System and method for optimally forming a grating of a diffractive optical element - Patents.com

Abstract

Optical grating elements and methods of formation are provided. In some embodiments, the methods include providing an optically transparent substrate and forming an optical grating layer on the substrate. The methods include forming an optical grating in the optical grating layer, the optical grating including a plurality of angled elements arranged at a non-zero angle with respect to a normal to the plane of the substrate. A first sidewall of the optical grating can have a first angle, and a second sidewall of the grating has a second angle different from the first angle. Modifying process parameters, including selectivity and beam angle spread, has the effect of changing the shape or dimensions of the plurality of angled elements. [Selected Figure] Figure 4D

Description

[Technical field]

[0001] This disclosure relates to optical elements, and more particularly, to approaches for optimally forming gratings in diffractive optical elements. [Background technology]

[0002]

[0002] Optical elements such as optical lenses have long been used to manipulate light for a variety of advantages. Recently, micro-diffraction gratings have been utilized in holographic and augmented / virtual reality (AR and VR) devices.

[0003]

[0003] Certain AR and VR devices are wearable display systems (e.g., headsets) configured to display images within a short distance of the human eye. Such wearable headsets, sometimes called head-mounted displays, are provided with a frame that displays an image within a few centimeters of the user's eyes. The image may be a computer-generated image on a display, such as a microdisplay. Optical components are arranged to transport light of the desired image, and light is generated on the display to the user's eyes such that the image is visible to the user. The display on which the image is generated may form part of a light engine, so that the image generates a collimated light beam that is directed by the optical components to bring the image visible to the user.

[0004]

[0004] Various kinds of optical components have been used to transfer images from a display to the human eye. To function well in an augmented reality lens or combiner, the shape of the optical grating can be designed to achieve various effects. In some devices, multiple different regions (e.g., two or more different regions) are formed on the surface of the lens, and the shape of the grating in one region is different from the shape of the grating in the other region. For example, many known devices include three elements, namely, an incoupler, a horizontal expander, and an outcoupler. To provide these different regions, different etches are used to etch the grating in the different regions, and as a result, the shape of the grating may differ between the different regions. Due to the complexity of the process, the optimal parameters for realizing an optical component with an angled grating are not known.

[0005]

[0005] Accordingly, the present disclosure is provided in light of at least the above-mentioned shortcomings. Summary of the Invention

[0006] In one embodiment, a method of forming an optical grating element is provided. The method may include providing an optical grating layer over a substrate and providing a hard mask over the optical grating layer. The method may further include etching the optical grating layer and the hard mask to form an optical grating in the optical grating layer. The optical grating may include a plurality of angled elements arranged at a non-zero angle with respect to a normal to a plane of the substrate. Etching of the patterned hard mask reduces faster in width than in height to form first and second sidewalls of the optical grating having distinct angles.

[0007] In another embodiment, a method of forming an optical grating element may include providing an optical grating layer over a substrate and providing a patterned hard mask over the optical grating layer. The method may further include etching the optical grating layer and the hard mask to form an optical grating in the optical grating layer, the optical grating including a plurality of angled elements disposed at a non-zero angle with respect to a normal to a plane of the substrate. Etching of the patterned hard mask reduces faster in width than in height to form first and second sidewalls of the plurality of angled elements having distinct angles.

[0008] In yet another embodiment, a method for forming an augmented / virtual reality device may include providing a patterned hard mask over an optical grating layer and etching the optical grating layer and the hard mask to form an optical grating in the optical grating layer. The optical grating may include a plurality of angled elements disposed at a non-zero angle with respect to a normal to a plane of the substrate. An etch of the patterned hard mask reduces faster in width than in height to form first and second sidewalls of the plurality of angled elements having distinct angles.

[0009]

[0009] The accompanying drawings illustrate exemplary approaches of the present disclosure, including practical applications of the principles of the present disclosure, such as: [Brief description of the drawings]

