Patent Description:
Augmented reality creates an experience for a user that can be viewed through display lenses of augmented reality glasses or using other HMD devices to view the surrounding environment. Augmented reality devices allow users to see images of virtual objects that are generated for display and appear as part of the environment. Augmented reality can include audio and haptic inputs, as well as virtual images, graphics, and video that enhances or augments the user's environment.

One challenge in augmented reality device design and fabrication is the display of a virtual image that is overlaid on an ambient environment. Augmented waveguide combiners are used to assist in overlaying images. Generated light is first in-coupled into an augmented waveguide combiner and propagated through the augmented waveguide combiner. The generated light is then out-coupled from the augmented waveguide combiner and overlaid on the ambient environment. Light is coupled into and out of augmented waveguide combiners using surface relief gratings. The intensity of the out-coupled light may not be adequately controlled using conventional designs.

Another challenge is that a waveguide combiner may use gratings with different slant angles depending on the properties desired of the augmented reality device. Additionally, a waveguide combiner may include gratings with different slant angles to adequately control the in-coupling and out-coupling of light, and the slant angles may be at angles different than the grating vector.

Document <CIT> describes optical components having diffraction gratings. In a microfabrication system, a tilting angle θ between an ion source and the substrate holder can be varied to create changing slanting angles. The tilting angle θ is also the angle of incidence of the beam relative to the surface i.e. θ is the amount by with the direction of the beam deviated from the normal to the surface.

Accordingly, what is needed is improved augmented waveguides combiners and methods of fabrication of gratings and grating masters.

In one or more embodiments, a method of forming a grating includes etching a hardmask layer to form a plurality of openings, the hardmask layer being disposed over a grating material layer that is disposed on a substrate and forming a first grating in the grating material layer through the plurality of openings of the hardmask layer, wherein the first grating has a first shape vector and a first grating vector. The first grating is formed by determining a first ion beam angle ϑ<NUM> relative to a first slant angle ϑ<NUM>' and an angle ϕ<NUM> which is between the first shape vector and the first grating vector and positioning a first portion of the grating material layer in a path of an ion beam at the first ion beam angle ϑ<NUM> relative to the substrate, the substrate being retained on a platen. The method also includes modulating one or more process parameters when the ion beam is at the first ion beam angle ϑ<NUM> to form a first plurality of fins of the first grating having the first shape vector, the first grating vector, and the first slant angle ϑ<NUM>' relative to a surface normal of the substrate such that the first plurality of fins are formed at the first slant angle ϑ<NUM>'. In some examples, the first grating is further formed by rotating the substrate about a central axis of the platen to a first rotation angle between the ion beam and the first grating vector of the first grating.

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 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 hardmask layer on the second grating material layer. The method further includes etching the hardmask 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 is formed by determining a first ion beam angle ϑ<NUM> relative to a first slant angle ϑ<NUM>' and an angle ϕ<NUM> which is between the first shape vector and the first grating vector, and by positioning a first portion of the substrate relative to an ion beam at the first ion beam angle ϑ<NUM>, the substrate being retained on a platen and the first ion beam angle ϑ<NUM> being measured relative to a plane parallel to the platen. The method also includes modulating one or more process parameters when the ion beam is at the first ion beam angle ϑ<NUM> and in contact with the first portion of the substrate. In some examples, the process parameter can be or include a duty cycle of the ion beam, a partial scan of the ion beam, a scan speed of the ion beam, a power source for generating the ion beam, or any combination thereof.

It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments.

Virtual and augmented reality devices that employ gratings can utilize depth-modulated slanted gratings, where the direction in which the grating(s) of a wedge is formed may not be aligned to the grating vector. The depth-modulated slanted gratings are etched in target materials using an ion beam that can accommodate a range of angles to form gratings of different slant angles and with differing depth gradients. The modulation of grating depth increases optical uniformity in optical devices such as waveguide combiners.

Using the systems and methods discussed herein, gratings are formed with depth gradients that are not aligned with the grating vector by rotating the substrate and by modulating a process parameter (e.g., a duty cycle of the ion beam), creating smooth gradient depth profiles at various orientations relative to the substrate. The systems and methods discussed herein can be employed to form waveguide combiners or other optical elements, and can be further employed to form masters for imprinting waveguide combiners or other optical elements. The gratings formed as discussed herein can be formed as wedges or to exhibit other cross-sectional shapes.

A grating as discussed herein is a pattern formed in a target material layer that is made up of a plurality of fins separated by a plurality of troughs. The plurality of fins can be formed to a plurality of depths and heights and are formed by etching the target material using an angled, adjustable ion beam and by rotating the substrate. The plurality of fins are formed at a slant angle relative to a substrate plane. The grating can be formed to have a cross-sectional geometry of a wedge, rectangle, or other polygonal or rounded shape or combinations of shapes. Gratings can be formed and subsequently modified in height and/or critical dimensions. Critical dimensions as discussed herein can refer to the fin height, pitch, width, or other dimensions of a grating depending upon the embodiment.

A grating vector is measured normal to the grating lines and aligned with the slant angle of the fins. A wedge direction (vector) can be measured by the change in depth of the gratings of the wedge, for example, the direction in which the depth of the find of a wedge-shaped grating increase. In one or more examples, the wedge vector is the same as a scanning direction of an apparatus in which the substrate is disposed for formation of the grating(s). An angle formed between a wedge vector and a grating vector can be used in combination with the slant angle of the fins to determine an ion beam angle to use to form a grating.

