WO2009157123A1

WO2009157123A1 - Sensor device and method for manufacturing the same

Info

Publication number: WO2009157123A1
Application number: PCT/JP2009/001935
Authority: WO
Inventors: 中村大佐; 山田一
Original assignee: 株式会社村田製作所
Priority date: 2008-06-26
Filing date: 2009-04-28
Publication date: 2009-12-30

Abstract

Provided are a sensor device and a method for manufacturing the same for forming convex/concave portions on the surface of a detection layer without complicating the manufacturing process. The sensor device (10) has at least one reaction detection element (11a). The reaction detection element (11a) includes: a detection layer (18) for detecting a specific object; and a temperature detection unit on which the detection layer (18) is arranged and which detects a temperature change of the detection layer (18) (a thermistor substrate (12a) and a detection electrode (14)). The detection layer (18) has cracks or voids formed therein and convex/concave portions on the surface thereof. When forming the detection layer (18) by deposition, an atmospheric gas is introduced so as to form cracks and voids inside the detection layer (18).

Description

Sensor device and manufacturing method thereof

The present invention relates to a sensor device and a manufacturing method thereof, and more particularly to a sensor device that detects heat due to a reaction between a gas and a catalyst and a manufacturing method thereof.

In a sensor having a detection layer for detecting a specific object, unevenness is formed on the surface of a thin film used as the detection layer, and the sensitivity tends to increase as the surface area increases. For this reason, various methods for forming irregularities on the surface of the thin film of the detection layer have been proposed.

For example, in Patent Document 1, (1) a first method in which an intermediate layer made of ultrafine particles is provided on a substrate and a metal oxide semiconductor film corresponding to the irregularities of the intermediate layer is formed thereon; (2) A second method of forming minute irregularities on the substrate surface itself on which the thin film is formed; and (3) forming minute irregularities on the substrate surface, and further providing an intermediate layer made of ultrafine particles thereon to form irregularities. A third method of forming a corresponding metal oxide semiconductor film is disclosed.

Patent Document 2 discloses that the surface of a sensitive body is etched with a volatile solvent vapor to form minute irregularities.

Patent Document 3 discloses that a gas excited in a vacuum atmosphere collides with the substrate surface to roughen the surface and form a thin film on the rough substrate surface.

JP-A-5-52790 JP 2001-165888 A JP 2001-296267 A

However, in the conventional method, since it is necessary to add a special process for forming irregularities on the base of the detection layer or forming irregularities on the surface of the detection layer itself, the manufacturing process becomes complicated.

In view of such circumstances, the present invention intends to provide a sensor device that can form irregularities on the surface of a detection layer without complicating the manufacturing process and a manufacturing method thereof.

In order to solve the above problems, the present invention provides a sensor device configured as follows.

The sensor device has at least one reaction detection element. The reaction detection element includes a detection layer for detecting a specific object, and a temperature detection unit on which the detection layer is disposed and detects a temperature change of the detection layer. The detection layer has at least one of cracks and voids formed therein, and has irregularities formed on the surface thereof. The temperature detector includes (a) a thermistor substrate made of a thinned bulk material, and (b) formed on the thermistor substrate, and detects a change in electrical resistance of the thermistor substrate due to a temperature change of the detection layer. And an electrode.

In the above configuration, cracks and voids formed inside the detection layer are connected to the surface of the detection layer and irregularities are formed on the surface of the detection layer. improves.

According to the above configuration, by appropriately selecting the conditions for forming the detection layer, cracks and voids can be formed inside the detection layer, and irregularities are formed on the surface of the detection layer. Therefore, it is not necessary to add a special process.

Preferably, the specific object is a gas. The detection layer is a reaction catalyst layer including a catalyst that increases a reaction rate of a chemical reaction accompanied by heat generation with respect to the gas.

In this case, the sensor device is a gas sensor. The sensitivity of the gas sensor is improved by increasing the surface area of the detection layer.

The present invention also provides a method of manufacturing a sensor device configured as follows.

The sensor device manufacturing method includes at least one reaction detection element including a detection layer for detecting a specific target object, and a temperature detection unit on which the detection layer is disposed and detects a temperature change of the detection layer. The manufacturing method of the sensor apparatus which has this. It includes a vapor deposition step of forming the detection layer by vapor deposition, and vapor deposition is performed by introducing an atmospheric gas in the vapor deposition step.

