TW202522062A - Blazed grating formation by staircase etch - Google Patents

Abstract

Embodiments herein are generally directed to methods of forming waveguide structures with blazed gratings. The method includes depositing a photoresist layer on a patterned hardmask disposed over a device layer or a substrate, exposing the photoresist layer to produce a plurality of photoresist segments, etching the device layer or the substrate to produce at least one step, the at least one step forming a blazed grating, trimming the plurality of photoresist segments horizontally, and removing the plurality of photoresist segments and the patterned hardmask. The method may further include repeating steps to produce a second step and a third step of the blazed grating.

Description

Flare grating formation using step etching

Embodiments of the present disclosure generally relate to optical waveguides. More particularly, embodiments described herein provide techniques for forming a waveguide having a flared grating.

Virtual reality is generally considered to be a computer-generated simulated environment in which the user has an apparent physical presence. The virtual reality experience can be generated in 3D and viewed using a head-mounted display (HMD), such as glasses, or other wearable display devices that have near-eye display panels as lenses to display the virtual reality environment in place of the real environment.

However, augmented reality enables an experience in which the user can still see the surrounding environment through the display lenses of glasses or other HMD devices, and can also see images of virtual objects that are generated for display and appear as part of the environment. Augmented reality can include any type of input, such as audio and tactile input, as well as virtual images, graphics, and video that enhance or expand the user's experience of the environment. As an emerging technology, augmented reality faces many challenges and design constraints.

Blazed gratings are needed in AR waveguides to achieve high diffraction efficiency of the target order. However, blazed facets are difficult to fabricate using conventional patterning. Currently, there is no scalable industrial solution to form blazed gratings for AR waveguides.

Therefore, there is a need for improved systems and methods for forming glare grating structures.

Embodiments herein are generally directed to methods of forming optical component structures such as glare gratings.

In an embodiment, a method for forming an optical element structure is provided. The method includes: depositing a photoresist layer on a patterned hard mask disposed above an element layer or a substrate; exposing the photoresist layer to produce a plurality of photoresist segments; etching the element layer or the substrate to produce at least one step, the at least one step forming a flare grating; horizontally trimming the plurality of photoresist segments; and removing the plurality of photoresist segments and the patterned hard mask.

In another embodiment, a method of forming an optical device structure is provided. The method includes: depositing a photoresist layer on a patterned hard mask having a plurality of hard mask segments disposed above a device layer or a substrate; exposing the photoresist layer to produce a plurality of photoresist segments; and etching the device layer or the substrate to produce a first step of a flare grating. The method also includes: horizontally trimming the plurality of photoresist segments; and repeatedly etching the device layer or the substrate; and horizontally trimming the plurality of photoresist segments to produce a second step of the flare grating. The method may further include repeatedly etching the device layer and horizontally trimming the plurality of photoresist segments to produce a third step of the blaze grating, and removing the plurality of photoresist segments and the patterned hard mask.

In another embodiment, a method of forming an optical device structure is provided. The method includes: depositing a photoresist layer on a patterned hard mask disposed above a device layer or a substrate; patterning the photoresist layer to produce a plurality of photoresist segments; etching the device layer or the substrate to produce a first step of a flare grating with a first line width; and horizontally trimming the plurality of photoresist segments. The method also includes: repeatedly etching the device layer or the substrate and horizontally trimming the plurality of photoresist segments to produce a second step of the flare grating with a second line width; and removing the plurality of photoresist segments and the patterned hard mask. In one aspect, the second line width of the second stage is non-uniformly larger than the first line width of the first stage.

Embodiments herein are generally directed to methods of forming a waveguide structure having a blazed grating. The methods include exposing a device layer disposed over a substrate having a patterned hard mask and an offset patterned photoresist to an etchant.

