WO2014020797A1

WO2014020797A1 - Infrared radiation element

Info

Publication number: WO2014020797A1
Application number: PCT/JP2013/002386
Authority: WO
Inventors: 桐原　昌男; 辻　幸司; 吉原　孝明; 吉祥永谷; 弘貴松浪
Original assignee: パナソニック株式会社
Priority date: 2012-08-02
Filing date: 2013-04-08
Publication date: 2014-02-06
Also published as: TW201407659A; JP2014032078A

Abstract

The infrared radiation element (1) of the present invention comprises: a substrate (2); a thin film section (3) that is provided to the surface (201) side of the substrate (2); a through hole (2a) that passes through the substrate (2) in the thickness direction thereof; and a first infrared radiation layer (4a) that has a grid-like form and that is provided to the side of the substrate (2) that is opposite from the side to which the thin film section (3) is provided. The infrared radiation element (1) comprises: a plurality of pads (9) that are electrically connected to the first infrared radiation layer (4a); and a second infrared radiation layer (4b) that is arranged so as to be separated from the first infrared radiation layer (4a) at the opening (4aa) of the first infrared radiation layer (4a), and that has a higher infrared radiation rate than the thin film section (3).

Description

Infrared radiation element

The present invention relates to an infrared radiation element.

Conventionally, an infrared radiation element manufactured using a manufacturing technology of MEMS (micro-electromechanical systems) has been researched and developed. This type of infrared radiation element can be used as an infrared source (infrared light source) such as a gas sensor or an optical analyzer.

As this type of infrared radiation element, for example, Japanese Patent Application Publication No. 9-184757 (hereinafter referred to as “Document 1”) discloses a radiation source having the configuration shown in FIGS.

The radiation source includes a substrate 13, a first insulating layer 22 formed on the substrate 13, a radiation surface layer 11 formed on the first insulation layer 22, and a second surface formed on the radiation surface layer 11. An insulating layer 24 and a plurality of extremely thin incandescent filaments 10 formed on the second insulating layer 24 are provided. In addition, the radiation source is formed so as to cover each incandescent filament 10, a third insulating layer 26 that protects each incandescent filament 10, and both ends of each incandescent filament 10 through openings formed in the third insulating layer 26. A pair of

metal pads

15 and 15 connected to each other is provided. The second insulating layer 24 is provided to electrically insulate the radiating surface layer 11 from the incandescent filament 10. Further, in Document 1, the incandescent filament 10 is surrounded by other elements (first insulating layer 22, radiation surface layer 11, second insulating layer 24, and third insulating layer 26) that form a multilayer structure as a uniform flat plate. It is stated that it is. Reference 1 describes that the purpose of providing the first insulating layer 22 and the third insulating layer 26 is to protect the incandescent filament 10 and the radiating surface layer 11 from oxidation.

Further, an opening 14 is formed in the substrate 13 corresponding to the radiation surface layer 11. Document 1 describes an aqueous potassium hydroxide (KOH) solution, an ethylenediamine aqueous solution to which a small amount of pyrocatechol is added, and tetramethylammonium hydroxide (TMAH) as an etching solution that can be used to form the opening 14. .

The substrate 13 is formed of a (100) oriented silicon chip. The first insulating layer 22 is made of a silicon nitride layer having a thickness of 200 nm. The radiation surface layer 11 is made of a polysilicon film having a thickness of about 1 μm and doped with boron, phosphorus or arsenic. The second insulating layer 24 is made of a silicon nitride layer having a thickness of about 50 nm. The incandescent filament 10 is made of a tungsten layer having a thickness of about 400 nm. The third insulating layer 26 is made of a silicon nitride layer having a thickness of about 200 nm. The metal pad 15 is made of, for example, aluminum, and forms ohmic contact with the incandescent filament 10 through an opening formed in the third insulating layer 26.

In the radiation source, the radiation surface layer 11 has an area of 1 mm ² . Regarding the dimensions of the incandescent filament 10, for example, the thickness is 0.1-1 μm, the width is 2-10 μm, and the interval is 20-50 μm.

Although the incandescent filament 10 is heated by the current flowing through the incandescent filament 10, the incandescent filament 10 is used exclusively for heating the radiating surface layer 11, and the radiating surface layer 11 is the main heat radiating source. Behave as.

By the way, an infrared radiation element that can radiate infrared light with higher efficiency is often desired from the viewpoint of reducing power consumption.

However, the radiation source described above uses the incandescent filament 10 exclusively for heating the radiation surface layer 11, and the radiation surface layer 11 behaves as the main heat radiation source, and the second insulating layer 24 and the radiation surface layer 11. Due to the respective heat capacities, it is difficult to emit infrared rays with high efficiency.

The present invention has been made in view of the above reasons, and an object of the present invention is to provide an infrared radiation element capable of emitting infrared radiation with higher efficiency.

The infrared radiation element (1) of the present invention penetrates in the thickness direction of the substrate (2), the thin film portion (3) provided on the one surface (201) side of the substrate (2), and the substrate (2). The through-hole (2a) and the substrate (2) side have a grid-like first infrared radiation layer (4a) provided on the opposite side of the thin film portion (3), and the first infrared radiation layer (4a ) And a plurality of pads (9) electrically connected to each other, and a plurality of pads (9) disposed inside the edges (4ae) of the plurality of openings (4aa) provided in the first infrared radiation layer (4a). The second infrared radiation layer (4b) is provided, and each of the second infrared radiation layers (4b) has an infrared emissivity higher than that of the thin film portion (3).

