Method for forming three-dimensional microstructures using etching and etching mask used therefor

Abstract

The present invention relates to a method for forming a three-dimensional microstructure using etching and an etching mask used therefor. Specifically, it relates to a method for forming an elaborate and complex three-dimensional microstructure by using a carbon-based thin film as an etching mask and deforming the carbon-based thin film during the etching process.

Description

Technical Field

[0001] The present invention relates to a method for forming a three-dimensional structure using etching and an etching mask used therefor. The present invention claims the benefit of the filing date of Korean Patent Application No. 10-2024-0036486, filed with the Korean Intellectual Property Office on March 15, 2024, and all of its contents are incorporated herein by reference.

Background Art

[0002] As the semiconductor industry demands higher levels of integration, there is an increasing need to form fine patterns using silicon or germanium-based semiconductor materials. This need is also growing in fields that require the formation of three-dimensional fine structures, such as micro-bio robots and biosensors. However, conventional techniques for forming three-dimensional fine structures are limited to realizing complex and delicate three-dimensional fine structures using only lithography processes, and a large number of process steps are required.

[0003] [[ID=,16]]On the other hand, in order to realize a delicate three-dimensional fine structure, the material used as a mask needs to have a high etching resistance ratio, be capable of forming fine patterns, have excellent mechanical strength and chemical safety, and the etching process is required to be precisely controllable.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technical problem to be achieved by the present invention is to provide a method capable of forming a delicate three-dimensional fine structure by etching a substrate.

[0005] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned should be clearly understood by those skilled in the art from the following description.

Means for Solving the Problems

[0006] One embodiment of the present invention provides a method for forming a three-dimensional structure by etching a substrate, comprising the steps of: forming a carbon-based thin film on the substrate; patterning the carbon-based thin film; using the patterned carbon-based thin film as an etching mask, primary etching the substrate using an etching gas containing fluorine; deforming the patterned carbon-based thin film so that the carbon-based thin film above the undercut region formed by the primary etching adheres to the primary etched substrate sidewall; and using the deformed carbon-based thin film as an etching mask, secondary etching the substrate using an etching gas containing fluorine.

[0007] Another embodiment of the present invention provides an etching mask used in a method for forming the three-dimensional structure, comprising a patterned carbon-based thin film. [Effects of the Invention]

[0008] The method for forming a three-dimensional structure according to the present invention makes it possible to form an elaborate and complex three-dimensional structure by etching a substrate.

[0009] The method for forming a three-dimensional structure according to the present invention can improve the omniphobic properties of the substrate surface by forming a reentrant structure on the substrate surface.

[0010] The method for forming a three-dimensional structure according to the present invention allows for precise control of the etching depth beneath the etching mask.

[0011] The effects of the present invention are not limited to those described above, and any effects not mentioned should be clearly understood by those skilled in the art from this specification and the accompanying drawings. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a flowchart of a method for forming a three-dimensional structure according to one embodiment of the present invention. [Figure 2a] Figure 2a is a schematic diagram showing each step of a method for forming a three-dimensional structure according to one embodiment of the present invention. [Figure 2b] Figure 2b is a schematic diagram showing each step of a method for forming a three-dimensional structure according to one embodiment of the present invention. [Figure 3] Figure 3 shows the shape of the patterned graphene thin films from Examples 5 to 16 and SEM images of the final formed three-dimensional structures. [Figure 4] Figure 4 shows the Raman spectrum for a graphene thin film synthesized by chemical vapor deposition for 120 minutes in Example 1. [Figure 5] Figure 5 shows the AFM height image (a), BF-TEM image (b), SAED image (c), and DF-TEM image (d) of a graphene thin film synthesized in Example 1 by chemical vapor deposition for 120 minutes. [Figure 6] Figure 6 shows SEM images of the substrate and graphene thin film obtained in Reference Examples 1-1 and 1-2. [Figure 7] Figure 7 shows SEM images of the substrates and 1- to 4-layer graphene thin films obtained in Reference Examples 2-1 to 2-4. [Figure 8] Figure 8 shows SEM images of the manufacturing process of Example 1 at the time when the primary etching was completed (a), when the graphene thin film was deformed to adhere closely to the sidewall of the etched substrate (b), and when the secondary etching was completed (c). [Figure 9] Figure 9 shows an SEM image of the substrate on which the three-dimensional structure obtained in Example 4 was formed. [Figure 10] Figure 10 shows an SEM image of the substrate on which the three-dimensional structures obtained in Examples 1 to 3 were formed. [Figure 11]FIG. 11 is a photograph taken by dropping an ethanol aqueous solution with a surface tension of 30 mN / m onto the surface of a substrate on which the three-dimensional structure obtained in Example 4 was formed and that had been treated with PFOTS (1H,1H,2H,2H-perfluorooctyltrichlorosilane). [Figure 12] FIG. 12 is a diagram showing the contact angles measured for the untreated surface and the PFOTS-treated surface of a general silicone substrate, the PFOTS-treated surface of the substrate surface on which the three-dimensional structure obtained in Example 4 was formed, and the PFOTS-treated surface of the substrate surface on which the structure obtained in Comparative Example 1 was formed. [Figure 13] FIG. 13 is a diagram showing the etching depth investigated for the substrate etched in Reference Example 3.

