METHOD OF FORMING AMORPHOUS TITANIUM DIOXIDE THIN FILM USING LOW TEMPERATURE ATOMIC LAYER DEPOSITION METHOD AND METHOD OF FABRICATING OPTICAL STRUCTURE

Abstract

Provided is a method of forming an amorphous titanium dioxide (TiO.sub.2) thin film on a substrate using a low temperature atomic layer deposition method, the method of forming an amorphous TiO.sub.2 thin film including supplying a titanium (Ti) precursor to the substrate provided in a process chamber to adsorb the Ti precursor on the substrate, forming a Ti precursor film on the substrate by exposing the Ti precursor to the substrate where the Ti precursor is not adsorbed, supplying an oxygen (O.sub.2) precursor to the Ti precursor film and reacting the O.sub.2 precursor with the Ti precursor film, and forming the TiO.sub.2 thin film on the substrate by exposing the O.sub.2 precursor to the Ti precursor film that has not reacted with the O.sub.2 precursor, and reacting the Ti precursor film with the O.sub.2 precursor.

Claims

1. A method of forming an amorphous titanium dioxide (TiO.sub.2) thin film on a substrate using a low temperature atomic layer deposition method, the method comprising: supplying a titanium (Ti) precursor to the substrate provided in a process chamber to adsorb the Ti precursor on the substrate; forming a Ti precursor film on the substrate by exposing the Ti precursor to the substrate where the Ti precursor is not adsorbed; supplying an oxygen (O.sub.2) precursor to the Ti precursor film and reacting the O.sub.2 precursor with the Ti precursor film; and forming the TiO.sub.2 thin film on the substrate by exposing the O.sub.2 precursor to the Ti precursor film that has not reacted with the O.sub.2 precursor, and reacting the Ti precursor film with the O.sub.2 precursor.

2. The method of forming an amorphous TiO.sub.2 thin film of claim 1, wherein the low temperature atomic layer deposition method is performed at a temperature lower than or equal to 200° C.

3. The method of forming an amorphous TiO.sub.2 thin film of claim 2, wherein the low temperature atomic layer deposition method is performed at a temperature that is higher than or equal to room temperature and lower than or equal to 100° C.

4. The method of forming an amorphous TiO.sub.2 thin film of claim 1, wherein the exposing of the Ti precursor is performed by exposing the Ti precursor in the process chamber to the substrate in a state in which an outlet of the process chamber is closed.

5. The method of forming an amorphous TiO.sub.2 thin film of claim 1, wherein the exposing of the O.sub.2 precursor is performed by exposing the O.sub.2 precursor in the process chamber to the Ti precursor film in a state in which an outlet of the process chamber is closed.

6. A method of fabricating an optical structure, the method comprising: forming, on a substrate, a mold including holes to expose a surface of the substrate; and forming an amorphous titanium dioxide (TiO.sub.2) thin film to fill the holes in the mold using a low temperature atomic layer deposition method, wherein the forming of the amorphous TiO.sub.2 thin film comprises: supplying a Ti precursor to the substrate exposed through the holes to adsorb the Ti precursor thereto; forming a Ti precursor film on the substrate by exposing the Ti precursor to the substrate where the Ti precursor is not adsorbed; supplying an O.sub.2 precursor to the Ti precursor film and reacting the 02 precursor with the Ti precursor film; and forming the TiO.sub.2 thin film on the substrate by exposing the O.sub.2 precursor to the Ti precursor film that has not reacted with the O.sub.2 precursor and reacting the Ti precursor film with the O.sub.2 precursor.

7. The method of fabricating an optical structure of claim 6, wherein the low temperature atomic layer deposition method is performed at a temperature lower than or equal to 200° C.

8. The method of fabricating an optical structure of claim 6, further comprising performing a planarization process on the TiO.sub.2 thin film after forming the TiO.sub.2 thin film to fill the holes.

9. The method of fabricating an optical structure of claim 6, wherein the mold comprises an organic material.

10. The method of fabricating an optical structure of claim 9, wherein the mold comprises a photoresist.

11. The method of fabricating an optical structure of claim 10, wherein the forming of the mold comprises: forming a photoresist layer on the substrate; and forming the mold comprising the holes by patterning the photoresist layer through a photolithography process.

