JP2009079946A - Thermopile type infrared sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an infrared sensor which provides stable output by reducing the effect of heat generation caused by the consumption current of an amplification circuit formed on the same semiconductor substrate as a thermopile element. <P>SOLUTION: An infrared detection section 1 comprising the thermopile element 10 and a signal amplification section 2 comprising the amplification circuit which amplifies the output of the thermopile element 10 are formed on the semiconductor substrate 50. A separation groove 3 is formed between the infrared detection section 1 and the signal amplification section 2. Heat conduction between the infrared detection section 1 and the signal amplification section 2 is reduced by the separation groove 3, thereby reducing the influence of the heat generation caused by the consumption current of the signal amplification section 2 on the cold junction temperature of the thermopile element 10 to provide stable output. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a thermopile type infrared sensor, and more particularly to an infrared sensor in which a thermopile element and an amplifier circuit that amplifies the output of the thermopile element are formed on the same semiconductor substrate.

A thermopile infrared sensor is composed of a thermopile element that converts infrared light into an electrical signal, a temperature sensor that detects the cold junction temperature of the thermopile element and corrects the sensor output, and an amplification circuit that amplifies the output. Is done. A conventional general thermopile type infrared sensor has a configuration in which a thermopile element and an amplifier circuit are formed on separate semiconductor substrates, and are connected in one package.

However, when the thermopile element and the amplifier circuit are formed on different semiconductor substrates, there is a problem that the noise from the outside increases as the wiring between the semiconductor substrates becomes longer. In order to solve such a problem, Patent Document 1 proposes an infrared sensor in which a thermopile element and an amplifier circuit are formed on the same semiconductor substrate.

An infrared sensor disclosed in Patent Document 1 is shown in FIG. The infrared sensor of FIG. 7 includes a thermopile element 91 that generates a signal according to the amount of received infrared light, a temperature sensor 92 that detects the cold junction temperature of the thermopile element 91, and an amplification circuit 93 that amplifies the output of the thermopile element 91. An amplification circuit 94 that amplifies the output of the temperature sensor 92 is formed on the semiconductor substrate 90.

In the infrared sensor of Patent Document 1, since the thermopile element 91 and the amplifier circuit 94 are formed on the same semiconductor substrate 90, the wiring connecting them can be made to the minimum length. The influence of all external noise can be suppressed. In the infrared sensor disclosed in Patent Document 1, the temperature sensor 92 is adjacent to a position farthest from the input / output pad 95 among the cold junctions of the thermopile element 91, so that a bonding wire via the input / output pad 95 is provided. Therefore, it is possible to make it less susceptible to environmental temperature changes.
JP 2001-091360 A

However, in the configuration of Patent Document 1, since the thermopile element 91 and the amplifier circuits 93 and 94 are adjacent to each other on the same semiconductor substrate, the thermopile element 91 is cooled by heat generated by the consumption current of the amplifier circuits 93 and 94. Contact temperature will rise. The thermopile type infrared sensor detects the temperature difference between the hot junction temperature and the cold junction temperature and generates an output voltage. The output voltage is not stable unless the cold junction temperature is stable. When the cold junction temperature of the thermopile element 91 fluctuates with fluctuations in current consumption, there is a problem that the output voltage becomes unstable.

In view of the above problems, an object of the present invention is to provide an infrared sensor that suppresses the influence of heat generation due to current consumption of an amplifier circuit formed on the same semiconductor substrate as a thermopile element and has a stable output.

  In order to solve the above problems, a thermopile type infrared sensor of the present invention amplifies the signal generated by the infrared detection unit including an infrared detection unit including a thermopile element that outputs a signal corresponding to the amount of received infrared rays. A thermopile type infrared sensor in which a signal processing unit including an amplifier circuit is formed on the same semiconductor substrate, wherein the infrared detection unit is formed between the infrared detection unit and the signal processing unit. And a heat separation unit that suppresses heat conduction between the signal processing unit and the signal processing unit.

