Waveguides

Abstract

The system and method described in this paper can be used to form gratings at various tilt angles on a single substrate across a grating material. This is achieved by determining the ion beam angle and changing the ion beam angle among multiple ion beam angles, thereby forming multiple gratings with varying angles and cross-sectional geometries. The substrate can be rotated about a central axis, and one or more process parameters (such as the duty cycle of the ion beam) can be controlled to form gratings with depth gradients.

Description

[Technical Field]

[0001] The embodiments disclosed herein generally relate to angled etching tools. More specifically, the embodiments described herein are provided for using angled etching tools to form gratings with different tilt angles, depth gradients, and wedge angles. [Previous Technology]

[0002] Augmented reality (AR) creates an experience for users to view their surroundings through the display lenses of AR glasses or other HMD devices. AR devices allow users to see images of virtual objects generated for display and appearing as part of the environment. AR can include sound and tactile input, as well as virtual images, graphics, and videos that can enhance or augment the user's environment.

[0003] One challenge in the design and fabrication of augmented reality devices is the display of virtual images superimposed on the surrounding environment. Enhancement waveguide combiners are used to facilitate this image superposition. First, the generated light is in-coupled to the enhancement waveguide combiner and propagates through it. Subsequently, the generated light is out-coupled from the enhancement waveguide combiner and superimposed on the surrounding environment. Surface-roughened gratings are used to couple the light into and out of the enhancement waveguide combiner. Using conventional designs may not adequately control the intensity of the output-coupled light.

[0004] Another challenge is that the waveguide combiner may use gratings with different tilt angles depending on the desired properties of the augmented reality device. Furthermore, the waveguide combiner may include gratings with different tilt angles to appropriately control the input and output coupling of light, and this tilt angle may have a different angle from the grating vector.

[0005] Therefore, what is needed is an improved method for manufacturing waveguide combiners and gratings and grating masters. [Summary of the Invention]

[0006] In one or more embodiments, a method of forming a grating includes: etching a hard mask layer to form a plurality of openings, the hard mask layer being disposed on a grating material layer disposed on a substrate; and forming a first grating in the grating material layer through the plurality of openings in the hard mask layer, wherein the first grating has a first shape vector and a first grating vector. The first grating can be formed by: determining a first ion beam angle ϑ1, the first ion beam angle ϑ1 being related to a first tilt angle ϑ1' and an angle φ1 between the first shape vector and the first grating vector; and positioning a first portion of the grating material layer in the path of an ion beam, the ion beam being at the first ion beam angle ϑ1 relative to the substrate, the substrate being held on a platform. The method also includes: adjusting one or more process parameters when the ion beam is at the first ion beam angle ϑ1 to form a first plurality of fins of the first grating, the first plurality of fins having the first shape vector, the first grating vector, and the first tilt angle ϑ1' relative to the surface normal of the substrate, such that the first plurality of fins are formed at the first tilt angle ϑ1'. In some examples, the first grating is further formed by rotating the substrate about the central axis of the platform to a first rotation angle between the ion beam and the first grating vector of the first grating.

[0007] In some embodiments, a method of forming a grating includes: etching a first grating material layer to form a first feature in the first grating material layer, the first grating material layer being disposed on a substrate; depositing an etch stop layer in the first feature; depositing a second grating material layer on the etch stop layer; and depositing a hard mask layer on the second grating material layer. The method further includes: etching the hard mask layer to form a plurality of openings; and forming a first grating in the second grating material layer through the plurality of openings, wherein the first grating has a first shape vector and a first grating vector. The first grating can be formed by: determining a first ion beam angle ϑ1, the first ion beam angle ϑ1 being related to a first tilt angle ϑ1' and an angle φ1 between the first shape vector and the first grating vector; and positioning a first portion of the substrate relative to an ion beam at the first ion beam angle ϑ1, the substrate being held on a platform, and the first ion beam angle ϑ1 being measured relative to a plane parallel to the platform. The method also includes adjusting one or more process parameters when the ion beam is at the first ion beam angle ϑ1 and in contact with the first portion of the substrate. In some examples, the process parameters may be or include the duty cycle of the ion beam, partial scanning of the ion beam, scanning speed of the ion beam, power supply for generating the ion beam, or any combination thereof.

[0008] In other embodiments, a method of forming a grating includes: etching a plurality of openings in a hard mask layer disposed on a grating material layer and the grating material layer disposed on a substrate; and etching the substrate through the plurality of openings in the hard mask layer to form a first grating in the grating material layer, the first grating including a plurality of fins formed in recesses, wherein the first grating has a first shape vector and a first grating vector. The first grating can be formed by: determining a first ion beam angle ϑ1, the first ion beam angle ϑ1 being related to a first tilt angle ϑ1' and an angle φ1 between the first shape vector and the first grating vector; and positioning a first portion of the grating material layer relative to an ion beam at the first ion beam angle ϑ1, the ion beam being adjustable relative to a plane parallel to the substrate in an angle range of about 15º to about 75º, the substrate being held on a platform. The method further includes: when the ion beam is at the first ion beam angle ϑ1, rotating the substrate about the central axis of the platform to a first rotation angle between the ion beam and the first grating vector of the first grating; and etching the first grating at the first angle to remove the top portions of the plurality of fins to form a wedge shape, wherein the first shape vector is a wedge vector.

Implementation Method

[0023] Virtual and augmented reality devices utilizing gratings can employ depth-tunable tilted gratings, wherein the direction in which the wedge-shaped grating is formed may not be aligned with the grating vector. Depth-tunable tilted gratings are etched into the target material using an ion beam capable of adapting to a range of angles, resulting in gratings with different tilt angles and depth gradients. The control of grating depth increases optical uniformity in optical devices such as waveguide combiners.

[0024] By using the systems and methods discussed herein, a grating with a depth gradient misaligned with the grating vector is formed by rotating the substrate and adjusting process parameters (e.g., the duty cycle of the ion beam), thereby generating a smooth gradient depth distribution curve relative to each orientation of the substrate. Waveguide assemblies or other optical elements can be formed using the systems and methods discussed herein, and further, masters for imprinting waveguide assemblies or other optical elements can be formed using the systems and methods discussed herein. The gratings formed as discussed herein can be formed in a wedge shape or exhibit other cross-sectional shapes.

[0025] The grating discussed herein is a pattern formed in a target material layer, the pattern consisting of a plurality of fins separated by a plurality of grooves. The plurality of fins can be formed with a plurality of depths and heights, and can be formed by etching the target material using an angled, adjustable ion beam and by rotating the substrate. The plurality of fins are formed at an angle relative to the plane of the substrate. The grating can be formed with a cross-sectional geometry having a wedge, rectangular, or other polygonal or circular shape or combination of shapes. The grating can be formed and then modified in height and / or critical dimensions. Depending on the embodiment, the critical dimensions discussed herein can refer to the fin height, pitch, width, or other dimensions of the grating.

[0026] The grating vector is measured perpendicular to the grating line, and this grating vector is aligned with the tilt angle of the fin. The wedge direction (vector) can be measured by a change in the depth of the wedge-shaped grating, for example, the direction in which the depth of the fin of the wedge-shaped grating increases. In one or more examples, the wedge vector is the same as the scanning direction of the device, and the substrate is configured in this scanning direction to form the grating. The angle formed between the wedge vector and the grating vector can be combined with the tilt angle of the fin to determine the ion beam angle used to form the grating.

