JPH1062239A - Infrared detection element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect with high sensitivity infrared rays of a characteristic wavelength emitted from a human body, by using an alumina-quality film as an infrared absorption film. SOLUTION: An alumina-quality film 2 is formed on a substrate 1 and a thermistor film 3 is further formed on the film 2. Confronting electrodes 4, 5 are placed on the thermistor film 3. Alternatively, confronting electrodes 4, 5 are formed on the substrate 1, the thermistor film 3 is formed to cover the confronting electrodes 4, 5 and a remaining exposed face of the substrate 1, and the alumina-quality film 2 is formed on the film 3. In a different arrangement, the lower electrode 4, thermistor 3 and upper electrode 5 are layered on the substrate 1 and the alumina-quality film 2 is formed to cover the upper electrode 5 and thermistor film 3 in the vicinity of the periphery of the electrode 5. In any case, infrared rays entering from above are absorbed by the alumina- quality film 2, whereby a temperature of the film 2 is raised. A temperature of thermistor film 3 is also raised because of the propagation of the heat of the film 2. As a result, a resistance of the thermistor film between the electrodes 4 and 5 is changed. Since the alumina-quality film 2 has a high absorbance of infrared rays of 7-14μm wavelength, a human body can be detected surely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an infrared detecting element using a thermistor whose resistance changes with a change in temperature.

[0002]

2. Description of the Related Art As an infrared detecting element, there is a type called a thermal infrared detecting element comprising an infrared absorbing film and a thermistor film formed on the infrared absorbing film. When infrared rays enter this infrared detecting element, the infrared absorbing film absorbs the infrared rays and the temperature rises, and the thermistor film also rises in temperature. Since the resistance of the thermistor changes with the temperature rise, infrared rays can be detected by detecting the change in resistance.

Conventionally, a silicon oxide film has been used as the infrared absorbing film as disclosed in Japanese Patent Application Laid-Open No. 7-120308.

[0004]

The infrared absorption pattern of silicon oxide has wavelength selectivity as shown in FIG. 2 (b), and on average, 7-14 μm emitted from the human body.
The absorptivity of infrared light of wavelength m is low. (That is, on average, the transmittance is high in the range of 7-14 μm.)
A thermal infrared detecting element using a silicon oxide film has low characteristics as an infrared detecting element for detecting a human body.

An object of the present invention is to provide an infrared detecting element which has an infrared absorbing film for sufficiently absorbing infrared rays emitted from a human body and is suitable for detecting a human body.

[0006]

The infrared detecting element of the present invention has an infrared absorbing film and a thermistor film formed on the infrared absorbing film, and detects infrared light based on the resistance of the thermistor film. In the infrared detecting element, the infrared absorbing film is an alumina film.

This alumina-based infrared absorbing film is shown in FIG.
As shown in (a), the absorptance of infrared rays in the 7 to 14 μm band is extremely high. (That is, the transmittance is low.) Therefore, by using this alumina-based infrared absorbing film, an infrared detecting element suitable for detecting a human body is provided.

[0008]

1A to 1C are cross-sectional views of an infrared detecting element according to an embodiment of the present invention.
An alumina-based infrared absorbing film (hereinafter sometimes referred to as an alumina-based film) 2, a thermistor film 3, an electrode 4,
5 is provided.

In FIG. 1A, an alumina film 2 is formed on a substrate 1, a thermistor film 3 is formed thereon, and opposing electrodes 4 and 5 are formed on the thermistor film 3 so as to form a pair. Has formed.

In FIG. 1B, counter electrodes 4 and 5 are formed on the substrate 1 so as to form a pair, and a thermistor film 3 is formed so as to cover these electrodes 4 and 5 and the remaining exposed surface of the substrate 1. Then, an alumina film 2 is formed thereon.

In FIG. 1C, a lower electrode 4 is formed on a substrate 1, a thermistor film 3 is formed thereon, and an upper electrode 5 is formed on the thermistor film 3. The alumina film 2 is formed so as to cover the thermistor film 3 near the periphery thereof.

