KR20090056038A - Surface-Modified Nanowire Sensor and Its Manufacturing Method - Google Patents

Abstract

The present invention relates to a surface-modified nanowire sensor for sensing the concentration of a substance and a method of manufacturing the same, forming a sensor structure having a trench structure on one surface of a flat substrate, and a nanowire sensing material on the sensing electrode of the sensor structure. Position the surface of the nanowire sensor by modifying the surface of the nanowire sensing material by flowing a surface modification solution in which a chemical reactant is dissolved in the trench valley formed in the sensor structure, and forming the surface modified nanowire sensor. The line sensing material is in contact with the sensing electrode, floats in the air of the trench valley between the sensing electrodes, and selectively interacts with a specific material to change the electrical conductivity, and to exclude the interference of the substrate surface. In addition, various and selective surface modifications can be easily performed along trench trenches.

Description

Surface-Modified Nanowire Sensor and Manufacturing Method Thereof {Fabrication method of surface-modified nanowire sensor}

The present invention relates to a sensor for detecting the concentration of a substance, and more particularly, to a surface-modified nanowire sensor and a method for manufacturing the nanowire sensing material mounted on a trench type sensor structure.

In recent years, research and development on the production of high sensitivity chemical and biosensors using nanowire materials having semiconductor characteristics have been of great interest. These factors are due to the unique physicochemical properties of the large surface, small size, and nanostructures of one-dimensional semiconductor nanomaterials. In particular, since the minute interaction with the sensing material may have a great influence on the electrical conductivity of the nanowire material, the one-dimensional semiconductor material having a cross section of several nm size may manufacture a high sensitivity sensor. As a specific example of this, the conventional technique is to study that the sensor driving temperature and the sensitivity of the sensor can be greatly improved when the sensor is manufactured using a single nanowire carbon nanotube (CNT) material (science 287, 622). ) Was announced. Such a conventional technology is applicable to various nanowire materials having semiconductor characteristics in addition to CNTs, and it is known that it is possible through many researches and developments. Typical one-dimensional semiconductor materials include silicon nanowires and metal oxide nanowire materials.

However, nanowire material synthesis technology and basic sensor detection ability have been confirmed, but there is a lack of high production yield and productivity using these nanowire sensing materials.

The conventional nanowire sensor manufacturing technology can be largely divided into a method of directly growing a nanowire material on a substrate and a method of dispersing the grown nanowire material in a solution and then transferring the nanowire material to a desired sensor substrate.

In the first method, by placing the catalyst required for nanowire growth in a desired position and growing the nanowire, it is possible to realize a material having excellent initial position and bonding properties. However, this method is very difficult to control the direction and length of growth, so it is very difficult to locate and connect it between two designated electrodes. Although there have been reports of such systems that can be connected and controlled, these methods can only be used under limited conditions, and there are practical limitations to developing them into common methods of manufacturing high-performance devices. In particular, in the case of the sensor can be realized in a variety of materials, and to be inexpensive to have industrial competitiveness, such a manufacturing method is not suitable.

The second method is a more realistic method than the first method. Currently, the fabrication method mainly used is based on a process of first placing a small amount of nanowire material on a substrate, confirming their position in advance through an electron microscope, and then forming an electrode using a semiconductor lithography process. This method has an advantage in that the device having excellent contact characteristics between the nanowire and the metal electrode can be formed. However, this method has a disadvantage in that the production yield and productivity are very low because it requires a process of confirming the position of each device in advance through an electron microscope.

On the other hand, a more realistic solution is to fabricate the sensor in the form of randomly arranged nanowire materials on the sensing area. This method can be controlled under experimental conditions such that the appropriate amount of nanowires are located on the substrate surface, thereby eliminating the positioning process for each device. The method using a nanowire network produces a sensor using a nanowire assembly, so that the yield is high. However, unlike a single nanowire sensor in which one nanowire exists between electrodes, various nanowire-nanowire junctions exist. As a result, the sensing response is complicated and high performance sensing characteristics of a single nanowire sensor may be degraded. In addition, since the sensing characteristics are determined by the chemical composition and physical variables (length, thickness, crystallinity, etc.) of the nanowire to be initially located, different materials showing different chemical compositions are generally used to fabricate various sensors having different sensing capacities. Sensor shall be manufactured using. Therefore, it is difficult to easily prepare various one-dimensional materials having good semiconductor characteristics in reality.

The most common method of preparing a variety of chemical (bio) sensors is the surface modification method of introducing various organics to the surface. Such surface modification is performed by immersing the entire sensor substrate in the reaction solution or dropping a small amount of solution onto the sensing material where the sensing takes place after fabricating the nanowire sensor. However, when the entire substrate is immersed in the solution, various problems occur due to exposure to the solution up to the undesired area, and in the method of dropping the solution, the film is formed on the nanowire material rather than modifying the nanowire surface only. It has a disadvantage that it is difficult to effectively control the detection ability of.

Further, according to the prior art, in the case of the sensor in which the nanowire sensing material is attached to the substrate surface, deformation in the sensor performance may occur due to the interaction between the substrate-nanowire and the sensing material-substrate.

In order to solve the problems described above, an object of the present invention is to provide a surface-modified nanowire sensor capable of mass-producing a sensor capable of detecting a concentration of various sensing target materials and having a high sensitivity, in high yield. .

In addition, an object of the present invention is to support a nanowire network in contact with the sensing electrode of the upper portion of the trench structure by using a trench-type sensor substrate to be supported on the trench bone, by flowing a surface modification solution along the valley to various surface modified It is intended to provide a method for fabricating a nanowire sensor.

The surface-modified nanowire sensor for achieving the above object of the present invention, a planar substrate formed by etching a portion of the trench trench; A protective layer formed on the planar substrate surface for electrical disconnection; A sensor structure comprising a sensing electrode formed on the protective layer in the protruding surface region of the planar substrate; And a nanowire sensing material formed in contact with the sensing electrode, buoyant in the air of the trench valley between the sensing electrodes, and selectively interacting with a specific material to change its electrical conductivity.

And a method for manufacturing a surface-modified nanowire sensor for achieving the objects of the present invention, the apparatus for achieving the objects of the present invention, forming a sensor structure having a trench structure on one surface of the planar substrate; Positioning a nanowire sensing material on a sensing electrode formed on the sensor structure; And modifying the surface of the nanowire sensing material by flowing a surface modification solution in which a chemical reactant is dissolved in the trench valley formed in the sensor structure, and selectively interacting with a specific material to change the electrical conductivity. The surface sensing material is in contact with the sensing electrode, and a surface-modified nanowire sensor for sensing the concentration of the material by floating in the air of the trench valley between the sensing electrode, characterized in that for producing.

Accordingly, the present invention has been made in order to achieve the above problems, in the sensor substrate having a trench structure to support the nanowire sensing material in the trench bone, and to flow the modification solution in the trench bone, to eliminate the interference action of the substrate surface In addition, there is an effect that can easily perform a variety of position-selective surface modification along the trench valleys.

In addition, the present invention has the effect that it is easy to manufacture a sensor array device having a variety of sensing characteristics by modifying only the surface of a variety of materials using the same nanowire material on a single substrate.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, embodiments of the present invention is provided to more completely describe the present invention to those skilled in the art. In the drawings, the size or thickness of films or regions is exaggerated for clarity.

 1 is a view showing a cross-sectional structure of a surface-modified nanowire sensor having a trench type sensor structure according to an embodiment of the present invention.

Referring to FIG. 1, the surface modified nanowire sensor is three types of network type nanowire sensors whose surfaces are modified with different materials. The surface-modified nanowire sensor (hereinafter, abbreviated as nanowire sensor) may be a planar substrate (semiconductor substrate) 110 having a trench type sensor structure, a protective layer 120a covering the upper portion of the trench type sensor structure, and the The sensing electrode 130 formed on the trench type sensor structure, and the nanowire sensing material 140a ~ 140c formed on the sensing electrode.

The nanowire sensor having such a structure is formed on the upper surface where the nanowire sensing materials 140a to 140c are entirely formed of metal sensing electrodes 130, so that the gap between the sensing electrodes 130 is sufficiently greater than the trench valleys. Only in the case of long nanowires, a structure supported by the trench structure forms an electrical connection between the sensing electrodes 130. Therefore, the nanowire sensing materials 140a to 140c participating in the sensor reaction have a feature in that only the sensing electrode 130 is in contact with the surface of the substrate and other portions are supported. If the length of the nanowires is smaller than the distance between the sensing electrodes 130, or if the arrangement of the nanowires is parallel to the trench structure, the nanowires exist only on the sensing electrodes 130, the trench top, or only on the trench walls. No connection is made.

Such a nanowire sensor is a process of fabricating a sensor structure having a trench structure, a process of placing a network type nanowire in a sensing area having a sensing electrode of a trench type sensor structure, and modifying the surface of the supported nanowire using a trench valley. It is made through three manufacturing processes.

First, a process of manufacturing a trench type sensor structure will be described in detail.