[0027] FIG1 depicts a perspective front view of an enhancement waveguide combiner 100 according to one or more embodiments. It should be understood that the enhancement waveguide combiner 100 described below is an exemplary enhancement waveguide combiner, and other enhancement waveguide combiners can be used in conjunction with the pattern disclosed herein, or other enhancement waveguide combiners can be modified to complete the pattern disclosed herein. The enhancement waveguide combiner 100 includes an input coupling region 102 defined by a first plurality of gratings 108, an intermediate region 104 defined by a second plurality of gratings 110, and an output coupling region 106 defined by a third plurality of gratings 112. The input coupling region 102 receives an incident beam of intensity from a microdisplay. Each of the plurality of gratings 108 divides the incident beam into a plurality of modes, each incident beam having a mode.

[0028] Different beam patterns respond differently to the enhancement waveguide combiner 100. For example, a zero-order mode (T0) beam is refracted back or lost in the enhancement waveguide combiner 100. In contrast to the T0 beam, a positive first-order mode (T1) beam is coupled to the intermediate region 104 through the enhancement waveguide combiner 100, and a negative first-order mode (T-1) beam propagates in the enhancement waveguide combiner 100 in the opposite direction to the T1 beam. Ideally, the incident beam is split into T1 beams with all the intensity of the incident beam to guide the virtual image to the intermediate region 104. In one or more embodiments, each of the plurality of gratings 108 is angled to suppress the T-1 and T0 beams. The T1 beam undergoes total internal reflection (TIR) ​​through the enhancement waveguide combiner 100 until it contacts a second plurality of gratings 110 in the intermediate region 104.

[0029] When the T1 beam contacts the gratings of the second plurality of gratings 110, the T1 beam is split into a T0 beam, a T1 beam, and a T-1 beam. The T0 beam is refracted back or lost in the enhancement waveguide combiner 100, and the T1 beams undergo TIR in the intermediate region 104 until the T1 beam contacts another grating of the second plurality of gratings 110, and the T-1 beam is coupled to the output coupling region 106 through the enhancement waveguide combiner 100. The T1 beams undergoing TIR in the intermediate region 104 continue to contact the second plurality of gratings 110 until one of the following occurs: (1) the intensity of the T1 beam coupled to the intermediate region 104 through the enhancement waveguide combiner 100 is exhausted, or (2) the remaining T1 beams propagating through the intermediate region 104 reach the end of the intermediate region 104. The second plurality of gratings 110 are adjusted to control the T1 beams coupled to the intermediate region 104 through the beam waveguide combiner 100. Adjusting the second plurality of gratings 110 controls the intensity of the T-1 beam coupled to the output coupling region 106 to modulate the field of view of the virtual image generated by the microdisplay from the user's perspective and increase the user's viewing angle of the virtual image.

[0030] In one or more embodiments, the second plurality of gratings 110 may be referred to herein as wedge-shaped and is defined by the tilt angle of the fins forming the wedge (discussed below), a first side 114, and an angled second side 116 opposite to the first side 114. The angled side 116 includes a first portion 116A and a second portion 116B. The second plurality of gratings 110 is further defined by a curved first end 118 and an angled second end defined by the first portion 120A and the second portion 120B. Depending on the embodiment, the curved first end 118 may take various curvatures. A first angle α is defined by the first portion 116A and the second portion 116B of the angled side 116. A second angle β is defined by the second portion 116B and the first portion 120A of the angled second end. A third angle γ may be defined by the first portion 120A and the second portion 120B of the angled second end. The fourth angle δ can be defined by the first side 114 and the second portion 120B of the angled second end. The systems and methods discussed herein form a wedge or other shape, wherein each fin of the second plurality of gratings 110 has a first end and a second end, the first end of which is positioned along the angled second side 116, and the second end of which is positioned along the first side 114. Each fin of the second plurality of gratings 110 can be further defined by various geometric features. For example, the first side of the fin can have a ramp (angle) such that each fin along the angled second side 116 has a ramp. The second side of each fin can have an undercut such that each fin along the first side 114 has an undercut.

[0031] Further, in FIG1, a depth gradient is defined in the direction from a first side 110A to a second side 110B of the plurality of gratings 110. FIG1 also illustrates the depth gradient for at least a second plurality of gratings 110 and a third plurality of gratings 112. Each depth gradient can be further defined by a depth gradient in a direction in which the depth of the fins of the gratings or plurality of gratings increases or decreases. The depth gradient is shown in shaded in FIG1. ​​For the second grating 110, the depth gradient increases from the first side 110A to the second side 110B, and from the top 112A to the bottom 112B of the third plurality of gratings 112. The grating vectors of the second plurality of gratings 110 (not shown here) are measured orthogonally to the second plurality of gratings 110. The wedge angle of the second plurality of gratings 110 can be defined as the angle between the grating vector and the depth gradient. Similarly, the grating vectors of the third complex gratings 112 (not shown here) are measured orthogonally to the third complex gratings 112.

[0032] The T-1 beam coupled to the output coupling region 106 through the enhancement waveguide combiner 100 undergoes a TIR within the enhancement waveguide combiner 100. The T-1 beam undergoes a TIR until it contacts one of the plurality of gratings 112, wherein the T-1 beam splits into (a) a T0 beam, which is refracted back or lost in the enhancement waveguide combiner 100; (b) a T1 beam, which undergoes a TIR in the output coupling region 106 until it contacts another grating of the plurality of gratings 112; and (c) a T-1 beam, which is coupled out from the enhancement waveguide combiner 100. The T1 beam undergoing a TIR in the output coupling region 106 continues to contact the gratings of the plurality of gratings 112 until the intensity of the T-1 beam coupled to the output coupling region 106 through the enhancement waveguide combiner 100 is exhausted, or the remaining T1 beam propagating through the output coupling region 106 has reached the end of the output coupling region 106. Multiple gratings 112 must be adjusted to control the T-1 beam coupled to the output coupling region 106 through the enhancement waveguide combiner 100, so as to control the intensity of the T-1 beam coupled out from the enhancement waveguide combiner 100, thereby further modulating the field of view of the virtual image generated from the microdisplay from the user's perspective, and further increasing the user's viewing angle of the virtual image.

[0033] FIG2A depicts a schematic cross-sectional side view of an angled etching system 200 according to one or more embodiments, and FIG2B depicts a schematic cross-sectional side view of the angled etching system 200. To form a grating with an angled tilt, the angled etching system 200 etches a grating material 212 disposed on a substrate 210. In one or more embodiments, the grating material 212 is disposed on an etch stop layer 211 disposed on the substrate 210, and a patterned hard mask 213 is disposed on the grating material 212. In one or more embodiments, the material of the grating material 212 is selected according to the tilt angle ϑ' of each grating and the refractive index of the substrate 210 to control the input and output coupling of light and to facilitate the propagation of light through the waveguide combiner. In some embodiments, the grating material 212 comprises a material containing silicon carbide (SiOC), titanium dioxide (TiO2), silicon oxide (e.g., silicon dioxide (SiO2)), vanadium (IV) oxide (VO2), aluminum oxide (Al2O3), indium tin oxide (ITO), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (SiN or Si3N4), titanium nitride (TiN), and / or zirconium dioxide (ZrO2). The refractive index of the grating material 212 is between about 1.5 and about 2.65. In yet another embodiment, the patterned hard mask 213 is an opaque hard mask that is removed after the waveguide combiner is formed. For example, the opaque hard mask comprises a reflective material such as chromium or silver.