In any of the infrared detecting elements, infrared light is incident from above the figure. The infrared rays are absorbed by the alumina film 2, and the temperature of the alumina film 2 rises. The temperature of the thermistor film 3 rises due to the propagation of the heat of raising the temperature of the alumina film 2, and the resistance of the thermistor film between the electrodes 4 and 5 changes. Since the alumina film has a high absorptivity of infrared rays having a wavelength of 7 to 14 μm, it is possible to reliably detect a human body.

The substrate 1 is made of silicon, quartz,
Silica glass, polyimide and the like are suitable, and among them, a silicon substrate having a thickness of about 30 to 500 μm, particularly about 30 to 200 μm is preferable.

FIG. 1 shows a conductive substrate such as silicon on a conductive substrate.
When a thermistor film is formed as in (b), an electric insulating layer is formed at the interface between the substrate 1 and the thermistor film 3. Such an electrically insulating layer has a thickness of 1000 to 3
Silicon oxide, silicon nitride, or the like with a thickness of about 0000 ° can be used.

On the substrate 1, a heat insulating layer for reducing the propagation of heat from the alumina film 2 or the thermistor film 3 may be provided. This heat insulating layer has a thickness of 1
Silicon oxide, silicon nitride, or the like having a thickness of about 000 to 30,000 is preferred. These electric insulating layers and heat insulating layers are preferably formed on the substrate 1.

The alumina film 2 preferably has a content of aluminum oxide of 80% by weight or more, particularly preferably a content of aluminum oxide of 99% by weight or more. Note that as components other than aluminum oxide, silicon oxide, boric acid, lead oxide, and the like may be included.

The thickness of the alumina film 2 is preferably 0.1 to 4 μm, particularly preferably about 0.1 to 3 μm.

The thermistor film 3 has a thickness of 0.1 to 1
An amorphous silicon film having a thickness of about 0 μm, especially about 0.5 to 2 μm, a Mn—Ni, Mn—Co-based oxide, or the like can be used.

The electrodes 4 and 5 have a thickness of 0.1 to 1 μm.
In particular, about 0.1 to 0.5 μm of chromium, nickel,
Aluminum, gold, silver, or the like can be used.

The method of forming these films 2 and 3 and the electrodes 4 and 5 is arbitrary, and various film forming methods such as CVD, sputtering and sol-gel method can be adopted.

The alumina film 2 and the thermistor film 3
Can be omitted as long as the substrate 1 can be held as it is. For example, the configuration may be such that the substrate 1 is omitted in FIG. 1C and the lower electrode 4 supports the thermistor film 3. Further, if the resistance of the thermistor film 3 can be detected, the electrodes 4 and 5 may be omitted.

The infrared detecting element is surrounded by a casing having an infrared transmitting window, for example, and it is preferable that a low heat conductive gas such as xenon is sealed in the casing. good.

[0023]

As described above, the infrared detecting element of the present invention uses an alumina film as the infrared absorbing film, and can detect infrared rays having a wavelength of 7 to 14 μm with high sensitivity.

[Brief description of the drawings]

FIG. 1A, FIG. 1B, and FIG. 1C are cross-sectional views of an infrared detecting element according to an embodiment.

FIG. 2 is an infrared transmission spectrum diagram of aluminum oxide and silicon oxide, in which the vertical axis indicates transmittance (%).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Alumina film 3 Thermistor film 4, 5 Electrode

Claims (5)

[Claims] 1. An infrared detecting element having an infrared absorbing film and a thermistor film formed on the infrared absorbing film, wherein the infrared detecting device detects infrared light based on the resistance of the thermistor film. An infrared detecting element characterized by being a film of. 2. The infrared detecting element according to claim 1, wherein said alumina film contains aluminum oxide in an amount of 80% by weight or more. 3. The infrared detecting element according to claim 1, wherein said alumina film contains aluminum oxide in an amount of 99% by weight or more. 4. The infrared detecting element according to claim 1, wherein the infrared absorbing film and the thermistor film are provided on a substrate. 5. The infrared detecting element according to claim 1, further comprising an electrode for measuring the resistance of the thermistor film.