KR100588468B1 - Fabrication of metal oxide nano-structure etch mask using azobenzene-functionalized polymer and application to nanopatterning - Google Patents

Abstract

The present invention relates to a metal oxide nanostructure etching mask prepared using an azobenzene group-containing compound and a nano patterning method using the same, and more particularly, to form a surface uneven structure formed by the photophysical material movement principle of the azobenzene group-containing compound. metal oxide nanostructure etch masks are fabricated using patterned relief gratings (SRGs) and patterned using them to enable patterning of sub-micron sizes, a limitation of conventional optical lithography techniques, ranging from tens of nanometers to thousands of nanometers. Nano patterning is possible, and unlike conventional methods such as electron beam lithography or laser patterning, various types of etching masks can be manufactured at low cost by simple chemical method without sophisticated control and can be manufactured industrially. Of area An improved nano patterning method that can be applied to information-electronic devices.

Azobenzene, Surface Uneven Structures (SRGs), Nano Structure Etch Masks, Nano Patterning

Description

Fabrication of metal oxide nano-structure etch mask using azobenzene-functionalized polymer and application to nanopatterning}             

1 is a schematic view showing a photoisomerization reaction of an azobenzene group used in the invention.

Figure 2 is an embodiment of a schematic diagram of an optical experimental apparatus for forming surface irregularities (SRGs).

3 is a structure of the azobenzene group-containing compound used in Examples 1 and 2.

FIG. 4 is a diagram schematically illustrating a method for fabricating a metal oxide nanostructure etching mask using a fine surface concavo-convex structure of an azobenzene group-containing compound and a patterning method by selective etching.

FIG. 5 is a photograph (a) showing an Atomic force microscopy (AFM) shape of the surface irregularities structure of the azobenzene material formed in Example 1 and a graph (b) showing depth distribution.

6 is a photograph (a) and a graph (b) showing an AFM shape of a titania nanowire etching mask fabricated using a surface uneven structure of an azobenzene material formed in Example 1. FIG.

7 is a photograph (a) showing the AFM shape of the final patterned ITO in Example 1 and a graph (b) showing the depth distribution.

8 is a scanning electron micrograph (a) and energy-dispersive X-ray spectroscopy (EDX) spectra of a titania nanowire etching mask formed in Example 1 (b) to be.

9 is a SEM photograph (a) and EDX spectrum (b) of the final patterned ITO in Example 1.

FIG. 10 is a SEM photograph (a) of a titania nanowire etch mask formed by surface irregularities at 500 nanometer intervals in Example 2, and a SEM photograph (b) of a final patterned FTO.

FIG. 11 is an SEM image (a) of a titania nanowire etch mask formed by surface irregularities at intervals of 1000 nanometers in Example 2, and an SEM image (b) of a final patterned FTO.

12 are SEM images of a two-dimensional niobium oxide nano structure etching mask prepared in Example 3. FIG.

The present invention relates to a metal oxide nanostructure etching mask prepared using an azobenzene group-containing compound and a nano patterning method using the same, and more particularly, to form a surface uneven structure formed by the photophysical material movement principle of the azobenzene group-containing compound. metal oxide nanostructure etch masks are fabricated using patterned relief gratings (SRGs) and patterned using them to enable patterning of sub-micron sizes, a limitation of conventional optical lithography techniques, ranging from tens of nanometers to thousands of nanometers. Nano patterning is possible, and unlike conventional methods such as electron beam lithography or laser patterning, various types of etching masks can be manufactured at low cost by simple chemical method without sophisticated control and can be manufactured industrially. Of area An improved nano patterning method that can be applied to information-electronic devices.

In the conventional patterning using optical lithography, the photoresist is first formed by spin coating, followed by complex steps such as the development process using soft baking and a mask. Is impossible.

New nano-patterning approaches are being introduced, and two of the most sought after are extreme ultraviolet (EUV) lithography and electron beam lithography.

EUV lithography has the advantage that it can be used without changing the equipment of the optical lithography that is being used as a way to form a small size pattern using the extreme ultraviolet rays, but the mask or lens It's hard to make. On the other hand, there is an X-ray lithography using a smaller wavelength for reference, but when making a mask, it is difficult to pattern because it can only be made 1: 1.

Electron-beam lithography has the advantage of finer patterning than EUV lithography by directly scanning and patterning the electron beam on the substrate, but it cannot be applied to devices because it requires expensive processes and sophisticated control. It is true.

In addition to the above-described method, a nano imprint method for patterning like a nano-sized mold is made and printed, a self-assembly method using the self-assembly properties of molecules, and a molecule for directly patterning molecules or atoms to make patterning ( Methods such as atomic (atomic) manipulation have been attempted.

