Optical metasurface structure and manufacturing method thereof

Abstract

An optical metasurface structure includes a substrate, a first metal rail structure, a second metal rail structure, a diffusion barrier layer, a high dielectric constant dielectric layer, and a liquid crystal material. The first metal rail structure and the second metal rail structure are disposed above the substrate. The diffusion barrier layer is disposed on the first metal rail structure and the second metal rail structure. The high dielectric constant dielectric layer is disposed on the diffusion barrier layer. The liquid crystal material is disposed above the substrate and at least a part of the liquid crystal material is located between the first metal rail structure and the second metal rail structure in a horizontal direction. The diffusion barrier layer has a first thickness, a portion of the high dielectric constant dielectric layer has a second thickness, and the first thickness is greater than the second thickness.

Description

[Technical Field]

[0001] This invention relates to an optical metasurface structure and its fabrication method, and more particularly to an optical metasurface structure including a metal track structure and its fabrication method. [Previous Technology]

[0002] Optical metasurfaces can alter many properties of incident radiation (e.g., incident light rays) (e.g., amplitude, phase, and / or polarization), thereby enabling various specific functions (e.g., beam manipulation, focusing, spectral filtering, etc.). By combining liquid crystal materials with the design of applied voltage conditions, tunable optical metasurfaces can be realized, thus expanding the application range of optical metasurfaces. [Summary of the Invention]

[0003] This invention provides an optical metasurface structure and its fabrication method, which utilizes a high dielectric constant dielectric layer to enhance the voltage difference provided to the liquid crystal material between metal track structures, thereby improving the operational performance of the optical metasurface structure.

[0004] One embodiment of the present invention provides an optical metasurface structure, including a substrate, a first metal orbital structure, a second metal orbital structure, a diffusion barrier layer, a high dielectric constant dielectric layer, and a liquid crystal material. The first metal orbital structure and the second metal orbital structure are disposed on the substrate, the diffusion barrier layer is disposed on the first metal orbital structure and the second metal orbital structure, and the high dielectric constant dielectric layer is disposed on the diffusion barrier layer. The liquid crystal material is disposed on the substrate, and at least a portion of the liquid crystal material is located between the first metal orbital structure and the second metal orbital structure in a horizontal direction. The diffusion barrier layer has a first thickness, a portion of the high dielectric constant dielectric layer has a second thickness, and the first thickness is greater than the second thickness.

[0005] One embodiment of the present invention provides a method for fabricating an optical metasurface structure, comprising the following steps: providing a substrate, and forming a first metal orbital structure and a second metal orbital structure on the substrate. Forming a diffusion barrier layer on the first metal orbital structure and the second metal orbital structure, and forming a high dielectric constant dielectric layer on the diffusion barrier layer. Forming a liquid crystal material on the substrate, wherein at least a portion of the liquid crystal material is located between the first metal orbital structure and the second metal orbital structure in a horizontal direction. The diffusion barrier layer has a first thickness, a portion of the high dielectric constant dielectric layer has a second thickness, and the first thickness is greater than the second thickness.

Implementation Method

[0006] The following detailed description of the invention discloses sufficient detail to enable those skilled in the art to practice the invention. The embodiments described below should be considered illustrative rather than restrictive. It will be apparent to those skilled in the art that various changes and modifications in form and detail can be made without departing from the spirit and scope of the invention.

[0007] Before further describing the various embodiments, the following will explain the specific terms used throughout the text.

[0008] The terms “on,” “above,” and “on top of” should be interpreted in the broadest sense, such that “on” means not only “directly on” something but also includes something with other intervening features or layers in between, and that “above” or “on top of” means not only “above” or “on top of” something but also includes something “above” or “on top of” without other intervening features or layers in between (i.e., directly on something).

[0009] The ordinal numbers used in the specification and the claims, such as “first” and “second”, are used to modify the elements of the claims. Unless otherwise specified, they do not imply or represent any previous ordinal number of the claimed element, nor do they represent the order of one claimed element with another claimed element, or the order of manufacturing methods. The use of these ordinal numbers is only to make it clear to distinguish one claimed element with a certain name from another claimed element with the same name.