12. The method of fabricating an optical structure of claim 9, wherein the mold comprises a spin-on-glass (SOG) material.

13. The method of fabricating an optical structure of claim 12, wherein the forming of the mold comprises: sequentially forming an SOG material layer and a photoresist layer on the substrate; patterning the photoresist layer through a photolithography process; and forming the mold comprising the holes by etching the SOG material layer using the patterned photoresist layer as an etching mask.

14. The method of fabricating an optical structure of claim 6, wherein the substrate comprises an image sensor wafer and a spacer layer provided on the image sensor wafer.

15. The method of fabricating an optical structure of claim 14, wherein the spacer layer comprises at least one of an spin-on-glass (SOG) material and a low temperature oxide (LTO).

16. An optical structure comprising: a substrate; and a first meta lens array provided on the substrate, wherein the first meta lens array comprises: a mold comprising an organic material, the mold having holes formed to expose the substrate; and an amorphous titanium dioxide (TiO.sub.2) thin film provided to fill the holes.

17. The optical structure of claim 16, wherein the mold comprises a photoresist or a spin-on-glass (SOG) material.

18. The optical structure of claim 16, further comprising an image sensor.

19. The optical structure of claim 18, wherein the substrate comprises an image sensor wafer and a spacer layer provided on the image sensor wafer.

20. The optical structure of claim 18, further comprising a second meta lens array provided on the first meta lens array.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and/or other aspects, features, and advantages of example embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0027] FIG. 1 schematically illustrates a method of forming an amorphous TiO.sub.2 thin film using a low temperature atomic layer deposition method according to an example embodiment;

[0028] FIG. 2 is a process diagram schematically illustrating a process of forming the amorphous TiO.sub.2 thin film illustrated in FIG. 1;

[0029] FIGS. 3A and 3B schematically illustrate operations of supplying a TDMAT in a process chamber and exposing the TDMAT to the substrate performed in the process chamber in FIG. 1;

[0030] FIG. 4 is a graph illustrating the results of measuring, with an ellipsometer, the refractive index of an amorphous TiO.sub.2 thin film formed by a low temperature atomic layer deposition method according to an example embodiment;

[0031] FIGS. 5A, 5B, 5C, 5D, and 5E are diagrams illustrating a method of manufacturing an optical structure according to an example embodiment;

[0032] FIGS. 6A, 6B, 6C, 6D, and 6E are diagrams illustrating a method of manufacturing an optical structure according to another example embodiment;

[0033] FIGS. 7A, 7B, 7C, and 7D are diagrams illustrating a method of manufacturing an image sensor according to an example embodiment; and

[0034] FIG. 8 is a diagram illustrating an image sensor according to another example embodiment.

DETAILED DESCRIPTION

[0035] Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the example embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the example embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, the expression, “at least one of a, b, and c,” should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0036] Hereinafter, example embodiments will be described in detail with reference to the accompanying drawings. In the following drawings, the same reference numerals refer to the same components, and the size of each component in the drawings may be exaggerated for clarity and convenience of description. Meanwhile, the embodiments described below are merely exemplary and various modifications are possible from these embodiments.

[0037] Hereinafter, the term “upper portion” or “on” may also include “to be present on a non-contact basis” as well as “to be in directly contact with”. The singular expression includes plural expressions unless the context clearly implies otherwise. In addition, when a part “includes” a component, this means that it may further include other components, not excluding other components unless otherwise opposed.

[0038] The use of the term “the” and similar indicative terms may correspond to both singular and plural. If there is no explicit description of an order for steps that make up a method or vice versa, these steps can be done in an appropriate order and are not necessarily limited to the order described.

[0039] Further, the terms “unit”, “module” or the like mean a unit that processes at least one function or operation, which may be implemented in hardware or software or implemented in a combination of hardware and software.

[0040] The connection or connection members of lines between the components shown in the drawings exemplarily represent functional connection and/or physical or circuit connections, and may be replaceable or represented as various additional functional connections, physical connections, or circuit connections in an actual device.

