Graphene-based biosensor having three-dimensional corrugated geometry, and manufacturing method thereof

Abstract

The technical idea of the present invention provides a method for manufacturing a graphene-based biosensor having a three-dimensional corrugated geometry, the method being characterized by comprising the steps of: etching an exposed upper surface of a silicon oxide film stacked on a substrate; transferring graphene on the etched upper surface of the silicon oxide film; and forming a pair of source / drain electrodes on the upper surface of the silicon oxide film, wherein a plurality of first high points and a plurality of first low points having a height difference are irregularly arranged on the lower surface of the graphene transferred on the etched upper surface of the silicon oxide film, and a plurality of second high points and a plurality of second low points having a height difference are irregularly arranged on the etched exposed upper surface of the silicon oxide film.

Description

Graphene-based biosensor with three-dimensional wrinkled geometry and its manufacturing method

[0001] The technical idea of ​​the present invention relates to a graphene-based biosensor having a three-dimensional wrinkled geometry and a method for manufacturing the same.

[0002] The recent COVID-19 pandemic has dramatically increased the need for rapid and accurate sensors for detecting biological substances such as DNA and RNA. While a variety of optical, mechanical, and electrical methods have been developed to detect biological substances, most sensors require extensive preprocessing to increase the concentration of the target substance in the solution. In particular, for patient samples such as cancer cells, viruses, and antibodies, the number of extractions from patients is limited, resulting in significantly smaller sample volumes. Furthermore, detection of the target substance requires lengthy and complex preprocessing. Among these, electrical sensors offer high sensitivity without the need for preprocessing to increase the target substance concentration in the solution, and thus, significant research is currently underway.

[0003] Graphene, a two-dimensional hexagonal carbon structure, has recently been actively researched worldwide as a new material that can replace semiconductors. Furthermore, graphene possesses electrically semi-metallic properties, yet because its internal charge acts as a zero-effective mass particle, it is known to possess extremely high electrical conductivity (an intrinsic electron mobility of 20,000 cm2 / Vs). In particular, after the discovery that graphene, a two-dimensional hexagonal carbon atom structure formed by mechanically exfoliating graphite, exhibits field effect characteristics when used in transistors, graphene has been attracting attention as a material that can replace conventional semiconductors such as silicon. Accordingly, extensive research is being conducted on technologies that enhance the selectivity and sensitivity of biosensors containing graphene while maintaining the inherently excellent electrical conductivity of graphene. Furthermore, research is being conducted on technologies for rapidly modifying the graphene surface and stably immobilizing bioreceptors without additional chemical reaction steps.

[0004] The technical problem of the present invention is to provide a graphene-based biosensor having a three-dimensional wrinkled geometry and a method for manufacturing the same.

[0005] In order to solve the above problem, the technical idea of ​​the present invention provides a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry, including the steps of: etching an exposed upper surface of a silicon oxide film stacked on a substrate; transferring graphene onto the etched upper surface of the silicon oxide film; and forming a pair of source / drain electrodes on the upper surface of the silicon oxide film, wherein the lower surface of the graphene transferred onto the etched upper surface of the silicon oxide film is characterized in that a plurality of first high points and a plurality of first low points having a height difference are arranged in an irregular shape, and the exposed upper surface of the etched silicon oxide film is characterized in that a plurality of second high points and a plurality of second low points having a height difference are arranged in an irregular shape.

[0006] According to one embodiment, a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry is provided, characterized in that, in the step of etching the exposed upper surface of the silicon oxide film, O2 is used at 3 to 5 Sccm and CF4 is used at 20 to 30 Sccm under the conditions of power of 80 to 120 W and frequency of 40 to 60 Hz.

[0007] According to one embodiment, a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry is provided, characterized in that a maximum height difference between the plurality of first high points and the plurality of first low points of the graphene is in a range of 20 nanometers to 30 nanometers.

[0008] According to one embodiment, a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry is provided, wherein the plurality of first high points of the graphene are irregularly arranged along the longitudinal direction at intervals ranging from 0.1 micrometer to 10 micrometers.

[0009] According to one embodiment, a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry is provided, characterized in that, in the step of transferring graphene onto the upper surface of the etched silicon oxide film, the upper surface of the silicon oxide film and the lower surface of the graphene form a coplanar surface.

[0010] According to one embodiment, a method for fabricating a graphene-based biosensor having a three-dimensional wrinkled geometry is provided, wherein the exposed upper surface of the silicon oxide film etched by a reactive ion etching process has a root mean square roughness of 3 nanometers to 5 nanometers.

[0011] According to one embodiment, a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry is provided, characterized in that a maximum height difference between the plurality of second high points and the plurality of second low points of the graphene is in a range of 20 nanometers to 30 nanometers.

[0012] According to one embodiment, a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry is provided, characterized in that, in the step of etching the exposed upper surface of the silicon oxide film, the etching is performed using a reactive ion etching process.

