JPH01138429A - Thermopile - Google Patents

Abstract

PURPOSE:To increase the mechanical strength of the hot contact part of a device and to shorten the interval between the hot contact part and cold contact part by racking the part of a couple of thermocouple wires of each thermocouple which includes the hot contact part on an air gap formed with a substrate. CONSTITUTION:After an Si oxide film 11 is formed on an Si substrate 10, photoresist or resin is applied in a trapezoid shape and then one surface is covered with an insulating film 12 including the photoresist or resin so as to form the air gap 13. Then, one thermocouple wire 15a and a black body part 14 are formed and then the other thermocouple wire 15b is formed. Lastly, the photoresist or resin is removed to form the air gap 13 and thus a radiation thermometer is completed. Consequently, the electromotive forces of the thermocouples 15a and 15b decrease by as much as the interval between the hot contact part 15c and cold contact part 15d is shortened, but that is compensated by an increase in the number of mounted thermocouples, the sensitivity is, therefore, improved effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thermopile as a radiation thermometer, and particularly to a thermopile having an air bridge structure at a hot junction.

[Prior Art] Conventionally, as shown in FIG. 4, this type of thermopile consists of an insulating film 2 formed on a Si substrate l having a hole 1a, and a completely black insulating film formed over the hole area S. It consists of a black body part 3 as a light receiving part, and a plurality of thermocouples 4 connected in series radially around the black body part 3, and the hot junction part 4C of the thermocouple wires 4a and 4b is arranged close to the black body part 3. , its cold contact part 4d
is formed at a position away from the black body portion 3.

[Problems to be Solved] However, the above thermopile has the following problems.

■The hot junction part 4C is the thin insulating film 2 (approximately 67t) on the hole area S.
1), the mechanical strength is poor, the yield is low, and the reliability is low.

■The hole area S is generally formed with a thickness of about 200 gm.
After first forming an insulator 1lI2 on the i-substrate l, the insulating film ? The hole 1a is formed by etching and removing the entire lower Si substrate part, but using a general etching solution (
Hydrofluoric acid, nitric acid, and acetic acid) have variations (heterogeneity) in their etching speed, and as a result, the area of the hole region S at one position,
Due to this, the distance between the hot junction part 4C and the cold junction part 4d cannot be shortened, so the cold junction part 4d
In order to reliably place these on the Si substrate 1 serving as a heat sink, it is necessary to make the interval long in advance. Therefore, it is difficult to reduce the size of the chip or achieve high integration of thermocouples.

Also, because the interval is long, the resistance is relatively large,
This becomes an obstacle to improving sensitivity, and furthermore, since the heat capacity is large, the thermal response is inferior.

[Object of the Invention] The present invention is intended to solve the above problems, and its purpose is to provide a thermopile whose hot junction has high mechanical strength and can shorten the distance between the hot junction and the cold junction. Our goal is to provide the following.

[Means for Solving Problems] In order to achieve the above object, in the thermopile according to the present invention, the portion of each thermocouple wire including the hot junction portion is connected to the air gap formed between the pair of thermocouple wires and the substrate. It is built above.

[Function] According to the thermopile having such a configuration, there is no need to make a hole through the substrate, and the hot junction part is built over the air gap, so the mechanical strength of the hot junction part is improved, and the integrated circuit By using manufacturing technology, the size of each thermocouple can be further miniaturized, so the plane distance between the hot junction and cold junction can be shortened compared to the conventional method, increasing the number of thermocouples mounted or reducing the chip area. It is possible to achieve downsizing, etc.

[Example] Next, embodiments of the present invention will be described based on the drawings.

FIG. 1(A) is an enlarged plan view showing the first embodiment of the thermopile according to the present invention, and FIG.
) is a cross-sectional view showing a state cut along the middle line IB-IB.

In the figure, 10 is a flat Si substrate, and a Si oxide film 11 is formed all over the surface of this substrate. This Si oxide film 11
An air gap 13 is provided thereon, and an insulating film 12 having a bridge portion 12a built over the air gap 13 is formed. A black body part 14, such as a completely black body part 14, is formed in the center of the bridge part 12a, and a hot junction part 15c formed as an overlapping part of thermocouple wires 15a and +5b is located near the black body part 14. A cold contact portion 15d formed as an overlapping portion of thermocouple wires 15a and 15b is located on the flat surface other than the bridge portion 12a. Therefore, each thermocouple wire 15a, 15b has a stepped portion 15e, 15f that rides on the bridge portion 12a, and the cold junction portion 15
d is located closer to the Si substrate 10 and lower than the hot junction portion 15c on the bridge 12a.

Such a thermopile is manufactured as follows. First, after forming the Si oxide film 11 on the Si substrate 10, a photoresist or resin is coated with a trapezoidal cross section to form an air gap 13, and then the entire surface including the photoresist or resin is covered with an insulating film 12. Next, after forming one thermocouple wire 15a and the black body part 14, the other thermocouple wire 1
Form 5b. Finally, the photoresist or resin is removed to form an air gap 13 and the thermopile is manufactured.

Due to its structure, the thermopile according to the first embodiment not only has higher mechanical strength than conventional ones, but also because it is created without using an etching process on the Si substrate itself, which increases the precision of creation and improves the cold junction area. 15d is always located on the Si substrate 10, it is possible to set the distance between the hot contact portion 15c and the cold contact portion 15d to about 50 cm. This makes it easier to form finer patterns of thermocouples and increases the number of thermocouples mounted on a chip (integration degree). Although the electromotive force of each thermocouple decreases because the distance between the hot junction part 15c and the cold junction part 15d becomes shorter than before, the increase in the number of thermocouples mounted more than compensates for this, so as a result, An improvement in sensitivity is achieved. Additionally, by being able to shorten the length of each thermocouple wire,
It is possible to lower the value of the total resistance, that is, the output resistance of the thermopile, and it is also possible to improve the thermal response.

