KR101169394B1 - Large Area Gas Sensor and Method for Fabricating the Same - Google Patents

Large Area Gas Sensor and Method for Fabricating the Same Download PDF

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KR101169394B1
KR101169394B1 KR20080123884A KR20080123884A KR101169394B1 KR 101169394 B1 KR101169394 B1 KR 101169394B1 KR 20080123884 A KR20080123884 A KR 20080123884A KR 20080123884 A KR20080123884 A KR 20080123884A KR 101169394 B1 KR101169394 B1 KR 101169394B1
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layer
gas sensor
flexible substrate
probe
oxide
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KR20080123884A
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Korean (ko)
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KR20100065518A (en
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문제현
박진아
이수재
정태형
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한국전자통신연구원
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Abstract

The present invention relates to a large area gas sensor and a method for manufacturing the same, the gas sensor according to the present invention comprises a flexible substrate; A double buffer layer formed on the flexible substrate; A metal electrode including a probe formed patterned on the double buffer layer; An oxide sensing layer formed on the metal electrode from which the probe is excluded, and a method of manufacturing the same includes depositing a double buffer layer on a flexible substrate; Depositing and patterning a metal on the double complete layer to form a metal electrode including a probe; Coating the probe with a photosensitizer and forming an oxide sensing layer on the metal electrode; Removing the photosensitizer; And heat treating the oxide sensing layer.

Gas Sensors, Flexible Substrates, Large Areas, Oxides, Sensing, Plastics

Description

Large Area Gas Sensor and Method for Fabricating the Same

The present invention relates to a large area gas sensor and a method of manufacturing the same, and more particularly, to a large area gas sensor formed on a flexible substrate and a method of manufacturing the same.

With the recent increase in environmental pollution and health concern, the need for detection of various harmful gases is greatly increased. As a result, there is a great need for a device or device capable of effectively detecting a noxious gas.

1 is a schematic diagram of a conventional metal oxide gas sensor. Referring to FIG. 1, an electrode 110 and an oxide sensing layer 120 are included on a substrate 100. The gas sensor having such a structure operates as follows. That is, when oxygen, carbon dioxide, and the like are adsorbed on the oxide surface, electrical properties such as specific resistance and dielectric constant appear. The degree of change also depends on the gas concentration in the atmosphere. Therefore, when the change in electrical characteristics is measured and the change value for each concentration is obtained through the measurement, the appearance and concentration of a specific gas in the atmosphere can be detected. The metal oxide for the gas sensor is clearly seen in the metal oxide having the characteristics of the semiconductor and should be a material having semiconductor characteristics. Among the metal oxides, materials having semiconductor properties include ZnO, SnO 2 , VO 2 , TiO 2 , In 2 O 3 , NiO, MoO 3 , and WO 3 .

In the conventional gas sensor having the structure of FIG. 1, a rigid substrate having electrical insulation properties, such as Al 2 O 3 , MgO, or SiO 2 / Si, is commonly used as the substrate 100. The use of such a substrate is to ensure that the change in the electrical signal is only due to gas adsorption on the oxide. In addition, the high temperature heat treatment process of the oxide layer can be easily performed by the selection of the substrate.

However, when manufacturing a sensor by selecting a flexible substrate vulnerable to high temperature, such as plastic, there is a limitation of heat treatment. For example, when the oxide deposition proceeds at room temperature, the oxide film on the substrate is amorphous. Amorphous oxides have very low gas sensitivity, so they must be obtained through crystallization. The formation of crystalline oxide requires heat treatment at a temperature above the glass transition temperature (approximately 200 ° C.) of the plastic substrate. However, when the crystallization heat treatment temperature is performed above the glass transition temperature, the flexible substrate is severely damaged.

In order to overcome such limitations, there is a need for a technique capable of instantaneously performing local heat treatment on the region where oxides are deposited instead of the entire heating of the substrate or protecting the flexible substrate during heat treatment.

