Hybrid integrated in-coupler and out-coupler grating structure

Abstract

A waveguide combiner includes a substrate and a first grating disposed within or over the substrate and comprising first grating structures. Each of the first grating structures include a first sidewall having a blazed surface, and a second sidewall opposing the first sidewall, the second sidewall is a vertical sidewall. A second grating is disposed within or over the substrate and comprises second grating structures, each of the second grating structures having a different height.

Description

44025302W001HYBRID INTEGRATED IN-COUPLER AND OUT-COUPLER GRATING STRUCTUREBACKGROUNDField

[0001] Embodiments of the present disclosure generally relate to optical devices for augmented, virtual, and mixed reality. More specifically, embodiments described herein provide waveguide combiners including one or more gratings that include grating structures of a different shape.Description of the Related Art

[0002] Virtual reality is generally considered to be a computer generated simulated environment in which a user has an apparent physical presence. A virtual reality experience can be generated in 3D and viewed with a head-mounted display (HMD), such as glasses or other wearable display devices that have near-eye display panels as lenses to display a virtual reality environment that replaces an actual environment.

[0003] Augmented reality, however, enables an experience in which a user can still see through the display lenses of the glasses or other HMD device to view the surrounding environment, yet also see images of virtual objects that are generated for display and appear as part of the environment. Augmented reality can include any type of input, such as audio and haptic inputs, as well as virtual images, graphics, and video that enhances or augments the environment that the user experiences. As an emerging technology, there are many challenges and design constraints with augmented reality. Accordingly, what is needed in the art are waveguide combiners including one or more gratings with asymmetric structures on a single substrate.SUMMARY

[0004] According to one or more embodiments, a waveguide combiner includes a substrate, a first grating disposed within or over the substrate and comprising first grating structures, each of the first grating structures including a first sidewall having a blazed surface, and a second sidewall opposing the first sidewall, the second sidewall is a vertical sidewall, and a second grating disposed within or over the substrate and including second grating structures, each of the second grating structures having a different height.44025302W001

[0005] According to one or more embodiments, a method includes forming a first grating disposed within or over a substrate, the first grating comprising first grating structures, each of the first grating structures including a first sidewall having a blazed surface, and a second sidewall opposing the first sidewall, the second sidewall is a vertical sidewall, and forming a second grating within or over the substrate, the second grating including second grating structures, each of the second grating structures having a different height.

[0006] According to one or more embodiments, a method includes forming first features and second features in a hardmask layer disposed over a grating layer disposed over a substrate having a first side opposing a second side, the first features formed over the first side of the substrate and the second features formed over the second side of the substrate, depositing a gap-fill layer over the hardmask layer, the gap-fill layer filling the first features and the second features, stripping the gap-fill layer from a field region of the hardmask layer, depositing a first patterned resist layer over the hardmask layer, the first patterned resist layer exposing the first features, etching a portion of the gap-fill layer disposed within the first features using an angled etch process to form slanted structures within the first features, forming first grating structures having a first shape on the first side of the substrate by etching the grating layer using a first etch process, stripping the first patterned resist layer and the gapfill layer; and forming second grating structures having a second shape over the second side of the substrate, the second shape being different than the first shape.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of scope, as the disclosure may admit to other equally effective embodiments.

[0008] FIG. 1 illustrates a perspective, plan view of a waveguide combiner, according to one or more embodiments.44025302W001

[0009] FIG. 2 illustrates a flow diagram of a method for fabricating a waveguide combiner according to one or more embodiments.

[0010] FIGS. 3A-3N illustrate perspective, cross-sectional views of the waveguide combiner during the method for fabricating the waveguide combiner.

[0011] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0012] Embodiments of the present disclosure generally relate to optical devices for augmented, virtual, and mixed reality. More specifically, embodiments described herein provide waveguide combiners including one or more gratings that include grating structures of a different shape.