[0013] In order to solve the above problem, the technical idea of ​​the present invention provides a graphene-based biosensor having a three-dimensional wrinkled geometry, including: a substrate; a silicon oxide film laminated on the substrate, the first surface having a plurality of high points and a plurality of low points having a height difference arranged in an irregular shape, and a second surface having a flat shape arranged on both sides of the first surface; graphene covering the first surface and forming a plane with the first surface; and a pair of source / drain electrodes arranged on the second surface, wherein the graphene is characterized in that the plurality of high points and the plurality of low points having a height difference are arranged in an irregular shape.

[0014] According to one embodiment, the first surface of the silicon oxide film provides a graphene-based biosensor having a three-dimensional wrinkled geometry, characterized in that it has a root mean square roughness of 3 to 5 nanometers.

[0015] A method for producing graphene with a three-dimensional wrinkled geometry according to the technical concept of the present invention comprises the steps of etching the upper surface of a silicon oxide film and then transferring graphene onto the etched upper surface. By directly transferring graphene onto the upper surface of the etched silicon oxide film, the graphene can easily have a three-dimensional wrinkled geometry.

[0016] The effects of the present invention are not limited to the effects described above, and effects not mentioned can be clearly understood by a person skilled in the art to which the present invention pertains from this specification and the attached drawings.

[0017] Figure 1 is a cross-sectional view illustrating the structure of a biosensor including graphene.

[0018] Figure 2 is a drawing for explaining the graphene illustrated in Figure 1.

[0019] Figure 3 is an enlarged view of the Q region of the graphene illustrated in Figure 2.

[0020] FIG. 4 is a flowchart of a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry according to one embodiment of the present invention.

[0021] FIGS. 5 to 8 are cross-sectional views sequentially illustrating a method for manufacturing a graphene biosensor having a three-dimensional crumpled geometry according to one embodiment of the present invention.

[0022] Figure 9 is a schematic cross-sectional view showing graphene transferred onto a silicon oxide film by reactive ion etching at different process times.

[0023] Figure 10 shows images of the upper surface of a silicon oxide film subjected to reactive ion etching at different process times, taken using an AFM (Atomic Force Microscope).

[0024] Figure 11 shows images of graphene transferred onto a silicon oxide film that was etched with reactive ion etching at different process times, taken with a scanning electron microscope (SEM).

[0025] The best mode for carrying out the present invention is a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry, comprising the steps of: etching an exposed upper surface of a silicon oxide film stacked on a substrate; transferring graphene onto the etched upper surface of the silicon oxide film; and forming a pair of source / drain electrodes on the upper surface of the silicon oxide film, wherein a lower surface of the graphene transferred onto the etched upper surface of the silicon oxide film is characterized in that a plurality of first high points and a plurality of first low points having a height difference are arranged in an irregular shape, and the exposed upper surface of the etched silicon oxide film is characterized in that a plurality of second high points and a plurality of second low points having a height difference are arranged in an irregular shape.

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below and may be embodied in various other forms. The following embodiments are provided not to fully complete the present invention, but rather to fully convey the scope of the present invention to those skilled in the art.

[0027] A biosensor comprising graphene having a three-dimensional wrinkled geometry according to embodiments of the present invention is used for gene expression profiling, genotyping, detection of mutations and polymorphisms such as SNPs (Single Nucleotide Polymorphisms), protein and peptide analysis, screening of potential drugs, development and manufacturing of new drugs, etc. by analyzing target substances contained in a sample.

[0028] A biosensor is equipped with appropriate probes depending on the target biological sample to be analyzed. Examples of probes that can be equipped in a biosensor include DNA probes, enzymes or antibodies / antigens, protein probes such as bacteriorhodopsin, microbial probes, and neuronal probes. A biosensor manufactured in the form of a chip is also referred to as a biochip. For example, depending on the type of probe equipped, the biochip may be referred to as a DNA chip, protein chip, cell chip, neuron chip, etc. A biosensor according to some embodiments of the present invention may include an oligomer probe as a probe. The oligomer probe implies that the number of monomers of the probe employed is at the oligomer level. Here, the term "oligomer" may be used to mean a polymer composed of two or more covalently bonded monomers and having a molecular weight of about 1000 or less. Specifically, it may include 2 to 500 monomers, and preferably 5 to 30 monomers. However, the meaning of the oligomer probe is not limited to the above number. The monomers constituting the oligomeric probe can be modified depending on the type of biological sample to be analyzed, and can be, for example, nucleosides, nucleotides, amino acids, peptides, etc. Nucleosides and nucleotides can include not only the known purine and pyrimidine bases, but also methylated purines, methylated pyrimidines, acylated purines, or acylated pyrimidines. Furthermore, nucleosides and nucleotides can include not only the conventional ribose and deoxyribose sugars, but also modified sugars in which one or more hydroxyl groups are substituted with halogen atoms or aliphatics, or functional groups such as ethers and amines are bonded. Amino acids can be L-, D-, and nonchiral amino acids found in nature, as well as modified amino acids, or amino acid analogs.A peptide refers to a compound formed by an amide bond between the carboxyl group of an amino acid and the amino group of another amino acid. Unless otherwise specified, the probes exemplified in the examples below are DNA probes, which are oligomeric probes covalently bonded with monomers of 5 to 30 nucleotides. However, the present invention is not limited thereto, and it is apparent that various probes described above can be applied.

