JP3109480B2 - Thermal infrared detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal infrared detecting element having a thermal isolation structure.

[0002]

2. Description of the Related Art In a thermal infrared detecting element, the temperature of the detecting section rises when the detecting section receives infrared rays, whereby the resistance value of the detecting section changes. By detecting the change in the resistance value, infrared rays are detected. In the case of a thermal infrared detecting element, in order to increase the sensitivity, it is necessary to increase the temperature rise of the detecting section due to the reception of infrared light.
Conventionally, in order to increase the detection sensitivity, there has been proposed a method of thermally separating a detection unit constituting a thermal infrared detection element from other elements to increase a temperature rise width of the detection unit.

For example, Japanese Patent Application Laid-Open No. 5-172630 discloses a configuration in which an insulating layer is laminated on a substrate, and an infrared detector is further laminated thereon. A proposal has been made in which a space portion for improving thermal separation is formed, and a plurality of metal wires are provided for reinforcing the support of the infrared detection unit by the formation of the space portion.

[0004] In addition, there has been proposed a thermal infrared detecting element which enhances thermal isolation by supporting a detecting section with two beams (for example, Radford et a).
l. : SPIE Vol. 2746, 1996, p.
82, Wada et al. : SPIE Vol.
3224, 1997, p. 82).

FIGS. 4 and 5 show plan views of a thermal infrared detecting element of the type in which this detecting portion is supported by two beams.
FIG. 6 is a cross-sectional view taken along line D-D in FIG. 4.

[0006] As shown in FIG. 4, the diaphragm 30, which is an infrared detecting unit, projects from the diaphragm 30 and is held by two beams 32 extending to a bank 36. Electrode 24 of the diaphragm 30 is electrical wiring in the contact 35 3
4 is connected.

As shown in FIGS. 5 and 6, the substrate 2
Banks 36 are formed on both sides of the upper surface of the substrate 2, and a complete reflection film 21 that reflects infrared rays is laminated on the upper surface of the substrate 22 sandwiched between the banks 36. A diaphragm 30 is provided above the substrate 22 through a cavity 29. The diaphragm 30 and the bolometer thin film 25 having electrodes 2 4 on each side, the protective film 36 is formed so as to cover them, it consists of an infrared absorbing film 37 is laminated on the upper surface of the protective film 36 I have.

The outline of infrared detection of the conventional thermal infrared detecting element shown in FIGS. 4 to 6 will be described below.

When the infrared ray 31 is applied to the infrared ray absorbing film 37, a part of the infrared ray is supposed to be reflected on the surface, and the rest is almost transmitted through the diaphragm 30 and is reflected by the perfect reflecting film 21 in the direction of the infrared ray absorbing film 37. This reflection component causes interference that cancels out infrared rays that are going to be reflected on the surface of the absorption film, and is absorbed by free carriers in the infrared absorption film 37. With such an infrared absorption mechanism, the temperature of the diaphragm 30 rises and the resistance value of the bolometer thin film 25 changes. The change in the resistance value is measured by the electrode 24, the contact 3
Infrared by detecting through 5 and electrical wiring 34 31
Will be detected.

At this time, in order to increase the sensitivity of infrared detection,
It is necessary to enhance the thermal separation of the bolometer thin film 25. For this reason, while being thermally insulated by the hollow portion 29 between the substrate 22 and the diaphragm 30, the diaphragm 30 is supported by two beams 32 in order to reduce heat escape to the bank 36 by direct heat conduction. ing.

As described above, the conventional thermal infrared detecting element is intended to enhance the thermal separation between the diaphragm 30 and the bank 36.

[0012]

However, in the above-mentioned conventional example in which an insulating layer is laminated on a substrate, and an infrared detector supported by a plurality of metal wires is further laminated thereon, There has been a problem in that thermal separation properties are not so improved because a plurality of metal wires serve as escape paths for heat from the infrared detecting section to the substrate.

[0013] Further, even in the conventional example of the type in which the diaphragm serving as the infrared detecting unit is supported by two beams, not only the heat separation property is still insufficient because heat escapes to the bank through a plurality of beams. In addition, there is a problem that the area occupied by the diaphragm is reduced due to the presence of the plurality of beams, and the fill factor is reduced.

Accordingly, the first object of the present invention is to provide a thermal infrared detecting element having high thermal separation. A second object is to provide a thermal infrared detecting element having a high fill factor.

