JPH0989655A - Infrared detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared detection apparatus in which an offset voltage is reduced and which uses a thermopile. SOLUTION: A thin film 8 is formed on the surface of a semiconductor substrate 7. In addition, a first recessed part 9 and a second recessed part 9b are formed so as to be passed through the semiconductor substrate 7, and a first thin-film part 8a and a second thin-film part 8b constitute ceiling parts of the first and second recessed parts 9a, 9b. In addition, a first metal 1 and a second metal 2, in a plurality of pieces, which are provided with the Seebeck effect are formed on the thin film 8. At this time, one end of the first metal 1 is bonded to the second metal 2 at a hot junction 3 on the first thin-film part 8a, and the other end is bonded to the second metal 2 at a cold junction 4 on the second thin-film part 8b. Then, the first and second metals 1, 2 in the plurality of pieces are connected alternately in series so as to be meandered in an S-shape, and a thermopile 10 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detector using a thermopile.

[0002]

2. Description of the Related Art Conventionally, an infrared detecting device using a thermopile having a structure as shown in FIG. 6 has been known. Such an infrared detector has a semiconductor substrate 7, a thin film 8 formed on the upper surface of the semiconductor substrate 7, a recess 9 provided through the semiconductor substrate 7, and a Seebeck effect formed on the thin film 8. First and second metals 1 and 2 having, and recess 9
And a diode 15 for temperature compensation provided on the upper surface of the thin film 8 on the outside.

Here, one end of the first metal 1 is connected to a second metal 2 formed in parallel with the first metal 1 by a hot junction 3 formed on the thin film 8 above the recess 9. , The other end is a cold junction 4 formed on the thin film 8 outside the recess 9,
It is connected to another second metal 2 which is also formed parallel to the first metal 1. Thus, the plurality of first and second metals 1 and 2 are alternately connected in series so as to meander in an S shape, and a thermopile is formed. Also,
Both ends of the plurality of first and second metals 1 and 2 connected in series are connected to the terminal 6 via the wiring 5.

At this time, when the thin film 8 receives infrared light from the object to be measured, the temperature of the hot junction 3 formed on the thin film 8 above the recess 9 rises in proportion to the amount of infrared light received. on the other hand,
Since the temperature of the cold junction 4 formed on the thin film 8 other than the thermally stable concave portion 9 does not fluctuate, a temperature difference occurs between the hot junction 3 and the cold junction 4, and a plurality of first and second cold junctions are formed. 2 metal 1,2
In the meantime, a thermoelectromotive force proportional to this temperature difference is generated. Thus, the sum of this thermoelectromotive force is output as the output voltage of the thermopile.

Since the amount of infrared rays received by the thin film 8 from the object to be measured is proportional to the difference between the absolute temperature of the object to be measured and the absolute temperature of the thin film 8 to the fourth power, the infrared radiation amount of the object to be measured is detected. In order to achieve this, the thin film 8 other than the concave portion 9 which becomes the reference temperature
It is necessary to detect the temperature of. Therefore, the infrared radiation amount of the object to be measured is measured from the output voltage of the thermopile and the temperature of the thin film 8 other than the recess 9 detected from the temperature characteristic of the forward voltage of the diode 15.

[0006]

In the infrared detecting device having the above structure, even if the thermopile formed of the plurality of first and second metals on the thin film does not receive infrared rays from the object to be measured. The temperature of the thin film above the recess rises due to infrared rays received from other than the object to be measured, and a slight temperature difference occurs between the thin film above the recess and the thin film other than the recess.This temperature difference causes an offset voltage to the thermopile. There was a problem that occurs.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an infrared detecting device in which the offset voltage of the thermopile is reduced.

[0008]

In order to achieve the above object, the present invention provides a thin film formed on the upper surface of a semiconductor substrate, and a thin film which constitutes a part of the thin film and is thermally coupled to each other. Insulated first and second thin film portions, a thermopile in which thermocouples are formed in series in an array on the thin film, a thermopile hot junction formed on the first thin film portion, and a second thin film It has a thermopile cold junction formed on the part, and since the thermopile hot junction and cold junction are both formed on the thin film portion having the same heat capacity, if infrared rays are not received from the DUT, The hot junction and cold junction have the same temperature, no thermoelectromotive force is generated, and no offset voltage is output.