In one embodiment of the present invention, it is preferable that the first infrared radiation layer (4a) and the second infrared radiation layer (4b) are made of the same material and have the same thickness.

In one embodiment of the present invention, the plurality of openings (4aa) include an opening (4aa) provided on a center part (4ad) side of the first infrared radiation layer (4a) and the first infrared radiation. An opening (4aa) provided on the outer peripheral portion (4ac) side of the layer (4a) is provided, and the size of the opening (4aa) provided on the central portion (4ad) side is the outer peripheral portion (4ac) side. It is preferable that it is smaller than the size of the opening (4aa).

In another embodiment of the present invention, it is preferable that the size of the opening (4aa) of the first infrared radiation layer (4a) decreases as it approaches the center from the periphery.

In one embodiment of the present invention, the first infrared radiation layer (4a) is located outside the outer peripheral portion (4ac), is spaced apart from the first infrared radiation layer (4a), and is more than the thin film portion. It is preferable to include a third infrared radiation layer (4c) having a high infrared emissivity.

In one embodiment of the present invention, the thin film part (3) includes a diaphragm part (3D) and a support part (3S), and the first infrared radiation layer (4a) is on the diaphragm part (3D). Preferably, the outer size of the first infrared radiation layer (4a) is smaller than the planar size of the diaphragm part (3D).

In one embodiment of the present invention, the through hole (2a) includes a closing surface (2aa) on the one surface (201) side of the substrate (2), and extends along the edge (2c) of the closing surface (2aa). The third infrared radiation layer (4c) is preferably provided.

In the infrared radiation element of the present invention, infrared radiation can be emitted with higher efficiency.

1A is a schematic plan view of an infrared radiation element according to an embodiment, FIG. 1B is a schematic cross-sectional view along AA in FIG. 1A, and FIG. 1C is a schematic cross-sectional view along BB in FIG. 1C. 2A to 2E are main process cross-sectional views for explaining the manufacturing method of the infrared radiation element of the embodiment. FIG. 3 is a plan view of a conventional radiation source. 4 is a cross-sectional view taken along the line AA of the radiation source of FIG.

Hereinafter, the infrared radiation element 1 of the present embodiment will be described with reference to FIG.

In the infrared radiation element 1 according to the present embodiment, the substrate 2 has a first surface 201 and a second surface 202 on the first and second sides in the first direction D1, which is the thickness direction of the substrate 2, respectively. The thin film portion 3 is provided on the first surface 201 of the substrate 2. The thin film portion 3 has a first surface 301 and a second surface 302. In the example of FIG. 1B and FIG. 1C, the 1st surface 201 of the board | substrate 2 and the 2nd surface 302 of the thin film part 3 are contacting. A part of the first surface 301 of the thin film portion 3 is provided so that each of the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c in a lattice shape is separated at a predetermined interval. The first infrared radiation layer 4 a, the second infrared radiation layer 4 b, and the third infrared radiation layer 4 c are covered with the protective layer 5 on the first surface 301 side of the thin film portion 3. The protective layer 5 has a first surface 501 and a second surface 502. In the example of FIGS. 1B and 1C, the first infrared radiation layer 4 a, the second infrared radiation layer 4 b, and the third infrared radiation layer 4 c are in contact with the first surface 301 of the thin film portion 3 and the first surface of the thin film portion 3. The remainder of 301 is in contact with the second surface 502 of the protective layer 5. Further,

electrodes

7 and 7,

wirings

8 and 8, and

pads

9 and 9 are provided on the first surface 501 of the protective layer 5 so as to be electrically connected. In the example of FIGS. 1A and 1B, the

wirings

8 and 8 and the

pads

9 and 9 are in contact with the first surface 501 of the protective layer 5. The protective layer 5 is provided with

contact holes

5a and 5a. The

electrodes

7 and 7 are in contact with one surface 4ab of the first infrared radiation layer 4a through

contact holes

5a and 5a, respectively, and are electrically connected to the first infrared radiation layer 4a.

The thin film portion 3 includes a silicon oxide film 31 and a silicon nitride film 32. The silicon oxide film 31 has a first surface 3101 and a second surface, and a silicon nitride film is formed on the first surface 3101 of the silicon oxide film 31. 32 is provided. The silicon nitride film 32 has a first surface and a second surface 3202. In the example of FIGS. 1B and 1C, the first surface 3101 of the silicon oxide film 31 and the second surface 3202 of the silicon nitride film 32 are in contact with each other. The second surface of the silicon oxide film 31 corresponds to the second surface 302 of the thin film portion 3, and the first surface of the silicon nitride film 32 corresponds to the first surface 301 of the thin film portion 3.

The substrate 2 is provided with a through-hole 2a penetrating so as to expose a part of the second surface 302 of the thin film portion 3, and the substrate 2 is formed as a frame-shaped substrate 2. The through hole 2a has a closing surface 2aa and an opening surface 2ab on the first and second sides in the first direction, respectively. Moreover, the board | substrate 2 which is the frame-shaped board | substrate 2 has the 1st edge part 2a and the 2nd edge part 2b on the 1st and 2nd side of the 2nd direction D2 which is the orthogonal direction of the 1st direction D1, respectively. Yes. That is, the first surface and the second surface of the frame-shaped substrate 2 correspond to the first surface 201 and the second surface 202 of the substrate 2, respectively.

