NZ792251A - Microlithographic fabrication of structures - Google Patents

Abstract

Disclosed herein is an optical device. The optical device comprises a substrate. The optical device also comprises a diffraction pattern on the substrate. The diffraction pattern comprises a plurality of asymmetric structures extending from a common surface of the substrate. Each structure of the plurality of asymmetric structures has a first side surface and a second side surface opposite the first side surface, and a profile of the first side surface is asymmetric with respect to a profile of the second side surface. At least one asymmetric structure of the plurality of asymmetric structures has an asymmetric chair profile. The first side surface of the at least one asymmetric structure has a linear profile. The second side surface of the at least one asymmetric structure comprises two or more portions. At least one of the two or more portions of the second side surface is sloping with respect to a surface of the substrate and angled with respect at least one other of the two or more portions of the second side surface. urality of asymmetric structures has a first side surface and a second side surface opposite the first side surface, and a profile of the first side surface is asymmetric with respect to a profile of the second side surface. At least one asymmetric structure of the plurality of asymmetric structures has an asymmetric chair profile. The first side surface of the at least one asymmetric structure has a linear profile. The second side surface of the at least one asymmetric structure comprises two or more portions. At least one of the two or more portions of the second side surface is sloping with respect to a surface of the substrate and angled with respect at least one other of the two or more portions of the second side surface.

Description

Atty Docket No.: 40589-0029WO1 MICROLITHOGRAPHIC FABRICATION OF STRUCTURES CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of the filing date of U.S. Provisional Application No. 62/397,604, filed on September 21, 2016. The contents of U.S.

Application No. 62/397,604 are incorporated herein by reference in their entirety.

TECHNICAL FIELD OF THE INVENTION This invention relates to micro- and nano- structures having d geometries, and to ithographic methods of fabricating such structures.

BACKGROUND OF THE INVENTION abrication includes the fabrication of very small structures that have features on the order of 100 nanometers or smaller. One application in which nanofabrication has had a sizeable impact is in the processing of integrated circuits. The semiconductor processing industry continues to strive for larger production yields while sing the circuits per unit area formed on a substrate, therefore abrication becomes increasingly important. Nano-fabrication provides greater process control while allowing continued reduction of the minimum feature dimensions of the structures formed. Other areas of development in which nano-fabrication has been employed e biotechnology, optical technology, mechanical systems, and the like.

Nano-fabrication can e sing of substrates to form various shaped micro- and nano- structures on or in the substrate. One example process for forming such structures is imprint lithography.

SUMMARY OF THE INVENTION This specification relates to forming micro- and nano- structures that have asymmetric profiles. tric structures may, for example, be useful in fabricating more efficient diffraction ns for optical waveguides. Implementations of the Atty Docket No.: 0029WO1 present disclosure include a method for fabricating asymmetric structures by selectively ng a g material to a substrate and etching portions of the substrate that are not covered by the masking material. For example, the masking material can be applied to regularly shaped discrete structures in a manner such that the subsequent etching sculpts the structures into an tric shape.

In general, innovative aspects of the subject matter described in this specification can be embodied in s that e the actions of forming a plurality of discrete structures ing from a common surface on a substrate. Applying a masking material over the structures under conditions that cause the masking material to trically cover the structures such that at least a portion of one side of each structure is free of the masking material. Etching an area of the structures that is not covered by the g material. And, stripping the g material from the structures. This and other implementations can each optionally include one or more of the following features.

In some implementations, the conditions that cause the masking material to asymmetrically cover the structures comprise inclining the substrate at a non-normal angle to a deposition direction from which the g material is applied by a deposition system.

In some implementations, the plurality of structures include a first region of structures and second region of ures. Applying the masking material to the structures asymmetrically can include masking the second region of structures while applying the masking material to the first region of structures. In some implementations, applying the masking material to the structures asymmetrically can include masking the first region of structures while applying the masking material to the second region of structures.

Atty Docket No.: 40589-0029WO1 In some implementations, etching an area of the ures comprises performing one of a wet etch process, a dry etch process, or an ion beam etching process.

In some implementations, the portion of one side of each structure that is free of the masking material is a first portion, and the method es applying a metal catalyst layer for metal assisted chemical etching (MACE) over the structures under second conditions that cause the metal catalyst layer to asymmetrically cover the structures such that at least a second portion of one side of each structure is free of the metal catalyst layer. In some implementations, the second portion is different from the first portion. In some entations, the conditions that cause the g material to asymmetrically cover the structures se inclining the substrate at a first mal angle to an direction from which the masking material is applied by a deposition system, and the second ions that cause the metal catalyst layer to asymmetrically cover the structures comprise inclining the substrate at a second rmal angle to an direction from which the metal catalyst layer is applied by the deposition system.

The second non-normal angle can be ent from the first rmal angle.

In some implementations, the structures are etched after stripping the masking material from the substrate.

In some implementations, the structures have a square profile, rectangular profile, trapezoidal profile, or a triangular profile before the step of etching the area of the structures.

In some implementations, the masking material includes one of: Cr, Ti, SiO2, Al2O3, ZrO2, Ag, Pt, or Au. In some implementations, the structures include one of: Si, SiO2, a polymer material, or an organic-inorganic hybrid material. In some implementations, the structures are nano-structures. In some implementations, the structures are micro-structures.

