detail. Detailed Implementation

[0014] The embodiments of this disclosure generally relate to optical elements for augmented, virtual, and mixed reality. More specifically, the embodiments described herein relate to an optical element and a method of forming an optical element with different optical element structures.

[0015] Figure 1 This is a perspective front view of optical element 100. In an embodiment, optical element 100 is a waveguide combiner. It should be understood that the optical element 100 described below is an exemplary waveguide combiner. Optical element 100 includes a substrate 102 having a first grating region 104A defined by a first plurality of optical element structures 109A, a second grating region 104B defined by a second plurality of optical element structures 109B, and a third grating region 104C defined by a third plurality of optical element structures 109C. In one embodiment that can be combined with other embodiments described herein, optical element 100 includes at least a first grating region 104A corresponding to an input coupling grating region of the waveguide combiner, and a third grating region 104C corresponding to an output coupling grating region of the same waveguide combiner. In other embodiments, optical element 100 may include at least a first grating region 104A corresponding to an input coupling grating region and a second grating region 104B corresponding to an intermediate grating region.

[0016] Figure 2This is a schematic cross-sectional view of a portion 200 of optical element 100. Portion 200 includes a plurality of blazed grating structures 202 and a plurality of binary grating structures 204 formed in a grating material layer 201 disposed above a substrate 102. In an embodiment, the plurality of blazed grating structures 202 and the plurality of binary grating structures 204 of portion 200 may correspond to a first plurality of optical element structures 109A and a second plurality of optical element structures 109B, respectively, in a first grating region 104A and a second grating region 104B. In the illustrated embodiment, the grating material layer 201 and the plurality of binary and blazed grating structures 202, 204 formed therein are disposed above the top surface 102A of the substrate 102. In another embodiment, the plurality of blazed grating structures 202 and the plurality of binary grating structures 204 of portion 200 may be formed in the substrate 102.

[0017] Multiple blazed grating structures 202 and multiple binary grating structures 204 may be spaced apart from each other in a direction parallel to the top surface 102A of the substrate 102. In an embodiment, the blazed grating structure 202 may include a blazed surface that is angled or inclined relative to the top surface 102A of the substrate 102. For example, Figure 2 The illustration shows the blazing surface 206 of the first blazed grating structure 202a and the blazing surface 208 of the second blazed grating structure 202b, which are inclined relative to the top surface 102A of the substrate 102.

[0018] In embodiments that can be combined with other embodiments described herein, the plurality of binary grating structures 204 may be formed having a top surface 224 parallel to the top surface 102A of the substrate 102. Furthermore, in some embodiments, the sidewalls of the plurality of binary grating structures 204 may be parallel to each other. For example, Figure 2 The illustration shows that the first sidewall 211 and the second sidewall 212 of the first binary grating structure 204a are parallel to the third sidewall 214 and the fourth sidewall 216 of the second binary grating structure 204b. Additionally, the sidewalls 211, 212, 214, and 216 may be oriented perpendicular to the top surface 102A of the substrate 102. In some embodiments, the plurality of binary grating structures 204 may include submicron critical dimensions, for example, nanometer-sized dimensions corresponding to the width of the space 218 between the individual binary grating structures in the plurality of binary grating structures 204.

[0019] In embodiments, substrate 102 can be any suitable material that sufficiently transmits light of a desired wavelength or wavelength range and can serve as sufficient support for portion 200 of optical element 100. In some embodiments that can be combined with other embodiments described herein, the material of substrate 102 includes, but is not limited to, one or more silicon (Si), silicon dioxide (SiO2), or sapphire-containing materials. For example, the material of substrate 102 may include at least one of silicon (Si), silicon dioxide (SiO2), silicon carbide (SiC), germanium (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), fused silica, quartz, or sapphire. In another embodiment, the material of substrate 102 includes a high refractive index transparent material, such as high refractive index (high RI) glass. In other embodiments that can be combined with other embodiments described herein, the material of substrate 102 includes, but is not limited to, materials with a refractive index between about 1.7 and about 2.0.