[0010] [Figure 1A] FIG. 1 illustrates a cross-sectional side view of an optical grating component according to an embodiment of the present disclosure. [Figure 1B] FIG. 1B illustrates a top view of the optical grating component of FIG. 1A according to an embodiment of the present disclosure. [Figure 2A] 1 shows a processing apparatus, depicted in schematic form, according to an embodiment of the present disclosure. [Figure 2B] FIG. 1 illustrates a top view of an extraction plate component and a substrate according to an embodiment of the present disclosure. [Diagram 3] FIG. 1 illustrates a cross-sectional side view of angled structures formed in an optical grating layer of an optical grating component according to an embodiment of the present disclosure. [Figure 4A-4D] 1 illustrates various stages of fabrication of an optical grating, according to an embodiment of the present disclosure. [Diagram 5] 13 is a graph showing selectivity input versus output angle for a sidewall of an angled structure according to an embodiment of the present disclosure. [Figures 6A-6D] 13A-13C show various angled structures with different selectivity values ​​according to embodiments of the present disclosure. [Figure 7A] 1A-1D are side cross-sectional views illustrating various ion beam angular spreads according to an embodiment of the present disclosure. [Figure 7B] 7B is a cross-sectional side view of a plurality of angled structures formed using the various ion beam angular spreads of FIG. 7A in accordance with an embodiment of the present disclosure. [Figure 8] 1 illustrates a process flow according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011]

[0021] The drawings are not necessarily to scale. The drawings are merely representational and are not intended to represent specific parameters of the present disclosure. The drawings are intended to illustrate exemplary embodiments of the present disclosure and therefore should not be considered limiting in scope. In the drawings, like numbers represent like elements.

[0012]

[0022] The present embodiments will now be described more fully with reference to the accompanying drawings, in which several embodiments are shown. The subject matter of the present disclosure may be embodied in many different forms and should not be construed as being limited to the embodiments presented herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, like numbers refer to like elements throughout.

[0013]

[0023] As used herein, elements or operations listed in the singular and preceded by the article "a" or "an" are understood to include plural elements or operations unless otherwise indicated. Furthermore, references to "one embodiment" or "some embodiments" of the present disclosure may be interpreted as including the existence of additional embodiments that also incorporate the recited features.

[0014]

[0024] Furthermore, terms such as "about" or "approximately" may be used interchangeably in some embodiments and may be described using any relative measure acceptable to one of ordinary skill in the art. For example, such terms may serve as a comparison to a reference parameter to indicate a deviation that may achieve the intended function. Without being limiting, the deviation from the reference parameter may be, for example, an amount of less than 1%, less than 3%, less than 5%, less than 10%, less than 15%, less than 20%, etc.

[0015]

[0025] Embodiments herein provide novel optical components, as well as systems and methods for forming optical components. Various embodiments relate to diffractive optical elements, and the term "optical lattice component" refers to a device or part having an optical lattice, including AR and VR headsets, eyepieces for AR and VR, or masters for forming optical lattices for eyepieces such as glasses.

[0016]

[0026] FIG. 1A shows a cross-sectional side view of an optical grating component 100 according to an embodiment of the present disclosure. FIG. 1B shows a top view of the optical grating component 100. The optical grating component 100 can be used as an optical grating disposed on or integrally formed in eyeglasses according to various embodiments of the present disclosure. The optical grating component 100 includes a substrate 102 and an optical grating 106 disposed on the substrate 102. In some embodiments, the substrate 102 is an optically transparent material such as glass as is known. In some embodiments, the substrate 102 is silicon. In the latter case, the substrate 102 is silicon and a separate process is used to transfer the grating pattern to a film on the surface of another optical substrate (e.g., glass or quartz). The embodiments are not limited in this context. As will be further described below, the optical grating 106 can be disposed in an optical grating layer 107. In the embodiment of FIG. 1A and FIG. 1B, the optical grating component 100 further includes an etch stop layer 104 disposed between the substrate 102 and the optical grating layer 107. According to some embodiments of the present disclosure, the optical grating layer 107 may be an optically transparent material (eg, silicon oxide, silicon nitride, glass, TiO2, or other material).

[0017]

[0027] According to some embodiments of the present disclosure, the optical grating 106 may include a grating height H in the range of 100 nm to 1000 nm. Thus, the optical grating 106 may be suitable for use in eyepieces of AR and VR devices. The embodiments herein are not limited in this context. According to some embodiments, the etch stop layer 104 may be an optically transparent material and may have a thickness of 10 nm to 100 nm. The embodiments are not limited in this context. Examples of suitable materials for the etch stop layer 104 include SiN, SiO2, TiN, SiC, and other materials. Particularly suitable materials in embodiments in which the optical grating 106 is applied to or incorporated into an eyepiece of a pair of glasses are optically transparent materials. In embodiments in which the optical grating component 100 forms a master for manufacturing an optical grating for an eyepiece, the etch stop layer 104 does not need to be optically transparent. Furthermore, the etch stop layer 104 may be omitted in some embodiments.