Atty Docket No.: 40589-0029WO1 Another l aspect can be embodied in a substrate that includes a plurality of ures on the substrate, each of the structures having a first side surface and a second side surface, opposite the first side surface, and where a profile of the first side surface is asymmetric with respect to a profile of the second side e. This and other implementations can each optionally include one or more of the following features.

In some entations, the structures include one of: Si, SiO2, a polymer material, or an organic-inorganic hybrid material. In some entations, the structures are nano-structures. In some implementations, the structures are microstructures.

In some implementations, the plurality of structures include a plurality of first structures having a first asymmetric profile and a plurality of second structures having a second asymmetric profile that is different from the first asymmetric profile.

In some implementations, the substrate is included in a l device. In some implementations, the optical device is an optical wave guide. In some entations, the optical device is a pair of augmented reality glasses. In some implementations, the plurality of structures form a ction pattern.

Particular implementations of the subject matter described in this specification can be implemented so as to realize one or more of the following advantages. entations of the present disclosure may improve the fabrication of micro- and nano- patterns of varying profile structures for large patterns of structures. Implementations may permit the fabrication of structures that have varying profiles over ent regions of a ate (e.g., an Si wafer). Implementations may permit the fabrication of more efficient wave (e.g., optical) diffraction patterns. Implementations may permit the manufacture of mechanically stable micro/nano-structures whit a high aspect ratio.

Atty Docket No.: 40589-0029WO1 [0017A] In another aspect there is provided an optical device comprising: a substrate; and a diffraction pattern on the substrate, the diffraction pattern comprising a plurality of tric structures extending from a common surface of the substrate, wherein each structure of the plurality of asymmetric structures has a first side e and a second side surface opposite the first side surface, and a profile of the first side surface is asymmetric with respect to a profile of the second side surface, wherein: at least one tric structure of the plurality of asymmetric structures has an asymmetric chair profile, the first side surface of the at least one asymmetric ure has a linear profile, the second side surface of the at least one asymmetric structure comprises two or more portions, and at least one of the two or more portions of the second side surface is sloping with respect to a surface of the substrate and angled with respect at least one other of the two or more portions of the second side surface. [0017B] In another aspect there is provided an optical device sing: a substrate; and a diffraction pattern on the substrate, the diffraction pattern comprising a plurality of asymmetric structures extending from a common surface of the substrate, n each structure of the plurality of asymmetric structures has a first side surface and a second side surface opposite the first side surface, and a profile of the first side surface is asymmetric with respect to a profile of the second side surface, wherein: at least one tric structure of the plurality of asymmetric structures has an asymmetric chair profile, the first side e of the at least one tric structure has a linear profile, the second side surface of the at least one asymmetric structure comprises two or more portions, and at least one of the two or more portions of the second side surface is sloping with respect to a e of the substrate and angled with respect at least one other of the two or more portions of the second side surface, and wherein the plurality of asymmetric structures are formed by a process sing: ng a metal catalyst layer over the ity of discrete structures under first conditions that cause the metal catalyst layer to asymmetrically cover the plurality of discrete ures such that at least a first portion of a first side of each structure of the plurality of discrete structures is free of the metal catalyst layer; after applying the metal catalyst layer, applying a Atty Docket No.: 40589-0029WO1 masking material over the plurality of discrete structures under second conditions that cause the masking material to asymmetrically cover the plurality of te structures such that at least a second portion of a second side of each structure is free of the masking material, wherein the masking material comprises one of SiO2, Al2O3, or ZrO2; etching a first area of the plurality of discrete ures that is not covered by the masking material; stripping the masking material from the plurality of discrete ures; and wet etching a second area of the plurality of structures with metal assisted chemical g to yield the asymmetric structures. [0017C] In another aspect there is provided an optical device comprising: a substrate; and a diffraction pattern on the substrate, the diffraction pattern comprising a plurality of asymmetric ures extending from a common surface of the substrate, wherein each structure of the plurality of asymmetric structures has a first side surface and a second side surface opposite the first side surface, and a profile of the first side surface is asymmetric with respect to a profile of the second side surface, wherein the first side surface and the second side surface are each sloping with t to a surface of the substrate, wherein the plurality of asymmetric structures include a ity of first asymmetric structures having a first asymmetric e and a plurality of second asymmetric structures having a second asymmetric profile that is different from the first asymmetric profile.

As used herein, the terms ,” -structure,” and “micro-feature” represent structures or features of a structure that have at least one ion that is less than or equal to 50 micrometers.

As used herein, the terms ” “nano-structure,” and “nano-feature” represent structures or features of a structure that have at least one dimension that is less than or equal to 500 nanometers.

Atty Docket No.: 40589-0029WO1 The details of one or more embodiments of the subject matter described in this ication are set forth in the anying drawings and the description below.

Other potential features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

DESCRIPTION OF DRAWINGS illustrates a simplified side view of a lithographic system. illustrates a simplified side view of a substrate having a patterned layer oned thereon.

FIGS. 3A-3C illustrate simplified side views of ates having example asymmetric structures ned thereon. illustrates an example process for fabricating tric ures in accordance with implementations of the present sure. illustrates a second example process for fabricating asymmetric structures in accordance with implementations of the present disclosure. illustrates a third example process for fabricating asymmetric structures in accordance with implementations of the present disclosure.