BEST MODE FOR CARRYING OUT THE INVENTION

[0013] Throughout this specification, when a part states that a certain component "includes" something, this means that, unless otherwise stated to the contrary, it can further include other components rather than excluding other components.

[0014] Throughout this specification, when a member is stated to be "above" another member, this includes not only the case where one member is in contact with the other member, but also the case where there is another member between the two members.

[0015] Throughout this specification, the unit "parts by weight" can mean the weight ratio between each component.

[0016] Throughout this specification, "A and / or B" means "A and B, or A or B".

[0017] Throughout this specification, the "re-entrant structure" can mean a structure including a column part and a lid part located on the column part and having a diameter larger than the diameter of the column part.

[0018] One embodiment of the present invention provides a method for forming a three-dimensional structure by etching a substrate, comprising the steps of: forming a carbon-based thin film on the substrate; patterning the carbon-based thin film; using the patterned carbon-based thin film as an etching mask, primary etching the substrate using an etching gas containing fluorine; deforming the patterned carbon-based thin film so that the carbon-based thin film above the undercut region formed by the primary etching adheres to the primary etched substrate sidewall; and using the deformed carbon-based thin film as an etching mask, secondary etching the substrate using an etching gas containing fluorine.

[0019] The method for forming a three-dimensional structure according to the present invention can form an elaborate and complex three-dimensional microstructure by etching a substrate.

[0020] Figure 1 is a flowchart of a method for forming a three-dimensional structure according to one embodiment of the present invention.

[0021] Figures 2a and 2b schematically show each step of a method for forming a three-dimensional structure according to one embodiment of the present invention.

[0022] The method for forming a three-dimensional structure according to the present invention involves using a patterned carbon-based thin film as an etching mask and performing a step of deforming the patterned carbon-based thin film, thereby enabling the formation of a three-dimensional structure that cannot be obtained by existing etching methods.

[0023] According to one embodiment of the present invention, the three-dimensional structure may be a reentrant structure. By etching the substrate to form a reentrant structure, the omniphobic properties of the substrate surface can be improved.

[0024] According to one embodiment of the present invention, the substrate may contain silicone (Si), germanium (Ge), silicone germanium (SiGe), or compounds thereof. When the substrate contains silicone (Si), germanium (Ge), silicone germanium (SiGe), or compounds thereof, the etching rate with the fluorine-containing etching gas may be increased.

[0025] According to one embodiment of the present invention, the method for performing the step of forming a carbon-based thin film on the substrate is not particularly limited, and may be, for example, by transferring a carbon-based thin film obtained by mechanical exfoliation onto the substrate, or by directly synthesizing it on the substrate using chemical vapor deposition (CVD) or sputtering.

