JP4530997B2 - Infrared sensor - Google Patents

Description

  The present invention relates to an infrared sensor using a PN junction diode as a thermal sensor.

In a conventional infrared sensor, a plurality of PN junction diodes connected in series are used as they are as infrared detection pixels. An infrared sensor having such a configuration is disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-364241 (Patent Document 1).
JP 2004-364241 A

  With the above-described configuration, the conventional infrared sensor has the following various problems. For example, when the differential resistance of the PN junction diode increases, there is a problem that the noise voltage (that is, noise) at the time of detection increases.

  Further, a reverse bias voltage is applied to the PN junction diode in the non-selected pixel. In this case, a slight reverse current is generated in the diode. When the number of pixels included in the infrared sensor increases, power loss due to reverse current tends to increase.

  Further, the characteristics (current-voltage characteristics) of the PN junction diode tend to vary from pixel to pixel. For this reason, distribution tends to occur in outputs from a plurality of pixels arranged in an array.

  The objective of this invention is providing the infrared sensor which can improve the detection performance of infrared rays compared with the past.

  In summary, the present invention is an infrared sensor comprising a plurality of detectors for detecting infrared rays. Each of the plurality of detectors includes at least one diode, a constant current source, and a differential amplifier. The at least one diode is electrically connected between the first and second nodes such that the direction from the first node to the second node is the forward direction, and the forward direction according to the incidence of infrared rays Change the voltage. The constant current source draws a constant current from the second node. The differential amplifier provides the first node with a potential determined according to the potential difference between the constant potential and the signal potential output from the second node.

  According to the infrared sensor of the present invention, it is possible to improve the infrared detection performance as compared with the conventional one.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

[Embodiment 1]
FIG. 1 is a perspective view showing a schematic configuration of the infrared sensor according to the first embodiment.

Referring to FIG. 1, infrared sensor 300 is a thermal infrared solid-state imaging device that performs infrared imaging. The infrared sensor 300 is mounted on, for example, a monitoring camera or a fire detection camera. In such a camera, by performing infrared imaging, imaging can be performed regardless of day and night, and the permeability to smoke and fog can be increased more than visible light.

  The infrared sensor 300 is formed on a substrate 301 made of a semiconductor such as silicon. The infrared sensor 300 includes a detector array 302, a plurality of drive lines 303, a plurality of signal lines 304, and a signal processing circuit 305.

  The detector array 302 includes a plurality of detectors 500 arranged in a matrix. FIG. 1 shows a configuration in which six detectors 500 are arranged in two rows and three columns as a configuration example of the detector array 302. Each of these detectors 500 detects infrared radiation. The principle of infrared detection by the detector 500 will be described later.

  The plurality of drive lines 303 are arranged corresponding to the respective rows of the plurality of detectors 500. The plurality of signal lines 304 are arranged corresponding to the respective columns of the plurality of detectors 500.

  The signal processing circuit 305 includes a vertical scanning circuit 306 and a horizontal scanning circuit 307. The vertical scanning circuit 306 sequentially selects a plurality of drive lines 303. The vertical scanning circuit 306 operates the detector 500 by applying a power supply potential to the selected drive line. The horizontal scanning circuit 307 sequentially selects a plurality of signal lines 304. The horizontal scanning circuit 307 reads the potential change of the selected signal line (that is, the change in the output potential of the detector 500) and outputs the result to the outside. As a result, the infrared sensor 300 can perform infrared imaging. Note that the horizontal scanning circuit 307 may perform processing such as amplifying a potential change of the signal line in addition to the above processing.

FIG. 2 is a plan view of the detector 500 of FIG.
FIG. 3 is a cross-sectional view in the III-III direction in FIG.

  Referring to FIGS. 2 and 3, detector 500 includes metal wiring 501, detection unit 504, support leg 505, recess 506, umbrella structure 507, and protective film 509. In FIG. 2, the umbrella structure 507 and the protective film 509 are not shown in order to facilitate understanding of the configuration of the detector 500.

  The detection unit 504 is provided in a hollow state on the recess 506 by the support leg 505. The recess 506 is formed by an etching process. The etching hole 508 is formed in order to introduce an etching gas or liquid into the substrate 301. The umbrella structure 507 is provided on and in contact with the detection unit 504.