<FIG> depicts a perspective, frontal view of an augmented waveguide combiner <NUM>, according to one or more embodiments. It is to be understood that the augmented waveguide combiner <NUM> described below is an exemplary augmented waveguide combiner and other augmented waveguide combiners may be used with or modified to accomplish aspects of the present disclosure. The augmented waveguide combiner <NUM> includes an input coupling region <NUM> defined by a first plurality of gratings <NUM>, an intermediate region <NUM> defined by a second plurality of gratings <NUM>, and an output coupling region <NUM> defined by a third plurality of gratings <NUM>. The input coupling region <NUM> receives incident beams of light having an intensity from a microdisplay. Each grating of the plurality of gratings <NUM> splits the incident beams into a plurality of modes, each incident beam having a mode.

Different beam modes react differently to the augmented waveguide combiner <NUM>. For example, zero-order mode (T0) beams are refracted back or lost in the augmented waveguide combiner <NUM>. In contrast to T0 beams, positive first-order mode (T1) beams are coupled though the augmented waveguide combiner <NUM> to the intermediate region <NUM>, and negative first-order mode (T-<NUM>) beams propagate in the augmented waveguide combiner <NUM> in a direction opposite to the T1 beams. Ideally, the incident beams are split into T1 beams that have all of the intensity of the incident beams in order to direct the virtual image to the intermediate region <NUM>. In one or more embodiments, each grating of the plurality of gratings <NUM> is angled to suppress the T-<NUM> beams and the T0 beams. The T1 beams undergo total-internal-reflection (TIR) through the augmented waveguide combiner <NUM> until the T1 beams come in contact with the second plurality of gratings <NUM> in the intermediate region <NUM>.

When the T1 beams contact a grating of the second plurality of gratings <NUM>, the T1 beams are split into T0 beams, T1 beams, and T-<NUM> beams. The T0 beams are refracted back or lost in the augmented waveguide combiner <NUM>, the T1 beams undergo TIR in the intermediate region <NUM> until the T1 beams contact another grating of the second plurality of gratings <NUM>, and the T-<NUM> beams are coupled through the augmented waveguide combiner <NUM> to the output coupling region <NUM>. The T1 beams that undergo TIR in the intermediate region <NUM> continue to contact the second plurality of gratings <NUM> until one of (<NUM>) the intensity of the T1 beams coupled through the augmented waveguide combiner <NUM> to the intermediate region <NUM> is depleted, or (<NUM>) the remaining T1 beams propagating through the intermediate region <NUM> reach the end of the intermediate region <NUM>. The second plurality of gratings <NUM> is tuned to control the T1 beams that are coupled through the augmented waveguide combiner <NUM> to the intermediate region <NUM>. Tuning the second plurality of gratings <NUM> controls the intensity of the T-<NUM> beams coupled to the output coupling region <NUM> to modulate a field of view of the virtual image produced from the microdisplay from a user's perspective and increase a viewing angle from which a user can view the virtual image.

In one or more embodiments, the second plurality of gratings <NUM> can be referred to herein as a wedge, and is defined by a slant angle (discussed below) of fins that form the wedge, a first side <NUM>, and an angled second side <NUM> opposite the first side <NUM>. The angled side <NUM> includes a first portion 116A and a second portion 116B. The second plurality of gratings <NUM> is further defined by a curved first end <NUM>, an angled second end that is defined by a first portion 120A and a second portion 120B. The curved first end <NUM> can take on various curvatures depending upon the embodiment. A first angle α is defined by the first portion 116A of the angled side <NUM> and the second portion 116B of the angled side <NUM>. 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 can be defined by the first portion 120A and the second portion 120B of the angled second end. A fourth angle δ can be defined by the first side <NUM> and the second portion 120B of the angled second end. The systems and methods discussed herein form wedges or other shapes where each fin of the second plurality of gratings <NUM> has a first end and a second end, the first end being located along the angled second side <NUM> and the second end of the fins being located along the first side <NUM>. Each fin of the second plurality of gratings <NUM> can be further defined by various geometric features. For example, the first side of the fin can have a ramp (angle) such that the fins along the angled second side <NUM> each have a ramp. The second side of each fin can have an undercut such that the fins along the first side <NUM> each have an undercut.

Further in <FIG>, a depth gradient is defined in a direction from a first side 110A of the plurality of gratings <NUM> to a second side 110B. <FIG> also illustrates depth gradients for at least the second plurality of gratings <NUM> and the third plurality of gratings <NUM>. Each depth gradient can be further defined by a depth gradient in a direction of an increase or decrease in the depth of the fins of a grating or of a plurality of gratings. The depth gradients are shown via shading in <FIG>, the depth gradient increases from the first side 110A to the second side 110B for the second grating <NUM> and increases from a top 112A of the third plurality of gratings <NUM> to a bottom 112B. A grating vector (not shown here) of the second plurality of gratings <NUM> is measured orthogonally to the second plurality of gratings <NUM>. A wedge angle of the second plurality of gratings <NUM> can be defined as the angle between the grating vector and the depth gradient. Similarly, a grating vector (not shown here) of the third plurality of gratings <NUM> is measured orthogonally to the third plurality of gratings <NUM>.