Pads

9 and 9 are provided on the

first surfaces

201 and 201 side of the first end 2a and the second end 2b, respectively. The

pads

9, 9 are arranged along a third direction D3 that is a direction orthogonal to the second direction D2.

The thin film portion 3 includes

support portions

3S and 3S positioned on the

first surfaces

201 and 201 side of the first end portion 2a and the second end portion 2b of the frame-shaped substrate 2, respectively, and an edge 2c of the closing surface 2aa. And a diaphragm portion 3D located inside. The diaphragm portion 3D is positioned on the first surface 201 side of the frame-shaped substrate 2 provided with the through hole 2a, and the

support portions

3S and 3S are positioned on the first surface 201 of the frame-shaped substrate 2. The first surface and the second surface of each support portion 3S correspond to the first surface 301 and the second surface 302 of the thin film portion 3, respectively, and the first surface and the second surface of the diaphragm portion 3D are the thin film portion 3 respectively. This corresponds to the first surface 301 and the second surface 302.

As in the example of FIG. 1A, the third infrared radiation layers 4c and 4c are provided along the edge 2c of the blocking surface 2aa. Each third infrared radiation layer 4c has a first end 4ca and a second end 4cb on the first and second sides in the third direction D2, respectively. The first end portions 4ca and 4ca of the third infrared radiation layer are separated from each other across the position where the wiring 8 is disposed in the third direction. The second end portions 4cb and 4cb of the third infrared radiation layer are separated from each other across the position where the wiring 8 is disposed in the third direction D3.

The first infrared radiation layer 4a is separated from the third infrared radiation layers 4c and 4c, and is provided on the inner side of each inner periphery of the third infrared radiation layers 4c and 4c. The first infrared radiation layer 4a has outer peripheral end portions 4af and 4af on the first and second sides in the second direction D2, respectively. The outer peripheral ends 4af and 4af of the first infrared radiation layer 4a are connected to the

electrodes

7 and 7, respectively. Furthermore, the first infrared radiation layer 4a has a plurality of openings 4aa. In the plurality of openings 4aa, each size of the opening 4aa provided on the central portion 4ad side of the first infrared radiation layer 4a is equal to that of the opening 4aa provided on the outer peripheral portion 4ac side of the first infrared radiation layer 4a. Smaller than each size. A second infrared ray 4b is provided inside each of the edges 4ae of the plurality of openings 4aa. Thereby, a plurality of second infrared rays 4b are arranged on the first surface 301 of the thin film portion 3 (the first surface 301 of the diaphragm portion 3D).

The infrared radiation element 1 includes a substrate 2, a thin film portion 3 provided on the one surface (first surface) 201 side of the substrate 2, and a through hole 2a penetrating in the thickness direction (first direction D1) of the substrate 2. And a lattice-shaped first infrared radiation layer 4a provided on the first surface 301 side of the thin film portion 3 opposite to the substrate 2 side (the second surface 302 side of the thin film portion 3) in the thin film portion 3. ing. In short, the infrared radiation element 1 is a surface of the substrate 2 opposite to the first infrared radiation layer 4a side (the first surface 301 side of the thin film portion 3 provided with the first infrared radiation layer 4a) in the thin film portion 3. A through hole 2a that exposes the (second surface 302 of the thin film portion 3) is formed. Thereby, the 2nd surface 302 of diaphragm part 3D which is a part of thin film part 3 is exposed. The infrared radiation element 1 emits infrared rays from the first infrared radiation layer 4a by energization to the first infrared radiation layer 4a.

In addition, the infrared radiation element 1 is disposed away from the first infrared radiation layer 4a at the two pads 9 electrically connected to the first infrared radiation layer 4a and the opening 4aa of the first infrared radiation layer 4a. And a second infrared radiation layer 4b having a higher infrared emissivity than the thin film portion 3. The infrared radiation element 1 is located on the outer peripheral portion 4ac side of the first infrared radiation layer 4a, is disposed away from the first infrared radiation layer 4a, and is a third infrared radiation layer having a higher infrared emissivity than the thin film portion 3. 4c.

The infrared radiation element 1 includes a pair of

electrodes

7 and 7 formed on the first surface 201 side of the substrate 2 so as to be in contact with the outer peripheral ends 4af and 4af of the first infrared radiation layer 4a, respectively. The electrode 7 is electrically connected to the above-described pad 9 through the wiring 8.

Further, the infrared radiation element 1 includes a first infrared radiation layer 4a and a second infrared ray on the first surface 301 side of the thin film portion 3 that is opposite to the second surface 302 of the thin film portion 3 (the substrate 2 side in the thin film portion 3). A protective layer 5 is provided to cover the radiation layer 4b and the third infrared radiation layer 4c. The protective layer 5 is formed of a material that is transparent to infrared rays emitted from the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c. In FIG. 1A, illustration of the protective layer 5 is omitted.

In the infrared radiation element 1, the first infrared radiation layer 4a generates heat by energizing the first infrared radiation layer 4a. Thereby, as for the infrared radiation element 1, the temperature of the 1st infrared radiation layer 4a rises. Then, the heat generated in the first infrared radiation layer 4a is transferred to the second infrared radiation layer 4b and the third infrared radiation layer 4c through the protective film 5. Thereby, the temperature of the second infrared radiation layer 4b and the third infrared radiation layer 4c also rises. Therefore, the infrared radiation element 1 emits not only infrared rays from the first infrared radiation layer 4a but also infrared rays from the second infrared radiation layer 4b and the third infrared radiation layer 4c.