[0026] According to one embodiment of the present invention, the step of forming a carbon-based thin film on the substrate may be performed by chemical vapor deposition (CVD) or sputtering. When a carbon-based thin film is formed on the substrate by chemical vapor deposition (CVD) or sputtering, a thin and uniform carbon-based thin film can be obtained, and the thickness can be easily adjusted.

[0027] According to one embodiment of the present invention, the carbon-based thin film is a thin film containing a carbon-based material, and preferably contains graphene or an amorphous carbon atom layer. By including graphene or an amorphous carbon atom layer in the carbon-based thin film, the carbon-based thin film can completely cover the surface of the substrate to be etched, and the etching gas containing fluorine can be prevented from penetrating to the substrate below the carbon-based thin film.

[0028] According to one embodiment of the present invention, the thickness of the carbon-based thin film may be 0.3 nm to 50 nm. More specifically, the thickness of the carbon-based thin film may be 1 nm to 20 nm. By ensuring that the thickness of the carbon-based thin film is within the aforementioned range, the carbon-based thin film can be easily deformed.

[0029] According to one embodiment of the present invention, the step of patterning the carbon-based thin film may be carried out by forming a patterning layer on the carbon-based thin film by lithography, forming a patterned carbon-based thin film by reactive ion etching (RIE) using the patterning layer as an etching mask, and removing the patterning layer. However, the method of patterning the carbon-based thin film is not limited thereto, and the carbon-based thin film may also be patterned by other methods known to the ordinary person in the art.

[0030] According to one embodiment of the present invention, the lithography may be photolithography or electron beam lithography. For example, the step of forming a patterning layer on the carbon-based thin film by photolithography may be performed by forming a photoresist material layer on the carbon-based thin film, irradiating it with light using a photomask, and then developing the pattern using a developer. The step of forming a patterning layer on the carbon-based thin film by electron beam lithography may be performed by forming an electron beam resist material layer on the carbon-based thin film, irradiating a selected area with an electron beam, and then developing the pattern using a developer. When the lithography is photolithography, a pattern of a three-dimensional structure can be formed even on a large-area substrate.

[0031] According to one embodiment of the present invention, the reactive ion etching (RIE) may be performed by removing the carbon-based thin film in areas not covered by the patterning layer, thereby patterning the carbon-based thin film with the same pattern as that formed on the patterning layer.

[0032] According to one embodiment of the present invention, the reactive ion etching (RIE) may use an oxygen plasma and / or a hydrogen plasma.

[0033] According to one embodiment of the present invention, the step of removing the patterning layer may be carried out using a solvent capable of selectively dissolving the patterning layer material.

[0034] According to one embodiment of the present invention, the patterned carbon-based thin film can have a variety of pattern designs depending on the shape of the three-dimensional structure to be formed.

[0035] The patterned carbon-based thin film may include openings and, depending on the embodiment, may further include a plurality of microholes.

[0036] According to one embodiment of the present invention, if the patterned carbon-based thin film further includes a plurality of microholes, the substrate below the region in which the plurality of microholes are formed can have its etching depth adjusted according to the size of the microholes.

[0037] According to one embodiment of the present invention, the size of the microhole may be between 0.01 μm and 10 μm.

[0038] According to one embodiment of the present invention, the steps of primary etching and secondary etching of the substrate may be performed by a chemical reaction between the fluorine-containing etching gas and the substrate, without using plasma.

[0039] Since the primary and secondary etching steps involve etching through a chemical reaction between the fluorine-containing etching gas and the substrate, substrate damage caused by radicals and ions that may occur during the plasma etching process is prevented, thus enabling the formation of more sophisticated three-dimensional structures. Furthermore, because the primary and secondary etching steps involve etching through a chemical reaction between the fluorine-containing etching gas and the substrate, etching of carbon-based thin films does not occur in the primary and secondary etching steps, making it effective for selective etching of the substrate.

[0040] According to one embodiment of the present invention, the upper surface of a carbon-based thin film exposed to an etching gas containing fluorine is fluorinated, and a fluorinated carbon atom layer can be formed. By forming a fluorinated carbon atom layer on the upper surface of the carbon-based thin film, the carbon-based thin film can have near-infinite etching resistance to an etching gas containing fluorine.

