Methods of greytone imprint lithography to fabricate optical devices

Abstract

A method for imprinting a pattern on a substrate is provided. The method includes forming a first pattern on a plurality of master molds using a method other than imprinting, the first pattern including a plurality of patterned features of different sizes; measuring the patterned features at a plurality of positions on each master mold; selecting a first master mold from the plurality of master molds based on the measurements of the patterned features on each master mold; forming a second pattern on an imprinting template using the first master mold; and imprinting the first pattern on a first device using the imprinting template.

Description

Technical Field

[0001] The embodiments described herein generally relate to optical devices for augmented, virtual, and mixed reality. More specifically, the embodiments described herein provide a method for manufacturing optical devices via grayscale lithography. Prior Technology

[0002] Virtual reality is generally considered to be a computer-generated simulated environment in which the user has an apparent physical presence. Virtual reality experiences can be generated in three dimensions (3D) and used for viewing on head-mounted displays (HMDs), such as glasses or other wearable display devices with near-eye display panels (such as lenses), to display virtual reality environments that replace the real environment.

[0003] However, augmented reality (AR) enables users to see their surroundings through the display lenses of glasses or other HMD devices, or handheld devices, and to see images of virtual objects generated on the display and appearing as part of the environment. AR can include any type of input, such as audio and haptic input, as well as virtual images, graphics, and visual information about the environment that can enhance or augment the user experience. As an emerging technology, AR faces many challenges and design constraints.

[0004] One such challenge is displaying a virtual image superimposed on the surrounding environment. Optical devices are used to facilitate this image superposition. The generated light propagates through a waveguide until it exits the waveguide and superimposes on the surrounding environment. Fabricating optical devices can be challenging because they tend to exhibit non-uniform characteristics. Therefore, this art requires improved systems and methods for fabricating optical devices. Summary of the Invention

[0005] In some embodiments, a method for imprinting a pattern on a substrate is provided. The method includes forming a first pattern on a plurality of master molds using a method other than imprinting, the first pattern including a plurality of patterned features of different sizes; measuring the patterned features at a plurality of locations on each master mold; selecting a first master mold from the plurality of master molds based on the measurements of the patterned features on each master mold; forming a second pattern on an imprinting template using the first master mold; and imprinting the first pattern on a first device using the imprinting template. A method for imprinting a pattern on a substrate is also provided. The method includes forming a first pattern on a plurality of dies on each of a plurality of master molds using a method other than imprinting, the first pattern on each die including a plurality of patterned features of different sizes; measuring the patterned features at a plurality of locations on each die on each master mold; selecting a first die on a first master mold from the plurality of master molds based on the measurements of the patterned features on each die of each master mold; forming a second pattern on an imprinting template using the first die on the first master mold; and imprinting the first pattern on a first die on a first device using the imprinting template. A method for imprinting a pattern on a substrate is provided. The method includes forming a first pattern on a plurality of grains in each of a plurality of master molds using a method other than imprinting, the first pattern on each grain including a plurality of patterned features of different sizes; measuring the patterned features at a plurality of positions on each grain in each master mold; selecting a first grain on a first master mold from the plurality of master molds based on the measurements of the patterned features on each grain of each master mold; forming a second pattern on a first imprinting template using the first grain on the first master mold; imprinting the first pattern on each grain in a plurality of grains of a new master mold using the first imprinting template; forming the second pattern on each grain in a plurality of grains of a second imprinting template using the plurality of grains of the new master mold; and imprinting the first pattern onto a plurality of grains on a first device using the second imprinting template. Simple Explanation of the Diagram

[0006] A more specific description of the present invention, briefly summarized above, can be obtained by referring to the embodiments, some of which are illustrated in the accompanying drawings, in a manner that enables a detailed understanding of the aforementioned features of the present invention. However, it should be noted that the drawings illustrate exemplary embodiments only and are therefore not intended to limit the scope of the present invention, and other equally effective embodiments are permissible.

[0007] Figure 1 is a process flow diagram of a method for imprinting a pattern on an optical device shown in Figure 2I according to an embodiment.

[0008] Figures 2A through 2I illustrate different stages of the method for forming a pattern on the optical device shown in Figure 2I, which is shown in Figure 1.

[0009] Figure 3 is a process flow diagram of a method for imprinting a pattern on the optical device shown in Figure 4I according to one embodiment.

[0010] Figures 4A through 4I illustrate different stages of the method for forming a pattern on the optical device shown in Figure 4I, which is shown in Figure 3.

[0011] Figure 5 is a process flow diagram of a method for imprinting a pattern on the optical device shown in Figure 6H according to one embodiment.

[0012] Figures 6A through 6H illustrate different stages of the method for forming a pattern on the optical device shown in Figure 5.

[0013] Figure 7 is a process flow diagram of a method for imprinting a pattern on an optical device shown in Figure 8N according to one embodiment.