[0020] In embodiments that can be combined with other embodiments described herein, the grating material layer 201 includes at least one of the following: silicon carbide (SiOC), titanium oxide (TiOx), TiOx nanomaterials, niobium oxide (NbOx), niobium germanium (Nb3Ge), silicon carbonitride (SiOCN), vanadium oxide (IV) (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 nitride carbon (SiCN), titanium nitride (TiN), zirconium dioxide (ZrO2), gallium phosphide (GaP), polycrystalline (PCD), nanocrystalline diamond (NCD), and materials containing doped diamond.

[0021] Figure 3 This is a flowchart of a method 300 for forming a part of an optical element 400 according to certain embodiments. Figures 4A to 4J This is a schematic cross-sectional side view of the optical element 400 during each operation of method 300.

[0022] At operation 302, a component material layer 404 is disposed above the surface of substrate 102. Component material layer 404 may be a single layer or a matrix stack comprising multiple layers. Component material layer 404 may be any material described above for grating material layer 201. For example, component material layer 404 may include at least one of silicon (Si), silicon dioxide (SiO2), silicon carbide (SiC), germanium (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), fused silica, quartz, or sapphire.

[0023] The element material layer 404 may be deposited on the surface of the substrate 302 by one or more of the following processes: physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD), flowable CVD (FCVD), atomic layer deposition (ALD), or spin coating. In one embodiment, which may be combined with other embodiments described herein, the element material of the element material layer 404 is selected based on the modulation depth and tilt angle of the optical structure to be formed in portion 200 of the optical element 100 and the refractive index of the substrate 102. In some embodiments that can be combined with other embodiments described herein, the element material layer 404 includes, but is not limited to, one or more of the following: materials containing silicon nitride (SiN), silicon carbide (SiOC), titanium oxide (TiOx), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium oxide (IV) (VOx), aluminum oxide (Al2O3), indium tin oxide (ITO), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (Si3N4), zirconium dioxide (ZrO2), or silicon carbonitride (SiCN). In some embodiments that can be combined with other embodiments described herein, the refractive index of the element material layer 306 may be between about 1.5 and about 2.65. In other embodiments that can be combined with other embodiments described herein, the refractive index of the element material layer 306 may be between about 3.5 and about 4.0.

[0024] At operation 304, a patterned hard mask 406 is formed over the element material layer 404. In embodiments, the patterned hard mask 406 can be made of any suitable material for patterning the element material layer 404 using a photolithography process, such as chromium or silicon nitride. In one embodiment, which can be combined with other embodiments described herein, the patterned hard mask 406 is opaque and is removed after the formation of portion 200 of the optical element 100. In another embodiment, the patterned hard mask 406 is transparent. In some embodiments, which can be combined with other embodiments described herein, the hard mask 312 includes, but is not limited to, materials containing chromium (Cr), silver (Ag), Si3N4, SiO2, TiN, or carbon (C). In some embodiments, forming a patterned hard mask 406 in operation 304 includes disposing a hard mask material layer 407 over a component material layer 404; disposing a photoresist layer over the hard mask material layer 407; patterning the photoresist layer to expose portions of the hard mask material layer 407; and removing the exposed portions of the hard mask material layer 407 to form a patterned hard mask 406 in which a hard mask structure 406a is patterned.

[0025] The hard mask material layer 407 can be disposed above the component material layer 404 using one or more of the following processes: liquid casting, spin coating, liquid spraying, dry powder coating, screen printing, doctor blade coating, PVD, CVD, PECVD, FCVD, ALD, vapor deposition, or sputtering. A hard mask 312 can be deposited such that its thickness is substantially uniform. In other embodiments, the hard mask 312 can be deposited such that its thickness varies from about 30 nm to about 50 nm at different points on the component material layer 306.

