JP2526247B2 - Thermopile - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermopile formed on a Si substrate by a thin film technique, and more particularly to a thermopile provided with a temperature element that compensates for temperature changes of the thermopile itself. is there.

[Prior Art] Conventionally, as a thermopile of this type, for example, JP-A-
The one disclosed in 61-259580 is known. As shown in FIG. 4, this is composed of a plurality of thermocouples 7 and 8 such as Bi—Sb radially formed on an insulating substrate 1 made of glass, ceramic, polymer film, etc. It is composed of a blackening film 5 formed in the central portion on the insulating film 4 to cover, and a temperature compensating thin film thermistor 6 formed on the front surface or the back surface of the substrate 1 in the vicinity of the cold junction of the thermocouple.

[Problems to be Solved] However, the thermopile provided with the temperature compensation thin film thermistor has the following problems.

Since the thermocouples 7 and 8 are directly formed on the substrate 1, the heat of the hot junction portion received from the black body portion 5 is easily dissipated through the substrate 1, and conversely, the substrate 1 is made of glass, ceramic,
Since it is an insulator such as a polymer fill, the thermal conductivity is poor and the heat sink at the cold junction is bad. Therefore, particularly in the low temperature region measurement, the temperature difference between the hot junction portion and the cold junction portion hardly appears, the thermoelectromotive force is a small value, and the sensitivity is low.

The temperature compensating thin film thermistor 6 is formed in the vicinity of the cold junction part. However, since a constant current constantly flows in the thermistor 6, the thermistor 6 itself acts as a heat radiator, and this is close to the cold junction part. If done too much, the thermistor 6, which measures the temperature of the cold junction itself, rather disturbs the temperature. In order to increase the temperature of the thermistor 6, it is necessary to increase the applied current value. However, the higher the temperature, the more the temperature of the cold junction portion is disturbed and the measurement accuracy deteriorates.

[Object of the Invention] The present invention is to solve the above-mentioned problems, and an object of the present invention is to make a temperature difference between a hot junction portion and a cold junction portion of a thermocouple easily appear, and to provide a temperature compensation resistance film. It is to provide a thermopile that can be measured as it is without disturbing the environmental temperature of the cold junction by devising the arrangement and the like.

[Means for Solving Problems] In order to achieve the above object, the achievement of the thermopile according to the present invention has the following constituent requirements.

Have a rectangular Si substrate with holes.

There is an insulating film formed on the surface of the Si substrate by closing the hole.

There is a black body portion formed on the insulating film in the hole region.

There are a plurality of thermocouples connected in series, each having a hot junction located in the hole region in proximity to the black body and a cold junction located outside the hole region on the insulating film.

There is a resistance film for temperature compensation formed on the insulating film at the corner of the Si substrate on the cold junction side using one of the thermocouple wire thin film materials of the outer thermocouple.

[Operation] According to the thermopile having such a configuration, since the black body portion is suspended in the hole area of the Si substrate, the heat capacity of the black body portion is small, and the response characteristics are improved, as well as the thermoelectricity. Since the pair of hot junctions are in the hole area, it is possible to reduce the escape of a slight amount of heat received from the black body, while the cold junction is located outside the hole area on the Si substrate. , The heat received by the cold junction is rapidly dissipated into the Si substrate due to the heat sink effect of the Si substrate, and the temperature gradient between the hot junction and the cold junction can be made higher than before. Further, since the temperature compensating resistance film is formed on the corner of the Si substrate having a large heat capacity and a relatively high thermal conductivity as a dead space through the thin insulating film, the resistance film is used as a cold junction part. Even if they are close to each other, the heat generated from the resistive film is dissipated more into the corners, so that the adverse effect on the cold junction can be suppressed.

[Embodiment] Next, an embodiment of a thermopile according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 (A) is an enlarged plan view showing an embodiment of the thermopile according to the present invention. FIG. 1 (B) is a vertical sectional view showing the same embodiment.