[0041] According to one embodiment of the present invention, the etching gas containing fluorine may contain at least one of xenon difluoride (XeF2), carbon tetrafluoride (CF4), and sulfur hexafluoride (SF6). Preferably, the etching gas containing fluorine may contain xenon difluoride (XeF2).

[0042] According to one embodiment of the present invention, the steps of primary etching and secondary etching of the substrate using an etching gas containing fluorine may be isotropic etching.

[0043] Since the primary etching step is isotropic etching, the primary etching can form an undercut region where etching has occurred beneath the patterned carbon-based thin film.

[0044] By adjusting the execution time of the primary etching step, the size of the undercut region formed by the primary etching can be adjusted, and by adjusting the size of the undercut region, the relative ratio between the height of the column portion and the thickness of the lid portion in the formed three-dimensional reentrant structure can be adjusted. More specifically, if the execution time of the primary etching step is reduced, the size of the formed undercut region will be smaller, and the relative thickness of the lid portion in the formed three-dimensional reentrant structure may be reduced. By adjusting the relative ratio between the height of the column portion and the thickness of the lid portion of the three-dimensional reentrant structure as described above, the surface characteristics of the substrate on which the three-dimensional reentrant structure is formed, such as the contact angle, can be changed.

[0045] According to one embodiment of the present invention, the execution time of the primary etching step and the secondary etching step may be adjusted to a range of 1 second to 60 minutes, but is not particularly limited thereto.

[0046] According to one embodiment of the present invention, by performing a step of deforming the patterned carbon-based thin film so that the carbon-based thin film above the undercut region formed by the primary etching adheres closely to the side wall of the primary etched substrate, the final structure can have not only a two-dimensional pattern but also a three-dimensional pattern.

[0047] According to one embodiment of the present invention, the step of deforming the patterned carbon-based thin film may be performed by applying a volatile liquid onto the patterned carbon-based thin film and evaporating it.

[0048] According to one embodiment of the present invention, the volatile liquid may be a low molecular weight organic compound. Specifically, the low molecular weight organic compound may be an alcohol, ether, ketone, or ester, and preferably an alcohol. For example, the volatile liquid may include 2-propanol, ethanol, methanol, or a combination thereof. When the volatile liquid is an alcohol, its low surface tension makes it suitable for adequately wetting the surface of the patterned carbon-based thin film, and its high volatility makes it easy to evaporate.

[0049] According to one embodiment of the present invention, a three-dimensional structure can be formed by performing a step of secondary etching the substrate using the fluorine-containing etching gas with the deformed carbon-based thin film as an etching mask.

[0050] Another embodiment of the present invention provides an etching mask used in the method for forming the aforementioned three-dimensional structure, comprising a patterned carbon-based thin film.

[0051] The etching mask, based on the high elastic modulus, mechanical safety, and thinness of the patterned carbon-based thin film, can undergo various deformations during the etching process and has near-infinite etching resistance to etching gases containing fluorine, thereby enabling precise etching.

[0052] A method for forming a three-dimensional structure according to one embodiment of the present invention may further include a step of removing the deformed carbon-based thin film after the secondary etching step.

[0053] Specifically, the deformed carbon-based thin film can be removed by performing a reactive ion etching process using a fluorine-free gas. For example, the deformed carbon-based thin film can be removed by performing a reactive ion etching process using oxygen plasma and / or hydrogen plasma. [Examples]

[0054] The present invention will be described in detail below with reference to examples. However, the examples of the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples herein are provided to give a more complete explanation of the present invention to a person of average skill in the art.

[0055] Example 1 (1) Step of forming a graphene thin film on a substrate As the substrate to be etched, a silicone (Si) substrate (thickness: 550 to 550 μm, P-type boron doped, Prime grade, manufactured by NAMKANG Hi-Tech) was prepared, and a graphene thin film was synthesized on the substrate using chemical vapor deposition (CVD). Specifically, the substrate was placed in a reaction chamber, hydrogen (H2) gas was supplied and the temperature was raised to 1020°C at a rate of approximately 16.6°C / min, and then methane (CH4) and hydrogen (H2) gas were supplied and synthesis was carried out for 120 minutes to synthesize a graphene thin film with a thickness of approximately 1.5 to 2 nm on the Si substrate.