[0013] FIG. 1 is a perspective, plan view of a waveguide combiner 100. It is to be understood that the waveguide combiner 100 described herein is an exemplary waveguide and that other waveguides may be used with or modified to accomplish aspects of the present disclosure. The waveguide combiner 100 includes a plurality of structures 102. The structures 102 may be disposed on a surface 103 of a waveguide substrate 101 , or disposed in the waveguide substrate 101. The waveguide substrate 101 has a substrate refractive index (Rl) nSub. The waveguide substrate 101 may be formed from any suitable material, provided that the waveguide substrate 101 can adequately transmit light in a selected wavelength or wavelength range and can serve as an adequate support for the waveguide combiner 100 described herein. Substrate selection may include substrates of any suitable material, including, but not limited to, amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, silicon oxide, polymers, and combinations thereof. In some embodiments, which may be combined with other embodiments described herein, the waveguide substrate 101 includes glass, silicon (Si), silicon dioxide (SiC>2), germanium (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), fused silica, quartz, sapphire (AI2O3), silicon carbide (SiC), lithium niobate (LiNbOs), indium tin oxide (ITO), or combinations thereof. In44025302W001 other embodiments, which may be combined with one or more of the embodiments described herein, the waveguide substrate 101 includes high-refractive-index glass. The high-refractive-index glass includes greater than 2 percent by weight of lanthanide (Ln), titanium (Ti), tantalum (Ta), or combinations thereof.

[0014] The structures 102 are nanostructures having a sub-micron critical dimension, e.g., a width less than 1 micrometer. Regions of the structures 102 correspond to one or more gratings 104. In one embodiment, which can be combined with other embodiments described herein, the waveguide combiner 100 includes at least a first grating 104a corresponding to an input coupling grating and a third grating 104c corresponding to an output coupling grating. In another embodiment, which can be combined with other embodiments described herein, the waveguide combiner 100 further includes a second grating 104b. The second grating 104b corresponds to a pupil expansion grating or a fold grating. A grating material of the structures 102 may include, but is not limited to, one or more of silicon oxycarbide (SiOC), titanium dioxide (TiO2), silicon dioxide (SiC>2), vanadium (IV) oxide (VOx), aluminum oxide (AI2O3), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tin dioxide (SnO2), zinc oxide (ZnO), tantalum pentoxide (Ta2Os), silicon nitride (SisN4), zirconium dioxide (ZrO2), niobium oxide (Nb20s), cadmium stannate (Cd2SnO4), or silicon carbon-nitride (SiCN) containing materials.

[0015] FIG. 2 illustrates a flow diagram of a method 200 for fabricating a waveguide combiner 100 according to one or more embodiments. FIGS. 3A-3N illustrate perspective, cross-sectional views of the waveguide combiner 100 during the method 200 for fabricating the waveguide combiner 100.

[0016] At operation 202, and as illustrated in FIG. 3A, a first patterned resist layer 306 is deposited onto the waveguide combiner 100. In one or more embodiments, the waveguide combiner 100 includes a hardmask layer 304 that is disposed over a grating layer 302 that is disposed over the waveguide substrate 101 . In one or more embodiments, the first patterned resist layer 306 may be deposited over the hardmask layer 304. In one or more embodiments, the first patterned resist layer 306 is an imprintable material that can be patterned by a nanoimprint process. In other embodiments, the first patterned resist layer 306 is a photosensitive material that may be patterned by a lithography process, such as grey-tone lithography,44025302W001 photolithography, or digital lithography, or by laser ablation process. In one or more embodiments, the hardmask material includes, but is not limited to, silicon oxide (SiOx), silicon nitride (SiNx), titanium oxide (TiOx), aluminum (Al), chromium (Cr), or combinations thereof.

