Patent Application
20230280505
This application claims priority to Korean Patent Application No. 10-2022-0027649, filed on Mar. 3, 2022, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety.
Example embodiments of the present disclosure relate to a method of forming an amorphous titanium dioxide (TiO2) thin film using a low-temperature atomic layer deposition method and a method of fabricating an optical structure.
Titanium dioxide (TiO2) is an oxide with a relatively high refractive index and a relatively low dielectric loss, and may be efficiently used for manufacturing an optical structure having a meta surface. The refractive index (n), extinction coefficient, transmittance according to a wavelength band, and the like of TiO2 may vary with the crystallinity of the TiO2. Therefore, TiO2 thin films are widely used for surface optical devices using light of a specific wavelength band, and research and development on a deposition method for TiO2 thin films have been also conducted.
One or more example embodiments provide a method of forming an amorphous titanium dioxide (TiO2) thin film using a low-temperature atomic layer deposition and a method of fabricating an optical structure.
Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of example embodiments of the disclosure.
According to an aspect of an example embodiment, there is provided a method of forming an amorphous titanium dioxide (TiO2) thin film on a substrate using a low temperature atomic layer deposition method, the method of forming an amorphous TiO2 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 (O2) precursor to the Ti precursor film and reacting the O2 precursor with the Ti precursor film, and forming the TiO2 thin film on the substrate by exposing the O2 precursor to the Ti precursor film that has not reacted with the O2 precursor, and reacting the Ti precursor film with the O2 precursor.
The low temperature atomic layer deposition method may be performed at a temperature lower than or equal to 200° C.
The low temperature atomic layer deposition method may be performed at a temperature that is higher than or equal to room temperature and lower than or equal to 100° C.
The exposing of the Ti precursor may be 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.
The exposing of the O2 precursor may be performed by exposing the 02 precursor in the process chamber to the Ti precursor film in a state in which an outlet of the process chamber is closed.
According to another aspect of an example embodiment, there is provided a method of fabricating an optical structure, the method including forming, on a substrate, a mold including holes exposing a surface of the substrate, and forming an amorphous titanium dioxide (TiO2) thin film to fill the holes in the mold using a low temperature atomic layer deposition method, wherein the forming of the amorphous TiO2 thin film includes 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 O2 precursor to the Ti precursor film and reacting the O2 precursor with the Ti precursor film, and forming the TiO2 thin film on the substrate by exposing the O2 precursor to the Ti precursor film that has not reacted with the O2 precursor and reacting the Ti precursor film with the O2 precursor.
The low temperature atomic layer deposition method may be performed at a temperature lower than or equal to 200° C.
The method of fabricating an optical structure may further include performing a planarization process on the TiO2 thin film after forming the TiO2 thin film to fill the holes.
The mold may include an organic material.
The mold may include a photoresist.
The forming of the mold may include forming a photoresist layer on the substrate, and forming the mold including the holes by patterning the photoresist layer through a photolithography process.
The mold may include a spin-on-glass (SOG) material.
The forming of the mold may include 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 including the holes by etching the SOG material layer using the patterned photoresist layer as an etching mask.
The substrate may include an image sensor wafer and a spacer layer provided on the image sensor wafer.
The spacer layer may include at least one of an spin-on-glass (SOG) material and a low temperature oxide (LTO).
According to another aspect of an example embodiment, there is provided an optical structure including a substrate, and a first meta lens array provided on the substrate, wherein the first meta lens array includes a mold including an organic material, and mold having holes formed to expose the substrate, and an amorphous titanium dioxide (TiO2) thin film provided to fill the holes.
The mold may include a photoresist or a spin-on-glass (SOG) material.
The optical structure may further include an image sensor.
The substrate may include an image sensor wafer and a spacer layer provided on the image sensor wafer.
The optical structure may further include a second meta lens array provided on the first meta lens array.
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:
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.
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.
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.
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.
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.
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.
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.