[0015]

In order to achieve the above-mentioned object, a thermal type infrared detecting element of the present invention comprises an infrared ray absorbing infrared ray.
It has a line absorbing film and one electrode at each end.
A bolometer thin film for detecting infrared rays, and the bolometer
Infrared including a thin film and an insulating protective film surrounding each of the electrodes
In the thermal type infrared detecting element having the line light receiving section, two
A first electrical wiring, which is disposed below the infrared receiving section;
Substrate, and the substrate and the infrared receiver are connected to each other.
A beam, and the beam is connected to the two first electric
Two wires for electrically connecting the wiring and each of the electrodes
It has a second electric wiring.

In the thermal infrared detecting element of the present invention configured as described above, the infrared receiving section is supported by only one beam with respect to the substrate. The path through which the heat escapes to the substrate is only the one beam described above.

The beam connects at least two second electric wires.
And the upper layer of two second electrical wirings is 2
Of One electrode is connected to one electrode, of the two second electric wiring lower layer has two electrodes, may be one connected to the other electrode, also, the two electrodes, the bolometer thin film May be provided on the upper surface of one end and the lower surface of the other end.

Further, a cavity layer may be formed between the infrared ray receiving section and the substrate, or the substrate may have a bank portion including two first electric wirings, and one beam may be provided. It may be supported by a bank.

[0019]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of the thermal infrared detecting element of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. 3 is a sectional view taken along line BB of FIG. Are respectively shown.

As shown in FIG. 1, the diaphragm 10
It is held by a single beam 12 extending from the diaphragm 10 through a base 13 and extending to a bank 16. The electrodes 4 a and 4 b of the diaphragm 10 are
Through the gas line 17a, the 17b, contact 15 a, 15
b In electrical wiring 14 a, are connected to 14b. A slit 8 is formed between the diaphragm 10 and the beam 12 and the bank 16.

As shown in FIGS. 2 and 3, banks 16 are formed on both sides of the upper surface of the substrate 2 which is a heat sink, and the upper surface of the substrate 2 sandwiched between the banks 16 has a complete reflection of infrared rays. The reflection film 1 is laminated. Bank 16 has electrical wiring 14 a, 14b of the two-layer structure therein.

A diaphragm 10 is provided above the substrate 2 via a cavity 9. This diaphragm 10
Is provided with an electrode 4a on the upper surface of one end of the bolometer thin film 5.
Except that the electrode 4b is provided on the lower surface of the other end.
Structure and function, ie, insulating protective film 6 and infrared ray
The structure and function of the absorbing film 7 are the same as those of a conventional diaphragm.
Is the same as

Two electric wires 17a, 17 passing through the beam 12
b is part of the beam 12 of the multi-layer structure, so are arranged at an interval in the vertical direction, and has a so as not to occupy as much as possible the width of the lateral direction arrangement.

When the infrared ray 11 is applied to the infrared ray absorbing film 7 from above the thermal infrared ray detecting element of the present invention, a part of the infrared ray absorbing film 7 tends to be reflected on the surface, and the rest almost passes through the diaphragm 10 and is completely reflected by the completely reflecting film 1. The light is reflected in the direction of the infrared absorbing film 7. This reflection component causes interference that cancels out infrared rays that are going to be reflected on the surface of the absorption film, and is absorbed by free carriers in the infrared absorption film 7. With such an infrared absorption mechanism, the temperature of the diaphragm 10 rises and the resistance value of the bolometer thin film 5 changes. The change in resistance value, and thus to detect the infrared 11 electrodes 4 a, 4b, the contact 1 5 a, 15b, electric wires 1 7a, 17b, electric wires 14a, 14b, by detecting through.
The electrodes 4a and 4b, the contacts 15a and 15b,
Air wiring 17a, 17b, electric wiring 14a, 14b,
Those with the same subscript are electrically connected to each other
Things.

At this time, in order to increase the sensitivity of infrared detection,
It is necessary to enhance the thermal separation of the bolometer thin film 5.
Therefore, the cavity 9 between the substrate 2 and the diaphragm 10
In order to reduce heat escape due to heat conduction directly to the bank 16, the diaphragm 10
Are supported by one beam 12.

Due to the above configuration, the thermal infrared detecting element of the present invention has one beam 12 and the beam 12 compared to the conventional diaphragm 30 supported by two beams 32.
Of the diaphragm 1
The amount of heat escaping from the heat conduction from zero to the bank 16 becomes extremely small, and the occupied area of the diaphragm 10 can be increased.

[0028]

Next, examples of the embodiment of the present invention will be described below.

