JPH04342177A - Thermopile - Google Patents

Abstract

PURPOSE:To improve the sensitivity of a thermopile by increasing the number of thermopiles disposed around an infrared absorber without reducing the width of first and second conductor lines of the thermopiles. CONSTITUTION:A plurality of thermopiles 3 are arranged in a pattern around an infrared absorber. First conductor lines 4 and second conductor lines 5 of each thermopile are joined together at the end thereof, the end being closer to the infrared absorber 2, to form a hot junction 7. Meanwhile, at a cold junction 8, the first conductor line 4 of one thermopile 3 is connected to the second conductor line 5 of another adjacent thermopile 3, thereby constituting a plurality of thermopiles connected in series. The first conductor lines and the second conductor lines 5 are densely arrayed on the same plane without a substantial gap therebetween, but they are different in level from each other, except for their hot and cold junctions 7 and 8, thereby rendering them in the noncontinuity state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermopile that detects infrared rays emitted from a human body using a thermocouple.

0002

2. Description of the Related Art Thermopiles that detect infrared rays emitted from the human body are used in security devices and various other fields.

FIGS. 11 to 15 show the configuration of a conventional general thermopile, in which a rectangular infrared absorber 2 made of gold black or the like is disposed above a membrane 1 made of a nitride film or the like. A plurality of thermocouples 3 are arranged in a pattern around this infrared absorber 2. The thermocouple 3 has a first conductive line 4 made of a material such as bismuth and a second conductive line 5 made of a material such as bismuth antimony (an alloy of bismuth and antimony) arranged adjacent to each other with a gap 6 in between. The first conductive line 4 and the second conductive line 5 are connected on the infrared absorber 2 side to form a hot junction 7. Warm junction 7 between first conductive line 4 and second conductive line 5
The opposite end is a cold junction 8, and the first conductive line 4 of the thermocouple on one side and the second conductive line 5 of the adjacent thermocouple on the other side form the cold junction. 8, and a plurality of thermocouples 3 are connected in series. A first electrode 10 is formed at the end of the first conductive line 4 on the starting end side of the series-connected thermocouples 3, and a second conductive line 4 on the terminal end side of the series-connected thermocouples 3 is formed. A second electrode 11 is formed at the end of the line 5, and the infrared detection output of the object to be detected is extracted from the first electrode 10 and the second electrode 11.

0004

[Problems to be Solved by the Invention] However, in the conventional thermopile, each thermocouple 3 has a gap 6 and the mounting density is low, that is, it is arranged roughly, so there is a problem of low sensitivity. .

[0005] In order to increase the sensitivity of the thermopile,
Ideally, the number of thermocouples to be installed could be increased by narrowing the width of each conductive line 4, 5 of the thermocouple 3, increasing the size of the infrared absorber 2, and increasing the circumference of the infrared absorber 2. It will be done.

However, there is a certain technical limit to reducing the width of the conductive lines 4, 5, and
If the width of the conductive lines 5 is made narrower, the electrical resistance of the conductive lines 4 and 5 becomes larger, which causes a problem that Johnson noise becomes larger.

Furthermore, when the size of the infrared absorber 2 is increased, the sensitivity of the thermopile is inversely proportional to the planar area of the infrared absorber 2, so the sensitivity decreases, and the number of thermocouples 3 is increased. However, the problem arises that the sensitivity of the thermopile does not increase.

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to increase the number of thermocouples and increase the sensitivity without narrowing the width of the conductive line of the thermocouple. The purpose is to provide thermopiles.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention is constructed as follows. That is, the present invention provides a membrane, an infrared absorber provided on the membrane, and a plurality of infrared absorbers connected in series, with hot junctions arranged near the infrared absorber and cold junctions arranged far away. In the thermopile consisting of a thermocouple, the membrane has a plurality of alternating lines of peaks and valleys on one surface to form a plurality of steps, and the thermocouple has a first conductive layer formed on the plurality of peaks. and a second conductive line formed at the bottom of a plurality of valleys and having a different thermoelectric power from the first conductive line.