FIG. 2(A) is an enlarged plan view showing a second embodiment of the thermopile according to the present invention, and FIG.
) is a cutaway view showing a state cut along the middle 118-IIS line.

20 is a flat Si substrate, on which a strip-shaped insulating film 21 is formed.
is formed. The insulating film 21 has a bridge portion 21 a that defines an air gap 23 . The hot junction portion 24c of the pair of thermocouple wires 24a and 24b is connected to the bridge portion 2.
1a, and the cold contact portion 24d is formed in the valley. A black body portion 25 of gold black or the like is provided on each hot junction portion 24c.

In the second embodiment, the hot junction portion 24c is supported on the air gap 23 by the thermocouple wires 24a and 24b at both ends, so the support structure is more solid than in the first embodiment. From this point of view, it becomes possible to directly mount the black body portion 25 on the hot junction portion 24c, and a thermopile with high sensitivity can be obtained. Further, since each hot junction portion 24c is formed on its own air gap 23, manufacturing is easier than in the case where one long air gap is shared as in the first embodiment.

FIG. 3(A) is an enlarged plan view showing a third embodiment of the thermopile according to the present invention, and FIG. 3(B) is an enlarged plan view showing the third embodiment of the thermopile according to the present invention.
) is a cross-sectional view showing a state cut along line IIIB-ItIB.

30 is a flat Si substrate, on which a Si oxide film 31 is formed over the entire surface. A pair of thermocouple wires 32a, 32b
has a hot junction part 32c on the air gap 33,
A black body portion 34 made of gold and black is provided on the hot junction portion 32c. The cold contact portion 32d is formed on the Sim film 31 at a lower location than the hot contact portion 32c. The thermocouple groups are arranged in a zigzag pattern as shown in FIG. 3(A), and each hot junction 32c is formed above each air gap 33.

The method for manufacturing this thermopile is to first form a Si oxide film 31 on a Si substrate 30, and then apply a photoresist or resin in a trapezoidal cross section to form an air gap 33. Next, an insulating film is formed on this. Thermocouple wires 32a, 32 are formed in order to create a self-supporting hot junction part 32c as an overlapping part on photoresist or resin with a trapezoidal cross section without forming the thermocouple wires 32a, 32.
A black body portion 34 made of gold black or the like is provided on the hot contact portion 32c created by sequentially laminating layers 11 and 11. Finally, the photoresist or resin is removed to form an air gap 33 and the thermopile is manufactured.

In the third embodiment, since there is no insulating film on the back surface of the hot junction portion 32c, the heat capacity is reduced and the thermal response time can be improved compared to the second embodiment.

[Effects of the Invention] As explained above, the thermopile according to the present invention is characterized in that the hot junction part is separated from the substrate and is positioned on the air gap, and therefore has the following effects. .

(2) Compared to a conventional thermopile in which a hot junction is provided on an insulating film formed on a substrate with holes, mechanical strength is higher, and yield and reliability are improved.

■When creating an air gap, etching of the board itself does not occur, and the hot junction is located on the air gap, and the cold junction is always located on the board. The number of thermocouples mounted above can be increased. By increasing the integration of such thermocouples, it is possible to improve the sensitivity, reduce the output resistance value of the thermopile, and improve the thermal response.

[Brief explanation of the drawing]

FIG. 1(A) is an enlarged plan view showing the first embodiment of the thermopile according to the present invention, and FIG.
) is a cross-sectional view showing a state cut along the middle line 1S-1-B. FIG. 2(A) is an enlarged plan view showing the second embodiment of the thermopile according to the present invention, and FIG. 3(B) is a plan view taken along the line IIB-FIB in FIG. 3(A). It is a cutaway view showing the state. FIG. 3(A) is an enlarged plan view showing a third embodiment of the thermopile according to the present invention, and FIG. 3(B) is an enlarged plan view of the third embodiment of the thermopile according to the present invention.
FIG. 3 is a cross-sectional view showing a state cut along the middle line mB-mB. FIG. 4(A) is a plan view showing an example of a conventional thermopile, and FIG. 4(B) is a plan view of IVB-IV in FIG. 4(A).
FIG. 3 is a cross-sectional view showing a state cut along line B; 10. 20, 30... Si substrate, 11, 31 Kai/Fist Sii film, 12, 21... Insulating film, 12a...
Bridge part, 15a, 15b, 24a, 24b
, 32a, 32b Yutaka... thermocouple wire, 15c,
24c, 32c...Fist temperature contact part, 15d, 24
d, 32d...Cold junction part, +3, 33...Air gap, '14.25.34φe・Black body part. Figure 3 (A) (B) Figure 4 (A Tsuma (B) Procedural amendment (method) % formula % ■, Indication of water matter Patent Application No. 185112 of 1985 2, Title of invention Thermopile 3, Amendment Relationship with the case of a person who does December 2, 1986
0th day 6, Subject of amendment ``Brief explanation of drawings in the specification, Column 7, Contents of amendment, page 10, line 3 of the specification, ``Figure 3 (B)'' was changed to ``Figure 2 (B)'' Figure (B)” is corrected. that's all

Claims (1)

[Claims] A thermopile consisting of a large number of thermocouples connected in series on a substrate, in which the portion of each thermocouple's pair of thermocouple wires, including the hot junction, is installed over the air gap formed between the thermopile and the substrate. A thermopile characterized by: