JPH10294165A - Infrared ray source and gas concentration detector using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared ray source having wavelength selectivity such that necessary wavelengths are selectively taken out of emitted infrared rays without use of an expensive infrared filter. SOLUTION: An infrared ray source includes a silicon substrate 1, a filament 2 formed on the silicon substrate 1 by a microbridge, and an electrode 4 for passing current to the filament 2. In this case, when the wavelength of an infrared ray to be radiated is λ, a multilayered reflecting film 6 formed by laminating thin films of different refractive indexes, each with a film thickness that is an integer multiple of λ/4, is provided below the filament 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an infrared light source having a microbridge-shaped filament on a silicon substrate.

[0002]

2. Description of the Related Art FIG. 9 shows a top view and a sectional view taken on line AA of a conventional infrared light source. Reference numeral 1 denotes a silicon substrate, a filament 2 on a substrate surface, and a pedestal 3 on which the filament 2 is placed.
In addition, an electrode 4 for passing a current through the filament 2 and a dug hole 5 are formed. In forming the pedestal 3 and the digging hole 5, the digging hole 5 is digged and formed by selectively etching the pedestal 3 from the front surface or the back surface of the silicon substrate 1 by wet etching. As the filament 2 formed on the pedestal 3, a resistor such as silicon single crystal, polysilicon, or a metal film is used.

In such an infrared light source, two electrodes 4
An electric current is passed between them to cause the filament 2 to generate heat, thereby emitting infrared rays.

[0004]

However, in the infrared light source having the above-described structure, the infrared output is only blackbody radiation, so that the wavelength of the emitted infrared light is widened from 1 μm to more than 10 μm. To control the spread, it was necessary to use an expensive infrared filter.

The present invention has been made in view of the above points, and has as its object to selectively use a wavelength required for emitted infrared rays without using an expensive infrared filter. Another object of the present invention is to provide an infrared light source having wavelength selectivity to be extracted.

[0006]

According to the first aspect of the present invention,
In an infrared light source including a silicon substrate, a filament formed by a microbridge on the silicon substrate, and an electrode for flowing a current through the filament, when the wavelength of infrared light to be emitted is λ, A multilayer reflective film in which thin films having a thickness of an integral multiple of 4 and different in refractive index are stacked is provided below the filament.

According to a second aspect of the present invention, in the infrared light source according to the first aspect, the shape of the multilayer reflection film below the filament is concave with respect to the filament.

According to a third aspect of the present invention, in the infrared light source according to the first aspect, a lens is added to the multilayer reflective film.

According to a fourth aspect of the present invention, a silicon substrate is provided.
In an infrared light source including a filament formed by a microbridge on the silicon substrate and an electrode for flowing a current to the filament, when the wavelength of infrared light to be emitted is λ, the silicon substrate below the filament is Are provided with a plurality of micropores having an integral multiple of λ / 4.

According to a fifth aspect of the present invention, in the infrared light source according to any one of the first to fourth aspects, a reflective film for reflecting infrared light is provided on the filament.

According to a sixth aspect of the present invention, in the infrared light source of the fifth aspect, a thin film having a thickness of an integral multiple of λ / 4 is interposed between the filament and the reflection film. is there.

According to a seventh aspect of the present invention, in the infrared light source according to the fifth or sixth aspect, an interval between the lower portion of the filament and the multilayer reflective film is an integral multiple of λ / 4. .

The invention according to claim 8 is a gas filling section for filling a gas whose concentration is to be detected, a first infrared ray having a wavelength easily absorbed by the sealed gas, and a second infrared ray having a wavelength hardly absorbed by the gas. And a detection unit for detecting the concentration of the sealed gas from the ratio of the output of the first infrared light and the output of the second infrared light that have passed through the sealed gas. In the detector, the infrared light source according to any one of claims 1 to 7 is used as the infrared light source for detection.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an infrared light source according to an embodiment of the present invention.

Reference numeral 1 denotes a silicon substrate, which includes a filament 2 on a substrate surface, a pedestal 3 on which the filament 2 is placed, an electrode 4 for supplying a current to the filament 2, and a digging hole 5
Are formed. In forming the pedestal 3 and the digging hole 5, the digging hole 5 is digged and formed by selectively etching the pedestal 3 from the front surface or the back surface of the silicon substrate 1 by wet etching. The filament 2 formed on the pedestal 3 is made of a resistor such as silicon single crystal, polysilicon and a metal film.

