Configuring an optical layer in an imprint lithography process

Abstract

The present invention relates to configuring an optical layer in a nanoimprint lithography process. The nanoimprint lithography method of configuring an optical layer includes imprinting first features having dimensions of a first order of magnitude on one side of a substrate using a patterned template, and simultaneously imprinting second features having dimensions of a second order of magnitude on the side of the substrate using the patterned template, the second feature dimensions being determined and arranged to define a gap between the substrate and an adjacent surface.

Description

[0001] This application is a divisional application of the patent application with application number 201780074523.2. The application date of the original application is September 14, 2017, and the name of the invention is "Configuring an optical layer in an imprint lithography process".

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of the filing date of U.S. Provisional Application No. 62 / 429,214, filed on December 2, 2016. The contents of U.S. Application No. 62 / 429,214 are incorporated herein by reference in their entirety. Technical Field

[0004] The present invention relates to configuring optical layers in an imprint lithography process, and more particularly to forming features having dimensions of different orders of magnitude on a substrate in one processing step. Background Art

[0005] Nanofabrication (e.g., nanoimprint lithography) can include the manufacture of very small structures with features of about 100 nanometers or less. One application where nanofabrication has had a significant impact is the processing of integrated circuits. The semiconductor processing industry continues to strive for greater throughput while increasing the number of circuits formed on a substrate per unit area of ​​the substrate. To this end, nanofabrication is becoming increasingly important for achieving desired results in the semiconductor processing industry. Nanofabrication provides better process control while allowing for a continued reduction in the minimum feature size of structures formed on a substrate. Other areas of development that have adopted nanofabrication include biotechnology, optical technology, mechanical systems, and the like. In some examples, nanofabrication includes manufacturing structures on a substrate that are assembled to form optical devices. Summary of the invention

[0006] The present invention relates to the recognition that improvements in imprinting three-dimensional (3D) patterns on substrates can increase accuracy and precision while reducing the cost and complexity associated with producing such patterns. Conventional imprint lithography processes may include imprinting a nanoscale pattern on a substrate in a first process step, and then imprinting larger features on the substrate in a second subsequent process step. For such processes, the nanoscale pattern may need to be cleaned and processed before the larger features are formed, which is associated with additional costs and additional time. In addition, aspects of forming larger features in subsequent processes sometimes jeopardize the mechanical integrity and / or functional integrity of the nanopatterned substrate. In this regard, various aspects of the disclosed imprint lithography methods can allow 3D structures with features of different orders of magnitude to be imprinted in a single imprint process step, the features having multiple functions (e.g., any of optical functions, anti-reflection, and spacing). These methods produce precise, accurate structures at reduced cost and duration compared to alternative methods.

[0007] One aspect of the present invention features an imprint lithography method for configuring an optical layer. The imprint lithography method includes imprinting a first feature having a size of a first order of magnitude on one side of a substrate using a patterned template, and simultaneously imprinting a second feature having a size of a second order of magnitude on the side of the substrate using the patterned template, wherein the second feature size is determined and arranged to define a gap between the substrate and an adjacent surface.

[0008] In some embodiments, imprinting the first features includes forming one or both of a diffraction grating and an anti-reflective feature on the face of the substrate.

[0009] In some embodiments, imprinting the second feature includes forming spacers on the side of the substrate.

[0010] In some embodiments, the method further comprises imprinting one or both of spacers and anti-reflective features along a peripheral edge of the face of the substrate.

[0011] In certain embodiments, the method further includes imprinting one or both of spacers and anti-reflective features within an interior region of the face of the substrate.

[0012] In some embodiments, the side of the substrate is a first side of the substrate, and the imprint lithography method further comprises imprinting a third feature having a size of the first order of magnitude on a second side of the substrate.

[0013] In some embodiments, imprinting the third feature includes forming a diffraction grating or an anti-reflective feature on the second side of the substrate.

[0014] In some embodiments, the second order of magnitude of the size is greater than the first order of magnitude of the size.

[0015] In certain embodiments, the first order of magnitude dimensions are nanometers and the second order of magnitude dimensions are micrometers.

[0016] In some embodiments, the method further includes imprinting a second feature on opposite sides of the first feature.

[0017] In certain embodiments, the method further includes creating a patterned template from a predecessor mold.

[0018] In some embodiments, the method further includes forming deep features having dimensions of a second order of magnitude in the precursor mold.