[0017] The waveguide substrate 101 has a first side 301 a that corresponds to the first grating 104a and a second side 301 b that corresponds to the second grating 104b and / or the third grating 104c. As illustrated, the first side 301 a and the second side 301 b are disposed on the same (e.g., upper) surface of the waveguide substrate 101. In one or more embodiments, the first patterned resist layer 306 is patterned to form first features 308 on the first side 301 a of the waveguide substrate 101 and second features 310 on the second side 301 b of the waveguide substrate 101. The first features 308 and the second features 310 extend through a portion of the first patterned resist layer 306. The first features 308 formed in the first patterned resist layer 306 have a first depth 312 of about 10 nm to about 300 nm and a first width 313 from about 50 nm to about 500 nm. The second features 310 formed in the first patterned resist layer 306 have a second depth 314 from about 10 nm to about 300 nm and a second width 315 from about 50 nm to about 500 nm. The first depth 312 and the second depth 314 may be the same or different depths. The first width 313 and the second width 315 may be the same or different widths.

[0018] As noted above, the method 200 forms a waveguide combiner 100 having gratings with different shapes. For example, the method 200 forms a waveguide combiner 100 that includes first grating structures on the first side 301 a (i.e., the first grating 104a) of the waveguide substrate 101 having a first shape and second grating structures on the second side 301 b of the waveguide substrate 101 (i.e., the second grating 104b and / or the third grating 104c) having a second shape. In one or more embodiments, the first shape and the second shape are different. Although the method 200 describes first grating structures having a first shape that is a jointed blaze shape and second grating structures having a binary shape (second shape), this is for example purposes only. The first shape and the second shape may be any suitable shape. The first shape and the second shape may include, but are not limited to, jointed or disjointed blazed shaped gratings, angled shaped gratings, binary shaped gratings, or the like. Furthermore, each of the first grating structures and second grating structures may have the same or differing heights.44025302W001

[0019] At operation 204, as illustrated in FIG. 3B, the hardmask layer 304 is patterned using a first etch process. The first features 308 and the second features 310 are etched into the hardmask layer 304 using the first patterned resist layer 306 as an etch mask during the first etch process. The first etch process may be any suitable etching process, including, but not limited to, ion beam etching, focused ion beam etching, electron beam etching, reactive ion beam etching, or the like. In one or more embodiments, the first features 308 and the second features 310 extend through the entire hardmask layer 304, exposing portions of the grating layer 302.

[0020] At operation 206, and as illustrated in FIG. 3C, a gap-fill layer 316 is deposited over the waveguide combiner 100. The gap-fill layer 316 is deposited over the hardmask layer 304 and fills the first features 308 and the second features 310. In one or more embodiments, the gap-fill layer is depositing using any suitable deposition method, including, but not limited to, a flowable chemical vapor deposition (CVD) process. The gap-fill layer 316 can be an organic planarization layer (OPL) and oxide containing layer, or combinations thereof.

[0021] At operation 208, and as illustrated in FIG. 3D, the gap-fill layer 316 is stripped. When the gap-fill layer 316 is stripped, portions of the gap-fill layer 316 contacting a field region 317 of the hardmask layer 304 are stripped. The portions of the gap-fill layer 316 disposed within the first features 308 and the second features 310 remain.

[0022] At operation 210, and as illustrated in FIG. 3E, a second patterned resist layer 318 is deposited on the waveguide combiner 100. The second patterned resist layer 318 is deposited over the patterned hardmask layer 304. In one or more embodiments, the second patterned resist layer 318 is a photosensitive material that may be patterned by a lithography process, such as grey-tone lithography, photolithography or digital lithography, or by laser ablation process. In other embodiments, the second patterned resist layer 318 is an imprintable material that can be patterned by a nanoimprint process. As illustrated in FIG. 3E, the second patterned resist layer 318 is patterned to expose the first features 308 on the first side 301a of the waveguide substrate 101 . The second patterned resist layer 318 may be formed of a same or different material than the first patterned resist layer 306.44025302W001

[0023] At operation 212, and as illustrated in FIG. 3F, an angled etch process is performed to form slanted structures 320. The angled etch process is performed using the second patterned resist layer 318 as an etch mask. The portions of the gapfill layer 316 that are disposed within the first features 308 and exposed by the second patterned resist layer 318 are etched to form the slanted structures 320. Stated otherwise, the exposed portions of the gap-fill layer 316 are etched at an angle so that the slanted structures 320 have a structure height 321 that changes (i.e., increases or decreases) across the first width 313 of the first features 308. In one or more embodiments, the slanted structures 320 are angled with respect to a surface normal n to the waveguide substrate 101 . Each of the slanted structures 320 have an angle 9 that may be measured with respect to a surface parallel p of the waveguide substrate 101 . Each of the slanted structures 320 may have a same or different angle 6. The angled etch process may be any suitable etch process, including, but not limited to, ion beam etching, focused ion beam etching, electron beam etching, reactive ion beam etching, or the like.