According to a second aspect of the invention, the thin film formed on the upper surface of the semiconductor substrate, the first and second thin film portions forming a part of the thin film and thermally insulated from each other, and the thermoelectric film on the thin film, respectively. First and second thermopiles in which pairs are formed in series in an array and connected in opposite polarities, cold junctions of the first thermopile formed on the first thin film portion, and on the second thin film portion A hot junction of the second thermopile formed in, and a hot junction of the first thermopile and a cold junction of the second thermopile formed on a thin film other than the first and second thin film portions, When the thin film portion does not receive infrared rays from the object to be measured, since the first and second thermopiles are connected with opposite polarities, the thermoelectromotive forces generated in the first and second thermopiles are offset and offset. No voltage is output.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the first and second thin film portions are provided with light shielding means for alternately and periodically blocking infrared rays received from the object to be measured. Therefore, the output signal of the thermopile becomes an AC signal, and the noise component and offset voltage included in the output signal of the thermopile can be easily removed by using a filter or the like. According to a fourth aspect of the present invention, in the first or second aspect of the invention, the first and second thin film portions are different from each other in that the first and second DUTs are different from each other. Since the means is provided, the difference between the infrared ray amounts of the first and second DUTs can be detected from the output signal of the thermopile without contact.
Here, that the light collecting means causes the first and second thin film portions to receive infrared rays from different first and second DUTs, respectively.
The state in which the condensing means causes the infrared rays from the first object to be measured to be received only by the first thin film portion and the infrared rays from the second object to be measured be received only by the second thin film portion.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 shows the structure of an infrared detector according to this embodiment. Such an infrared detection device has a semiconductor substrate 7
A thin film 8 formed on the semiconductor substrate 7, and first and second recesses 9a and 9b provided through the semiconductor substrate 7.
And a part of the thin film 8 to form the first and second recesses 9 respectively.
First and second thin film portions 8a, 8 forming a ceiling portion of a, 9b
b, and the first and second metals 1 and 2 having the Seebeck effect formed on the thin film 8.

Here, one end of the first metal 1 is connected to the second metal 2 formed in parallel with the first metal 1 at the hot junction 3 on the first thin film portion 8a, and the other end thereof. Is a cold junction 4 on the second thin film portion 8b, which is also connected to another second metal 2 formed in parallel with the first metal 1. Thus,
The plurality of first and second metals 1 and 2 are alternately connected in series so as to meander in an S shape, and a thermopile 10 is formed. Further, both ends of the plurality of first and second metals 1 and 2 connected in series are connected to the terminal 6 via the wiring 5.

At this time, the first and second thin film portions 8a, 8b
When the infrared ray is received, the first and second thin film portions 8a, 8
The temperature of b rises in proportion to the amount of received infrared rays. Therefore, in each of the plurality of first and second metals 1 and 2,
Due to the Seebeck effect, a thermoelectromotive force proportional to the temperature difference between the first thin film portion 8a and the second thin film portion 8b is generated, and the sum of the thermoelectromotive force becomes the output voltage of the thermopile 10. Here, since the heat capacities of the first and second thin film portions 8a and 8b are equal, the temperature difference between the two is proportional to the difference in the amount of infrared rays received. Therefore, the difference in the amount of infrared rays received by the first and second thin film portions 8a and 8b can be detected from the output voltage of the thermopile 10.

On the other hand, the first thin film portion 8a and the second thin film portion 8
When b does not receive infrared rays from the object to be measured, the heat capacities of the first and second thin film portions 8a and 8b are equal to each other.
And the temperatures of the second thin film portions 8a and 8b become equal. Therefore, since there is no difference in temperature between the hot junction 3 provided on the first thin film portion 8a and the cold junction 4 provided on the second thin film portion 8b, the first and second metals 1 and 2 are not separated. No thermoelectromotive force is generated at each junction, and no offset voltage of the thermopile 10 is generated.

In this embodiment, the junction of two kinds of metals having the Seebeck effect is formed on the thin film 8, but a plurality of PN junctions may be formed in series. (Embodiment 2) FIG. 2 shows the configuration of the infrared detector of this embodiment. This infrared detection device includes a semiconductor substrate 7, a thin film 8 formed on the semiconductor substrate 7, first and second recesses 9a and 9b provided through the semiconductor substrate 7, and a part of the thin film 8. To form the first and second recesses 9a and 9a, respectively.
first and second thin film portions 8a and 8b forming a ceiling portion of b,
It is composed of first and second thermopiles 10a and 10b made of the first and second metals 1 and 2 having the Seebeck effect, which are formed on the first and second thin film portions 8a and 8b, respectively.

Here, one end of the first metal 1 formed on the first thin film portion 8a is connected to the second metal 2 at the first hot junction 3a formed on the first thin film portion 8a. Connected,
The other end is connected to another second metal 2 by a first cold junction 4a formed on the thin film 8 other than the first and second thin film portions 8a and 8b. Thus, the n first and second metals 1 and 2 are alternately connected in series so as to meander in an S shape, and the first thermopile 10a is formed. Similarly, the first thin film portion 8b formed on the second thin film portion 8b
One end of the metal 1 is connected to the second metal 2 by the second hot junction 3b formed on the thin film 8 other than the first and second thin film portions 8a and 8b, and the other end is 2 thin film portion 8b
It is connected to another second metal 2 by the second cold junction 4b formed above. Thus, the n first and second metals 1 and 2 are alternately connected in series so as to meander in an S shape, and the second thermopile 10b is formed.

At this time, the first and second thermopile 10
a and 10b are formed from n first and second metals 1 and 2, respectively, and are the first thermopile 10a.
The first metal 1 located at one end of the second thermopile 10b is connected to the second metal 2 located at one end of the second thermopile 10b. Thus, the first and second thermopiles 10a, 10
b are connected so that their polarities are opposite to each other.

When there is a difference in the amount of infrared rays received by the first and second thin film portions 8a and 8b, the first and second thermopiles 10a and 10b have the first and second thin films, respectively. The thermoelectromotive force proportional to the amount of infrared rays received by the units 8a and 8b is generated. Where the first thermopile 1
0a and the second thermopile 10b are connected so that the polarities thereof are opposite to each other. Therefore, the infrared detection device of the present embodiment is configured so that the first thin film portion 8a and the second thin film portion 8b respectively receive the infrared ray amounts of Outputs a signal proportional to the difference.

On the other hand, when the first and second thin film portions 8a and 8b do not receive infrared rays from the object to be measured, the amounts of infrared rays received by the first and second thin film portions 8a and 8b are equal. Here, since the heat capacities of the first and second thin film portions 8a and 8b are equal, their temperatures are equal, and the thermoelectromotive forces generated in the first thermopile 10a and the second thermopile 10b are equal in magnitude. , The polarities are reversed. Therefore,
The thermoelectromotive forces generated in the first and second thermopiles 10a and 10b are canceled out, and no offset voltage is generated.

The hot junction 3a of the first thermopile 10a is formed on the first thin film portion 8a, and the second thin film portion 8b is formed.
The cold contact 4b of the second thermopile 10b is formed thereon, and the cold contact 4a of the first thermopile 10a and the temperature of the second thermopile 10b are formed on the thin film 8 other than the first and second thin film portions 8a and 8b. By forming the contact point 3b, the difference in the amount of infrared rays received by the first and second thin film portions 8a and 8b can be treated as a thermally stable first and second thin film portion 8a.
Since the temperature of the thin film 8 other than a and 8b is detected as a reference, the stability of the output signal of the infrared detection device can be improved and the accuracy can be improved.