In the above method, after forming all or part of the temperature detection unit and forming the detection layer in contact with it, after forming the detection layer, forming all or part of the temperature detection unit in contact with the detection layer. Also good.

According to the above method, cracks and voids can be formed inside the detection layer by introducing atmospheric gas in the vapor deposition process for forming the detection layer, and irregularities are formed on the surface of the detection layer. There is no need to add a special process in order to achieve this.

Preferably, the atmospheric gas is an inert gas.

When an inert gas is introduced and evaporated, the introduced gas can be prevented from adversely affecting the detection layer.

According to the present invention, it is possible to form irregularities on the surface of the detection layer without complicating the manufacturing process of the sensor device.

It is a cross section of a gas sensor. (Example 1) It is a cross section which shows the manufacturing process of a gas sensor. (Example 1) It is a cross section which shows the manufacturing process of a gas sensor. (Example 1) It is a photograph of the SEM image of the surface of the catalyst layer for reaction. (Comparative example, Example 1) It is a photograph of the AFM image of the surface of the catalyst layer for reaction. (Comparative example, Example 1) It is a photograph of the SIM image of the cross section of the catalyst layer for reaction. (Comparative example, Example 1)

Hereinafter, embodiments of the present invention will be described with reference to FIGS.

<Example> A gas sensor 10 according to an example of the present invention will be described with reference to a cross-sectional view of FIG.

As shown in FIG. 1, in the gas sensor 10, two

thermistor substrates

12 a and 12 b are joined to a support substrate 22 via a support unit 20, and a gap 24 is formed between the support substrate 22 and the

thermistor substrates

12 a and 12 b. It is supposed to be formed.

The support portion 20 can be formed in an arbitrary shape such as a frame shape, but is preferably formed in a column shape so that heat transfer from the

thermistor substrates

12a and 12b to the support substrate 22 is minimized. For example, columnar support portions 20 are formed of resin, solder, or the like at the four corners of the rectangular

thermistor substrates

12a and 12b.

The

thermistor substrates

12a and 12b are thinned bulk materials such as a Mn ₃ O ₄ -based NTC thermistor material to which Ni, Co, Fe, Al, Cu or the like is added, or a BaTiO ₃ -based PTC thermistor material. The

thermistor substrates

12a and 12b having a thin bulk material do not vary in composition as compared to the thermistors formed by the thin film process. As a result, when the

thermistor substrates

12a and 12b in which the bulk material is thinned are used, the sensor characteristics are stabilized as compared with the case where the thermistor formed by the thin film process is used.

Also, since the material of the composition that is difficult to produce with a thin film can be used for the bulk material of the

thermistor substrates

12a and 12b, sensor characteristics that are difficult to realize with a bulk ceramic or a thin film can be extracted.

Furthermore, if the

thermistor substrates

12a and 12b having a thin bulk material are used, the thin film process can be reduced, and the manufacturing cost can be reduced.

On the upper surface 12x of the

thermistor substrates

12a and 12b, a detection electrode 14, an extraction electrode 13, and a wiring pattern (not shown) for connecting the

electrodes

13 and 14 are formed using a conductive material. The detection electrode 14 is used to measure the electric resistance of the thermistor substrate 12 between the detection electrodes 14. The detection electrode 14 can be formed in an arbitrary shape.

For example, the detection electrode 14 is formed so that a pair of comb-shaped electrodes enter a gap between the other comb-teeth portions. In the case of such a comb-teeth electrode, by changing the length of the comb-teeth portion and the size of the gap (gap) between the comb-teeth portion of one electrode and the comb-teeth portion of the other electrode, Since the resistance value between the electrodes can be adjusted, matching with the peripheral circuit system can be easily achieved.

An insulating film 16 is formed on the top surfaces 12x of the

thermistor substrates

12a and 12b so as to cover the detection electrodes. Although a configuration without the insulating film 16 is possible, when the insulating film 16 is provided, the surface of the detection electrode 14 is protected and the deterioration of the detection electrode 14 is prevented, so that the highly accurate gas sensor 10 with stable characteristics is provided. it can.