[0056] (2) Step of patterning the graphene thin film A patterning layer was formed on the graphene thin film using electron beam lithography. Specifically, a polymethyl methacrylate (PMMA) solution (950 PMMA A6) was coated onto the graphene thin film to form a PMMA layer, and the PMMA layer was irradiated with an electron beam using a field emission scanning electron microscope (MIRA3XMH manufactured by TESCAN). Thereafter, the PMMA layer was immersed for 1 minute in a 3:1 solution of 2-propanol and Di water as a developer to form a PMMA patterning layer on the carbon-based thin film.

[0057] Using a PMMA patterning layer as an etching mask, a reactive ion etching apparatus (RIE-10NR manufactured by Samco) was used to etch the graphene thin film with carbon tetrafluoride (CF4) gas flowing at a flow rate of 20 sccm and a power of 30W for 3 minutes to obtain a patterned graphene thin film. Subsequently, the laminate of the substrate-patterned graphene thin film-PMMA patterning layer was immersed in acetone for 10 minutes to remove the PMMA patterning layer.

[0058] (3) A step in which the substrate is primary etched using an etching gas containing fluorine, with the patterned graphene thin film as an etching mask. The patterned graphene thin film was used as an etching mask, and a dry etching process was performed using xenon difluoride (XeF2) gas. An XeF2 etching apparatus (SAMCO VPE-4F) was used, and the etching gas pressure (P XeF2 ) = 3torr, processing time (t exposure The primary etching was performed at room temperature (approximately 20°C) for 220 seconds.

[0059] (4) Step of deforming the patterned graphene thin film The process of dropping 2-propanol onto the patterned carbon-based thin film and allowing it to air dry was repeated three times, deforming the graphene thin film that was floating above the undercut formed by the primary etching so that it adhered closely to the etched substrate sidewall.

[0060] (5) Using the deformed graphene thin film as an etching mask, the substrate is secondarily etched using an etching gas containing fluorine. A three-dimensional structure was formed by performing secondary etching in the same manner as the primary etching step, except that the deformed graphene thin film described above was used as an etching mask and the processing time was set to 50 seconds.

[0061] Example 2 (1) Step of forming a graphene thin film on a substrate A graphene thin film with a thickness of approximately 1.5 to 2 nm was synthesized on a Si substrate using the same method as in Example 1.

[0062] (2) Step of patterning the graphene thin film To form a three-dimensional structure over a large area on the substrate, a patterning layer was formed on the graphene thin film using photolithography. Specifically, AZ5214E ​​was coated onto the graphene thin film to a thickness of 1 μm as a photoresist, and after the photoprocessing was performed, it was immersed in AZ 917 MIF developer for about 1 minute for development.

[0063] (3) A step in which the substrate is primary etched using an etching gas containing fluorine, with the patterned graphene thin film as an etching mask. Processing time (t exposure Primary etching was performed in the same manner as in Example 1, except that the etching time was set to 180 seconds.

[0064] (4) Step of deforming the patterned graphene thin film In the same manner as in Example 1, the graphene thin film that was floating above the undercut formed by primary etching was deformed so that it adhered closely to the etched substrate sidewall.

[0065] (5) Using the deformed graphene thin film as an etching mask, the substrate is secondarily etched using an etching gas containing fluorine. A three-dimensional structure was formed by performing secondary etching in the same manner as in Example 1.

[0066] Example 3 In the primary etching step of the above-described embodiment 2, the processing time (t exposure A three-dimensional structure was formed in the same manner as in Example 2, except that the time was set to 120 seconds.

[0067] Example 4 In the above-described Example 2, after the secondary etching step, a further step was performed to remove the deformed graphene thin film.

[0068] Specifically, the graphene thin film was removed by flowing oxygen at a flow rate of 20 sccm and performing a reactive ion etching process for 2 minutes with a power of 100W.