[0034] In some embodiments, the patterned hard mask 213 is a transparent hard mask. In one or more embodiments, the etch stop layer 211 is an opaque etch stop layer that is removed after the waveguide combiner is formed. In some embodiments, the etch stop layer 211 is a transparent etch stop layer. The angled etch system 200 is configured to form an angled grating as discussed herein, for example, by executing a plurality of instructions using a controller (not shown). The plurality of instructions executed may include a tilt angle, an ion beam angle, a variation of the ion beam angle during grating formation, a wedge angle, a depth gradient, and / or other patterns of the wedge to be formed from the grating.

[0035] The angled etching system 200 includes an ion beam chamber 202 housing an ion beam source 204. The ion beam source is configured to generate an ion beam 216, such as a strip beam, a dot beam, or a beam spanning the entire substrate size. The ion beam chamber 202 is configured to guide the ion beam 216 at an angle α relative to the surface normal 218 of the substrate 210. The substrate 210 is held on a platform 206 coupled to a first actuator 208. The first actuator 208 is configured to move the platform 206 in a scanning motion along the y-direction and / or z-direction. In order to form a grating having a tilt angle ϑ' relative to the surface normal 218, the ion beam source 204 generates the ion beam 216, and the ion beam chamber 202 guides the ion beam 216 to the substrate 210 at an angle α. The first actuator 208 positions the platform 206 such that the ion beam 216 contacts the grating material 212 at an ion beam angle ϑ, and etches a grating with a tilt angle ϑ' on the desired portion of the grating material 212. One or more process parameters (e.g., the duty cycle of the ion beam 216) can be adjusted to form multiple fins of the grating at varying depths.

[0036] FIG3 depicts a schematic perspective view of a portion 300 of a substrate 302 according to one or more embodiments. The ion beam angle ϑ is between about 0° and about 90°. The ion beam angle ϑ is adjustable during grating fabrication, preferably between about 15° and about 75°, because an ion beam angle ϑ close to about 0° or about 90° will cause the grating 304 to have a tilt angle ϑ' of about 0° or about 90°, so that the grating 304 is not tilted. Therefore, the tilt angle ϑ' can be determined by the relative orientation between the ion beam angle and the rotational position of the substrate. The substrate 302 is rotated about the x-axis 306 of the platform 206, thereby creating a rotation angle ϕ between the grating vector of the grating 304 before rotation and the grating vector after rotation, which is measured orthogonal to the grating 304. In order to form a wedge as discussed herein, the duty cycle of the ion beam and / or other process parameters can be adjusted to change the etching depth.

[0037] In one or more examples, the process parameters can be or include the duty cycle of the ion beam, partial scanning of the ion beam, scanning speed of the ion beam, power supply (e.g., voltage) for generating the ion beam, or any combination of the above parameters. In some examples, the duty cycle is controlled from about 5% to about 85%, where 5% of the duty cycle forms shallow fins of the grating, and 85% of the duty cycle forms the fins of the grating to a deeper depth. In other examples, the partial scanning of the ion beam, the scanning speed of the ion beam, and / or the power supply for generating the ion beam can be independently controlled to form various depths of the grating fins (e.g., from relatively shallow to relatively deep). Although the formation of gratings with wedge profiles is discussed herein, in other examples, different gratings with varying depth gradients and tilt angles can be formed, resulting in gratings with curved, bow-shaped, angled, flat, or other cross-sectional profiles (which are combinations of various geometries).

[0038] In one or more embodiments, the ion beam angle ϑ is aligned with the depth gradient of the grating. The depth gradient discussed above is a measurement of the change in depth of the grating throughout the fin, and the depth gradient is the direction of the change in fin depth. The tilt angle of the fin can be determined by rotating the grating angle using the equation ϑ=atan(tan(ϑ') / cos(φ)), where ϑ=ion beam angle, ϑ'=tilt angle of the fin, and φ=angle between the shape vector (e.g., wedge vector) and the grating vector. The shape vector is the direction of the change in the depth gradient of the grating, e.g., the direction of increasing fin depth. The depth gradient is the change in depth of the grating throughout the fin. In one or more examples, for a 22.5° tilted grating, where the wedge is offset from the grating vector by 45°, ϑ=atan(tan(22.5°) / cos(45°)) ≈30.3°.

[0039] Figure 4 is a flowchart illustrating a method 400 for forming a grating according to one or more embodiments. Figures 5A to 5J illustrate the structures generated during different intervals in method 400. In method 400, in operation 402, a target stack is fabricated in a plurality of sub-operations that can include chemical vapor deposition (CVD). The target stack formed in operation 402 is shown in Figure 5A, which includes a substrate 502 and a grating material layer 504 formed on the substrate 502. The target stack further includes a hard masking layer 506 formed on the grating material layer 504. The substrate 502 can be formed of a silicon-based material such as SiO2, and the hard masking layer 506 can be formed of a metallic material such as chromium or titanium, or a dielectric material such as silicon carbonitride (SiCN). The grating material layer 504 can include silicon carbide (SiOC), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium oxide (VO2), aluminum oxide (Al2O3), indium tin oxide (ITO), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (Si3N4), titanium nitride (TiN), or zirconium dioxide (ZrO2). The stack shown in Figure 5A can be fabricated using various sub-operations, including CVD. In one or more examples, the grating material layer 504 is 150 nm to 350 nm thick, and the hard mask layer 506 is about 15 nm to about 70 nm thick.

[0040] At operation 404, a continuous portion of the hard mask layer 506 is removed to form an opening 508 in the hard mask layer 506. Operation 404 can be performed using one or more chemicals in a wet stripping etch operation to form the opening 508. Figure 5B shows the structure obtained due to the removal of this portion of the hard mask layer 506 in operation 404. In operation 406, a portion of the grating material layer 504 is etched (or otherwise removed) to form a feature 510. Figure 5C shows the structure obtained due to the formation of the feature 510 in operation 406. Operation 406 can be performed by using selective area processing (SAP) etching to remove one or more portions of the grating material layer 504. During operation 406, SAP etching can be used to form the feature 510, which can contain various cross-sections, including but not limited to the wedge-shaped cross-section of the feature 510 shown in Figure 5C. For example, although feature 510 is shown as wedge-shaped or triangular in Figure 5C, in other examples, various polygonal or combined shapes can be formed in operation 406 by using SAP etching. Feature 510 can be referred to as a recess and is defined by a first side 510A, a transition surface 510B, and a second side 510C. The second side 510C is opposite to the first side 510A, and the transition surface 510B extends between the first side 510A and the second side 510C. The transition surface 510B is formed at an angle 512 relative to the substrate 502. In the example in Figure 5C, the second side 510C is formed to a greater depth than the first side 510A.

[0041] In one or more embodiments, SAP can include a designed number of exposure cycles, wherein a given exposure cycle involves scanning the processing beam along a specific direction and subsequently rotating the substrate 502 to a new rotational position. In some examples, SAP etching can include 2 exposure cycles, 4 exposure cycles, 6 exposure cycles, 8 exposure cycles, or more exposure cycles. In some examples, SAP etching can include different exposure cycles, wherein the substrate 502 is positioned at different rotational positions such that each cycle is performed at a different rotational position. Additional forms of SAP etching are described and discussed in U.S. Patent No. 10,269,663 (column 4, line 34 through column 7, line 61) and U.S. Patent No. 10,302,826, which are incorporated herein by reference.