On the insulating film 16 on the one thermistor substrate 12a side, a reaction catalyst layer 18 is formed immediately above a portion between the detection electrodes 14 serving as a gas detection portion. The reaction catalyst layer 18 includes a catalyst that increases the reaction rate of a chemical reaction accompanied by heat generation for a specific gas. The catalyst contained in the reaction catalyst layer 18 is selected according to the gas to be detected.

For example, when detecting hydrogen gas, a Pt catalyst is used. In this case, hydrogen molecules dissociate into protons on the Pt catalyst, react with oxygen in the air to generate water, and heat is generated at this time. This heat is transmitted to the thermistor substrate 12a through the reaction catalyst layer 18 and the insulating film 16, and the electrical resistance of the thermistor substrate 12a between the detection electrodes 14 changes. By reading out the change in electrical resistance through the extraction electrode 13, hydrogen gas can be detected. For example, hydrogen gas is detected by a change in the output voltage of the extraction electrode 13.

The temperature detection unit composed of the thermistor substrate 12 a and the detection electrode 14 has a membrane structure on the support substrate 22 via the support unit 20, and an air layer is formed in the gap 24 between the thermistor substrate 12 a and the support substrate 22. Due to the presence, the temperature detection unit is thermally separated from the support substrate 22. Therefore, the ratio of the amount of heat transmitted from the reaction catalyst layer 18 to the temperature detection unit further to the support substrate 22 side is reduced, and the ratio of the amount of heat contributing to the temperature change of the thermistor substrate 12a is increased. . As a result, the gas detection sensitivity is improved, and the gas sensor 10 having good sensor characteristics can be provided.

Similarly, with respect to the other thermistor substrate 12b, the temperature detection unit constituted by the thermistor substrate 12b and the detection electrode 14 forms a membrane structure on the support substrate 22 via the support unit 20, and the thermistor substrate 12b and the support substrate 22 are provided. Therefore, the temperature detection unit is thermally separated from the support substrate 22. However, since the reaction catalyst layer 18 is not formed on the insulating film 16 on the other thermistor substrate 12b side, the electrical resistance of the thermistor substrate 12b changes only due to a temperature change due to the surrounding environment.

That is, the first portion 11a on the one thermistor substrate 12a side includes a reaction detection element including a reaction catalyst layer 18 and a temperature detection unit. The second portion 11b on the other thermistor substrate 12b side does not include the reaction catalyst layer 18 but includes an environmental temperature detection element including only the temperature detection unit.

The gas sensor 10 detects the temperature change due to the surrounding environment by the environmental temperature detection element of the second portion 11b, and thereby compensates the change of the resistance value due to the temperature change due to the surrounding environment for the reaction detection element of the first portion 11a. be able to. Therefore, it is possible to provide a highly accurate gas sensor 10 that is not affected by temperature changes due to the surrounding environment.

If high accuracy is not required, the environment temperature detecting element 11b may be omitted, and the gas sensor may be configured only by the reaction detecting element 11a.

The characteristics of the gas sensor 10 are determined by the catalyst capacity of the reaction catalyst layer 18, the heat capacity of the sensor, and the like. In particular, the sensor sensitivity varies greatly depending on the catalyst capability of the reaction catalyst layer 18. The ability of the catalyst in the reaction catalyst layer 18 varies depending on the surface area and temperature of the catalyst. The larger the surface area, the better the catalyst ability. Therefore, cracks and voids are formed inside the reaction catalyst layer 18 and irregularities are formed on the surface of the reaction catalyst layer 18.

For example, when the reaction catalyst layer 18 is formed by vapor deposition, vapor deposition is performed by introducing an atmospheric gas instead of a vacuum state. When vapor deposition is performed by introducing the atmospheric gas, cracks and voids are formed inside the reaction catalyst layer 18 that has been vapor-deposited under the influence of the atmospheric gas, and the cracks and voids are connected to the surface. Unevenness is formed on the surface. When irregularities are formed on the surface, the surface area of the reaction catalyst layer 18 that reacts with the gas increases, so that the sensitivity of the gas sensor 10 is improved.

Next, a method for manufacturing the gas sensor 10 will be described with reference to FIGS. 2 and 3 are cross-sectional views showing a process flow of the gas sensor 10. A plurality of gas sensors 10 are manufactured in a state of a collective substrate. FIG. 2 and FIG. 3 schematically show a part of the collective substrate.