The T-<NUM> beams coupled through the augmented waveguide combiner <NUM> to the output coupling region <NUM> undergo TIR in the augmented waveguide combiner <NUM>. The T-<NUM> beams undergo the TIR until the T-<NUM> beams contact a grating of the plurality of gratings <NUM> where the T-<NUM> beams are split into (a) T0 beams refracted back or lost in the augmented waveguide combiner <NUM>, (b) T1 beams that undergo TIR in the output coupling region <NUM> until the T1 beams contact another grating of the plurality of gratings <NUM>, and (c) T-<NUM> beams coupled out of the augmented waveguide combiner <NUM>. The T1 beams that undergo TIR in the output coupling region <NUM> continue to contact gratings of the plurality of gratings <NUM> until the either the intensity of the T-<NUM> beams coupled through the augmented waveguide combiner <NUM> to the output coupling region <NUM> is depleted, or remaining T1 beams propagating through the output coupling region <NUM> have reached the end of the output coupling region <NUM>. The plurality of gratings <NUM> must be tuned to control the T-<NUM> beams coupled through the augmented waveguide combiner <NUM> to the output coupling region <NUM> in order to control the intensity of the T-<NUM> beams coupled out of the augmented waveguide combiner <NUM> to further modulate the field of view of the virtual image produced from the microdisplay from the user's perspective and further increase the viewing angle from which the user can view the virtual image.

<FIG> depicts a side, schematic cross-sectional view and <FIG> depicts side, schematic cross-sectional view of an angled etch system <NUM>, according to one or more embodiments. To form gratings having slant angles, a grating material <NUM> disposed on a substrate <NUM> is etched by the angled etch system <NUM>. In one or more embodiments, the grating material <NUM> is disposed on an etch stop layer <NUM> disposed on the substrate <NUM> and a patterned hardmask <NUM> is disposed over the grating material <NUM>. In one or more embodiments, the materials of grating material <NUM> are selected based on the slant angle ϑ' of each grating and the refractive index of the substrate <NUM> to control the in-coupling and out-coupling of light and facilitate light propagation through a waveguide combiner. In some embodiments, the grating material <NUM> includes silicon oxycarbide (SiOC), titanium dioxide (TiO<NUM>), silicon oxide (e.g., silicon dioxide (SiO<NUM>)), vanadium (IV) oxide (VO<NUM>), aluminum oxide (Al<NUM>O<NUM>), indium tin oxide (ITO), zinc oxide (ZnO), tantalum pentoxide (Ta<NUM>O<NUM>), silicon nitride (SiN or Si<NUM>N<NUM>), titanium nitride (TiN), and/or zirconium dioxide (ZrO<NUM>) containing materials. The grating material <NUM> has a refractive index between about <NUM> and about <NUM>. In yet another embodiment, the patterned hardmask <NUM> is a non-transparent hardmask that is removed after the waveguide combiner is formed. For example, the non-transparent hardmask includes reflective materials, such as chromium or silver.

In some embodiments, the patterned hardmask <NUM> is a transparent hardmask. In one or more embodiments, the etch stop layer <NUM> is a non-transparent etch stop layer that is removed after the waveguide combiner is formed. In some embodiments, the etch stop layer <NUM> is a transparent etch stop layer. The angled etch system <NUM> is configured to execute a plurality of instructions, for example, using a controller (not shown), in order to form the angled gratings discussed herein. The plurality of instructions executed can include a slant angle, an ion beam angle, a change in ion beam angle in between formation of gratings, a wedge angle, a depth gradient, and/or other aspects of a wedge to be formed from the grating(s).

The angled etch system <NUM> includes an ion beam chamber <NUM> that houses an ion beam source <NUM>. The ion beam source is configured to generate an ion beam <NUM>, such as a ribbon beam, a spot beam, or full substrate-size beam. The ion beam chamber <NUM> is configured to direct the ion beam <NUM> at an angle a relative to a surface normal <NUM> of substrate <NUM>. The substrate <NUM> is retained on a platen <NUM> coupled to a first actuator <NUM>. The first actuator <NUM> is configured to move the platen <NUM> in a scanning motion along a y-direction and/or a z-direction. To form gratings having a slant angle ϑ' relative the surface normal <NUM>, the ion beam source <NUM> generates an ion beam <NUM> and the ion beam chamber <NUM> directs the ion beam <NUM> towards the substrate <NUM> at the angle α. The first actuator <NUM> positions the platen <NUM> so that the ion beam <NUM> contacts the grating material <NUM> at the ion beam angle ϑ and etches gratings having a slant angle ϑ' on desired portions of the grating material <NUM>. One or more process parameters (e.g., a duty cycle of the ion beam <NUM>) can be modulated to form fins of a grating to varying depths.

<FIG> depicts a schematic perspective view of a portion <NUM> of a substrate <NUM>, according to one or more embodiments. The ion beam angle ϑ is between about <NUM>° and about <NUM>°. The ion beam angle ϑ is adjustable during grating fabrication preferably between about <NUM>° and about <NUM>° as a ion beam angle ϑ close to about <NUM>° or about <NUM>° will result in gratings <NUM> having a slant angle ϑ' of about <NUM>° or about <NUM>°such that the gratings <NUM> are not slanted. Thus, the slant angle ϑ' can be determined by the relative orientation between the ion beam angle and the rotational position of the substrate. The substrate <NUM> is rotated about the x-axis of the platen <NUM> resulting in rotation angle φ between the ion beam <NUM> and a grating vector <NUM> of the gratings <NUM> is measured orthogonally to the gratings <NUM>. To form wedges as discussed herein, the duty cycle of the ion beam and/or other process parameters can be modulated to change the etch depth.

