KR101302058B1 - manufacturing method of gas sensor based on suspended carbon nanotube - Google Patents

Abstract

Disclosed is a gas sensor fabrication method using airborne carbon nanotubes. According to an embodiment of the present invention, a method of manufacturing a gas sensor using airborne carbon nanotubes includes a substrate in a method of manufacturing a gas sensor including airborne carbon nanotube (CNT) nanostructures as a sensing unit. Forming an electrode on the electrode; And synthesizing carbon nanotubes on the surface of the microelectrode by chemical vapor deposition (CVD, Chemical Vapor Deposition). It comprises a; detection synthesis step.

Description

Manufacturing method of gas sensor based on suspended carbon nanotube

The present invention relates to a method for manufacturing a gas sensor using airborne carbon nanotubes.

With the rise of environmental issues, researches on harmful gas detection sensors have been actively conducted worldwide. In particular, one-dimensional nanostructure-based gas detection sensors are unique to one-dimensional nanostructures. Its physical and chemical properties make it possible to detect low concentrations of gas with high sensitivity, replacing the existing gas detection sensors.

Hereinafter, the manufacturing methods of the one-dimensional nanostructure-based gas detection sensor according to the prior art will be briefly described.

Patterning chromium (Cr) on a glass substrate to form an electrode, spraying a solution of carbon nanotubes and ethanol on top of the substrate, and then Disclosed is a method of aligning carbon nanotubes between electrodes using a dielectrophoresis method, and drying and removing ethanol (J. Suero, G. Zhou, H. Imakiire, W. Ding, M. Hara, "Controlled fabrication of carbon nanotube NO2 gas sensor using dielectrophoretic impedance measurement," Sensors and Actuators B-Chemical, vol. 108, pp. 398-403, 2005.)

In addition, after depositing chromium (Cr) on a substrate on which silicon (Si) and silicon oxide (SiO ₂ ) are laminated, carbon nanotubes are placed on the upper surface of the substrate, and a mask is formed using electron beam lithography. And a process of depositing gold (Au) to be used as an electrode (T. Helbling, R. Pohle, L. Durrer, C. Stampfer, C. Roman, A). Jungen, M. Fleischer, C. Hierold, "Sensing NO2 with individual suspended single-walled carbon nanotubes," Sensors and Actuators B-Chemical, vol. 132, pp. 491-497, 2008.)

In addition, when the heat generated by applying a voltage to one side of the pair of micro-electrodes reaches a temperature suitable for fabricating the nanowires, the nanowires grow locally, and the process of causing the nanowires to reach and grow to the opposite microelectrode. (O. Englander, D. Christensen, J. Kim, L. Lin, "Post-processing techniques for locally self-assembled silicon nanowires," Sensors and Actuators A, vol. 135, pp. 10-15, 2007.)

Conventionally, in manufacturing a carbon nanotube-based gas sensor, a method of combining carbon nanotubes and micro electrodes is widely used after the carbon nanotube synthesis process and the micro-processing process for forming an electrode are separately performed as described above. In the case of separately fabricating the carbon nanotubes and the electrodes, there is a problem that the production yield is low and a long production time is consumed.

As a conventional technique for solving such a problem, a process of combining a carbon electrode with an external stimulus such as an electric field or a magnetic field in the process of synthesizing the carbon nanotube has been developed. In the case of manufacturing by using, additional elements for applying an electric field or a magnetic field when synthesizing carbon nanotubes are complicated, and the manufacturing yield is still low.

According to the prior arts, there is a limit in reducing the manufacturing cost of the device due to the low production yield due to complex synthesis and processing process, and in particular, the micro-electrode while placing the nano-sized microstructure in a desired position (designated position on the substrate). Difficulties in the process of bonding to and are acting as a major obstacle to the commercialization of nanostructure-based gas sensors.

The present invention devised to solve the problems as described above, the entire process of manufacturing carbon nanotube-based gas sensor can be made by a batch process, airborne type carbon nanotubes to enable high yield production through mass production An object of the present invention is to provide a gas sensor manufacturing method using.