[0010] The term "etching" is generally used herein to describe a process for patterning material such that at least a portion of the material is left after etching. When a material is "etched," at least a portion of the material is retained after etching. Conversely, when a material is "removed," essentially all of the material can be removed during the process. However, in some embodiments, "removal" may be considered a broad term that includes etching.

[0011] The terms “forming” or “setting” are used below to describe the behavior of applying a layer of material to a substrate. These terms are intended to describe any feasible layer forming technique, including but not limited to thermal growth, sputtering, evaporation, chemical vapor deposition, epitaxial growth, electroplating, etc.

[0012] Please refer to Figure 1. Figure 1 is a schematic diagram of an optical metasurface structure 101 according to a first embodiment of the present invention. As shown in Figure 1, the optical metasurface structure 101 includes a substrate 22, a first metal orbital structure (e.g., metal orbital structure RS1), a second metal orbital structure (e.g., metal orbital structure RS2), a diffusion barrier layer 50, a high dielectric constant dielectric layer 52, and a liquid crystal material 54. The metal orbital structures RS1 and RS2 are disposed on the substrate 22, the diffusion barrier layer 50 is disposed on the metal orbital structures RS1 and RS2, and the high dielectric constant dielectric layer 52 is disposed on the diffusion barrier layer 50. The liquid crystal material 54 is disposed on the substrate 22, and at least a portion of the liquid crystal material 54 is located between the metal orbital structures RS1 and RS2 in a horizontal direction D2. The diffusion barrier layer 50 has a first thickness (e.g., thickness TK1), and a portion of the high-dielectric-constant dielectric layer 52 has a second thickness (e.g., thickness TK2), with thickness TK1 being greater than thickness TK2. In some embodiments, the optical metasurface structure 101 may include a plurality of metal orbital structures RS (e.g., the aforementioned metal orbital structures RS1 and RS2) disposed on the substrate 22. By adjusting the voltage applied to each metal orbital structure RS, the arrangement of liquid crystal molecules in the liquid crystal material 54 can be controlled, thereby changing the angle of reflected light when the metal orbital structures RS and the liquid crystal material 54 reflect incident light, thus realizing a tunable optical metasurface structure. Furthermore, the high-dielectric-constant dielectric layer 52 can increase the voltage difference provided to the liquid crystal material 54 by the metal orbital structures RS, thereby improving the operational performance of the optical metasurface structure.

[0013] In some embodiments, a vertical direction D1 can be considered as the thickness direction of the substrate 22. The substrate 22 may have an upper surface and a bottom surface BS opposite each other in the vertical direction D1, and the aforementioned metal track structure RS1, metal track structure RS2, and liquid crystal material 54 may be disposed on one side of the upper surface. A horizontal direction that is substantially orthogonal to the vertical direction D1 (e.g., horizontal direction D2 and other directions orthogonal to the vertical direction D1) may be substantially parallel to the bottom surface BS of the substrate 22, but is not limited thereto. In this document, the distance in the vertical direction D1 between a relatively high position and / or between a component and the bottom surface BS of the base 22 may be greater than the distance in the vertical direction D1 between a relatively low position and / or between a component and the bottom surface BS of the base 22. The lower part or bottom of each component may be closer to the bottom surface BS of the base 22 in the vertical direction D1 than the upper part or top of that component. Another component above a certain component may be considered relatively far from the bottom surface BS of the base 22 in the vertical direction D1, while another component below a certain component may be considered relatively close to the bottom surface BS of the base 22 in the vertical direction D1. Furthermore, the upper surface and upper part of a specific component may respectively include the topmost surface and the uppermost part of that component in the vertical direction D1, and the bottom surface and bottom of a specific component may respectively include the bottommost surface and the bottommost part of that component in the vertical direction D1. The situation in which a specific component is disposed between two other objects in a certain direction may include, but is not limited to, the situation where the component is sandwiched between these two objects in this direction.