Sensor manufacturing is based on flat substrates, and silicon, GaAs substrates, glass substrates, ceramic substrates, and plastic substrates are commonly used. Among them, silicon substrates are widely used to process micro-sized microstructures. The fabrication process described below will be described with reference to FIG. 2 to form a trench type sensor structure using a silicon substrate as a planar substrate and using a deep reactive ion etch (DRIE) method.

Referring to FIG. 2, the trench-type sensor structure is first formed through a photolithography process. First, in step (a), the trench type sensor structure has a protective layer 120 having a uniform thickness on the entire surface of the flat substrate 110. An organic photoresist may be used as the etch protection layer 120, but a silicon oxide film having excellent dry etching resistance is ideal. Such a silicon oxide film can be formed by thermal oxidation or chemical vapor deposition.

The next step (b) represents a typical photolithography operation. In step (b), the trench type sensor structure is coated with a photoresist that reacts to the light on the entire surface of the flat substrate 110, and a photomask and a UV light source are applied. The desired pattern is formed on the photoresistor. Thereafter, the trench type sensor structure has the photoresist as a protective layer, and the etch protection layer 120 is etched, and the remaining photoresist is removed from the planar substrate 110. Here, if the photoresist can perform its own role as an etch protective layer 120, it is possible to pattern directly by using UV light in the etch protective layer without having to produce a pattern using the photoresistor. Do.

The next step (c) represents an etching, or DRIE process. In the step (b), the planar substrate 110 formed of silicon of the trench type sensor structure is anisotropically etched only in the depth direction while protecting the silicon wall while alternately performing silicon dry etching and forming a polymer protective layer. This process technology allows silicon to be etched vertically up to several hundred micrometers. Silicon can also be fabricated through wet etching, but due to the isotropic etching characteristic, the etched wall has a constant slope. In the embodiment of the present invention, a dry wall (DRIE) process is more advantageous than a wet process because vertical walls are preferred. Trench width and bone depth are very important experimental variables when forming the floating nanowire sensor on the top surface of the flat substrate 110. Therefore, these dimensions should be determined to have optimal performance by the size of the nanowires used and the semiconductor processes available. In general, the trench width should be about 0.1-50 μm, and the bone depth should be at least greater than the trench width in order to exclude nanowires shorter than the trench width.

As such, the silicon of the etched section after the DRIE etching is exposed to the outside. Therefore, in the exemplary embodiment of the present invention, since the conductivity is measured, the silicon on the exposed trench wall may act as a path of leakage current. Therefore, an additional protective layer 120a is formed on the etched trench sensor structure as shown in step (c) for electrical insulation between the planar substrate 110 and the sensing electrode 130.

The next step (d) shows forming the protective layer 120a on the trench type sensor structure subjected to the etching process. The formation of the protective layer 120a mainly uses silicon oxide as a masking layer for the RIE process, thereby forming additional silicon oxide on the surface by thermal oxidation. The silicon oxide produced by the thermal oxidation method has a dense structure and can reliably achieve electrical or thermal disconnection between the substrate and the sensing electrode. In addition, another material used to form the protective layer 120a may be a silicon nitride film.

If physical property compatibility is not secured between the etching protection layer 120 fabricated for the trench etching process and the protection layer 120a newly fabricated for electrical disconnection, the protection for electrical insulation after removing the etching protection layer 120 is performed. Layer 120a should be formed on the surface of the trench sensor structure. Other good methods for forming the protective layer 120a for electrical insulation include atomic layer deposition, chemical vapor deposition, and the like.

The next step (e) indicates that the trench type sensor structure is finally formed by an inclined anisotropic vacuum deposition method, and in the step (e), the nanowire formed by the subsequent process in the trench type sensor structure in which the protective layer 120a is formed. The sensing electrode 130 is formed to detect a change in electrical conductivity of the sensing material. At this time, in order to effectively deposit the metal electrode only on the trench structure, the sensing electrode is formed by inclining the substrate with respect to the direction in which the source comes out.

The sensing electrode 130 is formed in various shapes of electrodes in order to effectively measure the change in electrical conductivity. The two electrodes may be simply arranged in a line shape, or two comb teeth to maximize the contact area with the sensor. The structures of the shape may be arranged to be staggered with each other. Metal materials typically used in the sensing electrode 130 are gold (Au), platinum (Pt), aluminum (Al), titanium nitride (TiN), tungsten (W), polycrystalline silicon (p-Si), and the like. There is this.