In this embodiment, two kinds of metals having the Seebeck effect are formed in series on the thin film 8 in an array, but a plurality of PN junctions may be formed in series. (Embodiment 3) The structure of the infrared detector of this embodiment is shown in FIG. In the infrared detector of the first or second embodiment, as shown in FIG. 3, the first and second thin film portions 8a, 8
Among the infrared rays received by b, the semi-circular chopper 11 that completely blocks the infrared rays received by one side and allows the infrared rays received by the other side to be incident as they are is provided. Thin film parts 8a, 8b
The first and second thin film portions 8a and 8b alternately receive the infrared rays periodically by rotating the rotating shaft 12 above them at a constant cycle.

Here, a thermopile hot junction is provided on the first thin film portion 8a, and a thermopile cold junction is provided on the second thin film portion 8b. Therefore, when the first thin film portion 8a having the hot junction formed therein receives infrared rays, the output signal of the thermopile becomes positive, and the second thin film portion 8b having the cold junction formed therein receives infrared rays. Output, the thermopile output signal is negative.

By the way, the first and second thin film portions 8a, 8
When the amount of infrared rays received by b is equal,
Since the heat capacities of the first and second thin film portions 8a and 8b are equal, the temperatures of both are equal. Therefore, when the first and second thin film portions 8a and 8b respectively receive infrared rays,
, The temperature of the hot junction provided on the thin film portion 8a becomes equal to the temperature of the cold junction provided on the second thin film portion 8b, and the output signals of the thermopile have the same magnitude and opposite polarities. .

Therefore, the rotation cycle of the chopper 11 is the first.
And when it is sufficiently longer than the time constant of the thermopile provided on the second thin film portions 8a and 8b, as shown in FIG.
The output signal of the thermopile is a sine wave output (a in FIG. 4). Therefore, since the output signal of the thermopile of the present embodiment is an AC signal, it is possible to remove the noise component and the offset voltage included in the output signal by using a filter or the like, and the influence of the noise or the offset voltage of the thermopile is small. An output signal can be obtained.

The structure of the thermopile of this embodiment is as follows.
Since it is similar to the first or second embodiment, the description thereof is omitted. (Embodiment 4) The structure of the infrared detector of this embodiment is shown in FIG. In the infrared detection device according to the first or second embodiment, a first optical system lens 13a for causing the first thin film portion 8a to receive the infrared light from the first DUT 14a,
The second thin film portion 8b is provided with a second optical system lens 13b for receiving infrared rays from the second DUT 14b, and the first thin film portion 8a and the second thin film portion 8b are ,
First and second DUTs 14a and 14b which are different from each other
Infrared is received from.

Here, the first and second thin film portions 8a, 8b
However, when infrared rays are received from the first and second side fixed objects 14a and 14b, the temperatures of both of them change in proportion to the infrared ray amount of the received infrared rays. By the way, since the heat capacities of the first and second thin film portions 8a and 8b are equal,
The temperature difference between the first and second thin film portions 8a and 8b is proportional to the difference in the amount of infrared rays received by the two.

At this time, since the thermopile hot junction is provided on the first thin film portion 8a and the thermopile cold junction is provided on the second thin film portion 8b, the hot junction and the cold junction are formed. The thermopile output signal is generated in proportion to the temperature difference. Therefore, since the output signal of the thermopile is proportional to the difference in the amount of infrared rays received by the first and second thin film portions 8a and 8b, respectively, from the output signal of the thermopile of this embodiment, the first and second measured objects are measured. The difference in the amount of infrared rays received from the objects 14a and 14b can be detected.

The structure of the thermopile of this embodiment is as follows.
Since it is similar to the first or second embodiment, the description thereof is omitted.

[0029]

According to the invention of claim 1, as described above, the thin film formed on the upper surface of the semiconductor substrate and the first and second thin film portions forming a part of the thin film and thermally insulated from each other. A thermopile in which thermocouples are formed in series on the thin film in an array, a thermopile hot junction formed on the first thin film portion, and a thermopile cold junction formed on the second thin film portion. Therefore, when the first and second thin film portions do not receive infrared rays, the temperatures of the first and second thin film portions become equal and the temperature difference between the hot junction and the cold junction does not occur.
The effect is that no offset voltage is generated.