[0018]

[0028] As further shown in FIG. 1A, the optical grating 106 may include a plurality of angled structures, shown as angled structures 112, arranged at a non-zero angle of inclination with respect to a normal to the plane of the substrate 102. The angled structures 112 may be included within one or more fields of the angled grating, which together form a "microlens." As described in more detail below, the sidewalls 113 and 115 of each angled structure 112 may vary in angle (e.g., angle with respect to a normal to the plane of the substrate 102) and shape as the beam selectivity, beam angle spread, beam angle average, etc. are modified. As described in more detail below, the sidewalls 113 and 115 of each angled structure 112 may further vary in angle based on the selectivity between the angled structures 112 and a hard mask formed on the angled structures 112. Selectivity, as used herein, may be a product of the material or materials of the optical grating layer in which the angled structures 112 are formed, the chemistry of the etching ions, and the tool parameters (e.g., beam intensity, relative pressures of various gases, and temperature).

[0019]

[0029] Between the angled structures 112 are a number of trenches 114. The angled structures 112 may be arranged to define a uniform or variable height along a first direction. In the example of FIG. 1A, the angled structures 112 define a uniform height along a direction parallel to the Y-axis of the illustrated Cartesian coordinate system, the first direction (Y-axis) being parallel to the plane of the substrate 102, i.e., the XY plane. In other embodiments, the angled structures 112 may define a variable height along a direction parallel to the Y-axis.

[0020]

[0030] The width of the optical grating 106 along the Y direction may be on the order of a few millimeters to a few centimeters, and the grating height H may be on the order of 1 micrometer or less. Thus, the variation of the grating height H may be in the range of on the order of a few hundred nanometers or less. Examples of smooth variations in the grating height H or depth d include cases where the variation of the grating height H or depth d between adjacent lines of the grating is less than 10%, less than 5%, or less than 1%. The embodiments are not limited in this context. Thus, for an eyepiece, the grating height H may vary in a continuous and non-abrupt manner in a given direction along the surface of the eyepiece, for example, over lengths in the order of millimeters to centimeters. More specifically, a 50% variation of the grating height H over a distance of 5 mm is about 5x10 with a pitch of 1 micrometer. 3 This may involve continuously varying the grating height H across the line. This variation may involve a factor of 0.5 / 5×10 4 Or with an average variation in the relative heights of adjacent lines of about 0.01%.

[0021]

[0031] Referring now to FIG. 2A, there is shown a processing apparatus 200 depicted in schematic form. Processing apparatus 200 represents a processing apparatus for etching portions of a substrate or depositing on a substrate, for example to produce the optical grating of the present embodiment. Processing apparatus 200 may be a plasma-based processing system with a plasma chamber 202 for generating plasma 204 therein by any convenient method known in the art. As shown, an extraction plate 206 having extraction apertures 208 may be provided, and a non-uniform etch or non-uniform deposition may be performed to reactively etch or deposit an optical grating layer 107 (FIGS. 1A-1B). For example, a substrate 102 including the optical grating structure described above is placed in a processing chamber 224. The substrate plane of substrate 102 is represented by the XY plane of the illustrated Cartesian coordinate system, while a normal to the plane of substrate 102 extends along the Z axis (Z direction).

[0022]

[0032] 2A, as in known systems, the ion beam 210 may be extracted when a voltage difference is applied using a bias supply 220 between the process chamber 202 and the substrate 102 or substrate platen 214. The bias supply 220 may be coupled to the process chamber 224, where, for example, the process chamber 224 and the substrate 102 are held at the same potential.

[0023]

[0033] According to various embodiments, the ion beam 210 may be extracted along a normal line 226 or at a non-zero angle of incidence, denoted Φ, relative to the normal line 226 .

[0024]

[0034] The trajectories of the ions in the ion beam 210 may be parallel to each other or may be within a narrow angular spread (e.g., within 10 degrees of each other). In other embodiments, as described below, the trajectories of the ions in the ion beam 210 may converge or diverge from each other, for example, in a fan shape. Thus, the value of Φ may represent an average value of the incidence angle where the individual trajectories vary from the average value by a few degrees. In various embodiments, the ion beam 210 may be extracted as a continuous beam or as a pulsed ion beam, as in known systems. For example, the bias supply 220 may be configured to supply a voltage difference between the plasma chamber 202 and the processing chamber 224 as a pulsed DC voltage. In this case, the voltage, pulse frequency, and duty cycle of the pulsed voltage may be individually adjusted.