[0041] The use of all examples or exemplary terms is simply to describe technical ideas in detail, and the scope is not limited by these examples or exemplary terms unless the scope is limited by the claims.

[0042] A sol-gel method, a physical vapor deposition (PVD), a chemical vapor deposition (CVD), or the like has been used to obtain a crystalline TiO.sub.2 thin film. However, the TiO.sub.2 thin film deposited in these methods has a polycrystalline phase in which many grains are present instead of a single crystal phase, where the grains have different crystal orientations. Accordingly, the polycrystalline TiO.sub.2 thin film has anisotropic refractive characteristics, and uniform optical characteristics may not be obtained depending on the position on the thin film. In addition, the grain boundary of the polycrystalline crystal may have a significant influence on the dielectric loss, resulting in a decrease in the apparent dielectric constant.

[0043] In order to improve such degradation characteristics, a method of forming a crystalline TiO.sub.2 thin film is required, and in this case, temperature may be an additional limiting factor. In general, a high temperature process of 400° C. or higher is required to obtain a crystalline TiO.sub.2 thin film. However, at this high temperature, when a meta-optical structure is to be manufactured on an image sensor wafer provided with an organic material such as a photoresist, a spin-on-glass (SOG) material, and the like, it is nearly impossible to manufacture the meta-optical structure due to the heat-resistant temperature limit of the organic material (e.g., approximately 200° C. or less).

[0044] Nanocrystalline deposition using crystalline TiO.sub.2 nanocrystals may form a crystalline TiO.sub.2 thin film, but the TiO.sub.2 thin film formed is a porous thin film and is not suitable for manufacturing a high refractive index thin film due to air present in pores.

[0045] In manufacturing the meta-optical structure, it is necessary to secure a uniform deposition rate according to the surface shape. However, when a meta-optical structure is manufactured in a surface shape having a high aspect ratio, the related deposition method described above may cause a local refractive index inhibiting factor such as a void. Accordingly, the performance of the meta-optical structure may be seriously impaired.

[0046] Hereinafter, a method of forming a high refractive index amorphous TiO.sub.2 thin film using an atomic layer deposition (ALD) performed at a temperature of 200° C. or less and a method of manufacturing an optical structure (e.g., an image sensor) including an organic material will be described.

[0047] FIG. 1 schematically illustrates a method of forming an amorphous TiO.sub.2 thin film using a low temperature atomic layer deposition method according to an example embodiment. FIG. 2 is a process diagram schematically illustrating a process of forming the amorphous TiO.sub.2 thin film illustrated in FIG. 1. FIGS. 1 and 2 illustrate a one-cycle process in a low-temperature atomic layer deposition method.

[0048] Referring to FIGS. 1 and 2, a substrate 10 for depositing an amorphous TiO.sub.2 thin film is first prepared in a process chamber. The internal temperature of the process chamber may be maintained at 200° C. or less. For example, the internal temperature of the process chamber may be maintained at a temperature greater than or equal to room temperature and less than or equal to 100° C. As the substrate 10, for example, a glass substrate, a silicon substrate, or the like may be used, but embodiments are not limited thereto.

[0049] Subsequently, Tetrakis(dimethylamino)titanium (TDMAT), which is a titanium (Ti) precursor, is supplied into the process chamber in operation (a). Here, TDMAT is only an example, and other precursor materials may be used as Ti precursors.

[0050] The TDMAT supplied to the inside of the process chamber may form a flow inside the process chamber. FIG. 3A illustrates an operation in which TDMAT is supplied to flow through the process chamber (operation (a) of FIGS. 1 and 2). Referring to FIG. 3A, TDMAT is introduced into the process chamber through the inlet of the process chamber, and the TDMAT inside the process chamber is discharged to the outside through the outlet of the process chamber. Accordingly, the TDMAT forms a flow from the inlet to the outlet inside the process chamber.

[0051] In this way, when TDMAT is supplied to the inside of the process chamber, the TDMAT may be chemically or physically adsorbed on the surface of the substrate 10. In this process, since the inside of the process chamber is maintained at a relatively low temperature of 200° C. or less, TDMAT may not be adsorbed on a portion of the surface of the substrate 10.