FIG. 1A is a front view of the optical element 100. It should be understood that the optical element 100 described below is an exemplary optical element. In one embodiment that may be combined with other embodiments described herein, the optical element 100 is a waveguide combiner, such as an augmented reality waveguide combiner. In another embodiment that may be combined with other embodiments described herein, the optical element 100 is a flat optical element, such as a super-surface. The optical element 100 includes a plurality of element structures disposed in a substrate 101 (as shown in FIG. 1B) or on the substrate (as shown in FIG. 1C). As shown in FIG. 1C, the element structure is formed in an element layer 103 formed on the substrate 101. The element structure may be a nanostructure having a submicron size, such as a nano-size size, such as a critical size of less than 1 μm. The optical element 100 includes an input coupling region 102A, a waveguide region 102B, and an output coupling region 102C defined by a plurality of gratings 106 (as illustrated in FIGS. 1B and 1C ).

The input coupling region 102A receives an incident light beam (virtual image) with an intensity from the microdisplay. Each of the plurality of gratings 106 divides the incident beam into a plurality of modes. The zero-order mode (T0) beam is refracted back or lost in the optical element 100. The positive first-order mode (T1) beam passes through the optical element 100, undergoes total internal reflection (TIR) across the waveguide region 102B to reach the output coupling region 102C and is output for display. The negative first-order mode (T-1) beam propagates in the optical element 100 in the opposite direction to the T1 beam. In the diffraction order, only the T1 beam is output to the display via the output coupling region 102C, while other modes are lost due to different directivities. Therefore, it is crucial to increase the T1 beam intensity and reduce the intensity of other order beams to achieve higher element optical efficiency. One method for increasing the intensity of the T1 beam and reducing the intensity of other order beams is to control the shape of each of the plurality of gratings 106. The blaze shape of each of the plurality of gratings 106 provides improved optical efficiency.

FIG. 1B and FIG. 1C are schematic cross-sectional views of a plurality of blazed gratings 106 according to certain embodiments. In one embodiment that can be combined with other embodiments described herein, the plurality of blazed gratings 106 correspond to the input coupling region 102A of the optical element 100. The method 200 described herein forms a plurality of blazed gratings 106. A waveguide combiner according to one embodiment that can be combined with other embodiments described herein may include blazed gratings 106. Each of the blazed gratings 106 includes a blazed surface 108, a top surface 109, a sidewall 112, a depth h, and a line width d. The blazed surface 108 has a plurality of steps 110. In one embodiment that may be combined with other embodiments described herein, the blaze surface 108 includes at least 3 steps 110, such as greater than 16 steps 110, for example 32 steps 110. The blaze surface 108 has a blaze angle γ and a blaze line width d2. The blaze angle γ is the angle between the blaze surface 108 and a surface parallel to the substrate 101 and the angle between the surface normal of the substrate 101 and the facet normal f of the blaze surface 108. The depth h corresponds to the height of the sidewall 112, and the line width d corresponds to the distance between the sidewalls 112 of adjacent blaze gratings 106. The blaze line width d2 corresponds to the difference between the line width d and the width of the top surface 109 of each blaze grating 106.

In one embodiment that can be combined with other embodiments described herein, the blaze angles γ of two or more blaze gratings 106 are different. In another embodiment that can be combined with other embodiments described herein, the blaze angles γ of the two or more blaze gratings 106 are the same. In one embodiment that can be combined with other embodiments described herein, the depths h of two or more blaze gratings 106 are different. In another embodiment that can be combined with other embodiments described herein, the depths h of two or more blaze gratings 106 are the same. In one embodiment that can be combined with other embodiments described herein, the line widths d of two or more blaze gratings 106 are different. In another embodiment that can be combined with other embodiments described herein, the line widths d of one or more blaze gratings 106 are the same.

FIG2 is a flow chart of a method 200 for forming a plurality of blazed gratings 106 of an optical device structure 300 as shown in FIGS. 3A to 3I. In one embodiment, the optical device structure 300 corresponds to the input coupling region 102A of the optical device 100 and includes a plurality of blazed gratings etched in a substrate 302, the plurality of blazed gratings being similar to the blazed gratings 106 formed in the substrate 101 shown in FIG. 1B.