[0014] In some embodiments, the optical metasurface structure 101 may further include a dielectric layer (e.g., dielectric layer 24, etch stop layer 26, dielectric layer 28, etch stop layer 34, dielectric layer 36, and / or etch stop layer 38) and an interconnection structure CS, while the substrate 22 may include a silicon substrate or a substrate formed of other suitable semiconductor or non-semiconductor materials. The dielectric layer 24, etch stop layer 26, dielectric layer 28, etch stop layer 34, dielectric layer 36, and etch stop layer 38 may be sequentially stacked on the substrate 22 in the vertical direction D1, and the interconnection structure CS may be disposed in the dielectric layer 24, etch stop layer 26, dielectric layer 28, etch stop layer 34, dielectric layer 36, and etch stop layer 38. Dielectric layers 24, 28, and 36 may each comprise oxide dielectric materials (e.g., silicon oxide) or other suitable dielectric materials, while etch stop layers 26, 34, and 38 may each comprise nitride dielectric materials, carbide dielectric materials (e.g., nitrogen-doped carbides, NDC), or other suitable dielectric materials. In some embodiments, the connection structure CS may include a plurality of wires M1 and via conductors V1. Each wire M1 may be disposed in dielectric layer 24, etch stop layer 26, and 28, while the via conductor V1 may be disposed in etch stop layer 34, dielectric layer 36, and etch stop layer 38. The via conductor V1 may be disposed on the corresponding wire M1 in the vertical direction D1 and directly contact the wire M1 to form an electrical connection. Metal track structures RS can be disposed on the dielectric layer (e.g., dielectric layer 24, etch stop layer 26, dielectric layer 28, etch stop layer 34, dielectric layer 36 and etch stop layer 38) and the connection structure CS in the vertical direction D1, and the connection structure CS can be electrically connected to each metal track structure RS.

[0015] In some embodiments, each conductor M1 may include a barrier layer 30 and a conductive material 32 disposed on the barrier layer 30, and the through-hole conductor V1 may include a barrier layer 40 and a conductive material 42 disposed on the barrier layer 40, but is not limited thereto. The barrier layer 30 and the barrier layer 40 may respectively include titanium, titanium nitride, tantalum, tantalum nitride or other suitable conductive barrier materials, and the conductive material 32 and the conductive material 42 may respectively include materials with relatively low resistivity, such as copper, aluminum, tungsten, etc. In some embodiments, active elements (e.g., transistors, diodes, etc.), passive elements (e.g., capacitors, resistors, etc.) and / or related circuits (not shown) may be disposed on the substrate 22 as required by the design, and the metal track structure RS may be electrically connected to the above-mentioned elements and / or circuits through the connection structure CS, and the potential status of each metal track structure RS may be controlled by specific elements and / or circuits, but is not limited thereto. In some embodiments, the dielectric layer 24 and the substrate 22 may have the same material composition and may be regarded as a single substrate structure. The dielectric layer 24 and the substrate 22 may not contain the aforementioned components and / or lines. A plurality of bonding pads (not shown) may be disposed on the substrate 22. Each bonding pad may be electrically connected to the corresponding metal track structure RS through the connection structure CS, thereby transmitting signals to control the potential status of each metal track structure RS.

[0016] In some embodiments, each metal track structure RS may include a barrier layer and a metal layer disposed on the barrier layer. For example, metal track structure RS1 may include a barrier layer 46A and a metal layer 48A disposed on the barrier layer 46A, while metal track structure RS2 may include a barrier layer 46B and a metal layer 48B disposed on the barrier layer 46B. Due to the relevant process, the bottom surface of the barrier layer 46A located above the via conductor V1 may be higher in the vertical direction D1 than the bottom surface of the barrier layer 46B not located above the via conductor V1 in the vertical direction D1, but this is not a limitation. The barrier layer 46A and the barrier layer 46B may respectively include titanium, titanium nitride, tantalum, tantalum nitride or other suitable conductive barrier materials, while the metal layer 48A and the metal layer 48B may respectively include copper or other suitable metal materials.