[0069] Examples 5 to 16 A three-dimensional structure was formed in the same manner as in Example 1, except that in the step of patterning the graphene thin film in Example 1, a graphene thin film patterned to the shape shown in Figure 3 was formed.

[0070] SEM images were obtained for the three-dimensional structures of Examples 5 to 16 using a scanning electron microscope. Figure 3 shows the shape of the patterned graphene thin films of Examples 5 to 16 and the SEM images of the finally formed three-dimensional structures. Referring to Figure 3, it was confirmed that the three-dimensional structures formed by the method according to the present invention can realize complex and sophisticated three-dimensional structures.

[0071] Comparative Example 1 In the above-described Example 1, the deformation step and secondary etching step of the patterned graphene thin film were omitted, and only the primary etching step was performed as described in Example 1, to obtain a substrate on which a columnar structure was formed.

[0072] References 1-1 and 1-2 In the step of forming a graphene thin film on a silicone substrate in Example 1, the synthesis time was adjusted to 30 minutes (Reference Example 1-1) and 6 hours (Reference Example 1-2), respectively, to obtain graphene thin films formed on the silicone substrate. Then, each graphene thin film was patterned in the same manner as in Example 1, and this was used as an etching mask to perform primary etching on the substrate.

[0073] See examples 2-1 to 2-4 In the step of forming a graphene thin film on a silicone substrate in Example 1, one to four layers of graphene were obtained by a mechanical peeling method using Scotch tape, and each of the one to four graphene thin films was transferred onto the substrate. Subsequently, each of the transferred graphene thin films was used as an etching mask, and primary etching of the substrate was performed in the same manner as in Example 1.

[0074] Reference Example 3 In Example 1, the patterned graphene thin film was formed to include a first pattern portion containing multiple microholes of 0.6 μm size, a second pattern portion containing multiple microholes of 1.4 μm size, a third pattern portion containing multiple microholes of 2 μm size, and a fourth pattern portion containing multiple microholes of 3.6 μm size. The deformation step and secondary etching step of the patterned graphene thin film were omitted, and only the primary etching step was performed, as described in Example 1.

[0075] <Experimental Example 1. Confirmation of Synthesized Graphene Thin Film> For the graphene thin film obtained in the step of forming a graphene thin film on the substrate of Example 1, a Raman spectrum was obtained using a 532 nm laser with a Raman spectrometer (LabRAM HR Evolution, Horiba). In addition, an AFM image was obtained of the graphene thin film using an atomic force microscope (AFM, NX-10, Park Systems), and bright-field TEM (BF-TEM), selected-field electron diffraction (SAED), and dark-field TEM (DF-TEM) images were obtained using a cs-corrected monochromated TEM (Themis Z, Thermo Fisher) at an acceleration voltage of 80 kV.

[0076] Figure 4 shows the Raman spectrum for a graphene thin film synthesized by chemical vapor deposition for 120 minutes in Example 1.

[0077] Figure 5 shows the AFM height image (a), BF-TEM image (b), SAED image (c), and DF-TEM image (d) of a graphene thin film synthesized in Example 1 by chemical vapor deposition for 120 minutes.

[0078] Referring to Figures 4 and 5, it was confirmed that in Example 1, a graphene thin film with a thickness of approximately 1.5 to 2 nm was successfully formed by synthesizing graphene by chemical vapor deposition for 120 minutes.

[0079] Scanning electron microscope (SEM) images were obtained for the substrates and graphene thin films obtained in Reference Examples 1-1 to 1-2 and Reference Examples 2-1 to 2-4 using a scanning electron microscope.

[0080] Figure 6 shows SEM images of the substrate and graphene thin films obtained in Reference Examples 1-1 and 1-2. Referring to Figure 6, it was confirmed that the graphene thin film synthesized in Reference Example 1-1 over 30 minutes, being thin, had the graphene thin film above the undercut region formed by primary etching curve downwards and approach the partition wall even without the partition wall adhesion step using volatile liquid. In contrast, the graphene thin film synthesized in Reference Example 1-2 over 6 hours, being relatively thicker, maintained its shape without the graphene thin film above the undercut region curving before the partition wall adhesion step using volatile liquid was performed.