[0025]

[0035] In various embodiments, a gas, such as a reactive gas, may be supplied to the plasma chamber 202 by a source 222. The plasma 204 may produce a variety of etching or deposition species, depending on the exact composition of species supplied to the plasma chamber 202.

[0026]

[0036] In various embodiments, the ion beam 210 may be provided as a ribbon reactive ion beam having a long axis extending along the X direction of the Cartesian coordinate system shown in FIG. 2B. By scanning the substrate platen 214 containing the substrate 102 along a scan direction 230 relative to the extraction aperture 208 and thus the ion beam 210, the ion beam 210 may etch or deposit on the substrate 102. The ion beam 210 may be comprised of any convenient gas mixture including inert and reactive gases and may be provided with other gas species in some embodiments. In certain embodiments, the ion beam 210 and other reactive species may be provided to the substrate 102 as an etch recipe. This results in directional reactive ion etching of a layer such as the optical grating layer 107. As known in the art, such etch recipes may use known reactive ion etch chemistries to etch materials (e.g., oxides or other materials). In other embodiments, the ion beam 210 may be formed from inert species. In this case, the ion beam 210 is provided to etch the substrate 102 (more specifically, the optical grating layer 107) by physical sputtering as the substrate 102 is scanned relative to the ion beam 210.

[0027]

[0037] In the example of FIG. 2B, the ion beam 210 is provided as a ribbon reactive ion beam that extends to a beam width along the X direction, where the beam width is sufficient to expose the entire width of the substrate 102, even the widest portion along the X direction. Exemplary beam widths can range from 10 cm, 20 cm, 30 cm, or more, while exemplary beam lengths along the Y direction can range from 2 mm, 3 mm, 5 mm, 10 mm, or 20 mm. The embodiments are not limited in this context.

[0028]

[0038] In particular, the scan direction 230 may represent a scan of the substrate 102 in two opposing (180 degree) directions along the Y direction, or simply a scan to the left or right. As shown in FIG. 2B, the long axis of the ion beam 210 extends along the X direction, perpendicular to the scan direction 230. Thus, when the substrate 102 is scanned along the scan direction 230 at an appropriate length from the left side to the right side of the substrate 102, the entire substrate 102 may be exposed to the ion beam 210.

[0029]

[0039] In various embodiments, the processing apparatus 200 can be used to form optical grating layers with varying characteristics such as angles, thicknesses, and depths, as described in more detail below. The grating characteristics can be achieved by scanning the substrate 102 relative to the ion beam 210 using a process recipe. Briefly, the process recipe can involve modifying at least one process parameter of a set of process parameters. The process parameter has the effect of modifying, for example, an etching rate or a deposition rate caused by the ion beam 210 during scanning of the substrate 102. Such process parameters can include the scanning speed of the substrate 102, the ion energy of the ion beam 210, the duty cycle of the ion beam 210 when delivered as a pulsed ion beam, the spread angle of the ion beam 210, and the rotational position of the substrate 102. In at least some embodiments herein, the process recipe can further include one or more materials of the optical grating layer 107 and the chemistry of the etching ions 130. In yet other embodiments, the process recipe may include the starting geometry of the optical grating layer 107, including dimensions and aspect ratios, and the presence of the etch stop layer 104 (including whether under-etching or over-etching into the etch stop layer 104 is intended). The embodiments are not limited in this context. Because the deposition rate or etching rate caused by the ion beam 210 may change during scanning of the substrate 102, the thickness or height of the optical grating layer 107 may vary along the scanning direction (Y-axis), producing the resulting structure shown in FIG. 1A (after further processing operations, described in more detail below).

[0030]

[0040] 3, an example of a set of fins or angled structures 112 formed in the optical grating layer 107 by the etching process of the embodiments herein will be described in more detail. The angled structures 112 can be formed by any of the etching processes described above to fabricate the angled structures 112 with unique positions, shapes, three-dimensional orientations, etc. In some examples, the etching process can control or modify any of the lattice parameters of the set of angled structures 112, i.e., pitch, hard mask 108 thickness, and fin height. Additionally, the etching process can control or modify any of the lattice parameters of the set of angled structures 112, i.e., fin thickness (CD), corner radii β and α, overetch into the etch stop layer 104, healing, first sidewall angle ρ, second sidewall angle θ, and footing. In one non-limiting embodiment, based on the selectivity and shape (e.g., height and width) of the hard mask 108 and the shape of the optical grating layer 107, the hard mask 108 over each angled structure 112 can be etched away faster in the horizontal direction than in the vertical direction, forming sharp tips along each angled structure 112.