The present invention for achieving the object as described above, in the manufacturing method of a gas sensor having a nanostructure of carbon nanotubes (CNT, 41) as a sensing unit, micro on the substrate 10 An electrode forming step (S1) of forming an electrode 30; And synthesizing the carbon nanotubes 41 on the surface of the microelectrode 30 by chemical vapor deposition (CVD, Chemical Vapor Deposition), wherein the pair of the microelectrodes by longitudinal proliferation of the carbon nanotubes 41. A method of manufacturing a gas sensor using airborne carbon nanotubes, including a sensing synthesis step (S2), in which the mutual coupling between the carbon nanotubes 41 formed on each is made (S2).

The electrode forming step S1 may be performed by any one of bulk micromachining and surface micromachining, or a combination of bulk micromachining and surface micromachining.

In addition, the electrode forming step (S1), the insulating layer forming step of forming a silicon dioxide layer (SiO ₂ ) (11, 31) on both sides of a silicon on insulator (WI) substrate (W) by a thermal oxidation process. (S1-1a); A PR patterning step (S1-2) of patterning a photoresist (PR) on both sides of the SOI substrate (W) by a photolithography process; A mask patterning step (S1-3) of transferring the pattern to the silicon dioxide layers (11, 31) by using a reactive ion etching (RIE) process using the PR as a mask; Upper and lower silicon layers 30a and 10a of the SOI substrate W using a deep reactive ion etching (DRIE) process using the patterned silicon dioxide layers 11 and 31 as masks. Etching the substrate to form the micro electrode 30 (S1-4); And the buried oxide layer 20a between the upper and lower silicon layers 30a and 10a and the silicon dioxide layers 11 and 31 on both sides of the SOI substrate W by wet etching. It may include; insulating layer removing step (S1-5) to remove.

In addition, after the insulating layer forming step (S1-1a), Plasma Enhanced Chemical Vapor (PECVD) is applied to the lower silicon layer 10a that is relatively thick among the upper and lower silicon layers 30a and 10a of the SOI substrate W. It may further include; an insulating layer further forming step (S1-1b) for further forming a silicon dioxide layer 12 by a deposition process.

In addition, the substrate etching step (S1-4), the device layer etching step (S1-4a) for etching the upper silicon layer (30a) of the SOI substrate (W) to form a pair of the micro electrode (30); And a substrate layer etching step (S1-4b) of etching the lower silicon layer 10a of the SOI substrate W such that the pair of micro electrodes 30 form a cantilever shape in which free ends thereof face each other. have.

In addition, the detection unit synthesis step (S2), the catalyst deposition step (S2-1) of depositing a metal catalyst (C) on the surface of the opposite end of the micro electrode (30); And inserting the microelectrode 30 on which the metal catalyst (C) is deposited into a furnace chamber, injecting ammonia (NH ₃ ) and acetylene (C ₂ H ₂ ) gas precursor at a high temperature, It may include; CNT synthesis step (S2-2) of synthesizing the carbon nanotubes (41) on the portion where the metal catalyst (C) is deposited by the vapor deposition method.

In addition, the catalyst deposition step (S2-1) uses a shadow mask having a fine hole formed only at a position corresponding to the opposite end of the micro electrode 30, and uses an E-beam evaporation method. Can be made.

Alternatively, the insulating layer removing step (S1-5), the metal catalyst (C) in the catalyst deposition step (S2-1) is deposited so as to be connected to the upper, lower silicon layer (10a) of the SOI substrate (W). The buried oxide layer 20a may be overetched to prevent it from becoming.

In addition, after the sensing compatibility step (S2), connecting the resistance measuring device 50 for measuring the resistance change of the carbon nanotube 41 and the pair of micro-electrode 30 electrically connected (S3) It may further include;

In addition, an electrode connection step (S3-1) for electrically connecting one side of the first and second electrical conductors 51 to each of the pair of micro electrodes 30; And a device connection step (S3-2) of electrically connecting the other side portions of the first and second electrical conductors 51 to the resistance measuring device 50.

In addition, according to the present invention, the carbon nanotubes 41 formed on each of the pair of microelectrodes 30 are longitudinally interconnected by air in the longitudinal direction of the carbon nanotubes 41 synthesized on the surface of the microelectrode 30. The carbon nanotube nanostructure comprising a CNT assembly 40 having a shape in which both ends are connected to the pair of micro electrodes 30 while extending continuously in one direction is another technical gist.

In addition, the present invention provides a gas sensor having a floating structure carbon nanotube (CNT) nanostructure as a sensing unit, a pair of micro-electrodes 30 disposed to face each other; And the carbon nanotubes 41 formed on each of the pair of microelectrodes 30 by longitudinal growth of the carbon nanotubes 41 synthesized on the surface of the microelectrode 30. Gas sensor comprising a CNT assembly 40; another technical gist.

Here, the resistance change according to the reaction between the CNT binder 40 and the sensing gas is connected to the pair of micro electrodes 30 by an electric conductor 51 to measure the micro electrodes 30 and the electric conductor 51. The resistance meter 50 may be further included.

According to an embodiment of the present invention, a microelectrode is fabricated based on a micromachining process, and a carbon nanotube is synthesized on a surface of the microelectrode, but is multiplied to a length that is electrically interconnected. Carbon nanotube sensing unit can produce a one-dimensional nanostructure of the structure suspended.

Since the pairing between the pair of micro electrodes and carbon nanotubes is performed at the same time as the synthesis of the carbon nanotubes, the process of previously synthesizing the carbon nanotubes separately to a designated position on the substrate and combining with the micro electrodes is unnecessary. And the entire process, including carbon nanotube manufacturing process can be carried out under a general micro machining process.

The gas sensor element which can detect the polluting gas such as nitrogen oxide can be manufactured by the batch process as described above, so that it can be manufactured in high yield through mass production, and the process compatibility is excellent. It is expected to reduce the unit cost, commercialize the device, and revitalize related industries.

In addition, the conventional carbon nanotube sensing unit is bonded to the electrode in the form of one continuous one-dimensional structure, according to an embodiment of the present invention is added to the bonding between the carbon nanotubes and carbon nanotubes to measure the resistance change more sensitively This enables better gas detection performance.

1-perspective view showing a gas sensor according to a first embodiment of the present invention
2-a flow chart showing a gas sensor manufacturing method according to a first embodiment of the present invention
3A, 3B and 3C-perspective views sequentially illustrating a manufacturing process of a gas sensor according to a first embodiment of the present invention
4A, 4B, 4C, 4D, 4E, and 4F are cross-sectional views taken along the line AA of FIG. 3 sequentially illustrating a microelectrode fabrication process.
5-3 BB cross-sectional view
6-Scanning microscope photograph of a gas sensor according to a first embodiment of the present invention
Figure 7-Scanning microscope photograph of the carbon nanotube nanostructure of Figure 7
8-Graph showing change in resistance with gas concentration

The present invention synthesizes carbon nanotubes (CNT, Carbon Nano Tube) on the opposite surface of the microelectrode by chemical vapor deposition (CVD, Chemical Vapor Deposition) and at the same time the carbon nanotubes in accordance with the longitudinal growth of the carbon nanotubes The present invention relates to a method of manufacturing a gas sensor by connecting the pair of micro electrodes and an airborne carbon nanotube in the air by tube-to-tube contact, and a carbon nanotube nanostructure and a gas sensor manufactured by the method.

According to the present invention having the configuration described above, the microelectrode is fabricated by a micromachining technique, and the airborne carbon nanotube nanostructure is synthesized on the microelectrode and coupled to the pair of microelectrodes. The entire process can be done in batch at the wafer level.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view showing a gas sensor according to a first embodiment of the present invention, Figure 2 is a flow chart showing a gas sensor manufacturing method according to a first embodiment of the present invention.

Referring to FIG. 1, the gas sensor according to the first embodiment of the present invention includes a pair of micro electrodes 30 disposed to face each other, and the carbon nanotubes 41 formed on each of the pair of micro electrodes 30. ) Has a configuration including a CNT assembly 40 formed by interconnecting.

