JP3309957B2 - 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 an infrared detecting element for detecting a temperature change by using infrared light as heat and detecting a temperature change with a resistance temperature detector. The present invention relates to an infrared detecting element having low resistance.

[0002]

2. Description of the Related Art As a conventional infrared detecting element, there is a bolometer and the like. The bolometer converts infrared rays into heat by absorbing the infrared rays, and detects a temperature change using a resistance temperature detector to detect the infrared rays.

In order to increase the temperature change and improve the detection sensitivity, it is necessary to increase the infrared light receiving area.

However, in a conventional infrared detecting element having a structure in which a resistance thermometer is formed on a substrate, the light receiving area for receiving infrared light is the area of the resistance thermometer. Increasing the size increases the light receiving area, but at the same time increases the thermal conductance and heat capacity of the resistance temperature detector, resulting in a slow response speed.

Therefore, the area of the RTD is reduced to reduce the thermal conductance and the heat capacity, and a focusing means such as a lens is provided. The incident infrared light is focused on the RTD to change the temperature. It is devised to increase the size.

FIG. 5 is a sectional view showing an example of such a conventional bolometer. In FIG. 5, reference numerals 1 and 7 denote disc-shaped and cylindrical metal containers for accommodating bolometers, 2 denotes a substrate made of Si or the like, 3 denotes a temperature measuring resistor such as a thermistor which is an infrared absorber, 4a, 4b, 6a. And 6b are electrodes, 5a and 5b are internal wirings, 8 is a lens, and 100 is incident infrared light.

A temperature measuring resistor 3 such as a thermistor, which is an infrared absorber, is formed on a substrate 2 made of Si or the like, and electrodes 4 made of aluminum or the like are formed on both ends of the temperature measuring resistor 3 on the substrate 2.
a and 4b are formed.

The substrate 2 is fixed to the center of the disk-shaped container 1 and the electrodes 4a and 4b formed on the substrate 2 are provided on the container 1 by internal wirings 5a and 5b.
a and 6b.

On the other hand, a lens 8 is fixed to one opening of the cylindrical container 7, and the focal point of the lens 8 is
The other opening of the container 7 is fixed to the container 1 while aligning the optical axis so as to coincide with the above.

Now, the operation of the conventional example shown in FIG. 5 will be described. The incident infrared light 100 is condensed by the lens 8 on the temperature measuring resistor 3 which is an infrared absorber. Therefore, the temperature measuring resistor 3, which is an infrared absorber, absorbs the infrared light and converts the infrared light into heat, and this temperature change is output as a resistance value change.

The change in the resistance is measured by the electrode 4a and the internal wiring 5a.
In addition, infrared rays can be detected by taking out through the electrodes 6a and 4b, the internal wiring 5b and the electrode 6b.

As a result, the area of the resistance thermometer is reduced to reduce the thermal conductance and the heat capacity, and the incident infrared rays are condensed on the resistance thermometer as an infrared absorber by using the lens 8 as the light condensing means. As a result, the detection sensitivity can be improved without sacrificing the response speed.

[0013]

However, since the object to be detected is infrared light, the lens 8 used as the light condensing means must transmit the infrared wavelength region. Generally, a lens that transmits the infrared wavelength region is expensive. There was a problem that production was difficult.

In addition, there is a problem that the transmittance and the refractive index of the material of the lens 8 have wavelength dependence in the infrared wavelength region, so that the infrared detection element itself has wavelength dependence.

Further, when the container 1 and the container 7 are fixed, it is necessary to work while adjusting the optical axis so that the focal point of the lens 8 coincides with the resistance temperature detector 3, so that production is not easy. There was the problem I mentioned. Accordingly, an object of the present invention is to realize an infrared detecting element which is easy to manufacture and has little wavelength dependence in an infrared wavelength region.