However, all of the above methods have problems such as limited usable materials and poor reproducibility.

Accordingly, the present inventors have made efforts to solve the above problems, and when the azobenzene is exposed to linearly polarized light, the inventors have the property of perpendicularly aligning the linearly polarized light direction of the incident light, and when the azobenzene group-containing compound is exposed, Considering that the uneven structure is formed, the present invention has been proposed.                         

That is, the present invention uses the surface asperity structure formed on the surface of the azobenzene group-containing compound to prepare an etching mask in which a metal oxide forms a linear nanowire or a nanostructure forming a two-dimensional plane by a simple chemical method and selectively etching By introducing possible conditions, a pattern of 1 μm or less, which is a limitation of the conventional optical lithography technology, is made possible.

That is, according to the method of the present invention, it is possible to form patterns of various sizes and depths from tens of nanometers to thousands of nanometers inexpensively, easily, and reproducibly, compared to conventional nano-patterning techniques such as electron beam lithography. Was completed.

Accordingly, the present invention provides a metal oxide nanostructure etching mask prepared using an azobenzene group-containing compound applicable to a variety of industrially useful information-electronic devices regardless of the type of substrate and a nano patterning method using the same. Its purpose is to.

The present invention comprises the steps of coating an azobenzene group-containing compound on a substrate and then exposing to form a surface irregularities structure; Removing an azobenzene group-containing compound while forming a metal oxide nanostructure etching mask on the formed surface uneven structure; Selectively etching the substrate using the metal oxide nanostructure etching mask; And removing the metal oxide nanostructure etching mask.

Hereinafter, the present invention will be described in detail.

The present invention provides a metal oxide nanostructure etching mask using surface relief gratings (SRGs) formed by the photophysical mass transfer principle of an azobenzene group-containing compound, and patterned using the same, thereby limiting existing optical lithography techniques. Patterning of less than 1 micrometer in size allows nano-patterning of various sizes ranging from tens of nanometers to thousands of nanometers. Unlike conventional methods such as electron beam lithography or laser-patterned nano-patterning, it can be applied to simple chemical methods without sophisticated control. The present invention relates to an improved nanopatterning method that can be manufactured at low cost so as to reproducibly produce various types of etching masks such as linear nanowires or two-dimensional curved surfaces.

Hereinafter, the present invention will be described in detail step by step.

First, after coating the azobenzene group-containing compound on the substrate and exposed to form a surface uneven structure.

The present invention is a method that can be carried out without limitation to the selection of the substrate, in the embodiment of the present invention, as the substrate, indium-doped tin oxide (Indium-doped SnO ₂ , ITO) and also transparent Fluorine-doped tin oxide (Fluorine-doped SnO ₂ , FTO) is used, but it can be applied to various inorganic substrates including oxide.

First, the characteristics of the azobenzene group used in the present invention will be described in more detail as follows. An azobenzene group has a chemical structure in which two benzene groups are connected by two nitrogen atoms, and is an aromatic compound that is delocalized throughout the molecule by side overlap of an electron orbit. Each nitrogen atom connecting the two benzene groups has one unbonded electron pair, and photoisomerization occurs between the trans structure and the cis structure isomer by light energy.

When the compound containing such an azobenzene group is exposed to linearly polarized light, the property of orienting perpendicularly to the linear polarization direction of incident light is widely known. A schematic diagram illustrating such a light guide linear alignment characteristic is shown in FIG. 1.

Figure 2 is a schematic view of the optical device used to form the surface irregularities structure using the photo-induced linear alignment characteristics of the azobenzene group.

The exposure is preferably performed using a lambda / 2 wave plate optical material, the lambda / 2 wave plate optical material is a p-polarized and linear polarization plane within the range of 0 ~ 90 ° It is enough to have the property to rotate.

When the optical material having the above characteristics is used, the surface irregularities structure can be more effectively formed, and the metal oxide nanostructure etching mask spacing can be variously controlled by forming the surface irregularities structure at various intervals.

As the azobenzene group-containing compound, those having molecular weights ranging from thousands to hundreds of thousands can be used, but the higher the molecular weight, the slower the photophysical behavior with respect to exposure. Therefore, it is preferable to select and use molecular weight suitably. Specifically, when the organic glass (oganic glass) having a characteristic of less chain entanglement is used, the photophysical behavior with respect to the exposed light appears quickly, so that the formation and removal of the uneven structure may be performed in a short time.