In the figure, 10 is a rectangular Si substrate, and a hole 10a is formed in the center thereof. An insulating film 11 is formed on the surface of the Si substrate 10 while closing the hole 10a, and has a three-layer structure of a nitride film, an oxide film, and a nitride film. Hole area S on insulating film 11
A black body portion 12 as a light receiving portion of gold or the like is formed in the center of the inside. A large number of thermocouples 13 are connected in series around the black body portion 12. Each thermocouple 13 is a Te thermocouple wire 13a
And a thermocouple wire 13b of InSb, which are arranged radially and have a hot junction 13 near the black body 12 in the hole region S.
c is located, and the cold junction 13d is located outside the hole area S. 14a and 14b are bonding pads connected to both ends of the thermocouple 13 connected in series.

Reference numeral 15 is a temperature compensating resistance film as a thermistor formed outside the hole region S by the constituent material of one thermocouple wire 13a,
It is formed on the corner 10b (portion shown by an imaginary line) as a dead space on the rectangular Si substrate 10 in the vicinity of the cold junction 13d side. Bonding pads are provided on both ends of the resistive film 15.
15a and 15b are connected and formed, and are used as an electrode portion for flowing a constant current through the resistance film 15. Incidentally, 16 is a protective film.

As shown in FIG. 2, the thermopile 20 having the above structure is
It is mounted on the base 21 with silver paste or silicon resin, and is covered with a light-shielding cap 24 having an infrared filter window 23.
Are connected by the gold wire of the bonding wire, and the output voltage is taken out through the pin 22 to the outside.

The black body portion 12 of the thermopile 20 is heated by the heat rays radiated from the side temperature object, and receives energy almost proportional to the fourth power of the temperature of the side temperature object to cause a temperature change. Since it is formed on the thin insulating film 11 in the region S, the heat capacity of the insulating film 11 as the contact body of the black body portion 12 is much smaller than the conventional one, so that the escape of heat can be suppressed as much as possible, and It contributes to the improvement of the sensitivity of 13 pairs. Further, since the hot junction portion 13c of the thermocouple 13 is on the thin insulating film 11 in the hole area S, it is possible to suppress the dissipation of the amount of heat received from the black body portion 12. On the other hand, the cold junction portion 13d is not formed in the hole region S but is formed on the Si substrate 10 which is thicker than the insulating film 11 and has a large heat capacity and high thermal conductivity.
The heat sink of 13d becomes large, and the temperature of the cold junction 13d is
The state is substantially equal to the temperature of the substrate 10 (environmental temperature). Therefore, the temperature of the hot junction 13c of each thermocouple 13 is
Since the temperature of the cold junction part 13d follows the ambient temperature almost equally as well as the temperature of the
The temperature difference between the hot junction portion 13c and the cold junction portion 13d becomes apparent, and the thermocouple electromotive force can be increased even in the case of measurement in the low temperature region.

Further, since the resistance film 15 is formed on the corner portion 10b of the Si substrate 10, it has a heat sink effect and is arranged in the vicinity of the cold junction portion 13d. Since it does not spread to 13d and is dissipated into the thick Si substrate 10 through the thin insulating film 11, it is possible to measure the temperature of the cold junction 13d without disturbing it. In other words, the cold junction 13d should be used for temperature compensation.
The more directly the temperature of is measured with a resistive film as a thermistor, the colder the contact point 13 due to the heat generated by the resistive film.
Although the temperature of d is disturbed, by making the temperature of the cold junction portion 13d equal to the temperature of the Si substrate 10 having a high thermal conductivity and a large heat capacity, the resistance film 15 is not brought close to the cold junction portion 13d,
Even when a relatively high current is applied to the resistance film 15, the environmental temperature can be accurately measured. That is, the indirect measurement is realized without disturbing the temperature of the cold junction portion 13d by utilizing the corner portion 10b of the Si substrate 10 which acts as a heat reservoir as an intermediate medium. The Si substrate 10 as a semiconductor has higher thermal conductivity than an insulator and is more advantageous than the case where an insulator is used as an intermediate medium. The insulating film 11 is for preventing conduction between the resistance film 15, the thermocouple 13 and the Si substrate 10, but in this embodiment, the film thickness is about 6 μm, and the thickness of the Si substrate 10 is about 6 μm.
Since it is very thin compared to 200 μm, it can be ignored in terms of thermal action.