[0016]

In order to achieve the above object, according to the first aspect of the present invention, an infrared light is heated by an infrared absorber and the temperature change is measured by a temperature measuring resistor. In the infrared detecting element, a first substrate in which a concave which is a concave curved surface is formed and a first reflective film is formed in the concave portion, and an insulating film is formed, and a temperature measuring resistor is formed on the insulating film. Are formed and electrodes are formed at both ends of the resistance temperature detector on the insulating film, and a second reflection is formed in a concave of a curved surface formed on a side opposite to a side on which the insulating film is formed.
Forming a film, and the reflected light from the second reflection film is used for measuring the temperature.
A second substrate adapted to be incident on the resistor ,
Since the first and second substrates are joined so that the focal point of the concave mirror constituted by the first reflection film coincides with the resistance temperature detector, the production is easy and the wavelength dependence in the infrared wavelength region is improved. It is possible to realize an infrared detecting element having low resistance.

According to a second aspect of the present invention, in the infrared detecting element according to the first aspect of the present invention, a part of the insulating film is deleted to form a beam and the temperature measuring resistor is formed. By using an air bridge structure supported in the air by the beams, it is possible to improve the response speed.

[0018]

[0019]

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing the configuration of an embodiment of the infrared detecting element according to the present invention.

In FIG. 1, reference numerals 9 and 14 denote substrates such as Si,
10 is a reflection film, 11 is a bonding surface, 12a and 12b are electrodes, 13 is an insulating film such as SiO ₂ , 15 is a temperature measuring resistor which is an infrared absorber, 16a and 16b are antireflection films,
0a is incident infrared light.

A depression having a concave curved surface as shown in FIG. 1A is formed in the substrate 9, and a reflection film 10 is formed in the depression. The focal point of the concave mirror constituted by the reflection film 10 is formed so as to be located at the upper end and the center of the substrate 9.

An insulating film 13 is formed on the substrate 14, and a resistance temperature detector 15 is formed on the insulating film 13. Electrodes 12a and 12b are formed on the insulating film 13 and at both ends of the resistance temperature detector 15 with a metal such as aluminum.

On the other side of the substrate 14 on the side opposite to the side on which the insulating film 13 and the like are formed, and on the back side of the resistance temperature detector 15, there is provided a cylindrical hollow as shown in FIG. The anti-reflection films 16a and 16a are provided on the surface of the substrate 14 which is formed and the bottom of the dent and the side opposite to the side where the insulating film 13 and the like are formed.
6b is formed.

Finally, the insulating film 13 on the substrate 9 and the substrate 14
The electrodes 12a and 12b are joined at the joining surface 11 to be integrated. At this time, the focal point of the concave mirror constituted by the reflection film 10 is set at the temperature measuring resistor 15 formed on the substrate 14.
Is adjusted so that

Here, the operation of the embodiment shown in FIG. 1 will be described. In the infrared detecting element, the area of the temperature measuring resistor 15 which is an infrared absorber is made as small as possible, and the electrodes 12a and 12b are made as thin as possible so as not to increase the wiring resistance, thereby reducing the thermal conductance and the heat capacity.

In this state, the incident infrared light 100a passes through the antireflection film 16a and the insulating film 13 and is incident on the reflection film 10. The incident infrared light 100a incident on the reflection film 10 is reflected and condensed on the temperature measuring resistor 15 which is the focal point of the concave mirror formed by the reflection film 10.

That is, the incident infrared light 100a once transmitted through the insulating film 13 is reflected by the reflective film 10 and is incident on the opposite side to the incident direction, in other words, from the rear side of the resistance temperature detector 15.

For this reason, the temperature measuring resistor 15 which is an infrared absorber absorbs infrared rays on both surfaces thereof, thereby converting the infrared rays into heat, and this temperature change is output as a resistance value change. By extracting this change in the resistance value through the electrodes 12a and 12b, infrared rays can be detected.

As a result, the area of the temperature measuring resistor 15 which is an infrared absorber is made as small as possible, and the electrodes 12a and 12b are made as thin as possible so as not to increase the wiring resistance, thereby reducing the thermal conductance and the heat capacity. By condensing the incident infrared light 100a transmitted by the concave mirror constituted by the reflection film 10 from the back surface of the resistance temperature detector 15 as a light condensing means, the detection sensitivity can be improved without sacrificing the response speed. Will be possible.

