KR20090099361A - Gas sensor included carbon nano-tube wire and method of manufacturing the same - Google Patents

Abstract

A carbon nano tube gas sensor and a manufacturing method thereof are provided to realize mass production with high sensitivity without depending on an electric characteristic of a carbon nano tube. A carbon nano tube gas sensor includes a lower electrode(120), a catalyst layer(125), an insulating layer pattern(130), an upper electrode(140), a carbon nano tube(150) and a power supply unit(160). The catalyst layer is formed on a lower electrode. The insulating layer pattern has an opening which passes to expose a surface of the catalyst layer. The upper electrode is formed on the insulating layer pattern. The opening passes through the upper electrode. The carbon nano tube grows in the catalyst layer exposed to the opening. The carbon nano tube comprises a gas absorption site. The power supply unit is connected to the lower electrode and the upper electrode. A detector(170) is installed between the lower electrode and the power supply unit. The detector detects a vibration number change of a carbon nano tube to determine whether to absorb gas.

Description

Gas Sensor Included Carbon Nano-Tube Wire And Method Of Manufacturing The Same}

The present invention relates to a gas sensor comprising a carbon nanotube and a manufacturing method thereof, and more particularly to a gas sensor comprising a carbon nanotube reacting with a gas or physically and chemically.

The gas sensor is an element that detects the type and amount of gas as an electrical signal by the interaction between the gas and the sensitive material, and various types of sensors such as conductivity, piezoelectric, and MOSFET type have been developed so far. However, due to limitations and structural problems of most sensitive materials, there are many limitations in terms of high performance, integration, miniaturization, and batch production. For example, a conductive sensor using a metal oxide operates only at a high temperature, and a piezoelectric sensor using a vibrator can hardly be miniaturized and integrated.

Accordingly, a sensor using carbon nanotubes, which has recently been spotlighted as a new material, has been developed. The carbon nanotubes have a diameter of several nanometers to several tens of nanometers and a length of several tens of micrometers to several hundred micrometers, and have large anisotropy of the structure, and have the characteristics of a conductor or a semiconductor according to the wound form. It has a unique, one-dimensional structure that is different and exhibits unique quantum effects. In addition, the carbon nanotubes are mechanically strong (about 100 times as much as steel), have excellent chemical stability, high thermal conductivity, and hollow characteristics, and thus are widely applied as new functional materials that are expected to have various applications in microscopic and macroscopic aspects. It is becoming.

Several gas sensors using carbon nanotubes have already been proposed, and a representative method is a method of measuring a change in the amount of current flowing through a carbon nanotube used as a channel using a CNT-FET. To make gas sensor by this method, it is necessary to use semiconducting carbon nanotubes. Not only is it difficult to manufacture semiconducting carbon nanotubes, but also a method of making an array using semiconducting carbon nanotubes has not been developed yet. It is not true. A gas sensor using the electrical properties of multi-walled carbon nanotubes has also been proposed, and shows a ppm level sensitivity. However, since carbon nanotubes are configured in a mesh form, there is a limit in increasing sensitivity due to a large amount of electrical loss.

An object of the present invention for solving the above problems is to provide a method of manufacturing a carbon nanotube gas sensor that is excellent in sensitivity and capable of mass production, without depending on the electrical properties of the carbon nanotubes.

In addition, the present invention provides a carbon nanotube gas sensor having excellent sensitivity without being influenced by the electrical properties of the carbon nanotubes.

A semiconductor device including a carbon nanotube wiring according to an embodiment of the present invention for achieving the above object includes a lower electrode, a catalyst layer, an insulating film pattern, an upper electrode, carbon nanotubes, and a power supply. The lower electrode is formed on a substrate, and the catalyst layer is formed on the lower electrode. The insulating film pattern has an opening that exposes the surface of the catalyst layer. The carbon nanotubes are grown from the catalyst layer in the opening and have a gas adsorption site on the surface. The upper electrode is formed on the insulating layer pattern, and a power supply unit is connected to the lower electrode and the upper electrode to supply power, and at least one is provided.

The carbon nanotubes applied to the gas sensor of the present embodiment further include reactors that react chemically or physically with a specific gas on a surface thereof, and are vertically aligned in a state spaced apart from each other on the catalyst layer and higher than the upper surface position of the upper electrode. Has a length. The gas sensor may further include a detector configured to detect / detect a change in electrical conductivity or switching voltage of the carbon nanotube.

