KR102876052B1 - Metasurface absorber and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a metasurface absorber, and provides a metasurface absorber including: a metal layer including a cross-shaped cavity in which two rectangular cavities overlap; a dielectric layer formed on the metal layer; and a metal patch formed on the dielectric layer.
The metasurface absorber of the present invention can completely absorb light reflected at the interface between the photoresist and the substrate so as to enable desired patterning regardless of the thickness of the photoresist.

Description

Metasurface absorber and manufacturing method thereof {METASURFACE ABSORBER AND MANUFACTURING METHOD THEREOF}

The present invention relates to a metasurface absorber and a method for manufacturing the same, and more particularly, to a metasurface absorber capable of suppressing reflection occurring between a photoresist used in near-field nanopatterning and a substrate, and a method for manufacturing the same.

Technologies for shaping materials at the nano- and microscale are in high demand across various industries, and processes for this purpose are being developed. In particular, three-dimensional periodic material structures are primarily utilized in high-value-added industries such as semiconductors, optics, structural materials, sensors, and electrochemical materials. Existing lithography techniques for achieving this involve repeatedly fabricating a two-dimensional structure to create the desired structure. Because fabricating material structures layer by layer requires processes such as deposition, exposure, and etching, these processes suffer from significant drawbacks in terms of cost-effectiveness and mass production. Alternatives such as interference lithography and near-field nanopatterning have been developed to efficiently fabricate three-dimensional microstructures.

Interference lithography forms a three-dimensional interference pattern by incident multiple coherent light beams onto a photoresist, which is then materialized through a series of heat treatment and etching processes. This process can create a three-dimensional Bravais grating by controlling the number, intensity, and polarization of the incident light beams, enabling the creation of periodic structures with a high degree of freedom. However, this requires utilizing a single light source, such as a laser, with a complex optical system comprised of a beam splitter, lenses, mirrors, and polarizers. This leads to limitations in process area, poor stability and reproducibility, and high cost.

Near-field nanopatterning, which can overcome these shortcomings, creates periodic microstructures by contacting a phase mask with nano-micro periodic grids with photoresist, forming interference patterns and materializing them through an exposure process. Near-field nanopatterning offers the advantages of easy large-scale fabrication, stability, reproducibility, and relatively low processing costs.

The paper “High-Resolution 3D Interference Printing of Multilevel Ultralong Nanochannel Arrays for High-Throughput Nanofluidic Transport (J. Park, et al. Adv. Mater. 2015, 27, 8000-8006.)” discloses a method for creating two-dimensional nanochannels using a periodic one-dimensional grating phase mask, and the paper “and Large-Scale Fabrication of Full Color Woodpile Photonic Crystals via Interference from a Conformal Multilevel Phase Mask (S. Nam, et al. Adv. Funct. Mater. 2019, 29, 1904971)” discloses a method for creating a woodpile structure by stacking two periodic one-dimensional phase masks (gratings) vertically with different directions.

In this conventional near-field nanopatterning method, when the thickness of the photoresist is thick, the light transmitted through the phase mask travels straight, and the reflection occurring at the interface of the substrate on which the photoresist is deposited does not affect the existing diffraction mode, so clean 3D patterning is possible.

However, when the thickness of the photoresist is thin, the reflection occurring at the interface between the photoresist and the substrate interferes with the existing diffraction modes, which causes the interference field pattern to become complex and makes it difficult to achieve the desired patterning.

The purpose of the present invention is to solve the conventional problems and to provide a metasurface absorber that completely absorbs light reflected at the interface between a photoresist and a substrate, thereby enabling desired patterning regardless of the thickness of the photoresist.

In addition, the present invention provides a method for manufacturing a metasurface absorber capable of completely absorbing light reflected at the interface between a photoresist and a substrate.

According to one aspect of the present invention, a metasurface absorber is provided, comprising: a metal layer including a cross-shaped cavity in which two rectangular cavities overlap; a dielectric layer formed on the metal layer; and a metal patch formed on the dielectric layer.

The above metal layer may include at least one selected from Ag, Al, Cr, Au, Pt, Ni, Cu, In, Ru, Pd, Rh, Ir, Os, and W.

The metal layer may have a thickness of 5 to 100 nm.

The dielectric layer may include at least one selected from TiO ₂ , SiO ₂ , ZnO, BaTiO ₃ , MnO ₃ , ZrO ₂ , VO ₃ , Y ₂ O ₃ , IrO, RuO, RhO, TaO, Ta ₂ O ₃ , In ₂ O ₃ , Al ₂ O ₃ , Hf ₂ O ₃ , HfO ₂ , MgO, SrTiO ₃ , WO ₃ , epoxy compounds, polystyrene, and fused guartz.