In addition, oxide deposition should be carried out below the glass transition temperature, and large-area oxide deposition should be easy to increase the process yield. Flexible substrates are not limited to plastics but also include metal foils.

Accordingly, the present inventors have found that a gas sensor can be manufactured without damaging the flexible substrate when the gas-sensing oxide is deposited by a low temperature process and then subjected to an instant heat treatment for crystallization, thereby completing the present invention.

The first technical problem to be solved by the present invention is to provide an oxide gas sensor fabricated on a large area flexible substrate.

The second technical problem to be solved by the present invention is to provide a method for manufacturing an oxide gas sensor on the flexible substrate without damaging the substrate.

In order to solve the first technical problem, the present invention

Flexible substrates;

A double buffer layer formed on the flexible substrate;

A metal electrode including a probe formed patterned on the double buffer layer;

Provided is a gas sensor including an oxide sensing layer formed on a metal electrode except for a probe.

In the gas sensor according to the present invention, the flexible substrate is preferably one or more selected from the group consisting of polyimide, polyethylene, polyethersulfone and polycarbonate.

In addition, in the gas sensor according to the present invention, the double buffer layer preferably includes an amorphous silicon layer and an inorganic insulating layer formed on the flexible substrate, where the inorganic insulating layer is Al 2 O 3 , MgO, SrTiO and SiO 2. It is preferable that at least one selected from the group consisting of.

Oxides constituting the sensing layer of the gas sensor according to the present invention include n-type oxide semiconductors ZnO, TiO 2 , ZrO 2 , MgO, V 2 O 5 , Nb 2 O 5 , Ta 2 O 5 , MnO 3 , WO 3 , Al 2 O 3 , Ga 2 O 3 , In 2 O 2 , SnO 2 , ABO 3 perovsikite (BaTiO 3 , metal doped BaTiO 3 ) and p-type oxide semiconductors NiO, CuO, Y 2 O 3 , La 2 O 3 , CeO 2 , Mn 2 O 3 , Co 2 O 4 , PdO, Ag 2 O, Bi 2 O 3 , Sb 2 O 3 , TeO 2 , Fe 2 O 3 It is preferable that either one be selected. In addition, the sensing layer may be in the form of a thin film, nanoporous body or nanofiber.

In order to solve the second technical problem of the present invention, the present invention

Depositing a double buffer layer on the flexible substrate;

Depositing and patterning a metal on the double buffer layer to form a metal electrode including a probe;

Coating the probe with a photosensitizer and forming an oxide sensing layer on the metal electrode;

Removing the photosensitizer; And

It provides a method of manufacturing a gas sensor comprising the step of heat-treating the oxide sensing layer.

In the method of manufacturing a gas sensor according to the present invention, the double buffer layer is formed by sputtering, pulsed laser deposition, atomic layer deposition, or the like at room temperature. Specifically, the double buffer layer forming step includes: i) forming an amorphous silicon layer on the flexible substrate. And ii) forming an inorganic insulating film on the amorphous silicon layer.

In the method of manufacturing a gas sensor according to the present invention, the oxide sensing layer is formed by selecting a semiconductor oxide from the group consisting of sputtering, pulsed laser deposition, atomic layer deposition, and electrospinning deposition, and the oxide sensing layer Heat treatment by laser exposure is preferred, and the type of laser is selected from the group consisting of ArF (wavelength = 193 nm), KrF (wavelength = 248 nm), XeBr (wavelength = 282 nm) and XeCl (wavelength = 308 nm). It is preferable to be.

Oxide gas sensor and its manufacturing method according to the present invention has the following effects.

First, it is possible to freely apply the sensor to the curvature mounting surface using a flexible substrate.

Second, by applying the atomic layer deposition method and laser exposure heat treatment, it is possible to deposit and heat the large-area oxide sensing film below the glass transition temperature.

Third, mass production of gas sensors in the form of an array on a large area can reduce manufacturing costs.