[0017] In some embodiments, at least a portion of each metal track structure RS may have an inverted trapezoidal structure that is wider at the top and narrower at the bottom in a cross-sectional view of the optical metasurface structure 101 (e.g., Figure 1), and the width of at least a portion of each metal track structure RS may gradually and / or continuously decrease from the upper surface to the bottom surface of each metal track structure RS, but is not limited thereto. For example, the width of the metal track structure RS1 shown in Figure 1 may gradually and / or continuously decrease from the upper surface TS1 to the bottom surface, the width of the metal layer 48A may gradually and / or continuously decrease from the upper surface TS1 to the bottom surface BS1 (e.g., but not limited to gradually decreasing from width W12 to width W11), and the width of the metal layer 48B in the metal track structure RS2 may gradually and / or continuously decrease from the upper surface TS2 to the bottom surface BS2 (e.g., but not limited to gradually decreasing from width W22 to width W21). Therefore, the metal track structure RS1 may include a first portion P11 and a second portion P12, wherein the second portion P12 is disposed above the first portion P11 in the vertical direction D1, and the width of the second portion P12 is greater than the width of the first portion P11. Similarly, the metal track structure RS2 may include a first portion P21 and a second portion P22, wherein the second portion P22 is disposed above the first portion P21 in the vertical direction D1, and the width of the second portion P22 is greater than the width of the first portion P21.

[0018] In some embodiments, the sizes of the metal track structures RS may be substantially the same or different depending on design requirements. For example, the width of metal track structure RS2 (e.g., width W22) may be smaller than the width of metal track structure RS1 (e.g., width W12), but this is not a limitation. In some embodiments, at least a portion of each metal track structure RS may extend substantially along another horizontal direction (e.g., a horizontal direction orthogonal to both the horizontal direction D2 and the vertical direction D1, respectively), and the length of each metal track structure RS in the horizontal direction D2 may be considered as the aforementioned width, but this is not a limitation. In some embodiments, the bottom width of each metal track structure RS may be greater than the upper width of the corresponding through-hole conductor V1, so that the conductive material 42 of the through-hole conductor V1 can be covered by the barrier layer 40 and the barrier layer (e.g., barrier layer 46A) of the metal track structure RS to improve the barrier effect, but this is not a limitation.

[0019] In some embodiments, the diffusion barrier layer 50 may be substantially conformally disposed on each metal track structure RS and the etch stop layer 38, and the diffusion barrier layer 50 may have a substantially uniform thickness (e.g., thickness TK1), but is not limited thereto. The diffusion barrier layer 50 may include silicon nitride or other dielectric materials suitable for having the desired diffusion blocking effect. In some embodiments, a high dielectric constant dielectric layer 52 may be substantially conformally disposed on the diffusion barrier layer 50, and the high dielectric constant dielectric layer 52 may have a substantially uniform thickness (e.g., thickness TK2), but is not limited thereto. It is worth noting that thickness TK1 can be considered as the thickness of the diffusion barrier layer 50 located above the metal track structure RS in the vertical direction D1, while thickness TK2 can be considered as the thickness of the high dielectric constant dielectric layer 52 located above the metal track structure RS in the vertical direction D1. In some embodiments, the diffusion barrier layer 50 needs to have a certain thickness to provide the desired diffusion blocking effect, so the thickness TK1 can be greater than the thickness TK2. The thickness TK1 can be generally between 80 angstroms and 100 angstroms, and the thickness TK2 can be generally between 30 angstroms and 50 angstroms, and the ratio of the thickness TK1 to the thickness TK2 can be greater than or equal to 1.6, but is not limited thereto. Furthermore, the dielectric constant of the high dielectric constant dielectric layer 52 is higher than the dielectric constant of the diffusion barrier layer 50. In some embodiments, the dielectric constant of the high dielectric constant dielectric layer 52 can be greater than 10, while in other embodiments, the dielectric constant of the high dielectric constant dielectric layer 52 can be greater than or equal to 30, to further enhance the effect of increasing the voltage difference, but is not limited thereto. The high dielectric constant dielectric layer 52 may include hafnium oxide (e.g., HfxOy), zirconium oxide (e.g., ZrxOy), yttrium oxide (e.g., Y2O3), tantalum oxide (e.g., Ta2O5), titanium oxide (e.g., TiO2), lanthanum oxide (e.g., LaxOy) or other suitable high dielectric constant dielectric materials.