[0029] Figure 1 is a cross-sectional view illustrating the structure of a biosensor including graphene.

[0030] Referring to FIG. 1, a biosensor (10) according to one embodiment may include a substrate (100), a silicon oxide film (110), a gate electrode (112), a wiring structure (114), a gate dielectric film (116), a source / drain electrode (120), and graphene (210).

[0031] The substrate (100) may include a base structure made of a material such as silicon. In some embodiments, the base structure may include a complementary metal-oxide semiconductor (CMOS). The substrate (100) may include a semiconductor material, for example, a group IV semiconductor, a group III-V compound semiconductor, or a group II-VI oxide semiconductor. For example, the group IV semiconductor may include silicon (Si), germanium (Ge), or silicon-germanium. The substrate (100) may be provided as a bulk wafer or an epitaxial layer. In other embodiments, the substrate (100) may include glass or a polymer. In yet other embodiments, the substrate (100) may include a silicon-on-insulator (SOI) substrate or a germanium-on-insulator (GeOI) substrate.

[0032] According to one embodiment, a silicon oxide film (110) may be disposed on a substrate (100). The silicon oxide film (110) may be formed to have a constant thickness along the upper surface of the substrate (100). The silicon oxide film (110) may include silicon oxide. For example, the silicon oxide may include silicon dioxide (SiO2), but is not necessarily limited to the above examples.

[0033] In one embodiment, the gate electrode (112) can be connected to a power source through a wiring structure (114) to supply a gate voltage to the graphene (210). By observing the electrical parameters of the biosensor according to the gate voltage, the presence of a target substance in the sample can be determined. At this time, a change in the electrical parameters can correspond to the presence of the target substance. For example, the electrical parameters can include capacitance, voltage, average current, etc. The gate electrode (112) can include a conductive metal material. In one embodiment, the gate electrode (112) can be composed of silver (Ag). A gate dielectric film (116) can be positioned between the graphene (210) and the gate electrode (112).

[0034] According to one embodiment, a pair of source / drain electrodes (120) may be disposed on a silicon oxide film (110). The pair of source / drain electrodes (120) may be disposed to be spaced apart from each other in the horizontal direction. One of the pair of source / drain electrodes (120) may function as a source electrode, and the other may function as a drain electrode. The source / drain electrodes (120) may be formed of various materials and may include a metal or a metal alloy. For example, the pair of source / drain electrodes (120) may include copper (Cu), ruthenium (Ru), aluminum (Al), cobalt (Co), molybdenum (Mo), titanium (Ti), tantalum (Ta), nickel (Ni), platinum (Pt), chromium (Cr), or an alloy thereof.

[0035] Graphene (210) may be placed in the space between a pair of source / drain electrodes (120). The graphene (210) may have a three-dimensional wrinkled geometry. A specific description of the structure of the graphene (210) will be described in detail later in the description of FIGS. 2 and 3. The graphene (210) may be placed on a first surface (110a) of a silicon oxide film (110) and may extend horizontally along the first surface (110a) of the silicon oxide film (110). The first surface (110a) of the silicon oxide film (110) may be defined as a surface in which a plurality of high points and a plurality of low points having a height difference are arranged in an irregular shape along the length direction, and the second surface (110b) may be defined as a surface having a flat shape.

[0036] The sample (132) in contact with the graphene (210) may include a target substance. The sample (132) may include a biological solution such as protein, DNA, RNA, fragments having an arbitrary base sequence, blood, or saliva. The sample (132) may be placed in a sample storage container (130). The sample storage container (130) may be a container for containing the sample (132) and may be made of a polymer or non-polymer material. The sample (132) including the target substance in the reaction area (RA) inside the sample storage container (130) may react with a probe included in the graphene (210). In one embodiment, the sample storage container (130) may include silicone rubber.

[0037] Fig. 2 is a drawing for explaining the graphene (210) illustrated in Fig. 1. Fig. 3 is an enlarged view of the Q region of the graphene (210) illustrated in Fig. 2.