FIGS. 7A-7C illustrates an example process for asymmetrically applying a masking material to ures on a substrate in accordance with implementations of the present disclosure. shows a flowchart of an example method for fabricating asymmetric structures in accordance with implementations of the present disclosure.

Atty Docket No.: 40589-0029WO1 FIGS. 9A-9B show example devices in which asymmetric structures and be used.

DETAILED DESCRIPTION s examples of fabricating micro- and nano- structures that have asymmetric es are described below. Asymmetric structures may, for example, be useful in fabricating more efficient diffraction gratings for optical waveguides. Generally, these examples include selectively applying a masking material to a substrate and etching ns of the substrate that are not covered by the masking material. For example, the masking material can be applied to regularly-shaped discrete ures in a manner such that the subsequent etching sculpts the structures into an asymmetric shape. illustrates an imprint lithography system 100 that forms a relief pattern on a substrate 102. The substrate 102 may be coupled to a substrate chuck 104. In some examples, the ate chuck 104 can include a vacuum chuck, a pin-type chuck, a groove-type chuck, an electromagnetic chuck, and/or the like. In some examples, the ate 102 and the ate chuck 104 may be further positioned on an air bearing 106. The air bearing 106 provides motion about the x-, y-, and/or z-axes.

In some examples, the substrate 102 and the substrate chuck 104 are positioned on a stage. The air bearing 106, the substrate 102, and the substrate chuck 104 may also be positioned on a base 108. In some examples, a robotic system 110 positions the substrate 102 on the substrate chuck 104.

The substrate 102 can include a planar surface 111 positioned opposite the substrate chuck 104. In some examples, the substrate 102 can be ated with a thickness that is substantially uniform (constant) across the substrate 102.

The t lithography system 100 further includes an imprint raphy flexible template 112 that is coupled to one or more rollers 114, depending on design Atty Docket No.: 40589-0029WO1 considerations. The rollers 114 provide movement of a least a portion of the flexible template 112. Such movement may selectively provide different portions of the le template 112 in superimposition with the substrate 102. In some examples, the flexible template 112 includes a patterning surface that includes a plurality of structures, e.g., spaced-apart recesses and protrusions. However, in some examples, other configurations of structures are possible. The patterning surface may define any original pattern that forms the basis of a pattern to be formed on substrate 102. In some examples, the flexible template 112 may be coupled to a template chuck, e.g., a vacuum chuck, a pin-type chuck, a groove-type chuck, an electromagnetic chuck, and/or the like.

The imprint lithography system 100 may further se a fluid dispense system 120. The fluid dispense system 120 may be used to deposit a polymerizable material on the substrate 102. The polymerizable material may be positioned upon the ate 102 using techniques such as drop dispense, spin-coating, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), thin film deposition, thick film deposition, and/or the like. In some examples, the polymerizable material is positioned upon the substrate 102 as a plurality of ts.

Referring to Figs. 1 and 2, the imprint lithography system 100 may further comprise an energy source 122 coupled to direct energy towards the substrate 102. In some examples, the rollers 114 and the air g 106 are ured to on a desired portion of the flexible template 112 and the substrate 102 in a d positioning. The imprint lithography system 100 may be regulated by a processor in communication with the air bearing 106, the rollers 114, the fluid dispense system 120, and/or the energy source 122, and may operate on a computer readable program stored in a .

In some examples, the rollers 114, the air bearing 106, or both, vary a distance between the flexible te 112 and the substrate 102 to define a desired Atty Docket No.: 40589-0029WO1 volume therebetween that is filled by the polymerizable material. For example, the flexible template 112 contacts the polymerizable material. After the desired volume is filled by the polymerizable al, the energy source 122 produces energy, e.g., broadband ultraviolet radiation, causing the polymerizable al to solidify and/or cross-link conforming to shape of a surface of the ate 102 and a portion of the patterning surface of the flexible template 112, defining a patterned layer 150 on the substrate 102. In some examples, the patterned layer 150 may comprise a residual layer 152 and a plurality of structures shown as protrusions 154 and recessions 156.

FIGS. 3A-3C illustrate simplified side views of substrates 102 having patterned layer 150 with example asymmetric structures 300, 320, 340 patterned n. More ically, FIGS. 3A and 3B illustrate example structures 300, 320 that have a “chair-like” asymmetric profile and illustrates example structures 340 have an asymmetric triangular profile. The structures 300, 320, 340 each include a first side surface 302 and a second side surface 304. As shown, the second side surface 304 of each structure 300, 320, 340 is fabricated to be asymmetric to the respective first side surface 302.

The patterned layer 150 and structures 300, 320, 340 can be fabricated using materials ing, but not limited to, Si, SiO2, polymer materials, or organic-inorganic hybrid materials. An example, organic-inorganic hybrid material is a film or patterned layer composed of 8-tetramethylcyclotetrasiloxane d to Ar and oxygen based plasma under atmospheric or low pressure ions which forms a carbon r layer with methyl groups and silicon oxide. Another example, organic-inorganic hybrid material is lorodisilane which can be used to deposit silicon nitride on a substrate. In another example, lorodisilane can be used with Ar/O2 plasma to deposit silicon oxy-nitride to form a clear film of high index (n<1.7). These layers can be deposited and etched or deposited directly over relief structures. In addition, the structures 300, 320, 340 can be, for example, micro- or nano-structures.