  The detection unit 504 is provided with a metal wiring 501 and a detection film 510. A metal wiring 501 is also provided on the support leg 505. A protective film 509 is provided above the metal wiring 501. The detection film 510 is electrically connected to the vertical scanning circuit 306 or the horizontal scanning circuit 307 of FIG. A PN junction diode is formed on the detection film 510.

  Next, the principle of infrared detection by the detector 500 will be described. When infrared rays emitted from a subject to be imaged by the infrared sensor 300 enter the detector 500, the umbrella structure 507 mainly absorbs the infrared rays. As a result, the temperature of the detection unit 504 increases. The electrical characteristics of the detection film 510 (specifically, the forward voltage of the diode) change according to the temperature change of the detection unit 504.

  A change in electrical characteristics in each of the plurality of detectors 500 is read by the horizontal scanning circuit 307 in FIG. The horizontal scanning circuit 307 outputs a signal indicating a change in electrical characteristics of the detector 500 to the outside. A thermal image of the subject can be obtained by appropriately processing this signal.

  The substrate 301 and the detection unit 504 are connected by a support leg 505. The smaller the thermal conductance of the support leg 505, the greater the temperature change of the detection unit 504. Thereby, the detector 500 can detect infrared rays sensitively.

Next, the above infrared detection operation will be described in more detail.
FIG. 4 is an equivalent circuit diagram of a detector included in a conventional infrared sensor.

  Referring to FIG. 4, detector 500A includes a plurality of PN junction diodes 601 connected in series between nodes N1 and N2, and a constant current source 602 connected between node N2 and the ground node. Prepare. Node N1 is connected to drive line 303. A constant potential (power supply potential Vcc) is applied to node N1. Node N2 is connected to signal line 304.

FIG. 5 is a diagram generally showing the temperature dependence of the voltage-current characteristics of the diode.
Referring to FIG. 5, the forward voltage Vf corresponding to a certain amount of forward current If depends on the temperature of the diode. For example, the magnitude of the forward voltage Vf is V1 at a high temperature and V2 (however, V1 <V2) at a low temperature.

  A description will be given with reference to FIG. 4 again. The constant current source 602 draws a constant constant current from the node N2 regardless of the temperature. As a result, a constant forward current If flows through the PN junction diode 601 regardless of the temperature. When a temperature change occurs in detector 500A, forward voltage Vf (that is, a voltage between node N1 and node N2) changes, so that the potential of node N2 changes.

FIG. 6 is an equivalent circuit diagram of the detector 500 of FIGS.
6 and 4, detector 500 is different from detector 500A in that detector 500A in FIG. 4 is further provided with a differential amplifier 603 and a delay circuit DL. Since the configuration of other parts of detector 500 is the same as that of detector 500A, the following description will not be repeated.

  In FIG. 6, a plurality of PN junction diodes 601 are shown. Detector 500 can detect a minute temperature change by including a plurality of diodes. The plurality of PN junction diodes 601 are electrically connected between the node N1 and the node N2 so that the direction from the node N1 to the node N2 is the forward direction. However, in the present embodiment, it is sufficient that at least one PN junction diode 601 is electrically connected to the node N1 and the node N2.

  The differential amplifier 603 is applied with power supply potentials V + and V− for circuit operation. A non-inverting input terminal (indicated by symbol “+”) of the differential amplifier 603 is connected to the drive line 303. A power supply potential Vcc which is a constant potential is applied to the drive line 303. Thereby, the non-inverting input terminal of differential amplifier 603 is coupled to power supply potential Vcc. The potential Vout of the node N2 is fed back to the inverting input terminal (indicated by the symbol “−”) of the differential amplifier 603. Differential amplifier 603 gives potential VA obtained by amplifying the potential difference between potential Vout and power supply potential Vcc to node N1.

  Delay circuit DL includes a resistor 604 and a capacitor 605. Resistor 604 is connected between node N 2 and the inverting input terminal of differential amplifier 603. Capacitor 605 is connected between node N2 and the ground node.

In detector 500, forward current If flows from node N1 to node N2, similarly to detector 500A in FIG. The constant current source 602 keeps the forward current If constant regardless of the temperature. Therefore, the forward voltage Vf between the node N1 and the node N2 changes according to the temperature change.

  In the detector 500, a plurality of PN junction diodes 601 connected in series are inserted into the feedback loop of the differential amplifier 603. Thus, the detector 500 operates as an ideal diode circuit, that is, a diode whose forward voltage Vf becomes 0V.