[0052] Next, the TDMAT inside the process chamber is exposed to the substrate at the end of the process of supplying the TDMAT to the inside of the process chamber (operation (b) of FIGS. 1 and 2). Here, the exposure process (first exposure process) of TDMAT may partially overlap the supply process of TDMAT, but is not limited thereto.

[0053] FIG. 3B illustrates an operation in which the TDMAT inside the process chamber is exposed to the substrate (operation (b) of FIGS. 1 and 2). Referring to FIG. 3B, the TDMAT may be introduced through the inlet of the process chamber while the outlet of the process chamber is closed. In this state, TDMAT present in the process chamber may be adsorbed to the surface of the substrate 10 to which the TDMAT has not been adsorbed in operation (a). Thereafter, a first purging process is performed inside the process chamber using an inert gas to form a TDMAT film on the entire surface of the substrate (operation (c) of FIGS. 1 and 2).

[0054] Subsequently, water (H.sub.2O), which is an oxygen (O.sub.2) precursor, is supplied into the process chamber (operation (d) of FIGS. 1 and 2). Here, H.sub.2O is only exemplary, and other precursor materials may be used as the O.sub.2 precursor.

[0055] The H.sub.2O supplied to the inside of the process chamber may form a flow inside the process chamber. For example, H.sub.2O flows into the process chamber through the inlet of the process chamber, and H.sub.2O inside the process chamber is discharged to the outside through the outlet of the process chamber. Accordingly, the H.sub.2O forms a flow from the inlet to the outlet inside the process chamber.

[0056] The H.sub.2O supplied into the process chamber may react with the TDMAT film adsorbed on the surface of the substrate 10 to thereby form TiO.sub.2. In this process, since the inside of the process chamber is maintained at a relatively low temperature of 200° C. or less, a portion of the TDMAT film may not react with H.sub.2O.

[0057] Next, the H.sub.2O inside the process chamber is exposed to the TDMAT film at the end of the process of supplying the H.sub.2O to the inside of the process chamber (operation (e) of FIGS. 1 and 2). Here, the exposure process (secondary exposure process) of the H.sub.2O may partially overlap the supply process of the H.sub.2O, but embodiments are not necessarily limited thereto.

[0058] In the process of exposing H.sub.2O, H.sub.2O may be introduced through the inlet of the process chamber while the outlet of the process chamber is closed. In this state, H.sub.2O present in the process chamber may react with the TDMAT film in which TiO.sub.2 is not formed in operation (d) described above to thereby form TiO.sub.2. Thereafter, a secondary purging process is performed inside the process chamber using an inert gas to form an amorphous TiO.sub.2 thin film on the entire surface of the substrate 10 (operation (f) of FIGS. 1 and 2).

[0059] The amorphous TiO.sub.2 thin film having a high refractive index may be formed on the substrate 10 to a desired thickness by repeatedly performing the processes described above for several to hundreds of cycles.

[0060] The thickness of the TiO.sub.2 thin film was measured by depositing the TiO.sub.2 thin film on a 12-inch wafer using the above-described low temperature atomic layer deposition, and as a result, it was confirmed that the deposited TiO.sub.2 thin film had a thickness deviation of about 4% or less. Therefore, it may be seen that the TiO.sub.2 thin film was uniformly deposited on the wafer. In addition, it was confirmed that a TiO.sub.2 thin film containing no void was formed inside the hole having a diameter of approximately 100 nm to 400 nm and a depth of approximately 600 nm.

[0061] FIG. 4 is a graph illustrating the results of measuring, with an ellipsometer, the refractive index of an amorphous TiO.sub.2 thin film formed by the above-described low temperature atomic layer deposition method.

[0062] Referring to FIG. 4, the refractive index of the wavelength of about 430 nm was measured to be about 2.62, and the refractive index of the wavelength of about 540 nm was measured to be about 2.48. As described above, it may be seen that the amorphous TiO.sub.2 thin film formed by the above-described low temperature atomic layer deposition method has a high refractive index suitable for fabricating a meta-optical structure.