The dielectric layer may have a thickness of 5 to 100 nm.

In the first paragraph, the metal patch may include at least one selected from Ag, Al, Cr, Au, Pt, Ni, Cu, In, Ru, Pd, Rh, Ir, Os and W.

The above metal patch is rectangular and can be positioned at the center of the dielectric layer.

The width of the metal patch may be smaller than the width of the dielectric layer and may be 100 to 1,000 nm.

The length of the rectangular hollow body in the longitudinal direction may be 200 to 5,000 nm, and the length of the rectangular hollow body in the width direction may be 50 to 1,000 nm.

According to another aspect of the present invention, a metasurface absorbing layer comprising a plurality of the metasurface absorbers is provided.

According to another aspect of the present invention, a method for manufacturing a metasurface absorber is provided, comprising: (a) forming a metal layer including a cross-shaped hollow in which two grooves overlap; (b) forming a dielectric layer on the metal layer; and (c) forming a metal patch on the dielectric layer.

The metasurface absorber of the present invention can completely absorb light reflected at the interface between the photoresist and the substrate so as to enable desired patterning regardless of the thickness of the photoresist.

In addition, the method for manufacturing a metasurface absorber of the present invention can manufacture a metasurface absorber that can completely absorb light reflected at the interface between a photoresist and a substrate.

Figure 1 is a schematic diagram of a metasurface absorber according to one embodiment of the present invention.
Figure 2 is the electric field distribution of a photoresist using a completely absorbing layer.
Figure 3 shows the absorption calculation mapping results of the metasurface absorber.
Figure 4 is an absorption graph when the metal patch width is 100 nm.
Figure 5 is a comparison result with the electric field distribution of photoresist using a conventional substrate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention.

However, the following description is not intended to limit the present invention to a specific embodiment, and when explaining the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description is omitted.

The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, it should be understood that the terms "comprise," "include," or "have" indicate the presence of a feature, number, step, operation, component, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and the present invention is not limited thereto, and the present invention is defined solely by the scope of the claims set forth below.

Hereinafter, the metasurface absorber of the present invention will be described with reference to FIG. 1.

The metasurface absorber of the present invention comprises a metal layer including a cross-shaped cavity in which two rectangular cavities overlap; a dielectric layer formed on the metal layer; and a metal patch formed on the dielectric layer.

The above metal layer may include Ag, Al, Cr, Au, Pt, Ni, Cu, In, Ru, Pd, Rh, Ir, Os, W, etc.

The metal layer may have a thickness of 5 to 100 nm.

The dielectric layer may include a dielectric having no optical loss other than TiO ₂ , SiO ₂ , ZnO, BaTiO ₃ , MnO ₃ , ZrO ₂ , VO ₃ , Y ₂ O ₃ , IrO, RuO, RhO, TaO, Ta ₂ O ₃ , In ₂ O ₃ , Al ₂ O ₃ , Hf ₂ O ₃ , HfO ₂ , MgO, SrTiO ₃ , WO _{3 ,} epoxy compounds, polystyrene, and fused quartz, but any material used as the dielectric layer in the patterning process may be used.

The above dielectric layer may have a thickness of 5 to 100 nm. The range of the resonance wavelength can be freely changed depending on the thickness of the dielectric layer.

The above metal patch may include Ag, Al, Cr, Au, Pt, Ni, Cu, In, Ru, Pd, Rh, Ir, Os, W, etc.

The above metal patch is rectangular and can be positioned at the center of the dielectric layer.

The width (w) of the metal patch may be smaller than the width (p) of the dielectric layer and may be 100 to 1,000 nm. As the width of the metal patch increases, the resonance wavelength may shift to a longer wavelength.

The length (l) of the rectangular hollow body in the longitudinal direction may be 200 to 5,000 nm, and the length (h) of the rectangular hollow body in the width direction may be 50 to 1,000 nm.

The above metasurface absorber can be used in multiple forms to form a metasurface absorber layer, and when used in a near-field patterning process, it can be positioned between a photoresist and a substrate to absorb light reflected at the interface between the photoresist and the substrate.

At this time, any known light source can be used in the near-field patterning process, and preferably, 355 nm, i-line (365 nm), h-line (405 nm), g-line (436 nm), high-power pulse laser (700-800 nm), etc. are possible.