A sol-gel method, a physical vapor deposition (PVD), a chemical vapor deposition (CVD), or the like has been used to obtain a crystalline TiO2 thin film. However, the TiO2 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 TiO2 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.
In order to improve such degradation characteristics, a method of forming a crystalline TiO2 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 TiO2 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).
Nanocrystalline deposition using crystalline TiO2 nanocrystals may form a crystalline TiO2 thin film, but the TiO2 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.
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.
Hereinafter, a method of forming a high refractive index amorphous TiO2 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.
Referring to
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.
The TDMAT supplied to the inside of the process chamber may form a flow inside the process chamber.
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.
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
Subsequently, water (H2O), which is an oxygen (O2) precursor, is supplied into the process chamber (operation (d) of
The H2O supplied to the inside of the process chamber may form a flow inside the process chamber. For example, H2O flows into the process chamber through the inlet of the process chamber, and H2O inside the process chamber is discharged to the outside through the outlet of the process chamber. Accordingly, the H2O forms a flow from the inlet to the outlet inside the process chamber.
The H2O supplied into the process chamber may react with the TDMAT film adsorbed on the surface of the substrate 10 to thereby form TiO2. 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 H2O.
Next, the H2O inside the process chamber is exposed to the TDMAT film at the end of the process of supplying the H2O to the inside of the process chamber (operation (e) of
In the process of exposing H2O, H2O may be introduced through the inlet of the process chamber while the outlet of the process chamber is closed. In this state, H2O present in the process chamber may react with the TDMAT film in which TiO2 is not formed in operation (d) described above to thereby form TiO2. Thereafter, a secondary purging process is performed inside the process chamber using an inert gas to form an amorphous TiO2 thin film on the entire surface of the substrate 10 (operation (f) of
The amorphous TiO2 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.
The thickness of the TiO2 thin film was measured by depositing the TiO2 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 TiO2 thin film had a thickness deviation of about 4% or less. Therefore, it may be seen that the TiO2 thin film was uniformly deposited on the wafer. In addition, it was confirmed that a TiO2 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.
Referring to
Hereinafter, a method of manufacturing an optical structure provided with an amorphous TiO2 thin film with a high refractive index by using the above-described low temperature atomic layer deposition method will be described.
Referring to
Subsequently, the photoresist layer 120′ is patterned by a photolithography process. For example, referring to
Referring to
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.
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.
Subsequently, an O2 precursor (e.g., H2O) is supplied into the process chamber. The O2 precursor supplied to the inside of the process chamber may form a flow inside the process chamber. The O2 precursor supplied into the process chamber may react with the Ti precursor film adsorbed on the surface of the substrate 110 to thereby form TiO2. 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 O2 precursor.
Next, the O2 precursor inside the process chamber is exposed to the Ti precursor film at a time point when the supply of the O2 precursor is completed. In this state, the O2 precursor present in the process chamber may react with the Ti precursor film in which TiO2 has not been formed through the supply process of the O2 precursor to thereby form TiO2. Thereafter, a purging process is performed inside the process chamber using an inert gas to form an amorphous TiO2 film on the surface of the substrate 110. In addition, by repeatedly performing the processes described above, the amorphous TiO2 thin film 140 with a high refractive index may be formed to cover the mold 120.
Referring to
According to the example embodiment, in manufacturing an optical structure having a meta surface such as metaprism, an amorphous TiO2 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.
Referring to
Referring to
Referring to
According to the example embodiment, the amorphous TiO2 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.
Hereinafter, a method of manufacturing an image sensor including a meta lens array as an example of an optical structure will be described.
Referring to
Referring to
Referring to
Referring to
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.
Referring to
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.
The first meta lens array 450 may include a first mold 430 including a photoresist and a first amorphous TiO2 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 TiO2 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.
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.
According to the above example embodiment, in manufacturing an optical structure having a meta surface, the high refractive index amorphous TiO2 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.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0027649 | Mar 2022 | KR | national |