Substrate 302 may be any substrate used in the art and may be opaque or transparent to selected wavelengths of light depending on the use of substrate 302 as a substrate for a waveguide. Substrate selection may include substrates of any suitable material, including but not limited to amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, polymers, or combinations thereof. In some embodiments, the substrate 302 includes, but is not limited to, a silicon-containing material, a silicon and oxygen-containing compound, a germanium-containing material, an indium and phosphide-containing compound, a gallium and arsenic-containing compound, a gallium and nitrogen-containing compound, a carbon-containing material, a silicon and carbon-containing compound, a silicon, carbon and oxygen-containing compound, a silicon and nitrogen-containing compound, a silicon, oxygen and nitrogen-containing compound, a niobium and oxygen-containing compound, and a lithium, niobium and oxygen-containing compound, an aluminum and oxygen-containing compound, an indium, tin and oxygen-containing compound, a titanium and oxygen-containing compound, a lumen and oxygen-containing compound, a gadolinium and oxygen-containing compound, a zinc and oxygen-containing compound, a yttrium and oxygen-containing compound, a tungsten and oxygen-containing compound, a potassium and oxygen-containing compound, a phosphorus and oxygen-containing compound, a barium and oxygen-containing compound, a sodium and oxygen-containing compound, or a combination thereof. In other embodiments that may be combined with other embodiments described herein, the substrate 302 includes an oxide including one or more of a material containing gabbard, silicon, sodium, barium, potassium, tungsten, phosphorus, zinc, calcium, titanium, tantalum, niobium, lumber, zirconium, lithium, or yttrium. Exemplary materials of the substrate 302 include silicon (Si), silicon monoxide (SiO), silicon dioxide (SiO ₂ ), silicon carbide (SiC), fused silica, diamond, quartz germanium (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), sapphire, sapphire (Al ₂ O ₃ ), lithium niobate (LiNbO ₃ ), indium tin oxide (ITO), chromium oxide (La ₂ O ₃ ), gadolinium oxide (Gd ₂ O ₅ ), zinc oxide (ZnO), yttrium oxide (Y ₂ O ₃ ), tungsten oxide (WO ₃ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₃ ), sodium oxide (Na ₂ O), niobium oxide (Nb ₂ O ₅ ), barium oxide (BaO), potassium oxide (K ₂ O), phosphorus pentoxide (P ₂ O ₅ ), calcium oxide (CaO), or a combination thereof.

In another embodiment, the plurality of blazed gratings are etched in a device layer (not shown) formed above the substrate 302, similar to the blazed gratings 106 formed in the device layer 103 formed above the substrate 101 shown in FIG. 1C. In such embodiments, the device layer 103 and the substrate 101 comprise different materials. The device layer 103 comprises, but is not limited to, one or more oxides, carbides, or nitrides of silicon, aluminum, zirconium, tin, tantalum, zirconium, barium, titanium, tantalum, lithium, tantalum, cadmium, niobium, or combinations thereof. Exemplary materials for the device layer 103 include silicon carbide, silicon oxycarbide, titanium oxide, titanium dioxide, silicon oxide, silicon dioxide, vanadium oxide, aluminum oxide, aluminum-doped zinc oxide, indium tin oxide, tin oxide, zinc oxide, tantalum oxide, tantalum pentoxide, silicon nitride, titanium nitride, zirconium oxide, tantalum dioxide, and tantalum pentoxide. Zirconium, niobium oxide, cadmium stannate, silicon oxynitride, barium titanate, diamond-like carbon, niobium oxide, lithium niobate, silicon carbonitride, silver, cadmium selenide, mercury telluride, zinc selenide, silver indium gallium sulfide, silver indium sulfide, indium phosphide, gallium phosphide, lead sulfide, lead selenide, zinc sulfide, molybdenum sulfide, tungsten sulfide, or a combination thereof.

In an embodiment, before performing the method 200, a device layer 103 may be deposited on the substrate 101 to form the blazed grating 106 shown in FIG. 1C. Any suitable method for depositing the device layer 103 may be used. Examples of suitable thin film deposition methods include a physical vapor deposition (PVD) process (e.g., ion beam sputtering, magnetron sputtering, electron beam evaporation), a chemical vapor deposition (CVD) process, a plasma enhanced chemical vapor deposition (PECVD) process, an atomic layer deposition (ALD) process, an inkjet printing process, or a three-dimensional (3D) printing process.