Hereinafter, each component of the infrared radiation element 1 will be described in detail.

The substrate 2 is formed of a single crystal silicon substrate having a (100) plane on the first surface 201, but is not limited thereto, and may be formed of a single crystal silicon substrate having a (110) plane, for example. The substrate 2 is not limited to a single crystal silicon substrate, but may be a polycrystalline silicon substrate or other than a silicon substrate. The material of the substrate 2 is preferably a material having a higher thermal conductivity and a larger heat capacity than the material of the thin film portion 3.

The outer peripheral shape of the substrate 2 is rectangular. Although the external size of the board | substrate 2 is not specifically limited, For example, it is preferable to set to 10 mm □ (sq.) Or less (10 mm × 10 mm or less). Moreover, the board | substrate 2 makes the opening shape of the through-hole 2a rectangular. The through-hole 2a of the substrate 2 is formed in a shape in which the opening area on the other surface (second surface 202) side is larger than that on the first surface 201 side. Here, the through hole 2 a of the substrate 2 is formed in a shape in which the opening area gradually increases as the distance from the thin film portion 3 increases. The through hole 2 a of the substrate 2 is formed by etching the substrate 2. When a single crystal silicon substrate having a (100) plane as the first surface 201 is used as the substrate 2, the through hole 2a of the substrate 2 is formed by, for example, anisotropic etching using an alkaline solution as an etching solution. can do. The opening shape of the through hole 2a of the substrate 2 is not particularly limited. Therefore, the method for forming the through hole 2a of the substrate 2 is not limited to anisotropic etching using an alkaline solution as an etching solution, but employs dry etching using, for example, an inductively coupled plasma type dry etching apparatus. You can also. In addition, in the infrared emitting element 1, when the mask layer for forming the through-hole 2 a is made of an inorganic material during manufacturing, the mask layer may remain on the second surface 202 side of the substrate 2. As the mask layer, for example, a laminated film of a silicon oxide film and a silicon nitride film can be employed.

In the thin film portion 3, the portion of the substrate 2 that closes the through hole 2a on the first surface 201 side constitutes the diaphragm portion 3D, and the edge 2c of the closing surface 2aa of the through hole 2a on the first surface 201 side of the substrate 2 The portion formed on the outer side forms a support portion 3S that supports the diaphragm portion 3D.

The thin film portion 3 is formed on the silicon oxide film 31 formed on the first surface 201 side of the substrate 2 and on the first surface 3101 side of the silicon oxide film 31 (on the opposite side of the silicon oxide film 31 from the substrate 2 side). The silicon nitride film 32 is laminated. The thin film portion 3 is not limited to the laminated film of the silicon oxide film 31 and the silicon nitride film 32. For example, the thin film portion 3 may have a single layer structure of the silicon oxide film 31 or the silicon nitride film 32, or may be other than SiO ₂ and Si ₃ N ₄ . A single layer structure made of an electrically insulating material or a laminated structure of two or more layers may be used.

The thin film portion 3 also has a function as an etching stopper layer when the substrate 2 is etched from the second surface 202 side of the substrate 2 to form the through hole 2a when the infrared radiation element 1 is manufactured.

The 1st infrared radiation layer 4a, the 2nd infrared radiation layer 4b, and the 3rd infrared radiation layer 4c reduce the emissivity of infrared rays by impedance mismatch with the gas (for example, air, nitrogen gas, etc.) which the protective layer 5 contacts. The sheet resistance is set so as to suppress it.

The first infrared radiation layer 4a has a lattice shape in plan view. The outer size of the first infrared radiation layer 4a is preferably set smaller than the planar size of the surface of the diaphragm portion 3D facing the through hole 2a in the thin film portion 3. That is, it is preferable to set the outer size of the first infrared radiation layer 4a to be smaller than the planar size of the diaphragm portion 3D. Here, the planar size of the diaphragm portion 3D is not particularly limited, but is preferably set to 5 mm □ or less, for example.

The outer size of the first infrared radiation layer 4a is preferably set so that the outer size of the region excluding the contact regions where the electrodes 7 overlap each other is 3 mm □ or less.

The material of the first infrared radiation layer 4a is tantalum nitride. That is, the first infrared radiation layer 4a is made of a tantalum nitride layer. The material of the first infrared radiation layer 4a is not limited to tantalum nitride, for example, titanium nitride, nickel chromium, tungsten, titanium, thorium, platinum, zirconium, chromium, vanadium, rhodium, hafnium, ruthenium, boron, iridium, niobium, Molybdenum, tantalum, osmium, rhenium, nickel, holmium, cobalt, erbium, yttrium, iron, scandium, thulium, palladium, lutetium, or the like may be employed. Further, as the material of the first infrared radiation layer 4a, conductive polysilicon may be adopted. That is, the first infrared radiation layer 4a may be composed of a conductive polysilicon layer. For the first infrared radiation layer 4a, it is preferable to employ a tantalum nitride layer or a conductive polysilicon layer from the viewpoint of chemical stability at high temperatures and ease of design of sheet resistance. The tantalum nitride layer can change the sheet resistance by changing its composition. The conductive polysilicon layer can change the sheet resistance by changing the impurity concentration and the like. The conductive polysilicon layer can be constituted by an n-type polysilicon layer doped with an n-type impurity at a high concentration or a p-type polysilicon layer doped with a p-type impurity at a high concentration. When the conductive polysilicon layer is an n-type polysilicon layer and phosphorus is used as the n-type impurity, the impurity concentration is, for example, in the range of about 1 × 10 ¹⁸ cm ⁻³ to 5 × 10 ²⁰ cm ^−3. What is necessary is just to set suitably. Also, when the conductive polysilicon layer is a p-type polysilicon layer and boron is used as the p-type impurity, the impurity concentration is in the range of about 1 × 10 ¹⁸ cm ⁻³ to 1 × 10 ²⁰ cm ^−3. What is necessary is just to set suitably.