[0020] Due to the shape of the metal track structure RS, a portion of the diffusion barrier layer 50 may be disposed on the sidewall of the metal track structure RS and located directly below the sidewall of the metal track structure RS in the vertical direction D1. For example, a portion of the diffusion barrier layer 50 may be disposed on the sidewall SW1 of the metal track structure RS1 and located directly below the sidewall SW1 of the metal track structure RS1 in the vertical direction D1, while another portion of the diffusion barrier layer 50 may be disposed on the sidewall SW2 of the metal track structure RS2 and located directly below the sidewall SW2 of the metal track structure RS2 in the vertical direction D1. Furthermore, a portion of the high dielectric constant dielectric layer 52 may be sandwiched between the liquid crystal material 54 and the diffusion barrier layer 50 in the horizontal direction D2 and located directly below the diffusion barrier layer 50 in the vertical direction D1. In some embodiments, the thickness of the diffusion barrier layer 50 disposed on the sidewall of the metal track structure RS in the horizontal direction D2 may be substantially equal to the thickness of the diffusion barrier layer 50 disposed on the metal track structure RS in the vertical direction D1 (e.g., thickness TK1), and the thickness of the high dielectric constant dielectric layer 52 disposed on the sidewall of the metal track structure RS in the horizontal direction D2 may be substantially equal to the thickness of the high dielectric constant dielectric layer 52 disposed on the metal track structure RS in the vertical direction D1 (e.g., thickness TK2), but is not limited thereto.

[0021] In some embodiments, the arrangement of liquid crystal molecules in the liquid crystal material 54 can be controlled by adjusting the voltage applied to each metal track structure RS, thereby changing the angle of reflected light when the metal track structure RS and the liquid crystal material 54 reflect incident light. By adjusting the voltage applied to each metal track structure RS, the optical metasurface structure of the present invention can be used to reflect incident light with different angles into reflected light with a specific angle and / or reflect incident light with a specific angle into reflected light with different angles. Therefore, the optical metasurface structure of the present invention can be regarded as a tunable optical metasurface structure. In addition, the width, height, length of each metal track structure RS and the spacing between adjacent metal track structures RS can be adjusted according to the wavelength range of the corresponding operating light to produce the desired resonance effect. For example, the spacing between metal track structures RS can be smaller than the wavelength of the operating light, but is not limited thereto.

[0022] Please refer to Figure 1 and Figures 2 through 7. Figures 2 through 7 illustrate schematic diagrams of the fabrication method of the optical metasurface structure according to the first embodiment of the present invention, wherein Figure 3 illustrates the state after Figure 2, Figure 4 illustrates the state after Figure 3, Figure 5 illustrates the state after Figure 4, Figure 6 illustrates the state after Figure 5, and Figure 7 illustrates the state after Figure 6. In some embodiments, Figure 1 may be regarded as illustrating the state after Figure 7, but is not limited thereto. As shown in Figure 1, the fabrication method of this embodiment includes the following steps. First, a substrate 22 is provided, and a first metal orbital structure (e.g., metal orbital structure RS1) and a second metal orbital structure (e.g., metal orbital structure RS2) are formed on the substrate 22. A diffusion barrier layer 50 is formed on the metal orbital structures RS1 and RS2, a high dielectric constant dielectric layer 52 is formed on the diffusion barrier layer 50, and a liquid crystal material 54 is formed on the substrate 22. At least a portion of the liquid crystal material 54 is located between the metal orbital structures RS1 and RS2 in the horizontal direction D2. The diffusion barrier layer 50 has a first thickness (e.g., thickness TK1), a portion of the high dielectric constant dielectric layer 52 has a second thickness (e.g., thickness TK2), and the thickness TK1 is greater than the thickness TK2.