The method for manufacturing a metasurface absorber of the present invention comprises the steps of (a) forming a metal layer including a cross-shaped hollow in which two grooves overlap; (b) forming a dielectric layer on the metal layer; and (c) forming a metal patch on the dielectric layer.

[Example]

Hereinafter, preferred embodiments of the present invention will be described. However, these are provided for illustrative purposes only and the scope of the present invention is not limited thereby.

Manufacturing Examples 1 to 5: Phase Mask Manufacturing

A phase mask was manufactured using polyurethane acrylate (PUA) with a refractive index of 1.5. The phase mask has a nano-grating structure in which rectangular rods are periodically repeated, with the major axis being perpendicular to the polarization direction of the incident light and the minor axis being parallel to it. The fill factor (FF) of the nano-grating structure was fixed at 0.5, the periods were set to 300 nm, 350 nm, 400 nm, 450 nm, and 500 nm, and the height was set to 300 nm. Accordingly, the minor axis of the nano-grating was designed to be 150 nm, 175 nm, 200 nm, 225 nm, and 250 nm, and the major axis was set to infinity.

Examples 1-5: Aluminum metasurface absorber

Referring to Fig. 1, square metal patches with widths (w) of 100 nm, 150 nm, 200 nm, 250 nm, and 300 nm and a thickness of 10 nm were first manufactured using aluminum. The length (l) of the cross-shaped hollow was set to be 2.4 times the width (w), and the width (h) of the cross-shaped hollow was set to be 0.5 times the width (w). An aluminum metal layer including the cross-shaped hollow was manufactured, and the period of this unit consisting of metal patch/dielectric layer/cross-shaped hollow was set to be a length (p) that was 2.5 times the width (w).

A dielectric layer having a thickness of 15 nm was formed on the aluminum metal layer, and the metal patch was positioned at the center of the dielectric layer. The dielectric layer was made of titanium dioxide (TiO ₂ ).

Examples 6-10: Gold metasurface absorbers

An absorbent was manufactured in the same manner as in Examples 1 to 5, except that gold was used instead of aluminum.

Examples 11-15: Copper metasurface absorber

An absorber was manufactured in the same manner as in Examples 1 to 5, except that copper was used instead of aluminum.

Examples 16-20: Silver metasurface absorber

An absorber was manufactured in the same manner as in Examples 1 to 5, except that silver was used instead of aluminum.

Comparative Example 1: Perfectly matched layer (PML)

A completely absorbing layer, which is assumed to be able to completely absorb light in calculations, was used as a comparative example.

Comparative Example 2: Silicon wafer (Si wafer)

A silicon wafer was used as a comparative example.

Comparative Example 3: Gold-deposited substrate (Au)

A gold-deposited substrate was used as a comparative example.

Comparative Example 4: Quartz

A quartz substrate was used as a comparative example.

[Example Exam]

Test Example 1: Electric field distribution in photoresist using a completely absorbing layer

Figure 2 shows the electric field distribution generated in the photoresist when a 355 nm laser light is irradiated on a phase mask manufactured according to a manufacturing example.

In order to determine the exact electric field distribution of the photoresist, a perfectly matched layer (PML) according to Comparative Example 1 was formed on the photoresist. That is, the photoresist is positioned next to the phase mask on the optical path, and then the perfectly matched layer (PML) is positioned next.

The photoresist used above is SU-8, an epoxy-based negative-tone photoresist, and cross-linking of the photoresist was selectively performed only in areas where light was strongly formed through constructive interference. The refractive index of the photoresist is 1.627. FDTD software (Commercial FDTD software, Lumerical Inc.) was used to calculate the electric field distribution. At this time, the calculation was performed assuming that the thickness of the photoresist was infinite.

Referring to Figure 2, as the period of the phase mask increases, the pattern of the electric field generated by the diffraction mode becomes increasingly complex. For the most effective patterning, it was found that effective three-dimensional patterning was possible when the height was fixed at 300 nm and the period was set to 350 nm, as in the phase mask according to Manufacturing Example 3.

Experimental Example 2: Absorption calculation mapping of a metasurface absorber

Figure 3 shows the absorption calculation mapping results of the metasurface absorbers manufactured according to Examples 1 to 20.

Referring to Fig. 3, the gold metasurface absorbers (Au) manufactured according to Examples 6 to 10 and the copper (Cu) metasurface absorbers manufactured according to Examples 11 to 15 showed a broad absorption graph at a wavelength of 300 nm to 500 nm and an absorption rate of about 60 to 70%. The aluminum (Al) metasurface absorbers manufactured according to Examples 1 to 5 showed a narrow absorption graph at short wavelengths and the highest absorption rate of 90 to 100%.