The CNT assembly 40 has the carbon nanotubes 41 formed on each of the pair of microelectrodes 30 by longitudinal proliferation of the carbon nanotubes 41 synthesized on the surface of the microelectrode 30. It is connected to each other, and extends continuously in one direction, and has a shape in which both ends are connected to the pair of micro electrodes 30.

Conventional carbon nanotube detector has a structure bonded to the electrode in the form of one continuous one-dimensional structure, according to the first embodiment of the present invention between the carbon nanotube 41 and the carbon nanotube 41 As the junction portion CNT 42 (see FIGS. 1, 3C, 5, and 7), which is the junction portion, is further formed, the resistance change can be more sensitively measured in reactivity with the gas.

A resistance meter 50 is connected to the pair of micro electrodes 30 by an electric conductor 51 so that the resistance change according to the reaction between the CNT assembly 40 and the sensing gas is changed to the micro electrode 30 and the electric conductor 51. Measure through).

The gas sensor manufacturing method according to the first embodiment of the present invention relates to a method of manufacturing the gas sensor according to the first embodiment of the present invention having a structure as shown in FIG. , And has a configuration including an electrode forming step (S1) and a detection combining step (S2).

In the electrode forming step (S1), the microelectrode 30 is formed on the substrate 10, and in the sensing-combining step (S2), carbon nanoparticles are formed on the surface of the micro electrode 30 by chemical vapor deposition. A tube 41 is synthesized, and the carbon nanotubes 41 are formed so as to be mutually coupled between the carbon nanotubes 41 formed on each of the pair of micro electrodes 30 by longitudinal growth of the carbon nanotubes 41.

3A, 3B, and 3C are perspective views sequentially illustrating a manufacturing process of the gas sensor according to the first embodiment of the present invention.

As shown in FIG. 3A, the microelectrode 30 completed through the electrode forming step S1 has a free end positioned above the hollow portion (or recessed portion) of the substrate 10, and the free ends are mutually free. It has a cantilever shape arranged oppositely.

In the detection synthesis step (S2), as shown in Figure 3b, the catalyst deposition step of depositing a metal catalyst (C) (for example, Fe) on the surface of the opposite end of the micro electrode 30 (S2- 1) and the CNT synthesis step (S2-2) of synthesizing the carbon nanotubes 41 to the metal catalyst (C) deposited portion, as shown in FIG. 3C.

FIG. 4 is a cross-sectional view taken along line A-A sequentially illustrating a process of manufacturing the microelectrode 30 shown in FIG. 3A in the electrode forming step S1.

In manufacturing the micro electrode 30 by the micro machining process technology in the electrode forming step (S1), any one of bulk micromachining and surface micromachining, or bulk micromachining and surface micromachining It can be made by a combination of machining.

4A to 4F, the electrode forming step S1 may be divided into an insulating layer forming step S1-1a, a PR patterning step S1-2, a mask patterning step S1-3, and a substrate etching step. (S1-4), it may be made through the insulating layer removing step (S1-5) sequentially.

Referring to FIG. 4A, according to the first embodiment of the present invention, a silicon on layer (10a), a buried oxide layer (20a), and an upper silicon layer (30a) are stacked on top of each other. Insulator) substrate W is subjected to micro machining.

Referring to FIG. 4B, in the insulating layer forming step (S1-1a), silicon dioxide is formed on both surfaces of the SOI substrate W (lower silicon layer 10a and upper silicon layer 30a) by a thermal oxidation process. Layers (SiO ₂ ) 11, 31 are formed.

The lower silicon layer 10a of the SOI substrate W is relatively thicker than the upper silicon layer 30a, so that the lower silicon layer 10a may have a longer time or higher strength than the upper silicon layer 30a. Since it is exposed, it is necessary to form the oxide layer which becomes a mask function more firmly.

Accordingly, after the insulating layer forming step (S1-1a), the lower silicon having a relatively thick thickness among the upper and lower silicon layers 30a and 10a of the SOI substrate W by PECVD (Plasma Enhanced Chemical Vapor Deposition) process. It is preferable to further perform the insulating layer addition forming step (S1-1b) which further forms the silicon dioxide layer 12 on the layer 10a.