The heat separation part may be constituted by a groove region formed on a surface of the semiconductor substrate.

The groove region may be formed so as to surround the infrared detection unit.

The thermal separation unit may be a dummy thermopile element formed on the surface of the semiconductor substrate and having the same structure as the thermopile element.

A plurality of the dummy thermopile elements may be provided and may be formed so as to surround the infrared detection unit.

The dummy thermopile element may be configured to have the same dimensions as the thermopile element constituting the infrared detection unit.

Further, the cold junction temperature of the thermopile element included in the infrared detection unit in the same semiconductor substrate as the infrared detection unit, adjacent to the infrared detection unit, and in a region where heat conduction from the signal amplification unit is suppressed. The structure in which the temperature sensor which detects this is formed may be sufficient.

  According to the infrared sensor according to the present invention, since heat conduction between the amplifier circuit and the infrared detector is suppressed by a heat separation groove provided between the infrared detector and the amplifier circuit, The influence of the cold junction temperature of the thermopile element included in the infrared detector on the current consumption of the amplifier circuit can be reduced, and the output can be stabilized. Further, by providing a plurality of dummy elements between the infrared detection unit and the amplification circuit, heat conduction between the amplification circuit and the infrared detection unit is suppressed, and the output can be stabilized.

  Hereinafter, an infrared sensor of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing an infrared sensor according to the first embodiment of the present invention. FIG. 2 is a view showing a cross section taken along the line AA shown in FIG. The infrared sensor shown in FIG. 1 includes an infrared detection unit 1 made of a thermopile element, an amplifier circuit 2 as a signal processing unit, and a separation groove 3 as a heat separation unit formed in a semiconductor substrate 50.

  The thermopile element that constitutes the infrared detecting unit 1 forms a thermocouple by alternately connecting the p-type polysilicon 11 and the n-type polysilicon 12 in series, and the p-type polysilicon 11 and the n-type polysilicon 12 are connected. Are connected to the hot contact portion 14 covered with the infrared absorption film 13 and the cold contact portion 15 located at the peripheral portion thereof alternately. These thermopile and infrared absorption film are formed on the membrane 16. As shown in FIG. 2, the membrane 16 is formed so as to straddle the cavity 17, and the hot contact part 14 and the cold contact part 15 are thermally connected by positioning the hot contact part 14 on the cavity part. To be separated. A thermocouple composed of p-type polysilicon 11 and n-type polysilicon 12 detects a temperature difference between hot junction portion 14 and cold junction portion 15 and outputs it as a voltage signal.

  The signal amplification unit includes an amplification circuit 2 that amplifies the output signal of the thermopile element that constitutes the infrared detection unit 1. Although not shown, the amplifier circuit 2 and the infrared detection unit 1 are connected by a wiring or the like formed on the semiconductor substrate 50 and an output signal is transmitted. As described above, since the amplifier circuit 2 and the infrared detection unit 1 are both formed on the semiconductor substrate 50, the length of the wiring connecting them can be minimized, thereby suppressing the influence of external noise. be able to.

  As shown in FIG. 2, the separation groove 3 is a groove formed in the semiconductor substrate 50 between the infrared detection unit 1 and the amplifier circuit 2, and by this separation groove 3, the amplification circuit 2 directly connects the thermopile element. Heat flow is interrupted. Since the heat flow from the amplifier circuit 2 to the cold junction 15 via the side of the separation groove 3 and the side is sufficiently smaller than the heat flow directly from the signal amplifier 2 to the cold junction 15, the thermopile element The temperature of the included cold junction 15 is stabilized without receiving heat from the amplifier circuit 2. In the infrared sensor of this embodiment, the length of the separation groove 3 is formed to be equal to or longer than the length L of the thermopile element facing the amplifier circuit 2.