As shown in FIG. 3A , prior to operation 201 , a hard mask 306 is disposed and patterned on a substrate 302 (or the device layer 103 of FIG. 1C (if present)). The patterned hard mask 306 includes a plurality of hard mask segments, such as a first hard mask segment 306a, a second hard mask segment 306b, and a third hard mask segment 306c that are separated from each other. The spacing (e.g., distance) between the segments of the patterned hard mask 306 will determine the maximum width of the step surface 108 of each glare grating structure produced. Portions of the substrate 302 (or the device layer 103 of FIG. 1C (if present)) are then exposed by the spacing between the segments of the patterned hard mask 306. FIG. 3B is a schematic cross-sectional view of a substrate 302 at operation 201. In operation 201, as shown in FIG. 3B, a photoresist layer 308 is deposited or otherwise disposed over the hard mask segments 306 and the exposed portions of the substrate 302 (or the device layer 103 of FIG. 1C, if present). The material of the photoresist layer 308 is selected based on the substrate 302 etch chemistry (in embodiments where the substrate 302 is etched to form a blazed grating structure as shown in FIG. 1B) or the device layer 103 etch chemistry (in embodiments where the device layer 103 is etched to form a blazed grating structure as shown in FIG. 1C).

In operation 202 and as shown in FIG. 3C , the photoresist layer 308 is patterned by a lithography process (such as photolithography or digital lithography) or by a laser ablation process to form a plurality of photoresist sections 310. In an embodiment, the plurality of photoresist sections 310 include a first photoresist section 310a, a second photoresist section 310b, and a third photoresist section 310c formed over the patterned hard mask 306 and the substrate 302 (or the device layer 103 of FIG. 1C if present). Although only three photoresist segments 310a to 310c and three hard mask segments 306a to 306c are illustrated, the entire photoresist layer 308 and hard mask 306 can be etched so that a desired number of glare gratings 106 are formed in the substrate 302 (or the device layer 103 of FIG. 1C if present), depending on the intended design for the optical device structure 300.

The plurality of photoresist sections 310 are offset from the hard mask section 306 so that the photoresist section 310 directly contacts and covers a portion of the substrate 302 (or the device layer 103 of FIG. 1C if present), while exposing a portion of each hard mask section 306a, 306b, and 306c. Further, the photoresist section 310 does not extend to a subsequent hard mask section (e.g., from the first hard mask section 306a to the second hard mask section 306b). Instead, each photoresist section 310 ends at a distance from an adjacent subsequent hard mask section 306.

At operation 203, a plasma etchant 304 contacts the substrate 302, as shown in FIG. 3D. The substrate 302 is exposed to the plasma etchant 304 (such as free radicals and ion beams) in contact with the substrate 302. Exposing the substrate 302 (or the device layer 103 of FIG. 1C, if present) to the plasma etchant 304 may include an etching process such as ion etching and reactive ion etching (RIE). The plasma etchant 304 etches a first depth 320 of a plurality of depths 324 (as shown in FIGS. 3F to 3I ) of the at least one step 330 into portions of the substrate 302 (or the device layer 103 of FIG. 1C , if present) exposed between the patterned hard mask sections 306 a to 306 c and the plurality of photoresist sections 310. After operation 203, in addition to the first depth 320, the at least one step 330 also includes an initial leading sidewall portion 342 of the leading sidewall 344 (as shown in FIG. 3D ), a trailing sidewall 352, and a first line width 362 from the initial leading sidewall portion 342 to the trailing sidewall 352. The first line width 362 is controlled by a distance 332 between a leading edge plane 334 defined by a first side 312 of each photoresist segment 310 and a trailing edge plane 336 defined by an exposed side 314 in each hard mask segment 306 that contacts the substrate 302 (or the device layer 103 of FIG. 1C if present). The distance 332 corresponds to the first line width 362 because the plasma etchant 304 does not contact the substrate 302 (or the device layer 103 of FIG. 1C if present) outside the distance 332.