In general, a 488 nanometer laser beam of an argon laser is used as a light source, and the linearly polarized light passes through a λ / 2 wave plane and becomes p-polarized, and passes through a spatial filter and a lens to be exposed to a sample. Half of the parallel rays are then directly exposed to the sample and the other is reflected off the mirror-coated mirror surface.

Such exposure may form a two-dimensional surface uneven structure when repeatedly performed while rotating the substrate coated with the azobenzene group-containing compound, thereby manufacturing a two-dimensional metal oxide etching mask.

Secondly, the azobenzene group-containing compound is removed while the metal oxide nanostructure etching mask is formed on the surface irregularities.

The metal oxide nanostructure etching mask is formed using a metal oxide derivative solution, and the metal oxide may be one having a property to which a sol-gel process is applicable. In this case, when the above characteristics are not expressed, there is a problem that a complicated process is required in forming the metal oxide etching mask. The metal constituting the metal oxide may be titanium, zinc, niobium, nickel, tin and tungsten, and the like. Specifically, for example, derivatives of metal oxides that may be used in the present invention include alkoxides, nitrates, There are selected from precursors such as chloride and acetate.

It is preferable to use the above-mentioned metal oxide derivative which consists of a solvent and a volume ratio of 1: 10-200. As the solvent, a solvent having a property capable of reducing the metal oxide formation rate due to hydrolysis may be used. Specifically, for example, an alcohol-based organic solvent or strong acid water or a suitable combination thereof may be used. .

At this time, as the content of the metal oxide derivative in the solution is increased, the pattern interval is formed wide. If the content of the metal oxide derivative is less than the above range, the thickness of the nano-structure etching mask is thick, there may be a problem in the process of removing the final mask. If it exceeds the above range, it is difficult to manufacture a uniform nano-structured etching mask to properly adjust the concentration according to the use.

In addition, when 2 to 10% by volume of hydrochloric acid is included in the metal oxide derivative solution, it is possible to precisely control the rate of metal oxide formation due to the hydrolysis of the metal oxide derivative, thereby making nanostructure etching masks of various widths and thicknesses. In the case of using a two-dimensional surface asperity structure, an etching mask having various types of metal oxide nanostructures may be applied to fabrication and nanopatterning.

After forming the metal oxide nano-structure etching mask to perform a multi-step heat treatment to remove the azobenzene group-containing compound, the heat treatment is preferably carried out stepwise at a temperature in the range of room temperature (25 ℃) ~ 425 ℃. Preferably, the temperature is raised to room temperature to 100 ° C. for 20 minutes to 1 hour, and then maintained for 30 minutes to 2 hours, the temperature is slowly increased to 100 to 350 ° C. for 3 to 5 hours, and then maintained for 2 to 8 hours. It is good to keep it for 1 hour to 3 hours after raising the temperature to 425 ℃ for 40 minutes to 2 hours.

This is to prevent defects of the metal oxide etching mask that may occur when the azobenzene group-containing compound is removed, and a total heat treatment time of about 12 hours is appropriate by slowing down the temperature increase rate. After the heat treatment is completed, only the metal oxide nanostructure etching mask remains on the azobenzene group-containing compound-coated substrate.

When the manufacturing step of the metal oxide nanostructure etching mask as described above is repeatedly performed, it becomes possible to form a two-dimensional pattern.

Also, in the process of forming the surface uneven structure in the azobenzene group, when the sample is repeatedly exposed by rotating the sample, a special shape of the two-dimensional uneven structure is formed, and as a result, an etching having a linear nano wire or various two-dimensional metal oxide nano structures is performed. Fabrication of masks and patterning using the same is possible.

Thirdly, the substrate is selectively etched using the metal oxide nanostructure etching mask.

The etching may be performed by various methods such as wet etching and dry etching, and is more preferable when the dry etching process is adopted. Specifically, the etching method may include inductively coupled plasma (ICP) etching, reactive ion etching (RIE), or the like.

It is more preferable when the gas mixture selected from halogen gas, methane gas, hydrogen gas, methane tetrafluoride gas and the like is used as a reactant when etching the substrate, and the mixing conditions of the gas may be appropriately adjusted as necessary. do. In the above etching process, there is no limitation in controlling the depth that can be etched by using a condition that can selectively etch only the substrate with respect to the metal oxide nanostructure etching mask.

Fourthly, the metal oxide nanostructure etching mask remaining after the selective etching is removed.

In this case also, it is important to determine the selection and conditions of the reactor that can selectively remove only the metal oxide etch mask, and selectively remove only the metal oxide nanostructure etch mask without affecting the already etched substrate.