Fourth, the contact resistance between the electrode and the oxide sensing film can be reduced by applying an atomic layer deposition method having excellent surface and shape covering properties when depositing the oxide sensing film.

Fifth, it is possible to prevent damage to the flexible substrate during laser exposure by applying a double layer buffer film.

Sixth, it is possible to secure a probe without contamination.

Seventh, by using an inexpensive plastic substrate instead of the existing expensive alumina substrate, it is possible to reduce the cost of the substrate.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

2 is a cross-sectional view showing the structure of a gas sensor according to an embodiment of the present invention, Figure 3 is a plan view showing the structure of a gas sensor according to an embodiment of the present invention.

2 and 3, the gas sensor according to the present invention includes a flexible substrate 200, a double buffer layer 210 formed on the flexible substrate, and a metal including a probe portion 221 patterned on the inorganic buffer layer. And an oxide sensing layer 230 formed on the metal electrode 220 except for the probe 220.

In the gas sensor according to the present invention, the flexible substrate 200 may be formed of polyimide (PI), polyethylene (Polyethylene, PEN), polyether sulfone (PES), polycarbonate (PC), or the like. Plastic substrates may be used, and stainless steel foil may be used as the metal-based flexible substrate. Preferably, the plastic-based flexible substrate has a thickness of 100 to 200 μm, and the metal-based flexible substrate has a thickness of about 50 μm.

The double buffer layer 210 formed on the flexible substrate 200 may have a double layer structure of an amorphous silicon layer 211 and an inorganic insulating layer 212. The inorganic insulating layer 211 may include Al 2 O 3 , MgO, It may be selected from the group consisting of SrTiO, SiO 2 . The amorphous silicon layer 211 and the inorganic insulating layer 212 preferably have a thickness of 50 to 100 nm and 200 to 300 nm, respectively.

The metal electrode 220 including the probe 221 is introduced on the double buffer layer 210. The metal electrode is preferably a metal such as platinum or gold, and preferably has a thickness in the range of 100 to 200 nm. The metal electrode 220 may have a pair of interdigit type structures facing each other, but is not limited thereto. One end of the metal electrode 220 includes a probe part 221, and the probe part 221 is a part where an electrical signal is measured.

The oxide sensing layer 230 is included on the metal electrode 220 except for the probe 221. The oxide sensing layer 230 may be formed between the metal electrodes 220 of the comb-shaped structure facing each other except for the probe portion 221. The oxide constituting the sensing layer 230 may include an n-type oxide semiconductor or a p-type oxide semiconductor having a bandgap energy of 3.3 to 3.5 eV, and the n-type oxide semiconductor may include ZnO, TiO 2 , ZrO 2 , MgO, V 2 O 5 , Nb 2 O 5 , Ta 2 O 5 , MnO 3 , WO 3 , Al 2 O 3 , Ga 2 O 3 , In 2 O 2 , SnO 2 , ABO 3 Perovskite (BaTiO 3 , metal doped BaTiO 3 ), and p-type oxide semiconductors include NiO, CuO, Y 2 O 3 , La 2 O 3 , CeO 2 , Mn 2 O 3 , Co 2 O 4 , PdO , Ag 2 O, Bi 2 O 3 , Sb 2 O 3 , TeO 2 , Fe 2 O 3 , but are not limited thereto. In addition, the oxide layer is generally in the form of a thin film, but may have a form of nanostructures such as nanoporous bodies or nanofibers.

The gas sensor having such a structure includes depositing the double buffer layer 210 on the flexible substrate 200 as shown in FIG. 4 (S11); Depositing and patterning the metal on the double buffer layer 210 to form a metal electrode 220 including the probe unit 221 (S12); Coating the probe unit 221 with a photosensitive agent and forming an oxide sensing layer 230 on the metal electrode 220 (S13); Removing the photosensitizer (S14); And laser-heat-treating the oxide sensing layer 230 (S15).