When the electrical electrode 130 is formed as described above, the adhesive layer between the protective layer 120a and the metal material is easily peeled off, so that the trench-type sensor structure has an adhesive layer between the protective layer 120a and the electrical electrode 130. May not be formed). Representative adhesive layers include Cr, Ti, and the like. In addition, in order to easily fabricate the sensing electrode without the photolithography process, the entire region where the metal is to be deposited is set by using a shadow mask, and the metal sensing electrode is formed only on the trench type sensor structure using the anisotropic deposition method. You can use a method to make it work. Such representative anisotropic deposition method is an electron beam (e-beam) or the heat (theraml) evaporation method.

In the trench type sensor structure formed as described above, a network type nanowire is finally formed. As shown in FIG. 3, a nanowire sensing material 140 is formed on the trench type sensor structure.

The sensing material 140 is a material having a semiconductor characteristic used in the conductivity-changing sensor, carbon, silicon, tungsten oxide, tin oxide, indium oxide having a nanowire structure having a width of 1-500nm and a length of 1um or more , Titanium oxide, zinc oxide or the like. In particular, in the case of carbon nanotubes, a material having a width of 1-10 nm and a length of 1 μm or more can be produced in large quantities and is a promising nanowire sensing material because it is a very small material. Such nanowire sensing materials can be manufactured by various methods. Such methods include chemical vapor deposition (CVD), synthesis using arc, template method using anodic aluminum oxide or polycarbonate membrane polymer, and solvothermal method using heat and surfactant in solution.

Positioning the nanowire sensing material in the trench-type sensor structure is as shown in Figure 4 attached for example.

Referring to FIG. 4, first, after separating and purifying a nanowire material manufactured by various methods, nanowire molecules are dispersed and used in a nanowire solution. As a solvent, a general organic solvent such as ethanol was used, and physical shock such as ultrasonic waves was applied to promote dispersion of the nanowire molecules. The nanowire solution 160 prepared as described above is selectively dropped onto the sensing region 150 in which two or more sensing electrodes 130 exist in pairs using a drop coating method. In a subsequent process, the nanowire solution 160 is dried, i.e., heated, or vacuumed to remove the solvent, thereby placing the nanowire molecules in the desired sensing region 130. As the solvent is removed, only nanowire molecules remain on the sensing electrode 130. In order to improve the electrical contact characteristics, an additional heat treatment process, a close contact process by physical force, a fine welding process, a thin metal deposition process, and the like are performed.

On the other hand, another method for moving the nanowires to the top of the trench-type sensor structure is spin coating, spay coating or dip coating method.

As such, the nanowire sensing material formed on the trench type sensor structure must be modified with an organic material. To this end, a nanowire material is used to make a contact with two or more sensing electrodes on the upper portion of the trench, so that the nanowire material is present in the state in which the nanowire material is supported on the trench valley. This structure can allow the surface modification solution to flow along the trench valleys. In this way, the fluid flow can only be used to modify the sensors that are in the selective position. Referring to the accompanying drawings, an example of surface modification of such a nanowire material is as follows.

5 is a view illustrating a process of forming three sensors having different sensing characteristics on the same base in the trench type sensor structure using three different reforming solutions according to an embodiment of the present invention.

First, the three sensors flow the surface modification solution 170a along the leftmost bone, as shown in FIG. 5 (a) attached, and FIGS. 5 (b) and (c) As shown in the drawing, the surface modification solutions 170b and 170c having different characteristics are sequentially generated to have different surface modification organic materials while flowing to the right bone. As such, the hydrophilicity / hydrophobicity of the surface of the trench-type sensor structure and the structural characteristics of the trench valleys are very important for the surface modification solution to flow along the valleys. In general, since the organic solvent such as alcohol is used as the solvent, the three surfaces of the trench valleys are hydrophilic such that the fluid spontaneously flows through the trench valleys using capillary force. The top of the trench-type sensor structure is hydrophobic, preventing the nanowire solution from spreading around. The structural characteristics of such trench valleys are advantageous if they are narrow and deep. The method using the microflodix is an effective method of manufacturing various sensors using the same nanowire sensor.

Surface modification can be divided into physical methods of enclosing nanowires with organic materials using physical forces between organic molecular sieves and nanowires, and chemical methods of inducing and connecting new chemical bonds between organic materials and nanowires. Can be. The chemical method is advantageous in that the nanowire and the organic material are strongly connected only one layer at the molecular level, but the electrical conductivity of the nanowire may be greatly changed due to the new chemical bond.