By the above-mentioned method, the problem of impossible to form patterns of 1 μm or less by conventional photolithography can be solved, thereby obtaining a metal oxide etching mask having a pattern of several tens to thousands of nanometers. Using an etching mask, a substrate having a pattern of several tens to thousands of nanometers in size can be obtained.

 Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the following Examples.

Example 1 Indium-doped Tin Oxide Using a Titania Nanowire Etch Mask ₂ , ITO) Nano Patterning

PDO3 (Poly (disperse orange 3, see FIG. 3) was used as the azobenzene group-containing compound, and indium-doped tin oxide (Indium), which is the most widely used transparent electrode in the art, was shown by the method shown in FIG. -doped SnO ₂ , ITO) was patterned.

First, a solution prepared by dissolving PDO3 in hexanon with a cycle was spin-coated and deposited to a thickness of 500 nanometers, and dried in a vacuum oven at 100 ° C. to remove the remaining organic solvent to form a PDO3 film.

The PDO3 film was exposed to light for 1 hour with an argon laser of 488 nanometers using an optical device having a structure shown in FIG. 2 to form a surface asperity structure. Titanium isopropoxide, isopropanol and hydrochloric acid on the surface concave-convex structure and spin-coated a solution produced in a volume ratio of 1: 40: 4, and then heated to room temperature to 100 ℃ for 30 minutes and maintained for about 1 hour, 100 After slowly raising the temperature to ˜350 ° C. for 3 hours, the mixture was maintained for 5 hours, and heated to 350 ° to 425 ° C. for 30 minutes, and held for 2 hours. Through the heat treatment, PDO3 was completely removed and only the Titania nanowire etch mask remained on ITO.

By using the Titania nanowires remaining on the ITO as an etching mask, an inductively coupled plasma (ICP), which is one of the dry etching processes, is used to prevent residual ITO or additional etching of the side wall that may occur during wet etching. The substrate was selectively etched, and the remaining titania nanowire etching mask was removed by reactive ion etching (RIE). At this time, ITO was etched at 1000 W for 2 minutes, and as a reaction gas, argon (Ar) gas and methane (CH ₄ ) gas were mixed and used in a 9: 1 volume ratio. The Titania nanowire etch mask was etched at 200 W for 20 minutes, and methane tetrafluoride (CF4) gas was used as the reactant.

Referring to FIG. 5, it can be seen that the surface uneven structure having a gap of 500 nanometers and a depth of 130 nanometers was formed through the AFM shape and the depth distribution. Referring to FIG. 6, the width of the Titania nanowire etching mask was 250 nanometers. It can be seen that the meter.

In addition, it can be seen from FIG. 7 that ITO is patterned to a depth of 100 nanometers. 8 and 9 show SEM pictures and EDX spectra of the titania nanowire etching mask and the patterned ITO, respectively, and it can be seen that the titania nanowire etching mask was completely removed by reactive ion etching.

Example 2 Fluorine-Doped Tin Oxide Using a Titania Nanowire Etch Mask ₂ , FTO) Nano Patterning

PDO3 was used as the azobenzene group-containing compound, and the fluorine-doped tin oxide (Fluorine-doped SnO ₂ , FTO), a transparent electrode having thermal stability, was patterned by the method shown in FIG. 4.

The patterning process was performed in the same manner as in Example 1, and the FTO and titania nanowire etching masks were etched by inductively coupled plasma (ICP) and reactive ion etching (RIE).

The FTO was etched at 1000 W for 2 minutes, and the reactant was mixed with chlorine (Cl ₂ ) gas, methane (CH ₄ ) gas, hydrogen (H ₂ ) gas and argon (Ar) gas at 15: 4: 4: 8. Used. The Titania nanowire etch mask was etched at 200 W for 20 minutes and methane tetrafluoride (CF ₄ ) gas was used as the reactor.

In the accompanying drawings, a surface image of a Titania nanowire etching mask fabricated using a surface concave-convex structure having a gap of 500 nanometers and a patterned FTO using the same is shown in SEM images, respectively.

In particular, a solution of titanium isopropoxide, isopropanol, and hydrochloric acid in a ratio of 1: 20: 4 was used to increase the size of the mask, resulting in a mask wider than that of Example 1 of 350 nanometers.

FIG. 11 shows a SEM image showing the surface shape of a Titania nanowire etching mask fabricated using a surface irregularity structure having a wide interval of 1000 nanometers and a patterned FTO using the same.

In this case, the size of the mask was about 770 nanometers, it can be seen that each of the etched depth was constant about 150 nanometers.

Example 3 Fabrication of Two-Dimensional Niobium Oxide Nanostructure Etch Mask Using Two-Dimensional Surface Unevenness and Repeated Nanowire Etch Mask Fabrication Process

PDO3 was used as the azobenzene group-containing compound, and niobium chloride was used as a precursor to prepare a two-dimensional nanostructure etching mask as shown in FIG. 12.

In this example, two distinct methods were used to fabricate a two-dimensional etching mask. First, in order to fabricate a two-dimensional nanostructure etching mask having a shape as shown in (a) of FIG. 12, a film of PDO3, an azobenzene group-containing compound, was formed and subjected to exposure in the same manner as in Examples 1 and 2 and The sample was rotated at 90 ° to repeat exposure.

After repeated exposure, two-dimensional surface irregularities can be obtained, and niobium chloride, ethanol, and hydrochloric acid were spin-coated in a ratio of 1: 20: 4, and heat-treated stepwise as in Examples 1 and 2 above. The azobenzene group-containing compound PDO3 was completely removed. In the two-dimensional mask formed by the above process, the hole diameter was 120 nanometers, the gap between the holes was 380 nanometers, and the thickness of the etching mask was about 40 nanometers.

Secondly, after fabricating niobium nanowires in the same process as in Example 1 and 2 for fabricating a two-dimensional nanostructure etching mask, and then manufacturing nanowires rotated by 90 ° through an intentional repeating process, It is possible to produce a two-dimensional nanostructure etching mask in the form of a mesh as shown in FIG. The niobium nano wire was prepared by spin coating niobium chloride, ethanol, and hydrochloric acid at a ratio of 1: 20: 4, and thermally removing the azobenzene group-containing compound PDO3 in the same manner as in Examples 1 and 2 above. In the two-dimensional mask formed by the above process, the size of the net is about 200 x 300 nanometers.

As described above, according to the present invention, a metal oxide nanostructure etching mask is manufactured by a simple chemical method using surface relief gratings (SRGs) formed by the photophysical mass transfer principle of an azobenzene group-containing compound. Application to nano patterning solves the problem that patterning was not possible with sub-micron size, which was the limitation of conventional optical lithography technology, and it is easy and reproducible to patterning in various sizes from tens of nanometers to thousands of nanometers. It can be applied to the area.

In particular, the etching mask forming process of the present invention is not limited to the substrate to be applied, and it is possible to manufacture and pattern etching masks representing various types of metal oxide nanostructures using linear nanowires or two-dimensional uneven structures, which are industrially useful. When applied to information-electronic devices, it is possible to improve performance and reduce production costs.

Claims (14)

Coating and then exposing the azobenzene group-containing compound on the substrate to form a surface irregularity structure; Removing an azobenzene group-containing compound while forming a metal oxide nanostructure etching mask on the formed surface uneven structure; Selectively etching the substrate using the metal oxide nanostructure etching mask; And Removing the metal oxide nanostructure etch mask Nano patterning method comprising a. The nano-patterning method according to claim 1, wherein the azobenzene group-containing compound uses a molecular weight ranging from thousands to hundreds of thousands. The method of claim 1, wherein the exposure is performed using a lambda / 2 wave plate optical material. The nanopatterning method of claim 3, wherein the λ / 2 wave plate optical material is capable of rotating the p-polarized light and the linear polarized light within a range of 0 ° to 90 °. The nano-patterning method of claim 1, wherein the exposure is repeatedly performed while rotating the substrate coated with the azobenzene group-containing compound. The nano-patterning method of claim 1, wherein the azobenzene group-containing compound is removed by heat treatment at room temperature to 425 ° C. The nano patterning method of claim 1, wherein the metal oxide is applicable to a chemical sol-gel process. 8. The method of claim 7, wherein the metal is selected from titanium, zinc, niobium, tin, nickel and tungsten. The method of claim 1, wherein the forming of the metal oxide nanostructure etching mask is performed with a metal oxide derivative solution. 10. The method of claim 9, wherein the metal oxide derivative is selected from alkoxides, nitrates, chlorides and acetates of metal oxides. 10. The method of claim 9, wherein the metal oxide derivative is a nano patterning method, characterized in that consisting of a solvent and a volume ratio of 1: 10 to 200. The method of claim 9, wherein the metal oxide derivative solution comprises 2 to 10% by volume of hydrochloric acid. The method of claim 1, wherein forming the nanostructure etch mask is performed repeatedly. The nano-patterning of claim 1, wherein the selective etching of the substrate using the etching mask is performed using a gas mixture selected from argon gas, methane gas, hydrogen gas and methane tetrafluoride gas as a reactant. Way.

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