[0031]

[0041] 4A, a cross-sectional side view of an example optical grating component 100 is shown in one embodiment. In the embodiment shown, an optical grating layer 107 having a uniform height is disposed on an etch stop layer 104. A hard mask 108, such as a hard mask, is formed / patterned on the optical grating layer 107. The hard mask 108 may be any of a variety of materials, including carbon, SiO2, SiC, AlO x , ZrO xThe hard mask 108 may be formed of a material such as SiO2. According to various embodiments, a directional reactive ion etch process is performed to etch the optical grating layer 107. The directional reactive ion etch is represented by etching ions 130. The etch chemistry may include etching ions 130 and other non-ionic species and may be selected according to known reactive ion etch compositions to selectively etch the optical grating layer 107 and not the hard mask 108. For example, the etch chemistry may be selected to selectively etch SiO2 relative to carbon, in one example. In other embodiments, the etch chemistry and etch angle may be selected according to known reactive ion etch compositions to selectively etch both the optical grating layer and the hard mask 108.

[0032]

[0042] The etching ions 130 may be provided as a ribbon reactive ion beam, whose ion trajectories define a non-zero angle of inclination μ with respect to normal 132, as shown. The non-zero angle of incidence may be produced according to known techniques, such as using a beam blocker adjacent to the extraction aperture 208, adjusting the extraction aperture width along the Y-axis, and adjusting plasma conditions within the plasma 204, including gas pressure, to vary the curvature of the plasma sheath boundary 228 proximate the extraction aperture 208.

[0033]

[0043] According to some embodiments of the present disclosure, designed or theoretical input values ​​for a given optical grating can be calculated to optimize the performance of the optical grating. This grating profile can then be used to program a process recipe for the processing equipment 200 to generate the grating profile in the optical grating layer 107 using the etching ions 130.

[0034]

[0044] In FIG. 4B, further examples of processing the optical grating component 100 are shown. In a non-limiting embodiment, the optical grating layer 107 is partially etched by etching ions 130 to begin forming angled structures 112 separated by a plurality of trenches 114. Based on the selectivity and shape of the hard mask 108, the height "H" or thickness of the optical grating layer 107, and the width "W" of the optical grating layer 107, the hard mask 108 over each angled structure 112 etches away faster in the horizontal direction (155) than in the vertical direction (arrow 157). In doing so, the angled structures 112 are formed to have non-parallel sidewalls. The etching ions 130 can further deepen the plurality of trenches 114, as shown in FIG. 4C. In a non-limiting embodiment, the angled structures 112 define a first sidewall angle ρ and a second sidewall angle θ, where ρ ≠ θ. As shown, θ increases relative to ρ over a series of etching cycles.

[0035]

[0045] Although not shown, according to various embodiments, the etching chemistry for the etching ions 130 is configured such that the optical grating layer 107 is also etched selectively relative to the etch stop layer 104 and the hard mask 108. For example, once the etch stop layer 104 is encountered, the etching slows and the process with the etching ions 130 can be conveniently stopped. Once formed, the angled structures 112 define a first sidewall angle ρ and a second sidewall angle θ. As the optical grating layer 107 is etched, the hard mask 108 is also etched until it is no longer at a ratio of <<20:1, as shown in FIG. 4D. As shown, the angles ρ and θ are not identical, and therefore the sides of the angled structures 112 of the optical grating layer 107 are not parallel to each other. Instead, the first sidewall angle ρ and the second sidewall angle θ diverge as the optical grating layer 107 is etched down to the top surface 144 of the etch stop layer 104.

[0036]

[0046] 4D , overetch into the etch stop layer 104 is minimized and the trench 114 adjacent the top surface 144 of the etch stop layer 104 is relatively flat / planar. In the illustrated example, the selectivity (S) value is lower (e.g., S=2) such that there is a greater difference between the angle θ of the one or more first sidewalls 141 and the angle ρ of the one or more second sidewalls 142.