[0081] Figure 7 shows SEM images of the substrates and 1- to 4-layer graphene thin films obtained in Reference Examples 2-1 to 2-4. Referring to Figure 7, in Reference Example 2-1, where a single-layer graphene thin film was used as an etching mask, it was confirmed that because the thin film was thin and had low rigidity, it bent downward due to gravity and approached the partition wall even without performing the partition wall adhesion step using a volatile liquid. In contrast, in Reference Example 2-4, where a 4-layer graphene thin film was used as an etching mask, it was confirmed that because the thickness was relatively greater, the graphene thin film above the undercut region did not bend and maintained its shape before performing the partition wall adhesion step using a volatile liquid.

[0082] <Experimental Example 2. Confirmation of changes due to primary and secondary etching> SEM images were taken at the following points during the manufacturing process of Example 1: when the primary etching was completed, when the graphene thin film was deformed to adhere closely to the sidewall of the etched substrate, and when the secondary etching was completed.

[0083] Figure 8 shows SEM images of the manufacturing process in Example 1 at the time when the primary etching was completed (a), when the graphene thin film was deformed to adhere closely to the etched substrate sidewall (b), and when the secondary etching was completed (c). Referring to Figure 8, it is possible to confirm the state in which the undercut region was formed by the primary etching, the graphene thin film deformed to adhere closely to the etched substrate sidewall, and the three-dimensional structure obtained through secondary etching.

[0084] <Experimental Example 3: Verification of Reentrant Structure> To confirm the shape of the three-dimensional structures formed in Examples 1 to 4, the formed three-dimensional structures were photographed using a scanning electron microscope (SEM).

[0085] Figure 9 shows an SEM image of the substrate on which the three-dimensional structure obtained in Example 4 was formed. Referring to Figure 9, it was confirmed that the three-dimensional structure formed in Example 4 is a reentrant structure, and that a large area of ​​the three-dimensional reentrant structure pattern was formed on the substrate.

[0086] Figure 10 shows an SEM image of the substrate on which the three-dimensional structures obtained in Examples 1 to 3 were formed. Referring to Figure 10, it was confirmed that the shorter the execution time (processing time) of the primary etching step, the less the undercut region formed by primary etching decreased, and the relatively smaller the thickness of the lid portion of the final reentrant structure.

[0087] <Experimental Example 4. Confirmation of Changes in Contact Angle Characteristics> To confirm the changes in omniphobic properties, i.e., water-repellent and oil-repellent properties, of the substrate surface due to the formation of a three-dimensional reentrant structure, the contact angle of the substrate surface to an ethanol aqueous solution was measured. Specifically, the contact angle was measured for the substrate surface treated with PFOTS (1H,1H,2H,2H-perfluorooctyltrichlorosilane) on the substrate surface on which the three-dimensional reentrant structure obtained in Example 4 was formed, the substrate surface treated with PFOTS on the substrate surface on which the columnar structure obtained in Comparative Example 1 was formed, and for a comparison group, the contact angle was measured for the surface treated with PFOTS and the untreated surface of an unetched general silicone substrate (thickness: 550 to 550 μm, P-type boron doping, Prime grade, manufactured by NAMKANG Hi-Tech). The contact angle measurement of the substrate surface was performed by dropping an ethanol aqueous solution, whose surface tension was adjusted by mixing ethanol and water, onto the PFOTS-treated or untreated surface, and then using contact angle measuring equipment (model 250, manufactured by The Rame-Hart).

[0088] Figure 11 is a photograph taken after dropping an ethanol aqueous solution with a surface tension of 30 mN / m onto the substrate surface on which the three-dimensional structure obtained in Example 4 was formed, which had been treated with PFOTS.

[0089] Figure 12 shows the contact angles measured for an untreated surface of a general silicone substrate, a surface treated with PFOTS, a substrate surface on which the three-dimensional structure obtained in Example 4 was formed and treated with PFOTS, and a substrate surface on which the structure obtained in Comparative Example 1 was formed and treated with PFOTS.