When the above-mentioned gas is air, tantalum nitride is employed as the material of the first infrared radiation layer 4a, and the first infrared radiation layer 4a is heated to a desired use temperature of, for example, 500 ° C. The sheet resistance at which the infrared emissivity from the first infrared emitting layer 4a is maximized is 189 Ω / □ (189 Ω / sq.), And the maximum emissivity is 50%. That is, if the sheet resistance of the first infrared radiation layer 4a is 189 Ω / □, the infrared radiation element 1 can maximize the infrared emissivity by impedance matching with air. Therefore, in order to suppress a decrease in emissivity and ensure emissivity of, for example, 40% or more, the sheet resistance of the first infrared radiation layer 4a may be set in a range of 73 to 493 Ω / □. If the sheet resistance at which the emissivity is maximized at a desired use temperature is called a prescribed sheet resistance, the sheet resistance of the first infrared radiation layer 4a at the desired use temperature is a prescribed sheet resistance of ± 10%. It is more preferable to set the range.

The peak wavelength λ of infrared rays emitted from the first infrared emitting layer 4a in the infrared emitting element 1 depends on the temperature of the first infrared emitting layer 4a. Here, if the absolute temperature of the first infrared radiation layer 4a is T [K] and the peak wavelength is λ [μm], these satisfy the relationship of λ = 2898 / T. That is, the relationship between the absolute temperature T of the first infrared radiation layer 4a and the peak wavelength λ of the infrared radiation emitted from the first infrared radiation layer 4a satisfies the Vienna displacement law. Therefore, in the infrared radiation element 1, the first infrared radiation layer 4a constitutes a black body.

The infrared radiation element 1 can change Joule heat generated in the first infrared radiation layer 4a by adjusting input power applied between the pair of

pads

9 and 9 from an external power source (not shown), for example. The temperature of the infrared radiation layer 4a can be changed. Therefore, the infrared radiation element 1 can change the temperature of the first infrared radiation element 4a in accordance with the input power to the first infrared radiation layer 4a. In addition, the infrared radiation element 1 can change the peak wavelength λ of infrared radiation emitted from the first infrared radiation layer 4a by changing the temperature of the first infrared radiation layer 4a. For this reason, the infrared radiation element 1 can be used as a high-power infrared light source in a wide infrared wavelength range. For example, when the infrared radiation element 1 is used as an infrared light source of a gas sensor, it is preferable that the peak wavelength λ of infrared radiation emitted from the first infrared radiation layer 4a is about 4 μm. The temperature may be about 800K. Here, in the infrared radiation element 1, the first infrared radiation layer 4a forms a black body as described above. Thereby, in the infrared radiation element 1, it is estimated that the total energy E radiated per unit time in the unit area of the first infrared radiation layer 4a is approximately proportional to T ⁴ (that is, the Stefan-Boltzmann law is satisfied). Guessed) The infrared radiation element 1 can increase the amount of infrared radiation as the temperature of the first infrared radiation layer 4a is increased.

The first infrared radiation layer 4a is formed on the surface (the first surface 301 of the thin film portion 3) opposite to the second surface 302 of the thin film portion 3 (the substrate 2 side of the thin film portion 3). The first infrared radiation layer 4a has a lattice shape in plan view as described above. In the first infrared radiation layer 4a, the size of each opening 4aa may be the same, but it is preferable that the size of the opening 4aa decreases from the outer peripheral portion 4ac to the center portion 4ad as shown in FIG. 1A. That is, in the first infrared radiation layer 4a, it is preferable that the size of the opening 4aa close to the center 4ad is smaller than the opening 4aa on the outer peripheral portion 4ac side. Thereby, the infrared radiation element 1 can achieve a uniform temperature distribution of the first infrared radiation layer 4a, and can suppress the variation of the infrared wavelength depending on the position of the first infrared radiation layer 4a. Become.

The second infrared radiation layer 4 b is formed on the first surface 301 of the thin film portion 3 located on the opposite side of the second surface 302 of the thin film portion 3. Therefore, the second infrared radiation layer 4b and the first infrared radiation layer 4a are formed on the same plane.

The planar shape of the second infrared radiation layer 4b is a rectangular shape (in the illustrated example, a square shape) that is slightly smaller than the opening 4aa of the lattice-shaped first infrared radiation layer 4a. From the viewpoint of radiating infrared rays with higher efficiency, the infrared radiation element 1 is preferably arranged such that the second infrared radiation layer 4b is located on the inner side of each edge 4ae of all the openings 4aa in the first infrared radiation layer 4a. Has been.