Atty Docket No.: 40589-0029WO1 In some implementations, a ity of different types of asymmetric structures 300, 320, 340 are included on a single substrate. For example, substrate 102 can include a patterned layer 150 that is fabricated to e a structures 300 in a first region, structures 320 in a second , and structures 340 in a third region.

In some implementations, the asymmetrically profiled structures such as ures 300, 320, 340 are more mechanically stable while still providing a high aspect ratio geometry than some ric structures such as tall and narrow rectangular structures. For example, a high aspect ratio profile is desirable for fabricating a glancing angle deposition (GLAD) based imprints for wire grid polarizers over rigid or plastic ates. However, symmetric structures that have a high aspect ratio (e.g., as shown in may be less ically stable, whereas, mechanical stability can ed in structures that use an asymmetric profile. Furthermore, a greater volume of metal 310 (e.g., Al) can be asymmetrically deposited on a stable asymmetric profile (e.g., as shown in ) than on a less stable symmetric structure. In some examples, the metal 310 can also be packed higher vertically when deposited on an asymmetric structure than on symmetric structures. illustrates an example process 400 for ating asymmetric structures in accordance with implementations of the present disclosure. At step (402), a plurality of discrete structures 420 are formed on a ate 102. The structures 420 can be formed by, for example, imprint lithography, photo lithography and etching, or other appropriate fabrication techniques. For example, the structures 420 can be formed using an imprint lithography system 100, as described above. The structures 420 have a generally symmetric profile. In other words, the shape of one side 422a of each ure 420 is substantially the same as the shape of the opposite side 422b of each ure 420 forming a left-right symmetry. The starting profile of the structures 420 can include any generally symmetric shape including, but not limited to, a square profile, a rectangular profile, a trapezoidal profile, or a triangular profile. Additionally, the structures 420 can be micro- or nano-structures.

Atty Docket No.: 40589-0029WO1 At step (404), a masking material 424 is applied to the structures 420. The masking material 424 is applied under conditions that cause the masking material to asymmetrically cover the structures 420. For example, as shown, the masking material 424 completely covers side 422b of the structures 420, but does not cover side 422a of the structures 420. However, the masking material 424 need not be applied strictly as shown in The masking material 424 can be applied to cover the structures 420 in any desired asymmetric pattern. For e, side 422b may be only partially covered by the g material 424, but not completely covered. Side 422a may be partially covered by the masking material 424. For example, a portion of both sides 422a and 422b may be covered by the masking material 424. However, to maintain the asymmetric ation of the g material 424 to the structures 420, the portion of side 422a that is covered by the masking material 424 may be smaller than the portion of side 422b that is covered by the masking material 424.

The masking material 424 can be applied using deposition processes including, but not limited to, chemical vapor deposition (CVD) and physical vapor deposition (PVD). Example conditions for asymmetrically applying the masking material 424 are described in more detail below in reference to FIGS. 7A-7C. Further, the masking material 424 can e one or of the following materials: Cr, Ti, SiO2, Al2O3, ZrO2, Ag, Pt, or Au.

At step (406), the structures 420 are etched. Specifically, in the example shown, the patterned layer 150 is etched to modify the overall shape of the structures 420, thereby, producing an tric profile in the ures 420. For example, the portions of the structures 420 (and patterned layer 150) that are not covered by the masking material 424 are etched to form recessions 426. The structures 420 can be etched using g processes including, but not limited to, a wet etch s, a plasma etching process, a dry etch s, or an ion beam etching/milling process.

Atty Docket No.: 40589-0029WO1 At step (408), the masking material 424 is removed. For example, the g al 424 can be stripped from the structures 420 and patterned layer 150 using a plasma or chemical stripping process. As shown, removing the masking al reveals the asymmetric profile of the structures 420a produced by the asymmetric application of the masking al 424 and the subsequent etching.

In some implementations, at optional step (410), the asymmetric structures 420a are etched a second time to further alter their shape. For example, a second etch without a masking al d to the structures can be used to round or smooth the edges of the asymmetric structures 420a. The timing and/or techniques used to perform the second etch can be d to produce differing es such as profile 428 producing asymmetric structures 430 or profile 432 producing asymmetric ures 434. For example, the e 428 (asymmetric structure 430) can be produced from asymmetric structures 420a by using a relatively lower ion energy etch recipe (e.g., higher pressure, lower power) with CHF3, CF4, and Ar. T he more tapered profile 432 (asymmetric structure 434) can be produced from asymmetric structures 420a by using a relatively higher ion energy etch recipe (e.g., lower pressure, higher power) with CF4 and Ar.

FIGS. 7A-7C illustrate an example process for asymmetrically applying a masking material to structures on a substrate in accordance with implementations of the present disclosure. shows a fied block diagram of a deposition system 702. For example, deposition system 702 can be a CVD system or a PVD system. The deposition system 702 deposits a deposition material 704 (e.g., a masking material) on a substrate 102. The deposition material 704 is generally in a gaseous phase as it is transferred to the substrate 102. For example, in a CVD system the deposition material 704 may be a source gas, while in a PVD system the deposition material 704 may be a source material that is evaporated or sputtered onto the substrate 102.