In one or more examples, the process parameter can be or include a duty cycle of the ion beam, a partial scan of the ion beam, a scan speed of the ion beam, a power source (e.g., voltage) for generating the ion beam, or any combination thereof. In some examples, the duty cycle is modulated from about <NUM>% to about <NUM>%, where the <NUM>% duty cycle forms shallow fins of a grating and the <NUM>% duty cycle forms fins of the grating to a deeper depth. In other examples, the partial scan of the ion beam, the scan speed of the ion beam, and/or the power source for generating the ion beam can independently be modulated to form various depths (e.g., from relatively shallow to relatively deep) of grating fins. While the formation of gratings with wedge-shaped cross-sections is discussed herein, in other examples, different gratings can be formed with varying depth gradients and slant angles to form gratings with curved, bowed, angled, flat, or other cross-sectional profiles that are combinations of various geometries.

In one or more embodiments not according to the claimed invention, the ion beam angle ϑ is aligned with the depth gradient of a grating. A depth gradient, discussed above, is a measurement of an amount of change in depth in the fins across a grating, and a depth gradient is the direction in which the depth of the fins changes. The ion beam angle ϑ can be determined by rotation from a grating angle using equation ϑ = atan(tan(ϑ')/cos(ϕ)), to determine the slant angle of the fins where ϑ = ion beam angle, ϑ' = slant angle of the fin, ϕ = angle between a shape vector of the grating, for example, a wedge vector, and a grating vector. A shape vector is a direction in which the depth gradient of a grating changes, for example, a direction in which the depth of the fins increases. The depth gradient is the change in depth of fins across a grating. In one or more examples, for a <NUM>° slant grating, with the wedge offset <NUM>° from the grating vector, ϑ = atan(tan(<NUM>°)/cos(<NUM>°)) ≈ <NUM>°.

<FIG> is a flowchart illustrating a method <NUM> of forming a grating, according to one or more embodiments. <FIG> illustrate structures at different of intervals while being produced during the method <NUM>. In the method <NUM>, at operation <NUM>, a target stack is fabricated in a plurality of sub-operations that can include chemical vapor deposition (CVD). The target stack formed at operation <NUM> is shown in <FIG>, and includes a substrate <NUM> and a grating material layer <NUM> formed over the substrate <NUM>. The target stack further includes a hardmask layer <NUM> formed over the grating material layer <NUM>. The substrate <NUM> can be formed from a silicon-based material such as SiO<NUM>, and the hardmask layer <NUM> can be formed from a metallic material such as chromium or titanium, or from a dielectric material such as silicon carbonitride (SiCN). The grating material layer <NUM> can include silicon oxycarbide (SiOC), titanium dioxide (TiO<NUM>), silicon dioxide (SiO<NUM>), vanadium oxide (VO<NUM>), aluminum oxide (Al<NUM>O<NUM>), indium tin oxide (ITO), zinc oxide (ZnO), tantalum pentoxide (Ta<NUM>O<NUM>), silicon nitride (Si<NUM>N<NUM>), titanium nitride (TiN), or zirconium dioxide (ZrO<NUM>). The stack shown in <FIG> can be fabricated using various sub-operations including CVD. In one or more examples, the grating material layer <NUM> is from <NUM> to <NUM> thick, the hardmask layer <NUM> is from about <NUM> to about <NUM> thick.

At operation <NUM>, a contiguous portion of the hardmask layer <NUM> is removed to form an opening <NUM> in the hardmask layer <NUM>. Operation <NUM> can be performed using one or more chemicals in a wet strip etch operation to form the opening <NUM>. <FIG> shows a structure resulting from the removal of the portion of the hardmask layer <NUM> at operation <NUM>. At operation <NUM>, a portion of the grating material layer <NUM> is etched or otherwise removed to form a feature <NUM>. <FIG> shows a structure resulting from the formation of the feature <NUM> at operation <NUM>. Operation <NUM> can be executed using selective area processing (SAP) etch to remove one or more portions of the grating material layer <NUM>. During operation <NUM>, the SAP etch can be used to form a feature <NUM> that can contain various cross-sections, including but not limited to the wedge-like cross section of the feature <NUM> shown in <FIG>. For example, while the feature <NUM> is shown in <FIG> as a wedge or triangular shape, in other examples, various polygonal or combination shapes can be formed at operation <NUM> using SAP etch. The feature <NUM> can be referred to as a recess and is defined by a first side 510A, a transitional surface 510B, and a second side 510C. The second side 510C is opposite the first side 510A, and the transitional surface 510B extends between the first side 510A and the second side 510C. The transitional surface 510B is formed at an angle <NUM> relative to the substrate <NUM>. In the example in <FIG>, the second side 510C is formed to a greater depth than the first side 510A.