[0090] Referring to Figures 11 and 12, the surface of the substrate with the reentrant structure obtained in Example 4 that was treated with PFOTS had a significantly higher contact angle compared to the untreated surface of a general silicone substrate and the surface treated with PFOTS. Furthermore, even compared to the surface of the substrate of Comparative Example 1, which had a general columnar structure formed by isotropic etching (not a reentrant structure) and was treated with PFOTS, the contact angle of the surface with the reentrant structure obtained in Example 4 was significantly higher, confirming that the water-repellent properties of the substrate were improved by the formation of the reentrant structure.

[0091] <Experimental Example 5. Adjustment of Etching Depth by Adjusting the Size of Microholes> In Reference Example 3, the substrate obtained by primary etching was examined using a surface depth profiler (DektakXT-A from Bruker) to investigate the etching depth of the lower substrate corresponding to the first, second, third, and fourth pattern areas.

[0092] Figure 13 shows the etching depths investigated for the etched substrate in Reference Example 3. Referring to Figure 13, it was confirmed that the etching depth of the patterned portion is adjusted by the size of the microholes formed in the patterned graphene thin film, and that by etching using a patterned graphene thin film including the first to fourth patterned portions, a three-dimensional structure with five levels of etched depth can be formed.

[0093] Although the present invention has been described in limited embodiments, it is understood that the present invention is not limited thereto, and that various modifications and variations are possible within the equivalent scope of the technical concept of the present invention and the claims described below by persons with ordinary skill in the art to which the present invention pertains.

Claims

1. A method for forming a three-dimensional structure by etching a substrate, The steps include forming a carbon-based thin film on the substrate, The steps include patterning the carbon-based thin film, The steps include: first etching the substrate using the patterned carbon-based thin film as an etching mask and an etching gas containing fluorine; The step of deforming the patterned carbon-based thin film so that the carbon-based thin film above the undercut region formed by the primary etching adheres to the side wall of the primary etched substrate, The steps include: using the deformed carbon-based thin film as an etching mask, and performing secondary etching of the substrate using an etching gas containing fluorine; A method for forming a three-dimensional structure, including [the specified element].

2. The step of patterning the carbon-based thin film is as follows: The steps include forming a patterned layer on the carbon-based thin film by lithography, The steps include forming a patterned carbon-based thin film by reactive ion etching (RIE) using the patterning layer as an etching mask, The steps include removing the patterned layer, A method for forming a three-dimensional structure according to claim 1, comprising:

3. The method for forming a three-dimensional structure according to claim 1, wherein the step of deforming the patterned carbon-based thin film is performed by applying a volatile liquid onto the patterned carbon-based thin film and evaporating it.

4. The method for forming a three-dimensional structure according to claim 1, wherein the substrate comprises silicone (Si), germanium (Ge), silicone germanium (SiGe), or compounds thereof.

5. The etching gas containing fluorine is xenon difluoride (XeF). 2 ), carbon tetrafluoride (CF 4 ) and sulfur hexafluoride (SF 6 A method for forming a three-dimensional structure according to claim 1, comprising at least one of the following:

6. The method for forming a three-dimensional structure according to claim 1, wherein the three-dimensional structure is a reentrant structure.

7. The method for forming a three-dimensional structure according to claim 1, wherein the thickness of the carbon-based thin film is 0.3 nm to 50 nm.

8. The method for forming a three-dimensional structure according to claim 1, wherein the carbon-based thin film comprises graphene or an amorphous carbon atom layer.

9. A method for forming a three-dimensional structure according to claim 1, further comprising the step of removing the deformed carbon-based thin film after the secondary etching step.

10. The method for forming a three-dimensional structure according to claim 1, wherein the patterned carbon-based thin film further includes a plurality of microholes.

11. The method for forming a three-dimensional structure according to claim 1, wherein the primary etching step and the secondary etching step are performed by a chemical reaction between the fluorine-containing etching gas and the substrate without using plasma.

12. An etching mask used in a method for forming a three-dimensional structure according to claim 1, comprising a patterned carbon-based thin film.

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