An embodiment of the present invention will be described below with reference to FIG. (First embodiment) pixel size L1 is 50μm square, transverse dimension L2 is 45 [mu] m of the diaphragm 10, the longitudinal dimension L3 is 45 [mu] m, a width L4 of the beam 12 is 2 [mu] m, the width L5 of the slits 8 is 0.5 [mu] m, electricity < The thermal type infrared detecting element was manufactured by setting the width L6 of the wirings 17a and 17b to 1 μm. In this case, the fill factor is set to a conventional value (Wada et al .: SPIE Vol.
3224, 1997, p. 40) 51% to 81%
Can be increased to (1.6 times), a t h ermal conductance is indicative of thermal isolation simultaneously 0.
It could be improved from 2 μW / K to 0.15 μW / K (0.75 times). As a result, the sensitivity of the thermal infrared detecting element could be improved twice as compared with the conventional element. Second Embodiment A pixel size L is 30 μm square, a horizontal dimension L2 of the diaphragm 10 is 25 μm, a vertical dimension L3 is 25 μm, and a width L of the beam 12.
4 is 1.5 μm, the width L5 of the slit 8 is 0.5 μm,
A thermal infrared detecting element was manufactured by setting the width L6 of the air wirings 17a and 17b to 0.8 μm. In this case, the fill factor is set to a conventional value (Wada et al .: SPIEV).
ol. 3224, 1997, p. Can be increased from 51% of 40) to 69% (1.35 times), t h ermalconductance is indicative of simultaneous thermal separation
From 0.2 μW / K to 0.15 μW / K (0.75 times)
Could be improved. As a result, the sensitivity of the thermal type infrared detecting element could be improved slightly less than twice as compared with the conventional element.

[0030]

As described above, according to the present invention, since the infrared light receiving portion is supported by only one beam with respect to the substrate, the heat of the infrared light receiving portion generated by the irradiation of the infrared light is applied to the substrate. The only escape route is the one beam mentioned above.
It becomes a thermal type infrared detecting element having high thermal isolation. Further, since there is only one beam, the area occupied by the upper layer substrate for receiving infrared rays can be increased, and the fill factor also increases.

[Brief description of the drawings]

FIG. 1 is a plan view of a thermal infrared detecting element of the present invention.

FIG. 2 is a cross-sectional view taken along line AA of the thermal infrared detecting element of FIG.

FIG. 3 is a cross-sectional view of the thermal infrared detection element of FIG. 1 taken along line BB.

FIG. 4 is a plan view of a conventional thermal infrared detecting element.

5 is a cross-sectional view of the thermal infrared detecting element of FIG. 4 taken along line CC.

FIG. 6 is a cross-sectional view of the thermal infrared detection element of FIG. 4 taken along line DD.

[Explanation of symbols]

1,21 Complete reflection film 2,22 Substrate 4a, 4b , 24 electrode 5,25 Bolometer thin film 6,26 Insulation protection film 8,28 Slit 9,29 Cavity part 10,30 Diaphragm 11,31 Infrared light 12,32 Beam 13 , 33 base 14 a, 14b, 17a, 17b , 34 electrical wirings 15 a, 15b, 35 Contacts 16 and 36 bank

Claims (5)

(57) [Claims] An infrared absorbing film for absorbing infrared light, and both ends
Each part has one electrode to detect the infrared rays
A bolometer thin film, the bolometer thin film and each of the
It has an infrared light receiving section including an insulating protective film surrounding the electrodes
In the thermal type infrared detecting element, under the infrared light receiving portion, which has two first electric wires.
Yes and substrate disposed part, and a one beam connecting the substrate and the infrared receiver
The beam connects the two first electrical wires and the electrodes.
Each having two second electrical wires for electrical connection
A thermal infrared detecting element, characterized in that: 2. The beam according to claim 2, wherein at least the two second beams are provided.
A multi-layer structure including electric wiring, wherein the two second electric
The upper layer of the wiring is connected to one of the two electrodes
The lower layer of the two second electric wirings is
The heat according to claim 1, wherein the heat is connected to the other of the poles.
Type infrared detecting element. 3. The bolometer thin film according to claim 2, wherein said two electrodes are
On the upper surface at one end and the lower surface at the other end.
3. The thermal infrared detecting element according to claim 1 or 2. 4. An empty space between the infrared receiving section and the substrate.
4. The method according to claim 1, wherein a sinus layer is formed.
4. A thermal infrared detecting element according to claim 1. 5. The semiconductor device according to claim 1, wherein the substrate includes the two first electric wirings.
And the one beam is supported by the bank.
The thermal red according to any one of claims 1 to 4, wherein
Outside line detection element.