[0042] In operation 408, an etch stop layer 514 is deposited on feature 510. Figure 5D shows the structure obtained by depositing the etch stop layer 514 in operation 408. The etch stop layer 514 can be deposited in operation 408 via another process such as CVD, atomic layer deposition (ALD), or forming a conformal coating on feature 510. The etch stop layer 514 can be formed to a thickness of 15 nm to 50 nm. In one or more examples, the etch stop layer 514 is formed in operation 408 from a nitride such as tantalum nitride. In another example, the etch stop layer 514 is formed in operation 408 from a silicon-based material such as silicon oxide.

[0043] In operation 410, a second grating material layer 516 is deposited on the etch stop layer 514. The second grating material layer 516 can be deposited using CVD and formed on the inside of feature 510 and on either side of feature 510, resulting in an excess of material 516A. Figure 5E shows the structure obtained by depositing the second grating material layer 516 in operation 410. In one or more embodiments, each of the grating material layer 504 and the second grating material layer 516 is formed of at least one of the following materials: silicon carbide (SiOC), titanium oxide (e.g., titanium dioxide (TiO2)), silicon oxide (e.g., silicon dioxide (SiO2)), vanadium (IV) (VO2), aluminum oxide (Al2O3), indium tin oxide (ITO), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (SiN or Si3N4), titanium nitride (TiN), zirconium dioxide (ZrO2), oxynitrides of the above materials, or any combination of the above materials. The hard mask layer 506 is formed of silicon nitride, silicon oxide, a metal-based layer containing titanium or chromium, a dopant of the above materials, an alloy of the above materials, or any combination of the above materials.

[0044] Subsequently, in operation 412, excess material is removed (planarized) from the second grating material layer 516 to form a planarized surface 518. Planarization in operation 412 can be performed using SAP etching. Figure 5F shows the structure obtained by planarization in operation 412. In operation 414, a second hard mask layer 520 is deposited on the second grating material layer 516 and etched to form a plurality of openings 522. Figure 5G shows the structure obtained by depositing the second hard mask layer 520 in operation 414. The second hard mask layer 520 can be deposited in operation 414 using CVD and etched using deep ultraviolet (DUV) lithography to form a plurality of openings 522 (e.g., by forming a pattern using DUV, which is transferred to the hard mask layer 520 through the etching process). In other examples, a plurality of openings 522 can be formed by patterning the second hard mask layer 520 using nano-transfer lithography (NIL). In one or more examples of operation 414, a plurality of openings 522 can be formed in a plurality of sub-operations, including: depositing a photoresist (not shown) on the second hard mask layer 520, performing DUV photolithography to pattern the photoresist, and etching the second hard mask layer 520 through the patterned photoresist. The photoresist can then be removed before operation 416. The second hard mask layer 520 can be formed from a material similar to the material discussed above for forming the hard mask layer 506. In one or more examples, the second hard mask layer 520 is formed from a material different from the material of the etch stop layer 514, such that the two materials have different etch selectivity.

[0045] In operation 416, a first grating 524, including a first plurality of fins 526, is formed in the second grating material layer 516 through a plurality of openings 522 in the second hard mask layer 520. FIG. 5H shows the structure obtained by forming the first grating 524 in operation 416. Operation 416 can be performed using an angled etching system discussed above in FIGS. 2A and 2B to form the first plurality of fins 526 at a first tilt angle. During operation 416, in order to form the first grating 524, a first portion of the substrate 502 is positioned relative to the ion beam at a first ion beam angle. Operation 416 includes determining the first ion beam angle ϑ1 of the first grating 524. As discussed above, the first ion beam angle ϑ1 can be determined by rotation from the grating angle of the first grating using the equation ϑ1 = atan(tan(ϑ1') / cos(φ1)).

[0046] The substrate 502 is held on the platform, and as discussed above, a first ion beam angle is measured relative to a plane parallel to the platform. When the ion beam is at the first ion beam angle, the substrate 502 rotates about the central axis of the platform to a first rotation angle between the ion beam and the first grating vector of the first grating 524. The ion beam is a strip beam that forms an angle relative to the plane parallel to the platform, which can be adjusted from about 15 degrees to about 75 degrees. The first grating 524 has a first plurality of fins 526, such that the fins adjacent to the first end 524A of the first grating 524 are formed to a shallower depth than the fins adjacent to the second end 524B of the first grating 524. In one or more examples, the depth of the first grating is from about 10 nm to about 400 nm, and the width of each of the plurality of fins 526 is from about 30% to about 70% of the spacing between the plurality of fins 526. A plurality of fins 526 are formed at a first tilt angle as discussed above, which can range from about 0 degrees to about 60 degrees. The plurality of fins 526 can be associated with a first depth gradient, such that the height from the first side 524A to the second side 524B of the grating 524 increases, thereby increasing the etching depth. The height variation of the fins 526 along the bottom surface of the first grating 524 can create a wedge angle 528. The ion beam has one or more process parameters (e.g., duty cycle) that can be tuned to form the first grating 524. For example, the process parameters when the ion beam is at a first ion beam angle and in contact with a first portion of the substrate can be tuned between about 5% and about 85% of the duty cycle. Shorter tuning times for the process parameters (e.g., 5%) can be used to form fins of shallower depth, such as those at or near the first end 524A of the first grating 524. Similarly, a longer tuning time (e.g., 85%) for process parameters can be used to form fins with a greater comparative depth, such as those at or near the second end 524B of the first grating. In one or more embodiments, the first ion beam angle used to form the first grating 524 in operation 416 is aligned with a first depth gradient of the first grating 524.

[0047] In one or more embodiments, after the formation of the first grating 524, additional plurality of fins can be formed during subsequent repeated operations of operation 416. In this example, in operation 416, after the formation of the first grating, the first ion beam angle is changed to a second ion beam angle different from the first ion beam angle. Subsequent repeated operations of operation 416 include determining a subsequent ion beam angle ϑX, which may be different from the first ion beam angle ϑ1, for example, a second ion beam angle ϑ2 for the first grating 524 may be determined. As discussed above, the second ion beam angle ϑ2 can be determined using the equation ϑ2 = atan(tan(ϑ2') / cos(φ2)). When the ion beam is positioned at the second ion beam angle, a second portion of the substrate is positioned in the path of the ion beam. When the ion beam is at the second ion beam angle, the substrate is rotated about the central axis of the platform to a second rotation angle between the ion beam and the second grating vector of the second grating. Therefore, in operation 416, multiple gratings can be formed on a single substrate with different tilt angles and different depth gradients by changing the ion beam angle and rotating the substrate.

[0048] In operation 418, for example, the second hard mask layer 520 is removed by using wet stripping etching as discussed above with respect to operation 404. Figure 5I shows the structure obtained by removing the second hard mask layer 520 in operation 418. In some embodiments of method 400, in operation 420, a coating 526A is optionally formed on a plurality of fins 526 using an ALD process. In one or more examples, the coating 526A comprises one or more layers of oxide. Figure 5J shows the structure obtained by forming a coating on a plurality of fins 526 in operation 420. In examples where more than one grating is formed, in operation 420, some or all of the gratings may be coated. In one or more examples, an ALD process may be used in operation 420 to coat the plurality of fins 526 with oxide. In some examples, other methods for forming conformal coatings on the plurality of fins 526 may be employed. In one or more examples, it is possible to apply multiple fins 526 in operation 420 to adjust or refine the key dimensions of multiple fins 526.