[0014] Figures 8A to 8N illustrate different stages of the method for forming a pattern on the optical device in Figure 7 in Figure 8N.

[0015] To facilitate understanding, the same element symbols have been used where possible to indicate the same elements shared by the figures. It is contemplated that elements and features of one embodiment may be advantageously incorporated into other embodiments without further description. Implementation

[0016] The embodiments described herein relate to a method for fabricating optical devices via grayscale imprinting. Grayscale imprinting differs from grayscale photolithography. As described in detail below, grayscale imprinting uses imprinting templates with patterned features of different sizes (e.g., structures with different depths and / or widths) to imprint corresponding patterned features onto an imprinting resist layer disposed on a substrate. The imprinting templates can be reused to form the same patterned features on many substrates, for example, during the fabrication of optical devices, such as during the formation of gratings for waveguide combiners used in augmented reality applications.

[0017] On the other hand, grayscale photolithography uses radiation (e.g., visible light, ultraviolet light, etc.) rather than imprinting to form patterned features of different sizes (e.g., structures with different depths and / or widths). For example, a grayscale mask can be used to vary the amount of radiation exposed to different portions of the photoresist during the grayscale photolithography process. This varying amount of radiation across the substrate substantially alters the photoresist (e.g., changes its solubility relative to the developer) to different depths and / or widths across the substrate. After radiation exposure, the photoresist can be developed and subsequently processed to form patterned features of different sizes (e.g., height and width) across the surface of the substrate. Although grayscale photolithography can be used to form structures with different depths and / or widths, achieving consistent results using grayscale photolithography has always been a challenge. The following disclosure provides a solution to the problem of inconsistent results in grayscale photolithography by alternatively using a process that combines grayscale photolithography with imprinting. This combination of grayscale photolithography and imprinting can be referred to as grayscale imprinting.

[0018] Figure 1 is a process flow diagram of a method 1000 for imprinting a pattern on the optical device 120 shown in Figure 2I, according to one embodiment. Figures 2A to 2I illustrate different stages of the method 1000 for forming a pattern on the optical device 120. Method 100 is described with reference to Figures 1 and 2A to 2I.

[0019] At block 1002, referring to Figure 2A, a grayscale photoresist layer 103 is applied to the dielectric layer 102 of the master mold 100 (also referred to as the master mold substrate). The dielectric layer 102 may be disposed on the substrate 101 of the master mold 100. In some embodiments, the substrate 101 may be formed of silicon, quartz, or any other material commonly used for semiconductor substrates or optical device substrates. In some embodiments, the dielectric layer 102 may be formed of silicon oxide or other dielectric materials.

[0020] At block 1004, referring to Figure 2B, a grayscale photolithography process is performed on the grayscale photoresist layer 103. The grayscale photolithography process may include applying radiation R via a grayscale mask M to expose the grayscale photoresist layer 103 to radiation R. The grayscale mask M is a mask configured to allow different amounts of radiation to pass through different portions of the mask M when different portions of the mask (i.e., different portions in the XY plane of the mask) are exposed to radiation having the same characteristics (e.g., intensity, wavelength, frequency, duration, etc.). The varying amount of radiation R guided by the grayscale mask M allows the grayscale photoresist layer 103 to change to different depths in the Z direction.

[0021] After exposing portions of the grayscale photoresist layer 103 to radiation R using a grayscale mask M, the grayscale photoresist layer 103 can be developed to remove portions of the grayscale photoresist layer 103, such as uncured portions of the photoresist layer 103. Removing these portions of the grayscale photoresist layer 103 leaves a plurality of patterned features 103P, as shown in Figure 2B.

[0022] At block 1006, referring to Figure 2C, the patterned features 103P of the photoresist layer 103 and the underlying dielectric layer 102 can be etched back to form a plurality of patterned features 102P formed by portions of the dielectric layer 102. In some embodiments, the patterned features 102P have the same shape and size and can be arranged in the same pattern as the patterned features 103P of the photoresist layer 103. In some embodiments, the patterned features 102P of the dielectric layer 102 may be more suitable for subsequent processing than the patterned features 103P of the photoresist layer 103. For example, the patterned features 102P of the dielectric layer 102 may be more durable than the corresponding patterned features 103P of the photoresist layer 103 and may have properties more suitable for release from other materials (such as the imprinting materials described below).

[0023] At block 1008, referring to Figure 2D, a patterned feature 112P can be imprinted onto a template 110 using a master mold 100 having a patterned feature 102P. In some embodiments, the patterned feature 112P may be a mirror image of the patterned feature 102P of the master mold 100. The template 110 may include a substrate 111 and an imprinting layer 112 formed of an imprintable material. In one embodiment, the imprinting layer 112 may be an imprinting resist (i.e., a material that retains the imprinted pattern, and in some embodiments, the material may be configured to cure after imprinting).