[0038] Referring to FIGS. 2 and 3, the graphene (210) may include a body (212) in which a first high point (P_a) and a first low point (V_a) having a height difference are arranged in an irregular shape along the length direction, and a probe (214) that is arranged on one surface of the first high point (P_a) and the first low point (V_a) and is capable of chemically bonding with a target material to be detected. The probe (214) may be arranged not only at the first high point (P_a) and the first low point (V_a) of the body (212), but also between the first high point (P_a) and the first low point (V_a). The first high point (P_a) and the first low point (V_a) of the graphene (210) are distinct from the second high point (P_b) and the second low point (V_b) of the surface of the silicon oxide film (110) illustrated in FIG. 9.

[0039] In this specification, the longitudinal direction in which the first high point (P_a) and the first low point (V_a) of the body (212) are arranged in an irregular shape may be defined as the first direction (X direction). The direction that is perpendicular to the first direction (X direction) and in which the first high point (P_a) and the first low point (V_a) are elongated may be defined as the second direction (Y direction). In addition, the direction that is orthogonal to the first direction (X direction) and the second direction (Y direction) may be defined as the third direction (Z direction). The adjacent first high points (P_a) and the adjacent first low points (V_a) of the graphene (210) may be arranged to be spaced apart from each other in the first direction (X direction), and may each extend in the second direction (Y direction). A first low point (V_a) may be arranged between adjacent first high points (P_a) of the graphene (210), and a first low point (V_a) may be arranged between adjacent first high points (P_a). However, the wrinkled shape of the body (212) of the graphene (210) is not limited to that shown in FIGS. 2 and 3, and may be wrinkled into various shapes.

[0040] In one embodiment, the point having the highest level of the body (212) of the graphene (210) that is repeatedly crumpled in an irregular shape is defined as the first high point (P_a), and the point having the lowest level is defined as the first low point (V_a). In one embodiment, the adjacent first high points (P_a) and the adjacent first low points (V_a) of the graphene (210) may be spaced apart from each other by a variable gap (W). The gap (W) may be in the range of 0.1 micrometer to 10 micrometers. When the gap (W) is less than 0.1 micrometer, the graphene (210) may be crumpled too tightly, so that sufficient reaction space may not be formed for the probes (214) arranged on one surface of the graphene (210) to chemically bond with the target material (144). When the gap (W) is greater than 10 micrometers, the body (212) of the graphene (210) can be seen to have a flat geometry rather than a three-dimensionally wrinkled geometry.

[0041] As an example, the height difference in the vertical direction (Z direction) between the adjacent first high point (P_a) and the first low point (V_a) of the graphene (210) may not be constant in the range of 20 nanometers to 30 nanometers. That is, the slope of the first intermediate region (COL1) from the first low point (V_a) to the first high point (P_a) and the slope of the second intermediate region (COL2) from another first low point (V_a) to the first high point (P_a) may be different from each other.

[0042] As shown in the image (a) of FIG. 2, the graphene (210) may progress in a manner in which the first high point (P_a) and the first low point (V_a) are repeated along the longitudinal direction. In this case, the longitudinal direction may be the first direction (X direction), and the direction in which the first high point (P_a) or the first low point (V_a) extends may be the second direction (Y direction). However, as shown in the image (b) of FIG. 2, the graphene (210) may have the first high point (P_a) and the first low point (V_a) arranged irregularly. In this case, the first high point (P_a) and the first low point (V_a) do not progress in a manner in which they are repeated along a specific direction, but the first high point (P_a) and the first low point (V_a) may be arranged randomly.

[0043] The number of bodies (212) included in the graphene (210) is not limited to that shown in FIG. 2. In another embodiment, the graphene (210) may include a first body and a second body disposed on the first body. From a planar perspective, carbon atoms constituting the first body and carbon atoms constituting the second body may be disposed to overlap each other. In another embodiment, carbon atoms constituting the first body and carbon atoms constituting the second body may be disposed to be misaligned. Since the graphene (210) illustrated in FIGS. 2 and 3 includes one body (212), the expression that the graphene (210) has a three-dimensional wrinkled geometry may have substantially the same meaning as the expression that the body (212) of the graphene (210) has a three-dimensional wrinkled geometry.

[0044] In one embodiment, graphene (210) may have a three-dimensional wrinkled geometry. In the case of flat graphene, a special treatment process, such as a foreign substance doping process, must be performed on the surface of the graphene to open a finite band gap, thereby enabling the graphene to function as a semiconductor. In contrast, graphene with a three-dimensional wrinkled geometry can open a band gap without a foreign substance doping process, thereby enabling the graphene to function as a semiconductor.