[0019] In certain embodiments, the method further includes forming a shallow feature having a dimension of a first order of magnitude in the precursor mold.

[0020] In some embodiments, the substrate is a first substrate and the adjacent surface is defined by a second substrate.

[0021] In certain embodiments, the method further includes aligning the first and second substrates with each other.

[0022] In some embodiments, the method further includes dispensing an adhesive substance on top of the second features imprinted on the face of the first substrate.

[0023] In certain embodiments, the method further includes attaching the first and second substrates to each other at the adhesive substance imprinted on top of the second features on the face of the first substrate to form a gap between the first substrate and an adjacent surface defined by the second substrate.

[0024] In some embodiments, the method further comprises attaching the first and second substrates to each other at the adhesive substance imprinted on top of the second features on the face of the first substrate to form a multilayer optical device.

[0025] In certain embodiments, the method further includes defining an air layer between the first and second substrates, the thickness of which is determined by the height of the second feature.

[0026] In some embodiments, the gaps provide low refractive index regions.

[0027] In some embodiments, the low refractive index region is air, which has a refractive index of 1.

[0028] In some embodiments, the imprint lithography method further comprises providing the multilayer optical device with layers characterized by alternating refractive indices.

[0029] Another aspect of the invention features an optical layer that includes a substrate and a pattern imprinted on one side of the substrate using a patterned template. The pattern includes first features having a size of a first order of magnitude and second features having a size of a second order of magnitude. The second features are sized and arranged to define a gap between the substrate and an adjacent surface.

[0030] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the invention will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a diagram of an imprint lithography system.

[0032] Figure 2 Is Figure 1 Figure 1. Diagram of the patterned layer formed by the imprint lithography system.

[0033] Figure 3 is a top view of the optical layer.

[0034] Figure 4 yes Figure 3Side view of the optical layer.

[0035] Figure 5 Is with Figure 3 Configurations of the optical layers shown are top views of optical layers in different configurations.

[0036] Figure 6 Is with Figure 3 and Figure 5 Configurations of the optical layers shown are top views of optical layers in different configurations.

[0037] Figure 7 Yes Figure 3 An exploded perspective view of a portion of an optical device of an optical layer.

[0038] Figure 8 yes Figure 7 A side view of a portion of an optical device.

[0039] Fig. 9 It is used to form can be used to produce Figure 3 FIG. 1 is a diagram of a series of steps for patterning a mold for an optical layer.

[0040] Fig.10 is to use Fig. 9 Side view of the spacers formed by the patterning mold.

[0041] Fig.11 yes Fig.10 A perspective view of a spacer.

[0042] Fig.12 Is with Figure 3 and Figure 4 Configurations of the optical layer shown are side views of optical layers in different configurations.

[0043] Fig.13 Is with Figure 3 , 4 A side view of an optical layer having a configuration different from that of the optical layer shown in FIG. 12 .

[0044] Fig.14 is a flow chart of an exemplary process for configuring an optical layer in an imprint lithography process.

[0045] Like reference numerals in the various drawings represent like elements.

[0046] In some instances, the diagrams shown in the drawings may not be drawn to scale. DETAILED DESCRIPTION

[0047] An imprint lithography process for configuring optical layers is described below. The imprint lithography process involves imprinting multifunctional structures including features of varying magnitudes from a single template. This process can improve precision and accuracy and reduce the cost and complexity associated with producing such structures for forming multilayer optical devices.

[0048] Figure 1 An imprint lithography system 100 is shown, which is operable to form a relief pattern on a top surface 103 of a substrate 101 (e.g., a wafer). The imprint lithography system 100 includes a support assembly 102 that supports and transports the substrate 101, an imprint assembly 104 that forms a relief pattern on the top surface 103 of the substrate 101, a fluid dispenser 106 that deposits a polymerizable substance on the top surface 103 of the substrate 101, and a robot 108 that places the substrate 101 on the support assembly 102. The imprint lithography system 100 also includes one or more processors 128 that can operate in accordance with a computer-readable program stored in a memory and communicate with the support assembly 102, the imprint assembly 104, the fluid dispenser 106, and the robot 108 and is programmed to control these components.

[0049] Substrate 101 is a generally flat sheet, which is generally made of one or more materials, including silicon, silicon dioxide, aluminum oxide, sapphire, germanium, gallium arsenide (GaAs), alloys of silicon and germanium, indium phosphide (InP) or other exemplary materials. Substrate 101 generally has a generally circular or rectangular shape. Substrate 101 generally has a diameter in the range of about 50 mm to about 200 mm (e.g., about 65 mm, about 150 mm, or about 200 mm), or a length and width in the range of about 50 mm to about 200 mm (e.g., about 65 mm, about 150 mm, or about 200 mm). Substrate 101 generally has a thickness in the range of about 0.2 mm to about 1.0 mm. The thickness of substrate 101 is generally uniform (e.g., constant) across substrate 101. The relief pattern is formed on the top surface 103 of substrate 101 as a group of structural features (e.g., convex portions and suction structures) by a polymerizable substance, as will be discussed in more detail below.

[0050] The support assembly 102 includes a chuck 110 that supports and secures the substrate 101, an air bearing 112 that supports the chuck 110, and a base 114 that supports the air bearing 112. The base 114 is located in a fixed position, while the air bearing 112 can move in up to three directions (e.g., x, y, and z directions) to transport the chuck 110 (e.g., in some cases, carrying the substrate 101) to and from the robot 108, the fluid dispenser 106, and the imprint assembly 104. In some embodiments, the chuck 110 is a vacuum chuck, a pin-type chuck, a slot-type chuck, an electromagnetic chuck, or another type of chuck.

[0051] Still refer to Figure 1 , the imprint assembly 104 includes a flexible template 116 having a patterned surface defining an original pattern from which a relief pattern is complementarily formed on the top surface 103 of the substrate 101. Therefore, the patterned surface of the flexible template 116 includes structural features, such as protrusions and recesses. The imprint assembly 104 also includes a plurality of rollers 118, 120, 122 of various diameters, which rotate to allow one or more portions of the flexible template 116 to move along the x-direction within the processing area 130 of the imprint lithography system 100 to cause the selected portion of the flexible template 116 to be aligned (e.g., overlapped) with the substrate 101 along the processing area 130. One or more of the rollers 118, 120, 122 can be moved individually or together in a vertical direction (e.g., z-direction) to change the vertical position of the flexible template 116 in the processing area 130 of the imprint assembly 104. Thus, the flexible template 116 can push down the substrate 101 in the processing area 130 to form an imprint on top of the substrate 101. The arrangement and number of rollers 118, 120, 122 can vary depending on various design parameters of the imprint lithography system 100. In some embodiments, the flexible template 116 is coupled to (e.g., supported or secured by) a vacuum chuck, a pin-type chuck, a slot-type chuck, an electromagnetic chuck, or another type of chuck.

[0052] In operation of the imprint lithography system 100, the flexible template 116 and the substrate 101 are aligned at desired vertical and lateral positions by rollers 118, 120, 122 and air bearings 112, respectively. This positioning defines a volume within a processing region 130 between the flexible template 116 and the substrate 101. Once a polymerizable substance is deposited on the top surface 103 of the substrate 101 by the fluid dispenser 106, the volume can be filled with the polymerizable substance, and then the chuck 110 (e.g., carrying the substrate 101) is moved to the processing region 130 by the air bearings 112. Thus, both the flexible template 116 and the top surface 103 of the substrate 101 can be in contact with the polymerizable substance in the processing region 130 of the imprint lithography system 100. Exemplary polymerizable substances can be formulated from one or more substances, such as isobornyl acrylate, n-hexyl acrylate, ethylene glycol diacrylate, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, acrylate (2-methyl-2-ethyl-1,3-dioxolan-4-yl) methyl ester, hexanediol diacrylate, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone and various surfactants. Exemplary techniques that can be used to deposit polymerizable substances on the top of substrate 101 through fluid dispenser 106 include droplet distribution, spin coating, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), thin film deposition, thick film deposition and other techniques. In some examples, the polymerizable substance is deposited on the top of substrate 101 in multiple droplets.

[0053] Printing system 104 includes an energy source 126 that directs energy (e.g., broadband ultraviolet radiation) toward a polymerizable substance on top of substrate 101 within processing region 130. The energy emitted from energy source 126 cures and / or cross-links the polymerizable substance, thereby producing a patterned layer that conforms to the shape of the portion of flexible template 116 that contacts the polymerizable substance in processing region 130.

[0054] Figure 2 An exemplary patterned layer 105 formed on a substrate 101 by an imprint lithography system 100 is shown. The patterned layer 105 includes a residual layer 107 and a plurality of features including protrusions 109 extending from the residual layer 107 and recesses 111 formed by adjacent protrusions 109 and the residual layer 107 .

[0055] Although the imprint lithography system 100 is described and shown as a roll-to-plate or plate-to-roll system, imprint lithography systems having different configurations can also be used to produce the exemplary patterned layer 105 and the exemplary patterns discussed below. Such an imprint lithography system can have a roll-to-roll or plate-to-plate configuration.

[0056] In some embodiments, a substrate (e.g., substrate 101 of imprint lithography system 100) is processed (e.g., imprinted on one or both sides and cut to shape) to form an optical layer of a multilayer optical device (e.g., a wearable eyepiece, an optical sensor, or an optical film, such as an optical film used in a display). For example, Figure 3 and Figure 4 A top view and a side view of an optical layer 200 are shown, respectively, and the optical layer 200 includes a substrate 202, a functional pattern 204 embossed on the substrate 202, and an auxiliary pattern 206 embossed on the substrate 202. The substrate 201 can be laser cut from a larger substrate (e.g., substrate 101) and is provided as a layer of transparent or translucent plastic (e.g., flexible) or glass (e.g., rigid) made of one or more organic or inorganic materials according to the various material recipes described above with respect to the substrate 101. The substrate 202 has a maximum length of about 10 mm to about 500 mm and a maximum width of about 10 mm to about 500 mm. The substrate 202 has a relatively high refractive index in the range of about 1.6 to about 1.9 and a transmittance in the range of about 80% to about 95%.

[0057] Functional pattern 204 is embossed on top of upper surface 208 of substrate 202 and positioned along inner region 218 relative to peripheral edge 216 of substrate 202. Functional pattern 204 is a waveguide pattern formed by multiple diffraction gratings that provide basic working functions of optical layer 200. Diffraction gratings have a size in the range of about 10nm to about 500nm. Diffraction gratings are configured to project light of wavelengths in a specific range and focus virtual images at specific depth planes. The focused light, together with the focused light projected through the near optical layer, forms a polychromatic virtual image on one or more depth planes. The transmitted light may be red light with a wavelength in the range of about 560nm to about 640nm, green light with a wavelength in the range of about 490nm to about 570nm, or blue light with a wavelength in the range of about 390nm to about 470nm. The diffraction grating may include a variety of combinations and arrangements of convexities and concavities (e.g., such as convexities 109 and concavities 111), which together provide the desired optical effect. The diffraction grating includes an in-coupling grating 220 and forms an orthogonal pupil expansion region 222 and an exit pupil expansion region 224. The functional pattern 204 has a total length of about 10 mm to about 500 mm and a total width of about 10 mm to about 500 mm.

[0058] The auxiliary pattern 206 is imprinted on top of the upper surface 208 of the substrate 202 and surrounds the functional pattern 204. The auxiliary pattern 206 is also co-located with the inner region 218 of the substrate 202. The auxiliary pattern 206 includes both nano-scale anti-reflective features 210 and micron-scale spacers 212, which can be distributed in different numbers and arrangements on the auxiliary pattern 206. The auxiliary pattern 206 coincides with the inner region 218 of the substrate 202 and has a total length of about 10 mm to about 500 mm and a total width of about 10 mm to about 500 mm.

[0059] The anti-reflective features 210 may be arranged at any position within the auxiliary pattern 206. The anti-reflective features 210 are sized (e.g., having a height less than or equal to about 300 nm and a pitch of about 50 nm to about 150 nm) and shaped to reduce surface reflection at the face (e.g., upper face 208) of the substrate 202 on which the anti-reflective features 210 are imprinted. For example, the anti-reflective features 210 may reduce surface reflection of the substrate 202 by about 1.0% to about 4.5%. The anti-reflective features 210 are further sized and shaped to increase the transmittance of the substrate 202 to greater than about 98.5% (e.g., for a plastic substrate 202) and up to about 99.5% (e.g., for a glass substrate 202). The anti-reflective features 210 are also sized and shaped to give the substrate 202 a new effective refractive index in the range of about 1.2 to about 1.4. In addition, the anti-reflective features 210 may introduce birefringence to reduce or enhance the refraction of certain wavelengths of light passing through the substrate 202.

[0060] The spacer 212 is sized to create a gap (e.g., an air layer) between the optical layer 200 and an adjacent optical layer that, when adhered to one another, together form part of a multi-layer stacked optical device, as will be described below with reference to Figure 7 and Figure 8 Discussed in more detail. The spacer 212 can be arranged at any position within the auxiliary pattern 206 as needed to provide sufficient structural support for the substrate 202 and for the adjacent optical layer in contact with the spacer 212. In some embodiments, the spacer 212 (e.g., in a cured state) has an elastic modulus greater than 1 GPa. The spacer 212 can be embossed in a predetermined geometric shape (e.g., a tetrahedron, a cylinder, a cone, etc.), and therefore can have a cross-sectional shape such as a circle, a rectangle, etc. The spacer 212 can have a lateral dimension (e.g., a width or diameter) in the range of about 1 μm to about 100 μm and a vertical dimension (e.g., a height) of about 1 μm to about 50 μm. Each spacer 212 can be located at a position of about 5 μm to about 100 μm from another adjacent spacer 212, an anti-reflective feature 210, or a diffraction grating of a functional pattern 204.

[0061] Other arrangements of functional patterns and auxiliary patterns are possible. For example, Figure 5 A top view of an optical layer 300 is shown, which includes a substrate 202 and a functional pattern 204 of the optical layer 200, and an auxiliary pattern 306. The functional pattern 204 is embossed on top of the upper layer 208 of the substrate 202, as in the optical layer 200. The auxiliary pattern 306 is also embossed on top of the upper layer 208 of the substrate 202, and is substantially similar in structure and function to the auxiliary pattern 206, except that the auxiliary pattern 306 extends across the inner region 218 to the peripheral edge 216 of the substrate 202.

[0062] In another example embodiment, Figure 6 A top view of an optical layer 400 is shown, which includes a substrate 202 and a functional pattern 204 of the optical layer 200, and an auxiliary pattern 406. The functional pattern 204 is embossed on top of the upper layer 208 of the substrate 202, as in the optical layer 200. The auxiliary pattern 406 is also embossed on top of the upper layer 208 of the substrate 202, and is substantially similar in structure and function to the auxiliary pattern 206, except that the auxiliary pattern 406 is embossed along the peripheral edge 216 of the substrate 202 so that the inner area 218 of the substrate 202 remains unpatterned and surrounds the functional pattern 204. In other embodiments, the optical layer may include functional patterns and auxiliary patterns having different shapes and / or arrangements not shown in the exemplary optical layers 200, 300, 400.

[0063] Figure 7 An exploded perspective view of a portion of an optical device 500 (eg, a wearable eyepiece) including a plurality of optical layers including three exemplary optical layers 200 is shown. Figure 8 A (non-exploded) side view of the same portion of optical device 500 is shown. Optical device 500 includes additional optical layers that are not shown. Figure 7 and Figure 8 , the optical device 500 is formed by aligning the optical layers 200 with each other and bonding the optical layers 200 to each other using a drop of adhesive dispensed on top of the spacer 212. The optical layers 200 are then further adhered to each other with a sealant that serves as an attachment mechanism to which all peripheral edges 216 of the optical layers 200 are bonded. The optical device 500 may include a plurality of any of the optical layers 200, 300, 400, and other optical layers, and may include 3 to 20 optical layers in total.

[0064] For each optical layer 200 in the optical device 500, the spacers 212 together form a spacer layer that creates a gap 530 that defines an air layer between adjacent optical layers 200, such as Figure 82. The air layer defined by the spacers 212 has a low refractive index in the range of about 1.0 to about 1.2. The low refractive index air layers alternating with the high refractive index optical layers 200 enhance 3D visualization and reduce or eliminate optical coupling between adjacent optical layers 200. The support structure formed by the arrangement of the spacers 212 supports the substrate 202 on which the spacers 212 are printed and the adjacent substrates 202 in such a manner that warping of the substrate 202 that may otherwise occur is prevented or reduced if the optical layers 200 are to be adhered via a different technique, such as dispensing glue drops in the inner portion or along the peripheral edge 216 of the substrate 202.

[0065] Fig. 9 A series of steps for creating a patterned mold 600 (e.g., a patterned surface provided by a flexible template 116) from a precursor mold 642 (e.g., a featureless mold) is shown. The patterned mold 600 defines both shallow features 644 on the nanometer scale and deep features 646 on the micrometer scale. Thus, the shallow features 644 can be used to form the diffraction gratings of the functional pattern 204 and the anti-reflective features 210 of the auxiliary pattern 206 on the substrate 202, while the deep features 646 can be used to form the spacers 212 on the substrate 202 in a single imprinting step, as will be described below with reference to Fig.14 discussed in more detail.

[0066] In the first process (a) for forming patterned mold 600, deep features 646 are formed in precursor mold 642 via a process to produce microfeature mold 648. Exemplary process methods include photolithography and reactive ion etching. In the next process (b), a polymerizable substance 650 is deposited on top of microfeature mold 648 and patterned with nanoscale fine features 652, which are formed as described above with respect to Figure 1 and Figure 2646 of the patterned mold 600 are produced with improved precision and accuracy compared to spacer features that may be produced with other techniques including dispensing a substance to form spacer features for adhering to adjacent optical layers. In this regard, the height of the spacers 212 produced by the deep features 646 exhibits good coplanarity (e.g., within a tolerance of + / -100 nm over a span of approximately 50 mm), and the width or diameter of the spacers 212 is consistent within a tolerance of + / -100 nm. As a result, the spacers 212 formed on the substrate 202 by the deep features 646 of the patterning mold 600 provide the spacer layer with improved thickness uniformity across individual spacer layers, so that adjacent substrates 202 can be accurately aligned and oriented and warping is reduced or eliminated. In addition, compared to the use of dispensed glue drops, which often cause substrate warping, sometimes lack sufficient adhesion, and often expand into functional patterns imprinted on the substrate, the accuracy of the width of the deep features 646 advantageously allows for improved structural integrity and functional integrity along the inner region 218 of the substrate 202 according to the use of the spacers 212. In addition, in the case of a spacer height of about 25 μm, the dispensed glue drops can span a relatively large area on the substrate (e.g., a diameter of about 500 μm), while in the case of a spacer height of about 25 μm, the spacers 212 can span a limited area on the substrate (e.g., a diameter of about 10 μm to about 20 μm).

[0067] Fig.10 and Fig.11 A side view and a perspective view of the spacers 212 of the auxiliary pattern 206 formed by the deep features 646 of the patterning mold 600 are shown, respectively. Fig.10 and Fig.11 In the example of FIG. 2 , the spacer 212 has a generally cylindrical shape and has features (eg, height and effective diameter) in a range of about 5 μm to about 100 μm.

[0068] Although the optical layer 200 has been described and shown as having the functional pattern 204 and the auxiliary pattern 206 imprinted on a single side (eg, the upper side 208) of the substrate 202, other configurations are possible. Fig.12A side view of an optical layer 700 is shown, which includes a substrate 202 and a functional pattern 204 of the optical layer 200 imprinted on top of an upper side 208 of the substrate 202, and an auxiliary pattern 706 imprinted on a lower side 214 of the substrate 202. The auxiliary pattern 706 is substantially similar to the auxiliary pattern 206 in structure and function, except that the auxiliary pattern 706 has a size and shape different from that of the auxiliary pattern 206. For example, the auxiliary pattern 706 includes an anti-reflective feature 710 located opposite the functional pattern 204 and spanning a width greater than the total width of the span of the anti-reflective features 210 of the auxiliary pattern 206. The auxiliary pattern 706 also includes spacers 712 located on opposite sides of the anti-reflective feature 710. Since the functional pattern 204 and the auxiliary pattern 706 are located on opposite sides of the substrate 202, the functional pattern 204 and the auxiliary pattern 706 are patterned on the substrate 202 in separate imprinting processes, as opposed to being patterned in a single imprinting process in the case of the optical layer 200. Thus, a patterning mold having fine features and deep features corresponding to the configuration of auxiliary pattern 706 can be created for forming auxiliary pattern 706 in a manner similar to that described above with respect to patterning mold 600. A separate patterning mold having fine features corresponding to the configuration of functional pattern 204 can be created for forming functional pattern 204.

[0069] In another example, Fig.13 A side view of an optical layer 800 is shown, which includes a substrate 202 and a functional pattern 204 of the optical layer 200 imprinted on top of an upper surface 208 of the substrate 202, as well as a first auxiliary pattern 806 imprinted on top of the upper surface 208 of the substrate 202 and a second auxiliary pattern 860 imprinted on the lower surface 214 of the substrate 202. For example, the first auxiliary pattern 806 includes spacers 812 located on opposite sides of the functional pattern 204. The second auxiliary pattern 860 includes an anti-reflective feature 810 positioned opposite to the functional pattern 204. Therefore, a patterned mold having fine features and deep features corresponding to the configurations of the functional pattern 204 and the first auxiliary pattern 806 can be created in a single imprinting process in a manner similar to that described above with respect to the patterned mold 600 for forming the functional pattern 204 and the first auxiliary pattern 806. A separate patterned mold having fine features corresponding to the configuration of the second auxiliary pattern 860 can be created for forming the second auxiliary pattern 860. Since the functional pattern 204 and the first auxiliary pattern 706 are located on the surface of the substrate opposite to the surface of the substrate 202 on which the second auxiliary pattern 860 is located, the functional pattern 204 and the first auxiliary pattern 806 are patterned together on the substrate 202 in one imprinting process, and the second auxiliary pattern 860 is patterned on the substrate 202 in another imprinting process.

[0070] Fig.14 A flow chart of an exemplary process 900 for configuring an optical layer (e.g., optical layer 200, 300, 400) in an imprint lithography process is shown. A first feature having a size of a first order of magnitude is imprinted on a first side (e.g., upper side 208 or lower side 214) of a substrate (e.g., substrate 202) using a patterned template (e.g., patterned mold 600) (902). The first feature may include one or both of a diffraction grating (e.g., a diffraction grating provided by functional pattern 204) and an anti-reflection feature (e.g., an anti-reflection feature provided by auxiliary pattern 206, 306, 406). While the first feature is imprinted on the first side of the substrate using the patterned template, a second feature having a size of a second order of magnitude is imprinted on the first side of the substrate using the patterned template, wherein the second feature size is determined and arranged to define a gap (e.g., gap 530) between the substrate and an adjacent surface (e.g., an adjacent side of the substrate) (904). The second feature may include a spacer (e.g., a spacer provided by auxiliary pattern 206, 306, 406). In some examples, one or both of the spacer and the anti-reflective feature are embossed along a peripheral edge of the first face of the substrate (e.g., peripheral edge 216). In some examples, one or both of the spacer and the anti-reflective feature are embossed along an interior region of the first face of the substrate (e.g., interior region 218). In some examples, the second feature is embossed on opposite sides of (e.g., around) the first feature.

[0071] The second order of magnitude dimension is greater than the first order of magnitude dimension. In some examples, the first order of magnitude dimension is nanometer-scale and the second order of magnitude dimension is micrometer-scale. In some embodiments, the process further includes imprinting a third feature having the first order of magnitude dimension on a second side (e.g., upper side 208 or lower side 214) of the substrate. The third feature may include a diffraction grating or an anti-reflective feature.

[0072] In some embodiments, the process further includes creating a patterned template from a precursor mold (e.g., precursor mold 642). In some embodiments, the process further includes forming deep features (e.g., deep features 646) having dimensions of the second order of magnitude in the precursor mold. In some embodiments, the process further includes forming shallow features (e.g., shallow features 644) having dimensions of the first order of magnitude in the precursor mold.

[0073] In some examples, the substrate is a first substrate and the adjacent surface is defined by a second substrate. In some embodiments, the process also includes aligning the first and second substrates to each other. In some embodiments, the process also includes dispensing an adhesive substance (e.g., a drop of glue) on top of a second feature imprinted on the first side of the first substrate. In some embodiments, the process also includes attaching the first and second substrates to each other at an adhesive substance on top of the second feature imprinted on the first side of the first substrate to form a multilayer optical device (e.g., optical device 500). In some embodiments, the process also includes attaching the first and second substrates to each other at an adhesive substance on top of the second feature imprinted on the first side of the first substrate to form a gap between the first substrate and the adjacent surface defined by the second substrate. In some embodiments, the process also includes defining an air layer between the first and second substrates, the thickness of which is determined by the height of the second feature, so that the multilayer optical device has an alternating refractive index.

[0074] Advantageously, process 600 can be used to imprint multifunctional (e.g., any of functional, anti-reflective, and spacer) 3D structures in a single process step (e.g., by a single patterned mold) under ambient conditions (e.g., ambient temperature and ambient pressure), which reduces the complexity, duration, and cost associated with imprinting such 3D structures compared to producing 3D structures according to other processes. For example, conventionally formed anti-reflective patterns are deposited under vacuum and can be relatively expensive, with spacer components added in a separate subsequent process that can include imprinting large spacer structures, dispensing microspheres, or dispensing curable resist materials. Additional time and complexity are associated with cleaning and processing the anti-reflective pattern prior to performing such a second processing step.

[0075] Although many embodiments have been described for purposes of illustration, the foregoing description 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, modifications, and combinations within the scope of the following claims.

Claims

1. A multi-layer wearable eyepiece, include: A first optical layer, the first optical layer comprising: The first substrate, a first waveguide on a side of a first substrate, the first waveguide comprising: a functional pattern, wherein the functional pattern comprises a first feature having a size of a first order of magnitude at a first location, wherein the first feature comprises a first diffraction grating, the first diffraction grating being configured to project light of a first wavelength range and focus a virtual image at a first depth plane, wherein the first diffraction grating comprises a first incoupling grating and forms a first orthogonal pupil expansion region and a first exit pupil expansion region, and An auxiliary pattern surrounding the functional pattern, the auxiliary pattern comprising: additional first features having dimensions of said first order of magnitude, wherein said additional first features comprise anti-reflective features, and second features having dimensions of a second order of magnitude greater than the dimensions of the first order of magnitude at second locations laterally spaced from the first locations on the face of the first substrate, respectively; and a second optical layer attached to the second feature to define a gap having a size of the second order of magnitude between the first optical layer and the second optical layer, the second optical layer comprising: a second substrate, and A second waveguide comprising a second diffraction grating configured to project light of a second wavelength range and focus a virtual image at a second depth plane, wherein the second diffraction grating comprises a second incoupling grating and forms a second orthogonal pupil expansion region and a second exit pupil expansion region.

2. The multi-layer wearable eyepiece according to claim 1, in, The second features include spacers on the face of the first substrate.

3. The multi-layer wearable eyepiece according to claim 2, in, The spacers or the anti-reflective features or both are located at a peripheral edge of the face of the first substrate.

4. The multi-layer wearable eyepiece according to claim 2, in, The spacers or the anti-reflective features or both are located in an interior region of the face of the first substrate.

5. The multi-layer wearable eyepiece according to claim 1, in, A third feature having a dimension of a first order of magnitude is disposed on the second substrate.

6. The multi-layer wearable eyepiece according to claim 5, in, The third features include diffraction gratings or anti-reflective features located on the second substrate.

7. The multi-layer wearable eyepiece according to claim 1, in, The second order of magnitude dimension includes a height ranging from 1 μm to 50 μm, or a width ranging from 1 μm to 100 μm, or both.

8. The multi-layer wearable eyepiece according to claim 1, in, The first order of magnitude of dimensions includes a range up to 300 nm in height.

9. The multi-layer wearable eyepiece according to claim 1, in, The second feature is located on opposite sides of the first feature.

10. The multi-layer wearable eyepiece of claim 1, further comprising an adhesive substance on top of the second features on the face of the first substrate.

11. The multi-layer wearable eyepiece according to claim 10, in, The first optical layer and the second optical layer are attached to each other at an adhesive substance on top of the second features on the face of the first substrate to form the gap between the first optical layer and the second optical layer.

12. The multi-layer wearable eyepiece of claim 1, in, The first waveguide and the second waveguide are aligned with each other.

13. The multi-layer wearable eyepiece of claim 1, in, The gap provides a low refractive index region having a low refractive index in the range of 1.0 to 1.

2.

14. The multi-layer wearable eyepiece of claim 13, in, The low refractive index region includes air having a refractive index of 1.

15. The multi-layer wearable eyepiece of claim 1, in, Each second feature is laterally spaced apart from each first feature by 5 μm to 100 μm.

16. The multi-layer wearable eyepiece of claim 1, in, The first and second optical layers are attached to each other with a seal along peripheral edges of the first and second optical layers.

17. The multi-layer wearable eyepiece of claim 1, in, At least one of the first wavelength range and the second wavelength range corresponds to red light having a wavelength in the range of 560 nm to 640 nm, green light having a wavelength in the range of 490 nm to 570 nm, or blue light having a wavelength in the range of 390 nm to 470 nm.

18. The multi-layer wearable eyepiece of claim 1, in, The first depth plane and the second depth plane are the same.

19. The multi-layer wearable eyepiece of claim 1, in, The second features are laterally spaced apart from the additional first features on the face of the first substrate.

20. The multi-layer wearable eyepiece of claim 19, in, The second features are located 5 μm to 100 μm from the additional first features.

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