Atty Docket No.: 40589-0029WO1 The deposition system 702 directs the deposition material 704 onto the substrate along a general deposition direction 706 (e.g., along the y-axis as .

One of skill in the art will appreciate that while the deposition material 704 does not truly travel along a single straight path due to the random motions of gas molecules, a general deposition ion can be determined. That is, the deposition material 704 is generally directed towards the substrate from a narrow range of directions; not omnidirectionally. For simplicity, however, the deposition direction 706 will be referred to as a ht path.

The substrate 102 is inclined relative to the deposition direction 706. More specifically, the substrate 102 is inclined such that the substrate 102 forms a nonnormal angle to the deposition direction 706 of the deposition system. ing the substrate 102 at such an angle cause the deposition material 704 to be applied asymmetrically to any structures that extend outward from the substrate 102 (e.g., structures 420 of . For example, as shown in enlarged region “A” of the substrate, when ed one side of the structures 708 blocks or shadows the opposite side of the structures 708 from the path of the deposition material 704. The deposition material is therefore preferentially deposited on the unblocked side of the ures In some implementations, the substrate 102 can be mounted on a pilotable platform that allows the ate 102 to be ed at a variety of angles relative the deposition direction 706. In multi -step fabrication processes (as described below with t to this may permit the application of a first masking material at a first incline angle and subsequent making materials at different incline angles. rmore, the substrate 102 may be pivoted about multiple axes to produce different structure geometries by asymmetrically masking different sides of the ures 708. For example, while the substrate 102 shown in is illustrates as being inclined about the x-axis extending out of the page, for subsequent applications of masking material the substrate 102 may be pivoted about the z-axis.

Atty Docket No.: 40589-0029WO1 Referring to FIGS. 7B and 7C, in some implementations, the deposition substrate may include multiple different regions 730a, 730b, 730c of structures. For such implementations, the deposition system 702 can include a mask or shutter 732 to preferentially apply masking materials to one or more particular regions (e.g., region 730a) while preventing the deposition material 704 from contacting the other regions (e.g., region 730b, 730c). Either the substrate 102 or mask/shutter 732 can be rotated remotely to alternate between which regions 730a, 730b, 730c are exposed to the tion material 704 without the need to break pressure or ature conditions of the deposition system 702 or without the need to alter the incline angle of the substrate 102. For example, the substrate 102 can be ly rotated to alternately align each region 730a, 730b, 730c of structures with the window 734 in the hutter 730. In some implementations, the mask/shutter 732 may permit application of deposition material 704 to each region 730a, 730b, 730c of structures using a different e angle for the substrate 102 without the need to break re or temperature conditions of the deposition system 702.

In some implementations, process 400 can be repeated as shown in and discussed below. rates a second example s 500 for fabricating asymmetric structures. Process 500 is similar to process 400, r, process 500 includes le ions of the some of the steps of process 400.

At step (502), a plurality of discrete structures 520 are formed on a substrate 102. The structures 520 can be formed by, for example, imprint lithography, photo lithography and etching, or other appropriate fabrication techniques. For example, the structures 520 can be formed using an imprint lithography system 100, as described above. Similar to structures 420 discussed above, the structures 520 have a generally symmetric profile. Additionally, the structures 520 can be micro- or nano-structures.

Atty Docket No.: 40589-0029WO1 At step (504), a masking material 522 is applied to the structures 520. The masking material 522 is applied under conditions that cause the g material to trically cover the structures 520. For example, as discussed above with respect to masking material 424, the masking material 522 need not be applied strictly as shown in The masking material 522 can be applied to cover the structures 520 in any desired asymmetric pattern. The masking material 522 can be applied using deposition processes ing, but not limited to, chemical vapor deposition (CVD) and al vapor deposition (PVD). For example, as sed above with respect to FIGS. 7A-7C, the masking material 522 can be applied to the structures 520 by inclining the ate 102 at a rmal incline angle to the direction from which the g material is being deposited. Further, the masking material 522 can include one or of the ing materials: Cr, Ti, SiO2, Al2O3, ZrO2, Ag, Pt, or Au.

At step (506), the structures 520 are etched. Specifically, in the example shown, the patterned layer 150 is etched to modify the overall shape of the structures 520, thereby, producing an asymmetric profile in the structures 520. For example, the portions of the structures 520 (and patterned layer 150) that are not covered by the masking material 522 are etched to form recessions 524. The structures 520 can be etched using etching processes including, but not limited to, a wet etch process, a plasma etching process, a dry etch process, or an ion beam g/milling process.

At step (508), the masking material 522 is removed and a second masking material 526 is applied to the, now, modified ures 520a. As noted above, the masking material 522 can be stripped from the structures 520 and patterned layer 150 using a plasma or chemical stripping process. As shown, the ed structures 520a have an asymmetric provide ed by the asymmetric application of the masking material 522 and the subsequent etching. The shape of the modified structures 520a can be further altered by applying a second masking material 526 to the modified structures 520a. The second masking material 526 can be the same material or a different material from that of the first masking material 522.