Referring to FIG. 4C, in the PR patterning step S1-2, a photoresist (PR) (not shown) is patterned on both surfaces of the SOI substrate W by a photolithography process, and the mask patterning step (S1). In -3), the pattern is transferred to the silicon dioxide layers 11 and 31 by using a reactive ion etching (RIE) process using the PR as a mask.

4D and 4E, in the substrate etching step S1-4, the patterned silicon dioxide layers 11, 12, and 31 are used as a mask to perform a deep reactive ion etching (DRIE) process. The micro electrodes 30 are formed by sequentially etching the upper and lower silicon layers 30a and 10a of the SOI substrate W.

The substrate etching step (S1-4) is composed of a device layer etching step (S1-4a) and a substrate layer etching step (S1-4b), in the device layer etching step (S1-4a), shown in Figure 4d As described above, the upper silicon layer 30a of the SOI substrate W is etched to form a pair of the micro electrodes 30 disposed to face each other at a distance from each other in the longitudinal direction.

In the substrate layer etching step S1-4b, as shown in FIG. 4E, the lower silicon of the SOI substrate W is formed such that the pair of micro electrodes 30 form a cantilever shape in which free ends are opposed to each other in the air. A portion of the layer 10a, which is located under the opposing portions between the micro electrodes 30, is etched.

Referring to FIG. 4F, in the insulating layer removing step (S1-5), the buried oxide layer 20 a between the upper and lower silicon layers 30 a and 10 a is removed by a wet etching method. At the same time, the silicon dioxide layers 11, 12, and 31 formed on both surfaces of the SOI substrate W are removed together to complete the microelectrode shape as shown in FIG. 3A.

In etching the buried oxide layer 20a in the insulating layer removing step S1-5, the buried oxide layer 20a is formed between sidewalls formed by the upper and lower silicon layers 30a and 10a. Over etching to have a recessed shape.

By overetching the buried oxide layer 20a, the metal catalyst C is connected to the upper and lower silicon layers 10a of the SOI substrate W in the catalyst deposition step S2-1 (described below). The micro electrode 30 and the substrate 10 are not electrically shorted when the resistance is measured, and the current on the micro electrode 30 leaks to the substrate 10. Can be prevented.

In the catalyst deposition step (S2-1) of the detection unit synthesis step (S2), a shadow mask (not shown) in which fine holes are formed only at a position corresponding to the opposite end of the micro electrode 30 is used. In addition, a metal catalyst (C) is deposited on the surface of the opposite end of the micro electrode 30 by E-beam evaporation.

By depositing the metal catalyst (C) only in a portion corresponding to the opposite end of the micro electrode 30 using the shadow mask, the metal catalyst (C) component other than the opposite end of the micro electrode 30 The random attachment to the position can block the possibility that the insulation between the micro electrode 30 and the substrate 10 is not clearly made.

In the CNT synthesis step (S2-2), the microelectrode 30 in which the metal catalyst (C) is deposited is inserted into a furnace chamber and ammonia (NH ₃ ) and acetylene (C ₂ H ₂ ) at a high temperature. Injecting a gas precursor (precursor) and the carbon nanotubes 41 are synthesized in a portion where the metal catalyst (C) is deposited by chemical vapor deposition.

5 is a cross-sectional view taken along line BB of FIG. 3C showing a gas sensor according to an embodiment of the present invention, which is manufactured through the electrode forming step S1 and the sensing unit synthesis step S2 in sequence, and FIG. 6. , 7 are scanning electron microscopy (SEM) images of the gas sensor according to the first embodiment of the present invention, and enlarged scanning microscope images of the joints between the carbon nanotubes 41.

5 to 7, the carbon nanotubes 41 are synthesized on the surface of the opposite portion of the micro electrode 30 and are proliferated in the longitudinal direction to the extent that the carbon nanotubes 41 are finally brought into contact with each other. By this, the CNT coupling body 40 (airborne carbon nanotube nanostructure) for connecting the pair of micro electrodes 30 in the air is formed.

According to the exemplary embodiment of the present invention, the microelectrode 30 is manufactured on the substrate 10 by a micromachining technique as described above, and the CNT binder 40 is synthesized on the microelectrode 30. At the same time, the entire process of coupling with the pair of micro electrodes 30 may be performed in a batch process at the wafer level.

