JP2000321125A - Infrared sensor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve detecting sensitivity of an infrared sensor element by providing a resonance space between an infrared absorption layer and a reflecting layer, thereby reducing a thermal capacity of the element. SOLUTION: An infrared absorption layer 2 is supported to a reflecting layer 10 by using at least one heat transfer post 4 so as to form a resonance space 13 between the layer 2 and the layer 10, and the layer 10 is connected to a temperature sensitive layer 7 through an insulator film 14. A heat generated from the layer 2 is transferred to the layer 7 through the post 4, the layer 10 and the film 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an infrared sensor element. Specifically, the present invention relates to a thermal infrared sensor element.

[0002]

2. Description of the Related Art At present, active development of thermal type infrared sensor elements is being made. For example, an infrared sensor element miniaturized using a micromachining technique is in a practical stage. Such an infrared sensor element receives an infrared ray at a detection unit, generates a temperature change, converts the temperature change into a physical quantity such as electric resistance, spontaneous polarization or thermoelectromotive force, and detects the infrared ray as heat / temperature. . Therefore, in order to effectively convert the infrared light received by the detection unit into thermal energy, it is necessary to cut off the heat between the detection unit and the outside world. For this reason, with respect to the infrared sensor element, a structure for vacuuming the periphery of the detection unit, a structure for reducing heat transfer to the surroundings by convection, a structure for reducing heat conduction between the detection unit and the substrate, and the like have been proposed. .

FIG. 7 and FIG. 8 show a conventional infrared sensor element 70 disclosed in Japanese Patent Application Laid-Open No. 7-508095.
In the figure, 1 is a semiconductor substrate, 117 is a temperature sensing part, 120,
121 indicates a support leg, and 122 indicates a sensor area. The temperature sensing section 117 includes the temperature sensing layer 114, the absorption layer 116, and the temperature sensing layer 1
14 is composed of insulating layers 112 and 113.
The substrate 1 located below the temperature sensing part 117 and the heat separators 120 and 121 has been removed. Thus, the temperature-sensitive layer 117
Of the temperature-sensitive layer 117 by floating
Transfer of heat from the semiconductor substrate 1 to the semiconductor substrate 1 can be suppressed.

Next, the operation of the infrared sensor element 70 will be described. When the infrared rays enter the temperature sensing section 117, the temperature of the temperature sensing section 117 increases. This temperature rise is converted into an electric signal by the thermosensitive layer 114 which is a thermosensitive element. Next, the converted electric signal is guided to the substrate 1 by a wiring layer (not shown) formed on the support legs 120 and 121,
After being processed by a processing circuit or the like (not shown), it is output and infrared rays are detected.

The sensor area 122 of the infrared sensor element 70
Are formed with substrate removal holes 140 and 150,
The ratio of the temperature sensing portion 117 in the sensor area 122 is low. Therefore, the infrared ray that can be detected by the detection layer 114 is only a part of the infrared ray received by the sensor region 122, and thus the infrared sensor element 70 has a problem that the infrared ray detection sensitivity is low.

[0006] In order to solve the above-mentioned problems, Japanese Patent Laid-Open No. 10-2 is disclosed.
No. 09418 discloses an infrared sensor element 60 shown in FIG.
Has been proposed. The infrared sensor element 60 has a structure having an absorber 203 that absorbs infrared rays and a temperature-sensitive layer 208 that detects heat, and the absorber 203 is supported by connecting columns 211 and connected to the temperature-sensitive layer 208. The absorber 203 is made of an insulating film, and includes an infrared absorbing film 209 and a reflective layer 210. Further, the detection layer 208 is supported on the substrate 1 by the support legs 206 and forms a floating structure with respect to the substrate 1.

Next, the operation of the infrared sensor element 60 will be described. The infrared light received by the infrared absorption film 209 is reflected by the reflection film 210 and is optically resonated between the reflection film 210 and the infrared ray absorption film 209. The optically resonated infrared light is converted into heat energy by the absorber 203 and transmitted to the detection layer 208 via the connection pillar 211.
Further, in the sensing layer 208, thermal energy is converted into an electrical signal. Thus, the infrared sensor element 60 detects the infrared light received by the sensor area 122.