At operation 204, the photoresist sections 310a, 310b, and 310c are trimmed by an isotropic ion etching process that recesses the photoresist sections vertically and horizontally. This operation increases the distance from the first line width 362 (defined by the initial leading sidewall portion 342 to the trailing sidewall portion 352 shown in FIG. 3D) to the distance 332 between the leading sidewall 344 and the trailing edge plane 334 shown in FIG. 3F.

At optional operation 205, operations 203 and 204 may be repeated to etch at least one second depth 322 of the plurality of depths 324 of at least one step 330 into the substrate 302 (or the device layer 103 of FIG. 1C if present). As shown in FIG. 3E, each photoresist section 310 is trimmed to reduce the width of each photoresist section 310 so that the first side 312 of each photoresist section 310 is offset along the substrate 302, thereby increasing the distance 332.

As shown in FIG. 3F , in addition to the second depth 322, the step 330 includes a second leading sidewall portion 346 and a second line width 364 from the second leading sidewall portion 346 to the trailing sidewall portion 352. The second line width 364 is controlled by the distance 332 between the leading edge plane 334 and the trailing edge plane 336 increased by the optional operation 204. Since the distance 332 increases with each iteration of the operation 204, the second line width 364 is longer than the first line width 362. The distance 332 corresponds to the second line width 364 because the plasma etchant 304 does not contact the substrate 302 (or the device layer 103 of FIG. 1C if present) outside the distance 332. As shown in FIG. 3E , in various embodiments, the increase in the distance 332 between the photoresist segments 310 after trimming is uniform and equal to twice the first line width 362, for example, the second line width 364 is twice the length of the first line width 362, so that each step in the at least one step 330 is symmetrical. Alternatively, the second line width 364 may be increased non-uniformly beyond the first line width 362, for example, non-uniformly greater than the first line width. For example, the second line width 364 may be increased by 1.5 times the first line width 362, thereby producing an asymmetric step grating or a flare grating. Similarly, subsequent line widths may be increased symmetrically or asymmetrically.

As shown in FIGS. 3G and 3H , optional operation 205 includes repeating optional operation 204 after etching each second depth 322 of at least one step 330. For example, at optional operation 204, the photoresist section 310 is trimmed to further increase the distance 332. At optional operation 203, a third depth 326 of the plurality of depths 324 is created, as well as a third leading sidewall portion 348 and a third line width 366 from the third leading sidewall portion 348 to the trailing sidewall 352. The third line width 366 is controlled by the distance between the leading edge plane 334 and the trailing edge plane 336, and is increased by subsequent optional operation 202. The distance 332 corresponds to the third line width 366 because the plasma etchant 304 does not contact the substrate 302 (or the device layer 103 of FIG. 1C if present) beyond the distance 332 .

FIG. 3F is a schematic cross-sectional view of the optical element structure 300. Operations 203 and 204 are repeated until the optical element structure 300 is formed, at which time at least one step 330 has a plurality of depths 324, including a first depth 320 and at least one second depth 322 corresponding to the step depth. Reducing the first depth 320 and each second depth 322 will result in a smoother leading sidewall 344 of the at least one step 330.

FIG. 3I is a schematic cross-sectional view of the optical element structure 300 after operation 206 of the method 200. In one embodiment, the patterned hard mask 306 and the at least one photoresist layer 308 include non-transparent materials, which are removed at operation 206 after forming the optical element structure 300, as shown in FIG. 3I. For example, the patterned hard mask 306 and the at least one photoresist layer 308 include reflective materials, such as Cr or silver (Ag). In another embodiment, the patterned hard mask 306 and the photoresist layer 308 include transparent materials, so that the patterned hard mask 306 and the at least one photoresist layer 308 remain after forming the optical element structure 300.