[0049] FIG6 is a flowchart illustrating a method 600 for forming a grating according to one or more embodiments described and discussed herein. FIGS. 7A to 7G show structures generated during different intervals in method 600. Method 600 includes operations 402, 404, and 406, which have been discussed in detail above with respect to method 400 in FIG4. FIG7A illustrates the structure formed by operation 402, which includes a substrate 502, a grating material layer 504, and a hard mask layer 506. FIG7B illustrates the structure formed by operation 404, wherein an opening 508 is formed in the hard mask layer 506 using wet stripping (chemical) etching, as discussed above in method 400. FIG7C illustrates the structure formed by operation 406 after a portion of the first grating layer 504 is removed to form feature 510. Similar to that shown in Figure 5C, feature 510 can refer to a recess or an angled recess, and is defined by a first side 510A, a second side 510C opposite to the first side 510A, and a transition surface 510B extending between the first side 510A and the second side 510C. An angle 512 is formed between the transition surface 510B and the second side 510C. However, in method 600 of Figure 6, in contrast to method 400 in which an etch stop layer and a second grating material layer are deposited after operation 406, a hard mask layer 702 is deposited in operation 602. The hard mask layer 702 can be deposited in operation 602 using CVD. Figure 7D shows the structure obtained by the deposition of the hard mask layer 702 in operation 602. The hard mask layer 702 can be formed of a material similar to the materials discussed above with respect to the hard mask layer 506 and the second hard mask layer 520.

[0050] Subsequently, in operation 604, a hard mask layer 702 (which may be referred to herein as a second hard mask layer) is etched to form a plurality of openings 704. Figure 7E shows the structure obtained due to the formation of openings in the hard mask layer 702 in operation 604. In some examples, the hard mask layer 702 is also removed from multiple portions 710 of the grating material layer 504 during operation 604. A plurality of openings 704 can be formed in a plurality of sub-operations, including: depositing a photoresist (not shown) on the hard mask layer 702, performing DUV lithography to pattern the photoresist, and etching the hard mask layer 702 through the patterned photoresist. The photoresist can then be removed before operation 606. In other examples, a plurality of openings 704 can be formed using NIL in operation 604.

[0051] In operation 606, a grating 706 can be formed by using angled etching to include a plurality of fins 708 formed at an angle and with depth gradients and wedge angles as discussed above. Operation 606 includes determining a first ion beam angle ϑ1 for forming the grating 706. As discussed above, the first ion beam angle ϑ1 can be determined using the equation ϑ1 = atan(tan(ϑ1') / cos(φ1)). FIG7F shows the structure obtained by forming the grating 706 in operation 606. The grating 706 formed in operation 606 can be formed in a manner similar to one or more gratings discussed in operation 416 in FIG4, which is achieved by using an angled etching system by rotating the substrate 502 and changing the ion beam angle. For example, the grating 706 formed in operation 606 can be formed by angled etching, which is achieved by rotating the substrate 502 about a central axis perpendicular to the substrate and / or the platform on which the substrate is disposed. An ion beam (e.g., a strip beam) is positioned at a predetermined angle relative to the substrate 502, and this ion beam is used to form a plurality of fins 708 to varying depths by controlling the duty cycle of the ion beam. Operation 606 can be repeated as an abbreviated operation similar to operation 416 discussed above to form a plurality of gratings with varying tilt angles, depth gradients, and wedge angles. As discussed above, each ion beam angle ϑX can be determined for each grating subsequently formed in operation 606. In operation 608 of method 600, one or more portions 710 of the grating material layer 504 are removed from the grating 706 using SAP etching to form a wedge 712. Figure 7G shows the wedge 712 obtained after forming a plurality of fins 708 of the grating 706 after removing multiple portions 710 of the grating material layer 504 in operation 608. Figure 7G further shows the wedge 712 in which the hard mask layer 702 is removed, which can occur in operation 608 or other operations not discussed herein.

[0052] FIG8 is a flowchart illustrating a method 800 for forming a grating according to one or more embodiments described and discussed herein. FIGS. 9A to 9D illustrate the structures generated during different intervals in method 800. In operation 802 of method 800, a substrate including a grating material layer 902 is formed using, for example, CVD. FIG9A illustrates the structure obtained by forming the grating material layer 902 in operation 802. In particular, FIG9A shows the grating material layer 902, which can be formed using CVD from a silicon-based material to a thickness from about 200 nm to about 400 nm, the silicon-based material being derived from at least one of: silicon oxycarbide (SiOC), silicon oxide (e.g., silicon dioxide (SiO2)), silicon nitride (SiN or Si3N4), or silicon carbonitride (SiCN). A hard mask layer 904 is formed on the grating material layer 902 and can be formed of a metal or dielectric material, as discussed above with respect to methods 400 and 600.

[0053] In operation 804, a plurality of openings 906 are formed in the hard mask layer 904. Figure 9B shows the structure obtained by forming the hard mask layer 904 in operation 804. In operation 804, a plurality of openings 906 can be formed in a plurality of sub-operations, which include: depositing a photoresist (not shown) on the hard mask layer 904, performing DUV lithography and etching or NIL to pattern the photoresist, and etching the hard mask layer 904 through the patterned photoresist. The photoresist can then be removed before operation 806. Figure 9C shows the structure obtained by etching the hard mask layer 904 in operation 804.

[0054] In operation 806, a grating 908 is formed in the grating material layer 902 from a silicon-based material using an angled etching system as discussed herein. Operation 806 includes determining a first ion beam angle ϑ1 for forming the grating 908. As discussed above, the first ion beam angle ϑ1 can be determined using the equation ϑ1=atan(tan(ϑ1') / cos(φ1)). The grating 908 can be formed as a wedge-shaped grating, wherein the plurality of fins 910 of the grating 908 increase in size from a first end 908A of the grating 908 to a second end 908B of the grating 908. In operation 806, the grating 908 can be formed in a manner similar to the gratings in operations 416 and 606 described above. The duty cycle of an ion beam with an adjustable angle is controlled to form each of the plurality of fins 910 to a varying depth, and the substrate on which the grating material layer 902 is disposed can also be rotated. In contrast to method 400, an etch stop layer is not used in method 800. In operation 808, the hard mask layer 904 is removed, for example, using chemical etching via wet stripping. Figure 9D shows the structure obtained by removing the hard mask layer 904 in operation 808.

[0055] FIG10 is a flowchart illustrating a method 1000 for forming a grating according to one or more embodiments described and discussed herein. FIGS. 11A to 11D illustrate the construction of different sections generated during method 1000. Method 1000 includes operation 402, which is performed in a manner similar to operation 402 in method 400 of FIG. 4. FIG11A shows the structure obtained by operation 402 in method 1000. FIG11A shows a grating material layer 504 formed on a substrate 502 and a hard mask layer 506 formed on the grating material layer. In operation 1002, the hard mask layer 506 is opened to form a plurality of openings 1101 using DUV photolithography and etching or NIL in a manner similar to operations 404 and 804 discussed above. FIG11B shows the structure obtained by opening the hard mask layer 506 in operation 1002 in method 1000. This contrasts with operation 404 in method 400, where a continuous portion of the hard mask layer is removed. Subsequently, in operation 1004 of method 1000, as discussed above, a grating 1104 is formed in the grating material layer 504 using angled etching by rotating the substrate 502 and controlling the duty cycle of the ion beam. Operation 1004 includes determining a first ion beam angle ϑ1 for forming the grating 1104. As discussed above, the first ion beam angle ϑ1 can be determined using the equation ϑ1 = atan(tan(ϑ1') / cos(φ1)). Figure 11C shows the structure obtained by forming the grating 1104 by operation 1004 in method 1000. The grating 1104 is formed having a plurality of fins 1106, a first end 1104A, a second end 1104B, and a bottom 1104C, and is formed as a rectangle such that the first end 1104A and the second end 1104B are substantially right-angled with the bottom 1104C. In operation 1006, a portion of the fins 1106 is removed using SAP to form the top surface 1108 of the grating 1104, such that the grating 1104 has a wedge-shaped cross-section. This contrasts with the rectangle formed in operation 1004. Further in operation 1006, a plurality of portions 504A of the grating material layer 504 (shown in FIG. 11C) are removed, just as the hard mask layer 1102 is also removed. FIG. 11D shows the structure obtained by etching the grating 1104 in operation 1006 of method 1000. The portion of fin 1106 removed in operation 1006 is removed at a wedge angle α measured relative to substrate 502. Operations 1002, 1004, and 1006 can be repeated to form additional gratings in grating material layer 504 at other tilt angles using different ion beam angles, different substrate rotation angles, and duty cycle adjustments as discussed herein.