[0063] Hereinafter, a method of manufacturing an optical structure provided with an amorphous TiO.sub.2 thin film with a high refractive index by using the above-described low temperature atomic layer deposition method will be described.

[0064] FIGS. 5A to 5E are diagrams illustrating a method of manufacturing an optical structure according to an example embodiment.

[0065] Referring to FIG. 5A, a photoresist layer 120′ is formed on a substrate 110. As the substrate 110, for example, a glass substrate or a silicon substrate may be used, but embodiments are not limited thereto. The photoresist layer 120′ may include an organic material having a refractive index lower than that of amorphous TiO.sub.2 to be described later. For example, the photoresist layer 120′ may include an ultraviolet photoresist, an electron beam photoresist, or the like. However, embodiments are not limited thereto.

[0066] Subsequently, the photoresist layer 120′ is patterned by a photolithography process. For example, referring to FIG. 5B, a photomask 130 is provided above the photoresist layer 120′, and then light is emitted to the photoresist layer 120′ through the photomask 130 to perform an exposure process. Next, when a development process is performed on the exposed photoresist layer 120′, a mold 120 may be formed on the substrate 110 as shown in FIG. 5C. Holes 120a exposing the upper surface of the substrate 110 are formed in the mold 120.

[0067] Referring to FIG. 5D, an amorphous TiO.sub.2 thin film 140 is formed to cover the mold 120. Here, the TiO.sub.2 thin film 140 may be formed using the above-described low-temperature atomic layer deposition method. This will be described below in detail. First, the substrate 110 in which the mold 120 is formed is provided in the process chamber. Here, the internal temperature of the process chamber may be maintained at 200° C. or less. For example, the internal temperature of the process chamber may be maintained at a temperature greater than or equal to room temperature and less than or equal to 100° C.

[0068] Subsequently, a Ti precursor (e.g., TDMAT) is supplied into the process chamber. The Ti precursor supplied to the inside of the process chamber may form a flow inside the process chamber. In this way, when the Ti precursor is supplied to the inside of the process chamber, the Ti precursor may be adsorbed to the surface of the substrate 110 exposed through the holes 120a of the mold 120. In this process, since the inside of the process chamber is maintained at a relatively low temperature of 200° C. or less, the Ti precursor may not be adsorbed on a portion of the surface of the substrate 110.

[0069] Next, the Ti precursor inside the process chamber is exposed to the substrate 110 at a time point when the supply of the Ti precursor is completed. In this state, the Ti precursor present inside the process chamber may be adsorbed to the surface of the substrate 110 to which the Ti precursor has not been adsorbed even through the supply process of the Ti precursor. Thereafter, a purging process is performed inside the process chamber using an inert gas to form a Ti precursor film on the surface of the substrate 110.

[0070] Subsequently, an O.sub.2 precursor (e.g., H.sub.2O) is supplied into the process chamber. The O.sub.2 precursor supplied to the inside of the process chamber may form a flow inside the process chamber. The O.sub.2 precursor supplied into the process chamber may react with the Ti precursor film adsorbed on the surface of the substrate 110 to thereby form TiO.sub.2. In this process, since the inside of the process chamber is maintained at a relatively low temperature of 200° C. or less, a portion of the Ti precursor film may not react with the O.sub.2 precursor.

[0071] Next, the O.sub.2 precursor inside the process chamber is exposed to the Ti precursor film at a time point when the supply of the O.sub.2 precursor is completed. In this state, the O.sub.2 precursor present in the process chamber may react with the Ti precursor film in which TiO.sub.2 has not been formed through the supply process of the O.sub.2 precursor to thereby form TiO.sub.2. Thereafter, a purging process is performed inside the process chamber using an inert gas to form an amorphous TiO.sub.2 film on the surface of the substrate 110. In addition, by repeatedly performing the processes described above, the amorphous TiO.sub.2 thin film 140 with a high refractive index may be formed to cover the mold 120.