Further, since it is not necessary to use a lens which is expensive and difficult to align the optical axis as in the conventional example, the production becomes easy. Furthermore, since a lens having wavelength dependency in the infrared wavelength region is not used, the wavelength dependency of the infrared detecting element is reduced.

Here, the manufacturing method of the embodiment shown in FIG. 1 will be further described with reference to FIGS. 2 and 3 are process diagrams showing the manufacturing process of the embodiment, and the reference numerals in the drawings are the same as those in FIG.

In the step shown in FIG. 2A, an insulating film 13 transmitting the infrared wavelength region is formed on the substrate 14, and the measurement is performed on the insulating film 13 formed earlier in the step shown in FIG. The thermal resistor 15 is formed. At this time, the area of the resistance temperature detector 15 is made as small as possible to reduce the thermal conductance and the heat capacity.

In the step shown in FIG. 2C, electrodes 12a and 12b are formed at both ends of the resistance temperature detector 15 on the insulating film 13 by using aluminum or the like. At this time, the electrode 12
a and 12b are made as thin as possible without increasing the wiring resistance.

In the step shown in FIG. 2D, a cylinder as shown in "b" in FIG. 2 is provided on the back side of the resistance bulb 15 opposite to the side on which the insulating film 13 and the like of the substrate 14 are formed. A concave is formed by etching or the like.

Further, in the step shown in FIG. 2E, anti-reflection films 16a and 16b are formed on the bottom portion of the dent indicated by "b" in FIG.
To form

On the other hand, as shown in FIGS. 3 (a), 3 (b), 3 (c) and 3 (d), the substrate 9 is sequentially processed by etching or the like with a plurality of mask patterns in each step.
A concave is formed as a concave curved surface as shown in “a”.

Then, in the step shown in FIG. 3E, a reflection film 9 is formed in the recessed portion shown by "A" in FIG. At this time, the focal point of the concave mirror constituted by the reflection film 10 is formed so as to be located at the upper end and the center of the substrate 9.

In the last step, the focal point of the concave mirror formed by the reflection film 10 becomes the temperature measuring resistor 15 formed on the substrate 14 with the substrate 14 and the substrate 9 formed in the respective steps of FIGS. In this way, by aligning with an aligner and joining them together using a joining furnace or the like, an infrared detecting element as shown in FIG. 1 can be manufactured. At this time, since the bonding surface 11 between the substrate 14 and the substrate 9 is flat at the mirror level, Si and Si are strongly bonded via oxygen.

As a result, through the steps shown in FIGS. 2 and 3, the infrared detecting element shown in FIG. 1 can be manufactured.

In the embodiment shown in FIG. 1, if only the incident infrared light 100a incident from the vertical direction is condensed on the resistance bulb 15, the incident angle of the incident infrared light 100a is limited. Therefore, by providing a spectral unit such as an interference filter in front of the infrared detecting element, it is possible to use the detector as a detector for measuring the spectral intensity.

In the embodiment shown in FIG. 1, the antireflection film 16b is not formed on the surface of the substrate 14 on the side opposite to the side on which the insulating film 13 and the like are formed. .

FIG. 4 is a sectional view showing the structure of an embodiment of another infrared detecting element according to the present invention. In FIG. 4, reference numerals 9 to 11, 12a, 12b and 15 denote the same reference numerals as in FIG. 1, 13a denotes an insulating film, 14a denotes a substrate of Si or the like,
Reference numeral 17 denotes a reflection film, and 100b denotes incident infrared light.

The structure of the substrate 9 is the same as that of the embodiment shown in FIG. 1, and the structure of the substrate 14a is the same as that of FIG.
This is almost the same as the embodiment shown in FIG. However, the difference is that a part of the insulating layer 13a is removed by patterning to form several beams, and the insulating film 13a on which the resistance temperature detector 15 is formed.
Is an air bridge structure supported in the air by the beams.

Further, the substrate 14a is not a cylindrical depression as shown by "b" in FIG. 1, but is continuous with a depression having a concave curved surface as shown by "a" in FIG. The point is that a concave of a curved surface is formed, and the reflection film 17 is formed in this concave. At this time, the incident infrared light 100 b reflected by the reflection film 17 is formed so as to be incident on the resistance bulb 15.