Atty Docket No.: 40589-0029WO1 The second masking material 526 can be applied similarly to the first masking material (e.g., as . In other words, the second masking al can be applied asymmetrically to the same side of the structures 520a that the first masking material was applied to the structures 520. In some implementations, the second masking material can be applied trically to a different side of the structures 520a or in different proportions to various sides of the ures 520a than how the first masking material 522 was applied to the structures 520. For example, as discussed above, the first masking material 522 can be applied to the structures 520 by inclining the substrate 102 at a non-normal incline angle to the direction from which the masking material is being deposited. Accordingly, the second masking material 526 can be applied by inclining the substrate 102 at an angle different from that used to apply the first masking material 522. The substrate 102 can be d or inclined about a different axis such that the second masking material 526 is applied to a different side of the structures 520a than that to which the first masking material 522 was applied to the structures 520.

At step (510), the structures 520a are etched. Specifically, in the example shown, the patterned layer 150 is etched to modify the overall shape of the structures 520a, thereby, further modifying the asymmetric profile of the structures 520a. For example, the portions of the structures 520a (and patterned layer 150) that are not covered by the g al 526 are etched to form recessions 528. The structures 520a can be etched using etching processes including, but not limited to, a wet etch process, a plasma etching process, a dry etch process, or an ion beam etching/milling process.

At step (512), the g material 526 is removed. For example, the masking material 526 can be stripped from the structures 520 and ned layer 150 using plasma or al ing. As shown, removing the masking material reveals the asymmetric profile of the structures 520b produced by the asymmetric application of the masking al 526 and the subsequent etching.

Atty Docket No.: 40589-0029WO1 The optional step (408) of process 400 can be performed either after step (512), after the first masking material 522 is removed in step (506), or both. More specifically, either the asymmetric structures 520a, 520b, or both can be etched without a masking material d to further alter their shape. illustrates a third example process 600 for fabricating tric structures. s 600 includes the use of an asymmetrically applied metal assisted chemical etching (MACE) material for the fabrication of asymmetric structures. As in processes 400 and 500, a ity of discrete structures 620 are formed on a substrate 102. The structures 620 can be formed by, for e, imprint lithography, photo lithography and etching, or other appropriate fabrication ques. Similar to structures 420 and 520 discussed above, the structures 620 have a generally symmetric profile. Additionally, the structures 620 can be micro- or nano-structures.

At step (602), a masking material 622 and a MACE catalyst material 624 are applied to the structures 620. The g al 622 and a catalyst material 624 are applied under conditions that cause masking material 622 and a catalyst material 624 to asymmetrically cover the structures 620. For example, the masking material 622 and catalyst material 624can be applied using deposition processes including, but not limited to, CVD and PVD processes. Example ions for asymmetrically applying the masking material 622 and catalyst al 624are described in more detail below in reference to FIGS. 7A-7C. Further , the masking material 622 can include one or of the following materials: Cr, Ti, SiO2, Al2O3, ZrO2, Ag, Pt, or Au. The catalyst material 624 can include one or of the following materials: Au, Pt, Au-Pd alloy, In some implementations, the masking material 622 and the catalyst material 624 can be applied under different conditions to produce different asymmetric patterns, as shown in For example, the g material 622 may be applied by inclining the ate 102 at a first angle relative to a deposition direction of a deposition Atty Docket No.: 40589-0029WO1 system, and the catalyst material 624 can be applied by inclining the substrate 102 at a second angle that is different from the first angle.

In some implementations, the catalyst material 624 may be applied to the ures alone, t the masking material 622. Furthermore, although the g material is described and shown as being applied to the structures before the catalyst material 624, in some implementations, the catalyst material 624 may be applied before the masking material 622.

At step (604), the structures 620 are etched. Specifically, in the example shown, the patterned layer 150 is etched to modify the overall shape of the structures 620, thereby, producing an asymmetric profile in the ures 620. For example, the portions of the structures 620 (and patterned layer 150) that are not covered by the masking material 622 but which are d by the catalyst material 624 are etched to form recessions 626. The st material 624 causes those portions of the structures 620 and patterned layer 150 that are in contact with the st to be etch at a higher rate than the structures 620 and patterned layer 150 alone.

At step (606), the masking material 622 and any ing catalyst material 624 are removed. For example, the g material 622 and remaining catalyst material 624 can be stripped from the structures 620 and patterned layer 150 using a plasma or chemical stripping process. As shown, removing the masking material 622 and remaining catalyst al 624 reveals the asymmetric profile of the structures 620a produced by process 600. shows a flowchart of an example method 800 for fabricating asymmetric structures in accordance with implementations of the present disclosure.

The process 800 is illustrated as a collection of referenced acts arranged in a logical flow graph. The order in which the acts are described is not intended to be construed Atty Docket No.: 40589-0029WO1 as a limitation, and any number of the described acts can be combined in other orders and/or in parallel to implement the process.

A plurality of discrete structures are formed on a substrate (802). The structures can be formed by, for example, imprint lithography, photo lithography and etching, or other appropriate fabrication techniques. For example, the structures can be formed using an imprint raphy system 100, as described above. In some es, the structures have a generally symmetric profile. In other words, the shape of one side of each structure is substantially the same as the shape of the opposite side of each structure, y, forming a left-right symmetry. The starting profile of the structures can include any generally symmetric shape ing, but not limited to, a square profile, a rectangular profile, a trapezoidal profile, or a triangular profile. onally, the ures can be micro- or nano-structures.