In one or more embodiments, the SAP can include a designed number of exposure cycles, where a given exposure cycle entails scanning the processing beam along a particular direction and a subsequent rotation of the substrate <NUM> to a new rotational position. In some examples, an SAP etch can include <NUM> exposure cycles, <NUM> exposure cycles, <NUM> exposure cycles, <NUM> exposure cycles, or more. In some examples, an SAP etch can include different exposure cycles where the substrate <NUM> is positioned at different rotational positions, such that each cycle is performed at a different rotational position. Additional aspects of the SAP etch are described and discussed in <CIT> (column <NUM>, line <NUM> to column <NUM>, line <NUM>), and in <CIT>.

At operation <NUM>, an etch stop layer <NUM> is deposited on the feature <NUM>. <FIG> shows a structure resulting from the deposition of the etch stop layer <NUM> at operation <NUM>. The etch stop layer <NUM> can be deposited at operation <NUM> via a CVD process, an atomic layer deposition (ALD), or another process that forms a conformal coating on the feature <NUM>. The etch stop layer <NUM> can be formed to a thickness from <NUM> to <NUM> thick. In one or more examples, the etch stop layer <NUM> is formed at operation <NUM> from a nitride such as tantalum nitride. In another example, the etch stop layer <NUM> is formed at operation <NUM> from a silicon-based material such as silicon oxide.

At operation <NUM> a second grating material layer <NUM> is deposited on the etch stop layer <NUM>. The second grating material layer <NUM> can be deposited using CVD and is formed inside of the feature <NUM> as well as on either side of the feature <NUM>, resulting in excess of material 516A. <FIG> shows a structure resulting from the deposition of the second grating material layer <NUM> at operation <NUM>. In one or more embodiments, each of the grating material layer <NUM> and the second grating material layer <NUM> is formed from at least one of silicon oxycarbide (SiOC), titanium oxide (e.g., titanium dioxide (TiO<NUM>)), silicon oxide (e.g., silicon dioxide (SiO<NUM>)), vanadium (IV) oxide (VO<NUM>), aluminum oxide (Al<NUM>O<NUM>), indium tin oxide (ITO), zinc oxide (ZnO), tantalum pentoxide (Ta<NUM>O<NUM>), silicon nitride (SiN or Si<NUM>N<NUM>), titanium nitride (TiN), zirconium dioxide (ZrO<NUM>), oxynitrides thereof, or any combination thereof. The hardmask layer <NUM> is formed from silicon nitride, silicon oxide, a metal-based layer containing titanium or chromium, dopants thereof, alloys thereof, or any combination thereof.

Subsequently, at operation <NUM>, the excess material from the second grating material layer <NUM> is removed (planarized) to form a planarized surface <NUM>. The planarization at operation <NUM> can be performed using SAP etch. <FIG> shows a structure resulting from the planarization at operation <NUM>. At operation <NUM>, a second hardmask layer <NUM> is deposited on the second grating material layer <NUM> and etched to form a plurality of openings <NUM>. <FIG> shows a structure resulting from the deposition of the second hardmask layer <NUM> at operation <NUM>. The second hardmask layer <NUM> can be deposited at operation <NUM> using CVD and etched using deep ultraviolet (DUV) lithography to form the plurality of openings <NUM> (e.g., by using DUV to form a pattern that is transferred to the hardmask layer <NUM> via an etching process). In other examples, the second hardmask layer <NUM> can be patterned using nanoimprint lithography (NIL) to form the plurality of openings <NUM>. In one or more examples at operation <NUM>, the plurality of openings <NUM> can be formed in a plurality of sub operations including depositing a photoresist (not shown) on the second hardmask layer <NUM>, performing DUV lithography to pattern the photoresist, and etching the second hardmask layer <NUM> through the patterned photoresist. The photoresist can then be removed prior to operation <NUM>. The second hardmask layer <NUM> can be formed from materials similar to those used to form the hardmask layer <NUM> as discussed above. In one or more examples, the second hardmask layer <NUM> is formed from a material that is different than that of the etch stop layer <NUM> such that the two materials have differing etch selectivity.

At operation <NUM>, a first grating <NUM> including a first plurality of fins <NUM> is formed in the second grating material layer <NUM> through the plurality of openings <NUM> in the second hardmask layer <NUM>. <FIG> shows a structure resulting from the formation of the first grating <NUM> at operation <NUM>. Operation <NUM> can be executed using the angled etch system discussed above in <FIG> and <FIG> to form the first plurality of fins <NUM> at a first slant angle. During operation <NUM>, to form the first grating <NUM>, a first portion of the substrate <NUM> is positioned relative to an ion beam at a first ion beam angle. Operation <NUM> includes determining the first ion beam angle ϑ<NUM> for the first grating <NUM>. As discussed above, the first ion beam angle ϑ<NUM> can be determined by the rotation from a grating angle of the first grating using equation ϑ<NUM> = atan(tan(ϑ<NUM>')/cos(ϕ<NUM>)).