[0026] In an embodiment, as shown in Figure 4B, operation 304 may include depositing a photoresist stack 405 over a hard mask material layer 407. In an embodiment, the photoresist stack 405 includes an organic planarizing layer (OPL) 408, a silicon-containing anti-reflective coating (SiARC) 410, and a patterned photoresist layer 412. In an embodiment, OPL 408 may include any organic polymer and photoactive compounds having molecular structures that can be attached to the organic polymer. For example, OPL 408 may include a photosensitive organic polymer containing a photosensitive material that undergoes a chemical change upon exposure to electromagnetic (EM) radiation and is therefore configured to be removed using a developing solvent. In one embodiment, which may be combined with other embodiments described herein, a spin-coating process may be used to set OPL 408. In another embodiment that can be combined with other embodiments described herein, OPL 408 may include, but is not limited to, one or more of polyacrylate resin, epoxy resin, phenolic resin, polyamide resin, polyimide resin, unsaturated polyester resin, polyphenylene ether resin, polyphenylene sulfide resin, or benzocyclobutene (BCB). Next, SiARC 410 is formed over OPL 408. In an embodiment, SiARC 410 is formed from a silicon-based material using, for example, a chemical vapor deposition process or a spin-coating process.

[0027] Finally, a patterned photoresist layer 412 is formed by depositing a photoresist material on the SiARC 410 and developing the photoresist material. The patterned photoresist layer 412 defines a hard mask pattern for patterning the hard mask material layer 407. In one embodiment that can be combined with other embodiments described herein, a spin-coating process can be used to deposit the photoresist material on the OPL 408. In another embodiment that can be combined with other embodiments described herein, the patterned photoresist layer 412 may include, but is not limited to, a material containing a photosensitive polymer. In an embodiment, the patterned photoresist layer 412 may comprise a polymer material, such as polydimethylsiloxane (PDMS). In an embodiment, the patterned photoresist layer 412 may comprise a solvent, a photoresist resin, and a photoacid generator. The photoresist resin can be any positive or any negative photoresist resin. Representative photoresist resins include acrylates, phenolic varnish resins, poly(methyl methacrylate), and poly(olefin sulfone). Developing photoresist materials may include performing photolithography processes, such as photolithography and / or digital photolithography.

[0028] As described above, the patterned photoresist layer 412 defines a hard mask pattern for patterning the hard mask material layer 407 using the photoresist stack 405. After forming the patterned photoresist layer 412, the photoresist stack 405 and the hard mask material layer 407 are patterned using an etching process. It should be understood that patterning the hard mask material layer 407 using OPL 408 and SiARC 410 is an exemplary method. Other patterning methods can be used together. In some embodiments, the patterning method is chosen generally with respect to the size and shape of the structure to be patterned.

[0029] In operation 306, the photoresist stack 405 is removed using a suitable method (such as resist stripping). Stripping the patterned photoresist layer 412, SiARC 410, and OPL 408 yields a patterned hard mask 406. The patterned hard mask 406 includes a first portion 406A and a second portion 406B. The pattern in the first portion 406A exposes a first region 422 of the underlying component material layer 404, and the pattern in the second portion 406B exposes a second region 424 of the component material layer 404.

[0030] In operation 308, a first photoresist layer 414 is formed over the second portion 406B of the patterned hard mask 406 and the second region 424 of the component material layer 404, as shown in Figure 4D. The first photoresist layer 414 serves to protect the second region 424 of the component material layer 404 from damage during one or more etching processes in subsequent step 310. In a non-limiting example, the first photoresist layer 414 can be a photoresist film or a grayscale photoresist film. Alternatively, the first photoresist layer 414 can also be a hard mask, such as a chromium (Cr) hard mask prepared by thin film deposition and photolithographic patterning.

[0031] In operation 310, a first region 422 of the element material layer 404 exposed by the first portion 406A of the patterned hard mask 406 is etched to pattern the first region 422 of the element material layer 404 and form a plurality of optical element structures 109A in the element material layer 404, as shown in Figure 4E. In an embodiment, the plurality of optical element structures 109A formed in operation 310 include a plurality of binary optical features, as described above for... Figure 2 The multiple binary grating structures 204 are discussed. After forming multiple optical element structures 109A, the first photoresist layer 414 is removed from the patterned hard mask 406.

[0032] In operation 312, an organic dielectric layer (ODL) 418 is deposited over a patterned hard mask 406 and over a first region 422 and a second region 424 of a component material layer 404 exposed by the patterned hard mask 406. For example, the ODL 418 can be deposited by a vapor deposition process, such as by performing fluorination chemical vapor deposition over the patterned hard mask 406, the second region 424 of the component material layer 404, and the first region 422 of the component material layer 404 (including the space between the plurality of optical element structures 109A formed in the first region 422 of the component material layer 404).

[0033] In operation 314, ODL 418 can be etched, for example, by blanket etching, to remove excess portions of ODL 418 and expose the patterned hard mask 406. Operation 314 results in the formation of a flat surface on the top surface of the patterned hard mask 406 and ODL 418, such as... Figure 4G As shown.

[0034] In operation 316, a second photoresist layer 420 is deposited on the first portion 406A of the patterned hard mask 406, and the exposed section of ODL 418 is deposited over the first region 422 of the element material layer 404, as shown. Figure 4H As shown. Operation 316 includes keeping a second portion 406B of the patterned hard mask 406 and a segment of the ODL 418 deposited over a second region 424 of the element material layer 404 exposed. In contrast, a second photoresist layer 420 protects the segment of the ODL 418 exposed by the first portion 406A of the patterned hard mask 406 from erosion in one or more etching processes in subsequent step 318. While not limited, the second photoresist layer 420 may be a photoresist film or a grayscale photoresist film. Alternatively, the second photoresist layer 420 may also be a hard mask, such as a chromium oxide (CrO) hard mask prepared by thin film deposition and patterned by photolithography.

[0035] In operation 318, exposed sections of the ODL 418 above the second region 424 of the element material layer are selectively etched to form dielectric structures within the exposed ODL 418 sections. For example, operation 318 may include directional etching of the exposed sections of the ODL 418 to generate a plurality of blazed ODL structures 418A within openings in the second portion 406B of the patterned hard mask 406, as shown in Figure 4I. In embodiments, operation 318 may be performed using a selective etching process. The selective etching process may include, but is not limited to, at least one of IBE, RIE, or directional RIE. In embodiments where the ODL 418 is processed using an IBE process, the ion beam generated by the IBE may include, but is not limited to, at least one of a strip beam, a dot beam, or a full-substrate-size beam. The ion beam has an etching chemical that is selective for the patterned hard mask 306, i.e., etches only the exposed areas of the ODL 418. Performing the selective etching process etches away the exposed portions of the ODL 418 to form a plurality of blazed ODL structures 418A.

[0036] In operation 320, a transfer etching process is performed on multiple blazed ODL structures 418A of ODL 418 to form a second plurality of optical element structures 109B in the underlying element material layer 404. The result of operation 320 is as follows: Figure 4J As shown. In this embodiment, the transfer etching process removes ODL 418 and etches the element material layer 404 to create a second plurality of optical element structures 109B within a second region 424 of the element material layer 404. In this embodiment, the transfer etching process in operation 320 may be the same as the etching process (such as the IBE process) used in operation 318.

[0037] In operation 322, the second photoresist layer 420, segments of the ODL 418 deposited over the first region 422 of the element material layer 404, and the patterned hard mask 406 can then be removed, for example, by photoresist stripping and wet etching. Removal of the second photoresist layer 420, ODL 418, and patterned hard mask 406 results in portions 400 of the optical element 400, such as... Figure 4K As shown. In an embodiment, a portion of the optical element 400 formed by method 300 may correspond to a portion 200 of the optical element 100, said portion having a plurality of blazed grating structures 202 and a plurality of binary grating structures 204 formed in the grating material layer 201. In some embodiments, the patterned hard mask 406 may be made of a transparent material, such that the patterned hard mask 406 remains on the element material layer 404.