The resistance film 15 is composed of the constituent material Te of the thermocouple wire 13a. Te has a high resistivity ρ as shown in FIG. 3, and since the characteristic of temperature T vs. resistivity ρ is a substantially linear characteristic, it can be used as a thermistor material and is the same as one thermocouple wire 13a. Since it is a material, it can be formed at the same time as the process of forming the thermocouple wire 13a, so that the number of manufacturing steps can be reduced and a low-cost thermopile can be provided as compared with the conventional case.

[Advantages of the Invention] As described above, the thermopile according to the present invention forms a suspended black body portion in the hole area of the Si substrate, and the hot junction portion adjacent to this and the cold body located outside the hole area. Since the thermocouple having the contact portion is formed and the temperature compensation resistance film is formed at the corner portion of the Si substrate, the following effects can be obtained.

The black body part and the hot contact part are less likely to release heat, and the heat capacity of the insulating film contacting them is very small. On the other hand, the cold contact part is satisfactorily heat-sinked by the Si substrate with large heat conduction and heat capacity. Therefore, the temperature gradient between the hot junction portion and the cold junction portion can be increased as compared with the conventional case.

The dead space at the corners of the Si substrate is effectively used as a heat reservoir, and the cold junction and temperature compensation resistance film are formed on this to make the temperature of this portion the ambient temperature. It is possible to dispose the resistive film without adversely affecting the temperature of the resistive film, and even if the constant current of the resistive film is large and temperature compensation is performed with high sensitivity, it is possible to prevent the temperature fluctuation of the cold / hot contact point due to the heat generation of the resistive film. The environmental temperature, that is, the temperature of the cold junction can be accurately measured.

Further, since the resistance film is formed of the constituent material of one thermocouple wire, it is possible to form it simultaneously during the formation process of that thermocouple wire, which is coupled with the thin film formation of the semiconductor manufacturing process using the Si substrate as the base material. A thermopile with low manufacturing cost can be realized.

[Brief description of drawings]

FIG. 1 (A) is an enlarged plan view showing an embodiment of the thermopile according to the present invention. FIG. 1 (B) is an enlarged vertical sectional view showing the same embodiment. FIG. 2 is a vertical sectional view showing a completed product in which the same embodiment is incorporated in an envelope. FIG. 3 is a graph showing the characteristics of the temperature T vs. resistivity ρ of Te relating to the material for forming the low antibody for temperature compensation in the same Example. FIG. 4 (A) is a plan view showing an example of a conventional thermopile, and FIG. 4 (B) is a longitudinal sectional view thereof. 2 ... Thermopile, 10 ... Si substrate with holes, 10a ...
… Hole, S …… Hole area, 10b …… Corner, 11 …… Insulating film, 12
...... Black body part, 13 ...... Thermocouple, 13a, 13b ...... Thermocouple wire, 13c
...... Hot junction, 13d ...... Cold junction, 15 ...... Resistance film for temperature compensation, 14a, 14b, 15a, 15b ...... Bonding pad, 16 ...
…Protective film.

Claims (1)

(57) [Claims] 1. A rectangular Si substrate having a hole, an insulating film formed on the surface of the Si substrate by closing the hole, a black body portion formed on the insulating film in the hole region, A plurality of thermocouples connected in series, each having a hot junction close to the black body in the hole region and a cold junction located outside the hole on the insulating film, and one of the thermocouples. On the cold junction side with a pair of thin film materials,
A thermopile having a temperature compensation resistance film formed on the insulating film at a corner of a Si substrate.