[0045] Graphene Types Bond Type Bond Length (Å) Graphene with flat geometry C1-C2 1.417 Graphene with three-dimensional wrinkled geometry C1-C7 1.407 C15-C17 1.412 C12-C17 1.415 C2-C14 1.416 C10-C2 32.424 C11-C2 32.426 C2-C132.436 C6-C16 2.439 C7-C2 32.441

[0046] Table 1 shows measured data on the bond lengths between carbon atoms in graphene with a flat geometry and those in graphene with a three-dimensional wrinkled geometry. Referring to Table 1, the bond lengths between specific carbon atoms in graphene with a three-dimensional wrinkled geometry are approximately 1 angstrom longer than those in graphene with a flat geometry. This imbalance in bond lengths between carbon atoms can lead to differences in the electrical behavior of graphene. When graphene with a flat geometry is crumpled into a three-dimensional shape, its symmetry and planarity are destroyed, and peaks and valleys with different heights are arranged in a zigzag pattern along the length direction. This deformation induces a quantum confinement effect due to graphene's unique electronic structure, which can be a major contributor to the opening of the band gap in graphene.

[0047] In the case of graphene with a flat geometry, the band gap is not open, so the difference in current between the flowing and quiescent states is only about 20 to 30 times, making it difficult to function as a semiconductor device. However, graphene with a three-dimensional, wrinkled geometry can open a band gap due to an imbalance in the bond lengths between carbon atoms. Therefore, the difference in current between the flowing and quiescent states of graphene can be at least 100,000 times, increasing its utility as a semiconductor device.

[0048] Equilibrium energy (eV) for graphene with flat geometry - 324.453 dimensions; for graphene with wrinkled geometry - 3986.36 dimensions.

[0049] Table 2 shows the equilibrium state energy of graphene with a flat geometry and that of graphene with a three-dimensional wrinkled geometry. Referring to Table 2, the equilibrium state energy of graphene with a three-dimensional wrinkled geometry can be significantly lower than that of graphene with a flat geometry. Therefore, the carbon atoms constituting graphene with a three-dimensional wrinkled geometry may have higher stability than those constituting graphene with a flat geometry.

[0050] In the region between the first high point (P_a) and the first low point (V_a) of the graphene (210), more probes (214) can be placed compared to the first high point (P_a) and the first low point (V_a), and thus, more target materials can be included. However, this is not limited thereto, and more probes (214) can be placed in the first high point (P_a) and the first low point (V_a) than in the region between the first high point (P_a) and the first low point (V_a).

[0051] As an example, the distance (d1) from the line (A-A') crossing the center of the graphene (210) to the first high point (P_a) may be 10 nanometers to 15 nanometers. The distance (d2) from the line (A-A') crossing the center of the graphene (210) to the first low point (V_a) may be 10 nanometers to 15 nanometers. Accordingly, the height difference between the first high point (P_a) and the first low point (V_a) may be 20 nanometers to 30 nanometers. When the distance (d1) from the line (A-A') crossing the center of the graphene (210) to the first high point (P_a) or the distance (d2) from the line (A-A') crossing the center of the graphene (210) to the first low point (V_a) is less than 10 nanometers, the length in the third direction (Z direction) is shortened with respect to the length in the first direction (X direction) of the graphene (210), so that the graphene (210) can be viewed as having a flat geometry rather than a three-dimensionally wrinkled geometry. When the distance (d1) from the line (A-A') crossing the center of the graphene (210) to the first high point (P_a) or the distance (d2) from the line (A-A') crossing the center of the graphene (210) to the first low point (V_a) is greater than 15 nanometers, the length of the graphene (210) in the third direction (Z direction) becomes longer than the length in the first direction (X direction), so that the graphene (210) may have a densely wrinkled shape. In this case, a reaction space sufficient for the probes (214) arranged on one surface of the graphene (210) to chemically bond with the target material may not be formed.

[0052] According to one embodiment, the probe (214) disposed on one surface of the graphene (210) may be one of a polynucleotide, a peptide nucleic acid (PNA) probe, an aptamer, a protein, an antibody, or a capture agent. The probe (214) may be selected for binding to the target substance (144). For example, when the target substance (144) is DNA, the probe (214) may have a nucleotide sequence complementary to the nucleotide sequence of the DNA to be detected for binding to the DNA.

[0053] When graphene (210) has a three-dimensionally wrinkled geometry, the Debye length is longer compared to when it has a flat geometry, allowing for the capture of more DNA molecules. Therefore, the sensitivity of the probe (214) to the target substance can be increased despite the Debye shielding effect.

[0054] FIG. 4 is a flowchart of a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry according to an embodiment of the present invention, and FIGS. 5 to 8 are cross-sectional views sequentially illustrating a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry according to an embodiment of the present invention.

[0055] Referring to FIG. 5 together with FIG. 4, a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry according to one embodiment of the present invention may include a step (S110) of depositing a silicon oxide film (110) on a substrate (100).

[0056] According to one embodiment, a silicon oxide film (110) having a gate electrode (112), a wiring structure (114), and a gate dielectric film (116) embedded therein may be laminated on a substrate (100). At this time, the wiring structure (114) may be formed to be exposed to the lower surface of the silicon oxide film (110). The silicon oxide film (110) may be laminated to have a constant thickness along the upper surface of the substrate (100). The silicon oxide film (110) may include a silicon oxide such as SiO2, but is not necessarily limited to the above examples.