  In the infrared sensor according to the present embodiment, the heat conduction between the thermopile element and the amplifier circuit 2 is suppressed by the separation groove 3, so that the temperature of the cold junction part 15 included in the thermopile element generates heat of the signal amplifier 2. Therefore, the output as a sensor can be stabilized.

  In the present embodiment, the infrared detection unit 1 is shown as an example in which the thermopile elements 10 are configured as a single unit, but the thermopile elements may be configured by a thermopile array in which a plurality of rows and columns are arranged. FIG. 3 is a plan view of an infrared sensor having an infrared detection unit 1 constituted by a thermopile array. Like the above-described embodiment, the semiconductor substrate 50 between the infrared detection unit 1 and the amplifier circuit 2 has a gap between the two. A separation groove 3 is formed for suppressing the influence of heat.

  FIG. 4 is a plan view of an infrared sensor according to the second embodiment of the present invention. The infrared sensor shown in FIG. 4 includes an infrared detection unit 1 composed of a thermopile array in which thermopile elements 10 are arranged in a plurality of rows and columns, a signal amplification unit 2, and a separation groove 3 surrounding the infrared detection unit 1. All are formed on one semiconductor substrate. Although not shown, the amplifier circuit 2 and the infrared detection unit 1 are connected by a wiring or the like formed on the semiconductor substrate 50 and an output signal is transmitted. In order to provide a semiconductor substrate region for forming the wiring, a part of the separation groove 3 may be interrupted.

  According to the infrared sensor of the present embodiment, since the infrared detection unit 1 is surrounded by the separation groove 3, the infrared detection unit 1 also suppresses heat conduction with components other than the signal amplification unit 2, and the thermopile. The temperature of the cold junction 15 included in the element 10 is caused by temperature fluctuations due to components other than the signal amplifying unit 2, for example, heat from a bonding wire via a bonding pad (not shown) provided on the peripheral edge of the semiconductor substrate. Can also reduce the impact.

  FIG. 5 shows a plan view of an infrared sensor according to the third embodiment of the present invention. The infrared sensor shown in FIG. 5 is composed of an infrared detector 1 composed of a thermopile array in which thermopile elements 10 are arranged in a plurality of rows and columns, an amplifier circuit 2, and a plurality of dummy elements 4 arranged in a row. The

  A plurality of dummy elements 4 are arranged in parallel to the rows of the thermopile array facing the amplifier circuit 2. The dummy element 4 is manufactured in the same manufacturing process as the thermopile element 10 shown in FIG. 2 and has the same structure and the same area, but is electrically cut from other components. The cavities included in the respective dummy elements 4 spatially block the shortest path connecting the infrared detecting unit 1 and the signal amplifying unit 2 to restrict heat flow, thereby suppressing heat conduction.

  In the infrared sensor according to the present embodiment, a plurality of dummy elements 4 are inserted side by side between the infrared detector 1 and the amplifier circuit 2, so that the separation groove 3 is interposed between the infrared detector 1 and the amplifier circuit 2. An effect equivalent to that of the infrared sensor of the first embodiment in which is formed can be obtained. In addition, since the thermopile element 10 and the dummy element 4 are formed with the same structure and the same area in the infrared sensor according to the present embodiment, both can be manufactured by the same process, and the process can be simplified. Can do.

In the infrared sensor according to the present embodiment, the dummy element 4 may be configured with an area smaller than the thermopile element 10. The plurality of dummy elements 4 formed with a small area are arranged without gaps, so that the cavities 17 included in the respective dummy elements 4 are densely packed, and the semiconductor substrate 50 is directly passed from the amplifier circuit 2 to the infrared detection unit 1. Since the heat flow to reach decreases, the effect of suppressing heat conduction increases.
Similarly to the case where a groove is provided as a heat separation part, an infrared sensor having a thermopile array in which thermopile elements are arranged in a plurality of rows and a plurality of columns and a signal amplifying circuit also includes a thermopile. It is also possible to form the dummy element to be surrounded so as to surround the infrared detection unit.