In some implementations, the structures are formed in le te regions. For example, multiple fields of structures can be formed on a single ate.

In some cases, each region of structures is processed rly to form similarly shaped asymmetric structures. In other cases, each region of structures is processed differently to form differently shaped asymmetric structures on the same substrate.

A making material is asymmetrically applied to the structures (804). The masking material is applied under conditions that cause the masking al to form an asymmetric masking pattern that asymmetrically covers the ures. For example, for each or some of the structures, the masking material may completely cover a first side of a structures, but may not cover a second, opposite side of the structure. The masking material can be applied to cover the structures in any desired asymmetric pattern. For example, a first side of the structures may be only partially covered by the masking material, but not completely covered. A second, opposite side may also be partially covered by the masking material. However, to maintain the asymmetric application of the masking material to the ures, the portion of the first side that is Atty Docket No.: 40589-0029WO1 covered by the masking material may be r than the portion of second side that is covered by the masking material.

The masking material can be applied using deposition processes including, but not limited to, CVD and PVD ses. Conditions for asymmetrically applying the masking material can include inclining the substrate at a non-normal angle to a direction from which tion material is transferred to the substrate in a deposition system (e.g., as described above in nce to FIGS. 7A-7C). Further, the masking al can include one or of the following materials: Cr, Ti, SiO2, Al2O3, ZrO2, Ag, Pt, or Au. In some implementations, a MACE catalyst material can be asymmetrically applied to the structures in addition to or in place of the masking material (e.g., as described in reference to process 600 above).

Unmarked ns of the structures are etched (806). The structures and/or layer(s) of material below the structures is etched to modify the overall shape of the structures, and thereby, produce an asymmetric profile in the structures. For example, the portions of the structures that are not d by the masking material are etched to form recessions in the structures and/or a residual layer of material below the structures. The structures can be etched using etching processes including, but not limited to, a wet etch process, a plasma etching process, a dry etch process, or an ion beam etching/milling process.

The masking material is removed from the ures (808). For example, the masking material can be stripped from the structures and underlying layer(s) using a plasma or chemical ing process. Removing the masking material reveals the asymmetric profile of the structures produced by the asymmetric application of the masking al and the subsequent etching.

In some implementations, the s returns to step (804) and steps (804)- (808) are repeated, as indicated by dashed line 809. For example, as discussed with Atty Docket No.: 40589-0029WO1 respect to process 500 above, the steps (804)-(808) can be repeated to further alter the asymmetric shape of the structures. For example, another g material can be applied under different conditions to produce a different asymmetric masking n.

The ures are, optionally, etched without a masking material applied (810). For example, a second etch without a masking material applied to the structures can be used to round or smooth the edges of the asymmetric structures. The timing and/or techniques used to perform the second etch can be altered to produce differing profiles.

Asymmetric micro- and nano- structures can be used to create diffraction ns for use in optical devices. For example, diffraction patterns that include asymmetric structures may provide more efficient optical diffraction patterns for devices such as diffraction lenses or optical couplers used in l wave guides.

FIGS. 9A-9B show example devices in which asymmetric structures are used. shows a perspective of example an optical system 900. The optical system 900 is, for example, an optical projection system illustrated as a pair of virtual reality or augmented reality s. The example optical system can e diffraction lenses and rs to t an image on a lens 904 of the system 900. The system 900 can receive data representing image (e.g., from a processor) and project the image onto a region 902 on a lens 904 of the system 900. Accordingly, a user can view both an image projected in the region 902 as being overlaid on a scene that is visible through the lenses 904. Other example projection systems can include, but are not limited to, video tors, mobile video projectors, heads-up displays (e.g., heads-up displays for vehicles), microscopes, telescopes, and other optical devices. In other example optical systems 900 asymmetric structures can be used in reflective polarizer films (e.g., GLAD Wire Grid Polarizers). For e, asymmetric structures can be used in reflective polarizing films for LCD display systems such as those used in smartphones, LCD monitors, LCD televisions, tablet computers, etc.

Atty Docket No.: 0029WO1 shows a top view of a waveguide 950 for projecting an image within a lens 952 that can be positioned in front of a user’s eye. For example, waveguide 950 can be attached to a pair of glasses 954 to provide augmented reality images to the user. The waveguide 950 receives image data from a processor and projects the an image within the lens 952 of the waveguide 950.

Diffraction lenses and optical couplers in the projection system 900 and the waveguide 950 can include diffraction patterns with asymmetric micro- and/or nanostructures (as disclosed above) to improve the diffraction efficiency of such lenses and optical couplers. For example, improved ction efficiency may result in brighter, more visible images to a user. ed diffraction efficiency may also result in energy savings for ted reality and other optical systems.

Although diffraction patterns are described in reference to l systems, it should be tood that implementations of the present disclosure are not limited to diffraction patterns for visible light. Instead, the micro- and nano- structures described herein and processes to fabricate the same can be used to produce diffraction patterns for various electromagnetic waves having wavelengths ponding to features of the ated structures. For example, the micro- and nano- structures described herein may be functional in diffraction patterns for electromagnetic waves ranging from infrared (IR) wavelengths to ultraviolet (UV) wavelengths, and potentially to X-rays.

