JP2001194227A - Arrangement structure of thermocouple temperature contact of thermopile type infrared sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermopile type infrared sensor capable of giving the maximum efficiency when a body to be detected is rectangular, since a conventional thermopile type infrared sensor has temperature contacts of a thermocouple formed on the four sides or diagonals of a square, so when a body to be detected is square or circular in conformity with the temperature contact arrangement shape, infrared rays can be detected with maximum efficiency but when the body is rectangular having a radio (R=H/W) of 1.1 to 20.0 of width(W) to height(H) like a human body, the sensitivity decreases greatly, which is a practical problem. SOLUTION: A structure which has temperature contacts of a thermocouple arranged on an elliptic circumference or on the four sides of a rectangle is provided in the thermopile type infrared sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermopile type infrared sensor used for applications such as non-contact temperature measurement and stationary human body detection.

[0002]

2. Description of the Related Art A sensor using a thermal detection principle has been used as an infrared sensor for applications such as non-contact temperature measurement using an infrared sensor and detection of a stationary human body. Of the thermal infrared sensors, the thermopile method does not require a chopper such as a pyroelectric method, and does not require a high-precision DC power supply or a constant temperature control system such as a thermistor bolometer method. By combination with the circuit,
Since it is possible to easily detect a constant infrared ray, it is widely used in fields such as non-contact temperature measurement and stationary human body detection.

FIGS. 3 and 4 show the structure of a sensing element of an infrared sensor in a conventional thermopile system. A central portion of the Si substrate (1) is etched away to form a diaphragm wall (2) made of SiN or the like having a thickness of about 1 μm, and about 1 μm is formed on the diaphragm by photolithography.
00 thin film thermocouples are formed in series, and the cold junction is formed on the peripheral Si substrate. As shown in FIG. 3, hot junctions on four sides of a regular square are formed. In another general or well-known structure, the hot junction is formed on a diagonal of a square as shown in FIG. The arrangement of the hot junction of these thermocouples,
Have a big impact. Since the thermopile type infrared sensor generally has the maximum sensitivity at the position of the hot junction, in the case of the former thermopile, it has a square quadrangular sensitivity distribution,
The latter sensor has a square diagonal sensitivity distribution. Therefore, in the conventional hot junction arrangement of the thermopile type infrared sensor, when the object to be detected is a regular square or a circle similar to the shape of the hot junction arrangement, infrared rays can be detected with maximum efficiency. On the other hand, when the detected object is a human body, it has a substantially rectangular shape, and the ratio of the width (W) to the height (H) of the rectangle (R =
H / W) is about 1 when viewed from the front and about 20.0 when viewed from the side. In the case of having such a rectangular shape, a hot-junction region where infrared rays do not enter is generated, leading to a decrease in detection sensitivity. As described above, in the conventional thermopile type infrared sensor, due to the hot junction arrangement structure of the thermocouple, when the detection target has a rectangular shape or an elliptical shape,
The sensitivity is remarkably reduced, and there is a practical problem.

[0004]

In the conventional thermopile type infrared sensor, the hot junction of the thermocouple is formed on four sides of a regular square or on a diagonal line. In the case of a square or a circle, infrared rays can be detected with maximum efficiency. However, when the shape of the detected object does not match this, for example, when the ratio of the width (W) to the height (H) of the human body or the like (R = H / W) is 1.1 to 20.0, the rectangular shape is used. In this case, the sensitivity was remarkably lowered, and a problem remained in practical use. Therefore, an object of the present invention is to provide a thermopile-type infrared sensor that provides maximum efficiency when the detection target is rectangular.

[0005]

SUMMARY OF THE INVENTION In a thermopile type infrared sensor, there is provided a structure in which hot junctions of a thermocouple are arranged on an elliptical circumference or on four sides of a rectangular shape.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the thermopile type infrared sensor hot junction arrangement structure of the present invention, the elliptical or rectangular object to be detected is arranged by arranging the hot junction of the thermocouple on the circumference of the ellipse or on the four sides of the rectangle. The sensitivity to an object can be improved.