[0024] As noted above, the method 200 is described as forming first grating structures having a jointed blaze shape with a same height (i.e., a first shape) is for example purposes only. Therefore, in other embodiments, such as where the first shape is a binary shape (or the like), operations 206-210 are optional.

[0025] At operation 214, and as illustrated in FIG. 3G, first grating structures 322 are formed on the first side 301 a of the waveguide substrate 101 a. In one or more embodiments, the first grating structures 322 are formed by etching the grating layer 302 on the first side 301 a of the waveguide substrate 101 using a second etch process (i.e., forming the first grating 104a). The second etch process may be any suitable etching process, including, but not limited to, ion beam etching, focused ion beam etching, electron beam etching, reactive ion beam etching, or the like.

[0026] The second patterned resist layer 318 and the slanted structures 320 are used as an etch mask during the second etch process. In one or more embodiments, the second etch process causes the first features 308 to be further etched into the grating layer 302. On the other hand, the second features 310 remain filled by the gap-fill layer 316 because the second features 310 are covered by the second patterned resist layer 318. As illustrated in FIG. 3G, after the second etch process,44025302W001 the second patterned resist layer 318 and the gap-fill layer 316 disposed within the first features 308 are stripped.

[0027] As illustrated in FIG. 3G, the first shape (i.e. , the first grating structures 322) is a blazed shape (i.e., blazed grating structures) that abut each other (i.e., are jointed). The first grating structures 322 have a blaze shape due to the changing structure height 321 of the slanted structures 320. The first grating structures 322 include a first sidewall 322a and a second sidewall 322b. The second sidewall 322b is a vertical sidewall and the first sidewall 322a has a blazed surface. The first sidewall 322a has a blaze angle a. The blaze angle a is the angle between the first sidewall 322a and a facet normal f of the first sidewall 322a.

[0028] Each of the first grating structures 322 may also have a first linewidth d1 and a first height hi . In one embodiment, which can be combined with other embodiments described herein, the first linewidth d1 of two or more the first grating structures 322 are the same. In other embodiments, the first linewidth d1 of two or more of the first grating structures may be different. For example, the first linewidth d1 of the first grating structures 322 may change (vary) across the first side 301 a. Furthermore, the first height hi of two or more first grating structures 322 may be the same or different. As noted above, even though the first shape (i.e., the shape of the first grating structures 322) have a jointed blaze shape, the first shape may be any suitable shape.

[0029] At operation 216, and as illustrated in FIG. 3H, a third patterned resist layer 324 is deposited onto the waveguide combiner 100. The third patterned resist layer 324 may be the same or a different material than the first and second patterned resist layers 306, 318. The third patterned resist layer 324 fills the first features 308 and the second features 310. In one or more embodiments, the third patterned resist layer324 is patterned such that a thickness 325 of the third patterned resist layer 324 is different over each of the second features 310. Furthermore, the thickness 325 of the third patterned resist layer 324 is at a constant thickness on the first side 301a of the waveguide substrate 101 a to ensure that the first side 301 a of the waveguide substrate 101 is not etched in a subsequent etching step. For example, the thickness325 of the third patterned resist layer 324 decreases (or increases) between each of the second features 310. Advantageously, as noted above, this allows for grating44025302W001 structures having a second shape (i.e., binary grating structures having different heights) to be formed in a subsequent step. As understood by those with ordinary skill in the art, the thickness 325 on the second side of the waveguide substrate 101 can be controlled, and / or an gap-fill layer (in the same manner described in operations 208-212) may be used to form second grating structures on the second side 301 b of the waveguide substrate 101 having any suitable second shape.