  FIG. 7 is a diagram generally showing voltage-current characteristics of an ideal diode and a normal diode.

  Referring to FIG. 7, in an ideal diode, the forward resistance (voltage / current) is almost zero, and the reverse resistance is extremely large. Therefore, only a small amount of reverse current flows in an ideal diode. On the other hand, in the case of a normal diode, the voltage-current curve has a slope with respect to the forward voltage, and a reverse current of a certain magnitude is generated with respect to the reverse voltage.

  FIG. 8 is a diagram generally showing the relationship between the waveform of the input potential of the ideal diode and the waveform of the output potential.

  Referring to FIG. 8, the positive waveform of potential Vin input to the anode of the ideal diode appears as it is as the waveform of potential Vo output to the cathode. Therefore, if the potential Vin changes from 0 to the potential Vp, the potential Vo also changes from 0 to the potential Vp. When the potential Vin is negative, the potential Vo is 0V.

  Next, the operation of the detector 500 of FIG. 6 will be described. In order to facilitate understanding, a case will be described in which the delay circuit DL is not provided in the detector 500 and the inverting input terminal of the differential amplifier 603 is directly connected to the node N2.

  In this case, when the potential Vin of the non-inverting input terminal is 0, the potential VA of the node N1 is also 0. Therefore, the plurality of PN junction diodes 601 are turned off. At this time, the negative feedback loop from the node N2 to the inverting input terminal of the differential amplifier 603 is opened.

  When the potential Vin slightly changes to the positive side, the potential VA greatly changes due to the amplification action of the differential amplifier 603. As the plurality of PN junction diodes 601 become conductive, the differential amplifier 603 operates as a voltage follower. Therefore, the potential Vout of the node N2 becomes equal to the potential Vin. If the potential Vin is negative, the plurality of PN junction diodes 601 are turned off, so that the negative feedback loop of the differential amplifier 603 is opened. That is, the detector 500 of FIG. 6 can be regarded as an ideal diode circuit, that is, a diode having a forward voltage of 0 V and a reverse resistance of infinity.

  In an ideal diode circuit, the forward resistance is very small. Therefore, the infrared sensor 300 of FIG. 1 can reduce the noise voltage, so that the detection sensitivity can be increased. The reason why the noise voltage decreases is that the relationship of (noise voltage) = (noise current) × (resistance) is established. Examples of the noise voltage include “shot noise voltage” (noise generated when carriers that have passed through the depletion region of the PN junction diode are irregularly injected into the P-type region or N-type region), “flicker noise voltage”, etc. There is.

  In the detector 500 belonging to the non-selected row, the PN junction diode 601 is reverse-biased by the vertical scanning circuit 306 in FIG. In an ideal diode circuit, the reverse resistance is extremely large. Therefore, since reverse current (leakage current) is reduced in detector 500, infrared sensor 300 in FIG. 1 can reduce power loss.

  Further, the differential amplifier 603 forms a negative feedback loop so that the potential Vout becomes equal to the potential Vin of the non-inverting input terminal (that is, the power supply potential Vcc). Accordingly, variation in characteristics of the plurality of detectors 500 can be reduced. Thereby, the infrared sensor 300 in FIG. 1 can reduce the intensity distribution. Of course, it is necessary to set the power supply potentials V + and V− of the differential amplifier 603 so that a plurality of PN junction diodes 601 connected in series are conductive.

  When the delay circuit DL is not provided in the detector 500 of FIG. 6, even if the potential Vout changes once, it immediately returns to the potential Vcc. Therefore, the horizontal scanning circuit 307 in FIG. 1 cannot detect that the forward voltage of the PN junction diode 601 has changed (that is, the potential Vout has changed). For this reason, in the detector 500 of FIG. 6, the delay circuit DL is provided in the negative feedback loop of the ideal diode circuit.

  The delay circuit DL plays a role of adjusting the potential of the inverting input terminal of the differential amplifier so that the forward voltage of the diode changed in response to the incidence of infrared rays is maintained for a predetermined period. The delay circuit DL delays a change in the potential Vout by a period determined by (resistance value R of the resistor 604) × (capacitance value C of the capacitor 605) (that is, a predetermined period RC), and applies it to the inverting input terminal of the differential amplifier 603. introduce.