0010

[Operation] In the present invention having the above structure, the first conductive line and the second conductive line of the plurality of thermocouples arranged in a pattern are arranged closely together without any gap in a plane. The number of thermocouples can be increased by

[0011]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. In the description of this embodiment, the same reference numerals as those in the conventional example are given the same reference numerals, and detailed redundant explanation thereof will be omitted. FIG. 1 shows the pattern configuration of a first embodiment of the thermopile according to the present invention, FIG. 2 shows the overall configuration of the thermopile in the same embodiment, and FIGS. 1 shows an example of the configuration of conductive lines in the thermocouple pattern in the same embodiment.

As shown in FIG. 2, the thermopile of this embodiment has a base 12 and a stainless steel package (usually TO-
A window 14 that transmits infrared rays is formed in the center of the top of the package 13. On the upper side of the base 12 is a thermocouple forming body 1.
5 is placed and fixed.

The thermocouple forming body 15 is formed on the silicon substrate 1.
A thin diaphragm-like membrane 1 made of a nitride film or the like is formed on the upper side of the silicon substrate 16 , and the center portion of the silicon substrate 16 is hollowed out using an etching technique to form a space 17 . An infrared absorber 2 is provided in the center of the membrane 1 to face the window 14, and the upper surface of the membrane 1 around the infrared absorber 2 is etched using photolithography and etching techniques. Steps between peaks and valleys as shown in Fig. 6 are formed, and a pattern made of, for example, 100% antimony thermoelectric material is formed on the surface of the peaks of these steps using vapor deposition technology, photolithography technology, and etching technology. It constitutes a first conductive line 4. Further, on the surface of the valley of the step, a second conductive line 5 is patterned using a thermoelectric material having a different thermoelectric power from that of the first conductive line 4, for example, a bismuth antimony alloy having a composition of 90% bismuth and 10% antimony. are doing. And infrared absorber 2
As shown in FIG. As shown in FIG. 6, the second conductive line 5 of the thermocouple 3 on one side and the first conductive line 4 of the thermocouple 3 on the adjacent side are connected on the cold junction part 8 side of each thermocouple 3. A plurality of thermocouples 3 are connected in series. The pattern group of thermocouples 3 arranged on each side of the infrared absorber 2 is connected to the pattern group of adjacent thermocouples via a lead conductor 18 made of aluminum or the like.
All thermocouples 3 formed around the infrared absorber 2 are connected in series.

These thermocouples 3 in each group are arranged closely together without any gaps in a plane, and three-dimensionally by providing height differences due to steps, the first conductive line 4 is arranged as shown in FIG. and the second conductive line 5 are in a non-conducting state between the hot junction 7 and the cold junction 8;
Only in this case, the thermoelectric material of the first conductive line 4 overlaps the thermoelectric material of the adjacent second conductive line 5, so that the first conductive line 4 and the second conductive line 5 are connected. a first electrode 10 provided at the starting end side end portion of the thermocouple pattern;
and a second electrode provided at the terminal portion on the terminal side of the thermal electrode pattern.
The electrodes 11 are connected to terminals 21 and 22 by bonding wires 9, respectively, and infrared detection outputs are taken out from these terminals 21 and 22.

According to this embodiment, the first conductive line 4
Since the second conductive line 5 and the second conductive line 5 are closely arranged in a plane without the gap 6 of the conventional example, the number of thermocouples 3 can be increased by the amount that can reduce the gap 6 to almost zero, and the thermopile can be increased accordingly. sensitivity can be increased.

Moreover, in this embodiment, the conductive lines 4, 5
Since the number of thermocouples 3 can be increased without narrowing the width of the sensor, Johnson noise does not increase, which is very convenient.