[0037]

[0047] The relationship between the selectivity input angle ρ and the output angle θ is shown in graph 250 of FIG. 5. In an exemplary embodiment, increasing the selectivity makes the first sidewall angle ρ and the second sidewall angle θ more parallel. In a theoretical example, the selectivity is selected to be 50, thus providing parallel or nearly parallel sidewalls for each angled component. As shown, for S>10, the first sidewall angle ρ and the second sidewall angle θ become generally parallel.

[0038]

[0048] The embodiments of Figures 6A-6D show various optical grating elements having different selectivity values ​​(S). For example, S=2 for optical grating element 300A of Figure 6A, S=5 for optical grating element 300B of Figure 6B, S=10 for optical grating element 300C of Figure 6C, and S=20 for optical grating element 300D of Figure 6D. As the selectivity increases, the sidewalls of the angled elements become more parallel. As further shown, higher selectivity values ​​result in a hard mask 308 remaining on each angled structure of the optical grating layer 307.

[0039]

[0049] In another embodiment, as shown in FIG. 7A, the ion beam angular spread (BAS) and / or beam angle average impinging on the optical grating layer 407 of the optical grating element 400 disposed on the substrate 402 may be varied. For example, the directional reactive ion etch represented by the etching ions 430A may have a diverging beam spread, while the directional reactive ion etch represented by the etching ions 430B may have a converging beam spread. As shown in FIG. 7B, by varying the BAS to be either convergent or divergent, the first sidewall 441 and the second sidewall 442 of each fin 412 may be curved or concave. In some embodiments, the center portion 445 of each fin 412 is narrower (e.g., in the +-y direction) than the top portion 446 and bottom portion 447, respectively. By increasing the BAS, the curvature of each fin 412 may be increased. In other embodiments, excessively increasing the BAS and also selecting an overetch of the etch stop layer 404 may result in an excessively curved fin and / or a fin that is thinned along the bottom portion. Therefore, the BAS and overetch are optimized when selected together as part of a process recipe.

[0040]

[0050] According to further embodiments of the disclosure, fabrication of multiple optical gratings can be readily accomplished by performing variations of the processing of the optical grating layer described above. In some embodiments, multiple optical grating regions may be pre-patterned on one or more substrates, where one or more substrates are placed on a substrate platen 214 (FIGS. 2A-2B). In certain embodiments, a substrate can be fabricated having multiple distinct optical grating fields, where the orientation of the angled features in one optical grating field differs from another optical grating field. By way of background, a known AR eyepiece can be formed when multiple distinct optical gratings are placed on a transparent eyepiece to form a "microlens." A first optical grating may have angled structures oriented from the top to the bottom of the eyepiece, while a second optical grating may have angled structures oriented from the left to the right of the eyepiece.

[0041]

[0051] While the above embodiments have been mostly detailed in relation to forming an optical grating directly in the eyepiece, in other embodiments, the same grating structure as shown in, for example, Figures 1A, 1B, 5A, and / or 5B may be used to form a master. In other words, an optical grating component, or a similar grating component such as a Si wafer, with or without an etch stop layer and hard mask, may serve as a master to imprint a grating pattern in an optical grating layer on the eyepiece or to apply to the eyepiece. Notably, in embodiments in which an optical grating component serves as a master, the substrate, etch stop layer (if included), and optical grating layer need not be optically transparent.

[0042]

[0052] Additionally, while the above embodiments have focused on ribbon reactive ion beams to perform processing and angled etching, in various embodiments, the etching can be performed using a beam (e.g., a radical beam).

[0043]

[0053] Further, embodiments herein may be computer-implemented. For example, processing device 200 may include a computer processor that performs logical operations, computational tasks, control functions, and the like. In some embodiments, the computer processor may be a component of a processor. A computer processor may include one or more subsystems, components, modules, and / or other processors, and may include various logic components that are operable to latch data, advance logic states, synchronize computational and logical operations, and / or provide other timing functions using clock signals. In operation, the computer processor may receive signals transmitted over LANs and / or WANs (e.g., T1, T3, 56kb, X.25), broadband connections (ISDN, Frame Relay, ATM), wireless links (802.11, Bluetooth, etc.), and the like. In some embodiments, the signals may be encrypted, for example, using trusted key pair encryption. Various systems may transmit information using various communication paths (e.g., Ethernet or wireless networks, serial or parallel connections, USB, Firewire, Bluetooth, or other proprietary interfaces). (Firewire is a registered trademark of Apple Computer, Inc. and Bluetooth is a registered trademark of the Bluetooth Special Interest Group (SIG).)