When depositing the double buffer layer 210 on the flexible substrate (200) (S11), the double buffer layer should be deposited at room temperature to protect the flexible substrate 200, for example, preferably formed by the room temperature sputtering method Do. It is preferable to deposit both the amorphous silicon 211 and the inorganic insulating layer 212 constituting the double buffer layer 210 by the normal temperature sputtering method.

Subsequently, metal is deposited on the double buffer layer 210 and then patterned to form a metal electrode 220 including the probe 221 (S12). In this case, the metal electrode may be patterned to have a probe region at any one end while having a comb teeth shape opposite to each other. Here, the metal deposition may use an e-beam or sputtering method performed at room temperature. In the final pattern formation of the probe 221 and the metal electrode 220, when a metal such as platinum or gold is adopted, a lift-off process may be introduced.

Subsequently, before the oxide sensing layer 230 is formed on the metal electrode 220, a photoresist layer is formed on the probe 221 to prevent the oxide sensing material from being present on the probe 221. Next, an oxide sensing layer 230 is formed to cover the comb portion of the metal electrode or between the comb portions using the oxide sensing material (S13).

Here, the formation of the photosensitive agent layer may be applied to a process used for masks and lithography. As the photosensitizer material, photoresists commonly used in semiconductor processes may be used.

Meanwhile, in forming the oxide sensing layer 230, an atomic layer deposition method is used to achieve low temperature and large area deposition. The atomic layer deposition method is capable of depositing at room temperature, and has an advantage of excellent surface and shape covering properties, thus making contact between the metal electrode and the oxide sensing layer very dense, thus reducing the sensitivity of the sensor. Can be reduced.

The oxide sensing layer 230 is generally in the form of a thin film as described above, but may have a nanostructure, for example, a nanoporous body or a nanofiber form.

The nanoporous body can be formed by combining a colloidal template method and an oxide deposition method. That is, the nanoporous body can be formed by forming a template and then depositing an oxide on the template by a room temperature deposition method and then removing the template through a heat treatment process. The diameter of the polymer beads used in the colloidal template is preferably in the range of 200 to 800mm.

Nanofibers can be formed using an electrospinning apparatus. That is, when the oxide forming precursor solution is spun through the spray nozzle of the electrospinning apparatus, as the electric field is applied to the spray nozzle, the oxide forming precursor solution is collected in the form of nanofibers on the grounded substrate while being radiated from the spray nozzle. In this case, the diameter of the spray nozzle is preferably in the range of 300 to 700mm. In this case, the collected fibers are organic-inorganic composite nanofibers, and inorganic nanooxide fibers may be formed by removing organic components through subsequent heat treatment.

Subsequently, the photoresist layer formed on the probe part 221 is removed using solvents (S14). When the oxide remains in the probe part, the electrical signal measured through the probe part may be distorted and attenuated, which causes a decrease in sensitivity and reliability of the sensor. Thus, the present invention can produce a probe free of residue and contamination.

Subsequently, the oxide sensing layer 230 is heat-treated through laser exposure for 30 to 100 ns (S15). When laser exposure is used, instant localized heating and large area heat treatment are possible. Since the laser exposed to the metal part is reflected, the metal part is not damaged. In laser exposure, the flexible substrate absorbs the laser, which may cause breakage and distortion of the substrate. In the present invention, the double buffer layer including the amorphous silicon layer is prevented.

The following empirical formula exists between the light absorption and the bandgap.

(Wavelength) (bandgap energy) = 12345.

Here, the wavelength and the bandgap energy have units of angstroms (A = 10 -10 m) and electron volts (eV), respectively. In order for the exposed light to be absorbed by the material, light having a wavelength shorter than the wavelength obtained by using the above equation must be used. Since the oxide for gas sensor according to the present invention has a bandgap energy of 3.3 to 3.5 eV, a wavelength of 352.7 to 374 nm can be obtained using the above equation.