[0008]

However, the conventional infrared sensor element 60 has a problem that since the heat capacity of the absorber 203 is large, an afterimage is apt to remain and the sensitivity of detecting infrared rays is low for a fast moving subject. was there.

The present invention has been made to solve such a problem, and has as its object to provide an infrared sensor element having excellent infrared detection sensitivity.

[0010]

According to the infrared sensor element of the present invention, a temperature-sensitive layer provided on a semiconductor substrate at a distance from the semiconductor substrate by using a support leg, and a predetermined distance from each other on the temperature-sensitive layer. A reflection layer and an infrared absorption layer provided to face each other at a distance, and infrared rays are optically resonated between the infrared absorption layer and the reflection layer, and the infrared rays are detected by the thermosensitive layer as heat. An infrared sensor element, wherein at least one heat transfer column is used to support the infrared absorption layer on the reflection layer so that a resonance space is formed between the infrared absorption layer and the reflection layer, and The temperature-sensitive layer is joined to the temperature-sensitive layer via an insulator film. That is, by forming a resonance space between the infrared absorption layer and the reflection layer, the heat capacity of the region where infrared rays are optically resonated is reduced, and the detection sensitivity of the infrared sensor element is improved.

[0011] In the infrared sensor element of the present invention, one heat transfer column may be provided.

Further, in the infrared sensor element of the present invention,
To efficiently resonate infrared light optically, it is preferable to expose the reflection layer so as to face the infrared absorption layer.

In the infrared sensor element of the present invention, in order to improve the conversion efficiency from infrared to thermal energy,
It is preferable to form an infrared absorption layer from a first insulator film, a second insulator film, and a metal infrared absorption film sandwiched between the first insulator film and the second insulator film.

Further, in the infrared sensor element of the present invention, it is preferable that the first insulator film and the second insulator film are formed of the same material to prevent deformation of the infrared absorption layer due to internal stress. This makes it possible to maintain a constant distance between the reflection layer and the infrared ray absorption layer, and stabilizes the optical resonance of infrared rays generated between the reflection layer and the infrared ray absorption layer.

In the infrared sensor element of the present invention, an infrared absorption layer may be formed from an insulator film.

In the infrared sensor element of the present invention, the semiconductor substrate and the temperature-sensitive layer may be separated from each other by a gap formed in the semiconductor substrate.

Further, in the infrared sensor element of the present invention,
It is preferable that the temperature-sensitive layer be supported above the semiconductor substrate by supporting legs formed on the semiconductor substrate.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 First, an infrared sensor element 50 according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 2 shows a top view of the infrared sensor element 50 omitting the absorber 2, the heat conduction column 4, and the reflection layer 10.

The infrared sensor element 50 includes a semiconductor substrate 1,
It comprises a detector 3, an absorber 2, and support legs 6a, 6b. The absorber 2, the detector 3, and the support legs 6a, 6b are formed on the sensor region 20 of the semiconductor substrate 1. A part of the sensor area 20 is removed to form the gap 5.
The voids 5 are formed by etching the semiconductor substrate 1 using a known technique of crystal anisotropic etching. Embodiment 1
In the embodiment, the gap 5 is formed by removing a part of the sensor region 20 of the semiconductor substrate 1. However, the present invention is not limited to this, and the absorption 5 is formed above the sensor region 20 without forming the gap 5. The body 2, the detection body 3, and the support legs 6a and 6b may be formed (see Embodiment 2 below).

The detector 3 is formed by joining a temperature-sensitive layer 7 for converting heat into an electric signal, wiring layers 8a and 8b for transmitting an electric signal, and a reflective layer 10 by an insulating film 14.
More specifically, the surfaces of the temperature-sensitive layer 7 and the wiring layers 8a and 8b are covered with an insulator film 14, and the reflective layer 10 is provided on the temperature-sensitive layer 7 and the wiring layers 8a and 8b via the insulator film 14. Is located. Further, the surface of the reflection layer 10 is covered with the insulator film 14. That is, the surface of the detector 3 is covered with the insulator film 14. The insulator film 14 is, for example, a silicon oxide film,
It is formed of a silicon nitride film or the like. The temperature-sensitive layer 7 is formed of a bolometer thin film, and is formed of, for example, vanadium oxide, polysilicon, amorphous silicon, or the like.
The wiring layers 8a and 8b are formed of, for example, a metal film of aluminum, titanium, tungsten, or the like.
Is formed from a metal film such as aluminum.

The detector 3 including the temperature-sensitive layer 7 includes support legs 6a,
6b. A gap 5 is formed below the support legs 6a and 6b and the detection body 3. That is, the gap 5
As a result, the detector 3 has a floating structure and is thermally separated from the substrate 1. In addition, wiring layers 8a and 8b that are connected to the temperature-sensitive layer 7 are formed on the support legs 6a and 6b.

The absorber 2 is formed above the detector 3 and serves to absorb the received infrared light as thermal energy. The metal infrared absorbing film 9 is made of an upper insulator film 12a and a lower insulator film. 12b. The upper insulator film 12a and the lower insulator film 12b are formed of, for example, a silicon oxide film, a silicon nitride film or the like, and the metal infrared absorbing film 9 is formed of, for example, titanium nitride or the like. In the first embodiment, the thickness of each of the upper insulator film 12a and the lower insulator film 12b is set to 0.1 μm, and the thickness of the metal infrared absorbing film 9 is set to 0.1 μm. More specifically, when a metal having a resistivity of 2 μΩ · m is used as the metal infrared absorbing film 9, the conversion efficiency for far infrared rays is 90% or more.

The absorber 2 is supported by the heat transfer column 4 and is supported on the detector 3. Thus, the resonance space 13 is formed between the detector 3 and the absorber 2. Heat transfer column 4 connecting absorber 2 and detector 3
Is for guiding heat to the detector 3, and is formed of, for example, a silicon oxide film or a silicon nitride film. Further, the heat transfer column 4 also serves to maintain a constant distance between the absorber 2 and the detector 3. In the first embodiment, the number of the heat transfer columns 4 is five, and the height is about 2 microns. Therefore, absorber 2
The distance between the object and the detector 3 is maintained at 2 microns.

Next, the operation of the infrared sensor element 50 will be described. The infrared light that has entered the absorber 2 is reflected by the reflection layer 10, and a resonance space 13 between the absorber 3 and the reflection layer 10.
And is optically resonated at, and is converted into heat energy. Next, the converted thermal energy is transmitted to the temperature-sensitive layer 7 of the detector 3 via the heat transfer column 4. The transmitted heat energy is converted into an electric signal by the temperature-sensitive layer 7, and the electric signal is processed by a processing circuit (not shown) via the wiring layers 8a and 8b, and then output.

The absorber 2 and the reflection layer 10 correspond to the sensor area 2
Since it is formed so as to cover the area directly above the zero, it is possible to absorb all the infrared rays incident on the sensor area 20, convert it into thermal energy, and detect it. That is, the conversion efficiency of the infrared sensor element 50 is improved by forming the absorber 2 and the reflection layer 10 so as to cover the upper part of the sensor region 20.

The infrared sensor element 50 includes the absorber 2
A resonance space 13 is provided between the infrared sensor element 3 and the detector 3 to reduce the heat capacity of the infrared sensor element 50. By thus reducing the heat capacity, the response of the infrared sensor element 50 can be improved.

Further, since the infrared sensor element 50 has the gap 5 for thermally separating the temperature-sensitive layer 7 from the substrate 1 below the detector 3 having the temperature-sensitive layer 7, the sensor area 2 is provided.
Conduction of the thermal energy received at 0 to the substrate 1 can be suppressed.

When the infrared ray sensor element 50 was examined in detail, the following was found.

(1) First, when the distance between the absorber 2 and the reflection layer 10 was verified, the optical distance between the absorber 2 and the reflection layer 10 was changed to the wavelength of the infrared ray incident on the absorber 2. When it is set to 1/4, it is found that the infrared ray attenuated in the resonance space 13 decreases and the heat energy transmitted to the temperature-sensitive layer 7 increases, so that the conversion efficiency of the infrared sensor element 50 improves.

(2) Next, the thermal conductivity of the heat transfer column 4 was verified. It has been found that the thermal conductivity from the absorber 2 to the detector 3 by the heat transfer column 4 is more than two orders of magnitude higher than the thermal conductivity from the detector 3 to the substrate 1. That is, it was found that the heat transfer column 4 efficiently guides the infrared rays converted into the heat energy to the temperature-sensitive layer 7. Further, it has been found that even with one heat transfer column 4, the thermal conductivity from the absorber 2 to the detector 3 does not decrease. That is, it has been found that an infrared sensor element having a simple structure can be manufactured by using one heat transfer column 4.