[0023] Further explanation: The fabrication method of this embodiment may include, but is not limited to, the following steps. As shown in Figure 2, before the metal track structure is formed, a dielectric layer (e.g., dielectric layer 24, etch stop layer 26, dielectric layer 28, etch stop layer 34, dielectric layer 36, or / and etch stop layer 38) may be formed on the substrate 22, and an interconnection structure CS may be formed in the dielectric layer. After the dielectric layer and the interconnection structure CS are formed, a dielectric layer 44 may be formed on the substrate 22. The dielectric layer 44 may include tetraethoxysilane (TEOS) oxide or other suitable materials. Then, as shown in Figure 3, a plurality of trenches may be formed to penetrate the dielectric layer 44. For example, a first trench (e.g., trench TR1) and a second trench (e.g., trench TR2) may be formed to penetrate the dielectric layer 44. In some embodiments, the trenches described above may also be partially located in the etch stop layer 38, and the process used to form the trenches (e.g., but not limited to an etching process) may be affected by the via conductor V1, causing at least a portion of the trenches to be formed on the via conductor V1. As shown in Figure 4, a first barrier layer (e.g., barrier layer 46A) and a second barrier layer (e.g., barrier layer 46B) are formed in trenches TR1 and TR2, respectively, and a first metal layer (e.g., metal layer 48A) and a second metal layer (e.g., metal layer 48B) are formed in trenches TR1 and TR2, respectively. In some embodiments, a barrier material 46 may be conformally formed on trenches TR1, TR2, and dielectric layer 44, and a metal material 48 may be formed on the barrier material 46, thus providing a barrier layer. Barrier material 46 and metal material 48 may be partially formed in and partially formed outside trenches TR1 and TR2, and trenches TR1 and TR2 may be filled with barrier material 46 and metal material 48. Then, a planarization process (e.g., but not limited to chemical mechanical polishing) may be performed to remove the barrier material 46 and metal material 48 located outside trenches TR1 and TR2 to form barrier layer 46A, barrier layer 46B, metal layer 48A, and metal layer 48B.

[0024] Subsequently, as shown in Figures 4 and 5, a removal process 91 can be performed to remove the dielectric layer 44. In some embodiments, the dielectric layer 44 can be completely removed by the removal process 91, and a portion of the barrier layer 46A and a portion of the barrier layer 46B can be removed by the removal process 91. After the removal process 91, the remaining barrier layer 46A and the metal layer 48A can form a metal orbital structure RS1, and the remaining barrier layer 46B and the metal layer 48B can form a metal orbital structure RS2. The removal process 91 may include a buffer oxide etching (BOE) process or other suitable removal methods. It is worth noting that the method for forming the metal orbital structures RS1 and RS2 may include, but is not limited to, the steps shown in Figures 2 to 5 above, and other suitable methods may be used to form the metal orbital structures RS as required by the design. Then, as shown in Figures 5 and 6, a diffusion barrier layer 50 can be conformally formed on the metal orbital structures RS1, RS2, and the etch stop layer 38. As shown in Figures 4 through 6, in some embodiments, metal layers 48A and 48B may undergo a hydrogen treatment 92 after removal process 91 and before the formation of diffusion barrier layer 50. This hydrogen treatment can reduce the negative impact of removal process 91 on metal layers 48A and 48B that may be oxidized during removal process 91, but is not limited thereto. The hydrogen treatment 92 may include hydrogen plasma treatment or other suitable methods.

[0025] As shown in Figure 7, after the diffusion barrier layer 50 is formed, a high dielectric constant dielectric layer 52 can be conformally formed on the diffusion barrier layer 50. Due to the shape of the metal orbital structure RS, a portion of the diffusion barrier layer 50 can be formed on the sidewall of the metal orbital structure RS and located directly below the sidewall of the metal orbital structure RS in the vertical direction D1, while a portion of the high dielectric constant dielectric layer 52 can be formed on the sidewall of the metal orbital structure RS and located directly below the diffusion barrier layer 50 in the vertical direction D1. Then, as shown in Figure 1, a liquid crystal material 54 can be formed, thereby forming an optical metasurface structure 101.

[0026] The following description will focus on different embodiments of the present invention. For the sake of simplicity, the description will mainly focus on the differences between the embodiments and will not repeat the same points. In addition, the same elements in the embodiments of the present invention are marked with the same reference numerals to facilitate comparison between the embodiments.

