Freeform optical substrates in waveguide displays

Abstract

To provide methods of forming a substrate having the same thickness distribution at one or more eyepiece areas across the substrate.SOLUTION: Embodiments of the present disclosure generally relate to methods of forming a substrate 100 having a target thickness distribution 116 at one or more eyepiece areas across the substrate 100. The substrate 100 includes eyepiece areas 101 corresponding to areas where optical device eyepieces are to be formed on the substrate. Each eyepiece area 101 includes a target thickness distribution 116. A base substrate thickness distribution of a base substrate 106 is measured such that a target thickness change can be determined. The methods described herein are utilized along with the target thickness change to form a substrate with the target thickness distribution 116.SELECTED DRAWING: Figure 1B

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to optical devices. More particularly, embodiments described herein provide for forming a substrate having a uniform thickness distribution across the substrate at one or more eyepiece areas. [Background technology]

[0002] Virtual reality is generally thought of as a computer-generated simulated environment in which a user has an apparent physical presence. Virtual reality experiences are generated in 3D and may be viewed with a head-mounted display (HMD), such as glasses or other wearable display devices, that have near-eye display panels as optical devices eyepieces to display a virtual reality environment that replaces the real environment.

[0003] Augmented reality, however, allows for an experience in which a user can still look through the optical eyepieces of glasses or other HMD devices to view the surrounding environment, and can also see images of virtual objects that are generated for display and appear as part of the environment. Augmented reality can include any type of input, such as voice input or tactile input, as well as virtual images, graphics, and video that enhance or augment the environment the user experiences. As an emerging technology, there are many challenges and design constraints associated with augmented reality.

[0004] One such challenge is having a consistent thickness distribution in one or more areas across the substrate. It is difficult to predict the thickness distribution in each eyepiece area, and therefore, the thickness distribution in each eyepiece area cannot be compensated for in advance, resulting in uncontrolled sources of variation. Optical device eyepieces modeled and optimized under the assumption of a constant thickness distribution typically behave differently when the thickness distribution changes, resulting in performance issues. For example, unknown thickness distributions in each eyepiece area can result in poor optical efficiency and poor brightness and color uniformity across the field of view of the substrate or the optical device eyepiece formed thereon. Therefore, there is a need in the art for a method for forming a substrate having a consistent thickness distribution in one or more eyepiece areas across the substrate. Summary of the Invention

[0005] In one embodiment, a method is provided. The method includes measuring a base substrate thickness distribution across the base substrate. The method further includes determining a target thickness change. The target thickness change is determined by subtracting the base substrate thickness distribution from the target thickness distribution. The target thickness distribution corresponds to a thickness across one or more eyepiece areas of the substrate to be formed. The method further includes forming a substrate having the target thickness distribution at the one or more eyepiece areas.

[0006] In another embodiment, a method is provided. The method includes planarizing a base substrate having a base substrate thickness distribution. The method further includes determining a target thickness variation. The target thickness variation is determined by subtracting the base substrate thickness distribution from the target thickness distribution. The target thickness variation corresponds to a thickness across one or more eyepiece areas of the substrate to be formed. The method further includes forming a substrate having the target thickness distribution at the one or more eyepiece areas.

[0007] In yet another embodiment, a substrate is provided. The substrate includes a plurality of inactive areas. The substrate further includes a plurality of ocular areas disposed between the plurality of inactive areas. Each ocular area defines an area of ​​the substrate on which an optical device ocular is formed. Each of the plurality of ocular areas has a target thickness distribution across the ocular area. The target thickness distribution is defined by the distance between the top surface and the bottom surface of the substrate in the ocular area.

[0008] So that the above-recited features of the present disclosure can be understood in detail, a more particular description of the present disclosure briefly summarized above can be had by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only exemplary embodiments and therefore should not be considered limiting in scope, as other equally effective embodiments may be recognized. [Brief explanation of the drawings]

[0009] [Figure 1A] 1 is a schematic top view of a substrate according to an embodiment. [Figure 1B] 1 is a schematic cross-sectional view of a substrate having a target thickness distribution, according to an embodiment. [Figure 1C] 1 is a schematic cross-sectional view of a substrate having a target thickness distribution, according to an embodiment. [Figure 1D] 1 is a schematic cross-sectional view of a substrate having a target thickness distribution, according to an embodiment. [Figure 1E] 1 is a schematic cross-sectional view of a substrate having a target thickness distribution, according to an embodiment. [Figure 2] 4 is a flow diagram of a method for forming a substrate having a target thickness distribution as shown in FIGS. 3A-3D, according to an embodiment. [Figure 3A] 1 is a schematic cross-sectional view of an eyepiece area according to an embodiment. [Figure 3B] 1 is a schematic cross-sectional view of an eyepiece area according to an embodiment. [Figure 3C]1 is a schematic cross-sectional view of an eyepiece area according to an embodiment. [Figure 3D] 1 is a schematic cross-sectional view of an eyepiece area according to an embodiment. [Figure 4] 5A-5D are flow diagrams of sub-methods for forming a substrate having a target thickness distribution as shown in FIGS. 5A-5D, according to an embodiment. [Figure 5A] 5A-5C are schematic cross-sectional views of a base substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 5B] 5A-5C are schematic cross-sectional views of a base substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 5C] 5A-5C are schematic cross-sectional views of a base substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 5D] 5A-5C are schematic cross-sectional views of a base substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 6] 7C is a flowchart of a sub-method method for forming a substrate having a target thickness distribution as shown in FIGS. 7A and 7B, according to an embodiment. [Figure 7A] 5A-5C are schematic cross-sectional views of a base substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 7B] 5A-5C are schematic cross-sectional views of a base substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 8] 9A-9D is a flow diagram of a method for forming a substrate having a target thickness distribution as shown in FIGS. 9A-9D, according to an embodiment. [Figure 9A] 1 is a schematic cross-sectional view of an eyepiece area according to an embodiment. [Figure 9B] 1 is a schematic cross-sectional view of an eyepiece area according to an embodiment. [Figure 9C] 1 is a schematic cross-sectional view of an eyepiece area according to an embodiment. [Figure 9D] 1 is a schematic cross-sectional view of an eyepiece area according to an embodiment. [Figure 10A] 5A-5C are schematic cross-sectional views of a substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 10B] 5A-5C are schematic cross-sectional views of a substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 10C] 5A-5C are schematic cross-sectional views of a substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 10D] 5A-5C are schematic cross-sectional views of a substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 11A] 5A-5C are schematic cross-sectional views of a substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 11B] 5A-5C are schematic cross-sectional views of a substrate during sub-methods for forming a substrate having a target thickness distribution, according to an embodiment. [Figure 12A] 1 is a schematic cross-sectional view of an optical device eyepiece according to an embodiment. [Figure 12B] 1 is a schematic cross-sectional view of an optical device eyepiece according to an embodiment. [Figure 12C] 1 is a schematic cross-sectional view of an optical device eyepiece according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] For ease of understanding, the same reference numerals have been used where possible to indicate identical elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated into other embodiments without further description.

[0011] Embodiments described herein relate to a method for forming a substrate having a uniform thickness distribution at one or more eyepiece areas across the substrate. The method includes measuring a base substrate thickness distribution across the base substrate or planarizing a base substrate having a base substrate thickness distribution. The method further includes determining a target thickness variation. The target thickness variation is determined by subtracting the base substrate thickness distribution from the target thickness distribution. The target thickness distribution corresponds to a thickness across one or more eyepiece areas of the substrate to be formed. The method further includes forming a substrate having a target thickness distribution at one or more eyepiece areas. The substrate includes a plurality of inactive areas. The substrate further includes a plurality of eyepiece areas disposed between the plurality of inactive areas. Each eyepiece area defines an area of ​​the substrate on which an optical device eyepiece is formed. Each of the plurality of eyepiece areas has a target thickness distribution across the eyepiece area. The target thickness distribution is defined by the distance between the top and bottom surfaces of the substrate at the eyepiece area.

[0012] FIG. 1A is a schematic top view of substrate 100. Substrate 100 includes a plurality of eyepiece areas 101. Eyepiece area 101 is an area on substrate 100 where one of optical device eyepieces 1200A-1200C (shown in FIGS. 12A-12C) is to be formed. Although only nine of eyepiece areas 101 are shown in FIG. 1A, substrate 100 is not limited in the number of eyepiece areas 101 corresponding to the number of optical device eyepieces 1200A-1200C to be formed thereon.

[0013] 1B-1E are schematic cross-sectional views of substrate 100 having target thickness distribution 116. Substrate 100 includes eyepiece areas 101 disposed across substrate 100. Inactive areas 104 are disposed between eyepiece areas 101. Inactive areas 104 are areas of substrate 100 that do not have one of optical device eyepieces 1200A-1200C formed thereon. Substrate 100 includes a top surface 110 and a bottom surface 111.

[0014] Substrate 100 includes a base substrate 106. In some embodiments, which may be combined with other embodiments described herein, as shown in Figures 1C and 1E, an index-matching layer 108 is disposed on base substrate 106. Index-matching layer 108 has a refractive index that matches or nearly matches the refractive index of base substrate 106. Base substrate 106 includes a top surface 102 and a bottom surface 111.

[0015] The base substrate 106 and the index-matching layer 108 may be formed from any suitable material, provided that the substrate 100 can sufficiently transmit light at or within the desired wavelength or wavelength range and can serve as sufficient support for the optical device eyepieces 1200A-1200C (shown in FIGS. 12A-12C). The base substrate 106 and / or the index-matching layer 108 may be made of materials including, but not limited to, amorphous dielectrics, non-amorphous dielectrics, crystalline dielectrics, silicon oxides, polymers, and combinations thereof. In some embodiments, which may be combined with other embodiments described herein, the base substrate 106 and / or the index-matching layer 108 comprise a transparent material. By way of example, the base substrate 106 and / or the index matching layer 108 may include silicon (Si), silicon dioxide (SiO2), fused silica, quartz, silicon carbide (SiC), germanium (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), sapphire, or a combination thereof.

[0016] At least the eyepiece area 101 of the substrate 100 includes a target thickness distribution 116. The target thickness distribution 116 is a local thickness distribution determined to be replicated in each of the eyepiece areas 101. The target thickness distribution 116 is defined by the distance between the top surface 110 and the bottom surface 111 of the substrate 100 across the eyepiece area 101. The target thickness distribution 116 can be any linear or non-linear distribution.

[0017] 1B and 1C show a target thickness distribution 116 formed within the eyepiece area 101. The inactive areas 104 of the substrate 100 have an inactive thickness distribution 120, i.e., the inactive thickness distribution 120 does not match the target thickness distribution 116. The inactive thickness distribution 120 is defined by the distance between the top surface 110 and the bottom surface 111 across the inactive areas 104. As shown in FIG. 1B, the target thickness distribution 116 is formed from the base substrate 106 of the substrate 100 at each eyepiece area 101. As shown in FIG. 1C, the target thickness distribution 116 is formed from the index matching layer 108 of the substrate 100 at each eyepiece area 101.

[0018] 1D and 1E show target thickness distributions 116 formed in the eyepiece areas 101 and inactive areas 104. Thus, target thickness distributions 116 are identical in the eyepiece areas 101 and inactive areas 104. As shown in FIG. 1D, target thickness distributions 116 are formed from base substrate 106 of substrate 100 in each eyepiece area 101 and each inactive area 104. As shown in FIG. 1E, target thickness distributions 116 are formed from index matching layer 108 of substrate 100 in each eyepiece area 101 and each inactive area 104.

[0019] The target thickness distribution 116 is designed to improve the performance of the optical device eyepieces 1200A-1200C to be formed thereon. The target thickness distribution 116 is the same within at least each eyepiece area 101 of the substrate 100. The methods described herein achieve the target thickness distribution 116 in at least each eyepiece area 101. The target thickness distribution 116 is not limited to the target thickness distribution 116 shown in Figures 1B-1E, but can be any thickness distribution determined to be suitable and to improve the performance of the optical device eyepieces 1200A-1200C.

[0020] Although Figures 1B-1D show a base substrate 106 in which the distance between the bottom surface 111 and the top surface 102 of the base substrate 106 varies across the base substrate 106, in another embodiment that may be combined with other embodiments described herein, the base substrate 106 is planar, and therefore, as shown in Figure 1E, the distance between the bottom surface 111 and the top surface 102 of the base substrate 106 is constant across the base substrate 106.

[0021] Figure 2 is a flow diagram of a method 200 for forming a substrate 100 having a target thickness distribution 116 as shown in Figures 3A-3D. Method 200 can be used to form the target thickness distribution 116 in the eyepiece area 101 and / or inactive area 104 (shown in Figures 1B-1E) of substrate 100. Figures 3A-3D are schematic cross-sectional views of eyepiece area 101. While Figures 3A-3D correspond to eyepiece area 101, Figures 3A-3D are not limited to eyepiece area 101 and can also correspond to inactive area 104 where target thickness distribution 116 is to be formed.

[0022] 3A, a base substrate thickness distribution 212 of the base substrate 106 is measured. The base substrate thickness distribution 212 is defined by the distance between the bottom surface 111 and the top surface 102 of the base substrate 106 across the eyepiece area 101. The base substrate thickness distribution 212 is the measured thickness distribution of the base substrate 106 before forming the target thickness distribution 116.

[0023] In operation 202, a target thickness change is determined, which is the thickness change required to form the target thickness distribution 116 from the base substrate thickness distribution 212. The target thickness distribution 116 is determined using the following equation: ΔT=T target -T measured +C In the above equation, ΔT is the target thickness change, and T target is the target thickness distribution 116 (shown in FIGS. 1B-1E), and T measuredis the base substrate thickness distribution 212 found in operation 201, and C is a global shift constant corresponding to the position on the base substrate 106. In one embodiment, which may be combined with other embodiments described herein, the global shift constant is zero.

[0024] 3B, an index-matching layer 108 is disposed on the base substrate 106. The index-matching layer 108 may be disposed on the top surface 102 of the base substrate 106 by one or more PVD, CVD, PECVD, FCVD, ALD, or spin-on coating processes. The index-matching layer 108 has a refractive index that matches or nearly matches the refractive index of the base substrate 106.

[0025] In optional operation 204, one of sub-method 400 or sub-method 600 is performed. FIG. 4 is a flow diagram of sub-method 400 for forming a substrate 100 having a target thickness distribution 116 as shown in FIGS. 5A-5D. FIGS. 5A-5D are schematic cross-sectional views of a base substrate 106 during sub-method 400 for forming a substrate 100 having a target thickness distribution 116. In operation 401, as shown in FIGS. 5A and 5B, a resist 502 is disposed. FIG. 5A shows the resist 502 disposed on the base substrate 106. FIG. 5B shows the resist 502 disposed on the index-matching layer 108. The material of the resist 502 may include, but is not limited to, a photosensitive polymer-containing material. The resist 502 may be disposed by one or more of PVD, CVD, PECVD, FCVD, ALD, and spin-on processes.

[0026] In operation 402, as shown in Figures 5C and 5D, resist 502 is developed. Resist 502 is developed using a lithography process. In one embodiment, which may be combined with other embodiments described herein, the lithography process is a gray-tone lithography process. The lithography process forms a gray-tone distribution 504 in resist 502. The gray-tone lithography process may include photolithography or digital lithography. Gray-tone distribution 504 has a thickness distribution 506 that corresponds to the target thickness distribution 116 of substrate 100 to be formed. Figure 5C shows resist 502 developed on base substrate 106. Figure 5D shows resist 502 developed on index-matching layer 108.

[0027] FIG. 6 is a flow diagram of a sub-method 600 for forming a substrate 100 having a target thickness distribution 116 as shown in FIGS. 7A and 7B. FIGS. 7A-7B are schematic cross-sectional views of a base substrate 106 during the sub-method 600 for forming a substrate 100 having a target thickness distribution 116. In operation 601, a resist 702 is disposed. The material of the resist 702 may include, but is not limited to, a photosensitive polymer-containing material. The resist 702 may be disposed by an inkjet printing process to achieve a thickness distribution 704 corresponding to the target thickness distribution 116 to be formed. FIG. 7A shows the resist 702 disposed on the base substrate 106. FIG. 7B shows the resist 702 disposed on an index-matching layer 108.

[0028] In operation 205, a substrate 100 having a target thickness distribution 116 is formed, as shown in FIGS. 3C and 3D. The target thickness variation is used to determine the variation to the base substrate thickness distribution 212 required to form the target thickness distribution 116. By determining the target thickness variation, the process of operation 205 can be adjusted accordingly to form the target thickness distribution 116 as desired. FIG. 3C shows the target thickness distribution 116 formed in the base substrate 106 of the substrate 100. The substrate 100 in FIG. 3C corresponds to the eyepiece area 101 shown in FIG. 1B. The substrate 100 in FIG. 3C also corresponds to the eyepiece area 101 and the inactive area 104 shown in FIG. 1D. FIG. 3D shows the target thickness distribution 116 formed in the index-matching layer 108 of the substrate 100. The substrate 100 in FIG. 3D corresponds to the eyepiece area 101 shown in FIG. 1C.

[0029] In one embodiment, when sub-method 400 or sub-method 600 is performed, a target thickness variation is used to form target thickness distribution 116 by performing a transfer etch. The transfer etch may include at least one of, but is not limited to, ion implantation, ion beam etching (IBE), reactive ion etching (RIE), directional RIE, plasma etching, and thermal atomic layer etching. The transfer etch produces target thickness distribution 116 corresponding to thickness distribution 506 of sub-method 400 or thickness distribution 704 of sub-method 600. Any remaining portions of resist 502 or resist 702 disposed on substrate 100 are removed.

[0030] In another embodiment, which may be combined with other embodiments described herein, when sub-methods 400 and 600 are not used, index-matching layer 108 may be disposed on base substrate 106 such that index-matching layer 108 compensates for target thickness variations and forms target thickness profile 116 of substrate 100. Index-matching layer 108 may be disposed to achieve target thickness profile 116 by an inkjet printing process.

[0031] In yet another embodiment that may be combined with other embodiments described herein, when submethod 400 and submethod 600 are not used, a substrate 100 having a target thickness distribution 116 may be formed with a distributed etching process. The distributed etching process may include at least one of, but is not limited to, ion implantation, ion beam etching (IBE), reactive ion etching (RIE), directional RIE, plasma etching, and thermal atomic layer etching. The distributed etching process may directly etch the base substrate 106 or the index-matching layer 108 to compensate for the target thickness variation and form a substrate 100 having a target thickness distribution 116. In one embodiment that may be combined with other embodiments described herein, the base substrate 106 may be angled and rotated so that the distributed etching process can form the target thickness distribution 116. Furthermore, when the index-matching layer 108 is disposed on the upper surface 102 of the base substrate 106, the distributed etching process may directly etch the index-matching layer 108 to form a substrate 100 having a target thickness distribution 116.

[0032] 3C and 3D is a result of using the target thickness variation of method 200. Target thickness distribution 116 can be formed at each eyepiece area 101. Thus, the target thickness distribution 116 across substrate 100 at each eyepiece area 101 is identical. Each eyepiece area 101 with target thickness distribution 116 allows for reduced variability in the optical device eyepieces 1200A-1200C to be formed thereon.

[0033] Figure 8 is a flow diagram of a method for forming a substrate 100 having a target thickness distribution 116 as shown in Figures 9A-9D. Method 800 can be used to form the target thickness distribution 116 in the eyepiece area 101 and / or inactive area 104 of substrate 100. Figures 9A-9D are schematic cross-sectional views of the eyepiece area 101. Although Figures 9A-9D correspond to the eyepiece area 101, Figures 9A-9D are not limited to the eyepiece area 101, but can also correspond to the inactive area 104 where the target thickness distribution 116 is to be formed.

[0034] In operation 801, the base substrate 106 is planarized, as shown in FIG. 9A. The base substrate thickness distribution 212 is known across the base substrate 106 because it is constant or nearly constant. The base substrate thickness distribution 212 is defined by the distance between the bottom surface 111 and the top surface 102 of the base substrate 106 across the eyepiece area 101. The base substrate thickness distribution 212 is the measured thickness distribution of the base substrate 106 before forming the target thickness distribution 116.

[0035] In operation 802, a target thickness change is determined. The target thickness change is the thickness change required to form the target thickness distribution 116 from the base substrate thickness distribution 212. The target thickness change is determined using the following equation: ΔT=T target -T measured +C In the above equation, ΔT is the target thickness change, and T target is the target thickness distribution 116 (shown in FIGS. 1B-1E), and T measured is the base substrate thickness distribution 212 found in operation 801, and C is the global shift corresponding to the position on the base substrate 106. In one embodiment, which may be combined with other embodiments described herein, the global shift constant is zero.

[0036] 10B, the index-matching layer 108 is disposed on the base substrate 106. The index-matching layer 108 may be disposed on the top surface 102 of the base substrate 106 by one or more of PVD, CVD, PECVD, FCVD, ALD, and spin-on processes. In one embodiment, which may be combined with other embodiments described herein, the index-matching layer 108 has a refractive index that matches or nearly matches the refractive index of the base substrate 106.

[0037] In optional operation 804, one of the aforementioned sub-methods 400 or 600 is performed. FIGS. 10A-10D are schematic cross-sectional views of a base substrate 106 during sub-method 400 for forming a substrate 100 having a target thickness distribution 116. In operation 401, a resist 1002 is disposed, as shown in FIGS. 10A and 10B. FIG. 10A shows the resist 1002 disposed on the base substrate 106. FIG. 10B shows the resist 1002 disposed on the index-matching layer 108. The resist 1002 material may include, but is not limited to, a photosensitive polymer-containing material. The resist 1002 may be disposed by one or more of PVD, CVD, PECVD, FCVD, ALD, and spin-on processes.

[0038] In operation 402, as shown in FIGS. 10C and 10D, the resist 1002 is developed. The resist 1002 is developed using a lithography process. In one embodiment, which may be combined with other embodiments described herein, the lithography process is a gray-tone lithography process. The lithography process forms a gray-tone distribution 1004 in the resist 1002. Developing the resist 1002 may include performing a lithography process, such as photolithography or digital lithography. The gray-tone distribution 1004 has a thickness distribution 1006 that corresponds to the target thickness distribution 116 to be formed in the substrate 100. FIG. 10C shows the resist 1002 developed on the base substrate 106. FIG. 10D shows the resist 1002 developed on the index-matching layer 108.

[0039] 11A-11B are schematic cross-sectional views of a base substrate 106 during a sub-method 600 for forming a substrate having a target thickness distribution 116. In operation 601, a resist 1102 is disposed. The material of the resist 1102 may include, but is not limited to, a photosensitive polymer-containing material. The resist 1102 may be disposed by an inkjet printing process to achieve a thickness distribution 1104 corresponding to the target thickness distribution 116 to be formed in the substrate 100. FIG. 11A shows the resist 1102 disposed on the base substrate 106. FIG. 11B shows the resist 1102 disposed on an index-matching layer 108.

[0040] In operation 805, a substrate 100 having a target thickness distribution 116 is formed, as shown in FIGS. 9C and 9D. The target thickness variation is used to determine the variation to the base substrate thickness distribution 212 required to form the target thickness distribution 116. By determining the target thickness variation, the process of operation 805 can be adjusted accordingly to form the target thickness distribution 116 as desired. FIG. 9C shows the target thickness distribution 116 formed in the base substrate 106 of the substrate 100. The substrate 100 in FIG. 9C corresponds to the eyepiece area 101 shown in FIG. 1B. The substrate 100 in FIG. 9C corresponds to the eyepiece area 101 and the inactive area 104 shown in FIG. 1D. FIG. 9D shows the target thickness distribution 116 formed in the index-matching layer 108 of the substrate 100. The substrate 100 in FIG. 9D corresponds to the eyepiece area 101 and the inactive area 104 shown in FIG. 1E.

[0041] In one embodiment, when sub-method 400 or sub-method 600 is performed, target thickness distribution 116 is formed by performing transfer etching. Transfer etching may include at least one of, but is not limited to, ion implantation, ion beam etching (IBE), reactive ion etching (RIE), directional RIE, plasma etching, and thermal atomic layer etching. Transfer etching produces target thickness distribution 116 corresponding to thickness distribution 1006 of sub-method 400 or thickness distribution 1104 of sub-method 600. Any remaining portions of resist 1002 or resist 1102 disposed on substrate 100 are removed.

[0042] In another embodiment, which may be combined with other embodiments described herein, when sub-method 400 and sub-method 600 are not used, the index-matching layer 108 may be disposed on the base substrate 106 such that the index-matching layer 108 compensates for the target thickness variation and forms the substrate 100 having the target thickness distribution 116. The index-matching layer 108 may be disposed to achieve the target thickness distribution 116 by an inkjet printing process. A mask may be used during the inkjet printing process to deposit the index-matching layer 108 on the substrate 100.

[0043] In yet another embodiment that may be combined with other embodiments described herein, when submethod 400 and submethod 600 are not used, a substrate 100 having a target thickness distribution 116 may be formed with a distributed etching process. The distributed etching process may include, but is not limited to, at least one of ion implantation, ion beam etching (IBE), reactive ion etching (RIE), directional RIE, plasma etching, and thermal atomic layer etching. The distributed etching process may directly etch the base substrate 106 or the index-matching layer 108 to compensate for the target thickness variation and form a substrate 100 having the target thickness distribution 116. In one embodiment that may be combined with other embodiments described herein, the base substrate 106 may be angled and rotated so that the distributed etching process can form the target thickness distribution 116. Furthermore, when the index-matching layer 108 is disposed on the top surface 102 of the base substrate 106, the distributed etching process may directly etch the index-matching layer 108 to form the target thickness distribution 116.

[0044] 9C and 9D are the results of using the target thickness variation of method 800. Target thickness distribution 116 can be formed at each eyepiece area 101. Thus, the target thickness distribution 116 across substrate 100 at each eyepiece area 101 is identical. Each eyepiece area 101 with target thickness distribution 116 allows for reduced variability in optical device eyepieces 1200A-1200C to be formed thereon.

[0045] 12A-12C are schematic cross-sectional views of optical device eyepieces 1200A-1200C. Optical device eyepieces 1200A-1200C are formed in substrate 100. Optical device eyepieces 1200A-1200C include a plurality of optical device structures 1202. The plurality of optical device structures 1202 are formed in an eyepiece area 101 of the substrate. Eyepiece area 101 is the area of ​​substrate 100 in which optical device eyepieces 1200A-1200C are formed. Optical device eyepieces 1200A-1200C may be formed in substrate 100 following method 200 or method 800. In one embodiment, which may be combined with other embodiments described herein, optical device eyepieces 1200A-1200C may be formed from device material (not shown) disposed on top surface 110 of substrate 100. Each of the optical device eyepieces 1200A-1200C has a target thickness distribution 116. The target thickness distribution 116 can be any linear or non-linear distribution. The target thickness distribution 116 is the same for each of the eyepiece areas 101. A plurality of optical device structures 1202 are formed on the substrate 100 according to the target thickness distribution 116.

[0046] As shown in optical device lens 1200A of Figure 12A, a plurality of optical device structures 1202 are formed in base substrate 106 of substrate 100. As shown in optical device eyepieces 1200B and 1200C of Figures 12B and 12C, a plurality of optical device structures 1202 are formed in index matching layer 108 of substrate 100. In another embodiment, which may be combined with other embodiments described herein, a plurality of optical device structures 1202 are formed in both base substrate 106 and index matching layer 108. The plurality of optical device structures 1202 may be nanostructures having submicron dimensions, e.g., nano-sized dimensions.

[0047] In one embodiment that can be combined with other embodiments described herein, the optical device eyepieces 1200A-1200C are waveguide combiners, such as augmented reality waveguide combiners. In another embodiment that can be combined with other embodiments described herein, the optical device eyepieces 1200A-1200C are planar optical devices, such as metasurfaces. The plurality of optical device structures 1202 can correspond to input or output coupling gratings of the optical device eyepieces 1200A-1200C. The optical device eyepieces 1200A-1200C are not limited to the number of plurality of optical device structures 1202 shown in FIGS. 12A-12C. While the plurality of optical device structures 1202 shown in FIGS. 1A-1C are angled relative to the bottom surface 111 of the substrate 100, the plurality of optical device structures 1202 can be perpendicular to the bottom surface 111 of the substrate 100.

[0048] In summary, methods are described herein for forming a substrate having a target thickness distribution at one or more eyepiece areas across the substrate. The substrate includes eyepiece areas corresponding to areas where optical device eyepieces are to be formed on the substrate. Each eyepiece area includes a target thickness distribution for the substrate. The target thickness distribution is formed at each eyepiece area using the methods described herein. The base substrate thickness distribution of the base substrate is measured so that the target thickness variation can be determined. The methods described herein are used in conjunction with the target thickness variation to form a substrate having the target thickness distribution. The identical or nearly identical target thickness distribution at each eyepiece area achieves reduced variation between each optical device lens formed at each eyepiece area. Furthermore, the target thickness distribution can be designed in a manner beneficial to the performance of the optical device eyepiece. Forming the target thickness distribution does not require precise control of the thickness gradient of the substrate, such as by a precision polishing process, prior to performing the methods described herein. Therefore, material costs associated with precision polishing processes are reduced.

[0049] While the foregoing is directed to embodiments of the present disclosure, other embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the claims that follow.

Claims

1. measuring a base substrate thickness distribution across the base substrate; determining a target thickness variation, the target thickness variation being determined by subtracting the base substrate thickness distribution from a target thickness distribution, the target thickness distribution corresponding to a thickness across one or more eyepiece areas of a substrate to be formed; forming a substrate having the target thickness distribution at the one or more eyepiece areas; A method comprising:

2. 10. The method of claim 1, wherein forming the substrate with the target thickness distribution comprises disposing a resist on the base substrate and developing the resist using a lithography process to form a graytone distribution having a thickness distribution corresponding to the target thickness distribution.

3. 3. The method of claim 2, wherein forming the substrate with the target thickness distribution comprises performing a transfer etch in the substrate, the transfer etch forming a target thickness distribution in the substrate that corresponds to the thickness distribution of the graytone distribution.

4. The method of claim 1 , further comprising disposing an index-matching layer over the base substrate.

5. The method of claim 4 , wherein forming the substrate with the target thickness distribution comprises disposing the index matching layer with an inkjet printing process, wherein the index matching layer has the target thickness distribution.

6. The method of claim 4 , wherein forming the substrate with the target thickness profile comprises etching the index-matching layer or the base substrate to form the target thickness profile in the substrate.

7. 10. The method of claim 1, further comprising forming an optical device eyepiece at each of the eyepiece areas, the optical device eyepiece having the target thickness distribution at each of the eyepiece areas, and the optical device eyepiece including a plurality of optical device structures.

8. 10. The method of claim 1, wherein forming the substrate with the target thickness distribution comprises: disposing a resist on the base substrate in an inkjet printing process, the resist having a thickness distribution corresponding to the target thickness distribution; and performing a transfer etch in the substrate, the transfer etch forming the target thickness distribution in the substrate.

9. The method of claim 1 , wherein the target thickness variation determines a change to the base substrate thickness distribution to form the target thickness distribution.

10. planarizing a base substrate having a base substrate thickness distribution; determining a target thickness variation, the target thickness variation being determined by subtracting the base substrate thickness distribution from a target thickness distribution, the target thickness distribution corresponding to a thickness across one or more eyepiece areas of a substrate to be formed; forming a substrate having the target thickness distribution at the one or more eyepiece areas; A method comprising:

11. 11. The method of claim 10, wherein forming the substrate with the target thickness distribution comprises disposing a resist on the base substrate and developing the resist using a lithography process to form a graytone distribution having a thickness distribution corresponding to the target thickness distribution.

12. 12. The method of claim 11 , wherein forming the substrate with the target thickness distribution comprises performing a transfer etch in the substrate, the transfer etch forming a target thickness distribution in the substrate that corresponds to the thickness distribution of the graytone distribution.

13. The method of claim 10 further comprising disposing an index-matching layer over the base substrate.

14. 14. The method of claim 13, wherein forming the substrate with the target thickness distribution comprises disposing the index matching layer with an inkjet printing process, the index matching layer having the target thickness distribution.

15. 14. The method of claim 13, wherein forming the substrate with the target thickness profile comprises etching the index-matching layer or the base substrate to form the target thickness profile in the substrate.

16. 11. The method of claim 10, wherein forming the substrate with the target thickness distribution comprises: disposing a resist on the base substrate in an inkjet printing process, the resist having a thickness distribution corresponding to the target thickness distribution; and performing a transfer etch in the substrate, the transfer etch forming the target thickness distribution in the substrate.

17. The method of claim 10 , wherein the target thickness variation determines a change to the base substrate thickness distribution to form the target thickness distribution.

18. a plurality of inactive areas; a plurality of eyepiece areas disposed between the plurality of inactive areas, each eyepiece area defining an area of ​​the substrate on which an optical device eyepiece is formed, each of the plurality of eyepiece areas comprising: a target thickness distribution across the eyepiece area, the target thickness distribution being defined by the distance between the top and bottom surfaces of the substrate in the eyepiece area; a plurality of eyepiece areas, each having a A substrate comprising:

19. The substrate of claim 18 , wherein the target thickness distribution is formed by the plurality of eyepiece areas and the plurality of inactive areas.

20. 20. The substrate of claim 18, wherein the optical device eyepiece formed in each of the eyepiece areas includes a plurality of optical device structures corresponding to the target thickness distribution.

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