[0056] The embodiments disclosed in this case further relate to any one or more of the following paragraphs 1-29:

[0057] 1. A method of forming a grating, comprising: etching a hard mask layer to form a plurality of openings, the hard mask layer being disposed on a grating material layer disposed on a substrate; forming a first grating in the grating material layer through the plurality of openings of the hard mask layer, wherein the first grating has a first shape vector and a first grating vector, wherein forming the first grating comprises: according to the equation ϑ1 = atan(tan(ϑ1') / The first ion beam angle ϑ1 is determined by cos(φ1), where ϑ1' is the first tilt angle and φ1 is the angle between the first shape vector and the first grating vector; a first portion of the grating material layer is positioned in the path of the ion beam at the first ion beam angle ϑ1 relative to the substrate, and the substrate is held on the platform; the substrate is rotated about the central axis of the platform to a first rotation angle between the ion beam and the first grating vector; and when the ion beam is at the first ion beam angle ϑ1, control parameters are adjusted to form a first plurality of fins of the first grating, the first plurality of fins having the first shape vector, the first grating vector, and the first tilt angle ϑ1' relative to the surface normal of the substrate, thereby forming the first plurality of fins at the first tilt angle ϑ1'.

[0058] 2. A method of forming a grating, comprising: etching a first grating material layer to form a first feature in the first grating material layer disposed on a substrate; depositing an etch stop layer in the first feature; depositing a second grating material layer on the etch stop layer; depositing a hard mask layer on the second grating material layer; etching the hard mask layer to form a plurality of openings; and forming a first grating in the second grating material layer through the plurality of openings, wherein the first grating has a first shape vector and a first grating vector, wherein forming the first grating comprises: according to the equation ϑ1 = atan(tan(ϑ1') / The first ion beam angle ϑ1 is determined by cos(φ1), where ϑ1' is the first tilt angle and φ1 is the angle between the first shape vector and the first grating vector; the first portion of the substrate is positioned relative to the ion beam at the first ion beam angle ϑ1, the substrate is held on the platform, and the first ion beam angle ϑ1 is measured relative to a plane parallel to the platform; when the ion beam is at the first ion beam angle ϑ1, the substrate is rotated about the central axis of the platform to a first rotation angle between the ion beam and the first grating vector of the first grating; and when the ion beam is at the first ion beam angle ϑ1 and contacts the first portion of the substrate, the control program parameters are adjusted.

[0059] 3. A method of forming a grating, comprising: etching a plurality of openings in a hard mask layer disposed on a grating material layer and the grating material layer disposed on a substrate; etching the substrate through the plurality of openings in the hard mask layer to form a first grating in the grating material layer, the first grating including a plurality of fins formed in recesses, wherein the first grating has a first shape vector and a first grating vector, wherein forming the first grating includes: determining a first ion beam angle ϑ1 according to the equation ϑ1=atan(tan(ϑ1') / cos(φ1)), where ϑ1' is a first tilt angle and φ1 is the first ion beam angle. The angle between the shape vector and the first grating vector; positioning a first portion of the grating material layer relative to the ion beam at the first ion beam angle ϑ1, the ion beam being adjustable relative to a plane parallel to the substrate within an angle range of about 15º to about 75º, the substrate being held on the platform; and rotating the substrate about the central axis of the platform to a first rotation angle between the ion beam and the first grating vector of the first grating when the ion beam is at the first ion beam angle ϑ1; and etching the first grating at a first angle to remove the top portions of the plurality of fins to form a wedge shape, wherein the first shape vector is a wedge vector.

[0060] 4. A method of forming a grating, comprising: etching a hard mask layer to form a plurality of openings, the hard mask layer being disposed on a grating material layer, the photomask material layer being disposed on a substrate; forming a first grating in the grating material layer through the plurality of openings of the hard mask layer, wherein the first grating has a first shape vector and a first grating vector, wherein forming the first grating comprises: determining a first ion beam angle ϑ1, the first ion beam angle ϑ1 being an angle between a first tilt angle ϑ1' and the angle between the first shape vector and the first grating vector. The degree φ1 is related; a first portion of the grating material layer is positioned in the path of the ion beam, the ion beam being at the first ion beam angle ϑ1 relative to the substrate, the substrate being held on the platform; and when the ion beam is at the first ion beam angle ϑ1, the control program parameters are adjusted to form a first plurality of fins of the first grating, the first plurality of fins having the first shape vector, the first grating vector and the first tilt angle ϑ1' relative to the surface normal of the substrate, thereby the first plurality of fins being formed at the first tilt angle ϑ1'.

[0061] 5. A method of forming a grating, comprising: etching a first grating material layer to form a first feature in the first grating material layer disposed on a substrate; depositing an etch stop layer in the first feature; depositing a second grating material layer on the etch stop layer; depositing a hard mask layer on the second grating material layer; etching the hard mask layer to form a plurality of openings; and forming a first grating in the second grating material layer through the plurality of openings, wherein the first grating has a first shape vector and a first grating vector, wherein forming the first grating comprises: determining a first ion beam angle ϑ1, the first ion beam angle ϑ1 being related to a first tilt angle ϑ1' and an angle φ1 between the first shape vector and the first grating vector; positioning a first portion of a substrate relative to an ion beam at the first ion beam angle ϑ1, the substrate being held on a platform, and the first ion beam angle ϑ1 being measured relative to a plane parallel to the platform; and adjusting process parameters when the ion beam is at the first ion beam angle ϑ1 and contacts the first portion of the substrate.

[0062] 6. A method of forming a grating, comprising: etching a plurality of openings in a hard mask layer disposed on a grating material layer and the grating material layer disposed on a substrate; etching the substrate through the plurality of openings in the hard mask layer to form a first grating in the grating material layer, the first grating including a plurality of fins formed in recesses, wherein the first grating has a first shape vector and a first grating vector, wherein forming the first grating includes: determining a first ion beam angle ϑ1, the first ion beam angle ϑ1 being relative to a first tilt angle ϑ1' and the first shape vector and the first grating vector. The angle φ1 between the ion beams is related to the first portion of the grating material layer being positioned relative to the ion beam at a first ion beam angle ϑ1, the ion beam being adjustable relative to a plane parallel to the substrate within an angle range of approximately 15º to approximately 75º, the substrate being held on the platform; and when the ion beam is at the first ion beam angle ϑ1, the substrate is rotated about the central axis of the platform to a first rotation angle between the ion beam and the first grating vector of the first grating; and the first grating is etched at a first angle to remove the top portions of the plurality of fins to form a wedge shape, wherein the first shape vector is a wedge vector.