Examples of lasers satisfying such absorption conditions include excimer laser groups such as ArF (wavelength = 193 nm), KrF (wavelength = 248 nm), XeBr (wavelength = 282 nm), and XeCl (wavelength = 308 nm). Therefore, in the laser heat treatment, it is preferable to select from the excimer laser group.

The heating effect in laser heat treatment is not only due to the laser absorption of the oxide film, but also in part to the laser absorption of the lower inorganic insulating film. Other laser energy is absorbed by the amorphous silicon layer, converted to heat, and consumed for crystallization, thereby effectively protecting the lower flexible substrate from damage due to laser exposure. The amorphous silicon layer may be partially crystallized.

1 is a cross-sectional view showing the basic structure of the oxide gas sensor according to the prior art.

2 is a cross-sectional view showing a basic structure of an oxide gas sensor according to an embodiment of the present invention. 2, the probe part is omitted.

3 is a plan view showing the basic structure of the oxide gas sensor according to an embodiment of the present invention.

4 is a process chart showing the manufacturing process of the oxide gas sensor according to an embodiment of the present invention.

Claims (11)

Flexible substrates; A double buffer layer formed on the flexible substrate; A metal electrode including a probe formed patterned on the double buffer layer; An oxide sensing layer formed on the metal electrode from which the probe is excluded; Wherein the double buffer layer comprises an amorphous silicon layer and an inorganic insulating layer sequentially formed on the flexible substrate. The method of claim 1, The flexible substrate is at least one selected from the group consisting of polyimide, polyethylene, polyethersulfone and polycarbonate. delete The method of claim 1, The inorganic insulating layer is one or more selected from the group consisting of Al 2 O 3 , MgO, SrTiO and SiO 2 gas sensor. delete The method of claim 1, The oxide sensing layer is a gas sensor in the form of a thin film, nanoporous body or nanofiber. Depositing a double buffer layer on the flexible substrate; Depositing and patterning a metal on the double complete layer to form a metal electrode including a probe; Coating the probe with a photosensitive agent and forming an oxide sensing layer on the metal electrode; Removing the photoresist; And A method of manufacturing a gas sensor comprising the step of heat-treating the oxide sensing layer. 8. The method of claim 7, The double buffer layer forming step is a method of manufacturing a gas sensor is deposited by sputtering at room temperature. 8. The method of claim 7, The double buffer layer forming method includes the steps of: i) forming an amorphous silicon layer on the flexible substrate, and ii) forming an inorganic insulating film on the amorphous silicon layer. 8. The method of claim 7, And the oxide sensing layer is formed by atomic layer deposition, and the oxide sensing layer is heat-treated by laser exposure. The method of claim 10, The laser may be selected from the group consisting of ArF (wavelength = 193 nm), KrF (wavelength = 248 nm), XeBr (wavelength = 282 nm), and XeCl (wavelength = 308 nm).
KR20080123884A 2008-12-08 2008-12-08 Large Area Gas Sensor and Method for Fabricating the Same KR101169394B1 (en)

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CN109991286A (en) * 2019-05-05 2019-07-09 河北工业大学 A kind of preparation method of the double selectivity gas sensor of aluminium doped tungsten oxide base
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KR20190102196A (en) * 2016-12-28 2019-09-03 로베르트 보쉬 게엠베하 Sensor element for detecting at least one characteristic of the measuring gas in the measuring gas chamber
KR102518560B1 (en) 2016-12-28 2023-04-07 로베르트 보쉬 게엠베하 A sensor element for detecting at least one property of a measuring gas in the measuring gas chamber
CN107870225A (en) * 2017-11-06 2018-04-03 余帝乾 A kind of flexible stereo encapsulates gas sensor
CN109991286A (en) * 2019-05-05 2019-07-09 河北工业大学 A kind of preparation method of the double selectivity gas sensor of aluminium doped tungsten oxide base

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