[0007]

1 is a plan view and FIG. 2 is a sectional view of an embodiment of a thermopile infrared sensor according to the present invention. First, a diaphragm layer (2) made of SiN, SiO2 or the like is provided on a Si substrate (1) having a plane orientation (100) with LPCV on both surfaces.
D and the like. Next, one electrode of a thermocouple, a thin film of Sb or the like having a positive Seebeck coefficient in this embodiment was formed by vacuum evaporation, and then processed into a fine shape by photolithography (hereinafter abbreviated as photolitho). Similarly, the other electrode of the thermocouple, in the case of this example, a thin film of Bb or the like having a negative Seebeck coefficient was formed and then processed into a fine shape by photolithography. At this time, the cold junction of the thermocouple is formed on the outer peripheral portion (on the Si substrate) of the diaphragm region, and the hot junction (3) is formed on the elliptical periphery in the infrared sensing portion on the disk on which the infrared absorbing film is formed. Been formed. Next, formation of a passivation layer (4) for protecting the thermocouple electrode and perforation of a bonding pad portion were performed by photolithography.

Further, an Al bonding pad (5) and an infrared absorbing film (6) were formed by vacuum evaporation and photolithography. With the above process, the formation of the surface pattern was completed.
Next, the SiN layer on the back surface was perforated to a desired size by photolithography. The Si wafer was placed in a KOH 33% solution at a liquid temperature of about 80 ° C., and the Si substrate was subjected to anisotropic etching using the SiN layer as a mask. The Si substrate has a crystal plane anisotropy ((100) /
Since (111) = several hundreds), etching of a thick substrate can be realized while suppressing side etching. The prototype thermopile employs a method in which hot junctions are arranged on four sides of a rectangle of 0.5 mm × 2 mm. For comparison, a sample in which a hot junction was arranged on a 1 mm × 1 mm square was also prototyped.

In the evaluation, the detected object is a human body, and the focal length is 1
The light was condensed by a 0 mm Ge convex lens, formed an image on the infrared sensor of the sensor, and the output of the conventional sensor was compared with that of the sensor of the present invention. The human body is located 6 m in front of the convex lens, and the image size is calculated to be about 0.5 mm × 2.6 mm. At this time, the sensor output after 5000-fold amplification is about 60 mV in the case of the conventional type, whereas it is 130 mV in the case of the present invention.
About twice as much improvement as V was confirmed.

[0010]

According to the hot junction arrangement structure of the thermopile type infrared sensor of the present invention, the hot junction is arranged on four sides of a rectangle or on an ellipse circumference. In comparison with the square-shaped hot-junction arrangement type, an improvement of about twice was achieved. The thermopile-type infrared sensor of the present invention has high sensitivity in a rectangular or elliptical shape, so that the sensitivity can be expected to be improved particularly in applications for detecting a human body, and is valuable in engineering.

[Brief description of the drawings]

FIG. 1 is a plan view of an embodiment of a thermojunction type infrared sensor hot junction arrangement structure of the present invention.

FIG. 2 is a sectional view of an embodiment of a thermopile infrared sensor according to the present invention.

FIG. 3 is a plan view of a conventional thermopile type infrared sensor in which hot junctions are arranged on four sides of a regular square.

FIG. 4 is a plan view of a conventional thermopile type infrared sensor in which hot junctions are positioned on a regular square diagonal line.

[Explanation of symbols]

 1. 1. Si substrate 2. diaphragm layer 3. Thermocouple hot junction 4. Passivation layer 5. Bonding pad layer Infrared absorbing film layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsutomu Yamaguchi 372-4 Kumoyama, Tottori-shi, Tottori Japan Nippon Ceramics Co., Ltd. (72) Inventor Yoshiharu Taniguchi 372-4 Kumoyama, Tottori-shi, Tottori Nippon Ceramics F Term (reference) 2G065 AA20 AB02 BA11 BA34 CA27 DA20 2G066 AC13 BA08 CA08

Claims (1)

[Claims] 1. A thermocouple type infrared sensor, in which hot junctions of a plurality of thermocouples are arranged on an elliptical circumference or on four sides of a rectangle.