[0027] Please refer to Figure 8, which is a schematic diagram of the optical metasurface structure 102 according to the second embodiment of the present invention. As shown in Figure 8, in the optical metasurface structure 102, the thickness distribution of the high dielectric constant dielectric layer 52 located between adjacent metal track structures RS in the horizontal direction D2 can be adjusted to be thinner at the top and thicker at the bottom to compensate for the uneven distribution of the effect of the metal track structure RS (wider at the top and narrower at the bottom) on driving the liquid crystal material 54. For example, the high dielectric constant dielectric layer 52 disposed on the metal track structure RS1 may include a first part P31 and a second part P32. The first part P31 is sandwiched between the first part P11 of the metal track structure RS1 and the liquid crystal material 54 in the horizontal direction D2. The second part P32 is sandwiched between the second part P12 of the metal track structure RS1 and the liquid crystal material 54 in the horizontal direction D2. The thickness TK3 of the first part P31 in the horizontal direction D2 may be greater than the thickness TK4 of the second part P32 in the horizontal direction D2. Similarly, the high-dielectric-constant dielectric layer 52 disposed on the metal track structure RS2 may include a first portion P41 and a second portion P42. The first portion P41 is sandwiched between the first portion P21 of the metal track structure RS2 and the liquid crystal material 54 in the horizontal direction D2, and the second portion P42 is sandwiched between the second portion P22 of the metal track structure RS2 and the liquid crystal material 54 in the horizontal direction D2. The thickness TK5 of the first portion P41 in the horizontal direction D2 may be greater than the thickness TK6 of the second portion P42 in the horizontal direction D2, but is not limited thereto. In some embodiments, the thicknesses TK3 and TK5 may be greater than the thickness TK2 of the high-dielectric-constant dielectric layer 52 disposed on the metal track structure RS in the vertical direction D1, while the thicknesses TK4 and TK6 may be slightly smaller than the thickness TK2 of the high-dielectric-constant dielectric layer 52 disposed on the metal track structure RS in the vertical direction D1, but are not limited thereto. Furthermore, the thickness distribution of the high dielectric constant dielectric layer 52 described above can be achieved by adjusting the process conditions of the film deposition process for forming the high dielectric constant dielectric layer 52, the film deposition method (e.g., but not limited to forming the high dielectric constant dielectric layer 52 from bottom to top starting from the bottom of the space between the metal orbital structures RS) and / or performing a suitable partial removal process (e.g., but not limited to an etching process) after the film deposition process.

[0028] In summary, in the optical metasurface structure and its fabrication method of the present invention, the high dielectric constant dielectric layer can be used to increase the voltage difference provided to the liquid crystal material between the metal track structures, thereby improving the operational performance of the optical metasurface structure. Furthermore, in some embodiments, the thickness distribution of the high dielectric constant dielectric layer can be adjusted to compensate for the negative impact of the shape of the metal track structure on driving the liquid crystal material, thus further improving the operational performance of the optical metasurface structure. The above descriptions are merely preferred embodiments of the present invention; all equivalent variations and modifications made within the scope of the claims of this invention should be considered within the scope of this invention. [Simplified Explanation of the Diagram]

[0029] Figure 1 is a schematic diagram of the optical metasurface structure according to the first embodiment of the present invention. Figures 2 to 7 are schematic diagrams of the fabrication method of the optical metasurface structure according to the first embodiment of the present invention, wherein Figure 3 shows a schematic diagram of the situation after Figure 2; Figure 4 shows a schematic diagram of the situation after Figure 3; Figure 5 shows a schematic diagram of the situation after Figure 4; Figure 6 shows a schematic diagram of the situation after Figure 5; Figure 7 shows a schematic diagram of the situation after Figure 6. Figure 8 is a schematic diagram of the optical metasurface structure according to the second embodiment of the present invention.

Claims

1. An optical metasurface structure, comprising: One base; A first metal track structure and a second metal track structure are disposed on a substrate, and the first metal track structure includes: a first portion; and a second portion disposed on the first portion, wherein the width of the second portion is greater than the width of the first portion; a diffusion barrier layer disposed on the first metal track structure and the second metal track structure; a high dielectric constant dielectric layer disposed on the diffusion barrier layer; and a liquid crystal material disposed on the substrate, wherein at least a portion of the liquid crystal material is located in a horizontal direction between the first metal track structure and the second metal track structure, the diffusion barrier layer has a first thickness, a portion of the high dielectric constant dielectric layer has a second thickness, and the first thickness is greater than the second thickness.

2. The optical metasurface structure as described in claim 1, wherein the dielectric constant of the high dielectric constant dielectric layer is higher than the dielectric constant of the diffusion barrier layer.