The material of the second infrared radiation layer 4b can be the same material as that of the first infrared radiation layer 4a, but the same material as the first infrared radiation layer 4a is preferably employed. The thickness of the second infrared radiation layer 4b is preferably the same as the thickness of the first infrared radiation layer 4a. The infrared radiation element 1 includes the first infrared radiation layer 4a and the second infrared radiation layer 4b formed of the same material and having the same thickness. The layer 4b can be formed at the same time, and the cost can be reduced.

The second infrared radiation layer 4b preferably has a larger planar size as long as it does not contact the inner surface of the opening 4aa in the first infrared radiation layer 4a. Thereby, the temperature of the 2nd infrared radiation layer 4b becomes closer to the temperature of the 1st infrared radiation layer 4a, and it becomes possible to radiate infrared rays more efficiently.

The third infrared radiation layer 4c is formed on the first surface 301 of the thin film portion 3 (the surface of the thin film portion 3 opposite to the substrate 2 side). Therefore, the 3rd infrared radiation layer 4c, the 2nd infrared radiation layer 4b, and the 1st infrared radiation layer 4a are formed on the same plane.

In the example of FIGS. 1A to 1C, two third infrared radiation layers 4c are provided, and each planar shape is C-shaped. However, without being limited thereto, in the infrared radiation element 1 of the present embodiment, the plurality of third infrared radiation layers 4c surround the first infrared radiation layer 4a with the frame F interposed therebetween, and these third infrared radiation layers The layer 4c may be disposed so as to be separated from the first infrared radiation layer 4a. Here, the said frame F is comprised from the protective film 5, and is arrange | positioned on the 1st surface 301 of diaphragm part 3D along the outer shape of the 1st infrared radiation layer 4a. Moreover, although the 3rd infrared radiation layer 4c is formed ranging over the diaphragm part 3D of the thin film part 3, and the support part 3S, it should just be formed on the 1st surface 301 of the diaphragm part 3D at least.

The material of the third infrared radiation layer 4c can be the same material as that of the first infrared radiation layer 4a, but the same material as that of the first infrared radiation layer 4a is preferably employed. The thickness of the third infrared radiation layer 4c is preferably the same as the thickness of the first infrared radiation layer 4a.

The infrared radiation element 1 includes the first infrared radiation layer 4a and the third infrared radiation layer 4c formed of the same material and having the same thickness. The layer 4c can be formed at the same time, and the cost can be reduced.

The infrared radiation element 1 includes the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c formed of the same material and having the same thickness. The layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c can be formed at the same time, and the cost can be reduced.

The protective layer 5 is composed of a silicon nitride film. The protective layer 5 is not limited to a silicon nitride film, and may be formed of, for example, a silicon oxide film, or may have a stacked structure of a silicon oxide film and a silicon nitride film. The protective layer 5 preferably has a high transmittance with respect to infrared rays of a desired wavelength or wavelength range emitted from the first infrared radiation layer 4a when the first infrared radiation layer 4a is energized, but the transmittance is 100%. Is not a requirement.

The infrared radiation element 1 is a thin film in consideration of the stress balance of the sandwich structure composed of the thin film portion 3, the first infrared radiation layer 4a, the second infrared radiation layer 4b, the third infrared radiation layer 4c, and the protective layer 5. It is preferable to set the material and thickness of each of the portion 3 and the protective layer 5. Thereby, the infrared radiation element 1 can improve the stress balance of the above-described sandwich structure, and can further suppress the warpage and breakage of the sandwich structure, thereby further improving the mechanical strength. Can be achieved.

The thicknesses of the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c are reduced in the heat capacity of the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c. From the viewpoint of achieving this, the thickness is preferably 0.2 μm or less.

The total thickness of the thickness of the thin film portion 3, the thickness of the first infrared radiation layer 4a, and the thickness of the protective layer 5 reduces the heat capacity of the laminated structure of the thin film portion 3, the first infrared radiation layer 4a, and the protective layer 5. From the viewpoint of achieving this, for example, it is preferably set in the range of about 0.1 μm to 1 μm, more preferably 0.7 μm or less (specifically, 0.1 μm to 0.7 μm). For example, the infrared radiation element 1 is configured such that the thickness of the silicon oxide film 31 of the thin film portion 3 is 160 nm, the thickness of the silicon nitride film 32 of the thin film portion 3 is 160 nm, and the thickness of the protective layer 5 is 100 nm. What is necessary is just to set the thickness of the infrared radiation layer 4a suitably. These numerical values are examples and are not particularly limited.

The pair of

electrodes

7 and 7 are formed on the first surface 201 side of the substrate 2 so as to be in contact with the outer peripheral end portions 4af and 4af (left and right end portions in FIG. 1A) of the first infrared radiation layer 4a. Each electrode 7 is formed on one surface 4ab of the first infrared radiation layer 4a through a contact hole 5a formed in the protective layer 5, and is electrically connected to the first infrared radiation layer 4a. Here, each electrode 7 is in ohmic contact with the first infrared radiation layer 4a.

The material of each electrode 7 is Al-Si, which is a kind of aluminum alloy. The material of each electrode 7 is not particularly limited, and for example, Al—Cu, Al or the like may be adopted. Moreover, each electrode 7 should just be a material in which the part which contact | connects the 1st infrared radiation layer 4a at least can make ohmic contact with the 1st infrared radiation layer 4a, and not only a single layer structure but a multilayer structure may be sufficient as it. For example, each electrode 7 has a three-layer structure in which a first layer, a second layer, and a third layer are laminated in order from the first infrared radiation layer 4a side, and the first layer material in contact with the first infrared radiation layer 4a. May be a refractory metal (such as Cr), the second layer material may be Ni, and the third layer material may be Au. In the infrared radiating element 1, the temperature of the first infrared radiating layer 4 a is limited by the material of each pad 9 as long as at least a portion in contact with the first infrared radiating layer 4 a is formed of a refractory metal in each pad 9. It is possible to raise without any loss.