[0030] At operation 218, and as illustrated in FIG. 3I, second grating structures 326 having a second shape are formed on the second side 301 b of the waveguide substrate 101. In one or more embodiments, the second grating structures 326 are formed by etching the hardmask layer 304 and the grating layer 302 on the second side 301 b of the waveguide substrate 101 using a third etch process (i.e., forming the second grating 104b and / or the third grating 104c). The third etch process may be any suitable etching process, including, but not limited to, ion beam etching, focused ion beam etching, electron beam etching, reactive ion beam etching, or the like. In one or more embodiments, the third etch process causes the second features 310 to be further etched into the grating layer 302. Each of the second grating structures 326 may also have a second linewidth d2 and a second height h2. As noted above, due to the changing thickness 325 of the third patterned resist layer 324, each of the second features 310 extend into the grating layer 302 at different depths, causing the second height h2 between two or more second grating structures 326 to differ. In one embodiment, which can be combined with other embodiments described herein, the second linewidth d2 of two or more the second grating structures 326 are the same. In other embodiments, the second linewidths d2 may be different. For example, the second linewidth d1 of the second grating structures 326 may change (vary). In another embodiment, which can be combined with other embodiments described herein, the second linewidth d1 of the second grating structures 326 is the same (i.e., do not vary). As noted above, even though the second shape (i.e., the shape of the second grating structures 326) have a binary shape with differing second heights h2, the second shape may be any suitable shape, with the same and / or differing heights.

[0031] On the other hand, the first features 308 remain unaffected by the third etch process because the first features 308 are covered by the third patterned resist layer 324.44025302W001

[0032] At operation 220, and as illustrated in FIG. 3J the third patterned resist layer 324 and the hardmask layer 304 are stripped.

[0033] At operation 222, and as illustrated in FIG. 3K, a metal layer 328 is deposited over the waveguide combiner 100. The metal layer 328 may be deposited using any suitable metal layer deposition method, such as PVD, CVD, ALD, or the like. In one or more embodiments, the metal layer 328 fills the first features 308, fills the second features 310, and is formed over a field region 329 of the grating layer 302. The metal layer 328 includes, but is not limited to, aluminum, chrome, silver, or combinations thereof.

[0034] At operation 224, and as illustrated in FIG. 3L, a fourth patterned resist layer 330 is deposited over the first side 301a of the substrate. In one or more embodiments, the fourth patterned resist layer 330 is patterned to cover the first features 308 (and expose the second features).

[0035] At operation 226, and as illustrated in FIG. 3M, the portion of the metal layer 328 formed on the second side 301 b of the waveguide substrate 101 is stripped. The portion of the metal layer 328 formed on the second side 301 b of the waveguide substrate 101 is removed using the fourth patterned resist layer 330 as a mask. The portion of the metal layer 328 formed on the second side 301 b of the waveguide substrate 101 is stripped using a fourth etch process. The fourth etch process may be any suitable etching process, including, but not limited to, ion beam etching, focused ion beam etching, electron beam etching, reactive ion beam etching, or the like.

[0036] Because the fourth patterned resist layer 330 covers the first side 301 a of the waveguide substrate 101 , the metal layer 328 still fills the first features 308 and remains over the field region 329 of the grating layer 302 on the first side 301 a. On the other hand, because the second side 301 b is exposed, the portions of the metal layer 328 on the field region 329 of the grating layer 302 on the second side 301 b and within the second features 310 is removed.

[0037] At operation 228, and as illustrated in FIG. 3N, the fourth patterned resist layer 330 is stripped.44025302W001

[0038] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

44025302W001What is claimed is:1 . A waveguide combiner comprising: a substrate; a first grating disposed within or over the substrate and comprising first grating structures, each of the first grating structures comprising: a first sidewall having a blazed surface; and a second sidewall opposing the first sidewall, wherein the second sidewall is a vertical sidewall; and a second grating disposed within or over the substrate and comprising second grating structures, each of the second grating structures having a different height.