[0024] At block 1010, referring to Figure 2E, the imprinting template 110 is released from the master mold 100. After release, the patterned feature 112P can be cured (e.g., UV cured) for subsequent processing.

[0025] At block 1012, referring to Figure 2F, an imprinted resist material is applied to the dielectric layer 122 of the optical device 120 to form an imprinted resist layer 123. The dielectric layer 122 may be disposed on a substrate 121 of the optical device 120. In some embodiments, the substrate 121 may be formed of silicon, quartz, or any other material commonly used as a substrate for optical devices. In some embodiments, the dielectric layer 122 may be formed of silicon oxide or other dielectric materials.

[0026] At block 1014, referring to Figure 2G, the patterned feature 112P of the imprinting template 110 can be used to imprint the resist layer 123 of the optical device 120, and the patterned feature 123P is formed in the resist layer 123.

[0027] At block 1016, referring to Figure 2H, the imprinting template 110 is released from the optical device 120. After release, the patterned feature 123P can be cured (e.g., ultraviolet (UV) curing) for subsequent processing.

[0028] At block 1018, referring to Figure 2I, the patterned feature 103P of the imprinted resist layer 123 and the underlying dielectric layer 122 can be etched back to form a plurality of patterned features 122P formed by portions of the dielectric layer 122. In some embodiments, the patterned feature 122P of the dielectric layer 122 can be a component configured to transmit light through the optical device 120. For example, in one embodiment, the patterned feature 122P of the optical device can be or include a grating of a waveguide combiner to be used in an augmented reality device.

[0029] In some embodiments, patterned feature 102P has the same shape and size and can be arranged in the same pattern as patterned feature 103P of resist layer 123. Furthermore, patterned feature 122P can also have the same shape and size and can be arranged in the same pattern as patterned feature 102P of master mold 100, for example as shown in Figure 2C. Although patterned feature 122P of optical device 120 can be the same as or highly similar to patterned feature 102P of master mold 100, patterned feature 122P of optical device 120 can be formed consistently and accurately using imprint stencil 110, whereas the grayscale photolithography process used to form patterned feature 102P of master mold 100 produces significantly less consistent results when repeated. The following disclosure describes a process for consistently forming patterns on an optical device using grayscale photolithography and imprint lithography.

[0030] Figure 3 is a process flow diagram of a method 3000 for imprinting a pattern on an optical device 120 as shown in Figure 4I, according to one embodiment. The optical device 120 may be the same optical device 120 described above with reference to Figures 1 and 2A to 2I. Furthermore, method 3000 includes many of the same operations as method 1000 described above.

[0031] Figures 4A to 4I illustrate different stages of a method 3000 for forming a pattern on an optical device 120. The method 3000 is described with reference to Figures 3 and 4A to 4I, and also with reference to Figures 1 and 2A to 2I.

[0032] Figure 4A is a top view of three master molds 100 1 to 100 3. Figure 4B is a partial cross-sectional view of the first master mold 100 1 taken along section line 4B of Figure 4A. Each master mold 100 includes the patterned feature 102P shown in Figure 4B. The patterned feature 102P is formed above the substrate 101 of each master mold 100. The patterned feature 102P is the same as the patterned feature 102P described above with reference to Figure 2C. Three master molds 100 1 to 100 3 are shown in Figure 4A, but two or more master molds 100 may be used in method 3000. Except for pattern differences related to the accuracy of forming the patterned feature 102P on each individual master mold 100, each master mold 100 in Figure 4A may be the same as the other master molds 100 in Figure 4A and the master molds 100 described above with reference to Figures 1 and 2A to 2I.

[0033] Each master mold 100 includes a plurality of grains 104 (i.e., each square region on each master mold 100 in Figure 4A). As shown in Figure 4B, each grain 104 on each master mold 100 may include a plurality of patterned features 102P. For this illustration, each grain 104 corresponds to three of the six triangular regions in Figure 4B.

[0034] Method 3000 begins at block 3002. At block 3002, referring to Figures 4A and 4B, a plurality of patterned features 102P are formed on each of a plurality of master molds 100. The patterned features 102P can be formed on each master mold 100 using methods other than imprinting, such as etching and / or one or more of non-imprint lithography processes (e.g., lithography using one or more forms of radiation or electron beams). In one embodiment, the grayscale lithography and etching processes described above with reference to blocks 1002 to 1006 and Figures 2A to 2C can be performed on each master mold 100 in Figure 4A to form the patterned features 102P on each master mold 100.

[0035] At block 3004, referring to Figures 4A and 4C, a metrology process is performed on each master mold 100, and the first master mold 100 1 among the three master molds 100 1 to 100 3 is selected for subsequent processing, as shown in Figure 4C. For example, based on the measurements performed during the metrology process at block 3004, the master mold 100 with measurements most consistent with the target measurements of the predetermined design can be selected for subsequent processing. Various criteria can be used to determine which master mold 100 to select. For example, in one embodiment, a master mold 100 having the minimum variation in height in the Z direction of the patterned feature 102P with the expected structure height at various measurement locations (e.g., across 100 different locations on each master mold 100 or 100 different locations on each grain 104 of each master mold 100) can be selected as the most suitable master mold 100 for additional processing. In other embodiments, other measurements (such as the structure width and structure position on the master mold) may also be included to determine which master mold is most suitable.