According to the method of manufacturing a carbon nanotube gas sensor according to an embodiment of the present invention for achieving the above-mentioned other object, first to form a lower electrode on the substrate and then to form a catalyst layer on the lower electrode. Subsequently, an insulating film pattern having an opening exposing the surface of the catalyst layer and an upper electrode existing on the insulating film pattern are formed. The carbon nanotubes are vertically oriented from the catalyst layer exposed to the opening, grow from the catalyst layer in the virtual group opening, and have gas adsorption sites. Subsequently, at least one power supply unit is electrically connected to the lower electrode and the upper electrode. As a result, a carbon nanotube gas sensor having excellent detection sensitivity with respect to the gas is formed.

As described above, the gas sensor including a carbon nanotube having a structure can operate at room temperature despite having a simple structure and has a very good gas detection sensitivity. Unlike the conventional carbon nanotube gas sensor, the gas sensor operates smoothly even if there is a defect, and can detect various kinds of gases according to the type of the functional group of the carbon nanotube.

In addition, the gas sensor including the carbon nanotubes can be mass-produced by forming the lower electrode and the upper electrode by applying a conventional semiconductor manufacturing method and then aligning the carbon nanotubes perpendicularly to the substrate.

Hereinafter, a carbon nanotube gas sensor according to preferred 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 following embodiments, and those skilled in the art may implement the present invention in various other forms without departing from the technical spirit of the present invention. In the accompanying drawings, the dimensions of the substrates, layers (films), openings, patterns or structures are shown in greater detail than actual for clarity of the invention. In the present invention, when each layer (film), opening, pattern or structures is referred to as being formed "on", "upper" or "lower" of a substrate, each layer (film), opening or patterns Means that each layer (film), opening, pattern or structure is formed directly over or below the substrate, each layer (film), region, pad or patterns, or is a different layer (film), another opening, another pattern or Other structures may additionally be formed on the substrate.

Gas sensor of Example 1

1 is a view schematically showing a carbon nanotube gas sensor according to an embodiment of the present invention.

Referring to FIG. 1, the carbon nanotube gas sensor of the present embodiment includes a lower electrode 120, an insulating layer pattern 130, an upper electrode 140, a carbon nanotube 150, and a power supply unit formed on the substrate 110. Has a configuration that includes 160 and a detector 170.

The substrate 110 includes a silicon substrate, a silicon germanium substrate, an epitaxial substrate, and the like. The lower electrode 120 is electrically connected to the carbon nanotubes by a metal wire provided on the substrate. That is, the lower electrode 120 is a metal wiring including a metal having excellent conductivity such as tantalum, copper, tungsten, titanium, aluminum, or nitride thereof.

The catalyst layer 125 is applied to allow the carbon nanotubes to be vertically grown or vertically oriented quickly and easily from the surface of the lower electrode. The catalyst layer 125 includes a catalyst metal film or a porous active layer. As an example, the catalyst metal film is a thin film formed of tungsten, nickel, iron, cobalt, palladium, platinum, or gold and a transition metal, and has a thickness of several nm to several tens of nm. The porous active layer is formed by performing an ion etching process on the surface of the lower electrode to form fine grooves on the surface of the lower electrode. The distance of the carbon nanotubes to be formed may be adjusted according to the spacing of the grooves.

The insulating layer pattern 130 is a silicon oxide formed on the catalyst layer 125 and passes through an opening (not shown) exposing a portion of the surface of the catalyst layer. The opening defines a formation region of carbon nanotubes grown / orientated from the catalyst layer 125 and has a negative slope that decreases in width toward the bottom. Examples of the silicon oxides include boro-phosphor silicate glass (BPSG), phosphor silicate glass (PSG), undoped silicate glass (USG), spin on glass (SOG), plasma enhanced-tetra ethylorthosilicate (PE-TEOS), and the like. .

The upper electrode 140 is formed on the insulating layer pattern 130 and is a metal wiring including a metal such as tantalum, copper, tungsten, titanium, aluminum, or a nitride thereof. The upper electrode 140 communicates with the opening and is electrically connected to the power supply unit 160.