(3) Further, the material of the insulator layer forming the absorber was verified. Specifically, an absorber having an upper insulator film made of silicon oxide and a lower insulator film made of silicon nitride was produced, and the infrared conversion characteristics of an infrared sensor element provided with the absorber were verified. In such an absorber, since the internal stresses of the upper insulator film and the lower insulator film are different, distortion occurs in the absorber, and the distance between the absorber and the metal reflection film becomes uneven. Therefore, the conversion efficiency from infrared rays generated between the absorber and the metal reflection film to heat energy is reduced, which adversely affects the response efficiency of the infrared sensor element. From such verification, it has been found that the upper insulator film and the lower insulator film that form the absorber are preferably formed from the same material.

Embodiment 2 FIG. The infrared sensor element 51 according to the second embodiment of the present invention is one in which the detector 3 having the temperature-sensitive layer 7 is formed above the substrate 1 as shown in FIG. The detection body 3 is a support leg 6 formed on the semiconductor substrate 1.
a, 6b to form a floating structure. Detector 3 is substrate 1
, It is not necessary to remove a part of the substrate 1 in order to form the floating structure of the detector 3. The structure of the infrared sensor element 51 is the same as that of the infrared sensor 50 of the first embodiment, except that the detector 3 having the temperature-sensitive layer 7 is formed above the substrate 1.

The infrared sensor element 51 has the same operation and effect as the infrared sensor element 50 of the first embodiment. Further, since there is no area to be removed on the substrate 1 used for the infrared sensor element 51, the surface area of the semiconductor substrate 1 on which various electric circuits and the like can be formed is increased, and the integration degree of the infrared sensor element 51 is increased. Can be improved.

Embodiment 3 In the infrared sensor element 52 according to the third embodiment of the present invention shown in FIG. 4, the gap 5 of the substrate 1 is formed by dry etching. For details,
A groove surrounding the region 5 of the substrate 1 to be removed is formed by anisotropic etching, and an anti-removal film 11 of, for example, silicon oxide is formed to fill the groove. That is, the region 5 of the substrate 1 to be removed is replaced with the removal resistant film 11.
Surround with Further, the substrate 1 is removed by dry etching using, for example, a sulfur fluoride gas or a xenon fluoride gas to form a void 5.

The structure of the infrared sensor element 52 is the same as that of the infrared sensor element of the first embodiment except that the gap 5 is formed by dry etching. By employing dry etching for forming the gap 5, the infrared sensor element 52 can be easily manufactured with good reproducibility.

Embodiment 4 FIG. The infrared sensor element 53 according to the fourth embodiment of the present invention includes, as shown in FIG. 5, an absorber 2a formed only of the insulator film 12, and a detector 3a having a reflective layer 10 on the surface. . That is, the reflection layer 10 is exposed and faces the absorber 2a.

By exposing the metal reflective layer 10 to the surface of the detector 3a as in the case of the infrared sensor element 53, infrared rays received from the absorber 2a are directly reflected by the reflective layer 10, and the absorber 2a and the reflective layer Since optical resonance easily occurs between the infrared sensor element 10 and the optical sensor element 10, the detection sensitivity of the infrared sensor element 53 is improved.

The absorber 2a of the infrared sensor element 53
Is formed only with an insulator layer without using a metal infrared absorption layer. By forming the absorber 2a using only the insulator film, the manufacturing cost of the infrared sensor element 53 can be reduced.

[0039]

According to the infrared sensor element of the present invention, the infrared absorption layer is supported by the detection body including the reflection layer by the heat transfer column, and a resonance space is formed between the infrared absorption layer and the detection body. is there. By providing the resonance space between the infrared absorption layer and the reflection layer as described above, the heat capacity of the infrared sensor element is reduced, so that the detection sensitivity of the infrared sensor element can be improved.

In the infrared sensor element of the present invention, by using one heat transfer column, the structure of the infrared sensor element can be simplified.