[0063] 7. According to the method in any of paragraphs 1-6, wherein the first ion beam angle ϑ1 is determined according to the equation ϑ1 = atan(tan(ϑ1') / cos(φ1)).

[0064] 8. The method according to any one of paragraphs 1-7 further includes: rotating the substrate about the central axis of the platform to a first rotation angle between the ion beam and the first grating vector of the first grating.

[0065] 9. The method according to any one of paragraphs 1-8, further comprising: forming a second grating in the grating material layer, the second grating including a second plurality of fins having a second shape vector and a second grating vector, wherein forming the second grating includes: determining a second ion beam angle ϑ2, the second ion beam angle ϑ2 being related to a second tilt angle ϑ2' and an angle φ2 between the second shape vector and the second grating vector; positioning a second portion of the grating material layer in a second path of the ion beam at the second ion beam angle ϑ2 to form the second grating in the grating material layer; rotating the substrate about the central axis of the platform to create a second rotation angle between the ion beam and the second grating vector of the second grating; and adjusting control parameters when the ion beam is at the second ion beam angle ϑ2 to form the second plurality of fins, the second plurality of fins being formed at the second tilt angle ϑ2' and having the second shape vector and the second grating vector.

[0066] 10. According to the method of any of paragraphs 1-9, wherein the second rotation angle is different from the first rotation angle, and wherein the second ion beam angle ϑ2 is determined according to the equation ϑ2 = atan(tan(ϑ2') / cos(φ2).

[0067] 11. According to the method of any of paragraphs 1-10, wherein the ion beam is a ribbon beam.

[0068] 12. The method according to any one of paragraphs 1-11, wherein the first ion beam angle ϑ1 is about 15° to about 75° relative to the plane perpendicular to the substrate.

[0069] 13. The method according to any one of paragraphs 1-12 further includes: forming a second grating in the grating material layer, the second grating including a second plurality of fins having a second shape vector and a second grating vector, wherein forming the second grating includes: determining a second ion beam angle ϑ2 according to the equation ϑ2=atan(tan(ϑ2') / cos(φ2)), where ϑ2' is a second tilt angle and φ2 is the angle between the second shape vector and the second grating vector; positioning a second portion of the grating material layer in a second path of the ion beam at the second ion beam angle ϑ2 to form the second grating in the grating material layer; rotating the substrate about the central axis of the platform to create a second rotation angle between the ion beam and the second grating vector of the second grating; and adjusting control program parameters to form the second plurality of fins when the ion beam is at the second ion beam angle ϑ2, the second plurality of fins being formed at the second tilt angle ϑ2' and having the second shape vector and the second grating vector.

[0070] 14. According to the method of any of paragraphs 1-13, wherein the second rotation angle is different from the first rotation angle.

[0071] 15. The method according to any of paragraphs 1-14, wherein the processing parameters include the duty cycle of the ion beam, the partial scan of the ion beam, the scan rate of the ion beam, the power supply for generating the ion beam, or any combination of the above processing parameters.

[0072] 16. The method according to any one of paragraphs 1-15 further includes removing the hard mask layer after the first grating is formed.

[0073] 17. The method according to any of paragraphs 1-16, wherein the grating material layer comprises one or more of the following: silicon oxide, silicon oxide, silicon carbonitride, silicon nitride, or any combination of the above materials.

[0074] 18. The method according to any one of paragraphs 1-17, wherein each of the first grating material layer and the second grating material layer comprises one or more of the following: silicon oxide, titanium dioxide, silicon oxide, vanadium oxide, aluminum oxide, indium tin oxide, zinc oxide, tantalum pentoxide, silicon nitride, titanium nitride, or zirconium dioxide.

[0075] 19. The method according to any one of paragraphs 1-18, wherein the hard masking layer comprises silicon oxide, silicon nitride, or a combination of the above materials.

[0076] 20. The method according to any one of paragraphs 1-19, wherein the first feature includes a recess and is defined by a first side, a second side and a third side, the first side being formed to reach a first depth in the first grating material layer, the second side being defined by a second depth in the first grating material layer, the third side extending between the first side and the second side, the first depth being less than the second depth.

[0077] 21. The method according to any one of paragraphs 1-20, wherein the first grating includes a plurality of fins having a first tilt angle ϑ1' relative to the surface normal of the substrate.

[0078] 22. According to the method of any one of paragraphs 1-21, wherein the height of the first plurality of fins is reduced according to a first depth gradient from the first side of the recess to the second side of the recess.

[0079] 23. According to the method of any of paragraphs 1-22, wherein the first ion beam angle ϑ1 is aligned with the first depth gradient of the first grating.

[0080] 24. The method according to any one of paragraphs 1-23 further includes: removing the hard mask layer; and coating the first plurality of fins with an oxide layer.

[0081] 25. The method according to any one of paragraphs 1-24 further includes: after forming the first grating, changing the first ion beam angle ϑ1 to a second ion beam angle ϑ2 different from the first ion beam angle ϑ1; and forming a second grating in the second grating material layer, the second grating including a second plurality of fins having a second shape vector and a second grating vector, wherein forming the second grating includes: according to the equation ϑ2 = atan(tan(ϑ2') / The second ion beam angle ϑ2 is determined by cos(φ2), where ϑ2' is the second tilt angle and φ2 is the angle between the second shape vector and the second grating vector; the second portion of the substrate is positioned in the path of the ion beam at the second ion beam angle ϑ2; and when the ion beam is at the second ion beam angle ϑ2, the substrate is rotated about the central axis of the platform to a second rotation angle between the ion beam and the second grating vector of the second grating, wherein the ion beam contacts the second grating material layer at the second ion beam angle ϑ2 to form the second plurality of fins, the second plurality of fins having the second tilt angle ϑ2', the second shape vector, and the second grating vector.

[0082] 26. The method according to any one of paragraphs 1-25 further includes: after depositing the second grating material layer and before forming the first grating in the second grating material layer, planarizing the substrate in which the first grating is formed to remove a portion of the second grating material layer.

[0083] 27. The method according to any one of paragraphs 1-26 further includes: forming a conformal oxide coating on the plurality of fins.

[0084] 28. The method according to any one of paragraphs 1-27 further includes: forming a second grating in the grating material layer, the second grating including a second plurality of fins, a second shape vector, and a second grating vector, wherein forming the second grating includes: according to the equation ϑ2 = atan(tan(ϑ2') / The second ion beam angle ϑ2 is determined by cos(φ2), where ϑ2' is the second tilt angle and φ2 is the angle between the second shape vector and the second grating vector. The second portion of the substrate is positioned in the path of the ion beam at the second ion beam angle ϑ2 to form a second grating in the grating material layer. The substrate is rotated about the central axis of the platform to create a second rotation angle between the ion beam and the second grating vector of the second grating. When the ion beam is at the second ion beam angle ϑ2, the process parameters are adjusted to form a second plurality of fins, which have a second tilt angle ϑ2' relative to the surface normal of the substrate and have the second shape vector and the second grating vector. The process parameters include the duty cycle of the ion beam, the partial scan of the ion beam, the scan speed of the ion beam, the power supply for generating the ion beam, or any combination of the above process parameters.

[0085] 29. An apparatus or system for performing the method according to any one of paragraphs 1-28.