Therefore, it was found that the aluminum (Al) metasurface absorber manufactured according to Examples 1 to 5 could best absorb light reflected at the interface between the photoresist and the substrate in the near-field patterning process.

Test Example 3: Absorption graph when the metal patch width is 100 nm

FIG. 4 shows an absorption graph of an aluminum (Al) metasurface absorber having a metal patch width (w) of 100 nm, manufactured according to Example 1.

Referring to Fig. 4, it was confirmed that it was possible to implement a metasurface absorber having an absorption rate of more than 90% at a wavelength of 355 nm.

Test Example 4: Comparison of electric field distribution of photoresist using a conventional substrate

Figure 5 shows the calculated electric field distribution of the metasurface absorber manufactured according to Example 1 and the photoresist formed on the substrate of Comparative Examples 1 to 4.

At this time, the thickness of the photoresist was fixed at 1 μm and a laser with a wavelength of 355 nm was irradiated. The phase mask used was a phase mask (period: 350 nm, height: 300 nm) manufactured according to Manufacturing Example 2.

Referring to Fig. 5, when a thin photoresist of 1 μm is used, a complex pattern is formed because the reflection from the substrate greatly interferes with the existing diffraction mode. In the case of the silicon wafer (Si wafer) substrate of Comparative Example 2 and the gold-deposited substrate (Au) of Comparative Example 3, a lot of reflection from the substrate occurs, resulting in a more complex pattern, and in the case of the quartz substrate of Comparative Example 4, due to optical phenomena, there is almost no reflection from the substrate, but most light is transmitted and there is almost no absorption, making it difficult to form a clean 3D pattern.

In contrast, when the metasurface absorber manufactured according to Example 1 was used, similar patterning results could be obtained compared to the perfect absorption layer (PML) of Comparative Example 1.

Therefore, it was found that the metasurface absorber of the present invention has a light absorption rate comparable to that of a complete absorption layer that is assumed to completely absorb light.

Claims (11)

A metal layer comprising a cross-shaped cavity with two overlapping rectangular cavities;
a dielectric layer formed on the metal layer; and
A metal patch formed on the dielectric layer;
Including,
The above metal patch is rectangular and is located at the center of the dielectric layer,
A metasurface absorber characterized in that the width of the metal patch is smaller than the width of the dielectric layer and is 100 to 1,000 nm.
In the first paragraph,
A metasurface absorber characterized in that the metal layer comprises at least one selected from Ag, Al, Cr, Au, Pt, Ni, Cu, In, Ru, Pd, Rh, Ir, Os, and W.
In the first paragraph,
A metasurface absorber characterized in that the metal layer has a thickness of 5 to 100 nm.
In the first paragraph,
A metasurface absorber characterized in that the dielectric layer comprises at least one selected from TiO ₂ , SiO ₂ , ZnO, BaTiO ₃ , MnO ₃ , ZrO ₂ , VO ₃ , Y ₂ O ₃ , IrO, RuO, RhO, TaO, Ta ₂ O ₃ , In ₂ O ₃ , Al ₂ O ₃ , Hf ₂ O ₃ , HfO ₂ , MgO, SrTiO ₃ , WO ₃ , epoxy compounds, polystyrene, and fused guartz.
In the first paragraph,
A metasurface absorber characterized in that the dielectric layer has a thickness of 5 to 100 nm.
A metasurface absorber in claim 1, characterized in that the metal patch includes at least one selected from Ag, Al, Cr, Au, Pt, Ni, Cu, In, Ru, Pd, Rh, Ir, Os, and W.
delete delete In the first paragraph,
A metasurface absorber characterized in that the longitudinal length of the rectangular hollow is 200 to 5,000 nm, and the widthwise length of the rectangular hollow is 50 to 1,000 nm.
A metasurface absorbing layer comprising a plurality of metasurface absorbers according to any one of claims 1 to 6.
(a) forming a metal layer including a cross-shaped hollow in which two grooves overlap;
(b) forming a dielectric layer on the metal layer; and
(c) a step of forming a metal patch on the dielectric layer;
Including
The above metal patch is rectangular and is located at the center of the dielectric layer,
A method for manufacturing a metasurface absorber, characterized in that the width of the metal patch is smaller than the width of the dielectric layer and is 100 to 1,000 nm.