After operation 206, at least one step 330 is performed to retain and form the structure of the blazed grating 106. Although only three steps are illustrated in FIG. 3I, the optional operation 204 may be repeated to produce a desired number of steps, such as 5, such as 10, such as 25. As the number of steps increases, it is noted that the line width of each step (e.g., 362, 364) may be reduced, thereby producing a smoother leading sidewall portion (e.g., 342, 344) or blazed surface 108 for each blazed grating 106.

An advantage of the present disclosure is that a scalable method for forming a blazed grating for an AR waveguide using standard lithography and etching processes is provided. For example, the method 200 can enable forming a plurality of blazed gratings 106 by etching a plurality of step steps to form a blazed surface 108 of each blazed grating 106, which in turn each approximates a continuous blazed profile. Blazed gratings are often required in AR waveguides to improve diffraction efficiency.

When introducing elements of the present disclosure or exemplary aspects or embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements.

The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

The term "coupled" is used herein to refer to direct or indirect coupling between two objects. For example, if object A physically touches object B and object B touches object C, then objects A and C may still be considered coupled to each other—even if objects A and C are not directly physically touching each other. For example, a first object may be coupled to a second object even if the first object has never been in direct physical contact with the second object.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope of the present disclosure, and the scope of the present disclosure is determined by the appended claims.

100: optical element 101: substrate 102A: input coupling region 102B: waveguide region 102C: output coupling region 103: element layer 106: grating 108: surface 109: top surface 110: step 112: sidewall 200: method 201: operation 202: operation 203: operation 204: operation 205: operation 206: operation 300: optical element structure 302: substrate 304: plasma etchant 306: hard mask 306a-306c: hard mask segment 308: photoresist layer 310: photoresist segment 310a-310c: photoresist section 312: first side 314: side 320: first depth 322: second depth 324: depth 326: third depth 330: step 332: distance 334: edge plane 336: edge plane 342: initial leading sidewall portion 344: leading sidewall 346: second leading sidewall portion 348: third leading sidewall portion 352: sidewall 362: first line width 364: second line width 366: third line width

In order to understand the above features of the present disclosure in detail, the present disclosure briefly summarized above will be described in more detail with reference to the embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings illustrate only exemplary embodiments of the present disclosure and therefore should not be considered as limiting the scope thereof, and the present disclosure may allow other equally effective embodiments.

FIG. 1A is a perspective front view of an optical element according to certain embodiments.

1B and 1C are schematic cross-sectional views of multiple component structures according to certain embodiments.

FIG. 2 is a flow chart of a method for forming an optical element structure according to certain embodiments.

3A to 3I are schematic cross-sectional views of a waveguide structure undergoing a method for forming the waveguide structure of FIG. 2 according to certain embodiments.

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

200:Methods

201: Operation

202: Operation

203: Operation

204: Operation

205: Operation

206: Operation

Claims (20)