A second embodiment of the invention is shown in FIGS. 7-10. This second embodiment differs from the first embodiment in the hot junction 7 and cold junction 8 of the thermocouple 3.
When the thermoelectric material of the first conductive line 4 is overlapped with the second conductive line 5 on the adjacent side and electrically connected, the first conductive line 4
Rather than overlapping the thermoelectric materials over the entire width of the adjacent second conductive line 5, they are connected by providing a non-overlapping portion 20. By providing the non-overlapping portion 20 in this way, the step provided on the membrane 1, that is, the height difference between the first conductive line 4 and the second conductive line 5 can be made smaller than in the first embodiment. It is possible to prevent the hot junction 7 of the thermocouple 3 from being electrically connected to the warm junction 7 of an adjacent thermocouple 3 and the cold junction 8 from being electrically connected to the cold junction 8 of the adjacent thermocouple 3. In addition, the first conductive line 4 and the second conductive line
If the height difference between the conductive line 5 and the conductive line 5 is increased, the hot junction 7
When the thermoelectric material of the first conductive line 4 is stretched and overlapped with the adjacent second conductive line 5 at the cold joint part 8, the first conductive line 4 is However, as in this embodiment, if the first conductive line 4 and the second conductive line 4
By reducing the difference in height between the conductive lines 5, the occurrence of such cracks can be prevented, and a more reliable pattern of the thermocouples 3 can be formed.

Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented in various ways. For example, in each of the above embodiments, the infrared absorber 2 is formed into a rectangular shape, but the shape of the infrared absorber 2 can be any shape other than a rectangle. For example, the infrared absorber 2 can be a circular infrared absorber. can. In this case, a pattern of a plurality of thermocouples 3 is formed radially around the circular infrared absorber 2.

[0019]

[Effects of the Invention] The present invention has a plurality of thermocouple patterns in which the first conductive line and the second conductive line are arranged closely together without any gaps, so that the width of the conductive line can be reduced. The number of thermocouples formed around the infrared absorber can be increased without any problems, and the sensitivity of the thermopile can be effectively increased. In addition, when the number of thermocouples is the same as in the conventional one, the width of the distribution line without any gaps can be made wider, so the electrical resistance of the thermopile can be reduced, and as a result, the Johnson noise This has the effect of making it even smaller.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an arrangement configuration of thermocouple patterns of a first embodiment of a thermopile according to the present invention.

FIG. 2 is a sectional view showing the overall structure of the thermopile in the same embodiment.

FIG. 3 is an enlarged explanatory diagram of a thermocouple pattern in the same example.

FIG. 4 is a sectional view taken along line AA in FIG. 3;

FIG. 5 is a sectional view taken along line BB in FIG. 3;

FIG. 6 is a sectional view taken along line CC in FIG. 3;

FIG. 7 is an explanatory diagram of a thermocouple pattern of a second embodiment of the thermopile according to the present invention.

FIG. 8 is a sectional view taken along line AA in FIG. 7;

9 is a sectional view taken along line BB in FIG. 7. FIG.

10 is a sectional view taken along line CC in FIG. 7. FIG.

FIG. 11 is an explanatory diagram of a thermocouple pattern of a conventional thermopile.

FIG. 12 is an enlarged explanatory diagram of a thermocouple pattern in a conventional thermopile.

FIG. 13 is a sectional view taken along line AA in FIG. 12;

FIG. 14 is a sectional view taken along line BB in FIG. 12;

FIG. 15 is a sectional view taken along line CC in FIG. 12;

[Explanation of symbols]

1 Membrane 2 Infrared absorber 3 Thermocouple 4 First conductive line 5 Second conductive line 7 Warm junction 8 Cold joint

Claims (1)

[Claims] Claim 1: A membrane, an infrared absorber provided on the membrane, and a plurality of infrared absorbers connected in series, with warm junctions arranged near the infrared absorber and cold junctions arranged far away. In a thermopile consisting of a thermocouple, the membrane has a plurality of lines of peaks and valleys alternately provided on one surface to form a plurality of steps, and the thermocouple has a first conductive line formed on the plurality of peaks. and a second conductive line formed at the bottom of a plurality of valleys and having a different thermoelectric power from the first conductive line.