  Even in such a case, the infrared detection unit also suppresses heat conduction from the components other than the signal amplifier circuit, and the temperature of the cold junction portion included in the thermopile element is thermally increased from components other than the signal amplifier circuit. The impact can also be suppressed.

  FIG. 6 shows an infrared sensor according to a fourth embodiment of the present invention. The infrared sensor shown in FIG. 6 includes an infrared detection unit 1, a signal amplification unit 2, a separation groove 3, and a temperature sensor 5. The temperature sensor 5 detects the temperature of the cold junction 15 included in the thermopile element 10 constituting the infrared detection unit 1, is adjacent to the infrared detection unit 1, and is heated from the amplifier circuit 2 by the separation groove 3. It is formed in a region where the influence of conduction is suppressed. For example, it is composed of a thermistor or a band gap type analog sensor.

  In the infrared sensor according to the present embodiment, since the temperature sensor 5 is formed on the semiconductor substrate 50 together with the infrared detection unit 1, the wiring for connecting them to each other can be shortened. The error due to can be minimized. Further, since the heat conduction is suppressed between the temperature sensor 5 and the signal amplification unit 2 by the separation groove 3, the temperature of the cold junction unit 15 of the infrared detection unit 1 and The temperature of the cold junction part 15 included in the thermopile element 10 is more accurately determined than the infrared sensor in which the infrared detection part and the temperature sensor are formed on separate semiconductor substrates without being affected by the temperature detected by the temperature sensor 5. Can be detected.

  In the infrared sensor according to the present embodiment, the heat conduction between the infrared detection unit 1 and the signal amplification unit 2 is suppressed by the separation groove 3, but a plurality of dummy elements 4 are used instead of the separation groove 3. May be.

The top view of the infrared sensor which concerns on the 1st Example of this invention. Sectional drawing about A-A 'of FIG. 1 is a plan view of an infrared sensor having a thermopile array structure according to a first embodiment of the present invention. The top view of the other infrared sensor which concerns on the 2nd Example of this invention. The top view of the infrared sensor which concerns on the 3rd Example of this invention. The top view of the infrared sensor which concerns on the 4th Example of this invention. The top view showing the conventional infrared sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Infrared detection part 2 Amplifying circuit 3 Separation groove 4 Dummy element 5 Temperature sensor 10 Thermopile element 11 N type polysilicon 12 P type polysilicon 13 Infrared absorption film 14 Hot contact part 15 Cold contact part 16 Diaphragm 17 Cavity 50 Semiconductor substrate

Claims (7)

  A thermopile in which an infrared detection unit including a thermopile element that outputs a signal according to the amount of received infrared light and a signal processing unit including an amplification circuit that amplifies the signal generated by the infrared detection unit are formed on the same semiconductor substrate Separation that suppresses heat conduction between the infrared detection unit and the signal processing unit formed on the semiconductor substrate at least between the infrared detection unit and the signal processing unit Thermopile type infrared sensor characterized by having a part. The thermopile infrared sensor according to claim 1, wherein the heat separation part is a groove region formed on a surface of the semiconductor substrate. The thermopile infrared sensor according to claim 1, wherein the groove region is formed to surround the infrared detection unit. 2. The thermopile infrared sensor according to claim 1, wherein the heat separation part is a dummy thermopile element formed on a surface of the semiconductor substrate and having the same structure as the thermopile element. The thermopile type infrared sensor according to claim 4, wherein a plurality of the dummy thermopile elements are formed so as to surround the infrared detection unit. 6. The thermopile infrared sensor according to claim 4, wherein the dummy thermopile element is formed to have the same size as the thermopile element constituting the infrared detection unit. The cold junction temperature of the thermopile element included in the infrared detection unit is detected in a region adjacent to the infrared detection unit on the same semiconductor substrate as the infrared detection unit and in which heat conduction from the signal amplification unit is suppressed. The thermopile type infrared sensor according to any one of claims 1 to 7, wherein a temperature sensor is formed.

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