[0038] In summary, this paper describes a method for forming optical elements with blazed and binary grating structures on the same element material layer. The method includes forming a binary grating structure in a first region of the element material layer and a blazed grating structure in a second region of the element material layer. The blazed grating structure can be formed using selective etching processes (such as IBE), and the binary grating structure can be formed using a single-photolithography process. The method described herein can advantageously provide a way to readily form different optical structures in an element material layer to improve the optical performance of optical elements. For example, the method provides for forming a blazed grating structure that can be used as a grating structure for the input coupling region in a waveguide combiner. Due to the high diffraction efficiency of the blazed grating structure, it is well-suited for the input coupling region of an AR waveguide combiner. The method described herein can also be used to create element structures that serve as masters for nanoimprint lithography.

[0039] When describing the elements of this disclosure or their exemplary aspects or embodiments, the articles “a / an” and “the” are intended to mean the presence of one or more of the elements.

[0040] The terms “contains,” “includes,” and “have” are intended to be inclusive and mean that there may be additional elements besides those listed.

[0041] This article uses the term "coupling" to refer to direct or indirect coupling between two objects. For example, if object A is in physical contact with object B and object B is in physical contact with object C, then object A and object C can still be considered coupled to each other—even if object A and object C are not in direct physical contact with each other. For example, object A may be coupled to object B even if object B never has direct physical contact with object C.

[0042] Although the foregoing describes embodiments of this disclosure, other and additional embodiments of this disclosure may be devised without departing from the basic scope of this disclosure, and the scope of this disclosure is defined by the appended claims.

Claims

1. A method for forming an optical element, comprising the following steps: A patterned hard mask is formed over a component material layer deposited on the top surface of a substrate, wherein a first portion of the patterned hard mask exposes a first region of the component material and a second portion of the patterned hard mask exposes a second region of the component material layer. The first region of the element material layer is patterned to form a first plurality of optical features in the first region of the element material layer. A dielectric layer is deposited over the patterned hard mask and the element material layer; Selectively etch the dielectric layer and the component material layer to form a second plurality of optical features in the second region of the component material layer; as well as Remove the remaining portion of the dielectric layer deposited on the element material layer.

2. The method of claim 1, wherein the first plurality of optical features comprises a plurality of binary grating structures having a top surface substantially parallel to the top surface of the substrate and sidewalls substantially perpendicular to the top surface of the substrate.

3. The method of claim 1, wherein the second plurality of optical features comprises a plurality of blazed grating structures.

4. The method of claim 1, wherein the step of patterning the first region of the element material layer to form the first plurality of optical features includes the following steps: Photolithography and etching processes are performed in the first region of the component material layer.

5. The method of claim 1, wherein the step of selectively etching the dielectric layer and the component material layer comprises the following steps: The dielectric layer deposited on the second region of the element material layer exposed by the second portion of the patterned hard mask is oriented to form a plurality of dielectric structures over the second region of the element material layer, and the plurality of dielectric structures and the second region of the element material layer are etched to form a second plurality of optical features in the element material layer.

6. The method of claim 1, wherein the step of forming the patterned hard mask comprises the following steps: A hard mask material layer is deposited on the component material layer, and a nanoimprint lithography process is performed to pattern the hard mask material layer and form the patterned hard mask.

7. The method of claim 1, wherein the step of forming the patterned hard mask comprises the following steps: A hard mask material layer is deposited on the component material layer; A photoresist stack is formed on top of the hard mask material layer, the photoresist stack including an organic planarization layer (OPL), a silicon anti-reflective coating (SiARC), and photoresist; And etching the photoresist stack to form a pattern in the hard mask material layer.