[0072] Referring to FIG. 5E, the upper portion of the amorphous TiO.sub.2 thin film 140 is planarized using a planarization process such as a chemical mechanical polishing (CMP) process or an etch back process, thereby completing the optical structure. Accordingly, the amorphous TiO.sub.2 thin film 140 having a high refractive index may be formed to fill the inside of the holes 120a formed in the mold 120.

[0073] According to the example embodiment, in manufacturing an optical structure having a meta surface such as metaprism, an amorphous TiO.sub.2 thin film 140 having a high refractive index may be formed in the holes 120a of the mold 120 by using the low-temperature atomic layer deposition method which is performed at a temperature of 200° C. or less. Accordingly, an organic material such as a photoresist that is difficult to perform a high-temperature process may be used as the mold 120 in the example embodiment. In addition, since the patterned photoresist layer may be used as the mold 120 through the photolithography process without an etching process, the manufacturing process may also be simplified.

[0074] FIGS. 6A to 6E are diagrams illustrating a method of manufacturing an optical structure according to another example embodiment.

[0075] Referring to FIG. 6A, an SOG material layer 220′ is formed on a substrate 310. The SOG material layer 220′ may include an organic material having a refractive index lower than that of amorphous TiO.sub.2 to be described later. Then, a photoresist layer 230′ is formed on the SOG material layer 220′. Referring to FIG. 6B, the photoresist layer 230′ is patterned using a photolithography process. Since this has been described above, a detailed description thereof will be omitted. Holes 230a exposing the top surface of the SOG material layer 220′ may be formed in a patterned photoresist layer 230 similar to the photoresist layer 130 in FIG. 5B.

[0076] Referring to FIG. 6C, an etching process is performed on the SOG material layer 220′ by using the patterned photoresist layer 230 as an etching mask, and then the patterned photoresist layer 230 is removed. Accordingly, a mold 220 in which holes 220a exposing the upper surface of the substrate 210 are formed may be formed on the substrate 210.

[0077] Referring to FIG. 6D, an amorphous TiO.sub.2 thin film 240 is formed to cover the mold 220. Here, the amorphous TiO.sub.2 thin film 240 may be formed using the above-described low-temperature atomic layer deposition method. Since this has been described above, a detailed description thereof will be omitted. Referring to FIG. 6E, an optical structure is completed by planarizing an upper portion of the amorphous TiO.sub.2 thin film 240 using a planarization process. Accordingly, the amorphous TiO.sub.2 thin film 240 having a high refractive index may be formed to fill the inside of the holes 220a formed in the mold 220.

[0078] According to the example embodiment, the amorphous TiO.sub.2 thin film 240 having a high refractive index may be formed in the holes 220a of the mold 220 by using the low-temperature atomic layer deposition method performed at a temperature of 200° C. or less. Accordingly, an organic material such as the SOG material that is difficult to perform a high-temperature process may be used as the mold 220 in the example embodiment.

[0079] Hereinafter, a method of manufacturing an image sensor including a meta lens array as an example of an optical structure will be described.

[0080] FIGS. 7A to 7D are diagrams illustrating a method of manufacturing an image sensor according to an example embodiment.

[0081] Referring to FIG. 7A, a spacer layer 320 is formed on an image sensor wafer 310. Here, the image sensor wafer 310 includes a plurality of pixels 311, 312, 313, 314, and 315 that sense incident light of different wavelengths. The spacer layer 320 may include at least one of, for example, an SOG material and a low temperature oxide (LTO). However, embodiments are not limited thereto. The spacer layer 320 may have a single layer structure or a multilayer structure. As a specific example, the spacer layer 320 may include an SOG material layer provided on the image sensor wafer 310 and an LTC layer provided on the SOG material layer. A photoresist layer 330′ is formed on the spacer layer 320. The photoresist layer 330′ may include an organic material having a refractive index lower than that of amorphous TiO.sub.2 to be described later. An etch stop layer and/or a passivation layer may be additionally provided between the spacer layer 320 and the photoresist layer 330′ to prevent loss of the photoresist in a subsequent process.