The substrate <NUM> is retained on a platen and the first ion beam angle is measured, as discussed above, relative to a plane parallel to the platen. The substrate <NUM> is rotated about a central axis of the platen to a first rotation angle between the ion beam and a first grating vector of the first grating <NUM> when the ion beam is at the first ion beam angle. The ion beam is a ribbon beam with an angle adjustable from about <NUM> degrees to about <NUM> degrees with respect to the plane parallel to the platen. To form the first grating <NUM>, which has the first plurality of fins <NUM> formed such that the fin adjacent to a first end 524A of the first grating <NUM> is formed to a lesser depth than the fin adjacent to the second end 524B of the first grating. In one or more examples, a depth of the first grating is from about <NUM> to about <NUM> and a width of each fin of the plurality of fins <NUM> is from about <NUM>% to about <NUM>% of the pitch of the plurality of fins <NUM>. The plurality of fins <NUM> are formed at a first slant angle as discussed above, the first slant angle can be from about <NUM> degrees to about <NUM> degrees. The plurality of fins <NUM> 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 <NUM> increases, thus increasing the depth of the etching. The variation in height of the fins <NUM> along a bottom surface 524C can create the wedge angle <NUM>. The ion beam has one or more process parameters (e.g., a duty cycle) which can be modulated to form the first grating <NUM>. For example, the process parameter when the ion beam is at the first ion beam angle and in contact with the first portion of the substrate can be modulated from about <NUM>% to about <NUM>% of the duty cycle. A shorter modulation time for the process parameter (e.g., <NUM>%) can be used to form fins with a lesser depth, such as those at or near the first end 524A of the first grating <NUM>. Similarly, a longer modulation time for the process parameter (e.g., <NUM>%) 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 not according to the claimed invention, the first ion beam angle used to form the first grating <NUM> as operation <NUM> is aligned with the first depth gradient of the first grating <NUM>.

In one or more embodiments, additional pluralities of fins can be formed during subsequent iterations of operation <NUM> after formation of the first grating <NUM>. In this example, at operation <NUM>, subsequent to forming the first grating, the first ion beam angle is changed to a second ion beam angle that is different from the first ion beam angle. Subsequent iterations of operation <NUM> include determining subsequent ion beam angles ϑx that may be different from the first ion beam angle ϑ<NUM>, for example, a second ion beam angle ϑ<NUM> can be determined for the first grating <NUM>. As discussed above, the second ion beam angle ϑ<NUM> can be determined using the equation ϑ<NUM> = atan(tan(ϑ<NUM>')/cos(ϕ<NUM>)). A second portion of the substrate is positioned in a path of the ion beam when the ion beam is positioned at the second ion beam angle. The substrate is rotated about the central axis of the platen to a second rotation angle between the ion beam and a second grating vector of the second grating when the ion beam is at the second ion beam angle. Thus, multiple gratings can be formed on a single substrate at different slant angles and at different depth gradients by changing the ion beam angle and rotating the substrate at operation <NUM>.

At operation <NUM>, the second hardmask layer <NUM> is removed, for example, using a wet strip etch as discussed above with respect to operation <NUM>. <FIG> shows a structure resulting from the removal of the second hardmask layer <NUM> at operation <NUM>. In some embodiments of the method <NUM>, at operation <NUM>, a coating 526A is optionally formed on the plurality of fins <NUM> using an ALD process. In one or more examples, the coating 526A includes one or more layers of oxide. <FIG> shows a structure resulting from forming the coating on the plurality of fins <NUM> at operation <NUM>. In examples where more than one grating is formed, some or all gratings can have coating disposed thereon at operation <NUM>. In one or more examples, an ALD process can be used at operation <NUM> to coat the plurality of fins <NUM> with an oxide. In some examples, other methods of forming a conformal coating the plurality of fins <NUM> can be employed. In one or more examples, the plurality of fins <NUM> can coated at operation <NUM> to tune or refine critical dimensions of the plurality of fins <NUM>.

<FIG> is flowchart illustrating a method <NUM> of forming a grating, according to one or more embodiments described and discussed herein. <FIG> illustrate structures at different of intervals while being produced during the method <NUM>. The method <NUM> includes operations <NUM>, <NUM>, and <NUM> that are discussed in detail above with respect to the method <NUM> in <FIG>. <FIG> illustrates a structure formed by operation <NUM> that includes the substrate <NUM> and the grating material layer <NUM> and the hardmask layer <NUM>. <FIG> illustrates a structure formed by operation <NUM>, where an opening <NUM> is formed in the hardmask layer <NUM> using a wet strip (chemical) etch as discussed above in the method <NUM>. <FIG> illustrates a structure formed by operation <NUM> after the removal of a portion of the first grating layer <NUM> to form the feature <NUM>. Similar to what is shown in <FIG>, the feature <NUM> can be referred to as a recess or an angled recess and is defined by a first side 510A, a second side 510C opposite the first side 510A, and a transitional surface 510B extending between the first side 510A and the second side 510C. An angle <NUM> formed between the transitional surface 510B and the second side 510C. However, in the method <NUM> of <FIG>, in contrast to the method <NUM> where an etch stop layer and a second grating material layer are deposited subsequent to operation <NUM>, a hardmask layer <NUM> is deposited at operation <NUM>. The hardmask layer <NUM> can be deposited at operation <NUM> using CVD. <FIG> shows a structure resulting from the deposition of the hardmask layer <NUM> at operation <NUM>. The hardmask layer <NUM> can be formed from similar materials as discussed above with respect to the hardmask layer <NUM> and the second hardmask layer <NUM>.