8. The method of claim 1, further comprising the following steps: After the second plurality of optical features are formed in the element material layer, the patterned hard mask is removed.

9. The method of claim 1, wherein the step of selectively etching the dielectric layer and the component material layer comprises the following steps: The dielectric layer is patterned to form a plurality of dielectric structures over the second region of the element material layer; And etching the second region of the plurality of dielectric structures and the element material layer to form the second plurality of optical features in the second region of the element material layer.

10. A method for forming an optical element, comprising the following steps: A substrate is placed in a processing chamber, the substrate including a layer of element material deposited on the top surface of the substrate; A patterned hard mask is formed over the component material layer, a first portion of the patterned hard mask exposing a first region of the component material layer and a second portion of the patterned hard mask exposing a second region of the component material layer; A first photoresist layer is formed over the patterned hard mask, wherein the first photoresist layer prevents the second region of the element material layer from being etched; Etch the first region of the element material layer to form a first plurality of optical features in the element material layer; A dielectric layer is deposited over the first and second regions of the element material layer exposed by the patterned hard mask; A second photoresist layer is formed over the patterned hard mask, wherein the second photoresist layer prevents the section of the dielectric layer deposited over the first region of the element material from being etched; Selectively etch the sections of the dielectric layer exposed by the second portion of the patterned hard mask to form a plurality of dielectric structures over the second region of the element material layer; Etch the second region of the plurality of dielectric structures and the element material layer to form a second plurality of optical features in the second region of the element material layer; Remove the remaining portion of the second photoresist layer and the component material layer above the first region of the component material layer.

11. The method of claim 10, wherein the step of depositing the dielectric layer over the first and second regions of the element material layer comprises the following steps: The dielectric layer is deposited over the patterned hard mask, and the dielectric layer is etched to expose the patterned hard mask, forming a coplanar surface on the top surface of the dielectric layer and the top surface of the patterned hard mask.

12. The method of claim 10, wherein the first plurality of optical features comprises a plurality of binary grating structures, wherein the top surfaces of the plurality of binary grating structures are substantially parallel to the top surface of the substrate, and the sidewalls of the plurality of binary grating structures are substantially perpendicular to the top surface of the substrate.

13. The method of claim 10, wherein the second plurality of optical features comprises a plurality of blazed grating structures.

14. The method of claim 10, further comprising the following steps: The first photoresist layer is removed after the first plurality of optical features are formed, and the second photoresist layer is removed after the second plurality of optical features are formed.

15. The method of claim 10, further comprising the following steps: After removing the remaining portion of the dielectric layer above the first region of the element material layer, the patterned hard mask is removed.

16. The method of claim 10, wherein the step of forming the patterned hard mask comprises the following steps: A hard mask material layer is deposited on the component material layer; A photoresist stack is formed over the hard mask material layer, the photoresist stack comprising an organic planarization layer (OPL), a silicon antireflective coating (SiARC), and photoresist; as well as The photoresist stack is etched to form a pattern in the hard mask material layer.

17. An optical element, comprising: A substrate on which a component material layer is disposed; A first grating region is formed in the top surface of the element material layer. The first grating region is on a first portion of the element material layer and includes a plurality of binary grating structures. The top surfaces of the plurality of binary grating structures are substantially parallel to the top surface of the substrate, and the sidewalls are substantially perpendicular to the top surface of the substrate. as well as A second grating region is formed on a second portion of the element material layer in the top surface of the element material layer, and the second grating region includes a plurality of blazed grating structures.

18. The optical element of claim 17, wherein the first grating region and the second grating region correspond to the input coupling grating and the output coupling grating of the waveguide combiner, respectively.

19. The optical element of claim 17, wherein the plurality of blazed grating structures includes a blazed surface that is angled relative to the top surface of the substrate.

20. The optical element of claim 17, further comprising a patterned hard mask disposed above the element material layer, the patterned hard mask comprising a transparent material.

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