First, as shown in FIG. 2 (1), a comb-like electrode is formed on the upper surface 12x of a thermistor substrate 12k of a bulk material of Mn ₃ O ₄ system or BaTiO ₃ system using a method such as photolithography, vapor deposition, or sputtering. 14, an extraction electrode 13 and a wiring pattern (not shown) for connecting the

electrodes

13 and 14 are formed. As the comb electrode 14, a material configuration capable of obtaining ohmic contact with the thermistor material, for example, Al / NiCr (/ thermistor) is used. That is, a NiCr film is formed on the thermistor substrate 12k, and an Al film is formed thereon. Next, an insulating film 16 is formed on the comb-teeth electrode 14 with an insulating material such as SiO ₂ or Al ₂ O ₃ . Next, a reaction catalyst layer 18 is formed on the insulating film 16 directly above the gas detection unit using Pt and Pd for a hydrogen sensor and Au for a CO sensor. Thereby, a highly sensitive hydrogen sensor or CO sensor can be realized.

The reaction catalyst layer 18 is formed by introducing an atmospheric gas and performing vapor deposition.

When vapor deposition is performed in a vacuum state, the evaporated molecules and atoms fly in a certain direction and enter from one direction and adhere to form a uniform film. On the other hand, when vapor deposition is performed by introducing atmospheric gas, a film containing voids and cracks is formed inside due to the influence of molecules and atoms of the atmospheric gas. That is, when vapor deposition is performed by introducing atmospheric gas, the evaporated molecules / atoms collide with the molecules / atoms of the atmospheric gas and are scattered, enter from multiple directions, and form a film in a disordered state. A film containing voids and cracks is formed under the influence of the atmospheric gas, such as molecules and atoms of the atmospheric gas entering the inside.

The pressure of the atmospheric gas is preferably about 0.1 to 1.0 Pa, for example. If the pressure of the atmospheric gas is too high, vapor deposition itself cannot be performed. On the other hand, when the pressure of the atmospheric gas is too low, voids and cracks are not formed, which is the same as vapor deposition in a vacuum state.

For example, in the case of forming a Ni film, when vapor deposition is performed by introducing N ₂ O or CO ₂ gas, voids and cracks are formed in the vapor deposition film, but oxidation also occurs, and N ₂ gas is introduced. The film quality is different from the case of vapor deposition. Therefore, the introduced atmospheric gas is preferably an inert gas such as N ₂ or Ar that does not chemically react with the material constituting the deposited film so as not to adversely affect the deposited film.

The film thickness of the reaction catalyst layer 18 may be such that voids and cracks inside the film are connected to the surface. For example, when the reaction catalyst layer 18 having a film thickness of 50 nm, 100 nm, or 200 nm was formed under the same conditions except for the film thickness, the sensor sensitivity was not affected. From this, it is considered that the voids and cracks in the deep part of 50 nm or more are not connected to the surface, and therefore the sensor sensitivity is not affected.

Next, as shown in FIG. 2 (2), after the resin 80 is applied to the entire upper surface 12x of the thermistor substrate 12k and the support substrate 82 is adhered, the lower surface 12y side of the thermistor substrate 12k is shown in FIG. The thinning process is performed until the thermistor substrate 12 having a predetermined thickness is obtained. The thermistor substrate 12k is thinned to 50 μm or less using a method such as polishing, grinding, milling, or RIE (reactive ion etching). Polishing and grinding are suitable for cost reduction. Since the thinning process is performed in a state of being attached to the support substrate 82, the thermistor substrate 12k can be thinned without being destroyed.

Next, as shown in FIG. 3 (4), posts 20 a and 20 b used for bonding and heat separation are formed on the thinned surface 12 y of the thermistor substrate 12 and the support substrate 22. As a material of the

posts

20a and 20b, for example, a Cu—Sn solder material is used.

Next, as shown in FIG. 3 (5), the

posts

20a and 20b are joined to face each other. Thereby, the support substrate 22 and the thermistor substrate 12 are joined via the

posts

20a and 20b. At least a pressure process is used for bonding.

Next, as shown in FIG. 3 (6), the support substrate 82 and the resin 80 are peeled from the thermistor substrate 12.