Each wiring 8 and each pad 9 are preferably made of the same material as each electrode 7 and set to the same layer structure and the same thickness. Thereby, the infrared radiation element 1 can form each wiring 8 and each pad 9 simultaneously with each electrode 7. The thickness of the pad 9 is preferably set in the range of about 0.5 to 2 μm.

The number of pads 9 is not limited to two but may be plural. For example, two pads 9 may be connected to each electrode 7. In short, the number of the pads 9 is not particularly limited in the infrared radiation element 1 as long as the first infrared radiation layer 4a can be energized to cause the first infrared radiation layer 4a to generate heat.

Further, the infrared radiation element 1 only needs to include at least the first infrared radiation layer 4a and the second infrared radiation layer 4b as the infrared radiation layer, and may not have the third infrared radiation layer 4c.

Below, the manufacturing method of the infrared radiation element 1 is demonstrated based on FIG.

In manufacturing the infrared radiation element 1, first, the substrate 2 made of a single crystal silicon substrate or the like whose first surface 201 is (100) plane is prepared (see FIG. 2A).

After the substrate 2 is prepared, the structure shown in FIG. 2B is obtained by performing the first step of forming the thin film portion 3 on the first surface 201 side of the substrate 2. As a method for forming the silicon oxide film 31 in the thin film portion 3, for example, a thin film forming technique such as a thermal oxidation method or a CVD (Chemical Vapor Deposition) method can be adopted, and a thermal oxidation method is preferable. In addition, as a method for forming the silicon nitride film of the thin film portion 3, a thin film forming technique such as a CVD method can be used, and an LPCVD (Low Pressure Chemical Vapor Deposition) method is preferable.

After the first step, by performing a second step of forming the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c on the first surface 301 of the thin film portion 3, FIG. 2C The structure shown in is obtained. As a method for forming the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c, for example, a thin film formation technique such as a sputtering method, a vapor deposition method, or a CVD method, and a photolithography technique and an etching technique are used. Can be used.

After the second step, a third step for forming the protective layer 5 is performed, followed by a fourth step for forming the contact hole 5a, and then each electrode 7, each wiring 8, and each pad 9 are formed. By performing the fifth step, the structure shown in FIG. 2D is obtained. As a method for forming the protective layer 5 in the third step, for example, a thin film forming technique such as a CVD method and a processing technique using a photolithography technique and an etching technique can be used. As a CVD method for forming the protective layer 5, a plasma CVD method is preferable. In forming the contact hole 5a in the fourth step, a photolithography technique and an etching technique may be used. Etching in the fourth step may be wet etching or dry etching. In forming each electrode 7, each wiring 8, and each pad 9 in the fifth step, for example, a thin film forming technique such as a sputtering method, a vapor deposition method and a CVD method, and a processing technique using a photolithography technique and an etching technique are used. Can be used. Etching in the fifth step may be wet etching or dry etching.

After the fifth step, the sixth step of forming the diaphragm portion 3D by forming the through hole 2a in the substrate 2 is performed, thereby obtaining the infrared radiation element 1 having the structure shown in FIG. 2E. In forming the through hole 2a, for example, a laminated film (not shown) of a silicon oxide film and a silicon nitride film is formed on the second surface 202 side of the substrate 2 as a mask layer, and the substrate 2 is formed on the second surface 202 side. It may be formed by etching. In forming the mask layer, for example, first, a silicon oxide film serving as a base of the mask layer is formed on the second surface 202 side of the substrate 2 simultaneously with the formation of the silicon oxide film 31 of the thin film portion 3, and then the thin film portion 3. Simultaneously with the formation of the silicon nitride film 32, a silicon nitride film is formed on the second surface 202 side of the substrate 2. The patterning of the laminated film of the silicon oxide film and the silicon nitride film that is the basis of the mask layer may be performed using a photolithography technique and an etching technique. The etching of the substrate 2 employs anisotropic etching using an alkaline solution, but is not limited thereto, and can be formed by etching using, for example, an inductively coupled plasma type dry etching apparatus. Here, in the manufacturing method of the infrared radiation element 1 of the present embodiment, it is possible to increase the accuracy of the thickness of the thin film portion 3 by using the thin film portion 3 as an etching stopper layer when forming the through hole 2a. At the same time, it is possible to prevent a part of the substrate 2 and the residue from remaining on the second surface 302 (the through hole 2a side in the thin film portion 3) of the diaphragm portion 3D. Moreover, in the manufacturing method of the infrared radiation element 1 of this embodiment, it becomes possible to increase the accuracy of the thickness of the thin film portion 3 by using the thin film portion 3 as an etching stopper layer when forming the through hole 2a. It is possible to suppress variations in mechanical strength of the thin film portion 3 and variations in heat capacity of the diaphragm portion 3D for each infrared radiation element 1.

In manufacturing the infrared radiation element 1 described above, the process until the formation of the through hole 2a is completed at the wafer level, and after forming the through hole 2a, the individual infrared radiation elements 1 may be separated. That is, in manufacturing the infrared radiation element 1, for example, a silicon wafer as a base of the substrate 2 is prepared, and a plurality of infrared detection elements 1 are formed on the silicon wafer according to the above-described manufacturing method. What is necessary is just to isolate | separate to the detection element 1. FIG.