In the infrared sensor element of the present invention, by exposing the reflection film so as to face the infrared absorption layer,
Optical resonance can be efficiently generated in the resonance space, and the detection sensitivity of the infrared sensor element can be improved.

In the infrared sensor element according to the present invention, the infrared absorbing layer is formed of the first insulating film, the second insulating film, and the first insulating film.
By using the infrared absorbing metal film sandwiched between the insulator film and the second insulator film, the detection sensitivity of the infrared sensor element can be further improved.

In the infrared sensor element of the present invention, the first
By forming the insulator film and the second insulator film of the same material, the distortion of the absorber is prevented, the distance between the reflective layer and the absorber is stabilized, and the detection sensitivity of the infrared sensor element is improved. Can be done.

In the infrared sensor element of the present invention, the detection sensitivity of the infrared sensor element can be improved by forming the infrared absorbing layer from an insulating film.

In the infrared sensor element of the present invention, the temperature sensitive layer is thermally separated by separating the semiconductor substrate and the temperature sensitive layer by the gap formed in the semiconductor substrate, thereby improving the detection sensitivity of the infrared sensor element. Can be done.

Further, in the infrared sensor element of the present invention,
By supporting the temperature-sensitive layer above the semiconductor substrate with the support legs formed on the semiconductor substrate, the area of the surface of the semiconductor substrate on which various electric circuits can be formed is increased, and the integration of the infrared sensor element is performed. The degree can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an infrared sensor element according to a first embodiment of the present invention.

FIG. 2 shows a top view of the infrared sensor element according to the first embodiment of the present invention.

FIG. 3 is a sectional view of an infrared sensor element according to a second embodiment of the present invention.

FIG. 4 is a sectional view of an infrared sensor element according to a third embodiment of the present invention.

FIG. 5 is a sectional view of an infrared sensor element according to a fourth embodiment of the present invention.

FIG. 6 shows a cross-sectional view of a conventional infrared sensor element.

FIG. 7 shows a top view of a conventional infrared sensor element.

FIG. 8 shows a cross-sectional view of a conventional infrared sensor element.

[Explanation of symbols]

Reference Signs List 1 semiconductor substrate, 2 absorber, 2a absorber, 3
Detector, 3a Detector, 4 heat transfer column, 5 air gap, 6a support leg, 6b support leg, 7 thermosensitive layer, 9
Metal infrared absorbing film, 10 reflecting layer, 12a upper insulating film, 12b lower insulating film, 13 resonance space,
14 Insulator film.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takanori Sone 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term in Mitsubishi Electric Corporation (reference) 2G065 AA04 AB02 AB03 BA12 BA32 CA13

Claims (8)

[Claims] 1. A temperature-sensitive layer provided on a semiconductor substrate at a distance from the semiconductor substrate by using supporting legs, and a reflection layer provided on the temperature-sensitive layer at a predetermined distance from each other and facing each other. An infrared sensor element comprising a layer and an infrared absorbing layer, wherein the infrared sensor optically resonates infrared light between the infrared absorbing layer and the reflective layer, and detects the infrared light as heat in the temperature-sensitive layer, At least one heat transfer column is used to support the infrared absorption layer on the reflection layer so that a resonance space is formed between the infrared absorption layer and the reflection layer, and the reflection layer and the temperature-sensitive layer An infrared sensor element wherein the layers are joined via an insulating film. 2. The infrared sensor element according to claim 1, wherein the number of the heat transfer columns is one. 3. The method according to claim 1, wherein the reflection layer is exposed so as to face the infrared absorption layer.
The infrared sensor element as described in the above. 4. The infrared absorbing layer comprises: a first insulator film;
4. The method according to claim 1, further comprising a second insulator film and a metal infrared absorbing film sandwiched between the first insulator film and the second insulator film. Infrared sensor element. 5. The infrared sensor element according to claim 4, wherein said first insulator film and said second insulator film are made of the same material. 6. The infrared sensor element according to claim 1, wherein the infrared absorption layer is made of an insulating film. 7. The infrared sensor element according to claim 1, wherein the semiconductor substrate and the temperature-sensitive layer are separated from each other by a gap formed in the semiconductor substrate. 8. The semiconductor device according to claim 1, wherein the temperature-sensitive layer is supported above the semiconductor substrate by the support legs formed on the semiconductor substrate. Infrared sensor element.