A multilayer reflective film 6 is added below the digging hole 5 formed by etching. The multilayer reflective film 6 in the present embodiment means that the wavelength of infrared light to be radiated is λ.
In this case, at least one high-refractive index material and a low-refractive index material having a thickness of an integral multiple of λ / 4 are alternately laminated. As the film material, SiO ₂ or the like is used as the low refractive index material, and Ge or the like is used as the high refractive index material. Further, a space having a thickness of an integral multiple of λ / 4 may be provided in place of the low refractive index material.

The multilayer reflective film 6 may be provided on the filament 2. Next, the operation of the present embodiment will be described. When a current flows through the electrode 4, the filament 2 is heated, and infrared rays corresponding to the temperature of the filament 2 are emitted. Here, infrared rays are emitted from the filament 2, but the infrared rays incident on the multilayer reflective film 6 are:
The high-refractive-index material and the low-refractive-index material having a thickness of an integral multiple of λ / 4 reflect and interfere with each other, so that an infrared ray having a desired wavelength λ can be selectively emitted from a lower portion of the infrared light source.

According to the present embodiment, infrared rays having a desired wavelength can be radiated by reflecting and interfering infrared rays incident on the multilayer reflection film 6, so that an expensive infrared filter is not used. It is possible to selectively radiate a required wavelength with respect to the emitted infrared light.

FIG. 2 is a sectional view of an infrared light source according to another embodiment of the present invention. In the present embodiment, in the infrared light source shown in FIG. 2, the shape of the multilayer reflective film 6 is processed to be concave with respect to the filament 2.

As a method of processing the multilayer reflective film 6 into a concave shape, the back surface of the silicon substrate 1 is processed in a convex shape by dry etching or the like before depositing the multilayer reflective film 6. Then, a multilayer reflective film 6 is deposited, and the silicon substrate 1
By removing the silicon substrate 1 formed in a convex shape when forming the digging hole 5 from the surface by etching, a multilayer reflective film 6 having a concave shape with respect to the filament 2 is formed.

According to this embodiment, the concave multilayer reflective film 6
It is possible to deflect the infrared light transmitted through the substrate 2 into parallel light, so that the infrared light emitted from the filament 2 to the back side of the silicon substrate 1 can be emitted from the silicon substrate 1 as substantially parallel light.

FIG. 3 is a sectional view of an infrared light source according to another embodiment of the present invention. In the present embodiment, a lens 7 is added to the multilayer reflection film 6 of the infrared light source shown in FIG. By using a Fresnel lens as the lens 7, the thickness of the lens 7 can be reduced, and the size of the infrared light source can be reduced.

According to the present embodiment, by controlling the focal length of the lens 7, the infrared rays radiated on the lower surface of the silicon substrate 1 are radiated as parallel light, or high-intensity infrared rays are obtained by condensing. Becomes possible.

FIG. 4 is a sectional view of an infrared light source according to another embodiment of the present invention. In this embodiment, a plurality of micropores 8 having a diameter of an integral multiple of λ / 4 are formed below the silicon substrate 1 instead of the multilayer reflective film 6 of the infrared light source shown in FIG. .

According to this embodiment, the minute holes 8 having a diameter of λ / 4
Is formed below the filament 2, the infrared rays passing through the minute holes 8 interfere with each other, so that it is possible to output infrared rays of wavelength λ from the lower part of the infrared light source by the filter function.

FIG. 5 is a sectional view of an infrared light source according to another embodiment of the present invention. In this embodiment, a reflection film 9 for reflecting infrared rays is added to the upper part of the filament 2 of the infrared light source shown in FIG. The member of the reflection film 9 may be any member that reflects infrared rays, such as gold.

According to the present embodiment, by adding the reflection film 9 for reflecting infrared rays to the upper portion of the filament 2, the infrared ray radiated above the filament 2 is reflected below the filament 2, so that the multilayer film is formed. It is possible to increase the amount of infrared light incident on the reflection film 6.

FIG. 6 is a sectional view of an infrared light source according to another embodiment of the present invention. In the present embodiment, λ / 4 is placed between the filament 2 and the reflection film 9 of the infrared light source shown in FIG.
In this case, a thin film 10 having an integral multiple of the film thickness is added. As a member of the thin film 10 used here, an oxide film, a nitride film, an oxynitride film, or the like can be considered. Note that a space having a thickness of an integral multiple of λ / 4 may be provided between the filament 2 and the reflection film 9.