[0044]

[0054] Generally, a computer processor executes computer program instructions or code stored in a memory unit and / or storage system. For example, execution of the computer program instructions may cause the processing device 200 to receive inputs (e.g., any of the process parameters described herein) and provide outputs from the computer processor. In some embodiments, the computer processor executes and operates process recipes to form the optical grating components 100, 300A-D, and 400.

[0045]

[0055] While executing the computer program code, the computer processor may read and / or write data from the memory unit and / or storage system. The storage system may include a VCR, a DVR, a RAID array, a USB hard drive, an optical disk recorder, a flash storage device, and / or any other data processing and storage elements for storing and / or processing data. Although not shown, the processing device 200 may further include an I / O interface for communicating with one or more hardware components of a computer infrastructure, thereby allowing a user to interact with the processing device 200 (e.g., a keyboard, a display, a camera, etc.).

[0046]

[0056] 8, a method 500 according to an embodiment of the present disclosure is described in more detail. Specifically, at block 502, a substrate is provided. In some embodiments, the substrate is silicon. In other embodiments, the substrate may be a transparent material, such as glass.

[0047]

[0057] In block 504, an optical grating layer is formed on the substrate. In some embodiments, the optical grating layer may comprise an optically transparent material, including but not limited to silicon oxide, silicon nitride, glass, or other materials. In some embodiments, the optical grating layer is formed on an etch stop layer. The etch stop layer may be an optically transparent material and may have a thickness of 10 nm to 100 nm.

[0048]

[0058] At block 506, a hard mask is formed on the optical grating layer. In some embodiments, the mask includes a linear pattern. The linear pattern may have linear mask elements that extend along a second direction, perpendicular to the first direction, or along a scanning direction. In other embodiments, the mask includes a non-linear pattern. For example, the masking pattern may include one or more curved elements.

[0049]

[0059] At block 508, an optical grating may be formed in the optical grating layer. In some embodiments, the optical grating includes a plurality of angled elements arranged at a non-zero angle with respect to a normal to the plane of the substrate, and the optical grating layer and the hard mask are etched to form an optical grating in the optical grating layer. The optical grating may include a plurality of angled elements arranged at a non-zero angle with respect to a normal to the plane of the substrate. The patterned hard mask etch results in a faster decrease in width than in height to form first and second sidewalls of the optical grating having different angles.

[0050]

[0060] In some embodiments, block 508 includes forming the optical grating by performing an angled reactive ion etch in the optical grating layer. The angled reactive ion etch is formed with a ribbon reactive ion beam, and the substrate is scanned along a scan direction relative to the ribbon reactive ion beam using a process recipe. In some embodiments, the ribbon reactive ion beam has a converging beam spread or a diverging beam spread.

[0051]

[0061] In some embodiments, the process recipe can be modified. For example, a higher selectivity value can result in a first difference between the first angle of the first sidewall and the second angle of the second sidewall. A lower selectivity value results in a second difference between the first angle of the first sidewall and the second angle of the second sidewall, the first difference being smaller than the second difference.

[0052]

[0062] The process recipe may include process parameters that have the effect of changing the shape or dimensions of the angled components. The process parameters may include one or more of the material of the optical grating layer, the chemistry of the ribbon reactive ion beam relative to the chemistry of the optical grating layer and the fabrication layer, and the ribbon reactive ion beam intensity. The process parameters may further include the relative pressures of the various gases used to form the ribbon reactive ion beam, the temperature for forming the ribbon reactive ion beam, the ribbon reactive ion beam angle, the ribbon reactive ion beam spread, and the presence of an etch stop layer.

[0053]

[0063] In other embodiments, block 508 includes forming a master optical grating on a wafer (e.g., a Si wafer) and then transferring the pattern to an optically transparent substrate for use. For example, a nanoimprint lithography (NIL) process is used to transfer the pattern from the Si wafer to the optical grating layer.

[0054]

[0064] In summary, the various embodiments described herein provide an approach for forming optical grating components, including eyepieces for AR and VR, or a master for forming optical gratings for AR and VR eyepieces. Fabrication can be achieved by applying angled ions directly onto the substrate and / or the mask used to transfer the pattern to the target substrate. The first technical advantage of the present embodiment includes post-processing optimization, since there are some shapes that are undesirable for subsequent processing (e.g., nanoimprint lithography (NIL)). The second technical advantage is the optimization of the shape and size of the optical grating, which leads to optical "bending" forces. The two-dimensional projection system according to the embodiments herein involves more complex, multiple, and distributed optics.