The carbon nanotubes 150 are formed in the opening of the insulating layer pattern 130 and are electrically connected to the lower electrode 120. The carbon nanotubes 150 are formed by vertically growing / orienting nanotubes from the surface of the catalyst layer 125 exposed to the opening. The carbon nanotubes 150 have a length greater than the height of the upper surface of the upper electrode 140 and have a gas adsorption site for adsorbing gas. In addition, since the carbon nanotubes 150 have a negative profile that narrows toward the bottom of the opening penetrating the upper electrode 140 and the insulating layer pattern 130, the carbon nanotubes 150 are normally electrically connected to the upper electrode 140. Don't have The carbon nanotubes 150 of the present embodiment may have a change in vibration due to a change in mass when gas is adsorbed. As one example, the carbon nanotubes may further include a functional reactor (R) having a chemical or physical property to react with a specific reaction gas on the surface of the carbon nanotubes as shown in FIG. Examples of the functional reactor may include an amine group, a carboxyl group and a thiol group, and may be bonded to the carbon nanotubes through a chemical method.

The power supply unit 160 supplies power to the lower electrode 120 and / or the upper electrode 140 to vibrate the carbon nanotubes. Preferably, the power supply is an AV power supply. In addition, the detector 170 is provided between the lower electrode and the power supply to detect the change in the frequency of the carbon nanotubes to determine whether the gas is adsorbed. It is preferable that the detector of this embodiment is an impedance analyzer.

3 to 5 are diagrams illustrating a method of manufacturing a semiconductor device including the carbon nanotube wiring of FIG. 1.

Referring to FIG. 3, the lower electrode 120 is formed on the substrate 110. Specifically, a lower metal film is formed on the substrate 110. As an example, the lower metal layer is formed by depositing a metal such as tantalum, copper, tungsten, titanium, aluminum, or the like. Thereafter, a catalyst layer is formed on the surface of the lower metal film. The catalyst layer may include a catalyst metal film (not shown) or a porous active layer (not shown), and may have a number of collection nanometers from about several nanometers so that carbon nanotubes may be easily and quickly grown from the surface of the lower electrode 120. It is formed in thickness.

Subsequently, the catalyst layer and the lower metal layer are patterned by performing a dry etching process using a separate etching mask. As a result, the lower electrode 120 and the catalyst layer 125 are formed on the substrate 110.

Referring to FIG. 4, an insulating film pattern 130 and an upper electrode 140 are formed on the lower electrode 120 on which the catalyst layer is formed.

Specifically, the silicon oxide is deposited to form an insulating layer covering the lower electrode 120 on which the catalyst layer 125 is formed. Thereafter, an upper electrode forming metal film is formed on the insulating film. Subsequently, after forming an etching mask defining a formation region of the carbon nanotubes on the metal film, the metal film and the insulating film exposed to the etching mask are anisotropically etched in situ. As a result, openings are formed through the insulating film and the metal film to expose the surface of the catalyst layer 125 of the lower electrode 120. Due to the formation of the openings, the metal film and the insulating film are formed in-situ with the upper electrode and the insulating film pattern, respectively. The opening has a negative profile that becomes narrower downwards due to the etching characteristics of the anisotropic etching process. As another example, the insulating layer pattern and the metal layer pattern may be formed using separate etching masks.

Referring to FIG. 5, carbon nanotubes 150 are formed in the openings. The carbon nanotubes 150 may be formed by performing a chemical vapor deposition process in which a carbon gas is provided and a pressure condition of about 10 to 300 torr and a temperature of about 400 to 700 ° C. Specifically, when the carbon nanotubes 150 perform a chemical vapor deposition process using carbonization gas, the carbonization gas is thermally decomposed into a carbon state and introduced into the opening, and the introduced carbon is adsorbed by the catalyst layer 125. Carbon nanotubes are grown continuously. As a result, carbon nanotubes 150 electrically connected to the lower electrode 120 are formed in the opening. In this case, the carbon nanotubes 150 are each formed to be spaced apart at a predetermined interval, the length of the carbon nanotubes 150 has a length greater than the height of the upper surface of the upper electrode 140. Subsequently, although not shown in the drawings, a functional reactor (not shown) that reacts chemically or physically with a specific gas may be further formed on the surfaces of the carbon nanotubes.

Thereafter, the power supply unit 160 and the detection unit 170 are electrically connected to the lower electrode 120 and / or the upper electrode 140. Accordingly, the carbon nanotube gas sensor having the structure shown in FIG. 1 may be manufactured.