After the sensing unit synthesis step (S2), connecting the resistance measuring device 50 for measuring the resistance change of the carbon nanotube 41 and the pair of micro-electrode 30 and the measuring device connecting step (S3) In addition, the measuring instrument connecting step (S3) may be performed through the electrode connecting step (S3-1) and the device connecting step (S3-2) in sequence.

In the electrode connecting step (S3-1), one side of the first and second electrical conductors 51 is electrically connected to each of the pair of micro electrodes 30, and in the device connecting step (S3-2), the first electrode is connected. The other side of the two electrical conductors 51 is electrically connected to the resistance meter 50.

In the embodiment illustrated in FIG. 1, although the aluminum conductor is used as the electrical conductor 51, the electrical resistance capable of transferring the resistance change of the carbon nanotube 41 to the resistance meter 50 through the micro electrode 30. If provided, the connection path is not limited to a specific structure and shape.

The carbon nanotubes 41 (the CNT binder 40) electrically connected to the micro electrodes 30 react with a detection gas (eg, a pollutant gas such as nitrogen oxide (NO ₂ )) that is a detection target. In this case, the resistance change is displayed on the resistance meter 50 electrically connected through the micro electrode 30 and the electrical conductor 51 according to the sensing gas concentration.

8 (a) and 8 (b) are graphs showing the reactivity (resistance change according to gas concentration) of the gas sensor according to the embodiment of the present invention as the NO ₂ gas detection sensor.

Referring to (a) and (b) of FIG. 8, when the gas sensor according to the embodiment of the present invention is exposed to NO ₂ gas, a decrease in resistance of the carbon nanotubes 41 is observed as a result of the gas adsorption reaction. The higher the NO ₂ gas concentration, the greater the decrease in resistance change, and the lower the NO 2 gas concentration, the smaller the decrease change in resistance was confirmed.

Conventionally, since the carbon nanotubes are synthesized, the process of moving, placing and connecting the microelectrodes on the substrate on which the microelectrodes are formed is performed per pair of microelectrodes, and thus the process yield is low. Since each process, such as synthesis, bonding between micro electrodes and carbon nanotubes, had to be performed separately, mass production was not possible.

However, according to the embodiment of the present invention having the above configuration, hundreds of the micro electrodes (per wafer) (a SOI substrate (W) in the first embodiment of the present invention) by a batch process (MEMS process) 30) a microelectrode set consisting of 30) is fabricated, and the metal catalyst (C) is deposited at once using a shadow mask on the microelectrode set and inserted into a CNT synthesis chamber (furnace chamber). Mass production is possible by a process of simultaneously synthesizing the carbon nanotubes 41 on a set of micro electrodes.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is to be understood that the techniques which can be used by those skilled in the art to which the present invention belongs are included in the technical scope of the present invention.

10: substrate 10a: lower silicon layer
11, 12, 31: silicon dioxide layer 20: insulating film
20a: investment oxide layer 30: micro electrode
30a: top silicon layer 40: CNT binder
41: carbon nanotube 50: resistance measuring instrument
51: electrical conductor C: metal catalyst
S1: electrode forming step S1-1a: insulating layer forming step
S1-1b: insulation layer additional formation step S1-2: PR patterning step
S1-3: mask patterning step S1-4: substrate etching step
S1-4a: Device layer etching step S1-4b: Substrate layer etching step
S1-5: insulation layer removal step S2: detection compatibility step
S2-1: catalyst deposition step S2-2: CNT synthesis step
S3: measuring instrument connecting step S3-1: connecting electrode
S3-2: Device connection step W: SOI substrate

Claims (13)