As can be seen from the method for manufacturing the infrared radiating element 1 described above, the infrared radiating element 1 can be manufactured by using a MEMS manufacturing technique.

The infrared radiation element 1 of the present embodiment described above includes a substrate 2, a thin film portion 3 provided on the first surface 201 side of the substrate 2, a through hole 2a penetrating in the thickness direction of the substrate 2, and a diaphragm portion. A grid-like first infrared radiation layer 4a provided on the 3D first surface 301 side (the side opposite to the substrate 2 side in the thin film portion 3) is provided. The infrared radiation element 1 is disposed away from the first infrared radiation layer 4a at the plurality of pads 9 electrically connected to the first infrared radiation layer 4a and the opening 4aa of the first infrared radiation layer 4a. And a second infrared radiation layer 4b having a higher infrared emissivity than the thin film portion 3. Thereby, the infrared radiation element 1 emits infrared rays from the first infrared radiation layer 4a and the second infrared radiation layer 4b by energizing the first infrared radiation layer 4a to generate heat. Here, in the infrared radiation element 1, since the first infrared radiation layer 4a is formed in a lattice shape, it becomes possible to reduce the heat capacity of the first infrared radiation layer 4a, the temperature is likely to rise, Since the second infrared radiation layer 4b is disposed in the opening 4aa of the first infrared radiation layer 4a, the temperature difference between the second infrared radiation layer 4b and the first infrared radiation layer 4b can be reduced. Therefore, the infrared radiation element 1 can emit infrared rays with higher efficiency. In addition, the infrared radiation element 1 responds to the temperature change of the first infrared radiation layer 4a with respect to the voltage waveform applied between the pair of

pads

9, 9 by reducing the heat capacity of the laminated structure on the first surface 201 side of the substrate 2. As a result, the temperature of the first infrared radiation layer 4a is likely to rise, and it becomes possible to increase the output and the response speed.

Further, the infrared radiation element 1 is located outside the outer peripheral portion 4ac of the first infrared radiation layer 4a, is disposed away from the first infrared radiation layer 4a, and has a third infrared emissivity higher than that of the thin film portion 3. An infrared radiation layer 4c is provided. Thereby, the infrared radiation element 1 can emit infrared rays with higher efficiency.

In addition, the infrared radiation element 1 suppresses a decrease in infrared emissivity due to impedance mismatch with the gas in contact with the protective layer 5 with respect to the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c. The sheet resistance is set so as to. Therefore, the infrared radiation element 1 can suppress a decrease in the emissivity of the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer 4c. Therefore, the infrared radiation element 1 of the present embodiment can reduce power consumption.

Further, in the infrared radiation element 1, the substrate 2 is formed from a single crystal silicon substrate, and the thin film portion 3 is composed of a silicon oxide film 31 and a silicon nitride film 32. As a result, the infrared radiation element 1 has a larger heat capacity and thermal conductivity of the substrate 2 than the thin film portion 3, and the substrate 2 has a function as a heat sink. It is possible to improve the stability of infrared radiation characteristics.

In the infrared radiation element 1, the first infrared radiation layer 4a, the second infrared radiation layer 4b, the third infrared radiation layer 4c, the electrode 7, the wiring 8 and the pad 9 are arranged in a direction in which the pair of

electrodes

7 and 7 are arranged in plan view. It is preferable that the orthogonal infrared radiation elements 1 are arranged in line symmetry with the center line as the axis of symmetry.

In other words, in the infrared radiation element 1, the axis in the second direction passing through the central portion 4ad of the first infrared radiation layer 4a is the axis of symmetry, and the first infrared radiation layer 4a, the second infrared radiation layer 4b, and the third infrared radiation layer. It is preferable that 4c, the electrode 7, the wiring 8, and the pad 9 are arranged symmetrically with respect to the axis.

Thereby, the infrared radiation element 1 can further improve the mechanical strength, and can suppress in-plane variation of the temperature of the first infrared radiation layer 4a.

The infrared radiation element 1 is not limited to an infrared light source (infrared light source) for a gas sensor, but is used for an infrared light source for flame detection, an infrared light source for infrared light communication, an infrared light source for spectroscopic analysis, and the like. Is possible.

Claims

A substrate, a thin film portion provided on one surface side of the substrate, a through-hole penetrating in the thickness direction of the substrate, and a lattice-shaped first infrared ray provided on the opposite side of the thin film portion from the substrate side A radiation layer; a plurality of pads electrically connected to the first infrared radiation layer; and an opening of the first infrared radiation layer that is spaced apart from the first infrared radiation layer and is more infrared than the thin film portion. An infrared radiation element comprising: a second infrared radiation layer having a high emissivity.
The infrared radiation element according to claim 1, wherein the first infrared radiation layer and the second infrared radiation layer are formed of the same material and have the same thickness.
3. The infrared radiation element according to claim 1, wherein the first infrared radiation layer has a size of the opening that decreases from a peripheral portion toward a central portion.
4. The apparatus according to claim 1, further comprising a third infrared radiation layer that is disposed outside the first infrared radiation layer and spaced apart from the first infrared radiation layer and has a higher infrared emissivity than the thin film portion. The infrared radiation element according to item 1.