A method for forming an optical element structure comprises the following steps: Depositing a photoresist layer on a patterned hard mask having a plurality of hard mask segments disposed above a device layer or a substrate; Patterning the photoresist layer to produce a plurality of photoresist segments; Etching the device layer or the substrate to produce at least one step, the at least one step forming a flare grating; Horizontally trimming the plurality of photoresist segments; and Removing the plurality of photoresist segments and the patterned hard mask. The method as described in claim 1 further comprises the following steps: Before removing the plurality of photoresist segments and the patterned hard mask, repeatedly etching the device layer or the substrate and horizontally trimming the plurality of photoresist segments to produce a second stage of the flare grating. The method as described in claim 2 further comprises the following steps: Before removing the plurality of photoresist segments and the patterned hard mask but after generating a second stage of the flare grating, repeatedly etching the device layer or the substrate and horizontally trimming the plurality of photoresist segments to generate a third stage of the flare grating. A method as described in claim 1, wherein the plurality of photoresist segments are offset from the plurality of hard mask segments of the patterned hard mask so that a portion of each of the plurality of photoresist segments directly contacts a portion of the device layer or the substrate. A method as described in claim 1, wherein the at least one step includes a first line width, the first line width being controlled by a distance between a leading edge plane defined by a first side of a photoresist segment among the plurality of photoresist segments and a trailing edge plane defined by an exposed side of a hard mask segment among the plurality of hard mask segments. A method as described in claim 5, wherein the at least one step further includes a second step, the second step including a second line width, the second line width being controlled by a distance between a front edge plane and a rear edge plane defined by the first side of each of the plurality of photoresist segments after a second trimming of the plurality of photoresists, the second line width being longer than the first line width. The method as described in claim 1, wherein the step of etching the device layer or the substrate includes the following step: using reactive ion etching. The method of claim 1, wherein the at least one step comprises a first depth into the device layer or the substrate. A method as described in claim 2, wherein the at least one step includes a first depth into the device layer or the substrate, and the second step includes a second depth into the device layer or the substrate, the first depth being greater than the second depth. A method as described in claim 3, wherein the at least one step includes a first depth into the component layer or the substrate, the second step includes a second depth into the component layer or the substrate, and the third step includes a third depth into the component layer or the substrate, the first depth is greater than the second depth and the second depth is greater than the third depth. A method for forming an optical element structure, comprising the steps of: depositing a photoresist layer on a patterned hard mask having a plurality of hard mask segments disposed above a device layer or a substrate; patterning the photoresist layer to produce a plurality of photoresist segments; etching the device layer or the substrate to produce a first step of a flare grating; horizontally trimming the plurality of photoresist segments; repeatedly etching the device layer or the substrate and horizontally trimming the plurality of photoresist segments to produce a second step of the flare grating; repeatedly etching the device layer or the substrate and horizontally trimming the plurality of photoresist segments to produce a third step of the flare grating; and The plurality of photoresist segments and the patterned hard mask are removed. A method as described in claim 11, wherein the plurality of photoresist segments are offset from the plurality of hard mask segments of the patterned hard mask so that a portion of each of the plurality of photoresist segments directly contacts a portion of the device layer or the substrate. A method as described in claim 11, wherein the first stage includes a first line width, which is controlled by a distance between a leading edge plane defined by a first side of a photoresist segment among the plurality of photoresist segments and a trailing edge plane defined by an exposed side of a hard mask segment among the plurality of hard mask segments. A method as described in claim 13, wherein the second stage includes a second line width, the second line width is controlled by a distance between a leading edge plane defined by the first side of a photoresist segment among the plurality of photoresist segments and the trailing edge plane, the second line width being greater than the first line width. A method as described in claim 14, wherein the third stage includes a third line width, the third line width is controlled by a distance between a leading edge plane and the trailing edge plane defined by the first side of a photoresist segment among the plurality of photoresist segments, and the third line width is greater than the second line width. A method for forming an optical element structure comprises the following steps: Depositing a photoresist layer on a patterned hard mask disposed above a device layer or a substrate; Patterning the photoresist layer to produce a plurality of photoresist segments; Etching the device layer or the substrate to produce a first step of a flare grating with a first line width; Trimming the plurality of photoresist segments horizontally; Repeatedly etching the device layer or the substrate and trimming the plurality of photoresist segments horizontally to produce a second step of the flare grating with a second line width, the second line width being non-uniformly larger than the first line width; and Removing the plurality of photoresist segments and the patterned hard mask. A method as described in claim 16, wherein the plurality of photoresist segments are offset from the plurality of hard mask segments of the patterned hard mask so that a portion of each of the plurality of photoresist segments directly contacts a portion of the device layer or the substrate. A method as described in claim 16, wherein the first step includes a first depth into the device layer or the substrate, and the second step includes a second depth into the device layer or the substrate, the first depth is greater than the second depth. The method as described in claim 16 further includes the following steps: repeatedly etching the device layer or the substrate and horizontally trimming the multiple photoresist segments to produce a third step of the flare grating with a third line width, and the third line width is non-uniformly larger than the second line width. A method as described in claim 19, wherein the first step includes a first depth into the component layer or the substrate, the second step includes a second depth into the component layer or the substrate, and the third step includes a third depth into the component layer or the substrate, the first depth is greater than the second depth and the second depth is greater than the third depth.