According to the present embodiment, when the infrared rays radiated above the filament 2 are reflected below the filament 2, they pass through the thin film 10 having a thickness of an integral multiple of λ / 4. It is also possible to introduce wavelength selectivity for infrared rays emitted from the upper part, and it is possible to emit an infrared light source having a narrower band from the lower part of the infrared light source.

FIG. 7 is a sectional view of an infrared light source according to another embodiment of the present invention. In the present embodiment, in the infrared light source shown in FIG. 6, the interval between the lower portion of the filament 2 and the multilayer reflective film 6 is set to be an integral multiple of λ / 4.

According to the present embodiment, the resonance structure can be obtained by setting the interval between the multilayer reflective film 6 and the reflective film 9 to be an integral multiple of λ / 4, and only the desired wavelength λ is particularly enhanced. Narrow band infrared light can be obtained.

FIG. 8 is a schematic configuration diagram of a gas concentration detector using the infrared light source of the present invention. Reference numeral 11 denotes a gas filling section for filling a gas whose concentration is to be detected. 12
Is an infrared light source for detection, using an infrared light source having the above-described wavelength selectivity, using a first infrared ray having a wavelength easily absorbed by the gas sealed in the gas sealing portion 11 and a second infrared ray having a wavelength hardly absorbed by the gas sealed portion 11. Irradiates with infrared. A detection unit 13 detects the concentration of the sealed gas from the ratio of the output of the first infrared ray and the output of the second infrared ray that have passed through the sealed gas.

Note that two detection infrared light sources 12 may be prepared, and one may output the first infrared light and the other may output the second infrared light.

Next, the operation of this embodiment will be described. First, the detection infrared light source 1 is
2 alternately emits a first infrared ray and a second infrared ray. Then, the emitted infrared light is detected by the detection unit 13, and it is checked how much the infrared light is absorbed from the ratio of the output of the first infrared light to the output of the second infrared light. Output the density.

In the gas concentration detector constructed as in the present embodiment, the gas concentration is measured from the ratio between the output of the first infrared ray and the output of the second infrared ray. It is possible to reduce an error due to a change with time such as a change or an output change due to contamination in the radiation section.

According to this embodiment, it is possible to radiate infrared light having a desired wavelength into the enclosed gas without using an expensive infrared filter, so that an inexpensive gas concentration detector can be constructed. Become.

[0037]

As described above, according to the first aspect of the present invention, an infrared ray provided with a silicon substrate, a filament formed by a microbridge on the silicon substrate, and an electrode for flowing a current to the filament. In the light source,
When the wavelength of the infrared light to be emitted is λ, λ / 4
Since a multilayer reflective film in which thin films having different refractive indices having a thickness of an integral multiple of
By reflecting and interfering infrared light incident on the multilayer reflective film, it is possible to emit infrared light having a desired wavelength, and it is possible to select the required wavelength for the emitted infrared light without using an expensive infrared filter. An infrared light source having a wavelength selectivity that can be selectively extracted can be provided.

According to the second aspect of the present invention, there is provided the first aspect.
In the described invention, since the shape of the multilayer reflective film below the filament is made concave with respect to the filament, it becomes possible to deflect the infrared light transmitted through the concave multilayer reflective film to be parallel light, and from the filament to silicon. Infrared light emitted to the back side of the substrate can be emitted from the silicon substrate as substantially parallel light.

In the invention according to claim 3, claim 1 is
In the described invention, since a lens is added to the multilayer reflective film, the focal length of the lens is controlled so that infrared rays radiated on the lower surface of the silicon substrate are emitted as parallel light or condensed, thereby enhancing the efficiency. It becomes possible to obtain an output infrared ray.

According to the fourth aspect of the present invention, an infrared light source including a silicon substrate, a filament formed by a microbridge on the silicon substrate, and an electrode for flowing a current to the filament is intended to emit light. When the wavelength of the infrared light to be emitted is λ, a plurality of micropores having an integral multiple of λ / 4 is provided on the silicon substrate below the filament, so that the infrared rays passing through the micropores interfere with each other,
Since only infrared light having a wavelength near the desired wavelength λ passes through the micropores, it is possible to output infrared light of wavelength λ from below the infrared light source.