Gas sensor of Example 2

6 is a view schematically showing a carbon nanotube gas sensor according to another embodiment of the present invention.

Referring to FIG. 6, the carbon nanotube gas sensor of the present embodiment includes a lower electrode 220, an insulating layer pattern 230, an upper electrode 240, a carbon nanotube 250, and a first power source formed on the substrate 210. It has a configuration including a providing unit 262, a second power supply unit 264 and a detector 270. Here, detailed descriptions of the lower electrode 220, the insulating layer pattern 230, the upper electrode 240, and the carbon nanotubes 250 are omitted in the detailed description of FIG. 1.

In particular, the first power supply 262 and the second power supply 264 provide different voltages to the electrodes. For example, when the first power supply 262 applies a positive voltage to the lower electrode 220, the second power supply 264 applies a negative voltage to the upper electrode 240. The carbon nanotubes 250 are switched on. That is, the carbon nanotubes, which are conductors, come into contact with the upper electrode by electrical attraction, and thus are switched on. When the gas is adsorbed on the carbon nanotubes, the mass and electrical properties of the carbon nanotubes change, so that the switching voltage is changed to determine whether the gas is adsorbed. By using the phenomenon that the electrical conductivity of the carbon nanotubes are changed, it is possible to determine whether the gas is adsorbed.

The detector 270 is an IV analyzer provided between the first power supply 262 and the second power supply 264 to detect a change in electrical conductivity of carbon nanotubes, thereby detecting a change in the electrical conductivity frequency. Determine if the adsorption of

The gas sensor including the carbon nanotubes of the present invention having the structure described above is capable of operating at room temperature despite having a simple structure and has a very good gas detection sensitivity. In addition, unlike the conventional carbon nanotube gas sensor, the gas sensor operates smoothly even if there is a defect, and can detect various kinds of gases according to the type of functional group of the carbon nanotube.

In addition, the gas sensor including the carbon nanotubes can be mass-produced by forming the lower electrode and the upper electrode by applying a conventional semiconductor manufacturing method and then aligning the carbon nanotubes perpendicularly to the substrate.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified without departing from the spirit and scope of the invention described in the claims below. And can be changed.

1 is a view schematically showing a carbon nanotube gas sensor according to an embodiment of the present invention.

2 is a view schematically showing a carbon nanotube having a functional group in the carbon nanotube gas sensor of the present invention.

3 to 5 are diagrams illustrating a method of manufacturing a semiconductor device including the carbon nanotube wiring of FIG. 1.

6 is a view schematically showing a carbon nanotube gas sensor according to another embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

120: lower electrode 130: insulating film pattern

140: upper electrode 150: carbon nanotubes

160: power supply unit 170: detection unit

Claims (7)

Lower electrode; A catalyst layer formed on the lower electrode; An insulating film pattern through which openings exposing the surface of the catalyst layer pass; An upper electrode formed on the insulating layer pattern and through which the opening penetrates; Carbon nanotubes grown in the catalyst layer exposed to the opening and having gas adsorption sites; And Carbon nanotube gas sensor comprising at least one power supply connected to the lower electrode and the upper electrode. The carbon nanotube gas sensor of claim 1, wherein the carbon nanotubes further include reactors chemically or physically reacted with a specific gas on a surface thereof. The carbon nanotube gas sensor of claim 1, wherein the carbon nanotubes are vertically aligned with each other spaced apart from each other on the catalyst layer, and have a length greater than a height of an upper surface of the upper electrode. The carbon nanotube gas sensor of claim 1, further comprising a detector configured to detect / detect a change in electrical conductivity or switching voltage of the carbon nanotube. Forming a lower electrode; Forming a catalyst layer on the lower electrode; Forming an insulating layer pattern through the opening exposing the surface of the catalyst layer on the catalyst layer; Forming an upper electrode through the opening on the insulating layer pattern; Orienting carbon from the catalyst layer exposed by the opening to form nanocarbon tubes; And A method of manufacturing a carbon nanotube gas sensor comprising electrically connecting at least one power supply to the lower electrode and the upper electrode. The method of claim 5, wherein the carbon nanotubes further include forming reactors on the surface of the carbon nanotubes that react chemically or physically with a specific gas. 7. The method of claim 5, wherein the opening penetrates the upper electrode and the insulating layer pattern, and the upper electrode and the insulating layer pattern are formed in situ due to the formation of the opening.

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