[0086] Therefore, using the systems and methods discussed herein, it is possible to fabricate multiple gratings for enhancing waveguide combiners and / or master gratings for transferring grating materials. By using the embodiments discussed herein, it is possible to form gratings with varying depth gradients and tilt angles on a single substrate, achieved by at least changing the ion beam angle and controlling the duty cycle of the ion beam in combination with rotating the substrate relative to that ion beam angle.

[0087] Although the foregoing describes embodiments of the disclosure herein, other and further embodiments may be designed without departing from the basic scope of the disclosure, and the scope thereof is determined by the appended claims. All documents described herein are incorporated by reference, including any priority documents and / or test procedures to the extent that they are not inconsistent with this document. It will be apparent from the foregoing general description and specific embodiments that various modifications can be made to the disclosure, without departing from the spirit and scope of the disclosure. Therefore, it is not intended that the disclosure be limited thereto. Similarly, for legal purposes, the term "comprising" is considered synonymous with the term "including". Likewise, whenever the conjunction "comprising" precedes a component, element, or group of elements, it should be understood that we also consider the same component or group of elements: preceded by the conjunction "substantially constitutes", "consisting of", "selected from the group of", or "is", and vice versa.

[0088] Certain embodiments and features have been described using a set of upper and lower numerical limits. It should be understood that, unless otherwise indicated, the scope covers a range including any combination of two values, such as any lower value combined with any higher value, any combination of two lower values, and / or any combination of two higher values. Certain lower, upper, and range limits are presented in one or more of the claims below. [Simplified Explanation of the Diagram]

[0009] A more specific description of the disclosure briefly summarized above can be obtained through reference to the embodiments (some of which are illustrated in the accompanying drawings), thus enabling a detailed understanding of the aforementioned features of the disclosure. However, it should be noted that the drawings illustrate only exemplary embodiments and should not be considered as limiting the scope of the disclosure, and other equivalent embodiments are permissible.

[0010] Figure 1 depicts a perspective front view of an enhanced waveguide combiner according to one or more embodiments described and discussed herein.

[0011] FIG2A depicts a schematic side cross-sectional view of an angled etching system according to one or more embodiments described and discussed herein.

[0012] FIG2B depicts a schematic side cross-sectional view of an angled etching system according to one or more embodiments described and discussed herein.

[0013] FIG3 depicts a schematic perspective view of a portion of a substrate having an angled grating according to one or more embodiments described and discussed herein.

[0014] Figure 4 is a flowchart illustrating a method for forming a grating according to one or more embodiments described and discussed herein.

[0015] Figures 5A to 5J illustrate the structure of different intervals generated during the method depicted in Figure 4, according to one or more embodiments described and discussed herein.

[0016] Figure 6 is a flowchart illustrating another method of forming a grating according to one or more embodiments described and discussed herein.

[0017] Figures 7A to 7G illustrate the structures of different intervals generated during the method depicted in Figure 6, according to one or more embodiments described and discussed herein.

[0018] Figure 8 is a flowchart illustrating another method of forming a grating according to one or more embodiments described and discussed herein.

[0019] Figures 9A to 9D illustrate the structures of different intervals generated during the method depicted in Figure 8, according to one or more embodiments described and discussed herein.

[0020] Figure 10 is a flowchart illustrating another method of forming a grating according to one or more embodiments described and discussed herein.

[0021] Figures 11A to 11D illustrate the structure of different intervals generated during the method depicted in Figure 10, according to one or more embodiments described and discussed herein.

[0022] For the purpose of understanding, the same element symbols have been used to designate common elements in the drawings whenever possible. Elements and features of one embodiment may be beneficially incorporated into other embodiments without further description.

Claims

1. A waveguide, comprising: One substrate; A grating includes: a grating material disposed on a substrate, the grating material having a wedge shape disposed therein, the wedge having a first side and a second side, a depth of the grating material increasing from the first side to the second side; and a plurality of fins disposed on the grating material, the plurality of fins having an angle of inclination relative to a plane of the substrate, a shape vector and a grating vector, wherein a fin depth of the plurality of fins varies from a first fin of the plurality of fins on the first side to a second fin of the plurality of fins on the second side.

2. The waveguide as claimed in claim 1, wherein the plurality of fins have a coating formed on the fins.

3. The waveguide as described in claim 2, wherein the coating comprises one or more layers of oxide.

4. The waveguide as claimed in claim 1, wherein the plurality of fins have a conformal coating formed on the fins.

5. The waveguide as claimed in claim 1, wherein the grating is composed of at least one of the following: silicon oxide, titanium oxide, titanium dioxide, silicon oxide, silicon dioxide, vanadium(IV) oxide, aluminum oxide, indium tin oxide, zinc oxide, tantalum pentoxide, silicon nitride, titanium nitride, zirconium dioxide, or nitrogen oxides.

6. The waveguide as claimed in claim 1, wherein the second side is opposite to the first side, and a transition surface extends between the first side and the second side.

7. The waveguide as described in claim 6, wherein the transition surface increases in depth from the first side to the second side.

8. The waveguide as described in claim 6, wherein the transition surface is formed at an angle relative to the substrate.

9. A waveguide, comprising: An input coupler is disposed on a substrate and has a first plurality of fins; an intermediate region is disposed on the substrate and has a second plurality of fins; and an output coupler is disposed on the substrate and has a third plurality of fins disposed on the substrate, the third plurality of fins having a first tilt angle relative to a plane of the substrate, a shape vector and a grating vector, wherein the fin depth of the third plurality of fins varies from a first fin of the third plurality of fins on a first side of the output coupler to a second fin of the third plurality of fins on a second side of the output coupler.

10. The waveguide as claimed in claim 9, wherein the shape vector of the third plurality of fins is different from a shape vector of the second plurality of fins and also different from a shape vector of the first plurality of fins.

11. The waveguide as claimed in claim 9, wherein the first plurality of fins, the second plurality of fins, or the third plurality of fins have a coating formed on the fins.

12. The waveguide as described in claim 11, wherein the coating comprises one or more layers of oxide.

13. The waveguide as claimed in claim 9, wherein the first plurality of fins, the second plurality of fins, or the third plurality of fins have a conformal coating formed on the fins.

14. A waveguide, comprising a substrate; and a grating, comprising: A grating material is disposed on the substrate, the grating material having a wedge shape disposed therein, the wedge having a first side and a second side, a depth of the grating material increasing from the first side to the second side, wherein the second side is opposite to the first side, and a transition surface extending between the first side and the second side; and a plurality of fins are formed on the grating material, the plurality of fins having a first tilt angle relative to a plane of the substrate, a shape vector and a first grating vector, wherein the fin depth of the plurality of fins increases in depth from a first fin of the plurality of fins on the first side to a second fin of the plurality of fins on the second side.

15. The waveguide as claimed in claim 14, wherein the plurality of fins have a coating formed on the fins.

16. The waveguide as described in claim 15, wherein the coating comprises one or more layers of oxide.

17. The waveguide as claimed in claim 15, wherein the plurality of fins have a conformal coating formed on the fins.

18. The waveguide as claimed in claim 14, wherein the grating is composed of at least one of the following: silicon oxide, titanium oxide, titanium dioxide, silicon oxide, silicon dioxide, vanadium(IV) oxide, aluminum oxide, indium tin oxide, zinc oxide, tantalum pentoxide, silicon nitride, titanium nitride, zirconium dioxide, or nitrogen oxides.

19. The waveguide as claimed in claim 14, wherein the transition surface increases in depth from the first side to the second side.

20. The waveguide as claimed in claim 14, wherein the transition surface is formed at an angle relative to the substrate.

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