In the invention according to claim 5, claim 1 is
According to the present invention, the reflection film for reflecting infrared rays is provided on the filament, so that the infrared rays radiated above the filament are reflected below the filament and enter the multilayer reflection film. It is possible to increase the amount of infrared light.

According to the sixth aspect of the present invention, there is provided the fifth aspect.
In the described invention, λ is set between the filament and the reflective film.
Since the thin film having a thickness of an integral multiple of / 4 is interposed, when the infrared ray radiated above the filament is reflected below the filament, it passes through the thin film having a thickness of an integral multiple of λ / 4. Therefore, it is possible to introduce wavelength selectivity to infrared rays emitted from the upper part of the filament, and to emit an infrared light source having a narrower band from the lower part of the infrared light source.

In the invention according to claim 7, claim 5
Alternatively, in the invention according to claim 6, the interval between the lower part of the filament and the multilayer reflection film is set to be an integral multiple of λ / 4, so that a resonance structure can be obtained between the multilayer reflection film and the reflection film. Only the desired wavelength λ is particularly enhanced, and a narrow band infrared ray can be obtained.

According to the present invention, a gas filling portion for filling a gas whose concentration is to be detected, and a first infrared ray having a wavelength easily absorbed by the sealed gas and a second infrared ray having a wavelength hardly absorbed by the gas. (2) a detection infrared light source for irradiating infrared light of the second type and a detection unit for detecting the concentration of the sealed gas from the ratio of the output of the first infrared light and the output of the second infrared light transmitted through the sealed gas. In the gas concentration detector, the infrared light source according to any one of claims 1 to 7 is used as the infrared light source for detection, so that an infrared ray having a desired wavelength can be added to the enclosed gas without using an expensive infrared filter. It is possible to radiate, and an inexpensive gas concentration detector can be configured.

[Brief description of the drawings]

FIG. 1 is a sectional view of an infrared light source according to an embodiment of the present invention.

FIG. 2 is a sectional view of an infrared light source according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view of an infrared light source according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of an infrared light source according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of an infrared light source according to another embodiment of the present invention.

FIG. 6 is a cross-sectional view of an infrared light source according to another embodiment of the present invention.

FIG. 7 is a sectional view of an infrared light source according to another embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of a gas concentration detector using the infrared light source of the present invention.

FIG. 9 is a top view and an AA cross-sectional view of a conventional infrared light source.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Filament 3 Pedestal 4 Electrode 5 Drilled hole 6 Multilayer reflective film 7 Lens 8 Micro hole 9 Reflective film 10 Thin film 11 Gas filling part 12 Detection infrared light source 13 Detecting part

Claims (8)

[Claims] 1. An infrared light source including a silicon substrate, a filament formed by a microbridge on the silicon substrate, and an electrode for flowing a current to the filament, wherein the wavelength of infrared light to be emitted is λ. In this case, a multilayer reflective film in which thin films having different thicknesses and having a refractive index that is an integral multiple of λ / 4 is laminated is provided below the filament. 2. The infrared light source according to claim 1, wherein the shape of the multilayer reflection film below the filament is concave with respect to the filament. 3. The infrared light source according to claim 1, wherein a lens is added to said multilayer reflection film. 4. An infrared light source including a silicon substrate, a filament formed by a microbridge on the silicon substrate, and an electrode for flowing a current through the filament, wherein the wavelength of infrared light to be emitted is λ. In this case, a plurality of micropores having an integral multiple of λ / 4 are formed in the silicon substrate below the filament. 5. The apparatus according to claim 1, wherein a reflection film for reflecting infrared rays is provided on the filament.
An infrared light source according to claim 4. 6. The infrared light source according to claim 5, wherein a thin film having a thickness of an integral multiple of λ / 4 is interposed between said filament and said reflection film. 7. The infrared light source according to claim 5, wherein an interval between the lower part of the filament and the multilayer reflection film is set to an integral multiple of λ / 4. 8. A gas filling section for filling a gas whose concentration is to be detected, and a detecting means for irradiating a first infrared ray having a wavelength easily absorbed by the sealed gas and a second infrared ray having a wavelength hardly absorbed by the enclosed gas. A gas concentration detector comprising: an infrared light source; and a detection unit that detects a concentration of the sealed gas from a ratio of an output of the first infrared light and a second infrared light transmitted through the sealed gas. 8. A gas concentration detector, wherein the infrared light source according to claim 1 is used as an infrared light source for use.