  More specifically, first, the forward voltage of the diode changes. Next, the horizontal scanning circuit 307 reads the change in the potential Vout of the node N2 for each detector 500 and outputs a signal to the outside. At this time, the potential change of the node N2 is transmitted to the delay circuit DL, but not transmitted to the inverting input terminal of the differential amplifier 603. Then, the potential change at the node N2 is transmitted to the inverting input terminal of the differential amplifier 603 with a delay of a period RC determined by (resistance value R) × (capacitance value C).

  At this time, the output potential (potential VA) of the differential amplifier 603 changes so that the potential difference between the non-inverting input terminal and the inverting input terminal of the differential amplifier 603 is eliminated. Therefore, the potential Vout of the node N2 becomes equal to the original state, that is, the power supply potential Vcc.

  As described above, the delay circuit DL can adjust the potential change of the nodes N1 and N2 so that the potential Vout becomes equal to the power supply potential Vcc after the horizontal scanning circuit 307 in FIG. 1 detects the change of the potential Vout. For this purpose, it is desirable that the delay time in the delay circuit DL is equal to the time for scanning all the pixels in the detector array 302 one time. Such adjustment is possible by appropriately determining the product of the resistance value R and the capacitance value C.

  Next, an example of a method for manufacturing the infrared sensor according to Embodiment 1 will be described with reference to FIGS.

  9 to 15 are diagrams showing the first to seventh manufacturing steps of the detector 500, respectively.

  First, as shown in FIG. 9, a so-called SOI (Silicon On Insulator) substrate in which a silicon oxide film layer 801 and a silicon layer 802 are sequentially stacked on a substrate 301 is prepared. Next, as shown in FIG. 10, an isolation oxide film 805 is formed at a predetermined position by LOCOS (Local Oxidation of Silicon) isolation method or trench isolation method.

Subsequently, as shown in FIG. 11, circuit elements such as diodes, transistors, resistors, and capacitors are formed on the substrate 301 or the silicon layer 802. As a result, the detection film 510 in FIG. 2 (PN junction diode 601 in FIG. 6), the differential amplifier 603, the resistor 604, the capacitor 605, and the like in FIG. 6 are formed in the silicon layer 802. As described above, various elements are formed in the silicon layer 802. For convenience of explanation, in the description of FIGS. 12 to 15, it is assumed that the detection layer 510 is formed on the silicon layer 802.

  Subsequently, as shown in FIG. 12, an insulating film 806 is deposited so as to cover the entire surfaces of the isolation oxide film 805 and the detection film 510. An insulating film including the silicon oxide film layer 801, the isolation oxide film 805, and the insulating film 806 is shown as an insulating film 807 in FIGS. As shown in FIG. 13, a metal wiring 501 is formed in the insulating film 807. Next, a protective film 509 is formed on the metal wiring 501.

  Subsequently, as shown in FIG. 14, an etching hole 508 is opened at a predetermined position of the insulating film 807. Thereby, a part of the insulating film 807 is formed as the support leg 505. At this time, the etching holes 508 are formed point-symmetrically as shown in FIG. Next, a sacrificial layer 808 made of silicon is deposited, and an umbrella structure 507 is formed on the sacrificial layer 808.

  Subsequently, as shown in FIG. 15, an etchant such as xenon fluoride is introduced from the etching hole 508 to remove the sacrificial layer 808 and form a recess 506 inside the substrate 301. The protective film 509 functions to protect elements such as a diode and a resistor from the stress (for example, humidity or some physical contact) received from the surrounding environment during the etching process when removing the sacrificial layer 808 or after the detector 500 is completed. To do. In this way, the infrared sensor 300 of FIG. 1 equipped with the detector 500 is completed. The detector 500 includes a detection unit 504 and an umbrella structure 507 that are held in a hollow state by a support leg 505 made of an insulating film.

  As described above, according to the first embodiment, an ideal diode circuit in which a plurality of PN junction diodes connected in series are connected to a differential amplifier is configured in the detector. As a result, the resistance in the forward direction is almost infinitely small, so that the noise voltage can be made smaller than before.

  Further, according to the first embodiment, the resistance in the reverse direction is close to infinity, so that the power loss due to the reverse current can be reduced.

  Further, according to the first embodiment, the non-inverting input potential of the differential amplifier is equal to the output potential of the ideal diode circuit, so that the output distribution of the detector array can be reduced.