3. The optical metasurface structure as described in claim 1, wherein the dielectric constant of the high dielectric constant dielectric layer is greater than 10.

4. The optical metasurface structure as described in claim 1, wherein the dielectric constant of the high dielectric constant dielectric layer is greater than or equal to 30.

5. The optical metasurface structure as described in claim 1, wherein the ratio of the first thickness to the second thickness is greater than or equal to 1.

6.

6. The optical metasurface structure as described in claim 1, wherein the high dielectric constant dielectric layer comprises: A first part is sandwiched between the first part of the first metal track structure and the liquid crystal material in the horizontal direction; And a second portion, sandwiched in the horizontal direction between the second portion of the first metal track structure and the liquid crystal material, wherein the thickness of the first portion of the high dielectric constant dielectric layer in the horizontal direction is greater than the thickness of the second portion of the high dielectric constant dielectric layer in the horizontal direction.

7. The optical metasurface structure as claimed in claim 1, wherein a portion of the diffusion barrier layer is located directly below the sidewall of the first metal track structure in a vertical direction.

8. The optical metasurface structure as claimed in claim 1, wherein a portion of the high dielectric constant dielectric layer is located directly below the diffusion barrier layer in a vertical direction.

9. The optical metasurface structure as claimed in claim 1, wherein the first metal track structure has an inverted trapezoidal structure in a cross-sectional view of the optical metasurface structure.

10. A method for fabricating an optical metasurface structure, comprising: Provide a base; A first metal track structure and a second metal track structure are formed on the substrate; A diffusion barrier layer is formed on the first metal orbital structure and the second metal orbital structure; a high dielectric constant dielectric layer is formed on the diffusion barrier layer; and a liquid crystal material is formed on the substrate, wherein at least a portion of the liquid crystal material is located in a horizontal direction between the first metal orbital structure and the second metal orbital structure. The diffusion barrier layer has a first thickness, a portion of the high dielectric constant dielectric layer has a second thickness, and the first thickness is greater than the second thickness. The method of forming the first metal orbital structure and the second metal orbital structure includes: forming a dielectric layer on the substrate; forming a first trench and a second trench that penetrate the dielectric layer; forming a first barrier layer and a second barrier layer in the first trench and the second trench, respectively; forming a first metal layer and a second metal layer in the first trench and the second trench, respectively; and performing a removal process to remove the dielectric layer.

11. A method for fabricating an optical metasurface structure as described in claim 10, wherein a portion of the first barrier layer and a portion of the second barrier layer are removed by the removal process.

12. The method for fabricating the optical metasurface structure as described in claim 10 further includes: After the removal process and before the formation of the diffusion barrier layer, the first metal layer and the second metal layer are subjected to a hydrogen treatment.

13. A method for fabricating an optical metasurface structure as claimed in claim 10, wherein the diffusion barrier layer is conformally formed on the first metal orbital structure and the second metal orbital structure, and the high dielectric constant dielectric layer is conformally formed on the diffusion barrier layer.

14. A method for fabricating an optical metasurface structure as described in claim 10, wherein the dielectric constant of the high dielectric constant dielectric layer is higher than the dielectric constant of the diffusion barrier layer.

15. A method for fabricating an optical metasurface structure as described in claim 10, wherein the first metal track structure comprises: Part One; And a second part, disposed on top of the first part, wherein the width of the second part is greater than the width of the first part.

16. A method for fabricating an optical metasurface structure as described in claim 15, wherein the high dielectric constant dielectric layer comprises: A first part is sandwiched between the first part of the first metal track structure and the liquid crystal material in the horizontal direction; And a second portion, sandwiched in the horizontal direction between the second portion of the first metal track structure and the liquid crystal material, wherein the thickness of the first portion of the high dielectric constant dielectric layer in the horizontal direction is greater than the thickness of the second portion of the high dielectric constant dielectric layer in the horizontal direction.

17. A method for fabricating an optical metasurface structure as described in claim 10, wherein a portion of the diffusion barrier layer is located directly below the sidewall of the first metal track structure in a vertical direction.

18. A method for fabricating an optical metasurface structure as described in claim 10, wherein a portion of the high dielectric constant dielectric layer is located directly below the diffusion barrier layer in a vertical direction.

Images