Subsequently, at operation <NUM>, the hardmask layer <NUM>, which can be referred to herein as the second hardmask layer, is etched to form a plurality of openings <NUM>. <FIG> shows a structure resulting from the formation of openings in the hardmask layer <NUM> at operation <NUM>. In some examples, during operation <NUM>, the hardmask layer <NUM> is removed from portions <NUM> of the grating material layer <NUM> as well. The plurality of openings <NUM> can be formed in a plurality of sub operations including depositing a photoresist (not shown) on the hardmask layer <NUM>, performing DUV lithography to pattern the photoresist, and etching the hardmask layer <NUM> through the patterned photoresist. The photoresist can then be removed prior to operation <NUM>. In other examples, the plurality of openings <NUM> can be formed at operation <NUM> using NIL.

At operation <NUM>, a grating <NUM> can be formed using angled etching to include a plurality of fins <NUM> formed at a slant angle and to a depth gradient and a wedge angle as discussed above. Operation <NUM> includes determining a first ion beam angle ϑ<NUM> to use to form the grating <NUM>. As discussed above, the first ion beam angle ϑ<NUM> can be determined using the equation ϑ<NUM> = atan(tan(ϑ<NUM>')/cos(ϕ<NUM>)). <FIG> shows a structure resulting from the formation of the grating <NUM> at operation <NUM>. The grating <NUM> formed at operation <NUM> can be formed in a similar manner to the one or more gratings discussed at operation <NUM> in <FIG> using an angled etch system by rotating the substrate <NUM> and changing the angle of the ion beam. For example, the grating <NUM> formed at operation <NUM> can be formed by angled etching by rotating the substrate <NUM> around a central axis perpendicular to the substrate and/or a platen on which the substrate is disposed. An ion beam, for example, a ribbon beam, is positioned at a predetermined angle relative to the substrate <NUM> and used to form the plurality of fins <NUM> to varying depths by modulating the duty cycle of the ion beam. Operation <NUM> can be repeated similarly to the iterations of operation <NUM> discussed above to form multiple gratings at varying slant angles, depth gradients, and wedge angles. Each ion beam angle ϑx can be determined for each grating subsequently formed at operation <NUM> as discussed above. At operation <NUM> of the method <NUM>, one or more portions <NUM> of the grating material layer <NUM> are removed from the grating <NUM> using SAP etch to form a wedge <NUM>. <FIG> shows the wedge <NUM> resulting from the formation of the plurality of fins <NUM> of the grating <NUM> subsequent to the removal of the portions <NUM> of the grating material layer <NUM> at operation <NUM>. <FIG> further shows wedge <NUM> where the hardmask layer <NUM> is removed, which can occur at operation <NUM> or other operations not discussed herein.

<FIG> is flowchart illustrating a method <NUM> of forming a grating, according to one or more embodiments described and discussed herein. <FIG> illustrate structures at different of intervals while being produced during the method <NUM>. At operation <NUM> in the method <NUM>, a substrate including a grating material layer <NUM> is formed using, for example, CVD. <FIG> shows a structure resulting from formation of the grating material layer <NUM> at operation <NUM>. In particular, <FIG> shows the grating material layer <NUM> that can be formed from an Si-based material to a thickness from about <NUM> to about <NUM> using CVD from at least one of silicon oxycarbide (SiOC), silicon oxide (e.g., silicon dioxide (SiO<NUM>)), silicon nitride (SiN or Si<NUM>N<NUM>), or silicon carbonitride (SiCN). A hardmask layer <NUM> is formed over the grating material layer <NUM> and can be formed from a metallic or dielectric material as discussed above with respect to the methods <NUM> and <NUM>.

At operation <NUM>, a plurality of openings <NUM> are formed in the hardmask layer <NUM>. <FIG> shows a structure resulting from the formation of the hardmask layer <NUM> operation <NUM>. The plurality of openings <NUM> can be formed at operation <NUM> in a plurality of sub operations including depositing a photoresist (not shown) on the hardmask layer <NUM>, performing DUV lithography and etching or NIL to pattern the photoresist, etching the hardmask layer <NUM> through the patterned photoresist. The photoresist can then be removed prior to operation <NUM>. <FIG> shows a structure resulting from the etching of the hardmask layer <NUM> at operation <NUM>.

At operation <NUM>, a grating <NUM> is formed in the grating material layer <NUM> from the Si-based material using an angled etch system as discussed herein. Operation <NUM> includes determining a first ion beam angle ϑ<NUM> to use to form the grating <NUM>. As discussed above, the first ion beam angle ϑ<NUM> can be determined using equation ϑ<NUM> = atan(tan(ϑ<NUM>')/cos(ϕ<NUM>)). The grating <NUM> can be formed as a wedge-shaped grating, where a plurality of fins <NUM> of the grating <NUM> increase in size from a first end 908A of the grating <NUM> to a second end 908B of the grating <NUM>. The grating <NUM> can be formed at operation <NUM> in a similar manner to the gratings for at operations <NUM> and <NUM> discussed above. A duty cycle of the ion beam that is configured with an adjustable angle is modulated to form each of the plurality of fins <NUM> to varying depths, and the substrate on which the grating material layer <NUM> is disposed can be rotated as well. In contrast to the method <NUM>, no etch stop layer is used in the method <NUM>. At operation <NUM>, the hardmask layer <NUM> is removed, for example, using a chemical etch via wet strips. <FIG> shows a structure resulting from the removal of the hardmask layer <NUM> at operation <NUM>.