[Embodiment 2]
The configuration of the infrared sensor of the second embodiment is the same as the configuration of the infrared sensor 300 shown in FIG. Moreover, the top view and sectional drawing of the detector with which the infrared sensor of Embodiment 2 is provided are the same as FIG. 2 and FIG. 3, respectively. Therefore, the subsequent description of the configuration of the infrared sensor of Embodiment 2 will not be repeated.

  Further, since the infrared detection principle of the infrared sensor of the second embodiment is the same as that of the first embodiment, the following description will not be repeated.

FIG. 16 is a circuit diagram of a detector included in the infrared sensor of the second embodiment.
Referring to FIGS. 16 and 6, detector 500 </ b> B is detected in that it includes a sample and hold circuit SH provided between the output terminal of differential amplifier 603 and node N <b> 1 instead of resistor 604 and capacitor 605. Different from the vessel 500. Since other parts of detector 500B are similar to detector 500, the following description will not be repeated.

The sample hold circuit SH includes a switch 606, a buffer amplifier 607, and a capacitor 608. The switch 606 is provided between the output terminal of the differential amplifier 603 and the node N3. The switch 606 is made of a transistor, for example. Buffer amplifier 607 has an input terminal connected to node N3 and an output terminal connected to node N1. Capacitor 608 is connected between node N3 and the ground node.

  FIG. 17 is a general diagram showing the waveform of the input potential and the waveform of the output potential of the sample and hold circuit.

  Referring to FIG. 17, the output potential (potential Vo) is kept equal to the input potential (potential Vin) at time t1 during the period from time t1 to time t2. The operation of the sample and hold circuit at times t2 to t8 is similar to the operation at times t1 and t2.

  Similar to the first embodiment, in the second embodiment, the detector 500B constitutes an ideal diode circuit. Therefore, the infrared sensor of the second embodiment can make the noise voltage smaller than the conventional one. Moreover, the infrared sensor of Embodiment 2 can reduce power loss due to reverse current. In addition, the infrared sensor of the second embodiment can reduce the output distribution of the detector array.

FIG. 18 is a diagram illustrating a specific example of the operation of the detector 500B of FIG.
Referring to FIG. 18, changes over time are shown for each of the potential Vout of the node N 2, the potential VA of the node N 1, and the sample pulse input to the switch 606. Periods T1 and T2 indicate periods in which the switch 606 in FIG. 16 is in a conductive state and a non-conductive state, respectively. Periods T1 and T2 mean a sampling period and a hold period, respectively. The potential Vout is equal to the potential of the inverting input terminal of the differential amplifier 603.

  The sample hold circuit SH plays a role of adjusting the potential of the node N1 so that the forward voltage of the diode changed in response to the incidence of infrared rays is maintained for a predetermined period. The period T2 in FIG. 18 corresponds to this “predetermined period”.

  Assume that a temperature change has occurred, assuming that the sample-and-hold circuit SH is not provided in the second embodiment. At this time, even if the potential Vout of the node N2 changes, the potential Vout immediately becomes equal to the power supply potential Vcc. Therefore, the horizontal scanning circuit 307 in FIG. 1 cannot read the change in the forward voltage of the diode, that is, the change in the potential Vout.

  However, in this embodiment, a sample and hold circuit SH is provided between the differential amplifier 603 and a plurality of PN junction diodes 601 connected in series. The sample and hold circuit has a function of collecting an analog signal value at a certain moment and holding the value for a while. Therefore, according to the second embodiment, after the horizontal scanning circuit 307 in FIG. 1 detects the change in the potential Vout, the potential change of the nodes N1 and N2 can be adjusted so that the potential Vout becomes equal to the power supply potential Vcc. Specifically, the time interval of the sample pulses in the sample hold circuit SH (period T2 in FIG. 18) may be set to be equal to the time for scanning all the pixels in the detector array 302 in FIG.

  In the first embodiment, it is necessary to adjust the resistance value R of the resistor 604 and the capacitance value C of the capacitor 605 for realizing the required delay time. However, since the resistor 604 is not necessary in the second embodiment, it is only necessary to adjust the capacitance value C. In addition, since the switch 606 is used, timing adjustment is easy.

  The manufacturing method of the infrared sensor according to the second embodiment is the same as the manufacturing method shown in FIGS.

As described above, according to the second embodiment, by adding the sample hold circuit to the ideal diode circuit (detector), the forward voltage is maintained until the reading of the change in the forward voltage of the diode is completed. Is possible.