[0036] At block 3006, referring to Figures 4D, 4E, and 4F, a first master mold 1001 is selected for forming an imprinting template 110. The imprinting template 110 may be the same imprinting template 110 described above with reference to Figures 1 and 2A to 2I. As described above, the imprinting template 110 includes a substrate 111 and an imprinting layer 112.

[0037] As shown in Figure 4D, the selected first master mold 100 1 can be used to imprint patterned features 112P in the imprinting layer 112 of the imprinting template 110. As shown in Figure 4E, the imprinting template 110 is released from the first master mold 100 1.

[0038] Figure 4F illustrates a top view of the entire imprinting template 110. The imprinting template 110 may include grains 114 (i.e., square regions in Figure 4F) arranged in a pattern similar to the grains 104 described above with reference to Figure 4A. Each grain 114 may include patterned features 112P. The views of the template 110 in Figures 4D and 4E may be partial cross-sectional views of the imprinting template 110 along section line 4D of Figure 4F.

[0039] At block 3008, referring to Figures 4G, 4H, and 4I, the imprint stencil 110 can be used to form patterned features 122P on the optical device 120 (also referred to as a substrate, since the benefits of this invention are not limited to the optical device) (see Figure 4H). The patterned features 122P can be formed on the optical device 120 in the same manner as described above in blocks 1014 to 1018 of the method 1000 shown with reference to Figure 1. As shown in Figure 4G, the imprint stencil 110 can be used to form patterned features 123P in the imprint resist layer 123 of the optical device 120. Then, after releasing the imprint stencil 110, the patterned features 123P of the imprint resist layer 123 and the underlying dielectric layer 122 can be etched back to form a plurality of patterned features 122P formed by portions of the dielectric layer 122, as shown in Figure 4H.

[0040] Figure 4I illustrates a top view of the entire optical device 120 formed using method 3000. The optical device 120 may include grains 124 (i.e., the square regions in Figure 4I) arranged in a pattern similar to the grains 104 described above with reference to Figure 4A. Each grain 124 may include the patterned feature 122P shown in Figure 4H. The views of the optical device 110 in Figures 4G and 4H may be partial cross-sectional views of the optical device 110 along section line 4G in Figure 4I.

[0041] At block 3010, it is determined whether the target number of optical devices 120 have been imprinted using the imprinting template 110. Once the target number of optical devices 120 has been imprinted, method 3000 can end. On the other hand, if the target number of optical devices 120 have not been imprinted using the template 110, the imprinting template 110 can be reused (e.g., hundreds, thousands, etc.) by re-executing block 3008 to form additional optical devices 120 having the same patterned feature 123P shown in Figure 4G and the patterned feature 122P after the etching process as shown in Figure 4H. By using the imprinting template 110 to form the patterned feature 122P of multiple optical devices 120, compared with forming the patterned feature 122P using other methods, such as forming the patterned feature 122 using unimprinted grayscale photolithography, the patterned feature 122P of the optical devices 120 can be formed with higher consistency and accuracy.

[0042] Figure 5 is a process flow diagram of a method 5000 for imprinting a pattern on the optical device 120 shown in Figure 6H according to one embodiment. The optical device 120 may be the same optical device 120 described above with reference to Figures 1 and 2A to 2I. Furthermore, method 5000 includes many of the same operations as method 1000 described above with reference to Figure 1 and method 3000 with reference to Figure 3.

[0043] Figures 6A to 6H illustrate different stages of a method 5000 for forming a pattern on an optical device 120. The method 5000 is described with reference to Figures 5 and 6A to 6H, and further with reference to Figures 1 and 2A to 2I.

[0044] Figures 6A and 6B are identical to Figures 4A and 4B above. This document provides a brief overview of these figures, and further details can be found above with reference to Figures 4A and 4B. Figure 6A is a top view of the three master molds 100 1 to 100 3. Figure 6B is a partial cross-sectional view of the first master mold 100 1 taken along section line 6B of Figure 6A. Each master mold 100 includes a plurality of grains 104 as shown in Figure 6A. As shown in Figure 6B, each grain 104 on each master mold 100 may include a plurality of patterned features 102P. As shown, each grain 104 corresponds to three of the six triangular regions in Figure 6B.

[0045] Method 5000 begins at block 5002. At block 5002, referring to Figures 6A and 6B, a plurality of patterned features 102P are formed on each of a plurality of master molds 100. The patterned features 102P can be formed on each master mold 100 using methods other than imprinting, such as etching or one or more of non-imprint lithography processes (e.g., lithography using one or more forms of radiation, electron beam, etc.). In one embodiment, the grayscale lithography and etching processes described above with reference to blocks 1002 to 1006 and Figures 2A to 2C can be performed on each master mold 100 in Figure 6A to form the patterned features 102P on each die 104 of each master mold 100.

[0046] At block 5004, referring to Figures 6A and 6C, a metrology process is performed on each grain 104 of each master mold 100, and the first grain 104 1 of the first master mold 100 1 out of the three master molds 100 1 to 100 3 is selected for subsequent processing. For example, based on the measurements performed during the metrology process at block 5004, grain 104 1 may have measurements that best match the target measurements of the predetermined design. Various criteria can be used to determine which grain 104 to select. For example, in one embodiment, a grain 104 having the minimum variation in height of the patterned feature 102P in the Z direction from the expected structural height at various measurement locations (e.g., across 100 different locations on each grain 104 of each master mold 100) may be selected as the most suitable grain 104 for additional processing.

[0047] At block 5006, referring to Figures 6D and 6E, a selected first grain 1041 on the first master mold 100 1 is used to form an imprint template 110A. The imprint template 110A may be the same as the imprint template 110 described above with reference to Figures 3 and 4A to 4I, except that the imprint template 110A is smaller, and its size corresponds to the size of a single grain 1041 rather than the size of the master mold 100. As described above, the imprint template 110A includes a substrate 111 and an imprint layer 112.

[0048] As shown in Figure 6D, the selected first grain 104 1 of the first master mold 100 1 can be used to imprint patterned features 112P in the imprint layer 112 of the imprint template 110A. As shown in Figure 6, the imprint template 110A is released from the first master mold 100 1.

[0049] At block 5008, referring to Figures 6F, 6G, and 6H, the imprinting template 110A can be used as part of a process for forming a patterned feature 122P (see Figure 6G) on the optical device 120 (also referred to as a substrate, since the benefits of this invention are not limited to the optical device). In some embodiments, the patterned feature 122P can be formed on the optical device 120 in the same manner as described above in blocks 1014 to 1018 of the method 1000 shown with reference to Figure 1. As shown in Figure 6F, the imprinting template 110A can be used to form a patterned feature 123P on a portion of the imprinted resist layer 123 of the optical device 120.

[0050] At block 5010, referring to Figure 6F, it can be determined whether another imprinting should be performed on the current optical device 120 using the imprinting template 110A. Because the imprinting template 110A is based on the size of a single grain (i.e., the first grain 104 1) as described above, patterning on the optical device 120, which has a similar size to the master mold 100, is accomplished using a large number of imprints with the imprinting template 110A. If another imprinting is to be performed on the current optical device 120, the optical device 120 or the imprinting template 110A is stepped in one direction (e.g., the horizontal direction in the XY plane), and the next grain size region of the imprinted resist layer 123 is imprinted using the imprinting template 110A. This process of stepping and imprinting other regions of the imprinted resist layer 123 using the imprinting template 110A continues until all target portions of the imprinted resist layer 123 have been imprinted by the imprinting template 110A.

[0051] Then, after releasing the imprint template 110A from the final portion of the imprint resist layer 123, the patterned features 123P of the imprint resist layer 123 and the underlying dielectric layer 122 can be etched back to form a plurality of patterned features 122P formed by portions of the dielectric layer 122, as shown in Figure 6G.

[0052] Figure 6H shows a top view of the entire optical device 120 formed using method 5000. The optical device 120 may include grains 124 arranged in a pattern similar to the grains 104 described above with reference to Figure 6A (i.e., the square regions in Figure 6H). Each grain 124 may include patterned features 112P. The view of the optical device 120 in Figure 6G may be a partial cross-sectional view of the optical device 120 along section line 6G of Figure 6H.

[0053] At block 5012, it is determined whether the target number of optical devices 120 have been imprinted using the imprinting template 110A. Once the target number of optical devices 120 has been imprinted, method 5000 can end. On the other hand, if the target number of optical devices 120 has not yet been imprinted using the template 110A, the imprinting template 110A can be reused (e.g., hundreds, thousands, etc.) by re-executing blocks 5008 and 5010 to form additional optical devices 120 having the same patterned feature 123P shown in Figure 6F and the same patterned feature 122P after the etching process shown in Figure 6G. By using the imprinting template 110A to form the patterned features 122P of multiple optical devices 120, compared with forming the patterned features 122P by using other methods, such as using grayscale photolithography without imprinting, the patterned features 122P of the optical devices 120 can be formed with higher consistency and accuracy.

[0054] Figure 7 is a process flow diagram of a method 7000 for imprinting a pattern on an optical device 120 as shown in Figure 8N, according to one embodiment. The optical device 120 may be the same optical device 120 described above with reference to Figures 1 and 2A to 2I. Furthermore, method 7000 includes many operations identical to those described above with reference to Figure 1, Figure 3000, and Figure 5000.

[0055] Figures 8A to 8N illustrate different stages of a method 7000 for forming a pattern on an optical device 120. The method 7000 is described with reference to Figures 7 and 8A to 8N, and further with reference to Figures 1 and 2A to 2I.

[0056] Figures 8A and 8B are identical to Figures 4A and 4B above. This document provides a brief overview of these figures, and further details can be found above with reference to Figures 4A and 4B. Figure 8A is a top view of the three master molds 100 1 to 100 3. Figure 8B is a partial cross-sectional view of the first master mold 100 1 taken along section line 8B of Figure 8A. Each master mold 100 includes a plurality of grains 104 as shown in Figure 8A. As shown in Figure 8B, each grain 104 on each master mold 100 may include a plurality of patterned features 102P. As shown, each grain 104 corresponds to three of the six triangular regions in Figure 8B.

[0057] Method 7000 begins at block 7002. At block 7002, referring to Figures 8A and 8B, a plurality of patterned features 102P are formed on each of a plurality of master molds 100. The patterned features 102P can be formed on each master mold 100 using methods other than imprinting, such as using one or more etching and / or non-imprinting lithography processes (e.g., lithography using one or more forms of radiation or electron beams, etc.). In one embodiment, the grayscale lithography and etching processes described above with reference to blocks 1002 to 1006 and Figures 2A to 2C can be performed on each master mold 100 in Figure 8A to form the patterned features 102P on each master mold 100.

[0058] At block 7004, referring to Figures 8A and 8C, a metrology process is performed on each grain 104 of each master mold 100, and the first grain 104 1 of the first master mold 100 1 out of the three master molds 100 1 to 100 3 is selected for subsequent processing. For example, based on the measurements performed during the metrology process at block 7004, the first grain may have measurements that best match the target measurements of the predetermined design. Various criteria can be used to determine which grain 104 to select. For example, in one embodiment, a grain 104 having the minimum variation in height of the patterned feature 102P in the Z direction from the expected structural height at various measurement locations (e.g., across 100 different locations on each grain 104 of each master mold 100) may be selected as the most suitable grain 104 for additional processing.

[0059] At block 7006, referring to Figures 8D and 8E, a selected first grain 104 1 on the first master mold 100 1 is used to form an imprint template 110A. The imprint template 110A may be the same as the imprint template 110 described above with reference to Figures 3 and 4A to 4I, except that the imprint template 110A is smaller, and its size corresponds to the size of a single grain (i.e., the first grain 104 1) rather than the size of the master mold 100. The imprint template 110A includes a substrate 111 and an imprint layer 112.

[0060] As shown in Figure 8D, the selected first grain 104 1 of the first master mold 100 1 can be used to imprint patterned features 112P in the imprint layer 112 of the imprint template 110A. As shown in Figure 8E, the imprint template 110A is released from the first master mold 1001.

[0061] At block 7008, referring to Figure 8F, an imprinting template 110A can be used to form patterned features 123P on a portion of the imprinting resist layer 123 of the new master mold 120N. In some embodiments, the new master mold 120N may be the same as or comprise the same materials as the optical device 120 described above. In other embodiments, the new master mold 120N may comprise some of the materials used in the original master mold 100, such as the substrate 101 and dielectric layer 102 from the master mold 100 and the imprinting resist layer 123 from the optical device 120. In other embodiments, the new master mold 120N may comprise one or more materials not used in either the master mold 100 or the optical device 120.

[0062] At block 7010, referring to Figure 8F, it can be determined whether another imprinting should be performed on the new master mold 120N using the imprinting template 110A. Because the imprinting template 110A is based on the size of a single grain 1041 as described above, patterning on the new master mold 120N, which has a similar size to the master mold 100, is accomplished by extensive imprinting on the imprint resist layer 123 of the new master mold 120N with the imprinting template 110A. If another imprinting is to be performed on the new master mold 120N, the new master mold 120N or the imprinting template 110A is stepped in one direction (e.g., the horizontal direction in the XY plane), and the next region of the imprint resist layer 123 is imprinted with the imprinting template 110A. This process of stepping and imprinting other areas of the imprinting resist layer 123 of the new master mold 120N using imprinting template 110A continues until all target portions of the imprinting resist layer 123 of the new master mold 120N are imprinted by imprinting template 110A.

[0063] Then, after the imprinting template 110 is released from the final portion of the imprinting resist layer 123 of the new master mold 120N, the patterned features 123P of the imprinting resist layer 123 and the lower dielectric layer 122 can be etched back to form a plurality of patterned features 122P formed by portions of the dielectric layer 122, as shown in Figure 8G.

[0064] Figure 8H illustrates a top view of the complete new master mold 120N. The new master mold 120N may include a plurality of grains 124 arranged in the same pattern as the plurality of grains 104 included in the first master mold 100 1. Compared with the plurality of patterned features 102P of the first master mold 100 1, the plurality of patterned features 122P in the new master mold 120N have less variation from the intended design because each grain 124 in the new master mold 120N is based on an imprint derived using a template 110A formed by the first grain 104 1, wherein the first grain 104 1 has the smallest variation from the intended design among all the grains 104 of all three original master molds.

[0065] At block 7012, referring to Figures 8I, 8J, and 8K, a new master mold 120N is used to form a new imprinting template 110N. The new imprinting template 110N may be the same imprinting template 110 described above with reference to Figures 1 and 2A to 2I. As described above, the imprinting template 110N includes a substrate 111 and an imprinting layer 112.

[0066] As shown in Figure 8I, the new master mold 120N can be used to imprint patterned features 112P in the imprinting layer 112 of the new imprinting template 110N. As shown in Figure 8J, the new imprinting template 110N is released from the new master mold 120N.

[0067] Figure 8K illustrates a top view of the entire new imprinting template 110N. The new imprinting template 110N may include grains 114 (i.e., square regions in Figure 8K) arranged in a pattern similar to that of the grains 104 of the master mold 100 described above with reference to Figure 8A. Each grain 114 may include a patterned feature 112P. The views of the template 110N in Figures 8I and 8J may be partial cross-sectional views of the new imprinting template 110N along section line 8J of Figure 8K. The patterned feature 112P in each grain 114 of the template 110N may be the same as the patterned feature 112P in the template 110A of Figure 8E, but the larger size of the new imprinting template 110N allows the new imprinting template 110N to imprint optical devices (e.g., optical device 120) faster than the smaller imprinting template 110A shown in Figure 8E.

[0068] At block 7014, referring to Figures 8L and 8M, a new imprint stencil 110N can be used as part of a process for forming patterned features 122P (see Figure 8M) on an optical device 120 (also referred to as a substrate, since the benefits of this invention are not limited to the optical device). The patterned features 122P can be formed on the optical device 120 in the same manner as described above in blocks 1014 to 1018 of the method 1000 shown with reference to Figure 1. As shown in Figure 8L, the new imprint stencil 110N can be used to form patterned features 123P in the imprint resist layer 123 of the optical device 120. Then, after releasing the new imprint stencil 110N, the patterned features 123P of the imprint resist layer 123 and the underlying dielectric layer 122 can be etched back to form a plurality of patterned features 122P formed by portions of the dielectric layer 122, as shown in Figure 8M.

[0069] Figure 8N shows a top view of the entire optical device 120 formed using method 7000. The optical device 120 may include grains 124 arranged in a pattern similar to the grains 104 described above with reference to Figure 8A (i.e., the square regions in Figure 8N). Each grain 124 may include patterned features 122P. The views of the optical device 110 in Figures 8L and 8M may be partial cross-sectional views of the optical device 120 along section line 8L of Figure 8N.

[0070] At block 7016, it is determined whether the target number of optical devices 120 have been imprinted using the imprinting template 110N. Once the target number of optical devices 120 has been imprinted, method 7000 can end. On the other hand, if the target number of optical devices 120 has not been imprinted using the new imprinting template 110N, the new imprinting template 110N can be reused (e.g., hundreds, thousands, etc.) by re-executing block 7014 to form additional optical devices 120 having the same patterned feature 123P shown in Figure 8L and the same patterned feature 122P after the etching process as shown in Figure 8M. By using the new imprinting template 110N to form the patterned features 122P of multiple optical devices 120, compared with forming the patterned features 122P by using other methods, such as grayscale photolithography without imprinting, the patterned features 122P of the optical devices 120 can be formed with higher consistency and accuracy.

[0071] Although methods 5000 (Figure 5) and 7000 (Figure 7) are described as performing measurements on a plurality of master dies to select a single grain (e.g., the first grain 104 1), in some embodiments, the measurements of these methods may be performed on a single master die comprising two or more grains to select the grain that best matches the design. Furthermore, because methods 5000 and 7000 use a smaller imprint stencil 110A as part of the process, the final device (e.g., optical device 120) does not need to have the same dimensions as the original master die 100, as the smaller imprint stencil 110A can be used to apply patterns to other master dies or devices having various sizes and / or shapes.

[0072] Although the foregoing primarily describes pattern formation on optical devices, the benefits of this invention can be applied to any device or process used for embossing patterns. For example, this invention can benefit any process using lithography, such as the lithography process used in the semiconductor industry.

[0073] Although the foregoing content pertains to various embodiments of this case, other and further embodiments of this case may be designed without departing from the basic scope of this case, and the scope of this invention is determined by the following claims.

[0074] 100 1: Master mold 100 2: Master mold 100 3: Master mold 101:Substrate 102: Dielectric layer 102P: Patterned Features 103: Photoresist layer 103P: Patterned Features 104: Grain 104 1: First grain 110: Template 110A: Imprinting template 110N: Imprinting template 111: Base 112: Imprint layer 112P: Patterned Features 114: Grain 120: Optical device 120N: New female mold 121:Substrate 122: Lower dielectric layer 122P: Patterned Features 123: Inhibitor layer 123P: Patterned Features 124: Grain 1000: Method 1002: Steps 1004: Steps 1006: Steps 1008: Steps 1010: Steps 1012: Steps 1014: Steps 1016: Steps 1018: Steps 3000: Method 3002: Steps 3004: Steps 3006: Steps 3008: Steps 3010: Steps 5000: Method 5002: Steps 5004: Steps 5006: Steps 5008: Steps 5010: Steps 5012: Steps 7000: Method 7002: Steps 7004: Steps 7006: Steps 7008: Steps 7010: Steps 7012: Steps 7014: Steps 7016: Steps M: Grayscale mask R: Radiation X: Plane Y: Plane Z: Direction

[0075] Domestic storage information (please note in order of storage institution, date, and number) none Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. A method for imprinting a pattern on a substrate, the method comprising the steps of: forming a first pattern on a plurality of master molds, the first pattern including a plurality of patterned features; measuring the patterned features at a plurality of locations on each master mold; selecting a first master mold from the plurality of master molds based on the measurements of the patterned features on each master mold; and using the first master mold to form a second pattern on an imprinting template.

2. The method as described in claim 1, wherein the first pattern is formed on the plurality of master molds using grayscale photolithography.

3. The method as described in claim 1 further comprises the step of: imprinting the first pattern onto a plurality of devices using the imprinting template.

4. The method as described in claim 1, wherein each master mold comprises a plurality of spaced-apart grains, and the step of forming the second pattern on the imprinting template using the first master mold comprises the step of simultaneously imprinting the pattern from each grain onto the imprinting template.

5. The method as claimed in claim 1, wherein each master mold comprises a plurality of grains spaced apart from each other, and the step of measuring the patterned features at a plurality of locations on each master mold comprises the step of performing a measurement of the plurality of patterned features on each grain.

6. The method as described in claim 1 further comprises the step of: using the first pattern formed on the first master mold to form a plurality of patterned features on an optical device.

7. The method as described in claim 6, wherein the plurality of patterned features of the optical device are a plurality of gratings of a waveguide combiner.

8. A method for imprinting a pattern on a substrate, the method comprising the steps of: forming a first pattern on a plurality of dies in each of a plurality of master molds, the first pattern on each die including a plurality of patterned features; measuring the patterned features at a plurality of locations on each die in each master mold; selecting a first die on a first master mold in the plurality of master molds based on the measurements of the patterned features on each die in each master mold; and using the first die on the first master mold to form a second pattern on an imprinting template.

9. The method as described in claim 8 further comprises the step of: imprinting the first pattern onto a second die of the first device using the imprinting template.

10. The method as described in claim 8, wherein the first pattern is formed on the plurality of master molds using grayscale photolithography.

11. The method as described in claim 8 further comprises the step of: imprinting the first pattern on a plurality of devices other than the first device using the imprinting template.

12. The method as described in claim 8 further comprises the step of: using the first pattern formed on the first master mold to form a plurality of patterned features on an optical device.

13. The method as described in claim 12, wherein the plurality of patterned features of the optical device are a plurality of gratings of a waveguide combiner.

14. The method as described in claim 8, wherein the deviation between the measurements based on the patterning features of the first grain and a desired design is minimized, and the first grain of the first master mold is selected from all grains on all plurality of master molds.

15. A method for imprinting a pattern on a substrate, the method comprising the steps of: forming a first pattern on a plurality of grains on each of a plurality of master molds using a method other than imprinting, the first pattern on each grain including a plurality of patterned features; measuring the patterned features at a plurality of locations on each grain of each master mold; selecting a first grain on a first master mold among the plurality of master molds based on the measurements of the patterned features on each grain of each master mold; using the first grain on the first master mold to form a second pattern on a first imprinting template; imprinting the first pattern on each grain of a plurality of grains in a new master mold using the first imprinting template; and using the plurality of grains on the new master mold to form the second pattern on each grain of a plurality of grains in a second imprinting template.

16. The method as described in claim 15, wherein the first pattern is formed on the plurality of master molds using grayscale photolithography.

17. The method as described in claim 15 further comprises the step of: imprinting the first pattern on a plurality of devices using the second imprinting template.

18. The method as described in claim 15 further comprises the step of: using the first pattern formed on the first master mold to form a plurality of patterned features on an optical device.

19. The method as described in claim 18, wherein the plurality of patterned features of the optical device are a plurality of gratings of a waveguide combiner.

20. The method as described in claim 15, wherein the deviation of the measurements based on the patterning features of the first grain from a desired design is minimized, and the first grain of the first master mold is selected from all grains on all plurality of master molds.

Images