The operation of the embodiment shown in FIG. 4 will now be described. Since the insulating film 13a on which the resistance temperature detector 15 is formed has an air bridge structure, heat conductance and heat capacity are reduced.

In addition to the incident infrared light transmitted through the insulating film 13 as compared with the embodiment shown in FIG.
By condensing the incident infrared light 100b on the front surface of the temperature measuring resistor, the temperature change can be increased.

As a result, the area of the temperature measuring resistor 15 which is an infrared absorber is made as small as possible, and the electrodes 12a and 12b are made as thin as possible so as not to increase the wiring resistance, and are formed into an air bridge structure, so that the thermal conductance and the like are reduced. The response speed and the detection sensitivity can be improved by reducing the heat capacity and condensing the incident infrared light 100b from both surfaces of the resistance temperature detector 15 by the reflection films 10 and 17 as the light condensing means. .

[0049]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. According to the first aspect of the present invention, the area of the temperature measuring resistor which is an infrared absorber is made as small as possible, and the electrodes are made as thin as possible so as not to increase the wiring resistance, so that the heat conductance and heat capacity are reduced and the electrodes are collected. The incident infrared light transmitted by the concave mirror constituted by the first reflection film is condensed from the back surface of the resistance temperature detector as the light means, and the incident infrared light is reflected by the second reflection film by the resistance temperature detector.
The by condensing, production is easy, can be realized depends on the wavelength less infrared detector of the infrared wavelength region, detected
Sensitivity can be improved.

According to the second aspect of the present invention, the area of the temperature measuring resistor which is an infrared absorber is made as small as possible, and the electrodes are made as thin as possible so that the wiring resistance is not increased, and the air bridge structure is used. In addition, the thermal conductance and the heat capacity are reduced, and the incident infrared light transmitted by the concave mirror constituted by the first reflecting film is condensed on the temperature measuring resistor as a condensing means, and the incident infrared light is condensed by the second reflecting film. To the RTD
Lighting makes it possible to improve the response speed.

[0051]

[0052]

[Brief description of the drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of an infrared detecting element according to the present invention.

FIG. 2 is a process chart showing a manufacturing process of an example.

FIG. 3 is a process chart showing a manufacturing process of the example.

FIG. 4 is a sectional view showing the configuration of an embodiment of another infrared detecting element according to the present invention.

FIG. 5 is a sectional view showing an example of a conventional bolometer.

[Explanation of symbols]

 1,7 container 2,9,14,14a substrate 3,15 resistance temperature detector 4a, 4b, 6a, 6b, 12a, 12b electrode 5a, 5b internal wiring 8 lens 10,17 reflective film 11 bonding surface 13,13a insulation Film 16a, 16b Anti-reflection film 100, 100a, 100b Incident infrared light

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-229821 (JP, A) JP-A-63-108762 (JP, A) JP-A-7-318420 (JP, A) JP-A-9-209 218088 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01J 1/00-1/60 G01J 5/00-5/62

Claims (2)

(57) [Claims] 1. An infrared detecting element for converting infrared light into heat by an infrared absorber and detecting a temperature change thereof by a temperature measuring resistor, wherein a concave which is a concave curved surface is formed, and a first reflective film is formed in the concave portion . An insulating film is formed on the formed first substrate, a temperature measuring resistor is formed on the insulating film, and electrodes are formed on the insulating film at both ends of the temperature measuring resistor; A second reflective film is formed in a concave portion of a curved surface formed on the side opposite to the side on which the insulating film is formed , and
The reflected light from the second reflective film is incident on the resistance temperature detector.
And a second substrate bonded to the first and second substrates such that a focal point of a concave mirror formed of the first reflection film coincides with the temperature measuring resistor. Infrared detecting element. 2. An air bridge structure in which a part of the insulating film is removed to form a beam, and the insulating film on which the temperature measuring resistor is formed is supported in the air by the beam. The infrared detecting element according to claim 1.