[Embodiment 3]
The configuration of the infrared sensor of the third embodiment is the same as that of the infrared sensor 300 shown in FIG. Further, the plan view and the cross-sectional view of the detector of the infrared sensor according to Embodiment 3 are the same as those in FIGS. Therefore, the subsequent description of the configuration of the infrared sensor according to Embodiment 3 will not be repeated. The basic principle that the detector of the infrared sensor according to the third embodiment detects infrared rays is the same as that of the first embodiment, and therefore the following description will not be repeated.

FIG. 19 is a circuit diagram of a detector included in the infrared sensor of the third embodiment.
Referring to FIGS. 19 and 6, detector 500C is different from detector 500 in that switch 606 is included in place of resistor 604, but the other parts are the same as detector 500, so that the following description will be repeated. Absent. The switch 606 is provided between the inverting input terminal of the differential amplifier 603 and the node N2. The capacitor 605 is provided between the inverting input terminal of the differential amplifier 603 and the ground node. Note that the capacitor 605 and the switch 606 form an “adjustment circuit” in the present invention. The differential amplifier 603, the capacitor 605, and the switch 606 constitute a sample and hold circuit.

  Similar to the first embodiment, in the third embodiment, the detector 500C constitutes an ideal diode circuit. For this reason, the infrared sensor of Embodiment 3 can make a noise voltage smaller than before. Moreover, the infrared sensor of Embodiment 3 can reduce power loss due to reverse current. Moreover, the infrared sensor of Embodiment 3 can reduce the output distribution of the detector array.

  Detector 500C differs from detector 500B in FIG. 16 in that it includes a sample-and-hold circuit in which capacitor 605 and switch 606 are provided in the negative feedback loop of differential amplifier 603. The operation and effect of the sample and hold circuit in the detector 500C are the same as those of the sample and hold circuit SH in FIG. Since the operation waveform of detector 500C is the same as that shown in FIG. 18, the following description will not be repeated. As in the second embodiment, the period T2 corresponds to the “predetermined period” in the present invention.

  Also in the third embodiment, as in the second embodiment, the time interval of the sample pulses in the sample hold circuit SH (period T2 in FIG. 18) is a time for scanning all the pixels in the detector array 302 in FIG. Set to be equal. Thereby, also in the third embodiment, the potential Vout can be adjusted to be equal to the potential Vcc after the horizontal scanning circuit 307 in FIG. 1 reads the change in the potential Vout of the node N2.

In the second embodiment, a capacitance value that can hold the voltage between the plurality of PN junction diodes 601 connected in series is required for the capacitor 608 during a period from when the switch 606 is turned off to when it is turned on. However, since the input impedance of the differential amplifier 603 is infinite, the capacitance value of the capacitor 605 in FIG. 19 can be made smaller than the capacitance value of the capacitor 608 in FIG. Thereby, for example, since the area of the capacitor 605 can be reduced, the infrared sensor 300 of FIG. 1 can be highly integrated.

  Moreover, since the manufacturing method of the infrared sensor of Embodiment 3 is the same as that of the manufacturing method shown in FIGS. 9-15, subsequent description is not repeated.

As described above, according to the third embodiment, by adding the sample hold circuit to the ideal diode circuit (detector), the forward voltage is maintained until reading of the change in the forward voltage of the diode is completed. It becomes possible.

  In the infrared sensor of the present invention, the arrangement of the plurality of detectors is not limited to the matrix shown in FIG.

FIG. 20 is a diagram illustrating another example of the arrangement of a plurality of detectors.
Referring to FIG. 20, a plurality of detectors 500 are arranged in one dimension. Various arrangements of the plurality of detectors 500 are possible in addition to the arrangements shown in FIGS. 1 and 20.