[0057] Referring to FIG. 6 together with FIG. 4, a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry according to one embodiment of the present invention may include a step (S120) of etching an exposed upper surface of a silicon oxide film (110) laminated on a substrate (100) using a reactive ion etching process.

[0058] According to one embodiment, a mask pattern (MP) may be placed on the outer portion of the upper surface of the silicon oxide film (110). At this time, an area exposed between the mask patterns (MP) on the upper surface of the silicon oxide film (110) may be defined as a first surface (110a), and the upper surface of the silicon oxide film (110) covered by the mask pattern (MP) may be defined as a second surface (110b).

[0059] After a mask pattern (MP) is placed on the outer portion of the upper surface of the silicon oxide film (110), the exposed first surface (110a) of the silicon oxide film (110) can be etched through a reactive ion etching process. At this time, the reactive ion etching process is an etching method in which the silicon oxide film (110) is placed on a power transmission electrode and a gas (e.g., carbon tetrafluoride; CF4) that can chemically react with the silicon oxide film (110) is used. Ions incident with an appropriately high energy transfer momentum to the surface, thereby promoting a chemical reaction between radicals in the plasma and atoms on the substrate surface of the silicon oxide film (110). At this time, the etching speed of the part hit by the ions increases according to the ion energy and is much greater than the etching speed of the part not hit by the ions, so the etching can proceed in a direction perpendicular to the substrate surface in the direction of the ion incidence.

[0060] The substrate (100) on which the silicon oxide film (110) is laminated may be placed in a process chamber, and then a reactive ion etching process may be performed using a reactive gas selected from the group consisting of Ar, N2, Ne, and H2. According to one embodiment, the reactive ion etching process may be performed as anisotropic etching for 12 to 18 minutes with a reactive gas containing O2 and CF4. At this time, a preferable process time of the reactive ion etching process may be 15 minutes. When the reactive ion etching process is completed, the first surface (110a) of the silicon oxide film (110) becomes rough, and at this time, the first surface (110a) has a plurality of high points and a plurality of low points with a high height difference arranged in an irregular shape. A detailed description thereof will be provided later. The reactive ion etching process may be performed under the conditions of a power of 80 to 120 W and a frequency of 40 to 60 Hz. At this time, the reactive gas may include O2 and CF4, and O2 may be introduced toward the silicon oxide film (110) at a flow rate of 3 to 5 Sccm and CF4 may be introduced at a flow rate of 20 to 30 Sccm. However, the reactive gas used in the reactive ion etching process is not limited to the above-mentioned gases.

[0061] If the process time of the reactive ion etching process is 20 minutes or more, the height difference between the plurality of high points and the plurality of low points may become too high, so that a two-dimensional material such as graphene may not be properly transferred onto the upper surface of the silicon oxide film (110) thereafter. The two-dimensional material such as graphene must be transferred so as to be coplanar with the upper surface of the silicon oxide film (110). However, if the height difference between the plurality of high points and the plurality of low points becomes too high, a large gap space is formed between the upper surface of the silicon oxide film (110) and the lower surface of the two-dimensional material. If the process time of the reactive ion etching process is 20 minutes or less, the height difference between the plurality of high points and the plurality of low points becomes too low, so that even if a two-dimensional material such as graphene is transferred onto the upper surface of the silicon oxide film (110) thereafter, the two-dimensional material may not be properly crumpled, and the graphene (210) may not be able to properly maintain its shape.

[0062] However, the method of etching the exposed upper surface of the silicon oxide film (110) is not limited to the reactive ion etching process. For example, according to an embodiment, the exposed upper surface of the silicon oxide film (110) may be etched through a wet etching process. At this time, the exposed upper surface of the silicon oxide film (110) may be etched using a liquid containing hydrofluoric acid (HF) or the like using water as a catalyst. By using the wet etching process, isotropic etching may be performed in which the exposed upper surface of the silicon oxide film (110) is etched in a circle at a certain distance from the part in contact with the liquid.

[0063] Referring to FIG. 7 together with FIG. 4, a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry according to one embodiment of the present invention may include a step (S130) of transferring graphene (210) onto the upper surface of an etched silicon oxide film (110).

[0064] Specifically, graphene (210) can be transferred onto the first surface (110a) having a roughness of the silicon oxide film (110). As the graphene (210) is transferred onto the first surface (110a) of the silicon oxide film (110), the first surface (110a) of the silicon oxide film (110) and the lower surface of the graphene (210) can form a coplanar surface.

[0065] Referring to FIG. 8 together with FIG. 4, a method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry according to one embodiment of the present invention may include a step (S140) of forming a pair of source / drain electrodes (120) on the upper surface of a silicon oxide film (110).

[0066] To form source / drain electrodes (120), a mask pattern (MP) disposed on the upper surface of the silicon oxide film (110) may be removed. Thereafter, a pair of source / drain electrodes (120) may be formed on the flat second surface (110b) covered by the mask pattern (MP). The pair of source / drain electrodes (120) may be formed to be spaced apart from each other in the horizontal direction, and one of the pair of source / drain electrodes (120) may function as a source electrode, and the other may function as a drain electrode. The source / drain electrodes (120) may be formed by a plating process.

[0067] According to one embodiment, after forming the source / drain electrode (120), a sample storage container (130) surrounding the graphene (210) may be formed on the substrate (100). At this time, a sample (132) including a target material may be contained within the sample storage container (130).

[0068] Figure 9 is a schematic cross-sectional view showing graphene transferred onto a silicon oxide film by reactive ion etching at different process times.

[0069] Specifically, NCGr15 is an image of graphene transferred to the upper surface of a silicon oxide film when the process time of the reactive ion etching process is 15 minutes. NCGr30 is an image of graphene transferred to the upper surface of a silicon oxide film when the process time of the reactive ion etching process is 30 minutes. NCGr45 is an image of graphene transferred to the upper surface of a silicon oxide film when the process time of the reactive ion etching process is 45 minutes. At this time, the reactive ion etching process can be performed under the conditions of a power of 80 to 120 W and a frequency of 40 to 60 Hz. In addition, the reactive gas used in the reactive ion etching process can include O2 and CF4, and O2 can be introduced toward the silicon oxide film (110) at a flow rate of 3 to 5 Sccm, and CF4 can be introduced at a flow rate of 20 to 30 Sccm.

[0070] When the reactive ion etching process time is 12 to 18 minutes, preferably 15 minutes, the upper surface of the silicon oxide film (110) and the lower surface of the graphene (210) can form a coplanar surface. At this time, the first high point (P_a) of the graphene (210) can be in complete contact with the second high point (P_b) of the silicon oxide film (110), and the first low point (V_a) of the graphene (210) can be in complete contact with the second low point (V_b) of the silicon oxide film (110). When the reactive ion etching process time is 30 minutes, the upper surface of the silicon oxide film (110) is etched more, so the height difference between the second high point (P_b) and the second low point (V_b) of the silicon oxide film (110) can increase. Accordingly, the upper surface of the silicon oxide film (110) and the lower surface of the graphene (210) do not form a coplanar surface, and the first low point (V_a) of the graphene (210) and the second low point (V_b) of the silicon oxide film (110) may not be in contact. When the process time of the reactive ion etching process is 45 minutes, the height difference between the second high point (P_b) and the second low point (V_b) of the silicon oxide film may be greater than when the reactive ion etching process time is 30 minutes. In this case, the first low point (V_a) of the graphene (210) and the second low point (V_b) of the silicon oxide film (110) may not be in contact.

[0071] Figure 10 shows images of the upper surface of a silicon oxide film subjected to reactive ion etching at different process times, taken using an AFM (Atomic Force Microscope).

[0072] Referring to Fig. 10, image (a) is an image of the upper surface of a silicon oxide film before the reactive ion etching process. Image (b) is an image of the upper surface of a silicon oxide film after the reactive ion etching process was performed for 15 minutes. Image (c) is an image of a silicon oxide film after the reactive ion etching process was performed for 35 minutes, and image (d) is an image of a silicon oxide film after the reactive ion etching process was performed for 45 minutes.

[0073] As illustrated in Figure 10, as the process time of the reactive ion etching process increases, the roughness of the upper surface of the silicon oxide film may increase. An increase in roughness means a greater height difference between the high and low points of the upper surface of the silicon oxide film.

[0074] SampleMean(nm)RPV(nm)Rq(nm)NCGr00.4660.8150.152NCGr156.51725.8043.819NCGr3027.31246.5278.932NCGr4554.52085.48818.339

[0075] Table 3 summarizes the measurement values ​​of the image shown in Fig. 10. Here, Mean represents the median value of the height difference between the high and low points on the upper surface of the silicon oxide film, and RPV represents the height difference between the highest and lowest points. In addition, Rq represents the root mean square roughness, which means the value obtained by taking the root of the sum of all squared height values ​​based on the Mean value on the upper surface of the silicon oxide film, dividing by the width of the upper surface of the silicon oxide film, and then taking the root. A high Rq means that the roughness of the upper surface of the silicon oxide film is high. NCGr x means that the reactive ion etching process was performed for x minutes, as explained with reference to Fig. 9.

[0076] Looking at the results in FIG. 10 and Table 3 together with FIG. 9, if the reactive ion etching process takes more than 18 minutes, the roughness of the upper surface of the silicon oxide film becomes too high, and graphene may not be properly transferred onto the upper surface of the silicon oxide film. Here, the fact that graphene is not properly transferred onto the upper surface of the silicon oxide film means that the upper surfaces of the graphene and the silicon oxide film are not coplanar.

[0077] Figure 11 shows images of graphene transferred onto a silicon oxide film that was etched with reactive ion etching at different process times, taken with a scanning electron microscope (SEM).

[0078] Images A-1, B-1, C-1, A-2, B-2, and C-2 are images taken at a scale of 500 nanometers, respectively, and images A-3, B-3, and C-3 are images taken at a scale of 10 micrometers, respectively. A-1, A-2, and A-3 are images of graphene transferred onto silicon oxide films that were subjected to a reactive ion etching process for 15 minutes, respectively, and B-1, B-2, and B-3 are images of graphene transferred onto silicon oxide films that were subjected to a reactive ion etching process for 30 minutes, respectively. In addition, C-1, C-2, and C-3 are images of graphene transferred onto silicon oxide films that were subjected to a reactive ion etching process for 45 minutes, respectively.

[0079] Comparing the B-1, B-2, B-3, C-1, C-2, and C-3 images with the A-1, A-2, and A-3 images, it can be confirmed that when the reactive ion etching process treatment continued for more than 30 minutes, the graphene transferred onto the silicon oxide film did not properly maintain its shape and cracks, etc. occurred. This can be confirmed because, as explained with reference to Fig. 9, the graphene and the silicon oxide film did not properly form a coplanar surface and formed a gap space.

[0080] As described above, exemplary embodiments have been disclosed in the drawings and specifications. While specific terminology has been used to describe embodiments herein, it is intended solely to illustrate the technical concept of the present disclosure and is not intended to limit the scope of the present disclosure as defined in the claims. Therefore, those skilled in the art will appreciate that various modifications and equivalent embodiments are possible. Therefore, the true technical protection scope of the present disclosure should be determined by the technical concept of the appended claims.

[0081] The industrial applicability of the present invention lies in providing a graphene-based biosensor with improved selectivity and sensitivity and excellent reliability, and a method for manufacturing the same, thereby detecting biological substances quickly and accurately.

Claims

1. A step of etching the exposed upper surface of a silicon oxide film laminated on a substrate; A step of transferring graphene onto the upper surface of the etched silicon oxide film; and comprising a step of forming a pair of source / drain electrodes on the upper surface of the silicon oxide film; The lower surface of the graphene transferred onto the upper surface of the etched silicon oxide film is Multiple first high points and multiple first low points with different heights are arranged in an irregular shape, The exposed upper surface of the etched silicon oxide film is A method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry characterized by a plurality of second high points and a plurality of second low points having a height difference arranged in an irregular shape.

2. In paragraph 1, In the step of etching the exposed upper surface of the above silicon oxide film, A method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry, characterized in that the method is performed using 3 to 5 Sccm of O2 and 20 to 30 Sccm of CF4 under conditions of power of 80 to 120 W and frequency of 40 to 60 Hz.

3. In paragraph 1, A method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry, characterized in that the maximum height difference between the plurality of first high points and the plurality of first low points of the graphene is in the range of 20 nanometers to 30 nanometers.

4. In paragraph 1, A method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry, wherein the plurality of first peaks of the graphene are irregularly arranged along a spacing ranging from 0.1 micrometer to 10 micrometers.

5. In paragraph 1, In the step of transferring graphene onto the upper surface of the etched silicon oxide film, A method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry, characterized in that the upper surface of the silicon oxide film and the lower surface of the graphene form a coplanar surface.

6. In paragraph 1, The exposed upper surface of the silicon oxide film etched by the reactive ion etching process is A method for fabricating a graphene-based biosensor having a three-dimensional wrinkled geometry characterized by a root mean square roughness of 3 to 5 nanometers.

7. In paragraph 1, A method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry, characterized in that the maximum height difference between the plurality of second high points and the plurality of second low points of the graphene is in the range of 20 nanometers to 30 nanometers.

8. In paragraph 1, In the step of etching the exposed upper surface of the above silicon oxide film, A method for manufacturing a graphene-based biosensor having a three-dimensional wrinkled geometry, characterized in that the above etching is performed using a reactive ion etching process.

9. Substrate; A silicon oxide film having a first surface having a plurality of high points and a plurality of low points with height differences arranged in an irregular shape and a second surface having a flat shape arranged on both sides of the first surface, which is laminated on the substrate; Graphene covering the first surface and forming a plane with the first surface; and comprising a pair of source / drain electrodes arranged on the second surface; The above graphene is, A graphene-based biosensor having a three-dimensional wrinkled geometry characterized by an irregular arrangement of multiple high points and multiple low points with different heights.

10. In paragraph 9, The first surface of the above silicon oxide film is, A graphene-based biosensor having a three-dimensional wrinkled geometry characterized by a root mean square roughness of 3 to 5 nanometers.

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