Therefore, in the embodiment of the present invention, a solution in which a polymer is mainly dissolved as a surface modification solution is used. Representative polymers include both synthetic polymers such as Nafion and polyvinylpyrrolidone and biopolymers such as DNA.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

 1 is a cross-sectional view of a surface modified nanowire sensor having a trench type sensor structure according to an embodiment of the present invention;

2 is a view showing a manufacturing process flow of a trench type sensor structure according to an embodiment of the present invention;

3 is a cross-sectional view showing a trench type sensor structure equipped with a nanowire sensing material according to an embodiment of the present invention;

4 is a view showing a process for positioning a nanowire sensing material in the trench type sensor structure according to an embodiment of the present invention;

5 is a view illustrating a process of forming three sensors having different sensing characteristics on the same base in a trench type sensor structure using three different reforming solutions according to an embodiment of the present invention.

Claims (11)

A planar substrate on which some regions are etched to form trench valleys; A protective layer formed on the planar substrate surface for electrical disconnection; A sensor structure comprising a sensing electrode formed on the protective layer in the protruding surface region of the planar substrate; And The surface-modified type is characterized in that it comprises a nano-wire sensing material formed in contact with the sensing electrode, buoyant in the air of the trench valley between the sensing electrodes, and selectively interacts with a specific material to change the electrical conductivity. Route sensor. The method of claim 1, The sensor structure is characterized in that the sensing electrode having a distance between the electrode and the electrode is 0.1 ~ 50um is formed on the protective layer, the surface between the sensing electrode is formed a trench trench etched deeper than the distance between the electrodes Type nanowire sensor. The method of claim 2, The sensor structure is such that the trench bone of the sensor structure has a hydrophilic property, the upper plane has a hydrophobic property, and a surface modification solution for surface modification of the nanowire sensing material spontaneously flows along the inside of the trench valley. Surface modified nanowire sensor, characterized in that formed. The method of claim 1, The sensing electrode senses a change in the conductivity of the nanowire sensing material, and includes gold (Au), platinum (Pt), aluminum (Al), titanium nitride (TiN), tungsten (W), and polycrystalline silicon (p-Si). Surface modified nanowire sensor, characterized in that formed of one of the materials. The method of claim 1, The nanowire sensing material is a surface-modified nanowire sensor, characterized in that the nanowire molecules are dissolved in the nanowire solution, the nanowire solution is formed in a desired position by selectively dropping the nanowire solution on the sensing electrode and dried. The method of claim 5, The nanowire sensing material has a surface modification of 1 to 500 nm and has a surface modification of one of carbon, silicon, tungsten oxide, tin oxide, indium oxide, titanium oxide, or zinc oxide having a nanowire structure of 1 μm or more in length. Type nanowire sensor. Forming a sensor structure having a trench structure on one surface of the planar substrate; Positioning a nanowire sensing material on a sensing electrode formed on the sensor structure; And And modifying the surface of the nanowire sensing material by flowing a surface modification solution in which a chemical reactant is dissolved in a trench valley formed in the sensor structure.  The surface-modified nanowire sensor detects the concentration of a substance by contacting the nanowire sensing material with the sensing electrode to selectively change the electrical conductivity by interacting with a specific material and by raising the air in the trench valleys between the sensing electrodes. Method for producing a surface-modified nanowire sensor, characterized in that the manufacturing. The method of claim 7, wherein forming a sensor structure having a trench structure, Forming an etch protective layer on one surface of the planar substrate to a uniform thickness; Coating a photoresist on the entire surface of the flat substrate; Etching the etch protective layer by forming a desired pattern on the photoresist using the photomask and the UV light source; Etching the region of the planar substrate in contact with the region of the etch protection layer etched according to the formed pattern to form the trench valleys; Removing the remaining photoresist from the planar substrate; Forming a protective layer on the remaining etching protection layer and the trench valley; And And forming a sensing electrode on a portion of the protective layer. The method of claim 7, wherein the positioning of the nanowire sensing material, Dispersing the nanowire molecules separated and purified from the nanowire material in a nanowire solution; Selectively dropping the nanowire solution into a sensing region in which two or more of the sensing electrodes are present in pairs; And And drying the nanowire solution so that only the nanowire molecules remain, thereby forming the nanowire molecules as desired. The method of claim 7, wherein The modifying the surface of the nanowire sensing material may include modifying the surface modification solution to spontaneously flow along the trench valleys when the trench valleys of the sensor structure have hydrophilic properties and the upper plane has hydrophobic properties. Method for producing a surface-modified nanowire sensor characterized in that the flow. The method of claim 10, The nanowire sensing material has a surface modification of 1 to 500 nm and has a surface modification of one of carbon, silicon, tungsten oxide, tin oxide, indium oxide, titanium oxide, or zinc oxide having a nanowire structure of 1 μm or more in length. Method of manufacturing type nanowire sensor.

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