2. The waveguide combiner of claim 1 , wherein a linewidth of each of the first grating structures is different.

3. The waveguide combiner of claim 1 , wherein the first grating structures each have a different height.

4. The waveguide combiner of claim 1 , wherein the second grating structures each have a binary shape.

5. The waveguide combiner of claim 1 , wherein the first grating structures and the second grating structures comprise at least one of: silicon oxycarbide (SiOC), titanium dioxide (TiC ), silicon dioxide (SiC>2), vanadium (IV) oxide (VOx), aluminum oxide (AI2O3), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tin dioxide (SnO2), zinc oxide (ZnO), tantalum pentoxide (Ta2Os), silicon nitride (SisN4), zirconium dioxide (ZrO2), niobium oxide (Nb20s), cadmium stannate (Cd2SnO4), or silicon carbon-nitride (SiCN) containing materials.

6. The waveguide combiner of claim 1 , further comprising a metal layer disposed over the first grating structures.

7. The waveguide combiner of claim 6, wherein the metal layer comprises aluminum.44025302W0018. A method comprising: forming a first grating disposed within or over a substrate, the first grating comprising first grating structures, each of the first grating structures comprising: a first sidewall having a blazed surface; and a second sidewall opposing the first sidewall, wherein the second sidewall is a vertical sidewall; and forming a second grating within or over the substrate, the second grating comprising second grating structures, each of the second grating structures having a different height.

9. The method of claim 8, wherein a linewidth of each of the first grating structures is different.

10. The method of claim 8, wherein the first grating structures each have a different height.11 . The method of claim 8, wherein the second grating structures have a binary shape.

12. The method of claim 8, wherein the first grating structures and the second grating structures comprise at least one of: silicon oxycarbide (SiOC), titanium dioxide (TiO2), silicon dioxide (SiC>2), vanadium (IV) oxide (VOx), aluminum oxide (AI2O3), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tin dioxide (SnO2), zinc oxide (ZnO), tantalum pentoxide (Ta2Os), silicon nitride (Si3N4), zirconium dioxide (ZrO2), niobium oxide (Nb20s), cadmium stannate (Cd2SnO4), or silicon carbon-nitride (SiCN) containing materials.

13. A method comprising: forming first features and second features in a hardmask layer disposed over a grating layer disposed over a substrate having a first side opposing a second side, the first features formed over the first side of the substrate and the second features formed over the second side of the substrate; depositing a gap-fill layer over the hardmask layer, the gap-fill layer filling the first features and the second features;44025302W001 stripping the gap-fill layer from a field region of the hardmask layer; depositing a first patterned resist layer over the hardmask layer, the first patterned resist layer exposing the first features; etching a portion of the gap-fill layer disposed within the first features using an angled etch process to form slanted structures within the first features; forming first grating structures having a first shape on the first side of the substrate by etching the grating layer using a first etch process; stripping the first patterned resist layer and the gap-fill layer; and forming second grating structures having a second shape over the second side of the substrate, the second shape being different than the first shape.

14. The method of claim 13, further comprising: depositing a second patterned resist layer over the hardmask layer prior to forming the first features and the second features.

15. The method of claim 13, wherein the first grating structures comprise: a first sidewall having a blazed surface; and a second sidewall opposing the first sidewall, wherein the second sidewall is a vertical sidewall.

16. The method of claim 13, wherein the second grating structures each have a different height.

17. The method of claim 13, wherein forming the second grating structures having the second shape comprises: depositing a third patterned resist layer over the hardmask layer after forming the first grating structures; and forming the second grating structures by etching the hardmask layer and the grating layer using a second etch process.

18. The method of claim 13, further comprising depositing a metal layer over the first grating structures.44025302W00119. The method of claim 18, wherein depositing the metal layer over the first grating structures further comprises: stripping the hardmask layer; depositing the metal layer over the grating layer; depositing a fourth patterned resist layer over the metal layer, the fourth patterned resist layer exposing the first side of the substrate; and stripping a portion of the metal layer disposed over the second side of the substrate.

20. The method of claim 18, wherein the metal layer comprises aluminum.

Images