[0082] Referring to FIG. 7B, the photoresist layer 330′ is patterned using a photolithography process. Since this has been described above, a detailed description thereof will be omitted. Accordingly, a mold 330 including a photoresist may be formed on the spacer layer 320. Holes 330a exposing the surface of the spacer layer 320 are formed in the mold 330.

[0083] Referring to FIG. 7C, an amorphous TiO.sub.2 thin film 340 is formed to cover the mold 330. Here, the amorphous TiO.sub.2 thin film 340 may be formed using the above-described low-temperature atomic layer deposition method. Since this has been described above, a detailed description thereof will be omitted.

[0084] Referring to FIG. 7D, a meta lens array 350 is formed by planarizing an upper part of the amorphous TiO.sub.2 thin film 340 using a planarization process. The meta lens array 350 includes the mold 330 including a photoresist and the amorphous TiO.sub.2 thin film 340 having a high refractive index filling the holes 330a of the mold 330. The meta lens array 350 may include a plurality of meta lenses corresponding to the pixels 311 to 315 of the image sensor wafer 310. Here, the meta lenses may have different nano-patterns, and accordingly, each of the meta lenses may transmit light of a predetermined wavelength to be condensed into a corresponding pixel. More specifically, each of the meta lenses controls the phase of incident light to enable color separation and condensation of pixels for each color wavelength corresponding to each of the pixels 311 to 315. In addition, since the area of each of the meta lenses is designed to be larger than the area of each of the corresponding pixels 311 to 315, the amount of light condensed on each of the pixels is increased. Accordingly, the amount of light condensed for each color to the pixels in a small size may be increased by using the meta lenses. From another point of view, light incident on the meta lenses may be collected in the pixels without passing through the color filters, and thus light loss is reduced, thereby improving light efficiency. In addition, the thickness of the spacer layer 320 may be designed in consideration of the focal length required for the light passing through the meta-lens to be condensed on each of the pixels 311 to 315.

[0085] According to the example embodiment, an image sensor may be manufactured using the low-temperature atomic layer deposition method performed at a temperature of 200° C. or less. Here, an organic material such as a photoresist that is difficult to perform a high-temperature process may be used as the mold 330. In addition, since the patterned photoresist layer may be used as the mold 330 through the photolithography process without an etching process, the manufacturing process of the image sensor may also be simplified.

[0086] FIG. 8 a diagram illustrating an image sensor according to another example embodiment.

[0087] Referring to FIG. 8, the image sensor includes an image sensor wafer 310, a spacer layer 320 provided on the image sensor wafer 310, and a meta lens array provided on the spacer layer 320. Since the image sensor wafer 310 and the spacer layer 320 have been described above, descriptions thereof will be omitted.

[0088] The meta lens array has a multilayer structure. For example, the meta lens array may include a first meta lens array 450 provided on the spacer layer 320 and a second meta lens array 550 provided on the first meta lens array 450.

[0089] The first meta lens array 450 may include a first mold 430 including a photoresist and a first amorphous TiO.sub.2 thin film 440 provided to fill the holes of the first mold 430. The second meta lens array 550 may include a second mold 530 including a photoresist and a second amorphous TiO.sub.2 thin film 540 provided to fill the holes of the second mold 530. The first and second meta lens arrays 450 and 550 may be formed using the above-described low temperature atomic layer deposition method, respectively.

[0090] An etching stop layer and/or a passivation layer may be additionally provided between the spacer layer 320 and the first meta lens array 450 and between the first meta lens array 450 and the second meta lens array 550 to prevent loss of photoresist in a subsequent process.

[0091] According to the above example embodiment, in manufacturing an optical structure having a meta surface, the high refractive index amorphous TiO.sub.2 thin film may be formed in the holes of the mold by using the low-temperature atomic layer deposition method performed at a temperature of 200° C. or less. Accordingly, an organic material such as the photoresist or the spin-on-glass (SOG) material may be used as the mold. In addition, since the patterned photoresist layer may be used as the mold through the photolithography process without an etching process, the manufacturing process may also be simplified.

[0092] It should be understood that example embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each example embodiment should typically be considered as available for other similar features or aspects in other embodiments. While example embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims and their equivalents.