  Further, the infrared sensor of the present invention is not limited to the use of performing infrared imaging, and can be applied as, for example, a general infrared sensor.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a perspective view illustrating a schematic configuration of an infrared sensor according to Embodiment 1. FIG. It is a top view of the detector 500 of FIG. It is sectional drawing of the III-III direction in FIG. It is an equivalent circuit schematic of the detector contained in the conventional infrared sensor. It is a figure which shows generally the temperature dependence of the voltage-current characteristic of a diode. FIG. 4 is an equivalent circuit diagram of the detector 500 of FIGS. 1 to 3. It is a figure which shows generally the voltage-current characteristic of an ideal diode and a normal diode. It is a figure which shows generally the relationship between the waveform of the input potential of an ideal diode, and the waveform of an output potential. FIG. 10 is a diagram illustrating a first manufacturing process of the detector 500. FIG. 10 is a diagram illustrating a second manufacturing process of the detector 500. FIG. 10 is a diagram showing a third manufacturing process of the detector 500. It is a figure which shows the 4th manufacturing process of the detector. It is a figure which shows the 5th manufacturing process of the detector. It is a figure which shows the 6th manufacturing process of the detector 500. FIG. It is a figure which shows the 7th manufacturing process of the detector. 6 is a circuit diagram of a detector included in the infrared sensor of Embodiment 2. FIG. It is a general diagram showing a waveform of an input potential and an output potential of a sample and hold circuit. It is a figure which shows the specific example of operation | movement of the detector 500B of FIG. 6 is a circuit diagram of a detector included in an infrared sensor according to Embodiment 3. FIG. It is a figure which shows another example of arrangement | positioning of a some detector.

Explanation of symbols

300 infrared sensor, 301 substrate, 302 detector array, 303 drive line, 304 signal line, 305 signal processing circuit, 306 vertical scanning circuit, 307 horizontal scanning circuit, 500, 500A to 500C detector, 501 metal wiring, 504 detector , 505 Support leg, 506 recess, 507 umbrella structure, 508 etching hole, 509 protective film, 510 detection film, 601 PN junction diode, 602 constant current source, 603 differential amplifier, 604
Resistor, 605, 608 capacity, 606 switch, 607 buffer amplifier, 801
Silicon oxide film layer, 802 silicon layer, 805 isolation oxide film, 806, 807 insulating film, 808 sacrificial layer, DL delay circuit, N1-N3 node, SH sample hold circuit.

Claims (3)

An infrared sensor,
It has multiple detectors that detect infrared rays,
Each of the plurality of detectors is
It is electrically connected between the first and second nodes so that the direction from the first node to the second node is the forward direction, and the forward voltage is changed according to the incidence of the infrared rays. At least one diode;
A constant current source for drawing a constant current from the second node;
Look including a differential amplifier for applying a potential determined in accordance with the potential difference between the signal potential output a constant voltage from said second node to said first node,
The differential amplifier is
A first input terminal to which the constant potential is coupled;
A second input terminal to which the signal potential is fed back and provided;
The infrared sensor is
An adjustment circuit that adjusts the potential of the first node or the potential of the second input terminal so that the forward voltage changed according to the incidence of the infrared rays is maintained for a predetermined period;
The adjustment circuit is provided between the output terminal of the differential amplifier and the first node, and starts changing the forward voltage until the predetermined period elapses. Infrared sensor , a sample and hold circuit that keeps time . An infrared sensor,
It has multiple detectors that detect infrared rays,
Each of the plurality of detectors is
It is electrically connected between the first and second nodes so that the direction from the first node to the second node is the forward direction, and the forward voltage is changed according to the incidence of the infrared rays. At least one diode;
A constant current source for drawing a constant current from the second node;
A differential amplifier that provides the first node with a potential determined according to a potential difference between a constant potential and a signal potential output from the second node;
The differential amplifier is
A first input terminal to which the constant potential is coupled;
A second input terminal to which the signal potential is fed back and provided;
The infrared sensor is
An adjustment circuit that adjusts the potential of the first node or the potential of the second input terminal so that the forward voltage changed according to the incidence of the infrared rays is maintained for a predetermined period;
The adjustment circuit includes:
A switch provided between the second node and the second input terminal;
An infrared sensor including a capacitor having one end connected to the second input terminal and the other end connected to a ground node . The plurality of detectors are arranged in a matrix,
The infrared sensor is
A plurality of drive lines which are respectively arranged corresponding to the respective rows of the plurality of detectors, and in which the plurality of first input terminals are connected in common;
A plurality of signal lines arranged corresponding to each column of the plurality of detectors, wherein the plurality of second nodes are connected in common in the corresponding column;
A vertical scanning circuit that sequentially selects the plurality of drive lines and applies the constant potential to the selected drive lines;
Wherein the plurality of sequentially selects the signal line, further comprising a horizontal scanning circuit for reading a change of the signal potential in the selected signal lines, infrared sensor according to claim 1 or 2.

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