According to a second aspect of the present invention, the thin film formed on the upper surface of the semiconductor substrate, the first and second thin film portions forming a part of the thin film and thermally insulated from each other, and the thermoelectric film on the thin film, respectively. First and second thermopiles in which pairs are formed in series in an array and connected in opposite polarities, cold junctions of the first thermopile formed on the first thin film portion, and on the second thin film portion A hot junction of the second thermopile formed in, and a hot junction of the first thermopile and a cold junction of the second thermopile formed on a thin film other than the first and second thin film portions, When the first and second thin film parts do not receive infrared rays, the heat capacities of the first and second thin film parts are equal, so that the temperatures of both are equal and the first and second thin films connected to the opposite polarities are the same. The thermoelectromotive forces generated in the thermopile cancel each other out, and the offset voltage There is an effect that does not occur. Further, since the reference temperatures of the first and second thermopiles are the temperatures of the thin films other than the thermally stable first and second thin film portions, the reference temperature does not fluctuate and the output signal of the infrared detection device is stable. However, there is also an effect that accuracy is improved.

According to a third aspect of the present invention, the first and second thin film portions are provided with light shielding means for alternately and periodically blocking infrared rays received from the object to be measured, and the output signal of the thermopile becomes an AC signal. Therefore, there is an effect that signal processing can be easily performed and noise and offset voltage can be removed by using a filter or the like. The invention of claim 4 is the first and second aspects.
Since the thin film portion of the device is provided with a condensing means such as an optical system lens for receiving infrared rays from the first and second DUTs different from each other, the first and second DUTs are output from the thermopile output signal. By detecting the difference in the amount of infrared rays of the above, there is an effect that the difference in the amount of infrared rays of two different measured objects can be detected without contact.

[Brief description of drawings]

FIG. 1A is a plan view showing an infrared detection device according to a first embodiment. (B) It is sectional drawing same as the above.

FIG. 2A is a plan view showing an infrared detection device according to a second embodiment. (B) It is sectional drawing same as the above.

FIG. 3 is an external perspective view showing an infrared detection device according to a third embodiment.

FIG. 4 is a waveform diagram showing an operating state of the above.

FIG. 5 is an external perspective view showing an infrared detection device according to a fourth embodiment.

FIG. 6A is a plan view showing an infrared detection device of a conventional example. (B) It is sectional drawing same as the above.

[Explanation of symbols]

 1 1st metal 2 2nd metal 3 hot junction 4 cold junction 7 semiconductor substrate 8 thin film 8a 1st thin film part 8b 2nd thin film part 9a 1st recessed part 9b 2nd recessed part 10 thermopile

Claims (4)

[Claims] 1. A thin film formed on an upper surface of a semiconductor substrate, first and second thin film portions forming a part of the thin film and thermally insulated from each other, and thermocouples arranged in an array on the thin film. A thermopile formed in series, a hot contact of the thermopile formed on the first thin film portion, and a cold contact of the thermopile formed on the second thin film portion. Infrared detector featuring. 2. A thin film formed on an upper surface of a semiconductor substrate, first and second thin film portions forming a part of the thin film and thermally insulated from each other, and thermocouples on the thin film, respectively. First and second electrodes formed in series and connected in opposite polarities
A thermopile, a cold junction of the first thermopile formed on the first thin film portion, a hot junction of the second thermopile formed on the second thin film portion, the first and An infrared detecting device comprising: a hot contact of the first thermopile and a cold contact of the second thermopile formed on the thin film other than the second thin film portion. 3. The infrared detecting device according to claim 1, wherein the first and second thin film portions are provided with a light shielding means for alternately and periodically blocking infrared light received from the object to be measured. apparatus. 4. The first and second thin film portions are provided with a condensing means such as an optical system lens for receiving infrared rays from different first and second DUTs, respectively. The infrared detection device according to claim 1 or 2.