<FIG> is flowchart illustrating a method <NUM> of forming a grating, according to one or more embodiments described and discussed herein. <FIG> illustrate structures at different of intervals while being produced during the method <NUM>. The method <NUM> includes operation <NUM> that is executed in a similar fashion to operation <NUM> in the method <NUM> in <FIG>. <FIG> shows a structure resulting from operation <NUM> in the method <NUM>. <FIG> shows a grating material layer <NUM> formed over a substrate <NUM>, and a hardmask layer <NUM> formed over the grating material layer. At operation <NUM>, the hardmask layer <NUM> is opened to form a plurality of openings <NUM> in a similar manner to operations <NUM> and <NUM> discussed above using DUV lithography and etching or NIL. <FIG> shows a structure resulting from the opening of the hardmask layer <NUM> at operation <NUM> in the method <NUM>. This is in contrast to operation <NUM> in the method <NUM> where a contiguous portion of the hardmask layer is removed. Subsequently, at operation <NUM> of the method <NUM>, a grating <NUM> is formed in the grating material layer <NUM> using angled etching by rotating the substrate <NUM> and modulating the duty cycle of an ion beam as discussed above. Operation <NUM> includes determining a first ion beam angle ϑ<NUM> to use to form the grating <NUM>. As discussed above, the first ion beam angle ϑ<NUM> can be determined using the equation ϑ<NUM> = atan(tan(ϑ<NUM>')/cos(ϕ<NUM>)). <FIG> shows a structure resulting from the formation of the grating <NUM> operation <NUM> in the method <NUM>. The grating <NUM> is formed to have a plurality of fins <NUM>, a first end 1104A, a second end 1104B, and a bottom 1104C, and is formed to have a rectangular shape such that the first end 1104A and the second end 1104B are at a substantially right angle to the bottom 1104C. At operation <NUM>, a portion of the fins <NUM> is removed using SAP to form a top surface <NUM> of the grating <NUM> such that the grating <NUM> has a cross section of a wedge. This is in contrast to the rectangular shape formed at operation <NUM>. Further in operation <NUM>, portions 504A (shown in <FIG>) of the grating material layer <NUM> are removed, as is the hardmask layer <NUM>. <FIG> shows a structure resulting from the etching of the grating <NUM> at operation <NUM> in the method <NUM>. The portion of the fins <NUM> removed at operation <NUM> are removed at a wedge angle α measured relative to the substrate <NUM>. Operations <NUM>, <NUM>, and <NUM> can be repeated to form additional gratings in the grating material layer <NUM> at other slant angles, using different ion beam angles, different substrate rotation angles, and duty cycle modulation as discussed herein.

Thus, using the systems and methods discussed herein, multiple gratings for augmented waveguide combiners and/or masters for imprinting grating materials can be fabricated. Gratings of varying depth gradients and slant angles can be formed on a single substrate using embodiments discussed herein by at least changing the ion beam angle and modulating the duty cycle of the ion beam in combination with rotating the substrate relative to the ion beam angle.

While the foregoing is directed to embodiments of the disclosure, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. As is apparent from the foregoing general description and the specific embodiments, while forms of the present disclosure have been illustrated and described, various modifications can be made without departing from the scope of the present disclosure. Accordingly, it is not intended that the present disclosure be limited thereby. Likewise, the term "comprising" is considered synonymous with the term "including" for purposes of United States law. Likewise whenever a composition, an element or a group of elements is preceded with the transitional phrase "comprising", it is understood that we also contemplate the same composition or group of elements with transitional phrases "consisting essentially of," "consisting of", "selected from the group of consisting of," or "is" preceding the recitation of the composition, element, or elements and vice versa.

Claim 1:
A method (<NUM>) of forming a grating, comprising:
etching (<NUM>) a hardmask layer (<NUM>) to form a plurality of openings (<NUM>, <NUM>), the hardmask layer (<NUM>) being disposed over a grating material layer (<NUM>) that is disposed on a substrate (<NUM>);
forming (<NUM>) a first grating (<NUM>) in the grating material layer (<NUM>) through the plurality of openings (<NUM>, <NUM>) of the hardmask layer (<NUM>), wherein the first grating (<NUM>) has a first shape vector, the first shape vector being a direction in which a depth gradient of the first grating (<NUM>) changes, and a first grating vector not being aligned with the first shape vector, wherein forming the first grating (<NUM>) comprises:
determining (<NUM>) a first ion beam angle ϑ<NUM> relative to a first slant angle ϑ<NUM>' and an angle ϕ<NUM> which is between the first shape vector and the first grating vector;
positioning a first portion of the grating material layer (<NUM>) in a path of an ion beam (<NUM>) at the first ion beam angle ϑ<NUM> relative to the substrate, the substrate (<NUM>) being retained on a platen (<NUM>); and
modulating a process parameter when the ion beam (<NUM>) is at the first ion beam angle ϑ<NUM> to form a first plurality of fins (<NUM>) of the first grating (<NUM>) having the first shape vector, the first grating vector, and the first slant angle ϑ<NUM>' relative to a surface normal of the substrate (<NUM>) such that the first plurality of fins (<NUM>) are formed at the first slant angle ϑ<NUM>'.