While a number of examples have been described for illustration es, the foregoing ption is not intended to limit the scope of the invention, which is defined by the scope of the appended claims. There are and will be other examples and modifications within the scope of the following claims.

Claims (20)

CLAIMS :

1. An optical device comprising: a substrate; and a diffraction pattern on the substrate, the diffraction pattern comprising a plurality of asymmetric structures extending from a common e of the substrate, n each structure of the plurality of asymmetric structures has a first side e and a second side surface opposite the first side surface, and a profile of the first side surface is asymmetric with respect to a profile of the second side e, wherein: at least one asymmetric ure of the plurality of asymmetric ures has an asymmetric chair profile, the first side surface of the at least one asymmetric structure has a linear profile, the second side surface of the at least one asymmetric ure comprises two or more portions, and at least one of the two or more portions of the second side surface is sloping with respect to a surface of the substrate and angled with respect at least one other of the two or more portions of the second side surface.

2. The device of claim 1, wherein each structure of the ity of asymmetric ures has an asymmetric triangular profile.

3. The device of claim 1 or 2, wherein at least one of the asymmetric structures of the plurality of asymmetric structures has an asymmetric stepped profile comprising a sloping linear profile of the first side surface and a stepped profile of the second side surface, wherein the stepped profile of the second side surface comprises at least one sloping portion.

4. The device of any one of claims 1 to 3, wherein a recess is defined between adjacent structures of the plurality of asymmetric structures.

5. The device of claim 4, wherein a surface of the recess is substantially parallel to a e of the substrate.

6. The device of any one of claims 1 to 5, n the asymmetric structures comprise one of Si, SiO2, a polymer material, or an organic-inorganic hybrid material.

7. The device of any one of claims 1 to 6, wherein the structures are nano - structures.

8. The device of any one of claims 1 to 7, wherein the structures are micro - structures.

9. The device of any one of claims 1 to 8, wherein the plurality of asymmetric structures include a plurality of first asymmetric structures having a first asymmetric profile and a plurality of second tric structures having a second asymmetric profile that is different from the first asymmetric profile.

10. The device of any one of claims 1 to 9, wherein each structure of the plurality of asymmetric structures has rounded edges.

11. The device of any one of claims 1 to 10, wherein the device is a waveguide.

12. The device of any one of claims 1 to 11, wherein the device is an optical projection system.

13. The device of claim 12, wherein the device is a virtual reality system or an augmented y system.

14. The device of claim 12 or 13, wherein the device is a pair of eyeglasses.

15. A virtual or augmented reality system comprising the optical device of any one of claims 1 to 14.

16. An optical device comprising: a substrate; and a diffraction pattern on the substrate, the diffraction pattern sing a plurality of asymmetric structures extending from a common surface of the substrate, wherein each structure of the plurality of asymmetric structures has a first side surface and a second side surface opposite the first side surface, and a profile of the first side surface is asymmetric with respect to a profile of the second side e, wherein: at least one asymmetric structure of the ity of asymmetric structures has an asymmetric chair profile, the first side surface of the at least one asymmetric structure has a linear e, the second side surface of the at least one asymmetric structure comprises two or more portions, and at least one of the two or more portions of the second side surface is sloping with respect to a surface of the substrate and angled with respect at least one other of the two or more portions of the second side surface, and wherein the plurality of asymmetric structures are formed by a process comprising: applying a metal st layer over the plurality of discrete ures under first ions that cause the metal catalyst layer to asymmetrically cover the plurality of discrete ures such that at least a first portion of a first side of each structure of the plurality of discrete structures is free of the metal catalyst layer; after applying the metal catalyst layer, applying a masking material over the plurality of te structures under second conditions that cause the masking material to asymmetrically cover the plurality of discrete structures such that at least a second n of a second side of each structure is free of the masking material, wherein the masking material comprises one of SiO2, Al2O3, or ZrO2; etching a first area of the plurality of discrete structures that is not covered by the g material; stripping the masking material from the ity of discrete structures; and wet etching a second area of the plurality of structures with metal assisted chemical g to yield the asymmetric structures.

17. The device of claim 16, wherein the device is an optical projection system.

18. The device of claim 17, wherein the device is a virtual reality system or an augmented reality system.

19. A virtual or augmented reality system comprising the optical device of any one of claims 16 to 18.

20. An optical device sing: a substrate; and a diffraction pattern on the substrate, the diffraction pattern comprising a plurality of asymmetric structures extending from a common surface of the substrate, wherein each structure of the plurality of asymmetric structures has a first side surface and a second side surface te the first side surface, and a profile of the first side surface is asymmetric with respect to a profile of the second side surface, wherein the first side e and the second side surface are each sloping with respect to a surface of the substrate, wherein the ity of asymmetric structures include a plurality of first tric structures having a first asymmetric profile and a plurality of second asymmetric structures having a second asymmetric profile that is different from the first asymmetric profile. 5RERW J U D W H X F N D U LQ 6X E V W & K % H $ LU ),* ),* $ ),* % ),* & ),* $ WLRQ 6\VWHP ),* & ),* % )RUP GLVFUHWH VWUXFWXUHV $SSO