[0055]

[0065] The present disclosure should not be limited in scope by the specific embodiments described herein. Indeed, in addition to the embodiments described herein, various other embodiments of the present disclosure and modifications of the present disclosure will be apparent to those skilled in the art from the above description and the accompanying drawings. Thus, such other embodiments and modifications are intended to be included within the scope of the present disclosure. Furthermore, the present disclosure has been described herein in connection with specific implementations in specific environments for specific purposes. Those skilled in the art will recognize that the usefulness is not limited thereto, and the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Thus, the claims presented below should be construed in light of the full scope and spirit of the present disclosure as described herein.

Claims

1. 1. A method of forming an optical grating element, comprising: providing an etch stop layer over a substrate; providing an optical grating layer over the etch stop layer; providing a patterned hard mask over the optical grating layer; Etching the optical grating layer and the hard mask to form an optical grating in the optical grating layer. the optical grating comprises a plurality of angled elements arranged at a non-zero angle with respect to a normal to a plane of the substrate and a plurality of exposed regions of the etch stop layer interleaved with the angled elements, wherein the patterned hard mask reduces in width faster than in height to form the plurality of exposed regions of the etch stop layer and the optical grating having a pointed tip and first and second sidewalls with distinct angles.

2. The method of claim 1 , wherein forming the optical grating comprises etching into the optical grating layer.

3. The method of claim 1 , wherein the etching comprises an angled reactive ion etch.

4. 4. The method of claim 3, wherein the angled reactive ion etching is performed with a ribbon reactive ion beam, the substrate is scanned along a scan direction relative to the ribbon reactive ion beam using a process recipe, the ribbon reactive ion beam having a beam angle average value and a beam divergence, the beam divergence being one of converging or diverging.

5. The method of claim 4 , wherein the processing recipe includes a plurality of processing parameters that have the effect of changing a shape or size of the plurality of angled components.

6. 6. The method of claim 5, wherein the plurality of process parameters include one or more of: a material of the optical grating layer, a chemistry of the optical grating layer and the ribbon reactive ion beam relative to a hard mask formed on the optical grating layer, an etch stop layer formed below the optical grating layer, a ribbon reactive ion beam intensity, a relative pressure of various gases used to form the ribbon reactive ion beam, a temperature for forming the ribbon reactive ion beam, a ribbon reactive ion beam angle, and a ribbon reactive ion beam spread.

7. 10. The method of claim 1, wherein the etch removes the patterned hard mask before the optical grating layer is removed down to a top surface of an etch stop layer.

8. 1. A method of forming an optical grating element, comprising: providing an etch stop layer over a substrate; providing an optical grating layer over the etch stop layer; providing a patterned hard mask over the optical grating layer; Etching the optical grating layer and the hard mask to form an optical grating in the optical grating layer; the optical grating comprises a plurality of angled elements arranged at a non-zero angle with respect to a normal to a plane of the substrate and a plurality of exposed regions of the etch stop layer alternating with the angled elements, wherein the patterned hard mask reduces in width faster than in height to form the plurality of exposed regions of the etch stop layer and the plurality of angled elements having a pointed tip and first and second sidewalls with distinct angles.

9. The method of claim 8 , wherein forming the optical grating comprises etching into the optical grating layer using an angled reactive ion etch.

10. 10. The method of claim 9, wherein the angled reactive ion etch is performed with a ribbon reactive ion beam, the substrate is scanned along a scan direction relative to the ribbon reactive ion beam using a process recipe, the ribbon reactive ion beam having a beam angle average value and a beam divergence, the beam divergence being one of converging or diverging.

11. The method of claim 10 , wherein the process recipe includes a plurality of process parameters that have the effect of changing a shape or size of the plurality of angled components.

12. 12. The method of claim 11 , wherein the plurality of process parameters include one or more of: a material of the optical grating layer, a chemistry of the optical grating layer and the ribbon reactive ion beam relative to a hard mask formed on the optical grating layer, an etch stop layer formed below the optical grating layer, a ribbon reactive ion beam intensity, a relative pressure of various gases used to form the ribbon reactive ion beam, a temperature for forming the ribbon reactive ion beam, a ribbon reactive ion beam angle, and a ribbon reactive ion beam spread.

13. 9. The method of claim 8, wherein the etch removes the patterned hard mask before the optical grating layer is removed down to a top surface of an etch stop layer.

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