Next, as shown in FIG. 3 (7), the thermistor substrate 12 and the support substrate 22 are divided along the boundary line of the gas sensor 10 by a method such as dicing using a blade 84 and separated into individual pieces.

According to the manufacturing method described above, cracks and voids can be formed in the reaction catalyst layer 18 by introducing the atmospheric gas in the vapor deposition step for forming the reaction catalyst layer 18 and performing the vapor deposition. It is not necessary to add a special process in order to form irregularities on the surface of the reaction catalyst layer 18.

<Production Example> A Pt film was formed as the reaction catalyst layer 18 by EB (electron beam) deposition. At this time, N ₂ was introduced as an atmospheric gas. As a comparative example, a Pt film was formed by EB vapor deposition in a vacuum state.

The film forming conditions are shown in Table 1 below.

In Table 1, normal vapor deposition is a comparative example, and N ₂ introduction vapor deposition is a production example.

FIG. 4 is a photograph of an SEM image of the surface of the Pt film formed as the reaction catalyst layer 18. From the comparative example of FIG. 4A and the production example of FIG. 4B, it can be seen that when N ₂ is introduced and evaporated as in the production example, irregularities are formed on the surface.

FIG. 5 is a photograph of an AFM image of the surface of the Pt film formed as the reaction catalyst layer 18. Ra (arithmetic mean roughness) of the comparative example of FIG. 5A was 0.64 nm, and Ra of the preparation example of FIG. 6B was 6.4 nm. That is, the surface roughness of the production example was about 10 times that of the comparative example.

FIG. 6 is a photograph of a SIM image of the surface of the Pt film formed as the reaction catalyst layer 18. In the comparative example of FIG. 6 (a), there are no cracks or voids in the film and is uniform, whereas in the example of production in FIG. 6 (b), it is understood that cracks / voids are generated in the film. .

Further, when a specific surface analysis was performed, the surface area of the production example was about three times the surface area of the comparative example.

When the gas sensor 10 having the same configuration except for the reaction catalyst layer 18 of the production example and the comparative example was produced and the detection sensitivity of hydrogen gas was examined, the gas sensor 10 using the reaction catalyst layer 18 of the production example was the same as that of the comparative example. The sensitivity was improved by 30% compared with the gas sensor using the reaction catalyst layer.

<Summary> As described above, if a void or a crack is formed inside the reaction catalyst layer 18 when the reaction catalyst layer 18 is formed by introducing and vaporizing the atmospheric gas, the manufacturing process becomes complicated. In addition, irregularities can be formed on the surface of the reaction catalyst layer, and the sensor sensitivity can be improved.

It should be noted that the present invention is not limited to the above embodiment, and can be implemented with various modifications.

For example, the present invention can be applied to various sensor devices other than the gas sensor.

10 Gas sensor (sensor device)
12a, 12b Thermistor substrate (temperature detector)
14 Detection electrode (temperature detector)
16 Insulating film 18 Catalyst layer for reaction (detection layer)
20 support part 22 support substrate

Claims

A sensor device having at least one reaction detection element including a detection layer for detecting a specific object and a temperature detection unit on which the detection layer is disposed and detects a temperature change of the detection layer. And
The detection layer is
At least one of cracks and voids is formed in the interior, irregularities are formed on the surface,
The temperature detector is
A thermistor substrate made of a thinned bulk material;
A sensor device comprising: an electrode formed on the thermistor substrate for detecting a change in electrical resistance of the thermistor substrate due to a temperature change of the detection layer.
The specific object is a gas;
The sensor device according to claim 1, wherein the detection layer is a reaction catalyst layer including a catalyst that increases a reaction rate of a chemical reaction that generates heat with respect to the gas.
A method for manufacturing a sensor device having at least one reaction detection element comprising: a detection layer for detecting a specific object; and a temperature detection unit on which the detection layer is disposed and detects a temperature change of the detection layer. Because
A method for manufacturing a sensor device, comprising: a vapor deposition step of forming the detection layer by vapor deposition, wherein vapor deposition is performed by introducing an atmospheric gas in the vapor deposition step.
The method for manufacturing a sensor device according to claim 3, wherein the atmospheric gas is an inert gas.