In the manufacturing method of the gas sensor having a carbon nanotube (CNT, 41) nanostructure as a sensing unit,
An electrode forming step (S1) of forming the microelectrode 30 on the substrate 10; And
Synthesis of carbon nanotubes (41) on the surface of the micro electrode 30 by chemical vapor deposition (CVD, Chemical Vapor Deposition), a pair of the micro electrode by the longitudinal growth of the carbon nanotubes (41) 30) a sensing unit synthesizing step (S2) for mutual coupling between the carbon nanotubes 41 formed on each other;
Including;
The electrode forming step (S1),
An insulating layer forming step (S1-1a) of forming silicon dioxide layers (SiO ₂ ) 11 and 31 on both sides of a silicon on insulator (WI) substrate (W) by a thermal oxidation process;
A PR patterning step (S1-2) of patterning a photoresist (PR) on both sides of the SOI substrate (W) by a photolithography process;
A mask patterning step (S1-3) of transferring the pattern to the silicon dioxide layers (11, 31) by using a reactive ion etching (RIE) process using the PR as a mask;
Upper and lower silicon layers 30a and 10a of the SOI substrate W using a deep reactive ion etching (DRIE) process using the patterned silicon dioxide layers 11 and 31 as masks. Etching the substrate to form the micro electrode 30 (S1-4); And
The buried oxide layer 20a between the upper and lower silicon layers 30a and 10a and the silicon dioxide layers 11 and 31 on both sides of the SOI substrate W are removed by wet etching. Removing the insulating layer (S1-5);
Gas sensor manufacturing method using the air-floating carbon nanotubes, characterized in that configured to include a.
delete delete The method of claim 1,
After the insulating layer forming step (S1-1a), Plasma Enhanced Chemical Vapor Deposition (PECVD) on the lower thicker silicon layer 10a of the upper and lower silicon layers 30a and 10a of the SOI substrate W. Insulating layer further forming step (S1-1b) for further forming the silicon dioxide layer 12 by the process;
Gas sensor manufacturing method using a floating type carbon nanotubes further comprising a.
The method of claim 1,
The substrate etching step (S1-4),
An element layer etching step (S1-4a) of etching the upper silicon layer (30a) of the SOI substrate (W) to form a pair of the micro electrodes (30); And
A substrate layer etching step (S1-4b) for etching the lower silicon layer (10a) of the SOI substrate (W) such that the pair of micro electrodes (30) form a cantilever shape in which free ends are opposed to each other;
Gas sensor manufacturing method using a floating-type carbon nanotubes comprising a.
The method of claim 1,
The detection unit synthesis step (S2),
A catalyst deposition step (S2-1) of depositing a metal catalyst (C) on the surface of the opposite end of the micro electrode (30); And
The micro electrode 30 having the metal catalyst C deposited therein is inserted into a furnace chamber, and ammonia (NH ₃ ) and acetylene (C ₂ H ₂ ) gas precursors are injected at a high temperature, and chemical A CNT synthesis step (S2-2) of synthesizing the carbon nanotubes (41) on the portion where the metal catalyst (C) is deposited by a deposition method;
Gas sensor manufacturing method using a floating-type carbon nanotubes comprising a.
The method according to claim 6,
The catalyst deposition step (S2-1),
An airborne type carbon nanotube, which uses a shadow mask having a fine hole formed only at a position corresponding to the opposite end of the micro electrode 30, is formed by electron beam evaporation. Gas sensor manufacturing method using.
The method according to claim 6,
The insulating layer removing step (S1-5),
In order to prevent the metal catalyst C from being deposited to be connected to the upper and lower silicon layers 10a of the SOI substrate W in the catalyst deposition step S2-1, the buried oxide layer 20a Method for manufacturing a gas sensor using an airborne carbon nanotube, characterized in that the over etching ().
The method of claim 1,
After the sensing unit synthesis step (S2), the measuring device connecting step (S3) for electrically connecting the resistance meter (50) for measuring the resistance change of the carbon nanotubes (41) with the pair of micro electrodes (30);
Gas sensor manufacturing method using a floating type carbon nanotubes further comprising a.
10. The method of claim 9,
An electrode connection step (S3-1) of electrically connecting one side of the first and second electrical conductors 51 to each of the pair of micro electrodes 30; And
A device connection step (S3-2) for electrically connecting the other side portions of the first and second electrical conductors 51 to the resistance measuring instrument 50;
Gas sensor manufacturing method using a floating-type carbon nanotubes comprising a.
delete delete delete

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